Language：Japanese   Publisher：(一社)歯科基礎医学会  

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The conditions of stress contagion are induced in bystanders without direct experiences of stressful events. This study determined the effects of stress contagion on masseter muscle nociception in mice. Stress contagion was developed in the bystanders after cohabitating with a conspecific mouse subjected to social defeat stress for 10 days. On Day 11, stress contagion increased anxiety- and orofacial inflammatory pain-like behaviors. The c-Fos and FosB immunoreactivities evoked by masseter muscle stimulation were increased in the upper cervical spinal cord, while c-Fos expressions were increased in the rostral ventromedial medulla, including the lateral paragigantocellular reticular nucleus and nucleus raphe magnus in stress contagion mice. The level of serotonin in the rostral ventromedial medulla was increased under stress contagion, while the number of serotonin positive cells was increased in the lateral paragigantocellular reticular nucleus. Stress contagion increased c-Fos and FosB expressions in the anterior cingulate cortex and insular cortex, both of which were positively correlated with orofacial inflammatory pain-like behaviors. The level of brain-derived neurotrophic factor was increased in the insular cortex under stress contagion. These results indicate that stress contagion can cause neural changes in the brain, resulting in increased masseter muscle nociception, as seen in social defeat stress mice.

DOI： 10.1111/eos.12942

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Language：English   Publisher：新潟歯学会  

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Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publisher：医歯薬出版(株)  

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Other Link： https://search.jamas.or.jp/default/link?pub_year=2022&ichushi_jid=J00564&link_issn=&doc_id=20220804330001&doc_link_id=%2Faa7shitm%2F2022%2F014002%2F001%2F0217-0220%26dl%3D0&url=https%3A%2F%2Fwww.medicalonline.jp%2Fjamas.php%3FGoodsID%3D%2Faa7shitm%2F2022%2F014002%2F001%2F0217-0220%26dl%3D0&type=MedicalOnline&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00004_2.gif

Language：English   Publishing type：Research paper (scientific journal)  

We investigated the effects of social defeat stress (SDS) and treadmill running on masseter muscle nociception, which was quantified by the orofacial formalin test and c-Fos and FosB immunoreactivities in the upper cervical spinal cord (C1/C2) region in male mice. After daily SDS or non-SDS conditioning for 10 days, SDS-conditioned mice were categorized into SDS-susceptible versus resilient mice. Several mice, including non-SDS-conditioned, SDS-susceptible, and resilient mice, were selected to assess masseter muscle nociception on Day 11. SDS conditioning for 10 days increased masseter muscle-evoked nocifensive behaviors and c-Fos and FosB expression in SDS-susceptible compared to non-SDS and resilient mice. The remaining SDS-susceptible and non-SDS mice were subjected to an additional 10 days of SDS plus treadmill running or sedentary sessions before assessing masseter muscle nociception on Day 21. Daily treadmill running sessions reduced enhanced masseter muscle nociception in SDS-susceptible mice but not in non-SDS mice. The preventive effects of daily treadmill running immediately after each SDS conditioning for 10 days on orofacial nocifensive behaviors were assessed on Day 11. Treadmill running conducted immediately after daily SDS inhibited enhanced orofacial nocifensive behaviors. These findings indicate that repeated SDS increases masseter muscle nociception, which could be prevented by daily treadmill running exercise.

DOI： 10.1111/eos.12882

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jdsr.2021.10.002

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Language：English   Publishing type：Research paper (scientific journal)  

This study was designed to investigate the effects of Sake Lees extracts (SLE, Sake Kasu) on the functional activity of odontoblastic cells and tooth pulp of the rats. For in vitro studies, a rat clonal odontoblast-like cell line, KN-3 cells were cultured. SLE significantly decreased KN-3 cell proliferation, but showed no significant cytotoxicity. SLE effects on several protein productions of KN-3 cells were compared with PBS. SLE and PBS increased alkaline phosphatase (ALP), dentin sialoprotein (DSP), and osterix in a day-course dependent manner, while SLE increased the induction of ALP on day 9-21 and DSP on day 15-21. SLE also increased Runx2 expression on day 3 and 9 compared to PBS. Alizarin Red stainings revealed that SLE showed a subtle increase in mineralization of KN-3 cells on day 15 and 21. A histological investigation was conducted to assess if SLE induced reparative dentin formation after direct capping at the exposed tooth pulp in rats, suggesting that SLE could increase the reparative dentin formation more than PBS. These findings suggest that Sake Lees could have functional roles in the alterations of odontoblastic activity, which might influence the physiology of the tooth pulp.

DOI： 10.1007/s10266-021-00654-9

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：English   Publishing type：Research paper (scientific journal)  

Dystonin (Dst) is a causative gene for Dystonia musculorum (dt) mice, which is an inherited disorder exhibiting dystonia-like movement and ataxia with sensory degeneration. Dst is expressed in a variety of tissues, including the central nervous system and the peripheral nervous system (PNS), muscles, and skin. However, the Dst-expressing cell type(s) for dt phenotypes have not been well characterized. To address the questions whether the disruption of Dst in Schwann cells induces movement disorders and how much impact does it have on dt phenotypes, we generated Dst conditional knockout (cKO) mice using P0-Cre transgenic mice and Dst gene trap mice. First, we assessed the P0-Cre transgene-dependent Cre recombination using tdTomato reporter mice and then confirmed the preferential tdTomato expression in Schwann cells. In the Dst cKO mice, Dst mRNA expression was significantly decreased in Schwann cells, but it was intact in most of the sensory neurons in the dorsal root ganglion. Next, we analyzed the phenotype of Dst cKO mice. They exhibited a normal motor phenotype during juvenile periods, and thereafter, started exhibiting an ataxia. Behavioral tests and electrophysiological analyses demonstrated impaired motor abilities and slowed motor nerve conduction velocity in Dst cKO mice, but these mice did not manifest dystonic movements. Electron microscopic observation of the PNS of Dst cKO mice revealed significant numbers of hypomyelinated axons and numerous infiltrating macrophages engulfing myelin debris. These results indicate that Dst is important for normal PNS myelin organization and Dst disruption in Schwann cells induces late-onset neuropathy and sensory ataxia. MAIN POINTS: Dystonin (Dst) disruption in Schwann cells results in late-onset neuropathy and sensory ataxia. Dst in Schwann cells is important for normal myelin organization in the peripheral nervous system.

DOI： 10.1002/glia.23843

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Psychophysical stress can cause neural changes that increase nociception in the orofacial region, particularly the masseter muscle (MM). The nucleus raphe magnus (NRM), which is located in the brain stem, serves the crucial role of regulating nociception through descending modulatory pain control. However, it remains unclear if neural activities in the NRM are affected under psychophysical stress conditions. This study conducted experiments to assess (1) whether neural activity, indicated by Fos expression in an NRM that has experienced MM injury, is affected by the stress of repeated forced swim tests (FST); and (2) whether the selective serotonin reuptake inhibitor fluoxetine administered daily after an FST could affect the number of Fos-positive neurons in the NRM. Results revealed that the stress from repeated FSTs significantly increased the number of Fos-positive neurons in an NRM that had been affected by MM injury. Fluoxetine inhibited increases in the number of Fos-positive neurons in the NRM that occurred as a result of FSTs, but this was not observed in sham rats. These findings indicate that the stress from FSTs could increase nociceptive neural activity in an NRM that has experienced MM injury. This could be due, in part, to changes in serotonergic mechanisms.

DOI： 10.2334/josnusd.19-0320

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/09168451.2019.1662278

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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DOI： 10.1152/jn.00126.2018

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

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DOI： 10.1080/09168451.2018.1524705

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Other Link： https://search.jamas.or.jp/link/ui/2019253806

DOI： 10.1016/j.neuint.2017.10.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Verlag  

This study aimed to determine whether psychophysical stress conditionings had facilitatory effects on masseter muscle nociception in the central nervous system via serotonergic mechanisms in rats. Two experiments were conducted to assess: (1) whether repeated forced swim stress for 3 days increased the number of Fos-positive neurons evoked by masseter muscle injury due to formalin injection
and (2) whether serotonin-reuptake inhibitor, fluoxetine, administered daily after each stress conditioning, had modulatory roles on Fos expression. The number of Fos-positive cells was quantified in several areas within the trigeminal subnucleus caudalis (Vc) and upper cervical spinal cord regions (Vc areas), including the ventrolateral area of the trigeminal subnucleus interpolaris/Vc transition, and the middle or caudal portion of the Vc regions, since nociceptive neural activity in the Vc region could play critical roles in deep craniofacial nociception. We found that forced swim stress conditionings increased depression-like behaviors, which was prevented by fluoxetine. Repeated forced swim stress significantly increased Fos expression in all Vc areas compared with those of non-stressed rats, while systemic administration of fluoxetine significantly decreased Fos expression in all areas, but mainly in the caudal Vc region, in stressed rats. Fluoxetine had no effect on Fos expression in non-stressed rats. These results indicate that repeated forced swim stress conditionings increase Fos expression in the Vc areas, and the contribution of serotonergic mechanisms to masseter muscle nociception could be greater in stressed rats than in sham rats. These results support the hypothesis that changes in brain function, including serotonergic mechanisms, in the Vc areas play critical roles in enhanced masseter muscle nociceptive responses under psychophysical stress conditions.

DOI： 10.1007/s00221-018-5297-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer New York LLC  

The aim of this study was to determine if bolus and dry swallow showed similar pressure changes in the oropharynx using our newly developed device. A unique character of it includes that baropressure can be measured with the sensor being placed in the balloon and can assess the swallowing mechanics in terms of pressure changes in the oropharynx with less influences of direct contacts of boluses and oropharyngeal structures during swallow indirectly. Fifteen healthy subjects swallowed saliva (dry), 15 ml of water, 45 ml of water, and 15 ml of two different types of food in terms of viscosity (potage soup-type and mayonnaise-type foods). Suprahyoid muscle activity was recorded simultaneously. Three parameters, area under the curve (AUC), peak amplitude, and duration of pressure, were analyzed from each swallow. Almost all of the bolus swallowing events had biphasic baropressure responses consisting of an early phase and late phase (99%), whereas 90% of the saliva swallowing events had a single phase. AUC, peak, and duration displayed greater effects during the late phase than during the early phase. Baropressure of the early phase, but not of the late phase, significantly increased with increasing volume
however, small but significant viscosity effects on pressure were seen during both phases. Peak pressure of the late phase was preceded by maximum muscle activity, whereas that of the early phase was seen when muscle activity displayed a peak response. These findings indicated that our device with the ability to measure baropressure has the potential to provide additional parameter to assess the swallow physiology, and biphasic baropressure responses in the early and late phases could reflect functional aspects of the swallowing reflexes.

DOI： 10.1007/s00455-017-9836-9

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DOI： 10.1007/s40141-018-0192-y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

We determined the role of persistent monoarthritis of temporomandibular joint region (TMJ) on bilateral masseter muscle (MM) nociception in male rats using orofacial nocifensive behaviors, phosphorylated extracellular signal-regulated kinase and Fos induction at the trigeminal subnucleus caudalis/upper cervical spinal cord (Vc/C-2) region in response to formalin injection to the MM region. TMJ inflammation was induced by local injection of CFA into the left TMJ region. Orofacial nocifensive behaviors evoked by formalin injection ipsilateral or contralateral to the TMJ inflammation appeared to be increased at 1-14 days or at 1, 10 and 14 days after induction of TMJ inflammation, respectively, while increases in behavioral duration were seen mainly in the late phase rather than the early phase. The number of pERK positive cells was investigated in superficial laminae at the Vc/C-2 region at 3, 10, 20, 60 and 80 min after MM stimulation with formalin at 14 days after TMJ inflammation. TMJ-inflamed rats displayed greater responses of pERK expression by the ipsilateral MM stimulation at 3-60 min, while contralateral MM stimulation increased pERK expression at 3, 10 and 20 min compared to non-CFA rats. Fos expression by MM stimulation was increased at 14 days after induction of TMJ inflammation regardless of the affected side. These findings showed that persistent TMJ inflammation for 10 and 14 days is sufficient to enhance MM nociception indicated by behaviors and neural responses in superficial laminae at the Vc/C-2 region.

DOI： 10.1007/s00221-016-4852-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The act of eating is a source of pleasure for people and is a major factor in maintaining a good quality of life. Several types of products for dysphagia patients are available to decrease aspiration of food that often accompanies daily food intake. The final goal of these products is to improve the ease of forming a food bolus and/or the safety of the swallowing process; however, tastes of products are not a major concern with initiation of swallowing. In the present study, we investigated the effect of bitter taste stimuli (quinine) and the combination of quinine and umami (monosodium glutamate: MSG) applied to the oropharynx on reflex swallows evoked by electrical stimulation to the oropharyngeal mucosa. Each of the distilled water (DW), quinine and quinine-MSG mixture solution (volume of each solutions, 100 A mu l) was applied 1 s prior to electrical stimulation. No swallow was evoked when each of the solutions was applied without electrical stimulation. The application of DW and lower concentration of quinine (< 100 A mu M) did not affect the latency of reflex swallow, but 100 A mu M quinine application increased the latency of the reflex swallow. In addition, application of quinine-MSG mixture solution counteracted the increase in latency induced by quinine application alone. These findings suggest that MSG enhances the initiation of swallowing along with its well-known increase in appetite stimulation. Adding MSG might be effective when creating food to promote swallowing.

DOI： 10.1007/s10266-015-0226-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Quintessence Publishing Co. Inc.  

Aims: To examine the effects of local brain-derived neurotrophic factor (BDNF) produced after nerve injury on the functional regeneration of the damaged nerve. Methods: The inferior alveolar nerve was transected in adult male rats and 1 μg or 10 μg of BDNF antibody was administered at the injury site
a third group of rats received saline and a fourth group underwent nerve ligation. BDNF mRNA was quantified in the transected tissue and trigeminal ganglion by using realtime polymerase chain reaction (PCR). Head withdrawal thresholds following mechanical (tactile) stimulation (with von Frey filaments) of the mental region were measured for 3 weeks postoperatively. Electromyographic activity of the jaw opening reflex (JOR) was recorded from the anterior belly of the digastric muscle. Results: Within 24 hours, transection induced significant elevation of BDNF mRNA expression in the injured tissue (unpaired t test, P &lt
.01). The head withdrawal threshold to mechanical stimulation increased at 1 day after transection and then decreased (two-way repeated measures analysis of variance [ANOVA], P &lt
.001). At 2 weeks after surgery, the head withdrawal threshold was higher than before surgery in the group that received a higher dose of BDNF antibody (ANOVA, P &lt
.001), but not in the group that received a smaller dose (ANOVA, P &gt
.05). No significant differences were observed in the latency or threshold of the JOR between saline- and antibody-treated rats (unpaired t test, P &gt
.05). Conclusion: These results suggest that locally administered BDNF antibody neutralizes nerve injury-induced BDNF at the injury site and thus influences sensorimotor recovery.

DOI： 10.11607/ofph.1651

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BENTHAM SCIENCE PUBL LTD  

Mastication and swallowing are the first stage of digestion involving several motor processes such as food intake, intra-oral food transport, bolus formation and chewing and swallowing reflex. These complicated motor functions are accomplished by the well-coordinated activities in the jaw, hyoid, tongue, facial and pharyngeal muscles. Although the basic activity patterns of these movements are controlled by the brainstem pattern generators, these movements generate various peripheral sensory inputs. Among the sensory inputs, it is well-known that somatic sensory inputs play important roles in reflexively modulating the movements so that the final motor outputs fit the environmental demand. However, little is known about the effects of chemical sensory inputs such as taste and olfaction originating from the ingested foods by these movements. A possible reason could be raised that cognition of the chemical sensory inputs at the higher brain also influences the movements, so it is difficult to discuss the neural mechanisms underlying the observed effect. In this review, we focus on the effects of chemical sensory inputs on the masticatory movements and initiation of swallowing. We first summarize chemical sensory inputs occurring during mastication and swallowing, and their receptive mechanisms. In addition, we will introduce the effect of application of monosodium L-glutamate (MSG) solution as an umami taste to the oropharynx on the swallow initiation which is involuntary controlled and the possible neural mechanisms underlying this effect is discussed.

DOI： 10.2174/1381612822666160216151150

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KARGER  

Objective: We developed a novel device that simultaneously measures oral and intrapharyngeal baropressure. The transducer has the advantage that it can be placed in any region. We determined the effect of different speech samples on baropressure in these regions. Patients and Methods: Seven healthy individuals produced speech samples comprising vowels and consonants (e.g., /aka/, /apa/, and /ash/). Two transducers were installed into the experimental plate at the incisive papillae and center of the Ah-line; a third transducer was placed in the mid-pharyngeal cavity. During each task, 3 parameters were analyzed: peak pressure, mean pressure, and the temporal relationship between sound signals and pressure changes. Results: The mean pressure did not change during the production of a single vowel; however, the pressure transiently increased during the production of the speech samples, depending on the place of articulation. Moreover, the place of articulation affected the onset and peak timing of pressure changes. Conclusions: These findings indicate that pressure changes during the production of speech samples reflect the functional aspects of speech production. In particular, simultaneous pressure recordings at multiple locations would provide precise information about speech production, compared to pressure studies that used a single pressure transducer. (c) 2017 S. Karger AG, Basel

DOI： 10.1159/000481530

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

It has anatomically been revealed that the rostral part of the rat primary somatosensory cortex (S1) directly projects to the dorsal part of the trigeminal oral subnucleus (dorVo) and the dorsal part of juxtatrigeminal region (dorVjuxt), and that the dorVo and dorVjuxt contain premotoneurons projecting directly to the jaw-opening or jaw-closing motoneurons in the trigeminal motor nucleus (Vmo). However, little is known about how the rostral S1 regulates jaw movements in relation to its corticofugal projections. To address this issue, we performed intracortical microstimulation of the rat rostral S1 by monitoring jaw movements and electromyographic (EMG) activities. We for the first time found that low-frequency long-train stimulation of the rostral S1 induced single sustained opening of the jaw with elevated EMG activities of the anterior digastric muscles (jaw-opener). The effective sites for the low-frequency long-train stimulation overlapped the S1 sites where traditional high-frequency short-train stimulation was effective to induce single twitch-like jaw movement. We also found that the effective sites for the two kinds of train stimuli were included in the rostral S1 area, which has previously been identified to send direct projections to the dorVo or the dorVjuxt. Specifically, the most effective stimulation sites for the two kinds of train stimuli were located in the rostralmost part of S1 which has been reported to emanate strong direct projections to the dorVjuxt but less to the dorVo. Therefore, the present study suggests that the rat rostral S1, especially its rostralmost part, plays an important role in controlling jaw movements by activation of direct descending projections from the rostral S1 to the trigeminal premotoneuron pools, especially to the dorVjuxt. (C) 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.neuroscience.2014.09.072

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

To evaluate the mechanisms underlying orofacial motor dysfunction associated with trigeminal nerve injury, we studied the astroglial cell activation following chronic constriction injury (CCI) of the infraorbital nerve (ION) immunohistochemically, nocifensive behavior in ION-CCI rats, and the effect of the glutamine synthase (GS) blocker methionine sulfoximine (MSO) on the jaw-opening reflex (JOR), and also studied whether glutamate-glutamine shuttle mechanism is involved in orofacial motor dysfunction. GFAP-immunoreactive (IR) cells were observed in the trigeminal motor nucleus (motV) 3 and 14days after ION-CCI, and the nocifensive behavior and JOR amplitude were also strongly enhanced at these times. The number of GS- and GFAP-IR cells was also significantly higher in ION-CCI rats on day 7. The amplitude and duration of the JOR were strongly suppressed after MSO microinjection (m.i.) into the motV compared with that before MSO administration in ION-CCI rats. After MSO administration, the JOR amplitude was strongly suppressed, and the duration of the JOR was shortened. Forty minutes after m.i. of glutamine, the JOR amplitude was gradually returned to the control level and the strongest attenuation of the suppressive effect of MSO was observed at 180min after glutamine m.i. In addition, glutamine also attenuated the MSO effect on the JOR duration, and the JOR duration was extended and returned to the control level thereafter. The present findings suggest that astroglial glutamate-glutamine shuttle in the motV is involved in the modulation of excitability of the trigeminal motoneurons affecting the enhancement of various jaw reflexes associated with trigeminal nerve injury.

DOI： 10.1111/ejn.12562

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER IRELAND LTD  

To determine the cooperative effect of laryngeal afferent signals on the swallowing reflex, we examined whether afferent signals originating from the left and right superior laryngeal nerve (SLN) modulates elicitation of the swallowing reflex in urethane-anesthetized rats. Mylohyoid electromyographic activity was recorded to quantify the swallowing reflex. The onset latency of the swallowing reflex and the time intervals between successive swallows were used to quantify and compare the effects of unilateral and bilateral electrical stimulations of the SLN. The mean latency of the first swallow and the mean time interval between swallows evoked with low frequency stimulation were both significantly different between unilateral and bilateral stimulations of the SLN. These findings suggest that facilitatory effect of afferent signals originating from the SLN bilaterally increase the motoneuronal activity in the medullary swallowing center and enhance the swallowing reflex. (C) 2014 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.neulet.2014.01.017

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Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

DOI： 10.1109/EMBC.2014.6944842

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Other Link： https://dblp.uni-trier.de/rec/conf/embc/2014

Language：English   Publishing type：Research paper (scientific journal)  

Sleep-related movement disorders are characterized by the specific phenotypes of muscle activities and movements during sleep. However, the state-specific characteristics of muscle bursts and movement during sleep are poorly understood. In this study, jaw-closing and -opening muscle electromyographic (EMG) activities and jaw movements were quantified to characterize phenotypes of motor patterns during sleep in freely moving and head-restrained guinea pigs. During non-rapid eye movement (NREM) sleep, both muscles were irregularly activated in terms of duration, activity, and intervals. During rapid eye movement (REM) sleep, clusters of phasic bursts occurred in the two muscles. Compared with NREM sleep, burst duration, activity, and intervals were less variable during REM sleep for both muscles. Although burst activity was lower during the two sleep states than during chewing, burst duration and intervals during REM sleep were distributed within a similar range to those during chewing. A trigger-averaged analysis of muscle bursts revealed that the temporal association between the bursts of the jaw-closing and -opening muscles during REM sleep was analogous to the temporal association during natural chewing. The burst characteristics of the two muscles reflected irregular patterns of jaw movements during NREM sleep and repetitive alternating bilateral movements during REM sleep. The distinct patterns of jaw muscle bursts and movements reflect state-specific regulations of the jaw motor system during sleep states. Phasic activations in the antagonistic jaw muscles during REM sleep are regulated, at least in part, by the neural networks involving masticatory pattern generation, demonstrating that waking jaw motor patterns are replayed during sleep periods. Copyright © 2013 the American Physiological Society.

DOI： 10.1152/japplphysiol.00895.2012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

We designed an electrical stimulation system to safely and reliably evoke the swallowing reflex in awake humans, and then examined the neural control of reflex swallowing initiated by oropharyngeal stimulation. A custom-made electrode connected to a flexible stainless-steel coil spring tube was introduced into the pharyngeal region through the nasal cavity and placed against the posterior wall of the oropharynx. Surface electrodes placed over the suprahyoid muscles recorded the electromyogram during swallowing. Swallowing reflexes were induced several times by 30 s of repetitive electrical pulse stimulation (intensity: 0.2-1.2 mA, frequency: 10-70 Hz, pulse duration: 1.0 ms). The onset latency of the swallowing reflex was measured over the 10-70 Hz frequency range. In addition, the two time intervals between the first three swallows were measured. The onset latency of the swallowing reflex became shorter as the stimulus frequency increased up to a parts per thousand currency sign30 Hz. Once the frequency exceeded 30 Hz, there was no further reduction in the latency. This finding was consistent with those of previous studies in anesthetized animals. The time intervals between successive swallowing reflexes did not change with increased stimulus frequencies. Furthermore, prolonged stimulation often failed to elicit multiple swallowing reflexes. The frequency dependence of onset latency suggests that temporal summation of pharyngeal afferents is required to activate the medullary swallowing center. This reliable stimulation method may help in rehabilitation of dysphagic patients without causing aspiration.

DOI： 10.1007/s00455-012-9393-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Cannabinoids have been reported to be involved in affecting various biological functions through binding with cannabinoid receptors type 1 (CB1) and 2 (CB2). The present study was designed to investigate whether swallowing, an essential component of feeding behavior, is modulated after the administration of cannabinoid. The swallowing reflex evoked by the repetitive electrical stimulation of the superior laryngeal nerve in rats was recorded before and after the administration of the cannabinoid receptor agonist, WIN 55-212-2 (WIN), with or without CB1 or CB2 antagonist. The onset latency of the first swallow and the time intervals between swallows were analyzed. The onset latency and the intervals between swallows were shorter after the intravenous administration of WIN, and the strength of effect of WIN was dose-dependent. Although the intravenous administration of CB1 antagonist prior to intravenous administration of WIN blocked the effect of WIN, the administration of CB2 antagonist did not block the effect of WIN. The microinjection of the CB1 receptor antagonist directly into the nucleus tractus solitarius (NTS) prior to intravenous administration of WIN also blocked the effect of WIN. Immunofluorescence histochemistry was conducted to assess the co-localization of CB1 receptor immunoreactivity to glutamic acid decarboxylase 67 (GAD67) or glutamate in the NTS. CB1 receptor was co-localized more with GAD67 than glutamate in the NTS. These findings suggest that cannabinoids facilitate the swallowing reflex via CB1 receptors. Cannabinoids may attenuate the tonic inhibitory effect of GABA (gamma-aminobuteric acid) neurons in the central pattern generator for swallowing.

DOI： 10.1371/journal.pone.0050703

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Increased expression of the transient receptor potential vanilloid 1 (TRPV1) channels, following nerve injury, may facilitate the entry of QX-314 into nociceptive neurons in order to achieve effective and selective pain relief. In this study we hypothesized that the level of QX-314/capsaicin (QX-CAP) - induced blockade of nocifensive behavior could be used as an indirect in-vivo measurement of functional expression of TRPV1 channels. We used the QX-CAP combination to monitor the functional expression of TRPV1 in regenerated neurons after inferior alveolar nerve (IAN) transection in rats. We evaluated the effect of this combination on pain threshold at different time points after IAN transection by analyzing the escape thresholds to mechanical stimulation of lateral mental skin. At 2 weeks after IAN transection, there was no QX-CAP mediated block of mechanical hyperalgesia, implying that there was no functional expression of TRPV1 channels. These results were confirmed immunohistochemically by staining of regenerated trigeminal ganglion (TG) neurons. This suggests that TRPV1 channel expression is an essential necessity for the QX-CAP mediated blockade. Furthermore, we show that 3 and 4 weeks after IAN transection, application of QX-CAP produced a gradual increase in escape threshold, which paralleled the increased levels of TRPV1 channels that were detected in regenerated TG neurons. Immunohistochemical analysis also revealed that non-myelinated neurons regenerated slowly compared to myelinated neurons following IAN transection. We also show that TRPV1 expression shifted towards myelinated neurons. Our findings suggest that nerve injury modulates the TRPV1 expression pattern in regenerated neurons and that the effectiveness of QX-CAP induced blockade depends on the availability of functional TRPV1 receptors in regenerated neurons. The results of this study also suggest that the QX-CAP based approach can be used as a new behavioral tool to detect dynamic changes in TRPV1 expression, in various pathological conditions.

DOI： 10.1371/journal.pone.0044023

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The swallowing reflex is centrally programmed by the lower brain stem, the so-called swallowing central pattern generator (CPG), and once the reflex is initiated, many muscles in the oral, pharyngeal, laryngeal, and esophageal regions are systematically activated. The mylohyoid (MH) muscle has been considered to be a "leading muscle" according to previous studies, but the functional role of the digastric (DIG) muscle in the swallowing reflex remains unclear. In the present study, therefore, the activities of single units of MH and DIG neurons were recorded extracellularly, and the functional involvement of these neurons in the swallowing reflex was investigated. The experiments were carried out on eight adult male Japanese white rabbits anesthetized with urethane. To identify DIG and MH neurons, the peripheral nerve (either DIG or MH) was stimulated to evoke action potentials of single motoneurons. Motoneurons were identified as such if they either (1) responded to antidromic nerve stimulation of DIG or MH in an all-or-none manner at threshold intensities and (2) followed stimulation frequencies of up to 0.5 kHz. As a result, all 11 MH neurons recorded were synchronously activated during the swallowing reflex, while there was no activity in any of the 7 DIG neurons recorded during the swallowing reflex. All neurons were anatomically localized ventromedially at the level of the caudal portion of the trigeminal motor nucleus, and there were no differences between the MH and DIG neuron sites. The present results strongly suggest that at least in the rabbit, DIG motoneurons are not tightly controlled by the swallowing CPG and, hence, the DIG muscle is less involved in the swallowing reflex.

DOI： 10.1007/s00455-011-9363-z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BIOMED CENTRAL LTD  

Background: To determine the effects of inferior alveolar nerve transection (IAN-X) on masticatory movements in freely moving rats and to test if microglial cells in the trigeminal principal sensory nucleus (prV) or motor nucleus (motV) may be involved in modulation of mastication, the effects of microglial cell inhibitor minocycline (MC) on masticatory jaw movements, microglia (Iba1) immunohistochemistry and the masticatory jaw movements and related masticatory muscle EMG activities were studied in IAN-X rats.
Results: The number of Iba1-immunoreactive (IR) cells both in prV and motV was significantly larger in IAN-X rats compared with sham rats on day 3 after IAN-X. The intraperitoneal (i.p.) administration of MC caused a significant reduction of the number of Iba1-IR cells both in prV and motV that was evident on day 14 after IAN-X. Furthermore, a significant reduction of the number of Iba1-IR cells could be observed in motV but not in prV after microinjection (m.i.) of MC into the motV of IAN-X rats. The rats also exhibited a significant decrease in the head-withdrawal threshold on the side ipsilateral to the IAN-X compared to the threshold before IAN-X and it lasted to day 14. In addition, IAN-X markedly affected the ability to rat to carry out mastication. The number of complete masticatory sequences was significantly decreased. Furthermore, the total masticatory sequence time and food preparatory (PP) period duration was significantly elongated in compared to sham rats. Although IAN-X significantly affected the total number of chewing cycles within the RC period of a masticatory sequence, it had no effect on the duration of the chewing cycles. On the other hand, systemic administration of MC (both i.p. and m.i.) in IAN-X rats significantly improved decreased head-withdrawal threshold and the impaired masticatory jaw movements.
Conclusions: The present findings reveal that the strong modulation of masticatory jaw movements occurs following microglial cell activation after IAN-X, and the modulation recovers after inhibition of the microglial cell activation by MC, suggesting that microglial cell activation in the motV as well as in the prV has a pivotal role in modulating mastication following trigeminal nerve injury associated with orofacial neuropathic pain.

DOI： 10.1186/1744-8069-8-27

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The present study aimed to examine whether the jaw-opening reflex (JOR) is modulated during swallowing, and if so, to compare the modulation between the low- and high-threshold afferent-evoked reflex responses. Experiments were carried out on 11 anesthetized rabbits. The inferior alveolar nerve was stimulated to evoke the JOR in the digastric muscle. The stimulus intensity was either 1.5 (low threshold) or 4.0 (high threshold) times the threshold for eliciting the JOR. As a conditioning stimulation, the superior laryngeal nerve (SLN) was repetitively stimulated to evoke the swallowing reflex. The stimulus intensity ranged from 0.6 to 8.0 times the threshold to evoke the swallowing reflex during SLN stimulation over 20 s. Electromyographic (EMG) activities of the digastric and mylohyoid muscles were recorded, and the peak-to-peak EMG amplitude of the digastric muscle was measured and compared with and without SLN stimulation, as well as with and without swallowing. Comparisons were also made between low- and high-threshold afferent-evoked JORs. The JOR was strongly suppressed during SLN stimulation. The degree of suppression increased and the latency for the JOR was delayed when the stimulus current applied to the SLN was increased. Such modulation was apparent when the low-threshold afferent-evoked JOR was recorded. Effects of motor outputs of swallowing events and those of single-pulse stimulation of SLN on the inhibition of the JOR were not noted. These results suggest that the JOR evoked by both the low- and high-threshold afferents was inhibited during laryngeal sensory input and following swallowing, probably to prevent opposing jaw movements evoked by oral sensory input during swallowing. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2011.03.065

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The relationships between Jaw-closing muscle spindle unit discharge and the hardness of foods were evaluated during chewing in awake rabbits Spindle unit discharges recorded from the left mesencephalic trigeminal nucleus were correlated with the simultaneous recording of jaw movements and electromyo-graphic (EMG) activities of the left masseter (Jaw-closing) muscle during chewing soft and hard foods A chewing cycle was divided Into the fast-closing (FC) slow-closing (SC) and opening (OP) phases according to jaw movements The chewing was classified as ipsilateral and contralateral chewing according to ipsilateral and contralateral to the recording side of the neuron respectively Spindle unit discharge was significantly higher during the FC and SC phases of the hard food than the soft food during both ipsilateral and contralateral chewing The discharge was observed to be higher when the masseter muscle activity was higher A comparison between the chewing sides reveals that the discharge was significantly higher during the slow-closing phase of ipsilateral chewing than contralateral chewing From the above findings the relationship of the spindle unit discharge with the hardness of foods was observed Moreover this relationship exists even when an animal chews food on the contralateral side suggesting the significance of the muscle spindle information for smooth chewing In addition, the phase dependent difference of the spindle unit discharge between chewing sides suggests the distinct roles of the spindle information on the chewing and non-chewing sides (C) 2010 Elsevier Inc All rights reserved

DOI： 10.1016/j.brainresbull.2010.09.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHARMACEUTICAL SOC JAPAN  

Swallowing involves several motor processes such as bolus formation and intraoral transport of a food bolus (oral stage) and a series of visceral events that occur in a relatively fixed timed sequence but are to some degree modifiable (pharyngeal stage or swallow reflex). Reflecting the progressive aging of society, patients with swallowing disorders (i.e., dysphagia) are increasing. Therefore, there is expanding social demand for the development of better rehabilitation treatment of dysphagic patients. To date, many dysphagia diets have been developed and are available commercially to help bring back the pleasure of mealtimes to dysphagia patients. Texture modification of food to make the food bolus easier to swallow with less risk of aspiration is one of the important elements in dysphagia diets from the viewpoint of safety assurance. However, for the further development of dysphagia diets, new attempts based on new concepts are needed. One of the possible approaches is to develop dysphagia diets that facilitate swallow initiation. For this approach, an understanding of the mechanisms of swallow initiation and identification of factors that facilitate or suppress swallow initiation are important. In this review, we first summarize the neural mechanisms of swallowing and effects of taste and other inputs on swallow initiation based on data mainly obtained from experimental animals. Then we introduce a recently established technique for eliciting swallowing using electrical stimulation in humans and our ongoing studies using this technique.

DOI： 10.1248/bpb.33.1786

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Purpose: From the standpoint of dental medicine, denture wearing is considered to improve chewing ability, chewing comfort, and quality of life in elderly individuals. We attempted to clarify the effects of prosthodontic treatment on activation of the dorsal prefrontal cortex, which is involved in higher cognitive functions.
Methods: Three partially edentulous patients, one 60-year-old male, and two females, 57 and 64 years old, were enlisted as subjects. For detection of changes in cerebral blood flow, near infrared spectroscopy (NIRS) was used. EMG recording was also conducted to detect bilateral activities of the masseter muscles (Mm).
Results: Significant activation of the dorsal prefrontal cortex in the right and/or left hemisphere was shown while wearing partial denture prosthesis. Furthermore, Mm EMG activity was significantly increased while wearing a partial denture prosthesis.
Conclusions: We concluded that a partial dental prosthesis significantly stimulates both masticatory muscle and dorsal prefrontal cortex activities, which might contribute to the prevention of cognitive impairment in aged individuals. (C) 2009 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.

DOI： 10.1016/j.jpor.2009.02.005

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The present study aimed to determine if sensory inputs from the intraoral mechano-receptors similarly contributed to regulating the activity of the jaw-opening muscles throughout the masticatory sequence. We also aimed to determine if sensory inputs from the chewing and non-chewing sides equally regulated the activity of the jaw-opening muscles. Electromyographic (EMG) activities of jaw muscles (digastric and masseter) and jaw movements were recorded in awake rabbits. The entire masticatory sequence was divided into preparatory, rhythmic-chewing and preswallow periods, based on jaw muscles activity and jaw movements. The jaw-opening reflex (JOR) was evoked by unilateral low-intensity stimulation of the inferior alveolar nerve (IAN) on either the chewing or non-chewing side. Amplitude of the JOR was assessed by measuring peak-to-peak EMG activity in the digastric muscle, and was compared among the masticatory periods and between the chewing and non-chewing sides. The JOR was strongly suppressed during the jaw-closing phase in the rhythmic-chewing and preswallow periods, but this effect was transiently attenuated during the late part of the jaw-opening phase in these periods. However, modulation of the JOR varied from strong suppression to weak facilitation during the preparatory period. The patterns of JOR modulation were similar on the chewing and non-chewing sides in all masticatory periods. The results suggest that the sensory inputs from the intraoral mechanoreceptors regulate the activity of the jaw-opening muscles differently during the preparatory period compared with the other masticatory periods. Sensory inputs from both the chewing and non-chewing sides similarly regulate the activity of the jaw-opening muscles. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2008.11.084

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The effects of sound generated by an ultrasonic dental scaler and a dental turbine on heart rate, systolic and diastolic blood pressure, and hemodynamic changes in the frontal cortex were measured and compared with those of pure tone stimulation in 17 young volunteers. Near-infrared spectroscopy and the Finapres technique were used to measure hemodynamic and cardiovascular responses, respectively. The dental sound changed the various physiological parameters. To determine if this change was related to participants' previous experiences with dental treatment, participants were divided into two groups: those who had a previous unpleasant experience with dental treatment and those who had not. Participants with previous unpleasant dental experiences showed a significant decrease in cerebral blood flow. Participants who had not had an unpleasant dental experience did not show significant changes in cerebral blood flow. Thus, although sounds associated with dental treatment may reduce cerebral blood flow, this effect may depend on the dental experiences of the patient. It is recommended that dentists treat patients gently and with empathy to promote a friendly image of dentistry.

DOI： 10.1007/s10266-008-0086-z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The aim of the present study was to compare the effect of mastication on non-nociceptive orofacial sensory transmission of the somatosensory pathways and that on the jaw reflex arc. To achieve this, single-unit activities of the face primary somatosensory cortex (face-SI) neurons responding to low-intensity electrical stimulation of the inferior alveolar nerve (IAN) and the jaw-opening reflex (JOR) were recorded during mastication in awake rabbits. The entire masticatory sequence was divided into the preparatory period (PP), the rhythmic-chewing period (RC) and the preswallow period (PS). A total of 112 face-SI neurons were tested for the effects of mastication. The responsiveness of most neurons and the JOR were modulated during different periods of mastication. The IAN-evoked activity was attenuated in a majority of the neurons during at least one of the masticatory periods. The JOR was suppressed during the RC and PS, while the modulatory effect was variable during the PP. Regression analysis showed that the modulatory effect of mastication on the IAN-evoked neuronal activity and that on the JOR was not well correlated. It was notable that a considerable number of face-SI neurons showed mastication-related activity although their responsiveness to IAN stimulation was strongly suppressed (i.e. almost "gated out") during mastication. The findings indicate that (1) sensory transmissions of the somatosensory and reflex pathways may be modulated in a different manner during mastication, and that (2) activity of face-SI neurons during mastication may not necessarily be a simple reflection of movement-induced stimulation of orofacial mechanoreceptors. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.archoralbio.2006.11.001

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Changes in reflex responses in the genioglossus (GG) muscle evoked by electrical stimulation of the inferior alveolar nerve and GG muscle tone (background activity, BGA) were investigated during sleep-wakefulness stages in rabbits. The GG muscle showed two types of electromyographic activity patterns: a respiration-related phasic activity and non-respiration-related activity. GG reflex responses and BGA exhibited a stage-dependent decrease as they were constantly suppressed from quiet wakefulness to non-rapid eye movement sleep (NREMS) to rapid eye movement sleep (REMS). Degree of suppression of reflexes was much larger than that of BGA regardless of GG activity patterns. When amplitude of reflex responses was compared between with and without rapid eye movements during REMS, no difference between the conditions was noted. These results suggest that excitability of the GG muscle is affected by sleep stages by not only a modulation of excitability in motoneurons but also in interneurons involved in the reflex arc. (C) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2005.10.013

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The aim of this study was to determine the effect of unilateral acute inflammation of cramofacial deep tissues on the ipsilateral and contralateral jaw-opening reflex (JOR). The effects of mustard oil (MO), injected into the temporomandibular joint region, were tested on the JOR recorded in the digastric muscle and evoked by low-intensity electrical stimulation of the ipsilateral and contralateral inferior alveolar nerve in anesthetized rats. The MO injection induced a long-lasting suppression of the amplitude of both ipsilaterally and contralaterally evoked JOR, although the latency and duration of the JOR were unaffected. The suppressive effect was more prominent for the contralaterally evoked JOR, and observed even when background activity in the digastric muscle was increased by the MO injection. The results indicate that changes in the, JOR amplitude following MO injection do not simply reflect alterations in motoneuronal excitability, and suggest that inflammation of deep craniofacial tissues modulates low-threshold sensory transmission to the motoneurons. (c) 2005 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.brainresbull.2005.06.013

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Mastication is the first stage of digestion and involves several motor processes such as food intake, intra-oral food transport, bolus formation and chewing in its broad sense. These complicated motor functions can be accomplished by the well-coordinated activities in various cranial motoneurons innervating the jaw, hyoid, tongue and facial muscles. The brainstem masticatory central pattern generator (CPG) plays a crucial role in generating basic activity patterns of these cranial motoneuron groups. However, descending inputs from higher brain (e.g., cerebral cortex) and mastication-generated peripheral sensory inputs also play important roles in modulating the activity pattern of each motoneuron so that the final motor outputs fit the environmental demand. In this review, we focus on the coordination of the trigeminal, facial and hypoglossal motoneurons during mastication. We first summarize findings showing the activity patterns of muscles innervated by these motoneurons during natural mastication, and then discuss the possible neural mechanisms underlying their coordinated activities during mastication. (C) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.resp.2005.02.017

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Previous studies have shown that jaw reflexes and activity patterns of the jaw muscles were modulated in the presence of jaw muscle pain. However, there is no study comparing the modulatory effects on the jaw reflexes induced by noxious stimulation to the jaw muscle. To clarify this, effects of the application of mustard oil (MO), an inflammatory irritant, into the temporalis (jaw-closing) muscle on (1) jaw-opening reflex evoked by tooth pulp stimulation (TP-evoked JOR) as a nociceptive reflex, (2) jaw-opening reflex evoked by interior alveolar nerve stimulation as a non-nociceptive reflex and (3) jaw-closing reflex evoked by trigeminal mesencephalic nucleus stimulation as a proprioceptive reflex were investigated in anesthetized rats. The MO application induced suppression of all reflexes. and the effect on the TP-evoked JOR was more prominent than on the other reflexes. To elucidate the involvement of endogenous opioid system for the suppressive effect, a systemic administration of naloxone following the MO application was conducted. The MO-induced suppressive effect on the TP-evoked JOR was reversed by the naloxone administration. The results suggest that noxious stimulation to the jaw muscle modulate jaw reflexes particularly for the nociceptive jaw-opening reflex, and the modulatory effect includes both facilitatory and inhibitory aspects. The results also suggest that pain modulatory systems such as the endogenous opioid system play a crucial role in the suppression of the nociceptive transmissions related to nociceptive reflexes, and in some pathological states, defense reflexes may not be evoked properly. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2005.02.003

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The effects of physical characteristics of foods on the coordination of extrinsic tongue muscle activities during natural mastication were evaluated. Electromyograms of tongue-retractor (styloglossus, SG) and tongue-protractor (genioglossus, GG) muscles as well as the jaw-movement trajectories were recorded during raw rice and chow pellet chewing in the freely moving rabbit. Each masticatory cycle included a jaw closing (Cl) phase consisting of a fast-closing (FC) and a slow-closing (SC) phase, and a jaw opening (Op) phase. The duration of the Cl and SC phases was found to be much larger while the duration of the FC phase was much smaller during rice chewing than pellet chewing. The jaw movements during rice chewing had smaller amplitudes of the gape and lateral excursion of the jaw as compared with those during pellet chewing. The SG muscle had a double-peaked burst activity in each masticatory cycle with one peak during the Op phase (the SG1 burst) and the other during the Cl phase (the SG2 burst). They were significantly larger during pellet chewing as compared with rice chewing, but the duration of the SG2 burst was significantly longer during rice chewing than pellet chewing. The offset of the SG2 burst was delayed during rice chewing as compared with that during pellet chewing. There was little difference in the activity pattern of the GG burst between the foods. Our present results suggest that the SG muscle activity could be modified by the sensory feedback possibly to adapt to environmental demands during chewing. (C) 2004 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.neulet.2004.07.043

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To evaluate the coordination of tongue and suprahyoid muscle activities during natural mastication, electromyogratus (EMGs) of jaw-closer, jaw-opener, suprahyoid (mylohyoid, MH), tongue-retractor (styloglossus, SG) and tongue-protractor (genioglossus, GG) muscles were recorded as well as the jaw-movement trajectories in vertical and horizontal axes in awake rabbits. Each masticatory cycle had three components including the fast-closing (FC), slow-closing (SC) and opening (Op) phases. The duration of the SC phase was much longer during pellet chewing while the durations of the FC and Op phases were much shorter during pellet chewing than bread or banana chewing. The jaw movements during banana chewing had a small amplitude of lateral excursion and a large amplitude of gape as compared with those during pellet and bread chewing. The MH muscle exhibited double-peaked EMG bursts during the Op phase. The MH bursts in the late part of the Op phase were dominant on the non-chewing side during pellet and bread chewing. The SG muscle also exhibited double-peaked EMG bursts. During pellet and bread chewing, the SG bursts during the SC phase were significantly larger on the chewing side than the non-chewing side. These bursts were also dominant during pellet chewing as compared with banana chewing. There was little difference in the GG bursts between the chewing and non-chewing sides or among the foods. Our results suggest that patterns of the MH and SG muscle activity are affected by the peripheral inputs and/or chewing patterns while those of the GG muscle activity was less modulated regardless of the consistency of foods. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2004.06.047

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To clarify the jaw-closer and tongue-retractor muscle activity patterns during mastication, electromyographic activity of the styloglossus (SG) as a tongue-retractor and masseter (Mass) as a jaw-closer muscles as well as jaw-movement trajectories were recorded during cortically evoked rhythmic jaw movements (CRJMs) in anesthetized rabbits. The SG and Mass muscles were mainly active during the jaw-closing (C1) phase. The SG activity was composed of two bursts in one masticatory cycle; one had its peak during the jaw-opening (Op) phase (SG1 burst) and the other during the C1 phase (SG2 burst). The Mass activity during the C1 phase was dominant on the working side (opposite to the stimulating side) while the SG1 and SG2 bursts were not different between the sides. When the wooden stick was inserted between the molar teeth on the working side during CRJMs, the facilitatory effects on the SG1 and SG2 bursts on both sides were noted as well as those on the Mass bursts, but the effects on the SG1 burst seemed to be weak as compared with those on the Mass and SG2 bursts. The difference in the burst timing between the sides was noted only in the SG1 burst. When the trigeminal nerves were blocked, the peak and area of the SG and Mass burst decreased during CRJMs, and the facilitatory effects of the wooden stick application on the muscles were not noted. The results suggest that the jaw and tongue muscle activities may be adjusted to chew the food and make the food bolus. (C) 2004 Elsevier B.V. All rights, reserved.

DOI： 10.1016/j.brainres.2004.05.005

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To study peri-oral facial muscle activity patterns and coordination with jaw muscles during ingestive behavior, electromyographic (EMG) activities in the peri-oral facial (buccinator: BUC, orbicularis oris: ORB) and jaw (masseter, digastric) muscles along with jaw movement trajectories were recorded in awake rabbits. A standardized amount of apple in a cylindrical shape was used as the test food. The period from food intake to just before swallowing (the masticatory sequence) was divided into three masticatory periods (preparatory period, rhythmic chewing period and preswallow period) based on the activity pattern of jaw muscles and jaw movement trajectories, and jaw movements and EMG activities in both the jaw and facial muscles during each masticatory period were assessed. Both the jaw and facial muscles were active throughout the masticatory sequence, and the activity patterns of facial muscles and the pattern of coordination between the facial and jaw muscles varied for each masticatory period. No consistent pattern was noted for the BUC activity during the preparatory period, whereas the OR-B showed tonic activity throughout this period. During the rhythmic chewing and preswallow periods, both the ORB and BUC showed jaw-movement-related rhythmic bursts. However, significant differences were noted in the burst properties in both facial muscles and their temporal correlations with the jaw muscle activities between these two periods. Results Suggest that the neural mechanisms regulating facial muscle activities may differ between the masticatory periods, and such mechanisms may contribute to the well-coordinated orofacial movements required for smooth masticatory sequence. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2003.11.037

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The effects of stimulation of the cortical masticatory area (CMA) on swallowing evoked by superior laryngeal nerve (SLN) were studied in anesthetized rabbits. Electromyographic activity of the thyrohyoid, masseter, and digastric muscles and jaw-movement trajectories were recorded to monitor rhythmic jaw movements (RJMs) or swallowing. A systematic series of microelectrode penetrations within the CMA was made for each animal, and the effects of CMA stimulation on swallowing were tested by comparing the number of swallows evoked by stimulation of the CMA alone, the SLN alone, and simultaneous stimulation of the SLN and CMA. A significant facilitatory effect was observed in 49 (52%) of the 95 CMA loci tested. No significant effect was noted in the remaining 46 loci. Three different types of RJMs were evoked by CMA stimulation, and topographical organization was noted among CMA loci that evoked different types of RJMs. A high percentage of (77%) the CMA loci that evoked RJMs with a prominent horizontal excursion of the jaw facilitated swallowing and was located in the posterolateral and deep part of the CMA. A majority (88%) of the CMA loci that evoked RJMs with small circular jaw movements did not affect swallowing and was located in the anteromedial and shallow part of the CMA. The facilitatory effect of CMA stimulation on swallowing remained even after removal of peripheral sensory inputs by means of deafferentation of infraorbital and inferior alveolar nerves. Results suggest the existence of facilitatory descending pathways to the swallowing center from particular intracortical loci of CMA. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0006-8993(02)04204-X

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Genioglossus (Gg) reflexes elicited by electrical stimulation of the inferior alveolar nerve were examined in naturally chewing rabbits. To eliminate possible contaminations of the digastric (Dig) activity in the Gg responses, the Dig nerve was denervated bilaterally. Masticatory and tongue muscles were well coordinated during chewing after the denervation; i.e., there were no significant differences in the phase durations between before and after denervation. The Gg reflex measured was divided into three categories depending on the chewing phase (i.e., jaw-opening, OP; fast-closing, FC; and slow-closing, SC) in which the stimulus was delivered. The reflex amplitude was phasically modulated for the phases, in that the amplitude in the OP phase was larger than that in any other phase (P<0.05). On the other hand, the amplitude in the FC and SC phases was not significantly different to each other and from the control value obtained when the animal was awake and resting. The pattern of the modulation in the reflex amplitude was different from the previous report as to the Dig reflex in that OP<FCsimilar toSC<control was obtained. The results suggest that the modulatory mode in the Gg and Dig reflexes may be different in the pattern of the modulation under the natural chewing behavior and the Gg reflex is independent of the masticatory muscles in the nature. The reflex could be more sensitive to control the tongue movements collecting food bolus in the OP phase during chewing than in the jaw-closing phase. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0006-8993(02)03512-6

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It is known that intracortical microstimulation (ICMS) of the lateral pericentral cortex can evoke masticatory movements and swallowing in awake monkeys. The aim was to determine if the ability of monkeys to carry out mastication is affected by reversible bilateral cold block of the ICMS-defined cortical masticatory area/swallow cortex. A cranial chamber was implanted bilaterally in two monkeys and a warm or cold alcohol-water solution was pumped through thermodes placed bilaterally on the dura overlying the ICMS-defined cortical masticatory area/swallow cortex while monkeys chewed standardised amounts of fruit during pre-cool (thermode temperature, 37degreesC), cool (0-4degreesC), and post-cool (37degreesC) trials. Electromyographic (EMG) activity was recorded from masseter, genioglossus, anterior digastric, geniohyoid and thyrohyoid or perilaryngeal muscles. Vertical and horizontal jaw movements were recorded with a photodiode position transducer, which monitored movements of a light-emitting diode fixed to the mandible. Each masticatory period was divided into a food-preparatory phase, a rhythmic chewing phase and a preswallow phase. Both monkeys could readily accept and ingest the foodstuffs during pre-cool and post-cool trials. In contrast, cold block was associated with masticatory deficits, reflected in both monkeys as impaired food intake or manipulation and difficulty in carrying out a sequence of masticatory cycles, alterations in of the food-preparatory phase, and alterations in masticatory-related EMG patterns of the jaw and tongue muscles. The cold block-induced changes included significant (P < 0.05) prolongations of the total masticatory time, the food-preparatory phase duration, and burst durations of the jaw and tongue muscle EMG activities; furthermore, the amplitudes and temporal correlations of the EMG activities of the jaw and tongue muscles were significantly (P < 0.05) changed by cold block. These findings provide further evidence that the lateral pericentral cortex has a critical role in the initiation and regulation of masticatory movements in the primate, and that the programming of masticatory muscle activities may be dependent upon corticofugal influences for engaging masticatory motor activities appropriate to the masticatory conditions. (C) 2002 Elsevier Science Ltd. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The effects of reversible cold block-induced bilateral inactivation of the face primary motor cortex (face MI) on mastication and swallowing were studied in awake monkeys. A warm or cold alcohol-water solution was pumped through thermodes placed bilaterally on the dura overlying the intracortical microstimulation-defined face MI while the monkey chewed and swallowed food during pre-cool (thermode temperature 37 degreesC), cold block (4 degreesC), and post-cool (37 degreesC) sessions. Vertical and horizontal jaw movements and electromyographic (EMG) activity of several muscles were monitored. Each masticatory sequence was divided into three masticatory phases (i.e. food preparatory, rhythmic chewing, preswallow). The cold block markedly affected the ability of the monkey to carry out mastication although it did not prevent mastication from occurring. The masticatory deficit was characterized by a significant elongation of the total masticatory time, including in particular elongation of the food preparatory phase. The coordination of the jaw- and tongue-muscle activities was severely disrupted during the food preparatory phase. Face MI cold block also significantly affected the duration of some masticatory-related EMG activities and had some limited effects on the temporal relationships of the EMG activities during mastication. Although cold block significantly affected the duration and some EMG parameters of the preswallow phase, it had no significant effect on swallow duration or the EMG parameters during swallowing. These findings provide further evidence that the primate face MI plays a critical role in the regulation of mastication and that it plays a role in the preparation for swallowing. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0006-8993(02)02705-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSIOLOGICAL SOC  

The present study was undertaken to determine the firing patterns and the mechanoreceptive field (RF) properties of neurons within the face primary motor cortex (face-MI) in relation to chewing and other orofacial movements in the awake monkey. Of a total of 107 face-MI neurons recorded, 73 of 74 tested had activity related to chewing and 47 of 66 neurons tested showed activity related to a trained tongue task. Of the 73 chewing-related neurons, 52 (71.2%) showed clear rhythmic activity during rhythmic chewing. A total of 32 (43.8%) also showed significant alterations in activity in relation to the swallowing of a solid food (apple) bolus. Many of the chewing-related neurons (81.8% of 55 tested) had an orofacial RF, which for most was on the tongue dorsum. Tongue protrusion was evoked by intracortical microstimulation (ICMS) at most (63.6%) of the recording sites where neurons fired during the rhythmic jaw-opening phase, whereas tongue retraction was evoked by ICMS at most (66.7%) sites at which the neurons firing during the rhythmic jaw-closing phase were recorded. Of the 47 task-related neurons, 21 of 22 (95.5%) examined also showed chewing-related activity and 29 (61.7%) demonstrated significant alteration in activity in relation to the swallowing of a juice reward. There were no significant differences in the peak firing frequency among neuronal activities related to chewing, swallowing, or the task. These findings provide further evidence that face-MI may play an important role not only in trained orofacial movements but also in chewing as well as swallowing, including the control of tongue and jaw movements that occur during the masticatory sequence.

DOI： 10.1152/jn.00543.2001

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Although rhythmic jaw movement in feeding has been studied in mammals, such as rats, rabbits and monkeys, the cellular and molecular mechanisms underlying it are not well understood. Transgenic and gene-targeting technologies enable direct control of the genetic makeup of the mouse, and have led to the development of a new category of reagents that have the potential to elucidate the cellular and molecular mechanisms of neural networks. The present study attempts to characterize rhythmic jaw movements in the mouse and to demonstrate its relevance to rhythmic jaw movements found in higher mammals using newly developed jaw-tracking systems and electromyograms of the masticatory muscles. The masticatory sequence of the mouse during feeding was classified into two stages, incision and chewing, Small and rapid (8 Hz) open- close jaw movements were observed during incision, while large and slow (5 Hz) open-close jaw movements were observed during chewing. Integrated electromyograms of the masseteric and digastric muscles were larger during chewing than those observed during incision. Licking behavior was associated with regular (8 Hz), small open-close jaw movements with smaller masseteric activity than those observed during mastication. Grooming showed variable patterns of jaw movement and electromyograms depending on the grooming site. These results suggest that there are neuronal mechanisms producing different frequencies of rhythmic jaw movements in the mouse, and we conclude that the mouse is useful for understanding rhythmic jaw movements in higher mammals. (C) 2002 Elsevier Science Inc. All rights reserved.

DOI： 10.1016/S0031-9384(01)00662-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To study the coordination between the masticatory and extrinsic tongue muscles during natural chewing, electromyographic activities in the digastric (Dig) as a jaw opener, the masseter (Mas) as a jaw closer, the genioglossus (Gg) as a tongue protruder, and the styloglossus (Sg) as a tongue retractor as well as jaw movement trajectories were recorded while rabbits chewed soft. hard, and very hard foods. The Dig and Gg were active in the jaw-opening phase (OP active group), and the Mas and Sg were active in the jaw-closing phase (CL active group). Food consistency affected differently on the duration of burst activities between the muscle groups, i.e. in the CL active group, the duration was longer for the harder food, while there was no difference in the duration of the OP active group among the foods. During hard food chewing in particular, we confirmed our recent findings that reflexly-induced short but large bursts of activity could be documented in the Dig during the jaw-closing phase. Similar short bursts were also documented in the Gg as with the Dig in this study. Inhibitory periods were often observed in the Mas with the Dig short burst and were also observed in the Sg along with the Gg short burst: however the inhibitory effect in the Sg was less pronounced. These findings suggest that: (1) both masticatory and extrinsic tongue muscles are active in a well-coordinated manner during stable chewing, but that (2) reflex effects on antagonistic muscles (i.e. Dig vs. Mas in the masticatory muscles, Gg vs. Sg in the tongue muscles) evoked by tooth contact during chewing may not be analogous between the two muscle groups. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0006-8993(01)03392-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INFORMA HEALTHCARE  

Our previous studies have revealed that face primary somatosensory cortex (SI) as well as face primary motor cortex (MI) play important roles in the control of orofacial movements in awake monkeys, and that both face MI and face SI neurons may have an orofacial mechanoreceptive field and show activity related to orofacial movements. Since it is possible that the movement-related activity of face MI neurons could reflect movement-generated orofacial afferent inputs projecting to face MI via face SI, the present study used reversible cold block-induced inactivation of the monkey's face SI to determine if face MI neuronal activity related to a trained tongue-protrusion task, chewing or swallowing was dependent on the functional integrity of the ipsilateral face SI and if inactivation of face SI affects orofacial movements. The effects of face SI cold block were tested on chewing, swallowing and/or task-related activity of 73 face MI neurons. Both task and chewing and/or swallowing-related activity of most face MI neurons was independent of the functional integrity of the ipsilateral face SI since SI cold block affected the movement-related activity in approximately 25% of the neurons. Similarly, unilateral cold block of SI had very limited effects on the performance of the task and chewing, and no effect on the performance of swallowing. These findings suggest that movement-induced reafferentation via face SI may not be a significant factor in accounting for the activity of the majority of ipsilateral face MI neurons related to trained movements, chewing and swallowing.

DOI： 10.1080/0899022021000037728

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To study the function of the tongue and the coordination among jaw, tongue, and hyoid muscles during chewing and swallowing, we recorded the electromyographic activities from the masseter (Mas), digastric (Dig), mylohyoid (Myl), thyrohyoid (Thy), genioglossus (Gg) and styloglossus (Sg) muscles as well as jaw movement trajectories in the freely behaving rabbit. Three phases were identified in the chewing cycle (fast- and slow-closing and opening phases). The Gg (main tongue protruder) was active synchronously with the Dig during opening. The Sg (tongue retractor) showed two peaks in each cycle, one in the opening phase and the other in the closing phase. The latter may have a role in retracting the tongue during jaw closing. The co-contraction of the antagonists (i.e. Gg and S-) during opening may contribute to shape the tongue to be appropriate to gather the foodstuff. In the swallowing cycle, five phases were identified, two in the closing phase and three in the opening phase. Regression analysis revealed that swallowing cycles had a longer cycle duration than that of the chewing cycles due to an extra phase (a pause) inserted in the opening phase, where there was a small co-activation in the jaw opening and closing muscles. The findings suggest that the swallowing center affects masticatory center in the central nervous system, and may also support the view that the masticatory burst timing begins with the Dig activities in the middle of the opening phase. (C) 2001 Elsevier Science BY All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Rhythmical head movements and neck muscle activities associated with the masticatory jaw movement were investigated in rabbits. In natural mastication, head movements and neck muscle activities showed a rhythmical feature synchronized with jaw movement. During cortically induced rhythmical jaw movements, some neck muscle showed rhythmical activity induced by biting a wooden stick. Neck muscles may contribute to the rhythmical head movement after loading the tooth with food. (C) 2000 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI IRELAND LTD  

The aim of this study was to clarify the modulation of motoneuron excitability in masticatory muscles during sleep. For this purpose, changes in the reflex responses of the masseter and digastric muscles between sleep and wakefulness were studied in freely behaving rabbits. Stimulation of the jaw closing muscle spindle afferents induced the masseteric monosynaptic reflex (MMR). During quiet sleep (QS), which gradually replaced quiet wakefulness, the mean MMR amplitude showed no change. During active sleep (AS), MMR amplitudes were markedly reduced, but they were confounded by the occasional occurrence of facilitation in the amplitude. The facilitatory reflexes were often related to rapid eye movements (REMs). However, the excitatory input probably did not originate from the same region as the REM generator, since the REM and the large MMR did not always occur simultaneously. On the other hand, jaw opening reflexes remained inhibited. The results indicated that there is mainly a difference in the excitability between the two groups of motoneurons during AS; masseter motoneuron activity was inhibited but occasionally facilitated by excitatory inputs occurring in association with REMs, however, the digastric motoneuron activity was remained inhibited. The excitatory inputs may induce dysfunctional muscle contraction of the jaw closing muscles as seen in bruxism. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Bilateral cold block of the intracortical microstimulation (ICMS)-defined swallow cortex markedly affected the ability of monkeys to carry out swallowing. Significant changes also occurred in swallow-related electromyographic (EMG) activity patterns. These findings provide further evidence that the lateral pericentral cortex plays a critical role in the initiation and regulation of swallowing in the primate. (C) 1999 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

This paper reviews recent data from awake monkeys of the role of face primary somatosensory cortex (SI) as well as face primary motor cortex (MI) in orofacial motor control. Intracortical microstimulation (ICMS) evokes elemental orofacial movements only from MI but the semiautomatic movements of chewing and swallowing can be evoked from both SI and MI. Also bilateral cold block of face SI or MI may interfere with the animal's performance of a trained tongue task and also disrupt these semiautomatic movements. Many neurons in face SI as well as MI show task or semiautomatic movement-related activity and receive orofacial sensory inputs. However, uni lateral cold block of ipsilateral face SI has limited effects on MI neuronal activity related to task or semiautomatic movement performance or responses evoked by these inputs. Thus, face SI as well as face MI may play significant roles in the control of both trained and semiautomatic orofacial movements, but MI neuronal activity may not be heavily reliant on the functional integrity of ipsilateral face SI.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer New York  

Burst patterns in the digastric, mylohyoid, and masseter muscles and the resultant jaw movement orbits during chewing and swallowing were investigated in the freely behaving rabbit. Activities in the posterior mylohyoid fibers consisted of two continuous bursts. Peaks in the first burst of the posterior fibers occurred in the middle part of opening and preceded the digastric burst. Peaks in the second burst occurred in the final part of opening and coincided with those in the working side of the digastric burst. After removal of the bilateral digastric muscles, the gape size during chewing was largely reduced in the final part of opening and in the early part of closing. The results suggest that (a) the digastric may have a role in opening the mandible widely beyond the rest position but may not have a major role in the control of the horizontal (mediolateral) jaw movement, (b) the posterior mylohyoid fibers may have a function as an elevator of the tongue in the early part of opening, and (c) the posterior mylohyoid fibers may have a function as a depressor of the jaw in the late part of opening. Electromyographic burst in the mylohyoid muscle began with marked activity in the mid-closing phase. The results support a role for the mylohyoid muscle as a leading muscle of swallowing. Swallowing events in the rabbit are easily distinguished from the activities of the mylohyoid muscle and the thyrohyoid muscle.

DOI： 10.1007/PL00009591

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Effects of food consistency on the mode of the phase-linked modulation in the digastric reflex amplitude were examined in naturally chewing rabbits. Two test foods with different textures (bread as a soft food, pellet as a hard food) were used. The digastric reflex was elicited by electrical stimulation (10 train pulses at 2 kHz) of the inferior alveolar nerve. The amplitude of the digastric reflex measured was divided into three categories depending on the chewing phases in which the stimulus was delivered and each value was compared with the control response obtained when the animal was resting. The reflex was strongly inhibited in the jaw-opening phase and no difference was observed in the inhibitory effect between the foods. In the jaw-closing phase, larger digastric reflexes than those in the opening phase were elicited with both foods. This was the case in both the fast-closing and slow-closing phases. Reflex amplitude was significantly larger during chewing of the hard food than the soft food and, thereafter, inhibition of the reflex was observed only during chewing of the soft food in the closing phase. The results suggest the following: (1) food consistency may affect the central mechanism which regulates the digastric reflex and (2) the reflex may contribute to the regulation of masticatory force during chewing particularly hard food. (C) 1998 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To study central and peripheral control mechanisms maintaining rhythmical jaw behaviors, chewing movements with different foods in texture were obtained in the freely behaving rabbit. Jaw movement trajectories and muscle activities (masseter, digastric, thyrohyoid) were recorded and the durations in total cycle, fast closing (FC), slow closing (SC), and opening (OF) phases were obtained as well as the burst duration in the muscles. Durations varied cycle-by-cycle and among the foods, however, the total cycle duration was found to have little differences among the foods tested. Regression analyses were applied to seek time relations to the change in total cycle duration with the duration in its constituent phases. Results suggested that changes in the total cycle duration may be due to those in the SC duration (power phase) with hard food (heavy load), but due to those in the OP duration (reverse phase) with soft food (light load). The duration of the FC was fairly constant for all the foods tested. In conclusion, the chewing rhythm may be controlled centrally to be independent of the load, and chewing cycles may begin at the middle of the opening phase.

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Total pages：viii, 134p   Language：Japanese

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J-GLOBAL

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J-GLOBAL

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Language：Japanese  

J-GLOBAL

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J-GLOBAL

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Authorship：Lead author   Language：Japanese  

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J-GLOBAL

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

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Language：Japanese   Publisher：(公社)日本矯正歯科学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：更年期と加齢のヘルスケア学会((NPO)更年期と加齢のヘルスケア)  

【背景・目的】男女雇用機会均等法施行以降、女性の勤続年数は長期化の傾向にある。女性が40歳を超えて働くときに問題となるのが、更年期症状が職務に及ぼす影響である。更年期症状はホルモン補充療法(HRT)により改善するが、日本のHRT普及率は当該年齢女性の2%以下で、欧米諸国の30-66%と比較して著しく低い。HRTについては、米国の大規模臨床試験の中止に伴う発がん性に関する誤った報道が、普及の妨げとなった経緯がある。そこで、「日本でのHRTの普及は、メディアによる否定的な報道の影響がある」との仮説をたて、働く女性の更年期についての情報入手行動を調査した。【方法】首都圏で働く女性410名に郵送・無記名回答式の質問紙調査を実施し、(1)更年期症状の有無とHRT認知の関連、(2)更年期症状に関する情報源を、更年期群(45歳以上)と、更年期予備群(45歳未満)に分けて分析した。【結果】125名から回答が得られた(回収率30.5%)。更年期症状の緩和策としてのHRTの認知は全体で27名(21.6%)、更年期群(38名)で10名(26.3%)、予備群(87名)で17名(19.5%)であった。更年期症状の有無と、HRTの認知についての明確な関連はなかった。更年期症状に関する情報源について、1つ以上挙げた人は92名(73.6%)、1つも挙げなかった人、すなわち更年期情報を収集していない人は33名(26.4%)であった。各メディアの利用率では、予備群で、健康雑誌について認知群での利用率が有意に高かった(p<0.05)。更年期群では、友人について不認知群での利用率が有意に高かった(p<0.05)。HRTを認知する27名を対象にした「HRT使用の望否」の質問では、14名が否であった。その理由(複数選択可)としては、「十分な情報がない」が13名で最も多かった。【結論】働く女性にHRTの普及が進まないのは、否定的な報道によることを示す明確な結果は得られなかった。むしろ日本でHRTの普及率が低いのは、HRTの認知度が低いことが原因であることが示唆された。(著者抄録)

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

咀嚼は、生理学的には生命維持のための生体機能である消化・吸収の第一段階である。咀嚼を営む上で顎・口腔・顔面領域は「咀嚼運動を行うための運動器」、「最初の消化液としての唾液を分泌する分泌器」「食物や食塊、顎・口腔・顔面の動きから生じる感覚を受容するための感覚器」としての役割を果たす。これらの機能を制御するのが脳であり、様々な脳部位の活動が必要不可欠である。咀嚼運動は体性神経系の制御下に遂行される運動で、ほとんどが自律神経系と液性調節系で調節される消化・吸収機能の中では例外的な存在である。咀嚼運動は半自動運動に分類され、基本的なリズム形成は脳幹に存在する咀嚼中枢(CPG)によって行われるが、咀嚼運動に伴って様々な感覚情報が生じ、感覚情報に応じて反射が誘発されることで、咀嚼力をはじめとする最終出力がほぼ無意識下に調節され、円滑な運動の遂行に寄与している。また、感覚情報の一部は反射経路を介して無意識に自律神経系や液性の調節に反映されたり、上行路を介して高位脳で認知され、さらなる運動調節に反映されたり、意志とは無関係に情動を賦活して自律神経や液性調節系に反映されたりする。本稿では咀嚼運動調節のしくみと咀嚼時に生じる感覚情報の役目について神経生理学的な観点から解説したい。(著者抄録)

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Language：Japanese   Publisher：医歯薬出版(株)  

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Language：Japanese   Publisher：医歯薬出版(株)  

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Language：Japanese   Publisher：医歯薬出版(株)  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

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Language：English   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：日本歯科衛生学会  

介護保険施設入所者の健康保持、疾病予防のため口腔ケアが有効である。歯科医療専門職は人員配置基準に含まれないため、多くの施設で入所者の日常的な口腔ケアは介護職員(以下、職員)が担っている。よって職員の口腔ケアに対する意識および技術向上は重要である。本研究は、歯科衛生士が職員に行う歯科保健指導および専門的口腔清掃が、職員自身および入所者の口腔衛生状態におよぼす影響の検証を目的とした。対象は、介護老人福祉施設職員9名と入所者14名であった。歯科衛生士が職員個別に月1回ずつ3ヵ月間にわたり歯科保健指導および専門的口腔清掃を実施し、職員および入所者の口腔衛生状態を、指導前、指導期間終了時、指導期間終了12ヵ月後に日和見感染菌検査およびPCRを用い評価した。PCRは職員、入所者ともに、指導期間終了時で指導前と比較し有意に低下した。日和見感染菌が検出された入所者は指導前5名で、指導期間終了時2名となった。しかし、口腔衛生状態改善の効果は職員、入所者ともに指導期間終了12ヵ月後に消失もしくは減弱した。以上の結果より、歯科医療専門職の介入が少なく口腔ケアの介助量が多い要介護高齢者のいる施設において、歯科衛生士が介護職員に対し歯科保健指導および専門的口腔清掃を行うことが、介護職員の口腔衛生状態を改善すること、これにより間接的に入所者の口腔衛生状態が改善される可能性が示唆された。(著者抄録)

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Language：Japanese   Publisher：日本歯科医学教育学会  

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Language：Japanese   Publisher：新潟大学教育・学生支援機構  

新潟大学歯学部では,初年次教育として大学学習法を実施している.この授業は講義・演習での知識や技能をもとに,レポート作成とプレゼンテーションを行うもので,その学習活動を通して,間題解決能力,論理的思考力,表現力の開発をねらいとしている.今回,学習成果の直接評価に向けて,パフォーマンス評価を導入すべく,レポートからこれら能力を読み解くルーブリックづくりに取り組んだ.また,この経験からみえてきたパフォーマンス評価の難点とその対処について検討した.その結果,パフォーマンス評価により能力を把握できる可能性が示されたが,導入には教員の理解と協力,能力と関連した適切な評価観点の設定,評価の信頼性を高める工夫,評価と指導の一体化を考慮した授業デザインなど,いくつかの課題があることも明らかになった.The curriculum of Niigata University Faculty of Dentistry provides the "Study Skills" course as first year education. The ultimate goal of this course is to develop student abilities of problem solving, logical thinking and expression. For that purpose, each student is guided through the process of writing a report and presenting its content. To access the degree to which these abilities were achieved, we created a rubric and used it to evaluate the student reports. Based on the experience of this trial, we discussed problems for the introduction of performance assessment into the course. Although performance assessment has a high potential to grasp these abilities, there are some practical problems that may interfere with its introduction, such as "how to involve the faculty in assessment", "how to establish dimensions of the rubric that appropriately relate with the student abilities", "how to increase the reliability of assessment", "how to design the course to allow for a connection between assessment and instruction".

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

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Language：Japanese   Publisher：(公社)日本矯正歯科学会  

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Language：Japanese   Publisher：(公社)日本矯正歯科学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：日本疼痛学会  

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Language：Japanese   Publisher：甲北信越矯正歯科学会  

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Language：Japanese   Publisher：新潟歯学会  

摂食・嚥下機能を営む上で顎・口腔・顔面領域は「咀嚼や嚥下運動を行うための運動器」「最初の消化液としての唾液を分泌する分泌器」「食物や食塊、顎・口腔・顔面の動きから生じる感覚を受容するための感覚器」としての役割を果たす。これらの機能を制御するのが脳であり、摂食・嚥下を営むためには脳の様々な部位の活動が必要不可欠である。食欲の形成と先行期(認知期)、咀嚼期(準備期)、嚥下について述べた。

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Language：Japanese   Publisher：甲北信越矯正歯科学会  

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Language：Japanese   Publisher：(公社)日本農芸化学会  

近年脳血管障害の後遺症などで摂食・嚥下機能に障害をもつ患者が増加している。この私たちがふだん何気なく行っている「口から食べて飲む」という行為（摂食・嚥下）は、さまざまな運動要素が連続的・同時進行的に行われる複雑な運動である。また、それに伴いさまざまな感覚情報が生じ、これらは運動制御に利用されたり、大脳で認知され記憶にとどめられる。これらの機能を制御するのが脳であり、摂食・嚥下を営むためには脳のさまざまな部位の活動が必要不可欠である。本稿では摂食・嚥下機能を神経生理学の立場から解説したい。

DOI： 10.1271/kagakutoseibutsu.51.302

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

主原料および製法が異なる米菓の咀嚼進行に伴う最大荷重(硬さ)、付着性、凝集性の変化を調べ、主原料や製法が咀嚼時のテクスチャーに与える影響と、咀嚼時のテクスチャー変化と米菓のかたさ官能評価値との関連性を明らかにすることを本研究の目的とした。実験は健常成人男性6名(34.5±6.2歳)を対象に行った。試験食は咀嚼前の最大荷重、主原料配合(うるち米、米以外のでんぷん)、製法(焼成時の油の有、無、揚げ)が異なる市販米菓を5種類選択した。被験者に各試験食2.5gを10回、15回、20回、30回、40回、60回咀嚼させた後の咀嚼物の最大荷重、付着性、凝集性を測定した。咀嚼時の最大荷重は主原料による影響を受け、うるち米を用いた米菓が硬く、咀嚼開始から10回程度までの最大荷重の絶対値と最大荷重の減少率がかたさ官能評価に影響を与えること、揚げた米菓は咀嚼初期の最大荷重減少率が増加し、かたさ官能評価値を下げる効果があった。咀嚼時の米菓の付着性も主原料による影響を受け、米以外のでんぷんを混合した米菓は咀嚼初期に付着性が増加するが、うるち米を用いた米菓は咀嚼の進行に伴い付着性が増加した。油を使用したり、揚げた試料では付着性が低かった。米以外のでんぷんを混合した米菓や、揚げた米菓の咀嚼時の米菓の凝集性は、咀嚼初期に増加した。以上より米菓咀嚼中のテクスチャーは原料配合や製法によって変化し、米菓のかたさ官能評価に影響していることが示された。(著者抄録)

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：SPRINGER JAPAN KK  

Web of Science

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Language：Japanese   Publisher：松本歯科大学学会  

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

咀嚼・嚥下機能障害者には障害の内容に応じて調整された食事の提供が必要である。そこで全国2,000の介護保険施設で、食事形態・調理法をどのように工夫しているか、また、とろみの調整の有無についてアンケートを実施し、有効回答である704施設を分析対象とした。アンケートでは、障害区分(内容)に応じて咀嚼機能障害は9項目、嚥下機能障害では7項目および医師・歯科医師の指示による区分に分け、各区分に対応した主食および副食の形態を調べた。主食の形態は、咀嚼機能障害に関する区分では、「ご飯」「おかゆ」との回答が多く、嚥下機能障害に関する区分では、「おかゆ」「ミキサーかゆ」が多かった。医師・歯科医師の指示がある場合だけに食事の調整を行うと回答した中では、「経管流動食」が最も多かった。副食の形態では、咀嚼機能障害に関する区分においては、「素材の形を残しながら軟らかく調理」「粒が残る状態にきざむ」との回答が、嚥下機能障害に関する区分では、「粒がなく、滑らかな状態にする」との回答が多かった。介護保険施設ごとに経験的に工夫されていると思われる主食および副食の形態は、障害の内容とその程度に対応して調理・工夫が実施されていることが確認できた。また、医師・歯科医師の指示がある場合だけに選択される主食の形態があることから、その場合には専門的な指導が尊重されていると考えられた。(著者抄録)

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Language：Japanese   Publisher：(公社)日本矯正歯科学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：日本歯科医学教育学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：(公社)日本薬学会  

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Language：Japanese   Publisher：新潟歯学会  

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高齢者の味覚機能が低下する要因の一つとして口腔衛生状態の悪化が考えられている。そこで本研究は高齢者に口腔保健指導を実施し、口腔衛生状態が改善することが味覚機能に影響を及ぼすかを明らかにする目的で行った。対象は高齢者15名(男性3名、女性12名、平均年齢67.7±5.2、平均歯数25.4±2.9)とした。口腔保健指導の内容は歯磨き、舌清掃、唾液腺マッサージ、唾液分泌訓練とし12週間にわたり指導した。それぞれの指導内容が口腔衛生状態に及ぼす効果は、齲蝕活動性試験(カリオスタット)、カンジダ菌検出試験(ストマスタット)、刺激唾液分泌重量(サクソンテスト)によって評価した。また、味覚機能は塩味、甘味、酸味、苦味溶液の全口腔法での認知閾値で評価した。口腔保健指導の結果、カンジダ菌疑陽性者は全員が指導後3週間以内に陰性になった。一方、カリオスタット値は指導後6週目で低下した。また、刺激唾液分泌重量には変化がみられなかった。味覚機能の結果は被験者全員の平均認知閾値は4基本味とも口腔保健指導後3週間以内で低下した。顕著な味覚閾値低下が認められた被験者全員が指導開始後舌清掃を実施していたこと、舌清掃効果が発現した時期と4基本味の味覚閾値の低下した時期が一致したことから認知閾値の低下に寄与したものは舌清掃による舌苔除去であると考えられた。以上より舌清掃は高齢者の味覚機能の改善に寄与する可能性があることが示唆された。(著者抄録)

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

知的障害者は健常者に比べ口腔衛生状態が悪く、同年代の健常者と比べ、歯の喪失が早く現在歯数の少ないことが報告されている。喪失歯による食事形態の制限や審美性の欠如などで社会生活上の不都合の生じることが多い。そのため、健常者以上に歯科疾患の予防は重要である。われわれは、知的障害者の顔面の動きが乏しいことに着目し、このことが知的障害者の口腔衛生状態悪化の一因であると考えた。そこで、顔面運動により口腔の自浄作用を促すことは知的障害者の口腔衛生状態を改善するという仮説をたて、そのことを明らかにする目的で研究を行った。知的障害者授産施設に通所する21名の知的障害者を対象に、歯科衛生士が約1分の顔面口腔体操を指導し、3ヵ月間にわたり月曜日から金曜日まで毎日1回実施させた。口腔衛生状態は、う蝕活動性試験(カリオスタット)、前歯唇面の歯垢付着面積および歯肉の炎症指数によって評価した。体操開始後、歯肉の炎症指数には反映されないものの、前歯部唇面の歯垢付着域は減少した。また、う蝕活動性は調査開始時、危険域〜注意域であったが、体操開始初週に安全域〜注意域に低下し、体操期間中はその値を維持していた。一方、口唇閉鎖力や口腔の運動速度や巧緻性、顔面の可動性など口腔の運動機能は体操後も変化しなかった。以上から、知的障害者に顔面口腔体操を実施することにより、口腔の自浄作用が促進し、口腔衛生状態を改善させることが示唆された。(著者抄録)

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Language：Japanese   Publisher：(一社)日本口腔診断学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：クインテッセンス出版(株)  

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Language：Japanese   Publisher：クインテッセンス出版(株)  

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Language：Japanese   Publisher：クインテッセンス出版(株)  

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Language：Japanese   Publisher：クインテッセンス出版(株)  

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Language：Japanese   Publisher：日本歯科医学教育学会  

新潟大学歯学部では、教員の資質向上を目的として、平成14年にFD委員会を発足させた。今回、これまで行ってきたFaculty development(FD)活動の概要を報告するとともに、歯学部FDと大学院FDとの連携やスムースな移行を検討するための体系化マップを作成し、FDのあり方や方向性について検討した。これまでに行われてきたFD活動を列挙して体系化マップを作成し、これまでの問題点や改善点を検証して今後に必要なプログラムの立案を行った。委員会発足当初は、全教員を対象として学生教育に必須と考えられる基本的な知識・技能・態度の習得に力点をおいたFD活動が行われていた。しかし近年では、新任者から段階的に研修活動ができるようにFDプログラムの整備がなされ、計画的にFDを開催するとともに、個別対応型FDや参加・体験型FDへとその活動の中心が推移している。これまでの本委員会の活動を体系化マップとしてまとめることにより、平成19年度からは、その役割が、大学院教育の実質化促進へと展開しつつあることが明確になり、今後は歯学部FDで積み重ねた経験を基に、高いレベルの大学院FDに移行させるためのプログラム立案が可能と考えられた。今後は単なるイベント型FDのみならず、各教員の日常的な研修環境の整備やニーズに即したプログラムの企画を通して、教員の研究指導力の開発を目標とすることが重要であると思われた。(著者抄録)

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：(NPO)日本咀嚼学会  

分子生物学の飛躍的な発展により、さまざまな疾患モデルマウスや感覚・運動制御機構解明を目的とした遺伝子改変マウスの開発が進んでいる。顎口腔領域においても、口腔感覚入力の一部をノックアウトしたマウスなど咀嚼運動機構解明に向けた遺伝子改変マウスの作製が行われている。しかし、それらマウスが有する運動機能、特に咀嚼運動機能を評価するうえで、比較対象となる正常マウスの咀嚼運動様式を詳細に把握し、基準データを作成する必要があると考え、本研究計画を立案した。まず、基準データとして用いるために、遺伝子改変マウスの遺伝的背景に用いられるC57/B6マウスを用い、下顎運動と咀嚼筋筋電図の同時記録を行った。下顎運動は、われわれのグループで開発を行った三次元方向の記録装置を用い、筋電図は両側咬筋・右側側頭筋・顎二腹筋から記録を行った。飼料にはピーナッツを用い、自由運動下で記録を行った。下顎運動軌跡をもとに、取り込み相と食物粉砕相に、さらに食物粉砕相をその加速度の変化をもとに4相に区分した。側頭筋活動は有意に同側咬筋活動よりも早く活動を開始した。マウスの咀嚼運動様式は、下顎の運動方向が異なるものの筋活動様式は他の動物種と同様であり、現在までに明らかになっている他の動物種における機能的な解釈など基準データの作成に応用できることが示唆された。(著者抄録)

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Language：Japanese   Publisher：(公社)日本矯正歯科学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：English   Publisher：(一社)歯科基礎医学会  

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Language：English   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：日本味と匂学会  

高齢者社会に突入した現在の日本において、食事を口腔から摂取することが困難な患者が増加していることが、しばしば医療および介護の現場で問題になっている。我々の研究室では、摂食・嚥下障害の問題を解決するための応用研究に取り組んでいる。これまでの嚥下誘発に関する動物実験を詳細に検討し、ヒト経鼻的電極を考案した。ヒトの咽頭領域へ電気刺激を与えることにより、再現性のある嚥下誘発方法を開発した。さらに、実際の食事行動を想定し、ヒト嚥下誘発システムによる電気刺激と同時に咽頭・喉頭領域へ味刺激を与え、味覚刺激の嚥下誘発に対する効果を検討している。(著者抄録)

DOI： 10.18965/tasteandsmell.17.2_127

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Language：Japanese   Publisher：新潟歯学会  

通信制高等学校保健室における課題と健康支援の実態を明らかにし、健康支援プログラム作成のための指針を得ることを目的に、通信制高等学校保健室の常勤の養護教諭12人を対象とした半構成的面接を行った。面接内容はKJ法を使用し分類した。その結果、通信制保健室の課題として【生徒の健康状態の把握困難】【生徒の多様な健康問題】【通信制保健室体制】【健康診断】【養護教諭の健康支援】の5つが抽出された。それに対して、通信制保健室の支援実態として【通信制生徒にあった健康支援】【通信制保健室の体制作り】【生徒の実態把握の工夫】【健康診断に関する工夫】の4つが抽出された。その課題と健康支援の実態から1)生徒の健康実態の把握とその活用対策2)健康診断の受診率向上のための対策3)危機管理体制の整備4)通信制保健室体制の改善5)社会資源を取り入れた他職種との連携6)通信制生徒の健康意識を高める自己管理への健康教育が挙げられ、通信制高等学校保健室における現場に即した健康支援プログラム作成のための指針を得た。(著者抄録)

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Language：Japanese   Publisher：新潟歯学会  

目的:厚生労働省は平成14年、「福祉サービスにおける危機管理(リスクマネジメント)に関する取り組み指針」により、「質の高いサービスを提供することによって多くの事故が未然に回避できる」という指針を発表し、リスクマネジメントのあり方については福祉サービスの質の向上に向けた取り組みがまずは重要であると位置づけた。また、そのためには経営者の役割や責任が重要になることも指摘し、リスクマネジメントの視点を入れた体制づくりを関係者に呼びかけた。本研究では、これらの指針に示された具体的なポイントや対応策を基準に、また、介護保険制度下において介護福祉施設が常に良質の介護サービスを提供することが義務付けられていること等も勘案しながら、これら施設の実態と介護職員の意識について調査を行なった。方法:(1)静岡県内の介護老人福祉施設188ヶ所に勤務する主任または研修担当職員に郵送により無記名・自記式質問紙調査を実施。有効回答数107施設(有効回答率57%)。質問票及び分析は遠山らの「組織診断チェックシート」を使用。「組織構造」8問、「制度・ルール」8問、「人材・能力」8問、「風土・価値観」8問の計32問について回答者が自己診断したものを「組織の4S」概念(組織構造、制度・ルール、人材・能力、風土・価値観)に当てはめ、傾向を分析した。結果:組織スタッフの関係性は一つのチームとして協力し合い、スタッフ間の意見交換が積極的に行われ、教育・研修はほぼ推奨または実施され、利用者さん中心の価値観・風土も浸透している等が示唆された。また、評価などのルールについては確立されてはいるが、その後のフィードバック、改善策の検討が行われていないこと、組織的・標準的な学習機会が整備されていないこと等が示唆された。考察:職員同士の日常的な情報交換やコミュニケーションについての教育や啓発が必要であり、組織や制度の整備充実や介護職員の価値観の共有が進むことにより、人材・スキルに関する評価も上がることが示唆された。また、評価が低い施設でも、いずれかの分野の評価を高めることによって他の分野の評価も相乗して上がることが予測された。(著者抄録)

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Language：Japanese   Publisher：The Japanese Association for the Study of Taste and Smell  

高齢者社会に突入した現在の日本において、食事を口腔から摂取することが困難な患者が増加していることが、しばしば医療および介護の現場で問題になっている。我々の研究室では、摂食・嚥下障害の問題を解決するための応用研究に取り組んでいる。これまでの嚥下誘発に関する動物実験を詳細に検討し、ヒト経鼻的電極を考案した。ヒトの咽頭領域へ電気刺激を与えることにより、再現性のある嚥下誘発方法を開発した。さらに、実際の食事行動を想定し、ヒト嚥下誘発システムによる電気刺激と同時に咽頭・喉頭領域へ味刺激を与え、味覚刺激の嚥下誘発に対する効果を検討している。

DOI： 10.18965/tasteandsmell.17.2_127

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近年の我が国の社会経済構造等の変化に伴い「食」に関する様々な問題が顕在化しているが、歯学的な観点からこれらの問題を考えると、内含している問題点がライフステージにより異なる。高齢者においては平均寿命の延伸に伴い咀嚼・嚥下機能に障害を持つ要介護者が増加してきたことと、歯の喪失を予防する歯科保健対策が不十分であったことに起因する高い歯の喪失率による咀嚼能力の低下が問題である。一方歯科保健対策の効果が現れてきた若年〜壮年者においては、日常生活における食のプライオリティの低下と、食の軟食化に伴う咀嚼回数の減少が問題である。歯科医療を通して高齢者の咀嚼機能を保持することは、食を介して全身の健康を維持するとともに、健康感や生活の満足感を通じて生活の質を向上させ、健康寿命を延ばすことに繋がる。また食育を推進するとともに、良く噛んで味わい食事を楽しむ重要性を若い世代に認識させる啓発活動を行うことは、健全な食生活の実践を通じて生活の質を向上させ、健康寿命を延ばすことに繋がる。(著者抄録)

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近年の我が国の社会経済構造等の変化に伴い｢食｣に関する様々な問題が顕在化しているが, 歯学的な観点からこれらの問題を考えると, 内含している問題点がライフステージにより異なる. 高齢者においては平均寿命の延伸に伴い咀嚼・嚥下機能に障害を持つ要介護者が増加してきたことと, 歯の喪失を予防する歯科保健対策が不十分であったことに起因する高い歯の喪失率による咀嚼能力の低下が問題である. 一方歯科保健対策の効果が現れてきた若年～壮年者においては, 日常生活における食のプライオリティの低下と, 食事の軟食化に伴う咀嚼回数の減少が問題である. 歯科医療を通して高齢者の咀嚼機能を保持することは, 食を介して全身の健康を維持するとともに, 健康感や生活の満足感を通じて生活の質を向上させ, 健康寿命を延ばすことに繋がる. また食育を推進するとともに, 良く噛んで味わい食事を楽しむ重要性を若い世代に認識させる啓発活動を行うことは, 健全な食生活の実践を通じて生活の質を向上させ, 健康寿命を延ばすことに繋がる.

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The importance of somatosensory information arising from intraoral mechanoreceptors in intraoral sensory discrimination (e.g. detecting position, consistency, size and shape of an object in the oral cavity) should be stressed, since sensory discrimination in the oral cavity are performed without visual information by nature. Nonetheless, there is little information about how the somatosensory information is processed within the cerebral cortex during intraoral sensory discrimination tasks. For this, many studies showed that visual cortical areas are active during tactile discrimination such as Braille reading and blind discrimination of Mah-Jong tiles both in blind and normally sighted humans. The present study was conducted to investigate if visual cortical areas as well as prefrontal area are activated during intraoral form discrimination task by assessing total ([total-Hb]), oxygenated ([oxy-Hb]) and deoxygenated ([deoxy-Hb]) hemoglobin concentration changes using 44 channel near-infrared spectroscopy (NIRS) in normally sighted humans. Among 12 subjects tested (23-62 years old), increase in [total-Hb] and [oxy-Hb] was observed in visual cortical area in all subjects during the task. Also, such task-related increase in [total-Hb] and [oxy-Hb] in prefrontal area was observed in 8 subjects. The findings suggest that visual cortical areas play important roles in intraoral somatosensory discrimination and somatosensory processing patterns within the cerebral cortex may be variable among individuals. <b>[J Physiol Sci. 2008;58 Suppl:S145]</b>

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実験的に与えた痛み刺激が,顎運動機能を構成する重要な運動であり尚かつその神軽回路が比較的明確な開口反射に及ぼす影響を検討し,その背後にある神経機構を考察した.麻酔を行ったWistar系雄性ラットを用いた.実験的痛み刺激として,起炎剤であり選択的にC-線維を興奮させるMustard Oil(MO)を顎関節,咀嚼筋に投与した.MO投与は非注入側からの感覚情報伝達に対しても影響を与えることが示唆された.反射応答の抑制には疼痛変調系特に内因性オピオイドが関与し,反射応答の抑制には内因性オピオイドは関与していないことが示唆された.疼痛変調系が,侵害反射である開口反射を抑制することは,本来有害な外来性刺激に対して作用する防御機構を減弱させる可能性が示唆された

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Effects of mastication on the jaw-opening reflex (JOR) were studied in awake rabbits. The JOR was evoked by unilateral low-intensity electrical stimulation of the inferior alveolar nerve either chewing or non-chewing side before (control) and during mastication. The entire masticatory sequence (from food intake to just before swallow) was divided into three functionally different masticatory periods (preparatory, rhythmic-chewing and preswallow periods) based on the jaw movements and the related activity pattern of the jaw muscles, and each chewing cycle in each period was further divided into jaw-closing and jaw-opening phases. Then amplitude of the JOR was compared 1) among the masticatory periods and 2) between the stimulation sides (i.e. chewing or non-chewing sides). Overall, the JOR was suppressed during mastication. Although the suppressive effect on the JOR did not differ between the stimulation sides, considerable differences were noted in the suppressive effect among the masticatory periods. During rhythmic-chewing and preswallow periods, the JOR was strongly suppressed in the jaw-closing phase (8 to 20% of the control), but the suppressive effect was phasically weakened (30 to 61% of the control) in the late part of the jaw-opening phase. On the other hand, such phase-dependent fluctuation in the suppressive effect was not observed during the preparatory period. The findings suggest that neural mechanisms modulating the JOR during the preparatory period may be different from other masticatory periods. <b>[J Physiol Sci. 2006;56 Suppl:S189]</b>

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Previous studies have shown that the jaw-opening reflex (JOR) is modulated during mastication. However in these studies, analyses have been carried out for limited period within the masticatory sequence (i.e. from food intake to just before swallow). Our aim is to study if the modulatory pattern of the JOR is consistent throughout the masticatory sequence in awake rabbits. The masticatory sequence was divided into three masticatory periods (preparatory, rhythmic-chewing and preswallow periods) based on the jaw movement patterns and the activity pattern of the jaw muscles. Electromyographic activity of the jaw-opening muscle (Digastric) and the jaw movement trajectories were recorded. Repetitive electrical stimulation (single pulse, 0.2 ms duration at a rate of 1 Hz, 1.2 times the threshold) of the inferior alveolar nerve was conducted before (for control response) and during mastication to evoke the JOR. The amplitude of the JOR was normalized to the control response and the modulatory pattern of the JOR was compared among the masticatory periods. The JOR was generally suppressed during the rhythmic-chewing and the preswallow periods; the suppressive effect was phasically weakened in the middle part of the jaw opening during the rhythmic-chewing period. On the other hand, the reflex was not only suppressed but also facilitated during the preparatory period. The results suggest that the modulatory pattern of the jaw-opening reflex is different among the masticatory periods. <b>[Jpn J Physiol 55 Suppl:S172 (2005)]</b>

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Mastication is consisted of various jaw movements commencing with ingestion and ending with swallowing. The progress of mastication is dependent on the interaction of the motor mechanism with variable characteristics of chewed food. In the guinea pig, jaw movement patterns with the progress of mastication have not been clarified under freely moving condition. In this study we recorded EMG activities bilaterally from the masseter and the digastric muscles and simultaneously the jaw movements using a magnetic sensor system. The recordings were made for 1-hour ad libitum fed after 5 hours fast. Masticatory behavior was divided into two stages, (1) an intake-stage representing food intake and transport, and (2) a chewing-stage, food chewing. During the intake-stage, vertical jaw movements were associated with synchronous activations of bilateral masseter muscles. The chewing-stage was characterized mostly by alternate lateral jaw excursions with alternate EMG activity in right and left masseter muscles. Within the chewing-stage, jaw movement patterns altered along with the progress of mastication. These data suggests that masticatory stages in guinea pigs can be estimated by the EMGs and jaw movements. <b>[Jpn J Physiol 55 Suppl:S178 (2005)]</b>

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The aim of the present study was (1) to investigate how the tongue reflex is modulated during wakefulness and sleep and (2) to examine if modulation of the tongue reflex activities during active sleep is related with respiratory phases or rapid eye movements in the freely moving rabbit. Electromyographic (EMG) activity of tongue muscle was recorded in the genioglossus (tongue-protruder, GG) muscle, and the GG reflex was evoked by electrical stimulation of the inferior alveolar nerve. The current intensity of stimulus was set at 1.5 times threshold to evoke the reflex to evaluate the modulatory mode of GG reflex. Peak to peak amplitude of EMGs in the reflex was compared among wakefulness and sleep stages.GG activity showed a wide variation, some had respiratory-related activity and others did not. However, in all animals, the reflex was suppressed during sleep, and the inhibition was significantly stronger during active sleep than that during quiet sleep. In some cases, the reflex was completely suppressed during active sleep. Furthermore, during this sleep stage, the reflex amplitude during inspiratory phase was larger than that during expiratory phase. On the other hand, the rapid eye movements during active sleep were not related to the changes in the reflex activity during active sleep. Not only basic but also clinical studies have paid attention to loss of tone in upper airway muscles including tongue muscles during sleep. The neuronal mechanisms controlling tongue muscle activity in sleep were discussed. <b>[Jpn J Physiol 54 Suppl:S178 (2004)]</b>

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Tongue movements participate in oro-facial motor functions including chewing, sucking, swallowing, speech, respiration and so on. Although previous studies reported the coordination of jaw and tongue movements to clarify the patterns of tongue muscle activity, our knowledge as to the functional role of tongue muscles during chewing and swallowing in humans is still limited due to the technical difficulty to record the dynamic activity of tongue muscles. In this study, we recorded the EMG activity of left tongue protruder (genioglossus, GG), jaw-closer and supra- and infra-hyoid muscles during command swallow and natural mastication of test foods as well as rhythmic experimental open-close jaw movements in healthy subjects. For GG recording, the electrode assembly was fabricated on a dental acrylic resin. During command swallow, the subject was required to swallow test foods in different postures which were upright and head inclined w/ and w/o body reclinced to test the effects of head and body postures on the tongue activity. The activity pattern of GG muscle was different among the postures. During experimental rhythmic open-close jaw movements, all the muscles recorded were well-coordinated while the coordination was not observed in the case of natural mastication. Particularly, the GG activity did not always show the rhythmicity. The results suggest the variability of human tongue activity during mastication and swallowing. <b>[Jpn J Physiol 54 Suppl:S179 (2004)]</b>

DOI： 10.14849/psjproc.2004.0.S179.1

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DOI： 10.14858/soshaku1991.13.3

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Language：Japanese   Publisher：Japanese Society of Stomatognathic Function  

DOI： 10.7144/sgf.9.218

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Language：Japanese   Publisher：日本顎口腔機能学会  

ラットの右側側頭筋前腹に起炎剤のMustard oil(MO)を注入し,電気刺激により誘発した反射応答への影響を筋電図により検討した.歯髄誘発性開口反射応答量は,MO注入2分後より抑制傾向を認め,ピークは30分後で,注入前の74%であった.下歯槽神経誘発性開口反射応答量はMO注入による変化は認めなかった.三叉神経中脳路核誘発性閉口反射応答量は,MO注入直後より有意な抑制を認め,ピークは20分後で,注入前の7.6%であった

DOI： 10.7144/sgf.9.218

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DOI： 10.7144/sgf.9.218

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Publisher：Japanese Society for Mastication Science and Health Promotion  

The recent literature on the neural basis of semi-automatic movements such asmastication and swallowing has emphasized the crucial role of brainstem pattern generators in their genesis and regulation. While much less emphasis has been given to the role of higher brain centers, it has been shown that rhythmic jaw movements and swallowing can be evoked in primates by intracortical microstimulation (ICMS) as well as by electrical surface stimulation or transcranial magnetic stimulation of the lateral part of the pericentral cortex of both hemispheres, including the primary face motor cortex (face MI), the primary face somatosensory cortex (face SI), the principal part of the cortical masticatory area (CMA) /swallow cortex, and the deep part of CMA/swallow cortex. Furthermore, recordings of single neuronal activities and ICMS-evoked movements and EMG activities indicate that each of these cortical regions appears to have distinct sensory input and motor output patterns related to rhythmical jaw movements and swallowing, and many neurons in these areas show ingestion-related firing patterns, including activity associated with mastication and swallowing. Recent studies on the behavioral alterations using cold block technique on CMA/swallow cortex, face MI, and face SI indicated the peculiar effects on mastication and swallowing. Bilateral cold block of CMA/swallow cortex was associated with masticatory deficits, reflected as impaired food intake or manipulation and difficulty in carrying out a sequence of masticatory cycles, and alterations of the food-preparatory phase and masticatory and swallowing-related EMG patterns of jaw, tongue, and swallow muscles. Cold block of face MI markedly affected the ability of the monkey to carry out mastication and swallowing. The masticatory deficit was characterized by a significant elongation of the total masticatory time, including in particular elongation of the food preparatory phase. The coordination of the jaw- and tongue-muscle activities was severely disrupted during the food preparatory phase. Although cold block of face MI elongated the duration of the preswallow phase, but it had no significant effect on swallow duration or the EMG parameters during swallowing. Cold block of face SI affected to the total masticatory time, which was due principally to an increase in the preswallow phase time. Taking into consideration the above further evidences of effects by cold block of the CMA/swallow cortex, face MI and face SI, these three cortical regions may be differentially involved in the initiation and control of mastication and swallowing.

DOI： 10.14858/soshaku1991.13.3

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DOI： 10.7144/sgf.9.1

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DOI： 10.7144/sgf.9.1

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Language：Japanese   Publisher：新潟歯学会  

ラット閉口筋に微小振動を与え誘発される緊張性振動反射(TVR)を指標に閉口筋の興奮性評価の実験モデル確立と,このモデルを用いた痛み刺激の筋紡錘の活動性への影響について筋電図学的に検討した.実験ではWistar系ラットを用いてウレタン静注麻酔し,高頻度微小振動(120〜150Hz,1mm)を発生する振動モータを使用して下顎骨を振動させることで閉口筋に誘発されるTVR応答を両側咬筋・側頭筋と顎二腹筋筋電図にて記録した.TVR誘発実験モデルの確立の為,振動の頻度,振動方向,開口量について至適TVR誘発条件を検討した結果から得られた実験モデル(至適TVR条件は振動頻度150Hz,振動方向水平方向,開口量7mm)を用いて高張食塩水(5%)又はマスタードオイル(20% in mineral oil)を片側側頭筋に注入してTVRに与える影響について検討した.その結果,両刺激溶液の注入により,いずれもTVR応答は注入前より減弱され,その程度はマスタードオイルが強く,その変調様式は筋により相違が認められた

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Language：Japanese   Publisher：Niigata University  

To evaluate the activity of jaw closing muscles, we investigated the tonic vibration reflex (TVR) elicited in jaw closing muscles in rats. The experiments were performed on Wistar rats anaesthetized with urethane (1g/kg). The vibration (120-150Hz, 1mm) was applied to the mandible and the reflex activity was recorded bilaterally from the masseter, temporal and digastric muscles. Experiment I: To establish an experiment model, effective parameters such as vibration frequency, direction of vibration, and jaw position (muscle length) to elicit TVRs were determined. Experiment II: Using the established experimental model, We examined effects of hypertonic saline (5%) and mustard oil (20% in mineral oil) injection into the temporal muscle on TVRs. A vibration frequency of 150Hz in horizontal direction and jaw opening position of 7mm apart at the opposing incisor were determined to be the most effective parameters for TVRs. Both chemicals injected into the temporal muscle reduced the TVR amplitude, and the effect of mustard oil was more than that of hypertonic saline. However, the modulatory effect varied among the muscles tested. In conclusion, effective parameters to elicit TVRs were determined and the change in sensitivity of muscle spindles was suspected to be a factor that affect the response of TVRs to noxious stimuli applied to the jaw closing muscles.ラット閉口筋に微小振動刺激を与え誘発される緊張性振動反射(TVR)を指標に閉口筋の興奮性を評価する実験モデルの確立と、この実験モデルを用いて痛み刺激が筋紡錘の活動性にどのような影響を及ぼしているかについて筋電図学的に研究した。実験にはWistar系ラットを用いた｡麻酔はウレタン(1g/kg)を静脈内投与して行った｡高頻度微小振動(120-150Hz、1mm)を発生する振動モータを用い、下顎骨を振動させることで閉口筋に誘発されるTVR応答を両側咬筋、側頭筋ならびに顎二腹筋筋電図にて記録した｡実験Ⅰ)TVR誘発実験モデルを確立するために、振動の頻度、振動方向、開口量について至適TVR誘発条件を調べた｡実験Ⅱ)前項Ⅰで得られた実験モデルを用いて、高張食塩水(5%)あるいはマスタードオイル(20% in mineral oil)を片側側頭筋に注入しTVRに与える影響について検討した｡至適TVR誘発条件を、振動頻度は150Hz、振動方向は水平方向、開口量は7mmと決定した｡5%食塩水あるいはマスタードオイルの注入によって閉口筋に誘発されるTVR応答は変調された｡両刺激溶液ともTVR応答は注入前より減弱され、その減弱はマスタードオイルでより強く得られたが、その変調様式には記録した筋の種類によって相違が認められた｡以上の結果から、至適TVR誘発条件が設定され、痛み刺激が筋紡錘の活動性を変化させる可能性が示唆された｡

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：INT AMER ASSOC DENTAL RESEARCHI A D R/A A D R  

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Language：Japanese   Publisher：Japanese Society of Stomatognathic Function  

DOI： 10.7144/sgf.9.1

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：日本顎口腔機能学会  

ラット閉口筋に与えた痛み刺激が,閉口筋活動にどのような影響を及ぼしているかについて,緊張性振動反射(TVR)を指標として検索した.その結果,痛み刺激によりTVR応答は変調した.閉口筋への痛み刺激がTVR応答に及ぼした影響は,減弱と一過性の増強効果であった.閉口筋に与えた痛み刺激がγ運動神経に興奮性を変化させた可能性が示唆される

DOI： 10.7144/sgf.7.116

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Language：Japanese   Publisher：Japanese Society of Stomatognathic Function  

DOI： 10.7144/sgf.7.116

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Language：Japanese   Publisher：Niigata University  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：English   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：Japanese Society of Stomatognathic Function  

It has been shown in humans that during mastication the head moves rhythmically and coordinately with jaw movements. A neurophysiological explanation for the mechanism of this finding has not been given so far, matter which became the objective of this study. Head movement and EMG of neck(sternomastoid and splenius capitis)muscles were recorded simultaneously in awake unrestrained rabbits during bread and raw rice chewing. Also, EMG activity was recorded in anesthetized rabbits from the sternomastoid and semispinalis capitis muscles during cortically evoked fictive mastication. In voluntary mastication, the rabbits moved their heads rhythmically in a cycle similar to their chewing cycle and in an opposite direction to the jaw movement, Rhythmical EMG activity was observed in the sternomastoid, which showed biphasic activity in the jaw closing and opening movements during bread chewing ; however, during raw rice chewing it was active only in the jaw closing movements. The splenius muscle showed tonic activity and no rhythmic activity was observed regardless of the test food used. In cortically evoked fictive mastication the sternomastoid was activated only in the jaw closing movements. This activity increased when biting on wooden sticks between opposing molars took place. In the semispinalis capitis tonic activity was observed in both events. Rhythmical head movement coordinated with jaw movement was observed during mastication not only in humans but also in rabbits ; this observation indicates that rabbits are appropriate animal models to study head movement during mastication. From the results of this experiment we suggest that the sternomastoid may be reflexly coactivated with masticatory muscles by peripheral inputs such as periodontal afferents and afferents from propioceptors regulating sense of position during jaw opening and closing movements.

DOI： 10.7144/sgf.4.191

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：AMER ASSOC DENTAL RESEARCH  

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Language：Japanese   Publisher：Japanese Society of Stomatognathic Function  

It has been shown in humans that during mastication the head moves rhythmically and coordinately with jaw movements. A neurophysiological explanation for the mechanism of this finding has not been given so far, matter which became the objective of this study. Head movement and EMG of neck (sternomastoid and splenius capitis) muscles were recorded simultaneously in awake unrestrained rabbits during bread and raw rice chewing. Also, EMG activity was recorded in anesthetized rabbits from the sternomastoid and semispinalis capitis muscles during cortically evoked fictive mastication.<BR>In voluntary mastication, the rabbits moved their heads rhythmically in a cycle similar to their chewing cycle and in an opposite direction to the jaw movement. Rhythmical EMG activity was observed in the sternomastoid, which showed biphasic activity in the jaw closing and opening movements during bread chewing; however, during raw rice chewing it was active only in the jaw closing movements. The splenius muscle showed tonic activity and no rhythmic activity was observed regardless of the test food used.<BR>In cortically evoked fictive mastication the sternomastoid was activated only in the jaw closing movements. This activity increased when biting on wooden sticks between opposing molars took place. In the semispinalis capitis tonic activity was observed in both events.<BR>Rhythmical head movement coordinated with jaw movement was observed during mastication not only in humans but also in rabbits; this observation indicates that rabbits are appropriate animal models to study head movement during mastication. From the results of this experiment we suggest that the sternomastoid may be reflexly coactivated with masticatory muscles by peripheral inputs such as periodontal afferents and afferents from propioceptors regulating sense of position during jaw opening and closing movements.

DOI： 10.7144/sgf.4.191

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：Japanese   Publisher：新潟歯学会  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：AMER ASSOC DENTAL RESEARCH  

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

1)歯根膜に持続的な圧刺激を与えると,反射性に呼吸数の増加と横隔膜活動の増強および呼息筋活動の減弱が生じた。呼吸数の増加は主として呼息相の短縮に起因した。2)歯根膜に反復圧刺激を与えても,持続圧刺激を与えた場合と同様の呼吸反射が生じた。しかし,反復圧刺激を与えた場合の方が呼息相の短縮効果は大きかった。3)大脳皮質咀嚼野の電気刺激でリズミカルな開閉口運動を誘発し,木片咬合に伴う歯根膜入力を与えた。呼吸の周期性は皮質刺激に伴い不明瞭になり吸息活動も抑制されたが,歯根膜入力を与えて周期性の回復が促進された。木片咬合中は,手動で圧刺激を与えた際と類似した呼吸変化が観察された

DOI： 10.2330/joralbiosci1965.36.526

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Language：Japanese   Publisher：(一社)歯科基礎医学会  

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Event date： 2016.6

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Event date： 2012.12

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

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Event date： 2012.3

Language：Japanese   Presentation type：Symposium, workshop panel (nominated)  

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Event date： 2009.10

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