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

Previous studies showed that conduit artery blood flow rapidly increases after even a brief contraction of muscles within the dependent limb. Whether this rapid hyperemia occurs within contracted skeletal muscle in humans has yet to be confirmed, however. We therefore used diffuse correlation spectroscopy (DCS) to characterize the rapid hyperemia and vasodilatory responses within the muscle microvasculature induced by single muscle contractions in humans. Twenty-five healthy male volunteers performed single 1-s isometric handgrips at 20%, 40%, 60%, and 80% of maximum voluntary contraction. DCS probes were placed on the flexor digitorum superficialis muscle, and a skeletal muscle blood flow index (SMBFI) was derived continuously. At the same time, brachial artery blood flow (BABF) responses were measured using Doppler ultrasound. Single muscle contractions evoked rapid, monophasic increases in both SMBFI and BABF that occurred within 3 s after release of contraction. The initial and peak responses increased with increases in contraction intensity and were greater for BABF than for SMBFI at all intensities. BABF reached its peak within 5 to 8 s after the end of contraction. The SMBFI continued to increase after the BABF passed its peak and was decreasing toward the resting level and peaked about 10 to 15 s after completion of the contraction. We conclude that single muscle contractions induce rapid, intensity-dependent hyperemia within the contracted skeletal muscle microvasculature. Moreover, the characteristics of the rapid hyperemia and vasodilatory responses of skeletal muscle microvessels differ from those simultaneously evaluated in the upstream conduit artery.NEW & NOTEWORTHY Through the concurrent use of diffuse correlation spectroscopy and Doppler ultrasound, we provide the first evidence in humans that a single brief muscle contraction evokes rapid, intensity-dependent hyperemia within the contracted skeletal muscle microvasculature and the upstream conduit artery. We also show that the magnitude and time course of the contraction-induced rapid hyperemia and vasodilatory responses within skeletal muscle microvessels significantly differ from those in the conduit artery.

DOI： 10.1152/ajpheart.00761.2020

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

We investigated the integration of sympathetic vasoconstriction and local vasodilation in the skeletal muscle and skin microvasculature of humans. In 39 healthy volunteers, we simultaneously measured the blood flow index in the flexor carpi radialis muscle using diffuse correlation spectroscopy and the skin using laser-Doppler flowmetry. We examined the effects of acute sympathoexcitation induced by forehead cooling on relatively weak and robust vasodilatory responses during postocclusive reactive hyperemia (PORH) induced by 70-sec and 10-min arterial occlusion in the upper arm. To increase sympathetic tone during PORH, forehead cooling was begun 60 sec before the occlusion release and ended 60 sec after the release. In the 70-sec occlusion trials, acute sympathoexcitation reduced the peak and duration of vasodilation in both skeletal muscle and skin. The inhibition of vasodilation by sympathoexcitation was blunted in both tissues by the robust vasodilatory stimulation produced by the 10-min occlusion, and the degree of blunting was greater in skeletal muscle than in skin, especially the initial and peak responses. Sympathoexcitation reduced the peak vasodilation only in skin, while it accelerated the initial vasodilation only in skeletal muscle. However, the decline in vasodilation after the peak was significantly hastened in skeletal muscle, shortening the duration of the vasodilation. We conclude that, in humans, the integration of sympathetic vasoconstriction and local vasodilation has different effects in skeletal muscle and skin and is likely an important contributor to the selective control of perfusion in the microcirculations of different tissues.

DOI： 10.14814/phy2.14070

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BACKGROUND: Renal hypoxia is an aggravating factor for tubulointerstitial damage, which is strongly associated with renal prognosis in diabetic kidney disease (DKD). Therefore, urinary markers that can detect renal hypoxia are useful for monitoring DKD. OBJECTIVE: To determine the correlation between urinary liver-type fatty acid-binding protein (L-FABP) and renal hypoxia using a novel animal model of type 2 diabetes. METHODS: Male spontaneously diabetic Torii (SDT) fatty rats (n = 6) were used as an animal model of type 2 diabetes. Age- and sex-matched Sprague-Dawley (SD) rats (n = 8) were used as controls. Body weight, systolic blood pressure, and blood glucose levels were measured at 8, 12, 16, and 24 weeks of age. Urine samples and serum and kidney tissues were collected at 24 weeks of age. Microvascular blood flow index (BFI) was measured using diffuse correlation spectroscopy before sampling both the serum and kidneys for the evaluation of renal microcirculation at the corticomedullary junction. RESULTS: Obesity, hyperglycemia, and hypertension were observed in the SDT fatty rats. Focal glomerular sclerosis, moderate interstitial inflammation, and fibrosis were significantly more frequent in SDT fatty rats than in SD rats. While the frequency of peritubular endothelial cells and phosphoendothelial nitric oxide synthase levels were similar in both types of rats, the degree of renal hypoxia-inducible factor-1α (HIF-1α) expression was significantly higher (and with no change in renal vascular endothelial growth factor expression levels) in the SDT fatty rats. Urinary L-FABP levels were significantly higher and renal microvascular BFI was significantly lower in the SDT fatty rats than in the SD rats. Urinary L-FABP levels exhibited a significant positive correlation with renal HIF-1α expression and a significant negative correlation with renal microvascular BFI. CONCLUSIONS: Urinary L-FABP levels reflect the degree of renal hypoxia in DKD in a type 2 diabetic animal model. Urinary L-FABP may thus prove useful as a renal hypoxia marker for monitoring DKD in patients with type 2 diabetes in clinical practice.

DOI： 10.1159/000503926

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We propose a novel application of diffuse correlation spectroscopy to evaluate microvascular malfunctions of muscle tissue affected by hyperglycemia and determine their correlation with the severity of diabetic neuropathy at a later stage. Microvascular responses of the thigh muscle and the mechanical pain threshold of the hind paw of streptozotocin-induced type I diabetic rats were continuously monitored once per week for 70 days. Significantly decreased baseline blood flow and reactive hyperemia responses were observed as early as 1 week after hyperglycemia induction. The reactive hyperemia response at 2 weeks of hyperglycemia was highly correlated with the mechanical pain threshold at 8 weeks, at which time a decreased pain threshold was statistically confirmed in hyperglycemic rats relative to controls.

DOI： 10.1364/BOE.9.004539

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We used diffuse correlation spectroscopy to investigate sympathetic vasoconstriction, local vasodilation, and integration of these two responses in the skeletal muscle microvasculature of 20 healthy volunteers. Diffuse correlation spectroscopy probes were placed on the flexor carpi radialis muscle or vastus lateralis muscle, and a blood flow index was derived continuously. We measured hemodynamic responses during sympathoexcitation induced by forehead cooling, after which the effects of the increased sympathetic tone on vasodilatory responses during postocclusive reactive hyperemia (PORH) were examined. PORH was induced by releasing arterial occlusion (3 min) in an arm or leg. To increase sympathetic tone during PORH, forehead cooling was begun 60 s before the occlusion release and ended 60 s after the release. During forehead cooling, mean arterial pressure rose significantly and was sustained at an elevated level. Significant vasoconstriction and decreases in blood flow index followed by gradual blunting of the vasoconstriction also occurred. The time course of these responses is in good agreement with previous observations in animals. The acute sympathoexcitation diminished the peak vasodilation during PORH only in the vastus lateralis muscle, but it hastened the decline in vasodilation after the peak in both the flexor carpi radialis muscle and vastus lateralis muscle. Consequently, the total vasodilatory response assessed as the area of the vascular conductance during the first minute of PORH was significantly diminished in both regions. We conclude that, in humans, the integrated effects of sympathetic vasoconstriction and local vasodilation have an important role in vascular regulation and control of perfusion in the skeletal muscle microcirculation. NEW & NOTEWORTHY We used diffuse correlation spectroscopy to demonstrate that acute sympathoexcitation constrains local vasodilation in the human skeletal muscle microvasculature during postocclusive reactive hyperemia. This finding indicates that integration of sympathetic vasoconstriction and local vasodilation is importantly involved in vascular regulation and the control of perfusion of the skeletal muscle microcirculation in humans.

DOI： 10.1152/ajpheart.00010.2018

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Language：English   Publisher：Japanese Society for Medical and Biological Engineering  

Diffuse correlation spectroscopy (DCS) is an emerging optical technique for noninvasive measurement of hemodynamics of living tissues. Using emitter and detector optical probes attached to the body surface, DCS estimates the mean speed of blood flow in the tissue, through which the emitted near-infrared light propagates (blood flow index: BFI). The advantage of DCS is that the mean blood flow in deeper tissues such as muscle layers can be measured noninvasively. To investigate the sensitivity of DCS in detecting the physiological changes of blood flow in deep and shallow tissues, we measured the blood flow speed in 14 healthy participants during a reactive hyperemia test and skin temperature changes. In the reactive hyperemia test, blood flow returned to the steady state faster in deep tissues than in shallow tissues, and temperature-dependent reallocation of local blood flow in shallow and deep tissues was clearly observed. These results demonstrate that DCS can measure the differences in physiological blood flow dynamics in deep and shallow tissues, suggesting the potential use of DCS to noninvasively quantify changes at microcirculation level in both shallow and deep tissue layers.

DOI： 10.14326/abe.6.53

DOI： 10.1117/12.2288044_references_DOI_QwVep9aHJlEga3zaZ46iU17wem8

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Other Link： https://search.jamas.or.jp/link/ui/2018364077

Language：Japanese  

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Publisher：IEEE  

DOI： 10.1109/ipc48725.2021.9592861

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21K11457/

Using diffuse correlation spectroscopy we quantitatively verified that the manipulative therapy could significantly increase local muscle blood flow.

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Publisher：Optica Publishing Group  

<jats:p>We developed a dual-channel diffuse correlation spectroscopy system, which was validated by simultaneous blood flow measurement of the skeletal muscles of the upper and lower limbs during the head-up-tilt test.</jats:p>

DOI： 10.1364/boda.2021.jtu4a.7

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-21K11457/

Publisher：SPIE  

DOI： 10.1117/12.2545267

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17K19932/

Publisher：SPIE  

DOI： 10.1117/12.2542876

DOI： 10.1109/ipc48725.2021.9592861_references_DOI_RtEHdCfn1uEGzC802OFfSNE0sud

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17K19932/

Language：Japanese  

Manipulative therapy (MT) is a typical treatment applied to the motor organ with a therapeutic objective in various medical fields. In a current clinical practice, however, the effectiveness of MT is subjectively evaluated by a therapist and/or a patient. MT has been expected to increase local blood flow and decrease edema and pain. However, these physiological changes have not been fully clarified due to the lack of non-invasive and cost-effective methodology to evaluate muscle blood flow. We here used diffuse correlation spectroscopy (DCS), a novel technique to non-invasively measure blood flow velocity, to quantitatively evaluate the effect of MT on the blood flow of the target muscle. Healthy participants (3 men/3 women, age: 22.5±0.7) took part in the study. Participants took a supine position on the treatment table to have a hip joint flexion test. The right leg was elevated to the maximum hip joint flection, and the hip flexion angle and the subjective pain intensity (evaluated by visual analog scale: VAS) were measured. Subsequently, the blood flow of the posterior surface of the femoral region was measured for 5 minutes at rest as a baseline. The blood flow of the same site was measured again after 5 minutes of MT. Finally, we measured a post-MT VAS under the hip joint flexion to the same angle as in the first flexion. Participant received two sessions of MT and control conditions, in which they received MT and no treatment (quiet rest for 5 minutes) between the two hip joint flexion measurements, respectively, in a random and counterbalanced order. Subjective pain intensity with hip joint flexion tended to decrease after MT (p=0.08) while no change was observed in case of control condition (p=0.41). The blood flow velocity of the treated muscle was significantly increased after MT relative to that of the pre-treatment state (p<0.05). There was no change in the blood flow velocity throughout the measurement in case of control condition. These results suggest that MT-induced mechanical pressure to the skin and muscle tissues promote venous return and increase local blood flow.

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CiNii Books

J-GLOBAL

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Other Link： http://id.ndl.go.jp/bib/029769472

Publisher：SPIE  

DOI： 10.1117/12.2288044

DOI： 10.3389/fbioe.2021.800051_references_DOI_P3pwp2teSf4xwUd7dDM947V6Bug

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17K19932/

Event date： 2019

Language：Japanese  

拡散相関分光法(diffuse correlation spectroscopy: DCS)は、赤血球が近赤外光を拡散する性質に着目して、生体組織の血流速度を非侵襲的に計測する光学技術である。DCSは送光・受光プローブ間距離の変更によって深部組織の血流動態の情報を含むことができ、近赤外分光法との併用によって局所的な組織酸素消費動態(metabolic rate of oxygen extraction)を導出することができる。そのため、手術中や脳血管障害・睡眠時無呼吸症候群患者の脳血流動態のモニタリング・乳癌の位置検出・運動時筋血流の定量化など幅広い応用が期待されている。本発表では、DCSが組織血流の変化を高感度に検出可能であることを示す一例として、糖尿病モデルラットを用いた筋・腎組織の血流計測結果について紹介する。糖尿病モデルラットの下肢筋・腎皮質に対して定期的に反応性充血試験と血流計測を行い、DCSによる血流パラメータを取得したところ、感覚障害や筋力低下といった慢性症状の発言よりも早期に対照群に対する変化が生じ、糖尿病性合併症の早期診断におけるDCSの有用性を示すことができた。

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Event date： 2018.2

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17K19932/