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Biomedical subjects

Norio Murase

Publications and source records attributed to Norio Murase.

8 recordsLinked to original sources
PubMed2006

Age and activity status affect muscle reoxygenation time after maximal cycling exercise.

PURPOSE: The purpose of this study was to determine the interaction of age and habitual physical activity on recovery time of muscle oxygenation following maximal cycling exercise (CycEXmax). METHODS: Twelve sedentary middle-aged (50+/-6), 13 sedentary elderly (66+/-3), 13 active middle-aged (53+/-5), and 20 active elderly (67+/-5) women participated in this study. We evaluated the peak pulmonary oxygen uptake (VO2peak) during CycEXmax and the half-recovery time of muscle oxygenation (T1/2reoxy time) using near-infrared spectroscopy at the vastus lateralis (VL) during the recovery phase after CycEXmax. RESULTS: T1/2reoxy time was significantly greater in the elderly subjects than in the middle-aged subjects in both sedentary (P<0.05) and active groups (P<0.01). T1/2reoxy time of the active group was lower (P<0.01) than that of the sedentary group regardless of age. Age was significantly correlated to T1/2reoxy time in both sedentary and active groups (in both sedentary and active groups: P<0.01). The slope of T1/2reoxy time against age in the sedentary group was significantly greater (VL: P<0.05) than that of the active group. VO2peak showed significant inverse correlation with T1/2reoxy time at the VL in both sedentary and active groups. The slope of VO2peak against T1/2reoxy time showed no significant differences between middle-aged and elderly subjects. CONCLUSION: The results of this study suggest that T1/2reoxy time was prolonged with aging, regardless of habitual physical activity levels. However, habitual physical activity may prevent the age-related prolongation in T1/2reoxy time after CycEXmax. VO2peak appears to be one of the major factors determining T1/2reoxy time, not age.

Aged↗
PubMed2004

Noninvasive monitoring of deterioration in skeletal muscle function with forearm cast immobilization and the prevention of deterioration.

BACKGROUND: In this research inactivity was simulated by immobilizing the forearm region in a plaster cast. Changes in skeletal muscle oxidative function were measured using near-infrared spectroscopy (NIRS), and the preventative effect of the training protocol on deterioration of skeletal muscle and the clinical utility of NIRS were examined. METHODS: Fourteen healthy adult men underwent immobilization of the forearm of the non-dominant arm by plaster cast for 21 days. Eight healthy adult subjects were designated as the immobilization group (IMM) and six were designated as the immobilization + training group (IMM+TRN). Grip strength, forearm circumference and dynamic handgrip exercise endurance were measured before and after the 21-day immobilization period. Using NIRS, changes in oxidative function of skeletal muscles were also evaluated. Muscle oxygen consumption recovery was recorded after the completion of 60 seconds of 40% maximum voluntary contraction (MVC) dynamic handgrip exercise 1 repetition per 4 seconds and the recovery time constant (TcVO2mus) was calculated. RESULTS: TcVO2mus for the IMM was 59.7 +/- 5.5 seconds (average +/- standard error) before immobilization and lengthened significantly to 70.4 +/- 5.4 seconds after immobilization (p < 0.05). For the IMM+TRN, TcVO2mus was 78.3 +/- 6.2 seconds before immobilization and training and shortened significantly to 63.1 +/- 5.6 seconds after immobilization and training (p < 0.05). CONCLUSIONS: The training program used in this experiment was effective in preventing declines in muscle oxidative function and endurance due to immobilization. The experimental results suggest that non-invasive monitoring of skeletal muscle function by NIRS would be possible in a clinical setting.

Journal Article↗
PubMed2004

Synthesis of highly luminescent glasses incorporating cdte nanocrystals through sol-gel processing.

Highly photoluminescent glass was prepared by embedding water-soluble nanocrystals in a glass matrix using a novel sol-gel process. Thiol-stabilized CdTe nanocrystals and aminopropyltrimethoxysilane were found to be the best combination in the preparation. The synthesis process had to be optimized to avoid nanocrystal agglomeration. The nanocrystals thus embedded in the glass matrix did not show any deterioration of the surface condition. The obtained glass combines excellent optical properties of nanocrystals with the high stability of glass; it emits light of various colors with narrow emission spectra and high photoluminescent efficiency (41%).

Alloys↗
PubMed2003

Muscle oxygen consumption at onset of exercise by near infrared spectroscopy in humans.

In this study, we tried to continuously measure muscle oxygen consumption (m-VO2) by near infrared spectroscopy (NIRS) without arterial occlusions. We used an intermittent isometric exercise at high intensity, which elicits a spontaneous occlusion of the blood flow to the muscle due to an increase in intramuscular pressure. Changes in muscle oxygenation and phosphocreatine (PCr) concentration were monitored in 5 subjects during an intermittent isometric exercise (5 sec. contraction/5 sec. relaxation) at 50% of maximum voluntary contraction for 3 minutes. The rate of deoxygenation was measured from the 2nd sec. to the 3rd sec. of each muscle contraction. The rate of deoxygenation at the onset of exercise followed an exponential time course with a time constant of 42.0 +/- 12.5 sec. (mean +/- SD). This value agreed with the time constant of the decrease in PCr (48.2 +/- 10.2 sec.). This result suggests that m-VO2 was successfully monitored with a time resolution of 10 sec. by NIRS during exercise without arterial occlusion.

Adult↗
PubMed2003

Deterioration of muscle function after 21-day forearm immobilization.

PURPOSE: Although it is well known that immobilization causes muscle atrophy, most immobilization models have examined lower limbs, and little is known about the forearm. The purpose of this study was to determine whether forearm immobilization produces changes in muscle morphology and function. METHODS: Six healthy males (age: 21.5 +/- 1.4, mean +/- SD) participated in this study. The nondominant arm was immobilized with a cast (CAST) for 21 d, and the dominant arm was measured as the control (CONT). The forearm cross-sectional area (CSA) and circumference were measured as muscle morphology. Maximum grip strength, forearm muscle oxidative capacity, and dynamic grip endurance were measured as muscle function. Magnetic resonance (MR) imaging was used to measure CSA, and 31phosphorus MR spectroscopy was used to measure time constant (Tc) for phosphocreatine (PCr) recovery after submaximal exercise (PCr-Tc). Grip endurance was expressed by the number of handgrip contractions at 30% maximum grip strength load. All measurements were taken before and after the immobilization. RESULTS: After the 21-d forearm immobilization, no changes were seen for each measurement in CONT. CSA and the circumference showed no significant changes in CAST. However, maximum grip strength decreased by 18% (P < 0.05), PCr-Tc was prolonged by 45% (P < 0.05), and the grip endurance at the absolute load was reduced by 19% (P < 0.05) for CAST. CONCLUSION: In this model, 21-d forearm immobilization caused no significant changes in forearm muscle morphology, but the muscle function showed remarkable deterioration ranging from 18 to 45%.

Adult↗
PubMed2003

Post-exercise hyperemia after ischemic and non-ischemic isometric handgrip exercise.

Post-exercise related time course of muscle oxygenation during recovery provides valuable information on peripheral vascular disease. The purpose of the present study was to examine post-exercise hyperemia (forearm blood flow; FBF, Doppler ultrasound) assessed by peak FBF, excess FBF and the time constant for FBF (FBF(Tc)) following isometric handgrip exercise (IHE). Post-exercise hyperemia was assessed in an ischemic and non-ischemic state at different exercise intensities and durations. Peak FBF and excess FBF were defined as the maximum FBF during recovery, and the total amount of FBF volume, respectively. FBF(Tc) represents the time to reach approximately 37% of the change in FBF between peak FBF and resting FBF (delta peak FBF). Ten subjects performed IHE at "10% and 30% maximum voluntary contraction (MVC)" for 2 min with or without arterial occlusion (AO), followed by 2 min of AO alone (Study I). In Study II, six subjects performed 30%MVC-IHE with AO for "100%, 66%, 33% and 10% of the exhausted exercise duration" (time to exhaustion). In Study I, although peak FBF and excess FBF were significantly higher in ischemic than non-ischemic IHE for both 10% and 30%MVC (p<0.05), FBF(Tc) was similar in the ischemic and non-ischemic conditions. The peak FBF, excess FBF and FBF(Tc) were all significantly higher at 30% than at 10%MVC (p<0.05). In Study II, the peak FBF and excess FBF increased linearly compared to the absolute and relative exercise durations for ischemic IHE. FBF(Tc) increased exponentially when compared to the absolute and relative exercise durations. These data suggest the ischemic exercise has a larger hyperemic response compared to the non-ischemic exercise. In conclusion, the peak FBF, excess FBF and FBF(Tc) seen during post-exercise hyperemia are closely correlated with exercise intensity and duration, not only in non-ischemic, but also in the ischemic exercise. In combination with the ischemic exercise, these parameters could potentially prove to be valuable indicators of peripheral vascular disease.

Adult↗
PubMedDate not supplied

Two-dimensional diffraction study of ice crystallisation in polymer gels.

Ice crystallisation in crosslinked dextran (Sephadex) gels was studied by the method of two-dimensional X-ray diffraction (XRD) in combination with the simultaneous measurement of differential scanning calorimetry (DSC). With a Sephadex G25 gel where an exotherm due to ice crystallisation is observed in the DSC rewarming trace, it was indicated by the XRD pattern that small ice crystals less than approximately 10 microns in diameter are readily formed during freezing, and that the endothermic trend prior to the exotherm is not due to the glass transition but due to the melting of the small ice crystals. Moreover, the diffraction pattern observed with frozen Sephadex gels depended on the density of crosslink indicating that ice crystals of different size and dimension are formed in the gels.

Crystallization↗