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Biomedical subjects

S Katsuta

Publications and source records attributed to S Katsuta.

At least 37 records · Page 2Linked to original sources
PubMed1999

Changes in surface EMG parameters during static and dynamic fatiguing contractions.

The effect of contraction types on muscle fiber conduction velocity (MFCV), median frequency (MDF) and mean amplitude (AMP) of surface electromyography was examined in the vastus lateralis of 19 healthy male adults. The subjects performed knee extension both statically and dynamically until they were exhausted. The static contraction was a sustained isometric extension of the knee at a joint angle of 90 degrees with 50% of the maximum voluntary contraction (MVC) load. The dynamic contraction was a repetitive isotonic extension of the knee between the angles of 90 degrees and 180 degrees with the same 50% MVC load at a frequency of 10 times per minute. MFVC during the static contraction significantly decreased during the exercise (p < 0.01). On the other hand, MFVC during the dynamic contraction did not significantly change throughout the exercise. MDF decreased and AMP increased during both types of contractions (p < 0.01). Because the blood flow within the muscle is maintained during the dynamic contraction by enhanced venous return from the contracting muscle, these results suggested that MFVC is affected by the metabolic state in the muscle and the changes in MDF cannot be explained only by that of MFVC.

Adult↗
PubMed1999

Effects of exhaustive exercise on biochemical characteristics of sarcoplasmic reticulum from rat soleus muscle.

This study examined the effects of acute high-intensity and moderate-intensity exercise on Ca2+-stimulated adenosine triphosphatase (ATPase) activity and the Ca2+ and ATP dependence of Ca2+-ATPase of the sarcoplasmic reticulum (SR) in the soleus muscle. The rats were run on 10% grade at 50 m min(-1) or 25 m min(-1) until fatigued (avg. time to exhaustion 2.8 and 87.7 min, respectively). The catalytic activities of SR Ca2+-ATPase were significantly depressed immediately after both types of exercise. Kinetic analyses demonstrated that the Ca2+ affinity of Ca2+-ATPase was elevated by both types of exercise adopted in the present investigation whereas the increase in the ATP affinity was brought about by only high-intensity exercise. These results suggest that exhaustive exercise may induce in slow-twitch muscle fibre the environmental changes, which adversely affect SR Ca2+-ATPase activity and can overcome the positive influence arising from the increase in the Ca2+ and/or ATP affinities of SR Ca2+-ATPase.

Animals↗
PubMed1999

Muscle fibre number is a possible determinant of muscle fibre composition in rats.

The purpose of the present study was to investigate whether the muscle fibre composition is related to the number of muscle fibres. To resolve this issue, we developed fast-twitch fibre dominant rats (FFDR) by selective breeding and compared the findings to those of control rats (CR) obtained by random breeding. Percentage of type I fibres of the deep portion of gastrocnemius (DG), soleus (SOL), vastus intermedius (VI), adductor longus (AL), and biceps brachii (BB) muscles in FFDR were lower than CR. Percentage of type IIB fibres in DG, VI and AL and percentage of type IIA fibres of SOL in FFDR were higher than CR. However, fibre composition of plantaris (PLAN), extensor digitorum longus (EDL), rectus abdominis (RA), diaphragm (DIA), and palmaris longus (PL) muscles in FFDR were identical with CR. Total fibre numbers on the cross-sectional area in SOL, PLAN, EDL, AL and PL were counted. Numbers of type I fibres of all those muscles in FFDR were not different from CR. Numbers of type IIA fibres of SOL and AL and of type IIB fibres of AL in FFDR were greater than CR, but there were no significant differences in the number of type IIA or type IIB fibres of PLAN, EDL or PL between the two groups. Based on these observations, it is suggested that there are pleiotropic and muscle-specific effects on muscle fibre composition. In addition, the number of type II fibres is a possible determinant of muscle fibre composition.

Animals↗
PubMed1999

Early phase adaptations of muscle use and strength to isokinetic training.

The purpose of this study was to investigate the effect of short periods of isokinetic resistance training on muscle use and strength. Seven men trained the right quadriceps femoris muscles (QF) 9 d for 2 wk using 10 sets of 5 knee extensions each day. Isometric and isokinetic torques of QF were measured at six angular velocities. Cross-sectional areas (CSA) of QF were determined from axial images using magnetic resonance imaging (MRI). Transverse relaxation time (T2) and activated area of QF, which represented the area greater than the mean resting T2 + ISD in MR[pixels, were calculated at rest and immediately after repetitive isokinetic knee extensions based on T2-weighted MR images. Muscle fiber types, fiber area, and phosphofructokinase (PFK) activities were determined from biopsies of the vastus lateralis muscle. No changes were found in CSA of QF, muscle fiber types, fiber area, and PFK activities after the training. Isometric and isokinetic peak torques at 60-240 degrees x s(-1) and relative area of QF activated by knee extensions increased significantly after the training. These results suggest that muscle strength increases after short periods of isokinetic resistance training without muscle hypertrophy would be due to increased muscle contractile activity.

Adaptation, Physiological↗
PubMed1999

Age effect on expression of myosin heavy and light chain isoforms in suspended rat soleus muscle.

This study was designed to test the hypothesis that myosin heavy (MHC) and light chain (MLC) plasticity resulting from hindlimb suspension (HS) is an age-dependent process. By using an electrophoretic technique, the distribution of MHC and MLC isoforms was quantitatively evaluated in the soleus muscles from 3- or 12-wk-old rats after 1-3 wk of HS treatment was maintained. In normal 12- and 15-wk-old rats, the soleus muscles contained a predominance of MHCI ( approximately 94%) with small amounts of MHCIIa, but not MHCIId or MHCIIb. The suspended muscles of adult rats were characterized by the appearance of MHCIIb and MHCIId, the latter reaching approximately 6% after 3 wk of HS treatment. In contrast to changes in MHC, HS did not induce a transition in the MLC pattern in the soleus muscles from adult rats. Compared with adult rats, in juveniles HS had a much more pronounced effect on the shift toward faster MHC and MLC isoform expression. The soleus muscles of 6-wk-old rats after 3 wk of HS were composed of 37.0% MHCI, 19.1% MHCIIa, 23.7% MHCIId, and 20.2% MHCIIb. Changes in MLC isoforms consisted of an increase in MLC1f and MLC2f concomitant with a decrease in MLC2s. These results indicate the existence of a differential effect of HS on MHC and MLC transitions that appears to be age dependent. They also suggest that the suspended soleus muscles from young rats may acquire the intrinsic contractile properties that are intermediate between those in the normal soleus and typical fast-twitch skeletal muscles.

Aging↗
PubMed1998

Detraining effects on bone mass in young male rats.

The effects of exercise training and detraining on bone mass were assessed in young male Wistar rats. The rats were divided randomly into sedentary control (C) and exercise training (T) groups. The T rats were trained for 10 weeks followed by a 10-week detraining period. Training consisted of running exercise on a rodent treadmill at 35 m/min, +5-degree inclination, 60 min/day, 5 days/week. Training induced significant gain in fat-free dry weight and length of bones (femur, tibia, humerus and coxa) and bone mineral content (femur, tibia and humerus). Histological analysis at the tibial mid-shaft revealed a significant increase in total and cortical areas without a significant change in marrow area in the T group. Bone mass acquired through running exercise was retained for 10 weeks after cessation of training. These results indicate that running exercise leads to increased cortical bone associated with enhanced periosteal bone formation which is also maintained even after stopping exercise training, and suggest that training effects on the skeleton in bone mass level do not diminish immediately after cessation of training.

Absorptiometry, Photon↗
PubMed1998

Hereditary dominance of fast-twitch fibers in skeletal muscles and relation of thyroid hormone under physiological conditions in rats.

To investigate whether muscle fiber compositions of various skeletal muscles were correlated with each other and whether muscle fiber type composition was related to the serum thyroid hormone level, fast-twitch fiber dominant rats (FFDR), which had a higher percentage of fast-twitch (FT) fibers in the deep portion of the lateral head of the gastrocnemius muscle (GAS), were compared to a control group. The FFDR group was obtained by the selective breeding for high-percentage FT fibers in the GAS, and the control group was obtained by random breeding from the same base population. The percentages of FT fibers of the GAS, soleus (SOL), vastus intermedius (VI), biceps brachii (BB), rectus abdominis (RA) and extensor digitorum longus (EDL) muscles were analyzed. The percentages of FT fibers of the GAS, SOL, VI and BB in the FFDR group were significantly higher than in the control group (p<0.05), and percent FT fibers of the GAS were significantly correlated with those of the SOL (r = 0.62, p<0.01), VI (r = 0.45, p <0.05) and BB (r = 0.43, p<0.05). On the other hand, no significant differences between FFDR and the control group and no significant correlations with the GAS were observed in percent FT fibers of the RA and EDL. The total 3,3',5-triiodo-L-thyronine (T3) level in FFDR was not significantly different from the control group and was not significantly correlated with the percentage of FT fibers. These data suggest that the percentages of FT fibers of various skeletal muscles are genetically correlated with each other, but some FT muscles are not because they might be close to the upper limits of the genetic adaptive range. In addition, percentages of FT fibers are independent of the total T3 level under physiological conditions.

Animals↗
PubMed1997

Evaluation of Distribution Constants of Lanthanoid(III) Acetylacetonates between Sodium Dodecyl Sulfate Micelles and Water by Micellar Capillary Electrophoresis

The solubilization behavior of acetylacetonate complexes of lanthanoids(III) (Nd, Sm, Tb, and Tm) in sodium dodecyl sulfate micelles has been quantitatively evaluated by means of micellar capillary electrophoresis. From analysis of the migration times of the lanthanoid complexes, assuming incorporation of the cationic bis-acetylacetonates as well as the neutral tris-acetylacetonates into the anionic micelles, the distribution constant of each species between the micelles and water (Kmc/w) was determined. The distribution constants obtained were compared with those of the tris-acetylacetonates between heptane and water (Khep/w). The Kmc/w value of the neutral complex is smaller than that of the cationic one but much larger than the Khep/w value. The Kmc/w and Khep/w values of the neutral complex increase with increasing atomic number of the lanthanoid, whereas the opposite tendency was observed for Kmc/w of the cationic complex. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Denervation-induced region-specific changes in fibre types in the soleus and plantaris muscles of rats.

Muscle fibre composition was compared among the proximal (25%), middle (50%) and distal (75%) regions of muscle to investigate whether denervation induces region-specific changes of fibre types in the soleus and plantaris muscles of rats. Decreases in mass were observed in both muscles after denervation. In the soleus muscle, denervation increased the percentage of type I fibres with a concomitant increase in the proportion of type IIC and IIA fibres. The extent of such transformations was greater in the proximal region than the middle and distal regions. In normal plantaris muscle, the middle region showed a higher proportion of type IIA fibres with a lower percentage of type IIB fibres reciprocally than other regions. These regional differences in fibre types were not detected in the 4-week denervated plantaris muscle. These findings suggest that denervation-induced transformations from type I to type II fibres begin in the proximal region in the soleus muscle of rats. In addition, regional differences in fibre types along the muscle length could be regulated by neuromuscular activity through normal innervation in the plantaris muscle.

Animals↗
PubMed1997

Morphological adaptation of capillary network in compensatory hypertrophied rat plantaris muscle.

The aim of this study was to examine the morphological adaptation of the capillary network in hypertrophied plantaris muscles by examining both capillary numbers and luminal circumferences. Hypertrophy of the plantaris muscle was induced by myectomy of the gastrocnemius muscle. This hypertrophy was characterised by increases in muscle mass and fibre cross-sectional area. All capillary parameters were determined using morphometric methods in perfusion-fixed plantaris muscle. Increased capillary-to-fibre ratio was observed in the overloaded plantaris muscle while no change was observed in the capillary luminal circumference. No differences were observed in the capillary density and the capillary-to-fibre perimeter ratio of the normal and the hypertrophied plantaris muscle. These results indicated that chronic overload-induced neocapillarization, but not enlargement of capillary luminal circumference, contributed to the prevention of decreases in the capillary-to-fibre perimeter ratio in the plantaris muscle in the hypertrophied process.

Adaptation, Physiological↗
PubMed1997

Oxidative enzyme activity and soma size in motoneurons innervating the rat slow-twitch and fast-twitch muscles after chronic activity.

The effects of chronic activity induced by running training on the activity of the mitochondrial enzyme succinate dehydrogenase (SDH) and soma size in motoneurons innervating the slow-twitch soleus (SOL) and fast-twitch extensor digitorum longus (EDL) muscles were studied in rats using the retrograde neuronal tracer Nuclear Yellow. Rats were assigned to control and trained groups that were subjected to treadmill running for 10 weeks (2 h/day, 30 m/min, 5 days/week). After training, both SOL and EDL muscles showed clear adaptations (citrate synthase activity in the SOL muscle, and the fast-twitch oxidative-glycolytic fiber area of the EDL muscle increased significantly after training). The SDH activity of the motoneurons innervating both SOL and EDL muscles was unchanged by training. However, SOL motoneurons of trained rats had a significantly larger soma size and a significantly higher total SDH activity [SDH activity x soma size) than those of control. Total SDH activity was calculated to examine the absolute SDH protein content of the motoneurons. On the other hand, there was no difference in both soma size and total SDH activity of EDL motoneurons between the two groups. These data demonstrate that chronic activity has a considerably stronger impact on soma size and total oxidative enzyme activity of motoneurons innervating slow-twitch rather than fast-twitch muscles.

Animals↗
PubMed1997

Adaptation of myoglobin in compensatory hypertrophied rat muscle.

This study investigated the time course change of myoglobin concentration ([Mb]) in skeletal muscle during muscle hypertrophy in rats. Seven groups of Wistar rats (n = 7 per group) were examined. Compensatory hypertrophy of the plantaris muscle was induced by the bilateral ablation of the medial and lateral heads of the gastrocnemius muscle, and the effect of compensatory hypertrophy on the [Mb] of the plantaris muscle was examined at 7, 21 and 42 days post-ablation. The [Mb] expressed as mg g(-1) wet muscle weight tended to decline at 7 days post-ablation (-12.1%) and returned to the control level by 42 days post-ablation, as did the muscle protein concentration. However, the [Mb] expressed as mg g(-1) protein weight was not significantly different between the ablation and control groups throughout the experimental period. The estimated value of absolute Mb content in the whole plantaris muscle was significantly increased by 28.4% (P < 0.01) at 42 days post-ablation compared with the age-matched controls. Therefore, the longer period of compensatory activity allowed the Mb to increase in its absolute content, although the [Mb] did not exceed the level of control muscle. The capacity of facilitated oxygen diffusion and oxygen storage by Mb in the muscle cells will not change even when muscle enlargement takes place.

Animals↗
PubMed1997

Changes in insulin-stimulated glucose transport and GLUT-4 protein in rat skeletal muscle after training.

After running training, which increased GLUT-4 protein content in rat skeletal muscle by <40% compared with control rats, the training effect on insulin-stimulated maximal glucose transport (insulin responsiveness) in skeletal muscle was short lived (24 h). A recent study reported that GLUT-4 protein content in rat epitrochlearis muscle increased dramatically ( approximately 2-fold) after swimming training (J.-M. Ren, C. F. Semenkovich, E. A. Gulve, J. Gao, and J. O. Holloszy. J. Biol. Chem. 269, 14396-14401, 1994). Because GLUT-4 protein content is known to be closely related to skeletal muscle insulin responsiveness, we thought it possible that the training effect on insulin responsiveness may remain for >24 h after swimming training if GLUT-4 protein content decreases gradually from the relatively high level and still remains higher than control level for >24 h after swimming training. Therefore, we examined this possibility. Male Sprague-Dawley rats swam 2 h a day for 5 days with a weight equal to 2% of body mass. Approximately 18, 42, and 90 h after cessation of training, GLUT-4 protein concentration and 2-[1,2-3H]deoxy-D-glucose transport in the presence of a maximally stimulating concentration of insulin (2 mU/ml) were examined by using incubated epitrochlearis muscle preparation. Swimming training increased GLUT-4 protein concentration and insulin responsiveness by 87 and 85%, respectively, relative to age-matched controls when examined 18 h after training. Forty-two hours after training, GLUT-4 protein concentration and insulin responsiveness were still higher by 52 and 51%, respectively, in muscle from trained rats compared with control. GLUT-4 protein concentration and insulin responsiveness in trained muscle returned to sedentary control level within 90 h after training. We conclude that 1) the change in insulin responsiveness during detraining is directly related to muscle GLUT-4 protein content, and 2) consequently, the greater the increase in GLUT-4 protein content that is induced by training, the longer an effect on insulin responsiveness persists after the training.

Animals↗
PubMed1996

Relationships between fiber composition and NMR measurements in human skeletal muscle.

The purpose of this study was to examine the relationships between the relative contents of phosphocreatine (PCr), inorganic phosphate (Pi), beta-adenosine triphosphate (ATP), and transverse relaxation time (T2) with fiber composition, which determined histochemically in the human skeletal muscle. The vastus lateralis muscles of 28 volunteers were subjected to phosphorus nuclear magnetic resonance (31P NMR) spectroscopy, magnetic resonance imaging (MRI) and muscle biopsy. Muscle fibers were divided into type I and type II fibers using myosin ATPase stain. A wide range of fiber composition levels were observed in the subjects (27.3-74.6% type I fibers). The PCr/ATP, Pi/ATP and (PCr + Pi)/ATP ratios were positively related to the percentage of type II fibers (r = 0.695, p < 0.001, r = 0.429, p < 0.05 and r = 0.773, p < 0.001, respectively). There was no correlation between fiber composition and the PCr/Pi ratio (r 0.127, n.s.) or intracellular pH (r = 0.305, n.s.). Moreover, no correlation was found between T2 and fiber type (r = 0.144, n.s.). These results suggest that 31P NMR can detect the differences in relative content of phosphates between type I and type II fibers, thereby noninvasively evaluating fiber composition in human skeletal muscle.

Adenosine Triphosphate↗
PubMed1996

Creatine kinase release from regenerated muscles after eccentric contractions in rats.

The purpose of this study was to test the hypothesis that an increase in plasma creatine kinase (CK) activity after eccentric contractions (ECC) would be attenuated in regenerated muscle fibres. Adult male Wistar rats (aged 12-14 weeks) were randomly assigned to a treatment group (n = 14) or a control group (n = 10). In the treatment group, 1.2% barium chloride solution (BaCl2) was injected into the tibialis anterior (TA) and extensor digitorum longus (EDL) muscles to induce degeneration and subsequent regeneration. The same amount of isotonic saline solution was injected into TA and EDL for the control group. Histological observation showed that approximately 50% of the fibres in the transverse sections of both muscles underwent necrosis 2 days after BaCl2 injection. The CK activity increased about tenfold at 2-4 h after BaCl2 injection. At 4 weeks after BaCl2 injection, when the regeneration process was almost complete, the TA and EDL of anaesthetized rats from both groups were subjected to ECC in which maximal dorsiflexion was caused by nerve electrical stimulation and the flexed foot was forcibly extended by a lever arm connected to a motor. This action was performed in 2 sets of 30 repetitions. Maximal isometric torque of the dorsiflexors decreased to about 15% (P < 0.01) of the pre-ECC value immediately after the exercise. Blood samples were collected before and 2, 4, 12, 24, 48 h after ECC. The CK activity increased significantly (P < 0.01) and peaked at 2-4 h after ECC, and there was no significant difference in the amount of CK increase between the treatment [1007 (SEM 120) IU.l-1] and the control [1064 (SEM 120) IU.l-1] group. Contrary to the hypothesis, CK release after ECC was not attenuated in muscle regenerated from BaCl2-induced myonecrosis.

Animals↗
PubMed1996

Changes in fibre types in rat soleus and plantaris muscles following hypophysectomy and compensatory overload.

We investigated whether hypophysectomy could modify the change in muscle fibre types caused by compensatory overload. Male Wistar strain rats were assigned to groups of either normal control (NC), hypophysectomized control (HC), normal compensatory overloaded (NO), or hypophysectomized compensatory overloaded (HO). Compensatory overload was induced by the bilateral removal of the gastrocnemius muscle. Five weeks later, there were losses in the soleus and plantaris muscle weights as a result of hypophysectomy. Compensatory overload increased muscle weights independently of the hypophysectomy. Growth hormone and 3,5,3'-triiodothyronine levels were significantly decreased following hypophysectomy. In the soleus, hypophysectomy increased the percentage of type I fibres at the expense of type IIA fibres. Compensatory overload decreased type IIA fibres under the hypophysectomized condition. In the plantaris, the percentage of type IIC fibres was increased at the expense of both type IIA and IIB fibres following hypophysectomy. The decrease in type IIB fibres cause by compensatory overload was induced irrespective of hypophysectomy. The changes in muscle fibre types in the HO group were equal to the sum of the changes in the HC and NO groups. These results suggest that after a period of 5 weeks hypophysectomy may induced decrease in type IIA and IIB fibres in association with the lack of pituitary and thyroid hormones, and that the hypophysectomy could not modify the change in muscle fibre types caused by compensatory overload.

Aging↗