ABSTRACT
Disused rat hindlimb caused by sciatic denervation is characterized by osteopenia accompanying alterations in trabecular bone architecture. We studied the effects of short-term denervation followed by reinnervation on the 2-dimensional architecture of trabecular bone using a unilateral sciatic nerve freezing model rat of temporary disuse. Male Fischer-344 rats aged 11-weeks underwent unilateral hind-limb denervation by either sciatic neurectomy (SN) or nerve freezing (NF) by contact with a stainless steel rod cooled in liquid nitrogen, while control rats were sham-operated. Right and left tibiae of denervated and control rats were obtained at 0, 1, 2, 3, 4 and 5 weeks after surgery. Histomorphometric analyses were performed on longitudinal sections of proximal tibial metaphyseal secondary spongiosa. Sciatic denervation by SN or NF resulted in a marked loss of trabecular bone, mostly within first 2 weeks after denervation. Trabecular bone area decreased and gradually recovered with the breaking point at 3 weeks, returning to approximately 55% of basal-control levels (at 0 weeks) by 5 weeks after NF. Both the thickness and length of trabecular bone were significantly decreased after denervation. Trabecular thickness at 5 weeks after NF was significantly greater compared to that at 3 weeks after NF and at 5 weeks after SN, while decreased trabecular length after NF did not during the experimental period. These findings suggest that 1) sciatic nerve freezing results in marked loss of trabecular bone, mostly within the first 2 weeks after surgery ; 2) temporary denervation and subsequent reinnervation reversibly affects trabecular bone architecture, particularly trabecular thickness.
ABSTRACT
Disused rat hindlimb caused by sciatic neurectomy is characterized by skeletal muscle atrophy and bone loss accompanying alterations in trabecular bone architecture. We studied the time course responses of the two-dimensional architecture of trabecular bone and the relationships between bone loss and muscle atrophy using a unilateral sciatic nerve denervation model of disuse atrophy.<BR>Fischer-344 male rats aged 11 weeks were denervated. The right and left tibiae, soleus and extensor digitorum longus muscle of denervated and control rats were obtained at 1, 3, 7, 10 days and 2, 3, 4, 5, 6, 7, 8, 10 weeks after surgery. Histomorphometric analyses were performed on longitu-dinal sections of proximal tibial metaphyseal secondary spongiosa.<BR>Marked trabecular bone loss and muscle weight loss were observed mainly at 7-10 days and 1-3 days after denervation, respectively. Time courses of the percent decrease in trabecular width and length from 0 day (i, e., thinning rate; TR and fragmentation rate; FR) were not matched at 7-10 days and 5-6 weeks after denervation. The scatterplot for TR; FR showed that the FR changed stepwise with the first threshold between 12-25% of TR.
ABSTRACT
The effects of testosterone on the structural and contractile properties of the denervated rat skeletal muscles that were not influenced by neurotrophic-effects were investigated. Male Wistar strain rats (3-week-old, n=28) were used in the present study. All rats were divided into four (n=7, for each) groups; control (C), testosterone control (TC), denervated (DN), and denervated with testosterone (DNT) groups. Sciatic nerves of DN and DNT groups' rats were resected at the 4-week-old after birth. Testosterone that was melted in corn-oil was administered (40 mg/kg body weight/week) for the TC and DNT groups. At the end of breeding period (15-week-old), soleus (SOL) and extensor digitorum longus (EDL) muscles were dissected from both hindlimbs and contractile profiles were analyzed in vitro. Relative weight (muscle weight/body weight) of SOL muscle in the DNT group was significantly (p<0.01) higher than that of the DN group. There is no significant difference in EDL muscle between the DN and DNT groups. Time to peak tension and half relaxation time in EDL muscle of the DNT group was significantly (p<0.05) higher than those of the DN group. Maximum twitch tension was prone to decrease following denervation, and significantly (p<0.01) difference between the DN and DNT groups in both muscles regarding the maximum twitch tension was observed. There is no significant difference of myosin and actomyosin ATPase activities comparison of each group in SOL muscle, however, the TC group were significantly higher than those of the C group in EDL muscle. These results suggested that the effects of testosterone for the hypertrophy in skeletal muscles were not synergistic effects with the neurotrophiceffects, however, for the ATPase in fast muscle act synergistically with the neurotrophic effect to change of myosin ATPase. Moreover, it was also suggested that the sensitivity to the testosterone was different in each type of fiber.
ABSTRACT
The effects of different types of running trainings (sprint or endurance) on the glycolytic (lactate dehydrogenase : LDH, phosphofructokinase : PFK and pyruvate kinase : PK) and oxidative (succinate dehydrogenase : SDH and malate dehydrogenase : MDH) enzymes activities and on the mitochondrial contents in single muscle fiber of different types (slow-twitch oxidative : SO, fast-twitch oxidative glycolytic : FOG and fast-twitch glycolytic : FG) were studied employing biochemical and electron microscopic techniques. Male Wistar strain rats were trained by treadmill 5 days/week beginning the age of 3 weeks old for 16 weeks. Single muscle fibers were dissected from soleus and extensor digitorum longus muscles, and typed histochemically into SO, FOG and FG fibers. The remaining parts of the single muscle fiber were used for biochemical and electron microscopic analyses. Glycolytic enzymes activities were increased in FG and FOG fibers following sprint training. Oxidative enzymes activities were increased in all types of fiber following both trainings. Mitochondrial contents in single muscle fiber were increased in FOG fiber following sprint training and in SO fiber following endurance training. These results suggest that the increase of glycolytic enzymes activity following sprint training were depended on the the fast-type fiber specifically and that of oxidative enzymes activity were depended on all types of fiber in whole muscle. It seems that the increase of oxidative enzymes activity following exercise training alone was not only depended on the increase of mitochondrial contents in skeletal muscle fiber.
ABSTRACT
The active and passive grip strength, repeated grip strength, back lift strength, leg press, vertical jump and back extension were measured for 220 boys and 205 girls in the primary school to examine the similarity and difference between back lift strength and grip strength. The results were as follows;<BR>1) The strength of large muscle groups such as back lift strength and leg press in boys were significantly higher than in girls, but no differences were found in the strength of smaller muscle group like a grip strength.<BR>2) Higher increment rate of the passive grip strength to the active strength was found in younger grade of primary school children. They might possess a lower level of contractile force-integrating ability than older ones.<BR>3) No significant differences between boys and girls and among each grade were found in the decrement rate of repeated grip strength and no sigficant relationship between the decrement rate and maximum grip strength.<BR>4) Significant relationship was observed between back lift strength and active or passive grip strength, and the correlation coefficients with the passive strength were lower than the active strength.<BR>5) Significant relationship was observed between back lift strength and vertical jump and back extension in all grade of primary school girls and lower grade of the boys.
ABSTRACT
The inter of this study was to observe the effects of training on histochemical and biochemical properties in the skeletal muscle fibers.<BR>Wistar strain albino rats were assigned to endurance (E), sprint (S) and control (C) group at 4 weeks old. Animals of trained groups were trained by treadmill for 12 weeks. After training, all animals were sacrificed and M. Soleus (SOL) and M. Extensor Digitorum Longus (EDL) were taken out.<BR>Using histochemical staining methods for Hematoxylin and Eosin, Actomyosin ATPase and Succinate Dehydrogenase (SDH), area and composition of the three muscle fiber types were examined. Furthermore, the chemical properties of glycolytic and oxidative enzyme activities were examined.<BR>The results obtained were as follows:<BR>1. The E and S trained groups, respectivelly, showed lower increase of body weight than the control group.<BR>2. Hypertrophy of all fiber types in EDL were observed in the both trained groups. Area of SO fibers in SOL were also increased in the E group as compared to the C group.<BR>3. The differences observed for fiber composition among the three groups. The rate of FOG fiber in SOL decreased significantly in the both trained groups as compared to the C group. The rate of SO fiber in both muscles were slightly higer for the E group relative to the C Group, but these differences were no significant. However, in the E group significant increase was observed for oxidative enzyme activity. The Phosphofructo-kinase activity in EDL of the S group was significantly higher in comparison to the other groups.<BR>These results suggested that there is the discrepancy between histochemical proper-ties and biochemical properties in the effects of training on skeletal muscle fibers and that the necessity of histochemical and biochemical analysis.