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 insulin administration on the normal growth of mouse skeletal muscle and its effect on induction of muscle hypertrophy by tenotomy were investigated in this experiment.<BR>1) The influence of insulin dosage on rat body weight was investigated.<BR>The results of examining the influence of insulin dosage on body weight showed significant increases in body weight in the 8.0U/Kg dosage group and 16.0 U/Kg dosage group compared to the control group.<BR>2) The influence of insulin dosage on rat blood glucose levels was investigated.<BR>The blood glucose values of the 1.0 U/kg dosage group were significantly lower than in the control group. They were significantly lower in the 1.0 U/kg dosage group than in the other dosage groups. The positive utilization of glucose in the peripheral organization was suggested.<BR>3) The effect of insulin dosage on skeletal muscle weight was tested.<BR>ANOVA shows a significant difference in soleus muscle weight as the insulin dosage rose. Soleus muscle weight at the 1.0 U/kg dosage was significantly higher than in the other groups. By contrast, no significant differences in muscle weight were observed in the control group as the dose insulin increased. The weight of fast muscle was unaffected by the size of the insulin dosage.<BR>4) The influence of insulin dosage on the compensatory muscle hypertrophy was examined.<BR>The influence of insulin dosage to the compensatory muscle hypertrophy was examined after one week. A 75% increase in soleus muscle after tenotomy was observed in the control group. Although the plantaris muscle showed an average 30% increase, the difference was not significant. A tendency for the weight of soleus muscle and plantaris muscle to increase after tenotomy was observed in the 2.0 U/kg dosage group, but the increments were not significantly different. Effect of tenotomy was observed weight of the soleus from an average of 7.3% in the 16.0 U/kg dosage group, but the increment was not significant. On the other hand, plantaris muscle weight increased about 65% and the increment was significant.