Effects of hypokinesia/hypodynamia on contractile and histochemical properties of young and old rat soleus muscle.

To determine if the atrophic process was different in the young and in the aged slow-twitch soleus muscle, in which the aging process is clearly apparent, hind limb hypokinesia/hypodynamia was induced. After 3 weeks, we measured speed-related indices, tension indices, and tension producing capacities. Fiber type composition and fiber cross-sectional area were also investigated.

Enzymatic adaptations to suspension hypokinesia in skeletal muscle of young and old rats.

Hindlimb hypokinesia was induced in young and old rats. After 3 weeks, the activities of five enzymes have been measured in soleus and medial gastrocnemius muscles. Soleus showed increased activity of hexokinase and decreased activity of phosphofructokinase, lactate dehydrogenase and malate dehydrogenase in both groups.

Effect of endurance training and chronic isoproterenol treatment on skeletal muscle sensitivity to norepinephrine.

The purpose of this study was to determine the influence of metabolic stresses, such as endurance training and chronic isoproterenol treatment, on skeletal muscle sensitivity to norepinephrine. Using an isolated perfused rat hindlimb preparation, dose-response curves for skeletal muscle oxygen consumption (VO2) and vascular resistance were obtained with control, endurance trained, and isoproterenol treated rats. No significant difference was found between control and experimental groups for non-stimulated VO2.

Enzymatic activities in slow and fast denervated old rat muscles.

The activities of five enzymes have been studied quantitatively in denervated extensor digitorum longus, gastrocnemius and soleus muscles of 24-month-old rats. The results have been compared with those obtained from normal muscles of a similar age group of rats. Three weeks after denervation, the activity of hexokinase was increased in gastrocnemius and extensor digitorum longus.

Effects of exercise and time elapsed after exercise on VO2, VCO2 and R responses to norepinephrine in rats.

The effects of norepinephrine (NE) injection (300 microgram . kg-1 of body weight) on oxygen consumption (VO2), carbon dioxide production (VCO2) and respiratory exchange ratio (R) were investigated in female rats after 1 h of running on a treadmill (21.5 m .