W. J. Gonyea

Effect of radiation on satellite cell activity and protein expression in overloaded mammalian skeletal muscle

To gain insight into the role of satellite cells in skeletal muscle hypertrophy, the effect of radiation on small fiber formation, embryonic myosin heavy chain (embryonic MHC) production, and insulin‐like growth factor I (IGF‐I) production in overloaded adult rat soleus muscle was examined.

Muscle cross-sectional area and torque in resistance-trained subjects.

SummaryEight elite male bodybuilders (MB), five elite female bodybuilders (FB), eight male control (MC), and eight female control recreational weight-trainers (FC) performed maximal elbow flexions on an isokinetic dynamometer at velocities between 1.02 and 5.24 rad·s−1, from which peak torque (PT) was measured. Elbow flexor cross-sectional area (CSA) was measured by computed tomographic scanning. Flexor CSA·lean body mass−1 ratios were greater in MB than in other subject groups. Correlations of PT were positively related to CSA but negatively to CSA·lean body mass−1 and to PT·CSA−1. PT·CSA−1 at low-velocity contractions were greater in MC and FC than in MB and FB groups, suggesting a training effect. The velocity-associated declines in torque between velocities of 1.02 and 5.24 rad·−1 averaged 28.4 ± 0.9% and were statistically identical in men and women among the subject groups, suggesting that neither gender nor training had affected this variable.

Cardiac hypertrophy in response to an isometric training program in the cat.

Cats were operantly conditioned to perform isometric exercise to determine the effect of this type of training program on heart morphology. The hearts of 11 cats trained for 2–9 months were removed and weighed. Heart weight-to-body weight ratios were increased significantly in the exercised nnimnlB over 15 controls (3.88 vs. 2.91 g/kg, P < 0.001). Body weights were not significantly different between the two groups. All chambers of the heart were larger in the exercising animals, compared to controls, as evidenced by a significant increase in both left (2.58 vs. 1.9S g/kg, P < 0.001) and right ventricular weight-to-body weight ratios (0.77 vs. 0.58 g/kg, P < 0.002), and increased atrial weight-to- body weight ratios (0.51 vs. 0.37 g/kg, P < 0.01). The same conclusions were reached when the heart weights were not normalized to body weight. To study the progression of cardiac hypertrophy throughout the exercise regimen, we implanted radioopaque markers in the left ventricle of cats and monitored wall thickness on a monthly basis in these animals, using biplane cinefluorography. Eleven cats implanted with markers were trained for 1–6 months. Left ventricular wall thickness increased in the trained animals after 1 month (13.15%) and continued to increase until, at 6 months, wall thickness was increased 32.5% from the initial measurement The increase in wall thickness for the exercise period was correlated with the amount of isometric work that the cat performed, both total isometric work (r - 0.71, P < 0.02) and the mean daily isometric work (r - 0.78, P < 0.01). Males exercised longer, on the average, than females (6 vs. 3 months) and did significantly more total isometric work and mean daily isometric work, even after work was normalised to body weight. Males also exhibited larger increases in wall thickness than females (29.7% vs. 2.4%, P < 0.005). The change in wall thickness wai significantly correlated with lean body mass (r = 0.95, P < 0.05). In addition, muscle fiber diameter was significantly larger in exercised anlmnln than in controls (19.68 vs. 13.35 /un, P < 0.001).

Cardiovascular response to static exercise during selective autonomic blockade in the conscious cat.

Selective autonomic blockade with propranolol, atropine, and combined atropine and propranolol was used to elucidate the role of the autonomic nervous system in the cardiovascular responses that occur during voluntary static exercise in conscious cats. Seven animals were operantly conditioned to hold a bar against a fixed resistance for a constant time of 15 seconds and were then placed on an exercise regimen which consisted of small weekly increments in resistance. With a resistance of 100 g, heart rate (HR) increased by 7%. With exercise at a resistance of 200 g, HR (10%), left ventricular systolic pressure (LVSP, 16%), and LV max dp/dt (18%) increased, and significant changes in these parameters persisted throughout the remainder of the training period. β-Adrenergic receptor blockade with propranolol abolished the increase in LV max dp/dt, whereas HR and LVSP increased. After atropine, the increase in HR was abolished at the early training stages, whereas LVSP and LV max dp/dt increased. Administration of atropine and propranolol blocked the increase in HR and LV max dp/dt responses, whereas LVSP increased. In this study, the increased HR in response to exercise was mediated primarily by the parasympathetic nervous system, whereas the increases in LV max dp/dt were mediated by the sympathetic nervous system. Furthermore, the bradycardia accom-panying chronic performance of isometric exercise resulted from both an increase in vagal tone and a decrease in sympathetic tone. Circ Res 47: 530-535, 1980