Samuel Cannon

Histochemistry of the myocardium and its vasculature in the normal rat

Coronary arteries and arterioles in the left and right normal rat ventricle were examined histochemically to determine their metabolic activities. Aerobic metabolic capacity was determined by assessin

A Histochemical Evaluation of Metabolism in the Coronary Vasculature of the Primate

Coronary arteries and arterioles in the left ventricle from the primate Macaca fascicularis were histochemically examined to evaluate their metabolic profiles. Succinate dehydrogenase and cytochrome oxidase activities were assessed to evaluate aerobic metabolic capacity, while myosin ATPase activity was determined as an index of ATP utilization for contraction. Anaerobic capacity was evaluated from lactate dehydrogenase and glycogen reactivity. Glucose-6-phosphate dehydrogenase was examined to determine capacity of the hexose-monophosphate-shunt, while the amounts of deoxyribonucleicc and ribonuclei acids were assessed as possible indicators of protein synthesis. Succinate dehydrogenase and cytochrome oxidase demonstrated slight reactivity in both coronary arteries and arterioles indicating a low capacity for aerobic metabolism. Myosin ATPase showed strong activity in arteries and even stronger reactivity in arterioles, suggesting that arteriolar smooth muscle is more capable of utilizing ATP. Glucose-6-phosphate dehydrogenase activity was extremely low in both arteries and arterioles, while deoxyribonucleic and ribonucleic acids demonstrated only slight to moderate reactivity in both arteries and arterioles, indicating that under normal conditions the coronary vasculature appears quite stable with little cell proliferation.

Evidence for Increased Protein Synthesis in Myocardial Microvessels after Chronic Sympathectomy in the Dog

Using histochemical methods, evidence of increased protein synthesis was observed in microvessels (diameter less than 100 micrometers) from dog hearts which had been sympathectomized 2 weeks earlier when compared to controls. Such evidence consisted of increased staining intensity for the enzyme glucose-6-phosphate dehydrogenase and for the nucleic acids RNA and DNA. Increases in reaction intensities were noted in approximately 30% of the microvessels examined from the sympathectomized hearts, and may imply a vascular proliferation in these hearts. However, since no increase in capillary density was observed in sympathectomized hearts, a vascular proliferation, if it occurred, may have been involved in development of the coronary collateral circulation. These data support previous results indicating that collateral resistances are reduced following chronic cardiac sympathectomy while resistance of the coronary vascular bed itself is not altered.

Ethanol Alters Microvasculature Enzymes in the Rat Forebrain

Forebrain arterioles were analyzed histochemically to determine the effects of an acute administration of ethanol on key enzymes of aerobic and anaerobic metabolism as well as on the hexose monophosphate shunt in rats. The enzymes were glucose 6-phosphate dehydrogenase, cytochrome oxidase, lactate dehydrogenase, beta-hydroxybutyrate dehydrogenase, and isocitrate dehydrogenase. All enzymes were quantified under two conditions: 1 h and 2 days after ethanol administration. Significant changes were noted in four of the five enzymes measured after 1 h and in all five enzymes when measured 2 days after ethanol administration. Our data suggest that ethanol may cause impaired metabolism in the forebrain microvasculature, which, in turn, may account for some of the characteristic behavioral effects of acute ethanol administration.

A Histochemical Study of the Coronary Vasculature in Euthyroid and Hyperthyroid Rats

Coronary arteries and arterioles in the left and right ventricles from normal and hyperthyroid rats were examined histochemically to determine and to compare their metabolic activities. The test animals were made hyperthyroid by administration of desiccated thyroid for 8-10 weeks. Using histochemical techniques, selected enzymes and components of key metabolic pathways were examined. These pathways included an evaluation of aerobic (oxidative phosphorylation, Krebs cycle and respiratory chain) and anaerobic metabolic capacity, hexose-monophosphate shunt activity, amounts of deoxyribonucleic and ribonucleic acids present and activity of beta-oxidation of fatty acids. Our results indicate that normal coronary arteriolar metabolism is predominantly aerobic. The findings also suggest a reduction in aerobic metabolism with an accompanying increase in anaerobic potential in the hyperthyroid coronary arterioles. Thus, during thyrotoxicosis, the coronary arterioles may partially shift from aerobic to anaerobic metabolism. Moreover, in both the normal and thyrotoxic rat heart, the coronary microvasculature appears quite stable with little cell proliferation. In contrast, both the control and hyperthyroid rat coronary arteries appear to utilize primarily anaerobic pathways, while the control and hyperthyroid myocardium seem highly dependent upon aerobic metabolism. The tremendous reduction in glucose-6-phosphate dehydrogenase activity in hyperthyroid, when compared to normal coronary arteries and some larger arterioles, implies a reduced capacity for nucleic acid and protein synthesis in the test animals.

Mesencephalic arteriolar and neuronal metabolic profiles from fresh and in vitro incubated tissue sections in the mouse: a histochemical approach

Neuronal perikarya and arterioles of slices of mouse midbrain were examined histochemically to determine their metabolic profiles. No differences in reactivities of key metabolic enzymes were observed between fresh 400-micron tissue sections and sections undergoing in vitro incubation for 4 h at 35 degrees C. Both neurons and arterioles appear capable of aerobic and anaerobic metabolism, while fatty acid utilization is limited. An operative hexose-monophosphate shunt occurs in midbrain neurons and arterioles. These data strongly suggest that electrophysiological and neurochemical studies using the in vitro preparation yield similar data to those obtained from fresh tissue.