Biomedical subjects

P Harris

Publications and source records attributed to P Harris.

At least 361 records · Page 20Linked to original sources

PubMed1975

Changes in myocardial collagen in normal development and after beta blockade.

During development the total mass of collagen increases to the same degree in each ventricle independently of the mass of muscle. At birth the concentration of collagen is the same in each ventricle. Thereafter a greater quantity of muscle is developed in the left ventricle than in the right ventricle, so that the concentration of collagen in the right ventricle comes to exceed that in the left. In the mature rabbit the concentration of collagen is higher in the atria than in the ventricles, higher in the right ventricle than in the left ventricle, and higher in the epicardium than in the endocardium. Beta blockade has no effect on the content of myocardial collagen.

Aging↗

PubMed1975

Enzyme activities in red and white muscles of guinea-pigs and rabbits indigenous to high altitude.

The activities of several enzymes functioning in different areas of fuel catabolism were measured under standardized conditions, using crude homogenates of sartorius and ventricular muscle from outbred guinea-pigs and rabbits indigenous to high or low altitude. The activities of sartorius and myocardium were found to reflect the metabolic patterns known to be associated with white and red muscle. Both species had right ventricular hypertrophy at high altitude. The enzyme activities in the high altitude guinea-pig were not significantly different from those in the sea level animals. In the high altitude rabbit, compared with the low altitude rabbit, the activities of glyceraldehyde-3-phosphate deydrogenase and phosphofructokinase were greater in both the sartorius and myocardium. In addition, mitochondrial glycerol-3-phosphate dehydrogenase activity was greater in the sartorius at high altitude, while aspartate aminotransferase and beta-hydroxyacylcoenzyme A dehydrogenase activities were greater in the myocardium at high altitude. Succinate dehydrogenase activity was comparable at the two altitudes for both tissues. There was a greater proportion of skeletal muscle type lactate dehydrogenase in the high altitude rabbit myocardium but no difference was found with the guinea-pig.

Alcohol Oxidoreductases↗

PubMed1975

A theory concerning the course of events in angina and myocardial infarction.

Evidence is discussed which suggests that coronary arterial thrombosis need not be the primary event in myocardial infarction. If this is so, it is necessary to consider the initial changes which might occur in the myocardium rather than the effects of experiments in which the coronary arterial supply has been suddenly cut off. Results of recent investigations on patients suggest that, during the anginal attack, there is an inability of the affected myocardium to relax and a diminution in the flow of blood to the region. The former implies an increased myofibrillar concentration of calcium ions, the latter may be explained by the mechanical compression of small intramyocardial blood vessels. It is argued that these two factors may initiate vicious circles which could lead to the death of myocardial cells and thus to myocardial infarction.

Adenosine Triphosphatases↗

PubMed1975

The effects of hypoxia, hypertrophy, and diet on rat myocardial ornithine decarboxylase activity.

We have shown that there is a highly significant difference between right and left ventricular ornithine decarboxylase activity. The left ventricle had a much higher activity compared with the right ventricle. A restricted diet caused a decrease in ornithine decarboxylase activity after 24 hr. Hypoxia caused a depression of the ornithine decarboxylase activity during the first 2 days of the experiment. In the hypertrophied right ventricle there was an initial decrease in ornithine decarboxylase after 24 hr and then a gradual increase in ornithine decarboxylase activity during the 7 days of the experiment. The increase in ornithine decarboxylase activity became significant when an increase in tissue weight became apparent.

Animals↗

PubMed1975

Some properties of rat myocardial ornithine decarboxylase and the in vitro effects of nucleotides.

Myocardial ornithine decarboxylase appears to have characteristics similar to those of enzymes isolated from other tissues. Ornithine decarboxylase activity decreased very rapidly after the death of the animal. Storage of the cell sap fraction at 0 degrees C or -15 degrees C, however, led to only a small decrease in the enzyme activity up to 3 days after preparation. Pyridoxal phosphate at an optimum of 50 muM was essential for full enzyme activity. Thiol compounds did not increase the myocardial ornithine decarboxylase enzyme activity. The subcellular distribution of the enzyme in the myocardium was found to be different from that reported in other tissues. A partial purification of the enzyme was possible using the proteins precipitated at pH 5 from a cell-soluble fraction or by passing a soluble fraction through a Sephadex G 100 gel column. ATP, ADP, and AMP inhibited ornithine decarboxylase at high concentrations (5 mM), but GTP, CTP, and ITP inhibited at a 1 mM concentration and above.

Adenine Nucleotides↗

PubMed1975

Effects of chronic hypoxia on myocardial metabolism.

Chronic hypoxia had widespread effects on myocardial metabolism. In understanding these effects, it is necessary to take account of the indirect ways in which hypoxia may act on the heart. Two such important indirect actions are those which follow the development of pulmonary hypertension and anorexia. The experimental design reported here enables one largely to distinguish the effects of pulmonary hypertension and anorexia from the rest. Using such a design, we have presented a number of diverse aspects of myocardial metabolism under conditions of chronic alveolar hypoxia induced by a low atmospheric pressure.

Animals↗

PubMed1974