Biomedical subjects

K Gibson

Publications and source records attributed to K Gibson.

At least 73 records · Page 4Linked to original sources

PubMed1975

The effect of isoprenaline and propranolol on rat myocardial ornithine decarboxylase.

The intraperitoneal injection of isoprenaline in rats caused an increase in myocardial ornithine decarboxylase activity which reached a maximum of about four times the control value one hour after the injection. The intraperitoneal injection of dl-propranolol had no effect on myocardial ornithine decarboxylase activity. The injection of dl-propranolol 30 min before the injection of isoprenaline almost completely prevented the effect of isoprenaline.

Animals↗

PubMed1975

The effect of swimming exercise of rat myocardial ornithine decarboxylase activity.

Within 30 minutes of swimming exercise there was an increase in myocardial ornithine decarboxylase activity. The activity continued to increase throughout the two hour period of exercise, after which it decreased again. Two hours after exercise, the enzyme activity had returned to the resting level, and four hours after exercise myocardial ornithine decarboxylase activity was slightly less than the resting level. Repeated daily exercise was associated with a diminished response on the second and third days. Subsequently however, myocardial ornithine decarboxylase activity was again stimulated by two hours of swimming exercise.

Animals↗

PubMed1975

The effects of polyamines on cardiac protein biosynthesis.

Putrescine, spermine, and spermidine were able to stimulate cell-free protein biosynthesis at low Mg++ ion concentrations. The addition of polyamines to the perfusate of an isolated perfused rat heart preparation caused an increased rate of [14C]phenylalanine incorporation into myocardial protein. Spermine increased the uptake of alpha-aminoisobutyric acid into the myocardium.

Aminoisobutyric Acids↗

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

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