Additive effects of thyroid hormone, growth hormone and testosterone on deoxyribonucleic acid-dependent ribonucleic acid polymerase in rat-liver nuclei.

1. The stimulations of DNA-dependent RNA polymerase in isolated rat-liver nuclei by thyroid hormone, human growth hormone and testosterone are compared. 2.

Ribonucleic acid synthesis during the early action of thyroid hormones.

1. The effect on RNA synthesis in rat liver of thyroidectomy and the administration of thyroid hormone, especially during its physiological latent period, was studied by determining: (a) the activity of DNA-dependent RNA polymerase in isolated nuclei; (b) the rate of synthesis of nuclear and cytoplasmic RNA in vivo; (c) polyribosomal sedimentation profiles; (d) the response of microsomes and ribonucleoprotein particles to polyuridylic acid; (e) the effect of inhibitors of RNA and protein synthesis on the biological activity of hormones. 2.

The relationship between the structure and activity of rat skeletal muscle mitochondria after thyroidectomy and thyroid hormone treatment.

The fine structure of rat gastrocnemius muscle fibers has been studied after changes were induced in the basal metabolic rate (BMR) by thyroidectomy and L-thyroxine administration under anabolic conditions. Biochemical analysis of skeletal muscle mitochondrial respiration and phosphorylation from the same tissue preparations has been summarized, details having been published earlier (3). As estimated from electron micrographs, the total amount of mitochondria from thyroidectomized animals was enlarged 1.

THE STIMULATION BY TREATMENT IN VIVO WITH TRI-IODOTHYRONINE OF AMINO ACID INCORPORATION INTO PROTEIN BY ISOLATED RAT-LIVER MITOCHONDRIA.

1. Normal and thyroidectomized rats were treated with near-physiological doses of tri-iodothyronine. Liver mitochondria were isolated and incubated with radioactive amino acids.