PubMed Health⌕ Search

Biomedical subjects

E A Sellers

Publications and source records attributed to E A Sellers.

At least 19 recordsLinked to original sources
PubMed1977

Influence of cold exposure and thyroid hormones on regulation of adrenal catecholamines.

Since thyroid hormones influence urinary excretion of catecholamines after exposure to cold, the effects of hyper- and hypo-thyroidism on adrenal tyrosine hydroxylase (TH) (EC 1.14.16.2), phenylethanolamine-N-methyl transferase (PNMT) (EC 2.1.1.28), and serum dopamine-beta-hydroxylase (DbetaH) (EC 1.14.17.1) of rats of 23 and 4 degrees C were studied. TH changes resembled the urinary excretion pattern at 4 degrees C in being higher after 8 days than after 1 day of exposure, and in declining as acclimation occurred. At 23 degrees C, TH activity of hypothyroid rats was significantly higher than in euthyroid or hyperthyroid animals, and after 1 day at 4 degrees C the value increased even more. While in the hypothyroid animals at 4 degrees C the concentration of adrenal catecholamines was less, the epinephrine to norepinephrine ratio was higher than at 23 degrees C. Very high TH activity with a decline in catecholamine concentration suggests that the capacity of TH had been exceeded. PNMT activity was significantly elevated in this group. TH activity was not decreased in the hyperthyroid group at 23 degrees C, and was increased after 8 days at 4 degrees C, suggesting that circulating thyroid hormones have no direct inhibitory effect on TH. Serum DbetaH was elevated after exposure to 4 degrees C, regardless of thyroid hormonal status. The activation of adrenal TH in hypothyroid rats at 23 degrees C and of TH, PNMT, and serum DbetaH at 4 degrees C is probably the result of increased activity of the sympathetic nervous system.

Adrenal Glands↗
PubMed1976

Effects of hypophysectomy and short- aing electron-microscopic study.

The follicular architecture of the thyroid gland of the rat following experimentally induced states of hypo- and hyperactivity was investigated by scanning electron microscopy and the findings correlated with both light and transmission electron-microscopic observations. By scanning electron microscopy, the microvilli on the apical surfaces of the follicular cells showed the most striking changes; following hypophysectomy, the cells were flattened and the microvilli had decreased in both size and number, whereas following propylthiouracil (PTU) administration the epithelial cells were enlarged, and marked hyperplasia and hypertrophy of the microvilli was present. Of particular interest is that the changes observed following PTU appeared to be identical in short- and long-term PTU-treated rats. Similarly, the heterogeneity of the follicular cells observed within the follicles was maintained under the various experimental conditions. Although the functional significance of these observations is not quite clear, it appears justifiable to assume that a reduction of luminal surface area of the follicular epithelial cell may hinder, whereas an increase may facilitate transport process across the apical cell membrane.

Animals↗
PubMed1975

Ethanol metabolism and liver oxidative capacity in cold acclimation.

Exposure of rats to an ambient temperature of 5 degrees C for 4 to 6 weeks led to a 30 to 80 percent increase in the rate of oxygen consumption and a 50 percent increase in the rate of ethanol oxidation by liver slices, a 50 percent increase in mitochondrial alpha-glycerophosphate oxidase activity of liver, and a 100 percent increase in Na++K+-activated adenosine-triphosphatase, activity. Ouabain, an inhibitor of the Na++K+-activated adenosine-triphosphatase, completely blocked the extra respiration and ethanol oxidation. Dinitrophenol, which increases oxygen consumption and ethanol oxidation by liver slices from normal rats, was ineffective with slices from cold-exposed animals. Ethanol disappearance rate in vivo was also increased by cold acclimation, even though liver alcohol dehydrogenase activity was reduced. It is suggested that increased hydrolysis of ATP by the sodium pump system is responsible for the increased oxygen consumption and ethanol metabolism in the livers of cold-acclimated animals.

Acclimatization↗