Search PubMed⌕ Search

Biomedical subjects

D Powell

Publications and source records attributed to D Powell.

At least 181 records · Page 10Linked to original sources
PubMed1975

Stimulation of brain adenylate cyclase activity by the undecapeptide substance P and its modulation by the calcium ion.

Synthetic substance P stimulated adenylate cyclase activity in particulate preparations from rat and human brain. The concentration of substance P for half maximal stimulation in rat brain was 1.8-10-minus 7 M. The stimulatory effect of substance P on the rat brain adenylate cyclase activity was 88% compared with 48% by noradrenalin, 163% by prostaglandin E1 and 184% by prostaglandin E2. Both the basal and substance P-stimulated adenylate cyclase activity in rat brain were inhibited by concentration of Ca-2+ above 10-minus 6 M. The chelating agent ethyleneglycol-bis-(beta-aminoethylether)-N, N'-tetraacetic acid at a concentration of 0.1 mM reduced the basal adenylate cyclase activity by 64% and eliminated the substance P-stimulated activity. The inhibition by ethyleneglycol-bis-(beta-aminoethylether)-N, N'-tetraacetic acid was completely reversed by increasing concentrations of Ca-2+.

Adenylyl Cyclase Inhibitors↗
PubMed1975

Malignant histiocytosis in a patient presenting with leukocytosis, eosinophilia, and lymph node granuloma.

A patient with malignant histiocytosis presented with a number of unusual features including fever, leukemoid reaction, and eosinophilia. Other confusing findings included lymph node biopsies which showed reactive changes, noncaseating granuloma, and atypical Reed-Sternberg cells. These features are compared with cases appearing in the literature. The course was rapidly progressive despite combination chemotherapy.

Adult↗
PubMed1975

Parathyroid function in acromegaly.

Parathyroid function was assessed in six acromegalic subjects by measurement of serum levels of parathyroid hormone (PTH). Only one patient had increased PTH levels. These findings suggest that hyperparathyroidism does not uniformly occur in acromegaly.

Acromegaly↗
PubMed1973

Secretion of calcitonin in hypocalcemic states in man.

The control of calcitonin secretion in humans has been studied extensively only in patients with medullary thyroid carcinoma since the peripheral concentration of the hormone in normal subjects is too low for accurate measurement by existing assay procedures. However, we have recently found that the concentrations of calcitonin in the peripheral plasma of hypocalcemic subjects during provocative tests of hormone secretion were high enough to be measured by radioimmunoassay. Accordingly, the effect of calcium and pentagastrin infusions on plasma calcitonin was studied in nine patients with pseudohypoparathyroidism, seven patients with idiopathic hypoparathyroidism, and six patients with hypocalcemia not due to parathyroid disease. The infusion of calcium in these hypocalcemic subjects resulted in increases in plasma calcitonin to levels that could be readily detected by our radioimmunoassay. Pentagastrin infusion also caused an increase of plasma calcitonin in some subjects, but calcium was approximately 10 times more effective than gastrin in its stimulatory effect on hormone secretion. These results demonstrate that in humans as well as other mammals the secretion of calcitonin by parafollicular cells that are not involved by medullary thyroid carcinoma is directly related to plasma calcium and that gastrin can also stimulate hormone secretion. The results are consistent with the thesis that the secretion of calcitonin by normal human subjects does occur but at peripheral concentrations of the hormone below the detection limits of most existing immunoassays; hypocalcemia leads to increased stores of hormone that can be related by the appropriate stimuli.

Calcitonin↗