Does calcitonin modulate anterior pituitary hormone secretion?

In a group of 5 healthy subjects salmon CT (sCT) infusion was unable to induce significant variations on basal secretory levels of LH, FSH, PRL and TSH. In a second group of 5 normal subjects, GnRH and TRH tests were performed both during sCT and saline infusion; a clear inhibition of TSH-stimulated levels and of PRL area was documented, while gonadotropin secretion was not significantly affected by sCT infusion. These results suggest that CT effect might be attributed to a change in intracellular calcium of pituitary cells; however the different behavior between TRH-and GnRH-stimulated hormones might be due to a different hormonal release mechanism. Furthermore the widespread recognition of CT-like immunoreactivity in adenohypophysis and in portions of the central nervous system suggests that CT may be a neurotransmitter or paracrine regulator.     

Hematopoietic recovery after 10-Gy acute total body radiation

Considerable data suggest that very high doses of acute total body radiation destroy most hematopoietic stem cells and that recovery is possible only after a bone marrow transplant. We review data from a radiation accident victim exposed to about 10-Gy or more acute total body radiation. Total dose and uniformity of distribution were confirmed by physical measurements (paramagnetic resonance), computer simulation, and biologic dosimetry (granulocyte kinetics and cytogenetic abnormalities). Treatment consisted of supportive measures, transfusions, and hematopoietic growth factors (granulocyte-macrophage colony-stimulating factor and interleukin-3). Hematopoietic recovery occurred slowly. Granulocytes were detectable throughout the postexposure period, exceeding 0.5 x 10(9)/L by day 37. There was slower and incomplete recovery of red blood cells and platelets. Increases in blood cell production were paralleled by morphologic changes in bone marrow biopsies. Gastrointestinal toxicity was moderate. Death from a probable radiation pneumonitis infection occurred on day 130. These data indicate the possibility of hematopoietic recovery after approximately 10 Gy or more acute total body radiation without a transplant. They also suggest that lung rather than gastrointestinal toxicity may be dose-limiting under these circumstances.     

Fractional hepatic extraction of insulin in man: is it constant?

The present study was designed to compare insulin extraction by the liver following oral glucose administrations of different size, in order to evaluate insulin removal by the liver in relation to the insulin exposure, and to the amount of ingested glucose. Insulin secretion by the pancreas was estimated by the measurement of peripheral C-peptide levels, and insulin extraction by the liver by the analysis of peripheral C-peptide to insulin ratios and relations. Ten healthy subjects (5 males and 5 females), aged 16 to 66 yr, with normal bw, and without family history of diabetes mellitus were investigated by means of the administration, on alternate days, of 50 and 150 g oral glucose loads. After the 150 g oral glucose load plasma glucose levels were significantly higher than after the 50 g oral glucose administration: glucose incremental areas of 1.45 +/- 0.12 vs. 0.55 +/- 0.04 mmol/l X min, respectively (p less than 0.001). Similarly, insulin concentrations were significantly higher following 150 g than after 50 g glucose ingestion: insulin incremental areas of 0.52 +/- 0.09 vs. 0.20 +/- 0.04 nmol/l X min (p less than 0.001). Also C-peptide levels were higher after 150 vs. 50 g oral glucose load: C-peptide incremental areas of 1.85 +/- 0.41 vs. 0.64 +/- 0.13 nmol/l X min (p less than 0.01). C-peptide to insulin molar ratios were similar during the two glucose challenge, and averaged 5.25 +/- 0.42 vs. 5.08 +/- 0.50 after 50 and 150 g oral glucose loads, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)