Hormonal dependence of DNA synthesis in mammary carcinoma cells in vitro.

Explants of C3H-mouse and rat R3230AC mammary carcinomas were cultured on chemically defined medium for study of the effects of the hormonal environment on synthesis of DNA. Synthesis in the more slowly proliferating C3H carcinoma cells is stimulated by insulin and inhibited by estrogenic hormones as in normal mammary epithelial cells. Rat R3230AC mammary carcinoma cells can initiate synthesis of DNA independently of insulin or estrogenic hormones. Autonomous growth with respect to these hormonal controls correlates with rapid proliferation, but it is not an essential characteristic of the neoplastic mammary cell.

Lactose synthetase: progesterone inhibition of the induction of alpha-lactalbumin.

Lactose synthesis in the mammary gland is dependent on the hormonally controlled synthesis of the two protein components of lactose synthetase, alpha-lactalbumin and a galactosyltransferase. Prolactin induces the synthesis of both proteins in mammary gland explants treated with insulin and hydrocortisone, but the induction kinetics cannot account for the asynchronous synthesis of the two proteins that are observed in vivo. Progesterone appears to take part in the control of lactose synthesis and acts to repress the formation of alpha-lactalbumin throughout pregnancy. At parturition, when the concentration of progesterone in the plasma decreases, the rate of alpha-lactalbumin synthesis increases.

Stimulation of human prolactin secretion by intravenous infusion of L-tryptophan.

Previous studies have demonstrated that the secretion of human prolactin is regulated primarily by factors that influence catecholamines of the hypothalamus. In an effort to identify other factors that may regulate prolactin secretion, the amino acid L-tryptophan, a precursor in the synthesis of serotonin, was infused into normal human volunteers. Intravenous infusion of L-tryptophan, 5-10 g over a 20 min period, but not equivalent amounts of 17 other amino acids, induced marked increases in serum prolactin concentrations in eight normal human volunteers. Increases of 20-200 ng/ml above the control level were observed with peak values at 20-45 min after initiation of the infusion. In addition, infusion of L-tryptophan was associated with decreases in serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyrotropin in those subjects in whom the base-line serum hormone concentration was above the lower limits of assay detectability. No consistent change was observed in serum concentrations of growth hormone, cortisol, or glucose. Four subjects with juvenile diabetes demonstrated increases in serum prolactin values comparable with those observed in healthy individuals in response to infusions of L-tryptophan. Serum prolactin values in patients with surgically induced hypopituitarism were undetectable or deficient after infusion of 10 g of L-tryptophan. In this respect, infusion of L-tryptophan was equally effective in these subjects as the standard chlorpromazine stimulation test in identifying patients with hypopituitarism, indicating that the infusion of L-tryptophan may serve as a sensitive and reliable clinical test of prolactin secretory reserve. Further studies relating to the possible mechanism of action of L-tryptophan indicated that infusion of 5-hydroxytryptophan represents a much more potent stimulus for the secretion of prolactin and that premedication with the serotonin antagonist, methysergide maleate, serves to blunt the effect of L-tryptophan on prolactin secretion. These results support the concept that the effect of L-tryptophan on the secretion of human prolactin is mediated through its conversion to serotonin and are consistent with reported experimental observations that serotonin may participate in the reciprocal regulation of prolactin and gonadotropins.

Encephalopathy induced by oral hypoglycemic drugs.

Three patients experienced severe hypoglycemic encephalopathy during oral therapy of adult-onset diabetes mellitus. Disabling residual neurological deficits were observed in two of these patients. The insidious time course of drug-induced hypoglycemia appeared to prevent patient recognition of sustained hypoglycemia. These cases indicate the need for further caution in the administration of oral hypoglycemic agents.

Secretion of insulin or connecting peptide: a predictor of insulin dependence of obese "diabetics".

Ninety obese "diabetic" patients, including 55 treated with insulin injection, were characterized by measurement of levels of insulin or connecting peptide of proinsulin (C peptide) induced during oral glucose tolerance testing. After reduction of body weight to ideal values, patients whose peak serum insulin levels were initially 64 microunits/mL or greater had reductions of blood glucose values from 227 +/- 24 to 122 +/- 10 mg/dL (fasting) and from 400 +/- 49 to 160 +/- 11 mg/dL (two hours postprandial); at C-peptide peaks of 6.0 ng/mL or greater, these blood glucose values fell from 244 +/- 30 to 118 +/- 12 mg/mL and from 400 +/- 51 to 160 +/- 16 mg/dL, respectively. Patients with peak values of less than 60 microunits/ml for insulin or less than 6.0 ng/mL for C peptide did not normalize the blood glucose concentration after weight loss. This critical level of insulin secretory reserve separating these groups was similar to that previously reported for avoidance of diabetic retinopathy and neuropathy. These results suggest that levels of insulin or C peptide induced during glucose tolerance testing distinguish between two types of hyperglycemic obesity-insulin-dependent diabetes mellitus and insulin-resistant obesity. Blood glucose levels alone did not identify these groups. Among consecutive hyperglycemic obese patients, 36% achieved normoglycemia by weight loss alone, including 33% of those previously treated with insulin injection.

Hormonal regulation of isoenzymes of N-acetyl-beta-glucosaminidase and beta-galactosidase during spermatogenesis in the rat.

Isoenzymes of beta-galactosidase and of N-acetyl-beta-glucosaminidase were assayed during development of rat testis and as a function of hormonal treatments. Isoenzyme 1 of beta-galactosidase was highest in specific activity in the 4-day-old testis, at a point when Sertoli cells and gonocytes were the predominant cell type. Beta-galactosidase II, previously shown to be associated with the sperm acrosome, was undetectable through the spermatocyte stage of development, but increased in specific activity during the formation of spermatids. The specific activities of isoenzymes I and II of N-acetyl-beta-glucosaminidase increased markedly in association with the formation of spermatogonia and spermatocytes, and then declined with the appearance of spermatids. Following hypophysectomy of rats at 26 days of age or in adulthood the specific activities of the lysosomal enzymes beta-galactosidase I and N-acetyl-beta-glucosaminidase I and II increased markedly, while the acrosomal beta-galactosidase II was undetectable. The normal patterns of isoenzyme distributed were restored completely by administration of LH and FSH or testosterone to hypophysectomized animals. These results thus demonstrate specific patterns of isoenzyme concentration during spermatogenesis. Formation of the acrosome in developing spermatids is associated with the induction of new forms of beta-galactosidase (isoenzyme II) and N-acetyl-beta-glucosaminidase (sperm isoenzyme). These molecules appear to be specialized forms which may participate in fertilization, and their induction is dependent upon the actions of gonadotropins or testosterone.

Regulation by testosterone and serum protein of DNA synthesis in the developing epididymis of the rat.

Rates of DNA synthesis were measured as an index of cellular proliferation during the pubertal development of the rat epididymis. A highly reproducible pattern of DNA synthesis was defined by (1) a prepubertal, testosterone-insensitive peak of DNA synthesis at 25 days; (2) a dramatic decrease in DNA synthesis with the onset of puberty; (3) a major burst of testosterone-dependent synthesis peaking at 40 days in the head of the epididymis and at 40-60 days in the tail; (4) a fall to low levels as the adult organ weight was attained. An organ culture system was defined and utilized to analyse further the hormonal dependence of DNA synthesis in the epididymis. Testosterone and dihydrotestosterone failed to activate DNA synthesis at any stage of development in vitro. DNA synthesis was stimulated 100-300% by insulin at supra-physiological concentrations and by protein serum factor(s) at physiological concentrations. The serum activity was stable to heat treatment at 60 degrees C, destroyed by heating at 70 degrees C, and was present in the sera of hypophysectomized animals. These results indicate a primarily 'permissive' role for the action of testerone on DNA synthesis in the epididymis: testosterone acts to permit the expression of a developmental 'programme' of cell proliferation which is activated by specific protein(s) in serum.

Reversal of severe diabetic hyperlipidemia by prandial insulinization.

Severe hyperlipidemia was nearly completely corrected in 16 diabetic patients who were treated with regular insulin at breakfast and supper. Serum cholesterol levels fell from 572 +/- 52 mg/dl to 247 +/- 10 mg/dl, and serum triglycerides fell from 6,330 +/- 820 mg/dl to 354 +/- 40 mg/dl over a 4-month period of treatment. Establishment of comparable degrees of control of the fasting blood glucose and hemoglobin A1C levels by NPH insulin did not correct the hyperlipidemia. Regular insulin timed to act for the disposal of ingested substrates appears to provide physiologic actions important in the treatment of diabetic hyperlipidemia.