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Biomedical subjects

G Williams

Publications and source records attributed to G Williams.

At least 937 records · Page 52Linked to original sources
PubMed1965

Lithocholic acid in human-blood serum.

Lithocholic acid was present in the serum of three patients with, jaundice and, in smaller amounts, in two healthy adults. This bile acid occurs naturally in human feces but induces cirrhosis of the liver when fed to a wide variety of experimental animals. The finding of lithocholic acid in blood is of interest because of its possible role in injuring human liver.

Bile Acids and Salts↗
PubMedDate not supplied

Oestrone sulphate measurement in bovine serum during late pregnancy and its relationship with the number of calves born.

A radioimmunoassay developed for the measurement of oestrone sulphate in bovine serum was used to determine levels of hormone in cows. The cows were sampled as part of an embryo transfer programme designed to investigate the production of twin calves. The concentration of oestrone sulphate in serum was higher in cows carrying twin calves, but the difference did not become significant until around 220 days' gestation. The predictive value of the test could be used as a guide to increase feeding of cows pregnant with more than one calf.

Animals↗
PubMedDate not supplied

Proton NMR studies of two helices in tuna ferricytochrome c.

1H Nuclear magnetic resonance assignments are given for the NH and C alpha H protons of two alpha-helical segments of tuna ferricytochrome c. The assignments were obtained using two-dimensional nuclear magnetic resonance sequential assignment procedures and illustrate the applicability of these methods to medium-sized proteins. By comparing nuclear Overhauser intensities between the NH and C alpha H protons the precise structures of the two helical segments are compared and their deviations from ideality are discussed.

Animals↗
PubMedDate not supplied

Pancreastatin distribution and plasma levels in the pig.

Pancreastatin is a peptide isolated from porcine pancreas which has insulin-suppressive actions in vitro and sequence homology with chromogranin A. Using radioimmunoassay and immunocytochemistry we investigated whether pancreastatin has a more widespread distribution and a possible endocrine role in the pig. Pancreastatin immunoreactivity was found in plasma, adrenal gland, pancreas, anterior pituitary and throughout the gastrointestinal tract. The immunoreactivity was colocalized with chromogranin immunoreactivity in endocrine cells and ultrastructurally (in the pancreas) to storage granules. Characterization of pancreastatin-like immunoreactivity, using gel permeation and high performance liquid chromatography, separated 3 different pancreastatin-like immunoreactive forms: one molecular form, indistinguishable from synthetic pancreastatin 1-49, was predominant in pancreas and thyroid and released into the circulation postprandially. However, a high dose (greater than 1 nmol/l) infusion of pancreastatin 33-49 (the biologically active moiety in vitro) into conscious pigs had no effect on either basal or glucose-stimulated insulin secretion.

Adrenal Glands↗
PubMedDate not supplied

Acute fenfluramine administration reduces neuropeptide Y concentrations in specific hypothalamic regions of the rat: possible implications for the anorectic effect of fenfluramine.

Neuropeptide Y (NPY), a powerful central appetite stimulant, coexists in several hypothalamic areas with serotonin, which suppresses feeding. This study investigated the effect of acute administration of the serotonergic drug, fenfluramine, on NPY concentrations in microdissected hypothalamic nuclei. Adult male Wistar rats were given fenfluramine (10 mg/kg, n = 7) or saline (n = 7), intraperitoneally 1 h before darkness. Food was presented immediately before darkness and the rats were killed during the first 4 h of darkness. Fenfluramine injection significantly reduced food intake. In fenfluramine-injected animals, NPY levels in the ventromedial and dorsomedial nuclei and in the lateral hypothalamic and lateral preoptic areas were significantly lower than in saline-injected controls. The ventromedial and dorsomedial nuclei and the lateral hypothalamic area are sites which mediate the hyperphagic action of centrally injected NPY. Selective NPY changes in specific nuclei after fenfluramine injection suggest functional interaction between NPYergic and serotonergic systems, and may indicate that NPY is involved in mediating the anorectic effect of serotonergic agents.

Animals↗
PubMedDate not supplied

Unchanged hypothalamic neuropeptide Y concentrations in hyperphagic, hypoglycemic rats: evidence for specific metabolic regulation of hypothalamic NPY.

Hypothalamic concentrations of neuropeptide Y (NPY), a potent central appetite stimulant, increase dramatically in food-restricted and insulin-deficient diabetic rats. This suggest that NPY may drive hyperphagia in these conditions, which are characterized by weight loss and insulin deficiency. To test the hypothesis that insulin deficiency and weight loss are specific stimuli to hypothalamic NPY, we measured NPY concentrations in individual hypothalamic regions in rats with hyperphagia caused by insulin-induced hypoglycemia. Groups of 8 male Wistar rats were injected with ultralente insulin (20-60 U/kg) to induce either acute hypoglycemia (7 h after a single injection) or chronic hypoglycemia (8 days with daily injections). In hypoglycemic rats, plasma insulin concentrations were increased 6- to 7-fold compared with saline-injected controls; food intake was significantly increased with acute and chronic hypoglycemia and weight gain was significantly increased in the chronically hypoglycemic group. NPY concentrations were measured by radioimmunoassay in 8 hypothalamic regions microdissected from fresh brain slices. NPY concentrations were not increased in any region in either acute or chronic hypoglycemia. NPY therefore seems unlikely to mediate hyperphagia in hyperinsulinemia-induced hypoglycemia, supporting the hypothesis that weight loss is a specific stimulus to hypothalamic NPY and that insulin deficiency may be the metabolic signal responsible.

Animals↗
PubMedDate not supplied

Peripheral insulin administration attenuates the increase in neuropeptide Y concentrations in the hypothalamic arcuate nucleus of fasted rats.

Fasting increases neuropeptide Y (NPY) concentrations in the arcuate nucleus (ARC), its site of synthesis, and in other regions of the rat hypothalamus. Neuropeptide Y is a potent central orexigenic agent and may therefore stimulate appetite during fasting. We tested the hypothesis that low plasma insulin levels stimulate ARC levels of NPY in fasted rats. Compared with freely fed controls (n = 8), rats fasted for 72 h (n = 8) showed significantly lower plasma insulin levels (28.9 +/- 1.6 vs. 52.6 +/- 5.7 pmol/l; p < 0.001) and higher ARC NPY concentrations (14.2 +/- 1.8 vs. 8.4 +/- 2.2 fmol/micrograms protein; p < 0.001). Fasted rats treated with subcutaneous insulin (5 U/kg/day; n = 10), which nearly normalized plasma insulin (46.6 +/- 2.8 pmol/l), showed intermediate ARC NPY levels (11.2 +/- 1.4 fmol/micrograms protein; p < 0.01 vs. controls and untreated fasted rats). Insulin administered peripherally, therefore, attenuates fasting-induced NPY increases in the ARC, supporting the hypothesis that hypoinsulinemia stimulates hypothalamic NPY.

Animals↗
PubMedDate not supplied

Hypothalamic neuropeptide Y disturbances in the obese (cp/cp) JCR:LA corpulent rat.

Regional hypothalamic neuropeptide Y (NPY) concentrations were compared between cp/cp JCR:LA corpulent rats, which were grossly obese, hyperphagic, and hyperinsulinemic, and lean (+/+) controls. In freely fed cp/cp rats, NPY levels in the arcuate nucleus (ARC) were 31% higher than in lean rats (p less than 0.001). In lean rats, chronic food restriction significantly raised NPY levels by 22% in the ARC (p less than 0.05) and by 44% in the dorsomedial nucleus (DMH; p less than 0.05). By contrast, food-restricted cp/cp rats showed no change in the ARC, but NPY levels rose in the DMH (by 36%; p less than 0.05) and ventromedial nucleus (31%; p less than 0.05). Increased NPY levels in the ARC, the major site of hypothalamic NPY synthesis, suggests increased NPYergic activity in cp/cp rats; given the central actions of NPY, this could contribute to hyperphagia, obesity, and hyperinsulinemia in this syndrome. Abnormal NPY responses to food deprivation further suggest dysregulation of NPY in cp/cp rats.

Animals↗