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Biomedical subjects

H F Chou

Publications and source records attributed to H F Chou.

25 records · Page 2Linked to original sources
PubMed1988

Influence of age, strain, and beta-adrenergic agonist on insulin sensitivity in chicks as determined by an adaptation of the euglycemic clamp technique.

The euglycemic clamp technique has been widely used to examine changes in in vivo insulin sensitivity during physiological changes in mammals. The technique offers the advantage that the tissue uptake of glucose induced by a set dose of insulin is determined at the normal (steady state) circulating concentration of glucose (euglycemia). The euglycemic clamp technique has been modified to examine in vivo sensitivity to insulin in chickens. Insulin sensitivity is determined by the rate of infusion of exogenous glucose required to maintain euglycemia. Young (6 to 8-wk-old) male chickens (White Leghorn) are more sensitive to insulin than adult males of the same strain. There is, however, no difference in insulin sensitivity between young male chicks of broiler and White Leghorn strains. Chronic administration of beta-adrenergic agonist (L-640,033, donated by Merck, Sharp, and Dohme Research Laboratories, Rahway, NJ) in the diet, at levels of 0, .25, 1.0, and 4.0 ppm for 3 to 5 days also did not influence in vivo insulin sensitivity.

Adrenergic beta-Agonists↗
PubMed1988

Effect of gangliosides on primary and secondary plaque-forming cells responses and on suppressor T-cells induction.

This study was designed to determine the suppressive effect of bovine brain gangliosides on primary and secondary anti-sheep red blood cell (SRBC) plaque-forming cells (PFC) response. Spleen cells from inbred C57BL/6J mice were used as sources of lymphocytes. The result showed that levels of gangliosides at 50 and 100 micrograms/ml suppressed primary anti-SRBC PFC responses about 30% and 60%, respectively, of normal control. In contrast, secondary anti-SRBC PFC were not suppressed by the same levels of gangliosides. Likewise, PFC response from mixing SRBC-primed T-cells with naive B-cells was not suppressed by gangliosides. In addition, induction of suppressor T-cells was reduced by 50 and 100 micrograms/ml of gangliosides, 57% and 63%, respectively, versus 86% of suppression of PFC response by the control suppressor T-cells. These results further suggest the role of gangliosides as immunomodulators.

Animals↗
PubMed1987

Luteinizing hormone secretion from anterior pituitary cells of the cockerel: evidence for an ultradian rhythm.

Studies were conducted to characterize the secretory pattern of luteinizing hormone (LH) from perfused anterior pituitary cells of the cockerel in the presence and absence of secretagogues. Basal LH secretion was found to occur in a rhythmic pattern, with the mean cycle period for 5 different perfusion columns estimated to be 66.4 +/- 4.0 min. By contrast, when cells were repeatedly exposed to luteinizing hormone-releasing hormone (LHRH) at 90-min intervals, the period of the LH rhythm was altered to approximate the interval of LHRH pulses (96.7 +/- 6.1 min; n = 3 perfusion columns). Exposure of cells to media containing 50 mM potassium chloride (KCl) augmented the release of LH and slightly decreased the cycle period compared to that which occurs during basal secretion (49.2 min) but did not eliminate the rhythm. Finally, perifusion of cells with medium containing 10 microM colchicine eliminated the rhythm of secretion. These data suggest that there exists an ultradian rhythm of LH secretion from the chicken pituitary which is expressed in the absence of hypothalamic input and is modified by the hypothalamic releasing factor, LHRH. In addition, the rhythm does not seem to be affected in the short-term by a small depolarization of the membrane as occurs with the addition of KCl to the perifusion media but does seem to be dependent upon microtubule function.

Activity Cycles↗
PubMed1985

Luteinizing hormone releasing activity of [Gln8]-LHRH and [His5, Trp7, Tyr8]-LHRH in the cockerel, in vivo and in vitro.

The luteinizing hormone (LH)-releasing activity of two distinct chicken luteinizing hormone releasing hormones ([Gln8]-LHRH and [His5, Trp7, Tyr8]-LHRH) were evaluated in white Leghorn cockerels. In the first study, thirty birds were randomly allotted to five groups and injected, i.v., with 0.9% saline, [Gln8]-LHRH (cLHRH I, 1 microM or 10 microM) or [His5, Trp7, Tyr8]-LHRH, (cLHRH II; 1 microM or 10 microM). Blood samples were drawn prior to and through 60 min following the injection, and plasma was collected for LH determination. In the second study, anterior pituitary cells from cockerels were dispersed and preincubated for 1 hr. Approximately 1.5 X 10(5) cells per tube were incubated with either Medium 199 buffer (control), 8-bromo-cAMP or various doses of cLHRH I or cLHRH II at final concentrations ranging from 0.02 to 100.0 nM. At the end of a two hour incubation, supernatant was collected and the concentration of LH determined. Injection of cLHRH I or cLHRH II at 1 microM and 10 microM levels caused a significant increase in blood LH concentrations which peaked 5 min following injection. There were, however, no differences between the stimulatory effect of cLHRH I compared to cLHRH II at either dose. On the other hand, cLHRH II was found to be 4.7 times more potent than cLHRH I in stimulating LH release from dispersed pituitary cells. It is suggested that cLHRH II may have greater affinity for the gonadotroph receptor, greater uptake by the cell, and/or that it may be more resistant to in vitro degradation than cLHRH I. On the other hand, an extra pituitary site of degradation may be more effective in metabolizing cLHRH II, resulting in its equipotency with cLHRH I, in vivo.

Animals↗
PubMed1979

Intestinal calcium absorption and bone morphology in magnesium deficient chicks.

Calcium absorption was measured by 47Ca disappearance from ligated duodenal loops and 47Ca uptake by tibiae in chicks fed diets containing one of four levels of Mg for two weeks. The diets, otherwise identical, contained 88 (group 1), 150 (group 2), 200 (group 3) and 1000 (group 4) ppm Mg. There were no statistically significant differences in 47Ca absorption. Mucosal CaBP and intestinal alkaline phosphatase were slightly, but not significantly, elevated in the Mg depleted chicks in groups 1 and 2 compared to groups 3 and 4. Microscopic examination of the tibiae showed marked alterations in morphology in chicks fed the 88 ppm Mg diet. The thickness of the epiphyseal plate was reduced, and the morphologic signs of osteolysis and chondrolysis, normally observed in the metaphysis, appeared to be absent. The mid-diaphysis was thickened and showed marked reduction in both osteoblast and osteocytie activity. Blood calcium levels were significantly reduced in the Mg deficient chicks. It was concluded that Mg depletion in chicks altered Ca homeostasis primarily by changing bone structure and function.

Alkaline Phosphatase↗