Biomedical subjects

F R Dunshea

Publications and source records attributed to F R Dunshea.

42 records · Page 3Linked to original sources

PubMed1992

Effect of porcine somatotropin on in vivo glucose kinetics and lipogenesis in growing pigs.

Crossbred barrows were used for in vivo studies investigating hormonal regulation of lipogenesis. The first experiment examined an in vivo method for determining rates of lipogenesis. Three barrows were infused with [U-14C]glucose and incorporation of radioactivity into triglycerides was determined in up to five biopsies of subcutaneous adipose tissue obtained over 7 h. Incorporation was linear after blood glucose specific radioactivity had reached a plateau and was constant over the entire infusion. For the second experiment, eight pigs (71 +/- 2.5 kg) were allocated to one of two treatments involving daily injections of excipient (control) or porcine somatotropin (pST; 120 micrograms/kg of BW). On d 10, beginning 15 h after injection, glucose incorporation into adipose tissue lipid was determined under both basal and hyperinsulinemic/euglycemic conditions. Basal glucose incorporation into lipid, particularly fatty acids, was markedly reduced (greater than 90%) during pST treatment. Although glucose incorporation was increased to a similar extent in both groups by hyperinsulinemia, the pST-treated pigs still exhibited markedly lower rates. Based on kinetic data, the decrease in lipid accretion of pST-treated pigs was primarily the result of a decrease in the rate of de novo synthesis. Furthermore, the reductions in glucose incorporation into fatty acids, glucose irreversible loss rate, and feed intake that occur with pST treatment were quantitatively similar.

Adipose Tissue↗

PubMed1990

Body composition changes in goats during early lactation estimated using a two-pool model of tritiated water kinetics.

A two-pool model of tritiated water kinetics was used to estimate the major body water pools, and hence body composition, in goats at days 10, 38 and 76 of lactation. Between days 10 and 38 of lactation goats were, on average, in negative calculated energy balance and were estimated to have mobilized 59 g body fat stores/d. Mean calculated energy balance over days 38-76 of lactation was slightly positive and there was little change in estimated body fat. Gut fill increased over the early part of lactation when goats were mobilizing body fat. Consequently, live weight did not differ at any stage of lactation and did not provide a good index of body fat status of the goats. There were also no significant differences in empty-body-weight, water, protein, ash or fat-free mass at the three stages of lactation. As average calculated energy balance and changes in energy stored as fat were highly correlated, it is concluded that the two-pool model of tritiated water kinetics is a useful means of serially estimating changes in body fat content in unfasted lactating goats.

Animals↗

PubMed1990

Non-esterified fatty acid and glycerol kinetics and fatty acid re-esterification in goats during early lactation.

Non-esterified fatty acid (NEFA) and glycerol kinetics were studied in lactating goats to gain insight into the mechanisms by which animals in early lactation can initially mobilize and later replenish body fat reserves. Kinetic measurements were made at days 10, 38 and 76 post-partum in ten multiparous lactating does. Plasma NEFA concentrations and NEFA entry rate decreased as lactation advanced, being significantly higher at day 10 than at either days 38 or 76 of lactation. Both plasma NEFA concentrations and NEFA entry rate were negatively correlated with calculated energy balance. In contrast, glycerol entry rate was significantly higher at day 76 than at day 10 of lactation and was positively related to both calculated energy intake and energy balance. Apparent intracellular fatty acid re-esterification was lower at day 10 than at later stages of lactation and was positively related to calculated energy balance. It is suggested that during early lactation, substantial shifts in adipose tissue fat reserves can occur via altering rates of fatty acid re-esterification and de novo lipogenesis, without major changes in the rate of lipolysis.

Animals↗

PubMed1990

Somatotropin in lactating cows: effect on response to epinephrine and insulin.

The dose dependence of plasma nonesterified fatty acids (NEFA) and glycerol responses to epinephrine was determined in lactating cows treated with bovine somatotropin (bST). Also, the effects of insulin on lipolysis and glucose clearance were examined. Lactating cows (190 +/- 24 days postpartum) received daily subcutaneous injections of methionyl bST (40 mg) or excipient during two 12-day treatment periods. Epinephrine challenges (0.1, 0.2, 0.4, 0.8, 1.2, and 1.6 micrograms/kg body wt) were administered intravenously on days 6-11 and an insulin challenge (1 microgram/kg) on day 12. Milk energy secretion increased 55% without any change in voluntary feed intake during bST treatment. Circulating concentrations of NEFA were chronically elevated and reciprocally paralleled changes in net energy balance. Maximal response of plasma NEFA and glycerol to epinephrine was markedly increased during bST treatment, whereas the dose of signal-producing half-maximal response (ED50) was unchanged. Antilipolytic effects of insulin were also enhanced, whereas the effect of insulin on the fractional rate of glucose change was reduced. Thus bST alters tissue response to homeostatic signals to allow more nutrients to be partitioned for milk synthesis. Furthermore, the alterations in response to epinephrine and insulin appear to predominantly occur at a postreceptor level.

Animals↗

PubMed1989

Relations between plasma non-esterified fatty acid metabolism and body fat mobilization in primiparous lactating goats.

During early lactation ruminants can mobilize considerable amounts of body fat to maintain milk production. The aim of the present study was to evaluate the efficacy of tritiated water (TOH) and non-esterified fatty acid (NEFA) kinetics as means of monitoring adipose tissue fat mobilization in lactating goats. Body fat, as estimated by a two-pool model of TOH kinetics, and NEFA entry rate were measured in four primiparous goats at days 11, 37 and 72 post partum. Estimated body fat decreased by an average of 64 g/d between days 11 and 37 of lactation, tending to increase between days 37 and 72. Plasma NEFA concentrations and NEFA entry rate decreased as lactation advanced, being significantly lower at day 72 than at day 11 of lactation. Both plasma concentrations of NEFA and NEFA entry rate were negatively correlated with calculated energy balance. Plasma NEFA concentrations and NEFA entry rate at days 11 and 37 of lactation were positively related to average body fat losses over the subsequent stage of lactation. These results demonstrate that NEFA kinetics reflect fat mobilization in primiparous lactating goats, particularly during negative energy balance.

Adipose Tissue↗

PubMed1988

Relations between plasma non-esterified fatty acid metabolism and body tissue mobilization during chronic undernutrition in goats.

1. Eleven mature goats were offered 140 kJ metabolizable energy/kg per d (M) of lucerne (Medicago sativa) hay-oaten grain (1:1, w/w) for at least 1 month before plasma non-esterified fatty acid (NEFA) kinetics and tritiated water space (TS) were determined. 2. Goats were then fed at M, 0.5 M or 0.25 M for 34 (SE 6) d, at which time the experimental procedures were repeated. 3. Chronic undernutrition resulted in elevated NEFA concentrations and NEFA entry rate, with a tendency for the ratio plasma NEFA:glycerol to increase, suggesting that body-fat mobilization during prolonged underfeeding is due more to decreased lipogenesis and intracellular NEFA re-esterification rather than to increased lipolysis. 4. Plasma NEFA concentrations and NEFA entry rate, as well as being highly correlated with each other, were significantly related to calculated energy balance and body fat losses estimated from changes in live weight and TS. 5. Increases in NEFA entry rate were highly correlated with, and of the same magnitude as, body fat losses, confirming that NEFA kinetics do quantitatively reflect lipid mobilization.

Animals↗