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Biomedical subjects

R L Prior

Publications and source records attributed to R L Prior.

At least 73 records · Page 4Linked to original sources
PubMed1983

Lipogenesis and adipose tissue cellularity in steers switched from alfalfa hay to high concentrate diets.

An experiment was conducted to 1) evaluate the effects of diet (alfalfa hay vs high concentrate) on adipose tissue cellularity and rates of in vitro lipogenesis and 2) determine if there was a relationship between in vitro lipogenic rates from acetate and lactate and rates of L- or D-lactate disappearance from plasma. Number of adipose cells/g of tissue decreased with time on experiment; however, hay-fed steers had fewer, but larger cells/g of subcutaneous adipose tissue compared with concentrate-fed steers (.78 +/- .04 vs 1.20 +/- .13 X 10(-6)/g, respectively). These results, however, are likely due to a higher (approximately 25%) intake of dry matter and metabolizable energy by the hay-fed steers. Carcass data obtained at slaughter (460 kg) indicated that the concentrate-fed steers had as much or more adipose tissue compared with the hay-fed steers. Characteristics describing D- or L-lactate disappearance from plasma were not highly correlated with lactate utilization for fatty acid synthesis. Utilization of acetate as a substrate for fatty acid synthesis in vitro was correlated (r = .64) with the rate of lactate utilization for fatty acid synthesis.

Acetates↗
PubMed1983

Plasma clearance of L- and D-lactate in steers fed alfalfa hay or high concentrate diets.

Experiments were conducted with 40 steers to evaluate the effects of diet (alfalfa hay vs high concentrate) on the rates of elimination of D- and L-lactate from plasma. Plasma L- and D-lactate clearance rates were determined before (Period I) and 114 d after (Period II) an abrupt switch from the alfalfa hay to the high concentrate diet. One group of steers received the hay diet throughout the experiment. Diet or period did not alter the rate of disappearance of L-lactate from plasma; the half-life was 13.5 to 15.5 min. D-lactate disappearance from plasma followed an exponential decay curve with at least two components; however, diet or period did not alter the calculated rates of disappearance. The half-life of the first component was 9 to 28 min and the second component was 207 min. Characteristics describing D- or L-lactate metabolism were not highly correlated with lactate utilization for fatty acid synthesis. These data demonstrate that, in steers adapted to a high concentrate diet consuming 18.2 Mcal ME X head-1 X d-1, clearance of D(-)- or L(+)-lactate is not different from that in steers fed alfalfa hay consuming 23.1 Mcal ME X head-1 X d-1.

Animals↗
PubMed1982

The effect of 3-mercaptopicolinic acid and substrate interactions on the incorporation of lipogenic precursors into glyceride-glycerol, glyceride-fatty acids and nonesterified fatty acids in bovine adipose tissue.

The effects of 3-mercaptopicolinic acid, an inhibitor of phosphoenolpyruvate carboxykinase, were studied in bovine subcutaneous adipose tissue slices in vitro. Lactate and glucose stimulated the incorporation of [U-14C]acetate into total lipids and nonesterified fatty acids. 3-Mercaptopicolinic acid abolished the stimulatory effect of lactate on total synthesis but had no effect on that from glucose. The inhibitor decreased glyceride-glycerol and glyceride-fatty acid synthesis from L-[U-14C]lactate by 90 and 30%, respectively; glyceride-glycerol synthesis from D-[U-14C]glucose was refractory to inhibition by 3-mercaptopicolinic acid, whereas the inhibitor tended to increase glyceride-fatty acid synthesis from glucose. The presence of lactate plus glucose in the incubation media elicited a greater than additive stimulation of acetate incorporation into total lipids. Glucose doubled the incorporation of lactate into glyceride-fatty acids, but had no effect on the net incorporation of lactate into nonesterified fatty acids. Lactate, but not glucose, stimulated the incorporation of [1-14C]palmitate into glyceride-fatty acids; 3-mercaptopicolinic acid increased this rate for all substrate combinations studied, although this was opposite to expected results. As determined with 3H2O, lactate and glucose stimulated the synthesis of total lipids, and 3-mercaptopicolinic acid decreased the stimulatory effects of lactate and glucose on 3H2O incorporation. The results suggest that lactate, and possibly glucose, stimulate the incorporation of acetate into fatty acids by increasing the availability of alpha-glycerophosphate.

Adipose Tissue↗
PubMed1982

Mineral accretion during prenatal growth of cattle.

Angus, Hereford and Red Poll crossbred yearling heifers (n = 81) were mated to Brown Swiss bulls. Pregnant heifers were assigned on the bases of weight and breed cross to one of three diets and fed to achieve maternal weight gains of 0, .5 or 1.0 kg/d. Heifers from each treatment group were slaughtered at about 120, 150, 180, 210, 240, or 255 d postmating. Reproductive tracts were recovered at slaughter. Weights of the gravid uterus, fetus, fetal membranes, fetal fluids, uterus, cotyledons and placenta were obtained and have been reported previously. Fetuses were frozen and later ground, mixed and sampled. Dry matter was determined. Samples of each fetus were ashed, and concentrations of Ca, P, Na, K, Mg, Fe and Zn were determined. Relationships between total fetal content of each mineral and day postmating were obtained, and daily fetal accretion rates of each mineral were estimated for several stages of gestation. Daily requirements and allowances of each mineral for pregnancy in beef cows were estimated. Estimated allowances for Ca, P, Na, K, Fe and Zn were small during early gestation but increased rapidly and reached maxima of 8.4 g, 5.2 g, .76 g, .63 g, 65 mg and 21 mg, respectively, at about 250 d postmating.

Animals↗
PubMed1982

Hormonal effects on partitioning of nutrients for tissue growth: role of insulin.

Understanding factors that potentially regulate pathways of nutrient utilization is essential to the development of means of manipulating tissue growth to optimize the type and quality of product produced. Insulin is one hormone that has pronounced effects on carbohydrate and protein metabolism. Relative to most monogastric animals, ruminants absorb little glucose directly from the gastrointestinal tract. Therefore, it might be expected that insulin would have a less important role in regulating glucose and carbohydrate metabolism in the ruminant animal. Effects of insulin on lipogenesis and lipolysis both in vitro and in vivo in the ruminant appear to be small. Insulin may promote lipid deposition by increasing adipocyte membrane permeability to glucose with subsequent metabolism to alpha-glycerolphosphoric acid and thereby stimulating fatty acid esterification. Insulin also stimulates adipose lipoprotein lipase, which would increase the supply of fatty acids for esterification in adipose tissue. Insulin appears to indirectly alter hepatic glucose production by decreasing the release of gluconeogenic precursors from peripheral tissues. The known effects of insulin on lipid and carbohydrate metabolism have tended to direct attention away from protein metabolism, a process on which insulin may have a more significant role in the ruminant. Insulin or insulin and glucose have marked effects on regulating plasma levels of branched-chain amino acids, presumably by promoting their uptake or by decreasing their catabolism by muscle tissue. More information is needed to fully understand the role of insulin in regulating muscle protein metabolism.

Adipose Tissue↗
PubMed1982

Gluconeogenesis in the ruminant fetus: evaluation of conflicting evidence from radiotracer and other experimental techniques.

Conflicting evidence exists as to whether the gluconeogenetic process is active in the late gestation fetal lamb. In vitro evidence based on measurements of enzyme activity and substrate flux into glucose indicates that the capacity for gluconeogenesis exists in fetal liver. The in vivo conversion of [14C]lactate and [14C]alanine into glucose in the lamb fetus has been demonstrated. Lactate and alanine account for 49 and 2.3% of the fetal glucose pool, respectively. Although gluconeogenesis can occur in the fetal lamb, alterations in net rates of umbilical uptake of glucose or lactate, fetal blood glucose concentrations, fetal or maternal glucose replacement rates, or maternal nutrition may alter the observed rates of fetal gluconeogenesis.

Animals↗
PubMed1981

Influence of diet on amino acid absorption in beef cattle and sheep.

Six sheep and three steers were fed pelleted alfalfa hay prior to and during the first blood sampling period (BSP) and then switched to an 85% concentrate (HC) diet at least 28 days before a second BSP. Portal plasma flow rates were higher in steers than sheep (7.9 versus 5.0 liters/hr per kg0.75). With HC feeding, sheep and cattle had higher plasma femoral arterial concentrations of glycine and 3-methylhistidine and lower concentrations of valine and isoleucine than when fed hay. When fed HC diets, sheep, but not cattle, had lower glutamate and histidine and higher serine concentrations than when fed hay. Sheep had higher concentrations of aspartate, asparagine, threonine, glycine, tyrosine, phenylalanine, valine, leucine, citrulline, arginine, lysine, 3-methylhistidine and histidine than cattle. Diet did not affect the portal venous-arterial concentration difference or the net portal amino acid appearance (NPAAA) rate of any of the amino acids in sheep or cattle. With sheep, there was a tendency for the NPAAA rate to be higher for all amino acids, except aspartate, with HC compared to hay feeding. Expressed on the basis of metabolic body size, NPAAA rate was qualitatively and quantitatively similar between sheep and cattle.

Absorption↗
PubMed1981

Glucose and lactate absorption and metabolic interrelationships in steers changed from low to high concentrate diets.

Cannulas were surgically implanted in the portal and mesenteric veins and femoral artery of eight crossbred steers averaging 270 kg. They were given primed, continuous 3-hour infusions of U-[14C]-L-lactate and 2-[3H]- or 6-[3H]-glucose into the jugular vein and para-aminohippuric acid (portal blood flow indicator) into the mesenteric vein before and after being changed from a pelleted alfalfa hay to a pelleted 85% concentrate diet. Blood samples were collected at 20-minute intervals during infusions. Reliable blood flow data were obtained on four of the eight steers during the first infusion; the other four were not infused the second time. Dry matter intake, portal blood flow, net portal D-lactate absorption (P less than 0.10), net portal glucose absorption and L-lactate turnover rate (P less than 0.10) increased as a result of increased concentrate (energy) intake. Glucose turnover rate (P less than 0.10), L-lactate absorbed as a percentage of turnover rate, L-lactate converted to glucose and glucose derived from L-lactate concomitantly decreased. Net portal L-lactate absorption was not affected. The direction of the response for portal blood flow, net portal D-lactate absorption, net portal glucose absorption, L-lactate turnover and L-lactate absorbed as a percentage of turnover was the same as that previously observed in lambs under similar experimental protocol. Differences in responses between lambs and steers for glucose turnover and L-lactate converted to glucose may be attributable to differences in dry matter or energy intake or both.

Absorption↗
PubMed1980

Effects of intravenous infusions of glucose, lactate, propionate or acetate on the induction of lipogenesis in bovine adipose tissue.

Crossbred steers (seven to nine per treatment) fed a pelleted alfalfa hay diet were biopsied (preinfusion) to obtain subcutaneous adipose tissue (SAT). Five days later a continuous intravenous infusion was begun of either 0.9% NaCl, glucose (2.75 moles/day), DL-lactate (5.5 moles/day of L-lactate), propionate (5.5 moles/day) or acetate (8.25 moles/day); after infusion for 14 days, a second biopsy sample of SAT was obtained. Glucose and DL-lactate infusion increased acetyl-CoA carboxylase activity about 12-fold compared to preinfusion activity of 5.3 +/- 4.2 nmoles/minute/g of wet weight. Glucose infusion induced activities of fatty acid synthetase (2.6 fold) and NADP+-malate dehydrogenase (7-fold) relative to preinfusion activities of 26.8 +/- 5.2 and 30.3 +/- 15.5 nmoles/minute/g of wet weight, respectively. Glucose, DL-lactate and propionate infusion increased NADP-isocitrate dehydrogenase activity 20-30% compared to preinfusion activity. Activity of NAD-malate dehydrogenase was not altered by any infusion treatment (P > 0.05). Activity of ATP-citrate lyase was decreased 48% by lactate infusion. Glucose, lactate and propionate infusion increased the rates of lactate and glucose incorporation into fatty acids in SAT incubated in vitro three to fourfold over preinfusion incorporation rates. Increased availability of glucose or gluconeogenic precursors may be responsible for induction of lipogenesis in steers fed high concentrate diets.

Acetates↗
PubMed1980

Glucose and lactate absorption and metabolic interrelationships in lambs switched from low to high concentrate diets.

Two experiments were conducted to measure glucose and lactate absorption and metabolic interrelationships in lambs either switched gradually (experiment 1) or abruptly (experiment 2) from hay to a high concentrate diet. In experiment 1, seven lambs were given primed, continuous, 3-hour infusions of 2-0[3H]glucose, U-[14C]L-lactate and para-aminohippuric acid (portal blood flow indicator) before and after switching from a pelleted hay to a pelleted, 85% concentrate diet. Blood samples were collected at 20-minute intervals during infusions. In experiment 2, four lambs were abruptly switched from a pelleted hay to an all-concentrate diet. Portal and arterial blood samples were collected before and up to 1 week after the diet switch. As a result of increased concentrate intake (experiment 1) net portal absorption and turnover of L-lactate and glucose increased. Percentage of glucose derived from L-lactate decreased. Net portal D-lactate absorption, L-lactate absorption as a percentage of turnover and conversion of L-lactate to glucose were not affected by diet. Lambs in experiment 2 did not become acutely acidotic. The insult to acid-base status peaked 12-16 hours after the diet switch, concurrent with maximum arterio-venous differences in plasma L-lactate and glucose. Arterio venous differences in plasma D-lactate were not significantly affected.

Absorption↗
PubMed1980

Glucose and lactate metabolism in vivo in ovine fetus.

The metabolism of glucose and lactate by the ovine fetus (123-128 days of gestation) was studied; a primed, continuous infusion of [2-3H]glucose and [U-14C]lactate into the brachial vein of six fetuses was used. Fetal plasma lactate concentrations averaged 2.12 +/- 0.25 mM and glucose concentrations averaged 9.3 +/- 1.3 mg/100 ml. Total plasma turnover of lactate was 5.22 +/- 0.7 nmol/h and that of glucose was 3.48 +/- 0.63 nmol x h-1 x kg fetal weight-1. Lactate was converted to glucose at a rate of 1.35 +/- 0.64 mmol x h-1 x kg fetal weight-1, which represented 21.6 +/- 6.0% of the lactate turnover. The percentage of glucose coming from lactate was 48.9 +/- 15.2. The specific activity of maternal plasma glucose was less than 4% of the specific activity of glucose observed in fetal plasma. No radioactivity could be detected in maternal plasma lactate. The data show that the ovine fetus or the fetal-placental unit can convert lactate to glucose by days 123-128 of gestation. A general model presented describes carbohydrate metabolism in the ovine placenta and fetus.

Animals↗