Search PubMed⌕ Search

Biomedical subjects

B Borrebaek

Publications and source records attributed to B Borrebaek.

At least 19 recordsLinked to original sources
PubMed1991

Glycogen accumulation and histological changes in the livers of lambs with alveld and experimental sporidesmin intoxication.

Alveld is a hepatogenous photosensitization disease seen in lambs grazing Narthecium ossifragum pastures in Norway. Mycotoxins, possibly sporidesmin, have been suspected to cause the liver damage in alvled as in facial eczema. The histological changes in the liver of alveld cases and in lambs photosensitized after experimental sporidesmin intoxication were compared. The liver damage, characterized by necrosis in single centrilobular hepatocytes, was of the same type in both conditions. Minor to moderate portal fibroplasia and bile duct proliferation were almost always present. Accumulated glycogen was seen in hepatocytes in the centrilobular areas. This was significantly correlated to the enzymatically measured glycogen content and there was good correlation between parenchymal damage and glycogen accumulation. The glucose-6-phosphatase and glycogen phosphorylase activities were normal. These findings indicate that parenchymal damage, rather than obstruction of the bile ducts, caused the retention of phylloerythrin both in alveld cases and in experimentally sporidesmin-intoxicated lambs. The accumulation of glycogen could not be explained.

Animals↗
PubMed1991

Insulin and glucagon family peptides in relation to activities of hepatic hexokinase and other enzymes in fed and starved Atlantic salmon (Salmo salar) and cod (Gadus morhua).

1. Plasma levels of insulin, glucagon, and glucagon-like peptide (Glp) were all reduced by starvation of salmon and cod. In the salmon the drop in Glp was larger than in insulin and glucagon. 2. After starvation the activity of hexokinase (EC 2.7.1.1) was increased in salmon liver, but decreased in cod liver. The salmon hepatic hexokinase activity was inversely correlated with the Glp/insulin ratio. 3. Activities of hepatic glycogen phosphorylase (EC 2.4.1.1) and phosphofructokinase (EC 2.7.1.11) were increased in starved as compared to fed salmon. In cod, starvation resulted in decreased or unchanged activity of phosphorylase. This discrepancy may be related to different degrees of environmental and handling stress. 4. Intraperitoneal injection of human insulin in salmon gave increased hepatic phosphorylase and hexokinase activities and reduced plasma levels of glucagon, Glp and endogenous fish insulin at sampling after 30 hr. 5. No differences in hepatic hexokinase activities or plasma hormone levels were observed between cod fed low and high carbohydrate diets. Apparently, regulation of glucose phosphorylation by dietary carbohydrate does not occur.

Animals↗
PubMed1991

Glucose dehydrogenase, glucose-6-phosphate dehydrogenase and hexokinase in liver of rainbow trout (Salmo gairdneri). Effects of starvation and temperature variations.

1. Activities of trout liver glucose dehydrogenase (GDH, EC 1.1.1.47) and glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) were increased after a sudden drop in water temperature, but not in long-time cold acclimated as compared with warm acclimated trout. 2. Possibly, the activities of GDH and G6PD were temporarily increased in connection with metabolic adaptation to the lower temperature. 3. The activities of GDH and G6PD were not changed by the stress of handling. 4. Partially purified trout liver GDH has a lower activation energy with glucose than with glucose-6-phosphate as substrate, and the Km (glucose) decreases with decreasing assay temperature. 5. At low temperatures, the activity of trout liver GDH with glucose as substrate may be comparable to that of glucose-6-phosphate. 6. Partially purified beef liver GDH has a high activation energy with glucose as substrate, and the Km (glucose) does not change with the assay temperature. 7. Hexokinase (HK, EC 2.7.1.1) and GDH activities were unchanged when trout were deprived of food for 4 weeks. Apparently, the trout liver glucose utilization did not adapt to the starvation.

Acclimatization↗
PubMed1990

Plasma glucose, ketone bodies, insulin, glucagon and enteroglucagon in cows: diurnal variations related to ketone levels before feeding and to the ketogenic effects of feeds.

Ingestions of a moderately ketogenic silage twice daily were followed by transient increments in plasma insulin and ketone bodies and decreases in plasma glucose. Ketone bodies and glucose were negatively correlated throughout the day, but the insulin elevations culminated before the maximal effects on ketone bodies and glucose were established. Cows with varying glucose levels before morning feeding reacted to a highly ketogenic silage by decreasing their glucose level uniformly to about 3 mmol/l, in spite of a widely varying feeding-induced insulin increment. Hay-feeding caused insulin increments of the same magnitude as silage-feeding, but the glucose decrease and the ketone increment was much smaller. The results indicate some direct action of ketone bodies on blood sugar regulation, in addition to effects mediated by insulin. The role of ketone bodies as the insulinotropic factor was not confirmed. The insulin level after feeding seems to be determined by the carbohydrate status of the animal before feeding. No significant changes in plasma glucagon were observed after feeding, and no consistent differences in plasma levels of this hormone were found when non-ketonemic, ketonemic, and clinically ketotic cows were compared. The plasma level of enteroglucagon (GLI) was positively correlated to the relative amount of concentrates consumed, but no relation to plasma glucose was found.

Animal Feed↗
PubMed1985

Some observations on mitochondrial-bound hexokinase and creatine kinase of the heart.

A large part of the hexokinase activity of the rat brain 20,000g supernatant became mitochondrial bound when incubated with rat heart mitochondria which had been pretreated with glucose-6-phosphate. This binding was dependent on small-molecular compounds (as yet unidentified) of the brain supernatant. Divalent cations, spermine, and pentalysine strongly stimulated the binding of brain supernatant hexokinase to heart mitochondria. Inorganic phosphate, alpha-glycerophosphate, and fructose-1,6-diphosphate showed some stimulatory effect. No effect was observed with insulin or glucose. Mitochondria isolated from hearts of fasted rats had less specific hexokinase activity than mitochondria from fasted and then carbohydrate refed rats. This dietary treatment had no significant effect on the total heart hexokinase activity. Oligomycin did not inhibit the formation of creatine phosphate or glucose-6-phosphate by isolated rabbit heart mitochondria incubated in the presence of phosphoenolpyruvate and pyruvate kinase. However, the presence of creatine inhibited the formation of glucose-6-phosphate when the ATP/ADP ratio was low, indicating that creatine kinase has a greater access to ATP/ADP translocation than has hexokinase.

Adenosine Triphosphate↗
PubMed1984

Determination of malonyl-coenzyme A in rat heart, kidney, and liver: a comparison between acetyl-coenzyme A and butyryl-coenzyme A as fatty acid synthase primers in the assay procedure.

The malonyl-CoA assay was nonlinear at low malonyl-CoA concentrations when labeled acetyl-CoA was used as fatty acid synthase primer. Linearity was obtained with low concentrations of both fatty acid synthase and labeled acetyl-CoA, but then the assay was disturbed by the diluting effect of endogenous acetyl-CoA. The problems of nonlinearity and dilution of radioactivity by endogenous compounds were absent when labeled butyryl-CoA was used as primer. The levels of malonyl-CoA in rat heart, kidney, and liver were determined. The use of butyryl-CoA gave higher values of malonyl-CoA.

Acetyl Coenzyme A↗
PubMed1984

Varying effects of calcium on the oxidation of palmitate and alpha-ketoglutarate in isolated rat liver mitochondria incubated in KCl-based and sucrose-based media.

Isolated mitochondria from rat liver were incubated in the presence of [U-14C]palmitate, ATP, CoA, carnitine, EGTA (ethylene glycol bis (beta-aminoethyl ether) N,N'-tetraacetic acid) and varying amounts of calcium. When a KC1-based incubation medium was used, the oxidation of palmitate was inhibited when the concentration of free calcium was increased from about 0.1-10 microM. When a sucrose-based incubation medium was used, the basal rate of palmitate oxidation was about half of that observed with the KC1-medium and calcium had a stimulatory effect. With the KC1-medium the rate of oxygen consumption was inhibited by calcium with alpha-ketoglutarate as well as palmitate as the respiratory substrate. No inhibitory effect of calcium was observed with succinate or beta-hydroxybutyrate. With the KC1-medium and with alpha-ketoglutarate as the respiratory substrate, state 3 respiration but not state 4 respiration was inhibited by calcium. When the sucrose-medium was used, state 3 respiration was first inhibited by calcium, but this inhibition was gradually relieved and the respiratory rate finally became higher than it was before calcium addition.

Adenosine Diphosphate↗
PubMed1984

The effect of glucagon on the carbon flux from palmitate into glucose, lactate and ketone bodies, studied with isolated hepatocytes.

Glucagon induced a rapid (within 3 min) increase in glucose radioactivity and a decrease in the labeling of ketone bodies when isolated hepatocytes were incubated in the presence of [1-14C]palmitate. Simultaneously, the hormone induced a decrease in the levels of pyruvate and Krebs cycle intermediates and an increase in the level of phosphoenolpyruvate (PEP). The glucagon-induced increase in glucose radioactivity was much larger than the simultaneous decrease in lactate labeling. A comparison of the incorporation of labeled carbon from [1-14C]palmitate and [U-14C]palmitate into glucose and CO2 indicates a selective stimulatory action of glucagon on the flux through the phosphoenolpyruvate carboxykinase (PEPCK) reaction.

Animals↗
PubMed1983

The action of vasopressin and calcium on palmitate metabolism in hepatocytes and isolated mitochondria from rat liver.

Vasopressin inhibits fatty acid oxidation and stimulates fatty acid esterification, glycogenolysis, and lactate production in hepatocytes from fed rats. In cells from fasted rats, the effect of the hormone on palmitate oxidation was absent, while gluconeogenesis was stimulated. The inhibitory action of vasopressin on palmitate oxidation was not due to the increased lactate production. Neither was it correlated to glycogen content or stimulation of glycogenolysis, which were restored earlier than the vasopressin effect on palmitate oxidation when previously fasted rats were refed a carbohydrate diet. The level of malonyl-CoA was moderately increased by vasopressin. Isolated mitochondria from rat liver were incubated in the presence of [U-14C]palmitate, ATP, CoA carnitine, glycerophosphate, ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid, and varying amounts of calcium. The oxidation of palmitate was inhibited when the concentration of free calcium was increased from about 0.1 to 10 microM. Simultaneously, palmitate esterification was stimulated. This effect of calcium was observed also with mitochondria from fasted rats and with octanoate as well as palmitate as the substrate. Carnitine acylation was not affected by calcium. The possibility that the observed effects of calcium on mitochondrial fatty acid utilization is part of the mechanism of action of vasopressin on hepatocyte fatty acid metabolism is discussed.

Animals↗
PubMed1983

Separation of different cell populations of rat liver by density gradient centrifugation in a vertical rotor with self-generated Percoll gradients.

A procedure is described which, with good resolution, separates viable rat liver parenchymal cells from other cell populations present in crude suspensions of liver cells. Fractionation is carried out by vertical rotor centrifugation in a self-generated Percoll gradient. Kupffer cells can be separated from other sinusoidal cells, resulting in a separate peak of peroxidase negative non-parenchymal cells, composed mainly of endothelial cells.

Animals↗
PubMed1983

Effects of FSH, isoproterenol, and cyclic AMP on the production of lactate and pyruvate by cultured Sertoli cells.

We have examined the hormonal regulation of the secretion of lactate and pyruvate from cultured rat Sertoli cells. FSH and isoproterenol caused 3-6-fold stimulation of lactate and pyruvate secretion, whereas ovine LH, TSH, and prolactin were ineffective. Dibutyryl cyclic AMP (10(-4) M) stimulated the secretion of lactate and pyruvate to the same extent as FSH. Much lower stimulation was observed when Sertoli cells from 43-day old rats were exposed to FSH or isoproterenol. FSH increased lactate secretion in a concentration-dependent manner. The concentration of FSH (NIH-S14) causing half-maximal stimulation of lactate secretion (150 ng/ml) was similar to that causing 50% maximal stimulation of Sertoli cell adenylyl cyclase. Both FSH and isoproterenol caused a time-dependent increase in lactate levels in the incubation medium during the first 6-9 hr after the addition of hormones, after which levels were constant or decreased. Thus, the production of lactate and pyruvate by cultured Sertoli cells is stimulated both by FSH and isoproterenol and these effects are exerted via cyclic AMP.

Animals↗
PubMed1981

Clofibrate.

Explore the source record for details and available documents.

Animals↗
PubMed1980

Regulation of palmitate esterification/oxidation by glucagon in isolated hepatocytes: the role of alpha-glycerophosphate concentration.

Lipolysis was measured as the disappearance of [3H]glycerol previously incorporated into triacylglycerol, diacylglycerol and phosphatidic acid. There was no effect of glucagon on the lipolysis of any of these lipids. A transient increase in cellular alpha-glycerophosphate was induced by addition of glycerol during incubation. This resulted in an immediate and temporary decrease in oxidation and increase in esterification of palmitate while the uptake of palmitate from the incubation medium was unchanged. The change in alpha-glycerophosphate was also correlated with a transient drop in acyl-CoA and acylcarnitine. The lactate/pyruvate ratio was increased by the glycerol addition, but was still elevated for some while after the transient change in alpha-glycerophosphate. Similar effects were obtained by addition of dihydroxyacetone instead of glycerol. It is concluded that fatty acid esterification/oxidation can be changed by variations in the concentration of alpha-glycerophosphate, and that glucagon acts on lipid metabolism by decreasing the level of this metabolite.

Animals↗