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Biomedical subjects

A Ktorza

Publications and source records attributed to A Ktorza.

67 records · Page 4Linked to original sources
PubMed1986

Effect of gestational hyperglycemia on insulin secretion in vivo and in vitro by fetal rat pancreas.

The effects of gestational hyperglycemia on B-cell function were studied in near-term fetuses from unrestrained pregnant rats made slightly or highly hyperglycemic using continuous glucose infusion during the last week of pregnancy. Pancreatic and plasma insulin and insulin secretion in vitro were studied in the fetuses. Compared with controls, slightly hyperglycemic fetuses showed increased pancreatic and plasma insulin concentrations and similar insulin release in response to glucose in vitro. In highly hyperglycemic fetuses, pancreatic and plasma insulin concentrations were unchanged compared with controls, and insulin release in vitro was insensitive to glucose and to the mixture glucose plus theophylline. These results confirm that glucose is able to stimulate insulin secretion in normal or slightly hyperglycemic fetuses and suggest that severe hyperglycemia per se, without association of other metabolic disorders or toxic injuries, profoundly alters the stimulus-secretion coupling of the fetal rat B-cell.

Animals↗
PubMed1986

Effects of pancreatic hormones and glucocorticosteroids on argininosuccinate synthetase and argininosuccinase activities of rat liver during the perinatal period: in vivo and in vitro studies.

The activity changes of two urea cycle enzymes, argininosuccinate synthetase (ASS) and argininosuccinase (ASL), were followed after corticosteroid and pancreatic hormone treatments in utero and in primary cultured fetal hepatocytes. The ASL activity which was induced by glucagon or by (Bu)2cAMP administration was enhanced by a treatment with streptozotocin for 2 days, although ASS was not changed under these conditions. The activity of both enzymes was enhanced by cortisol administration in utero only in streptozotocin-treated fetuses, suggesting an inhibitory effect of insulin. In cultured fetal hepatocytes, dexamethasone produced a marked increase of the two enzyme activities, which was abolished by the simultaneous addition of insulin. The parallel results obtained with these two experimental models allow one to conclude that the high plasma insulin level in late gestation might repress the development of ASS and ASL activities in utero and antagonize the effect of corticosteroids on these enzyme activities.

Animals↗
PubMed1986

Impaired glucose homeostasis in adult rats from hyperglycemic mothers.

The purpose of our study was to investigate whether nondiabetic gestational hyperglycemia during fetal life could have additional effects on glucose homeostasis and insulin secretion in the adult rat. Hyperglycemia without the main other metabolic disorders and vascular injuries associated with diabetes was produced in unrestrained pregnant rats by continuous glucose infusion during the last week of pregnancy. Control rats were infused with distilled water. Compared with controls, the newborns from hyperglycemic rats were hyperglycemic and hyperinsulinemic. When studied longitudinally up to 3 mo, they showed slightly but significantly increased basal plasma glucose levels and normal basal insulin concentrations compared with controls. Glucose tolerance and insulin secretion in response to a glucose load (0.5 mg/kg, i.v.) were altered: Plasma glucose values were more increased at 5 min and remained higher 90 min after glucose injection; incremental plasma insulin values and the insulinogenic indexes (delta IRI/delta G) were always lower in rats from hyperglycemic mothers than in controls. These alterations were more and more marked with advancing age (1-3 mo). These data show that gestational hyperglycemia may lead to persistent impairment of glucose homeostasis and insulin secretion in the adult rat.

Animals↗
PubMed1985

Insulin and glucagon during the perinatal period: secretion and metabolic effects on the liver.

Insulin and glucagon are detected in the plasma of most species early in gestation. In the fetus at term, insulin and glucagon secretion can be modified by long-term changes in glucose concentration but the responsiveness of A and B cells to glucose is lower than in the adult. The plasma insulin/glucagon molar ratio is high in the fetus at term, then decreases dramatically immediately after birth and remains low during the first hours of extrauterine life. This situation results in favored hepatic glycogen storage and prevented gluconeogenesis in utero, and sharp glycogen breakdown and active gluconeogenesis during the early postnatal period.

Animals↗
PubMed1985

Effects of gestational hyperglycemia on glucose metabolism and its hormonal control in the fasted, newborn rat during the early postnatal period.

To evaluate the effects of gestational hyperglycemia on glucose metabolism and its regulation in the fasted rat during the early postnatal period, unrestrained rats were continuously infused with glucose during the last week of pregnancy. Control rats were infused with distilled water. Newborns were studied during the first six postnatal hours. At birth, newborns from glucose-infused rats, compared with controls, showed higher plasma glucose levels, increased plasma insulin, and lower plasma glucagon and catecholamine concentrations. Between birth and 2 h postpartum, newborn rats from both groups exhibited a marked hypoglycemia, which was, however, more severe in newborns from glucose-infused rats (15 mg/dl) than in controls (26 mg/dl). During the first four postnatal hours, plasma insulin concentration remained higher, while plasma glucagon and catecholamine concentrations remained lower in newborns from hyperglycemic rats. At 6 h, the glycemia reached normal values and the concentrations of the different hormones were similar in controls and newborns from glucose-infused mothers. Concurrently, in the newborns from glucose-infused rats, hepatic glucose production was altered, as they were unable to mobilize liver glycogen stores during the six postnatal hours. Despite slightly delayed phosphoenolpyruvate carboxykinase induction, the rate of gluconeogenesis from 10 mmol/L lactate estimated on isolated hepatocytes was higher in newborns from hyperglycemic mothers than in controls. These results show that gestational hyperglycemia compromises the metabolic and hormonal adaptation of the newborn rat to early extrauterine life; the striking feature of these neonates is the absence of mobilization of liver glycogen stores, which can probably be explained by fetal and neonatal hyperinsulinism associated with the defect of counterregulatory hormones.

Age Factors↗
PubMed1983

Hyperglycaemia induced by glucose infusion in the unrestrained pregnant rat: effect on body weight and lipid synthesis in post-mature fetuses.

Mild hyperglycaemia was induced in unrestrained pregnant rats from day 20.5 to day 23.5 of pregnancy, using a continuous glucose infusion. Control rats were infused with distilled water. In post-mature fetuses from glucose-infused rats, raised plasma glucose and insulin concentrations were related to increased body weight (6.03 +/- 0.07 g) and total carcass fat (2.02 +/- 0.04% of fresh weight) compared with control fetuses of the same age (5.35 +/- 0.07 and 1.5 +/- 0.04 g, respectively). Concurrently, the rate of lipogenesis in the carcass, estimated from the incorporation of tritium from tritiated water into fatty acids, was significantly increased in fetuses from glucose infused rats compared with control rats (6.00 +/- 0.34 versus 2.62 +/- 0.27 and 3H2O X h-1 X g tissue-1, respectively.

Animals↗
PubMed1983

[Maternal hyperglycemia and fetal development in the rat: effects of a continuous glucose perfusion in the rat at the end of gestation].

Continuous glucose infusion was used to induce mild hyperglycemia in unrestrained pregnant rats during the last three days of pregnancy. Control rats were infused with distilled water. Compared with the controls, fetuses from glucose-infused rats showed higher plasma glucose levels, increased plasma insulin and lower plasma glucagon concentrations. Pregnancy prolonged until day 23.5 resulted in a sharp decrease in plasma insulin concentrations and a dramatic increase in plasma glucagon concentrations. In 23.5-day old fetuses from both groups, plasma insulin concentration rose when phentolamine was injected but not when propanolol was injected. Plasma glucagon concentration in 23.5-day old fetuses from glucose-infused rats dropped with propanolol injection. In fetuses from control rats, liver phosphoenolpyruvate activity increased markedly and liver glycogen stores decreased sharply. In fetuses from glucose-infused rats, liver phosphoenolpyruvate carboxykinase activity rose and glycogen content decreased, but to a lesser degree. Moreover, in postmature fetuses from glucose-infused rats, elevated plasma glucose and insulin concentrations were related to increased body weight and total carcass fat. Concurrently, the rate of lipogenesis in the carcass of these fetuses (estimated from the incorporation of 3H from 3H2O into fatty acids) was significantly increased.

Animals↗
PubMed1982

Effects of slimming and composition of diets on VO2 and thyroid hormones in healthy subjects.

Oxygen consumption and plasma thyroid hormone concentrations are modified by both low- and high-calorie diets. It has been suggested that the trigger may be changes in weight ("adipostatic" hypothesis involving the difference between the actual weight and the "set point") or changes in amount of carbohydrate in the diet ("carbohydrate" hypothesis). Two experiments were performed in order to test both hypotheses. Fourteen young healthy volunteers were studied: 1) at their spontaneous stable weight; 2) while losing weight rapidly on a calorically restricted diet; 3) and then at their stable new weight when consuming a refeeding diet. The calorie restricted diet resulted in decrease of VO2, and T3, and an increase of rT3; the refeeding diet resulted in values of VO2, T3, and rT3 intermediate between those of the spontaneous diet and those of the restricted diet. Another group of nine subjects were studied at their spontaneous caloric and proteic levels, comparing a diet containing only protein and carbohydrate with a diet containing only protein and fat. During the low carbohydrate diet rT3 increased and T3 decreased but they remained unchanged during the carbohydrate-rich diet. Thus neither the adipostatic hypothesis nor the carbohydrate hypothesis is sufficient alone to explain the observed changes in serum T3 and rT3.

Adolescent↗
PubMed1981

Hyperglycaemia induced by glucose infusion in the unrestrained pregnant rat during the last three days of gestation: metabolic and hormonal changes in the mother and the fetuses.

Continuous glucose infusion was used to induced mild hyperglycaemia in unrestrained pregnant rats during the last three days of pregnancy. Control pregnant rats were infused with distilled water. Fetuses were studied after normal or prolonged pregnancy. Fetuses from glucose-infused rats, compared with controls, showed higher plasma glucose levels, increased plasma insulin and lower plasma glucagon concentrations. Pregnancy prolonged until day 23.5 resulted in a rise in the glucagon/insulin ratio from 6.5 to 67 in fetuses from control rats and from 1.3 to 13 in fetuses from glucose-infused rats. Concurrently in fetuses from control rats, liver phosphoenolpyruvate carboxykinase activity increased markedly and liver glycogen stores decreased sharply. In fetuses from glucose-infused rats, liver phosphoenolpyruvate carboxykinase activity rose and glycogen content decreased, but to a lesser extent. These results show that both the A and B cells of the rat fetal pancreas are sensitive to chronic glucose stimulation.

Animals↗
PubMedDate not supplied

Effects of counterregulatory hormones on insulin-induced glucose utilization by individual tissues in rats.

The effect of counterregulatory hormones (epinephrine, norepinephrine and glucocorticoids) on insulin-induced glucose utilization in individual tissues of normal rats was investigated in vivo. This was done in normoglycaemic conditions, using the euglycaemic hyperinsulinaemic clamp combined with an injection of 2-[1-3H]-deoxyglucose. The main effect of these hormones was to reduce insulin-induced glucose utilization in skeletal muscles and particularly in the oxidative one. No changes were observed in heart diaphragm and adipose tissues. These results emphazise the role of counterregulatory hormones on glucose utilization and demonstrate that muscles are their major site of action. They support the notion that the increase in plasma concentrations of these hormones could play a role in states of insulin resistance like obesity and diabetes.

Adipose Tissue↗