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Biomedical subjects

J Grizard

Publications and source records attributed to J Grizard.

At least 73 records · Page 4Linked to original sources
PubMed1986

Assessment of in vivo protein synthesis in lamb tissues with [3H]valine flooding doses.

Week-old lambs received an intravenous injection of 4.3, 8.5, 12.8 or 17.1 mmol [3H]valine/5 kg body weight, i.e., 3.6-14.4-times the whole-body free valine content. To ensure that protein synthesis measurements in lambs are reliable within a 30-min period, these large amounts of valine must account for at least around 11-times the total free pool of valine. This amounted to 12.8 mmol valine/5 kg body weight. There were no significant variations in plasma insulin and plasma glucagon levels 5, 13 and 30 min after the injection of so much valine. The fractional rates of protein synthesis were determined in tissues of animals receiving either 12.8 or 17.1 mmol valine/5 kg body weight. The rates of protein synthesis in the jejunum (87.5%/day), liver (106.6%/day) and tensor fasciae latae muscle (18.8%/day) of lambs injected with the 12.8 mmol [3H]valine flooding dose, were in the range of data obtained in immature rats. Increasing the flooding amount of valine up to 17.1 mmol/5 kg body weight did not significantly alter protein synthesis rates in the jejunum, liver or skeletal muscle. This suggested that both the flooding-dose method in itself and valine had no effect on in vivo protein synthesis.

Animals↗
PubMed1986

Relationship between plasma glucagon disappearance and tissue uptake in rats.

The fate of plasma glucagon has been analyzed in detail by Desbuquois and Postel-Vinay. The present work was carried out to clarify the relationships between plasma glucagon disappearance and its tissue uptake. For the purpose, we injected rats intravenously with 125I-glucagon alone or with concomitant or sequential injections of native glucagon. Plasma 125I-glucagon was analyzed by Biogel P10 chromatography. Liver and kidney glucagon kinetics were studied from the point of view of the evolution of the total radioactivity present in each tissue a few minutes after glucagon injection. 125I-glucagon was rapidly cleared from the plasma (half-life within 2 min); it was intensively associated with liver and kidneys. Liver radioactivity rapidly declined within the first 5 min after injection, whereas kidney radioactivity increased. The concomitant injection of increasing amounts of native glucagon with 125I-glucagon progressively reduced the liver radioactivity, indicating that glucagon was trapped in a saturable compartment. In contrast, kidney radioactivity remained unchanged. The sequential injection of 125I-glucagon and excess native glucagon resulted in a shift to the right in the plasma 125I-glucagon decay curve which suggests that the glucagon excess displaced 125I-glucagon from its distribution compartment back into the plasma. The compartment where glucagon uptake occurred a few minutes after 125I-glucagon injection displayed some of the fundamental properties of glucagon receptors, i.e. saturatibility and reversibility.

Animals↗
PubMed1986

Effect of dietary protein level on the first steps of glucagon action in rat liver plasma membranes.

Binding of glucagon and glucagon-stimulated cyclic AMP production were studied in highly purified liver plasma membranes from growing rats fed a 12% protein diet (group 1) or 20% protein diet; this latter was given either in normal (group 2) or restricted (group 3) amounts. Groups 2 and 3 exhibited significantly higher peripheral glucagonemia than group 1 (amounting to 286 and 160% of group 1, respectively). Specific [125I]iodoglucagon binding to plasma membranes was similar in all groups. Scatchard analysis revealed no further differences between affinity constants and binding capacities in the three groups. Hormone degradation was constant. As membrane recovery and membrane purity were unaltered, these results suggest that hyperglucagonemia caused by increasing dietary protein level is not associated with any significant modification of glucagon binding sites in rat liver. In the presence of a potent phosphodiesterase inhibitor (3-isobutyl-1-methyl xanthine 0.2 mM) the glucagon-stimulated cyclic AMP production was higher in rats fed the 20% protein diet, which was given in normal amounts, than in rats fed the 12% protein diet. In contrast when the 20% protein diet was given in restricted amounts the glucagon-stimulated cyclic AMP production was similar to that in the 12% protein-fed rats.

Animals↗
PubMed1986

[Hormonal control of hepatic metabolism in ruminants].

Insulin/glucagon control of hepatic metabolism, i.e. a endocrine-nervous system, is one of the general systems of integration in vertebrates. In this system, substrates coming from the digestive tract or from extrahepatic metabolism are important messenger molecules. Liver uptake of insulin and glucagon mainly accounts for high metabolic clearance rates of these hormones in both ruminants and non-ruminants. Glucagon infusion into ruminants results in an increase in the net hepatic uptake of glucose precursors and gluconeogenesis. Glucagon effects have also been demonstrated in isolated hepatocytes. Glucagon, through its effect on pyruvate carboxylase (EC 6.4.1.1.) may regulate gluconeogenesis. Insulin infusion induces hypoglycaemia. As a result, glucagon secretion increases and counterregulates insulin action. However, it has been shown that hepatic gluconeogenesis decreases during euglycaemic hyperinsulin clamp, mainly due to a decrease in the hepatic supply of glucose precursors following insulin action in extrahepatic tissues. Insulin fails to elicit any significant effect in vitro. Hepatocytes exhibit insulin and glucagon receptors. The apparent characteristics of hormone binding in vitro are similar in ruminants and non-ruminants, but the characteristics of postreceptor events are unknown in the former. Glucagon, which influences hepatic glucose synthesis, may be a major hormone in ruminants.

Amino Acids↗
PubMed1985

Sensitivity to satiating and taste qualities of glucose in obese Zucker rats.

A general "glucoreceptor" defect, demonstrable in pancreatic islet and taste cells, may contribute to the metabolic and taste abnormalities of adult onset diabetes and possibly, if present at the level of the hypothalamus, could produce hyperphagia and the obesity seen in diabetics. To determine if a glucoreceptor defect generally accompanies obesity and glucose intolerance, behavioral responsiveness to glucose was examined in nine obese and nine lean female Zucker rats. Daily food and fluid intake were measured during three two-bottle preference tests, in which rats chose between water and one of several glucose solutions (1%, 3%, and 12%). Taste responsiveness to glucose of obese rats appeared normal; however, increased satiating effects of glucose were found in obese rats, possibly due to an enhanced delivery of glucose to neurons that inhibit feeding, caused by glucose intolerance. Also, obese rats had (a) increased brain weights, and (b) increased volumes of ventromedial and paraventricular hypothalamic nuclei. These findings, perhaps explainable by an increased delivery of nutrients to the developing brain, indicate that the hyperphagia of Zucker rats is due neither to an overt hypothalamic lesion nor to insensitivity to glucose.

Animals↗
PubMed1984

Glucagon kinetics in growing rats fed different levels of protein and/or energy.

The present work was carried out to evaluate the kinetic parameters of glucagon in growing rats divided into three groups: T, H and E. Group T (Control group) was fed a control diet (crude protein: 11.8%). Groups H and E received a high protein diet (crude protein: 19%) distributed in either equal (Group H) or restricted amounts (Group E) with respect to the control. Thus, the main characteristic of Group H was the high level of protein intake (+ 68%) when Group E rats underwent a moderate increase in protein intake but a striking caloric deprivation (-25%). In all cases, the animals were fed a meal every 4 hours. The kinetic parameters of glucagon metabolism were estimated from the plasma disappearance curves of 125I-glucagon for five minutes following a pulse injection of purified 125I-glucagon (1 muCi, about 3.8 ng/100 g BW). Plasma 125I-glucagon was measured after gel filtration of plasma on Biogel P-10. Tissue radioactivity (mainly liver and kidneys) was recorded seven minutes after 125I-glucagon injection. The results showed that the plasma 125I-glucagon level was higher in Group H than in the other groups 1 min after the injection. At all other times (2, 3.5 and 5 min) it was similar in all groups. 125I-glucagon was rapidly cleared from plasma and rapidly taken up by the liver and kidneys. In the 3 experimental groups, mean half-life and metabolic clearance rate were estimated to be 2 min and 6 ml/min/100 g BW, respectively. Excess protein intake resulted in a reduction in the apparent initial distribution volume of 125I-glucagon without modifying significantly its turn-over rate and metabolic clearance rate. Kidneys and liver (6% BW) accounted for about 20% of the 125I-glucagon uptake by tissues 7 min after injection. Group H kidneys and liver were more labelled than in other groups. These results suggest that increased protein intake (without further caloric deprivation) can induce some changes in glucagon metabolism which could partially contribute to the increase in glucagonemia usually observed in animals fed high protein diets.

Animals↗
PubMed1983

Glucagon binding to purified liver plasma membranes from growing rats undergoing energy restriction.

The purpose of this work was to investigate liver glucagon receptors in growing rats fed a control diet (11.8% crude protein) or a high-protein diet (19.8% crude protein) given in restricted amounts. The animals were fed every 4 hours. 125I-glucagon binding to purified liver plasma membranes was studied. Membrane purity was analysed with marker enzymes. The alteration of glucagon during incubation was measured. The results show that specific 125I-glucagon binding increased with time at 30 degrees C, reaching a maximal value within 120 min. The increasing level of unlabelled glucagon inhibited 125I-glucagon binding at steady state. Apparent specific 125I-glucagon binding at steady state was lower in experimental animals than in controls. This correlated with the increase in glucagon breakdown and decrease in membrane purity. Alternatively, glucagon binding to its receptors could drop. Unlabelled glucagon excess produced a time-dependent dissociation of glucagon-receptor complexes (half-life: up to 1 h). Feeding the experimental diet increased the dissociation of labelled glucagon-receptor complexes.

Animals↗
PubMed1983

Plasma insulin and insulin kinetics in growing sheep. Influence of age and diet.

This study was carried out to clarify the nutritional control of insulin metabolism in growing sheep fed a control or an experimental diet low in crude protein and high in propionic acid used as a feed additive. Daily variations in blood insulin and the disappearance from the circulation of unlabelled injected insulin were investigated. These data were used to calculate the metabolic clearance rate of insulin and insulin secretion. At 23 kg of body weight (BW), blood insulin showed an increase in the control group at 10 a.m. (i.e. 2 h after feeding) and a large peak in the experimental group at 3 p.m. At 33-kg BW, blood insulin in both groups showed a peak at 10 a.m. and a moderate increase at 3 p.m. Mean plasma insulin throughout the day (except at 3 p.m.) rose with increasing BW. It was lower in the experimental than in the control group. Injected insulin disappeared rapidly from the circulation; its half-life was constant (13 min). In both groups, the insulin level along the disappearance curve was higher at 33-kg BW than at 23-kg BW, and insulin metabolic clearance rate decreased. Except at 3 p.m., the mean insulin secretion rate over the day was lower in the control group at 33-kg BW than at 23-kg BW. Feeding the experimental diet increased the insulin level along the disappearance curve. In young animals, it decreased insulin metabolic clearance rate and diminished mean insulin secretion rate over the day, except at 3 p.m. when the insulin secretion rate increased. In old animals, the experimental diet did not significantly change the kinetic parameters of insulin metabolism.

Aging↗
PubMed1983

Insulin binding to liver plasma membranes from growing ruminating sheep. Maintained on different diets.

The purpose of this work was to investigate insulin receptors in growing ruminant sheep given a control diet or undergoing nitrogen restriction. Live weights ranged within 30-36 kg in both groups. Before the animals were fed (i.e. at 8 a.m.) blood insulin was not significantly different in the two groups (0.39 vs 0.53 nM in experimentals and controls, respectively). The 125I-monoiodoinsulin binding to purified liver plasma membranes was studied. Membrane recovery and purity were similar in both groups. Results showed that specific 125I-iodoinsulin binding increased with time and reached a maximum value within 60-120 min. Increasing the nonlabelled insulin level inhibited 125I-iodoinsulin binding at steadystate. Among the animals from both groups, specific insulin binding decreased significantly with increased live weight. In addition, specific insulin binding lowered with increasing blood insulin. The latter relationship partly reflected the insulin binding-live weight-blood insulin relationships. The insulin binding was similar in both groups. Furthermore Scatchard analysis indicated no significant differences between apparent affinity constants and apparent binding capacities in the two groups.

Animals↗
PubMed1982

Testicular receptors of human chorionic gonadotrophin in adult men. Binding and degradation of the hormone.

Binding and degradation of human chorionic gonadotrophin (hCG) to testicular tissue obtained by biopsy from 9 men with gonadal disorders were investigated. Vacant hCG receptors were assayed in partially purified testicular homogenates using [125I]hCG (radioiodinated with chloramine T). Degradation of [125I]hCG during exposure to human testicular preparations was measured in terms of the ability of supernatants to specifically bind to rat testicular receptors. Binding of [125]hCG was time and temperature dependent. At 37 degrees C, a maximum was reached at 8 h. It was also found to be a saturable process with respect to homogenate and hormone concentrations. Association constants and number of binding sites determined in 9 men, using Scatchard plot and saturation curve analysis ranged, respectively, from 0.2 to 1.8 x 10(10) M-1 and from 92 to 3427 fmol/g testis or 7 to 380 fmol/mg protein. Degradation of [125I]hCG increased with temperature and time of exposure to human testicular homogenate. It increased also with increasing human testicular homogenate concentration and substrate concentrations. For a similar concentration of [125I]hCG, per cent of degraded hormone ranged from 32 to 57, according to the subjects. These results show that human testicular homogenates are capable of binding and degrading hCG in vitro. Biological and physiological implications of degradation for hormone binding are discussed.

Adult↗
PubMed1982

[Effect of the kinetics of gastric emptying of food on blood insulin levels in the preruminant calf].

The aim of this work was to clarify the possible role of blood metabolites (glucose, aminoacids, triglycerides) in the regulation of postprandial blood insulin in the preruminant calf. The animals used were 6 male Friesian bull calves with an average weight of 80 kg. They were divided into groups I and II. During the first experimental period (A), group I received a control diet that contained skim-milk powder as the only protein source, whereas group II received an experimental diet containing fish protein concentrate as the main protein source. During the second experimental period (B), the diets were switched. It was previously shown that the rate of fat and amino acid absorption increased when milk proteins in such milk substitutes were replaced by hydrolyzed fish proteins (Guilloteau et al., 1975). The results showed that during any experimental period in the control group, there was a decrease in the postprandial blood free amino nitrogen. Blood triglycerides exhibited a small increase at 0.5 h after the meal but a large decrease at 1-4.5 h. The meal also resulted in a very large increase in blood glucose with maximal values occurring at 1-4.5 h. Blood insulin showed a large increment at 0.5 h then increased slowly, peaking at 2-3 h. The postprandial increase in blood insulin was less during the first experimental period than during the second one. In calves fed the fish diet, blood free amino nitrogen and blood triglycerides showed a large postprandial increase. Blood glucose exhibited a smaller postprandial increment than in the controls and began to decrease at half an hour. In contrast, the trend of changes in blood insulin was the same as in the controls (i.e. a maximum at 3 h occurring after a large increase at 0.5 h). There were no significant differences in blood insulin between the two experimental periods. It was lower in the calves fed the fish diet than in the controls during the first experimental period; during the second period, it was similar in both groups. From these observations, it may be inferred that, as compared to the control diet, the fish diet resulted in a decrease in glucose stimulation of postprandial insulin secretion; in contrast, the effect of aminoacids and lipids may be increased.

Amino Acids↗
PubMed1980

[Effect of hyperinsulinemia on liver insulin receptors of the growing rat subjected to energy restriction].

Two experiments (I and II) were carried out to study the interaction of insulin with amino acid metabolism in rats subjected to a restricted energy allowance (Grizard et al., 1975). 61 male rats, weighing 94 g at the beginning of the experiments, were divided into 4 groups and fed every 4 hrs. Group T was fed a balanced diet, and groups -E1, -E2 and -E3 were given a restricted energy allowance (table 1). The rats of group -E3 were injected with insulin at 11 a. m. every day, and those of group -E2 at that hour on the day they were killed. When the animals of a group had a mean body weight of 157 g, they were killed between 2 p. m. and 6 p. m., i. e. between two meals. Plasma insulin and insulin binding to liver plasma membranes were recorded. Reducing dietary energy intake resulted in a small decrease of postprandial plasma insulin and in a small increase of the plasma insulin clearance rate (table 2). It also augmented (125I) iodoinsulin binding to liver plasma membranes (fig. 1). This change could explain the increment of the liver protein synthesis observed in such animals (Arnal, Fauconneau and Pech, 1972). Exogenous insulin induced a resistance to insulin effects (Grizard, Prugnaud and Pion, 1977), and caused a large increase of plasma insulin and a small decline in (125I) iodoinsulin binding to liver plasma membranes for 3 to 5 h after the injection (fig. 1). A large increment in insulin binding was then noted (fig. 1). Increased insulin binding and decreased plasma insulin might be correlated. The enhanced insulin binding could not explain the resistance to the effects of insulin.

Animals↗
PubMed1977

[Effect of energy restriction during late pregnancy on plasma insulin, blood glucose, blood urea and blood free amino acids in pregnant and suckling sheep].

The experiment was carried out in autumn using 27 Limousine ewes during pregnancy and lactation. Some blood essential and non-essential free amino acids increase during late pregnany. Blood glucose, blood urea and blood free threonine, valine and glycine increase after parturition. Reducing the energy supply of the ration during late pregnancy results in a decrease of plasma insulin and blood free tyrosine, phenylalanine and alanine.

Amino Acids↗
PubMed1977

[The effect of eating behavior on the circadian rhythm of plasma corticosterone in growing rats].

The circadian rhythm of plasma corticosterone was studied in growing Rats fed on an ad libitum or controlled feeding schedule (six meals per day). Circadian plasma corticosterone rhythm was conventional in ad libitum Rats. Increases of circulating hormone occurred during the last light hours and the first dark hours. Plasma corticosterone rhythm was modified by controlled feeding. Meal feeders exhibited a high value during the last light hours and a secondary hump at midnight. Feeding schedule was not the main synchronizing factor in rat circadian corticosterone rhythm.

Animals↗
PubMed1976

[Influence of L-leucine overloading on the level of free amino acids in the diabetic rat].

Alloxan injection in the rat results in a large increase of branched free amino acids (leucine, isoleucine, valine) in the blood, liver and muscle; it decreases most of the non essential free amino acids in liver. L-leucine administration in the diabetic rat results in a large decrease of plasma corticosterone. It increases free leucine but decreases free isoleucine and valine in blood and muscle. It decreases most of the essential free amino acids in liver.

Amino Acids↗
PubMed1976

[Influence of feeding rhythm on blood insulin in growing rats].

Plasma insulin in ad libitum fed growing rats increases during dark hours and decreases during light hours. In contrast, meal fed growing rats [6 equal meals at regular interval during the day] exhibit a constant plasma insulin level. It may be inferred that improvement of nitrogen retention in meal fed rats is not related to an increase in insulin secretion.

Animals↗