Biomedical subjects

C Burlet

Publications and source records attributed to C Burlet.

At least 73 records · Page 4Linked to original sources

PubMed1992

Changes in hypothalamic neurotensin concentrations and food intake in rats fed a high fat diet.

Neurotensin (NT), a peptide present both in the brain and in the gastrointestinal tract, has potent anorexigenic effects when centrally injected in rats and is secreted after fat ingestion. High fat diets are often associated with increased energy intake. The aim of this study was therefore to evaluate the role of neurotensin in the feeding behaviour of rats fed on a high fat (HF) diet. Adult Long-Evans rats were fed for two weeks either a control (C) well-balanced diet (n = 10) or a fat-rich diet containing about two-thirds of its energy as fat (margarine and peanut oil; n = 10). Neurotensin was measured by a specific radioimmunoassay in the plasma and in several microdissected brain nuclei involved in the regulation of feeding behaviour. Ingestion of the HF diet induced an increased body weight gain (47.6 +/- 7.7 g (HF) vs. 37.6 +/- 9.3 g (C); P less than 0.05) and an increased energy intake (+ 7.2%; P less than 0.05). Plasma fasting NT concentrations were not affected by the HF diet. In the hypothalamus, significant decreases in NT concentrations were measured in the HF rats in two nuclei important in the regulation of food intake, i.e. the paraventricular nucleus (1.72 +/- 0.16 (HF) vs. 2.27 +/- 0.15 (C) ng/mg protein; P less than 0.05) and the lateral hypothalamus (1.87 +/- 0.16 (HF) vs. 2.37 +/- 0.19 (C) ng/mg protein; P less than 0.05). On the other hand, no variations were measured in the ventral tegmental area, an important site for the metabolism and regulatory action of neurotensin and in other hypothalamic nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

[Atrial natriuretic factor after heart-lung transplantation. Consequences of cardiac denervation].

Due to the discovery and elaboration of alpha ANP, the heart can be considered a veritable endocrine gland involved in fluid and electrolyte homeostasis as well as blood pressure regulation. Nevertheless, the mechanisms regulating the synthesis and release of this new hormone are far from being understood. Heart-lung transplantation provides an interesting research model for evaluating the consequences of allograft denervation on alpha ANP synthesis and release, without the disadvantage of significantly increasing the overall atrial tissue mass, as observed in orthotopic heart transplantation. To appreciate better these consequences, we studied the changes in alpha ANP release following heart-lung transplantation. Five patients were included in the study. It began during the immediate postoperative period and went on to the 8th postoperative day. Alpha ANP levels were determined using radioimmunoassay. The postoperative course was characterized by a rapid significant increase in hormone levels as of the 6th postoperative day (45.6 +/- 5.5 fmol/ml). These findings were comparable to those found in a previous study involving orthotopic heart transplantation alone. Thus, the heart-lung group was also capable of high levels of alpha ANP release from the onset. However, this rapidly increasing release was not found to be correlated with the changes in hemodynamic parameters observed postoperatively (blood and cardiac filling pressures). Moreover, we observed no episodes of rejection which might explain the increased release of this hormone. Finally, the fact that increased alpha ANP release occurs despite a smaller increase in the overall tissue mass is more than noteworthy. In conclusion, as we found in our initial study involving heart transplant recipients, the sustained high levels of alpha ANP observed following heart-lung transplantation are in favour of a possible modulating role played by cardiac innervation on the release of this hormone.

Adult↗

PubMed1991

[The effect of glucocorticoids on the diluting capacity of the kidney of a desert rodent: Gerbillus campestris].

The ability to excrete a water load was studied in Wistar rats and in gerbils (Gerbillus campestris). The rat excreted the entire water load in less than 2 h whereas Gerbillus campestris excreted less than 60% of the water load in 4 h. The gerbils which had received a dose of 15 micrograms/100 g body weight dexamethasone improved their rate of excretion which attained 92 +/- 6% in 2 h 30 min. The antidiuretic hormone (ADH) measured by radioimmunoassay at the time of maximum diuresis was undetectable in rats; in contrast, in gerbils the level of ADH remained relatively high (55.4 +/- 6.7 pg/ml). We conclude that the partial inability of the gerbil's kidney to excrete a water load is due to a high ADH level and probably to a low concentration of glucocorticoids.

Animals↗

PubMed1990

Diurnal rhythm of neuropeptide Y-like immunoreactivity in the suprachiasmatic, arcuate and paraventricular nuclei and other hypothalamic sites.

The diurnal rhythm of neuropeptide Y (NPY)-like immunoreactivity was examined in 9 discrete hypothalamic sites of rats maintained on a 12:12 h light/dark cycle. Significant bimodal rhythms of NPY concentration were detected in the suprachiasmatic and arcuate nuclei, with significant peaks just prior to onset of the nocturnal period and also at onset of the light period. In the parvocellular division of the paraventricular nucleus, a unimodal NPY peak was observed prior to dark onset. No diurnal rhythm was seen in the magnocellular division of the paraventricular nucleus, nor in 5 other hypothalamic areas examined.

Animals↗

PubMed1990

Rapid and localized alterations of neuropeptide Y in discrete hypothalamic nuclei with feeding status.

Neuropeptide Y (NPY) is believed to regulate the normal eating behavior and body weight in rats via central mechanisms. We have investigated whether NPY, which stimulates food intake, may in turn be modified by the nutritional state of the animals. Thus the impact of food deprivation (FD) (48 h) and subsequent refeeding on the levels of NPY in discrete hypothalamic areas was examined in this study. The results showed site specific change in only 3 of 7 hypothalamic sites. A 5-fold increment in NPY was reported in the paraventricular nucleus (PVN) and a 10-fold increase was observed in the arcuate nucleus-median eminence (ARC-ME). While subsequent refeeding for 6 h reversed the effect of FD in the ARC-ME, the levels of NPY in the PVN remained high in the refed rats. The perifornical lateral hypothalamus displayed a different pattern, namely, a significant increase in NPY content in refed as compared to satiated and deprived rats. The NPY levels in 4 other hypothalamic sites, namely, the dorsomedian, ventromedian, supraoptic and suprachiasmatic nuclei, and two extrahypothalamic sites, namely caudate nucleus and nucleus accumbens, showed total resistance to any change following deprivation and refeeding. These data emphasize the important and specific role of the paraventricular and arcuate nuclei in NPY's regulation of food intake and provide support for the idea that the variations of hypothalamic NPY after food deprivation reflect a specific physiological response of feeding regulatory system to alterations in the animal nutritional state and body weight.

Animals↗

PubMed1990

In vitro vasoconstriction induced by calcium in renovascular hypertensive or old rats.

We studied the changes in calcium-induced vasoconstriction in isolated tail arteries from young (2 months) and old (12 months) normotensive, and young renovascular hypertensive rats (3 months old, with unilateral renal artery clipping at 6 weeks), pretreated with reserpine. The tail artery was removed and perfused/superfused with either a high potassium Krebs depolarizing solution or Krebs solution plus phenylephrine. Concentration-response curves to calcium were produced. Old rats had a low plasma renin activity and their depolarized tail arteries showed a weak vasoconstrictor response to calcium. Renovascular hypertensive rats had a high mean blood pressure and plasma renin activity. Responses of their depolarized tail arteries to calcium were greater. Responses to calcium in tail arteries perfused with phenylephrine were similar in all groups. We conclude that age and renovascular hypertension produce opposite changes in vasoconstriction induced by calcium in depolarized tail arteries.

Aging↗

PubMed1990

Hypothalamic neuropeptide Y (NPY) in obese Zucker rats: implications in feeding and sexual behaviors.

Neuropeptide Y (NPY), a peptide of the pancreatic polypeptide family, is actually considered to be the most potent stimulator of food intake in rats when centrally injected. It has also suppressive effects on several components of sexual behavior. It was measured in discrete microdissected brain nuclei in obese hyperphagic Zucker fa/fa rats also characterized by a deficient reproductive function, as well as in their lean homozygous (Fa/Fa) and heterozygous (Fa/fa) counterparts. When compared with the lean (Fa/Fa) rats, NPY concentrations were significantly increased in the obese rats in the arcuate nucleus-median eminence (ARCME, +300%), in the paraventricular (PVN, +60%), suprachiasmatic (SCH, +90%), accumbens (+100%) and supraoptic (+40%) nuclei, as well as in the median preoptic area (MPOA, +70%). As PVN is one of the most important nuclei involved in the control of food intake and one site of NPY action, the high levels found in this nucleus might be a major component at the origin of hyperphagia in the obese animals. Food intake might be overstimulated by a sustained production of NPY as shown by the high concentrations found in the ARCME. NPY might also intervene in the pattern of food intake, for NPY contents were also largely modified in the SCH, the nucleus regulating feeding periodicity and in the MPOA, which is possibly involved in the regulation of energy balance. Finally, as the MPOA is the only site of action of NPY on sexual behavior, the higher levels measured in this area might contribute to the defective reproductive function of the obese Zucker fa/fa rat.

Animals↗

PubMed1990

Ingestive behaviors of the rat deficient in vasopressin synthesis (Brattleboro strain). Effect of chronic treatment by dDAVP.

Spontaneous manipulator and locomotor activities, food and fluid intake have been recorded from rats suffering from a genetic lack of central vasopressin (VP) synthesis (Brattleboro strain, DI), their heterozygous litter mates (HZ) or Long Evans (LE) rats. The daily patterns of activities did not differ, except for their drinking behavior. This was mainly associated with food intake during the dark period with LE rats but was distributed equally during light and dark periods with DI rats. HZ rats showed a behavioral heterogeneity, some of them following the daily pattern of LE rats, and others, that of DI rats. The daily feeding pattern was identical in the three genotypes but the selection between two isocaloric contrasted diets was different. When they were fed ad lib, HZ and DI rats consumed less carbohydrate than LE rats, the protein intake being unchanged. On the contrary, when the DI rats were only fed during the dark period, they ate more carbohydrate than LE rats. The peripheral infusion of a V2 AVP agonist (dDAVP) restored a normal hydric balance in DI rats but failed to modify the diet selection. These data show that in the rats, the lack of central VP synthesis disturbs both the selection of diets and the efficiency of the satiety signals. These disturbances were unchanged by the peripheral VP treatment which suggested the direct involvement of the central release of the neuropeptide.

Animals↗

PubMed1990

Influence of diet composition on food intake and hypothalamic neuropeptide Y (NPY) in the rat.

Ingestion of a high carbohydrate (HC) or high fat (HF) diet induces obesity in association or not with modifications of the feeding behaviour. Effects of diet composition on NPY, a powerful stimulant of weight gain and food intake (particularly carbohydrates), are not known. That is why we measured NPY in 10 microdissected brain nuclei of rats fed either a HC diet (69% of energy from carbohydrates), a HF diet (68% of energy from fat) or a control well-balanced diet (54% of energy from carbohydrates; 30% of energy from fat) during a 14-day period. Total caloric intake was significantly greater (+12%) in rats fed on the HF diet than in the control and HC rats. HF rats also gained more weight than the two other groups (47.5 +/- 2.4 g vs 37.6 +/- 2.6 g (control) and 29.1 +/- 1.4 g (HC); p less than 0.001). NPY variations were restricted to two hypothalamic areas. In the parvocellular part of the paraventricular nucleus, NPY was smaller with the HC diet than with the HF diet (42.1 +/- 2.3 vs 49.5 +/- 2.7 ng/mg protein; p less than 0.05). A decrease was observed in the lateral hypothalamus with the HF diet when compared with the control diet (11.3 +/- 0.7 vs 14.6 +/- 1.1 ng/mg protein; p less than 0.05). No variations were observed either in other hypothalamic nuclei such as arcuate, dorsomedian, ventromedian or suprachiasmatic nuclei or in extra-hypothalamic areas such as the ventral tegmental area or submamillary bodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Hyperphagia in obesity is associated with a central peptidergic dysregulation in rats.

Hyperphagia and obesity are often associated, and the origins of the biochemical modifications leading to these syndromes might be in the hypothalamus. Indeed, food intake is regulated by numerous neuropeptides in various hypothalamic nuclei, including the paraventricular (PVN), arcuate (ARC), ventromedian (VMN) and suprachiasmatic (SCH) nuclei. Among these peptides, neuropeptide Y (NPY) is the most potent inducer of food intake whereas neurotensin (NT) decreases food intake. We measured these two peptides in microdissected hypothalamic nuclei in obese Zucker rats that ate 30% more food than their lean counterparts. Neuropeptide Y and neurotensin levels varied in opposite directions: In the hyperphagic obese Zucker rats, the NPY concentrations were significantly greater than those in the lean normophagic rats in the ARC (+30%), PVN (+60%) and SCH (+94%) nuclei, whereas the NT levels were significantly lower in the ARC (-40%), PVN (-31%) VMN (-66%) and SCH (-47%) nuclei. Both these variations tend to increase food intake. Feeding periodicity might also be modified because large variations of the two peptides have been measured in the supra-chiasmatic nucleus, which is considered the most important regulator of feeding rhythm. The results reinforce the hypothesis that hyperphagia in obesity is associated with a biochemical modification in the central nervous system because the peripheral status of NT and NPY was not modified in the obese rats. Because levels of other hypothalamic peptides, such as opioid peptides and somatostatin, are also slightly modified, it can be concluded that hyperphagia in obesity is associated with a central peptidergic dysregulation. Research on drugs reacting specifically with the receptor of these peptides might have interesting implications for the treatment of hyperphagia and, therefore, of obesity.

Animals↗

PubMed1990

Chronic treatment with the angiotensin I converting enzyme inhibitor, perindopril, restores the lower limit of autoregulation of cerebral blood flow in the awake renovascular hypertensive rat.

Chronic hypertension shifts the lower limit of cerebral blood flow autoregulation to a higher pressure level. Although acute administration of angiotensin converting enzyme inhibitors restores the lower limit of cerebral blood flow autoregulation the chronic effects have not received much attention. We studied the effect of the angiotensin converting enzyme inhibitor, perindopril, on mean arterial pressure, basal cerebral blood flow and cerebral blood flow autoregulation in renovascular hypertensive (two-kidney, one clip model) and normotensive male Wistar rats. Seven weeks after renal artery clipping or sham operation rats received daily intraperitoneal injections of perindopril. The dose was increased from 1 to 8 mg/kg over the first 4 weeks until blood pressure was normalized. Chronic renovascular hypertension caused a marked shift in the lower limit of cerebral blood flow autoregulation but did not alter basal cerebral blood flow. Treatment of hypertensive rats with perindopril normalized blood pressure and restored cerebral blood flow autoregulation. Chronic treatment of normotensive rats with perindopril increased basal cerebral blood flow. In conclusion, chronic treatment of renovascular hypertensive rats with perindopril causes a shift in the lower limit of cerebral blood flow autoregulation towards the value observed in normotensive rats.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1989

Neurotensin in microdissected brain nuclei and in the pituitary of the lean and obese Zucker rats.

Neurotensin (NT) is a tridecapeptide common to the gastrointestinal tract and central nervous system which suppresses food intake when centrally injected in various regions of the hypothalamus. We measured neurotensin levels in several microdissected brain nuclei as well as in the pituitary in 10 obese hyperphagic Zucker (fa/fa) rats, 9 heterozygous Fa/fa and 5 Fa/Fa lean rats. The greatest NT concentration and content were observed in the anterior lobe of the pituitary in the median eminence and in the lateral preoptic area (500 to 1000 pg/area, 3 to 5 ng/mg protein). NT was also detected in the median preoptic area, paraventricular (PVN), supraoptic, ventromedian nuclei (VMN) (about 250 pg/nucleus, 1.5 to 2 ng/mg protein). The smallest amounts were found in the suprachiasmatic (SCH) and accumbens nucleus (about 100 pg/nucleus, 1 ng/mg protein) and the peptide was absent in the cortex. NT content in the obese rat was significantly lower in all brain nuclei examined except the accumbens nucleus. This was most evident in the three nuclei involved in the regulation of feeding behaviour: PVN (276 +/- 38 (Fa/Fa) vs 188 +/- 15 (fa/fa) pg/nucleus, P less than 0.05), VMN (226, +/- 21 (Fa/Fa) vs 75 +/- 22 (fa/fa) pg/nucleus, P less than 0.001), and SCH (98 +/- 14 (Fa/Fa) vs 52 +/- 11 (fa/fa) pg/nucleus, P less than 0.05). There was no difference in the pituitary lobes between lean and obese rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Vasopressin neuron is the target of monoclonal antibodies raised against vasopressin-neurophysin injected in vivo.

Monoclonal antibodies (MAbs) raised against the neurophysin (NP) specifically synthesized with vasopressin (VP, VP-NP) were injected into the paraventricular nucleus (PVN) of the rat hypothalamus. Their fate was studied by immunocytochemistry from 1 min to 3 h after the end of injection. It could be demonstrated that the VP-NP MAbs penetrated in vivo into some magnocellular neurons of the injected PVN and were transported ipsi- and contralaterally in individual neurons and in accessory magnocellular groups. When the time after injection was longer than 15 min, the VP-NP MAbs were also carried in the fibers of the median eminence. The prior treatment of rats with colchicine did not prevent the uptake of VP-NP MAb in the neurons but inhibited the transport towards the eminential fibers, the individual neurons and accessory groups. The detection of the PVN endogenous peptides (VP and oxytocin) on the same brain sections indicates that the neuronal uptake was specific. It only occurred in the neurons which synthesized VP and never appeared in the brain of rats suffering from a genetic defect of the central VP synthesis (Brattleboro rat). These data support the hypothesis of the location on the cell surface of the VP-NP precursor in magnocellular neurons which synthesize VP. This membrane signal identifies the neuron and allows the immunological recognition of the neurosecretory neurons in vivo.

Animals↗

PubMed1989

[Nutrition behavior in adolescent students (15-19 years of age) in the Nancy metropolitan area. A comparison with the recommended nutritional intake of the French population].

This paper describes the food behavior of 495 adolescents (15-19 years old) sample living in Nancy (France). The results are compared with the Recommended Dietary Allowances (RDA) for French adolescent population. The RDA are not satisfied for important percentages of girls for the daily energy intake (26.3% of girls have allowances less than 30% RDA), for the calcium intake (28.7% of girls have allowances less than 40% RDA), and for the protein intake (17.6% of girls have allowances less than 20% RDA). Lipids consumption is excessive (19.9% of boys and 23.4% of girls have allowances greater than 20% RDA) and energy intake from breakfast are low (25% of adolescents provide less 10% of daily energy intake by breakfast) for all these teen-agers. These results confirm the data observed in two others studies concerning the food behavior of French adolescents.

Adolescent↗

PubMed1988

[Stress and feeding behavior].

It has been easy to demonstrate, both in humans and animals, that the stresses which disturbed either the physiological homeostasis, the behavioural homeostasis or both simultaneously, induced the modifications of the food intake; these disorders often found expression in the inappropriate eating or, less frequently, in temporary anorectic phases. The most relevant hypotheses localized, in the anterior and median hypothalamus (paraventricular nuclei, ventral median nuclei, lateral hypothalamic area), the neurobiological mechanisms which were involved in this stress/eating behaviour relationship. In the brain, both aminergic and peptidergic systems were concerned; the stress-induced hyperphagia required the functionality of the dopamine, dorsal noradrenergic bundle and endogenous opioids of the central nervous system. The dramatic stress-induced anorexia was based upon the reciprocal actions of serotonin, norepinephrine and CRF systems. Other peptides, which some of them belonged to the brain-gut peptide group, could interfere with these mechanisms. The neuropeptides being common in the stress and eating physiological systems, the regulatory mechanisms were most coherent; nevertheless, the precise nervous structures and neurochemical circuits that produced the stress-induced hyperphagia or stress-induced anorexia, remain unknown.

Animals↗

PubMed1985

Human and animal fat cell size determination using an image analyzing computer.

An automatization of the fat cell's morphological parameters determination with an image analyzing computer is proposed. The results obtained with this technique are compared to results obtained from the usual methods. Combined with frozen cut slices of adipose tissue, this automatized determination of fat cell size is well adapted for the large number of samples necessary for a specialized hospital service.

Adipose Tissue↗

PubMed1984

Behaviour of thyroid tissue from patients with Graves' disease in nude mice.

Thyroid tissue from five patients with hyperthyroidism due to Graves' disease was transplanted into nu/nu mice (2 to 4 mice per thyroid) in order to assess whether the tissues would remain hyperfunctional. Before surgery, the patients received only propranolol and iodine for ten days. Transplants were removed from the mice after 10, 20, 30 or 57 days, and compared to the initial tissue, as well as toxic nodules from two patients and thyroid tissue from two normal subjects grafted similarly. All transplants survived, as proven by histology and autohistoradiography with 131I uptake, while all signs of hyperfunction and dysimmunity disappeared. Conversely, both transplanted toxic nodules remained hyperfunctional. These results indicate that, in spite of the in situ presence of most factors of auto-immune reactions, thyroid tissue from patients with Graves' disease is not autonomous and depends on the extra-thyroid environment.

Adult↗

PubMed1984

Transplantation of human hyperthyroid tissue to the nude mouse. An experimental model.

This study analyzes the outcome of human normal and hyperfunctioning thyroid tissue transplanted to the nude mouse. Thyroid fragments from 7 patients with Graves' disease were transplanted to nude mice (nu/nu). Before surgery, the patients had been treated with propranolol and iodine; none had received antithyroid therapy. The transplants were removed on the 12th day following transplantation and were studied by light microscopy and autohistoradiography. At this time, all immunologic disorders found on the operative samples had disappeared, and the tissue had lost its hyperfunctioning characteristics. In contrast, transplants from toxic adenoma remained hyperfunctioning, with elevated serum T3 and T4 levels. Similarly, transplants from normal thyroid tissue remained unchanged, and serum T3 and T4 levels remained within the normal range, as if under the influence of the hypothalamic and pituitary regulation of the mice. These findings emphasize the role of the extrathyroid immunologic environment in the regulation of Graves' disease, whereas toxic adenoma remains autonomous.

Adenoma↗