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Biomedical subjects

G Pelletier

Publications and source records attributed to G Pelletier.

At least 577 records · Page 32Linked to original sources
PubMed1982

Further studies on the identification of neurons containing immunoreactive alpha-melanocyte-stimulating hormone (alpha-MSH) in the rat brain.

In order to identify more accurately the organelles containing immunoreactive alpha-melanocyte-stimulating hormone (alpha-MSH) in the rat brain, attempts were made to improve the ultrastructural preservation of the neural tissue used for immunostaining of the peptide. With the post-embedding staining technique, the quality of the preservation was not adequate since only low concentrations (0.2-0.5%) of OsO4 could be used for postfixation. Higher concentrations of OsO4 completely destroyed the antigenicity of alpha-MSH. With the pre-embedding technique in which the immunostaining is performed prior to postfixation with OsO4, a good preservation could be obtained making possible the identification of organelles and classification of endings containing immunoreactive alpha-MSH. In the dendrites, the staining was rather diffuse without any clear association with organelles. In the endings, the staining was mostly restricted to dense core vesicles with some degree of diffusion in the cytoplasm. None of the positive endings were seen making synaptic contact. These results support the hypothesis that alpha-MSH could be released in sites other than the classical synaptic junction and act as a local hormone.

Animals↗
PubMed1982

Effect of chronic treatment with [D-Ala6, des-Gly-NH210]LHRH ethylamide on ovarian histology in the rat.

The effect of chronic treatment with the LHRH agonist [D-Ala6, des-Gly-NH210]LHRH ethylamide (LHRH-A) on ovarian histology was studied in adult female rats injected with 5 micrograms of the peptide, once every second day, for 0, 2, 4 or 8 weeks. Using light microscopy, we examined the number of small medium, large and atretic follicles, as well as the number of normal and regressing corpora lutea. Using the point-counting method, we measured the relative surface occupied by luteal cells. It was found that treatment with LHRH-A for up to 8 weeks led to no significant change in any of the parameters studied. Moreover, resumed meiotic maturation of an abnormally high number of atypical fragmentations of the ova could not be observed. At least at the dose used, the LHRH agonist does not appear to induce any histological alteration in ovarian morphology and supports the potential clinical use of LHRH agonists as a new approach in female contraception and for the treatment of estrogen-dependent pathologies.

Animals↗
PubMed1982

Glycoprotein synthesis and migration in beta cells of the islets of Langerhans as shown by quantitative light- and electron-microscopic radioautography.

L-3H-fucose was injected intravenously into rats that were killed from 10 min to 7 days after isotope administration. Semi-thin and thin sections of the islets of Langerhans were processed for light- and electron-microscopic radioautography, respectively, and analyzed quantitatively. L-3H-fucose was incorporated into newly synthesized glycoproteins in the Golgi apparatus of the beta cells and subsequently labeled glycoproteins migrated to secretory granules and plasma membrane. Therefore, some of the glycoproteins synthesized by the beta cells of the islets of Langerhans are destined for the renewal of plasma membrane. Although the labeling of the secretory granules was clearly demonstrated, it was not possible to decide if the newly formed glycoproteins are incorporated into the content or into the membrane of the granule. Thus, the fate as well as the function of secretory-granule glycoproteins could not be determined precisely. Several hypothesis concerning the presence of glycoproteins in the secretory granules in relation with insulin metabolism are considered.

Animals↗
PubMed1982

Distribution of luteinizing hormone-releasing hormone receptors in the rat ovary.

The distribution of luteinizing hormone-releasing hormone (LHRH) receptors was studied in the adult rat ovary using autoradiography after injection of the stable LHRH agonist 125I-labelled [D-Ser(TBU)6,des-Gly-NH2(10)]LHRH ethylamide (Buserelin) and by radioreceptor assay using the same tracer. In intact cycling female rats, no differences in ovarian LHRH receptor levels could be observed between day diestrus I and day proestrus. Moreover, similar levels are observed in total ovarian homogenate, corpora lutea and the remaining ovarian tissue in adult animals treated with PMSG (pregnant mare's serum gonadotropins) and hCG (human chorionic gonadotropin). Radioautographic data show a comparable distribution of grains over theca interna and externa, granulosa and luteal cells. The present findings indicate the presence of LHRH receptors in both the interstitial and follicular cells throughout all stages of cellular differentiation.

Animals↗
PubMed1982

Serum and intestinal secretory IgA in alcoholic cirrhosis of the liver.

Serum and intestinal secretory IgA (sIgA) were investigated in control subjects and patients with alcoholic cirrhosis of the liver. Intestinal secretions were sampled by intraluminal perfusion with a balloon catheter. Monomeric IgA and sIgA were assayed by reversed radial immunodiffusion and nephelometry after separation by Ultrogel column filtration. High levels of serum sIgA were found only in patients with severe cirrhosis accompanied by jaundice. The intestinal rate of secretion of sIgA measured in these patients was significantly lower than that observed in either controls or the patients with compensated cirrhosis. Such an intestinal sIgA deficiency, which could be explained either by a fall in small intestinal immunocyte synthesis or by a defect in the transenterocyte transport system, could be partially responsible for the high incidence of intestinal infection observed in severe cirrhosis.

Albumins↗
PubMed1982

Development of the pancreas during gestation and lactation in swine.

This study examined the development of the pancreas during gestation and lactation in swine. Forty-two mated sows and 42 unmated controls were sacrificed after 30, 70, and 110 days of gestation; 7, 14, and 28 days of lactation; and 11 days after weaning. Their pancreas were excised, weighed, and fragments homogenized for evaluation of protein, amylase, chymotrypsin, RNA, and DNA contents. Data indicate that all these parameters were reduced at the end of the gestation period when compared with controls. During lactation, pancreatic weights, enzyme, protein, and RNA contents showed regular increases. DNA contents were significantly increased after weaning, an indication of pancreatic hyperplasia. A return to control values is not complete 11 days after weaning. These changes in the pancreas can be related to increased food intake during lactation and are probably mediated by the endogenous release of the gastrointestinal hormones cholecystokinin and secretin.

Amylases↗
PubMed1981

Effect of hypophysectomy and pituitary stalk transection on alpha-melanocyte-stimulating hormone-like immunoreactivity in the brain of the frog, Rana ridibunda Pallas.

The existence of an alpha-MSH-like molecule in the frog brain led us to investigate the role of the pituitary gland in the maintenance of the alpha-MSH content in 3 different regions of the brain. Acetic acid extracts of hypothalamus, rhombencephalon and telencephalon were analyzed by means of a highly specific radioimmunoassay for alpha-MSH in normal, sham-operated, pituitary disconnected and hypophysectomized frogs. Transection of the pituitary stalk gave rise to a significant decrease in alpha-MSH content in the intermediate lobe of the pituitary gland (-71% after 3 days), but did not affect alpha-MSH content in the distal lobe or in the brain. Eight days after total hypophysectomy, an alpha-MSH immunoreactive compound, co-eluting with synthetic alpha-MSH on Sephadex G-25, was found in the 3 brain regions studied. Removal of the whole pituitary gland did not significantly modify alpha-MSH content in the hypothalamus and the telencephalon. A slight increase in alpha-MSH was even observed in the rhombencephalon of hypophysectomized animals. Furthermore, no modification in alpha-MSH immunoreactivity occurred in any region of hypophysectomized animals. These results demonstrate the existence of alpha-MSH-like material in the brain of Rana ridibunda and establish that brain alpha-MSH in the frog is not of pituitary origin.

Animals↗
PubMed1981

Differential projections of two immunoreactive alpha-melanocyte stimulating hormone (alpha-MSH) neuronal systems in the rat brain.

Immunocytochemical localization of alpha-MSH was performed in the brain of rats of which the arcuate nucleus has been destroyed by treatment with monosodium glutamate in the neonatal period. In these animals, alpha-MSH cell bodies normally found in the arcuate nucleus were almost completely absent. The reactive fibers found in the ACTH-beta-LPH pathway were also markedly decreased. On the other hand, alpha-MSH cell bodies located in the dorsolateral hypothalamus as well as fibers located outside the ACTH-beta-LPH pathway were not decreased. These results strongly suggest that alpha-MSH cell bodies in dorsolateral hypothalamus have projections completely different from those located in the arcuate nucleus.

Animals↗
PubMed1981

Electron immunocytochemistry in vasoactive intestinal peptide (VIP) in the rat brain.

In order to clearly identify the cellular elements as well as the organelles containing vasoactive intestinal peptide (VIP), an immunocytochemical localization of this peptide was performed in the rat brain. Ultrastructural localization studies involving use of both pre- and post-embedding staining techniques clearly demonstrated that VIP immunoreactivity was associated with dendrites and axonal processes. In dendrites, the labeling was rather diffuse throughout the cytoplasm whereas in terminals it was observed in large dense core vesicles and not within the small clear vesicles. About 50% of positive endings were observed forming typical synaptic contact. These results support the hypothesis that VIP can act as a neurotransmitter.

Animals↗
PubMed1981

Immunohistochemical localization of gamma-melanocyte-stimulating hormone in the rat pituitary gland.

A third melatropin fragment named gamma-MSH has been described in the N-terminal portion of the common precursor of bovine ACTH and beta-LPH by Nakanishi et al. (Nakanishi, S., Inoue, A., Kita, K., Nakamura, M., Chang, A.C.Y., Cohen, S.N. and Numa, S., Nature, 278 (1979) 423-427). In order to determine if immunoreactive gamma-MSH was present in the rat pituitary gland and to accurately localize this peptide, an immunocytochemical localization of gamma-MSH was conducted at both light and electron microscopic levels. Specific immunostaining was detected in stellate cells scattered throughout the pars distalis and in all the cells of the pars intermedia. At the ultrastructural level, immunoreactive gamma-MSH was only observed in the lipocorticotrophs. Using serial ultrathin sections, it was shown that the secretory granules which contain ACTH were also labeled for gamma-MSH. These results suggest that fragment(s) of the common precursor of ACTH and beta-LPH and/or the whole common precursor is released with peptides of known biological activity.

Animals↗