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Biomedical subjects

G Pelletier

Publications and source records attributed to G Pelletier.

At least 595 records · Page 33Linked to original sources
PubMed1981

Sensitivity of rat adenohypophyseal cells to estradiol and LHRH during long-term culture.

To determine possible effects of the time in culture on the responsiveness of the different pituitary cell types to estrogens, rat anterior pituitary cells were incubated up to 20 days in the presence or absence of 10 nM 17 beta-estradiol. Whereas spontaneous luteinizing hormone (LH) and thyroid-stimulating hormone (TSH) release decreased by 85-90%, follicle-stimulating hormone (FSH) and prolactin accumulation in medium were only 50% decreased after 20 days in culture, thus suggesting that the secretion of FSH and prolactin is less dependent on extrinsic stimulatory factors. Estradiol increased spontaneous LH release and its responsiveness to luteinizing hormone-releasing hormone (LH-RH) up to day 16 in culture, whereas the stimulatory effect of the estrogen on FSH secretion was significant only up to day 6. The stimulatory effect of estradiol on basal TSH release was seen up to day 8 in culture, whereas that on spontaneous prolactin release increased progressively after day 8 in culture up to the last time interval studied (20 days). As revealed by immunocytochemistry, the stimulatory effect of estradiol was not due to changes of cell growth.

Animals↗
PubMed1981

Attempts to demonstrate peptide localization and secretion in primary cell cultures of fetal rat hypothalamus.

Primary cultures of dispersed hypothalamic cells were prepared from 18- to 19-day-old rat fetuses. Morphological studies revealed two types of cells having typical glial and neuronal appearances. Immunostaining of cells in culture was positive for neurophysin. The incubation medium contained radioimmunoassayable luteinizing hormone-releasing hormone, vasopressin, beta-endorphin and adrenocorticotropin hormone. The present data suggest that hypothalamic cells in primary culture secrete immunoreactive hormones or peptides; however, they do not seem to store significant amounts of these peptides.

Adrenocorticotropic Hormone↗
PubMed1981

Immunocytochemical detection of peptides in osmicated and plastic-embedded tissue. An electron microscopic study.

In an attempt to improve the ultrastructural preservation of tissue immunostained with the postembedding staining technique, we verified the effect of postfixation with OsO4 on the antigenicity of several pituitary hormones and neuropeptides. For this purpose, the rat pituitary and central nervous system (CNS) were perfused with 2.5% glutaraldehyde and postfixed in two different ways: a) postfixation by immersion of small fragments in a mixture of 1% OsO4 and 1% potassium ferrocyanide, and b) postfixation with perfusion of 500 ml of 0.5% OsO4. The results obtained were similar with the two types of postfixation. In the pituitary gland, all the hormones could be very easily detected, although the staining was less intense for the glycoprotidic hormones. In the CNS the following neuropeptides: somatostatin, luteinizing hormone-releasing hormone (LHRH), Leu-enkephalin and substance P could be immunostained. These results indicate that a variety of polypeptidic antigens, including small neuropeptides, can survive postfixation with OsO4. In both the pituitary and CNS, the ultrastructural preservation was very good with a high contrast of membranes, thus permitting a clear identification of positive organelles. Moreover, it appears that, since the synaptic junctions are well-preserved after postfixation with OsO4, postembedding staining can now be utilized to identify and classify the different categories of endings containing neuropeptides.

Animals↗
PubMed1980

Identification of a second category of alpha-melanocyte-stimulating hormone (alpha-MSH) neurons in the rat hypothalamus.

An immunocytochemical localization of alpha-melanocyte-stimulating hormone (alpha-MSH) as well as ACTH and a fragment (16K) of the common precursor of ACTH and beta-lipotropin (beta-LPH) was performed in rat brain. Two different groups of neuronal cell bodies showing alpha-MSH-like immunoreactivity (alpha-MSH-LI) were observed in the hypothalamus. One group of neurons located in the arcuate nucleus was shown to contain not only alpha-MSH-LI, but also ACTH and the 16K fragment. A second category of alpha-MSH-LI-containing neurons was characterized by the complete absence of staining for ACTH and 16K fragment. These neurons were mainly located in the dorsal-lateral portion of the hypothalamus. Immunoelectron microscopy showed that immunostaining for alpha-MSH was restricted to dense core vesicles in the positive perikarya. Nerve fibers staining for alpha-MSH (but not for ACTH and 16K fragment) were also observed outside the ACTH-beta-LPH pathway, especially in the cortex, caudate-putamen nucleus and hippocampus. These findings strongly suggest the presence of two different neuronal systems reacting with antibodies to alpha-MSH.

Adrenocorticotropic Hormone↗
PubMed1980

Refractory variant angina controlled with combined drug therapy in a patient with a single coronary artery.

A young man with a single left coronary artery and refractory variant angina is described. Spontaneous coronary artery spasm developed during coronary arteriography at the site of a 50% fixed left anterior descending coronary artery stenosis. Frequent episodes of rest angina with transient ST segment elevation persisted in hospital in spite of treatment with three different calcium antagonist drugs. Symptoms disappeared only when the combination of nifedipine, diltiazem, isosorbide dinitrate, and nitroglycerin ointment were given. Ergonovine testing was used to objectively assess the response to treatment.

Adult↗
PubMed1980

Glycoprotein secretion in the hypothalamo-neurohypophyseal system of the rat.

Although the secretory products of the hypothalamo-neurohypophyseal system are not glycoproteins, synthesis and migration of these macromolecules occur within its secretory neurons. After being labeled with 3H-fucose in the Golgi apparatus, newly synthesized glycoproteins migrate to secretion granules, lysosomes and the plasma membrane of the secretory neurons, as demonstrated by quantitative electron-microscopic radioautography. Secretion granules bearing newly synthesized glycoproteins migrate to the pars nervosa, the labeling pattern of which was studied in rats killed from 4 h to 14 days after the isotope injection. Most of the silver grains were observed to overly the secretory axons. Labeling of pituicytes was negligible and the number of silver grains over the perivascular spaces was about 10% of the total at certain postinjection intervals. In the secretory axons, most of the silver grains over the different portions of the secretory axons changed with time. At the longer intervals, the percentage of silver grains increased over the nerve swellings (including Herring bodies) and decreased concomitantly in the undilated portions of the axons and in the nerve endings. This labeling pattern conforms with observations of the secretion products. Water deprivation increased the release of neurosecretion as well as glycoproteins from the pars nervosa. However, glycoproteins inside the Herring bodies were not easily releasible. There was a parallel decrease in the amount of secretion granules and 3H-fucose-labeled glycoproteins indicating that the glycoproteins are predominantly a constituent of the granule content. Some newly synthesized glycoproteins were probably also used in the renewal of the axonal membrane. The labeling of smooth vesicles in nerve endings was discussed. In conclusion, most of the glycoproteins synthesized in the perikarion of the hypothalmic secretory neurons migrate inside secretion graules along the axon to the pars nervosa where they are secreted.

Animals↗
PubMed1980

Comparative localization of prolactin-binding sites in different rat tissues by immunohistochemistry, radioautography and radioreceptor assay.

Prolactin was localized in various rat tissues, using two different histological approaches: immunohistochemistry and autoradiography. Following injection of ovine prolactin (oPRL) to intact rats, oPRL was localized in the proximal convoluted tubules (PCT) of the kidney using an immunoperoxidase technique. Diffuse and weak staining was observed in the liver while no staining was observed on sections of adrenal, testis and brain. Incubation of [125I]oPRL on frozen cryostat tissue sections followed by radioautographic processing revealed specific radioautographic grains on cells of convoluted tubules of the kidney. Specific grains were also seen on hepatocytes of the liver, cells of the adrenal cortex, interstitial cells of the testis and epithelial cells of the choroid plexus of the brain. The amount of specific radioautographic grains seen per tissue agreed well with in vitro binding values of [125I]oPRL to crude membrane preparations in the same tissues. Our observations clearly show that in the rat specific binding sites for prolactin are present on cells of the proximal convoluted tubules of the kidney, hepatocytes of the liver, glandular cells of the zona reticularis, zona fasiculata and zona glomerulosa of the adrenal, interstitial cells of the testis and epithelial cells of the choroid plexus. These studies demonstrate the necessity of using more than one morphological approach in the identification of prolactin-binding sites in different tissues at the cellular level.

Adrenal Glands↗
PubMed1980

Ultrastructural localization of a fragment (16K) of the common precursor for adrenocorticotropin (ACTH) and beta-lipotropin (beta-LPH) in the rat hypothalamus.

With an antiserum to a fragment (16K) of the 31K common precursor for both adrenocorticotropin (ACTH) and beta-lipotropin (beta-LPH), the immunohistochemical localization of this 16K fragment was performed in the rat hypothalamus. At light microscopic level, 16K fragment was detected in the same neuronal cell bodies which also contain ACTH in the arcuate nucleus. Using serial thin sections for immunoelectron microscopy, it has been possible to demonstrate that 16K fragment and ACTH are present not only in the same cell bodies and fibers but also in the same dense core vesicles. These results indicated that in the central nervous system ACTH is originating from the 31K common precursor and that the active peptides (ACTH and endorphins) are stored in the same vesicles which also contain the common precursor and/or its fragment(s).

Adrenocorticotropic Hormone↗
PubMed1980

Changes of cell morphology and prolactin secretion induced by 2-Br-alpha-ergocryptine, estradiol, and thyrotropin-releasing hormone in rat anterior pituitary cells in culture.

The secretion of prolactin in cultured pituitary cells was studied in correlation with the cellular changes induced by stimulatory or inhibitory agents. The techniques used in this study were: radioimmunoassay, immunocytochemistry, scanning (SEM) as well as transmission (TEM) electron microscopy. Prolactin secretion was stimulated by 17 beta-estradiol (10 nM) as well as thyrotropin-releasing hormone (TRH) (3 nM) and inhibited by 2-Br-alpha-ergocryptine (CB-154) (1 muM). The total prolactin (release and cell content) increased between 2 and 8 d of estradiol treatment, indicating an increase of both synthesis and release of prolactin. This finding was in agreement with TEM observations because, in estradiol-treated prolactin cells, the Golgi saccules were distended and Golgi elements were increased, thus indicating increased synthetic activity of these cells. The addition of TRH over a 4-h period resulted in a significant degranulation of prolactin cells. In contrast, prolactin secretory granules became accumulated in the cells after CB-154 treatment for a period ranging from 4 to 24 h. In agreement, light microscope immunocytochemistry showed an increased reaction for prolactin after short-term (< 24 h) incubation with CB-154. Because prolactin cells represent approximately 70% of the glandular cell population as revealed by immunocytochemistry, it was then possible to observe the changes of cell surface by SEM. In most cells, estradiol and TRH led to an increase in the number and prominence of microvilli and blebs, whereas CB-154 treatment resulted in a slightly decreased number of microvilli and an increased occurrence of membrane foldings. This report thus provides morphological evidence for the stimulatory effects of estradiol and TRH, and the inhibitory effects of CB-154 on prolactin secretion in pituitary cells in primary culture. These data, moreover, show that acute changes in secretory activity of prolactin-secreting cells are accompanied by marked changes of their morphological characteristics.

Animals↗
PubMed1980

Localization of a 16,000-dalton fragment of the common precursor of adrenocorticotropin and beta-lipotropin in the rat and human pituitary gland.

To clearly identify cells and organelles containing the common precursor (31,000 dalton) for both adrenocorticotropin (ACTH) and beta-lipotropin (beta-LPH), an immunohistochemical localization of a fragment (16,000 dalton) of the precursor that is not common to beta-LPH and ACTH was conducted in rat and human pituitary glands. With the help of specific antibodies that do not cross-react with beta-LPH and ACTH, the 16,000-dalton fragment was localized in the cells that also produce ACTH and beta-LPH in both the pars distalis and pars intermedia of the rat pituitary. At the electron microscope level, the secretory granules that contain ACTH were also stained for 16,000-dalton fragment. In the human pituitary, the 16,000-dalton fragment was also observed in all the secretory granules of lipocorticotrophs. These results suggest that, after enzymatic cleavage, fragment(s) of the common precursor and/or the whole common precursor remain packaged within the secretory granules with peptides of known activity.

Adrenocorticotropic Hormone↗
PubMed1980

Immunohistochemical localization of gamma-endorphin in the rat pituitary gland and hypothalamus.

To gain more information about cells and organelles involved in the secretion of gamma-endorphin in the rat pituitary gland, an immunohistochemical localization of this peptide was conducted at both light and electron microscopic levels. Using an antiserum to gamma-endorphin which shows little cross-reactivity with beta-lipotropin (beta-LPH) and beta-endorphin, it has been demonstrated that gamm-endorphin is present in all cells of the intermediate lobe and the corticotropic cells of the anterior lobe. At the electron microscopic level, staining for gamma-endorphin was restricted to the secretory granules which also contain ACTH and beta-LPH, suggesting that all of these peptides are released concomitantly during exocytosis. In the hypothalamus, immunostaining possibly related to both gamma- and beta-endorphin but not to beta-LPH was also observed in nerve fibers and not in cell bodies.

Animals↗