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Biomedical subjects

G Morel

Publications and source records attributed to G Morel.

At least 55 records · Page 3Linked to original sources
PubMed1996

Interactive effect of combined exposure to glycol ethers and alcohols on toxicodynamic and toxicokinetic parameters.

Ethylene glycol monomethyl ether (EGME) exhibits testicular toxicity and ethylene glycol monobutyl ether (EGBE) is a solvent with haemolytic effects in rats. The study of the interaction of two glycol ethers (EGME and EGBE) and three alcohols (ethanol, n-propanol and n-butanol, 10 or 30 mmol/kg), orally co-administered in male rats, was carried out from a toxicodynamic and toxicokinetic point of view. Administered alone, EGME (10 mmol/kg) caused a 30- and 5-fold increase in the urinary creatine/creatinine ratio at 24 and 48 h, respectively, and 24 h urinary excretion of methoxyacetic acid was of 0.71 +/- 0.042 mmol 24 h (mean +/- SE). The simultaneous administration of one of the three alcohols at either of the doses mentioned above did not significantly modify the urinary creatine/creatinine ration (24 and 48 h), or the 24 h urinary excretion of methoxyacetic acid. Administered alone, EGBE (5 mmol/kg) caused an average decrease of 26% in the number of circulating red blood cells and a strong (250 times) increase in the level of plasma haemoglobin 4 h after treatment. Urinary excretion of butoxyacetic acid in rats treated with EGBE (1 mmol/kg) was 0.083 +/- 0.0039 mmol/24 h (mean +/- SE). The simultaneous injection of 30 mmol/kg alcohol (ethanol, n-propanol or n-butanol) almost totally inhibits the haemolytic effect of EGBE, and decreases the urinary excretion of butoxyacetic acid by 43-31%. A strong dose of alcohol (30 mmol/kg) decreases the haemolytic effect due to EGBE, and reduces the urinary excretion of butoxyacetic acid. In contrast, the coadministration of alcohol did not modify the testicular toxicity of EGME, or the 24 h urinary excretion of methoxyacetic acid. It is possible that competitive inhibition of alcohol dehydrogenase by alcohols results in the diversion of EGBE metabolism.

Alcohols↗
PubMed1996

Kinetics of internalization and subcellular binding sites for T3 in mouse liver.

The intracellular fate of radiolabeled T3 taken up by mice hepatocytes in vivo was determined at specific time intervals (2-120 min) after injection by quantitative electron microscopic radioautography. Injection of a 200-fold excess of unlabeled T3 together with [125I]-T3 resulted in a more than 90% inhibition of radioactivity detected in hepatocytes. A simple grain density (GD) analysis of radioautograms revealed that a specific labeling (GD > 1) was displayed by only five cell compartments: the plasma membrane, lipid droplets, mitochondria, nuclear envelope and nuclear matrix whereas other compartments were not labeled. Labeled compartments showed distinct changes in the pattern of labeling over time: the plasma membrane was labeled only 2 min after T3 injection, whereas labeling of the nuclear envelope was high at 2 min, decreased at 15 min and progressively increased to maximal measured levels at 120 min. After a lag time of 30 min, nuclear matrix labeling increased progressively with time. Mitochondrial labeling was found to be specific at any time point studied but showed no change over time. These ultrastructural data have been confirmed in vitro by the interaction of T3 with plasma membrane, nuclear membrane, nuclear matrix and mitochondria by real-time biospecific interaction analysis in a BIAcore system. These results demonstrate that T3 binds to hepatocytes before internalization, is transported both to mitochondria and to the nuclear envelope and translocated into the nuclear matrix.

Animals↗
PubMed1996

Cellular trafficking of exogenous growth hormone in dwarf rat pituitary.

In order to determine the processing of growth hormone (GH) by its pituitary target cells, male rats were injected intracardially with 125I-bGH and their pituitaries removed at specific time intervals (2-120 min). Autoradiographic analysis performed at the electron-microscopic level showed that only three cell populations specifically took up 125I-bGH: somatotropes, lactotropes and gonadotropes. Specificity was demonstrated by concomitant injection with an excess of unlabeled bGH. A time course study indicated that eight compartments had distinct labeling patterns. The plasma membrane was highly labeled after as little as 2 min, and showed biphasic labeling 2 and 60 min after injection. The secretory granules of the somatotropes were more intensely labeled than those of the other cell populations. The rough endoplasmic reticulum was more intensely labeled in the gonadotropes. The Golgi apparatus was specifically labeled only in the gonadotropes. The mitochondria showed the highest degree of labeling at 15 and 120 min after injection. The lysosome compartment showed triphasic labeling, with maxima at 2, 30 and 120 min after injection. The labeling of the nuclear membrane showed a biphasic pattern, firstly at 15 min, then at 120 min after injection, except in the gonadotropes, and the labeling in the nuclear matrix showed similar biphasic pattern and maxima. These results show that GH is specifically taken up in the anterior pituitary by the somatotropes, lactotropes and gonadotropes, where, after binding to the plasma membrane, it is internalized into several cellular compartments, including the nucleus. The differences in cellular localization and processing between these cell types may reflect different paracrine and autocrine roles for GH.

Animals↗
PubMed1996

Constitutive nuclear localization of Janus kinases 1 and 2.

Both GH and the GH receptor have been reported to undergo rapid nuclear translocation. Janus kinases (JAK) 1 and 2 have been implicated in GH receptor signaling, and both of these kinases are phosphorylated by GH stimulation. In this report, we have investigated the subcellular distribution of JAK1 and JAK2. Both JAK1 and JAK2 exhibit a nucleocytoplasmic distribution by immunocytochemistry in unstimulated serum deprived CHO cells stably transfected with rat GH receptor complementary DNA (cDNA). The nucleocytoplasmic localization of JAK2 was verified by immunogold electron microscopy in both rat liver hepatocytes and CHO cells stably transfected with rat GH receptor cDNA. Nucleocytoplasmic localization of JAK2 was also verified by transient tranfection of CHO cells with a Haemophilus influenzae haemagglutinin (HA) epitope tagged JAK2 expression plasmid and subsequent localization of HA immunoreactivity. Western blot analysis of purified nuclear extracts revealed the presence of immunoreactive JAK1 at 130 kDa and immunoreactive JAK2 at 128 kDa. No change in the nuclear content of JAK1 or JAK2 was observed upon ligand stimulation of GH receptor cDNA transfected cells with 100 nM human GH for 5, 10, 15, 30, or 60 min. GH stimulation caused, however, the appearance of tyrosine phosphorylated 42- and 44-kDa proteins as well as tyrosine phosphorylated JAK2 in the nucleus. The constitutive nuclear localization of the Janus Kinases is suggestive of a novel nuclear role for JAK family members, in addition to their described cytosolic function and presents an interesting challenge to the subcellular site of hormone action.

Animals↗
PubMed1996

Cellular distribution of prolactin receptors in human digestive tissues.

In the present study we analyzed the expression of prolactin receptors (PRLR) in human digestive tissues by immunohistochemistry. PRLR immunoreactivity was primarily localized in the cytoplasm. However, in some organs (liver and salivary glands) a nuclear positivity was also found. The liver was used as control and showed a diffuse immunostaining in the parenchymal cells. In the gastrointestinal tract, PRLR immunoreactivity was observed in the mucosa, muscularis layer, and nervous plexuses. The more intense immunostaining in the mucosa of the different segments was as follows: esophagus, superficial layers of the stratified squamous epithelium and mucous glands; stomach, parietal cells; small intestine, absorptive and Paneth cells; and colon, surface epithelium and superficial half of the crypts of Lieberkühn. In the salivary glands, immunoreactivity was strong in the mucous tubules, moderate in the ducts, and weak in the serous cells. Endocrine pancreas showed a more intense immunoreactivity than the pancreatic acini. By serial sections of the islets of Langerhans we showed that immunostaining was confined to B cells. These findings demonstrate the widespread distribution of PRLR in human digestive tissues and its localization both in cytoplasms and nuclei.

Cell Nucleus↗
PubMed1996

Incorporation of proteins into (Xenopus) oocytes by proteoliposome microinjection: functional characterization of a novel aquaporin.

Xenopus laevis oocytes are widely used as an expression system for plasma membrane proteins, achieved by cytoplasmic microinjection of messenger RNA. In the present study, we propose an alternative system allowing functional insertion of exogenous proteins into the plasma membrane of Xenopus oocytes. We microinjected proteoliposome suspensions into the cytoplasm and then analyzed membrane protein function. The proteins used in this work were members of the MIP family: the human erythrocyte water channel aquaporin 1 (AQP1), the major intrinsic protein (MIP26) from bovine eye lens and a 25 kDa polypeptide (P25) from a water shunting complex found in the digestive tract of an homopteran sap-sucking insect (Cicadella viridis). Proteoliposomes containing either AQP1, MIP26, or P25 were injected into Xenopus oocytes. The subsequent insertion of these proteins into the plasma membrane of oocytes was demonstrated by immunocytochemistry. Oocytes microinjected with either AQP1 or P25-proteoliposomes exhibited significantly increased osmotic membrane water permeabilities (Pf = 3.16 +/- 026 and 4.03 +/- 0.26 x 10(-3) cm/second, respectively) compared to those measured for oocytes injected with liposomes alone or with MIP26-proteoliposomes (Pf = 1.39 +/- 0.07 and 1.44 +/- 0.10 x 10(-3) cm/second, respectively). These effects were inhibited by HgCl2 in a reversible manner. Arrhenius activation energies of water transfer were low when AQP1 or P25 were present in oocyte plasma membranes (Ea = 2.29 and 3.01 kcal/mol, respectively, versus Ea = 11.75 kcal/mol for liposome injected oocytes). The properties observed here for AQP1 are identical to those widely reported following AQP1 cRNA expression in oocytes. From the present study, we conclude that: (1) exogenous plasma membrane proteins incorporated into liposomes and microinjected into the cytoplasm of Xenopus oocytes are subsequently found in the plasma membrane of the oocytes in a functional state; and (2) in this system, the P25 polypeptide from the MIP family found in the digestive tract of Cicadella viridis exhibits properties similar to those described for the archetype of water channels AQP1, and thus is a new member of the aquaporin family.

Animals↗
PubMed1995

An attempt to explain interindividual variability in 24-h urinary excretion of inorganic arsenic metabolites by C57 BL/6J mice.

Forty C57 BL/6J mice, injected subcutaneously with 0.5 mg/kg arsenic as sodium arsenite, were examined for 24-h urinary excretion of total arsenic metabolites, creatinine and S-adenosylmethionine (SAM) and for 24-h faecal excretion of arsenic and levels of arsenic in the blood, liver, kidneys, lung, skin, spleen and bone at 24-h post-dose. Total urinary arsenic metabolites were calculated by summing up the inorganic (Asi), monomethylated (MMA) and dimethylated (DMA) derivatives directly measured by selective arsine generation-atomic absorption spectrometry (AG-AAS) or were measured by AG-AAS following complete mineralization. Both sets of results showed interindividual differences varying by as much as 7-fold and correlated with the 24-h urinary excretion of both SAM (r = 0.84 and r = 0.86, respectively) and creatinine (r = 0.82 and r = 0.87, respectively). There was interindividual variability of about a 30-fold range in 24-h faecal excretion of arsenic which correlated inversely with 24-h urinary excretion of arsenic metabolites (r = -0.69) and 24-h urinary excretion of both creatinine (r = -0.70) and SAM (r = -0.67). Body tissue levels of arsenic were low and not related to 24-h urinary excretion of arsenic metabolites, SAM and creatinine. Taken together, the results indicate that differences in the profile of urinary arsenic excretion and in the retention of arsenic in a particular organ do not contribute to interindividual variability in 24-h urinary excretion of arsenic metabolites by C57 BL/6J mice, but that variability in faecal excretion does, at least in part. It is speculated that there is most likely a predominant contribution from a diffuse tissue retention of arsenic or from a third route of arsenic elimination, i.e. respiratory, to this phenomenon in view of the small faecal contribution.

Animals↗
PubMed1995

Ultrastructural study of intestinal lactase gene expression.

The distribution of the mRNA encoding rat intestinal lactase-phlorizin hydrolase (LPH) was analyzed by ultrastructural in situ hybridization, and compared to the distribution of the cognate protein. Different pictures were obtained depending on the epithelial cell position along the crypt-villus axis: i) cells localized at the crypt base were devoid of LPH mRNA and protein; ii) cells of the crypt-villus junction and of the villus base showed a high level of mRNA but a low amount of enzyme; and iii) enterocytes of the middle and upper part of the villi exhibited an intense protein immunolabeling, but a low content of LPH mRNA. The analysis of the intracellular distribution of the LPH mRNA revealed a gradient of concentration along the cellular axis, as the transcripts were the most abundant in the apical and subapical domains of the enterocytes. In addition, LPH mRNA labeling was often paired or arranged in a circular shape, suggesting that the transcripts may be located in closed vicinity to rounded structures within the cytoplasm. The results indicate that distinct patterns of mRNA and protein occur along the villus height during the continuous process of cell differentiation of the intestinal epithelium. In addition, the emergence of the functional polarity of the enterocytes comes together with the establishment of an intracellular gradient of concentration of the mRNA encoding a brush border enzyme. A link between the intracellular distribution of LPH mRNA molecules and the membranous flow is proposed.

Animals↗
PubMed1995

In situ gene expression of growth hormone (GH) receptor and GH binding protein in adult male rat tissues.

Pituitary growth hormone (GH) acts as a growth promoter in a wide range of tissues after binding to its specific GH receptor (GHR) or to a cytosolic circulating GH binding protein (GHBP). To further characterize GH target cells in the rat, in situ hybridization was used to investigate the tissue and cell distribution of mRNAs encoding GHR and GHBP, and their hepatic developmental expression was examined. Cryostat sections of adult male rat tissue were hybridized with [35S]dATP-labeled oligonucleotide antisense probes, one directed against a specific sequence of the intracellular domain of rat GHR mRNA, the other against the hydrophilic tail of rat GHBP mRNA. Several tests were carried out to validate the in situ detection of mRNA. Co-expression of the two transcripts in liver, spleen, thymus, kidney, adrenal, skin, muscle, heart, and pituitary was autoradiographically detected. However, relative expression levels, as demonstrated by computer-assisted microdensitometry, appeared to be variable. Both transcripts showed higher levels of expression in the liver, anterior and intermediate pituitary lobes, outer kidney medulla, adrenal cortex, skin epidermis, heart and muscle, but lower levels in spleen, thymus, hypodermis, adrenal medulla and posterior pituitary lobe. As a physiological control, hepatic levels of expression were examined during development, and the two forms of mRNA were found to be present at low levels in fetal liver, increasing considerably after birth. These results permit the identification in the adult male rat of cells that might be directly responsive to GH, and demonstrate the differential expression of rGHR and rGHBP transcripts.

Adrenal Glands↗
PubMed1995

Interindividual variability in the urinary excretion of inorganic arsenic metabolites by C57 BL/6J mice: possible involvement of a thiol/disulfide exchange mechanism.

The 24-h urine of 75 C57 BL/6J mice injected s.c. with 0.5 mg/kg arsenic as sodium arsenite were examined for creatinine, S-adenosylmethionine (SAM), urea and inorganic arsenic metabolites including inorganic arsenic (ASi), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). There was interindividual variability of about a 10-fold range in the 24-h urinary excretion of creatinine (80-642 micrograms/24 h, variability (cv) of 33%), SAM (7.5-67.2 micrograms/24 h, cv of 38%), urea (9.5-89.7 mg/24 h, cv of 36%), ASi (0.1-1.6 microgram/24 h, cv of 48%), MMA (0.17-2.1 micrograms/24 h, cv of 50%), DMA (0.73-8.13 micrograms/24 h, cv of 32%) and total arsenic metabolites (1.0-10.4 micrograms/24 h, cv of 31%). Interindividual differences, varying by as much as 5-7-fold, were also found in the urinary proportion of ASi (3-23%, cv of 41%) and MMA (5-22%, cv of 37%), but not in the urinary proportion of DMA (64-90%, cv of 7%). The 24-h urinary excretion of all arsenic metabolites correlated with the 24-h urinary excretion of urea (r = 0.81), creatinine (r = 0.88) and SAM (r = 0.83) as did the 24-h urinary excretion of urea with creatinine (r = 0.94) and SAM (r = 0.86), and the 24-h urinary excretion of creatinine with SAM (r = 0.94). Taken together, these results suggest that the overall intracellular glutathione (GSH)-dependent redox state, as reflected by the 24-h urinary excretion of SAM and creatinine, is involved in the interindividual variability in total arsenic metabolite excretion by C57 BL/6J mice. These preliminary results were also discussed with regard to the involvement of intracellular GSH-dependent redox state in the regulation of the reduction and of the methylation steps of arsenic, and to interindividual variability in the urinary excretion of total arsenic metabolites as a possible complicating factor in the biological monitoring of occupational exposure to arsenic.

Animals↗
PubMed1995

Localization of mRNA coding for the three subtypes of atrial natriuretic factor (ANF) receptors in rat anterior pituitary gland cells.

Atrial Natriuretic Factor (ANF) action is mediated by highly selective and specific receptors. Three subtypes have been characterized and cloned: ANF receptor-A, -B and -C. These subtypes are all expressed in the anterior pituitary of the rat. In the present study, the mRNA for each subtype was detected by in situ hybridization. The amounts of ANFR-A and -B mRNA were found to be similar, and to be twice that of ANFR-C mRNA. At the ultrastructural level, the three types of ANFR mRNA were expressed in three anterior pituitary cell types, namely lactotrophs, corticotrophs, and gonadotrophs, identified by their hormonal content. No signal was revealed in somatotrophs or thyrotrophs. The different forms of mRNA were similar in terms of subcellular localization: in the cytoplasmic matrix and the nuclear euchromatin. These data indicate that the anterior pituitary is an important target tissue for ANF action.

Animals↗
PubMed1995

Oxytocin receptor messenger ribonucleic acid: characterization, regulation, and cellular localization in the rat pituitary gland.

The hypothalamic neuropeptide oxytocin (OT) stimulates the release of several pituitary hormones, including ACTH, LH, and PRL. Although specific OT receptors have been identified in anterior pituitary membranes, the structure and cellular localization of these binding sites have not been elucidated. We previously cloned a rat OT receptor (OTR) gene and showed that its expression in rat uterus results in several transcripts ranging in size from 2.9-6.7 kilobases. In this study we show, by using Northern blot analysis, reverse transcriptase-polymerase chain reaction, and ultrastructural in situ hybridization that the same OTR gene is also expressed in the pituitary, where it gives rise to a 6.7- and a 4.8-kilobase messenger RNA. Ultrastructural in situ hybridization combined with immunogold labeling indicated that pituitary OTR gene expression is highly cell-specific and restricted to lactotrophs. In accordance with this finding, only the lactotroph-derived cell line MMQ expressed the OTR gene among several pituitary cell lines tested. Northern blot analysis, reverse transcriptase-polymerase chain reaction, and in situ hybridization analysis indicated a dramatic increase in pituitary OTR gene expression at the end of gestation and after estrogen treatment. Our results suggest that the OT effect on lactotrophs is direct, whereas OT actions on gonadotrophs and corticotrophs are either indirect or mediated via different receptors. Moreover, our findings imply that OT exerts its full potential as a physiological PRL-releasing factor only towards the end of gestation, and that therefore the role of OT as a hypothalamic PRL-releasing factor may so far have been underestimated.

Animals↗
PubMed1995

Cellular localization of the growth hormone receptor/binding protein in the human anterior pituitary gland.

The increasing use of GH therapy has led to the description of its target cells in human tissues, but no data are yet available on the localization of the GH receptor in the human pituitary. In the present study, we used immunocytochemistry to detect the presence of GH receptor/binding protein (GHR/BP), and we examined its distribution among the different types of human anterior pituitary cells. Human pituitaries were taken from autopsies and were processed for embedding in paraffin wax. Immunocytochemistry was performed by using monoclonal antibody 263 raised against purified rat and rabbit GHR/BP, which cross-reacts with the human GH receptor. In order to determine the types of cells that display immunoreactivity for GHR/BP, adjacent pituitary sections were used to detect immunoreactivity for GH, PRL, ACTH, TSH, LH, and FSH. Several controls were carried out to verify the specificity of the immunostaining. Receptor immunoreactivity was found in the cytoplasm and nuclei of the somatotrophs, lactotrophs, and gonadotrophs but not in the thyrotrophs or corticotrophs. In order to demonstrate that the detected GHR/BP immunoreactivity was not caused solely by a cellular capture, we also investigated the cellular distribution of GHR gene expression. This was performed by in situ hybridization with use of complementary oligonucleotide radioactive probes encoding distinct domains of the GHR. Several tests were carried out to validate the detection of gene expression. In situ hybridization demonstrated the presence of GHR messenger RNAs in the anterior lobe of human pituitary, and examination of the signal strengthened the cell-specificity of GHR gene expression. These results demonstrate the presence of GHR/BP in discrete human pituitary cells and indicate a paracrine, autocrine, or intracrine role for GH in the pituitary.

Adult↗
PubMed1995

[Essential bone cysts in children. Value of systematic cystography. Apropos of a series of 42 cysts].

INTRODUCTION: The treatment of children's essential bone cysts, is controversial. Intra focal injection of a corticoid, the Methylprednisolone, described by Scaglietti in 1974, given in most of the case serials, a rate of healing of more than 30 per cent. MATERIAL AND METHODS: The case serial we present include 42 essential bone cysts treated between 1975 and 1992 in the orthopaedic department of Necker Enfants Malades hospital. These children have been reviewed with a mean follow up of 4 years. A healing rate over 35 per cent has been noticed. However, some failures stayed completely an understanding even if nothing at the beginning let suppose a slower evolution. RESULTS: Attempting to explain those phenomenes, the authors realised in 70 per cent cases, an opaque cystography, before the Methylprednisolone injection. This simple radiological technique permitted to reveal abnormal aspect in 75 per cent cases. Most of the time, it shows massive-veinous licks in an abnormal veinous system or one or plurial separations of the cystic area. This type of picture could perfectly explain the defect of the corticoids action by a lick of the solution or by a partial unefficacity of the solution because of the separation in the cyst area. The hypothetic idea has been completed by the calcul of the duration of the evolution. Effectively, the cysts showing an abnormal cystography had a longer healing delay compared to the cyst whose cystography was normal. CONCLUSION: The opaque cystography is for us a necessary element in the treatment of essential bones cysts, once the diagnostic is certain and the indication of intra focal corticoid injection has been retained. The radiographic study of the cyst area permits to precise the treatment; for example multiplying the injections in the areas of the cysts when there is separations and overseing the evolution.

Adolescent↗
PubMed1994

Receptor-mediated nuclear translocation of growth hormone.

We have previously shown that the growth hormone (GH) receptor-binding protein is associated with the nucleus. We show here both by electron microscopy and nuclear isolation that GH is subject to rapid nuclear translocation. The intracellular fate of intravenously injected 125I-bovine growth hormone (bGH) was examined in the rat hepatocyte by electron microscopic autoradiography. The hormone appeared rapidly at the plasma membrane, then sequentially in lysosomal and multivesicular bodies and/or the nuclear membrane before final translocation to the nuclear matrix. Maximal translocation to the nuclear matrix occurred within 30 min of injection. Nuclear translocation of 125I-hGH was also studied by isolation of nuclei from cells stably transfected with cDNAs encoding the GH receptor, GH-binding protein, and a membrane bound but cytoplasmic domain-deficient receptor. Specific internalization and nuclear translocation of hormone only occurred in cells transfected with the full-length receptor. The translocation was rapid and became saturated within 1 h after addition of hormone to the culture media. SDS-polyacrylamide gel electrophoresis of isolated nuclei showed that GH is transported to the nucleus as the intact molecule. Pretreatment of cells with lysosomotropic agents (chloroquine, ammonium chloride, and bacitracin) decreased hormone degradation and increased nuclear translocation of GH. The nuclear translocation of GH was achieved independent of the cytoskeletal system (microtubular, microfilament, and intermediate filament networks). Thus, GH is subject to rapid receptor-dependent nuclear translocation via the endosomal pathway.

Ammonium Chloride↗
PubMed1994

Internalization and nuclear localization of peptide hormones.

The presence of neuropeptide receptors on the plasma membrane is well accepted, as is its internalization and down-regulation. The analysis of the fate of these peptides within their target-cells is difficult. Endogenous peptides or administered native peptides are visualized in these cells using immunocytology after cryoultramicrotomy. Labelled peptides can be injected and their internalization kinetics studied using ultrastructural autoradiography. The pituitary gland is a suitable model for the study of the neuropeptide mechanism, with the lactotroph function being taken as an example in the present case. Prolactin (PRL) release depends on two main neuropeptides: thyrotropin-releasing hormone (TRH) and somatostatin (SS). The TRH immunoreactivity obtained from endogenous as well as injected material was restricted to the plasma membrane, secretory granules, cytoplasmic matrix and nucleus. The internalization kinetics of exogenous native TRH showed an increase of immunoreactive material in all compartments including the nucleus. The endogenous SSs (SS14 and SS28) were detected in the same subcellular lactotroph compartments. Injection of 125I-SS showed a rapid binding of SS at the plasma membrane level before internalization. For 60 min of in vivo uptake, 125I-SS28, the large SS molecule, was detected in the cytoplasm only, while 125I-SS14 was found in the nuclear matrix. In vitro 125I-SS28 was restricted to the nuclear membrane. Under physiological conditions the endogenous neuropeptides were visualized in the nucleus, but after injection of labelled peptides only small molecules were found in the nucleus. The significance of the presence of these neuropeptides is discussed.

Animals↗
PubMed1994

Ultrastructural localization of endogenous hormones and receptors in bone tissue: an immunocytological approach in frozen samples.

In addition to their well-known mechanical role, bones are essential for the regulation of calcium phosphate metabolism. Most of the peptide and steroid hormones acting on bone tissue exert their cellular effects directly on bone cells after binding to cell receptors. A combined method using immunocytology on ultrathin frozen sections has been applied to bone tissue and made possible the ultrastructural localization of endogenous hormones and hormone receptors. There is immunocytological evidence, at the osteoblast level, for: (1) the presence of calcitonin, parathyroid hormone, growth hormone, 1,25 dihydroxyvitamin D3, aldosterone, corticosterone and progesterone; (2) the existence of 1,25 dihydroxyvitamin D3 and progesterone receptors; (3) the absence of estradiol and receptors, testosterone and gonadoliberin. Ultimate goals of future studies are to extend the ultrastructural localization of hormones at the osteoclast level, to assess the distribution of adhesive proteins and of their receptors in bone cells and matrix, and to use well-calcified human bone samples in order to evaluate better the role of therapeutic agents.

Animals↗