Biomedical subjects

M A Ghatei

Publications and source records attributed to M A Ghatei.

At least 253 records · Page 14Linked to original sources

PubMed1989

Evidence for neuropeptide Y synthesis in the rat anterior pituitary and the influence of thyroid hormone status: comparison with vasoactive intestinal peptide, substance P, and neurotensin.

Neuropeptide Y (NPY), a 36-amino acid member of the pancreatic polypeptide family, was found to be present by RIA and immunocytochemistry in the rat anterior pituitary gland. NPY prohormone messenger RNA (mRNA) was identified in the pituitary by Northern blot analysis. The possible regulation of NPY was examined by determining the effects of thyroid hormone manipulation on peptide synthesis. Three other anterior pituitary neuropeptides, neurotensin (NT), substance P (SP), and vasoactive intestinal peptide (VIP), were studied for comparison. Hypothyroidism was found to significantly increase the pituitary content of NPY, SP, and VIP and their respective mRNAs but to decrease the quantity of NT. Immunocytochemistry revealed very weak NPY immunoreactivity in scattered cells in control rat anterior pituitaries, but in hypothyroid rats a greater number of positive cells were seen, and the staining was relatively intense. These positive cells were identified as a subset of thyrotropes. In T4-induced hyperthyroidism NPY, NT, and VIP levels were unaffected whereas SP concentrations fell considerably. TRH treatment produced a decrease in NT and had no effect on NPY, SP, or VIP. These changes were found only in the pituitary; no net change occurred in hypothalamic peptide and mRNA levels. Since the changes in pituitary peptide and mRNA levels occurred coordinately it appears that regulation by thyroid hormone status occurs, at least in part, directly at the level of gene transcription. The changes in these 4 regulatory peptides in hypothyroidism and their known powerful effects on pituitary function suggest that they may have a significant paracrine or autocrine influence in controlling the alterations in pituitary secretion.

Animals↗

PubMed1989

A new pituitary protein 7B2 is increased in patients with high alpha- or beta-hCG.

The presence of 7B2 (a 180 amino acid peptide first extracted from the porcine pituitary) was investigated by a specific radioimmunoassay and gel filtration chromatography in the plasma of three groups of patients known to have increased levels of alpha- and beta-hCG subunits. Plasma 7B2 immunoreactive equivalents (7B2-IE) were increased in postmenopausal women (range 67-143 pmol/l, median: 94 pmol/l, N = 20, P less than 0.05), in patients with Klinefelter's syndrome (range 195-230 pmol/l), median 213 pmol/l, N = 4, P less than 0.01) and in 17 patients with malignant endocrine gastrointestinal tumours (range 66-20,000 pmol/l, N = 32) compared with healthy controls (range 23.6-98.2 pmol/l, median 41.5 pmol/l, N = 40). Tumour tissue from 4 patients with endocrine pancreatic tumours had significantly higher 7B2-IE concentrations than normal pancreatic tissue, with the highest concentration in an insulinoma (449 pmol/g, normal: 28 pmol/g). During therapy almost parallel changes in plasma 7B2 and other hormones were noted and 7B2-IE therefore might be an additional marker for cancers of the APUD system.

Adolescent↗

PubMed1989

Production of endothelin 1 by cultured bovine retinal endothelial cells and presence of endothelin receptors on associated pericytes.

Endothelinlike immunoreactivity was detected by radioimmunoassay in medium conditioned by cultured endothelial cells obtained from bovine retinal microvessels (9.2 +/- 6.5 pM, n = 4). Sephadex G-25 column chromatography and fast-protein liquid chromatography revealed that most of the endothelinlike immunoreactivity was eluted in an identical position to synthetic endothelin 1. Retinal capillary pericyte-conditioned medium contained 2.9 pM endothelinlike immunoreactivity. In contrast to endothelial cells, retinal pericytes were found to bind endothelin. The dissociation constant and binding capacity were 0.14 nM and 1.5 x 10(5) sites/cell (n = 3), respectively. These findings suggest that endothelin produced by the retinal endothelial cells binds to the pericytes, adding support to the suggestion that pericytes in the retina may have a musclelike function.

Animals↗

PubMed1988

Isolation and characterisation of GLP-1 7-36 amide from rat intestine. Elevated levels in diabetic rats.

Glucagon-like peptide-1 (GLP-1) was purified to homogeneity by HPLC and anion-exchange chromatography. A molecular mass of 3297.4 Da was obtained by FAB mass spectrometry which corresponded exactly to GLP-1 7-36 NH2, providing evidence that amidation occurs at an arginine residue during the post-translational processing of GLP-1. The distribution of GLP-1 7-36 NH2-like immunoreactivity (GLP-1 7-36 NH2 IR) was determined in the rat gastrointestinal tract. Highest concentrations were found in terminal ileum and colon. Streptozocin-induced diabetic rats, who showed a significant increase in food intake, had a significant increase of GLP-1 7-36 NH2 IR in the colon.

Animals↗

PubMed1988

Identification and characterization of glucagon-like peptide-1 7-36 amide-binding sites in the rat brain and lung.

High-affinity binding sites for glucagon-like peptide-1 7-36 amide (GLP-1 7-36 NH2) were identified in rat brain and lung membranes. Binding of [125I]GLP-1 7-36 NH2 was rapid, reversible, specific, saturable and pH dependent. Specific binding in the central nervous system was particularly high in the hypothalamus and the brain stem. Oxyntomodulin, glucagon-like peptide-1, glucagon-like peptide-2 and glucagon were 100-1000-fold less potent than GLP-1 7-36 NH2 in competition for this binding site.

Animals↗

PubMed1988

The presence and molecular forms of cardiodilatin immunoreactivity in the human and rat right atrium.

A sensitive and specific radioimmunoassay has been developed for cardiodilatin, the N-terminal peptide sequence of the atrial natriuretic peptide (ANP) prohormone. Cardiodilatin-immunoreactivity (-IR) concentrations in the human right atrial appendage were found to correlate with ANP-IR concentrations, determined by an established radioimmunoassay, (cardiodilatin-IR = 13.2 +/- 1.2 nmol/g, ANP-IR = 19.8 +/- 2.0 nmol/g, r = 0.80, p less than 0.001). Characterisation of the cardiodilatin-IR in the human and rat right atrium by gel permeation and fast protein liquid chromatography revealed only two cardiodilatin-IR molecular forms. The larger more hydrophobic form, the majority of the cardiodilatin-IR, contained in addition ANP-IR and therefore represents the prohormone. The smaller, less hydrophobic form, lacked ANP-IR and thus represents the cleaved N-terminal peptide sequence of the prohormone. These findings indicate that the prohormone is the major molecular form in the human and rat atrium. Furthermore, they demonstrate that a single large N-terminal peptide, cardiodilatin, derived from the prohormone, may exist as a distinct molecular form in the atrium of these species.

Animals↗

PubMed1988

Isolation of human pancreastatin fragment containing the active sequence from a glucagonoma.

The primary structure of a human pancreastatin-like peptide was determined from a pancreatic glucagonoma. The 28-amino acid peptide was identified using a specific antibody raised against porcine pancreastatin 1-49 and showed a 75% sequence homology with porcine pancreastatin 22-49 and bovine chromogranin A 267-294. Several forms of pancreastatin-like immunoreactivity were found in human endocrine tumors of which the purified peptide was the smallest and contained the active sequence of pancreastatin.

Adenoma, Islet Cell↗

PubMed1988

Localisation of mRNA and co-expression and molecular forms of GRP gene products in endocrine cells of fetal human lung.

The presence of bombesin (gastrin-releasing peptide, GRP)-like immunoreactivity in mucosal endocrine cells of human fetal lung is well established. In this study we have investigated the localisation of pro-GRP mRNA and GRP gene products and compared the distribution and levels of extractable GRP- and C-terminal flanking peptide of human pro-GRP-like immunoreactivity in order to verify synthesis and to investigate their coexistence and molecular forms. Human fetal lungs (14 to 23 weeks gestation) were immunostained, and extracts were assayed using region-specific antisera to pro-GRP. Additional antisera to chromogranin and protein gene product 9.5 (PGP 9.5) were used for immunostaining by the peroxidase anti-peroxidase technique and for double immunofluorescence staining using antisera raised in two species. Immunoreactivity for both bombesin (GRP) and flanking peptide was seen mainly in the same endocrine cells, but more cells were stained with antisera to flanking peptide than with antiserum to bombesin (GRP). In situ hybridisation showed that pro-GRP mRNA was present and thus synthesis of the peptides was taking place. Endocrine cells and nerve fibres were PGP 9.5-immunoreactive, and a subset of cells was immunoreactive for bombesin gene products. Radioimmunoassay and chromatography show that pro-GRP is present in both the uncleaved and cleaved forms, and, in agreement with immunocytochemistry results, that an excess of C-terminal peptide of pro-GRP is detectable. It is therefore concluded that GRP-like peptides and flanking peptide are co-localised in human pulmonary endocrine cells, but the latter is found in larger concentrations than free GRP. Thus GRP-like peptides may be secreted separately from the flanking peptide(s) of pro-GRP.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, Gel↗

PubMed1988

Elevated 7B2 levels during normal human pregnancy.

In a cross-sectional study the plasma concentrations of immunoreactive 7B2, a novel protein originally isolated from the pituitary gland, was measured in 60 healthy pregnant and postpartum women. The mean circulating concentration of 7B2 immunoreactive equivalents was found to be significantly increased throughout pregnancy (10 to 12 weeks, 52.2 +/- 13.1 pmol/L; 20 to 22 weeks, 74.4 +/- 20.1 pmol/L; 30 to 32 weeks, 56.0 +/- 12.9 pmol/L; and 36 to 40 weeks, 85.7 +/- 13.6 pmol/L) when compared with a group of 32 age-matched nonpregnant controls (19.7 +/- 5.0 pmol/L); (p less than 0.01). The highest 7B2 plasma concentrations were found shortly before delivery (36 to 40 weeks) and fell sharply after birth, returning to normal within 4 to 6 weeks. Fetal plasma from both umbilical artery and vein was found to have particularly high concentrations of 7B2-like immunoreactivity (396 +/- 19 and 361 +/- 24 pmol/L, respectively), and 7B2 was extractable from the placenta. Chromatographic analysis of plasma and tissue extracts showed the main peak of immunoreactivity to coincide with that originally described in the pituitary gland. Although the function of 7B2 is at present unknown, our data suggest that 7B2 immunoreactivity in fetal blood originates from the fetus and may play an important role in pregnancy.

Adolescent↗

PubMed1988

Differential expression of alpha-CGRP and beta-CGRP by primary sensory neurons and enteric autonomic neurons of the rat.

Expression of the calcitonin gene-related peptide, alpha-calcitonin gene-related peptide (CGRP), and the homologous beta-CGRP were compared in sensory and enteric nerves of the rat. Analysis of CGRP-like immunoreactivity by cation exchange chromatography and radioimmunoassay showed that in the dorsal root ganglia, dorsal spinal cord and in those peripheral tissues where CGRP-like immunoreactivity is primarily localized to sensory fibres, alpha-CGRP concentrations were three to six times greater than beta-CGRP concentrations. In the intestine, however, beta-CGRP concentrations were up to seven times greater than alpha-CGRP concentrations. Only beta-CGRP was detected in the intestines of capsaicin-treated rats. Northern blot and in situ hybridization to alpha-CGRP- and beta-CGRP-specific probes showed that while both alpha-CGRP and beta-CGRP messenger ribonucleic acids occurred in the dorsal root ganglia, only beta-CGRP messenger ribonucleic acid occurred in the intestine, where it was localized to enteric neurons. Receptor binding sites on membranes of rat heart and colon had approximately equal affinities for alpha-CGRP and beta-CGRP. The two peptides were equipotent in increasing the rate and force of atrial contractions but alpha-CGRP was slightly (2.6 times) more potent than beta-CGRP in relaxing colonic smooth muscle. Thus, both alpha-CGRP and beta-CGRP occur in the rat nervous system and are both biologically active. Sensory neurons and enteric neurons have been identified as populations which preferentially express alpha-CGRP and beta-CGRP, respectively.

Animals↗

PubMed1988

The distribution of melanin-concentrating hormone-like immunoreactivity in the central nervous system of rat, guinea-pig, pig and man.

The distribution of melanin-concentrating hormone-like immunoreactivity was investigated by radioimmunoassay in the CNS of rat, guinea-pig, pig and man. Highest concentrations of melanin-concentrating hormone-like immunoreactivity were found in the hypothalamus of all the species: rat 204.4 +/- 14.9; guinea-pig 159.5 +/- 23.3; pig 10.9 +/- 4.5 and man 80.1 +/- 19.1 pmol/g. Gel chromatographic analysis of hypothalamic extracts showed five immunoreactive peaks of melanin-concentrating hormone-like immunoreactivity in the rat and pig and six in the guinea-pig and man. High-performance liquid chromatography analysis of hypothalamic extracts showed five immunoreactive peaks in rat, guinea-pig, pig and four in man. However, these peaks appeared at different retention times from that of the single peak of salmon melanin-concentrating hormone. Examination of subcellular fractions of whole rat brain showed that most of the melanin-concentrating hormone-like immunoreactivity is found in the synaptosome fraction. Stimulation of melanin-concentrating hormone-like immunoreactivity release from rat hypothalamic slices revealed that potassium in the presence of calcium stimulated melanin-concentrating hormone-like immunoreactivity release. These findings suggest that mammalian melanin-concentrating hormone-like immunoreactivity has a different amino acid sequence from salmon melanin-concentrating hormone and may exist in multiple molecular forms. It is possible that melanin-concentrating hormone may play a role as a neurotransmitter or modulator in the mammalian CNS.

Adult↗

PubMed1988

Cerebellin-like peptide: tissue distribution in rat and guinea-pig and its release from rat cerebellum, hypothalamus and cerebellar synaptosomes in vitro.

We have developed a specific radioimmunoassay for "cerebellin", a 16-amino acid peptide recently isolated from rat cerebellum. In both rat and guinea-pig, cerebellin-like immunoreactivity was highest in the cerebellum but was also present in high concentrations elsewhere in the central nervous system, especially in the hypothalamus. In both species, cerebellin-like immunoreactivity was found in other organs (heart, kidney and stomach) and at lower concentrations in the gastrointestinal tract. In the brain of both species, cerebellin-like immunoreactivity consisted of a single molecular form with an elution position on gel filtration and high-performance liquid chromatography identical to that of synthetic rat cerebellin. However, peripheral tissue contained an additional immunoreactive peak of higher molecular weight. Cerebellin was concentrated in synaptosomal preparations of rat brain, and its subcellular distribution pattern in rat brain was identical to that of two other known synaptosomal peptides, vasoactive intestinal polypeptide and substance P. Studies with superfused cerebellar synaptosomes and slices of rat cerebellum and hypothalamus demonstrated calcium-dependent cerebellin release when stimulated by high potassium concentrations as well as the addition of the calcium ionophore A23187. Cerebellin has therefore a widespread distribution and fulfils two criteria for a neurotransmitter, in that it is found in brain synaptosomes and shows calcium dependent, depolarization-induced release from nervous tissues and isolated nerve endings. It may, therefore, be a component of a novel neurotransmitter system.

Animals↗

PubMed1988

The occurrence of pancreastatin in tumours of the diffuse neuroendocrine system.

We have reported previously the localization of the 49 amino acid peptide pancreastatin to all identifiable endocrine cells of porcine gut, pancreas and adrenal, thyroid and pituitary glands. In this study, we have investigated the occurrence of pancreastatin in a series of human neuroendocrine tumours using an antibody to whole synthetic porcine pancreastatin. The most consistent immunostaining for pancreastatin was found in carcinoid tumours of ileum (four out of six), rectum (four out of six), ovary (two out of two) and lung (nine out of 10). Radioimmunoassay of tumour extracts showed that the concentrations of pancreastatin in ileal carcinoids were very high (mean 71.6, range 31.0-184.0 pmol g-1). The high rate of positivity in lung carcinoids contrasted sharply with the results of 10 pulmonary small cell carcinomas which displayed no immunoreactivity and contained minimal concentrations of pancreastatin (mean 2.0, range 0-6.0 pmol g-1). Extra-adrenal paragangliomas also contained pancreastatin (seven out of 10), but although radioimmunoassay detected peptide in phaeochromocytomas (mean 29.8, range 8.0-69.0 pmol g-1), immunocytochemistry did not. Porcine pancreastatin shows structural homology with bovine chromogranin A, an observation which has led to suggestions that chromogranin is a precursor for the peptide. More recently, a sequence homologous to porcine pancreastatin has been identified in the human chromogranin A molecule. In this study, immunostaining with an antiserum to human chromogranin gave positive results in most cases of each tumour type except the small cell carcinomas. The lack of consistent relationships between chromogranin and pancreastatin immunoreactivities may reflect the fact that the antiserum to pancreastatin was raised against the porcine peptide. When antibodies to human pancreastatin become available, the peptide may prove to be a more consistent marker for neuroendocrine tumours.

Adenocarcinoma↗

PubMed1988

Does resection enhance the response of the intestine to urogastrone-epidermal growth factor in the rat?

1. The objective of this study was to see whether another proliferative stimulus could modify the marked proliferative effect of human epidermal growth factor (urogastrone-epidermal growth factor, URO-EGF) on the gastrointestinal epithelium. 2. The response of the gastrointestinal tract to URO-EGF was investigated in rats maintained on total parenteral nutrition (TPN) with or without 75% small bowel resection. 3. Continuous infusion of 60 micrograms of recombinant beta-urogastrone/day per rat increased proliferation in the stomach by over four times (P less than 0.01), doubled proliferation in the small intestine (P less than 0.001) and increased it by four and a half times in the colon (P less than 0.001) in the control group. No significant effect of urogastrone was observed in the stomach of the resected groups, but proliferation was also increased in the small intestine by one and a half times (P less than 0.001) and by nearly four times in the colon (P less than 0.001). 4. Two-way analysis of variance showed that resection had a significant effect (P less than 0.01) on proliferation below the anastomosis and in the ileum. However, the response of the ileum was only half that observed in orally fed rats, which confirms the importance of 'luminal nutrition' in the response to resection. 5. Intestinal resection in the TPN rat was associated with a small rise in plasma enteroglucagon levels, suggesting that this hormone may be implicated in the adaptive response of the small intestine to resection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Reduced hypothalamic somatostatin and neuropeptide Y concentrations in the spontaneously-diabetic Chinese hamster.

Hypothalamic concentrations of six regulatory peptides having central effects on appetite and/or glucoregulation were measured by radioimmunoassay in spontaneously-diabetic Chinese hamsters and in age- and sex-matched non-diabetic control animals. In the diabetic hamsters, hypothalamic concentrations of somatostatin and neuropeptide Y were significantly reduced by 25-30% below controls. None of the other four peptides examined (bombesin, galanin, neurotensin and vasoactive intestinal peptide) differed significantly between the two groups. Disturbances in neuropeptide Y (the most potent central appetite stimulant yet discovered) and in somatostatin could be related to hyperphagia, an early and possibly primary abnormality of the diabetic syndrome in the Chinese hamster.

Animals↗

PubMed1988

Cloning, characterization, and sequence of a porcine cDNA encoding a secreted neuronal and endocrine protein.

This report describes the cloning, sequence, and characterization of a cDNA which encodes a protein synthesized in the brain and endocrine tissue, including pituitary, adrenal medulla, and ovary. The deduced 207-amino-acid sequence of the 23-kD protein contains a hydrophobic signal peptide suggesting that it is secreted. Northern blot analysis utilizing the cDNA clone identifies a single RNA of approximately 1400 nucleotides in porcine brain, adrenal medulla, pituitary, and ovary, as well as in human endocrine tumors. Very high levels of RNA were observed in one human pancreatic tumor. Southern blot analysis suggests that sequences homologous to the porcine cDNA are present in human, cow, rat, and salmon DNA, indicating that the gene(s) have been highly conserved during evolution.

Amino Acid Sequence↗

PubMed1988

Localization of bombesin-like peptides in tumors.

The localization of bombesin gene products in neuroendocrine tumors was achieved by a number of techniques used in combination. These included immunocytochemistry, radioimmunoassay, and chromatographic procedures using a variety of region-specific antibodies recognizing separate portions of probombesin. In situ hybridization using cRNA probes was employed to analyze bombesin gene expression at a cellular level. A novel procedure using a divalent form of bombesin and gold-labeled monoclonal antibodies for the localization of bombesin binding sites at the ultrastructural level was employed in this study. Antibodies to neuron-specific enolase and electron microscopy were employed for the determination of neuroendocrine differentiation. Surgical samples of pulmonary (n = 250) and nonpulmonary (n = 28) small cell carcinomas, 49 carcinoids, and 62 atypical lung carcinoids were investigated and compared with 169 control tumors, including lymphomas, adenocarcinomas, squamous cell carcinomas, and non-small-cell undifferentiated tumors. Cell lines cultured from pulmonary small cell carcinoma and smear preparations of pleural effusions from patients with small cell carcinoma of the lung were also investigated. Strong immunostaining for neuron-specific enolase was noted in all neuroendocrine tumors investigated, and no immunoreactivity was noted in control cases. Electron-dense neurosecretory granules were abundant in carcinoid tumors, scattered in small cell carcinoids, and absent in control cases. Immunostaining for bombesin was particularly strong in benign carcinoids, whereas the more malignant neuroendocrine tumors (e.g., small cell carcinomas) stained best with antibodies to the carboxyl-terminal flanking portion of human probombesin (proGRP). These findings were further validated by radioimmunoassay and chromatography of tissue extracts. Specific binding sites for bombesin were demonstrated on the surface of small cell carcinoma cells maintained in culture. In situ hybridization demonstrated mRNA for preprobombesin in all small cell carcinomas investigated, including surgical samples, cytological preparations, and cell lines. Hybridization reactions varied in intensity, with some cells in autoradiograms almost masked by silver grains and others showing much lighter deposits.

Bombesin↗

PubMed1988

Increase in plasma concentrations of cardiodilatin (amino terminal pro-atrial natriuretic peptide) in cardiac failure and during recumbency.

Plasma concentrations of cardiodilatin, the peptide sequence at the amino terminal of the pro-atrial natriuretic peptide, in 17 normal subjects ranged from 59 to 202 (mean 118 (SEM) (9] pmol/l. Recumbency increased the mean (SEM) concentration to 160 (13) pmol/l. The plasma concentration of cardiodilatin in 24 patients with congestive cardiac failure was much higher (964 (175) pmol/l) than in the normal subjects. It was highest in those with heart failure in New York Heart Association functional classes III and IV and the concentration correlated both with atrial natriuretic peptide concentrations and left ventricular ejection fraction. Concentrations rose during induced tachycardia in three patients tested. Chromatography showed a single clean peak of plasma cardiodilatin immunoreactivity. It seems that cardiodilatin is a second circulating cardiac peptide that is jointly released with atrial natriuretic peptide by common stimuli. Other workers have reported that, like atrial natriuretic peptide, three partial cardiodilatin sequences can stimulate renal particulate guanylate cyclase and increase cyclic guanosine monophosphate. The simultaneous release of cardiodilatin in higher circulating concentrations than atrial natriuretic peptide may be relevant to the finding that appropriate concentrations of exogenous atrial natiuretic peptide alone do not produce the full renal effects associated with endogenous peptide release.

Adult↗