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S R Bloom

Publications and source records attributed to S R Bloom.

At least 253 records · Page 14Linked to original sources
PubMed1993

Increases in neuropeptide Y content and gene expression in the hypothalamus of rats treated with dexamethasone are prevented by insulin.

The neurotransmitter neuropeptide Y (NPY) is abundant in the hypothalamus where its actions include the potent stimulation of food intake. The peripheral metabolic and hormonal signals involved in its regulation are not clear. The aim of this study was to investigate possible actions of corticosteroids and insulin on hypothalamic NPY synthesis and content in vivo. We measured NPY content in individual hypothalamic nuclei, and hypothalamic NPY mRNA by Northern blotting in whole hypothalamus in rats treated with dexamethasone (0.4 mg/kg/day) and dexamethasone plus insulin (60 U/kg/day), compared to controls. The effect of stopping dexamethasone treatment was also studied. Dexamethasone treatment produced significant increases in NPY in the paraventricular (11.0 +/- 1.3 vs. 7.1 +/- 0.4 fmol/micrograms protein, p < 0.05) and arcuate (6.2 +/- 0.3 vs. 3.8 +/- 0.2 fmol/microgram protein, p < 0.001) nuclei of the hypothalamus, paralleled by a 38% increase in total hypothalamic NPY mRNA (p < 0.05). These changes were not seen in the group treated with dexamethasone plus insulin. In the group in whom dexamethasone was stopped, NPY mRNA was unchanged compared to controls, but peptide content remained increased in the arcuate but not the paraventricular nucleus (arcuate 7.7 +/- 0.7 vs. 5.5 +/- 0.7, PVN 4.9 +/- 1.0 vs. 4.7 +/- 0.9 fmol/microgram protein). Thus hypothalamic NPY and its mRNA were increased by corticosteroid administration, and this effect was prevented by systemic insulin treatment. This dual regulatory system for hypothalamic NPY may be important in the control of food intake by corticosteroids and insulin.

Animals↗
PubMed1993

Increased neuropeptide-Y messenger ribonucleic acid (mRNA) and decreased neurotensin mRNA in the hypothalamus of the obese (ob/ob) mouse.

The obese hyperglycaemic ob/ob mouse exhibits hyperphagia and other abnormalities of hypothalamic function. We measured hypothalamic concentrations of four peptides implicated in the control of appetite and energy expenditure, neuropeptide-Y (NPY), neurotensin, galanin, and somatostatin, by RIA and their respective mRNAs using semiquantitative Northern blotting. Using lean (+/+) mice as controls, we found unchanged concentrations of NPY, galanin, and somatostatin and a 25% reduction in neurotensin (P < 0.01). Neurotensin mRNA was similarly decreased (by 30%; P < 0.02), while NPY mRNA was increased 3-fold (P < 0.01). Centrally administered neurotensin decreases food intake, whereas NPY potently stimulates food intake. An increase in NPY gene expression together with reductions in neurotensin concentration and mRNA in the hypothalamus may be implicated in the development of hyperphagia and other neuroendocrine abnormalities seen in the ob/ob mouse.

Animals↗
PubMed1993

A role for neuropeptide-Y, dynorphin, and noradrenaline in the central control of food intake after food deprivation.

A marked increase in food intake is observed in the rat after central injection of neuropeptide-Y (NPY), dynorphin, or noradrenaline (NA). Levels of both NPY and dynorphin are increased in the hypothalamus of food-deprived rats. The aim of this study was to explore the role of NPY, dynorphin, and NA in the central control of feeding after a period of food deprivation. We have investigated the effect of intracerebroventricular injection of a monoclonal antibody to NPY (NPYAb), a potent and selective kappa-opioid receptor antagonist norbinaltorphimine (norBNI), and the alpha-adrenergic antagonist phentolamine on fast-induced food intake. In animals provided with food after a 24-h fast, NPYAb given 10 min before presentation of food reduced food intake by 30% (P < 0.01) compared to that of animals pretreated with an antibody to chloroquine. A similar (34%; P < 0.05) reduction in fast-induced feeding occurred after pretreatment with norBNI. If norBNI was given together with NPYAb, then a reduction of 51% (P < 0.05) was observed. Pretreatment with phentolamine reduced fast-induced food intake by 39% (P < 0.05), with no evidence of an additive effect when phentolamine was given together with NPYAb. These data would support a role for endogenous NPY, dynorphin, and NA in the mediation of fast-induced feeding. NPY would seem to act independently of dynorphin, but through the same mechanism as NA.

Animals↗
PubMed1993

Characterization of the rat uterine neuromedin U receptor.

Neuromedin U (NmU) is a novel peptide that potently contracts smooth muscle, including rat uterus in vitro. No receptors have so far been demonstrated in any tissue. We have characterized the receptor for NmU in rat uterine membrane preparations. The binding of [125I] rat NmU was saturable, specific, reversible, and time, temperature, and pH dependent. The nonhydrolysable analog of GTP, GTP-gamma-S, reduced binding in a dose-dependent manner, suggesting that the binding site is coupled to a G-protein. Scatchard analysis of saturation binding studies showed a single class of binding site with a maximal binding capacity of 580 +/- 140 fmol/mg membrane protein and a dissociation constant of 0.35 +/- 0.09 nM (n = 3). Rat NmU and NmU-8 (the C-terminal region of the larger molecule) displaced [125I]rat NmU, displaying an IC50 of 1 x 10(-9) M and 6 x 10(-8) M, respectively. Chemical cross-linking studies demonstrated NmU binding sites on the rat uterus to have an M(r) of 48,500. This band was absent in the presence of 0.2 microM NmU. Thus the rat uterus contains specific NmU binding sites through their physiological role awaits identification.

Amino Acid Sequence↗
PubMed1993

Molecular identification of binding sites for calcitonin gene-related peptide (CGRP) and islet amyloid polypeptide (IAPP) in mammalian lung: species variation and binding of truncated CGRP and IAPP.

We have investigated the binding of rat [125I]islet amyloid polypeptide (IAPP) and [125I]calcitonin gene-related peptide (CGRP) to lung membranes from the rat, rabbit, and bull and have characterized the mol wt (M(r)) of the binding site for each ligand by chemical crosslinking. Results imply the existence of three distinct types of binding site demonstrated by both [125I]CGRP and [125I]IAPP in each of the three species investigated. These were differentiated by the relative potencies of displacement by rat CGRP, human CGRP-(8-37), rat IAPP, and the rat IAPP fragments IAPP-(8-37), IAPP-(12-37), IAPP-(25-37), and IAPP-(28-37). High affinity binding sites were identified for [125I]CGRP [rat Ki, 0.119 +/- 0.027 nM (n = 6); rabbit Ki, 0.944 +/- 0.075 nM (n = 6); bull Ki, 0.20 +/- 0.031 nM (n = 6)], and CGRP-(8-37) was found to displace [125I]CGRP in all species [rat Ki, 6.63 +/- 0.91 nM (n = 6); rabbit Ki, 22.70 +/- 3.79 nM (n = 6); bovine Ki, 26.9 +/- 0.21 nM (n = 3)]. Compared to CGRP-(8-37), displacement by IAPP also showed varying affinities that were similar to that of CGRP-(8-37) (rat), lower than that of CGRP-(8-37) (rabbit), or higher than that of CGRP-(8-37) (bull). Truncation of IAPP caused large parallel decreases in its affinity for [125I]CGRP in the rabbit and bull by the loss of residues 1-8 (rabbit) and 1-12 (bull), but was not as pronounced in the rat. [125I]IAPP demonstrated high affinity binding in each species [rat Ki, 5.86 +/- 0.86 nM (n = 6); rabbit Ki, 18.72 +/- 2.90 nM (n = 6); bull Ki, 1.97 +/- 0.40 nM (n = 6)]. Truncation of IAPP caused a reduction of its affinity for [125I]IAPP in all species by the loss of residues 1-28. Chemical cross-linking analysis indicated binding of both ligands to sites of 64,000 M(r) in the rat and 50,500 and 51,000 M(r) in the rabbit and bull, respectively. In addition, [125I]IAPP bound to to a site of 100,000 M(r) in the rat. [125I]CGRP and [125I]IAPP binding were reduced in the presence of guanosine 5-o-(3-Thiotriphosphate) in all species, indicating an association with G-proteins. This study implies the existence of CGRP/IAPP-binding sites in the lungs of these species that show varying and complex patterns of displacement by CGRP, IAPP, and their fragments.

Amino Acid Sequence↗
PubMed1993

Islet amyloid polypeptide-like immunoreactivity in human tissue and endocrine tumors.

We have detected islet amyloid polypeptide (IAPP)-like immunoreactivity (-LI) in human pancreas and in a range of endocrine tumors, including oat cell carcinoma of the lung and pancreatic tumours producing insulin, gastrin, glucagon, and vasoactive intestinal peptide. Gel permeation chromatography of the IAPP-LI revealed that, except in the carcinoid, more than 80% coeluted with synthetic human IAPP. The remaining immunoreactivity consisted of variable amounts of larger and smaller molecular forms. The concentration of IAPP-LI in the circulation of patients with diagnosed pancreatic endocrine tumors was not significantly elevated above normal fasting levels. IAPP is, therefore, produced by a range of endocrine tumors and may relate to the deposition of endocrine amyloid.

Adult↗
PubMed1993

Distribution, molecular characterization of pituitary adenylate cyclase-activating polypeptide and its precursor encoding messenger RNA in human and rat tissues.

The distribution of a novel neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP), was studied in the brain of the rat and man and a variety of other rat tissues using Northern blot hybridization and two radioimmunoassays for PACAP 1-38 and PACAP 1-27. The assay, using PACAP 1-38 as standard and an antibody to PACAP 21-38 and radiolabelled tracer, revealed immunoreactive PACAP in all brain regions examined, with the highest concentrations in the rat being in the hypothalamus, nucleus accumbens and substantia nigra (380 +/- 34, 310 +/- 37 and 346 +/- 30 pmol/g wet tissue, means +/- S.E.M., n = 5 respectively), whilst in man the highest concentrations were found in the pituitary gland (15.8 +/- 4.7 pmol/g). Immunoreactive PACAP 1-38 was also detected in the rat gastrointestinal tract, adrenal gland and testis. The assay using PACAP 1-27 as standard and label and an antibody to PACAP 1-27 detected immunoreactive PACAP only in the rat hypothalamus (12.6 +/- 1.8 pmol/g wet tissue, n = 5). PACAP mRNA of approximately 2.7 kb in size was detectable in all brain regions of both rat and man, and its distribution paralleled that of the immunoreactive peptide. Gel permeation chromatography of different regions of human and rat hypothalamus, and also rat spinal cord and small intestine, showed a broad immunoreactive peak corresponding to PACAP 1-38. Fast protein liquid chromatography (FPLC) resolved this peak into two immunoreactive peaks, the majority eluting in the position of synthetic PACAP 1-38.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Vasoactive intestinal peptide, but not pituitary adenylate cyclase-activating peptide, modulates the responsiveness of the gonadotroph to LHRH in man.

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are hypothalamic peptides sharing considerable sequence homology which are postulated to be hypophysiotrophic releasing factors. When infused into man, PACAP has no effect on anterior pituitary hormone levels, while VIP causes a significant increase in circulating prolactin concentrations. However, PACAP has recently been shown to augment the release of LH and FSH in response to LHRH in rat anterior pituitary cell culture. In order to ascertain if either peptide has a similar effect in man, PACAP and VIP were infused at 3.6 pmol/kg per min into six healthy male volunteers, and an LHRH test was performed 30 min after the infusion was commenced. Infusion of PACAP did not alter the gonadotrophin response to LHRH significantly. However, VIP augmented the release of LH significantly, both during the infusion and for 30 min thereafter, although there was no effect on FSH release. Thus VIP, but not PACAP, potentiates the release of LH after LHRH injection in man.

Follicle Stimulating Hormone↗
PubMed1993

Influence of islet amyloid polypeptide and the 8-37 fragment of islet amyloid polypeptide on insulin release from perifused rat islets.

IAPP, or amylin, is a 37-amino acid peptide that is co-secreted with insulin from the pancreatic beta-cells. We have determined the effects of IAPP and the antagonist 8-37 fragment of IAPP on the secretion of insulin from isolated rat islets studied in a perifusion system. Insulin secretion was stimulated by 8 mM glucose and 0.2 microM carbachol. IAPP at 10(-7) M reduced insulin release by 32% from 7.1 (95% Cl 5.8-8.6) to 4.8 (3.0-7.5) fmol.min-1 x islet-1 (P = 0.046, n = 7). IAPP at 1.5 x 10(-6) M reduced insulin release by 62% from 6.5 (3.4-12.3) to 2.5 (1.4-4.4) fmol.min-1 x islet-1 (P = 0.001, n = 6). IAPP at 10(-5) M decreased insulin release by 70% (P < 0.001, n = 6). When IAPP (8-37) at 10(-5) M was added to IAPP at 1.5 x 10(-6) M, there was only a 22% reduction of insulin release (P = 0.06, n = 6) compared with control chambers with no peptide added. This reduction was less (P = 0.002) than observed with IAPP (1.5 x 10(-6) M) alone. IAPP (8-37) at 4 x 10(-5) M in the absence of exogenously added IAPP increased insulin secretion by 48% (P = 0.01, n = 6), but IAPP (8-37) at 10(-5) M did not alter insulin secretion. These findings demonstrate that IAPP decreases insulin secretion from islet beta-cells, an effect that can be antagonized by the 8-37 fragment of IAPP.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloid↗
PubMed1993

Pleural involvement in the carcinoid syndrome.

Tissue fibrosis is a recognized complication of the carcinoid syndrome but pleural changes have not been described. Prompted by the finding of severe pleural thickening in two patients with the metastatic carcinoid syndrome but no thoracic metastases or previous pleural disease we reviewed the chest radiographs and CT scans in 50 patients with the carcinoid syndrome investigated from 1981 to 1990. Pleural abnormality was noted in 14 of the 50 patients (28%), five of whom had other possible causes for pleural disease. However, nine (18%) patients had 'idiopathic' pleural thickening. Pleural disease had developed within 2 years of the diagnosis in all cases, and seven of the nine patients had fibrosis elsewhere (heart valves, skin or mesentery). There were no features to suggest a more rapid disease progression in the patients with pleural disease. We suggest that the pleural abnormality is a complication of metastatic carcinoid disease.

Humans↗
PubMed1992

The purification and sequence analysis of an avian neuromedin U.

In this study we have purified an avian homologue of neuromedin U from the chicken. Each step of the purification process was followed by a specific radioimmunoassay developed using porcine neuromedin U. Microsequence analysis characterised the peptide to be 25 amino acid residues long with the following sequence: Y-K-V-D-E-D-L-Q-G-A-G-G-I-Q-S-R-G-Y-F-F-F-R-P-R-N. Chicken neuromedin U has marked sequence similarity with the porcine peptide at its bioactive C-terminal region. Our findings demonstrate that the amino acid sequence of neuromedin U is markedly conserved in species which have diverged millions of years ago in evolutionary terms.

Amino Acid Sequence↗
PubMed1992

The physiology of calcitonin gene-related peptide in the islet compared with that of islet amyloid polypeptide (amylin).

Following the discovery of a second gene containing a CGRP-like sequence, we demonstrated that "beta-CGRP" was indeed translated as a 37-amino acid peptide in vivo and was the predominant form of CGRP produced by the enteric nervous system. The presence of CGRP in the islet has been reported by several groups. We now show that beta-CGRP is again the major form. Another 37-amino acid peptide was recently isolated from islet amyloid deposits and found to have approximately 50% amino acid sequence homology with CGRP. Islet amyloid polypeptide, or amylin, is co-localized with insulin to the beta-cell secretory granule and is synthesized and released in parallel with insulin in response to a range of physiological and pharmacological stimuli. IAPP was subsequently shown, like CGRP, to inhibit the release of insulin pharmacologically. Interestingly, it was also shown to decrease the uptake of glucose by striated muscle, though it was considerably less potent than CGRP. This led to the suggestion that IAPP might be a circulating hormone regulating peripheral insulin sensitivity. Infusion of IAPP in human volunteers to produce plasma concentrations more than 100-fold higher than those seen physiologically, however, failed to alter peripheral glucose disposal. We conclude that beta-CGRP and IAPP are likely to play a role in local paracrine control of the islet.

Amyloid↗
PubMed1992

Neuropeptide content of purified rat brain cholinergic synaptosome subpopulations.

Cholinergic synaptosomes from rat cerebral cortex were isolated by a magnetic immunoaffinity technique, i.e. immunomagnetophoresis. This subpopulation was extracted and subjected to radioimmunoassay for 4 neuropeptides:neuropeptide Y (NPY); vasoactive intestinal peptide (VIP); substance P (SP); and somatostatin (SRIF). Three of the 4 neuropeptides were enriched in the sorted fraction compared with the mother fraction with respect to the cytosolic marker lactate dehydrogenase (LDH). The most enriched neuropeptide was NPY followed by SP and VIP. Somatostatin was not enriched in the cholinergic synaptosome subpopulation. The presence of NPY has not previously been reported in cortical cholinergic neurones.

Animals↗
PubMed1992

Investigation of the interaction of VIP binding sites with VIP and PACAP in human brain.

We have compared the binding of [125I]vasoactive intestinal polypeptide (VIP) to human brain membranes with that of [125I]PACAP27. [125I]VIP was displaced by PACAP27, VIP and two synthetic peptides, peptide-1 (N-terminal PACAP27/C-terminal VIP) and peptide-2 (N-terminal VIP/C-terminal PACAP27), but the IC50 of PACAP27 and peptide-1 were 10-20 times lower than those of VIP and peptide-2. [125I]PACAP27 was readily displaced by PACAP27 and peptide-1, with an IC50 of less than 1 nM, but poorly by VIP and peptide-2. Chemical cross-linking revealed that both labels were bound to polypeptides of Mr 66,000 and Mr 50,000. The results indicate that in human brain membranes both binding sites have a higher affinity to the N-terminal sequence of PACAP27, and VIP binding sites prefer PACAP27 to VIP itself.

Adenylyl Cyclases↗
PubMed1992

Glucose transporter expression and glucose utilization in skeletal muscle and brown adipose tissue during starvation and re-feeding.

Starvation (48 h) decreased the concentration of mRNA of the insulin-responsive glucose transporter isoform (GLUT 4) in interscapular brown adipose tissue (IBAT) (56%) and tibialis anterior (10%). Despite dramatic [7-fold (tibialis anterior) and 40-fold (IBAT)] increases in glucose utilization after 2 and 4 h of chow re-feeding, no significant changes in GLUT 4 mRNA concentration were observed in these tissues over this re-feeding period. The results exclude changes in GLUT 4 mRNA concentration in mediating the responses of glucose transport in these tissues to acute re-feeding after prolonged starvation.

Adipose Tissue, Brown↗
PubMed1992

Gut hormones and gastrointestinal motility in children with cystic fibrosis.

Intestinal dysmotility may be an important factor contributing to various gastrointestinal complications associated with cystic fibrosis. Motilin, enteroglucagon, neurotensin, and peptide YY may each play a role as endocrine hormones influencing gastrointestinal motor activity. Fasting children with cystic fibrosis (N = 8) and controls (N = 18) received a liquid nutrient test meal (fat 4 g/100 ml, protein 4 g/100 ml, carbohydrate 20 g/100 ml, 125 kcal/100 ml; 200 ml/m2) containing lactulose (5 g/100 ml), and the plasma concentrations of these peptides were studied. Mouth-to-cecum transit time was simultaneously studied using the breath H2 technique. Fasting levels of peptide YY and the postprandial response of all four peptides were significantly increased in those with cystic fibrosis. In repeat studies on those with cystic fibrosis after a period of altered pancreatic enzyme supplementation, no significant changes in peptide concentrations were observed. A rise in breath H2 permitting estimation of mouth-to-cecum transit time was noted in 17 control subjects (70-220 min, median 140). In contrast, a rise occurred in only two with cystic fibrosis after low-dose enzyme (70 and 180 min), and four after high-dose enzyme replacement (120-230 min, median 155). Altered gut hormone secretion may play a role in the pathophysiology of intestinal dysmotility in patients with cystic fibrosis.

Adolescent↗
PubMed1992

Nutrient-independent increases in proglucagon and ornithine decarboxylase messenger RNAs after jejunoileal resection.

To assess potential mediators of adaptive bowel growth, ileal proglucagon messenger RNA (mRNA) ornithine decarboxylase (ODC) mRNA, plasma enteroglucagons, and plasma glucagonlike peptide I (GLP-I) were analyzed in rats soon after jejunoileal resection or control transection. Analyses were performed before and after refeeding to establish whether responses are nutrient dependent. The elevation of ileal proglucagon and ODC mRNAs within 12 hours after resection and before refeeding shows a nutrient-independent component of the adaptive response. The onset of adaptive growth of the ileum required luminal nutrient but occurred very rapidly, within 4 hours of refeeding. The onset of adaptive growth was accompanied by transient elevation of ileal ODC mRNAs. Ileal proglucagon mRNA and plasma GLP-I levels were also elevated, and these increases were sustained up to 8 days after resection. These early and sustained increases in proglucagon mRNA and plasma GLP-I indicate that in addition to the enteroglucagons, other intestinal proglucagon-derived peptides must be considered as potential mediators of adaptive growth after jejunoileal resection.

Adaptation, Physiological↗