Biomedical subjects

S R Bloom

Publications and source records attributed to S R Bloom.

At least 685 records · Page 38Linked to original sources

PubMed1985

Localisation of receptors using a dimeric ligand and electron immunocytochemistry.

The role of regulatory peptides and the existence of specific peptide receptors are becoming established. However, techniques for the ultrastructural localisation of these receptors are fraught with difficulties. We propose here a novel technique for receptor localisation using a dimeric peptide ligand and electron microscopical immunocytochemistry. The dimeric ligand is used as a bridge between the receptor and a specific anti-ligand antibody. By this method we have localised receptors for bombesin in cells of small cell lung carcinoma in culture. The results support previous biochemical evidence for the existence of said receptors and the technique should be applicable for the localisation of other receptors recognising small ligands.

Bombesin↗

PubMed1985

Calcitonin gene-related peptide (CGRP)-immunoreactive sensory and motor nerves of the mammalian palate.

The distribution of calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibres in the palate of rat, cat and monkey was studied using immunocytochemistry and radioimmunoassay. CGRP-containing nerve fibres were found, in all species studied, to form a rich plexus in the subepithelial and submucous layers, around excretory ducts and blood vessels. A small number of CGRP-containing nerve fibres penetrated the epithelium of the hard and soft palate, and terminated as free endings. Some CGRP-containing nerve fibres were found in the vicinity of the mucous glands. CGRP-immunoreactive motor end plates were seen in the striated muscle (tensor veli palatini) of the soft palate. Following capsaicin treatment a small depletion in CGRP-immunoreactive nerve fibres in the rat palate epithelium was noted. In contrast, CGRP immunoreactive fibres forming rich plexuses in other layers of the palate, including motor end plates, were not affected. The extractable CGRP showed no significant depletion (normal animals [n = 10] 21.7 +/- 2.4 pmol/g compared with capsaicin-treated animals [n = 10] 17.5 +/- 1.8 pmol CGRP/g wet weight). The reduction in the number of visible immunoreactive nerves following capsaicin application tends to confirm the sensory character of the CGRP-containing nerve fibres terminating in the epithelium of the hard and soft palate. The capsaicin insensitive CGRP-immunoreactive nerve fibres may thus have a predominantly motor function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Glucagon-like peptide-1 does not have a role in hepatic carbohydrate metabolism.

Glucagon-like peptide-1 does not have specific, high-affinity receptors on rat liver membranes, does not displace glucagon from glucagon receptors on these membranes and does not stimulate the production of cyclic AMP by isolated rat hepatocytes. In the presence of glucagon, high concentrations of glucagon-like peptide-1 do not significantly alter the production of cyclic AMP. Thus, glucagon-like peptide-1 appears unlikely to have a direct action on hepatic carbohydrate metabolism.

Animals↗

PubMed1985

Quantitation and characterization of human plasma neurotensin-like immunoreactivity in response to a meal.

The secretion and metabolism of endogeneous neurotensin-like immunoreactivities after a test meal were studied in five healthy human subjects. Intact neurotensin and the N-terminal metabolic fragment, neurotensin 1-8, were quantified by radioimmunoassay with C- and N-terminally directed antisera in conjunction with gel filtration of plasma samples obtained at timed intervals. Both C- and N-terminal neurotensin-like immunoreactivities rose after the meal, reaching a plateau level after 20 and 30 min, respectively. During the plateau phase, which lasted for the rest of the experimental period of 180 min, the molar ratio of intact neurotensin to neurotensin 1-8 remained approximately constant at 1:4.6. Meal-stimulated immunoreactive neurotensin appeared to be metabolized in a manner comparable to that of exogenously infused neurotensin in man. The results suggest that intact neurotensin is secreted at an approximately constant rate during the plateau phase. The relatively low plateau level of neurotensin 1-8, which has a much longer half-life than intact neurotensin in the circulation, implies that only a fraction of the secreted intact neurotensin is metabolized to neurotensin 1-8, indicating the existence of alternative pathways of neurotensin metabolism.

Adolescent↗

PubMed1985

Bile exclusion from the duodenum. Its effect on gastric and pancreatic function in the dog.

The effect of diverting bile from the duodenum in four dogs with cholecystojejunostomy was studied using a double-marker perfusion technique. After the diversion procedure, a liquid meal increased acid secretion from 0.8 mmol H+/min to 1.48 mmol H+/min (P less than 0.05, paired t test); there was an associated rise in serum levels of gastrin 120 min after feeding (P less than 0.001, paired t test). Pancreatic secretion of trypsin decreased from 3.91 IU/min to 2.66 IU/min after bile diversion (P less than 0.01, paired t test), and the level of CCK was significantly lower 60 min after feeding (P less than 0.05, paired t test). There was no significant change in the rate of gastric emptying after bile diversion, but the pH of duodenal contents was lower in the later stages of digestion. These changes may explain the reported increase of peptic ulcer after diverting bile from the duodenum, and the procedure should not be considered unless the consequences of acid hypersecretion and pancreatic inhibition have been anticipated.

Amylases↗

PubMed1985

Plasma peptide YY (PYY) in dumping syndrome.

The newly isolated hormonal peptide PYY is mainly localized to endocrine cells of the lower intestinal mucosa. The release of PYY by oral glucose was studied in six patients with the dumping syndrome to ascertain the effect of this condition on PYY release. Plasma PYY concentrations were greatly increased following oral glucose in patients with the dumping syndrome compared with healthy controls. In a separate series of experiments, the effect of somatostatin infusion on the PYY release by glucose in these patients was investigated. The release of PYY was completely blocked by infusion of somatostatin, and its release from the bowel in normal subjects may therefore be modulated by local somatostatin in the gut. PYY has been shown to inhibit gastric acid secretion and emptying, at plasma concentrations similar to those seen after glucose, in patients with the dumping syndrome. PYY may therefore be a factor involved in the pathophysiological changes associated with this condition.

Chromatography, Gel↗

PubMed1985

Malnutrition after gastric surgery. Association with exaggerated distal intestinal hormone release.

This study was designed to investigate the mechanism of excessive weight loss following gastric surgery. Twelve weight-stable and six weight-losing postoperative subjects were studied. The weight-losing subjects had lesser body mass based upon anthropometric measurements. All weight-losing subjects and six weight-stable subjects excreted excess breath hydrogen after a standard meal. The quantities of hydrogen excreted by the weight-losing subjects and weight-stable subjects with positive tests were not different, implying similar degrees of carbohydrate malabsorption. Peak breath hydrogen concentration occurred earlier in weight-losing subjects than in weight-stable subjects (2 vs 5 hr), indicating more rapid oral-cecal transit of the test meal in weight-losing subjects. Analyses of postprandial blood samples for eight different gastrointestinal hormones demonstrated exaggerated postprandial elevations in the concentrations of enteroglucagon and neurotensin. The results of these studies demonstrate close correlations between excessive weight loss after gastric surgery, rapid gastrointestinal transit as measured by excess breath hydrogen excretion, and increased release of hormones from the distal intestine. We conclude that these hormones are secreted in excess due to the rapid gastrointestinal transit and that rapid gastrointestinal transit may play a role in excessive weight loss after gastric surgery.

Aged↗

PubMed1985

Growth hormone secretion dynamics in a patient with ectopic growth hormone-releasing factor production.

A female patient with acromegaly, hypercalcemia, and Zollinger-Ellison syndrome was found to have a very high plasma concentration (average 2,300 pmol/liter; normal less than 50 pmol/liter) of growth hormone-releasing factor as measured by a radioimmunoassay to human pituitary growth hormone-releasing factor-1-44. The plasma concentration of growth hormone averaged 25 mIU/liter (normal less than 5 mIU/liter) and there was no rise following an intravenous 100 micrograms bolus of human pituitary growth hormone-releasing factor-1-44. Plasma growth hormone and growth hormone-releasing factor levels were unaffected by bromocriptine, insulin-induced hypoglycemia, and sleep. A long-acting somatostatin analogue lowered both the growth hormone-releasing factor and the growth hormone levels. Thyrotropin-releasing hormone stimulation and oral glucose tolerance tests produced significant increases in plasma growth hormone levels whereas the growth hormone-releasing factor level remained unchanged, suggesting that when normal somatotrophs are exposed to maximal growth hormone-releasing factor stimulation, thyrotropin-releasing hormone becomes a secretagogue of growth hormone from the pituitary. It is proposed that in the absence of a radioimmunoassay for growth hormone-releasing factor, a lack of growth hormone response to growth hormone-releasing factor in a patient with acromegaly is compatible with a source of ectopic growth hormone-releasing factor production.

Apudoma↗

PubMed1985

Nippostrongylus brasiliensis: changes in plasma levels of gastrointestinal hormones in the infected rat.

Plasma concentrations of gastrointestinal hormones were measured by radioimmunoassay in fasted rats 9 days after infection with a range of doses of Nippostrongylus brasiliensis. Values for infected rats fed ad libitum were compared with those of weight matched, pair fed, uninfected rats to control for the possible effects of dose-dependent reductions in food intake associated with infection. The plasma concentrations of some of the gastrointestinal hormones in infected rats were very different from those of their pair fed partners. The magnitude and direction of the changes varied according to the hormone being examined. Plasma concentrations of gastrin and pancreatic polypeptide were similar in pair fed and infected rats at all doses used. For the other hormones assayed, infection was associated with dose-related changes. The plasma concentrations of cholecystokinin and insulin were slightly but significantly reduced in infected rats. In contrast, secretin, enteroglucagon, and pancreatic glucagon concentrations were markedly increased. At the highest dose given (52 larvae/g body wt), the plasma levels of secretin and enteroglucagon in infected rats were elevated 9 X and 15 X, respectively. A comparison of the changes seen in N. brasiliensis-infected rats with those reported for other helminth infections revealed striking differences. The possible etiology of alterations in plasma gastrointestinal hormone concentrations and their contribution to the pathological changes seen in animals infected with helminths are discussed.

Animals↗

PubMed1985

Human distribution and release of a putative new gut hormone, peptide YY.

A radioimmunoassay has been developed for the new intestinal hormonal peptide tyrosine tyrosine [peptide YY (PYY)]. Peptide YY concentrations were measured in separated layers of the human gastrointestinal tract, where PYY was found exclusively in the mucosal epithelium which contained the endocrine cells. Peptide YY was found throughout the small intestine, in very low concentrations (5 pmol/g) in duodenum (6 pmol/g) and jejunum (5 pmol/g), but in higher concentrations in the terminal ileum (84 pmol/g). High concentrations were found throughout the colon (ascending 82 pmol/g, sigmoid 196 pmol/g), being maximum in the rectum (480 pmol/g). The major molecular form of PYY-like immunoreactivity in human intestine appeared to be identical to pure porcine hormone, both as judged by gel permeation chromatography and by reverse-phase high-pressure liquid chromatography. Basal plasma concentrations of PYY were low but rose in response to food, remaining elevated for several hours postprandially. The known potent biologic actions of PYY, its high concentrations in gut endocrine cells, and its release into the circulation after a normal meal suggest that this peptide may function physiologically as a circulating gut hormone.

Adult↗

PubMed1985

Effect of peptide YY on gastric, pancreatic, and biliary function in humans.

The effect of peptide YY (PYY) on gastric and pancreatico-biliary secretion was studied in humans. Peptide YY was infused into groups of 6 healthy volunteers at doses of 0.59, 0.20, and 0.064 pmol X kg-1 X min-1. The two higher doses caused a significant suppression of gastric acid and pepsin output during background stimulation with pentagastrin. The middle dose of PYY (0.20 pmol X kg-1 X min-1) that increased plasma PYY levels by 27 +/- 2 pM caused a 90% +/- 18% (mean +/- SEM; p less than 0.001) reduction in the incremental gastric volume response to pentagastrin. Similarly this dose of PYY caused a substantial inhibition of the acid (77% +/- 14%; p less than 0.005) and pepsin (96% +/- 22%; p less than 0.01) response to pentagastrin; in 2 subjects, pepsin output fell to below basal levels. In contrast, the highest dose of PYY (0.62 pmol X kg-1 X min-1) had no significant influence on duodenal juice volume, output of bicarbonate, trypsin, or bilirubin during low dose stimulation with secretin (0.25 pmol X kg-1 X min-1) and cholecystokinin-8 (0.15 pmol X kg-1 X min-1). Thus PYY concentrations in the circulation similar to those seen after the ingestion of food cause a marked reduction in gastric secretion. This peptide should therefore be considered as one of the possible candidates for the classical enterogastrone.

Adolescent↗

PubMed1985

Molecular forms of peptide histidine isoleucine-like immunoreactivity in the gastrointestinal tract. Nonequimolar levels of peptide histidine isoleucine and vasoactive intestinal peptide in the stomach explained by the presence of a big peptide histidine isoleucine-like molecule.

Regional specific antibodies and chromatography were used to analyze the distributions and molecular forms of peptide histidine isoleucine (PHI) and vasoactive intestinal peptide (VIP) in the porcine intestine. Both peptides were present along the entire length of the intestine, the highest concentrations occurring in the colon. Concentrations of PHI immunoreactivity, measured with three different antisera, and VIP immunoreactivity were approximately equal in all parts of the gastrointestinal tract except in the stomach. In the stomach, the concentration of PHI immunoreactivity, measured with the N-terminally directed antibody R8403, although equal to the corresponding VIP concentration, was two to four times higher than the PHI immunoreactivity detected with the two C-terminally directed PHI antisera T33 and T41. Chromatographic analysis on Sephadex G-50 superfine of gastric extracts revealed only one VIP immunoreactive peak that eluted in the same position as the porcine VIP standard, at Kav 0.53. A PHI immunoreactive peak was also detected with the C-terminally directed PHI antisera in the same position as porcine PHI standard. However, with the N-terminally directed PHI antiserum R8403, an additional PHI immunoreactive peak was detected in gastric extracts constituting the predominant form present, and this peak eluted earlier at Kav 0.37. The PHI immunoreactive material that eluted earlier was present in the rest of the intestine in only small amounts. As VIP and PHI are believed to be derived from a common precursor, it is suggested that in the stomach the posttranslational enzymic processing of the precursor is different from that in the other parts of the intestine.

Animals↗

PubMed1985

Calcitonin gene-related peptide immunoreactive sensory and motor nerves of the rat, cat, and monkey esophagus.

In the mammalian esophagus calcitonin gene-related peptide (CGRP)-immunoreactive nerves form abundant subepithelial plexuses and penetrate the mucosa. The levels of extractable CGRP in separated epithelial layers are 15.8 +/- 2.4 pmol/g wet wt of tissue (n = 8, mean +/- SEM). Treatment of neonatal rats with capsaicin and ablation of the central portion of the feline nodose ganglion led to a marked reduction in the numbers of CGRP-immunoreactive nerve fibers. The loss of CGRP nerves demonstrated by immunocytochemistry was accompanied by a parallel reduction in the tissue content of CGRP, as measured by radioimmunoassay (1.5 +/- 0.5 pmol/g in capsaicin-treated animals compared with 9.4 +/- 1.9 pmol/g in vehicle-treated controls; p less than 0.0025). These findings indicate the sensory nature of the CGRP-immunoreactive nerves. Substance P-immunoreactive nerve fibers innervated in particular the blood vessels of the lamina propria; very few penetrated the esophageal epithelium and these were only partially depleted after removal of the central portion of the nodose ganglion. The esophageal muscle contained nerves immunoreactive for substance P and, in particular, for CGRP which was also found in the motor end plates of the striated muscle. No changes in the CGRP-containing motor end plates were observed either after treatment of neonatal rats with capsaicin or ablation of cell bodies from the central portion of the nodose ganglion. These nerve fibers may originate from rostral areas of the nucleus ambiguus, where CGRP-immunoreactive motor neurons have previously been described. Thus, our findings reveal dual components, motor and sensory, of the CGRP-containing innervation of the esophagus.

Animals↗

PubMed1985

Presence of the predicted C-flanking peptide of neuropeptide Y (CPON) in tissue extracts.

Isolation of the DNA sequence encoding neuropeptide Y (NPY) has suggested the presence of a precursor peptide consisting of 97 aminoacids. Three peptide products have been predicted from this precursor; an N terminal signal peptide, neuropeptide Y and a C terminal 30 amino acid flanking peptide. This study has demonstrated by a novel radioimmunoassay that this C-flanking peptide for NPY occurs naturally in tissues. The peptide is present in abundance throughout the central nervous system and qualitatively in both the brain and peripheral structures, it has the same distribution as NPY. Chromatographic analysis demonstrated that the measured CPON-immunoreactivity elutes in the position of the peptide synthesised according to the predicted sequence.

Adrenal Glands↗

PubMed1985

Peptide histidine methionine (PHM) and the human male genitalia.

Peptide histidine methionine-like immunoreactivity (PHM-IR) has been demonstrated to be present in the human penis both by radioimmunoassay and immunohistochemistry with particularly high levels in the corpus cavernosum and vas deferens. In the cavernosa, PHM-IR has been localised entirely, in nerves around arteries. High performance liquid chromatography indicated that this PHM-IR co-eluted with synthetic PHM but not porcine PHI. The presence of PHM-IR in the penis suggests that this neuropeptide may play a functional role in penile function.

Fluorescent Antibody Technique↗

PubMed1985

Infusion of a novel peptide, calcitonin gene-related peptide (CGRP) in man. Pharmacokinetics and effects on gastric acid secretion and on gastrointestinal hormones.

Calcitonin gene-related peptide (CGRP) is a recently discovered widespread regulatory peptide which is encoded in the same gene as calcitonin. We assessed the effect of systemic infusion of synthetic rat CGRP at low dose (range 0.32-2.56 pmol/kg per min) on submaximal pentagastrin-stimulated gastric secretion and on gastrointestinal hormones. To assess its pharmacokinetic parameters in man the MCR and plasma half-life were estimated by the continuous infusion method. Gastric acid output and pepsin secretion were significantly reduced by CGRP (-29% of basal, P less than 0.01 and -40% of basal, P less than 0.005, respectively). There was a significant fall in basal levels of gastrin (-39%, P less than 0.001); gastric inhibitory peptide (-44.7%, P less than 0.001); enteroglucagon (-25%, P less than 0.001) and neurotensin (-33%, P less than 0.05). There was no significant change in plasma levels of insulin, motilin, pancreatic polypeptide or glucose. Suppression of gastric secretion and the fall in gastrointestinal hormones was prolonged and basal levels were not re-established after stopping the CGRP infusion. The disappearance curve of immunoreactive CGRP from the plasma was bi-exponential. The plasma half-life of immunoreactive CGRP was calculated as 6.9 +/- 0.9 min for the fast decay and 26.4 +/- 4.7 min for the slow decay. The calculated MCR was 11.3 +/- 1.2 ml/kg per min. Except for flushing of the face no untoward effects were observed. The results of this study suggest the possibility that CGRP could play a role in the regulation of gastric secretion and gastrointestinal hormone release.

Adult↗

PubMed1985

Rat immunoreactive cholecystokinin (CCK): characterization using two chromatographic techniques.

Acid and neutral extracts of rat cerebral cortex and upper small intestine were prepared and the endogenous concentrations of cholecystokinin-like immunoreactivity (CCK-LI) measured by three new CCK-specific radioimmunoassays. The characterization of the immunoreactive CCK molecular forms was undertaken using gel permeation chromatography in the presence of 6 M urea to minimise problems relating to peptide adsorption or aggregation. Reverse-phase high-performance liquid chromatography (HPLC) was also performed on the rat tissue extracts. Rat cortex contained 268 +/- 12 pmol/g CCK-LI, and over 90% resembled the sulphated CCK-8, which was preferentially extracted at neutral pH. In contrast, the rat upper small intestine (97 +/- 8 pmol/g of CCK-LI) contained less than 20% CCK-8, the majority of immunoreactive CCK being of larger molecular size and being preferentially extracted at acid pH. In the small intestine the predominant molecular form(s) was intermediate in size between CCK-33 and CCK-8. Large amounts of CCK-33 and of a molecular form larger than CCK-33 were also detected. It is concluded that post-translational cleavage of CCK differs in rat brain and gut.

Animals↗

PubMed1985

Distribution and chromatographic characterisation of CGRP-like immunoreactivity in the brain and gut of the rat.

Radioimmunoassay, chromatography and immunocytochemistry were used to study the occurrence of calcitonin gene-related peptide in the brain and gastrointestinal tract of the rat. In the brain, the highest concentrations of the peptide were found in the medulla oblongata (58.3 +/- 6.8 pmol/g) where immunocytochemistry showed the presence of immunoreactive cell bodies. Significant concentrations were also found in the pancreas and throughout the gastrointestinal tract, the highest levels occurring in the pyloric sphincter (48.0 +/- 6.0 pmol/g). CGRP-like immunoreactivity in the gastrointestinal tract was restricted to nerve fibers. Chromatographic analysis of the CGRP-like immunoreactivity occurring in these tissues showed that at least 70% was indistinguishable from the synthetic peptide. However, there was also evidence of a number of smaller cross-reacting molecular species.

Animals↗