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Biomedical subjects

M G Bryant

Publications and source records attributed to M G Bryant.

At least 37 records · Page 2Linked to original sources
PubMed1981

Mixed pancreatic apudoma with symptoms of excess vasoactive intestinal polypeptide and insulin: improvement of diarrhoea with metoclopramide.

A female patient is described with a single pancreatic tumour producing vasoactive intestinal polypeptide (VIP), insulin, and pancreatic polypeptide. The initial presentation was with diarrhoea and hypokalaemia and a raised plasma VIP was demonstrated. Her symptoms improved with metoclopramide administration and absolute concentrations of 28 aminoacid (peak IV) VIP were found to have fallen. She then developed hypoglycaemia with hyperinsulinism. All symptoms resolved after surgical excision. This case emphasises the potential of these tumours to contain more than one endocrine cell type synthesising different biologically active peptides.

Apudoma↗
PubMed1981

Pancreatic tumours produce neurotensin.

Tumour tissue may secrete substances which are not normally secreted by the original tissue. We have found that 6 out of 21 pancreatic tumours producing vasoactive intestinal peptide also produce neurotensin-like peptides. These are sometimes secreted and very high plasma levels of neurotensin-like immunoreactivity may be found in the circulation.

Female↗
PubMed1981

Decrease of pancreatic somatostatin in neonatal nesidioblastosis.

The inappropriate insulin release that is characteristic of severe neonatal hypoglycemia and nesidioblastosis was thought to be principally due to a marked proliferation of B-cells. A possible deficiency of somatostatin, one of the factors controlling insulin release, has only recently been considered. We report have a significant decrease of pancreatic somatostatin cells and somatostatin content in nesidioblastosis, as compared with appropriate controls. Pancreatic tissue from five babies with severe hypoglycemia, hyperinsulinemia, and nesidioblastosis was examined for insulin, somatostatin, and glucagon by immunocytochemistry and radioimmunoassay. There was a variable insulin cell hyperplasia among the nesidioblastotic specimens but no significant difference from controls was detected. In contrast, there was a consistent and highly significant (P less than 0.02) decrease (of more than 50%) of somatostatin cells (controls, 1.29 +/- 0.22%; nesidioblastosis, 0.53 +/- 0.14%, mean +/- SEM). Similarly, there was no significant alteration in insulin content, although a slight increase was found in non-microadenomatous areas of the diseased pancreata (controls, 42.3 +/- 4.1; nesidioblastosis, 58.6 +/- 9.4 nmol/g wet weight of tissue, mean +/- SEM). However, somatostatin content was almost 60% below control values (controls, 0.365 +/- 0.038; nesidioblastosis, 0.16 +/- 0.039 nmol/g), a statistically significant difference (P less than 0.01). Thus, a marked reduction in the content of somatostatin was present in the pancreata of these infants with nesidioblastosis, resulting in a distinct alteration of the normal pancreatic hormone balance.

Fluorescent Antibody Technique↗
PubMed1981

Molecular forms of motilin in the mammalian and human gut and human plasma.

Regional specific antibodies and gel permeation chromatography were used to analyze the molecular forms of motilin in the human gut and plasma and in the porcine gut. The same antibodies were also used for immunocytochemical localization of the cell of origin of motilin. Two main molecular forms of motilin were identified, peak I eluting at a volume suggesting a larger molecular weight substance (Kav = 0.16) and peak II coeluting with the porcine motilin standard (Kav = 0.67). Peak I accounted for over 50% of the total motilin immunoreactivity in the human gut, whereas in the porcine intestine it represented less than 5%. Peak I thus appeared to have a greater N-terminal sequence similarity with the porcine motilin standard. Chromatographic analysis of human plasma showed the presence of both immunoreactive peaks in approximately equal amounts which were both suppressed following infusion of somatostatin. Infusion of porcine motilin resulted in the expected rise of plasma immunoreactivity in the peak II position, whereas peak I was significantly depressed, suggesting the possibility of a negative feedback. Immunocytochemistry revealed that both antibodies immunostained equally the non argentaffin cell, which contained small round, electron-dense granules. In addition some argentaffin enterochromaffin cells were stained predominantly with the N-terminal specific antibody.

Adult↗
PubMed1980

Enkephalin-, VIP- and substance P-like immunoreactivity in the carotid body.

The carotid body type I cell contains amines and has features, both morphological and cytochemical, which indicate that it may also produce a peptide. Many regulatory peptides are now known to be present in both central and peripheral tissues. In the periphery these neuropeptides occur in both classical endocrine (APUD) cells and the neurones of the autonomic nervous system. We have now investigated the possible presence of neuropeptides in the cat carotid body using both immunocytochemistry and radioimmunoassay. Met- and Leu-enkephalin-like material occurred in considerable quantities in carotid body extracts and enkephalin-like immunoreactivity was localised in type I cells. Both vasoactive intestinal polypeptide (VIP)- and substance P-like immunoreactivity was also present but was localised in nerve fibres distributed throughout the organ. These active neuropeptides are widely distributed in mammalian tissues, forming a diffuse regulatory system which now seems to include the carotid body.

Animals↗
PubMed1980

VIP in the rat brain: evidence for a major pathway linking the amygdala and hypothalamus via the stria terminalis.

We report here on the detailed distribution of VIP-like immunoreactivity in the rat brain by a combined immunological approach using immunocytochemistry and radioimmunoassay. VIP-like immunoreactivity was widely distributed. Cell bodies and and fibres were noted principally in the cortex, hippocampus, amygdala, suprachiasmatic nucleus and brain stem. In addition dense areas of immunoreactive fibres and terminals were seen in the stria terminalis and its bed nucleus. The fibres appear to form a major VIP-containing pathway which links the amygdaloid complex with the hypothalamus. Although the functional significance of VIP in the brain is unknown, its presence in the amygdala, the hypothalamus and their linking pathway, as well as its pharmacological actions suggest that it may play a role in neuroendocrine regulation and the modulation of hypothalamic function.

Amygdala↗
PubMed1980

The differential distribution of vasoactive intestinal polypeptide in the normal human female genital tract.

VIP-like immunoreactive material is present in the female reproductive tract, with a distinct pattern of distribution. The highest concentrations of extractable material and immunoreactive nerve fibres were found in the cervix and vagina. In the cervix these fibres were seen below the surface epithelium and around cervical glands as well as in association with blood vessels and smooth muscle bundles. In the vagina the nerve fibres were most abundant in th superficial regions of the lamina propria. Scattered fibres were also present in the rest of the uterus and in the fallopian tubes. Chromatographic evidence indicates that this VIP-like material is of a similar molecular size to that extracted from other organs. Possible roles for VIP in the regulation of myometrial activity and of cervical and vaginal dilation and secretion are proposed.

Adult↗
PubMed1980

The location of VIP in the pancreas of man and rat.

VIP has powerful stimulatory effects on both endocrine and exocrine pancreas but its localisation within the gland has not been established. In this study, human pancreas was obtained fresh at surgery (eleven) or within four hours of death (seven). The pancreas was also removed from rats (twenty-two). Immunocytochemical staining showed VIP to be present in fine nerve fibres in all areas of the pancreas. Many fibres were seen in the exocrine pancreas, running between the acini, and around ducts and blood vessels. In addition, dense networks of fibres were observed forming meshes around islets and occasional ganglia were found containing immunoreactive cell bodies. In general, there were fewer VIP fibres in the rat pancreas than in the human, but overall distribution was identical. The mean VIP content of whole human pancreatic tissue was 42 +/- 10 pmol/g wet weight (38 +/- 9 pmol/g in head, 49 +/- 6 pmol/g in body and 42 +/- 11 pmol/g in tail). Whole rat pancreatic tissue contained 28 +/- 7 pmol/g wet weight while preparations of isolated islets were found to contain 374 +/- 30 pmol/g. It is possible that the heavy VIP innervation of the islets described here indicates a role in the regulation of islet hormone release.

Animals↗
PubMed1980

Subcellular fractionation studies of human gastric antrum: localization of the mucosal peptide hormones.

1. Analytical subcellular fractionation techniques have been applied to endoscopic human gastric antral biopsies to study the localization of gastrin, somatostatin, vasoactive intestinal peptide and the properties of the principal subcellular organelles. 2. The peptide hormones, detected by radioimmunoassay, showed particulate localizations with single peaks in the density gradients for somatostatin (modal density 1.23) and vasoactive intestinal peptide (modal density 1.17). Gastrin showed a more complex distribution with a distinct peak (modal density 1.18) and a substantial shoulder extending into the denser regions of the gradient. 3. The following organelles, characterized by their marker enzymes, were located in the density gradients: plasma membrane (5'-nucleotidase), mitochondria (malate dehydrogenase), peroxisomes (catalase), lysosomes (beta-N-acetyl-D-glucosaminidase), endoplasmic reticulum (neutral alpha-aminidase), cytosol (lactate dehydrogenase). 4. This technique can be applied to investigate disease of the gastric antrum at a subcellular level.

Acetylglucosaminidase↗
PubMed1980

Subcellular fractionation studies of human rectal mucosa: localization of the mucosal peptide hormones.

1. Analytical subcellular fractionation techniques have been applied to endoscopic human rectal biopsies to study the localization of enteroglucagon, somatostatin, vasoactive intestinal peptide and the properties of the principal subcellular organelles. 2. The peptide hormones, detected by radioimmunoassay, showed particulate localizations with single peaks in the density gradients for enteroglucagon (modal density 1.25) and somatostatin (modal density 1.23). Vasoactive intestinal peptide showed a less discrete localization but demonstrated a major peak (modal density, 1.17) with a small subsidiary peak (modal density 1.24). 3. The following organelles, characterized by their marker enzymes, were located in the density gradients; plasma membrane (5'-nucleotidase), mitochondria (malate dehydrogenase), peroxisomes (catalase), lysosomes (beta-N-acetyl-D-glucosaminidase), endoplasmic reticulum (neutral alpha-D-glucosidase) and cytosol (lactate dehydrogenase). 4. This technique can be used to investigate disease of the human rectum at a subcellular level.

Centrifugation, Isopycnic↗
PubMed1980

Subcellular localization of serotonin and motilin in the human jejunum.

1. Analytical subcellular fractionation techniques have been applied to human jejunal homogenates to study the localization of serotonin and motilin. 2. Serotonin, detected by a fluorimetric assay, showed two distinct particulate distributions in the density gradients with modal densities of 1.14 and 1.20. Motilin, whether detected by N-terminal or C-terminal specific antibodies showed similar density distributions with a modal density of 1.20, coinciding with the denser peak of serotonin. 3. These results lend support to the histochemical suggestions that motilin is located in a a serotonin-containing granule.

Centrifugation, Isopycnic↗
PubMed1980

Separation of the gut hormone endocrine-cell storage granules of human jejunum using analytical subcellular fractionation.

Analytical subcellular fractionation techniques in combination with specific radioimmunoassays have been used to investigate the properties of the hormone-containing granules in human jejunal biopsy specimens. After gentle homogenisation, for all hormones except VIP, over 90% of the immunoreactivity was released in intact granules into the post-nuclear supernatant. Approximately 50% of the VIP immunoreactivity sedimented with the low speed pellet, probably reflecting the presence of this peptide in nerve fibres. The following hormone granules (equilibrium densities between parentheses) were separated by isopycnic centrifugation on the sucrose density gradients: VIP (1 x 17), motilin (1 x 20), and secretin (1 x 24). Gastrin and GIP granules were not resolved, both having the same modal density of 1 x 22 g/cm3. This combination of procedures thus provides a new quantitative technique for studying the properties of the gastrointestinal hormone-containing granules, and should therefore be of value in investigating pathophysiological problems in a variety of gastrointestinal diseases.

Cell Fractionation↗
PubMed1980

A radioimmunoassay of gastric inhibitory polypeptide in human plasma.

A sensitive radioimmunoassay for the measurement of human gastric inhibitory polypeptide (GIP), using pure porcine GIP, has been developed. Cross-reactivity of the antiserum with all available mammalian gut peptide preparations was negligible with the exception of glucagon when it was approximately 1%. Two major molecular forms of GIP were detectable in plasma and tissue extracts, one of large molecular size and the other corresponding to the elution coefficient of pure porcine standard. Concentrations of GIP in plasma from 50 normal subjects after overnight fasting were 9 +/- 1.0 (S.E.M.) pmol/l rising to a peak of 34 +/- 2.8 pmol/l following the ingestion of a small mixed test meal. Ingestion of glucose or fat resulted in a similar rise of plasma GIP, whereas no change was observed after the ingestion of protein.

Adult↗
PubMed1980

Abnormalities of vasoactive intestinal polypeptide-containing nerves in Crohn's disease.

The possible involvement of nerves containing vasoactive intestinal polypeptide in Crohn's disease was investigated by immunocytochemistry and radioimmunoassay of specimens from 17 patients with well-defined clinical and histologic features of the disease. The characteristic pattern of slender fibers, evenly distributed across the gut wall, was seen in specimens taken from controls, which consisted of (a) specimens from uninvolved areas of gut from carcinoma resection (n = 17) and (b) jejunoileal specimens obtained during bypass operation for obesity (n = 8) as well as in four of the six specimens from patients with ulcerative colitis. In contrast, this characteristic pattern was lost in all 17 patients with Crohn's disease, the pattern being replaced by thickened and more intensely immunostained fibers. These changes were consistently found in the mucosa and submucosa, and in 13 of the Crohn's disease cases, the abnormal pattern was totally transmural, involving both the myenteric and submucous plexus as well as the muscle layers. There was a > 200% increase in VIP content, as determined by radioimmunoassay, in Crohn's disease (294 +/- 29 pmol/g wet wt, mean +/- SEM) in comparison with (a) ulcerative colitis (93 +/- 5 pmol/g [P < 0.001]), and (b) controls consisting of carcinoma resection (108 +/- 39) and bypassed gut from obese patients (86 +/- 27 [P < 0.001]). At least part of the previously documented autonomic nerve changes in Crohn's disease are, thus, due to an increase in vasoactive intestinal polypeptide innervation.

Adolescent↗
PubMed1979

Gut hormones in tropical malabsorption.

Concentrations of various gut hormones were measured after a test breakfast in eight patients with severe tropical malabsorption and 12 controls. The patients with tropical malabsorption had greatly raised basal plasma motilin and enteroglucagon concentrations, but their postprandial release of both gastric inhibitory polypeptide and insulin was significantly reduced. The pattern of gut hormone release differed from that found in coeliac disease. The measurement of gut hormones, each of which has a specific site and function, thus throws new light on the pathophysiology of tropical malabsorption and may suggest approaches of treatment.

Adult↗
PubMed1979

Distribution of the gut hormones in the primate intestinal tract.

Reliable and specific radioimmunoassays have been developed for the gut hormones secretin, gastrin, cholecystokinin, pancreatic glucagon, VIP, GIP, motilin, and enteroglucagon. Using these assays, the relative pattern of distribution of the gut hormones has been determined using the same bowel extracts for all measurements. VIP occurred in high concentration in all regions of the bowel, whereas secretin, GIP, motilin, and CCK were predominantly localised in the proximal small intestine. Pancreatic glucagon was almost exclusively confined to the pancreas. Like VIP, enteroglucagon also exhibited a wide pattern of distribution but was maximal in the ileum. The acid ethanol extraction method that was used was found to be unsuitable for gastrin. On gel chromatography of the extracts, motilin and VIP eluted as single molecular species in identical position to the pure porcine peptides. CCK, pancreatic glucagon, enteroglucagon and GIP were all multiform.

Animals↗