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Biomedical subjects

G J Dockray

Publications and source records attributed to G J Dockray.

At least 199 records · Page 11Linked to original sources
PubMed1981

Neuropeptides in the gut: quantification and characterization of cholecystokinin octapeptide-, bombesin- and vasoactive intestinal polypeptide-like immunoreactivities in the myenteric plexus of the guinea-pig small institute.

The localization of CCK8-, bombesin- and VIP-like immunoreactivities in the myenteric plexus of the guinea pig small intestine has been studied by radioimmunoassay of extracts of longitudinal muscle strips obtained with and without adherent myenteric plexus; concentrations were compared with those in other regions of the gut. In innervated strips of longitudinal muscle of ileum there was approximately 14 pmol/g CCK8-, 32 pmol/g bombesin- and 135 pmol/g VIP-like immunoreactivity; concentrations were reduced by over 70% in denervated strips. Gel filtration and ion exchange chromatography indicated that over 80% of CCK immunoreactivity was due to CCK8; no evidence was found of significant amounts of smaller COOH-terminal fragments. Bombesin immunoreactivity occurred in two forms, the major one resembling the amphibian tetradecapeptide in its elution from gel filtration columns. Immunoreactive VIP differed markedly from porcine VIP in immunochemical and chromatographic properties; the data suggest that guinea pig VIP is less basic than porcine VIP and that the two peptides differ in structure in their NH2-terminal regions. Some functional implications of these findings are discussed.

Animals↗
PubMed1981

Regional distributions of somatostatin and cholecystokinin-like immunoreactivities in rat and bovine brain.

The distribution of somatostatin- and cholecystokinin octapeptide (CCK-8)-like immunoreactivities in the central nervous system of bovine and rat has been studied using a sensitive and specific radioimmunoassay. The most interesting information is the high concentration of CCK-8 in the various cortical areas in rat and bovine. The nuclei of amygdala contain the highest amount of octapeptide in rat while in bovine brain, this structure contains the second highest concentration after polus frontalis.

Animals↗
PubMed1981

Transport of cholecystokinin-octapeptide-like immunoreactivity toward the gut in afferent vagal fibres in cat and dog.

1. The distributions of gastrin- and cholecystokinin-like immunoreactivities in the dog and cat vagus nerves have been studied after nerve section and ligation. 2. In dogs, there was an increase in cholecystokinin-octapeptide-like immunoreactive material on the cranial side of ligatures on the thoracic or cervical vagi. When pairs of ligatures were tied on the cervical vagi there was accumulation proximal, and a slight decrease distal to, the upper ligature. There was also a modest increase distal to the lower ligature. 3. In cats, section of the vagus above the nodose ganglion, and hence degeneration of the efferent fibres, did not prevent increases in cholecystokinin-octapeptide-like immunoreactivity on the cranial side of ligatures which were later tied below the ganglion. Removal of the superior cervical ganglion had no effect on the accumulation of immunoreactive material above the ligatures. Section of the vagus below the nodose ganglion, and hence degeneration of both afferent and efferent fibres, abolished the accumulation on the cranial side of ligatures which were later tied below the section. Cholecystokinin-octapeptide-like material is therefore localized to afferent fibres with cell bodies in the nodose ganglion. 4. Immunoreactive forms were characterized by gel filtration and ion exchange chromatography, and the use of region-specific antisera. In all cats, and all but one dog, a molecule with the properties of sulphated cholecystokinin octapeptide was found to predominate. In some cats (30%) and dogs (26%) a molecule with the properties of heptadecapeptide gastrin (G17) was identified; concentrations of G17 were generally low compared with cholecystokinin octapeptide. In three dogs (20%) there was an accumulation of heptadecapeptide gastrin above the ligatures. 5. Axonal transport of cholecystokinin octapeptide in the vagus is consistent with a neuro-regulatory role for this peptide. However, the functional significance of its localization in afferent fibres, and transport towards the periphery, remains to be determined.

Animals↗
PubMed1981

Family studies of hypergastrinemic, hyperpepsinogenemic I duodenal ulcer.

Antral G-cell hyperfunction is a rare cause of hypergastrinemia, hyperchlorhydria, and duodenal ulcer disease. We found evidence for a familial basis for this disorder. The probands were two young men with aggressive duodenal ulcer who had basal and postprandial hypergastrinemia, hyperpepsinogenemia I, and basal and pentagastrin-stimulated hyperchlorhydria. All characteristics returned to normal after antrectomy and vagotomy. Antral gastrin concentrations and quantitative G-cell counts were normal, indicating hyperfunction of G-cells rather than hyperplasia. Four of 10 first-degree relatives of the two patients shared with them the combination of postprandial hypergastrinemia and hyperpepsinogenemia I. The aggregation of these abnormalities in tow families, each identified by a proband with hypergastrinemic, hyperpepsinogenemic l duodenal ulcer, suggests that antral G-cell hyperfunction may have a genetic basis.

Adolescent↗
PubMed1980

Relations between neuropeptides and gut hormones.

Certain peptides have a dual distribution in brain and in neurons or endocrine cells, or both, in the gut. Substance P, neurotensin and somatostatin have been isolated from brain and gut (or pancreas); cholecystokinin has been isolated from intestine as peptides of 33 and 39 residues and their active C-terminal octapeptide has been isolated from brain, which suggests differences between biosynthetic processing pathways for cholecystokinin in neurons and those in endocrine cells. Identification of other peptides (vasoactive intestinal peptide, bombesin, enkephalin etc.) rests in part on immunochemical evidence and needs to be confirmed by isolation. The combined evidence of immunochemical and physiological studies suggests that gut target cells can receive peptides in at last four ways: (1) as hormones in the blood; (2) from intrinsic neurons in the enteric plexuses; (3) from extrinsic nerves like the vagus; (4) by local (paracrine) release from mucosal endocrine-like cells, possibly by basal axon-like processes.

Amino Acid Sequence↗
PubMed1980

Cholecystokinins in rat cerebral cortex: identification, purification and characterization by immunochemical methods.

Cholecystokinins in rat cerebral cortex were studied by radioimmunoassay using an antiserum specific for the COOH-terminus of CCK8. Total concentrations of immunoreactive CCK in cortex were 3-4 fold higher than in jejunum. Rat cerebral CCK was purified by immuno-affinity adsorption to the IgG fraction of CCK antisera conjugated to Sepharose beads, and by gel filtration and ion exchange chromatography. Over 90% of immunoreactive CCK in cortex was accounted for by a factor with the properties of synthetic CCK8, and by a closely related slightly less acidic peptide. In contrast, intestinal CCK consisted of about equal amounts of CCK8-like activity and a larger less acidic immunoreactive component. In both cortex and intestine CCK8-like activity was obtained in substantially higher yield after extracting at neutral pH in boiling water than after extracting in either 0.2 M HCl or 0.5 M acetic acid. However, the larger molecular weight forms of CCK in the intestine were recovered in similar yield by acid and neutral extraction. The principal large form of rat CCK was distinguishable from porcine CCK33 on the basis of both optimum extraction conditions and chromatographic properties. It is suggested that the different distribution of immunoreactive CCK in rat brain and gut can be explained in terms of different biosynthetic processing pathways.

Amino Acid Sequence↗
PubMed1980

The distribution and cellular origin of vasoactive intestinal polypeptide in the avian gastrointestinal tract and pancreas.

The distribution and origins of vasoactive intestinal peptide (VIP) in the gut and pancreas of the turkey were studied by radioimmunoassay of tissue extracts and by immunocytochemistry. Several antisera were used that vary in their specificity for different regions of porcine or chicken VIP. Radioimmunoassays using NH2-terminal specific antisera that react almost equally with porcine and chicken VIP's revealed signficant amounts of immunoreactive VIP in extracts of pancreas, brain and all regions of the gastrointestinal tract from crop to colon. Highest concentrations (300 pmol/g) were found in the colon muscle, and concentrations were generally low (< 20 pmol/g) in the mucosal layers of the small intestine. After ion exchange chromatography of extracts on CM-Sephadex three immunoreactive forms of VIP were separated corresponding to the three molecular forms previously found in mammalian gut extracts. In immunocytochemical studies nerve fibres were found throughout the gut, and in the pancreas. Immunoreactive nerve cell bodies were also identified in the submucous plexus throughout the gut, but were particularly prominent in the oesophagus and pancreas. It has previously been shown that VIP is a strong stimulant of the flow of pancreatic juice in birds whereas the structurally related hormone secretion, which is known to control the flow of pancreatic juice in mammals, is a weak stimulant. It is proposed that in birds VIP might regulate the pancreas, and other aspects of gut function, as a neurotransmitter or neurohormone.

Animals↗
PubMed1980

The radioimmunoassay of buprenorphine.

Antisera to buprenorphine were obtained in rabbits immunised with 3-0-carboxymethylbuprenorphine and N-hemisuccinyl-norbuprenorphine conjugated to bovine serum albumin. Using the latter antiserum and tritium labelled buprenorphine a radioimmunoassay have good accuracy and precision was developed for concentrations as low as 50 picograms in 1 ml of plasma. The N-hemisuccinyl antiserum crossreacted with norbuprenorphine, and the 3-0-glucuronide conjugate with the 3-0-carboxymethyl antiserum. Cross-reactivity of both antisera to other pharmacologically related compounds was negligible. The assay was employed to determine plasma buprenorphine concentration following its parenteral administration to dog and man.

Animals↗
PubMed1980

Immunochemical studies on big gastrin using NH2-terminal specific antisera.

Methods are described for obtaining antisera specific for the NH2-terminal regions of human and porcine big gastrin (G34) that can be used in radioimmunoassays. Three antisera have been characterized in detail: one (L66) raised to human 1--15 (Tyr7-Pro8-Ser9) G34 has an antigenic determinant in the 1--6 region of human G34; a second (L107) raised to 1--19 hG34 has an antigenic determinant in the 1--12 region. Both these antisera react weakly with porcine G34. A third antiserum (L33) raised to porcine G34 has an antigenic determinant in the 1--12 region of this peptide, and reacts weakly with human G34. In human antral extracts fractionated on Sephadex G50, L66 and L107 revealed a minor peak of immunoreactivity corresponding to G34, and a major peak corresponding to the NH2-terminal tryptic peptide of G34. Concentrations of the latter peptide were closely similar to those of G17 (i. e.) the COOH-terminal tryptic peptide of G34), consistent with the idea that G34 is cleaved within G-cells by a trypsin-like enzyme to yield G17. Antiserum L33 revealed small amounts of immunoreactivity in antral extracts of dog and cat, but did not reveal significant immunoreactivity in rat antral extracts. In contrast, L66 reacted with rat antral extracts, but not dog or cat. The sequences of G34 in these species are not known, but the results suggest significant differences compared with human and porcine G34, and indicate a high degree of species-specificity with NH2-terminal G34 antisera.

Amino Acid Sequence↗
PubMed1980

Molecular forms of gastrin in peptic ulcer: comparison of serum and tissue concentrations of G17 and G34 in gastric and duodenal ulcer subjects.

We have studied the relationships between the main molecular forms of gastrin (G17 and G34) in the serum, antral and duodenal mucosa of duodenal (DU) and gastric (GU) ulcer patients. Fasting serum G17 was similar in both DU and GU (about 6 pmol/l) and in both groups increased about three-fold with feeding. In contrast, basal serum G34 was significantly higher in GU (29 pmol/l) than in DU (12 pmol/l) and the peak post prandial increase over basal of G34 was also higher in GU (57 pmol/l) compared with DU (10 pmol/l). In sharp contrast, in the same groups of DU and GU patients mean total antral gastrin concentrations were similar (about 12 nmol/g), and in both groups 95% of antral gastrin was G17, most of the remainder being G34. In both groups total duodenal gastrin concentrations were about 20% those in antral mucosa and about 70% of duodenal gastrin was attributable to G34. The higher serum G34 in GU could therefore be explained by increased secretion of duodenal gastrin, but further work is needed to examine whether there might also be preferential secretion of antral G34 in GU, or a difference in the metabolism (or volume of distribution) of gastrin variants in GU and DU.

Adult↗
PubMed1980

Atropine does not abolish cephalic vagal stimulation of gastrin release in dogs.

1. The effect of atropine was studied on serum gastrin responses to feeding in conscious gastric fistula dogs. Intragastric pH was monitored and could be maintained at pH 6.0 by infusion of sodium bicarbonate into the gastric fistula.2. A standard liquid meal was consumed by the dogs in less than a minute. Serum gastrin increased from a basal concentration of 8 pmol/l to a peak of 27 pmol/1 at 4-7 min, and intragastric pH fell to less than 3.0 after 20 min. Since vagotomy abolished the early gastrin response to feeding, and instillation of the meal directly into the fistula produced only a modest and delayed increase in serum gastrin, we conclude that cephalic vagal stimulation played a major part in mediating the gastrin responses. When intragastric pH was maintained at 6.0 serum gastrin was significantly higher at all times from 4 to 50 min after feeding, indicating the importance of acid inhibition in the control of gastrin secretion.3. After atropine (25 or 100 mug/kg), acid secretion was abolished and intragastric pH was about 6.0 at all times. The low dose of atropine enhanced the gastrin response to feeding, but the time course and magnitude of the response closely resembled that to normal meals pH-stated to 6.0. The high dose of atropine decreased, but did not abolish serum gastrin responses to feeding.4. When the meal was allowed to drain freely from the gastric fistula (virtually eliminating stimulation of gastrin release by luminal mechanisms) serum gastrin again reached a peak after 4-7 min, and neither dose of atropine significantly changed the response.5. It is concluded that cephalic vagal stimulation of gastrin release is atropine resistant and so unlikely to be mediated by muscarinic receptors. The enhanced gastrin response to feeding caused by moderate doses of atropine can be attributed to the loss of acid inhibition of gastrin release. The neuropeptide bombesin is a candidate neurotransmitter for the action of post-ganglionic vagal nerves on gastrin cells.

Animals↗
PubMed1980

Serum gastrin in patients with chronic renal failure.

The realisation that circulating gastrin is heterogeneous necessitates a reappraisal of gastrin's role in the increased incidence of duodenal ulcer disease that occurs in chronic renal failure. Radioimmunoassays employing region-specific antisera have been used to examine renal and extrarenal factors controlling serum gastrin concentration in patients with chronic renal failure. The present study has shown that basal serum gastrin concentrations measured with a carboxyl-terminal specific antibody were significantly higher in eight patients with chronic renal failure treated by dietary restriction (388+/-196 pM) than in 14 patients with chronic renal failure treated by haemodialysis (28.7+/-4.6 pM). However, basal gastrin concentrations in both groups of patients were significantly higher than in 25 normal subjects (12.3+/-1.8 pM) and showed significant negative correlations with maximal gastric acid secretion (p < 0.01). Markedly raised basal gastrin concentrations were observed only in chronic renal failure patients who were also achlorhydric. Although the peak postprandial increment in big gastrin concentration in 11 chronic renal failure patients (34.0+/-7.5 pM) was significantly greater (p < 0.05) than in 25 normal subjects (19.5+/-4.6 pM), the little gastrin responses were not significantly different. In addition, clearance of exogenous little gastrin was similar in four chronic failure patients (clearance half time: 8.1+/-0.7 min) and four normal subjects (clearance half time: 6.5+/-1.2 min). These studies suggest that the human kidney is unimportant in the metabolism of little gastrin. As circulating little gastrin is six times more potent than big gastrin in stimulating acid secretion, these studies suggest that the raised gastrin concentrations observed in patients with chronic renal failure have little significance in terms of their increased incidence of duodenal ulcer disease.

Food↗
PubMed1980

N-Terminal sequence of human big gastrin: sequence, synthetic and immunochemical studies.

The previously assigned structure of human big gastrin is revised as a result of sequencing and immunological studies on synthetic peptides. A nonadecapeptide has been synthesized and found to have full immunochemical potency compared with natural human G34 in a radioimmunoassay which is specific for the N-terminal sequence. Syntheses of the peptides were achieved using the stepwise procedure with benzyloxycarbonyl-amino acids and fragment couplings mediated mainly by the dicyclohexylcarbodiimide procedure in the presence of either N-hydroxysuccinimide or 1-hydroxybenzotriazole. Purification of the peptide fragments was by Sephadex LH-20 chromatography and removal of protecting groups was effected using 90% trifluoroacetic acid in the presence of scavengers. Purification of the nonadecapeptide was achieved by high performance liquid chromatography.

Amino Acid Sequence↗