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Biomedical subjects

H J Tracy

Publications and source records attributed to H J Tracy.

17 recordsLinked to original sources
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↗
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↗
PubMed1979

Minigastrin; corrected structure and synthesis.

Evidence is presented that minigastrin is the C-terminal tetradecapeptide amide of gastrin and not the tridecapeptide amide as previously reported. Synthesis of the tetradecapeptide amide sequence, Trp-Leu-[Glu]5-Ala-Tyr-Gly-Trp-Met-Asp-Phe-Nh2, was achieved by a series of fragment couplings which were mediated by the dicyclohexylcarbodiimide procedure in presence of either N-hydroxysuccinimide or 1-hydroxybenzotriazole. Purification of all intermediate fragments, and of the final protected tetradecapeptide amide, was by Sephadex LH-20 chromatography. Removal of the protecting groups was effected by treatment with 90% trifluoroacetic acid in the presence of a large excess of scavengers. Purification by ion-exchange chromatography afforded the pure tetradecapeptide amide. This material had full physiological activity.

Amino Acid Sequence↗
PubMed1974

Isolation of two minigastrins from Zollinger-Ellison tumour tissue.

A pair of gastrin tridecapeptides (;minigastrins') have been isolated from Zollinger-Ellison tumour tissue; they correspond to the fragment 5-17 of the heptadecapeptides isolated from the same source. In one (type II) the tyrosine residue present is sulphated, in the other (type I) it is not. The proportion of types I and II is approximately 2:1 similar to that for the ;big' gastrins and the heptadecapeptides isolated from the same source and from human antral mucosa. Both minigastrins are potent stimulants of gastric acid secretion. Immunological evidence exists to indicate that both are present as circulating forms of the hormone gastrin in patients with the Zollinger-Ellison syndrome and in fed normal subjects.

Amino Acids↗
PubMed1969

Aminoacid constitution of two gastrins isolated from Zollinger-Ellison tumour tissue.

Two peptides which are potent stimulants of gastric acid secretion are isolated from Zollinger-Ellison tumour tissue. They have aminoacid constitutions identical with those of human gastrin types I and II as isolated from human antral mucosa, and they are present in similar proportions. Their electrophoretic and chromatographic behaviour corresponds to that of human gastrins. Evidence is presented in respect of the one isolated in greater amount that its aminoacid sequence is probably identical with that of human gastrin type I.

Amino Acid Sequence↗
PubMedDate not supplied

Big gastrin.

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Amino Acids↗