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Biomedical subjects

G J Dockray

Publications and source records attributed to G J Dockray.

At least 235 records · Page 13Linked to original sources
PubMed1978

Multiple immunoreactive forms of vasoactive intestinal peptide in human colonic mucosa.

Extracts of human colon mucosa and muscle were fractionated by gel filtration and ion exchange chromatography and molecular forms of vasoactive intestinal peptide (VIP) estimated by radioimmunoassay. Total concentrations of immunoreactive VIP in mucosa were 237.1 +/- 53.9 and 119 +/- 26.0 pmoles per g in muscle. In muscle, over 90% of the immunoreactivity was accounted for by a single component indistinguishable from porcine VIP by gel filtration and ion exchange chromatography. In contrast, mucosa contained four components with VIP-like immunoreactivity. One of these had the chromatographic properties of porcine VIP; the others were less positively charged. Two of the new VIP-like components had gel filtration properties similar to those of VIP and are, therefore, probably of similar size to the porcine octacosapeptide, and the remaining component emerged later on Sephadex and is, therefore, probably a smaller peptide. Immunoreactive VIP in muscle extracts is believed to originate from nerve fibers, and this form of VIP is likely to be identical to the previously characterized form of VIP. However, immunoreactive VIP in mucosal extracts may originate either from endocrine cells or nerve fibers. The possibility arises, then, that there are different immunoreactive forms of VIP in nerves and endocrine cells.

Animals↗
PubMed1977

Immunochemical characterization of gastrin in pancreatic islets of normal and genetically obese mice.

Material with gastrin-like immunoreactivity has been extracted from micro-dissected islets and from antral mucosa of normal and genetically obese mice. The islet and antral extracts cross-reacted with antisera specific for the CO2H-terminal portion of human heptadecapeptide gastrin, but did not cross-react with antisera specific for the NH2-terminal region or with an antiserum specific for the entire, intact, molecule. With the antiserum showing highest cross- reactivity, the concentration of immunoreactive gastrin in normal islet tissue (138 pmol/g, standard human G17-I) was approximately 50% that in obese mouse islets (204 pmol/g) and 2% that in normal antral mucosa (6-1 nmol/g). Following fractionation on Sephadex G-50 the principal forms of gastrin in the islet and antral extracts had similar elution volumes to human heptadecapeptide gastrin, although other, probably smaller, forms of gastrin were also noted in the islet extracts.

Animals↗
PubMed1976

Heptadecapeptide gastrin: measurement in blood by specific radioimmunoassay.

The characteristics are described of an antibody (designated L6) which has virtually absolute specificity for heptadecapeptide gastrin. This antibody binds G17, but does not bind peptide fragments or molecular forms of gastrin comprising G17 with either amino acid deletions, or additions, at the carboxyl- and amino-terminals. In serum from patients with Zollinger-Ellison syndrome the only form of gastrin revealed by L6 was compatible with G17, and there was good agreement between estimated G17 concentrations in serum analyzed by gel filtration and by direct radioimmunoassay using L6. Using L6 in conjunction with antibodies specific for carboxyl- and amino-terminals of G17 it has been possible to measure concentrations of different forms of gastrin in serum of normal subjects after a meal in greater detail than previously possible. After a light meal consisting of eggs, toast, and Oxo, serum concentrations of G17 measured by L6 increased to a peak 20 min after feeding (delta gastrin, 19 pmoles per liter; n = 17). In contrast, concentration of G34 peaked at 50 min (delta gastrin, 27 pmoles per liter). Small amounts of amino-terminal fragments of G17 were present throughout the digestive period. Applying the known ratio of biological potencies of G34 and G17 for stimulation of acid secretion in man, it is estimated that G17 accounts for about 75% of the biological activity in blood after a meal, even though G34 is present in higher molar concentrations.

Adolescent↗
PubMed1975

Caerulein secretion by dermal glands in Xenopus laevis.

Since gastrin and its related peptides are secreted by a minority population of widely dispersed cells in mamamalian tissues it has, in the past, been difficult to study the subcellular aspects of their secretion. From published reports (1, 2) it seemed possible that a satisfactory system for such studies might be provided by the skin of certain amphibians such as Xenopus laevis since in these tissues high concentrations of peptides such as caerulein exist, and there is some indication (3) that this, or a similar gastrin-like peptide, may be a dermal gland secretory product. We have therefore explored this possibility by studying the structure, secretory process, and secretory product of the most prominent non mucous type of gland in the skin of X. laevis. These studies clearly demonstrate that most, if not all, of the caerulein in which the skin is contained in secretion granules within the dermal glands and that its release can be specifically evoked by adrenergic stimulation. The release process by a holocrine mechanism expels all of the stored secretion onto the skin surface and thus for biosynthetic studies it should now be possible to synchronize the processes which lead to the replenishment of the peptide.

Animals↗
PubMed1975

Comparison of the actions of porcine secretin and extracts of chicken duodenum on pancreatic exocrine secretion in the cat and turkey.

1. Extracts were prepared of chicken duodenum and their actions on pancreatic secretion in urethane anasthetized turkeys and in conscious cats were compared with those of pure natural porcine secretin. 2. The chicken extracts and porcine secretin stimulated dose-dependent increases in the rate of flow, but not the rate of protein secretion, from the pancreas in cats and turkeys. 3. Porcine cholecystokinin stimulated both the rate of flow and the rate of protein secretion from the pancrease in turkeys. 4. The doses of chicken extract required to evoke half maximal rates of flow of pancreatic juice were similar in the turkey (0-55 mg/kg) and in the cat (0-72 mg/kg). The highest concentration of bicarbonate recorded in the turkey responses was 30 m-equiv/l. compared with 112 m-equiv/l. in the cat. 5. The dose of porcine secretin required for half maximal rate of flow in the bird (5-9 mug/kg) was 180 times higher than in the mammal (0-33 mug/kg). In the cat the duration of responses to porcine secretin was significantly greater than to the chicken extract. 6. It is concluded that in birds there is a factor with biological properties similar but not identical to those of porcine secretin, and that this factor may regulate pancreatic secretion by a mechanism resembling the secretin mechanism in mammals.

Animals↗