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I MacIntyre

Publications and source records attributed to I MacIntyre.

258 records · Page 15Linked to original sources
PubMedDate not supplied

Calcitonin gene-related peptide in the hepatic and splanchnic vascular systems of the rat.

The distribution and origin of calcitonin gene-related peptide immunoreactive structures in hepatic and splanchnic vasculature of the rat were investigated by the immunofluorescent technique. Calcitonin gene-related peptide immunoreactive fibers were dissociated from compact thick calcitonin gene-related peptide immunoreactive fiber bundles located around the hepatic and splanchnic vasculature, and reached the tunica adventitia of the vasculature. Some fibers penetrated further into the tunica media of the vasculature. In the tunica adventitia of the vasculature, calcitonin gene-related peptide immunoreactive fibers formed a fine meshwork which could be traced to the branches and arterioles. In the liver, calcitonin gene-related peptide immunoreactive innervation extended from porta hepatis to portal triads, running with branches of the hepatic artery and portal vein. Some calcitonin gene-related peptide immunoreactive fibers separated from thinner calcitonin gene-related peptide immunoreactive fiber bundles in portal triads and coursed into the immediately adjacent parenchyma. In the dorsal spinal ganglia (T8-10, L1), calcitonin gene-related peptide immunoreactive cells accounted for about 60% of the total number of ganglion cells. Bilateral vagotomy just below the diaphragm or bilateral transection of the greater splanchnic nerve resulted in a marked decrease of the number of calcitonin gene-related peptide immunoreactive fibers in the vasculature, whereas a combined operation was followed by the complete depletion of calcitonin gene-related peptide immunoreactive fibers. These results indicate that calcitonin gene-related peptide immunoreactive innervation in hepatic and splanchnic vasculature may have a dual origin. In conclusion, the widespread distribution of calcitonin gene-related peptide immunoreactive fibers in the hepatic and splanchnic vasculature suggest that calcitonin gene-related peptide innervation may be involved in sensory transmission.

Animals↗
PubMedDate not supplied

Coronary vasodilatation induced by calcitonin gene-related peptide in the anaesthetised pig.

The ability of CGRP to increase blood flow in the coronary circulation of the anaesthetized pig was studied in a constant pressure perfusion model. Human alpha-CGRP, when infused close-arterially into the left anterior descending coronary artery perfused at constant pressure, produced a marked and prolonged dose-related increase in coronary flow, at doses above 10 pmol min-1. The gradient of the flow/pressure curves at each dose increased with an increase in pressure, indicating a drop in the resistance of the coronary bed. No significant change was observed in heart rate, left ventricle pressure, mean arterial pressure or cardiac output.

Animals↗
PubMedDate not supplied

1,25-dihydroxyvitamin-D-receptor in breast cancer cells.

A specific receptor for 1,25-dihydroxyvitamin D has been demonstrated in a cultured human breast cancer cell line. This is the first such demonstration in any cancer cell. It may explain the high incidence of metastatic bone destruction and hypercalcaemia in this common malignancy, and the limited success of other steroid-receptor assays in predicting the response of breast cancer to therapy.

Binding, Competitive↗
PubMedDate not supplied

Isolation and characterization of human calcitonin gene-related peptide.

The rat calcitonin gene has recently been shown to encode a novel peptide (rat calcitonin gene-related peptide, rCGRP) thought to be produced in nervous tissue after tissue-specific RNA processing. This peptide has so far been identified only in rat tissue, by immunocytochemistry and immunoassay. We now report the isolation of a related (89% homology) peptide from human tissue (hCGRP) which we have sequenced using a novel mass spectrometric approach, fast atom bombardment (FAB) mapping. The human peptide differs significantly from the predicted rCGRP structure in four positions in the amino acid sequence (three effecting charge changes), and the presence of a disulphide bridge and an amide, surmised in the rat work, is proven in the hCGRP molecule. hCGRP was present in plasma from 10 patients with medullary thyroid carcinoma (MTC) and in 6 MTC tumours removed at surgery, suggesting the tissue distribution may differ from that in the rat where the peptide is reported to be absent from thyroid tissue. hCGRP is shown to have biological activity and it is possible that its presence in MTC plasma may be responsible for some of the symptoms in this disease.

Amino Acid Sequence↗
PubMedDate not supplied

Calcitonin gene-related peptide is a potent vasodilator.

A novel peptide, calcitonin gene-related peptide (CGRP), has been predicted to result from alternative processing of the primary RNA transcript of the calcitonin gene in the rat. Several lines of evidence suggest that CGRP is a transmitter in the central and peripheral nervous system. Human CGRP has been isolated and characterized, and shown to have potent effects on the heart. The observations presented here indicate that human and rat CGRP also have potent effects on blood vessels. Intradermal injection of CGRP in femtomole doses induces microvascular dilatation resulting in increased blood flow, which we have detected in the rabbit by using a 133Xe clearance technique. In human skin, CGRP induces persistent local reddening. Microscopic observation of the hamster cheek pouch in vivo revealed that topical application of CGRP induces dilatation of arterioles. Furthermore, CGRP relaxes strips of rat aorta in vitro by an endothelial cell-dependent mechanism. Therefore, we suggest that local extravascular release of CGRP may be involved in the physiological control of blood flow and that circulating CGRP may contribute to hyperaemia in certain pathological conditions.

Amino Acid Sequence↗