Biomedical subjects

N D Christofides

Publications and source records attributed to N D Christofides.

93 records · Page 6Linked to original sources

PubMedDate not supplied

The distributions of PHI and VIP in porcine gut and their co-localisation to a proportion of intrinsic ganglion cells.

VIP and PHI share sequence homology and certain biological actions. Immunocytochemistry and radioimmunoassay were used to see if the two peptides also have similar distributions in the gut of the pig. PHI-immunoreactive fibres were found, like those containing VIP, in all layers of the bowel wall but in lesser numbers. Unlike VIP-immunoreactive nerves, however, which are ubiquitous in the gastrointestinal tract, PHI-containing neurons were numerous in all areas except the fundus, where only few fibres and no ganglion cells were found to be reactive to PHI antibodies. PHI and VIP immunoreactive materials were also quantified by specific radioimmunoassay of tissue extracts. The concentrations of PHI and VIP were similar in all regions of the gut, except in the fundus where the quantities of VIP-immunoreactivity far exceeded those of PHI. The presence of both VIP- and PHI-immunoreactivities in ganglion cells of the sub-mucous plexus allowed investigation of the co-localisation of the peptides. Serial sections through ganglion cells revealed that a major proportion contain both PHI- and VIP-immunoreactivity. Some cells contained VIP alone, or VIP and weak, equivocal immunostaining of PHI, and a sub-population contained no peptide-immunoreactivity. The presence of both VIP- and PHI-immunoreactivities in the same ganglion cell supports the recent reports of the isolation and characterisation, using genetic technology, of their common precursor molecule. The finding of VIP and not PHI in the fundic region suggests the differential expression of the two peptides.

Animals↗

PubMedDate not supplied

Studies on the distribution of PHI in mammals.

We have developed a sensitive and specific radioimmunoassay to PHI and investigated its distribution in four mammalian species (man, cat, guinea-pig and rat). PHI was present in high concentrations, not only in intestine but also in brain, respiratory tract, urogenital tract and other peripheral tissues. Its distribution was similar to that of VIP and in each tissue examined there was always a significant correlation between the concentrations of these two peptides. In a survey of endocrine tumours, PHI was found to be produced only in those tumours that also produced VIP. In addition PHI was only elevated in the plasma of patients that also had high plasma VIP concentrations. This parallel distribution and release was found to be due to the co-synthesis of VIP and PHI in the same pro-hormone peptide. However, the variable ratio of VIP/PHI in different anatomical areas suggest that in these areas there is a different post-translational enzyme processing of the precursor protein.

Animals↗

PubMedDate not supplied

Distribution of galanin immunoreactivity in the genitourinary tract of man and rat.

Galanin has been shown to be present in substantial quantities in the human and rat genitourinary tract by radioimmunoassay and immunocytochemistry. The highest concentrations measured by radioimmunoassay were found in the human vas deferens, corpus cavernosum and spongiosum and in the vagina and cervix. In man gel chromatographic analysis showed two molecular forms. The earlier eluting peak was different from porcine galanin standard. There was only one molecular form in the rat which emerged in an earlier position than the porcine standard. Galanin immunoreactive nerve fibres demonstrated in the genitourinary tract were found both in man and rat. They were found within smooth muscle and in close relationship to blood vessels. The presence and distribution of galanin in the genitourinary system suggest the possibility that this neuropeptide could play a role in the regulation of smooth muscle tone, blood flow and motility.

Animals↗