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W McDonald

Publications and source records attributed to W McDonald.

24 records · Page 2Linked to original sources
PubMed1984

Angiotensin biosynthesis and concentrations in brain of normotensive and hypertensive rats.

We report here on the extraction and characterization of angiotensin I (ANG I) and angiotensin II (ANG II) from the brain of rats. High pressure liquid chromatography (HPLC) with different mobile phases combined with specific radioimmunoassays (RIA) proved to be a powerful tool for peptide characterization in biological samples; (Ile5)-ANG I, (Ile5)-ANG II and (Ile5)-ANG III could clearly be identified in cerebrospinal fluid (CSF), incubated in vivo and in vitro with renin, in total brain extracts, as well as in hypothalamus (HT), medulla oblongata (MO), cerebellum (CER) and cortex (CO). Angiotensin cleaved from CSF angiotensinogen and angiotensin extracted from brain showed retention times identical to those of plasma angiotensin and synthetic standard peptides, indicating that their amino acid sequence is probably identical. ANG I and ANG II were highest in the HT and lowest in the CO. Following bilateral nephrectomy (NX) both ANG I and ANG II persisted at control levels. Young 10 week old spontaneously hypertensive rats (SHRSP) showed significantly lower ANG I and ANG II concentrations in the HT compared with Wistar Kyoto rats (WKY). Intracerebroventricular (i.c.v.) administration of the converting enzyme inhibitor captopril caused a significant increase in ANG 1 in nephrectomized SHRSP but not in WKY. These differences were not found in 40 week old SHRSP. The data show that ANG I and ANG II are synthetized in the brain of rats. The lower concentrations and the enhanced accumulation of ANG I after converting enzyme blockade in nephrectomized young SHRSP indicate an increased turnover of angiotensin in hypertensive rats.

Angiotensin I↗
PubMed1983

Contact tracing in hepatitis B infection.

In an epidemiological study of patients diagnosed as having hepatitis B virus (HBV) infection during a 12 month period in a London health district, 98 (67%) of 144 index cases and 146 (67%) of 218 of their named contacts were interviewed. The problems and benefits of using conventional contact tracing techniques in the management of this infection are discussed. Named contacts in stable relationships were more easily traced than young homosexuals with frequent anonymous contacts, and drug addicts. Information on the disease and the risk of its transmission to others was, however, welcomed by some homosexuals who were concerned to establish ways of identifying chronic carriers, immune men, and those at risk. A self help group was started as a result of this study.

Hepatitis B↗
PubMed1980

The sustained antihypertensive effect of chronic cerebroventricular infusion of angiotensin antagonist in spontaneously hypertensive rats.

The angiotensin antagonist [Sar1-Ile8]angiotensin II was infused into the lateral ventricles of mature spontaneously hypertensive and normotensive Wistar-Kyoto rats. Infusions were maintained at rats of 1200 ng/h for 6 days, and blood pressure was measured daily in the unanesthetized state. Blood pressure reduction occurred promptly and only in the hypertensive animals. This antihypertensive effect persisted for several days after discontinuation of the infusion. In contrast, iv infusion of the angiotensin antagonist at comparable doses failed to alter blood pressure in any significant fashion. These data suggest that the brain isorenin system participates in the maintenance of hypertension in the spontaneously hypertensive rat.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMedDate not supplied

Effects of radiation on a three-dimensional model of malignant glioma invasion.

An experimental model of malignant glioma growth involving implantation of spheroids into a gel matrix of collagen type I has been developed. This model has been used to characterize changes in glioma cell invasion in response to single dose and fractionated radiation treatment. Suspensions of C6 astrocytoma cells were grown in spinner culture flasks to yield spheroids of varying size (300-1000 microm). Implantation of spheroids into a gel matrix of collagen type I was associated with measurable invasion of the surrounding gel by individual tumor cells. Changes in the distance of invasion in response to single dose and fractionated radiation were measured. Changes in apoptosis and proliferative indices in different regions of the spheroids in response to radiation were also assessed. In unirradiated gels, maximum depth of invasion, 1300-1750 microm, was achieved by 5 days after implantation. A radiation dose-dependent inhibition of invasion was noted and was most profound for larger spheroids. Fractionation of the radiation dose was associated with a partial recovery of invasion. Changes in apoptotic and proliferative indices in response to radiation depended on the region of the spheroid examined. Increases in apoptosis were noted for cells at the surface of the spheroid and invading cells while cells at the centre of the spheroid demonstrated virtually no increase in apoptosis. Likewise, a dose-dependent decrease in proliferative indices following radiation was noted among the invading cells and cells at the surface of the spheroid but not at the centre of the spheroid. We have described a model of malignant glioma invasion which possesses many of the qualities of in vivo malignant gliomas. Within this model, invasion appeared to be inhibited by radiation in a dose- and fractionation-dependent fashion. Measurement of apoptotic and cell proliferation indices favour a direct cytotoxic effect on the invading cells as the most likely mechanism for this phenomenon.

Animals↗