Biomedical subjects

M R Roach

Publications and source records attributed to M R Roach.

111 records · Page 7Linked to original sources

PubMedDate not supplied

Effects of high static pressures on human cerebral arteries in vitro.

Static elastic properties were obtained from pressure, volume, and length measurements of 34 isolated human cerebral arteries from 23 circles of Willis of patients aged 23-76 years. No significant difference in initial or final elastance was observed with age or branch in the circle of Willis. Twenty-four of the arteries from 18 circles of Willis were then subjected to transmural pressures of 200-300 mm Hg for periods of less than or equal to 5 minutes and the elastic properties restudied. In general, this had little effect on the arteries except for a significant increase in the initial radius for the less than or equal to 40 year age group. In the less than or equal to 40 year group, female arteries tended to show a greater increase in initial elastance than the males. Histological studies to look for elastin fragmentation in the intima were inconclusive.

Adult↗

PubMedDate not supplied

A model study of why some intracranial aneurysms thrombose but others rupture.

A perspex model of a dog aortic trifurcation was machined to scale and perfused with steady flow from a constant pressure reservoir. The tail artery was plugged to produce a flow model of an intracranial saccular aneurysm. At all flow rates, no flow occurred beyond 2.5 tube diameters of the tail artery down-stream from the mouth of the aneurysm. This was assumed to explain why large aneurysms thrombose. Measurements of velocity fluctuations were made with a hot film anemometer and recorded on tape. Frequency analysis showed that the peak frequency was a function of flow rate, and suggested that eddies were shed from the origin of the aneurysm. This was presumed to be an artifact due to sharp entrance produced by machining the perspex. The total energy at any one point in the aneurysm was independent of the size of the aneurysm but increased with flow rate. The maximum fluctuations were comparable in the center and in the sides of the aneurysm, but were less on the top and bottom of it (assuming the central plane was in the plane of the trifurcation). This difference presumably would be less if the aneurysm were spherical rather than cylindrical.

Animals↗

PubMedDate not supplied

The effects of cadmium on the structure and elastic properties of carotid arteries from rats.

Cadmium chloride (0.6 mg/kg) was injected intraperitoneally into seventy-five rats to determine if this material altered the static elastic properties of the carotid arteries. Control rats were either injected with saline or left untreated. The elastic properties were determined from cylindrical segments of artery which were distended with water of known volume. The pressure and length were measured. Experiments were done either at constant in vivo length or with the artery untethered so the length altered with pressure. Comparison of the methods allowed analysis of the role of elastin and collagen oriented circumferentially, longitudinally, of helically. The major changes occurred in the longitudinal direction. The initial part of the curve has previously been shown to be due to elastin, and the final part to collagen. Collagen increased more than elastin and muscle (as determined from point counting of trichrome-stained sections), but appeared to have the same elastic modulus as normal collagen. The major change was in the "cross-linking" between collagen fibres. This increased with time on the CdCl2 in a manner comparable to that seen with age in humans. Many of the changes were biphasic, and changes that occurred between one and four weeks on the CdCl2 were often recovered with continued treatment. The reason for this is obscure.

Animals↗