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Biomedical subjects

M R Roach

Publications and source records attributed to M R Roach.

At least 91 records · Page 5Linked to original sources
PubMed1977

The effects of enzymatic digestion on the elastic properties of isolated human cerebral arteries.

Measurement of volume, pressure, and length were made on eight segments of human cerebral arteries perfused with chymotrypsin (CT) (EC 3.4.21.1) solution (pH = 7.8) for no more than 19 h, and on nine arterial segments perfused with combined enzyme (CT, trypsin (EC 3.4.21.4), elastase (EC 3.4.21.11)) solutions (pH = 7.8) for no more than 4 h. Circumferential tension-strain (and absolute radius) curves were obtained through the Law of Laplace (tension = pressure X radius). Initial and final elastances (tension/strain) were calculated after 0, 0.5, 1.0, 2.0, and 4.0 h of perfusion under the combined enzyme category, and after 0, 0.5, 1.0, 2.0, 4.0, 6.0, and 19.0 h of perfusion with CT. The initial elastance showed a significant increase (0.02 less than p less than 0.05) after about 6 h of perfusion. Increases in the final elastance became significant only after prolonged periods of perfusion with CT. Histological studies using light and scanning electron microscopy confirmed the removal of the elastic lamina as well as portions of the medial region. Fragmentation of the internal elastic lamina did not appear to affect the distensibility of major cerebral arteries in the 50- to 80-year-old age group.

Adult↗
PubMed1977

Elastin fragmentation in the pulmonary artery of the newborn rabbit.

Pulmonary arteries of rabbits aged 1 day to 2 months were distended at 44 mm Hg pressure and sectioned for study with the light microscope. Photographs were enlarged, and the frequency distributions of elastin lengths obtained at different ages. Maximum fragmentation occurred in the inner third of the artery, and was most marked at 3 weeks of age. No significant growth, or change in number of elastin lamellae occurred at this age. The fibres tended to be circumferential except in rabbits 4 weeks of age, where they were slightly helical.

Animals↗
PubMed1976

The effect of the duration of cholesterol feeding on the development of sudanophilic lesions in the rabbit aorta.

Polar coordinate mapping was used to determine the rate of growth of individual sudanophilic lesions on the aortic wall around several major branches of the aortae of cholesterol fed rabbits. Four groups, with 6 8-month old male albino white rabbits in each, were used in the study. One group served as a control and the remaining 3 were fed a diet of 2% cholesterol and 6% heated corn oil mixed with ground rabbit pellets for 4, 8, and 10 weeks each. Animals were sacrificed, the aortae removed, stained with Sudan III, pinned at in vivo dimensions, and mapped by the polar coordinate method. No sudanophilic lesions were observed in the control animals. In the experimental groups, the early lesions, except the coronaries, were almost entirely distal to the orifices, and maintained roughly the same contour while spreading around the orifice. The coronary lesions completely encircled the orifices as described previously. As lesions progressed, they became elevated and often granular, so that the lesions themselves may have affected flow profiles around the orifices. Lesions around adjacent orifices were fused in 48% of the cases after 10 weeks on the diet, as opposed to 2% after 4 weeks on the diet. More prolonged experiments were not possible with this diet as the animals developed jaundice and diarrhea. Hemodynamically, these results suggest that early sudanophilic lesions in cholesterol-fed rabbits develop on the aortic wall in areas of high shear stress.

Animals↗
PubMed1976

Interference of bronchographic agents with lung surfactant.

Dionosil Oily (a suspension of propyliodone crystals in peanut oil and powdered tantalum were introduced into the right principal bronchi of rabbit lungs. The left lungs were used as controls. Pressure-volume characteristics of excised lungs with Dionosil Oily or peanut oil demonstrated significantly reduced compliance on inflation at a pressure of 3-4 cm H2O. These lungs also retained less air on deflation and therefore demonstrated a significantly reduced stability index. Histological sections revealed microatelectasis closely associated with crystals and/or peanut oil. Lungs with tantalum powder were not measurably influenced by the bronchographic agents. Surface balance experiments with lung surfactant and synthetic dipalmitoyl phosphatidylcholine (DPPC) demonstrated an increased minimum surface tension due to the oil suspension of propyliodone, peanut oil and particles (propyliodone and tantalum). There is good evidence that the oil suspension of propyliodone reduced the surface activity of lung surfactant in situ. Particles also may prevent the minimum surface tension from reaching relatively low values if they enter the alveoli in sufficient quantities.

Animals↗
PubMed1975

A scanning electron microscope study of human cerebral arteries.

Human cerebral arteries were obtained from autopsy, fixed under pressure, cut open, and tacked onto pieces of cork. For one artery the intima was partly teased away, exposing the media, and treated with a silver nitrate process. For another artery the adventitia was exposed. Both arteries were processed through graded ethanols and coated with gold paladium for the scanning electron microscope. The collagen fibers of the adventitia were approximately 5 mum in diameter and consisted of a bundle of microfilaments, each of which had a diameter of 800-1000 A (1 A = 10(-10) m). The collagen fibers were oriented parallel to the long axis of the artery. The muscle cells of the media had a diameter of 2-5 mum and were arranged circumferentially with a pitch of approximately 20 degrees. The collagen fibers of the media travel perpendicular to the muscle cells, and parallel to the long axis of the artery. The fibrillar components of the elastin in the intima had a diameter of approximately 700-1000 A and were arranged parallel to the long axis of the artery. It was postulated that the fibrillar part of the elastin was the elastic component of the elastin.

Aged↗
PubMed1975

Effect of vibration on isolated dog bronchi.

Vibratory stress, induced by turbulent flow, has been shown to alter the structural properties in arteries. Since turbulent flow can exist in the lungs it seems important to know whether a similar effect can occur in bronchi. To answer that question air was passed through isolated dog bronchi. Turbulent flow was created by having, at one end, a cannula acting as a stenosis, producing vibrations or a "flitter" in the wall. A measure of the elastic properties was obtained by coupling pressure-volume data with photographs taken at different pressures. The results demonstrate a significant alteration in the structural properties, localized to ares under maximum vibration. A "yielding" in the direction of maximum stress was observed with a corresponding structural rearrangement (radius decreased, length increased). This effect and its relation to structural fatigue is discussed. The physiological significance of the results are that the bronchi become more resistant to deformation under positive pressures and less resistant to collapse under negative pressures.

Animals↗