Experimental measurements of elastic properties of media and adventitia of bovine carotid arteries.

An experimental procedure is described which has been developed to measure the elastic properties of the outer (adventitial) and inner (medial) layers of excised bovine carotid arteries. The data analysis is based on a two-layered arterial wall model and the theory of large elastic deformations. The energy density functions for both layers are exponentials. The results show that the media and the adventitia are anisotropic; that the media is stiffer, more non-linear, and subjected to higher stresses than commonly assumed; and that both layers are stiffer in the axial direction than in the tangential direction.

Efficacy of oral and systemic antibiotic prophylaxis in colorectal operations.

A cooperative Veterans Administration study of the septic complication rate during large-bowel surgery was undertaken in two groups of patients. The first group received oral neomycin and erythromycin base plus parenteral placebo; the second, the oral antibiotics plus parenteral cephalothin sodium. During a five-year period, 1,128 patients were studied. The overall septic complication rate was 7.8% in patients receiving only oral antibiotics, and 5.7% in patients receiving both oral and parenteral antibiotics. This difference was not significant. The only significant finding was a greater incidence of fever of unknown origin in patients receiving only oral antibiotics. None of those patients were treated with additional antibiotics, and all fevers cleared spontaneously. There seems to be no discernible benefit from adding parenteral antibiotic prophylaxis when performing elective colon surgery if appropriate mechanical cleansing and oral neomycin and erythromycin therapy are employed.

Pressor responses to norepinephrine in rabbits with 3-day and 30-day renal artery stenosis. The role of angiotensin II.

Pressor responses to norepinephrine (NE) infusions were examined in normal rabbits, in rabbits with renal artery stenosis of over 30 days' duration (chronic renal hypertensive rabbits), and in rabbits with renal artery stenosis of 3 days' duration (3-day clipped rabbits). The 3-day clipped rabbits did not have hypertension, but they showed the same increased pressor responses to NE as did the chronic renal hypertensive rabbits, which was about 2.5 times that of the normal rabbits. Plasma renin activity (PRA) was the same in the 3-day clipped rabbits as in the normal group, but in the chronic renal hypertensive rabbits the PRA was significantly below normal. Infusions of angiotensin II (A II) in either subpressor or pressor amounts potentiated the pressor responses to NE in normal rabbits, whereas, in 3-day clipped rabbits and chronic renal hypertensive rabbits, A II in subpressor or pressor doses did not alter the pressor responses to NE. Infusion of the A II antagonist, [1-sarcosine, 8-isoleucine]angiotensin II, did not alter the pressor responses of normal rabbits to NE, but this A II analogue completely abolished the pressor hyperresponsiveness to NE in the 3-day clipped rabbits and greatly reduced the NE hyperresponsiveness in the chronic renal hypertensive rabbits; this A II antagonist did not alter the control arterial pressure in any of the three groups of rabbits. These studies show that the increased pressor response to NE in rabbits with renal artery stenosis occurs before the onset of hypertension and thus is not merely a result of the hypertension. Also, these results provide evidence that A II plays an important role in the increased pressor responses to NE in hypertensive and prehypertensive rabbits.

Pathology of the adrenal gland in refractory low-renin hypertension.

The adrenal glands of 13 patients with low-renin hypertension that was refractory to medical treatment were examined. Eight patients underwent total adrenalectomies and five underwent subtotal adrenalectomies. All of these patients had grossly visible adrenocortical changes. Ten patients had gross cortical nodules, and ten showed nonnodular cortical hyperplasia; seven had both. All ten patients with gross nodules had microscopic nodules as well. Of the 13 patients with low-renin hypertension, 12 (92%) had substantially lower blood pressure postoperatively without medication. During a follow-up period ranging from 14 to 38 months, three patients were normotensive without medication, nine patients had lowered blood pressures without medication and were easily maintained normotensive on antihypertensive medication, and one patient had no significant reduction in blood pressure postoperatively and no improvement in blood pressure control with antihypertensive drugs.

Role of the renin-angiotensin system in dogs with perinephritis hypertension.

Cellophane perinephritis hypertension was produced in four dogs, while five additional dogs served as normotensive controls. A competitive antagonist of angiotensin II, 1-sarcosine-8-alanine angiotensin II, was infused iv into these conscious dogs at a rate of 6 mug/min/kg of body weight for 45 min. Arterial pressure averaged 170 +/- 11 (SEM) mm Hg in the dogs with perinephritic hypertension, and was not altered significantly during infusion of the angiotensin antagonist. In the normal dogs the arterial pressure averaged 100 +/- 10 mm Hg and likewise, did not change during administration of the angiotensin analog. Plasma renin activity values were essentially the same in these two groups of dogs and did not change during infusion of the angiotensin antagonist. These studies provide strong evidence that the renin-angiotensin system is not involved in maintaining the elevated arterial pressure in dogs with chronic hypertension produced by cellophane perinephritis.