Regional variation in the permeability of rat thoracic aorta.

The permeability and ultrastructure of the intercostal orifices and interostial regions of rat thoracic aorta have been compared in the present study. The ostial regions consist of two different portions, an annulus and an inflow tract, the latter being continuous with the intercostal artery. The wall of the inflow tract has a sharp bend, demarcating inner and outer portions.

The cellular pathology of experimental hypertension. 7. Structure and permeability of the mesenteric vasculature in angiotensin-induced hypertension.

Acute hypertension was produced in rats by the infusion of angiotensin amide for 2 to 4 hours. These animals were injected intravenously prior to sacrifice with either colloidal carbon or iron dextran particles. The mesenteric vessels from hypertensive and control animals were processed for electron microscopy.

The cellular pathology of experimental hypertension. VI. Alterations in retinal vasculature.

The ultrastructure of retinal arterial vessels from rats with severe renal hypertension has been studied. The permeability of retinal vessels has also been examined by means of vascular labeling technics utilizing horseradish peroxidase and microperoxidase as tracer substances. Small retinal arteries and arterioles exhibit foci of smooth muscle necrosis characterized initially by fragmentation of medial smooth muscle cells, and subsequently by loss of myofilaments and release of free vesicles, vacuoles and other cytoplasmic organelles extracellularly.