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Biomedical subjects

W E Stehbens

Publications and source records attributed to W E Stehbens.

At least 19 recordsLinked to original sources
PubMed1992

Experimental induction of atherosclerosis associated with femoral arteriovenous fistulae in rabbits on a stock diet.

Chronic femoral arteriovenous fistulae were surgically produced in stock-fed rabbits. The aortic bifurcation and branching sites of the ilio-femoral arteries from each side were examined histologically by the serial section technique in rabbits killed at varying times from 121 to 800 days postoperatively. Similar preparations were examined from old multiparous breeding does and rabbits with a control femoral arteriotomy. Tears of the internal elastic lamina were prominent in the abdominal aorta and homolateral ilio-femoral arteries of those with fistulae but were only occasional and sporadic in contralateral arteries and control animals. Intimal proliferation at branching sites proximal to the fistula exhibited varying degrees of enlargement, extension and progression to overt atherosclerosis with lipid accumulation, fibrin deposition and calcification. Such changes were minimal proximally in contralateral vessels of a few rabbits and non-existent in control material. These results (i) constitute the first experimental induction of the progression of intimal proliferation to overt atherosclerosis at branching sites in stock-fed animals and (ii) substantiate the importance of haemodynamics in atherogenesis.

Animals↗
PubMed1992

Combined pathological and radiological study of the effect of atherosclerosis on the ostia of segmental branches of the abdominal aorta.

A combined pathological and radiological study of descending aortae from 15 subjects from 2 to 80 yrs of age was conducted to investigate changes in the segmental vessels with advancing aortic atherosclerosis. There were (i) small hillocks of musculo-elastic intimal thickening adjacent to the apex (centre of the flow divider) in the ostia of the segmental vessels in young subjects, (ii) progressive intimal thickening, distortion and narrowing of the ostia of the segmental vessels (iii) obliteration or loss of some ostia in advanced atherosclerosis of the distal abdominal aorta and (iv) gross discrepancy in severity of atherosclerosis between the aorta and its branches, the intimal proliferation tapering rapidly in the branches and often being minimal in the outer part of their intramural courses. Distal ramifications exhibited occlusions which radiographically were probably embolic or possibly artifactual. Atherosclerosis was rarely of significant degree histologically within the proximal 2 cm of the segmental branches.

Adolescent↗
PubMed1992

Endothelium and elastic tears in the afferent arteries of experimental arteriovenous fistulae in rabbits.

The endothelium and underlying internal elastic lamina of the arteries from 16 carotid-jugular arteriovenous fistulae in rabbits were examined using the en face technique and scanning electron microscopy respectively. Tears appeared in the internal elastic lamina of the arteries 3 days post-operatively. The overlying endothelium exhibited cytoplasmic pallor, loss of argyrophilia of cell borders, and at times attenuated endothelial cells bridging thrombus covered regions of denudation. Early endothelial lesions repaired rapidly and were found only 3-7 days post-operatively despite progressive increase in frequency and extent of tears and the development of interconnecting longitudinal tears with time. Following repair endothelial cells over the tears were small with hyperchromatic nuclei and oriented mostly parallel to the arterial axis. Endothelial cell density overlying these elastic tissue tears increase to three times that in contralateral arteriotomized common carotid arteries. These endothelial changes were sharply delineated by the margins of the elastic tears. Cell density over the tears reached its maximum 9-11 days post-operatively with mitotic figures both in the floor of the tears and over islands of residual elastic lamina. With time the cell density progressively diminished and endothelial cells assumed a more conventional elongated spindle shape.

Animals↗
PubMed1979

Granulomatous angiitis of the CNS.

A 25-year-old man had granulomatous angiitis of the CNS. The disease began with symptoms of an upper respiratory tract infection; it had a relentless course, simulating viral encephalitis, with the patient dying some six months after the onset of symptoms. The lesions were confined to small intracranial arteries and veins, predominantly about the cerebellum. An unusual feature was the occurrence of a small (2 mm) aneurysm on a leptomeningeal artery deep in a cerebellar sulcus. There is a need for pooling data and pathological material by an international body to enable detailed expert analysis of large numbers of cases of cerebral angiitis that do not now constitute a homogeneous group.

Adult↗
PubMed1979

Chronic changes in the walls of experimentally produced aneurysms in sheep.

Twenty-seven saccular aneurysms were fashioned on the common carotid arteries of sheep using the venous transplants with a side-to-side anastomosis. The vessels were examined at varying intervals up to eight months postoperatively. The venous sacs exhibited severe phlebosclerosis of rapid progression and gross loss of muscle, and elastica was most prominent at the fundus. Some aneurysms leaked, some contained mural thrombus and several exhibited minimal quantities of lipid. The histologic changes were similar to those in man and experimental models entailing severe hemodynamic stress and can be regarded as atherosclerotic in nature.

Animals↗
PubMed1978

Endothelial permeability in experimental aneurysms and arteriovenous fistulas in rabbits as demonstrated by the uptake of Evans blue.

Rabbits with chronic experimental arteriovenous fistulas or different types of aneurysm fashioned by microvascular surgery have been examined for changed in endothelial permeability by means of a protein-bound tracer dye technique. The aneurysms and anastomosed veins of the arteriovenous aneurysms exhibited pronounced dye-uptake in contrast to low uptake at sites of sham operation. The results demonstrate the importance of haemodynamic factors in altered endothelial function, as shown with a tracer dye technique in these experimental vascular models.

Aneurysm↗
PubMed1975

The role of lipid in the pathogenesis of atherosclerosis.

An experimental model of atherosclerosis sheep veins identical to the human disease indicates (i) that ingestion of an atherogenic diet is not a prerequistie in atherosclerosis and (ii) that haemodynamic stress must be the dominant aetiological factor in atherosclerosis. Ultrastructural studies reveal that the early lipid deposition in spontaneous human atherosclerosis and in haemodynamically induced atherosclerosis is related to the trasnformation of extracellular vesicular debris into closely packed membranous profiles with electron-translucent centres. It is postulated that the vesicular dtsintegration of mural cells is due to the same haemodynamic stresses which induce degenerative changes in the vascular connective tissues, and that the lipid accumulation within the vesicular disintegration of mural cells is due to the same haemodynamic stresses which induce degenerative changes in the vascular connective tissues, and that the lipid accumulation within the vesicular debris is a cellular debris which have not undergone resolution or phagocytosis.

Animals↗
PubMed1975

Ultrastructure of aneurysms.

The fine structure of five cerebral aneurysms, four early aneurysmal changes, and three arteriovenous aneurysms (two cerebral and one spinal) were investigated from surgical and autopsy specimens. Each lesion was characterized by thickening, lamination, redundancy, and separation of basement membranes, abundant cellular debris, and a paucity or absence of elastica. In several instances, extracellular lipid and lipophages were present. These vascular lesions were remarkably similar to one another and also to the degenerative changes in experimental arteriovenous aneurysms, thus substantiating the concept that they, too, are essentially degenerative in nature.

Adult↗
PubMed1975

Venous atherosclerosis associated with arteriovenous fistulas for hemodialysis.

In two patients, venous loops fashioned into arteriovenous anastomoses for long-term hemodialysis developed gross irregularity and narrowing of the lumen. Histological and ultrastructural examination of the affected vein in one patient revealed atherosclerosis similar to that that develops in the anastomosed veins of experimental arteriovenous fistulas in sheep. The second patient, with angiographically similar changes in the venous loop, developed on aneurysm followed by thrombotic occlusion of the arteriovenous fistula. The development of venous atherosclerosis in these patients was analogous to that in the experimental animal, and was attributed to local hemodynamic stresses in the vein associated with the shunt.

Adult↗