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Biomedical subjects

H L Abrams

Publications and source records attributed to H L Abrams.

135 records · Page 8Linked to original sources
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Renal collateral blood supply after acute unilateral renal artery occlusion.

Preformed arterial collaterals are critical to renal parenchymal survival after acute total renal artery occlusion. This study was designed to delineate and quantify preformed collaterals and assess their response to vasodilators. A Swan-Ganz catheter induced a sudden, total occlusion of a renal artery sufficient to reduce distal arterial pressure to near zero and prevent perfusion through the renal artery. Arteriography assessed the effectiveness of the occlusion and delineated the collateral arterial pathways. Strontium, cerium-, and chromium-labeled microspheres measured renal blood flow and cardiac output 1, 60, and 120 minutes after occlusion. In two additional series of experiments either contralateral nephrectomy was performed 5 to 8 days before the study, or dibenzylene, dopamine, or glucagon were administered in an attempt to increase blood flow through the collaterals. Collateral renal blood flow was demonstrated in all dogs. Mean blood flow to the occluded kidneys ranged from 0.13 +/- 0.05 cm3/minute/g to 0.22 +/- 0.08 cm3/minute/g, about 5% of control values. Neither prior contralateral nephrectomy nor vasodilator agents increased the flow to the obstructed kidneys. In the dogs with intact contralateral kidneys, however, there was a progressive decrease in cardiac output during the experiment, which was not found in uninephrectomized animals. We concluded that preformed arterial channels are available to maintain a small, but probably critical level of perfusion following sudden total occlusion of the renal artery. Neither hypertrophy due to prior contralateral nephrectomy nor active vasodilators modify flow through the preformed channels. It is likely that total renal ischemia provides a maximal stimulus for vasodilatation. The pattern of hind limb collaterals differed strikingly from those of the kidney, with maintenance of a greater portion of a normal flow and rapid increase in flow within 1 hour after femoral artery occlusion. Thus, data concerning collateral circulation cannot be generalized from one vascular bed to another even in the same species.

Animals↗
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Increased collateral arterial and venous endothelial cell turnover after renal artery stenosis in the dog.

Renal artery stenosis was induced in dogs and collateral arterial formation assessed by serial angiography and histology. Endothelial cell turnover was estimated by radioautography in five normal and five collateral-forming kidneys 18-39 days following stenosis with tritiated thymidine. Normal arterial endothelial labeling was 0.1% with a highly significant (p less than 0.0005), 55-fold increase in endothelial labeling in arterial collateral vessels. A smaller but statistically significant increase in the labeling index was also found in endothelial cells of the renal vein, from a normal of 0.065% to 0.4% (p less than 0.005). An excellent correlation was found between endothelial cell labeling in small arteries and the renal veins (r = 0.97; p less than 0.01). A marked increase in epithelial cell labeling of the ureters draining the stenotic kidneys was also evident (p less than 0.005). Thus, collateral vessel development is characterized by active DNA synthesis in cellular elements, and a humoral factor is implicated in the vascular response.

Angiography↗
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Balloon-occlusion superior mesenteric arteriography for improved visualization of the mesenteric and portal venous anatomy of dogs.

The superior mesenteric arteries of twelve dogs were occluded with an inflated balloon on the tip of an endhole catheter while diatrizoate meglumine and diatrizoate sodium (Renografin 76) was injected distal to the occlusion. The balloon was immediately deflated at the end of contrast injection. Films taken over a 33-second period showed consistently excellent visualization of the mesenteric arteries and veins as well as the portal veins. Comparison with studies performed by the conventional, nonocclusion technique confirmed the superiority of the films obtained with the balloon occlusion method. Histologic examination of the mesenteric artery at the site of balloon inflation and of the small and large bowel revealed no abnormalities.

Angiography↗
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Timing and magnitude of the postural effect on the distribution of pulmonary blood flow.

The magnitude and timing of the effects of postural change on pulmonary blood flow distribution were studied in dogs by means of computed tomography (CT) and radioactive microspheres. A change in the mean attenuation values was demonstrated by CT in the anterior and posterior lung zones after change from the supine to the prone position. Similarly, a significant shift in blood flow distribution, as measured by microspheres, occurred rapidly, within 1 minute of the time of change from upright to supine position. These data confirm the importance of gravity in determining blood flow distribution in the lungs and demonstrate that maximum readjustments occur within 1 minute after postural change.

Animals↗
PubMedDate not supplied

Collateral arterial formation. Lymph draining ischemic kidneys contains a neovascular stimulating agent of high molecular weight.

An agent has been identified in lymph from rat kidneys rendered ischemic by partial renal artery occlusion that induces a striking neovascular response in a hamster cheek-pouch assay system. The factor has a high molecular weight, cannot be identified in lymph from normal kidneys, and is associated with a marked increase in vascularity and in endothelial cell turnover in the cheek pouch employed for assay. This factor may play an important role in the production of the collateral arterial circulation found in the presence of renal artery stenosis and renal ischemia.

Angiogenesis Inducing Agents↗