PubMed Health⌕ Search

Biomedical subjects

H L Goldsmith

Publications and source records attributed to H L Goldsmith.

At least 55 records · Page 3Linked to original sources
PubMed1984

Platelet aggregation in poiseuille flow: II. Effect of shear rate.

Using a double infusion technique described in the previous paper, the effect of shear rate, G, on platelet aggregation was studied in citrated platelet-rich plasma in Poiseuille flow over a range of mean linear flow rates, u3 from 50 to 1500 microns-1 corresponding to G from 2 to 54 sec-1. At 1 micron ADP, aggregates were formed at all u3 and, except at the lowest flow rate, both the degree of aggregation (net fraction of cells in aggregates, A') and size of the aggregates increased with distance down the tube. The degree of aggregation was both time and shear rate-dependent. Over the first 10 sec, A' appeared to be independent of the mean transit time indicating that the collision capture efficiency decreased with increasing G. Thereafter, A' increased with increasing shear rate leading to the formation of an appreciable number of aggregates greater than 10 cells at G greater than 24 sec-1. Small aggregates initially formed near the tube wall and, as they grew in size, migrated toward the axis as their rotation was physically impeded by the wall. In addition, the values of A' in cPRP from five female donors were significantly greater than those from five male donors.

Adult↗
PubMed1984

Role of blood cell-wall interactions in thrombogenesis and atherogenesis: a microrheological study.

The relationship between blood flow and the localization of thrombosis and atherosclerosis in vivo was investigated using the approach and techniques of microrheology. The flow patterns and wall-adhesion of platelets were studied in the captive annular vortex formed at a sudden tubular expansion at various hematocrits in steady and pulsatile flow. The adhesion density exhibited a peak within the vortex and just downstream of the reattachment point, which is also a stagnation point. The peaks flattened out with increasing Reynolds number in steady flow and also in pulsatile flow. Platelet adhesion increased markedly with increasing hematocrit. The localization of adhesion peaks was explained by curvature of the streamlines carrying platelets to the wall on either side of the reattachment point. The relevance of these results to the circulation is that stagnation points are found in regions of disturbed flow at various sites in the arterial and venous circulations. This was shown in experiments using a technique whereby flow was visualized in isolated transparent natural blood vessels prepared from dogs and humans postmortem. In dog saphenous vein bileaflet valves, there was a large primary spiral vortex as well as a smaller secondary vortex, the latter acting as a trap and generator of thrombi. Recirculation zones also existed in the dog aorta at T-junctions of the celiac, cranial mesenteric and renal arteries. Finally, in the human carotid bifurcation, a large standing recirculation zone consisting of spiral secondary flows formed in the carotid sinus at physiological flow conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

Fluid mechanical stress and the platelet.

Platelet thrombi in suspensions stirred in an aggregometer or subjected to shear flow in a Couette viscometer or circular tube can only form as a result of collisions between the cells. In whole blood, the presence of the red cells results in pronounced lateral displacements of the paths of the platelets through the vessel, which in turn increases the frequency of collisions between platelets and also makes possible platelet-wall interactions. In addition, blood cells in a suspension undergoing shear flow are subjected to fluid stresses which can result in their deformation. Such stresses may locally attain high values in the arterial circulation at bifurcations, sharp bends and stenoses where the flow is disturbed. Since platelet thrombi have been found downstream of sites of such geometry, the effects of high and variable shear stress on the platelet release reaction and aggregation were investigated. Washed platelets containing C14-serotonin in Tyrodes-albumin solution were subjected to oscillatory flow at 37 degrees C and provided the time average wall velocity gradient was above 2,000 sec-1, the thrombin-induced release of serotonin was appreciably greater than in the corresponding controls incubated at rest. No measurable serotonin was released as a result of flow alone. This synergistic effect of oscillatory shear flow was also noted in the presence of inhibitors of the release reaction.

Blood Flow Velocity↗