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Biomedical subjects

J A Ware

Publications and source records attributed to J A Ware.

97 records · Page 6Linked to original sources
PubMed1983

Defective platelet aggregation in patients undergoing surgical repair of cyanotic congenital heart disease.

Fifteen patients undergoing cardiopulmonary bypass for repair of cyanotic congenital defects were examined for evidence of platelet aggregation abnormalities by means of electronic particle sizing. Eight patients with polycythemia whose hematocrits were greater than or equal to 50% before bypass were compared with 7 patients without polycythemia whose hematocrits were less than 50%. Patients also were compared with 11 healthy volunteers. Before bypass, platelets in blood from the patients with polycythemia formed markedly smaller platelet aggregates (8.9 +/- 0.8 X 10(3) mu 3; mean +/- standard error of the mean) in response to adenosine diphosphate than those of the other group of patients (21.7 +/- 1.9 X 10(3) mu 3; p less than 0.001) or healthy volunteers (25.8 +/- 2.1 X 10(3) mu 3; p less than 0.001). Mean platelet aggregate sizes were not different between patients without polycythemia and normal volunteers (p greater than 0.05). In samples taken after bypass, patients with polycythemia again had smaller aggregates than the other group of patients (p less than 0.005). This platelet defect is quantitatively related to polycythemia, and may be a mechanical effect of the excess erythrocytes.

Adenosine Diphosphate↗
PubMed1982

Platelet aggregation during and after cardiopulmonary bypass: effect of two different cardiotomy filters.

Patients undergoing cardiopulmonary bypass with a membrane oxygenator were studied to determine the effects of two cardiotomy filters on platelet number and function. A Dacron wool filter removed significantly more microemboli than a 40 mu X 40 mu pore-mesh filter. Postoperatively, there were fewer platelets and a lower total volume of platelets in patients who had a Dacron wool filter in the extracorporeal circuit. However, the volume of adenosine diphosphate-induced aggregates was nearly identical in the two patient groups (p greater than 0.1). The study documents an increased number of circulating platelets after pore-mesh filtration, and suggests that the microaggregates reinfused during pore-mesh filtration represent aggregated platelets that dissociate and subsequently circulate in the patient but do not function.

Adult↗
PubMedDate not supplied

Inhibition of platelet aggregation by verapamil: quantification by in vivo and in vitro techniques.

Platelet aggregation appears to play a prominent role in myocardial ischemia. Verapamil, a slow-channel blocking agent with important antiarrhythmic and vasodilating actions, has been shown to inhibit in vitro platelet aggregation. We used an electronic particle size analyzer to evaluate the effects of verapamil on platelet aggregation in vitro and in vivo in 88 rats. The intravenous injection of verapamil (0.4 mg/kg) did not change the platelet count compared to control animals receiving an equal volume of normal saline (verapamil, 1.1 +/- 0.04 x 10(6)/mm3, vs. control, 1.2 +/- 0.09 x 10(6)/mm3, (p greater than 0.05). The mean size of platelet aggregates induced by adenosine diphosphate (0.2 microM), was reduced by verapamil (verapamil, 15.3 +/- 1.2 x 10(3) micron3 vs. control 24.4 +/- 2.7 x 10(3) micron; p less than 0.01). Platelet aggregates induced in vivo, following a standardized technique of extravasation of right iliac artery blood into the peritoneal cavity, were also smaller following verapamil infusion (verapamil, 12.6 +/- 1.1 x 10(3)micron3, vs control, 17.3 +/- 0.9 x 10(3) micron3 p less than 0.001). We conclude that verapamil exerts and inhibitory effect on platelet aggregation both in vitro and in vivo. This property may add an important new dimension to its potential therapeutic usefulness in ischemic heart disease.

Adenosine Diphosphate↗
PubMedDate not supplied

Effects of ethanol and hemolysis on in vivo and in vitro platelet aggregation.

In vivo and in vitro platelet function were measured in male rats after intravenous injection of ethanol or water. There was a dose-related ethanol suppression of platelet aggregation induced by extravasation. Increased volumes of preformed microaggregates were seen in samples taken directly from the vena cava after injection of ethanol in doses that caused hemolysis. Lower doses of ethanol produced no demonstrable microaggregates or hemolysis: however, extravasation-induced aggregation was inhibited. Hemolysis was noted after intravenous injection of water, which also reduced the total volume and mean aggregate size of platelet aggregates induced by extravasation. Blood drawn from the inferior vena cava after induction of hemolysis had an increased volume of microaggregates, regardless of the agent producing hemolysis. In vitro studies revealed changes in spontaneous and ADP-induced aggregation only at very high concentrations of ethanol (greater than 3,000 mg/dl) and no effects at ethanol levels that altered in vivo aggregation. Ethanol, in doses that do not hemolyze erythrocytes, decreases platelet aggregation.

Animals↗
PubMedDate not supplied

Inhibition of platelet aggregation by oral digoxin and reversal with nifedipine.

To study the effect of cardiac glycosides on platelet function, we obtained serial blood samples from 18 normal male volunteers before and 3, 5, and 7 weeks after beginning digoxin therapy (0.375 mg daily). The combined effect of digoxin and nifedipine (mean dose, 57 mg/day) was assessed during the 5th week. Spontaneous platelet aggregation and platelet response to adenosine diphosphate (ADP) were measured in whole blood by electronic particle sizing. Digoxin (mean serum concentration, 0.9 ng/ml) caused significant reduction in total volume and mean size of platelet aggregates formed in response to ADP. However, with addition of nifedipine, the volume and mean size of aggregates returned to baseline measurements. In vitro administration of digoxin to whole blood failed to inhibit ADP-induced platelet aggregation. The volume of spontaneously induced aggregates decreased with digoxin; however, the decrease was not statistically significant. These data indicate that digoxin given in vivo for several weeks inhibits platelet response to ADP; this effect is reversed by the addition of nifedipine.

Adenosine Diphosphate↗