Interaction of ethanol, prostacyclin, and aspirin in determining human platelet reactivity in vitro.

Ethanol partitions into cellular membranes and alters membrane-associated phenomena in numerous cell types. Since platelet aggregation and its inhibition by prostacyclin are mediated by membrane-associated receptors and enzymes, we examined the interaction of ethanol, prostacyclin, and aspirin on human platelet reactivity. Using platelet-rich plasma, we examined the effect of increasing concentrations of ethanol (0.

Vitamin E supplementation effect on human platelet function, arachidonic acid metabolism, and plasma prostacyclin levels.

A randomized, placebo-controlled double-blind trial was conducted on 20 adults to assess the effect of vitamin E (800 IU/d 727 mg/d for 5 wk) on platelet function, arachidonic acid metabolism, and prostacyclin generation. Platelet aggregation was measured in response to collagen, arachidonic acid, and adenosine diphosphate. Thromboxane B2 was assayed in serum and in the supernatant plasma after platelet aggregation.

Altered arachidonic acid metabolism and platelet size in atopic subjects.

The release and metabolism of endogenous arachidonic acid (AA) in physiologically activated platelets obtained from 11 atopic patients with allergic rhinitis and/or asthma was compared to that of sex- and age-matched nonatopic controls. Prelabeled [3H]AA platelets were stimulated with thrombin or collagen and the amount of free [3H]AA and radiolabeled metabolites released were measured by high-performance liquid chromatography. The results obtained indicate that although the incorporation of [3H]AA into platelet phospholipids and total release of 3H-radioactivity upon stimulation were comparable in the two groups, the percentage of 3H-radioactivity released from platelets as free AA was significantly lower (P less than 0.

Effect of chronic low dose aspirin on platelet and vascular eicosanoid metabolism in nonhuman primates (Macaca fascicularis).

It has been suggested that inhibition of platelet cyclooxygenase by chronic low dose aspirin may spare vascular prostacyclin production. Conventional doses of aspirin (greater than 5 mg/kg) have been shown to inhibit the generation of both thromboxane A2 and prostacyclin. Low dose aspirin inhibits prostacyclin production by excised human venous tissue, thus questioning the selectivity of such regimens.

Low-dose enteric-coated aspirin: a practical approach to continuous-release low-dose aspirin and presystemic acetylation of human platelet cyclooxygenase.

Using a granular enteric-coated aspirin (ECA) preparation, we achieved continuous release of low-dose aspirin and associated inhibition of platelet reactivity. The lowest once-daily dose that produced greater than 90% inhibition of serum thromboxane (TX) A2 after 7 days was 80 mg. The time course of inhibition after the first dose indicated a gradual release of aspirin over a period of 8 hours.

Cumulative antiplatelet effect of low-dose enteric coated aspirin.

Enteric coated aspirin (ECA) at doses of 325-1300 mg is an effective alternative to regular aspirin for inhibition of platelet activity while avoiding gastric irritation. The objectives of this study were to determine: (1) the lowest chronic dose of ECA providing effective inhibition of platelet activities, (2) the time course of the inhibition, and (3) the reappearance of platelet cyclo-oxygenase activity. Seven subjects were studied before and after seven daily doses of 40-325 mg ECA.

Modulation of forskolin binding to rat brain membranes.

High affinity binding sites for [3H]forskolin have been identified in rat brain membranes. These sites have a Kd of 15 nM and a Bmax of about 200 fmol/mg protein. The binding of [3H]forskolin to those high affinity sites in rat brain membranes is increased about two-fold by addition of MgCl2 or MnCl2.

The effect of dopamine on tracheal smooth muscle.

Dose-response curves to dopamine were obtained on guinea-pig, dog and human tracheal smooth muscle. Dopamine produced a relaxation of the guinea-pig tracheal chain, and this relaxation was completely blocked by propranolol. The potency of dopamine as a beta-agonist was 1/10 000 that of isoprenaline, 1/250 that of adrenaline and 1/50 that of noradrenaline.

Binding of [3H]forskolin to rat brain membranes.

[12-3H]Forskolin (27 Ci/mmol) has been used to study binding sites in rat brain tissue by using both centrifugation and filtration assays. The binding isotherm measured in the presence of 5 mM MgCl2 by using the centrifugation assay is described best by a two-site model: Kd1 = 15 nM, Bmax1 (maximal binding) = 270 fmol/mg of protein; Kd2 = 1.1 microM; Bmax2 = 4.

Arachidonic acid metabolism by platelets of differing size.

The relationship between mean platelet volume (MPV) and platelet arachidonic acid metabolism was examined by studying the ability of human platelets of different size to incorporate and metabolize tritiated arachidonic acid ([3H]AA). Platelet phospholipids were labelled with [3H]AA and the platelets were then fractionated into size-dependent subpopulations by counterflow centrifugation. The incorporation of [3H]AA increased through the fractions proportional to the MPV.

Effect of membrane cholesterol on phospholipid metabolism in thrombin-stimulated platelets. Enhanced activation of platelet phospholipase(s) for liberation of arachidonic acid.

The cholesterol to phospholipid mole ratio (C/PL) of human platelets was increased 1.3-fold or maintained at a normal value by incubating platelets with sonicated dispersions of cholesterol and phosphatidylcholine (PC) (C/PL = 3 or 1, respectively). Thrombin-induced mobilization of [3H]arachidonic acid from prelabeled phospholipids and subsequent formation of labeled cyclo-oxygenase and lipoxygenase products were increased in cholesterol-enriched platelets as a function of thrombin concentration.

Platelet arachidonic acid metabolism and platelet function in ten patients with chronic myelogenous leukemia.

We have compared the pathways of arachidonic acid (C 20:4) metabolism in platelets from ten patients with Philadelphia chromosome-positive CML with those of seven normal subjects. Platelets were incubated with 3H-arachidonic acid, gel-filtered, and treated with thrombin (5 U/ml). The cyclooxygenase and lipoxygenase-derived products and free arachidonic acid released from the platelets were separated by high pressure liquid chromatography and their radioactivity determined.

The use of high pressure liquid chromatography (HPLC) for the separation of radiolabeled arachidonic acid and its metabolites produced by thrombin-treated human platelets. II. Establishment of optimal assay conditions.

We have utilized HPLC to develop optimal conditions for assaying the transformation of arachidonic acid in thrombin-treated human platelets. In the presence of increasing amounts of albumin, the total amount of radioactivity released from thrombin-treated platelets pre-labeled with 3H-arachidonic acid is first enhanced and then inhibited. Maximal release, reflecting primarily enhanced amounts of free labeled arachidonic acid, occurs at a final albumin concentration of 0.

The Ito "Flow-Through" Centrifuge. A new device for long-term (24 hours) plasmapheresis without platelet deterioration.

An efficacious procedure for continuous plasmapheresis in long-term extracorporeal circulation has not yet been devleoped. This technique could be important in plasma exchange or cross-exchange and in artificial organ support if it could be accomplished safely using heparin as the anticoagulant. When sheep were connected to the Celltrifuge for 23 hours and administered 150 units/kg per hour heparin anticoagulant, we found gross platelet clumping in separated plasma and a 60 per cent fall in platelet count.

The pathogenetic significance of intravascular coagulation in experimental acute renal failure.

Serum and urine fibrin(ogen) degradation products (FDP), FDP clearances, and serum urea nitrogen (SUN) concentrations of rats challenged with glycerol-induced myohemoglobinuria were measured serially over a period of 4 days. The results obtained in animals that developed acute renal failure (ARF) were compared with those obtained in rats made refractory to renal failure by long-term salt loading or recent recovery from prior renal failure. Only the rats susceptible to ARF experienced a major rise in serum FDP concentration.

Activation of the kallikrein system in hyperbetalipoproteinemia.

In 30 patients with hyperlipoproteinemia (19 type II and 11 type IV), the role of the intrinsic coagulation pathway was evaluated by assays of preK, Kl's, and Hageman factor (factor XII). Analysis of the plasma of type II patients suggested activation of the intrinsic pathway characterized by a 40% decrease in preK (p less than 0.01) and a 50% decrease Kl (p less than 0.

Effect of clofibrate on intravascular coagulation in hyperlipoproteinemia.

Intravascular coagulation (IVC) was evaluated in 19 patients with type II and 11 with type IV hyperlipoproteinemia before and after clofibrate therapy by measurements of soluble fibrin complexes (SFC) in plasma; fibrinolysis was estimated by quantitation of fibrin (ogen) degradation products in serum. Untreated type II and type IV patients had increased SFC (P less than 0.01).

Coagulation abnormalities in women taking oral contraceptives.

Thirteen asymptomatic women taking oral contraceptives (OCs) were compared with normal subjects. Platelet aggregation and serotonin (tagged with carbon 14) release with adenosine diphosphate, epinephrine, and collagen did not differ from controls. Activation of the intrinsic coagulation pathway was evaluated by measurements of factor XII, prekallikrein, and kallikrein inhibitors.

A class of bounded pseudo-differential operators.

Pseudo-differential operators of order -M and type rho, delta(1), delta(2) are shown to be bounded in L(2) provided that 0 View Article and Find Full Text PDF