Arachidonic acid and isolated human umbilical vein: concentration-limited prostacyclin generation and absence of direct toxic effects on endothelial integrity

Previous studies show that administration of high doses of arachidonic acid to rabbits causes disruption of vascular integrity. To examine if similar changes would occur in isolated human vascular tissue, we treated human umbilical veins with arachidonic acid (0, 0.01, 0.1, 1.0 mM). Prostacyclin biosynthesis was quantitated in the supernatants and the endothelial integrity was evaluated by scanning electron microscopy. Prostacyclin synthesis was maximum at low concentrations (0.01-0.1 mM) with no additional increase with higher concentrations of arachidonic acid (1mM) confirming previous observations. There was no evidence for endothelial disruption with any concentration of arachidonic acid. This study shows that arachidonic acid has no direct effects on the vascular lining of isolated human umbilical vein, arachidonic acid-induced sudden death in experimental animals is not due to limitation of prostacyclin synthesis.

Decreased platelet aggregation but increased thromboxane A2 generation in polycythemia vera

Patients with polycythemia vera have been described to have hemorrhagic as well as thrombotic tendencies. In a patient with polycythemia vera and angina pectoris, we observed markedly decreased platelet aggregation response to epinephrine but increased platelet and whole-blood thromboxane A2 generation compared with normal subjects. Electron microscopy mostly showed partially activated forms of platelets, which may account for decreased aggregation response in vitro and hemorrhagic tendencies. Young and large platelets found in this disease, however, can generate large amounts of vasoconstrictor and platelet proaggregatory prostanoid thromboxane A2 in response to endogenous thrombin, which may be a basis for thrombotic tendencies.

Lack of efficacy of nafazatrom, a novel anti-thrombotic compound, in patients with coronary artery disease

Nafazatrom (Bay G 6575) is a novel antithrombotic compound, which acts by stimulation of prostacyclin as well as by inhibition of lipoxygenase enzymes. To determine its effects on exercise performance in coronary artery disease patients, a double-blind study was conducted. Twenty patients with coronary artery disease underwent an exercise stress test before and 2 hours after administration of placebo or nafazatrom (1.2 gm). Before the drug administration, there was evidence of enhanced platelet activity, as reflected by elevated resting plasma beta thromboglobulin and thromboxane B2 concentrations. Plasma 6-keto-PGF1 alpha levels were undetectable in most patients. All coagulation tests were in the normal range. None of these parameters changed with exercise. Administration of placebo or nafazatrom before the exercise stress test did not significantly influence any of the coagulation or platelet function parameters or plasma concentrations of thromboxane B2 and 6-keto-PGF1 alpha. This lack of effect was evident both at rest and upon exercise. Compared to placebo, nafazatrom did not significantly increase exercise tolerance time or exercise-induced symptoms. In conclusion, nafazatrom did not influence exercise performance in patients with coronary disease.

Prostacyclin and thromboxane A2 production by human cardiac atrial tissues

We examined the generation of prostacyclin and thromboxane A2 in the right atrial tissues obtained from patients undergoing coronary bypass surgery. In all instances, the capability of atrial tissues to produce these potent prostaglandins was identified. The identity of prostacyclin and thromboxane A2 was confirmed by use of specific radioimmunoassays of stable metabolites and by use of specific thromboxane A2 synthetase and cyclo-oxygenase inhibitors.

Platelet function and biosynthesis of prostacyclin and thromboxane A2 in whole blood after aspirin administration in human subjects

Small doses of aspirin have been shown to inhibit platelet thromboxane A2 while sparing vascular prostacyclin synthesis. Because leukocytes generate prostacyclin and participate in thrombosis along with platelets, the effects of three different doses of aspirin (40, 325 and 650 mg) on platelet function as well as on endogenous biosynthesis of thromboxane A2 and prostacyclin in whole blood were examined. In normal volunteers given a single 40 mg dose of aspirin, platelet aggregation and adenosine triphosphate release were inhibited for 24 hours. In contrast, platelet function was inhibited for 4 to 7 days in volunteers given 325 or 650 mg of aspirin. Platelet and whole blood generation of thromboxane A2 was inhibited less than 60% by the 40 mg dose, but almost completely by both the 325 and 650 mg doses. Likewise, whole blood generation of prostacyclin was inhibited 70% by the 40 mg dose and over 90% by the larger doses. Inhibition of thromboxane A2 as well as of prostacyclin was evident for 4 days with the 40 mg dose and for 7 days with the larger doses. Decreases in whole blood thromboxane A2 and prostacyclin with any dose of aspirin were of similar magnitude. These data indicate that aspirin in doses of 40 to 650 mg inhibits platelet function and biosynthesis of thromboxane A2 and prostacyclin in whole blood in human beings in a dose-dependent fashion.

Decreased stabilization of prostacyclin activity in patients with bone tumors

Tumor metastasis is mediated in part by platelet activation. Since prostacyclin regulates platelet activity, we examined stabilization of bioactivity of exogenous prostacyclin in plasma of patients with malignant bone tumors. Bioactivity of prostacyclin (platelet aggregation inhibition) incubated in patient plasma was found to be significantly less compared to that in normal plasma. In addition, the duration of bioactivity of prostacyclin was considerably less in plasma of patients with bone tumors. These preliminary data indicate decreased prostacyclin activity in plasma of patients with malignant bone tumors, which may be a mechanism of platelet-tumor cell aggregate formation and subsequent evolution of metastasis.

Biochemical and ultrastructural integrity of the saphenous vein conduit during coronary artery bypass grafting. Preliminary results of the effect of papaverine

Factors associated with early and late graft patency related to aorta-coronary artery bypass grafting with a reversed segment of saphenous vein are clinically important. The present investigation examines the biochemical and electron microscopic integrity of this venous conduit intraoperatively with regard to pharmacologic manipulation with papaverine. Portions of saphenous vein were analyzed in 22 patients undergoing coronary artery bypass operations. Levels of a stable derivative of prostacyclin, 6-keto-PGF1 alpha, were measured by radioimmunoassay. Scanning as well as transmission electron microscopy was also performed. In particular, the efficacy of local vein treatment with papaverine, a phosphodiesterase inhibitor, was evaluated. We found that levels of 6-keto-PGF1 alpha in venous effluent showed a biphasic response with initial elevation followed by a relative depression after papaverine exposure. There were no such changes observed in veins subjected to a balanced electrolyte solution (Plasma-Lyte). In addition, levels of the platelet-inhibitory substance 6-keto-PGF1 alpha in venous tissue were less in papaverine-treated veins than those found in veins treated only with the balanced electrolyte solution (Plasma-Lyte). Furthermore, evidence for ultrastructural damage was also somewhat greater in the papaverine-treated group. An alternative method of dilating the saphenous vein after harvesting, which involves the creation of the proximal aorta-coronary anastomosis first and gentle finger manipulation subsequently, appeared to minimize venous injury. Under present clinical conditions, it appears that some amount of injury is inevitable during harvesting and suturing of the human saphenous vein during coronary bypass grafting.

Antimicrobial effect of chlorhexidine and povidone-iodine on vaginal bacteria

The antimicrobial potency of 4 per cent chlorhexidine gluconate was compared with that of 10 per cent povidone-iodine (1 per cent free iodine) on the vaginal bacteria of 150 premenopausal, non-pregnant women. From 30 of the women blood samples were taken before and at either 15, 30 or 60 minutes after vaginal cleansing with chlorhexidine for chlorhexidine analysis. Five minutes after applying either chlorhexidine or povidone-iodine almost 99 per cent of bacteria present on the lateral wall of the vagina were killed. Chlorhexidine was significantly more effective than povidone-iodine. Serosanguineous , mucoid or white-yellowish vaginal discharge did not alter the effectiveness of either antimicrobial agent. In contrast to povidone-iodine, vaginally applied chlorhexidine was not absorbed in measurable amounts (sensitivity of detection method: 0 X 1 mg/l) into the bloodstream. Chlorhexidine may therefore prove of value for treating vaginitis especially during pregnancy and also for combating microbes such as Group B streptococci which are potentially harmful to the newly-born child.

Improved response of patients refractory to random-donor platelet transfusions by intravenous gamma globulin

Because of frequent unavailability of HLA-compatible platelets or their inefficiency in increasing platelet counts in patients requiring platelet transfusions, platelet refractoriness remains a major problem. Since human gamma globulin has been shown to interfere with the binding of platelet-reactive immunoglobulin G (IgG) to platelets in vitro, and since gamma globulin has proved effective in reversing destruction of platelets in idiopathic thrombocytopenic purpura, we decided to investigate intravenous gamma globulin as an adjunct to random-donor platelet transfusions. We studied three patients, one with acute T-cell leukemia, and two with aplastic anemia. When a total dose of 2 g/kg of body weight of intravenous gamma globulin was infused over five to six days in these patients, two of them showed a remarkable increment in platelet counts and improved hemostasis with random-donor platelet transfusions. We conclude that intravenous gamma globulin may be used in critical situations to improve the response of patients refractory to random-donor platelet transfusions.

Activity of Carbetimer in a human tumor cloning system

The antitumor activity of Carbetimer was tested against 171 patient's tumors in a human tumor cloning system. Sixty-seven tumor specimens had adequate growth to be considered evaluable. In 21 specimens survival of tumor colony forming units was less than or equal to 50% that in control plates. Antitumor effect was most impressive in carcinomas of the breast, ovary, and lung. This information will be useful in planning disease oriented Phase II trials.

Thromboxane release in coronary artery disease: spontaneous versus pacing-induced angina

To determine thromboxane A2 release in coronary artery disease, we measured its stable metabolite thromboxane B2 by radioimmunoassay in 20 patients. In 15 patients with stable disease (last angina episode greater than 96 hours before study), coronary venous thromboxane B2 concentrations were lower than in aortic blood (mean 109 +/- 36 vs 194 +/- 40 pg/ml, p less than 0.001). In contrast, in five other patients with spontaneous angina, coronary venous thromboxane B2 concentrations were higher than aortic thromboxane B2 concentrations during the angina episode (mean 1716 +/- 316 vs 875 +/- 388 pg/ml, p less than 0.02). Plasma thromboxane B2 levels were in the normal range (mean 175 +/- 35 pg/ml) in patients with stable angina but significantly (p less than 0.02) higher in patients with spontaneous angina. With atrial pacing to the point of chest pain and/or ECG changes in patients with stable coronary artery disease, aortic thromboxane B2 concentrations increased in 10 of 13 patients (mean 283 +/- 70 pg/ml, p less than 0.02). Coronary venous thromboxane B2 concentrations increased in seven patients at peak pacing rates (mean 223 +/- 76 pg/ml) and in three other patients after termination of pacing. These data indicate that release of thromboxane A2 is much greater during spontaneous angina than with pacing stress in patients with coronary artery disease. Thromboxane A2 released during spontaneous or pacing-induced angina may modulate coronary and systemic vascular tone. Enhanced thromboxane A2 activity may either precede or follow myocardial ischemia and could be a factor in the initiation and propagation of the ischemic episode.

Potential role of platelets in the pathogenesis of tumor metastasis

Platelet activity may be involved in tumor metastasis. The tumor cells, after detachment from the primary site, adhere to vascular endothelium at distant sites and proliferate. Platelets form aggregates with tumor cells in circulation, facilitating their adhesion to the vascular endothelium. Formation of platelet-tumor cell aggregates and their sequestration in various end-organs may result in thrombocytopenia. Certain tumor cell lines directly stimulate platelet activity, some by releasing platelet-aggregating material, a urea-extractable membrane component, others by release of cathepsin, and still others by undefined mechanisms. The direct effect of platelets on tumor cells may be of pathogenic significance. For example, platelet-derived factors stimulate growth of some tumors, whereas others increase vascular permeability and thus facilitate migration of tumor cells across the vessel wall. Lack of these platelet factors, as in thrombocytopenic animals, may indeed inhibit tumor metastasis. Arachidonic acid metabolism in platelets and the vessel walls may contribute to metastatic process. In particular, thromboxane A2 and prostacyclin generation capabilities appear to be important in modulating platelet-tumor cell deposition and growth. To alter the metastatic process, several preliminary trials of platelet-inhibitory agents have been performed. However, the results of these trials have been equivocal, perhaps related to nonspecific effects of these agents on arachidonic acid metabolism. Studies directed at specific pathways of platelet-vessel wall interaction on some tumors appear promising. These newer agents may be of therapeutic value in man.

Spontaneous rupture of splenic artery aneurysm: sixth instance of both maternal and fetal survival

Spontaneous rupture of a splenic artery aneurysm in the third trimester of pregnancy is a catastrophic event associated with a very high fetal and maternal mortality rate. There are only five reported instances of both maternal and fetal survival after spontaneous rupture of a splenic artery aneurysm. This report not only documents the sixth such case, but also recommends a different therapeutic approach for the management of such cases.