Prostacyclin, a potent, naturally occurring prostaglandin exerts a variety of cardiovascular and cellular actions of potential value in acute myocardial ischemia. These properties include the reduction of systemic blood pressure without changing heart rate, the lowering of coronary vascular and total peripheral resistance, the inhibition of platelet aggregation and the concomitant formation of thromboxane B2, and the reduction of the release of lysosomal enzymes.

Prostaglandins continue to be a major and fast-developing area of research in the chemical and biological sciences. Increasing evidence has recently prompted some researchers to suggest that the important physiological actions of these hormones are exerted by their unstable arachidonic acid pathway intermediates, the endoperoxides, thromboxanes, and prostacyclin. The importance of these substances in physiology and medicine and the challenge they pose to synthetic chemistry place them in the forefront of chemical and biochemical investigation. Current biological research has greatly benefited by synthetic advances which have made available large quantities of some of these naturally occurring intermediates and several analogs with increased stabilities. Following a brief review of the primary prostaglandins, the present article describes recent biosynthetic developments, partial and total syntheses of prostaglandin endoperoxide analogs, thromboxane B2, and prostacyclins, and the biological properties of these molecules.

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Structural components of the coat of free tumor cells, particularly from epithelial malignancies, may be stained both by the Hale and the PAS procedures( 1 ) . The Hale positive material can be removed by active neuramidase, indicating the presence of sialic acid. The PAS positive component is not influenced by lipid extraction and diastase digestion, excluding lipids and simple polysaccharides. This leaves simple sugars of the neutral mucins(2) of the coat or neuraminic (sialic) acid(2,3) as the most likely PAS positive components. On testing the participation of sialic acid, we found that treatment with a potent neuramidase from Streptomyces albus only slightly diminished the intensity of the PAS reaction in the cell coat. Therefore, simple sugars of the neutral mucins are probably the main PAS positive material of the cell surface.Sugars or amino sugars are known to be the basic components of the blood group substances and specific sugars of these blood group substances can be split off by specific glycosidases from Clostridium perfringens or Trichomonas foetus, a treatment that changes their serological specificity (4). We performed analogous experiments with glycosidases, to test our cytochemical interpretations and to investigate which sugars of the tumor cell coat are responsible for its PAS positive reaction.Methods. TA3 cells from a 4 days old ascites tumor were used throughout the work. This tumor originated in the mammary gland of a female mouse from strain A ( 5 ) . TA3 cells were washed with a culture medium without serum (Eagle or NCTC-109), fixed for one hour in a formalin-mercury chloride solution ( 6) , and paraffin embedded for sectioning a t 3 p . After removal of mercury * This work was supported by grant from Nat.Inst. Health, Bethesda, Md. and before being stained with a Hale iron technique(7) or the PAS method (7), sections were subjected to lipid extraction or enzyme incubation.Lipids were extracted for 24-48 hours by using 95 '/o phenol ( 4 ) or a chloroform-metha-no1 solution at 60°C. Sections were incubated at 37°C in the presence of one of the following enzymes: 1 ) malt diastase (Nutritional Biochemicals Corp.)-50 mg per 50 ml of 0.1 M phosphate buffer, pH 6, containing 0.4% NaCl; 2 ) receptor destroying enzyme (RDE) from Vibrio cholerae (Behringwerke Ag., Marburg-Lahn, Germany)usually 4 I.U. of neuramidase per 0.