When [14C]oleate-bovine serum albumin complexes were incubated in vitro with rat liver plasma membranes (LPM), specific, saturable binding of oleate to the membranes was observed. Maximal heat-sensitive (i.e., specific) binding was 3.2 nmol/mg of membrane protein. Oleateagarose affinity chromatography of Triton X-100-solubilized

Ingestion of 1.5 g of aspirin, but not of sodium salicylate, produced a significant prolongation of the bleeding time in six normal male subjects when compared with the effects of a placebo. Similar differences in the effect of the two drugs on platelets was also observed. Aspirin ingestion resulted in impaired platelet aggregation by connective tissue and was associated with a decreased release of platelet adenosine diphosphate (ADP); sodium salicylate had no effect on these values. In vitro, incubation of platelet-rich plasma with an optimum aspirin concentration of 0.50 mmole/liter (0.045 mg/ml) inhibited both the adhesion of platelets to connective tissue and the release of ADP as well as the secondary wave of platelet aggregation produced with ADP or epinephrine; sodium salicylate had no effect on these reactions, which were also normal in patients with von Willebrand's disease. The inhibitory effect produced by ingesting a single 1.8 g dose of aspirin was detectable for 4-7 days at which time salicylate was no longer detectable in the blood, which suggested an irreversible effect on the platelet. Aspirin also inhibited the release of platelet adenosine triphosphate (ATP), but had no effect on the platelet surface charge, available platelet ATP or ADP, or the destruction of ADP by plasma ADPase. These studies lend further support to the hypothesis that ingestion of aspirin, in contrast to sodium salicylate, prolongs the bleeding time by inhibiting the release of platelet An abstract of some of the material presented here has been previously reported in

Two molar urea (pH 7.5) and column chromatography on Sepharose 4B were used to separate clathrin (coat protein) from the membrane of coated vesicles from bovine brain. Lytron (polystyrene) particles were used for study of the interaction of ciathrin with contractile proteins. Muscle G-actin, F-actin, and a-actinin were bound by clathrin-coated Lytron particles, while no interaction was found when muscle tropomyosin and serum albumin were tested. Clathrin molecules dispersed in a solution of 20 mM Tris*HCl (pH 7.5) were found to e elongated. When the pH was adjusted from 7.5 to 6.5, clathrin molecules associated into basketlike or cage structures similar in size and shape to those observed in enriched preparations of coated vesicles. Below pH 6.0, cages or baskets became amorphous aggregates. Raising the pH from 6.5 to 8.0, addition of 5-10 mM ATP or EDTA, or addition of 200 mM KCI resulted in the disassembly of baskets and the formation of filamentous arrays of various widths. Because of clathrin's biochemical and biophysical properties, its interaction with contractile proteins, and its presence in the membrane of vesicles of various cell types, we classified clathrin in the group of mechanochemical proteins.

No abstract

Summary. Sedimentation characteristics of factor VIII were investigated by ultracentrifugation in 10–40% w/v sucrose gradient in pH 7.2 imidazole buffered saline at 65 000 rpm for 6 hr. Following dialysis of fractions for 12 hr against buffered saline, the factor‐VIII activity was assayed by a one‐stage method and other proteins were identified by immunological techniques. In human citrated plasma, two regions of factor‐VIII activity were detected, a main fast sedimenting activity in the region ofγM macroglobulin and a minor slow sedimenting activity in the region of fibrinogen. Cryoprecipitate activity was all of the fast type, while the activity in its supernatant was of the slow type. When plasma was fractionated in a sucrose gradient prepared in 0.4 or 1 M NaCl, the factor‐VIII activity was found in the slow fraction, suggesting that fast‐sedimenting factor VIII is a non‐covalently bound polymer. Incubation of plasma with thrombin (0.035 u/ml for 10 min at 37°C) markedly increased the factor‐VIII activity, all of which appeared in the slow fraction. Although this suggests the possibility that the fast fraction represents a factor VIII‐fibrinogen complex, immunological analysis of this fraction failed to reveal the presence of any fibrinogen. Alternatively, the fast fraction may be composed of sub‐units of factor VIII which are both released and activated by thrombin.