Platelet facilitation of clot lysis was studied using the dilute clot lysis assay, a standardized assay for fibrinolysis shown to correlate with the development of postoperative deep vein thrombosis. Clots prepared from dilute platelet poor plasma showed prolonged clot lysis when compared with clots prepared in a similar fashion from dilute platelet rich plasma. Since in the presence of platelets clot retraction or contraction occurred, we evaluated a possible direct contribution of retraction to clot lysis. Dilute platelet poor plasma clots were compacted by centrifugation, to a similar extent as that achieved during clot retraction in dilute platelet rich plasma. These clots now lysed at a rate that approached that seen with dilute platelet rich plasma clots. Using an alternate alternate approach, dilute platelet rich plasma clots were treated with cytochalasin B to prevent clot retraction. Such clots now showed prolonged lysis similar to that seen with dilute platelet poor plasma. The prolonged lysis of cytochalasin B treated dilute platelet rich plasma clots was corrected by artificial compaction of the clots. The results suggest that clot retraction markedly facilitates clot lysis, and shows that a major role of platelets to facilitate clot lysis is the effect of these cells to cause clot retraction.

Events accompanying electron transport in the membrane fraction of liver and other tissues have led us to propose a specific function for α‐tocopherol based on a sequence of biochemical changes we observed to occur in these membranes and on pertinent information from other laboratories. The activity of a membrane‐bound enzyme system (TPNH oxidase) which involves transport of electrons from substrate to oxygen, has been shown to promote simultaneous formation of peroxide functions on the β position polyunsaturated fatty acids (PUFA) of phospholipids in the membrane. The phospholipid peroxides then undergo a chain cleavage reaction producing phospholipids containing a variety of carbonyl moieties in the β position. The process results in marked alteration of the membrane structure. During the overall reaction α‐tocopherol present in the membrane is converted to a compound more polar than tocopheryl quinone and the conversion is dependent on the same enzymic factors promoting the phospholipid alterations. The membrane alteration process is enhanced in microsomes from animals fed diets containing relatively high levels of PUFA or diets low in α‐tocopherol, and is diminished by low levels of dietary PUFA or relatively high levels of α‐tocopherol. The experimental data indicate that enzymic electron transport associated with TPNH oxidation by the microsomal membrane involves free radical functions. The latter apparently can promote extensive peroxidative alterations of phospholipids that result in structural changes in the membrane unless adequate α‐tocopherol is present in this organelle. This system appears to be part of the microsomal drug metabolizing system.

In our preceding paperx) we described the isolation and structure elucidation of antibiotic A83094A(16-deethylindanomycin) from the biomass of Streptomyces setonii. The culture filtrate from a fermentation of this same organism contains two broad-spectrum antibiotics which were isolated and determined to be 5-hydroxymethylblasticidin S (A83094B) and blasticidin S (A83094C) as shown in Fig. 1.The flow diagram for the isolation of 5-hydroxymethylblasticidin S and blasticidin S as a complex is presented in Fig. 2. The antibiotic levels at each step were determined both by disc plate assay vs. Salmonella gallinarum and by HPLC.HPLCassays were run on a ywBondapak C18 column (3.9 x 300 mm) using a mobile phase ofCH3CN -H2O (4 : 96) containing 1 % NH4OAc (w/v) and UV detection at 225 nm.Separation of the complex into individual antibiotics was accomplished using semi-preparative HPLC. The reversed phase chromatography system consisted of a M6000 pump, /*Bondapak C18 column (9.8 x 300 mm), Model 490 variable wavelength detector.U6K man- and mobile phase (as described above for analytical HPLC) pumped at 4ml/minute. Eight separate chromatographic runs were performed as follows: 20 jul aqueous sample, containing 2 mgantibiotic mixture, was applied.16 ml of eluate was discarded; then fractions were collected at 20-second intervals and assayed by HPLC. Fractions containing >95% of each component were combined and lyophilized.Each lyophile was dissolved in 1.0 ml water and desalted by injection on a^Bondapak C18 column (3.9x300mm).After washing the column with 20ml water, the antibiotic was elutedwith CH3CN-H2O (50 : 50). The CH3CN was removed under reduced pressure and the remaining solution lyophilized to provide samples for physico-chemical analyses. The *H NMR of A83094B (500 MHz, DMSOd6) was compared to authentic blasticidin S and indicates that they are structurally similar (see Table 1). The differences are in the loss of 5-H in A83094B and the addition of a hydroxymethylene at <5H 4.21. A nuclear Overhauser effect (NOE) is observed between the new methylene and 6-H. The presence of a hydroxymethylene is consistent with the mass spectral data. Based on recently published data, the structure of A83094B is similar to Sch 366054).