The action of thrombin on intact human platelets has been studied with the aid of polyacrylamide gel electrophoresis in sodium dodecylsulfate. A single major membrane protein band with a molecular weight of 190,000 disappears after thrombin treatment, while a new membrane protein with a molecular weight of 107,000 appears. This may represent hydrolysis of the thrombinsensitive protein. When platelets are disrupted or when the thrombin-sensitive protein is solubilized from membranes prior to thrombin treatment, no hydrolysis occurs. The effect of thrombin on the platelet membrane protein is complete within 2 min which suggests that hydrolysis of this membrane protein may trigger the physiological effects of thrombin on platelets.Platelets are anucleate circulating particles, with a diameter of 2-4 Mum in man, which function in hemostasis. These "cells" are metabolically active and catalyze the formation of fatty acids, phospholipids, glycogen, and even protein (1). Both glycolytic and Krebs cycle oxidative pathways are active in these cells.Blood platelets are rapidly converted from free floating cells to an aggregated mass of intact platelets during the process of hemostasis or of thrombus formation. This obvious change in the platelet surface is accompanied by a variety of morphological and biochemical changes which have been termed "viscous metamorphosis" (1). The most potent agent known to induce this process is the proteolytic enzyme thrombin, which is generated from reactions of the coagulation pathway. Characterization of the role of thrombin in producing viscous metamorphosis is integral to understanding thrombus formation and may also provide some insight into the membrane specification of cell-cell interactions.Previous work done in our laboratory (2) has shown that thrombin causes a 7-fold increase in the rate of incorporation of glycerol into phosphatidyl serine in the platelet membrane. This burst in the rate of lipid synthesis is maximal within 2 min of the addition of thrombin and such synthesis returns to the pre-thrombin rate by 20 min. Studies of the mechanism of this thrombin effect indicate that proteolysis is involved, since the effect can be mimicked by trypsin and inhibited by prior incubation of trypsin with soybean trypsin inhibitor. Human platelets, collected and isolated as described previously (2), were washed twice in a pH 6.5 isotonic buffer containing 0.113 M NaCl, 0.0043 M K2HPO4, 0.0043 M\I Na2HPO4, 0.0244 M NaH2PO4, and 1 mg/ml glucose. After washing, l)latlets were resuspended in either 0.154 M NaCl-0.154 A Tris HCl (pH 7.4) 9:1 with 1 mg/ml glucose, or in a pH 7.5 buffer containing 0.109 M NaCl, 0.043 M K2HP04, 0.0106 M Na2HPO4, 0.0083 MI NaH2PO4, and 1 mg/ml glucose.Platelets were incubated at 370C at 1-2 X 109 cells/ml in resuspension buffer with or without 1 U/ml thrombin and 2.5 mM CaCl2. The cells were disrupted by no-clearance-pestle homogenization (5), glycerol loading, and hypotonic lysis (6) Samples were solubilized in 1-3%o SDS-1%o 0-mercaptoethanol -0.1 AM so...

No abstract

A prospective pilot study of 23 patients with non-Hodgkin's lymphoma involving the stomach was undertaken to assess the efficacy of surgical resection followed by chemotherapy with adjuvant cyclical cyclophosphamide, vincristine, and prednisolone (CVP) in early stage disease, and cyclical cyclophosphamide, vincristine, prednisolone, and doxorubicin (CHOP) in advanced disease. One of 18 evaluable patients died postoperatively; 17 of 18 completed therapy and are alive and disease-free at a median follow-up of 41 months after surgery (range, 5 to 111 months), including four patients with stage IV disease who remain in complete remission 19 to 47 months after surgery. There was one postoperative death, giving an actuarial survival rate of 94% in the study group. Three of five inoperable patients were treated with CHOP, with two achieving complete remission. Two untreated patients died. Overall actuarial disease-free survival was 82.6%. Surgical resection plus chemotherapy is capable of producing long-term remission and cure in both localized and advanced non-Hodgkin's lymphoma of the stomach. Intensive supportive care plus chemotherapy may salvage a proportion of patients with inoperable tumors.

A B S T R A C T Washed human platelets were incubated with 0.1-1.0 U/ml human thrombin and the effects on adenyl cyclase activity and on a platelet membrane protein (designated thrombin-sensitive protein) were studied. Adenyl cyclase activity was decreased 70-90% when intact platelets were incubated with thrombin. The Ti for loss of adenyl cyclase activity was less than 15 sec at 1 U/ml thrombin. There was no decrease of adenyl cyclase activity when sonicated platelets or isolated membranes were incubated with these concentrations of thrombin. Loss of adenyl cyclase activity was relatively specific since the activities of other platelet membrane enzymes were unaffected by thrombin. Prior incubation of platelets with dibutyryl cyclic adenosine monophosphate (AMP), prostaglandin El, or theophylline protected adenyl cyclase from inhibition by thrombin.Incubation of intact but not disrupted platelets with thrombin resulted in the release of thrombin-sensitive protein from the platelet membrane. The rapid release of this protein (Ti < 15 sec) at low concentrations of thrombin suggested that removal of thrombin-sensitive protein from the platelet membrane is an integral part of the platelet release reaction. This hypothesis is supported by the parallel effects of thrombin on adenyl cyclase activity and thrombin-sensitive protein release in the presence of dibutyryl cyclic AMP, prostaglandin Ei, and theophylline at varying concentrations of thrombin.

Langerhans cell histiocytosis (LCH) is a rare disorder which frequently involves the lungs of affected adults. Recent evidence suggests it is a clonal neoplastic disorder. Prognosis in this disease is variable, but in its multisystem form or when associated with progressive respiratory dysfunction, prognosis is poor. Recent case reports and a phase II trial of the antimonocyte drug 2-chlorodeoxy-adenosine (2CDA) have described success in treating LCH. We used 2CDA to treat a young Australian man with LCH involving lungs and bone. A complete symptomatic remission was achieved with no evidence of recurrence some 5 years after completion of chemotherapy.