Evaluation of the inhibition by heparin and hirudin of coagulation activation during r-tPA-induced thrombolysis

Thrombin bound to a fibrin clot remains active and poorly accessible to heparin-AT III complex. During fibrinolysis, thrombin is released as thrombin-FDP complex and is inactivated by heparin-AT III. However, as successive fibrin layers are removed, inaccessible molecules of thrombin are exposed at the surface of the residual clot, possibly contributing to the occurrence during thrombolytic therapy of coagulation that is poorly controlled by heparin. We have investigated the accessibility of fibrin-bound thrombin to hirudin. The results clearly show that two recombinant hirudin variants neutralize thrombin both in solution and fibrin bound. Furthermore, we have found that in in vitro models, hirudin present in the surrounding medium of a clot under lysis is more efficient than heparin in preventing the activation of coagulation. This observation suggests that hirudin may be effective in the prevention of the rethrombotic process frequently encountered during thrombolytic therapy.

[The diagnostic significance of isoantigens ABH in oral leukoplakia]

The ABH blood group isoantigens on the cell membrane of leukoplakia (LK) and normal oral tissue, squamous cell carcinoma and hyperkeratosis (HK) as controls were observed in this study and the results showed that there was a significant difference of the antigens in LK from those in normal tissue and HK, whereas, no significant difference between LK and carcinoma. Furthermore, the loss of antigens was in direct proportion with severity of dysplasia. The HRP-WGA technique was used to detect the WGA receptor on the cell membrane of LK, normal tissue and carcinoma. It was found that the receptor was present in the normal tissue, but decreased obviously and even disappeared in carcinoma. It should be emphasized that the receptor in LK also had some changes. Our findings show that when in mild dysplasia, it is possible to provide a clue to determine whether the dysplasia can be reversible through observation of the change of ABH antigens.

Parallel induction of fibrinolysis and receptors for plasminogen and urokinase by interferon gamma on U937 cells

A new cell sorter technique was employed to study the role of interferon gamma (INF gamma) in fibrinolysis induced by U937 monocytic cells. INF-gamma induced the differentiation of U937 cells as evidenced by the appearance of CD 14 antigen on the cell surface. Scatchard analysis and dose response curves showed a parallel increase in the number of receptors on U937 cells capable of accepting exogenous plasminogen and urokinase (UPA) synthetized by differentiating U937 monocytic cells. This would favour an activation of plasminogen by UPA. This adds a new parameter in the regulation of cell-mediated fibrinolysis and may be important in a number of biological processes.

Effects of hematopoietin-1 and interleukin 1 activities on early hematopoietic cells of the bone marrow

Hematopoietin-1 (H-1) was purified from the human cell line 5637 and two amino acid sequences were observed in the preparation. One sequence was identical to that of interleukin 1 alpha (IL 1 alpha) and the other to that of IL 1 beta. The action of recombinant IL 1 alpha and other hematopoietic growth factors was studied using (a) a high proliferative potential colony-forming cell assay that uses primitive hematopoietic precursors from bone marrow, and (b) a spleen colony-forming unit assay. The results indicate that the IL 1 alpha target cell population is different than the target cell populations of IL 3, granulocyte-macrophage colony-stimulating factor; that IL 1 alpha in combination with mononuclear phagocyte colony-stimulating factor provides a proliferative stimulus; and that IL 1 alpha has at least a survival-enhancing and possibly proliferation-inducing effect on primitive hematopoietic stem cells.

Enhanced expression of urokinase activity on U 937 cell line by 1,25-dihydroxyvitamin D3 induction

1,25 Dihydroxyvitamin D3 is a differentiation inducer for monocytic cell. It can induce a monoblastic cell line U937 to differentiate. In this paper, we report that by inducing the differentiation of U937, 1,25-dihydroxyvitamin D3 increased urokinase activity expression on U937 cell surfaces. After incubation of the cell with various concentrations of 1,25-dihydroxyvitamin D3, the cell line showed a remarkable progressively increasing membrane-associated urokinase activity in a dose dependent manner. On the contrary, plasminogen activator inhibitor activity which was found in the culture medium is not modified by the 1,25-dihydroxyvitamin D3 induction. This results suggests another role of 1,25-hydroxyvitamin D3 in the treatment of myelofibrosis, since enhanced plasmin generation can accelerate the activation of procollagenase. The induced plasmin and collagenase activities surrounding the monocytic cells may participate in the physiological and pathological events, especially in the connective tissue degradation.

Defective thrombolysis due to collagen incorporation in fibrin clots

The migration of fibroblasts into a clot may be responsible at least in part, for its organization, thus leading to a defective thrombolysis. We have shown that collagen incorporated in a fibrin clot induces a dramatic decrease in fibrinolysis. Despite the fact that plasminogen binds to collagen, tissue plasminogen activator induced plasminogen activation in the presence of fibrin is only slightly decreased by the presence of collagen. This rather suggests that collagen induces a modification in clot structure, by rendering fibrin less accessible to fibrinolytic enzyme.

Regulation of thrombopoiesis: effects of the degree of thrombocytopenia on megakaryocyte ploidy and platelet volume

We have established a murine model and techniques with which to serially study thrombocytopoiesis after induction of experimental immune thrombocytopenia of variable severity and duration. Bone marrow megakaryocyte ploidy distribution was determined by using unfractionated bone marrow, a polyclonal megakaryocyte-specific probe, and two-color, fluorescence-activated flow cytometry. With these techniques, the modal megakaryocyte ploidy class in normal murine bone marrow was 16N. Serial studies of bone marrow megakaryocyte ploidy after the induction of acute, severe thrombocytopenia (platelet count, less than 0.05 X 10(6) microL) demonstrated no detectable change in the ploidy distribution at 12, 24, and 36 hours after the onset of thrombocytopenia. At 48 hours, the modal ploidy class shifted from 16N to 32N, and the 64N class increased significantly (P less than .001). The ploidy distribution returned to normal 120 hours after the onset of thrombocytopenia. A lesser degree of thrombocytopenia (platelet count reduction to 0.100 to 0.200 X 10(6)/microL) delayed the modal ploidy class shift from 16N to 32N until 72 hours after the onset of thrombocytopenia. Chronic, severe thrombocytopenia (platelet count, less than 0.05 X 10(6)/microL for seven days) resulted in a modal ploidy class shift from 16N to 32N during the thrombocytopenic phase and an enhanced increase in the 64N megakaryocyte class during the recovery phase. Mean platelet volume (MPV) was simultaneously measured on isolated total platelet populations after induction of thrombocytopenia. MPV was significantly increased (P less than .001) as early as eight hours after the onset of acute, severe thrombocytopenia, 40 hours before a shift in the ploidy distribution. Mild thrombocytopenia (platelet count reduction to 0.400 X 10(6)/microL) was not associated with a ploidy shift but did result in a significantly increased MPV (P less than .001). These studies demonstrate that the temporal relationship and magnitude of the effects of thrombocytopenia upon megakaryocyte ploidy distribution are dependent upon the degree and the duration of the thrombocytopenic stimulus and that the effects of experimental thrombocytopenia on platelet volume and megakaryocyte ploidy are dissociated.

Recombinant human granulocyte colony-stimulating factor: effects on normal and leukemic myeloid cells

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D+) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in Escherichia coli. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with 125I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D+) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D+) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D+) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be O-glycosylated and to have a molecular weight of 19,600.

Recombinant human granulocyte colony-stimulating factor: effects on normal and leukemic myeloid cells

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D+) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in Escherichia coli. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with 125I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D+) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D+) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D+) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be O-glycosylated and to have a molecular weight of 19,600.