Biomedical subjects

E M Conway

Publications and source records attributed to E M Conway.

24 records · Page 2Linked to original sources

PubMed1989

Tissue factor gene expression in acute myeloblastic leukemia.

We have studied tissue factor gene expression in the leukocytes of 22 patients with acute myeloblastic leukemia (AML). Total RNA from peripheral blood or bone marrow cells depleted of monocytes was analyzed by Northern blot analysis using a 32P-labeled tissue factor cDNA probe. Cells from 10 cases expressed tissue factor mRNA and positive cases were distributed among the myeloblastic, myelomonocytic, and monocytic subtypes of AML. Tissue factor transcripts were not detected in cells derived from normal bone marrow. The expression of this gene product on the surface of leukemic cells could contribute to the excessive thrombin generation that has been observed in some individuals with this disorder.

Blood Coagulation Factors↗

PubMed1989

Tumor necrosis factor enhances expression of tissue factor mRNA in endothelial cells.

We have examined the effect of recombinant tumor necrosis factor on the expression of tissue factor activity and tissue factor mRNA levels in vascular endothelial cells. Following exposure of human umbilical vein endothelial cells to this cytokine, the appearance of tissue factor procoagulant activity was detected following cell disruption, and was maximal at 6 hours. Northern blot analysis of cytokine-treated cells demonstrated a similar increase in the synthesis of tissue factor mRNA, followed by a gradual decline to the basal level by 18 hours. Cycloheximide by itself induced the accumulation of high levels of tissue factor mRNA in these cells. This result suggests that the proteins necessary for transcription of the tissue factor gene are present in the endothelial cell prior to cytokine stimulation, and synthesis of the tissue factor mRNA may be controlled, in part, by a labile repressor protein.

Cells, Cultured↗

PubMed1988

Tumor necrosis factor suppresses transcription of the thrombomodulin gene in endothelial cells.

Tumor necrosis factor (TNF) dramatically alters the levels of various surface components of the blood vessel wall, such as blood coagulation enzyme receptors, leukocyte-adhesive receptors, and class 1 major histocompatibility complex antigens, which may have relevance to its effects in septic shock, angiogenesis, and tumor growth. However, the precise mechanism by which the cytokine is able to accomplish this remodeling of the endothelial cell surface has not been defined. We have demonstrated that exposure of bovine and human endothelial cells to TNF leads to suppression of the functional cell surface thrombin receptor, thrombomodulin (TM), and TM mRNA of virtually identical magnitude. The cytokine has no significant effect on the stability of TM mRNA or endothelial receptor turnover. Nuclear run-on studies reveal that the treatment of endothelial cells with TNF for short periods reduces TM gene transcription to as little as 3% of control values and that this inhibition does not require new protein synthesis.

Amanitins↗

PubMed1987

Suppression of hemostatic system activation by oral anticoagulants in the blood of patients with thrombotic diatheses.

RIAs for hemostatic system activation were employed to study patients who were anticoagulated with warfarin. The mean prothrombin fragment F1 + 2 concentration in stably anticoagulated individuals without an inherited thrombotic diathesis (mean prothrombin time [PT] ratio [PT of patient/PT of normal plasma pool] = 1.74) was 0.231 nM as compared with a mean plasma F1 + 2 level of 1.68 nM for a nonanticoagulated control group (P less than 0.0001). The initiation of oral anticoagulants in two subjects who did not exhibit protein C deficiency led to a paradoxical increase in F1 + 2 levels during the first day of therapy. We have also shown that a relatively low intensity regimen of warfarin (PT ratio less than 1.2) may reduce elevated concentrations of F1 + 2 into the normal range in patients with a history of recurrent thromboembolism. The mean F1 + 2 level in antithrombin-deficient individuals on warfarin was significantly elevated (mean = 0.714 nM) as compared with that in anticoagulated subjects with protein C deficiency (mean = 0.205 nM) or in those without an inherited thrombotic disorder (P less than 0.01) at equivalent levels of intensity of oral anticoagulation. We therefore conclude that the effect of warfarin on hemostatic system activation is modulated by the endogenous heparan sulfate-antithrombin mechanism.

Administration, Oral↗

PubMed1987

Development of a radioimmunoassay for quantitating prethrombin 2 in human plasma.

We have developed a radioimmunoassay (RIA) for prethrombin 2 (Pr2), a potential intermediate in the transformation of prothrombin to thrombin. Antisera against human Pr2 were raised in rabbits and the respective immunoglobulin G fractions were chromatographed on prothrombin-Sepharose. The specific antibody population obtained was used to construct a double-antibody RIA capable of measuring as little as 0.05 nmol/L of this component. The immunoreactivity of prothrombin was approximately 40,000 times less than that of Pr2 on a molar basis. Because of nonspecific contributions of plasma constituents to the immunoreactive signal, the measurement of Pr2 in this milieu required the use of a titration curve in which Pr2 was added back to Pr2-depleted plasma. This assay was then used to determine the levels of this species in two patient populations with increased prothrombin activation as determined by the prothrombin fragment F1 + 2 RIA, a measure of the in vivo cleavage of prothrombin by factor Xa. The mean Pr2 concentrations in eight patients with disseminated intravascular coagulation and six asymptomatic individuals with congenital antithrombin deficiency not receiving antithrombotic therapy were not significantly elevated as compared with those of normal controls (0.244 nmmol/L and 0.242 nmol/L vs. 0.184 nmol/L, respectively). Our studies show that Pr2 is cleared from the plasma of dogs with a t1/2 of approximately 25 minutes. Given that the t1/2 of F1 + 2 is estimated to be approximately 90 minutes, the low plasma levels of Pr2 observed in patients with thrombophilia cannot result from rapid clearance of this component.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Anticoagulantly active heparin-like molecules from cultured fibroblasts.

Heparin-like molecules, isolated from cultured rat and human skin fibroblasts, accelerated the inactivation of purified human thrombin via purified human antithrombin. Only 15% of the biologic activity of the complex carbohydrates derived from human skin fibroblasts was expressed when the heparin-binding domain an antithrombin was chemically modified at the Trp 49 residue. Human skin fibroblasts were metabolically labeled with [35S]Na2SO4, and radiolabeled heparin-like molecules were isolated utilizing ion-exchange chromatography and fractionated into two separate populations employing immobilized antithrombin. The species which bound with high avidity to the affinity matrix represented about 12% of the radiolabeled heparin-like molecules, accounted for almost 95% of the initial anticoagulant activity, and exhibited a specific activity of 3.98 USP units/10(6) 35S-cpm.

Antithrombins↗