[Bernard-Soulier syndrome].
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Bernard-Soulier Syndrome↗
Biomedical subjects
A Eldor
Publications and source records attributed to A Eldor.
The effect of antibodies to human platelet membrane and cytoplasmic myosins on myosin ATPase activity and platelet aggregation.
Myosins were purified from the membrane fraction and the cytoplasm of human platelets. Polyclonal antibodies to the purified myosins were induced in rabbits. Their effects on the ATPase activity of the purified myosins as well as on the process of platelet aggregation were studied. A strong cross reactivity was found between the two myosins and their respective antibodies by the ELISA technique. It was found that the antibodies preferentially bind to the "head" segment of the myosins, since purified myosin "rod" reacted only weakly with the two kinds of antibodies. The two antimyosin antibodies strongly inhibited the K+(EDTA) ATPase activity of both myosins, as well as the activity of the isolated myosin "heads". The amount of antimembrane myosin antibody required to inhibit the above enzymatic activity was smaller than that of the anticytoplasmatic myosin antibody. Similar results were observed with F(ab)2 fragments of the two kinds of antibodies. No effect of these antibodies or their F(ab)2 fragments was observed on platelet aggregation induced by various agonists, although their inhibitory effect on the platelet myosin ATPase activity was strong.
Adenosine Triphosphatases↗
The procoagulant effect of zinc on fibrin clot formation.
The influence of Zn+2 on fibrin clot formation was investigated by measuring its effect on the clotting times of fibrinogen exposed to thrombin. It was observed with either human or bovine thrombin that 0.01-0.1 mM Zn+2 induced significant reductions of clotting times in a concentration-dependent manner. The procoagulant effect of Zn+2 occurred in the presence of Ca+2 but was inhibited by metal chelating agents. Higher levels of Zn+2 (greater than 0.2 mM final concentration) were required to accelerate thrombin-induced clot formation in the presence of citrate or oxalate. Similarly with oxalated human plasma, greater than 0.2 mM Zn+2 decreased the clotting time. Cations such as Mg+2 and Mn+2 caused little change in clotting times. As an extension of these findings, we examined the effect of Zn+2 on the inhibition of thrombin by antithrombin-III (AT-III). The presence of as little as 0.006 mM Zn+2 in an incubating mixture of thrombin and AT-III severely reduced the inhibitory activity of AT-III towards thrombin. It was observed that the relative intrinsic fluorescence emission of human thrombin decreased upon exposure to Zn+2 but was unaffected by Mg+2 or Mn+2. It is suggested that Zn+2 can form a complex with thrombin, which results in altered reactivity towards fibrinogen and decreased inhibition by AT-III.
Animals↗
Production and characterization of interferon from endothelial cells.
The capacity of cultured bovine aortic, capillary, and corneal endothelial cells as well as of human umbilical cord endothelial cells to produce interferon (IFN) was investigated. The endothelial cells of the two species produced significant amounts of IFN in response to various viruses and poly (I) poly (C). The IFN produced by human umbilical cord endothelial cells was a mixture of alpha- and beta-IFN, as determined by neutralization with antibodies directed against these two types of IFNs as well as by measuring the antiviral activity on heterologous cells. Bovine endothelial cells also produced a mixture of at least two IFN subspecies, one of them labile at pH 2 and active on human cells and the other stable at pH 2 and inactive on human cells.
Animals↗
Immunohistochemical studies with antibodies to myosins from the cytoplasm and membrane fraction of human blood platelets.
Antibodies were raised to myosins extracted from the cytoplasm and solubilized membranes of human blood platelets. Both antibodies had similar titers as shown by enzyme-immunoassay and bound to the same sites as shown by immunohistochemistry. They were specific for cytoplasmic myosins (e.g., in human white blood cells, platelets and fibroblasts and rat endothelial cells). They showed no crossreaction with human or rat smooth muscle.
Animals↗
The antiproliferative effect of interferon and the mitogenic activity of growth factors are independent cell cycle events. Studies with vascular smooth muscle cells and endothelial cells.
We studied the antagonistic effects of interferon (IFN) and growth factors in G0/G1-arrested normal bovine aortic smooth muscle cells (SMC) which were stimulated by serum, or purified platelet derived growth factor (PDGF), supplemented with plasma-derived serum (PDS). The growth response, measured as [3H]thymidine incorporation into DNA, was dependent on the concentration of the mitogen. Human IFN alpha, recombinant human IFN alpha 2, or a crude bovine-IFN preparation prepared from virus-infected bovine aortic endothelial cells, inhibited SMC growth induced by either serum or PDGF with PDS. The extent of IFN inhibition was inversely related to the concentration of the mitogenic stimulus. We also investigated whether IFN inhibited the early events in G1 phase, stimulated by the competence factor PDGF, or the progression of the cell into the S phase induced by PDS. The results indicated that IFN inhibited these two stages of the G1 phase independently. In addition, we investigated the antiproliferative effect of IFN on bovine aortic endothelial cells (BAEC), which do not respond to PDGF but to the mitogenic activity of fibroblast growth factor (FGF). IFN inhibited the mitogenic activity of FGF in a dose-dependent manner. The results indicate that the anti-proliferative activity of IFN and the mitogenic effects of different growth factors are independent.
Animals↗
Congenital afibrinogenemia and recurrent early abortion: a case report.
The role of the fibrinogen molecule in the maintenance of normal pregnancy is not yet well understood; however, several cases have been previously reported in which failure to complete normal pregnancy was associated with either hypofibrinogenemia, dysfibrinogenemia, or deficiency in factor XIII (fibrin-stabilizing factor) which is important for the crosslinking of the fibrin. A case of congenital afibrinogenemia is described. The patient, a 22-yr-old woman, who suffered from a moderate hemorrhagic tendency associated with very low (less than 10 mg/dl) plasma fibrinogen levels, had three consecutive spontaneous abortions. In view of the previous cases reported, the question is raised whether patients with low or abnormal fibrinogen should be treated with plasma transfusions in order to maintain a normal pregnancy.
Abortion, Habitual↗
The effect of suppression of prostaglandin synthesis on renal function in rats with intact and reduced renal mass.
The present study was undertaken to assess the role of prostaglandin system in the compensatory response to reduced nephron population, respective to renal function and electrolyte excretion. Intact and 5/6 nephrectomized rats were divided in 4 groups: 1) rats pretreated with indomethacin, 2) rats pretreated with the vehicle of indomethacin, 3) rats pretreated with sulindac, and 4) rats pretreated with the vehicle of sulindac. In normal rats, indomethacin administration resulted in a mild decrease in creatinine clearance and a significant reduction of the urinary Na excretion. In the rats with reduced renal mass treated with indomethacin, the creatinine clearance did not differ from that in the control group. The 24 h urinary sodium excretion and the fractional excretion of sodium, however, were significantly lower in the indomethacin treated animals than in the control rats. No change in the creatinine clearance or in the sodium excretion was observed in all groups pretreated with sulindac. The urinary PGE2 and thromboxane excretion was significantly lower in the indomethacin treated intact rats and the rats with reduced renal mass. Sulindac induced a slight decrease in urinary excretion of PGE2 in intact rats. No significant change in urinary excretion of PGE2 or thromboxane was seen after sulindac in the rats with reduced renal mass. The antinatriuretic effect of indomethacin was dissociated from changes in urine flow in all groups of animals, suggesting that the increase in Na reabsorption took place in a water impermeable segment of nephron. These results suggest that the compensatory increase in urinary Na excretion per nephron in rats with reduced nephron population at least partly depends on an intact prostaglandin synthesis.
Animals↗
Platelet-tumor cell interaction with the subendothelial extracellular matrix: relationship to cancer metastasis.
Dissemination of neoplastic cells within the body involves invasion of blood vessels by tumor cells. This requires adhesion of blood-borne cells to the luminal surface of the vascular endothelium, invasion through the endothelial cell layer and local dissolution of the subendothelial basement membrane. Platelets may participate in each of these steps and thus play a role in the pathogenesis of tumor cell metastasis. To learn more about the possible involvement of platelets we studied the interaction of platelets and tumor cells with cultured vascular endothelial cells and their secreted basement membrane-like extracellular matrix (ECM). Whereas the apical surface of the vascular endothelium lacks adhesive glycoproteins and hence protect the vessel wall against platelet and tumor cell adhesion, the underlying ECM constitute a highly adhesive and thrombogenic surface. Interaction of platelets with this ECM was associated with platelet activation, aggregation and degradation of heparan sulfate in the ECM by means of the platelet heparitinase. The activity of a similar enzyme has been previously correlated with the metastatic potential of various tumor sublines. Biochemical and scanning electron microscopy (SEM) studies have demonstrated that platelets may detect even minor gaps between adjacent endothelial cells and degrade the ECM heparan sulfate. This may expose a larger area of the subendothelium and facilitate subsequent adhesion of blood borne tumor cells. Platelets were also shown to recruit lymphoma cells into minor gaps in the vascular endothelium, that otherwise do not constitute a preferential site of invasion. It is suggested that the platelet heparitinase is involved in the impairment of the integrity of the vessel wall and thus play a role in tumor cell metastasis.
Animals↗
Effect of ticlopidine on neutrophil chemotaxis in rats.
The ex vivo effect of oral administration of ticlopidine on rat neutrophil chemotaxis was evaluated. Rats received either 3 oral doses (100 mg/kg body weight) of the drug, within a period of 48 h, via a gastric tube, or the drug was administered in drinking water for 14 days at a dosage of 75 mg/kg/day. Absorption of the drug was manifested by significant inhibition of adenosine diphosphate-(ADP-)induced platelet aggregation. No impairment of neutrophil chemotaxis toward zymosan-activated serum was observed in the ticlopidine-treated animals. These results indicate that concentrations of ticlopidine that significantly inhibit platelet function in rats are without effect on neutrophil chemotaxis toward zymosan-activated serum.
Adenosine Diphosphate↗
Zinc-induced platelet aggregation is mediated by the fibrinogen receptor and is not accompanied by release or by thromboxane synthesis.
We demonstrate that zinc (0.1 to 0.3 mmol/L) induces aggregation of washed platelet suspensions. Higher concentrations (1 to 3 mmol/L) of zinc were needed to aggregate platelets in platelet-rich plasma obtained from blood anticoagulated with low-molecular-weight heparin, probably due to the binding of zinc to the plasma proteins. Zinc-induced aggregation of normal washed platelets required added fibrinogen and no aggregation occurred with thrombasthenic platelets or with normal platelets pretreated with a monoclonal antibody (10E5) that blocks the platelet fibrinogen receptor. These data indicate that the platelet membrane fibrinogen receptor-glycoproteins IIb and IIIa mediate the effect of zinc. Zinc-induced aggregation was blocked by the agent TMB-8, which interferes with the internal calcium flux, and by prostacyclin, which elevates platelet cyclic adenosine monophosphate levels. Zinc-induced aggregation was not accompanied by thromboxane synthesis or by the secretion of dense-body serotonin and was not affected by preexposure of platelets to acetylsalicylic acid. Experiments with creatine phosphate/creatine phosphokinase showed that the zinc effect on platelets was independent of extracellular adenosine diphosphate (ADP). Zinc had an additive effect when platelet aggregation was stimulated with subthreshhold concentrations of collagen or ADP. Together with the known effects of nutritional zinc on in vivo bleeding, on platelet aggregation, and on lipid metabolism, the results suggest that zinc may have an important bearing on normal hemostasis, thrombosis, and atherosclerosis.
Adenosine Diphosphate↗
Platelet interaction with subendothelial extracellular matrix: platelet-fibrinogen interactions are essential for platelet aggregation but not for the matrix-induced release reaction.
Cultured endothelial cells produce an extracellular matrix (ECM) to which platelets adhere and spread, ultimately resulting in platelet aggregation, thromboxane B2 production, and serotonin release. We have investigated the role of fibrinogen binding to the platelet GPIIb/IIIa complex in these reactions by comparing normal platelet-rich plasma (PRP), PRP from patients with Glanzman's thrombasthenia (whose platelets lack the GPIIb/IIIa complex), PRP in the presence of a monoclonal antibody that blocks the binding of fibrinogen to the GPIIb/IIIa complex, platelets washed free of fibrinogen, and washed platelets to which fibrinogen was added. Although platelet aggregation was virtually completely inhibited in the samples in which the normal interaction between fibrinogen and GPIIb/IIIa was impaired, adhesion of platelets to the matrix, spreading, and release of [14C]-serotonin were not affected. All of the platelet preparations released significant amounts of T X B2 with time, but there was a decrease in the amount produced by both the thrombasthenic and antibody-treated platelets. We conclude that the interaction of fibrinogen with platelet GPIIb/IIIa is not required for platelet adhesion to ECM or for adhesion-induced shape change or serotonin release. On the other hand, the platelet-fibrinogen interaction may play some role in augmenting adhesion-induced T X B2 production, and it is absolutely required for adhesion-induced platelet aggregation.
Animals↗
Megakaryocyte interaction with subendothelial extracellular matrix is associated with adhesion, platelet-like shape change, and thromboxane A2 production.
We have examined the morphological and secretory behavior of rat and guinea pig megakaryocytes exposed for up to 24 hours to extracellular matrix produced by cultured bovine endothelial cells. By phase-contrast microscopy of living cells and in more detail by scanning electron microscopy, the megakaryocytes showed a nonreversible adherence, an extensive formation of filopodia around the periphery like the rays of the sun, and a tendency toward flattening. These filopodia were generally linear with attenuated tips and were larger than, but resembled the filopodia of, rat or guinea pig platelets exposed to this extracellular matrix. In contrast, isolated megakaryocytes on glass or on uncoated plastic surfaces did not show these responses; adherence, in the face of gentle agitation before fixation, was minimal, with rare filopodia and no flattening. Megakaryocytes that interacted with the extracellular matrix produced significant amounts of thromboxane A2, but this did not occur on uncoated surfaces and could not be attributed to other contaminating cells in the megakaryocyte suspensions. The appearance in megakaryocytes of these typical platelet responses indicates that megakaryocytes acquire the functional capabilities of platelets by the synthesis and assembly of platelet substances and organelles. Thromboxane production by megakaryocytes stimulated by the extracellular matrix is a readily quantifiable measure of this capacity.
Animals↗
Characterization of the ATPase activities of myosins isolated from the membrane and the cytoplasmic fractions of human platelets.
Myosin was purified from the membrane fraction and the cytoplasm of human platelets, and the K+(EDTA)- and Ca2+-dependent ATPase activities were studied under various experimental conditions. The ATPase activity of the myosin from the membrane fraction was slightly lower than that of its cytoplasmic counterpart, regardless of the different assay conditions (pH, ionic strength, and temperature). Both myosins showed the same pH optima and a similar ionic strength dependence for the two ATPase activities measured. In addition, they exhibited the same substrate specificity using ATP, CTP, and GTP as substrates. The activation energy of the Ca2+-dependent ATPase activity was essentially the same for the two myosins, while the activation energy of the K+(EDTA)-dependent ATPase activity of the membrane myosin was higher than that of the cytoplasmic myosin. The ATPase activity of the membrane myosin was found to be more sensitive to freezing and thawing than the cytoplasmic myosin. The alkylation of the thiol groups by N-ethylmaleimide or N-iodoacetyl-N-(5-sulfo-1-naphtyl)ethylenediamine, and the trinitrophenylation of the lysyl residues by 2,4,6-trinitrobenzenesulfonate caused a significant decrease in the K+(EDTA)-dependent ATPase activity of the two myosins. However, the membrane myosin was much less affected than the cytoplasmic myosin. Actin induced inhibition of the K+ (EDTA) ATPase of both myosins, and much smaller quantities of actin were needed to inhibit the cytoplasmic myosin ATPase compared to quantities needed to inhibit the myosin ATPase from the membrane fraction. This indicates that the membrane myosin has a lower affinity toward actin. The observed variations in the ATPase activity of the myosins isolated from the membrane and the cytoplasm fractions of human platelets may reflect differences in their respective physiological functions.
Actins↗
The inhibitory effect of heparin and related glycosaminoglycans on neutrophil chemotaxis.
Clinical observations have shown that heparin has antiinflammatory activities. The effect of heparin on neutrophil chemotaxis was evaluated in vitro in the Boyden Chamber. This method enabled differentiation between the direct effects of heparin on neutrophil migration and locomotion, and its effects on chemotactic factors. Heparin inhibited both the random migration and directed locomotion of human neutrophils toward zymosan-activated serum (ZAS) and F-met-leu-phe (FMLP). Inhibition was found to be dependent on the concentrations of the heparin and of the chemotactic factors. No specific binding of heparin to the neutrophils could be demonstrated, and heparin's inhibitory effects were eliminated by simple washing of the cells. When added directly to the chamber containing chemotactic factor, heparin inhibited the chemotactic activity of ZAS but not that of FMLP, suggesting a direct inhibitory effect against C5a, the principal chemotactic factor in ZAS. Experiments performed with low-molecular-weight heparin, N-desulfated heparin, dextran sulfate, chondroitin sulfate and dextran indicated that the inhibitory effects of heparin on neutrophil chemotaxis are not related to its anticoagulant activity, but probably depend on the degree of sulfation of the heparin molecule.
Cell Movement↗
The effect of oral administration of dipyrone on the capacity of blood platelets to synthesize thromboxane A2 in man.
Platelet aggregation and thromboxane A2 (TXA2) production induced by arachidonic acid and collagen were studied in 10 healthy volunteers prior to and at various times after the oral administration of a single dose of 1 g dipyrone. The plasma concentrations of four dipyrone metabolites were also determined. Dipyrone inhibited platelet aggregation and markedly decreased TXA2 synthesis induced by threshold concentrations of both agonists. Maximal inhibition was noted 1 hour after drug administration and in some subjects it lasted as long as 72 h. At all times the effect of the drug could be abolished by increasing the concentration of the agonist. This is consistant with a competitive inhibitory effect of dipyrone on prostaglandin synthetase activity. The mean plasma concentration of the main dipyrone metabolite methylaminoantipyrine at 1 h was 11 micrograms/ml. There was no correlation between individual plasma levels and the parameters of platelet function. At 24h the mean concentration of each of the metabolites studied was up to 1 microgram/ml, and these levels, too, did not correlate with the biological effect of the drug.
Administration, Oral↗
The effect of T-2 toxin on human platelets.
Human platelets were incubated with T-2 toxin, the most toxic component of Fusarium fungi, at doses of 5 to 500 micrograms/10(9) platelets. A dose-related inhibition of platelet aggregation and release of dense bodies (these consist mainly of serotonin-containing granules) were observed. A change in membrane permeability in the absence of shape changes was also demonstrated by a heavy metal impregnation technique. There was no correlated inhibition of thromboxane synthesis or significant alterations in platelet calcium content. The microtubular system was also unaffected. Suppressed platelet aggregation may contribute to the lethal hemorrhagic phenomenon associated with intoxication by fusarial toxins in man and animals.
Blood Platelets↗
Disseminated intravascular coagulation in two patients with histiocytic medullary reticulosis.
Two young adults with characteristic features of histiocytic medullary reticulosis (HMR) are described. Of particular interest was the development of striking clinical and laboratory features of disseminated intravascular coagulation (DIC), in the absence of sepsis in both cases. Both patients had a marked and fatal bleeding tendency. The association between neoplasia and DIC is well established, but, to the best of our knowledge, DIC presenting a major feature of HMR has not yet been described. The possible pathogenesis of DIC in HMR is discussed.
Adult↗