Communication between spermatozoa and egg before contact by chemotaxis appears to be prevalent throughout the animal kingdom. In non-mammalian species, sperm chemotaxis to factors secreted from the egg is well documented. In mammals, sperm chemotaxis to follicular factors in vitro has been established in humans and mice. The attractants of female origin in non-mammalian species are heat-stable peptides or proteins of various sizes, or other small molecules, depending on the species. Species specificity of the attractants in non-mammalian species may vary from high species specificity, through specificity to families with no specificity within a family, to absence of specificity. The mammalian sperm attractants have not been identified but they appear to be heat-stable peptides. The claim that progesterone is the attractant for human spermatozoa has failed to be substantiated, neither have claims for other mammalian sperm attractants been verified. The molecular mechanism of sperm chemotaxis is not known. Models involving modulation of the intracellular Ca2+ concentration have been proposed for both mammalian and non-mammalian sperm chemotaxis. The physiological role of sperm chemotaxis in non-mammalian species appears to differ from that in mammals. In non-mammalian species, sperm chemotaxis strives to bring as many spermatozoa as possible to the egg. However, in mammals, the role appears to be recruitment of a selective population of capacitated ('ripe') spermatozoa to fertilize the egg. (+info)
Age-related changes in blood coagulation and fibrinolysis in mice fed on a high-cholesterol diet.
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To investigate the pathogenesis of hyperlipidemia-induced atherosclerosis, we examined age-dependent changes in platelet activity, blood coagulation and fibrinolysis in susceptibility to a high cholesterol diet (HCD) feeding in male ICR mice. Pretreatment of platelet-rich-plasma from HCD feeding mice for 3 days with epinephrine (300 microM) resulted in a marked enhancement of adenosine 5'-diphosphate (ADP: 0.1 microM) or collagen (0.7 microgram/ml)-stimulated aggregation compared with the same in control mice. Yohimbine as alpha 2-adrenergic blocker antagonized these aggregations in a dose-dependent manner. A significant increase in plasma total cholesterol and VLDL (very low-density lipoprotein)-LDL (low-density lipoprotein)-cholesterol and the liver/body weight ratio was observed in mice fed on HCD for 3 months (3-month HCD mice). In the early phase of this experiment, a significant increase in fibrinogen was observed. In the middle phase, increases in the activity of antithrombin III (ATIII) and alpha 2-plasmin inhibitor (alpha 2-Pl) followed. Plasminogen content gradually decreased in both normal diet and HCD mice throughout the experiment. The activity of plasminogen activator inhibitor (PAI) decreased in 3-month HCD mice. Morphological observation of the aortic arch from 3-month HCD mice revealed apparent atheromatous plaques not seen in control mice. These results suggest that 3-month HCD mice can be a convenient hyperlipidemia-induced atherosclerotic model and the changes in platelet activity, coagulation and fibrinolysis in the early phase may be a cause of pathologic changes in this model. (+info)
Single and combined prothrombotic factors in patients with idiopathic venous thromboembolism: prevalence and risk assessment.
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The inherited thrombophilias--deficiencies of protein C, protein S, and antithrombin III--and the prothrombotic polymorphisms factor V G1691A and factor II G20210A predispose patients toward venous thromboembolism (VTE). The aim of this study was to determine the prevalence of single and combined prothrombotic factors in patients with idiopathic VTE and to estimate the associated risks. The study group consisted of 162 patients referred for work-up of thrombophilia after documented VTE. The controls were 336 consecutively admitted patients. In all subjects factor V G1691A, factor II G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T were analyzed by specific polymerase chain reactions and restriction enzymes. Activities of antithrombin III and protein C, free protein S antigen, and lupus anticoagulant were determined in a subset of 109 patients who were not receiving oral anticoagulants. The prevalences of heterozygotes and homozygotes for factor V G1691A and factor II G20210A among patients and controls were 40.1% versus 3.9% and 18.5% versus 5.4%, respectively (P=0.0001). The prevalence of homozygotes for MTHFR C677T in patients was 22.8% and in controls, 14.3% (P=0.025). Heterozygous and homozygous factor V G1691A, factor II G20210A, and homozygous MTHFR C677T were found to be independent risk factors for VTE, with odds ratios of 16.3, 3.6, and 2.1, respectively. Two or more polymorphisms were detected in 27 of 162 patients (16.7%) and in 3 of 336 controls (0.9%). Logistic regression analysis disclosed odds ratios of 58.6 (confidence interval [CI], 22.1 to 155.2) for joint occurrence of factor V and factor II polymorphisms, of 35.0 (CI, 14.5 to 84.7) for factor V and MTHFR polymorphisms, and of 7.7 (CI, 3.0 to 19.6) for factor II and MTHFR polymorphisms. Among 109 patients in whom a complete thrombophilic work-up was performed, 74% had at least 1 underlying defect. These data indicate that in most patients referred for evaluation of thrombophilia due to idiopathic VTE, 1 or more underlying genetic predispositions were discernible. The presence of >1 of the prothrombotic polymorphisms was associated with a substantial risk of VTE. (+info)
Oxidation of methionine residues in antithrombin. Effects on biological activity and heparin binding.
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Commercially available human plasma-derived preparations of the serine protease inhibitor antithrombin (AT) were shown to contain low levels of oxidation, and we sought to determine whether oxidation might be a means of regulating the protein's inhibitory activity. A recombinant form of AT, with similarly low levels of oxidation as purified, was treated with hydrogen peroxide in order to study the effect of oxidation, specifically methionine oxidation, on the biochemical properties of this protein. AT contains two adjacent methionine residues near the reactive site loop cleaved by thrombin (Met314 and Met315) and two exposed methionines that border on the heparin binding region of AT (Met17 and Met20). In forced oxidations with hydrogen peroxide, the methionines at 314 and 315 were found to be the most susceptible to oxidation, but their oxidation did not affect either thrombin-inhibitory activity or heparin binding. Methionines at positions 17 and 20 were significantly oxidized only at higher concentrations of peroxide, at which point heparin affinity was decreased. However at saturating heparin concentrations, activity was only marginally decreased for these highly oxidized samples of AT. Structural studies indicate that highly oxidized AT is less able to undergo the complete conformational change induced by heparin, most probably due to oxidation of Met17. Since this does not occur in less oxidized, and presumably more physiologically relevant, forms of AT such as those found in plasma preparations, oxidation does not appear to be a means of controlling AT activity. (+info)
Dose response of intravenous heparin on markers of thrombosis during primary total hip replacement.
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BACKGROUND: Thrombogenesis in total hip replacement (THR) begins during surgery on the femur. This study assesses the effect of two doses of unfractionated intravenous heparin administered before femoral preparation during THR on circulating markers of thrombosis. METHODS: Seventy-five patients undergoing hybrid primary THR were randomly assigned to receive blinded intravenous injection of either saline or 10 or 20 U/kg of unfractionated heparin after insertion of the acetabular component. Central venous blood samples were assayed for prothrombin F1+2 (F1+2), thrombin-antithrombin complexes (TAT), fibrinopeptide A (FPA), and D-dimer. RESULTS: No changes in the markers of thrombosis were noted after insertion of the acetabular component. During surgery on the femur, significant increases in all markers were noted in the saline group (P < 0.0001). Heparin did not affect D-dimer or TAT. Twenty units per kilogram of heparin significantly reduced the increase of F1+2 after relocation of the hip joint (P < 0.001). Administration of both 10 and 20 U/kg significantly reduced the increase in FPA during implantation of the femoral component (P < 0.0001). A fourfold increase in FPA was noted in 6 of 25 patients receiving 10 U/kg of heparin but in none receiving 20 U/kg (P = 0.03). Intraoperative heparin did not affect intra- or postoperative blood loss, postoperative hematocrit, or surgeon's subjective assessments of bleeding. No bleeding complications were noted. CONCLUSIONS: This study demonstrates that 20 U/kg of heparin administered before surgery on the femur suppresses fibrin formation during primary THR. This finding provides the pathophysiologic basis for the clinical use of intraoperative heparin during THR. (+info)
Effect of thrombin inhibition in vascular dementia and silent cerebrovascular disease. An MR spectroscopy study.
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BACKGROUND AND PURPOSE: Silent cerebrovascular disease (CVD) has been proposed as a predisposing condition for clinically overt stroke and vascular dementia. Recently, we found increased thrombin generation in silent CVD patients. Here, we report the effect of thrombin inhibition using a potent selective thrombin inhibitor on the cerebral metabolism and function in peripheral arterial occlusive disease (PAOD) patients with or without silent CVD. METHODS: We examined 17 mild chronic PAOD patients, including 2 cases of vascular dementia. We divided the patients into 2 groups: 1 was the advanced CVD group with multiple lacunar infarction and/or advanced periventricular hyperintensity detected by brain MRI (n=12), and the other was the no CVD group that had none of these abnormalities (n=5). We assessed the cerebral biochemical compounds in the deep white matter area and cerebellar hemisphere (8 cm3) by proton MR spectroscopy before and after infusion of argatroban (10 mg/d IV) over 2 hours for 7 days. RESULTS: The ratio of N-acetylasparate (NAA) to total creatine (Cre) in the deep white matter area was significantly lower in the advanced CVD group than in the no CVD group, whereas there were no significant differences in this ratio in the cerebellar hemisphere between the 2 groups. In the former group, this decreased NAA/Cre ratio significantly increased after argatroban therapy, whereas there was no change in the latter group. The 2 patients with vascular dementia showed clinical improvement with marked increases in the NAA/Cre ratio and mini-mental score. CONCLUSIONS: These results suggest that increased thrombin generation may have some pathophysiological roles in developing vascular dementia and its chronic predisposing conditions. Thrombin inhibition may break this vicious cycle and lead to clinical improvement. (+info)
Comparison of the antithrombotic effect of PEG-hirudin and heparin in a human ex vivo model of arterial thrombosis.
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Polyethylene glycol (PEG)-hirudin is a derivative of hirudin with a long plasma half-life. We have compared the efficacy of PEG-hirudin with unfractionated heparin (UH) in preventing arterial thrombosis. Arterial thrombus formation was induced ex vivo in 12 healthy human volunteers by exposing a tissue factor-coated coverslip positioned in a parallel-plate perfusion chamber to flowing nonanticoagulated human blood drawn directly from an antecubital vein at an arterial wall shear rate of 2600 s-1 for 3.5 minutes. PEG-hirudin, UH, or saline (as control) were administered ex vivo through a heparin-coated mixing device positioned proximal to the perfusion chamber. Platelet and fibrin deposition was quantified by immunoenzymatic measure of the P-selectin and D-dimer content of dissolved plasmin-digested thrombi, respectively. UH was administered to a plasma concentration of 0.35 IU/mL. This concentration prolonged the activated partial thromboplastin time from 32+/-1 seconds to 79+/-4 seconds (P<0.01). UH did not significantly prevent platelet deposition. However, fibrin deposition was reduced by 39% (P<0.05). PEG-hirudin in plasma concentrations of 0.5, 2.5, and 5 microg/mL prolonged the activated partial thromboplastin time to 48+/-2, 87+/-4, and 118+/-4 seconds, respectively. In contrast to UH, PEG-hirudin prevented both platelet and fibrin deposition in a dose-dependent manner with a >80% reduction at 5 microg/mL (P<0.01). Furthermore, the plasma level of PEG-hirudin required to significantly prevent fibrin deposition (0.5 microg/mL) corresponded to a much shorter prolongation of activated partial thromboplastin time (48+/-2 seconds) than that needed for UH (79+/-4 seconds). Thus, our results are compatible with the view that thrombin is greatly involved in recruitment of platelets in evolving thrombi, and that PEG-hirudin is an effective agent for preventing arterial thrombosis in a human ex vivo experimental model. (+info)
Prognostic significance of elevated hemostatic markers in patients with acute myocardial infarction.
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OBJECTIVES: The purpose of this study was to determine whether the elevated levels of hemostatic markers in the early phase of myocardial infarction may serve as risk factors for subsequent cardiac mortality. BACKGROUND: Increased plasma hemostatic markers were noted in acute myocardial infarction, indicating that the blood coagulation system is highly activated in those patients. However, there are few clinical data concerning the association between the elevated hemostatic markers and survival in patients with myocardial infarction. METHODS: Blood samples were obtained from 64 patients (mean age 67 +/- 11 years; 49 male) with acute myocardial infarction within 12 h after the onset of symptoms and before the initiation of any antithrombotic treatment. We measured plasma concentrations of fibrinopeptide A (FPA), prothrombin fragment 1+2 (F1+2) and thrombin-antithrombin complex (TAT) using the enzyme-linked immunosorbent assay method, and examined the associations between the level of these markers and survival with Cox proportional hazards models. RESULTS: The follow-up time was 27 +/- 17 months, and 19 patients died of cardiac causes during the follow-up. Univariate survival analysis identified Killip class IV (hazard ratio 4.86; 95% confidence interval [CI] 1.55-15.19), left ventricular ejection fraction (hazard ratio 0.94; 95% CI 0.90-0.99), FPA (hazard ratio 1.54; 95% CI 1.13-2.10), F1+2 (hazard ratio 2.03; 95% CI 1.17-3.53) and TAT (hazard ratio 1.88; 95% CI 1.27-2.79) as significant factors associated with cardiac mortality. In multivariate analyses, only FPA level (hazard ratio 1.84; 95% CI 1.03-3.30) and left ventricular ejection fraction (hazard ratio 0.93; 95% CI 0.88-0.98) were independent predictors of cardiac mortality. CONCLUSIONS: Elevated FPA in the early phase of myocardial infarction identifies patients with increased risk for subsequent cardiac death. This association appears to be independent of residual left ventricular function after infarction. (+info)