Fibrinogen Lima: a homozygous dysfibrinogen with an A alpha-arginine-141 to serine substitution associated with extra N-glycosylation at A alpha-asparagine-139. Impaired fibrin gel formation but normal fibrin-facilitated plasminogen activation catalyzed by tissue-type plasminogen activator.

An A alpha-arginine-141 to serine substitution has been identified in a homozygous dysfibrinogen, fibrinogen Lima, associated with impaired fibrin polymerization. The point mutation created an asparagine-X-serine-type glycosylation sequence, and indeed, extra, mainly disialylated biantennary oligosaccharides have been isolated from A alpha asparagine-139 of the patient's fibrinogen. This type of glycosylation sequence is unique for human fibrinogen, because the sequences shown for normal and abnormal fibrinogens are all asparagine-X-threonine types. The terminal sialic acids of the extra oligosaccharides seem to have largely contributed to the impaired fibrin gel formation, as evidenced by its correction to a near normal level by desialylation. Nevertheless, the polymerizing fibrin facilitated tissue-type plasminogen activator-catalyzed plasmin formation in a normal fashion, indicating that the initial two-stranded fibrin protofibrils had been constructed normally. Thus the impaired fibrin gel formation could be attributed to the delay in their subsequent lateral association, most probably because of the repulsive forces generated by the negative electric charge of the extra sialic acids. The substitution of a basic residue arginine to a noncharged residue serine may also have contributed to the impaired function in a similar manner or by steric hindrance in association with bulky extra oligosaccharide chains.

Antifibrinolytic amino acids for acquired coagulation disorders in patients with liver disease.

BACKGROUND: Upper gastrointestinal bleeding is one of the most frequent causes of morbidity and mortality in the course of liver cirrhosis. Patients with liver disease frequently have haemostatic abnormalities, which include accelerated fibrinolysis. Several primary treatments are used for upper gastrointestinal bleeding in patients with liver diseases. Supplementary interventions are often used as well. One of them could be antifibrinolytic amino acids administration. OBJECTIVES: To assess the beneficial and harmful effects of antifibrinolytic amino acids for upper gastrointestinal bleeding in patients with acute or chronic liver disease plus acquired coagulation disorders. SEARCH STRATEGY: We searched The Cochrane Hepato-Biliary Group Controlled Trials Register (March 2006), the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Issue 1, 2006), MEDLINE (1950 to March 2006), EMBASE (1980 to March 2006), Science Citation Index EXPANDED (1945 to March 2006), LILACS (1982 to March 2006), ClinicalTrials.gov (at www.clinicaltrials.gov) (accessed August 2006), ISI Web of Science (April 2006), and the International Standard Randomised Controlled Trial Number Register (at http://controlled-trials.com/isrctn/search.asp) (accessed August 2006). We also checked the reference lists of all the trials identified by the above methods. SELECTION CRITERIA: We searched for randomised clinical trials irrespective of blinding, language, or publication status. DATA COLLECTION AND ANALYSIS: We intended to summarise data by standard Cochrane Collaboration methodologies. MAIN RESULTS: We could not find any randomised clinical trials with antifibrinolytic amino acids for upper gastrointestinal bleeding in patients with acute or chronic liver disease plus acquired coagulation disorders. AUTHORS' CONCLUSIONS: We were unable to identify randomised clinical trials on the safety and efficacy of antifibrinolytic amino acids for upper gastrointestinal bleeding in patients with liver disease (acute or chronic) plus acquired coagulation disorders. The effects of antifibrinolytic amino acids has to be tested in randomised clinical trials.

Role of red blood cells in the early stages of platelet activation by collagen.

Red blood cells (RBC) increase the proaggregatory capacity of a cell-free supernatant obtained by stimulating platelet-rich plasma (PRP) samples with collagen (1 microgram/ml) as measured by the BASIC wave; this effect increases with the number of RBC and is proportionally greater with a lower number of platelets or when lower collagen concentrations are used. Aspirin (ASA) modifies the RBC behaviour in relation to their platelet-collagen interaction. This is demonstrated by the fact that when PRP and RBC obtained from the same subjects before and two hours after the ingestion of ASA (0.5 g) were mixed, it was found that non-ASA-RBC stimulate ASA-PRP, probably through a platelet cyclooxygenase independent pathway; ASA-RBC, however, stimulate non-ASA-PRP, but not ASA-PRP, which suggests that they may need an active platelet cyclooxygenase system for their action. This effect of ASA on RBC is not transient and was also observable 48 h after ASA ingestion. In addition, it was found that ASA-RBC greatly increase the activation of a mixture containing a small proportion of non-ASA-PRP in ASA-PRP, a situation that is expected to be encountered "in vivo" after ASA treatment. This effect of ASA-RBC on platelet activation may help to explain the sometimes contradictory clinical effect of aspirin as an antithrombotic drug.

Early platelet-collagen interactions in whole blood and their modifications by aspirin and dipyridamole evaluated by a new method (BASIC wave).

It is shown that the supernatant of unstirred whole blood at 37 degrees C, stimulated by 1 microgram/ml of collagen for 10 sec, produces a rapid generation of pro and antiaggregatory compounds with a final proaggregatory activity which can be detected for more than 60 min on a platelet rich plasma (PRP) by turbidometric aggregometry. A reversible aggregation wave that we have called BASIC wave (for Blood Aggregation Stimulatory and Inhibitory Compounds) is recorded. The collagen stimulation of unstirred PRP produces a similar but smaller BASIC wave. BASIC's intensity increases if erythrocytes are added to PRP but decreases if white blood cells are added instead. Aspirin abolishes "ex vivo" the ability of whole blood and PRP to generate BASIC waves and dipyridamole "in vitro" significantly reduces BASIC's intensity in whole blood in every tested sample, but shows little effect in PRP.

Four heparin preparations: anti-Xa potentiating effect of heparin after subcutaneous injection.

Four different heparin preparations--sodium and calcium salts of the same batch of heparin (mean molecular weight 15,000), low molecular weight sodium heparin (mean m.w. 9,000) and high molecular weight sodium heparin (mean m.w. 22,000) were injected subcutaneously on different days each into 6 healthy young volunteers in a randomized trial. Plasma heparin levels were measured using the anti-Xa assay at 1 hour, 3-4 hours and 6-7 hours after the injection. The highest anti-Xa potentiating effect was obtained after the injection of the low molecular weight sodium heparin (mean 0.381 i.u./ml) at 3-4 hours after the injection. With sodium heparin (m.w. 15,000) the highest values (0.135 i.u./ml) were found at 1 hour. Significantly lower anti-Xa potentiating effect was obtained 1 hour after the injection of calcium heparin and in particular after the injection of high molecular weight heparin (mean values 0.072 i. u./ml and 0.043 i. u./ml respectively). Both these preparations showed an increase from 1 hour after injection to 3-4 hours after injection (mean values 0.082 i. u./ml and 0.057 i. u./ml at 3-4 hours after injection). These results indicate that the salt and the molecular weight of the preparation may strongly influence the degree of anticoagulation achieved after subcutaneous injection.

Severe inherited "homozygous" protein C deficiency in a newborn infant.

A relapsing clinical syndrome of skin lesions and disseminated intravascular coagulation (DIC) that showed remission with the infusion of fresh frozen plasma is described in a newborn infant with homozygous deficiency of protein C antigen. This patient presented since birth a recurrent clinical picture of DIC and ecchymotic skin lesions that resembled typical ecchymosis except for the fact that they showed immediate improvement with the administration of fresh frozen plasma. Using an enzyme linked immunosorbent assay method, the determination of protein C antigen levels in the patient, without ingestion of coumarin drugs, showed very low values (less than 1%). No other deficiencies in the vitamin-K-dependent factors or in antithrombin III, antiplasmin, and plasminogen were found. Seven relatives of the infant had heterozygous deficiency in protein C antigen (values between 40-55%), without clinical history of venous thrombosis. The pedigree analysis of this family suggests an autosomal recessive pattern of inheritance for the clinical phenotype, although an autosomal dominant pattern has been postulated until now in other reported families. We conclude that our patient has a homozygous deficiency in protein C and this homozygous state may be compatible with survival beyond the neonatal period.

Simple screening tests for the diagnosis of isolated clotting factor defects. With special reference to 'contact factor' defects.

Reagents may be prepared from normal plasma and used with the prothrombin time and partial thromboplastin time tests to distinguish isolated defects of factors I, II, VII, VIII, IX, X, XI, or XII.

Effects of dipyridamole, pentoxifylline or dipyridamole plus pentoxifylline on platelet reactivity in patients with ischemic cerebrovascular insufficiency.

Platelet activation and the subsequent platelet recruitment induced by activated platelets released products constitute the initial events of platelet thrombus formation. We have evaluated the recruiting activity of collagen-stimulated whole blood in patients with ischemic cerebrovascular insufficiency. This was done using an experimental approach that allows independent evaluation of platelet activation and recruitment. The effects of of treating the patients with dipyridamole (DIP) (300 mg/day), pentoxifylline (POX) (1200 mg/day) or a combination of the two drugs at the same doses was also evaluated before and after 7, 15, and 45 days of treatment. DIP decreased the recruiting activity in a time-dependent manner, while POX did not show any effect. However, the combined treatment with DIP+POX was more effective than DIP alone in reducing platelet recruitment, which was abolished after 45 days of treatment. Studies using the drugs in vitro indicated a greater inhibitory activity of the drug association than either drug individually. The effects of the drug association in vitro, even at high concentrations, was lower than those observed ex vivo after 45 days of treatment. This suggests that DIP+POX in vivo may have effects that condition a reduced platelet response.

Very low doses of unfractionated heparin potentiate the anti-Xa activity of low molecular weight heparin (enoxaparin)

Some previous reports indicated that a minimal amount of anti-IIa is necessary for the optimal anti-Xa activity of low molecular weight heparin (LMW-H). To know if we could improve the prophylactic activity of LMW-H, providing a mild antithrombin effect, we conducted an experiment in which we administered subcutaneously to 10 volunteers, very low doses of unfractionated heparin (UFH), (1000 IU), a LMW-H (enoxaparin, 2000 IU = 20mg), or both heparins together on alternate days, and measure the anti-Xa activity before, and 4 hours after injection. We found that the anti-Xa activity in the first group (UFH), increased by 33%, over the basal values; in the second group (LMW-H), by 93%, but it increased by 282%, in the third group (UFH + LMW-H) showing clearly (p < 0.0069), that UFH could increase synergistically, more than additive, the anti-Xa activity of enoxaparin. The impact on the cost-effectiveness of antithrombotic prophylaxis and the therapeutic results with the herein combined scheme should be evaluated.

Antiplatelet activity of dipyridamole in non anticoagulated whole blood.

Dipyridamole has been reported to inhibit platelet aggregation in citrate anticoagulated whole blood (WB). However, citrate may alter the response of platelets and/or the effect of antiplatelet drugs. The present study evaluates the "ex vivo" effect of dipyridamole, two hours after a single dose (3 mg/Kg) in 25 normal subjects in non-anticoagulated (native) WB and in WB anticoagulated with citrate or hirudin. We have used the BASIC anticoagulated with citrate or hirudin. We have used the BASIC wave as analytical method, which can evaluate the early steps of platelet activation with collagen in less than 1 min after venoclysis, thus allowing the study in native WB. The results show that dipyridamole significantly inhibits (p less than 0.001) platelet activation to collagen in citrated WB (66%) while the drug's effect is much lower (21%) and non-significant if evaluated in native or hirudine anticoagulated WB. These results suggest that citrate or low calcium concentration amplify the drug's platelet inhibitory action in WB and, therefore, the laboratory results may overestimate the drug's effect "in vivo".

Fibrinogen Lima. A new dysfibrinogenaemia with a high-molecular-weight alpha-chain and effective polymerization.

A patient with transient microhaematuria was studied. Coagulation tests revealed prolonged thrombin and reptilase times concomitant with abnormal fibrin polymerization rate (also abnormal in both parents). In the patient and her patients, the abnormal fibrin polymerization rate was only slightly corrected by addition of calcium ions. The alpha-chain had a molecular weight higher than normal and there was deficient formation of alpha-polymers. The molecule showed a more anodal migration than the control. The abnormality described has been classified as Fibrinogen Lima.

[Prevalence of the activated protein C resistance in indigenous and Black populations of the western Venezuela]. / Prevalencia de la resistencia a la proteína C activada en poblaciones indígena y negra del occidente de Venezuela.

The Activated Protein C Resistance (APCR) is the common phenotype of Factor V Leiden (arg506gln), which is considered as a thrombotic risk factor. The aim of this study was to determine the prevalence of APCR and its association with Factor V Leiden in indian and black populations from Zulia State in western Venezuela. Blood samples were taken from 80 Yukpa indians from Sierra de Perijá and 91 black individuals from the southeast of Lago de Maracaibo. APCR was determined by the Dahlback's method with the modifications of Jorquera et al. and Trossaert et al. The results were expressed as n-APC-SR (positive value < or = 0.75). Factor V Leiden genotype was identified by PCR and restriction analysis standard methods at the Institute of Human Genetics (Greifswald, Germany). No significative difference was found between n-APC-SR from indians (mean +/- SEM 1.13 +/- 0.02, CI 95% = 1.07-1.19) and black people (1.07 +/- 0.02, CI 95% = 1.03-1.12). APCR prevalence from indians was 1.25% (1 out of 80) who was heterozygote case for F V Leiden and 4.4% (4 out of 91) from blacks (one case was heterozygous for F V Leiden). No thrombotic event personal or familial was demonstrate. Our data represent the first report related to the association between APCR and F V Leiden in venezuelan indian and black individuals. APCR without the Factor V Leiden expression suggest a different type of mutation in the Factor V molecule. In spite of high endogamy in the indian group, we can not discard the role of foreign genes in both populations. The determination of the prevalence of this phenotype and its molecular marker in various ethnic groups is important for the interpretation of their role as risk factors for thrombotic disease.

A standardized bioassay for platelet factor 3 released by kaolin.

The test for platelet factor 3 described by Hardisty & Hutton (1975) has been modified to conform to the usual design for a parallel-line bioassay. Manchester Comparative Thromboplastin has been used as assay Standard, allowing an arbitrary unit of activity to be adopted. However, experiments suggested that the platelet activity measured was different from tissue factor activity. Platelets are tested as platelet-rich plasma diluted in a standardized mixture of plasma and fibrinogen, so that differences between the clotting factors of the test samples are eliminated, as verified by experiments on haemophiliacs and patients on anticoagulant treatment. Sonication and repeated freezing and thawing of platelet-rich plasma showed that approximately 15% of the PF3 is released by kaolin. In vivo, a single dose of 600 mg of aspirin reduced the PR3-release to half the previous value in 2 h; initial values were regained in 5-8 days.

Possible homozygous factor VIIR disorder associated with fibrinolytic hyperactivity.

A family with inherited factor VII deficiency is described. The propositus is a 9-year-old girl with chronic haemorrhagic history of epistaxis and bleeding after tooth extractions. Her factor VII coagulant activity was less than 3% using rabbit thromboplastin. She had a factor VII antigen level of 50%. Both parents were heterozygous for factor VII deficiency. The father had procoagulant factor VII (VII-C) of 44% and factor VII antigen (VII-Ag) of 74%, and the mother had 54% of factor VII-C and 85% of VII-Ag. Her only brother had normal levels of factor VII-C (100%). Additionally, some abnormalities in the fibrinolytic system were detected both in the propositus and her brother with shortened euglobulin lysis times and increased functional levels of plasminogen activator. To our knowledge, the clinical association of inherited factor VII deficiency and familial fibrinolytic disturbances has not been described so far.

Thromboxane A2 and prostacyclin do not modulate the systemic hemodynamic response to cold in humans.

The immersion of a limb in a mixture of water and ice induces in normal humans an initial vasoconstriction mediated mainly by catecholamine release. In some studies the cold pressor test was associated with an increase in vasoconstrictor thromboxane A2 and in vasodilating prostacyclin. Dazoxiben hydrochloride, a thromboxane synthase inhibitor, has been reported to suppress cold-induced vasoconstriction. We compared in a double-blind, crossover, placebo-controlled study the effects of indomethacin (a cyclooxygenase inhibitor), dazoxiben hydrochloride, and BM13.177 (a novel thromboxane receptor antagonist) on the changes in cutaneous vascular resistance and arterial blood pressure induced by cold in 12 healthy volunteers. Cold challenge produced an increase in blood pressure and an initial decrease in finger blood flow, reflecting an increase in cutaneous vascular resistance. Neither effective suppression of thromboxane A2 generation or of the effects of thromboxane A2 on platelets by the three active treatments nor increase in prostacyclin generation after ingestion of dazoxiben hydrochloride modified the hemodynamic response to cold. In conclusion, thromboxane A2 and prostacyclin do not play a significant role in the modulation of the systemic hemodynamic response to cold. In addition, thromboxane receptor antagonism in normal humans does not influence basal blood pressure.

Prevalence of factor V Leiden mutation in various populations.

Resistance to activated protein C (APC) is the most common inherited risk factor for venous thrombosis. Most cases of APC resistance are caused by the point mutation nt 1691 G-A in factor V gene, referred to as factor V Leiden mutation. As initially shown in a Dutch population, this mutation has a carrier rate of 2.9%, the most frequent genetic disposition for thrombophilia and deep venous thrombosis. By large-scale epidemiological studies we have determined the prevalence of factor V Leiden mutation in populations from Poland (200), Argentina (215), Venezuela (126), Costa Rica (196), and India (150). The prevalences have been estimated for Poland (Warsaw) 5.0%, Argentina (Buenos Aires) 5.1%, Venezuela (Valencia) 1.6%, Costa Rica (San José) 2.0%, and India (Punjab) 1.3%. Based on worldwide distribution, it can be hypothesized that the factor V Leiden mutation has originated and accumulated in central European Caucasians and spread over the world by migration.