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Biomedical subjects

I Elalamy

Publications and source records attributed to I Elalamy.

At least 37 records · Page 2Linked to original sources
PubMed1999

[Resistance to activated protein C and portal vein thrombosis: two new cases and review of the literature].

INTRODUCTION: Resistance to activated protein C is the most common inherited factor at the origin of deep venous thrombosis. As portal vein thrombosis is rare, causes such as cirrhosis, intra-abdominal infection, primary hepatocellular carcinoma, myeloproliferative disorders or coagulation abnormalities must be investigated. EXEGESIS: We report two cases of portal vein thrombosis associated with resistance to activated protein C. This association is not frequent, as only 12 cases have been reported in the literature. These studies show that resistance to activated protein C was rarely the only factor, as other prothrombotic abnormalities were present in more than 70% of cases. CONCLUSION: Resistance to activated protein C is rarely associated with portal vein thrombosis. When present, other causes should not be overlooked. The potential existence of resistance to activated protein C should be systematically investigated in case of either portal vein thrombosis in patients with personal or familial thrombosis history, association with multiple thrombosis, or when the disease etiology remains unknown.

Activated Protein C Resistance↗
PubMed1999

Clinical aspects and laboratory problems in hereditary thrombophilia.

Hereditary thrombophilia is a multifactorial disease which is mono- or plurigenic and its clinical expression is associated with a heterogeneous expression. Factor V (FV) Leiden and FII gene mutations are more frequent than antithrombin, and protein C and S deficiencies. All thrombophilias are not the same. Heterozygous carriers of FV Leiden or FII gene mutation have a weaker risk of venous thrombosis. The mean age at the first episode is older in the former and higher rate of recurrences is observed in the latter. The cosegregation of mutations significantly increases the risk of thrombosis. Both mutations have a geographic and ethnic distribution in relation with a gene founder effect. Clinical expression consists of deep or superficial venous thrombosis with or without pulmonary embolism, thromboses at unusual sites (e.g. cerebral, portal, mesenteric) or with an increased incidence of fetal loss and abortion. A precipitating cause is present in more than 50% of patients. The risk pf arterial thromboses seems to be restricted to some protein S and FII gene mutations. Laboratory diagnosis strategy should be oriented by careful selection of patients and preanalytical variables should be considered. It is highly probable that other unindentified gene mutations are, at least partly, other causes of the heterogeneous expression of hereditary thrombophilia.

Blood Coagulation Factors↗
PubMed1999

[New thrombolytic agents in myocardial infarction].

Myocardial infarction is the result of thrombotic coronary artery occlusion. Although present-day thrombolytics have major value by increasing the frequency of reopening of arteries responsible for myocardial infarction, by preserving myocardial function and, thereby, significantly reduce mortality. Nevertheless, they are subject to the following limitations: 1) excellent arterial partency is only obtained in 50% of cases: 2) reocclusion occurs in 5 to 10% of cases; 3) severe complications such as cerebral haemorrhage are observed in about 0.5% of cases. Therefore, the search to improve thrombolytic agents is intense. This article reports the recent advances in concept and production of new thrombolytic agents. The most recent results concern the production of mutants of T-PA (tissue plasmogen activator). Of these mutants, the reteplase (r-PA) has already received authorization for its commercialisation. Other t-PA mutants under development (phase 3) include TNK-t-PA and lanoteplase. Over the last few years, there has been renewed interest in staphylokinase. The results of the initial clinical trials with this agent have also been reported. Paradoxically, the mode of action of thrombolytic agents has an inherent pro-thrombotic effect. This explains some of the interest for anti-thrombotic agents as an adjuvant treatment of thrombolysis. The initial results of the association of thrombolytics with new glycoprotein IIb/IIIa platelet inhibitors and anti-thrombin agents are reported.

Coronary Disease↗
PubMed1999

[Diagnosis and development of heparin-induced thrombocytopenia. Biological and clinical aspects].

Two types of thrombocytopenia occur during treatment with heparin: type I and type II heparin-induced thrombocytopenia (HIT). Type I HIT is due to a direct interaction between heparin and platelets. They are asymptomatic, occur early, mild and transitory. Type II HIT which is immunoallergic in nature is the most important complication of this treatment. The thrombocytopenia has a different presentation, acute with a fall in platelets over 30 per cent and is often associated with the occurrence or worsening of a venous or arterial thrombotic episode. The major problems of this secondary type are threefold: its recognition, its confirmation and its management should be as early as possible to avoid the development of often dramatic complications which compromise the prognosis. Laboratory investigations are required by highly reliable specialist laboratories following a careful clinical history. The natural history of the platelet count should enable the difficult diagnosis of HIT to be made more accurately. The treatment of confirmed HIT and/or symptomatic HIT often requires a multidisciplinary approach from a specialized team involving clinicians and hematologists. Two therapies with the benefit of large experience have just been obtained in France with marketing approval (AMM) for the management of HIT: danaparoid (Orgaran) and recombinant hidurin, lepirudin (Refludan). A declaration to the regional drugs monitoring center should not be omitted. In addition, each patient should be given a certificate confirming the immunallergy thus avoiding any further exposure with potentially dramatic consequences.

Anticoagulants↗
PubMed1998

Comparison of activated clotting times to heparin management test for adequacy of heparin anticoagulation in percutaneous transluminal coronary angioplasty.

The aim of this study was to compare the activated clotting time (ACT) obtained with the Hemochron device and the Heparin Management Test (HMT) on a new automated whole-blood coagulometer, the Thrombolytic Assessment System, in patients undergoing angioplasty. Fifty patients undergoing balloon angioplasty were prospectively enrolled. The mean ACT after a 10,000 unit bolus of heparin was 283 +/- 39 sec at the end of the procedure. The mean HMT after 10,000 units of heparin was 286 +/- 31 sec at the end of the procedure in the same patients. The correlation between the two methods was significant (r = 0.6; P < 0.01). The HMT appears to correlate well with standard values obtained with the Hemochron ACT monitor in patients undergoing percutaneous transluminal coronary angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1998

Cellular source of human platelet secretory phospholipase A2.

Platelets are one source of the group II extracellular form of phospholipase A2 (sPLA2) which is involved in the amplification of local and systemic inflammation. Although sPLA2 protein has been described in human platelets, its presence in human megakaryocytes has not been yet established. We demonstrated in this study that the human erythroleukaemia (HEL) cell line, which has megakaryoblastic features, constitutively expresses sPLA2. Using an anti-rhsPLA2 monoclonal antibody (mAb BA11) and dot-blot detection, we showed that HEL cells and platelets release sPLA2 into incubation medium upon stimulation by thrombin. Similar results were obtained for sPLA2 activity detected by a spectrofluorescence assay. Enzymatic activity was abolished by mAb BA11 and by protamine. In both cell types, although released, the major part of sPLA2 remained in the cell pellet, and was probably adsorbed at non-specific membrane sites. Double labelling experiments using mAb BA11 and an anti-GPIIb antiserum revealed the presence of sPLA2 in human bone-marrow megakaryocytes. The use of reverse transcription-polymerase chain reaction conjugated with hybridization analysis demonstrated the presence of mRNA encoding for sPLA2 in platelets and HEL cells. Expression of sPLA2 in platelets and megakaryocytes at both transcriptional and post-translational levels strongly argues in favour of a megakaryocytic origin of platelet sPLA2 and rules out a role for endocytosis of the enzyme from plasma by circulating platelets.

Blood Platelets↗
PubMed1998

[Staphylokinase and its mutants: a new generation of thrombolytic agents].

Staphylokinase which is extracted from Staphylococci has been known for more than 40 years as a profibrinolytic compound. It has been obtained more recently by genetic engineering. Staphylokinase activates plasminogen into plasmin. It is a promising new thrombolytic agent for the treatment of acute myocardial infarction and thromboembolic disease in general. It is a fibrin specific thrombolytic agent which does not decrease plasma fibrinogen level in treated patients. However it is antigenic and the group of Louvain has made much effort to reduce its antigenicity without decreasing its thrombolytic activity. Mutants with a reduced antigenic activity have been recently obtained. These new thrombolytic agents could be superior to currently used drugs. Staphylokinase mutants could have a better benefit/cost ratio than other thrombolytic agents.

Amino Acid Sequence↗
PubMed1998

[Staphylokinase].

Myocardial infarction is due to thrombotic occlusion of a coronary artery. Current thrombolytic agents have demonstrated their major value by inducing a significant reduction of mortality, but they nevertheless present certain limits: 1) excellent arterial patency is obtained in only about 50% of cases; 2) reocclusions persist in 5 to 10% of cases; 3) very severe complications, such as cerebral haemorrhages, have not disappeared (about 0.5% of cases). There is therefore a large field of action for development of the optimal thrombolytic agent. Research concerning staphylokinase, classified among third generation thrombolytic agents, is therefore situated in this context. Staphylokinase is a protein known to possess profibrinolytic properties for more than four decades, but has been the subject of renewed interest over recent years. This article reviews the characteristics, mechanism of action and fibrinolytic properties of staphylokinase. It recalls the main results obtained in animal models and summarizes the main clinical trials in man.

Animals↗
PubMed1998

[Heparin-induced thrombopenia: significance and difficulties of precise identification of the immunologic mechanism].

Heparin-induced thrombocytopenia (HIT) is a drug induced immunohematologic adverse reaction which is a rare but potentially very severe accident. Its diagnosis is important for epidemiologic and drug surveillance studies and in order to decide the most appropriate treatment. Its importance is enhanced since there is no gold standard diagnostic criteria. In clinical practice the diagnosis is based on a group of criteria related to clinical events and laboratory tests. We have established a score based on anamnestic criteria which allowed us to evaluate and compare two different laboratory tests: a platelet aggregation test (PAT) and a test for the detection of heparin dependent antibodies (Heparin Platelet Induced Antibodies or HPIA). The functional test PAT which is commonly used in expert laboratories detects antibodies inducing platelet aggregation in the presence of heparin. The HPIA test more recently developed is an ELISA test which detects antibodies directed at heparin-platelet factor 4 complexes. The relative value of theses two methods for the diagnosis of HIT is not well documented. We have analysed the results of these two tests in 273 consecutive patients with a suspicion of HIT. The results were concordant in 70% of patients. In selecting the patients with the lowest and the highest probability of HIT according to the score, PAT was found a more sensitive and HPIA a more specific test than the other. At low probability PAT is more often positive than HPIA 18% and 9% respectively. No test is 100% reliable, the specificity being limited for both tests since in about 20% of cases one or both tests are negative contrasting with a highly probable HIT. In this last group of patients, PAT was more frequently positive (86%) than HPIA (72%). Both tests are negative in 6% of patients suggesting the existence of presently unknown antigenic targets. Considering a group of 19 patients with a high probability of HIT, we have found antibodies against IL-8 or NAP-2 in only 7 patients. The discrepancy between a HPIA positive and a PAT negative encountered in 8% of patients may be explained by the existence of IgA or IgM immunoglobulins since in contrast to IgG they are unable to promote platelet aggregation via the CD32 platelet membrane receptor. This work suggests than neither test is 100% reliable and that they play a complementary role in the diagnosis of HIT. The potential advantage of using both tests should be confirmed in complementary studies

Aged↗
PubMed1997

[Multigenic thrombophilia: genetic anomaly of factor II and mutation of factor V Leiden. Study in a French family].

BACKGROUND: A genetic variation of the prothrombin (factor II) gene, a G to A transition at nucleotide position 20210, was recently found in patients with familial thrombophilia (predisposition to venous thrombosis). It seems to be frequent in patients with the factor V Leiden mutation. We report a family with the factor V Leiden and/or the genetic variation of prothrombin in 3 members. CASE REPORT: The patient had repeated episodes of deep vein thromboses starting at the age of 30 during the 4th pregnancy. She is a heterozygous carrier of both the factor V Leiden nutation and the prothrombin mutation 20210 A. She has 4 asymptomatic children, aged 28 to 32 and 3 of them have been explored: one son has the prothrombin mutation, one daughter the factor V Leiden and one has none of them. DISCUSSION: This case report illustrates the polygenic nature of thrombophilia which may explain the heterogeneity of clinical expression observed in isolated congenital abnormalities, especially in factor V Leiden mutation.

Chromosome Aberrations↗
PubMed1997

Signal transduction involved in the platelet adenylate cyclase sensitization associated with PGH2/TxA2 receptor desensitization.

The exposure of human platelets to prostaglandin H2 analogue (PGH2, U46619) induces homologous desensitization and a concomitant adenylate cyclase (AC) sensitization. We demonstrate the involvement of phospholipase C (PLC) in this enzyme sensitization. Pre-incubation of platelets with neomycin, a PLC activity inhibitor, prevented AC sensitization but not PGH2/thromboxane (Tx)A2 receptor desensitization. PGH2/TxA2 receptor desensitization, although necessary, is not sufficient to induce AC sensitization, since neomycin, which prevents AC sensitization, failed to prevent receptor desensitization. Inositol phosphate formation, determined in parallel, was also inhibited. Interestingly, no guanylate cyclase sensitization was noted, suggesting a specific relationship between PGH2/TxA2 receptor desensitization and AC sensitization. In addition, using alkaline phosphatase, a dephosphorylating enzyme, and the tyrosine kinase inhibitor erbstatin, we examined the role of phosphorylation-dephosphorylation on AC sensitization. Effectively, alkaline phosphatase, which has no effect by itself, enhances the cAMP production triggered by prostacyclin in control but not in desensitized platelets. In contrast, erbstatin failed to modify this synthesis, indicating the non-involvement of tyrosine kinase pathway in this process. Our results indicate that the AC sensitization was mediated by PLC and also suggest the participation of other mechanisms, including phosphorylation-dephosphorylation processes. This specific enzyme sensitization may be relevant for the in vivo modulation of platelet activation, in different thrombotic diseases with an increased TxA2 generation.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1997

Comparative effects of recombinant staphylokinase and streptokinase on platelet aggregation.

Recombinant staphylokinase (RSTA) has been shown to offer promise as a thrombolytic agent. In contrast to streptokinase (SK), few studies have been devoted to possible effects of RSTA on platelets. We have compared the capacity of RSTA and SK to trigger platelet aggregation and to modify ADP (2.5 microM) response in platelet-rich plasma (PRP) of 125 healthy subjects. Thus, exposure of PRP to SK (40 to 50 micrograms/ml) induced platelet aggregation in 6 out of 25 subjects. However, under the same conditions, RSTA failed to induce platelet aggregation in all cases (25 out of 25 subjects). In contrast to RSTA, SK (0.4 to 50 micrograms/ml) greatly reduced ADP-induced platelet aggregation in 12 out of 25 subjects. Preincubation of plasma with SK is associated with a decrease in the fibrinogen concentration. Furthermore, there was a good correlation between SK-induced fibrinogenolysis and SK-induced platelet aggregation defect (r2 = 0.9; p = 0.001). No fibrinogenolysis was observed when different amounts of RSTA (0.4 to 50 micrograms/ml) were incubated in plasma for one min. However, there was a marked decrease in fibrinogen level (about 50%) when the plasma was incubated for five min with a very high concentration of RSTA. SK markedly enhanced the platelet response to ADP in 13 out of 25 subjects. In PRP of 6 out of 25 subjects, SK induces platelet aggregation and potentiates platelet response to ADP, however in PRP of 7 out of 25 subjects, SK caused only the increase of platelet response to ADP. The monoclonal antibody anti-Fc gamma RIIa1, I-3 (2 micrograms/ml), abolished SK-induced platelet aggregation and SK-enhanced ADP-induced platelet aggregation. In all cases (25 out of 25 subjects), RSTA failed to potentiate platelet response to ADP. These findings confirm that RSTA has a lesser fibrinogenolytic ability than SK and suggest its negligible effect on platelet function.

Adenosine Diphosphate↗
PubMed1997

[Comparison of two groups of 22 women homozygous or heterozygous for factor V Leiden mutation].

Clinical characteristics of thrombophilia associated with heterozygous mutation of factor V are well characterized. In contrast, they are not well documented in homozygous subjects who are rare. Moreover, estroprogestative intake and pregnancy are important precipitating factors of venous thromboembolism in women with factor V mutation. In order to determine difference in clinical expression between homo and heterozygous subjects, two groups of 22 age matched women were compared. A modified technique for the diagnosis of activated protein C resistance has been used, and its great specificity and sensitivity has been confirmed. In these two small series of patients, a greater severity of clinical profile was not clearly evident. However, recurrences and thrombosis during pregnancy were more frequent in homozygous than in heterozygous women. However, the differences did not reach significance. Molecular markers of hypercoagulable states were not regularly increased even in homozygous untreated patients, but they were more often increased in untreated than in treated patients. In contrast, to other varieties of thrombophilia, homozygous mutation of factor V may be associated with a minor clinical severity suggesting the role of environmental factors and/or still unknown molecular alterations.

Factor V↗
PubMed1996

Evidence for cAMP-dependent platelet ectoprotein kinase activity that phosphorylates platelet glycoprotein IV (CD36).

The dephosphorylating enzyme alkaline phosphatase, by removing phosphate groups from the external platelet membrane proteins, modulates platelet activation (Hatmi, M., Haye, B., Gavaret, J. M., Vargaftig, B. B., and Jacquemin, C. (1991) Br. J. Pharmacol. 104, 554-558). This observation, together with findings reported by others (Ehrlich, Y. H., Davis, T. B., Bock, E., Kornecki, E., and Lenox, R. H. (1986) Nature 320, 67-70; Dusenbery, K. E., Mendiola, J. R., and Skubitz, K. M. (1988) Biochem. Biophys. Res. Commun. 153, 7-13), indicate the existence of ectoprotein kinase activity on the blood platelet surface. In this study, we demonstrate that washed human platelets phosphorylate the synthetic heptapeptide kemptide in a cAMP-dependent mode. The intensity of the phosphorylation was concentration-dependent for kemptide. In addition, incubation of platelets with [gamma-32P]ATP resulted in a rapid incorporation of [32P] phosphate into proteins at the outer membrane surface that was sensitive to alkaline phosphatase treatment. When cAMP was added to the medium, major phosphorylation of an 88-kDa ectoprotein occurred. Its isoelectric point determined by isoelectric focusing SDS-polyacrylamide gel electrophoresis was around pH 6.2. Phosphorylations of this 88-kDa polypeptide and of the exogenous kemptide substrate were both prevented by the specific protein kinase A inhibitor peptide. When platelets were preincubated with [32P]inorganic phosphate to label intracellular proteins, the protein phosphorylation pattern was different from that obtained with [gamma-32P]ATP, indicating that the latter occurred at the outer surface of the cells. Prostacyclin, which induces the increase of intracellular cAMP levels and, consequently, its liberation into the extracellular medium, increased phosphorylation of both kemptide and platelet 88-kDa polypeptide. The major protein of 88-kDa, which was phosphorylated in the presence of cAMP and external [gamma-32P]ATP, was identified by immunoprecipitation to GPIV (CD36), one of thrombospondin and collagen binding sites on platelets. The phosphorylation of CD36 also occurred in platelet-rich plasma, suggesting a physiological role for this ectoenzyme. In the present study, we clearly demonstrate the presence of an ectoprotein kinase A activity at the surface of intact human platelets, and we revealed its principal endogenous substrate as being CD36.

Blood Platelets↗
PubMed1996

Reversible inhibition by protamine of human synovial and rabbit platelet secretory phospholipase A2.

We investigated the effects of protamine on the release and the activity of 14 kDa type II phospholipase A2 (sPLA2). Protamine blocks both release and activity of sPLA2 from thrombin-stimulated platelets in a concentration-dependent manner. Heparin, an anionic sulfate polysaccharide which has a high affinity for this enzyme, has no inhibitory effect on sPLA2 by itself but it is able to reverse the inhibitory effect of protamine. The liberation by thrombin of platelet factor 4, an alpha-granule constituent, unlike to that of ATP stored in dense bodies, was suppressed by protamine. Platelet aggregation, determined in parallel, was not affected by protamine. Also, protamine did not inhibit platelet arachidonic acid liberation, which is mainly produced by cytosolic PLA2. The non-proteinaceous polycationic hexadimethrine and acidic protein casein failed to inhibit platelet sPLA2 activity. By contrast, the basic polypeptides poly(L-arginine) and poly(L-lysine) potently inhibited sPLA2 activity, indicating the important role of basic amino acids in the inhibitory effect evoked by protamine. Activities of the human recombinant sPLA2 and the unpurified synovial enzyme of patients with rheumatoid arthritis were also inhibited by the same range of protamine, poly(L-arginine) and poly(L-lysine) concentrations. Our results demonstrate that protamine, unlike heparin, blocks platelet sPLA2 release and exerts a reversible inhibitory effect on its activity, probably through the interaction of basic amino acids with the enzyme.

Animals↗
PubMed1996

A fatal low-molecular-weight heparin-associated thrombocytopenia after hip surgery: possible usefulness of PF4-heparin ELISA test.

In 37 patients undergoing total hip replacement, a prophylactic treatment by a low-molecular-weight heparin (LMWH) was conducted for 2 weeks. They belonged to a group of 499 patients included in a multicenter clinically controlled trial comparing two LMWHs. Blood was collected 1 day before surgery (D-1) and at D+1 or D+2 and D+5 or D+6 as well as D+10 through D+14 after surgery for determinations of platelets counts and anti-Xa. Bilateral venography was performed between D+10 and D+14. A fatal heparin-associated-thrombocytopenia (HAT) occurred on D+9 in one patient and was associated with a positive platelet aggregation test. This finding was confirmed with a recent ELISA test which evidenced a high concentration of PF4-heparin dependent antibodies 72 h before the detection of thrombocytopenia. This led us to study retrospectively PF4-heparin ELISA results by testing the plasma samples of 36 other surgical patients treated under the same conditions and during the same period (four measurements per patient). Among these patients, seven had a venous thrombotic event as a treatment failure. Although some authors claimed that some post-operative thromboses may be facilitated by the presence of heparin-dependent antibodies associated with or without thrombocytopenia, no thrombocytopenia and no positive PF4-heparin ELISA test was observed in this group. Out of the 144 tests performed in these 36 patients for the detection of PF4-heparin complexes dependent antibodies, 15 results were borderline in ten patients and three results in two patients were positive. No relation was evidenced between a positive ELISA test and the occurrence of venous thrombosis. This study points out the possible usefulness of the PF4-heparin ELISA test for HAT-antibodies detection. A daily platelet count in a postoperative patient under heparin therapy, showing thrombocytopenia associated with the detection of heparin-dependent antibodies could allow an earlier and more reliable diagnosis of HAT.

Aged↗
PubMed1996

Diagnosis and clinical characteristics of inherited activated protein C resistance.

The diagnostic strategies and clinical characteristics of thrombophilia associated with heterozygous or homozygous factor V Leiden mutation have been determined according to the literature and to a personal study in 51 families. Factor V mutation was present in the 51 propositi and in 84 out of 125 family members (81 heterozygous, 3 homozygous). Venous thrombosis was observed in all the propositi, in 17 of the 84 family members with the mutation and in 6 of the 41 with a normal APC resistance test and no mutation. An associated protein C or protein S deficiency was present in 5 families (10%). The most frequent clinical manifestations were superficial or deep vein thrombosis and/or pulmonary embolism, but also thrombosis at an unusual site (cerebral, mesenteric or central retinal vein). A causal relationship is frequently difficult to demonstrate. A precipitating factor was observed in 84% of cases and a recurrent thrombotic episode occurred in 50% of propositi. The risk of thrombosis associated with pregnancy was high in the post-partum period, especially in homozygous women. In the 28 homozygous subjects, markers of coagulation activation were frequently elevated in untreated patients. Finally, the efficacy of anticoagulant treatment is suggested but the long period often observed between treatment interruption and a recurrence does not militate in favour of long term treatment.

Anticoagulants↗