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Biomedical subjects

A Bezeaud

Publications and source records attributed to A Bezeaud.

51 records · Page 3Linked to original sources
PubMed1984

Prothrombin Salakta: an abnormal prothrombin characterized by a defect in the active site of thrombin.

An abnormal prothrombin has been detected in a 17 yr-old female originating from Tunisia. There was no history of excessive bleeding. Prothrombin time and activated partial thromboplastin time were moderately prolonged. Prothrombin activity was 15-18% when measured using either the classical one-stage and two-stage assays, or assays with Echis carinatus venom or staphylocoagulase, whereas prothrombin antigen was 100%. In keeping with current nomenclature practices, the abnormal molecule has been designated prothrombin Salakta. The electrophoretic behaviour and calcium binding properties of the abnormal prothrombin did not differ significantly from normal, as assessed by crossed immunoelectrophoresis. Prothrombin Salakta was isolated by chromatography on DEAE-Sephadex and Dextran sulphate sepharose. Electrophoretic migration of purified prothrombin Salakta on SDS polyacrylamide gels or alkaline disc gels was normal. Upon activation by either bovine factor Xa or Echis carinatus venom, thrombin activity produced by prothrombin Salakta was only 15% of normal, even when the incubation period was prolonged for 24 hours. The pattern of factor Xa-catalyzed proteolysis of prothrombin Salakta, investigated by SDS polyacrylamide gel electrophoresis, was found to be normal. These results indicated that prothrombin Salakta was characterized by a defective thrombin enzymatic activity. Thrombin Salakta was therefore isolated by heparin-sepharose chromatography. Affinity for heparin and molecular weight of thrombin Salakta were found to be normal. Biological activity of thrombin Salakta, determined by clotting assay, was 535 u/mg versus 3 200 u/mg for normal thrombin. Amidolytic activity of thrombin Salakta parallelled its clotting activity, suggesting that the defect resides either in the catalytic site or in the residues adjacent to the catalytic site and implicated as contact residues, rather than in the fibrinogen recognition site.

Adolescent↗
PubMed1984

Quantitation of prothrombin activation products in human urine.

Urine samples obtained from 37 normal individuals have been screened for the presence of prothrombin activation products using radioimmunoassays developed for fragment 1, fragment 2 and prothrombin derivatives bearing the thrombin region. The cross-reacting materials detected in urine were isolated by affinity chromatography on insolubilized antibodies, and analysed by SDS polyacrylamide gel electrophoresis. The only prothrombin derivatives detected were fragment 1 (37/37) and fragment 2 (22/37). The mean values of daily urinary fragment 1 and fragment 2 excretion were respectively 13.4 nM and 1.5 nM. The excretion of prothrombin derivatives has been quantitated in 14 normal pregnant women, during the third trimester of gestation. The mean values of urinary excretion were 47.2 nM per day for fragment 1 (P less than 0.005) and 6.4 nM per day for fragment 2 (P less than 0.05). The significant increase in fragment 1 and fragment 2 excretion observed in a condition known to be associated with the so-called hypercoagulable state suggest that the measurement of prothrombin derivatives in urine could be a useful tool for the non-invasive detection of thromboembolic diseases or prethrombotic states.

Adolescent↗
PubMed1981

Anti-spectrin in sera containing smooth muscle autoantibodies from patients with chronic active hepatitis.

Sera from patients with chronic active hepatitis containing anti-smooth muscle autoantibodies (SMA) react against rabbit muscle actin as well as human red cell spectrin. These anti-spectrin antibodies recognize the same antigen as rabbit anti-human spectrin antibodies and are not involved in the staining pattern given by SMA-containing sera tested with smooth muscle sections. These anti-spectrin antibodies probably recognize an antigenic structure common to both spectrin and another as yet undetermined molecule (which however is not likely to be myosin).

Actins↗
PubMed1979

Congenital deficiency of blood clotting factors II, VII, IX, and X.

A patient congenitally deficient in factors II, VII, IX, and X has been further investigated after a follow-up of 15 yr. At birth, these factors, when determined by clotting assays, were undetectable. Following therapy with vitamin K1, the clotting activity of these factors rose but never exceeded 18% of normal. Immunologic assays revealed much higher levels of these factors than did clotting assays, thus suggesting that the vitamin-K-dependent factors were present in abnormal forms. Two-dimensional crossed immunoelectrophoresis showed that at least two forms of prothrombin were present in the patient's plasma. One form was similar to normal prothrombin; the other had the same mobility as acarboxyprothrombin. In addition, the majority of this fast-migrating peak was not adsorbable onto insoluble barium salts. These observations suggested that some molecules of the patient's prothrombin lacked the normal complement of gamma-carboxyglutamic acid residues. This observation was confirmed by a specific assay for gamma-carboxyglutamate. Since malabsorption of vitamin K, warfarin intoxication, and hepatic dysfunction were excluded as causes of this patient's syndrome, this rare congenital abnormality could represent either a defective gamma-carboxylation mechanism within the hepatocyte or faulty vitamin K transport.

Adolescent↗
PubMed1978

The mechanism of activation of human prothrombin by an activator isolated from Dispholidus typus venom.

Purified human prothrombin was activated, both in the absence and in the presence of thrombin inhibitors (diisopropylfluorophosphate or hirudin), by a coagulant principle isolated from Dispholidus typus venom. The process of activation was monitored by sodium dodecyl sulfate polyacrylamide gel electrophoresis. In the absence of thrombin inhibitor, prolonged incubation of prothrombin with the purified venom yielded thrombin, fragment 1 (F 1) and fragment 2 (F 2). In the presence of diisopropylfluorophosphate, which in the experimental conditions used inhibited only partially the thrombin generated activity, products obtained upon activation of prothrombin by venom were F 1 and a two-chain, disulfide-bridged protein of 58 000 daltons called meizothrombin (des F 1). In the presence of hirudin, which fully inhibited thrombin generated activity, prothrombin activation by the venom did not liberate any fragment, but prothrombin was converted to a derivative composed of two disulfide-bridged polypeptide chains of 48 000 and 37 000 daltons, called meizothrombin. These results are similar to those reported by others when studying the process of prothrombin activation by Echis carinatus venom and allow to conclude that Dispholidus typus venom cleaves a bond linking the A and B chains of thrombin, converting prothrombin into meizothrombin. This enzyme is then responsible for the cleavage of the bond linking F 1 and F 2 and the bond linking F2 the A chain of thrombin.

Animals↗
PubMed1976

[Study of factors favoring infection in total hip prosthesis. Twenty-five observations].

The authors report 25 cases of infection following total hip replacement and individual factors are analysed. The role of immunological abnormalities is discussed. They distinguish early infection due to the operative conditions from late infection where individual factors are the most important. A few preventive measures are proposed, they emphasise the necessity of a large scale study of factors favouring late infection.

Hip Joint↗
PubMedDate not supplied

Multivariate analysis of prognostic factors in fulminant hepatitis B.

We assessed prognostic factors in 115 patients with serologically defined fulminant hepatitis B. The diagnosis in each case was based on the finding of IgM antibody to the hepatitis B core antigen in serum. Multivariate analysis showed that factor V level (p less than 0.001), patient's age (p = 0.001), absence of detectable HBsAg by radioimmunoassay (p = 0.06) and serum alpha-fetoprotein concentration (p = 0.07) were independent predictors of survival. The survival rate in the 21 patients in whom HBsAg was not detected was 47%, which was significantly higher than the survival rate of 17% observed in the 94 HBsAg-positive patients (p = 0.006). In patients with fulminant hepatitis B, the absence of HBsAg in serum as detected by radioimmunoassay has an independent, favorable prognostic value.

Adolescent↗
PubMedDate not supplied

[Rapid centrifugation for routine coagulation testing].

Routine coagulation assays are performed with platelet-poor plasma obtained after centrifugation of whole citrated blood. Usually clinical laboratories centrifuge blood from 2,000 to 2,500 g for 15-30 minutes. Thirty two blood samples routinely submitted to coagulation tests, were assayed for the prothrombin time, activated partial thromboplastin time, and fibrinogen level, in order to compare results obtained using 2 types of centrifugation : centrifugation at 2,500 g for 15 minutes and rapid centrifugation on StatSpin Express 2 at 4,440 g for 2 minutes. A good correlation was observed for the prothrombin time, activated partial thromboplastin time, and fibrinogen levels being respectively 1,009, 0,908 and 1. We concluded that rapid centrifugation at 4,440 g for 2 minutes does not modify results and contributes, by decreasing duration of the pre-analytical variable to reduce the completion time of these tests.

Blood Coagulation Tests↗