Contexto social y científico al momento de la llegada de la Dra. C. D. Pasqualini / Social and scientific context at the moment of the arrival of Dr. C. D. Pasqualini

Este capítulo pretende localizar en tiempo (mediados del siglo XX) y circunstancias la organización social y los eventos políticos de la Academia Nacional de Medicina y su Instituto de Investigación Hematológica. Puntualmente, cómo el Dr. Alfredo Pavlovsky, discípulo de Castex y Houssay y colega/amigo de Alfredo Lanari construyó un gran instituto donde trabajó la Dra. Pasqualini, una investigadora franco/canadiense de McGill University que vino a Buenos Aires con una beca para el Instituto del Dr Houssay. Desafíos, conflictos, desacuerdos y encuentros.

This chapter intends to locate in time and circumstances the social organization and the political events of the National Academy of Medicine of Buenos Aires and its Hematological Research Institute. Punctually, how Dr Alfredo Pavlovsky builded a great Institute where worked Dr Dosne de Pasqualini, a fellow from McGill University with a grant of Dr Houssay´ Institute. Challenges, conflicts, meetings and disagreements of the protagonists

Identificación por nuestro grupo de una nueva mutación en el gen GP1BA (P.W246L) asociada al fenotipo PT-VWD. Sexta mutación reportada internacionalmente / Identification by our group of a novel mutation in the GP1BA gene (P.W246L) responsible for PT-VWD. The 6th mutation internationally reported

La enfermedad de von Willebrand tipo plaquetario (PT-VWD) y tipo 2B (2B-VWD) son trastornos hemorrágicos raros, caracterizados por agregación plaquetaria a bajas concentraciones de ristocetina (RIPA). El diagnóstico diferencial no es fácil y representa un desafío. Hasta el presente, sólo se habían reportado cinco mutaciones en el gen GP1BA relacionadas con este desorden. Describimos aquí la sexta mutación relacionada con PT-VWD, en un paciente con sintomatología hemorrágica severa, macro-trombocitopenia, leve agregación plaquetaria espontánea, RIPA positivo a 0,3 y 0,4 mg/mL, VWF:RCo/VWF: Ag<0,2 y estudios discriminatorios positivos para PT-VWD. VWFpp/VWF: Ag resultó normal a diferencia del 2B-VWD que en algunas oportunidades resulta afectado. El exón 28 del gen VWF del paciente y su madre no reveló mutaciones. Identificamos una sustitución G>T en el nucleótido 3805 en el gen GP1BA del paciente, resultando en un cambio de Trp a Leu en el residuo 246 (p.W246L), en la región de la GPIBa que une al VWF. Esta mutación no se identificó en su madre ni en 100 controles sanos. Es considerada como dañina por análisis in sílico. Consideramos que esta sustitución es responsable del fenotipo PT-VWD del paciente. Dada la ausencia de la misma en los 100 normales estudiados, no se considera un polimorfismo

Platelet-type von Willebrand disease (PT-VWD) and type 2B von Willebrand disease (2B-VWD) are rare bleeding disorders characterized by increased ristocetin-induced platelet aggregation (RIPA) at low concentrations. Diagnosis of either condition is not easy and the differential diagnosis is especially challenging. Five mutations in the GP1BA gene related to PT-VWD and near 50 patients are currently reported worldwide. We herein describe a patient with severe bleeding symptoms, macro thrombocytopenia, mild spontaneous platelet aggregation, positive RIPA at 0.3 and 0.4 mg/mL, VWF: RCo/VWF: Ag <0.2, normal VWFpp/VWF: Ag ratio, and RIPA mixing tests and cryoprecipitate challenge positive for PT-VWD. GP1BA gene was studied in the patient, his mother, and 100 healthy control subjects. We identified a substitution G>T at nucleotide 3805 in the patient's GP1BA gene, resulting in a Trp to Leu amino acid change at residue 246 (p.W246L), within the VWF binding region. This mutation was absent in his unaffected mother and also in the 100 controls, and was predicted as damaging by in silico analysis. The residue is located in a strongly conserved position in the phylogenetic tree. These findings argue in favor of considering this substitution does not represent a polymorphism, and is therefore responsible for the PT-VWD phenotype of the patient

Biological and clinical response to desmopressin (DDAVP) in a retrospective cohort study of children with low von Willebrand factor levels and bleeding history.

The diagnosis and management of von Willebrand disease (VWD) in paediatrics is challenging. Our aim was to review patient's characteristics related to biological and clinical response to DDAVP in children with low von Willebrand factor (VWF) levels and bleeding history from a single institution. We included a retrospective cohort of 221 children (median age 11 years; 137 females): 27 type 1 (VWF levels within 15-30 IU dL-1) and 194 possible type 1 (VWF levels within 31-49 IU dL-1). The DDAVP infusion-test was performed in 214/221 children, 93.4% of whom showed good response. Patients with type 1 were at higher risk of DDAVP-test failure: 9/26 (34.6%) vs. 18/188 (9.6%) with possible type 1 (RR 3.44, 1.75-6.79; p= 0.002, Fisher's exact test). In 68 children, the clinical response to DDAVP was evaluated 87 times: i) to stop bleeding: menorrhagia (13), mucocutaneous (12), haemarthrosis (1); and ii) to prevent surgical bleeding: adenotonsillectomy (17), major (15) and minor surgery (10); and dental procedures (19). No major adverse events or bleeding were observed. The treatment was effective with one single dose of DDAVP in almost all patients, without antifibrinolytic or local therapy, except in a girl with severe haemorrhage during menarche who required replacement therapy. In conclusion, patients with VWD type 1 were at higher risk of no response to DDAVP infusion-test. In this series, one dose of DDAVP proved effective and safe for children with VWD. Since this is a safe, effective and affordable therapy, we consider that a wider use should be promoted, especially in developing countries.

Thrombotic complications in adult patients with lymphoma: a meta-analysis of 29 independent cohorts including 18 018 patients and 1149 events.

Thrombotic complications in hematologic malignancies have important clinical implications. In this meta-analysis we sought to obtain accurate estimates of the thrombotic risk in lymphoma patients. Articles were searched in electronic databases and references. Eighteen articles were identified (29 cohorts, 18 018 patients and 1149 events). Pooled incidence rates (IRs) were calculated by the use of a method based on the exact maximum likelihood binomial distribution. The global IR of thrombosis was 6.4% (95% confidence interval [CI] 6.0%-6.8%). The global IRs of venous or arterial events were 5.3% (95% CI, 5.0%-5.7%) and 1.1% (95% CI, 0.9%-1.2%), respectively. The IR of thrombosis observed in subjects with non-Hodgkin lymphoma (NHL) was 6.5% (95% CI, 6.1%-6.9%), significantly greater than that observed for patients with Hodgkin lymphoma (4.7%; 95% CI, 3.9%-5.6%). Within NHL, patients with high-grade disease had a greater risk of events (IR 8.3%; 95% CI, 7.0%-9.9%) than low-grade disease (IR 6.3%; 95% CI, 4.5%-8.9%). This meta-analysis shows that the IR of thrombosis in lymphoma patients is quite high, especially in those with NHL at an advanced stage of the disease. These results may help better defining lymphoma populations at high thrombotic risk, to whom prophylactic approaches could be preferentially applied.

Pilot study of homocysteine and cysteine in patients with thrombosis in different vascular sites. Epidemiology and response to folate.

Hyperhomocysteinemia is a risk factor for arterial and venous thrombosis. However, lowering homocysteine (Hcy) with vitamins not only failed to improve outcomes but also may lead to recurrent events. Our objectives were to evaluate Hcy and cysteine (Cys) levels in patients with thrombosis in different vascular sites, and their response to folate. One hundred and sixty four consecutive patients with thrombosis (42.1% arterial (AT), 36% venous (VT), 4.9% both venous and arterial thrombosis (AVT) and 17% unusual site (UST)) were included. Hcy and Cys were highest in patients with AVT and UST (p=0.0006). Ninety-three patients were treated, 70% were followed-up. Hcy levels normalized after therapy in all patients. Cys levels tended to vary after therapy according to the site of thrombosis. We observed a significant correlation between folate and Hcy (r: 0.48; p=0.005) among homozygous for MTHFR. A significant inverse relation was observed between Hcy and folate among homozygous and heterozygous (r: 0.462, p=0.007 and r: 0.267; p=0.04, respectively). No correlation was observed between folate and Cys. In conclusion, our observations suggest that Hcy and Cys might be implicated in thrombosis in different vascular sites, and respond differently to folate.

Uso de desmopresina durante el embarazo en enfermedad de Von Willebrand / Desmopressin use during pregnancy in Von Willebrand diseases

La enfermedad de Von Willebrand es el desorden hemorragíparo más frecuente. Las mujeres constituyen una población particularmente sintomática debido al desafío hemostático de las menstruaciones y el parto. Nosotros revisamos las historias médicas de 54 mujeres con niveles disminuidos de factor von Willebrand (VWF) e historia de sangrado, quienes hubieran usado desmopresina durante el embarazo. No se observaron efectos adversos ni en las mujeres ni en los recién nacidos, incluso en los 5 expuestos a la medicación en el primer trimestre de gestación. No se observaron complicaciones locales asociadas a la colocación del catéter epidural. La DDAVP fue efectiva para prevenir el sangrado posparto. La desmopresina merece ser considerada como la primera elección de tratamiento; en aquellas pacientes con bajo niveles de VWF presentan complicaciones hemorrágicas, incluyendo mujeres embarazadas. Aunque el sangrado posparto aparece en una pequeña proporción de mujeres con VWD, no hay un modo apropiado de identificar quiénes van a sangrar. El uso de profilaxis con DDAVP debería ser tenido en cuenta como una alternativa segura y efectiva.

The von Willebrand disease (VWD) is the most frequent hemorrhagic disorder. Women with VWD are more symptomatic than men because the challenged of menses and delivery. We reviewed the records of 54 women with a low plasmatic VWF level and bleeding history, who had used desmopressin during pregnancy. No adverse effects were observed in mothers or newborns, incluiding those exposed to the drug during the first trimester. No local complication of epidural placement was observed. DDAVP was effective to prevent post-partum hemorrhage. DDAVP merits to be considered as the first choice of therapy, when patients with a previous or current low plasmatic VWF level present bleeding complications, including pregnant women. Although post-partum bleeding will appear in a small proportion of VWD women, there is no accurate way to identify who is going to bleed. The use of DDAVP should be regarded as a highly valuable option.

Effect of nitroxyl on human platelets function.

There is a growing body of evidence on the role of nitric oxide (NO) in human platelet physiology regulation. Recently, interest has developed in the functional role of an alternative redox form of NO, namely nitroxyl (HNO/NO-), because it is formed by a number of diverse biochemical reactions. The aim of the present study was to comparatively analyze the effect of HNO and NO on several functional parameters of human platelets. For this purpose, sodium trioxodinitrate (Angeli's salt,AS) and sodium nitroprusside (SNP) were used as HNO and NO releasers, respectively. BothAS and SNP significantly inhibited platelet aggregation and ATP release induced by different agonists and adrenaline. AS or SNP did not modify the expression of platelet glycoproteins (Ib, IIb-IIIa, la-IIa, IV), whereas they substantially decreased the levels of CD62P, CD63 and of PAC-1 (a platelet activated glycoprotein IIb/IIIa epitope) after the stimulation with ADP. AS and SNP significantly increased cGMP accumulation in a 1H-[1,2,4]oxadiazolo [4,3-a] quinoxalin-1-one (ODQ)-sensitive manner. However, while L-cysteine reduced the effect of AS, it increased the effect of SNP on this parameter. Accordingly, a differential effect of L-cysteine was observed on the antiaggregatory effect of both compounds. In summary, these results indicate that HNO is an effective inhibitor of human platelet aggregation.

Assessment of platelet activation in myeloproliferative disorders with complementary techniques.

Bleeding and thrombosis in myeloproliferative disorders (MPD) are common events, sometimes both are present in the same patient during the course of the disease. Platelet activation in patients with MPD is often suggested. The present study analyses the presence of circulating activated platelets, using simultaneously flow cytometry and aggregometric studies in MPD. We studied 28 patients: 13 with polycythaemia vera, seven with essential thrombocythaemia, and eight chronic myeloid leukaemia. We performed functional tests, aggregation and adenosine triphosphate (ATP) release and flow cytometric assays (mepacrine staining and platelet activation markers CD62, CD63 and fibrinogen binding (B-FG)). Twenty-one MPD samples (75%) had reduced aggregation and ATP release. Acquired delta-SPD was detected in 11 of 28 MPD patients (39%), and we found no association between reduced mepacrine labelling and abnormal ATP release. High levels of activation markers were obtained: CD62 in 19 of 28 patients (68%), CD63 in 13 of 28 patients (46%) and B-FG in 19 of 28 patients (68%). The most prevalent abnormality was a reduced aggregation and ATP release. The lack of association between ATP release and mepacrine labelling suggests that other mechanisms, besides the deficit of intraplatelet ATP/adenosine diphosphate, might occur. High levels of activation markers were also observed. We conclude that both tests are complementary and necessary to understand the functional status of platelets in MPD.

Nitridergic platelet pathway activation by hementerin, a metalloprotease from the leech Haementeria depressa.

Hementerin (HT) is an 80 kDa fibrino(geno)lytic metalloprotease, purified from saliva of the leech Haementeria depressa. In the present report, the effect of HT on several functional parameters of human platelets was assessed. HT inhibited platelet aggregation and ATP release induced by different agonists such as ADP, adrenaline, collagen, thrombin, and arachidonic acid. HT did neither modify the expression of platelet glycoproteins (Ib, IIb-IIIa, Ia-IIa, IV) nor intraplatelet fibrinogen levels, whereas it markedly decreased CD62P and CD63 levels after the stimulation with thrombin. HT significantly increased thrombin-induced platelet Ca2+ intracellular levels, cGMP content and nitric oxide synthase (NOS) activity. The effect of HT on platelet aggregation was reversed by two NOS inhibitors, N(omega)-Nitro-L-arginine methyl ester and 2 N(G)-Nitro-L-arginine. In summary, these results indicate that HT is an effective inhibitor of human platelet aggregation, presumably through activation of the platelet's nitridergic pathway.

A prothrombin activator from Bothrops erythromelas (jararaca-da-seca) snake venom: characterization and molecular cloning.

A novel prothrombin activator enzyme, which we have named 'berythractivase', was isolated from Bothrops erythromelas (jararaca-da-seca) snake venom. Berythractivase was purified by a single cation-exchange-chromatography step on a Resource S (Amersham Biosciences) column. The overall purification (31-fold) indicates that berythractivase comprises about 5% of the crude venom. It is a single-chain protein with a molecular mass of 78 kDa. SDS/PAGE of prothrombin after activation by berythractivase showed fragment patterns similar to those generated by group A prothrombin activators, which convert prothrombin into meizothrombin, independent of the prothrombinase complex. Chelating agents, such as EDTA and o -phenanthroline, rapidly inhibited the enzymic activity of berythractivase, like a typical metalloproteinase. Human fibrinogen A alpha-chain was slowly digested only after longer incubation with berythractivase, and no effect on the beta- or gamma-chains was observed. Berythractivase was also capable of triggering endothelial proinflammatory and procoagulant cell responses. von Willebrand factor was released, and the surface expression of both intracellular adhesion molecule-1 and E-selectin was up-regulated by berythractivase in cultured human umbilical-vein endothelial cells. The complete berythractivase cDNA was cloned from a B. erythromelas venom-gland cDNA library. The cDNA sequence possesses 2330 bp and encodes a preproprotein with significant sequence similarity to many other mature metalloproteinases reported from snake venoms. Berythractivase contains metalloproteinase, desintegrin-like and cysteine-rich domains. However, berythractivase did not elicit any haemorrhagic response. These results show that, although the primary structure of berythractivase is related to that of snake-venom haemorrhagic metalloproteinases and functionally similar to group A prothrombin activators, it is a prothrombin activator devoid of haemorrhagic activity. This is a feature not observed for most of the snake venom metalloproteinases, including the group A prothrombin activators.

Von Willebrand factor cleaving protease activity in the physiopathology of microangiopathic disorders

The von Willebrand factor cleaving protease (VWFCP) modulates the von Willebrand factor (VWF) multimeric size in normal plasma. VWFCP activity levels are decreased in different physiological and pathologic situations. Different techniques have been developed to unfold the purified VWF (perfusion at high shear rate, dialysis against urea in nitrocellulose filters), to detect the VWFCP activity on it (multimeric analysis of VWF, collagen binding to VWF assay) and to use the patient plasma both as the source of the enzyme and substrate. In this paper we compared the above mentioned methods with new ones: normal plasma dialyzed on membranes instead of purified VWF, dialysis of the samples against urea in tubing instead of nitrocellulose filters, and sonicated plasma to remove the endogenous VWF. The perfusion assay and detection by multimeric analysis showed a limit of detection (25%) of VWFCP activity. Dialysis against urea in both supports and detection by multimeric analysis, showed a better limit of detection (3%), but the recovery of the samples was not as efficient in nitrocellulose filters as it was in tubing. The detection by collagen binding to VWF has more advantages because it allows to analyze more samples than the multimeric analysis does in the same assay. The dialysis of plasma by membranes to obtain the source of exogenous VWF requires no complex equipment. The method, which uses patient plasma as the source of the enzyme and substrate, was inapplicable in our experience because the values could not be interpolated in the reference curve

Acquired von Willebrand factor abnormalities in myeloproliferative disorders and other hematologic diseases: a retrospective analysis by a single institution.

BACKGROUND AND OBJECTIVES: Acquired von Willebrand syndrome (AVWS) is a rare acquired disorder. In most cases it is associated with lymphoproliferative disorders and monoclonal gammopathies, while less frequently myeloproliferative disorders (MPD) are involved. Although bleeding is the most important symptom, thrombotic complications have also been observed in cases associated with MPD. Our aim was to review the clinical and laboratory findings in AVWS patients from a single institution. DESIGN AND METHODS: The records of 99 patients with AVWS were reviewed to identify the underlying diseases, the symptoms and the laboratory parameters. RESULTS: In 75% of cases the AVWS was associated with MPD. The most frequent pattern was type 2 (67.7%). Abnormalities of bleeding time, factor VIII levels or platelet retention to glass beads were observed in 83.8% of cases. Bleeding was present in 38.4% of patients, more frequently in the not-MPD-associated (58.3%) vs. MPD-associated cases (32%) (p=0.022), with a significant predominance in females, irrespective of the underlying disease (p=0.0007). In 32% of patients with MPD, thrombotic manifestations, mostly microvascular and arterial episodes, were observed. INTERPRETATION AND CONCLUSIONS: AVWS in MPD seems to be mainly a laboratory diagnosis, without clinical symptoms in most cases, although bleeding as well as ischemic events can be present. In contrast, AVWS in not-MPD-associated cases is most frequently associated with severe bleeding symptoms. Performing appropriate laboratory tests may be useful for screening for AVWS.

Medicina hoy: presente y futuro de los anticoagulantes orales / Medicine today: present and future of oral anticoagulants

El número de pacientes bajo tratamiento anticoagulante oral se ha incrementado notablemente en los últimos años al incorporarse la población de pacientes con fibrilación auricular crónica. Su manejo se ha facilitado al contar actualmente con reactivos comerciales sensibles y calibrados. No obstante este avance, las complicaciones hemorrágicas siguen siendo uno de los peligros de este tratamiento. En nuestra experiencia, las hemorragias mayores se correlacionan sobre todo con la intensidad de la anticoagulación y la duración del tratamiento. También la variabilidad del RIN (Razón Internacional Normatizada) (la desviación del RIN del rango deseado) puede asociarse con mayor sangrado. La necesidad de ajustar la dosis con pruebas de laboratorio, los controles frecuentes, la interacción con otras medicaciones, la estrecha ventana terapéutica y la alta variación en la relación dosis-respuesta, hacen surgir la necesidad de nuevos agentes antitrombóticos, igualmente eficaces, pero que permitan prescindir del ajuste por el laboratorio. Inhibidores de trombina de bajo peso molecular disponibles por vía oral están actualmente en período de prueba y constituirían una alternativa al tratamiento con antagonistas de vitamina K.

Evaluación de las alteraciones de la hemostasia inducidas por el embarazo normal / Evaluation of the hemostatic changes induced by normal pregnancy

Se estudiaron 91 embarazadas normales. Hubo 2 casos de plaquetopenia leve en el 2§ trimestre y 6 en el 3§; se observó aumento del factor von Willebrand. El Fibrinógeno aumentó hacia el tercer trimestre. La proteína S (PS) biológica e inmunológica libre disminuyeron. La Resistencia a la Proteína C Activada observó un acortamiento entre el primer y segundo trimestre. Aumentó el tiempo de lisis de euglobulinas basal y disminuyó la diferencia entre euglobulinas pre y post isquemia. Dentro de la marcación de receptores plaquetarios sólo la unión de fibrinógeno resultó incrementado (p<0.05). Se analizaron las causas que inducen la aparición de 2 o más abortos/pérdidas fetales (a/PF) y la frecuencia de alteraciones de la hemostasia. La población se dividió en 3 grupos. A: A/PF primarias (media 32 años, 204 gestas, 190 A/PF espontáneas, 73 por ciento 1er. trimestre (T), 18 por ciento 2do. T, 9 por ciento 3er. T). B: A/PF secundarias (32 años, 164 gestas, 96 pérdidas espontáneas, 57 por ciento 1er. T, 35 por ciento 2do. T, 8 por ciento 3er. T). C: misceláneas (30 años, 35 gestas, 21 pérdidas espontáneas, 45 por ciento 1er. T, 15 por ciento 2do. T, 40 por ciento 3er. T). Hallamos anormalidades de la hemostasia en los 3 grupos estudiados (A: 94 por ciento, B: 92 por ciento y C: 100 por ciento), como defectos aislados (36 por ciento) o combinados (58 por ciento). Se detallan los porcentajes de anomalías encontradas en las pacientes que han concluído la evaluación.

Utilidad de la detección de anticuerpos anti-factor VIII por Elisa en hemofílicos / Usefulness of detection of afVIII antibodies by Elisa in haemophiliacs

Los hemofílicos pueden desarrollar en forma concomitante inhibidor lúpico (LA) e inhibidor neutralizante anti-factor VIII (a-fVIII). El diagnóstico diferencial es complejo ya que el LA interfiere en la identificación de los a-fVIII. A fin de detectar a-fVIII sin interferencia de LA, desarrollamos un ELISA utilizando fVIII recombinante libre de fosfolípidos como antígeno con la muestra y revelamos la IgG unidad mediante un anticuerpo anti-IgG humana-fosfatasa. El sistema permitió detectar un anticuerpo monoclonal a-fVIII al ser revelado con el antisuero anti-IgG ratón. Como control inespecífico se utlizaron anticuerpos monoclonales anti-GPIIIa y anti-factor von Willebrand. Para evaluar la utilidad del ELISA, se analizaron plasmas de pacientes hemofílicos con a-fVIII, con o sin LA y hemofílicos sin inhibidor. Como controles negativos se incluyeron plasmas con LA y normales. Los plasmas de hemofílicos con a-fVIII dieron valores de absorbancia >X Normalñ3DE; algunos plasmas hemofílicos sin inhibidor también mostraron absorbancias superiores al normal, aunque inferiores a las observadas para a-fVIII. Las lecturas de los controles no fueron significativas. No observamos interferencias por la presencia de LA. El ELISA a-fVIII sería un elemento diagnóstico complementario, al permitir evidenciar anticuerpos capaces de unirse al fVIII, aún en plasmas LA.

Anticoagulación en embarazadas con prótesis valvulares mecánicas / Anticoagulation in pregnant patients with mechanical valve prostheses

La anticoagulación oral durante el embarazo es un tema controvertido y no hay uniformidad de criterios sobre cuál es el tratamiento más adecuado para las pacientes embarazadas con prótesis valvulares mecánicas. Los anticoagulantes orales pueden inducir una embriopatía si son administrados entre la 6ª y 12ª semana del embarazo, sus sustitución por heparina previene esta complicación pero su eficacia en la prevención de complicaciones trombóticas ha sido cuestionada. Ambos anticoagulantes también son responsables del mayor riesgo de abortos o pérdidas fetales. Evaluamos el resultado de 92 embarazos consecutivos en 59 pacientes con prótesis valvulares mecánicas desde 1986 hasta junio de 1997. En 31 embarazos se suspendió la anticoagulación oral durante el 1er. trimestre y se indicó heparina SC ajustada por APTT. En 61 embarazos se continuó con anticoagulación oral. Para el parto se utilizó nuevamente heparina ajustada. Los abortos o pérdidas fetales fueron similares en las que recibieron anticoagulación oral el 1er. trimestre (13/61=25 por ciento) comparado con las que recibieron heparina (6/31=19 por ciento). Los episodios embólicos fueron más frecuentes en el período tratado con heparina (4.92 por ciento) que en el tratado con anticoagulantes orales (0.33 por ciento). Las embolias fueron cerebrales y transitorias. No se observaron malformaciones en los 71 recién nacidos excepto 1 caso de hidrocefalia. La única muerte materna resultó de una hemorragia mayor luego del parto de un feto muerto prematuro. Aunque la anticoagulación oral parece ser más segura para la madre, la heparina ajustada ofrece una protección adecuada de fenómenos tromboembólicos.

Requirement of a plasma fraction for the loss of large Von Willebrand factor multimers induced by high wall shear rate

The perfusion of serum, citrated whole blood and citrated plasma, through a simple tube system resulted in a significant loss of large von Willebrand factor (vWf) multimers, without decrease in antigen levels. Maximum loss of large multimers was observed at a shear rate of 15,000 s(-1) for 15 min. Heparin, aprotinin, soybean trypsin inhibitor, phenylmethylsulphonylfluoride, N-ethylmaleimide, leupeptin or calpain inhibitor peptide could not prevent the loss of large vWf multimers in citrated plasma. The addition of EDTA calcium salt partially prevented it, and it was totally prevented by EDTA without calcium. Perfusion of purified vWf did not induce the loss of large multimers, but this did happen after the addition of either whole serum or a plasma fraction. The activity of this plasma fraction disappeared at pH < 6.8. Besides, we have found that the binding to subendothelium of purified vWf diluted in dialized serum was lower at pH 7.2 than at pH 6.0. Chromatographic studies demonstrated that the loss of large vWf multimers, induced by high shear rates, involves a plasma substance(s) of molecular weight larger than 200 kD; calpain and granulocyte or cysteine proteases do not seem to be this plasma substance(s).

Inhibidor neutralizante e inhibidor lúpico en hemofilia: un nuevo problema diagnóstico / Anti-factor VIII inhibitors and lupus anticoagulants in hemophilia: a diagnostic problem

Los hemofílicos pueden desarrollar inhibidores neutralizantes (a-ŸVIII) y/o inhibidores lúpicos (IL). Durante 1993-1994, evaluamos 170 hemofílicos. Aquellos cuyo tiempo de tromboplastina parcial activado (TTPA) no corregía con plasma normal fueron reestudiados. En 43 pacientes (25 por ciento) se confirmó el inhibidor, realizándose a continuación: TTPA de la mezcla (1:1) luego de 1 h de incubación a 37§C; prueba con veneno de víbora Russell diluido (dRVVT), corrección (1:1) con normal y neutralización con plaquetas. El IL fue asignado en base a los resultados del dRVVT y el a-ŸVIII al detectarse efecto neutralizante contra ŸVIII e IL negativo. Siete (16 por ciento) pacientes presentaron a-ŸVIII e IL (-) (A). Los 36 (84 por ciento) restantes fueron IL (+); el efecto inhibitorio potenció con la incubación en 12 (B), fue leve en 6 (C) y negativo en 18 (D). Los antecedentes de a-ŸVIII fueron positivos en A:6/6, B:9/11, C:1/6 y D:9/17. La prevalencia de a-ŸVIII fue bajo (4 por ciento) y alto (50 por ciento) el porcentaje de IL tiempo dependiente. Estos resultados sugieren la coexistencia de a-ŸVIII con IL, o su desaparición. Se hace pues necesario el desarrollo de pruebas específicas que permitan identificar a-ŸVIII en presencia de IL.

Respuesta fibrinolítica a la 1-deamino-8-angina vasopresina (DDAVP) en pacientes con alteraciones de la hemostasia / Fibrinolytic response of 1-deamino-8-D-arginine vasopresin (DDAVP) in patients with hemostasis alteration

Decrease fibrinolytic response after infusion of 1-deamino-8-D-arginine vasopressin (DDAVP) was reported in patients with von Willebrand disease (vW) (Nouv. Rev. Fr.Hematol.1992, 34:55-60), suggesting an association between vW factor and syntesis or/and realese of t-PA by endothelial cells. In the present study we measured the activity of plasmatic euglobulin fractions by fibrin plate method in 65 patients with hemostatic disorders: 36 vW type I, 9 hemophilics A (HA), 6 storage pool disease (SPD), 6 primary hemostasis alteration (PHA), 8 PHA and decrease factor VIII (PHAH), and 5 normals (N). DDAVP was administrated intravenously at 0,4 ug/Kg body weight. The means SD (mm) of the difference between the diameter of lysis area from the highest and basal response were: N 4,60ñ1,55; vWd 6,38ñ2,77; HA 4,77ñ2,95; SPD 4,9ñ1,69; PHA 5,63ñ4,3:PHAH 4,35ñ2.09. No statistical difference was obtained between N and patients. A higher than normal fibrinolytic response was observed in vW 12/365, HA 2/9, PHA 2/6, PHAH 2/8. A decrease response was showed by vWd 0/36, HA 1/9, SPD 0/6, and PHAH 0/8. Our observation suggest that the FvW is not related with the plasmatic fibrinolytic activity