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Biomedical subjects

A Eldor

Publications and source records attributed to A Eldor.

At least 73 records · Page 4Linked to original sources
PubMed1998

Expansion of megakaryocyte progenitors from human umbilical cord blood using a new two-step separation procedure.

Cord blood (CB) transplantation is primarily performed in children, rather than in adults, due to the low number of haemopoietic progenitor cells obtained from the small volume of a single CB collection. Prolonged thrombocytopenia is a major problem following CB transplantation. Efforts are currently underway to expand the number of CB progenitor cells ex vivo, in order to enable transplantation in adults and to decrease the period of thrombocytopenia. In this study we investigated different techniques for enrichment and expansion of megakaryocyte (Mk) progenitor cells and haemopoietic stem cells from CB. CBs from 20 normal deliveries were depleted of red blood cells (RBC) by dividing each sample and testing cell separation on 3% gelatin, Hespan, Ficoll-Paque or a two-step 3% gelatin followed by Ficoll-Paque separation. The two-step procedure was found to be superior to the other methods in enrichment of the Mk progenitor cells (CFU-Mk) (34.3-fold), while at the same time retaining the number of myeloid and erythroid progenitors, CD34+ and CD41+ cells. In short-term (14d) liquid culture of non-adherent nucleated cells isolated by gelatin and Ficoll-Paque, a 40-fold expansion of clonable Mk progenitor cells was obtained in the presence of thrombopoietin (r-hu-TPO) and stem cell factor (r-hu-sCF. In similar cultures of isolated CD34+ cells, a 100-fold clonable Mk progenitor was obtained at day 14. Therefore this new technique may facilitate the ex vivo expansion of Mk progenitor cells and be adopted for future use in CB transplantation.

Adult↗
PubMed1998

Anti-endothelial cell antibodies in the sera of hyperprolactinemic women.

Prolactin (PRL) is closely associated with autoimmune diseases in animal models and humans, and several disease-related autoantibodies were reported in increased titers in patients with hyperprolactinemia (HPRL). We studied the presence of anti-endothelial cell antibodies (AECA) and other autoantibodies in sera of female patients with HPRL. Sera from 25 HPRL patients and 10 healthy female controls were tested for AECA (against both macrovascular and microvascular endothelial cell antigens), anti-dsDNA, and anti-cardiolipin (anti-CL) using ELISA. Sera were considered positive for the autoantibody when the optical density (OD) value was more than 3 s.d. above the mean of the OD in normal controls. Sera from 13 patients were obtained repeatedly during dopaminergic anti-PRL treatment, to relate PRL level or anti-PRL treatment with the autoantibody levels. Elevated micro and/or macrovascular AECA were observed in sera from 19/25 patients (76%). Elevated titers of anti-CL Abs, all beta2-GPI-dependent, and low levels of anti-dsDNA antibodies (Abs) were also observed in the HPRL patients. Inhibition studies showed that the affinity purified AECAs bound the endothelial cell (EC) antigens in a dose-dependent manner. Titers of AECA as well as anti-DNA and anti-CL autoantibodies did not correlate with PRL level nor with the use or duration of anti-PRL treatment. None of the HPRL patients presented clinical manifestations of autoimmune disease. We conclude that elevated levels of AECA as well as anti-DNA and anti-CL autoantibodies are frequent in hyperprolactinemia. Our results further support the association of PRL and autoimmunity, and may point to a relationship between AECA-associated diseases and HRPL. The presence of autoantibodies in patients with HPRL might portend an increased risk for future development of autoimmune disease.

Antibodies, Anticardiolipin↗
PubMed1997

[Macroenzymes: an interesting laboratory finding, without clinical relevance].

Macroenzymes are complexes of serum enzymes with proteins which have a higher molecular weight and longer plasma half-life than the normal enzyme. The presence of macroenzymes is suggested by finding increased serum enzyme activity, not associated with symptoms. Thus, macroenzymes can cause diagnostic errors and the performance of unnecessary tests or invasive procedures. We describe 2 patients with highly elevated serum levels of lactate dehydrogenase (LDH) and creatine kinase (CK) due to formation of complexes with immunoglobulin G. 1 patient had LDH of 4500 u/L but was otherwise normal and in the second CK was elevated with no evidence of ischemic heart disease. Awareness of the phenomenon of macroenzymes may save the patient long and sometimes invasive investigation.

Adult↗
PubMed1997

Immature human megakaryocytes produce nuclear-associated acetylcholinesterase.

Acetylcholinesterase (AChE) is expressed in murine megakaryocytes (MK), where its antisense inhibition suppresses differentiation, yet was never detected in human MK. Here, we report that AChE is produced in normal human bone marrow MK and in cell lines derived thereof. Reverse transcriptase-polymerase chain reaction (RT-PCR) amplification showed two ACHEmRNA forms in human megakaryoblastic DAMI cells. In situ hybridization demonstrated ACHEmRNA surrounding the nucleus of small DAMI cells and the nuclear lobes of large, polyploid cells. Differentiation induction with phorbol ester and exposure to recombinant human thrombopoietin suppressed both ACHEmRNA and AChE activity. The residual AChE in mature differentiated cells acquired higher stability and detergent-sensitivity as compared with AChE in small proliferating cells. AChE activity was primarily associated with nuclei of both DAMI cells and small (10 microm) primary proliferating human bone marrow MK identified with GPIIb/IIIa antibodies. This activity was significantly reduced in medium size MK (10 to 25 microm) and was almost undetectable in large MK (>25 microm), yet was twofold more abundant in some large MK from idiopathic thrombocytopenia purpura (ITP) patients with accelerated MK maturation. The loss of AChE activity at the transition from proliferating to differentiating MK highlights species-specific differences in its expression, suggesting a distinct role for AChE in human MK development.

Acetylcholinesterase↗
PubMed1997

A single genetic origin for a common Caucasian risk factor for venous thrombosis.

A common genetic risk factor for venous thrombosis among Caucasoid subpopulations is a polymorphism, nt G1691A, in blood coagulation factor V that replaces Arg506 with Gln and imparts resistance of factor Va to the anticoagulant, activated protein C. Haplotype analyses using six dimorphic sites in the factor V gene for 117 Caucasian subjects of Jewish, Arab, Austrian, and French origin who were homozygous for nt A1691 compared with 167 controls (nt G1691) support a single origin for this polymorphism. The nt G1691A mutation is estimated to have arisen circa 21,000 to 34,000 years ago, ie, after the evolutionary divergence of Africans from non-Africans and of Caucasoid from Mongoloid subpopulations.

Arginine↗
PubMed1997

Highly elevated lactate dehydrogenase level in a healthy individual: a case of macro-LDH.

Macroenzymes are complexes of serum enzymes with a plasmatic protein. They have a higher molecular weight and a more prolonged serum half-life than those of unbound enzymes. Although macroenzymes may be found in the serum of post-myocardial infarction patients, they are not usually associated with any specific disease. Their presence, however, can cause an elevation in the serum levels of an enzyme, possibly leading to errors in diagnosis. We report a patient with extremely elevated serum levels of lactate dehydrogenase (LDH) due to the formation of complexes with immunoglobulin G. She had undergone a myriad of clinical examinations until the macroenzyme responsible for this finding was detected. We also review the literature on the clinical significance of macro-LDH. We propose that awareness of this rare and probably benign phenomenon can spare the patient from the distress of exhaustive investigations.

Blood Proteins↗
PubMed1997

The procoagulant activity of red blood cells from patients with severe preeclampsia.

OBJECTIVE: Our purpose was to determine whether red blood cells from patients with severe preeclampsia may exhibit increased membrane exposure of procoagulant phospholipids (i.e., phosphatidylserine), which may initiate intravascular clotting and platelet activation. STUDY DESIGN: The study group comprised 28 women: 9 with severe preeclampsia in the third trimester of pregnancy, 10 normotensive with uncomplicated pregnancies, and 9 age-matched, nonpregnant, healthy women. The exposure of phosphatidylserine on the outer membrane phospholipid layer was analyzed with use of isolated, washed red blood cells that were added as a source of phospholipids to a "prothrombinase" coagulation complex. RESULTS: The resultant thrombin formed was measured by an amidolytic assay. Thrombin generation significantly increased on the addition of red blood cells from women with preeclampsia (741 +/- 132 mU/ml/min) compared with red blood cells from normotensive pregnant (422 +/- 228 mU/ml/min) and nonpregnant women (316 +/- 268 mU/ml/min, p = 0.0008). CONCLUSION: This study indicates that in patients with preeclampsia the red blood cells exhibit a significant procoagulant surface that may trigger thrombin formation, thereby playing a role in the hypercoagulable state.

Adult↗
PubMed1997

Bilateral retinal vein occlusion associated with 5,10-methylenetetrahydrofolate reductase mutation.

PURPOSE: To report on the occurrence of 5,10-methylenetetrahydrofolate reductase (MTHFR) deficiency, known to cause mild to moderate hyperhomocystinemia and increased risk of vascular occlusive disease, in a young patient with bilateral central retinal vein occlusion. METHODS: A 25-year-old man was initially examined with central retinal vein occlusion in the right eye, followed 4 months later by a central retinal vein occlusion in the left eye. Studies for risk factors predisposing to thrombosis were performed. RESULTS: Hematologic studies failed to detect any pathology. However, the patient was found to be homozygous for 677C-T mutation in MTHFR enzyme. CONCLUSION: Central retinal vein occlusion may be associated with a mutation in MTHFR.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗
PubMed1997

In-vivo platelet activation correlates with red cell anionic phospholipid exposure in patients with beta-thalassaemia major.

Several clinical and laboratory findings suggest the presence of a chronic hypercoagulable state in patients with beta-thalassaemia major (TM). We have previously shown that isolated TM red blood cells (RBC) strongly enhance prothrombin activation, suggesting an increased membrane exposure of procoagulant phospholipids (i.e. phosphatidylserine). In this study we quantitated the procoagulant activity of RBC in TM and thalassaemia intermedia (TI) patients. We also determined the fraction of activated platelets expressing p-selectin (CD62p) or CD63 in these subjects. Both assays were performed by dual-colour flow cytometry. A significantly (P < 0.01) higher fraction of FITC-annexin V-labelled RBC was found in TM and TI patients, compared to the controls. A highly significant correlation (P < 0.001) was found in TM patients between the number of RBC-bound annexin V molecules and the fraction of CD62p (p-selectin) or CD63-positive platelets. This association between annexin V binding to TM RBC and the expression of platelet activation markers was also found in individual TM patients over time. Thus, the procoagulant surface of TM RBC may accelerate thrombin generation in vivo which, in turn, triggers platelet activation.

Adolescent↗
PubMed1997

Danaparoid for cardiopulmonary bypass in patients with previous heparin-induced thrombocytopenia.

Anticoagulation for cardiopulmonary bypass in patients with heparin-induced thrombocytopenia requires the use of other anticoagulants. We report a case in whom this was achieved using the heparinoid danaparoid (Orgaran). Based on our experience and a review of the literature, we provide guidelines for managing these rare patients. A danaparoid dose substantially lower than that recommended by the manufacturer may minimize bleeding complications.

Anticoagulants↗
PubMed1997

Pathogenicity of human anti-platelet factor 4 (PF4)/heparin in vivo: generation of mouse anti-PF4/heparin and induction of thrombocytopenia by heparin.

Heparin-induced thrombocytopenia/thrombosis (HIT) is a severe thrombotic disorder that occurs in approximately 1% of patients treated with heparin. Affected patients commonly develop antibodies that recognize PF4/heparin complexes that may form on the surface of activated platelets and on the endothelium. However, it has not been established that anti-PF4/heparin antibodies are responsible for the clinical manifestations of HIT. To address this issue, we employed a recently developed model of active immunity to study the effect of IgG anti-PF4/heparin antibody in vivo. In previous studies we have shown that it is possible to induce autoimmune diseases such as systemic lupus erythematosus (SLE), anti-phospholipid syndrome (APS) or vasculitis in naive mice by active immunization with anti-DNA, anti-cardiolipin and anti-neutrophil cytoplasmic antibodies, respectively. Immunized animals develop anti-idiotypic antibodies (Ab2) and, after 2-4 months, anti-anti-idiotypic antibodies (Ab3). Ab3s generated in this manner often simulate the binding activity of Ab1 and their expression correlates with the development of specific clinical manifestations typical of the respective human disease. Based on this experience, naive BALB/c mice were immunized with IgG anti-PF4/heparin antibodies isolated from two patients with HIT. The actively immunized mice developed mouse anti-PF4/heparin antibody (Ab3). Administration of unfractionated heparin, but not low molecular weight heparin (LMWH), to the actively immunized animals induced thrombocytopenia by day 4 of drug exposure. There was no evidence of thrombosis. The results of this study support the importance of anti-PF4/heparin antibodies in the pathogenesis of HIT. Further, this model may help to elucidate the factors responsible for thrombosis as well as providing means to assess new treatment options for patients with this disorder.

Animals↗
PubMed1997

The urokinase-receptor (CD87) is expressed in cells of the megakaryoblastic lineage.

Megakaryocytopoiesis is governed in the bone marrow microenvironment by cellular interactions that include various adhesion receptor systems and pericellular proteolysis for proper regulation of cell motility and differentiation. In order to define the role of cell surface molecules required for these processes, we searched for protease receptors on these cells. In an in vitro system utilizing different cell lines of the megakaryoblastic lineage (MEG-01, Dami), low level surface expression of the urokinase (uPA) receptor was noted. Following stimulation with phorbolester (PMA), a 3-6 fold higher expression of uPA receptor over a period of up to 5 days could be observed by fluorescent activated cell-sorting as well as by direct ligand-binding of amino-terminal fragment of uPA or vitronectin. Together with elevated expression of alpha IIb beta 3-integrin (glycoprotein IIb/IIIa complex), double immuno-fluorescence staining of stimulated cells confirmed the increased cell surface localization of uPA receptor. Semi-quantitative RT-PCR, ligand blot analysis and measurement of cell-bound proteolytic activity revealed a differentiation-dependent upregulation of the uPA receptor expression in megakaryoblastic cell lines as in monocytic cells. Due to its glycolipid anchorage, incubation with phosphatidylinositol-specific phospholipase C reduced uPA receptor-mediated ligand binding by about 60%, uPA receptor mRNA was expressed in cultured megakaryocytes derived from bone marrow, whereas no uPA receptor mRNA was detectable in platelets. These results indicate a differentiation-dependent increase in the expression of uPA receptor in megakaryoblastic cells. The characteristics of surface expression and functionality of the receptor on megakaryocytic cells may influence their maturation by regulating cellular communication in the bone marrow micro-environment.

Cell Differentiation↗
PubMed1996

Platelet dysfunction associated with experimental acute canine ehrlichiosis.

To determine whether platelet dysfunction occurs in canine ehrlichiosis, platelet aggregation studies in response to collagen/epinephrine, thrombin and adenosine diphosphate (ADP) were carried out by the indirect method, using sera from six dogs experimentally infected with Ehrlichia canis. Samples of serum taken before infection and four and 20 days after infection were tested by incubation with platelet-rich plasma from a seronegative healthy dog. Platelet aggregation was significantly inhibited in five of six infected dogs in response to at least one of the agonists used. A significant increase in preaggregation lag time was recorded in response to collagen/epinephrine in sera taken 20 days after infection from three of five dogs (P < 0.05). When compared with the preinfection values, a significant increase of 45 per cent in the mean preaggregation lag time was detected (P < 0.05). Maximal relative aggregation responses to ADP decreased significantly in one serum sample taken four days and one taken 20 days after infection (P < 0.01) and there was a significantly lower relative slope for one serum sample 20 days after infection (P < 0.05). Maximal relative aggregation responses to thrombin were significantly decreased together with their relative slopes in serum samples from two of four dogs four days after infection (P < 0.05). The results suggest that platelet dysfunction may occur in the acute stage of canine ehrlichiosis, and may be a contributing factor to the tendency to bleed commonly observed in this disease. Antiplatelet antibodies directed against platelet glycoproteins may play a role in the inhibition of platelet aggregation.

Adenosine Diphosphate↗
PubMed1996

Programmed endothelial cell death induced by an avian hemangioma retrovirus is density dependent.

Hemangiomas are localized tumors of vascular cells which appear frequently in humans and animals, and their mode of induction is unknown. Recently, a new field strain of avian retrovirus, avian hemangioma virus (AHV), was isolated from spontaneous hemangiomas in layer hens. Sequence analysis of the AHV genome revealed the presence of three prototypic retroviral genes, gag, pol, and env, but no oncogenes. AHV was capable of inducing hemangiomas in hens in vivo, but it induced a strong cytopathic effect in cultured endothelial cells. The AHV envelope glycoprotein, gp85, was found to be responsible for the cell-killing effect. Four independent lines of experimental evidence indicated that AHV induces a cytopathic effect through a typical programmed cell death, apoptosis: (i) morphological changes in cells visualized by light microscopy, (ii) nuclear condensation and fragmentation indicated by 4',6-diamidino-2- phenylindole staining, (iii) intranucleosomal degradation of DNA demonstrated by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining, and (iv) flow cytometry analysis of the DNA content of the infected cells. Quiescent endothelial G0/G1 cells were much more sensitive to AHV-induced apoptosis than actively dividing cells, suggesting that the AHV ability to induce apoptosis is dependent on the proliferative state of the infected cells.

Animals↗
PubMed1996

Low molecular weight heparin for the prevention of veno-occlusive disease of the liver in bone marrow transplantation patients.

Hepatic veno-occlusive disease (VOD), a common complication of bone marrow transplantation (BMT), is a result of intensive conditioning by chemo-radiotherapy. Endometrial injury causes fibrin deposition in the affected hepatic venules, leading to abnormal laboratory parameters followed by lethal full-blown disease. Previous studies have shown that unfractionated heparin can prevent VOD in BMT patients. Since low molecular weight heparin (LMWH) preserves the antithrombotic, but not the anticoagulant, activity of unfractionated heparin, we initiated a pilot study to determine the safety of LMWH for the prevention of VOD. Sixty-one patients undergoing BMT (allogeneic, n=24; autologous, n=37) were randomized to receive subcutaneous injection of enoxaparin (40 mg/day x 1) or a placebo prior to BMT conditioning and until day 40 after transplantation or discharge from the hospital. LMWH administration did not influence marrow engraftment, nor was it associated with bleeding tendency. Hemorrhagic events occurred significantly less frequently (P=0.025) were shorter duration (P=0.006) in the LMWH group than in the placebo group. Time to platelet recovery was significantly shorter (16.5 vs 29.6 days, (P=0.0075), and platelet transfusion requirements were lower (p=0.05) in the LMWH patients. VOD parameters occurred less frequently in the experimental group, including duration of elevated bilirubin levels (P=0.01) and incidence of hepatomegaly (P=0.04). LMWH, which seems to enhance platelet recovery, may be safely administrated to BMT patients in an attempt to prevent VOD of the liver.

Adult↗
PubMed1996

Therapy and prevention of thrombotic thrombocytopenic purpura during pregnancy: a clinical study of 16 pregnancies.

Thrombotic thrombocytopenic purpura (TTP) is a severe multisystem disorder of unknown pathogenesis, with preference to women. The mortality rate of patients with TTP was 90% until the introduction of plasma therapy that increased the survival rate to 70-80%, with minimal or no sequelae. Of the survivors, 30-60% suffer from relapses, often in association with precipitating factors such as infections, surgery, and pregnancy. Women who are either pregnant or in the postpartum period make up 10-25% of TTP patients, and once the disease occurs during a pregnancy, it tends to recur in subsequent ones. We treated five women who suffered at least one TTP episode during pregnancy. They had a total of 16 pregnancies, eight of which were complicated by TTP. They suffered seven additional TTP episodes that were not associated with pregnancy. We assessed the severity of each TTP episode with a scoring system used in our previous studies. Presented is the course of their disease and their pregnancies, and guidelines for the management and prevention of TTP during pregnancy are provided.

Adrenal Cortex Hormones↗
PubMed1996

Low molecular weight heparin stimulates megakaryocytopoiesis in bone-marrow transplantation patients.

The use of low molecular weight heparin (LMWH) as prophylaxis for veno-occlusive disease of the liver has been studied in patients undergoing bone marrow transplantation (BMT). The present study analyzes the effect of LMWH on the time course of platelet recovery after BMT. Significantly accelerated platelet recovery in conjunction with lessened requirements of platelet transfusions was observed in the LMWH-treated patients.

Anticoagulants↗