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D Mezzano

Publications and source records attributed to D Mezzano.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Hemophilia A: analysis of intron 18 and intron 7 of factor VIII gene and their role in a diagnostic strategy for carrier detection in a Chilean population].

Hemophilia A is an X-linked disorder of coagulation caused by a deficiency of factor VIII. A larger number of different mutations in the VIII gene have been identified. Thus, the detection of female carriers, depends upon the analysis of DNA polymorphisms in and near the factor VIII gene. Our aim was to develop a strategy, earlier reported, for carrier testing in families at risk of hemophilia A. In this study, we analyzed the DNA polymorphisms in 26 affected families, with use of the factor VIII intragenic polymorphisms identified by the restriction enzymes BclI and AlwNI, and by differential hybridization with sequence-specific oligonucleotide probes recognizing BclI and AlwNI polymorphism. While the DNA polymorphism detected by BcilI site in intron 18 of the factor VIII gene was informative for 38% families studied, the AlwNI/intron 7 polymorphism provided additional information (4%). The carrier status of the remaining 58% could be determined utilizing the other polymorphisms suggested by strategy. The two polymorphic sites used combined with the other polymorphisms, intragenic and extragenic, can generate levels of informativeness greater than 98%. We concluded that the strategy for carrier testing would be a good alternative in genetic counselling for hemophilia A, but its limitations must be carefully taken into account.

Chile↗
PubMed1995

Platelet autoantibodies in patients with chronic liver disease.

The thrombocytopenia in chronic liver disease (CLD) has been attributed mainly to hypersplenism, although other factors such as reduced mean life span with increased platelet turnover have also been demonstrated. Immunological abnormalities have been described in the pathogenesis and progression of CLD. In this sense, many studies have reported elevated levels of platelet associated IgG (PAIgG) in patients with CLD, and it has been suggested that PAIgG could represent true antiplatelet antibody. In this study we used a glycoprotein (GP)-specific immunoassay (MACE) to determine whether PAIgG or circulating antiplatelet antibodies, reacted against the GPIIb/IIIa or GPIb/IX complexes, in patients with CLD. Thirty-six patients with CLD of diverse etiology were studied (20 female, mean age 53 years, range 38-75 years). 23 out of 36 patients (64%) had anti-GP antibodies in MACE. Particularly, 12 had anti-GPIb, 4 anti-GPIIb/IIIa, and 7 had both types of autoantibodies. The existence of these anti-GP antibodies was not related with the blood platelet count or etiology of CLD. These data show that in patients with CLD of diverse origin, there is a high prevalence of autoantibodies reacting specifically with platelet membrane GP, which constitutes the first evidence of the specific nature of platelet-bound IgG in CLD. These findings suggest that in patients with CLD, an immune mechanism may participate in inducing or aggravating the thrombocytopenia.

Adult↗
PubMed1995

Decreased platelet counts and decreased platelet serotonin in poststreptococcal nephritis.

Mean platelet survival time in patients with acute poststreptococcal glomerulonephritis (APSGN) is reduced to 50-60% of the control values, and glomerular deposits of platelet factor 4 are found in these patients. In order to investigate further systemic platelet changes of pathogenic, clinical or prognostic significance, we measured the platelet serotonin (5-HT) content and the blood platelet counts during the 1st week of the disease in 27 patients with APSGN. Platelet 5-HT was significantly reduced in patients with APSGN as compared with patients with impetigo without glomerular involvement (785 +/- 54 vs. 1,329 +/- 94 ng 5-HT/10(9) platelets; p < 0.001). Similarly, the mean blood platelet count was reduced to 247 +/- 16 x 10(3) as compared with 303 +/- 14 x 10(3) in the controls (p < 0.05). Thirteen (48%) of these patients had individual values of platelet 5-HT lower than the 95% confidence interval calculated in the control group. No significant correlation was observed between the concentration of 5-HT and either the severity of the disease judged by the amount of urinary protein excretion and the serum creatinine value or the presence of circulating immune complexes. Significant correction of the platelet 5-HT content (to 1,180 +/- 111 ng/10(9) platelets; p < 0.01) and of the platelet counts (to 309 +/- 21 x 10(3); p < 0.01) were observed in the longitudinal study at least 2 weeks later. Platelet activation, with secretion of granular content and increased consumption, may explain these findings. Additionally, the reduced mean age of the circulating platelets could contribute to their decreased 5-HT levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

Bleeding time in preeclampsia.

The association of preeclampsia with thrombocytopenia and prolonged bleeding time is reported. The analysis of bleeding time (Simplate II) and the platelet count (Automatic Coulter Counter) in 41 patients with different grades of preeclampsia is presented. Our results suggest that the decrease in the bleeding time observed in moderate preeclampsia and the increase observed in severe preeclampsia are not mainly dependent on the platelet count.

Adult↗
PubMed1994

[Evaluation of commercial kits used for Chagas disease diagnosis in blood banks in Chile. II. Routine application].

Aiming to study the applicability and reproducibility of four commercial kits used for the serological detection of Chagas disease (Chagatest-Inst Invest Paraguay, Ortho Chagas, Abbott Chagas (ELISA tests) and Estabilgen Hemo Chagas (indirect hemagglutination test)), a comparative serological study was performed in 256 sera samples coming from a highly endemic area, 249 samples from a low endemic area, 180 reference sera and 2264 samples coming from three blood banks. Specificity of the kits was excellent and sensitivity ranged from 60 to 100%. The indirect hemagglutination test has the lower sensitivity. Some disagreements in the results were observed in the three blood banks, probably due to an unsatisfactory reactive management. We conclude that ELISA tests should be recommended for routine detection of Chagas disease and that for this purpose, a net of laboratories under the direction of a national reference center should exist. This center should assess new commercial products, train technicians and supervise the laboratories.

Blood Banks↗
PubMed1994

Accumulation of 5-hydroxytryptamine by aging platelets: studies in a model of suppressed thrombopoiesis in dogs.

Thrombocytopenia was induced in healthy, male mongrel dogs by intramuscular injection of a single dose of estradiol valerate (1 mg/kg). A steady, almost linear decay of the blood platelet count starting about day 6 post-estradiol and attaining a mean value of 14 x 10(3) platelets/microliters one week later was observed. Thrombocytopenia is explained mainly by suppression of thrombocytopoiesis, as established by two independent ways: 1. Megakaryocytes in the bone marrow were markedly reduced. 2. Kinetic studies with 111In labeled autologous platelets revealed a nearly linear decay of the radioactivity and mean survival times within the expected range. The progressive reduction in the platelet count is associated with an increase in the mean age of the platelets still circulating. Following estradiol injection, platelet 5-hydroxytryptamine (5-HT) increased from a basal value of 130 +/- 30 ng/10(8) platelets (platelet count of 351 +/- 53 x 10(3) platelets/microliters) to 343 +/- 100 ng/10(8) platelets eleven days latter, when the platelet count dropped to 32 +/- 18 x 10(3) platelets/microliters. No significant changes in the number or affinity of the 5-HT uptake receptors could be demonstrated in platelets exposed in vitro and in vivo to estradiol. Our results indicate that aging platelets accumulate 5-HT, probably by a sustained exposure to the monoamine in plasma, confirming previous observations based on models in which thrombopenia was induced by immune and mechanical means.

Animals↗
PubMed1993

[Diagnosis of von Willebrand's disease subtypes by the analysis of multimeric composition of plasma von Willebrand factor].

The accurate diagnosis of the type of von Willebrand's disease (vWD) is important for a better understanding of its pathogenesis and for adequate treatment decision. We assessed the usefulness of the analysis of the multimeric composition of von Willebrand factor (vWF) in the diagnosis of vWD variants. vWF is purified by gel filtration and polyclonal, heterologous antibodies are raised in rabbits, which are immunopurified and radioiodinated. These are used to reveal, by autoradiography, the bands of vWF of various molecular weights separated by electrophoresis in agarose gels. This procedure reveals that 74 (80%) out of 92 patients with vWD suffer the classic type (I) of the disease, 6 (6.5%) type as IIA, 6 (6.5%) as IIB and 6 (6.5%) as III. The test is necessary for the correct classification of the patients, but is complex, laborious and expensive; it should be performed in patients with high probability of vWD or after the generic diagnosis of vWD has been made.

Adolescent↗
PubMed1992

Total sialic acid in human and canine platelets does not change with the platelet age.

Total platelet sialic acid (SA) was measured in three experimental conditions: (1) human and canine platelet density subpopulations obtained by centrifugation in arabinogalactan gradients, (2) circulating canine platelets during recovery from experimental immune and mechanical thrombocytopenias, and (3) platelets obtained from a patient with chronic immune thrombocytopenic purpura before and after splenectomy. The density of human and canine platelets is, in part, determined by their age. We found no significant differences in total SA between high-density (HD) and low-density (LD) platelets (9.32 +/- 2.0 vs. 9.55 +/- 1.3 micrograms/mg of platelet protein in dogs and 9.02 +/- 2.3 vs. 9.10 +/- 2.9 micrograms/mg in humans). In the human and canine thrombocytopenic models, the entrance of new platelets from the bone marrow is followed by their aging in the circulation. In these models, no significant changes in total SA content were detected in sequential measurements during the recovery of the thrombocytopenia. Accordingly, we conclude that total SA in human and canine platelets is unrelated to their age in circulation. These results do not support the notion that the loss of SA from membrane glycoproteins determines the recognition and removal of platelets from the circulation.

Animals↗
PubMed1992

Glomerular localization of platelet factor 4 in streptococcal nephritis.

Since platelet factor 4 (PF4), a cationic (pI 7.6) platelet secretory protein, binds avidly to glomerular polyanions both in vitro and in vivo, and is implicated in neutrophil chemotaxis, we studied by indirect immunofluorescence microscopy the presence of PF4 deposits in glomeruli of patients with poststreptococcal nephritis (APSGN). Goat antihuman PF4 serum was used as primary antibody and fluorescein-conjugated IgG fraction of rabbit antigoat IgG as second antibody. Controls consisted of nonimmune goat serum or anti-PF4 serum preabsorbed with human PF4, as primary antibodies. Glomerular deposits of PF4 were demonstrated in renal tissues obtained by biopsy in 14 of 20 patients studied; the deposits were particularly intense in 9 patients. PF4 was bound to the mesangium and to the capillary walls. There was a significant positive correlation between intraglomerular deposits of PF4 and the levels of proteinuria (p = 0.024). These findings provide further evidence for a role of platelets in the pathogenesis of APSGN and suggest that PF4 may contribute to alter the glomerular permeability in this disease.

Adult↗
PubMed1992

[Frequency of platelet specific alloantigens HPA-1a (P1A1) and HPA-4a (Pen(a)) expression in Chilean population].

The phenotype frequency of platelet-specific alloantigens has been reported to vary with the ethnic composition of the population under study and the only two HPA-4a negative individuals found in the United States were of Hispanic origin; therefore, the aim of this work was to define the frequency of expression of these systems in the Chilean population. Using an ELISA with captured antigen by monoclonal antibodies, 604 blood donors were typed for the platelet-specific antigen systems HPA-1 and HPA-4. Eight samples typed negative for HPA-1a (1.32%) and 596 typed positive (98.68%). The calculated gene frequencies were 0.88 for HPA-1a (gene frequency > 0.99). Since these antigens are involved in thrombocytopenic disorders such as neonatal alloimmune thrombocytopenia and post-transfusion purpura, their frequency in a population is of clinical relevance. The gene frequency found for HPA-1a is higher than in Europeans (0.85) and lower than in Mapuche Indians (0.99), which is to be expected from the ethnic origin of our population. The absence of HPA-4a negatives in this study does not support our original hypothesis of a higher polymorphism of this system among hispanics.

Antigens, Human Platelet↗
PubMed1992

[Neonatal autoimmune purpura: laboratory study of 5 cases].

Maternal alloimmunization against fetal platelets can cause fetal and neonatal thrombocytopenia. We report our experience in the study of five cases with severe neonatal-thrombocytopenia. Using an ELISA with antigen capture and other serologic tests on platelets, we investigated the sera of the five mothers. Sera from four mothers contained a platelet-specific alloantibody, anti-HPA-1a (PlA1) whereas the platelets typed as HPA-1b/b. In one case despite extensive serological investigation and clinically unequivocal diagnosis of AINT, no antibodies were demonstrated. The use of monoclonal antibodies for antigen immobilization, showed to be a reliable and sensitive test for the detection and identification of platelet antibodies in AINT. These techniques could also be used in the follow-up of patients at risk (e.g. pregnant HPA-1b/b women) and in the screening of blood donors lacking of certain antigens, whose platelets are collected to be transfused in patients with platelet-specific antibodies.

Antigens, Human Platelet↗
PubMed1991

Platelet 5-hydroxytryptamine increases with platelet age in dogs.

Thrombocytopenia was induced in mongrel dogs by two mechanisms: immunologically, by intravenous injection of heterologous antiplatelet antibody, and non-immunologically, by circulating the blood through glass beads in anesthetized animals. The platelet content of 5-HT was monitored before and during the recovery of the blood platelet counts. This period is associated with the normalization of the mean platelet survival time and with a progressive increase in the mean age of the circulating platelet population. A continuous increment in platelet 5-HT closely followed the increase in platelet counts in both models of thrombocytopenia, and a strong correlation was found between the platelet age and 5-HT content. These findings support the concept that platelets accumulate 5-HT during their physiological aging process, contradicting the notion that a negative balance in 5-HT content results at the end of their physiological lifespan in circulation. These results are not in conflict with the concept that circulating platelets release and re-uptake 5-HT.

Animals↗
PubMed1990

Palmitoyl-CoA and the acyl-CoA thioester of the carcinogenic peroxisome-proliferator ciprofibrate potentiate diacylglycerol-activated protein kinase C by decreasing the phosphatidylserine requirement of the enzyme.

To gain insight into the mechanism by which long-chain acyl-CoA thioesters potentiate diacylglycerol-activated protein kinase C, the cofactor dependence of this activating effect was studied with purified rat brain enzyme and histone H1 as substrate. Using two different assay systems, palmitoyl-CoA was found to decrease greatly the amount of phosphatidylserine required to activate the kinase. No relative changes were observed in the dependence of the enzyme for other cofactors (diacylglycerol, ATP, and Ca2+) in the presence of palmitoyl-CoA. The potentiating effect of palmitoyl-CoA and the decrease in phosphatidylserine requirement of the kinase was also demonstrated using the 47-kDa protein of human platelets as substrate and platelet protein kinase C as source of enzyme. The acyl-CoA thioester of the carcinogenic peroxisome-proliferator ciprofibrate was also found to decrease the phosphatidylserine requirement of protein kinase C. The data suggest that acyl-CoAs may play a role in the regulation of protein kinase C activity.

Acyl Coenzyme A↗
PubMed1990

[von Willebrand's disease].

von Willebrand's disease is the most frequent congenital disorder of primary hemostasis; it is transmitted in an autosomal manner and according to type there is an alteration in structure, function and/or synthesis or release of von Willebrand's factor. Patients present with muco-cutaneous hemorrhages of varying severity. Significant advances in the understanding of the molecular defect and laboratory diagnosis of the different subtypes of the disease have been made in the last years, but we still face the emergence of new subtypes and the difficulties posed by the genetic, clinical and laboratory variability of the disorder.

Humans↗