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M Contreras

Publications and source records attributed to M Contreras.

At least 19 recordsLinked to original sources
PubMed1992

[Serologic diagnosis of Lyme disease in patients with undifferentiated arthritis. Diagnostic problems].

BACKGROUND: Arthritis is a frequent manifestation of Lyme disease. The diagnosis of this disease is especially supported by serological techniques which however have false positives or negatives. The aim of this study was to establish the frequency of serologies positive to Borrelia burgdorferi in patients with non-filiated arthritis and in other well defined rheumatic diseases. METHODS: A prospective study was performed to detect antibodies (AB) versus Borrelia burgdorferi in 43 patients with undifferentiated arthritis and in 100 patients with articular disease of precise diagnosis (rheumatoid arthritis, systemic lupus erythematosus, psoriasis arthropathy, and reactive arthritis/Reiter's syndrome). The technique was performed by indirect immunofluorescence and was repeated by enzymoimmunoassay in doubtful or positive results. Titers greater than 1/256 were considered as positive. RESULTS: Positive serology was found in two patients with undifferentiated arthritis and in one patient with Reiter's syndrome. None of the three patients referred the antecedent of erythema chronicum migrans. Positive serology was not observed in any of the patients with rheumatoid arthritis, systemic lupus erythematosus or psoriatic arthritis. CONCLUSIONS: A small proportion of patients with undifferentiated arthritis or Reiter's syndrome presented positive serology at low titers versus Borrelia burgdorferi with the interpretation of these results being difficult. The frequency of seropositivity in rheumatoid arthritis and systemic lupus erythematosus is very low.

Adult↗
PubMed1992

Transport of fatty acids into human and rat peroxisomes. Differential transport of palmitic and lignoceric acids and its implication to X-adrenoleukodystrophy.

The different topology of palmitoyl-CoA ligase (on the cytoplasmic surface) and of lignoceroyl-CoA ligase (on the luminal surface) in peroxisomal membranes suggests that these fatty acids may be transported in different form through the peroxisomal membrane (Lazo, O., Contreras, M., and Singh, I. (1990) Biochemistry 29, 3981-3986), and this differential transport may account for deficient oxidation of lignoceric acid in X-adrenoleukodystrophy (X-ALD) (Singh, I., Moser, A. B., Goldfisher, S., and Moser, H. W. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 4203-4207). To define the transport mechanism for these fatty acids through the peroxisomal membrane and its possible implication to lignoceric acid metabolism in X-ALD, we examined cofactors and energy requirements for the transport of palmitic and lignoceric acids in isolated peroxisomes from rat liver and peroxisomes isolated from X-ALD and control fibroblasts. The similar rates of transport of palmitoyl-CoA (87.6 +/- 6.3 nmol/h/mg protein) and palmitic acid in the fatty acid activating conditions (83.4 +/- 5.1 nmol/h/mg protein) and lack of transport of palmitic acid (4% of palmitoyl-CoA transport) when ATP and/or CoASH were removed or substituted by alpha,beta-methyleneadenosine-5'-triphosphate (AMPCPOP) and/or desulfoCoA-agarose from assay medium clearly demonstrate that transport of palmitic acid requires prior synthesis of palmitoyl-CoA by palmitoyl-CoA ligase on the cytoplasmic surface of peroxisomes. The 10-fold higher rate of transport of lignoceric acid (5.3 +/- 0.6 nmol/h/mg protein) as compared with lignoceroyl-CoA (0.41 +/- 0.11 nmol/h/mg protein) and lack of inhibition of transport of lignoceric acid when ATP and/or CoASH were removed or substituted with AMPCPOP or desulfoCoA-agarose suggest that lignoceric acid is transported through the peroxisomal membrane as such. Moreover, the lack of effect of removal of ATP or substitution with AMPOPCP (a nonhydrolyzable substrate) demonstrates that the translocation of palmitoyl-CoA and lignoceric acid across peroxisomal membrane does not require energy. The transport, activation, and oxidation of palmitic acid are normal in peroxisomes from X-ALD. The deficient lignoceroyl-CoA ligase (13% of control) and oxidation of lignoceric acid (10% of control) as compared with normal transport of lignoceric acid into peroxisomes from X-ALD clearly demonstrates that pathogenomonic accumulation of very long chain fatty acids (greater than C22) in X-ALD is due to the deficiency of peroxisomal lignoceroyl-CoA ligase activity.

Acyl Coenzyme A↗
PubMed1992

Mononuclear phagocyte assays, autoanalyzer quantitation and IgG subclasses of maternal anti-RhD in the prediction of the severity of haemolytic disease in the fetus before 32 weeks gestation.

In 40 cases of haemolytic disease of the fetus due to RhD immunization where the fetus required intrauterine transfusion, fetal packed cell volume was compared with the following parameters of maternal anti-D: (a) concentration, (b) IgG subclass, (c) activity in a macrophage binding assay, and (d) activity in a monocyte antibody-dependent cell mediated cytotoxicity (ADCC) assay. The anti-D concentration exceeded 4 iu/ml in all cases, correctly indicating the risk of haemolytic disease. A relationship between IgG subclass composition of the anti-D and severity of anaemia was not observed; IgG1, IgG3 and IgG1 + 3 antibodies were all detected. The ADCC assay gave the best correlation between assay results and fetal packed cell volume; high results correctly indicated fetal anaemia in 95% of cases. Macrophage binding assay results were only considered as high in 70% of cases. Overall, these results indicate that serological tests and bioassays in highly immunized mothers may not generate any information that proves more useful than ultrasonography and their previous obstetric history.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1992

Guidelines for the use of fresh frozen plasma. British Committee for Standards in Haematology, Working Party of the Blood Transfusion Task Force.

Fresh frozen plasma should only be used to treat bleeding episodes or prepare patients for surgery in certain defined situations. Definite indications for the use of FFP: 1. Replacement of single coagulation factor deficiencies, where a specific or combined factor concentrate is unavailable. 2. Immediate reversal or warfarin effect. 3. Acute disseminated intravascular coagulation (DIC). 4. Thrombotic thrombocytopenic purpura (TTP). Conditional uses: FFP only indicated in the presence of bleeding and disturbed coagulation: 1. Massive transfusion. 2. Liver disease. 3. cardiopulmonary bypass surgery. 4. Special paediatric indications. No justification for the use of FFP: 1. Hypovolaemia. 2. Plasma exchange procedures. 3. 'Formula' replacement. 4. Nutritional support. 5. Treatment of immunodeficiency states.

Adult↗
PubMed1992

U.K. multicentre study on blood donors for surrogate markers of non-A non-B hepatitis. Part I: Alanine transferase and anti-HBc testing.

Blood samples from 9,215 blood donors in three U.K. centres (North London, Bristol and Manchester) were tested for their alanine aminotransferase (ALT) level and the presence of anti-HBc and anti-HCV. This paper presents the results of the ALT and anti-HBc tests. The prevalence of ALT > 45 IU/l was 3.1% overall (North London 3.06%, Bristol 4.56% and Manchester 1.97%). Manchester results were skewed by the methodology used for ALT measurement, highlighting the need for standard test methods. Anti-HBc was detected using the Wellcome enzyme-immunosorbent assay (EIA) and confirmatory testing was performed using a radioimmunoassay (RIA) and the Corecell haemagglutination assay. Repeat reactive rates were 0.9, 0.79 and 0.94% for North London, Bristol and Manchester, respectively, with an overall rate of 0.9%. The confirmed positive rate was 0.73, 0.53 and 0.65% for the three centres with an overall rate of 0.63%. Donors with an ALT > 45 IU/l, or with confirmed anti-HBc, were interviewed with a medical questionnaire for risk factors. The major contributing factors in donors with a raised ALT were alcohol consumption and obesity.

Adolescent↗
PubMed1992

Severe haemolytic disease in an infant born to an Rh(null) proposita.

A 35-year-old Brazilian woman (gravida 4, para 2) was delivered of a severely anaemic child whose cord red blood cells had a strongly positive direct antiglobulin test and who required two exchange transfusions within 24 h of birth. Because of the emergency of the situation and the lack of a local immunohaematology reference laboratory, the phenotype of the mother and the specificity of the relevant antibody could not be determined. Hence, compatible blood was not immediately available and the infant had to be given repeated exchange transfusions with incompatible group 0 Rh-negative blood. The infant is now healthy and thriving. The mother's red cells were subsequently found to lack all the antigens of the Rh system, and her serum reacted with all red cell samples except those of two unrelated Rh(null) individuals. Her serum gave high titres (i.e. 1,024-4,096) by the indirect antiglobulin test against red cells of normal Rh phenotype, as well as against cells with partially deleted Rh phenotypes (titres = 128-512 with -D-/-D- and .D./.D. samples, respectively), and was extremely active in antibody-dependent cell-mediated cytotoxicity and monocyte monolayer assays against red cells of normal Rh phenotypes.

Adult↗
PubMed1992

[Clinical significance of platelet antigens].

During the last years, platelet immunology has shown an accelerated progress associated with the development of new highly specific and sensitive techniques. This progress has allowed the description of many new "platelet specific" alloantigens. In 1990, an International Workshop on Platelet Serology of the ISBT and ISH grouped the accepted alloantigens into five systems, named HPA-1 to HPA-5. Recent progress in molecular genetics techniques has also enabled the definition of the primary molecular structure of platelet glycoproteins which carry the specificity of the platelet-specific antigens. From the clinical point of view, the role of immunization against platelet-specific alloantigens has been established in neonatal alloimmune thrombocytopenia and in posttransfusion purpura, with anti-PIA1 (anti-HPA-1) being the antibody most frequently involved. An adequate diagnosis and management of these conditions can avoid devastating consequences like severe bleeding and even death. Associated with an increase in the administration of platelet transfusions, immunological refractoriness to platelet transfusions limits the benefits of such therapy, in most cases associated with HLA antibodies. Refractoriness can be efficiently prevented to large extent by using leucocyte-poor blood components in multitransfused patients.

Antigens, Human Platelet↗
PubMed1992

[The need for national transfusion services].

Continuing advances in medical and surgical treatment have resulted in increasing demands for blood and blood derivatives. In most developed countries and in many developing ones, the blood transfusion services are organised centrally either as National Blood Transfusion Services or under the auspices of organisations such as the League of Red Cross or Red Crescent Societies. Centrally organised services have been shown clearly to be superior to hospital based transfusion services. Although hospital based services may be a convenient alternative under certain circumstances, in most cases there is inefficient use of resources and difficulties in setting, achieving and enforcing quality standards. This is so particularly in developing countries. The need to change from a remunerated or replacement donor system is emphasised, with the ultimate goal being national self-sufficiency in blood and blood derivatives. Attention is also drawn to the importance of education and motivation of staff working in the blood transfusion services if these objectives are to be met.

Blood Banks↗
PubMed1992

Anti-HBs detection: a modified passive haemagglutination assay.

Modification of a commercial haemagglutination assay for the detection of anti-HBs has reduced the test time from over one hour to approximately 25 min. increased sensitivity ten-fold without any prozoning, maintained specificity and reduced costs by 90%. The modification consists of diluting the reagent cells ten-fold; these are then added to dilutions of test serum in a V-well microplate. After incubation, plates are centrifuged and then inclined at 70 degrees. Positive and negative reactions can be clearly distinguished within approximately 10 minutes.

Animals↗
PubMed1991

Low incidence of non-A, non-B post-transfusion hepatitis in London confirmed by hepatitis C virus serology.

To see whether the introduction of screening tests for post-transfusion non-A, non-B hepatitis (NANBH) in the UK would be worth while, the incidence of such hepatitis was assessed among patients receiving blood during operations at five hospitals served by the North London Blood Transfusion Centre. 387 patients, who each received blood or blood components from an average of 3 donors were followed up prospectively and blood samples were taken every 2 weeks for 3 months and then each month for a further 3 months. 229 patients also provided a sample at 12 months. All available patient and donor samples were tested for alanine aminotransferase concentrations and for antibody to hepatitis C virus (anti-HCV) by ELISA. Repeatedly anti-HCV positive samples were submitted to supplementary HCV assays. 1 of the 387 patients showed biochemical evidence of acute post-transfusion NANBH after exclusion of non-viral causes. Anti-HCV developed in this patient and the seroconversion was confirmed by recombinant immunoblot assay and polymerase chain reaction. Serum from 1 of the 8 donors whose blood he received was positive for anti-HCV by all three methods. In another patient HCV seroconversion was shown by ELISA but alanine aminotransferase concentrations remained normal throughout follow-up. His samples and those of his 2 donors were negative for HCV by the polymerase chain reaction. A third patient showed rises in alanine aminotransferase compatible with post-transfusion NANBH, but serology and polymerase chain reaction assays for HCV were negative for her samples and those of her donors. Anti-HCV reactivity likely to be false positive (negative by both confirmatory tests and no adverse effects in recipients) was seen in 6 of 1283 donors. This study, despite its being carried out in the part of the UK with the highest frequency of infectious markers in blood donations, has shown a very low incidence of post-transfusion NANBH.

Acute Disease↗
PubMed1991

Effect of ciprofibrate on the activation and oxidation of very long chain fatty acids.

The effect of ciprofibrate, a hypolipidemic drug, was examined in the metabolism of palmitic (C16:0) and lignoceric (C24:0) acids in rat liver. Ciprofibrate is a peroxisomal proliferating drug which increases the number of peroxisomes. The palmitoyl-CoA ligase activity in peroxisomes, mitochondria and microsomes from ciprofibrate treated liver was 3.2, 1.9 and 1.5-fold higher respectively and the activity for oxidation of palmitic acid in peroxisomes and mitochondria was 8.5 and 2.3-fold higher respectively. Similarly, ciprofibrate had a higher effect on the metabolism of lignoceric acid. Treatment with ciprofibrate increased lignoceroyl-CoA ligase activity in peroxisomes, mitochondria and microsomes by 5.3, 3.3 and 2.3-fold respectively and that of oxidation of lignoceric acid was increased in peroxisomes and mitochondria by 13.4 and 2.3-fold respectively. The peroxisomal rates of oxidation of palmitic acid (8.5-fold) and lignoceric acid (13.4-fold) were increased to a different degree by ciprofibrate treatment. This differential effect of ciprofibrate suggests that different enzymes may be responsible for the oxidation of fatty acids of different chain length, at least at one or more step(s) of the peroxisomal fatty acid beta-oxidation pathway.

Activation Analysis↗