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Biomedical subjects

M Contreras

Publications and source records attributed to M Contreras.

At least 73 records · Page 4Linked to original sources
PubMed1996

Evaluation of anastomotic hyperplasia progression using the cyclin specific antibody MIB-1.

BACKGROUND: Delayed failure of prosthetic arterial grafts is primarily due to the development of anastomotic intimal hyperplasia. This report follows the proliferation of smooth muscle cells that ensues after prosthetic arterial grafting, using the cyclin-specific antibody MIB-1. METHODS: Six-mm expandable polytetrafluoroethylene (ePTFE) grafts were placed end-to-end in the carotid arteries of mongrel dogs. Animals were randomly assigned to sacrifice intervals of 2, 7, 14, and 30 days. Serial coronal sections were cut and immunohistocytochemistry performed using the MIB-1 antibody. RESULTS: The control carotid artery had no definable proliferation. Two days after grafting, there was brisk proliferation in the upper one third of the arterial media. By 7 days, proliferation and migration of smooth muscle cells was seen above the internal elastic lamina, in which 50% of the cells were MIB-1 positive. Fourteen days after graft placement, proliferation continued in the neointima; however, the proliferation index was diminished compared with previous time intervals. At 30 days, despite a dramatic increase in lesional increase, there was a marked decrease in the overall proliferation of cells. CONCLUSIONS: Following placement of a prosthetic arterial graft, there is initial brisk proliferation of cells in the arterial media, with migration, ongoing proliferation, and resultant development of a localized cellular neointima. Over a 30-day period, the percentage of cells proliferating subsides in contrast to the progressive increase in the size of the neointima. Immunohistocytochemistry with the MIB-1 antibody is a useful tool in defining the cellular kinetics after prosthetic arterial grafting.

Anastomosis, Surgical↗
PubMed1996

Cytokine levels in platelet concentrates: quantitation by bioassays and immunoassays.

Some adverse reactions to the transfusion of platelet concentrates (PCs) cannot be attributed to antibodies against blood cells or to subclinical microbial agents. It has been suggested that leucocyte-derived inflammatory cytokines such as interleukin (IL)-1, IL-6 and tumour necrosis factor (TNF) may contribute to a larger number of unexplained non-antibody-mediated adverse reactions. Three types of PCs, containing different levels of leucocytes, are currently produced. Filtration is used on demand to further reduce leucocyte contamination of these components. we have monitored the plasma of PCs prepared by the platelet-rich plasma method (PRP), the buffy-coat method or by apheresis for IL-6, IL-1, transforming growth factor-beta (TGF-beta), TNF and interferon gamma (IFN gamma). Biologically active IL-6 increased in stored PRP-PCs from a mean of 140 pg/ml on day 1 to 2395 pg/ml on day 5/6. Elevated levels of IL-8, as detected by immunoassay, were evident in PRP-PCs during routine storage under blood bank conditions. Small amounts of immunoreactive IL-1 with only minimal biological activity were present in some PRP-PCs by day 5/6. No significant increase in the levels of IL-8, IL-6 or IL-1 were seen in buffy-coat PCs during storage for 5/6 d. For apheresis PCs, an increase in IL-8 content, but not in IL-6 over 6 d was observed. In all three types of PCs, elevated amounts of both bioactive and immunoreactive TGF beta were present, but there was no evidence of any biologically active or immunoreactive TNF alpha. Pre-storage filtration of PRP-PCs for depletion of leucocytes prevented the increase in IL-8 and IL-6 levels of these PCs. Our results show that leucocyte reduction by buffy-coat method reduces cytokine levels to a comparable level to filtered or apheresis PCs, containing low levels of leucocytes, but use of these PCs in minimizing the severity and incidence of reactions in recipients will require clinical evaluation. This is the first comprehensive and comparative study which, on the basis of biological activity of cytokines, directly indicates that the mode of platelet production grossly influences the levels of cytokines.

Biological Assay↗
PubMed1996

Myelodysplastic syndrome with karyotype abnormality is associated with elevated F-cell production.

A sensitive F-cell assay has been used to examine the production of fetal haemoglobin (Hb F) in a group of 77 adult patients with myelodysplastic syndrome (MDS), and a control group composed of 100 normal blood donors. Although the mean F-cell percentage in the MDS group (6.0%) is not statistically different from that in the normal blood donors (3.1%), a higher proportion of myelodysplastic patients have elevated F-cell values and the magnitude of the increases is greater than that observed in blood donors. In order to investigate the association further, the karyotypes of the MDS patients have been examined. 13/21 (61.9%) of the MDS patients with karyotypic abnormalities have F-cell values > 5%, compared to only 6/56 (10.9%) of the MDS patients with a normal karyotype and 11/100 (11%) of the blood donors. The observed difference in the distributions of F cells between the two subgroups of patients with MDS is highly significant (P < 0.0001).

Adult↗
PubMed1996

A prospective study of the incidence of red cell allo-immunisation following transfusion.

To establish the incidence and timing of red cell allo-immunisation following transfusion, pretransfusion and serial post-transfusion samples were screened for allo-antibodies in a total of 452 patients who had undergone elective surgery. Antibody screening was performed by 2-stage papain, manual polybrene and indirect antiglobulin techniques (IAT). Red cell allo-antibodies were found in 42 patients and 38 of these (8.4% overall) demonstrated antibodies only after transfusion; 76% of them had Rh specificity. This rate of red cell allo-immunisation is higher than what would be expected if transfused patients were tested only once post-transfusion, as has been the case in several previous studies. For the type of patients studied, this finding may not be of clinical relevance at present because most patients undergoing elective surgery do not require further transfusion in their lifetime. However, this is changing with the longer life expectancy of the population and the increased probability of repeat surgery. Twenty-two (58%) of the antibodies were initially detected by the 2-stage papain and/or polybrene techniques, when the IAT was negative, although later 19 became positive by IAT; this added sensitivity of techniques other than the IAT, to detect early allo-immunisation may be relevant in pretransfusion testing to prevent haemolytic transfusion reactions in patients requiring repeated transfusions.

Adult↗
PubMed1996

Bronchoalveolar oxyradical inflammatory elements herald bronchopulmonary dysplasia.

OBJECTIVES: To quantify oxyradical inflammatory markers in serial endotracheal tube aspirates obtained from premature neonates at risk for developing bronchopulmonary dysplasia, and to correlate these parameters with clinical manifestations of the disease. DESIGN: Prospective cohort study. SETTING: Tertiary neonatal intensive care unit. PATIENTS: Twenty-eight intubated, premature infants, with 15 infants displaying simple respiratory distress syndrome and 13 infants eventually developing bronchopulmonary dysplasia. INTERVENTIONS: Endotracheal tube aspirates were collected and clinical severity scores were calculated longitudinally from an inception cohort during the first week of life. Diagnosis of bronchopulmonary dysplasia by standard criteria was recorded at 30 days of life. Various biochemical analyses related to pulmonary oxyradical stress were determined on endotracheal tube aspirates and were normalized according to the magnitude of serum/aspirate urea ratios. The demographic, illness severity, and biochemical characteristics of infants with simple respiratory distress syndrome and those characteristics of infants developing bronchopulmonary dysplasia were evaluated by masked comparison. MEASUREMENTS AND MAIN RESULTS: Populations of respiratory distress syndrome and bronchopulmonary dysplasia infants could be differentiated during the first week of life by means of the following parameters: gestational age; birth weight; Score of Neonatal Acute Physiology; Neonatal Therapeutic Intervention Scoring System; epithelial lining fluid leukocytes; elastase; myeloperoxidase; xanthine oxidase and catalase enzyme activities; and total sulfhydryls. CONCLUSIONS: Infants with simple respiratory distress syndrome could be segregated from those infants who developed bronchopulmonary dysplasia by the magnitude of the epithelial lining fluid oxyradical inflammation markers. While infants developing bronchopulmonary dysplasia typically exhibited increased concentrations of these markers during the first week of life, those infants with simple respiratory distress syndrome displayed low, uniform, or decreasing values of these markers over this interval. Infants developing bronchopulmonary dysplasia demonstrate an early pulmonary inflammatory response, and one key aspect of this response involves various oxyradical-generating systems.

Bronchi↗
PubMed1996

Prenatal testing to predict the severity of hemolytic disease of the fetus and newborn.

The severity of hemolytic disease of the fetus or newborn can be assessed with certainty only by measurement of fetal parameters. However, these invasive procedures are not without risk for the fetus. Most erythrocyte antibodies do not cause significant hemolytic disease of the fetus or newborn and various assays are available to assist obstetricians in predicting the likely effect of maternal alloantibodies on fetal erythrocytes. Initially, immunohematologic tests are performed on maternal serum to identify antibodies with a potential for causing hemolytic disease of the fetus or newborn. Antibody concentration is measured by indirect antiglobulin technique titration, or where possible (for anti-D or -c), by quantitation. When used consecutively throughout pregnancy, these tests will reveal a trend that helps to predict the likelihood of hemolytic disease of the fetus or newborn. Functional assays (antibody-dependent cell-mediated cytotoxicity and chemiluminescence) are probably superior to serologic tests for predicting hemolytic disease of the fetus or newborn. Unfortunately, the assays do not reflect accurately the in vivo conditions for a given patient. Knowledge of the immunoglobulin subclass can help to assess the hemolytic potential of maternal antibody, but quantitative measurement of subclasses is still experimental. Diagnostic testing should be approached in a structured manner, commencing with simple serology, followed, in selected cases, by more complex functional assays and indirect fetal tests to identify those fetuses at greatest risk. This approach will enable direct fetal tests to be undertaken only when there is strong suspicion of severe hemolytic disease of the fetus or newborn.

Erythroblastosis, Fetal↗
PubMed1996

Significantly reduced expression of the proteoglycan decorin in Alzheimer's disease fibroblasts.

Aims-To investigate whether proteoglycan synthesis is altered in skin fibroblasts in patients with Alzheimer's disease compared with normal subjects.Methods-Cell lines obtained from donors with Alzheimer's disease and healthy controls were incubated with radioactive sulphate. The proteoglycans synthesised were determined and analysed by chromatographic, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and glycosaminoglycans-lyase treatment. The amount of decorin synthesised by each cell line was quantified using western blot analysis. Transcripts for human decorin were determined using northern blot analysis.Results-No significant changes in total sulphate incorporation and glycos-aminoglycan (GAG) composition were detected in the incubation media of these cells. However, chromatographic and SDS-PAGE analysis of the proteoglycans secreted by the cell lines showed that a dermatan sulphate proteoglycan of 150-125 kilodaltons was substantially reduced in Alzheimer's disease fibroblasts. The molecular characteristics of this proteoglycan correspond to decorin. Western blot analysis indicated that decorin was reduced in Alzheimer's disease incubation medium compared with normal medium. Northern blotting indicated that in Alzheimer's disease fibroblasts decorin transcripts were significantly reduced compared with normal fibroblasts. Glypican concentrations, a cell surface heparan sulphate proteoglycan, remained the same.Conclusions-These results strongly suggest that the expression and synthesis of decorin is affected in Alzheimer's disease skin fibroblasts.

Journal Article↗
PubMed1995

Red cell alloantibody development associated with heart and lung transplantation.

The development and persistence of clinically significant red cell alloantibodies were studied in 1132 patients who underwent a heart and/or lung transplant at Harefield Hospital. Clinically significant antibodies were detected in 15 patients (1.3%) preoperatively and appeared in a further 15 (2.1%) of 704 patients followed up 1-404 weeks after surgery. Anti-D developed in only 1 of 52 D-negative recipients of a D-positive donor graft and in only 2 of 6 D-negative patients who were transfused with between 6 and 32 units of D-positive red cells. Most antibodies that appeared after transplantation remained detectable for only a few weeks. Antibodies detected preoperatively that reacted only with papain-treated cells became persistently undetectable in 4 patients who were transfused with red cells expressing the corresponding antigen specificity. By contrast, antibodies detected preoperatively by indirect antiglobulin test were still detectable after periods of up to 260 weeks in 4 patients who received only antigen-negative red cells. Immunosuppressive therapy appeared to profoundly affect the natural history of red cell alloantibody production in these patients. The underlying mechanisms warrant further study.

ABO Blood-Group System↗
PubMed1995

Platelet activation by healing ePTFE grafts.

The purpose of this study was to examine the effect of the in vivo maturing ePTFE graft surface on platelet activation. Ten canines were randomized to receive either a carotid to infrarenal aorta ePTFE graft or sham operation. Animals were sampled at specific time points up to 3 months postoperatively. Whole blood platelet aggregometry (arachidonic acid, ADP, and collagen agonists) and ATP secretion (in response to arachidonic acid, ADP, collagen, and thrombin) were measured. Additionally, complete hematologic analysis and histology were performed. With time, graft animals showed significantly more decrease in platelet aggregation in response to ADP compared to sham animals (P = .023). The total amount of ATP per platelet was not different, as demonstrated by equivalent ATP release per platelet in response to thrombin. Over the first week, grafted dogs developed a decrease in systemic platelet count of 50% (P < .001) that persisted over the 3-month follow-up period. With time, overall regression model slopes of graft and sham platelet count data were not statistically different (P = .29). Histologically, the grafts demonstrated limited cellular ingrowth at both anastomoses, with fibrin matrix along the remainder of the blood-biomaterial interface. These data suggest that, similar to Dacron, exposure to an ePTFE surface results in significant changes in platelet biology, and these platelet-ePTFE interactions persist even after the graft has formed a mature pseudointima. The pseudointima appears to be the primary determinant of the blood-biomaterial interaction.

Adenosine Triphosphate↗
PubMed1995

Differential clinical and epidemiological features in children with Campylobacter diarrhoea, mixed-agent diarrhoea and Campylobacter diarrhoea plus parenteral infections.

A prospective study of 111 young Peruvian children with Campylobacter jejuni diarrhoea showed that it behaves as an endemic enterotoxigenic-like, waterborne, milkborne, and zoonotic disease. Although there were no definite differential features between pure C. jejuni diarrhoea, mixed-agent diarrhoea, and C. jejuni diarrhoea plus parenteral infections, children with C. jejuni diarrhoea plus parenteral infections were all inpatients, were more frequently malnourished and more frequently exhibited systemic symptoms. Campylobacter jejuni associated with other enteric pathogens did not seem to act synergistically as the disease was not particularly severe in this group.

Campylobacter Infections↗
PubMed1995

Prediction of the severity of haemolytic disease of the newborn. Quantitative IgG anti-D subclass determinations explain the correlation with functional assay results.

Sera containing anti-D, taken from 44 RhD-negative women with RhD-positive infants, were tested in antibody-dependent cellular cytotoxicity (ADCC) and monocyte monolayer assays (MMA) which used similar target and effector cell populations. In addition, the anti-D concentration was measured in the Auto Analyzer and the number of IgG1 and IgG3 anti-D molecules bound to the target red cells was measured by flow cytometry. The results of the functional assays and Auto Analyzer quantitation were examined for correlation with IgG subclass quantitation and all results were compared for their ability to predict the severity of haemolytic disease of the newborn (HDN). ADCC correctly predicted HDN in 39/44 (88.6%) cases, Auto Analyzer quantitation in 35/44 (79.5%) and the MMA in 32/44 (72.7%). For all three assays, the number of correct predictions was highest when the maternal serum contained both IgG1 and IgG3 anti-D. ADCC activity and HDN were correlated with the number of cell-bound IgG1 molecules (r > or = 0.58), but MMA activity was most closely correlated with the number of cell-bound IgG3 molecules (r = 0.68). Hence the superior predictive value of ADCC is due to its ability to reflect the IgG1 component of maternal anti-D, which has a better correlation than IgG3 anti-D with the severity of HDN.

Autoanalysis↗
PubMed1994

The protein coded by the X-adrenoleukodystrophy gene is a peroxisomal integral membrane protein.

The gene for adrenoleukodystrophy (X-ALD), a peroxisomal disease characterized by excessive accumulation of very long-chain (VLC) fatty acids (> C22:0), has recently been identified by positional cloning, and it is predicted to encode a protein (ALD-P) of 745 amino acids [(1993) Nature 361, 726]. Using Western blot analysis of subcellular organelles purified by isopycnic density gradient centrifugation from X-ALD and control fibroblasts, we show that the monoclonal antibodies directed against ALD-P cross-react with a 75 kDa protein in intact peroxisomes and that ALD-P is an integral component of the peroxisomal membrane. Moreover, no signal for ALD-P was detected in peroxisomes from X-ALD patients with deletion of the ALD gene.

Adrenoleukodystrophy↗