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Biomedical subjects

R Barrera

Publications and source records attributed to R Barrera.

At least 37 records · Page 2Linked to original sources
PubMed1999

Temporal variations in blood glutathione peroxidase (GSHPx) activity in sheep at pasture in a Mediterranean area.

The present study evaluates blood GSHPx activity in 18 sheep flocks at range, to identify those seasons with the highest risk of selenium deficiency. Samples were taken from 1108 15-day-old lambs during the two usual lambing periods in this geographical area (autumn-winter and spring-summer). The overall mean values in the first period (146.69 +/- 3.41 i.u./g Hb) was higher than in the second one (107.50 +/- 3.53 i.u./g Hb). This may be explained by the special features of the climate in the Mediterranean area, which allow an optimum growth of grass from October to May. Therefore, the lambs born in spring-summer are from pregnancies in months when feeding is based only upon grazing. However, lambs born in autumn-winter comes from ewes gestating during the summer, when supplementation with cereal grains is given. As a conclusion, lambs born in spring-summer in this area are at higher risk to selenium-deficiency related disorders.

Animals↗
PubMed1999

Genetic and phenotypic changes accompanying the emergence of epizootic subtype IC Venezuelan equine encephalitis viruses from an enzootic subtype ID progenitor.

Recent studies have indicated that epizootic Venezuelan equine encephalitis (VEE) viruses can evolve from enzootic, subtype ID strains that circulate continuously in lowland tropical forests (A. M. Powers, M. S. Oberste, A. C. Brault, R. Rico-Hesse, S. M. Schmura, J. F. Smith, W. Kang, W. P. Sweeney, and S. C. Weaver, J. Virol. 71:6697-6705, 1997). To identify mutations associated with the phenotypic changes leading to epizootics, we sequenced the entire genomes of two subtype IC epizootic VEE virus strains isolated during a 1992-1993 Venezuelan outbreak and four sympatric, subtype ID enzootic strains closely related to the predicted epizootic progenitor. Analysis by maximum-parsimony phylogenetic methods revealed 25 nucleotide differences which were predicted to have accompanied the 1992 epizootic emergence; 7 of these encoded amino acid changes in the nsP1, nsP3, capsid, and E2 envelope glycoprotein, and 2 were mutations in the 3' untranslated genome region. Comparisons with the genomic sequences of IAB and other IC epizootic VEE virus strains revealed that only one of the seven amino acid changes associated with the 1992 emergence, a threonine-to-methionine change at position 360 of the nsP3 protein, accompanied another VEE virus emergence event. Two changes in the E2 envelope glycoprotein region believed to include the major antigenic determinants, both involving replacement of uncharged residues with arginine, are also candidates for epizootic determinants.

Amino Acid Sequence↗
PubMed1999

Temporal and spatial patterns of malaria reinfection in northeastern Venezuela.

We stratified the risk of malaria transmission (Plasmodium vivax) in 35 villages along a coastal range in northeastern Venezuela (51 km2) where the main vector is the mosquito Anopheles aquasalis. After 20 years without local malaria transmission, reinfection of the entire area occurred from May to December 1985 by local (continuous) and jump (discontinuous) dispersal. Epidemiologic, environmental, and vector variables were investigated with the aid of a Geographic Information System. Risk factors for malaria transmission were human population density, proximity to pre-adult mosquito habitats (< 500 m), and the number of pre-adult habitats nearby. Most inhabitants, immature mosquito habitats, and malaria cases were located at low elevations and on gentle slopes. High prevalence of malaria during the dry seasons was associated with the presence of permanent bodies of water containing An. aquasalis. Occurrence of a La Niña event in 1988 (wet and cool phase of the El Niño Southern Oscillation) triggered malaria transmission to unusually high levels, consolidating infection in the area, and rendering traditional control efforts useless. We recommend tracking malaria persistence per village and associated risk factors as methods to reduce the cost of malaria control programs.

Adolescent↗
PubMed1998

Predictive respiratory complication quotient predicts pulmonary complications in thoracic surgical patients.

BACKGROUND: This study was designed to develop an accurate preoperative index of prediction of outcome and hospital charges after lung resection with standard available pulmonary tests in a tertiary cancer center. METHODS: Sixty-one consecutive patients undergoing pulmonary resections were evaluated. All patients underwent spirometry, carbon monoxide diffusion capacity, split lung function testing, and room air blood gas analysis at rest and after a 2-minute step climb. The thoracic prospective data base and patient charts were reviewed for length of hospitalization, postoperative length of stay, and complications requiring therapy. Logistic regression analysis of the preoperative data, operation and postoperative outcome was used to develop a new postoperative predictive index: the predictive respiratory complication quotient (PRQ). We describe the design of the equation for the probability of serious pulmonary complications, hospital stay, and hospital charges based on PRQ. RESULTS: Ten of 12 patients with a PRQ less than 2,200 suffered serious pulmonary complications of pneumonia, respiratory insufficiency, hypoxemia, and death. Forty-nine patients with a PRQ more than 2,200 did not experience any pulmonary complications. Postoperative length of stay and hospital charges correlated with the PRQ. CONCLUSIONS: A construct such as the PRQ may provide a better prediction of outcome than its individual parts. We identified an important underlying relationship between intensive care unit stay, hospital stay and charges, and our index. A PRQ of less than 2,200 was associated with an increased risk of pulmonary complications and mortality.

Algorithms↗
PubMed1997

Relationships between some soil parameters and the blood glutathione peroxidase activity of grazing sheep.

The relationships between some soil parameters and blood glutathione peroxidase (GSHPx) activity in 15-day-old lambs was studied on 18 sheep farms. Soil samples were analysed for the proportions of sand, silt and clay, pH, and the concentrations of calcium, phosphorus, iron, nitrogen and sulphates. On the farms where the lambs had adequate GSHPx activity (> or = 130 i.u./g Hb) the soils contained significantly more clay, phosphorus and sulphates, and significantly less iron and nitrogen, than on the farms where the lambs did not have adequate GSHPx activity.

Animals↗
PubMed1996

Acute complications of central line placement in profoundly thrombocytopenic cancer patients.

BACKGROUND: Morbidities associated with the insertion of central venous catheters in severely thrombocytopenic cancer patients were analyzed in this prospective observational study. One hundred fifteen consecutive thrombocytopenic patients requiring central venous access (internal jugular or subclavian vein cannulation by a modified Seldinger technique) were evaluated. METHODS: One hundred fifteen catheters were inserted. For each patient, the following factors were documented: age; sex; diagnosis; previous catheterization; prior neck, chest, breast, or axillary surgery or radiation therapy; presence of other lines prior to venipuncture; site and indication for line insertion; complications; PT and PTT; platelet counts; and hematocrit. RESULTS: Of the total number of catheters inserted, 63 (55%) were subclavian and 52 (45%) were internal jugular. Successful cannulations with no complications (n = 91; 79% of the total) were achieved with 1.2 +/- 0.5 attempts. Twenty-four major and minor complications (20%) occurred with an average of 1.6 +/- 1 attempts (P = 0.003). The mean preprocedure platelet counts were 14.8 +/- 4.5 x 10(9)/L for the subclavian group and 14.3 +/- 4.8 x 10(9)/L for the internal jugular group. With platelet transfusion, the mean postprocedure platelet counts for the subclavian and internal jugular groups were 23.9 +/- 12.8 x 10(9)/L and 24.6 +/- 15 x 10(9)/L, respectively. In the subclavian group, seven patients (6%) experienced minor complications. There were 17 minor complications (15%) and 1 pneumothorax in the internal jugular group. Patients experiencing more than one attempt at cannulation had more complications (P = 0.003). CONCLUSIONS: With the appropriate precautions and platelet transfusions, central venous catheters can be inserted safely with minimal complications into thrombocytopenic cancer patients. Fewer attempts are associated with fewer complications. High risk procedures should be attempted only by experienced personnel or under their direct and strict supervision.

Adult↗
PubMed1995

Simulium metallicum cytospecies E larval habitat characterization in the Altamira focus of onchocerciasis, northern Venezuela.

Simulium metallicum sibling species E was identified cytotaxonomically from an onchocerciasis focus at Altamira in northern Venezuela. S. metallicum E larvae were sampled monthly from two small mountain streams over a 15-month period (July 1990 to September 1991) and eleven habitat variables were measured at two altitudes. One stream consistently harboured much higher densities of S. metallicum E larvae than the other, with three annual peaks of abundance: during the dry season and at the beginning and end of the rainy season. These peak densities were correlated with high rainfall 4 months previously. Larvae were most abundant on submerged rocks and fallen leaves, in small shallow areas characterized by slow water current, high conductivity and sparse terrestrial vegetation cover. Stream variables which best explained the temporal changes in abundance were water discharge and conductivity. The population dynamics of S. metallicum E appeared to be influenced primarily by interactions between stream discharge and substrate stability. Relevance of these results to vector control with larvicides is discussed.

Animals↗
PubMed1995

[Blood insulin in fasting conditions as a simple marker of insulin resistance in hypertensive patients].

Insulin resistance is associated to hypertension, obesity and diabetes and may be an independent cardiovascular risk factor. The exact assessment of insulin resistance requires complex metabolic studies. However, there is a good correlation between this parameter and fasting serum insulin levels. The aim of this work was to study fasting serum insulin levels by radio immuno analysis in 43 hypertensive patients aged 56 +/- 5.5 years old (27 male, 17 obese and 8 diabetics) and 20 normotensive controls aged 50 +/- 4.8 years old (13 male). Insulin levels were 3.8 UI/L in controls, 12.1 UI/L in normal weight, 15.5 UI/L in obese and 18.3 UI/L in diabetic hypertensives (ANOVA p < 0.001). These levels were above two standard deviations of control values in 50% of normal weight, 66% of obese and 62% of diabetic hypertensives. It is concluded that normal weight, obese and diabetic hypertensive subjects have high fasting insulin levels.

Adult↗
PubMed1995

Public service deficiencies and Aedes aegypti breeding sites in Venezuela.

The 1992 study reported here assessed relationships between potable water supply and trash collection practices and the prevalence of dengue vector mosquito (Aedes aegypti) breeding sites in 30 towns located along the north coast of Venezuela. Within each study town, 100 homes were chosen. At each of these homes the number of water-bearing containers and containers harboring A. aegypti were determined and interviews were conducted to obtain information about the local water supply, trash collection services, and excreta disposal. In general, A. aegypti breeding indexes were high: 55% of the residences were found to harbor A. aegypti immature forms; there was an average of 118 breeding sites per 100 residences; and 24% of the water-bearing receptacles were observed to contain the mosquito. The statistical method of principal component analysis was employed to rank the 30 towns in terms of variables describing public service deficiencies, and correlations existing between the variables studied were determined. Direct correlations were found between two water supply variables (frequency and duration of water supply interruptions), between the excreta disposal and trash collection variables, between the duration of water supply interruptions and the Aedes breeding indexes, and between the duration of water supply interruptions and the mean number of A. aegypti breeding sites found in water storage containers. Overall, the towns with the poorest services were found to have the highest breeding indexes and the greatest numbers of water storage containers harboring the mosquito. It is concluded that public service (water supply and waste disposal) deficiencies were largely responsible for A. aegypti propagation in the study towns. Accordingly, it is recommended that local programs be implemented for recycling containers, constructing water storage tanks that cannot harbor Aedes larvae, and conducting health education and community participation campaigns directed against the mosquito.

Aedes↗
PubMed1994

Vector competence of Simulium metallicum s.l. (Diptera: Simuliidae) in two endemic areas of human onchocerciasis in northern Venezuela.

Experimental infections of Simulium metallicum s.l. with Onchocerca volvulus were carried out in two onchocerciasis foci, Altamira and Trincheras, in northern Venezuela, to determine vector competence. Wild-caught flies, fed on infected volunteers, were maintained in the laboratory for 13-15 days at 27 degrees C. Parasite development was complete but asynchronous and retarded. No differences in the vector competence of the two populations of S. metallicum s.l. were found. However, a less efficient development of the parasite occurred during the dry season at both localities. The distribution of the parasite within the vector was aggregated and also displayed seasonal variation. The seasonal susceptibility may be a consequence of a density-dependence regulation mechanism of the parasite within the vector. These results indicate a relatively low vector competence for S. metallicum s.l. in northern Venezuela.

Animals↗
PubMed1994

Influence of anticoagulants on the determination of blood glutathione peroxidase activity.

The influence of lithium heparin and heparin iodoacetate on the determination of blood glutathione peroxidase activity was investigated. Samples with each anticoagulant were taken from 393 lambs. Glutathione peroxidase activity was much higher in the lithium heparin samples (109.00 +/- 3.71 U/g Hb) than in the heparin iodoacetate group (31.05 +/- 1.55 U/g Hb). This difference was statistically significant (p < 0.001), and it was due to inhibition of glutathione peroxidase by heparin iodoacetate. Heparin iodoacetate therefore cannot be used as an anticoagulant in the determination of glutathione peroxidase in blood.

Animals↗
PubMed1993

Unreliable supply of potable water and elevated Aedes aegypti larval indices: a causal relationship?

We investigated the hypothesis that a deficient supply of piped water was causing a high prevalence of water storage containers, which in turn, become important aquatic habitats of Aedes aegypti in a small town in Venezuela. The House (71.2%) and Breteau indices (229) were considerably elevated. Prevalent positive containers were: metal drums, small disposable containers (bottles, tins, etc.), tires, house plants (flowers in vases and plants in pots with earth) and tanks. Most people reported frequent interruptions in the supply of piped water and considered it to be unreliable. The frequency of interruptions in the supply of water was positively correlated with the House and Container indices, and with the number of positive containers, water-storage devices and positive water-storage devices per house. Even people who considered that they had an adequate supply of water kept numerous water storage containers. Most people (60%) said they would not stop storing water even in the event of the establishment of a reliable supply of piped water.

Aedes↗
PubMed1992

Keratoconjunctivitis sicca and diabetes mellitus in a dog.

Diabetes mellitus and keratoconjunctivitis sicca were diagnosed in a female Poodle. The dog was treated for diabetes and keratoconjunctivitis sicca until blood glucose concentrations were within normal limits. Treatment for keratoconjunctivitis sicca was suspended then, and signs of this disorder did not appear again. Most of the factors known to predispose to keratoconjunctivitis sicca were not applicable to this dog. On the basis of observations made in this dog, we suggest that diabetes mellitus and keratoconjunctivitis sicca may be linked. Clinical signs of the disorders developed simultaneously and resolved when diabetes mellitus was controlled with insulin.

Animals↗
PubMed1992

Immunologic and genetic characterization of S180, a cell line of murine origin capable of growing in different inbred strains of mice.

Some of the immunologic and genetic properties of the cell line S180 have been examined. These cells grew without restrictions in the peritoneal cavity of different inbred strains of mice and invariably killed the animals. With Northern blots it was demonstrated that S180 cells contained class I mRNAs but failed to transcribe B2m genes. However, under experimental conditions, a protective humoral immune response mediated by cytotoxic antibodies and complement against S180 cells was obtained through non-H-2 antigens in C57BL/6J mice.

Animals↗
PubMed1992

Changes in the plasma concentrations of lipids and lipoprotein fractions in dogs infected with Leishmania infantum.

A study was made of serum concentrations of cholesterol, phospholipids, triglycerides, cholesterol bound to high-density lipoproteins (HDL), HDL1-cholesterol, HDL2-cholesterol and cholesterol bound to low-density lipoproteins (LDL) in 16 dogs naturally infected with Leishmania infantum (ZMON-1) taken from an endemic focus. Results were compared with those of a control group of ten healthy dogs. Statistically significant increases in cholesterol, triglyceride and LDL-cholesterol levels were observed. There was, however, a statistically significant decrease in HDL-cholesterol level, mainly at the expense of the HDL2-cholesterol subfraction. Cholesterol transport is therefore shown to undergo changes which may be attributed to the consumptive evolution of the disease, immunocomplex deposits in cells, hepatic disorders and interactions between the parasite and the normal cholesterol metabolism of the host.

Animals↗
PubMed1992

Immunohistochemical analysis of p53 expression in malignant lymphomas.

p53 is a tumor suppressor gene that commonly undergoes mutations in human tumors, including lymphomas. Because p53 mutations are not restricted to a single locus, immunohistochemistry is useful to detect p53 expression and correlate this finding with lymphoma phenotype. Cryostat sections from 125 cases of lymphoma were analyzed for p53 expression using three different monoclonal antibodies (pAb 421, 1801, 240) which react with human cellular p53 and a common conformational epitope on mutant p53. A control antibody (pAb 246) reacts only with wild type p53 of murine origin and was negative in all cases. Tissue from 29 cases of lymphoid hyperplasia, including six from human immunodeficiency virus-positive (HIV+) patients, were negative for p53. p53 was predominantly localized in nuclei of high-grade lymphomas, including 14 of 46 cases of B cell immunoblastic lymphomas and two of five T cell immunoblastic lymphomas. p53 expression was relatively common in lymphomas from HIV+ patients, and unusual in intermediate and low-grade lymphomas of follicular center cell type. Low-grade lymphoma of small lymphocytic type disclosed p53+ large cells (paraimmunoblasts) that may play a role in tumor progression in this lymphoma subtype. p53 was also strongly expressed in the nuclei of Reed Sternberg cells from 19 of 37 cases of Hodgkin's disease, including six cases of mixed cellularity, and 13 cases of nodular sclerosing type. Immunohistochemical staining is a rapid method to identify p53 expression in lymphomas.

Animals↗