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Biomedical subjects

V Souza

Publications and source records attributed to V Souza.

At least 37 records · Page 2Linked to original sources
PubMed1995

Chronic and acute ethanol treatment modifies fluidity and composition in plasma membranes of a human hepatic cell line (WRL-68).

The aim of this study was to compare the effects of chronic (0.1 mol/L ethanol exposure during 30 days) and acute (0.5 mol/L ethanol exposure during 24 h) ethanol treatment on the physical properties and the lipid composition of plasma membranes of the WRL-68 cells (fetal human hepatic cell line). Using fluorescence polarization we found that ethanol treatment reduced membrane anisotropy due to disorganization of acyl chains in plasma membranes and consequently increased fluidity, as measured with the diphenylhexatriene probe. Addition of ethanol in vitro reduced anisotropy in control plasma membranes, whereas chronically ethanol-treated plasma membranes were relatively tolerant to the in vitro addition of ethanol. Acutely ethanol-treated plasma membranes exhibited a smaller anisotropy parameter value than control plasma membranes. We found a decrease in total phospholipid content in acute ethanol WRL-68 plasma membranes. Cholesterol content was increased in both ethanol treatments, and we also found a significant decrease in phosphatidylinositol and phosphatidylcholine and an increase in phosphatidylethanolamine content in ethanol-treated plasma membranes. Our data showed that ethanol treatment decreased the anisotropy parameter consistently with increased fluidity, while increasing the cholesterol/phospholipid ratio of plasma membranes of WRL-68 cells, but only chronically ethanol-treated plasma membranes exhibited tolerance to the in vitro addition of ethanol. It is important to note that some changes that were interpreted as a result of chronic ethanol treatment were also present in short-period ethanol treatments.

Cell Line↗
PubMed1995

The effect of chronic and acute ethanol treatment on morphology, lipid peroxidation, enzyme activities and Na+ transport systems on WRL-68 cells.

In this study we measured some parameters that are associated with ethanol damage to the liver. The method allowed us to determine the injury that chronic and acute ethanol treatments produce at the cellular level without interference from homeostatic or compensatory mechanisms. The system used is a hepatic fetal human cell line, WRL-68, which retains, in culture, many of the liver-specific functions. WRL-68 cells do not metabolise ethanol, and consequently we could evaluate the effect of ethanol alone. We explored two different conditions: 30 days with 0.1 M ethanol (chronic treatment) and 24 h in the presence of 0.5 M ethanol (acute treatment). 1. The transmission electron microscopy studies revealed, in both treatments, the presence of granules not usually present in the cytoplasm of control cells and morphological mitochondrial alterations in chronically treated cells. 2. Lipid peroxidation, measured as the rate of malondialdehyde production, increased three and a half times in acutely treated cells and about twofold in chronically treated cells. 3. The percentage of total activity (activity in the medium/(activity in the medium + activity of the cells). 100) and the enzymatic activity in the culture medium of gamma glutamyl transpeptidase (GGT), alanine amino transferase (ALAT), aspartate amino transferase (ASAT) and alkaline phosphatase (AI-P), increased. 4. We measured some parameters related to the transport of sodium across the membrane. Cells chronically treated with ethanol had higher rate constants and effluxes than control cells. There was no difference between the total and passive efflux. Ethanol treated cells apparently lacked the ouabain sensitive pathway. In acutely treated cells, the total sodium efflux and the rate constant were enhanced. Sodium pools in the acutely treated cells were diminished and active sodium pumping was seven times higher than in control cells. 5. We determined the number of high affinity ouabain binding sites per cell. Ethanol did not alter the number of pumps, rather it seems to induce a functional alteration. Our results indicate that ethanol per se induces lipid peroxidation, alters enzymatic activities, sodium transport systems, sodium pools and cellular morphology, and that all these changes may be partly responsible for ethanol-induced hepatotoxicity. The data compare favourably with those reported in the literature for many different systems. Therefore our model for studying the mechanism of alcohol effects appears to be valid, with the advantage of being able to compare experiments that can be done in the same system and under the same conditions.

Alcohol Dehydrogenase↗
PubMed1995

[The role of low-molecular-weight heparin in unstable angina, acute myocardial infarction and post-elective percutaneous transluminal coronary angioplasty].

PURPOSE: To evaluate the clinical efficacy and safety of subcutaneous (SC) low molecular weight heparin (LMWH) compared to intravenous (IV) non fractioned heparin (NFH) in unstable angina, acute myocardial infarction and post-percutaneous transluminal coronary angioplasty. METHODS: From September/92 to April/94, 314 patients were randomized in two groups. Group I-- 154 patients treated with SC LMWH, using in the 1st phase SC LMWH with a dosage of 160 UaXa IC/kg/day (group IA--92 patients), and in the 2nd, a dosage of 320 UaXa IC/kg/day (group IB--62 patients). Group II--160 patients treated with IV NFH 100UI/kg (bolus), followed by 1000UI/h with adjusted dosage by activated partial thromboplastin time. RESULTS: There was not a statistically significant difference among the three groups in relation to cardiac events, hemorrhagic complications and deaths. CONCLUSION: The clinical efficacy and safety of SC LMWH in patients with unstable angina, acute myocardial infarction and post-percutaneous transluminal coronary angioplasty were similar to IV NFH with the dosages used in this study.

Angina, Unstable↗
PubMed1994

Expression of some hepatocyte-like functional properties of WRL-68 cells in culture.

Some morphologic and functional characteristics of an hepatic fetal human epithelial cell line (WRL-68 cells) were determined to validate the use of these cells as an in vitro hepatic model. WRL-68 cells have a morphologic structure similar to hepatocytes and hepatic primary cultures. They secrete alpha-feto protein and albumin and exhibit a cytokeratin pattern similar to other hepatic cultures. WRL-68 cells preserve the activity of some characteristic or specific liver enzymes or both used in clinical chemistry for the diagnosis of hepatic disorders, i.e. alanine amino transferase, aspartate amino transferase, gamma-glutamyl transpeptidase, and alkaline phosphatase.

Albumins↗
PubMed1994

Methodological considerations in measurement of the P300 component of the auditory oddball ERP in schizophrenia.

Twenty-three schizophrenic patients and 26 age-matched control subjects were studied using the P300 recorded during the auditory oddball task, with counting. Our aim was to assess the most suitable method of measurement and analysis of P300 amplitude and latency for use in clinical studies of schizophrenia. The effect of high-pass filtering, peak definition method and recording electrode site were all investigated. We have developed a technique, based on a least-mean-squares approximation to data, which seems particularly well suited to dealing with multi-peak P300 complexes. We have also investigated the spectral composition of the P300 and have found some evidence to support a proposed 2-frequency model of the P300 complex.

Acoustic Stimulation↗
PubMed1994

Epistatic effects of promoter and repressor functions of the Tn10 tetracycline-resistance operon of the fitness of Escherichia coli.

We have been studying the effects of expression of plasmid-borne, Tn10-encoded, tetracycline resistance on the fitness of Escherichia coli K12. We previously demonstrated large reductions in fitness resulting from induced or constitutive expression of the resistance protein; however, any residual expression by the repressed operon was so slight that possession of an inducible resistance function imposed essentially no burden in the absence of antibiotic. Here, we demonstrate two distinct disadvantages for inducible genotypes relative to isogenic constitutive constructs. During the transition from antibiotic-free to antibiotic-containing media, the inducible genotype experiences a longer lag phase prior to growth. In the sustained presence of antibiotic, full induction of the resistance function in the inducible genotype is prevented by the continued action of its repressor. However, these disadvantages may be reduced by increasing the strength of the promoter for the resistance gene in the inducible genotype. Simultaneous consideration of the mode of gene regulation (i.e. constitutive or inducible) and the strength of the resistance-gene promoter (i.e. maximum level of expression) indicates an adaptive landscape with very strong epistasis and, perhaps, multiple fitness peaks.

Epistasis, Genetic↗
PubMed1994

Correlation of regional cerebral blood flow equivalents measured by single photon emission computerized tomography with P300 latency and eye movement abnormality in schizophrenia.

Single photon emission tomography with the intravenous blood flow marker 99mTc-exametazime was carried out in 14 acutely ill drug-free schizophrenic patients from whom P300 event-related potential, smooth eye pursuit eye tracking and verbal fluency were measured within a few days of scanning. Smooth pursuit eye movement abnormality correlated significantly with abnormal tracer uptake in superior pre-frontal cortex on the right and left and inferior pre-frontal cortex on the left. Abnormal eye movement was also associated with higher tracer uptake in left anterior cingulate and left posterior cingulate. P300 latency was significantly correlated with higher tracer uptake in left superior pre-frontal and left parietal regions. Verbal fluency performance was negatively correlated with tracer uptake in left frontal region. Eye tracking abnormality in schizophrenia is associated with bilateral frontal lobe disturbance and P300 latency increase with left-sided frontal and temporoparietal dysfunction. There was, however, a significant inverse relation between eye tracking abnormalities and abnormal perfusion in the left anterior cingulate region.

Adult↗
PubMed1994

Genetic Structure of Rhizobium etli biovar phaseoli Associated with Wild and Cultivated Bean Plants (Phaseolus vulgaris and Phaseolus coccineus) in Morelos, Mexico.

The genetic structure of Rhizobium etli biovar phaseoli was determined for five populations in three different locations in the state of Morelos, Mexico, by using starch gel electrophoresis for five to nine polymorphic loci. Two populations were sampled during two different years from nodules of cultivated and wild common bean plants (Phaseolus vulgaris). The three other populations were associated with wild runner beans (P. coccineus) and sampled during 1988. The Rhizobium populations differ genetically both among sites and among populations within the same site in different years, as shown by differences in allelic frequencies, genetic differentiation analysis, and differences in electrotypes. The total genetic diversity for the five populations during 1988 was H = 0.487; there were also high levels of genetic variation within each population. We found the highest linkage disequilibrium in a global analysis for all the populations. At a local scale, we also found significant linkage disequilibrium in two populations, although the distribution of the D' suggest some recombination at a local scale. The other three rhizobium populations exhibit low linkage disequilibrium. A cluster analysis (UPGMA) of pairwise genetic distances showed that bacteria isolated from most wild Phaseolus spp. are grouped by population, whereas those obtained from cultivated P. vulgaris are very heterogeneous. The analysis of the genetic structure of Rhizobium strains may allow the identification of strains that are naturally well adapted to a wide range of different environments, which may be useful for agricultural purposes or as a starting point for developing improved Rhizobium strains.

Journal Article↗
PubMed1993

Single-photon emission computed tomography with 99mTc-exametazime in unmedicated schizophrenic patients.

We examined 20 actively psychotic unmedicated schizophrenic patients and 20 matched control subjects by using single-photon emission, computed tomography (SPECT) with 99mtechnetium-exametazime. Patients showed a hyperfrontal pattern of tracer uptake with significant relative increases in superior prefrontal cortex. This abnormality was less pronounced in patients with higher symptom scores for psychomotor poverty. In addition, patients showed associations between certain schizophrenic syndrome scores, such as psychomotor poverty, disorganization, and reality distortion, and tracer uptake to a number of cortical and subcortical brain regions. This syndrome-related pattern of tracer uptake was, at least in part, consistent with similar associations previously reported in chronically medicated schizophrenic patients. SPECT therefore provides a readily available method to examine the relationship between symptom pattern and regional brain metabolism in psychotic patients. Any observed patterns of association will depend on the current mental and medication status of the patients examined.

Adult↗
PubMed1992

Hierarchical analysis of linkage disequilibrium in Rhizobium populations: evidence for sex?

Many bacterial species exhibit strong linkage disequilibrium of their chromosomal genes, which apparently indicates restricted recombination between alleles at different loci. The extent to which restricted recombination reflects limited migration between geographically isolated populations versus infrequent mixis of genotypes within populations is more difficult to determine. We examined the genetic structure of Rhizobium leguminosarum biovar phaseoli populations associated with wild and cultivated beans (Phaseolus spp.) over several spatial scales, ranging from individual host plants to throughout the Western Hemisphere. We observed significant linkage disequilibrium at scales at least as small as a cultivated plot. However, the amount of disequilibrium was much greater among isolates collected throughout the Western Hemisphere than among isolates from one area of Mexico, even when disequilibrium was quantified using an index that scales for allelic diversity. This finding suggests that limited migration between populations contributes substantially to linkage disequilibrium in Rhizobium. We also compared the genetic structure for R. leguminosarum bv. phaseoli taken from a cultivated plot with that for Escherichia coli obtained from one human host in an earlier study. Even at this fine scale, linkage disequilibrium in E. coli was very near the theoretical maximum level, whereas it was much less extreme in the local population of Rhizobium. Thus, the genetic structure for R. leguminosarum bv. phaseoli does not exclude the possibility of frequent mixis within local populations.

Enzymes↗
PubMed1987

Cytogenetic study of a group of workers exposed to thinner.

The frequency of sister-chromatid exchanges (SCE) was evaluated in a group of 24 workers exposed to thinner in a luminous advertisements factory and in three workshops for painting sheet metal in Mexico City. 50 metaphases for each exposed individual and each control were analysed; air samples of the working places were also studied; it was observed that among all the components of thinner, only benzene exceeded advisable limits. The cytogenetic data were subject to one-way analyses of variance indicating that no significant differences existed between both groups; also, there are no significant differences among workers with a long exposure time and those with fewer than 5 years of exposure. Nevertheless, use of tobacco increased significantly the SCE frequencies among the exposed group, but did not increase SCE in the control group.

Air Pollutants, Occupational↗
PubMed1985

In vitro and occupational induction of sister-chromatid exchanges in human lymphocytes with furfuryl alcohol and furfural.

Sister-chromatid exchanges (SCEs) in human lymphocytes were studied using the FPG technique in order to determine the cytogenetic effect of furfural and furfuryl alcohol. The induction of SCEs was also investigated in workers occupationally exposed to these solvents that are commonly used in the manufacture of furoic resins. The results obtained from the in vitro treatments show that furfural increased the number of SCEs, while furfuryl alcohol did not. In exposed workers, neither of these solvents increased the spontaneous frequency of SCEs per metaphase.

Adult↗
PubMed1983

The effect of the filling material in the tissue reactions following apical plugging of the root canal with dentin chips. A histologic study in monkeys' teeth.

The object of the present work was to observe whether the root canal filling material has some influence in the periapical healing process after apical plugging with dentin chips. Monkeys' teeth were filled with nine different filling materials in use today. Ninety days after the treatment, the histologic data showed no differences in the results with the nine materials studied. This fact suggests that the filling material does not influence the healing process when the plug is present.

Animals↗
PubMed1980

Apical hard-tissue deposition in adult teeth of monkeys with use of calcium hydroxide.

The periapical tissues of adult teeth of monkeys were examined histologically after root canal treatment with calcium hydroxide. Healing, as evidenced by complete apical closure with a hard tissue bridge and an inflammation-free periodontal ligament, occurred more frequently where canals were instrumented 1 mm short of the apex. Overinstrumented canals exhibited a significantly decreased incidence of apical closure.

Animals↗