PubMed Health⌕ Search

Biomedical subjects

S Visentin

Publications and source records attributed to S Visentin.

41 records · Page 3Linked to original sources
PubMed1984

Barium-induced blockade of the inward rectifier in calf Purkinje fibres.

The Ba-induced blockade of iK1 in calf Purkinje fibres was studied in the low concentration range (3-1,000 microM). The results showed that the blockade induced by hyperpolarizations was time-dependent, and that the rate of blockade increased with the Ba concentration and the negative pulse amplitude. At Ba concentrations higher than 1 mM the time course of iK1 blockade was not separable from the capacity transient. At these concentrations, and in a limited voltage range, the Ba-sensitive instantaneous current displayed a marked inward rectification and behaved with external K as expected for a pure K+ current, suggesting that under these conditions the only current affected by Ba was iK1. The Ba-sensitive current deceased with time during hyperpolarizations even when high external K was present, indicating that a voltage-dependent inactivation process could be at least in part responsible for the observed current decline.

Animals↗
PubMedDate not supplied

Correspondence analysis applied to grouped cohort data.

In this paper we investigate application of generalized correspondence analysis (GCA) to model a two-way table of rates consisting of a cross-classification of case numerators and person-time denominators. The GCA reconstitution formula is proposed as a correlation model for analysing these data. This provides two major advantages over the techniques usually applied. The number of interaction parameters to be estimated is reduced, and moreover, they have useful interpretation; the singular values and the scores are measures of row-column modification/interaction effects; in addition the scores allow graphical display of these effects. An asymmetrical plot is proposed for optimal representation of interaction parameters as distances. Finally, two examples are presented to illustrate the method of analysing a two-way table of covariate by exposure and a two-way table derived from a cross-classification of two exposure factors.

Adult↗
PubMedDate not supplied

[Evaluation to the exposure to polycyclic aromatic hydrocarbons, benzene, toluene and xylenes in workers in a power plant fueled with heavy oil].

Occupational exposure to polycyclic aromatic hydrocarbons (PAHs) has been demonstrated in many industrial sectors. However, up to date there are few studies in the literature on PAH exposure in thermoelectric power plants. The study was aimed at the evaluation of personal exposure to PAHs in workers of a power plant fueled with heavy oil. Exposure to polycyclic aromatic hydrocarbons (PAHs) and to benzene, toluene and xylenes (BTX) was evaluated on power plant workers exposed to heavy fuel oil; the control group consisted of office workers of the same power plant. Altogether 39 subjects were studied, for a total of 84 days of monitoring. Personal environmental exposure, cutaneous exposure and urinary concentrations of 1-hydroxypyrene (1-OHP), trans,trans-muconic acid (TTMA) and nicotine were measured. Personal environmental exposure to PAHs was very low; only maintenance workers showed exposure to total carcinogenic PAHs significantly higher than controls (median levels 3.05 and 0.88 ng/m3 respectively). All workers showed very low levels of dermal exposure to PAHs (less than 1 ng). The median 1-OHP urinary concentrations were 0.16, 0.11 and 0.08 mumol/mol creatinine in the groups of exposed workers and 0.08 mumol/mol creatinine in the control group. Neither the exposed workers nor the controls showed a significant increase in 1-OHP urinary concentrations across the shift. The regression analysis showed a significant effect of cigarette smoking on urinary 1-OHP, while no association was observed between occupational exposure and diet. Personal environmental exposure levels to BTX were very low. TTMA urinary concentrations of the exposed subjects were similar to those of the controls. No significant increase in the TTMA urinary concentrations was observed across the shift and, as expected, smokers showed higher values than non-smokers. The study did not show a measurable intake of PAHs and BTX in power plant workers that could be ascribed to occupational exposure, thus confirming the efficacy of the protective measures in force.

Benzene↗
PubMedDate not supplied

[Occupational exposure to fungicides in floriculture in Ecuador].

Floriculture represents one of the major sources of income in the Ecuadorian Andean Region that can be carried out either in open fields as in greenhouses by using chemical compounds, growing hormones and xenobiotics. Among pesticides, ethylenbisdithiocarbamate (EBDTCs) fungicides represent the most extensively used. The aim of the study was the assessment of exposure to EBDTCs in Ecuadorian floricultural workers by the determination of the urinary excretion of the main metabolite of these compounds, ethylenethiourea (ETU). For this purpose, thirty-six floriculture workers and 7 unexposed healthy subjects were recruited for the study. Median level of ETU excretion in agricultural workers before the work shift was 3.2 micrograms/g creatinine, ranging from 0.4 to 34.5 micrograms/g creatinine. After pesticide application, urinary ETU increased to 6.2 micrograms/g creatinine (1.5-26.5) microgram/g creatinine. Urinary ETU resulted significantly higher in overall workers, taken as pre- and post-shift samples, when compared to controls (0.7, 0.4-2.1 micrograms/g creatinine, p < 0.01). According to jobs, applicators showed the highest levels of ETU excretion whereas growing, post-harvesting and maintenance workers showed similar levels of exposure. Higher level ETU excretion was observed in greenhouse compared to open field workers.

Agriculture↗