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J Dorval

Publications and source records attributed to J Dorval.

9 recordsLinked to original sources
PubMed2003

Role of glutathione redox cycle and catalase in defense against oxidative stress induced by endosulfan in adrenocortical cells of rainbow trout (Oncorhynchus mykiss).

The role of antioxidants in maintaining the functional integrity of adrenocortical cells during in vitro exposure to endosulfan, an organochlorine pesticide, was investigated in rainbow trout (Oncorhynchus mykiss). Aminotriazole (ATA), an inhibitor of catalase (CAT), L-buthionine sulfoximine (L-BSO), an inhibitor of glutathione (GSH) synthesis, and N-acetyl cysteine (NAC), a glutathione precursor, were used to investigate the role of CAT and GSH redox cycle in protection against the adrenal toxicity of endosulfan, a pesticide that impairs cell viability (LC50 366 microM) and cortisol secretion (EC50 19 microM) in a concentration-related manner. Pretreatment with ATA and L-BSO enhanced the toxicity of endosulfan (LC50 and EC50, respectively, 302 and 2.6 microM with ATA, 346 and 3.1 microM with L-BSO), while pretreatment with NAC had no significant effect on cell viability and increased the EC50 of endosulfan to 51 microM. CAT activity was significantly reduced following exposure to endosulfan when cells were pretreated with ATA. Pretreatment with L-BSO significantly decreased glutathione peroxidase (GPx) activity and reduced glutathione (GSH) levels in a concentration-related manner following exposure to endosulfan, while GSH levels were significantly higher in NAC pretreated cells compared to untreated cells. Finally, pretreatment with ATA and L-BSO increased, while pretreatment with NAC decreased, lipid hydroperoxides (LOOH) levels. CAT, GPx, and GSH were identified as important antioxidants in maintaining the function and integrity of rainbow trout adrenocortical cells and ATA, L-BSO, and NAC were identified as effective modulators of CAT and GSH redox cycle. Moreover, this study suggests that the glutathione redox cycle may be more efficient than catalase in protecting adrenocortical cells against endosulfan-induced oxidative stress.

Acetylcysteine↗
PubMed2003

Oxidative stress and loss of cortisol secretion in adrenocortical cells of rainbow trout (Oncorhynchus mykiss) exposed in vitro to endosulfan, an organochlorine pesticide.

The effects of endosulfan, a widely used organochlorine pesticide, on cortisol secretion, cell viability, antioxidants and lipid peroxidation were investigated in enzymatically dispersed head kidney cells of rainbow trout (Oncorhynchus mykiss). ACTH- and dbcAMP-stimulated cortisol secretion, and cell viability were impaired in a dose-related manner following acute in vitro exposure to endosulfan (EC(50) 19 microM, LC(50) 366 microM) and the loss of cortisol secretion was detected even at concentrations of endosulfan that did not decrease cell viability. Stimulation with dbcAMP did not restore cortisol secretion in endosulfan exposed cells while stimulation with pregnenolone maintained cortisol secretion until viability of cells was affected. Thus endosulfan may disrupt processes between the step generating cAMP and the step where pregnenolone is used. Activity of catalase increased at concentrations of endosulfan that did not impair cortisol secretion, and decreased at higher doses. Glutathione peroxidase (GPx) activity was significantly reduced at doses of endosulfan that also reduced levels of glutathione, an essential cofactor of GPx. Exposure up to 1 x 10(-7) M endosulfan increased the activity of glutathione transferase. The present in vitro study identified endosulfan as a chemical inducing a loss of secretory responses in teleost adrenocortical steroidogenic cells and alterations in the activity of enzymes known to be involved in oxidative stress pathways. Moreover, the significant increase in lipid hydroperoxides levels provided further evidence for endosulfan-induced oxidative stress.

Adrenal Cortex↗
PubMed1987

Measuring higher cognitive levels by multiple choice questions: a myth?

Available evidence is inconclusive as to the ability of multiple choice items to measure different taxonomic levels of the cognitive domain. The present study analysed the tests of the Examen de Synthèse for the years 1982, 1983 and 1984. Items used in the study were those for which a consensus was reached between three judges and committees for a given taxonomic level. The initial part of the study showed that judges do not classify items at random but according to a mental representation which is individual, personal and relatively stable. In examining results obtained by students, the study failed to show any significant difference in item difficulty or discrimination for items classified as measuring memorization, interpretation of data and problem-solving. Correlations between results (scores and ranks) obtained for items involving memorization and those obtained for items involving higher cognitive levels fail to show that different traits are measured. If further studies corroborate these results, then future efforts should be directed at developing other instruments to measure higher cognitive levels.

Clinical Competence↗
PubMed1977

[Diphtheria epidemic occurring on the North Shore of the St. Lawrence River in the fall of 1974].

An outbreak of diphtheria occurred on the North Shore of the St. Lawrence River at the beginning of September 1974. It started with the death of an 18-year-old forest worker Sept. 5, spread over a vast area of the North Shore and lasted until the end of October that year. Eleven strains of toxigenic Corynebacterium diphtheriae intermedium, type K were isolated. Eleven of the 12 patients had characteristic diphtheritic pharyngitis with pseudomembranes. Preventive measures, set forth immediately after the third case was declared, included the following: (a) daily surveillance of all contacts, (b) isolation or preventive hospitalization of persons with all types of pharyngitis, (c) mass vaccination of all susceptible persons and (d) search for healthy carriers of the germ. No strains of toxigenic C. diptheriae were isolated from patients preventively hospitalized or from the 1235 individuals among whom carriers were sought. Among the main characteristics of this epidemic, the mean age of the patients (17 years), their mobility and their habits are factors that could have made it almost uncontrollable. It is also remarkable that this outbreak occurred in such a scattered population of adolescents, in 82% of whom the Schick test was negative.

Adolescent↗