Search PubMed⌕ Search

Biomedical subjects

H Thomas

Publications and source records attributed to H Thomas.

414 records · Page 23Linked to original sources
PubMedDate not supplied

A direct, highly sensitive fluorometric assay for a microsomal cytochrome P450-mediated O-demethylation using a novel coumarin analog as substrate.

A highly sensitive fluorometric assay for the determination of monooxygenase activity in liver microsomes is described. The assay is based on the use of 3-chloro-7-methoxy-4-methylcoumarin which is demethylated to 3-chloro-7-hydroxy-4-methylcoumarin. The rate of formation of 3-chloro-7-hydroxy-4-methylcoumarin was recorded as an increase of fluorescence (lambdaA = 380 nm, lambdaF = 480 nm) with time. When 3-chloro-7-methoxy-4-methylcoumarin was incubated in the presence of MgCl2 and NADPH with rat liver microsomes, a continuous increase of the fluorescence could be measured. The reaction proceeded linearly for about 10 min and at least up to a concentration of 0.1 mg/ml of microsomal protein. Besides 3-chloro-7-hydroxy-4-methylcoumarin a hydroxylated derivative of the substrate was formed as a second metabolite during the incubation. Using an excitation wavelength of 380 nm and a fluorescence/emission wavelength of 480 nm, the fluorescence of this substance (lambdaA = 338 nm, lambdaF = 422 nm) amounted only to about 1% of the fluorescence of the main product. The use of 3-chloro-7-methoxy-4-methylcoumarin as substrate enables the fluorometric determination of the O-dealkylation activity of a cytochrome P450-dependent monooxygenase system in rat liver which is inducible by phenobarbital but not by 3-methylcholanthrene.

Animals↗
PubMedDate not supplied

[Extracurricular activities of adolescents useful for smoking prevention programs. OCTOPUS team].

BACKGROUND: The cigarette smoking habit continues to be prevalent to a greater degree than would be desirable among teenagers. Innovative prevention programs are needed. This descriptive cross-sectional study sets out the behavior variables related to the cigarette smoking habit and the extracurricular activities in which teenagers are most frequently involved which are useful for setting out extracurricular prevention programs. METHODS: The data was collected by means of a questionnaire validated in a representative sample of school age youths (ages 10-11 and 13-14) from Asturias. The variables entailed in cigarette smoking were analyzed using the regression method. RESULTS: The starting smoker percentage is 14.5%-42.5%, regular smokers totaling 1.1% and 12.4%, respectively. Two models were constructed with the variables significantly related to smoking behavior, which are properly classified into smoker/non-smoker by 98.85% and 91.39% of the children, by ages. The environmental variables (availability of cigarettes and alcoholic beverages and regular visits to places entailing risk) are the major aspects comprising the model. The most common extracurricular activities are: watching TV, reading and listening to music and watching or playing sports. CONCLUSION: The findings provide keys to planning extracurricular activities tailored to fit in with the activities most popular among teens: TV commercials and ads on music media (CD's, tapes, etc.) and printed information mailed directly to teens at their homes, with messages conveyed by opinion-leaders among teens in the fields of sports, music and television.

Adolescent↗
PubMedDate not supplied

[6.7-Dihydroxycoumarin (Aesculetin) as a substrate for catechol-o-methyltransferase (author's transl)].

6,7-Dihydroxycoumarin (Aesculetin) was found to be a substrate of rat liver Catechol-O-methylfransferase (COMT) (EC 2.1.1.6). Incubation of this substrate with S-Adenosyl-L-[methyl-14C]methionine and/or S-Adenosylmethionin-hydrogensulfate in the presence of COMT yields the highly fluorescent compounds 7-hydroxy-6-methoxycoumarin (Scopoletin) and 6-hydroxy-7-methoxycoumarin (Isoscopoletin) in the ration of about 2:1. The O-methylated products obtained from Aesculetin were identified after separation by thin layer chromatography mainly by the reversed isotope dilution technique. The fluorescence of the isolated methylethers was proportional to concentration within the range from 10(-5)-10(-7) M. A reciprocal plot of activity versus substrate concentration gives a Km of 1 X 10(-6) M.

Animals↗
PubMedDate not supplied

[O-Methylation of epinephrine, 3,4-dihydroxybenzoic acid and 6,7-dihydroxycoumarin in yeasts (author's transl)].

In the yeasts C. albicans, C. tropicalis, and C. stellatoidea but not in C. krusei, R.rubra, and S. cerevisiae enzyme activity was found by which--as by the catechol-O-methyltransferase (EC 2.1.1.6) found in the liver--the O-methylation of epinephrine to metanephrine and paranephrine, of 3,4-dihydroxybenzoic acid to 4-hydroxy-3-methoxybenzoic acid and 3-hydroxy-4-methoxybenzoic acid, and of 6,7-dihydroxycoumarin to 7-hydroxy-6-methoxycoumarin and 6-hydroxy-7-methoxycoumarin is catalysed. When the substrates 3,4-dihydroxybenzoic acid, or 6,7-dihydroxycoumarin or epinephrine were incubated in the presence of S-adenosyl-L-[methyl-14C]methionine and S-adenosylmethionine hydrogensulfate with a 100 000 X g supernatant of C. albicans, C. tropicalis or C. stellatoidea the corresponding O-methylethers were detected in the extracts of the incubation medium by thin-layer chromatography. Final identification of the isomeric radioactive O-methylethers obtained from 3,4-dihydroxybenzoic acid and 6,7-dihydroxycoumarin was performed after thin-layer chromatographic separation by the reversed isotope dilution technique. The radioactive m- and p-O-methyl derivatives from epinephrine were separated by thin-layer chromatography and then cleaved with periodate to the corresponding aldehydes which were also identified mainly by the reversed isotope dilution technique.

Candida↗
PubMedDate not supplied

[A fluorometic test for microsomal monooxygenase activity in the rat liver with scoparone as substrate (author's transl)].

A sensitive fluorometric test for the determination of monooxygenase activity in liver microsomes from rats is described. The assay is based on the O-demethylation of 6,7-dimethoxycoumarin (scoparone) to 7-hydroxy-6-methoxycoumarin and 6-hydroxy-7-methoxycoumarin. Pretreatment of rats with phenobarbital or polycyclic hydrocarbons (benzo[a]pyrene, 3-methylcholanthrene) causes a significant increase in the amount of microsomal dealkylation activity.

Animals↗
PubMedDate not supplied

The level and the persistence of islet cell antibodies in healthy schoolchildren are associated with polymorphic residues of the HLA-DQ beta chain.

Cytoplasmic islet cell antibodies (ICA) were determined in a group of non-diabetic Caucasian schoolchildren (n = 4208). The prevalence rate for ICA positivity was 1.05 per cent (95 per cent confidence interval: 0.8-1.4 per cent). Analysis of HLA risk factors revealed that HLA-DRB1*03 (p less than 0.01), HLA-DRB1*04 (p less than 0.01) and HLA haplotypes with non-charged amino acids (non-Asp) at codon 57 of the HLA-DQ beta (p less than 0.01) chain were significantly increased when compared to controls. High levels of islet cell antibodies, i.e. Juvenile Diabetes Federation units (JDF units) equal to or greater than 30 JDF units were found to be associated with amino acids other than aspartic acid at codon 57 of the DQ beta chain molecule. Also the persistence of circulating ICA was found to be associated with non-Asp homozygosity of the proband (p less than 0.03).

Adolescent↗
PubMedDate not supplied

[Competitive inhibition of catechol-O-methyltransferase by the tetrahydroisoquinoline alkaloids salsolidine and 1-carboxysalsoline].

The tetrahydroisoquinoline alkaloids salsolidine (1-methyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) and 1-carboxysalsoline (1-carboxy-1-methyl-6-hydroxy-7-methoxy-1,2,3,4-tetrahydroisoquinoline), which are themselves not substrates for the enzyme catechol-O-methyltransferase, are - contrary to a hitherto existing view - able to inhibit competitively the methylation of the catecholamine metabolite 3,4-dihydroxybenzoic acid by the enzyme enriched from rat liver. The inhibitor constants were determined to be Ki = 0.19 mM for salsolidine and Ki = 0.44 mM for 1-carboxysalsoline.

Animals↗
PubMedDate not supplied

Child abuse.

Explore the source record for details and available documents.

Child↗
PubMedDate not supplied

A systematic overview of the effectiveness of home visiting as a delivery strategy for public health nursing interventions.

The purpose of this systematic overview was to assess the evidence for the effectiveness of public health nursing interventions when carried out by the strategy of home visiting. A search of published and unpublished literature resulted in retrieval of 108 articles; 77 articles were judged to be relevant. Validity criteria included method of allocation to the study groups, level of agreement to participate in the study, control for confounders, method of data collection (pretesting of data collection tools, blinding of data collectors to group allocation of study participants), quantitative measure of effect and percentage of participants available at follow-up. Using these criteria, 9 articles were judged to be strong, 5 moderate and 63 weak. There were no reported negative effects of home visiting in the 9 strong articles. Positive outcomes included improvement in children's mental development, mental health and physical growth; reduction in mother's anxiety, depression, and tobacco use; improvement in maternal employment, nutrition and other health habits; government cost saving; and reduced level of care required for the elderly.

Canada↗
PubMedDate not supplied

A systematic overview of adolescent suicide prevention programs.

The purpose of this systematic overview was to summarize evidence about the effectiveness of adolescent suicide prevention curricula programs. A comprehensive search of published and unpublished literature resulted in retrieval of 11 relevant studies. The findings, of this overview indicate that there is currently insufficient evidence to support curriculum-based suicide prevention programs. The evidence suggests that there may be both beneficial and harmful effects of the programs on students. In most studies, knowledge related to suicide improved as a result of the programs. However, studies found both beneficial and harmful effects on attitudes related to suicide. One study found in increase in hopelessness and maladaptive coping for males following the intervention. The literature suggests that more broadly based comprehensive school health programs should be evaluated for their effectiveness in addressing the determinants of adolescent risk behaviour.

Adaptation, Psychological↗
PubMedDate not supplied

Evaluation research in public health: barriers to the production and dissemination of outcomes data.

Health outcomes are becoming the currency of health care exchange, and a call for evidence dominates decision making at all levels. This discussion paper reviews methodological and sociopolitical barriers that impede the production and dissemination of outcome research in public health, with particular reference to nursing. Barriers to the production of high-quality research evidence include inaccessible graduate education and inadequate research funding. Also, randomized controlled trials (the ideal design for interventions studies) are uniquely difficult to implement for public health services. Practical and ethical difficulties arise in defining the intervention, implementing random allocation methods, selecting and measuring outcomes, and articulating adequate theoretical frameworks. When health care activity is defined as output, there is a tendency to exclude the ethical standing of preventive, supportive and communitarian functions. The production and interpretation of research results must remain part of a social, political and ethical debate, not a purely scientific one.

Canada↗
PubMedDate not supplied

[Educational intervention in schools for the prevention of smoking: evaluation of the process. Project: OCTOPUS].

BACKGROUND: The published data on the effectiveness of programs in schools to prevent addiction to tobacco are not consistent. These programs have not been sufficiently studied, and their variables give rise to confusion. The aim of this study was to evaluate the process of educational action taken in schools. METHOD: Student leaders and teachers, who were trained and given guides, developed a socially based program. Two students selected at random from each class were interviewed, using a validated and directed questionnaire. A total of 318 children were interviewed. The Kappa Index was used to measure confidence, and the Inter-Class Coefficient of Correlation and Pearson's Coefficient were used together with analysis of individual differences to compare the data for program adjustment, as supplied by pupils and teachers. RESULTS: Mean adjustment per class was 30.07 points (48-100% adjustment). 26% of children were unable to mention any alternative to the advantages of smoking, 71.7% were unaware of the frequency of consumption amongst adults and 19.5% were unable to mention any of the tricks used in cigarette advertising. Less than half had performed psychodrama on this subject, as was required. The ICC was 0.21, Pearson's Coefficient was 0.25 (p = 0.02) and the interval of agreement between the descriptions of teachers and students was 6.93 points (-1.70 to 5.23). CONCLUSIONS: The degree to which implementation complied with the proposed model of program was insufficient. We found little agreement between the self-assessment of teachers and the score attained by pupils in compliance with the program. It is essential that this process be evaluated for its impact to be evaluated correctly.

Adolescent↗