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Biomedical subjects

R Bolton

Publications and source records attributed to R Bolton.

At least 19 recordsLinked to original sources
PubMed2006

Lignin from rice straw Kraft pulping: effects on soil aggregation and chemical properties.

Lignin contained in pulping liquor that is generated during the pulping process for papermaking is a disposal problem for the pulp and paper industry. Separating lignin and other organic components from pulping liquor with inorganic acids may improve its applicability to fields as a beneficial soil amendment while offering a potential disposal alternative. Sulfuric acid-precipitated lignin from rice straw pulping liquor applied at rates of 1.67 and 3.34 g C kg(-1) soil was incubated to evaluate its effects on soil properties over 8 weeks of incubation. Addition of this acid-precipitated lignin at these rates decreased soil pH by 0.24-0.53 units over 8 weeks of incubation, suggesting that this sulfuric acid-precipitated lignin from pulping liquor may have potential as a soil acidifying agent. Soil electrical conductivity (EC) only increased by up to 0.36 d Sm(-1), but highest EC levels were less than 4 d Sm(-1), indicating that lignin applied at both rates would not cause salinity problems. Application of this lignin increased soil organic C by 1.46 and 3.13 g C kg(-1), and total soil N by 0.07 and 0.17 g N kg(-1) over the incubation period. Lignin improved the macroaggregation of >2mm size fraction, and increased wet microaggregate stability of >2mm and 0.5-0.25 mm aggregates compared to a nonamended control. The results of this study suggest that this acid-precipitated lignin from pulping liquor may have potential as a beneficial soil amendment.

Agriculture↗
PubMed2001

The cognitive structure of the domain of safe and unsafe gay sexual behaviour in Belgium.

This study compares the cognitive structure of sexual techniques of safe versus unsafe gay men older than 30 years. Subjects rated 25 sexual techniques by six bipolar adjective scales making up a short version of the semantic differential. Scales measured subjects' perception of the safety and gratification potential of the sexual techniques. We used cluster analysis, multidimensional scaling and factor analysis. Subjects reporting no unprotected anal sex with non-steady partners (N = 312) differ from men reporting unsafe behaviour (N = 19). Safe and unsafe men used different main categories to structure the domain of sexual behaviour. Within the group of safe men, the domain of sexual behaviour structured by perceptions of gratification and safety seem to mirror the epidemiological structuring of sexual techniques using the non-penetration versus penetration, and transmission of body fluids versus no transmission of fluids dimension. Among risky men, this structuring is not that clearly present. We found different estimations of the level of risk associated with unprotected insertive versus receptive anal sex in combination with a higher perception of the gratification potential of the former. Unsafe men seem to make a noticeable difference between their own and their partner's risk and gratification.

Adolescent↗
PubMed1997

Reasons for having sex and sexual risk-taking: a study of heterosexual male STD clinic patients.

Individuals report a variety of reasons for having sex. Understanding these reasons can improve HIV and STD prevention efforts because they may constitute an important component in the aetiology of sexual risk-taking behaviours. Relationships between self-reported reasons for having sex and frequency of participation in sexual practices among 146 heterosexual men recruited from public STD clinics in Southern California were examined. Using a self-administered questionnaire, respondents reported how often they engaged in sex for each of 16 reasons and how frequently they participated in high, moderate, and low-risk sexual practices. A principal components analysis identified five factors used to construct scales: love; compliance; pleasure; altered states; and potency. Higher-risk sexual practices were positively associated with the pleasure and potency scales, whereas lower-risk practices were positively associated with the love scale. These findings suggest that some reasons men report for having sex may influence sexual risk-taking. Interventions to reduce unsafe sex should explicitly address how men can practise safer sex and still experience pleasure and potency.

Adult↗
PubMed1997

Younger versus older gay men: risks, pleasures and dangers of anal sex.

This study reports on the practice and the pleasure and danger perceptions of protected and unprotected anal sex of young adult gay men (< or = 30) and older gay men (30+). It is assumed that, if prevention efforts were successful, younger gay men-sexually socialized during the AIDS era-should have more favourable perceptions of anal sex with a condom. Data from a cohort of gay men in Flanders, Belgium (1993, n = 553) are used in this analysis. The results indicate that younger gay men do not differ from older gay men in the riskiness/safety of their actual sexual behaviour. However, younger men hold different valuations regarding anal sex. They report a higher appraisal for both insertive and receptive anal sex with a condom. The perceived safety of protected anal sex is also higher among the younger men. We also found that younger men with a steady partner report more gratification from insertive anal sex with a condom than do older partnered men. We interpret these findings as evidence of the effectiveness of HIV prevention efforts.

Adolescent↗
PubMed1996

The social support of Flemish gay men: an exploratory study.

This study describes the sources and level of social support of Flemish gay men using data from surveys conducted in 1989 (n = 379) and 1993 (n = 553). Five indicators of social support were used: positive appraisal, perceived isolation, enacted social support, perceived material support, and perceived emotional support. The main results, which are cross validated across the two samples, are as follows. Most men score high on all five indicators of social support. Social relationship conflicts are either nonspecific or related to the steady partner. Isolation and lack of positive appraisal are also nonspecific or related to gay friends. Parents still function as important sources of material support. Men without a steady partner and men with low socioeconomic status experience more isolation. Single men also report less positive appraisal, while older men have less material support.

Adolescent↗
PubMed1996

Patterns of sexual risk-taking among heterosexual men.

Heterosexual male STD (sexually transmitted disease) clinic patients (N=146) were classified by cluster analysis into four groups based on their self-reported frequency of participation in eleven sexual behaviors that varied in risk for contracting an STD or HIV. Significant differences among the four groups were found in their participation in some sexual practices that were not used in the clustering, and men in the four groups differed significantly by ethnicity, education, type of relationship, and motivations for engaging in sex. Results of this study have implications for the design of effective AIDS prevention programs to encourage safer-sex among heterosexual men. Given the differences in men's sexual practices, safer-sex messages need to be tailored to reach subgroups of STD patients with similar risk-taking patterns.

Adult↗
PubMed1994

Inhibition of rat liver cytosolic glutathione S-transferase by silybin.

1. The naturally occurring hepatoprotective compound silybin is a potent inhibitor of glutathione S-transferase isoenzymes 1-1, 2-2, 3-3, and 4-4, displaying a high degree of isoenzyme selectivity. 2. Using CDNB at a fixed concentration of 1 mM and varying the GSH concentration, silybin exhibited competitive inhibition of isoenzyme 2-2 with a Ki of 32 microM, non-competitive and predominantly non-competitive inhibition of isoenzymes 1-1 and 4-4 with Kis of 20 and 1.2 microM, respectively, and uncompetitive inhibition of isoenzyme 3-3 with a Ki of 0.2 microM. 3. With CDNB as the variable concentration substrate silybin exhibited competitive inhibition of isoenzyme 1-1 with a Ki of 8 microM, non-competitive inhibition of isoenzyme 2-2 with a Ki of 41 microM, and non-competitive inhibition of isoenzymes 3-3 and 4-4 with Kis of 0.8 and 0.5 microM, respectively.

Animals↗
PubMed1994

Another routine case: gunshot trauma.

This case study describes the surgical repair of noncomplicated gunshot wounds in a young man. The preoperative assessment and surgical procedures, including bullet retrieval, is given. A systematic routine for handling emergency gunshot wound patients is shared as intraoperative nursing is described. Direct cost of this surgery to the operating room is explored.

Adolescent↗
PubMed1993

Coming out and AIDS-related high-risk sexual behavior.

How the withdrawal of social support associated with the coming out of gay men influences AIDS-related sexual risk-taking among Flemish (Belgian) gay men is analyzed. Recruited via key persons, the 379 gay men in this nonclinical cohort completed a lengthy, computerized questionnaire dealing with diverse aspects of gay life and culture. Independent variables include demographic characteristics, AIDS knowledge, coming-out histories, six social support dimensions, and personal resources. The dependent variables were insertive and receptive anal intercourse with and without a condom. Stepwise regression explained, respectively, 41.2, 38.4, 18.4, and 14.2% of the variance. Absence of appraisal (the view that others approve of the way one does things or feels about things) led to higher frequencies of insertive anal sex (both with and without a condom). The experience of emotional conflict lowered the use of condoms by the insertive partner in anal intercourse. Disapproval by significant others of being gay also led to higher levels of receptive anal intercourse without a condom. Subjects with a high belief in mastery had higher frequencies of risk-taking, suggesting that the combination of the experience of negative reactions and high mastery lead to greater involvement in risky sexual behavior. Findings are interpreted within the theoretical framework of the coming-out process and gay identity formation.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Selective elution of subunit 4-containing rat liver glutathione S-transferases using affinity chromatography.

Glutathione S-transferase (GST) isoenzymes of rat liver cytosol were purified from a S-hexylglutathione Sepharose affinity column without using S-hexyl-glutathione for elution. The method involves an initial elution of GSTs 3-4 and 4-4 from the affinity matrix with 10 mM glutathione in 50 mM Tris-HCl (pH 7.0), followed by the elution of GSTs 1-1, 1-2, 2-2 and 3-3 with 10 mM glutathione in 50 mM Tris-HCl (pH 9.6). These two fractions were then chromatofocused simultaneously to separate the individual GST dimers. The ampholytes used in this process were subsequently removed by ultrafiltration, as the standard techniques (Sephadex G25 column, and dialysis) were not effective. This method provides improved yields and reduced losses of GST activity, by halving the preparation time.

Animals↗
PubMed1992

AIDS and promiscuity: muddles in the models of HIV prevention.

AIDS has been blamed on promiscuity and the promiscuous, and a major goal of many HIV-prevention programs has been to induce people to reduce the number of their sexual partners. Despite the salience of this concept in the AIDS discourse of scientists, policymakers, the media, religious leaders, and the gay community, critical analysis of the role of promiscuity in this epidemic has been lacking. Following a review of promiscuity in various genres of AIDS discourse, this article discusses promiscuity in American society and in HIV-prevention campaigns. The relative risks associated with monogamy, abstinence and promiscuity are examined, and the author concludes that the partner-reduction strategy, instead of contributing to a reduction in HIV transmission has been an impediment to AIDS prevention efforts, exacerbating the problem by undermining the sex-positive approaches to risk reduction that have proven effective. Responsibility for this misguided strategy is attributed to a moralistic approach to AIDS and to the misapplication of epidemiological concepts and inappropriate social science models to the task of promoting healthy forms of sexuality.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Alcohol and risky sex: in search of an elusive connection.

Since the publication of the 1986 article by Stall, McKusick, Wiley, Coates and Ostrow, the conclusion that drinking alcohol prior to or during erotic encounters increases the probability of engaging in high-risk sexual behavior has been widely accepted, despite some contradictory findings from research on this hypothesis. This paper presents the results of tests of the alcohol/risky-sex hypothesis in a cohort of gay men in Flanders, Belgium. Failing to find evidence to support the hypothesis of a general effect of alcohol on sexual risk taking, we argue that previous conclusions on this matter must be viewed with extreme caution, especially in light of the implications that this failure to replicate has for AIDS prevention programs. Cultural, social, and methodological factors that could account for this failure to replicate are discussed in the context of a review of the literature on this hypothesis.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Hodgkin's disease presenting as liver abscesses.

A patient is reported who presented with sterile hepatic abscesses which proved to be the first manifestation of Hodgkin's disease. He failed to improve with antibiotic treatment but responded to combined chemotherapy. Liver involvement as the first sign of Hodgkin's disease is rare. Liver abscesses due to Hodgkin's disease seem to be previously unreported.

Adult↗