Biomedical subjects

G Marks

Publications and source records attributed to G Marks.

At least 19 recordsLinked to original sources

PubMed2006

Communication of HIV viral load to guide sexual risk decisions with serodiscordant partners among San Francisco men who have sex with men.

The objective of this study was to estimate frequency and correlates of discussing HIV viral load (VL) with serodiscordant sex partners to guide decisions about sexual activities among men who have sex with men (MSM). We conducted a cross-sectional survey of 573 San Francisco MSM. Among 507 who knew their HIV status, 397 (78%) were familiar with the term 'viral load', and half (n=199) had a serodiscordant partner in the prior year. These 199 respondents (n=130 [65%] HIV-positive; n=69 [35%] HIV-negative) were the focus of this analysis. A majority (n=111, 56%) discussed VL in the prior year with serodiscordant partners specifically to guide decisions about sexual risk behaviour. Discussion was more common among HIV-positive than HIV-negative participants (adjusted odds ratio [AOR], 3.5; 95% confidence interval [CI], 1.6-7.6), and African Americans compared to whites (AOR, 3.7; 95% CI, 1.5-9.5). HIV-negative men who discussed VL were more concerned about becoming infected, but also more willing to engage in risky behaviour with a partner whose VL is undetectable, than men not discussing VL. Some HIV-negative men may be discussing VL to engage in higher risk behaviour upon learning of an HIV-positive partner's undetectable VL. Interventions targeting MSM should explain that while risk of transmission is likely reduced with a low blood plasma VL, it is not necessarily eliminated.

Adult↗

PubMed2006

Cost-effectiveness of current and optimal treatment for adult asthma.

BACKGROUND: This article is part of a project to determine the cost-effectiveness of averting the burden of disease. We used population data to investigate the costs and benefits of allocating resources to optimal treatment for asthma in adults, using a burden of disease framework. METHODS: We calculated the population burden of asthma in the absence of any treatment as years lived with disability (YLD), ignoring the years of life lost. We then estimated the proportion of burden averted with current interventions, the proportion that could be averted with optimally implemented current evidence-based guidelines and the direct treatment cost-effectiveness ratio in dollarA per YLD averted for both current and optimal treatment. RESULTS: The direct treatment cost of current treatment of adult asthma in Australia was dollar A452 million and averted 25% of the burden with a cost-effectiveness ratio of dollar A14 000/YLD averted. Optimal treatment and optimal compliance would cost dollar A627 million and avert 69% of the burden with a cost-effectiveness ratio of dollar A7000/YLD averted. CONCLUSION: Implementation of optimal treatment for asthma is affordable, will be more cost-effective and will significantly decrease disability.

Adult↗

PubMed2006

Methamphetamine and sildenafil (Viagra) use are linked to unprotected receptive and insertive anal sex, respectively, in a sample of men who have sex with men.

OBJECTIVES: There is evidence that methamphetamine and sildenafil (Viagra) use are associated with sexual risk behaviour among men who have sex with men (MSM). We investigated the association of methamphetamine, sildenafil, and other substance use with unprotected receptive and insertive anal sex among MSM by conducting an encounter specific analysis. METHODS: Data were from a cross sectional, community based survey of MSM in San Francisco regarding behaviour during their most recent anal sex encounter. Mulitvariate regression analysed independent associations of specific substance use and demographic variables with unprotected anal sex behaviours. RESULTS: The sample (n = 388) was diverse in race/ethnicity, age, income, education, HIV status, and homosexual/bisexual identification. More than half (53%) reported unprotected anal sex, including insertive (29%) and receptive (37%) during their most recent anal sex encounter; 12% reported unprotected insertive and 17% reported unprotected receptive anal sex with an HIV discordant or unknown partner. Methamphetamine was used by 15% and sildenafil was used by 6% of the men before or during the encounter; 2% used both drugs. In multivariate analysis controlling for demographic factors and other substance use, methamphetamine use was associated with unprotected receptive (odds ratio (OR), 2.03; 95% confidence interval (CI), 1.09 to 3.76) and sildenafil use was associated with unprotected insertive (OR, 6.51; CI, 2.46 to 17.24) anal sex. Effects were stronger with HIV discordant or unknown sex partners specifically. CONCLUSION: Encounter specific associations of methamphetamine and sildenafil use with unprotected receptive and insertive anal sex, respectively, indicate the importance of assessment specificity and tailoring risk reduction efforts to address certain drugs and sexual behavioural roles among MSM.

Adolescent↗

PubMed2004

Increased motor drive and sleep loss in mice lacking Kv3-type potassium channels.

The voltage-gated potassium channels Kv3.1 and Kv3.3 are widely expressed in the brain, including areas implicated in the control of motor activity and in areas thought to regulate arousal states. Although Kv3.1 and Kv3.3-single mutants show some physiological changes, previous studies revealed relatively subtle behavioral alterations suggesting that Kv3.1 and Kv3.3 channel subunits may be encoded by a pair of redundant genes. In agreement with this hypothesis, Kv3.1/Kv3.3-deficient mice display a 'strong' mutant phenotype that includes motor dysfunction (ataxia, myoclonus, tremor) and hyperactivity when exposed to a novel environment. In this paper we report that Kv3.1/Kv3.3-deficient mice are also constitutively hyperactive. Compared to wildtype mice, double mutants display 'restlessness' that is particularly prominent during the light period, when mice are normally at rest, characterized by more than a doubling of ambulatory and stereotypic activity, and accompanied by a 40% sleep reduction. When we reinvestigated both single mutants, we observed constitutive increases of ambulatory and stereotypic activity in conjunction with sleep loss in Kv3.1-single mutants but not in Kv3.3-single mutants. These findings indicate that the absence of Kv3.1-channel subunits is primarily responsible for the increased motor drive and the reduction in sleep time.

Animals↗

PubMed2003

Serostatus disclosure, sexual communication and safer sex in HIV-positive men.

This study assessed HIV-positive men's sexual behaviours with partners at risk for infection, and examined the extent to which safer sex was associated with interpersonal communication variables, namely, (1). disclosure of one's seropositive status and (2). specific communication with partners about safer-sex practices. A total of 105 HIV-positive men (43% homosexual, 38% bisexual, 19% heterosexual), randomly sampled at an HIV outpatient clinic in Los Angeles, completed a behavioural questionnaire assessing events in their most recent sexual encounter with an HIV-negative or unknown serostatus partner. Results indicated that men who disclosed their seropositive status and explicitly discussed the topic of safer sex with their at-risk partners had a significantly higher prevalence of protected anal or vaginal intercourse than did men who disclosed only. The findings suggest that post-test counselling regarding the importance of disclosing one's seropositive status to sex partners should be augmented by behavioural interventions that enhance seropositive persons' skills in communicating explicitly with partners about safer sex to help reduce transmission of HIV.

Adult↗

PubMed2002

Predictors of high house dust mite allergen concentrations in residential homes in Sydney.

BACKGROUND: In parts of coastal Australia, house dust mite allergen concentrations in homes are often very high with at least 80% of homes in Sydney exceeding concentrations of 10 microg of allergen per gram of fine dust. In this study, we report the relation between characteristics of the home environment and house dust mite allergen concentrations at three sites in Sydney homes. METHODS: A total of 616 families were recruited as part of the Childhood Asthma Prevention Study (CAPS). Information about the home environment and structural aspects of the home was collected using a questionnaire. Samples of dust were collected from the parents' bed, the bedroom floor and the living room floor and assayed for Der p 1. RESULTS: A total of 68% of participants' beds, 65% of bedroom floors and 56% of living room floors had Der p 1 concentrations above 10 microg/g, with the highest concentrations of allergen in the bed. The most significant predictor of high Der p 1 concentrations in the bed and floors was the age of the home. We also found that beds with mattresses over two years old and with woollen or synthetic blankets or synthetic quilts had higher Der p 1 concentrations. Carpeted floors had higher Der p 1 concentrations than hard floors. CONCLUSION: The finding that high Der p 1 allergen concentrations in homes with carpets and older mattresses indicates that control strategies directed at these sources are likely to be effective in reducing exposure. Alternatives such as the use of house dust mite impermeable mattress encasings on older mattresses may also be effective in reducing exposure.

Air Pollution, Indoor↗

PubMed2001

Drug use and sexual risk behavior among gay and bisexual men who attend circuit parties: a venue-based comparison.

CONTEXT: HIV risk behavior among urban gay/bisexual men has recently increased. High-risk sexual activity and drug use may be particularly high during circuit party (CP) weekends, during which gay/bisexual men congregate for social activities and dancing. OBJECTIVES: To compare prevalence of risk behaviors during CP weekends with those during non-CP weekends. DESIGN: Cross-sectional study. PARTICIPANTS: 295 gay/bisexual men from the San Francisco Bay Area. MAIN OUTCOME MEASURES: Drug use and sexual risk behavior during a San Francisco CP weekend, a CP weekend held in another geographic area (distant weekends), and two non-CP weekends. RESULTS: During their most recent distant CP weekend, 80% of participants used methylenedioxymethamphetamine (ecstasy), 66% ketamine, 43% crystal methamphetamines, 29% gamma-hydroxybutyrate or gamma-butyrolactone (GHB/GBL), 14% sildenafil (Viagra), and 12% amyl nitrites (poppers); 53% used four or more drugs. Drug use prevalence was greater during CP than non-CP weekends ( p <.001). Unprotected anal sex with partners of unknown or opposite HIV serostatus was most prevalent during distant CP weekends, reported by 21% of HIV-positive and 9% of HIV-negative participants. In multivariate analysis, predictors of unprotected anal sex with opposite or unknown HIV serostatus partners included being HIV-positive (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4-7.5), and weekend use of crystal methamphetamines (OR 2.4; 95% CI, 1.1-4.9), sildenafil (OR, 3.8; 95% CI, 2.0-7.3), and amyl nitrites (OR, 2.2; 95% CI, 1.3-4.0). CONCLUSIONS: Prevalence of high-risk activity during these weekends suggests significant potential for HIV transmission in this population. Public health programs in communities hosting CPs should aim to reduce rates of drug use and sexual risk behavior among CP participants, especially HIV-positive men.

Adult↗

PubMed2001

HIV-positive men's sexual practices in the context of self-disclosure of HIV status.

OBJECTIVE: To examine whether disclosure of HIV-positive status to sex partners at risk for HIV infection is associated with safer sex practices and to examine the prevalence and correlates of specific disclosure/sexual behavior patterns. METHODS: Cross-sectional assessment of 206 HIV-positive men (41% homosexual, 35% bisexual, 24% heterosexual) sampled randomly at an outpatient HIV clinic in Los Angeles, who reported that their most recent sex partner was HIV-negative or of unknown serostatus. Unsafe sex was defined as unprotected anal or vaginal intercourse with that partner. RESULTS: Twenty-five percent of the men engaged in unsafe sex, and 48% of the total sample withheld disclosure from the partner. The prevalence of safer sex was not significantly higher among disclosers than among nondisclosers (unadjusted odds ratio = 1.29; 95% confidence interval: 0.69-2.45), and disclosure was not significantly associated with safer sex in any of 25 demographic or partner subgroups examined in the study. In the full sample, 40% of the men disclosed and engaged in safer sex (informed protection), 35% withheld disclosure and engaged in safer sex (uninformed protection), 12% informed their partner and engaged in unsafe sexual behavior (informed exposure), and 13% withheld disclosure and engaged in unsafe sex (uninformed exposure). Risky behavior patterns were associated with using alcohol/drugs before sex, having an HIV-unknown partner, being less emotionally involved with one's partner, and testing seropositive in the previous 3 years. CONCLUSIONS: Interventions for seropositive men that focus primarily on increasing disclosure of serostatus to sex partners may not reduce the prevalence of unsafe sex. Interventions are needed to address the social and psychologic processes that give rise to risky behavior patterns in HIV-infected men. Improved substance abuse counseling also may be needed.

Adult↗

PubMed2001

Are negative affective states associated with HIV sexual risk behaviors? A meta-analytic review.

This meta-analytic review examined whether negative affective states (depressive symptomatology, anxiety, anger) are associated with sexual behaviors that place people at risk for contracting or transmitting HIV. The results from 34 study samples were included in the analysis. Contrary to popular belief, the findings as a whole provide little evidence that negative affect is associated with increased sexual risk behavior. The average weighted correlation for the overall association was .05. The effect size was nonsignificantly higher for anger (r = .10) than for depressive symptoms (r = .04) or anxiety (r = .03). The variability of effect sizes was not accounted for by type of sexual risk measure, subject population, or methodological aspects of the studies. Conceptual and methodological limitations of the literature are identified and directions for future research are discussed.

Adult↗

PubMed2001

The unreliability of the Kato-Katz technique limits its usefulness for evaluating S. mansoni infections.

The Kato-Katz technique, a (semi) quantitative stool examination technique, is generally recommended for diagnosis and evaluation of Schistosoma mansoni infection by schistosome experts. However, egg counts are subject to important variability. In order to quantify the reproducibility of egg counts using the Kato-Katz technique, field data of 1255 observations on 299 subjects infected with Schistosoma mansoni were analysed. Agreement between repeated observations was assessed both categorically (kappa statistic) and continuously (analysis of variance). The day-to-day variation of egg counts was much greater than the variation due to different observers or different slides. The quantitative reproducibility was low: the weighted kappa statistic was 0.39 between specimens of different days, 0.62 between slides of the same specimen and 0.81 between observers of the same slide. Therefore the classification of individual patients into groups based on egg counts, used as a measure of morbidity, must be interpreted with great care, especially in longitudinal studies. Usefulness of the Kato-Katz technique appears limited. Its reproducibility is low. It cannot be recommended as a routine test in a primary health care setting or in a hospital laboratory because safety and detection of other parasites are better assured by other techniques. It can be used in epidemiological studies and evaluation of schistosomiasis control programmes, but here too, other techniques might be preferred.

Humans↗

PubMed2001

Parental smoking and respiratory tract infections in children.

The adverse health consequences of exposing children to tobacco smoke have been well documented. Re-calculation of the data available from cohort and cross-sectional studies worldwide shows that between 500-2500 excess hospitalisations and between 1000 to 5000 excess diagnoses per 100 000 young children as result from respiratory infections can be directly attributed to parental smoking. Results of published meta-analyses support these figures, which are probably under-estimated because of the effects of non-differential misclassification bias. These excess infections are a source of preventable morbidity and have a high cost to the community. They also have important long-term consequences because children who have respiratory infections in early life are at an increased risk of developing asthma in later childhood. More effective strategies that prevent smoking in young people before they become parents have the potential to lead to reductions in these high rates of unnecessary morbidity in the next generation of children.

Child, Preschool↗

PubMed2001

Effects of housing relocation on immunocompetence and psychosocial functioning in older adults.

BACKGROUND: The psychological and physical response to moderate life stressors among older adults has not been well characterized. This research examines effects of voluntary housing relocation on distress and immune function in healthy older adults as a model for studying the effects of moderate life stress. METHODS: Thirty older adults moving to congregate living facilities were assessed 1 month premove, 2 weeks postmove, and 3 months postmove. Twenty-eight nonmoving control subjects were assessed at similar time points. Subjects completed psychosocial questionnaires and had early morning blood draws in their homes. Blood samples were assayed for natural killer cell cytotoxicity (NKCC), interleukin-6 (IL-6), and IgG antibody titers to the Epstein Barr virus (EBV) viral capsid antigen. RESULTS: Movers demonstrated decreased vigor and elevated thought intrusion 1 month premove and 2 weeks postmove. By the 3-month follow-up, vigor increased, and intrusion decreased to levels commensurate with the controls. Averaged across all time points, movers showed lower NKCC than controls; however, post-hoc analyses indicate that by the 3-month follow-up time point, these differences were no longer significant. There were no differences between groups in IL-6 or in EBV antibody titers. Independent of the effects of group, higher levels of vigor were associated with greater NKCC at all assessments and with lower EBV titers at 2 weeks postmove. CONCLUSIONS: Findings suggest that in general, healthy older adults recover well psychologically from moderate. temporary life stressors such as moving. Whereas movers showed generally lower NKCC than controls, IL-6 and EBV antibody titers appeared not to be strongly affected by the stress of moving.

Adaptation, Psychological↗

PubMed2001

Use of V4R in patients who sustain blunt chest trauma.

OBJECTIVE: In blunt chest trauma, the right ventricle is more vulnerable than the left. The purpose of this study was to determine whether recording V4R in patients with blunt chest trauma would provide additional useful information to that already obtained from the standard 12-lead electrocardiogram (ECG). METHODS: Forty-five patients with blunt chest trauma and 40 unmatched control subjects without blunt chest trauma had standard 12-lead ECG and right precordial leads recorded. The ECGs were read blindly by three physicians. RESULTS: Patients with chest trauma were distinguishable from controls on the basis of the left-sided ECGs (odds ratio, 2.9; 95% confidence interval, 1.71-4.90). This was not the case using V4R (odds ratio, 1.23; 95% confidence interval, 0.59-2.0). CONCLUSION: Patients with a significant mechanism and physical findings of blunt chest trauma were more likely than controls to have an abnormal ECG. They were not more likely to have abnormalities in V4R. We recommend that a 12-lead ECG, but not V4R, be routinely obtained on these patients.

Adolescent↗

PubMed2001

Preferences about the characteristics of future HIV prevention products among men who have sex with men.

This study of men who have sex with men (MSM) examined preferences about the characteristics of a potential product for preventing sexual transmission of HIV, such as a rectal microbicide. MSM were recruited in West Hollywood, California. They self-administered a questionnaire and rated 48 product characteristics representing seven dimensions. Overall, the ratings were highest for effectiveness in preventing HIV and other sexually transmitted diseases, followed by characteristics reflecting the physical or secondary effects of the product and logistics of use. Physical attributes, convenience/accessibility, and psychological aspects had intermediate ratings; interpersonal dynamics had the lowest rating. Men with negative attitudes about using condoms to prevent HIV infection were more likely than their counterparts to prefer a product that does not reduce sexual sensation or pleasure, does not break the mood, and can be used after a sexual encounter ends. A similar pattern was observed when participants were stratified by whether or not they had engaged in unprotected anal intercourse in the past 12 months. The findings inform the development, testing, and marketing of a future HIV prevention product for MSM.

Adult↗

PubMed2001

The Circuit Party Men's Health Survey: findings and implications for gay and bisexual men.

OBJECTIVES: This study examined characteristics of gay and bisexual men who attend circuit parties, frequency of and motivations for attending parties, drug use and sexual behavior during circuit party weekends, and use of risk reduction materials available at parties. METHODS: A cross-sectional survey was conducted among 295 gay and bisexual men from the San Francisco Bay Area who had attended a circuit party in the previous year. RESULTS: One fourth of the men reported a drug "overuse" incident in the previous year. Nearly all respondents reported use of drugs during circuit party weekends, including ecstasy (75%), ketamine (58%), crystal methamphetamine (36%), gamma hydroxybutyrate or gamma butyrolactone (25%), and Viagra (12%). Two thirds of the men reported having sex (oral or anal), 49% reported having anal sex, and 28% reported having unprotected anal sex during the 3-day period. An association was found between use of drugs and sexual risk behavior. Prevention materials were observed at party events by some men; however, relatively few men used the materials. Common motivations for attending the parties were "to listen to music and dance" and "to be with friends." CONCLUSIONS: Intensive, targeted health promotion efforts are needed for gay and bisexual men who attend circuit parties.

Adult↗

PubMed2000

Is 'knowing people with HIV/AIDS' associated with safer sex in men who have sex with men?

OBJECTIVE: To examine the sexually protective role of knowing person(s) with HIV/AIDS (PWHA) by conducting a multidimensional analysis distinguishing the number of PWHA known (by disease status and relationship category) and aspects of the relationship with the closest PWHA (emotional closeness, length of time known, disease status, type of relationship). DESIGN: Cross-sectional study of white, Latino, and African-American men who have sex with men recruited at street locations in West Hollywood, California, in 1997. METHODS: The analyses conducted with linear regression models focused on men (n = 334) who reported that they were seronegative or of unknown serostatus and thus at risk for HIV infection. Unprotected sex was defined as percentage of anal intercourse partners in the past 12 months with whom unprotected anal intercourse (UAI) occurred at least once. RESULTS: The number of PWHA known was not associated with the percentage of UAI partners in multivariate or univariate analyses. Greater emotional closeness to a person who was HIV-positive without AIDS was associated with reduced UAI in multivariate models even after excluding participants whose close PWHA was a lover or sex partner. Younger men (18-25 years) knew fewer PWHA, reported less emotional closeness to a PWHA, and had a higher level of UAI than did older men. CONCLUSIONS: Emotional closeness to a seropositive person without AIDS may be a sexually protective factor. The results suggest the possibility that lower levels of emotional closeness to a PWHA may partially underlie the elevated sexual risk behavior of younger men who have sex with men.

Adolescent↗

PubMed2000

Preoperative chemoradiation in fixed distal rectal cancer: dose time factors for pathological complete response.

PURPOSE: Preoperative chemoradiation is being utilized extensively in the treatment of rectal cancer. However, a variety of dose time factors in both delivery of chemotherapy and irradiation remain to be established. This study was undertaken to examine the impact of dose time factors on pathological complete response (pCR) rates following preoperative chemoradiation for fixed rectal cancer. METHODS AND MATERIALS: Thirty-three patients with fixed rectal cancers were treated with combined 5-fluorouracil (5-FU) chemotherapy and pelvic radiation. Twenty-one patients received bolus 5-FU during the first 3-5 days of radiation and repeated on days 28-33 of their radiation treatment. Twelve patients were treated with continuous infusion (CI) 5-FU, 225 mg/m(2) for the duration of the pelvic radiation. Fifteen patients received a planned total radiation dose of 45 to 50 Gy and 18 patients received a dose of 55 to 60 Gy. Surgical resection was then carried out 6-8 weeks after completion of treatment. RESULTS: Diarrhea was the most frequent acute toxicity. Grade 3 diarrhea was observed in 6 patients requiring treatment interruption and was not related to the chemotherapy regimen. There was no Grade 4 or 5 toxicity. pCR was observed in 2 of 21 (10%) patients treated with bolus 5-FU as compared to 8 of 12 (67%) for patients treated with CI (p = 0.002). pCR were observed in 8 of 18 (44%) patients receiving radiation dose > or = 5500 cGy as compared to 2 of 15 (13%) patients treated to a dose < or = 5000 cGy (p = 0.05). In the high-dose radiation (> or = 5500 cGy) group, a significant difference in pCR rate was observed in patients treated with CI, 8 of 12 (67%) (p = 0.017) as compared with bolus 5-FU (0 of 6). There was no significant difference in operative morbidity or in wound healing between patients treated with bolus 5-FU or CI or within the groups treated with low or high doses of radiation. Three patients have developed local recurrence at 14 and 24 months, two in the low-dose group treated with bolus 5-FU and one patient in the CVI group. The overall 5-year survival for the whole group is 71%. CONCLUSION: Dose intensity of 5-FU and dose of radiation correlate significantly with the likelihood of achieving a pCR. Continuous infusion 5-FU (CI) and a preoperative radiation dose of 5500 cGy or higher can achieve pCR rates of approximately 50%, even in fixed cancers of the rectum.

Adult↗

PubMed2000

Age-related risk for HIV infection in men who have sex with men: examination of behavioral, relationship, and serostatus variables.

The study examined behavioral, relationship, and serostatus variables that potentially contribute to HIV infection risk in three age groups of men who have sex with men (MSM). MSM recruited in West Hollywood, California self-administered a questionnaire measuring unprotected insertive anal intercourse (UIAI) and unprotected receptive anal intercourse (URAI) with primary and nonprimary partners. The following relationship/serostatus variables were also assessed: recency of HIV testing, knowledge of own HIV serostatus, perception of partner's serostatus, seroconcordance (self and partner seronegative), and self-reported monogamy status. The prevalence of UIAI and URAI was higher with primary than nonprimary partners. These sexual risk behaviors with primary partners were substantially more prevalent among men younger than 25 years of age than among men aged 25 to 30 or over age 30. UIAI and URAI with nonprimary partners were uncommon in each age group, and there were no significant age differences on the serostatus and relationship variables. The findings suggest that young MSM may be at elevated risk for contracting HIV by virtue of their sexual risk behavior with primary partners. Targeted interventions for MSM need to address sexual risk in the context of primary relationships.

AIDS Serodiagnosis↗