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Biomedical subjects

Mark Davis

Publications and source records attributed to Mark Davis.

26 records · Page 2Linked to original sources
PubMed2004

Hepatitis C and its risk management among drug injectors in London: renewing harm reduction in the context of uncertainty.

AIM: Recognizing the dearth of qualitative research on hepatitis C virus (HCV) infection associated with injecting drug use in the UK, this paper summarizes qualitative insights from a study exploring the social relations of HCV risk management among drug injectors in London. METHOD: Adopting an inductive approach to data collection and analysis, 59 depth tape-recorded qualitative interviews were undertaken in 2001 with drug injectors recruited via drug user networks. RESULTS: While access to injecting equipment was reportedly good, needle and syringe sharing continued in exceptional circumstances and in the context of 'trust relationships'. Analyses of drug injectors' accounts of variations of 'I never share' showed that this construction denoted less a descriptor of actual risk behaviour than presentation of perceived risk status. Paraphernalia sharing, including spoons and filters, was common. There was much confusion and uncertainty concerning HCV knowledge, including its medical and transmission risks. Injectors were aware of the provisionality and partiality of their HCV knowledge. Confusion also surrounded the meaning of HCV antibody test results, with some feeling that their positive diagnosis had been 'trivialized' by their experiences of HCV testing. Injectors tended to make sense of HCV risk in relation to HIV. With most viewing HCV prevalence as high and HCV transmission as an inevitable consequence of injecting, HCV risk was perceived as ubiquitous and unavoidable. CONCLUSIONS: There is an urgent need to renew UK policies of harm reduction in order to support perceptions that HCV is avoidable and preventable.

Adolescent↗
PubMed2003

Effects of MECP2 mutation type, location and X-inactivation in modulating Rett syndrome phenotype.

Rett syndrome (RTT) is a clinically defined disorder that describes a subset of patients with mutations in the X-linked MECP2 gene. However, there is a high degree of variability in the clinical phenotypes produced by mutations in MECP2, even amongst classical RTT patients. In a large-scale screening project, this variability has been examined by looking at the effects of mutation type, functional domain affected and X-inactivation. Mutations have been identified in 60% of RTT patients in this study (25% of whom were atypical), including 23 novel mutations and polymorphisms. More mutations were found in classical patients (63%) compared to atypical patients (44%). All of the pathogenic mutations were de novo in patients for whom parent DNA was available for screening. A composite phenotype score was developed, based on the recommendations for reporting clinical features in RTT of an international collaborative group. This score proved useful for summarising phenotypic severity, but did not correlate with mutation type, domain affected or X-inactivation, probably due to complex interactions between all three. Other correlations suggested that truncating mutations and mutations affecting the methyl-CpG-binding domain tend to lead to a more severe phenotype. Skewed X-inactivation was found in a large proportion (43%) of our patients, particularly in those with truncating mutations and mutations affecting the MBD. It is therefore likely that X-inactivation does modulate the phenotype in RTT.

Australia↗
PubMed2002

CD4(+) T cells from glutamic acid decarboxylase (GAD)65-specific T cell receptor transgenic mice are not diabetogenic and can delay diabetes transfer.

Glutamic acid decarboxylase (GAD)65 is an early and important antigen in both human diabetes mellitus and the nonobese diabetic (NOD) mouse. However, the exact role of GAD65-specific T cells in diabetes pathogenesis is unclear. T cell responses to GAD65 occur early in diabetes pathogenesis, yet only one GAD65-specific T cell clone of many identified can transfer diabetes. We have generated transgenic mice on the NOD background expressing a T cell receptor (TCR)-specific for peptide epitope 286-300 (p286) of GAD65. These mice have GAD65-specific CD4(+) T cells, as shown by staining with an I-A(g7)(p286) tetramer reagent. Lymphocytes from these TCR transgenic mice proliferate and make interferon gamma, interleukin (IL)-2, tumor necrosis factor (TNF)-alpha, and IL-10 when stimulated in vitro with GAD65 peptide 286-300, yet these TCR transgenic animals do not spontaneously develop diabetes, and insulitis is virtually undetectable. Furthermore, in vitro activated CD4 T cells from GAD 286 TCR transgenic mice express higher levels of CTL-associated antigen (CTLA)-4 than nontransgenic littermates. CD4(+) T cells, or p286-tetramer(+)CD4(+) Tcells, from GAD65 286-300-specific TCR transgenic mice delay diabetes induced in NOD.scid mice by diabetic NOD spleen cells. This data suggests that GAD65 peptide 286-300-specific T cells have disease protective capacity and are not pathogenic.

Abatacept↗
PubMed2002

Investigation of the potential release of polychlorinated dioxins and furans from PCP-treated utility poles.

The United States (US) Environmental Protection Agency (EPA) estimated that the use of technical grade pentachlorophenol (PCP) between 1970 and 1995 to treat wood was approximately 400,000 metric tons in the US, and that between 4800 and 36,000 g of 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents (TEQs) were incorporated annually in treated wood. The EPA has been unable, however, to estimate the rate of release of polychlorinated dibenzo-p-dioxins and dibenzofurans (CDD/Fs) from treated utility poles into the environment. There is some evidence that CDD/Fs leach from treated poles into the surrounding soils, but these studies do not allow for the calculation of a rate of release from this mechanism. Another possible release mechanism is the volatilization of dioxins into the atmosphere, but there are no data to demonstrate, much less quantify, this release. While not directly measuring the release of dioxins from treated utility poles into the environment, this study was designed to examine the potential for such release. The general approach taken was to collect PCP-treated poles of varying ages, to remove and analyze multiple samples from each pole cross-section, and to compare the spatial distribution of CDD/F congeners among poles of different ages. Evidence of concentration-depth profile changes over time may provide insight into the potential for dioxins to migrate through and then out of PCP-treated utility poles. It was found that the CDD/F concentrations were consistently higher in the outer portions of the poles than the center. This trend tends to be most marked in older poles and for the lower chlorinated congeners. The trend for dioxins to concentrate in the outer portions of the pole over time suggest migration within the poles, and this migration may result in some environmental release. Other possible explanations were also offered.

Benzofurans↗
PubMedDate not supplied

Sex and the Internet: gay men, risk reduction and serostatus.

Access to the Internet has increased dramatically over the past decade as has its use for meeting sexual partners (e-dating), particularly among gay men. Between June 2002 and January 2004, 128 gay/bisexual men living in London were interviewed one-to-one about their experience of e-dating, sexual risk and HIV prevention. The men were recruited both online (through the Internet) and offline (in clinics and the community); 32 men were HIV-positive, 59 HIV-negative, while 13 had never had an HIV test. A key finding was that both identity as well as anonymity are vital to e-dating. Through a process of online filtering and sero-sorting, HIV-positive men are able to meet other positive men for anal sex without condoms. While this does not present a risk of HIV transmission to an uninfected person it does have implications for the potential transmission of other STIs such as syphilis and LGV. Through e-dating, HIV-positive gay men can also avoid abuse, discrimination and sexual rejection. Our findings do not support the suggestion that the attraction of e-dating is that it affords absolute anonymity. We found that the gradual expression of identity is vital for e-dating among gay men. Internet-based HIV prevention campaigns need to take account of the different ways in which gay reflexively manage aspects of their identity online.

Adult↗
PubMedDate not supplied

Blindness of clinical evaluators, parents, and children in a placebo-controlled trial of fluvoxamine.

OBJECTIVE: Few of the increasing number of pediatric clinical trials of selective serotonin reuptake inhibitors (SSRIs) in children have been evaluated for level of blindness of investigators, children, and parents. The success of the masking procedures used in a double-blind, pediatric trial of fluvoxamine in children was examined. METHOD: Clinical evaluators, parents, and children were asked to guess individual treatment assignment at the end of an 8-week, placebo-controlled trial of fluvoxamine conducted in 128 outpatients (6-17 years of age) with anxiety disorders. The relationship between treatment attribution and improvement status or presence of adverse events was examined. RESULTS: The rate of correct guesses was significantly greater than chance among clinical evaluators (78%), parents (81%), and children (67%) (for all, p < 0.001). Attribution to fluvoxamine was associated with presence of clinical improvement, and attribution to placebo with lack of improvement (p < 0.001) in both the fluvoxamine and placebo group. There was no association between presence of adverse events and direction of the guess. Accuracy of the guess did not improve with time. CONCLUSIONS: The tendency to attribute improvement to active treatment and lack of improvement to placebo was consistent across investigators, parents, and children and was applied regardless of actual treatment received by the patient. Adverse events did not influence treatment attribution.

Adolescent↗
PubMedDate not supplied

Discourse complexity of college writers with and without disabilities: a multidimensional analysis.

The purpose of this study was to examine specific word- and sentence-level features most frequently used in the expository writing of four groups of college writers. Three groups were writers who demonstrated disabilities. Group 1 students (n = 87) demonstrated learning disabilities (LD); Group 2 (n = 50), attention-deficit/hyperactivity disorder (ADHD); and Group 3 (n = 58), combined LD and ADHD. Group 4 consisted of writers with no history of a documented disability (n = 92). Computer-based analysis and structural equation modeling were used to group specific linguistic features identified in the expository essays across all four groups. The frequency of linguistic features, not errors, was analyzed. Four communication dimensions (factors) were identified for the four groups of writers, but the factor loadings and correlations were significantly different across groups. Furthermore, the relationships of specific linguistic features were studied as to their impact on the verbosity, quality, and lexical complexity of students' expository essays. It is interesting to note that very high correlations were found between verbosity, quality, and lexical complexity, suggesting that these constructs are not as separate in their functioning as might be supposed. Implications for assessment and instruction are provided.

Adult↗