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Biomedical subjects

P M Davies

Publications and source records attributed to P M Davies.

At least 19 recordsLinked to original sources
PubMed1998

Sexual HIV risk behaviour among men who have sex with both men and women.

The aim of this study was to describe the sexual behaviour of men who had sex with both men and women in the preceding five years (behaviourally bisexual men), specifically to examine their needs in relation to HIV prevention. Anonymous telephone interviews were carried out with respondents recruited though advertisements in UK newspapers and magazines with (sexual) 'personal' or 'contact' sections. Data are reported from 745 respondents. Respondents report relatively high and approximately equal numbers of male and female sexual partners in the year preceding interview. There is a clear patterning of sexual activity by type of partner (regular or casual). A high proportion report anal intercourse with female and male partners. A third disclose their homosexual practices to regular female partners. Although self-reported HIV seroprevalence is low (less than 1%), the levels of unprotected sex with multiple sexual partners indicate substantial potential for transmission of sexually transmitted infections, including HIV. While low seroprevalence suggests that there is little overlap with existing core groups of HIV infection, the study provides information to judge the priority of targeting HIV prevention initiatives and suggests ways in which initiatives could be undertaken.

Adolescent↗
PubMed1998

Dietary influence on the urinary excretion of polyamines.

The amino groups of amino acids, the constituents of proteins, are catabolized in the urea cycle. One intermediate of this cycle, ornithine, is a precursor molecule of polyamines. The influence of dietary protein intake on the production and excretion of polyamines in the urine is yet unclear. The aim of this study was to investigate the excretion of polyamines in the urine following three days of creatine-free, creatine-free and low-polyamine diet in four persons. On the fourth day they were loaded with creatine-free, creatinine-free and low-polyamine high-protein diet (80 g/70 kg body weight). High-protein diet resulted in no increase of urinary polyamine excretion. The low-polyamine diet caused a non-significant decrease in urinary polyamine excretion (by 15%).

Adult↗
PubMed1996

Adenine phosphoribosyltransferase-deficient mice develop 2,8-dihydroxyadenine nephrolithiasis.

Adenine phosphoribosyltransferase (APRT) deficiency in humans is an autosomal recessive syndrome characterized by the urinary excretion of adenine and the highly insoluble compound 2,8-dihydroxyadenine (DHA) that can produce kidney stones or renal failure. Targeted homologous recombination in embryonic stem cells was used to produce mice that lack APRT. Mice homozygous for a null Aprt allele excrete adenine and DHA crystals in the urine. Renal histopathology showed extensive tubular dilation, inflammation, necrosis, and fibrosis that varied in severity between different mouse backgrounds. Thus, biochemical and histological changes in these mice mimic the human disease and provide a suitable model of human hereditary nephrolithiasis.

Adenine↗
PubMed1996

HPRT-APRT-deficient mice are not a model for lesch-nyhan syndrome.

Complete hypoxanthine-guanine phosphoribosyl-transferase (HPRT) deficiency in humans results in the Lesch-Nyhan syndrome which is characterized, among other features, by compulsive self-injurious behavior. HPRT-deficient mice generated using mouse embryonic stem cells exhibit none of the behavioral symptoms associated with the Lesch-Nyhan syndrome. Administration of drugs that inhibit adenine phosphoribosyltransferase (APRT) in HPRT-deficient mice has produced the suggestion that deficiency of APRT in combination with HPRT-deficiency in mice may lead to self-mutilation behavior [C.L. Wu and D.W. Melton (1993) Nature Genet. 3, 235-240]. To test this proposition, we bred HPRT-APRT-deficient mice. Although the doubly-deficient mice excrete adenine and its highly insoluble derivative, 2,8-dihydroxyadenine, which are also associated with human APRT deficiency, additional abnormalities or any self-injurious behavior were not detected. Thus, APRT-HPRT-deficient mice, which are devoid of any purine salvage pathways, show no novel phenotype and are not a model for the behavioral abnormalities associated with the Lesch-Nyhan syndrome as previously suggested.

Adenine Phosphoribosyltransferase↗
PubMed1996

No aggregate change in homosexual HIV risk behaviour among gay men attending the Gay Pride festivals, United Kingdom, 1993-1995.

OBJECTIVES: To examine aggregate changes in homosexual HIV risk-taking among gay men attending the Gay Pride festival in the United Kingdom over a 3-year period during which HIV prevention activity targeted at this population increased considerably. DESIGN: Three cross-sectional self-completion questionnaires at yearly intervals asking identical questions on sexual behaviour in the preceding year. SETTING: Lesbian and Gay Pride festival held in London, June 1993, 1994 and 1995. PARTICIPANTS: Men attending the festival who were UK resident, had ever had sex with another man and who were willing to fill out a questionnaire (n = 1620, 1753 and 1168 in 1993, 1994 and 1995, respectively). MAIN OUTCOME MEASURES: Self-reported numbers of sexual partners, sexual partners with whom anopenile intercourse occurred and sexual partners with whom anopenile intercourse occurred without a condom. RESULTS: Over the 3-year period there were no changes in the proportion of men engaging in any of the sexual behaviour measures. At each cross-section, one in three men (514 out of 1566, 511 out of 1612, 351 out of 1059 in 1993, 1994 and 1995, respectively) had engaged in anopenile intercourse without a condom with at least one male partner in the preceding year and one in 10 (162 out of 1566, 156 out of 1612, 103 out of 1059 in 1993, 1994 and 1995, respectively) had done so with more than one male partner. CONCLUSION: Despite an increase in prevention work targeted at this population, aggregate levels of sexual risk-taking have remained very stable. A reassessment of the efficacy of current HIV prevention messages and methods with this population is urgently required.

Adult↗
PubMed1995

Measuring disadvantage: changes in the underprivileged area, Townsend, and Carstairs scores 1981-91.

OBJECTIVE: To compare the intercensal change for each of the underprivileged area (UPA), Townsend, and Carstairs scores calculated from 1981 and 1991 census data. SETTING: England and Wales. METHODS: The method described enables comparison of change in composite scores such as the UPA, Townsend, and Carstairs scores which are derived from normalised variables. The national values of equivalent variables derived from the censuses are calculated and normalised on the same baseline of the 1981 electoral ward mean and SD values. The resultant change in composite scores for different censuses can then be compared directly. MAIN OUTCOME MEASURE: Change in the composite score values for the 1991 census when compared with the 1981 census. RESULTS: For England and Wales, the UPA score increased by 5.62 units (0.35 of the SD) but the Townsend and Carstairs scores fell by 2.39 and 1.13 units respectively (0.71 and 0.33 of the SDs). CONCLUSION: The Townsend and Carstairs scores are good measures of material deprivation and show a general improvement as such between 1981 and 1991. The UPA score, however, includes additional factors relating to family structure, social deprivation, and health need and shows a decline in the overall situation.

Data Interpretation, Statistical↗
PubMed1994

The allopurinol loading test for identification of carriers for ornithine carbamoyl transferase deficiency: studies in a healthy control population and females at risk.

The increase in orotidine excretion following a 300 mg allopurinol dose has been used for carrier detection in ornithine carbamoyl transferase (OCT) deficiency. This test was evaluated, using three collection periods, in 23 healthy women, 4 obligate heterozygotes and 32 other women at risk of being carriers of OCT deficiency. Four methods for the analysis of orotidine and orotic acid were compared. Using the most reproducible method, the excretion of orotic acid in controls was found to be consistently higher than that of orotidine in all three periods. The distribution of both orotic acid and orotidine excretion of controls was skewed so that standard deviations (S.D.) were calculated after logarithmic transformation. All four obligate heterozygotes showed orotic acid and orotidine excretion in excess of 3 S.D. above the control mean and a further 7 women had one or more excretion values in excess of 3 S.D., while 16 gave a value of less than 2 S.D. for both metabolites. We conclude that the predictive value of the test is good, that both orotic acid and orotidine should be measured to reduce the risk of misclassification and that values greater than 2 S.D. for both in one or more periods should be used as the cut-off point to identify carriers.

Adolescent↗
PubMed1994

Gay men as victims of nonconsensual sex.

Incidents of nonconsensual sexual activity among 930 homosexually active men living in England and Wales are analyzed. Of these men, 27.6% said they had been sexually assaulted or had sex against their will at some point in their lives; one third had been forced into sexual activity (usually anal intercourse) by men with whom they had previously had, or were currently having, consensual sexual activity. The contention that male rape is usually committed by heterosexually identified men, primarily as an expression of power and control, is not supported. Recognition that gay men rape other gay men is needed, both by the gay community and support services for victims.

Adolescent↗
PubMed1993

Changes in condom use by gay men.

Cross sectional and longitudinal data on condom use among homosexually active men is presented. Data pertain to two waves of interviewing (1987/8 and 1991) from Project SIGMA, a large longitudinal study of male homosexual behaviour in the light of HIV. Aggregate changes across the time-period indicate an increase in condom use for both insertive and receptive anal intercourse, particularly with casual partners. Condom use is still much more prevalent with casual rather than regular partners. Longitudinal analysis show considerable changes at the individual level, with almost a third of men changing their practices. Half of those decreased their risk behaviours, whilst the other half increased them. Less than 1% used condoms for fellatio in the year preceding the 1991 interview, but 8.3% had used other barriers during sex, primarily for hygiene and fun reasons, rather than as disease prophylaxis. Some implications are drawn for condom promotion and HIV prevention.

Adolescent↗
PubMed1993

No connection between alcohol use and unsafe sex among gay and bisexual men.

OBJECTIVE: To investigate the relationship between alcohol use and unsafe sexual behaviour. METHODS: The paper discusses data collected from 461 gay and bisexual men interviewed in England and Wales by Project SIGMA during 1991-1992. These data were collected during face-to-face interviews using retrospective weekly diary techniques and include details of all sexual sessions and alcohol use. The 819 reported sexual sessions with other men are divided into those that involved alcohol use (30.6%) and those that did not. RESULTS: Differences in the incidence of HIV risk behaviours between sexual sessions that involved alcohol use and those that did not are small, and none are statistically significant. Furthermore, for those men who engaged in sexual behaviour whilst under the influence of alcohol, the quantity of alcohol consumed had no effect on sexual behaviour. CONCLUSIONS: Among gay and bisexual men, sex under the influence of alcohol is no more likely to be unsafe than sex among men who have not consumed alcohol.

Alcohol Drinking↗
PubMed1993

Sex role separation in sexual diaries of homosexual men.

OBJECTIVE: To measure types of sex role prevalence in common and risk-related behaviours among gay men for modelling HIV transmission. DESIGN: Cohort study of 385 homosexually active men recording sexual diaries over 1-month periods. METHODS: Measures of incidence of behavioural sex roles for masturbation, fellatio, anal intercourse and anilingus by relationship type, derived from 1-month sexual diary data. RESULTS: Low behavioural role rigidity for masturbation and fellatio, but higher rigidity for anal intercourse and anilingus. Participants with no regular partner showed a relatively low frequency of anal intercourse, whereas those in closed relationships showed a high frequency. CONCLUSION: Although anal intercourse shows a certain degree of behavioural role rigidity, this rigidity is not large enough to conclude that gay men exclusively engage in either an active or a passive role. Typical rates for exclusive active and passive roles for anal intercourse during the month the diaries were recorded were in the range of 12-15%; the dual role was significantly higher.

Adolescent↗
PubMed1993

The testing of saliva samples for HIV-1 antibodies: reliability in a non-clinic setting.

AIMS: To assess the reliability of saliva samples as a means of testing for HIV-antibodies outside clinic settings. METHODS: Men taking part in a non-clinic longitudinal study of homosexually active men provided samples of saliva and blood. Sera were screened using a competitive ELISA (Wellcozyme) and positive sera were confirmed by an indirect ELISA (Abbott). Saliva samples were screened either using an IgG captive radioimmunoassay or an amplified ELISA. RESULTS: A total of 534 paired saliva and blood samples were tested. Overall sensitivity was 96.2% and specificity was 100%. None of the saliva tests were falsely positive for HIV-1 antibodies. CONCLUSIONS: HIV-1 saliva tests can reliably be used in a non-clinic or field setting. However, if results are to be given to respondents, it is necessary to offer adequate counselling and consider the mechanisms for referral and follow-up for those that are found to be HIV-1 antibody positive.

HIV Antibodies↗
PubMed1993

Respiratory gas exchange and metabolic responses during exercise in McArdle's disease.

During normal progressive exercise, the gas exchange anaerobic threshold occurs when CO2 production (VCO2) and ventilation (VE) increase so as to depart from a linear relationship to O2 consumption (VO2). This is thought to represent a gas exchange response to metabolic acidosis due to lactate accumulation. Patients with McArdle's disease have previously been reported to exhibit a steepened ventilatory response relative to VCO2, despite an inability to produce lactate. However, the VCO2 response has not been studied. We therefore investigated the VCO2-VO2 and VE-VO2 relationships in seven McArdle's disease patients and seven control subjects during symptom-limited maximal treadmill exercise. Analysis of gas exchange showed that whereas all control subjects had an easily identifiable anaerobic threshold, four of the patients had none and the other three displayed an attenuated threshold. The occurrence of the threshold in one patient was associated with a small rise in lactate and in another patient with an abrupt rise in leg discomfort, suggesting a pain response. Ammonia and the purine metabolite hypoxanthine were elevated during exercise in all patients, suggesting that ammonia may be a product of adenosine monophosphate degradation. Free fatty acid levels were also elevated, and a shift toward utilization of lipid may contribute to abnormal gas exchange responses. It is concluded that lactic acidosis contributes to the gas exchange anaerobic threshold but that other factors, such as discomfort, may be involved in the excess Ve seen during heavy exercise.

Adolescent↗