PubMed Health⌕ Search

Biomedical subjects

T J McManus

Publications and source records attributed to T J McManus.

At least 19 recordsLinked to original sources
PubMed1992

The sexual behaviour of young gay men in England and Wales.

Much research has concluded that young gay men are at disproportionately higher risk of HIV infection through unsafe sexual behaviour. This paper is the first report on this particular group in the UK. As part of a larger cohort study, 111 young (less than 21) gay and bisexual men were interviewed about their sexual behaviour, knowledge of AIDS and HIV, particularly safer sexual practices and other factors. Three per cent had not had sex and 13% had not had anal intercourse with a man at the time of interview. Forty-five per cent had sexual experience with a woman and 34% had engaged in vaginal intercourse. The average age at first homosexual experience was just under 15 years and this is higher than other age groups in the cohort. Median number of male partners in the year before interview was 5, with 1 of whom anal intercourse occurred. Sexual repertoire was relatively restricted compared to older men. Condom use was slightly more consistent and levels of knowledge not significantly different. From these findings, the contention that young gay men are at higher risk of HIV infection through risky sexual behaviour is not supported.

Adolescent↗
PubMed1992

Maintenance of open gay relationships: some strategies for protection against HIV.

The role of sexual exclusivity (monogamy) in relation to HIV, and the use of rule making in non-exclusive (open) relationships, are discussed. Data from interviews with 387 homosexually active men are presented. The most common sexual/relational configuration amongst these men is that of open relationships. Sexual non-exclusivity was found to be associated with longer relationships, and a greater age difference between partners. The strategies some of these men are using to maintain sexually non-exclusive relationships are outlined. These rules pertain both to interpersonal dynamics and HIV prevention. Differing epidemiological significance of the rules and some implications for health education are discussed.

Adolescent↗
PubMed1992

Naturally occurring soluble CD4 in patients with human immunodeficiency virus infection.

To investigate its use as a marker of disease severity, serum soluble CD4 (sCD4) was measured by ELISA in patients with human immunodeficiency virus (HIV) infection. Levels of sCD4 were higher in patients than in controls (P less than .001) but did not increase with disease severity. sCD4 release per CD4 lymphocyte showed a linear increase with disease severity and performed as well as beta 2-microglobulin, a widely used marker. To study the role of sCD4 in the pathogenesis of HIV infection, an ELISA to detect sCD4 complexed with glycoprotein 120 (gp120) HIV envelope protein was developed. Preformed sCD4-gp120 complexes were not detectable in patient serum, but addition of recombinant gp120 showed that circulating sCD4 is capable of binding HIV envelope proteins. This study indicates that the sCD4-to-CD4 lymphocyte ratio increases linearly with disease severity and may be a useful marker of CD4 lymphocyte damage. In addition, serum sCD4 can bind viral particles, which may have implications for the use of recombinant sCD4 as a therapy in HIV infection.

AIDS-Related Complex↗
PubMed1991

Condom use in a large cohort of homosexually active men in England and Wales.

As part of a prospective study of the seroprevalence of HIV, a cohort of 930 men were interviewed regarding their condom use. Of the 270 respondents that engaged in insertive anal intercourse in the month preceding interview 38.9% always used a condom, 49.6% never used one, and 11.5% sometimes used one. Of the 254 respondents that engaged in receptive anal intercourse in the same time period 42.5% always used a condom, 45.7% never used one, and 11.8% sometimes used one. Compared to other research the proportion of respondents who always use a condom for anal intercourse is relatively high, though use is by no means universal. Condom use is more widespread and consistent with casual rather than regular sexual partners, and it is significantly more common within open rather than monogamous relationships. Out of a wide range of other factors only geographical location (London against outside), marital status, perceived HIV status, number of sexual partners, and how seriously respondents take safer sex are correlated with condom use.

Adult↗
PubMed1991

Coordinated regulation of shrinkage-induced Na/H exchange and swelling-induced [K-Cl] cotransport in dog red cells. Further evidence from activation kinetics and phosphatase inhibition.

Hypertonic shrinkage of dog red cells caused rapid activation of Na/H exchange and rapid deactivation of [K-Cl] cotransport. Hypotonic swelling caused delayed deactivation of Na/H exchange and delayed activation of [K-Cl] cotransport. Okadaic acid stimulated shrinkage-induced Na/H exchange and inhibited swelling-induced [K-Cl] cotransport. The data are compatible with the kinetic model of Jennings and Al-Rohil (1990. J. Gen. Physiol. 95:1021-1040) for volume regulation of [K-Cl] cotransport in rabbit red cells and suggest that in dog red cells Na/H exchange and [K-Cl] cotransport are controlled by a common regulatory system. The proposal of Jennings and Schulz (1991. J. Gen. Physiol. 96:799-817) that activation/deactivation of volume-sensitive transport involves phosphorylation/dephosphorylation of a regulatory protein is supported by these observations.

Animals↗
PubMed1991

Sexual partners, penetrative sexual partners and HIV risk.

This paper argues that the notion of sexual partners per se is insufficient for estimating levels of HIV risk behaviour or changes in HIV risk over time, even though it is a crucial element of most epidemiological models of HIV. The concept of a penetrative sexual partner (PSP) is introduced as a considerably more accurate measure of HIV risk. Using data from a longitudinal study of 930 homosexually active men in England and Wales, this paper demonstrates that variation in numbers of PSPs (and thus HIV risk) is not related to variation in the gross numbers of sexual partners.

Adolescent↗
PubMed1990

Heterosexual behaviour in a large cohort of homosexually active men in England and Wales.

This paper seeks to outline the range and type of heterosexual behaviour in a large non-clinic cohort of homosexually active males. A cohort of 930 homosexually active men were interviewed as part of a prospective study of the seroprevalence of HIV. The paper indicates that over 60% of these men have had at least one sexual experience with a female and that about 90% of these males have engaged in vaginal intercourse with a female. Twelve per cent of the cohort had sexual contact with females in the last year, and 5% had sex with females, in the month preceding interview. Amongst these behaviourally bisexual males the number of female partners is significantly lower than the number of male partners. However, the proportion of female partners with whom penetration occurs is very much higher than for male partners.

Adult↗
PubMed1990

Coordinated regulation of Na/H exchange and [K-Cl] cotransport in dog red cells.

Swelling-activated [K-Cl] cotransport and shrinkage-activated Na/H exchange were studied in dog red cells with altered internal Mg or Li content. The two pathways responded in a coordinated fashion. When cells were depleted of Mg, [K-Cl] cotransport was stimulated and Na/H exchange was inhibited. Raising internal Mg had the opposite effect: [K-Cl] cotransport was inhibited and Na/H exchange was stimulated. Li loading, previously shown to stimulate Na/H exchange, inhibited [K-Cl] cotransport. From these reciprocal effects and from other evidence, we surmise that the regulation of Na/H exchange and [K-Cl] cotransport is conducted and coordinated by a discrete mechanism that responds to changes in cell volume and is sensitive to cytoplasmic Mg and Li concentrations.

Animals↗
PubMed1990

Seroprevalence of HIV-1 infection in a cohort of homosexually active men.

A non-clinic cohort of 525 homosexually active men from London and South Wales were recruited in 1988 for a study by interview of sexual behaviour. A sample of blood was tested for HIV-1 antibodies. Seropositivity in London was 9.2% compared with 3.4% in South Wales. Men who were not regular STD clinic attenders had a lower rate of seropositivity than did those who were regular attenders. Men who were seropositive reported more sexual partners with whom they had anal intercourse and also reported more episodes of syphilis. Overall, rates of seropositivity were lower than those reported by studies from STD clinics.

Adolescent↗
PubMed1990

Foreign anion substitution for chloride in human red blood cells: effect on ionic and osmotic equilibria.

In human red blood cells, when chloride was replaced isosmotically with a permeant chaotropic anion of the lyotropic series (NO3, I, or SCN), an immediate and significant loss of cell water was observed. In contrast, replacement of chloride by a substituted monovalent sulfonate, such as methanesulfonate or sulfamate, had no significant effect on cell water. Cell water loss in the presence of lyotropic anions was not the result of hemolysis or cation loss but was associated with a significant fall in the distribution ratios of protons (out/in) and chloride (in/out), suggesting an increase in nondiffusible intracellular negative charges. This hypothesis was examined using the equilibrium dialysis technique of Freedman and Hoffman (J. Gen. Physiol. 74: 157-185, 1979) in which fixed charges are titrated in cells permeabilized by nystatin. The equilibrium concentration ratios (in/out) of potassium, sodium, and chloride were determined at various external pH (pHo) values. The point at which anion and cation ratios are equal is the effective isoelectric point for the intracellular charges. In normal chloride-containing medium at 24 degrees C, this point was found at a pHo of 6.93. When chloride was replaced by a chaotropic anion, the isoelectric point at 24 degrees C shifted to a lower pHo: NO3 (6.38), I (5.98), and SCN (5.70). The substituted monovalent sulfonates had little effect on isoelectric point: methyl sulfate (6.81), sulfamate (7.00), and methanesulfonate (7.07). Calculation of the intracellular charges from titration data, as well as equilibrium distribution studies with [14C]SCN, suggests that lyotropic anion binding to intracellular sites (mainly hemoglobin) is responsible for the observed changes in cell water, cell pH, and chloride distribution.

Anions↗
PubMed1989

Cation-anion cotransport.

Two methods have been described for the study of cation-chloride cotransport systems. The zero-trans efflux method is designed to determine stoichiometric relationships between cotransported ions under conditions where ion exchanges cannot occur. These exchanges (e.g., Na+/Na+, K+/K+) may occur as partial or incomplete reactions of a cotransport process and can lead to erroneous determinations of the stoichiometry of the cotransport process. The zero-trans efflux method can also be used to study the effects of cell volume, pH, and intracellular ion concentrations on cotransport processes. The valinomycin method is used to determine the electrogenicity or electroneutrality of transport, and in this regard can be used in conjunction with other methods such as those employing potential-sensitive dyes or microelectrodes. Other, more recently developed ionophores with specificity for lithium rather than potassium have now been used to study the effect of Em on the ATP-dependent Na+/K+ pump. It may be possible to use such ionophores to confirm the suspected electroneutrality of (K+ + Cl-) cotransport systems, as well as for other studies of specific potassium transport processes in which valinomycin obviously cannot be used. Both methods discussed in detail in this chapter, and particularly the valinomycin method, were originally devised for use in red blood cells in order to take advantage of (or circumvent) properties of the red cell membrane, such as its low permeability to sodium and potassium and relatively high permeability to chloride. However, valinomycin has been used successfully to demonstrate the electroneutrality of (Na+ + K+ + 2Cl-) cotransport in MDCK cells, and the zero-trans efflux method should be applicable to the study of transport processes in other types of cells in suspension, so long as the transport system being studied can be accurately defined (e.g., as an inhibitor-sensitive or chloride-dependent cation flux) and comprises a significant fraction of the total salt efflux.

Animals↗
PubMed1989

Role of Mg in the activation of Na-H exchange in dog red cells.

Depleting dog red cells of Mg prevents activation of Na-H exchange by cell shrinkage but has no effect on activation by acidification of the cytosol. Replacing cell Mg restores the activation of Na-H exchange by cell shrinking. We conclude that Mg is required, not for the transport process per se, but for the transduction of the volume stimulus.

Amiloride↗
PubMed1978

Posture in labour.

Explore the source record for details and available documents.

Evaluation Studies as Topic↗
PubMed1978

Upright posture and the efficiency of labour.

The claim that an upright maternal posture during labour improves the efficiency of the uterus to the benefit of both mother and fetus has been investigated in a randomised prospective study. 40 patients undergoing induction of labour were allocated to a recumbent group or an upright group. No differences were found between the groups in the length of labour, mode of delivery, requirements of oxytocic and analgesic drugs, or fetal and neonatal condition. Our data do not support calls to change conventional intrapartum nursing attitudes.

Adult↗