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Biomedical subjects

J Dawson

Publications and source records attributed to J Dawson.

At least 145 records · Page 8Linked to original sources

Gay men, social support and HIV disease: a study of social integration in the gay community.

As part of a large study of the effects of HIV and AIDS on gay male sexual behaviour, we investigated the extent to which gay men in the UK have access to social support and informal care at times of illness. The study sample (n = 502) demonstrated high levels of willingness to disclose sexuality to others, sociability and social integration. Over 90% reported that they had access to people whom they could turn for practical help at times of temporary incapacity. Between 42% and 46% have known a person, or persons, with HIV symptomatic disease, AIDS or someone who has died of AIDS, although men recruited in larger towns and cities were more likely to know people at every stage of HIV infection and AIDS than those from smaller towns. Twenty-five per cent had provided practical help and support to at least one person with AIDS; men in this situation were more likely to have had a close friend, lover or former lover who had died of AIDS. It is argued that it is not possible to expect the gay community to provide fully for the non-medical care of its members and, whilst some needs can be fulfilled on an informal care basis, the demands of long-term serious illness are such that adequate support services should be available in the community.

Adolescent↗

Factors influencing condom use in a sample of homosexually active men.

A sample of 502 homosexually active men were recruited from genitourinary medicine clinics and non clinic sources and interviewed in relation to their sexual behaviour and factors that might influence their use of condoms. Three hundred and eighty three men (76%) reported penetrative anal sex in the previous year. Ninety four (25%) had not used condoms in penetrative sex. Failure to use condoms was associated with unfavourable attitudes to them, not knowing close friends or partners who had HIV-related health problems, having fewer sexual partners and being in a closed monogamous relationship. On the other hand levels of awareness about the risks of unprotected anal sex and involvement in gay networks and social groups were not predictors of condom use.

Acquired Immunodeficiency Syndrome↗

Lymphocyte kinetics in a murine model of chronic inflammation.

A modification of the air pouch system [1], has been developed to investigate the role of lymphocytes in an inmmunologically driven model of chronic inflammation. Radiolabelled spleen and lymph node mononuclear cells from mice presensitised with Bordatella pertussis vaccine (BPV) were infused intravenously into mice also presensitised with BPV and challenged with BPV into 6 day old air pouches. Cell migration was monitored by gamma counting of tissues sampled 4 hours after infusion. The percentage increase in counts obtained in air pouch tissue compared to control skin, over a time course of 30 days, reached a peak at 10 days after BPV challenge. Vessels with features of high endothelial venules, and clusters of lymphocytes have been demonstrated histologically and immunohistochemically in air pouch tissue at this time.

Animals↗

Evaluating labour ward services: the art of the possible.

Midwives have contended that midwifery and obstetric workloads could not be measured and that only a 1:1 ratio of mother to midwife should occur, at least in the labour ward environment. This would appear to be true if traditional hospital statistics are used. However, this project set out to measure workload and staffing requirements. Using clinically based process and outcome criteria, dependency classification enabled daily, weekly and monthly workload and patterns of workload to be studied. Contrary to widely held beliefs it was demonstrated that mothers could be classified according to levels of need which form consistent patterns of distribution. A mean average of the total time spent on the labour wards by mothers was calculated for each level of need using 11 months' data. This produced a positive correlation with the dependency classification. Dependency classification and total time spent on the labour wards provides a mechanism for measuring workloads. To enable economic use of resources, a level of dependency for which a 1:1 ratio of staff:mother is considered essential has to be agreed. To assist with this decision two surveys designed to collect information concerning the percentage of the mothers' time spent in contact with the nursing/midwifery staff was conducted. The results were remarkably similar and again demonstrated a positive correlation with dependency classification. It was recognized that midwifery is a chronically understaffed service and that midwives working within the service felt unable to give the care they considered a woman in labour deserves.(ABSTRACT TRUNCATED AT 250 WORDS)

England↗

Heterosexual sexual behaviour in a sample of homosexually active men.

Three hundred and fifty six homosexually active men were recruited in 1988 for a study by interview of sexual behaviour. Thirty two per cent had homosexual passive anal sex in the previous month and 60% in the year before interview. Anal sex and unprotected anal sex were more common with regular than non-regular partners. Heterosexual sex was reported by 4% of men in the last month and 10% for the last year. Sixteen per cent of heterosexually active men reported anal sex with a female partner. Fewer men described themselves as bisexual than would be expected from the sample's recent sexual histories. More attention is needed to the definition and measurement of "bisexuality" to understand its role in HIV transmission.

Adolescent↗

Platelet activating factor as a mediator of equine cell locomotion.

Equine polymorphonuclear (PMN) and mononuclear (MN) leucocytes were separated on Percoll gradients and used to study the chemoattractant properties of the polar ether-linked phospholipid, platelet activating factor (PAF). Six concentrations of PAF ranging from 1 ng/ml to 100 micrograms/ml were studied in each of two in vitro assay systems, the agarose microdroplet and a microfilter technique. Very significant (p less than 0.01) increases in the movement of both PMN and MN cells were obtained with most concentrations of PAF. In two instances there was no apparent concentration-response relationship, although the action of PAF was approximately bell-shaped in two others. The possible significance of these findings for equine inflammatory conditions is discussed.

Animals↗

Quantitative analysis of resting membrane electrogenesis in insect (diptera) skeletal muscle. I. Intracellular K+, Na+ and Cl- activities, measured using liquid ion-exchanger and neutral ion-carrier microelectrodes.

Electrophysiological properties of skeletal body-wall muscles of prepupal Calliphora erythrocephala were investigated using double-barrelled intracellular ion-sensitive microelectrodes. The most realistic estimate of the intracellular K+ activity, obtained using K+-sensitive microelectrodes based on a neutral carrier, was 115 mmoll-1. The K+ equilibrium potential was consistently more negative than the prevailing resting potential, the average difference being -15 mV. The intracellular Na+ activity and the Na+ equilibrium potential were 7 mmoll-1 and +46 mV on average, respectively. The mean value of the intracellular Cl- activity was 40 mmoll-1, and this was apparently higher than that required for passive distribution of Cl-. However, when reversibly exposed to a Ringer containing no Cl-, cells could rapidly exchange most of their intracellular Cl-, although the resting membrane potentials were only transiently affected. It is concluded that an anionic interferent exists inside muscles, that this artefactually elevates the measured intracellular Cl- activities, and that Cl- makes no contribution to resting membrane electrogenesis.

Animals↗

Quantitative analysis of resting membrane electrogenesis in insect (diptera) skeletal muscle. II. Testing of a model involving contributions from potassium and sodium ions, and the anomalous effect of reducing extracellular sodium.

A model of resting membrane electrogenesis in skeletal muscles of prepupal Calliphora erythrocephala was formulated. From experiments in which reversible effects of changing extracellular K+ and Na+ activities on the membrane potential (EM) were measured, three different values of alpha (the ratio of the partial permeabilities of the membrane to Na+ and K+) were derived, each from a different range of extracellular Na+ and K+ activities. Two independent tests were carried out to determine the most realistic value of alpha. Intracellular K+ and Na+ activities and EM values were measured in a population of cells, and the EM values predicted using the Goldman-Hodgkin-Katz equation for different values of alpha. The best fit for the data was obtained for alpha = 0.036. In ionic substitution experiments, in which passive movements of Cl- were prevented or minimized, the changes in EM around the resting level could be explained with a high degree of accuracy by assuming again that alpha = 0.036. However, tests of the model by investigation of direct effects of reducing extracellular Na+ concentration over a wide range of EM values gave an anomalous result. In low-Na+ Ringer, EM values became more positive than the respective resting levels. The anomalous effect of low-Na+ Ringer on EM did not involve a change in the K+ equilibrium potential. Instead, it was probably due to a reduction in the K+ permeability of the membrane. Possible mechanisms underlying this effect are discussed.

Animals↗

Susceptibility of dogs to infection with Ehrlichia risticii, causative agent of equine monocytic ehrlichiosis (Potomac horse fever).

Adult dogs 1 to 5 were inoculated IV and/or SC with 3, 5, or 6 ml of a suspension containing 1.2 x 10(4) Ehrlichia risticii-infected cells (derived from primary canine monocyte cell cultures)/ml. Dogs 6 to 8 were inoculated IV and/or SC with 3 or 6 ml of 1.2 x 10(5) organism-free cultured canine monocytes/ml. Ehrlichia risticii was isolated in cultures from inoculated dogs 3, 4, and 5 on postinoculation days (PID) 10 to 16, but not from dogs 6 to 8. Dogs inoculated with E risticii seroconverted between PID 6 and 12. Clinical signs of illness were not observed in these 5 E risticii-inoculated dogs. A pony, inoculated with E risticii isolated from inoculated dog 5, developed clinical signs of equine monocytic ehrlichiosis, including fever, anorexia, depression, and diarrhea, and E risticii was isolated from the pony's blood. This E risticii isolate was then inoculated into susceptible dog 9, and E risticii was repeatedly isolated from dog 9 during PID 6 to 17. Dogs were susceptible to infection with E risticii and may serve as a reservoir of the organism in the field.

Animals↗

Cellular aspects of inflammation. The Ciba-Geigy Prize for Research in Animal Health.

The migration of leucocytes to sites of acute and chronic inflammation is an event of central importance to the maintenance of inflammatory processes; extravascular leucocytes are responsible for generating chemical mediators of inflammation and the phagocytosis of particulate matter. They may also be involved in the conversion of acute to chronic inflammatory lesions. Leucocytes are attracted to sites of tissue injury by a range of chemoattractants. This paper describes the development of a method for separating on Percoll gradients purified populations of equine polymorphonuclear and mononuclear leucocytes and use of the isolated cells in vitro studies. Two independent assay methods, the agarose microdroplet and the Boyden chamber microfilter techniques, were used. The assays were utilised in three ways: (a) to investigate the sensitivity of polymorphonuclear and mononuclear leucocytes to two standard chemoattractants, zymosan activated plasma and n-formyl-methionyl-leucyl phenylalanine; (b) to study the chemoattractant properties of leukotriene B4 and prostaglandin E2 for equine leucocytes; and (c) to investigate the inhibitory actions of several nonsteroidal anti-inflammatory drugs (NSAIDs) on equine leucocyte movement.

Acute Disease↗

A commentary on the inhibition by retinoids of leukotriene B4 production in leukocytes.

The order of potency of retinoids as inhibitors of A23187-induced production of leukotriene B4 (LTB4) in human polymorphonuclear leukocytes (PMN) was retinoic acid greater than retinal greater than retinol. However, the conversion of exogenous arachidonate (AA) to LTB4 by PMN homogenates was inhibited in the rank order retinol greater than retinal much greater than retinoic acid. The agreement between active concentrations of retinol in these two systems is consistent with this compound acting directly to inhibit AA metabolism: this is not so for the other retinoids. The order of potency for inhibition of phorbol dibutyrate (PDBu)-stimulated superoxide (O-2) production in HL60 granulocytes was retinol greater than retinoic acid much greater than retinal (inactive); neither retinol nor retinal displaced [3H]PDBu from HL60 cells. We conclude that inhibition of LTB4 production by retinoic acid and retinal is neither through inhibition of AA metabolism nor through inhibition of protein kinase C.

Arachidonic Acid↗