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Biomedical subjects

J McLean

Publications and source records attributed to J McLean.

At least 37 records · Page 2Linked to original sources
PubMed1996

Electrodiagnostic study of carpal tunnel syndrome in wheelchair basketball players.

UNLABELLED: OBJECTIVE-DESIGN-SUBJECTS: Compression neuropathies are common injuries about the wrist in wheelchair athletes. Thirty-three world-class wheelchair basketball players were studied electrodiagnostically to determine the prevalence and severity of median neuropathy at the wrist in these athletes. RESULTS: Thirty percent of these athletes had symptoms consistent with carpal tunnel syndrome (CTS), and 70% of these had electrodiagnostic confirmation of this injury. Overall, 52% of the 33 athletes had electrodiagnostic findings of median neuropathy at the wrist with nine athletes (27%) exhibiting bilateral abnormalities. Four athletes (12%) had abnormal electrodiagnostic findings involving the ulnar nerve at the wrist. CONCLUSIONS: This prevalence of CTS in wheelchair basketball players appears to be similar to that found in the general paraplegic population. Early recognition and treatment of CTS in these athletes are recommended to avoid chronic problems.

Adult↗
PubMed1996

Do parents and professionals agree on the developmental status of high-risk infants?

OBJECTIVES: To examine the degree of agreement between parental reporting of the development of high-risk infants and professional assessment by a multidisciplinary team. METHODS: The developmental status of 196 infants discharged from neonatal intensive care units (NICUs) was assessed by their parents using the Infant Monitoring Questionnaire (IMQ) at 4, 8, or 12 months' corrected age. On the same day, a clinical assessment was done by a multidisciplinary team consisting of a developmental pediatrician, physical therapist, and psychologist. The kappa statistic was used to measure agreement between the assessments. Logistic regression was used to investigate factors that might influence agreement. RESULTS: Both the IMQ and the multidisciplinary team classified infants as developing normally ("normal"), being at risk for abnormal development ("suspect"), or developing abnormally ("abnormal"). Although the same proportion of children fell into the three categories by both assessments, parents and the multidisciplinary team showed poor agreement with respect to the classification of individual infants (kappa = 0.276). No infant or family characteristic was found to have an influence on agreement. CONCLUSIONS: For a group of high-risk infants discharged from NICUs, the agreement between parental assessment of developmental status using the IMQ and the professional assessment by a multidisciplinary team is poor in the first year of life. We do not recommend the use of this questionnaire as a substitute for clinical assessment of biologically at-risk infants discharged from NICUs. However, it may be useful for those groups of infants for whom no other information is available or as an adjunct to clinical assessment when infants are not behaving typically because of an unfamiliar setting or concurrent illness.

Adult↗
PubMed1995

A 60-Hz magnetic field increases the incidence of squamous cell carcinomas in mice previously exposed to chemical carcinogens.

The exposure of tumor-bearing SENCAR mice to a magnetic field of 2 mT at a frequency of 60 Hz for 52 weeks, was found to increase the rate of malignant conversion in chemically-induced dorsal skin papillomas. Detailed histopathology revealed the presence of squamous cell papillomas and squamous cell carcinomas in both sham and magnetic field exposed mice at week 52. However, of the nine mice assessed as having squamous cell carcinomas, eight came from the group exposed to magnetic fields, a difference which is statistically significant at P = 0.03.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Arg21 is the preferred kexin cleavage site in parathyroid-hormone-related protein.

Parathyroid-hormone-related protein (PTHrP) contains several potential sites for proteolytic processing. Although there is considerable evidence for the existence of cleaved products in vivo, little is known about the post-translational processing of PTHrP. We have used purified kexin (Kex2) protease to identify which cleavage sites in recombinant PTHrP(1-141) might be of physiological significance. Cleavage products were identified by N-terminal sequencing. Kex2 preferentially cleaved PTHrP(1-141) carboxy to the triplet arginine site Arg-Arg-Arg21 with a Km of 3.3 +/- 1.7 microM and a kcat of 6 +/- 1.2 s-1. Substitution of alanine for Arg19 resulted in substantially reduced conversion, while no detectable cleavage occurred when alanine was substituted for either Arg20 or Arg21. In contrast, the degree of Kex2 cleavage at Arg21 in PTHrP(1-34) was lower. No detectable cleavage occurred in an unrelated synthetic peptide containing both double and triple arginine sites. Low levels of cleavage also took place carboxy to Lys-Arg97, Lys-Arg105, Arg-Arg106 and Thr-Arg108. Cleavage carboxy to Lys-Arg105, the best of these minor sites, occurred with a Km of 8.4 +/- 2.7 microM and a kcat of 0.8 +/- 0.2 s-1. These studies indicate that the preferred Kex2 cleavage site in PTHrP(1-141) is carboxy to Arg-Arg-Arg21, which effectively destroys its parathyroid-hormone-like biological activity. Cleavage of this site by Kex2-related mammalian convertases in vivo may be an important mechanism for full elaboration of the non-parathyroid-hormone-like paracrine actions of PTHrP in a tissue-specific manner.

Arginine↗
PubMed1995

Gay men's accounts of unsafe sex.

This paper provides a qualitative analysis of the explanations given by a sample of 78 gay men in England of the most recent occasion on which they engaged in anal intercourse without a condom. Explanations are analysed and interpreted from the sociological perspective of 'accounts': that is, they are not viewed as exact descriptions of the 'real' motives for behaviour but are seen as a powerful resource that can illuminate the knowledge, assumptions and values that inform behaviour. Four distinct types of accounts were identified from the men's descriptions of the circumstances and motivations surrounding their most recent unsafe sexual encounter. These related to: (i) their emotional needs and drives; (ii) the calculus of risk; (iii) issues of trust; and (iv) lapses of control. Each of these types of account is described and the implications of the typology are considered, both for our understanding of the meanings, considerations and constraints surrounding high-risk sexual behaviour and for developing more relevant health education interventions.

Adolescent↗
PubMed1995

Suicidal ideation and behaviours among university students in Australia.

OBJECTIVE: The aim of the study was to investigate the prevalence and demographic correlates of suicidal ideation and behaviours among university students in Australia and the utilisation of mental health services by this population. METHOD: Suicidal ideation and behaviours and demographic variables were assessed in a population of 1,678 undergraduate students by use of a modified Suicide Ideation Scale (SIS) and questionnaire. RESULTS: Sixty two percent of students surveyed showed some suicidal ideation and 6.6% reported one or more suicide attempts. Over half of the group who reported suicide attempts did not use any type of mental health services. Suicidal ideation was found to be highly correlated with previous use of mental health services. In examining the relationship between suicidal ideation (SI) and demographic variables, SI was not significantly different for gender or parental marital status but was related to living arrangements, racial groups, religious affiliation and father's education. CONCLUSIONS: The results suggest that a higher proportion of students reported suicidal ideation and behaviours than that documented in related studies undertaken in the USA. While these findings draw attention to a higher level of suicidal ideation in students who utilise mental health assistance, more than half of those who reported suicide attempts did not use any kind of mental health service. The study has particular implications for detecting and assisting young people with a high suicide risk within the university environment.

Adolescent↗
PubMed1994

Noradrenergic modulation of cat area 17 neuronal responses to moving visual stimuli.

Orientation and velocity tuning curves were obtained from neurons in cat primary visual cortex before, during and after the iontophoretic application of norepinephrine (NE). While no consistent effects on orientation tuning were observed, the most consistently observed effect of NE on velocity tuning was enhancement of the selectivity for stimulus speed and direction. This was evidenced by a narrowing of velocity tuning curves in 16/28 of the neurons we encountered as well as by an increase in the measured direction index for 13/28 cells. In contrast to NE, acetylcholine and gamma-amino-n-butyric acid (GABA) simply increased and decreased, respectively, the visually-evoked discharges, and in no case altered the shape of the velocity tuning curve. These data suggest that the spatiotemporal tuning of visual cortical neurons may be dependent not only on local interactions between visual afferents and target neurons, but in addition, depend on the activation state of the noradrenergic coeruleo-cortical projection system.

Animals↗
PubMed1994

Application of the radical pair mechanism to free radicals in organized systems: can the effects of 60 Hz be predicted from studies under static fields?

The influence of 60-Hz magnetic fields on free radical reactions can be quantitatively predicted from the knowledge of the effect of static fields on free radical behavior. Studies of radical reactions in micellar systems show that the behavior under a 60-Hz field is identical to that under a static field at any given point in time.

Benzophenones↗
PubMed1994

The effects of a pulsed application of chlorpyrifos on macroinvertebrate communities in an outdoor artificial stream system.

The results of an experiment examining the effects of pulsed application of a pesticide, chlorpyrifos, in an outdoor replicated artificial stream system are described. Two levels of chlorpyrifos were used, 0.1 microgram.liter-1 (low dose) and 5.0 micrograms.liter-1 (high dose), and applied for 6 hr. Low-dose streams showed little impact from the treatment and were indistinguishable from control streams. Significant reductions in invertebrate density occurred in the high-dose streams and were mainly due to reductions in density of chironomid larvae. There were no significant reductions in taxon richness associated with the treatments indicating no localized extinctions of species. Diversity measures were insensitive to the changes observed in the streams. Ordination and classification procedures were more illuminating and indicated that the major effect of pesticide application was to interfere with the normal pattern of community change occurring within the system. Recovery following treatment was rapid. The results are discussed with reference to the use of indicator species and biological monitoring strategies intended to identify human-mediated disturbance.

Analysis of Variance↗
PubMed1994

Regular partners and risky behaviour: why do gay men have unprotected intercourse?

Studies in both the UK and the USA continue to show that gay and bisexual men put themselves at risk of exposure to HIV through unprotected intercourse, most often with regular partners. As part of a larger study of homosexually active men, 310 men who had had unprotected anal intercourse with a man in the previous year were asked to describe the last occasion on which this had happened. The majority of men had had unprotected intercourse with a regular partner and did not perceived it as risky, although most did not know the HIV status of their partner. Regular and non-regular partners were perceived differently. Men were more likely to be emotionally involved in regular partners and to perceive unprotected penetrative sex with a regular partner as not risky. Future health education initiatives must take into account men's emotional involvement in regular partners and their perception of unprotected intercourse with such partners as not risky.

Adolescent↗
PubMed1994

Model for the rationalization of magnetic field effects in vivo. Application of the radical-pair mechanism to biological systems.

A model for magnetic field effects in biological systems is proposed. This model employs the basic concepts of the radical pair mechanism, and predicts that magnetic fields will increase the average radical concentration, lengthen their lifetime and enhance the probability of radical reactions with cellular components. The relevance of these effects in relation to cancer initiation, promotion and progression is discussed.

Free Radicals↗
PubMed1994

Typhoid fever associated with adult respiratory distress syndrome.

Adult respiratory distress syndrome (ARDS) is rarely reported in association with typhoid fever despite the fact that sepsis is a common manifestation and endotoxemia has been described in this multisystem condition. We describe the course of a patient with ARDS and typhoid fever. With conventional treatment of the lung injury and with specific antimicrobial therapy, the patient survived. Recent consensus definitions of sepsis and ARDS simplified reporting of this case. Clinicians caring for individuals from or recent visitors to developing countries should be aware of the association of typhoid fever, sepsis, and ARDS.

Adult↗
PubMed1994

Awareness of sexual partners' HIV status as an influence upon high-risk sexual behaviour among gay men.

OBJECTIVE: To evaluate the extent to which 'high-risk' sexual behaviour is influenced by awareness of partners' HIV status among gay men. DESIGN: Structured interviews and collection of saliva samples for anonymous linked testing for HIV-1 antibodies. SETTING: Genitourinary medicine clinics and the gay community. SUBJECTS: Men (n = 677) who reported sexual contact with another man in the last 5 years. RESULTS: The majority of respondents (63%) had had an HIV-antibody test. Analysis of data showed that in 15% of the respondents' 1380 partnerships, HIV status was known by both parties. However, the majority of partnerships involved only safe sex. Only 26% of the partnerships in which unprotected penetrative anal sex had occurred involved mutual knowledge of HIV status and was most likely to occur with regular rather than non-regular/causal partners. Logistic regression revealed that this latter association could not be explained in terms of mutual HIV status knowledge. CONCLUSIONS: Despite widespread HIV testing, the majority of gay men engaging in high-risk sex are unaware of their partner's HIV status.

Adolescent↗
PubMed1994

Perceptions of general practice among homosexual men.

BACKGROUND: Primary care has an important role to play in the prevention and management of the human immunodeficiency virus (HIV). It has been suggested that homosexual men experience a variety of problems in relation to primary care. AIM: As part of a larger study, it was decided to examine the extent to which a sample of homosexually active men experienced difficulties in general practice and whether they consulted their general practitioner for problems related to HIV or the acquired immune deficiency syndrome (AIDS). METHOD: Homosexual men were recruited for interview in 1991-92 from a variety of sources including genitourinary clinics and homosexual organizations. RESULTS: Of 623 men registered with a general practitioner 44% had not informed their general practitioner of their sexual orientation and 44% of the 77 men who were HIV antibody positive, as confirmed by the study, had not informed their general practitioner of this fact. Men who viewed their practice as unsympathetic towards homosexual men were less likely to have informed their general practitioner of their sexual orientation or HIV status. The majority of men (87%) nevertheless viewed primary care as an appropriate source of HIV/AIDS advice. CONCLUSION: There is considerable scope for improvement in the acceptability of general practice to homosexual men.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Risk behaviour, anti-HIV and anti-hepatitis B core prevalence in clinic and non-clinic samples of gay men in England, 1991-1992.

OBJECTIVE: To describe the sexual risk behaviour of and HIV and hepatitis B antibody prevalence in gay men in England. DESIGN: Cross-sectional. RESPONDENTS: Gay men recruited from community settings (bars, clubs, gay organizations) and genito-urinary clinics in London, Manchester, the Midlands and Bristol; men who participated in an earlier study. METHODS: Interview including demographic information, sexual behaviour, partner type and health service use. Subjects donated saliva, which was screened for antibodies to HIV-1 by immunoglobulin G (IgG) antibody capture enzyme-linked immunosorbent assay (GACELISA) and to hepatitis B core (HBc) antigen by IgG antibody capture radioimmunoassay (GACRIA). RESULTS: Ninety-four out of 580 (16.2%) men were HIV-antibody-positive; 6.2% of men aged < or = 25 years were positive versus 19.5% of men aged > or = 26 years. HIV-antibody prevalence was highest in London (21.1%), and twice that previously reported outside London (10.5%). Ninety-four out of 568 (16.5%) men were HBc-antibody-positive; 6.9% of men aged < or = 25 years were positive versus 19.7% of men aged > or = 26 years. Anti-HBc prevalence was highest in London (19.8 versus 12.7% outside London). Manual workers were more likely to be anti-HBc-positive, as were men who reported recent high-risk intercourse. Sexually transmitted diseases associated with frequent partner change (gonorrhoea, non-specific urethritis) were reported. CONCLUSION: The HIV epidemic in gay men in England continues, particularly outside London, where prevalence was double that of previous studies. We found relatively high rates of infection in young men whose main sexual experience has been in a time of unprecedented awareness of AIDS. Our data on hepatitis B suggests that further pro-active immunization programmes are urgently required. These findings add to concerns about provision of interventions targeting gay men.

Adult↗
PubMed1992

Predictors of high risk sexual behaviour in gay and bisexual men.

Evidence of high risk sex between gay men continues to be reported, as does a range of sexual behaviour. Three hundred and sixty-nine homosexually active men from different areas of England were each assessed twice at an an interval of 9 months in order to examine the extent to which a number of social-psychological factors predicted subsequent high risk sexual behaviour. Few of the variables were significantly related to unprotected receptive anal sex in the way that the Health Belief Model predicted, except for some perceptions of costs and benefits of safer sex. However, whether or not men were involved in a regular relationship with a partner was strongly associated with high risk behaviour. The implications of these results are that health education interventions should focus on alerting all men to the social context in which high risk sex is more likely to happen: the regular partnership.

Attitude to Health↗