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Biomedical subjects

D Mitchell

Publications and source records attributed to D Mitchell.

At least 73 records · Page 4Linked to original sources
PubMed1999

Role conflict and confidentiality in multidisciplinary athlete support programmes.

As medical and scientific staff have increasingly been called upon to provide multidisciplinary support to elite performers the potential for ethical, professional, and legal conflicts has also increased. Although this has been recognised, little guidance has been provided to help resolve such conflicts. This paper identifies key issues in the provision of effective support and specifically addresses the roles of medical and scientific staff and their relations to coaches and performers. An athlete charter is presented that has successfully been used to resolve ethical conflicts and clarify the lines of communication, confidentiality, and responsibility within a national governing body.

Confidentiality↗
PubMed1999

High nocturnal body temperatures and disturbed sleep in women with primary dysmenorrhea.

Primary dysmenorrhea is characterized by painful uterine cramps, near and during menstruation, that have an impact on personal life and productivity. The effect on sleep of this recurring pain has not been established. We compared sleep, nocturnal body temperatures, and hormone profiles during the menstrual cycle of 10 young women who suffered from primary dysmenorrhea, without any menstrual-associated mood disturbances, and 8 women who had normal menstrual cycles. Dysmenorrheic pain significantly decreased subjective sleep quality, sleep efficiency, and rapid eye movement (REM) sleep but not slow wave sleep (SWS), compared with pain-free phases of the menstrual cycle and compared with the controls. Even before menstruation, in the absence of pain, the women with dysmenorrhea had different sleep patterns, nocturnal body temperatures, and hormone levels compared with the controls. In the mid-follicular, mid-luteal, and menstrual phases, the dysmenorrheics had elevated morning estrogen concentrations, higher mean in-bed temperatures, and less REM sleep compared with the controls, as well as higher luteal phase prolactin levels. Both groups of women had less REM sleep when their body temperatures were high during the luteal and menstrual phases, implying that REM sleep is sensitive to elevated body temperatures. We have shown that dysmenorrhea is not only a disorder of menstruation but is manifest throughout the menstrual cycle. Furthermore, dysmenorrheic pain disturbs sleep, which may exacerbate the effect of the pain on daytime functioning.

Adult↗
PubMed1999

Oral antibiotics reduce body temperature of healthy rabbits in a thermoneutral environment.

Nonabsorbable oral antibiotics, which reduce gut flora, decrease the daytime and night-time body temperatures of rats and mice. We investigated whether oral antibiotics would also lower the body temperature of healthy rabbits. Six rabbits received neomycin sulphate in their drinking water for ten days, and seven rabbits received a mixture of chloramphenicol and dihydroxystreptomycin for six days. Body temperatures, recorded using intra-abdominal radiotelemeters, decreased significantly, by 0.2-0.3 degree C, after three days of antibiotic treatment in both groups of rabbits. The drop in body temperature was transient; after six days body temperatures returned to pre-antibiotic levels. Antibiotic treatment had no effect on either the acrophase or the amplitude of the circadian rhythm in body temperature. Oral antibiotics therefore reduce body temperature of rabbits, without influencing the circadian rhythm in body temperature. Our results are consistent with the hypothesis that an agent arising from intestinal bacteria sustains an elevated body temperature in healthy animals.

Animals↗
PubMed1998

A juxtacrine mechanism for neutrophil adhesion on platelets involves platelet-activating factor and a selectin-dependent activation process.

The aim of this study was to identify the molecular mechanisms involved in neutrophil adhesion to immobilized platelets with particular focus on the possible existence of a juxtacrine system for neutrophil-platelet interactions. Platelets were immobilized onto collagen (type I)-coated coverslips that were placed in a flow chamber and neutrophils were perfused across these confluent monolayers at a shear stress of 1 to 4 dynes/cm2. Neutrophils rolled, and a significant proportion (25% to 50%) adhered to platelet monolayers. P-selectin was expressed in very large quantities on the surface of platelets and mediated all of the rolling, whereas the beta2-integrin mediated firm adhesion. An activation mechanism for adhesion was necessary inasmuch as fixed neutrophils continued to roll on immobilized platelets, but did not adhere. Platelets adherent to collagen produced significant levels of platelet-activating factor (PAF). Accordingly, the firm adhesion of neutrophils to platelets was significantly inhibited by a PAF receptor antagonist (WEB 2086). Treatment of only the platelets with acetylhydrolase, which converts membrane-associated PAF to lyso-PAF, prevented 60% of the adhesion. These data suggest that PAF, on the surface of platelets, mediated a significant portion of the adhesive interaction. Addition of some selectin-binding carbohydrates (fucoidan or soluble SLEx analogs but not dextran sulfate) to the platelets caused rolling neutrophils to immediately adhere, an event that was not observed on histamine or thrombin-treated endothelium or P-selectin transfectants. These data support the view that a juxtacrine activation process exists on immobilized platelets for neutrophils. This process can be greatly enhanced on platelets and may involve a signaling mechanism through P-selectin.

Anticoagulants↗
PubMed1998

Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission

The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.

Journal Article↗
PubMed1998

Mechanism of inhibition of electron transfer by amino acid replacement K362M in a proton channel of Rhodobacter sphaeroides cytochrome c oxidase.

The three-dimensional structure of cytochrome coxidase (COX) reveals two potential input proton channels connecting the redox core of the enzyme with the negatively charged (N-) aqueous phase. These are denoted as the K-channel (for the highly conserved lysine residue, K362 in Rhodobacter sphaeroides COX) and the D-channel (for the highly conserved aspartate gating the channel at the N-side, D132 in R. sphaeroides). In this paper, it is shown that the K362M mutant form of COX from R. sphaeroides, although unable to turnover with dioxygen as electron acceptor, can utilize hydrogen peroxide as an electron acceptor, with either cytochrome c or ferrocyanide as electron donors, with turnover that is close to that of the wild-type enzyme. The peroxidase activity is similar to that of the wild-type oxidase and is coupled to the generation of a membrane potential and to proton pumping. In contrast, no peroxidase activity is revealed in the D-channel mutants of COX, D132N, and E286Q. Reduction by dithionite of heme a3 in the fully oxidized oxidase is severely inhibited in the K362M mutant, but not in the D132N mutant. Apparently, mutations in the D-channel arrest COX turnover by inhibiting proton uptake associated with the proton-pumping peroxidase phase of the COX catalytic cycle. In contrast, the K-channel appears to be dispensable for the peroxidase phase of the catalytic cycle, but is required for the initial reduction of the heme-copper binuclear center in the first half of the catalytic cycle.

Amino Acid Substitution↗
PubMed1998

Spontaneous movements during sleep in children: temporal organization and changes with age.

Developmental changes in the temporal organization of spontaneous movements during sleep was studied in children between 9 months and 11 years of age. Subjects were monitored in the home environment for the entire sleep period using actigraphy and videography. Rhythmicity in sleep-related spontaneous movements was examined using FFT and chi-square periodogram time series analyses. A dominant periodicity of 60-120 minutes was identified which was found to progressively lengthen with age. A microanalysis of the temporal structure of movements revealed a developmental decline in bout duration, but a paradoxical increase in bout frequency. These results show that motor activity becomes less robust and more fragmented as development progresses while retaining underlying rhythmic integrity, and argue for the dynamic influence of CNS maturation on the organization and expression of sleep-related spontaneous movements.

Age Factors↗
PubMed1998

Purposeful activity for people with enduring mental health problems: reflections from a case study.

The desire to work is deeply rooted in the human psyche and involves both intrinsic and extrinsic factors. If this is indeed the case, then this form of human activity should be considered to be an important element of our lives and therefore worthy of intervention when circumstances restrict an individual's engagement with it. To investigate the therapeutic nature of work for people with enduring mental health problems, the author conducted a pilot case study of a work rehabilitation scheme in the United Kingdom. The main theme to emerge from the study was that of purposeful activity.

Goals↗
PubMed1998

Promoting enjoyment and self-belief through work rehabilitation.

There has been a resurgence of interest in work rehabilitation in recent years. A variety of service models are in operation in a number of countries, all, to varying degrees, assisting mental-health clients achieve an optimum level of employment participation. However, little research has been conducted to examine how (and if) such schemes are structured to promote psycosocial rehabilitation. To explore such issues, the author carried out a pilot case study of a work-rehabilitation organization in Lincolnshire, United Kingdom. Two of the main themes, that emerged during the study, Hedonic Experiences and Self-Efficacy, are discussed in this article.

Health Promotion↗
PubMed1998

Power, professions and evidence-based guidelines: lessons from an organizational case study.

AIM: This paper addresses the issues of evidence-based practice (EBP) in relation to power, professionalism and the British National Health Service reforms. BACKGROUND: There has been little discussion at organizational level over issues of professional boundaries, roles and tensions, which are inextricably linked with the drive for an evidence-based culture. METHODS: The paper is a reflection on the findings of a recent case study, which examined the management and organization of an independent sector provider of mental health services in its drive to address issues of EBP. FINDINGS: New managerial hegemony had altered the balance of power within the organization, there was an extension of managerial surveillance, competing political relationships and a general decline in medical dominance. CONCLUSION: Organizations should avoid 'personalizing' the debate on establishing a research-based culture. EBP requires structures to support it and groups representing the health care professions within the organization should be involved in identifying and making recommendations on EBP issues.

Evidence-Based Medicine↗
PubMed1998

Different nocturnal body temperatures and sleep with forced-air warming in men and in women taking hormonal contraceptives.

We studied how forced-air warming, conventionally used to control body temperature during and after anaesthesia, affected the nocturnal rectal temperatures and sleep composition of young men and women. Seven healthy women who were taking oral or injection contraceptives, and six healthy men spent 3 nights in a controlled environment: an adaptation night followed by 2 nights when they slept under either a down duvet (baseline) or a quilt perfused with warm air (hot). Repeated analysis of variance (ANOVA) revealed significant gender differences in the body temperature responses. On the baseline night, despite sleeping under the same conditions, the women did not show a nocturnal drop in body temperature as shown by the men. Forced-air warming increased body temperature to a similar extent in the men and the women, and resulted in enhanced hyperthermia in the women, and blunted the drop in body temperature in the men, compared to their baseline nights. The significant increases in body temperature had no consequences, however, for the subjective sleep quality of either the men or women, and only minor consequences for objective sleep composition. Both men and women had increased amounts of Stage 2 sleep on the hot night (P < 0.04). In addition, the women had reduced rapid eye movement (REM) sleep when compared to their baseline night (P < 0.04). Our results confirm that in a passive thermal environment, women who are taking oral or injection contraceptives have higher nocturnal body temperatures than men. Also, as sleep architecture was minimally affected by the increases in body temperature of between 0.2 and 0.3 degree C on the hot night in the men and women, and subjective sleep quality was unaffected, our results question the existence of a tight association between sleep and body temperature.

Adult↗
PubMed1998

The independent evolution of resistance to ciprofloxacin, rifampicin, and fusidic acid in methicillin-resistant Staphylococcus aureus in Australian teaching hospitals (1990-1995). Australian Group for Antimicrobial Resistance (AGAR).

Methicillin-resistant Staphylococcus aureus (MRSA) is endemic in teaching hospitals in eastern Australian states, with prevalence rates averaging 25-30% of all S. aureus. Between 1990 and 1995, 1467 non-duplicate MRSA isolates from clinically infected sites were tested in Sydney, Melbourne, and Brisbane as part of a national survey of staphylococcal susceptibility. We reviewed the differing evolution of resistance to ciprofloxacin, rifampicin, and fusidic acid. Despite similarities in community and hospital antibiotic use and MRSA prevalence rates, trends in resistance to the oral antibiotics in these cities have progressed independently of each other. In the 1995 survey in individual hospitals in Melbourne, 16-24% of strains were ciprofloxacin-resistant, compared with 80-100% in Sydney and 30-44% in Brisbane. There was great diversity of phage type patterns for ciprofloxacin-resistant strains, suggesting heterogeneous development of resistance. Rifampicin resistance was more closely associated with distinct dominant epidemic phage types, common to institutions in the same city, but without spread to the other cites. Between 1990 and 1995, these comprised 30-60% of all MRSA in Brisbane, compared with 5-10% in Melbourne and < 25% in Sydney. Fusidic acid resistance was uncommon and sporadic (< 5%), and was distributed equally between methicillin-resistant and methicillin-susceptible strains. Resistance to the oral agents in MRSA is due to a complex mix of antibiotic selection pressures and cross-infection with local and epidemic strains in closely related institutions. Each of these mechanisms can predominate, dependent on local factors and the antibiotics used.

Anti-Bacterial Agents↗
PubMed1998

Chronic cough in the Holmes-Adie syndrome: association in five cases with autonomic dysfunction.

The Holmes-Adie syndrome consists of unilateral or bilateral tonic pupils with near light dissociation and tendon areflexia. It is associated with autonomic disturbances affecting sudomotor and vasomotor function. Five such patients are reported on who also had a troublesome chronic dry cough, which was of unknown aetiology and was resistant to a range of treatments. The cough may be related to involvement of afferent or efferent pathways in the vagus. Chronic cough may be an accompaniment in the Holmes-Adie syndrome, like other forms of autonomic dysfunction.

Adie Syndrome↗
PubMed1998

Brain and abdominal temperatures at fatigue in rats exercising in the heat.

We measured brain and abdominal temperatures in eight male Sprague-Dawley rats (350-450 g) exercising voluntarily to a point of fatigue in two hot environments. Rats exercised, at the same time of the day, in three different trials, in random order: rest 23 degrees C, exercise 33 degrees C; rest 23 degrees C, exercise 38 degrees C; and rest 38 degrees C, exercise 38 degrees C. Running time to fatigue was 29.4 +/- 5.9 (SD), 22.1 +/- 3.7, and 14.3 +/- 2.9 min for the three trials, respectively. Abdominal temperatures, measured with intraperitoneal radiotelemeters, at fatigue in the three trials (39.9 +/- 0.3, 39.9 +/- 0.3, and 39.8 +/- 0.3 degrees C, respectively) were not significantly different from each other. Corresponding brain temperatures, measured with thermocouples in the hypothalamic region (40.2 +/- 0.4, 40.2 +/- 0.4, and 40.1 +/- 0.4 degrees C), also did not differ. Our results are consistent with the concept that there is a critical level of body temperature beyond which animals will not continue to exercise voluntarily in the heat. Also, in our study, brain temperature was higher than abdominal temperature throughout exercise; that is, selective brain cooling did not occur when body temperature was below the level limiting exercise.

Abdomen↗
PubMed1998

The origins of learning disability nursing.

Learning disability nursing has always had an ambivalent relationship with the rest of the nursing profession. This article examines the origins of the discipline in the early part of the twentieth century and argues that its development was closely tied to changes in service provision, loose definitions of nursing work and the emerging speciality of mental deficiency within psychiatry.

History, 20th Century↗
PubMed1998

Depletion of EBV-infected cells in donor marrow by counterflow elutriation.

Epstein-Barr virus (EBV)-associated posttransplantation lymphoproliferative disease (PTLD) is a well-recognized complication of T cell-depleted (TCD) allogeneic bone marrow transplantation (BMT). Certain methods of TCD, such as counterflow elutriation (CE), have not been associated with an increased incidence of PTLD. Since CE depletes B cells as well as T cells, the hypothesis that CE depletes donor marrow of EBV-infected cells was tested in this study. Marrow samples from 70 donors were assayed by qualitative and semi-quantitative polymerase chain reaction (PCR) amplification to detect EBV DNA in four cellular fractions produced by elutriation: a small cell fraction (F70), two intermediate-sized cell fractions (F110 and F140), and a large cell (hematopoietic precursor-enriched, lymphocyte-depleted) rotor-off (R/O) fraction. The distribution of B cells in elutriation fractions was 21% (F70), 59% (F110), 18% (F140), and 2% (R/O). Qualitatively, the frequency of EBV DNA detected in fractions was 49% (F70), 57% (F110), 73% (F140), and 44% (R/O). The relative concentration of EBV DNA in each fraction was determined by semiquantitative PCR. The mean number of EBV DNA copies per 150,000 cells was 0.57 (F70), 4.6 (F110), 5.7 (F140), and 0.61 (R/O). Relative EBV DNA load in each fraction was calculated by multiplying the mean concentration of EBV DNA per fraction and mean mononuclear cell content in each fraction. The relative distribution of EBV DNA was 0.5, 58, 40, and 1.5% in the F70, F110, F140, and R/O fractions, respectively. No correlation between the amount of EBV in the graft and development of PTLD could be made, because only one of the 70 recipients developed PTLD and this was following autologous hematopoietic recovery. Although these results demonstrate that the majority of EBV-infected cells in marrow are separated from the TCD graft by counterflow elutriation, further studies are required to differentiate the role of this phenomenon from that of other potential factors, such as the amount of T cell depletion and recovery of EBV immunity in the pathogenesis of PTLD after BMT.

Bone Marrow Cells↗