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Biomedical subjects

Simon Clarke

Publications and source records attributed to Simon Clarke.

At least 19 recordsLinked to original sources
PubMed2006

Bone changes in adolescent girls with anorexia nervosa.

PURPOSE: To clarify the effect of chronological age, height, lean tissue mass, and menstrual status on standard reported DXA (dual-energy x-ray absorptiometry) measures. METHODS: Growth and DXA data from a retrospective longitudinal cohort of 30 adolescent females with anorexia nervosa (AN) were examined. Areal bone mineral density (aBMD), total body bone mineral content (BMC) and total body bone area were measured and standardized for age, height, lean tissue mass, and total bone area. We then examined the changes in these parameters after 12 months of multidisciplinary treatment. RESULTS: The subjects had lower BMC and aBMD than the age- and height-matched reference population at baseline, there were further decreases in these parameters with treatment. BMC adjusted for lean tissue mass and bone area were normal at baseline and there was no significant change with treatment. Bone area adjusted for height was low at baseline and decreased despite treatment. CONCLUSION: Our data suggest that the low age- and height-adjusted bone mineral content and bone mineral density in females with AN is secondary to poor bone growth leading to low bone area. These subjects had relatively normal bone mineral content for their bone size and lean tissue mass. Changes in bone size were proportional to changes in lean tissue mass.

Absorptiometry, Photon↗
PubMed2006

Distractibility in AD/HD predominantly inattentive and combined subtypes: the P3a ERP component, heart rate and performance.

The current study aimed to investigate whether children and adolescents diagnosed with Attention Deficit/Hyperactivity Disorder Predominantly Inattentive (AD/HD-in; Child n = 24, Adolescent n = 33) and Combined (AD/HD-com; Child n = 30, Adolescent n = 42) subtypes were more distractible than controls (Child n = 54; Adolescents n = 75), by assessing event-related potential (ERP), performance and peripheral arousal measures. All AD/HD groups displayed smaller amplitudes and/or shorter latencies of the P3a ERP component - thought to reflect involuntary attention switching - following task-deviant novel stimuli (checkerboard patterns) embedded in a Working Memory (WM) task. The P3a results suggested that both AD/HD-in and AD/HD-com subtypes ineffectively evaluate deviant stimuli and are hence more "distractible". These abnormalities were most pronounced over the central areas. AD/HD groups did not display any abnormalities in averaged heart rate over the WM task, a measure of peripheral arousal. They did display abnormalities in performance measures from the task, but these were unrelated to P3a abnormalities. AD/HD groups also displayed a number of deficits on Switching of Attention and Verbal Memory tasks, however, the pattern of abnormality mostly reflected general cognitive deficits rather than resulting from distraction.

Adolescent↗
PubMed2006

Verbal overshadowing of perceptual discrimination.

We examined effects of verbal interference on a perceptual discrimination task. Participants were presented with a series of faces, described (or did not describe) an additional face, and then made face/ nonface decisions to both the original faces and new faces, intermingled with nonfaces. This enabled us to examine the effect of making a verbal description, relative to an unrelated filler task in a control condition, on the perceptual discrimination of faces seen for the first time and faces encountered previously, and also on repetition priming (i.e., the facilitative effect of an encounter with a stimulus on subsequent processing of the same stimulus). Verbalization interfered with performance on both new and studied faces, but it did not interfere with priming. We argue that verbalization encouraged a relatively long-lasting shift (over a number of trials) toward greater visual processing of individual facial features at the expense of more global visual processing, which is generally beneficial for the recognition of faces and important for discriminating faces from nonfaces in the face decision task.

Discrimination, Psychological↗
PubMed2005

Two models of ethics committees.

A distinction is made between two models of ethics committees. According to the Mirror Model, ethics committees ought to reflect the values of society. The Critical Model says committees are to critically examine these standards rather than merely reflect them. It is argued that the Critical Model should be accepted because a society's ethical standards can be mistaken and a society that has Critical rather than merely Mirror ethics committees is more likely to have such mistakes revealed. Some implications of the Critical Model are discussed.

Animal Care Committees↗
PubMed2005

Responses to methylphenidate in adolescent AD/HD: evidence from concurrently recorded autonomic (EDA) and central (EEG and ERP) measures.

This paper aims to examine the effects of methylphenidate (MPH) on integrated baseline and event-related psychophysiological measures in AD/HD. Thirty-four unmedicated AD/HD adolescents (11-17 years; 6 females) were first compared to 34 age- and sex-matched controls, and then re-tested at least 4 weeks after methylphenidate (MPH) medication. In each testing session, EDA was recorded simultaneously with EEG during a resting eyes open condition, and with ERPs during an auditory oddball task. Unmedicated AD/HD subjects were compared to controls and then AD/HD subjects were compared pre- and post-medication. Correlations between the change in EEG theta and the remaining psychophysiological variables were undertaken to provide information about post MPH treatment changes. In the unmedicated state, AD/HD was characterized by abnormally enhanced theta, across fronto-central sites, generally reduced P2 responses, with larger non-specific and oddball-elicited SCRs and poor behavioural performance on the oddball task. Following treatment, AD/HD showed a 'normalization' of theta activity (particularly in the right hemisphere), a reduction in the rate of decrement of EDA and a general increase in P3 amplitude. These findings suggest that methylphenidate is associated with a robust 'normalization' of low frequency EEG activity during the resting brain state, but has less impact on task-related brain activity or phasic changes in autonomic function. This dissociation of resting and task-related activity may prove to be useful in elucidating the effects of stimulant versus new non-stimulant medications in AD/HD.

Adolescent↗
PubMed2005

Best evidence topic report. Do non-steroidal anti-inflammatory drugs cause a delay in fracture healing?

A short cut review was carried out to establish whether there is any evidence that non-steroidal anti-inflammatory drugs (NSAIDs) might delay fracture healing. A total of 514 papers were found using the reported search, of which three represent the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these best papers are tabulated. At present, although there are theoretical concerns about the adverse effects of NSAIDs on fracture healing, there is not enough clinical evidence to deny patients with simple fractures their analgesic benefits.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2005

Predicting stimulant medication response in ADHD: evidence from an integrated profile of neuropsychological, psychophysiological and clinical factors.

There have been significant advances in understanding the neurobiology of Attention-Deficit/Hyperactivity Disorder (ADHD) and it is timely to examine the ability of biological and psychological markers to predict medication response in this disorder. We evaluated prediction of medication response in adolescent ADHD using neuropsychological testing and psychophysiological measures of central and autonomic function. Fifty ADHD adolescents participated in pre- and post-stimulant medication testing. Separately ranked performance in auditory oddball and visual Working Memory (WM) tasks determined 20 "responders" and 20 "non-responders" with 10 "neutrals" excluded from the discriminant function analyses (DFA). For both oddball and WM performance rankings, the two groups did not differ in age, sex, or handedness. However, responders did have higher levels of symptomatology than non-responders at baseline. Pre-stimulant medication psychophysiology variables were used as predictors in each DFA. Oddball performance correctly classified 85.0% of responders and 95.0% of non-responders. Better response was associated with increased resting beta power (left posteriorly), delayed oddball target N1 (frontally), decreased oddball target P2 (left posteriorly) and decreased WM distractor P3 (right frontally). Working memory performance classified 80.0% of responders and 90.0% of non-responders, with a broadly similar profile of psychophysiological predictors. These finding indicate the value of integrating neuropsychological and psychophysiological data in predicting medication response in ADHD.

Adolescent↗
PubMed2005

Understanding affective and cognitive self-evaluations about the body for adolescent girls.

OBJECTIVE: The aim of this study was to understand relations between cognitive and affective self-evaluations about the body for adolescent girls in the context of their diverse experiences of the body. METHOD: The project involved adolescent girls (N = 141), including underweight to overweight schoolgirls, and hospitalized girls with anorexia nervosa (AN). Materials were brief, reliable inventories of self-concepts about body, movement and appearance, and feelings about the body. RESULTS: Measurement models confirmed the related yet discrete self-concepts about the body, movement and appearance, and feeling OK, guilt, worry, disgust, and anger about the body. Self-concepts and feelings were not correlated with body weight, and were sensitive and specific for girls with AN versus low-weight schoolgirls. Relations among self-concepts and feelings about the body vary with the context. In particular, self-concepts and feelings about the body were incongruent for AN girls with acute experiences of making self-evaluations of their bodies. DISCUSSION: It is clear that self-evaluations by adolescent girls do not necessarily reflect actual body weight. Findings suggest that associations between thoughts and feelings about the body vary with diverse experiences of the body. Results support brief, reliable, and valid indicators of self-concepts and feelings about the body that are vital in the design of prevention, intervention, and monitoring, and the evaluation of programmes for girls in clinical and educational settings.

Adolescent↗
PubMed2004

Percutaneous endoscopic colostomy of the left colon: a new technique for management of intractable constipation in children.

BACKGROUND: The antegrade colonic enema is accepted as effective for management of intractable constipation in children when conventional bowel management has failed. This study describes experience with a new, minimally invasive technique, the distal antegrade colonic enema, which involves percutaneous endoscopic colostomy of the left colon. METHODS: Fifteen children with refractory constipation and soiling who had radiographic evidence of megarectum and/or distal colonic delay were selected for the procedure. The junction of the descending and the sigmoid colon was identified colonoscopically, and the percutaneous endoscopic colostomy tube, through which antegrade distal colonic enema are administered, was inserted. RESULTS: Fourteen children underwent distal percutaneous endoscopic colostomy insertion. The median time required for the procedure was 30 minutes (20-50 minutes). Excluding one child (technical difficulties with percutaneous endoscopic colostomy placement), median post-procedural hospital stay was 4 days (2-27 days). Thirteen children were no longer soiling, and improvement in quality of life was reported at 2 months' follow-up. At 6 months' follow-up, 90% of children were clean during intervals between enemas. All children evaluated at 12 months' follow-up remained clean. Median duration of follow-up was 12.5 months (2-51 months). CONCLUSIONS: The distal percutaneous endoscopic colostomy is a simple alternative to established methods for delivery of antegrade enemas. It is less invasive and on reversal leaves only minor scarring.

Child↗
PubMed2004

Assessment of the potential effects of population changes in attitudes, awareness and beliefs on self-reporting of occupational ill-health.

BACKGROUND: It is important to take account of the effects of population changes in attitudes, awareness and beliefs when interpreting temporal trends in self-reported occupational ill-health. Aim To assess how changes in population attitudes, awareness and beliefs have influenced trends in the self-reporting of occupational and other types of ill-health. METHOD: A review of relevant literature was carried out. The criterion for inclusion was that papers must be based on empirical evidence; theoretical discussion papers were included only where empirical examples were included. RESULTS: Several examples were identified where raised awareness of a health problem following intended or unintended publicity was followed by an increase in self-reports of this problem. The magnitude of the increase varied widely according to the situation. One example was identified where self-reports decreased following a publicity programme designed to prevent the occurrence and worsening of the problem in the population. Potential mechanisms identified as influencing changes in self-reporting of ill-health following raised awareness included changes in symptom/illness management, perception of symptoms, tolerance of symptoms, recognition and diagnosis of illness, attribution of illness; social desirability and legitimacy and recall. CONCLUSION: The effects of changes in population attitudes, awareness and beliefs on trends in self-reports of occupational and other illness are difficult to predict for any given situation.

Awareness↗
PubMed2003

Structure-activity relationships of some opiate glycosides.

A number of analogues of morphine-6-glucuronide 1 have been prepared and evaluated as potential analgesic agents by competitive mu-receptor binding assay and in vivo antinociceptive activity. The analogues show variation in the nature of the carbohydrate residue, the N-substituent, the O(3)-substituent and saturation of the 7,8-double bond compared to 1. In general, only the 6beta-glucoside or beta-glucuronide carbohydrate residues showed potent agonism; other modified carbohydrates were less active or exhibited potential antagonism. Variations in N-substituent led to either reduced agonism (N-H) or potential antagonism [N-allyl, N-(cyclopropyl)methyl]; a polar N-substituent, carboxymethyl, failed to bind. Saturation of the 7,8-double bond led to increased agonism compared to the parent compound in all three examples studied.

Animals↗
PubMed2003

Does transitional zone pull-through in Hirschsprung's disease imply a poor prognosis?

PURPOSE: Accurate frozen section interpretation of intraoperative biopsies is critical to the success of the Duhamel procedure. Errors during sampling or interpretation may result in an abnormal pull-through. The authors' aim was to determine the incidence and outcome of transitional zone pull-through (TZPT). METHODS: Ninety-six children who underwent a Duhamel procedure between January 1987 and May 2002 were followed up prospectively. The outcome of 18 children with TZPT was compared statistically with that of a cohort of 58 patients with a ganglionic pull-through. RESULTS: The incidence of TZPT was 18.8%. Concordance rate between frozen and paraffin-section analyses was 88.5%. The incidence of enterocolitis (P =.003) and intractable constipation (P =.02) was found to be significantly higher in TZPT. There was no significant difference in continence (P =.34), rectal sensation (P =.35), and control (P =.53). Five (27.8%) TZPT patients required a revisional surgery for failure of conservative management. The incidence of stoma placement and revision was significantly less in the ganglionic group (3.4%, P =.007). CONCLUSIONS: Up to one third of patients with TZPT will require revisional surgery for intractable symptoms. Vigilance is warranted in view of the greater risk of enterocolitis. Continence is not significantly affected.

Cohort Studies↗
PubMed2003

The effectiveness of treatments of diabetic autonomic neuropathy is not the same in autonomic nerves supplying different organs.

The aim of the study was to investigate antioxidant (alpha-lipoic acid [LA]) and gamma-linolenic acid treatments in the prevention of changes in autonomic nerves induced in streptozotocin-diabetic rats. Autonomic nerves supplying the heart, penis, and gut were examined using immunohistochemical and biochemical techniques. LA and gamma-linolenic acid (present in evening primrose oil [EPO]) were administered as dietary supplements ( approximately 80 and 200 mg. kg(-1). day(-1), respectively). LA treatment prevented the diabetes-induced decrease of norepinephrine (NA) in the heart and of type I nitric oxide synthase (NOS-I) expression in erectile tissue of the penis but failed to prevent diabetes-induced changes in NA-, vasoactive intestinal polypeptide-, or calcitonin gene-related peptide-containing nerves supplying the ileum. LA partially prevented and EPO totally prevented the increase in NOS-I activity induced by diabetes in the ileum. EPO treatment failed to prevent any other diabetes-induced changes in the heart, penis, or ileum. These results demonstrate that, whereas LA treatment is more effective than EPO in preventing diabetes-induced changes in autonomic nerves, the effectiveness of LA treatment varies with the target organ studied. Diabetes-induced changes in nerves supplying the ileum are more resistant to treatment than those of the heart and penis.

Animals↗
PubMed2002

Dispersion management for solitons in a Korteweg-de Vries system.

The existence of "dispersion-managed solitons," i.e., stable pulsating solitary-wave solutions to the nonlinear Schrodinger equation with periodically modulated and sign-variable dispersion is now well known in nonlinear optics. Our purpose here is to investigate whether similar structures exist for other well-known nonlinear wave models. Hence, here we consider as a basic model the variable-coefficient Korteweg-de Vries equation; this has the form of a Korteweg-de Vries equation with a periodically varying third-order dispersion coefficient, that can take both positive and negative values. More generally, this model may be extended to include fifth-order dispersion. Such models may describe, for instance, periodically modulated waveguides for long gravity-capillary waves. We develop an analytical approximation for solitary waves in the weakly nonlinear case, from which it is possible to obtain a reduction to a relatively simple integral equation, which is readily solved numerically. Then, we describe some systematic direct simulations of the full equation, which use the soliton shape produced by the integral equation as an initial condition. These simulations reveal regions of stable and unstable pulsating solitary waves in the corresponding parametric space. Finally, we consider the effects of fifth-order dispersion. (c) 2002 American Institute of Physics.

Journal Article↗
PubMed2002

Role blurring--does it have implications for staff structure and development?

Within recent times medical illustration departments have been changed dramatically by computers and new working methods. For photographers and illustrators alike this has resulted in an overlap or 'blurring' of roles. This paper discusses typical core skills that cause this overlap and looks at the necessity for everyone within the profession to acquire them.

Education, Continuing↗
PubMed2002

Towards evidence based emergency medicine: best BETs from the Manchester Royal Infirmary. Oral or intravenous antidote for paracetamol overdose.

A short cut review was carried out to establish whether there was any evidence to decide between oral or intravenous antidote in paracetamol (acetaminophen) poisoning. Altogether 330 papers were found using the reported search, of which two presented the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these best papers are tabulated. A clinical bottom line is stated.

Acetaminophen↗