Biomedical subjects

Simon Clarke

Publications and source records attributed to Simon Clarke.

11 recordsLinked to original sources

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↗

PubMed2002

Towards evidence based emergency medicine: best BETs from the Manchester Royal Infirmary. Vomiting in paracetamol overdose.

A short cut review was carried out to establish whether vomiting was a significant consequence of paracetamol (acetaminophen) overdose. Altogether 48 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↗

PubMed2002

Towards evidence based emergency medicine: best BETs from the Manchester Royal Infirmary. Intravenous or intramuscular/subcutaneous naloxone in opioid overdose.

A short cut review was carried out to establish whether intramuscular/subcutaneous naloxone is better than intravenous naloxone in opioid overdose. Altogether 185 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.

Adult↗

PubMed2002

Towards evidence based emergency medicine: best BETs from the Manchester Royal Infirmary. Discharge of patients who have taken an overdose of opioids.

A short cut review was carried out to establish whether patients with no recurrence of symptoms one hour after receiving naloxone for an opioid overdose can safely be discharged. Altogether 195 papers were found using the reported search, of which five 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.

Adult↗

PubMed2002

Towards evidence based emergency medicine: best BETs from the Manchester Royal Infirmary. Intravenous bolus or infusion of naloxone in opioid overdose.

A short cut review was carried out to establish whether intravenous boluses of naloxone are better than intravenous infusion in opioid overdose. Altogether 188 papers were found using the reported search, of which one 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 this best paper is tabulated. A clinical bottom line is stated.

Adult↗

PubMed2000

On the generation of solitons and breathers in the modified Korteweg-de Vries equation.

We consider the evolution of an initial disturbance described by the modified Korteweg-de Vries equation with a positive coefficient of the cubic nonlinear term, so that it can support solitons. Our primary aim is to determine the circumstances which can lead to the formation of solitons and/or breathers. We use the associated scattering problem and determine the discrete spectrum, where real eigenvalues describe solitons and complex eigenvalues describe breathers. For analytical convenience we consider various piecewise-constant initial conditions. We show how complex eigenvalues may be generated by bifurcation from either the real axis, or the imaginary axis; in the former case the bifurcation occurs as the unfolding of a double real eigenvalue. A bifurcation from the real axis describes the transition of a soliton pair with opposite polarities into a breather, while the bifurcation from the imaginary axis describes the generation of a breather from the continuous spectrum. Within the class of initial conditions we consider, a disturbance of one polarity, either positive or negative, will only generate solitons, and the number of solitons depends on the total mass. On the other hand, an initial disturbance with both polarities and very small mass will favor the generation of breathers, and the number of breathers then depends on the total energy. Direct numerical simulations of the modified Korteweg-de Vries equation confirms the analytical results, and show in detail the formation of solitons, breathers, and quasistationary coupled soliton pairs. Being based on spectral theory, our analytical results apply to the entire hierarchy of evolution equations connected with the same eigenvalue problem. (c) 2000 American Institute of Physics.

Journal Article↗