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Biomedical subjects

G Lewis

Publications and source records attributed to G Lewis.

At least 163 records · Page 9Linked to original sources
PubMed1996

Computerized assessment of common mental disorders in primary care: effect on clinical outcome.

OBJECTIVE: A randomized controlled trial was conducted to examine the clinical effectiveness of providing general practitioners (GPs) with the results of a self-administered computerized assessment of common mental disorders. METHOD: Attenders at a general practice in a deprived inner city area of South London were identified using case finding questionnaires. Six hundred and eighty-one subjects were randomly allocated to three groups which differed in the information provided to the GP: 1) no additional information was given to the GP; 2) the results of the 12 item General Health Questionnaire (GHQ) were given to the GP (the GHQ is a paper and pencil questionnaire that assesses common mental disorders); 3) the results of a self-administered computerized assessment (PROQSY) of common mental disorders were provided for the GP. RESULTS: Clinical outcome was assessed using the 12-item GHQ. Consultations with the GP, prescriptions and referrals within and outside the practice were also recorded. The group in whom the GP received the results of the computerized assessment showed a modest clinical improvement, relative to the other two groups after 6 weeks. There was no difference in clinical outcome between the groups at 6 months. There appeared to be no increase in consultations or prescriptions in the computerized assessment group. CONCLUSIONS: Self-administered computerized assessments for psychiatric disorder have potential as a means of improving the clinical outcome of patients in primary care. It is likely that the effectiveness of the approach would be greatly increased by linking the results of computerized assessments to clinical practice guidelines, tailored to the individual patient by means of computerized technology.

Adolescent↗
PubMed1996

Specific cleavage of immunoglobulin G by copper ions.

The hinge region of a recombinant-DNA-produced human IgG1 (Campath 1H) is specifically cleavable at a single copper-sensitive peptide bond, yielding a distinct fragment resolved by size-exclusion high-performance liquid chromatography. This novel metal ion-catalysed cleavage at slightly alkaline pH is inhibited by EDTA and its rate is reduced at slightly acidic conditions (pH 5-6) and accelerated by increasing concentrations of cupric ion and higher temperature. Complete cleavage was observed after incubation at pH 8 for 24 h with 1 mM CuCl2. Sequence analysis determined the cleavage site to be the Lys226-Thr227 bond in the hinge-region sequence DKTHT. Cleavage of other IgGs was observed to varying degrees, and specific cleavage of synthetic peptides containing this pentapeptide sequence was also observed.

Alemtuzumab↗
PubMed1996

Effect of early life experiences and personality on the reporting of psychosocial distress in general practice. A preliminary investigation.

BACKGROUND: About 25% of primary care attenders are 'somatic presenters'; individuals consulting for physically-attributed somatic symptoms in the presence of psychiatric morbidity. We tested the hypothesis that somatic presenters differed from psychological presenters on measures of personality ad childhood experience. METHOD: Case-control study of 'psychological presenter' and 'somatic presenters'. RESULTS: Psychological presenter reported significantly greater insecurity in intimate relationships, and recalled their fathers as significantly less caring and more over-protective, than somatic presenters. These difference remained after adjusting for differences in the severity and duration of psychiatric symptoms. CONCLUSIONS: Personality and childhood experiences may be associated with specific types of adult illness behaviour, independent of associations with the prevalence of psychiatric disorder.

Adolescent↗
PubMed1996

Are SSRIs a cost-effective alternative to tricyclics?

BACKGROUND: Selective serotonin reuptake inhibitors (SSRIs) are more expensive than tricyclics. Reports have suggested that SSRIs are cost-effective because they are better tolerated and safer in overdose. METHOD: A systematic review of all randomised controlled trials (RCTs), meta-analyses, and cost-effectiveness studies comparing SSRIs and tricyclic antidepressants (TCAs). RESULTS: None of the RCTs provided an economic analysis and there were methodological problems in the majority which would preclude this approach. Meta-analyses suggest that clinical efficacy is equivalent but slightly fewer patients prescribed SSRIs drop out of RCTs. Cost-effectiveness studies have been based on crude 'modelling' approaches and over-estimate the difference in attrition rates and the cost of treatment failure. It appears impossible to evaluate the economic aspects of suicide because of its rarity. CONCLUSIONS: There is no evidence to suggest that SSRIs are more cost-effective than TCAs. The debate will only be concluded when a prospective cost-effectiveness study is done in the setting of a large primary care based RCT.

Antidepressive Agents, Tricyclic↗
PubMed1996

Parametric stress analysis of bonded "combination-materials" type of orthodontic brackets.

The finite element analysis method and a two-dimensional idealization were used to conduct a detailed parametric study of the stresses in and displacement of models of bonded edgewise "combination-materials" type of orthodontic brackets when subjected to loading and constraint conditions that are deemed to be the same as those that exist in vivo. A "combination-materials" type bracket is herein defined as one in which different materials are used in fabricating the main body and the archwire slot. The present study was conducted in three parts. In Part 1, 16 model cases were analyzed, involving 4 different combinations of materials (for the main body of the bracket and its archwire slot) and 4 different overall bracket configurations (comprising main body, base and slot). The focus of Part 2 was the model bracket configuration that was, on the basis of Part 1 results, deemed to show the "optimum performance". In this part, the parameter investigated was the value of the modulus of elasticity of the adhesive, Eadh. In Part 3, the concept of an efficiency index of the bonded bracket-archwire system, eta, was introduced and explained. The dependence of eta on stated characteristics of a rectangular archwire, for the "optimum performance" model, was explored. Part 1 results led to the conclusion that the "optimum performance" model has equally angulated buccal and lingual edges and the main body and archwire slot are fabricated from glass fiber-reinforced polycarbonate and stainless steel, respectively. Part 2 results showed that, for the aforementioned "optimum performance" model, the longitudinal displacement of the archwire slot is fairly insensitive to Eadh. Part 3 results showed that eta is intimately related to each of the wire characteristics studied (namely cross-sectional dimensions, "interbracket distance" and modulus of rigidity of the material).

Adhesives↗
PubMed1996

Effect of debonding forces on bonded orthodontic brackets: finite element study.

The finite element analysis method was used to obtain values of the von Mises equivalent stress (SEQV) at selected locations within the adhesive layer of two-dimensional models of bonded orthodontic brackets. In all, 39 model cases were analyzed involving 4 overall bracket configurations, 3 combinations of materials of fabrication of the bracket, 3 types of debonding forces and 4 adhesives. The results are presented to show the sensitivity of SEQV to each of the parameters studied. Comments are made on the usefulness of the results in the development of a standard protocol for experimental determination of the bond strength of adhesives used in securing orthodontic brackets.

Computer Simulation↗
PubMed1996

The elbow joint and its total arthroplasty. Part I. A state-of-the-art review.

Various pathologies, notably rheumatoid arthritis and/or trauma, are all known to cause severe pain and/or reduction of functional motion at the elbow joint. Implantation of a total arthroplasty, in such cases, has emerged as the first choice for management. For acceptable clinical performance, such an arthroplasty should be designed fully cognizant of various germane aspects of the anatomy, kinesiology and biomechanics of the normal joint. These aspects, together with a critical appraisal of the different classes of arthroplasty designs and a discussion of areas for further research (aimed at improving the in vivo performance of the prosthesis), are the subjects of the present review.

Elbow Joint↗
PubMed1996

The elbow joint and its total arthroplasty. Part II. Finite element study.

The stresses in various sections of two-dimensional models of the elbow joint, without and with a prosthesis (the humeral component of a total elbow prosthesis), were obtained using the finite element analysis method. Three parameters were varied: type of applied load; method of fixation of the prosthesis to the contiguous bone; and shape of the head of the prosthesis. The results are discussed with particular reference to stress shielding and overload in the cortical and cancellous bones, respectively, and a qualitative comparison between the present values and those given by previous workers who used three-dimensional models. Comments are made regarding the clinical implications of the results.

Adult↗
PubMed1995

Is the General Health Questionnaire (12 item) a culturally biased measure of psychiatric disorder?

There have been suggestions that some self-administered questionnaires designed to assess psychiatric disorder tend to overestimate prevalence in samples from Latin America. This phenomenon may be obscured when the General Health Questionnaire (GHQ) is used, as it is recommended that researchers determine the threshold in each setting by comparing the GHQ with a standardised interview. Reports in the literature suggest that Latin American samples have a higher threshold for case definition using the GHQ than that found in British samples. The present study confirmed this finding when comparing the 12-item GHQ in a Chilean primary care sample with a sample of primary care attenders from the United Kingdom. The increase in GHQ scores in the Chilean sample persisted after adjustment for age, sex, marital status and the score on the Revised Clinical Interview Schedule (CIS-R). The increase in scores seen in the Chilean sample was only found in that half of the GHQ that asks about negative aspects of mental health.

Adult↗
PubMed1995

Are there neurological and sensory risk factors for schizophrenia?

The association between left-handedness, epilepsy, and hearing impairment with schizophrenia was investigated using data from a cohort of 50,000 male Swedish conscripts linked to the Swedish National Register of Psychiatric Care. Though epilepsy was rare in this cohort, no association with schizophrenia was found. Left-handedness was associated with neither schizophrenia nor other psychoses. The study shows that, when studied from a population base, the apparent increase in neurodevelopmental anomalies in schizophrenia may be an artefact of bias. However, schizophrenia was 1.81 (95% CI 1.2-2.7) times higher amongst those with severe hearing loss, which may be preventable.

Adolescent↗
PubMed1995

A thoracic spine testbed for the comparative biomechanical evaluation of spinal instrumentations.

This study focuses on the design, materials selection, and fabrication of a human thoracic spine (T-3 to T-12) mechanical analog testbed and an examination of its suitability for use in the comparative evaluation of biomechanical characteristics of spinal instrumentations. In this case, two constructs involving the Texas Scottish Rite Hospital (TSRH) system (namely, a specially assembled unilateral rod and the standard dual rod scoliosis arrangements) were compared. It was found that there is no statistically significant difference between the direct axial compressive stiffnesses of the constructs using these arrangements. In addition, the von Mises stresses at three selected locations on one of the vertical rods constituting the instrumentation showed statistically significant decreases when the standard dual-rod construct was used compared to the case when the unilateral-rod construct was used. It was found that the relative change in stiffness between the constructs approximated that observed in previous cadaveric and animal studies. It is thus concluded that the testbed is suitable for the stated purpose.

Biomechanical Phenomena↗
PubMed1995

Biochemical effects of losartan, a nonpeptide angiotensin II receptor antagonist, on the renin-angiotensin-aldosterone system in hypertensive patients.

We investigated the effects of angiotensin II (Ang II) type 1 receptor blockade with losartan on the renin-angiotensin-aldosterone system in hypertensive patients (supine diastolic blood pressure, 95 to 110 mm Hg). Qualifying patients (n = 51) were allocated to placebo, 25 or 100 mg losartan, or 20 mg enalapril. Blood pressure, plasma drug concentrations, and renin-angiotensin-aldosterone system mediators were measured on 4 inpatient days: end of placebo run-in, after first dose, and 2 and 6 weeks of treatment. Plasma drug concentrations were similar after the first and last doses of losartan. At 6 weeks, 100 mg losartan and 20 mg enalapril showed comparable antihypertensive activity. Four hours after dosing, compared with the run-in day, 100 mg losartan increased plasma renin activity 1.7-fold and Ang II 2.5-fold, whereas enalapril increased plasma renin activity 2.8-fold and decreased Ang II 77%. Both drugs decreased plasma aldosterone concentration. For losartan, plasma renin activity and Ang II increases were greater at 2 than at 6 weeks. Effects of losartan were dose related. After the last dose of losartan, plasma renin activity and Ang II changes were similar to placebo changes by 36 hours. These results indicate that long-term blockade of the feedback Ang II receptor in hypertensive patients produces modest increases of plasma renin activity and Ang II that do not appear to affect the antihypertensive response to the antagonist.

Adult↗
PubMed1995

The prevalence and costs of psychiatric disorders and learning disabilities.

BACKGROUND: The economic burden of psychiatric disorders and learning disability is assessed in order to aid decisions on priorities for research funding. METHOD: A wide variety of data sources both on prevalence and on the usage and costs of relevant services were used to measure the economic burden of each condition. RESULTS: Despite methodological problems and problems with the data, an attempt is made to estimate the relative economic burden imposed by each condition. No attempt is made to sum up the costs for each condition across the agencies and individuals involved. CONCLUSIONS: Our findings show that learning disability, schizophrenia and neurotic conditions (including depression) are major burdens on the National Health Service; senile dementia and depression in older people impact largely on local authority social services. Senile dementia, schizophrenia and learning disability are also heavy charges on the social security system. It is also notable that the large numbers with less severely disabling neurotic disorders generate a burden that, according to our figures, is comparable to schizophrenia and other psychotic disorders.

Adolescent↗
PubMed1995

Finite element stress analysis of the wrist joint without and with an endoprosthesis.

The finite element analysis method was used to obtain the lateral deformation profile and values of the von Mises stress in the cortical and cancellous regions of the various bones in models of a selected space in the coronal plane of a human wrist joint, without and with a prosthesis. The prosthesis was the metacarpal component of the Trispherical design of the total wrist joint arthroplasty. The models included all the bones, the associated network of ligaments, and the intervening soft muscle tissue. Each type of model was completely constrained along its entire proximal surface and subjected to either a static point force (in the axial compressive or anteroposterior tensile direction) acting at the center of the distal tip of the third metacarpal cortical bone. For the models containing the prosthesis, a parametric study was conducted involving the method of anchorage of the prosthesis to the contiguous bones and the material of fabrication of the prosthesis. It was found that: (1) the axial force produces lower stresses in the bones compared with the anteroposterior one; (2) no clear-cut case can be advanced, from the stress viewpoint, for press-fitting the prosthesis to the contiguous bones rather than using bone cement for such anchorage; and (3) any alloy with modulus of elasticity in the 79 to 196 GPa range and Poisson's ratio of about 0.3 may be used to fabricate the prosthesis. The approximations used and the associated limitations of the work are fully discussed, as are the design implications and clinical significance of the results.

Humans↗
PubMed1995

The total wrist joint arthroplasty: biomechanical considerations and research directions.

A review of the state-of-the-art knowledge base on the biomechanics of the wrist joint, with emphasis on total wrist joint arthroplasty, is presented. The reasons for the reported high rate of aseptic loosening of the metacarpal component of such an implant are unknown at this time. It is suggested that detailed stress analyses of models of the joint, without and with the aforementioned implant, will yield results that will increase understanding of this problem and improve implant design, resulting in enhanced clinical performance of these replacements. For this purpose, it is recommended that the finite element analysis method be used.

Arthroplasty↗
PubMed1995

Characterization of biomedical polymer surface interaction with human factor Xa.

Two surface analytical spectroscopic techniques (namely, angular-dependent X-ray photoelectron spectroscopy and static secondary ion mass spectrometry) were used to characterize the nature and composition of the surface and near-surface layers formed on three biomedical polymers (namely, low-density polyethylene, expanded polytetrafluoroethylene, and a silicone elastomer) when exposed to Factor Xa in a buffer solution under adsorption conditions. It is shown that the results extracted from the spectroscopic measurements are consistent with each other. The clinical significance of the results is discussed in terms of screening biomedical polymers for use in fabricating cardiovascular system components.

Biopolymers↗
PubMed1995

Somatic presentation of psychiatric morbidity in general practice.

BACKGROUND: Twenty per cent of new illnesses in general practice, and 3% of consecutive attenders, are incident cases of 'pure' somatization. AIM: This study set out to estimate the prevalence of consultations by patients with psychiatric morbidity who present only somatic symptoms (somatic presentation), and to compare this with the likely prevalence of pure somatization. METHOD: A cross-sectional survey of consecutive general practice attenders was carried out. Psychiatric morbidity was measured using the general health questionnaire. Pure somatization was defined as medical consultation for somatic symptoms that were judged by a psychiatrist during an interview to be aetiologically attributable to an underlying psychiatric disorder but which were not recognized as such by the patient. RESULTS: Of attenders 25% were identified as somatic presenters. Of the somatic presenters interviewed one in six were estimated to be pure somatizers, which would extrapolate to 4% of attenders. Though all somatic presenters were probable cases of psychiatric disorder, subjects in this group had lower scores on the general health questionnaire than those who presented with psychological symptoms. General practitioner recognition of psychiatric morbidity was significantly lower among somatic presenters than for other subjects with psychiatric morbidity. CONCLUSION: General practitioner recognition of psychiatric morbidity could be improved for all types of somatic presentation, regardless of the aetiology of patients' somatic symptoms. There is a danger that concentrating attention on pure somatization may mean that psychiatric morbidity in the more common undifferentiated form of somatic presentation will be overlooked.

Adult↗