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Biomedical subjects

C Stark

Publications and source records attributed to C Stark.

At least 37 records · Page 2Linked to original sources
PubMed1998

Vignettes of a pulmonary rehabilitation team.

A successful comprehensive pulmonary rehabilitation program depends on these key pieces: thorough planning, an experienced coordinator who is a patient advocate, a dedicated and supportive medical director, enthusiastic and committed team members, the use of program graduates as volunteers, and providing the essential components of pulmonary rehabilitation, which consist of assessment, patient training, exercise, psychosocial intervention, and follow-up. The patients are the most important members of the team. Their courage, dedication, and determination to make their quality of life the best it can be is truly an inspiration to all of us.

California↗
PubMed1997

Psychological reactions after multifetal pregnancy reduction: a 2-year follow-up study.

This study had two objectives. Firstly we assessed the effects of multifetal pregnancy reduction on the mothers' emotional well-being and the relationship with the children during the 2 years following intervention. Secondly at 2 years we compared mothers who had a reduction with mothers who had not and had delivered triplets. The comparisons focused on the mothers' health and their relationship with the children. Women having had a reduction in two hospitals in Paris, between May 1992 and June 1993, were contacted just after intervention for a prospective study. In all, 18 women were included. At 1 and 2 years, 10 women participated. At 2 years, 10 additional women were included. The answers of these 20 mothers were compared to those of 11 consecutive mothers of 2 year old triplets, assessed by the same psychologist in a previous prospective study. Semi-structured interviews were conducted at home. The mothers' social characteristics, their parity, the children's condition at birth and 4 months were very similar between the reduction and triplet groups. One year after birth one-third of the women in the reduction group reported persistent depressive symptoms related to the reduction, mainly sadness and guilt. The others made medical and rational comments expressing no emotion. At 2 years all but two women seemed to have overcome the emotional pain associated with the reduction. The comparison with mothers of triplets indicated that the mothers' anxiety and depression, and difficult relationship with the children were less acute in the reduction group. These results presented some limitations, since a high number of women who miscarried or refused to participate in the follow-up were not assessed at 1 and 2 years. However, a majority of women who participated in the study 2 years after intervention seemed able to accept a multifetal pregnancy reduction to achieve parental goals.

Adult↗
PubMed1997

School injuries in the west of Scotland: estimate of incidence and health service costs.

Injuries are an important cause of morbidity and mortality in childhood. Injuries at school account for up to 30% of accident and emergency department attendances in school age children in England and Wales. Routine school reports are a possible source of information on these injuries, but work in other countries indicates that schools under-report injuries to children, making it difficult to estimate incidence. Over a four-week period, children attending an Accident and Emergency Department at a District General Hospital in the West of Scotland as a result of a school accident were compared to those included in routine school incident reports in the area for the same time period. One hundred and forty-eight children were identified as attending the Accident and Emergency Department after sustaining an injury which met the definition of a school accident. This would indicate a rate of injuries resulting in hospital treatment of 47 per 1,000 pupils per year. The prospective data collection identified school under-reporting of accidents requiring hospital treatment of 705%. This information obtained allowed estimation of hospital costs to the NHS. The cost of the Accident and Emergency Department attendances, out-patient treatment and in-patient costs for this group of children was estimated at Pounds 7,715. At this rate, the cost of hospital treatment for school accidents for Argyll and Clyde Health Board is estimated at Pounds 134,760 per year. Applied to the Scottish population, costs would be over Pounds 1.8 million per year. These figures supply the first UK estimates of health care costs of school accidents, and hence assist services in deciding the priority to accord school accident prevention.

Adolescent↗
PubMed1996

Simulation of titration curves indicated with two indicator electrodes (biamperometry).

A rigorous method to simulate titration curves with indication using two indicator electrodes (biamperometry) is presented. Computer simulations can be carried out for reversible as well as for irreversible systems. The different parameters like the area of the individual electrodes, applied potential difference, heterogeneous rate constant, and the kinetic parameter alpha were varied and investigated as to their influence upon the shape of the titration curves. The theoretically derived effects match with the effects obtained by experiment. Considering the effects described here, it is possible to tailor the shape of the titration curve by the experimental conditions for specific applications in order to get an optimum shape at the end point of the titration.

Journal Article↗
PubMed1996

Bivoltametric titrations using electrodes with innovative geometry.

Electrodes with different surface areas were investigated for the determination of reversible, quasireversible, irreversible or electroinactive substrates. Two kinds of electrodes were constructed, a helical electrode with a given asymmetry and a platinum array electrode with a variable area. These electrodes were applied for the cerimetry of ammonium iron(II) sulfate and for the bromatometry of various organic substances. The theoretically derived effects on the shape of the voltametric titration curve are verified experimentally. It is possible to sharpen one side of the peak and to broaden the other side, depending on the system and the side of the peak one is interested in. It is possible to improve the bivoltametric determination of hydroquinone, benzocaine and sulfaguanidine by bromatometry by the directed employment of electrodes of different areas. For the bromatometric determination of electrochemically irreversible substrates the use of the electrode geometries proposed is a way to obtain a sharp bend and a steep decrease of titration curves with low values of the constant current which is a basic requirement for the accuracy.

Journal Article↗
PubMed1996

Comparison of the size and morphology of UHMWPE wear debris produced by a hip joint simulator under serum and water lubricated conditions.

This paper investigates the effect of lubricant on the size and morphology of ultra-high molecular weight polyethylene (UHMWPE) wear debris produced by a hip joint simulator. Bovine serum and water were chosen as the lubricants for comparison. When bovine serum was used as lubricant, the majority of the wear debris produced was submicron sized and equiaxed or elongated in shape; no transfer film was found on the femoral heads. When water was used as lubricant, large pieces of thin UHMWPE flakes about 2-3 mm across were produced and patches of transfer films were observed on the femoral heads. These large flakes were comprised of numerous smaller thin flakes compacted together. While the size and shape of the wear debris produced with serum lubrication are similar to those reported from clinical studies in total hip replacement, the debris produced with water lubrication bears no resemblance to what has been seen clinically.

Animals↗
PubMed1996

Two years of school injuries in a Scottish education sub-division.

Injuries sustained in schools account for 20-30% of all accident and emergency attendances in school age children. Little information has been available on the epidemiology of school accidents in the United Kingdom. Two years of routine school incident reports were analysed from Renfrew Sub-Region, an area with a school roll of 55,521 children attending 135 schools. Schools returned 1,660 report forms in the two year period, of which 1,440 referred to injuries to school children. The peak incidence of injuries was in the 10-12 year age group. The male:female ratio was 1.37:1. Cuts/ laceration and fractures were the commonest diagnoses reported for both Primary and Secondary Schools. Injuries to face and features were commonest in Primary, and upper limb injuries in Secondary Schools. Uncontrolled areas, e.g. playgrounds, stairways and corridors were the most frequent places of occurrence in Primary Schools (Relative Risk 5.24, 95% C.I. 3.28-8.35). Report accuracy was assessed by comparing one year of school reports in a Local Government District to records in the local District General Hospital. This identified 156 children who had attended hospital as the result of a school accident. Schools overestimated the number of fractures by 27%, but where schools had not provided a diagnosis, 15.4% were identified as fractures in hospital records. Each child seen at the hospital received an average of 2.1 X-rays. Nine children underwent manipulations under general anaesthetic. Seventeen children were admitted to hospital, and the group required 103 outpatient follow-up appointments.

Adolescent↗
PubMed1996

Psychological aspects of excimer laser surgery for myopia: reasons for seeking treatment and patient satisfaction.

AIMS: To determine the reasons patients seek excimer laser treatment for myopia and to measure levels of patient satisfaction with each phase of this relatively new treatment. METHODS: A unique 38 item visual analogue questionnaire was developed and applied to 100 consecutive patients (n = 100) who had undergone excimer laser photorefractive keratectomy for myopia or myopic astigmatism at a single centre. All subjects underwent extensive ophthalmic assessment and patient education before treatment. RESULTS: A 90% response rate was achieved (n = 90). Improved unaided vision (85.6%), freedom from spectacles (83.3%), and difficulties with contact lens wear (72.7%) were the most common reasons for seeking treatment. The majority of patients felt that the quality of their life had improved (85.5%) and 82% felt that the quality of their unaided vision was as good as they had anticipated. overall, 95.5% of patients were pleased that they had undergone this procedure. The vast majority (98.9%) of patients felt that they fully understood the operation pretreatment but almost one quarter (23.9%) found the actual operation distressing. Only 15.7% found postoperative pain did not respond adequately to prescribed analgesia. CONCLUSIONS: This study demonstrates a very high level of patient satisfaction after excimer laser treatment for myopia and myopic astigmatism. It suggests that most patients seek treatment to enjoy better vision free from optical aids and that a high level of patient education preoperatively may establish realistic expectations and satisfaction with overall outcome.

Adult↗
PubMed1996

Mechanistic and morphological origins of ultra-high molecular weight polyethylene wear debris in total joint replacement prostheses.

The mechanistic and morphological origins of microscopic wear debris generated from UHMWPE articular surfaces in total joint replacement prostheses are investigated in this study. It was found experimentally that the molecular chain structure at the articulating surface of UHMWPE undergoes a re-organization process due to strain accumulation caused by surface traction. This molecular re-organization process creates a fibre-like surface texture that exhibits an anisotropic behaviour similar to a unidirectionally reinforced polymer composite. This composite responds to stresses favourably if loaded along the fibre axis but unfavourably if loaded off axis. Due to the very complex multi-axial motion/loading nature at the articular surfaces in total joint replacements, the stress tensors applied to each localized asperity contact area continuously change their directions and magnitudes. These changes in the localized stress field create an off-axis loading situation at each localized contact zone with respect to the orientation of the molecular chains. Depending on the off-axis angle, failure of the molecular structure occurs in three different ways: tensile rupture at very small off-axis angles, shear rupture at intermediate off-axis angles and transverse splitting at large off-axis angles. These failure mechanisms all produce similar fibre-like wear debris. However, the failure stresses differ significantly among the three modes. According to this molecular wear theory, the preferred polymer microstructure for optimal wear resistance would be a three-dimensionally strong network connected by covalent bonds between molecular chains. For UHMWPE, a three-dimensional molecular network can be created by radiation induced cross-linking. Experiments conducted on both gamma irradiated and unirradiated UHMWPE specimens using a linear wear machine and multi-axial joint simulators confirmed the validity of the molecular wear theory.

Biocompatible Materials↗
PubMed1996

Epi- and metaphyseal morphology in the long bones of BDIX/Han rats.

Development and morphology of the epiphyses of the long bones were investigated in 93 adult rats of 7 different strains (BDIX/Han, BDE/Han, BN/Han, DA/Han, LEW/Han, AVN/IpcV/Wistar/Rehbrücke, Shoe: WIST) from the age of 14 weeks up to the age of 78 weeks. Strain-related differences were found in the development of the secondary centre of ossification, which was retarded in the BDIX/Han rats. Furthermore, closure of the growth plate started earlier in the BDIX/Han rats. In addition various regressive changes were detected in the growth plates of long bones of all rats, but not of the ribs. The frequency and extent of these changes varied between individuals and strains. Degeneration of the matrix and necrosis were already observed at 14 weeks of age.

Animals↗
PubMed1996

Long-term safety of the aminobisphosphonate alendronate in adult dogs. II. Histomorphometric analysis of the L5 vertebrae.

Osteoporosis is a major health problem. Bisphosphonates are synthetic compounds that are taken up preferentially by the skeleton and suppress osteoclast-mediated bone resorption. Alendronate (ALN) is an aminobisphosphonate used in the treatment of diseases characterized by increased bone resorption including osteoporosis. The purpose of this study was to rule out possible adverse effects of the chronic administration of ALN on the quality of bone. Thirty-one 20- to 21-month-old beagles (n = 7-8 per group, females and males) were treated p.o. for 157 weeks with ALN at 0.00, 0.25, 0.5 or 1.00 mg/kg/day and labeled in vivo with oxytetracycline and calcein. Undecalcified bone sections obtained from the fifth lumbar vertebra were evaluated by static and dynamic histomorphometry. Cortical or cancellous bone volume and indices of architecture were not affected by treatment. Osteoid thickness and mineralization lag time were not changed by treatment. Tissue level bone turnover was inhibited in a dose-dependent manner in males. The results indicate that long-term ALN administration at up to 5 times the dose used for treatment of osteoporosis in clinical trials causes no abnormalities in bone remodeling or bone structure.

Alendronate↗
PubMed1995

Role of cyclic plastic deformation in the wear of UHMWPE acetabular cups.

The mechanisms of wear in ultra-high-molecular-weight polyethylene (UHMWPE) acetabular cups were investigated on both laboratory simulator-tested cups and a clinically retrieved component. Two different levels of wear process were identified: one characterized by the formation and detachment of platelet-like flakes from initial machining marks, and the other by the formation of fine ripple and fibrils by repeated passes of microscopic asperities on the femoral head. Both wear processes could be described by a criterion of critical plastic strain. A theoretical model was developed to account for the generation of the microscopic wear particles based on such a critical strain criterion. Its predictions of the dependence of the UHMWPE wear rate on surface roughness and applied load were in excellent agreement with previously published experimental correlations.

Acetabulum↗
PubMed1995

Induction of beta-lactamase by cefoxitin in anaerobic intestinal microflora.

Beta-lactamases produced by two anaerobic bacterial strains, Bacteroides ovatus Ax34:1 and Clostridium butyricum NBL3, were shown to be significantly inducible under anaerobic conditions in subinhibitory concentrations of cefoxitin. The induction ratio of beta-lactamase production for Bacteroides ovatus was 2.6 and for Clostridium butyricum 1.6. Incubation of faecal samples with different concentrations of cefoxitin did not result in any induction of beta-lactamase production. When adding a highly inducible aerobic strain (Citrobacter freundii F72:6, induction ratio of 26.5 in broth culture) to faecal samples, an induction ratio of 4.5 was reached. Faeces seem to inhibit beta-lactamase induction in aerobic and anaerobic bacteria. The inducible enzymes produced by the anaerobic strains did not have the same properties as beta-lactamases from aerobic inducible strains, according to substrate profiles and inhibition studies. The results of the present study indicate that increased levels of beta-lactamases in the normal intestinal microflora, which often are observed after administration of beta-lactam agents, are probably due to selection of stably derepressed mutants rather than to induction of beta-lactamase production.

Anti-Bacterial Agents↗