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Biomedical subjects

C Stark

Publications and source records attributed to C Stark.

At least 19 recordsLinked to original sources
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

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↗
PubMed1994

Run an emergency helpline.

Telephone helplines are an effective way of dealing with health related incidents in which large numbers of people need personal counselling or information for reassurance or case finding. Helplines often have to be set up at short notice, which is labour intensive and makes recruitment of appropriate staff difficult. They should ideally be part of local emergency planning resources. Doctors need to be included in the team organising the helpline to ensure that staff are properly briefed, to determine what data need to be collected, and to deal with specialised queries.

Counseling↗
PubMed1994

Violence at work.

Explore the source record for details and available documents.

Emergency Service, Hospital↗
PubMed1994

The relationship between an increase in beta-lactamase activity after oral administration of three new cephalosporins and protection against intestinal ecological disturbances.

Forty-four healthy volunteers were given either amoxycillin (ten subjects), cefpodoxime proxetil (ten subjects), ceftibuten (14 subjects) or cefuroxime axetil (ten subjects) orally for 7-10 days, in order to study the ecological effects on the intestinal microflora. In all three groups receiving oral cephalosporins there was a significant increase in beta-lactamase activity during administration (P < 0.05). There was also an inverse correlation between enzyme activity in faeces during administration compared with the concentration of drug in the intestines and the level of ecological disturbance in the normal intestinal microflora. In volunteers given amoxycillin, only small alterations in the faecal microflora were observed although overgrowth by new amoxycillin resistant enterobacteria occurred in all volunteers. There was an overgrowth of enterococci and yeasts during treatment with cefpodoxime proxetil, ceftibuten or cefuroxime axetil, whereas the numbers of enterobacteria were reduced. Colonization with resistant enterobacteria did not occur, but 14 of 34 subjects receiving oral cephalosporins were colonized by Clostridium difficile. Side-effects were mild and not associated with the ecological alterations in the intestinal microflora.

Administration, Oral↗