The influence of wear paths produced by hip replacement patients during normal walking on wear rates

Variation in wear paths is known to greatly affect wear rates in vitro, with multidirectional paths producing much greater wear than unidirectional paths. This study investigated the relationship between multidirectional motion at the hip joint, as measured by aspect ratio, sliding distance, and wear rate for 164 hip replacements. Kinematic input from three-dimensional gait analysis was used to determine the wear paths. Activity cycles were determined for a subgroup of 100 patients using a pedometer study, and the relationship between annual sliding distance and wear rate was analyzed. Poor correlations were found between both aspect ratio and sliding distance and wear rate for the larger group and between annual sliding distance and wear rate for the subgroup. However, patients who experienced a wear rate <0.08 mm/year showed a strong positive correlation between the combination of sliding distance, activity levels, and aspect ratio and wear rate (adjusted r2?=?55.4%). This group may represent those patients who experience conditions that most closely match those that prevail in simulator and laboratory tests. Although the shape of wear paths, their sliding distance, and the number of articulation cycles at the hip joint affect wear rates in simulator studies, this relationship was not seen in this clinical study. Other factors such as lubrication, loading conditions and roughness of the femoral head may influence the wear rate.

Chemical etching of optical fibre tips - experiment and model

The formation of chemically etched fibre tips for use in optical scanning probe microscopy is addressed. For tips formed at a cleaved fibre end in the bulk of a buffered HF acid solution the morphological features (tip height, cone angle) are found to depend strongly on the temperature and etchant composition. The tip formation process is analysed and explained in terms of a simple model in which the only pertinent physical parameters are the fibre core diameter and etch rates of the fibre core and cladding. The etch rates are determined in separate experiments as a function of temperature (in the range 24-50 degreesC) for etchant solutions of de ionised water: 50% HF acid: 40% NH4F in the volume ratio 1 : 1 : X for X=2, 4 and 6, and used in the model to yield a correct description of the experimental tip cone angles. The model is successfully extended to the intriguing case of negative tip formation which initiates in a normal, positive tip structure. By contrast, tip formation in the meniscus region of a bare fibre/etchant/organic solvent system is found to be independent of etchant composition and temperature. (C) 2000 Elsevier Science B.V. All rights reserved.

Evaluation of glycated glucagon-like peptide-1(7-36)amide in intestinal tissue of normal and diabetic animal models

Glucagon-like peptide-1(7-36)amide (tGLP-1) is an important insulin-releasing hormone of the enteroinsular axis which is secreted by endocrine L-cells of the small intestine following nutrient ingestion. The present study has evaluated tGLP-1 in the intestines of normal and diabetic animal models and estimated the proportion present in glycated form. Total immunoreactive tGLP-1 levels in the intestines of hyperglycaemic hydrocortisone-treated rats, streptozotocin-treated mice and ob/ob mice were similar to age-matched controls. Affinity chromatographic separation of glycated and non-glycated proteins in intestinal extracts followed by radioimmunoassay using a fully crossreacting anti-serum demonstrated the presence of glycated tGLP-1 within the intestinal extracts of all control animals (approximately 19%., of total tGLP-1 content). Chemically induced and spontaneous animal models of diabetes were found to possess significantly greater levels of glycated tGLP-1 than controls, corresponding to between 24-71% of the total content. These observations suggest that glycated tGLP-1 may be of physiological significance given that such N-terminal modification confers resistance to DPP IV inactivation and degradation, extending the very short half-life (