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Summary Introduction Autologous osteochondral grafting is in widespread use for focal defects of articular cartilage. There is major concern over the nature of the tissue bridging graft elements and graft/recipient cartilage. Chondrocyte viability is thought to be an important determinant of the quality of repair. The aim of the current study was to compare the zone of death for osteochondral grafts harvested with the commercially available Acufex , and an osteotome with a specially designed cutting-edge. Materials/methods The circular osteotomes were the Acufex 4.5mm MP (Smith & Nephew) and the Lissimore , which has a different cutting-tip geometry and sharpness. These implements were used to harvest osteochondral plugs from macroscopically non-degenerate human lateral condyle explants obtained from the anterior femoral cuts of knee replacement surgery. Confocal laser scanning microscopy with vital staining was used to quantify the zone of marginal chondrocyte death for the entire perimeter of the plugs. Results The increase in cartilage plug diameter (reference the osteotome minimal internal diameter) was significantly greater for the Acufex (Mann–Whitney; n =5; P =0.0079), with the diameter (mm) increasing by 0.49±0.03 (10.9%), compared with 0.16±0.02 (3.3%) for the Lissimore . Osteochondral plugs had a significantly (Mann–Whitney; n =5; P =0.0079) lower mean margin of cell death with the Lissimore osteotome (117.8±8.97μm) than the Acufex MP (315.3±5.90μm). Conclusions Cutting-tip profile is an important factor in determining the extent of marginal death in circular osteochondral grafts. We have designed and assessed an alternative cutting-tip, which caused significantly less marginal death than the commercially available Acufex . We conclude that there is scope for improvement of osteochondral harvest techniques.

A brief outline of the history of sheep scab in the UK is presented together with the current chemical methods used for its control and problems associated with these. Possible alternative approaches to control are discussed, as are selected aspects of the physiology of Psoroptes ovis and the pathogenesis of the scab lesion from the perspective of control through immunisation. Evidence is provided that immunity to the disease can indeed be acquired, both naturally after a previous infection and following inoculation of mite proteins in adjuvant. These results support the view that control by vaccination may be possible, although little is known to date about the antigens involved or the mechanism of protection.

Among the various toxins produced by the bacterial species Vibrio cholerae is HlyA, a cytolytic protein commonly called the El Tor hemolysin. HlyA is synthesized and processed in a complex manner involving various processed or degraded forms, that may co-purify and complicate the interpretation of biochemical and physiological experiments. In this study a single form of HlyA was purified by gel filtration and chromatofocusing using fast protein liquid chromatography in the presence of protease inhibitors. A 45-fold purification was obtained, with a final recovery of 17% of pure 60,000 mol. wt HlyA. A significant improvement in specific activity to 8.5 × 10 6 Chinese hamster ovary tissue culture units per mg protein was obtained. Physiological activity studies indicated that cytolysis of erythrocytes (hemolysis) was inhibited by oxygen: storage of HlyA under oil, and experimentation in N 2 -flushed buffers maintained activity. HlyA-mediated lysis of human erythrocytes was characterized by a significant lag phase, followed by a rapid induction of hemolysis. Hemolysis was inhibited by sucrose, an osmotic protectant, suggesting that the initial action of HlyA on erythrocytes is to raise the basal cation permeability of the cell membrane. The most likely cytolytic mechanism is thus the formation of transmembrane lesions such as homopolymer pores in target cells, as has been found for toxins from numerous other bacterial pathogens.

Vibrio parahaemolyticus is an important enteric pathogen that produces an exotoxin prepared as Kanagawa haemolysin (KH). Isotope flux techniques were used to analyse toxin action on the basal permeability of human erythrocytes. KH induced a cation leak that was (i) rapid in onset (lag phase < 1 min), (ii) ‘pore-like’ in terms of kinetic characteristics, and (iii) of high magnituve initially (first 10 min) and then subsequently lower (but still raised with reference to control cells). The susceptibilities of the induced flux pathway to washout in initial and later periods suggested a protracted binding time course for toxin action. Neuraminidase treatment of erythrocytes enhanced both haemolysis and flux induced by KH, suggesting that the affinity of the toxin for the membrane had increased, possibly as a result of additional toxin receptors being unmasked by this enzyme. These results show that KH elevates the basal permeability of human erythrocytes in a complex manner, a process that probably unherlies the veleterious effects of this toxin on cellular function.