Microstructural analysis of collagen and elastin fibres in the kangaroo articular cartilage reveals a structural divergence depending on its local mechanical environment

Objective: To assess the microstructure of the collagen and elastin fibres in articular cartilage under different natural mechanical loading conditions and determine the relationship between the microstructure of collagen and its mechanical environment. Method: Articular cartilage specimens were collected from the load bearing regions of the medial femoral condyle and the medial distal humerus of adult kangaroos. The microstructure of collagen and elastin fibres of these specimens was studied using laser scanning confocal microscopy (LSCM) and the orientation and texture features of the collagen were analysed using ImageJ. Results: A zonal arrangement of collagen was found in kangaroo articular cartilage: the collagen fibres aligned parallel to the surface in the superficial zone and ran perpendicular in the deep zone. Compared with the distal humerus, the collagen in the femoral condyle was less isotropic and more clearly oriented, especially in the superficial and deep zones. The collagen in the femoral condyle was highly heterogeneous, less linear and more complex. Elastin fibres were found mainly in the superficial zone of the articular cartilage of both femoral condyle and distal humerus. Conclusions: The present study demonstrates that the collagen structure and texture of kangaroo articular cartilage is joint-dependent. This finding emphasizes the effects of loading on collagen development and suggests that articular cartilage with high biochemical and biomechanical qualities could be achieved by optimizing joint loading, which may benefit cartilage tissue engineering and prevention of joint injury. The existence of elastin fibres in articular cartilage could have important functional implications

The effects of field margins on the distribution and biocontrol potential potential of polyphagous predatory arthropods in arable crops

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Feeding responses of carabid beetles to dimethoate-contaminated prey

1 The feeding responses of Pterostichus madidus Fab., P. melanarius Illiger and Nebria brevicollis Fab. (Coleoptera: Carabidae) to dimethoate-contaminated prey were investigated in 'no-choice' and 'choice' feeding tests. 2 In the no-choice tests, starved beetles were presented with aphid prey treated with four concentrations of dimethoate. In the choice tests, treated and untreated prey were presented together and the feeding preferences of the starved beetles observed. 3 No avoidance or rejection behaviour was seen in any of the carabids in either of the tests, i.e. no discrimination of the treated and untreated prey was observed. 4 Sufficient dimethoate was consumed with the aphid prey to cause significant mortality levels in the carabids. 5 The concentrations of dimethoate used in these experiments are comparable to field exposure, so carabids feeding in treated fields and field margins could potentially suffer lethal effects via the indirect exposure route of consuming contaminated prey