Mechanical properties and adaptations of some less familiar bony tissues

This review attempts to show the bone community that there are many ways of being a ‘bone’, and that the range of mechanical properties of bone material is much greater than is conventionally thought to be the case. However the structure–function relationships have in many cases hardly moved beyond mere assertion. There is a pressing need for an examination of some material properties of a whole variety of bones, always using exactly the same testing method, for instance nanoindentation of wet material, so that firm comparisons can be made.     

Exercise of young thoroughbred horses increases impact strength of the third metacarpal bone

Exercise can have a profound effect on bone mass but little is known of its effect on bone's material properties. In this experiment, our hypothesis was that a large difference in the training regimen of young thoroughbreds would produce a measurable difference in the mechanical properties of their bone material. When they were about 19 months old, eight thoroughbred racehorses were given one of two exercise regimens that lasted for 19 weeks: four horses (controls) were walked for 40 minutes a day but had no other exercise, and the remaining four (exercised) were additionally trotted for 20 minutes a day and given progressively intensive exercise on a treadmill. Mechanical testing to failure was performed on longitudinal beam specimens of the mid-diaphysis of the metacarpal. There was no difference in Young's modulus or bending strength between the two groups, although these properties varied somewhat depending on the position within the cortex from which the specimens had come. The specimensfrm the exercised horses had a slightly higher toughness, as measured by work (area under the load-deformation curve). They had a considerably higher impact strength. The impact strength of specimens from, the outer coitex was also higher than that of those from the inner cortex in both groups. Impact strength correlated positively with the amount of micro-cracking produced during testing. Microcracking is related to structural and microstructural features in the bone. Increased loading caused the bone to respond in a way lhat enhanced its ability to microcrack and hence its toughness.     

Adolescents' perceptions of violence and its prevention

OBJECTIVE: To explore aspects of aggression, in particular fighting and weapon carrying, among high school students. This was in response to an earlier survey of Dunedin young people and will assist in the development of a broader quantitative study on aggression among high schools students. METHODS: A qualitative investigation using eight focus groups of 41 participants was conducted in Otago, New Zealand, between November 2004 and February 2005. The focus groups were analysed to identify common themes and critical issues. RESULTS: Results suggest there are different levels of fighting, but participants agreed that a fight should be defined as serious as opposed to a play fight. Fights often begin as verbal and escalate to physical. Differences were found in fighting at school and outside of school. Whether an item was considered a weapon or not depended on the intended use of the item. Participants suggested that some items may be reported as weapons, even though they are not being carried for such purposes. If so, the estimates provided in the prior Dunedin survey may be unduly high. CONCLUSIONS: Surveys such as the Youth Risk Behaviour Survey provide a snapshot of youth aggression, but may hide significant differences in the nature of the aggression being reported. IMPLICATIONS: Prevention should concentrate on changing the social environment of our schools and communities. Further research should include more in-depth questions on fighting and weapon carrying, both at school and outside of school, to better estimate the prevalence of these behaviours and the context in which they occur.     

Spontaneous rupture of the spleen in rheumatoid arthritis.

Two patients with rheumatoid arthritis without splenomegaly or Felty's syndrome developed spontaneous rupture of the spleen. The histological appearance was consistent with involvement of the splenic capsule by the rheumatoid process, and this may have predisposed to splenic rupture.     

Behavioral treatment of obesity. Limitations and results with the chronically obese

Results of behavioral treatment for obese persons during the first 18 months of clinical operation are presented and other reports in the literature are reviewed. Baseline and follow-up data were gathered from a population of 144 female, chronically obese patients, most of whom were experiencing medical complications associated with obesity. Treatment results were disappointing in comparison with results of similar programs. Difference in patient population groups is offered as a possible explanation for this phenomenon. Covariant analyses of demographic and psychosocial variables failed to yield any clear predictors of weight loss; it is suggested that biological factors may be important to treatment outcome for some overweight patients.     

Conversion from daily to alternate daily corticosteroids in rheumatoid arthritis.

An attempt was made to convert 24 patients on corticosteroid treatment from a daily to an alternate daily regimen. Ten patients were successfully converted, 11 failed to convert, and 3 had to be withdrawn for irrelevant reasons. A simple tetracosactrin stimulation test gave some indication of which patients were more likely to convert successfully. Success was not influenced by severity or duration of disease, nor by dose of duration of steroid therapy. Conversion did not influence various clinical and laboratory measures of undesirable steroid side effects, but the follow-up period was probably too short to judge this. The evidence of others suggests that conversion is worth attempting.