Fracture-induced pain-like behaviours in a femoral fracture mouse model.

This study is the first comprehensive characterisation of the pain phenotype after fracture using both evoked and naturalistic behaviours in adult male and ovariectomised female mice. It also shows that an anti-nerve growth factor (NGF) therapy could be considered to reduce pain after fracture surgery. INTRODUCTION: Bone fractures are common due to the ageing population and very painful even after healing. The phenotype of this pain is still poorly understood. We aimed to characterise it in a femoral fracture model in mice. METHODS: We employed both adult male, and female ovariectomised (OVX) mice to mimic osteoporotic fractures. Mice underwent a unilateral femoral fracture maintained by an external fixator or a sham surgery. Pain behaviours, including mechanical and thermal sensitivity, weight bearing and LABORAS, were measured from baseline to 6 weeks after fracture. The effect on pain of an antibody against nerve growth factor (anti-NGF) was assessed. Changes in nerve density at the fracture callus were analysed by immunohistochemistry. RESULTS: Following surgery, all groups exhibited high levels of invoked nociception. Mechanical and thermal hyperalgesia were observed from 1 week after surgery, with nociceptive sensitization in the fracture group maintained for the 6 weeks, whereas it resolved in the sham group after 3 weeks. OVX induced reduction in pain thresholds, which was maintained after fracture. The frequency of naturalistic behaviours did not change between groups. Anti-NGF administered before and weekly after surgery alleviated fracture-induced mechanical nociception. The density of nerve fibres in the fracture callus was similar in all groups 6 weeks after surgery. CONCLUSIONS: Fractures in rodent models are highly painful in both sexes. This pain-like phenotype is prolonged and should be routinely considered in fracture healing studies as it can affect the study outcome. The anti-NGF alleviates fracture-induced mechanical pain.

Psychosocial predictors of HIV/STI risk behaviours in a sample of homosexual men.

OBJECTIVES: To determine the prevalence of STI/HIV risk behaviours in a sample of homosexual men and investigate the psychosocial and cognitive variables associated with these behaviours. METHOD: A sample of 123 users of a homosexual men's sexual health clinic completed a questionnaire which included demographic information, psychometric measures, history of sexual risk behaviour, and history of non-consensual sex (NCS). RESULTS: High rates of sexual risk were found in this sample behaviour (36% of men had risky sex in the previous month) despite using a narrower definition than other recent studies. Comparable rates of non-consensual sex were found in this sample (26% of the sample had experienced NCS); however, this variable was not directly linked to increased risk behaviour. Depression and cognitions associated with controllability or predictability of risk were associated with increased HIV/STI risk behaviour. CONCLUSIONS: Clinical measures of depression are associated with risk behaviour in this sample as are cognitions about the uncontrollability of risk and reducing chances of exposure to HIV by insertive sexual practices and fidelity. Demographic variables, a history of non-consensual sex and depression are not predictors of risk behaviour when sexual risk cognitions are used to predict unsafe sexual practices indicating that cognitions are foremost in driving risk behaviours, demographic variables, and the NCS history of the subject. Given the considerable costs of providing medical care to patients with HIV it is likely that even modest reductions in rates of HIV infection through proactive psychological interventions to modify erroneous cognitions will prove highly cost effective.

Autoradiographic detection of IgG and viral antigens.

Autoradiographic methods can be used as an alternative to indirect immunofluorescence to detect viral antigen expression or the presence of IgG in tissue sections. Iodinated protein A isolated from Staphylococcus aureus detects an influx of IgG into the central nervous system of mice inoculated with the coronavirus SD. Antispecies antibody that has been iodinated detects coronavirus antigen expression for 24 days post-inoculation while it is only detectable for 10 days by immunofluorescence. A direct comparison of indirect fluorescence and autoradiographic methods indicates that the autoradiographic techniques are considerably more sensitive. This increased sensitivity is sufficient to permit the detection of viral antigen in formalin fixed paraffin embedded tissue sections.