Both intra- and extravascular events were found attributing to the steroid-associated ON based on our experimental protocol with a single low-dose LPS injection and subsequent three injections of high-dose MPS. Both high ON incidence and no mortality in rabbits treated with this inductive protocol suggested its effectiveness for future studies on evaluation of therapeutic efficacy of interventions developed for prevention of steroid-associated ON.

This study aimed to conduct a systematic review to sum up evidence of the associations between different aspects of night shift work and female breast cancer using a dose-response meta-analysis approach. We systematicly searched all cohort and case-control studies published in English on MEDLINE, Embase, PSYCInfo, APC Journal Club and Global Health, from January 1971 to May 2013. We extracted effect measures (relative risk, RR; odd ratio, OR; or hazard ratio, HR) from individual studies to generate pooled results using meta-analysis approaches. A log-linear dose-response regression model was used to evaluate the relationship between various indicators of exposure to night shift work and breast cancer risk. Downs and Black scale was applied to assess the methodological quality of included studies. Ten studies were included in the meta-analysis. A pooled adjusted relative risk for the association between 'ever exposed to night shift work' and breast cancer was 1.19 [95% confidence interval (CI) 1.05-1.35]. Further meta-analyses on dose-response relationship showed that every 5-year increase of exposure to night shift work would correspondingly enhance the risk of breast cancer of the female by 3% (pooled RR = 1.03, 95% CI 1.01-1.05; Pheterogeneity < 0.001). Our meta-analysis also suggested that an increase in 500-night shifts would result in a 13% (RR = 1.13, 95% CI 1.07-1.21; Pheterogeneity = 0.06) increase in breast cancer risk. This systematic review updated the evidence that a positive dose-response relationship is likely to present for breast cancer with increasing years of employment and cumulative shifts involved in the work.

PE was able to exert beneficial effect on preventing steroid-associated ON in rabbits with inhibition of both thrombosis and lipid deposition.

Objective. To examine the features of the intraosseous vasculature, the size of the marrow stem cell pool (MSCP), and expression of vascular endothelial growth factor A (VEGF) during inadequate repair of steroid-associated osteonecrotic lesions in rabbits.Methods. Steroid-associated osteonecrosis was induced in male rabbits. At 0, 1, 2, 4, and 6 weeks postinduction, vascularization and permeability indices were quantified by dynamic magnetic resonance imaging (MRI). In addition, the size of the MSCP in the hematopoietic and mesenchymal compartments was determined, and marrow mononuclear cells expressing specific surface markers for endothelial progenitor cells or periendothelial mural precursor cells were counted. At various time points after the rabbits were killed, the proximal femora were dissected to examine the intraosseous vasculature by angiography, histomorphometry, and ultramorphology. In addition, osteonecrotic lesion repair and marrow VEGF expression were evaluated.Results. Lesion formation without repair was observed at 2 weeks after induction of steroid-associated osteonecrosis. Rabbits displaying destructive repair (DR؉) and those displaying reparative osteogenesis (DR؊) from 4 weeks to 6 weeks postinduction were identified. From week 2 to week 6, the vascularization index was significantly lower in DR؉ rabbits compared with DR؊ rabbits, whereas the permeability index was significantly higher in DR؉ rabbits compared with DR؊ rabbits. The features of the intraosseous vasculature determined by angiography, histomorphometry, and ultramorphology were consistent with those determined by dynamic MRI. The MSCP size and number of marrow mononuclear cells expressing specific surface markers were all significantly lower in DR؉ rabbits than in DR؊ rabbits from week 1 to week 6. The increased VEGF expression at 2 weeks was maintained through week 6 in DR؉ rabbits, whereas VEGF expression decreased in DR؊ rabbits from week 2 to week 6.Conclusion. Continuous occurrence of both insufficient neovascularization and elevated vascular permeability is accompanied by a continuously lowlevel MSCP and uncontrolled VEGF expression during inadequate repair of steroid-associated osteonecrotic lesions.Pulsed steroids are frequently prescribed as lifesaving agents for serious infectious diseases such as severe acute respiratory syndrome and acquired immunodeficiency syndrome, or as disease-modifying agents for chronic autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. However, pulsed administration of steroids often results in osteonecrosis (also known as avascular necrosis). Orthopedic surgeons face the challenge of managing subchondral

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