Relationship between Exercise Capacity and Brain Size in Mammals

A great deal of experimental research supports strong associations between exercise, cognition, neurogenesis and neuroprotection in mammals. Much of this work has focused on neurogenesis in individual subjects in a limited number of species. However, no study to date has examined the relationship between exercise and neurobiology across a wide range of mammalian taxa. It is possible that exercise and neurobiology are related across evolutionary time. To test this hypothesis, this study examines the association between exercise and brain size across a wide range of mammals.Controlling for associations with body size, we examined the correlation between brain size and a proxy for exercise frequency and capacity, maximum metabolic rate (MMR; ml O(2) min(-1)). We collected brain sizes and MMRs from the literature and calculated residuals from the least-squares regression line describing the relationship between body mass and each variable of interest. We then analyzed the correlation between residual brain size and residual MMR both before and after controlling for phylogeny using phylogenetic independent contrasts. We found a significant positive correlation between maximum metabolic rate and brain size across a wide range of taxa.These results suggest a novel hypothesis that links brain size to the evolution of locomotor behaviors in a wide variety of mammalian species. In the end, we suggest that some portion of brain size in nonhuman mammals may have evolved in conjunction with increases in exercise capacity rather than solely in response to selection related to cognitive abilities

Knee and hip arthroplasty infection rates in persons with haemophilia: a 27 year single center experience during the HIV epidemic.

Total joint replacement (TJR) is an option for the management of chronic haemophilic arthropathy. Because surgery is technically challenging, there is a high rate of deep prosthetic infections, particularly in human immunodeficiency virus (HIV)-infected individuals. We determined the incidence of deep infection rates following total knee and hip arthroplasties in HIV-seropositive and HIV-seronegative persons with haemophilia. Fifty-one primary joint replacements were performed on 32 patients seen at a regional comprehensive haemophilia care center from 1975 to 2002. Thirty prostheses were placed in patients who were HIV-seropositive prior to surgery (n = 14) or seroconverted later (n = 16). Median age at the time of surgery was 33 years (range: 20-61) among 19 HIV-seropositive patients and 35 years (range: 26-74) among 13 HIV-negative patients. Median duration of follow-up was 83 months (range: 2-323). Rate of primary joint infection per artificial joint-year by HIV status was compared by Poisson regression. Main outcome measures were the incidence of primary replacement joint infections by HIV status. Deep infections developed in five (9.8%) of 51 replacement joints. There were two infections during 204.15 joint-years without HIV infection and three infections during 205.28 joint-years with HIV infection. The incidence rate of joint infection (0.98 vs. 1.46 per 100 joint-years) was not increased with HIV (relative risk, RR: 1.49, 95% CI: 0.25-8.93, P = 0.66). We conclude that HIV infection is not a contraindication to knee or hip replacement arthroplasty in the appropriate clinical setting