High volumes of resistance exercise are not required for greater bone mineral density during growth.

PURPOSE: The purpose of this study was to determine the minimum amount of resistance exercise that would stimulate bone formation, via an elevation in bone mineral density (BMD), during the growth period in male rats. METHODS: Forty male rats were randomly divided into control group (Con, n = 8), one ladder climb resistance-trained group (1LC, n = 8), two ladder climb resistance-trained group (2LC, n = 8), three ladder climb resistance-trained group (3LC, n = 8), and four ladder climb resistance-trained group (4LC, n = 8). All exercised groups were conditioned to climb a vertical ladder with weights appended to their tail 3 d·wk(-1) for a total of 6 wk. RESULTS: After 6 wk, left tibia BMD (mean ± SE) was significantly greater for 2LC, 3LC, and 4LC (0.233 ± 0.003 g·cm(-2)) when compared with Con (0.218 ± 0.003 g·cm). Left femur BMD was significantly greater for 2LC, 3LC, and 4LC (0.318 ± 0.003 g·cm(-2)) when compared with 1LC (0.299 ± 0.008 g·cm(-2)) and Con (0.289 ± 0.010 g·cm(-2)).There were no significant differences in BMD between 2LC, 3LC, and 4LC groups. CONCLUSION: The results suggest that during growth, a low amount of resistance exercise was just as effective as high volumes of strength training for stimulating bone modeling.

Lobster attack induces sensitization in the sea hare, Aplysia californica.

Studies of the neural mechanisms of learning, especially of sensitization, have benefitted from extensive research on the model species, Aplysia californica (hereafter Aplysia). Considering this volume of literature on mechanisms, it is surprising that our understanding of the ecological context of sensitization in Aplysia is completely lacking. Indeed, the widespread use of strong electric shock to induce sensitization (an enhancement of withdrawal reflexes following noxious stimulation) is completely unnatural and leaves unanswered the question of whether this simple form of learning has any ecological relevance. We hypothesized that sublethal attack by a co-occurring predator, the spiny lobster, Panulirus interruptus, might be a natural sensitizing stimulus. We tested reflex withdrawal of the tail-mantle and head of individual Aplysia before and after attack by lobsters. Lobster attack significantly increased the amplitude of both reflexes, with a temporal onset that closely matched that observed with electric shock. This result suggests that electric shock may indeed mimic at least one naturally occurring sensitizing stimulus, suggesting, for the first time, an ecological context for this well studied form of learning.

Expression of a novel gene, MafB, in Dupuytren's disease.

PURPOSE: Dupuytren's disease (DD) is characterized by fibroblastic proliferation of the palmar fascia, often leading to flexion contracture in the hand. Although there is a strong genetic component the genome-wide expression of novel genes is not known. The purpose of this study was to use DNA microarray technology to identify upregulated genes in DD. METHODS: Human tissue samples were harvested from 3 patient sources: DD cord tissue (n = 20), normal-appearing adjacent control fascia (n = 15), and palmar fascia from patients having carpal tunnel release (n = 15). DNA microarray analysis was performed on amplified sample RNA. Novel genes were compared with known gene functions. A candidate gene of interest was studied further by using immunohistochemistry on DD tissue samples and controls. RESULTS: Several novel genes not described previously in the study of DD were upregulated significantly, including MafB, collagen type V, alpha-2 (COL5A2), collagen type VIII, alpha-1 (COL8A1), contactin I (CNTN1), and leucine-rich repeat containing 17 (LRRC17). These upregulated genes were compared with their known gene-expression profiles in other tissues and their purported functions. MafB was found to be of particular interest because of its prominent role in tissue development and cellular differentiation. MafB immunohistochemistry showed positive staining in 50% of the DD specimens but complete absence of MafB in all control tissues (adjacent control fascia, carpal tunnel fascia). Co-localization experiments with MafB and alpha-smooth muscle actin showed staining properties in similar regions but these 2 proteins were not confined solely to the same cells. CONCLUSIONS: Microarray analysis of DD tissue has identified significant upregulated gene expression of MafB. MafB protein also is found in Dupuytren's cords but not in control fascia. Co-localization data suggest that the association of MafB with DD is not related exclusively to myofibroblast proliferation. Because of its role in fibroblastic transformation in other models MafB and its relationship to the pathogenesis of DD deserves further study.