To date, the cell and molecular mechanisms regulating tendon healing are poorly understood. Here, we establish a novel model of tendon regeneration using neonatal mice and show that neonates heal via formation of a ‘neo-tendon’ that differentiates along the tendon specific lineage with functional restoration of gait and mechanical properties. In contrast, adults heal via fibrovascular scar, aberrant differentiation toward cartilage and bone, with persistently impaired function. Lineage tracing identified intrinsic recruitment of Scx-lineage cells as a key cellular mechanism of neonatal healing that is absent in adults. Instead, adult Scx-lineage tenocytes are not recruited into the defect but transdifferentiate into ectopic cartilage; in the absence of tenogenic cells, extrinsic αSMA-expressing cells persist to form a permanent scar. Collectively, these results establish an exciting model of tendon regeneration and uncover a novel cellular mechanism underlying regenerative vs non-regenerative tendon healing.

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BackgroundOur aim was to examine the relationship between motor skill proficiency and perceptions of competence of children in their first year of school. We also explored gender-based differences.FindingsParticipants were 260 kindergarten children (mean age = 5y 9 m; boys = 52%) from eight schools; representing 78% of eligible children in those schools. Motor skills were measured using the Test of Gross Motor Development-2 and perceptions of physical competence were assessed using the Pictorial Scale of Perceived Competence and Social Acceptance for Young Children. Motor skill scores were generally low (percentile ranks ranged from 16 - 24) but perceptions of physical competence were positive (boys = 18.1/24.0, girls = 19.5/24.0). A MANOVA showed a significant overall effect for gender (Wilk's lambda = .84 with F (3, 254) = 15.84, p < 0.001) and univariate F tests were significant for all outcome variables. The relationship between object control skills and perceptions of physical competence among girls was not significant; however all other correlations were modest but significant.ConclusionsAlthough motor skill levels were quite low, the children generally held positive perceptions of their physical competence. These positive perceptions provide a window of opportunity for fostering skillfulness. The modest relationships between perceptions of competence and motor skill proficiency suggest that the children are beginning to make self-judgments at a young age. Accordingly, opportunities for children to become and feel physically competent need to occur early in their school or preschool life.

This study examines which personal student background and college characteristics are associated with marijuana use. A self-administered survey was mailed to a national representative sample of 17592 students at 140 American colleges. One of four (24.8%) students reported using marijuana within the past year. Rates of use among the colleges ranged from zero per cent at the lowest use schools to 54% at the highest use schools. Multiple regression models, constructed to determine the college and student characteristics predicting marijuana use, suggest that use was higher among students at non-commuter colleges and at colleges with pubs on campus. Student characteristics associated with marijuana use included being single, white, spending more time at parties and socializing with friends, and less time studying. Marijuana use was higher among students who participate in other high risk behaviors such as binge drinking, cigarette smoking and having multiple sexual partners, and among students who perceived parties as important, and religion and community service as not important. The study points to the social nature of drug use in college, and demonstrates that this behavior is of continuing concern for public health.