A tapered channel microfluidic device for comprehensive cell adhesion analysis, using measurements of detachment kinetics and shear stress-dependent motion

We have developed a method for studying cellular adhesion by using a custom-designed microfluidic device with parallel non-connected tapered channels. The design enables investigation of cellular responses to a large range of shear stress (ratio of 25) with a single input flow-rate. For each shear stress, a large number of cells are analyzed (500–1500 cells), providing statistically relevant data within a single experiment. Besides adhesion strength measurements, the microsystem presented in this paper enables in-depth analysis of cell detachment kinetics by real-time videomicroscopy. It offers the possibility to analyze adhesion-associated processes, such as migration or cell shape change, within the same experiment. To show the versatility of our device, we examined quantitatively cell adhesion by analyzing kinetics, adhesive strength and migration behaviour or cell shape modifications of the unicellular model cell organism Dictyostelium discoideum at 21 °C and of the human breast cancer cell line MDA-MB-231 at 37 °C. For both cell types, we found that the threshold stresses, which are necessary to detach the cells, follow lognormal distributions, and that the detachment process follows first order kinetics. In addition, for particular conditions’ cells are found to exhibit similar adhesion threshold stresses, but very different detachment kinetics, revealing the importance of dynamics analysis to fully describe cell adhesion. With its rapid implementation and potential for parallel sample processing, such microsystem offers a highly controllable platform for exploring cell adhesion characteristics in a large set of environmental conditions and cell types, and could have wide applications across cell biology, tissue engineering, and cell screening.     

Active relatives and health-related physical fitness in European adolescents: The HELENA Study

Abstract High physical fitness in childhood and adolescence is positively associated with favourable health-related outcomes. Our aim was to examine the relationship between relatives' (father, mother, brother, sister, and best friend) physical activity engagement and encouragement on adolescents' physical fitness. Adolescents were part of the HELENA study, a multi-centre study conducted in 10 cities from nine European countries in 2006-2008. Participants were 3288 adolescents (48% boys, 52% girls) aged 12.5-17.5 years with valid data on at least one of the three fitness variables studied: muscular strength (standing long jump), speed/agility (4×10 m shuttle run), and cardiorespiratory fitness (20 m shuttle run). The adolescents reported their relatives' physical activity engagement and encouragement. Analysis of covariance showed that relatives' physical activity engagement (father, mother, brother, and best friend) was positively related to cardiorespiratory fitness (P?相似文献   

Gifted students with learning disabilities: who are they?

More than 20 years ago, psychologists first described gifted students with learning disabilities (LD). In the past decade, several sets of identification criteria have been proposed for this population. Many of the suggested assessment practices are unsupported by research in psychoeducational assessment, and some have been directly contradicted by recent research. We argue that an uncritical acceptance of the concept of concomitant giftedness and LD has led to unsound identification procedures and to interventions that are not targeted properly. Specific recommendations for future research and implications for current clinical practice are discussed.     

College Women Mentoring Adolescent Girls: The Relationship between Mentor Peer Support and Mentee Outcomes

In this study, we examined the effectiveness of peer support for college women mentors who engaged in one-to-one and group mentoring with at-risk adolescent girls. Using data from 162 mentoring pairs, results suggested that mentor support positively predicted mentees’ self-reported improvement after a year of mentoring. An examination of mentees’ self-esteem outcomes revealed that mentor peer support was associated with higher outcomes only for those mentees who had higher pre-program scores; for those with below average pre-scores, mentor support was associated with lower self-esteem. Taken together, these results indicate that mentor support may serve as an important function beyond ongoing training, though its effectiveness may vary based on mentee characteristics. Implications are discussed.