Interplay between motility and cell-substratum adhesion in amoeboid cells

The effective migration of amoeboid cells requires a fine regulation of cell-substratum adhesion. These entwined processes have been shown to be regulated by a host of biophysical and biochemical cues. Here, we reveal the pivotal role played by calcium-based mechanosensation in the active regulation of adhesion resulting in a high migratory adaptability. Using mechanotactically driven Dictyostelium discoideum amoebae, we uncover the existence of optimal mechanosensitive conditions—corresponding to specific levels of extracellular calcium—for persistent directional migration over physicochemically different substrates. When these optimal mechanosensitive conditions are met, noticeable enhancement in cell migration directionality and speed is achieved, yet with significant differences among the different substrates. In the same narrow range of calcium concentrations that yields optimal cellular mechanosensory activity, we uncovered an absolute minimum in cell-substratum adhesion activity, for all considered substrates, with differences in adhesion strength among them amplified. The blocking of the mechanosensitive ion channels with gadolinium—i.e., the inhibition of the primary mechanosensory apparatus—hampers the active reduction in substrate adhesion, thereby leading to the same undifferentiated and drastically reduced directed migratory response. The adaptive behavioral responses of Dictyostelium cells sensitive to substrates with varying physicochemical properties suggest the possibility of novel surface analyses based on the mechanobiological ability of mechanosensitive and guidable cells to probe substrates at the nanometer-to-micrometer level.     

Achievement of English as New Language Learners in Monitor Status: A Cross Sector Comparison from Denver

This study uses administrative data to measure the effect of attending a charter school in Denver, Colorado on the achievement of reclassified English as New Language (ENL) students during their monitor period in the mainstream classroom environment. We utilize school choice data from Denver’s Common Enrollment System (CES) to control for each school a family selected entering grade six, a typical time for a structural move, in order to better control of unobserved variable bias. Results indicate charter attendance increases achievement in mathematics and English on state testing. Charter school success in the CES environment provides insights for districts serving large numbers of ENL students.     

Differential susceptibility to adolescent externalizing trajectories: examining the interplay between CHRM2 and peer group antisocial behavior

The present study characterized prototypical patterns of development in self-reported externalizing behavior, between 12 and 22 years of age, within a community sample of 452 genotyped individuals. A Caucasian subset (n = 378) was then examined to determine whether their probabilities of displaying discrete trajectories were differentially associated with CHRM2, a gene implicated in self-regulatory processes across a range of externalizing behaviors, and if affiliating with antisocial peers moderated these associations. Findings indicate that relative to a normative "lower risk" externalizing trajectory, likelihood of membership in two "higher risk" trajectories increased with each additional copy of the minor allelic variant at CHRM2, and that this association was exacerbated among those exposed to higher levels of peer group antisocial behavior.     

Broadcasting

Jack Lyle's The People Look at Public Television: 1974 (Washington: Corporation for Public Broadcasting, 1975—$1.00, paper)

Ken Coleman's So You Want to be a Sportscaster (New York: Hawthron Books, 1973—$5.95)

Joseph Fletcher Littell (ed.) Coping with Television (Evanston, Ill.: McDougal, Littell, 1973— cost not given, paper)

Joseph Julian's This Was Radio: A Personal Memoir (New York: Viking, 1975—$8.85)

Dick Cavett and Christopher Porterfield's Cavett (New York: Harcourt, Brace Jevanovich, 1974—$8.95)     

Disclosure of information by children in social networking—Not just a case of “you show me yours and I’ll show you mine”

This paper reports the results of a study of MySpace use, by Sydney high school children. It examines the reasons why children disclose information on the website and their understanding of some of the privacy issues involved. The study provides a useful beginning for further work in this area. Regression is used to validate a proposed model of the factors influencing information disclosure and cluster analysis provides an indication of characteristics shared by children who disclose sensitive information, such as name, address and telephone number. It also suggests that children who are taught to value privacy are less likely to disclose sensitive information on-line.