Biopolymer system for cell recovery from microfluidic cell capture devices

Microfluidic systems for affinity-based cell isolation have emerged as a promising approach for the isolation of specific cells from complex matrices (i.e., circulating tumor cells in whole blood). However, these technologies remain limited by the lack of reliable methods for the innocuous recovery of surface captured cells. Here, we present a biofunctional sacrificial hydrogel coating for microfluidic chips that enables the highly efficient release of isolated cells (99% ± 1%) following gel dissolution. This covalently cross-linked alginate biopolymer system is stable in a wide variety of physiologic solutions (including EDTA treated whole blood) and may be rapidly degraded via backbone cleavage with alginate lyase. The capture and release of EpCAM expressing cancer cells using this approach was found to have no significant effect on cell viability or proliferative potential, and recovered cells were demonstrated to be compatible with downstream immunostaining and FISH analysis.     

Measurements of the relative momentum accommodation coefficient for different gases with a viscosity vacuum gauge

The viscosity vacuum gauges are based on the gas momentum transfer phenomena between a moving part of the gauge and a stationary surface. Thus, they may be used for the study of the momentum accommodation coefficient for various combinations of gas species and surfaces. The aim of the present work is to determine the momentum accommodation coefficient by means of the viscosity vacuum gauge with vibrating metal ribbon. The relative accommodation coefficient was computed from the measurements for Xe, Ar, He and H₂ on the bronze ribbon of the gauge in the molecular conditions. The values of the relative coefficients were 0.90 for Xe, 0.95 for Ar, 1 for He (values were normalised to data obtained for He) and 0.94 for H₂.     

On selecting indicators for multivariate measurement and modeling with latent variables: When "good" indicators are bad and "bad" indicators are good.

Selecting indicators is as important for the generalizability of research designs as selecting persons or occasions of measurement. Elaborating on the extant knowledge base regarding indicator selection, the authors examine selection influences on the validity and reliability of multivariate representations. A simulation that systematically varied 4 key dimensions of indicator selection was used to investigate their effects on the fidelity of construct representations and the relative ability of exploratory and confirmatory analyses to recover within- and between-construct information. Confirmatory analyses, for example, yielded valid and unbiased estimates of the relations between constructs, even under conditions of very low internal consistency. Design, procedural, and analysis recommendations based on an expanded taxonomy of indicator selection and the simulation results are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The complex nature of unique and shared effects in hierarchical linear regression: Implications for developmental psychology.

Hierarchical linear regression and related techniques, such as commonality analysis, path analysis, and linear structural equation models with mediator variables, are often used to determine the extent to which the influence of an exogenous variable on a dependent variable, A, is "unique" to this exogenous variable, or "shared with" another predictor variable, B. The authors formally show that shared and unique effects are related to the partial correlation between A and B controlling for the exogenous variable. We discuss the implications of this property of hierarchical linear regression with a special consideration of the role of chronological age in developmental psychology and warn against the uncritical use of hierarchical linear regression procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adverse effects of citrate/gold nanoparticles on human dermal fibroblasts

Nanoscale engineering is one of the most dynamically growing areas at the interface between electronics, physics, biology, and medicine. As there are no safety regulations yet, concerns about future health problems are rising. We investigated the effects of citrate/gold nanoparticles at different concentrations and exposure times on human dermal fibroblasts. We found that, as a result of intracellular nanoparticle presence, actin stress fibers disappeared, thereby inducing major adverse effects on cell viability. Thus, properties such as cell spreading and adhesion, cell growth, and protein synthesis to form the extracellular matrix were altered dramatically. These results suggest that the internal cell activities have been damaged.     

On the power of multivariate latent growth curve models to detect correlated change.

We evaluated the statistical power of single-indicator latent growth curve models (LGCMs) to detect correlated change between two variables (covariance of slopes) as a function of sample size, number of longitudinal measurement occasions, and reliability (measurement error variance). Power approximations following the method of Satorra and Saris (1985) were used to evaluate the power to detect slope covariances. Even with large samples (N=500) and several longitudinal occasions (4 or 5), statistical power to detect covariance of slopes was moderate to low unless growth curve reliability at study onset was above .90. Studies using LGCMs may fail to detect slope correlations because of low power rather than a lack of relationship of change between variables. The present findings allow researchers to make more informed design decisions when planning a longitudinal study and aid in interpreting LGCM results regarding correlated interindividual differences in rates of development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Plasticity of memory for new learning in very old age: A story of major loss?

Longitudinal survivors of the Berlin Aging Study (N = 96, mean age = 84 years, range 75-101 years) were instructed and trained in a mnemonic skill to examine plasticity of episodic memory performance in very old age. Performance gains after mnemonic instruction were modest, and most individuals were unable to further enhance their performance during 4 sessions of mnemonic practice. Whereas the proportion of variance explained by measures from the broad fluid-ability domain (e.g., perceptual speed) increased with training, the proportion of variance explained by crystallized-ability domain (e.g., word knowledge) and sociobiographical variables decreased. Furthermore, prior 6-year longitudinal changes (loss) in perceptual speed predicted individual differences in plasticity. Results suggest that aging-induced biological factors are a prominent source of individual differences in cognitive plasticity in very old age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decline in life satisfaction in old age: Longitudinal evidence for links to distance-to-death.

Using 12-year longitudinal data from deceased participants of the Berlin Aging Study (N = 414; age 70-103 years, at first occasion; M = 87 years, SD = 8.13), the authors examined whether and how old and very old individuals exhibit terminal decline in reported life satisfaction at the end of life. Relative to age-related decline, mortality-related decline (i.e., distance-to-death) accounted for more variance in interindividual differences in life satisfaction change and revealed steeper average rates of decline, by a factor of 2. By applying change-point growth models, the authors identified a point, about 4 years before death, at which decline showed a two-fold increase in steepness relative to the preterminal phase. For the oldest old (85+ years), a threefold increase was observed. Established mortality predictors, including sex, comorbidities, dementia, and cognition, accounted for only small portions of interindividual differences in mortality-related change in life satisfaction. The authors conclude that late-life changes in subjective well-being are related to mechanisms predicting death and suggest routes for further inquiry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assembly of the human neutrophil NADPH oxidase involves binding of p67phox and flavocytochrome b to a common functional domain in p47phox

The human neutrophil NADPH oxidase is a multi-component complex composed of membrane-bound and cytosolic proteins. During activation, cytosolic proteins p47(phox), p67(phox), Rac2, and possibly p40(phox) translocate to the plasma membrane and associate with flavocytochrome b to form the active superoxide-generating system. To further investigate the role of p67(phox) in this complex assembly process, experiments were performed to identify possible regions of interaction between p67(phox) and other NADPH oxidase proteins. Using random sequence peptide phage-display library analysis of p67(phox), we identified a novel region in p47(phox) encompassing residues 323-332 and a previously identified SH3 binding domain encompassing p47(phox) residues 361-370 as p67(phox) binding sites. Synthetic peptides mimicking p47(phox) residues 323-332 inhibited the p47(phox)-p67(phox) binding interaction in an affinity binding assay; however, peptides mimicking flanking regions were inactive. Surprisingly, this same region of p47(phox) was found previously to represent a site of binding interaction for flavocytochrome b (DeLeo, F. R., Nauseef, W. M., Jesaitis, A. J., Burritt, J. B., Clark, R. A., and Quinn, M. T.(1995) J. Biol. Chem. 270, 26246-26251), and this observation was confirmed in the present report using two different in vitro assays that were not evaluated previously. Using affinity binding assays, we also found that p67(phox) and flavocytochrome b competed for binding to p47(phox)after activation, suggesting that prior to full NADPH oxidase assembly the 323-332 region of p47(phox) is associated with p67(phox) and at some point in the activation process is transferred to flavocytochrome b. Thus, taken together our data demonstrate that both p67(phox) and flavocytochrome b utilize a common binding site in p47(phox), presumably at distinct stages during the activation process, and this p47(phox) region plays a key role in regulating NADPH oxidase assembly.