Density and Dichotomous Family History Measures of Alcohol Use Disorder as Predictors of Behavioral and Neural Phenotypes: A Comparative Study Across Gender and Race/Ethnicity.

BACKGROUND: Family history (FH) is an important risk factor for the development of alcohol use disorder (AUD). A variety of dichotomous and density measures of FH have been used to predict alcohol outcomes; yet, a systematic comparison of these FH measures is lacking. We compared 4 density and 4 commonly used dichotomous FH measures and examined variations by gender and race/ethnicity in their associations with age of onset of regular drinking, parietal P3 amplitude to visual target, and likelihood of developing AUD. METHODS: Data from the Collaborative Study on the Genetics of Alcoholism (COGA) were utilized to compute the density and dichotomous measures. Only subjects and their family members with DSM-5 AUD diagnostic information obtained through direct interviews using the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) were included in the study. Area under receiver operating characteristic curves were used to compare the diagnostic accuracy of FH measures at classifying DSM-5 AUD diagnosis. Logistic and linear regression models were used to examine associations of FH measures with alcohol outcomes. RESULTS: Density measures had greater diagnostic accuracy at classifying AUD diagnosis, whereas dichotomous measures presented diagnostic accuracy closer to random chance. Both dichotomous and density measures were significantly associated with likelihood of AUD, early onset of regular drinking, and low parietal P3 amplitude, but density measures presented consistently more robust associations. Further, variations in these associations were observed such that among males (vs. females) and Whites (vs. Blacks), associations of alcohol outcomes with density (vs. dichotomous) measures were greater in magnitude. CONCLUSIONS: Density (vs. dichotomous) measures seem to present more robust associations with alcohol outcomes. However, associations of dichotomous and density FH measures with different alcohol outcomes (behavioral vs. neural) varied across gender and race/ethnicity. These findings have great applicability for alcohol research examining FH of AUD.

Actin motility: staying on track takes a little more effort.

The pigment cells of amphibians and fish have provided excellent models for understanding how actin and microtubule motors move organelles along the complex trailway of filaments in the cytoplasm. Recent work provides more evidence that these motors are engaged in a continuous tug-of-war.

The role of substrate curvature in actin-based pushing forces.

The extension of the plasma membrane during cell crawling or spreading is known to require actin polymerization; however, the question of how pushing forces derive from actin polymerization remains open. A leading theory (herein referred to as elastic propulsion) illustrates how elastic stresses in networks growing on curved surfaces can result in forces that push particles. To date all examples of reconstituted motility have used curved surfaces, raising the possibility that such squeezing forces are essential for actin-based pushing. By contrast, other theories, such as molecular ratchets, neither require nor consider surface curvature to explain pushing forces. Here, we critically test the requirement of substrate curvature by reconstituting actin-based motility on polystyrene disks. We find that disks move through extracts in a manner that indicates pushing forces on their flat surfaces and that disks typically move faster than the spheres they are manufactured from. For a subset of actin tails that form on the perimeter of disks, we find no correlation between local surface curvature and tail position. Collectively the data indicate that curvature-dependent mechanisms are not required for actin-based pushing.

Binding between particles and proteins in extracts: implications for microrheology and toxicity.

Understanding and controlling the interactions between foreign materials and cytoplasmic proteins is key for the design of intracellular probes, and for uncovering mechanisms of micro and nanoparticle toxicity. Here we examine these interactions by characterizing protein adsorption from cell extracts to a range of micron and sub-micron particles, and by measuring the Brownian motions of particles in live cells and reconstituted networks as an in situ measure of association. Testing SiO2, TiO2 and polystyrene particles with varying surface carboxylation, together with protein and polyethylene glycol surface coatings, we find that cellular associations and protein binding both strongly depend on particle surface chemistry. Cytoskeletal proteins, most notably actin and intermediate filament family members, are among the proteins most concentrated on the surfaces of all particles tested. The nanoscale movements of microinjected particles that primarily bind vimentin intermediate filaments are larger than particles that can also bind actin. This difference disappears when the same particles are endocytosed, suggesting that endocytic membranes mask particle surfaces. We discovered one brand of carboxylated SiO2 particles that is remarkably resistant to protein binding in extracts. By coupling the actin binding molecule phalloidin to these particles, we converted their surface from non-binding to actin-binding. We illustrate the efficacy of the conversion in reconstituted actin gels.

The influence of protein adsorption on nanoparticle association with cultured endothelial cells.

As materials are produced at smaller scales, the properties that make them especially useful for biological applications such as drug delivery, imaging or sensing applications also render them potentially harmful. There has been a reasonable amount of work addressing the interactions of biological fluids at material surfaces that demonstrates the high affinity of protein for particle surfaces and some looking at the role of particle surface chemistry in cellular associations, but mechanisms have been too little addressed outside the context of intended, specific interactions. Here, using cultured endothelium as a model for vascular transport, we demonstrate that the capacity of nanoparticle surfaces to adsorb protein is indicative of their tendency to associate with cells. Quantification of adsorbed protein shows that high binding nanoparticles are maximally coated in seconds to minutes, indicating that proteins on particle surfaces can mediate cell association over much longer time scales. We also remove many of the most abundant proteins from culture media which alters the profile of adsorbed proteins on nanoparticles but does not affect the level of cell association. We therefore conclude that cellular association is not dependent on the identity of adsorbed proteins and therefore unlikely to require specific binding to any particular cellular receptors.