Developing Motion Picture Appreciation

Abstract

A well-dressed art viewer (who appears to be affluent and highly educated) is observed gazing at several contemporary works in an art museum gallery. Out of this gentleman's view, in an adjacent gallery, a blue-collar worker enters carrying a new and attractive, but ordinary-looking door that he quickly but carefully places on the floor, leaning it against a wall near several artworks. The worker exits the gallery just as the art viewer enters it. With great concentration, the viewer contemplates all of the artworks he sees. His attention is immediately drawn to the door left behind by the workman. The viewer is intrigued by the door, which he obviously mistakes for a work of art. The door is studied intensively and at length by the viewer who seems to be searching for layers of meaning. That deep intellectual pursuit is interrupted abruptly, however, when the worker reenters the gallery, picks up the door, and carries it away. Evidently, the worker's job is to install the door elsewhere in the museum, no doubt where it will not be mistaken for a work of art. Had he been asked to comment on the art viewer's encounter with the door, the worker would surely have expressed some degree of puzzlement and criticism because—from the worker's viewpoint—anyone with even a small measure of common sense (something the “expert” art viewer apparently lacks) knows the difference between a door and a work of art, no matter how finely crafted the door may be.     

Measuring Dilution of Microbicide Gels with Optical Imaging

We present a novel approach for measuring topical microbicide gel dilution using optical imaging. The approach compares gel thickness measurements from fluorimetry and multiplexed low coherence interferometry in order to calculate dilution of a gel. As a microbicide gel becomes diluted at fixed thickness, its mLCI thickness measurement remains constant, while the fluorimetry signal decreases in intensity. The difference between the two measurements is related to the extent of gel dilution. These two optical modalities are implemented in a single endoscopic instrument that enables simultaneous data collection. A preliminary validation study was performed with in vitro placebo gel measurements taken in a controlled test socket. It was found that change in slope of the regression line between fluorimetry and mLCI based measurements indicates dilution. A dilution calibration curve was then generated by repeating the test socket measurements with serial dilutions of placebo gel with vaginal fluid simulant. This methodology can provide valuable dilution information on candidate microbicide products, which could substantially enhance our understanding of their in vivo functioning.     

Surface Charges of the Membrane Crucially Affect Regulation of Na,K-ATPase by Phospholemman (FXYD1)

The human α₁/His₁₀-β₁ isoform of Na,K-ATPase has been reconstituted as a complex with and without FXYD1 into proteoliposomes of various lipid compositions in order to study the effect of the regulatory subunit on the half-saturating Na⁺ concentration (K _1/2) of Na⁺ ions for activation of the ion pump. It has been shown that the fraction of negatively charged lipid in the bilayer crucially affects the regulatory properties. At low concentrations of the negatively charged lipid DOPS (<10 %), FXYD1 increases K _1/2 of Na⁺ ions for activation of the ion pump. Phosphorylation of FXYD1 by protein kinase A at Ser68 abrogates this effect. Conversely, for proteoliposomes made with high concentrations of DOPS (>10 %), little or no effect of FXYD1 on the K _1/2 of Na⁺ ions is observed. Depending on ionic strength and lipid composition of the proteoliposomes, FXYD1 can alter the K _1/2 of Na⁺ ions by up to twofold. We propose possible molecular mechanisms to explain the regulatory effects of FXYD1 and the influence of charged lipid and protein phosphorylation. In particular, the positively charged C-terminal helix of FXYD1 appears to be highly mobile and may interact with the cytoplasmic N domain of the α-subunit, the interaction being strongly affected by phosphorylation at Ser68 and the surface charge of the membrane.     

Stalking the wild Tetrahymena

We live on a microbial planet. Microorganisms dominate in terms of numbers of lineages, numbers of organisms, biomass and evolutionary innovations. Yet much remains to be learned about our microbial neighbours. We have gotten to know a few species that have been transformed into ‘laboratory rats’ (i.e. model organisms), but even here our understanding of the natural history of these lineages remains inadequate as there are few data from populations living in natural habitats. Zufall et al. (2013) move beyond this trend by providing insights into the natural history of Tetrahymena thermophila, a ciliate that has been used in many studies of cellular and molecular biology. Characterization of T. thermophila sampled from numerous ponds across this ciliate's range in Eastern North America reveals the following: (i) considerable differentiation among isolates, with the greatest diversity among lineages in New England, and (ii) a relatively small effective population size for this model ciliate. Such population data are fundamental for inferences about the origins of the numerous remarkable features of T. thermophila.     

Accuracy and response-time distributions for decision-making: linear perfect integrators versus nonlinear attractor-based neural circuits

Animals choose actions based on imperfect, ambiguous data. “Noise” inherent in neural processing adds further variability to this already-noisy input signal. Mathematical analysis has suggested that the optimal apparatus (in terms of the speed/accuracy trade-off) for reaching decisions about such noisy inputs is perfect accumulation of the inputs by a temporal integrator. Thus, most highly cited models of neural circuitry underlying decision-making have been instantiations of a perfect integrator. Here, in accordance with a growing mathematical and empirical literature, we describe circumstances in which perfect integration is rendered suboptimal. In particular we highlight the impact of three biological constraints: (1) significant noise arising within the decision-making circuitry itself; (2) bounding of integration by maximal neural firing rates; and (3) time limitations on making a decision. Under conditions (1) and (2), an attractor system with stable attractor states can easily best an integrator when accuracy is more important than speed. Moreover, under conditions in which such stable attractor networks do not best the perfect integrator, a system with unstable initial states can do so if readout of the system’s final state is imperfect. Ubiquitously, an attractor system with a nonselective time-dependent input current is both more accurate and more robust to imprecise tuning of parameters than an integrator with such input. Given that neural responses that switch stochastically between discrete states can “masquerade” as integration in single-neuron and trial-averaged data, our results suggest that such networks should be considered as plausible alternatives to the integrator model.