Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Conflicts of Interest, Disclosure, and (Costly) Sanctions: Experimental Evidence

Conflicts of interest may compromise individuals' independence in providing advisory services. Full disclosure is a commonly recommended remedy for the adverse effect of conflicts of interest. Yet prior study shows that disclosure may not have the intended effect because it provides individuals with moral license to engage in self-interested behavior, thereby exacerbating biases. We follow up on this research and seek to determine whether other institutional factors may negate the potentially harmful effects of disclosure. We conduct a laboratory experiment, focusing on behavior in an investor/financial adviser dyad, including important representative features in this setting. Our results suggest that disclosure is not necessarily detrimental. We find that investors are better off when conflicts of interest are disclosed and sanctions are available, even though initiating sanctions is costly to investors. Under such conditions, advisers' bias is dampened markedly. (c) 2009 by The University of Chicago. All rights reserved..

How Effective is Advice from Interested Parties? An Experimental Test Using a Pure Coordination Game

This study experimentally investigates whether and how the effect of non-binding advice in coordination is influenced by knowledge of the adviser’s motive. We use pure coordination games in which a non-playing adviser makes a recommendation of which strategy to play. The advisor either does or does not have a stake in the final payoff of the game. We find that if the advice appears to be “self-interested” (i.e., the adviser has a monetary stake in the advice being followed), it is less effective than if the same advice is given by a neutral independent party with no economic interest in the game. That is, the effectiveness of advice appears to be affected by knowledge of the adviser’s motive. We discuss the significance of our results for the effectiveness of advice in real-world economic and organizational situations

Lying: An Experimental Investigation of the Role of Situational Factors

Individuals often lie for psychological rewards (e.g., preserving self image and/or protecting others), absent economic rewards. We conducted a laboratory experiment, using a modified dictator game, to identify conditions that entice individuals to lie solely for psychological rewards. We argue that such lies can provide a ready means for individuals to manage others\u27 impression of them. We investigated the effect of social distance (the perceived familiarity, intimacy, or psychological proximity between two parties) and knowledge of circumstances (whether parties have common or asymmetric information) on the frequency of lying. We found that lying occurs more frequently when social distance is near and that the effect is exacerbated when information is asymmetric. Our theoretical development suggests that, under these conditions, individuals\u27 need to manage others\u27 impression is magnified. We discuss the implications of our findings

Pharmacological And Functional Comparisons Of α6/α3β2β3-Nachrs And α4β2-Nachrs Heterologously Expressed In The Human Epithelial Sh-Ep1 Cell Line

Neuronal nicotinic acetylcholine receptors containing α6 subunits (α6 * -nAChRs) show highly restricted distribution in midbrain neurons associated with pleasure, reward, and mood control, suggesting an important impact of α6 * -nAChRs in modulating mesolimbic functions. However, the function and pharmacology of α6 * -nAChRs remain poorly understood because of the lack of selective agonists for α6 * -nAChRs and the challenging heterologous expression of functional α6 * -nAChRs in mammalian cell lines. In particular, the α6 subunit is commonly co-expressed with α4 * -nAChRs in the midbrain, which masks α6 * -nAChR (without α4) function and pharmacology. In this study, we systematically profiled the pharmacology and function of α6 * -nAChRs and compared these properties with those of α4β2 nAChRs expressed in the same cell line. Heterologously expressed human α6/α3 chimeric subunits (α6 N-terminal domain joined with α3 trans-membrane domains and intracellular loops) with β2 and β3 subunits in the human SH-EP1 cell line (α6 * -nAChRs) were used. Patch-clamp whole-cell recordings were performed to measure these receptor-mediated currents. Functionally, the heterologously expressed α6 * -nAChRs exhibited excellent function and showed distinct nicotine-induced current responses, such as kinetics, inward rectification and recovery from desensitization, compared with α4β2-nAChRs. Pharmacologically, α6 * -nAChR was highly sensitive to the α6 subunit-selective antagonist α-conotoxin MII but had lower sensitivity to mecamylamine and dihydro-β-erythroidine. Nicotine and acetylcholine were found to be full agonists for α6 * -nAChRs, whereas epibatidine and cytisine were determined to be partial agonists. Heterologously expressed α6 * -nAChRs exhibited pharmacology and function distinct from those of α4β2-nAChRs, suggesting that α6 * -nAChRs may mediate different cholinergic signals. Our α6 * -nAChR expression system can be used as an excellent cell model for future investigations of α6 * -nAChR function and pharmacology