Development of a heating stage for an optical trapping microscope

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaves 24-25).The Lang Laboratory specializes in the study of biological systems through research using optical tweezers. Currently, experiments involving force and position manipulations of cellular molecules take place at room temperature. Experiments with these molecules have the potential to yield more information about biological systems were these experiments performed at the temperature at which the molecules naturally operate. Since the microscopes in the laboratory are geared with sensitive lasers, mirrors, and detectors that make up the optical traps, a custom designed microscope stage heater is necessary to execute research at body temperature (37°C). A custom temperature controller, equipped with controller unit and slide heating aluminum plates, is built to warm the slide sample to and maintain it at 37°C without interfering with the operation of the specified microscope.by Lynn Wang.S.B

Analysis of neural circuits in vitro

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2010.Cataloged from PDF version of thesis.Includes bibliographical references.This thesis is a collection of manuscripts addressing connectivity of neural circuits in cultured hippocampal neurons. These studies begin with an investigation of dopaminergic modulation of excitatory synapses in small circuits of neurons grown on glial micro islands. We found that dopamine transiently depressed excitatory synaptic transmission. Scaling up to larger circuits of neurons proved more challenging, since finding connected pairs became combinatorially more improbable. The discovery and use of light-activatable ion channel channel rhodopsin-2 (ChR2) promised to revolutionize the way in which we could map connectivity in vitro. We successfully delivered the gene for ChR2 in hippocampal cultures using recombinant adeno-associated virus and characterized the spatial resolution, as well as the reliability of stimulating action potentials. However, there were limitations to this technique that would render circuit maps ambiguous and incomplete. More recently, the engineering of rabies virus (RV) as a neural circuit tracer has produced an exciting method whereby viral infection can be targeted to a population of neurons and spread of the virus restricted to monosynaptically connected neurons. We further investigated potential mechanisms for previous observations which claim that RV spread is restricted to synaptically connected neurons by manipulating neural activity and synaptic vesicle release. We found that RV spread increased for blockade of synaptic vesicle exocytosis and for blockade of neural activity. The underlying premise for pursuing these methods to elucidate connectivity is that the computational power of the brain comes from changeable, malleable connectivity and that to test network models of computation in a biological brain, we must map the connectivity between individual neurons. This thesis builds a framework for experiments designed to bridge the gap between computational learning theories and networks of live neurons.by Jennifer Lynn Wang.Ph.D

The Impact of magnitude salience on prix fixe menu price judgment

The flat price structure of prix fixe menus (i.e., fixed food prices and fixed service gratuities) affords restaurant operators the opportunity to present the same menu price in different ways. This report examined customers’ responses to financially equivalent prix fixe menu prices with a built-in gratuity (i.e., all-inclusive prices), a separately listed percentage gratuity and a separately listed dollar gratuity in terms of deal perception. Through an online experiment, we found that prix fixe menu prices with a percentage gratuity below (above) the conventional 15% were perceived more (less) favorably than their all-inclusive counterparts. However, there was no significant difference between prix fixe menu prices with a percentage gratuity and those with a dollar gratuity at all surcharge levels. The implications of these findings for presenting prix fixe menu prices are discussed

The Indirect Effects of Tipping Policies on Patronage Intentions through Perceived Expensiveness, Fairness, and Quality

Many service firms allow their employees to be directly compensated by customers via the institution of tipping despite the fact this practice exposes firms to substantial risks, such as collusion between employees and customers against the firm. This paper examines a potential reason businesses may accept these risks. Specifically, it reports on a study finding that voluntary tipping policies increase potential demand by reducing perceived expensiveness, increasing perceived tipping policy fairness, and increasing a-priori expectations of service quality

Metabolomic analysis of cricket paralysis virus infection in Drosophila S2 cells reveals divergent effects on central carbon metabolism as compared with silkworm Bm5 cells

High-throughput approaches have opened new opportunities for understanding biological processes such as persistent virus infections, which are widespread. However, the potential of persistent infections to develop towards pathogenesis remains to be investigated, particularly with respect to the role of host metabolism. To explore the interactions between cellular metabolism and persistent/pathogenic virus infection, we performed untargeted and targeted metabolomic analysis to examine the effects of Cricket paralysis virus (CrPV, Dicistroviridae) in persistently infected silkworm Bm5 cells and acutely infected Drosophila S2 cells. Our previous study (Viruses 2019, 11, 861) established that both glucose and glutamine levels significantly increased during the persistent period of CrPV infection of Bm5 cells, while they decreased steeply during the pathogenic stages. Strikingly, in this study, an almost opposite pattern in change of metabolites was observed during different stages of acute infection of S2 cells. More specifically, a significant decrease in amino acids and carbohydrates was observed prior to pathogenesis, while their abundance significantly increased again during pathogenesis. Our study illustrates the occurrence of diametrically opposite changes in central carbon mechanisms during CrPV infection of S2 and Bm5 cells that is possibly related to the type of infection (acute or persistent) that is triggered by the virus

The Effects of Service Charges versus Service-included Pricing on Deal Perception

Study participants rated menu prices with an automatic percentage service gratuity as better deals than equivalent service-included prices when the service component of price was below the standard 15 percent tipping rate. However, the reverse was true when the service component of price was above 15 percent. Furthermore, a move from percentage service gratuity toward dollar service gratuity impeded participants’ menu price judgment. These findings provide some insights regarding which pricing alternative to tipping should be implemented if and when restaurateurs decide to abandon voluntary tipping

Metabolomics-based biomarker discovery for bee health monitoring : a proof of concept study concerning nutritional stress in Bombus terrestris

Bee pollinators are exposed to multiple natural and anthropogenic stressors. Understanding the effects of a single stressor in the complex environmental context of antagonistic/synergistic interactions is critical to pollinator monitoring and may serve as early warning system before a pollination crisis. This study aimed to methodically improve the diagnosis of bee stressors using a simultaneous untargeted and targeted metabolomics-based approach. Analysis of 84 Bombus terrestris hemolymph samples found 8 metabolites retained as potential biomarkers that showed excellent discrimination for nutritional stress. In parallel, 8 significantly altered metabolites, as revealed by targeted profiling, were also assigned as candidate biomarkers. Furthermore, machine learning algorithms were applied to the above-described two biomarker sets, whereby the untargeted eight components showed the best classification performance with sensitivity and specificity up to 99% and 100%, respectively. Based on pathway and biochemistry analysis, we propose that gluconeogenesis contributed significantly to blood sugar stability in bumblebees maintained on a low carbohydrate diet. Taken together, this study demonstrates that metabolomics-based biomarker discovery holds promising potential for improving bee health monitoring and to identify stressor related to energy intake and other environmental stressors

To Live or to Die: Prosurvival Activity of PPARγ in Cancers

The role of PPARγ in tumorigenesis is controversial. In this article, we review and analyze literature from the past decade that highlights the potential proneoplastic activity of PPARγ. We discuss the following five aspects of the nuclear hormone receptor and its agonists: (1) relative expression of PPARγ in human tumor versus normal tissues; (2) receptor-dependent proneoplastic effects; (3) impact of PPARγ and its agonists on tumors in animal models; (4) clinical trials of thiazolidinediones (TZDs) in human malignancies; (5) TZDs as chemopreventive agents in epidemiology studies. The focus is placed on the most relevant in vivo animal models and human data. In vitro cell line studies are included only when the effects are shown to be dependent on the PPARγ receptor

Challenges of Court Interpreting: Implications for Interpreter Education

This article aims to examine the findings of a research study into challenges faced by court interpreters in New Zealand. Despite the research being conducted on court interpreters who were based in New Zealand, implications of this article may also be applicable to overseas court interpreter educators and practitioners. The research included an online survey followed by interviews with practicing court interpreters. A total of 30 court interpreters throughout the country participated in the survey, and 11 volunteered to be interviewed. Survey respondents were asked about challenges encountered at work, including legal terminology, terminology in other domains, tag questions, and so on. Based on the survey results, five questions were generated as an outline for semi-structured interviews. The authors report on the lexical and discursive aspects of these challenges established from the online survey and the interviews. It is hoped that the findings of this study can be used to improve court interpreter education and practice, and promote equal access to legal rights for limited English proficient (LEP) individuals residing in not only New Zealand but also other English-speaking countries

Label-free high-throughput photoacoustic tomography of suspected circulating melanoma tumor cells in patients in vivo

Significance: Detection and characterization of circulating tumor cells (CTCs), a key determinant of metastasis, are critical for determining risk of disease progression, understanding metastatic pathways, and facilitating early clinical intervention. Aim: We aim to demonstrate label-free imaging of suspected melanoma CTCs. Approach: We use a linear-array-based photoacoustic tomography system (LA-PAT) to detect melanoma CTCs, quantify their contrast-to-noise ratios (CNRs), and measure their flow velocities in most of the superficial veins in humans. Results: With LA-PAT, we successfully imaged suspected melanoma CTCs in patients in vivo, with a CNR >9. CTCs were detected in 3 of 16 patients with stage III or IV melanoma. Among the three CTC-positive patients, two had disease progression; among the 13 CTC-negative patients, 4 showed disease progression. Conclusions: We suggest that LA-PAT can detect suspected melanoma CTCs in patients in vivo and has potential clinical applications for disease monitoring in melanoma