Browsing by Subject "Persistence"

Now showing 1 - 3 of 3
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    A Member of an Ancient Family of Bacterial Amino Acids Transporters Contributes to Chlamydia Nutritional Virulence and Immune Evasion
    (American Society for Microbiology, 2023) Banerjee, Arkaprabha; Sun, Yuan; Muramatsu, Matthew K.; Toh, Evelyn; Nelson, David E.; Microbiology and Immunology, School of Medicine
    Many obligate intracellular bacteria, including members of the genus Chlamydia, cannot synthesize a variety of amino acids de novo and acquire these from host cells via largely unknown mechanisms. Previously, we determined that a missense mutation in ctl0225, a conserved Chlamydia open reading frame of unknown function, mediated sensitivity to interferon gamma. Here, we show evidence that CTL0225 is a member of the SnatA family of neutral amino acid transporters that contributes to the import of several amino acids into Chlamydia cells. Further, we show that CTL0225 orthologs from two other distantly related obligate intracellular pathogens (Coxiella burnetii and Buchnera aphidicola) are sufficient to import valine into Escherichia coli. We also show that chlamydia infection and interferon exposure have opposing effects on amino acid metabolism, potentially explaining the relationship between CTL0225 and interferon sensitivity. Overall, we show that phylogenetically diverse intracellular pathogens use an ancient family of amino acid transporters to acquire host amino acids and provide another example of how nutritional virulence and immune evasion can be linked in obligate intracellular pathogens.
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    An Empirical Test of the Dimensionality of Self-Control
    (2013-08-23) Tunze, Chloe Ann; Rand, Kevin L.; Cyders, Melissa A.; Rexroth, Daniel F.; Stewart, Jesse C.; Ashburn-Nardo, Leslie; Hazer, John
    Minimal attention has been devoted to examining the dimensionality of self-control. The present study tested a multidimensional model of self-control in which dimensions were based on the nature of the behavior required (i.e., persistence, initiation, cessation, or prevention). A total of 336 undergraduates completed measures of self-control and psychological well-being. Seventy-four of these participants completed behavioral self-control tasks representing the proposed subtypes. Participants’ GPAs were obtained from the Registrar. Stop self-control was inversely related to previously-validated measures of persistence (β = -.61, p = .010) and prevention (β = -.56, p = .040) self-control and demonstrated differential predictive ability of persistence and prevention compared to the other proposed subtypes. Initiation self-control was inversely related to life satisfaction (β = -.35, p = .012) and demonstrated differential predictive ability of life satisfaction compared to stop self-control. These results were interpreted with caution due to inadequate power and questionable validity of several of the behavioral self-control tasks. Both handgrip persistence (r = -.25, p = .033) and blinking prevention (r = -.29, p = .023) were associated with depression. These pairwise correlations were not significantly different from each other, suggesting that no conceptual distinction should be made between persistence and prevention self-control. Confirmatory factor analyses of self-report data revealed that items clustered based on domain rather than on type of behavior required for self-control exertion. Thus, the structure of self-control remains unclear. Limitations of the present study and implications for future research are discussed.
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    Factors in African American social work student persistence
    (2014-07-30) Green, Jacqualyn F.; Barton, William H., 1949-; Brown, O. Gilbert; Haas, Linda; Hull, Grafton H.; Smith, Linda A.
    Population estimations for the year 2000 indicate an increase in poor and minorities in the United States (Loden & Rosener, 1991). In view of this growth trend, Berger (1989) suggests a need for social workers with sensitivity to such populations. The presence of minority perspectives provides a valuable contribution to service delivery (Mullen et al., 1993). Efforts to enhance student persistence in graduate schools of social work will contribute to the pool of social workers available in the next century. The purpose of this study is to determine the factors that contribute to African American student persistence in graduate schools of social work. This study applies aspects of Astin's, Tinto's and Green's theories of persistence. Astin's theory of involvement (1975) considers student investment of time in educational pursuits. Tinto's (1975) theory of departure includes background, social and academic aspects in persistence decisions. Green's (1997) theory focuses on the ability of the student to cope with racial issues (racial resilience) and the racial climate of the school (racial responsiveness). One hundred and thirty-five students from two predominantly white and two historically black universities participated in surveys administered to determine the effect of involvement, background, academic, social, resilience factors, and college type upon student persistence outcomes. Interviews held with administrative personnel at each institution provided contextual data. Correlations were used to examine the relationships among all of the variables in the study. T-Tests were conducted to compare outcomes due to university type. Multiple regressions were used to explore the relationships between significant independent variables and persistence. The findings of this study indicate that persistence outcomes of African American graduate social work students are influenced by: (a) academic performance, faculty-student relationships, (c) health, (d) the ability to deal with stress, and (e) ethnic pride (impressions of ethnic group). These findings suggest that social work programs that incorporate aggressive grade monitoring practices, provide diverse opportunities for student-faculty interaction, offer opportunities for health care, stress alternatives, and a culturally relevant curriculum, may positively influence African American student persistence.