Christopher C. Liu

Disruption of dopamine D1 receptor gene expression attenuates alcohol-seeking behavior

The role of the dopamine D1 receptor subtype in alcohol-seeking behaviors was studied in mice genetically deficient in dopamine D1 receptors (D1 -/-). In two-tube free choice limited (1-5 h) and continuous (24 h) access paradigms, mice were exposed to water and increasing concentrations of ethanol (3%, 6% and 12% w/v). Voluntary ethanol consumption and preference over water were markedly reduced in D1 -/- mice as compared to heterozygous (D1 +/-) and wild-type (D1 +/+) controls, whereas overall fluid consumption was comparable. When offered a single drinking tube containing alcohol as their only source of fluid for 24 h, D1 -/- mice continued to drink significantly less alcohol than D1 +/+ and D1 +/- mice. Dopamine D2 receptor blockade with sulpiride caused a small but significant reduction in alcohol intake and preference in D1 +/+ mice and attenuated residual alcohol drinking in D1 -/- mice. Dopamine D1 receptor blockade with SCH-23390 very effectively reduced alcohol intake in D1 +/+ and D1 +/- mice to the level seen in untreated D1 -/- mice. These findings suggest involvement of both dopamine D1 and D2 receptor mechanisms in alcohol-seeking behavior in mice; however, these implicate D1 receptors as having a more important role in the motivation for alcohol consumption.

Ectopic Overexpression of Asparagine Synthetase in Transgenic Tobacco

Here, we monitor the effects of ectopic overexpression of genes for pea asparagine synthetase (AS1) in transgenic tobacco (Nicotiana tabacum). The AS genes of pea and tobacco are normally expressed only during the dark phase of the diurnal growth cycle and specifically in phloem cells. A hybrid gene was constructed in which a pea AS1 cDNA was fused to the cauliflower mosaic virus 35S promoter. The 35S-AS1 gene was therefore ectopically expressed in all cell types in transgenic tobacco and constitutively expressed at high levels in both the light and the dark. Northern analysis demonstrated that the 35S-AS1 transgene was constitutively expressed at high levels in leaves of several independent transformants. Furthermore, amino acid analysis revealed a 10- to 100-fold increase in free asparagine in leaves of transgenic 35S-AS1 plants (construct z127) compared with controls. Plant growth analyses showed increases (although statistically insignificant) in growth phenotype during the vegetative stage of growth in 35S-AS1 transgenic lines. The 35S-AS1 construct was further modified by deletion of the glutamine-binding domain of the enzyme (gln[delta]AS1; construct z167). By analogy to animal AS, we reasoned that inhibition of glutamine-dependent AS activity might enhance the ammonia-dependent AS activity. The 3- to 19-fold increase in asparagine levels in the transgenic plants expressing gln[delta]AS1 compared with wild type suggests that the novel AS holoenzyme present in the transgenic plants (gln[delta]AS1 homodimer) has enhanced ammonia-dependent activity. These data indicate that manipulation of AS expression in transgenic plants causes an increase in nitrogen assimilation into asparagine, which in turn produces effects on plant growth and asparagine biosynthesis.

Pulling Closer and Moving Apart: Interaction, Identity, and Influence in the U.S. Senate, 1973 to 2009

This article reconciles two seemingly incompatible expectations about interpersonal interaction and social influence. One theoretical perspective predicts that an increase in interaction between two actors will promote subsequent convergence in their attitudes and behaviors, whereas another view anticipates divergence. We examine the role of political identity in moderating the effects of interaction on influence. Our investigation takes place in the U.S. Senate—a setting in which actors forge political identities for public consumption based on the external constraints, normative obligations, and reputational concerns they face. We argue that interaction between senators who share the same political identity will promote convergence in their voting behavior, whereas interaction between actors with opposing political identities will lead to divergence. Moreover, we theorize that the consequences of political identity for interpersonal influence depend on the local interaction context. Political identity’s effects on influence will be greater in more divided Senate committees than in less divided ones. We find support for these hypotheses in analyses of data, spanning over three decades, on voting behavior, interaction, and political identity in the Senate. These findings contribute to research on social influence; elite integration and political polarization; and identity theory.

An Intraorganizational Ecology of Individual Attainment

This paper extends niche theory to develop an intraorganizational conceptualization of the niche that is grounded in the activities of organizational members. We construe niches as positions in a mapping of individuals to formal and informal activities within organizations. We posit that positional characteristics in this activity-based system are critical determinants of members’ access to information and relationships—two of the vital resources for advancement in organizations. Because activities are difficult to observe, we propose a novel empirical strategy to depict niches: we exploit a census of memberships in electronic mailing lists. We assess three niche dimensions—competitive crowding, status, and diversity—and show that these attributes affect the allocation of rewards to employees. Propositions are tested in two empirical settings: an information services firm and the R&D division of a biopharmaceutical company. Results indicate that people in competitively crowded niches had lower levels of attainment, whereas those in high status and diverse niches enjoyed higher attainment levels. We conclude with a discussion of email distribution lists as a tool for organizational research.

Virtues, Vices, and Political Influence in the U.S. Senate

What qualities make a political leader more influential or less influential? Philosophers, political scientists, and psychologists have puzzled over this question, positing two opposing routes to political power—one driven by human virtues, such as courage and wisdom, and the other driven by vices, such as Machiavellianism and psychopathy. By coding nonverbal behaviors displayed in political speeches, we assessed the virtues and vices of 151 U.S. senators. We found that virtuous senators became more influential after they assumed leadership roles, whereas senators who displayed behaviors consistent with vices—particularly psychopathy—became no more influential or even less influential after they assumed leadership roles. Our results inform a long-standing debate about the role of morality and ethics in leadership and have important implications for electing effective government officials. Citizens would be wise to consider a candidate’s virtue in casting their votes, which might increase the likelihood that elected officials will have genuine concern for their constituents and simultaneously promote cooperation and progress in government.

Pulling Closer and Moving Apart

This article reconciles two seemingly incompatible expectations about interpersonal interaction and social influence. One theoretical perspective predicts that an increase in interaction between two actors will promote subsequent convergence in their attitudes and behaviors, whereas another view anticipates divergence. We examine the role of political identity in moderating the effects of interaction on influence. Our investigation takes place in the U.S. Senate—a setting in which actors forge political identities for public consumption based on the external constraints, normative obligations, and reputational concerns they face. We argue that interaction between senators who share the same political identity will promote convergence in their voting behavior, whereas interaction between actors with opposing political identities will lead to divergence. Moreover, we theorize that the consequences of political identity for interpersonal influence depend on the local interaction context. Political identity’s effects on influence will be greater in more divided Senate committees than in less divided ones. We find support for these hypotheses in analyses of data, spanning over three decades, on voting behavior, interaction, and political identity in the Senate. These findings contribute to research on social influence; elite integration and political polarization; and identity theory.

What Goes on Beneath the Surface of Reconfiguration? The Impact of Redeployment via Activity Addition and Subtraction on Firm Scope and Turnover

Abstract Strategy research has long understood that reconfiguration of the scope of the activities a firm engages in over time is critical to its long-run success, while under-emphasizing differences in redeployment strategy that underlie apparently similar scope and changes in scope. In this paper, we build on the idea that a firm’s number of activities (scope) and change in activities (turnover) arise from two fundamental rates of redeployment: the rate at which activities are added and the rate at which activities are subtracted. In net, the turnover rate reflects how actively a firm reconfigures its resource base by redeploying resources via addition and subtraction of activities. We develop a model that links addition and subtraction with the composition of a firm’s activities and then provide an empirical illustration using data from the U.S. Patents and Trademarks Office. As an example of one extension, the model can be generalized to incorporate elements of absorptive capacity. The analysis contributes to our understanding of how firms reconfigure their activities and provide managers with a clearer understanding of tools that guide redeployment of existing resources.

Stamps of power and conflict: Imprinting and influence in the U.S. Senate, 1973-2009

Gains in power are often assumed to lead to greater influence. Yet people vary in their ability to convert power into influence. We bring a temporal, historical perspective to account for this heterogeneity. We propose that — even when they have had considerable prior experience — people can acquire organization-specific imprints when they join a new organization and that these career imprints can affect how influential they become when they later gain or lose power. We theorize about two such imprints: a stamp of power, which refers to rigidities that accrue to individuals who enter an organization as part of a dominant coalition; and a stamp of conflict, which references the learning benefits that people gain when they participate early on in conflictual work groups. We propose that the former negatively moderates, while the latter positively moderates, a person’s ability to translate downstream changes in power into influence. We evaluate and find support for these propositions in analyses of the U.S. Senate from 1973 to 2005. We discuss implications for research on power, conflict, and imprinting.

From the Ground Up: Gender, Self-Employment, and Space in a Colombian Housing Project

Researchers have documented a persistent wage gap between self-employed men and women. In this paper, we identify a novel intervention that boosts women’s earnings and reduces this gap in an inform...

Geography and opportunities for collaborative relationships: Evidence from the us senate chamber

While numerous studies have examined the consequences of relationships and networks, little research has examined the sources of relationships, particularly in the workplace. This paper examines the micro-geographic structure of relationships in a workplace setting: the United States Senate. Using a dyad fixed-effects approach, coupled with a number of institutional idiosyncrasies, we find that a distance of several meters between senators in the US Senate Chamber affects the likelihood that they co-sponsor bills. Moreover, Chamber distance disproportionately influences senators with few alternative venues for interaction or low organizational tenure, suggesting that geographic constraints do not bind uniformly. These results speak to the literature on relationships and networks, with an emphasis on the micro-geographic scaffold upon which relationships are built.