低氧和氧化应激中 NO介导培养神经元损伤机理的实验研究

目的探讨低氧、氧化应激中一氧化氮（NO）和氧自由基之间关系及其对培养神经元的损伤机理。方法对培养的新生大鼠神经细胞分别进行低氧、H2O2氧化应激处理和超氧化物歧化酶（SOD）抗氧化应激处理,用比色法等检测培养上清液中NO、丙二醛（MDA）、乳酸脱氢酶（LDH）和SOD含量变化指标。结果与对照组比较,低氧组和H2O2组的NO、LDH、MDA含量均显著增高,SOD含量显著降低,NO与SOD含量变化呈负相关关系。预先给予终浓度为200U/ml的SOD处理,可使神经细胞的NO、LDH和MDA释放量明显减少。各组间NO含量与LDH、MDA含量呈正相关关系。结论低氧、氧化应激促使神经元NO产生增多,NO有增加氧自由基对神经细胞的损伤作用。SOD具有清除氧自由基和减轻NO对神经元的损伤作用。     

A House Divided? Roll Calls,Polarization, and Policy Differences in the U.S. House, 1877–2011

The study of political conflict in legislatures is fundamental to understanding the nature of governance, but also difficult because of changes in membership and the issues addressed over time. Focusing on the enduring issue of civil rights in the United States since Reconstruction, we show that using current methods and measures to characterize elite ideological disagreements makes it hard to interpret or reconcile the conflicts with historical understandings because of their failure to adequately account for the policies being voted upon and the consequences of the iterative lawmaking process. Incorporating information about the policies being voted upon provides a starkly different portrait of elite conflict—not only are contemporary parties relatively less divided than is commonly thought, but the conflict occurs in a smaller, and more liberal, portion of the policy space. These findings have important implications for a broad range of work that uses elite actions to compare political conflict/polarization across time.     

Ritual Demonstrations versus Reactive Protests: Participation Across Mobilizing Contexts in Mexico City

Using an innovative survey of protest participants and nonparticipants from five major street demonstrations in Mexico City in 2011 and 2012, this study tests the assumption that influences on protest participation vary across different types of events; namely, ritual demonstrations and reactive protests. The comparison is based on two assumptions: that these are two of the dominant forms of protest in contemporary Latin America, and that specifying the context for different types of social movement participation provides a better understanding of the individual mobilization process for groups seeking to defend their rights or gain new benefits. The comparative analyses reveal some crucial differences. Political interest and previous political experience are more influential in the decision to take part in reactive demonstrations. For ritual demonstrations, the decision to participate tends to be driven more by personal and organizational connections.     

THE TIMING OF DELINQUENT BEHAVIOR AND ITS IMPLICATIONS FOR AFTER-SCHOOL PROGRAMS*

Research Summary: This study examines self-reports from two samples to assess the timing of delinquency. Results imply that the after-school hours are a time of elevated delinquency, but that the peak is modest compared with that observed in official records. Additionally, children who are unsupervised during the after-school hours - the primary target population for after-school programs - are found to be more delinquent at all times, not only after-school. Policy Implications: This finding suggests that factors (including social competencies and social bonding) in addition to inadequate supervision produce delinquency during the after-school hours and that the effectiveness of after-school programs for reducing delinquency will depend upon their ability to address these other factors through appropriate and high quality services.