Muscarinic Receptor Activation Affects Pulmonary Artery Contractility in Sheep: The Impact of Maturation and Chronic Hypoxia on Endothelium-Dependent and Endothelium-Independent Function.

Giang, Michael, Demosthenes G. Papamatheakis, Dan Nguyen, Ricardo Paez, Carla Blum Johnston, Joon Kim, Alexander Brunnell, Quintin Blood, Ravi Goyal, Lawrence D. Longo, and Sean M. Wilson. Muscarinic receptor activation affects pulmonary artery contractility in sheep: the impact of maturation and chronic hypoxia on endothelium-dependent and endothelium-independent function. High Alt Med Biol. 17:122-132, 2015.-Muscarinic receptor activation in the pulmonary vasculature can cause endothelium-dependent vasodilation and smooth muscle-dependent vasoconstriction. Chronic hypoxia (CH) can modify both of these responses. This study aimed to assess the combined influence of CH and maturation on endothelium-dependent and endothelium-independent muscarinic-induced vasoreactivity. This was accomplished by performing wire myography on endothelium-intact or endothelium-disrupted pulmonary arterial rings isolated from normoxic or CH fetal and adult sheep. In endothelium-intact arteries, vasodilation was evaluated using cumulative bradykinin doses in phenylephrine and carbachol precontracted pulmonary arterial segments; and vasoconstriction was examined using cumulative doses of carbachol following bradykinin predilation. Effects of nonselective (atropine) and selective M1 (pirenzepine), M2 (AFDX116), and M3 (4-DAMP and Dau5884) muscarinic receptor antagonists were assessed in disrupted arteries. In normoxic arteries, bradykinin relaxation was twofold greater in the adult compared to fetus, while carbachol contraction was fourfold greater. In adult arteries, CH increased bradykinin relaxation and carbachol contraction. In vessels with intact endothelium, maturation and CH augmented maximal response and efficacy for carbachol constriction and bradykinin relaxation. Approximately 50%-80% of adult normoxic and CH endothelium-disrupted arteries contracted to acetylcholine, while ∼50% of fetal normoxic and ∼10% of CH arteries responded. Atropine reduced carbachol-induced contraction in all vessels. Adult normoxic vessels were most responsive to M3 antagonism, fetal to M2 antagonism, while M1 inhibition had no effect. Overall, muscarinic-induced pulmonary arterial contraction is partially endothelium dependent and appears to develop after birth. Fetuses are more reliant on M3 receptors while M2 receptors predominate in adults, whereas CH augments muscarinic-dependent pulmonary vasoconstriction in both.

Online racial discrimination and psychological adjustment among adolescents.

PURPOSE: To examine associations between individual and vicarious racial discrimination via the Internet and psychological adjustment. METHODS: This study was a cross-sectional survey using a school-based sample of adolescents. Two hundred sixty-four high school students aged 14-18 completed the online survey. RESULTS: Twenty percent of whites, 29% of African Americans and 42% of multiracials/other experienced individual discrimination and approximately 71% of African Americans and whites and 67% of multiracials witnessed discrimination experienced by same-race and cross-race peers. Hierarchical linear regressions revealed that individual racial discrimination was significantly related to depression and anxiety over and above offline measures. Vicarious discrimination was not related to psychological adjustment measures. CONCLUSIONS: Adolescents frequently experienced both individual and vicarious discrimination online. Consistent with offline studies, online racial discrimination was negatively associated with psychological functioning. This study highlights the need to address racial issues in Internet safety prevention.

Ethnic identity, intergroup contact, and outgroup orientation among diverse groups of adolescents on the Internet.

The relationship among adolescents' (N = 228) ethnic identity, outgroup orientation, and online intergroup experiences was examined across three groups: European Americans, ethnic minorities (i.e., Latino and African Americans), and multiracials. Similar to previous studies, ethnic minorities reported significantly higher ethnic identity than European Americans and multiracials. Although outgroup orientation did not differ among ethnic groups, European Americans reported that they had more online intergroup contact than the other ethnic groups; greater intergroup contact was also related to higher outgroup orientation for this group. These results show that ethnic identity remains stronger for ethnic minorities, but intergroup interaction has become a salient and influential aspect of the online experience for European Americans. Implications are drawn for understanding and improving online and offline intergroup relations.

Using latent class analysis to identify aggressors and victims of peer harassment.

This study used latent class analysis (LCA) to identify and classify individuals into aggressor and victim latent classes. Participants were over 2,000 sixth grade students who completed peer nomination procedures that identified students who had reputations as perpetrators and/or victims of physical, verbal, or relational harassment. Results showed five latent classes. Consistent with previous research, LCA identified latent classes of victims, aggressors, and socially adjusted students. However, rather than a single aggressive-victim subgroup, LCA identified latent classes of highly-victimized aggressive-victims and highly-aggressive aggressive-victims. Comparisons showed differences in mean profiles and classification criteria between LCA and traditional dichotomization approaches. Adjustment outcomes showed that highly-victimized aggressive-victims generally experienced greater negative psychological and social adjustment outcomes than highly-aggressive aggressive-victims. Implications of these findings for better assessment of victim and aggressor subgroups were discussed.

Implications of adolescents' acculturation strategies for personal and collective self-esteem.

Berry, Trimble, and Olmedo's (1986) acculturation model was used to investigate the relationship among adolescents' acculturation strategies, personal self-esteem, and collective self-esteem. Using data from 427 high school students, factor analysis results distinguished Collective Self-esteem Scale constructs (Luhtanen & Crocker, 1992) from both ethnic identity and outgroup orientation subscales of the Multigroup Ethnic Identity Measure (Phinney, 1992). Subsequent results showed that: 1) both acculturation dimensions were correlated with personal and collective self-esteems, 2) integrationists shared similar levels of personal and collective self-esteems with assimilationists and/or separationists, and 3) marginalizationists generally had the lowest levels of personal and collective self-esteems. Implications are drawn for understanding acculturation among adolescents and for the utility of group-level measures of self-esteem.