The response of olfactory Schwann cells was assessed at 2, 4, and 7 days following intranasal zinc sulfate irrigation in 1-month-old mice. Ultrastructural and immunohistochemical observations showed dramatic differences between experimental and control mice which had been washed with saline intranasally. Two days after zinc sulfate treatment, many olfactory nerve bundles contained patchy areas of axonal degeneration, while the cell bodies of the olfactory Schwann cells appeared to have increased in electron density and to have shifted peripherally. Some of the cell bodies protruded from the surface of the axon fascicle, suggesting that the olfactory Schwann cells were in the initial process of migrating away. On the fourth day when most of the olfactory axons had degenerated, some olfactory Schwann cells were aligned immediately beneath the basal lamina of the olfactory epithelium. These cells were immunopositive for the S-100 protein and possessed an expanded perinuclear space. Many olfactory Schwann cells were present in the region beneath the cribriform plate, while some appeared to have passed through the gaps between the bony plates to reach the olfactory bulb. Hence, the results showed that many olfactory Schwann cells migrated towards the olfactory bulb following loss of axonal contact. Furthermore, on the seventh day following zinc sulfate treatment, some olfactory Schwann cells in the vicinity of the olfactory bulb appeared phagocytic, as indicated by their extension of processes around fragments of cell debris and the presence of lysosome-like organelles in the perikaryon. The control mice which had been intranasally irrigated with saline did not demonstrate massive olfactory axonal degeneration, and the morphology of the nasal cavity region was similar to that of normal mice.
Strains of Aeromonas veronii biotype sobria isolated from clinical and environmental sources were examined for their expression of surface structures under a variety of culture conditions. When grown on solid media at 37 C, more than 95% of bacteria from the majority of strains isolated from human diarrheal feces and chicken carcasses were non-piliated or expressed only a few pili of long, flexible morphology per cell. Strains isolated from water or other foods were much more likely to express pili. Heavily piliated strains (all sources) possessed pili of several morphological types, including long, flexible pili of varying widths and rigid pili of varying lengths. Expression of pili was favored by growth at temperatures ca. 20 C and below and growth in liquid medium. Most fecal strains expressed some pili under these conditions. In addition, other surface structures (fibrillar aggregates, fibrillar networks, bundle-forming pili) were seen on some strains from most sources. These were also seen most frequently when bacteria were grown in liquid media at temperatures ca. 20 C and below. Pili expression was not dramatically influenced by growth under anaerobic conditions, or in iron-depleted media, or by combinations of the above conditions. The role of the above surface structures in Aeromonas pathogenicity remains to be elucidated.
No abstract
Parental monitoring, conceptualized as parental knowledge of adolescents’ activities and whereabouts, is a robust predictor of adolescent engagement in risk behaviors. Influenced by the parenting triad framework of parental motivations/beliefs, monitoring, and behavior management, we investigated how knowledge is associated with (a) domains of parent-adolescent conflict; and (b) parent and adolescent behavior during a conflict discussion task using the Actor-Partner Interdependence Model. We expected an inverse relationship between parental knowledge and conflict processes: greater knowledge would be associated with less conflict. The sample was 87 adolescents (agem=15.18; 55% female) and parents. Dyads completed surveys about parental knowledge and its sources, and separate interviews on domains of conflict. A subset (n = 65) completed a parent-adolescent discussion task: dyads interacted for 5 minutes about an adolescent-identified conflict topic. Results indicated that one domain of conflict (different beliefs) was significantly negatively related to parental knowledge: parents’ reports of different beliefs was associated with their own and adolescents’ reports of knowledge, solicitation, and disclosure. Adolescents’ reports of different beliefs were negatively associated with adolescents’ reports of solicitation and disclosure. Next, adolescent reports of parental knowledge were associated with adolescent secure base use during a conflict discussion task. Adolescent-reported parental solicitation was associated with more adolescent secure base behavior and less hostility. Adolescent-reported disclosure was associated with more adolescent and parent secure base and less hostility. Findings reveal links between monitoring and conflict, confirming the importance of understanding how monitoring represents an important domain of parent-adolescent relationship with implications for adolescent problematic behavior.
Compared to childhood and adulthood, adolescence is a time of greater risk-taking behavior, potentially resulting in serious consequences. Theories of adolescent brain development highlight the imbalance between neural circuitry for reward vs. regulation. Although this imbalance may make adolescents more vulnerable to impaired decision-making in the context of heightened arousal, not all adolescents exhibit problematic risk behavior, suggesting other factors are involved. Relatedly, parent-adolescent conflict increases in mid-adolescence, and is linked to negative outcomes like substance use related risk-taking. However, the mechanism by which parent-adolescent conflict and risk-taking are linked is still unknown. Therefore, we investigated this association using a multi-method experimental design. Parent-adolescent dyads were randomly assigned to complete a discussion task together on the topic of either the adolescent’s dream vacation or an adolescent-identified conflict topic. During the task, adolescent peripheral psychophysiology was measured for later calculation of heart rate variability (HRV), an index of self-regulation. Immediately after the discussion task, adolescents completed a performance-based measure of risk-taking propensity that indexes real-world risk behaviors. We hypothesized that parent-adolescent conflict would predict greater adolescent risk-taking propensity, and that increased behavioral arousal in the context of conflict, coupled with impaired self-regulation, would explain this link. Results indicated no direct effect of parent-adolescent conflict on adolescent risk-taking propensity. However, there was a significant conditional indirect effect: lower HRV, indexing worse regulatory ability, mediated the relation between conflict and risk-taking propensity but only for adolescents exhibiting behavioral arousal during the discussion task. We discuss implications for understanding adolescent risk-taking behavior.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.