Effects of S-adenosylmethionine decarboxylase, polyamines, amino acids, and weak bases (amines and ammonia) on development and ribosomal RNA synthesis in Xenopus embryos.

We have been studying control mechanisms of gene expression in early embryogenesis in a South African clawed toad Xenopus laevis, especially during the period of midblastula transition (MBT), or the transition from the phase of active cell division (cleavage stage) to the phase of extensive morphogenesis (post-blastular stages). We first found that ribosomal RNA synthesis is initiated shortly after MBT in Xenopus embryos and those weak bases, such as amines and ammonium ion, selectively inhibit the initiation and subsequent activation of rRNA synthesis. We then found that rapidly labeled heterogeneous mRNA-like RNA is synthesized in embryos at pre-MBT stage. We then performed cloning and expression studies of several genes, such as those for activin receptors, follistatin and aldolases, and then reached the studies of S-adenosylmethionine decarboxylase (SAMDC), a key enzyme in polyamine metabolism. Here, we cloned a Xenopus SAMDC cDNA and performed experiments to overexpress the in vitro-synthesized SAMDC mRNA in Xenopus early embryos, and found that the maternally preset program of apoptosis occurs in cleavage stage embryos, which is executed when embryos reach the stage of MBT. In the present article, we first summarize results on SAMDC and the maternal program of apoptosis, and then describe our studies on small-molecular-weight substances like polyamines, amino acids, and amines in Xenopus embryos. Finally, we summarize our studies on weak bases, especially on ammonium ion, as the specific inhibitor of ribosomal RNA synthesis in Xenopus embryonic cells

Factors associated with social support in child-rearing among mothers in post-disaster communities

Background: Natural disasters have long-term negative impacts on the health and socioenvironmental conditions of a population, affecting the physical environment as well as the relationships within the community, including social networks. Mothers in post-disaster communities may have difficulty receiving social support not only from family members and relatives but also from members of their community, such as people in their neighborhoods. This study focused on mothers with infants and preschool-aged children in post-disaster communities. The associations of social support with sociodemographic characteristics and socioenvironmental conditions related to child-rearing among mothers in post-disaster communities were assessed. Methods: An anonymous self-administered questionnaire survey was conducted in October 2015 in 988 households in areas affected by the Great East Japan Earthquake and Tsunami. The data collected on sociodemographic and socioenvironmental characteristics included the presence of pre-disaster acquaintances in the neighborhood and social support for child-rearing. The associations of sociodemographic and socioenvironmental characteristics with social support were examined. Results: We analyzed 215 completed questionnaires from mothers living in different houses from those they lived in before the disaster to reflect continuous relationships with people from the pre-disaster communities. Social support was significantly associated with infant sex, extended family, support obtained from relatives not living together, pre-disaster acquaintances, use of child support resources, and no perceived difficulties in child-rearing. In addition, the presence of pre-disaster acquaintances was associated with categories of mental/physical place of comfort and child-rearing support, with adjusted odds ratios of 1.88 (95% CI 1.03-3.44) and 2.84 (95% CI 1.46-5.52) compared with mothers who did not have any pre-disaster acquaintances. Conclusions: Factors associated with the obtainment of social support in child-rearing among mothers in post-disaster communities were attributed not only to mothers themselves and family members but also to socioenvironmental factors such as the presence of pre-disaster acquaintances. The presence of pre-disaster acquaintances promoted rich social support in child-rearing in post-disaster communities. When reconstructing a community following changes in residence location after a disaster, the pre-disaster relationships among the community dwellers should be considered from the viewpoint of child-rearing support