Human embryogenesis entails complex signalling interactions between embryonic and extra-embryonic cells. However, how extra-embryonic cells direct morphogenesis within the human embryo remains largely unknown due to a lack of relevant stem cell models. Here, we have established conditions to differentiate human pluripotent stem cells (hPSCs) into yolk sac-like cells (YSLCs) that resemble the post-implantation human hypoblast molecularly and functionally. YSLCs induce the expression of pluripotency and anterior ectoderm markers in human embryonic stem cells (hESCs) at the expense of mesoderm and endoderm markers. This activity is mediated by the release of BMP and WNT signalling pathway inhibitors, and, therefore, resembles the functioning of the anterior visceral endoderm signalling centre of the mouse embryo, which establishes the anterior-posterior axis. Our results implicate the yolk sac in epiblast cell fate specification in the human embryo and propose YSLCs as a tool for studying post-implantation human embryo development in vitro.
The purpose of this study was to determine whether values clarification or behavioral counseling was more effective in reducing maladaptive and interfering behaviors among ninth-grade male students in a residential school. Ninety-six subjects were randomly assigned to one of the following treatments: values clarification, behavioral counseling, placebo, or no treatment. The subjects, in groups of eight, received counseling for 15 weeks. Duringvthe 15 weeks of treatment and 15 weeks of posttreatment, data were collected on behavioral indicators of unhappiness (actions which suggest that the student is experiencing unhappiness with student life) and acts of maladaptive behavior (student actions that violate the behavior code of the school and require disciplinary action). Self-reported irrationality and houseparent opinion data were collected as a pretest and two posttests. Values clarification and behavioral group counseling were found to be equally effective in reducing the frequency of observed negative behaviors. An important finding was that the effects of group counseling did not appear during the treatment period. Only during the 15 weeks of posttreatment were treatment differences found for the dependent variables.
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