Экспериментальные качественные задачи по физике как средство активизации учебно-познавательной деятельности обучающихся

В работе проанализированы понятия «экспериментальная качественная задача» и «экспериментальная количественная задача», выявлена структура и различия между ними. Изучена методика решения экспериментальных качественных задач для активизации познавательной деятельности учеников на уроках физики основной школы и во внеурочной работе

Human Primordial Germ Cell Formation Is Diminished by Exposure to Environmental Toxicants Acting through the AHR Signaling Pathway

Historically, effects of environmental toxicants on human development have been deduced via epidemiological studies because direct experimental analysis has not been possible. However, in recent years, the derivation of human pluripotent stem cells has provided a potential experimental system to directly probe human development. Here, we used human embryonic stem cells (hESCs) to study the effect of environmental toxicants on human germ cell development, with a focus on differentiation of the founding population of primordial germ cells (PGCs), which will go on to form the oocytes of the adult. We demonstrate that human PGC numbers are specifically reduced by exposure to polycyclic aromatic hydrocarbons (PAHs), a group of toxicants common in air pollutants released from gasoline combustion or tobacco smoke. Further, we demonstrate that the adverse effects of PAH exposure are mediated through the aromatic hydrocarbon receptor (AHR) and BAX pathway. This study demonstrates the utility of hESCs as a model system for direct examination of the molecular and genetic pathways of environmental toxicants on human germ cell development

Human germ cell differentiation from fetal- and adult-derived induced pluripotent stem cells

Historically, our understanding of molecular genetic aspects of human germ cell development has been limited, at least in part due to inaccessibility of early stages of human development to experimentation. However, the derivation of pluripotent stem cells may provide the necessary human genetic system to study germ cell development. In this study, we compared the potential of human induced pluripotent stem cells (iPSCs), derived from adult and fetal somatic cells to form primordial and meiotic germ cells, relative to human embryonic stem cells. We found that ∼5% of human iPSCs differentiated to primordial germ cells (PGCs) following induction with bone morphogenetic proteins. Furthermore, we observed that PGCs expressed green fluorescent protein from a germ cell-specific reporter and were enriched for the expression of endogenous germ cell-specific proteins and mRNAs. In response to the overexpression of intrinsic regulators, we also observed that iPSCs formed meiotic cells with extensive synaptonemal complexes and post-meiotic haploid cells with a similar pattern of ACROSIN staining as observed in human spermatids. These results indicate that human iPSCs derived from reprogramming of adult somatic cells can form germline cells. This system may provide a useful model for molecular genetic studies of human germline formation and pathology and a novel platform for clinical studies and potential therapeutical applications

A Tetrahymena thermophila G4-DNA Binding Protein with Dihydrolipoamide Dehydrogenase Activity

G4-DNA is a four-stranded structure that is formed by guanine-rich sequences. We report here the purification and characterization of a novel G4-DNA binding protein from Tetrahymena thermophila, designated TGP2. TGP2 was found to preferentially bind to G4-DNA oligonucleotides with adjacent single-stranded domains containing phosphorylated 5‘ ends and the sequence element, 5‘-ACTG-3‘. The amino acid sequence of TGP2 has high similarity to dihydrolipoamide dehydrogenase (DLDH) from a variety of species, and TGP2 was shown to have DLDH activity. Purified DLDH from porcine heart and bovine intestinal mucosa were shown to bind specifically to G4-DNA oligonucleotides. On the basis of these results we conclude that TGP2 is DLDH in T. thermophila and suggest that the G4-DNA binding capability of TGP2/DLDH may be biologically relevant.Reprinted (adapted) with permission from A Tetrahymena thermophila G4-DNA Binding Protein with Dihydrolipoamide Dehydrogenase Activity. Kehkooi Kee, Luming Niu, and Eric Henderson. Biochemistry 1998 37 (12), 4224-4234. DOI: 10.1021/bi9716377. Copyright 1998 American Chemical Society.</p

Human primordial germ cell formation is diminished by exposure to environmental toxicants acting through the AHR signaling pathway.

Historically, effects of environmental toxicants on human development have been deduced via epidemiological studies because direct experimental analysis has not been possible. However, in recent years, the derivation of human pluripotent stem cells has provided a potential experimental system to directly probe human development. Here, we used human embryonic stem cells (hESCs) to study the effect of environmental toxicants on human germ cell development, with a focus on differentiation of the founding population of primordial germ cells (PGCs), which will go on to form the oocytes of the adult. We demonstrate that human PGC numbers are specifically reduced by exposure to polycyclic aromatic hydrocarbons (PAHs), a group of toxicants common in air pollutants released from gasoline combustion or tobacco smoke. Further, we demonstrate that the adverse effects of PAH exposure are mediated through the aromatic hydrocarbon receptor (AHR) and BAX pathway. This study demonstrates the utility of hESCs as a model system for direct examination of the molecular and genetic pathways of environmental toxicants on human germ cell development

Single-cell profiling of lncRNAs in human germ cells and molecular analysis reveals transcriptional regulation of LNC1845 on LHX8

Non-coding RNAs exert diverse functions in many cell types. In addition to transcription factors from coding genes, non-coding RNAs may also play essential roles in shaping and directing the fate of germ cells. The presence of many long non-coding RNAs (lncRNAs) which are specifically expressed in the germ cells during human gonadal development were reported and one divergent lncRNA, LNC1845, was functionally characterized. Comprehensive bioinformatic analysis of these lncRNAs indicates that divergent lncRNAs occupied the majority of female and male germ cells. Integrating lncRNA expression into the bioinformatic analysis also enhances the cell-type classification of female germ cells. Functional dissection using in vitro differentiation of human pluripotent stem cells to germ cells revealed the regulatory role of LNC1845 on a transcription factor essential for ovarian follicle development, LHX8, by modulating the levels of histone modifications, H3K4me3 and H3K27Ac. Hence, bioinformatical analysis and experimental verification provide a comprehensive analysis of lncRNAs in developing germ cells and elucidate how an lncRNA function as a cis regulator during human germ cell development