A study of high efficiency CO2 refrigerant VRF air conditioning system adopting multi-stage compression cycle

CO2 refrigerant is expected to be use for air conditioners due to its environmental property of GWP = 1, non-flammability and low toxicity and has already been applied to hot water supply system, refrigerators and freezers. However, since cycle COP of CO2 is poorer than that of HFC in applying to air conditioner, it cannot be expected to improve the performance significantly by simply improving the efficiency of a conventional single-stage cycle and components consisting of the cycle.  Therefore, it is important to improve the cycle efficiency, especially in the performance of cooling which is a weak point of CO2. Challenges also lie in reducing weight of components such as compressor and heat exchangers resulted in weight gain to resist high pressure and to achieve high efficiency in the system. In this study, a prototype of CO2 refrigerant VRF air conditioning system is constructed and evaluates the performance. The system is adopting the four-stage compression cycle applying a new type compressor and heat exchangers and so on aimed for high efficiency cycle and reducing weight As a result of the evaluation, it is confirmed that CO2 cycle performance can be improved in similar extent to HFC refrigerant cycle. On the other hand, this high efficiency cycle consists of a lot of components and becomes more complex than HFC refrigerant cycle; therefore the size and weight of outdoor unit increases to house these components. Further technical development will be necessary to overcome these weaknesses

GATA transcription factors, SOX17 and TFAP2C, drive the human germ-cell specification program

ヒト生殖細胞の運命決定機序を解明 --転写因子のみによる生殖細胞の誘導. 京都大学プレスリリース. 2021-03-01.Master regulator for human germ cell specification. 京都大学プレスリリース. 2021-03-01.The in vitro reconstitution of human germ-cell development provides a robust framework for clarifying key underlying mechanisms. Here, we explored transcription factors (TFs) that engender the germ-cell fate in their pluripotent precursors. Unexpectedly, SOX17, TFAP2C, and BLIMP1, which act under the BMP signaling and are indispensable for human primordial germ-cell-like cell (hPGCLC) specification, failed to induce hPGCLCs. In contrast, GATA3 or GATA2, immediate BMP effectors, combined with SOX17 and TFAP2C, generated hPGCLCs. GATA3/GATA2 knockouts dose-dependently impaired BMP-induced hPGCLC specification, whereas GATA3/GATA2 expression remained unaffected in SOX17, TFAP2C, or BLIMP1 knockouts. In cynomolgus monkeys, a key model for human development, GATA3, SOX17, and TFAP2C were co-expressed exclusively in early PGCs. Crucially, the TF-induced hPGCLCs acquired a hallmark of bona fide hPGCs to undergo epigenetic reprogramming and mature into oogonia/gonocytes in xenogeneic reconstituted ovaries. By uncovering a TF circuitry driving the germ line program, our study provides a paradigm for TF-based human gametogenesis

Contribution of epigenetic landscapes and transcription factors to X-chromosome reactivation in the inner cell mass.

X-chromosome inactivation is established during early development. In mice, transcriptional repression of the paternal X-chromosome (Xp) and enrichment in epigenetic marks such as H3K27me3 is achieved by the early blastocyst stage. X-chromosome inactivation is then reversed in the inner cell mass. The mechanisms underlying Xp reactivation remain enigmatic. Using in vivo single-cell approaches (allele-specific RNAseq, nascent RNA-fluorescent in situ hybridization and immunofluorescence), we show here that different genes are reactivated at different stages, with more slowly reactivated genes tending to be enriched in H3meK27. We further show that in UTX H3K27 histone demethylase mutant embryos, these genes are even more slowly reactivated, suggesting that these genes carry an epigenetic memory that may be actively lost. On the other hand, expression of rapidly reactivated genes may be driven by transcription factors. Thus, some X-linked genes have minimal epigenetic memory in the inner cell mass, whereas others may require active erasure of chromatin marks

Establishment of macaque trophoblast stem cell lines derived from cynomolgus monkey blastocysts

The placenta forms a maternal-fetal junction that supports many physiological functions such as the supply of nutrition and exchange of gases and wastes. Establishing an in vitro culture model of human and non-human primate trophoblast stem/progenitor cells is important for investigating the process of early placental development and trophoblast differentiation. In this study, we have established five trophoblast stem cell (TSC) lines from cynomolgus monkey blastocysts, named macTSC #1-5. Fibroblast growth factor 4 (FGF4) enhanced proliferation of macTSCs, while other exogenous factors were not required to maintain their undifferentiated state. macTSCs showed a trophoblastic gene expression profile and trophoblast-like DNA methylation status and also exhibited differentiation capacity towards invasive trophoblast cells and multinucleated syncytia. In a xenogeneic chimera assay, these stem cells contributed to trophectoderm (TE) development in the chimeric blastocysts. macTSC are the first primate trophoblast cell lines whose proliferation is promoted by FGF4. These cell lines provide a valuable in vitro culture model to analyze the similarities and differences in placental development between human and non-human primates

SC3-seq: A method for highly parallel and quantitative measurement of single-cell gene expression

Single-cell mRNA sequencing (RNA-seq) methods have undergone rapid development in recent years, and transcriptome analysis of relevant cell populations at single-cell resolution has become a key research area of biomedical sciences. We here present single-cell mRNA 3-prime end sequencing (SC3-seq), a practical methodology based on PCR amplification followed by 3-prime-end enrichment for highly quantitative, parallel and cost-effective measurement of gene expression in single cells. The SC3-seq allows excellent quantitative measurement of mRNAs ranging from the 10, 000-cell to 1-cell level, and accordingly, allows an accurate estimate of the transcript levels by a regression of the read counts of spike-in RNAs with defined copy numbers. The SC3-seq has clear advantages over other typical single-cell RNA-seq methodologies for the quantitative measurement of transcript levels and at a sequence depth required for the saturation of transcript detection. The SC3-seq distinguishes four distinct cell types in the peri-implantation mouse blastocysts. Furthermore, the SC3-seq reveals the heterogeneity in human-induced pluripotent stem cells (hiPSCs) cultured under on-feeder as well as feeder-free conditions, demonstrating a more homogeneous property of the feeder-free hiPSCs. We propose that SC3-seq might be used as a powerful strategy for single-cell transcriptome analysis in a broad range of investigations in biomedical sciences

X-Chromosome Inactivation in Mouse Embryonic Stem Cells: Analysis of Histone Modifications and Transcriptional Activity Using Immunofluorescence and FISH

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SC3-seq: a method for highly parallel and quantitative measurement of single-cell gene expression

Tomonori Nakamura, Yukihiro Yabuta, Ikuhiro Okamoto, Shinya Aramaki, Shihori Yokobayashi. Kazuki Kurimoto, Kiyotoshi Sekiguchi, Masato Nakagawa, Takuya Yamamoto, and Mitinori Saitou, "SC3-seq: a method for highly parallel and quantitative measurement of single-cell gene expression", Nucleic Acids Research, Vol. 43 (9), e60, Oxford University Press, 201

The embryonic ontogeny of the gonadal somatic cells in mice and monkeys

In the early fetal stage, the gonads are bipotent and only later become the ovary or testis, depending on the genetic sex. Despite many studies examining how sex determination occurs from biopotential gonads, the spatial and temporal organization of bipotential gonads and their progenitors is poorly understood. Here, using lineage tracing in mice, we find that the gonads originate from a T⁺ primitive streak through WT1⁺ posterior intermediate mesoderm and appear to share origins anteriorly with the adrenal glands and posteriorly with the metanephric mesenchyme. Comparative single-cell transcriptomic analyses in mouse and cynomolgus monkey embryos reveal the convergence of the lineage trajectory and genetic programs accompanying the specification of biopotential gonadal progenitor cells. This process involves sustained expression of epithelial genes and upregulation of mesenchymal genes, thereby conferring an epithelial-mesenchymal hybrid state. Our study provides key resources for understanding early gonadogenesis in mice and primates