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The primary function of the placenta is to act as an interface between the dam and fetus. The anatomic structure of the chorioallantoic placenta in eutherian mammals varies between different animal species. The placental types in eutherian mammals are classified from various standpoints based on the gross shape, the histological structure of the materno-fetal interface, the type of materno-fetal interdigitation, etc. Particularly, the histological structure is generally considered one of the most useful and instructive classifications for functionally describing placental type. In this system, three main types are recognized according to the cell layers comprising the interhemal area: (1) epitheliochorial type (horses, pigs and ruminants), (2) endotheliochorial type (carnivores) and (3) hemochorial type (primates, rodents and rabbits). The number of cell layers in the interhemal area is considered to modify the transfer of nutrients between maternal and fetal blood and is one of the important factors with respect to the difference in placental permeability between animal species. Therefore, in reproductive and developmental toxicity studies, careful attention should be paid to the histological structure of the interhemal area when extrapolating information concerning placental transfer characteristics to different animal species. 相似文献
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Satoshi HARA Takashi TAKANO Mio OGATA Reina YAMAKAMI Yusuke SATO Tomohiro KONO Yayoi OBATA 《The Journal of reproduction and development》2014,60(3):250-255
Transgenic mice are essential research tools in developmental biology studies. The 2A peptide allows multiple genes to be
expressed simultaneously at comparable levels in somatic cells, but there are no reports of it being used successfully in
germ cells. We constructed a Cre/loxP-based conditional vector containing the 2A peptide to significantly enhance the
expression of a reporter and target gene from a constitutive promoter in oocytes. Mice with a transgene insertion containing
the chicken β-actin promoter, floxed EGFP-polyA cassette, mCherry reporter, 2A peptide and target gene DNA methyltransferase
3A2 (Dnmt3a2) were crossed with TNAP- or Vasa-Cre mice to produce offspring, in which mCherry and DNMT3A2
proteins were highly expressed in oocytes upon Cre-mediated removal of EGFP-polyA. This novel transgenic mouse line based on
the 2A expression system can serve as a useful tool for examining gene function during oogenesis. 相似文献
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Thinning alters crown dynamics and biomass increment within aboveground tissues in young stands of Chamaecyparis obtusa 总被引:1,自引:0,他引:1
Qingmin Han Daisuke Kabeya Satoshi Saito Masatake G. Araki Tatsuro Kawasaki Chiharu Migita Yukihiro Chiba 《Journal of Forest Research》2014,19(1):184-193
The stand density of a forest affects the vertical distribution of foliage. Understanding the dynamics of this response is important for the study of crown structure and function, carbon-budget estimation, and forest management. We investigated the effect of tree density on the vertical distribution of foliage, branch, and stem growth, and ratio of biomass increment in aboveground tissues; by monitoring all first-order branches of five trees each from thinned and unthinned control stands of 10-year-old Chamaecyparis obtusa for four consecutive years. In the control stand, the foliage crown shifted upward with height growth but the foliage quantity of the whole crown did not increase. In addition, the vertical distribution of leaf mass shifted from lower-crown skewed to upper-crown skewed. In the thinned stand in contrast, the foliage quantity of individual crowns increased two-fold within 4 years, while the vertical distribution of leaf mass remained lower-crown skewed. The two stands had similar production rates, numbers of first-order branches per unit of tree height, and total lengths of first-order branches. However, the mortality rate of first-order branches and self-pruning within a first-order branch were significantly higher in the control stand than in the thinned stand, which resulted in a higher ratio of biomass increment in branch. Thinning induced a higher ratio of biomass increment in foliage and lower in branch. The increased foliage quantity and variation in ratio of biomass increment after thinning stimulated stem growth of residual trees. These results provide information that will be useful when considering thinning regimes and stand management. 相似文献
66.
Satoshi Yamashita Tsutomu Hattori Shin Abe Hideaki Goto Hiroki Sato 《Journal of Forest Research》2014,19(1):143-153
Improvement cutting, which decreases tree density by cutting and thinning while leaving logging residues, has been practiced on Okinawa Island since the 1970s and changes not only the vegetation composition but also the amount and composition of woody debris on the forest floor. To quantitatively compare the effect of improvement cutting with the effects of woody debris and vegetation on the community structure of aphyllophoraceous fungi, we conducted a field survey of vegetation composition, the amount and composition of woody debris, and the aphyllophoraceous fungi flora on Okinawa Island in December 2006. We established 3 plots in forest stands without logging and 13 plots in a forest that had undergone improvement cutting from 1 to 22 years before our field survey. The number and volume of woody debris tended to be highest soon after improvement cutting. We recorded 1,172 fungal samples belonging to 81 species in four orders. Fungal species richness was correlated with the composition of the woody debris. Fungal species composition in forest plots 1 year after improvement cutting differed from most of the other logged forests. Variation partitioning revealed that the effects of improvement cutting explained 14.1 % of the total variation in fungal species composition, and that differences in woody debris and vegetation not related to improvement cutting explained 40.4 %. Changes in the composition of woody debris caused by improvement cutting explained at most 2.7 % of the variation. This suggests that improvement cutting does not have a strong effect on fungal community structure, but woody debris does. 相似文献
67.
Masaru Matsuda Yoshitaka Nagahama Tohru Kobayashi Chika Matsuda Satoshi Hamaguchi Mitsuru Sakaizumi 《Fish physiology and biochemistry》2003,28(1-4):135-139
Although the sex-determining gene Sry has been identified in mammals, no comparable genes have been found in non-mammalian vertebrates. To clone positionally the sex-determining region of the medaka, Oryzias latipes, we generated a Y congenic strain to highlight the genetic differences between the X and Y chromosomes from inbred strains of medaka. We used recombinant breakpoint analysis and deletion analysis of the Y chromosome of a congenic XY female to restrict the sex-determining region to 250-kb stretch of the Y chromosome. Shotgun sequencing of this region predicted 27 genes. Three of these genes were expressed during sexual differentiation. However, only one gene was Y specific. The full-length cDNA sequence of this gene encodes a putative protein of 267 amino acids, including the highly conserved DM domain. We thus named it DMY. To establish a role for DMY during sexual differentiation, we screened wild medaka populations for naturally occurring DMY mutants. Two XY females with distinct mutations in DMY were found in separate populations. The first heritable mutant – a single insertion in exon 3 and the subsequent truncation of DMY – resulted in all XY female offspring. Similarly, the second XY mutant female showed reduced DMY expression with a high proportion of XY female offspring. Furthermore, during normal development, DMY is expressed only in somatic cells of XY gonads. These findings strongly suggest that the sex-specific DMY is required for normal testicular development and is a prime candidate for the medaka sex-determining gene. 相似文献
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