Cellular analysis of cleavage-stage chick embryos reveals hidden conservation in vertebrate early development

Nagai, Hiroki,Sezaki, Maiko,Kakiguchi, Kisa,Nakaya, Yukiko,Lee, Hyung Chul,Ladher, Raj,Sasanami, Tomohiro,Han, Jae Yong,Yonemura, Shigenobu,Sheng, Guojun The Company of Biologists 2015 Development (Cambridge) Vol.142 No.7

<▼1><P>Birds and mammals, phylogenetically close amniotes with similar post-gastrula development, exhibit little conservation in their post-fertilization cleavage patterns. Data from the mouse suggest that cellular morphogenesis and molecular signaling at the cleavage stage play important roles in lineage specification at later (blastula and gastrula) stages. Very little is known, however, about cleavage-stage chick embryos, owing to their poor accessibility. This period of chick development takes place before egg-laying and encompasses several fundamental processes of avian embryology, including zygotic gene activation (ZGA) and blastoderm cell-layer increase. We have carried out morphological and cellular analyses of cleavage-stage chick embryos covering the first half of pre-ovipositional development, from Eyal-Giladi and Kochav stage (EGK-) I to EGK-V. Scanning electron microscopy revealed remarkable subcellular details of blastomere cellularization and subgerminal cavity formation. Phosphorylated RNA polymerase II immunostaining showed that ZGA in the chick starts at early EGK-III during the 7th to 8th nuclear division cycle, comparable with the time reported for other yolk-rich vertebrates (e.g. zebrafish and <I>Xenopus</I>). The increase in the number of cell layers after EGK-III is not a direct consequence of oriented cell division. Finally, we present evidence that, as in the zebrafish embryo, a yolk syncytial layer is formed in the avian embryo after EGK-V. Our data suggest that several fundamental features of cleavage-stage development in birds resemble those in yolk-rich anamniote species, revealing conservation in vertebrate early development. Whether this conservation lends morphogenetic support to the anamniote-to-amniote transition in evolution or reflects developmental plasticity in convergent evolution awaits further investigation.</P></▼1><▼2><P><B>Summary:</B> Early chick embryos share previously unappreciated features with anamniote embryos such as the timing of zygotic gene activation and yolk syncytial layer formation.</P></▼2>

Visualization of the heat flux distribution on a blunt-nosed body with an aerospike in hypersonic flow

Seungwon Ha,Hiroki Nagai,Keisuke Asai,Kazuyuki Nakakita,Nobuyuki Tsuboi 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-

A blunt body in hypersonic flow is subjected to severe aerodynamic heating and drag. This is one of the most critical problems of designing the hypersonic vehicles such as Reusable Launch Vehicles (RLV). It is well known that spiked-nose (aerospike) concept is effective for aerodynamic drag reduction on asymmetric blunt bodies in hypersonic flow. In this study, we investigated the heat flux distribution on a blunt-nosed body with an aerospike in hypersonic flow. The spike length and the angle of attack were changed to verify the heat reduction effect. The experiment was conducted at Mach l0in the JAXA 0.44-m Hypersonic Wind Tunnel and the temperature of body was measured by using Temperature-Sensitive Paint (TSP), which is a global temperature measurement technique based on photochemical reaction. In addition, the heat flux distribution calculated increase rate or temperature. The flow field around a blunt-nosed body is visualized by schlieren images and compared with TSP images and CFD results to discuss the heat flux distribution. It was found from the result that the heat flux amount is decreased as the length of spike longer and the heat flux distribution is changed widely with the angle of attack. In this study, moreover, the heat-flux and the flow field relation ware clarified by shock/shock interaction analysis of the flow field for different angle-of-attack.

Flow-induced Vibration of a High-speed Train Running in a Tunnel

Takeyuki KODERA,Hiroki NAGAI,Keisuke-ASAI,Osamu Terashima 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-

In recent years, flow-induced vibration on the tail car of a high-speed train cruising in a tunnel has become a critical aerodynamic problem because it makes a ride comfort of the train poor. To further increase the train speed, it is required to identify the cause of this phenomenon and take necessary countermeasures. The objective of the present study is to clarify the effects of the tunnel wall on vibrations of a high-speed train running inside a tunnel. We conducted wind tunnel tests of a simplified train model with a flat plate simulating the effect of tunnel wall. Pressure transducers were used to measure unsteady pressure fluctuations on the tunnel wall and Pressure Sensitive Paint (PSP) was applied to measure time-averaged surface pressure distribution on the train model. In addition, we conducted Large Eddy Simulation (LES) calculation for the same model and test condition. In the experiment, pressure fluctuations with the Strouhal number similar to the actual case were observed near the tail car locations. The results of LES calculation indicated that LES could reconstruct the spectrum of pressure fluctuation that observed in the experiment. It was suggested from these results that the vibrations on the tail car were caused by the interaction of the flow separated from the tunnel side of the tail car with the tunnel wall.

Experimental study on three-dimensional shock interference flow of a supersonic Busemann biplane

Soshi Oyama,Hiroki Nagai,Keisuke Asai 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-

In supersonic flight, an airplane generates shock waves that cause large wave drag as well as strong sonic boom. A supersonic airplane based on Busemann biplane was proposed as an innovative solution to realize supersonic transport. Shock waves are generated at the leading edge of the Busemann biplane and are cancelled by expansion waves generated from the ridgeline or the wings so that shock waves are confined inside the biplane and the drag and the sonic boom are dramatically reduced. The objective of this study is to investigate the three-dimentional shock interactions of a Busemann biplane by experiment. A supersonic biplane model with the aspect ratio of 2.5 was tested in a blow-down supersonic wind tunnel at M∞ = 1.5 to 1.7. Interacting flow around the wings was visualized by schlieren method and the pressure distribution on an inner surface of the wing was measured using pressure-sensitive paint (PSP). CFD calculations were also made to compare with experimental results. On the basis of these experimental and computational studies, the complicated three-dimensional interference phenomenon between the two wings, including shock wave/boundary layer interactions were analyzed and the three-dimensional flow effects on the start/uri start characteristics of the Busemann biplane are discussed.

Static behaviors of self-anchored and partially earth-anchored long-span cable-stayed bridges

Xie, Xu,Yamaguchi, Hiroki,Nagai, Masatsugu Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.6

In this paper, three dimensional static behaviors of the self-anchored and partially earth-anchored cable-stayed bridges, with a span of 1400 meters, under wind loading are studied by using a 3D geometrical nonlinear analysis. In this analysis, the bridges both after completion and under construction are dealt with. The wind resistant characteristics of the both cable-stayed systems are made clear. In particular, the characteristics of the partially earth-anchored cable systems, which is expected to be a promising solution for extending the span of the cable-stayed systems further, is presented.

FRT Operation for Single-Phase Grid-Tied Inverter with Active Power Decoupling Capability

Jun-ichi Itoh,Satoshi Nakamura,Satoshi Nagai,Hiroki Watanabe 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper proposes a Fault Ride-Through (FRT) operation for a single-phase grid-tied inverter with an active power decoupling capability. The power decoupling circuit achieves the double-line-frequency power pulsation compensation with a small capacitance; consequently, a transient response with a sudden load change becomes worsen because a large energy buffer, i.e. bulky electrolytic capacitors, does not apply. In particular, high overshoot voltages occur in a DC-link voltage when the grid voltage sag of the single-phase grid occurs, resulting in the interrupt of the FRT operation due to the over voltage protection. In order to solve this problem, the buffer capacitance is designed in the consideration of the overshoot amount of the DC-link voltage. The theoretical value of the overshoot amount is verified with a 1-kW prototype. As an experimental result, The error between the experimental and the calculation value is within 10%. Furthermore, the proposed control achieved both the FRT operation and the active power decoupling capability.

Production of Interspecific Germline Chimeras via Embryo Replacement1

Choi, Hee Jung,Lee, Hyung Chul,Kang, Kyung Soo,Lee, Hyo Gun,Ono, Tamao,Nagai, Hiroki,Sheng, Guojun,Han, Jae Yong Oxford University Press 2015 BIOLOGY OF REPRODUCTION Vol.93 No.2

<P>In avian species, primordial germ cells (PGCs) use the vascular system to reach their destination, the genital ridge. Because of this unique migratory route of avian germ cells, germline chimera production can be achieved via germ cell transfer into a blood vessel. This study was performed to establish an alternative germ cell-transfer system for producing germline chimeras by replacing an original host embryo with a donor embryo, while retaining the host extraembryonic tissue and yolk, before circulation. First, to test the migratory capacity of PGCs after embryo replacement, Korean Oge (KO) chick embryos were used to replace GFP transgenic chick embryos. Four days after replacement, GFP-positive cells were detected in the replaced KO embryonic gonads, and genomic DNA PCR analysis with the embryonic gonads demonstrated the presence of the GFP transgene. To produce an interspecific germline chimera, the original chick embryo proper was replaced with a quail embryo onto the chick yolk. To detect the gonadal PGCs in the 5.5-day-old embryonic gonads, immunohistochemistry was performed with monoclonal antibodies specific to either quail or chick PGCs, i.e., QCR1 and anti-stage-specific embryonic antigen-1 (SSEA-1), respectively. Both the QCR1-positive and SSEA-1-positive cells were detected in the gonads of replaced quail embryos. Forty percent of the PGC population in the quail embryos was occupied by chick extraembryonically derived PGCs. In conclusion, replacement of an embryo onto the host yolk before circulation can be applied to produce interspecies germline chimeras, and this germ cell-transfer technology is potentially applicable for reproduction of wild or endangered bird species.</P>