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News Article | April 28, 2017
Site: phys.org

Researchers at the Institute for Molecular Science, National Institutes of Natural Sciences (Japan) have developed a method for high performance doping of organic single crystal. Furthermore, they succeeded in the Hall effect measurement of the crystal -- the world's first case. The research has been published in the Advanced Materials. Credit: Institute for Molecular Science Researchers at the Institute for Molecular Science, National Institutes of Natural Sciences (Japan) have developed a method for high performance doping of organic single crystal. Furthermore, they succeeded in the Hall effect measurement of the crystal—the world's first case. The research has been published in the Advanced Materials. Controlling "holes" and "electrons" responsible for electric conduction of p-type and n-type semiconductors by doping—adding a trace amount of impurity—had been the central technology in the 20th century's inorganic single crystal electronics represented by silicon chips, solar cells, and light emitting diodes. The number of carriers (holes and electrons) created by doping and their moving speed (mobility) can be freely evaluated by "Hall effect measurement" using a magnetic field. However, in the field of organic electronics emerging in the 21th century, no one has ever attempted to dope impurities into an organic single crystal itself nor measure its Hall effect. "We have combined the rubrene organic single crystal growth technique with our original ultra-slow deposition technique of one billionth of a nanometer (10- 9 nm) per second, which includes a rotating shutter having aperture." explains Chika Ohashi, a PhD student, SOKENDAI in the group. "For the first time, we have succeeded in producing the 1 ppm doped organic single crystal and have detected its Hall effect signal." The doping efficiency of the organic single crystal was 24%, which is a much higher performance compared to 1% for the vacuum deposited amorphous film of the same material. Lab head Prof. Masahiro Hiramoto sees the present results have the meaning of dawn of organic single crystal electronics similar to the silicon single crystal electronics. In future, devices such as high performance organic single crystal solar cells may be developed. Explore further: Gold foil discovery could lead to wearable technology More information: Chika Ohashi et al, Hall Effect in Bulk-Doped Organic Single Crystals, Advanced Materials (2017). DOI: 10.1002/adma.201605619


News Article | April 20, 2017
Site: www.eurekalert.org

Have you ever wondered why just seeing food can make your mouth start to water? By visualizing neuronal activity in specific areas of the zebrafish brain, scientists at the National Institute of Genetics (NIG) in Japan have revealed a direct link between visual perception of food and feeding motivation. The study, published in the April 20, 2017 issue of Nature Communications, suggests that "eating with the eyes" is deeply rooted in evolution. "In vertebrate animals, feeding behavior is regulated by a brain area called the hypothalamus. The hypothalamic feeding center integrates information about bodily energy requirements and environmental food availability. Zebrafish, like humans, mostly use vision for recognition of food or prey. It was not known how the hypothalamus receives visual information about prey. We first demonstrated that neurons in the hypothalamus do indeed respond to the sight of prey. Then we looked for neurons in the visual system that responded to prey and discovered 'prey detector' neurons in an area called the pretectum. Furthermore, we found a direct neural link connecting the prey detector neurons to the hypothalamic feeding center", Dr. Muto, the leading author of the study, explained. The key to this discovery has been recent progress in the development and improvement of the highly sensitive, genetically encoded calcium indicator GCaMP, which can be used to monitor neuronal activity in the form of calcium signals. Another important technology is the ability to control the specific neurons in which GCaMP is expressed. This was critical for recording distinct calcium signals from identifiable neurons. Prof. Kawakami, the senior author, showed us his zebrafish facility where thousands of fish tanks can be seen, each of which contains genetically different fish that can turn on, or drive the GCaMP expression in different types of cells in the brain or in the body. This collection of driver fish lines is being used to study various tissues and cell types by zebrafish researchers all over the world. Of the nearly 2,000 such driver fish lines in the lab, two played important roles in the current study: one for the imaging of the prey detector neurons, and the other for the feeding center in the hypothalamus. "Successful brain imaging was made possible through development of our genetic resources on which I have spent more than twenty years. This is the power of zebrafish genetics. This work showcases a successful application of our genetic resources in the study of brain function", Prof. Kawakami said. "Our study demonstrates how tightly visual perception of food is linked to motivational feeding behavior in vertebrate animals. This is an important step toward understanding how feeding is regulated and can be modulated in normal conditions as well as in feeding disorders", Dr. Muto said. This study was supported by JSPS KAKENHI Grant Numbers JP25290009 and JP25650120, and also partly supported by JSPS KAKENHI Grant Numbers JP15H02370 and JP16H01651, and NBRP from Japan Agency for Medical Research and Development (AMED). This work was also supported in part by the Center for the Promotion of Integrated Sciences (CPIS) of SOKENDAI.


News Article | April 28, 2017
Site: www.eurekalert.org

Researchers at the Institute for Molecular Science, National Institutes of Natural Sciences (Japan) have developed a method for high performance doping of organic single crystal. Furthermore, they succeeded in the Hall effect measurement of the crystal -- the world's first case. The research has been published in the Advanced Materials. Controlling "holes" and "electrons" responsible for electric conduction of p-type and n-type semiconductors by doping -- adding a trace amount of impurity -- had been the central technology in the 20th century's inorganic single crystal electronics represented by silicon chips, solar cells, and light emitting diodes. The number of carriers (holes and electrons) created by doping and their moving speed (mobility) can be freely evaluated by "Hall effect measurement" using a magnetic field. However, in the field of organic electronics emerging in the 21th century, no one has ever attempted to dope impurities into an organic single crystal itself nor measure its Hall effect. "We have combined the rubrene organic single crystal growth technique with our original ultra-slow deposition technique of one billionth of a nanometer (10- 9 nm) per second, which includes a rotating shutter having aperture." explains Chika Ohashi, a PhD student, SOKENDAI in the group. "For the first time, we have succeeded in producing the 1 ppm doped organic single crystal and have detected its Hall effect signal." The doping efficiency of the organic single crystal was 24%, which is a much higher performance compared to 1% for the vacuum deposited amorphous film of the same material. Lab head Prof. Masahiro Hiramoto sees the present results have the meaning of dawn of organic single crystal electronics similar to the silicon single crystal electronics. In future, devices such as high performance organic single crystal solar cells may be developed.


Takahashi A.,National Institute of Genetics NIG | Shiroishi T.,SOKENDAI | Shiroishi T.,National Institute of Genetics NIG | Koide T.,National Institute of Genetics NIG
Frontiers in Neuroscience | Year: 2014

The Japanese wild-derived mouse strain MSM/Ms (MSM) retains a wide range of traits related to behavioral wildness, including high levels of emotionality and avoidance of humans. In this study, we observed that MSM showed a markedly higher level of aggression than the standard laboratory strain C57BL/6J. Whereas almost all MSM males showed high frequencies of attack bites and pursuit in the resident-intruder test, only a few C57BL/6J males showed aggressive behaviors, with these behaviors observed at only a low frequency. Sexually mature MSM males in their home cages killed their littermates, or sometimes female pair-mates. To study the genetic and neurobiological mechanisms that underlie the escalated aggression observed in MSM mice, we analyzed reciprocal F1 crosses and five consomic strains of MSM (Chr 4, 13, 15, X and Y) against the background of C57BL/6J. We identified two chromosomes, Chr 4 and Chr 15, which were involved in the heightened aggression observed in MSM. These chromosomes had different effects on aggression: whereas MSM Chr 15 increased agitation and initiation of aggressive events, MSM Chr 4 induced a maladaptive level of aggressive behavior. Expression analysis of mRNAs of serotonin receptors, serotonin transporter and Tph2, an enzyme involved in serotonin synthesis in seven brain areas, indicated several differences among MSM, C57BL/6J, and their consomic strains. We found that Tph2 expression in the midbrain was increased in the Chr 4 consomic strain, as well as in MSM, and that there was a strong positive genetic correlation between aggressive behavior and Tph2 expression at the mRNA level. Therefore, it is possible that increased expression of the Tph2 gene is related to escalated aggression observed in MSM. © 2014 Takahashi, Shiroishi and Koide.


News Article | December 23, 2015
Site: phys.org

Some reptiles such as crocodilians and some turtles are known to display temperature-dependent sex determination (TSD), where the ambient temperature of the developing eggs determines the individual's sex. For example in the American alligator's eggs, incubation at 33 ºC produces mostly males, while incubation at 30 ºC produces mostly females. An international joint research team between Japan and the US have determined that the thermosensor protein TRPV4 is associated with TSD in the American alligator. The research has been published in Scientific Reports. The research team headed by Professor Taisen Iguchi of the National Institute for Basic Biology (Okazaki Institute for Integrative Bioscience) and PhD student Ryohei Yatsu of SOKENDAI (The Graduate University for Advanced Studies), in collaboration with Professor Makoto Tominaga of the National Institute for Physiological Sciences (Okazaki Institute for Integrative Bioscience) and Professor Louis J. Guillette Jr. and assistant professor Satomi Kohno of the Medical University of South Carolina, have investigated the molecular mechanism of how temperature determines sex. In their research using American alligators, they found that a thermosensitive protein called TRPV4 is present within the developing alligator gonad inside the egg. Alligator TRPV4 is responsive to warm temperatures near mid-30s, and can activate cell signaling by inducing calcium ion influx. The current study also demonstrates that by specific pharmacological inhibition of TPRV4 protein function in the developing egg, genes important for male development (for example, genes encoding anti-Müllerian hormone and SOX9) are influenced, and partial feminization at male producing temperatures have been observed. From these results the authors demonstrate that TRPV4 may significantly influence the male gonadal sex determination pathway at a molecular level during TSD in the alligator. This is the first demonstrated report of a biomolecule associated with regulation of the very unique temperature-dependent sex determination mechanism. PhD student Ryohei Yatsu said, "Reptiles can be difficult to study at times, but we were delighted to obtain such an interesting result and elucidate part of the alligator TSD mechanism. We still have much to research, but we are interested in how our results relate with other TSD species diversity and evolution". Professor Taisen Iguchi said, "Organisms that have adopted TSD systems may be more susceptible to the risks of environmental change, such as global warming. In future, we would like to know how an unstable environmental factor such as incubation temperature was able to establish itself as a sex determination factor." More information: Ryohei Yatsu et al. TRPV4 associates environmental temperature and sex determination in the American alligator, Scientific Reports (2015). DOI: 10.1038/srep18581


Castellano E.,SOKENDAI
Proceedings - 2017 IEEE/ACM 39th International Conference on Software Engineering Companion, ICSE-C 2017 | Year: 2017

Given a model of the environment's behaviour, a set of system goals, and a set of controllable actions, the controller synthesis problem is to automatically generate a controller that only restricts controllable actions. Qualitative controller synthesis techniques yield controllers that guarantee achieving a given goal in the presence of an adversarial environment. However, synthesis produces one out of many possible solutions and no support for expressing preference over them is provided. Quantitative synthesis techniques are a natural way of optimising control with respect to preferences, however, they require quantitative modelling, which in many cases is not available, possible, or desired, and incur in high computational complexity. In this work, we aim to develop a qualitative preference framework for control problems. © 2017 IEEE.


Sada A.,Sokendai | Hasegawa K.,National Institute of Genetics | Pin P.H.,Sokendai | Saga Y.,Sokendai | Saga Y.,National Institute of Genetics
Stem Cells | Year: 2012

Stem cells are maintained by both stem cell-extrinsic niche signals and stem cell-intrinsic factors. During murine spermatogenesis, glial cell line-derived neurotrophic factor (GDNF) signal emanated from Sertoli cells and germ cell-intrinsic factor NANOS2 represent key regulators for the maintenance of spermatogonial stem cells. However, it remains unclear how these factors intersect in stem cells to control their cellular state. Here, we show that GDNF signaling is essential to maintain NANOS2 expression, and overexpression of Nanos2 can alleviate the stem cell loss phenotype caused by the depletion of Gfra1, a receptor for GDNF. By using an inducible Cre-loxP system, we show that NANOS2 expression is downregulated upon the conditional knockout (cKO) of Gfra1, while ectopic expression of Nanos2 in GFRA1-negative spermatogonia does not induce de novo GFRA1 expression. Furthermore, overexpression of Nanos2 in the Gfra1-cKO testes prevents precocious differentiation of the Gfra1-knockout stem cells and partially rescues the stem cell loss phenotypes of Gfra1-deficient mice, indicating that the stem cell differentiation can be suppressed by NANOS2 even in the absence of GDNF signaling. Taken together, we suggest that NANOS2 acts downstream of GDNF signaling to maintain undifferentiated state of spermatogonial stem cells. © AlphaMed Press.


Nishimura K.,National Institute of Genetics | Ishiai M.,Kyoto University | Horikawa K.,National Institute of Genetics | Fukagawa T.,SOKENDAI | And 4 more authors.
Molecular Cell | Year: 2012

DNA interstrand crosslinks (ICLs) are highly toxic lesions that stall the replication fork to initiate the repair process during the S phase of vertebrates. Proteins involved in Fanconi anemia (FA), nucleotide excision repair (NER), and translesion synthesis (TS) collaboratively lead to homologous recombination (HR) repair. However, it is not understood how ICL-induced HR repair is carried out and completed. Here, we showed that the replicative helicase-related Mcm family of proteins, Mcm8 and Mcm9, forms a complex required for HR repair induced by ICLs. Chicken DT40 cells lacking MCM8 or MCM9 are viable but highly sensitive to ICL-inducing agents, and exhibit more chromosome aberrations in the presence of mitomycin C compared with wild-type cells. During ICL repair, Mcm8 and Mcm9 form nuclear foci that partly colocalize with Rad51. Mcm8-9 works downstream of the FA and BRCA2/Rad51 pathways, and is required for HR that promotes sister chromatid exchanges, probably as a hexameric ATPase/helicase. © 2012 Elsevier Inc..


Okubo Y.,SOKENDAI | Okubo Y.,Japan National Institute of Health Sciences | Sugawara T.,National Institute of Genetics | Abe-Koduka N.,National Institute of Genetics | And 4 more authors.
Nature Communications | Year: 2012

The synchronized oscillation of segmentation clock is required to generate a sharp somite boundary during somitogenesis. However, the molecular mechanism underlying this synchronization in the mouse embryos is not clarified yet. We used both experimental and theoretical approaches to address this key question. Here we show, using chimeric embryos composed of wild-type cells and Delta like 1 (Dll1)-null cells, that Dll1-mediated Notch signalling is responsible for the synchronization mechanism. By analysing Lunatic fringe (Lfng) chimeric embryos and Notch signal reporter assays using a co-culture system, we further find that Lfng represses Notch activity in neighbouring cells by modulating Dll1 function. Finally, numerical simulations confirm that the repressive effect of Lfng against Notch activities in neighbouring cells can sufficiently explain the synchronization in vivo. Collectively, we provide a new model in which Lfng has a crucial role in intercellular coupling of the segmentation clock through a trans-repression mechanism. © 2012 Macmillan Publishers Limited. All rights reserved.


News Article | October 6, 2016
Site: phys.org

An international team of astronomers using the Subaru Telescope and led by a graduate student member of SOKENDAI (The Graduate University of Advanced Studies, Japan) has discovered companions circling "intermediate-mass" stars. These are stars that are heavier than the Sun and the companions were thought to be either planets or possibly small stars. The excellent performance of the Subaru Telescope enabled the detection of faint objects circling around three of six bright stars surveyed.

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