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RISS 인기검색어
- 검색키워드
- 저자 : Osamu Tokunaga (검색결과 3 건)
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EST analysis of regenerating newt retina
Hisatomi, Osamu,Hasegawa, Akiyuki,Goto, Tatsushi,Yamamoto, Shintaro,Sakami, Sanae,Kobayashi, Yuko,Tokunaga, Fumio Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2
A vertebrate retina is an organ belonging to the central nerve system (CNS), and is usually difficult to regenerate except at an embryonic stage in life. However, certain species of urodele amphibians, such as newts and salamanders, possess the ability to regenerate a functional retina from retinal pigment epithelial (RPE) cells even as adults. After surgical removal of neural retinas from adult newt eyes, the remaining RPE cells lose their pigment granules, transdifferentiate into retinal progenitor cells, which further differentiate into various retinal neurons, and then finally reform a functional neural network. To understand the molecular mechanisms of CNS regeneration, we attempted to investigate the genes expressing in regenerating newt retina. mRNAs were isolated from regenerating retinas at 18-19 days after the surgical removal of the normal retina, and a cDNA library (regenerating retinal cDNA library) were constructed. Our EST analysis of 112 clones in the regenerating cDNA library revealed that about 70% clones are closely related to the genes previously identified. About 40% clones are housekeeping genes, and about 15% clones encode proteins related to the regulation of gene expression and to the proliferation of the cells. Sequences similar to neural retina- and RPE-specific genes were not detected at all. These results led us to suppose that the regenerating retinal cells are in a state considerably different from those of neither neural retina nor RPE cells.
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Evolution of Visual Pigments and Related Molecules
Hisatomi, Osamu,Yamamoto, Shintaro,Kobayashi, Yuko,Honkawa, Hanayo,Takahashi, Yusuke,Tokunaga, Fumio Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2
In photoreceptor cells, light activates visual pigments consisting of a chromophore (retinal) and a protein moiety (opsin). Activated visual pigments trigger an enzymatic cascade, called phototransduction cascade, in which more than ten phototransduction proteins are participating. Two types of vertebrate photoreceptor cells, rods and cones, play roles in twilight and daylight vision, respectively. Cones are further classified into several subtypes based on their morphology and spectral sensitivity. Though the diversities of vertebrate photoreceptor cells are crucial for color discrimination and detection of light over a wider range of intensities, the molecular mechanism to characterize the photoreceptor types remains unclear. We investigated the amino acid sequences of about 50 vertebrate opsins, and found that these sequences can be classified into five fundamental subfamilies. Clear relationships were found between these subfamilies and their characteristic spectral sensitivities. In addition to opsins, we studied other phototransduction proteins. The amino acid sequences of phototransduction proteins can be classified into a few subfamilies. Even though their spectral sensitivity is considerably different, cones fundamentally share the phototransduction protein isoforms which are different from those found in rods. It is suggested that the difference in phototransduction proteins between rods and cones is responsible for their sensitivity to light. Isoforms and their selective expression may characterize individual photoreceptor cells, thus providing us with physiological functions such as color vision and daylight/twilight visions.
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Tracking of 3D Sound Source Location by Particle Filter with TDOA and Signal Power Ratio
Norikazu Ikoma,Osamu Tokunaga,Hideaki Kawano,Hiroshi Maeda 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
A new sound source tracking method in 3 dimensional space using state space modeling approach and particle filter as a state estimation method has been proposed. Not only TDOA (Time Difference Of Arrival) as our previous works including by the authors, but also using power ratio of two sound signals from microphone pair are effectively used in formulation of state space model. Simulational experiments consisting of 1) fundamental tracking with four microphones and 2) human head tracking in car cabin have been conducted with efficient performance in SNR 20dB environment with about 3,000 number of particles.
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