研究者データベース

西村 吾朗(ニシムラ ゴロウ)
電子科学研究所 附属社会創造数学研究センター
助教

基本情報

所属

  • 電子科学研究所 附属社会創造数学研究センター

職名

  • 助教

学位

  • 理学博士(大阪大学)
  • 理学修士(大阪大学)

ホームページURL

ORCID ID

J-Global ID

研究キーワード

  • 生物物理学   光計測学   生体計測学   Biophysics (4306)   Biomedical Optics (1301)   

研究分野

  • 自然科学一般 / 生物物理、化学物理、ソフトマターの物理
  • ナノテク・材料 / 光工学、光量子科学
  • ライフサイエンス / 生体材料学
  • ライフサイエンス / 生体医工学

職歴

  • 2015年04月 - 現在 北海道大学 電子科学研究所 附属社会創造数学研究センター 助教
  • 2012年04月 - 2015年03月 北海道大学 電子科学研究所 数理科学研究部門 助教
  • 2007年10月 - 2012年03月 北海道大学 電子科学研究所 電子計測制御部門 助教
  • 2007年04月 - 2007年09月 北海道大学 電子科学研究所電子機能素子部門 助教
  • 1992年04月 - 2007年03月 北海道大学 電子科学研究所電子機能素子部門 助手
  • 1992年 - 2007年 Research Associate
  • 1989年07月 - 1992年04月 北海道大学 応用電気研究所 生体物理部門 助手
  • 1989年 - 1992年 Research Associate,1989.7 Instructor, Hokkaido University

所属学協会

  • SPIE   日本光学会   米国光学会   物理学会   生物物理学会   Optical Soceity of Japan   Optical Society of America   The Biophysical Society of Japan   The Physical Society of Japan   

研究活動情報

論文

  • 野村 航希, 藤井 宏之, 小林 一道, 渡部 正夫, 西村 吾朗
    Proceeding of the 7th Asian NIR symposium (ANS2020) 2020 AFI-0006 12 - 13 2020年02月 [査読有り][通常論文]
  • 藤井 宏之, 西村 吾朗, 遠藤 茂樹, 野村 航希, 小林 一道, 渡部 正夫
    Proceeding of the 7th Asian NIR symposium (ANS2020) 2020 AFI-0007 14 - 15 2020年02月 [査読有り][通常論文]
  • Fast and robust reconstruction algorithm for fluorescence diffuse optical tomography assuming a cuboid target
    Chunlong Sun, Gen Nakamura, Goro Nishimura, Yu Jiang, Jijun Liu, Manabu Machida
    Journal of the Optical Society America A 37 2 231 - 239 2020年01月 [査読有り][通常論文]
  • The stability condition for the FDTD of the optical diffusion equations
    Hidemitsu Toba, Satoru Odate, Katsura Otaki, Goro Nishimura
    Optical Review 27 1 81 - 89 2019年11月 [査読有り][通常論文]
  • 西村 吾朗
    Biomedical Optics Express 10 3 1234 - 1249 2019年02月 [査読有り][通常論文]
  • Fluorescence Image Contrast Improvement by a Time-domain Method
    西村 吾朗
    OSA Biophotonics Congress on CD-ROM JTu3A.2.  2018年04月 [査読有り][通常論文]
  • Kernel Prieto, Goro Nishimura
    OPTICAL REVIEW 24 2 242 - 251 2017年04月 [査読有り][通常論文]
     
    A new scheme for reconstruction of a fluorophore target embedded in a semi-infinite medium was proposed and evaluated. In this scheme, we neglected the presence of the fluorophore target for the excitation light and used an analytical solution of the time-dependent radiative transfer equation (RTE) for the excitation light in a homogeneous semi-infinite media instead of solving the RTE numerically in the forward calculation. The inverse problem for imaging the fluorophore target was solved using the Landweber-Kaczmarz method with the concept of the adjoint fields. Numerical experiments show that the proposed scheme provides acceptable results of the reconstructed shape and location of the target. The computation times of the solution of the forward problem and the whole reconstruction process were reduced by about 40 and 15%, respectively.
  • Kernel Prieto, Goro Nishimura
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE 10059 2017年 [査読有り][通常論文]
     
    We investigated the feasibility of a two-step scheme for reconstruction of a fluorophore target embedded in a semi-infinite medium. In this scheme, we neglected the presence of the fluorophore target for the excitation light and used an analytical solution of the time-dependent radiative transfer equation (RTE) for the excitation light in a homogeneous semi-infinite media instead of solving the RTE numerically in the forward calculation. In the first step of this reconstruction scheme, we implemented a pixel-based reconstruction using the Landweber method with adjoint fields. The second step uses this result as an initial guess for solving the shape and contrast value reconstruction problem using the level set method. Numerical experiments using Monte Carlo data measurements, show that the proposed scheme provides reconstructions of shape, location and contrast value of the target with rather good accuracy. The computation times of the solution of the forward problem and the whole reconstruction process were reduced by about forty and fifteen percent, respectively.
  • 近赤外光を用いた次世代生体イメージング:拡散光・蛍光・光音響トモグラフィー
    大川晋平, 石原美弥, 西村吾朗, 星 詳子
    計測と制御 56 11 863 - 868 2017年 [査読有り][通常論文]
  • Kernel Prieto, Goro Nishimura
    OPTICAL TOMOGRAPHY AND SPECTROSCOPY OF TISSUE XII 10059 2017年 [査読有り][通常論文]
     
    We investigated the feasibility of a two-step scheme for reconstruction of a fluorophore target embedded in a semi-infinite medium. In this scheme, we neglected the presence of the fluorophore target for the excitation light and used an analytical solution of the time-dependent radiative transfer equation (RTE) for the excitation light in a homogeneous semi-infinite media instead of solving the RTE numerically in the forward calculation. In the first step of this reconstruction scheme, we implemented a pixel-based reconstruction using the Landweber method with adjoint fields. The second step uses this result as an initial guess for solving the shape and contrast value reconstruction problem using the level set method. Numerical experiments using Monte Carlo data measurements, show that the proposed scheme provides reconstructions of shape, location and contrast value of the target with rather good accuracy. The computation times of the solution of the forward problem and the whole reconstruction process were reduced by about forty and fifteen percent, respectively.
  • Takahiro Suzuki, Ryohei Saito, Nobuo Kitada, Takuji Koike, Shojiro Maki, Yukihiro Michiwaki, Goro Nishimura, Haruki Niwa, Yukio Yamada
    2017 IEEE INTERNATIONAL CONFERENCE ON CYBORG AND BIONIC SYSTEMS (CBS) 24 - 28 IEEE 2017年 [査読有り][通常論文]
  • Goro Nishimura, Kamlesh Awasthi, Daisuke Furukawa
    JOURNAL OF BIOMEDICAL OPTICS 21 7 75013  2016年07月 [査読有り][通常論文]
     
    Fluorescence lifetime in heterogeneous multiple light scattering systems is analyzed by an algorithm without solving the diffusion or radiative transfer equations. The algorithm assumes that the optical properties of medium are constant in the excitation and emission wavelength regions. If the assumption is correct and the fluorophore is a single species, the fluorescence lifetime can be determined by a set of measurements of temporal point-spread function of the excitation light and fluorescence at two different concentrations of the fluorophore. This method is not dependent on the heterogeneity of the optical properties of the medium as well as the geometry of the excitation-detection on an arbitrary shape of the sample. The algorithm was validated by an indocyanine green fluorescence in phantom measurements and demonstrated by an in vivo measurement. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
  • 藤井 宏之, 西村 吾朗, 服部 聖仁, 小林 一道, 渡部 正夫
    Proceeding of the fifth Asian NIR symposium (ANS2016) 2016 P-86 288 - 289 2016年 [査読有り][通常論文]
  • 服部 聖仁, 藤井 宏之, 西村 吾朗, 小林 一道, 渡部 正夫
    Proceeding of the fifth Asian NIR symposium (ANS2016) 2016 O-6 72 - 73 2016年 [査読有り][通常論文]
  • Goro Nishimura
    REVIEW OF SCIENTIFIC INSTRUMENTS 86 10 106108  2015年10月 [査読有り][通常論文]
     
    of photons on multiple channels with down to a 1-ns resolution and to transfer all data to a host computer in real-time through universal serial bus with more than 10 M events/s transfer rate. The main concept is that photon time series can be regarded as a serial communication data stream. This recorder was successfully applied for simultaneous measurements of fluorescence fluctuation and lifetime of near-infrared dyes in solution. This design is not only limited to the fluorescence fluctuation measurement but also applicable to any kind of photon counting experiments in a nanosecond time range because of the simple and easily modifiable design. (C) 2015 AIP Publishing LLC.
  • Yoshikazu Tsukasaki, Masatoshi Morimatsu, Goro Nishimura, Takao Sakata, Hidehiro Yasuda, Akihito Komatsuzaki, Tomonobu M. Watanabe, Takashi Jin
    RSC ADVANCES 4 77 41164 - 41171 2014年 [査読有り][通常論文]
     
    Near-infrared (NIR) fluorescence imaging at wavelengths from 1000 to 1500 nm (2nd-NIR window) is a promising modality for in vivo fluorescence imaging because of the deeper tissue penetration with lower tissue scattering of the 2nd-NIR light. For such in vivo fluorescence imaging, highly fluorescent probes in the 2nd-NIR wavelength region are needed. Although single-walled carbon nanotubes and Ag2S quantum dots (QDs) have recently appeared as 2nd-NIR fluorescent probes, their fluorescence brightness is relatively low (quantum yields <6%). In this study, we developed a synthetic method for preparing highly fluorescent PbS/CdS core-shell QDs (quantum yields, 17% in water) with narrow band widths (<200 nm) that emit in the 2nd-NIR region. By overcoating of a CdS shell onto a PbS QD core, we could easily control the emission wavelengths of the PbS/CdS QDs at 1000 to 1500 nm. To use the QDs for in vivo imaging, we investigated the optical properties of QDs (penetration depth and blurring of fluorescence images in slices of skin, brain, and heart in mice) in the 2nd-NIR region. We found that the 2nd-NIR fluorescence imaging at ca.1300 nm using the PbS/CdS QDs results in the highest signal to background ratio with a low blurring for in vivo imaging. To confirm the capabilities of the PbS/CdS QDs for in vivo imaging, we conducted fluorescence angiography imaging of a mouse head.
  • 西村 吾朗
    SPIE Proc 8578 85782B  2013年05月 [査読有り][通常論文]
  • Goro Nishimura, Daisuke Furukawa, Kamlesh Awasthi
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8578 2013年 [査読有り][通常論文]
     
    A non-contact type time-domain system for the fluorescence diffuse optical tomography was designed. The system is evaluated by a phantom with a fluorescence target. The contamination of the non-specific scattering superimposed on the excitation profile but it could be reduced with closely locating the detection fiber to the surface (̃1 mm). Next, we analyzed the contamination in the temporal profiles with an Intralipid solution phantom with a fluorescent target. The contamination to the excitation profile is not clearly observed but that to the fluorescence is strong with a short distance between the excitation source and detection. Finally, we have concluded that a larger distance of source and detector yields better fluorescence sensitivity because the background is limiting the fluorescence detection. On the other hand, the signal quality depends on the statistics and thus the optimum range of the distance comes around 30 mm. Finally, this research gives the idea for the design of the source and detection configuration. © 2013 Copyright SPIE.
  • Goro Nishimura, Kamlesh Awasthi, Kitsakorn Locharoenrat, Shinpei Okawa, Yukio Yamada
    OPTICAL TOMOGRAPHY AND SPECTROSCOPY OF TISSUE IX 7896 78962Q  2011年 [査読有り][通常論文]
     
    We are reporting the first trial image reconstruction of a implanted fluorescent target into a live rat abdomen. We use a simplified algorithm for fluorescence diffuse optical tomography (FDOT), so-called the Total-light algorithm to obtain the absorption image of the target from the measured mean-transit time (MTT). We reconstructed two absorption images with and without a fluorescence target. It is difficult to identify something in the absorption images. However, the difference image between the two images highlights the target. This suggests that our algorithm is robust to the artifacts in the images in the real situation of in vivo measurements.
  • Kamlesh Awasthi, Goro Nishimura
    PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES 10 4 461 - 463 2011年 [査読有り][通常論文]
     
    The time-dependent nature of the complexes of IR806 dye and other similar near-infrared cyanine dyes in human serum albumin (HSA) have been studied by employing absorption, emission and time-correlated single photon counting techniques. The complex formation of IR806 with HSA modifies the native structure of IR806, resulting in time-dependent changes in its optical properties. The modification process of the dye and its complex formation with HSA is very slow and takes about 90 min. The process of the formation of the new complex is irreversible and totally controlled by the initial complex of IR806 and HSA. As far as we know, this new property of cyanine dyes has not been reported before. These properties are very important for near-infrared fluorescence imaging.
  • Goro Nishimura, Kamlesh Awasthi, Kitsakorn Locharoenrat, Shinpei Okawa, Yukio Yamada
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE 7896 2011年 [査読有り][通常論文]
     
    We are reporting the first trial image reconstruction of a implanted fluorescent target into a live rat abdomen. We use a simplified algorithm for fluorescence diffuse optical tomography (FDOT), so-called the Total-light algorithm to obtain the absorption image of the target from the measured mean-transit time (MTT). We reconstructed two absorption images with and without a fluorescence target. It is difficult to identify something in the absorption images. However, the difference image between the two images highlights the target. This suggests that our algorithm is robust to the artifacts in the images in the real situation of in vivo measurements. © 2011 SPIE.
  • Quantification of Fluorescence Target in Tissue Phantoms by Time‐Domain Diffuse Optical Tomography with Phantoms—Total‐Light Approach
    Goro Nishimura, Kamlesh Awasthi, Kitsakorn Locharoenrat, Shinpei Okawa, Yukio Yamada
    OSA Topical Meeting, Biomedical Optics (BIOMED), Abstract Book BTuD11  2010年04月 [査読有り][通常論文]
  • Phantom experiments of fluorescence diffuse optical tomography
    A. Yano, A. Marjono, K. Uchida, T. Abe, S. Okawa, G. Nishimura, Y. Hoshi, F. Gao, Y. Yamada
    Proceedings of APBP2009 137 - 138 2009年05月 [査読無し][通常論文]
  • 西村 吾朗
    脈管学 : 日本脈管学会機関誌 : the journal of Japanese College of Angiology 49 2 139 - 145 2009年04月25日 [査読無し][通常論文]
  • Goro Nishimura, Chan-Gi Pack, Mamoru Tamura
    EXPERIMENTAL AND MOLECULAR PATHOLOGY 82 2 175 - 183 2007年04月 [査読有り][通常論文]
     
    In this paper, we report on phosphorescence measurements for oxygen dynamics in cells by means of a correlation method, which is an expansion of the fluorescence correlation spectroscopy. The intensity correlation function of the emission excited by a pulsed light source was measured. With changing the pulse timing, both the fluorescence correlation function and the decay time of phosphorescence could be analyzed. This method was applied for the analysis of the oxygen dynamics in HeLa cells stained by Pd(II)-porphine. The decay function consisted of two exponential components, which might be attributed to free and protein-bound forms of Pd(II)-porphine in the cell, respectively. The relative change of the oxygen concentration under normal and uncoupled respiration conditions was also measured. The simplicity of this method is a great advantage in the biological applications. Although the current system we used was limited in the temporal resolution, the method is in principle applicable to faster decay time measurements down to the nano-second range of the fluorescence decay times. (C) 2007 Elsevier Inc. All rights reserved.
  • Goro Nishimura, Changi Pack, Mamoru Tamura
    JOURNAL OF BIOMEDICAL OPTICS 12 2 020503  2007年03月 [査読有り][通常論文]
     
    We report on a simple correlation method for lifetime measurements using a random modulated excitation light source. We use an intensity correlation function of emission for lifetime analyses. In this method, no reference timing of the excitation is required. We apply the correlation method to measure phosphorescence decays and successfully demonstrate in the analysis of the phosphorescence decay from Pd (II) porphine in HeLa cells under aerobic and anaerobic conditions to understand the oxygen dynamics in individual cells. The method is applicable to faster decay time measurements down to a nanosecond range when the detection system is improved. Current fluorescence correlation setups can easily be modified for lifetime measurements, expanding the applicability in biological problems. (C) 2007 Society of Photo-Optical Instrumentation Engineers.
  • Goro Nishimura, Ikuhiro Kida, Mamoru Tamura
    PHYSICS IN MEDICINE AND BIOLOGY 51 11 2997 - 3011 2006年06月 [査読有り][通常論文]
     
    Time- and space-resolved diffuse reflectance measurements were used to identify the optical parameters, the reduced scattering and absorption coefficients, of bulk living tissue in the region from 1.15 to 1.52 mu m. Although in this region the detector was limited in its temporal resolution, we applied a peak-time shift analysis successfully to determine these coefficients in a human forearm, and then determined the absorption spectrum by space-resolved diffuse reflectance measurements. The absorption spectrum of a water content of 52% determined by magnetic resonance imaging experiments is in good agreement with the absorption coefficient obtained by optical measurements. Moreover, magnetic resonance imaging measurements suggest that the deviation of the absorption coefficients from the water spectrum in the strong water absorption band is caused by the heterogeneity of water distribution in tissue: the low content of water in the skin. These findings indicate that this optical method is potentially applicable to the non-invasive measurement of water in tissue, especially in a region lower than about 1.3-1.35 mu m, which may be useful in monitoring oedema and tissue swelling.
  • S Yano, S Kuroda, JB Lee, H Shichinohe, T Seki, J Ikeda, G Nishimura, K Hida, M Tamura, Y Iwasaki
    JOURNAL OF NEUROTRAUMA 22 8 907 - 918 2005年08月 [査読有り][通常論文]
     
    Recent experimental studies have shown that bone marrow stromal cells (BMSC) differentiate into neural cells and reduce neurological deficits when transplanted into traumatized spinal cord. These findings have been derived primarily from histological analyses. We conducted a study directed chiefly at developing a non-invasive system for tracking BMSC transplanted into the spinal cord of living animals. In this study, we induced spinal cord injury (SCI) in rats with a pneumatic device. BMSC were harvested from transgenic mice expressing green fluorescence protein (BMSC-GFP), and were transplanted stereotactically into a control group of rats without SCI (n = 6) and a group with SCI (n = 3). At 2 and 4 weeks after transplantation, the dura mater was exposed and green fluorescence derived from the transplanted BMSC-GFP was observed. The distribution and differentiation of the transplanted cells were subsequently evaluated with immunohistochemistry. Green fluorescence could be detected around the transplantation site in three of six of the control rats. In all three rats subjected to SCI, green fluorescence was shown to spread from the site of BMSC-GFP injection toward the injury site, suggesting that the transplanted cells had migrated toward the lesion within the 4-week post-transplantation period. Histological evaluation suggested that the detected green fluorescence was emitted by cells that had distributed in the dorsal white matter, and demonstrated that some of the transplanted cells expressed neuronal or astrocytic markers. These results suggest the possibility of tracking BMSC transplanted into the spinal cord in living animals. Such noninvasive bioimaging techniques would be valuable for monitoring the fate of these transplanted cells and assessing the safety and efficacy of their transplantation.
  • Nishimura G, Kinjo M
    Applied optics 44 3458 - 3467 17 2005年06月 [査読有り][通常論文]
  • G Nishimura, M Kinjo
    APPLIED OPTICS 44 17 3458 - 3467 2005年06月 [査読有り][通常論文]
     
    The dead time of the detector significantly distorts the fluorescence correlation function of fluorescent particles in solution. This distortion of the correlation function is similar to the saturation effect of the correlation function in a high-power excitation region. The correlation amplitude is significantly reduced by the dead time. The deviations in the number of molecules and the diffusion time are empirically given by the deviation of the fluorescence intensity linearity. The empirical curves of the deviations can be applied to the systematic error estimation of the parameters. The proportionality of the number of molecules to the concentration of fluorophores is no longer maintained with a large dead time, although almost all of the proportionality of the diffusion time to the inverse diffusion constant remains. This fact makes the dead-time effect different from the saturation effect, which is due to photokinetics. In practice, these distortions can be reduced by use of a smaller excitation power in which the proportionality of the fluorescence intensity is maintained. (c) 2005 Optical Society of America.
  • G Nishimura, M Tamura
    PHYSICS IN MEDICINE AND BIOLOGY 50 6 1327 - 1342 2005年03月 [査読有り][通常論文]
     
    The least-squares (LS) method in fluorescence decay analyses and in time-domain analyses of the diffuse scattering light for data measured by the time-correlated single photon counting (TCSPC) technique is experimentally evaluated, and the artefact in LS analysis for data with different counting statistics is discussed. In single exponential decay analysis, the error of the decay parameter by the LS method is smaller than 10% of the expected true value when the average number of counts per bin (N/k) is more than 1, and the fitting region covers a period on the order of the decay time. In multi-exponential analysis, the decay parameters are sensitively dependent on the counting statistics. In contrast, the fitting by the maximum likelihood estimation (MLE), assuming Poissonian statistics, greatly reduces such dependence of parameters on the counting statistics. In another application, time-domain diffuse scattering measurements, the LS method is only accurate at N/k > 50 (10% error in the absorption coefficient). In particular, the absorption coefficient is largely dependent on the count. In both examples, the problem of stability in the fitting process by MLE still remains: the convergence of the fitting is critically dependent on the selection of initial guesses of the parameters in contrast to the convergence in the LS method. Thus, a hybrid method using the LS method for the determination of the initial guesses is a practical solution to this problem.
  • Goro Nishimura, Mamoru Tamura
    Journal of Biomedical Optics 10 2 2005年03月 [査読有り][通常論文]
  • G Nishimura, M Tamura
    JOURNAL OF BIOMEDICAL OPTICS 10 1 14016  2005年01月 [査読有り][通常論文]
     
    Analysis of time-of-flight (TOF) data is sometimes limited by the instrumental response function, and optical parameters are extracted from the observed response curve by several mathematical methods, such as deconvolution. In contrast to this, we demonstrate that a method using shifts of the peak time of the response curve with different source-detector separations can yield the average path length of the light traveling in a tissue-like sample without deconvolution. In addition, combining the intensity information allows us to separate the scattering and absorption coefficients. This simple method is more robust in signal-to-noise ratio than the moment analysis, which also does not require the cleconvolution procedure, because the peak position is not significantly dependent on the baseline fluctuation and the contamination of the scattering. The analysis is demonstrated by TOF measurements of an Intralipid solution at 800 nm, and is applied to the measurements at 1.29 mu m, where the temporal response of photomultiplier tubes is not sufficiently good. (c) 2005 Society of Photo-Optical Instrumentation Engineers.
  • A Masuda, K Ushida, G Nishimura, M Kinjo, M Tamura, H Koshino, K Yamashita, T Kluge
    JOURNAL OF CHEMICAL PHYSICS 121 21 10787 - 10793 2004年12月 [査読有り][通常論文]
     
    The distance dependence of the diffusion coefficient (DDDC) of a globular protein (cytchrome c) in aqueous hyaluronan (HA) solution, which is a model system for extracellular matrices (ECMs), was measured by a combination of three kinds of spectroscopic measurements of diffusion coefficients, the time and space samplings of which are different. The results of the three methods are plotted against the diffusion distance derived from the consideration of each experimental condition. Due to the characteristic morphology of HA with an effective mesh structure, the proteins showed two extreme diffusion modes: (1) short (<10 nm) diffusion with rare contact with polymer chains; (2) long (>100 nm) diffusion significantly disrupted by polymer chains showing an approximate to30% reduction in diffusion coefficient. The transition from the short diffusion to the long one occurs in a very narrow range (10-100 nm) of diffusion distance and this unique character of HA realizing anomalous diffusion should provide suitable environments for various bioactivities when involved in ECM. (C) 2004 American Institute of Physics.
  • H Shichinohe, S Kuroda, JB Lee, G Nishimura, S Yano, T Seki, J Ikeda, M Tamura, Y Iwasaki
    BRAIN RESEARCH PROTOCOLS 13 3 166 - 175 2004年08月 [査読有り][通常論文]
     
    Recent experimental studies have indicated that bone marrow stromal cells (BMSC) improve neurological deficits when transplanted into the animal models of various neurological disorders, although precise mechanism still remains unclear. In this study, we developed a new in vivo fluorescence optical imaging protocol to sequentially track the transplanted into the brain of the living animals subjected to cerebral infarct. Mice BMSC were harvested from transgenic mice expressing green fluorescent protein (BMSC-GFP). They were stereotactically transplanted into the ipsilateral striatum of mice subjected to permanent middle cerebral artery occlusion after 7 days of ischemia (n = 12). During 12 weeks after transplantation, the skull was exposed and the green fluorescence emitted from the brain surface was sequentially observed, using in vivo fluorescence optical microscopy. As the results, regional green fluorescence was detected in the ipsilateral parietal region 4-12 weeks after transplantation in all animals and became more apparent over the time. The images obtained through the skull were very similar to those acquired by thinning or removing the skull. Immunohistochemistry evaluation revealed that the transplanted cells migrated towards the ischemic boundary zone and expressed the neuronal or astrocytic marker, supporting the findings on fluorescence optical images. Sequential visualization of the BMSC transplanted into the brain of living animals would be valuable for monitoring the migration, growth and differentiation of the transplanted cells to explore the fate and safety of stem cell transplantation for various neurological disorders. (C) 2004 Elsevier B.V. All rights reserved.
  • G Nishimura, M Kinjo
    ANALYTICAL CHEMISTRY 76 7 1963 - 1970 2004年04月 [査読有り][通常論文]
     
    The distortion of the fluorescence correlation function of a dye solution becomes larger with the increase in the excitation power, and eventually the parameters, such as the number of molecules and the diffusion time, obtained by the fluorescence correlation function systematically change. The most fundamental reason for this change is thought to be the distortion of the Gaussian excitation-detection field due to the saturation of the photocycle of the chromophore. The deviation from linearity of the fluorescence intensity causes the distortion of the fluorescence correlation function. Consequently, a smaller excitation power reduces the distortion and ensures an accurate measurement of the absolute value of these parameters. At the same time, the measurements at a fixed excitation power can be used to quantitatively determine the relative value of concentration and of the diffusion time. The deviation in the linearity of the fluorescence intensity and the deviation of the parameters show a high degree of correlation, and a 10% deviation of the intensity results in a prediction of a similar to 10% deviation in the number of molecules and a similar to5% in the diffusion time.
  • F Fujii, Y Nodasaka, G Nishimura, M Tamura
    BRAIN RESEARCH 999 1 29 - 39 2004年02月 [査読有り][通常論文]
     
    It is important to monitor mitochondrial conditions, and light scattering (LS) measurements have been applied to the detection of morphological changes in mitochondria in vivo. Little is known about the morphological and LS responses of brain mitochondria to oxygen withdrawal, a critical factor in cell death. We have therefore investigated the morphological and LS responses of isolated brain mitochondria to anoxia. Anoxia induced an increase in LS, reflecting mitochondrial matrix shrinkage. This response was reversible, but was reduced by adding digitonin, which disrupted the outer membrane selectively. This suggested that integrity of the outer membrane was necessary for the matrix response. We further examined the effects of Mg2+ and ATP on the responses because both exist in cells and modulate the changes in matrix volume. Although Mg2+ and ATP reduced the rates of increase and decrease in LS, respectively, the magnitudes of the increases in LS caused by anoxia stayed at over 80% of the control level (no Mg2+) in the presence of Mg2+ and ATP. This suggested that the increase in LS occurred in cells containing Mg2+ and ATP during anoxia. In contrast, that caused by inhibitors of the electron transport chain was reduced to below 30% of the control level in the presence of Mg2+. The present in vitro study provides a basis for interpretation of LS signals from mitochondria in brain research during oxygen withdrawal. (C) 2003 Elsevier B.V. All rights reserved.
  • G Nishimura, M Tamura
    APBP 2004: SECOND ASIAN AND PACIFIC RIM SYMPOSIUM ON BIOPHOTONICS, PROCEEDINGS 127 - 128 2004年 [査読有り][通常論文]
     
    The time-of-flight (TOF) method and the diffuse reflectance (DR) method were applied for the characterization of optical parameters in living tissue in the region of 1-2 mu m. The absorption coefficient obtained by the TOF method was consistent with the content of water in the tissue. The DR measurement indicates the very large attenuation in the wavelength region above 1.4 mu m. In this region, it is suggested that the optical transport does not diffuse well and it is localized at the light source.
  • Goro Nishimura, Mamoru Tamura
    Biomedical Topical Meeting WF40  Optical Society of America ({OSA}) 2004年 [査読有り][通常論文]
  • G Nishimura, M Tamura
    PHYSICS IN MEDICINE AND BIOLOGY 48 21 N283 - N290 2003年11月 [査読有り][通常論文]
     
    An application of a digital storage oscilloscope for nanosecond time-resolved spectroscopic measurements is demonstrated in the range from the single-photon region to the multi-photon region. In comparison to the time-correlated single photon counting (TCSPC) method, the measurement setup can be greatly simplified by averaging the signals measured by the oscilloscope. Moreover, the multi-photon events of the fluorescence emissions can be tracked by this simple setup although there still exist some disadvantages in the dynamic range of the signal due to radio frequency noise, and the temporal response of the photo-multiplier tube. This method can simplify time-resolved optical measurements in the nanosecond range, such as fluorescence decay and time-of-flight measurements of diffusing light. Thus, this simple method will be applicable in many clinical and industrial uses.
  • G Nishimura, M Kinjo
    OPTICAL REVIEW 10 6 588 - 591 2003年11月 [査読有り][通常論文]
     
    A multi-photon excitation fluorescence correlation system has been developed. The emission from tryptophan methylester solution was observed by this system and analyzed by the intensity correlation function of the visible emission, which originates from the two-photon excitation of photo products generated through a five-photon process. The intensity and the product concentration were proportional to the concentration of tryptophan methylester at a lower concentration range and thus the generation process is a single molecular reaction. The correlation analysis determined the concentration of tryptophan methylester down to 5 muM. The photo product generation from tryptophan solution was enhanced by a potassium iodide addition. These results suggest a new quantification method of tryptophan derivatives.
  • G Nishimura, M Kinjo
    JOURNAL OF PHYSICAL CHEMISTRY B 107 24 6012 - 6017 2003年06月 [査読有り][通常論文]
     
    Strong visible emission from a tryptophan methylester solution was observed by a confocal microscope with a 795-nm femtosecond pulsed laser. The, emission was presumably similar to that observed in 5-hydroxytryptamine (serotonin) solution. In contrast to the intensity in 5-hydroxytryptamine solution, the intensity was proportional to the seventh power of the excitation intensity. The fluctuation analysis of the intensity, which was used to characterize the emission, showed that the concentration of the species of the emission was proportional to the fifth power of the excitation intensity, and its brightness, to the second power. Thus, the emission is attributed to the emission from the two-photon excited state of a photoproduct generated by the five-photon process. The decay time of the correlation function was significantly shortened with an increase in the excitation power. This suggests that the photoproduct converts a nonradiative species, such as a nonfluorescent product, from its excited state generated by the two-photon process. The fluctuation analysis of the novel emission of tryptophan can be applied to tryptophan residues in proteins.
  • JP Gong, T Kurokawa, T Narita, G Kagata, Y Osada, G Nishimura, M Kinjo
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 123 23 5582 - 5583 2001年06月 [査読有り][通常論文]
  • CG Pack, G Nishimura, M Tamura, K Aoki, H Taguchi, M Yoshida, M Kinjo
    CYTOMETRY 36 3 247 - 253 1999年07月 [査読有り][通常論文]
     
    Fluorescence correlation spectroscopy (FCS) provides information about translational diffusion properties of fluorescent molecules in tiny detection volume and allows the analysis of binding processes of biomolecules in homogeneous solution. In this study, FCS was used to measure equilibrium binding constants of disulfide-reduced apo-alpha-lactalbumin (rLA), denatured pepsin, and apo-cytochrome c (apo-cyt c) bound by chaperonin GroEL at different salt concentrations. The results indicate that apo-cyt-c has a much stronger affinity to GroEL than denatured pepsin and rLA have. Titration experiments of GroEL to each substrate with various concentrations of four kinds of salts (K+, Na+, Ca2+, and Mg2+) show that the binding constant of denatured pepsin and rLA to GroEL depends on the salt concentration. The dependence of denatured pepsin binding to GroEL on salt concentration is much stronger than that of rLA. However, the interaction of positively charged apo-cyt c with GroEL is not affected by the salt concentration. Furthermore, the divalent cation promotes the binding of GroEL to denatured pepsin and rLA more strongly than does the monovalent cation. Cytometry 36:247-253, 1999. (C) 1999 Wiley-Liss, Inc.
  • M Kinjo, G Nishimura, T Koyama, U Mets, R Rigler
    ANALYTICAL BIOCHEMISTRY 260 2 166 - 172 1998年07月 [査読有り][通常論文]
     
    The cleavage of fluorescence-labeled M13DNA (7250 bp) using HaeIII, HgaI, BsmAI, and BspMI was analyzed by fluorescence correlation spectroscopy (FCS) in a small volume (1.5 x 10(-15) liters). The digestion process can be monitored by the decrease in amplitude of the fluorescence correlation function while the original DNA molecule is divided into several fragments by the enzymes. To analyze this reaction by FCS, we derived a practical equation for estimating the number of molecules in the FCS measurements. Under standard enzymatic conditions, HaeIII and BsmAI digested fluorescence-labeled DNA to completion in the range of 8 h, whereas HgaI and BspMI digested the DNA after 40 h. The comparison of recognition sequences suggested that some tagged nucleotides could be inserted between the recognition site and the cleavage site of the slow enzyme group. The decrease in amplitude in the fluorescence correlation function quantitatively monitors the hydrolysis of DNA during the digestion process. (C) 1998 Academic Press.
  • 中井 達也, 西村 吾朗, 山本 克之
    電子情報通信学会論文誌. C-I, エレクトロニクス, I-光・波動 81 2 81 - 88 一般社団法人電子情報通信学会 1998年02月25日 [査読無し][通常論文]
     
    光拡散方程式中の拡散係数の形式は実験により決定した.散乱媒質中の光の伝搬を記述する際に一般的に用いられる光拡散方程式中の拡散係数Dには, 吸収係数μ_aを含むものと含まないものの二つが提案されているが, 本研究では両者の差が明確になる吸収の大きな媒質中で定常光を用いて散乱光の測定を行い, どちらの拡散係数が現実をより正しく記述しているかを検証した.その結果, 吸収がほぼ0から等価散乱係数μ_s'に近い値まで変化しても拡散係数は吸収の影響を受けず, その値は(3μ_s')^<-1>とよく一致した.このことから光拡散方程式中の拡散係数には吸収係数は含まれず, D=(3μ_s')^<-1>で表わされることが確認された.
  • T Nakai, G Nishimura, K Yamamoto, M Tamura
    PHYSICS IN MEDICINE AND BIOLOGY 42 12 2541 - 2549 1997年12月 [査読有り][通常論文]
     
    The optical diffusion coefficient in a homogeneous turbid medium with high absorption was determined by steady-state measurements of the light transmission under the infinite-boundary condition. The intensity of the transmission was well described by the solution of the optical diffusion equation. Moreover, the optical diffusion coefficient D was given by a constant, (3 mu(s)')(-1), where mu(s)' is the reduced scattering coefficient, up to the absorption coefficient of about 0.3 mu(s)'. These results mean that attenuation by absorption only contributes to exponential attenuation along the optical path defined by the scattering coefficient and geometry of the system even in high-absorption turbid media such as the pathological living tissues of bleeding or haematoma.
  • DA Boas, G Nishimura, AG Yodh
    OPTICAL TOMOGRAPHY AND SPECTROSCOPY OF TISSUE: THEORY, INSTRUMENTATION, MODEL, AND HUMAN STUDIES II, PROCEEDINGS OF 2979 468 - 477 1997年 [査読有り][通常論文]
     
    The non-invasive determination of the depth of severe burns is an important problem whose solution would offer medical practitioners a valuable tool for diagnosing and treating severe burns. Burned tissue is essentially a turbid medium with spatially varying dynamics: light is multiply scattered by the tissue and layers of burned tissue are distinguished by the degree of blood flow. The dynamical properties of turbid media can be probed by monitoring the temporal fluctuations of scattered light speckles. Information on a system's dynamics is obtained from the temporal autocorrelation function of these intensity fluctuations. We have recently shown that the correlation diffusion equation (CDE) accurately predicts the temporal correlation function for turbid systems with spatially varying dynamics and that the dynamical properties of such systems can be imaged using standard reconstruction algorithms. In this contribution, we demonstrate the sensitivity of temporal field correlation measurements to variations of 100 mu m in burn thickness and the potential applicability of the CDE for quantitation of burn thickness. Results are presented from burn phantoms and pig models. The combination of diffusing temporal light correlation with diffuse reflectometry for enhanced burn diagnosis is investigated.
  • Goro Nishimura, Rudolf Rigler, Masataka Kinjo
    Bioimaging 5 3 129 - 133 1997年 [査読有り][通常論文]
     
    The cleaving process of rhodamine labeled DNA with T7-exonuclease was monitored using the fluorescence correlation method. The fluorescence correlation function, formulated so as to take into account the fluorescence efficiency of the fragment, was derived to allow analysis of the two- component system. The reaction was well represented by the two-component model, allowing monitoring of the progressive cleavage of DNA. The analysis yielded not only the size of the polymer fragment but also the efficiency of the incorporation of rhodamine and the ratio of its quantum yield in DNA and in solution.
  • Masataka Kinjo, Goro Nishimura
    Bioimaging 5 3 134 - 138 1997年 [査読有り][通常論文]
     
    Fluorescence correlation spectroscopy (FCS) provides information about two important parameters in molecular biology. These are the average number of molecules in the detection volume, and the translational diffusion coefficient of the molecules. Although the properties of the translational diffusion reflect the molecular weight and shape, our work focuses on the analysis of the number of cleaved DNA fragments in solution. The cleavage of fluorescently labelled M13 DNA and pUC19 DNA was carded out with three kinds of restriction enzymes (HaeIII, HgaI and BsmAI), and the number of DNA fragments was monitored using FCS. The reciprocal value of the autocorrelation function at time τ = 0 is consistent with the number of fragments that are expected from restriction enzyme maps of the DNA. Our study indicates the capability of FCS as a tool for finding genetic differences in DNA sequences.
  • G Nishimura, K Katayama, M Kinjo, M Tamura
    OPTICS COMMUNICATIONS 128 1-3 99 - 107 1996年07月 [査読無し][通常論文]
     
    The intensity autocorrelation function of light through a dense intralipid suspension in the presence of an absorber was investigated by the photon correlation method. Then, we demonstrated that the parameter of the scattering can be obtained through the absorption effect with the diffusing-wave spectroscopy: diffusing-wave absorption spectroscopy. Firstly, the relation of the Laplace transform between the autocorrelation and path distribution functions was confirmed by using the time-of-flight method. Then, the linear shifts along the time axis of the autocorrelation function due to the absorption were also validated and the transport mean free path was obtained. Furthermore, this was also estimated from the intensity change by absorption.
  • M Oda, Y Yamashita, G Nishimura, M Tamura
    PHYSICS IN MEDICINE AND BIOLOGY 41 3 551 - 562 1996年03月 [査読有り][通常論文]
     
    Using time-resolved spectroscopy, we have developed an experimental approach to obtain the absolute changes in concentration in the scattering medium of living tissues. The time-resolved Beer-Lambert equation can be applied to living tissue due to the fact that the optical attenuation by absorption can be separated from that by scattering, and the intensity of the light along the non-linear scattered optical path is exponentially attenuated by the absorption. Based on the above, the absolute concentration of haemoglobin as well as oxygen saturation in the rat head can be determined in situ under various respiratory conditions where multiwavelength measurements were performed. The optically assessed values agree with those determined directly by the gas analysis of our previous report. The present method is very simple and therefore opens up wide applications for time-resolved spectrophotometry in clinical medicine as a technique for quantitative near-infrared oxygen monitoring.
  • Oda, I, H Eda, Y Tsunazawa, M Takada, Y Yamada, G Nishimura, M Tamura
    APPLIED OPTICS 35 1 169 - 175 1996年01月 [査読有り][通常論文]
     
    The concept of the temporally extrapolated absorbance method (TEAM) for optical tomography of turbid media has been verified by fundamental experiments and image reconstruction. The TEAM uses the time-resolved spectroscopic data of the reference and object to provide projection data that are processed by conventional backprojection. Optical tomography images of a phantom consisting of axisymmetric double cylinders were experimentally obtained with the TEAM and time-gating and continuous-wave (CW) methods. The reconstructed TEAM images are compared with those obtained with the time-gating and CW methods and are found to have better spatial resolution. (C) 1996 Optical Society of America .
  • M WAKITA, G NISHIMURA, M TAMURA
    JOURNAL OF BIOCHEMISTRY 118 6 1151 - 1160 1995年12月 [査読無し][通常論文]
     
    By extensively examining the experimental conditions for time-resolved spectrophotometry of non-transparent light scattering systems, we demonstrated the feasibility of quantitative analysis of both the fluorescence lifetime and intensity of reduced pyridine nucleotides in living tissues, suspensions of isolated liver mitochondria, and hepatocytes, as well as hemoglobin-free perfused rat liver being used systematically for measurements, The fluorescence decay was analyzed by the maximum likelihood method with a 4-component decay model, The lifetime of NADH observed in mitochondria (mean: 2.8+/-0.2 ns) was much longer than that of the free form in an aqueous solution (mean: 0.43+/-0.01 ns), and it was characterized as a protein-bound form, The lifetime was not affected by either aerobic or anaerobic conditions nor by the energy state, though the intensity changed markedly, The decay curves of isolated hepatocytes under normal aerobic conditions were the same as those of isolated mitochondria, though cytosolic NADH and NADPH were superimposed, Under the conditions of ''unphysiological'' acidosis, the mean lifetime became about 1.5 times longer than that under normal conditions, With perfused liver, the relative contributions of cytosolic NADH and NADPH mere determined by infusing lactate and tert-butylhydroperoxide. Cytosolic NADH did not contribute to the overall fluorescence of pyridine nucleotides, In contrast, about 70% of the total fluorescence intensity was due to cytosolic NADPH, but its decay parameters were essentially the same as those of mitochondrial NADH, No free form of either NADH or NADPH was detected in the cytosolic and mitochondrial spaces, We concluded that the changes in fluorescence intensity observed under the various conditions can be simply explained by a change in the amount of reduced pyridine nucleotides in tissues, rather than by changes in the microscopic environment, The wide applicability of time-resolved fluorescence photometry to in vivo studies is well documented.
  • K KATAYAMA, G NISHIMURA, M KINJO, M TAMURA
    APPLIED OPTICS 34 31 7419 - 7427 1995年11月 [査読有り][通常論文]
     
    Optical absorption in highly turbid media was quantified by the time shift of the electric field autocorrelation function of diffused photons. The intensity autocorrelation function was analyzed by the third-order cumulant expansion and a linear relationship between the time shift and the absorber concentration was observed. The slope of the fitted line gave the molecular extinction coefficient of the absorber. The absorption spectra were also obtained from the time shift. Applicability to dual-wavelength absorption measurement is also discussed. We demonstrate for the first time, as far as we know, the feasibility of absorbance quantification in turbid media by the photon correlation method. (C) 1995 Optical Society of America
  • Kaoru Katayama, Goro Nishimura, Masataka Kinjo, Mamoru Tamura
    Applied Optics 34 31 7419 - 7427 1995年 [査読有り][通常論文]
     
    Optical absorption in highly turbid media was quantified by the time shift of the electric field autocorrelation function of diffused photons. The intensity autocorrelation function was analyzed by the third-order cumulant expansion and a linear relationship between the time shift and the absorber concentration was observed. The slope of the fitted line gave the molecular extinction coefficient of the absorber. The absorption spectra were also obtained from the time shift. Applicability to dual-wavelength absorption measurement is also discussed. We demonstrate for the first time, as far as we know, the feasibility of absorbance quantification in turbid media by the photon correlation method. © 1995 Optical Society of America.
  • ODA, I, H EDA, Y TSUNAZAWA, M TAKADA, Y YAMADA, G NISHIMURA, M TAMURA
    PHOTON TRANSPORT IN HIGHLY SCATTERING TISSUE, PROCEEDINGS OF 2326 505 - 515 1995年 [査読有り][通常論文]
  • M ODA, Y YAMASHITA, G NISHIMURA, M TAMURA
    OPTICAL TOMOGRAPHY, PHOTON MIGRATION, AND SPECTROSCOPY OF TISSUE AND MODEL MEDIA: THEORY, HUMAN STUDIES, AND INSTRUMENTATION, PROCEEDINGS OF, PTS 1 AND 2 2359 770 - 778 1995年 [査読有り][通常論文]
  • Masanori Tanaka, Goro Nishimura, Takashi Kushida
    Phys. Rev. B 49 24 16917 - 16925 American Physical Society ({APS}) 1994年06月 [査読有り][通常論文]
     
    The 5D0-F-7(0) transition mechanism has been investigated for the Eu3+ ion in two kinds of oxide glasses, polyvinyl alcohol film, and Y2O2S Crystal powder, from the analysis of the laser-induced fluorescence spectra. In the case of Eu3+ in sodium silicate glass and sodium germanate glass, it has been found that the 5D0-F-7(0) transition probability of the ions site-selected by the laser-light excitation is approximately proportional to the square of the axial second-order crystal-field parameter B20. The interpretation of this result is that the dominant mechanism of this transition in these two glasses is due to the borrowing of intensity from the 5D0-F-7(2) (M(J) = 0) transition by the J-mixing effect. In the case of polyvinyl alcohol:Eu3+ and Y2O2S:Eu3+, on the other hand, the contribution of this mechanism has been found to be negligible, from the analysis of the intensity ratio between the 5D0-F-7(0) and 5D0-F-7(2) transitions. Furthermore, in the above two kinds of glass samples, the site-to-site variations in the energy of the F-7(0) state and the mean energy of the three F-7(1) Stark levels are explained well by the mixing of the F-7(2) state due to the second-order crystal-field potential. To explain the above energy variations in polyvinyl alcohol:Eu3+, however, it is necessary, in addition to this effect, to take into account the mixing of the charge-transfer state and/or the J mixing due to the other components of the crystal-field potential.
  • G NISHIMURA, T KUSHIDA
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 60 2 695 - 703 1991年02月 [査読有り][通常論文]
     
    The laser-induced fluorescence spectra of Eu3+ in Ca(PO3)2 glass are analyzed in detail. It is shown that the site-to-site variation of the energies of several levels of Eu3+ is expressed using the second-order crystal-field parameters B20 and \B2+/-2\. From the analysis of the spectral shape of the laser-induced fluorescence lines, the distributions of the above two parameters are determined. The fluorescence linewidth has been found to be very different for the lines to excite. This is explained by the difference in the dependence of the energies of the levels concerned on the crystal-field strength. The inhomogeneously broadened lineshape of the 5D0-7F0 fluorescence excited by the broad-band ultraviolet light is shown to be reproduced by assuming Gaussian distributions of the crystal-field parameters.
  • G NISHIMURA, T KUSHIDA
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 60 2 683 - 694 1991年02月 [査読有り][通常論文]
     
    Fluorescence spectra have been measured in Ca(PO3)2:Eu3+ at 77 K under dye laser excitation at various energies within the absorption lines due to the transitions 7F0, 7F1-5D0, 5D1. It has been found that the 5D0-7F0 transition probability and the mean energy of the three 5D0-7F1 lines are linearly correlated with the energy of the 5D0-7F0 line, and also that this energy is quadratically correlated with the transition energy between 5D0 and the lowest level of 7F1. These results are interpreted in terms that the spreads of these energies and the transition probability are due to the site-to-site variation in the second-order crystal-field parameter. Further, the forbidden 5D0-7F0 transition is concluded to be allowed by the borrowing of the intensity from the 5D0-7F2 (M(J) = 0) line through the J-mixing. Using polarization characteristics of fluorescence, whether the lines are due to the electric or magnetic dipole transition is determined and the Stark levels of the 7F1 and 5D1 manifolds are assigned. It is also shown that the point symmetry of the Eu3+ site is C2v or C2.
  • G NISHIMURA, M TANAKA, A KURITA, T KUSHIDA
    JOURNAL OF LUMINESCENCE 48-9 473 - 476 1991年01月 [査読有り][通常論文]
     
    Luminescence properties have been studied for the Eu3+ ion in glass, crystal powder and a polymer film under monochromatic laser-light excitation. In the case of Eu3+ in Ca(PO3)2 glass, it has been found that the transition strength of the site-selected 5D0-7F0 line is proportional to the square of the second-order crystal-field parameter B20. This suggests that the 5D0-7F0 transition in this material is partially allowed by the crystal-field mixing of the M(J) = 0 component of the 7F2 manifold into 7F0. The analysis of the intensity ratio between the 5D0-7F0 and the 5D0-7F2 lines gives support to this interpretation. For Y2O2S:Eu3+, on the other hand, a fluorescence measurement under hydrostatic pressure has revealed that the transition probability of the 5D0-7F0 line is rather insensitive to the value of B20. The same result has also been obtained for Eu3+-doped polyvinyl alcohol from a fluorescence line-narrowing experiment. Therefore, it is concluded that there exist at least two kinds of mechanisms in the 5D0-7F0 transition of Eu3+. Probable mechanisms are discussed.
  • G NISHIMURA, T KUSHIDA
    PHYSICAL REVIEW B 37 15 9075 - 9078 1988年05月 [査読有り][通常論文]
  • T KUSHIDA, G NISHIMURA
    JOURNAL OF LUMINESCENCE 40-1 111 - 112 1988年02月 [査読有り][通常論文]

書籍

  • 非侵襲・可視化技術ハンドブック
    エヌ・ティー・エス 2007年
  • 測定法シリーズ 、42.蛍光分光とイメージングの手法
    日本分光学会・学会出版センター 2006年
  • Fluorescence spectroscopy and imaging
    2006年
  • DOS/V科学計測入門
    HFS出版 1994年

講演・口頭発表等

  • 生体組織中にある蛍光ターゲットの高感度検出(3)  [通常講演]
    Optics and Photonics Japan 2019年12月 口頭発表(一般)
  • 生体組織中に局在する蛍光体の高感度検出  [招待講演]
    西村 吾朗
    第3期第5回「レーザーバイオ医療」技術専門委員会 2019年07月 口頭発表(招待・特別)
  • 生体組織の光学計測  [招待講演]
    西村 吾朗
    「光×質量分析」の可能性 2019年03月 ポスター発表
  • Goro Nishimura
    A3 Workshop in Applied Inverse Problems 2019年01月 口頭発表(招待・特別)
  • 医療応用のための近赤外蛍光プローブの高感度検出  [通常講演]
    西村 吾朗
    第34回近赤外フォーラム 2018年11月 口頭発表(一般)
  • 生体組織中にある蛍光ターゲットの高感度検出 (2)  [通常講演]
    西村 吾朗
    Optics and Photonics Japan 2018 2018年10月 口頭発表(一般)
  • Time-Domain Optical Tomography For Fluorescence Objects  [招待講演]
    西村 吾朗
    Tianyuan Workshop on Mathematical and Computational Challenges of Medical Imaging and Inverse Problems 2018年08月 シンポジウム・ワークショップパネル(指名)
  • 組織深部拡散蛍光トモグラフィー:時間領域からのアプローチ  [招待講演]
    西村 吾朗
    第37回日本医用画像工学会大会 2018年07月 口頭発表(招待・特別)
  • Fluorescence Image Contrast Improvement by a Time-domain Method  [通常講演]
    西村 吾朗
    2018 OSA Biophotonics Congress: Biomedical Optics 2018年04月 ポスター発表
  • Optical tomography for near-infrared fluorescence imaging  [招待講演]
    西村 吾朗
    Inverse problems and medical imaging 2018年02月 シンポジウム・ワークショップパネル(公募)
  • Diffuse Correlation Spectroscopy: Analysis of Moving Particles  [招待講演]
    西村 吾朗
    Inverse problems and medical imaging 2018年02月 シンポジウム・ワークショップパネル(公募)
  • 散乱光の時間応答関数と入射出射ジオメトリ  [招待講演]
    西村 吾朗
    輸送理論と生体医用光学 2018年02月 シンポジウム・ワークショップパネル(公募)
  • メロンにおける光学特性値算出と光伝搬モデルによる数値解析  [通常講演]
    服部 聖仁, 藤井 宏之, 西村 吾朗, 小林 一道, 渡部 正夫
    第31回近赤外フォーラム 2017年11月 口頭発表(一般)
  • 生体組織中にある蛍光ターゲットの高感度検出  [通常講演]
    西村 吾朗
    Optics and Photonics Japan 2017 2017年10月 ポスター発表
  • Aspiration Risk Detection Using Oral Administratio n of Fluorescent Food -- Preliminary Experiments Using Meat Phantoms  [通常講演]
    SUZUKI T, SAITO R, KITADA N, KOIKE T, MAKI S, MICHIWAKI Y, NISHIMURA G, NIWA H, YAMADA Y
    2017 IEE E International Conference on Cyborg and Bionic Systems 2017年10月 ポスター発表
  • Time-domain fluorescence diffuse optical tomography for quantitative imaging of a fluorescence target in deep biological tissue  [通常講演]
    西村 吾朗
    第94回日本生理学会大会 2017年03月 口頭発表(招待・特別)
  • A novel approach for the time-domain fluorescence imaging of a semi-infinite turbid medium: Monte Carlo evaluation  [通常講演]
    PRIETO Kernel, 西村 吾朗
    Bios SPIE Photonics West 2017年01月 口頭発表(一般)
  • Quantitative method to determine the optical properties of melons by the photon diffusion equation  [通常講演]
    HATTORI K, FUJII H, 西村 吾朗, KOBAYASHI K, WATANABE M
    Asian NIR Symposium 2016 2016年11月 口頭発表(一般)
  • Near-infrared optical properties of white bread using the light propagation model  [通常講演]
    FUJII H, 西村 吾朗, HATTORI K, KOBAYASHI K, WATANABE M
    Asian NIR Symposium 2016 2016年11月 ポスター発表
  • 反射型拡散蛍光トモグラフィ ー 半無限媒体中の蛍光ターゲットイメージング  [通常講演]
    PRIETO Kernel, 西村 吾朗
    Optics and Photonics Japan 2016 2016年10月 口頭発表(一般)
  • Optical properties of melons determined by an analysis based on the photon diffusion equation  [通常講演]
    HATTORI K, FUJII H, 西村 吾朗, KOBAYASHI K, WATANABE M
    First Food Chemistry Conference - Shaping the Future of Food Quality, Health and Safety 2016年10月 ポスター発表
  • Near-infrared fluorescence detection and its medical applications  [通常講演]
    西村 吾朗
    The 10th ICME International Conference on Complex Medical Engineering 2016年08月 口頭発表(招待・特別)
  • A new strategy of the time-domain fluorescence imaging for a semi-infinite turbid media  [通常講演]
    PRIETO Kernel, 西村 吾朗
    2nd Biomedical Imaging and Sensing Conference 2016 2016年05月 口頭発表(一般)
  • 拡散干渉計測と時間分解計測の同時測定による散乱体動態解析  [通常講演]
    西村 吾朗
    Optics and Photonics Japan 2015 2015年10月 口頭発表(一般)
  • A novel fluorescence lifetime analysis for in vivo measurements  [通常講演]
    西村 吾朗
    The 14th Conference on Methods and Applications in Fluorescence 2015年09月 ポスター発表
  • Diffuse Optical Tomography - Actual Problems in Reconstruction with Time-domain Data  [招待講演]
    西村 吾朗
    The 9th ICME International Conference on Complex Medical Engineering 2015年06月 口頭発表(招待・特別)
  • Near-infrared fluorescence fluctuation measurement system -- Its design and applications  [通常講演]
    西村 吾朗
    5th Asian and Pacific Rim Symposium on Biophotonics 2015年04月 ポスター発表
  • Study on a reconstuction technique using time domain reflectance measurements data  [通常講演]
    古川 大介, 西村 吾朗
    5th Asian and Pacific Rim Symposium on Biophotonics 2015年04月 口頭発表(一般)
  • ヒト組織深部のイメージングを可能とする定量的蛍光分子イメージング基盤技術の確立  [招待講演]
    西村 吾朗
    第53回日本生体医工学会大会 2014年06月 シンポジウム・ワークショップパネル(指名)
  • Fluorescence decay measurement in tissue-like scattering medium  [通常講演]
    西村 吾朗, 古川 大介, AWASTHI Kamlesh
    OSA Topical meeting Biomedical Optics 2014年04月 ポスター発表
  • 西村 吾朗
    第15回光科学技術で拓く脳・精神科学平和探求研究会 2014年02月 口頭発表(招待・特別)
  • 時間分解法による生体組織計測へ向けて  [招待講演]
    西村 吾朗
    香川大学社会連携・知的財産センター技術協力会 2013年03月 公開講演,セミナー,チュートリアル,講習,講義等
  • 西村 吾朗
    Bios SPIE Photonics West 2013年02月 口頭発表(招待・特別)
  • 散乱体中での蛍光寿命計測  [通常講演]
    西村 吾朗
    日本光学会年次学術講演会 OPJ2012 2012年10月 口頭発表(一般)
  • 蛍光を用いた蛍光物質の吸収の拡散光イメージング ーその考え方と実験データの考察  [通常講演]
    西村 吾朗
    日本光学会年次学術講演会 OPJ2011 2011年11月 口頭発表(一般)
  • 西村 吾朗
    第49回日本生物物理学会年会 2011年09月 口頭発表(一般)
  • 西村 吾朗
    Bios SPIE Photonics West 2011年01月 口頭発表(一般)
  • 時間領域蛍光イメージング -時間応答関数の性質と定量的イメージング  [通常講演]
    西村 吾朗
    日本光学会 (OPJ2010) 2010年11月 口頭発表(一般)
  • 1μm波長域での組織光計測  [通常講演]
    西村 吾朗
    第14回酸素ダイナミクス研究会 2010年09月 シンポジウム・ワークショップパネル(指名)
  • 西村 吾朗, 田村 守
    生物物理 2004年11月
  • 西村 吾朗, 田村 守
    生物物理 2003年08月
  • 益田 晶子, 丑田 公規, 西村 吾朗, 金城 政孝, 田村 守, 越野 広雪, 山下 宏一
    日本物理学会講演概要集 2002年08月
  • 西村 吾朗, 金城 政孝
    生物物理 2000年08月
  • 西村 吾朗, 金城 政孝
    生物物理 1999年09月
  • 西村 吾朗, 金城 政孝
    生物物理 1999年03月 
    Fluorescence correlation spectroscopy (FCS) method has been attractive as an analytical tool, particularly in biophysics and biochemistry, with the recent developments of the method. FCS with confocal optics of microscope and real time correlator equipment achieves analysis of fluorescent species in single molecu1e level from a very small sample area (<1 mm) and volume (〜fl) in almost real time (sec〜min). An application to the analysis of enzymatic reaction in solution with FCS is demonstrated as a basis of the analysis to tackle the problems in vivo. The concept of FCS and future view are also discussed.
  • 西村 吾朗, 金城 政孝
    日本物理学会講演概要集 1999年03月
  • 西村 吾朗, WEITX D.A, YODH A.G
    日本物理学会講演概要集 1998年03月
  • 白 燦基, 西村 吾朗, 金城 政孝, 田村 守, 青木 勝彦, 田口 英樹, 吉田 賢右
    生物物理 1997年09月
  • 白 燦基, 西村 吾朗, 金城 政孝, 青木 勝彦, 田口 英樹, 吉田 賢右
    日本物理学会講演概要集 1997年03月
  • 金城 政孝, 西村 吾朗, 小山 富康
    日本分子生物学会年会プログラム・講演要旨集 1996年08月
  • 西村 吾朗, 金城 政孝
    日本物理学会講演概要集. 秋の分科会 1995年09月
  • 小田元樹, 山下豊, 西村吾朗, 田村守
    応用物理学会学術講演会講演予稿集 1995年08月
  • 西村吾朗, 片山薫, 金城政孝, 田村守
    日本生物物理学会年会講演予稿集 1995年08月
  • 小田元樹, 山下豊, 太田和義, 西村吾朗, 田村守
    応用物理学関係連合講演会講演予稿集 1994年03月
  • 小田元樹, 山下豊, 太田和義, 西村吾朗, 田村守
    応用物理学会学術講演会講演予稿集 1993年09月
  • 脇田 政嘉, 西村 吾朗, 田村 守
    年会講演予稿集 1992年03月
  • 西村 吾朗, 脇田 政嘉, 田村 守
    年会講演予稿集 1992年03月
  • 西村 吾朗, 栗田 厚, 櫛田 孝司
    秋の分科会講演予稿集 1988年09月
  • 西村 吾朗, 栗田 厚, 櫛田 孝司
    年会講演予稿集 1988年03月
  • 西村 吾朗, 櫛田 孝司
    秋の分科会講演予稿集 1987年09月
  • 西村 吾朗, 櫛田 孝司
    秋の分科会講演予稿集 1984年09月

その他活動・業績

特許

  • 特願2017-199471:解析装置、撮像システムおよび解析方法  2017年10月13日
    西村 吾朗, 大舘 暁, 鳥羽 英光, 大滝 桂, 山崎 康子, 菅原 貴光
  • 特願2017-181583:生体検査装置及び生体検査方法  2017年09月21日
    西村 吾朗
  • Arrangement and method to apply diffusing wave spectroscopy to measure the properties of multi-phase systems, as well as the changes terein (AE,AL,AM,AT,AU,AZ,BA,BB,BG,BR,BY,CA,CH,CN,CU,CZ,DE,EE,ES,FL,GB,GD,GB,GH,GM,HR,HU,ID,IL,IN,IS,JP,KE,KG,KP,KR,KZ,・・・
    WO99/51954 Arrangement and method to apply diffusing wave spectroscopy to measure the properties of multi-phase systems, as well as the changes terein (AE,AL,AM,AT,AU,AZ,BA,BB,BG,BR,BY,CA,CH,CN,CU,CZ,DE,EE,ES,FL,GB,GD,GB,GH,GM,HR,HU,ID,IL,IN,IS,JP,KE,KG,KP,KR,KZ,LC,LK,LR,LS,LT,LU,LV,MD,MG,MK,MN,MW,MX,NO,NZ,PL,PT,RO,RU,SD,SE,SG,SI,SK,SL,TJ,TM,TR,TT,US,UG,US,UZ,YN,YU,ZA,ZW)
  • 散乱媒質中における吸光物質の濃度測定方法
    特開平9-33433
  • 散乱媒質内吸光物質の濃度測定方法および装置
    特許第3310390号

共同研究・競争的資金等の研究課題

  • 生体組織内部にある蛍光体の高感度検出を可能とするタイムドメイン蛍光法
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 西村 吾朗, 藤井 宏之
  • 蛍光食品を用いた非侵襲誤嚥検査法の研究開発
    日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2018年06月 -2020年03月 
    代表者 : 山田 幸生, 小池 卓二, 丹羽 治樹, 牧 昌次郎, 西村 吾朗, 道脇 幸博
     
    蛍光食品を用いた非侵襲誤嚥検査法の開発に向けた研究において,ヒトを用いた実験に先立ち,生体模擬試料を用いて予備実験を行い,生体内部の蛍光体からの蛍光検出が可能な蛍光体の深さ,生体表面に接触させる光プローブの照射・検出点間距離の最適化,蛍光体として食品に混入させる薬品(インドシアニングリーン,ICG)の最適な濃度,ICGを混入させる最適な食品などを調べた.具体的には,ヒトの生体組織と近赤外波長域(700 nm ~ 1200 nm)での光学特性が似ていると言われている牛肉のブロックを用い,その中にICGを混入させた牛乳や寒天など(ICG食品)をおよそ0.6 mL含んだカプセルを牛肉ブロック内のある深さに埋め込み,牛肉ブロックの表面に光プローブを接触させて,蛍光強度を計測した.牛肉からも蛍光(自家蛍光)が発生するが,自家蛍光よりもICG食品からの蛍光が強ければ計測可能とし,その結果,光プローブの照射・検出点間距離としては30 mmが最適で深さ25 mm程度までの蛍光が観察可能という結果が得られた.その後,ヒトを用いた実験に対する倫理審査委員会の承認を得たのち,ヒトでの実験を行った.60歳以上の健常高齢者2名を被験者として実験を行い,被験者の頸部に光プローブを接触させながら,ICG牛乳やICG寒天を経口摂取するとその直後から蛍光を計測することができた.また,嚥下内視鏡検査を行いながらおよそ10 mLのICG食品を摂取する実験も行い,咽頭内へのICG食品の滞留と蛍光計測との強い相関を得ることができ,蛍光食品を用いた非侵襲誤嚥検査法の原理を検証することができた.
  • JST:産学共創基礎基盤研究
    研究期間 : 2011年12月 -2017年03月 
    代表者 : 西村 吾朗
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2012年04月 -2015年03月 
    代表者 : 西村 吾朗
     
    組織を透過した散乱光強度ゆらぎ解析による組織診断イメージング技術の確立のために、高時間分解能、多点の光子計数システムを試作し光子相関解析を行った。さらに、定量的なイメージングを行うために、散乱光の時間分解解析と光子相関解析とを同時に出来るシステムを構築した。そのシステムを用いて組織模擬散乱体と生きたラット腹部の計測を行った。その結果、皮膚表面から腹部内部の血流に支配されるゆらぎの計測と同時に血液の吸収などに依存する吸収係数および組織の構築などに依存する散乱係数を決定し画像化することが出来た。この技術をガンなどの病態の評価へと応用することにより新しい光学的診断技術が確立すると考えられる。
  • リアルタイム分光イメージングによる食品の安全性モニタリングおよび通電加熱による高効率殺菌技術の開発
    JST:重点地域研究開発推進プログラム、育成研究
    研究期間 : 2009年04月 -2012年03月 
    代表者 : 澤山 一博
  • 分子イメージング機器研究開発プロジェクト/新規悪性腫瘍分子プローブの基盤技術開発
    NEDO:新規悪性腫瘍分子プローブの基盤技術開発
    研究期間 : 2009年01月 -2010年03月 
    代表者 : 西村 吾朗
  • JST:シーズ発掘試験
    研究期間 : 2007年08月 -2008年03月 
    代表者 : 西村 吾朗
     
    本研究は光学的手法により脳浮腫を早期にモニタ可能とする技術を確立することが目的である。1μmを超える近赤外光領域を利用し浮腫形成を反映する組織の水の吸収および散乱特性を主として時間分解計測法を用いて評価する。これらのために高感度計測法を検討するとともに、小動物モデルを用いた組織の光学特性評価を行う。それにより、実用化に適した波長などの光学測定条件などを決定し、モニタリング手法の基礎技術を確立する。この結果をさらに、今までのMRIと異なるベッドサイドなどでのモニタが可能となるシステムへと展開することができる。
  • 多点同時測定蛍光相関分光装置の試作と細胞内分子間相互作用の解析
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2003年 -2005年 
    代表者 : 金城 政孝, 田村 守, 西村 吾朗, 宮崎 忠昭, 野村 保友, 南波 昭宏
     
    細胞内の微視的な領域、例えば、外界に近い細胞膜の近傍と核に近い深部などや、また個々の小器官、エンドソームや小胞体、ミトコンドリアなどでは、細胞内の位置により、物質の偏りやpH、イオン濃度、また酸素濃度勾配の違いなどを始め、様々な物質の分布の偏りが予想される。細胞内の局所の位置により(空間的に)、また物質の代謝の状態により(時間的)、その内部環境は異なっていることが予想される。そこで本研究は生きた細胞内のダイナミックな分子間相互作用明らかにするために単一分子レベルの高感度で多点同時測定の蛍光相関分装置(Fluorescence Correlation Spectroscopy、FCS)の試作と基礎研究を行う事を目的とした。 本研究課題ではまず試作機を作ることに重点を置き初年度は2色の蛍光が励起できるようにFCCS測定視野を作った。2年度までにその測定視野を最大4ヶ所測定移動して測定可能な装置として稼働することを確認した。さらに最終年度はそのうちの2箇所の測定場所を交互に測定する時間を短縮し、約10ミリ秒まで可能とし、データが取得できることを確認した。 測定対象は当研究室で経験のある、細胞質から核内へ移動して遺伝子の転写調節を行うグルココルチコイドレセプター(GR)を最初の研究対象とした。TPA刺激後に細胞質から核へGRが移動するとともに,FCSで測定された分子数が細胞質では減少,核では増加する過程が観察された。また、さらに、拡散時間の時間的変化、1分子あたりの蛍光強度の変化についても検出、解析を行った。2点同時測定が可能となったので、2点間のシグナルの相関をとることで、空間相互相関法の測定を行なった。 細胞内の物質が移動する場合、その方向性があれば、2点間の場所に相関が出ることが期待でき、新たな測定法ならびに細胞内の解析法の基礎を築いた。
  • 集団分子診断を目指した蛍光相関遺伝子検出システムの開発
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2000年 -2002年 
    代表者 : 金城 政孝, 石館 文善, 野村 保友, 西村 吾朗, 堀 邦夫
     
    特定遺伝子やその遺伝子の発現の検出には、様々な手法の中でもPCR(Polymerase Chain Reaction)やRT-PCR法がよく知られている。申請者等は極微小領域を出入りする蛍光分子の動きに由来する蛍光揺らぎを測定する蛍光相関分光法(Fluorescence Correlation Spectroscopy, FCS)を利用することで、その簡便な検出法の開発を行った。FCSはサブフェムトリットル(10-15L)オーダーの極微小な溶液の中を観察する事でブラウン運動に由来する1分子レベルの蛍光強度の揺らぎを検出し、分子の数や運動を測定する方法である。一本鎖短鎖DNA(プライマー)から二本鎖長鎖DNA(ターゲットDNA)へ長さが長くなる(分子量の増加)と同時にランダムコイル構造から剛直な円柱構造へ変化し、そのため並進拡散定数(ブラウン運動の速さ)が大きく変化する。その速度変化を蛍光相関分光法を用いて簡便に、しかも単一分子レベルの高感度で測定することで標的遺伝子の増幅過程を反応溶液中にて定量することを目的とした。 そのためにこれまでPCRを行う時に、2種類用意するPCRの反応プライマーのうち蛍光標識標識プライマーの量を極端に少なくすることで、FCSに最適なPCR法の確立を行った(FA-PCR法)。 これまでに、装置の試作をおこない、既設のFCS装置の試料台の電動化を行い、96ウェルならびに384ウェルのコントロールが可能な事を示した。装置の改良に重点を置いた。さらに、今年度はこれまで顕微鏡ベースの装置を利用してきたが、半導体レーザーと、顕微鏡レンズを利用することで非常にコンパクトな装置の試作を行い、実証した。 今後の課題としては、2色の蛍光色素を用いることでどの程度まで感度を上昇させることが可能か明らかにする必要がある
  • 燐光プローブを用いた低酸素誘導因子が活性化される細胞内酸素濃度の測定
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2000年 -2001年 
    代表者 : 野村 保友, 西村 吾朗
     
    生体が遺伝子レベルで低酸素に適応するときの細胞内酸素濃度を燐光寿命から明らかにすることを目的にした。平成12年度科学研究費補助金により燐光寿命測定装置の性能は大幅に改善した。安定した燐光寿命を測定でき、その寿命の値は文献値とよく一致した。これを受けて本年度は細胞内酸素濃度と遺伝子レベルの低酸素応答の関係を解析するために、低酸素に対する細胞の応答を詳細に検討した。酸素消費速度は温度を密接な関係があるため、まず密閉型フローセル内の灌流温度を37度に厳密に保てることを確認した。細胞内在の酸素濃度インジケーターとして、低酸素時の細胞内NADHの蛍光強度変化の検出を試みたが、単一細胞からの信号は非常に弱かった。低酸素誘導因子の活性化に伴う核移行を抗体を用いて確実に検出できる条件を検討した。ウェスタンブロツトではコバルト処理により低酸素誘導因子の分子量に相当するバンドが強く現れた。一方、固定した細胞の免疫染色では明確な核移行を確認できず、低酸素誘導因子抗体に適した固定法を検討中である。低酸素負荷が低酸素誘導因子の活性化によって生存へ向かわせるのかあるいはアポトーシスへ向かうのかを検討するために、アポトーシス促進の指標としてBAX遺伝子活性化をRT-PCRで検出できるようにした。今後は燐光寿命測定装置を用いて、培養細胞の細胞内酸素濃度を評価し、低酸素誘導因子の核移行による標的遺伝子活性化を、そのメッセンジャーRNAやタンパクの発現と対応させる予定である。
  • 蛍光相互相関分光法による三重鎖DNA分子間相互作用の解析
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 1999年 -2000年 
    代表者 : 金城 政孝, 西村 吾朗
     
    本研究の目的は分子間相互作用を高感度に検出する蛍光相互相関分光法(Fluorescence Cross Correlation Spectroscopy、FCCS)を用い、蛍光標識二重鎖DNA+蛍光標識オリゴDNAを対象にして、三重鎖DNA生成時の分子間相互作用の特徴を明らかにすることである。これまで我々の開発してきた蛍光相関分光法(FCS)ではその検出は分子の大きさ、分子を球としたときのその半径、そのため2重鎖+1重鎖のように分子量変化が2倍程度の時はFCSの測定パラメータである拡散時間の変化は1.2倍の相違しか検出が期待できない。そこで、発光波長の異なる2種類の蛍光分子の揺らぎの「同時性」を解析することに基づくFCCSを用いて、分子が結合して同時に動く時の、同時に揺らいでいる信号を検出し、それを解析することで三重鎖形成解析のための定量的手法を確立し、安定化機構を明らかにしようとするものである。 FCCSでは2種類の蛍光色素を用いて、それぞれ別のオリゴDNA鎖に結合させて、その蛍光強度の揺らぎを測定する。これまでにRhodamine GreenとCy5の組み合わせが最適であることが分かった。また、相補的な20塩基対、相補的な40塩基対並びに、相補的でない20塩基と40塩基の組み合わせで、それぞれFCCSの測定を行った。その結果、相補的な20塩基並びに40塩基の組み合わせにおいては明確な相互相関の信号が得られ、それぞれ2重鎖の形成率が43%と50%であること、また一方、相補的でない組み合わせでは信号が得られなかった。 一方、DNA結合蛋白質である、Fos、Junとその認識DNA配列の組み合わせを用いたモデル実験では、色素と蛋白もしくはDNAの組み合わせによっては凝集体ができたりして、条件によっては測定が不可能な事があることが分かった。 現在これらの結果をもとに3重鎖形成の過程をFCCSを用いて測定解析を進めている。
  • 単一分子検出法による三重鎖DNAの作用機序の研究
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 1995年 -1996年 
    代表者 : 金城 政孝, 西村 吾朗
     
    [目的]本研究は単一分子検出法の一つである蛍光相関分光法(Fluorescenc Correlation Spectroscopy,FCS)を用いて,溶液中での3重鎖DNAの形成機序の解明を目的とした。このために3重鎖DNAの一つのモデルとして蛍光標識(ロ-ダミン)オリゴT15DNAをプローブとし,ホモプリン:ホモピリジン鎖で形成された2重鎖DNAをターゲットとして,プローブDNAの並進拡散速度の変化から3重鎖生成過程をとらえ、それを用いて3重鎖DNA作用機序の解明を行なおうとしたものである。初年度はFCS法を3重鎖DNAの生成過程の定量化法として確立した。次年度は実際の3重鎖形成過程をFCSを用いて測定を行い,その過程を解析した。 [方法]まず,光標識モノマー(Flu-dUTP)存在下でPCR法を用いる事により,DNA鎖長をコントロールしながら,蛍光標識を導入す方法を開発した。これにより,50塩基対から7000塩基対までの様々の長さのDNAの並進拡散速度を調べる事が可能となった。また,3重鎖DNAの生成過程と比較するために蛍光標識一本鎖DNAが相補的なDNA鎖に結合し2重鎖DNAを生成する過程を解析した。 [結論]FCSで求められた2重鎖DNAの並進拡散速度はDNAを剛体棒状分子として数値計算した結果と非常に良い一致を示した。3重鎖DNAはさらに強固な構造を取ることが考えられるため,FCSを用いて3重鎖DNAの形成過程を解析できる事を明かにした。 3重鎖DNAの生成速度は2重鎖DNAに比較して遅い事,また,2重鎖DNAでは加えたプローブDNAの全量が結合したのに対し,3重鎖DNAでは8割しか結合していないことが分かった。今後,塩基配列を変えたプローブDNAやターゲットDNAを用いてミスマッチの影響を調べて行く予定である。
  • Tissue imaging using near-infrared light

大学運営

委員歴

  • 2013年04月 - 2015年03月   応用物理学会分科会日本光学会   幹事
  • 2009年 - 2010年   日本光学会   幹事   日本光学会
  • 2010年   生物物理学会   分野別専門委員   生物物理学会

社会貢献活動

  • 光で生体組織を見る!
    期間 : 2016年10月25日
    役割 : 講師
    主催者・発行元 : 北海道新聞社
    イベント・番組・新聞雑誌名 : 国民との科学・技術対話
  • 光と生体観察・計測
    期間 : 2015年01月22日 - 2015年01月23日
    役割 : 講師
    主催者・発行元 : 日本光学会
    イベント・番組・新聞雑誌名 : 第51回冬期講習会


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