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鈴木 芳代; 服部 佑哉; 坂下 哲哉; 舟山 知夫; 横田 裕一郎; 池田 裕子; 小林 泰彦
JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 88, 2015/03
The nematode 
is a good 
model system to examine radiation effects on vital functions such as locomotion, feeding, learning and memory. Using , we recently investigated the radiation effects on locomotion (snake-like crawling motion) and found that whole-body irradiation significantly reduced locomotion. Furthermore, we focused on the pharyngeal pumping motion (chewing and swallowing), which is a rapid periodic motion, and found that the proportion of pumping-motion arrest increased after whole-body irradiation. As the next step, we started to examine whether or not the effects observed after whole-body irradiation could be induced by microbeam irradiation to a very limited region. In this report, we summarize the results of microbeam irradiation experiments we carried out in the past few years. Main findings in this study are the following: (1) Effects of the region-specific microbeam irradiation differ depending on types of motion, and (2) effects of whole-body irradiation tend to be more effective than those of the region-specific microbeam irradiation at the same irradiation dose. Further studies on the mechanisms underlying the radiation-induced changes of movements are required.
and simulation of chemotaxis-related information processing in the neural network坂本 一馬*; 曽 智*; 鈴木 芳代; 栗田 雄一*; 辻 敏夫*
Proceedings of SAI Intelligent Systems Conference 2015 (IntelliSys 2015), p.668 - 673, 2015/00
The nematode () is a simple multi-cellular organism consisting of approximately 1,000 cells including 302 neurons, and is the only creature whose connectome has been fully mapped. For these reasons, is ideal for studying information-processing mechanisms embedded in the neural network. This paper proposes a neural network model of with the actual neural structure preserved to simulate the worm's attraction to sodium chloride (NaCl). To implement attractant behavior, the worm's neural network must calculate the temporal and spatial gradients of NaCl concentration; however, the mechanism behind this complex information processing in the worm's neural network has not yet been fully elucidated. As a first step to analyze the information processing mechanism, the parameters of the neural network model were adjusted using the backpropagation through time (BPTT) algorithm, and the neural network model was verified for its ability to generate temporal and spatial gradients. Simulation for neuron ablation experiment was then carried out, and the results exhibited same trends as the biological experiment indicating that our approach can be used to predict the results of biological experiments, and can therefore be used as a tool to provide guidelines for such experiments.
in consideration of whole-body movements曽 智*; 鈴木 芳代; 栗田 雄一*; 辻 敏夫*
Proceedings of SAI Intelligent Systems Conference 2015 (IntelliSys 2015), p.651 - 656, 2015/00
The tiny roundworm () is one of the simplest multicellular organisms known, with a neural circuit consisting of just 302 neurons. Despite its simplicity, the worm can navigate efficiently to the source of a target chemical - a movement known as chemotaxis. Recent studies have revealed that the worm utilizes only two sensory neurons to determine the temporal and spatial gradients of chemical substances for chemotaxis, but its neural computation mechanism is not yet fully understood. The authors propose a mathematical model based on measurement data and neural connection structure to simulate chemotaxis and using a robot simulator platform in order to account for wholebody movements. The simulation results are used as a basis for discussion of how chemical gradients are calculated in neurons.
鈴木 芳代; 坂下 哲哉; 服部 佑哉; 小林 泰彦
no journal, ,
We recently found that whole body irradiation reduced locomotion in , though the mechanisms are not clear. It is well known that free radicals such as OH
and H are produced following exposure of ionizing radiation. The reactions of free radicals cause the production of oxidative stress including hydrogen peroxide (H
O). Oxidative stress is known as an important factor of aging, and may relate to the decrease of motility observed in the aging process. We therefore explored the potential effectiveness of HO in the suppression of 's locomotion. Wild-type animals were exposed to graded doses of HO and the locomotory rate was evaluated. The locomotory rate was significantly decreased in HO-exposed animals, in which the dose response was similar to that in the irradiated animals. We subsequently investigated the radiation effects on the pharyngeal pumping motion (chewing and swallowing) and the involvement of oxidative stress. As a result, the proportion of the pumping-motion arrest significantly increased after whole body irradiation and the pumping-motion arrest was restored within several hours. Furthermore, the response in HO-exposed animals was similar to that in the irradiated animals. These results support the possibility that radiation-induced suppression of both locomotion and pumping motion in was caused by radiation-produced HO.
Ide, Kazunori*; Ishikawa, Tomoya*; Arai, Shingo*; Morioka, Tatsuya*; Kaneda, Hiroki*; 鈴木 芳代; 坂下 哲哉; 石井 直明*; 簗瀬 澄乃*
no journal, ,
Oxidative stress threatens cellular and extracellular targets including lipids, proteins and nucleic acids. As a result, oxidative stress causes or influence apoptosis, degenerative diseases and aging. Not only that, we found an abnormal posture in short-lived mutant such as 
, which is a paraquat (methylviologen)-sensitive strain, exposed to hyperoxia. In this study, we detected the hyperoxia-induced abnormal posture in mutant compared with wild-type N
and long-lived 
strains. 4-day-old animals placed on a NGM agar plate with a fixed bacterial lawn were exposed to hyperoxia (90% of oxygen) overnight. After the exposure, some animals were immediately recorded as digital images with up to 400-fold magnification of the microscope. The images were analyzed using image processing software, Wriggle Tracker and Move-tr/2D, by a previously published method (Hattori et al., 2012). The body line was skeletonized and evenly divided into 12 segments. Subsequently, X- and Y-coordinates of each point on the body were acquired. To evaluate the posture of the body, we introduced a novel standard, namely the "posture index" as the absolute average of the relative angle, 
, between adjacent dividing points. As a result of this investigation, we can not only intuitively but also quantitatively and statistically understand a tendency of the behavior in a short-lived mutant under stressful conditions.
鈴木 芳代; 坂下 哲哉; 服部 佑哉; 小林 泰彦
no journal, ,
動物に対する放射線の影響を理解するには、分子・細胞レベルでの影響解析に加えて、運動機能や学習・記憶といった生命維持に重要な生体機能に着目した個体レベルの影響解析が重要である。我々は、線虫に放射線を全身照射すると、一時的に運動が抑制されることを見出した。しかし、このメカニズムは不明のままである。一般に、放射線照射によってOHやHといったフリーラジカルが産生されることが知られている。これらのフリーラジカル同士が反応することで、過酸化水素のような活性酸素種(ROS)が生成する。そこで、本研究では、放射線による線虫の運動の一時的な抑制における放射線産生ROSの関与を探った。放射線照射によって産生されるROSの一種である過酸化水素を線虫に曝露したところ、放射線照射直後と類似した応答が観られた。本実験の結果は、放射線照射直後の線虫の運動抑制が、過酸化水素をはじめとする放射線産生ROSによって誘因されている可能性を支持する。
鈴木 芳代; 服部 佑哉; 坂下 哲哉; 舟山 知夫; 横田 裕一郎; 小林 泰彦
no journal, ,
Using , we recently investigated the radiation effects, and found that whole-body irradiation significantly reduced locomotion. Furthermore, we found that the proportion of pumping-motion arrest increased after whole-body irradiation. As the next step, we aimed to examine whether or not the effects observed after whole-body irradiation could be induced by region-specific microbeam irradiation. To investigate the effects of region-specific microbeam irradiation, we used energetic carbon ions generated at TIARA (JAEA-Takasaki). To inhibit free motion during irradiation an animal was enclosed in a ditch of a polydimethylsiloxane device with buffer solution. The "head" region, "middle" region, and "tail" region were targeted independently; these regions were irradiated with 12,000 carbon ions. Microbeam irradiation in each region did not decrease locomotion. On the other hand, the proportion of pumping-motion arrest increased only in the head-irradiated animals, suggesting that an increase of the proportion of pumping-motion arrest after whole-body irradiation reflects radiation effects on the head region. Main findings in this study are the following: (1) effects of the region-specific microbeam irradiation differ depending on types of motion, and (2) effects of whole-body irradiation tend to be more effective than those of the region-specific microbeam irradiation at the same irradiation dose.
and analyses of effects on muscular movements鈴木 芳代; 服部 佑哉; 坂下 哲哉; 舟山 知夫; 横田 裕一郎; 小林 泰彦
no journal, ,
We have investigated the radiation effects on muscular movements in . We have so far found that whole-body irradiation significantly reduce locomotion (snake-like crawling motion) and also increase the proportion of individuals who arrest pharyngeal pumping-motion (chewing and swallowing). As the next step of the whole-body irradiation, we aimed to investigate the effects of region-specific microbeam irradiation on muscular movements immediately after irradiation, and developed a novel method for targeting a specific region of without anesthesia. In this method, an animal was enclosed in a ditch of a polydimethylsiloxane device with buffer solution in order to inhibit free motion during irradiation. The "head" region including the pharynx, "middle" region around the vulva and intestine, and "tail" region were targeted independently; these regions were irradiated with 12,000 carbon ions. Main findings are as follows: (1) effects of the region-specific microbeam irradiation differ depending on types of muscular movements, and (2) effects of whole-body irradiation tend to be more effective than those of the region-specific microbeam irradiation at the same dose. Further studies involving the effects of microbeam irradiation on are in progress.
鈴木 芳代; 坂下 哲哉; 服部 佑哉; 小林 泰彦
no journal, ,
Oxidative stress such as hydrogen peroxide (HO) has been identified as one of the important factors in aging, and this may be related to the decrease in motility observed during the aging process. In the present study, we therefore explored the potential effectiveness of HO in the suppression of ' locomotion (crawling). Young adult wild-type animals were exposed to S-basal buffer containing graded doses of HO. Exposure to HO induced reduction of locomotion similar to that observed after whole-body irradiation. To investigate the radiation effects and the involvement of oxidative stress on other types of movement, we subsequently focused on the pharyngeal pumping motion (chewing and swallowing). The proportion of animals in which the pumping motion has stopped immediately after HO exposure increased. This response was similar to that of irradiated animals. These results support the possibility that radiation-induced suppression of both locomotion and pumping motion in was caused by radiation-produced HO. In this presentation, we will give an outline of the radiation effects on and discuss the involvement of the radiation-induced oxidative stress in the phenomena.
服部 佑哉; 鈴木 芳代; 辻 敏夫*; 小林 泰彦
no journal, ,
We proposed a simulation-based approach to estimate the control mechanisms involved in pharyngeal pumping motion in . To conduct the simulations, we previously developed a pharyngeal muscle model including 20 muscular cells and 9 marginal cells. Output in each cell was represented by the membrane potential based on FitzHugh-Nagumo equations. These cells were connected by gap junctions based on the real connection structure of the pharyngeal muscle. The gap junctions transmitted the outputs among the cells. The EPG was used to measure the biological signals from pharyngeal pumping, and the model represented the EPG using the outputs of individual cells. To estimate the signal patterns of certain neurons involved in rhythm control, we virtually input various electrical signals as neuronal signals to muscular cells in the model, and calculated the EPG based on outputs of individual membrane potential models. It was found that some signal patterns induced the EPG, which was similar to what was observed in wild-type . The cycle length of the EPG was synchronized with that of neuronal signals. These results suggest that the neuronal signal could control the rhythm of the pumping motion. Our approach shows potential for elucidating important signal factors (e.g., amplitude and cycle length) involved in the control of the pumping motion.
Matsuda, Sakiyo*; Nitta, Nazuki*; Tamura, Miku*; 鈴木 芳代; 坂下 哲哉; 石井 直明*; 簗瀬 澄乃*
no journal, ,
Oxidative stress threatens cellular constructs including lipids, proteins and nucleic acids. As a result, oxidative stress causes or influence apoptosis, degenerative diseases and aging. Recently, we found an abnormal posture in short-lived mutants such as 
and 
, exposed to hyperoxia. In this study, we detected the hyperoxia-induced abnormal posture in and mutants compared with wild-type N and long-lived 
strains. 4-day-old animals placed on a NGM agar plate with a fixed bacterial lawn were exposed to hyperoxia (90% of oxygen) overnight. After the exposure, some animals were immediately recorded as digital images with up to 400-fold magnification of the microscope. The images were analyzed using image-processing software by a previously published method. To evaluate the posture of the body, we introduced a novel standard, namely the "posture index" as the absolute average of the relative angle between adjacent dividing points. As a result of this investigation, we can not only intuitively but also quantitatively and statistically understand a tendency of the behavior in various postural responses under stressful conditions in the short-lived mutants.
鈴木 芳代; 服部 佑哉; 小林 泰彦
no journal, ,
本研究では、線虫の成虫がなぜ放射線に強いのか?を探るための第一歩として、線虫の放射線応答の基礎データを得ることを目的に、2種類の運動(這行運動及び餌の咀嚼・嚥下運動)に着目して照射影響を調べた。線虫の成虫の全身に放射線(コバルト60-
線または炭素線、0-1.5kGy)を照射すると、這行運動と咀嚼・嚥下運動はいずれも線量依存的に抑制された。この応答は、線照射と炭素線照射の両者で同様であった。さらに、いずれの運動も照射後数時間で回復したことから、これらの照射による運動抑制は放射線に起因した組織の壊死などによる機能不全ではなく、シグナル伝達の一時的な攪乱などによるものであると考えられた。発表では、線虫の放射線応答について紹介すると共に、寿命を指標として放射線の影響が生じる線量の閾値を探るわれわれの最近の試みについても触れる。
