長谷川 克也

The human being dynamically and highly controls the head-trunk with redundant mechanical structures to maintain a stable upright standing position that is inherently unstable. The posture control strategies are also affected by the differences in the conditions of sensory inputs. However, it is unclear how the head-trunk segmental properties are altered to respond to situations that require appropriate changes in standing posture control strategies. We used a data-driven approach to conduct a multipoint measurement of head-trunk sway control in a quiet standing position with differences in the conditions of sensory inputs. Healthy young subjects with 22 accelerometers attached to their backs were evaluated for head-trunk vibration during quiet standing under two conditions: one with open eyes and one with closed eyes. The synchronization of the acceleration and the instantaneous phase was then calculated. The results showed that the synchronization of acceleration and instantaneous phase varied depending on the visual condition, and there were some continuous coherent patterns in each condition. Findings were that the structural redundancy of the head-trunk, which is multi-segmental and has a high mass ratio in the whole body, must be adjusted adaptively according to the conditions to stabilize upright standing in human-specific bipeds.

BACKGROUND: During walking, the friction between the foot and the ground surface causes a free moment (FM), which influences the torsional stress on the lower extremity. However, few studies have investigated the FM during natural walking. The main aim of this study was to examine the relationship between the FM and the absolute and relative rotation angles of the foot and pelvis. METHODS: The rotation angles of foot and pelvic were measured in 18 healthy men using a motion capture system. Rotation angles were measured in absolute and relative coordinates as well as in reference to the line connecting the center of pressure (CoP) line under the right and left feet to evaluate the effects of the opposite lower limb on the FM. The absolute and relative rotation angles of the foot and pelvis were entered into forced-entry linear regression models to evaluate the influence on the FM. FINDINGS: Only the relative angle of rotation between the foot and pelvis could explain the prediction equations significantly. In the Pearson's product-moment correlation coefficient, the rotation angles of the foot and pelvis defined using the bilateral CoP points had not significantly correlated with FM. No joint rotation movement was correlated with FM. INTERPRETATION: The torsion of the entire lower extremity should be performed principally through hip internal rotation. When evaluating the FM as a torsional stress, focusing on the rotation of the entire lower extremity, rather than on one segment, is beneficial.

The intracellular positioning of both lysosomes and mitochondria meets the requirements of degradation and energy supply, which are respectively the two major functions for cellular maintenance. The positioning of both lysosomes and mitochondria is apparently affected by the nutrient status of the cells. However, the mechanism coordinating the positioning of the organelles has not been sufficiently elucidated. Lysosome-associated membrane proteins-1 and -2 (LAMP-1 and LAMP-2) are highly glycosylated proteins that are abundant in lysosomal membranes. In the present study, we demonstrated that the siRNA-mediated downregulation of LAMP-1, LAMP-2 or their combination enhanced the perinuclear localization of mitochondria, in the pre-osteoblastic cell line MC3T3-E1. On the other hand, in the osteocytic cell line MLO-Y4, in which both the lysosomes and mitochondria originally accumulate in the perinuclear region and mitochondria also fill dendrites, the effect of siRNA of LAMP-1 or LAMP-2 was barely observed. LAMPs are not directly associated with mitochondria, and there do not seem to be any accessory molecules commonly required to recruit the motor proteins to lysosomes and mitochondria. Our results suggest that LAMPs may regulate the positioning of lysosomes and mitochondria. A possible mechanism involving the indirect and context-dependent action of LAMPs is discussed.

The ability to maintain the body relative to the external environment is important for adaptation to altered gravity. However, the physiological limits for adaptation or the disruption of body orientation are not known. In this study, we analyzed postural changes in mice upon exposure to various low gravities. Male C57BL6/J mice (n = 6) were exposed to various gravity-deceleration conditions by customized parabolic flight-maneuvers targeting the partial-gravity levels of 0.60, 0.30, 0.15 and μ g (<0.001 g). Video recordings of postural responses were analyzed frame-by-frame by high-definition cineradiography and with exact instantaneous values of gravity and jerk. As a result, the coordinated extension of the neck, spine and hindlimbs was observed during the initial phase of gravity deceleration. Joint angles widened to 120%-200% of the reference g level, and the magnitude of the thoracic-curvature stretching was correlated with gravity and jerk, i.e., the gravity deceleration rate. A certain range of jerk facilitated mouse skeletal stretching efficiently, and a jerk of -0.3~-0.4 j (g/s) induced the maximum extension of the thoracic-curvature. The postural response of animals to low gravity may undergo differential regulation by gravity and jerk.

臨床医学において心臓手術などにおける組織・細胞の酸化還元状態を観察すると、手術の継続可否などを判断するのに重要な情報を与える。梗塞や運動などの影響で、生体組織の酸素濃度が低くなるとNADH（reduced nicotinamide adenine dinucleotide,還元型ニコチンアミドアデニンジヌクレオチド）が多く生成される。これまでの研究では励起光として紫外線を照射し、 NADHの蛍光強度を観察することで梗塞部位の確認などがなされてきた。 しかし、NADHの蛍光像を撮像して解析すると、生体組織の酸化還元状態の変化に起因したNADH映像の変化とともに、撮影状況の変化によるアーチファクトも発生し、細胞内の酸素濃度低下といった動的現象を NADHの発する蛍光像により定量的に評価するのは難しい。 そこで本研究では、撮影状態の変化による影響を排除し、心筋細胞のミトコンドリアの酸化還元状態を可視化してその動態観察を可能とするため、NADHの観察とあわせて組織中に酸素が十分な時に多く存在する、FAD（flavin adenine dinucleotide,フラビンアデニンジヌクレオチド）の蛍光像を撮影し、NADHの蛍光強度との比をもとめて画像とした。この方法により心臓細胞中の酸化還元状態を解析することの妥当性を検討した。 NADHとFADの２つの化学種は異なる波長の励起光により蛍光を発する。2つの蛍光像を撮影するには2台のカメラを用いる方法や、波長選択を行う装置を用い1台のカメラにより撮影する方法を用いる方法などがあるが、複数台のカメラによる撮影では光学的視差が解析誤差要因となり、波長選択装置等を用いる場合は機器構成が複雑化する欠点があった。そこで本研究では、１台のカメラにより時分割で2波長の蛍光像を撮像し、これにより得られた情報を動的に画像として提供するシステムを開発した。