Masafumi Yano

Active sliding movement of latex beads coated with skeletal muscle myosin onChara actin bundles

SummaryLatex beads coated with rabbit skeletal muscle myosin were introduced by intracellular perfusion intoChara cells from which the tonoplasts had been removed. Mg · ATP dependent movement of the beads along files ofChara chloroplast layers was observed. The movement was in opposite directions on the two sides of the indifferent line, indicating that the movement was dependent on the polarity of the actin bundles. This suggests that the unknown factor responsible for generating the motive force for cytoplasmic streaming inChara endoplasm is myosin. The advantages of the present experimental system for studying the sliding mechanism of actomyosin are discussed.

Development of extracellular electric pattern around Lepidium roots: its possible role in root growth and gravitropism.

SummaryUsing a vibrating probe technique, four distinct electric patterns around growing cress roots were observed. The growth rate of the root with a particular one of them was apparently faster than that with the others. No direct correlation between the intensity of electric field and the root growth rate could be found. When gravistimulation was applied to the root, the electric pattern changed to be suitable for elongation of the gravitropic curvature. It is probable that change in electric pattern is related to growth of the root under a given environment.

A self-organizing model of walking patterns of insects

It is well known that the motor systems of animals are controlled by a hierarchy consisting of a brain, central pattern generator, and effector organs. An animals walking patterns change depending on its walking velocities, even when it has been decerebrated, which indicates that the walking patterns may, in fact, be generated in the subregions of the neural systems of the central pattern generator and the effector organs. In order to explain the self-organization of the walking pattern in response to changing circumstances, our model incorporates the following ideas: (1) the brain sends only a few commands to the central pattern generator (CPG) which act as constraints to self-organize the walking patterns in the CPG; (2) the neural network of the CPG is composed of oscillating elements such as the KYS oscillator, which has been shown to simulate effectively the diversity of the neural activities; and (3) we have introduced a rule to coordinate leg movement, in which the excitatory and inhibitory interactions among the neurons act to optimize the efficiency of the energy transduction of the effector organs. We describe this mechanism as “the least dissatisfaction for the greatest number of elements”, which is a self-organization rule in the generation of walking patterns. By this rule, each leg tends to share the load as efficiently as possible under any circumstances. Using this self-organizing model, we discuss the control mechanism of walking patterns.

Pattern Recognition Based on Holonic Information Dynamics: Towards Synergetic Computers

One of the most striking features of biosystems, their ability to percept and generate information is in contrast to the properties of conventional machines which only transform information. Conventional pattern recognition machines identify and classify the input information only. Since their ability is limited to strongly restricted situations, they have only deductive but not inductive capacity. This is not the case for biosystems. Biosystems have a high ability of cognition of unknown events. Animals have survived in the long history of biological evolution under severe circumstances, aquiring the ability to see immediately whether an object is food, enemy or indifferent (neither food nor enemy). This is also true even if the object to be proved is new as is frequently seen in the wild world. WITTGENSTEIN pointed out that in cognitive processes input information is interpreted in terms of stored information, “Vorverstandniss” [1]. A similar mechanism has been proposed by MARR for pattern recognition in his book “Vision” [2]. However, no clear explanation has been given to the mechanism of the self-interpretation of input information.

Regulation of myosin sliding alongChara actin bundles by native skeletal muscle tropomyosin

SummaryNative tropomyosin from rabbit skeletal muscle introduced by intracellular perfusion intoChara cells inhibited the cytoplasmic streaming irrespective of the Ca2+ concentration. To find the action site of native tropomyosin inChara, the cytoplasmic streaming was reconstituted by introducing isolated endoplasm into actin donorChara cells from which native endoplasm had been removed. The reconstituted streaming was inhibited by pretreatment of the actin donor cells with native tropomyosin but not by that of the endoplasm, suggesting that the native tropomyosin inhibited the cytoplasmic streaming by binding toChara actin bundles. Staining of the actin bundles with FITC-labeled native tropomyosin also showed that the native tropomyosin could bind to the actin bundles. Streaming reconstituted fromChara actin bundles and skeletal muscle myosin was insensitive to Ca2+, but became sensitive on application of the native tropomyosin.

Relationship between endoplasmic and ectoplasmic oscillations during chemotaxis of Physarum polycephalum

SummaryThe plasmodium ofPhysarum polycephalum usually migrates coordinately as one whole body even in a complicated environment. By measuring oscillation phenomena in endoplasm and ectoplasm separately during chemotactic process, we studied the mechanism of information processing to achieve such a coordination. (1) The interaction between endoplasmic oscillators was long-range, competitive according to the length of period, and fast (18 cm/min). Ectoplasmic one was short-range. (2) After a partial stimulation of attractant to the organism, the period at the stimulated portion decreased first, and a global phase gradient appeared in endoplasm. Then ectoplasm at the non-stimulated portion was entrained to the endoplasmic pattern, and the migration direction at each part changed in accordance with the phase gradient as a whole body. (3) When the endoplasmic interaction was interrupted, the above coordinated response was not observed. These facts suggest that two-layer coupled oscillator system composed of endoplasm and ectoplasm play important roles for such an information integration.

Development of spatio-temporal pattern of Ca2+ on the chemotactic behaviour ofPhysarum plasmodium

SummaryThe development of a spatio-temporal pattern of Ca2+ concentration by a plasmodium ofPhysarum polycephalum during chemotaxis was studied using fura-2. Whenever the cell displayed coordinated migration in one direction as a whole body, a spatiotemporal pattern was established with a characteristic feature along the longitudinal axis. Calcium concentration oscillated with a period of a few minutes within the cell; the mean concentration at the front was higher than that at the rear. When the cell was given an attractant only at the rear end, the mean concentration rose at the site of application with an immediate increase in the frequency of oscillation. First, the change of the frequency is propagated toward the other end and then the mean level of the Ca2+ concentration at the non-stimulated site decreases. As a result, the Ca2+ gradient is reversed along the cell, which then begins to migrate in a coordinated manner in the reverse direction. This study showed that the spatiotemporal pattern of Ca2+ concentration is closely related to information processing for coordinated migration in chemotaxis. The role of the pattern in that process is discussed.

Radular mechanosensory neuron in the buccal ganglia of the terrestrial slug, Incilaria fruhstorferi

A radular mechanosensory neuron, RM, was identified in the buccal ganglia of Incilaria fruhstorferi. Fine neurites ramified bilaterally in the buccal ganglia, and main neurites entered the subradular epithelium via buccal nerve 3 (n3). When the radula was distorted by bending, RM produced an afferent spike which was preceded by an axonic spike recorded at n3. The response of RM to radular distortion was observed even in the absence of Ca2+, which drastically suppressed chemical synaptic interactions. Therefore, RM was concluded to be a primary radular mechanoreceptor.During rhythmic buccal motor activity induced by food or electrical stimulation of the cerebrobuccal connective, RM received excitatory input during the radular retraction phase. In the isolated buccal ganglia connected to the radula via n3s, the afferent spike, which had been evoked by electrical stimulation of the subradular epithelium, was broadened with the phasic excitatory input. Since the afferent spike was also broadened by current injection into the soma, depolarization due to the phasic input may have produced the spike broadening.Spike broadening was also observed during repetitive firing evoked by current injection. The amplitude of the excitatory postsynaptic potential in a follower neuron increased depending on the spike broadening of RM.

Control of feeding rhythm in the terrestrial slug Incilaria bilineata

A modulatory neuron of feeding rhythm was newly identified in the buccal ganglia of the isolated central nervous system (CNS) of the terrestrial slug Incilaria bilineata. This neuron was termed the feeding rhythm modulator (FRM). Its morphological and electrical properties were compared with those of the MGC (metacerebral giant cell, a cerebral modulatory neuron of feeding rhythm). There was no direct connection between FRM and MGC. In order to investigate the control mechanism of the buccal central pattern generator, feeding rhythm was observed by varying the activities of MGC and FRM simultaneously. At a lower level of activity of MGC, feeding rhythm was not only sensitive to the activity of MGC but also to that of FRM. As the level of activity of MGC increased, feeding rhythm was exclusively controlled by the activity of MGC, and became unaffected by the activity of FRM. This indicates that cerebral neurons such as MGC primarily control feeding rhythm and modulate the contribution of FRM in a hierarchical manner.

Ca2+ Regulation of Myosin Sliding Along Characeae Actin Bundles

Internodal cells of Characeae have bundles of actin filaments at the inner surface of the chloroplast layer which are anchored to the gel ectoplasm. It is believed that the motive force for cytoplasmic streaming is generated by the sliding of myosin in the flowing sol endoplasm along these fixed actin bundles. Since heavy meromyosin isolated from skeletal muscle can bind to Characeae actin bundles (Williamson 1974), it was thought that myosin from other organisms may be able to move along the actin bundles. In the present study, wereconstituted the sldding movement of myosin extracted from skeletal muscle, Physarum and scallop and studied Ca2+control of the reconstituted sliding.