We have recently developed a new type of multi-microelectrode system, with which electrical neural activities of adjacent neurons can be simultaneously recorded. To date, we have reported on the architecture and fabrication techniques of this multi-microelectrode system.
In order to synthetically evaluate the characteristics of this multi-microelectrode system and then to clarify its practical availability, this paper deals with the following aspects : (1) electrochemical properties of, Pt-Co alloy used as the microelectrode material; (2) mechanical and electrical properties accompanied with magnetic coupling of each microelectrode; (3) measurement of magnetic field distribution in the vicinity of a fine Pt-Co alloy microelectrode tip; (4) application of a silver sulfide method for high sensitive identification of the locations of multi-microelectrodes in the brain; (5) simultaneous recording of the impulse trains of four adjacent neurons within the columnar neural area of 0.5mm∅×0.2mm in the brain.

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Pressure-flow relationships in the microvasculature of the rat mesentery have been studied by the intravital microscopic technique in order to obtain fundamental hemodynamic data as the basis of microcirculatory mass transfer studies. Two-channel sample hold system for analyzing blood velocity on the monitor TV screen of microscopic images was newly developed.
Forty eight microvessels of 11 rats ranging from 4 to 24 micra in diameter were subjected to the measurement of blood velocity. Results showed that considerably good linear correlation existed between the blood velocity and arterial pressure. The pressure-flow relationships thus obtained from all microvessels were found to be classified into three major groups. Vessels of the first group showed 40 to 50 mmHg of aparent critical closing pressure (CCP). In these microvessels to-and-fro movement of blood flow was observed. The second group showed 5 to 20 mmHg of CCP, as is the case with most true capillaries. The third one showed negative CCP corresponding to the precapillaries or postcapillaries. These findings seem interesting since they suggest that close correlation exists between the functional flow behavior and the morphological dimensions of the microvessels.

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It is well known that when blood flows steadily, the electrical impedance of blood changes from its resting value. The impedance change of flowing blood is principally due to the orientation of red blood cells, if blood flows steadily. However, the effects of pulsatile flow upon the impedance of blood have not yet been discussed. When the blood flow is pulsatory, the electrical impedance of blood varies with time. The following, are discussed :
(1) the impedance waveforms of sinusoidally flowing blood in rectangular conduit,
(2) the relations between the impedance change and the flow rate of both the sinusoidal and the pulsatile flows, and
(3) the relations between the impedance change and the frequency of the various flows. From the results :
(1) it is concluded that the resistance change of blood is mainly caused by the orientation of red blood cells;
(2) the waveform of the resistance change of the sinusoidally flowing blood is similar to the fullwave rectification of sinusoidal flow, because the resistance can only change unidirectionally;
(3) when blood flow is pulsatory, not only the resistance change is pulsatory, but the mean resistance also changes simultaneously, because the orientation of red blood cells can not follow the rapid change of flow, therefore, the pulsatile and the mean resistance changes are affected by both the amplitude and the frequency of pulsatile flow;
(4) the relaxation time of the orientation is about one sixth of a second;
(5) both the pulsatile and the mean resistance changes due to the orientation of red blood cells in aorta are about from 4% to 10%; and
(6) the resistance change due to the orientation of red blood cells in both vein and capillary is much less than that in aorta.

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A very real need has existed for the development of simple, inexpensive, and yet functionally significant gait assessment systems that could be used in clinical practice. This paper describes a new scheme for data processing of the signals from a simple foot-force measuring device previously reported by the authors.
Only vertical forces exerted on the fore-foot and the heel are measured continuously. From these signals, the muscle moment acting on the ankle, and the center of pressure in one foot and in both feet are calculated. Thus, information on the muscle activities at the ankle and on the transfer of body weight in the progressional direction is derived.
A brief description of the mathematical background is given first, and the clinical relevance of this method is discussed with several illustrations of preliminary results on normal and pathological subjects.

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Correlation was studied between the driving energy of a time-varying capacitance model of the left ventricle and cardiac oxygen consumption. The model is known to simulate ventricular pressure-volume dynamics. When the model changes its capacitance from a diastolic to an end-systolic level while ejecting volume against pressure load, it requires energy supply (driving energy) equal to the sum of its external work and the increment in the potential energy. This potential energy increment corresponds theoretically to the specific area in the pressure-volume diagram that is bounded by the end-diastolic and end-systolic curves and the pressure-volume trajectory during isovolumic relaxation. Using data, found in literature and also obtained in my own experiments, I found a close correlation between the ventricular pressure-volume area corresponding to the driving energy and the oxygen consumption in the real heart. The specific pressure-volume area, which can be measured simply by planimetry, seems to be a promising candidate for the practically useful predictor of cardiac oxygen consumption.

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The origin of the difference in cold sensation in response to immersion in various liquids is studied by psychophysical experiment and computer simulation.
The temperature of subjective equality among various liquids during immersion in water, glycerin and alcohol are measured by the method of limits. Further, the rate of decrease of skin temperature during the liquid immersion is measured. The results show a possibility that the difference in the transient change of the skin temperature would be responsible for the difference in the dynamic cold sensation. According to the experimental results, an analog simulator realizing the static and dynamic characteristics of the cutaneous cold receptor to temperature stimulation is constructed. Variations in the receptor temperature and afferent impulse frequencies in response to immersion in water and alcohol at various temperatures are calculated.
As a result of this study, it has been confirmed that the difference in cold sensation, during immersion in various liquids depends on the difference in the decreasing rate of skin temperature.
The results obtained in this study would serve for the analysis of the dynamic characteristics of the human temperature regulatory system.

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Model calculations are presented for several properties of development in the retinotectal projection of amphibians and fishes, using the Gierer-Meinhardt equations. It has been assumed that the connections between retinal and tectal cells were made on the correspondence of positional information which were given by the monotonic function of the specific activator concentration in each cell-array.
The monotonic distributions of the activator and the existence of the critical period were shown by computer simulation, both in the proliferating retina and tectum. Several variances of the retinotectal projection after surgical experiments have also been explained.

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