A mathematical model for the contractile mechanism of cardiac muscle hasbeen devised. It consisted of three subsystems; (i) the regulatory mechanism of contraction by Ca²⁺, (ii) the cross-bridge cycle coupled with actin-myosin interaction and (iii) dynamics of contraction. Most parameters of the model were determined from the experimental data obtained in the tetanic contraction of frog's ventricular muscle at 20°C, such as force-velocity-load, internal load-velocity, tension-length and tension-pCa relations, but several were estimated by simulation techniques. Time courses of isometric twitch tension under different physiological conditions were calculated by the model with a digital computer, and the calculated curves showed satisfactory agreement with the experimental ones. It is concluded that this model can explain the inotropic effects of adrenaline and extracellular Ca²⁺ as well as the effects of muscle length and action potential duration on tension curve.

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This paper describes a new multi-microelectrodes system which has been developed to measure simultaneously the activities of adjacent neurons constituting local neural networks of the brain. This multi-microelectrodes system aims at 'the following features : (1) minimization of the brain tissue area occupied by total microelctrodes and possibility of simultaneous recording of single-unit potentials of closely spaced neurons in such a local fine area; (2) clarification of the recording locations of microelectrodes in measuring the activities of neurons; (3) possibility of independent and parallel driving of each microelectrode into the brain.
To accomplish all these features, it is necessary to find a solution to satisfy the following antinomy requirements : that is, shaping an electrode wire into much finer structure and also improving the structural strength of an electrode wire. To solve these problems, the architecture of our new type of multi-microelectrodes is as follows : (1) reinforcement of the structural strength of a microelectrode by means of coupling the set of microelectrodes tightly to each other; (2) magnetical coupling of adjacent microelectrodes so that each of them can be driven independently.
Especially, as a microelectrode material, a platinum-cobalt alloy wire is used from the fine structural workability and excellent magnetical characteristic points of view. In addition to the description of the structural features of multi-microelectrodes, this paper also deals with several newly developed techniques concerned with the microelectrode fabrication : (1) thermal processing of Pt-Co alloy to achieve excellent magnetical characteristics; (2) electrolytic polishing method to taper a Pt-Co alloy wire tip; (3) coating method of the thin and strong electrical insulation layer on a microelectrode; (4) excoriation processing of the fine insulation layer on the tip by heating the microelectrode tip; (5) multi-dimensional micromanipulator for the independent penetration of each microelectrode.

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Two fan beam reconstruction algorithms were compared by computer simulations. One of these algorithms was proposed by Herman et al. and is called here a direct method because of direct use of the convolution method. The other is an improved version of the fan beam method achieved by rearranging fan beam data into parallel beam data. It is called here an interpolation method since it obtains parallel beam data from fan beam data by interpolation. Reconstruction errors, noise propagations and resolutions of two methods were considered. It was concluded that the two methods had their merits and demerits respectively, and though they were somewhat inferior to the parallel algorithms, they were applicable to actual CT-scanners.

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An experimental approach was made in an attempt to achieve a rational system in which the clinical decision-making could be formulated. Using a model physicians diagnose any one of four possible pancreatic diseases using the results of four clinical special tests and select one of five available treatments. The difference of utility of undesirability and that of life expectancy between the treatment and non-treatment were added for all the probable results, and an “expected utility” was obtained by multiplying the sum by the occurring probabilities of the results. Then the “mean expected gain” which was obtained by multiplying the expected utility of a patient by a posteriori probability of a disease was used for the selection of an optimal treatment for a patient. Satisfactory coincidence between a treatment recommended from the model and that employed effectively in the actual clinical management was certified. Utilization of personal probability and evaluation of utility were very useful in the clinical decision analysis.

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In this paper, a procedure for recognizing blood vessel shadows (VSL) in the lung in the chest photofluorograms is presented together with experimental results.
The construction of the presented procedure is basically the same as that which was used in the software $ystem for automated interpretation of chest roentgenograms AISCR-V 2 developed previously by the authors' group. This procedure consists of three steps; (1) extraction of candidate components, (2) calculation of features and (3) classification. In the first step, the second order differential linear filter is applied to the digitized input picture. Connected components are extracted from the filter output by the threshold operation. In the second step, five features about the position, the area, and the average density are measured from each connected' component. Components, of which the feature values are far from those admissible as VSL's, are eliminated. The remaining components are considered as candidates for VSL s. In the last step, candidates of VSL's are classified into VSL and others using linear discriminant functions which were designed by an iterative learning procedure based upon the training sample set. The procedure was applied to thirty-seven chest photofluorograms taken in mass screening, and all of main parts and about, 82% of smaller, parts of vessel images were recognized correctly. By adding this procedure to the previous system AISCR-V 2, it becomes possible for the first time to construct the automated pattern recognition system of chest, photofluorograms which makes it possible to recognize all of three major component patterns-heart, ribs and vessels.

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