Thallium-201(T1-201) kinetics will offer useful information on the interpretation of clinical data. The fractionation principle has been believed to be applicable to the uptake of T1-201 which shows recirculation, but it seems to be applied as approximation. In this paper, the uptake was simulated in the system where T1-201 level of blood leaving the myocardium reaches an equilibrium with that of myocardium at each moment. Fick's principle was used. In this system, the flow rate was found to affect only the early phase of the uptake process. The final level was mostly defined by the blood level of T1-201 and the partition coefficient. The dependency of uptake level on the blood level was found in the two-successive administrations of T1-201. Changes in heart rate or glucose and insulin solution were found to affect the final level of T1-201 uptake. This may mean the possibility of an alteration in the blood-myocardium transport capability, when these interventions were given.

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A mathematical model of the biological immune system is proposed. The model quantitatively simulates the immune response caused by the B cell system. In order to describe the immune system, four parameters are used, i. e., the numbers of antigen, antibody, plasma cells and memory cells.The relations among the four parameters are described in four equations, considering the dynamical properties of immunological cells and on the basis of the clonal selection theory by F. M. Burnet. The T cell-B cell interaction is also included in the model. It is assumed that suppressor T cell controls the duplication time of B cell. The result of computer simulation agreed well with the actual immune response both in primary and secondary responses. The correlation coefficient between the experimental curve and the simulated one is 0.924. As an antigen, DNP-Dx (dinitro-phenol-dextran) is used and IgM (immunoglobulin M) is measured as an antibody, using a laser nephelometer. The peak time of the primary response came on the 11th day, and the peak time of the secondary response came on the 8th day both in the simulated curve and in the experimental curve.
Several points have been noticed from the simulation :
(1) When the ratio between the secondary and the primary responses is below 2, it seems that what is called immunological memory cannot be obtained.
(2) The amount of the antigen has little to do with the response curve within a certain range, and seems to have a role only as a trigger.
(3) The productive factor of the immunological cell plays an important role in changing the ratio of peaks.
(4) The self-collapsing coefficient of the plasma cell is probably 78-80 hours.
(5) The absolute numbers of antibody and plasma cell agree well with the reference values. With these results this model agrees well with the actual immunological phenomenon.

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Mechanical instabilities of canine arterial walls were theoretically analyzed. The unstable conditions of arterial walls were determined on the basis of the solutions of differential equations which described the equilibrium conditions of membrane forces both in the radial and axial directions under the condition of small deformation superimposed on the deformed cylindrical membrane. It was assumed that the blood vessel wall was represented as a cylinder of constant thin wall-thickness and of circular cross section, and also was composed of homogeneous, isotropic, incompressible material.
With canine abdominal aorta, common carotid and femoral arteries having normal tissue properties the unstable conditions never emerged. However, when the mechanical properties of the tissue were changed and it became more deformable, the likelihood of the cylindrical vessel having unstable conditions and of inducing the blow-out phenomena or vibration of the wall could be presumed. This unstable conditions depended also on the aspect ratio of the cylinder, i. e., the ratio of length to the radius. The mechanism described above was proposed as a new theory on the formation of abdominal aortic aneurysm. In view of the experimental evidence reported by Newman et al. to the effect that the incremental elastic modulus of aortic tissues of atherosclerotic cockrels had much lower values than normal ones in the early stages of atherogenesis, it could be pointed out that the elastic modulus was a dominant factor in early atherogenesis and that the localized dilatation of abdominal aorta might have occurred by the mechanical instability of aortic tissue if the elastic modulus fell to the level lower than some critical value in this early stage.

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Using the thermograph and other instruments, a new and noninvasive method of evaluating the skin blood flow rate has been developed. Supply of heat to the skin depends on heat transportation by blood flow, on conduction from deep tissue and on the metabolic production in the skin. On the other hand, the skin loses the heat to surroundings through radiation, evaporation and convection. The heat in each case can be expressed as a function of temperature. In a comfortably air-conditioned room, there is little change in the skin temperature. Therefore, the heat flowing into the skin is presumed to equilibrate the heat flowing out. Rearranging these equations, the formula for the skin blood flow rate is obtained. For calculation, skin temperature, core temperature, ambient temperature and diameter of the leg were measured and other figures were postulated on the basis of anatomical or physiological data. Skin temperature was measured using a thermograph. Core temperature was measured by the use of deep body thermometer. Both procedures are noninvasive. Six points in a patient were subjected to the measurement. These included 10cm above the knee, 10cm below the knee and dorsum of the foot on each limb.
The skin blood flow rates calculated by this method were found to be15.0±9.7ml/1009/min (n=88) on the thigh, 14.5±10ml/100g/min (n=85) on the leg and 13.3±11.0ml/100g/min (n=87) on the foot. These values corresponded well with the values reported by others, who used the plethysmographic or clearance method. The relationship between skin temperature and skin blood flow was exponential as has been pointed out by Montogomery and others. After unilateral lumbar sympathectomy in thirteen cases, the skin blood flow rate and the skin temperature on the side operated on showed statistically higher values than on the side not operated on. Especially the skin blood flow rate on the foot was higher by 50%. This fact was also compatible with previous studies on the effects of sympathectomy.
As a. result, this noninvasive method of evaluating the skin blood flow is practically acceptable and will be a new addition to diagnostic armamentarium for various diseases.

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