Biomedical subjects
Publications and source records attributed to S Tanada.
The CT findings in a case of calcified gastric carcinoma of the mucin-producing type are described. These findings include localized thickening of the gastric wall and multiple tiny calcific nodules within it.
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Cerebral perfusion images were investigated in patients with carotid artery occlusion, using single photon emission computed tomography with the infusion of krypton-81m into the internal, common carotid and vertebral arteries. The contribution of the circle of Willis and cerebral cortical anastomoses to the maintenance of adequate blood supply into the involved hemisphere was analysed. It was concluded that the cerebral perfusion image is superior to angiography in evaluating collateral circulation, and in the case of carotid occlusion, the circle of Willis is important in preventing infarction in the territory of the perforating arteries, while the cerebral cortex mainly receives its blood supply through the cortical leptomeningeal anastomoses, illustrating the major role of the leptomeningeal anastomosis as a collateral channel.
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Selective arteriographic infusion of krypton-81m was used to obtain cerebral single photon emission computed tomograms. These were then superimposed on X-ray computed tomograms to assess topographically the perfusion of the entire brain. This method enhances the detecting capability for abnormal perfusion areas and has been used in 21 patients with various brain diseases.
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The effect of electrical stimulation on hypothalamic nuclei was studied by using a stereotaxic operation and in vitro bioassay of luteinizing hormone (LH) in the macaca fuscata. The results were as follows: The serum LH level was increased when the arcuate nucleus or the ventromedial nucleus was stimulated at 250 mu A and 500 mu A. The serum LH level was not increased when the paraventricular nucleus or supraoptic nucleus was stimulated at 250 mu A and 500 mu A. When the medial preoptic nucleus was stimulated at 250 mu A, the serum LH level was not increased. However, the stimulation of 500 mu A increased the serum LH level. The stimulation of the lateral preoptic nucleus did not increase the serum LH at 250 mu A and 500 mu A. The half lives of LH were 35.4 min., 33.4 min., 48.4 min., 43.1 min. These results were different from the half life of human LH. The contribution of various hypothalamic nuclei to the release of LH was discussed.
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The present investigation was undertaken to see to what extent the alpha-amino group of the amino acid, the side chain of the amino acid of aminoacyl-tRNA, and the tRNA structure are involved in determining the affinity of aminoacyl-tRNA for bacterial elongation factor Tu-GTP complex. Various aminoacyl-tRNAs, mis-aminoacylated tRNAs, and formylated aminoacyl-tRNAs were prepared, and the dissociation constants of the ternary complexes of aminoacyl-tRNA with ET-Tu: GTP were determined by the RNase-resistance assay. The results indicated that the free amino-acid group of the amino acids in aminoacyl-tRNA is strongly required for binding with EF-Tu : GTP. In this concentration, the biological significance of formylation for Met-tRNAMetf species is discussed.
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Jekowsky et al. reported recently that elongation factor Tu:GTP complex from Escherichia coli protected aminoacyl-tRNA from digestion by pancreatic RNase (I). On the basis of their finding, we have developed the "RNase-resistance assay" for determination of the dissociation constant of aminoacyl-tRNA from aminoacyl-tRNA:EF-Tu:GTP complex. By the use of this sensitive assay, the dissociation constants were estimated to be 3.6 x 10(-7) M for Ala-tRNA1Ala (Torulopsis utilis), 7.9 x 10(-8) M for Phe-tRNAPhe (Escherichia coli), 8.1 x 10(-7) M for initiator Met-tRNAfMet (Escherichia coli), and 5.4 x 10(-6) M for Gly-tRNA1Gly (Staphylococcus epidermidis) participating in cell wall biosynthesis. Moreover, using a relatively large amount of EF-Tu:GTP, we have been able to detect the ternary complexes of initiator Met-tRNAfMet and Gly-tRNA1Gly with EF-Tu:GTP even by the method of gel filtration.
Effects of physical stimulus and psychic stimulus on the galvanic skin response (GSR) in rats were evaluated. A significant change in the GSR was observed after exposing the rat to the noise of hand-clapping, and introducing another rat into the cage. The latter stimulus had a much greater effect than the former. Changes in GSR were measured after various animals were introduced into the test cage. A shift in the GSR in intrusion of guinea pig or rabbit was significantly greater than that in intrusion of Wistar rat, but no difference was observed in intrusion of rat and mouse. Changes in GSR were studied by introducing another animal into the test cage containing a single rat (isolated state) or a pair of rats (grouped state). The change in the GSR in the grouped state was generally smaller than that in the isolated state, but there was no difference in the score between these states when a rabbit was introduced. When the effect of drugs on changing of GSR was investigated, we found that elevation of GSR value, as induced by exogenous stimuli, was inhibited by tranquilizers such as chlorpromazine, carpipramine and diazepam. These tranquilizers in a remarkably small dose had an apparent effect on the psychic, mutual relation in GSR test in rats.
Dissociation constant of aminoacyl-tRNA:EF-Tu:GTP complex into aminoacyl-tRNA and EF-Tu:GTP was estimated by the RNase-resistance assay developed by us. The experimental results showed that EF-Tu:GTP has a high affinity for Met-tRNAfMet (E. coli) and Met-tRNAmMet, but not fMet-tRNAfMet. The process of the formylation for Metm-tRNAfMet may provide a security against incorrect translation at GUG (valine) and UUG (leucine) codons in the elongation step.