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Biomedical subjects

T Ichikawa

Publications and source records attributed to T Ichikawa.

At least 667 records · Page 37Linked to original sources
PubMed1976

[Experimental and clinical studies on the accuracy of geometry-independent counter].

For the purpose to conduct precise geometry-independent radioassay of large biological samples, the authors constructed an apparatus with the "peak+scatter" counting method slightly modified from that of Gibbs, et al. and studied its accuracy from the basic and clinical aspects. The apparatus, an opposed-head counter, consisted of two matched 2 x 2-in. NaI crystal detectors and photomultipliers that were connected in parallel to a pulse-height spectrometer. The crystal faces were separated by 54 cm. The detectors were enclosed in 5cm-thick shield built with lead and the sample chamber was a 15 cubic cm-box type of 3 mm-thick Lucite. A 13 cmphiX7.7 cm styrene topper container was used for the sample container. It was found that the relation of primary gamma energy of six radioisotopes and geometry-independent counting threshold turned out to be linear. The assay accuracy with 131I was about +/- 5% in fluid samples irrespective of its sizes (up to 500 ml) or homogeneity. In solid samples the accuracy approached that of fluid by the addition of water up to the height of it. The range, in which the activity could be measured within 5% error originating from statistical fluctuations or loss of counts due to instrument dead time, proved to be about 34 approximately .06 micronCi with 57Co in assay time of 10 min. On the basis of the basic investigations, the geometry-independent counting was used for the radioassay of stool and urine. Since the assay could be done simply up to a relatively large volume without need of material adjustment, it served well in the assay of urine and stool of clinical practice as well as in animal radioassay.

Evaluation Studies as Topic↗
PubMed1975

Characteristics of thermoluminescence bands of intact leaves and isolated chloroplasts in relation to the water-splitting activity in photosynthesis.

Plant materials (intact leaves, chloroplasts or subchloroplast particles) pre-illuminated at a low temperature (e.g. -60 degrees C) were rapidly cooled to -196 degrees C and then the luminescence emitted from the sample on raising the temperature was measured as a function of temperature, by means of a sensitive photo-electron counting technique. Mature spinach leaves showed five luminescence bands at different temperatures which were denoted as ZV, A, B1, B2 and C bands. The A, B1, B2 and C bands appeared at constant temperatures, -10, +25, +40 and +55 degrees C, respectively, being independent of the illumination temperature, but the ZV band appeared at a variable temperature slightly higher than the illumination temperature. The B1 and B2 bands were absent in the thermoluminescence profiles of samples devoid of the oxygen-evolving activity, such as heat-treated spinach leaves, wheat leaves greened under intermittent illumination and photosystem-II particles prepared with Triton X-100. It was deduced that these luminescence bands arise from the energy stored by the electron flow in photosystem II to evolve oxygen, and other bands were ascribed to charge-separation in some other sites not related to the oxygen evolving system.

Chloroplasts↗
PubMed1975

Occurrence of phosphorylserine in the spore coat of Bacillus subtilis NRRL B558.

Phosphorylserine was isolated from the spores of Bacillus subtilis NRRL B 558. This phosphorylated amino acid was only found in the spore coat protein and was not detectable in vegetative cells. The compound was characteristically synthesized at a late stage of sporulation and its turnover did not occur until the completion of mature spore formation. The protein which contains phosphorylserine was not solubilized from the spore coat by digestion with pronase or treatment with any detergents.

Bacillus subtilis↗
PubMed1974

Deficiencies or excesses of metabolites interfering with differentiation.

Auxotrophic mutants of Bacillus subtilis need much higher concentrations of the required adenine, nicotinic acid, riboflavin, thiamine, or tryptophan for optimal sporulation than for maximal growth. Acetate can partially replace thiamine, indicating the importance of the pyruvate dehydrogenase system for differentiation. A glycerol-requiring mutant can sporulate only if its cells contain a small concentration of L-alpha-glycerol phosphate during development. This can best be achieved by excess (>/=5 mM) of extracellular alpha-glycerol phosphate, which enters B. subtilis very slowly. The results show that both biosynthetic and catabolic enzymes are often needed to maintain the precise balance of metabolites required for differentiation. Mutants unable to catabolize fructose 6-phosphate, glucose 6-phosphate, or alpha-glycerol phosphate do not sporulate as long as these compounds accumulate inside the cells; their development is blocked before prespore septa have formed.

Bacillus subtilis↗