Narrow Results

Priming X-irradiation with 0.3-0.5 Gy induces radio-resistance in C57BL/6 strain of mice 2 weeks afterward. Elements in the bone marrow, sampled 11 days after challenging exposure to 5.0 Gy, were determined by PIXE. The challenging irradiation decreased Mg, P, S, K, Ca and Zn as well as dried bone marrow weight. The pre-irradiation enhanced recovery of these levels, indicating stimulated recovery of the metabolism in the tissue. Fe in both control (without pre-irradiation) and experimental groups increased to about twice the original value, showing elevated hemoglobin synthesis after challenging exposure. In previous studies we have reported that recovery of peripheral blood cell counts after sub-lethal irradiation was enhanced by the pre-irradiation. Further, study on accumulation of p53 and Bax proteins, which lead to apoptotic cell death, revealed that the pre-irradiation significantly suppressed accumulation of these proteins in the spleen after challenging irradiation with 3 Gy. These results and our present study suggest that the pre-irradiation decreased the spleen cell death, and favored re-growth of the spleen cells, resulting in stimulated recovery of metabolism for hematopoiesis in the bone marrow as well as in the spleen after challenging high dose irradiation. Stimulated recovery of Mg, P, S, K, Ca and Zn levels might indicate the importance of these elements in hematopoiesis.

Balance of essential elements in organisms is possibly changed by environmental stresses. Small toleost fish, Medaka, was burdened with X-ray irradiation (total dose: 17Gy) and salty water (70% NaCl of sea water). These stresses are not lethal dose. Essential elements in various organs in the fish were. measured by PIXE method and compared with a control fish to determine the effect of two types of the burdens in the elemental contents. Fe, Cu, Zn and Mn are examined in brain, eye, liver, ovary, spleen and intestine. In the liver and spleen, the contents of these elements in stressed fishes are higher than in the control fish. The change of the contents of the elements in brain was small in both cases of X-ray and salty water. It is provided that the balance shift of essential elements occurred in Medaka with the stresses can be observed using PIXE method.

It is not only important for maintenance and improvement of health, but also indispensable for diagnosis and remedy of diseases to make inquiries into the biological defence mechanisms. Yonezawa et al. came across an induction of yet unknown defence mechanism(s) in mice which acquired radioresistance two weeks after low dose X-irradiation with 0.5 Gy. The 30-day survival rate after midlethal X-irradiation of the mice significantly increased by the pre-irradiation, but contrary to the common knowledge on radiation protection, recovery of the blood cell counts of thrombocytes, leukocytes and erythrocytes were not stimulated by the pre-irradiation. This study was planned to find some keys to elucidate the mechanism for the acquired radioresistance. Metal ions are well known to be important for enzyme activities as well as for metabolisms. Eleven elements, Cl, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Se and Br were analysed in mice sera by PIXE.

It is important for maintenance and understanding of health to make inquiries into the biological defence mechanisms. Yonezawa et al. came across an induction of yet unknown defence mechanisms in mice which acquired two types of radioresistance (decrease in bone-marrow death rate after midlethal exposure): one occured 2 weeks after preirradiation with 0.3–0.5 Gy and the other 2 months after 0.05–0.10 Gy of X-rays. To elucidate the acquired radioresistance induced after preirradiation with 0.5 Gy (in a shorter time case). recovery of blood cell counts after sublethal irradiation were measured in mice of ICR strain. Contrary to the common knowledge on radiation protection. recovery of blood cell counts of thrombocytes. leukocytes and erythrocytes after sublethal irradiation were not stimulated by the preirradiation. This study was planned to find some keys to elucidate the mechanism for the acquired radioresistance. Eleven elements. Cl. K. Ca. Cr. Mn. Fe. Ni. Cu. Zn. Se and Br. were analysed clearly in mice sera by PIXE.

Pre-irradiation with 0.3-0.5 Gy of X-rays induces radioresistance (decreased bone marrow death) in ICR and C57BL strains of mice 2 weeks afterward. Recovery of blood cell counts of thrombocytes, leukocytes and erythrocytes was enhanced by the pre-irradiation. And the radio-resistance is acquired even in splenectomized C57BL mice. Elements in the bone marrow 11 days after the challenging dose of 5.0 Gy was determined by a PIXE analysis in three groups of mice: intact (with no irradiations), without pre-irradiation (control) and pre-irradiation (experimental) groups. Challenging irradiation decreased Mg, P, S, K, Ca and Zn levels, and the pre-irradiation enhanced the recovery of those levels, i.e. stimulated metabolism in bone marrow of irradiated mice. Increase in Fe in both control and experimental groups would indicate stimulated hemoglobin synthesis after challenging irradiation.