Comparison of Chromosome Aberration Formation in Human Lymphocytes and Cultured Mouse m5S Cells by 137Cs gamma-rays as Reference Radiation

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	137Cs gamma-rays (Reference radiation for cultured m5S cells)																			□ m5S cells
	Source: GammaCell 40 Exactor
	Material: Cultured mouse m5S cells (G1-arrested stationary phase)
	Dose	No. of	Cells		Aberrations										Distribution of cells with indicated number of aberrations
	(Gy)	cells	Cu	Cs	Tet	Tri	Dic	Rc	Ra	aM	F	del	S	del	Aberr	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
	1.0	300	27	0	0	0	11	0	1	0	20	9	7	7	Dic	289	11
															D+R	288	12
															Del	284	16
															All cs	273	26	1
	2.0	300	38	0	0	0	26	0	1	0	36	10	7	7	Dic	274	26
															D+R	273	27
															Del	285	13	2
															All	262	33	4	1
	3.0	250	70	0	0	0	43	0	4	0	63	21	11	10	Dic	210	37	3
															D+R	207	39	4
															Del	220	29	1
															All	180	63	6	1
	4.0	250	90	0	0	0	70	0	5	0	90	20	19	19	Dic	193	45	11	1
															D+R	189	48	12	1
															Del	215	31	4
															All	160	70	16	4
	5.0	250	116	0	0	0	98	0	7	0	127	34	32	30	Dic	173	60	13	4
															D+R	168	64	14	3	1
															Del	197	42	11
															All	134	73	37	3	2	1
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	Ref:	Endo, S., Hoshi, M., Takada, J., Takatsuji, T., Ejima, Y., Saigusa, S., Tachibana, A. and Sasaki, M. S. (2006) Development, beam characterization and chromosomal effectiveness of X-rays of
		RBC characteristic X-ray generator. J. Radiat. Res., 47:103-112.
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Mouse m5S cells are less sensitive to the induction of chromosome aberrations by ionizing radiation as compared with human lymphocytes. This is not due to the acrocentric nature of mouse chromosomes because interstitialdeletions (Ra and S) are also less frequent. The m5S cells may retain the low susceptibility to chromosome exchange aberrations by radiation which is intrinsic to the mouse embryonic stem cells. This differs from that od human embryonic cells; Human embryonic cells are as sensiive as the adult fibroblasts and peripheral blood lymphocytes. (Sasaki, M. S., Mutation Res., 29:433-448, 1975). Caution must be taken in extrapolating mouse embryonic data to the events in human embryo and vice versa.