DNA Content of Micronuclei in Human Lymphocytes

Abstract

We have calculated the distribution of DNA contents in micronuclei (MN) induced by ionizing radiation in human lymphocytes on two assumptions: the MN arise from acentric chromosome fragments (ACF), and the ACF result from the random breakage and rejoining of chromosomes. Measurements show that about 80 per cent of MN have a DNA content in the range of 0.5-6 per cent of the G1 nucleus. This group is consistent with the model and shows little dependence on radiation dose over the dose range of 0.5-4 Gy, or on lymphocyte culture time, varying from 48 to 76 hours. The MN with DNA content from 6 to 20 per cent of the G1 nucleus are probably the result both of spindle defects and of DNA synthesis in MN.

In vitro micronucleus-centromere assay to detect radiation-damage induced by low doses in human lymphocytes

“…Attem pts to discrim inate betw een M N arising from w hole chrom osom es and acentric fragm en ts include m easurem en t of M N size (Yam am oto andKikuch i 1980, H o È gstedt andKarlsson 1985), C -banding (Verschaeve et al 1988), m easurem ent of D N A content (Pincu et al 1985, Vanderkerken et al 1989, antikinetochore antibody (C REST) staining (D egrassi and Tanzarella 1988, Eastm ond an d Tucker 1989, Fen ech and M orley 1989, Weissenborn an d Streffer 1991, N orppa et al 1993) an d m ore recently in situ hybridization with D N A probes that bind speci® cally to th e centrom eric region s of th e chrom osom es (Becker et al 1990, M iller et al 1992, Salassidis et al 1992, Norppa et al 1993, Surralles et al 1995, H uber et al 1996, M igliore et al 1996. A m inor num ber of radiation-induced M N m ay arise from w hole chrom osom es that lag behind during an aphase due to som e defect at the level of the spindle or the kinetochore protein.…”

A Modified Harlequin Stain For Cell Kinetics

“…While the digitizer's grey level resolution was 4 bits, this was increased to 6 bits by averaging 16 frames per image, yielding about fifty significant grey level values per pixel. Non-uniformity correction was done by creating an optical density image using a flood field obtained from a clear area of the slide (Pincu, 1983). The resulting image was segmented by simple histogram thresholding, and object-boundaries were found by the boundary-chain-code algorithm (Castleman, 1979).…”