| It has been well known for some time that
radiation can induce aberrations in the chromosomes of exposed cells.
The frequency of occurrence of such aberrations increases with radiation
dose, and certain kinds of aberrations persist throughout life,
so the frequency of chromosome aberrations in human blood lymphocytes
can be a useful indicator of the radiation dose received by the
body. The cytogenetics program has studied chromosome aberrations
in a subset of atomic-bomb survivors who participate in the Adult
Health Study via several methods. Classical Giemsa staining
allows one to visualize the chromosomes through a microscope and
can detect about 2/3 of all chromosome aberrations. An extensive
chromosome study using this traditional staining method was also
conducted on about 16,000 children born to A-bomb survivors.
The cytogenetics laboratory now utilizes fluorescence in situ hybridization (FISH) to study the chromosomes of A-bomb survivors. In
a multiple-step process that involves painting the chromosomes different
colors, aberrations become apparent as hybrids of multi-colored chromosomes
are detected. The FISH technique has enabled a more accurate and rapid
identification of chromosomal aberrations than previous methods employed.
Although not a cytogenetics technique, electron spin resonance (ESR)
in tooth enamel has been used as another indicator of radiation
exposure. An ESR detector was installed in the cytogenetics laboratory
in 1995 and has been used to examine several hundred tooth samples
donated by A-bomb survivors. ESR is a powerful method for estimating
individual radiation doses and the findings obtained to date corroborate
the A-bomb survivors' chromosome aberration data.