Basics of Biodosimetry
Part 2
Lecture
Module 3
IAEA
International Atomic Energy Agency
What aberrations do we analyse
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Dicentrics (and rings)
Micronuclei in binucleate cells
Translocations by the FISH method
Fragments and rings in prematurely
condensed chromosomes
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The dicentric
F
D
A dicentric and its fragment
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Essential features
Dicentric
• Most experience – the ‘gold standard’
• Ideal for use soon after the accident
• Needs 48h cultures
• Needs skill in analysis
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The centric ring
R
D
R
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Essential features
Centric ring
• Seen in the dicentric preparations
• Induced too rarely to be used alone as a
biodosemeter
• Can be combined with the dicentrics during
analysis
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The micronucleus
Binucleate cells with zero, one and two micronuclei
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Essential features
Micronucleus
• Needs 72h cultures
• Less skill required in analysis
• Faster analysis than dicentric
• Not so accurate at low doses as dicentric
• Unless combined with FISH centromere probe
but slower and more expensive slide processing
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The translocation
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A reciprocal translocation
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Essential features
Translocation
• Better for older exposures
• Better for delayed discovery high doses
• Needs 48h cultures
• More expensive than dicentric
• Slide processing more complicated
• Needs skill in analysis
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Premature Chromosome Condensation
(PCC)
Purpose: To cause the chromosomes to
condense at stages of the cell cycle when
the chromatin is normally diffuse.
Why: Because aberrations can only be
observed in the condensed state
How: Two methods:
• fusion to a mitotic cell
• chemically induced
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Fusion PCC
The condensed human chromosomes are single stranded
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Fusion PCC
Stained to highlight centromeres and thus dicentrics
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Essential features
Fusion PCC
• Very rapid- results ready in ~5h from receipt
of sample
• No culturing needed
• Technically difficult
• Needs skill in analysis
• Images can be equivocal
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PCC rings
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Essential features
PCC ring
• Needs culturing
• Technically as easy as the dicentric
• Suited for exceptionally high doses >10 Gy
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Summary of the assays
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Blood sampling for biodosimetry (1)
Basics:
• A 10ml blood sample
• In lithium heparin anticoagulant
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Blood sampling for biodosimetry (2)
Timing:
• 24 hours after the exposure is best
• If later, as soon as possible
• Before any confounding treatments such as
transfusion
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Blood sampling for biodosimetry (3)
Transporting blood:
• Transit times of 2-3 days are OK
• Avoid excessive temperatures during transit
• Avoid security x-rays during transit
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Blood sampling for biodosimetry (4)
Packaging:
• Blood is considered as a bio-hazard
• National regulations may apply for mailing
• International regulations exist for air
transport
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Blood sampling for biodosimetry (5)
Packaging that
conforms to the UN
regulations is available
commercially
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Blood sampling for biodosimetry (6)
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Conclusions
This lecture has introduced:
• Various types of aberrations that are used for
biodosimetry
• will be addressed more fully later in the course
• Essential features of different aberration assays
• Correct blood samples needed for biodosimetry
• Packaging requirements for transporting blood
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