Fibroblasts from ataxia telangiectasia (AT) and AT heterozygotes show an enhanced level of residual DNA double-strand breaks after low dose-rate gamma-irradiation as assayed by pulsed field gel electrophoresis. 1991

D Blöcher, and D Sigut, and M A Hannan
Biomedical Physics Department, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.

Skin fibroblasts from ataxia telangiectasia (AT) patients, obligate AT heterozygotes (ATH) and normal individuals were studied for colony-forming ability and repair of DNA double-strand breaks (dsb) after gamma-irradiation. AT cells were three to four times more radiosensitive than normal cells at high and low dose-rate exposures; ATH cells, however, showed a marginally increased radiosensitivity after high dose-rate gamma-irradiation and an intermediate response after low dose-rate exposure. The repair of DNA dsb was studied by pulsed field gel electrophoresis. After high dose-rate gamma-irradiation the repair time constant (t1/2) was around 1 h for normal, ATH and AT cells. After low dose-rate gamma-irradiation the fraction of residual dsb was 1.4% for normal, 2.1% for ATH and 5.2% for AT cells, demonstrating a deficiency in the repair of a small fraction of dsb in AT. Thus the fraction of residual dsb after low dose-rate exposure was not only four times higher in AT than in normal cells, but was also significantly increased in ATH compared to normal cells.

UI MeSH Term Description Entries
D002470 Cell Survival The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability. Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D003037 Cobalt Radioisotopes Unstable isotopes of cobalt that decay or disintegrate emitting radiation. Co atoms with atomic weights of 54-64, except 59, are radioactive cobalt isotopes. Radioisotopes, Cobalt
D004247 DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D004249 DNA Damage Injuries to DNA that introduce deviations from its normal, intact structure and which may, if left unrepaired, result in a MUTATION or a block of DNA REPLICATION. These deviations may be caused by physical or chemical agents and occur by natural or unnatural, introduced circumstances. They include the introduction of illegitimate bases during replication or by deamination or other modification of bases; the loss of a base from the DNA backbone leaving an abasic site; single-strand breaks; double strand breaks; and intrastrand (PYRIMIDINE DIMERS) or interstrand crosslinking. Damage can often be repaired (DNA REPAIR). If the damage is extensive, it can induce APOPTOSIS. DNA Injury,DNA Lesion,DNA Lesions,Genotoxic Stress,Stress, Genotoxic,Injury, DNA,DNA Injuries
D004260 DNA Repair The removal of DNA LESIONS and/or restoration of intact DNA strands without BASE PAIR MISMATCHES, intrastrand or interstrand crosslinks, or discontinuities in the DNA sugar-phosphate backbones. DNA Damage Response
D004307 Dose-Response Relationship, Radiation The relationship between the dose of administered radiation and the response of the organism or tissue to the radiation. Dose Response Relationship, Radiation,Dose-Response Relationships, Radiation,Radiation Dose-Response Relationship,Radiation Dose-Response Relationships,Relationship, Radiation Dose-Response,Relationships, Radiation Dose-Response
D005347 Fibroblasts Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules. Fibroblast
D005720 Gamma Rays Penetrating, high-energy electromagnetic radiation emitted from atomic nuclei during NUCLEAR DECAY. The range of wavelengths of emitted radiation is between 0.1 - 100 pm which overlaps the shorter, more energetic hard X-RAYS wavelengths. The distinction between gamma rays and X-rays is based on their radiation source. Gamma Wave,Gamma Radiation,Nuclear X-Rays,Radiation, Gamma,X-Rays, Nuclear,Gamma Radiations,Gamma Ray,Gamma Waves,Nuclear X Rays,Nuclear X-Ray,Ray, Gamma,Wave, Gamma,Waves, Gamma,X Rays, Nuclear,X-Ray, Nuclear
D006579 Heterozygote An individual having different alleles at one or more loci regarding a specific character. Carriers, Genetic,Genetic Carriers,Carrier, Genetic,Genetic Carrier,Heterozygotes
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man

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