scholarly journals Oxygen Effect in γ-irradiated DNA

1970 ◽  
Vol 25 (11) ◽  
pp. 1264-1268 ◽  
Author(s):  
Christine Lücke-Huhle ◽  
Arnim Braun ◽  
Ulrich Hagen
Keyword(s):  
Double Strand Breaks ◽  
Single Strand ◽  
Oxygen Atmosphere ◽  
Oxygen Effect ◽  
Dna Molecules ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Radiation Induced ◽  
Γ Rays ◽  
Induced Changes

Purified, dry DNA and dry nucleoprotein were irradiated with 60Co-γ-rays under a nitrogen or oxygen atmosphere. The DNA was isolated from the irradiated nucleoprotein. In the DNA the following radiation induced changes were investigated: Double strand breaks, single strand breaks and crosslinks between the DNA molecules. An oxygen effect (OER > 1) was found for all of these events except for crosslinks in irradiated DNA. In the nucleoprotein, the oxygen effect is more marked than in pure DNA.

scholarly journals Radiosensitivities of DNA molecules in lymphocytes from the circulating blood of man

Blood ◽  
1975 ◽  
Vol 45 (4) ◽  
pp. 503-509
Author(s):  
Y Hashimoto ◽  
T Ono ◽  
S Okada
Keyword(s):  
Sucrose Gradient ◽  
Gradient Centrifugation ◽  
Single Strand ◽  
Alkaline Condition ◽  
Transformed Cells ◽  
Dna Molecules ◽  
Strand Breaks ◽  
Sucrose Gradient Centrifugation ◽  
Single Strand Breaks ◽  
Radiation Induced

The radiosensitivities of DNA molecules from lymphocytes of human circulating blood were examined by alkaline sucrose gradient centrifugation. The single-strand breaks of DNA per rad, including the breaks formed under the present alkaline condition, were 1.2 plus or minus 0.1 breaks per 10–12 daltons DNA per rad. When the cells were transformed, the number of breaks was found to increase to 1.8 plus or minus 0.2 breaks per 10–12 daltons DNA per rad. The lymphocytes are capable of rejoining radiation-induced single-strand breaks of DNA. The rate of rejoining was dependent upon types of the suspending medium. The rate increased to ten times of that of the non-transformed cells upon transformation.

scholarly journals Radiosensitivities of DNA molecules in lymphocytes from the circulating blood of man

Blood ◽  
1975 ◽  
Vol 45 (4) ◽  
pp. 503-509 ◽  
Author(s):  
Y Hashimoto ◽  
T Ono ◽  
S Okada
Keyword(s):  
Sucrose Gradient ◽  
Gradient Centrifugation ◽  
Single Strand ◽  
Alkaline Condition ◽  
Transformed Cells ◽  
Dna Molecules ◽  
Strand Breaks ◽  
Sucrose Gradient Centrifugation ◽  
Single Strand Breaks ◽  
Radiation Induced

Abstract The radiosensitivities of DNA molecules from lymphocytes of human circulating blood were examined by alkaline sucrose gradient centrifugation. The single-strand breaks of DNA per rad, including the breaks formed under the present alkaline condition, were 1.2 plus or minus 0.1 breaks per 10–12 daltons DNA per rad. When the cells were transformed, the number of breaks was found to increase to 1.8 plus or minus 0.2 breaks per 10–12 daltons DNA per rad. The lymphocytes are capable of rejoining radiation-induced single-strand breaks of DNA. The rate of rejoining was dependent upon types of the suspending medium. The rate increased to ten times of that of the non-transformed cells upon transformation.

scholarly journals DNA DAMAGE AND REPAIR IN EUKARYOTIC CELLS

Genetics ◽  
1974 ◽  
Vol 78 (1) ◽  
pp. 139-148
Author(s):  
R B Painter
Keyword(s):  
Ionizing Radiation ◽  
Excision Repair ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Premature Aging ◽  
Cross Linking ◽  
Base Damage ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Post Replication Repair

ABSTRACT Damage in DNA after irradiation can be classified into five kinds: base damage, single-strand breaks, double-strand breaks, DNA-DNA cross-linking, and DNA-protein cross-linking. Of these, repair of base damage is the best understood. In eukaryotes, at least three repair systems are known that can deal with base damage: photoreactivation, excision repair, and post-replication repair. Photoreactivation is specific for UV-induced damage and occurs widely throughout the biosphere, although it seems to be absent from placental mammals. Excision repair is present in prokaryotes and in animals but does not seem to be present in plants. Post-replication repair is poorly understood. Recent reports indicate that growing points in mammalian DNA simply skip past UV-induced lesions, leaving gaps in newly made DNA that are subsequently filled in by de novo synthesis. Evidence that this concept is oversimplified or incorrect is presented.—Single-strand breaks are induced by ionizing radiation but most cells can rapidly repair most or all of them, even after supralethal doses. The chemistry of the fragments formed when breaks are induced by ionizing radiation is complex and poorly understood. Therefore, the intermediate steps in the repair of single-strand breaks are unknown. Double-strand breaks and the two kinds of cross-linking have been studied very little and almost nothing is known about their mechanisms for repair.—The role of mammalian DNA repair in mutations is not known. Although there is evidence that defective repair can lead to cancer and/or premature aging in humans, the relationship between the molecular defects and the diseased state remains obscure.

Matching of single-strand breaks to form double-strand breaks in DNA

Biopolymers ◽  
1969 ◽  
Vol 7 (5) ◽  
pp. 681-693 ◽  
Author(s):  
David Freifelder ◽  
Bruce Trumbo
Keyword(s):  
Double Strand Breaks ◽  
Single Strand ◽  
Strand Breaks ◽  
Single Strand Breaks

scholarly journals Artificial and Solar UV Radiation Induces Strand Breaks and Cyclobutane Pyrimidine Dimers in Bacillus subtilis Spore DNA

2000 ◽  
Vol 66 (1) ◽  
pp. 199-205 ◽  
Author(s):  
Tony A. Slieman ◽  
Wayne L. Nicholson
Keyword(s):  
Bacillus Subtilis ◽  
Uv Irradiation ◽  
Double Strand Breaks ◽  
Single Strand ◽  
Complex Spectrum ◽  
Cyclobutane Pyrimidine Dimers ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Pyrimidine Dimers ◽  
Solar Uv

ABSTRACT The loss of stratospheric ozone and the accompanying increase in solar UV flux have led to concerns regarding decreases in global microbial productivity. Central to understanding this process is determining the types and amounts of DNA damage in microbes caused by solar UV irradiation. While UV irradiation of dormant Bacillus subtilis endospores results mainly in formation of the “spore photoproduct” 5-thyminyl-5,6-dihydrothymine, genetic evidence indicates that an additional DNA photoproduct(s) may be formed in spores exposed to solar UV-B and UV-A radiation (Y. Xue and W. L. Nicholson, Appl. Environ. Microbiol. 62:2221–2227, 1996). We examined the occurrence of double-strand breaks, single-strand breaks, cyclobutane pyrimidine dimers, and apurinic-apyrimidinic sites in spore DNA under several UV irradiation conditions by using enzymatic probes and neutral or alkaline agarose gel electrophoresis. DNA from spores irradiated with artificial 254-nm UV-C radiation accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, while DNA from spores exposed to artificial UV-B radiation (wavelengths, 290 to 310 nm) accumulated only cyclobutane pyrimidine dimers. DNA from spores exposed to full-spectrum sunlight (UV-B and UV-A radiation) accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, whereas DNA from spores exposed to sunlight from which the UV-B component had been removed with a filter (“UV-A sunlight”) accumulated only single-strand breaks and double-strand breaks. Apurinic-apyrimidinic sites were not detected in spore DNA under any of the irradiation conditions used. Our data indicate that there is a complex spectrum of UV photoproducts in DNA of bacterial spores exposed to solar UV irradiation in the environment.

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