The enhancement of X-ray-induced DNA degradation in Micrococcus radiodurans by phenethyl alcohol

1971 ◽  
Vol 17 (4) ◽  
pp. 487-493 ◽  
Author(s):  
A. A. Driedger ◽  
M. J. Grayston
Keyword(s):  
Dna Synthesis ◽  
Excision Repair ◽  
Dna Degradation ◽  
Prolonged Incubation ◽  
Strand Breaks ◽  
X Ray ◽  
Phenethyl Alcohol ◽  
Single Strand Breaks ◽  
High Doses ◽  
Common Target

The effects of phenethyl alcohol on DNA synthesis and X-ray-induced DNA excision–repair were studied in Micrococcus radiodurans. At 0.20% concentration, the drug selectively inhibited DNA synthesis. Higher concentrations and prolonged incubation promoted DNA breakdown.Irradiation and PEA together promoted increased DNA breakdown in a characteristic fashion depending upon the time at which it was added. This effect was lost after the cells had undergone one postirradiation division. PEA did not inhibit repair of X-ray-induced single strand breaks. At high doses the two agents no longer enhanced each other's action and this suggests that they acted on a common target. It is proposed that X-ray-induced DNA breakdown is at least partly due to damage of a non-DNA structure such as the cell membrane, since persistent breaks in the DNA are not required for X-ray-induced, PEA-potentiated DNA degradation.

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.

scholarly journals Toxicity of Commercial Neem Extract to Earthworms (Pheretima peguana)

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Ptumporn Muangphra ◽  
Ravi Gooneratne
Keyword(s):  
Comet Assay ◽  
Body Wall ◽  
Micronucleus Test ◽  
Agricultural Practices ◽  
Recommended Dosage ◽  
Neem Extract ◽  
Strand Breaks ◽  
Single Strand Breaks ◽  
Radial Thickness ◽  
High Doses

The LC50of commercial neem extract (Sadao Thai III containing azadirachtin; NEEM) on filter paper in the earthwormPheretima peguanaat 48 h and 72 h was 3.79 and 3.33 g , respectively. In earthworms exposed to five NEEM concentrations from 0.39 (~10% of 48-h LC50) to 3.13 (~80% of 48-h LC50) g , the radial thickness of the epidermis and body wall significantly () decreased, and thickness of intestinal epithelium increased but only at high doses, approximately 25-fold above the concentration permitted for use as an insecticide in field applications (0.09 g ). NEEM significantly () increased the number of binucleated coelomocytes in the micronucleus test (detects chromosomal aberrations) at 3.13 g , approximately 35-fold higher than the recommended dose, but it did not cause coelomocyte DNA single-strand breaks in the comet assay. Thus, NEEM is cytotoxic (increase in binucleates through the inhibition of cytokinesis) but not genotoxic to earthworm coelomocytes. This study demonstrates that the recommended dosage of commercial neem extract as an insecticide in agricultural practices is safe for earthworms.

DNA synthesis is blocked by cigarette tar-induced DNA single-strand breaks

1987 ◽  
Vol 8 (10) ◽  
pp. 1517-1520 ◽  
Author(s):  
Edward T. Borish ◽  
William A. Pryor ◽  
Sheela Venugopal ◽  
Walter A. Deutsch
Keyword(s):  
Dna Synthesis ◽  
Single Strand ◽  
Strand Breaks ◽  
Single Strand Breaks
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