Cells exposed to densely ionizing radiation (high-LET) experience more severe biological damage than do cells exposed to sparsely ionizing radiation (low-LET). The prevailing hypothesis is that high-LET radiations induce DNA double strand-breaks (DSB) that are more complex and clustered, and are thereby more challenging to repair. Here, we present experimental data obtained by atomic force micr...

abstract accumulation of gene changes and chromosomal instability in response to cellular dna damage lead to cancer. dna damage induces cell cycle checkpoints pathways. checkpoints regulate dna replication and cell cycle progression, chromatin restructuring, and apoptosis. checkpoint kinase 2 (chk2) is activated in response to dna lesions. atm phosphorylate chk2. the activated chk2 kinase can p...

this study was conducted to determine chromatin integrity and dna damage by dna electrophoresis and comet assays of buffalo fresh and frozen semen. semen samples were collected from four buffalo bulls and evaluated after freezing for semen motility, viability, sperm abnormalities, chromatin integrity and dna damage. a significant variation was found in semen parameters after thawing. highly sig...

background: sperm dna damage is an important factor in the etiology of male infertility. objective: the aim of the study was to evaluate the association of oxidative stress induced sperm dna damage with the pathogenesis of male infertility. materials and methods: the study comprised a total of 66 subjects, including fertile men (n=25) and infertile men (n=41) matched by age. seminal malondialde...

Cells in tissues and organs are continuously subjected to oxidative stress and free radicals on a daily basis. This free radical attack has exogenous or endogenous (intracellular) origin. The cells withstand and counteract this occurrence by the use of several and different defense mechanisms ranging from free radical scavengers like glutathione (GSH), vitamins C and E and antioxidant enzymes l...

background: exposure to ionizing radiation is known to induce oxidative stress followed by damage to critical biomolecules like lipids, proteins and dna through radiolysis of cellular water. since radiation has been widely used as an important tool in therapy of cancer, the detailed investigation regarding the dna damage and repair kinetics would help to predict the radiation sensitivity of cel...

Lesions in the DNA arise under ionizing irradiation conditions or various chemical oxidants as a single damage or as part of a multiply damaged site within 1-2 helical turns (clustered lesion). Here, we explored the repair opportunity of the apurinic/apyrimidinic site (AP site) composed of the clustered lesion with 5-formyluracil (5-foU) by the base excision repair (BER) proteins. We found, tha...

Growing interest in proton and heavy ion therapy has reinvigorated research into the fundamental biological mechanisms underlying the therapeutic efficacy of charged-particle radiation. To improve our understanding of the greater biological effectiveness of high-LET radiations, we have investigated DNA double-strand breaks (DSBs) following exposure of plasmid DNA to low-LET Co-60 gamma photon a...