Analysis of chromosomal aberrations and γH2A.X foci to identify radiation-sensitive ataxia-telangiectasia patients.

Ataxia-telangiectasia (AT) is a rare inherited recessive disorder which is caused by a mutated Ataxia-telangiectasia mutated (ATM) gene. Hallmarks include chromosomal instability, cancer predisposition and increased sensitivity to ionizing radiation. The ATM protein plays an important role in signaling of DNA double-strand breaks (DSB), thereby phosphorylating the histone H2A.X. Non-functional ATM protein leads to defects in DNA damage response, unresolved DSBs and genomic instability. The aim of this study was to evaluate chromosomal aberrations and γH2A.X foci as potential radiation sensitivity biomarkers in AT patients. For this purpose, lymphocytes of 8 AT patients and 10 healthy controls were irradiated and induced DNA damage and DNA repair capacity were detected by the accumulation of γH2A.X foci. The results were heterogeneous among AT patients. Evaluation revealed 2 AT patients with similar γH2A.X foci numbers as controls after 1 h while 3 patients showed a lower induction. In regard to DNA repair, 3 of 5 AT patients showed poor damage repair. Therefore, DNA damage induction and DNA repair as detected by H2A.X phosphorylation revealed individual differences, seems to depend on the underlying individual mutation and thus appears not well suited as a biomarker for radiation sensitivity. In addition, chromosomal aberrations were analyzed by mFISH. An increased frequency of spontaneous chromosomal breakage was characteristic for AT cells. After irradiation, significantly increased rates for non-exchange aberrations, translocations, complex aberrations and dicentric chromosomes were observed in AT patients compared to controls. The results of this study suggested, that complex aberrations and dicentric chromosomes might be a reliable biomarker for radiation sensitivity in AT patients, while non-exchange aberrations and translocations identified both, spontaneous and radiation-induced chromosomal instability.

Age-dependent differences in DNA damage after in vitro CT exposure.

PURPOSE: Age dependent radiation sensitivity for DNA damage after in vitro blood exposure by computer tomography (CT) was investigated. MATERIALS AND METHODS: Radiation biomarkers (dicentrics and gammaH2AX) in blood samples of newborns, children under five years and adults after sham exposure (0 mGy), low-dose (41 mGy) and high-dose (978 mGy) in vitro CT exposure were analyzed. RESULTS: Significantly higher levels of dicentric induction were found for the single and combined newborns/children group compared to adults, by a factor of 1.48 (95% CI 1.30-1.68), after exposure to 978 mGy. Although a significant dose response for damage induction and dose-dependent repair was found, the gammaH2AX assay did not show an age-dependent increase in DNA damage in newborns/children compared to adults. This was the case for the gammaH2AX levels after repair time intervals of 30 minutes and 24 hours, after correcting for the underlying background damage. For the low dose of 41 mGy, the power of the dicentric assay was also not sufficient to detect an age-dependent effect in the sample size investigated. CONCLUSION: A 1.5-fold increased level of dicentric aberrations is detected in newborns and children under five years after 1 Gy radiation exposure.

The rabbit model serves as a valuable operative experience and helps to establish new techniques for abdominal and thoracic endosurgery.

Minimally invasive surgery in infants requires great experience and highly specialised skills. However, in most paediatric surgical departments, the number of patients requiring such surgery is usually small and the personal experience of the surgeon limited. An experimental setting with small animals could improve these training conditions if it adequately simulates the underlying situation and conveys beneficial surgical experiences. The authors implemented an endosurgical training model with New Zealand white rabbits. The mean body weight was 3.3 (range 2.9-3.5) kg. The abdominal cavity had a volume of about 580 ml and the thoracic cavity a volume of about 250 ml, comparable with those of a newborn baby. Several relevant techniques were established (gastrostomy, colostomy, gut biopsies, lung biopsies, and anastomosis of the oesophagus). Overall, the rabbit model served to refine technical skills and operative experience. In paediatric surgical departments with a specific focus on endosurgery in the abdominal and thoracic cavities, this training model could help to introduce new techniques and add valuable educational strategies.