Determination of the initial DNA damage and residual DNA damage remaining after 12 hours of repair in eleven cell lines at low doses of irradiation

PURPOSE: To determine the relationship between DNA damage and radiosensitivity at low doses (1-10 Gy) for the initial DNA damage and residual DNA damage remaining after 12-h repair. MATERIALS AND METHODS: Eleven cell lines, normal human lung epithelial L132, HT29 human colon carcinoma, ATs4 human ataxia telangiectasia, normal CHO-K1 hamster, repair-deficient xrs1 and xrs5 mutants, repair-deficient SCID rodent cell line, the human normal fibroblast 1BR.3, human ataxia telangiectasia fibroblast AT1BR and the repair-deficient fibroblasts 180BR.B and 46BR.1 were irradiated with 60Co gamma-rays. Radiosensitivity was measured by clonogenic survival assay. DNA damage was measured by fluorometric analysis of DNA unwinding (FADU). RESULTS: The radiosensitivity in the 11 cell lines ranged from SF2 of 0.02-0.61. By FADU assay, the undamaged DNA at 5-Gy ranged from 56 to 93%. The initial DNA damage and radiosensitivity were highly correlated (r2 = 0.81). After 5-Gy irradiation and 12-h repair, two groups of cell lines emerged. Group 1 restored undamaged DNA to a level ranging from 94 to 98%. Group 2 restored the undamaged DNA to a level ranging from 77 to 82%. No correlation was seen between residual DNA damage remaining after 12-h repair and radiosensitivity. CONCLUSION: It is shown that the initial DNA damage correlates with radiosensitivity at low doses of irradiation. This suggests that the initial DNA damage must be considered as a determinant for radiosensitivity.     

Acute bacterial meningitis

In the past 10 years the epidemiology of bacterial meningitis has changed, with a decreased incidence of meningitis caused by Haemophilus influenzae and an increasing incidence of meningitis caused by penicillin- and cephalosporin-resistant strains of Streptococcus pneumoniae. Meningococcal meningitis has become an increasing threat to college students. Successful outcome from meningitis requires not only eradication of the bacterial pathogen but also management of the neurological complications of raised intracranial pressure, stroke, and seizure activity. In this article, the pathophysiology, etiology, clinical presentation, differential diagnosis, and management of acute bacterial meningitis are reviewed. The present recommendations for the use of dexamethasone in the treatment of this infection, the use of chemoprophylaxis, and the indications for vaccinations are included.     

A new heparin fragment decreases liver ischemia-reperfusion injury

<正>To the Editor:Ischemia-reperfusion injury following surgery and transplantation can lead to irreversible multiorgan failure.Intracellular calcium overload is associated to cellular death during ischemiareperfusion.A recently discovered heparin fragment (HF),trisulfated disaccharide (TD),that acts on sodium-calcium exchanger(NCX) decreasing intracellular Ca²⁺,showed effectiveness on protecting hepatocytes from ischemia-reperfusion injury [1],     

下肢周围动脉闭塞性疾病病人行心电图触发非对比增强MR血管成像(TRANCE)和数字减影血管造影(DSA)的对比研究

目的对心电触发非对比增强MR血管成像(TRANCE)和数字减影血管造影(DSA)诊断下肢(包括足部)周围动脉闭塞的诊断价值进行前瞻性对比研究。方法43例有症状的周围动脉闭塞疾病(PAOD)病人在DSA检查前进行TRANCE检查。将MR血管成像(MRA)显示下肢