Objective To investigate the clinical and genetic characteristics of a cohort of Chinese patients with large-scale single deletion in mitochondrial DNA (mtDNA).Methods Long-range PCR was performed to search large scale deletions in 70 patients' muscle mtDNA who were diagnosed with mitochondrial disease by clinical and muscle pathological examination.Then multiple restriction enzyme digestion of long-range PCR product followed by short-cycle PCR were used to define the exact size and location of large-scale deletions.We summarized the clinical phenotypes of patients,and analyzed the correlations between clinical phenotypes and size of mtDNA deletions in those patients with single large-scale deletion.Results Sixty-one patients were identified to have single large-scale deletion in their muscle mtDNA,including 54 patients with chronic progressive external ophthalmoplegia (CPEO),6 with KearnsSayre syndrome (KSS) and 1 with mitochondrial myopathy,encephalopathy,lactic acidosis and stroke-like episodes.Totally 37 patterns of mtDNA deletions were detected in this cohort of patients.The "common deletion",4 977 bp deletion appeared in 39.3％ (24/61) patients.The mean size of single deletion in CPEO patients was (5 052.17 ± 1 390.96) bp,while in KSS patients it was (5 912.43 ± 1 262.15) bp.There was no significant difference between CPEO patients group and KSS patients group.The size of deletions was correlated with onset age (r =-0.415,P =0.001).Conclusions Large-scale single deletion of mtDNA mainly causes CPEO and KSS.Patients with larger deletions present with earlier onset of disease.The mtDNA "common deletion" is also common in Chinese patients.

<span id="ChDivSummary" name="ChDivSummary" class="abstract-text">目的　探讨宫内γ线照射对仔鼠脑发育的影响。方法　采用整体动物实验 ,于SD大鼠孕 17天给予 1 0Gyγ线照射 ,观察生后 1,4 ,7,14及 2 1日龄仔鼠脑重、脑DNA和蛋白质含量的动态变化。结果　照射组仔鼠生后 1,4 ,7,14及 2 1日龄脑重、脑 /体比值及脑组织蛋白质含量 ,与对照组比较均显著降低 ;对照组仔鼠出生后脑组织DNA含量逐天下降 ,至生后第 4天后又逐渐增高 ,照射组仔鼠第 1及 2 1日龄脑组织DNA含量显著低于对照组。结论　孕 17天大鼠受 1 0Gyγ线照射可影响仔鼠脑发育 ,表现为脑重、脑DNA和蛋白质含量的降低</span>