不同结构类型双着丝粒体建立的剂量-效应曲线估算剂量可行性研究

目的 探讨基于不同结构类型双着丝粒体（dicentrics,dic）建立的剂量-效应曲线估算生物剂量的可行性。方法 采集两名健康人外周血样品,用0、0.5、1、2、3、4、5和6 Gy ⁶⁰Co γ射线（剂量率为0.27 Gy/min）离体照射人外周血,常规培养、收获和制备染色体标本,镜下分析并记录不同结构类型dic;应用CABAS软件建立dic剂量-效应曲线;并对两验证样本进行剂量估算。结果 不同结构类型dic率均随受照剂量的增加而升高（R²=0.886~0.943,P<0.01）,各剂量点经典型和单端型dic构成比之和约占所有类型dic的92%以上,而近距型dic和双端型dic分别在各照射剂量点的构成比均<4%。不同结构类型dic剂量-效应曲线的R²值均达到0.998;应用4条曲线估算的受照射剂量差异无统计学意义（P>0.05）。经典型dic剂量-效应曲线估算较高剂量时（3.9 Gy）,相对偏差均≤13.08%。结论 基于不同结构类型dic建立的剂量-效应曲线具有估算生物剂量的可行性。     

Molecular characterisation of a case of dicentric Y presented as nonobstructive azoospermia with testicular early maturation arrest

The dicentric Y chromosome is the most common cytogenetically visible structural abnormality of Y chromosome. The sites of break and fusion of dicentric Y are variable, but break and fusion at Yq12 (proximal to the pseudoautosomal region 2/PAR 2) is very rare. Dicentric Y chromosome is unstable during cell division and likely to generate chromosomal mosaicism. Here, we report a case of infertile male with nonmosaic 46,XY where chromosome Y was dicentric with break and fusion at Yq12 (proximal to PAR 2). Clinical presentation of the case was nonobstructive azoospermia due to early maturation arrest at the primary spermatocyte stage. Various molecular techniques such as FISH, STS‐PCR and DNA microarray were carried out to characterise genetic defect leading to testicular maturation arrest in the patient. The break and fusion was found at Yq12 (proximal to PAR 2) and resulted in near total duplication of Y chromosome (excluding PAR 2). The reason for maturation arrest seems due to CNVs of PARs (gain in PAR 1 and loss of PAR 2) and azoospermia factors (gain).     

Mosaicism for ring and isopseudodicentric chromosome 13

A three-month-old female infant with multiple malformations was noted on routine cytogenetic evaluation to have dicentric/ring mosaicism of chromosome 13. Additional cytogenic investigations indicated that the dicentric could be further defined as an isopseudodicentric. Unlike the double chromosome break in the more common ring 13 cases, the mechanism for isopseudodicentric/ring generation is attributed to chromosome and chromatid breaks with subsequent bridging, breaking and fusion. The phenotypic features are those of a combined duplication-deficiency of chromosome 13.     

双着丝粒染色体自动分析研究进展

双着丝粒染色体分析作为生物剂量估算的“金标准”,在大规模核辐射事件中对于快速做出临床决策至关重要。传统人工分析费时费力,通量低,且对人员的技术要求高,难以满足大规模核事故情况下大量人员剂量估算的要求。近年来,针对大规模辐射事件下受照人员高通量、快速、准确的剂量估算需求,研究者们开发了多种策略。本文介绍了双着丝粒染色体自动分析检测方法的研究进展,为国内同行开展基于双着丝粒染色体指标估算生物剂量研究提供参考。     

双着丝粒染色体自动分析生物剂量估算研究

目的 基于遗传工作站,探讨建立双着丝粒染色体自动分析剂量-效应曲线,实现高通量自动化生物剂量估算。方法 使用⁶⁰Co放射源对3名健康志愿者外周血进行离体照射,常规培养、制片。使用遗传工作站进行染色体中期分裂相采集及双着丝粒自动分析,并人工确认,拟合双着丝粒染色体自动分析剂量-效应曲线。使用另一组不同剂量照射的离体外周血样本对拟合的双着丝粒染色体自动分析剂量-效应曲线进行准确性验证。结果 拟合的双着丝粒染色体自动分析剂量-效应曲线为Y=0.018 06D²+0.012 79D+0.000 489 1（R²=0.961）,该剂量-效应曲线可以准确地进行生物剂量估算,并且每例人工分析时间仅需数分钟。结论 成功地建立了新的双着丝粒染色体自动分析生物剂量估算方法,可以大量节省人工分析时间,对大规模核事故应急具有重要意义。     

Low-level complex mosaic with multiple cell lines affecting the 18q21.31q21.32 region in a patient with de novo 18q terminal deletion

We describe a 5-year-old girl who was diagnosed at birth with 18q de novo homogeneous deletion at G-banding karyotype. Her clinical condition, characterized by hypotonia, psychomotor retardation, short stature, deafness secondary to bilateral atresia of the external auditory canals, was in agreement with the 18q deletion syndrome though presence of coloboma of a single eye only suggested a mosaic condition as an unusual sign. By combining multiple technologies including array-CGH, FISH, and WGS, we found that the terminal deletion 18q21.32q23 (21 Mb) was in segmental mosaicism of the proximal region 18q21.31q21.32 (2.7 Mb), which showed a variable number of copies: one, two, or three, in 7, 41 and 55% of the cells respectively. Breakpoint junction analysis demonstrated the presence of an inv-dup del (18q) with a disomic segment of 4.7 kb between the inverted and non-inverted copies of the duplicated region 18q21.31q21.32. From these results, we propose that all three types of abnormal chr18 (the inv-dup del and the two 18q terminal deletions of different sizes) arisen from breaks in a dicentric mirror chromosome 18q, either in more than one embryo cell or from subsequent breaking-fusion-bridge cycles. The duplication region was with identical polymorphisms as in all non-recurrent inv-dup del rearrangements though, in contrast with most of them, the 18q abnormality was of maternal origin. Taking into account that distal 18q deletions are not rarely associated with inv-dup del(18q) cell lines, and that the non-disjunction of chromosome 18 takes place especially at maternal meiosis II rather than meiosis I, multiple rescue events starting from trisomic zygotes could be considered alternative to the postmitotic ones. From the clinical point of view, our case, as well as those of del(18q) in mosaic with the dic(18q), shows that the final phenotype is the sum of the different cell lines that acted on embryonic development with signs typical of both the 18q deletion syndrome and trisomy 18. Asymmetrical malformations, such as coloboma of the iris only in the right eye, confirm the underlying mosaicism regardless of whether it is still detectable in the blood.     

Multicentric evaluation of conventional dosimetry vs bio-dosimetry over a period of two years for a three-point contact

BackgroundDental radiology represents the best model for evaluating the effects of low-dose ionizing radiation. Therefore, this study evaluated the awareness on radiation hygiene among dental ancillary personnel through a questionnaire and their absorbed doses by physical and biologic dosimetry.MethodsThe multicentric study included two groups. Group I (N = 30) consisted of dental staff involved in dental radiology. An equal number of personnel who were not related to radiology formed the control group. Knowledge (K), attitude (A), and practice (P) of participants were assessed using a KAP questionnaire. Radiation exposure was evaluated by physical dosimetry at 3 time periods: at the beginning of the study (T1), after 10 months (T2), and at the end after 20 months (T3). Similarly, biologic dosimetry was also carried out at 3 time points by dicentric chromosome aberration assay. The data were compared using percentage analysis, analysis of variance (one-way analysis of variance), and Student's t- test.ResultsThe KAP survey demonstrated enhanced understanding of radiation protection measures and its sound practice by the participants. Physical dosimetry showed a significant increase in absorbed dose at 3 time points: T1, T2, and T3. However, no chromosomal aberrations were observed in blood lymphocytes for any of the participants in the optimized 4-day biodosimetry protocol.ConclusionGood radiation protection protocols—safe distance from the radiation source and wear of lead aprons and thyroid collars—ensured low absorbed doses. The 4-day protocol is an important step toward developing biodosimetry laboratories in the Armed Forces Medical Services for clinical and national radiation countermeasure strategies.     

Laparoscopic diagnosis and treatment of a phenotypic girl with mosaic 45,XO/46,X,idic(Y) mixed gonadal dysgenesis

We report our experience with laparoscopic gonadal biopsy and gonadectomy for a girl with a dicentric Y chromosome in mixed gonadal dysgenesis (MGD). A 4-year-old phenotypic girl was referred to our hospital because of slight enlargement of the clitoris. Fluorescence in situ hybridization analysis with Y chromosome-specific probes showed a karyotype with 45,XO/46,X,+idic(Y)(p11.32) and presence of the sex-determining region Y sequence. The pathologic finding by frozen section technique using laparoscopic biopsy specimens during the operation demonstrated a left streak gonad and right testis, and she was diagnosed with MGD. Finally, we performed laparoscopic bilateral gonadectomy. Laparoscopic management is a good approach for patients with sexual development disorders, including MGD because it provides minimally invasive surgery for children and enables all necessary procedures, including evaluation, biopsy, and gonadectomy, for diagnosis and treatment.     

Cytogentic studies of a patient with mosaicism of isochromosome 13q and a dicentric (Y; 13) translocation showing differential centromeric activity

A case is presened in which both an isochromosome and a dicentric translocation with differential centromere activity are found in one individual. Three karyotypes are present: 46, XY, -13, isochromosome 13q is found in 23% of cells in blood and 5% in skin. The dicentric (Y;13), + i(13q)/45,X, -13, + psu dic(13)t(13;Y)/45,X, -13, + psu dic(Y)t(Y;13). The isochromosome in all of the remaining cells displays differential centromeric activity; the ratio of cells with the acitve 13 centromere to the acstive Y centromere is about 3.5:1.
The formation of the isochromosome 13q was a de novo gametic event. The translocation producing the dicentric occurred after fertilization with the breakpoints at band Yq12 and the juxta-centromeric region of the isochromosome 13. The finding of differential centromeric activity in this chromosome indicates that centromere inactivation is not always permanent in a dicentric translocation.     

双着丝粒染色体自动分析生物剂量估算影响因素研究

目的 研究不同实验条件对双着丝粒染色体自动生物剂量估算结果的影响。方法 不同方法制备染色体标本,遗传工作站自动分析双着丝粒畸变后,用本实验室拟合的"双着丝粒染色体自动分析剂量-效应曲线"进行生物剂量估算。结果 受照血液20℃室温放置50 h、滴片细胞悬液浓度、中期分裂相分散度、染色深浅、重复扫描、遗传工作站扫描灵敏度设置、玻片细胞采集部位均不影响自动生物剂量估算结果（P > 0.05）。结论 双着丝粒染色体自动分析对实验中的一般性影响因素不敏感,有利于该方法在不同实验室间的推广。