Replication stalling at unstable inverted repeats: interplay between DNA hairpins and fork stabilizing proteins

DNA inverted repeats (IRs) are hotspots of genomic instability in both prokaryotes and eukaryotes. This feature is commonly attributed to their ability to fold into hairpin- or cruciform-like DNA structures interfering with DNA replication and other genetic processes. However, direct evidence that IRs are replication stall sites in vivo is currently lacking. Here, we show by 2D electrophoretic analysis of replication intermediates that replication forks stall at IRs in bacteria, yeast, and mammalian cells. We found that DNA hairpins, rather than DNA cruciforms, are responsible for the replication stalling by comparing the effects of specifically designed imperfect IRs with varying lengths of their central spacer. Finally, we report that yeast fork-stabilizing proteins, Tof1 and Mrc1, are required to counteract repeat-mediated replication stalling. We show that the function of the Tof1 protein at DNA structure-mediated stall sites is different from its previously described effect on protein-mediated replication fork barriers.     

微卫星不稳定性恶性肿瘤合成致死新靶点WRN的研究进展

微卫星不稳定性（microsatellite instability,MSI）是一种肿瘤细胞中由错配修复受损或缺陷导致而出现新的微卫星等位基因的现象。MSI可以导致肿瘤细胞基因组进一步紊乱和突变,从而促进恶性肿瘤的发生发展,是公认的重要致癌途径之一。Werner syndrome protein （WRN）解旋酶是属于RecQ家族的DNA解旋酶,该酶在DNA修复和维持基因组稳定性中发挥着重要的作用。近年来研究发现,MSI恶性肿瘤的生长高度依赖WRN解旋酶,提示WRN是潜在的MSI恶性肿瘤合成致死新靶点。文章系统综述了WRN解旋酶的结构和生物学功能,总结该蛋白作为合成致死新靶点的最新进展,以及WRN解旋酶抑制剂的研究进展,以期为MSI恶性肿瘤的治疗和WRN抑制剂研发提供参考。     

关节镜下自体掌长肌腱移植治疗7例慢性下尺桡关节不稳

目的：观察关节镜辅助下取自体掌长肌腱解剖重建远端桡尺韧带治疗慢性下尺桡关节不稳的临床疗效。方法对7例保守治疗无效的慢性下尺桡关节不稳患者,腕关节探查明确诊断,然后取自体掌长肌腱解剖重建远端桡尺韧带;平均随访12个月,记录患者手术前后的握力、腕关节活动度;采用视觉模拟评分（VAS）评估腕关节的疼痛状况,利用MMWS评分和DASH评分评估腕关节的功能状态。结果在腕关节活动时VAS评分从术前的（7±2）分恢复至术后的（3±3）分,MMWS评分为术前（50±9）分,术后（83±11）分,DASH评分从术前（37±15）分提升至术后（16±10）分,差异有统计学意义;握力术前为84．5±16．0,术后93．4±11．0,差异有统计学意义。腕关节屈伸活动度,术前为93．5％±6．0％,术后为96．4％±3．0％,旋前旋后活动度术前为92．6％±7．0％,术后为97．2％±5．0％,虽有增加,但差异没有统计学意义。结论在关节镜辅助下解剖重建远端桡尺韧带是治疗慢性下尺桡关节不稳的有效方法,短期随访效果满意。     

Assessment of oxidative stress responses and the cytotoxic and genotoxic potential of the herbicide tembotrione in HepG2 cells

Tembotrione is a triketone herbicide, usually used for post-emergence weed control in corn. Currently, there is little or no published data on its genotoxicity to human cells either in vitro or in vivo. This study evaluated the impact of acute (4 and 24 h) exposure to low concentrations of tembotrione [corresponding to the acceptable daily intake (0.17 μg/mL), residential exposure level (0.002 μg/mL) and acceptable operator exposure level (0.0012 μg/mL)] on human hepatocellular carcinoma cell line HepG2, using biomarkers of oxidative stress, CCK-8 colorimetric assay for cell viability, alkaline comet assay, and cytokinesis-block micronucleus “cytome” assay. Tembotrione applied at concentrations likely to be encountered in occupational and residential exposures induced cytogenetic outcomes in non-target cells despite non-significant changes in the values of oxidative stress biomarkers. We assume that the observed effects were mainly the consequence of impaired metabolic pathways in HepG2 cells due to the inhibition of the enzyme 4-hydroxyphenyl-pyruvate-dioxygenase by tembotrione, which possibly caused a depletion of folate levels leading to excess formation of nuclear buds in the affected cells. Regardless of the fact that tembotrione was previously reported negative for mutations and chromosome aberrations in vitro, our findings call for more precaution in its use.     

辛伐他汀对不稳定斑块模型家兔血栓形成的影响

[目的]探讨辛伐他汀对动脉粥样硬化(AS)不稳定斑块家兔模型血栓形成的影响。[方法]将雄性新西兰家兔随机分两组,其中一组(假手术组)始终给予正常饮食,另一组给予高脂饲料喂养4周后,行腹主动脉球囊拉伤术,术后继续4周高脂饮食后转为正常饮食,并随机分为模型组和辛伐他汀组,辛伐他汀组给予辛伐他汀[10 mg/(kg·d)]灌胃4周,假手术组和模型组则给予等体积的生理盐水灌胃。各组家兔于药物干预4周后处死,处死前48 h和24 h两次行腹膜下注射蛇毒(0.15 mg/kg)和耳缘静脉注射组胺(0.02 mg/kg)药物触发斑块破裂。处死后取腹主动脉于体视镜下观察血栓形成情况,采用酶联免疫吸附法(ELISA法)检测血管性血友病因子抗原(v WF:Ag)和D-二聚体,放免法检测血栓素B2(TXB2)和6-酮-前列腺素F1α(6-keto-PGF1α)的浓度,并计算TXB2/6-ketoPGF1α的比值。[结果]辛伐他汀干预4周后,体视显微镜下观察斑块部位血栓形成减少,与模型组相比差异有统计学意义(P0.05),血浆v WF:Ag和D-二聚体水平均降低,与模型组相比差异有统计学意义(P0.01),血浆TXB2浓度降低、6-keto-PGF1α浓度升高,与模型组相比差异有统计学意义(P0.05),TXB2/6-keto-PGF1α降低,与模型组相比差异有统计学意义(P0.01)。[结论]辛伐他汀能够修复受损血管内皮细胞,改善血液高凝状态,抑制血小板聚集等,进而发挥抗血栓形成的作用,为辛伐他汀临床针对AS不稳定斑块患者,预防其血栓形成提供了实验依据。     

创伤性腕关节不稳定应用手术治疗的疗效分析

目的 探讨应用手术治疗对创伤性腕关节不稳定患者的疗效.方法 收集本院2013年1月至2014年1 1月入院的80例创伤性腕关节不稳定患者随机分为两组.对照组患者给予手法复位石膏固定治疗,实验组患者则给予手术治疗,比较两组患者治疗前后Jiranek与Gartland-Werley评分、整体治疗效果与腕关节稳定情况.结果 实验组治疗后患者Jiranek评分(169.24±25.28)分,显著高于对照组的(136.04±18.25)分,Gartland-Werley评分为(3.76±2.03)分,显著低于对照组的(10.36±3.95)分,差异有统计学意义(t=6.734,9.399,P＜0.01);实验组患者整体治疗效果显著优于对照组,差异具有统计学意义(Z=-2.979,P＜0.01);实验组患者出院后6个月(95.00％)与12个月腕关节稳定率(80.00％)显著高于对照组(65.00％,30.00％),差异具有统计学意义(x2=11.250,2.202,P＜0.01).结论 应用手术治疗对创伤性腕关节不稳定患者的疗效显著,具有借鉴性.     

Recent Advances in Pathology: the 2019 Annual Review Issue of The Journal of Pathology

In this Annual Review Issue of The Journal of Pathology, we present 15 invited reviews on topical aspects of pathology, ranging from the impacts of the microbiome in human disease through mechanisms of cell death and autophagy to recent advances in immunity and the uses of genomics for understanding, classifying and treating human cancers. Each of the reviews is authored by experts in their fields and our intention is to provide comprehensive updates in specific areas of pathology in which there has been considerable recent progress. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Anteroposterior distance between the tibial tuberosity and trochlear groove in patients with patellar instability

BackgroundOur objective was to describe a measurement to assess sagittal tibial tuberosity (TT)–trochlear groove (TG) distance and to compare this between asymptomatic (control) patients and patients with symptomatic patellar instability.MethodsWe compared static CT images of 22 fully extended knees of patients with symptomatic patellar instability with images of 22 asymptomatic knees. TT–TG distance was measured to quantify lateralization of the TT, and anteroposterior TT–TG distance was used to quantify the sagittal distance between these two points. Lateral trochlear inclination, sulcus angle, and trochlear depth were measured. Groups were compared using paired t tests (alpha = 0.05). Correlations of anteroposterior TT–TG distance with lateral trochlear inclination, sulcus angle, and trochlear depth were assessed using linear and multivariate regression.ResultsMean TT–TG distances were 19.9 ± 4.4 mm (symptomatic) and 16.8 ± 5.5 mm (control) (mean ± std deviation) (P = 0.002). Mean anteroposterior TT–TG distances were 8.3 ± 7.8 mm (symptomatic) and ? 0.5 ± 4.6 mm (control) (P < 0.0001). The symptomatic group had greater measurements of trochlear dysplasia, with lower lateral trochlear inclination, greater sulcus angle, and lower trochlear depth (all P < 0.0001). Anteroposterior TT–TG distance and trochlear depth were strongly negatively correlated (r = 0.62, R² = 0.39, P < 0.0001).ConclusionsIn asymptomatic patients, the anteroposterior TT–TG distance was ? 0.5 mm, indicating that the TG and TT were nearly in the same coronal plane. In patients with symptomatic patellar instability, the TG was almost nine millimeters anterior, and this distance correlated with measurements of trochlear dysplasia.Level of evidenceIII, case control study.     

Referencing the trochlear groove based on three-dimensional computed tomography imaging improves the reliability of the measurement of the tibial tuberosity–trochlear groove distance in patients with higher grades of trochlea dysplasia

BackgroundTo determine whether 3D-CT imaging technique is valid and reproducible compared to conventional CT measurement technique (CCT) for the detection of a femoropatellar instability.MethodsPatients who had undergone surgery for femoropatellar instability (patellar instability group) between 2010 and 2016 (n = 37 knees of 35 patients) were retrospectively enrolled. For the matched control group, patients who had acute anterior cruciate ligament injury (< 4 weeks previously; n = 30) were recruited. Preoperative CT data had been obtained in all patients. Inter-rater reliability was calculated for both measurement protocols, and inter-method reliability was calculated between the two imaging modalities. The results are reported using intraclass correlation coefficients (ICCs) and Bland–Altman 95% limits of agreement.ResultsAll patients in the patellar instability group had femoral trochlear dysplasia (Dejour types A: four, B: 19, C: seven, and D: six), but no dysplasia was noted in the control group. In the patellar instability group, the CCT technique showed a poor inter-rater agreement (ICC = 0.74), and the 3D-CT technique still showed excellent inter-rater agreement (ICCs = 0.91). In the sub-analysis of the patellar instability group according to the trochlear dysplasia grade, ICCs were markedly decreased with severe trochlear dysplasia when using CCT technique; however, the 3D-CT technique could provide excellent reliability even with severe trochlear dysplasia.ConclusionThe 3D-CT imaging technique for the measurement of the TT–TG distance can be suggested as a better measurement technique for patellar instability patients with bone abnormality.     

Lateral patellar maltracking due to trochlear dysplasia: A computational study

BackgroundThe study focuses on the influence of trochlear dysplasia on patellar tracking related to patellar instability.MethodsKnee extension against gravity and dual-limb squatting were simulated with seven models representing knees being treated for recurrent instability. Trochlear depth was altered to represent lateral trochlear inclination (LTI) values of 6°, 12° and 24°. Repeated measures analyses compared patellar lateral shift (bisect offset index) across different LTI values. Peak bisect offset index during extension and squatting was correlated with patella alta (Caton–Deschamps index) and maximum lateral position of the tibial tuberosity.ResultsBisect offset index varied significantly (p < 0.05) between different LTI values at multiple flexion angles throughout simulated knee extension and squatting. Average bisect offset values were 1.02, 0.95, and 0.86 for LTI = 6°, 12°, and 24°, respectively, at 0° of flexion for knee extension. The strongest correlation occurred between peak bisect offset index and lateral position of the tibial tuberosity for knee squatting with LTI = 6° (r² = 0.81, p = 0.006). The strength of the correlation decreased as LTI increased. Caton–Deschamps was only significantly correlated with patellar tracking for LTI = 24° during knee squatting.ConclusionsA shallow trochlear groove increases lateral patellar maltracking. A lateral tibial tuberosity in combination with trochlear dysplasia increases lateral patellar tracking and the risk of patellar instability. Patella alta has relatively little influence on patellar tracking in combination with trochlear dysplasia due to the limited articular constraint provided by the trochlear groove.