A test of the chromosomal theory of ecotypic speciation in Anopheles gambiae

The role of chromosomal inversions in speciation has long been of interest to evolutionists. Recent quantitative modeling has stimulated reconsideration of previous conceptual models for chromosomal speciation. Anopheles gambiae, the most important vector of human malaria, carries abundant chromosomal inversion polymorphism nonrandomly associated with ecotypes that mate assortatively. Here, we consider the potential role of paracentric inversions in promoting speciation in A. gambiae via "ecotypification," a term that refers to differentiation arising from local adaptation. In particular, we focus on the Bamako form, an ecotype characterized by low inversion polymorphism and fixation of an inversion, 2Rj, that is very rare or absent in all other forms of A. gambiae. The Bamako form has a restricted distribution by the upper Niger River and its tributaries that is associated with a distinctive type of larval habitat, laterite rock pools, hypothesized to be its optimal breeding site. We first present computer simulations to investigate whether the population dynamics of A. gambiae are consistent with chromosomal speciation by ecotypification. The models are parameterized using field observations on the various forms of A. gambiae that exist in Mali, West Africa. We then report on the distribution of larvae of this species collected from rock pools and more characteristic breeding sites nearby. Both the simulations and field observations support the thesis that speciation by ecotypification is occurring, or has occurred, prompting consideration of Bamako as an independent species.     

三明治构型大鼠原代肝细胞长期培养及功能测定

目的观察三明治构型大鼠原代肝细胞长期培养的形态学变化,并对其功能进行测定。方法采用改良原位两步法门静脉胶原酶灌注分离单肝细胞,台盼蓝拒染实验观察细胞活力,利用三明治培养构型培养成年大鼠原代肝细胞,倒置显微镜下连续观察肝细胞的形态学变化,定期收集培养细胞上清液,检测所培养肝细胞的分泌及生物转化功能,并与单层胶原培养肝细胞比较。结果平均每个鼠肝可获取(2～3)×108个肝细胞,存活率为(93±3)%;体外肝细胞培养第3天,细胞活力、清蛋白分泌功能恢复到最佳状态;三明治构型培养第7天,地西泮24h代谢量达到最高峰。三明治构型培养的肝细胞形成肝索样结构,并逐渐形成胆小管网络;在培养的21d内,清蛋白分泌、地西泮代谢始终维持较高的水平;肝细胞形态维持可达28d以上。结论三明治构型肝细胞培养体系更接近于肝细胞体内生长环境,肝细胞可在较长时间内保持良好的形态结构和功能。三明治构型不仅可以应用于肝细胞的基础研究,而且为肝细胞移植和生物人工肝治疗肝衰竭奠定了一定的基础。     

Rare recombination events generate sequence diversity among balancer chromosomes in Drosophila melanogaster

Multiply inverted balancer chromosomes that suppress exchange with their homologs are an essential part of the Drosophila melanogaster genetic toolkit. Despite their widespread use, the organization of balancer chromosomes has not been characterized at the molecular level, and the degree of sequence variation among copies of balancer chromosomes is unknown. To map inversion breakpoints and study potential diversity in descendants of a structurally identical balancer chromosome, we sequenced a panel of laboratory stocks containing the most widely used X chromosome balancer, First Multiple 7 (FM7). We mapped the locations of FM7 breakpoints to precise euchromatic coordinates and identified the flanking sequence of breakpoints in heterochromatic regions. Analysis of SNP variation revealed megabase-scale blocks of sequence divergence among currently used FM7 stocks. We present evidence that this divergence arose through rare double-crossover events that replaced a female-sterile allele of the singed gene (sn^X2) on FM7c with a sequence from balanced chromosomes. We propose that although double-crossover events are rare in individual crosses, many FM7c chromosomes in the Bloomington Drosophila Stock Center have lost sn^X2 by this mechanism on a historical timescale. Finally, we characterize the original allele of the Bar gene (B¹) that is carried on FM7, and validate the hypothesis that the origin and subsequent reversion of the B¹ duplication are mediated by unequal exchange. Our results reject a simple nonrecombining, clonal mode for the laboratory evolution of balancer chromosomes and have implications for how balancer chromosomes should be used in the design and interpretation of genetic experiments in Drosophila.Balancer chromosomes are genetically engineered chromosomes that suppress crossing over with their homologs and are used for many purposes in genetics, including construction of complex genotypes, maintenance of stocks, and estimation of mutation rates. Balancers typically carry multiple inversions that suppress genetic exchange or result in the formation of abnormal meiotic products if crossing over does occur (Fig. 1A); for example, single crossovers inside the inverted segment create acentric or dicentric chromosomes that will fail to segregate properly during meiosis or large deletions or duplications that will likely result in inviable gametes (1, 2). Balancers also often carry recessive lethal or sterile mutations to prevent their propagation as homozygotes as well as dominant markers for easy identification. First developed for use in Drosophila melanogaster, balancer chromosomes remain some of the most powerful tools for genetic analysis in this species (3).Open in a separate windowFig. 1.Consequences of a single or double crossover between a WT X chromosome and an X chromosome carrying a single inversion, In(1)dl-49. Euchromatin is shown in blue, heterochromatin is shown in gray, and centromeres are depicted as circles. Thin white lines mark locations of inversion breakpoints, and yellow crosses/thin lines mark locations of crossover events. (A) A single crossover event within the inverted segment results in the formation of chromosomes with deletions and zero (acentric) centromeres or duplications and two (dicentric) centromeres, neither of which will segregate properly during meiosis. (B) A double crossover within an inverted segment results in intact chromosomes with one centromere that will segregate properly during meiosis.Despite their widespread use, very little is known about the organization of Drosophila balancer chromosomes at the molecular level. Since their original syntheses decades ago, balancers have undergone many manipulations, including the addition or removal of genetic markers. Moreover, rare recombination events can cause spontaneous loss of deleterious alleles on chromosomes kept over balancers in stock, as well as loss of marker alleles on balancer chromosomes themselves (3). Likewise, recent evidence has shown that sequence variants can be exchanged between balancer chromosomes and their wild type (WT) homologs via gene conversion during stock construction or maintenance (4, 5). Thus, substantial variation may exist among structurally identical balancer chromosomes owing to various types of sequence exchange.To gain insight into the structure and evolution of balancer chromosomes, we have undertaken a genomic analysis of the most commonly used X chromosome balancer in D. melanogaster, First Multiple 7 (FM7). We have focused on FM7 because this X chromosome balancer series lacks lethal mutations and thus can be easily sequenced in a hemizygous or homozygous state. In addition, the FM7 chromosome has been shown to pair normally along most of its axis with a standard X chromosome, providing a structural basis for possible exchange events (6). Moreover, although details of how early balancers in D. melanogaster were created are not fully recorded, the synthesis and cytology of the FM7 series is reasonably well documented (3).The earliest chromosome in the FM7 series, FM7a, was constructed using two progenitor X chromosome balancers, FM1 and FM6, to create a chromosome carrying three inversions—In(1)sc⁸, In(1)dl-49, and In(1)FM6—relative to the WT configuration (7, 8) (Fig. 2A). Subsequently, a female-sterile allele of singed (sn^X2) was introduced onto FM7a to create FM7c, which prevents the loss of balanced chromosomes carrying recessive lethal or female-sterile mutations (9). More recently, versions of FM7a and FM7c have been generated that carry transgene insertions that allow the determination of balancer genotypes in embryonic or pupal stages (10–14).Open in a separate windowFig. 2.Structure of the FM7 balancer chromosome. Euchromatin is shown in blue, and heterochromatin is shown in gray. (A) Schematic view of the organization of WT and FM7 X chromosomes. FM7 contains three inversions—In(1)sc⁸, In(1)dl-49, and In(1)FM6—relative to WT. The six breakpoint junctions for the three inversions are numbered 1–6 and are shown in detail in B. (B) Location and organization of inversion breakpoints in FM7. Each inversion has two breakpoints that can be represented as A/B and C/D in the standard WT arrangement and as A/C and B/D in the inverted FM7 arrangement, where A, B, C, and D represent the sequences on either side of the breakpoints. Locations of euchromatic breakpoints are on Release 5 genome coordinates, and the identity of the best BLAST match in FlyBase is shown for heterochromatic sequences. Primers used for PCR amplification are shown above each breakpoint; details are provided in Methods and Datasets S2 and S3. Forward and reverse primers are named with respect to the orientation of the assembled breakpoint contigs, not the orientation of the WT or FM7 X chromosome.To identify the inversion breakpoints in FM7 balancers and to study patterns of sequence variation that may have arisen since the origin of the FM7 series, we sequenced genomes of eight D. melanogaster stocks carrying the FM7 chromosome (four FM7a and four FM7c). We discovered several megabase-scale regions in which FM7c chromosomes differ from one another, which presumably arose via double-crossover (DCO) events from balanced chromosomes (Fig. 1B). These DCOs eliminate the female-sterile sn^X2 allele in the centrally located In(1)dl-49 inversion and are expected to confer a fitness advantage to sn⁺ chromosomes, either by allowing propagation of sn⁺ FM7 as homozygotes in females or by sn⁺ FM7 males outcompeting sn^X2 FM7 males in culture. We found that loss of the sn^X2 allele is common in FM7c chromosomes by screening other FM7c-carrying stocks at the Bloomington Drosophila Stock Center. We also identified the breakpoints of the B¹ duplication carried on FM7, and found direct molecular evidence for the role of unequal exchange in the origin and reversion of the B¹ allele (15–19). Our results provide clear evidence that the common assumption that balancers are fully nonrecombining chromosomes is incorrect on a historical timescale, and that substantial sequence variation exists among balancer chromosomes in circulation today.     

FSE PDWI联合T2WI STIR在寰枢关节半脱位诊断中的应用

目的探讨寰枢关节半脱位规范化诊断方法,尤其是FSE PDWI和T2WI STIR序列在诊断寰枢关节半脱位中的价值。方法对31例有颈部活动受限、X线或CT检查发现齿状突偏移≥1mm患者,应用FSE PDWI和T2WISTIR序列对寰枢关节进行扫描。评价翼状韧带、横韧带损伤情况,结合临床对寰枢关节损伤情况进行分析,以指导临床治疗。结果本组患者均未发现横韧带形态及信号改变。23例翼状韧带呈均匀低信号,其中4例有增粗表现;8例翼状韧带增粗合并信号增高。所有患者均未见寰枢椎骨质骨折和脊髓受压损伤征象,保守治疗后效果良好。结论 FSE PDWI联合T2WI STIR序列对寰枢关节韧带损伤显示良好。对齿状突偏移≥1mm而怀疑寰枢关节半脱位患者有鉴别诊断价值,可以作为寰枢关节半脱位规范化诊断方法的选择。     

T1 Mapping and Extracellular Volume Fraction in Dilated Cardiomyopathy: A Prognosis Study

ObjectivesThe aim of this study is to examine the prognostic value of T1 mapping and the extracellular volume (ECV) fraction in patients with dilated cardiomyopathy (DCM).BackgroundPatients with DCM with functional left ventricular remodeling have poorer prognoses. Noninvasive assessment of myocardial fibrosis using T1 mapping and the ECV fraction may improve risk stratification of patients with DCM; however, this has not yet been systematically evaluated.MethodsA total of 659 consecutive patients with DCM (498 men; 45 ± 15 years) who underwent cardiac magnetic resonance with T1 mapping and late gadolinium enhancement (LGE) imaging with a 1.5-T magnetic resonance scanner were enrolled in this study. Primary endpoints were cardiac-related death and heart transplantation. Secondary endpoints were hospitalization for heart failure, ventricular arrhythmias, and implantable cardioverter-defibrillator or cardiac resynchronization therapy implantation. Survival estimates were calculated by Kaplan-Meier curves with the log-rank test.ResultsDuring a mean follow-up of 66.3 ± 20.9 months, 122 and 205 patients with DCM reached the primary and secondary endpoints, respectively. The presence of LGE had an association with both of the primary and secondary endpoints observed in the patients with DCM (both P < 0.001). The maximum native T1 (HR: 1.04; 95% CI: 1.02-1.09) and maximum ECV fraction (HR: 1.14; 95% CI: 1.08-1.21) had associations with the primary endpoints in the patients with positive LGE (both P < 0.001), whereas the mean native T1 (HR: 1.13; 95% CI: 1.10-1.36) and mean ECV fraction (HR: 1.32; 95% CI: 1.12-1.53) had the best associations in the patients with negative LGE (all P < 0.001).ConclusionsT1 mapping and the ECV fraction had prognostic value in patients with DCM and were particularly important in patients with DCM without LGE. Using a combination of T1 mapping, ECV fraction, and LGE provided optimal risk stratification for patients with DCM.     

Dark-Blood Delayed Enhancement Cardiac Magnetic Resonance of Myocardial Infarction

Objectives

This study introduced and validated a novel flow-independent delayed enhancement technique that shows hyperenhanced myocardium while simultaneously suppressing blood-pool signal.

急性心肌梗死后T波极性变化与左心功能的关系

目的探讨Q波性心肌梗死从急性期到慢性期心肌损害、心功能与T波方向变化的关系.方法选择急性前壁心肌梗死病人93例,持续T波倒置组44例,T波直立组49例,按T波恢复直立的时间不同又分4个亚组:＜3月组6例;(3～6)月组16例;(6～12)月组23例;持续直立组4例.测量各组的左室射血分数、舒张末径、室壁运动记分等超声心动图指标.结果除持续T波直立亚组外,其他T波直立亚组的左室射血分数高于T波倒置组,左室舒张末径、室壁运动记分低于T波倒置组.结论早期T波由倒置变为直立的病人,左心功能改善显著;有Q波的导联倒置T波正常化的早晚可以用来评估左心功能.     

Electrophysiological evidence of facial inversion with rapid serial visual presentation

Using measurements of event-related potentials (ERPs) during a facial recognition task, we aimed to investigate the facial inversion effect and the role of time-based attention in processing upright and inverted faces. We presented upright and inverted faces at the T2 (target 2) position using a rapid serial visual presentation paradigm. Our results indicate that the N170 component shows the usual face inversion effect (FIE), in which inverted faces elicit larger N170 amplitudes and a longer elicit N170 latency. We also found that upright faces elicit larger P1 amplitudes than inverted faces over the left hemisphere. This study indicates that the N170 and P3, but not the P1, components are modulated by time-based attention. In addition, we found that the N170 amplitude was modulated by an attentional blink (AB) based on behavioral data. These results suggest that the disruption of facial configuration processing caused by inverted faces is relatively independent of attentional resources.     

液体衰减反转恢复序列血管高信号征与急性缺血性卒中的临床及影像学相关研究

目的 探讨FLAIR序列血管高信号（FLAIR vascular hyperintensity,FVH）征对急性缺血性卒中（acute ischemic stroke,AIS）患者动脉狭窄程度、卒中病情严重程度及梗死灶分布部位的评估价值。 方法 回顾性分析2017年1月-2019年6月在河北医科大学第三医院连续就诊的大脑中动脉（middle cerebral artery,MCA）供血区AIS患者的临床及影像学资料。依据DWI显示MCA供血区梗死灶的分布特 点,将梗死分为穿支动脉型、分水岭型、区域型及混合型。利用ASPECT评分对MCA皮层供血区的划分 方法,分别计算MCA各皮层区域FVH,计算FVH评分（0～7分）分值,并分为FVH≥4分和<4分两组。比 较两组患者一般资料、血管狭窄程度、入院NIHSS评分及梗死部位差异。应用Spearman分析FVH评分与 血管狭窄程度的相关性,ROC曲线分析FVH评分对血管闭塞的诊断价值。 结果 共纳入214例患者进行分析,FVH≥4分患者51例,<4分患者163例。FVH≥4分组分水岭梗死 比例（43.1% vs 20.9%）、颈内动脉颅内段病变比例（41.7% vs 22.3%）、入院NIHSS评分[4（2～6）分 vs 3（1～4）分]均高于FVH<4分组,而穿支动脉梗死型比例（19.6% vs 52.8%）低于FVH<4分组,以上 差异均有统计学意义。FVH≥4分组血管闭塞比例高于FVH<4分组（54.9% vs 9.2%,P＜0.001）,血管 轻度狭窄比例低于FVH<4分组（9.8% vs 54.0%,P＜0.001）。Spearman分析显示FVH评分与同侧颈内动 脉颅内段及MCA狭窄程度呈正相关（r =0.504,P＜0.001）。ROC曲线分析示FVH评分预测血管闭塞的 最佳界值为3分,其诊断血管闭塞的敏感度为74.4%,特异度为80.1%。 结论 对于MCA供血区AIS患者,FVH评分可间接评估颅内动脉狭窄程度,也可反映入院时卒中严重 程度及梗死灶部位。