Smed-betacatenin-1 is required for anteroposterior blastema polarity in planarian regeneration

Planarian flatworms can regenerate heads at anterior-facing wounds and tails at posterior-facing wounds throughout the body. How this regeneration polarity is specified has been a classic problem for more than a century. We identified a planarian gene, Smed-betacatenin-1, that controls regeneration polarity. Posterior-facing blastemas regenerate a head instead of a tail in Smed-betacatenin-1(RNAi) animals. Smed-betacatenin-1 is required after wounding and at any posterior-facing wound for polarity. Additionally, intact Smed-betacatenin-1(RNAi) animals display anteriorization during tissue turnover. Five Wnt genes and a secreted Frizzled-related Wnt antagonist-like gene are expressed in domains along the anteroposterior axis that reset to new positions during regeneration, which suggests that Wnts control polarity through Smed-betacatenin-1. Our data suggest that beta-catenin specifies the posterior character of the anteroposterior axis throughout the Bilateria and specifies regeneration polarity in planarians.     

Polarized notum activation at wounds inhibits Wnt function to promote planarian head regeneration

Regeneration requires initiation of programs tailored to the identity of missing parts. Head-versus-tail regeneration in planarians presents a paradigm for study of this phenomenon. After injury, Wnt signaling promotes tail regeneration. We report that wounding elicits expression of the Wnt inhibitor notum preferentially at anterior-facing wounds. This expression asymmetry occurs at essentially any wound, even if the anterior pole is intact. Inhibition of notum with RNA interference (RNAi) causes regeneration of an anterior-facing tail instead of a head, and double-RNAi experiments indicate that notum inhibits Wnt signaling to promote head regeneration. notum expression is itself controlled by Wnt signaling, suggesting that regulation of feedback inhibition controls the binary head-tail regeneration outcome. We conclude that local detection of wound orientation with respect to tissue axes results in distinct signaling environments that initiate appropriate regeneration responses.     

东亚三角涡虫DjStag基因干扰载体的构建及干扰效果鉴定

 构建DjStag基因的RNA干扰表达载体,诱导表达产生dsRNA后喂食涡虫,观察DjStag表达变化及对涡虫再生的影响。本文以含有东亚三角涡虫DjStag基因的pcDNA3 DjStag重组质粒为模板,经PCR 扩增目的片段,将其克隆到干扰载体L4440 上,构建重组质粒L4440 DjStag后转化入大肠杆菌HT115感受态细胞中, IPTG 诱导表达dsRNA后喂食涡虫。显微观察涡虫再生过程中的表型变化,Real time PCR检测干扰后涡虫DjStag基因表达的变化。结果表明,成功构建了DjStag基因的RNA干扰表达载体;DjStag基因 RNA干扰后,涡虫不能正常再生,再生片段显示出明显的再生缺陷;涡虫体内DjStag基因的表达受到抑制,DjStag mRNA的表达水平显著下降。     

Effect of ribonuclease on retention of conditioned response in regenerated planarians

Conditioned planarians were transected and allowed to regenerate in a ribonuclease solution or in pond water. Heads which had regenerated in ribonuclease displayed a retention level equal to that of head and tail sections which had regenerated in pond water. However, tails regenerated in ribonuclease performed randomly although they could be retrained to criterion.     

Clonogenic neoblasts are pluripotent adult stem cells that underlie planarian regeneration

Pluripotent cells in the embryo can generate all cell types, but lineage-restricted cells are generally thought to replenish adult tissues. Planarians are flatworms and regenerate from tiny body fragments, a process requiring a population of proliferating cells (neoblasts). Whether regeneration is accomplished by pluripotent cells or by the collective activity of multiple lineage-restricted cell types is unknown. We used ionizing radiation and single-cell transplantation to identify neoblasts that can form large descendant-cell colonies in vivo. These clonogenic neoblasts (cNeoblasts) produce cells that differentiate into neuronal, intestinal, and other known postmitotic cell types and are distributed throughout the body. Single transplanted cNeoblasts restored regeneration in lethally irradiated hosts. We conclude that broadly distributed, adult pluripotent stem cells underlie the remarkable regenerative abilities of planarians.     

黄河鲤肌间骨发育的形态学观察

采用整体骨骼染色、形态学解剖的方法,对黄河鲤(Cyprinus carpio haematopterus)仔稚鱼肌间骨的形态发生及成鱼肌间骨数目、形态、分布进行研究。结果显示,黄河鲤14 dpf(day post fertilization,体长11.29mm)肌间骨首先在尾部出现,此时其他骨骼包括主轴骨及附肢骨均已骨化完全。伴随鱼体生长,肌间骨由尾向头依次骨化,26 dpf(体长15.60 mm)肌间骨骨化全部完成。黄河鲤肌间骨数在93~104之间,平均为98根;鱼体一侧髓弓小骨平均为34枚,脉弓小骨平均为15枚。黄河鲤肌间骨存在7种形态:"I"形、"卜"形、"Y"形、一端多叉形、两端两分叉形、两端多叉形和树枝形,越靠近鱼体前端肌间骨形态越复杂。研究结果为今后揭示黄河鲤肌间骨骨化的分子机制,培育少肌间骨甚至无肌间骨的黄河鲤提供了形态学基础。     

魁蚶精子发生的超微结构

利用透射电镜(TEM)技术观察了魁蚶精子发生过程的超微结构变化。结果表明:魁蚶精子发生经历了精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子形成等过程,在精子形成中的主要细胞学事件包括顶体的发育、核形态变化及尾部的形成等。此过程中,前顶体颗粒聚集、融合,形成顶体囊,然后发育为圆锥形顶体;核的形态由圆形或卵圆形变为鼓形,核内染色质由团块状到颗粒状,再到高电子密度均质;线粒体聚集、融合、体积变大,迁移至核的后端,参与精子中段的形成。成熟精子由头部、中段及尾部组成,头部由顶体及核构成,中段由5个线粒体围绕远端中心粒组成,尾部为细长的鞭毛。研究亮点:魁蚶为我国重要的海产经济贝类之一,目前对其精子发生过程的超微结构未见研究报道。利用透射电镜技术观察了魁蚶精子发生过程中精子顶体的形成、核的形态建成等主要细胞学事件,探明了魁蚶精子属原生型,顶体物质的合成始于初级精母细胞时期,细胞核在精子发生过程中形态变化不大等问题,为蚶科精子发生机制的深入研究提供了参考。     

SMEDWI-2 is a PIWI-like protein that regulates planarian stem cells

We have identified two genes, smedwi-1 and smedwi-2, expressed in the dividing adult stem cells (neoblasts) of the planarian Schmidtea mediterranea. Both genes encode proteins that belong to the Argonaute/PIWI protein family and that share highest homology with those proteins defined by Drosophila PIWI. RNA interference (RNAi) of smedwi-2 blocks regeneration, even though neoblasts are present, irradiation-sensitive, and capable of proliferating in response to wounding; smedwi-2(RNAi) neoblast progeny migrate to sites of cell turnover but, unlike normal cells, fail at replacing aged tissue. We suggest that SMEDWI-2 functions within dividing neoblasts to support the generation of cells that promote regeneration and homeostasis.     

似锥低颈吸虫和宫川棘口吸虫体被超微结构研究（复殖目：棘口科）

应用扫描电镜和透射电镜对棘口科（Ｅｃｈｉｎｏｓｔｏｍａｔｉｄａｅ）的似锥低颈吸虫（Ｈｙｐｏｄｅｒａｅｕｔｎｃｏｎｏｉｄｅｕｍ）和宫川棘口吸虫（Ｅｃｈｉｎｏｓｔｏｍａｍｉｙａｇａｗｅｉ）的成虫体被超微结构进行了研究．前者头领呈半圆形，头棘埋于体被皱襞中，依稀可见。体棘自头领分布至腹吸盘处，棘呈鳞片状，瓦片状重叠排列。后者头领发达，头棘３７枝清晰可见。体棘自头领后分布至虫体后１／３处，前１／３部体棘分布最密，腹吸盘后逐渐分布稀疏，棘呈扁长形和鳞片状。似锥低颈吸虫皮层明显厚于宫川棘口吸虫。两虫皮层含杆状和圆形分泌小体，但似锥低颈吸虫皮层中部还有较多的线粒体。     

Geckos: adaptive significance and energetics of tail autotomy

Coleonyx variegatus is adapted to readily sacrifice its tail to predators. This adaptation is associated with characteristic tail behavior and rapid tail regeneration. There is no facultative metabolic increase associated with tail regeneration, and energy normally allocated to body growth and maintenance is diverted to tail regeneration. This supports the contention that tail behavior, autotomy, and rapid regeneration evolved as mechanisms promoting survival in terms of predator escape.     

正向生成单链表算法的研究

许多《数据结构》教材只讨论了从表尾到表头逆向生成单链表的算法,而没有讨论从表头到表尾正向生成单链表的算法。本文对单链表进行研究,并提出了从表头到表尾正向生成单链表的算法。     

Stimulus polarity and conditioning in planaria

Orientation in the monopolar pulse field used as the unconditioned stimulus was found to influence formation of a conditioned response to light in planarians. Planarians trained while oriented with the head toward the cathode reached maximal response rates rapidly, while those trained while oriented toward the anode showed no evidence of conditioned response formation.     

Region-specific neural induction of an engrailed protein by anterior notochord in Xenopus

Anterior-specific neural induction can be assayed by means of an antibody that recognizes the Xenopus homeobox-containing protein En-2. The En-2 antigen is an excellent early marker, since it is present as a discrete band in the anterior neural plate of neurula embryos. Regional induction was assayed by combining dorsal mesoderm with competent ectoderm. Anterior notochord from the early neurula induced En-2 frequently, while posterior notochord induced En-2 less frequently. Presumptive somitic mesoderm and presumptive head mesoderm, though they induced neural tissue, were not strong inducers of En-2. Thus, anterior notochord may be the primary mesodermal tissue responsible for the patterning of the anterior neural plate.     

甘蓝型油菜脂肪酸延长酶FAE1 RNA干扰体的构建

利用来源于油菜fael基因编码区的长498bp的2个片段，反向连接于1个83bp的内含子两端，构建成RNAi载体，以期在油菜中转录后能有效抑制fael基因的表达。所构建的RNAi载体最终序列全长2066bp，经限制性内切酶消化及序列测定验证，其序列结构与设计一致。通过农杆菌介导的油菜转化，获得油菜再生株系29个。     

白斑红点鲑精子形态和超微结构的研究

应用扫描和透射电镜观察了白斑红点鲑(Salvelinus leucomaenis)精子的形态和超微结构。白斑红点鲑精子由头部、中段和尾部组成。头部呈椭球形,主要结构是细胞核,核前端无顶体,后端有植入窝,植入窝较深,凹入细胞核的1/3,核中染色质致密,存在着不规则的网络状间隙;中段包括中心粒复合体和袖套,中心粒复合体主要由近端中心粒和远端中心粒组成,近端中心粒为典型的9组三联微管结构,与远端中心粒相互垂直,远端中心粒向下延伸形成轴丝。袖套与细胞核后端相连,含有丰富的线粒体和囊泡,部分线粒体彼此融合,形成复合线粒体,囊泡有两种;白斑红点鲑精子尾部细长,主要结构是轴丝,为典型的9+2微管结构,轴丝被许多囊泡包围,质膜向外突出形成上下对称,但大小不同的两个侧鳍。     

80 cm高度障碍马肢体角度与越障步态特征关联性分析

【目的】测定障碍马80 cm高度越障性能,研究其静态肢体角度和4个阶段步态特征之间的相关性,筛选出与越障性能相关的肢体角度指标,为障碍马体型结构研究提供理论依据。【方法】使用高速摄像机拍摄20匹障碍马静态肢体角度和越障时步态特征。并借助Kinovea视频分析软件提取马匹静态肢体角度和四个时期步态特征数据,分析肢体角度和步态特征的关联性。【结果】在起跳阶段时,头俯仰角和后位后蹄支撑相关系数为0.495^＊,即呈显著正相关(P<0.05),与起跳位置呈显著负相关(P<0.05)。在悬空阶段时,后球关节和前位后蹄摆动相相关系数为0.564^＊＊,即呈极显著正相关(P<0.01)。头俯仰角和跳跃距离呈显著负相关(P<0.05)。在着陆阶段时,后飞节和前肢双支撑相呈显著正相关(P<0.05)。后球关节和前肢双支撑相相关系数为0.568^＊,即呈极显著正相关(P<0.01)。在缓冲阶段,前球关节和步频呈显著正相关(P<0.05)。股骨倾角和后位前蹄摆动相呈显著正相关(P<0.05)。膝关节和腾空期步幅呈显著正相关(P<0.05)。头俯仰角和前位前蹄摆动相相关系数为0.570^＊＊,即呈极显著正相关(P<0.01)。【结论】在80 cm越障过程中,障碍马头俯仰角变异系数为14.59％对起跳阶段,悬空阶段、缓冲阶段有显著影响。髋骨倾角变异系数为20.22％对起跳阶段和着陆阶段有显著影响。后球关节角变异系数为3.83％对悬空阶段和着陆阶段有显著影响。头俯仰角、髋骨倾角、后球关节角等关节角度可作为重要的障碍马体型结构指标,用于评估马匹的越障性能。     

Determination of anteroposterior polarity in Drosophila

The principles of pattern formation in embryogenesis can be studied in Drosophila by means of a powerful combination of genetic and transplantation experiments. The segmented pattern of the Drosophila embryo is organized by two activities localized at the anterior and posterior egg poles. Both activities exert inducing and polarizing effects on the pattern when transplanted to other egg regions. A small set of maternal genes have been identified that are required for these activities. Mutants in these genes lack either the anterior or posterior part of the segmented pattern. The unsegmented terminal embryonic regions require a third class of genes and form independently of the anterior and posterior centers.     

Fissioning in planarians: control by the brain

Reduced population densities lead to increased rates of fissioning in planarians whereas higher population densities suppress fissioning. This effect is not primarily due to mucus deposition or substances secreted into the water. Experiments are presented which show a system of population feedback control. In the presence of other planarians, the brain exerts an influence (probably neurohormonal) to suppress fissioning. This influence becomes attenuated with axial distance from the brain.     

Centrosome loss in the evolution of planarians

The centrosome, a cytoplasmic organelle formed by cylinder-shaped centrioles surrounded by a microtubule-organizing matrix, is a hallmark of animal cells. The centrosome is conserved and essential for the development of all animal species described so far. Here, we show that planarians, and possibly other flatworms, lack centrosomes. In planarians, centrioles are only assembled in terminally differentiating ciliated cells through the acentriolar pathway to trigger the assembly of cilia. We identified a large set of conserved proteins required for centriole assembly in animals and note centrosome protein families that are missing from the planarian genome. Our study uncovers the molecular architecture and evolution of the animal centrosome and emphasizes the plasticity of animal cell biology and development.     

卢斯垫刃线虫新种和广东垫刃线虫新种描述（线虫门：垫刃科）

卢斯垫刃线虫新种 (Tylenchuslucin .sp .)和广东垫刃线虫新种 (Tylenchusguangdongensisn .sp .)分别采集于广东省深圳光明农场的玉米 (Zeamays)和宝安马田菜场的葱 (Alliumfistulosum)根际土壤。前者以角质层无明显环纹、有明显的后阴子宫囊等特征明显区别于相似种小垫刃线虫 (TylenchusminorXie&Feng ,1997)和拟小垫刃线虫 (TylenchusparaminorXie&Feng ,1997) ;以口针长 8.3～ 10 .4μm、后阴子宫囊明显和尾短于或等于肛阴距等特征明显区别于相似种微针垫刃线虫 (TylenchusstylolusXie&Feng ,1995 )。后者以头部环纹明显、后阴子宫囊显著等特征区别于相似种小垫刃线虫 (T .minor)和拟小垫刃线虫 (T .paraminor) ;以尾长于肛阴距 ,交合刺较长等特征区别于相似种卢斯垫刃线虫新种 (T .lucin .sp .)和亚戴维恩垫刃线虫 (T .subdavaineiMukhina,1981)。