家蚕复眼突变系光泽眼（lu）和光泽小眼（ve）的复眼形态观察

家蚕Bombyx mori复眼突变系光泽眼(lustrous, lu）及光泽小眼(varnished eye, ve）都是由单基因控制的隐性突变, 目前为止, 其突变基因及突变机理还未知。为了了解其复眼突变性状内外部形态结构差异, 本研究以家蚕正常品系大造Dazao （Dz）为对照, 利用光学显微镜及扫描电镜对家蚕Dz, lu和ve的成虫复眼和幼虫单眼表面进行观察, 并利用石蜡切片HE染色技术对3个品系复眼内部结构进行观察。结果表明： 突变体lu和ve的复眼表面形态除了典型的富有光泽外, 复眼形状、 大小和小眼形态、 排列及数量上都与正常型明显不同。突变体lu和ve的角膜、 晶锥、 感杆束及色素细胞均发生了异常。lu和ve不仅是复眼表面形态发生了变化, 其内部结构也发生了很大的变化。本研究为lu和ve突变基因的克隆及突变机理的阐明提供了参考信息。     

家蚕油蚕oc突变体突变基因的精细定位

【目的】油蚕oc突变体是家蚕Bombyx mori油蚕突变体的一种,经典遗传学连锁图谱已经将oc突变基因定位在5号染色体40.8 c M座位。本研究旨在对oc突变体候选基因进行精细定位并克隆,探究oc性状形成的分子机制。【方法】以油蚕oc突变品系和野生型家蚕品系大造(Dz)为亲本,其杂交产生的F1代雄性个体与oc突变的雌性个体进行回交得到的1 397头BC_1代个体为定位材料,以家蚕已经报道的基因组序列为参考设计markers,通过亲本及F1代个体筛选多态性markers,并利用多态性markers和BC_1代个体对oc突变基因进行精细定位。通过半定量RT-PCR和实时荧光定量PCR(q PCR)筛选oc紧密连锁区间内的候选基因,确定目标候选基因,继而克隆和测序该基因,分析油蚕oc突变的原因。【结果】利用1 397头BC_1代个体和11对有效的多态性markers将oc突变基因定位在M10与M11两个markers之间,物理图谱距离大约为234 kb。通过家蚕基因组数据库对oc连锁区域内的基因进行检索发现该区域有5个预测基因。对这5个预测基因在10个家蚕品系中进行的表达分析发现,只有BGIBMGA003572基因在oc突变个体体壁的表达量明显比正常个体中的低。通过基因的同源分析发现该基因编码的蛋白和人类单羧酸转运蛋白9(可能的尿酸转运蛋白)是同源蛋白,推测其为oc突变的候选基因。对BGIBMGA003572进行的克隆和测序结果显示其编码序列有5个氨基酸在oc突变体中发生了突变。【结论】通过定位克隆,本研究将oc突变基因定位在了234 kb的紧密连锁区间,其中编码单羧酸转运蛋白9的BGIBMGA003572可能和oc突变体的表型有关。     

对家蚕第18连锁群隐性基因elp、ch-2和mln测交系的分子定位分析

家蚕长形卵(elp)、第二隐性赤蚁(ch-2)、暗化型(mln)均为第18染色体上的隐性突变, 在经典连锁图谱上的顺序和遗传距离已经排定。文章采用正常卵、正常黑蚁及正常白蛾品种P50与包含此3个隐性突变的三隐性测交系W18组配正反交群体, F1回交W18后获得回交群体(P50×W18)♀×W18♂ 和W18♀×(P50×W18)♂, 分别记作BC1F和BC1M, 利用已构建的家蚕SSR分子连锁图谱和根据家蚕基因组精细图设计的STS标记, 对这3个突变基因elp、ch-2、mln进行了分子定位研究, 并根据家蚕基因组精细图, 将第18连锁群的经典遗传图、分子连锁图和基因组物理图进行了对应。整合后的图谱遗传距离为94.2 cM, 突变基因和分子标记的排列顺序分别与形态标记连锁图和基因组精细图相一致, 研究结果对家蚕第18 染色体上其他突变的定位与克隆有重要的借鉴作用。     

家蚕黄血抑制基因的SSR定位

家蚕黄茧性状主要由3个基因控制, 分别是黄血基因(Yellow blood, Y), 黄血抑制基因(Yellow inhibitor, I)和黄茧基因(Out-layer yellow cocoon, C)。I基因阻止类胡萝卜素从中肠上皮细胞到血淋巴的转运, 是天然黄茧形成过程中的重要控制基因。利用家蚕雌性不发生交换的特点, 采用黄血黄茧品系KY和白血白茧品系巴格达特(Ba)组配正反交群体(Ba×KY)×KY和KY×(Ba×KY), 分别记作BC1F和BC1M, 根据已经构建的家蚕SSR分子标记连锁图谱对I基因进行了定位及连锁分析。筛选出3个与I基因连锁的SSR标记。BC1F群中的所有白血个体均表现出与(Ba×KY) F1相同的杂合型带型; 而所有黄血个体带型与亲本KY一致, 为纯合型。利用另一个群体BC1M构建了关于I基因的遗传连锁图, 连锁图的遗传距离为38.4 cM, 与I基因最近的引物为S0904, 图距为7.4 cM。     

家蚕非滞育红卵突变体Re-nd突变基因的定位克隆

【目的】家蚕Bombyx mori非滞育红卵突变体Re-nd是唯一在非滞育状态下卵色呈现鲜红色的突变品种。本研究通过基因连锁分析和定位克隆的方法确定Re-nd的突变基因所在的染色体及紧密连锁位置,为后续Re-nd的功能研究及应用奠定基础。【方法】以家蚕卵色突变体Re-nd和野生型大造进行杂交,配制基因连锁分析群体材料和定位克隆群体材料;针对家蚕全染色体进行SNP标记开发,利用BC₁代群体材料进行基因连锁分析,确定Re-nd的突变基因所在的染色体;针对定位的Re nd的突变基因所在染色体进行SNP标记开发,利用BC₁群体材料对Re-nd的突变基因进行定位克隆。【结果】基因连锁分析结果显示Re-nd的突变表型与第6号染色体上的SNP标记完全连锁;初步定位克隆结果显示Re-nd的突变基因位于SNP标记SNP7和SNP17之间,物理距离4.04 Mb;以SNP7和SNP17之间筛选出的6个SNP标记和25个重组个体进行精细定位克隆,结果显示Re-nd的突变基因所在的区域位于SNP10和SNP12两个SNP标记之间的nscaf2853上,物理距离949.3 kb左右。【结论】将Re-nd的突变基因定位于第6号染色体的2个SNP标记SNP10和SNP12之间,物理距离约949.3 kb。本研究为后续Re-nd突变基因的精细定位及功能应用研究奠定了基础。     

天宫二号航天蚕后代小茧突变体sc的发现与基因定位

【目的】从2016年天宫二号空间实验室经历33 d后返回的1头成活“秋丰×白玉”杂交后代雌蚕Bombyx mori与地面“白玉”雄蚕交配的后代个体中,发现有结小茧突变体,进而分离并建立了飞天蚕(space silkworm)正常茧品系TG和小茧突变体品系sc。本研究通过对sc进行遗传分析和基因定位,旨在揭示产生小茧突变体的基因。【方法】对TG和sc进行表型分析;以sc, TG和正常大茧品系0223V1为试验材料,组配(sc♀×0223V1♂)F₁及回交群体BC₁F——(sc♀×0223V1♂)F₁♀×sc♂和BC₁M——sc♀×(sc♀×0223V1♂)F₁♂。以sc, 0223V1和F₁基因组DNA为模板,每个连锁群随机选10个SSR引物进行PCR扩增,筛选多态性SSR标记。利用雌性家蚕减数分裂染色体不交换的特点,用BC₁F确定sc基因所属连锁群;再根据家蚕SSR分子标记连锁图谱,用BC1M进行基因定位。【结果】表型分析表明sc幼虫体型小于TG幼虫的,蚕茧重约为TG的1/2。遗传分析表明突变受一对隐性基因sc控制;基因定位结果表明该基因位于家蚕基因组第3连锁群S2930-363和S2930-289 SSR标记之间,物理距离为684 kb,包含33个候选基因。【结论】飞天蚕小茧突变受位于家蚕基因组第3连锁群的一对隐性基因sc控制。     

家蚕性连锁平衡致死系致死基因的SSR定位

家蚕性连锁平衡致死系(S-14)雄蚕的两条Z染色体分别携带有一个非等位、紧密连锁的隐性胚胎期致死基因l1(lethal gene1)和l2(lethal gene2)。两个致死基因的致死时期分别是转青期和G2期。将S-14品系的雄蚕和家蚕P50品系的野生型雌蚕杂交,F1代雄蚕和P50品系雌蚕回交,即P50×(P50×S14)。回交后代雌蛾根据父本(F1代雄蚕)携带l1或l2基因分成两类BC1-l1和BC1-l2,分别用来做l1和l2基因定位。利用公布的家蚕全基因组序列筛选l1基因和l2基因所在Z染色体与P50品系Z染色体间的差异SSR标记,分别获得16个和18个差异性SSR标记,用差异性标记检测BC1-l1和BC1-l2,最终将l1基因定位在Z染色体物理图谱中的19.79Mb位点到染色体末端约2.60Mb范围内,将l2基因定位在Z染色体物理图谱的17.86Mb位点到18.55Mb位点约0.69Mb范围内。     

结合SSR标记和STS标记对家蚕无鳞毛翅基因的定位

家蚕突变表型无鳞毛翅(non-lepis wing, nlw)由隐性基因nlw控制。由于家蚕雌性不发生交换, 文章采用有鳞毛翅品系P50和无鳞毛翅品系U06两个品系组配F1代及BC₁回交群体, (U06×P50)×U06和U06×(U06×P50)分别记作BC₁F和BC₁M, 根据已经构建的家蚕SSR分子标记连锁图谱及已经发表的有关序列对nlw基因进行了连锁及定位分析。得到8个与nlw基因连锁的SSR(Simple sequence repeat)标记和1个STS(Sequence-tagged sites)标记。BC₁F群中的所有正常翅个体均表现出与(U06×P50)F₁相同的杂合带型; 而所有无鳞毛个体带型与亲本U06一致, 为纯合型。利用BC₁M群体构建了关于nlw基因的遗传连锁图, 连锁图的遗传距离为125.7 cM, 与nlw基因最近的引物为STS标记cash2p, 图距为11.4 cM。     

SNP标记对角膜混浊小鼠 突变相关基因的精细定位

为深入研究前期工作中以ENU诱变技术建立的遗传性角膜混浊突变系小鼠(B6-Co)的遗传机制, 利用 SNP标记对其突变基因进行精细定位, 将该品系中具有角膜混浊表型的小鼠(B6-CoP)与DBA/2小鼠(简称D2)配种得到F₁代, 再回交D2亲本品系得到F₂代, 提取F₂代角膜混浊小鼠鼠尾DNA。在MGI数据库中选取小鼠13号染色体已定位区间附近5个在C57BL/6(简称B6)和D2两个品系之间有差异的SNP, 应用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)技术及连锁分析方法对B6-Co小鼠突变基因进行精细定位。结果表明: B6-Co小鼠突变基因定位于13号染色体上112 546 283~113 397 654 bp之间, 因该区间内有5个已知基因, 其中Map3k1基因与小鼠眼睛形态生成和眼睑闭合密切相关, 提示Map3k1是B6-Co小鼠突变的强力候选基因。     

家蚕AFLP分子连锁图谱的构建及绿茧基因定位

利用改进的AFLP技术,对家蚕品系C100和大造的回交一代BC,群体进行连锁图谱的构建。经28对引物组合的选择性扩增,共获得了3956条带,平均每对引物产生141．3条带,获得多态性带只有1018条,多态性带的比率为25．7％。其中693(68．1％)个多态性位点符合1：1孟德尔分离比例。利用Mapmaker／Exp3．0软件进行连锁分析,构建了一张含有408个标记位点、33个连锁群、总图距为3676．7cM的连锁图谱,并将绿茧基因定位在该图谱的22连锁群上,表明该连锁群与家蚕经典遗传学的第15染色体相对应。     

Ectogenesis and the case against the right to the death of the foetus

Ectogenesis, or the use of an artificial womb to allow a foetus to develop, will likely become a reality within a few decades, and could significantly affect the abortion debate. We first examine the implications for Judith Jarvis Thomson’s violinist analogy, which argues for a woman’s right to withdraw life support from the foetus and so terminate her pregnancy, even if the foetus is granted full moral status. We show that on Thomson’s reasoning, there is no right to the death of the foetus, and abortion is not permissible if ectogenesis is available, provided it is safe and inexpensive. This raises the question of whether there are persuasive reasons for the right to the death of the foetus that could be exercised in the context of ectogenesis. Eric Mathison and Jeremy Davis have examined several arguments for this right, doubting that it exists, while Joona Räsänen has recently criticized their reasoning. We respond to Räsänen’s analysis, concluding that his arguments are unsuccessful, and that there is no right to the death of the foetus in these circumstances.     

On the diversity of the Cladocera in the tropics

The mythical concept of an impoverished tropical cladoceran fauna is refuted. On a planetary scale, around half of the cladoceran species presently known occur exclusively in the tropics-subtropics, often with considerable restriction to particular geographical subzones. On a regional (political) scale, the situation is often unclear because of the continued fragmentary nature of studies, and because political units are not a good basis for biogeographical comparisons. At the finest level of resolution (lake-perlake comparisons), there appears to be an upper limit of c. 50 cladoceran species per individual lake. No significant difference between lakes in the temperate zone and in the tropics could be established here. Daphnia is largely absent from the tropics, but is replaced by more Sidids, Moinids, and Bosminids, such that the average cladoceran community in the limnetic zone of a tropical lake is not characterized by less species but rather by lower population densities. This, in turn, is considered a consequence of higher prevalent predation levels in the tropics.     

Tubular networks in the terminal endings of the visual receptor cells in the human,the monkey,the cat and the dog

Summary A tubular network was found in the terminal endings of the visual receptor cells in the human, the monkey (Macaca mulatta), the cat and the dog. These tubules are arranged in close groups in the vicinity of the synaptic lamellae and the invaginated dendrites. According to the form, diameter, density of the tubules and to the consistence of the network formed by them one can distinguish at these places an initial type (type I), a transitory (type II) and a vesicular one (type III). In the the type III branching, bizarre forms are frequent. The diameter of all the tubules reaches 500–600 Å, their density and walls being the same as in the synaptic vesicles.Similar networks also occur in the axons of the visual receptor cells of the monkey.

---

Zusammenfassung In den Endigungen der Photorezeptorzellen von Mensch, Affe (Macaca mulatta), Katze und Hund kommen aus Tubuli bestehende Komplexe vor. Organellenartig in geschlossenen Gruppen angeordnet, liegen sie in Nähe der synaptischen Lamellen und der invaginierten Dendriten. An diesen Stellen kann man nach Form, Durchmesser, Dichte und Konsistenz der von den Tubuli gebildeten Komplexe drei Typen unterscheiden: 1. einen initialen (Typus I), 2. einen Übergangstypus (Typus II) und 3. einen vesiculären Typus (Typus III). In letzterem kommen häufig verzweigte, bizarre Formen vor. Der Durchmesser sämtlicher Tubuli erreicht 500–600 Å. Ihre Dichte und ihre Wand gleicht denen der synaptischen Vesikel.Ähnliche Komplexe fanden wir auch in den Axonen der Photorezeptorzellen vom Affen.

     

Assessing the Physiological State of the Fucoids from the Barents Sea Littoral by the End of the Polar Night

Methods of amperometry and potentiometric titration were used to follow dark respiration (DR) and apparent photosynthesis (AP) in the fucoids Ascophyllum nodosum (L.) Le Jol, Fucus vesiculosus L., and F. serratus L. from the Barents Sea littoral by the end of the 40-day-long polar night. The macroalgae were shown to manifest species-specific low rates of photosynthesis and respiration. However, in spite of their low photosynthetic status due to the effects of subzero temperature and prolonged low or zero illumination, the macroalgae have been able to restore DR and AP to the initial level already by the day 9; the ability to restore AP depended on the level of illumination. The study of the changes in the carbonate–bicarbonate system in the light and darkness demonstrated that the macroalgae grown in darkness, in contrast to those grown in twilight, could absorb bicarbonate in darkness; however, they lost this capacity after two-day-long illumination at an irradiance of 7 mol/(m² s). Bicarbonate uptake in darkness and the capacity to restore the systems of photosynthesis and respiration in fucoid cells are discussed in the context of algal energy metabolism under the polar night conditions.     

Arranging the elements of the potassium channel: the T1 domain occludes the cytoplasmic face of the channel

The voltage-gated potassium channel is currently one of the few membrane proteins where functional roles have been mapped onto specific segments of sequence. Although high-resolution structures of the transmembrane portions of three bacterial potassium channels, the tetramerization domain and the cytoplasmic ball are available, their relative spatial arrangement in mammalian channels remains a matter of ongoing debate. Cryo-electron microscopic images of the six transmembrane voltage-gated Kv channel have been reconstructed at up to 18 Å resolution, revealing that the T1 domain tetramerizes and is suspended below the transmembrane segments. However, the resolution of these images is insufficient to reveal the location of the third piece of the puzzle, the inactivating ball domain. We have used the aberrant interactions observed in a series of chimæric channels to establish that an assembled T1 domain restricts access to the cytoplasmic face of the channel, suggesting that the N-terminal ball and chain may be confined in the space between the T1 domain and the transmembrane portion of the channel.     

Feeding the vertebrate retina from the Cambrian to the Tertiary

The retina of the vertebrate eye is metabolically active and requires nutritive support. During the last 540 million years it has evolved into forms as complicated and nutritionally demanding as those found in avian or primate eyes. Diffusion from the choroid is generally able to supply the metabolic needs of thin retinae. However, when the thickness exceeds the limits of diffusion, structures are needed to supplement the vascular supply from the choroid. These supplemental nutritive devices include the choroidal gland, the falciform process and preretinal vascular plexus of fish, the conus papillaris of lizards, the pecten oculi of birds, the intraretinal vessels of mammals and a few novel systems that remain difficult to classify. These vascular systems are among the most variable features of the vertebrate eye. Here, we review classical and recent findings regarding such retinal nutrition systems, propose a three category classification for them based on histologic origins and speculate on the evolutionary forces which drove their development.     

Observations on the permeability of the choriocapillaris of the eye

Summary The choriocapillaris is a fenestrated capillary bed located posterior to the retinal pigment epithelium. It serves as the main source of supply to the photoreceptors, retinal pigment epithelium, and other cells of the outer retina. The permeability of these capillaries to intravenously injected ferritin (MW — approx. 480,000; mol. diam. 11 nm) was examined in the mouse, rabbit, and guinea pig, each of which is characterized by a different type of retinal vascularization. In all three species, the bulk of the ferritin remained in the capillary lumina, where it appeared to be blocked at the level of the diaphragmed fenestrae. Some ferritin was present in endothelial cell vacuoles. The results confirm previous work on the rat choriocapillaris and indicate that the barrier function of the choriocapillary endothelium is present even among species in which the retinal circulation differs significantly.Supported by NIH grant EY03418     

Separation of the pineal vesicle from the wall of the third ventricle during the post-hatching development of the chicken

Summary According to light- and electron-microscopic observations the pineal organ of the 3-day-old chicken consists of a prominent end vesicle and a tapering parenchymal stalk. During this stage the pineal lumen is in open communication with the third ventricle. However, in the 40-day-old chicken, which still possesses a well-developed end vesicle, the proximal portion of the pineal stalk displays regressive changes leading to local fragmentation. At this stage the pineal stalk is reduced, and the pineal lumen is missing. In 1-year-old chickens the parenchyma of the proximal portion of the stalk is further diminished, and in 3-year-old domestic fowl is completely displaced by bundles of collagenous fibers, only some nerve fibers being present. This post-hatching pineal development may reflect the sequence of changes leading from pineal sense organs to pineal glands.This work was supported by a grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan