古生代轮藻类的演化和分类

本文通过对古生代轮藻类群形态结构的比较研究,认为Ｔｒｏｃｈｉｌｉｓｃｕｓ和Ｍｏｅｌｌｅｒｉｎａ具有不同的起源。前者藏卵器包围细胞右旋具横脊,底部结构两侧对称,起源于Ｓｙｃｉｄｉｕｍ;后者的左旋轮藻类包围细胞简单,底部结构辐射对称源于具简单直立包围细胞的Ｘｉｎｊｉａｎｇｏｃｈａｒａ。根据底部结构的对称性,将轮藻门划分为Ｓｙｃｉｄｉｐｈｙｃｅａｅ和Ｃｈａｒｏｐｈｙｃｄｅａｅ两个纲,Ｓｙｃｉｄｉｐｈｙｃ     

Chara zeylanica Wildenow（现生轮藻）藏卵器几个特征的统计分析

本文对采自广西涠洲岛的现生轮藻Ｃｈａｒａ ｚｅｙｌａｎｉｃａ藏卵器的几个特征作了统计分析,结果表明,藏卵器的最大长度,最大宽度和螺旋环数等性状的变异有一定范围,服从统计规律,单变量的变化呈正态分布,具一明显峰值;ＬＰＡ是ＬＥＤ的线性函数,呈正相关。藏卵器乌黑细胞的钙化程度与成熟度有关。未成熟藏卵器的顶部构造为典型的轮藻型,成熟藏卵的顶部构造与有盖轮藻型接近。因此认为,Ｃｒａｍｂａｓｔｉｃｈａｒａ     

西南地区中泥盆世的直立轮藻

本文描述了中泥盆世的直立轮藻5种、1型,分别属于Sycidium 和Chovanella 两属。文中讨论了这两个属的分类位置问题,详细阐述了Sycidium 藏卵器的发育特点,提出了关于藏卵器包围细胞分裂发育过程的新认识,同时提出了含化石地层的时代应相当于中泥盆世晚期的吉维特期。     

莴苣叶疫病和茎腐病的病原

2021年3–6月,从甘肃省的生菜(叶用莴苣)叶片和青海省的莴笋(茎用莴苣)茎秆罹病样本上分离得到腐霉属卵菌。通过Koch’s法则明确了分出菌株的致病性。依据形态学和分子生物学特征,将3个菌株鉴定为嗜导管腐霉Pythium tracheiphilum。在核糖体DNA内转录间隔区(rDNA-ITS)、细胞色素氧化酶亚基1(cox1)和核糖体DNA28S大亚基(rDNA-LSU)基因联合系统发育树中,甘肃菌株(LPy-B)和青海菌株(LPy-C和LPy-D)被聚在P. tracheiphilum的不同亚群里,不同菌株的适宜生长温度和产孢特性存在差异。孢子囊顶生、间生或侧生,球形,17.13–53.73μm,或近球形至葫芦状,24.58–56.72×18.62–53.73μm;休止孢球形,6.70–9.68μm;藏卵器光滑,顶生或间生,球形,15.64–23.09μm;每个藏卵器有雄器1–2个,雄器与藏卵器同丝或异丝生;卵孢子满器或近满器,球形,直径13.41–20.11μm,卵孢子壁厚0.74–2.23μm。致病性测定结果表明,除莴苣外,嗜导管腐霉还可侵染菊科的华蒲公英和刺儿菜、十字花科的...     

豚鼠耳蜗螺旋动脉平滑肌细胞和内皮细胞静息膜电位特性

目的:多种内耳疾病和内耳微循环障碍有关,但目前对提供内耳主要血供的耳蜗螺旋动脉平滑肌(SMC)和内皮细胞(EC)的生理学特性还不十分清楚,需要进一步研究。方法:本研究采用双细胞内微电极记录技术和细胞荧光染色技术,研究耳蜗螺旋动脉平滑肌和内皮细胞的膜电位特性和细胞间的通讯联系。结果:研究发现耳蜗螺旋动脉SMC和EC具有高、低两种静息膜电位(RP)状态,两种静息膜电位状态的细胞对乙酰胆碱和高K+的反应完全不同。双微电极可同时记录到EC-ECS、MC-SMC和SMC-EC不同类型的细胞,两个细胞的静息膜电位也可以是双高RP、双低RP和一高一低RP。实验所记录的一高一低RP均是SMC-EC类型,而且EC初始膜电位均为高电位,SMC初始膜电位均为低电位。而双高RP和双低RP可以是SMC-SMC或EC-EC或SMC-EC类型。结论:结果表明耳蜗螺旋动脉的SMC和EC在0.3~0.5 mm的范围内,同类细胞之间有很好的通讯联系,能很好的保持功能的协同和一致,血管壁异类细胞则不同。     

四川江油中泥盆纪的一种轮藻化石*

1955年9月杨敬之先生及王水在川北江油县马角坝中泥盆纪石灰岩所夹的灰色薄层钙质页岩中采集了很多小化石,笔者等在其中发现一种轮藻类的藏卵器(Oogonium)化石,即本文所描述的Sycidium。和此种化石共生的有介形虫化石。根据侯祐堂先生的鉴定,这些介形虫化石是属于中、下泥盆纪的类型,而不像上泥盆纪的产物。Sycidium 属于Sycidiaceae 科,外形作球状,藏卵器为16行、18行或20行纵分排列的许多细胞所组成,每一个细胞的外表,由于钙化程度的不同而有所不同,如钙化不完全则成小凹陷(pits)(见插图1之b 和插图2之b),钙化完全则成小突起(tuber-     

内耳免疫反应诱导Fas和FasL表达与凋亡的关系

目的研究内耳免疫反应过程中是否存在细胞凋亡,以及细胞凋亡是否与Fas和FasL信号转导有关.方法选用雌性白色豚鼠16只,随机分为实验组和对照组各8只,以钥孔虫戚血蓝蛋白(keyhole limpet hemocyanin,KLH)全身免疫后,实验组以相同抗原进行内耳免疫,对照组内耳注射等量的磷酸盐缓冲生理盐水(phosphate buffered saline,PBS),在内耳免疫5d后处死动物,取内耳免疫侧耳蜗做石蜡切片.通过脱氧核糖核苷酸末端转移酶介导的缺口末端标记技术(terminal-deoxynucleotidyl transferase mediated nick end labeling,TUNEL)检测内耳凋亡细胞,免疫组化检测内耳Fas和FasL的表达.结果实验组豚鼠内耳Corti器毛细胞,血管纹的缘细胞和螺旋神经节细胞存在TUNEL染色阳性细胞,而对照组动物切片仅在支持细胞、血管纹和螺旋神经节细胞中发现极少数TUNEL染色阳性细胞.免疫组化染色实验组Corti器、螺旋神经节细胞、血管纹和螺旋韧带Fas和FasL蛋白表达阳性,而对照组只有螺旋神经节细胞和血管纹有较弱的Fas蛋白表达,FasL蛋白表达阴性.结论内耳免疫反应可诱导细胞凋亡的发生,Fas-FasL途径是参与此过程重要的信号转导途径之一.     

澳大利亚轮藻植物LYCHNOTHAMNUS BARBATUS(MEYEN)LEONHARDI藏卵器统计分析及与欧洲同类植物的对比研究

Lychnothamnus(Characeae)为一分布于欧洲和大洋洲的单型属,该类植物日趋衰落。过去十年中,仅在澳大利亚昆士兰州华莱士湾发现数量丰富生长良好的L．barbatus(Meyen)Leonhardi。本文对澳大利亚现生L．barbatus藏卵器进行描述、统计分析和扫描照相,并与其它地区同类现生和化石藏卵器进行对比,结果表明澳大利亚的藏卵器除形状偏长球形、宽度较小、钙化较弱外,其余特征与欧洲植物较为一致。钙化减弱的原因可能与澳大利亚热带地区由季风造成的洪水泛滥降低了水体中离子的浓度有关。     

脉红螺神经细胞和胶质细胞光镜及电镜观察

脉红螺(Rapana venosa)神经节存在三种细胞,它们是神经细胞、星形胶质细胞和无突胶质细胞。从结构上看,神经细胞与后鳃类软体动物海兔(Aplysia)的神经细胞不尽相同。电镜观察表明,脉红螺右足神经节细胞体区的星形胶质细胞与海兔腹神经节内包围神经细胞体的星形胶质细胞很相似。但在脉红螺,星形胶质细胞的突起与神经细胞之间的拓朴学关系尚不清楚。无突胶质细胞在脉红螺神经节内广泛存在,它的核类似于海兔神经细胞的核。这类细胞的功能尚不清楚。     

复合感染建兰花叶病毒和齿兰环斑病毒的兰花超微结构观察及病原物快速鉴定

通过负染和超薄切片观察到蝴蝶兰(Phalaenopsis amabilis)病叶中线状和杆状病毒颗粒。组织切片观察,同时发现两种病毒粒子的典型聚集体:线状粒子的带状聚集体,粒子多层排列,层间呈一定角度或螺旋相叠;杆状粒子的平行、角层状或螺旋型排列聚集体。二种病毒聚集体均出现于薄壁细胞、细胞间隙和输导组织细胞中。感病细胞中叶绿体发育不全;线粒体增生、肿胀甚至空化;细胞核膨大、空化。进一步的多重RT-PCR与病毒核酸序列分析,同时扩增到建兰花叶病毒(CymMV)和齿兰环斑病毒(ORSV)的外壳蛋白基因,与GenBank已知分离物同源性分别达到98%和99%-100%。从细胞和分子层面揭示了蝴蝶兰受CymMV和ORSV复合侵染并可能导致严重病症的事实,分析和明确了感病兰细胞超微结构的病变特征以及田间病症发生的细胞病理学依据。     

Morphological changes in the oocyte and its surrounding vestments during in vivo fertilization in the dasyurid marsupial Sminthopsis crassicaudata

This light and transmission electron microscopical study shows that the first polar body is given off before ovulation and that part of its cell membrane and that of the surrounding oocyte have long microvilli at the time of its ejection. Several layers of cumulus cells initially surround the secondary oocyte and first polar body, but the ovulated oocytes in the oviducts in the process of being fertilized do not have cumulus cells around them. Partly expelled second polar bodies occur in the oviduct; they are elongated structures that lack organelles and have electron-dense nuclei. A small fertilization cone appears to form around the sperm tail at the time of sperm entry into the egg and an incorporation cone develops around the sperm head in the egg cytoplasm. In three fertilized eggs a small hole was seen in the zona, which was presumably formed by the spermatozoon during penetration. Cortical granules, present in ovarian oocytes, are not seen in fertilized tubal or uterine eggs; release of their contents probably reduces the chances of polyspermy, although at least one polyspermic fertilized egg was seen and several other fertilized eggs had spermatozoa within the zona pellucida. In the zygote the pronuclei come to lie close together, but there was no evidence of fusion. A "yolk mass," which becomes eccentric before ovulation, is extruded by the time the two-cell embryos are formed, but many vacuoles remain in the non-yolky pole of the egg. A shell membrane of variable thickness is present around all uterine eggs but its origin remains undetermined.     

Fertilization of the eggs ofCynops pyrrhogaster (japanese newt) after immersion in water

Summary Cynops pyrrhogaster oviducal eggs with and without jelly envelopes (jelly egg and dejellied egg respectively) were immersed in water, and then inseminated artificially. After 1 h of immersion in water, more than half the dejellied eggs were fertilized and developed, but no jelly eggs developed. The rapid decrease in the ability of jelly eggs to be fertilized after immersion in water is not due to a deficiency in the egg. Our results make it clear that hydrated jelly envelopes prevent the eggs from fertilizing. The ability of the egg to be fertilized decreases for a long time in water and this decrease proceeds more slowly in De Boer's solution or Holtfreter's balanced salt solution than in water.     

How does a millimeter-sized cell find its center?

Microtubules play a central role in centering the nucleus or mitotic in eukaryotic cells. However, despite common use of microtubules for centering, physical mechanisms can vary greatly, and depend on cell size and cell type. In the small fission yeast cells, the nucleus can be centered by pushing forces that are generated when growing microtubules hit the cell boundary. This mechanism may not be possible in larger cells, because the compressive force that microtubules can sustain are limited by buckling, so maximal force decreases with microtubule length. In a well-studied intermediate sized cell, the C. elegans fertilized egg, centrosomes are centered by cortex-attached motors that pull on microtubules. This mechanism is widely assumed to be general for larger cells. However, re-evaluation of classic experiments in a very large cell, the fertilized amphibian egg, argues against such generality. In these large eggs, movement of asters away from a part of the cell boundary that they are touching cannot be mediated by cortical pulling, because the astral microtubules are too short to reach the opposite cell boundary. A century ago, Herlant and Brachet discovered that multiple asters within a single egg center relative to the cell boundary, but also relative to each other. Here, we summarize current understanding of microtubule organization during the first cell cycle in a fertilized Xenopus egg, discuss how microtubule asters move towards the center of this very large cell, and how multiple asters shape and position themselves relative to each other.     

Regeneration of Fertile Barley Plants from Mechanically Isolated Protoplasts of the Fertilized Egg Cell

A simple procedure is described for the mechanical isolation of protoplasts of unfertilized and fertilized barley egg cells from dissected ovules. Viable protoplasts were isolated from ~75% of the dissected ovules. Unfertilized protoplasts did not divide, whereas almost all fertilized protoplasts developed into microcalli. These degenerated when grown in medium only. When cocultivated with barley microspores undergoing microspore embryogenesis, the protoplasts of the fertilized egg cells developed into embryo-like structures that gave rise to fully fertile plants. On average, 75% of cocultivated protoplasts of fertilized egg cells developed into embryo-like structures. Fully fertile plants were regenerated from ~50% of the embryo-like structures. The isolation-regeneration techniques may be largely genotype independent, because similar frequencies were obtained in two different barley varieties with very different performance in anther and microspore culture. Protoplasts of unfertilized and fertilized eggs of wheat were isolated by the same procedure, and a fully fertile wheat plant was regenerated by cocultivation with barley microspores.     

The magic of four： induction of pluripotent stem cells from somatic cells by Oct4, Sox2, Myc and Klf4

The developmental process from a fertilized egg to agrown adult is programmed with remarkable accuracy.While the genetic information of the fertilized egg and itsdescendent somatic cells are the same, it is the selectiveexpressions of the same genome that give rise to the 200or so different cell types in an adult. The differentiatedstates of these adult cells are maintained epigenetically,presumably through the modification of chromatins and theassociated histones. In higher mammals, it was thought thatthe differentiation process is irreversible until the successfulcloning of Dolly [1]. By transferring a nucleus from a fullydifferentiated cell in the mammary gland, Wilmut and col-leagues were able to generate an exact replica of a highermammal, the Doily [1]. This work not only demonstratedthat the genome of differentiated cells can be reprogrammedinto an embryonic state and then to resume a full-fledgeddevelopmental process to generate a normal adult, but alsorejuvenated the field of animal cloning. The prospect thata somatic cell from a patient may be reprogrammed to the     

Absence of furrowing activity following regional cortical tension reduction in sand dollar blastomere and fertilized egg fragment surfaces

The purpose of the present investigation was to test experimentally the possibility that division mechanism establishment at the equator of sand dollar eggs may be a consequence of cortical tension gradients between the equator and the poles. Cytochalasin has been shown to decrease tension at the sea urchin egg surface. The concave ends of cytochalasin D-containing agarose cylinders were held against regions of the surface of Echinarachnius parma blastomeres and enucleated fertilized egg fragments. The ability to interfere with normal furrowing activity was used as a biological indicator of the effectiveness of cytochalasin. When agarose containing 2 microg/mL cytochalasin contacted the equatorial region of the blastomeres resulting from the first cleavage, or the equatorial surfaces of nucleated fertilized egg halves, furrowing was blocked, stalled or delayed, indicating that the concentration of cytochalasin was effective. When the same concentration of cytochalasin was applied to the poles, the cells and nucleated fertilized egg fragments divided in the same way as the controls, indicating that the effectiveness of the cytochalasin did not spread from the poles to the equator and that bisection did not interfere with the division of nucleated fertilized egg fragments. When the same concentration of cytochalasin was applied to diametrically opposed surfaces of enucleated, spherical egg fragments, there was no evidence of furrowing activity between the areas that contacted the cytochalasin or in any other part of the surface. Because of the tension-reducing effect of cytochalasin, a tension gradient existed between the regions affected and unaffected by cytochalasin. The results strongly suggest that establishment of the division mechanism by simple gradients of tension at the surface is unlikely.     

THE FERTILIZATION CANAL IN PLODIA INTERPUNCTELLA (HÜBNER) (PYRALIDAE: LEPIDOPTERA)

The spermathecal duct of Plodia interpunctella (Hübner) was studied with light and transmission electron microscopy. The lumen in the duct is enclosed by a thin chitinous wall that has a thicker band that spirals along the length of the duct. The thick spiral band pinches off part of the lumen and creates a smaller canal, which it encloses. Although the two canals are not separated, the duct appears to have a double lumen. The thin wall of the main canal provides a flexibility in which the lumen widens or narrows concomitantly with contractions of the spermatheca and the portion of the duct adjoining the spermatheca. Sperm is transferred from the spermatheca to the vestibulum where the egg is fertilized. The distention of the canal and contractions of the spermatheca thus account for the speed at which eggs are fertilized and deposited.     

Isolation and in vitro culture of zygotes and central cells of Oryza sativa L.

 All component cells of the embryo-sac before and after fertilization in rice were isolated by manual microdissection under conditions either free of enzymes or combined with a short pulse of enzymatic treatment.In general, the frequency of isolated unfertilized or fertilized egg cells or central cells reached 15–40%. Various component cells of the embryo-sac after isolation were distinguished by their own morphological characteristics. The isolated cells were cultured in a microchamber and fed with dividing rice suspension cells. Both unfertilized and fertilized egg cells and central cells were induced to divide. Among them only the fertilized egg cells (the zygotes) developed into proembryo-like multicellular structures. The frequency of the first zygotic division and the frequency of multicellular structures were higher using the non-enzymatic method than using the enzymatic one. Received: 14 January 1999 / Revision received: 25 March 1999 / Accepted: 17 April 1999     

Fusion of fertilized and unfertilized sea urchin eggs : Maintenance of cell surface integrity

Here we report that immediately after the fusion of a fertilized and an unfertilized egg, the two halves of the fused egg retain their respective cell surface organizations. Long microvilli are present on that area of the surface contributed by the fertilized egg, and the unfertilized portion remains comparatively smooth. Cortical granules are absent in the cortex contributed by the fertilized egg, whereas these organelles are present in the cortex of the unfertilized portion. There are distinct boundaries formed by the presence or absence of long microvilli and of undischarged cortical granules. However, following the synchronous prophase of the two nuclei, the original fertilized and unfertilized portions are no longer distinguishable. The observations indicate that the unfertilized portion of the fused egg is capable of maintaining its original surface properties but can, during prophase, undergo changes equivalent to those that take place at fertilization.