Morphological diversity of Paramoeba perurans trophozoites and their interaction with Atlantic salmon,Salmo salar L., gills

Amoebic gill disease (AGD) caused by the ectoparasite Paramoeba perurans affects several cultured marine fish species worldwide. In this study, the morphology and ultrastructure of P. perurans in vitro and in vivo was investigated using scanning and transmission electron microscopy (SEM and TEM, respectively). Amoebae cultures contained several different morphologies ranging from a distinct rounded cell structure and polymorphic cells with pseudopodia of different lengths and shapes. SEM studies of the gills of AGD‐affected Atlantic salmon, Salmo salar L., revealed the presence of enlarged swellings in affected gill filaments and fusion of adjacent lamellae. Spherical amoebae appeared to embed within the epithelium, and subsequently leave hemispherical indentations with visible fenestrations in the basolateral surface following their departure. These fenestrated structures corresponded to the presence of pseudopodia which could be seen by TEM to penetrate into the epithelium. The membrane–membrane interface contained an amorphous and slightly fibrous matrix. This suggests the existence of cellular glycocalyces and a role for extracellular products in mediating pathological changes in amoebic gill disease.     

玉米南方锈病菌的超微结构研究

认识玉米南方锈菌的超微结构特征和侵染过程的细胞学特征,可为南方锈菌致病机理和玉米抗锈机制研究提供重要依据。本研究采集玉米品种‘郑丹958’和‘先玉335’自然发病的南方锈病病叶,4%戊二醛固定液抽气固定,采用扫描电镜和透射电镜技术进行观察。结果表明,玉米南方锈病菌的胞间菌丝呈丝状,胞间菌丝和胞内菌丝细胞核在不同感病玉米品种之间具有单核或者双核的差异;胞间菌丝与寄主细胞接触诱导吸器母细胞的分化,吸器母细胞穿透寄主细胞壁在细胞内形成吸器;寄主细胞质膜在吸器的侵入部位内陷,随着吸器的发育,在吸器颈部周围形成胼胝质并将吸器颈部完全包围起来;夏孢子表面具密致、交错排列的刺突,刺突基部外围存在圆形凹陷的脊。本研究揭示了玉米南方锈菌基本超微结构特征和侵染机构(吸器)细胞学特征,并对其在不同品种细胞内的核相进行了分析,为玉米南方锈菌组织病理学研究奠定重要基础。     

马铃薯Y病毒两分离物特性及其侵染寄主的超微结构比较研究

报道了马铃薯Y病毒两分离物的生物学和血清学特性、病毒粒体形态大小以及它们引起的寄主细胞病变特征等方面的差异.从山东省主要烟草和马铃薯种植区病毒样品中分离到两个马铃薯Y病毒分离物,分别为PVY-T 和PVY-P.两分离物在寄主植物上的症状表现、体外抗性、蚜传特性、血清学以及病毒粒体大小等方面存在着明显的差异.同时,这些结果与作对照的PVY标准株系PVYN 和PVYO相比较,初步推测分离物PVY-T属于PVYO株系 ,而P VY-P则属于PVYN.通过对受侵染寄主的细胞超微结构观察比较发现,这两种PVY分离物在寄主细胞内的分布特征、内含体以及与寄主互作后所引起的细胞病变也明显不同,这些可能成为区别PVY不同株系的依据之一.     

诱导栉孔扇贝雌核发育时精子入卵的扫描电镜观察

取栉孔扇贝 (Chlamysfarreri)精子在 80 0 μW/(cm2 ·s)的紫外线下辐射 ,然后与正常卵子受精 ,每隔 0 .5min取“受精卵”固定。在扫描电镜下连续观察精子的入卵过程 ,然后与正常精子的入卵过程进行比较。结果表明 ,紫外辐射后的精子可以划分为 3种类型 :I类精子 ,基本无明显变化 ,可以激发卵黄膜举起形成受精膜 ,同时诱发卵子发生皮层反应 ,在受精锥的作用下正常入卵 ,但入卵的时间较正常精子晚 ;II类精子 ,顶体膜破裂 ,顶体丝伸出 ;III类精子 ,顶体丝伸出 ,鞭毛脱落。由于II、III类精子在紫外辐射条件下诱发了顶体反应 ,融解卵膜的酶提前释放 ,因而不能入卵。精子鞭毛的脱落 ,使精子丧失了运动能力 ,是导致卵表面附着的精子数量较少的原因之一。无论是正常精子还是辐射后的精子 ,入卵后在卵表面都留下一个类似受精孔的通道。实验组中未发现有多精入卵现象     

Leaf litter decomposition in a chaparral ecosystem, Southern California

Decomposition losses from leaves of three evergreen chaparral species, scrub oak (Quercus dumosa), ceanothus (Ceanothus crassifolius), and manzanita (Arctostaphylos glauca), were quantified over a 2-y field exposure using litterbags. Changes in ash-free dry mass, C, and N were monitored at 2- to 6-month intervals at four replicate sites composed of patches of these three chaparral species. Three proximate C fractions were extracted from fresh and decomposing litter samples: polar and non-polar extractives (EXT), acid-solubles (ACID), and acid-insolubles (KLIG). The chemical structure of fresh and decomposed litter was additionally characterized using high-resolution solid-state ¹³C NMR spectroscopy, while morphological properties were examined by scanning electron microscopy (SEM). After 2 y, the litters had lost between 20.7%±1.2 (Ceanothus) and 35.2%±6.8 (Quercus) of their original ash-free dry mass. The manzanita decomposed at a significantly faster rate than the other two litter types during the first few months of field exposure. Yet, after 2 y, mass loss was greater for the oak. Differences in decomposition rates could not be accounted for based on a single litter quality index. Fresh manzanita exhibited a significantly higher N content, which could explain its initially faster decay rate. Fresh oak litter, on the other hand, had a relatively high ACID and O-alkyl C (O-ALK) content, which may have been responsible for its decay pattern. Fresh ceanothus contained a relatively low KLIG content, yet it decomposed more slowly than the two other species. The solid-state ¹³C NMR spectra of the ceanothus litter had two peaks characteristic of proanthocyanidins, which likely contributed to the recalcitrance of this litter type. SEM revealed that ceanothus leaf surfaces were left nearly unchanged after field exposure. In comparison, the oak and manzanita leaf surfaces were pitted and covered by microbial growth to the point of being unrecognizable. Taken together, our results indicate that a combination of biological, physical and chemical factors need to be examined to clarify the different decomposition rates and patterns of these three chaparral species.     

6种枇杷属植物花粉形态扫描电镜观察

应用扫描电镜,对1个栽培品种(早钟6号),5个野生类型(椭圆枇杷、大渡河枇杷、栎叶枇杷、台湾枇杷、台湾枇杷恒春变型)的花粉进行了形态观察。结果表明,6种枇杷属植物的花粉粒均为长球形,具3条萌发沟,萌发沟以等间距环状分布,属于N3P4C5型花粉。6种枇杷属植物的花粉外壁属于条纹-穴状纹饰类型,外壁均具条嵴,嵴洼处散生有覆盖层穿孔,但条嵴及穿孔的形态和分布差异明显。最后,结合花粉形态的演化规律,对大渡河枇杷的系统学位置及枇杷属植物的起源与进化进行了讨论。     

浅谈电算化条件下的审计

随着经济迅猛发展，计算机在我国已广泛应用于各个领域，并很快向更大范围扩展，审计工作中实施电算化已是当务之急。本文拟从我国电算化审计的现状入手，剖析原因，提出加快实施电算化审计的初步思路。     

犬冠状病毒在犬体内分布的初步研究

对电镜检查粪便中发现有犬冠状病毒的 4只犬 ,进行了血常规、尿常规、肝肾功能和心电图检查 ,均未发现明显异常。扑杀后经电镜负染检查 ,除肠内容物外 ,在其肝、心、脾、肾和肺等实质脏器中均发现冠状病毒粒子