RECONSTRUCTION OF THE FEEDING APPARATUS IN PLOEOTIA COSTATA (EUGLENOPHYTA) AND ITS RELATIONSHIP TO OTHER EUGLENOID FEEDING APPARATUSES

The ultrastructure of the feeding apparatus in Ploeotia costata Farmer and Triemer was determined and compared to other euglenoid feeding apparatuses. The feeding apparatus opened subapically onto the ventral surface and extended nearly the entire length of the cell. It consisted of four parts at the anterior surface: a comb, cytostome/pocket, vanes, and supporting rods. The comb was a multilayered structure of three horizontal microtubular rows encased in cement and formed the dorsal lip of the apparatus. The cytostome/pocket was located between the comb and the supporting rods, tapered into the cell as the cytopharynx and was surrounded by five vanes. The electron-opaque vanes extended the entire length of the feeding apparatus and were lined with microtubules for most of their length. Finally, two cement supporting rods that were joined by a crosspiece at the anterior end formed the ventral lip. The rods separated briefly before merging with the vanes. As the merged rods and vanes descended into the cell, they gradually narrowed and terminated. Comparisons of the feeding apparatus with Ploeotia vitrea, Diplonema ambulator, Lentomonas applanatum, and other euglenoids have led to the conclusion that the Type II feeding apparatus is found only in Ploeotia species.     

An Ultrastructural Study of Lentomonas applanatum (Preisig) N. G. (Euglenida)

ABSTRACT. Lentomonas applanatum (syn. Entosiphon applanatum Preisig) is a biflagellate, phagotrophic euglenid found in intertidal salt marshes. Lentomonas applanatum bears a superficial similarity to Entosiphon sulcatum , however, an ultrastructural study of L. applanatum revealed many features that are atypical for other described species of the genus Entosiphon . These features include number and organization of pellicular strips, construction of the feeding apparatus, nature of the flagellar transition zone and flagellar apparatus, and point of flagellar emergence. These differences show that L. applanatum is related more closely to phagotrophic genera such as Ploeotia than to E. sulcatum . The construction of the feeding apparatus and pellicle suggest that L. applanatum has retained many of the pleisiomorphic characters that were present in the earliest euglenids. The presence of similar structures in other related protists may provide important clues as to the evolution of the Euglenida.     

Organelle association visualized by three-dimensional ultrastructural imaging of the yeast cell

This study was aimed at a better understanding of organelle organization in the yeast Saccharomyces cerevisiae with special emphasis on the interaction and physical association of organelles. For this purpose, a computer aided method was employed to generate three-dimensional ultrastructural reconstructions of chemically and cryofixed yeast cells. This approach showed at a high level of resolution that yeast cells were densely packed with organelles that had a strong tendency to associate at a distance of <30 nm. The methods employed here also allowed us to measure the total surface area and volume of organelles, the number of associations between organelles, and the ratio of associations between organelles per surface area. In general, the degree of organelle associations was found to be much higher in chemically fixed cells than in cryofixed cells, with endoplasmic reticulum/plasma membrane, endoplasmic reticulum/mitochondria and lipid particles/nuclei being the most prominent pairs of associated fractions. In cryofixed cells, similar preferences for organelle association were seen, although at lower frequency. The occurrence of specific organelle associations is believed to be important for intracellular translocation and communication. Membrane contact as a possible means of interorganelle transport of cellular components, especially of lipids, is discussed.     

鄂西地区发现的我国裸藻门新记录

1981年5—6月,作者在鄂西一带,对各种生态环境中的藻类进行了一次采集。随后,又对采得的浮游藻类中的裸藻门植物进行鉴定和研究,发现了不少在我国尚未报道过的种类。有些还是较为罕见的种类。它们分别隶属于裸藻属(Euglena)的有8种(包括变种,下同),扁裸藻属(Phacus)的有5种,囊裸藻属(Trachelomonas)的有1种,陀螺藻属(Strombomonas)的有2种,柄裸藻属(Colacium)的有1种,变     

小儿心脏超声图像三维重构和显示方法

采用坐标变换和线性插值的方法,对由超声仪采集而来的二维小儿心脏超声切面图像进行重构,产生三维模型,并显示出在该模型中任意位置和角度的切面图像,对3种显示切面图像的方法在效果和时间复杂度上进行了比较,表明了这些方法在显示切面图像方面的可行性。     

Three-dimensional ultrastructural analysis of peroxisomes in HepG2 cells

Peroxisomes in the human hepatoblastoma cell line, HepG2, exhibit distinct alterations of shape, size, and distribution, dependent on culture conditions (cell density, duration in culture, and presence of specific growth factors). Although many cells with elongated tubular peroxisomes are present in thinly seeded cultures, spherical particles forming large focal clusters are found in confluent cultures. The authors have analyzed the ultrastructure and the spatial relationship of peroxisomes of HepG2 cells at different stages of differentiation, using three-dimensional (3D)-reconstruction of ultrathin serial sections, and electronic image processing. Cells were prepared for immunofluorescence using different antibodies against peroxisomal matrix and membrane proteins, as well as for electron microscopy after the alkaline 3,3′-diaminobenzidine staining for catalase. The results indicate that the tubular peroxisomes, which can reach a length of several microns, are consistently isolated, and never form an interconnected peroxisomal reticulum. At the time of disappearance of tubular peroxisomes, rows of spherical peroxisomes, arranged like beads on a string, are observed, suggesting fission of tubular ones. In differentiated confluent cultures, clusters of several peroxisomes are seen, which, by immunofluorescence, appear as large aggregates, but after 3D reconstruction consist of single spherical and angular peroxisomes without interconnections. The majority of such mature spherical peroxisomes (but not the tubular ones) exhibit tail-like, small tubular and vesicular attachments to their surface, suggesting a close functional interaction with neighboring organelles, particularly the endoplasmic reticulum, which is often observed in close vicinity of such peroxisomes.     

Three-Dimensional Reconstruction of Rabbit-Derived Pneumocystis carinii from Serial-Thin Sections I: Trophozoite

The highly complex ultrastructural morphology of the endomembrane system in Pneumocystis carinii led us to perform three-dimensional reconstruction from serial-thin sections using the CATIA (Conception Assistée Tridimensionnelle Inter Active) Dassault system program. The three-dimensional reconstruction of a small trophozoite made it possible to better understand the morphological relationship among organelles and to suggest cytophysiological hypotheses. By reconstructing other parasite stages, we gathered information about the evolution of organelles during the life cycle and about their physiology.     

湖北省裸藻门植物的新种类

湖北省地处长江中游,气候温暖,雨量充沛,湖沼众多,沟塘密布,适宜裸藻类植物繁殖生长。作者自1974年起即从事本省裸藻类植物的标本采集和研究,已经鉴定的有200多种。在本文中,仅对其中的15个新种、3个新变种和1个新变型作一报道。在这些新发现的种类中,计有裸藻属(Euglena)3种,鳞孔藻属(Lepocinclis)2变种,扁裸藻属(Phacus)1种及1变型,囊裸藻属(Trachelomonas)1种及1变种,陀螺藻属(Strombomonas)1种,卡克藻属(Khawkinea)2种,变胞藻属(Astasia)2种,辦胞藻属(Petalomonas)1种,异丝藻属(Heteronema)3种和袋鞭藻属(Peranema)1种。这些种类的模式标本均保存在中国科学院水生生物研究所藻类标本室。     

鄂西地区裸藻的初步研究

在鄂西的五峰、宜都、宜昌、当阳及神农架林区一带,采集到裸藻门植物16属140种(包括变种和变型)。属于绿色裸藻类的有116种,无色裸藻类的有24种,其中有5个新种,7个新变种,3个新变型,有20种是我国新记录。在采集区域内的地形大体上可以分成三种不同的类型,即:山岳地区(采得裸藻5种),河谷盆地地区(采得裸藻40种)和沿长江丘陵地区(采得裸藻128种)。静止水体由于地形的差异,体积的大小和水质的肥沃程度不同,都对裸藻门植物的生长有重要的影响。     

Euglenophyta of Bangladesh. I. Genus Trachelomonas EHR.

A total of 55 taxa belonging to Trachelomonas (Euglenophyta) are reported from Bangladesh. Of these, 5 varieties (Tr. allorgei var. madaripurense, Tr. anguste-ovata var. ellipsoidea, Tr. armata var. rangpurense, Tr. hispida var. subcoronata, Tr. asymmetrica var. crenulata) and one forma (Tr. anguste-ovata fa. minor) are described as new to science.     

Three-dimensional structure determination of capsid of Aedes albopicus C6/36 cell densovirus

The three-dimensional structure of capsid of Aedes albopictus C6/36 densovirus was determined to 14-(A) resolution by electron cryomicroscopy and computer reconstruction. The triangulation number of the capsid is 1. There are 12 holes in each triangular face and a spike on each 5-fold vertex. The validity of the capsid and nucleic acid densities in the reconstructions was discussed.     

Isolation and characterization of paracrystalline structures from transgenic P<Emphasis Type="Italic">ssu-ipt</Emphasis> tobacco

Distinct crystalloids were found in chloroplasts of transgenic Pssu-ipt tobacco (Nicotiana tabacum L. cv. Petit Havana SR1) overproducing endogenous cytokinins. They were present both in rooted (T) and grafted (TC) transgenic plants contrary to control tobacco (C). The fractions enriched by crystalloids were isolated from chloroplasts using a continuous or a discontinuous Percoll gradient. Chlorophyll (Chl) fluorescence emission spectra at 77 K indicated the presence of aggregates of light-harvesting complex proteins (LHC2) that was not connected to reaction centres of photosystem 2 both in isolated chloroplasts and in the fraction of 80 % Percoll gradient from both types of transgenic tobacco. Further analyses, i.e. pigment contents, polypeptide composition by SDS-PAGE, and immunoblotting support our hypothesis that crystalloids inside chloroplasts of transgenic tobacco are formed by LHC2 aggregates. Treatment with two distinct detergents, chosen with respect to their effects (i.e. β-dodecyl maltoside or Triton X-100), resulted in different degree of disintegration of Chl a/b proteins in transgenic plants compared to the control. Electron microscopic observations and immunogold labelling with specific LHC2 antibodies carried on the resin embedded leaf sections or free suspensions of chloroplasts showed that gold particles were bound preferentially on the outer surface of crystalloids. Three-dimensional reconstruction of chloroplasts and crystalloids proved that paracrystalline structures varied moderately in their size and took up a significant portion of total chloroplast volume.     

女性尿道阴道瘘数字化三维重建在临床治疗中的初步应用

目的:基于CT扫描图象建立精确的女性尿道阴道瘘数字化模型,探讨其在临床诊断及治疗中的应用。方法:选择1例女性尿道阴道瘘病例,进行尿道CT连续断层扫描,扫描结果导入Mimics软件中进行三维重建,利用三维重建模型指导临床。结果:建立女性尿道阴道瘘及周围结构的三维立体模型,可以方便地从任意角度和方向观察瘘管情况,测量有关的数据;还可以在数字化模型上进行手术设计。结论:女性尿道阴道瘘的数字化三维模型能够更直观、准确地反映病变部位的三维立体结构。对女性尿道阴道瘘的诊断、手术规划等有较大帮助。