广东肝血簇虫在宿主内脏裂体生殖时期超微结构的研究

本文详细描述了广东肝血簇虫(Hepatozoon guangdongensis)在实验宿主、中国水蛇肺部裂体生殖整个发育过程各期虫体的超微结构。成熟裂殖体内的裂殖子与肺部毛细血管内皮细胞内的裂殖子的超微结构是相似的。裂殖子(3.4×1.3μm)外被由外膜和内膜构成的表膜,它与球虫一样具有包括类锥体在内的完全顶复结构。内皮细胞内的裂殖子和滋养体都没有围虫泡和围虫泡膜包绕。具有内膜的长形滋养体变圆,并外被由宿主细胞产生的围虫泡和围虫泡膜包绕,转变成为圆形的幼期裂殖体,然后发育成为成熟的裂殖体。成熟裂殖体(23×10μm)内含30—50个裂殖子。裂殖体内没有观察到残余体存在。     

Low concentrations of dimethyl sulphoxide accelerate conjugation and incorporation of glycine and glucosamine intetrahymena

Summary Dimethyl sulphoxide at relatively low comentrations, 0.01 to 1 mM, enhanced the conjugation and cell-to-cell adhesion of complementary strains of matingTetrahymena thermophila. The time required to form stable conjugates was reduced by dimethyl sulphoxide. This chemical stimulated the uptake of glycine and glucosamine from the suspending media. Incorporation of 2-¹⁴C-glycine and 6-³H-D-glucosamine into protein and glycoprotein was enhanced in whole cells, surface membrane and cilia. Incorporation of glucosamine into the microsomal fraction was increased in the dimethyl sulphoxidetreated cells while there was little change in glycine incorporation. There were no detectable changes in glycine and glucosamine incorporation into the nuclear fractions isolated from conjugatingTetrahymena exposed to dimethyl sulphoxide.     

De novo glucan synthesis by mutans streptococcal glucosyltransferases present in pellicle promotes firm binding of Streptococcus gordonii to tooth surfaces

Adherence of 3H-labelled cells of Streptococcus gordonii and Streptococcus milleri to artificial pellicles prepared from saliva supplemented with glucosyltransferases from mutants streptococci was examined using a new assay for sucrose-dependent cell-to-pellicle attachment. Results indicate that S. gordonii, but not S. milleri, could attach tightly to hydroxylapatite surfaces through de novo glucan synthesis by mutants streptococcal glucosyltransferases present in the experimental salivary pellicles.     

Ultrastructural Localization of Adenosine Triphosphatase Activity in Stigma Cells of Populus lasioearpa and Its Changes During Development

The ultrastructural localization of adenosine triphosphatase (ATPase) activities in stigmatic cells in various developmental stages of PopUlus lasiocarpa was investigated using the cytochemical method Of read phosphate precipitation. The results show as follows: 1. Lead deposits which marked the ATPase activities were observed on the pellicle of stigmas. The ATPase activities greatly increased in receptive stage, but they were few or even absent in young and old stages. The changes Of pellicle ATPase strongly exhibited that ATPase was correlated with the pollen-stigma interaction. 2. In the stigma ceils inreceptive stage, ATPase was mainly located at mitochondria cristae, chloroplast lamellae and endoplasmic reticulum. Lead deposits were also visible on the plasmalemma, plasmodesma, nuclear membrane and in nucleoli. No lead deposits were found on dictyosome and vacuole membrane. 3. During the degeneration of stigmatic ceils; the location of ATPase changed. The distribution of ATPase was in vacuole membrane, digestive vesicle, mitochondrium envelop, chloroplast envelop, and digested fragment. The mitochondrium cristae and chloroplast lamellae where ATPase was the most active in previous stage now lost their ATPase activities.     

Characterisation of Structures in Salivary Secretion Film Formation. An Experimental Study with Atomic Force Microscopy

The purpose of the present study was to characterise the structure dynamics of pure salivary secretions retained on controlled surfaces with different surface energies in the early stage of salivary film formation. Germanium prisms prepared to have either low surface energy or medium surface energy were incubated in fresh secretions of either human parotid saliva (HPS) or human submandibular/sublingual saliva (HSMSLS) for 15, 90, and 180 min. After controlled rinsing with distilled water, the surfaces were air dried and thereafter imaged with atomic force microscopy (AFM). The amount of adsorbed material and the size of the structures detected increased with increased saliva exposure time. The film thicknesses varied from 10 to 150 nm, and both HPS and HSMSLS films contained structures with diameters varying from 40 nm to 2 μm. Some of these were clustered into special formations. The HPS films exhibited a more granular morphology than the HSMSLS films. Furthermore, branched lines were detected on the low surface energy germanium prisms incubated in saliva. The results indicate that exposure time, surface energy, and type of salivary secretion all are factors affecting the adsorption characteristics of salivary films.     

Plasmodium lophurae: the ultrastructure of the exoerythrocytic stages

The fine structure of the exoerythrocytic stages of Plasmodium lophurae was studied. in specimens grown in tissue cultures of avian cells. Specimens were prepared for sectioning by a method which minimizes disturbance and permits precise selection and orientation specimens.Plasmodium lophurae is similar in many aspects to P. fallax. Merozoites are highly specialized and differentiated. Analysis of their ultrastructure revealed the polar complex to be a specialization of the pellicular envelope and its associated underlying microtubules. The polar rings may simply be a modification of the inner membrane of the pellicle and not discrete structures as previously reported. The electron-dense polar organelles are separated on morphological grounds into three groups: the large paired organelles and the small dense bodies which are both linked to microducts, and the transitional bodies, a third organelle being reported for the first time. Transitional bodies are without microducts, occur in fully mature merozoites and persist only for a short period. All three of these organelles appear to be related to and possibly even derived from internal membrane systems and ribosomes. The apolar end of the merozoite contains the mitochondrion and its associated spherical body. Detailed study of the latter shows it to be cylindrical.Upon entering the host cell, the parasite adds a third membrane at the interface between it and the cell. The merozoite becomes spherical and undergoes transformation into a trophozoite. During this reorganization phase, dedifferentiation occurs and is followed by a rapid growth phase. The end of the growth phase is signaled by the appearance of germinal clefts and nuclear division. The entire process of schizogony culminates in a highly synchronized formation of merozoites.Processes of the limiting membrane forming the host parasite interface were observed extending deply into the cytoplasm of the host cell and often appeared to form bridges between two or more parasites. The significance of this new observation is not yet established.     

Toxoplasma gondii: ultrastructure and antigenicity of purified tachyzoite pellicle.

When purified Toxoplasma gondii tachyzoites were treated with hemolysin, DNase, and RNase, the organisms yielded a three-component system containing the outer membrane (pellicle), microtubules, and conoid in relatively normal morphological configuration. Further treatment of this preparation with protease digested all but the pellicle which was more collapsed in appearance. These two preparations were used in rabbit anti-toxoplasma and goat anti-rabbit ferritin labeling experiments. The three-component system showed ferritin label on the conoid and equal ferritin label on the outer and inner surfaces of the pellicle. The microtubules were unlabeled. The pellicle after protease treatment was labeled equally on its outer and inner surfaces, which indicated that the rabbit anti-toxoplasma serum contained antibodies against antigens on the outer and inner surfaces of the pellicle.     

An ultrastructural comparison of the mitotic apparatus,feeding apparatus,flagellar apparatus and cytoskeleton in euglenoids and kinetoplastids

Summary The euglenoids and kinetoplastids form a diverse assemblage of organisms which show no obvious phylogenetic relationship with other flagellates. An ultrastructural examination and comparison of the flagellar apparatus, the feeding apparatus, and mitotic nucleus indicate a number of shared morphological features which support a common ancestry for the two groups. Of particular interest is the euglenoid,Petalomonas cantuscygni, which shares many of the ultrastructural features common to both groups. Based on the data presented, we hypothesize that a euglenoid with features similar to those now present inP. cantuscygni was ancestral to both the euglenoid and kinetoplastid lines.Abbrevation MTR complex of reinforcing microtubules     

Characteristics of the membranes of the pellicle of the ciliatePseudomicrothorax dubius

Summary The membranes of the pellicle of the ciliatePseudomicrothorax dubius are investigated using thin section electron microscopy and freeze-fracture replicas. The plasma membrane is covered by a surface coat and is connected to the outer alveolar membrane by short, sometimes branched, bridges. The inner alveolar membrane is coated on both sides. The epiplasm lies in intimate contact with the cytoplasmic surface of this membrane, and there is a corresponding deposit on the other surface. This deposit is regularly striated.The epiplasmic layer and the alveoli are interrupted at sites of cytotic activity,e.g., the attachment sites of trichocysts, the cytoproct, and the parasomal sacs. The striated deposit ends where the epiplasm ends, indicating a direct relationship between these two epimembranous layers.There is a deposit along the sides of the first part of the tip of the trichocysts, and in this region the trichocyst membrane is free of intramembranous particles.The membrane of the parasomal sacs has a coat on both surfaces. That on the extraplasmic surface is similar to the surface coat of the plasma membrane. The origin of the cytoplasmic coat is unknown. The cytotic activity of these sacs is indicated by their highly irregular profiles.     

Visualization of initial bacterial colonization on dentine and enamel in situ

Bacterial colonization of dentine is of high relevance in cariology, endodontology and periodontology. The aim of the present in situ study was to establish recent methods for visualization and quantification of initial bacterial adherence to dentine in comparison to enamel. For this purpose, bovine enamel and dentine slabs were fixed on buccal sites of individual upper jaw splints worn by 6 subjects for 30 min, 120 min and 360 min, respectively. Adherent bacteria on the slabs were visualized and quantified with DAPI-staining (4′,6-diamidino-2-phenylindole) and fluorescence in situ hybridization (FISH) of streptococci and eubacteria using the CLSM (confocal laser scanning microscopy) as well as an epifluorescence microscope. In addition, the number of colony forming units was quantified after desorption. Representative samples were processed for SEM (scanning electron microscopy) and TEM (transmission electron microscopy). All methods clearly indicated that a significantly higher number of bacteria adhered to dentine than to enamel. Furthermore, the amount of bacteria on the dentine increased with increasing oral exposure time, but remained rather constant on the enamel. The CLSM allowed visualization of bacteria in the dentinal tubules. Bacteria were found preferentially at the openings of the dentine tubules, but were distributed randomly on the enamel.In conclusion, the adopted methods are suitable for visualization and quantification of bacterial adhesion to dentine. Even the initial bacterial colonization of dentine is much more pronounced than bacterial adherence to the enamel.