摘要:

Summary—Changes in the shape of neuronal perikarya and other ganglionic structures were observed by electron microscopy in the frog sympathetic ganglia at different times after axotomy. Degenerating and hypertrophic profiles appeared to reflect a remodelling process affecting preganglionic fibres. The shape of neuronal perikarya was modified by the formation of infoldings occupied by preganglionic fibres and/or by that of short winding dendrites often bearing a synapse. The origin of these changes is discussed. In frog sympathetic ganglia, the period of recovery after axotomy was marked by specific reactions which affected neuronal shape and preganglionic fibres, and are not known to occur in the ganglia of mammal

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90081-W

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The subcellular distribution of clathrin has been examined in developing hypothalamic neurons cultured in a chemically defined medium up to synapse formation (12–13 daysin vitro) and exposed, or not, to a depolarizing concentration of KCl (60 mM for 3 min) followed, or not, by a return to control KCl concentration (3 mM KCl for 3 min). Previous studies have shown that such treatments induce in synaptic boutons a rapid vesicle depletion followed by massive restoration. Using an enzyme immunoassay, we have compared the relative proportion of assembled and unassembled pools of clathrin as a function of exposure to depolarizing or repolarizing concentrations of KCl. In parallel we have localized clathrin at the electron microscopic level using immunoperoxidase. Clathrin concentration in culture is lower (0.36vs0.75%) and the proportion of unassembled clathrin is much higher than in the adult brain (82vs14%). These proportions were not affected by depolarizing or repolarizing treatments. Morphologically clathrin was exclusively detected in two neuron compartments: perikarya and synaptic boutons. In perikarya clathrin was localized as a thick coat on plasma membrane coated pits and in the Golgi zone on coated buds and vesicles, presumably located in atranscompartment. In synaptic boutons clathrin immunoreaction was found as an irregular thin rim around synaptic vesicles, whatever the polarization state of the cells, but coated vesicles were extremely rare. Taken together these findings raise the problem of the functional meaning and localization of the large unassembled pool of clathrin in such neurons and question its role in vesicular traffic in synaptic bout

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90082-X

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—Using antisera (α‐R and α‐C7Ag) directed against the conserved Gly‐Gly‐Met‐Pro‐epitope of the hsp70 family, a single antigen was identified in the humanBabesia divergensRouen 1987 isolate by Western immunoblotting and immunoprecipitation experiments. ThisB divergenshsp70 is highly conserved as shown by the analysis of five other geographicalB divergensisolates from different hosts (human and bovine). Indirect immunofluorescence assay performed on the asexual intraerythrocytic stages showed that the hsp70 is mainly cytoplasmic and stage‐independent. Heat‐shock experiments, with 20 min incubation at 40°C followed by a 10 to 50 min shift to 37°C in the presence of [35S]‐methionine, led to an increase of two hsp of 85 and 70 kDa while protein synthesis in general decreased within 10 min. Immunoprecipitations of [35S]‐methionine radiolabelled proteins with human, ox and gerbil antisera raised against variousB divergensisolates, showed the presence of aB divergens70 kDa protein which was demonstrated to be a hsp70 by coupling immunoblotting assays with α‐C7Ag serum on the same immunoprecipitated material. During human babesiosis, theB divergenshsp70 appears as an early antigen during the acute phase. These results are in agreement with the use of theB divergenshsp70 as an essential valence antigen i

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90083-Y

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—Two peculiar morphological features, observed in the marine algaT suecicaare described in this report. An ultrastructural study of actively swimming cells showed an unusual abundance of starch in the stroma and the pyrenoid and this uncommon storage was discussed in relation to growth factors. Numerous osmiophilic vesicles, infrequent in this species, were also found; they contained lipids. After 5 days exposure to Cu or Ag (50 μg 1−1and 20 μg 1−1respectively), the algae responded by storing these elements in the pre‐existing osmiophilic vesicles. The analysis by electron probe microanalysis (EPMA) revealed a coprecipitation of Cu, Ag, Pb, Ca, P and S in these structures and led us to relate these vesicles to polyphosphate‐bodies, already described in algae. Osmiophilic vesicles were devoid of phosphate in control samples. Following Cu exposure, this storage could be explained as an active detoxification process for most algae whose other structures were well preserved. After Ag exposure, the storage occurred in a few algae presenting some morphological damage. In both cases (Cu or Ag exposure), the metabolism was modified as starch was absent after Cu exposure and stored only in the pyrenoid after

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90084-Z

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—Cryofixation followed by cryosubstitution, without the use of any chemical fixatives, was carried out on cultured mouse P815 cells. The principal aim of our work, which was to show that these techniques provide excellent morphological preservation of cellular and in particular nuclear components, was demonstrated. All nuclear structural components, nucleolar or nucleoplasmic, were clearly revealed using this technology. The cells were cryofixed by impact freezing onto a copper miror cooled with liquid nitrogen or helium, cryosubstituted in acetone and embedded in either Lowicryl K11M or 1R White acrylic resin. Ultrathin sections were contrasted using either the usual uranyl acetate‐lead citrate double staining, a differential staining for nuclear nucleoprotein structures, or the silver staining revealling nucleolar organizer regions. In view of the absence of conventional fixatives, the specimens prepared in this way would offer to be material of choice for ultrastructural identification of intra‐nuclear antigens, especially those sensitive to conventional fixatives such as, for example, aldehydes. Advantages and differences of these techniques with regard to more conventional electron microscopic procedures are disc

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90085-2

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—We investigated the nuclear ultrastructure of HeLa cells using cryotechniques. The cells were cultured as monolayers, quick‐frozen and cryosubstituted in acetone without chemical fixatives. Half the samples were then treated with 1% osmium tetroxide in acetone and embedded in Epon, protocol A. The other half was cryo‐embedded in Lowicryl K11M at −60°C, protocol B. The efficiency of cryofixation was observed with both types of procedure. There was no fixation gradient detectable within the monolayer. The nuclei were well preserved, showing no reticulation of the chromatin. The different nuclear structures which have been observed after chemical fixation were also visible in these preparations. We noted improved visualization of the lamina and nucleolar chromatin, a very sharp limit between the fibrillar center and the dense fibrillar component, and variability in the appearance of the nuclear pores. Immunolabeling with an auto‐immune serum was possible on sections processed by protocol A and protocol B, but not on sections obtained by chemical fixation and cryo‐embedding procedures. Therefore, in the present work we showed that cryofixation, cryosubstitution and cryo‐embedding of cell monolayers can ensure a good preservation of the nuclear structures. Furthermore, detection of nucleolar antigenic determinants is facilitated and rapid nuclear events can easil

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90086-3

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The fine structure of the insect Sf9 cell nucleolus has been investigated by means of different cytochemical and immunocytochemical techniques at the electron microscope level. Apart from a few perinucleolar condensed chromatin clumps, the insect cell nucleolus comprises two compartments. The first of these consists of a roundish compact zone formed of fibrillar material. The other is composed of fibrillar and granular structures organized into a network separated by interstitial spaces. But, unlike mammalian cell nucleoli, any fibrillar center has been observed in the Sf9 cell nucleolus, even after actinomycin D treatment. We also show that the compact fibrillar zone of Sf9 cell nucleoli contains silver‐stainable material and DNA. In actinomycin D‐treated cells, a preferential contact of this compact fibrillar zone with condensed chromatin has been visualized. Finally, silver‐stainable material has been found to persist throughout the whole mitosis. These results suggest that the compact fibrillar zone at the insect Sf9 cell nucleolus should, at least partly, correspond to the fibrillar center of mammalian cell n

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90087-4

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The basement membranes elaborated by corneal epithelium in the chick embryo and in culture conditions have been studied by quick‐freezing and deep‐etching methods. Electron microscope observations ofen faceunidirectional platinum shadow castings revealed a polygonal network comparable to the type IV collagen network described in human amniotic basement membrane and EHS mouse tumor matrix [22]. The material deposited in culture contained type IV collagen, as demonstrated by immunofluorescence labeling using anti‐type IV collagen antibodies and formed delicate networks. Fine filaments and granules composing this network were interpreted respectively as linear and globular NCI domains of the type IV collagen molecule. These loose networks were considered as first steps in basement membrane assembly. Staggered superimposition of comparable networks could lead to the dense network organization as observed for basement membranesin situ. These observations showed that the basement membrane of the chick embryo corneal epithelium is also organized in a complex polygonal framework that is preserved even when secreted in cultrue con

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90088-5

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—The geometrical characteristics of fibrillar organizations are studied by electron microscopy in structures obtainedin vitroin cell‐free assembled collagen gels, andin vivoin dermal tracts of anuran skin. We analyze several characteristics of the fibrils including the diameter, the outline, the curvature and the extrafibrillar space. We analyze also the variation of fibrillar orientation (twist) in longitudinal and transverse thin sections of these structures. The results are compared in theDiscussionto determine to what extent these fibrillar patterns are similar to liquid crystalline organizations and to what extent they result from a self‐assembly or a cell‐assembly

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90089-6

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Summary—Using the frog palate as a representative model of human mucociliary epthelium, we analyzed, after quick freezing fixation, the three‐dimensional (3‐D) respiratory mucus secretory release with high voltage (200–300 kV) transmission electron microscopy (TEM). The 3‐D vision of the mucus release from the secretory cells was obtained as stereo‐pairs and “bas‐relief” images after analysis of stereo‐pairs using an image analyzer. After standard glutaraldehyde fixation, the secretory cells showed a typical goblet shape with secretory granules heterogeneous in size and electron‐density which often fuse together. On the other hand, quick‐frozen secretory cells exhibited a columnar shape and their membrane‐bound secretory granules contained a homogeneously dark matrix. The expanded gel mucus layer was preserved and its depth never exceeded 2 μm. When the epithelium was immersed in culture medium in presence of cholinergic agonist, a marked discharge of mucus was observed and the granules swelled at the apex of the secretory cell before being discharged in the lumen. In native cryofixed epithelium, the secretory granules exhibited a marked deformability during the process of their extrusion from the secretory cell. Clusters of secretory granules surrounded by cytoplasmic material were observed in the extracellular lumen, suggesting an apocrine‐type secretion. These observations indicate that rapid cryofixation and 3‐D stereoscopic imaging enable a unique opportunity to analyze, without artifact, the mucous secretory process. We speculate that, apart from the classical merocrine‐type secretion mechanism, the respiratory mucus may be released, at least part

ISSN:0248-4900    

DOI:10.1016/0248-4900(91)90090-A

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY