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Cytoplasmic Vesicles (cytoplasmic + vesicle)
Selected AbstractsUltrastructural Study of Encystation and Excystation in Acanthamoeba castellaniiTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005BIBIANA CHÁVEZ-MUNGUÍA Abstract. Encystation and excystation of Acanthamoeba castellanii were studied by transmission electron microscopy. The differentiation process was induced in asynchronous cultures grown axenically. Cytoplasmic vesicles containing a dense fibrous material very similar in appearance to the cyst wall were observed in trophozoites induced to encyst. When these trophozoites were incubated with calcofluor white m2r, fluorescence was observed in cytoplasmic vesicles, suggesting that the material contained in these vesicles corresponded to cyst wall precursors. Semithin cryosections of mature cysts with the same treatment showed fluorescence in the ectocyst and a less intense fluorescence in the endocyst, suggesting the presence of cellulose in both structures of the cyst wall. In mature cysts induced to excystation, small structures very similar to electron-dense granules (EDG) previously described in other amoebae were frequently observed. The EDGs were either sparsely distributed in the cytoplasm or associated with the cytoplasmic face of the plasma membrane. Many of them were located near the ostiole. In advanced phases of excystation, endocytic activity was suggested by the formation of endocytic structures and the presence of vacuoles with fibrous content similar to that of the cyst wall. Electron-dense granules in the process of dissolution were also observed in these vacuoles. Furthermore, the formation of a pseudopod suggests a displacement of the amoeba toward the ostiole. [source] A dual infection by infectious cuticular epithelial necrosis virus and a Chlamydia -like organism in cultured Litopenaeus vannamei (Boone) in EcuadorAQUACULTURE RESEARCH, Issue 11 2001R Jimenez During 1996, microscopic examinations of post larvae and juveniles of moribund Litopenaeus vannamei showed multifocal necrosis in the cuticular epithelial tissues. In addition to these severe degenerative alterations in the epithelial cells typical of infectious cuticular epithelial necrosis virus (ICENV), columnar cells of the epithelium displayed small round intracytoplasmic inclusions in the necrotic tissue. Examination by electron microscopy of affected tissues demonstrated prokaryotic organisms in the cytoplasm of epithelial cells delineated by a distinct cytoplasmic vesicle; the prokaryotic organisms were morphologically similar to the genus Chlamydia. The necrotic tissue also showed the presence of particles of ICENV; the double infection by two different organisms in cuticular epithelial cells has not been reported previously. Two distinct stages in the intracellular development of a Chlamydia -like organism were recognized: (1) pleomorphic elementary bodies (EBs) that were spherical to oval were often observed in the process of division or in forming a common chain of three cells, the cells were surrounded by a rigid cell envelope and the presence of a cap or plaque hexagonally arrayed; (2) the reticular bodies (RBs) were forms often in the process of division. These cells had an electron-dense cytoplasm and contained a loose network of nuclear fibrils and a more fragile cell envelope. Regardless of the development stages of the Chlamydia -like organism within the cytoplasmic vesicles, ICENV particles were observed, either dispersed or in clusters, surrounded or inside the vesicles. The potential adverse impact of this dual infection on shrimp culture should be considered, especially in high-density operations. [source] Enhanced generation of Alzheimer's amyloid-, following chronic exposure to phorbol ester correlates with differential effects on alpha and epsilon isozymes of protein kinase CJOURNAL OF NEUROCHEMISTRY, Issue 2 2009Odete A. B. Da Cruz e Silva Abstract Alzheimer's amyloid precursor protein (APP) sorting and processing are modulated through signal transduction mechanisms regulated by protein phosphorylation. Notably, protein kinase C (PKC) appears to be an important component in signaling pathways that control APP metabolism. PKCs exist in at least 11 conventional and unconventional isoforms, and PKC, and PKC, isoforms have been specifically implicated in controlling the generation of soluble APP and amyloid-, (A,) fragments of APP, although identification of the PKC substrate phospho-state-sensitive effector proteins remains challenging. In the current study, we present evidence that chronic application of phorbol esters to cultured cells in serum-free medium is associated with several phenomena, namely: (i) PKC, down-regulation; (ii) PKC, up-regulation; (iii) accumulation of APP and/or APP carboxyl-terminal fragments in the trans Golgi network; (iv) disappearance of fluorescence from cytoplasmic vesicles bearing a green fluorescent protein tagged form of APP; (v) insensitivity of soluble APP release following acute additional phorbol application; and (vi) elevated cellular APP mRNA levels and holoprotein, and secreted A,. These data indicate that, unlike acute phorbol ester application, which is accompanied by lowered A, generation, chronic phorbol ester treatment causes differential regulation of PKC isozymes and increased A, generation. These data have implications for the design of amyloid-lowering strategies based on modulating PKC activity. [source] Intracellular uptake and trafficking of Pluronic micelles in drug-sensitive and MDR cells: Effect on the intracellular drug localizationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2002Natalya Rapoport Abstract The intracellular uptake and localization of a fluorescently labeled Pluronic P-105 in HL-60 leukemia cells and in A2780 drug-sensitive and A2780/ADR MDR ovarian carcinoma cells were characterized by flow cytometry and fluorescence microscopy. Pluronic P-105 molecules were labeled with a pH-sensitive fluorescent label, 5-(and 6-)carboxy-2,7,-dichlorofluorescein. The fluorescence intensity of labeled Pluronic was about twofold higher at pH 7.4 than at pH 5.5. At Pluronic concentrations exceeding the critical micelle concentration (cmc), flow cytometry histograms manifested bimodal distribution of cell fluorescence for all types of cells. Cell population characterized by higher fluorescence intensity presumably resulted from Pluronic transfer from the acidic environment of cytoplasmic vesicles (endosomes or lysosomes) into the neutral environment of the cytoplasm and cell nuclei, which suggested the permeabilization of the membranes of acidic vesicle by Pluronic molecules. For the MDR cells, the bimodal distribution of cell fluorescence was already observed at very low Pluronic concentrations in the incubation medium (i.e., below the cmc). The data suggest that the membranes of acidic vesicles of MDR cells are more susceptible to the action of polymeric surfactants than those of drug-sensitive cells. Permeabilization of acidic vesicles had a dramatic effect on the intracellular trafficking of drugs: when delivered in PBS, the anthracyclin drug ruboxyl (Rb) sequestered in cytoplasmic vesicles and was excluded from cell nuclei; however, when delivered in Pluronic micelles, drug accumulated in cell nuclei. Drug uptake from/with Pluronic micelles was substantially enhanced by ultrasound. These findings suggest that the nuclear accumulation of drugs internalized via fluid-phase endocytosis can be enhanced by the application of Pluronic micelles and can be further augmented by ultrasonic irradiation. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:157,170, 2002 [source] Differential expression of lysosomal associated membrane protein (LAMP-1) during mammalian spermiogenesisMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2003Ricardo D. Moreno Abstract The mammalian acrosome is a secretory vesicle of mature sperms that plays an important role in fertilization. Recent evidence had pointed out that some components found at endosomes in somatic cells are associated with the developing acrosome during the early steps of spermiogenesis. Moreover, the mammalian acrosome contains many enzymes found within lysosomes in somatic cells. In this work, we studied the dynamics of some components of the endosome/lysosome system, as a way to understand the complex membrane trafficking circuit established during spermatogenesis. We show that the cation independent-mannose-6-phosphate receptor (CI-MPR) is transiently expressed in the cytoplasm of mid-stage spermatids (steps 5,11). On the other hand, ,-adaptin, an adaptor molecule of a complex involved in trafficking from the Golgi to lysosomes, was expressed in cytoplasmic vesicles only in pachytene and Cap-phase spermatids (steps 1,5). Our major finding is that the lysosomal protein LAMP-1 is differentially expressed during spermiogenesis. LAMP-1 appears late in spermatogenesis (Acrosome-phase) contrasting with LAMP-2, which is present throughout the complete process. Both proteins appear to be associated with cytoplasmic vesicles and not with the developing acrosome. None of the studied proteins is present in epididymal spermatozoa. Our results suggest that the CI-MPR could be involved in membrane trafficking and/or acrosomal shaping during spermiogenesis. Mol. Reprod. Dev. 66: 202,209, 2003. © 2003 Wiley-Liss, Inc. [source] Ultrastructural Study of Encystation and Excystation in Acanthamoeba castellaniiTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005BIBIANA CHÁVEZ-MUNGUÍA Abstract. Encystation and excystation of Acanthamoeba castellanii were studied by transmission electron microscopy. The differentiation process was induced in asynchronous cultures grown axenically. Cytoplasmic vesicles containing a dense fibrous material very similar in appearance to the cyst wall were observed in trophozoites induced to encyst. When these trophozoites were incubated with calcofluor white m2r, fluorescence was observed in cytoplasmic vesicles, suggesting that the material contained in these vesicles corresponded to cyst wall precursors. Semithin cryosections of mature cysts with the same treatment showed fluorescence in the ectocyst and a less intense fluorescence in the endocyst, suggesting the presence of cellulose in both structures of the cyst wall. In mature cysts induced to excystation, small structures very similar to electron-dense granules (EDG) previously described in other amoebae were frequently observed. The EDGs were either sparsely distributed in the cytoplasm or associated with the cytoplasmic face of the plasma membrane. Many of them were located near the ostiole. In advanced phases of excystation, endocytic activity was suggested by the formation of endocytic structures and the presence of vacuoles with fibrous content similar to that of the cyst wall. Electron-dense granules in the process of dissolution were also observed in these vacuoles. Furthermore, the formation of a pseudopod suggests a displacement of the amoeba toward the ostiole. [source] The Mucosa of the Digestive Tract in Micropogonias furnieri: A Light and Electron Microscope ApproachANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 4 2008A. O. Diaz Summary The histomorphological aspects as well as the histochemical content and distribution of glycoproteins (GPs) in the mucosa of the digestive tract of the white croaker Micropogonias furnieri were studied. The buccopharyngeal cavity and the esophagous showed a squamous stratified epithelium with mucous cells. The stomach presented three portions: cardias, fundus and pylorus. Tubular glands formed by a single type of gland cell were located along the cardias and fundus. Histochemical tests showed that the buccopharyngeal cavity and the esophagous presented the largest amount of the different types of mucosubstances. Both organs showed abundant secretory mucous cells that synthesize large quantities of neutral, sulphated and sialylated GPs. The surface epithelium in the cardias and fundus synthesized and secreted scarce sialylated and neutral GPs whereas the secretions of the apical surface were abundant. The pylorus secreted large amounts of neutral as well as sulphated and sialylated GPs. Gland cells secreted neutral GPs. The ultrastructural features of the gut cells were quite similar to those of other teleosts. The buccopharyngeal cavity and the esophagous surface epithelial cells, identified by their superficial localization, were characterized by cytoplasmic vesicles of different size. Abundant goblet cells with secretory mucous granules were also present. Gastric glands in the stomach contained just one form of cell with a fine structure similar to cells that secrete pepsinogen. [source] A dual infection by infectious cuticular epithelial necrosis virus and a Chlamydia -like organism in cultured Litopenaeus vannamei (Boone) in EcuadorAQUACULTURE RESEARCH, Issue 11 2001R Jimenez During 1996, microscopic examinations of post larvae and juveniles of moribund Litopenaeus vannamei showed multifocal necrosis in the cuticular epithelial tissues. In addition to these severe degenerative alterations in the epithelial cells typical of infectious cuticular epithelial necrosis virus (ICENV), columnar cells of the epithelium displayed small round intracytoplasmic inclusions in the necrotic tissue. Examination by electron microscopy of affected tissues demonstrated prokaryotic organisms in the cytoplasm of epithelial cells delineated by a distinct cytoplasmic vesicle; the prokaryotic organisms were morphologically similar to the genus Chlamydia. The necrotic tissue also showed the presence of particles of ICENV; the double infection by two different organisms in cuticular epithelial cells has not been reported previously. Two distinct stages in the intracellular development of a Chlamydia -like organism were recognized: (1) pleomorphic elementary bodies (EBs) that were spherical to oval were often observed in the process of division or in forming a common chain of three cells, the cells were surrounded by a rigid cell envelope and the presence of a cap or plaque hexagonally arrayed; (2) the reticular bodies (RBs) were forms often in the process of division. These cells had an electron-dense cytoplasm and contained a loose network of nuclear fibrils and a more fragile cell envelope. Regardless of the development stages of the Chlamydia -like organism within the cytoplasmic vesicles, ICENV particles were observed, either dispersed or in clusters, surrounded or inside the vesicles. The potential adverse impact of this dual infection on shrimp culture should be considered, especially in high-density operations. [source] | ||||||||||