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  • 1
    Electronic Resource
    Electronic Resource
    Activation of the autophagy, c-FOS and ubiquitin expression, and nucleolar alterations in Schwann cells precede demyelination in tellurium-induced neuropathy (1999)
    Springer
    Acta neuropathologica 97 (1999), S. 143-155 
    Details
    ISSN: 1432-0533
    Keywords: Key words Schwann cell ; Early intermediate genes ; Endoplasmic reticulum ; Macroautophagy ; Nucleolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have used an experimental model of tellurium (Te)-induced demyelinating neuropathy in the rat to study cellular mechanisms involved in the early response of myelinating Schwann cells (SCs) to injury, prior to demyelination. Starting at postnatal day 21, weaned rats were fed a diet containing 1.1% elemental Te. The animals were killed daily within the 1st week of Te diet and the sciatic nerves were processed for the ultrastructural and immunocytochemical studies. Immunohistochemistry revealed that Te induces an increased nuclear expression of c-Fos in SCs. By electron microscopy analysis, the early cytoplasmic alteration was a dramatic disorganization of the rough endoplasmic reticulum (ER) with cisternal dilations and redistribution and loss of membrane-bound ribosomes. This was followed by a prominent activation of the macroautophagy in SCs. This process involved the formation of autophagosomes containing well-preserved cell organelles, autolysosomes with cellular remnants in various phases of degeneration and lysosomes. Te treatment also induced the expression of free ubiquitin in the perikaryal region of the SC cytoplasm. Immunogold electron microscopy showed the subcellular distribution of ubiquitin in the cytosol, around of dilated ER cisterns and in the matrix of autolysosomes and residual bodies. At the nucleolar level, fibrillarin immunofluorescence revealed nucleolar segregation in SCs exposed to Te. The ultrastructural study confirmed the segregation of the nucleolar components with a peripheral distribution of the dense fibrillar component. These results support the hypothesis that the depletion of cholesterol induced by Te treatment triggers a stress response in myelinating SCs mediated by immediate early genes of the fos family. The cellular response includes a severe disruption of the protein synthesis machinery, namely the rough ER and nucleolus, with the subsequent activation of both ubiquitin and autophagic pathways of proteins and cell organelle degradation. This cytoplasmic remodeling may represent a cytoprotective mechanism in the response of SCs to a neurotoxic stress. Furthermore, it must be a prerequisite for the induction of phenotypic changes and cell repair mechanisms in SCs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050967
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Number of nucleoli and coiled bodies and distribution of fibrillar centres in differentiating Purkinje neurons of chick and rat cerebellum (1995)
    Springer
    Anatomy and embryology 191 (1995), S. 359-367 
    Details
    ISSN: 1432-0568
    Keywords: Nucleoli ; Coiled bodies ; Nucleolar organizer regions ; Fibrillar centres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We used differentiating chick and rat Purkinje cells to investigate in homologous neurons the influence of the number of nucleolar organizer regions (two in the chick and six in the rat) on the behaviour of the nucleolus and coiled bodies. We employed specific silver-staining methods on smear preparations and on semithin and ultrathin sections. In chick Purkinje cells the number of nucleolar silver-staining granules increased from 15.7±3 (mean±SD) at embryonic day 13 to 23.8±3 at post-hatching day 7. These nucleolar granules were unevenly distributed between the two nucleoli of binucleolated cells. Electron-microscopic cytochemistry showed that nucleolar granules are equivalent to the fibrillar centres with their associated shell of dense fibrillar component. A reduction in the number of nucleoli was found during the differentiation of both chick and rat Purkinje cells, although in mature cells the average number of nucleoli per cell was higher in the chick (1.60) than in the rat (1.07). The number of coiled bodies decreased from 1.33 in newborn rats to 0.47 at postnatal day 90 in the rat. Coiled bodies were not observed in homologous chick Purkinje cells. The dynamic behaviour of nucleoli and coiled bodies during neuronal differentiation and the relationship of these two nuclear organelles with the number of nucleolar organizer regions is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00534689
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  • 3
    Electronic Resource
    Electronic Resource
    Apoptosis induced by methylazoxymethanol in developing rat cerebellum: organization of the cell nucleus and its relationship to DNA and rRNA degradation (1997)
    Springer
    Cell & tissue research 289 (1997), S. 25-38 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Cell death ; Cerebellar granule cells ; Chromatin ; Nucleolus ; Dispersed ribosomes ; DNA ladder ; Rat (Sprague Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We present a cytological and biochemical study of the cell death of granule cell precursors in developing rat cerebellum following treatment with the cytotoxic agent methylazoxymethanol (MAM) during the first postnatal week. The density of apoptotic figures per square millimeter progressively increases after 6, 12, 24 and 44 h of treatment, whereas cells immunoreactive for proliferating cell nuclear antigen tend to disappear in the external granular layer (EGL). DNA migration on gel electrophoresis reveals a typical ladder pattern of internucleosomal cleavage following MAM treatment, whereas gel electrophoresis of rRNA shows a conspicuous degradation of both 28S and 18S rRNAs. Ultrastructural analysis has revealed the alterations of structures containing chromatin and ribonucleoprotein (RNP) in dying cells of the EGL. The typical granular beaded configuration of the condensed chromatin changes to a denser, more homogeneous texture suggesting nucleosomal disruption. The reorganization of RNP nuclear domains is reflected by the appearance of dispersed nucleoplasmic RNP particles and the formation of a coiled-body-like structure. However, typical nuclear domains involved in the splicing of RNAs, namely interchromatin granule clusters and typical ”coiled bodies”, are not found in apoptotic cells. Intranuclear bundles of filaments have also been detected. In the cytoplasm, the presence of dispersed single ribosomes is an initial sign of apoptosis. The massive dispersion and disruption of ribosomes detected after 24 h and 44 h of MAM treatment is reflected by the degradation of both 28S and 18s rRNAs. These results show that MAM treatment provides a useful experimental model for the study of apoptosis in the developing central nervous system. The organization of the cell nucleus in cells undergoing apoptosis clearly reflects a disruption of the nuclear compartments involved in transcription and the processing and transport of RNA and is related to the patterns of DNA and rRNA degradation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050849
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    Paper (German National Licenses)
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