Search results for "cytoskeleton"
showing 10 items of 272 documents
Microtubules and the Establishment of Apparent Cell Wall Invaginations in Mesophyll Cells of Pinus silvestris L.
1995
Summary Ridges of cell wall material protruding into the cellular lumen are characteristic of Pinus silvestris mesophyll cells. These ridges, e.g., appear to increase the inner surface for optimal dispersal of organelles, especially of chloroplasts. We show that the ridges are the result of local, brace-like wall reinforcements deposited during early turgor-driven expansion growth of postmitotic cells. The reinforced sites resist expansion and become the base of deep, narrow folds representing the ridges, while the intervening thin-walled areas evaginate as the cell volume increases. Cell wall material is deposited uniformly after expansion to stabilize the protrusions. There is a distinct …
Cytochemical Cell Typing of Metastatic Tumors According to their Cytoskeletal Proteins
1986
Conventional staining methods alone are often insufficient to make accurate histodiagnosis of malignant tumors. However, additional information about the cell type and the state of differentiation of tumor cells can be provided by several molecular markers. To be relevant diagnostically, these markers must be conservative, i.e. expressed not only in well differentiated tumors but also in poorly differentiated tumors and in metastases. These criteria are fulfilled by certain components of the cytoskeleton, notably the proteins forming the intermediate-sized filaments (IFs) and the desmosomal plaque proteins.
Culture medium induced vimentin reorganization associates with enhanced baculovirus-mediated gene delivery.
2009
Baculoviruses can express transgenes under mammalian promoters in a wide range of vertebrate cells. However, the success of transgene expression is dependent on both the appropriate cell type and culture conditions. We studied the mechanism behind the substantial effect of the cell culture medium on efficiency of the baculovirus transduction in different cell lines. We tested six cell culture mediums; the highest transduction efficiency was detected in the presence of RPMI 1640 medium. Vimentin, a major component of type III intermediate filaments, was reorganized in the optimized medium, which associated with enhanced nuclear entry of baculoviruses. Accordingly, the phosphorylation pattern…
The effect of cadmium on brain cells in culture
2009
Cadmium is a long-living heavy metal, abundantly present in the environment, which accumulates in the body. In this study, we investigated the effects of cadmium on the expression of molecular chaperones, and of certain cell-specific proteins, in a variety of brain cell types in culture, namely primary cultures of rat cortical neurons and astrocytes, a brain capillary endothelial cell line (RB4E.B cells), and pheochromocytoma cells (PC12), induced or not to differentiate by NGF treatment. The metal induces a dose-dependent increase of Hsp70 in all cell types. Responses to the metal are cell-specific in the case of Hsc70 and Hsp90: i) in astrocytes, as well as in PC12 cells, cadmium has no s…
Microtubules and cell shaping in the mesophyll ofNigella damascena L.
1993
Cell shaping in the mesophyll ofNigella damascena was investigated with the aim of determining the origin of the arm-like protrusions, which are characteristic of, e.g., arm-palisade cells. It was found that hoops of cell wall were deposited during the early stages of cell expansion. The hoops were interconnected, thus embracing the cells with a wide-meshed net of local wall reinforcement. The pattern of wall deposition in the extra-cellular matrix correlated with a pattern of bands of microtubules in the cortical cytoplasm of the cells. During lateral expansion bulges were forced through the comparatively thin walls of spaces between the meshes, giving rise to the arm-like protrusions. Aft…
Structural and regulatory functions of keratins.
2007
The diversity of epithelial functions is reflected by the expression of distinct keratin pairs that are responsible to protect epithelial cells against mechanical stress and to act as signaling platforms. The keratin cytoskeleton integrates these functions by forming a supracellular scaffold that connects at desmosomal cell-cell adhesions. Multiple human diseases and murine knockouts in which the integrity of this system is destroyed testify to its importance as a mechanical stabilizer in certain epithelia. Yet, surprisingly little is known about the precise mechanisms responsible for assembly and disease pathology. In addition to these structural aspects of keratin function, experimental e…
Changes in tubulin protein expression accompany reorganization of microtubular arrays during cell shaping in barley leaves
1998
Barley (Hordeum vulgare L.) leaves grow from the base and thus exhibit a smooth developmental gradient. Developing mesophyll cells acquire their typical lobed shape synchronously along this gradient. Successive changes in the patterns of cortical microtubules are involved in the shaping process. The changes include formation and dispersal of band-like structures, the establishment of a random network and a dramatic loss of microtubules after completion of cell shaping. When the relative tubulin contents were determined in consecutive segments taken along the leaf, two tubulin maxima were found. They coincided with the establishment of the microtubular bands and the random network, respectiv…
Cell shaping and microtubules in developing mesophyll of wheat (Triticum aestivum L.)
1990
Differentiated mesophyll cells ofTriticum aestivum (cv. Star) exhibit a lobed outline resembling tube-shaped balloons with almost regularly spaced constrictions. It was shown that these constrictions are probably the result of hoops of wall reinforcements laid down during early stages of cell expansion. It appears that these hoops prevent expansion in the corresponding regions and thus give rise to the peculiar cell shape. The comparatively thin cell walls of the bulges are uniformly reinforced after the lobed shape is established. By using immunofluorescence techniques a change in the pattern of cortical microtubule arrangement was observed which corresponded to the pattern of cell wall de…
Mutations in spalt cause a severe but reversible neurodegenerative phenotype in the embryonic central nervous system ofDrosophila melanogaster
2002
The gene spalt is expressed in the embryonic central nervous system of Drosophila melanogaster but its function in this tissue is still unknown. To investigate this question, we used a combination of techniques to analyse spalt mutant embryos. Electron microscopy showed that in the absence of Spalt, the central nervous system cells are separated by enlarged extracellular spaces populated by membranous material at 60% of embryonic development. Surprisingly, the central nervous system from slightly older embryos (80% of development) exhibited almost wild-type morphology. An extensive survey by laser confocal microscopy revealed that thespalt mutant central nervous system has abnormal levels o…
Identification of an Antigen Related to the Sea Urchin RNA-Binding Protein LP54 in Mammalian Central Nervous System
2001
LP54 is an RNA-binding protein involved in localization of maternal messengers in sea urchin egg and embryos. Using a polyclonal antibody directed against Paracentrotus lividus LP54 we detected a 66-kDa cross-reacting antigen in undifferentiated and differentiated SH-SY5Y human neuroblastoma cells. After treatment of undifferentiated cells with detergent, the 66-kDa antigen was found to be enriched in the cytoskeletal fraction. By Western blot the expression of this antigen was also analyzed in regions of the CNS and in tissues of the adult rat and its exclusive presence in the hippocampus and thalamus was revealed. The immunoreactivity with P. lividus antibody against LP54 in hippocampal l…