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| 2. |
- Henriksson, M, et al.
(författare)
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Nuclear colocalization of c-myc protein and hsp70 in cells transfected with human wild-type and mutant c-myc genes
- 1992
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Ingår i: Experimental Cell Research. - 0014-4827. ; 203:2, s. 94-383
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Tidskriftsartikel (refereegranskat)abstract
- Using immunofluorescence and electron microscopy we have studied the localization of wild-type and mutant c-myc proteins transiently expressed in CV-1 cells. In agreement with our previous observations, wild-type c-myc protein accumulated in large amorphous globules in the nucleus. All mutant proteins tested accumulated in the nucleus as well, but gave rise to morphologically different inclusion bodies. Many small globules appeared in cells transfected with D145-262 (deletion of amino acids 145-262), while cells transfected with D371-412 or D414-433 generated structures looking like a fine network or like beads on a string. In addition, a particulate cytoplasmic staining appeared in some cells transfected with the wild-type gene and in cells transfected with mutants D145-262 or D414-433. Since the c-myc protein has been reported to stimulate expression of exogenous hsp70 protein, we also examined the intracellular distribution of hsp70 in the transfected cells. Double immunofluorescence microscopy revealed that hsp70 codistributed with the c-myc protein in distinct globules in the nucleus of many but not all myc-positive cells. However, the levels of hsp70 transcripts were not significantly raised compared to nontransfected and vector-transfected cells. Likewise, the levels of hsp70 protein did not vary significantly. These findings indicate that overexpression of c-myc stimulates translocation of preexisting hsp70 from the cytoplasm into the nucleus, rather than influencing hsp70 expression. Conceivably, this may represent one of several mechanisms whereby the cell deals with excessive amounts of c-myc protein.
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| 3. |
- Moskalewski, S., et al.
(författare)
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Influence of colchicine and vinblastine on the Golgi complex and matrix deposition in chondrocyte aggregates. An ultrastructural study
- 1975
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827. ; 95:2, s. 440-454
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Tidskriftsartikel (refereegranskat)abstract
- Fetal guinea-pig epiphyseal chondrocytes were isolated enzymatically, aggregated, and the aggregates maintained in organ culture. As revealed by light and electron microscopy, the cultures produced a typical cartilaginous matrix, but no calcification occurred. Exposure of aggregating cells, or preformed aggregates, to colchicine or vinblastihe at 10-5 M concentration led to disappearance of the microtubules, dissociation of the Golgi complex into single dictyosomes, and clustering of lysosomes. Thus, in treated cells the dictyosomes with accompanying vesicular structures were dispersed throughout the cytoplasm, whereas they were localized in a well-defined juxtanuclear region in control cells. The number and size of the cisternae forming a dictyosome were often reduced. Cells treated with vinblastine displayed macrotubules and an increased number of phagosomes. Both drugs reduced the deposition of intercellular matrix. In cells first exposed to either of the drugs for 2 or 5 days and then transferred to fresh medium for 3 or 6 days, the microtubules reappeared, the Golgi complex regained its normal appearance, and the amount of matrix increased. These findings are discussed in view of present concepts of the role of microtubules in cell secretion.
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| 4. |
- Thyberg, J., et al.
(författare)
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Proteoglycans of hyaline cartilage. Electron microscopic studies on isolated molecules
- 1975
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Ingår i: Biochemical Journal. - 0264-6021. ; 151:1, s. 157-166
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Tidskriftsartikel (refereegranskat)abstract
- Proteoglycan monomers from guinea pig costal cartilage, bovine nasal and bovine tracheal cartilage were observed in the electron microscope after being spread in a monomolecular layer with cytochrome c. The proteoglycan molecule appeared as an extended central core filament to which side chain filaments were attached at various intervals. The molecules from the three sources displayed great ultrastructural similarities. On average, the core filament was about 290 nm long, there were about 25 side chain filaments per core filament, the side chain filaments were about 45 nm long, and the distance between the attachment points of the side chain filaments to the core filament was about 11 nm. With regard to overall size of the molecules, no evidence of distinct subpopulations was obtained. Good correlation was found between ultrastructural data for the proteoglycan molecules and chemical data obtained by enzyme digestions and gel chromatography. Together these data strongly support the interpretation of the electron microscopic pictures as indicating a central filament corresponding to the protein core and side chain filaments corresponding to the chondroitin sulphate chain clusters of the proteoglycan monomers.
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| 5. |
- Thyberg, J., et al.
(författare)
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Ultrastructure of the epiphyseal plate of the guinea pig in experimental scurvy
- 1971
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Ingår i: Virchows Archiv B Cell Pathology Zell-pathologie. - 0042-6431. ; 9:1, s. 45-57
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Tidskriftsartikel (refereegranskat)abstract
- The ultrastructure of the upper tibial epiphyseal plate during the development of acute, experimental scurvy in the guinea pig was investigated. The cartilage was examined after the animals had been maintained, under standardized conditions, on a scorbutogenic diet for 8, 15, or 23 days. Progressive fine structural changes were observed in the experimental animals. Within the chondrocytes, the cisternae of the endoplasmic reticulum were rounded, non-continuous, and reduced in extensiveness. There was a decreased number of ribosomes on the cisternal membranes and, concomitantly, an increased amount of free ribosomes in the ground cytoplasm. The secretory vacuoles of the Golgi complex were few. Lysosomes were more frequent than in the controls. Signs of autophagocytosis were often observed. In the ground cytoplasm lipid droplets occurred somewhat more often than in the control animals. In the intercellular substance the amount of collagen fibrils and proteoglycan particles was decreased. Electron-dense matrix vesicles were numerous in the longitudinal septa. The nature of these changes is discussed with regard to the biochemical alterations that have been observed in this disorder.
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