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- Moskalewski, S., et al.
(author)
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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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In: Experimental Cell Research. - : Elsevier BV. - 0014-4827. ; 95:2, s. 440-454
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Journal article (peer-reviewed)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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| 7. |
- Lohmander, S., et al.
(author)
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Secretion of proteoglycans by chondrocytes. Influence of colchicine, cytochalasin B, and β-d-xyloside
- 1979
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In: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861. ; 192:1, s. 148-157
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Journal article (peer-reviewed)abstract
- Chondrocytes obtained from epiphyseal cartilage of fetal guinea pigs or ear cartilage of young rabbits were cultured in monolayer. The influence of colchicine, cytochalasin B, and p-nitrophenyl-β-d-xylopyranoside on secretion of proteoglycans was investigated. Radioactive sulfate was used as a precursor. As observed previously in other systems, β-d-xylosides initiated the synthesis of free chondroitin sulfate chains, competing with the endogenous proteoglycan core protein acceptor. The molecular weights of the chondroitin sulfate chains synthesized both on the xyloside and on the core-protein acceptor in maximally stimulated cells were similar and significantly lower than in proteoglycans synthesized in the absence of xyloside. The size of the chondroitin sulfate chains synthesized on the xyloside was inversely related to the concentration of this compound. This finding suggests that the chain length is dependent on the ratio between available acceptor and chain-lengthening enzymes or precursors. Cytochalasin B, a microfilament-modifying agent, inhibited proteoglycan synthesis, without any effect on secretion. Cells treated with cytochalasin B could be stimulated with β-d-xyloside to synthesize free chondroitin sulfate chains to the same relative degree as cells with intact microfilaments. Colchicine, an antimicrotubular agent, partially inhibited synthesis and secretion of proteoglycan. However, cells treated with colchicine could be stimulated with β-d-xyloside to synthesize and secrete free chondroitin sulfate chains to about the same relative degree as cells with intact microtubules. The data suggest that microtubules may have a facilitatory rather than an obligatory role in the secretion of proteoglycans and that at least part of the effect of colchicine is located at or after the site of glycosaminoglycan synthesis.
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| 9. |
- Thyberg, J., et al.
(author)
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Proteoglycans of hyaline cartilage. Electron microscopic studies on isolated molecules
- 1975
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In: Biochemical Journal. - 0264-6021. ; 151:1, s. 157-166
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Journal article (peer-reviewed)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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