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- Florén, Claes-Henrik, et al.
(författare)
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Binding, interiorization and degradation of cholesteryl ester labelled chylomicron remnant particles by rat hepatocyte monolayers
- 1977
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Ingår i: The Biochemical journal. - : Portland Press Ltd.. - 0264-6021. ; 168:3, s. 483-494
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Tidskriftsartikel (refereegranskat)abstract
- 1. The cholesteryl ester of isolated chylomicron-remnant particles was efficiently degraded by hepatocyte monolayers. The degradation was sensitive to metabolic inhibitors. 2. With increasing amounts of remnant cholesteryl ester the rate of uptake approached saturation and conformed to a linear double-reciprocal plot. The V(max.) was determined as 80ng of cholesteryl ester/h per mg of protein and the apparent K(m) as 1.4mug of cholesteryl ester per mg of protein. The time course for the uptake and hydrolysis suggested that binding of particles to the cell surface preceded the degradation. 3. Cholesteryl esters of native chylomicrons were degraded to a much smaller extent and their presence had only a small inhibitory effect on the degradation of chylomicron remnants. Intestinal very-low-density lipoproteins were degraded somewhat faster than chylomicrons, and caused more inhibition of remnant degradation. Rat high-density lipoproteins inhibited the hydrolysis of remnant cholesteryl ester by up to 50%, but had less influence on the amount of cholesteryl ester that was bound to the cells. Serum decreased both the uptake and hydrolysis, whereas d=1.21 infranatant had no effect. 4. The cholesteryl ester hydrolysis after the uptake by the cells was inhibited by chloroquine and by colchicine. Only 28-36% of the unhydrolysed cholesteryl ester could be released from these cells by trypsin treatment, indicating that the major portion was truly intracellular. The particles that could be released from the cell surface by trypsin and those remaining in the medium had the same triacylglycerol/cholesteryl ester ratio as the added remnant particles. Significant amounts of denser particles were thus not formed during contact with the cell surface. 5. The presence of heparin, as well as preincubation of the cells with heparin, increased the uptake of chylomicron remnants. This effect was most marked in the presence of serum. A much smaller proportion of the other serum lipoproteins was taken up, and this proportion was not increased by heparin.
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- 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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