7-ketocholesterol inhibits VLDL secretion by cultured human and rabbit hepatocytes.

7-ketocholesterol, one of the major product of autoxidation of dietary cholesterol, was found to inhibit secretion of very low density lipoprotein [14C]cholesterol, [14C]triacylglycerol and [35S]apoprotein B,E,C by cultured human and rabbit hepatocytes. A parallel inhibition (about 35%) of cholesterol synthesis but not of triacylglycerol formation was observed. Incubation with 10 micrograms/ml of oxysterol also reduced the total apo-B secretion measured by ELISA and increased intracellular apo-B mRNA level.

VLDL apoprotein secretion and apo-B mRNA level in primary culture of cholesterol-loaded rabbit hepatocytes.

Incubation of cultured rabbit hepatocytes with beta very low density lipoproteins (beta-VLDL) induces a dose-dependent increase in cell cholesterol (CH) content and VLDL apoprotein (apo) B and E secretion without change in apo-B mRNA level. These data suggest that beta-VLDL may exert a stimulatory effect on hepatic apo-B production at the co-translational and/or posttranslational level.

Immunologically related proteins in cytoplasmic and mitochondrial ribosomes of yeast Saccharomyces cerevisiae.

Ribosomal proteins from the cytoplasm and mitochondria of the yeast Saccharomyces cerevisiae were compared by immunoblotting techniques. Antibodies raised against cytoplasmic ribosomal proteins cross-react with five mitochondrial ribosomal proteins, four of which are located in the large and one in the small mitochondrial subunits. The possible existence of common ribosomal proteins for cytoplasmic and mitochondrial ribosomes is discussed.

Relationship between cytoplasmic and mitochondrial apparatus of protein synthesis in yeast Saccharomyces cerevisiae.

A conditional respiratory deficiency in yeast Saccharomyces cerevisiae is expressed as a result of a nuclear mutation in sup1 and sup2 genes (II and IV chromosomes, respectively), coding for a component of cytoplasmic ribosomes (Ter-Avanesyan et al. 1982). One such strain is studied here in detail.