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T Chojnacki

Publications and source records attributed to T Chojnacki.

At least 73 records · Page 4Linked to original sources
PubMed1983

Separation of dolichol and dolichyl-P in microsomal and lysosomal compartments of hepatocytes.

The distribution, labeling and interrelationship of microsomal and lysosomal dolichol and dolichyl-P in rat liver was investigated. After membrane induction with phenobarbital, N-nitrosodiethylamine and diethylhexylphthalate, the amount of microsomal and lysosomal dolichols are modulated independently. Liposomal labeled dolichol injected into the portal vein appears only in lysosomes and even after 8 days is still limited to the lysosomes. After in vivo labeling with [3H]mevalonate, high initial labeling of dolichol and dolichyl-P is present in microsomes and the labeling in microsomes is greater than that in lysosomes even after 8 h. The results demonstrate compartmentalization of the intracellular dolichols in hepatocytes. These lipids may have independent roles at different membrane locations.

Animals↗
PubMed1983

Separation, quantitation and distribution of dolichol and dolichyl phosphate in rat and human tissues.

Two procedures for quantitative determination of dolichol were studied and these were applied to analyze tissue and subcellular distribution. In the first procedure the dolichols were oxidized with Cr2O3 and reduced with NaB3H4. The radioactivity in the individual dolichols was measured using reversed-phase thin-layer chromatography. In the second procedure, dolichols were analyzed by high-pressure liquid chromatography. For determination of dolichyl phosphates the lipid extract was subjected to acid and alkaline hydrolysis, and after hydrolysis with acid phosphatase the distribution was determined by high-pressure liquid chromatography. Recovery was monitored by the addition of dolichol D15 and D23 phosphate to the homogenate. Rat spleen had the highest dolichol content (114 micrograms/g) followed by lower content in rat liver and brain. The distribution pattern was similar in all organs, with 18 and 19 isoprene residues as dominating components. Human organs contain considerably higher concentrations of dolichol, with the 19 and 20 isoprene residues as the main components. In rat liver, outer mitochondrial and Golgi membranes, lysosomes and plasma membranes contain considerable amounts of dolichol. A drastic increase in dolichol content was observed in rat liver hyperplastic nodules while human liver cirrhosis and hepatocarcinoma showed a marked decrease in dolichol. In the latter case, the distribution pattern was also changed. Of the total amount of dolichol present in the tissues, 2% was phosphorylated in human liver, 10% in human testis and 18% in rat liver. In rat liver mitochondria and in microsomes 4 and 31%, respectively, of the polyprenols were in activated form. The results demonstrated that dolichyl phosphate and dolichol concentrations were regulated by different mechanisms and that the two forms possessed an independent distribution.

Animals↗
PubMed1983

The uptake of dietary polyprenols and their modification to active dolichols by the rat liver.

The uptake of dietary polyprenols was studied by administering, through a gastric tube, labeled alpha-saturated and alpha-unsaturated polyprenols, with 11 and 19 isoprene residues. The lipids appeared in all organs but mostly in the liver after 16 h where those with 11 isoprenes were in much higher concentration than the prenols with 19 isoprene residues; the distribution in the liver was studied in detail. About 45% of the polyprenols taken up were esterified with fatty acids. A part of the radioactivity (6-30%) appeared in the supernatant but mostly in water-soluble form. Among subcellular fractions, the highest uptake was found in the outer mitochondrial membranes. After 16 h, both 11- and 19-residue alpha-unsaturated injected prenols were present to a large extent as alpha-saturated compounds in liver homogenates and subcellular fractions. About 10-15% of the lipids were phosphorylated. The results suggest that a part of the dolichol phosphate pool, participating in glycosylation reactions, may derive from dietary unsaturated polyprenols which after uptake can be reduced and phosphorylated.

Animals↗
PubMed1982

Enrichment of the intracellular dolichol pool in isolated liver cells.

Isolated hepatocytes were incubated with egg lecithin liposomes containing dolichol(C55), dolichol(C95), and dolichol phosphate(C55) in order to enrich intracellular membranes with these polyprenols. After incubation, the lipids were recovered from various membrane fractions and from the supernatant. The highest concentration was found in the microsomes. A part of the dolichol in microsomes, as well as in other fractions, was phosphorylated. This phosphorylation is mediated by the CTP-specific kinase that is present only on the outer surface of the microsomes and uses alpha-saturated polyprenols as substrates. The isolated microsomes enriched with dolichol in vivo exhibited increased lipid and protein glycosylation upon incubation with nucleotide sugars and it was demonstrated that the increased lipid glycosylation was due to transfer of the sugar to the exogenous incorporated dolichol.

Animals↗
PubMed1980

Induction of an attachment and spreading on glass of Ehrlich ascites tumour cells by alpha-saturated polyprenols.

It has been observed that a dolichol, alpha dihydro-undecaprenol, induces phenotypic changes in Ehrlich ascites tumour [EAT] cells. In the presence of this dolichol in the medium. EAT cells attach to glass and spread on it but grow in an overlapping pattern. This spreading takes place after a lag of between 72-96 hours at continuous exposure to the dolichol. When cells, once induced to spread, are trypsinized, they can spread once more within 3-6 hours in the dolichol-free medium. It is suggested that dolichols, which act as lipid intermediates in protein glycosylation, may represent a class of compounds which by interference with the biosynthesis of plasma membrane constituents influence surface properties of EAT cells and induce spreading. The results presented in this paper support the view that sugar moieties of plasma membrane constituents play a role in controlling cell attachment, spreading, and intercellular communication.

Animals↗
PubMed1979

Acyl esters of polyprenols: specificity of microsomal transacylase for polyprenols of different chain length and saturation.

Transfer of fatty acids from phospholipids to polyprenols, catalysed by the transacylase from rat liver microsomes, was investigated. The specificity of the enzyme for polyprenols of different chain length and different degree of saturation was studied using individual isoprenologues, the preparation of which in highly tritiated form is described. It was found that short-chain polyprenols are better substrates for the enzyme than long-chain polyprenols, and alpha-saturated better than unsaturated or multiply saturated polyprenols. Short-chain, alpha-saturated single isoprenologues were several-fold more active as acyl acceptors than natural dolichol.

Acyl Coenzyme A↗
PubMed1978

Glycosyl transfer from nucleotide sugars to C85- and C55-polyprenyl and retinyl phosphates by microsomal subfractions and Golgi membranes of rat liver.

The capacity of isolated membrane fractions to catalyse transfer of sugars from sugar nucleotides to alpha-saturated and non-saturated forms of phosphorylated C85 and C55 polyprenols and retinyl phosphate was examined. The amount of endogenous lipid acceptor present for various sugars was also measured. It appears that the types and amounts of polyprenyl phosphates present in rough- and smooth-microsomal fractions and Golgi membranes are different and the individual polyprenyl phosphates exhibit specificity as sugar acceptors.

Animals↗
PubMed1977

Enzymic synthesis of ether types of choline and ethanolamine phosphoglycerides by microsomal fractions from rat brain and liver.

The formation of product by ethanolamine phosphotransferases (EC 2.7.8.1) and cholinephosphotransferases (EC 2.7.8.2) in microsomal fractions from brains and livers of mature rats is increased several fold by 1,2-diacyl-sn-glycerols. With the addition of 1-alkyl-2-acyl-sn-glycerols, we have found an 11-fold increase with brain microsomes and a 20-fold increase with lvier microsomes in the synthesis of choline ether lipids (1-alkyl-2-acyl- and 1-alk-1'-enyl-2-acyl-sn-glycero-3-phosphorylcholines). For the synthesis of ethanolamine ether lipids (1-alkyl-2-acyl and 1-alk-1'-enyl-2-acyl-sn-glycero-3-phosphorylethanolamines), the stimulation of alkylacylglycerols was 7-fold for brain microsomes and 18-fold for liver microsomes. The alkylacyl glycerols (8 mM) also inhibited the synthesis of diacyl phosphoglycerides by 44 to 65%, indicating that the same ethanolaminephosphotransferases and cholinephosphotransferases are utilized for the synthesis of alkylacyl phosphoglycerides and diacyl phosphoglycerides. A desaturation of the alkyl groups may take place in the same reaction mixture. The rate of incorporation of phosphorylcholine into alkenylacyl glycerophosphorylcholines (choline plasmalogens) with alkylacylglycerols, cytidine diphosphate choline, and liver microsomes was 15 nmoles per mg protein per hour. The in vitro synthesis of choline plasmalogens with alkylacylglycerols had not been observed previously. The corresponding rate of incorporation of phosphorylethanolamine into ethanolamine plasmalogens was 10 nmoles per mg protein per hour, a value greater than any of the previously reported values for ethanolamine plasmalogen formation from alkylacyl glycerophosphorylethanolamines.

Animals↗
PubMed1976

C55-Dolichol: occurrence in pig liver and preparation by hydrogenation of plant undecaprenol.

Apart from the long-chain dolichols (C80-C110), pig liver contains also a family of much shorter polyprenols with dominating C55-polyprenol. This compound was identified as cis/trans-dihydroundecaprenol in which the OH-terminal isoprene residue was saturated. The number of internal trans isoprene residues in this compound was three in comparison with two such residues in long-chain C95-dolichol. Chemical preparation of dihydroundecaprenol with a selectively saturated OH-terminal isoprene residue from fully unsaturated plant undecaprenol is presented.

Animals↗
PubMed1976

Phage-dependent changes in Shigella flexneri type antigen synthesis.

Lysogenic conversion of Shigella flexneri type antigens was studied with the aid of wild-type and thermosensitive mutant phages. With all wild-type phages, the appearance of glycosylated antigen was accompanied by the appearance of polyprenyl phosphate glucose synthetase activity. With some of the mutant phages, the appearance of glycosylated antigen was not followed by the formation of lipid-linked glucose in the enzyme assay. The reverse has also been observed, i.e., the high rate of formation of lipid-linked glucose and the lack of V-type antigen.

Antigens, Bacterial↗