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J Hradec

Publications and source records attributed to J Hradec.

At least 91 records · Page 5Linked to original sources
PubMed1985

Enhanced utilization of 14-methylhexadecanoic acid for the synthesis of lipids during the growth of Walker 256 carcinoma in rats.

Labeled 14-methylhexadecanoic acid was administered to normal rats, animals bearing the Walker 256 tumor at various stages of its growth and to tumor-resistant rats and its distribution in lipids (free fatty acids, triglycerides, phospholipids and cholesteryl esters) was studied during 15 min to 3 hours following its injection in the liver, blood and tumor tissue. The period of the most active tumor growth was associated with a significantly better utilization of this fatty acid for the synthesis of lipids. The quantities of radioactive triglycerides, phospholipids and cholesteryl ester in the liver were highly increased during this time. In tumor-resistant animals the levels of radioactive lipids were similar to those in control normal animals but the turn-over of 14-methylhexadecanoic acid was considerably slower than in controls. The turn-over of the cholesteryl 14-methylhexadecanoate in the liver was significantly changed at the late stages of the tumor growth. The level of this cholesteryl ester in the blood decreased progressively during the tumor growth whereas that of triglycerides increased. No significant changes were associated with the free fatty acid and phospholipids in the blood. The total radioactivity present in the tumor increased from 0.05% up to nearly 1% of the administered 14-methylhexadecanoic acid during the growth of the Walker 256 tumor. The level of radioactive cholesteryl 14-methylhexadecanoate in the tumor tissue increased progressively during 3 hours following the injection of 14-methylhexadecanoic acid. Thus the tumor growth is apparently accompanied by significant changes in the metabolism of 14-methylhexadecanoic acid and results in an enhanced synthesis of lipids in the liver tissue. The newly synthesized lipids, in particular cholesteryl 14-methylhexadecanoate, are transported in the blood stream into the tumor where they accumulate.

Animals↗
PubMed1984

CTP can replace GTP in reactions catalyzed by eukaryotic peptide elongation factor 1.

In several reactions catalyzed by highly purified peptide elongation factor 1 from rabbit reticulocytes, GTP may be fully replaced by CTP but not by ATP or UTP. This holds true for the factor-dependent binding of aminoacyl-tRNA to ribosomes, GTPase activity, GTP-dependent autophosphorylation of the factor protein and binding of cholesteryl 14-methylhexadecanoate by the factor.

Adenosine Triphosphate↗
PubMed1984

Particulate protein-synthesis factors associated with translatable mRNA in mouse hybridoma cells.

Besides of mRNA, the postribosomal pellet of mouse hybridoma cells contains RNA species which become labeled more rapidly than rRNA. Their synthesis is inhibited by actinomycin D. Density-gradient centrifugation of the postribosomal pellet yielded fractions of approx. 55-60 and 90S, synthesizing after the addition of both ribosomal subunits and energy-sources light and heavy chains of immunoglobulin, as demonstrated by indirect immunoprecipitation. Analysis of translation products by electrophoresis indicated the presence of precursors of mRNAs for immunoglobulin chains in these particles. Postribosomal pellets thus apparently contain different particles composed of similar polypeptide chains and containing protein-synthesis factors associated with translatable mRNA.

Animals↗
PubMed1984

Purification of mRNA for immunoglobulin kappa-chains from myeloma and hybridoma cells using hybridization to immobilized complementary DNA.

The principle of mRNA purification by hybridization to an immobilized DNA fragment was applied to the isolation of mRNA coding for immunoglobulin kappa-chains of mouse myeloma MOPC 21 and mouse hybridoma PTF-02. The DNA fragment comprising the 3'-untranslated region and a part of the constant region of the kappa-chain gene was covalently attached to diazobenzyloxymethyl-cellulose and used as an affinity adsorbent. A homogeneous 14S mRNA species was obtained by hybridization of total mRNA to the affinity adsorbent at 52 degrees C and by elution at 60 degrees C. Addition of the purified mRNA to a fractionated cell-free translation system resulted in a significant increase in the radioactivity immunoprecipitated by pig anti-mouse immunoglobulin antibodies. A single radioactive polypeptide of apparent Mr of 25,000, corresponding obviously to the kappa-chain, was identified as the only translation product.

Animals↗
PubMed1984

Microsome-mediated stimulation of the aminoacylation of rat liver initiator transfer ribonucleic acid by benzo[alpha]pyrene and 3,3-dimethyl-1-phenyltriazene.

The charging of initiator tRNAmetF with L-methionine was significantly stimulated by pre-incubation of unfractionated tRNA from rat liver with benzo [alpha]pyrne (BP) or 3,3-dimethyl-1-phenyltriazine (DMPT). The presence of microsomal enzymes from rat liver and of NADPH was absolutely required for this effect. Maximum enhancement was obtained after 60 min of incubation with 10(-4)-10(-8) mumol/ml of either compound tested. It appears that either proximate carcinogen, BP or DMPT, must be converted by microsomal enzymes into its direct-acting metabolites (ultimate carcinogens) which interact with initiator tRNA and thereby specifically modulate its aminoacylation.

Amino Acyl-tRNA Synthetases↗
PubMed1983

The postribosomal particle of rabbit liver contains protein-synthesis factors and serum albumin mRNA.

As demonstrated by indirect immunoprecipitation and polyacrylamide gel electrophoresis, an 85S particle separated by sucrose density-gradient centrifugation from the postribosomal pellet of rabbit liver, is able to synthesize serum albumin if supplemented with both ribosomal subunits and sources of energy. It is retained on heparin bound to Sepharose 4B, contains translatable mRNA and apparently all protein factors required for translation. This particle may represent a highly organized protein synthesizing machinery, the combination of which with ribosomes results in formation of new protein molecules.

Amino Acyl-tRNA Synthetases↗
PubMed1983

Biosynthesis of rabbit serum albumin in a heterologous fractionated subcellular system.

As demonstrated by a simple procedure based on indirect immunoprecipitation, proteins retained on heparin-Sepharose 4B from postmitochondrial supernatants of rat liver and Zajdela hepatoma catalyse the translation of rabbit serum albumin mRNA in the presence of ribosomal subunits from rat liver, Zajdela hepatoma or rabbit reticulocytes. The albumin synthesis shows an optimum at 1.5 mM MgCl2 and 25 mM KCl and requires ATP and GTP. It is significantly stimulated by tRNA and proceeds for more than 2 h, suggesting a high rate of reinitiation. At the optimum ribosomes:mRNA ratio of 13:1, the immunoprecipitable radioactivity exceeds 15-20-times the blank values. Fluorography of polyacrylamide slabs after electrophoresis of immunoprecipitates revealed the presence of only complete full-size serum albumin without any smaller peptides resulting from premature terminations of polypeptide chains, demonstrating faithful translation. In stained gels only, both heavy and light chains of immunoglobulin G were found, indicating that the assay procedure is highly specific and reliable. The fractionated heterologous protein-synthesizing system described in this paper may be generally useful for studies on the synthesis of specific proteins and factors affecting their rates since, unlike comparable translation assays, a precise calculation of the balance of newly synthesized proteins is possible.

Animals↗