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Biomedical subjects

B Barbiroli

Publications and source records attributed to B Barbiroli.

At least 91 records · Page 5Linked to original sources
PubMed1983

RNase-sensitive glucocorticoid-receptor complexes from HELA cell nuclei.

Dexamethasone-receptor complexes can be extracted from HeLa cell nuclei by mild sonication. These complexes can account for 800-1000 binding sites/cell, and are indistinguishable from salt-extractable ones as judged by sucrose gradient centrifugation in the presence of 0.3 M KCl, showing a sedimentation coefficient of 3.6 S. These complexes, however, broadly sediment in the 7 to 3.6 S region of low salt sucrose gradients. Enzymatic treatment of soluble extracts from nuclear sonicates shows that RNA is associated to dexamethasone-receptor complexes.

Cell Nucleus↗
PubMed1980

Distribution of pteroylglutamates in rat liver during regeneration after partial hepatectomy.

1. Liver pteroylpolyglutamate distribution was studied during regeneration after partial hepatectomy in rats maintained under controlled feeding conditions. 2. Pteroylhexaglutamate, pteroylpentaglutamate and pteroyltetraglutamate concentrations decrease from 12 to 72 h after operation, then increase and reach normal values at 180 h. Pteroyltriglutamate concentration, already high at 12 h, remains so in the subsequent periods. Pteroyldiglutamate concentration was unchanged. Monoglutamate concentrations at first decrease, and at 180 h exceed normal values. 3. The decrease in polyglutamate derivatives with a high number of glutamate residues, at present considered to be the coenzyme forms of folate, could be related not to a decreased synthesis, but to a greater requirement for these compounds during the early periods of regeneration, when biosynthetic processes are markedly increased. It is indeed probable that the increased availability of the preferred substrate of pteroylpolyglutamate synthetase, i.e. tetrahydrofolate, enhances conversion of folate into coenzyme forms.

Animals↗
PubMed1977

Functional modification of liver form-B RNA polymerase activity by a protein fraction from rats accustomed to controlled feeding schedules.

A protein fraction extracted from the liver of rats accustomed to eating during the first 8 h of a daily 12 h dark period is able to increase homologous form-B RNA polymerase activity. When the protein factor is added to RNA polymerase extracted at the end of the daily fasted period (0.9:OOh) the sensitivity of enzyme to ionic strength is modified, and resembles that of the enzyme extracted during the eating period (15:00 h) either using liver deproteinized DNA or chromatin as template. The chromatin-bound RNA polymerase activity is also modified in the presence of the factor, showing a modification of enzyme sensitivity to ionic strength similar to the one induced by food intake.

Animals↗
PubMed1975

Modification of the template capacity of liver chromatin for form-B ribonucleic acid polymerase by food intake in rats under controlled feeding schedules.

Nuclei from liver of rats accustomed to eating during the first 8h of a daily 12h dark period demonstrate an increased capacity to synthesize RNA 6H after the beginning of the feeding period. 2. This increase is accompanied by a higher yield of extractable form-B DNA-dependent RNA polymerase activity. 3. The endogenous RNA polymerase activity associated with nuclear chromatin is also stimulated by food intake. Both purified and chromatin-associated form-B enzyme activities exhibit different ionic strength requirements after food intake. 4. The sensitivity of exogenous (added) form-B-enzyme to changes in ionic strength changes after feeding when chromatin is used as template. 5. Chromatin extracted from the liver of fed rats is a better template for form-B-enzyme than chromatin extracted from starved rats.

Ammonium Sulfate↗
PubMed1975

The effect of spermine on transcription of mammalian chromatin by mammalian deoxyribonucleic acid-dependent ribonucleic acid polymerase.

Isolated rat liver nuclei demonstrate an increased ability to synthesize RNA in the presence of either spermine or spermidine. Spermidine has more effect on the low-salt alpha-amanitin-insensitive reaction, and spermine has more effect on the high-salt alpha-amanitin-sensitive reaction. Spermine is effective at concentrations of 0.1 mM and 1 muM, showing a biphasic effect. The RNA polymerase activity associated with nuclear chromatin is increased in the presence of spermine only at a concentration of 0.1 mM. Aso the transcription of deproteinized liver DNA by liver form-B polymerase or Escherichia coli enzyme is more efficient in the presence of 0.1 mM-spermine. Only when liver chromatin is transcribed by its homologous enzyme (and not by E. coli enzyme) is spermine active at both 0.1mM and 1 muM as in purified nuclei. The lower concentration of spermine (1 muM) is able to affect chromatin transcription by increasing the affinity of chromatin for the enzyme. Our findings suggest a regulatory role of spermine at the level of genome transcription.

Amanitins↗
PubMed1975

Folate metabolism in the rat liver during regeneration after partial hepatectomy.

1. Folate metabolism was studied during the early phases of liver regeneration after partial hepatectomy in rats accustomed to eating during the first 8h of a daily 12h dark period. 2. The content of 5-CH(3)-H(4)folate was drastically decreased during the first hours of regeneration. 3. The total HCO-H(4)folate coenzymes showed a constant decrease during the first 3 days of regeneration, and a continuous interconversion between 5-HCO-H(4)folate and 10-HCO-H(4)folate. 4. 10-HCO-H(4)folate synthetase, serine hydroxymethyl-transferase and 5,10-CH(2)-H(4)folate dehydrogenase activities were relatively low during the first hours after the operation, and increased only several hours later. 5. The increase in enzyme activities showed a stepwise pattern, apparently due to an interaction between the regeneration process and the controlled feeding schedules.

Animals↗