Biomedical subjects

R Comolli

Publications and source records attributed to R Comolli.

At least 55 records · Page 3Linked to original sources

PubMed1981

Polyamine concentration, activity of the ribosomal dissociation factor and proportion of ribosomes active in protein synthesis in the 4-dimethylaminoazobenzene-induced rat hepatoma.

4-Dimethylaminoazobenzene (DAB) induced liver tumour tissue showed a reduced proportion of ribosomes active in protein synthesis compared with control liver. Tumour cell extracts caused an increased association of ribosome subunits into inactive 80 S monomers, compared with the dissociation into active subunits caused by normal liver extracts. These findings may be explained, at least in part, by the increased proportion of spermidine to putrescine found in tumour tissue which would predispose towards association of the subunits.

Animals↗

PubMed1980

Activity of a purified nonsteroidal gametic factor on the inducibility of hepatic delta-aminolevulinic acid synthetase, NADPH-oxidase and tyrosine aminotransferase in senescent rats.

The effect of a water soluble nonsteroidal factor extracted from the male gamete on the activity of certain liver inducible enzymes during aging has been examined. Three enzymes have been studied: delta-aminolevulinic acid synthetase, NADPH-oxidase and tyrosine aminotransferase whose inducibility by ethanol, phenobarbital and ACTH, respectively, show age dependent alterations. The results here reported show that this factor is able to restore the enzyme inducibility in the liver of aging (600-day-old) rats without affecting the response of young (40-day-old) rats. Since the enzyme inducibility is altered during aging, and in the majority of rat hepatomas this factor might enter, possibly, in the regulation of enzyme activity also of neoplastic cells.

5-Aminolevulinate Synthetase↗

PubMed1980

Reassociation of eukaryotic ribosomal subunits and polyamine concentration in Yoshida ascites hepatoma and Ehrlich ascites carcinoma cells during growth.

The activity on ribosome monomers of dissociation factor preparations obtained by high salt wash from ribosomes and from the post-ribosomal supernatant (cytosol) of Yoshida rat ascites hepatoma and Ehrlich mouse ascites carcinoma cells and from the liver of control and tumor-bearing animals has been determined at different periods of intraperitoneal tumor growth. The concentration of the polyamines spermine, spermidine and putrescine has also been measured under the same conditions. Results here reported show the presence of an association factor activity on subunit ribosomes at low Mg2+ concentrations in the post-ribosomal supernatant fractions of Yoshida ascites hepatoma and Ehrlich ascites carcinoma cells during tumor growth. An association factor activity also takes place in the ribosomal high salt wash extracts of Yoshida ascites cells at the terminal stages of tumor growth. Since an increase of spermidine to putrescine ratios occurs during tumor growth the changes in the rate of ribosome monomer dissociation into units here observed might be attributable, at least in part, to changes in polyamine concentrations under the conditions studied.

Animals↗

PubMed1979

Reassociation of eukaryotic ribosomal subunits by a factor from rat ascites hepatoma cytosol.

Post-ribosomal supernatant extracts from Yoshida AH 130 ascites hepatoma cells promote the in vitro association of ribosomal subunits at low Mg2+ concentration. Comparable extracts from rat liver show, on the contrary, dissociation factor activity on ribosome monomers.

Animals↗

PubMed1979

Increased activity of the ribosomal dissociation factor in the pre-replicative phase of liver regeneration after partial hepatectomy.

The activity of the ribosomal dissociation factor and the formation in vitro of free 60S and 40S subunits increased in the first 12--48 h after partial hepatectomy. This suggests an accelerated reconversion into active subunits of ribosomes that complete a translation cycle in the early phases of liver regeneration.

Animals↗

PubMed1979

Changes in the activity and distribution of the ribosomal dissociation factor of rat liver during growth.

In order to assess the relationships between the rate of growth and the activity of the initiation factors of protein synthesis, the activity and intracellular distribution of partially purified preparations of the ribosomal dissociation factor, obtained from the 0.5 M KCl wash of the ribosomes and from the high-speed supernatant (cytosol) of rat liver, were investigated in animals aged 1, 30, 60, 90 and 180 days. During the early phases of growth the activity of the dissociation factor was found mostly in the KCl wash of ribosomes. With advancing age, this activity decreased whereas that of the supernatant was found to increase. The activity of the supernatant was similar to that of ribosomes at 60, 90 and 180 days of age. The older rats showed, however, a decline in the activity of the dissociation factor. These observations suggest an increased rate of protein synthesis initiation in the early phases of growth in rat liver. With advancing age, a progressive reduction of ribosome recycling into subunits might take place, due to the increased accumulation of the dissociation factor in the cytosol. This might suggest a lowering of the initiation reactions of protein synthesis in such conditions.

Aging↗

PubMed1977