Search PubMed⌕ Search

Biomedical subjects

R Bernardi

Publications and source records attributed to R Bernardi.

At least 37 records · Page 2Linked to original sources
PubMed1994

Dose-dependent zinc inhibition of DNA ladder in apoptotic HeLa cells regulates the activity of poly(ADP-ribose) polymerase and does not protect from death induced by VP-16.

Zinc ions exert an inhibitory effect on Ca(2+)Mg(2+)-dependent endonuclease which is supposed to be responsible for the fragmentation of DNA during apoptosis. In the experimental system we used, that is HeLa cells treated with VP-16, the protection from internucleosomal DNA degradation is modulated by Zn concentration and appears to be dependent on the time after treatment. This effect does not prevent cell death or occurrence of apoptotic parameters, suggesting that DNA ladder appearance is not a crucial event in apoptosis. The activation of poly(ADP-ribose)polymerase following the administration of VP-16, is not observed in cells in which DNA fragmentation has been abolished by zinc, supporting the hypothesis that this event is regulated by the appearance of small-sized DNA fragments.

Journal Article↗
PubMed1993

The effect of the chemotherapeutic drug VP-16 on poly(ADP-ribosylation) in apoptotic HeLa cells.

We have studied the effect of the chemotherapeutic drug VP-16 (etoposide) on the metabolism of HeLa cells by analysing different cellular parameters; in particular we have focused on changes in cellular morphology that are considered as markers of apoptosis. By immunofluorescence experiments we have shown that VP-16 causes the complete disruption of nucleoli and induces chromatin margination and fragmentation. Agarose gel electrophoresis of DNA from cells treated with 10-100 microM VP-16 showed the appearance of a characteristic ladder due to the internucleosomal DNA cleavage. The effect of etoposide on DNA integrity was not prevented by preincubation of cells with the protein synthesis inhibitor cycloheximide. These results provide experimental evidence indicating that the typical features of apoptosis are visible in HeLa cells exposed to VP-16. In this experimental system we have investigated whether the ADP-ribosylation process could be regulated by the presence of DNA fragments. By means of the activity gel technique, which allows the direct evaluation of automodified poly(ADP-ribose)polymerase, we have observed that in extracts from cells where etoposide-induced DNA fragmentation occurred, the autoribosylated form of the enzyme is greatly increased. Ribosylated poly(ADP-ribose)polymerase has been isolated by affinity chromatography on boronate column from cells permeabilized and labelled with [32P]NAD. Drug exposure caused a strong augmentation of modified enzyme. These observations suggest that activation of ADP-ribosylation process occurs in cells that show the typical features of apoptosis.

Apoptosis↗
PubMed1980

Bacterial toxins and glucagon in liver cAMP regulation: a physiopathological role in liver diseases?

Alterations of the specific enzymes located in the cell membranes might promote changes of the cyclic nucleotides ratio which is regulatory in growth stimulation of hepatocytes. Bacterial toxins, hormones and drugs affecting cyclic nucleotides system can interfere with this process in liver diseases. The Authors have determined hepatic cAMP concentrations by means of cAMP radioimmunoassay, in vivo, in rats treated with cholera toxin (CT), E. coli endotoxin (LPS) and glucagon. CT (0.15 mg i.v./rat/4th hr) and glucagon (0.8 mg/i.v./10') (significantly p less than 0.01) increase liver cAMP from 1.72 n mol/g wet wt (controls) to 2.62 and 4.13 n mol/g wet/wt respectively. Serum transaminases levels were unmodified. LPS (1.5 mg/hg/i.v./3th hr) significantly (p less than 0.01) raises serum transaminase activity while liver cAMP was not affected. Kinetics study however show that LPS, at lower dosage (0.5 mg/hg i.v.) enhances liver cAMP before cytotoxicity is observed.

Animals↗
PubMed1979

Control of endotoxinemia in liver disease by lactulose and paromomycin.

Through the use of the Limulus test research has been carried out on gram-negative endotoxin in patients with hepatic cirrhosis, chronic hepatitis, acute hepatitis, and in a control group. The positivity of this test in patients with cirrhosis and chronic hepatitis was 93.3% and in cases of acute hepatitis it was 90.9%. The effect of the combined administration of lactulose and paromomycin on endotoxin blood levels has been evaluated in a group of 9 patients with acute hepatitis, 8 with cirrhosis, 1 in hepatic coma, and 1 patient with chronic persistent hepatitis: in 18 of the 19 patients the Limulus test became negative. The results have been discussed in relation to clinical and laboratory data, and to recent data concerning the interaction between intestinal bacterial flora, endotoxin, and liver. Hypotheses have been proposed regarding the hepatocellular c-AMP mediated mechanism of endotoxin action.

Chronic Disease↗