Biomedical subjects

F Romano

Publications and source records attributed to F Romano.

At least 109 records · Page 6Linked to original sources

PubMed1985

The stimulation by the tumour promoters 12-O-tetradecanoylphorbol-13-acetate and phenobarbital of the growth of primary neonatal rat hepatocytes.

A single exposure to a wide range of concentrations (10(-15)-10(-4) mol/l) of the tumour promoters 12-O-tetradecanoylphorbol-13-acetate (TPA) and phenobarbital (PB) significantly stimulated the flow into DNA synthesis and mitosis of neonatal rat hepatocytes in 4-day-old primary cultures kept in high-calcium (1.8 mmol/l) Eagle's FBS-MEM. Maximal effects were observed in the dose range 10(-12)-10(-6) mol/l. Moreover, both xenobiotics retained their full mitogenic effectiveness when given to hepatocytes incubated in calcium-deficient (0.01 mmol/l) FBS-MEM, thereby evoking a neoplastic phenotype in otherwise normal (i.e., non-initiated) cells. Proliferation kinetic studies showed that TPA and PB acted according to the actual cell cycle setting of the cells: they committed a fraction of the quiescent (GO) hepatocytes to grow, and enabled hepatocytes previously poised at the G1/S and G2/M boundaries to start cycling again, but exerted no influence on liver cells already engaged by themselves in active cycling. These diverse activities of TPA and PB were independent of serum (growth) factors; they were also fully elicited in hepatocytes grown in synthetic media (Eagle's MEM or HiWoBa2000), and were not changed by the addition of a mitogenically effective dose (10(-10) mol/l) of epidermal growth factor/urogastrone (EGF) with or without FBS. Conversely, the addition of the specific plasmalemmal calcium chelator, EGTA, or displacer, La3+, or of the anticalmodulin drugs, W-13 and calmidazolium (or R24571: an agent hardly entering cells) fully inhibited the mitogenic activities of tumour promoters in quiescent and intra-cycle-blocked hepatocytes, while having no effect on untreated or xenobiotic-treated liver cells already cycling by themselves. Such inhibitory effects were in all instances independent of the actual extracellular calcium concentration and took place according to time-related double kinetics. Hence, xenobiotic-activated processes taking place at the plasmalemmal level and involving the activation of calcicalmodulin-dependent enzymes were of critical importance for both the G0/G1 and G1/S transitions in primary hepatocytes.

Animals↗

PubMed1985

Primary cultures of neonatal rat liver as an assay system to identify compounds belonging to the tumor promoters class.

A single exposure to a low concentration (10-10 mol/L) of tumor promoters (like 12-0-tetradecanoylphorbol-13-acetate (TPA), phenobarbital, and nafenopin) or of hormones (as epidermal growth factor (EGF), glucagon and insulin) or of drugs (like imidazole and indomethacin) stimulated the 24-h flow into DNA synthesis and mitosis of primary neonatal rat hepatocytes incubated in high-calcium (1.8 mmol/L) Eagle's MEM-FBS medium. However, only tumor promoters acted as enhancers of hepatocytic DNA synthesis when a low-calcium (0.1 mmol/L) FBS-MEM medium was used. The tumor promoters' activity was completely suppressed by the simultaneous (or nearly such) addition of low doses (from 25.0 to .25 micrograms/ml; activity, from 100 to 1.0 unit/ml) of exogenous bovine liver Cu,Zn-superoxide dismutase (SOD), whatever the medium's calcium concentration. By contrast, SOD did not inhibit the growth stimulation elicited by hormones and drugs in hepatocytes exposed to the high-calcium FBS-MEM medium. Moreover, several tumor promoters (namely TPA, phenobarbital, nafenopin, saccharin, teleocidin, benzoyl peroxide, BHT, DDT, lindane, clofibrate, and melittin) stimulated DNA synthesis even when the hepatocytes were incubated in the serumless HiWoBa2000 medium, whatever its calcium concentration. In this synthetic medium, the tumor promoter's stimulatory activity was again completely written off by the simultaneous administration of exogenous (superoxide dismunate) SOD. These results disclose the existence of two quite different mechanisms by which neonatal rat hepatocyte growth can be stimulated: (i) the physiological-pharmacological extracellular calcium-dependent SOD-insensitive machinery, mediating the effects of EGF, glucagon, insulin, imidazole, and indomethacin; and (ii) the pathological extracellular calcium-independent SOD-suppressible mechanism operated by agents belonging to the tumor promoters class and involving, as a critical step, the generation of superoxide anions at the surface of the hepatocyte's plasma membrane. The present results also indicate that primary cultures of neonatal rat hepatocytes may constitute a useful tool for promptly and safely identifying compounds endowed with tumor promoters' capabilities.

Animals↗

PubMed1984

The tumor promoters TPA, phenobarbital, and nafenopin and the prostaglandins of A, E, and F series overcome the G1/S block imposed by extracellular calcium deprivation on neonatal rat hepatocytes.

A single exposure to a low concentration (10(-9) mole/l) of exogenous arachidonic acid or of prostaglandins of A, E, and F series significantly stimulated primary neonatal rat hepatocytes to enter S phase irrespective of whether the extracellular calcium concentration was high (i.e., 1.8 mmole/l) or markedly reduced (i.e., 0.01 mmole/l). Similarly, a single treatment with an even smaller (10(-10) mole/l) dose of the known tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA), phenobarbital, and nafenopin enhanced hepatocytic DNA synthesis when the environmental calcium level was both high and low. By contrast, a single application of a small concentration (10(-11)-10(-10) mole/l) of hormones such as epidermal growth factor (EGF), glucagon, and insulin, and of drugs such as imidazole and indomethacin only increased the hepatocytic flow into DNA synthesis when the extracellular calcium was high. These findings reveal that the mechanisms of physiological or pharmacological, calcium-dependent stimulation of hepatocellular growth are likely to be different from those of pathological, calcium-independent stimulation, as the latter, but not the former, would involve prostaglandin-mediated metabolic processes.

Animals↗

PubMed1984

Exogenous Cu,Zn-superoxide dismutase suppresses the stimulation of neonatal rat hepatocytes' growth by tumor promoters.

A single exposure to a low concentration (10(-10) mol/l) of tumor promoters [such as 12-O-tetradecanoylphorbol-13-acetate (TPA), phenobarbital and nafenopin] or hormones [such as epidermal growth factor (EGF), glucagon and insulin] or drugs [such as imidazole and indomethacin] stimulated the 24-h flow into DNA synthesis and mitosis of primary neonatal rat hepatocytes incubated in high-calcium (1.8 mmol/l) Eagle's FBS(10% v/v)-MEM. However, only tumor promoters acted as enhancers of hepatocytic DNA synthesis when a low-calcium (0.01 mmol/l) FBS-MEM was used. The activity of tumor promoters was totally suppressed by the simultaneous (or nearly such) addition of low doses (from 25.0 to 0.25 micrograms/ml; activity, from 100 to 0.7 U/ml) of exogenous bovine liver and ox and dog erythrocyte superoxide dismutase (SOD), independent of the calcium concentration of the medium. Even at the minimal dose administered, SOD effectively inhibited the stimulatory actions of TPA concentrations up to 10(-6) mol/l. SOD's blocking effect depended upon its enzymatic activity, as it was prevented by a specific inhibitor of SOD, sodium diethyldithiocarbamate (DDC). By contrast, SOD did not inhibit the growth stimulation elicited by hormones and drugs in hepatocytes maintained in high-calcium FBS-MEM. Moreover, several tumor promoters (namely TPA, phenobarbital, nafenopin, saccharin, teleocidin, benzoyl peroxide, BHT, DDT, lindane, clofibrate and melittin) stimulated DNA synthesis even when the hepatocytes were incubated in the serumless HiWoBa2000 medium, whatever its calcium concentration. In this synthetic medium, tumor promoters' stimulatory activity was again completely inhibited by the simultaneous administration of exogenous SOD. Known antioxidants such as retinoids, vitamin E, selenous acid, and 7,8-benzoflavone, when given simultaneously with TPA, also prevented the stimulation of hepatocytic growth. These results disclose the existence of two quite different mechanisms by which the growth of neonatal rat hepatocytes can be stimulated: (i) the physiological-pharmacological extracellular calcium-dependent SOD-insensitive system mediating the effects of EGF, glucagon, insulin, imidazole, and indomethacin; and (ii) the pathological extracellular calcium-independent SOD- and antioxidant-suppressible mechanism operated by agents belonging to the tumor promoters class and involving, as a critical step, the generation of superoxide anions on the surface of the hepatocyte plasmalemma.

Animals↗

PubMed1983

Viruses associated with acute respiratory infections in children admitted to hospital in Naples, 1979-82.

A survey of the virological and epidemiological features of acute respiratory diseases in children admitted to hospital in Naples has been carried out; the results of three years of research are reported.Between April 1979 and March 1982, 787 nasopharyngeal swabs were examined. There were 287 (36.5%) positive samples, with the highest isolation rate being found in children with bronchiolitis (39.5%).Among the different viruses isolated, adenovirus was the most common (161 positive samples, 56%); this agent appeared regularly in the different age and disease groups, with a marked increase in prevalence during the winter of 1980. Isolations of herpesvirus, respiratory syncytial virus and enterovirus were less frequent; however, echovirus 3 caused an epidemic in the summer of 1980. Influenza and parainfluenza viruses were seen fairly infrequently; two cases of Reye's syndrome yielded strains of influenza B.

Acute Disease↗

PubMed1982