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Biomedical subjects

R Pascale

Publications and source records attributed to R Pascale.

34 records · Page 2Linked to original sources
PubMed1987

Benzo(a)pyrene metabolism by lymphocytes from normal individuals and individuals carrying the Mediterranean variant of glucose-6-phosphate dehydrogenase.

In vitro growing human lymphocytes (HL) and fibroblasts, isolated from glucose-6-phosphate dehydrogenase (G6PD)-deficient subjects (Mediterranean variant), show a sharp decrease in this enzymatic activity and in NADPH:NADP+ ratio. These cells are less able than controls to hydroxylate benzo(a)pyrene (BaP) when tested in the absence of an exogenous NADPH-generating system. They exhibit great resistance to the toxic effect of BaP. G6PD-deficient fibroblasts are less prone than controls to in vitro transformation by BaP. To investigate whether this depends on a decreased production of active BaP metabolites and BaP:DNA adducts by G6PD-deficient cells, BaP metabolism was studied in G6PD-deficient HL cultured in vitro in the presence of mitogens and treated with BaP for 24 hr. HPLC profiles of organo- and water-soluble metabolites revealed that both types of benzo(a)anthracene (BaA)-induced HL produced: 4,5-, 7,8-, 9,10-diols, 1,3-, 3,6-quinones, 3-, 9-hydroxy and 2 peaks of more polar metabolites. There was a 25-76% decrease of organo- and water-soluble metabolites in the G6PD-deficient cells. When HL were incubated with 7,8-diol, the formation of metabolites mutagenic for Salmonella typhimurium (His-) was very low in G6PD-deficient cells. BaP:deoxyadenosine (dAde) and BaP:deoxyguanosine (dGua) adducts were identified after incubation of both types of HL with BaP. There was a 31-79% fall in adduct formation by G6PD-deficient cells. Our results indicate that G6PD-deficient human lymphocytes are less able to metabolize BaP than normal lymphocytes. We suggest that the NADPH pool is inadequate, in deficient cells, for active BaP metabolism.

Benzo(a)pyrene↗
PubMed1987

Decreased stimulation by 12-O-tetradecanoylphorbol-13-acetate of superoxide radical production by polymorphonuclear leukocytes carrying the Mediterranean variant of glucose-6-phosphate dehydrogenase.

Polymorphonuclear leukocytes (PMNs) from individuals carrying the Mediterranean variant of glucose-6-phosphate dehydrogenase (G6PD) exhibit a great decrease in this enzymatic activity and in hexose monophosphate shunt (HMS). 12-O-tetradecanoylphorbol-13-acetate (TPA) greatly stimulates HMS of normal PMNs, while it does not affect that of the deficient PMNs. Similarly, the stimulation of HMS by methylene blue is largely reduced in G6PD-deficient PMNs. These changes are paralleled by a 58% decrease in TPA-stimulated superoxide radical (O2-) formation by the deficient PMNs. G6PD activity is not detectable in the deficient PMNs incubated with dehydroepiandrosterone, and these cells show a near complete inhibition of O2- production. It thus seems that the low ability of G6PD-deficient PMNs in the production of O2- depends on the low NADPH generation by HMS in these cells. The decrease in TPA-stimulated O2- production suggests a reduced response of G6PD-deficient cells to promoting agents.

Adult↗
PubMed1987

Variations of ornithine decarboxylase activity and S-adenosyl-L-methionine and 5'-methylthioadenosine contents during the development of diethylnitrosamine-induced liver hyperplastic nodules and hepatocellular carcinoma.

Liver ornithine decarboxylase (ODC) activity and content of S-adenosyl-L-methionine (SAM) and its catabolite 5'-methylthioadenosine (5'-MTA) were determined in the late stages of hepatocarcinogenesis. Wistar rats received one diethylnitrosamine dose, followed by a partial hepatectomy at the midpoint of a 15-day treatment with 2-acetylaminofluorene (2-AAF), and then by an 18-week phenobarbital (PB) treatment. Thirty-eight per cent of liver was gamma-glutamyltranspeptidase (GGT)-positive and no visible nodules and hepatocellular carcinomas developed 16 weeks after starting 2-AAF feeding. Hyperplastic nodules and hepatocellular carcinomas were found on weeks 24 and 56 respectively. On weeks 24 and 56 only approximately 10% of liver was occupied by GGT-positive foci. At all times studied the foci exhibited a low labeling index (LI), and liver ODC activity was near control values. By contrast, a high ODC activity and LI and a low SAM and 5'-MTA levels were found in hyperplastic nodules and neoplasia. These tissues exhibited a high 5'-MTA phosphorylase activity. SAM administration during PB treatment, caused a 25-36% fall of GGT-positive liver and prevented the development of hyperplastic nodules and hepatocellular carcinomas. This was coupled to a sharp increase of SAM and 5'-MTA liver contents. SAM and 5'-MTA inhibited hepatocyte DNA synthesis in vitro. The addition of 5'-MTA to the reaction mixture for the ODC assay strongly inhibited ODC activity. However, the preincubation of SAM with liver homogenates or hepatocytes, used to prepare crude ODC, was necessary to inhibit ODC activity by SAM. Adenine, an inhibitor of 5'-MTA-phosphorylase, enhanced inhibition of DNA synthesis and ODC activity by SAM and 5'-MTA. Thus, during a prolonged promoting treatment a selected population of GGT-positive foci appears to acquire a stable phenotype characterized by a high DNA and polyamine synthesis. The development of nodules and carcinomas is associated with low SAM and 5'-MTA contents and high ODC activity and LI. 5'-MTA accumulation, during SAM administration, is probably responsible for the inhibition of promotion by SAM.

2-Acetylaminofluorene↗
PubMed1987

The variations of S-adenosyl-L-methionine content modulate hepatocyte growth during phenobarbital promotion of diethylnitrosamine-induced rat liver carcinogenesis.

A decrease in liver S-adenosyl-L-methionine (SAM) content and an increase in ornithine decarboxylase (ODC) activity occurred between the 2nd and the 5th week after starting 2-acetylaminofluorene (AAF) feeding in diethylnitrosamine (DENA)-initiated rats. These rats then received a 0.05% phenobarbital (PB)-containing diet for 18 weeks after the end of AAF feeding. Two weeks after starting AAF, an increase in the hepatocyte labeling index (LI) also occurred in gamma-glutamyl-transpeptidase (GGT)-positive foci and surrounding tissue. LI returned to control values in a few days in surrounding tissue, while it remained high for at least 4 weeks in the foci. Analogous changes were observed, but for a shorter period of time, in the rats subjected to partial hepatectomy (PH) plus AAF, in which no GGT-positive foci developed. Twenty-four weeks after starting AAF, 30% of the liver was occupied by visible nodules. ODC activity and LI were high and SAM was low in nodules, but they were near to control values in surrounding liver. SAM administration reconstituted the liver SAM pool, inhibited ODC activity, and prevented visible nodule development. SAM inhibition of ODC activity occurred in vitro only after preincubation with liver homogenate and was enhanced by adenine, an inhibitor of methylthioadenosine (MTA) phosphorylase. MTA addition to the reaction of mixture for ODC determination was inhibitory. The SAM decrease in both liver and nodules was coupled with a decrease of MTA content. SAM administration caused MTA accumulation in the liver. It is suggested that liver SAM content by influencing MTA level, could be a rate-limiting factor for growth and promotion, through a modulation of polyamine synthesis.

2-Acetylaminofluorene↗
PubMed1987

Control of glucose-6-phosphate dehydrogenase deficiency on the formation of mutagenic and carcinogenic metabolites derived from benzo(a)pyrene.

It has been observed that human lymphocytes (HL) and fibroblasts, isolated in vitro from donors carrying the Mediterranean variant of glucose-6-phosphate dehydrogenase (G6PD), show a great decrease in this enzymatic activity, the hexose monophosphate shunt, and the NADPH/NADP+ ratio. This effect is associated with a decreased sensitivity of G6PD-deficient cells to the benzo(a)pyrene (BaP) cytotoxic effect and to a decreased in vitro transformation of BaP-treated fibroblasts. Further, benzo(a)anthracene (BaA)-induced BaP hydroxylase activity is lower in G6PD-deficient cells, when measured in the presence of endogenous NADPH. It has been hypothesized that the NADPH level could be rate-limiting for the NADPH-dependent steps of BaP metabolic activation. To test this hypothesis, the formation of BaP metabolites was studied in normal and G6PD-deficient HL incubated with the carcinogen. HPLC profiles of organic-soluble metabolites revealed that both types of HL produced all the following known BaP metabolites: 9,10-, 4,5- and 7,8-dihydrodiols, quinones, 9- and 3-hydroxy and two peaks of more polar metabolites. There was a great decrease of the various metabolites in the deficient HL. A decrease of total water-soluble BaP metabolites also occurred. HL formed mutagenic metabolites for S. typhimurium TA100 (his-) when incubated with the rat liver S9 fraction. When intact HL substituted S9 fraction, a significant reversed mutation occurred only with normal HL. This could indicate that the NADPH pool is inadequate in G6PD-deficient HL for active BaP metabolism. Accordingly, deficient HL formed lower amounts of BaP:DNA adducts than control during incubation with BaP.

Benzo(a)pyrene↗
PubMed1987

Inhibition by dehydroepiandrosterone of liver preneoplastic foci formation in rats after initiation-selection in experimental carcinogenesis.

The effect of dehydroepiandrosterone (DHEA) on the development of liver preneoplastic foci was evaluated. The experimental protocol used initiation by diethylnitrosamine (DENA), followed by selective growth induced by partial hepatectomy (PH), in rats fed an N-acetylamino-fluorene (AAF)-containing diet, and followed by a standard diet with or without 0.05% phenobarbital (PB). DHEA (0.6%) was administered in the diet for 4 or 7 weeks after DENA injection (treatments A and B) or for 3 weeks after the end of AAF feeding (treatment C). On the 7th week after DENA injection, DHEA treatments A and C caused slight decrease of body weight and 40-60% increase in liver weight and cell size; number of nuclei per g of liver was not changed. The dietary treatment also caused a marked decrease of liver glucose-6-phosphate dehydrogenase (G6PD) activity and of the percentage of the gamma-glutamyltranspeptidase (GGT)-positive liver. PB increased G6PD activity and GGT-positive liver. This effect was oblated by DHEA treatments A and C. On the 7th week, the labeling index (LI) was low in surrounding liver, and high in GGT-positive foci. PB had an enhancing effect, while DHEA treatments A and C were inhibitory. G6PD was low at the end of DHEA treatment B, but it returned to normal values 4 weeks after the end of this treatment. At this time no effect of DHEA treatment B was observed on the extent of GGT-positive liver and LI.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Acetylaminofluorene↗
PubMed1986

Effect of the variations of S-adenosyl-L-methionine liver content on fat accumulation and ethanol metabolism in ethanol-intoxicated rats.

The protective effect of S-adenosyl-L-methionine against rat liver steatosis induced by chronic ethanol ingestion was investigated. S-Adenosyl-L-methionine given during ethanol treatment prevented steatosis and accelerated recovery from steatosis when given after ethanol withdrawal. It also caused a slight inhibition of blood ethanol consumption in both acutely and chronically intoxicated rats. About 30% inhibition of alcohol dehydrogenase, but not of the microsomal ethanol oxidation system, occurred in rats subjected to acute ethanol toxicity as well as in normal rats as a consequence of S-adenosyl-L-methionine treatment. A comparison between S-adenosyl-L-methionine and pyrazole, as concerns inhibition of ethanol oxidation and fat accumulation, revealed that a greater inhibition of ethanol metabolism by pyrazole was associated with incomplete prevention of steatosis, while a lower inhibition by S-adenosyl-L-methionine was coupled to a complete prevention. Ethanol induced a drastic decrease of reduced glutathione liver content as well as 630 and 133% increases of blood and liver acetaldehyde contents, respectively. S-Adenosyl-L-methionine treatment almost completely reconstituted the liver reduced glutathione pool and caused a large decrease of the liver and blood acetaldehyde contents. 1-Chloro-2,4-dinitrobenzene, which depletes the cellular reduced glutathione, and diethylethanolamine, an inhibitor of the phosphatidylethanolamine methylation, abolished the S-adenosyl-L-methionine-induced modifications of the reduced glutathione, acetaldehyde, and triacylglycerol contents in the liver of ethanol-treated rats. Neither S-adenosyl-L-methionine nor reduced glutathione inhibitors affected the liver acetaldehyde dehydrogenase activity. It is suggested that, although S-adenosyl-L-methionine induced a small inhibition of ethanol metabolism in the liver, its antisteatosic effect could largely depend on its role as a modulator of the reduced glutathione liver content.

Acetaldehyde↗
PubMed1985

Early stimulation of polyamine biosynthesis during promotion by phenobarbital of diethylnitrosamine-induced rat liver carcinogenesis. The effects of variations of the S-adenosyl-L-methionine cellular pool.

A decrease of S-adenosyl-L-methionine liver content was observed between the 14th and the 35th day after the start of 2-acetylaminofluorene feeding in diethylnitrosamine-initiated rats according to the 'resistant-hepatocyte' model of hepatocarcinogenesis. The decrease was enhanced by phenobarbital given to the animals after the end of 2-acetylaminofluorene feeding. These changes were associated with an increase in ornithine decarboxylase activity and the spermidine:spermine ratio. S-adenosyl-L-methionine administration to rats caused a great fall in the percentage of gamma-glutamyltranspeptidase-positive liver as well as in polyamine synthesis. An increase in ornithine decarboxylase activity, associated with a decrease in the liver S-adenosyl-L-methionine pool, also occurred in normal animals on the first day following a partial hepatectomy and was enhanced by phenobarbital. The association of 2-acetylaminofluorene feeding with partial hepatectomy resulted in a slower liver regeneration, while the decrease in S-adenosyl-L-methionine level and the increase in polyamine synthesis were observed over a longer period of time after partial hepatectomy. These changes were further prolonged in diethylnitrosamine-initiated rats in which gamma-glutamyltranspeptidase-positive foci developed. In these animals a high level of polyamine synthesis was still present when liver regeneration was complete. At this stage of the observation period the labeling index was very low in surrounding liver, but still high in the gamma-glutamyltranspeptidase-positive areas. Phenobarbital stimulated polyamine synthesis and cell growth and further prolonged the period of time during which a high ornithine decarboxylase activity and labeling index were present. These results indicate that the liver lipotrope content could be a rate-limiting factor for cell growth and liver neoplasia promotion and this could depend on the modulation of polyamine biosynthesis.

2-Acetylaminofluorene↗
PubMed1984

Modulatory mechanisms of chemical carcinogenesis: the role of the NADPH pool in the benzo(a)pyrene activation.

Human lymphocytes and human skin fibroblasts isolated in vitro from subjects carrying the Mediterranean variant of glucose-6-phosphate dehydrogenase (G6PD) exhibit an 86-87% decrease of this enzymatic activity. This is coupled with 51% and 61% decreases of the NADPH/NADP+ ratio in the G6PD-deficient human lymphocytes (HL) and human skin fibroblasts (HSF), respectively. There also occurs a 63-67% decrease of the hexose monophosphate shunt (HMS) in the deficient cells. Incubation with 0.1 mM methylene blue stimulates the HMS of normal HL 15-fold and that of deficient lymphocytes only 2.4-fold. These figures are, respectively, 7 and 2.2 in the case of HSF. This behavior of G6PD-deficient HL and HSF is coupled with an increase of the resistance to the cell death induced by benzo(a)pyrene (BP). This effect is mimicked by the incubation of normal HSF with dehydroepiandrosterone (DEA) which strongly inhibits G6PD. In contrast, no differences between normal and deficient HSF occur as a result of the effect of methylnitrosourea (MNU), a carcinogen that does not need metabolic activation. The NADPH-cytochrome c (P450) reductase of G6PD-deficient HL and HSF homogenates becomes lower than that of controls when endogenous G6PD and exogenous glucose 6-phosphate (G6P) and NADP+ are used as a hydrogen donor system in place of NADPH. Normal and G6PD-deficient HL, having comparable BP-hydroxylating activities, in the presence of exogenous G6P, NADP+, and G6PD, were studied to determine the effect of the absence of exogenous G6PD in the reaction system.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzo(a)pyrene↗
PubMed1984

Modulatory effect of glucose-6-phosphate dehydrogenase deficiency on benzo(a)pyrene toxicity and transforming activity for in vitro-cultured human skin fibroblasts.

Human skin fibroblasts isolated in vitro from subjects carrying the Mediterranean variant of glucose-6-phosphate dehydrogenase exhibit an 85% decrease of this enzymatic activity. There is a 26% and a 94% decrease of the hexose monophosphate shunt and of the reduced nicotinamide adenine dinucleotide phosphate/nicotinamide adenine dinucleotide phosphate ratio, respectively. Incubation with 0.1 mM methylene blue activates the hexose monophosphate shunt 7 times that of normal fibroblasts and only 2.2 times that of glucose 6-phosphate-deficient cells. This behavior is coupled with an increase of the resistance to cell death induced by benzo(a)pyrene, a carcinogen, the activation of which proceeds through a reduced nicotinamide adenine dinucleotide phosphate-dependent arene oxide formation. In contrast, no difference between the normal and the deficient fibroblasts exists as regards the toxic effect of methylnitrosourea, a carcinogen that does not need metabolic activation. A growth-retarding effect of benzo(a)pyrene was observed in both normal and deficient cells during 9 days in vitro. This effect is lower in the fibroblasts carrying the Mediterranean glucose-6-phosphate dehydrogenase variant. Glucose-6-phosphate dehydrogenase deficiency protects human fibroblasts against the benzo(a)pyrene-induced in vitro transformation. This effect is mimicked by the incubation of normal fibroblasts with dehydroepiandrosterone, a strong inhibitor of glucose-6-phosphate dehydrogenase. The deficiency of this enzymatic activity, either genetically transmitted or induced by dehydroepiandrosterone, is coupled with a reduced rate of benzo(a)pyrene conversion to water-soluble metabolites by human skin fibroblasts.

Benzo(a)pyrene↗
PubMed1983

The subcellular distribution and properties of aldehyde dehydrogenase of hepatoma AH-130.

Aldehyde dehydrogenase subcellular distribution and activity were studied in the Yoshida hepatoma AH-130 and rat liver. NAD+- and NADP+-dependent dehydrogenase activities were lower in all hepatoma subfractions (except the cytosol) than in liver subfractions. In the presence of 0.025 mM substrate 78-80% of the liver NAD+- or NADP+-dependent aldehyde dehydrogenase was found in the mitochondria. With 10 mM substrate the enzyme activity was primarily in the mitochondria and microsomes. In the hepatoma a sharp increase of the soluble aldehyde dehydrogenase (either NAD+- or NADP+ dependent) was observed at all substrate concentrations. The Km of the different isoenzymes (either identified by their localization or coenzyme dependency) were of the same order for liver and hepatoma. However, a high Km enzyme was present in liver mitochondria outer membranes but not in hepatoma. Hepatoma acetaldehyde dehydrogenase was inhibited, as was the liver enzyme, by diethyldithiocarbamate. The return of activity was slower for the hepatoma and neonatal liver than for the adult liver enzyme.

Acetaldehyde↗
PubMed1982

Effect of glucose-6-phosphate dehydrogenase deficiency on the benz(a)pyrene toxicity for in vitro cultured human skin fibroblasts.

Human skin fibroblasts, isolated in vitro, from donors carrying the Mediterranean variant of glucose-6-phosphate dehydrogenase, exhibit a sharp decrease of hexose monophosphate shunt and NADPH/NADP+ ratio when compared to the fibroblasts from normal donors. This behavior is coupled to an increase of the resistance to cell death and growth inhibition induced by benz(a)pyrene, whose activation proceeds through the NADPH-dependent arene oxide formation. No differences were observed in the toxic effects of methylnitrosourea, a carcinogen that does not need metabolic activation, on normal and variant fibroblasts.

Benzo(a)pyrene↗
PubMedDate not supplied

Changing the way we change.

More and more companies struggle with growing competition by introducing improvements into every aspect of performance. But the treadmill keeps moving faster, the companies keep working harder, and results improve slowly or not at all. The problem here is not the improvement programs. The problem is that the whole burden of change typically rests on so few people. Companies achieve real agility only when every function and process--when every person--is able and eager to rise to every challenge. This type and degree of fundamental change, commonly called revitalization or transformation, is what many companies seek but rarely achieve because they have never before identified the factors that produce sustained transformational change. The authors identify three interventions that will restore companies to vital agility and then keep them in good health: incorporating employees fully into the principal business challenges facing the company, leading the organization in a different way in order to sharpen and maintain incorporation and constructive stress, and instilling mental disciplines that will make people behave differently and then help them sustain their new behavior. The authors discovered these basic sources of revitalization by tracking the change efforts of Sears, Roebuck & Company, Royal Dutch Shell, and the United States Army. The organizations used these interventions to alter the way their people experienced their own power and identity, as well as the way they dealt with conflict and learning. As at Sears, Shell, and the U.S. Army, any major shift in those four elements will create a landmark shift in any organization's operating state or culture.

Commerce↗