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B Lombardi

Publications and source records attributed to B Lombardi.

At least 37 records · Page 2Linked to original sources
PubMed1989

Reduced accumulation of I-compounds in liver DNA of rats fed a choline-devoid diet.

Groups of rats were fed for 1, 4 or 7 months choline-devoid or choline-supplemented diets, that provided approximately 50% of the methionine, and 0.15% or 150% of the choline requirements of young, growing rats. Liver DNA was isolated and analyzed by the nuclease P1-enhanced version of the 32P-postlabeling assay, which detects aromatic/hydrophobic DNA adducts and I-compounds (adduct-like DNA modifications shown to accumulate in tissue of aging rats). DNA adducts and qualitative differences in the patterns of I-compounds were not observed in rats fed the two diets. However, in rats fed the choline-devoid diet there was a drastic reduction in the accumulation of I-compounds, compared with that in rats fed the control diet. These results extend previous evidence of a lack of relevant DNA adducts in the liver of rats fed the choline-devoid diet, and suggest the possibility of a role of I-compounds in the carcinogenicity of this diet.

Animals↗
PubMed1989

Free radicals and lipid peroxidation in liver of rats kept on a diet devoid of choline.

Rodents kept on a choline devoid (CD) diet up to 14 months develop hepatic lesions progressing through two broad stages. The first is characterized by severe steatosis and increase in cell turnover, the second by a gradual clearance of the deposited fat and fibrosis. Hepatocellular carcinomas eventually arise in rats fed for over 12 months, even though the animals aer not exposed to chemical carcinogens. It has been suggested that the diet may trigger generated thereby may be responsible for initiation of liver cancer and promotion. The radicals would lead to DNA damage, and the altered DNA in a proliferating liver would result in initiation of the carcinogenic process. In this communication we present evidence that the diet used in the above studies contained stable fatty acid isomers with conjugated dienes, which are absorbed and deposited in rat liver. This finding cast doubts on whether a CD diet does indeed cause a peroxidation of cellular membrane lipids. Electron spin resonance (ESR) spectroscopy was also used to investigate whether any abnormal pattern of free radicals exists in the liver of rats fed a CD diet. No significant differences were noted in ESR spectra of either transition metal-centered signals, or organic free radicals.

Animals↗
PubMed1988

Liver cell proliferation and incidence of hepatocellular carcinomas in rats fed consecutively a choline-devoid and a choline-supplemented diet.

A group-set of male Fischer 344 rats was kept on a choline-devoid (CD) diet for 3, 6, 9, 12 or 16 months. A second set was fed the same diet for 3, 6 and 9 months, followed by a control, choline-supplemented diet for 3 months. A third set was fed the CD diet for 0, 3, 6, 9 and 12 months and the control diet for the duration (16 months) of the experiment. [3H]Thymidine was injected into some of the animals to assess the extent of liver cell proliferation. In the latter animals, liver triacylglycerols were also determined as an index of the hepatonecrogenic action of a CD diet. Foci of enzyme-altered hepatocytes were detected histochemically and the presence of tumors was established histologically. Cell proliferation and triacylglycerols were both high after 3 months and declined steadily as the length of CD diet feeding increased. Upon subsequent feeding with the control diet, triacylglycerols promptly cleared from the liver, while cell proliferation remained at reduced but still relatively high levels for at least 3 months. Increasing but small numbers of foci of enzyme-altered hepatocytes were detected in some of the rats under experimentation for 6 months or longer. The incidence of hepatocellular carcinomas was 13, 27, 33 and 73% respectively in rats fed the CD diet for 3, 6, 9 or 12 months and the control diet for the duration of the experiment. On the other hand, only 26% of the rats fed exclusively the CD diet for 16 months developed carcinomas. The results were taken as evidence that: (i) liver cell proliferation persists beyond discontinuation of a CD diet; (ii) the liver contains initiated cells--capable of full evolution to cancer even in the absence of active promotion--after a relatively short 3-month exposure to a CD diet; and (iii) occurrence of a late event(s) is critical for the genesis of the tumors. Whether a CD diet is a complete carcinogen able to initiate de novo liver cells or acts merely as a promoter of the evolution of endogenous initiated cells is briefly discussed.

Animals↗
PubMed1987

32P-postlabeling analysis of liver DNA adducts in rats chronically fed a choline-devoid diet.

Liver DNA, obtained at various time intervals from rats chronically fed a choline-devoid diet, was analysed for the presence of aromatic or alkyl adducts by the 32P-postlabeling assay. Alkyl adducts were not detected. Aromatic DNA adduct lesions were revealed, but only at levels (1 adduct per 0.5-3 X 10(9) nucleotides) which are at the limits of the extremely high sensitivity of the method used, levels which remained constant throughout the period of feeding. Thus, contamination of the total environment of the animals with chemical carcinogens does not appear to be responsible for the genesis of the hepatocellular carcinomas that develop in rats chronically fed a choline-devoid diet. The diet, therefore, either acts as a complete carcinogen, or promotes the evolution to cancer of endogenous, 'spontaneously' initiated liver cells.

Animals↗
PubMed1987

alpha-Fetoprotein gene methylation and hepatocarcinogenesis in rats fed a choline-devoid diet.

We studied the alpha-fetoprotein (AFP) gene methylation of DNA from livers of rats fed choline-devoid or control choline-supplemented diets, and from hepatocellular carcinomas induced by the choline-devoid diet. Chronic choline deficiency caused a reduction in the level but not the pattern of methylation in hepatocytes. The tumors, however, had an altered methylation pattern with a marked increase in methylation at the 3' end, even those tumors that had low average DNA methylation. At the same time, there was a decrease in DNA methylation at the 5' end. The tumor methylation pattern resembled that of the active AFP gene of fetal liver but there was no increase in the steady-state level of AFP mRNA in the tumors. The 3' demethylated region is characteristic of the inactive adult liver AFP gene, but it disappears in the final stages of neoplastic transformation of hepatocytes. The methylation changes are not sufficient to activate the gene.

Animals↗
PubMed1987

Liver cell turnover in rats fed a choline-devoid diet.

Liver DNA was labeled in a group of weanling Fischer-344 male rats by placing mini-osmotic pumps, loaded with [methyl-3H]thymidine, under the dorsal skin for 14 days. The animals were then placed on either a choline-supplemented or a choline-devoid diet, and subgroups on each diet were killed after 1, 2, 4, 8 and 16 weeks. Liver DNA total and specific radioactivities were determined in all rats. The results were used to estimate the half-life (t1/2) of liver cells, and the fractional rates of liver cell death (Kd) and proliferation (Kp). In rats fed the control choline-supplemented diet, liver cells were estimated to die at an overall Kd of 0.16% per day, and to have a t1/2 of 439.5 days; Kp was higher in younger than in older rats. In rats fed the choline-devoid diet, liver cells diet at a Kd ranging from 4.82 down to 0.93% per day, as the length of the feeding period increased; corresponding t1/2S were 14.3 and 74.6 days. In these rats, Kp was more than sufficient to compensate for cell loss. The results show that liver-cell death represents a major consequence of feeding a choline-devoid diet to rats, and that the necrogenic action of the diet is a major factor responsible for the highly increased turnover of liver cells present in these animals. However, evidence was obtained that the diet has also a primary mitogenic action, beyond those related to replacement of dead cells, and to cell accretion due to normal growth of the animals and the liver.

Animals↗
PubMed1987

Analysis of ras genes and linked viral sequences in rat hepatocarcinogenesis.

After long-term feeding of a choline-devoid diet to rats, the authors analyzed rasK, rasH, and rasN transcripts and gene structure in livers and liver tumors. They controlled their analysis by studying cell lines derived from chemically induced hepatomas. Transcripts from all three genes were elevated in all tumors, but not in the livers from which they arose. The transcript elevations may represent an effect of active cell proliferation in the tumors. Clone HiHi-3, derived from the Kirsten murine sarcoma virus, detected a large number of hybridization bands, most of which were not part of the rasK-p21 gene. Most tumors had an altered band at 2.6 kb; some had other altered bands. No alterations were seen in liver DNA, and none of the cell lines showed the 2.6 kb band. At low stringency, a rasH probe, which contains a short segment of a similar viral sequence, also detected altered bands in tumors and a single treated liver. These changes in endogenous viral sequences of the rat genome appear to be characteristic of carcinogenesis by a choline-devoid diet.

Animals↗
PubMed1986

Bile ductular cells and the phenotypic heterogeneity of the population of hepatic non-parenchymal epithelial cells induced in rats by chemical carcinogens.

Single doses of diethylnitrosamine, N-hydroxy-2-acetylaminofluorene or N-methyl-N-nitrosourea were administered to rats, before or after obstruction of the common bile duct, and liver sections were stained for alpha-fetoprotein, albumin and glucose-6-phosphatase. In these animals, cells expressing hepatocytic traits were not observed in the resulting expanded population of non-parenchymal epithelial cells. A derivation of non-parenchymal epithelial cells with hepatocytic traits from bile ductular cells is not supported, but not completely ruled out, by these findings. In rats with an obstructed bile duct and administered a single carcinogen dose, serum alpha-fetoprotein was slightly increased, to levels comparable with those occurring after a partial hepatectomy. In these rats, and in partially hepatectomized rats, the cellular source of serum alpha-fetoprotein was not apparent, since no alpha-fetoprotein-positive cells were detected in their liver.

Albumins↗
PubMed1986

DNA methylation and hepatocarcinogenesis in rats fed a choline-devoid diet.

Groups of male Fischer-344 rats were fed either a choline-supplemented or a choline-devoid (CD) diet, for up to 14 months. In rats fed the CD diet, hepatic lesions developed and progressed through two distinct stages, the first characterized by severe steatosis and an increase in cell turnover and the second by gradual clearance of the deposited fat, fibrosis and parenchymal nodularity. Large hepatocellular carcinomas were found in rats killed at 14 months. DNA was purified from the livers of all groups of rats and from the tumors, and its level of methylation was analyzed using the restriction endonucleases HpaII and MspI. DNA undermethylation was detected only in the livers of rats fed the CD diet for 14 months, whether bearing tumors or not, and in three of four hepatocellular carcinomas. Undermethylation of liver total DNA is therefore a late effect of dietary choline deficiency in the rat.

Animals↗
PubMed1985

Stage dependent enhanced induction of hepatocellular carcinomas in rats administered a second dose of diethylnitrosamine.

An experiment was performed to investigate whether the incidence of chemical carcinogen-induced liver tumors in rats is increased by administration, during promotion, of a second dose of carcinogen. Seven groups of male Fischer-344 rats were administered a dose of diethylnitrosamine (DEN), and were placed, 1 month thereafter, on a liver-tumor promotion-regimen, consisting of a choline-devoid diet containing 0.06% phenobarbital. A second dose of the carcinogen was administered, at monthly intervals of promotion, to some of the groups of animals. The experiment was terminated after 7 months of promotion, and the incidence of hepatic tumors was determined histopathologically. In rats administered the second dose of carcinogen after 2 months of promotion, the incidence of hepatocellular carcinomas was 2-3 times greater than that in the other groups of rats. The results are consistent with the proposal, advanced by others, that development of hepatocellular carcinomas may be a multi-hit process, and indicate that, after the first induced at initiation, further genomic alteration(s) may have to occur at very discrete stage(s) in the evolution of initiated cells to tumors.

Animals↗
PubMed1985

Endogenous hepatic growth-modulating factors and effects of a choline-devoid diet and of phenobarbital on hepatocarcinogenesis in the rat.

The activities of an endogenous inhibitor and of a stimulator of cell proliferation were assayed in the livers of sham-operated (SO) or partially hepatectomized (PH) adult rats; rats fed a choline-supplemented (CS) or a choline-devoid (CD) diet; the same diets followed by acute CCl4 intoxication; the same diets supplemented with phenobarbital (PHB); or a CD diet containing DL-ethionine (ETH). The inhibitor and the stimulator were semipurified by fractional ethanol precipitation of a liver cytosolic fraction, and their activities were assessed by means of bioassays in vitro. The livers of SO rats and of rats fed the CS diet contained only inhibitor activity. Following PH, a CD diet, or CCl4 intoxication the inhibitor activity was suppressed, and there was a simultaneous appearance of a stimulator activity. Thus, PH, a CD diet, and CCl4 intoxication cause similar cellular (loss and regeneration) and humoral-homeostatic changes in adult rat livers. We propose that these changes constitute a basic attribute of the mechanism whereby the three conditions affect similarly hepatocarcinogenesis in the rat, especially in the case of a CD diet, because the changes it induces are chronic rather than acute. PHB, another promoter of chemical hepatocarcinogenesis, affected neither the inhibitor nor the stimulator activity. Thus, PHB seems to be acting by a different mechanism than that of the other three agents. ETH did not modify the shift in the balance of the growth-modulating factors induced by a plain CD diet. This shift may account for the marked stimulation of carcinogen-induced oval cell proliferation exerted by a CD diet. The significance of these results is discussed in the context of known effects of a CD diet and of PHB on hepatocarcinogenesis in rats.

Animals↗
PubMed1985

Hepatocarcinogenic and promoting action of a choline-devoid diet in the rat.

Male Fisher 344 rats were solely fed a choline-supplemented diet for 65 to 105 weeks or a choline-devoid diet for 24 to 102 weeks. Hepatocellular carcinomas developed in the latter animals, beginning at 24 weeks. Other groups of rats were given a single dose of 20 mg diethylnitrosamine/kg, 18 h after a partial hepatectomy and were fed, 4 weeks thereafter, either a choline-supplemented, or a choline-devoid diet for up to 48 weeks. In rats fed the choline-supplemented diet, the only relevant lesion observed was a small transect number of foci of enzyme-altered hepatocytes. On the other hand, a significant number of foci, of preneoplastic nodules, and of hepatocellular tumors developed in rats fed the choline-devoid diet. The results obtained are consistent with those previously reported by others, indicating that diets devoid of choline, or of choline and methionine, are carcinogenic. The diets appear to act as complete carcinogens, since they are also efficient promoters of chemical hepatocarcinogenesis, as shown again, in the present study, by the results obtained in the diethylnitrosamine-pretreated rats.

Animals↗
PubMed1983

Diffuse arachnoiditis following epidural analgesia.

Four cases of spinal arachnoiditis are reported, which occurred as a delayed complication of epidural anaesthesia. Different causes are considered: the most convincing hypothesis is that there was a subarachnoid hyperergic reaction to the drugs injected during epidural anaesthesia.

Adolescent↗
PubMed1983

Effects of dietary choline deficiency on the mutagenic activation of chemical carcinogens by rat liver fractions.

Salmonella mutagenesis assays were used to evaluate the mutagenicity of several chemical carcinogens as mediated by liver S-9 fractions from rats fed a choline-supplemented (CS) or choline-devoid (CD) diet. The liver S-9 fraction from CD diet-fed rats was found to have a significantly decreased ability to activate 2-acetylaminofluorene (2-AAF), 2-aminoanthracene (2-AA) and 6-aminochrysene (6-AC), but not N-hydroxy-2-acetylaminofluorene (HO-N-2-AAF) and dimethylnitrosamine (DMN). The same liver S-9 fraction was also less effective in deactivating N-methyl-N1-nitro-N-nitrosoguanidine (MNNG) but not methylnitrosourea (MNU). A decrease (20%) in the cytochrome P-450 content was found in liver microsomes of CD diet-fed rats. Although it has been shown that feeding a CD diet to rats enhances chemical hepatocarcinogenesis, the data presented here suggest that CD diet does not increase the activation of the chemical procarcinogens tested.

Animals↗
PubMed1983

Modulation of tumor promotion in liver carcinogenesis.

Earlier, we demonstrated that feeding to rats a diet devoid of choline, a lipotropic factor, markedly enhances hepatoma induction by several chemical carcinogens, and that the diet acts as a strong promoter of the evolution of initiated cells to foci of altered hepatocytes. The ability of several factors to modulate the action of the choline-devoid (CD) diet as a promoter was investigated by quantitating the foci of gamma-glutamyl transpeptidase-positive hepatocytes developed in rats exposed to a single injection of diethylnitrosamine. Addition to the diet of phenobarbital (PHB) resulted in a promoting action stronger than those of the CD diet or of PHB alone. Two other barbiturates, amobarbital (AMB) and pentobarbital (PTB) exerted an effect similar to that of PHB, while barbituric acid (BA) had no effect. In other studies, lowering the fat content of the CD diet reduced its efficacy as a promotor, while the addition of a hypolipidemic agent, BR931, 4-chloro-6-(2,3 xylidino)-2-pyrimidinylthio (N-beta-hydroxy-ethyl)acetamide, completely abolished the promoting action of the CD diet. In rats not exposed to carcinogen, feeding the CD diet caused a marked enhancement of liver DNA synthesis and of cell proliferation. Inclusion of PHB, PTB or AMB in the CD diet inhibited these effects, while BA exerted no inhibition. The increased rate of DNA synthesis and cell proliferation in the liver were not affected by the level of fat in the CD diet. These results suggest that beside a stimulation of liver cell proliferation, other factor(s) determine the efficacy with which a CD diet exerts its promoting action.

Animals↗
PubMed1983

Anaplastic carcinomas in nude mice and in original donor strain rats inoculated with cultured oval cells.

Male Sprague-Dawley rats were fed for 4-5 weeks a choline-devoid diet containing 0.1% DL-ethionine. Preparations of nonparenchymal epithelial cells, enriched in oval cells, were isolated from the livers of these animals and were placed in culture. Six lines of hepatic epithelial cells were thus established. The lines underwent transformation after several passages, became tumorigenic in nude mice and 3 lines also in rats of the same strain of origin of the isolated cells. The tumors were uniformly highly anaplastic carcinomas. Preliminary morphologic, cytologic, and cytochemical results were consistent with the tumoral cells being hepatocytelike cells. These findings are viewed and discussed in terms of the cellular source, in vivo, of longterm cultures of rat liver epithelial cells, and in relation to a possible role of hepatic nonparenchymal epithelial cells in the process of hepatocellular tumor induction by chemical carcinogens.

Animals↗
PubMed1982

Progression of carcinogen-induced foci of gamma-glutamyltranspeptidase-positive hepatocytes to hepatomas in rats fed a choline-deficient diet.

Following previous findings that feeding a choline-deficient (CD) diet to rat strongly promotes the evolution of liver cells, initiated by a chemical carcinogen, to foci of gamma-glutamyltranspeptidase (gamma GT)-positive hepatocytes, we investigated whether a CD diet could also promote the evolution of gamma GT-positive foci to hepatomas. gamma GT-positive foci were induced in male Sprague-Dawley rats by administration of a single dose of diethylnitrosamine followed by 2 weeks' feeding on a CD diet containing 0.02% acetylaminofluorene. Immediately thereafter, one group of rats was fed a plain CD diet and the other a choline-supplemented (CS) diet, and subgroups of animals were killed periodically for analysis of the number and size of gamma GT-positive foci and development of hepatomas. During the first 7 weeks after switching the diets, the number and size of the foci increased in both groups. At 12 and 16 weeks, the number and size of foci began to decline in rats fed the CS diet. However, in the CD group, there was a progressive increase in the size with coalescence of the foci, as well as development of neoplastic nodules. These lesions were followed at 20 and 28 weeks by development of hepatomas at a high incidence rate. In rats fed the CS diet, a few scattered gamma GT-positive foci, and small neoplastic nodules remained in the liver at 20 and 28 weeks, but no hepatomas developed. These results show that the CD diet is a potent promoter of the evolution of foci of altered hepatocytes to hepatomas, and that most of the gamma GT-positive foci are reversible lesions.

2-Acetylaminofluorene↗