Biomedical subjects

B Lombardi

Publications and source records attributed to B Lombardi.

At least 19 recordsLinked to original sources

PubMed1997

Hot-spot mutations in the p53 gene of liver nodules induced in rats fed DL-ethionine with a methyl-deficient diet.

Male F-344 rats were fed for 15 weeks a methyl-deficient L-amino acid defined diet containing 0.05% DL-ethionine. Nodules protruding from the surface of the liver were dissected free of surrounding tissue, and polyadenylated RNA isolated from the nodules was reverse transcribed. The region of the p53 gene comprising codons 120-290 was amplified by the polymerase chain reaction, and cDNAs were sequenced. Mutations were detected in nodules obtained from 7 of 12 rats. In all seven cases, the same two point mutations were present. The first was at the first base of codon 246 and consisted of a C-->T transition (C:G-->T:A, Arg-->Cys), while the second was at the second base of codon 247 and consisted of a G-->T transversion (G:C-->T:A, Arg-->Leu). It is concluded that the hepatocarcinogen ethionine induces specific hot-spot p53 gene mutations; this is in contrast to the mutations at various sites previously observed to occur in rats fed a hepatocarcinogenic methyl-deficient diet alone. The results also provide the first evidence that ethionine is mutagenic in the rat.

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PubMed1994

On the role of compensatory mitogenesis in the hepatocarcinogenicity of choline and multiple-lipotrope devoid diets.

Female F-344 rats, in contrast to male rats of the same strain, are largely resistant to the hepatonecrogenic and hepatocarcinogenic actions of a diet devoid of choline and restricted in methionine (CD diet). A study was performed to determine whether the resistance would be overcome by feeding a diet devoid not only of choline, but also of methionine, vitamin B12 and folic acid (MGD diet). Three experiments were performed, to compare the degrees of steatosis and cell death and proliferation, and the onset of pre-neoplastic and neoplastic lesions, in the liver of female F-344 rats fed either the CD or the MGD diet. Limited responses were again observed in rats fed the CD diet. On the other hand, feeding the MGD diet resulted in degrees of steatosis and of compensatory mitogenesis comparable to those previously found to occur in male F-344 rats fed the CD diet. It resulted also in the development of a marked cirrhosis, of neoplastic nodules and of hepatocellular carcinomas. The results indicate that in female F-344 rats overall availability of methyl groups may be more critical than the dietary supply of choline in determining the severity and spectrum of hepatopathology. They emphasize also the importance of compensatory mitogenesis in the induction of neoplastic lesions by methyl-group deficient or devoid diets.

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PubMed1994

Association of increased fibrin turnover and defective fibrinolytic capacity with leg atherosclerosis. The PLAT Group.

Patients with peripheral arterial disease have a high risk of death from cardiovascular events. As defective fibrinolysis associated with leg atherosclerosis has been suggested as a predisposing factor, we sought a relation among decreased fibrinolysis, the presence of leg atherosclerosis and the incidence of thrombotic events in a case-control study nested in the PLAT. Fifty-eight patients with coronary and/or cerebral atherothrombotic disease, free of leg atherosclerosis at Doppler examination, were compared with 50 atherosclerotic patients with leg involvement. High D-dimer (153.0 vs 81.3 ng/ml, p < 0.001) and tPA antigen before venous stasis (14.4 vs 11.8 ng/ml, p < 0.03), and low tPA antigen (6.7 vs 15.6 ng/ml, p < 0.01) and fibrinolytic activity released after venous stasis (fibrinolytic capacity: 113.2 vs 281.4 mm2, p < 0.001) were found in patients with leg atherosclerosis. D-dimer and fibrinolytic capacity, in addition to age, were selected by stepwise discriminant analysis as characterizing patients with leg atherosclerosis. Moreover, higher D-dimer and tPA inhibitor characterized patients with leg atherosclerosis who subsequently experienced thrombotic events. These findings constitute evidence of high fibrin turnover and impaired fibrinolytic potential in patients with leg atherosclerosis. Thus impaired fibrinolysis may contribute to the prothrombotic state in these patients.

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PubMed1993

Lack of mutations of the p53 tumor suppressor gene in hepatocellular carcinomas induced in rats by a peroxisome proliferator.

Immunohistochemical, immunoblotting, and DNA-sequencing analyses were performed on hepatocellular carcinomas induced in rats chronically fed BR931, a peroxisome proliferator, to determine whether the tumors carried mutations or other alterations of the p53 gene. None were detected. Inactivation of this tumor suppressor gene does not appear, therefore, to be involved in the carcinogenicity of BR931, a nongenotoxic chemical hepatocarcinogen.

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PubMed1993

Low frequency of retinoblastoma gene alterations in rat hepatocellular carcinomas.

Abnormalities of the retinoblastoma (Rb) gene have been reported in some human cancers, including hepatocellular carcinomas (HCCs). We examined by Southern blotting the status of the Rb gene in HCCs induced in rats in four experimental models. A low frequency of Rb gene alterations, detected as novel hybridizing bands unique to each tumor, was observed. Expression of the Rb protein product was examined in the HCCs and in seven established rat hepatoma cell lines studied. It appears, therefore, that alterations in the structure or expression of the Rb gene do occur but probably do not contribute in a major way to hepatocarcinogenesis in the rat.

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PubMed1993

p53 mutations in hepatocellular carcinomas induced by a choline-devoid diet in male Fischer 344 rats.

Analyses were performed on livers and hepatocellular carcinomas from male Fischer 344 rats fed a choline-devoid diet, to assess whether they carried alterations of the p53 tumor suppressor gene. The analyses consisted of immunoperoxidase staining of tissue sections with monoclonal antibodies to p53, Western blotting and cDNA sequencing. Immunostaining revealed the presence of mutant p53 proteins in 22/27 tumors analyzed and immunoblotting in 18/20. Immunochemical evidence was obtained that occurrence of the mutations precedes tumor development. cDNA sequencing was performed on 11 hepatocellular carcinomas that expressed mutant p53 gene proteins. Seven were found to contain point mutations within the 120-290 codon region of the gene, and one a microdeletion in the same region. No mutational hot spot was observed. It is concluded that mutations within the p53 gene, along with a c-myc gene amplification previously detected in these tumors, most likely contribute to the neoplastic transformation of liver cells in this nutritional model of hepatocarcinogenesis. The results are discussed also in view of recent literature on the presence of p53 mutations in human hepatocellular carcinomas.

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PubMed1993

Increased fibrin turnover and high PAI-1 activity as predictors of ischemic events in atherosclerotic patients. A case-control study. The PLAT Group.

A case-control comparison within the framework of the prospective, multidisciplinary PLAT Study was performed to assess whether altered baseline fibrinolytic variables were associated with an elevated risk of ischemic thrombotic events in patients with documented coronary, cerebral, and/or peripheral atherosclerotic disease. Fibrinogen, D-dimer, tissue plasminogen activator (t-PA) antigen, and fibrinolytic activity before and after venous stasis (delta = difference between the two values), t-PA inhibitor, and lipid levels in 60 atherosclerotic patients with a thrombotic event during the first year of follow-up were compared with those in 94 atherosclerotic patients without such events, who were matched for age, sex, and diagnosis at enrollment. Events were associated with a higher release of delta t-PA antigen (P = .047), higher D-dimer (P = .024), and higher t-PA inhibitor (P = .001) levels. delta Fibrinolytic activity was correlated inversely with t-PA inhibitor (P < .01) and triglycerides (P < .05). D-Dimer was also correlated with systolic blood pressure (P < .01). Atherosclerotic patients at higher risk of thrombotic ischemic events are characterized by increased fibrin turnover and impaired fibrinolytic activity due to high t-PA inhibitor levels. This hemostatic disequilibrium may participate with conventional risk factors such as elevated triglyceride levels and systolic blood pressure in the multifactorial mechanism of ischemic sequelae in patients with preexisting vascular atherothrombotic disease.

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PubMed1992

The PLAT Study: hemostatic function in relation to atherothrombotic ischemic events in vascular disease patients. Principal results. PLAT Study Group. Progetto Lombardo Atero-Trombosi (PLAT) Study Group.

The Progetto Lombardo Atero-Trombosi (PLAT) Study was a prospective, multicenter, multidisciplinary study of the association among hemostatic variables, conventional risk factors, and atherothrombotic events in four groups of patients with preexisting vascular ischemic disease (335 myocardial infarction survivors, 123 patients with stable angina pectoris, 160 with transient ischemic attacks, and 335 with peripheral vascular disease). In the myocardial infarction group, univariate analysis showed that atherothrombotic events were associated with high fibrinogen (p = 0.001), factor VIII:C (p less than 0.001), and von Willebrand factor antigen (vWF:Ag) (p = 0.004) levels and with low high density lipoprotein cholesterol (p = 0.043), factor VII (p = 0.019), and protein C (p = 0.044) levels; multivariate analysis produced associations with high fibrinogen and factor VIII:C levels and low protein C levels. By both univariate and multivariate analysis, events in the angina pectoris group were associated with high vWF:Ag (p = 0.026) and leukocyte (p = 0.033) levels and the presence of carotid arterial stenosis (p = 0.063); associations with high leukocyte (p = 0.037) and factor VIII:C (p = 0.186) levels, family history (p = 0.031), and diabetes (p = 0.061) were also found in the group with transient ischemic attacks. In those with peripheral vascular disease, events were associated with Fontaine stage greater than or equal to IIB (p = 0.024), high factor VIII:C levels (p = 0.073), and low protein C (p = 0.028), fibrinogen (p = 0.030), antithrombin III (p = 0.054), and factor VII (p = 0.057) levels by univariate analysis and with Fontaine stage and low fibrinogen levels by multivariate analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1991

Nutritional model of hepatocarcinogenesis. Rats fed choline-devoid diet.

Rats fed a choline-devoid diet as the sole treatment develop hepatocellular carcinomas, the pathogenesis of which appears to reside exclusively in effects of the diet on the liver. Among the latter, most prominent is the induction of repeating cycles of liver cell injury, death, and regeneration. Two other models have been described recently in the literature, in which development of hepatic neoplastic lesions occurs after protracted periods of liver cell injury, death, and regeneration, without exposure of the animals to chemical carcinogens. The possibility is considered that an abnormal increase in cell turnover may result in all of the genomic alterations that are required for initiation, promotion, and neoplastic transformation of liver cells in these models of hepatocarcinogenesis. The possible involvement, in the same models, of endogenously initiated liver cells also is discussed briefly.

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PubMed1991

The PLAT Study: a multidisciplinary study of hemostatic function and conventional risk factors in vascular disease patients.

In this paper are reported the basal results of a multidisciplinary, multicenter study designed to explore in a population with ischemic disease the relation between hemostatic variables, conventional risk factors and atherothrombotic sequelae. 953 patients less than or equal to 69 yrs with documented coronary, cerebral or peripheral atherosclerotic disease were studied and followed-up for 24 months. Examinations included hemostatic and lipid laboratory assays, arterial Doppler examination, cerebral computerized tomography and nuclear magnetic resonance, exercise electrocardiogram and coronary angiography. Fibrinogen (301.4 +/- 71.52 mg/dl) correlated positively with antithrombin III (r = 0.27) and leukocytes (r = 0.25), negatively with HDL-cholesterol (r = 0.18) and tended to increase with smoking. Heavy smokers had higher leukocyte counts than non-smokers (8.0 +/- 2.0 vs. 7.2 +/- 2.1 x 10(3)/microliters), higher triglycerides (1.87 +/- 1.12 vs. 1.53 +/- 1.35 mmol/l) and lower HDL-cholesterol (0.93 +/- 0.27 vs. 1.00 +/- 0.25 mmol/l). FVII correlated positively with triglycerides (r = 0.16) and protein C (r = 0.45). vWF:Ag (145.4 +/- 70.58%) ad FVII:C (139.7 +/- 59.10%) were positively correlated (r = 0.44). FVIII:C correlated positively with fibrinogen (r = 0.21). Myocardial infarction survivors with associated cerebral and peripheral vascular lesions had higher FVIII:C, FVII, fibronogen and vWF:Ag. These findings suggest that hemostatic factors may enhance and/or mediate the effects of conventional risk factors in atherothrombotic ischemic events.

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PubMed1991

Expression of p53 mutant protein(s) in diethylnitrosamine-induced foci of enzyme-altered hepatocytes in male Fischer-344 rats.

Several types of human and animal tumors have been shown to carry mutations in the p53 gene. While the translation product of the wild type gene has tumor suppressor properties, mutant alleles of the gene produce proteins that can cooperate with other oncogene products in transforming cells. In this paper, evidence is presented indicating that a p53 gene mutation(s) occurs in foci of enzyme-altered hepatocytes induced by diethylnitrosamine in male Fisher-344 rats. The evidence was obtained by means of immunohistochemical and immunoblotting techniques, using antibodies directed against mutant forms of the p53 protein.

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PubMed1991

Resistance of female Fischer-344 rats to the hepatonecrogenic and hepatocarcinogenic actions of a choline-devoid diet.

A series of experiments was performed to investigate the response of female Fischer-344 rats to a choline-devoid (CD) diet. In contrast to findings previously made in male Fischer-344 rats, hepatocellular carcinomas did not develop in females chronically fed the diet. Their liver actually showed only minimal histopathological changes. For these reasons, the steatogenic and hepatonecrogenic actions of a CD diet were compared in male and female Fischer-344 rats. Young adult females were found to be largely resistant to both. The results were taken as further evidence of the primary and essential role played by an enhanced cell turnover in the pathogenesis of the carcinomas induced in male Fischer-344 rats by this non-chemical, nutritional model of hepatocarcinogenesis. A high incidence of preneoplastic and benign lesions developed in breast, pancreas or stomach of females chronically fed the CD diet. However, a similar spectrum and high incidence of lesions was observed in control rats fed a choline-supplemented diet. These findings were attributed to an enhanced occurrence of spontaneous lesions, most likely due to the high fat content (15%) of the two diets used.

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PubMed1991

Preneoplastic and neoplastic lesions in the pancreas of rats fed choline-devoid or choline-supplemented diets.

Groups of male Fischer 344 rats were chronically fed semipurified choline-devoid or choline-supplemented diets, high in fat (15%), and containing or not containing 0.06% phenobarbital. Atypical acinar cell nodules were observed in the pancreas of the rats, irrespective of the diet fed, with incidences varying from 38% to 100% in the various groups. No consistent differential effects of the dietary treatments on the incidence and growth of the nodules were evident, even though the diameter of the nodules tended to be greater in some of the groups fed the basal choline-devoid diet. The vast majority of the nodules were of the acidophilic type. More advanced pancreatic acinar cell lesions were observed in a few of the rats. Since the rats were not exposed to a chemical carcinogen(s), development of the nodules and of the more advanced lesions, even in rats fed the control diets, was most likely due to evolution of endogenous (spontaneous) initiated pancreatic cells, promoted primarily by the feeding of semipurified diets with a high fat content.

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PubMed1990

Persistent reduction of indigenous DNA modification (I-compound) levels in liver DNA from male Fischer rats fed choline-devoid diet and in DNA of resulting neoplasms.

Reduced levels of putative indigenous DNA modifications (I-compounds) in liver DNA of male Fischer 344 rats fed a hepatocarcinogenic choline-devoid (CD) diet for up to 7 mo have been previously reported. To investigate the persistence of this effect and possible relationships between I-compounds and hepatocarcinogenesis, liver DNA modifications of tumor-free male rats fed a CD diet for 3, 6, 9, or 12 mo, followed by a choline-supplemented (CS) diet to 16 mo, were compared with those in rats fed exclusively the CD or CS diet for 16 mo by a 32P-postlabeling assay. In addition, DNA from nontumorous and tumorous tissues of rats fed the CD diet similarly for 12 or 16 mo was analyzed. It was found that total I-compound levels in male rats consecutively fed CD and CS diets for various lengths of time were similar to those in rats fed the CD diet only and significantly lower than those in rats fed the CS diet only. I-compound levels of nontumorous regions from tumor-bearing livers were 73% of those in tumor-free livers from the same treatment group. I-compound levels were further reduced, some to undetectable levels, in tumor tissues and exhibited an inverse relationship with tumor incidence. The patterns and levels of I-compounds in liver DNA of CD diet-fed female rats, which were not susceptible to CD diet-induced hepatocarcinogenesis, on the other hand, were not significantly different from those of controls. Thus, reduction of I-compound levels by feeding a CD diet lasted for many months after changing from the CD to the CS diet. Whether this persistent DNA alteration contributes to carcinogenesis remains to be determined.

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PubMed1990

Conjugated diene and trans fatty acids in a choline-devoid diet hepatocarcinogenic in the rat.

It has been postulated that the hepatocarcinogenicity of a choline-devoid diet in rats stems from peroxidation of liver lipids. We have investigated whether the diet contains conjugated dienes that could account directly for those detected in liver lipids of rats fed a choline-devoid diet. Analyses were performed on samples of corn oil and of a partially hydrogenated fat used to prepare semipurified choline-devoid and choline-supplemented diets, and on fat extracted from two pairs of diets, one set containing 5% corn oil and 10% partially hydrogenated fat, and the other only corn oil (15%). The analyses consisted of quantitation of conjugated dienes by UV spectrophotometry, separation of fatty acids with conjugated dienes by HPLC, and quantitation of trans fatty acids by IR spectrophotometry. Small levels of conjugated diene and trans fatty acids were present in the corn oil, but much higher amounts were found in the partially hydrogenated fat. HPLC analysis yielded distinct elution profiles for the fatty acids with conjugated dienes present in the two fats, and similar results were obtained with fat extracted from the diets. However, no differences were observed between choline-devoid and control choline-supplemented diets. The results indicate that caution must be exercised in interpreting data from UV analysis of tissue lipids of rats fed diets containing a partially hydrogenated fat.

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PubMed1990

Conjugated diene and trans fatty acids in tissue lipids of rats fed an hepatocarcinogenic choline-devoid diet.

Groups of male Fischer-344 rats were fed two pairs of semi-purified choline-devoid and choline-supplemented diets, one set containing 5% corn oil and 10% partially hydrogenated fat, and the other only corn oil (15%). Analyses were performed on lipids extracted from whole liver, liver nuclei and adipose tissue of the rats. The analyses consisted of quantitation of conjugated dienes by UV spectrophotometry, separation of fatty acids with conjugated dienes by HPLC and quantitation of trans fatty acids by IR spectrophotometry. Conjugated dienes and conjugated diene and trans fatty acids were observed in adipose tissue total lipids, at concentrations that reflected those in the diets fed. The same was true of trans fatty acids in liver lipids. However, no conjugated dienes, or fatty acids with conjugated dienes, were detected in liver lipids of rats fed the diets formulated with only corn oil. In contrast, conjugated dienes were detected in total and neutral lipids, but not in phospholipids, of whole liver and liver nuclei of rats fed the diets formulated with partially hydrogenated fat. The neutral lipids contained fatty acids with conjugated dienes that eluted with the retention time of conjugated diene fatty acids, present in the dietary partially hydrogenated fat. It is concluded that a choline-devoid diet, which is hepatocarcinogenic in the rat, does not induce a peroxidation of liver cell membrane lipids, and that not only trans fatty acids, but also fatty acids with conjugated dienes present in a partially hydrogenated fat, are absorbed and assimilated in rat tissue lipids.

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PubMed1990

No enhancement by phenobarbital of the hepatocarcinogenicity of a choline-devoid diet in the rat.

An experiment was performed to test whether inclusion of phenobarbital in a choline-devoid diet would increase the hepatocarcinogenicity of the diet. Groups of 5-week old male Fischer-344 rats were fed for 7-25 months semipurified choline-devoid or choline-supplemented diets, containing or not 0.06% phenobarbital. No hepatic preneoplastic nodules or hepatocellular carcinomas developed in rats fed the plain choline-supplemented diet, while one preneoplastic nodule and one hepatocellular carcinoma developed in two rats fed the same diet containing phenobarbital. The incidence of preneoplastic nodules and of hepatocellular carcinomas was 10% and 37%, respectively, in rats fed the plain choline-devoid diet, and 17% and 30%, in rats fed the phenobarbital-containing choline-devoid diet. The results evinced no enhancement of the hepatocarcinogenicity of the choline-devoid diet by phenobarbital. Sporadic neoplastic lesions were observed in organs other than the liver of some of the animals, irrespective of the diet fed.

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PubMed1989

c-myc gene amplification during hepatocarcinogenesis by a choline-devoid diet.

Liver tumors arise in rats fed a choline-devoid diet without added carcinogens. We found amplification of the c-myc gene in 13/13 of these tumors. The amplification ranged from 2- to 70-fold and was accompanied by an increase in c-myc gene expression. Amplification of c-myc was larger in tumors of rats fed a choline-devoid diet followed by a choline-supplemented diet than in tumors from animals fed a choline-devoid diet exclusively. In the former animals, low levels of c-myc gene amplification were also detected in nontumorous regions of tumor-bearing livers. The choline-devoid diet provides an in vivo experimental model for the induction of gene amplification in the rat liver. In this setting, amplification of the c-myc gene may be an early and critical event in carcinogenesis.

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