RESUMO
Genetic factors, specially those related to serotoninergic activities, and childhood maltreatment have both been implicated in suicidal behaviour (SB). However, little attention has been paid to the possible interaction between genes and childhood maltreatment in the comprehension of SB. Brain-derived neurotrophic factor (BDNF) plays an important role in the growth of serotoninergic neurons during childhood and therefore is a good candidate for studies on SB. Moreover, decreased levels of BDNF have been found in the prefrontal cortex of suicide victims. In our study we wanted to see if Val66Met (a BDNF functional single-nucleotide polymorphism) could moderate the effect of childhood maltreatment on the onset, number and violence of SB in a sample of 813 Caucasian suicide attempters. Childhood maltreatment was evaluated using the Childhood Trauma Questionnaire. We used a regression framework to test the interaction between Val66Met and childhood maltreatment. Childhood sexual abuse was associated with violent suicide attempts (SA) in adulthood only among Val/Val individuals and not among Val/Met or Met/Met individuals (P = 0.05). The severity of childhood maltreatment was significantly associated with a higher number of SA and with a younger age at onset of suicide attempt. This result suggests that Val66Met modulates the effect of childhood sexual abuse on the violence of SB. It is proposed that childhood sexual abuse elicits brain structural modifications through BDNF dysfunction and enhances the risk of violent SB in adulthood.
Assuntos
Substituição de Aminoácidos , Fator Neurotrófico Derivado do Encéfalo/genética , Abuso Sexual na Infância/psicologia , Tentativa de Suicídio/psicologia , Violência/psicologia , Adulto , Criança , França , Frequência do Gene , Genótipo , Humanos , Entrevistas como Assunto , Metionina , Reação em Cadeia da Polimerase , Polimorfismo de Nucleotídeo Único , Suicídio , Suíça , ValinaRESUMO
Phase I and Phase II xenobiotic-metabolising enzyme families are involved in the metabolic activation and detoxification of various classes of environmental carcinogens. Particular genetic polymorphisms of these enzymes have been shown to influence individual cancer risk. A brief overview is presented about recent research of the relationship between metabolic genotypes and internal dose, biologically effective dose and cytogenetic effects of complex and specific genotoxic exposures of human study populations, and we report our new results from two molecular epidemiological studies. We investigated the effects of multiple interactions among CYP1A1 Ile462Val, CYP1A1 MspI, CYP1B1 Leu432Val, CYP2C9 Arg144Cys, CYP2C9 Ile359Leu, NQO1 Pro189Ser, GSTM1 gene deletion and GSTP1 Ile105Val genotypes on the levels of carcinogen-DNA adducts determined by (32)P-postlabelling and PAH-DNA immunoassay in peripheral blood lymphocytes from workers occupationally exposed to polycyclic aromatic hydrocarbons in aluminium plants, and in bronchial tissue from smoking lung patients. A statistically significant positive linear correlation was observed between white blood cell aromatic DNA adduct and urinary 1-hydroxypyrene (1-OHPY) levels from potroom workers with GSTM1 null genotype (P=0.011). Our results suggest interactions between GSTM1 and GSTP1 alleles in modulation of urinary 1-OHPY levels and white blood cell DNA adduct levels in the PAH-exposed workers. Interactions between GSTM1 and GSTP1 alleles, in association with particular genotype combinations of CYPs, were also recognised in bronchial aromatic DNA adduct levels of smoking lung patients. The impact of single metabolic genotypes and their combinations on biomarkers of exposure was usually weak, if any, in both our studies and reports of the literature. The effect of special metabolic gene interactions may be better recognised if the compared groups of individuals are stratified for multiple potential modulators of the observable biomarker end-point, and/or if chemical structure-specific biomarker methods are applied.
Assuntos
Hidrocarboneto de Aril Hidroxilases , Biomarcadores/análise , Citocromo P-450 CYP1A1/genética , Glutationa Transferase/genética , Exposição Ocupacional , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Esteroide 16-alfa-Hidroxilase , Brônquios/metabolismo , Brônquios/patologia , Citocromo P-450 CYP1B1 , Citocromo P-450 CYP2C9 , Sistema Enzimático do Citocromo P-450/genética , Adutos de DNA/sangue , Glutationa S-Transferase pi , Humanos , Hungria/epidemiologia , Isoenzimas/genética , Pulmão/cirurgia , Neoplasias Pulmonares/epidemiologia , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/cirurgia , Linfócitos/efeitos dos fármacos , Linfócitos/metabolismo , Metalurgia , Pirenos/análise , Fumar , Esteroide Hidroxilases/genéticaRESUMO
In evaluating the health state of the population one of the most reliable parameter is mortality. The development of statistical and spatial analytical methods gave a tool for evaluating mortality and morbidity in small areas. GIS mapping helps in the assessment of health state of small areas, to investigate causal relationship and create plans of intervention. Within the frames of the National Environmental Health Action Programme (NEHAP, 1996) a spatial statistical information system was elaborated. By the help of this system, mortality from cancer of the lip, oral cavity and pharynx (ICD-X.: C00-C14) was analysed for 1986-1997 and morbidity for 1997-1999 by computing standardised mortality and morbidity ratio. Regions with unfavourable mortality and morbidity were defined, statistical significance was tested. After age and gender stratification, a cluster analysis was also carried out. An international comparison of mortality was done as well. According to our data, mortality - most frequent in both sexes according to the international comparison - as well as morbidity showed a typical spatial distribution. An excess in mortality and morbidity is observable in the central part of the country, as well as in the Northern part and in traditional wine producing areas. The spatial accumulation of mortality is very similar to that of mortality from chronic liver diseases (ICD-X.: K70). In the primary prevention of oral cancer smoking cessation and the decrease of alcohol consumption is of great importance. Screening activity of GPs and dental doctors is of major importance in secondary prevention.
RESUMO
Sensitivity, specificity and correlations among several biomarkers for monitoring occupational exposure to complex mixtures of genotoxic agents were assessed in occupational environments in Hungarian study populations. The studies have been focused on DNA adduct formation, urinary metabolites, mutations and micronuclei induced by exposures to complex organic mixtures. In two Hungarian aluminium plants, increased DNA adduct and 1-hydroxypyrene (1-OH-PY) levels were observed in workers as compared to controls. However, no association between the biomarker levels was evident on an individual basis. In Hungarian garage mechanics, DNA adduct determinations did not show increased genotoxic exposure as compared to the controls. However, ambient air measurements, significantly enhanced 1-OH-PY levels, and slightly enhanced frequency of micronuclei indicated increased polycyclic aromatic hydrocarbon (PAH) exposure in the garages, as compared to the general environment. In a Hungarian vulcanizing plant, DNA adduct determinations and 1-OH-PY did not show significantly elevated exposure levels as compared to controls. The glycophorin A (GPA) somatic mutation assay was also negative for this occupational exposure. The results support previous observations of a lack of correlation between DNA adducts detectable by 32P-postlabelling and those measured by the PAH-DNA immunoassay in the same DNA sample. These studies also demonstrate a lack of close correlation between levels of DNA adducts and urinary 1-OH-PY in the same individual.
Assuntos
Dano ao DNA , Monitoramento Ambiental , Exposição Ocupacional/efeitos adversos , Poluentes Ocupacionais do Ar/análise , Alumínio , Biomarcadores/sangue , Biomarcadores/urina , Indústria Química , Adutos de DNA/sangue , Feminino , Glicoforinas/genética , Glicoforinas/metabolismo , Humanos , Imidazóis , Estudos Longitudinais , Linfócitos/efeitos dos fármacos , Masculino , Metalurgia , Testes para Micronúcleos , Exposição Ocupacional/análise , Radioisótopos de Fósforo , Pirenos/análise , Borracha , Sensibilidade e Especificidade , Emissões de Veículos/efeitos adversos , Emissões de Veículos/análiseRESUMO
Carcinogen-DNA adducts may represent an intermediate end-point in the carcinogenic cascade and may reflect exposure to chemical carcinogens, as well as susceptibility and, ultimately, cancer risk. Interindividual variability in activity of enzymes involved in the metabolism of polycyclic aromatic hydrocarbons to mutagenic diol epoxides may predict adduct levels and, indirectly, lung cancer risk. Using 32P-postlabeling methods, the levels of bulky DNA adducts were determined in macroscopically normal bronchial tissues obtained from resected lobes of 143 Hungarian patients with lung malignancy and other pulmonary conditions. DNA from normal tissue was also evaluated for polymorphisms in cytochrome P450 2C9 (CYP2C9) at two sites, codons 144 (Arg/Cys) and 359 (Ile/Leu), for glutathione S-transferase P1 (GSTP1) at codon 105 and for NAD(P)H:quinone oxidoreductase (NQO1) at codon 187 (Pro/Ser). Using the Mann-Whitney U-test and analysis of variance, levels of adducts were evaluated in relation to variant genotypes, separately for smokers and non-smokers. As previously reported, bulky DNA adduct levels in smokers (n = 104) were estimated to be 54% higher than in non-smokers (n = 39) (8.6 +/- 4.2 versus 5.6 +/- 3.3 per 10(8) nucleotides, respectively, P < 0.01). Adduct levels were 16-29% higher in individuals with the homozygous Ile359/Ile359 CYP2C9 allele than in those heterozygous for the variant allele (Ile359/Leu359) [8.8 +/- 4.3 (n = 84) versus 7.6 +/- 3.5 (n = 20) for smokers and 5.8 +/- 3.5 (n = 32) versus 4.5 +/- 1.3 (n = 7) for non-smokers], although differences were not statistically significant. There were no clear differences in adduct levels in relation to genotypes of NQO1 or GSTP1. Although numbers of patients in this study are large in relation to many studies of carcinogen-DNA adducts, it is still possible that significant differences were not noted for polymorphisms in xenobiotic metabolizing enzymes due to relatively small numbers in stratified data.
Assuntos
Hidrocarboneto de Aril Hidroxilases , Brônquios/metabolismo , Sistema Enzimático do Citocromo P-450/genética , Adutos de DNA/metabolismo , Glutationa Transferase/genética , Pneumopatias/genética , NAD(P)H Desidrogenase (Quinona)/genética , Esteroide 16-alfa-Hidroxilase , Esteroide Hidroxilases/genética , Sequência de Bases , Citocromo P-450 CYP2C9 , Primers do DNA , Humanos , Hungria , Pneumopatias/etnologiaRESUMO
Relationships between smoking status and levels of bulky DNA adducts were investigated in bronchial tissue of lung patients in relation to their GSTM1 and CYP1A1 MspI genotypes. A total of 150 Hungarian patients undergoing pulmonary surgery were included in the study, 124 with lung malignancies and 26 with non-malignant lung conditions. There were significant relationships between smoking status and bulky DNA adduct levels, as determined by 32P-post-labelling analysis, in macroscopically normal bronchial tissues. There was a highly significant difference in the adduct levels of a combined group consisting of current smokers and short-term ex-smokers (< or = 1 year abstinence) compared with life-time non-smokers and long-term ex-smokers (> 1 year abstinence) (P = 0.0001). The apparent half-life was estimated to be 1.7 years for bulky DNA adducts in the bronchial tissue from ex-smokers. There were no statistically significant correlations between (i) daily cigarette dose and DNA adduct levels in current smokers, (ii) DNA adduct level and histological type of lung cancer, or (iii) GSTM1 and CYP1A1 MspI genotypes and DNA adduct levels after adjustment for either smoking status or malignancy. By multiple logistic regression analysis, smoking and GSTM1 null genotype were found to be risk factors for squamous cell carcinoma. However, bulky DNA adduct levels in bronchial tissue did not appear to be a statistically-significant risk factor for the major histological types of lung cancer.
Assuntos
Citocromo P-450 CYP1A1/genética , Adutos de DNA , Glutationa Transferase/genética , Pneumopatias/genética , Neoplasias Pulmonares/genética , Fumar/efeitos adversos , Adulto , Idoso , Brônquios/metabolismo , Desoxirribonuclease HpaII/metabolismo , Feminino , Genótipo , Humanos , Neoplasias Pulmonares/patologia , Masculino , Pessoa de Meia-Idade , Polimorfismo GenéticoRESUMO
Aminosteroids were prepared and acylated with protected amino acids by means of the mixed anhydride or the active ester method. The tert-butyloxycarbonyl- (BOC) protecting group was eliminated by acidolysis, and the benzyloxycarbonyl- (Z) group by catalytic hydrogenation. 3 beta- and 6 beta-Glycylamidosteroids were prepared by indirect amination of chloroacetamido derivatives, formed by the Ritter reaction on the corresponding 3 alpha,5 alpha-cyclo and 5 alpha,6 alpha-epoxy steroids. Water-soluble double salts were produced from the compounds for pharmacological investigations.
Assuntos
Aminoácidos/química , Esteroides/síntese química , Androstanos/química , Pregnanos/química , Pregnatrienos/química , Solubilidade , Esteroides/químicaRESUMO
A longitudinal human biomonitoring study has been performed in two Hungarian primary aluminium production plants that operated Söderberg cells. Carcinogen-DNA adducts have been determined by 32P-postlabelling and competitive enzyme-linked immunosorbent assay in peripheral blood lymphocytes from potroom workers and occupationally unexposed control individuals. Blood samples were collected on three occasions; the first two occasions were 1 year apart during normal operation, and the last samples were taken 6 months after close-down of aluminium production. Assays of the first set of samples demonstrated no significant difference between the control group and workers in Plant I. Workers in Plant II had significantly higher DNA adduct levels than individuals in the control group and workers in Plant I. One year later a significant elevation of DNA adducts was detected in Plant I so that values approached those seen in Plant II, which remained unchanged. In the last sample set there was no difference between former potroom workers and occupationally unexposed individuals. The results suggest that carcinogen-DNA adducts are a useful biomarker for monitoring occupational genotoxic exposure to polycyclic aromatic hydrocarbons, and that the findings can contribute to improved health risk assessment.
Assuntos
Alumínio/efeitos adversos , Alumínio/análise , Adutos de DNA/análise , Leucócitos Mononucleares/efeitos dos fármacos , Exposição Ocupacional/efeitos adversos , Adulto , Monitoramento Ambiental , Ensaio de Imunoadsorção Enzimática , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Testes de Mutagenicidade , Radioisótopos de Fósforo , Compostos Policíclicos , Fatores de TempoRESUMO
O6-Alkylguanine-DNA alkyltransferase (AGAT) activity was determined in macroscopically normal peripheral lung tissues from 122 patients undergoing lung surgery. AGAT activity of smokers was 1.4-fold higher than that of lifetime non-smokers (P = 0.030). Less than one year of abstinence from smoking did not cause a significant decrease in AGAT activity in former smokers, however, longer abstinence resulted in a decrease in AGAT activity to the level detected in lifetime non-smokers. There was no significant difference between levels of AGAT activity in lung cancer and noncancer patients. The results demonstrate that the level of AGAT activity in human peripheral lung tissue is influenced by smoking habits but does not have a diagnostic correlation to lung cancer.
Assuntos
Pulmão/enzimologia , Metiltransferases/metabolismo , Fumar/metabolismo , Adulto , Idoso , Feminino , Humanos , Neoplasias Pulmonares/enzimologia , Masculino , Pessoa de Meia-Idade , O(6)-Metilguanina-DNA MetiltransferaseRESUMO
Testosterone trans-4-n-butylcyclohexyl carboxylate releases continuous physiological levels of testosterone into the circulation of men or monkeys over a period of 8 to 10 weeks from an intramuscular depot and may, therefore, be an agent of choice for androgen replacement therapy. The purpose of this study was to investigate the metabolism of the ester and its side chain. The ester was hydrolysed by blood sera of guinea-pig, rabbit and rat, but not horse or man. It was slowly hydrolysed by rat and cynomolgus liver and the testosterone metabolites androstenedione and androstanediol were formed. Bucyclic acid (trans-4-n-butylcyclohexyl carboxylate) was slowly metabolized to two metabolites, M1 and M2, by cynomolgus liver homogenates. The acid metabolites were analysed by chromatography and mass spectrometry after reaction with diazomethylpyrene to form fluorescent pyrenyl esters. When compared with synthetic compounds using the criteria of chromatographic mobility and mass spectral analysis, the polar metabolite was identified as hydroxy-4-n-butylcyclohexyl carboxylate. The less polar metabolite could not be definitively identified.
Assuntos
Fígado/metabolismo , Testosterona/análogos & derivados , Animais , Esterases/metabolismo , Feminino , Cobaias , Cavalos , Humanos , Hidrólise , Técnicas In Vitro , Macaca fascicularis , Masculino , Espectrometria de Massas , Coelhos , Ratos , Testosterona/metabolismo , Fatores de TempoRESUMO
A competitive enzyme-linked immunosorbent assay (ELISA), the most frequently used immunoassay for the determination of polycyclic aromatic hydrocarbon-DNA adducts in human tissues, has been modified to achieve approximately a 6-fold increase in sensitivity. The new assay, a competitive dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) has utilized the same rabbit antiserum as the ELISA, antiserum elicited against DNA modified with benzo[a]pyrene. However, the alkaline phosphatase conjugate has been replaced with a biotin-europium-labeled streptavidin signal amplification system, and the release of europium into the solution forms a highly fluorescent chelate complex that is measured by time-resolved fluorometry. The DELFIA has achieved a 5- to 6-fold increase in sensitivity for measurement of DNA samples modified in vitro with benzo[a]pyrene, for cultured cells exposed to radiolabeled benzo[a]pyrene, and for human samples from occupationally exposed workers. The assay has been validated by comparison of adduct levels determined by DELFIA, ELISA, and radioactivity in DNA from mouse keratinocytes exposed to radiolabeled benzo[a]pyrene. Human lymphocyte DNA samples from 104 Hungarian aluminum plant workers were assayed by ELISA and compared to blood cell DNA samples from 69 Italian coke oven workers assayed by DELFIA. The standard curves demonstrated that the limit of detection of 4.0 adducts in 10(8) nucleotides for polycyclic aromatic hydrocarbon-DNA adducts by ELISA, using 35 micrograms of DNA/microtiter plate well, has been decreased to 1.3 adducts in 10(8) nucleotides by DELFIA, using 20 micrograms of DNA/microtiter well. If 35 micrograms of DNA were used in the DELFIA, the calculated detection limit would be 0.7 adducts in 10(8) nucleotides.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
DNA/análise , Fluorimunoensaio/métodos , Compostos Policíclicos/análise , Alumínio , Proteínas de Bactérias , Benzo(a)pireno , Indústria Química , Coque , Desoxiguanosina/análise , Ensaio de Imunoadsorção Enzimática , Európio , Fluorescência , Fluorometria , Humanos , Hungria , Itália , Linfócitos/metabolismo , Metais Terras Raras , EstreptavidinaRESUMO
The acidic dehydration of 17 alpha-ethynyl-17 beta-hydroxysteroids (1-3) was investigated. On reaction with thionyl chloride, phosphorus oxychloride, and formic acid, the desired dehydration was accompanied by chlorination, Wagner-Meerwein rearrangement, and D-homoaromatic rearrangement. The structure of the product from the transformation of 17 beta-hydroxypregn-20-yne derivative (3) on reaction with formic acid was misjudged. It was regarded as a pregn-16-en-20-yne (10) instead of the actually rearranged D-homoaromatic compound (11). As a consequence, physical data corresponding to this latter structure have been cited in the literature as those of pregn-16-en-20-yne derivative (10). This confusion prompted us to prepare compounds of both types (4, 9, 10, and 11), the characterization of which is here described.
Assuntos
Etisterona/química , Mestranol/química , Noretindrona/química , Compostos de Fósforo , Água/química , Formiatos/química , Indicadores e Reagentes , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Fósforo/química , Óxidos de Enxofre/químicaRESUMO
We describe the chemical synthesis of the 2 beta-propionate-17 beta- hemisuccinate and 2 beta-hemisuccinate-17 beta-propionate diesters of anordiol (2 alpha,17 alpha-diethynyl-A-nor-5 alpha-androstane-2 beta,17 beta-diol) and the method for coupling them to bovine serum albumin and Affi-gel 102, in order to prepare antibodies for radioimmunoassay of anordrin. In addition, we describe the chemical synthesis of the following derivatives: 2 beta-ol-17 beta-propionate, 2 beta-propionate-17 beta-ol, 2 beta-hemisuccinate-17 beta-ol, and 2 beta-ol-17 beta-hemisuccinate.
Assuntos
Anticoncepcionais Pós-Coito/análise , Anticoncepcionais Pós-Coito/química , Norandrostanos/análise , Norandrostanos/química , Radioimunoensaio/métodos , Anticorpos , Anticoncepcionais Pós-Coito/imunologia , Esterificação , Ésteres , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Norandrostanos/imunologiaRESUMO
32P-Postlabeling analysis and enzyme-linked immunosorbent assay (ELISA) have been used to detect DNA adducts in peripheral blood lymphocytes from primary aluminum production plant workers who were exposed occupationally to a mixture of polycyclic aromatic hydrocarbons (PAHs). Preliminary results reported here are from a comparative study being performed in two aluminum plants. The levels of aromatic DNA adducts have been determined by the 32P-postlabeling assay in samples collected on two occasions, 1 year apart. PAH-DNA adduct levels have also been determined by competitive ELISA in the second set of DNA samples. The results show the necessity of follow-up biomonitoring studies to detect possible alterations in biological effect induced by changing exposures. The comparison of the results obtained by 32P-postlabeling and ELISA may lead to a better understanding of the power and weaknesses of the two methods applied in these studies.
Assuntos
Alumínio , DNA/sangue , DNA/efeitos dos fármacos , Exposição Ocupacional , Compostos Policíclicos/efeitos adversos , Monitoramento Ambiental/métodos , Ensaio de Imunoadsorção Enzimática , Estudos de Avaliação como Assunto , Humanos , Linfócitos/efeitos dos fármacos , Linfócitos/metabolismo , Masculino , Radioisótopos de Fósforo , Compostos Policíclicos/sangueRESUMO
16 alpha-Ethyl-21-hydroxy-19-norpregn-4-ene-3,20-dione (ORG 2058) is a ligand widely used in progesterone receptor assays. An improved synthesis of the compound is reported, starting from norethisterone acetate. The preparation of the tritiated radioligand [3H]ORG 2058 is also described.
Assuntos
Marcação por Isótopo , Pregnenodionas/síntese química , Congêneres da Progesterona/síntese química , Trítio , Estrutura Molecular , Noretindrona/análogos & derivados , Noretindrona/química , Acetato de NoretindronaRESUMO
Aromatic DNA adduct levels were determined in macroscopically normal bronchial tissues from 98 patients undergoing pulmonary surgery. The mean DNA adduct level for the 45 current smokers was significantly higher than that of the 16 life-time non-smokers. There was a weak association between adduct levels and daily cigarette consumption above 10 cigarettes per day. DNA adduct levels in the 37 former smokers suggested an exponential form of adduct elimination with a rapid initial and a slower later phase after cessation of smoking. There was no quantitative association between bronchial DNA adduct levels and lung cancer.
Assuntos
Dano ao DNA , DNA de Neoplasias/análise , DNA/análise , Neoplasias Pulmonares/química , Fumar/efeitos adversos , Fumar/metabolismo , Adulto , Idoso , Autorradiografia , Brônquios/química , Feminino , Humanos , Neoplasias Pulmonares/etiologia , Masculino , Pessoa de Meia-Idade , Radioisótopos de FósforoRESUMO
The modifying action of chronic liver injury on the process of hepatocarcinogenesis was investigated. To induce cirrhosis or fibrosis F344 rats received CCl4 alone or in combination with phenobarbital, either before (model 1) or after (model 2) the application of initiator, diethylnitrosamine (DENA). In these models, morphology, tumor incidence as well as polysubstrate monooxygenase system, gamma-glutamyltransferase (GGT) and glucose-6-phosphatase (G-6-Pase) were studied. The data presented show that in model 1 the tumor incidence was much lower than in rats treated with DENA alone. This reduction appeared to be associated with the decrease in cytochrome P450 content occurring in model 1 after DENA administration. Promotion of the hepatocarcinogenic process was observed when CCl4 injury followed the application of DENA (model 2). Comparison of marker enzymes in cirrhotic livers and in tumors either with or without cirrhosis indicated that changes in cytochrome P450 and G-6-Pase were rather the results of parenchymal damage, while GGT was elevated only in tumorous livers. In tumorous livers none of the xenobiotic metabolizing activities decreased as much as the cytochrome P450 content of the same samples. Thus conceivably the cytochrome P450 operates more rapidly in tumors than in normal livers.