Induction of the rat hepatic cytosolic arylamine oxidase by a series of polychlorinated biphenyls: association with the Ah locus

The objective of the present study was to identify the polychlorinated biphenyl congeners of Aroclor 1254 that are responsible for the induction of the cytosolic bioactivation of aromatic amines. Various chlorobiphenyls, ranging from di- to hexa-substituted, were administered to rats and the ability of the hepatic cytosol to bioactivate 2-aminoanthracene and 2-aminofluorene was investigated. These studies revealed that the induction of the cytosolic activation of aromatic amines increased with the increasing extent of chlorination; moreover, planar congeners were more effective inducers of this activity compared to their non-planar isomers. This observation prompted us to investigate whether the cytosolic activation of aromatic amines is associated with the Ah receptor. Treatment of mice with Aroclor 1254 stimulated the cytosolic activation of aromatic amines in C57BL6 mice, an Ah-responsive strain, whereas it had no effect in DBA2 mice, a non-responsive strain. These findings indicate that the bioactivation of aromatic amines by the liver cytosol is linked to the Ah receptor.

Reconstruction of extensive defects of the parotid region: experience with the pectoralis major and free latissimus dorsi flaps

Large defects of the parotid region resulting from excision of malignant tumours, or necrotic tissue due to radiotherapy, should not always be closed with local tissue, for several reasons. Occasionally, myocutaneous flaps are indicated, giving better results. We describe the problems of such tissue defects and our experience over a 10-year period using 2 different flap reconstruction techniques. A total of 28 cases, 25 with malignant tumours of the parotid or the external ear, 2 with extensive radionecrosis of the parotid region and 1 with a burn, were evaluated. The defects were restored with a pectoralis major flap in 21 cases and with a free latissimus dorsi flap in 7 cases. The follow-up ranged from 18 to 60 months. The flaps were successful in achieving stable wound healing, restoration of tissue volume and in helping patients to return to normal life activities. There were complications in 28.5% of the cases. There were 2 early deaths due to encephalitis. Two pectoralis major flaps (9.5%) failed partially. All latissimus dorsi flaps survived. The pectoralis major proved to be useful, especially in older and medically compromised patients, whereas the latissimus dorsi fared well in younger female patients and in cases of a hemifacial resection defect. Numerous technical points in both methods are emphasized.

Diaminonaphthalenes and related aminocompounds: mutagenicity, CYP1A induction and interaction with the Ah receptor

Using 1- and 2-aminonaphthalene as model substrates, we investigated the effect of insertion of a second amino group on mutagenicity, binding to the cytosolic Ah receptor and CYP1A inducibility, and the effects were compared to those elicited by 3,3'-diaminobenzidine and 1-naphthylethylenediamine. 1,5- and 1,8-diaminonaphthalene were effective inducers of CYP1A activity, more potent than 1-aminonaphthalene. 2,3-Diaminonaphthalene was also an inducer of CYP1A, but the effect was similar to that elicited by 2-aminonaphthalene. In contrast, 3,3'-diaminobenzidine and 1-naphthylethylenediamine did not induce CYP1A activity. All aminonaphthalenes displaced [3H]TCDD from the Ah receptor, whereas 3,3'-diaminobenzidine and 1-naphthylethylenediamine failed to do so. The latter two compounds did not elicit a mutagenic response in the Ames test. Introduction of a second amino group at the 3-position of 2-aminonaphthalene did not modulate its mutagenicity. In the case of the non-mutagenic 1-aminonaphthalene, introduction of a second amino group at position 5 had no effect but when it was incorporated at position 8, mutagenic potential was conferred to the molecule. Computer modelling of the putative active site of CYP1A2 revealed that 1,5-diaminonaphthalene is orientated so that the distance of the second amino group from the iron-oxene is 4.037 A while in the case of 1,8-diaminonaphthalene the distance is shorter, 2.744 A, favouring its activation through N-hydroxylation. Of the compounds studied, 1,8-diaminonaphthalene and, to a lesser extent, 2,3-diaminonaphthalene autoinduced their activation. It is concluded that insertion of a second amino group at the 5- or 8-position of 1-aminonaphthalene may enhance biological activity but in the case of 2-aminonaphthalene insertion of a second amino group at position 3 had no major effect.

Mass-spectrometric analysis of naturally processed peptides recognized by ovarian tumor-associated CD8(+) CTL

Antigens recognized by cytotoxic T cells (CTL) are expressed as peptides presented by MHC class I molecules. To isolate peptides from the MHC molecule HLA-A2.1 and identify epitopes that define the activity profile of ovarian CD8(+) CTL, peptides were separated by reverse-phase high-pressure liquid chromatography (HPLC), and analyzed by electrospray ionization-tandem mass spectrometry (ES-MS). HLA-A2.1-bound peptides were extracted from the ovarian tumor line SKOV3 transfected with the HLA-A2.1 (clone 1E4) and C1R.A2 cells transfected with HCA-A2.1 and HER-2 (clone HER-2.J) by immunoaffinity chromatography. At least five peaks of distinct retention times (termed 1, 2A, 2B, 2C, and 3) were recognized by an ovarian HER-2(high) (HER-2(hi)) tumor-associated HLA-A2(+), CD8(+) CTL line. ES-MS analysis was performed for peak 2B peptides from both types of cells. In the four consecutive fractions of peak 2B, at least 27 and 16 ion species of mass-to-charge (m/z) ratio between 760-1300 were detected in 1E4 and HER-2.J cells, respectively. The abundance of four 1E4 and six HER-2.J ions believed to be peptides in four consecutive HPLC fractions in this peak matched the CTL activity profile. Of these, two ions with actual m/z ratios 497.3-498.4 and 792.8-793.2, were found in the peak 2B from both types of cells. Since little is known about the tumor Ag recognized in human cancers, characterization of these ions may lead to identification of novel tumor Ag in breast and ovarian cancers. This may also be useful in developing quantitative approaches to the identification of tumor Ag and the determination of epitope density on tumor and normal cells. This may help characterize the relationship between tumor immunity and epitope tolerance in human epithelial cancers.

Effect of vitamin C supplementation on hepatic cytochrome P450 mixed-function oxidase activity in streptozotocin-diabetic rats

The effect of vitamin C supplementation on hepatic cytochrome P450 expression was investigated in streptozotocin (STZ) diabetic male Wistar Albino rats. STZ-treated rats displayed the usual characteristics of diabetes including; hyperphagia, polydipsia, decreased body weight gain and also the increased expression and activity of hepatic CYP1A, 2B, 2E and 4A proteins. Vitamin C administration in drinking water (2% w/v) was associated with significant decreases in the levels of hyperglycaemia (P < 0.05), glycosylated haemoglobin (P < 0.05), hyperlipidaemia (P < 0.001), and hyperketonaemia (P < 0.001) associated with STZ-diabetes. Vitamin C-treatment selectively reduced the activity and expression of CYP2E proteins (P < 0.001). These effects on CYP2E expression may be mediated by the reduced levels of circulating ketone bodies, however, a direct effect on CYP2E expression in diabetes cannot be discounted.

A comparison of the antimutagenic potential of green, black and decaffeinated teas: contribution of flavanols to the antimutagenic effect

The present study was undertaken to compare the antimutagenic activity of aqueous extracts, at the concentrations used for human consumption, from green, black and decaffeinated black tea. Antimutagenic potential was evaluated against three indirect-acting dietary carcinogens, Glu-P-1, benzo(a)pyrene and nitrosopyrrolidine. All three types of tea gave rise to strong and concentration-dependent suppression of the mutagenicity of the three premutagens in the presence of an activation system. No major difference in the antimutagenic potential of the three types of tea could be discerned. Black tea, decaffeinated black tea and, to a lesser extent, green tea also antagonized the mutagenicity of the direct-acting mutagen 9-aminoacridine. All three types of tea inhibited markedly the NADPH-dependent reduction of cytochrome c and the O-dealkylations of ethoxy-, methoxy- and, to a much lesser extent, pentoxy-resorufin. When the microsomal metabolism was terminated, after the metabolic activation of the premutagens, incorporation of the aqueous tea extracts into the activation system caused a concentration-dependent suppression of mutagenic response. No significant difference in the antimutagenic activity of the three types of tea in this system was evident. Bearing in mind the much higher concentration of flavanols in green tea compared with the black teas, it may be concluded either that these compounds are unlikely to be the major tea components responsible for the antimutagenic, and possibly anticarcinogenic, properties of tea or that their fermentation products are similarly active.

COMPACT and molecular structure in toxicity assessment: a prospective evaluation of 30 chemicals currently being tested for rodent carcinogenicity by the NCI/NTP

A new series of 30 miscellaneous National Toxicology Program chemicals has been evaluated prospectively for carcinogenicity and overt toxicity by COMPACT (Computer Optimised Molecular Parametric Analysis for Chemical Toxicity. CYP1A and CYP2E1). Evaluations were also made by Hazardexpert, and for metal ion redox potentials; and these, together with COMPACT, were compared with results from the Ames test for mutagenicity in Salmonella, the micronucleus test, and 90-day subchronic rodent pathology. Seven of the 30 chemicals (nitromethane, chloroprene, xylenesulphonic acid, furfuryl alcohol, anthraquinone, emodin, cinnamaldehyde) were positive for potential carcinogenicity in the COMPACT evaluation; xylenesulphonic acid and furfuryl alcohol were only equivocally positive. Four of the 30 chemicals-scopolamine, D&C Yellow No. 11, citral, cinnamaldehyde-were positive by Hazardexpert; 6 of 30-D&C Yellow No. 11, 1-chloro-2-propanol, anthraquinone, emodin, sodium nitrite, cinnamaldehyde-were positive in the Ames test; 2 of 30-phenolphthalein and emodin-were positive in the in vivo cytogenetics test; and 3 of 30-molybdenum trioxide, gallium arsenide, vanadium pentoxide-were metal compounds with redox potentials of the metal/metal ion indicative of possible carcinogenicity. The overall prediction for carcinogenicity was positive for 12 of 30 chemicals: nitromethane, chloroprene, D&C Yellow No. 11, molybdenum trioxide, 1-chloro-2-propanol, furfuryl alcohol, gallium arsenide, anthraquinone, emodin, sodium nitrite, cinnamaldehyde, vanadium pentoxide). This overall prediction has been made on the basis of the results of the computer tests and from consideration of the information from bacterial mutagenicity, together with likely lipid solubility and pathways of metabolism and elimination.

Contribution of phenols, quinones and reactive oxygen species to the mutagenicity of white grape juice in the Ames test

The purpose of this study was to evaluate the role of phenols, quinones and reactive oxygen species in the mutagenicity of white grape juice in the Ames mutagenicity test. Mutagenicity was markedly suppressed by reduced glutathione but was not influenced by superoxide dismutase or catalase. In the presence of grape polyphenol oxidase, the mutagenicity of grape juice was markedly increased. When hepatic cytosol from Aroclor 1254-induced rats, supplemented with a reduced nicotinamide adenine dinucleotide phosphate-generating system. served as an activation system, an increase in the mutagenicity of grape juice was observed. The cytosol-induced mutagenicity of grape juice was attenuated in the presence of superoxide dismutase, catalase and glutathione. It is concluded that polyphenol oxidase-catalysed oxidation of phenolic compounds generates genotoxic species that are, at least partly, responsible for the mutagenicity of grape juice. In the presence of hepatic cytosol, one-electron reduction of grape juice quinones leads to the production of reactive oxygen species resulting in an increase in the mutagenic response.

Interaction with the aromatic hydrocarbon receptor, CYP1A induction, and mutagenicity of a series of diaminotoluenes: implications for their carcinogenicity

The present study was undertaken to provide a rationale for the marked difference in carcinogenic potential among isomeric diaminotoluenes, in relation to their ability to induce their own bioactivation through CYP1A induction, their genotoxic potential, and their ability to bind to the cytosolic aromatic hydrocarbon (Ah) receptor. Of the four possible diaminotoluenes only the 2,3- and, to a lesser extent, the 2,4-isomer induced CYP1A activity. Similarly, only these two isomers could displace [3H]T-CDD from the hepatic cytosolic Ah receptor. In the presence of Aroclor 1254- induced microsomes, 2,4- and 2,6-diaminotoluene were potent mutagens in the Ames test. Only 2,4-diaminotoluene could autoinduce its activation. Of the four isomers only 2,4-diaminotoluene is an established carcinogen and this is compatible with the present observations that it is the only isomer that stimulates its own activation through CYP1A induction, is metabolically converted to genotoxic intermediates, and binds to the Ah receptor. 2,6-Diaminotoluene is recognized as a mutagenic noncarcinogen and in the present studies it elicited a positive mutagenic response in the Ames test but failed to induce CYP1A activity and its own activation, and could not bind to the Ah receptor even at concentrations as high as 5 x 10(-4) M. The present findings demonstrate that in vitro studies are very useful tools in predicting the carcinogenic potency of isomeric chemicals.

Mutagenicity of white grape juice in the Ames test

The mutagenicity of commercially available white grape juice was evaluated in the Ames mutagenicity test. Grape juice elicited a positive mutagenic, response in Salmonella typhimurium strain TA104 and a weaker response in strains TA97, TA98, TA100 and TA1530. The mutagenic response was evident in the absence of an activation system and inclusion of such a system did not influence mutagenicity. The grape juice-mediated mutagenic response was not due to histidine residues in the juice or likely treatment with sulfite. Moreover, freshly prepared grape juice displayed a similar mutagenic response. Three different brands of commercially available white grape juice were investigated in the Ames test; they all provoked a clear positive mutagenic response, but the degree of mutagenicity differed and could not be attributed to differences in the content of solids. It is concluded that grapes contain direct-acting genotoxic component(s).

Expression and inducibility of cytochrome P450 proteins in the liver of chick embryo

The expression and inducibility of cytochrome P450 proteins in the liver of chick embryo were investigated using substrate probes and/or immunologically using polyclonal antibodies to the mammalian isoforms. Antibodies to CYP1A1 recognised a single protein which was inducible by structurally diverse chemicals, including aminocompounds, and was parallelled by increases in the O-dealkylations of ethoxy- and methoxyresorufin and in the bioactivation of Glu-P-1. When probed with antibodies to CYP2E1 an immunoreacting protein was revealed which was induced by phenobarbital but not acetone; a second protein became apparent following the treatment with phenobarbital. The increase in apoprotein levels was accompanied by similar increases in p-nitrophenol hydroxylase. Antibodies to CYP2C11 recognised two immunorelated proteins, of which one was inducible by phenobarbital. The same inducer, but not dexamethasone, enhanced the N-demethylation of erythromycin but antibodies to rat CYP3A1 failed to detect any proteins. Finally, lauric acid hydroxylation was not detectable in chick embryo and, moreover, no immunoreacting band was visible following probing of microsomes with anti-CYP4A1. It is concluded that proteins immunorelated to the mammalian CYP1 and CYP2 families are expressed in chick embryo but the regulation of the latter family in the embryo by exogenous chemicals differs markedly from that established for mammals.

CT findings in osteoradionecrosis of the mandible

CT scans of ten patients in whom the diagnosis of mandibular osteoradionecrosis was proven pathologically or by clinical follow-up were reviewed. All ten patients had bony abnormalities (cortical interruptions and loss of spongiosa trabeculation) on the symptomatic side. These were predominantly seen in the body of the mandible (premolar and molar region, eight patients), in some of these cases extending into the retromolar triangle (two patients) or mandibular angle (two patients). In the remaining two patients the abnormalities were in the ramus and angle. The two patients treated with iridium implantation showed localized lingual-sided cortical destruction. Three patients had a pathological fracture. The cortical destruction was buccal-sided in two and both buccal- and lingual-sided in three of the other five patients. Contralateral bony abnormalities were present in four patients. Soft tissue thickening on the symptomatic side was seen in nine patients. As the bony abnormalities in mandibular osteoradionecrosis are often associated with a soft tissue mass, CT differentiation from tumor recurrence can be difficult. The association with cortical defects distant from the position of the original tumor (buccal surface or opposite side of mandible) should evoke the possibility of mandibular osteoradionecrosis.

Defective expression of cytochrome P450 proteins in the liver of the genetically obese Zucker rat

The hepatic expression of xenobiotic-metabolising cytochrome P450 isoforms in the genetically obese Zucker rat, a model of obesity, was compared to that of its lean littermate. Cytochrome P450 (CYP) levels were determined using diagnostic substrates and/or immunologically in Western blot analyses. When compared with the lean Zucker rat, the obese animal exhibited hyperglycaemia, hypercholesterolaemia, marked hyperinsulinaemia and hypertriglyceridaemia but was normoketonaemic. CYP3A and CYP1A2 levels were higher in the obese Zucker rat when compared with the lean littermate but, in contrast, a protein recognised by human CYP2D6 and, to a lesser extent, CYP2C11 levels were lower. Pretreatment with acetone, dexamethasone and clofibrate resulted in enhanced p-nitrophenol hydroxylase (CYP2E), erythromycin N-demethylase (CYP3A) and lauric acid hydroxylase (CYP4A) activities respectively in the liver of the lean Zucker rat but, in contrast, the obese Zucker rat was refractive to such treatment; similarly, hepatic apoprotein levels of the CYP2E and CYP4A subfamilies were increased markedly only in the lean Zucker rat. It is concluded that CYP2E, CYP3A and CYP4A subfamilies are poorly expressed in the obese Zucker rat, and this rat strain may serve as a good model for elucidating the molecular mechanisms of induction of these cytochrome P450 proteins.

Induction of hepatic CYP1A2 by the oral administration of caffeine to rats: lack of association with the Ah locus

Caffeine was administered to male Wistar albino rats for two weeks at three concentrations, namely 0.1, 0.2 and 0.3%, and hepatic cytochrome P450-dependent mixed-function oxidase determined. Caffeine administration gave rise to a marked, dose-dependent increase in the O-deethylation of ethoxyresorufin and, to a lesser extent, in the O-depentylation of pentoxyresorufin. Erythromycin N-demethylase, p-nitrophenol hydroxylase and lauric acid hydroxylase activities, as well as total cytochrome P450 content were unaffected by this treatment. Immunoblot analysis revealed that caffeine gave rise to a dose-dependent increase in the hepatic CYP1A2, and at the highest dose only, CYP2B apoprotein levels. Apoprotein levels of CYP3A and CYP2E1 were not modulated by the treatment with caffeine at all dose levels studied. Caffeine could not displace [3H]TCDD from the rat hepatic cytosolic Ah receptor. Computer analysis showed that caffeine is essentially a planar molecule with an area/depth ratio 4.8, characteristic of CYP1A substrates/inducers. Molecular modelling revealed that the caffeine molecule could orientate itself within the putative CYP1A2 active site so as to facilitate demethylation of the N-1, N-3 and N-7 positions. However, at physiological pH, the N-9 nitrogen atom is likely to be partially protonated, allowing it to participate in an electrostatic interaction with the negatively-charged glutamate 318-residue, favouring N-3 demethylation, the major pathway of metabolism in both humans and animals. In conclusion caffeine, being essentially planar, is an inducer of CYP1A2 in rat liver.

Species variation in the metabolism of 15,16-dihydro-11-methylcyclopenta[a]phenanthren-17-one to its 3,4-dihydrodiol, the proximate carcinogen

The title compound is a strong carcinogen, similar in potency to benzo[a]pyrene in mouse skin assay. This paper describes a comparison of its in vitro metabolism by hepatic microsomal preparations from mouse, rat, rabbit, hamster, dog, monkey and man. Metabolites were isolated by preparative high pressure liquid chromatography from the ethyl acetate extractable material and their structures tentatively assigned on the basis of their retention times and ultraviolet spectra, when possible by direct comparison with authentic synthetic specimens. Mass spectrometry was then used to confirm these assignments. All these animals produce the same range of metabolites derived exclusively from oxidation at the benzo-ring A, the five-membered ring D, and at the 11-methyl group. However, the amounts of individual metabolites varied substantially. In particular all the animals yielded the proximate carcinogen 3,4-dihydroxy-11-methyl-3,4,15, 16-tetrahydrocyclopenta[a]phenanthren-17-one, from which it is reasoned that all might be susceptible to its carcinogenic action. A rationalization for the observed distribution of the metabolites is proposed on the basis of a molecular model of the active site of cytochrome P450 1A1, the oxidative enzyme involved.

Quantitative structure-activity relationships and COMPACT analysis of a series of food mutagens

Quantitative structure-activity relationships between chemical structure and Ames mutagenicity for a group of 24 food mutagens, including 17 cooked-food heterocyclic amines, have been determined. For the TA98 strain of Salmonella typhimurium (frameshift mutagens) the best correlation of mutagenicity is with molecular diameter (R = 0.91), while for the TA100 strain (base-pair mutations) the best correlation is with delta E, the energy difference between the lowest unoccupied and highest occupied molecular orbitals. High mutagenicity is related to high values of molecular diameter, hence to planarity and to high values of the COMPACT ratio ([area/depth2]/delta E). High mutagenicity is also related to low values of delta E. Consequently, highly mutagenic and potentially carcinogenic food chemicals can readily be identified as substrates of cytochrome P4501 (CYP1) and may therefore be detected by the COMPACT procedure. Highly mutagenic compounds also exhibit high values of dipole moment.

Extrahepatic expression of P450 proteins in insulin-dependent diabetes mellitus

1. Male Wistar rats were rendered diabetic by the administration of a single intraperitoneal dose of streptozotocin; the levels of the xenobiotic-inducible P450 proteins were determined in the lung and kidney using diagnostic substrates and immunoblotting employing polyclonal antibodies. The glutathione conjugation system in the cytosol of these tissues was also investigated. 2. The onset of insulin-dependent diabetes did not influence the O-dealkylations of methoxyresorufin, ethoxyresorufin and pentoxyresorufin in either kidney or lung. 3. Lauric acid hydroxylase activity, however, was induced in the kidney but no activity was detectable in the lung. Immunoblot analysis of kidney microsomes using antibodies to P4504A1 revealed the presence of two bands, both of which were clearly inducible in diabetes. In pulmonary microsomes a single faint band was detected which also appeared to be higher in the diabetic rats. 4. Aniline p-hydroxylase activity was not detectable in the kidney, but activity was measurable in the lung and was suppressed in diabetes. Immunoblot analysis of pulmonary microsomes using antibodies to P4502E1 immunodetected a single band which was suppressed in diabetes. In the kidney microsomes a single band was also detected which was, however, markedly elevated in diabetes. 5. Glutathione S-transferase activity was modestly higher in the kidney, but not lung, of the diabetic animals. Glutathione reductase and total glutathione levels were not influenced by the presence of diabetes. 6. It is concluded that streptozotocin-induced insulin-dependent diabetes modulates extrahepatic P450 proteins, the effect being both tissue- and isoform-specific.

A quantitative structure-activity relationship study on a series of 10 para-substituted toluenes binding to cytochrome P4502B4 (CYP2B4), and their hydroxylation rates

Molecular structural and molecular orbital calculations (AM1 method) are reported on a series of 10 para-substituted toluene derivatives and this structural information has been used to rationalize the differences between both rates of hydroxylation catalysed by cytochrome P4502B4 and binding to the same cytochrome P450, via the generation of quantitative structure-activity relationships (QSARs). It was found that the rate constant for hydroxylation can be described by a two-variable expression involving the dipole moment and volume of the solvent-accessible molecular surface (r = 0.98), whereas binding free energies are well characterized by combinations of molecular volume and various electronic frontier orbital parameters (r = 0.98 and 0.99). This study represents an advance on a previous evaluation by White and McCarthy (Arch Biochem Biophys 246: 19-32, 1986) who used empirical physico-chemical parameters to obtain similar results which were generally of lower statistical significance to those of the present work. The QSAR expressions suggest that both binding to P450 and metabolism for this series of compounds are dependent on the relative ability of the molecules to desolvate and occupy the heme binding site, together with electronic properties of the whole molecule and of the methyl group which undergoes hydroxylation.

Expression and inducibility of cytochrome P450 proteins belonging to families 2,3 and 4 in the rabbit aorta

The expression and inducibility of cytochrome P450 proteins belonging to families CYP2, CYP3 and CYP4 in the aorta of rabbits were investigated immunologically using polyclonal antibodies to the hepatic proteins. Antibodies to CYP2B recognised two proteins, only one of which was inducible by phenobarbitone. One protein was detected by anti-CYP2E1 which was modestly inducible by imidazole. A highly expressed protein was recognised by antibodies to CYP3A1, the levels of which diminished following treatment with rifampicin. Finally, antibodies to CYP4A1 immunoreacted with a single protein in the aorta which was refractive to treatment with ciprofibrate. The data demonstrate that the rabbit aorta expresses a number of cytochrome P450 families which, although inducible in the liver, are not always inducible in the aorta.

The role of free pericranium grafts in augmentation rhinoplasty

Various tissues and materials have been used in augmentation rhinoplasty. This paper presents a retrospective analysis of 14 patients, 8 female and 6 male, in whom free pericranium grafts were used in order to restore postsurgery or posttraumatic nasal defects. There were no complications from either the donor or the recipient site. The early and medium term results were satisfactory. It is concluded that free pericranium, compared with other autografts, is a good alternative due to its several advantages and hardly any disadvantages. In selected cases it can even be the material of choice.

Computer graphics analysis of the interaction of alkoxy methylenedioxybenzenes with cytochromes P4501

A quantitative structure-activity relationship (QSAR) in a homologous series of alkoxy methylenedioxybenzenes (MDBs) is reported. Measurements of molecular dimensions from computer-generated space-filling structures have provided values for the shape parameter area/depth2. These have been shown to correlate with the extent of inhibition of ethoxyresorufin O-deethylase activity by a series of MDBs. The implication of this is that the MDB nucleus fits the cytochrome P4501 substrate binding site and that this ability decreases with increase in the alkyl chain length of the alkoxy substituent. These findings are in agreement with previous results relating to the spatial dimensions of the cytochrome P4501 binding site, showing that substrate specificity can be rationalized in terms of overall molecular shape.

A retrospective evaluation of COMPACT predictions of the outcome of NTP rodent carcinogenicity testing

The carcinogenic potentials of 40 National Toxicology Program chemicals previously predicted by Computer Optimised Molecular Parametric Analysis for Chemical Toxicity (COMPACT), based on the identification of potential substrates of cytochromes P4501A and 2E (CYP1A and CYP2E), have been compared with new rodent carcinogenicity results. The COMPACT predictions have also been compared with published Ames mutagenicity data and with our own Hazardexpert predictions for carcinogenicity. Concordance evaluations between rodent carcinogenicity (1/4 segments positive) and predictions by COMPACT or Hazardexpert were 64% for COMPACT (CYP1A only), 72% for COMPACT (CYP1A plus CYP2E), 70% for Hazardexpert alone, and 86% for COMPACT (CYP1A plus CYP2E) plus Hazardexpert. Sensitivities of the predictions were for COMPACT, 75%; Hazardexpert, 60%; and Ames, 54%. Positive predictivities were for COMPACT, 75%; Hazardexpert, 78%; and Ames 81%. Negative predictivites were for COMPACT, 62%; Hazardexpert, 52%; and Ames, 42%.

CYP1 induction, binding to the hepatic aromatic hydrocarbon receptor and mutagenicity of a series of 11-alkoxy cyclopenta[a]phenanthren-17-ones: a structure activity relationship

A series of four 11-alkoxy cyclopenta[a]phenanthren-17-ones, ranging from the methoxy to the butoxy derivative, has been synthesised in order to investigate the effect of the size of the 11-substituent on the mutagenicity and ability of these compounds to induce hepatic CYP1 activity in rats. The latter was monitored by using as diagnostic probes methoxy and ethoxy-resorufin, and immunologically in Western blots employing anti-CYP1A1 antibodies. All four members of the series induced both CYP1A1 and CYP1A2 activities and apoprotein levels, but the methoxy- and ethoxy-CPP-17-ones were clearly the most potent. Of the four isomers, only 11-methoxy-CPP-17-one displaced 3H-TCDD from the cytosolic Ah receptor. Similarly only 11-methoxy-CPP-17-one elicited a positive mutagenic response in the Ames test in the presence of an Aroclor 1254-induced activation system. The relevance of these findings to the carcinogenicity of these compounds in the mouse skin painting model is discussed.

Stimulation of rat hepatic UDP-glucuronosyl transferase activity following treatment with green tea

Studies were conducted to investigate whether aqueous extracts of green tea, administered to rats at concentrations consumed by humans, could influence the phase II conjugation reactions in the liver, and so contribute to its established anticarcinogenic activity. Exposure of rats to green tea (2.5%, w/v), as the sole drinking fluid, for 4 wk did not influence sulfotransferase, epoxide hydrolase nor glutathione S-transferase activities. UDP glucuronosyl transferase activity, when determined using 2-aminophenol as the substrate, was increased by 100% following treatment with tea. Finally, green tea had no effect on the enzymes affording protection against reactive oxygen species, namely catalase, glutathione peroxidase and superoxide dismutase. It is postulated that the enhanced glucuronidation may contribute to the anticarcinogenic effect of green tea by facilitating the metabolism of chemical carcinogens into inactive, readily excretable products.

Sudden death and staged therapy for hemodynamic stabilization in patients enrolled in a heart transplantation program

To investigate the impact of staged therapy for advanced heart failure on therapeutic endpoints, 236 consecutive patients (coronary artery disease/dilated cardiomyopathy in 61/175 patients, left ventricular ejection fraction 14% +/- 5%, New York Heart Association Class II/III/IV in 102/79/55 patients, respectively) with advanced heart failure were prospectively followed. One hundred thirty-seven patients enrolled from January 1989 to December 1991 were treated conventionally with digoxin, furosemide, and low dose angiotension converting enzyme (ACE) inhibition. Patients refractory to this therapy underwent urgent heart transplantation. Ninety-nine patients enrolled from January 1992 to August 1993 underwent staged therapy: stage 1: maximal tolerated ACE inhibition; stage 2: therapy with PGE1 for pre- and afterload reduction to achieve hemodynamic stabilization; or stage 3: refractory patients bridged to heart transplantation with continuous outpatient dobutamine. Sudden death was defined as death within 1 hour of symptoms if heart failure symptoms remained stable over the previous 7 days. Conventionally treated patients were followed for 10 +/- 9 months; patients who underwent staged therapy for 9 +/- 5 months. In the group of patients that underwent standard therapy, 39 of 137 (28%) patients died: 5 (13%) deaths occurred suddenly, and death due to progressive pump failure occurred in the remaining 34 (87%) patients. In the group of patients that underwent staged therapy, 25 of 99 (25%) patients died: 13 (52%) deaths occurred suddenly, and 12 (48%) deaths occurred due to progressive pump failure.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of dihydrodiol conformation on the metabolic activation of cyclopenta[a]phenanthrenes

The present study was undertaken in order to rationalise the apparent biological inactivity of 15,16-dihydro-6-methylcyclopenta[a]phenanthren-17- one (4) when other methyl isomers of 15,16-dihydrocyclopenta[a]phenanthren- -17-one, e.g. the 11-methyl derivative (2), display appreciable tumorigenicity. In vitro metabolism of the 6-methyl-ketone-17-one (4) demonstrated that its principal metabolite was the 3,4-dihydro-3,4-diol (3,4-dihydroxy-6-methyl-3,4,15,16- tetrahydrocyclopenta[a]phenanthren-17-one) (5) which, in the case of the active 11-methyl derivative, is the proximate genotoxin. Thus the inactivity of this 6-methyl-17-ketone cannot be ascribed to lack of formation of the 3,4-dihydro-3,4-diol, the precursor of the 3,4-diol-1,2-epoxides (the ultimate mutagens in this series). However, the 6-methyl-3,4-dihydro-3,4-diol exists in a pseudo-diaxial rather than a pseudo-diequatorial conformation characteristic of the 3,4-dihydro-3,4-diols of the other members of the series. It is therefore suggested that a diequatorial conformation in the dihydrodiol is essential to the metabolic activation of the cyclopenta[a]phenanthren-17-ones.

Surgical management of the osteoradionecrotic mandible with free vascularised composite flaps

Osteoradionecrosis (ORN) of the mandible is a serious sequel to radiotherapy administered for malignant neoplasms of the head and neck. In a retrospective/prospective study, 28 patients with mandibular defects due to ORN were reviewed. Monocortical and bicortical defects as well as pathological fractures were reconstructed by means of a free serratus anterior/rib (n = 8) or a vascularised iliac crest flap (n = 25). All the former survived; a pathological fracture, however, occurred postoperatively in 2 of the patients (25%). Five iliac crests were lost (20%). The remaining bone struts healed well. The donor site morbidity was very low. Clinical and radiological longterm follow-up showed that a very acceptable functional and cosmetic result was achieved in all cases. Progress of ORN was prevented in ca. 90% of all patients. The radiological follow-up was facilitated with the use of high-resolution CT-scans.

Safety evaluations of food chemicals by "COMPACT". 1. A study of some acyclic terpenes

A group of 19 acyclic terpenes have been evaluated for potential toxicity/carcinogenicity by molecular orbital determinations of their spatial and electronic parameters, and hence prediction of their metabolic activation or detoxication by the cytochrome P-450 (CYP) superfamily of mixed-function oxidase enzymes. Previous studies have characterized the spatial dimensions of the CYP1A1, 1A2 and 2E1 enzymes, which are known to activate mutagens and carcinogens and to be involved in other mechanisms of toxicity. None of the terpenes was found to have shape or electronic parameters appropriate for metabolic activation by CYP1A1 or 1A2, and hence they are unlikely to be carcinogenic or mutagenic. Furthermore, none of these chemicals had spatial parameters critical for substrates of CYP2E, and they are therefore unlikely to induce the formation of reactive oxygen species (ROS) or to initiate or promote malignancy or toxicity by mechanisms involving ROS. However, citral, and others of these terpenes, are known to undergo metabolism to carboxylic acids that may induce CYP4, and are therefore possible inducers of hepatic peroxisomal proliferation at high dosage, which may have implications for possible hepatotoxicity.

Effect of high fat diet on liver microsomal oxygenations in ferret

1. Ferret on a high fat diet accumulated large amounts of fat in its liver and had blood acetoacetate and beta-hydroxybutyrate concentrations 250 and 375% of those in control animals. 2. The high fat diet alone increased ferret liver microsomal 7-ethoxyresorufin O-deethylase (EROD) activity by 90%, but had no effect on 7-methoxy-, 7-pentoxy-, or 7-benzyloxy-resorufin, O-dealkylase activities. Administration of 3-methylcholanthrene (MC) increased only liver EROD activity, by 5- to 6-fold, in ferret on both high fat and control diets. Induction of EROD, but not MROD activity, in ferret on the high fat diet indicates that P4501A1, but not P4501A2, is induced. 3. Activation of 3H-paracetamol, measured by covalent tissue binding to ferret liver microsomal fractions, was increased three-fold in ferret on the high fat diet, nine-fold by MC administered to ferret on a control diet, and 13-fold by MC given to ferret on the high fat diet. Similar results were obtained with activation of the cooked-food amine, Glu-P-1, by ferret liver microsomes. 4. Western blots with antibodies to rat liver P450s showed that ferret liver contains proteins orthologous with rat liver P4504A1 and bifunctional protein. However, whereas clofibrate, similar to high fat diets, induced these two proteins in rat liver, no increase of these proteins occurred in liver of ferret fed a high fat diet. Western blots also showed that ferret liver contains no P4501A1 or 1A2, and although these two proteins were induced by MC, no induction occurred when ferret was fed the high fat diet alone. Ferret liver microsomes also contain a protein recognized by rat anti-P4502E1 but of a lower molecular weight. 5. Immunosorbent (ELISA) analyses of ferret liver for P4501A1 and 4A1 showed that the high fat diet increased a protein orthologous to rat P4501A1 but did not increase any protein orthologous to rat P4504A1. 6. These findings indicate that the high fat diet does not induce ferret liver bifunctional protein or P4504A1 enzyme protein, but may enhance liver P4501A1 and 1A2 activities through the hyperketonaemia resulting from the high dietary fat. The conflicting P450 results, namely Glu-P-1 activation but no MROD activity for P4501A2, high EROD activity and ELISA quantification of P4501A1, but no positive Western blot, are probably due to differences in substrate specificity and immunological characteristics between rat and ferret enzymes.

Selective induction of rat hepatic CYP1 and CYP4 proteins and of peroxisomal proliferation by green tea

Rats were exposed to freshly prepared aqueous extracts of green tea (2.5% w/v) as the sole source of drinking water for 4 weeks. Hepatic cytochrome P450 activity was determined using chemical probes, showing selectivity for particular isoforms, and by immunoblot analysis employing polyclonal antibodies. Exposure to green tea gave rise to increases in the O-demethylation of methoxyresorufin and, to a lesser extent, in the dealkylations of ethoxyresorufin and pentoxyresorufin. An increase was also seen in lauric acid hydroxylation but, in contrast, the N-demethylation of erythromycin was inhibited. p-Nitrophenol oxidase activity was unaffected by the same treatment. Immunoblot analysis revealed increases in the apoprotein levels of CYP1A2 and CYP4A1 following treatment with green tea. A significant increase was also noted in the CN(-)-insensitive palmitoyl CoA oxidation and this was paralleled by an increase in the levels of the peroxisomal trifunctional protein determined immunologically. Hepatic S9 and microsomal preparations from tea-treated animals were more effective than controls in activating 2-amino-3-methylimidazol[4,5-f]quinoline and 2-aminoanthracene to mutagens in the Ames test. When N-nitrosopyrrolidine served as the promutagen, tea did not influence its mutagenicity when isolated microsomes comprised the activation system but a significant inhibition was observed when hepatic S9 was used. The above findings are discussed within the context of the established anticarcinogenic and anti-mutagenic properties of green tea.

Inhibition of rat hepatic aryl hydrocarbon hydroxylase activity by a series of 7-hydroxy coumarins: QSAR studies

1. Molecular orbital calculations, by the Modified Intermediate Neglect of Differential Overlap (MINDO/3) method, of a series of twenty-five 8-acyl-7-hydroxy coumarins show that the inhibition of aryl hydrocarbon hydroxylase (AHH) activities (cytochrome P4501, CYP1 activity, primarily CYP1A1) for 23 of these compounds is related to their structural parameters. The two remaining compounds are the only chlorinated derivatives; these are inactive towards the AHH system and were excluded from the quantitative structure-activity relationship (QSAR) analysis. 2. The results of multiple regression analyses show that AHH activity is dependent on the energy of the highest occupied molecular orbital, E(HOMO), in a single variable expression for the 23 compounds. However, a three-variable expression involving superdelocalizabilities provides a more significant correlation with biological activity. 3. The inactivity of the two chlorinated derivatives can be rationalized in terms of their low degree of molecular planarity, as estimated by the area/depth2 parameter, which presumably precludes them from interaction with CYP1.

Evaluation of the antimutagenic potential of anthracene: in vitro and ex vivo studies

The present study was undertaken in order to evaluate the in vitro and ex vivo antimutagenicity of anthracene against the food-borne carcinogen IQ (2-amino-3-methylimidazo[4,5-f]quinoline). Anthracene caused a marked, concentration-dependent decrease in the mutagenicity of IQ in the Ames test, whether hepatic S9 or isolated microsomes from Aroclor 1254-induced rats served as the activation systems. Anthracene gave rise to a concentration-dependent inhibition of the 0-deethylation of ethoxyresorufin, a diagnostic probe for CYP1A (cytochrome P450 family 1, subfamily A) activity, and of the metabolic activation of Glu-P-1 (2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole, a diagnostic probe for CYP1A2. When microsomal metabolism of IQ was terminated by menadione, incorporation of anthracene into the incubation mixture once again inhibited the mutagenicity of IQ. All the above observations indicate that anthracene owes its antimutagenic response against IQ to: (a) inhibition of its CYP1A-mediated activation and (b) direct interaction between anthracene and the reactive intermediate(s) of IQ leading to their inactivation. Treatment of rats with anthracene did not greatly influence the ability of hepatic preparations to bioactivate IQ to mutagens. Similarly, administration of anthracene 2 h before sacrifice to Aroclor 1254-pretreated rats, did not modulate the hepatic activation of IQ. These findings demonstrate that the in vitro mechanisms of the antimutagenicity of anthracene are not operative in vivo, and further illustrate the inadequacy of in vitro studies, conducted in isolation, in predicting such effects.

The use of computers in the safety evaluation of drugs and other chemicals

The toxicity and carcinogenicity of drugs and other chemicals is, in most cases, mediated by highly reactive intermediates which are generated following metabolism catalysed by the enzymic apparatus of the exposed organisms. These reactive intermediates readily interact covalently with vital cellular components to provoke toxicity and carcinogenicity. The ubiquitous cytochrome P450-dependent mixed-function oxidases are the most important enzyme system in the activation of chemicals. This enzyme system comprises a number of families, each of which contains one or more subfamilies. The CYPIA and CYP2E subfamilies are the most closely associated with the production of reactive intermediates and, consequently, the manifestation of toxicity and carcinogenicity. A computer based molecular structure procedure (COMPACT) has been developed which, via a calculation of the molecular and electronic structure of the chemical, determines whether the chemical will interact with either of these two cytochrome P450 subfamilies and hence be metabolised to form reactive intermediates that manifest toxicity. As the basal levels of these two subfamilies are generally low, the ability of a chemical to induce them selectively, on repeated administration, is an important determinant of its toxic and carcinogenic potential. This inductive capability may be determined in short-term studies (ENACT) using only a small number of animals. Thus the combination of COMPACT and ENACT provides a rapid and inexpensive means for the preliminary screening of chemicals for toxicity and carcinogenicity before undertaking the long-term and expensive rodent lifetime bioassays.

Sequence motifs of human her-2 protooncogene important for Peptide binding to hla-A2

Tumor progression and metastasis are often associated with overexpression of specific cellular proteins. In 1991, we introduced a hypothesis that epitopes of nonmutated overexpressed proteins can be targets of a specific cellular immune response against tumor mediated by T cells (Mol Carcinogen 6: 77-81, 1992) and that, when T cell epitopes are present, distinction between tumor immunity/autoimmunity and unresponsiveness can be predicated on the protein concentration as a limiting factor of epitope supply. In support of this hypothesis, we demonstrated that CTL from patients with ovarian tumors which overexpress HER-2 proto-oncogene can recognize both autologous tumor and synthetic analogs of a specific epitope from HER-2, which was identified based on the convergence of all criteria for selection of HLA-A2 associated epitopes recognized by T cells. In this study, we identified all epitopes in HER-2 containing nonapeptides with HLA-A2 anchors. Of these, analysis of potential amphiphilic sites identified both sequences and specific mutations that positively affected the reactivity of conformationally dependent HLA-A2 specific mAb which served as an indication of HER-2 peptide binding. We also report the in vitro induction of cellular responses to these peptides by PBMC from healthy HLA-A2+ volunteers as an indication of their ability to stimulate/ restimulate pre-existing T cell responses to HER-2. The peptides induced proliferative responses in one of four donors tested and CTL responses (one of three peptides tested in two of three donors). This strategy may allow selection of immunogenic HER-2 peptides and elucidation of mechanisms operating in induction of tolerance to defined epitopes on self-proteins.

Marked antimutagenic potential of aqueous green tea extracts: mechanism of action

In the present study aqueous extracts of green tea, at the concentrations customarily consumed by humans, were evaluated for their antimutagenic activity against major classes of dietary and occupational carcinogens. Green tea extracts caused a very marked and concentration-dependent inhibition of the Aroclor 1254-hepatic S9-mediated mutagenicity of heterocyclic amines (IQ and Glu-P-1) and polycyclic aromatic hydrocarbons (benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene) and of the isoniazid-induced S9-mediated mutagenicity of nitrosamines (nitrosopiperidine and nitrosopyrrolidine). Similar inhibition was seen in the mutagenicity of the two aromatic amines, namely 2-amino-fluorene and 2-aminoanthracene, whether Aroclor 1254-S9, isolated microsomes or cytosol served as the activation system. Finally, the mutagenicity of the direct-acting mutagens 9-aminoacridine and MNNG was also suppressed by green tea extracts, but the effect was less pronounced when compared with the indirect-acting mutagens. Green tea extracts caused a marked and concentration-dependent decrease in the O-dealkylation of methoxyresorufin, ethoxyresorufin and pentoxyresorufin. A similar inhibition of the NADPH-dependent reduction of cytochrome c was also observed. Following the termination of the microsomal metabolism of the various promutagens, incorporation of green tea extracts into the activation system resulted in a comparatively modest inhibition of their mutagenic response. It is concluded that aqueous extracts of green tea possess marked antimutagenic potential against a variety of important dietary and environmental mutagens. Two mechanisms appear to be responsible. The first involves a direct interaction between the reactive genotoxic species of the various promutagens and nucleophilic tea component(s) present in the aqueous extracts.(ABSTRACT TRUNCATED AT 250 WORDS)

Mutagenicity and CYP1A induction by azobenzenes correlates with their carcinogenicity

The genotoxicity of six azobenzenes was evaluated in the Ames test, in the presence of an activation system derived from Aroclor 1254-treated rats. Moreover, the ability of these azobenzenes to induce rat hepatic CYP1A activities and apoprotein levels, and stimulate their own bioactivation to mutagens, was also determined. In the presence of the Aroclor 1254-activation system, o-aminoazotoluene and 3-methoxy-4-aminoazobenzene were potent mutagens, whereas 4-amino-azobenzene and 4-diethylaminoazobenzene failed to elicit a positive mutagenic response. A very weak mutagenic response was induced by 2-methyl-4-dimethylaminoazobenzene and by azobenzene. o-Aminoazotoluene and 3-methoxy-4-aminoazobenzene were potent inducers of CYP1A activities and apoprotein levels, whereas the remaining four compounds displayed either very weak or no induction capability. None of the azobenzenes studied could induce its own activation to mutagens in the Ames test. All six azobenzenes displaced [3H]tetrachlorodibenzo-p-dioxin from the cytosolic Ah receptor, with o-aminoazotoluene and 3-methoxy-4-aminoazobenzene being the most effective. A correlation appears to exist between carcinogenic activity of azobenzenes in the rat on one hand, and of their mutagenic potential and hepatic CYP1 induction on the other. Possible mechanisms accounting for this relationship are discussed.

Bioactivation of 6-aminochrysene by animal and human hepatic preparations: contributions of microsomal and cytosolic enzyme systems

6-Aminochrysene was converted into mutagen(s), in the Ames test in the presence of Aroclor 1254-induced hepatic S9, microsomal and cytosolic fractions, the first being the least and the last the most efficient activation system. The cytosolic activation of 6-aminochrysene decreased in the presence of increasing amounts of microsomes. The Aroclor 1254-induced rat microsomal and cytosolic systems differed markedly in a number of properties, including their cofactor requirements and responses to prototype inducers of the cytochrome P450-dependent mixed-function oxidase system. The cytosolic activation system could also convert 2-aminochrysene to mutagens but not 2- and 6-methylchrysene. Human hepatic cytosol could convert 6-aminochrysene and 2-aminoanthracene to mutagens in the Ames test. It is concluded that a hepatic cytosolic oxygenase exists, totally different from the microsomal oxygenases, which metabolizes aminopolycyclic aromatic hydrocarbons to mutagens, presumably through N-oxidation. This oxygenase activity appears to be present in human hepatic cytosol.

Molecular modelling of cytochrome CYP1A1: a putative access channel explains differences in induction potency between the isomers benzo(a)pyrene and benzo(e)pyrene, and 2- and 4-acetylaminofluorene

The present studies were undertaken to provide a rationale for the observation that benzo(a)pyrene and 2-acetylaminofluorene induce the hepatic CYP1A1 protein, whereas their non-carcinogenic isomers benzo(e)pyrene and 4-acetylaminofluorene are, at best, relatively very weak inducers. Using amino acid sequence alignment, a molecular model of the CYP1A1 was constructed by analogy to CYP101, the bacterial protein for which the 3-dimensional structure is known from X-ray crystallographic analysis. The putative structure of the active site of the CYP1A1 protein shows the presence of two phenylalanine residues preferentially aligned in parallel orientation, presumably functioning as a 'sieve' for planar molecules, the established substrates of CYP1A1. The molecular dimensions of this putative access channel show a width and depth of 8.321 and 3.261 A, respectively. The width of 4-acetylaminofluorene, 8.794 A, and benzo(e)pyrene, 9.153 A, precludes their passage through this channel access in contrast to benzo(a)pyrene and 2-acetylaminofluorene having a width of 7.150 and 5.283 A, respectively, explaining their difference in CYP1A1 induction potential.

Interaction of a series of nitriles with the alcohol-inducible isoform of P450: computer analysis of structure-activity relationships

1. Structural studies are reported on a series of 20 nitriles of varying rates of P4502E-mediated oxidative metabolism. 2. Parameters of molecular and electronic structure have been calculated for the generation of quantitative structure-activity relationships (QSARs) with the rates of oxidative metabolism of the nitriles, and with their acute toxicity. 3. Correlations between molecular polarizability, excitation energy and biological activity are presented as a result of QSAR analysis.

Modulation of the rat hepatic cytochrome P450 composition by long-term streptozotocin-induced insulin-dependent diabetes

The effects of long-term insulin-dependent diabetes on the enzymatic activities of hepatic cytochrome P450 isozymes were determined in rats rendered diabetic by the administration of streptozotocin and killed 4, 8, and 12 weeks following treatment. The O-dealkylations of ethoxyresorufin and pentoxyresorufin were elevated in the diabetic animals throughout the study, the extent of increase being similar at all three time points. p-Nitrophenol hydroxylase activity was induced in the diabetic animals 4 weeks following treatment with streptozotocin, but the extent of increase became less pronounced with the progress of the disease. A modest increase in ethylmorphine N-demethylase activity was also observed but only in the diabetic animals killed 4 weeks after the induction of diabetes. Finally, lauric acid hydroxylase activity was elevated in the diabetic animals 4 weeks following streptozotocin administration but then declined rapidly with the duration of the disease. It is concluded that the duration of diabetes modulates the hepatic cytochrome P450 profile, with the effect being isoenzyme specific. Mechanisms that may account for these changes are discussed.

Induction of hepatic microsomal CYP4A activity and of peroxisomal beta-oxidation by two non-steroidal anti-inflammatory drugs

The effects of the non-steroidal anti-inflammatory drugs fenbufen and ibuprofen on hepatic cytochrome P450 activities and peroxisomal proliferation were investigated in the rat, following intraperitoneal administration at three dose levels. At the two highest doses, 30 and 150 mg/kg, ibuprofen stimulated lauric acid hydroxylase activity but no other dose-dependent effects on cytochrome P450 activities were evident. Fenbufen, at the highest dose of 150 mg/kg, decreased cytochrome P450 content and related activities, and this effect was attributed to the toxicity of the drug at this dose. Immunoblot studies employing solubilized microsomes from ibuprofen-treated rats revealed that ibuprofen increased the apoprotein levels of CYP4A1, at the two higher doses. The same treatment with ibuprofen, at the highest dose only, increased the beta-oxidation of palmitoyl CoA, determined in liver homogenates, and immunoblott analysis showed an increase in the apoprotein levels of the trans-2-enoyl CoA hydratase trifunctional protein. Fenbufen did not influence palmitoyl beta-oxidation. Computer graphic overlays with clofibric acid showed that ibuprofen, when compared with fenbufen, displayed a better overall fit to clofibric acid. Finally, interaction energies between the two drugs and the putative peroxisome proliferator-activated receptor ligand domain revealed that ibuprofen had a higher affinity for the receptor than fenbufen, but the difference was modest. It is concluded that ibuprofen, at doses far exceeding those employed clinically, is a weak inducer of both CYP4A1 activity and peroxisomal proliferation and these effects may be attributed to the presence of an aryl propionic acid moiety.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissimilar tcr v-Beta frequencies in til from different sites of the same tumor

Tumor infiltrating lymphocytes (TIL) cultured long term in media containing IL-2 were shown to mediate in vitro and in vivo anti-tumor responses. To understand the anti-tumor activity of TIL T cells, we used polymerase chain reaction (PCR) to characterize the TCR Vbeta repertoire of ovarian TIL which were isolated from three tumor sites of the same patient at the same time and cultured under identical conditions, resulting in CD3+ cells with similar CD8:CD4 ratios. TIL isolated from ovary and ascites expressed a broad distribution of Vbeta repertoire, while the Vbeta phenotype of the TIL from a secondary tumor (omentum) was more restricted. After 5 months, cultured TIL from the primary tumor (ovary) maintained a diverse TCR Vbeta repertoire, but the Vbeta phenotype of TIL from the secondary site was dominated by the Vbeta-1, -11 and -14 families. Importantly, the percentages of Vbeta-11 and Vbeta-1 expression in both omentum and ovary TIL at 3 and 5 months was found to correlate with the levels of lysis of the tumor localized to omentum (p =0.003 and p=0.014, respectively). No statistical correlation was found between cytotoxicity and the use of any other individual Vbeta families or the sum of any other families, including TCR Vbeta-3 or -20 found increased at certain time points. This suggests that where certain TCR Vbeta families are selected in tumor reactive T cells this selection may reflect tumor Ag recognition at either primary or distant tumor sites. To our knowledge, this is the first documentation of complete TCR Vbeta repertoire of ovarian TIL and of a correlation between Vbeta usage and tumor lysis, by effectors from different sites.

Mutagenicity testing of 9-N-substituted adenines and their N-oxidation products

Adenine together with certain 9-N-substituted derivatives such as 9-methyl, 9-benzyl, 9-benzhydryl, and 9-trityl were tested against Salmonella typhimurium strains TA97, TA98, and TA100 in the absence and presence of rat hepatic S9 prepared from Aroclor 1254 pretreated rats. All compounds were positive toward TA98 in the presence of the metabolic activating system, whereas they all lacked mutagenic activity in the absence of S9, and toward TA97 and TA100 with or without S9 when tested at 100 ng/plate. A similar pattern was observed for the corresponding 1-N-oxides. 6-Hydroxylaminopurine was not mutagenic toward TA100 at 100 ng/plate, whereas it was toxic toward TA97 and TA98 at this level. When tested at 1 ng/plate, hydroxylaminopurine was still toxic to TA98 but produced twice the spontaneous reversion rate to TA97 without metabolic activation. Surprisingly, 9-methyl-6-hydroxylaminopurine was only active toward TA98 in the presence of S9, whereas 9-benzyl-6-hydroxylaminopurine was highly active toward TA97 and TA100 in the absence of S9 and even more active in the presence of S9. This compound was inactive toward TA98 in the absence of S9. The results generally support the concept that nuclear N-oxidation of aminoazaheterocycles is a detoxication process, whereas N-hydroxylation of the exo amino group is a toxication reaction.

Cytochrome P450-dependent metabolism and mutagenicity of 15,16-dihydro-11-methylcyclopenta[a]phenanthren-17-one and their implications in its carcinogenicity

Methylation of the non-carcinogen 15,16-dihydrocyclopenta[a]phenanthren-17-one (CPP-17-one) at the bay region to form 11-CH3-CPP-17-one confers carcinogenic potential. In the present study we have investigated the in vitro metabolism and mutagenicity of the methylated compound by hepatic microsomal preparations from rats pretreated with various prototype inducers of cytochrome P450 proteins in order to provide a rationale for this marked difference in carcinogenic activity. The most effective metabolism of 11-CH3-CPP-17-one occurred in the presence of Aroclor 1254-induced microsomes, the principal metabolites being oxidative products of the A- and D-rings and of the methyl substituent. When benzo[a]pyrene-induced microsomes served as the metabolising system, the major A-ring metabolite was the 3,4-diol. A similar metabolic pattern was seen with microsomes from rats treated with 11-CH3-CPP-one itself, but the overall effect of metabolism was lower than that observed with benzo[a]pyrene-treated microsomes but higher than that of control animals. In contrast, microsomes from rats treated with clofibrate, dexamethasone, isoniazid and phenobarbitone failed to enhance the metabolism of 11-CH3-CPP-17-one when compared with control microsomes and the metabolites reflected primarily oxidation of the D-ring. When 11-CH3-CPP-17-one was employed as a promutagen in the Ames test, a mutagenic response was evident only in the presence of microsomes from benzo[a]pyrene-induced rats, but induction with phenobarbitone, isoniazid, dexamethasone, clofibrate and the compound itself, failed to elicit a positive mutagenic response. When 3,4-dihydroxy-11-CH3-CPP-17-one served as the promutagen, a mutagenic response was observed in the presence of benzo[a]pyrene-induced and, to a lesser extent, 11-CH3-CPP-17-one-induced microsomes. Treatment of rats with 11-CH3-CPP-17-one caused a marked increase in the O-deethylation of ethoxyresorufin and, to a much lesser extent in epoxide hydrolase activity. It is concluded that (i) 11-CH3CPP-17-one is an inducer of the CYP1 family; (ii) under the present experimental conditions only the CYP1 family can oxidise the A-ring to form the 3,4-dihydroxy-11-CH3-CPP-17-one, the precursor of the ultimate carcinogen and (iii) only the CYP1 family oxidizes the diol to generate the ultimate carcinogen.(ABSTRACT TRUNCATED AT 400 WORDS)

Contribution of phenolic and quinonoid structures in the mutagenicity of the edible mushroom Agaricus bisporus

The objectives of this work were to establish the contribution of agaritine in the mutagenicity of ethanolic extracts from Agaricus bisporus and to examine the possible involvement of phenolic and quinonoid compounds in the mutagenic response to mushrooms. The mutagenic profile of agaritine in the Ames test, in the absence of an activation system, was different from that of the mushroom ethanolic extracts. Incorporation of rat hepatic cytosolic fractions as the activation system increased the mutagenicity of the mushroom ethanolic extracts in Salmonella typhimurium strain TA 104 but did not influence the mutagenicity of agaritine. It was concluded that agaritine is not the principal mutagenic component in the mushroom. The cytosol-induced mutagenicity of the mushroom extracts required NADPH, and was inhibited by dicoumarol and menadione. Moreover, the mutagenic response in the presence of cytosolic fractions was inhibited by superoxide dismutase, catalase, glutathione and dimethyl sulfoxide, thus implicating reactive oxygen species. Finally, tyrosinase, the enzyme converting mushroom phenols to quinones, increased the mutagenicity of the mushroom extracts. Collectively, the above results indicate that phenolic and quinonoid compounds, presumably through the generation of reactive oxygen species, may play a significant role in the mutagenicity of mushroom extracts.