Abstract  Delayed (or incomplete) ossification of developing fetal bones and wavy ribs are some of the most common skeletal variations encountered in regulatory guideline developmental toxicity studies. Although they tend to be regarded as minor effects, they can be quite sensitive and consequently may influence the study lowest-observed-adverse-effect levels (LOAELs), and thus, impact classification, labeling, and risk assessment. In this study, we review the underlying mechanisms of these skeletal variations, evaluate different scenarios in which they have been observed, offer guidance for their interpretation, and comment on their use for risk assessment. Both minor delays in ossification and wavy ribs seem to be readily repairable via postnatal skeletal remodeling, are not mechanistically linked to malformation, and often are seen in the presence of maternal or fetal toxicity. As such, these minor variations would not generally be considered adverse in and of themselves but should be interpreted in the context of other maternal and fetal findings, information available on normal skeletogenesis patterns, mode of action of the test agent, and historical control incidence using a weight of evidence approach.

Abstract  Peroxisome proliferator-activated receptor alpha (PPARalpha) is responsible for peroxisome proliferator-induced pleiotropic responses, including the development of hepatocellular carcinoma in rodents. However, it remains to be determined whether activation of PPARalpha only in hepatocytes is sufficient to induce hepatocellular carcinomas. To address this issue, transgenic mice were generated that target constitutively activated PPARalpha specifically to hepatocytes. The transgenic mice exhibited various responses that mimic wild-type mice treated with peroxisome proliferators, including significantly decreased serum fatty acids and marked induction of PPARalpha target genes encoding fatty acid oxidation enzymes, suggesting that the transgene functions in the same manner as peroxisome proliferators to regulate fatty acid metabolism. However, the transgenic mice did not develop hepatocellular carcinomas, even though they exhibited peroxisome proliferation and hepatocyte proliferation, indicating that these events are not sufficient to induce liver cancer. In contrast to the transgenic mice, peroxisome proliferators activate proliferation of hepatic non-parenchymal cells (NPCs). Thus, activation of hepatic NPCs and/or associated molecular events is an important step in peroxisome proliferators-induced hepatocarcinogenesis.

Abstract  In a continuing review of long-term toxicology and carcinogenesis studies in rats and mice, the National Toxicology Program (NTP) is confronted with many problems concerning the interpretation of tumor data. A frequently raised question is: "Should certain neoplasms be combined for overall assessment of rodent carcinogenesis data?" NTP policy is that certain neoplasms may be combined for statistical assessment of tumor data and that hyperplastic responses may be used as supportive evidence. The primary reason for combining neoplastic lesions is to gain more insight into the evidence of the carcinogenicity of a given chemical in that species of animal. This report gives the rationale, criteria, and guidelines used by the NTP for combining neoplasms for the evaluation of long-term rodent toxicology and carcinogenesis studies. The guidelines are based mainly on lesions occurring in the F344/N inbred rat and (C57BL/6 X C3H)F1 mouse and may or may not be appropriate for other strains or species. The concepts of combining neoplasms and sites should be viewed in terms of the study as a whole, since tumor formation is only one of many responses caused by chemicals in mammals. The resulting information becomes part of the "weight of the evidence" for estimating the potential hazard of a given chemical.

Abstract  Chronic toxicity of diphenyl and its ability to promote carcinogenesis by N-ethyl-Nhydroxyethylnitrosamine (EHEN) in the kidney, were studied in Wistar rats. In the study of chronic toxicity, diphenyl at doses of 0, 0.25. and 0.5% was given in the diet to Wistar rats of both sexes for 75 weeks. Diphenyl dose-dependently induced urolithiasis, and stones, accompanied by hematuria. were observed in the kidney, ureter, and urinary bladder as early as 16 weeks after the beginning of the experiment. At the dose of 0.5% of diphenyl, the incidence of stones in the kidney and urinary bladder was 46.2 and 15.4%, respectively, in females and 31.9 and 27.7%, respectively, in males. Kidney stones were black and composed of protein, but urinary bladder stones were yellowish-white and composed of ammonium magnesium phosphate. In the promotion experiment, EHEN, at a dose of 0.1%. was given in the diet for 2 weeks as the initiator of carcinogenesis, and then diphenyl, at doses of 0, 0.125, and 0.5% was supplied in the diet for 34 weeks, to male Wistar rats. Neither doses of diphenyl affected the incidences of dysplastic foci and renal cell tumors induced by EHEN in the kidney. However, 0.5% of diphenyl, in spite of inducing urolithiasis, significantly decreased the mean numbers of both dysplastic foci and renal cell tumors per cm2 of the kidney. These results indicated that diphenyl induced urolithiasis but exhibited rather inhibitory effect on the induction of kidney carcinogenesis by EHEN in rats.

Abstract  Carcinogenicity and Chronic Toxicity in Mice and Rats Administered Vinyl Acetate Monomer in Drinking Water: Yumi Umeda, et al. Japan Bioassay Research Center, Japan Industrial Safety and Health Association-Carcinogenicity and chronic toxicity of vinyl acetate monomer (VA) were examined in male and female Crj:BDF1 mice and F344/DuCrj Rats. Groups of 50 mice and 50 rats of each sex were orally administered VA in drinking water containing 0, 400, 2,000 or 10,000 ppm (g/g) VA for 104 wk. Squamous cell tumors were clearly evident in the upper digestive tract of treated mice and rats, and in the larynx of treated mice of both sexes. In mice, squamous cell carcinomas and papillomas were observed in the oral cavity, esophagus, forestomach and larynx of the 10,000 ppm group, together with basal cell hyperplasia, squamous cell hyperplasia and epithelial dysplasia. In rats, incidences of squamous cell carcinomas and papillomas were increased in the oral cavity of the 10,000 ppm group of both sexes, and an esophagus squamous cell carcinoma was observed in a 10,000 ppm female. Pre-neoplastic hyperplasias were also noted. Mapping of the neoplastic and pre-neoplastic lesions in the oral cavity of the 10,000 ppm group revealed that both the lesions occurred predominantly at Level V in mice and at Level VI in rats. A lower confidence limit of a benchmark dose (BMDL10) of 477 mg/kg/d was obtained from a dose-response relationship between combined incidence of squamous cell carcinomas and papillomas in the oral cavity of mice and rats and the estimated daily VA intakes per body weight, and compared with literature values.

Abstract  This study was designed to investigate the possible genotoxic and teratogenic actions of diphenyl (DP), diphenyl ether (DPE), and their eutectic mixture, in a comparative approach including different test systems. Two microbial systems and a metazoan model were used: (1) diploid D7 strain of Saccharomyces cerevisiae; (2) Salmonella typhimurium strains TA100, TA98, TA1535, TA1537, TA1538, TA1532, TA2636; and (3) sea urchins (Paracentrotus lividus and Sphearechinus granularis). Both compounds resulted in severe toxicity in all of test organisms at levels greater than or equal to 10(-5) M (approximately 2 ppm). DP caused genetic effects in yeast with and without activating system, while the two chemicals appeared to be ineffective in Salmonella up to toxic levels. The action of DP and DPE on sea urchins resulted in developmental defects and mitotic abnormalities, following exposure of embryos or by pretreatment of sperm or eggs. In this system DPE appeared to be more effective than DP by about one order of magnitude (minimal active concentrations: 10(-5) M vs 10(-4) M). The eutectic mixture, industrially used as a heat transfer medium, was tested in its virgin and used form, for genotoxicity and embryotoxicity. The latter appeared to be more effective than the virgin eutectic. This increase in the embryo- and genotoxicity of the used eutectic may be related to the appearance of newly formed compounds in the heat transfer process. These compounds have been separated by high-pressure liquid chromatography and detected by fluorimetry.

Abstract  The effects of dietary exposure to sodium L-ascorbate (Na-AsA), butylated hydroxyanisole (BHA), and diphenyl on the development of urinary bladder tumors in a mouse two-stage carcinogenesis model were examined. Male B6C3F1 mice received 0.05% N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in the drinking water for 4 weeks and were then treated with 5% Na-AsA, 1% BHA, or 1% diphenyl for 32 weeks. None of these chemicals enhanced the development of either preneoplastic or neoplastic lesions in the urinary bladder. Furthermore, DNA synthesis levels of urinary bladder epithelium in mice treated with each substance alone for 8 weeks were not elevated significantly, although Na-AsA was associated with a significant increase in the urinary pH value and Na+ concentration. The results indicate that Na-AsA, BHA, and diphenyl do not exert an enhancing influence on mouse bladder carcinogenesis, in clear contrast to the case in the rat.

Abstract  Carcinogenicity and chronic toxicity of biphenyl was examined in the male and female BDF1 mice fed a diet containing biphenyl at 667, 2,000 or 6,000 ppm for 2 years. There was no difference in survival rate between any biphenyl-containing diet-fed group of either sex and the respective control. Body weights of the males and females fed 6,000 ppm diet were significantly lower than the respective control. Incidences of hepatocellular carcinomas and hepatocellular adenomas in the females fed diets containing biphenyl were significantly increased in a dose-related manner, and exceeded a range of the historical control data in the Japan Bioassay Research Center. Incidences of basophilic cell foci in the liver were increased in the females fed 2,000 and 6,000 ppm diets. There was no increase in tumor or tumor-related lesion in the males fed diets containing biphenyl. Chronic toxicity of biphenyl was characterized by increased incidences of urothelial desquamation in the renal pelvis in males and females and mineralization in the inner stripe of renal outer medulla in females, as well as changes in serum levels of BUN, ALP and some electrolytes in males and females. In conclusion, the 2-year oral administration of biphenyl-containing diets induced pre-neoplastic and neoplastic lesions in the liver of females and non-neoplastic lesions in the kidney of males and females. Causative factors for the biphenyl-induced hepatocarcinogenicity were discussed in light of our published finding of peroxisome proliferation.

Abstract  The metabolic conversion of biphenyl to phenolic metabolites was studied in the rat. The metabolites were identified by mass spectrometry and quantified by gas chromatography following conversion to their trimethylsilyl (TMS) ethers. The main route of excretion was via the urine, and the major part (22.3 %) of the biphenyl metabolites was excreted in the first 24 hrs. The total urinary recovery 96 hrs after administration was 29.5 % of the dose and the metabolites detected were conjugates of mono–, di– and tri–hydroxy derivatives of biphenyl as well as the meta– and para–methyl ethers of the catecholic compounds. The two main urinary metabolites were 4–hydroxybiphenyl (7.7 %) and 4,4′–dihydroxybiphenyl (11.4 %). The experiments also showed that biphenyl has to be hydroxylated and then conjugated before it appears in the rat bile. Thus, 5.2% of the dose was found in the 24 hrs bile as conjugates, mainly of 4–hydroxy–, 4,4′–dihydroxy– and 3,4,4′–trihydroxy–biphenyl. Faecal excretion of phenolic biphenyl derivatives was found to be of minor importance, but 4.7 % of the dose was detected during the first 24 hrs after dosing. The following previously undetected metabolites of biphenyl were found: 3,4′–dihydroxy–, 3,4,4′–trihydroxy–, 3,4′–dihydroxy–4–methoxy– and 4,4′–dihydroxy–3–methoxy–biphenyl.

Abstract  A comparative study of the effects of biphenyl and Kanechlor-400 (KC-400) on the respiratory and energy linked activities of rat liver mitochondria was made, and some differences in effects caused by the chlorination of biphenyl were clarified. The inhibition of state 3 respiration with succinate by biphenyl was less than that observed with alpha-ketoglutarate/malate. By contrast, KC-400 exhibited the opposite trend; state 3 respiration with succinate was more sensitive to inhibition than that observed with alpha-ketoglutarate/malate. Thus the inhibition of state 3 respiration with NAD+-linked substrate was decreased, whereas the inhibition of state 3 respiration with succinate was increased by the chlorination of aromatic rings. Biphenyl also instantaneously stimulated state 4 respiration. The extent of stimulation with succinate by biphenyl was larger than with alpha-ketoglutarate-malate. On the other hand, there was about a 1-2 minute lag period before stimulation of state 4 respiration by KC-400 became obvious. Furthermore, state 4 respiration in the presence of alpha-ketoglutarate/malate was more intensely stimulated by KC-400 than by succinate. Biphenyl and KC-400 dissipated the membrane potential across the mitochondrial membranes. The dissipation of membrane potential by biphenyl was instantaneous whereas that caused by KC-400 was preceded by a lag period (1-2 min). Biphenyl and KC-400 altered the permeability properties of mitochondrial membranes as evidenced by the release of endogenous K+. The release of K+ due to biphenyl was instantaneous but KC-400 induced K+-release was preceded by a lag period (1-2 min). Thus membrane perturbation by biphenyl was faster than that induced by KC-400. Therefore, it is clear that the chlorination of aromatic rings delays the perturbation in the state of membrane lipids.

Abstract  Groups of rats were fed biphenyl at various dose levels in a semisynthetic diet and in a commercial chow. The effect levels for induction of polycystic kidney lesions were established by means of urinalysis, organ weight changes, light and electron microscopy, and enzyme histochemistry. The no-effect level, was less than 50 mg/kg bw./day and 300 mg/kg bw./day, when feeding the semisynthetic diet and the commercial chow respectively. This difference in effect level due to the diet is an indication that the diet is of great influence on the results of toxicological experiments.

Abstract  The Toxic Substances Control Act (TSCA) became law on October 11, 1976. The Act authorized EPA to secure information on all new and existing chemical substances, as well as to control any of the substances that were determined to cause unreasonable risk to public health or the environment. The current PCB regulations were published pursuant to this act. Current PCB regulations can be found in the Code of Federal Regulations (CFR) at 40 CFR 761.

Abstract  Reactivities of o-phenylphenol and its metabolites (2,5-dihydroxybiphenyl, 2-phenyl-1,4-benzoquinone) with DNA were investigated by a DNA sequencing technique, and the reaction mechanism was studied by UV-visible and ESR spectroscopies. In the presence of Cu(II), 2,5-dihydroxybiphenyl caused strong DNA damage even without piperidine treatment. Catalase, methionine, and methional inhibited the DNA damage completely, whereas mannitol, sodium formate, ethanol, tert-butyl alcohol, and superoxide dismutase did not. 2,5-Dihydroxybiphenyl plus Cu(II) frequently induced a piperidine-labile site at thymine and guanine residues. The addition of Fe(III), Mn(II), Co(II), Ni(II), Zn(II), Cd(II), or Pb(II) did not induce DNA damage with 2,5-dihydroxybiphenyl. When H2O2 was added, 2-phenyl-1,4-benzoquinone also induced DNA damage in the presence of Cu(II). Cu(II) accelerated the autoxidation of 2,5-dihydroxybiphenyl to quinone. An ESR study revealed that the semiquinone radical is an intermediate of the autoxidation. Catalase had no inhibitory effect on the acceleration by Cu(II). Superoxide dismutase promoted both the autoxidation of 2,5-dihydroxybiphenyl and the initial rate of semiquinone radical production. ESR spin trapping experiments showed that the addition of Fe(III) produced hydroxyl radical during the autoxidation of 2,5-dihydroxybiphenyl, whereas the addition of Cu(II) hardly did so. The results suggest that DNA damage by 2,5-dihydroxybiphenyl plus Cu(II) is due to active species other than hydroxyl free radical.

Abstract  We have previously reported the qualitative results of a major study on 65 pesticides (Waters et al., 1982). Dose information from this investigation (either lowest effective or highest ineffective dose tested) has now been incorporated into a computerized data management system. This report focuses on the qualitative profiles of genetic activity produced by these pesticides and our efforts to classify them according to their genotoxic effects and chemical structures. Three main categories may be distinguished based on the qualitative results: Category 1 pesticides were active in most of the in vitro and in vivo assays employed. These 9 compounds include the structurally similar organophosphate insecticides, acephate, demeton, monocrotophos and trichlorfon; the phthalimide fungicide analogues, captan and folpet; and the thiocarbamate herbicide analogues, diallate, sulfallate and triallate. The 26 Category 2 compounds demonstrated fewer positive results and may be subdivided into two parts, one of which contains 12 halogenated aromatic or heterocyclic ring compounds, including the phenoxy herbicides, 2,4-D, 2,4-DB and 2,4,5-T. The remaining part of Category 2 (14 compounds) consists of structurally similar organophosphate insecticides, azinphos-methyl, crotoxyphos, disulfoton, methyl parathion; three similar ethylenebisdithiocarbamate fungicides, maneb, mancozeb, and zineb; three similar pyrethroid insecticides, allethrin, chrysanthemic acid, and ethyl chrysanthemate; and four structurally diverse compounds, cacodylic acid, dinoseb, sec.-butylamine and benomyl. The third category of 30 pesticides gave negative results in all tests and represents structurally diverse compounds. Using the computerized profile matching methodology, from 2080 possible pairwise chemical combinations of the 65 pesticides, 20 statistically significant pairs were selected, 6 groups of pesticides were identified which were substantially similar to groups of pesticides we had formed previously (Waters et al., 1982) based on genetic activity and chemical structure. The matches showed excellent qualitative and, in most cases, excellent quantitative agreement. Hence it appears that specific patterns of test results present in the genetic activity profiles are related directly to chemical structure. Conversely, the data suggests that certain groups of compounds may be recognized by a well defined series of concordant tests results. As additional data is added, comparison of test results for new chemicals with existing data for known genotoxicants should aid in the evaluation of potential genetic health hazards.

Abstract  An in vitro assay has been developed to detect DNA damage and repair following chemical treatment of human diploid fibroblasts. DNA damage is measured by following the Escherichia coli DNA polymerase I-catalyzed incorporation of radiolabeled deoxycytidine triphosphate (dCTP) into the DNA of lysolecithin-permeabilized cells. DNA strand breaks with free 3' OH termini serve as template sites for incorporation, and decrease of this incorporation with time, following removal of the test chemical, indicates loss (repair) of initial damage. Inhibition of the DNA excision repair process by the addition of the repair inhibitors arabinofuranosyl cytosine (ara-C) and hydroxyurea (HU) during the incubation period gives rise to an increased number of template sites, manifesting itself in increased incorporation and indicating the induction of long-patch excision repair. This nick translation assay, originally proposed by Nose and Okamoto [1983], is very sensitive, allows detection and quantitation of both DNA damage and repair, distinguishes between various types of induced damage, does not require radioactive prelabeling of cells, and circumvents some of the problems inherent in unscheduled DNA synthesis (UDS) assays. The assay is also useful in detecting those agents that inhibit replicative DNA synthesis and/or the excision repair process. Results presented demonstrate that all 14 direct-acting carcinogens tested and 8 of 14 carcinogens requiring metabolic activation give positive indication of DNA damage, repair, or both. Eleven of 14 noncarcinogens tested were scored as negative, the other 3 having previously been shown to interact with cellular DNA. This assay is shown to have predictive capability at least equal to that of UDS assays but to allow a broader spectrum of genotoxic effects to be analyzed.

Abstract  The filter elution method used for the detection of DNA strand breaks has been modified to quantitate chemically induced DNA repair which is measured as unscheduled DNA synthesis (UDS) in suspension of freshly isolated rat hepatocytes. Our method is based on DNA purification by retention on polyvinyl chloride filters, and is capable of handling a large number of samples simultaneously. By using the present assay system, positive dose-dependent UDS data was obtained on the following carcinogens: aflatoxin B1, 2-acetylaminofluorene, 4-aminobiphenyl, 2-aminofluorene, methyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, and 4-nitroquinoline-1-oxide. In contrast, non-carcinogenic biphenyl, fluorene, and sodium ascorbate did not elicit any detectable levels of UDS at all concentrations tested. Thus, UDS as measured by the present filter retention method may serve as an efficient and reliable means of screening chemical mutagens/carcinogens.

Abstract  Tissue distribution of UDP-glucuronyltransferase was investigated using two substrate groups which were shown to be conjugated by two different forms of this enzyme in previous studies with rat liver. These enzyme forms were found to be differentially inducible by 3-methylcholanthrene (form 1) and phenobarbital (form 2). Group 1 substrates (conjugated by form 1) include 1-naphthol, N-hydroxy-2-naphthylamine and 3-hydroxybenzo[a]pyrene; group 2 substrates (conjugated by form 2) comprise 4-hydroxybiphenyl, morphine and chloramphenicol. Group 1 substrates are conjugated in a number of tissues, for example, liver, kidney, small intestinal mucosa, lung, skin, testes and spleen. However, conjugation of group 2 substrates is detectable only in liver and intestine to an appreciable extent. It is concluded that enzyme(s) efficient in the conjugation of group 1 substrates is ubiquitous in the investigated organs, whilst only liver and intestine possess enzyme(s) efficient in the conjugation of group 2 substrates. In contrast to 3-hydroxybenzo[a]pyrene, benzo[a]pyrene 7,8-dihydrodiol cannot be clearly associated with only one of the 2 substrate groups. Glucuronidation of benzo[a]pyrene 7.8-dihydrodiol is enhanced by both phenobarbital and 3-methylcholanthrene in liver. Conjugation of the dihydrodiol is detectable in all tissues examined. However, enzyme activity towards the dihydrodiol is much lower than that towards 3-hydroxybenzo[a]pyrene. It is disproportionately low with skin microsomes.

Abstract  Chemicals can increase carcinogenic risk by either directly damaging DNA or increasing cell replication or they can do both. These effects have different implications for a biologically-based extrapolation from rodent bioassays to humans. 2-Acetylaminofluorene (2-AAF) administered at low doses to mice for a lifetime has a different dose-response for the liver (approximately linear) compared to the urinary bladder (apparent no effect dose of 45 ppm with a sigmoidal dose response at 60-150 ppm), which can be explained if carcinogen metabolism, DNA adduct formation and cell proliferation effects are considered. In contrast to 2-AAF and other genotoxic chemicals, chemicals which form calculi in the urine do not generally damage DNA directly but increase cell proliferation dramatically by eroding the bladder surface, leading to regenerative hyperplasia. This occurs only at doses at which calculi form; lower doses do not produce calculi and, therefore, do not increase cell proliferation or cause tumors. Extrapolation to humans from the rodent bioassay should be dependent on dose requirements for formation of calculi rather than any type of statistical extrapolation to lower doses. Saccharin and other sodium salts administered at high doses to rats also produce bladder cancer by increasing cell proliferation. These salts do not affect mice, hamsters, guinea pig or monkeys. Based on dose and mechanistic considerations, saccharin and these other sodium salts are unlikely to be human carcinogens. Extrapolation to possible human cancer risk requires biological determinations rather than simply using statistical formulations.

Abstract  ortho-Phenylphenol (OPP) is a widely used fungicide and antibacterial agent that is also known to be highly effective in inducing bladder tumors in male F344 rats. At present, neither the role of the urinary bladder in the bioactivation of OPP metabolites nor the nature of the molecular target is understood. To address these issues, we investigated the relationship between OPP dosage and macromolecular adduct formation in the urinary bladder of male F344 rats. Male F344 rats were treated with 0, 15, 50, 125, 250, 500, 1000 mg/kg of OPP and its radiocarbon analogue via oral gavage. The dosed rats were euthanized after 24 h, and the proteins were extracted from the liver, kidney, and bladder. The amount of radioactivity associated with the extracted protein was quantified using highly sensitive accelerator mass spectrometry. Protein binding in liver and kidney exhibited a linear or modest curvilinear relationship over the dose range studied. In the urinary bladder, however, a pronounced nonlinear relationship between protein adduct levels and administered dose was observed. The measured protein adduct levels were in agreement with the predicted concentrations of phenylbenzoquinone based on a proposed mechanism involving free phenylhydroquinone autoxidation in the urine. Unlike protein binding, DNA adducts measured from the same bladder samples did not show a significant difference from the control group. These data are consistent with the hypothesis that OPP is an indirect acting carcinogen, and that regenerative hyperplasia due to OPP-metabolite cytotoxicity and/or binding of OPP metabolites to protein targets may play an important role in OPP-induced bladder carcinogenesis.

Abstract  The liver represents one of the major sites of human glucuronidation. Many therapeutic drugs are substrates for UDP-glucuronosyltransferases (UGT) leading to the formation of usually inactive glucuronides. Hepatic glucuronidation undergoes significant changes during fetal and neonatal development requiring age adapted drug therapy. Regulation of individual UGT genes during hepatic development has not been defined.

Expression of 13 UGT genes and glucuronidation activities were analysed in 16 paediatric liver samples (aged 7-24 months), two fetal samples, and 12 adult liver samples (aged 25-75 years) using duplex reverse transcription-polymerase chain reaction, western blot, and specific catalytic UGT activity assays.

No UGT transcripts were detected in fetal liver at 20 weeks' gestation. In contrast, UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B4, UGT2B7, UGT2B10, and UGT2B15 transcripts were present without variation in all 28 hepatic samples after six months of age. Significantly lower expression of UGT1A9 and UGT2B4 mRNA was identified in paediatric liver. Hepatic glucuronidation activity in children aged 13-24 months was found to be lower than in adults for ibuprofen (24-fold), amitriptyline (16-fold), 4-tert-butylphenol (40-fold), estrone (15-fold), and buprenorphine (12-fold).

An early phase characterised by the appearance of UGT gene transcripts and a later phase characterised by upregulation of UGT expression is demonstrated during human hepatic development. The differential regulation of UGT1A9 and UGT2B4 expression extends beyond two years of age and is capable of influencing hepatic glucuronidation of common therapeutic drugs in children. The development of hepatic UGT activities is significant for paediatric drug therapy and the prevention of adverse drug effects.

Abstract  2-Aminobiphenyl (2-ABP), 3-aminobiphenyl (3-ABP) and 4-aminobiphenyl (4-ABP), but not benzidine (Bz) and biphenyl (Bp), were found to be inhibitory to the growth of human intestinal bacteria Bifidobacterium infantis ATCC 15697, B. bifidium ATCC 11863, Clostridium perfringens ATCC 13124, Escherichia coli ATCC 25922, E. coli ATCC 35218, Enterobacter cloacae ATCC 13047 and Salmonella typhimurium TA98, TA100, YG1041 at 10-200 microg/ml in culture broth. Bacteroides distasonis ATCC 8503, B. fragilis ATCC 25285, B. theataiotaomicron ATCC 29741, C. paraputrificum ATCC 26780, C. clostridiiforme ATCC 25537, Lactobacillus acidophilus ATCC 4356 and Enterococcus faecium ATCC 19434 were not inhibited by the above mentioned compounds in concentrations up to 200 microg/ml. The Ames Salmonella/microsome assay was employed to test the mutagenicity of the above-mentioned compounds using strains TA98 and TA100 in the presence and absence of Aroclor 1254-induced rat S9 mix. It was found that 4-ABP was mutagenic to both TA98 and TA100, and Bz was mutagenic to TA98 in the presence of rat S9 mix. 2-Aminobiphenyl, 3-ABP, and Bp were not mutagenic to both strains tested. 2-Aminobiphenyl and 3-ABP are chemical isomers of 4-ABP and are as strong as 4-ABP in inhibiting the growth of intestinal bacteria but not as mutagenic as 4-ABP. Evidence suggested that the mechanism of growth inhibition is not involved with the interaction of DNA that causes mutations, but rather on the electron transport system of these organisms.

Abstract  This position paper delineates the expert recommendations of the Regulatory Affairs Committee of the American Society for Veterinary Clinical Pathology for the use of preclinical, clinical pathology endpoints in assessment of the potential for drug-induced hepatic injury in animals and humans. Development of these guidelines has been based on current recommendations in the relevant preclinical and human clinical trial literature; they are intended to provide a method for consistent and rigorous interpretation of liver-specific data for the identification of hepatic injury in preclinical studies and potential liability for hepatic injury in human patients.

Abstract  The aim of this study was to determine the possible genotoxic effects of biphenyl (E230), which is used as an antimicrobial agent in food by using sister chromatid exchanges (SCEs), chromosome aberrations (CAs), and micronucleus (MN) tests in human peripheral lymphocytes. The human peripheral lymphocytes were treated with four concentrations of biphenyl (10, 30, 50, and 70 microg/mL) for 24- and 48-h treatment periods. In the present study, biphenyl significantly increased the frequency of SCEs, CAs, and the frequency of MN when compared with both untreated control and solvent (dimethyl sulfoxide) control. The inductions of these abnormalities were in a dose-dependent manner. Biphenyl was capable to induce the structural CAs instead of numerical CAs. Biphenyl also showed a cytotoxic effect by decreasing the replication index at the highest two concentrations for 48 h and nuclear division index at the highest two concentrations for the 24- and 48-h treatment periods. However, biphenyl did not affect the mitotic index (MI).