Controlling the atomic distribution in PtPd nanoparticles: thermal stability and reactivity during NO abatement.

In situ X-ray absorption spectroscopy and mass spectrometry measurements were employed to simultaneously probe the atom specific short range order and reactivity of Pd and PtPd nanoparticles towards NO decomposition at 300 °C. The nanoparticles were synthesized by a well controlled, eco-friendly wet chemical reduction of metal salts and later supported on activated carbon. Particularly for the bimetallic PtPd samples, distinct atomic arrangements were achieved using a seeding growth method, which allowed producing a random nanoalloy, or nanoparticles with Pt- or Pd-rich core. X-ray photoelectron spectroscopy, transmission electron microscopy, and X-ray diffraction provided additional insights on their electronic, morphological and long range order structural properties. The results revealed that the higher the thermal induced atomic migration observed within the nanoparticles during thermal treatments, the least were their reactivity for NO abatement.

Charge transfer effects on the chemical reactivity of Pd(x)Cu(1-x) nanoalloys.

This work reports on the synthesis and characterization of PdxCu1-x (x = 0.7, 0.5 and 0.3) nanoalloys obtained via an eco-friendly chemical reduction method based on ascorbic acid and trisodium citrate. The average size of the quasi-spherical nanoparticles (NPs) obtained by this method was about 4 nm, as observed by TEM. The colloids containing different NPs were then supported on carbon in order to produce powder samples (PdxCu1-x/C) whose electronic and structural properties were probed by different techniques. XRD analysis indicated the formation of crystalline PdCu alloys with a nanoscaled crystallite size. Core-level XPS results provided a fingerprint of a charge transfer process between Pd and Cu and its dependency on the nanoalloy composition. Additionally, it was verified that alloying was able to change the NP's reactivity towards oxidation and reduction. Indeed, the higher the amount of Pd in the nanoalloy, less oxidized are both the Pd and the Cu atoms in the as-prepared samples. Also, in situ XANES experiments during thermal treatment under a reducing atmosphere showed that the temperature required for a complete reduction of the nanoalloys depends on their composition. These results envisage the control at the atomic level of novel catalytic properties of such nanoalloys.

Further arguments in favour of direct covalent binding of Ochratoxin A (OTA) after metabolic biotransformation.

Ochratoxin A (OTA) is nephrotoxic to all animal species, carcinogenic for rats and mice and probably implicated in human Balkan endemic nephropathy and the associated urothelial tract tumour. Controversial results concerning genotoxicity and biotransformation of OTA have been generated. By (32)P post-labelling technique, a dose- and time-dependent DNA adduct formation is observed in vivo and in vitro. Use of several inducers or inhibitors of biotransforming enzymes (including cytochrome P 450, cyclooxygenase, lipoxygenase, glutathione-S-transferase), demonstrated that OTA is biotransformed into genotoxic derivatives damaging for DNA. Authentic C8dG-OTA standards have been synthesized by photo-oxidation. Both of them (C-C8 & O-C8) co-migrate on TLC with two adducts formed by in vitro incubation of OTA in the presence of kidney microsomes, and in vivo in kidney of pig or rodent fed OTA as well as in kidney and bladder tumour of humans exposed to OTA. Several OTA metabolites have been isolated from tissues or cells treated by OTA. The open ring lactone (OP-OTA) and quinone OTA (OTQ) are genotoxic.

New data on the occurrence of ochratoxin A in human sera from patients affected or not by renal diseases in Tunisia.

Ochratoxin A is often found in the sera of people exposed to this mycotoxin in their food (cereals such as barley, coffee, wines, fruit juices, spices, products of animal origin such as pig and poultry offal). Ochratoxin A is suspected of playing a role in the Balkan Endemic Nephropathy, a nephropathology described in Balkan areas where ochratoxin A is often found in cereals and in pork-derived products. In North Africa like Tunisia where high incidence of chronic interstitial nephropathies of unknown aetiology are pointed out, the involvement of ochratoxin A was suspected but contradictory studies on the degree of human exposure did not succeed in evidencing the role of ochratoxin A. In the present work, sera from 47 volunteers hospitalised for nephropathic damages including bladder tumours (21 people), and from 62 patients hospitalised for disorders other than nephropathic ones, were analysed for ochratoxin A contents. The determination of ochratoxin A in sera was done by a validated immunoaffinity-HPLC method. Sera from unaffected population exhibited percentages of 74.2%, 22.6% and 3.2% containing ranges of ochratoxin A as <0.10-0.5 microg/l, 0.51-1.0 microg/l and above 1.0 microg/l respectively. For patients affected with renal diseases, percentages were 59.5%, 25.5% and 14.9% on the same ranges of ochratoxin A levels respectively. The average ochratoxin A concentration for patients with urinary tract disease excluding cancer patients was 0.99+/-1.28 microg/l while that for the non-nephropathic patients was 0.53+/-1.00 microg/l. However the average levels in the cancer patients was only 0.26+/-0.20 microg/l. Those results are in line with most of previously published works and did not confirm very high ochratoxin A contents found in other reports from same regions.

Implication of nitro group reduction in the mutagenic and chromosome damaging activities of 22 new 5-nitroisoquinolines by the Salmonella mutagenicity test and the cytokinesis-blocked micronucleus assay.

The mutagenic (MUT) and chromosome-damaging (CHR) activities of 22 potential antimalarial drugs (5-nitroisoquinoline derivatives) were evaluated by the Salmonella test and the cytokinesis-blocked micronucleus assay (CBMN). The Salmonella mutagenicity test was performed with and without metabolic activation (S9 mix) in S. typhimurium strains TA100 and YG1042 (an overproducing nitroreductase and O-acetyltransferase TA100 strain). The CBMN was carried out on human lymphocytes without metabolic activation. Four concentrations were tested: 1, 10, 100 and 1000 ng/ml. MUT was expressed as minimal mutagenic concentrations (MMC, microM) and CHR was expressed as minimal chromosome-damaging concentrations (MCDC, nM) to compare both activities. All the 5-nitroisoquinoline compounds were mutagenic in TA100. MMC ranged from 0.1 to 52.9 microM in TA100. A statistically significant decrease in MMC was observed in YG1042 (8 x 10(-3) to 3.5 microM), implicating reduction of the nitro group. Modulation of MUT by S9 mix was not significant in TA100 and YG1042. CHR was detected in 13 products for at least one concentration. Among the chromosome-damaging compounds, the MCDC ranged from 2.9 x 10(-3) to 3.6 nM. No relationship was found between MUT and CHR, suggesting two distinct pathways of DNA damage.

Development and validation of a new bitumen fume generation system which generates polycyclic aromatic hydrocarbon concentrations proportional to fume concentrations.

Bitumen fumes emitted during road paving and roofing contain polycyclic aromatic compounds (PACs) of potential health concern. Little information is available for an experimental device devoted to inhalation experiments with animals exposed to bitumen fumes, and in all studies the systems were never validated for a range of fume concentrations, which prohibited their use for toxicological concentration-effect studies. Therefore, the purpose of this study was to validate a new experimental device able to generate bitumen fumes at different total particulate matter (TPM) concentrations with a linear correlation between TPM and the concentrations of different PACs, thus allowing toxicological dose-response studies with fumes representative of those in the field. Atmosphere samples collected from an animal exposure chamber allowed the determination of TPM, toluene soluble matter, polycyclic aromatic hydrocarbons (PAHs) and semi-volatiles. The particulate size distributions were determined in order to assess the deposition pattern in the respiratory tract. The temperature of 170 degrees C was chosen by analogy with the upper range of the temperature used during paving operations. The temperature of the air passing over the fume emission area was regulated to 20 degrees C and stirring of the heated bitumen was restricted to 90 r.p.m. The data show that the objective of developing a static fume generation system that reproducibly produces fumes in the inhalation chamber for specified target concentrations (TPM) were successful. The within-day variation coefficients for TPM were between 2.5 and 6.1%. The day-to-day variations for TPM concentration were between 4.1 and 5.8%. The concentrations of the 4-5 ring PAHs and the polycyclic aromatic sulphur heterocycles were proportional to the TPM concentration. The 2 and 3 ring PAH concentrations showed a deviation from proportionality with the TPM, probably due to their re-evaporation during sampling. The mass median aerodynamic diameter of airborne particles varied from 1.4 micro m at a fume concentration of 5 mg/m(3) to 3.2 micro m at 100 mg/m(3). In conclusion, this equipment was suitable for nose-only inhalation studies in the 5-100 mg/m(3) range of TPM. Bitumen fumes were generated with a good reproducibility under well-controlled conditions. Finally, the PAH profiles from atmospheric samples were in good agreement with those measured during road paving.

Balkan endemic nephropathy and associated urinary tract tumours: a review on aetiological causes and the potential role of mycotoxins.

A series of publications in the 1950s described a kidney disease in Bulgaria, the former Yugoslavia and Romania that became known as Balkan endemic nephropathy (BEN). The disease was qualified by World Health Organisation (WHO) experts as 'progressive and very gradually developing renal failure with insidious onset.... The last stage shows marked fibrosis...'. BEN is characterized by tubular degeneration, interstitial fibrosis and hyalinization of glomeruli accompanied by enzymuria and impaired renal function without nephrotic syndrome. Later, an association between BEN and tumours of the kidney pelvis and ureter was recognized, so that the problem of BEN became not only nephrological, but also oncological. There may also be an association with increased urinary bladder cancer incidence, although many confounding factors may interfere in the analysis of data for this organ. In view of the very intimate association between BEN and the urinary tract tumours (UTT), the term 'endemic uropathy' has been proposed. Several hypothesis concerning the aetiology of these diseases has been investigated, which include: predisposing genes factors, environmental factors (heavy metals, minerals, bacteria, leptospira, viruses, fungal toxins and, most recently, pliocene lignites). This paper reviews the different hypotheses about the aetiology of endemic uropathy and pays particular attention to the role of fungal toxins.

Bitumen fumes: review of work on the potential risk to workers and the present knowledge on its origin.

Bitumens fumes contain polycyclic aromatic compounds (PAC). There is a possibility of long-term health effects following chronic exposure by inhalation or skin contamination in asphalt road pavers and highway maintenance workers. Epidemiological and experimental studies on this topic are reviewed and the possible causes of cancer discussed with a primary focus on heterocyclic polyaromatic compounds. In 2001, the results of the IARC epidemiological study confirmed an excess of lung cancer despite a lower cancer mortality. In vitro genotoxicity and mechanistic studies demonstrated a mutagenic effect of bitumen fume condensates (BFC) and some data suggested that the polycyclic aromatic hydrocarbons (PAH) analysed were not the major genotoxic compounds in bitumen fume condensates. Other compounds such as nitrogen-, sulfur- and/or oxygen-containing PAH or their alkyl substituted analogues, mutagenic in the Ames mutation assay, may be involved in the genotoxic effect of BFC. After skin painting with BFC, DNA adducts were found in skin, lung and lymphocytes of all the treated animals. Differences in the adduct patterns were also observed, but a more polar adduct was common to the three tissues and not observed in those from rats treated with coal-tar fume condensates (CTFC). Rat inhalation experiments with bitumen fumes confirmed the presence of a DNA-adduct in the lungs with the same Rf as the previous polar adduct. This adduct therefore merits further investigation as a potential biomarker in lymphocyte DNA to follow exposed workers. All the analytical data and the mechanistic data are complementary and suggest the potential role of thiophenes in the genotoxicity of bitumen fumes. Some thiophenes have lower mutagenic activity than their isosteric PAH, whereas others are very potent carcinogens. Generally, the sulfur analogues of PAH (SPAH) in bitumen fumes have a higher concentration than the PAH of similar molecular weight, whereas the SPAH in coal-tar fumes have a much lower concentration than the corresponding PAH. This may explain why the more polar adducts have been detected only in animals exposed to bitumen fume. In a skin carcinogenicity study of condensed asphalt roofing fumes, it has been demonstrated that the most active fractions were those containing a variety of aromatic SPAH. In conclusion to this review, there is an interest in determining the chemical identity of the major DNA adducts induced by BFC. This would allow experimental studies on the carcinogenic potency of these compounds and their validation as potential biomarkers. These compounds could thus merit further analytical investigation in preference to the PAH included in the list of the US Environmental Protection Agency that are currently being analysed by the industry in field studies.

The induction and persistence of altered sphingolipid biosynthesis in rats treated with fumonisin B1.

The fumonisins produced by Fusarium spp. are carcinogenic in rodents and possibly carcinogenic to humans. One action of fumonisins is to inhibit the enzyme ceramide synthase and as a consequence disrupt de novo sphingolipid biosynthesis. Measurement of the ratio of sphinganine (Sa) to sphingosine (So) in urine, serum and tissues has thus been made in various animal species as a marker of exposure to this mycotoxin. In this study in male BDIV rats, the effect of increasing daily gavage doses (0.01-5 mg/kg b.w.) of fumonisin B1 (FB1) on the Sa/So ratio in various tissues and urine was examined as was the persistence of the effects after cessation of treatment. The lowest dose of FB1 which induced an alteration of Sa/So in any tissue was 1 mg/kg b.w. The tissue most affected was the kidney, with the liver affected to a much lesser extent and the lung and oesophagus not at all. Only a modest indication of an alteration in Sa/So ratio was obtained in the urine. The large interindividual variations in urinary Sa and So in this strain of rat, even in the absence of FB1 treatment, made interpretation of these data difficult. After cessation of treatment, the Sa/So ratio returned to normal in kidney after a period of 1-3 weeks. These data suggest that altered Sa/So ratios reflect recent exposure to FB1 in the rat.

Inhalation study on exposure to bitumen fumes. Part 1: Development and validation of the equipment.

Bitumen fumes emitted during road paving or roofing contain polycyclic aromatic hydrocarbons (PAHs). Experimental studies have been previously performed to test the carcinogenic potency of bitumen fumes. Some of them have been criticised either on the grounds that the fume condensates were not representative of fumes to which humans are exposed or because the fumes were never characterised in terms of particle size and poorly in terms of composition and concentration in the chambers. For a nose-only inhalation study, we have evaluated the ability of a new fume generation system to deliver stable and reproducible atmospheres of bitumen fumes to an inhalation chamber and investigated the representativity of the fumes generated at a concentration level of 5 mg/m3. The fume generator comprises: (1) an insulated 20 l heated kettle (200 degrees C for bitumen); (2) an insulated inlet pipe with a needle valve to adjust the flow of the test compound from the kettle; (3) a fume generation chamber equipped with a series of interchangeable channels of different width. The fume concentration in the exposure chamber can be controlled by changing the channel width or by restricting the evaporation surface with aluminium foil, and/or by changing the flow rate. Samples of the atmosphere in the chamber were collected and analysed for quantitative determination of total particulate matter (TPM), soluble matter, benzo[a]pyrene (B[a]P) content of the fumes and other PAHs, and evaluation of the particle size distribution. The representativeness of the fumes has been tested by comparison with fumes generated in the Shell small-scale fume rig, which was previously validated against field fumes collected during paving operations. Evaporative losses from the filters during sampling, transport and storage have been also assessed. At 5 mg/m3 TPM, the agreement between laboratories was quite good for the TPM analyses and was good for the soluble matter and B[a]P. Evaporative losses may lead to underestimation of the true exposure level in the inhalation chambers but the use of an XAD-2 cartridge backup is one approach to partially recover losses which occur on the filter. The particle size distributions are somewhat different from those reported for fumes associated with roofing and indoor mastic laying works, in that we found more than 85% of particles to be smaller than 1 micron, compared with 40% particles in the previous analyses. In conclusion, this equipment allows reproducible generation of fumes at the 5 mg/m3 TPM that are fairly representative of those produced in the field with the same bitumen.

Inhalation study on exposure to bitumen fumes. Part 2: Analytical results at two exposure levels.

During the hot application of bitumen-containing materials, e.g. in road paving or roofing, fumes are emitted that contain traces of polycyclic aromatic compounds (PACs). Although worker's exposure to these fumes is low, it might lead to health problems. For studying DNA adduct formation as a consequence of inhalation of bitumen fumes we developed and validated an inhalation system (a dynamic fume generator plus a nose only inhalation chamber). This paper presents and discusses the analytical results from the different laboratories involved in this study on the fumes sampled in the inhalation chamber during three series of experiments where the animals were exposed to fumes at the 5 mg/m3 and 50 mg/m3 level, coming from bitumen heated at 200 degrees C and, as a positive control, fumes from coal tar, heated to 110 degrees C at the 5 mg/m3 level. The following parameters were controlled: temperatures at different key places in the generator; humidity of the chamber; the bitumen or coal tar flow rate; and Total Particulate Matter (TPM). Analyses were performed for Benzene Soluble Matter (BSM), the EPA polycyclic aromatic hydrocarbon (PAH) mixture and for a number of heteroatom-containing PACs. The data show that the coal tar fumes produced at 110 degrees C were very volatile and that most of the differences in particulate matter found between the laboratories can be attributed to evaporative losses. The bitumen fumes boil 25-50 degrees C higher and contain higher boiling compounds. A comparison is made between the PAC exposure profiles for bitumen experiments aimed at 5 and 50 mg/m3. Although the same molecules are found in both fumes their proportion is dramatically different. This effect is largest with the 2- and 3-ring PACs, the ratio of the concentrations found in the 50 mg/m3 TPM concentration to that in the 5 mg/m3 experiment gradually declines from 5500 for acenaphthene to 500 for pyrene, for the 5-ring PACs this ratio is 20-30. As function of their vapour pressure, the ratios of the concentrations of the hetero PACs follow the same trend as that of the 16 EPA PAHs and are of the same order of magnitude. In conclusion, for the compounds investigated, the equipment delivers a fume atmosphere in a reproducible manner. The 50 mg/m3 bitumen fumes are not representatives of field fumes. The reason for these quantitative differences is unclear and further work would be needed to clarify this. Nevertheless it was felt that these fumes at 50 mg/m3 might be a useful tool for qualitative detection of DNA adducts in an animal exposure study.

Activation of mitogen-activated protein kinase by fumonisin B(1) stimulates cPLA(2) phosphorylation, the arachidonic acid cascade and cAMP production.

Activation of mitogen-activated protein kinase (MAPK) results in pleiotropic effects such as modulation of the transcription and activation of enzymes involved in signal transduction. One such enzyme is the cytoplasmic phospholipase A(2) (cPLA(2)), which releases arachidonic acid (AA). AA is the precursor of prostaglandins and leukotrienes, two inflammatory mediators, which regulate gene expression and protein kinase (PK) activity. Fumonisin B(1) (FB(1)) was shown to increase PKC translocation and stimulate MAPK. We have investigated the effect of FB(1) on the AA cascade in a human epithelial cell line and the signal transduction pathway regulating PLA(2) activation. We observed that FB(1) stimulated cPLA(2) activity and increased AA release by a mechanism independent of PKC activation and that the activation of cPLA(2) is a two-step process: the first is phosphorylation of cPLA(2) by MAPK; the second is a consequence of the increase in sphingosine inside and outside the cells after 2 h, which is known to induce a rise in intracellular free calcium. Overall, this suggests that the effect of FB(1) on cells is partially dependent on the action of FB(1) on the enzymes involved in the cell cycle, such as MAPK and PKA, and on bioactive fatty acids, such as the prostaglandins and leukotrienes, and also on disruption of sphingolipid metabolism. In addition, we have observed down-regulation of cPLA(2) activity and AA metabolism by a mechanism involving prostaglandin production, cAMP synthesis and PKA activation.

Standardization and validation of DNA adduct postlabelling methods: report of interlaboratory trials and production of recommended protocols.

The aim of this project was to devise and test improved protocols of the 32P-postlabelling assay for the detection of carcinogen-DNA adducts. The intention was to reverse the drift of different investigators using increasingly divergent experimental conditions. This would lead to a more standardized assay that can be used in future applications by different investigators for the monitoring of human exposure to genotoxic agents, permitting more meaningful comparisons between different studies or between different participants in the same study. As part of this process, there was perceived to be a need for carcinogen-modified DNA standards of known levels of adducts for use as positive controls, as standards for normalization of results with unknown samples and to assist interlaboratory comparisons. The preparation of characterized DNA standards modified by benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH), 4-aminobiphenyl (ABP), an aromatic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic amine, and N-methyl-N-nitrosourea (MNU), a methylating agent yielding DNA containing O6-methylguanine, was carried out. A critical appraisal of all aspects of the 32P-postlabelling procedure and investigations to examine the influence of a number of key variations on the assay were conducted. There followed testing of a consensus protocol in a first interlaboratory trial involving 25 participants in Europe and the USA, conducted on the prepared synthetic DNA standards, the assessment of interlaboratory variability and the reasons for it. Revision of the protocols was followed by further testing in a second interlaboratory trial in which liver DNA from mice treated with BaP or ABP were assayed together with the synthetic DNA standards. Adduct levels were found to be significantly lower by 32P-postlabelling than by 3H incorporation. A recommended set of procedures has been developed for the detection and quantitation of DNA adducts formed by PAHs, aromatic amines and methylating agents. These trials have led to a much clearer idea as to what are the critical features and procedures of the 32P-postlabelling assay and there is a set of standard DNA samples for use in quality control and against which biological samples can be normalized. Use of these standards and procedures has reduced interlaboratory variability in quantitation of DNA adducts.

Sex- and strain-specific expression of cytochrome P450s in ochratoxin A-induced genotoxicity and carcinogenicity in rats.

Ochratoxin A (OTA), a nephrotoxic and carcinogenic mycotoxin, is implicated in the etiology of Balkan endemic nephropathy (BEN), a chronic disease affecting populations in the Balkans. Patients suffering from Balkan endemic nephropathy, urinary-tract tumors, or both are more frequently extensive metabolizers of debrisoquine than persons unaffected by these conditions. As shown previously (Castegnaro et al., Int J Cancer, 77:70-75, 1998), OTA induction of renal tumors is markedly sex- and strain-specific in Dark Agouti (DA) and Lewis rats, with DA males being most responsive and DA females being resistant; only DA females were phenotyped as slow debrisoquine metabolizers. Formation of OTA-related DNA adducts in the kidney was closely correlated with renal carcinogenicity. To elucidate the critical biotransformation enzymes involved in OTA genotoxicity and carcinogenicity, the expression of cytochrome P450s (CYPs) 1A, 2A, 2B, 2C, 2D, and 3A in the kidney and liver microsomes of untreated and OTA-treated DA and Lewis rats (both sexes) was determined by western blot analysis. Chronic OTA treatment was found to modify CYP expression in kidney and liver. In the animals most susceptible to renal OTA carcinogenicity and DNA adduct formation, the OTA-toxifying isoforms (CYPs 2C11, 1A2, and 3A) were highly expressed in the liver, and little of the OTA-detoxifying isoforms (CYPs 1A1 and 2A) was detected. CYP2D was not expressed in DA rats and therefore is not involved in these phenomena. Our results confirm that the strain- and sex-specific genotoxic response of OTA is controlled, in part, by CYP-mediated metabolic reactions that convert OTA into DNA-reactive intermediates.

Formation of DNA adducts in tissues of mouse progeny through transplacental contamination and/or lactation after administration of a single dose of ochratoxin A to the pregnant mother.

Ochratoxin A (OTA) is a mycotoxin which has been detected in foods of plant origin, in edible animal tissues, and in human sera, urine, and milk in many countries. OTA is nephrotoxic and carcinogenic in mice and rats and is suspected to play a key role in the etiology of Balkan endemic nephropathy and/or associated urinary tract tumors. In the present study, some early signs of genetic impairment, including the presence of DNA adducts in target tissues from the progeny of mice after administration of a single OTA dose during late pregnancy, have been investigated. By the 32P-postlabeling method, several characteristic DNA adducts with the same Rf values were detected in kidney and liver of both the OTA-treated mice and their progeny the fetus and the offspring. No adduct was found in tissues from control animals. Different adducts were most important in kidney and liver DNA and some were organ-specific. High levels of DNA adducts were detected in the kidneys of male progeny, whereas in the female progeny and the mothers they were detected almost exclusively in the liver. This result correlates well with the carcinogenicity in mice: the target organ for males is the kidney, while for females it is the liver. High levels of DNA adducts were also found in fetuses. These results provide evidence for a direct genotoxic action of OTA in the progeny through transplacental contamination, which constitutes a new serious health hazard of exposure to this toxin.

Chemical degradation of wastes of antineoplastic agents amsacrine, azathioprine, asparaginase and thiotepa.

As a part of a program devoted to the destruction of antineoplastic agents, three chemical methods readily available in the hospital environment, viz. oxidation with sodium hypochlorite (NaClO, 5%), hydrogen peroxide (H2O2, 30%), and Fenton reagent (FeCl2.2H2O; 0.3 g in 10 ml H2O2, 30%), were tested for the degradation of four anticancer drugs: Amsacrine, Azathioprine, Asparaginase and Thiotepa. The efficiency of the degradation was monitored by high-performance liquid chromatography. The mutagenicity of the degradation residues were tested by Ames test using tester strains Salmonella typhimurium TA 97a, TA 98, TA 100 and TA 102 with and without an exogenous metabolic activation system. Using sodium hypochlorite, 98.5% of Amsacrine, 99.0% of Azathioprine, 99.5% of Asparaginase and 98.7% of Thiotepa were destroyed after 1 hr. The hydrogen peroxide treatment destroyed 99% of Asparaginase and 98.7% of Thiotepa in 1 hr. However, this procedure was not efficient for the treatment of Amsacrine (28% after 16 hr) and of Azathioprine (53% degradation in 4 hr). The action of Fenton reagent resulted in the destruction of 98% of Amsacrine, and 99.5% of Azathioprine, 98.5% of Asparaginase and 98.7% of Thiotepa in 1 hr. In all cases where a high degree of degradation was achieved, the residues obtained weee non mutagenic.

Sex- and strain-specific induction of renal tumors by ochratoxin A in rats correlates with DNA adduction.

Ochratoxin A (OTA), a nephrotoxic and carcinogenic mycotoxin, has been implicated as an etiologic agent in the Balkan endemic nephropathy (BEN), a chronic disease affecting populations in the Balkans. Compared with unaffected individuals, patients suffering from BEN and/or urinary tract tumors were more frequently found to have a capacity for rapid debrisoquine (DB) metabolism, a metabolic reaction related mostly to cytochrome P450 (CYP) 2D in humans. Earlier studies, using female DA and Lewis rats phenotyped as poor or extensive DB metabolizers respectively, revealed a parallelism between DB-4 hydroxylation and OTA-4 hydroxylation. To investigate whether genetic polymorphism modifies tumor induction, we have compared both OTA-induced renal carcinogenicity and DNA adducts in DA and Lewis rats of both sexes. OTA induced renal adenocarcinoma, DA male rats being most responsive, while DA females were resistant. Lewis rats showed an intermediate renal tumor response. OTA also induced malignant transitional cell carcinomas of the bladder in DA male rats only. DNA adducts in the kidney, as judged by the nature of spots and prevalence in OTA-treated animals, were significantly correlated with renal carcinogenicity of OTA, being highest in DA males and lowest in DA females. A parallelism between karyomegalies and tumors of the kidney was observed. In conclusion, our results classify OTA as a genotoxic carcinogen in rats, with sex-specific response controlled in part by drug-metabolizing enzymes that convert OTA into reactive intermediates.

Analytical method for the determination of sphinganine and sphingosine in serum as a potential biomarker for fumonisin exposure.

The toxins produced by Fusarium moniliforme, which include fumonisins, are possible human carcinogens. Fumonisins are inhibitors of de novo sphingolipid biosynthesis. Alterations of the ratio of sphinganine (Sa) to sphingosine (So) in urine and serum has been proposed as a possible biomarker of exposure to this toxin. A new method was developed for their analysis in tissues and urine. This work describes the further adaptation of the method to the analysis of Sa and So in serum and its validation in sera of untreated and fumonisin B1 (FB1 ) treated rats and mice. No significant differences in the Sa/So ratios were observed in the FB1 treated rats. In mice, the increase was only of marginal statistical significance. Determination of Sa/So ratios in human sera could readily be made in small volumes (from 0.3 to 0.5 ml) of serum.