TY - JOUR A1 - Zimmermann, U. A1 - Stopper, Helga T1 - Elektrofusion und Elektropermeabilisierung von Zellen : Eine neuartige Methode der Biotechnologie zur gezieltenVeränderung der genetischen Eigenschaften von Zellen N2 - No abstract available KW - Toxikologie Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63514 ER - TY - JOUR A1 - Viviani, A. A1 - Lutz, Werner K. A1 - Schlatter, C. T1 - Time course of the induction of aryl hydrocarbon hydroxylase in rat liver nuclei and microsomes by phenobarbital, 3-methylcholanthrene, 2,3,7,8-tetrachloro-dibenzo-p-dioxin, dieldrin and other inducers N2 - Aryl hydrocarbon hydroxylase (AHH) has been measured in male rat Jiver nucJei and microsomes after treatment of adult animals with various inducers for up to 14 days. After daily i.p. injections of 3-methylcholanthrene (MC, 20 mg/kg) the nuclear activity increased to a maximum of 600 per cent of the control activity after 4 days whereas the microsomal activity was 400 per cent of control at the same date. After 12 days, both activities equilibrated at 400 per cent. A similar time course was found after a single i.p. injection of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD, 0.01 mg/kg) with an induction to .500 and 300 per cent for nuclei and microsomes, respectiveJy. after 2 days, and to 400 per cent for both after 12 days. PhenobarbitaJ (PB) was given continuously in the drinking water (I g/1) and induced the microsomal activity to 200 per cent after 8 days and 170 per cent after 14 days. The nuclear activity was only slightly induced to a constant Ievei of 130 per cent between day 8 and 14. Dieldrin did not significantly increase the microsomal activity after daiJy i.p. injections (20 mg/kg), but the nuclear activity raised to 200 per cent after 3 days and levelled down tocontrol valuesafter 12 days. Other inducers tested were benz[a)anthracene (BA), hexachlorobenzene (HCB} and 1,1.1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT). The induction pattern with BA was similar tothat of MC, a modeJ compound for the group of cytochrome P448 inducers. The induction by HCB and DDT resembled that by PB. a typical cytochrome P450 inducer. KW - Toxikologie Y1 - 1978 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61182 ER - TY - JOUR A1 - Viviani, A. A1 - Lutz, Werner K. T1 - Modulation of the binding of the carcinogen benzo(a)pyrene to rat liver DNA in vivo by selective induction of microsomal and nuclear aryl hydrocarbon hydroxylase activity N2 - The lnfluence of mlcrosomal and nuclear aryl hydrocarbon hydroxylase (AHH) actlvlty on the covalent blndlng of [G·3H]benzo(a )pyrene to rat llver DNA was evaluated in viWJ. lnductlon of mlcrosomal AHH was obtalned alter phenobarbltal treatment (160% of control), whlch also lncreased DNA blndlng to 190%, but left the nuclear actlvlty unchanged. Nuclear AHH was lnduced wlth dleldrln (150%), and the blndlng was decreased to 75%, whereaa the mlcrosomal AHH was at control Ievei. The lncreaslng effect of mlcrosomal AHH lnductlon as weil as the decreaslng effect of nuclear AHH lnductlon on the blndlng was shown clearly when the data of the Individual rata were uaed to solve the equatlon Binding = e•(mlcroeomal AHH) + b•(nuclear AHH) + c Multiple linear regresslon analysls wlth the data from 10 anlmala reaulted ln positive valuea for a and c, a negative value for b, and a good multiple correlatlon coefflclent of r = 0.974. Pretreatment wlth 3-methylcholanthrene ln· duced mlcrosomal AHH to 380% of control and nuclear AHH to 590% and lncreased the blndlng' to 175,.-o. The blndlng was hlgher than predlcted by the formula found, probably because the lncreaslng lnfluence of lnduced mlcrosomal AHH overahadowed the decreaslng effect of the nuclear AHH. The study ahows clearly that the blndlng of a forelgn compound to DNA in viWJ Ia dependent not only on mlcrosomal enzyme actlvltles but also on nuclear actlvltles even lf the latter are conslderably lower than thoae of mlcrosomes. KW - Toxikologie Y1 - 1978 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61150 ER - TY - JOUR A1 - Viviani, A. A1 - Däniken, A. von A1 - Schlatter, C. A1 - Lutz, Werner K. T1 - Effect of selected induction of microsomal and nuclear aryl hydrocarbon monooxygenase and epoxide hydrolase as well as cytoplasmic glutathione S-epoxide transferase on the covalent binding of the carcinogen benzo(a)pyrene to rat liver DNA in vivo N2 - Groups of four adult male rats [ZUR:SIV -Z] were pretreated with corn oil (control; 2 ml/kg/day i. p. for 3 days), trans-stilbene-oxide (SO; 200 mg/kg/day i. p. for 2 days), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 10 \(\mu\)g/kg i. p. once, 4 days before killing), phenobarbital (PB; 1 gjliter in the drinking water for 8 days), and dieldrin (20 mg/kg/day i. p. for 3 or 9 days). They received an injection of [G-\(^3\)H]benzo(a)pyrene (BaP, 31 \(\mu\)g/kg, 7.4. 10\(^9\) dpm/kg; i. v.) 16 h before killing. In the liver of each rat, five enzymatic activities and the covalent binding of BaP to DNA have been determined. The rnicrosomal aryl hydrocarbon monooxygenase activity (AHM) ranged frorn 75% of control (SO) to 356% (TCDD), the nuclear AHM from 63% (SO) to 333% (TCDD). Microsomal epoxide hydrolase activity (EH) was induced up to 238% (PB), nuclear EH ranged from 86% (TCDD) to 218% (PB). A different extent of induction was observed in the two compartments. Highest induction of glutathione S-epoxide transferase activity (GST) was found with PB (202%). The DNA binding of BaP was modulated within 79% (dieldrin, 9 days) and 238% of control (TCDD). An enzyme digest of control DNA was analysed by Sephadex LH-20 chromatography. Multiple linear regression analysis with all data expressedas o/o of control yielded the following equation: DNA Binding = 1.49 · Microsomal AHM- 1.07 · Nuclear AHM+ 0.33 · Microsomal EH- 0.52 · N uclear EH+ 0.11 · Cytoplasmic GST + 58.2. From this analysis it is concluded that (1) AHM located in the endoplasmic reticulum is most important in the formation of DNA-binding metabolites, (2) EH in the same compar.tment is not determinative in thls respect nor has it a protective effect, (3) both membrane-bound enzyme activities located in the nucleus may inactivate potential ultimate carcinogens, and ( 4) cytoplasmic GST probably cannot reduce DNA binding due to its subcellular localization. KW - Toxikologie KW - Carcinogen KW - Benzo(a)pyrene-DNA binding KW - Enzyme induction KW - Aryl hydrocarbon rnonooxygenase KW - Epoxide hydrolase KW - Glutathione Stransferase Y1 - 1980 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61114 ER - TY - JOUR A1 - van Calker, D. A1 - Steber, R. A1 - Klotz, Karl-Norbert A1 - Greil, W. T1 - Carbamazepine distinguishes between adenosine receptors that mediate different second messenger responses N2 - The mechanism of the therapeutic and prophylactic effects of carbamazepine (CBZ) in affective psychoses is unknown but may in part be related to the potent competitive interaction of CBZ with adenosine-binding sites in the brain. The antioonvulsant and sedative properties of CBZ are reminiscent of the effects evoked by adenosine-agonists and contrast sharply with the opposite aclions of adenosine-antagonists like caffeine. However. indirect evidence suggests an antagonist- rather than an agonist-like activity of CBZ at adenosi11e-receptors. We have used various model systems, in which adenosine receptor subtypes mediate different second messenger-responses, to investigate this apparent paradox. CBZ was found to antagonize the A\(_1\) receptor-mediated inhibition of cydic AMP accumulation in cultured astroblasts and in GH3-cells. Furthermore, CBZ also inhibits the adenosine-induced increase in the level of cyclic AMP in cultured astroblasts, which is mediated by low-affinity A\(_{2b}\)-receptors. ln contrast, CBZ does not block the inhibition elicited by adenosine-agonists of the agonist-induced increased formation of inositolphosphates in human neutrophils, which is mediated by high-affinity A\(_{2a}\)-receptors. The specific antagonism by CBZ of A\(_1\)- but not of high-affinity A\(_{2a}\)-receptors was further supported by binding experiments using rat brain membranes. These results suggest tbat the paradox of CBZ's antagonistic effects at adenosine-receptors might be at least partially reconciled by a selective antagonistic action of CBZ at A\(_1\)recertors but not at high-affinity A\(_{2a}\)-receptors. KW - Toxikologie Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60392 ER - TY - JOUR A1 - Ukena, D. A1 - Schirren, C. G. A1 - Klotz, Karl-Norbert A1 - Schwabe, U. T1 - Evidence for an A\(_2\) adenosine receptor in guinea pig lung N2 - Adenosine receptors in guinea pig lung were characterized by measurement of cyclic AMP formation and radioligand binding. 5'-N-Ethylcarboxamidoadenosine (NECA) increased cyclic AMP Ievels in lung slices about 4-fold over basal values with an EC\(_{50}\) of 0.32 \(\mu\)mol/l. N\(^6\) - R-(- )-Phenylisopropyladenosine (R-PIA) was 5-fold less potent than NECA. 5'-N-Methylcarboxamidoadenosine (MECA) and 2-chloroadenosine had EC\(_{50}\)-values of 0.29 and 2.6 \(\mu\)mol/l, whereas adenosine and inosine had no effect. The adenosine receptors in guinea pig Iung can therefore be classified as A\(_2\) receptors. Several xanthine derivatives antagonized the NECA-induced increase in cyclic AMP levels. 1,3-Diethyl-8-phenylxanthine (DPX; K\(_i\) 0.14 \(\mu\)mol/l) was the most potent analogue, followed by 8-phenyltheophylline (K\(_i\) 0.55 \(\mu\)mol/l), 3-isobutyl-1-methylxanthine (IBMX; K\(_i\) 2.9 \(\mu\)mol/l) and theophylline (K\(_i\) 8.1 \(\mu\)mol/l). In contrast, enprofylline (1 mmol/1) enhanced basal and NECA-stimulated cyclic AMP formation. In addition, we attempted to characterize these receptors in binding studies with [\(^3\)H]NECA. The K\(_D\) for [\(^3\)H] NECA was 0.25 \(\mu\)mol/l and the maximal number of binding sites was 12 pmol/mg protein. In competition experiments MECA (K\(_i\) 0.14 \(\mu\)mol/l) was the most potent inhibitor of [\(^3\)H] NECA binding, followed by NECA (K\(_i\) 0.19 \(\mu\)mol/l) and 2-chloroadenosine (K\(_i\) 1.4 \(\mu\)mol/l). These results correlate well with the EC\(_{50}\)- values for cyclic AMP formation in lung slices. However, the K\(_i\)-values of R-PIA and theophylline were 240 and 270 \(\mu\)mol/l, and DPX and 8-phenyltheophylline did not compete for [\(^3\)H]NECA binding sites. Therefore, a complete characterization of A\(_2\) adenosine receptors by [\(^3\)H] NECA binding was not achieved. In conclusion, our results show the presence of adenylate cyclase-coupled A\(_2\) adenosiile receptors in lung tissue which are antagonized by several xanthines. KW - Toxikologie KW - Adenosine receptors KW - Cyclic AMP KW - Lung KW - Theophylline Y1 - 1985 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60202 ER - TY - THES A1 - Trösken, Eva-Regina T1 - Toxicological evaluation of azole fungicides in agriculture and food chemistry T1 - Toxikologische Beurteilung der Anwendung von Azolfungiziden in der Landwirtschaft und Lebensmittelchemie N2 - Azole sind wichtige Chemikalien, die als Fungizide in der Landwirtschaft und der Medizin eingesetzt werden. Auch als Zytostatika in der Humanmedizin finden sie Anwendung. Die fungizide Wirkung beruht auf der Hemmung der Lanosterol-14α-Demethylase (CYP51), die die Demethylierung von Lanosterol zum „Follicular Fluid Meiosis Activating Steroid (FF-MAS)“ katalysiert. Für Pilze ist das später resultierende Ergosterol ein essentieller Bestandteil der Zellmembran. Exponierten Pilzen fehlt Ergosterol was zu einem Zusammenbruch der Zellmembran führt. Säugetiere können Cholesterol, das spätere Produkt der Lanosterol-14α-Demethylierung, das zur Synthese von z.B. Gallensäuren und Sexualhormonen nötig ist, mit der Nahrung aufnehmen. FF-MAS und das resultierende T-MAS (Testis Meiosis Activating Steroids), die direkten Produkte der CYP51 katalysierten Reaktion, wirken als Meiose-aktivierende Steroide auf Ovarien und Hoden und werden nicht mit der Nahrung aufgenommen. Eine Hemmung der CYP51 Aktivität könnte das endokrine System beeinflussen und wird daher als unerwünschte Nebenwirkung der Azole betrachtet. Aromatase (CYP19) katalysiert die Demethylierung von Testosteron zu Östradiol und wird durch Azole gehemmt. Die Verringerung der Östrogenspiegel durch CYP19-Inhibition ist das Wirkprinzip der als Zytostatika genutzten Azole, bei den Fungiziden wird es als unerwünschte Nebenwirkung angesehen. Ein ideales Azol sollte Pilz-CYP51 stark inhibieren, aber sowohl humanes CYP19 wie auch humanes CYP51 sollten durch ein solches Azol nicht inhibiert werden. Ein ideales Azol-Zytostatikum sollte eine starke inhibitorische Potenz gegenüber humanem CYP19 aufweisen, hingegen sollten humanes und Pilz-CYP51 nicht inhibiert werden. Ziel dieser Arbeit war es nun festzustellen: sind Fungizide und Antimykotika starke Inhibitoren von Pilz-CYP51? Zeigen Fungizide und Antimykotika keine Aktivität gegenüber humanem CYP19 und humanem CYP51? Sind Zytostatika starke Inhibitoren von humanem CYP19? Zeigen Zytostatika keine Aktivität gegenüber humanem CYP51 und Pilz-CYP51? Die inhibitorische Potenz von 22 Azolen, aus den drei Anwendungsgebieten, wurden an vier Systemen getestet: i) an humanem CYP19 und einem fluoreszierenden Pseudosubstrat, ii) an CYP19 und Testosteron als Substrat, iii) an humanem CYP51 und iv) Candida albicans CYP51 und Lanosterol als Substrat. Die Produktbildung wurde mittels Hochdruckflüssigkeitschromatographie gekoppelter Tandem-Massenspektrometrie nach Photosprayionisation gemessen. Das humane CYP51 wurde von „BD Gentest Cooperation“ zur Verfügung gestellt. Ein katalytisch aktiver Enzymkomplex bestehend aus der Lanosterol-14α-Demethylase von Candida albicans und der Oxidoreduktase von Candida tropicalis, wurde im Baculovirussystem exprimiert. Ein Vergleich der inhibitorischen Wirkstärke der Substanzen auf menschliches CYP19 und CYP51 und Pilz-CYP51 zeigt, dass einige Azole das erwünschte Bild zeigen. Dazu gehören die beiden Zytostatika Fadrozol und Letrozol, sowie Fluconazol und Itraconazol, zwei Antimykotika aus der Humanmedizin, und einige Fungizide z.B. Cyproconazol und Hexaconazol. Ein unerwünschtes Bild zeigen z.B. Prochloraz, Bifonazol, Ketoconazol und Miconazol. Sieben Azole weisen ein gemischtes Bild an inhibitorischen Wirkstärken auf. Um einen modellartigen Eindruck der Rückstände von Azolen in Lebensmitteln zu erhalten, wurde eine auf LC-ESI-MS/MS basierende Rückstandsanalytik für Azole im Wein entwickelt. Alle gefunden Rückstände lagen unterhalb der behördlich festgelegten Rückstandshöchstmengen. Um die inhibitorische Wirkung der Azole auf die verschiedenen Enzymsysteme in einem größeren Zusammenhang zu bringen, wurden die IC50 Werte mit Expositionsdaten von Bauern, maximalen Plasmaspiegeln in Patienten nach der Einnahme von Antimykotika und mit Expositionsgrenzwerten für die Langzeitaufnahme von Pflanzenschutzmittelrückständen („Acceptable Daily Intake Levels“, ADI) verglichen. Basierend auf den dargestellten Ergebnissen können folgende Schlussfolgerungen gezogen werden. Das Risiko für landwirtschaftliche Arbeiter durch Exposition gegenüber Azolfungiziden kann im Bezug auf menschliches CYP19 und CYP51 als vernachlässigbar eingestuft werden, wenn die entsprechenden Sicherheitsvorkehrungen getroffen werden. Im medizinischen Bereich muss grundsätzlich der Einsatz von Bifonazol, Miconazol und Ketoconazol mit Blick auf die hohe inhibitorische Potenz gegenüber menschlichem CYP19 und 51 kritisch betrachtet werden. Unter der Annahme, dass die ADI Werte eingehalten werden, stellen Rückstände auf Lebensmitteln in Bezug auf die genannten Enzymsysteme keine Bedrohung für den Verbraucher da. Die Inhibition von CYP19 muss als Störung des Hormonsystems angesehen werden. Die Bedeutung von FF-MAS und T-MAS im endokrinen System muss noch abschließend geklärt werden und damit auch die Frage, wie viel Bedeutung der Inhibition von menschlichem CYP51 beigemessen werden muss. N2 - Azoles are important chemicals used as antifungal agents in agriculture and human medicine, but also as cytostatic drugs in tumour chemotherapy. Antifungal activities are based on inhibition of lanosterol-14α-demethylase (CYP51). CYP51 catalyses the oxidative removal of the methyl group # 32 of lanosterol to produce follicular fluid meiosis activating steroid (FF-MAS). For fungi the later resulting ergosterol is an essential compound of the cell membrane. Exposed fungi lack ergosterol, which leads to a collapse of the cell membrane. In mammals cholesterol, the downstream product of lanosterol-14α-demethylation necessary for the synthesis of bile acids, mineral corticoids, glucocorticoids and sex steroids, can be supplemented with food intake. However FF-MAS and the resulting T-MAS (testis meiosis activating steroids), the direct products of the CYP51 reaction, act as meiosis-activating steroids on ovaries and testes and are not supplemented with food intake. Inhibition of CYP51 in humans may therefore affect the endocrine system and is an unwanted side effect of azoles. Aromatase (CYP19) catalyses the demethylation of testosterone to estradiol and is inhibited by azoles. Reduction of estrogen levels by CYP19 inhibition is the working principle of cytostatic drugs used in breast cancer therapy but is considered an unwanted side effect for azoles used to treat fungal infections. A favourable fungicide or antifungal drug should be a strong inhibitor of fungal CYP51. In contrast human CYP51 and human CYP19 should not be inhibited by an azole fungicide or antifungal agent. The favourable cytostatic drug should show a high potency towards human CYP19. Neither human CYP51 nor fungal CYP51 should be inhibited by a cytostatic drug. The aim of this work was to assess: are fungicides and antifungal drugs strong inhibitors of fungal CYP51? In return do they not inhibit human CYP51 and human CYP19? Do cytostatic drugs strongly inhibit human CYP19? And in return do they not inhibit human CYP51 or fungal CYP51? Inhibitory potencies of 22 azole compounds used for the three purposes were tested in four inhibition assays: i) on commercially available human CYP19 utilising a fluorescent pseudo substrate dibenzylfluorescein (DBF) ii) on CYP19 utilising testosterone as substrate iii) on human CYP51 and iv) Candida albicans CYP51 utilising lanosterol as substrate. Product formation was measured by liquid chromatography – tandem mass spectrometry utilising photospray ionisation (APPI). A functional human CYP51 was available from BD Gentest Cooperation. A functional enzyme complex comprising of the Candida albicans lanosterol-14α-demethylase and the Candida tropicalis oxidoreductase was expressed in the baculovirus system. When comparing inhibitory potencies on CYP19, human CYP51 and Candida albicans CYP51 a number of agents show desirable patterns of inhibition e.g. the two cytostatic drugs, or two antifungal agents used in human medicine, fluconazole and itraconazole, and a wide variety of the fungicides, e.g. cyproconazole and hexaconazole. Undesirable patterns of inhibition were exhibited by a number of compounds, e.g. prochloraz, bifonazole, ketoconazole and miconazole. Seven compounds show a more complex picture of inhibitory potencies though. To get a picture of residue levels of azoles in food in a model case an LC-ESI-MS/MS method was developed for the determination of azole compounds in wine. All residues were below the maximum residue levels set by authorities. To classify the inhibitory potencies on the different enzyme systems IC50 values obtained were compared to exposure levels measured in farmers, maximum plasma concentrations in humans reported after exposure to antifungal drugs and to acceptable daily intake levels set by authorities. Based on the findings presented, the following conclusions can be drawn. The risk for agricultural workers set by exposure to azole fungicides with respect to human CYP51 and CYP19 can be regarded as negligible when safety measures are adhered to. As a matter of principle however, the usage of bifonazole, miconazole and ketoconazole has to be viewed with caution in respect to the high level of inhibition of human CYP51 and/or CYP19. Under the assumption that the acceptable daily intake amounts set by authorities for azole compounds are not exceeded the residues do not pose a threat to consumer safety judged by our findings. Inhibition of CYP19 with the consequence of a reduction of estradiol levels has to be regarded as a possible disrupting effect of the hormone balance. The relevance of FF-MAS and T-MAS in the endocrine system however still has to be evaluated completely bringing with it the question of how much importance has to be attached to the inhibition of human CYP51. KW - Azole KW - Fungizid KW - Toxikologie KW - CYP19 KW - CYP51 KW - Azole KW - Toxikologie KW - CYP19 KW - CYP51 KW - Azoles KW - Toxicology Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-17016 ER - TY - JOUR A1 - Tawfik-Schlieper, H. A1 - Klotz, Karl-Norbert A1 - Kreye, V. A. W. A1 - Schwabe, U. T1 - Characterization of the K\(^+\)-channel-coupled adenosine receptor in guinea pig atria N2 - In the present work we studied the pharmacological profile of adenosine receptors in guinea pig atria by investigating the effect of different adenosine analogues on 86Rb + -efflux from isolated left atria and on binding of the antagonist radioligand 8-cyclopentyl-1 ,3-[\(^3\)H]dipropylxanthine ([\(^3\)H]DPCPX) to atrial membrane preparations. The rate of \8^{86}\)Rb\(^+\) -effiux was increased twofold by the maximally effective concentrations of adenosine receptor agonists. The EC50-values for 2-chloro-N\(^6\)-cyclopentyladenosine (CCPA), R-N\(^6\)-phenylisopropyladenosine (R-PIA), 5'-Nethylcarboxamidoadenosine (NECA), and S-N\(^6\)-phenylisopropyladenosine (S-PIA) were 0.10, 0.14, 0.24 and 12.9 \(\mu\)M, respectively. DPCPX shifted the R-PIA concentration-response curve to the right in a concentration-dependent manner with a K\(_B\)-value of 8.1 nM, indicating competitive antagonism. [\(^3\)H]DPCPX showed a saturable binding to atrial membranes with a Bmax·value of 227 fmol/mg protein and a K\(_D\)-value of 1.3 nM. Competition experiments showed a similar potency for the three agonists CCPA, R-PIA and NECA. S-PIA is 200 times less potent than R-PIA. Our results suggest that the K\(^+\) channel-coupled adenosine receptor in guinea pig atria is of an A\(_1\) subtype. KW - Toxikologie KW - A1 Adenosine receptors KW - K + -channels KW - Atria KW - Radioligand binding - 86Rb + -efflux Y1 - 1989 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60333 ER - TY - JOUR A1 - Tas, P. A1 - Stopper, Helga A1 - Koschel, K. A1 - Schiffmann, D. T1 - Influence of the carcinogenic oestrogen diethylstilboestrol on the intracellular calcium level in C6 rat glioma cells N2 - The ~fthetic oes~rog~n diethylsti~boestrol (DES) causes a dose-dependent elevation of the cytoplasuuc Ca concentratton m C6 rat ghoma cells. This Ca2+ rise is caused neither by Ca2+ influx nor ~-r release from the ~a2 + stores of the endoplasmic reticulum. Therefore it seems likely that DES mob!hzes Ca2+ from a nutochondrial source. The DES-induced Ca2+ signal is remarkably similar to the one mduced by the. tumou~ promotor ~hapsigargin. As this compound causes leakage of calcium from the endoplasmt~ rettculum tt ~ms posstble that DES induces a similar leakage from mitochondrial Ca2+ stores. It remaans to be estabhshed whether the DES-mediated rise in intracellular calcium is causally related to the tumour-promoting properties of this compound KW - Toxikologie Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63459 ER - TY - JOUR A1 - Stopper, Helga A1 - Zimmermann, U. A1 - Wecker, E. T1 - High yields of DNA-transfer into mouse L-cells by electropermeabilization N2 - no abstracts available KW - Toxikologie KW - Gene Transfer KW - Electric Field KW - Stable Transformation KW - Neomycin Resistance Y1 - 1985 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-82408 ER - TY - JOUR A1 - Stopper, Helga A1 - Zimmermann, U. A1 - Neil, G. A. T1 - Increased efficiency of transfection of murine hybridoma cells with DNA by electropermeabilization N2 - Dispase-treated murine hybridoma cells (SP2/0-Ag14) were transfected with the G418 resistance gene bearing plasmid pSV2-neo by electropermeabilization with a high degree of efficiency. The cells were subjected to intermittent multiple high-voltage short duration (5 p.s) DC pulses at intervals of 1 min in a weakly conducting medium followed by selection in G418-containing medium. The transfection medium, temperature, pulse duration, and voltage were empirically determined by preliminary electropermeabilization experiments. Increasing the number of pulses resulted in a higher percentage of transfected cells, but a decrease in the number of viable cells, with the optimal transfectant yield resulting when five pulses of 10 kV jcm were administered. This method allows the rapid and efficient injection of DNA into mammalian cells, and permits the rapid production of stable, drug resistant hybridoma celllines for use in subsequent fusion experiments. KW - Toxikologie KW - DNA transfection KW - Electropermeabilization KW - Eukaryotic cell KW - Hybridoma KW - Drug resistance Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63488 ER - TY - JOUR A1 - Stopper, Helga A1 - Pechan, R. A1 - Schiffmann, D. T1 - 5-azacytidine induces micronuclei in and morphological transformation of Syrian hamster embryo fibroblasts in the absence of unscheduled DNA synthesis N2 - lt is known that 5-azacytidine (5-AC) induces tumors in several organs of rats and mice. The mechanisms of these effects are still poorly understood although it is known that 5-AC can be incorporated into DNA. Furthermore, it can inhibit DNA methylation. The known data on its clastogenic andjor gene mutation-inducing potential are still controversial. Therefore, we have investigated the kinds of genotoxic effects caused by 5-AC in Syrian hamster embryo (SHE) fibroblasts. Three different endp6ints (micronucleus formation, unscheduled DNA synthesis (UDS) and cell transforrnation) were assayed under similar conditions of metabolism and dose at target in this cell system. 5-AC induces morphological transformation of SHE cells, but not UDS. Therefore, 5-AC does not seem to cause repairable DNA lesions. Furthermore, our studies revealed that 5-AC is a potent inducer of mkronuclei in the SHE system. Immunocytochemical analysis revealed that a certain percentage of these contain kinetochores indicating that 5-AC may induce both clastogenic events and numerical chromosome changes. KW - Toxikologie KW - 5-Azacytidine KW - Micronuclei KW - Kinetochores KW - Unscheduled DNA synthesis KW - Cell transformation Y1 - 1992 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63443 ER - TY - JOUR A1 - Stopper, Helga A1 - Metzler, M. T1 - Carcinogenic oestrogens induce respiration deficiency mutation in yeast N2 - In addition to hormonal activity, genetic darnage has been proposed as an important factor in oestrogen-mediated carcinogenesis. However, as short-term tests for oestrogens usually fail to show DNA mutations, lesions other than dassie nuclear DNA mutation have to be considered. Oestrogeninduced mitochondrial darnage was studied in the yeast Saccharomyces cerevisiae. Stilbene-type, but not steroidal, oestrogens were found to induce respiration-dcficient petite mutation. The effect was inversely correlated with cytotoxicity and required aromatic hydroxyl groups at the stilbene molecule. It only occurred under growth conditions and apparently was not due to the A TPase inhibitory qualities of stilbene oestrogens. Other studies have shown that petite mutation clones, which can be induced by a variety of substances, contain altered mitochondrial DNA. The mechanism of petite mutation induction might be important in tumorigenesis by also acting on nuclear DNA or facilitating carcinogenesis by disturbance of mitochondrial function. KW - Toxikologie Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63466 ER - TY - JOUR A1 - Stopper, Helga A1 - Kühnel, A. A1 - Podschun, B. T1 - Combination of the chemotherapeutic agent 5-fluorouracil with an inhibitor of its catabolism results in increased micronucleus induction N2 - The rate limiting step in 5-fluorouracil catabolism is catalyzed by the enzyme dihydropyrimidine dehydrogenase. Since degradation of 5-fluorouracil decreases its efficacy in chemotherapy, the inhibition of its catabolism is a promising tool. We investigated the formation of micronuclei in vitro in mouse L5178Y cells. 5-fluorouracil induced an increase in micronucleus frequency, which could significantly be enhanced by the concurrent application of 2,6-dihydroxypyridine, an inhibitor of dihydropyrimidine dehydrogenase. The 5-fluorouracil concentration necessary to reach maximal genotoxic effects could be reduced to half in the presence of inhibitor. 2,6-Dihydroxypyridine alone and the naturally occuring enzyme substrate uracil did not induce micronucleus formation. Combined application of the chemotherapeutic agent 5-fluorouracil and an inhibitor of its could reduce side-effects by lowering the effective dose of the active drug. With this study we provide further support for the usefulness of this concept. KW - Toxikologie Y1 - 1994 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63383 ER - TY - JOUR A1 - Stopper, Helga A1 - Körber, C. A1 - Spencer, D. L. A1 - Kirchner, S. A1 - Caspary, W.J. A1 - Schiffmann, D. T1 - An investigation of micronucleus and mutation induction by oxazepam in mammalian cells N2 - Tbe benzodiazepines are a class of d.rugs that are widely used in the treatment of various psychiatric disorders. One member of um ~' oxazepam, is also a common metabolite of sevmd other benzod.iazepines. Since the evidence for the genetic toxicity and carcinogenic properties of these compounds is incol:lsb1ent, we investigated the oxazepam-induced fonnation of micronuclei in Syrian Hamster embryo fibroblast (SHE) cells, human amniotic fluid fibroblast-like (AFFL) cells and LS178Y mouse cells. A dose-dependent increase in micronucleus fractions was found in all tbree ceU llnes. The time course of micronucleus induction in L5178Y cells showed a maximum at 5 h after treatment, suggesting that the micronuclei were fonned in the first mitosis after treatment. Kinetochore staining (CREST -antiserum) revealed the presence of kinetochores in -SO% of the micronuclei in aU tbree ceU types. ThJs resu1t was further confinned by in situ bybridization in LS178Y cells and indicates tbe presence of wbole Chromosomes or centric fragments as weU as acentric fragments in the oxazepam-induced micronuclei. The LS178Y cells did not show a mutagenic response to oxazepam at any of the doses or expression times used. KW - Toxikologie Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63404 ER - TY - JOUR A1 - Stopper, Helga A1 - Körber, C. A1 - Schiffmann, D. A1 - Caspary, W. J. T1 - Cell-cycle dependent micronucleus formation and mitotic disturbances induced by 5-azacytidine in mammalian cells N2 - 5-Azacytidine was originally developed to treat human myelogenous leukemia. However, interest in this compound has expanded because of reports of its ability to affect cell differentiation and to alter eukaryotic gene expression. In an ongoing attempt to understand the biochemical effects of this compound, we examined the effects of 5-azacytidine on mitosis and on micronucleus formation in mammalian cells. In L5178Y mouse cells, 5-azacytidine induced micronuclei at concentrations at which we and others have already reported its mutagenicity at the tk locus. Using CREST staining and C-banding studies, we showed that the induced micronuclei contained mostly chromosomal fragments although some may have contained whole chromosomes. By incorporating BrdU into the DNA of SHE cells, we determined that micronuclei were induced only when the compound was added while the cells were in S phase. Microscopically visible effects due to 5-azacytidine treatment were not observed until anaphase of the mitosis following treatment or thereafter. 5-Azacytidine did not induce micronuclei via interference with formation of the metaphase chromosome arrangement in mitosis, a common mechanism leading to aneuploidy. SupravitalUV microscopy revealed that chromatid bridges were observed in anaphase and, in some cases, were sustained into interphase. In the first mitosis after 5-azacytidine treatment we observed that many cells were unable to perform anaphase separation. All of these observations indicate that 5-azacytidine is predominantly a clastogen through its incorporation into DNA. KW - Toxikologie KW - Micronuclei KW - L5178Y cells KW - 5-Azacytidine KW - Berenil KW - DES KW - Ethionine KW - Mitosis Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63411 ER - TY - JOUR A1 - Stopper, Helga A1 - Kirchner, S. A1 - Schiffmann, D. A1 - Poot, M. T1 - Cell cycle disturbance in relation to micronucleus formation induced by the carcinogenic estrogen diethylstilbestrol N2 - In addition to its tumor-promoting activity in honnone-receptive tissue, the carcinogenic estrogen diethylstilbestrol (DES) has been found to induce cell transformation, aneuploidy and micronucleus formation in mammalian cells. The majority of these micronuclei contained whole chromosomes and were fonned during mitosis. Here a possible relationship between a disturbance in cell cycle progression and micronucleus fonnation is investigated by exposing Syrian hamster embryo (SHE) cells to DES. Continuous bromodeoxyuridine labeling followed by bivariate Hoechst 33258/ethidium bromide flow cytometry was employed for analysis of cell cycle transit and related to the time course of micronucleus formation. Treatment of SHE cells with DES resulted in delayed and impaired cell activation (exit from the GO/G 1 phase), impaired S-phase transit and, mainly, G2-phase traverse. Cells forming micronuclei, on the other hand, were predominantly in G2 phase during DES treatment. These results suggest that impairment of Sand G2 transit may involve a process ultimately leading to micronucleus formation. KW - Toxikologie KW - Flow cytometry KW - Micronucleus formation KW - Diethylstilbestrol KW - Hoechst 33258 dye KW - Bromodeoxyuridine labeling KW - continuous Y1 - 1994 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-82250 ER - TY - JOUR A1 - Stopper, Helga A1 - Jones, H. A1 - Zimmermann, U. T1 - Large scale transfection of mouse L-cells by electropermeabilization N2 - Mouse L-cells were transfected by electropenneabilization using the selectable plasmid pSV2-neo which confers resistance to G-418 (Geneticin). 1be DNA concentration used was 1 l'gfml, the field strength was 10 kV fcm, the duration of the pulse was S ~s. Transfeetion yield was optimal at a temperature of 4°C when using a time in between consecutive pulses of 1 minute compared to shorter (of the order of seoonds) or Ionger (3 minutes) time intervals. A more detailed study of the relationship between the number of pulses applied (up to 10) and transfection yield showed it to be almost linear in this range at 4 o C. The yield of transfectants in response to 10 pulses was up to 1000 per 106 cells (using 3.3 pg DNA per cell). The inßuence of the growth phase of the cells on the transfection yield and I or the subpopulation of the mouse L--ceU line used was shown. Furthennore the clone yield depended on the DNA per ceU ratio within a very small range. KW - Toxikologie KW - Electrical breakdown KW - Electropermeabilization KW - Volume distribution KW - Gene transfer KW - Transfection KW - (Mouse L-cell) Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63497 ER - TY - JOUR A1 - Stopper, Helga A1 - Eckert, I. A1 - Schiffmann, D. A1 - Spencer, D. L. A1 - Caspary, W. J. T1 - Is micronucleus induction by aneugens an early event leading to mutagenesis? N2 - This study was designed to investigate a previously unidentified potential mechanism for mutation induction as well as to clarify a biological comequence of micronucleus formation. We compared the induction of micronuclei with mutation inductioo as measured by trißuorothymidine (TFI') resistance in mouse L5178Y cells using four aneugens: colcemid, diethylstilbestrol, griseofulvin and vioblastine. AU four compounds induced micronuclei which appeared in the first cell cycle after treatment. More than 85% of the micronuclei induced by each compound stained positive for the presence of kinetochores implying that the micronuclei contained wbole cbromosomes. However, these same compounds were unable to induce TFf resistance under tbree different treatment regimes. We concluded that tbese compounds, under conditions where tbey induce primarily kinetochore positive micronuclel, were not able to induce mutations. Thus, the induction of micronuclei containing wbole chromosomes barborlog a select.able gene is not an early event leadlog to mutations in these cells. KW - Toxikologie Y1 - 1994 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63390 ER - TY - THES A1 - Sieber, Maximilian T1 - Evaluation of 1H-NMR and GC/MS-based metabonomics for the assessment of liver and kidney toxicity T1 - Bewertung von 1H-NMR und GC/MS-Metabonomics zur Erkennung von Leber- und Nierentoxizität N2 - For the assessment of metabonomics techniques for the early, non-invasive detection of toxicity, the nephrotoxins gentamicin (s.c. administration of 0, 60 and 120 mg/kg bw 2x daily for 8 days), ochratoxin A (p.o. administration of 0, 21, 70 and 210 µg/kg bw 5 days/week for 90 days) and aristolochic acid (p.o. administration of 0, 0.1, 1.0 and 10 mg/kg bw for 12 days) were administered to rats and urine samples were analyzed with 1H-NMR and GC/MS. Urine samples from the InnoMed PredTox project were analyzed as well, thereby focusing on 1H-NMR analysis and bile duct necrosis as histopathological endpoint. 1H-NMR analysis used water supression with the following protocol: 1 M phosphate buffer, D2O as shift lock reagent, D4-trimethylsilyl­propionic acid as chemical shift reference, noesygppr1d pulse sequence (Bruker). For multivariate data analysis, spectral intensity was binned into 0.04 ppm wide bins. GC/MS analysis of urine was carried out after protein precipitation with methanol, drying, derivatization with methoxyamine hydrochloride in pyridine and with methyl(trimethylsilyl)­trifluoroacetamide on a DB5-MS column using EI ionization. The chromatograms were prepared for multivariate data analysis using the R-program based peak picking and alignment software XCMS version 2.4.0. Principal component analysis (PCA) to detect and visualize time-point and dose-dependent differences between treated animals and controls and orthogonal projection to latent structures discriminant analysis (OPLS-DA) for identification of potential molecular markers of toxicity was carried out using SIMCA P+ 11.5 1H-NMR-based markers were identified and quantified with the Chenomx NMR Suite, GC/MS based markers were identified using the NIST Mass Spectral Database and by co-elution with authentic reference standards. PCA of urinary metabolite profiles was able to differentiate treated animals from controls at the same time as histopathology. An advantage over classical clinical chemistry parameters regarding sensitivity could be observed in some cases. Metabonomic analysis with GC/MS and 1H-NMR revealed alterations in the urinary profile of treated animals 1 day after start of treatment with gentamicin, correlating with changes in clinical chemistry parameters and histopathology. Decreased urinary excretion of citrate, 2-oxoglutarate, hippurate, trigonelline and 3-indoxylsulfate increased excretion of 5-oxoproline, lactate, alanine and glucose were observed. Ochratoxin A treatment caused decreased excretion of citrate, 2-oxoglutarate and hippurate and and increased excretion of glucose, myo-inositol, N,N-dimethylglycine, glycine, alanine and lactate as early as 2 weeks after start of treatment with 210µg OTA/kg bw, correlating with changes in clinical chemistry parameters and histopathology. Integration of histopathology scores increased confidence in the molecular markers discovered. Aristolochic acid treatment resulted in decreased urinary excretion of citrate, 2-oxoglutarate, hippurate and creatinine as well as increased excretion of 5-oxoproline, N,N-dimethylglycine, pseudouridine and uric acid. No alterations in clinical chemistry parameters or histopathology were noted.Decreased excretion of hippurate indicates alterations in the gut microflora, an effect that is expected as pharmacological action of the aminoglycoside antibiotic gentamicin and that can also be explained by the p.o. administration of xenobiotica. Decreased Krebs cycle intermediates (citrate and 2-oxoglutarate) and increased lactate is associated with altered energy metabolism. Increased pseudouridine excretion is associated with cell proliferation and was observed with aristolochic acid and ochratoxin A, for which proliferative processes were observed with histopathology. 5-oxoproline and N,N-dimethylglycine can be associated with oxidative stress. Glucose, a marker of renal damage in clinical chemistry, was observed for all three nephrotoxins studied. Single study analysis with PCA of GC/MS chromatograms and 1H-NMR spectra of urine from 3 studies conducted within the InnoMed PredTox project showing bile duct necrosis revealed alterations in urinary profiles with the onset of changes in clinical chemistry and histopathology. Alterations were mainly decreased Krebs cycle intermediates and changes in the aromatic gut flora metabolites, an effect that may result as a secondary effect from altered bile flow. In conclusion, metabonomics techniques are able to detect toxic lesions at the same time as histopathology and clinical chemistry. The metabolites found to be altered are common to most toxicities and are not organ-specific. A mechanistic link to the observed toxicity has to be established in order to avoid confounders such as body weight loss, pharmacological effects etc. For pattern recognition purposes, large databases are necessary. N2 - Zur Bewertung von Metabonomics-Techniken zur frühen, nicht-invasiven Erkennung von Toxizität wurde Rattenurin nach wiederholter Gabe von Nephrotoxinen mit 1H-NMR und GC/MS analysiert. Untersucht wurden Gentamicin (s.c.-Gabe von 0, 60 und 120 mg/kg Körpergewicht (KG) 2x tägl. über 8 Tage), Ochratoxin A (p.o.-Gabe von 0, 21, 70 und 210 µg/kg KG 5xl wöchentlich für 90 Tage) und Aristolochiasäure (p.o.-Gabe von 0, 0.1, 1.0 und 10 mg/kg KG über 12 Tage). Proben von 16 Studien des InnoMed PredTox Projekts wurden mit 1H-NMR auf den histopathologischen Endpunkt Gallengangnekrose (BDN) untersucht. Folgende Parameter wurden zur 1H-NMR-Analyse mit Wasserunterdrückung verwendet: 1 M Phosphatpuffer, shift lock Reagenz D2O und Referenzierung der chemischen Verschiebung auf D4-Trimethylsilyl­propionsäure, noesygppr1d-Pulssequenz (Bruker). Zur multivariaten Datenanalyse wurden die Spektren in 0.04 ppm große „bins“ unterteilt. Zur GC/MS-Analyse wurden nach Proteinfällung mit Methanol die Urinproben getrocknet und mit Methoxyaminhydrochlorid in Pyridin und Methyl(trimethylsilyl)trifluoracetamid derivatisiert und auf einer DB5-MS -Säule getrennt. Die GC/MS-Chromatogramme wurden mit dem R-Programm-basierten XCMS-Softwarepaket Version 2.4.0 zur multivariaten Datenanalyse vorbereitet. Hauptkomponentenanalyse (PCA) zur Visualisierung von zeit- und dosisabhängigen Unterschieden zwischen Kontrollen und behandelten Tieren und „orthogonal projection to latent structures“-Diskriminantenanalyse (OPLS-DA) zur Identifizierung von Toxizitätsmarkern erfolgte mit SIMCA P+11.5 Die Chenomx-NMR-Suite wurde zur Identifizierung und Quantifizierung von 1H NMR-basierten Markern verwendet; GC/MS-basierte Marker wurden mit der „NIST Mass Spectral Database“ und durch Koelution mit Referenzstandards identifiziert. PCA unterschied Kontroll- von behandelten Tieren zum gleichen Zeitpunkt wie Histopathologie. Gegenüber klinisch-chemischen Parametern war Metabonomics in einigen Fällen empfindlicher. Gentamicin induzierte nach Tag 1 erniedrigte Ausscheidung von Citrat, 2-Oxoglutarat, Hippurat, Trigonellin und 3-Indoxylsulfat Urin, sowie erhöhte Ausscheidung von Lactat, Alanin, 5-Oxoprolin und Glucose, begleitet von geringfügigen Änderungen in klinisch-chemischen Parametern. Ochratoxin A verursachte nach zwei Wochen in einzelnen Tieren eine erniedrigte Ausscheidung von Citrat, 2-Oxoglutarat und Hippurat sowie eine erhöhte Ausscheidung von Glucose, myo-Inositol, N,N-Dimethylglycin, 5-Oxoprolin, Glycin, Alanin und Lactat, korrelierend mit Veränderungen in klinisch-chemischen Parametern und in der Histopathologie. Verwendung von Histopathologiedaten in multivariaten Modellen zur Markeridentifizierung erhöhte die Konfidenz der Marker. Aristolochiasäure induzierte eine erniedrigte Ausscheidung von Citrat, 2-Oxoglutarat, Hippurat und Creatinin und eine erhöhte Ausscheidung von 5-Oxoprolin, N,N-Dimethylglycin und Pseudouridin, ohne Veränderung der klinisch-chemischen Parameter oder der Histopathologie. Erniedrigte Ausscheidung von Hippurat weist auf eine veränderte Darmmikroflora hin; für das Aminoglykosid-Antibiotikum Gentamicin ist dies ein pharmakologischer Effekt, der für die perorale Gabe von Xenobiotica zu erwarten ist. Erniedrigte Ausscheidung von Citrat und 2-Oxoglutarat und erhöhte Ausscheidung von Lactat zeigt einen veränderten Energiestoffwechsel. Erhöhte Ausscheidung von Pseudouridin ist mit Zell­proliferation assoziiert und wurde nach Gabe der Kanzerogene Ochratoxin A und Aristolochiasäure beobachtet, bei denen proliferative Prozesse in der Histopathologie gefunden wurden. 5-Oxoprolin und N,N-Dimethyl­glycin deuten auf erhöhten oxidativen Stress hin. Erhöhte Glucose im Urin, ein Parameter zur Diagnose von Nierenschäden in der klinischen Chemie, wurde in allen drei Studien mit Nephrotoxinen beobachtet. GC/MS- und 1H-NMR-Daten von InnoMed-Studien mit Gallengang­nekrosen als histopathologischen Endpunkt zeigten Veränderung im Urin zeitgleich mit klinisch-chemischen Parametern und Histopathologie; hauptsächlich erniedrigte Ausscheidung von Citratzyklusintermediaten und Veränderungen bei Darmflora-assoziierten Metaboliten, – ein Effekt, der wahrscheinlich veränderten Gallenfluss zurückzuführen ist. Metabonomics ist prinzipiell zum gleichen Zeitpunkt wie klinisch-chemische Parameter und Histopathologie zur Erkennung von toxischen Veränderungen geeignet. Die veränderten Metaboliten sind jedoch zumeist nicht organspezifisch und können mit allgemeinen Toxizitätsmechanismen, wie oxidativem Stress oder Zellproliferation, in Verbindung gebracht werden. Für die Bewertung der Ergebnisse von Metabonomics-Studien ist ein mechanistisches Verständnis der Veränderungen im Urinprofil notwendig, um eine Trennung von toxischen Effekten und solchen, die auf pharmakologische Wirkung, Körpergewichtsverlust etc. zurückzuführen sind, zu erreichen. Für eine Vorhersage von toxischen Mechanismen aufgrund der Urinprofile ist eine größere Datengrundlage notwendig. KW - Toxikologie KW - Protonen-NMR-Spektroskopie KW - GC-MS KW - Multivariate Analyse KW - Niere KW - Leber KW - Metabonomics KW - Toxicology KW - Metabonomics KW - GC/MS KW - 1H-NMR-Spectroscopy KW - multivariate analysis KW - kidney KW - liver Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-43052 ER -