@article{KlotzJesaitis1994,
  author    = {Klotz, Karl-Norbert and Jesaitis, A. J.},
  title     = {Neutrophil chemoattractant receptors and the membrane skeleton},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60471},
  year      = {1994},
  abstract  = {Signal transduction via receptors for N-formylmethionyl peptide chemoattractants (FPR) on human neutrophils is a highly regulated process which involves participation of cytoskeletal elements. Evidence exists suggesting that the cytoskeleton and/or the membrane skeleton controls the distributJon of FPR in the plane of the plasma membrane, thus controlling the accessibility of FPR to different proteins in functionally distinct domains. In desensitized cells, FPR are restricted todomains which are depleted of G proteins but enriched in cytoskeletal proteins such as actin and fodrin. Thus, the G protein signal transduction partners of FPR become inaccessible to the agonist-occupied receptor, preventing cell activation. The mechanism of interaction of FPR with the membrane skeleton is poorly understood but evidence is accumulating that suggests a direct binding of FPR (and other receptors) to cytoskeletal proteins such as actin.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{KlotzJesaitis1994,
  author    = {Klotz, Karl-Norbert and Jesaitis, A. J.},
  title     = {Physical coupling of N-formyl peptide chemoattractant receptors to G protein is not affected by desensitization},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60483},
  year      = {1994},
  abstract  = {Desensitization of N-formyl peptide chemoattractant receptors (FPR) in human neutrophils results in association of these receptors to the membrane skeleton. This is thought to be the critical event in the lateral segregation of receptors and guanyl nucleotide-binding proteins (G proteins) within the plane of the plasma membrane resulting in an interruption of the signaling cascade. In this study we probed the interaction of FPR with G protein in human neutrophils that were desensitized to various degrees. Human neutrophils were desensitized using the photoreactive agonist N-formyl-met-leu-phelys- N\(^\epsilon\)-[\(^{125}\)I]2(p-azidosalicylamido )ethyl-1 ,3 '-dithiopropionate (/MLFK-[\(^{125}\)I]ASD). The interaction if FPR with G protein was studied via a reconstitution assay and subsequent analysis of FPR-G protein complexes in sucrose density gradients. FPR-G protein complexes were reconstituted with solubilized FPR from partially and fully desensitized neutrophils with increasing concentrations of Gi purified from bovine brain. The respective EC\(_{50}\) values for reconstitution were similar to that determined for FPR from unstimulated neutrophils (Bommakanti RK et al., J Bio[ Chem 267: 757~7581, 1992). We conclude, therefore, that the affinity of the interaction of FPR with G protein is not affected by desensitization, consistent with the model of lateral segregation of FPR and G protein as a mechanism of desensitization.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{KlotzJesaitis1994,
  author    = {Klotz, Karl-Norbert and Jesaitis, A. J.},
  title     = {The interaction of N-formyl peptide chemoattractant receptors with the membrane skeleton is energy-dependent},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60499},
  year      = {1994},
  abstract  = {Desensitization of N-fonnyl peptide chemoattractant receptors (FPR) in human neutrophils is thought to be achieved by lateral segregation of receptors and G proteins within the plane of the plasma membrane resulting in an interruption of the signalling cascade. Direct coupling of FPR to membrane skeletal actin appears to be the basis of this process~ however, the molecular mechanism is unknown. In this study we investigated the effect of energy depletion on formation of FPR-membrane skeleton complexes. In addition the effect of the protein kinase C inhibitor stauroporine and the phosphatase inhibitor okadaic acid on coupling of FPR to the membrane skeletonwas studied. Human neutrophils were desensitized using the photoreactive agonist N-formy1-met-leu-phe-1ys-N'[\(^{125}\)I]2(p-azidosalicylamido)ethyl-1,3'-dithiopropionate (fMLFK-[\(^{125}\)I]ASD) after ATP depletion with NaF or after incubation with the respective inhibitors. The interaction of FPR with the membrane skeleton was studied by Sedimentation of the membrane skeleton-associated receptors in sucrose density gradients. Energy depletion of the cells markedly inhibited the formation of FPR-membrane skeleton complexes. This does not appear tobe related to inhibition of protein phosphorylation due to ATP depletion because inhibition of protein kinases and phosphatases bad no significant effect on coupling of FPR to the membrane skeleton. We conclude, therefore, that coupling of FPR to the membrane skeleton is an energy,dependent process which does not appear to require modification of the receptor protein by phosphorylation.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{ShephardLutzSchlatter1994,
  author    = {Shephard, S. E. and Lutz, Werner K. and Schlatter, C.},
  title     = {The lacI transgenic mouse mutagenicity assay: quantitative evaluation in comparison to tests for carcinogenicity and cytogenetic damage in vivo},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-60638},
  year      = {1994},
  abstract  = {The detection Iimit of the lacl transgenic mouse mutagenicity assay lies, in practice, at approximately a 50-100\% increase in mutant frequency in treated animals over controls. The sensitivity of this assay in detecting genotoxins can be markedly improved by subchronic rather than acute application of the test compound. The lac/ transgenic mouse mutagenicity assay was compared quantitatively to rodent carcinogenicity tests and to presently used in vivo mutagenicity assays. With the genotoxic carcinogens tested thus far, a rough correlation between mutagenic potency and carcinogenic potency was observed: on average, to obtain a doubling in lacl mutant frequency the mice bad to be treated with a total dose equal to 50 times the TD50 daily dose Ievel. This total dose could be administered eilher at a high dose rate within a few days or, preferably, at a low dose rate over several weeks. This analysis also indicated that a lacl experiment using a 250-day exposure period would give a detection Iimit approximately equal to that of a long-term carcinogenicity study. In comparison to the micronucleus test or the chromosome aberration assay, acute sturlies with the presently available lacl system offered no increase in sensitivity. However, subchronic lacl sturlies (3-4-month exposure) resulted in an increase in sensitivity over the established tests by 1-2 orders of magnitude (shown with 2-acetylaminofluorene, N-nitrosomethylamine, N-nitrosomethylurea and urethane). 1t is concluded that a positive result in the lacl test can be highly predictive of carcinogenicity butthat a negative result does not provide a large margin of safety.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{StopperKirchnerSchiffmannetal.1994,
  author    = {Stopper, Helga and Kirchner, S. and Schiffmann, D. and Poot, M.},
  title     = {Cell cycle disturbance in relation to micronucleus formation induced by the carcinogenic estrogen diethylstilbestrol},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-82250},
  year      = {1994},
  abstract  = {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.},
  subject      = {Toxikologie},
  language  = {en}
}
@phdthesis{Troesken2005,
  author    = {Tr{\"o}sken, Eva-Regina},
  title     = {Toxicological evaluation of azole fungicides in agriculture and food chemistry},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-17016},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2005},
  abstract  = {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-14\&\#945;-Demethylase (CYP51), die die Demethylierung von Lanosterol zum „Follicular Fluid Meiosis Activating Steroid (FF-MAS)" katalysiert. F{\"u}r Pilze ist das sp{\"a}ter resultierende Ergosterol ein essentieller Bestandteil der Zellmembran. Exponierten Pilzen fehlt Ergosterol was zu einem Zusammenbruch der Zellmembran f{\"u}hrt. S{\"a}ugetiere k{\"o}nnen Cholesterol, das sp{\"a}tere Produkt der Lanosterol-14\&\#945;-Demethylierung, das zur Synthese von z.B. Gallens{\"a}uren und Sexualhormonen n{\"o}tig 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 Aktivit{\"a}t k{\"o}nnte das endokrine System beeinflussen und wird daher als unerw{\"u}nschte Nebenwirkung der Azole betrachtet. Aromatase (CYP19) katalysiert die Demethylierung von Testosteron zu {\"O}stradiol und wird durch Azole gehemmt. Die Verringerung der {\"O}strogenspiegel durch CYP19-Inhibition ist das Wirkprinzip der als Zytostatika genutzten Azole, bei den Fungiziden wird es als unerw{\"u}nschte 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 gegen{\"u}ber 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 Aktivit{\"a}t gegen{\"u}ber humanem CYP19 und humanem CYP51? Sind Zytostatika starke Inhibitoren von humanem CYP19? Zeigen Zytostatika keine Aktivit{\"a}t gegen{\"u}ber 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 Hochdruckfl{\"u}ssigkeitschromatographie gekoppelter Tandem-Massenspektrometrie nach Photosprayionisation gemessen. Das humane CYP51 wurde von „BD Gentest Cooperation" zur Verf{\"u}gung gestellt. Ein katalytisch aktiver Enzymkomplex bestehend aus der Lanosterol-14\&\#945;-Demethylase von Candida albicans und der Oxidoreduktase von Candida tropicalis, wurde im Baculovirussystem exprimiert. Ein Vergleich der inhibitorischen Wirkst{\"a}rke der Substanzen auf menschliches CYP19 und CYP51 und Pilz-CYP51 zeigt, dass einige Azole das erw{\"u}nschte Bild zeigen. Dazu geh{\"o}ren die beiden Zytostatika Fadrozol und Letrozol, sowie Fluconazol und Itraconazol, zwei Antimykotika aus der Humanmedizin, und einige Fungizide z.B. Cyproconazol und Hexaconazol. Ein unerw{\"u}nschtes Bild zeigen z.B. Prochloraz, Bifonazol, Ketoconazol und Miconazol. Sieben Azole weisen ein gemischtes Bild an inhibitorischen Wirkst{\"a}rken auf. Um einen modellartigen Eindruck der R{\"u}ckst{\"a}nde von Azolen in Lebensmitteln zu erhalten, wurde eine auf LC-ESI-MS/MS basierende R{\"u}ckstandsanalytik f{\"u}r Azole im Wein entwickelt. Alle gefunden R{\"u}ckst{\"a}nde lagen unterhalb der beh{\"o}rdlich festgelegten R{\"u}ckstandsh{\"o}chstmengen. Um die inhibitorische Wirkung der Azole auf die verschiedenen Enzymsysteme in einem gr{\"o}ßeren Zusammenhang zu bringen, wurden die IC50 Werte mit Expositionsdaten von Bauern, maximalen Plasmaspiegeln in Patienten nach der Einnahme von Antimykotika und mit Expositionsgrenzwerten f{\"u}r die Langzeitaufnahme von Pflanzenschutzmittelr{\"u}ckst{\"a}nden („Acceptable Daily Intake Levels", ADI) verglichen. Basierend auf den dargestellten Ergebnissen k{\"o}nnen folgende Schlussfolgerungen gezogen werden. Das Risiko f{\"u}r landwirtschaftliche Arbeiter durch Exposition gegen{\"u}ber Azolfungiziden kann im Bezug auf menschliches CYP19 und CYP51 als vernachl{\"a}ssigbar eingestuft werden, wenn die entsprechenden Sicherheitsvorkehrungen getroffen werden. Im medizinischen Bereich muss grunds{\"a}tzlich der Einsatz von Bifonazol, Miconazol und Ketoconazol mit Blick auf die hohe inhibitorische Potenz gegen{\"u}ber menschlichem CYP19 und 51 kritisch betrachtet werden. Unter der Annahme, dass die ADI Werte eingehalten werden, stellen R{\"u}ckst{\"a}nde auf Lebensmitteln in Bezug auf die genannten Enzymsysteme keine Bedrohung f{\"u}r den Verbraucher da. Die Inhibition von CYP19 muss als St{\"o}rung des Hormonsystems angesehen werden. Die Bedeutung von FF-MAS und T-MAS im endokrinen System muss noch abschließend gekl{\"a}rt werden und damit auch die Frage, wie viel Bedeutung der Inhibition von menschlichem CYP51 beigemessen werden muss.},
  subject      = {Azole},
  language  = {en}
}
@phdthesis{Sieber2009,
  author    = {Sieber, Maximilian},
  title     = {Evaluation of 1H-NMR and GC/MS-based metabonomics for the assessment of liver and kidney toxicity},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-43052},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {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.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{FoertschHuppMaetal.2011,
  author    = {F{\"o}rtsch, Christina and Hupp, Sabrina and Ma, Jiangtao and Mitchell, Timothy J. and Maier, Elke and Benz, Roland and Iliev, Asparouh I.},
  title     = {Changes in Astrocyte Shape Induced by Sublytic Concentrations of the Cholesterol-Dependent Cytolysin Pneumolysin Still Require Pore-Forming Capacity},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-69084},
  year      = {2011},
  abstract  = {Streptococcus pneumoniae is a common pathogen that causes various infections, such as sepsis and meningitis. A major pathogenic factor of S. pneumoniae is the cholesterol-dependent cytolysin, pneumolysin. It produces cell lysis at high concentrations and apoptosis at lower concentrations. We have shown that sublytic amounts of pneumolysin induce small GTPase-dependent actin cytoskeleton reorganization and microtubule stabilization in human neuroblastoma cells that are manifested by cell retraction and changes in cell shape. In this study, we utilized a live imaging approach to analyze the role of pneumolysin's pore-forming capacity in the actin-dependent cell shape changes in primary astrocytes. After the initial challenge with the wild-type toxin, a permeabilized cell population was rapidly established within 20-40 minutes. After the initial rapid permeabilization, the size of the permeabilized population remained unchanged and reached a plateau. Thus, we analyzed the non-permeabilized (non-lytic) population, which demonstrated retraction and shape changes that were inhibited by actin depolymerization. Despite the non-lytic nature of pneumolysin treatment, the toxin's lytic capacity remained critical for the initiation of cell shape changes. The non-lytic pneumolysin mutants W433F-pneumolysin and delta6-pneumolysin, which bind the cell membrane with affinities similar to that of the wild-type toxin, were not able to induce shape changes. The initiation of cell shape changes and cell retraction by the wild-type toxin were independent of calcium and sodium influx and membrane depolarization, which are known to occur following cellular challenge and suggested to result from the ion channel-like properties of the pneumolysin pores. Excluding the major pore-related phenomena as the initiation mechanism of cell shape changes, the existence of a more complex relationship between the pore-forming capacity of pneumolysin and the actin cytoskeleton reorganization is suggested.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{HintzscheJastrowKleineOstmannetal.2012,
  author    = {Hintzsche, Henning and Jastrow, Christian and Kleine-Ostmann, Thomas and K{\"a}rst, Uwe and Schrader, Thorsten and Stopper, Helga},
  title     = {Terahertz electromagnetic fields (0.106 THz) do not induce manifest genomic damage in vitro},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-76268},
  year      = {2012},
  abstract  = {Terahertz electromagnetic fields are non-ionizing electromagnetic fields in the frequency range from 0.1 to 10 THz. Potential applications of these electromagnetic fields include the whole body scanners, which currently apply millimeter waves just below the terahertz range, but future scanners will use higher frequencies in the terahertz range. These and other applications will bring along human exposure to these fields. Up to now, only a limited number of investigations on biological effects of terahertz electromagnetic fields have been performed. Therefore, research is strongly needed to enable reliable risk assessment. Cells were exposed for 2 h, 8 h, and 24 h with different power intensities ranging from 0.04 mW/cm2 to 2 mW/cm2, representing levels below, at, and above current safety limits. Genomic damage on the chromosomal level was measured as micronucleus formation. DNA strand breaks and alkali-labile sites were quantified with the comet assay. No DNA strand breaks or alkali-labile sites were observed as a consequence of exposure to terahertz electromagnetic fields in the comet assay. The fields did not cause chromosomal damage in the form of micronucleus induction.},
  subject      = {Toxikologie},
  language  = {en}
}