TY - JOUR A1 - Abdelmohsen, Usama Ramadan A1 - Szesny, Matthias A1 - Othman, Eman Maher A1 - Schirmeister, Tanja A1 - Grond, Stepanie A1 - Stopper, Helga A1 - Hentschel, Ute T1 - Antioxidant and Anti-Protease Activities of Diazepinomicin from the Sponge-Associated Micromonospora Strain RV115 N2 - Diazepinomicin is a dibenzodiazepine alkaloid with an unusual structure among the known microbial metabolites discovered so far. Diazepinomicin was isolated from the marine sponge-associated strain Micromonospora sp. RV115 and was identified by spectroscopic analysis and by comparison to literature data. In addition to its interesting preclinical broad-spectrum antitumor potential, we report here new antioxidant and anti-protease activities for this compound. Using the ferric reducing antioxidant power (FRAP) assay, a strong antioxidant potential of diazepinomicin was demonstrated. Moreover, diazepinomicin showed a significant antioxidant and protective capacity from genomic damage induced by the reactive oxygen species hydrogen peroxide in human kidney (HK-2) and human promyelocytic (HL-60) cell lines. Additionally, diazepinomicin inhibited the proteases rhodesain and cathepsin L at an IC50 of 70–90 μM. It also showed antiparasitic activity against trypomastigote forms of Trypanosoma brucei with an IC50 of 13.5 μM. These results showed unprecedented antioxidant and anti-protease activities of diazepinomicin, thus further highlighting its potential as a future drug candidate. KW - Biologie KW - diazepinomicin KW - anti-protease KW - antioxidant KW - actinomycetes KW - Micromonospora Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-76279 ER - TY - JOUR A1 - Adam, W. A1 - Ahrweiler, M. A1 - Saha-Möller, C. R. A1 - Sauter, M. A1 - Schönberger, A. A1 - Epe, B. A1 - Müller, E. A1 - Schiffmann, D. A1 - Stopper, Helga A1 - Wild, D. T1 - Genotoxicity studies of benzofuran dioxetanes and epoxides with isolated DNA, bacteria and mammalian cells N2 - 1.2-Dioxetanes, very reactive and high energy molecules. are involved as labile intermediates in dioxygenase- activated aerobic metabolism and in physiological processes. Various toxico1ogica1 tests reveal that dioxetanes are indeed genotoxic. In supercoiled DNA of bacteriophage PM2 they induce endonucleasesensitive sites, most of them are FPG protein-sensitive base modifications (8-hydroxyguanine, fonnamidopyrimidines). Pyrimidinedimersand sites ofbase loss (AP sites) which were probed by UV endonuclease and exonuclease 111 are minor lesions in this system. While the alky1-substituted dioxetanes do not show any significant mutagenic activity in different Salmonella typhimurium strains, heteroarene dioxetanes such as benzofuran and furocoumarin dioxetanes are strongly mutagenic in S. typhimurium strain TA I 00. DNA adducts formed with an intermediary alkyJating agent appear to be responsible for the mutagenic activity of benzofuran dioxetane. We assume that the benzofuran epoxides, generated in situ from benzofuran dioxetanes by deoxygenation are the ultimate mutagens of the latter. since benzofuran epoxides are highly mutagenic in the S. typhimurium strain TAIOO and they form DNA adducts. as detected by the 212Ppostlabelling technique. Our results imply that the type of D NA darnage promoted by dioxetanes is dependent on the structural feature of dioxetanes. Furthermore, the direct photochemical DNA darnage by energy transfer. i.e., pyrimidine dimers, plays a minor role in the genotoxicity of dioxetanes. Instead, photooxidation dominates in isolated DNA. while radical darnage and alkylation prevail in the cellular system. KW - Toxikologie KW - 1 KW - 2-Dioxetane KW - Benzefuran dioxetane KW - Benzefuran epoxide KW - DNA damage KW - Mutagenicity KW - DNA adduct . Repair endonuclease KW - FPG protein Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63420 ER - TY - JOUR A1 - Awad, Eman A1 - Othman, Eman M. A1 - Stopper, Helga T1 - Effects of resveratrol, lovastatin and the mTOR-inhibitor RAD-001 on insulin-induced genomic damage in vitro JF - Molecules N2 - Diabetes mellitus (DM) is one of the major current health problems due to lifestyle changes. Before diagnosis and in the early years of disease, insulin blood levels are elevated. However, insulin generates low levels of reactive oxygen species (ROS) which are integral to the regulation of a variety of intracellular signaling pathways, but excess levels of insulin may also lead to DNA oxidation and DNA damage. Three pharmaceutical compounds, resveratrol, lovastatin and the mTOR-inhibitor RAD-001, were investigated due to their known beneficial effects. They showed protective properties against genotoxic damage and significantly reduced ROS after in vitro treatment of cultured cells with insulin. Therefore, the selected pharmaceuticals may be attractive candidates to be considered for support of DM therapy. KW - genomic damage KW - insulin KW - resveratrol KW - lovastatin KW - mTOR-inhibitor RAD-001 Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159260 VL - 22 IS - 12 ER - TY - JOUR A1 - Balasubramanian, Srikkanth A1 - Othman, Eman M. A1 - Kampik, Daniel A1 - Stopper, Helga A1 - Hentschel, Ute A1 - Ziebuhr, Wilma A1 - Oelschlaeger, Tobias A. A1 - Abdelmohsen, Usama R. T1 - Marine sponge-derived Streptomyces sp SBT343 extract inhibits staphylococcal biofilm formation JF - Frontiers in Microbiology N2 - Staphylococcus epidermidis and Staphylococcus aureus are opportunistic pathogens that cause nosocomial and chronic biofilm-associated infections. Indwelling medical devices and contact lenses are ideal ecological niches for formation of staphylococcal biofilms. Bacteria within biofilms are known to display reduced susceptibilities to antimicrobials and are protected from the host immune system. High rates of acquired antibiotic resistances in staphylococci and other biofilm-forming bacteria further hamper treatment options and highlight the need for new anti-biofilm strategies. Here, we aimed to evaluate the potential of marine sponge-derived actinomycetes in inhibiting biofilm formation of several strains of S. epidermidis, S. aureus, and Pseudomonas aeruginosa. Results from in vitro biofilm-formation assays, as well as scanning electron and confocal microscopy, revealed that an organic extract derived from the marine sponge-associated bacterium Streptomyces sp. SBT343 significantly inhibited staphylococcal biofilm formation on polystyrene, glass and contact lens surfaces, without affecting bacterial growth. The extract also displayed similar antagonistic effects towards the biofilm formation of other S. epidermidis and S. aureus strains tested but had no inhibitory effects towards Pseudomonas biofilms. Interestingly the extract, at lower effective concentrations, did not exhibit cytotoxic effects on mouse fibroblast, macrophage and human corneal epithelial cell lines. Chemical analysis by High Resolution Fourier Transform Mass Spectrometry (HRMS) of the Streptomyces sp. SBT343 extract proportion revealed its chemical richness and complexity. Preliminary physico-chemical characterization of the extract highlighted the heat-stable and non-proteinaceous nature of the active component(s). The combined data suggest that the Streptomyces sp. SBT343 extract selectively inhibits staphylococcal biofilm formation without interfering with bacterial cell viability. Due to absence of cell toxicity, the extract might represent a good starting material to develop a future remedy to block staphylococcal biofilm formation on contact lenses and thereby to prevent intractable contact lens-mediated ocular infections. KW - medicine KW - marine sponges KW - actinomycetes KW - Streptomyces KW - staphilococci KW - biofilms KW - contact lens Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171844 VL - 8 ER - TY - JOUR A1 - Bankoglu, Ezgi Eyluel A1 - Arnold, Charlotte A1 - Hering, Ilona A1 - Hankir, Mohammed A1 - Seyfried, Florian A1 - Stopper, Helga T1 - Decreased chromosomal damage in lymphocytes of obese patients after bariatric surgery JF - Scientific Reports N2 - The number of bariatric surgeries being performed worldwide has markedly risen. While the improvement in obesity-associated comorbidities after bariatric surgery is well-established, very little is known about its impact on cancer risk. The peripheral lymphocyte micronucleus test is a widely used method for the monitoring of chromosomal damage levels in vivo, and micronucleus frequency positively correlates with cancer risk. Therefore, the aim of this study was to compare the micronucleus frequency before and after bariatric surgery in obese subjects. Peripheral blood mononuclear cells were collected from 45 obese subjects before and at two time-points after bariatric surgery (6 and 12 months) to assess spontaneous micronucleus frequency. Consistent with the increased cancer risk previously shown, bariatric surgery-induced weight loss led to a significant reduction in lymphocyte micronucleus frequency after 12 months. Interestingly, comorbidities such as type 2 diabetes mellitus and metabolic syndrome further seemed to have an impact on the lymphocyte micronucleus frequency. Our findings may indicate a successful reduction of cancer risk in patients following weight loss caused by bariatric surgery. KW - obesity KW - bariatric surgery KW - cancer risk Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-177090 VL - 8 IS - 11195 ER - TY - JOUR A1 - Bankoglu, Ezgi Eyluel A1 - Schuele, Carolin A1 - Stopper, Helga T1 - Cell survival after DNA damage in the comet assay JF - Archives of Toxicology N2 - The comet assay is widely used in basic research, genotoxicity testing, and human biomonitoring. However, interpretation of the comet assay data might benefit from a better understanding of the future fate of a cell with DNA damage. DNA damage is in principle repairable, or if extensive, can lead to cell death. Here, we have correlated the maximally induced DNA damage with three test substances in TK6 cells with the survival of the cells. For this, we selected hydrogen peroxide (H\(_{2}\)O\(_{2}\)) as an oxidizing agent, methyl methanesulfonate (MMS) as an alkylating agent and etoposide as a topoisomerase II inhibitor. We measured cell viability, cell proliferation, apoptosis, and micronucleus frequency on the following day, in the same cell culture, which had been analyzed in the comet assay. After treatment, a concentration dependent increase in DNA damage and in the percentage of non-vital and apoptotic cells was found for each substance. Values greater than 20-30% DNA in tail caused the death of more than 50% of the cells, with etoposide causing slightly more cell death than H\(_{2}\)O\(_{2}\) or MMS. Despite that, cells seemed to repair of at least some DNA damage within few hours after substance removal. Overall, the reduction of DNA damage over time is due to both DNA repair and death of heavily damaged cells. We recommend that in experiments with induction of DNA damage of more than 20% DNA in tail, survival data for the cells are provided. KW - Cell death and comet assay KW - DNA damage KW - DNA repair Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265339 VL - 95 IS - 12 ER - TY - JOUR A1 - Bankoglu, Ezgi Eyluel A1 - Stipp, Franzisca A1 - Gerber, Johanna A1 - Seyfried, Florian A1 - Heidland, August A1 - Bahner, Udo A1 - Stopper, Helga T1 - Effect of cryopreservation on DNA damage and DNA repair activity in human blood samples in the comet assay JF - Archives of Toxicology N2 - The comet assay is a commonly used method to determine DNA damage and repair activity in many types of samples. In recent years, the use of the comet assay in human biomonitoring became highly attractive due to its various modified versions, which may be useful to determine individual susceptibility in blood samples. However, in human biomonitoring studies, working with large sample numbers that are acquired over an extended time period requires some additional considerations. One of the most important issues is the storage of samples and its effect on the outcome of the comet assay. Another important question is the suitability of different blood preparations. In this study, we analysed the effect of cryopreservation on DNA damage and repair activity in human blood samples. In addition, we investigated the suitability of different blood preparations. The alkaline and FPG as well as two different types of repair comet assay and an in vitro hydrogen peroxide challenge were applied. Our results confirmed that cryopreserved blood preparations are suitable for investigating DNA damage in the alkaline and FPG comet assay in whole blood, buffy coat and PBMCs. Ex vivo hydrogen peroxide challenge yielded its optimal effect in isolated PBMCs. The utilised repair comet assay with either UVC or hydrogen peroxide-induced lesions and an aphidicolin block worked well in fresh PBMCs. Cryopreserved PBMCs could not be used immediately after thawing. However, a 16-h recovery with or without mitotic stimulation enabled the application of the repair comet assay, albeit only in a surviving cell fraction. KW - human biomonitoring KW - DNA damage KW - DNA repair KW - comet assay KW - blood samples Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265326 VL - 95 IS - 5 ER - TY - JOUR A1 - Bankoglu, Ezgi Eyluel A1 - Tschopp, Oliver A1 - Schmitt, Johannes A1 - Burkard, Philipp A1 - Jahn, Daniel A1 - Geier, Andreas A1 - Stopper, Helga T1 - Role of PTEN in Oxidative Stress and DNA Damage in the Liver of Whole-Body Pten Haplodeficient Mice JF - PLoS One N2 - Type 2 diabetes (T2DM) and obesity are frequently associated with non-alcoholic fatty liver disease (NAFLD) and with an elevated cancer incidence. The molecular mechanisms of carcinogenesis in this context are only partially understood. High blood insulin levels are typical in early T2DM and excessive insulin can cause elevated reactive oxygen species (ROS) production and genomic instability. ROS are important for various cellular functions in signaling and host defense. However, elevated ROS formation is thought to be involved in cancer induction. In the molecular events from insulin receptor binding to genomic damage, some signaling steps have been identified, pointing at the PI3K/AKT pathway. For further elucidation Phosphatase and Tensin homolog (Pten), a tumour suppressor phosphatase that plays a role in insulin signaling by negative regulation of PI3K/AKT and its downstream targets, was investigated here. Dihydroethidium (DHE) staining was used to detect ROS formation in immortalized human hepatocytes. Comet assay and micronucleus test were performed to investigate genomic damage in vitro. In liver samples, DHE staining and western blot detection of HSP70 and HO-1 were performed to evaluate oxidative stress response. DNA double strand breaks (DSBs) were detected by immunohistostaining. Inhibition of PTEN with the pharmacologic inhibitor VO-OHpic resulted in increased ROS production and genomic damage in a liver cell line. Knockdown of Pten in a mouse model yielded increased oxidative stress levels, detected by ROS levels and expression of the two stress-proteins HSP70 and HO-1 and elevated genomic damage in the liver, which was significant in mice fed with a high fat diet. We conclude that PTEN is involved in oxidative stress and genomic damage induction in vitro and that this may also explain the in vivo observations. This further supports the hypothesis that the PI3K/AKT pathway is responsible for damaging effects of high levels of insulin. KW - insulin KW - mouse models DNA damage KW - oxidative stress KW - mammalian genomics KW - fatty liver KW - micronuclei KW - insulin signaling Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-146970 VL - 11 IS - 11 ER - TY - JOUR A1 - Cheng, Cheng A1 - Othman, Eman M. A1 - Stopper, Helga A1 - Edrada-Ebel, RuAngelie A1 - Hentschel, Ute A1 - Abdelmohsen, Usama Ramadan T1 - Isolation of petrocidin A, a new cytotoxic cyclic dipeptide from the marine sponge-derived bacterium \(Streptomyces\) sp. SBT348 JF - Marine Drugs N2 - A new cyclic dipeptide, petrocidin A (\(\textbf{1}\)), along with three known compounds—2,3-dihydroxybenzoic acid (\(\textbf{2}\)), 2,3-dihydroxybenzamide (\(\textbf{3}\)), and maltol (\(\textbf{4}\))—were isolated from the solid culture of \(Streptomyces\) sp. SBT348. The strain \(Streptomyces\) sp. SBT348 had been prioritized in a strain collection of 64 sponge-associated actinomycetes based on its distinct metabolomic profile using liquid chromatography/high-resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR). The absolute configuration of all α-amino acids was determined by HPLC analysis after derivatization with Marfey’s reagent and comparison with commercially available reference amino acids. Structure elucidation was pursued in the presented study by mass spectrometry and NMR spectral data. Petrocidin A (\(\textbf{1}\)) and 2,3-dihydroxybenzamide (\(\textbf{3}\)) exhibited significant cytotoxicity towards the human promyelocytic HL-60 and the human colon adenocarcinoma HT-29 cell lines. These results demonstrated the potential of sponge-associated actinomycetes for the discovery of novel and pharmacologically active natural products. KW - biology KW - sponges KW - actinomycetes KW - streptomyces KW - cyclic dipeptide KW - cytotoxic Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172644 VL - 15 IS - 12 ER - TY - JOUR A1 - Djelić, Ninoslav A1 - Borozan, Sunčica A1 - Dimitrijević-Srećković, Vesna A1 - Pajović, Nevena A1 - Mirilović, Milorad A1 - Stopper, Helga A1 - Stanimirović, Zoran T1 - Oxidative stress and DNA damage in peripheral blood mononuclear cells from normal, obese, prediabetic and diabetic persons exposed to thyroid hormone in vitro JF - International Journal of Molecular Sciences N2 - Diabetes, a chronic group of medical disorders characterized byhyperglycemia, has become a global pandemic. Some hormones may influence the course and outcome of diabetes, especially if they potentiate the formation of reactive oxygen species (ROS). There is a close relationship between thyroid disorders and diabetes. The main objective of this investigation was to find out whether peripheral blood mononuclear cells (PBMCs) are more prone to DNA damage by triiodothyronine (T\(_3\)) (0.1, 1 and 10 μM) at various stages of progression through diabetes (obese, prediabetics, and type 2 diabetes mellitus—T2DM persons). In addition, some biochemical parameters of oxidative stress (catalase-CAT, thiobarbituric acid reactive substances—TBARS) and lactate dehydrogenase (LDH) were evaluated. PBMCs from prediabetic and diabetic patients exhibited increased sensitivity for T\(_3\) regarding elevated level of DNA damage, inhibition of catalase, and increase of TBARS and LDH. PBMCs from obese patients reacted in the same manner, except for DNA damage. The results of this study should contribute to a better understanding of the role of thyroid hormones in the progression of T2DM. KW - diabetes KW - oxidative stress KW - DNA damage KW - lymphocytes KW - thyroid hormone Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-285988 SN - 1422-0067 VL - 23 IS - 16 ER - TY - JOUR A1 - Epe, B. A1 - Harttig, U. A1 - Stopper, Helga A1 - Metzler, M. T1 - Covalent binding of reactive estrogen metabolites to microtubular protein as a possible mechanism of aneuploidy induction and neoplastic cell transformation N2 - Neoplastic cell transfonnation induced by estrogens and some other carcinogen& such as benzene appears to involve the induction of mitotic aneuploidy rather than DNA damage and point mutations. As metabolic activation may also play an important roJe in the mechanism of carcinogenesis of these nongenotoxic compounds, we have studied the Interaction of reactive quinone metabolites of various estrogens and of benzene with the major microtubular protein, tubulin, in a cell-free system. Covalent binding of the radioactively labeled metabolites to the a- and 13-subunit of tubulin was found to depend on the structure of the metabolite. When the adducted tubulins were tested in vitro for their ability to polymerize to microtubules, Inhibition of microtubule assembly was obsened in every case, although to varying extents. It is proposed that the fonnation of covalent tubulin adducts may impair the formation of mitotic spindies and thus contribute to chromosomal nondisjunction and aneuploidy induction. KW - Toxikologie Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63478 ER - TY - JOUR A1 - Epe, Bernd A1 - Häring, Martin A1 - Ramaiah, Danaboyina A1 - Stopper, Helga A1 - Abou-Elzahab, Mohamed M. A1 - Adam, Waldemar A1 - Saha-Möller, Chantu R. T1 - DNA damage induced by furocoumarin hydroperoxides plus UV (360 nm) N2 - Wben irradiated at 360 nm, furocoumarins with a hydroperoxide group in a side chain effciently give rise to a type of DNA damage that can best be explained by a photoinduced generation of hydroxyl radicals from the excited pbotosensitizers. The observed DNA damage profiles, i.e. the ratios of single-strand breaks, sites of base loss (AP sites) and base modifications sensitive to fonnamidopyrimidine-DNA glycosylase (FPG protein) and endonuclease m, are similar to the DNA damage profile produced by hydroxyl radicals generated by lonizing radiation or by xanthine and xanthine oxidase in the presence of Fe(III)-EDTA. No such damage is observed with the corresponding furocoumarin alcohols or in the absence of near-UV radiation. The damage caused by the photo-excited hydroperoxides is not influenced by superoxide dismutase (SOD) or catalase or by D2O as solvent. The presence of t-butanol, however, reduces both the formation of single-strand breaks and of base odifications sensitive to FPG protein. The cytotoxicity caused by one of the hydroperoxides in L5178Y mome lymphoma cells is found to be dependent on the near-UV irradiation and to be much higher than that of the corresponding alcohol. Therefore the new type of photoinduced damage occurs inside cells. Intercalating photosensitizers with an attached hydroperoxide group might represent a novel and versatile class of DNA damaging agents, e.g. for phototherapy. KW - DNS-Schädigung Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86870 ER - TY - JOUR A1 - Hadi, Naji Said Aboud A1 - Bankoglu, Ezgi Eyluel A1 - Stopper, Helga T1 - Genotoxicity of pyrrolizidine alkaloids in metabolically inactive human cervical cancer HeLa cells co-cultured with human hepatoma HepG2 cells JF - Archives of Toxicology N2 - Pyrrolizidine alkaloids (PAs) are secondary plant metabolites, which can be found as contaminant in various foods and herbal products. Several PAs can cause hepatotoxicity and liver cancer via damaging hepatic sinusoidal endothelial cells (HSECs) after hepatic metabolization. HSECs themselves do not express the required metabolic enzymes for activation of PAs. Here we applied a co-culture model to mimic the in vivo hepatic environment and to study PA-induced effects on not metabolically active neighbour cells. In this co-culture model, bioactivation of PA was enabled by metabolically capable human hepatoma cells HepG2, which excrete the toxic and mutagenic pyrrole metabolites. The human cervical epithelial HeLa cells tagged with H2B-GFP were utilized as non-metabolically active neighbours because they can be identified easily based on their green fluorescence in the co-culture. The PAs europine, riddelliine and lasiocarpine induced micronuclei in HepG2 cells, and in HeLa H2B-GFP cells co-cultured with HepG2 cells, but not in HeLa H2B-GFP cells cultured alone. Metabolic inhibition of cytochrome P450 enzymes with ketoconazole abrogated micronucleus formation. The efflux transporter inhibitors verapamil and benzbromarone reduced micronucleus formation in the co-culture model. Furthermore, mitotic disturbances as an additional genotoxic mechanism of action were observed in HepG2 cells and in HeLa H2B-GFP cells co-cultured with HepG2 cells, but not in HeLa H2B-GFP cells cultured alone. Overall, we were able to show that PAs were activated by HepG2 cells and the metabolites induced genomic damage in co-cultured HeLa cells. KW - co-culture KW - micronuclei KW - mitotic disturbance KW - cytochrome P450s KW - membrane transporters KW - pyrrolizidine alkaloids Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324708 VL - 97 IS - 1 ER - TY - JOUR A1 - Hintzsche, Henning A1 - Jastrow, Christian A1 - Kleine-Ostmann, Thomas A1 - Kärst, Uwe A1 - Schrader, Thorsten A1 - Stopper, Helga T1 - Terahertz electromagnetic fields (0.106 THz) do not induce manifest genomic damage in vitro N2 - 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. KW - Toxikologie Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-76268 ER - TY - JOUR A1 - Hintzsche, Henning A1 - Montag, Gracia A1 - Stopper, Helga T1 - Induction of micronuclei by four cytostatic compounds in human hematopoietic stem cells and human lymphoblastoid TK6 cells JF - Scientific Reports N2 - For mutagenicity testing, primary lymphocytes or mammalian cell lines are employed. However, the true target for carcinogenic action of mutagenic chemicals may be stem cells. Since hematopoietic cancers induced by chemical agents originate at the hematopoietic stem cell (HSC) stage and since one of the side effects of chemotherapeutic cancer treatment is the induction of secondary tumors, often leukemias, HSC may be a suitable cell system. We compared the sensitivity of HSC with the genotoxicity testing cell line TK6 for chromosomal mutations. HSC were less sensitive than TK6 cells for the genotoxic effects of the model genotoxins and chemotherapeutic agents doxorubicin, vinblastine, methyl methanesulfonate (MMS) and equally sensitive for mitomycin C (MMC). However, loss of viability after mitomycin C treatment was higher in HSC than in TK6 cells. Among the factors that may influence sensitivity for genomic damage, the generation or response to reactive oxygen species (ROS) and the effectiveness of DNA damage response can be discussed. Here we show that HSC can be used in a standard micronucleus test protocol for chromosomal mutations and that their sensitivity was not higher than that of a classical testing cell line. KW - apoptosis KW - haematopoietic stem cells KW - TK6 cells KW - micronuclei Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-176210 VL - 8 IS - 3371 ER - TY - JOUR A1 - Holler, E. A1 - Fischer, H. A1 - Weber, C. A1 - Stopper, Helga A1 - Steger, H. A1 - Simek, H. T1 - A DNA polymerase with unusual properties from the slime mold Physarum polycephalum N2 - Two forms of a DNA polymerase have been purified from microplasmodia of Physarum polycephalum by poly(ethyleneimine) precipitation and chromatography on DEAE-Sephacel, phosphocellulose, heparin Sepharose, hydroxyapatite, DNA-agarose, blue-Sepharose. They were separated from DNA polymerase cx on phosphocellulose and from each other on heparin-Sepharose. Form HS1 enzymewas 30-40% pure and form HS2 enzyme 60% with regard toprotein contents of the preparations. Form HS2 enzymewas generated from form HS1 enzyme on prolonged standing of enzyme preparations. The DNA polymerases were obtained as complexes of a 60-kDa protein associated with either a 135-kDa (HS1) or a 110-kDa (HS2) DNA-polymerizing polypeptidein a 1:1 molar stoichiometry. The biochemical function of the 60-kDa protein remained unknown. The complexes tended to dissociate during gradient centrifugation and during partition chromatography as weil as during polyacrylamide gradient gel electrophoresis under nondenaturing conditions at high dilutions of samples. Both forms existed in plasmodia extracts, their proportions depending on several factors including those which promoted proteolysis. The DNA polymerases resembled eucaryotic DNA polymerase ß by several criteria and were functionally indistinguishable from each other. It is suggested that lower eucaryotes contain repair DNA polymerases, which are similar to those of eubacteria on a molecular mass basis. KW - Toxikologie Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63501 ER - TY - JOUR A1 - Ilin, Alexander A1 - Kulmanov, Murat A1 - Nersesyan, Armen A1 - Stopper, Helga T1 - Genotoxic activity of the new pharmaceutical FS-1 in Salmonella/microsome test and mouse lymphoma L5178Y cells JF - Journal of BUON N2 - Purpose: The purpose of this study was to determine possible genotoxic effects of a new very promising antibacterial/ antiviral drug FS-1. Methods: The drug was tested in TA98, TA100, TA102, TA 1535 and TA1537 strains of Salmonella (Ames test) with and without metabolic activation, and also in mouse lymphoma L5178Y cells by means of micronucleus and comet assays. In microbes the drug was tested at concentrations up to 500 \(\mu\)g/plate and in mouse lymphoma cells up to 2,000 \(\mu\)g/ml. Results: In both test-systems in all experiments completely negative results were obtained although FS-1 was tested at maximum tolerated doses. Conclusions: The drug is not genotoxic. This is advantageous because many antibacterial/antiviral drugs possess such activity. KW - mutagenicity KW - antibacterial/antiviral drug KW - comet assay KW - mouse lymphoma L5178Y KW - Salmonella/microsome assay KW - micronucleus test Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-143769 VL - 20 IS - 2 ER - TY - JOUR A1 - Janevski, J. A1 - Choh, V. A1 - Stopper, Helga A1 - Schiffmann, D. A1 - De Boni, U. T1 - Diethylstilbestrol alters the morphology and calcium levels of growth cones of PC12 cells in vitro N2 - Diethylstilbestrol (DES) is a synthetic estrogen with carcinogenic properties. DES is known to alter cytoskeletal components, including the organization of actin stress fibres in C6 rat glioma cells. ln a test of the hypothesis that DES disrupts actin Filaments of growth cones in neuron-like cells, DES-induced changes in filopodial lengths were quantified in rat pheochromocytoma (PC12) cells in vitro. DES significantly altered growth cone morphology, with collapse of growth cone filopodia and neurite retraction invariably occurring at a concentration of 10 MikroM. At 5 MikroM DES, transient reductions in total filopodiallengths occurred. At DES concentrations of 0.1 nM and 1 nM, reductions in total filopodiallengths occurred in a fraction of growth cones. Evidence exists which shows that growth cone activity and morphology are intimately linked to Ieveis of intracellular, free calcium and that DES increases such levels. Measurements of free intracellular calcium levels by fluorescence microscopy, at times concurrent with the DES-induced reduction in total filopodial lengths, showed that calcium levels were indeed significantly increased by 10 MirkoM DES. Labelling of filamentaus actin (f-actin) with FITC-phalloidin showed that the f-actin distribution in growth cones exposed to DES could not be differentiated from the distribution found in spontaneously retracting growth cones. Tagether with evidence which showed that growth cone motility was not affected, the results are taken to indicate that DES, rather than acting directly on the cytoskeleton, exerts its effects indirectly, by a calcium-induced destabilization of actin filaments in the growth cone. KW - Calcium KW - Zellskelett KW - Wachstumskonus KW - Diethylstilbestrol KW - Diethylstilbestrol KW - rat pheochromocytoma cells KW - growth cone KW - cytoskeleton KW - calcium Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86858 ER - TY - JOUR A1 - Kannen, Vinicius A1 - Hintzsche, Henning A1 - Zanette, Dalila L. A1 - Silva Jr., Wilson A. A1 - Garcia, Sergio B. A1 - Waaga-Gasser, Anna Maria A1 - Stopper, Helga T1 - Antiproliferative Effects of Fluoxetine on Colon Cancer Cells and in a Colonic Carcinogen Mouse Model N2 - The antidepressant fluoxetine has been under discussion because of its potential influence on cancer risk. It was found to inhibit the development of carcinogen-induced preneoplastic lesions in colon tissue, but the mechanisms of action are not well understood. Therefore, we investigated anti-proliferative effects, and used HT29 colon tumor cells in vitro, as well as C57BL/6 mice exposed to intra-rectal treatment with the carcinogen N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) as models. Fluoxetine increased the percentage of HT29 cells in the G0/G1 phase of cell-cycle, and the expression of p27 protein. This was not related to an induction of apoptosis, reactive oxygen species or DNA damage. In vivo, fluoxetine reduced the development of MNNG-induced dysplasia and vascularization-related dysplasia in colon tissue, which was analyzed by histopathological techniques. An anti-proliferative potential of fluoxetine was observed in epithelial and stromal areas. It was accompanied by a reduction of VEGF expression and of the number of cells with angiogenic potential, such as CD133, CD34, and CD31-positive cell clusters. Taken together, our findings suggest that fluoxetine treatment targets steps of early colon carcinogenesis. This confirms its protective potential, explaining at least partially the lower colon cancer risk under antidepressant therapy. KW - Medizin Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-75879 ER - TY - JOUR A1 - Kirchner, S. A1 - Stopper, Helga A1 - Papp, T. A1 - Eckert, I. A1 - Yoo, H. J. A1 - Vig, B. K. A1 - Schiffmann, D. T1 - Cytogenetic changes in primary, immortalized and malignant mammalian cells N2 - Some chromosomes in transformed rat cells and somatic cell hybrids fail to display the presence of kinetochore proteins as detected by antikinetochore antibodies. Suchchromosomes (K- Chromosomes) may constitute a novel mechanism for the genesis of aneuploidy. Wehave analyzed primary~ immortalized and malignant marnmalian cells for the presence of kinetochore proteins and micronuclei. Our resuJts suggest a correlation of the K- chromosome and micronucleus frequency with the variability in chromosome number. Upon in situ hybridization with the minor satellite and alpha satellite sequences some Kchromosomes showed a signal. This indicates that the observed lack of kinetocbores is not necessarily due to a lack of centromeric DNA. We conclude that dislocated K- chromosomes may become incorporated into micronuclei which are prone to loss. Such events would be associated with the generation of aneuploidy. KW - Toxikologie KW - Micronuclei KW - Kinetochore KW - Chromosome distribution Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63439 ER -