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Fernale BALB/c mice were administered intragastrically with equimolar amounts of either [2-\(^{14}\)C]2-amino-3,8-dimethyi[ 4,5-J]qulnoxaline (MeiQx) or 2-acetylamino[9-\(^{14}\)C]fluorene (2AAF). DNA was isolated from tissues of mice killed either 6 or 24 h after administration. Analysis of liver DNA nucleotide digests by HPLC analysis revealed that all of the radioactivity was attributable to adduct formation. Tbe specific activities of DNA samples were converted to covalent bindlog indices (CBI, J.LIDOI adduct per mol DNA nucleotides/mmol chemical app6ed per kg animal body weight). CBI values of 25 and 9 were detennined for 2AAF and MeiQx in tbe llvers of mice killed 6 h after dosing. The values were in general agreement with the moderate carcinogenic potency of these compounds. The specific activities of DNA preparations obtained from the lddneys, spleens, stomachs, small intestines and large intestlnes of mice treated witb MeiQx and killed 6 h after doslng were S- to 35-times less tban those obtained witb the llver. DNA isolated from tbe lungs (a target organ for MeiQx tumorigenicity) of MeiQx-treated mice was not radiolabeUed at tbe limit of detection (CBI <0.3). With tbe exception of tbe gastrolntestinal tract, the specific activities of DNA samples isolated from mice killed 6 h after administration were higher than those from mice killed after 24 h.
Spatially restricting cAMP production to discrete subcellular locations permits selective regulation of specific functional responses. But exactly where and how cAMP signaling is confined is not fully understood. Different receptors and adenylyl cyclase isoforms responsible for cAMP production are not uniformly distributed between lipid raft and non-lipid raft domains of the plasma membrane. We sought to determine the role that these membrane domains play in organizing cAMP responses in HEK293 cells. The freely diffusible FRET-based biosensor Epac2-camps was used to measure global cAMP responses, while versions of the probe targeted to lipid raft (Epac2-MyrPalm) and non-raft (Epac2-CAAX) domains were used to monitor local cAMP production near the plasma membrane. Disruption of lipid rafts by cholesterol depletion selectively altered cAMP responses produced by raft-associated receptors. The results indicate that receptors associated with lipid raft as well as non-lipid raft domains can contribute to global cAMP responses. In addition, basal cAMP activity was found to be significantly higher in non-raft domains. This was supported by the fact that pharmacologic inhibition of adenylyl cyclase activity reduced basal cAMP activity detected by Epac2-CAAX but not Epac2-MyrPalm or Epac2-camps. Responses detected by Epac2-CAAX were also more sensitive to direct stimulation of adenylyl cyclase activity, but less sensitive to inhibition of phosphodiesterase activity. Quantitative modeling was used to demonstrate that differences in adenylyl cyclase and phosphodiesterase activities are necessary but not sufficient to explain compartmentation of cAMP associated with different microdomains of the plasma membrane.
Einfluß der Dialysetherapie auf den Genomschaden von Nierenpatienten in einer prospektiven Studie
(2007)
Patienten mit terminaler Niereninsuffizienz haben im Vergleich zur Normalbevölkerung eine deutlich erhöhte Inzidenz maligner Erkrankungen. Frühere Untersuchungen zeigten, dass periphere Blutlymphozyten dieser Patienten einen höheren genetischen Schaden aufweisen, wodurch das Risiko einer malignen Entartung steigt. In dieser Arbeit wurde der genetische Schaden mithilfe zweier Testverfahren, Comet Assay und Mikrokerntest, untersucht. Es handelte sich um eine prospektive Studie mit zwei Patientenkollektiven. Die erste Gruppe bestand aus Patienten, die aufgrund einer terminalen Niereninsuffizienz innerhalb der nächsten Monate eine Dialysetherapie mittels konventioneller Hämodialyse beginnen mußten. Die zweite Gruppe bildeten Dialysepatienten, die im Verlauf von konventioneller Dialyse auf Hämodiafiltration umgestellt wurden. Bei allen Patienten wurde der genetische Schaden der peripheren Blutlymphozyten in den Monaten vor und nach Therapiebeginn bzw. Therapieumstellung regelmäßig untersucht. Unsere Ergebnisse zeigen, dass 4 der 10 Prädialysepatienten nach Beginn der Dialyse einen niedrigeren genetischen Schaden hatten, 2 Patienten hatten unterschiedliche Werte in Comet Assay und Mikrokerntest und bei 2 Patienten ergab sich im Verlauf eine höhere DNA-Schädigung. Die verbliebenen 2 Patienten mußten aufgrund einer konstant bleibenden Niereninsuffizienz nicht mit der Dialysetherapie beginnen. Bei Zusammenfassung aller Einzelwerte zeigte sich, dass das Kollektiv der Prädialysepatienten insgesamt vom Beginn der Behandlung profitiert hat. In der Gruppe der Dialysepatienten hatte 2 von 7 Patienten nach Umstellung auf Hämodiafiltration eine geringere DNA-Schädigung, 2 Patienten zeigten unterschiedliche Ergebnisse im Comet Assay und Mikrokerntest und 2 weitere Patienten wiesen eine höheren genetischen Schaden in den Lymphozyten auf. Ein Patient konnte bei fehlenden Vorwerten nicht berücksichtigt werden. Im Gruppenvergleich zeigte sich für alle Dialysepatienten ein gleichbleibender DNA-Schaden, gemessen mithilfe des Comet Assays bei leicht erhöhten Mikrokernraten. Jedoch hatte sich die Zellproliferation ebenfalls etwas verbessert. Zusammenfassend ergibt sich somit in beiden Gruppen kein eindeutiges Ergebnis, woraus neue Therapieempfehlungen für Patienten mit terminaler Niereninsuffizienz abzuleiten wären. Um weiter Einflußvariablen auf die Höhe des genetischen Schadens festzustellen, sind weiter Untersuchungen mit größeren Patientenkollektiven erforderlich.
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.
Infants and young children (IYC) remain the most vulnerable population group to environmental hazards worldwide, especially in economically developing regions such as sub-Saharan Africa (SSA). As a result, several governmental and non-governmental institutions including health, environmental and food safety networks and researchers have been proactive toward protecting this group. Mycotoxins, toxic secondary fungal metabolites, contribute largely to the health risks of this young population. In SSA, the scenario is worsened by socioeconomic status, poor agricultural and storage practices, and low level of awareness, as well as the non-establishment and lack of enforcement of regulatory limits in the region. Studies have revealed mycotoxin occurrence in breast milk and other weaning foods. Of concern is the early exposure of infants to mycotoxins through transplacental transfer and breast milk as a consequence of maternal exposure, which may result in adverse health effects. The current paper presents an overview of mycotoxin occurrence in foods intended for IYC in SSA. It discusses the imperative evidence of mycotoxin exposure of this population group in SSA, taking into account consumption data and the occurrence of mycotoxins in food, as well as biomonitoring approaches. Additionally, it discusses the health implications associated with IYC exposure to mycotoxins in SSA.