Autoradiographische Untersuchungen zu nukleären DNA-Strangbrüchen in unterschiedlichen Zellarten im Gehirn der Maus nach einer achtwöchigen 50-Hz-Magnetfeldexposition

The aim of this study was to use in-situ nick translation (ISNT) to investigate the relative number of unrepaired nuclear (n) DNA nicks in different cell types in the brain of the 9-month-old mouse after a 2-month exposure to a 50 Hz magnetic field with 0 mT (control), 0.1 mT or 1 mT. 5 minutes after the end of the magnetic field exposure, the mice were injected with 555 kBq ³H-thymidine (TdR) per gram of body mass, in order to carry out additional UDS tests on these animals. Two hours after ³H- TdR injection the animals were sacrificed, their organs removed and preserved with a fixative for several weeks. Paramedian sagittal paraffin sections were prepared with a thickness of 3 µm. To investigate the cell type-specific content of unrepaired nDNA nicks (i.e. DNA single strand breaks), the sections were subjected to an ISNT with DNA polymerase I and ³H-thymidine triphosphate; finally autoradiograms were prepared. Under the microscope, at a 1250x primary magnification, 100 successive cells per cell type were analyzed according to their nuclear grain numbers and a computer-assisted measurement of the corresponding nuclear profile area was performed. By correcting for background labelling and normalization to nuclear DNA content, a direct comparison between the new results and those of the literature was possible. It should bementioned that the grain numbers connted were analyzed using cumulative frequency distributions to identify possible artifacts. After calculating the mean of the remaining data, the animal cohorts were compared using univariance analysis and post-hoc t-tests with consideration of a Bonferroni correction. All results with of p < 0.05 were considered as statistically significant. Finally, linear regression analyses were used with p<0.05 to compare the results with corresponding values of the literature. With respect to the content of unrepaired DNA nicks, this study yielded in the univariance analysis a statistically significant correlation to the magnetic field dose only for hippocampus granule cells. However, this results could not be confirmed with post-hoc t-test. On the other hand, however, the results of the UDS tests conducted in parallel (Füller, 2009) showed that, if magnetic field-induced DNA damage had in fact occurred, this damage was repaired no more than 24 hours after switching off the magnetic field. In the case of cell types from the caudate nucleus (neurons, glial cells and endothelial cells), as well as the plexus epithelial cells in the lateral ventricle and (separately from it) in the IV ventricle, no clear significant result could be obtained. For the measured values of the nuclear profile areas which, according to the literature, are positively correlated with cell metabolism in the case of a globose nucleus, statistically reliable correlations were only detected for the neurons of the caudate nucleus and the hippocampus granule cells. The nuclear profile areas were significantly reduced here in comparison to the animals not exposed to a magnetic field, both for an exposure to 0.1 mT and also to 1 mT. It is worthy to note that only the findings for the caudate nucleus were confirmed in the UDS test conducted in parallel (Braun, 2009).

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2009

Author dc:creator

• Born, Tatjana Barbara

Contributors dc:contributor

• Korr, Hubert

• info:eu-repo/classification/ddc/610
• Magnetfeld
• Autoradiographie
• DNS-Synthese
• DNS-Reparatur
• Replikation
• DNS-Schädigung
• DNS-Strangbruch
• DNS-abhängige-DNS-Polymerasen
• DNS
• UDS
• Comet Assay
• Thymidin
• Thymidinstoffwechsel
• Hippocampus
• Nucleus caudatus
• Plexus chorioideus
• Medizin
• Nulleffekt
• ß-Selbstabsorption
• in situ nick-translation
• ISNT
• background
• unscheduled dna synthesis

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113539%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A51227