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R K Zahn

Publications and source records attributed to R K Zahn.

239 records · Page 14Linked to original sources
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[Environmentally-induced causes of aging-dependent DNA modifications and possible consequences: current methods for the assessment of genotoxic potential of mixed pollution].

The deoxyribonucleic acid (DNA) is subject of a series of modifications with time, which are connected with the development of cancer and the process of aging. However, an efficient and nearly perfect repair system works against them, which eliminates most but not all of these changes. A series of tests has been developed for assessment of genotoxic potential of compounds and mixed pollution of environment. Three fast assay systems (umu test, DIT test, and Visko test) are discussed, whose results are obtained more quickly than by using conventional methods (e.g., Ames test or sister chromatid exchange).

Aging↗
PubMedDate not supplied

[Age-related changes in the activity and post-translational modification of DNA topoisomerase II in the quail oviduct].

In the present work, we show that the activity of DNA topoisomerase II in quail oviduct nuclei significantly increases with age. Posttranslational modifications of the nuclear-matrix-associated enzyme by matrix-bound poly(ADP-ribose) synthetase and protein kinase, whose activities change with age, are demonstrated and offer possible mechanisms by which the age-dependent change in enzyme activity may be caused. It is assumed that the age-correlated enhancement of DNA-topoisomerase-II activity may cause changes in the topological state of DNA, with possible consequences for DNA replication, transcription, and repair with age.

Animals↗
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[Age-dependent gene induction in the quail oviduct. VIII. A survey of experimental data].

1974 we introduced the biological model of the progesterone-caused avidin biosynthesis in the quail oviduct for studies in the field of molecular gerontology. Using this model it is possible to determine quantitatively the biochemical events of the age-dependent reduction of the progesterone-caused gene-induction. In a series of experiments it was found that the main parameters of the age dependent reduction might be found on the level of transcription and post-transcription. Therefore the enzymic processes involved in the transcription of genetic information from the DNA to the heterogenous nuclear RNA as well as those processing this RNA species to mRNA are studied. During the progress in this field we could isolate and purify some enzymes (poly[A] nucleases) which are involved in the age-dependent "maturation" of mRNA. On the basis of the interrelation between the poly(A)-binding proteins and the specific poly(A) nucleases, an explanation of the age-dependent reduction of the progesteron-caused mRNA synthesis seems to be possible.

Aging↗