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ePaper created 2017-06-21, 10:00:36 | version 1.38.0
| study temperature-related damage of the DPSC Fig. 8 Fig. 8: TEM: Thermal treatment at 60 °C. Parts of the cytoplasm are cell proteins as well as a production of HSP which is not related to thermal stress. damaged or dissolved as can be seen by the mitochondria (M) with inflated or wound-up christae (arrows). The nucleus (K) shows severely condensed areas (*). 36 roots 2 2017 Similarly, a temperature level of 60 °C only lead to light colouration, which can be explained by the immediate lethal effect resulting in a missing time scale for the biosynthesis of HSP. In general, it should be noted that the first HSP examinations did not exhibit the expected intracellular resolution due to a low specificity. The results of REM and TEM at the different guide values of 37 °C, 46.5 °C, 50 °C, 60 °C and 65 °C fit very well with the results from light microscopy. The effects of a sudden and massive heating to more than 46 °C on the exterior cell shape (rounding and partial reduction of external structures) are dis- tinctly visible. The extremely fast contraction of the cells at temperatures around 50 °C might result in the observed tearing of cytoplasm-processes. Ther- mally-related membrane openings were not de- tected via REM even at temperatures of 60 °C and above. These high temperatures probably resulted in an immediate coagulation of membrane proteins and other intracellular proteins, which lead to a “conservation” or fixation of the cells in their cur- rent shape. While the external cell shape was main- tained because of the lacking time window for mor- phological modification, irreversible damages to the organells, nuclear membranes, nuclei and cyto- plasm were detected electron-microscopically. Starting at a temperature of 46.5 °C, a vacuo- lated cell membrane was observed via TEM in the rounded cells. Nucleus, organells and cytoskeleton were subject to beginning morphological changes. The cells reacted differently on heating, probably because their differences in physiological age, ac- tivity and cycle states influenced immediately visi- ble effects. For example, the cells differed in the level of microvilli reduction. If the survival of thermally treated cells will prevail for a time span of more than 24 h and if there are thermally-related damages of the reproductive be- haviour remains to be examined by further studies. However, it may be postulated with caution that the presented data indicate a chance of survival of the examined DPSC up to a temperature of 46 °C. These results on the thermal damage behaviour of human dental pulp stem cells are important for the devel- opment of ultrashort dental laser systems._ Acknowledgements: The authors would like to thank Dr Walter Richter, Dr Iris Riemann and Mr Helmut Hörig (Clinical Centre of FSU Jena, Germany) for their support in producing electron microscopic and light microscopic images. contact Prof. Karsten König Saarland University Campus A5.1, Room 2.35 66123 Saarbrücken Germany Tel.: +49 681 302-3451 Fax: +49 681 302-3090 k.koenig@blt.uni-saarland.de Dr Anton Kasenbacher Obere Hammerstraße 5 83278 Traunstein Germany Tel.: +49 861 4692 Fax: +49 861 12853 a.k@ts-net.de