Entwicklung von in vivo NMR-Techniken zur Untersuchung der Auswirkung von Ozeanversauerung und -erwärmung auf die Neurophysiologie Antarktischer Fische

• Main Author: Wermter, Felizitas Charlotte
• Other Authors: Dreher, Wolfgang, Pörtner, Hans-Otto
• Format: Doctoral or Postdoctoral Thesis
• Language: German
• Published: Universität Bremen 2018
• Subjects: Chemical exchange saturation transfer (CEST); NMR spectroscopy; glutamate; taurine; pH; temperature; marine ectotherms; fish brain; 500; 500 Science; ddc:500; Antarctic; Antarc*; Antarktis*; Ocean acidification; polar cod
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1389; https://nbn-resolving.org/urn:nbn:de:gbv:46-00106428-16

Ocean acidification and warming as a consequence of climate change affect marine organisms. Thus, for example, neurological changes could be observed in polar cod, which were induced by ocean acidification and warming. As a potential cause, a connection between the neurological impairments and changes in intracellular pH (pHi) has been postulated as it was described for animal models in preclinical research. Therefore, the non-invasive determination of pHi with high spatial and temporal resolution is of great interest. A promising tool for non-invasive pH measurements is the CEST contrast (Chemical Exchange Saturation Transfer), which enables the indirect detection of endogenous or exogenous molecules with exchangeable protons using changes in the NMR signal of the water pool. The CEST effect mainly depends on the concentration of a metabolite and the exchange rate between this metabolite and water, which in turn is influenced by physical and physiological parameters. These properties allow for CEST to be used for in vivo determination of changes in metabolite concentration and pH. The present thesis describes the development and adaption of the measurement method CEST MRI (Magnetic Resonance Imaging) and its application for determining changes in pHi with a high temporal and spatial resolution in the brain of marine fish. CEST from glutamate to water (GluCEST) was experimentally investigated in a broad temperature and pH range. The applicability of GluCEST to determine relative changes in pH even at low temperatures depends on glutamate concentration and on the parameters used in the experiments. Localized 1H NMR spectroscopy in combination with the application of quantification algorithms is an established method for the quantification of metabolite concentrations. In most cases, these algorithms use model functions based on chemical shifts at 37AdegreeC. Therefore, the temperature dependency of the chemical shifts for important metabolites has been examined in order to avoid systematic quantification errors ...