Development of in vivo NMR techniques for studying the impact of Ocean acidification and warming on the neurophysiology of Antartic fishes

海洋酸化和变暖的最显著影响预计在极地地区，即，温度升高和二氧化碳浓度升高对极地生物（南极和北极物种）的影响最大。据证明，热带鱼表现出神经功能障碍的CO2浓度升高，预计从2100年的气候变化情景已经，虽然鱼类有一个体面的酸碱调节。这些损伤涉及从感觉到行为变化的不同神经功能障碍，被认为是由于CO2对GABA神经递质功能的影响。全球变暖可能会加剧这些干扰。因此，在南极洲的鳗鱼中，研究表明，细胞内pH值的酸碱调节在4°C以上的温度下受损。然而，负责观察到的海洋鱼类的干扰的机制仍然不清楚。体内NMR技术，特别是局部31P和1H NMR光谱被广泛用于研究动物和人类大脑中的代谢状态或代谢变化，包括观察神经递质的变化以及酸碱调节。然而，这些测量的固有的低灵敏度，限制了空间和时间resolution.In目前的研究项目，我们正在申请延长，我们开发的新方法的化学位移饱和转移（CEST）的pH值映射和间接代谢imaging。CEST磁共振成像（MRI）允许高空间和时间分辨率的测量，因为代谢物的可交换质子的饱和纵向磁化被转移到水中并积累。我们已经证明，CEST MRI在极地温度下是可行的，并且CEST MRI的特异性可以通过适当的射频（RF）预饱和进行调整，从而实现重要代谢物的逆成像和pH标测。 除了基于谷氨酸的CEST MRI（GluCEST），我们计划开发基于牛磺酸的CEST MRI（TauCEST）。TauCEST将是一种新的CEST选择，它似乎适用于低温。使用新的9.4T NMR成像系统，预计将于2016年1月在AWI投入使用，将允许提高质量的体内测量。CEST MRI和局部1H和31P MRS将用于研究在预期的海洋酸化和变暖情景下南极鱼类大脑的代谢变化和酸碱调节。这些研究应提高我们的理解的机制，观察到的神经系统的变化，在极地鱼类。

The most dramatic effects of ocean acidification and warming are expected in Polar regions, i.e., the impact of elevated temperatures and CO2 concentrations will be highest on Polar organisms (Antarctic and Arctic species). It was demonstrated that tropical fishes show neurological impairments under elevated CO2 concentrations expected from climate change scenarios for 2100 already, although fishes have a decent acid-base regulation. The impairments involved different neurological dysfunctions from sensory to behavioural changes and were supposed to be due to the influence of CO2 on the neurotransmitter function of GABA. Global warming might amplify these disturbances. Thus, in Antarctic eelpout it was shown that acid-base regulation of intracellular pH became impaired at temperatures above 4°C.Polar fishes can show similar or more severe neurological changes under conditions of ocean acidification and warming. However, the mechanisms responsible for the observed disturbances of marine fishes are still not understood. In vivo NMR techniques, in particular localised 31P and 1H NMR spectroscopy were extensively used to characterise the metabolic status or metabolic changes in the brain of animals and humans, including observations on changes of neurotransmitters as well as acid-base regulation. However, these measurements are limited by the inherently low sensitivity, restricting the spatial and temporal resolution.In the current research project, the prolongation of which we are applying for, we exploit the novel approach of chemical shift saturation transfer (CEST) for pH mapping and indirect metabolic imaging. CEST magnetic resonance imaging (MRI) allows measurements with high spatial and temporal resolution because the saturated longitudinal magnetisation of exchangeable protons of metabolites is transferred to water and accumulated. We have shown that CEST MRI is feasible down to polar temperatures and that the specificity of CEST MRI can be adjusted by appropriate radiofrequency (RF) pre-saturation, allowing both inverse imaging of important metabolites and pH mapping. Besides CEST MRI based on glutamate (GluCEST), we plan to develop CEST MRI based on taurine (TauCEST). TauCEST will be a novel CEST option, which seems to be applicable at low temperatures. Using the new 9.4T NMR imaging system, which is expected to be operational in January, 2016, at the AWI, will allow in vivo measurements with improved quality. Both CEST MRI and localized 1H and 31P MRS will be used for studying metabolic changes and acid-base regulation in the brain of Antarctic fishes under expected ocean acidification and warming scenarios. These studies should improve our understanding of the mechanisms underlying the observed neurological changes in Polar fishes.