Ruiliang Bai1, Charles S Springer2, Dietmar Plenz3, Peter J Basser1. 1. Section on Quantitative Imaging and Tissue Sciences, DIBGI, NICHD, National Institutes of Health, Bethesda, Maryland, USA. 2. Advanced Imaging Research Center, Oregon Health & Science University, Portland, Oregon, USA. 3. Section on Critical Brain Dynamics, LSN, NIMH, National Institutes of Health, Bethesda, Maryland, USA.
Abstract
PURPOSE: Water homeostasis and transport play important roles in brain function (e.g., ion homeostasis, neuronal excitability, cell volume regulation, etc.). However, specific mechanisms of water transport across cell membranes in neuronal tissue have not been completely elaborated. METHODS: The kinetics of transcytolemmal water exchange were measured in neuronal tissue using simultaneous, real-time fluorescence and nuclear magnetic resonance (NMR) measurements of perfused, active brain organotypic cortical cultures. Perfusion with a paramagnetic MRI contrast agent, gadoteridol, allows NMR determination of the unidirectional rate constant for steady-state cellular water efflux (kio ), and the mole fraction of intracellular water ( pi), related to the average cell volume (V). Changes in intracellular calcium concentration [Cai2+] were used as a proxy for neuronal activity and were monitored by fluorescence imaging. RESULTS: The kio value, averaged over all cultures (N = 99) at baseline, was 2.02 (±1.72) s-1 , indicating that on average, the equivalent of the entire intracellular water volume turns over twice each second. To probe possible molecular pathways, the specific Na+ -K+ -ATPase (NKA) inhibitor, ouabain (1 mM), was transiently introduced into the perfusate. This caused significant transient changes (N = 8): [Cai2+] rose ∼250%, V rose ∼89%, and kio fell ∼45%, with a metabolically active kio contribution probably eliminated by ouabain saturation. CONCLUSIONS: These results suggest that transcytolemmal water exchange in neuronal tissue involves mechanisms affected by NKA activity as well as passive pathways. The active pathway may account for half of the basal homeostatic water flux. Magn Reson Med 79:3207-3217, 2018.
PURPOSE:Water homeostasis and transport play important roles in brain function (e.g., ion homeostasis, neuronal excitability, cell volume regulation, etc.). However, specific mechanisms of water transport across cell membranes in neuronal tissue have not been completely elaborated. METHODS: The kinetics of transcytolemmal water exchange were measured in neuronal tissue using simultaneous, real-time fluorescence and nuclear magnetic resonance (NMR) measurements of perfused, active brain organotypic cortical cultures. Perfusion with a paramagnetic MRI contrast agent, gadoteridol, allows NMR determination of the unidirectional rate constant for steady-state cellular water efflux (kio ), and the mole fraction of intracellular water ( pi), related to the average cell volume (V). Changes in intracellular calcium concentration [Cai2+] were used as a proxy for neuronal activity and were monitored by fluorescence imaging. RESULTS: The kio value, averaged over all cultures (N = 99) at baseline, was 2.02 (±1.72) s-1 , indicating that on average, the equivalent of the entire intracellular water volume turns over twice each second. To probe possible molecular pathways, the specific Na+ -K+ -ATPase (NKA) inhibitor, ouabain (1 mM), was transiently introduced into the perfusate. This caused significant transient changes (N = 8): [Cai2+] rose ∼250%, V rose ∼89%, and kio fell ∼45%, with a metabolically active kio contribution probably eliminated by ouabain saturation. CONCLUSIONS: These results suggest that transcytolemmal water exchange in neuronal tissue involves mechanisms affected by NKA activity as well as passive pathways. The active pathway may account for half of the basal homeostatic water flux. Magn Reson Med 79:3207-3217, 2018.
Authors: Nathan H Williamson; Rea Ravin; Teddy X Cai; Dan Benjamini; Melanie Falgairolle; Michael J O'Donovan; Peter J Basser Journal: J Magn Reson Date: 2020-07-08 Impact factor: 2.229
Authors: Wei Huang; Yiyi Chen; Andriy Fedorov; Xia Li; Guido H Jajamovich; Dariya I Malyarenko; Madhava P Aryal; Peter S LaViolette; Matthew J Oborski; Finbarr O'Sullivan; Richard G Abramson; Kourosh Jafari-Khouzani; Aneela Afzal; Alina Tudorica; Brendan Moloney; Sandeep N Gupta; Cecilia Besa; Jayashree Kalpathy-Cramer; James M Mountz; Charles M Laymon; Mark Muzi; Paul E Kinahan; Kathleen Schmainda; Yue Cao; Thomas L Chenevert; Bachir Taouli; Thomas E Yankeelov; Fiona Fennessy; Xin Li Journal: Tomography Date: 2019-03