The Na+,K+-ATPase generates electrochemical gradients for sodium and potassium that are vital to animal cells, exchanging three sodium ions for two potassium ions across the plasma membrane during each cycle of ATP hydrolysis. Here we present the X-ray crystal structure at 3.5 A resolution of the pig renal Na+,K+-ATPase with two rubidium ions bound (as potassium congeners) in an occluded state in the transmembrane part of the alpha-subunit. Several of the residues forming the cavity for rubidium/potassium occlusion in the Na+,K+-ATPase are homologous to those binding calcium in the Ca2+-ATPase of sarco(endo)plasmic reticulum. The beta- and gamma-subunits specific to the Na+,K+-ATPase are associated with transmembrane helices alphaM7/alphaM10 and alphaM9, respectively. The gamma-subunit corresponds to a fragment of the V-type ATPase c subunit. The carboxy terminus of the alpha-subunit is contained within a pocket between transmembrane helices and seems to be a novel regulatory element controlling sodium affinity, possibly influenced by the membrane potential.

Purpose A novel dissolution dynamic nuclear polarization (dDNP) polarizer platform is presented. The polarizer meets a number of key requirements for in vitro, preclinical, and clinical applications. Method It uses no liquid cryogens, operates in continuous mode, accommodates a wide range of sample sizes up to and including those required for human studies, and is fully automated. Results It offers a wide operational window both in terms of magnetic field, up to 10.1 T, and temperature, from room temperature down to 1.3 K. The polarizer delivers a 13C liquid state polarization for [1‐13C]pyruvate of 70%. The build‐up time constant in the solid state is approximately 1200 s (20 minutes), allowing a sample throughput of at least one sample per hour including sample loading and dissolution. Conclusion We confirm the previously reported strong field dependence in the range 3.35 to 6.7 T, but see no further increase in polarization when increasing the magnetic field strength to 10.1 T for [1‐13C]pyruvate and trityl. Using a custom dry magnet, cold head and recondensing, closed‐cycle cooling system, combined with a modular DNP probe, and automation and fluid handling systems, we have designed a unique dDNP system with unrivalled flexibility and performance.

In a mouse mutagenesis screen, we isolated a mutant, Myshkin (Myk), with autosomal dominant complex partial and secondarily generalized seizures, a greatly reduced threshold for hippocampal seizures in vitro, posttetanic hyperexcitability of the CA3-CA1 hippocampal pathway, and neuronal degeneration in the hippocampus. Positional cloning and functional analysis revealed that Myk/؉ mice carry a mutation (I810N) which renders the normally expressed Na ؉ ,K ؉ -ATPase ␣3 isoform inactive. Total Na ؉ ,K ؉ -ATPase activity was reduced by 42% in Myk/؉ brain. The epilepsy in Myk/؉ mice and in vitro hyperexcitability could be prevented by delivery of additional copies of wild-type Na ؉ ,K ؉ -ATPase ␣3 by transgenesis, which also rescued Na ؉ ,K ؉ -ATPase activity. Our findings reveal the functional significance of the Na ؉ ,K ؉ -ATPase ␣3 isoform in the control of epileptiform activity and seizure behavior.alpha3 Na ϩ ,K ϩ ATPase ͉ BAC rescue ͉ epilepsy ͉ forward genetic screen ͉ mouse

Endogenous period is extended in Myk/ + due to longer periods of (I) activity (α). All data are presented as means ± SEM, *P < 0.05, **P < 0.01; ***P < 0.001 compared with +/+ mice.

The calibration parameters of a vector magnetometer are estimated only by the use of a scalar reference magnetometer. The method presented in this paper differs from those previously reported in its linearized parametrization. This allows the determination of three offsets or signals in the absence of a magnetic field, three scale factors for normalization of the axes and three non-orthogonality angles which build up an orthogonal system intrinsically in the sensor. The advantage of this method compared with others lies in its linear least squares estimator, which finds independently and uniquely the parameters for a given data set. Therefore, a magnetometer may be characterized inexpensively in the Earth's magnetic-field environment. This procedure has been used successfully in the pre-flight calibration of the state-of-the-art magnetometers on board the magnetic mapping satellites Ørsted, Astrid-2, CHAMP and SAC-C. By using this method, full-Earth-field-range magnetometers (±65536.0 nT) can be characterized down to an absolute precision of 0.5 nT, non-orthogonality of only 2 arcsec and a resolution of 0.2 nT.

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Unipolar depression and bipolar depression are prevalent and debilitating diseases in need of effective novel treatments. It is becoming increasingly evident that depressive disorders manifest from a combination of inherited susceptibility genes and environmental stress. Genetic mutations resulting in decreased neuronal Na + ,K + -ATPase (sodium-potassium adenosine triphosphatase) activity may put individuals at risk for depression given that decreased Na + ,K + -ATPase activity is observed in depressive disorders and animal models of depression. Here, we show that Na + ,K + -ATPase α3 heterozygous mice (Atp1a3 +/− ), with 15% reduced neuronal Na + ,K + -ATPase activity, are vulnerable to develop increased depression-like endophenotypes in a chronic variable stress (CVS) paradigm compared to wild-type littermates (Atp1a3 +/+ ). In Atp1a3 +/+ mice CVS did not decrease Na + ,K + -ATPase activity, however led to despair-like behavior in the tail suspension test (TST), anhedonia in a sucrose preference test and a minimal decrease in sociability, whereas in Atp1a3 +/− mice CVS decreased neuronal Na + ,K + -ATPase activity to 33% of wild-type levels, induced despair-like behavior in the TST, anhedonia in a sucrose preference test, anxiety in the elevated plus maze, a memory deficit in a novel object recognition task and sociability deficits in a social interaction test. We found that a mutation that decreases neuronal Na + ,K + -ATPase activity interacts with stress to exacerbate depression. Furthermore, we observed an interesting correlation between Na + ,K + -ATPase activity and mood that may relate to both unipolar depression and bipolar disorder. Pharmaceuticals that increase Na + ,K + -ATPase activity or block endogenous Na + , K + -ATPase inhibition may provide effective treatment for depressive disorders and preclude depression in susceptible individuals.