Neurotransmitter modulation of extracellular H+ fluxes from isolated retinal horizontal cells of the skate

Self-referencing H+-selective microelectrodes were used to measure extracellular H+ fluxes from horizontal cells isolated from the skate retina. A standing H+ flux was detected from quiescent cells, indicating a higher concentration of free hydrogen ions near the extracellular surface of the cell as compared to the surrounding solution. The standing H+ flux was reduced by removal of extracellular sodium or application of 5-(N-ethyl-N-isopropyl) amiloride (EIPA), suggesting activity of a Na+–H+ exchanger. Glutamate decreased H+ flux, lowering the concentration of free hydrogen ions around the cell. AMPA/kainate receptor agonists mimicked the response, and the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) eliminated the effects of glutamate and kainate. Metabotropic glutamate agonists were without effect. Glutamate-induced alterations in H+ flux required extracellular calcium, and were abolished when cells were bathed in an alkaline Ringer solution. Increasing intracellular calcium by photolysis of the caged calcium compound NP-EGTA also altered extracellular H+ flux. Immunocytochemical localization of the plasmalemma Ca2+–H+-ATPase (PMCA pump) revealed intense labelling within the outer plexiform layer and on isolated horizontal cells. Our results suggest that glutamate modulation of H+ flux arises from calcium entry into cells with subsequent activation of the plasmalemma Ca2+–H+-ATPase. These neurotransmitter-induced changes in extracellular pH have the potential to play a modulatory role in synaptic processing in the outer retina. However, our findings argue against the hypothesis that hydrogen ions released by horizontal cells normally act as the inhibitory feedback neurotransmitter onto photoreceptor synaptic terminals to create the surround portion of the centre-surround receptive fields of retinal neuron

Critical properties of S=1/2 Heisenberg ladders in magnetic fields

The critical properties of the $S=1/2$ Heisenberg two-leg ladders are investigated in a magnetic field. Combining the exact diagonalization method and the finite-size-scaling analysis based on conformal field theory, we calculate the critical exponents of spin correlation functions numerically. For a strong interchain coupling, magnetization dependence of the critical exponents shows characteristic behavior depending on the sign of the interchain coupling. We also calculate the critical exponents for the $S=1/2$ Heisenberg two-leg ladder with a diagonal interaction, which is thought as a model Hamiltonian of the organic spin ladder compound ${Cu}_2({1,4-diazacycloheptane})_2{Cl}_4$. Numerical results are compared with experimental results of temperature dependence of the NMR relaxation rate $1/T_1$.Comment: REVTeX, 10 pages, 8 figures, accepted for Phys. Rev.

Nursing assistants matters—An ethnographic study of knowledge sharing in interprofessional practice

© 2017 John Wiley & Sons Ltd Interprofessional collaboration involves some kind of knowledge sharing, which is essential and will be important in the future in regard to the opportunities and challenges in practices for delivering safe and effective health care. Nursing assistants are seldom mentioned as a group of health care workers that contribute to interprofessional collaboration in health care practice. The aim of this ethnographic study was to explore how the nursing assistants’ knowledge can be shared in a team on a spinal cord injury rehabilitation ward. Using a sociomaterial perspective on practice, we captured different aspects of interprofessional collaboration in health care. The findings reveal how knowledge was shared between professionals, depending on different kinds of practice architecture. These specific cultural–discursive, material–economic, and social–political arrangements enabled possibilities through which nursing assistants’ knowledge informed other practices, and others’ knowledge informed the practice of nursing assistants. By studying what health care professionals actually do and say in practice, we found that the nursing assistants could make a valuable contribution of knowledge to the team

Observation of Field-Induced Transverse N\'{e}el Ordering in the Spin Gap System TlCuCl3_3

Neutron elastic scattering experiments have been performed on the spin gap system TlCuCl$_3$ in magnetic fields parallel to the $b$-axis. The magnetic Bragg peaks which indicate the field-induced N\'{e}el ordering were observed for magnetic field higher than the gap field $H_{\rm g}\approx 5.5$ T at $Q=(h, 0, l)$ with odd $l$ in the $a^*-c^*$ plane. The spin structure in the ordered phase was determined. The temperature and field dependence of the Bragg peak intensities and the phase boundary obtained were discussed in connection with a recent theory which describes the field-induced N\'{e}el ordering as a Bose-Einstein condensation of magnons.Comment: 4 pages, 5 eps figures, jpsj styl

Lattice Instability in the Spin-Ladder System under Magnetic Field

We study theoretically the lattice instability in the spin gap systems under magnetic field. With the magnetic field larger than a critical value h_{c1}, the spin gap is collapsed and the magnetization arises. We found that the lattice distortion occurs in the spin-ladder at an incommensurate wavevector corresponding to the magnetization, while it does not occur in the Haldane system. At low temperatures the magnetization curve shows a first order phase transition with this lattice distortion.Comment: 10 pages, REVTEX, 2 figures(ps file), minor change

A differential pressure instrument with wireless telemetry for in-situ measurement of fluid flow across sediment-water boundaries

© 2009 The Authors. This article is distributed under the terms of the Creative Commons Attribution (3.0) License. The definitive version was published in Sensors 9 (2009): 404-429, doi:10.3390/s90100404.An instrument has been built to carry out continuous in-situ measurement of small differences in water pressure, conductivity and temperature, in natural surface water and groundwater systems. A low-cost data telemetry system provides data on shore in real time if desired. The immediate purpose of measurements by this device is to continuously infer fluxes of water across the sediment-water interface in a complex estuarine system; however, direct application to assessment of sediment-water fluxes in rivers, lakes, and other systems is also possible. Key objectives of the design include both low cost, and accuracy of the order of ±0.5 mm H2O in measured head difference between the instrument’s two pressure ports. These objectives have been met, although a revision to the design of one component was found to be necessary. Deployments of up to nine months, and wireless range in excess of 300 m have been demonstrated

α-Synuclein-112 impairs synaptic vesicle recycling consistent with its enhanced membrane binding properties

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Soll, L. G., Eisen, J. N., Vargas, K. J., Medeiros, A. T., Hammar, K. M., & Morgan, J. R. α-Synuclein-112 impairs synaptic vesicle recycling consistent with its enhanced membrane binding properties. Frontiers in Cell and Developmental Biology, 8, (2020): 405, doi:10.3389/fcell.2020.00405.Synucleinopathies are neurological disorders associated with α-synuclein overexpression and aggregation. While it is well-established that overexpression of wild type α-synuclein (α-syn-140) leads to cellular toxicity and neurodegeneration, much less is known about other naturally occurring α-synuclein splice isoforms. In this study we provide the first detailed examination of the synaptic effects caused by one of these splice isoforms, α-synuclein-112 (α-syn-112). α-Syn-112 is produced by an in-frame excision of exon 5, resulting in deletion of amino acids 103–130 in the C-terminal region. α-Syn-112 is upregulated in the substantia nigra, frontal cortex, and cerebellum of parkinsonian brains and higher expression levels are correlated with susceptibility to Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and multiple systems atrophy (MSA). We report here that α-syn-112 binds strongly to anionic phospholipids when presented in highly curved liposomes, similar to α-syn-140. However, α-syn-112 bound significantly stronger to all phospholipids tested, including the phosphoinositides. α-Syn-112 also dimerized and trimerized on isolated synaptic membranes, while α-syn-140 remained largely monomeric. When introduced acutely to lamprey synapses, α-syn-112 robustly inhibited synaptic vesicle recycling. Interestingly, α-syn-112 produced effects on the plasma membrane and clathrin-mediated synaptic vesicle endocytosis that were phenotypically intermediate between those caused by monomeric and dimeric α-syn-140. These findings indicate that α-syn-112 exhibits enhanced phospholipid binding and oligomerization in vitro and consequently interferes with synaptic vesicle recycling in vivo in ways that are consistent with its biochemical properties. This study provides additional evidence suggesting that impaired vesicle endocytosis is a cellular target of excess α-synuclein and advances our understanding of potential mechanisms underlying disease pathogenesis in the synucleinopathies.This study was supported by a research grant from the National Institutes of Health (NIH NINDS/NIA R01 NS078165 to JM), as well as research funds from the Marine Biological Laboratory (to JM)

Quasiparticles governing the zero-temperature dynamics of the 1D spin-1/2 Heisenberg antiferromagnet in a magnetic field

The T=0 dynamical properties of the one-dimensional (1D) $s=1/2$ Heisenberg antiferromagnet in a uniform magnetic field are studied via Bethe ansatz for cyclic chains of $N$ sites. The ground state at magnetization $0<M_z<N/2$, which can be interpreted as a state with $2M_z$ spinons or as a state of $M_z$ magnons, is reconfigured here as the vacuum for a different species of quasiparticles, the {\em psinons} and {\em antipsinons}. We investigate three kinds of quantum fluctuations, namely the spin fluctuations parallel and perpendicular to the direction of the applied magnetic field and the dimer fluctuations. The dynamically dominant excitation spectra are found to be sets of collective excitations composed of two quasiparticles excited from the psinon vacuum in different configurations. The Bethe ansatz provides a framework for (i) the characterization of the new quasiparticles in relation to the more familiar spinons and magnons, (ii) the calculation of spectral boundaries and densities of states for each continuum, (iii) the calculation of transition rates between the ground state and the dynamically dominant collective excitations, (iv) the prediction of lineshapes for dynamic structure factors relevant for experiments performed on a variety of quasi-1D antiferromagnetic compounds, including KCuF$_3$, Cu(C$_4$H$_4$N$_2)(NO_3)_2$, and CuGeO$_3$.Comment: 13 pages, 12 figure