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At the cerebellar parallel fiber-Purkinje cell synapse, isolated presynaptic activity induces fast excitatory postsynaptic currents via ionotropic glutamate receptors while repetitive, high-frequency, presynaptic activity can also induce a slow excitatory postsynaptic current that is mediated by metabotropic glutamate receptors (mGluR1-EPSC). Here we investigated the involvement of glutamate uptake in the expression of the mGluR1-EPSC. Inhibitors of glutamate uptake led to a large increase of the mGluR1-EPSC. d-aspartate (0.4 mM) andl(−)-threo-3-hydroxyaspartate (0.4 mM) increased the mGluR1-EPSC ∼4.5 and ∼9-fold, respectively, while dihydrokainic acid (1 mM), had no significant effect on the mGluR1-EPSC.d-aspartate (0.4 mM) shifted the concentration-response curve of the depression of the mGluR1-EPSC by the low-affinity mGluR1 antagonist ( S)-a-Methyl-4-carboxyphenylglycine [( S)-MCPG] to higher concentrations and decreased the stimulus intensity and the number of necessary stimuli to evoke an mGluR1-EPSC. Depression of the mGluR1-EPSC by rapid pressure application of ( S)-MCPG at varying time intervals after tetanic stimulation of the parallel fibers indicated that the glutamate concentration in the peri- and extrasynaptic space decayed with time constants of 36 and 316 ms under control conditions and with inhibition of glutamate uptake, respectively. These results show that expression of the slow mGluR-mediated excitatory postsynaptic current is controlled by glutamate transporter activity. Thus in contrast to fast glutamatergic synaptic transmission, metabotropic glutamate receptor-mediated transmission is critically dependent on the activity and capacity of glutamate uptake.

This paper describes mathematical and software developments needed for the effective solution of differential algebraic equations of index 1 in the integrated computing environment MATLAB and the dynamic simulation package Simulink. The developments are applicable to other problem-solving environments and some are applicable to general scientific computation.

A VO2 single-crystal has been subject of a combined investigation by high resolution XPS, x-ray emission spectroscopy with electron and energy-selective x-ray excitation (V L-alpha, V K-beta-5- and O K-alpha emission) and x-ray absorption spectroscopy (O1s). We performed first principles tight-binding LMTO band structure calculations of VO2 in both monoclinic and tetragonal rutile structures and compare the densities of states with the experimental data. From this we conclude that the electronic structure of VO2 is more bandlike than correlated.

The phase diagram of the ternary system Sr/Mo/O has been determined at a temperature of 1000°C. Powder samples of the ternary compounds SrMoO4, Sr3MoO6, SrMoO3, Sr2MoO4 and SrMo5O8 were prepared by solid state reactions. The thermochemical data of all ternary compounds were determined. A new compound, Sr3Mo2O7, with a layered perovskite structure (a = 3.967(1), c = 20.588(5) Å, I4/mmm) was found. Rietveld analysis based on powder X-ray diffraction data confirms that the compound Sr2MoO4 has the K2NiF4 structure (I4/mmm) with a = 3.9176(1), c = 12.8545(4) Å.

The phase diagram of the ternary system Ca/Mo/O has been determined. Powder samples of the ternary compounds CaMoO4, CaMoO3, CaMo5O8, Ca16.5Mo13.5O40 and Ca5.45Mo18O32 were prepared by solid state reactions. Rietveld analysis based on powder X-ray diffraction data shows that the compound CaMo5O8 has monoclinic structure (P21/c) with a = 7.549, b = 9.064, c = 9.974 Å, β = 110.04°. CaMo5O8, Ca16.5Mo13.5O40 and Ca5.45Mo18O32 are semiconductors over the temperature range 75 to 300 K.

This paper describes mathematical and software developments for a suite of programs for solving ordinary differential equations in MATLAB.

The ternary compounds Ca 2 CuO 3 , Sr 2 CuO 3 , and their solid solution Sr 2− x Ca x CuO 3 have been prepared by the decomposition of coprecipitated oxalates and/or by conventional solid state reaction. Both reaction methods are compared. The obtained compounds crystallize in the orthorhombic system. The lattice constants were determined, and the formation of solid solution crystals over the whole range of composition was obtained. The compounds were characterized concerning their thermal stability and their decomposition in moist air. Thermogravimetric, X ray, and vapor pressure measurement show that the compounds are of a very slight variation in oxygen stoichiometry. First measurements of the specific heat and IR spectra are discussed.

The temperature dependencies of the heat capacity of MnMoO 4 and Mn 2 Mo 3 O 8 have been investigated from 5 K to 300 K with a vacuum-jacketed adiabatic calorimeter. The thermodynamic functions have been calculated on the basis of experimental results on C p,m ( T ). The standard values at the temperature 298.15 K for MnMoO 4 are: C p,m = 13.924 · R; S S o m = 17.992 · R ; H o m (T) − H o m (0) = 2556.7 · R · K; and Φ o m = 9.417 · R . For Mn 2 Mo 3 O 8 the same quantities are equal to 29.575 · R , 30.609 · R , 4797.7 · R · K and 14.517 · R , respectively. The λ-anomalies connected with the magnetic-ordering phase transitions were observed and studied in detail. The phase-transition temperatures for MnMoO 4 and Mn 2 Mo 3 O 8 correspond to 10.5 K and 39.44 K, respectively. A sharp increase of the thermal-relaxation time has been revealed in MnMoO 4 at T

Triosmium pentadecatin tetradecaoxide, Os 3 Sn 15 O 14 , is isostructural with Ru 3 Sn 15 O 14 . It is a metal-rich stannate and contains osmium-centred tin octahedra. These OsSn 6 octahedra form triple chains in which the Sn atoms which link the octahedra have the oxidation state +1.

We found direct experimental evidence for an orbital switching in the V $3d$ states across the metal-insulator transition in ${\mathrm{VO}}_{2}$. We have used soft-x-ray absorption spectroscopy at the V ${L}_{2,3}$ edges as a sensitive local probe and have determined quantitatively the orbital polarizations. These results strongly suggest that, in going from the metallic to the insulating state, the orbital occupation changes in a manner that charge fluctuations and effective bandwidths are reduced, that the system becomes more one dimensional and more susceptible to a Peierls-like transition, and that the required massive orbital switching can only be made if the system is close to a Mott insulating regime.

To determine the electrophysiological properties of Müller (glial) cells from experimentally detached rabbit retinas.A stable local retinal detachment was induced by subretinal injection of a sodium hyaluronate solution. Müller cells were acutely dissociated and studied by the whole-cell voltage-clamp technique.The cell membranes of Müller cells from normal retinas were dominated by a large inwardly rectifying potassium ion (K+) conductance that caused a low-input resistance (100 M(Omega)) and a high resting membrane potential (-82 +/- 6 mV). During the first week after detachment, the Müller cells became reactive as shown by glial fibrillary acidic protein (GFAP) immunoreactivity, and their inward currents were markedly reduced, accompanied by an increased input resistance (200 M(Omega)). After 3 weeks of detachment, the input resistance increased further (300 M(Omega)), and some cells displayed significantly depolarized membrane potentials (mean -69 +/- 18 mV). When PVR developed (in 20% of the cases) the inward K+ currents were virtually completely eliminated. The input resistance increased dramatically (1000 MOmega), and almost all cells displayed strongly depolarized membrane potentials (-44 +/- 16 mV).Reactive Müller cells are characterized by a severe reduction of their K+ inward conductance, accompanied by depolarized membrane potentials. These changes must impair physiological glial functions, such as neurotransmitter recycling and K+ ion clearance. Furthermore, the open probability of certain types of voltage-dependent ion channels (e.g., Ca2+-dependent K+ maxi channels) increases that may be a precondition for Müller cell proliferation, particularly in PVR when a dramatic downregulation of both inward current density and resting membrane potential occurs.

To determine differences of K+ channel activity between Müller glial cells obtained from retinas of healthy human donors and of patients with retinal detachment and proliferative vitreoretinopathy.Müller cells were enzymatically isolated from retinas of healthy donors and from excised retinal pieces of patients. The whole-cell and the cell-attached configurations of the patch-clamp technique were used to characterize the current densities of different K+ channel types and the activity of single Ca2+ -activated K+ channels of big conductance (BK).Cells from patients displayed a less negative mean membrane potential (-52.8 mV) than cells from healthy donors (-80.6 mV). However, the membrane potentials in cells from patients scattered largely between -6 and -99 mV. The inwardly rectifying K+ permeability in cells from patients was strongly reduced (0.3 pA/pF) when compared with cells from healthy donors (6.0 pA/pF). At the resting membrane potential, single BK channels displayed a higher mean activity (open probability, Po, and channel current amplitude) in cells from patients (Po, 0.30) than in cells from healthy donors (Po: 0.03). The variations of BK current amplitudes were correlated with the variations of the membrane potential.The dominant expression of inwardly rectifying channels in cells from healthy donors is thought to support important glial cell functions such as the spatial buffering of extracellular K+. The downregulation of these channels and the less negative mean membrane potential in cells from patients should impair spatial buffering currents and neurotransmitter clearance. The increased activity of BK channels may support the proliferative activity of gliotic cells via feedback regulation of Ca2+ entry and membrane potential.

To define the role of vecuronium in the occurrence of bradyarrhythmia, haemodynamic changes after the induction of anaesthesia were studied in 96 patients undergoing coronary artery bypass grafting. Patients were assigned to one of six groups according to different combinations of induction agents (etomidate 0.3 mg kg-1 or thiopentone 3 mg kg-1, with fentanyl 0.003 mg kg-1; etomidate 0.4-0.5 mg kg-1 or thiopentone 4-6 mg kg-1, without fentanyl) and neuromuscular blocking drugs (vecuronium 0.112 mg kg-1, pancuronium 0.112 mg kg-1 or suxamethonium 1 mg kg-1). Anaesthesia was maintained with enflurane and nitrous oxide in oxygen. After initial diverse changes, heart rate decreased in all groups. Thirty minutes after intubation, the reduction of heart rate showed statistically significant differences between the different combinations of drugs: fentanyl-etomidate-vecuronium (group I) (the largest reduction) greater than etomidate-vecuronium (II) = fentanyl-thiopentone-vecuronium (IV) greater than thiopentone-vecuronium (V) = fentanyl-thiopentone-suxamethonium (VI) = fentanyl-etomidate-pancuronium (III). Five patients in group I, two in group IV and one each in groups II and V had a heart rate slower than 45 beat min-1, whereas a similar value was never seen in groups III and VI. These results indicate that vecuronium has a bradycardic effect. This effect is more pronounced in association with etomidate than in association with thiopentone, and is augmented by the addition of fentanyl.