Change of membrane fluidity and protein conformation involved in [Ca2+]i overload in neuronal cells induced by ONOO−

Considerable evidence indicates that the formation of peroxynitrite (ONOO⁻) with superoxide anion (O₂^−⊙ot) may be involved in the neuronal toxicity of NO. Here, the effects of ONOO⁻ on intracellular free calcium concentration ([Ca²⁺]_i) in single MN9D cells was studied by the Fura-2 microfluorometric technique. The results showed that [Ca²⁺]_i was increased dose-dependently with the addition of ONOO⁻ (0–40 μmol/l) after 5 s and then decreased rapidly back to the basal level after ONOO⁻ was removed. [Ca²⁺]_i response to ONOO⁻ can be blocked by removing Ca²⁺ from the bath or adding L-type calcium channel antagonist nifedipine (10 μmol/l) to the bath. [Ca²⁺]_i transients by ONOO⁻ were substantially inhibited by dithiothreitol (DTT), which indicated ONOO⁻ may alter the L-type calcium channel on neuronal cell by thiol oxidation. To elucidate the mechanism of ONOO⁻ on [Ca²⁺]_i, the electron spin resonance spin-labeling technique was used to study the effects of ONOO⁻ on the membrane fluidity and the membrane protein conformation on freshly dissociated neurons. The results indicate that ONOO⁻ decreases membrane fluidity both near the surface and deep in the membrane and affects protein conformation. The fact that DTT effectively inhibits the deterioration supports the conclusion that the change of membrane fluidity and protein conformation is involved in [Ca²⁺]_i overload in neuronal cells induced by ONOO⁻.     

Protection of cortical cells by equine estrogens against glutamate-induced excitotoxicity is mediated through a calcium independent mechanism

Background  

High concentrations of glutamate can accumulate in the brain and may be involved in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease. This form of neurotoxicity involves changes in the regulation of cellular calcium (Ca²⁺) and generation of free radicals such as peroxynitrite (ONOO^-). Estrogen may protect against glutamate-induced cell death by reducing the excitotoxic Ca²⁺ influx associated with glutamate excitotoxicity. In this study, the inhibition of N-methyl-D-aspartate (NMDA) receptor and nitric oxide synthase (NOS) along with the effect of 17β-estradiol (17β-E₂) and a more potent antioxidant Δ⁸, 17β-estradiol (Δ⁸, 17β-E₂) on cell viability and intracellular Ca²⁺ ([Ca²⁺]_i), following treatment of rat cortical cells with glutamate, was investigated.     

Topological and physical effects of rotation and spin in the general relativistic theory of gravitation

Interrelations of the intrinsic momentum (spin), rotation of material distributions, and intrinsic momentum of the gravitational field are investigated in the context of the general relativistic theory of gravitation involving the general relativity theory (GRT) and the Einstein-Cartan theory. It is demonstrated that the spin density vector of the gravitational field s _g ⁱ is equal to the rotor of the tetrad reference point ωⁱ=ɛ^iklm e _k ^(a) e_(a)l,m/2 to within the factor 1/κ (s _g ⁱ =ω/κc). It is demonstrated that the vector s _g ⁱ is proportional to the spin density vector of the gravitating field sⁱ (ω)=jc(Ψγⁱγ₅Ψ)/2 as well as the pseudovector of space-time torsion Qⁱ in the Einstein-Cartan theory, which in both cases induces a cubic nonlinearity of the spinor field. An expression for the energy-momentum density tensor of the eddy gravitational field is derived. It is also demonstrated that the free eddy gravitational field with polarized spin can form “mole holes.” An ideal fast-rotating self-gravitating fluid can cause a similar effect. The corresponding exact solutions of joint systems of the Einstein and rotating ideal fluid equations are presented. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 57–60, October, 2007.     

Determination of Trace Mercury by Solid Substrate-Room Temperature Phosphorimetry Quenching Method Based on Catalytic Effect of Hg2+on Formation of the Ion Association Complex [Sn(XO)6]4+·[(Fin)4]

A new method for the determination of trace mercury by solid substrate-room temperature phosphorimetry (SS-RTP) quenching method has been established. In glycine-HCl buffer solution, xylenol orange (XO) can react with Sn⁴⁺ to form the complex [Sn(XO)₆]⁴⁺. [Sn(XO)₆]⁴⁺ can interact with Fin⁻ (fluorescein anion) to form the ion associate [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which can emit strong and stable room temperature phosphorescence (RTP) on polyamide membrane (PAM). Hg²⁺ can catalyze H₂O₂ oxidizing the ion association complex [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which causes the RTP to quench. The ΔIp value is directly proportional to the concentration of Hg²⁺ in the range of 0.016–1.6 fg spot⁻¹ (corresponding concentration: 0.040–4.0 pg ml⁻¹, 0.40 μl spot⁻¹), and the regression equation of working cure is ΔIp=10.03+83.15 m Hg²⁺ (fg spot⁻¹), (r=0.9987, n=6) and the detection limit (LD) is 3.6 ag spot⁻¹(corresponding concentration: 9.0×10^–15 g ml⁻¹, the sample volume: 0.4 μl). This simple, rapid, accurate method is of high selectivity and good repeatability, and it has been successfully applied to the determination of trace mercury in real samples. The reaction mechanism for catalyzing H₂O₂ oxidizing the ion association complex ([Sn(XO)₆]⁴⁺·[(Fin)₄]⁻) SS-RTP quenching method to determine trace mercury is also discussed.     

Simultaneous registration of Ca2+ transients and volume changes in rat mesangial cells: Evaluation of the effects of protein kinase C down-regulation

The intracellular free Ca²⁺ concentration ([Ca²⁺]_i) could be correlated with the contractile response in rat mesangial cells using an apparatus which measured both biochemical processes simultaneously. Long-term pretreatment of mesangial cells with 12-O-tetradecanoly-phorbol 13-acetate (24 h, 500 nM) increased the (20 nM) angiotensin II-induced mobilization of Ca²⁺ and led to an enhanced and sustained contraction of the cells. The contractile response was delayed by approximately 3.5 s with respect to the intracellular increase in Ca²⁺ concentration. The simultaneous registration of Ca²⁺ transients and cell contractions confirms that [Ca²⁺]_i is the major determinant of the angiotensin II-mediated mesangial cell contraction.Dedicated to Professor Horst H. A. Linde on the occasion of his 60th birthday.     

Simultaneous Registration of Contraction and Cytosolic Calcium ([Ca2+]i) of Smooth Muscle Strips Using Front-Surface Fluorimetry

Using front-surface fluorimetry with fura-2-loaded smooth muscle strips, simultaneous registration of the cytosolic calcium concentration ([Ca²⁺]_i) changes and tension development was done under the action of 40 mM KCl and the myotropic peptide 10^–6 M angiotensin II. The strips were mounted vertically, connected to a force transducer that keeps a basal isometric tension of 0.5 g, and maintained in a bathing solution oxygenated at 37°C. The fiber-optic platform FluoroMax-2 accessory 1950F was used to do the remote sensing for the samples. Light from the excitation spectrometer (FluoroMax-2), alternating between 340 and 380 nm, was focused onto the fiber-optic bundle and directed to the smooth muscle strip. The fluorescence (505 nm) was collected and redirected to the emission port of the fluorimeter FluoroMax-2. The ratiometric method (R340/380) was used as an index of [Ca²⁺]_i change during smooth muscle contraction. All data, R340/380 and tension, were recorded using a computerized data acquisition system: Soft & Solution and GRAMS/386 of Galatic Industries Corporation.     

Thepin structure employed as current amplifier

Injection of excess carriers into thei region of a forward biasedpin diode diminishes proportionally its resistivity (primary circuit). Resistivity variations in thei region are used to control higher currents and powers in the secondary circuit. This basic idea is developed quantitatively for a simplified symmetrical model of thepin structure in a stationary regime and then generalized for the asymmetrical case. The frequency characteristics of the electronic device are studied. For demonstration of the theoretical results thepin structure in silicon with known parameters is used.Notation 2d [m] length ofi region - D [m² s^–1] ambipolar diffusion constant - e [C] electron charge - E ₂ [Vm^–1] electric field strength iny direction - i ₁ [Am^–2] current density inx direction - i ₂ [Am^–2] current density iny direction - i _m [Am^–2] current density due to recombination of carriers ini region - i _1ef ,i _2ef [Am^–2] effective values of currentsi ₁,i ₂ - i _ns ,i _ps [Am^–2] saturated current densities from the heavily dopedn, p regions - i intrinsic region - I [A] total current throughp-n junction - I ₁ [A] total current in pin diode - I ₂ [A] current in secondary circuit - k[J grad^–1] Boltzmann's constant - L=(D) [m] ambipolar diffusion length of carriers in middle region - n(x) [m^–3] excess electron concentration in middle region - ¯n [m^–3] average value of electron concentration in middle region - n _i [m^–3] intrinsic electron concentration - n _A [m^–3] acceptor concentration inp region - n _D [m^–3] donor concentration inn region - p(x) [m^–3] excess hole concentration in middle region - q [m²] area of electrodes 3 and 4 - Q [C] charge stored ini region - R [m^–3 s^–1] recombination rate - s [m] width of diode - t [m] thickness of diode - T [K] absolute temperature - U [V] voltage acrossp-n junction - U ₁ [V] voltage acrosspin diode - U ₂ [V] voltage across terminals of secondary circuit - U _m [V] voltage drop acrossi region - V _D [V] voltage drop acrossn — i andp — i junctions at zero load - W ₁ [W] power inpin diode circuit - W ₂ [W] power in secondary circuit - x [m] distance from center of diode - coefficient in current amplification factor - [rad] phase shift of diode current with respect to applied voltage - [s] life time of excess carriers ini region - [m² V^–1 s^–1] carrier mobility ini region in the symmetrical model - _n [m² V^–1 s^–1] electron mobility ini region - _p [m² V^–1 s^–1] hole mobility ini region - [^–1 m^–1] conductivity     

Effective nonlinear optical properties of shape distributed composite media

The effective linear and nonlinear optical properties of metal/dielectric composite media, in which ellipsoidal metal inclusions are distributed in shape, are investigated. The shape distribution function P(L _x, L _y) is assumed to be 2Δ^-2θ(L _x - 1/3 + Δ/3)θ(L _y - 1/3 + Δ/3)θ(2/3 + Δ/3 - L _x - L _y), where θ( ^{. . .} ) is the Heaviside function, Δ is the shape variance and L_i are the depolarization factors of the ellipsoidal inclusions along i-symmetric axes (i = x, y). Within the spectral representation, we adopt Maxwell-Garnett type approximation to study the effect of shape variance Δ on the effective nonlinear optical properties. Numerical results show that both the effective linear optical absorption α ∼ ωIm() and the modulus of the effective third-order optical nonlinearity enhancement |χ⁽³⁾ _e|/χ⁽³⁾ ₁ exhibit the nonmonotonic behavior with Δ. Moreover, with increasing Δ, the optical absorption and the nonlinearity enhancement bands become broad, accompanied with the decrease of their peaks. The adjustment of Δ from 0 to 1 allows us to examine the crossover behavior from no separation to large separation between optical absorption and nonlinearity enhancement peaks. As Δ → 0, i.e., the ellipsoidal shape deviates slightly from the spherical one, the dependence of |χ⁽³⁾ _e|/χ⁽³⁾ ₁ on Δ becomes strong first and then weak with increasing the imaginary part of inclusions' dielectric constant. In the dilute limit, the exact formula for the effective optical nonlinearity is derived, and the present approximation characterizes the exact results better than old mean field one does. Received 10 December 2002 Published online 4 June 2003 RID="a" ID="a"e-mail: lgaophys@pub.sz.jsinfo.net     

Spatiotemporal Aspects of Prolactin-Induced Calcium Signaling

We have examined the spatiotemporal aspects of PRL-induced Ca²⁺ signals using high-speed fluo-3 confocal imaging. We found that PRL stimulated Ca²⁺ entry and intracellular Ca²⁺ mobilization. Ca²⁺ influx was seen as a peripheral increase in [Ca²⁺]_i without amplification in the nucleus region. Intracellular Ca²⁺ mobilization was seen as a propagating intracellular calcium wave with a strong amplification in the nuclear region. The amplitude of PRL-induced Ca²⁺ increases would be sufficient to stimulate cell proliferation. Furthermore, PRL induced an increase in [³H]thymidine incorporation. These data suggest that PRL would be able to induce mitogenesis through a Ca²⁺-dependent pathway.     

Magnetism,exchange and crystal field parameters in the orbitally unquenched Ising antiferromagnet FePS3

FePS₃ is a layered antiferromagnet (T _N=123 K) with a marked Ising anisotropy in magnetic properties. The anisotropy arises from the combined effect of the trigonal distortion from octahedral symmetry and spin-orbit coupling on the orbitally degenerate⁵ T _2g ground state of the Fe²⁺ ion. The anisotropic paramagnetic susceptibilities are interpreted in terms of the zero field Hamiltonian, ℋ=Σ_i [δ(L _iz ² −2)+|λ|L _i .S _i ]−Σ _ij J _ij S _i .S _j . The crystal field trigonal distortion parameter Δ, the spin-orbit coupling λ and the isotropic Heisenberg exchange,J _ij, were evaluated from an analysis of the high temperature paramagnetic susceptibility data using the Correlated Effective Field (CEF) theory for many-body magnetism developed by Lines. Good agreement with experiment were obtained for Δ/k=215.5 K; λ/k=166.5 K;J _nn k=27.7 K; andJ _nnn k=−2.3 K. Using these values of the crystal field and exchange parameters the CEF predicts aT _N=122 K for FePS₃, which is remarkably close to the observed value of theT _N. The accuracy of the CEF approximation was also ascertained by comparing the calculated susceptibilities in the CEF with the experimental susceptibility for the isotropic Heisenberg layered antiferromagnet MnPS₃, for which the high temperature series expansion susceptibility is available.     

Photophysics and Fluorimetric Titrations of Fluorescent Ion Indicators

A test based on time-resolved fluorescence experiments (Anal. Biochem. 245, 28–37, 1997) allows one to assess the interference of the excited-state association with the fluorimetric determination of the ground-state dissociation constant K _d of fluorescent ion:indicator complexes. If an inflection point occurs in the plot of the fluorescence signal vs – log[ion] in the ion concentration range where both decay times are invariant, this inflection point can be associated with the correct K _d. Here we apply this test to the fluorescent ion indicators SBFO (for Na⁺), Mag-fura-2 (for Mg²⁺), and APTRA-BTC (for Ca²⁺). In all three cases the decay times are invariant in the concentration ranges of the respective ions where the fluorescence titrations show unique inflection points, indicating that the fluorimetrically determined K _d values are the true K _d values.     

Multi-Hamiltonian structure of kdv hierarchy by Drienfeld-Sokolov formalism

Conserved quantities and the multi-Hamiltonian structure for the integrable coupled kdv system which is associated with the isospectral flow [(∑ _i=0 ^N−1 ε _i λ ⁱ )∂² + ∑ _i=0 ^N−l V ₁λ ⁱ ]φ=λ ^N φ are deduced by the Drienfeld-Sokolov formalism.     

Eigenvalues of Laplacian with Constant Magnetic Field on Non-Compact Hyperbolic Surfaces with Finite Area

We consider a magnetic Laplacian −Δ _A = (id + A)^* (id + A) on a non-compact hyperbolic surface M with finite area. A is a real one-form and the magnetic field dA is constant in each cusp. When the harmonic component of A satisfies some quantified condition, the spectrum of −Δ _A is discrete. In this case, we prove that the counting function of the eigenvalues of −Δ _A satisfies the classical Weyl formula, even when dA=0.     

Future of neutrino experiments

Atmospheric, solar, reactor and accelerator neutrino oscillation experiments have measured Δm ₁₂², sin² θ ₁₂, |Δm ₂₃²| and sin² 2θ ₂₃. The next stage of the oscillation studies should be the observation of a finite sin² 2θ ₁₃. If a non-zero sin² 2θ ₁₃ is observed, the subsequent goals should be the observation of the CP violation and the determination sign of Δm ₂₃². Possible future neutrino oscillation experiments that could assess these questions are discussed.      

A spin-3/2 Ising model on a square lattice

The spin-3/2 Ising model described by the most general Hamiltonian with up-down symmetry, −βH=Σ_〈ij〉{JS _i S _j +KS ₂ ⁱ S ₂ ^j +LS ₃ ⁱ S ₃ ^j +M/2(S _i S ₃ ^j +S _j S ₃ ⁱ )}−ΔΣ_i S ₂ ⁱ , is investigated on a square lattice. It is shown that this model is reducible to an eight-vertex model on a surface in the parameter space spanned by the coupling constants J, K, L, and M. It is shown that this model is equivalent to an exactly solvable free fermion model along two lines in the parameter space. Consequently, the critical behavior and, in particular, the critical temperature for the second-order phase transitions of the model is found exactly. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 4, 270–275 (25 February 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

19F NMR and Structure of Pt (IV) Hexafluorocomplexes

The present work cites the investigation results of ¹⁹F NMR spectra in polyerystalline compounds of the Me _n[PtF₆]_m type, where Me - Li⁺, Na⁺, K⁺, Ca²⁺, Sr²⁺, Ba²⁺, La³⁺ and Ag⁺. The use of a NMR spectrometer with high field stress (～24 kOe) made possible the observation of different chemical shifts in solids of NMR signals from two nonequivalent fluorine types in octahedric complexes of [PtF₆]^2-.¹⁹ NMR and Structure of Pt (IV) Hexafluorocomplexes     

Relation between spectroscopic constants with limited Dunham coefficients

Statement of Kaur and Mahajan [1] about the definition of Δ used by Chandra [2] is not correct. Even if we take Δ = μω _e ² r _e ² /2D_e, the relation between Δ and G(=8ω_ex_e/B_e) is obtained as Δ = 4.21452856G, provided the vibrational energy of a diatomic molecule is expressed in terms of limited Dunham coefficients, Y₁₀, Y₂₀, Y₀₁ and Y₁₁. This relation is still different from that of Kaur and Mahajan [3]     

Two Higgs bi-doublet left-right model with spontaneous P and CP violation

A left-right symmetric model with two Higgs bi-doublet is shown to be a consistent model for both spontaneous P and CP violation. The flavor changing neutral currents can be suppressed by the mechanism of approximate global U(1) family symmetry. The constraints from neural K meson mass difference Δm _K are calculated and it is demonstrated that a right-handed gauge boson W ₂ contribution in box-diagrams with mass well below 1 TeV is allowed due to a cancelation caused by a light-charged Higgs boson with a mass range of 150–300 GeV. The W ₂ contribution to ε _K can be suppressed from an appropriate choice of additional CP phases appearing in the right-handed Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully consistent with B ⁰ mass difference Δm _B and the mixing induced CP violation sin2β _{J/ Ψ}, which is usually difficult for the model with only one Higgs bi-doublet. The new physics beyond the standard model can be directly searched at the colliders LHC and ILC. Supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. 10475105 and 10491306) and the Key Project of Chinese Academy of Sciences (CAS)     

Systematics of high-spin isomers in N = 83 isotones and a high-spin isomer beam

Isomers in N = 83 isotones of Z = 60-66, were studied systematically. Their spins and parities are 49/2⁺ and 27⁺ for odd and odd-odd nuclei, respectively. Nearly constant excitation energies of these isomers indicated a decrease of a Z = 64 shell gap energy as Z decreases from 64 to 60 within the framework of a deformed independent-particle model (DIPM). Their configurations are [ν(f _7/2 h _9/2 i _13/2),π(h _11/2)²]_49/2+ and [ν(f _7/2 h _9/2 i _13/2),π(h _11/2)²(d _5/2)^-1]₂₇₊ for odd and odd-odd nuclei, respectively. The shape of the yrast states changes suddenly at spin 49/2(odd) and 27(odd-odd) from a near spherical to an oblate shape. Transitions from isomers are highly hindered because of the shape changes. They may be categorized to be shape isomers. The development of a secondary beam produced by using these high-spin isomers is also described. Received: 1 May 2001 / Accepted: 4 December 2001     

Liouville Type Equations with Singular Data¶and Their Applications to Periodic Multivortices¶for the Electroweak Theory

Motivated by the study of multivortices in the Electroweak Theory of Glashow–Salam–Weinberg [33], we obtain a concentration-compactness principle for the following class of mean field equations: on M, where (M,g) is a compact 2-manifold without boundary, 0 < a≤K(x)≤b, x∈M and λ > 0. We take with α _i > 0, δ _{p i} the Dirac measure with pole at point p _i ∈M, i= 1,…,m and ψ∈L ^∞(M) satisfying the necessary integrability condition for the solvability of (1)_λ. We provide an accurate analysis for solution sequences of (1)_λ, which admit a “blow up” point at a pole p _i of the Dirac measure, in the same spirit of the work of Brezis–Merle [11] and Li–Shafrir [35]. As a consequence, we are able to extend the work of Struwe–Tarantello [49] and Ding–Jost–Li–Wang [21] and derive necessary and sufficient conditions for the existence of periodic N-vortices in the Electroweak Theory. Our result is sharp for N= 1, 2, 3, 4 and was motivated by the work of Spruck–Yang [46], who established an analogous sharp result for N= 1, 2. Received: 24 September 2001 / Accepted: 7 December 2001