Effect of ultrasonic exposure on Ca2+-ATPase activity in plasma membrane from Aloe arborescens callus cells

We investigated the effect of ultrasound on plasma membrane (PM) Ca2+-ATPase activity of Aloe arborescens callus cells in solid culture. The calluses were exposed by a 20 kHz digital sonifier at the powers of 2 and 10 W from the effective exposure times of 2-10 s. PM Ca2+-ATPase activity was almost significantly higher at 2 W both in continuous wave and 10% duty cycle than that of the control (no ultrasound) at effective exposure times of 5 and 10 s. However, its activity decreased at 10 W in continuous wave exposure. It is possible that the PM Ca2+-ATPase configuration or structure may be partly damaged by high-energy ultrasound at 10 W. Our results showed that low-energy ultrasound exposure was a useful physical field to stimulate A. arborescens callus cells to adapt environmental stress through PM Ca2+-ATPase activity increase.     

Mode shaping in mixed ion crystals of 40Ca2+ and 40Ca+

We present studies of mixed Coulomb crystals of ⁴⁰Ca⁺ and ⁴⁰Ca²⁺ ions in a linear Paul trap. Doubly charged ions are produced by photoionization of trapped ⁴⁰Ca⁺ with a vacuum ultraviolet laser source and sympathetically cooled via Doppler cooled ⁴⁰Ca⁺ ions. We investigate experimentally and theoretically the structural configurations and the vibrational modes of these mixed crystals. Our results with ⁴⁰Ca²⁺ are an important step towards experimental realization of the proposals for mode shaping in a linear crystal and spin-dependent configuration changes from zigzag to linear as proposed by Li et al. (Phys Rev A 87:052304, 2013) and Li and Lesanovsky (Phys Rev Lett 108:023003, 2012) using ions excited to Rydberg states.     

Antisense-mediated isoform switching of steroid receptor coactivator-1 in the central nucleus of the amygdala of the mouse brain

Background

Antisense oligonucleotide (AON)-mediated exon skipping is a powerful tool to manipulate gene expression. In the present study we investigated the potential of exon skipping by local injection in the central nucleus of the amygdala (CeA) of the mouse brain. As proof of principle we targeted the splicing of steroid receptor coactivator-1 (SRC-1), a protein involved in nuclear receptor function. This nuclear receptor coregulator exists in two splice variants (SRC-1a and SRC-1e) which display differential distribution and opposing activities in the brain, and whose mRNAs differ in a single SRC-1e specific exon.

Methods

For proof of principle of feasibility, we used immunofluorescent stainings to study uptake by different cell types, translocation to the nucleus and potential immunostimulatory effects at different time points after a local injection in the CeA of the mouse brain of a control AON targeting human dystrophin with no targets in the murine brain. To evaluate efficacy we designed an AON targeting the SRC-1e-specific exon and with qPCR analysis we measured the expression ratio of the two splice variants.

Results

We found that AONs were taken up by corticotropin releasing hormone expressing neurons and other cells in the CeA, and translocated into the cell nucleus. Immune responses after AON injection were comparable to those after sterile saline injection. A successful shift of the naturally occurring SRC-1a:SRC-1e expression ratio in favor of SRC-1a was observed, without changes in total SRC-1 expression.

Conclusions

We provide a proof of concept for local neuropharmacological use of exon skipping by manipulating the expression ratio of the two splice variants of SRC-1, which may be used to study nuclear receptor function in specific brain circuits. We established that exon skipping after local injection in the brain is a versatile and useful tool for the manipulation of splice variants for numerous genes that are relevant for brain function.     

Problems Caused by High Concentration of ATP on Activation of the P2X7 Receptor in Bone Marrow Cells Loaded with the Ca2+ Fluorophore fura-2

Fura-2 is one of the most used fluorophore for measuring intracellular calcium concentration ([Ca2+]i). In mouse bone marrow cell suspensions ATP produces a biphasic effect: till 1 mM, ATP produces increases in [Ca2+]i; from 1 mM on an increase is observed, that is followed by the decrease in the 340/380 nm ratio (R340/380). At high ATP (4 mM) concentration fura-2 leaked from loaded bone marrow cell suspensions. We observed that ATP decreases fluorescence in the absorption and excitation spectra of fura-2, consequently the emitted one is decreased including the isobestic point (360 nm). ATP analogs: BzATP, ATPyS and UTP, but not alphabetaATP, ADP or AMP, promote decrease of fluorescence in the isobestic point of fura-2. The physical/chemical process that reduces the absorption and excitation of fura-2 by ATP is unknown. The P2X7 inhibitors, Mg2+ (5 mM), OxATP (300 microM) and Brilliant Blue (100 nM), blocked the efflux of fura-2 and ATP-induced R340/380 decrease. The J774 cell line and mononuclear cells with a higher expression of P2X7 receptors show the same decrease in R340/380 as that induced by ATP. In the HL-60 cell line, myeloid cells and erythroblasts extracted from bone marrow, such effect does not occur. It is concluded that the use of the fluorescent Ca2+ indicator fura-2 does not allow the correct measurement of [Ca2+]i in these cells in the presence of a higher concentration of ATP which activated the P2X7 receptor.     

Electron paramagnetic resonance and luminescence of Gd3+ in the mixed fluorides Ca1-xLaxF2+x and Ca1

Abstract

In this paper we present an study on the EPR and photoluminiscence spectra of Gd³⁺ in the mixed crystals Ca_0.998-xR_xGd_0.002F_0.002+x(x≤0.35, R=La or Y). For x <0.1 the EPR spectrum shows a main signal due to cubic Gd³⁺ that is broadened as x increases. Different broadenings are found for La and Y samples For high x values the EPR spectrum is similar to that in glass matrices. The results are explained taking to account a random second rank crystal field due to the extra charges associated with R³⁺ and fluorine intersitials. The ⁶P→⁶S emission of Gd³⁺ also has been measured. The influence of R concentration on this luminiscence has been studied.     

Raman and X‐ray investigations of the incorporation of Ca2+ and Cd2+ in the ZrO2 structure

The formation of solid solution and ZrO₂ phase stabilization were investigated by Raman spectroscopy and X‐ray diffraction (XRD) in calcium‐containing and cadmium‐containing zirconium oxide samples heated at 1073 K in air. The adopted preparation procedure led to the incorporation of calcium and cadmium in solid solution into the zirconia structure. The solid solution favored the tetragonal and cubic zirconia phases at the expense of the thermodynamically stable monoclinic modification. Combined macro‐ and micro‐Raman spectroscopy disclosed that instead of forming a homogeneous phase t″, intermediate between the tetragonal t′ and the cubic phase, the tetragonal and cubic phases coexisted in the range 9.49–13.89 mol% for Ca and 11.88–17.23 mol% for Cd. At higher dopant contents the cubic form stabilized. The impurity content necessary to stabilize the high‐symmetry phases was defined. Copyright © 2007 John Wiley & Sons, Ltd.     

Comment on fusion cross sections in the40Ar+40Ca and40Ca+40Ca systems

Using a strongly mismatched transfer reaction,¹³⁸Ba (¹⁴C,¹⁵N), the spin orbit potential for¹⁵N projectiles has been derived in terms of the reaction asymmetry. The strength and sign of the L·S-potential are consistent with a previous determination using an (¹⁶O,¹⁵n) reaction; the signis opposite to that for nucleons and agrees with a model where the last P_1/2 nucleon is responsible for the L·S potential.     

EXAFS and XANES Structure determination of Mn2+ binding in ATP complexes

Summary The binding of Mn²⁺ ions to ATP molecules has been studied by means of the fine-structure analysis of X-ray absorption spectra (EXAFS and XANES) at theK-edge of Mn using the synchrotron, radiation facility PULS in Frascati. The results obtained in both freeze-dried and liquid samples of aqueous solutions at room temperature of the Mn-ATP complex under diffrent values ofpH and Mn:ATP ratio are reported and discussed. The Mn²⁺ ion appears to be octahedrally coordinated, the phosphate oxygen atoms being in the first co-ordination shell. Values of (2.15±0.05) ? and (3.4±0.05) ?, respectively, have been found for Mn-O and Mn-P distances. Theoretical considerations together with experimental results do not support the existence of a direct binding of the Mn to the N(7) atom of the adenine ring. The coordination numbers for the first and second shell are consistent with the formation of a Mn(ATP)₂ complex in solution atpH=9 and Mn: ATP=1:10, while a Mn-ATP 1:1 complex is found at lowerpH and higher Mn: ATP ratios. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Exploration of large amplitude motions in the Ca+Ar2 complex

ABSTRACT

We present a theoretical study of the ground electronic state potential of the Ca⁺Ar₂ complex and of its photoabsorption spectra, simulated at temperatures ranging between 20 and 220?K. These calculations exploit a Monte-Carlo (MC) method, based on a one-electron pseudo-potential approach. A pairwise additive potential fitted to coupled cluster ab initio points, is used to model the Ca⁺Ar₂ complex. Our study shows that the most stable form of Ca⁺Ar₂ is a bent C_2v structure, whereas the linear isomer is located at around 90?±?10?cm^?1 above in energy. The analysis of the photoabsorption spectra establishes that a structural transition from bent Ca⁺Ar₂ to linear ArCa⁺Ar occurs at T～100?K. Trends in binding energies of both isomers, bond lengths and bond angles are also discussed. Molecular orbital overlaps provide an explanation for the order of stability between the bent and linear structures.     

Identification of a set of genes showing regionally enriched expression in the mouse brain

Background

We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.

Results

Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.

Conclusion

Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.     

NMR determination of the Sternheimer antishielding factor of Ca2+

The experimental determination of the Sternheimer antishielding factor gamma(infinity) for Ca2+ in a sold material is reported for the first time. The gamma(infinity) value was obtained by comparing the quadrupole frequency measured by 43Ca NMR with the electric field gradient calculated in a frame of the point charge approximation in the high-Tc superconducting compound, Tl0.5Pb0.5Sr2CaCu2O7. The deduced value (gamma(infinity)= -6.1+/-.9) is about one-third of that obtained from the quantum mechanical calculations, whereas in the same sample, the gamma(infinity)value for O2- deduced by the same procedure (gamma(infinity)= -13.7+/-2.0) is very close to the calculated one.     

Charge states of atoms in the lattices of the high-temperature superconductors Tl2Ba2Ca n−1CunO2n+4 and Bi2Sr2Ca n−1CunO2n+4

To determine the charges of atoms in the lattices of the compounds Tl₂Ba₂Ca _n?1Cu_nO_2n+4 and Bi₂Sr₂Ca _n?1Cu_nO_2n+4 (n=1,2,3), the parameters of the electric field gradient tensor at the copper sites of the indicated lattices were found by emission Mössbauer spectroscopy on the isotopes ⁶¹Cu(⁶¹Ni) and ⁶⁷Cu(⁶⁷Zn), and a calculation of these parameters was performed in the point-charge approximation. A comparison of the resulting values and the published data on ⁶³Cu nuclear quadrupole resonance showed that agreement between the experimental and computed values of the parameters obtains for models in which the holes resulting from a reduction in the valence of some of the thallium (bismuth) atoms are localized predominantly at oxygen sites located in the same plane as the copper atoms (for the compounds Tl₂Ba₂Ca₂Cu₃O₁₀ and Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O₁₀—at oxygen sites in the same plane as the Cu(2) atoms).     

Separation of laser-cooled 42Ca+ and 44Ca+ in a linear Paul trap

Rare calcium isotope ions, ⁴²Ca⁺ and ⁴⁴Ca⁺, were efficiently separated from a laser-cooled ionic cloud in a linear Paul trap which was loaded from an atomic source of a natural isotope mixture of calcium, in spite of their negligibly small abundances (0.647% and 2.086%, respectively) compared with that of ⁴⁰Ca (96.94%). Selective heating and cooling that arise from the isotope shifts were mainly used for the elimination of the isotopes; selective heating and cooling enable flexible separation when combined with other mechanisms such as the inherent mass selectivity of RF traps. Received: 7 July 2000 / Published online: 10 January 2001     

Combined fitting of optical and millimeter wave data: The linked A2Π-X2Σ+ and B2Σ+-X2Σ+ systems of Ca79Br and Ca81Br

Adiabatic corrections to the Born-Oppenheimer potential energy curve for the $\text{B″}{}^1\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ state of the hydrogen molecule has been computed using a 60-term variational wavefunction in the form of an expansion in elliptic coordinates and depending explicitly on the interelectronic distance. For three internuclear separations new Born-Oppenheimer energies are also given which represent corrections of the previously published values. For H₂ the adiabatic correction to the dissociation energy amounts to 57.5 cm^?1. The computed dissociation energies for H₂, HD, and D₂ are by 23–25 cm^?1 smaller than the experimental values, the discrepancy being probably due to the convergence error of the Born-Oppenheimer potential. A few lowest vibrational levels and vibrational quanta have been calculated for H₂, HD and D₂, and compared with the experimental results.     

Self-consistent analysis of sub-barrier fusion enhancement effect in Ca+Ca and Ni+Ni

The fusion dynamic mechanism of heavy ions at energies near the Coulomb barrier is complicated and still not very clear up to now. Accordingly, a self-consistent method based on the CCFULL calculations has been developed and applied for an ongoing study of the effect of the positive Q-value neutron transfer (PQNT) channels in this work. The typical experimental fusion data of Ca+Ca and Ni+Ni is analyzed within the unified calculation scheme. The PQNT effect in near-barrier fusion is further confirmed based on the self-consistent analysis and extracted quantitatively.     

Fractal aggregates induced by liposome-liposome interaction in the presence of Ca2+

We present a study of the fractal dimension of clusters of large unilamellar vesicles (LUVs) formed by egg yolk phosphatidylcholine (EYPC), dimyristoylphosphocholine (DMPC) and dipalmitoylphosphocholine (DPPC) induced by Ca²⁺ . Fractal dimensions were calculated by application of two methods, measuring the angular dependency of the light scattered by the clusters and following the evolution of the cluster size. In all cases, the fractal dimensions fell in the range from 2.1 to 1.8, corresponding to two regimes: diffusion-limited cluster aggregation (DLCA) and reaction-limited cluster aggregation (RLCA). Whereas DMPC clusters showed a typical transition from the RLCA to the DLCA aggregation, EYPC exhibited an unusual behaviour, since the aggregation was limited for a higher concentration than the critical aggregation concentration. The behaviour of DPPC was intermediate, with a transition from the RLCA to the DLCA regimes with cluster sizes depending on Ca²⁺ concentration. Studies on the reversibility of the aggregates show that EYPC and DPPC clusters can be re-dispersed by dilution with water. DMPC does not present reversibility. Reversibility is evidence of the existence of secondary minima in the DLVO potential between two liposomes. To predict these secondary minima, a correction of the DLVO model was necessary taking into account a repulsive force of hydration.     

Mass yield distributions for the reactions Ca+Ca,Nb+Nb at EA = 400 MeV and Ca+Ca at EA = 800 MeV in the molecular-dynamical model

Mass yield distributions obtained on the basis of the molecular-dynamical model are presented for the reactions Ca+Ca, Nb+Nb at $\text{E}\text{A}\text{= 400}\text{MeV}$ and Ca+Ca at $\text{E}\text{A}\text{= 800}\text{MeV}$. For the fragments with masses up to a quarter of the mass of the initial nucleus the model predicts a power law for mass spectra with almost the same value of the exponent. Such behaviour is roughly a result of the superposition of the fireball break-up and the disintegration of spectator regions.     

Energy gaps and phonon structures in tunneling spectra of Bi2Sr2Ca1Cu2O8+x and Bi2Sr2Ca2Cu3O10+y superconductors

Polycrystalline Bi-2212 or Bi-2223 systems and single crystals of the Bi-2212 system were investigated at several temperatures by means of the break-junction and point-contact tunneling techniques, respectively. In the case of Bi-2223 we obtained an averaged gap value 2=65±4 meV. The Bi-2212 system yields 2= 45±5 meV in the case of polycrystalline samples and 2=47±5 meV in the case of single crystals. Hence there result BCS-ratios 2/k _B T _c of 7.3, 6.8 and 6.5, respectively. A dc-Josephson-type supercurrent could be observed in polycrystalline Bi-2212 samples in addition to the usual gap structure. The point-contact tunneling spectra of Bi-2212 single crystals exhibit structures in the second derivative d² I/d V ² which we interpret as inelastic tunneling processes due to electron-phonon scattering most likely in the barrier region. The phonon energies deduced from these structures are in accordance with data obtained from inelastic neutron scattering and Raman spectroscopy. Good agreement is obtained with a lattice dynamical calculation of the partial phonon densities of states of individual atoms in the unit cell.     

Axial configuration of Z+2-centres in Ca doped KCl

It is shown that optimum positions of the Z⁺₂-centres electron with minimum ground state energy are situated off the vacancy centre towards the Ca²⁺ ion. At these intermediate positions, the calculated transition energies in absorption are in better agreement with the experimentally assigned values. Energy levels were calculated numerically using perturbation theory, the point ion model forces the defect electron to “collapse” into the Ca²⁺ ion but the inclusion of core repulsions from the modified Bartram, Stoneham and Gash ion-size corrections removes this anomalous behaviour and predict electronic concentration at about 0.3 of the nearest neighbour distance from the vacancy centre in comfirmation of the Paus and Schen model for the Z⁺₂-centre.     

Spatiotemporal dynamics of Ca2+ signaling and its physiological roles

Changes in the intracellular Ca²⁺ concentration regulate numerous cell functions and display diverse spatiotemporal dynamics, which underlie the versatility of Ca²⁺ in cell signaling. In many cell types, an increase in the intracellular Ca²⁺ concentration starts locally, propagates within the cell (Ca²⁺ wave) and makes oscillatory changes (Ca²⁺ oscillation). Studies of the intracellular Ca²⁺ release mechanism from the endoplasmic reticulum (ER) showed that the Ca²⁺ release mechanism has inherent regenerative properties, which is essential for the generation of Ca²⁺ waves and oscillations. Ca²⁺ may shuttle between the ER and mitochondria, and this appears to be important for pacemaking of Ca²⁺ oscillations. Importantly, Ca²⁺ oscillations are an efficient mechanism in regulating cell functions, having effects supra-proportional to the sum of duration of Ca²⁺ increase. Furthermore, Ca²⁺ signaling mechanism studies have led to the development of a method for specific inhibition of Ca²⁺ signaling, which has been used to identify hitherto unrecognized functions of Ca²⁺ signals.