Neuroprotective effect of peroxiredoxin 6 against hypoxia-induced retinal ganglion cell damage

Background  

The ability to respond to changes in the extra-intracellular environment is prerequisite for cell survival. Cellular responses to the environment include elevating defense systems, such as the antioxidant defense system. Hypoxia-evoked reactive oxygen species (ROS)-driven oxidative stress is an underlying mechanism of retinal ganglion cell (RGC) death that leads to blinding disorders. The protein peroxiredoxin 6 (PRDX6) plays a pleiotropic role in negatively regulating death signaling in response to stressors, and thereby stabilizes cellular homeostasis.     

Laser-induced photodynamic effects of chlorinse 6 andp 6 on an isolated neuron

Photodynamic effects of chlorins e₆ and p₆ on an isolated mechanoreceptor neuron of a fluvial crayfish are investigated. A He−Ne laser (632.8 nm, 0.3 W/cm²) was used as an excitation source. The impulsive activity of neurons was found to be extremely sensitive to the photodynamic effect of low concentrations of chlorins e₆ and p₆ (0.005–6.000 and 0.05–0.50 μM, respectively). Cell reactions consisted of several phases of acceleration and inhibition of pulsations followed by an irreversible cancellation of nervous pulse generation. The type of reaction depended on the photosensitizer form and concentration. It is supposed that the phases of acceleration of impulsive activity are connected with the photodynamic damage of the cell membrane, and the inhibition phases are connected with the photodynamic effect on intracell organells. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 250–255, March–April, 1999.     

Neuroprotective effects of bis(7)-tacrine against glutamate-induced retinal ganglion cells damage

Background  

Glutamate-mediated excitotoxicity, primarily through N-methyl-D-aspartate (NMDA) receptors, may be an important cause of retinal ganglion cells (RGCs) death in glaucoma and several other retinal diseases. Bis(7)-tacrine is a noncompetitive NMDA receptors antagonist that can prevent glutamate-induced hippocampal neurons damage. We tested the effects of bis(7)-tacrine against glutamate-induced rat RGCs damage in vitro and in vivo.     

Solvent effects on the gain of rhodamine 6G

The effect of solvents on the gain and the peaks of gain spectra is investigated for rhodamine 6G (R6G) under nitrogen laser pumping. The non-specific solute-solvent interaction for R6G is found to be mainly dispersive. Additional shifts produced for R6G in certain solvents are explained as due to hydrogen bonding. The gain characteristics are interpreted on the basis of the position and overlap of absorption and fluorescence spectra, the quantum yield, the absorption at the pumping wavelength and the refractive index of the solvent. For the solvents studied it is found that R6G has high gain in solvents with low refractive index and high polarity. Amongst the solvents studied the alcohols displayed the highest gain with methanol being the most suitable solvent. The lowest gain amongst the alcohols was with capryllic alcohol which gave a gain that was 69% of that obtained with methanol. Amongst all the solvents studied the lowest gain was with chloroform, being only 34% of the gain in methanol.     

Elastic and magnetoelastic effects in CeB6

Elastic constants of CeB₆ were redetermined by ultrasonic and Brillouin scattering measurements. We found all elastic constants to be positive, especiallyc ₁₂. The temperature and magnetic field dependence of the elastic modesc ₄₄ and (c ₁₁-c ₁₂)/2 is explained on the basis of the newly proposed crystalline-electric-field level scheme for CeB₆ with the ₇ level 545 K above the ₈ ground state. The deduced quadrupolar coupling constants give an antiferroquadrupolar ordering temperature of 3.3 K in agreement with experiment.Supported by the DFG, SFB65, SFB125 and SFB126     

单向压力对碳纳米管(6, 6)晶体电子结构的影响

通过第一性原理计算研究了垂直于碳纳米管轴向的单向压力对碳纳米管(6,6)晶体电子结构特性的影响.计算研究发现：由碳纳米管(6,6)组成的四方结构晶体(t相)具有金属特性,电子可以沿碳纳米管管壁运动;在单向压力作用下,t相发生结构相变形成非成键相,随着压力的进一步增大,碳纳米管间产生键合,形成了成键相;单向压力对碳纳米管(6,6)晶体的能带结构影响主要表现在π能带和π^*能带,伴随着单向压力的增加,碳纳米管晶体的电学性质经历从金属到半导体再到活泼金属的转变;非成键相的电子被局域在碳纳米管附近使晶体具有半导体特性,而成键相的电子不仅可以沿着碳纳米管管壁运动,还可以在碳纳米管之间(即成键方向)运动,从而使成健相晶体具有活泼的金属特性. 关键词： 碳纳米管晶体 第一性原理计算 金属—半导体转变     

Core-polarization and open-shell effects in E6 transitions

The problem of isomeric E6 transitions recently measured in the fp shell is investigated. In the shell model these E6 decay rates require negative proton polarization charges and are quite anomalous in the context of usually enhanced E2 and E4 transitions. We demonstrate that usual core-polarization mechanisms cannot be invoked to explain the data and that the quadrupole deformations of the open shell that must be taken into account are instrumental in yielding negative P₆ moments.     

GT1b-induced neurotoxicity is mediated by the Akt/GSK-3/tau signaling pathway but not caspase-3 in mesencephalic dopaminergic neurons

Background  

Gangliosides, sialic acid-containing glycosphingolipids exist in mammalian cell membranes particularly neuronal membranes. The trisialoganglioside (GT1b) is one of the major brain gangliosides and acts as an endogenous regulator in the brain. We previously showed GT1b induces mesencephalic dopaminergic (DA) neuronal death, both in vivo and in vitro. We further investigate the underlying mechanisms of GT1b neurotoxicity.     

UF_6分子价轨道相对论效应的理论电子动量谱学研究

用非相对论、标量相对论和二分量相对论三种不同的密度泛函方法对UF_6分子的电子结构进行了量子化学计算,并利用编写的程序计算出了三种方法下各个价轨道的电子动量谱,比较了三种方法计算的价轨道能级及动量分布的差异.结果表明,相对论效应不仅使UF_6的能级劈裂和移动,而且对部分价轨道电子动量分布有显著的影响.     

Impact of thermal effects induced by ultrasound on viability of rat C6 glioma cells

In order to have consistent and repeatable effects of sonodynamic therapy (SDT) on various cancer cells or tissue lesions we should be able to control a delivered ultrasound energy and thermal effects induced. The objective of this study was to investigate viability of rat C6 glioma cells in vitro depending on the intensity of ultrasound in the region of cells and to determine the exposure time inducing temperature rise above 43 °C, which is known to be toxic for cells. For measurements a planar piezoelectric transducer with a diameter of 20 mm and a resonance frequency of 1.06 MHz was used. The transducer generated tone bursts with 94 μs duration, 0.4 duty-cycle and initial intensity I_SATA (spatial averaged, temporal averaged) varied from 0.33 W/cm² to 8 W/cm² (average acoustic power varied from 1 W to 24 W). The rat C6 glioma cells were cultured on a bottom of wells in 12-well plates, incubated for 24 h and then exposed to ultrasound with measured acoustic properties, inducing or causing no thermal effects leading to cell death. Cell viability rate was determined by MTT assay (a standard colorimetric assay for assessing cell viability) as the ratio of the optical densities of the group treated by ultrasound to the control group. Structural cellular changes and apoptosis estimation were observed under a microscope. Quantitative analysis of the obtained results allowed to determine the maximal exposure time that does not lead to the thermal effects above 43 °C in the region of cells for each initial intensity of the tone bursts used as well as the threshold intensity causing cell death after 3 min exposure to ultrasound due to thermal effects. The averaged threshold intensity was found to be about 5.7 W/cm².     

Dynamic effects in one-dimensional A′3ABO6

Low-dimensional transition metal oxides provide excellent model systems to study magnetic properties induced by the interplay between low-dimensionality character and frustration. In this work, we study polycrystalline Sr₃NiIrO₆ and Ca₃CoIrO₆ compounds which exhibit at low temperatures a frozen state with notable dynamic effects that can be attributed to the low-dimensionality character. These dynamic effects are probed by AC susceptibility measurements.     

New Wannier-Stark localization effects in natural 6H-SiC superlattice

A premature electric breakdown caused by the formation of a strong-field domain under conditions of negative differential conductivity in the 6H-SiC n⁺-n^?-n⁺ structure optimized for ultrahigh-frequency measurements was observed in the range of electric fields corresponding to the Bloch oscillation regime in a natural 6H-SiC superlattice. The experimental results and ensuing estimates indicate that this domain is mobile and, hence, oscillating, allowing the microwave oscillations that are rapidly damped under conditions of avalanche break-down in a natural 6H-SiC superlattice to be forecasted. Crystal perfectness of a natural 6H-SiC superlattice made it possible to directly observe the Wannier-Stark localization up to electric breakdown, i.e., during the natural crystal lifetime. This was accomplished by the optical photoelectric transformation method in the multiplication regime for a photocurrent created by photons with above-bandgap energy. It was shown that the Wannier-Stark localization, which involves only electrons, occurs in natural 6H-SiC superlattice up to fields that are almost equal to the breakdown field in 6H-SiC, unresponsively to band mixing, i.e., to the fundamental destroyer of the Wannier-Stark localization.     

Geometrical effects on the isotopically selective photodissociation of SF6 under CO2 laser pulses

A linear relationship is found between the³⁴S isotopic enrichment factor per pulse and the focal distance of the lens used to concentrate the laser beam. From this, one derives a threshold power of 26 MW/cm² for photodissociation, a mean absorption of 100 photons of 10.59 μm wavelength per³²SF₆ dissociation, and a dependence of the enrichment factor on the 3/2 power of the laser pulse energy.     

Environment effects on the lasing photostability of Rhodamine 6G incorporated into organic-inorganic hybrid materials

The effect on the lasing photostability of Rhodamine 6G (Rh6G), and the rigidity of a hybrid inorganic-organic matrix by controlled addition of di-, tri- and tetrafunctionalized alkoxides has been evaluated. The dye was incorporated into hybrid matrices of (2-hydroxyethyl methacrylate) (HEMA) or vol/vol copolymers of methyl methacrylate (MMA) and HEMA with different weight proportions of polycondensated dimethyldiethoxysilane (DEOS), methyltriethoxysilane (TRIEOS), and tetraethoxysilane (TEOS). The laser samples were transversaly pumped at 534 nm at 5.5 mJ/pulse and up to a 10 Hz repetition rate. The dependence of the laser photostability on organic-inorganic composition, pH of the medium, and thermal treatment of the samples was studied. Good stability, with a drop of the initial laser output of only 13% after 10000 pump pulses at 10 Hz in a thermally postcured (HEMA-15 wt%TRIEOS) matrix was obtained. Careful control of the synthesis process is required to reach the necessary photostability for a solid-state dye laser based on hybrid matrices to become competitive with liquid dye lasers. PACS 81.05.Lg; 81.05.Zx; 81.20.Fw; 42.55.Mv; 42.55.Rz; 42.60.Lh; 42.62.b; 42.70a; 42.70-Hj; 42.70.Jk     

The tumor affinity of chlorin e6 and its sonodynamic effects on non-small cell lung cancer

ObjectiveSonodynamic therapy (SDT) is a promising new approach for cancer therapy. The aim of this study was to investigate the tumor affinity of chlorin e6, a photosensitizer, and its sonodynamic effects on NSCLC.MethodsHuman lung adenocarcinoma cells SPCA-1 and mice bearing SPCA-1 tumor xenograft were exposed to ultrasound in the presence or absence of chlorin e6. Chlorin e6 distribution was detected by laser scan confocal microscope. Cell apoptosis and necrosis were studied by flow cytometry analysis. Tumor size and weight were measured after different treatments.ResultsThe concentration of chlorin e6 in tumor tissue was remarkably higher than that in normal muscle near tumor, and the difference was greatest at 18 h (the fluorescence intensity was 5.38-fold higher in tumor than in muscle, P < 0.05). In vivo, ultrasound (0.4–1.6 W/cm²) or chlorin e6 (10–40 mg/kg) alone had no remarkable anti-tumor effects, but the combination of ultrasound (1.6 W/cm²) with chlorin e6 (SDT) hampered tumor growth significantly (P < 0.05). Intraperitoneal injection of 40 mg/kg chlorin e6 exerted no notable side effect on blood, liver and kidney function. Flow cytometry analysis showed that chlorin e6-mediated sonodynamic effect was mainly through the induction of cell necrosis.ConclusionChlorin e6 is a promising sonosensitizer and chlorin e6-mediated SDT may provide a new approach for NSCLC therapy.     

Substitutional effects on the electrical properties of the purple bronze Li0.9Mo6O17

Dopant-level substitution of tungsten for molybdenum in Li_0.9Mo_6−xW_xO₁₇ solid solutions is shown to have a large effect on the electrical transport properties, which might be attributed to W interfering with the overlap of t_2g 4d Mo and π 2p orbitals forming the conduction band. With increasing concentration of W, the metal-to-metal transition broadens and shifts to higher temperature. At ∼6 at.% W content the material becomes semiconducting. Effects on the electronic properties are much less dramatic by alkali metal substitution in (Na_1−xLi_x)_0.9Mo₆O₁₇ alloys, since the alkali metals are only indirectly involved in the formation of the band structure. With x = 0, 0.25 and 0.5 the electrical resistivity behaves similar to Na_0.9Mo₆O₁₇. At x = 0.75 the electrical transport properties are nearly identical to that Li_0.9Mo₆O₁₇ and the supercond uctivity at 2 K is still observed.     

MRI effects on the teratogenicity of x-irradiation in the C57BL/6J mouse

This investigation was undertaken in order to ascertain the combined effects of magnetic resonance imaging (MRI) fields and x-irradiation on the developing eye of the mouse strain C57B1/6J. Dams in groups of 15 were subjected to absorbed doses of 5, 15, and 30 cGy. Other dams (N = 15) were exposed to T2 spin-echo MRI fields under clinically realistic conditions following exposure to 30 cGy of x-irradiation. The developing eye was the biological end point studied. It was found that the 30-cGy dose resulted in teratogenic significance (p less than or equal to .05) for the C57B1/6J mouse. Groups exposed to both types of radiation fields demonstrated malformation levels similar to the 30-cGy irradiated animals with no additive or synergistic effects detected. The malformation rates and degree of statistical significance varied somewhat with unit of measurement, and analytical method. The results confirmed low level X-ray teratogenicity and suggested that the MRI techniques employed for this investigation did not enhance the teratogenicity of x-irradiation on eye malformations produced in the C57B1/6J mouse.     

Structural effects and potential changes in growth factor signalling in penis-projecting autonomic neurons after axotomy

Background  

The responses of adult parasympathetic ganglion neurons to injury and the neurotrophic mechanisms underlying their axonal regeneration are poorly understood. This is especially relevant to penis-projecting parasympathetic neurons, which are vulnerable to injury during pelvic surgery such as prostatectomy. We investigated the changes in pelvic ganglia of adult male rats in the first week after unilateral cavernous (penile) nerve axotomy (cut or crush lesions). In some experiments FluoroGold was injected into the penis seven days prior to injury to allow later identification of penis-projecting neurons. Neurturin and glial cell line-derived neurotrophic factor (GDNF) are neurotrophic factors for penile parasympathetic neurons, so we also examined expression of relevant receptors, GFRα1 and GFRα2, in injured pelvic ganglion neurons.