Dispersion Relations for Thermally Excited Waves in Plasma Crystals

Thermally excited waves in a Plasma crystal were numerically simulated using a Box_Tree code. The code is a Barnes_Hut tree code proven effective in modeling systems composed of large numbers of particles. Interaction between individual particles was assumed to conform to a Yukawa potential. Particle charge, mass, density, Debye length and output data intervals are all adjustable parameters in the code. Employing a Fourier transform on the output data, dispersion relations for both longitudinal and transverse wave modes were determined. These were compared with the dispersion relations obtained from experiment as well as a theory based on a harmonic approximation to the potential. They were found to agree over a range of 0.9<k<5, where k is the shielding parameter, defined by the ratio between interparticle distance a and dust Debye length lD. This is an improvement over experimental data as current experiments can only verify the theory up to k = 1.5.Comment: 8 pages, Presented at COSPAR '0

Plantas Oleaginosas Amazônicas: Química e Atividade Antioxidante de Patauá (Oenocarpus bataua Mart.)

The Amazon oilseeds, especially from native palm trees are significant species belonging to the Amazon landscape and culture. The Amazon species produce oil with great potential to generate valuable medicines, cosmetics, nutraceuticals and energy. The Oenocarpus bataua (patawa) is an edible species and from its fruits is produced the "vinho de patauá", a well-known beverage, considered very nutritive and energetic. Fresh fruits collected nearby Manaus-AM, were separated into peel, pulp and seeds. The methanolic extracts from pulp and seeds were evaluated in different antioxidant assays and both extracts were considered active. The seed extract showed antioxidant activity compared to the positive control (quercetin) in the radical scavenging-DPPH assay. The pulp extract were fractionated guided by TLC-antioxidant analysis that led to the isolation of the stilbene, piceatannol. This is the first report of an isolated compound from patawa. Piceatannol is considered a bioactive compound and in some cases was considered more active than resveratrol, a well-known bioactive compound. These results showed the great potential of patawa to produce nutraceutical products

Dynamic behaviors of dust particles in the plasma-sheath boundary

A variety of dynamic behaviors in dusty plasmas is expected under the experimental condition of weak friction with gas molecules. The device "KAGEROU" provides such an environment for dynamic collective phenomena. Self-excited dust oscillations in Coulomb crystals have been observed at low values of plasma density and gas pressure. An instability mechanism was identified to be delayed charging in an inhomogeneous equilibrium dust charge in the sheath. The theoretical growth rate was formulated in relation to the destabilization of a transverse dust lattice wave (T-DLW), which was found to be very sensitive to the presence of a small amount of hot electrons which produces a substantial positive equilibrium charge gradient &#8711;Qd-eq around the equilibrium position of dust particles in the plasma-sheath boundary. The first experimental observation of a correlated self-excited vertical oscillations in a one-dimensional dust chain indicates a destabilization of T-DLW. The experimental condition is very consistent with the parameter area which predicts numerically an instability of T-DLW

Characterization of bergenin in endopleura uchi bark and its anti-inflammatory activity

Endopleura uchi (Huber) Cuatrec. is an Amazon species traditionally used for the treatment of inflammations and female disorders. Pure bergenin was isolated from the methanolic extract of bark of E. uchi, firstly by using liquid-liquid partition chromatography followed by column chromatography over Sephadex LH-20 and then silica gel 60 flash chromatography. The structure of bergenin was identified on the basis of its NMR spectra. The in vitro anti-inflammatory activity was determined by the measurement of the inhibitory concentration (IC) of bergenin against three key enzymes: COX-1, COX-2 (cyclooxygenases) and phospholipase A2 (PLA2). These enzymes were selected because they are important targets for the discovery of new anti-inflammatory drugs associated with the biosynthesis of prostaglandins. The IC50 of bergenin for phopholipase A2 was determined as 156.6 μmol L-1 and bergenin was not considered active as compared to the positive control, tioetheramide PC. Bergenin did not inhibit COX-1 as well (IC50 = 107.2 μmol L-1). However, bergenin selectively inhibited COX-2 (IC50 = 1.2 μmol L-1). Because of the use of E. uchi in traditional medicine, bergenin was quantified in teas prepared as prescribed in traditional medicine by RP-HPLC as being 3% in the bark of E. uchi. The inhibitory activity towards COX-2 is important, since selective inhibitors of COX-2 have been clinically validated as anti-inflammatory therapeutics due to their enhanced gastrointestinal safety. ©2009 Sociedade Brasileira de Química

Messenger RNA Oxidation Occurs Early in Disease Pathogenesis and Promotes Motor Neuron Degeneration in ALS

BACKGROUND: Accumulating evidence indicates that RNA oxidation is involved in a wide variety of neurological diseases and may be associated with neuronal deterioration during the process of neurodegeneration. However, previous studies were done in postmortem tissues or cultured neurons. Here, we used transgenic mice to demonstrate the role of RNA oxidation in the process of neurodegeneration. METHODOLOGY/PRINCIPAL FINDINGS: We demonstrated that messenger RNA (mRNA) oxidation is a common feature in amyotrophic lateral sclerosis (ALS) patients as well as in many different transgenic mice expressing familial ALS-linked mutant copper-zinc superoxide dismutase (SOD1). In mutant SOD1 mice, increased mRNA oxidation primarily occurs in the motor neurons and oligodendrocytes of the spinal cord at an early, pre-symptomatic stage. Identification of oxidized mRNA species revealed that some species are more vulnerable to oxidative damage, and importantly, many oxidized mRNA species have been implicated in the pathogenesis of ALS. Oxidative modification of mRNA causes reduced protein expression. Reduced mRNA oxidation by vitamin E restores protein expression and partially protects motor neurons. CONCLUSION/SIGNIFICANCE: These findings suggest that mRNA oxidation is an early event associated with motor neuron deterioration in ALS, and may be also a common early event preceding neuron degeneration in other neurological diseases

Increased levels of RNA oxidation enhance the reversion frequency in aging pro-apoptotic yeast mutants

Despite recent advances in understanding the complexity of RNA processes, regulation of the metabolism of oxidized cellular RNAs and the mechanisms through which oxidized ribonucleotides affect mRNA translation, and consequently cell viability, are not well characterized. We show here that the level of oxidized RNAs is markedly increased in a yeast decapping Kllsm4Δ1 mutant, which accumulates mRNAs, ages much faster that the wild type strain and undergoes regulated-cell-death. We also found that in Kllsm4Δ1 cells the mutation rate increases during chronological life span indicating that the capacity to han- dle oxidized RNAs in yeast declines with aging. Lowering intracellular ROS levels by antioxidants recovers the wild- type phenotype of mutant cells, including reduced amount of oxidized RNAs and lower mutation rate. Since mRNA oxidation was reported to occur in different neurodegen- erative diseases, decapping-deficient cells may represent a useful tool for deciphering molecular mechanisms of cell response to such conditions, providing new insights into RNA modification-based pathogenesis

Sulforaphane Potentiates RNA Damage Induced by Different Xenobiotics

Background: The isothiocyanate sulforaphane (SFN) possesses interesting anticancer activities. However, recent studies reported that SFN promotes the formation of reactive oxygen species (ROS) as well as DNA breakage. Methodology/Principal Findings: We investigated whether SFN is able to damage RNA, whose loss of integrity was demonstrated in different chronic diseases. Considering the ability of SFN to protect from genotoxicity, we also examined whether SFN is able to protect from RNA damage induced by different chemicals (doxorubicin, spermine, S-nitroso-Nacetylpenicillamine, H2O2). We observed that SFN was devoid of either RNA damaging and RNA protective activity in human leukemic cells. It was able to potentiate the RNA damage by doxorubicin and spermine. In the first case, the effect was attributable to its ability of modulating the bioreductive activation of doxorubicin. For spermine, the effects were mainly due to its modulation of ROS levels produced by spermine metabolism. As to the cytotoxic relevance of the RNA damage, we found that the treatment of cells with a mixture of spermine or doxorubicin plus SFN increased their proapoptotic potential. Thus it is conceivable that the presence of RNA damage might concur to the overall toxic response induced by a chemical agent in targeted cells. Conclusions/Significance: Since RNA is emerging as a potential target for anticancer drugs, its ability to enhance spermineand doxorubicin-induced RNA damage and cytotoxicity could represent an additional mechanism for the potentiatin