Role of NMDA receptor subtypes in different forms of NMDA-dependent synaptic plasticity

Background  

The involvement of different NMDA receptor (NMDAR) subunits has been implicated in several forms of synaptic plasticity. However, it is still controversial to what extent the involvement is specific, and little is known about the role of NMDAR subunits in certain "non-conventional" forms of plasticity. In this study we used subunit-specific blockers to test the roles of NR2A- and NR2B-containing NMDARs in a type of chemical long-term depression (LTD) induced by brief bath application of the NMDAR agonist NMDA to hippocampal slices from 12–18 days old rats. For comparison, we also examined other forms of plasticity, including a "slow LTD" induced by 0.1 Hz stimulation under low Mg²⁺ conditions as well as long-term potentiation (LTP).     

Regularity analysis of an individual-based ecosystem simulation

We analyze the results of a large simulation of an evolving ecosystem to evaluate its complexity. In particular, we are interested to know how close to a stochastic or a deterministic behavior our simulation is. Four methods have been used for this analysis: Higuchi fractal dimension, correlation dimension, largest Lyapunov exponent, and P&H method. Besides, we use a surrogate data test to reach a final decision about analysis. As we expect, our results show that there is a deterministic and chaotic behavior in ecosystem simulation.     

Multinuclear (Sn/Pd) complexes with disodium 2,2′-(dithiocarboxyazanediyl)diacetate hydrate; Synthesis,characterization and biological activities

Bimetallic chlorodi-/triorganotin(IV) derivatives of general formulas R₂(H₂O)SnLCSSSn(Cl)R₂ (R=Me: 1; Ph: 2) and R₃Sn(Na)LCSSSnR₃·H₂O (R=Bu: 3; Ph: 4) were prepared by reaction of iminodiacetic acid disodium salt hydrate (Na₂LH) with CS₂ and R₂SnCl₂/R₃SnCl in methanol. The reaction between Na₂LH, CS₂, and PdCl₂ produced [Na₂LCSS]₂Pd·2H₂O (5) which was treated with R₃SnCl to synthesize the heterobimetallic derivatives [R₃Sn(Na)LCSS]₂Pd·2H₂O (R=Me: 6; Ph: 7). The complexes were characterized by microanalysis, spectroscopic, and thermogravimetric analyses. Elemental analysis data, mass fragmentation, and thermal degradation patterns supported the molecular composition of the complexes. FT-IR data indicated monodentate binding of carboxylate while a chelating coordination mode of the dithiocarboxylate was verified in the solid state. A five-coordinate tin(IV) was demonstrated in the solid state. In solution, a tetrahedral/trigonal bipyramidal configuration around Sn(IV) and a square planar geometry of Pd(II) was indicated by multinuclear NMR (¹H and ¹³C) and UV-visible studies. The Pd(II) derivatives showed interaction with salmon sperm-DNA and caused an inhibition of alkaline phosphatase (ALPs). The antibacterial/antifungal potential of the coordination products varied with the nature of incorporated metal and a substitution pattern at tin(IV); the palladium metallation decreased the antimicrobial activities. The triorganotin(IV) products exhibited more powerful action against bacteria/fungi as compared to their diorganotin(IV) counterparts. The complexes displayed sufficiently lower hemolytic effects in vitro as compared to triton X-100 and slightly higher than PBS.     

Synthesis and structure of (H2O·HBF4)2(18-crown-6)

The title compound has been prepared by the addition of fluoroboric acid to 18-crown-6 in toluene. The compound crystallizes in the triclinic space group P¯1 witha=7.341(2),b=8.364(2),c=10.631(3)Å,=71.48(2),=67.91(2), =67.94(2)°, andD _c =1.44 g cm^–3 forZ=1. The final conventionalR value was 0.079 based on 1575 observed reflections. The molecule resides on a center of inversion. The (H₂O·HBF₄) moieties are best viewed as fluoroboric acid monohydrate molecules hydrogen bonded to the crown ether, one above and one below the plane of the crown. The FO(water) hydrogen bond separation is 2.474(5)Å, and the O(crown)O(water) separations are 2.834(5) and 2.841(6) Å. The oxygen atoms of the crown ether are planar to 0.23 Å.     

Thermo-oxidative degradation kinetics and mechanism of the system epoxy nanocomposite reinforced with nano-Al2O3

We have synthesized epoxy nanocomposites with various percents of nanoalumina by using ultrasonic dispersion treatment. Scanning calorimetry studies revealed that the composition having 1% nanoalumina results in the highest value of cross-link density as evidenced by the glass transition temperature (T _g). Thermal degradation of the systems consisting of diglycidyl ether bisphenol A (DGEBA)/1,3-Poropane diamine and with 1% and without nanoalumina were studied by thermogravimetry analysis to determine the reaction mechanism in air. The obtained results indicated that a relatively low concentration of nanoalumina led to an impressive improvement of thermal stability of epoxy resin. The Coats?CRedfern, Van Krevelen, Horowitz?CMetzger, and Criado methods were utilized to find the solid state thermal degradation mechanism. Analysis of our experimental results suggests that the reaction mechanism is depending on the applied thermal history. For the nanocomposite, the mechanism was recognized to be one-dimensional diffusion (D₁) reaction at low heating rates and it changes to be a random nucleation process with one nucleus on the individual particle (F₁) at high heating speeds. The results also indicated that the degradation mechanism of organic phase is influenced by the presence of inorganic nanofiller.     

An efficient regioselective synthesis of highly functionalized 3-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidines via an isocyanide-based three-component reaction

We present a novel, convenient, and efficient method for synthesizing polysubstituted 3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidines via a three-component reaction. The zwitterions generated from the reaction of isocyanides and dialkyl acetylenedicarboxylates react with 2-imino-1,3-thiazolidin-4-one to produce the title compounds in good yields.     

A green one-pot synthesis of N-alkyl-2-(2-oxoazepan-1-yl)-2-arylacetamide derivatives via an Ugi four-center,three-component reaction in water

This work describes a green and efficient one-pot synthesis of N-alkyl-2-(2-oxoazepan-1-yl)-2-arylacetamide derivatives via an Ugi four-center, three-component reaction of 6-aminohexanoic acid, aromatic aldehydes, and isocyanide derivatives in water under reflux conditions in the absence of a catalyst.     

Heat-resistant and soluble fluorinated poly(amide imide)s based on non-coplanar ortho-linked diimide-dicarboxylic acid

A series of novel fluorinated heat-resistant poly(amide imide)s (PAIS) based on non-coplanar diimide-diacid monomer (DIDA) were synthesized and characterized. The poly(amide imide)s were obtained in high yields and possessed inherent viscosities in the range of 0.47-0.91 dL g⁻¹. All of the polymers were amorphous in nature, showed outstanding solubility and could be readily soluble in common organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidinoned, dimethyl sulfoxide, N,N-dimethylformamide, pyridine and tetrahydrofuran. Glass transition temperatures were in the range of 221-263 °C, as determined by differential scanning calorimetry. Degradation temperatures for 10% weight loss occurred all above 520 °C and char yields was more than 50% at 700 °C in nitrogen atmosphere. Moreover, these PAIs possessed low refractive indexes (n = 1.58-1.59), birefringence (Δn = 0.008-0.013), and dielectric constants (? ≈ 2.5) due to the trifluoromethyl pendent groups and ortho-catenated aromatic rings that interrupt chain packing and increase free volume.