The Influence of CB2-Receptor Ligands on the Memory-Related Responses in Connection with Cholinergic Pathways in Mice in the Passive Avoidance Test

Background: Dysfunction of the cholinergic system is associated with the development of Alzheimer’s disease (AD). One of the new possible strategies for the pharmacological modulation of memory-related problems typical of AD, is connected with the endocannabinoid system (ECS) and the cannabinoid (CB: CB1 and CB2) receptors. Methods: The aim of the study was to determine the influence of the selective CB2 receptor ligands: agonist (JWH 133) and antagonist (AM 630) on different stages of memory and learning in mice, in the context of their interaction with cholinergic pathways. To assess and understand the memory-related effects in mice we used the passive avoidance (PA) test. Results: We revealed that co-administration of non-effective dose of JWH 133 (0.25 mg) or AM 630 (0.25 mg/kg) with the non-effective dose of cholinergic receptor agonist - nicotine (0.05 mg/kg) enhanced cognition in the PA test in mice; however, an acute injection of JWH 133 (0.25 mg/kg) or AM 630 (0.25 mg/kg) had no influence on memory enhancement induced by the effective dose of nicotine (0.1 mg/kg). Co-administration of JWH 133 (0.25 mg) or AM 630 (0.25 mg/kg) with the effective dose of the cholinergic receptor antagonist scopolamine (1 mg/kg) attenuated the scopolamine-induced memory impairment in the PA test in mice. Conclusion: Our experiments have shown that CB2 receptors participate in the modulation of memory-related responses, especially those in which cholinergic pathways are implicated.     

Determination of volatile organic compounds in human breath for Helicobacter pylori detection by SPME-GC/MS

Helicobacter pylori living in the human stomach release volatile organic compounds (VOCs) that can be detected in expired air. The aim of the study was the application of breath analysis for bacteria detection. It was accomplished by determination of VOCs characteristic for patients with H. pylori and the analysis of gases released by bacteria in suspension. Solid-phase microextraction was applied as a selective technique for preconcentration and isolation of analytes. Gas chromatography coupled with mass spectrometry was used for the separation and identification of volatile analytes in breath samples and bacterial headspace. For data calculation and processing, discriminant and factor analyses were used. Endogenous substances such as isobutane, 2-butanone and ethyl acetate were detected in the breath of persons with H. pylori in the stomach and in the gaseous mixture released by the bacteria strain but they were not identified in the breath of healthy volunteers. The canonical analysis of discrimination functions showed a strong difference between the three examined groups. Knowledge of substances emitted by H. pylori with the application of an optimized breath analysis method might become a very useful tool for noninvasive detection of this bacterium.     

Depth profile studies of ZrTiN coatings by laser ablation inductively coupled plasma mass spectrometry

The feasibility of depth profiling was studied by using a 193-nm ArF* excimer laser ablation system (GeoLas, MicroLas, Goettingen, Germany) with a lens array-based beam homogenizer in combination with an ICP-QMS Agilent 7500. Two ablation cells (20 and 1.5 cm³) were compared at the laser repetition rate of 1 Hz, laser beam energy of 135 mJ and the carrier gas flow rate 1.5 L min^–1 He + 0.78 L min^–1 Ar. The ablation cell dimensions are important parameters for signal tailing; however, very small cell volumes (e.g. 1.5 cm³) may cause memory effects, which can be probably explained by dominant inertial losses of aerosol on cell walls with its delayed mobilization. The 20-cm³ ablation cell seems to be appropriate for depth profiling by continuous single-hole drilling. The study of the influence of the pit diameter magnitude on the waning and emerging signals under small crater depth/diameter aspect ratios, which range between 0.75 and 0.0375 for the 3-m-thick coatings and pit diameters 4–80 m, revealed that the steady-state signals of pure coating and pure substrate (out of interface) were obtained at crater diameters between 20 and 40 m. Depth resolution defined by means of slopes of tangents in the layer interface region depend on the pit diameter and has an optimum value between 20 and 40 m and gives 0.6 m for the 20-m pit. In-depth variation of concentration of coating constituent (Ti) was proved to be almost identical with two different laser/ICP systems.Viktor Kanický performed this work while on leave at ETH Zurich     

Voltammetry of lead cations on a new type of silver composite electrode in the presence of other cations

A new type of silver composite electrode was examined, prepared from silver, graphite powder, and methacrylate resin. The effects of the presence of various cations (cadmium, copper, bismuth, thallium), anions (chlorides), surface-active substances (Triton X-100), and oxygen on the anodic-stripping voltammetric determination of lead were studied. It was found that the effect of underpotential deposition at the composite electrode differs from that produced at a metallic silver electrode, mainly at low concentrations of the deposited metal. The use of this type of silver composite electrode in differential pulse anodic-stripping voltammetry enables direct determination of lead in natural water samples without elimination of surface-active substances (LOD about 3 g L^–1).     

Development and validation of HPLC method for the determination of α-tocopherol in human erythrocytes for clinical applications

In this work, a simple isocratic reversed-phase HPLC method for determination of alpha-tocopherol in human erythrocytes has been developed and validated. After separation of plasma the erythrocytes were washed three times with 0.9% sodium chloride containing 0.01% butylated hydroxytoluene (BHT) as antioxidant and then were diluted 1:1 (v/v) with the same solution. In the liquid-liquid extraction (LLE) procedure, 2500 microL of n-hexane was added to 500 microL of erythrocytes. After 2 min this mixture was deproteinized by addition of cool ethanol (500 microL, 5 min) denatured with 5% methanol containing alpha-tocopherol acetate (20 micromol L(-1)), as internal standard, and then extracted for 5 min by vortex mixing. After centrifugation (10 min, 1600xg) an aliquot (2000 microL) of the clean extract was separated and evaporated under nitrogen. The residue was dissolved in 400 microL methanol and analysed by reversed-phase HPLC on a 4.6 mmx150 mm, 5 microm Pecosphere C18 column; the mobile phase was 100% methanol, flow rate 1.2 mL min(-1). The volume injected was 100 microL and detection was by diode-array detector at a wavelength of 295 nm. The extraction recovery of alpha-tocopherol from human erythrocytes was 100.0+/-2.0%. The detection limit was 0.1 micromol L(-1) and a linear calibration plot was obtained in the concentration range 0.5-20.0 micromol L(-1). Within determination precision was 5.2% RSD (n=10), between determination precision was 6.1% RSD (n=10). The method was applied successfully in a clinical study of patients with acute pancreatitis and for determination of the reference values in the healthy Czech population.     

Equilibrium study of selected divalent d-electron metals adsorption on A-type zeolite

The objective of the presented study was to investigate the adsorption of Cu, Co, Mn, Zn, Cd and Mn on A-type zeolite. The isotherms for adsorption of metals from their nitrates were registered. The following adsorption constants K of metals were found: 162,890, 124,260, 69,025, 16,035, 10,254, and 151 [M(-1)] for Cu, Co, Mn, Zn, Cd, and Ni, respectively, for the concentration range 10(-4)-10(-3) M. On the other hand, the investigation of pH influence on the distribution constants of metals showed that the adsorption of metals proceeds essentially through an ion-exchange process, surface hydrolysis, and surface complexation. The supplementary results from DRIFT, scanning electron microscopy, and X-ray diffraction methods confirmed the presumption about the possible connection between the electronic structure of divalent ions and their adsorption behavior, showing that ions with d5 and d10 configurations such as Mn2+, Zn2+, Cd2+, with much weaker hydrolytic properties than Cu2+ and Ni2+, strongly interact with the zeolite framework and therefore their affinity to the zeolite phase is much stronger when compared with that of the Ni2+ ion, but at the same time not as strong as the affinity of the Cu2+ ion, the latter forming a new phase during the interaction with zeolite framework. For Zn2+, during inspection of the correlation between the proton concentration H/Al and zinc concentration Zn/Al on the zeolite surface, the formation of the surface complex [triple bond]S-OZn(OH) was proposed. A correlation between the heterogeneity of proton concentrations H/Al on Me-zeolite surfaces and the hydrolysis constants pKh of Me2+ ions was found.     

On the stability of the bioactive flavonoids quercetin and luteolin under oxygen-free conditions

The natural flavonoid compounds quercetin (3,3′,4′,5,7-pentahydroxyflavone) and luteolin (3′,4′,5,7-tetrahydroxyflavone) are important bioactive compounds with antioxidative, anti-allergic, and anti-inflammatory properties. However, both are unstable when exposed to atmospheric oxygen, which causes degradation and complicates their analytical determinations. The oxidative change of these flavonoids was observed and followed by UV–visible spectrophotometry, both in aqueous and ethanolic solutions. The distribution of the degradation products in aqueous media was monitored by LC–MS and LC–DAD analysis. The amounts of oxidative reaction products increase with the exposure time. The oxidative degradation reduces the pharmacological efficiency of these antioxidants and renders analytical determination inaccurate. The oxidative changes in flavonoid test solutions can explain the inconsistent dissociation constants reported in the literature. Dissociation constants of quercetin and luteolin were determined both by alkalimetric titration and by UV–visible spectrophotometry under deaerated conditions. The values pK ₁ = 5.87 ± 0.14 and pK ₂ = 8.48 ± 0.09 for quercetin, and pK ₁ = 5.99 ± 0.32 and pK ₂ = 8.40 ± 0.42 for luteolin were found.     

Allylic alcohols as synthetic enolate equivalents: isomerisation and tandem reactions catalysed by transition metal complexes

Allylic alcohols can be isomerised into carbonyl compounds by transition metal complexes. In the last few years, catalyst design and development have resulted in highly efficient isomerisations under mild reaction conditions, including enantioselective versions. In addition, the isomerisation of allylic alcohols has been combined with C-C bond forming reactions when electrophiles such as aldehydes or imines were present in the reaction mixture. Also, C-F bonds can be formed when electrophilic fluorinating reagents are used. Thus, allylic alcohols can be treated as latent enol(ate)s. In this article, we highlight the latest developments concerning the isomerisation of allylic alcohols into carbonyl compounds, focusing in particular on tandem isomerisation/C-C or C-heteroatom bond formation processes. Significant attention is given to the mechanistic aspects of the reactions.     

Five-membered heterocycles. Part III. Aromaticity of 1,3-imidazole in 5+n hetero-bicyclic molecules

The aromaticity (in the form of HOMA index) of 1,3-imidazole ring and its bicyclic derivatives was studied on the basis of statistical data from Cambridge Structural Database and X-ray investigations performed by authors. As a starting point, aromaticity of the 1,3-imidazoles with exocyclic X substituent at C2 (XN, O or S) was calculated. Subsequently, the HOMA index was calculated for various 5+n bicyclic skeletons with N, O, and S as endocyclic heteroatoms in the second ring. For the isolated 1,3-imidazole ring, aromaticity depends on exocyclic substituent at C2 and decreases in sequence N, S, O. For bicyclic derivatives it was found that both rings are aromatic and coplanar in very few molecules (17% of investigated ones), and positive charge—located on endocyclic heteroatom—increases the aromaticity. For remaining compounds, presence of sp³ carbons excludes possibility of aromatic ring existence.