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At least 1,045 records · Page 58Linked to original sources
PubMed1998

Modulation of the neuronal response to N-methyl-D-aspartate by selective sigma2 ligands.

It has now been accepted for several years that sigma (sigma) receptors exist in, at least, two distinct entities denoted sigma1 and sigma2. Previous electrophysiological studies from our laboratory have demonstrated that several selective sigma1 ligands potentiate the neuronal response to NMDA. The nonselective sigma1/sigma2 ligand DTG also potentiates the NMDA response. However, when DTG is administered at doses between 3 and 40 microg/kg, the increase of NMDA-induced activation turns to an epileptoid activity. Until recently, the physiological role of sigma2 receptors had been less studied due to the lack of selective sigma2 ligands. The goal of the present electrophysiological studies was to assess the effect of the intravenous administration of new selective sigma2 ligands on the neuronal response to NMDA in the CA3 region of the rat dorsal hippocampus. Lu 28-179 and BD 1008 potentiated dose-dependently the NMDA response and generated bell-shaped dose-response curves. These ligands failed to generate any epileptoid activity on their own but the subsequent administration of a low dose of a sigma1 agonist (JO-1784) induced an epileptoid activity. Interestingly, the potentiations of the NMDA response induced by Lu 28-179 or BD 1008 were not reversed by haloperidol, by the neurosteroid progesterone, nor by the selective sigma1 antagonist NE-100. Ibogaine, a high affinity sigma2 ligand, slightly increases the NMDA response, which was reversed by progesterone. These data suggest that, similarly to sigma1 ligands, sigma2 agonists potentiate the NMDA response and that the coactivation of sigma1 and sigma2 receptors could be necessary to induce an epileptoid activity. They also suggest that haloperidol may not act as a sigma2 antagonist and that several subtypes of sigma2 receptors could exist.

Animals↗
PubMed1999

Effects of bromoethylamine on antioxidant capacity, lipid peroxidation, and morphological characteristics of rat liver.

Administration of bromoethylamine (BEA, 1.2 mmol/kg) to fed rats induced a significant diminution in the activity of hepatic superoxide dismutase (at 1 h after treatment), catalase, and glutathione peroxidase and in the content of nonprotein sulfhydryls (at 15 h after treatment). The content of thiobarbituric acid reactants by the liver was enhanced by 1.9 times over control values (at 3 h). Light microscopy studies revealed that BEA (72 h after treatment) induced periportal fatty accumulation, focal liver cell necrosis, and diffuse inflammatory infiltrates, in addition to hypertrophic Kupffer cells and mitotic hepatocytes. Also, hypertrophic middle tunic or hypertrophic smooth muscle layers of arterioles was observed in the periportal space, with dilated sinusoidal capillaries and free macrophage infiltration. It is concluded that BEA induces a derangement in the antioxidant status of the liver with the consequent lipid peroxidation response, which may constitute a significant hepatotoxic mechanism of the haloaklylamine.

Animals↗
PubMedDate not supplied

Cyclohexylamine additives for enhanced peptide separations in reversed phase liquid chromatography.

While the choice of stationary phase, organic modifier, and gradient strength can have significant effects on biomolecule separations, mobile phase additives can also have a significant effect on the chromatographic selectivity, recovery, efficiency and resolution. Given the importance of stationary phase coverage, the beneficial, silanol-masking properties of amines, and the potential for selectivity modification through ion-pair interactions, cyclohexylamine was examined as a mobile phase additive and compared with triethylamine and trifluoroacetic acid. Greatly improved separation was possible when cyclohexylamine was used as compared with phosphate buffer, and cyclohexylamine did not require purification before use, while triethylamine required distillation before 'clean' chromatograms were obtained.

Chromatography, High Pressure Liquid↗
PubMed1999

Cross-linked poly(N-acetylethylenimine) as an isoelectric focusing matrix.

Agarose and polyacrylamide are the gels used for most analytical and micropreparative electrophoresis of biopolymers. In an alternative approach that offers different physico-chemical properties from these standard gels, nonionic hydrogels and amphigels composed of poly(N-acetylethylenimine) (PAEI) and a variety of cross-linkers were prepared and used as anticonvective matrices for isoelectric focusing. PAEI was prepared from the ring opening, ionic polymerization of 2-methyl-2-oxazoline. The N-acetyl side chains were hydrolyzed with aqueous sodium hydroxide to produce secondary amine sites which were used for the attachment of cross-linkers. Several cross-linkers were tested for their suitability for electrophoresis, and the cross-linker system based on the Diels-Alder reaction between a furan and maleimide tethered to PAEI gave a moldable gel that can be reversibly converted to a sol at 80 degrees C. This gel was used for isoelectric focusing under both denaturing and nondenaturing conditions. Several protein standards were resolved as well as was achieved with polyacrylamide.

Animals↗
PubMed2001

Separation of lidocaine and its metabolites by capillary electrophoresis using volatile aqueous and nonaqueous electrolyte systems.

The separation of the basic drug lidocaine and six of its metabolites has been investigated both by using volatile aqueous electrolyte system, at low pH and by employing non-aqueous electrolyte systems. In aqueous systems, the best separation of the compounds under the investigated conditions was achieved by using the electrolyte 60 mM trifluoroacetic acid (TFA)/triethylamine (TEA) at pH 2.5 containing 15% methanol. With this electrolyte, all seven compounds were well separated with high efficiency and migration time repeatability. The separations with bare fused-silica capillaries and polyacrylamide-coated capillaries were compared with higher separation efficiency with the latter. On the other hand, near baseline separation of all the seven compounds was also obtained by employing the non-aqueous electrolyte, 40 mM ammonium acetate in methanol and TFA (99:1, v/v), with comparable migration time repeatability but lower separation efficiency relative to the aqueous system.

Acetates↗
PubMed2001

Capillary electrophoresis of high-molecular chitosan: the natural carbohydrate biopolymer.

Due to its high resolving power and diverse application range, capillary electrophoresis (CE) has been successfully applied to the analysis of carbohydrates. In this paper, a method for the determination of high-molecular chitosan (Mr 200,000) using CE is presented. We studied the optimal condition of buffer pH and type, and column type for determination of chitosan. Optimal CE performance was found when employing 100 mM triethylamine (TEA)-phosphate buffer, pH 2.0 and untreated fused-silica capillary (50 microm x 27 cm) for the chitosan analysis. Under optimum conditions, excellent linear responses were obtained in the concentration range of 1.25-20 microM, with a linear correlation coefficient of 0.9983. The standard deviations of the migration time and peak area were found to be 2.5 and 6.4%, respectively. This method could be readily applied to chitosan determination in real biological samples and commercial products.

Animals↗
PubMed1989

Metabolism of triethylamine in polyurethane foam manufacturing workers.

In 20 workers studied before, during, and after exposure to triethylamine (TEA) in a polyurethane-foam producing plant the amount of TEA and its metabolite triethylamine-N-oxide (TEAO) excreted in urine corresponded to an average of 80% of the inhaled amount. An average of 27% was TEAO, but with a pronounced interindividual variation. Older subjects excreted more than younger ones; less than 0.3% was excreted as diethylamine. The data indicate half-lives for TEA and TEAO excretion in urine of about 3 hr. The postshift level of TEA in urine and plasma are good indicators of the time-weighted average air level during the preceding work day, and might thus be used for biological monitoring. An air level of 10 mg/m3 (proposed occupational standard) corresponds to a urinary excretion of 65 mmol TEA/mol creatinine and a plasma level of 1.9 mumol/liter (biological exposure indices).

Adolescent↗