Preparation of novel derivatives of pyridothiazine-1,1-dioxide and their CNS and antioxidant properties.

Starting from isothiazolopyridine-1,1-dioxide (1), corresponding derivatives of 3-aryl-4-hydroxypyrido[3,2-e]-1,2-thiazine-1,1-dioxide (6) possessing the 3-[4-(substituted-phenyl)piperazinyl]propyl or 3-(4-substituted-piperidinyl)propyl side chain by the nitrogen atom of the thiazine ring were prepared. Under pharmacological central nervous system (CNS) screening in animal models (mice), all of the six pyridothiazines 6 tested exhibited analgesic action as the predominant profile of their activity ('writhing' test 12.5-50 mg/kg). Moreover, the radical scavenging activity against peroxyl radicals of the representative pyridothiazines 6 was evaluated in vitro in water environment and some of them proved to be moderate antioxidants.

Retention modelling of electrostatic and adsorption effects of aliphatic and aromatic carboxylic acids in ion-exclusion chromatography. II. Calculations of adsorption coefficients in unbuffered eluents.

Previous models for the retention behaviour of carboxylic acids in ion-exclusion chromatography are applicable only when the degree of ionisation of the analyte is constant over the entire chromatographic peak. When solutions of sulfuric acid are used as eluents, this condition applies only when the eluent concentration is considerably higher than that of the analyte. Since it is common for dilute solutions of sulfuric acid to be used as eluents, a retention model which accounts for unbuffered eluents has been developed. This model also considers the effects on retention of hydrophobic adsorption of the undissociated and dissociated forms of the analyte onto the stationary phase substrate, as well as the effects of organic solvents added to the eluent. The derivation of this model is presented and it has been evaluated using a comprehensive set of retention data obtained using three different sulfonated stationary phases over a range of eluent conditions. The adsorption coefficients calculated from the model are in accordance with expected trends and showed that both the undissociated and dissociated forms of the analyte acids were retained by hydrophobic adsorption effects, although this adsorption was much stronger for the undissociated analytes.

[Influence of NMDA receptor stimulation in brain cortex and hippocampus on NO dependent cGMP synthase. Effect of ischemia on NO related biochemical processes during recirculation]. / Wplyw stymulacji receptora NMDA w hipokampie i korze mózgu na synteze cGMP zaleznego od NO. Procesy biochemiczne tlenku azotu w okresie recyrkulacji po krótkotrwalej ischemii mózgu.

Stimulation of NMDA receptor increases NO-dependent cGMP synthesis. A significantly higher cGMP level was observed in hippocampus (about 8-fold increase) than in cerebral cortex (2.5-fold increase), as compared to basal value. The activity of NO synthase (NOS) and the basal level of cGMP in unstimulated slices were only slightly higher in hippocampus than in the cortex. About 60% of NOS total activity was found in the brain membrane fraction. The enzyme activity was not affected by glucocorticoids, even after 20 days of hydrocortisone treatment in dose of 40 mg/kg b.w. Brain ischemia induced by ligation of the both common carotid arteries in gerbils (Meriones unquiculatus) significantly increased NOS activity as well as cGMP and putrescine concentrations but decreased mono-ADP-ribosolation of proteins. Changes of NOS activity and cGMP concentration evoked by ischemia were decreased by specific inhibitor of the neuronal form of NOS (nNOS), 7-nitrodazole and the inhibitor of guanylate cyclase, LY 83,583 administered respectively in a dose of 25 mg/kg b.w. and 6 mg/kg b.w. 5 min. before ischemia. The inhibitor of nNOS, 7NI, did not change the concentration of putrescine during ischemia and reperfusion. Our results indicated that these inhibitors could protect the brain against excessive production of nitric oxide and biochemical processes dependent on it. In this way they may offer a new strategy in the therapy of brain ischemia.

Ion exclusion chromatography: parameters influencing retention.

Ion Exclusion Chromatography (IEC) finds application in the separation of a wide range of small, neutral or partially ionized molecules. In IEC, the strong as well as weak electrolytes are eluted unseparated, the first at the beginning and the latter at the end of the elution. The retention volumes of the remaining electrolytes are found to be proportional to their dissociation constant values. The dead and inner volumes of the chromatographic column can be determined from the observed dependence of retention volumes on dissociation constant values. The retention mechanism is described by the analytical equations and by the results obtained from the computer simulation of the column performance (using global thermodynamic and chromatographic equations or the Craig method). The mixed retention mechanism involving hydrophobic adsorption and screening effect is observed for weak electrolytes and aromatic compounds. Aromatic compounds are found to be retained almost solely by a reverse-phase mechanism involving interaction of the solute with the unfunctionalized regions of the stationary phase. The purpose of this paper is to survey the field. Using theoretical and experimental approaches, I show how different parameters can influence ion-exclusion solute retention. Although this retention is affected by the physicochemical parameters of the sorbent, stationary and mobile phases especially, this study primarily deals with the structural solute parameters, stationary phase form and column temperature, that have had little or no discussion in literature.

NMDA receptor mediated nitric oxide dependent cGMP synthesis in brain cortex and hippocampus. Effect of ischemia on NO related biochemical processes during reperfusion.

The stimulation of NMDA receptor activates NO dependent cGMP biosynthesis with dynamic and extent different for hippocampus and brain cortex. The significantly higher NO mediated cGMP level was observed in hippocampus than in brain cortex. NMDA receptor stimulation increases NO mediated cGMP formation about 8 fold in hippocampus and 2.5 fold in brain cortex as compared to basal value (2 mM CaCl2). The activity of NO synthase and the basal level of cGMP in unstimulated slices were only slightly higher in hippocampus then in brain cortex. The CA2+ calmodulin dependent NO synthase was found in brain membrane and cytosol fraction. The enzyme activity was not affected by glucocorticoids, even after 20 days of hydrocortisone treatment in a dose of 40 mg/kg b.w. Brain ischemia induced by ligation of both common carotid arteries in gerbils increases significantly NOS activities as well as the level of cGMP and putrescine but decreases mono-ADP-ribosylation of brain proteins during reperfusion period. The ischemia evoked changes of NOS/cGMP were eliminated by specific inhibitor of neuronal form of NOS, 7-Nitrodazole (7NI) administered in a dose of 25 mg/kg b.w. 5 min. before ischemia. This inhibitor has no effect on the level of putrescine enhanced during ischemia and also biphasically during reperfusion. The inhibitor of guanylate cyclase, LY 83583 administered in a dose of 6 mg/kg b.w. 5 min before ischemia diminishes not only the enhanced level of cGMP but also NOS activity stimulated by ischemia. These results indicate that activation of NMDA receptor stimulates more significantly NO/cGMP production in hippocampus than in brain cortex suggesting the role of NO in neuronal form of NOS and inhibitor of guanylate cyclase protect the brain against excessive production of nitric oxide and cGMP during ischemia-reperfusion. These compounds may offer a new strategy in the therapy of brain ischemia.