Phase formation during synthesis of the LaSr2Mn2O7 compound

The processes of formation of the LaSr₂Mn₂O₇ compound are investigated in the temperature range 800–1400°C. The formation of the LaSr₂Mn₂O₇ compound is found to occur through intermediate phases, namely, LaMnO₃ and Sr₂MnO₄. It is revealed that the decomposition of the LaSr₂Mn₂O₇ compound is caused by a decrease in both the temperature and the oxygen pressure.     

Characterization of combustible shale from the Dmitrievskoe deposit in the Kuznetsk Basin

A sample of combustible shale from the Dmitrievskoe deposit (Kuzbass) was studied with the use of various chemical and physicochemical methods of analysis (proximate and ultimate analysis, low-temperature extraction, pyrolysis, chemical analysis of ash, thermogravimetric analysis, and IR spectroscopy) in order to evaluate its chemical and technological properties.     

Digitalis-like and vasoconstrictor effects of endogenous digoxin-like factor(s) from the venom of Bufo marinus toad

Digitalis glycoside-like properties of the Bufo marinus toad crude venom and one of its constituents, bufalin, were studied in various assay systems. In concentrations 0.3-30 micrograms/ml crude venom increased the contractility of isolated electrically driven rat atria, constricted rat aortic rings, inhibited ouabain-sensitive Na+,K(+)-ATPase in rat erythrocytes and the Na+,K(+)-pump in rat aorta, and cross-reacted with antidigoxin antibody from the dissociation enhanced lanthanide fluoroimmunoassay (DELFIA). These effects were unaffected by adrenoceptor blockers and the 5-HT antagonist, deseril, but were blocked by antidigoxin antibody. Bufalin (10-30 microM) increased myocardial contractility and inhibited Na+,K(+)-ATPase in rat erythrocytes similarly to crude Bufo marinus venom. In rat aorta bufalin showed weak and delayed vasoconstrictor activity which was antagonized by 2 microM phentolamine, and had a biphasic effect on the Na+,K(+)-pump; 0.5-1.0 microM bufalin stimulated the pump, while higher concentrations inhibited its activity. Although the effects of bufalin were blocked by antidigoxin antibody, bufalin showed very low digoxin-like immunoreactivity in the DELFIA. These observations suggest that, in addition to bufalin, Bufo marinus venom contains at least one more digitalis-like steroid with significant intrinsic vasoconstrictor activity which, unlike bufalin, constricts the blood vessels acting directly via inhibition of the sodium pump in the vascular smooth muscle membrane.