Activity of Cuban propolis extracts on Leishmania amazonensis and Trichomonas vaginalis

In this paper we analyzed the antiprotozoal effects of eighteen Cuban propolis extracts (brown, red and yellow type) collected in different geographic areas, using Leishmania amazonensis (as a model of intracellular protozoa) and Trichomonas vaginalis (as a model of extracellular protozoa). All evaluated propolis extracts caused inhibitory effect on intracellular amastigotes of L. amazonensis. However, cytotoxicity on peritoneal macrophages from BALB/c mice was observed. Only five samples decreased the viability of T. vaginalis trophozoites at concentrations lower than 10 microg/mL. No correlation between the type of propolis and antiprotozoal activity was found. Cuban propolis extracts demonstrated activity against both intracellular and extracellular protozoa model, as well as the potentialities of propolis as a natural source to obtain new antiprotozoal agents.     

Structure-activity relationships for apomorphine congeners. Conformational energies vs. biological activities

Summary A series of apomorphine congeners has been studied with respect to their ability to mimic the structural requirements of the dopamine pharmacophore in the potent and stereoselective dopamine receptor agonist (R)-apomorphine. Conformational energies of the mimicking structures calculated by molecular mechanics (MMP2) correlate well with the observed biological activities.     

Avoided level crossings and singular points

Avoided crossings of discrete states as well as of resonance states are traced back to the existence of branch points (BPs) which are singular points in the complex energy plane. They cannot be identified with exceptional points. At a BP width bifurcation occurs, different Riemann sheets evolve and the levels do not cross anymore when the system is still further opened. The BPs are physically meaningful: they influence the dynamics of open as well as of closed quantum systems. The geometric phase that arises by encircling a BP, is different from the phase that appears by encircling a diabolic point. This is found to be true even for the two BPs into which the diabolic point is unfolded by opening the system. Presented at the 3rd International Workshop “Pseudo-Hermitian Hamiltonians in Quantum Physics”, Istanbul, Turkey, June 20–22, 2005.     

Ionic conductivity of crystalline and glassy Mg4.5Na7(P2O7)4

In our work single crystals of Mg_4.5Na₇(P₂O₇)₄ were prepared, pulverized, pressed into pellets and sintered in order to measure the electrical conductivity of polycrystalline specimens. The conductivity was also measured on glassy specimens obtained by the melting of previously prepared crystals. The electrical conductivities at 25°C with values of the order of 10⁻¹⁶ Ω⁻¹ cm⁻¹ for polycrystalline samples and a value of the order of 10⁻¹⁴ Ω⁻¹ cm⁻¹ for glass, show that the glassy phase of Mg_4.5Na₇(P₂ because of its greater molar volume and loosely packed structure, is a better matrix for ionic motion.