Epicuticular waxes from caatinga and cerrado species and their efficiency against water loss

The effects of the contents and chemical composition of the foliar epicuticular waxes of species from the caatinga (Aspidosperma pyrifolium, Capparis yco, Maytenus rigida and Ziziphus joazeiro) and cerrado (Aristolochia esperanzae, Didymopanax vinosum, Strychnos pseudoquina and Tocoyena formosa) were evaluated as to the resistance to water loss by means of an experimental device constructed for this purpose. In general, the waxes of the caatinga species investigated were more efficient against water loss than cerrado species. Increase of the thickness of the waxy deposits from 40 to 90m g.cm-2 had no significant effect on the resistance to water loss. The chemistry of the wax constituents was shown to be an important factor to determine the degree of resistance to evaporation. n-Alkanes and alcoholic triterpenes were the most efficient barriers, while hentriacontan-16-one (a ketone) and ursolic acid (an acid triterpene) revealed lowefficiency. The higher efficiency of the waxes of the leaves from caatinga species (mainly those of C. yco and Z. joazeiro) is probably accounted for the predominance of n-alkanes in their composition. The lower efficiency of the waxes of A. pyrifolium (caatinga), T. formosa and A. esperanzae (both species from the cerrado) is probably a consequence of the predominance of triterpenoids in the waxes of the two former species and hentriacontan-16-one in the latter

Avaliaçäo do nível de impermeabilizaçäo radicular externa frente ao estudo da permeabilidade dentinária apical / Evaluation of the level of externa radicular impermeabilization in a study of apical dentin permeability

O propósito deste estudo foi verificar, em canais radiculares obturados, as alteraçöes decorrentes do nível de impermeabilizaçäo radicular frente à penetraçäo do corante azul de metileno em dois tempos experimentais. Sessenta dentes unirradiculares tiveram suas raízes instrumentadas, obturadas e agrupadas, variando o nível de impermeabilizaçäo radicular externa (a 0,0 mm, 1,0 mm e 2,0 mm aquém do ápice radicular), sendo imersas em soluçäo de azul de metileno a 0,5 por cento, pH 7,2 variando também o tempo de imersäo (72 e 168 horas). Pudemos concluir que a impermeabilizaçäo radicular externa é imprescindível nos casos em que a penetraçäo apical de corantes é utilizada com o intuito da verificaçäo do selamento da obturaçäo, sendo que a variável distância do forame näo se mostrou estatisticamente significante