RESUMO
The rivers originating in the southern Andes (18°-55°S) support numerous ecosystems and a large number of human populations and socio-economic activities in the adjacent lowlands of Chile, Argentina and Bolivia. Here we show that ca. 75% of the total variance in the streamflow records from this extensive region can be explained by only eight spatially coherent patterns of variability. Five (three) of these Andean patterns exhibit extreme dry (wet) conditions in recent years, with strong interannual variations in northern Chile; long-term drying trends between 31° and 41°S; a transitional pattern in the central Patagonian Andes; and increasing trends in northwestern Argentina and southern Bolivia, the Fueguian Andes, and the eastern portion of the South Patagonian Icefield. Multivariate regression analyses show that large-scale indices of ENSO variability can predict 20% to 45% of annual runoff variability between 28° and 46°S. The influence of Antarctic and North Pacific indices becomes more relevant south of 43°S and in northwestern Argentina and southern Bolivia, respectively, but their overall skill as predictors of Andean streamflows is weak. The analyses provide relevant new information to improve understanding of the spatial coherence, the main temporal features, and the ocean-atmospheric forcings of surface runoff across the southern Andes.
RESUMO
13C-NMR has been applied to the study of the metabolism of [1-13C]glucose by macrofilariae of Dipetalonema viteae under conditions of restricted glucose supply. In a medium buffered with 13C-labelled bicarbonate, succinate labelled in the carboxyl position is formed in good yield. Quinolinic acid, a known inhibitor of phosphoenol pyruvate carboxykinase (PEPCK) has been shown to suppress the formation of labelled succinate from [1-13C]glucose. Both sets of experiments support the formation of succinate through the PEPCK-mediated carboxylation of phosphoenol pyruvate, followed by the operation of a partial tricarboxylic acid cycle.
