Germ band retraction as a landmark in glucose metabolism during Aedes aegypti embryogenesis

<p>Abstract</p> <p>Background</p> <p>The mosquito <it>A. aegypti </it>is vector of dengue and other viruses. New methods of vector control are needed and can be achieved by a better understanding of the life cycle of this insect. Embryogenesis is a part of <it>A. aegypty </it>life cycle that is poorly understood. In insects in general and in mosquitoes in particular energetic metabolism is well studied during oogenesis, when the oocyte exhibits fast growth, accumulating carbohydrates, lipids and proteins that will meet the regulatory and metabolic needs of the developing embryo. On the other hand, events related with energetic metabolism during <it>A. aegypti </it>embryogenesis are unknown.</p> <p>Results</p> <p>Glucose metabolism was investigated throughout <it>Aedes aegypti </it>(Diptera) embryonic development. Both cellular blastoderm formation (CBf, 5 h after egg laying - HAE) and germ band retraction (GBr, 24 HAE) may be considered landmarks regarding glucose 6-phosphate (G6P) destination. We observed high levels of glucose 6-phosphate dehydrogenase (G6PDH) activity at the very beginning of embryogenesis, which nevertheless decreased up to 5 HAE. This activity is correlated with the need for nucleotide precursors generated by the pentose phosphate pathway (PPP), of which G6PDH is the key enzyme. We suggest the synchronism of egg metabolism with carbohydrate distribution based on the decreasing levels of phosphoenolpyruvate carboxykinase (PEPCK) activity and on the elevation observed in protein content up to 24 HAE. Concomitantly, increasing levels of hexokinase (HK) and pyruvate kinase (PK) activity were observed, and PEPCK reached a peak around 48 HAE. Glycogen synthase kinase (GSK3) activity was also monitored and shown to be inversely correlated with glycogen distribution during embryogenesis.</p> <p>Conclusions</p> <p>The results herein support the hypothesis that glucose metabolic fate changes according to developmental embryonic stages. Germ band retraction is a moment that was characterized as a landmark in glucose metabolism during <it>Aedes aegypti </it>embryogenesis. Furthermore, the results also suggest a role for GSK3 in glycogen balance/distribution during morphological modifications.</p

Climate versus in-lake processes as controls of the development of community structure in a low-arctic lake (South-West Greenland)

The dominant processes determining biological structure in lakes at millennial timescales are unclear. In this study, we used a multi-proxy approach to determine the relative importance of autogenic versus allogenic processes on the Holocene development of an oligotrophic lake in SW Greenland (66.99º N, 50.97º W). A 14C and 210Pb-dated sediment core covering ~8400 years BP was analysed for organic-inorganic carbon content, pigments, diatoms, chironomids, zooplankton and stable isotopes (13C, 18O). Relationships among the different proxies and a number of independent controlling variables (Holocene temperature, the 8.2 Kyr event, and immigration of Betula nana into the catchment) were explored using redundancy analysis (RDA) independent of time. The main ecological trajectories in the lake biota were captured by ordination first axis sample scores (18 – 32% variance explained). The importance of the arrival of Betula (ca. 6500 yBP) into the catchment was indicated by a series of partial-constrained ordinations, uniquely explaining ~15% of the variance in chironomids and ~9% in pigments. Climate influences on lake biota were strongest during the 8.2 Kyr cooling event, when all proxies responded rapidly although only chironomids had a unique component (in a partial-RDA) explained by the 8.2 Kyr event (8%). Holocene climate explained less variance than either catchment changes or biotic relationships. The sediment record at this site indicates the importance of catchment factors for lake development, the complexity of community trends even in relatively simple systems (invertebrates are the top predators in the lake) and the challenges of deriving palaeoclimate inferences from sediment records in low arctic freshwater lakes