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We combine biochemical, physiological and molecular biological approaches in the study of insects. Our major experimental insects are the yellow fever mosquito Aedes aegypti and the tobacco hornworm Manduca sexta. Regulation of trypsin synthesis in the midgut of Aedes aegypti following a blood meal. The conversion of protein from a blood meal into yolk proteins and lipids for the developing oocytes is an essential part of the reproductive cycle. Blood feeding by a female Aedes aegypti mosquito initiates a series of events in the midgut, the fat body and the ovaries. Female mosquitoes ingest more than their own weight in blood in a short time and then spend the next 36 hours converting the amino acids from the blood proteins into the constituents of their eggs. The regulation of digestive enzyme synthesis in the midgut occurs in two phases. The early phase begins immediately after ingestion of the meal and involves activation of translation. The synthesis of early trypsin serves as a model for this phase. The late phase begins 6-8 hours after the meal and involves activation of transcription. The synthesis of late trypsin serves as a model for this phase. Working Hypothesis: In the first 30 minutes, in addition to the midgut filling, a peptide or small molecule is present in whole body extracts, which makes an in vitro midgut preparation competent for early trypsin translation. After 30 minutes, a phosphorylation cascade is initiated in the midgut which leads to activation of translation of early trypsin. About 6 hours after feeding, late trypsin transcription in the midgut is initiated. We have recently found that ecdysone, and an uncharacterized factor present in extracts prepared from fat bodies of fed mosquitoes, are involved in late trypsin gene induction. Regulation of amino acid metabolism in mosquitoes Regulation of blood meal amino acid metabolism in mosquitoes. This is a relatively new project in which we are analyzing the factors that control the partitioning of blood protein amino acids between synthesis of energy reserves in the female and production of egg proteins. We are particularly interested in how larval nutrition affects this partitioning. In collaboration with Dr. Vicki Wysocki of the Chemistry Department, we are pioneering the use of 15N-ammonia and mass spectrometry to study ammonia metabolism and the use of 2H2O and 13C-labeled substrates combined with mass spectrometry to study whole body metabolism. In collaboration with Dr. Joanna Masel of the Ecology and Evolutionary Biology Department we are developing quantitative models to describe whole body metabolism in mosquitoes. Hopefully, such studies will determine critical metabolic pathways that could be targets for a new series of biorational control agents. Lipoprotein metabolism in Manduca sexta.  Currently, we are focusing on these areas of research  Characterization of lipoprotein receptors. We use vertebrate tissue culture cells for expression cloning of lipoprotein receptors and stably transformed cell lines to characterize the properties of the receptors.  Studies on the mechanism of lipid transport. We are interested in how lipids cross membranes both during lipid absorption in the gut and in lipid transfer from lipoproteins to cells. We are expression cloning fatty acid and sterol receptors from the midgut and isolating factors that facilitate lipid transfer from cells to lipoprotein. A recent review highlights our current interests -" Lipid Storage and Mobilization in Insects: Current Status and Future Directions." E. L. Arrese, L. E. Canavoso, Z. E. Jouni, J. E. Pennington, K. Tsuchida, and M. A. Wells, Insect Biochem. Molec. Biol. 31, 7-17 (2001) (PDF reprint).  Science Education using Insects I also maintain the Manduca Project, which provides caterpillars eggs and diet to elementary school classes. See our web site http://www.manducaproject.com/ for more details.