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- Ph.D., Organic Chemistry, Stanford University, 1968
- B.S., Chemistry, New Mexico Highland University, 1963
Insect growth and development differs from that of mammals, and the hormones controlling this development have no counterpart in vertebrates. Ecdysone is a steroid which causes the shedding of the exoskeleton necessary for the insect to molt. Juvenile hormone modulates the action of ecdysone, controlling whether a larva molts to a larva or to a pupa. Juvenile hormone must be absent for a pupa to molt to an adult: this forms the basis of the insecticide methoprene, a synthetic molecule with juvenile hormone activity. I was involved in the development of this product before moving to University of Nevada, Reno.
My group identified four of the six known insect juvenile hormones and a related juvenile hormone from crabs. We have studied how insects create these sesquiterpenoids, four of which are biosynthetically unique with ethyl side branches replacing the usual methyl group. We found that the "extra" carbon atoms in these molecules comes from propionate, which is converted to homologs of normal terpene precursors. The glands producing these hormones vigorously metabolize the amino acids valine and/or isoleucine to a coenzyme A ester of propionate. We showed that the ability of the insect to produce the ethyl branched juvenile hormones is related to its ability to metabolize isoleucine or valine.
I have also done a great deal of research on the identification and biochemistry of insect peptide hormones which control a variety of processes. We identified from cockroach brains two peptides which raise its blood sugar levels, and later identified from Manduca sexta the hormones which stimulate (allatotropin) and stop (allatostatin) juvenile hormone production by the corpora allata, as well as the eclosion hormone, a 62 amino acid peptide which initiates the behavior necessary for an insect to escape from the old exoskeleton after it molts. We also identified a diuretic hormone from Manduca which stimulates ion secretion leading to urine production. This peptide is related to a vertebrate peptide known as CRF. We have done extensive research on this family of peptides, showing how Manduca DH is metabolized, identified seven more of these CRF-like DH from five other species of insects, and are currently trying to determine the intracellular mechanisms by which these peptides stimulate the vacuolar ATPase which powers cation secretion. From a cockroach we identified the first member of another family of diuretic hormones related to calcitonin, a controller of calcium balance in mammals. Using genomic data, we have synthesized diuretic hormones from Drosophila melanogaster and Anopheles gambiae (the malaria mosquito) and studied their physiological effects with Geoff Coast from Birkbeck College. We showed that the Anopheles calcitonin-like DH is the specific form which causes the massive excretion of sodium required when the adult female mosquito takes a blood meal. We are also interested in studying the differences in action of these two different families of peptides, both of which elevate intracellular cyclic AMP but with different outcomes in different species.
Awards, Honors, & Professional Recognition
- 1990- Baxter, Burdick, and Jackson International Award; Agrochemical Division, American Chemical Society
- 1993- Nevada Agricultural Foundation Arvin Boerlin Research Award
- 1993- University of Nevada Foundation Professor
- 2003- UNR College of Ag., Biotech., and Natural Resources Teacher of the Year
- 2004- UNR Outstanding Researcher Award
- 2004- University of Nevada Regents Researcher Award
- 2006- Ted Hopkins Insect Physiologist Award, Kansas State University
- 2007- Kenneth A. Spencer Award, Kansas City American Chemical Society Section