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Jeffrey H. Spring

1973 B.Sc (Honours Biology) University of Waterloo, Waterloo, Ontario, Canada

1976 M.Sc (Insect Physiology) University of Waterloo, Waterloo, Ontario, Canada

1979 Ph.D (Zoology) University of British Columbia, Vancouver, BC, Canada

Primary research interests center around the mechanisms and control of ion and water balance in arthropods. Using the house cricket, Acheta, as our experimental animal, my graduate students and I employ a variety of microtechniques to analyze the function and control of the excretory system. Ion analysis of picoliter droplets of fluid is performed either using energy-dispersive X-ray microanalysis (EDS) or atomic absorption (AA) spectroscopy. Separation, purification and identification of neuropeptide hormones from the corpora cardiaca (CC) and other ganglia are done using high-performance liquid chromatography (HPLC), and synthesis/release of peptides can be followed using radiotracers.

We have discovered three factors in the CC that alter the secretion rate of the tubules. One factor (ADH) is antidiuretic (i.e., inhibits secretion) and can be mimicked by the calcium ionophore, A23187. The other two, one of which can be mimicked by cyclic-AMP, are diuretic (DH's), although they exhibit different time courses and appear to affect different transport mechanisms. Our current model for the mechanisms of action of these factors is shown below. We believe that DH1 is responsible for rapid, short-term fluid secretion, whereas the action of DH2 is slower in onset and more sustained. These two presumably interact synergistically to produce the normal response seen when CC homogenates are applied. Our understanding of these processes is complicated by the fact that the tubules are divided into morphologically discrete regions, and recent work using single tubules has shown that the responses of the different regions to second messengers is not only different, but often antagonistic.

I am also engaged in a long-term study of the Eastern Lubber Grasshopper, Romalea. These insects are seasonally present in great numbers in Louisiana and are easily collected for study. In collaboration with Dr. Gerd Gade of the University of Capetown, I am studying the hormonal control of carbohydrate and lipid metabolism. Romalea is very useful for these studies from a comparative standpoint because, although itself flightless, it produces large quantities of the hormones (AKH/RPCH family) thought to be responsible for the tremendous upsurge in metabolism that accompanies sustained migratory flight.