Diuretic neurohormones in the tobacco budworm, Heliothis virescens /
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| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | An in vitro diuretic hormone bioassay was established using Malpighian tubules from fifth-instar larvae (LI-V) of Heliothis virescens and [14C] urea as an indicator for water transfer. Na+ was important for basal fluid secretion in vitro. Tubules from starved larvae were more sensitive to diuretic factors in brain extracts than tubules from fed larvae. Diuretic factors were present throughout the entire nervous tissues, but most activity was located in the Heliothis brain. Diuretic activity was heat stable but sensitive to trypsin and chymotrypsin. Basal fluid secretion was decreased by ethacrynic acid, and furosemide, but ouabain did not affect it. Fluid secretion in response to diuretic factors in brain extracts of pharate adult was sensitive only to ethacrynic acid. Both furosemide and ethacrynic acid decreased cAMP related-fluid secretion by Heliothis tubules. This indicated that cAMP was not likely the second messenger for Heliothis diuretic factors. Neither cyclic AMP nor cyclic GMP appeared to serve as the second messengers for Heliothis diuretic factors. Extracellular Ca[^2+] was also not important for basal fluid secretion or for fluid secretion stimulated by Heliothis diuretic factors. Phorbol 12,13-dibutyrate (PDBU), an activator of protein kinase C (PKC), and A23187, a Ca[^2+] ionophore, increased basal fluid secretion in the presence of Ca[2+] but not in the absence of Ca[^2+]. Synergism occurred between PDBU and diuretic factors in brain extracts proposed that PKC with intracellular Ca+2, are the best candidates as second messengers for Heliothis diuretic factors. The brain-retrocerebral complex (BR-CC-CA) contained antidiuretic and diuretic activity in both feeding and starved LI-V of H. virescens. BR-CC-CA secreted antidiuretic activity into the medium when incubated with the natural neurotransmitters: acetylcholine, octopamine or dopamine. BR-CC-CA incubated in high K+ medium, or with gamma-aminobutyric acid (GABA), or norepinephrine secreted diuretic activity into the medium. MasDH had diuretic activity with isolated tubules and inhibited feeding by Heliothis larvae in vivo. Diuretic and antidiuretic factors are present in the nervous tissues of H. virescens larvae. Synthetic Manduca diuretic hormone inhibited feeding by the larvae of H. virescens. It is speculated that Heliothis diuretic and antidiuretic factors regulate feeding behavior in lepidopteran larvae. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Entomology." |
| Physical Description: | xiii, 143 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |