Pharmacological Study of Intracellular Second Messengers that Affect Active Ion Transport in the Midgut of Tobacco Hornworm, Manduca sexta

2003 ◽  
Vol 33 (3) ◽  
pp. 133-137
Author(s):  
Kyeong-Yeoll LEE
Keyword(s):  
Ion Transport ◽  
Manduca Sexta ◽  
Second Messengers ◽  
Pharmacological Study ◽  
Tobacco Hornworm ◽  
Active Ion Transport ◽  
Intracellular Second Messengers

Changes in midgut active ion transport and metabolism during larval-larval molting in the tobacco hornworm (Manduca sexta)

1997 ◽  
Vol 200 (3) ◽  
pp. 643-648 ◽  
Author(s):  
M Chamberlin ◽  
C Gibellato ◽  
R Noecker ◽  
E Dankoski
Keyword(s):  
Ion Transport ◽  
Manduca Sexta ◽  
Aerobic Capacity ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Tobacco Hornworm ◽  
Maximal Aerobic Capacity ◽  
Posterior Midgut ◽  
Molting Process ◽  
Active Ion Transport

Ion transport and metabolism in the posterior midgut before, during and after the molt to the fifth instar of the tobacco hornworm Manduca sexta were investigated. In situ measurements reveal that the transepithelial potential difference of the posterior midgut falls during the molting process. This finding was confirmed by in vitro experiments in which it was demonstrated that both the transepithelial potential and the short-circuit current are lower in molting fourth instars compared with feeding fourth instars. The short-circuit current increases after ecdysis, with a maximal rate being achieved approximately 4 h after the molt. Resumption of feeding after the molt is not necessary to initiate this increase in active ion transport. The metabolic organization of the tissue also changes during the molting process. The maximal activities of glycolytic enzymes and 3-hydroxyacyl-CoA dehydrogenase, an enzyme of lipid ss-oxidation, decrease during the molting process and increase after ecdysis. Although citrate synthase activity, an index of maximal aerobic capacity, decreases during the molt and increases again after ecdysis, tissue respiration is the same in feeding fourth instars and molting larvae. This result indicates that a greater percentage of maximal aerobic capacity is used during molting and that energy may be diverted to cell proliferation and differentiation and away from the support of active ion transport at this time.

Molecular characterization and cell-specific expression of an ion transport peptide in the tobacco hornworm, Manduca sexta

2007 ◽  
Vol 329 (2) ◽  
pp. 391-408 ◽  
Author(s):  
Anna L. Drexler ◽  
Christina C. Harris ◽  
Myra G. dela Pena ◽  
Marilyn Asuncion-Uchi ◽  
Sook Chung ◽  
...  
Keyword(s):  
Ion Transport ◽  
Molecular Characterization ◽  
Manduca Sexta ◽  
Tobacco Hornworm ◽  
Specific Expression

Inhibition of midgut ion transport by allatotropin (Mas-AT) and Manduca FLRFamides in the tobacco hornworm Manduca sexta.

1998 ◽  
Vol 201 (22) ◽  
pp. 3067-3074 ◽  
Author(s):  
K Y Lee ◽  
F M Horodyski ◽  
M E Chamberlin
Keyword(s):  
Ion Transport ◽  
Manduca Sexta ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Dependent Manner ◽  
Additive Effects ◽  
Maximal Inhibition ◽  
Posterior Midgut ◽  
Active Ion Transport ◽  
Dose Dependent

Short-circuit current (Isc) across the posterior midgut of day 2 fifth-instar tobacco hornworms (Manduca sexta) is inhibited by Manduca allatotropin (Mas-AT) and two Manduca FLRFamides (F7G and F7D). Another FLRFamide, F10, and the related molluscan tetrapeptide FMRFamide elicited only a modest inhibition of Isc. Mas-AT, F7G and F7D inhibited the Isc in a dose-dependent manner. Maximal inhibition of Isc by Mas-AT was achieved at a concentration of 50 nmol l-1. At 100 nmol l-1, Mas-AT produced a significantly greater inhibition of Isc than did F7G and F7D. The inhibition caused by Mas-AT was reversed by removing the peptide. Furthermore, the action of Mas-AT could be blocked by preabsorption with its antiserum. When F7G or F7D was added after the Isc had been inhibited by Mas-AT, a further reduction in the Isc was observed. No additive effects were seen when F7G and F7D were added together. In comparison with the anterior and middle regions, the posterior section of the midgut was the most sensitive to these three peptides. The Isc of midguts dissected from feeding fourth instars was inhibited by Mas-AT, F7D and F7G, whereas the Isc of midguts dissected from pharate fifth instars or wandering fifth instars was virtually unaffected by these peptides. Active ion transport across the posterior midgut of the silk moths Hyalophora cecropia and Bombyx mori was unaffected by these peptides.

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