Evidence for Ecdysteroid Feedback on Release of Molt-Inhibiting Hormone From Crab Eyestalk Ganglia

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Marine Biological Laboratory is collaborating with JSTOR to digitize, preserve and extend access to Biological Bulletin This content downloaded from 128.252.67.66 on Mon, ABSTRACT The content and release of molt-inhibiting hormone activity (MIH) in isolated eyestalk ganglia of crabs (Cancer antennarius S.) were measured in vitro as a function of exposure in vivo to elevated or reduced hemolymph ecdysteroid levels. Ecdysteroid titers of intermolt crabs injected with 20-hydroxyecdysone (two 45 tug injections/24 h) rose 8-to 10-fold; MIH released from subsequently isolated ganglia was significantly less than that released from ganglia of saline-injected controls, while MIH content of ganglia from treated crabs was increased. The hemolymph ecdysteroid level of intermolt crabs was low (6 ng/ml) and was further reduced by 40% 6 days after Y-organectomy. MIH release from ganglia of both Y-organectomized and sham-operated control crabs was high, similar to that of unoperated controls, but MIH content of ganglia from both Y-organectomized and sham groups was significantly reduced relative to controls. The results indicate a negative feedback regulation of MIH release but not synthesis by ecdysteroids and are discussed in relation to the patterns of ecdysteroid titers observed in the normal crustacean molt cycle.

The nuclear receptor E75 from the swimming crab, Portunus trituberculatus: cDNA cloning, transcriptional analysis, and putative roles on expression of ecdysteroid-related genes

“…20E has been proposed to affect ecdysteroid biosynthesis in Yorgan (Dell et al, 1999), chitin metabolism in epidermis (Qian et al, 2014;Rocha et al, 2012), and neuropeptide synthesis in eyestalk (Mattson and Spaziani, 1986;Techa and Chung, 2015). Accordingly, PtSad, PtChi1, and PtMIH were selected as the candidate downstream genes controlled by 20E.…”

Hemolymph ecdysteroids during the last three molt cycles of the blue crab, Callinectes sapidus: quantitative and qualitative analyses and regulation

“…However, the mechanism (s) regulating such activity is not clearly defined, compared to the current information in insects. The increase in YO activity is generally believed to be due to the absence or low level of circulating MIH through a negative feedback of ecdysteroids on the eyestalk (Mattson and Spaziani, 1986). On the contrary, the injection of ecdysteroids reduced the activity of YO (Dell et al, 1999), perhaps through induction of ecdysone metabolic enzyme (Williams et al, 1997).…”

Moult cycle‐related changes in biological activity of moult‐inhibiting hormone (MIH) and crustacean hyperglycaemic hormone (CHH) in the crab, Carcinus maenas

“…Furthermore, as the MIH transcript number is not downregulated during premoult, feedback inhibition of MIH transcription by ecdysteroids during the time of maximal titre (D 2 ) is not likely. However, on the basis that premoult eyestalk neural tissues express high levels of ecdysteroid receptor (EcR) in Uca pugilator [35] and the observation that high concentrations of injected ecdysteroid reduced secretable MIH-like activity from Cancer antennarius eyestalk ganglia, negative feedback loops have been suggested [36].…”