Spontaneous and evoked release of prothoracicotropin from multiple neurohemal organs of the tobacco hornworm

Abstract

Release ofneurohormone from putative cephalic neurohemal organs was directly demonstrated in an insect. The prothoracicotropic hormone (PTTH) of the tobacco hornworm, Manduca sexta, was measured indirectly by its ability to stimulate the secretion of a-ecdysone by inactive prothoracic glands; the ecdysone was measured by radioimmunoassay. The PTTH released spontaneously from intact brain-retrocerebral complexes was localized to the retrocerebral complex by placing a waxy barrier across the nerves connecting the corpora cardiaca to the brain. Isolated corpora allata spontaneously released much more PTTH than did either isolated corpora cardiaca or isolated brains. Media containing 100 mM potassium stimulated PTTH release from both isolated corpora allata and isolated corpora cardiaca. In calcium-free media, spontaneous PTTH release was diminished and release could not be stimulated by high potassium. These results indicate that depolarization ofthe neurosecretory cells is correlated with calcium-dependent neurohormone release and that there are multiple neurohemal organs for PITH. The biological activities of stored and circulating PTTH are compared.

Regulation of fat body glycogen phosphorylase in larval tobacco hornworm, Manduca sexta

“…By contrast, in Carrow saline [12] enzyme activation at both temperatures went through an intermediate maximum after ca. 15 min.…”

“…In the in vitro system with Carrow saline [12] used in the present investigation, enzyme activation to 60-70% can be induced within 15 min which is much faster than in ligated abdomens, since the drop of core temperature is faster. The in vitro response to chilling was studied in two different solutions.…”

“…Fat body pieces were removed from ligated abdomens, briefly blotted on filter paper and either immediately sonicated (MSE sonicator; Crawley, England; 20-30s) in 1 ml of buffer (50 mM TEA-HC1, pH 7, 20 mM NaF, 5 mM NazEDTA, 1 mM N-phenylthiourea) or placed into 10 ml of filter-sterilized lepidopteran saline either according to Carrow et al [12] (21 mM KC1,12 mM NaC1,3 mM CaC12,18 mM MgC12,170 mM glucose, 9 mM KOH, 5 mM PIPES, pH 6.6) or to Jungreis et al [13] (110 mM KCI, 4 mM NaC1, 15 mM MgC12, 4 mM CaC12,5 mM KH2P04, pH 6.5) and sonicated after the times indicated in the figures. Samples were then centrifuged (10 min, 12,0008) and the supernatants used for the determination of phosphorylase activities (see below).…”

Hormonal regulation of sex pheromone biosynthesis in the turnip moth, Agrotis segetum

“…Nervous tissues were dissected under cold 0.9% NaC1, homogenized in modified Weever's saline (1 braid10 y1) (Carrow et al, 1981), and then centrifuged at 12,0008 for 10 min. The supernatant (10 pl) was immediately injected laterally into the fifth to sixth abdominal segment of decapitated females.…”

Endogenous control of circadian rhythms of pheromone production in the turnip moth, Agrotis segetum

“…In addition, VNC was also extracted during the late-photophase. Nervous tissues were dissected under cold 0.9% NaCl, homogenized in modified Weever's saline (Carrow et al, 1981), and then centrifuged at 12,000g at 4°C for 10 min. The supernatant of one female equivalent was immediately injected laterally into the 5-6th abdominal segment of 2-day-old females in the mid-photophase.…”