Induction of non-diapause eggs by injection of anti-diapause hormone rabbit serum into the diapause type of the silkworm, Bombyx mori

Abstract

Polyclonal antiserum was raised by immunizing rabbits with the synthetic diapause hormone (BomDH-I[19-Cys]) of the silkworm, Bombyx mori. By immunological analyses, the antiserum was demonstrated to specifically recognize the diapause hormone. The antiserum was injected into larvae, pupae and pharate adults of the Daizo strain that were destined to lay diapause eggs, to see whether the serum is able to act in vivo as an anti-hormone agent. Injection of the antiserum at various stages from the fourth larval instar to the early pharate adult stage induced moths to lay non-diapause eggs. The effect of the antiserum injection declined suddenly from the middle of the pharate adult stage, when diapause hormone is secreted actively. The dose-response curve demonstrated the maximal dose to be a 1.0 μl injection of the antiserum and a half-maximal dose of 0.1 μl. When neutralized in vitro with the synthetic diapause hormone, the antiserum lost its ability to induce non-diapause eggs, which indicates that the antiserum inactivates diapause hormone through immunoneutralization. A transplantation experiment using suboesophageal ganglia preexposed to the antiserum indicated that the antiserum had no cytotoxic effects. Following injection of the antiserum trehalase activity and glycogen content in developing ovaries were reduced to the levels found after removal of the suboesophageal ganglion. The results indicate the potential for using rabbit IgG as a simple tool for the control of neuropeptide hormone titers in insect hemolymph.