Abstract
Two immunochemically discrete protein yolk precursors or vitellogenins appear in the blood of adult Periplaneta americana on day 4 or 5 after emergence. Ovariectomy results in a 20-fold increase in blood vitellogenin concentration. Allatectomy prevents the appearance of blood vitellogenin, while normal levels occur following the implantation of corpora allata into allatectomized females or the injection of farnesyl methyl ether into decapitated females, although implanting corpora cardiaca or brains is apparently ineffective. That yolk deposition requires the presence of juvenile hormone, in addition to blood vitellogenin, is indicated by the failure of vitellogenin injections to stimulate yolk deposition in allatectomized females.
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