Abstract
The profiles and activity of polysomes obtained from the integument of larvae of the blowfly Calliphora erythrocephala during the late third instar as well as of ligated, and ligated ecdysone-treated larvae have been investigated. Polysomes are almost absent in 6–7-day-old animals, appear in 8-day-old larvae and are maximally developed in white prepupae. Incorporation of orotic acid into RNA of polysomes shows a similar dependence on larval stage, maximal incorporation being observed in white prepupae where two groups of polysomes are highly labelled. Leucine incorporation into protein also increases with progressing age, most of the incorporated radioactivity being found as soluble protein and only small amounts connected with polysomes. Preparations from ligated larvae show characteristics similar to those from 6–7-day-old larvae. Injection of ecdysone into ligated animals maximally stimulates within 3 h the formation of polysomes. Five hours after hormone administration the polysomal peaks diminish. Incorporation of 3H-orotic acid into RNA is stimulated within 1 h after hormone administration. Most of the radioactivity is found in the 30–60S region of the gradient, corresponding in part to RNA in form of RNP-particles, as shown by CsCl centrifugation. Three hours after ecdysone injection incorporation of orotic acid into RNA is maximal. Labelled RNA is found in significant amounts on the same groups of polysomes which are also labelled in white prepupae, whereas radioactivity in the 30–60S region shows a decline. Five hours after hormone administration, incorporation of orotic acid into RNA, although still being above control values, decreases both in the polysomal as well as in the 30–60S region. Part of the labelled RNA appearing in the polysomal region is found there in the form of RNP-particles with a buoyant density in CsCl centrifugation of 1.46.
Published Version
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