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Site of Synthesis and Phylogenetic Distribution of a Hemolymph Trophic Factor of the Tobacco Hornworm, Manduca sexta

J. J. Wielgus, L. B. Aden and R. M. Franks
In Vitro Cellular & Developmental Biology. Animal
Vol. 30A, No. 10 (Oct., 1994), pp. 696-701
Stable URL: http://www.jstor.org/stable/4294311
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Site of Synthesis and Phylogenetic Distribution of a Hemolymph Trophic Factor of the Tobacco Hornworm, Manduca sexta
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Abstract

Identification of fifth instar larval Manduca sexta fat body and epidermis as sites of synthesis of a hemolymph protein (hemolymph trophic factor or HTF) was achieved using in vitro $^{3}H-leucine$ incorporation into protein and subsequent immunoprecipitation of tissue homogenates. Fat body is the primary site of HTF synthesis with a maximal rate on Day 1; epidermis is a secondary site with peak synthesis on Day 0. In vitro radiolabelling followed by TCA precipitation of general protein of fat body and epidermal homogenates suggest that fat body actively elaborates protein on Days 0-5 with peak rates on Days 1 and 4, while epidermis is active on Days 0-5 with a peak rate on Day 3. Based on Anti-HTF ELISA estimates, HTF [500 to $1000 \mug/ml$] was found in the hemolymph of representatives of the insect orders Blattodea, Hemiptera, Orthoptera, and Lepidoptera and in the class Crustacea, but not in the class Merostomata. These studies suggest a possible fundamental role for HTF among modern arthropods in cuticular deposition involving both epidermis and fat body. The physiological role of HTF is undetermined.

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