. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Table I Identification of insulin-like peptides in invertebrates by immunocytochemistry Figure 1. A phylogenetic tree, showing the polyphyletic origin of the various phyla in the animal kingdom. (Modified and extended after Karlson, 1983). in a range of different species, primarily insects and mol- luscs (Table I). In molluscs, immunoreactivity occurs not only in neuronal tissue, but also in the epithelia of the gut and hepatopancreas. Of course, there are problems and pitfalls in immuno- cytochemistry. The epitope for anti-
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Table I Identification of insulin-like peptides in invertebrates by immunocytochemistry Figure 1. A phylogenetic tree, showing the polyphyletic origin of the various phyla in the animal kingdom. (Modified and extended after Karlson, 1983). in a range of different species, primarily insects and mol- luscs (Table I). In molluscs, immunoreactivity occurs not only in neuronal tissue, but also in the epithelia of the gut and hepatopancreas. Of course, there are problems and pitfalls in immuno- cytochemistry. The epitope for anti-insulin deduced from structure-activity analyses, is formed by the region including residues 8, 9, and 10 of the A-chain, and resi- dues 2, 3, and 4 of the B-chain of insulin. The ability of invertebrate tissues to bind anti-mammalian insulin is surprising because non-mammalian insulins, insulin- like growth factors, and relaxin are variable in this region and, therefore, do not bind antibodies to mammalian in- sulin. However, the neuroendocrine light green cells in the cerebral ganglia of the central nervous system of the freshwater snail have been identified as anti-porcine in- sulin immunopositive cells (Fig. 2). Indeed, these cells produce an insulin-related peptide with a different epi- tope region (see below). The second approach in the identification of insulin- related peptides is biochemistry: extraction, purification, and chemical characterization. Several early reports of insulin-like substances in invertebrates relied upon rather simple or even crude tissue extraction procedures followed by heterologous bioassays (Table II). Later on, RIA and purification studies were performed. Studies on the blowfly, Calliphora vomitoria. by Thorpe and Duve Insecta Calliphora \omiloria Median neuro- Duve and Thorpe, 1979 secretory cells Bombyx mori Median neuro- \\i\ 1980 secretory cells Locust migratoria Median neuro- Orchard and Loughton. secretory cells 1980 Manduca sexta
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