Histochemical Analysis of the Goblet Cell Matrix in the Larval Midgut of Manduca sexta

Abstract

Experimental analyses were made to histochemically determine the composition of the goblet cell matrix material in the larval midgut of the tobacco hornwormn, Manduca sexta. Techniques employed following fixation in Carnoy fluid were the periodic acid-Schiff reaction and the alcian blue stain at pH 1.0 and pH 2.5 and following inethylation and subsequent saponification. The cumulative evidence suggests that the plug material is an acid mucosubstance. The microscopic anatomy of midguts from larval stages of Lepidoptera has been studied in a number of species: Hyalophora cecropia (Anderson & Harvey, 1966; Schultz & Jungreis, 1977a), Heliothis zea (Chauthani & Callahan, 1967), Bombyx mori (Akai, 1969), Ephestia kuhniella (Smith et al., 1969), and Manduca sexta (Schultz & Jungreis, 1977b; Cioffi, 1979). These investigators describe a simple epithelium consisting of columnar, goblet, and (often) regenerative cells suprapositional to a basal lamina, which in turn is surrounded by a muscularis and strands of connective tissue. This seeming simplicity in organization, when coupled with the large size attained by mature feeding larvae, makes the larval midgut an excellent model for the study of transepithelial solute movement. The larval midgut of Manduca sexta (L.) is presently receiving attention as a physiological model for epithelial transport (Blankemeyer & Harvey, 1977). Potassium and other monovalent alkali metals are actively transported uphill against a concentration gradient from hemolymph to gut lumen (see Supported in part by Pan American University Faculty Research Grant No. 1595 to TWS and the Office of Health and Environmental Research, U.S. Department of Energy, under Contract W-7405-eng-26 with the Union Carbide Corporation (GL). Gratitude is expressed to Dr. A. M. Jungreis who graciously provided the insects used in these studies from his insectory supported in part by National Institutes of Health Grant AI-12779, and for his critical reading of the manuscript. 2 Present address: Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee