Junctional structures in the midgut cells of lepidopteran caterpillars
Open Access
- 1 January 1975
- journal article
- Published by The Company of Biologists in Journal of Cell Science
- Vol. 17 (1), 221-239
- https://doi.org/10.1242/jcs.17.1.221
Abstract
The junctional structures present between the midgut cells of 2 lepidopteran caterpillars have been examined using freeze-etching, conventional staining and lanthanum tracer techniques. The bonding junction present in this type of tissue is the so-called continuous junction. Septa have only occasionally been reported in conventionally stained cross-sections of these junctions. During the present study septa have been observed in such sections but were more readily located in tissue treated with lanthanum tracer. Tangential sections of lanthanum-impregnated tissue show that these septa are parallel-sided, in contrast to the honeycomb appearance of the septa in septate junctions. The septa in freeze-etch replicas of glutaraldehyde-fixed tissue often show continuous rods on one membrane face, suggesting that the continuous junction may be more akin to the tight junction than to the normal septate junction. However, freeze-etch replicas of unfixed tissue appear much more like replicas of normal septate junctions. The main differences between septate and continuous junctions appear to be that the intermembrane septa of the continuous junction are parallel-sided in tangential section, as against the honeycomb appearance of the septate junction, and that the particles which delineate the septa in freeze-etched preparations appear to be both somewhat differently bonded and closer together in the continuous junction. A diagram is presented showing the internal and intermembrane structures of the 2 types of junction based on the present study, and suggesting a possible explanation of the fact that septa are more readily seen in cross-sections of septate junctions than in continuous junctions. As septa are present in both types of junction, and because their freeze-etch appearances are not very different, it is suggested that the two types of septate junction be called ‘smooth septate’ and ‘pleated septate’ junctions, to indicate their characteristic appearances in tangential section.Keywords
This publication has 35 references indexed in Scilit:
- Plasma membrane differentiations of keratinizing cells of the wool follicle: I. Gap junctionsJournal of Ultrastructure Research, 1973
- Homocellular and heterocellular gap junctions in Limulus: A thin-section and freeze-fracture studyJournal of Ultrastructure Research, 1973
- The Fine Structure of Membranes and Intercellular Communication in InsectsAnnual Review of Entomology, 1973
- SEPTATE AND GAP JUNCTIONS IN MOLLUSCAN GILL EPITHELIUMThe Journal of cell biology, 1971
- Intercellular attachments of cockroach nymph epidermal cellsJournal of Ultrastructure Research, 1970
- Frozen-etched septate junctionsProtoplasma, 1970
- STRUCTURE OF COUPLED AND UNCOUPLED CELL JUNCTIONSThe Journal of cell biology, 1968
- ACTIVE TRANSPORT BY THE CECROPIA MIDGUTThe Journal of cell biology, 1966
- STUDIES ON AN EPITHELIAL (GLAND) CELL JUNCTIONThe Journal of cell biology, 1964
- INTERCELLULAR CONNECTIONS IN THE OUTGROWING STOLON OF CORDYLOPHORA The Journal of cell biology, 1963