Studies on the posterior silk gland of the silkworm Bombyx mori. VI. Distribution of microtubules in the posterior silk gland cells.

Abstract

There are 2 microtubule systems in the posterior silk gland cells. One is a radial microtubule system in which the microtubules run radially from the basal to the apical cytoplasm and in which fibroin globules (secretory granules of fibroin) and mitochondria are arranged along these microtubules, composing a canal system which is probably responsible for the intracellular transport of fibroin globules. The other is a circular microtubule system in the apical cytoplasm, composed of bundles of microtubules and microfilaments running in a circular arrangement around the glandular lumen at an interval of .apprx. 4 .mu.m at the end of the 5th instar. This system may be concerned with secretion and/or intraluminal transport of fibroin.