In vitro studies in Tubularia: a morphological role for digestive cells

Abstract

ABSTRACT A chemically defined in vitro system for Tubularia has been developed. At 24 h after explantation of coenosarc, digestive cells attached to the substrate and migrated from the explant. The digestive cells migrated by a gliding motion with a fan-like membrane acting as a leading edge. Within 48 h a digestive cell monolayer was formed and invasion of this area by epithelio-muscular, gland and interstitial cells occurred. Autoradiographic study of 48-72 h cultures treated with [3H]thymidine showed nuclear incorporation of the label in digestive, epithelio-muscular, interstitial, cnidoblast and gland cells. When explants were grown on collagen-coated coverslips, accelerated attachment and migration of digestive cells was observed. Explants were also grown on Millipore filters. No digestive cell attachment occurred but epithelio-muscular, gland and interstitial cell attachments to the filter were observed. From these experiments, a morphological role for the digestive cells as a substrate for other cells of the coenosarc is postulated. Hydranth extract was supplemented to the culture medium. Studies with this material were performed with coenosarc from ‘late summer’ animals in which only 10-15% of the explants normally entered culture. However, with the addition of the extract, 100% of the explants went into culture. Interstitial cell populations increased 2-3 times in extract-treated explants.