Puffing changes in incubated and in ecdysone treated Chironomus tentans salivary glands.

Abstract

1. Incubation of salivary glands of Chironomus tentans in a variety of media led to more or less drastic changes of the puffing patterns. Degree and pattern of these changes varied with concentration and composition of the media. Sodium and potassium chloride solutions of physiological concentrations (0.1 M) did not significantly affect the puffing pattern while incubations in solutions of higher concentrations (0.18 M) led to the appearance of oversized puffs and irreversible changes of the chromosome structure. The pattern of puffing changes that were induced by these media seemed to be identical and did never resemble the pattern of changes that is induced by the molting hormone, ecdysone. The pattern of loci affected by other culture media was different from the one affected by sodium and potassium chloride solutions, though some loci were affected by all the media tested. 2. The puffing pattern of prepupal glands did not change after incubation in physiological sucrose or sodium chloride solutions for 30 minutes or two hours. A “rejuvenation” of these patterns to larval ones, i.e. a disappearance of the puffs characteristic for the prepupal stage, was never observed under these conditions. 3. Ecdysone had in most of the media tested the same effect as in vivo, i.e. it induced puffs I-18-C and IV-2-B. Among the media tested was a 0.6% sodium chloride solution which did not contain any potassium ions. An addition of potassium ions did not influence the result. After incubations for longer periods of time (more than 20 hours) the chromosomes lost their ability to respond to ecdysone though they still incorporated H3-uridine in a normal fashion. 4. Our results do not support the idea that ecdysone influences puffing via a change of the intracellular K+/Na+ ratio.