The planulae ofHydractinia, the metamorphosis of which normally is induced by certain bacteria, will undergo transformation into polyps also when exposed to a lithiumpulse. The optimal concentration and incubation period for rapid and complete transformation have been determined at 24 mM Li and 2 hrs respectively. 96 mM K applied for 2 hrs will also result in some induction. The possible mode of action exerted by the Li-ion as compared with induction caused by bacteria is discussed.

An epithelial cell line from Chironomus tentans exhibits acetylcholinesterase activity (specific activity 0.05-0.2 nkat/mg protein), which rises 30- to 40-fold after addition of 10 M 20-OH-ecdysone. The first visible increase occurs after 4 days of incubation with hormone. The enzyme has an apparent K of 2.3±0.2×10 M for acetylthiocholine iodide as substrate and is inhibited by eserine and BW284 C51 (50% inhibition at 5×10 M for both inhibitiors) as well as by high concentrations of substrate, but not by tetraisopropylpyrophosphamide. The sensitivity against inhibitors is the same in extracts from hormone-treated cells and from controls. The cholinesterase activity correlates with morphological changes (shape and cell arrangement) and is indepenent of neuronal differentiation. We therefore propose a function for this activity during morphogenesis.

No abstract

The inhibitory activities of several allosamidin derivatives on two family 18 chitinases, an insect enzyme from the epithelial cell line from Chironomus tentans, and a bacterial enzyme, chitinase A from Serratia marcescens, were evaluated. The following structural requirements are necessary for inhibition of the Chironomus enzyme :1. One N-acetylallosamine residue can be omitted without impairment of enzyme inhibition. 2. At least one N-acetylallosamine sugar must be present. 3. Glucosamine can replace the allosamine moiety without a negative e †ect on the inhibitory activity. 4. The spatial arrangement of the allosamizoline moiety is important for inhibition. 5. If one sugar is omitted and the arrangement of the cyclitol residue is changed, the inhibitory e †ect is diminished further.For puriÐed chitinase A from Serratia marcescens the arrangement of the aglycone moiety is equally important, but recognition of the sugar is di †erent :1. Omission of one allosamine residue decreases the inhibitory activity considerably. 2. Inhibition is improved if the remaining N-acetylallosamine is replaced by the epimer N-acetylglucosamine.Only endochitinase activity is a †ected, since chitin formation (up to 10~4 M) and N-acetylglucosaminidase activity (up to 10~3 M) are not impaired, at least in