Effects of Starvation, Low Temperature and the Dorsal Body Hormone On the in Vitro Synthesis of Galactogen and Glycogen in the Albumen Gland and the Mantle of the Pond Snail Lymnaea Stagnalis

Abstract

Previous experiments showed that the synthesis of polysaccharides (mainly galactogen) in the albumen glands of starving pond snails is severely reduced. The present experiments deal with the in vitro synthesis of galactogen in albumen glands and of glycogen in mantle tissue, taken from snails kept under various experimental conditions. The syntheses were studied by the addition of 14 C-glucose to the snail-Ringer medium. Within 3 days starvation causes a decrease in the synthetic activity of the albumen gland of about 80%. During long periods of starvation (up to 6 weeks) it remained at this low level. The wet weights of the glands decreased gradually by about 65%. Also the total polysaccharide content of the albumen glands decreased considerably during starvation. At low temperature (6°C) the rate of incorporation of label in the polysaccharides of the albumen glands declined similar as in starving snails, but the wet weights and the polysaccharide contents of the glands did not differ significantly from those of glands of snails kept at 19°C. In snails from which the Dorsal Bodies (DB) had been extirpated-these animals feed normally but produce no egg masses-the synthetic activity of the albumen glands had decreased with about 80% after 18 days, i.e. to the same level as found after 2 weeks of starvation or of low temperature. The weights of the organs decreased considerably, but the polysaccharide content only a little. When immediately after the operation DB are implanted, the glands remained normal in all respects. From these results it is concluded that the Dorsal Body Hormone (DBH) stimulates the synthesis of galactogen in the albumen gland, and that in starved snails the release of the DBH will be inhibited. The inactivation of the DB is most likely caused by the ceased influx of dietary glucose in the haemolymph of starving snails. It is suggested that in the absence of the DBH, the galactogen in the albumen gland is no longer protected against catabolism, which becomes manifest during starvation. A decrease in the galactogen content was not observed in the low temperature experiments. However, DBH is not absent from the haemolymph of these snails. The influence of the DBH on the albumen gland may be either directly, or indirectly via a gonadal hormone. The glycogen synthetizing system of the mantle is not markedly affected by starvation, low temperature or the absence or presence of DBH, when measured with the in vitro technique. In view of the literature it is suggested that the relatively high glucose concentration of the incubation medium had a direct and rapid effect on the glycogen phosphorylase-synthetase system, resulting in an activation of glycogen synthetase in all mantle pieces, taken from the snails of the various experimental groups. This means that the synthesis of glycogen in the mantle is independent of the DBH and is influenced directly by the glucose levels of the haemolymph. A tentative scheme of the factors involved in the control of galactogen and glycogen metabolism is presented.