A comparative study on the secretory activity of the subcommissural organ in the European green frogs: Rana esculenta, rana lessonae and Rana ridibunda

1. 1. The subcommissural organ (SCO), present in all vertebrates, is situated in the roof of the third brain ventricle, and secretes into this ventricle a glycoproteinaceous, fibre-like structure, the liquor fibe (LF). 2. 2. The three forms of European green frogs diner from each other in the three parameters used to measure the secretory activity of the SCO: the amounts within the SCO of stained secretory material and of secretory material labelled by a radioactive precursor, and the growth rate of LF. 3. 3. The observed differences indicate that the secretory activity of the SCO is distinctly higher in Rana ridibunda than in Rana lessonae, whereas in Rana esculenta this activity is intermediate. 4. 4. These findings confirm the hybrid character of esculenta, which is in many morphological, physiological and ecological features intermediate between lessonae and ridibund

Endocytosis in adipokinetic hormone (AKH)-producing cells of the migratory locust, locusta migratoria, in rest and during flight

Intrinsic gland cells of the corpus cardiacum of Locusta synthesize AKH, and release it into the haemolymph shortly after onset of flight. AKH stimulates the release of diacylglycerol — the fuel for the flight muscles — from the fat body. The peak of haemolymph AKH is reached after about 30 min flight. Release of AKH mainly occurs from short processes of the gland cells, by means of exocytosis. It may be expected that this release is followed by compensatory re-uptake of membrane material by means of endocytosis near the site of exocytosis. To get information on the location of endocytotic activity and on the intracellular endocytotic pathway, the uptake of the tracer horse-radish peroxidase (HRP) by the gland cells in flying and in resting locusts was studied electron microscopicall