Brain Ca2+/Mg(2+)-ATPase activity and seasonal adaptation of the Djungarian dwarf hamster Phodopus sungorus

Behavioural and biochemical investigations of the influence of altered gravity on the CNS of aquatic vertebrates during ontogeny

Quantitative data are presented on the influences of hyper-gravity (3 +/- 1g) and of simulated weightlessness (approximately 0g) during early ontogeny of cichlid fish (Oreochromis mossambicus) and clawed toad (Xenopus laevis, Daudin) demonstrating changes in the swimming behaviour and the brain energy and plasma membrane metabolism. After return to 1g conditions, hyper-g reared fish and toads express the well known "loop-swimming" behaviour. By means of a computer based video analyzing system different types of swimming movements and velocities were quantitatively determined. Analyses of the brain energy and plasma-membrane metabolism of hyper-g fish larvae demonstrated an increase in energy availability (glucose 6Pi dehydrogenase, G-6P-DH), a decrease of cellular energy transformation (creatine kinase activity, CK) but no changes in energy consumptive processes (e.g. ATPases) and cytochrome oxidase activity (Cyt.-Ox). In contrast hypo-g fish larvae showed a slight increase in brain CK activity. In addition, unlike 1g controls, hyper-g fish larvae showed pronounced variations in the composition (=polarity) of sialoglycosphingolipids (=gangliosides), typical constituents of the nerve cell membranes, and a slight increase in the activity of sialidase, the enzyme responsible for ganglioside degradation.

Brain creatine kinase activity during ontogeny of the cichlid fish oreochromis mossambicus and the clawed toad Xenopus laevis, influence of gravity?

The development of creatine kinase (CK) activity was studied in the brain of cichlid fish and clawed toads. The activity of CK in the whole brain of the fish decreases immediately after hatching (stage 6) from values of about 135 nmol substrate cleaved/mg protein/min to a value of about 105 at stage 8 (5 days post hatch at 20 degrees C). With the exception of a significant peak (125 nmol) between stages 9 and 10 (7 and 9 days respectively, post hatch at 20 degrees C) and a small intermediate peak at stages 12 and 13 (about 10 days post hatch at 20 degrees C) a constant level of about 100 nmol cleaved substrate is maintained until maturity. In contrast, CK activity was determined to be 3-fold higher in the whole brain of the clawed toad. With the exception of two significant peaks at stages 47 and 49 (5 and 12 days respectively, post fertilization at 23 degrees C) a value of about 360 nmol was found during larval development and metamorphosis, as well as in the adult brain. In investigating the possible influence of gravity on CK activity during early ontogeny of the brain both animal species were exposed to hyper-gravity (3 +/- 1 g) for 7 days. A significant decrease of total CK activity of 20% was found in the fish brain and of about 5% in the toad.(ABSTRACT TRUNCATED AT 250 WORDS)