[Temperature dependence of the acetylcholinesterase activity in synaptic membranes of the rat brain].

The temperature dependence (5-40 degrees C) of the acetylcholinesterase activity in synaptic membranes of the rat brain at different substrate concentrations was studied. At low substrate concentrations, the Arrhenius plot has two linear sections. At high concentration, there is one linear section throughout the temperature range.

[The effect of hypothermia on kinetic characteristics of the rat brain synaptic membrane Na,K-ATPase].

The effect of profound hypothermia (acute or prolonged) on Km for ATP, Vm and strophanthine K affinity to Na,K-ATPase in the rat brain synaptosomal membranes was investigated. The temperature dependence of Na,K-ATPase activity in temperature range 5-40 degrees C was also studied. Hypothermia decreases Km and Vm, and increases affinity of strophanthine K to the enzyme.

Effect of hypothermia on kinetic characteristics of acetylcholine esterase in rat erythrocyte membranes.

We studied kinetic and thermodynamic characteristics of acetylcholine esterase in rat erythrocyte membrane after whole-body hypothermia (20 degrees C) of different duration. Hypothermia increased the degree of substrate inhibition for acetylcholine esterase, maximum rate, and Michaelis constant. The temperature dependence of acetylcholine esterase activity remained practically unchanged.

[Effect of hypothermia on Na(+)-K(+)-ATPase activity and hemoglobin binding in the rat erythrocyte membranes].

The activity of Na+/K(+)-ATPase and hemoglobin binding in membranes of rat erythrocytes during hypothermia (20 degrees C) was studied. Hypothermia causes an increase in hemoglobin binding and a decrease in Na+/K(+)-ATPase activity. It was found in in vitro experiments that the addition of hemoglobin to the membranes does not affect the Na+/K(+)-ATPase activity in control animals and decreases the activity of the enzyme in hypothermia.

[Temperature compensation for enzyme activity in homoiothermal animals].

The dependence of lactate gehydrogenase activity on body temperature of homoiothermal animals upon hypothermia was studied. New data indicating the induction of thermal compensation for enzymic activity in warm-blooded under these conditions were obtained.

[Temperature compensation in homeothermic animals].

Low temperature optimum of the glutaminase activity in synaptosomal fraction of the brain occurs in deep hypothermia, similar phenomenon occurring in hibernation. The optimum depends on the animal body temperature. The data obtained suggest a manifestation of the temperature compensation.

[Temperature dependence of glutaminase activity from the rat brain under hypothermia].

The temperature dependence of the glutaminase activity in rat brain homogenates and at different steps of enzyme purification was studied under normal and hypothermic (20 degrees) conditions. Under normal conditions the enzyme activity shows a complex temperature dependence. Under hypothermic conditions a site with negative temperature dependence appears on the temperature dependence curve.

[Alteration of activities of alanine- and aspartate transaminases in rat brain under conditions of hypothermia of various duration and in adrenalectomy].

Cooling of rats down to the rectal temperature of 20 degrees decreased the alanine- and aspartate transaminase activities in brain tissue. Activity of the enzymes studied was increased after prolongation of the hypothermia within 2 hrs. In adrenalectomized animals hypothermia was responsible for activation of aspartate transaminase and for a decrease in activity of alanine transaminase.