Ultrastructure of cells from the liver-endocrine pancreas system in hibernating animals

In hibernated ground squirrel (Citellus erythrogenys) during various periods of hibernation morphological changes in organs participating in insurance of energoplastic homeostasis (liver, endocrine part of the pancreas) have been followed. At the beginning of hibernation certain signs of functional strain in the liver are observed-shortening and swelling of the endoplasmic reticulum (ER) canaliculi, decreases of glycogen resources and activation of the lysosomal apparatus, as well as certain features demonstrating its decreased activity--shortening cisterns in the Golgi complex, poorly manifested granular ER, tightening of mitochondrial matrix. At a deep hibernation, the signs of strain disappear, ultrastructure of hepatocytes corresponds to a new lower level of functioning in comparison to that in the active state and at the beginning of hibernation. During these periods the structure of endocrine cells in the pancreas demonstrates certain changes in the character of functioning of the cells. Ultrastructural transformations in the liver and endocrine part of the pancreas in the ground squirrel are mutually correlated.     

Seasonal characteristics of the monoaminergic regulation of the behavior of hibernating animals

The stimulating effect of L-DOPA on exploratory activity of the ground squirrel in the hole-board and open field experiments was stronger in the spring than in autumn, whereas the regulating effect of the 5-HTP on adaptive behaviour of hibernating animals was stronger in autumn. Results of the biochemical analysis of the MAO A activity with serotonin or noradrenaline as substrates revealed a seasonal dependence of the substrate specific changes of this enzyme activity in hibernating animals. The data obtained suggest that the seasonal distinctions in effects of similar pharmacological agents depend on activity of the brain monoaminergic systems' activity in hibernating animals in different periods of the annual cycle.     

Phospholipase A activity determines the rate of respiration of the mitochondria in hibernating animals

The mechanisms for regulating the rate of respiration and oxidative phosphorylation in liver mitochondria from hibernating ground squirrels were studied. The microviscosity of the mitochondrial membrane in hibernating squirrels was found to be higher than that in active animals. Probably, a high microviscosity of the membrane causes a decreases in the rate of the transport of oxidation substrates into the mitochondrial matrix, which in turn may be one of the main reasons for the inhibition of mitochondrial respiration in hibernating squirrels. The activation of phospholipase A2 in a hypotonic medium results in the acceleration of the respiration and phosphorylation in the mitochondria from hibernating squirrels and is accompanied by the increase of the transport of substrates across the mitochondrial membrane. The inhibition of phospholipase A2 decreases Ca2+--induced acceleration of the transport of substrates and prevents the activation of the respiration and phosphorylation in a hypotonic medium.     

Changes in the activity of the brain renin-angiotensin system and in the functional state of the pituitary-adrenal system of rats under the influence of captopril]

While studying the effect of peroral captopril injections on the activity of renin-angiotensin system (RAS), the activity of angiotensin-converting enzyme (ACE) and angiotensin II content from anterior and mediobasal hypothalamus, medulla and adenohypophysis of intact rats has been established to decrease. Captopril administration decreases ACE activity which increases after hydrocortisone injection in rat medulla and striatum. Captopril results in no potentiation of hormonal effect in hypothalamus and in adenohypophysis where ACE activity decreases following hydrocortisone injection. A decrease in the RAS activity of brain structures and adenohypophysis induced by captopril administration to rats is accompanied by the inhibition of the activity in the pituitary-adrenal system. A decrease in ACTH level and in 11-hydroxycorticosteroids of the rat blood plasma has been determined after single captopril injection in the dosage of 10 and 50 mg/kg of body weight. Duration of the effect depends on the captopril dosage.     

Seasonal changes of the activity of calcium-transporting systems in the heart and skeletal muscles of hibernating animals

In a short review of literature and according to our own data the molecular mechanisms providing seasonal adjustments of the activity of membrane Ca-transporting systems (Ca-channels and Ca-pumps) in muscle tissues of animals which spent winter time in a deep torpor state (hibernation), were analyzed. Special attention was paid to changes of protein composition of sarcoplasmic reticulum membranes--the key intracellular structure responsible for excitation-contraction coupling in different types of muscles, as well as to participation of endogenous protein kinases in regulation of functional activity of plasma membrane Ca-channels and sarcoplasmic reticulum Ca-ATPase during hibernation.     

Ultrastructural organization of cardiomyocyte sarcolemma in hibernating animals

It was shown by electron microscopy that a highly convoluted sarcolemma, its numerous invaginations, well developed T-system contacting mainly with myofibrillar mitochondria and Z-zones were characteristic of cardiomyocytes of hibernants. In these cells lipid inclusions amounted as much as 3-4% of the cytoplasm. Cardiomyocytes of the arousing ground squirrels often revealed a complex of structures in the perinuclear area, responsible for protein synthesis and vesicle formation. Along with it the number of vesicles, including delineated ones, the majority of whom are contacting the sarcolemma, were manifested in the cell near-membrane area. A possible mechanism of cardiomyocyte plasma membrane rearrangements in ground squirrels and of alteration of their properties at the arousal, through a gradual replacement of plasma membrane material for the cytoplasmic vesicle bilayer, is discussed.     

Behavioral characteristics and stress reaction of the pituitary-adrenal system in prenatally stressed rats

Mothers' stress was shown to considerably diminish the orienting-studying activity of male rats in the dioestrus stage, as well as enhancement of anxiety. In prenatally stressed male rats, on the contraty, the anxiety diminished while their behaviour in the open field tests remained practically unaltered. The prenatal stress affected the stressor response of the hypophysis-adrenal systems in both sexes. The data obtained suggest that the mothers' stress affects both behaviour and stressor response in male as well as female rats.     

Specifics of monoaminergic regulation of the central nervous system of hibernating animals (Citellus undulatus)

Seasonal features of open-field behavior of Yakut ground squirrels (Citellus undulatus) and changes in the brain MAO A activity were studied. It was found that all parameters of exploratory activity in the open field and holeboard test reached the values characteristic of summer animals very rapidly, within a few days or (in some cases) even within the first 24 hours after the arousal from hibernation in the middle of April. In autumn these parameters decreased to their minimum values 1.5-2 months prior to hibernation. Biochemical analysis showed that in April the activity of MAO A measured with serotonin as a substrate in the hippocampus was 1.8 times (p < 0.05) higher than the activity of MAO A with respect to noradrenaline. In contrast, in autumn the MAO A activity determined with noradrenaline as a substrate was 2.5 (p < 0.05) times higher than the activity a MAO A with respect to serotonin. Taken together, these data indicate that the seasonal features of the higher nervous activity of hibernating animals depend on the balance between serotonergic and noradrenergic systems in different periods of the annual cycle.