Changes in the content of glycolysis products in the myocardium of adult and older rats under stress]

The experiments on adult (8-10 months) and old (24-26 months) male rats have been performed to determine the glucose content in myocardium as well as the content of pyruvic and lactic acid after the stress impact. Findings show that the maximum accumulation of glycolysis products and the reduction of glucose content occur 18-60 hours after the stress, the effect being more pronounced in old animals.     

Catalase activity in the myocardium during stress in adult and aged rats]

The study of catalase myocardium activity at stress in adult and old rats has been performed. It has been revealed that the formation of immobilization stress is accompanied by the enzyme activity stimulation. The expression of this effects is more significant in adult animals. Experimental data concerning the possible role of peroxidation lipids in myocardium catalase stress activation and its age modulation are given.     

Peculiarities of tricarboxylic acid cycle in the myocardium of adult and old rats in the case of immobilization stress

Indices showing Krebs cycle functioning in the hearts of adult and old rats subjected to 30-minutes immobilization were studied in order to find out the causes of age-related increase of heart sensitivity to stress. The studies have shown that compensatory changes of energy metabolism promoting limitation of stress-induced decrease of energy supply of the heart muscle took place in the myocardium mitochondria in adult and old rats during immobilization stress. The changes are associated with maintenance of high rate of redox reactions in the Krebs cycle and increase of myocardium respiration in old rats, and with an increase of the FAD-dependent processes in tissue respiration in adult rats.     

Change in temperature in young and old rats exposed to emotional-noise and immobilization stress]

Experiments with rats have shown that thermoregulation under normal conditions and in response to stressful factors (immobilization, emotionally significant sound) is different in animals of different age. The effect of these stressful factors leads to more significant temperature changes in the group of young animals, as compared with the adult ones.     

DNA-polymerase activity of the liver of adult and old rats

The DNA-polymerase activity was determined in the cytosol of the intact and regenerating liver of adult and old rats under conditions of free passage of enzymes from nuclei and mitochondria. The DNA-polymerase activity of the intact liver is significantly increased in adult rats. The regeneration results in about 2-fold and 10-fold increase of the activity in the liver of adult and old rats, respectively. As a result, the DNA-polymerase activity in the regenerating liver of old rats significantly increased as compared to that of adult rats. The revealed age-related changes in the DNA-polymerase activity of the liver do not correlate with the decrease in the replication rate in the process of aging.     

NADP pool state and activity of NADP-dependent dehydrogenases in the heart tissue of adult and old rats during immobilization stress

To reveal the reasons of age-specific change of heart sensitivity to stress, the content of oxidized and reduced NADP and activity of NADP-dependent dehydrogenase in myocardium of adult and old immobilized rats have been studied. It has been established that in the process of aging the amount of reduced NADP decreases in the old rat heart. At the same time the activity of NADP-dependent dehydrogenase decreases in postmitochondrial fraction of old rat myocardium as compared to adult rats. There is no change in the amount of reduced NADP in the heart of both rat age groups after 30-minute immobilization. The activity of NADP-dependent dehydrogenase in postmitochondrial fraction of myocardium in adult rats remains on the initial level while activation of NADP-dependent malate dehydrogenase and glucose 6-phosphate dehydrogenase appears in old rats.     

Changes in the selfexcitation reaction in rats under the effect of modulated electromagnetic field]

The effect of electromagnetic field with various modulation frequencies (2, 7, and 50 hertz) on the reaction of selfstimulation was studied in rats. The frequency of 2 hertz proved to cause a primary increase in the incidence of the selstimulation reaction, followed by its depression; the frequency 7 hertz at first failed to alter the selfstimulation intensity and then led to the gradual reduction of the incidence of the selfstimulation reaction; the frequency of 50 hertz depressed the selfstimulation reaction practically from the very beginning. The changes in the selfstimulation reaction were independent of the localization of the stimulating electrodes, but were determined by the frequency of the EMF modulation.     

Testosterone and GHRH gene expression in adult and old rats

The effect of castration and testosterone replacement on GHRH gene expression was evaluated in adult male rats. Castration for 21 days did not affect GHRH mRNA levels, and also ineffective in this context was acute or chronic administration of testosterone to castrated rats. Hypothalamic GHRH mRNA was significantly reduced in aged male rats, but restoration of plasma testosterone concentrations via implanted capsules did not modify the low levels of GHRH mRNA. All in all, these findings support the notion that in adult and aged male rats GHRH-producing structures are insensitive to androgens.     

Changes in hepatocyte ultrastructure under the influence of chronic furacillin administration to rats]

The ultrastructure of rat liver cells was studied during a 6 months' furacilline (5-nitro-2-furtfurilsemicarbazon) feeding in dose of 40 mg per day, and also during the next 8 months after the treatment cessation. An irregular swelling of membranous structure in addition to disorganization and partial reduction of the granular endoplasmic reticulum were found in the hepatocyte cytoplasm after the prolonged furacilline feeding as well as glycogen depletion and the tendency of the agranular endoplasmic reticulum to enlargement. These changes rarely reached the essential intensity with the transition to necrobiosis. They disappeared already a month after the cessation of furacilline treatment. In all the terms of experiment, the nucleoli were hypertrophied and retained their loose nucleoloneme structure. No sings of furacilline carcinogenic activity were found in rat liver during the 14 months of investigation.     

Changes in several lipid metabolism indices following death and resuscitation]

The lipolytic activity in the adipose tissue, unesterified fatty acids (UFA) in the blood and adipose tissue, as well as ketone bodies and beta-lipoproteins in the blood were determined in dogs during dying of acute blood loss and the restorative period after the revival of the organism. During agony the activation of lipolysis in the adipose tissue, a decrease of UFA and beta-lipoproteins and an increase of ketane bodies contents in the blood were detected. At the end of the third minute of clinical death there occurred a depression of lipolysis and an increase of UFA content in the adipose tissue. One hour after the revival of the organism the blood UFA content and beta-proteins decrease, but the ketone bodies content rises; simultaneously there occurs some reduction of lipolytic activity of the adipose tissue. At the late postreanimation period (in 1, 3, and 7 days) an activation of lipolysis in the adipose tissue and an increase of UFA, ketone bodies, and beta-lipoproteins content in the blood was noted. The adipose tissue UFA content was low during the postreanimation period. The given results have shown that the changes in the lipid metabolism could play some role in the pathogenesis of non-reversibility during dying and after the revival of the organism.     

Changes in cephalic and peripheral use of glucose and glutamine under the influence of hyperammonemia in rats]

Arterio-venous differences of glucose and glutamine were determined across the brain and across the hind limb in normal and ammonium salt infused rats, before and during an insulin tolerance test, in an attempt to study the effect of hyperammonemia on cephalic and muscular metabolism. The results demonstrate that 1) hyperammonemia reduces the hind limb uptake of glucose without affect the cephalic uptake of glucose which is lowered during hypoglycemia, 2) the reduction of the cephalic and muscular glutamine output induced by the hypoglycemia is masked in presence of an hyperammonemia. In conclusion, it may be assume that, at the concentration obtained in this study, hyperammonemia does not act directly in the pathogenesis of hepatic coma in which a decrease in cerebral glucose uptake described; on the other hand, ammonium plays an important role in the muscle metabolism.     

The neurochemical and behavioral indices of an acquired alcohol craving in rats under conditions of information loading]

The state of neurotransmitter systems was studied in the groups of Wistar rats discriminated by striving for alcohol and rejecting it after the information load (alimentary instrumental conditioning in a labyrinth). The specific activities of neurotransmitter metabolizing enzymes (MAO A and B, acetylcholinesterase, and acetylcholinetransferase) and the content of biogenic amines and their metabolites (serotonin, 5-hydroxyindoleacetic acid, noradrenaline, and dopamine) were measured in homogenates and subfractions of sensorimotor cortex and caudate nucleus. It was found out that the biochemical indices correlated with cognitive abilities of animals. Stress-resistant rats, which were capable for acquisition of the complex skill, refused alcohol after the information load and were characterized by activation of the brain neurotransmitter systems. The rats, which were unable to fulfill the cognitive task, began to abuse alcohol and were characterized by suppression of the neurotransmitter systems. It seems possible that the brain neurotransmitter metabolism adequately reflects the characteristics of the higher nervous activity of animals and their resistance to alcohol.     

Biogenic amines in the brain structures of rats from genetically diverse strains under stress]

The content was studied of biogenic amines and their metabolites (by the method of high-effective fluid chromatography electrochemical detection) in the reticular formation of the midbrain, locus coeruleus and sensorimotor cortex in the rats of Wistar and August lines, differing in the behaviour in the open field, in conditions of immobilization stress. The dependence was revealed of the biogenic amines level on the animals genotype and individual characteristics. Most probably, the level of biogenic amines metabolism in central brain structures determines the stability of the animals against emotional stress.