[State of autonomic regulation of heart rhythm in young and aged rats before and after application of different regimens of rhythmic extreme cooling.]

The influence of various rhythmic extreme cold effects on the state of autonomic regulation of heart rate in young and aged rats was studied. According to the spectral analysis of heart rate variability, it has been found that in young rats, using rhythmic extreme cold exposures (RECE) temperature regimens of (-120 °Ð¡; -120 °Ð¡; -120 °Ð¡) and (-60 °Ð¡; -120 °Ð¡; -120 °Ð¡) significantly increased adaptive capabilities of the body due to the activation of its own homeostatic regulatory systems. At the same time, the combined regimen of RECE (-60 °Ð¡; 120 °Ð¡; -120 °Ð¡) occurred to be the most optimal for aged animals, since its use was not accompanied with an excessive activation of sympathoadrenal system at the early stages of experimental studies, in contrast to the regimen (120 °Ð¡; -120 °Ð¡; -120 °Ð¡). In addition, the use of this cooling mode contributed to a statistically significant increase in the total power of spectrum of neurohumoral regulation not so much due to a rise in activity of humoral-metabolic regulation link, the prevalence of which is characteristic of an old age, but due to an increase in the tone of vegetative centers, herewith the parasympathetic effects on the myocardium prevailed sympathetic ons.

[Structural changes in myocardium of aged rats on background at stress-induced arterial hypertension.]

Here, we assessed the histological changes in myocardial structure in old rats against the background of persistent arterial hypertension. This study was aimed to investigate the structural organization of tissues and vessels of animal myocardium to days 3, 7 and 30 after development of stress-induced arterial hypertension. The experiments were performed in 28-30-month-old white outbred male rats. The pathological state was simulated according to the patented technique under specialized cage conditions with a combined impact of stimuli (light, sound, electricity). Histological and histochemical assessments of the myocardium within these research terms showed the development of destructive and dystrophic disorders in myocardial tissues and vessels, the progression of interstitial and perivascular oedema, the occurrence of diapedetic hemorrhages. Significant differences in morphological structure of the myocardium in hypertensive old rats as compared with the control normotensive animals were established. These findings make it possible to clarify the pathogenesis of the stress-induced arterial hypertension development, which is a key element in designing the current anti-stress and antihypertensive therapy.

[Lipid peroxidation during extreme hyperthermia of rats].

The influence of extremal cryoeffects on the state of prooxidant and antioxidant systems in the blood serum and heart tissues was studied in young and old rats. It is shown that kinematic parameters of chemiluminescence after cold effects are less expressed in the blood serum of old animals than in young ones. The level of TBA-active products in the blood of young rats was lower than in old ones. After the 6th and 9th cold effect the content of TBA-active products in old animal appoaches such indices in young animals. Three weeks after the cold effects the content of TBA-active products in the myocardium of old rats corresponded to control indices, while in the young ones they were considerably lower. The fermentative link state was investigated in the antioxidant protection system. After the extremal cryoeffects glutathione reductase and glutathione peroxidase activity in old animals approaches its indices in intact rats, while catalase activity increases. Three weeks after cryoeffects one can observe a stable increase of fermentative activity of heart tissues both in old and young animals compared with the control that can evidence for the increase of the organism cold resistance.

[Proteinase-proteinase inhibitor system in aged rats with stimulated hypertension exposed to cord blood]. / Sistema proteinaza-ingibitor proteinaz u starykh krys so stimulirovannoi gipertenziei pod vliianiem kordovoi krovi.

The proteinases, nontrypsinlike proteinases (NTLP), alpha-1-proteinase inhibitor, alpha-2-macroglobulin (alpha-2-MG) activities were researched in serum, tissues of hypothalamus, cerebral cortices, lung, heart, liver, kidneys in old rats with hypertension caused by electricity current at introduction of cord and mature blood preparations. The increase of proteinase and NTLP activities were revealed on the background of alpha-2-MG level reduction. The changes caused by stimulated hypertension, can be corrected by introduction of blood preparations and the effect of cord blood is more manifested.