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Autonomic regulation of the heart was examined in 5 groups of rats: intact, sham-operated, experimental chronic obstructive pulmonary disease, acute cerebral ischemia, and acute cerebral ischemia modeled against the background of chronic obstructive pulmonary disease. The latter was provoked by combination of inhaled papain and intraperitoneal bacterial LPS, whereas acute cerebral ischemia was modeled by single-stage bilateral occlusion of the common carotid arteries. Chronic obstructive pulmonary disease was verified by X-ray computed microtomography. The disturbances in autonomic control of the heart during comorbid pathologies were most prominent; they were manifested by overstrain and decompensation of the mechanisms implicated in the heart control and systolic-diastolic arterial hypotension. The correlations were established between blood oxygenation, respiration rate, and some parameters of autonomic cardiac regulation. The data attest to relevance and usefulness of the developed model of respiratory and cerebrovascular comorbidity in assessment of pathophysiological mechanisms underlying dysregulation of the heart and the development of personalized approaches for its pharmacological correction.

The efficiency of neomitilan, a polysaccharide isolated from Crenomytilus grayanus mussels, was studied in experimental model of radiation pneumonia (irradiation of the animal lungs with a total dose of 14 and 28 Gy). Histological study showed that an increase in the number of nucleated components in the lungs of animals subjected to neomitilan inhalation prior to irradiation. Proliferation of bronchial epitheliocytes and the formation of additional lymphoid structures were also revealed in these animals. The absence of a tendency to lung tissue recovery in animals irradiated with 28 Gy is due to extreme radiation toxicity.

The effects of exogenous normobaric hypoxic hypoxia on vegetative control of the heart and BP were examined in Wistar rats. The reference ranges of variation pulsometry parameters were determined in rats with normoxemia for 3 physiological variants of autonomic homeostasis: eutony, sympathicotony, and vagotony. Most rats (80%) demonstrated autonomic eutony. The study showed that saturation of arterial blood with oxygen is the most adequate assessment of severity of acute exogenous normobaric hypoxic hypoxia progressing within a closed hypoxic chamber, which standardizes this method and minimizes inaccuracies resulting from individual sensitivity to hypoxic stress. The changes in functional activity of systems that control the heart rhythm closely correlated with the drop in arterial blood oxygenation. While a small arterial hypoxemia activated the ergotropic elements of autonomic nervous system central subdivision accompanied by elevation of systolic BP, the moderate hypoxemia augmented the cholinergic influences and moderated the adrenergic ones under maintaining mobilization of the central autonomic nervous system-control loop and normotension. Severe hypoxemia was manifested by augmented influences from autonomic nervous system central subdivisions on the heart rate, disadaptation of the control systems, and systolic-diastolic arterial hypotension.

Effects of hypothermia and subsequent self-warming on activity of Ca(2+)-dependent neutral proteases were studied in tissues of ground squirrels and rats. Moderate hypothermia did not significantly change activity of Ca(2+)-dependent neutral proteases in the analyzed tissues of ground squirrels, but reduced protease activity in rat heart. Severe hypothermia reduced enzyme activity in the analyzed tissues of rats and ground squirrels. Differences in activity of Ca(2+)-dependent neutral proteases after long-term hypothermia and subsequent self-warming were found only in the heart.