[Regulation of human respiration during a combination of resistive loading and muscular activity].

In 9 healthy subjects, effects of additional non-elastic resistance (the resistive load) on parameters of the respiration control were shown to be slight in resting whereas in muscular activity they involved a rearrangement of the respiration pattern and a considerable increase of inspiratory and expiratory activities. As opposed to these adaptive responses, however, the resistive load, the inspiratory-expiratory one in particular, reduced the increment of lung ventilation associated with the load, and led to a hypercapnia. Physiological mechanisms of these shifts are discussed.

[Correction of hypocapnia in hypoxic humans using biofeedback of alveolar carbon dioxide pressure].

Reactions of the respiratory system to the inhalation of a hypoxic gas mixture were compared when the test subjects (young healthy men) practised normal breathing or breathing with a stable alveolar PCO2. In the latter case the test subjects controlled their lung ventilation using the biofeedback technique. In this manner hyperventilation and related hypocapnia were eliminated.

[Human breathing patterns in hypercapnia and hypoxia].

In 3 young males with different types of breathing pattern, the responses of lung ventilation to hypercapnia and hypoxia were studied. Both kinds of the chemoreceptor activation of respiration increased the depth as well as the frequency of breathing. The subject with tachypnoic pattern of respiration responded to the hypercapnic and hypoxic stimuli mainly with an increase in the tidal volume whereas the bradypnoic subject almost exclusively responded with a faster breathing.

[Importance of chemoreceptor stimuli to the speed of switching the respiratory response to exertion on and off].

The magnitude of the exercise respiratory response and its switch on and switch off rates were studied in 12 normal men breathing different gas mixtures. It was shown that hypercapnic stimulus reinforced and accelerated the respiratory response to exercise. Hypoxic stimulus mostly resulted in the increased though transient changes in the ventilatory rate at the start and at the end of exercise.

[Body's reaction to controlled hypercapnia during muscular exercise].

The respiratory response to the monitored alveolar hypercapnia was studied in normal young men at rest and minute 5 after graded muscular exercise. The exercise did not produce consistent changes in the slope of the regression line that reflected the growth of pulmonary ventilation by 1 mm Hg, pCO2 and therefore did not change the sensitivity of the respiration control apparatus to hypercapnia. At the same time this line moved to the left proportionally to the degree of the exercise as a result of the displacement of the point crossing with the "zero" ventilation axis towards less values of pCO3.

[Criteria for quantitative assessment of respiratory system reactions].

In anesthetized cats and in healthy humans, lung ventilation, activity of diaphragmal motoneurons and intercostal muscles, shift of the intrathoracic pressure, inspiratory occlusional pressure, and maximal rate of the initial increase in inspiratory pressure, were studied. Depending on conditions of the respiratory system functioning, any one from among the above parameters can reflect the efferent output of the respiratory center. Each of them, however, has limitations of its own.

[Analysis of the imperative stimulus restricting voluntary breath holding].

In 5 healthy young men, the maximal voluntary breath holding--was studied under conditions of different initial values of PACO2--after oxygen inhalation at ordinary minute volume of respiration or at hyperventilation, or after breathing with oxygen mixtures with 2, 4, 6, 8 or 10% CO2. PACO2 was recorded at the moment of resuming of the intercostal muscles electric activity and at the point of breaking up the apnoea. A mathematical model was constructed.

[Seasonal changes in several ultrastructural indices of lake frog heart ventricle myocytes].

The method of electron microscopy with morphometric analysis was applied to the study of some ultrastructural indices of frog heart (ventricle) myocardium - the interlocated discs, the lateral junctions and mitochondria - in spring and in autumn. The results obtained pointed to seasonal differences in the cardiomyocyte ultrastructure, this being confirmed by the quantitative analysis.

[Mechanism of the fast neurogenic component of the respiratory response to muscular work].

Dynamics of pulmonary ventilation, electric activity of the intercostal muscles and of the alveolar gas composition was studied in 12 healthy men during dosaged muscular work; these men were given different gas mixtures to breathe. The respiratory response at the initial period of work in inhalation of the hypoxic-hypercapnic gas mixture was greater than that in persons who breathed room air. This response practically disappeared after oxygen hyperventilation.

[Human perception of one's own respiratory volume].

In young healthy subjects, the ability of correct estimation of own respiratory volume and of rather exact reproduction of its given value, was shown. However, on artificial increase in the resistance to breathing the subjects percept the respiratory volume as a greater than actual one and, having been told to decrease the respiratory volume, reduced it to a greater than necessary extent. An opposite phenomenon was noted on reducing the resistance to respiration.