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Biomedical subjects

N P Aleksandrova

Publications and source records attributed to N P Aleksandrova.

At least 19 recordsLinked to original sources
PubMed2005

[The effect of head-down hypokinesia on functional state of diaphragm in rats].

The effects of long-term (21 days) head-down (-30 degrees) hypokinesia (HDH) on respiratory system and a functional state of diaphragm were investigated in rats. Minute ventilation, oesophageal and abdominal pressure, integrated electrical activity of diaphragm were measured in control and experimental group (after 21 days of HDH) of animals. The measurements were made in several body positions atresting and in occlusion breathing. The results indicate that HDH causes reduction in minute ventilation of lungs, decrease in orthostatic stability and functional reserve of the respiratory system capacity. It was established that the basic mechanism of HDH respiratory effects is contractile failure of diaphragm related to damage in excitation-contraction coupling in its muscular fibres.

Animals↗
PubMed2004

Chemoreceptor and vagal influences on genioglossal muscle responses to inspiratory resistive load.

The present study was undertaken to determine the mechanisms underlying the involvement of upper airway dilating muscles in compensatory responses to added inspiratory resistive load. Experiments were performed in tracheostomized, anaesthetised rabbits. The effect of inspiratory resistive loading on the electromyographic activity of the genioglossus muscle, the major dilating muscle of the pharynx, was studied in vagotomized and vagally intact rabbits during spontaneous breathing with a hypoxic gas mixture (10% O(2) in N(2)) or oxygen. In the vagally intact animals the peak value and duration of genioglossus muscle inspiratory activity increased in the first loaded breath before any noticeable change in the arterial blood gases. Hyperoxia decreased, whereas hypoxia increased the immediate response of the genioglossus activity to inspiratory loading. Removal of vagal volume-related feedback (by vagotomy) significantly increased the genioglossus muscle activity; the increase being more under hypoxia than under hyperoxia. In contrast to vagally intact animals, there was no first-breath increase in genioglossus activity during loading. The results indicate that the immediate involvement of the genioglossus muscle in response to inspiratory resistive load is mediated by vagal-volume feedback. Baseline oxygen tension before loading modulates the immediate reflex vagal-related response of the genioglossus muscle.

Animals↗
PubMed2002

Mechanisms of genioglossus responses to inspiratory resistive load in rabbits.

The purpose of the present study has been to determine whether pharyngeal dilator muscles participate in inspiratory load compensatory responses and if so, to elucidate role of upper airway mechanoreceptors in these responses. The experiments were performed on anaesthetized rabbits. Each animal was tested in three ways by the imposition of inspiratory resistive load: (1) at upper airways via face mask, (2) at the tracheostomic cannula placed below larynx (all upper airway receptors were 'bypassed') and (3) at the mouth after the section of the hypoglossus nerves (motor denervation of genioglossus muscle). The inspiratory load applied to the upper airways evoked significant increases in integrated genioglossus activity (to 129 +/- 14.7% of control) and its inspiratory duration (to 113 +/- 5% of control) already within the first loaded breath (P < 0.05). The increases in the inspiratory activity of musculius genioglossus were relatively greater than the simultaneous increases in the activity of the diaphragm. Motor denervation of the pharynx dilator muscles (including m. genioglossus) increased airway resistance to 184 +/- 19% of control (P < 0.05) and induced obstructive alterations in the breathing pattern during unloaded breathing: decrease in maximal inspiratory flow (-13%) and increase in the level of negative oesophageal pressure (+14%) and the peak diaphragm activity (+6%). After nervi hypoglossus sections additional increases in motor and pressure outputs were required in order to maintain unaltered ventilation at the same degree of loading as before denervation. The results indicate that the pharyngeal dilator muscles have a role in compensation of added inspiratory load. Activation of these muscles facilitate the load compensating function of 'pump' muscles by decreasing airway resistance. Tracheostomy did not reduce the genioglossus response to inspiratory loading, ruling out any role for upper airways receptors in the genioglossus response to inspiratory load compensations.

Adaptation, Biological↗
PubMed2001

[Involvement of pharyngeal muscles in compensatory responses of the respiration system to inspiration resistance load].

The present study was undertaken to test the hypothesis that recruitment of upper airway muscles in loaded breathing is a result of integration of peripheral chemoreceptor and pulmonary mechanoreceptor afferents. Experiments were performed in spontaneously breathing tracheostomized anesthetized rabbits. It had been studied the effects of inspiratory resistive loading to EMG activity of genioglossus muscle. In the intact rabbits the peak value and duration of inspiratory activity of genioglossus increased in loading. Imposition of resistive load in vagotomized animals did not evoke alteration in inspiratory activity of genioglossus in the first loaded breath. Hyperoxia decreased the response of genioglossus muscle to inspiratory loading and vagatomy. We conclude that hypoxic stimulation of peripheral chemoreceptors and decrease in volume-related afferent activity from pulmonary stretch receptors are major mechanisms of the upper airway muscle recruiment in inspiratory resistive loading.

Animals↗
PubMed2000

Identification of a respiratory related area in the rat insular cortex.

The aim of this study was to map areas within the rat insular cortex from which respiratory responses originate and compare those sites with gastrointestinal control regions. The insular cortex was systematically microstimulated and histological location of responsive sites determined. Increased inspiratory airflow and decreased respiratory cycle duration were considered to be respiratory excitatory responses. The responses were localized in dysgranular and agranular insular cortex at levels caudal to the joining of the anterior commissure. More rostrally, respiratory inhibitory responses were elicited: these were manifested as a decrease in inspiratory airflow without a significant alteration in respiratory cycle duration. Respiratory inhibitory responses were usually accompanied by changes in gastric motility. These results suggest that the respiratory area in the rat insular cortex consist of two distinct zones which overlap a region modulating the gastrointestinal activity.

Animals↗
PubMed1998

[The role of pharyngeal muscles in the regulation of airway resistance during inspiration resistive load in rabbits].

In anesthetised spontaneously breathing rabbits, an increase in the inspiratoryactivity m.genioglossus was greater than a simultaneous increase in the respiratory activity of the diaphragm cluring loaded breathing. A bypass of the air flow via tracheostoma did not affect the response of the m.genioglossus to a resistive load. The difference seems to be due to different functional inputs from the lung mechanoreceptors to phrenic and hypoglossal neuronal pools.

Airway Resistance↗
PubMed1998

[Effects of the local stimulation of the insular cortex on respiration in rats].

Two distinct patterns of respiratory responses to electrical microstimulation were elicited from the rat insular cortex: a decrease in respiratory airflow and tidal volume with no alteration of the respiratory rate (the inhibition response) and an increase in respiratory rate and inspiratory airflow (the excitation response). Gastric motility changes could also be elicited from the anterior insular cortex simultaneously with the inhibition response. The data suggests overlapping of the inhibition response area in the anterior insular cortex with a gastrointestinal representation there, and of the excitation response area in the posterior insular cortex with a cardiovascular representation.

Animals↗
PubMed1997

Central and peripheral components of diaphragmatic fatigue during inspiratory resistive load in cats.

The development of fatigue was investigated in the diaphragm of anaesthetized, tracheostomized, spontaneously breathing cats during restricted air flow. Ventilation, transdiaphragmatic pressure (Pdi), integrated electrical activity of diaphragm (Edi) and phrenic nerve (Eph) were measured simultaneously and expressed as a percentage of values at unloaded breathing. Inspiratory loads were 60, 70 and 80% of Pdi max. The Pdi max was measured by airway occlusion at functional residual capacity. The duration of loads was 40-60 min. The diaphragmatic fatigue developed only during heavy inspiratory loading (80% Pdi max). During the first 10 min of heavy load Pdi, Edi and Eph increased to 905 +/- 60%, 248 +/- 20% and 229 +/- 24%, respectively (P < 0.01), and then began to fall gradually. Ventilation declined to 39 +/- 3% after 60 min of heavy load (P < 0.01), resulting in acute hypercapnia and hypoxia. Initial fatigue appeared as a decrease in Pdi (to 781 +/- 63%) and parallel decline in Edi (to 233 +/- 21%) after 30 min of load (P < 0.05). Phrenic nerve activity did not change during this stage. These data suggest a peripheral basis of diaphragmatic fatigue, related to disorders in neuromuscular transmission. After 60 min of heavy load, Pdi fell to 675 +/- 49%, Edi declined to 209 +/- 28% and Eph decreased to 189 +/- 25%. We interpret the decrease in phrenic nerve activity as a weakening of central inspiratory drive and development of the central component of diaphragmatic fatigue in the last stage.

Animals↗
PubMed1993

[Electron microscopic study of erythrocyte form after extracorporeal ultraviolet and red coherent irradiation of blood].

The results of these experiments demonstrate that extracorporeal ultraviolet and red coherent blood irradiation make the energetics of erythrocyte membrane broken. This deviation has been manifested in changing of erythrocyte's form. The degree of these disorders and of inertia of the recovering process of the erythrocyte's form was greater under ultraviolet blood irradiation.

Animals↗
PubMed1993

[The mechanism of apnea during difficult breathing].

The experiments on anesthetized cats demonstrated that only a combination of hypoxia and inspiratory resistive loading induced respiratory arrest. The findings suggest that both central and peripheral mechanisms of apnea exist due to functional insufficiency of respiratory muscles as a result of synaptic disorder and excitatory contractility disorder in diaphragmatic muscle fibers.

Animals↗
PubMed1993

[The relative contribution of the muscles of the chest cavity and diaphragm to the work of breathing under inspiratory resistive loading].

The inspiratory resistive load decreases the relative contribution of the diaphragm into formation of the respiratory volume, as has been show in anesthetised cats. The phenomenon can be due to both a sharp increase in the external intercostal muscles activity and to a fatigue of the diaphragmatic muscle in the inspiratory load. The contraphasic changes of these muscles' activity seem to be an adaptive response aiding to a more efficient overcoming of the resistance against breathing.

Airway Resistance↗
PubMed1992

[An analysis of respiratory muscle fatigue under a resistive load with the breathing of gas mixtures with different oxygen levels].

In anesthetized cats, the respiration muscles' fatigue under normoxia occurred in heavy mechanical load equal to 80% of the maximal inspiratory effort. Under hypoxia the force of the diaphragm contraction did never decrease whereas when breathing with hypoxic gas mixture weakening of the contractile ability occurred yet under moderate load. In breathing with additional mechanical load under hypoxia, mainly the peripheral part of the respiratory system's motor apparatus suffers, as the weakening of diaphragm's electrical activity and reduction of its contractions' force occurred during unfalling activity of the diaphragmatic nerve. The oxygen content in arterial blood affects the contractile ability of respiratory muscles. However, the increase in the energy supply level does not necessarily exclude the possibility of respiratory muscles' fatigue, but just decelerates its development.

Air↗
PubMed1991

[Rheologic characteristics of blood in patients with chronic post-embolic pulmonary hypertension].

Examination of blood rheologic properties in 38 patients with chronic ++post-embolic pulmonary hypertension revealed an elevated blood viscosity at all shift rates and a reduced erythrocyte deformability. A close positive correlation was found between blood viscosity and perfusion deficit. Hemorheologic disorders in patients with chronic post-embolic + pulmonary hypertension are caused by pachyhemia and blood acid-base imbalance due to respiratory failure. They deteriorate pulmonary and systemic hemodynamic disturbances and contribute to progression of blood flow derangement.

Adult↗
PubMed1990

[Hemorheological aspects of the Arvin therapy of acute thromboses of the magistral veins of the lower extremities].

The rheologic blood properties were studied in patients with acute venous thrombosis during Arvin therapy. A marked correcting effect of the agent in removing the hemorheological disorders was demonstrated. It was found that the action of Arvin, linked with reduction of fibrinogen concentration, is attended by a decrease of blood viscosity, diminished aggregation of blood formed elements, and improvement of the functional condition of the microcirculatory bed during the whole course of treatment. The duration of the positive hemorheological effect of Arvin exceeds that in treatment by a complex of antithrombotic agents.

Adult↗