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Biomedical subjects

V P Krotov

Publications and source records attributed to V P Krotov.

At least 19 recordsLinked to original sources
PubMed2002

[Basic results of the investigation of the effects of antiorthostatic hypokinesia on the functioning of various systems in monkey's organism].

Presented are results of comprehensive studies of functioning various body systems of Macaca mulatta after 4 weeks in antiorthostatic hypokinesia (head-down tilting, HDT). HDT deteriorated monkeys' tolerance of +Gz, altered the higher nervous functioning, and brought about serious disorders in coordination and locomotion. It also impacted energy metabolism, reduced hydration of organism, caused various shifts in the neuroendocrine system, circulation and its controls, and protein, carbohydrate and mineral metabolism. HDT resulted in inhibition of the lymphoid activity of structural components of the lymph nodes, changes in the musculoskeletal apparatus of the lower limbs, atrophic developments in the iliac crest spongiosis, and reduction of the oxidative potential of fibers in the crus extensors, and the number of capillaries in a fiber. These observations are ascribed to redistribution of the body fluids, hypokinesia per se and absence of the effects of support. This HDT model can be applied to monkeys for studying processes of the hypokinetic syndrome and developing countermeasures.

Animals↗
PubMed2000

Oxygen tension in the somatosensory cortex of rhesus monkeys in space.

Oxygen tension (pO2) in the somatosensory cortex of rhesus monkeys was measured polarographically. Immediately after insertion into orbit (the first 40-60 min), the parameter increased significantly and then fell below the baseline. However, at later flight stages pO2 was adequate, indicating that cerebral circulation regulation adapted well to the space environment and that the somatosensory cortex was not exposed to hypoxemia.

Animals↗
PubMed2000

Bion 11 mission: primate experiments.

A summary is provided of the major operations required to conduct the wide range of primate experiments on the Bion 11 mission, which flew for 14 days beginning December 24, 1996. Information is given on preflight preparations, including flight candidate selection and training; attachment and implantation of bioinstrumentation; flight and ground experiment designs; onboard life support and test systems; ground and flight health monitoring; flight monkey selection and transport to the launch site; inflight procedures and data collection; postflight examinations and experiments; and assessment of results.

Adaptation, Physiological↗
PubMed1999

[The use of pharmacological agents for the increase of +Gz tolerance in macaca mulatta].

Tolerance of rhesus monkeys to increased +Gz loads was studied in relation to the conditions of the blood circulation functioning. In four anaesthetised monkeys, the external carotid arteries were ligated and a biomedical cuff was implanted on the common carotid arteries to measure blood pressure, linear blood velocity, and to register EKG. Blood flow in the carotid artery nearing the zero served as the criterion for termination of rotation with a gradient of 0.01 units/s Each animal was centrifuged 4 times at a week interval: first when intact and then after injection of m-cholinolytic metacine, adrenomimetic metazone and or reopolyglucin which increases the plasma volume. These studies demonstrated that the reflex effect on the heart (elevated CO and increased arterial pressure as a result of moderate tachicardia conditioned by metacine) or vessels (activation of alfa-receptors by metazone) as well as an increase in the volume of intravascular fluids, are almost equally favourable to the maintenance of the central blood volume, and the +Gz-tolerance, i.e. about 35% (delta = 1.62-1.77 units).

Adrenergic alpha-Agonists↗
PubMed1998

Evidence for increased cardiac compliance during exposure to simulated microgravity.

We measured hemodynamic responses during 4 days of head-down tilt (HDT) and during graded lower body negative pressure (LBNP) in invasively instrumented rhesus monkeys to test the hypotheses that exposure to simulated microgravity increases cardiac compliance and that decreased stroke volume, cardiac output, and orthostatic tolerance are associated with reduced left ventricular peak dP/dt. Six monkeys underwent two 4-day (96 h) experimental conditions separated by 9 days of ambulatory activities in a crossover counterbalance design: 1) continuous exposure to 10 degrees HDT and 2) approximately 12-14 h per day of 80 degrees head-up tilt and 10-12 h supine (control condition). Each animal underwent measurements of central venous pressure (CVP), left ventricular and aortic pressures, stroke volume, esophageal pressure (EsP), plasma volume, alpha1- and beta1-adrenergic responsiveness, and tolerance to LBNP. HDT induced a hypovolemic and hypoadrenergic state with reduced LBNP tolerance compared with the control condition. Decreased LBNP tolerance with HDT was associated with reduced stroke volume, cardiac output, and peak dP/dt. Compared with the control condition, a 34% reduction in CVP (P = 0.010) and no change in left ventricular end-diastolic area during HDT was associated with increased ventricular compliance (P = 0.0053). Increased cardiac compliance could not be explained by reduced intrathoracic pressure since EsP was unaltered by HDT. Our data provide the first direct evidence that increased cardiac compliance was associated with headward fluid shifts similar to those induced by exposure to spaceflight and that reduced orthostatic tolerance was associated with lower cardiac contractility.

Animals↗
PubMed1998

[The effect of a two-week anti-orthostatic hypokinesia on the cardiac function and on the latter's regulation in monkeys].

Investigated were the effects of 2-week exposure of four Macaca mulattas to the head-end tilted downward at 10 degrees on contractility of the left myocardium and its controls basing on the data of functional loading tests on the tilting table and at two regimes of centrifugation. The experiment included registration of the left heart pressure, volumetric blood flow in the aorta, and EKG in order to determine stroke volume, maximal isovolumetric pressure, end-systolic and end-diastolic pressures, maximal contraction and relaxation velocities, end-systolic myocardial elasticity, and a constant of the isovolumetric relaxation. As was stated, HDT does not impair contractility of the left myocardium; however, sensitivity of the HR baroreflex control wakens.

Animals↗
PubMed1997

[Effects of microgravity on indices of hemodynamics in monkeys during postural tests].

Effects of the 6-day flight on board Cosmos 1667 on the dynamics of arterial pressure (AP) and the linear velocity of blood flow in the common carotid artery were studied with modified postural tests in the experiment with Macaca mulatta No. 18933. Initially, the postural test procedure and the method of mitigating the psychoemotional stress due to transition of the tilt-table were tried out on 21 primates. Administration of the functional test in microgravity was found to exert both qualitative and quantitative effects. The last mentioned were registered only in the primates tilted downward and included lowered AP vs. elevated AP in the control, and absence of typical bradycardia.

Animals↗
PubMed1995

[Intracranial pressure in monkeys during the flight of Cosmos-2229].

The paper contains data of the experiment aboard biosatellite Cosmos-2229 which embraced registration of the intracranial pressure (ICP) in primates during space flight. ICP exhibited a small increase (25-30%) comparing with mean values over 20 hours of the prelaunch period and did not go beyond the limits of physiological norm. In the second part of the flight, ICP tended to return to the preflight level. The ICP pulse wave pattern was considerably changed on account of the venous component on the initial days of orbiting and nearly assumed its preflight form further in flight. The diurnal ICP rhythm was found to be gradually altering in the course of the flight.

Animals↗
PubMed1994

Effects of hindlimb suspension training on the central and regional hemodynamic responses during 24 hours antiorthostatic hypokinesia in the awake rat.

To date the hindlimb suspension model utilizing rats has a wide application to simulate weightlessness. In our previous study we have examined the cardiovascular responses in the tail suspension model using the radiolabeled microspheres technique. We have reported increases of cardiac output (CO) and decreases of total peripheral vascular resistance (TPVR) after 24 hours of head-down tilt (HDT). However, there is no comparison of arterial and venous systems parameters with blood flow changes in organs and tissues. Apart from the preliminary HDT training influence on these parameters is unknown. Thus we aimed to evaluate the role of HDT training in central circulation responses, venous tone and regional blood flow.

Animals↗
PubMed1994

[Intracranial pressure in monkeys under microgravity].

The results of measurement of the intracranial pressure (ICP) in monkeys on board of the biosatellite "Cosmos-2229" are presented. The ICP grew insignificantly in microgravity. The ICP pulse waveform changed significantly in the first day of the flight but returned to normalcy later.

Animals↗
PubMed1991

[The dynamics of the intracranial pressure at rest and during a shift in body posture].

A long-term investigation was carried out to study the relationship between epidural and subdural methods of intracranial pressure registration during postural changes. Parameters were determined for intracranial pressure variations associated with different physiological acts during rest and during functional loadings. The ability of physiological mechanisms to register different degrees of intracranial pressure compensation during changes in body positions was confirmed. The obtained data shows the absence of reliable differences between the results of epidural and subdural intracranial pressure measurements.

Animals↗
PubMed1990

[Systemic and regional hemodynamics in conscious rats during 24-hour antiorthostatic posture].

The systemic and regional hemodynamics during antiorthostatic hypokinesia were studied in male Wistar rats using the radioactive microsphere technique. The animals were hanged up by the tail with the head tilted down (30 degrees) and were able to exercise using only front limbs. Twenty four hours long exposure to antiorthostasis induced significant changes in systemic hemodynamics as well as in regional blood flow in skeletal muscles, spleen, liver and pancreas. Antiorthostasis induced blood flow changes in lungs, heart and brain were less pronounced.

Animals↗
PubMed1987

Cardiovascular results from a rhesus monkey flown aboard the Cosmos 1514 spaceflight.

Pressure and flow relationships to the head were measured before and during spaceflight by means of a chronically implanted cuff placed about the left common carotid artery in one of two rhesus monkeys flown aboard Cosmos 1514. Measurements were obtained daily for 4 min every 2 h during the 5-d spaceflight and compared to identical recordings obtained during a 35-h pre-flight control period 9 d before flight and a 12-h period while on the launch pad. Mean arterial pressure demonstrated a 10% increase compared to control levels immediately on insertion into orbit and maintained a 16-27% increase over the first few hours of flight before returning to baseline levels. Blood flow velocity showed a marked increase (approximately 8 cm/s) compared to pre-flight control while on the launch pad which was maintained over the duration of the flight. Blood flow showed reciprocal changes to pressure on orbital insertion. Cardiovascular system changes persisted into the second day of flight and were most clearly indicated by a decrease in relative differences between blood flow to the head and total cardiac output as measured by impedance plethysmography. Signs of adaptation appeared on days 3-5 of flight.

Animals↗
PubMed1980

[Characteristics of the formation of human cardiovascular system reactions to acute hypoxia].

"Emergency" adaptation of the cardiovascular system of a healthy person to acute hypoxia produced by inspiration of a gas mixture containing 11% oxygen was accomplished in two ways: (a) with prevalence of the cardiac component, increase in the cardiac and systolic indices and end-diastolic volume in unaltered ejection fraction and diminished general vascular tonus; (b) with prevalence of the vascular component, decrease in the cardiac and systolic indices, end-diastolic volume, and muscular and skin blood flow and increase in peripheral resistance. After 10 days of training for hypoxia in a pressure chamber the reaction of the cardiorespiratory system to the hypoxia test was less pronounced but its trend was maintained.

Acute Disease↗
PubMed1976

[Influence of prolonged hypokinesia on the water and fat composition of the human body].

A study was made of a combined action of prolonged hypokinesia (period - up to 30-49 days) and of different position of persons under trial (healthy men) to the gravitation vector on the body composition. Changes in total water content in the organism largely depended not on the limited mobility, but on the body position in space. In antiorthostatic position of persons under trial water "elimination" occurred chiefly during the first several days. The "lean mass of the body" decreased as a result of prolonged hypokinesia, and water content fell in it; but water content was rapidly restored with the restoration of the motor activity.

Body Water↗