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Biomedical subjects

V I Lobachik

Publications and source records attributed to V I Lobachik.

At least 19 recordsLinked to original sources
PubMed2004

Mechanisms of the decrease in human postural stability during prolonged head-down tilt.

In 3 identical experiments with head-down bed rest lasting 60, 90, and 120 days and involving 18 volunteers, dynamics of the development of cardiovascular system (C.V.S) deconditioning was studied. A set of radioisotopic research techniques was used. Volumes of hemocirculation, body fluids, and metabolic activity of the bone marrow were investigated. Functions of the central and peripheral hemodynamics were studied. To determine the extent of C.V.S. deconditioning during the baseline period, on days 60, 90, and 120 of hypokinesia and during recovery, an orthostatic test was performed. The degree of gravitational blood shifting in regions (the head, thorax, the abdomen, the lower extremities) was recorded. Critical thresholds of blood shifting in the body were determined. It was established that the blood pooled in the splanchnic region participates in the decrease of central hypovolemia. Because of the insufficient number of observations, this research should be continued. During recovery, the sign of (CVS) deconditioning noted demonstrated a clear tendency to normalization.

Bed Rest↗
PubMed2000

The effect of a 14-day flight on body fluids in primates.

Using isotopes, two Bion 11 monkeys were examined 36 hours after flight. Total body water and all fluid compartments, particularly extracellular and interstitial fluid, were found to diminish. Blood volume and red blood cell mass also decreased. Forty-two days after flight, fluid compartments returned to normal. After the simulated flight, fluid compartments also tended to decrease but in a lesser degree than after real flight.

Animals↗
PubMed1998

[Methodologic aspects of body water kinetic dynamic studies].

In studying the level of hydration and liquid phases (LPs) in a space mission there use the stable and/or radioactive isotopes. The investigations are unique, the methods are adequate but not adapted in full measure to the challenges of the problem under study. The methodical approaches to the study of the dynamics of water metabolism are not available. Repeated introduction of the markers for these purposes is not acceptable. Another problem associates with taking the markers orally. In this case, a concentration of the markers will depend on the absorption and excretion processes. Prior to, during and in the readaptation period these functions will be different, making a correlation of the accumulated data difficult. There advances a possible version of solving these problems, namely, to use for the dynamic studies the residual contents of the markers in the LPs after single injection. However, this approach calls for investigating the kinetics of markers in weightlessness or during its ground-based simulation. The kinetics of tritium water has been studied in 6 volunteers under conditions of the 5-day bedrest and in 9 healthy men during free motor activity. There determined the characteristics of marker kinetics in a healthy man during his routine living activities. Under bedrest conditions there have been noted slowing-down of the rate and a decrease in the degree of marker accumulation in the body after its single injection, the shift of a period of relative stabilization of marker content in LP to the more late dates of experiment, slowing-down of the marker excretion rate from the body.

Adaptation, Physiological↗
PubMed1991

Hemodynamic effects of microgravity and their ground-based simulations.

Hemodynamic effects of simulated microgravity were investigated, in various experiments, using radioactive isotopes, in which 40 healthy men, aged 35 to 42 years, took part. Blood shifts were evaluated qualitatively and quantitatively. Simulation studies included bedrest, head-down tilt (-5 degrees and -15 degrees), and vertical water immersion, it was found that none of the methods could entirely simulate hemodynamic effects of microgravity. Subjective sensations varied in a wide range. They cannot be used to identify reliably the effects of real and simulated microgravity. Renal fluid excretion in real and simulated microgravity was different in terms of volume and time. The experiments yielded data about the general pattern of circulation with blood displaced to the upper body.

Adult↗
PubMed1988

[An automated device for x-ray fluorescence analysis and its use in space and clinical medicine].

An experimental unit for radiofluorescent analysis using the REIS-I x-ray emitter, a Si (Li) detector, an analyser with the NOIKA LP-4900 microprocessor and appropriate soft ware was devised for a study of some aspects of metabolism and kinetics of a number of electrolytes playing an important role in the state of water-salt homeostasis of the organism of man and animals. Methodological approaches to quantitative determination of the native content of plasma trace elements and macrocells: S, Cl, K, Ca and stable bromine administered for determination of extracellular fluid volume--were developed. This method can be used for determination of quantitative indices of the above functions in healthy men and animals during outer space flights, ground mock-up experiments, for clinical investigations in diagnosis of subpathological conditions and for control of therapeutic efficacy.

Aerospace Medicine↗
PubMed1976

Antiorthostatic hypokinesia as a method of weightlessness simulation.

Physiological effects seen in eight test subjects during a 5-d bedrest experiment in the head-down position (0,-4,-8,-12degrees) were studied. It was shown that the antiorthostatic hypokinesia at -12degrees could reproduce physiological responses shown by space crewmembers more closely than recumbent bedrest. Our observations help to stimulate an acute stage of human adaptation to the weightless state and to assess the part played by gravity-induced blood redistribution in the development of physiological changes.

Adult↗
PubMedDate not supplied

Efficacy of periodic centrifugation of primates during 4-week head-down tilt.

Creation of artificial force of gravity (AFG) to counteract the negative consequences of microgravity in manned space missions of extended duration is one of the high-priority problems of space biology and medicine. However, there are a number of especial effects of AFG (namely, structural changes in muscles and bones, and some other system) which need implantation of electrodes and sensors and are possible only with animals. That is why it is of particular interest to make studies with monkeys whose reactions to changed gravity bear much resemblance with human. The purpose of the investigation was development of a protocol of periodic gravity loads as a counter-measure against the hypokinetic syndrome in Macaca mulatta. Two series of experiments were performed. In the series, animals were split into two groups of 6 species each who were motor restrained with the head end tilted downward at 5 degrees (HDT) for 28 days. Monkeys of group-2 were periodically subjected to centrifugation (HDT+G). During the first series of experiments rotation was conducted in the +Gz direction at g-loads from 1.2 to 1.6 units for 30-40 minutes 4-5 times a week. In the second series, g-load was equal to 1.2 units and the animals were rotated 30 min. 2-3 time a week. The criterion of Y-training protocol efficacy was a test +Gz run at 3 units for 30 s. during which functioning of the cardiovascular systems and its controls was evaluated. The test run was performed prior to and after HDT. Following HDT the animals of group HDT+G were more resistant to the test than their counterparts who had not been trained on the centrifuge. Data of the investigation imply that following HDT and HDT+G alike reduced the amount of total bodily fluids (by approximately 5%), the intracellular component (approximately 4%), and plasma volume (by 6-7%). Yet, there are radical differences between the groups in the levels of reduction in extracellular fluids (by 11% and 6.5%, respectively, P<0.05) and the interstitial component (by 11.5% and 6.5, respectively, P<0.05). Prophylactic centrifugation during HDT was also positive to the muscular blood flow in lower extremities.

Adaptation, Physiological↗
PubMedDate not supplied

[Prevention of the adverse effects of head-down tilting on the infrastructure of body fluids and postural stability of primates by exposure to g-loads].

Experiments with 24 primates (Macaca mulatta) demonstrated that head-down tilting (-5 degrees) altered their hydration status as was manifested by a significant diminution of the amount of extracellular fluids, the interstitial fraction specifically. Blood circulation in leg muscles reduced almost in half In addition, return of the animals to the orthostatic position at the end of the experiment did not cause so intensive blood redistribution in leg vessels as in the group of tilted but not rotated animals.

Animals↗
PubMedDate not supplied

[Body fluids during 120-day anti-orthostatic hypokinesia].

Body fluid variations were examined during 120-day antiorthostatic (-5 degrees) hypokinesia in 21 test subjects, 9 of which comprised a control group (Group 1). The remaining 12 subjects formed three groups (four subjects each) who received drugs to normalize mineral and lipid metabolism (Group 2), or performed specially developed exercises (Group 3), or were on the combined treatment (Group 4). Total body water (TBW), intracellular fluid volume (IFV), extracellular fluid volume (EFV), and EFV composition were measured by nuclear physical methods. Measurements were taken prior to exposure, on head-down tilt days 1, 60 and 120, and on recovery day 15. Body composition and K40 content were investigated before and after head-down tilt. The controls showed body dehydration that began on tilt day 1 at the expense of vascular fluid and continued by day 60 at the expense of interstitial fluid and by day 120 at the expense of IFV. Group 2 subjects exhibited variations that were similar to those of controls. Group 3 subjects were in better shape due to the beneficial effect of exercise which diminished as head-down tilt continued. In the recovery period the above changes regressed.

Blood Volume↗
PubMedDate not supplied

[Individual characteristics of water-mineral metabolism during 120-day head-down tilt hypokinesia and the effectiveness of prophylactic measures].

Sodium balance and circulating plasma, intracellular, extracellular and interstitial fluid volumes were measured in the test subjects exposed for 120 days to head-down tilt at -5 degrees. The large scatter of the above parameters was associated with individual variations and with the use of different countermeasures against demineralization (exercise and drugs-xydiphone and glucamak). The effect of the countermeasures was different both in qualitative and quantitative terms. It appears that the target of their action was different. The best prophylactic effect was seen when exercise and drugs were used in combination. These findings suggest that individual variations of fluid-electrolyte metabolism during prolonged hypokinesia are related to the different capacity of tissues for water and electrolytes.

Adult↗
PubMedDate not supplied

[Effect of space flight factors on the blood circulation function in primates].

Using radioactive isotopes, central, peripheral and organ blood circulation was investigated in two rhesus-monkeys before the 7-day space flight, 1.5 hours after touchdown, and 4 months after recovery. Blood distribution and shifts were measured in different body segments, viz. head, chest, abdomen, legs. Postflight measurements revealed a decrease of plasma and blood volume. They also demonstrated changes in cardiac output and stroke volume, decrease of total peripheral resistance, reduction of mean arterial pressure and a slight increase of heart rate. Pulmonary blood flow velocity and time varied insignificantly and in a different manner. Blood was pooled in the legs. Blood flow velocity in the skin of the upper and lower body decreased while in muscles it increased above the baseline values. Postflight, muscles acted as a hemodynamic blood pool. The tolerance of both monkeys to the tilt test was satisfactory. It can be concluded that the monkeys tolerated the 7-day space flight well enough.

Animals↗