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Biomedical subjects

I B Kozlovskaya

Publications and source records attributed to I B Kozlovskaya.

At least 19 recordsLinked to original sources
PubMed2004

Mechanisms of disorders of the characteristics of fine movements in long-term hypokinesia.

The precision and electromyographic characteristics of single-joint voluntary movements of the human foot, of the programmed and tracking types, were studied, along with the characteristics of rhythmic activity of motor units before and during 120-day antiorthostatic hypokinesia. This latter was accompanied by significant decreases in the precision of the control system, evident as decreases in the number of discriminable force gradations, increases in the absolute and differential thresholds for movements of the programmed type, and sharp increases in the variability of integrated EMG traces from the working muscles during tracking movements. The direction and dynamics of changes in the activity of motor units at different stages of antiorthostatic hypokinesia were different: during the first 14-30 days (stage I), there was a sharp increase in the variability of interspike intervals and an increase in the extent of synchronization of motor unit activity; from day 30 onwards (stage II), there was a reproducible decrease in the duration of interspike intervals, along with disappearance of the synchronization of motor units, while the high level of variability of spike activity persisted. The results obtained here suggest that impairments of precision during stages I and II of antiorthostatic hypokinesia are different in nature and are associated with reflex responses to support unloading at stage I and with atrophic processes in muscles in stage II.

Electromyography↗
PubMed2004

Afferent and peripheral control of muscle fiber properties during gravitational unloading.

The present paper covers two series of the experiment studies performed in attempt to analyze the support-triggered cellular mechanisms, controlling the maintenance of tonic muscle fiber characteristics. Exposure to 7 day dry immersion induced significant decline of the human soleus single fiber peak isometric tension and the Ca(2+)-sensitivity of myofibrils. 30-40% losses of the relative content of titin and nebulin were found after immersion. The application of the plantar support stimulation device prevented all these alterations. In the second experimental series the treatment of hindlimb suspended rats with the Ca(2+)-binding agent (EGTA) allowed to prevent or attenuate all the above mentioned unloading-induced soleus fiber alterations. Thus it is concluded that resting Ca2+ accumulation in the unloaded fibers may be among the mechanisms involved in the changes of fiber properties during unloading.

Animals↗
PubMed2004

Effect of dry immersion in combination with stimulation of foot support zones upon muscle force-velocity characteristics.

The complex of motor disturbances arising under conditions of real and simulated microgravity that include decrease of contractile characteristics of postural muscles is likely to be a result of withdrawal of support stimuli. Artificial stimulation of support zones of feet is shown to diminish partially or prevent completely the negative effects of microgravity on the motor system. The aim of the study was to evaluate and compare the changes of contractile properties of extensors and flexors of knee joint measured in isokinetic and isotonic regimes under conditions of simulated microgravity (7 days dry immersion).

Foot↗
PubMed2004

Effects of artificial support stimulation on fiber and molecular characteristics of soleus muscle in men exposed to 7-day dry immersion.

Artificial support stimulation is known to attenuate or prevent many motor or skeletal muscle effects of actual or simulated microgravity. The present study was purposed to analyze the effects of artificial support on human soleus fibers after 7-day exposure to supportless environment. 8 healthy male volunteers were exposed to dry immersion in supine position for 7 days according to Shulzhenko and Vil-Villiams (1972). 4 of them worn the support device which provided them with plantar stimulation in regime described elsewhere.

Connectin↗
PubMed2004

Serum creatine kinase levels and the number of sarcolemmal dystrophin disruptions in human skeletal muscle fibers under conditions of 7-day "dry" immersion.

9 male volunteers took part in the experiment. They were divided in two groups. 5 volunteers (control group) have been in "dry" immersion for 7 days. 4 volunteers (stimulated group) in addition to "dry" immersion were treated with artificial support stimulation. We investigated the number of muscle fibers with the disruptions of sarcolemmal dystrophin and serum creatine kinase levels. 7-day "dry" immersion does not change the mean number of muscle fibers with dystrophin disruptions, it leads to significant decrease of serum creatine kinase levels and does not influence on the sensitivity of sarcolemma to injury. Artificial support stimulation does not influence on these parameters.

Creatine Kinase↗
PubMed2004

Effect of mechanical stimulation of the support zones of soles on the muscle stiffness in 7-day dry immersion.

Stiffness of m. soleus (Sol.) and m. tibialis anterior (TA) was evaluated in 16 volunteers during exposure to 7-days dry immersion alone and to the combination of immersion and mechanic stimulation of foot support zones. It was shown that Sol. stiffness decreased progressively starting from day-1 of immersion, whereas TA stiffness, on the contrary, made a sharp rise. Mechanic stimulation of foot support zones slowed down the rate and extent of changes in both muscles.

Adult↗
PubMed2004

Dynamics of physical performance during long-duration space flight (first results of "Countermeasure" experiment).

The efficacy of countermeasure exercise for diminishing disturbances induced by microgravity in motor system and its visceral supply during different stages of long-duration flight was evaluated. The results of both bicycle and locomotor testing indicate that physical fitness of cosmonaut does not become worse in the course of the long-duration flight. On the contrary, the lowest fitness was recorded at the first stage of mission, just after one month of flight. The "dead period" at the beginning of space flight seems to be a manifestation of the acute decrease in physical condition on transition from 1 G to microgravity, when none of the regular countermeasure regimes is sufficiently effective and acute increase of volume and intensity of training is impossible under the conditions of space flight.

Aerospace Medicine↗
PubMed2003

Characteristic of changes in the structure and metabolism of the vastus lateralis muscles in monkeys after space flight.

Monkeys subjected to space flight were found to have significant decreases in the sizes of slow and rapid fibers in the vastus lateralis muscle, due not only to weightlessness but also, to some extent, to restriction of movement activity within the capsule. The quantity of total protein in muscle fibers did not decrease. The respiratory peak in the pool of vastus lateralis muscle fibers decreased after space flight, as did the activity of oxidative enzymes (particularly in rapid fibers of the vastus lateralis muscle).

Animals↗
PubMed2003

Effects of weightlessness and movement restriction on the structure and metabolism of the soleus muscle in monkeys after space flight.

After humans and animals have been in conditions of real and modeled weightlessness, the most marked changes are seen in the "slow" tonic muscles, particularly soleus. Studies of the effects of weightlessness and movement restriction on the soleus muscle in monkeys demonstrated significant reductions in the sizes of slow and rapid fibers due mainly to the actions of real weightlessness (rather than movement restriction in the space capsule). Protein loss in soleus muscle fibers in monkeys following space flight was more marked than loss of other components, including water. The level of atrophy of soleus muscle fibers in these conditions was greater than the decrease in the number of capillaries. Succinate dehydrogenase activity in soleus muscle fibers decreased proportionally to the reduction in fiber size.

Animals↗
PubMed2002

Goals of biomedical support of a mission to Mars and possible approaches to achieving them.

The main medical and biological problems associated with a piloted mission to Mars are discussed. Prerequisites for the mission are described, based on our experience with biomedical support of prolonged piloted missions. The most important factors are developing countermeasures against the prolonged effects of microgravity and hypogravity; solving a complex of psychological problems; developing methods to protect against cosmic radiation; and creating effective and reliable life support systems. Some aspects of the likely risks involved in such a mission are also reviewed.

Aerospace Medicine↗
PubMed2002

Structural and metabolic characteristics of human soleus fibers after long duration spaceflight.

The fiber size decline, alterations in fiber metabolic potential and increase of connective tissue component were shown in human m. vastus lateralis after short and long-duration space flights and in m.soleus and m.vastus lateralis after 120 day head down tilt bed rest. It is known from rat and monkey studies that the exposure to weightlessness leads to the most pronounced changes in postural muscles, e.g. m.soleus. It was shown that 17 day space flight induced significant decrease of fiber cross-sectional area and slow-to-fast fiber type transformation in human soleus. But in the cited work the fiber population under study was limited like in most single fiber technique analyses. The present study was purposed to investigate the structural and metabolic properties of soleus muscle in Russian cosmonauts exposed to 129-day space flight on board of the International Space Station.

Journal Article↗
PubMed2002

Muscle transverse stiffness and venous compliance under conditions of simulated supportlessness.

Supportlessness arising as a result of 7 hrs dry immersion is accompanied by decreased transverse stiffness and increased calf venous compliance, as well as impaired orthostatic tolerance. Stimulation of support zones of foot is associated with smoothening of these effects. The latter may be considered as an indirect evidence in favor of the concept of support deafferentation triggering role in development of enumerated unfavorable effects of simulated microgravity.

Journal Article↗
PubMed2001

Effect of long-duration spaceflight on postural control during self-generated perturbations.

This report is the first systematic evaluation of the effects of prolonged weightlessness on the bipedal postural control processes during self-generated perturbations produced by voluntary upper limb movements. Spaceflight impacts humans in a variety of ways, one of which is compromised postflight postural control. We examined the neuromuscular activation characteristics and center of pressure (COP) motion associated with arm movement of eight subjects who experienced long-duration spaceflight (3--6 mo) aboard the Mir space station. Surface electromyography, arm acceleration, and COP motion were collected while astronauts performed rapid unilateral shoulder flexions before and after spaceflight. Subjects generally displayed compromised postural control after flight, as evidenced by modified COP peak-to-peak anterior-posterior and mediolateral excursion, and pathlength relative to preflight values. These changes were associated with disrupted neuromuscular activation characteristics, particularly after the completion of arm acceleration (i.e., when subjects were attempting to maintain upright posture in response to self-generated perturbations). These findings suggest that, although the subjects were able to assemble coordination modes that enabled them to generate rapid arm movements, the subtle control necessary to maintain bipedal equilibrium evident in their preflight performance is compromised after long-duration spaceflight.

Adult↗
PubMed2000

Effects of three days of dry immersion on muscle sympathetic nerve activity and arterial blood pressure in humans.

The present study was performed to determine how sympathetic function is altered by simulated microgravity, dry immersion for 3 days, and to elucidate the mechanism of post-spaceflight orthostatic intolerance in humans. Six healthy men aged 21-36 years old participated in the study. Before and after the dry immersion, subjects performed head-up tilt (HUT) test to 30 degrees and 60 degrees (5 min each) with recordings of muscle sympathetic nerve activity (MSNA, by microneurography), electrocardiogram, and arterial blood pressure (Finapres). Resting MSNA was increased after dry immersion from 23.7+/-3.2 to 40.9+/-3.0 bursts/min (p<0.005) without significant changes in resting heart rate (HR). MSNA responsiveness to orthostasis showed no significant difference but HR response was significantly augmented after dry immersion (p<0. 005). A significant diastolic blood pressure fall at 5th min of 60 degrees HUT was observed in five orthostatic tolerant subjects despite enough MSNA discharge after dry immersion. A subject suffered from presyncope at 2 min after 60 degrees HUT. He showed gradual blood pressure fall 10 s after 60 degrees HUT with initially well-maintained MSNA response and then with a gradually attenuated MSNA, followed by a sudden MSNA withdrawal and abrupt blood pressure drop. In conclusion, dry immersion increased MSNA without changing MSNA response to orthostasis, and resting HR, while increasing the HR response to orthostasis. Analyses of MSNA and blood pressure changes in orthostatic tolerant subjects and a subject with presyncope suggested that not only insufficient vasoconstriction to sympathetic stimuli, but also a central mechanism to induce a sympathetic withdrawal might play a role in the development of orthostatic intolerance after microgravity exposure.

Adult↗
PubMed2000

Bion 11 science objectives and results.

The results from the Bion 11 mission were the most comprehensive set of data ever collected on primate physiology and behavior before, during, and after spaceflight. An international team of scientists representing neuromuscular and behavioral, neurosensory, regulatory, and bone physiology disciplines conducted a wide range of studies, which are briefly summarized herein. New insights were obtained, which can be expected to lead to new, efficient countermeasures for space-related changes, thereby facilitating long-duration human space voyages and providing additional assurance of human health and performance. These data will likely benefit medical areas on Earth that have overlap with challenges in space biology and medicine.

Adaptation, Physiological↗
PubMed2000

Bion 11 mission hardware.

The mission hardware provided for Bion 11 shared primate experiments included the launch vehicle, biosatellite, spaceflight operational systems, spacecraft recovery systems, life support systems, bioinstrumentation, and data collection systems. Under the unique Russia/US bilateral contract, the sides worked together to ensure the reliability and quality of hardware supporting the primate experiments. Parameters recorded inflight covered biophysical, biochemical, biopotential, environmental, and system operational status.

Animals↗
PubMed2000

Fiber size and myosin phenotypes of selected rhesus lower limb muscles after a 14-day spaceflight.

Muscle biopsies were taken from the rhesus (Macaca mulatta) soleus (Sol, a slow ankle extensor), medial gastrocnemius (MG, a fast ankle extensor), tibialis anterior (TA, a fast ankle flexor), and vastus lateralis (VL, a fast knee extensor) muscles in vivarium controls (n=5) before and after either a 14-day spaceflight (Bion 11, n=2) or a 14-day ground-based flight simulation (n=3). Myosin heavy chain (MHC) composition (gel electrophoresis), fiber type distribution (immunohistochemistry), and fiber size were determined. Although there were no significant changes, each muscle showed trends towards adaptation.

Animals↗