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At least 703 records · Page 39Linked to original sources
PubMed1987

Fluid shifts in weightlessness.

Studies of leg volumes in space by multiple girth measurements showed reductions of 1.9 L (12.8% of leg volume) with 1.1 L from the non-dominant leg on Skylab 4. On landing, 65% of postflight leg volume increase was complete at 1.5 h. Measurement of the dominant leg during the equivalent period on Shuttle showed a mean loss of 0.9 L which was 90% complete at 150 min. Postflight increases were 87% complete at 1.5 h postlanding. Mass measurements during and after Skylab 4 showed a loss of 2.5 kg over the first 4 d on-orbit with a gain of 2.7 kg over the first 4 d of recovery. These changes are assumed to be tissue fluids secondary to changes in hydrostatic pressures and are much greater than those seen in bed rest. Rate and magnitude of inflight and postflight changes have significant operational impact.

Arm↗
PubMedDate not supplied

[Effect of weightlessness on the DNA replicative function of rat hepatocytes].

The replicative function of DNA of liver cells of rats exposed to strong stress-effects, e.g. suspension for 2.5 hours a day for 6 days, decreased. The rat studies onboard biosatellites of the Cosmos series have demonstrated that a prolonged exposure to microgravity (up to 22 days) is not a stressogenic factor for the DNA synthetic system of liver cells. The transition from 1 g to microgravity cannot be viewed as a strong stressor either, because the rate of DNA synthesis in liver cells at an early period of adaptation to microgravity remains within the normal limits. However, this parameter decreases significantly during the recovery period following 18-22-day flights. Therefore changes in cellular processes related to the DNA replicating function in hepatocytes should be expected to occur in the postflight period rather than at an early period of adaptation to microgravity.

Animals↗
PubMedDate not supplied

[Effect of weightlessness on the skeletal development of the rat fetus].

The size of the ossified areas of skeletal bones of fetuses of white rats flown onboard Cosmos-1514 during their pregnancy days 13 to 18 was compared with that of synchronous and vivarium controls. The effect of zero-g on the pregnant animals in the course of an active formation of fetal bones involved a distinct (13-17%) arrest of the development of nearly every area of the fetal skeleton. The signs of the arrest development were more manifest in less mature skeletal structures. Since the Ca2 content was identical in the flight and control rats, it can be concluded that the inhibited ossification of the flight fetuses was produced by the impairment of mechanisms controlling Ca2+ incorporation into the growing skeleton. The ossified areas in the skeleton of the flight newborns were significantly larger than those of the synchronous and vivarium controls. This means that during the readaptation period (pregnancy days 18 to 23) the inhibited ossification of the fetal skeleton was completely compensated and that the flight newborns (i. e. the rats whose prenatal development occurred in part in zero-g) were ahead of the controls with respect to the ossification rate.

Animals↗
PubMedDate not supplied

[Quantitative study of the osteoblasts and osteoclasts in the bones of rats during the simulation of weightlessness].

Tibia and vertebrae of rats exposed to hypokinesia or head-down suspension were investigated by quantitative histomorphometry. It was found that 35- and 60-day hypokinesia as well as 35-day suspension caused osteoporosis in the tibial and vertebral spongiosa. The development of osteoporosis was accompanied by a significant reduction in the number of osteoblasts in the primary spongiosa of tibia and vertebrae whereas no noticeable changes in osteoclasts were observed either in hypokinetic or suspended rats. The only exception was lumbar vertebrae in which the amount of osteoclasts decreased as a result of 60-day hypokinesia. It is assumed that the reduction in the number and activity of osteoblasts plays the major part in the development of osteoporosis during hypokinesia and suspension.

Animals↗
PubMedDate not supplied

[Determining the Bacillus subtilis biomass increase coefficient in weightlessness].

This paper presents the results of a microbiological experiment carried out by the Soviet and GDR scientists onboard Salyut-6. The experiment was performed using a Bacillus subtilis suspension in the Jena unit. The purpose of the experiment was to study the time-course variations of the cell biomass increase in zero-g. The cell culture development was measured with respect to the utilization rate of glucose or casein hydrolyzate in the nutrient medium and the rate of protein accumulation in cells. It has been shown that the rate of biomass increment in zero-g lags behind the 1 g level. It can be concluded that the decreased metabolic activity of bacterial cells in zero-g is associated with changes in the cell population distribution and physicochemical parameters of the nutrient medium.

Bacillus subtilis↗
PubMed1986

Effect of simulated weightlessness on exercise-induced anaerobic threshold.

Ventilation (VE), CO2 output (VCO2), oxygen uptake (VO2), respiratory exchange ratio (R), and the ventilatory equivalents for VO2 and VCO2 were measured during graded exercise before and after 10 d of continuous bed rest (BR) in the -6 degrees head-down position to determine the effect of deconditioning on the anaerobic threshold (AT), i.e., the highest workrate or VO2 which was achieved without evidence of lactic acidosis, as judged from the profile of ventilatory and gas exchange responses. Ten healthy male subjects performed a supine graded cycle ergometer test before (pre) and after (post) BR which consisted of 4 min of unloaded pedaling at 60 rpm followed by an increased workrate of 15 W X min-1 until volitional fatigue (max). VE, VCO2, VO2, R, VE/VO2 and VE/VCO2 were measured every 30 s and used collectively to identify the AT. Plasma (PV) and blood (BV) volumes were measured pre- and post-BR by T-1824. Following BR, VO2max decreased from 2.42 +/- 0.17 to 2.25 +/- 0.13 L X min-1 (7.0%, p less than 0.05). BR significantly (p less than 0.05) reduced the AT from 1.26 +/- 0.09 to 0.95 +/- 0.05 L X min-1 VO2; from 52.2 +/- 2.0 to 42.6 +/- 1.6% VO2max; and from 93 +/- 9 to 65 +/- 6 W. A correlation coefficient (r) of -0.11 (NS) was found between the change in VO2max and change in AT. A decrease in BV of 8.8% (p less than 0.05) was due to the 11.0% reduction in PV; red cell volume remained constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMedDate not supplied

[Forced expiration indices of the healthy human being in simulated weightlessness].

Lung volumes and forced expiratory volumes during 3-hour water immersion as well as in the upright and supine positions were measured. Water immersion up to the neck decreased the functional residual capacity, peak and maximum velocities of air flows during inspiration and expiration with various lung volumes and increased the forced expiratory time and pulmonary time constant. These changes seem to be produced by a higher inelastic resistance as well as by additional hydrostatic pressure upon the chest and abdomen. During the transfer from the upright to the supine position these changes were identical but of smaller magnitude.

Adult↗