Changes in the content of bile acids and lipids in human bile during head-down tilt hypokinesia and their correction

The spectrum of bile acids and bile lipids in men exposed to 120-day head-down tilt was investigated. The test subjects were subdivided in to four groups: group 1-bed rest per se, group 2-bed rest + exercise, group 3-bed rest + drugs normalizing calcium metabolism, and group 4-bed rest + exercise + drugs. It was anticipated that biliary concrements would primarily be formed in group 1 and 2 subjects. They showed a low level of bile acids and a high content of total Ca and cholesterol in the bile, which was more pronounced in the C portion (decrease of the cholate/cholesterol coefficient). Group 2 subjects displayed a modified synthetic function of the liver: prevalence of tauroconjugates in the bile (decrease of the ratio of glucoconjugates to tauroconjugates). Group 3 and 4 subjects showed a faster synthesis of bile acids in the liver and a lower content of total calcium and cholesterol in the bile, the latter being more distinct in group 4 subjects. Positive dynamics of these parameters is a factor responsible for a reduced lithogeny of the bile. However, the test subjects of these groups exhibited hazardous changes that may be responsible for concrement formation. This is indicated by a lower concentration of the lipid complex in the bile, possibly at the expense of a lower content of phospholipids. This emphasizes the necessity of further search for prophylactic procedures aimed at normalizing the synthetic function of the liver under hypokinetic conditions.     

Effect of a 30-day period of hypokinesia on various physiologic and biochemical indicators during maximal physical load

Exercise tolerance of test subjects who remained bed rested (Group A) and who exercised while being supine (Group B) was measured before and after 30-day head-down tilt (-8 degrees). Special attention was given to the parameters that characterize energy supply of working muscles. The data obtained after 30-day bed rest did not reveal any changes in the Group B subjects and showed the following changes in the Group A subjects: maximum oxygen consumption decreased by 10.1% (p less than 0.05), the time within which the anaerobic metabolism threshold was attained decreased by 17.2% (p less than 0.05), and lactate concentration at the workload end decreased by 24.7%, while the pyruvate concentration and the lactate/pyruvate ratio remained unchanged. The results indicate that prolonged aerobic workload after 30-day bed rest seems to be limited by functional changes in oxygen transport rather than by the factors associated with changes in energy supply of working muscles.     

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.     

Lipid peroxidation in the human blood during a 120-day period of anti-orthostatic hypokinesia

Time-course variations in the accumulation of endogenous products of lipid peroxidation and the state of antioxidative enzymes--superoxide dismutase and catalase--in blood of men exposed to antiorthostatic hypokinesia (-4.5 degrees) for 120 days were investigated. It was found that bed rest led to stimulation of lipid peroxidation which was measured as increased concentrations of lipid hydroperoxides and final products of lipid peroxidation in blood. Vitamin E and drugs with a specific metabolic action produced a normalizing effect on the content of products of lipid oxidative destruction. Special exercise regimens had a similar but less significant effect.     

Effect of hypoxia on water-electrolyte metabolism and human renal function with different degrees of motor activity]

It was demonstrated that a prolonged (24 days) bed rest at altitudes of 2200 m and 3200 m as well as at sea level was accompanied by an increased renal excretion of fluids and osmotically active substances, including electrolytes. Exercises done during bed rest indiced a smaller increase of the renal excretion of sodium and potassium. However, as bed rest continued the differences between the groups of test subjects disappeared. The levels of hypoxia and exercises used in the study proved inefficient to prevent changes in the fluid-electrolyte metabolism occurring during bed rest.     

Functional evaluation of the musculoskeletal system under an autonomous life support regimen based on data on blood biochemical indices

The functional state of the musculo-skeletal system of healthy male volunteers of three age groups (Group 1--19-21 years, n = 16; Group 2--25-43 years, n = 26; Group 3--48-59 years, n = 30) was evaluated. The subjects were kept in an enclosure for 30 days. Creatine phosphokinase (CPK), lactate dehydrogenase (LDH), alkaline phosphatase, aspartate aminotransferase (AAT), calcium, P1 were measured in blood. The test subjects of the three groups showed a decrease of CPK, LDH, AAT and creatinine. The correlation coefficient between the enzymes varied from 0.64 to 1.00. By the end of the study alkaline phosphatase increased in the Group 1 and 2 subjects and decreased in the Group 3 subjects. Calcium variations were less distinct. The Pi content declined significantly in the Group 3 subjects. Some of the Group 3 subjects who performed regular exercises during the study exhibited smaller decreases of CPK, LDH, AAT and greater stability of calcium and phosphorus.     

Effect of long-term hypokinesia on the serum lipid spectrum

The effect of 120-day head-down tilt on the lipid spectrum of blood serum was investigated. By thin-layer and gas liquid chromatography lipids (total lipids, phospholipids, cholesterol and its esters, nonesterified fatty acids, triglycerides) and higher fatty acids were identified. It was found that cholesterolemia increased at the expense of the ester bound fraction, phospholipids decreased drastically, the ratio of phospholipids to total cholesterol decreased, and triglyceridemia diminished. Until bed rest day 70 saturated fatty acids were predominant, with linoleic acid being deficient, and thereafter the relative content of unsaturated fatty acids increased. The above changes in the lipid spectrum can be considered as risk factors with respect to preclinical stages of atherosclerosis.     

Motor activity and the prevention of the sequelae of hypokinesia (according to tissue metabolic indices)

The content of protein, DNA and RNA was measured in rats that had been exposed to 90-day hypokinesia: hypokinesia alternating with unrestrained maintenance and hypokinesia combined with exercises (swimming). Adverse effects of hypokinesia on metabolism seemed to build up. Short-term passive rest was insufficient to make up deficiency in motor activity. The recovery of metabolic disorders after prolonged hypokinesia proceeded in a non-uniform and slow manner: most parameters did not return to the initial level within one month. During the first two weeks exercises produced effects similar to those of hypokinesia. By the 30th and 60th days they shower their normalizing effect on tissue metabolism. When developing work-rest cycles for the people who are exposed to partial hypokinesia during work and do exercises as a countermeasure against hypokinetic effects, biochemical analysis of blood (nonesterified fatty acids, acetone bodies, cholesterol, beta-lipoproteins, urea) and urine (potassium, calcium, creatinine) should be made to measure metabolic processes in tissues.     

Calf muscle area and strength changes after five weeks of horizontal bed rest

Nine male volunteers participated in a 10 week metabolic study in which subjects underwent 5 weeks of ambulatory control and 5 weeks of complete horizontal bed rest. Bed rest is a model commonly used to simulate space flight. The changes in muscle area and strength of the calf dorsiflexors and plantar flexors were measured before and after bed rest using magnetic resonance imaging (MRI) and a Cybex II dynamometer. The muscle area of the plantar flexors (gastrocnemius and soleus) decreased 12%, whereas the muscle area of the dorsiflexors was not significantly decreased. The maximal muscle strength of the plantar flexors decreased 26%; the muscle strength of the dorsiflexors was not significantly decreased. These results, which demonstrate differential muscle atrophy and a larger loss in strength relative to muscle area, have important implications in the development of exercise counter-measures to be implemented during space flight. The results also have implications for patients who have severe orthopaedic disorders and must be bed rested for long periods of time, and for persons who are voluntarily inactive (a large number of the elderly).     

Changes in serotonin and histamine levels in human blood after 370-day anti-orthostatic hypokinesia

Ten healthy men took part in a 360-day antiorthostatic hypokinesia study. They were subdivided into two equal groups that differed in terms of time when they started using counter-measures: Group A began exercising on the first day of exposure and Group B on bed rest day 120. As compared to the baseline, the test subjects showed a decrease of serotonin (Ser) and histamine (HA). The only exception was HA increase on bed rest day 50 in the Group A subjects. The difference in Ser and HA concentrations in Group A and B subjects was insignificant on bed rest days 110 through 350. On the 60th day after the study Ser and HA concentrations did not yet return to norm. These observations indicate that changes in the serotonin- and histaminergic systems cannot be compensated within the above period of time.     

Effect of hypokinesia on human nutritional status

In three series of experiments of 120, 49 and 180 days in duration 36 test subjects were exposed to clinostatic and antiorthostatic hypokinesia. Human requirements for various nutrients were defined under hypokinetic conditions. It was demonstrated that during bed rest exercises together with adequate nutrition and after bed rest certain nutrients can serve as efficient countermeasures against metabolic changes.     

Effects of resistance training during bed rest on the viscoelastic properties of tendon structures in the lower limb

The purpose of this study was to investigate the effects of resistance training on the tendon properties in knee extensors during 20 days of bed rest. Sixteen men were assigned to the resistance training group (BR-Tr) or the non-training, control group (BR-Con). Leg-press exercises were performed as five sets of 10 repetitions at 90% of maximum load daily for 20 days during bed rest. Before and after bed rest, the elongation of the tendon structures of the vastus lateralis muscle during isometric knee extension was determined using ultrasonography, while subjects performed ramp isometric contraction up to the voluntary maximum, followed by a ramp relaxation. The relationship between estimated muscle force ( F _m) and tendon elongation ( L ) was fitted to a linear regression curve, the slope of which was defined as stiffness. The hysteresis was calculated as the ratio of the area within the F _m– L loop to the area beneath the load portion of the curve. The stiffness decreased significantly after bed rest for BR-Con, but not for BR-Tr. Similarly, the hysteresis increased significantly after bed rest for BR-Con, but not for BR-Tr. These results suggested that the bed rest caused the stiffness of tendon structures to decrease and their hysteresis to increase, and that leg-press training prevents the deconditioning of the tendon structures in knee extensors.     

Responses of human skeletal muscle fibers to a 370-day antiorthostatic hypokinesis associated with physical exercise

Gastrocnemius muscle biopsies of 10 healthy volunteers, aged 27 to 44 years, who were exposed to head-down tilt (-8 degrees) for 370 days, were examined. The test subjects were subdivided into two equal groups that were assigned exercises of different type and workload. This prolonged bed rest caused atrophic changes in skeletal myofibers and decrease of their metabolic rate. Regular exercise produced a beneficial effect on the myofibers and reversed hypokinesia-induced changes but partially. The efficacy of the countermeasures depended, to a certain extent, on the time, when they were initiated, and the intensity, with which they were performed: the efficacy was higher and atrophic changes were delayed, if the subjects began exercising earlier and did it more actively.     

Effect of physical loads on lipid and carbohydrate metabolic indices in hypokinesis

Experiments on 140 white rats kept under hypokinetic conditions for 15, 30, 60 and 90 days showed a significant decrease of the glycogen content in the liver and skeletal muscles, acceleration of lipolysis in the adipose tissue, progressive increase of the content of nonesterified fatty acids, ketone bodies and cholesterol in the blood, decrease of the content of total lipids and increase of the cholesterol content in the skeletal muscles and liver. Hypokinetic rats exposed to exercises (swimming) also exhibited changes in carbohydrate and lipid metabolism; however the content of ketone bodies in the blood increased a little, the glycogen content in tissues decreased to a lesser extent, the cholesterol level in the and skeletal muscles increased only on the 15th day, remained at the control level at later stages and even decreased in the skeletal muscles. Thus, during an exposure to hypokinesia and its combination with exercises the role of lipids on the energy balance of the animal body increases. Exercises facilitate better utilization of lipids, thus delaying adverse effects of hypokinesia.     

Various individual features of human adaptation to altitude

Two groups of young healthy men--natives of lowlands who for one year lived and worked in chronic hypoxia (Group 1 at an altitude of 1680 m with PO2 = 120 mm Hg and Group 2 at an altitude of 3650 with PO2 = 90 mm Hg) were examined. It was found that after this prolonged exposure the subjects showed a higher sensitivity of the respiration system to hypoxia, an enhanced lung ventilation and circulation, a lower gas exchange and physical work capacity. The concentration of lactic acid at rest in the Group 2 subjects was 47% higher than in the Group 1 subjects. The lactate/pyruvate ratio in the Group 2 subjects increased by 46% thus indicating an enhanced rate of anaerobic processes. A higher deficiency of buffer bases, a lower concentration of bicarbonates in blood at rest and during exercise tests of the Group 2 subjects pointed to metabolic acidosis. The subjects with a higher rate of anaerobic metabolism in a low PO2 environment displayed a diminished sensitivity of the hypoxic stimulation of respiration, an increased tolerance to the very low PAO2 and a reduced work capacity in chronic hypoxia.     

Mismatch of F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and Tc-99m pertechnetate single photon emission computed tomography (SPECT) in a euthyroid multinodular goiter

Imaging results of F-18 fluorodeoxyglucose (FDG) PET/CT scanning and Tc-99m pertechnetate scintigraphy of the thyroid gland are described and compared with pathology in a patient who was followed after left nephrectomy for renal cell carcinoma diagnosed 10 years earlier. On F-18 FDG PET/CT scanning, a multinodular struma with increased localized F-18 FDG uptake in 4 nodules was seen. Two nodules with increased glucose metabolism appeared normal on Tc-99m pertechnetate scintigraphy. Pathology indicated hyperplastic nodules. High focal F-18 FDG uptake was also seen in a lesion that corresponded with a "cold" nodule on Tc-99m pertechnetate scintigraphy, suggesting malignant disease. However, pathology revealed hyperplastic nodules with a background of aspecific lymphocytic thyroiditis. A fourth nodule with increased F-18 FDG uptake appeared mixed ("cold"/"hot") on Tc-99m pertechnetate scintigraphy. On pathology, a well-differentiated follicular carcinoma was found. These findings, in a single patient, illustrate the wide spectrum of matched and mismatched F-18 FDG and Tc-99m pertechnetate thyroid uptake along with their variable pathologic correlates.     

Intensive cycle training with artificial gravity maintains muscle size during bed rest

INTRODUCTION: The present study aimed to investigate the effect of intensive cycle training with short-arm centrifuge-induced hypergravity during bed rest on muscle size and function. METHODS: This study involved 10 healthy men who were divided into 2 groups: a countermeasure group, BR-CM (n = 5); and a control group, BR-Cont (n = 5). The BR-CM subjects partook in intensive cycle training (to 90% of maximum HR) with short-arm centrifuge-induced artificial gravity on alternate days during 20-d bed rest. Muscle volume of the thigh and maximum voluntary contraction (MVC) during isometric knee extensions was measured before and after bed rest. Muscle functional magnetic resonance imaging (mfMRI) and electromyogram (EMG) of the quadriceps femoris were obtained during submaximal knee extension exercises at a load of 30% MVC. RESULTS: The volume of the total thigh muscles was maintained in the BR-CM group (-1%), whereas it was not in the BR-Cont group (-9%, p < 0.05). MVC decreased in the BR-CM (7%) and BR-Cont groups (23%). EMG activity in the BR-CM group after bed rest was significantly lower than that of before; however, no significant change was found in the BR-Cont group. There were no significant changes in the resting and exercised mfMRI signals in either the BR-CM or BR-Cont groups. CONCLUSION: These results suggest that intensive cycle training with hypergravity maintained the size of human skeletal muscles during bed rest.     

Importance of a nutritional factor in the changes in carbohydrate and lipid metabolism in a human under neuro-emotional stress

Two experiments were performed on 16 test subjects (13 men and 3 women) to study stress-effects on the blood content of sugar and cholesterol. The test subjects were given a nutritionally balanced diet of canned food-stuffs. The caloric value of the diet was adequate to energy expenditures. In the first experiment, the test subjects were also given vitamin E, nicotinic acid and other vitamins constituting the polyvitamin complex Aerovit. In the second experiment, they were additionally supplemented with calcium and potassium salts, glucose and phosphatid concentrate. The stress-agent was a test in the rotating chair in the first experiment and a psychologic test (mental work within a limited period of time to reach success or failure) in the second experiment. The content of sugar and cholesterol before and after the stress-effects did not differ significantly. This can be attributed to the prophylactic effect of the nutritional factor on carbohydrate and lipid metabolism in an emotionally stressed man.     

The red blood system in men during long-term head-down bed rest]

Red blood was analyzed in six 25 to 40 yr. old male volunteers in a 120-d head-down bedrest (HDBR) study. The hematological investigation included morphological analyses (erythrocyte count and hemoglobin), and determination of iron turnover, erythrocyte IgA, IgG and IgM, metabolism, lipids and phospholipids, and lipid peroxidation rate (LPO). At the beginning of HDBR (day 7), the erythrocyte count and hemoglobin content were found increased w/o any visible changes in the other parameters. Further exposure to HDBR (days 50-100) resulted in modification of intracellular metabolism in erythrocytes, increases in serum iron, and serum and erythrocyte ferritin. On HDBR days 50 and 100, and post-HDBR day 9, cholesterol was increased, LPO intensified and antioxidant activities inhibited, which suggested destabilization of the cell membrane. Hematological shifts in the bedrested volunteers were of the type and pattern similar to those in cosmonauts who fulfilled extended space missions.     

Features of humoral regulation of metabolism during modelling of space flight factors

Hormonal regulation of metabolism was investigated in test subjects of three age groups: group 1 included test subjects of 41-50 years old, group 2 test subjects of 50-57 years old, and group 3 test subjects of 26-33 years old. Test subjects from groups 1 and 2 were exposed to head down tilt (-8 degrees) as well as linear acceleration of 3 GZ for 1 min and exercises of 450-1050 kgm before and after the tilt test. Group 3 test subjects were exposed to neuro-emotional stress before, during and after the head-down test. Exposure to head-down tilt, acceleration and exercises caused adaptive changes in humoral regulation of metabolism in the test subjects of groups 1 and 2. Food supplements given to group 3 test subjects produced a normalizing effect on humoral regulation of metabolism.