Search

In a 105-day experiment simulating crew life in a space exploration vehicle, shifts in the nutritional status were assessed in 6 test subjects differing in the body mass index, basal metabolism, attitude to the diet, physical exercise and workload. Results of the investigation showed that because of the hard physical work the nutritional status of test subjects was described by more intensive basal metabolism, elevated metabolism of carbohydrates and lipids, and their increased mobilization from depots. Food ration, though it was sufficient to sustain health and fairly high performance, failed to meet fully individual taste preferences and energy needs for physical activities. The heavy workloads required mobilization of lipids from adipose depots, and a decrease of the hepatic detoxification and metabolic capacities. Self-limitation of eating protein-rich desserts led to a relative deficiency of protein intake. These faults of the diet were the reason why 4 out of 6 test subjects reduced their basal metabolism and lost body mass. Recovery of metabolism and slowdown of the body mass loss were achieved by supplementing meals with available protein-containing products.

Two groups of male volunteers for 4-day dry immersion with and w/o countermeasures (support load imitator (SLI) or high-frequency electrostimulator) underwent ultrasonic investigation (USI) of the liver, gastroduodenal organs and vessels, and blood biochemical analysis. Two other groups of volunteers performed the 13C-methacetin breath test (13C-MBT) to study the effects of immersion and SLI on the liver detox activity and metabolic capacity. In immersion, USI diagnosed slowdown of blood flow along the hepatic vein and signs of plethora in the abdominal venous system. In addition, immersion was accompanied by increases in blood pepsinogen, pancreatic amylase, total bilirubin, the "indirect" fraction specifically, insulin and C-peptide. 13C-MBT detected deceleration of 13C-methacetin inactivation and diminution of the liver metabolic capacity. Administration of the countermeasures did not improve the ultrasonic image of hemodynamic alterations in the liver and abdomen significantly. High-frequency electrostimulation cancelled out changes in all biochemical parameters except C-peptide; SLI was favorable to recovery of pepsinogen and amylase baseline values only. Besides, the SLI wearing prevented loss of the 13C-methacetin inactivation rate but was not effective enough against diminution of the hepatic metabolic capacity.

Ultrasonic investigations of 8 male volunteers for bed rest at -15 degrees showed plethora in peritoneal veins and slow blood flow through the liver with no effect on biochemical parameters. Breath test with 100 mg of 13C-methacetine (MBT) pointed to diminution of the metabolic capacity and decline of the hepatic detoxification activity due to the hemodynamic effects. MBT can be used as a nonintrusive method for diagnosing functional changes in the liver induced by hemodynamic developments in microgravity and other situations triggering similar hemodynamic mechanisms.

The research excretory and incretory of activity of a stomach and pancreas is carried out at astronauts in the early period after completion of space flights of various duration. It is shown, that the increase of the contents of gastric and pancreatic enzymes and hormones (insulin and C-peptide) in blood reflects increased excretory and incretory activity of organs of gastroduodenal area which arises in weightlessness. The complex of countermeasures, which prevent ingress of subjects, infected by Helicobacter pylori in space flight crew, excluded participation of this microorganism in the mechanism of increase of secretory activity of a stomach. The absence of interrelation between increase of secretory activity of gastroduodenal area organs and space flights' duration has allowed to exclude the hypokinetic mechanism which determined by duration of stay in weightlessness. It was shown that after the end of space flights the increase ofbasal excretory activity of organs of gastroduodenal area occurs simultaneously with increase of a fasting insulin secretion. The changes in gastroduodenal area organs revealed after space flights were are compared to similar changes received in ground-based experiments, simulating hemodynamic reorganization in venous system of abdominal cavity, arising in weightlessness. The conclusion is made, that the basic mechanism of changes of a functional condition of digestive system in space flights, is determined by reorganization venous hemodynamic in abdominal cavity organs reproduced in ground experiments. Increase insulin and C-peptide after space flights are considered as hormonal component of this hemodynamic mechanism.

The clinical significance and potential of respiratory tests for diagnostics of Helicobacter pylori infection was estimated in 76 patients. Results of 13C and 14C-urease tests were in especially good agreement with those oh histological studies. The 13C-urease test should be preferred in the examination of both in-patients and out-patients whereas NH3-urease test is much inferior to 13C and 14C-urease tests in terms of informative value.

The radioisotope researches (RR) ofcholeresis function of a liver, the ultrasonic researches (USR) of a liver, the contractile gallbladder function (GF) and the gastroduodenoscopy (GDS) were carried out at 8 men after 24 hour duration of stay in antiorthostatic position--12 degrees (AOP), simulating arising in weightlessness of hemodynamics changes in abdominal cavity. The dynamic difficulty of venous blood outflow from a liver at simulated in antiorthostatic position changes of activation choleresis on an empty stomach was produced, by increase of a zone central perfusion of a liver parenchyma, biliary ductules dilation and of a gallbladder reduction, and were accompanied by choleresis in duodenum. The activation choleresis in a liver was accompanied by of reduction of the area of radioactive marker distribution in a liver, the decrease of hepatocytes metabolic activity and concentration function ofbiliary excretion system. Specificity of a functional condition of a liver within AOP reflects reaction caused by plethoric changes induced by body position, which is negative to vector of gravity. The mechanism of the revealed changes includes occurrence dynamic venous plethora in a liver, centralization hepatic blood flow with activation choleresis activity against the background tissual blood flow depletion in peripheral zones, reduction of hepatocytes metabolic activity and concentration function biliary excretion system.

Six male volunteers for dry immersion (DI) modeling the microgravity effects on human organism were subjects in the GI evacuatory function investigation. The investigation was aimed to evaluate liquid food evacuation from the stomach (13C-acetate test) and time of chymus orocecal transit (H2-inulin test). The 13C-acetate test did not reveal changes in stomach evacuatory activity after 4 days in DI. The H2-inulin test demonstrated shortening of chymus transit along the small intestine and extension of chymus passage from the ileum to cecum. Subsequent reduction of inulin metabolism in the large intestine suggested inhibited passage of these GI segments. The results showed that stability of liquid evacuation from the stomach and acceleration of chymus transit along the small intestine hinder evacuation of the large intestine content which is the primary cause for inhibition of GI evacuatory activity in DI.

Determination of the stomach secretory activity and ultrasonic investigation of the gastroduodenal organs and vessels were performed in test-subjects tilted at -12 degrees and -15 degrees. Short HDT(12-24 hrs.) as a hypokinesia factor was minimized which caused enlargement of the parenchymatous and thickening of walls of the hollow organs. Increased filling of the abdominal veins was paralleled by rise in pepsinogen levels in blood and urine, and increase in the intravitelline content in fasting subjects. Elevated tone of the pylorus and retarded evacuation from the stomach indicated active hydrochloric acid secretion. Concurrently, bile and pancreas juices were secreted more profusely and intestinal content in the duodenum increased. It was shown that modeled increase of abdominal vein filling stimulates secretion as by fasting stomach so by the liver and pancreas.

Functioning of the digestive system was investigated in 10 volunteers for 7-day dry immersion. The experimental conditions were found to raise secretory activities of the stomach, pancreas and liver, and to increase spectral indices of the GI electrical activity on the background of a higher than usual insular secretion and lowered gastrin secretion. The elevated GI electrical activities and changes in their ratios were a fallout of the increased gastric secretion and elevated intestines tone in fasting test-subjects and displayed a close similarity to the changes induced by caffeine stimulation, long-term bed rest or space flight.

The paper deals with type of changes in gastroduodenal organs associated with hypersecretion of the stomach induced by simulation of some effects of microgravity. Subjects in the investigation were 13 males volunteered for a 4-month bedrest study. Biochemical changes in blood, urine and gastric juices were analyzed in comparison with ultrasonic images of the gastroduodenum organs and data of stomach and duodenum endoscopy. The investigations showed increased blood and urine levels of pepsinogen indicative of gastric hypersecretion characterized by more intensive secretion of gastric juices, lowered pH, elevated pyloric tone, activation of duodenal secretion and cholepoiesis. Gastric hypersecretion was concomittant to the development of plethora in the abdominal veins. The highest gastric secretion was observed after two months of bed rest. Further bed rest extension was marked by fading of the signs of hypersecretion by the stomach and appearance of some signs of chronic stress. Our results expand the knowledge of changes in the gastroduodenal organs during bed rest, space flights and other conditions provocative of the hypersecretory transformation of the stomach.

Ultrasonic investigations of the abdominal organs and splanchnic veins were performed in essentially healthy subjects tilted at 12 degrees and 15 degrees for the period of 12 hrs. and 24 hrs. Tilting produced typical redistribution of venous blood and body liquids toward the cranial end. In its turn, blood redistribution caused excessive venous plethora and abdominal stasis. These were succeeded by expansion of large veins in the abdomen, enlargement of parenchymal organs and contraction of their echogenicity, and thickening of the hollow organs walls. Changes in the gastrointestinal functions before meal included elevated gastric, hepatic and pancreatic secretion, and an increased amount of intestinal content. The investigations demonstrated that stasis of the splanchnic veins altered functioning of the digestive organs in tilted human subjects.

Experimental results were compared with data of cutaneous electro-gastroenterography and USI of the gastrointestinal tract in human subjects at different tilt angles and after different periods of tilting. It was shown that increased GIT electrical activity in tilted subjects before meal is representative of increasing intracavetary contents of the stomach and small intestine. More intensive electrical activity results from elevation of the GIT tone and peristalsis. Extension of tilt duration raises GIT tone and peristalsis and, consequently, stimulates the GIT electrical activity. Further increase of the tilt angle suppresses evacuation and, therefore, the electrical activity Analysis of the results allows conclusion that increased parameters of the total energy of GIT electrical potentials are reflective of elevated tone of GIT walls, whereas elongation of the potential peaks envelope implies activation of peristalsis.

Prevention and treatment of digestive dysfunction due to hostile environments can be effected by prebiotics i.e. carbohydrates undigestible by the upper GI tract but favorable to selective stimulation of the growth and metabolizing activity of nonpathogenic commensal microflora. There are empiric evidence of the prebiotics positive action on GI cells and tissues, large intestine micro-ecology, mineral and lipid metabolism, and the immune status of humans and animals. Therefore, there is good reason to seek to develop brand new foods that would contain prebiotics, and recommendations on their use in common and extraordinary conditions.

In 62 normal males and females gastrointestinal (GI) electrical activity was evaluated before and after standard breakfast with the method of epicutaneous electrogastroenterography (EGEG) with the use of AgCl electrodes and original hard- and software "Gastroenterograph" developed by the authors. Spectral analysis (SA) of GI electrical potentials enabled quantification of the electrical activity of the stomach, duodenum, jejunum, ileum and the whole of the small intestine. The stomach and the small intestine were main contributors to the total GI electrical activity during fasting. Changes in the functional activity of the digestive system after the meal were characterized by increases in selected SA parameters (length of the spectral curve and area underneath), dissociation between their values and redistribution of ratios in different GI segments.

Data on the hypokinesia-induced transformation of the glycemic profile and ultrasonic changes in the pancreas structure are presented. The AOH study gave further evidence of transforming glycemic curves. Moreover, increased sizes of tail and head of the pancreas and a decrease in its echogeneity were observed in all test-subjects. Structural changes in the pancreas were confirmed by biochemical investigations which revealed increased levels of blood enzymes and activation of insulin secretion. Increases in the liver size, thickness of the wall of the stomach, diameter of the splenic vein were indicative of progressing venous plethora in the portal vein system. It was shown that venous plethora are the main cause for changes in the upper GI, and in the pancreas state in particular, which can be qualified as dysfunctional. These structural changes in the pancreas could suppress its functional activity manifested by increases in blood enzymes and hormones and transformation of the glycemic profile during the glucose load.

Change in functional activity of digestive system in space flight usually is associated with phenomenon of hypokinesia which takes place in microgravity. However, it is marked that the reorganization of a gastrointestinal tract in space flight occurs on a background of the phenomenon of venous plethora in abdominal cavity, which can also result in changes of functional activity in organs of digestive system. Insignificant amount of studies of venous plethora in abdominal cavity carried out in conditions of space flight does not allow to create a complete picture of this phenomenon. Hemodynamical changes comparable to microgravity are well-simulated in conditions of a long-term antiorthostatic hypokinesia (AH)--bed-rest in a head-down tilt. The present research was performed with the aim to study venous plethora in abdominal cavity in conditions of long-term AH.

The effect of three exposures to Coriolis acceleration on the frequency and amplitude of fasting stomach contractions was investigated in 6 resistant and 16 susceptible to motion sickness test subjects. After tests all of them underwent gastroduodenoscopy and 4 subjects from each group were subjected to echography to measure gall bladder contractility in response to glucose-milk loads. After tests the motor activity of the stomach increased slightly in resistant subjects due to an increase of the amplitude and a slight decrease of biopotential frequency. During gastroscopy antral and pyloric sphincters were closed. In the stomach there was an insignificant amount of contents without gall. In the susceptible group, the motor activity was, on the contrary, inhibited due to a significant decline of the wave amplitude and frequency (by 40% and 11%, respectively). In the stomach, one or both sphincters were widely open; it also contained a large amount of gastric juice and gall. In 36% of susceptible and 17% resistant subjects, diaphragmatic hernia (at the esophageal opening) was found. Ultrasonic examination of the gall bladder showed that susceptible subjects developed its faster and stronger contraction when compared to resistant subject in response to glucose-milk loading. This pointed to a more prolonged duration of the gall excretion phase. Reactive changes of the gastroduodenal zone in response to motion tests facilitated duodenal-gastric reflux and major gastrointestinal symptoms of motion sickness.

On mission days 216-219 two crewmembers collected urine and recorded their food and water consumption during three days on end. The cosmonaut-physician withdrew blood samples from the vein and finger. In addition, he made venipuncture to himself and drew blood. Urine and blood samples were frozen and returned to the ground for analysis. In spite of individual variations of each cosmonaut, they all showed a trend for water and sodium retention which was provided by adequate hormonal rearrangement, i. e. increased production of ADH and aldosterone. No disorders in calcium and phosphorus metabolism were seen. Immediately postflight the cosmonauts displayed typical changes in fluid-electrolyte balance and renal function that suggested body dehydration and adjustment to Earth's gravity.

Changes in ACTH, cortisol, beta-endorphin have been investigated during vestibulo-vegetative syndrome (VVS) and injections of dalargin (leu-enkephalin analog) and nalorphine (agonist-antagonist of opioid receptors) in 9 volunteers with low level vestibulo-vegetative stability. Cumulative coriolis acceleration test during rotations on a special chair was used for VVS modelling. Dalargin (1-4 mg), nalorphine (5 mg) and placebo (NaCl solution) were injected intravenously 5-15 min before rotation. A significant increase in ACTH, cortisol and beta-endorphin plasma levels has been observed. Mean positive linear correlation (r greater than +0.6) between ACTH and beta-endorphin and ACTH and cortisol was noted immediately after the test only when dalargin was injected. It is suggested that in VVS there develops a hormonal conflict, i. e. an adequate hormonal release is disturbed.

During 30 days rats were centrifuged at 1.1 and 2.0 G. On centrifugation day 30 the rats showed body mass losses, decrease of plasma ACTH, activation of the renin-angiotensin-aldosterone system (RAAS) and ultrastructural changes in the mossy fiber terminals in the nodulus cortex which were indicative of the state of excitation (at 1.1 G) or excess excitation (at 2.0 G) in the system of the utriculus receptor cell and vestibular ganglion neuron (RCN). On the 2nd day after centrifugation the ultrastructural changes in the terminals pointed to a lower activity of the RCN system which was below the physiological norm. As compared to centrifugation day 30, the RAAS became more active on the 2nd day of recovery. On the 7th day of recovery (after centrifugation at 1.1 G) the RCN ultrastructure, RAAS and ACTH concentrations returned to the normal. The general trends of the RAAS and RCN changes seen on the 2nd day of recovery and identified by other authors at an acute stage of adaptation to microgravity suggest that the data obtained on the 2nd day of recovery may be used to analyze certain effects which develop during an acute stage of adaptation to microgravity in mammalian organs and systems responsible for the perception of modified gravity and their adaptation to a new level of gravity.

The emotional stress simulated by examinations taken by medical students led to a decrease of sodium concentration in blood. This was a result of a simultaneous increase of mineralocorticoids and a decrease of glucocorticoids responsible for sodium concentration in blood. Both inhibition of glucocorticoids and stimulation of mineralocorticoids were associated with a high activity of plasma renin and a low concentration of adrenocorticotropic hormone.

Biochemical analysis of blood of rats sacrificed 4 to 8 hours after Cosmos-1667 flight revealed a significant increase of corticosterone, decrease of 11-dehydroxycortisol, testosterone, total and bound thyroxine, and increase of glucose, phosphate, creatinine, alanine aminotransferase and total antioxidative activity. Changes in hormonal concentrations, glucose content and stimulation of antioxidant defense system were associated with a moderate gravitational stress. Increases in the creatinine and inorganic phosphate concentrations can be viewed as specific effects of microgravity related to musculo-skeletal or fluid-electrolyte changes.

After short-term flights renal excretion of aldosterone increased, thus suggesting its enhanced production and metabolism. An adequate increase of aldosterone synthesis was accompanied by an increase of its concentration in blood. An inadequate activation of mineralocorticoids manifested as a lower concentration of blood aldosterone and a greater excretion of aldosterone in the urine. These differences in the mineralocorticoid activity were determined by the renin-angiotensin system whose activity was associated not only with fluid-electrolyte metabolism but also with changes in the concentration of cyclic nucleotides and prostaglandins that reflect the vascular tone and sympatho-adrenal activity. An increased activity of the renin-angiotensin system seen in most cosmonauts at an acute stage of readaptation was correlated with a higher concentration of cAMP and a lower concentration of depressor prostaglandins. The activity of the renin-angiotensin system declined in parallel with the decrease of the blood content of cAMP.

Cortisol, insulin, somatotropin, thyreotropin, thyroxine, triiodothyronine, testosterone, aldosterone, c-AMP, c-GMP, prostaglandins (PGF1-x, PGF2-x, PGA + E), and renin concentrations in serum or plasma of the venous blood of the third international crew of the scientific orbital complex of "Soyuz 29 - Salyut 6 - Soyuz 31" were determined following the 7-day space flight. The increased activity of the renin-angiotensin-aldosterone system before the flight as well as variations in the pressor/depressor prostaglandin ratios indicate an increased strain during the pre-flight period. During the first stage of the post-flight period some parameters were changed due to the landing process and the returning to earth gravity. The associated physical load and the onset of reactions for enhancement of the orthostatic tolerance resulted in an increase of cyclic nucleotid and thyroxine concentrations. The relatively higher levels of the pressor PGs of group F in comparison with the prostaglandins A + E could be evaluated as a compensatory reaction for enhancement of the orthostatic tolerance. The cortisol and STH concentrations increased with growing motor activity. The variations seen after the 7-day space flight were essentially within the reference areas. It may be assumed that the readaptation was not yet totally accomplished by the 8th day after landing.

The thyroid and parathyroid glands of 65 Wistar rats centrifuged for 30 days at 1.1 and 2.0 G were examined histologically and biochemically. The centrifugation led to a higher activity to C-cells, an increased rate of thyro-calcitonin (TCT) synthesis and excretion, i.e. C-cell degranulation, and a significant (two-fold) increase of TCT in plasma. The stimulation effect of the TCT-producing system persisted during 7-post-rotation days and was very distinct in the animals exposed to 2.0 G. There were no morphological changes in the parathyroid glands or in the PTH concentration in the plasma.

The rats exposed to prolonged hypokinesia showed hypocalciemia, lower PTH and higher calcitonin concentrations in the serum, decreased calcium absorption in the small intestine, and a trend toward nephro- and arteriocalcinosis. Prophylactic administration of 24,25-hydroxy D3. 1,25-hydroxy D3 and their combinations enhanced calcium absorption and alleviated hypocalciemia. The changes in the hormonal regulation of calcium homeostasis can be viewed as a factor responsible for calcium metabolic disorders associated with hypokinesia.