A comparative analysis of the excretory and incretory activity of the stomach and pancreas in astronauts soon after completion of space flights of various durations was performed. An increase in the fasting activity of gastric and pancreatic enzymes and hormones (insulin and C-peptide) in blood, reflecting the increased excretory and incretory activity of organs of the gastroduodenal region developing in microgravity, was demonstrated. The absence of subjects infected with Helicobacter pylori in the space flight crew excluded the involvement of this microorganism in the mechanism underlying the increase in the gastric secretory activity. The absence of correlation between the increase in the secretory activity of organs of the gastroduodenal region and the duration of the space flight allowed us to rule out the hypokinetic mechanism, which is associated with the duration of exposure to microgravity. It was concluded that the main mechanism underlying the changes in the functional state of the digestive system in space flight may be determined by the rearrangement of the venous hemodynamics of organs of the abdominal cavity, unrelated to the duration of exposure to microgravity. It was shown that, after completion of space flights and in ground-based experiments simulating the hemodynamic rearrangement occurring in microgravity, the increase in the basal excretory activity of gastroduodenal organs was not caused by gastrin secretion and occurred simultaneously with an increase in the secretion of insulin, which is considered as a putative hormonal component of the hemodynamic mechanism.
Research Containing: Human Research
Heart rate variability during centrifugation in astronauts prior to and after long duration spaceflight: Preliminary data
Spaceflight is known to induce vestibular and cardiovascular deconditioning. The current ESA SPIN project conducts research on vestibular and cardiovascular deconditioning after long duration spaceflight. Hereto, vestibular function and cardiovascular parameters are evaluated during centrifugation and during a tilt test in astronauts prior to and after spaceflight. The experiments are conducted using the ‘Visual and Vestibular Investigation System’. During rotation, cardiovascular and breathing parameters are recorded by means of the ‘Lifeshirt® system’ (Vivonoetics). The current analysis focuses on the cardio-respiratory response during 2 consecutive centrifugation runs, a counter clockwise (CCW) and a clockwise (CW). The RR-interval recorded postflight during the second CW rotation decreased significantly compared to the preflight data. No significant effects were observed on the parameters (amplitude, marker of vagal activity, and phase) of the respiratory sinus arrhythmia (RSA). However, the time of respiration and the amplitude of the RSA were correlated. Our preliminary results suggest a postflight recovery problem of the sympathetic nervous system after activation and show that the respiration has a large influence on the RSA amplitude.
TL dose measurements on board the Russian segment of the ISS by the “Pille” system during Expedition-8, -9 and -10
The “Pille-MKS” thermoluminescent (TL) dosimeter system developed by the KFKI Atomic Energy Research Institute (KFKI AEKI) and BL-Electronics, consisting of 10 CaSO 4 :Dy bulb dosimeters and a compact reader, has been continuously operating on board the International Space Station (ISS) since October 2003. The dosimeter system is utilized for routine and extravehicular activity (EVA) individual dosimetry of astronauts/cosmonauts as part of the service system as well as for on board experiments, and is operated by the Institute for Biomedical Problems (IBMP). The system is unique in that it regularly provides accurate dose data right on board the space station, a feature that became increasingly important during the suspension of the Space Shuttle flights. Seven dosimeters are located at different places of the Russian segment of the ISS and are read out once a month. Two of these dosimeters are dedicated to EVAs and one is kept in the reader and will be read out automatically every 90 min. During coronal mass ejections impacting Earth some of the dosimeters serve for individual monitoring of the astronauts with readouts once or twice every day. In this paper we report the results of dosimetric measurements made on board the ISS during Expedition-8, -9 and -10 using the “Pille” portable thermoluminescent detector (TLD) system and we compare them with our previous measurements on different space stations.
Two recent reports have indicated increased arterial stiffness in predominantly male astronauts returning from short- and long-duration missions. These results suggesting reduced arterial distensibility have widespread health implications. In addition to cushioning against the high pulsatile pressures from reaching the microcirculation and minimizing left ventricular work, the elastic nature of the aorta and carotid arteries is important for ensuring adequate coronary perfusion and for baroreflex-mediated regulation of sympathetic activity. The altered fluid distribution associated with microgravity affects arterial distending pressures, and can acutely decrease functional distensibility and potentially stimulate processes involved with vascular remodelling. PURPOSE: We are currently testing the hypothesis that long-duration exposure to microgravity is associated with reduced common carotid artery (CCA) distensibility on return to earth. METHODOLOGY: The first three participants included one man and two women. Each astronaut underwent a comprehensive vascular assessment before launch and one day after return to earth following six months aboard the International Space Station. Distensibility was assessed by ultrasonic imaging (M-mode) of the right CCA to examine rhythmic changes in vessel diameter, while simultaneously holding a pressure transducer on the left CCA. RESULTS: Contrary to our hypothesis, long duration exposure to microgravity was not associated with a reduction in distensibility (post-flight vs. pre-flight; 0.006 mmHg-1 vs. 0.004 mmHg-1). In addition, changes in secondary indicators of arterial stiffness, including carotid-ankle pulse wave transit time (PWTT) and carotid pulse pressure (cPP), were not indicative of arterial stiffening following spaceflight (PWTT: 151 ms vs. 138 ms; cPP: 48 mmHg vs. 60 mmHg). The likelihood of structural adaptation within these central arteries is not ruled out as noted by a small, but consistent increase in the diastolic cross-sectional area of the CCA lumen (0.27 cm2 vs. 0.25 cm2). CONCLUSIONS: The inability to detect signs of arterial stiffening following exposure to microgravity contrasts with earlier reports. These disparate findings, albeit by different methods, might be a consequence of the small sample number to date or the inclusion of women, who may be relatively protected from vascular change. Alternatively, it might be that current countermeasures, including daily exercise regimens, are sufficient to maintain central arterial distensibility during a six-month exposure to microgravity. Supported by Canadian Space Agency.