Postflight changes in muscle volume, calf muscle transverse relaxation time, and total body composition were measured in 4 crewmembers after a 17-day mission and in 14-16 crewmembers in multiple shuttle/Mir missions of 16- to 28-wk duration. During the 17-day mission, all muscle regions except the hamstrings significantly decreased 3-10% compared with baseline. During the shuttle/Mir missions, there were significant decreases in muscle volume (5-17%) in all muscle groups except the neck. These changes, which reached a new steady state by 4 mo of flight or less, were reversed within 30-60 days after landing. Postflight swelling and elevation of calf muscle transverse relaxation time persisted for several weeks after flight, which suggests possible muscle damage. In contrast to the 17-day flight, in which loss in fat, but not lean body mass, was found (25), losses in bone mineral content and lean body mass, but not fat, were seen after the longer shuttle/Mir missions. The percent losses in total body lean body mass and bone mineral content were similar at approximately 3.4-3.5%, whereas the pelvis demonstrated the largest regional bone loss at 13%.

The loss of bone mineral in NASA astronauts during spaceflight has been investigated throughout the more than 40 years of space travel. Consequently, it is a medical requirement at NASA Johnson Space Center (JSC) that changes in bone mass be monitored in crew members by measuring bone mineral density (BMD) with dual-energy x-ray absorptiometry (DXA) before and after flight on astronauts who serve on long-duration missions (4-6 months). We evaluated this repository of medical data to track whether there is recovery of bone mineral that was lost during spaceflight.Our analysis was supplemented by BMD data from cosmonauts (by convention, a space traveler formally employed by the Russia Aviation and Space Agency or by the previous Soviet Union) who had also flown on long-duration missions. Data from a total of 45 individual crew members -a small number of whom flew on more than one mission -were used in this analysis.Changes in BMD (between 56 different sets of pre-and postflight measurements) were plotted as a function of time (days after landing). Plotted BMD changes were fitted to an exponential mathematical function that estimated: i) BMD change on landing day (day 0) and ii) the number of days after landing when 50% of the lost bone would be recovered ("50% recovery time") in the lumbar spine, trochanter, pelvis, femoral neck and calcaneus. In sum, averaged losses of bone mineral after long-duration spaceflight ranged between 2-9% across all sites with our recovery model predicting a 50% restoration of bone loss for all sites to be within 9 months.Recovery of spaceflight-induced bone loss 3

Seven male rats were exposed to 7 days of weightlessness in the Soviet mission COSMOS 1667 and compared with seven control rats by bone histomorphometric methods. In proximal tibial metaphysis, the trabecular bone volume was markedly reduced in flight animals. Trabeculae were decreased in number and thickness; this probably leads to alteration of bone mechanical properties. Formation activity (reflected by measurements of osteoid seams) was decreased at trabecular and endosteal levels. Resorption activity (estimated by count of osteoclast number and active resorption surfaces using a histoenzymologic method) remained unchanged. The imbalance between these cellular activities appears to be responsible for the loss of trabecular bone mass. In proximal femoral metaphysis, measurements were performed in an area located under the muscular insertions. The trabecular bone volume, despite a slight decrease in flight rats, was not significantly different from that of control rats. Furthermore, osteoclastic and osteoid parameters were unchanged. Differential responses between these two long bones need additional investigations. In thoracic and lumbar vertebrae no detectable change in bone mass and bone resorption parameters was found.

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We combined dual-photon absorptiometry, iliac crest histomorphometry, and backscattered electrons analysis to characterize bone mineralization effects of a spaceflight on young monkeys. Two 4- to 5-kg male rhesus monkeys (Macaca mulatta) were flown during a 11.5-day spaceflight that took place onboard Cosmos 2229 biosatellite (Bion 10). Vivarium (n = 4) and Earth-based chair (n = 4) control situations were studied for comparison. Flight monkeys exhibited lower values of iliac cancellous bone volume, associated with nonsignificantly thinner trabeculae. Bone mineralization rate and the proportion of trabecular bone surface involved in mineralization processes were found markedly reduced after spaceflight. Analysis of embedded sections by backscattered electrons imaging showed a nonsignificant shift to lower mineralization in the flight biopsies vs. postflight mock-up biopsies. These results were in accordance with dual-photon absorptiometry evaluations showing a tendency for decreased bone mineral content during flight and recovery thereafter. The ground simulation experiment performed on the same monkeys more than 1 mo after landing suggests that the observed effects were specifically related to spaceflight and that the animals had only partially recovered. Additional animals on future flights will be required to confirm these findings.

No 1/2005 Остеопороз и остеопатии2 ВВЕДЕНИЕ В предыдущей статье [14] были описаны основ-ные феномены в костной ткани человека, сопро-вождающие его полет на орбитальной станции (ОС) "МИР" длительностью 5-7 месяцев. Одним из основных выводов было доказательство того факта, что потери костной массы в трабекулярных структурах костей нижней половины скелета за данный период времени в среднем по группе не создают ситуации, которую по принятому ВОЗ регламенту можно было бы квалифицировать как остеопороз. В целом совокупность изменений состояния костной ткани в космическом полете данной длительности рассматривается как проявление фун-кциональной адаптации. Однако это не исключает необходи-мости более внимательного анализа некоторых выявленных в процессе исследований определенных закономерностей, или тенденций и особенностей описанных изменений, что и является задачей настоящей публикации. Вектор гравитации и феномен перераспределения минералов в скелетеПоказана зависимость направленности и выраженности изменений минеральной плотности различных сегментов скелета от их положения относительно вектора гравитации, с одной стороны, и от соотношения в них трабекулярной и кортикальной структур -с другой.Наибольшие отрицательные изменения минеральной плотности костной ткани (МПКТ) были обнаружены при использовании метода DEXA в костях таза, поясничных поз-вонках и проксимальном отделе бедра, что может быть свя-зано как с их биомеханической функцией (бόльшая весовая нагрузка при 1 g), так и с преимущественно трабекулярной структурой. Потери в длинных трубчатых костях ног были менее существенны, по всей вероятности, в связи с тем, что в этом случае в зоне сканирования находится относительно большая масса кортикальной кости.В костях черепа и шейных позвонках, как правило, выявляется достоверное повышение содержания костных минералов (СКМ), а в костях плечевого пояса, рук и в реб-рах -увеличение МПКТ, которое чаще всего не превышало двойной ошибки метода, иными словами, было недосто-верным. Вопрос о направленности и выраженности изме-нений минерализации костей черепа и шейных позвонков, а также ребер и костей рук остается дискуссионным, и это объясняется метрологическими особенностями измерения МПКТ и СКМ в данных сегментах скелета. Основные трудности при проведении исследований связаны со сравнительно высокой минеральной плотностью костей черепа при небольшой массе окружающих мягких тканей и невозможностью строгого позиционирования головы и рук в процессе обследования. Предполагается, что с учетом Рассматриваются возможные механизмы некоторых особенностей изменений костной ткани космонавтов после полетов длительностью 5-7 месяцев, выявленных на основе данных остеоденситометрии методом двухэнергети-ческой рентгеновской абсорбциометрии. Избирательная остеопения в трабекулярных структурах костей нижней половины скелета связана с их большей весовой нагруженностью в условиях ускорения 1g. Увеличение содержания ми-нералов в костях верхней половины скелета и гиперминерализация губчатой ткани тел поясничных позвонков, обнару-женная методом...

To determine the effects of the relative inactivity and unloading on the strength of the tibias of monkeys, Macaca mulatta, we used a non-invasive test to measure bending stiffness, or EI (Nm2), a mechanical property. The technique was validated by comparisons of in vivo measurements with standard measures of EI in the same bones post-mortem (r2 = 0.95, P < 0.0001). Inter-test precision was 4.28+/-1.4%. Normative data in 24 monkeys, 3.0+/-0.7 years and 3.6+/-0.6 kg, revealed EI to be 16% higher in the right than left tibia (4.4+/-1.6 vs. 3.7+/-1.6 Nm2, P < 0.05). Five monkeys, restrained in chairs for 14 days, showed decreases in EI. There were no changes in EI in two chaired monkeys that lost weight during a 2-week space flight. The factors that account for both the decreases in bone mechanical properties after chair restraint at 1 g and lack of change after microgravity remain to be identified. Metabolic factors associated with body weight changes are suggested by our results.