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All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Skeletal abnormalities in rats induced by simulated weightlessness

A hypokinetic model has been developed which attempts to simulate the weightlessness experienced during space flight. Male rats were suspended from the model with a head-down tilt for a two-week period. Total mechanical unloading of the hind limbs and partial unloading of the fore limbs occurred. In comparison to pair-fed control rats, the skeletal alterations in the proximal tibial and humeral metaphyses of suspended rats were determined to be a diminished rate of longitudinal bone growth, a reduced mass of mineralized tissue, and an accumulation of marrow fat. Also, suspended rats exhibited decreased numbers of osteoblasts and increased numbers of osteoclasts immediately adjacent to the growth plate-metaphyseal junction at both skeletal sites. Although the reduction in mineralized tissue and the fat accumulation were more marked in the tibia, the skeletal changes in the proximal tibial and humeral metaphyses were generally comparable. The observed abnormalities may be due to mechanical unloading and/or a hypersecretion of corticosteroids.

Wronski, T. J.↗
NASA NTRS1983

Effects of spaceflight on trabecular bone in rats

Alterations in trabecular bone were observed in growing male Wistar rats after 18.5 days of orbital flight on the COSMOS 1129 biosatellite. Spaceflight induced a decreased mass of mineralized tissue and an increased fat content of the bone marrow in the proximal tibial and humeral metaphyses. The osteoblast population appeared to decline immediately adjacent to the growth cartilage-metaphyseal junction, but osteoclast numbers were unchanged. These results suggested that bone formation may have been inhibited during spaceflight, but resorption remained constant. With the exception of trabecular bone mass in the proximal tibia, the observed skeletal changes returned to normal during a 29-day postflight period.

Jee, W. S. S.↗
NASA NTRS1984

Sensitivity of bone cell populations to weightlessness and simulated weightlessness

A rat suspension model for simulating certain aspects of weightlessness is discussed. Perturbations in physiological systems induced by this head down suspension model are verified by flight data. Findings of a suppression of osteoblast differentiation help explain the inhibition of bone formation inflight and during Earth-bound simulations. Since the anatomical site for these studies was in the maxilla, which is gravity loaded but non weightbearing in ground-based simulations, the similarity of bone cell kinetic changes, both inflight and in the ground-based model, suggest that fluid shifts rather than unloading may play an important role in bone alterations, at least at this sampling site.

Roberts, W. E.↗
NASA NTRS1983

Alterations in calcium homeostasis and bone during actual and simulated space flight

Skeletal alteration in experimental animals induced by actual and simulated spaceflight are discussed, noting that the main factor contributing to bone loss in growing rats placed in orbit aboard Soviet Cosmos biosatellites appears to be diminished bone formation. Mechanical unloading is seen as the most obvious cause of bone loss in a state of weightlessness. Reference is made to a study by Roberts et al. (1981), which showed that osteoblast differentiation in the periodontal ligament of the maxilla was suppressed in rats flown in space. Since the maxilla lacks a weight-bearing function, this finding indicates that the skeletal alterations associated with orbital flight may be systemic rather than confined to weight-bearing bones. In addition, the skeletal response to simulated weightlessness may also be systemic (wronski and Morey, 1982). In suspended rats, the hindlimbs lost all weight-bearing functions, while the forelimbs maintained contact with the floor of the hypokinetic model. On this basis, it was to be expected that there would be different responses at the two skeletal sites if the observed abnormalities were due to mechanical unloading alone. The changes induced by simulated weightlessness in the proximal tibia and humerus, however, were generally comparable. This evidence for systemic skeletal responses has drawn attention to endocrine factors.

Wronski, T. J.↗
NASA NTRS1983

Inhibition of cortical and trabecular bone formation in the long bones of immobilized monkeys

Tetracycline derivatives are administered on three separate occasions to label the sites of bone formation. Determinations are made of the tetracycline-labeling frequency and mineral apposition rate of osteons and trabecular bone surfaces in the humerus and femur. The inhibition of bone formation induced by immobilization is found to be more pronounced in trabecular bone. The immobilized monkeys exhibit a moderate, but statistically nonsignificant, reduction in the percentage of osteons forming bone. Conversely, the dramatic decline in the percentage of trabecular surfaces undergoing bone formation in the monkeys is found to be highly significant. The diminished rate of mineral apposition in osteons is seen as suggesting that osteoblastic activity is impaired in cortical bone during immobilization.

Wronski, T. J.↗
NASA NTRS1985

Changes in bone structure and metabolism during simulated weightlessness: Endocrine and dietary factors

The role of vitamin D, PTH and corticosterone in the skeletal alterations induced by simulated weightlessness was examined. The first objective was to determine if changes in the serum concentrations of Ca, P sub i, osteocalcin, 25-OH-D, 24,25(OH)2D or 1,25(OH)2D also occur following acute skeletal unloading. Animals were either suspended or pair fed for 2, 5, 7, 10, 12 and 15 days and the serum concentrations of Ca, P sub i, osteocalcin and the vitamin D metabolites measured. Bone histology was examined at day 5 after suspension. Acute skeletal unloading produced a transient hypercalcemia, a significant fall in serum osteocalcin and serum 1,25(OH)2D, a slight rise in serum 24,25(OH)2D, but did not affect the serum concentrations of P sub i or 25-OH-D. At the nadir in serum 1,25(OH)2D serum osteocalcin was reduced by 22%, osteoblast surface by 32% and longitudinal bone growth by 21%.

Halloran, B. P.↗
NASA NTRS1983

The role of 1,25-dihydroxyvitamin D in the inhibition of bone formation induced by skeletal unloading

Skeletal unloading results in osteopenia. To examine the involvement of vitamin D in this process, the rear limbs of growing rats were unloaded and alterations in bone calcium and bone histology were related to changes in serum calcium (Ca), inorganic phosphorus (P sub i), 25-hydroxyvitamin D (25-OH-D), 24,25-dihydroxyvitamin D (24,25(OH)2D and 1,25-dihydroxyvitamin D (1,25(OH)2D. Acute skeletal unloading induced a transitory inhibition of Ca accumulation in unloaded bones. This was accompanied by a transitory rise in serum Ca, a 21% decrease in longitudinal bone growth (P 0.01), a 32% decrease in bone surface lined with osteoblasts (P .05), no change in bone surface lined with osteoclasts and a decrease in circulating (1,25(OH)2D. No significant changes in the serum concentrations of P sub i, 25-OH-D or 24,25(OH)2D were observed. After 2 weeks of unloading, bone Ca stabilized at approximately 70% of control and serum Ca and 1,25(OH)2D returned to control values. Maintenance of a constant serum 1,25(OH)2D concentration by chronic infusion of 1,25(OH)2D (Alza osmotic minipump) throughout the study period did not prevent the bone changes induced by acute unloading. These results suggest that acute skeletal unloading in the growing rat produces a transitory inhibition of bone formation which in turn produces a transitory hypercalcemia.

Halloran, B. P.↗
NASA NTRS1984

Alterations in bone forming cells due to reduced weight bearing

A reduction in new bone formation occurred as a result of space flight (Cosmos 1129) and in the suspended animal model of Morey-Holton (1979, 1980). The results indicate that alkaline phosphatase activity of the bone-forming cells is also reduced under these conditions, and the cells in the diaphysis are more affected than those in the metaphyseal region. In addition, these cells show (1) reduced proline incorporation into bone matrix, and (2) increased intracellular lysosomal activity. A change in the cytoskeleton could be the common factor in explaining these results. This suggestion is futher supported by the previous observations that colchicine injections result in decreased osteoblastic function.

Doty, S. B.↗
NASA NTRS1990

Life sciences research using a lunar laboratory

The necessity for life sciences research on the lunar surface in order to determine the consequences of returning from extended missions in various low gravity environments and of transiting through high multiple gravity forces during decelerations is discussed. The functions of a lunar gravitational biology laboratory are outlined. Lunar science objectives include investigations in developmental biology including the evaluation of the capacity of diverse organisms to undergo normal development and the evaluation of the use of the lunar environment to study specific developmental phenomena in ways that cannot be accomplished by earth-based research. The need for musculoskeletal studies to examine the dynamics of osteoclast and osteoblast formation and breakdown and to address bone and demineralization problems is discussed. Biological adaptation to hypogravic environments and the effects of radiation and electromagnetic environmental factors are also considered.

Cipriano, Leonard F.↗
NASA NTRS1992

Effects Of Stress On Bone-Formation Markers In Rats

Report describes experiments involving simultaneous measurement of concentrations, in blood, of two substances indicative of formation of bone in rats. Measurements performed after flight in outer space plus 48 h of postflight environmental stress. Results emphasize critical influences of adrenal status and diet on functions of osteoblasts.

Arnaud, Sara B.↗
NASA NTRS1992

Effect of microgravity and mechanical stimulation on the in vitro mineralization and resorption of fetal mouse long bones (7-IML-1)

Mechanical forces play an important role in the differentiation, growth, and remodeling of skeletal tissues. An increase in the normal loading pattern of the skeleton leads to an increase in bone mass. An overall decrease in the functional load exerted on the skeleton produces mineral loss and osteoporosis. However, the responses of the skeletal tissue cells to various loading conditions are still largely unresolved, as is the mechanism of the cellular response to changed mechanical environment. Using an in vitro approach, we hope to avoid some problems encountered in the use of in vivo animal and man models, which have been extensively used in the past. In a number of experiments we have demonstrated that 16 and 17 day old fetal mouse long bone rudiments (metatarsalia), cultured in a liquid culture medium, are very suitable to study mineralization and resorption, respectively. We have also demonstrated that under hydrostatic compression, mineralization is increased while resorption is decreased. Culture of long bone rudiments under noncompressed control conditions can be regarded as a situation of partial unloading, showing some phenomena of a disuse situation. Under microgravity conditions, responses of osteoblasts and chondrocytes (involved in mineralization) and osteoclasts (involved in mineral resorption), to culture with and without compression, may be much more outspoken. This will have advantages for the study and the interpretation of the role of cellular events in the process of mineralization and resorption of developing skeletal tissues under various loading conditions. The BONES Experiment is carried out in four type I/O and four type I/E containers. Various aspects of the investigation are discussed.

Veldhuijzen, J. Paul↗
NASA NTRS1992

Morphological studies of bone and tendon

The Soviet biosatellite Cosmos 2044 carried adult rats on a spaceflight that lasted 13.8 days and was intended to repeat animal studies carrier out on Cosmos 1887. Skeletal tissue and tendon from animals flown on Cosmos 2044 were studied by light and electron microscopy, histochemistry, and morphometric techniques. Studies were confined to the bone cells and vasculature from the weight-bearing tibias. Results indicated that vascular changes at the periosteal and subperiosteal region of the tibia were not apparent by light microscopy or histochemistry. However, electron microscopy indicated that vascular influsions were present in bone samples from the flight animals. A unique combination of microscopy and histochemical techniques indicated that the endosteal osteoblasts from this same middiaphyseal region demonstrated a slight (but not statisticallly significant) reduction in bone cell activity. Electron-microscopic studies of the tendons from metatarsal bones showed a collagen fibril disorganization as a result of spaceflight. Thus changes described for Cosmos 1887 were present in Cosmos 2044, but the changes ascribed to spaceflight were not as evident.

Doty, Stephen B.↗
NASA NTRS1992

Preosteoblast production in Cosmos 2044 rats - Short-term recovery of osteogenic potential

The influence of a 13.8-day spaceflight and about 8.5-11 h of recovery at 1 g on fibro blastlike osteoblast precursor cells was assessed in the periodontal ligament of rat maxillary first molars. Preosteoblasts (C + D cells), less differentiated progenitor cells (A + A prime cells), and nonosteogenic fibroblastlike cells (B cells) were identified by nuclear volume analysis. No differences were observed among flight, synchronous vivarium, and basal control groups in the A + A prime or C + D cell compartments. Compared with previous spaceflight experiments, the present data are consistent with a postflight response to replinish preosteoblasts and restore periodontal ligament osteogenic potential. These data emphasize the need to unequivocally determine the flight effect by killing the animals in-flight and further assess the postflight recovery phenomenon.

Garetto, Lawrence P.↗
NASA NTRS1993

Cellular responses to low-gravity: Pilot studies on suborbital rockets and orbiting spacecraft

The allocated funding supported, in part, experiments conducted on two Consort sounding rockets and five Shuttle flights. The primary parameters investigated were signal transduction in response to various mediators, cellular differentiation and metabolism in microgravity, and effect of microgravity on cytoskeletal morphology. Achievements include: demonstration of effect of spaceflight on the actin cytoskeleton in mouse osteoblasts and frog cells; confirmation that the T cell receptor-mediated signal transduction pathway in T lymphocytes is not affected by low-gravity compared to non-TCR-mediated stimulation (Con-A) which classically does not promote proliferative response; indication that microgravity may allow separation of proliferative signaling and secretory function in lymphocytes; demonstration that T lymphocytes and bone cells utilized less glucose indicating a shift in metabolism and confirming Spacelab results with WI-38 cells which used significantly less glucose, during spaceflight; confirmation that activation of human splenic B cells with a number of different mediators is not affected during spaceflight; demonstration of increased prostaglandin synthesis during reduced bone cell growth suggesting an effect of microgravity on prostaglandin-induced mitogenesis. The funding contributed significantly to the database described above and resulted in submission of six collaborative abstracts in 1993 (five to the ASGSB Annual Meeting and one to the ASCB Annual Meeting). Two abstracts were presented at the 1992 ASGSB Annual Meeting in Tucson. In addition, several peer reviewed papers are being generated and data will be included as background in preparation of future proposals, which hopefully will allow us to continue this type of extremely productive collaborative research.

Lewis, Marian L.↗
NASA NTRS1996

Mechanisms of Bone Mineralization and Effects of Mechanical Loading

The data suggest that PTH and PKC inhibit nodule formation, and that alternative energy sources are utilized by osteoblasts in the process of mineralization. The conditions and techniques to grow, fix, photograph, and measure bone mineralization in vitro were defined. The results are presently in preliminary form and require further assessment as follows; quantitate the surface area of nodules + treatments via computer-aided image analysis; use PTH + inhibitors of signaling pathways to determine the mechanism of nodule formation; determine how protein kinase C is involved as a promotor of nodule formation; cell proliferation vs. cell death affected by modulation of signal transduction (i.e., PTH, enzyme inhibitors and activators); identify mRNA induced or decreased in response to PTH and signaling modulators that encode proteins that regulate cell morphology, proliferation, and nodule formation. Therefore, several follow-up studies between the laboratories at NASA-Ames Research Center and my laboratory at the University of Illinois have been initiated.

Babich, Michael↗
NASA NTRS1997

Anabolic Vitamin D Analogs as Countermeasures to Bone Loss

We demonstrated for the first time that vitamin D3 influences the effect of PTH on bone cell calcium ion levels. This is a rapid effect, taking place within seconds/minutes. This may prove to be a critical contribution to our understanding of bone physiology in that these two hormones are among the most potent regulators of bone calcium content and of systemic calcium homeostasis. Together with the data gathered from the study of astronauts exposed to microgravity for extended periods, these observations suggest the interaction of vitamin D3 and PTH as a possible therapeutic target in the treatment of bone loss disorders such as osteoporosis and disuse atrophy. Chronic exposure of cultured osteoblasts to vitamin D, altered the number of voltage-sensitive Ca(+2) channels expressed. Estrogen treatment yielded a similar result, suggesting that there is overlap in the mechanism by which these hormones elicit long-term effects on bone cell calcium homeostasis.

Li, Wei↗
NASA NTRS1998

Cell Kinetic and Histomorphometric Analysis of Microgravitational Osteopenia: PARE.03B

Previous methods of identifying cells undergoing DNA synthesis (S-phase) utilized H-3 thymidine (3HT) autoradiography. 5-Bromo-2'-deoxyuridine (BrdU) immunohistochemistry is a nonradioactive alternative method. This experiment compared the two methods using the nuclear volume model for osteoblast histogenesis in two different embedding media. Twenty Sprague-Dawley rats were used, with half receiving 3HT (1 micro Ci/g) and the other half BrdU (50 microgram/g). Condyies were embedded (one side in paraffin, the other in plastic) and S-phase nuclei were identified using either autoradiography or immunohistochemistry. The fractional distribution of preosteoblast cell types and the percentage of labeled cells (within each cell fraction and label index) were calculated and expressed as mean q standard error. Chi-Square analysis showed only a minor difference in the fractional distribution of cell types. However, there were significant differences (p less than 0.05) by ANOVA, in the nuclear labeling of specific cell types. With the exception of the less-differentiated A+A'cells, more BrdU label was consistently detected in paraffin than in plastic-embedded sections. In general, more nuclei were labeled with 3H-thymidine than with BrdU in both types of embedding media. Labeling index data (labeled cells/total cells sampled x 100) indicated that BrdU in paraffin, but not plastic gave the same results as 3HT in either embedding method. Thus, we conclude that the two labeling methods do not yield the same results for the nuclear volume model and that embedding media is an important factor whenusing BrdU. As a result of this work, 3HT was chosen for used in the PARE.03 flight experiments.

Roberts, W. Eugene↗
NASA NTRS1998

Cell Kinetic and Histomorphometric Analysis of Microgravitational Osteopenia: PARE.03B

Previous methods of identifying cells undergoing DNA synthesis (S-phase) utilized 3H-thymidine (3HT) autoradiography. 5-Bromo-2'-deoxyuridine (BrdU) immunohistochemistry is a nonradioactive alternative method. This experiment compared the two methods using the nuclear volume model for osteoblast histogenesis in two different embedding media. Twenty Sprague-Dawley rats were used, with half receiving 3HT (1 micro-Ci/g) and the other half BrdU (50 micro-g/g). Condyles were embedded (one side in paraffin, the other in plastic) and S-phase nuclei were identified using either autoradiography or immunohistochemistry. The fractional distribution of preosteoblast cell types and the percentage of labeled cells (within each cell fraction and label index) were calculated and expressed as mean +/- standard error. Chi-Square analysis showed only a minor difference in the fractional distribution of cell types. However, there were,significant differences (p less than 0.05) by ANOVA, in the nuclear labeling of specific cell types. With the exception of the less-differentiated A+A' cells, more BrdU label was consistently detected in paraffin than in plastic-embedded sections. In general, more nuclei were labeled with 3H-thymidine than with BrdU in both types of embedding media (Fig 2.). Labeling index data (labeled cells/total cells sampled x 100) indicated that BrdU in paraffin, but not plastic gave the same results as 3HT in either embedding method. Thus, we conclude that the two labeling methods do not yield the same results.

Roberts, W. Eugene↗