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At least 19 recordsLinked to original sources
PubMed1987

Echocardiographic evaluation of space shuttle crewmembers.

Echocardiographic measurements were obtained before and after space flight from 17 members of four shuttle crews. Measurements obtained 1 h after landing (L+0) compared with preflight values (n = 7) demonstrated an increase in heart rate (HR) (16 beats/min, 30.5%, P less than 0.05), mean arterial pressure (12%, P less than 0.05), and systemic vascular resistance (34%, P less than 0.05). End-diastolic volume index (EDVI) fell 17 ml/m2 (-23%, P less than 0.005) and stroke volume index (SVI) fell 15 ml/m2 (-28%, P less than 0.05). Repeat measurements taken 1-2 wk later (n = 17) demonstrated that HR had returned to normal (4 beats/min, P less than 0.05); however, EDVI remained significantly below preflight levels (-11%, P less than 0.005). End-systolic volume index (ESVI) was also still significantly lower (-23%, P less than 0.01). This delayed recovery occurred despite ability of the subjects to fully ambulate and exercise during the postflight period. These results indicate that spaceflight induces significant changes in heart volume affecting left ventricular function. The exact reasons for these specific changes remain unknown and will require additional measurements before, during, and after flight. The prolonged recovery period for the present subject group probably relates to their high level of aerobic conditioning.

Adult↗
PubMed1990

Effects of spaceflight on levels and activity of immune cells.

Experiments were carried out on cells from rats that had been flown on Soviet Biosputnik Cosmos 1887 to explore the effects of spaceflight on immune responses. Rat bone marrow cells were examined for their response to colony stimulating factor-M. Rat spleen and bone marrow cells were stained with antibodies directed against cell surface antigenic markers. The results of the studies indicate that bone marrow cells from flown rats showed a decreased response to colony stimulating factor. There was a higher percentage of spleen cells from flown rats staining positively for pan-T-cell, suppressor-T-cell and interleukin-2 receptor cell surface antigens. A small increase in the percentage of cells staining positively for helper-T-cell antigens was also noted. In addition, a higher percentage of cells that appeared to be part of the myelogenous population of bone marrow cells from flown rats stained positively for surface immunoglobulin.

Animals↗
PubMedDate not supplied

Hypogravity-induced atrophy of rat soleus and extensor digitorum longus muscles.

Prolonged exposure of humans to hypogravity causes weakening of their skeletal muscles. This problem was studied in rats exposed to hypogravity for 7 days aboard Spacelab 3. Hindlimb muscles were harvested 12-16 hours postflight for histochemical, biochemical, and ultrastructural analyses. The majority of the soleus and extensor digitorum longus fibers exhibited simple cell shrinkage. However, approximately 1% of the fibers in flight soleus muscles appeared necrotic. Flight muscle fibers showed increased glycogen, lower subsarcolemmal staining for mitochondrial enzymes, and fewer subsarcolemmal mitochondria. During atrophy, myofibrils were eroded by multiple focal losses of myofilaments; lysosomal autophagy was not evident. Tripeptidylaminopeptidase and calcium-activated protease activities of flight soleus fibers were significantly increased, implying a role in myofibril breakdown. Simple fiber atrophy appears to account for muscle weakening during spaceflight, but fiber necrosis is also a contributing factor.

Aminopeptidases↗
PubMed1992

Quantitative autoradiographic analysis of muscarinic cholinergic and GABAA (benzodiazepine) receptors in the forebrain of rats flown on the Soviet Biosatellite COSMOS 2044.

The quantitative autoradiographic analysis of muscarinic cholinergic and GABAA (benzodiazepine) receptors was performed on selected regions of the cerebral cortex and striatum of rats flown in the Soviet Biosatellite COSMOS 2044. An age- and strain-matched synchronous ground-based control group was employed for comparison. Muscarinic cholinergic receptor density was found to be significantly lower in the striatum of the flight animals as compared with that in the synchronous control group. No significant differences between flight and synchronous control groups were found in the other regions examined. GABAA (benzodiazepine) receptors showed no significant differences between the flight and control groups in any of the regions sampled. Although additional studies are needed to reach definitive conclusions, the decrease in muscarinic cholinergic receptors observed in the striatum suggests spaceflight-related alterations in motor activity.

Animals↗
PubMed1992

Linear vestibuloocular reflex during motion along axes between nasooccipital and interaural.

Linear vestibuloocular reflexes (LVORs) stabilize retinal images by producing eye movements to compensate for linear head motion. LVOR response characteristics depend upon gaze relative to the motion axis and binocular fixation distance. LVOR sensitivity during NO-axis motion increases as gaze eccentricity relative to the motion axis increases and as binocular fixation distance decreases. To fixate targets during forward head motion and rightward gaze, eyes must move to the right, but when looking left, the eyes must move to the left. In this study, LVORs were measured (binocular search coils) during 5.0 Hz horizontal motion along axes between and including NO and IA. This reorients head and otolith inputs relative to linear motion. We found that LVORs follow the same kinematics regardless of eye position in the head or head orientation relative to motion. Eye position information must be quickly and accurately integrated with otolith inputs to determine eye position (gaze) relative to linear head motion in space. The LVOR provides a behaviorally useful reflex for maintaining ocular fixation on visual targets during translation along any axis.

Animals↗
PubMed1987

Fragility and composition of growing rat bone after one week in spaceflight.

To gain some insight into the early effects of spaceflight on skeletal metabolism, we quantified the major chemical constituents and a noncollagenous protein, osteocalcin, in the third-lumbar vertebrae and humeri from 8-wk-old rats that were part of the 7-day NASA Spacelab 3 flight experiments. The ratio of calcium to hydroxyproline in the humeral diaphysis increased from 8.5 in preflight to 9.8 in ground simulation control and only to 8.9 in flight bones. There was no demonstrable change in the fraction of nonmineralized collagen. Osteocalcin content was reduced in the humerus and vertebra. Reduced accumulation of mineral and osteocalcin with no associated decrease in collagen in flight animals suggests that both mineralization and collagen metabolism are impaired in growing animals during spaceflight within a few days after launch. Strength tests of the humeri of flight rats showed substantial deficits that appeared to be related, not only to the reduced bone mass, but also to the composition and quality of new bone formed.

Animals↗
PubMed1987

Nuclear morphometric analysis of osteoblast precursor cells in periodontal ligament, SL-3 rats.

Five small (55 days old, 196 +/- 5 g) (mean +/- SE) and five large (83 days old, 382 +/- 4 g) Sprague-Dawley strain, specific pathogen-free rats were exposed to a 7-day spaceflight and 12-h postflight recovery period. As measured in 3-micron sections, periodontal ligament (PDL) fibroblastlike cells were classified according to nuclear size: A + A' (40-79), B (80-119), C (120-169), and D (greater than or equal to 170 microns 3). Since the histogenesis sequence is A----A'----C----D----osteoblast, the relative incidence of A + A' to C + D is an osteogenic index. No difference in A + A' or C + D cells in small rats may reflect partial recovery of preosteoblast formation (A----C) during the 12-h postflight period. Large flight rats demonstrated increased numbers of A + A', indicating an inhibition of preosteoblast formation (A----C). At least in the older group, a 7-day flight is adequate to reduce PDL osteogenic potential (inhibition in PDL osteoblast differentiation and/or specific attrition of C + D cells) that does not recover by 12-h postflight.

Animals↗
PubMed1987

Histomorphometric analysis of rat skeleton following spaceflight.

Male Sprague-Dawley rats were placed in orbit for 7 days aboard the space shuttle. Bone histomorphometry was performed in the long bones and lumbar vertebrae of flight rats and compared with data derived from ground-based control rats. Trabecular bone mass was not altered during the 1st wk of weightlessness. Strong trends were observed in flight rats for decreased periosteal bone formation in the tibial diaphysis, reduced osteoblast size in the proximal tibia, and decreased osteoblast surface and number in the lumbar vertebra. For the most part, histological indexes of bone resorption were normal in flight rats. The results indicate that 7 days of weightlessness are not of sufficient duration to induce histologically detectable loss of trabecular bone in rats. However, cortical and trabecular bone formation appear to be diminished during the 1st wk of spaceflight.

Animals↗
PubMed1988

Effects of a 1-wk spaceflight on morphological and mechanical properties of growing bone.

The morphological and mechanical responses of tibia and humerus were assessed in growing male rats after a 1-wk spaceflight aboard NASA Spacelab 3. In contrast to flights of longer duration, changes in middiaphysial cross-sectional morphology were minimal. Inhibition of longitudinal growth was not found in the tibia but was apparent in the humerus. The normal age-related increase in tibial middiaphysial density was not observed in the flight animals. Three-point bending tests indicated that a 1-wk spaceflight impeded the maturation of bone strength and stiffness, with the effects more pronounced in the tibia than in the humerus. Material property alterations in bone thus overshadowed morphological factors in determining the bone's mechanical response. It is likely that deprivation of normal weight-bearing loads was a major factor contributing to the observed changes, but endocrine and other local factors must also be considered.

Animals↗
PubMed1988

Influence of spaceflight on rat skeletal muscle.

The size, succinate dehydrogenase (SDH) and alpha-glycerolphosphate dehydrogenase (GPD) activities, and alkaline myofibrillar adenosinetriphosphatase (ATPase) staining properties were determined from quantitative histochemical analyses of single fibers from five hindlimb muscles of six male rats exposed to a 7-day National Aeronautics and Space Administration spaceflight mission (SL-3). These same properties were determined in a group of ground-based control rats housed under simulated environmental conditions. The wet weight of each of the flight muscles was significantly reduced relative to control. However, the loss of mass varied from 36% in the soleus to 15% in the extensor digitorum longus. The cross-sectional areas of fibers in the flight muscles also were reduced, except for the dark ATPase fibers in the medial gastrocnemius. The greatest relative fiber atrophy occurred in the muscles with the highest proportion of light ATPase fibers. An increase in the percentage of dark ATPase fibers also was observed in flight muscles with a predominance of light ATPase fibers. Also, there was an increase in the biochemically determined myofibrillar ATPase activity of tissue sections of the flight soleus. No changes in histochemical or biochemical measures of ATPase activity were observed in the flight extensor digitorum longus. In general, the SDH activity of flight muscles was maintained, whereas GPD activity either was maintained or increased. Based on a metabolic profile of ATPase, SDH, and GPD, there was an increase in the proportion of fast oxidative-glycolytic fibers in some muscles.

Adenosine Triphosphatases↗
PubMed1992

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 carried 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 inclusions 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 mid-diaphyseal region demonstrated a slight (but not statistically 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.

Adaptation, Physiological↗
PubMed1992

Preosteoblast production in COSMOS 2044 rats: short-term recovery of osteogenic potential.

The influence of a 13.8-day spaceflight and approximately 8.5-11 h of recovery at 1 g on fibroblast-like osteoblast precursor cells was assessed in the periodontal ligament of rat maxillary first molars. Preosteoblasts (C + D cells), less differentiated progenitor cells (A + A' cells), and nonosteogenic fibroblast-like cells (B cells) were identified by nuclear volume analysis (i.e., A + A' = 40-79 microns 3; B = 80-119 microns 3; C + D greater than or equal to 120 microns 3). No differences were observed among flight (F), synchronous (SC), vivarium, and basal control groups in the A + A' (F: 28.0 +/- 3.7 vs. SC: 27.4 +/- 2.2), B (F: 33.1 +/- 1.4 vs. SC: 32.4 +/- 2.4), or C + D (F: 38.4 +/- 4.5 vs. SC: 39.2 +/- 1.6) cell compartments (mean +/- SE, n = 5). Compared with previous spaceflight experiments, the present data are consistent with a postflight response to replenish preosteoblasts and restore periodontal ligament osteogenic potential. These data emphasize the need to 1) unequivocally determine the flight effect by killing the animals in-flight and 2) further assess the postflight recovery phenomenon.

Animals↗
PubMed1992

Adaptations of young adult rat cortical bone to 14 days of spaceflight.

To determine whether mature humeral cortical bone would be modified significantly by an acute exposure to weightlessness, adult rats (110 days old) were subjected to 14 days of microgravity on the COSMOS 2044 biosatellite. There were no significant changes in peak force, stiffness, energy to failure, and displacement at failure in the flight rats compared with ground-based controls. Concentrations and contents of hydroxyproline, calcium, and mature stable hydroxylysylpyridinoline and lysylpyridinoline collagen cross-links remained unchanged after spaceflight. Bone lengths, cortical and endosteal areas, and regional thicknesses showed no significant differences between flight animals and ground controls. Our findings suggest that responsiveness of cortical bone to microgravity is less pronounced in adult rats than in previous spaceflight experiments in which young growing animals were used. We hypothesize that 14 days of spaceflight may not be sufficient to impact the biochemical and biomechanical properties of cortical bone in the mature rat skeleton.

Adaptation, Physiological↗
PubMed1992

Role of atrial natriuretic peptide in systemic responses to acute isotonic volume expansion.

Atrial natriuretic peptide (ANP) may activate multiple mechanisms that protect against circulatory volume overload. We hypothesized that a temporal relationship exists between increases in cardiac filling pressure and plasma ANP concentration and also between ANP elevation and vasodilation, fluid movement from plasma to interstitium, and increased urine volume (UV). We infused 30 ml/kg isotonic saline at 100 ml/min in seven supine male subjects and monitored responses for 3 h postinfusion. Right atrial pressure (RAP) was measured via a central catheter. ANP (pmol/l) was measured by radioimmunoassay. Transcapillary fluid transport (TFT) equaled infused volume minus UV, insensible fluid loss, and change in plasma volume (PV, measured with Evan's blue). Systemic vascular resistance (SVR) was calculated as (mean arterial pressure-RAP)/cardiac output (determined by acetylene rebreathing). Plasma oncotic pressure (OP) was measured directly. During infusion, mean TFT (+/- SE) increased from net reabsorption during control of 111 +/- 27 ml/h to net filtration of 1,219 +/- 143 ml/h (P < 0.01). At end infusion, mean RAP, heart rate, and PV exhibited peak increases of 146, 23, and 27%, respectively. Concurrently, SVR and OP achieved nadirs 29 and 31% below control, respectively. Mean plasma ANP and UV peaked (45 and 390%, respectively) at 30 min postinfusion. Systemic vasodilation and capillary filtration resulted from and compensated for infusion-induced circulatory pressure increases and hemodilution. By 1 h postinfusion, most cardiovascular variables had returned toward control levels, and net reabsorption of extravascular fluid ensued.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Vitamin D metabolites and bioactive parathyroid hormone levels during Spacelab 2.

The purpose of this study was to determine whether plasma levels of the vitamin D hormone and parathyroid hormone (PTH), two potent activators of bone remodeling sites, were altered in four astronauts during the 8-day (d) Spacelab 2 mission (SL2). Increased circulating levels of either hormone could change calcium homeostasis and bone cell activity and, thus, contribute to bone loss in crewmembers in space. The vitamin D hormone was elevated in all astronauts at the end of the first inflight day but returned to normal by the seventh day. Biologically active PTH tended to be normal throughout the mission. Both hormones were within the normal range by the end of the 8-d flight of this SL2 crew. Plasma levels of 25OHD, 24,25(OH)2D, calcium, phosphorus, and albumin were essentially normal during the mission.

24,25-Dihydroxyvitamin D 3↗
PubMed1991

The pituitary: aging and spaceflown rats.

Decrements in growth hormone (GH) release we observed in two spaceflight experiments and four tail-suspended rat studies mimic age-associated changes in the mammalian pituitary GH system seen by Meites and others. The spaceflight data suggest that formation of high molecular weight bioactive disulfide-linked aggregates of the 20 and 22K monomeric GH forms may be reduced in microgravity, thereby, reducing target tissue activity. Correlative studies to confirm spaceflight as a model for pituitary GH system aging should include: 1) investigation of mechanisms of intracellular hormone packaging, 2) consequences to biological activity of the hormone molecule, and 3) study of intracellular microtubule dynamics.

Aging↗
PubMed1987

Changes in pituitary growth hormone cells prepared from rats flown on Spacelab 3.

Anterior pituitaries from "small" (250 g) and "large" (400 g) rats flown on the 7-day Spacelab 3 mission were pooled and trypsinized into two single-cell suspensions. Compared with ground-based controls, flight cells appeared to contain more intracellular growth hormone (GH) but release less GH over a 6-day culture period. After implantation into hypophysectomized rats, both sets of flight cells released only 50% of the GH compared with the control cells. Glands from large flight rats contained 44% somatotrophs compared with 37% for controls; small animals showed no difference. There were no striking differences in somatotroph ultrastructure between cells in the four groups. Western blot analysis indicated that there were no major differences in immunoactive GH variants. High-performance liquid chromatography fractionation of culture media indicated that small flight cells released much less of a high-molecular weight variant rich in GH bioactivity. The results suggest that GH cells from rats exposed to microgravity may experience secretory dysfunction. The possibility that this occurs directly at the pituitary cell level is discussed.

Animals↗