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  • LIFE SCIENCES (GENERAL)
  • 1980-1984  (84)
  • 1950-1954
  • 1930-1934
  • 1982  (51)
  • 1980  (33)
  • 1
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    Effect of space flight on bone strength (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: To test the possibility that spaceflight has a deleterious effect on bone mechanical properties, femur breaking strength by torsional loading in rats that had been flown for 19 days aboard Cosmos 936 was determined. The results showed that femurs from flight rats were less stiff than the flight controls, and failed under torsion at a lower torque and energy of absorption. The defect was corrected following space flight and could be prevented during space flight by centrifuging the rats at 1 x g. Altered bone geometry due to inhibition of bone formation at the periosteal surface provides the most likely explanation for the decrease in bone strength during spaceflight.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: p. S-75
    Format: text
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  • 2
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    Effects of hypergravity on rat liver regeneration (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The effects of centrifugation on liver regrowth were examined by measuring mitotic activity. The results indicate that the increased gravity caused a delay in the onset of mitotic activity and a significant decrease in overall mitotic activity.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: Space Gerontology; p 53-54
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  • 3
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    Evidence for arrested bone formation during spaceflight (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Addressing the question of whether the bone formed in space is unusual, the morphology of bone made at the tibial diaphysis of rats before, during, and after spaceflight is studied. Evidence of arrest lines in the bone formed in space is reported suggesting that bone formation ceases along portions of the periosteum during spaceflight. Visualized by microradiography, the arrest lines are shown to be less mineralized than the surrounding bone matrix. When viewed by scanning electron microscopy, it is seen that bone fractures more readily at the site of an arrest line. These observations are seen as suggesting that arrest lines are a zone of weakness and that their formation may result in decreased bone strength in spite of normalization of bone formation after flight. The occurrence, location, and morphology of arrest lines are seen as suggesting that they are a visible result of the phenomenon of arrested bone formation.
    Keywords: LIFE SCIENCES (GENERAL)
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  • 4
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    Atrophy of rat skeletal muscles in simulated weightlessness (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A hypokinetic rat model was used for elucidation of the mechanism of skeletal muscle wasting which occurs in weightlessness. Rats were suspended from a back-harness with the head tilted downward and the hind limbs totally unloaded. A progressive decrease in the size of the soleus muscle from suspended rats was observed as a function of time. The rate of protein degradation of the homogenates from the soleus muscles of suspended and control animals was not significantly different. The rate of cell-free protein synthesis was severely repressed in the atrophied muscle. An initial rise in the levels of plasma glucose and corticosterone was observed on the second day of suspension, but they subsequently returned to normal values.
    Keywords: LIFE SCIENCES (GENERAL)
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  • 5
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    Retinal changes in rats flown on Cosmos 936 - A cosmic ray experiment (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Ten rats, five centrifuged during flight to simulate gravity and five stationary in flight and experiencing hypogravity, orbited the Earth. No differences were noted between flight-stationary and flight-centrifuged animals, but changes were seen between these two groups and ground controls. Morphological alterations were observed comparable to those in the experiment flown on Cosmos 782 and to the retinal cells exposed to high-energy particles at Berkeley. Affected cells in the outer nuclear layer showed swelling, clearing of cytoplasm, and disruption of the membranes. Tissue channels were again found, similar to those seen on 782. After space flight, preliminary data indicated an increase in cell size in montages of the nuclear layer of both groups of flight animals. This experiment shows that weightlessness and environmental conditions other than cosmic radiation do not contribute to the observed damage of retinal cells.
    Keywords: LIFE SCIENCES (GENERAL)
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  • 6
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    Calcium transport from the intestine and into bone in a rat model simulating weightlessness (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The objective of this study was to determine whether a defect in transport of calcium in the duodenum was related to decreased bone formation in the suspended rat. Rats were suspended by the tail at a 40 deg angle for up to 15 days. Ca-45 was injected into the ligated duodenum in situ 15 minutes prior to sacrific. Blood, tibia, vertebra and humerus were obtained for total calcium and Ca-45 analyses. Intestinal calcium transport did not appear to be significantly altered by suspension. However, by 5 days of suspension a significant decrease in accumulation of Ca-45 into tibia and vertebra was observed. A trend of decreasing bone mineral and mass was established in tibia and vertebra by the fifth day of suspension. The humerus failed to demonstrate a significant weight decrease or change in Ca-45 accumulation after 15 days of suspension. Results from this simulated weightlessness model suggest that transport of calcium from intestine into bone is decreased within 5 days of suspension. This deficiency appears to be associated with a progressive decrease in total mass of non-weightbearing bones.
    Keywords: LIFE SCIENCES (GENERAL)
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  • 7
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    Otoconial formation in the fetal rat (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Otoconial formation in the fetal rat is examined by scanning and transmission electron microscopy, and by X-ray elemental analysis. The primitive otoconia appear highly organic, but are trigonal in cross section, indicating that they already possess a three-fold axis of symmetry and a complement of calcite. These otoconia develop into spindle-shaped and, subsequently, dumbbell-shaped units. Transmission electron microscopy of dumbbell-shaped otoconia not exposed to fluids during embedment showed that calcite deposits mimicked the arrangement of the organic material. X-ray elemental analysis demonstrated that calcium was present in lower quantities in the central core than peripherally. It is concluded that organic material is essential to otoconial seeding and directs otoconial growth.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: Annals of Otology; vol. 89
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  • 8
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    Effects of centrifugation stress on pituitary-gonadal function in male rats (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The effects of centrifugation for various lengths of time on circulating levels of luteinizing hormone (LH) and testosterone in male rats were investigated. In a chronic 52-day experiment, centrifugation at 4.1 G significantly reduced LH and testosterone levels for the entire period. Centrifugation at 2.3 G had less effect inasmuch as LH levels were not significantly decreased and testosterone levels were significantly reduced only during the first few days of centrifugation. In more acute experiments, centrifugation at 4.1 G for 4 h resulted in reduced testosterone levels, whereas centrifugation for 15 min did not significantly alter the hormone levels. These results indicate that centrifugation can decrease circulating LH and testosterone levels if the gravitational force is of sufficient magnitude and is maintained for a period of hours. Chronic centrifugation may also inhibit the acute excitatory response of LH to handling and ether stress.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: Journal of Applied Physiology: Respiratory; vol. 48
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  • 9
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    Effect of simulated weightlessness on the immune system in rats (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Rats suspended in a model system designed to simulate many aspects of weightlessness were immunized with sheep red blood cells. Parameters measured on these and control rats included titers of anti-sheep red blood cell antibodies, serum immunoglobulin levels, spleen and thymus weights, hematocrits, and leukocyte differential counts on peripheral blood. No significant differences were found between test and weight-bearing, harnessed controls; however, the thymuses of animals in both these groups were significantly smaller than untreated cage controls. The lack of an effect of simulated weightlessness on the immune system is an interesting result, and its significance is discussed.
    Keywords: LIFE SCIENCES (GENERAL)
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  • 10
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    A radiative transfer model for remote sensing of laser induced fluorescence of phytoplankton in non-homogeneous turbid water (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A radiative transfer computer model was developed to characterize the total flux of chlorophyll a fluoresced or backscattered photons when laser radiation is incident on turbid water that contains a non-homogeneous suspension of inorganic sediments and phytoplankton. The radiative transfer model is based on the Monte Carlo technique and assumes that: (1) the aquatic medium can be represented by a stratified concentration profile; and (2) that appropriate optical parameters can be defined for each layer. The model was designed to minimize the required computer resources and run time. Results are presented for an anacystis marinus culture.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: NASA-CR-163155
    Format: application/pdf
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