EXPERIMENT INFORMATION
Effects of Spaceflight on the Development of the Circadian Timing System (9303024)
Research Area:
Developmental biology
Endocrinology
Species Studied
Scientific Name: Rattus norvegicus Species: Rat Strain: Sprague-Dawley
Objectives:The objectives of this experiment were to determine the effect of spaceflight on: retinal development; development of the suprachiasmatic nucleus (SCN), the circadian pacemaker of the circadian timing system (CTS); maturation of the retino-hypothalamic tract (RHT); and the development and maturation of circadian rhythms.
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Approach:
Retinas were dissected, sectioned and mounted on slides, counterstained and analyzed for thickness of the inner plexiform, inner nuclear, outer nuclear and outer plexiform layers. Differences in the initiation and maturation rate of laminar thickness were compared between animal groups. Coronal sections were made through the hypothalamus and mounted on slides that were counterstained and analyzed for mean soma diameter of neurons within the SCN. Coronal sections through the SCN were examined for cytochrome oxidase (CYOX) staining both within the SCN and in the surrounding regions at each age. As a provocative test of SCN function, animals from each group were either exposed to a light pulse (LP) or not (NLP). Sections through the SCN and surrounding hypothalamus were immunohistochemically stained for c-Fos reactive neurons. Brain sections containing c-Fos labeled neurons were mounted, counterstained and examined by light microscopy to determine differences in the number of immunoreactive SCN neurons between LP and NLP animals at the age that the RHT projection becomes functional.
Results:
Histological examination of the retina revealed no differences in development between the Flight (FLT) and Flight Delayed Synchronous (FDS) retina at G20, PN1, PN3, and PN8. The pattern of cFos activation within the SCN of the G20 animals indicated that the FLT group was significantly delayed from the FDS group at this age. These differences disappeared by PN1. There was no difference between groups in the responsiveness of the SCN to light stimulation; a robust response was present by PN5.
Hoban-Higgins TM, Murakami DM, Fermin C, Fuller CA: Development of circadian rhythms of body temperature and activity in Sprague-Dawley rat pups. Society for Neuroscience, vol. 21, 1995, pp. 955.
Murakami DM, Tang IH, Hoban-Higgins TM, Fuller CA: The development of the photic induction of c-Fos in the retina and SCN. Society for Neuroscience, vol. 21, 1995, pp. 956.
Murakami DM, Tang IH, Hoban-Higgins TM, Fuller CA: The effect of spaceflight on retino-hypothalamic development. Journal of Gravitational Physiology, vol. 4, 1997, pp. 67.
Circadian rhythm
Proto-oncogene proteins
Suprachiasmatic nucleus
Retina
Hypothalamus
Data Availability
Archiving in Progress. Some data exist for this experiment.
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Activity, circadian rhythm, Rat, Microgravity
Circadian rhythm amplitude
Circadian rhythm onset
Inner nuclear development: retina
Inner plexiform development: retina
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Outer nuclear development: retina
Outer plexiform development: retina
Oxidative metabolism: suprachiasmatic nucleus
Photic responsiveness: suprachiasmatic nucleus
Soma size: suprachiasmatic nucleus
Temperature, AEM, NIH.R2, Ambient temperature recorder (ATR)
Temperature, Rhythm, rat
Mission/Study Information
Mission
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Launch/Start Date
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Landing/End Date
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Duration
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STS-70
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07/13/1995
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07/22/1995
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9 days
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Managing NASA Center
Ames Research Center (ARC)
Responsible NASA Representative
Ames Research Center LSDA Level 3
Project Manager: Martha Del Alto
Institutional Support
National Aeronautics and Space Administration (NASA)
Protocol / Approach
Delayed synchronous control
Vivarium control
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