A Strategy for Research in Space Biology and Medicine in the New Century (1998) / Chapter Skim
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3 Developmental Biology
3 Developmental Biology
Pages 37-48
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From page 37... ...
In the Goldberg report published in 1987,~ two primary concerns were stressed regarding future investigations conducted in space on developmental processes: Can organisms undergo normal development in microgravity? and, Are there developmental phenomena that can be studied better in microgravity than on Earth?
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Developmental Genetics Molecular Conservation The second major advance has been the recognition that molecular mechanisms are conserved across phylogeny. The initial discovery of the homeobox sequence in Drosophila and its conservation
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Thus, newly discovered genetic interactions now can be integrated quickly into a developmental model that can be tested by direct experimentation (e.g., Quiring et al., 1994~.~8 Genome Sequencing Project The third advance in new information has been provided by the genome sequencing projects that are transforming the identification of the components of cellular and developmental processes. Today, the field of developmental biology is focused on a small number of model organisms that allow for detailed analysis of development at the cellular, genetic, and molecular levels.
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From page 40... ...
In addition, continued analysis of the development of the gravity-sensing systems, including the vestibular system and other systems that interact with it in vertebrates, should be carried out to determine the importance of gravity in their normal development and maintenance. Complete Life Cycles in Microgravity Critically testing hypotheses regarding the effect of microgravity on specific developmental processes continues to be extremely difficult because of the engineering demands and the difficulty of repeating experiments in space.
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From page 41... ...
concerned with posture and balance.26 In every other sensory system known, especially those that make up the neural space maps in the brainstem,27 sensory stimulation has been implicated in the initial specification of the connections28 and physiological properties29 of the constituent neurons. Another example is the development of the visual system, where activity in the retinal pathway influences the specification of the connections determining how visual information is processed in the cerebral cortex.30 3~ Only in the otolithic gravitational pathway has it been impossible to study the role of sensory deprivation, because there is no way to deprive the system of gravitational stimulation on Earth.
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From page 42... ...
Neural Space Maps in the Brainstem Neural Space Maps Vertebrate brains form and maintain multiple neural maps of the spatial environment, which provide distinctive, topographical representations of different sensory and motor systems. For example, visual space is mapped onto the retina in a two-dimensional coordinate plan.42 This plan is then remapped in the central nervous system in several places, including the superior colliculus (optic tectum)
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From page 43... ...
· Studies should be designed to address how neurons of the various sensory and motor systems interact with vestibular neurons in the normal assembly and function of the neural space maps. · Studies should be performed to determine the influence of decreased stimulus (as experienced in microgravity)
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From page 44... ...
there is some atrophy of neuronal cell size but seldom cell death and degeneration.83 In infants or embryos, however, such deprivation can result in cell death in the central nervous system and seriously disrupt the establishment of neural connections. 84 85 In consideration of these observations made in many other sensory systems, it is important to study how microgravity, which probably represents decreased stimulation of the vestibular system, affects the vestibular neural pathway.
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1997. Expression of radical fringe in limb-bud ectoderm regulates apical ectodermal ridge formation.
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1989. Neural maps of interaural time and intensity differences in the optic tectum of the barn owl.
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1995. Afferent influences on brainstem auditory nuclei of the chicken: Regulation of transcriptional activity following cochlea removal.
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1991. Afferent influences on brainstem auditory nuclei of the chick: Nucleus magnocellularis neuronal activity following cochlea removal.
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