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Twinning of amphibian embryos by centrifugationIn the frog Xenopus laevis, the dorsal structures of the embryonic body axis normally derive from the side of the egg opposite the side of sperm entry. However, if the uncleaved egg is inclined at lg or centrifuged in an inclined position, this topographic relationship is overridden: the egg makes its dorsal axial structures according to its orientation in the gravitational/centrifugal field, irrespective of the position of sperm entry. Certain conditions of centrifugation cause eggs to develop into conjoined twins with two sets of axial structures. A detailed analysis of twinning provided some insight into experimental axis orientation. First, as with single-axis embryos, both axes in twins are oriented according to the direction of centrifugation. One axis forms at the centripetal side of the egg and the other forms at the centrifugal side, even when the side of sperm entry is normal to the centrifugal force vector. Second, if eggs are centrifuged to give twins, but are inclined at lg to prevent post-centrifugation endoplasmic redistributions, only single-axis embryos develop. Thus, a second redistribution is required for high-frequency secondary axis formation. This can be accomplished by lg (as in the single centrifugations) or by a second centrifugation directed along the egg's animal-vegetal axis.
Document ID
19840010805
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Black, S. D.
(California Univ. Berkeley, CA, United States)
Date Acquired
August 12, 2013
Publication Date
February 1, 1984
Publication Information
Publication: NASA. Washington NASA Space Biol. Program
Subject Category
Life Sciences (General)
Accession Number
84N18873
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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