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Biographical Memoirs Volume 73 (1998) / Chapter Skim
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JOHANNES HOLTFRETER
Pages 208-229

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From page 209...
... inductive signals, cell competence, en c! cellular morphogenetic activities sprang from Holtfreter's finclings en c!
From page 210...
... · Discovery of conditions to produce urodele exogastrulae in which neural tissue floes not form. These embryos provided evidence that the organizer may exclusively transmit neuralizing signals to the ectoderm by a vertical path in urodeles (1933~.
From page 211...
... rye fielcis. By Holtfreter's own account, he grew up in a stable supportive family en c!
From page 212...
... a systematic stucly of Spemann's, which involves! operating on gastrula stage amphibian embryos to remove small clumps of cells from various locations of one embryo en c!
From page 213...
... Later analysis confirmed! that, in the presence of this particular graft, the nearby host tissues incleec!
From page 214...
... HoTtfreter chose to extent! the organizer studies of Spemann's laboratory by aciciressing questions of how instructive the organizer is to surrounding cells versus how self-instructive are these cells regarding their choices of clevelopmental paths.
From page 215...
... either by the organizer or by heterologous sources such as chick embryo extract or HeLa cells. Joseph Neec~ham en c!
From page 216...
... that uroclele embryos cleveloping in a hypertonic salt solution retain a solic! interior of cells because they fail to inflate the blastocoel.
From page 217...
... At the University of Munich, Holtfreter began a systematic study of the capacity of small pieces of the gastrula embryo to develop and differentiate in isolation in his balanced salts solution, that is, in the absence of signals from the organizer. This is currently called a specification test, and was then called a differentiation capacity test, or a test of the cells' state of determination.
From page 218...
... into English by Viktor Hamburger.4 The results lee! HoTtfreter to suggest that, except in the case of the neural induction of ectoderm, the organizer does not provide detailed instructions for the differentiation of neighboring cells.
From page 219...
... He fount! a research position at Montreal's McGill University, supportec!
From page 220...
... At the same time, the layer of ectoclermal cells expancis to cover cells of the lower half clue to the insertion of creep cells into a surface sheet of cells, thereby increasing its area. Although he observed the convergent extension of organizer cells, he gave this morphogenetic activity a lesser role in gastrulation than the tugging force of bottle cells, recent studies give it the primary role.
From page 221...
... that the sub-lethal conditions of the medium dissociate or inactivate the suppressive agent, allowing other agents to become active en c! initiate neural clevelopment of the tissue.
From page 222...
... cells from clifferent germ layers of a neurula-stage embryo, which were then mixed and reaggregated randomly in different combinations. Ectodermal and endodermal cells segregated strongly from one another in these mixtures while ac~hering to like cells, eventually forming separate spheres.
From page 223...
... the organization of these recombinates en c! of the normal embryo's germ layers.
From page 224...
... The author did not have the opportunity to know Johannes Holtfreter personally, but he has greatly admired Holtfreter's research contributions for many years. It is the fate of nonagenarians that few of their contemporaries survive who could have written a more personal account.
From page 225...
... The Heritage of Experimental Embryology. New York: Oxford Press, 1988.
From page 226...
... Der Einfluss von Wirtsalter und verschiedenen Organbezirken auf die Differenzierung von angelagertem Gastrulacktoderm.
From page 227...
... 138:522-656. Differenzungspotenzen isolierter Teile der Anurengastrula.
From page 228...
... 123:53-120. 1991 Reminiscences on the life and work of Johannes Holtfreter.


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