Lens competence in Amblystoma punctatum

The peripheral sensory nervous system in the vertebrate head: A gene regulatory perspective

“…One of the most surprising findings is that despite their diversity, placodes arise from a common territory of multipotent precursors, the preplacodal region (PPR), and their progenitors initially share common properties (Bailey et al, 2006;Martin and Groves, 2006;for review: Schlosser, 2006for review: Schlosser, , 2010Streit, 2007Streit, , 2008)-a hypothesis originally proposed almost 50 years ago (Jacobson, 1963a, b, c; see also Torres and Giraldez, 1998). Placode progenitors are specified from ''the border'', a region where neural and non-neural gene expression overlaps and where cells are initially competent to give rise to neural, neural crest and placodal derivatives, as well as epidermis (Baker et al, 1999;Basch et al, 2000;Bhattacharyya and BronnerFraser, 2008;Gallagher et al, 1996;Gallera and Ivanov, 1964;Groves and Bronner-Fraser, 2000;Hans et al, 2007;Köster et al, 2000;Kwon et al, 2010;Liedke, 1942Liedke, , 1951Martin and Groves, 2006;Nieuwkoop, 1958;Pieper et al, 2012;Selleck and BronnerFraser, 1995;Servetnick and Grainger, 1991;Storey et al, 1992;Streit et al, 1997;Waddington, 1934Waddington, , 1935Waddington and Needham, 1936). Specification of placode progenitors is controlled through a balance of inductive and repressive signals emanating from surrounding tissues: the adjacent neural plate and future epidermis and the underlying mesoderm (Ahrens and Schlosser, 2005;Brugmann et al, 2004;Litsiou et al, 2005).…”

Immunohistological Studies on Lens Differentiation Experimentally Induced in Vitro in the Epiblast of Chick Blastoderm

“…The inductive capacity of the head meso-and endoderm for lens formation has repeatedly been suggested by many authors (Mangold, 1931;Okada and Mikami, 1937;Liedke, 1951;Twitty, 1955;Coulombre, 1965 ;Jacobson, 1966) , though there is little doubt about the role of the optic vesicle in the lens formation in normal development of the vertebrate embryos (Spemann, 1901;Waddington and Cohen, 1936;Alexander, 1937;van Deth, 1940;McKeehan, 1951;Langman, 1956;Muthukkaruppan, 1965). Recently one of us has found that the lens with fibres is invariably induced in the epiblast of the presumptive head region of young chick blastoderm in the absence of the optic vesicle, when this epiblast is cultured in vitro combined with a fragment of the dorsal skin dermis from 6.5-day embryo for six days ( Mlzuno,1970( Mlzuno, ,1972 .…”

An Immuno-embryological Study on the Chick Lens

“…Nevertheless, the independant development of lenses shows that the eye eup is not the only part which may be involved in lens development. Liedke (1951 ) showed that the belly ectoderm of Amblystoma punctatum was not capable of developing a lens when transplanted just before the formation of the optic vesicle, but was able to rea ct i f trans pl anted in the neurula st a ge. It f ollows that to be able to react the ectoderm must be in position sorne time before the contact with the optic vesicle is established.…”