Prior to the Spemann-Mangold organizer experiment, Spemann had focused on constricting salamander eggs at the blastopore lip by tying single strands of his baby son’s hair around the tiny eggs. Experimental embryologists used micropipettes to remove cells from developing gastrulas, and transplant the cells to new sites. The rubber could be depressed by the thumb of the user to create a minute amount of suction and was useful for transplantation experiments. Additionally, Spemann created micropipettes that relied on the suction created by a piece of rubber covering the top of the hollow, thin glass rod. When heated and drawn a second time, the needle had an even finer point that allowed experimental embryologists to take embryos out of the jelly membranes in which they were ensconced. The thin needle-like part of the rod was broken off, and then placed over a smaller burner called a micro-burner, another one of Spemann’s inventions. To make a glass needle, Spemann held a glass rod over a burner and pulled it apart so that it became incredibly thin in the middle. Spemann also developed the microtools needed for early experimental embryology, namely glass needles and micropipettes. In the first three decades of the twentieth century, Hans Spemann experimented and led graduate students in conducting experiments with South African clawed frog embryos ( Xenopus laevis) and newt embryos ( Triturus taeniatus and Triturus cristatus). The Spemann-Mangold organizer drew the attention of embryologists, and it spurred numerous experiments on the nature of induction in many types of developing embryos. Spemann received the Nobel Prize in Medicine in 1935 for his work in describing the process of induction in amphibians. Now integral to the field of developmental biology, induction is the process by which the identity of certain cells influences the developmental fate of surrounding cells. The discovery of the Spemann-Mangold organizer introduced the concept of induction in embryonic development. Hilde Mangold was a PhD candidate who conducted the organizer experiment in 1921 under the direction of her graduate advisor, Hans Spemann at the University of Freiburg in Freiburg, Germany. North Holland, Amsterdam, The Netherlands.The Spemann-Mangold organizer, also known as the Spemann organizer, is a cluster of cells in the developing embryo of an amphibian that induces development of the central nervous system. (1997) Head induction by simultaneous repression of Bmp and wnt signalling in Xenopus. Glinka, A., Wu, W., Onichtchouk, D., Blumenstock, C., and Niehrs, C. (1997) Structurally related receptors and antagonists compete for secreted wnt ligands. (1991) Overexpression of a homeodomain protein confers axis-forming activity to uncommitted Xenopus embryonic cells. (1989) Interaction between peptide growth factors and homeobox genes in the establishment of antero-posterior polarity in frog embryos. (1994) The Einsteck-method: position and structure of projections formed by implants of a ventral character. (1996) The vertebrate organizer: structure and molecules. This process is experimental and the keywords may be updated as the learning algorithm improves. These keywords were added by machine and not by the authors. However, the Einsteck can be also carried out with heterologous material, cell pellets, and injected animal caps ( 3, 4) and is more versatile than the organizer transplant. While the Einsteck is much easier to perform than the organizer transplant, the position of the implant can be less well controlled, which needs to be considered when interpreting the results ( 2). This results in the formation of an induced structure which, depending on the embryonic stage of the upper blastopore lip, is a head, trunk, or a tail. Organizer activity is revealed either by transplantation of the upper dorsal blastopore lip into the ventral side of a host gastrula or by inserting the tissue into the gastrula blastocoel (Einsteck method). Its two major inducing activities are neural induction and dorsalization of ventral mesoderm differentiation. The amphibian organizer corresponding to the upper dorsal blastopore lip of the early gastrula, is one of the classical systems in which embryonic patterning has been studied ( 1).
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