John W. Saunders Jr. (November 12, 1919 – December 26, 2015) was an American scientist whose research in the field of developmental biology and zoology played an integral part in helping to understand how various vertebrate limbs develop.
This research was critical in recognizing growth factors that are secreted from the AER and are important in assisting the pattern of developing vertebrate limbs.
[3] The lack of money and available jobs due to the Great Depression made it hard for Saunders and his family to make end meets during his childhood, and World War II forced him to put his graduate education on hold to serve his country in the US Navy.
[3] Saunders also studied French while in junior college and he had a classmate, whose father was an Oklahoma legislature senator, that was failing the class.
[3] At the time, Richards was the chairman of the Department of Zoology at the University of Oklahoma, and he was also a former doctoral student of Princeton Professor Edwin Grant Conklin.
Saunders started his master's degree in 1940 at the University of Oklahoma's zoology department where he wrote his thesis titled "Aberrant Mitosis in the Amnion of the Guinea Pig".
[3] However, Saunders's salary at this job was not sufficient for him to provide for his family while living in Chicago, so he left Weiss's lab after a year.
[6] Saunders spent the summer of 1954 doing research at the Mount Desert Island (MDI) Biological Laboratory, located in Salisbury Cove, Maine.
[1] While he was doing research at Marquette University, Saunders, along with his fellow colleague Mary Gasseling, studied the zone of polarizing activity (ZPA) and they were essential in identifying its role in the development of chick embryos.
[9] Based on this, Saunders conducted further research and was able to deduce that the distal portion of the wing is formed from the mesoderm in a small area at the top of the bud, which he termed as a region of "apical growth".
[9][10] Saunders continued to study the AER and followed up his early work with more research on the apical zone as well as its role in the formation of wing limbs in chick embryos.
[11] However, he also found that, even in the absence of the apical ridge, limb buds with remaining ectodermal cells present after treatment with EDTA could still develop in their distal regions.
[14] During the 1970s, Saunders focused his work back on studying the AER and its role in the development of limbs in chick embryos.
[15] He made this inference based on the conclusion that the AER transfers developmental information by means of signal induction in a manner that remains constant between the various stages and levels that the bud goes through in its development.
[15] Furthermore, Saunders also found that the AER can induce the formation of the entire wing until stage 29 of development, but from this point onwards, it no longer possesses this ability.
[15] In 1973, Saunders published a paper, in which he was a co-author, titled "Spatiotemporal distribution of mechanisms that control outgrowth and anteroposterior polarization of the limb bud in the chick embryo".
[17] After this, Saunders set out to explore what happens to the marginal vasculature in the wings of chick embryos when the AER is removed at various stages during their development.
He did exactly this and published his findings, along with Richard N. Feinberg, in their 1982 article titled "Effects of excising the apical ectodermal ridge on the development of the marginal vasculature of the wing bud in the chick embryo".
After this, they observed how the vascular pattern during the development of the marginal vein of the chick embryos was affected by the removal of the AER.
[18] After his work with the AER and the development of embryotic avian limb buds in the 1980s, Saunders continued to study them more and published a few more papers during this time.
He published his last paper in 2003 about his dear friend, and fellow scientist, John Philip Trinkaus, who had died earlier that year.