User:Bmooney2015/sandbox

Article Evaluation - Organogenesis
This article simply defined organogenesis. However, it only defines it from one source from one expert in this field. I think that for this article to be better it needs to have several experts expressing this same opinion on what organogenesis clearly is. It also does not explain the various periods of development of an embryo to explain how this topic fits in (what stages come before and after organogenesis). I think that this article is good though because it does make an effort to define what the process is in both plants and animals.

Blastema Formation
As stated above, there are several different types of organisms that can utilize a regenerative blastema as an adult. These organisms include urodele amphibians, zebrafish, and planarian flatworms as major creatures of study. In flatworms, the formation of a blastema needs adult stem cells that are called neoblasts for any type of regeneration to occur. Flatworms use these undifferentiated cells for regeneration after paracrine factors can provide signals from the surface of the wound. The cells in the blastema are also referred to as clonogenic neoblasts (cNeoblasts) that are able to move to the site of the wound and reform the tissue. In urodele amphibians, studies suggest that dedifferentiation of cells leads to the formation of a blastema that is able to form multiple tissue types after the amputation of their tails and wound healing occurs. In zebrafish, and in general, it seems as if experts are still uncertain of what truly forms the blastema. However, two common theories that have often been expressed are cell dedifferentiation and the recruitment of stem cells to the wound site.

Involved Signaling Pathways
There are several different signaling pathways that have been shown to be involved with limb regeneration through the formation of the blastema. In flatworms, studies suggest that after using RNA interference (RNAi) Smed-betacatenin-1 was found to set up the anterior-posterior axis. Inhibitions to this results in reversed polarity across the blastema. Urodeles use hedgehog for dorsal-ventral patterning of their regenerating tail and its surrounding tissue. This was suggested by its inhibition leading to reduced blastemas. Zebrafish seem to use IGF signaling in limb regeneration as its inhibition led to clues of them being required for blastema function.