Chalaza

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http://www.geauga4h.org/poultry/egg_labeled.gif

Yesterday, in lab, I came across the word "chalaza" while looking at an egg yolk under the microscope. Not only was I confused as to what this word meant, but I also had no idea to pronounce it. "A chalaza (plural chalazae) is a structure inside an egg which helps to keep the yolk in place. The chalazae attach to either end of the yolk and anchor to the inside of the eggshell, essentially suspending the yolk. Chalazae prevent the yolk from being damaged, promoting the healthy development of the embryonic bird. This structure is also present in some plants, performing a similar function in plant ovules." A chalaza, then, is the visibly white part attached to the egg yolk, helping to anchor the yolk. It is pronounced "kuh-LEY-zuh," emphasis provided by: http://dictionary.reference.com/browse/chalaza.

The information was sourced from the following website:
http://www.wisegeek.com/what-is-chalaza.htm.

Stem Cells for the Brain



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http://www.clipartguide.com/_named_clipart_images/
0511-0811-1701-0815_Cartoon_of_a_Man_Listening_to_
the_Radio_While_Driving_clipart_image.jpg

Yesterday, I was listening to the radio, 103.5 FM, with my dad in the car and I heard a news story on stem cells acting on the brain. Scientists (at one university I can't recall the name of) injected embryonic stem cells into a human with brain cancer. The hES cells were injected with medication needed to target the brain cells. These injected cells were attracted to the mutated cells in the brain, being the cancerous cells, and changed the fate of the cells. They became specialized as fully functioning neurons, and because the medication was targeted specifically to that area, the hopes are that the tumor will diminish greatly, if not disappear completely. This was really interesting to me because hES cells are powerful in that they are totipotent. They can become anything, relating to autonomous specification that we learned about previously in class. The really unique feature of these cells, however, is that they also exhibit conditional specification because they become the cells they are around. For example, hES cells in the brain become neurons. It will be interesting to see if this experiment works, and if so, how much cancer will be treated in the future.

Epiboly



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http://worms.zoology.wisc.edu/frogs/gast/epiboly.gif

During a fierce round of tic-tac-toe yesterday in class, I came across the word epiboly. I had first discovered the term in the textbook, but yesterday's discussion made me realize how important it is in Development Biology. The term is defined as "the movement of epithelial sheets (usually of ectodermal cells) that spread as a unit (rather than individually) to enclose the deeper layers of the embryo. Epiboly can occur by the cells dividing, by the cells changing their shape, or by several layers of cells intercalating into fewer layers. Often, all three mechanisms are used." Essentially, during epiboly, a sheet of cells spreads by thinning to cover the embryo.

The information referenced above was taken from the following reference: Gilbert, Scott F. "Early Development in Selected Invertebrates - Gastrulation." Developmental Biology. Vol. 9. Sunderland, MA: Sinauer Associates, 2010. 164. Print.