User:Kzanganeh/sandbox

= Article Evaluation = Egg Cell

The content seems relevant to the title of the page, everything is in regard to the egg. There are multiple images, some of which are not thoroughly explained in the article. For example, the second image of the diagram of the egg shows all the structures in the egg with a brief description. I do believe that the editor could go more in depth about each individual structure. Some of the references used to support this article are slightly out of date. For instance one reference is from 1959, while another is from 1977. The most recent source was in 2013, which for some might be considered out of date since new experiments are being tested. However, the links to the references do work and also the links throughout the article work as well. The tone is neutral and everything is presented in a factual manner. Nothing seems to appear biased in the article. However some information could be slightly underrepresented. For example, there is no specific size given for the human ovum, the ovum is just said to be "visible to the naked eye." A quantitative measurement would be much more beneficial to the article. This article is of the WikiProject Molecular and Cell Biology along with the WikiProject of both Medicine and Animal Anatomy. This article is rated as a start-class article but has a high importance scale for the Animal Anatomy WikiProject. The conversations regarding the article mainly deal with the peer-readers wanting clarification on some statements made in the article. However, this article goes slightly deeper into the topic of the ovum from what we have spoken about in class so it was beneficial to someone who need a brief understanding of the characteristics of the ovum.

Liver Regeneration

There are two events in which the liver has the capability to regenerate, one being a partial hepatectomy and the other being damage to the liver by toxins or infection (1). The processes described below deal with the pathways triggered after a partial hepatectomy.

Following the event of a partial hepatectomy, there are three phases for the process of regeneration. The first phase is the priming phase and during this portion, hundreds of genes are activated and prepare the liver for regeneration. This priming phase occurs within 0-5 hours after the hepatectomy and deals mainly with events prior to entering the cell cycle and ensuring that hepatocytes can maintain their homeostatic functions. The second phase deals with the activation of various growth factors such as EGFR (epidermal growth factor receptor) and c-Met. These two factors are major components of liver regeneration. The final phase deals with termination of proliferation by TGF-β.

Immediately after a hepatectomy there is an activation of numerous signaling pathways that start the process of regeneration. The first being an increase in urokinase activity. Urokinase is known to activate the matrix remodeling. This remodeling causes the release of HGF (hepatic growth factor) and from this release now c-Met can also be activated. EGFR is also activated by the same way as c-Met,and these two growth factors play a major role in the regeneration process. These processes occur outside of the hepatocyte and prime the liver for regeneration. Once these processes are complete, hepatocytes are able to enter the liver to start the process of proliferation. This is because there is a communication between β-catenin (inside the hepatocyte) and the growth factors of EGFR and c-Met (outside the hepatocyte). This communication can occur because β-catenin and Notch-1 move to the nucleus of the hepatocyte approximately 15-30 minutes after the hepatectomy. The presence of these two proteins increases the regenerative response and the HGF and EGFR act as direct mitogens and can produce a strong mitogenic response for the hepatocytes to proliferate.

After the regeneration process has completed, TGF-β (transforming growth factor beta) puts an end to the proliferation by inducing apoptosis. TGFβ1 inhibits the proliferation of hepatocytes by repressing HGF. As mentioned above, urokinase activated the release of HGF; therefore, TGFβ1 also represses the urokinase activity. This process is able to bring the hepatocytes back into their quiescent state.

Sometimes, hepatocytes do not have the ability to proliferate and an alternative form of regeneration is able to take place to rebuild the liver. This can happen with the help of biliary epithelial cells have the capability of turning into hepatocytes when the original hepatocytes have problems proliferating. This is due to the fact that biliary cells have two functions, one being the normal transport of bile and the other becoming stem cells for hepatocytes. The same also occurs vice versa, with hepatocytes being able to turn into biliary cells when they cannot proliferate. Both of these kinds of cells are facultative stem cells for each other. Facultative stem cells originally have one fate but upon injury of another type of cell, can function as a stem cell. These two types of cells can repair liver tissue even when the normal mechanism of liver regeneration fails.