User:Ablair2/sandbox

Article evaluation
Overall

The article is relevant to the topic of embryogenesis, and is very detailed. The only thing that I found confusing was the different headings and use of bullets throughout the article. A good article should be consistent with bold and special characters.

The article was fairly neutral, based mainly on vertebrates and mammals.

Axis formation was underrepresented in the article. This could have been presented before organogenesis.

The first citation link that I tried clicking on, so before inserting the reference link, the author should make sure it worked before publishing.

The talk page refers to some problems referring to the article Embryogenesis.
 * Spelling errors throughout article
 * Too broad article title, so should make more specific to the information presented

Observations
 * 1) Good use of figures
 * 2) Good use of bullets for the movements of cell, under the title heading Formation of the gastrula

Fertilization in Zebrafish
The zebrafish must go through processes for oocyte maturation before fertilization can begin. The female oocyte goes through four stages before it is fully matured. Stages I, II, and III the oocyte is growing, and some maternal mRNA is distributed throughout the oocyte and other mRNA is specifically localized. There is a difference in the size of the mature oocytes between species. The zebrafish oocytes are anywhere from 7-700 micrometers (0.74 m). Zebrafish oocytes are transcriptionally active. Zebrafish egg form a Balbiani body, which is a visible cloud of mitochondria. The gene bucky ball (buc) is essential for the Balbiani body formation in zebrafish. A study has shown that without buc, the zebrafish egg is unable to form a Balbiani body, which affects the animal-vegetal polarity.

The oocyte forms yolk granules for preparation of fertilization. The mature oocyte in zebrafish is released when a rise in gonadotrophin and a steroid is produced. The nucleus resides in the animal pole of the oocyte. Fertilization in zebrafish are external, meaning the eggs and sperm are released outside of the body for fertilization. The zebrafish sperm doesn’t have an acrosome. The sperm enter through the micropyle usually near the animal pole on the oocyte, which allows the sperm to penetrate the chorion. At this point, fertilization has begun. After the sperm enters the oocyte through the micropyle, there is a rise in calcium in the newly fertilized egg. The calcium transient spreads from the sperm entry to the animal pole.

(Figure inserted here) Figure. A study was done by researchers to show the analysis of calcium signaling in the zebrafish oocyte, and when the calcium is released. The rise in calcium is important for the rise of animal pole after oocyte has been fertilized. This figure shows the rise in calcium by calcium green fluorescence. At 2.0 min after sperm was injected, the calcium was most apparent.

The sperm can only enter through this small hole, known as the micropyle on the female egg. The micropyle allows for only one sperm to enter inside the oocyte. The gene buc prevents polyspermy from happening, by not forming multiple micropyles. Once the male sperm haploid genome is released into the zygote, the gene futile cycle (fue) is required for female nuclear migration toward the sperm nucleus. After the egg is fertilized and the nuclei are fused together forming a diploid zygote, a cytoplasmic cap is formed at the top of the animal pole, in preparation for cleavage.

Neurulation in Zebrafish
Neurulation in Zebrafish is the development of a neural tube from the ectoderm layer, which is stated in gastrulation, and the neural plate.

(Figure inserted here). This figure shows the simple organization of the developing neural tube in zebrafish embryo. The researchers used in situ hybridization against a specific mRNA found in the layers of the neural tube.

After gastrulation, the mesodermal layer meets the ectoderm, inducing neural induction. Neural induction is the first step in the neural tube formation. Some signals which are expressed early in neurogenesis is Wnt, Fgf, Nodal proteins, and retinoic acid. These are pattern signals that help with axis formation during the formation of the neural plate. A prechordal plate and the lateral region form from the central part of embryo. The dorsal ectoderm later becomes the neural plate. The neural plate is a flat sheet of neuroepithelium cells, which comes from the thickening of epiblast cells. The lateral ends of the neural plate begin to thicken, and fuse together forming a neural keel. The neural keel then fuses at the midline, forming the neural rod. This process happens at about 16 hours of embryo development, forming a solid neural rod from the neural plate. There are some structural proteins, Pard3 and Rab11a involved in the midline polarization, during the formation of the neural rod. The neural rod goes through a process called secondary neurulation to form the neural tube. During neurogenesis, the mesoderm contains somites that are continuously differentiating for future organ development.