Sea Urchin Fertilization

On Thursday, I was able to watch fertilization occur!

In lab, we used sea urchins (SU) to watch fertilization. I scooped out my own sea urchin from the tank and put it in the holding bin. While there, named the SU Terry (a unisex name). As Terry was getting acclimated to that water, I got a cup filled with sea water, a petri dish, a needle, potassium chloride, and paper towels. I also put on gloves. It was time.

I got Terry and placed it on the petridish. I turned it over to expose its bottom. Poor thing was not happy. The needle was filled with 1 milliliter of potassium chloride. Angling the needle between the needle portion and the opening, I injected Terry with 0.5 milliliters of potassium chloride. Poor thing was in pain and writhing around. :(

After about a minute, the gametes started flowing out of Terry. It was white, so we determined that Terry was in fact a boy! So we collected the rest of the sperm in the petri dish.

To watch fertilization, I got another group's eggs and put 1 drop of it on a microscope slide and covered it with a cover slip. Then, I got a small beaker and filled it with 10 ml of water. I then pipetted some of the sperm in the water to activate it. After focusing on the eggs under the microscope on the 40x objective, a drop of sperm solution was added to the slide. Looking at the slide, I was able to see the sperm vigorously swimming around. Looking at the eggs, it was clear to see which sperm fertilized eggs. It was also cool to see the fast block prevent polyspermy. The most awesome part was watching the fertilization envelope develop.

Just to watch what we have been learning occur before my very eyes was beautiful. It helps to make a lot of the concepts make sense.

Craniosynostosis

Craniosynostosis is a condition where an infant has premature fusing of the sutures in his head, leading to ossification. What is interesting is that the ossification is of mesenchyme. The sutures that hold the bones of the head together are made from fibrous tissue. But they have two more important functions: to allow the baby's head to fit through the birth canal, and separation of the bones that make up the skull cap.

Membrane ossification of the cranial bones occurs during the first few weeks of fetal development, the first trimester of pregnancy. The 4 bones that make up the skull cap are the frontal, parietal, and occipital (anterior + squamosal). What determines the fusion of these bones are many factors such as transcription factors, EM molecules, and cytokines. The precise process is not known. A combination of genetic and environmental factors cause craniosynostosis. Below is a table that discusses the types of craniosynostosis and the characteristics associated with them. The table also comes from the reference below.

BUROKAS, LAURA. "Craniosynostosis: Caring For Infants And Their Families." Critical Care Nurse 33.4 (2013): 39-51. Academic Search Premier. Web. 21 Sept. 2014.

Some Unfamiliar terms

Theca cells - These make up a layer of ovarian follicles. One of the layers of theca cells produce androstenedione, which is converted to estradiol by aromatase.

Zona Pellucida - It is a membrane made of glycoproteins that surrounds the cell membrane of the oocyte. It is the structure that sperm bind to and start the acrosome reaction.

Corona Radiata - This is the inner layer of the cumulus oophorus. It provides essential proteins to the developing cell

Graafian follicle - also known as an antral follicle; It is a stage in folliculogenesis where the antrum forms next to the oocyte.

"Mom... What Am I?!"

People don't usually ask what they are in terms of gender. You know definitively if you are a male or female. But this wasn't the case in the Law and Order: SVU episode entitled 'Identity'.  

In this episode, the suspects were a set of identical twins that were a boy and girl. Honestly, that should raise a red flag right now. Identical twins can only be one gender. So that fact that it was both a boy and girl should suggest that some gender reassignment has occurred.

When the twin boys went in for circumcision, the doctor botched one of the twins circumcision. This led the parents to then raise that child as a girl. It was fine at first, but as the girl reached puberty, she found herself liking girls. She was very confused as who she was because she felt like a boy on the inside. She soon found out that she was actually a boy, and the 'vitamins' her parents have been giving her were actually estrogen pills. So the girl stops taking the pills so she can go back to her original gender: a boy.

It was an interesting episode that discussed the science and ethics behind gender roles and reassignment.

http://lawandorder.wikia.com/wiki/Identity_(SVU)