STEM CELLS

 STEM CELLS?

Stem cells are non-specialized cells which can create other types of cells. These cells are within us in our bodies our whole life. They are fasinating to learn about and can help change the world in so many ways yet people still lack knowledge about them.  For one thing, they have the potential to create new cells in the fetus than in the adult body; and some types of stem cells have the capability of creating other types of cells in the body. Other stem cells can repair and then replace tissues or cells in the body that were previously damaged.

Embryonic Stem cells: These stem cells are derived from embryos. Most embryonic stem cells come from embryos that develop from eggs that have been fertilized. They may eventually be donated for research purposes with informed consent of the donors. These stem cells are not derived from eggs fertilized in a woman's body.

iPS Stem cells: Also known as induced pluripotent stem cells. These cells have been created from some type of adult cell (skin, stomach, liver, etc) through the introduction of genes that reprogram the cell and transform it into a cell that has all of the characteristics of an embryonic stem cell.

Adult/ Somatic Stem cells: Known to be an "undifferentiated" cell. It is found among differentiated cells within a tissue or organ. These can renew themselves and can differentiate to stop some or all of the major specialized cell types of the tissue or of the organ. 

Thanks to scientists in this day in age we are able to use Stem cells in order to treat (and hopefully cure) numerous different diseases because they have the ability to become any kind of tissue. Stem cells are capable of generating into any form of a healthy cell which is why they can treat diseases. Diseases such as Parkinson's, MS, and Alzheimer's have been explored and scientists are continuing to the attempt to find a cure to these horrible diseases that millions of people are faced with every year.  New research and tests have shown that stem cells may also have the potential for treating spinal cord injuries. It is important for people to know the benefits of stem cells and why the research for these projects are so important and critical for everyone.

  Cells are grown in a laboratory via culturing. Culturing simply means that cells are grown in a controlled condition. In some cases these cells are grown in a broth that is high in nutrients. The term for this is a culture medium. The cells will begin to divide and cover the surface of the petri dish they are in but only if the culturing is successful. Once the successful process of culturing is complete it is then re-cultured and a cell line is established. It is crazy to think that in one small petri dish millions of cells exist. Not only are there just millions of new cells bu they are also genetically identical to the original cells. It is possible of course that these cell lines could develop abnormalities which leaves the cells to be different genetically from the original samples of the cell. Interestingly, cells can be frozen and shipped to labs around the world. This makes research convenient for scientists and they can share their findings not just through paper or via their experiments but others will be able to see the results themselves and even do their own experiments with the new cells.

EMBRYOLOGY

Embryology: The scientific study of the development of an embryo from the point of the ovum's fertilization to the fetus stage in its growth.

In Embryology....The first step of fertilization is The acrosomal reaction.  This is when the sperm must fuse and penetrate the egg in order to fertilize it. This is generally very easy for the sperm but it can be hard to break through the egg's outer shell. It is very hard and used for protection.  This is the reason for why the sperm go through the acrosome reaction. This acrosome is a cap-like structure on the head of the sperm. It is composed of  surface antigens and numerous enzymes. Its job is to break down the egg's outer shell. Once the sperm approach the zona pellucida of the egg, they undergo this acrosomal reaction. During the reaction the membrane around the acrosome fuses with the plasma membrane of the sperm and exposes the contents of the acrosome. This allows for fertilization to occur. 

The next step is for the cortical reaction to occur. Once the sperm reaches the egg's plasma membrane it triggers calcium to be released from the egg. From this, the cortical granule membranes mix with the plasma membrane of the egg. This frees the contents of the granules to the extracellular space. As this calcium circles the egg a wave of cortical granule fusion occurs. It is important to note that the contents of the granules are different among species of humans and other creatures.


Sea Urchin example:

The granule contents alter a protein coat on the vitelline layer, so that it is released from the membrane. This process of freeing the protein is referred to as "elevation of the fertilization envelope". Due to this, non-fertilizing sperm are lifted away from the egg’s membrane and are prevented from entering the egg. This prohibits polyspermic fertilization (this is when an egg is fertilized by more than one sperm). 




Once the egg is fertilized it is now time for the organism to develop. Cleavage is the first step in this process of developing all of the multicellular organisms. This is the division of the cells in the early stages of the growth of the embryo. The zygote (single-cell) expands into what is called a multi-celled embryo. Due to the process mitosis, the blastula is produced. The blastula is made up from a spherical layer of cells that surround the blastocoel. This blastocoel is like a fluid filled cavity. The size of the cells decrease because of the rapid division of the cells that takes place. This increases the cell's surface to volume ratio. Because of this a more efficient oxygen exchange takes place among the cells and the environment they are in. Throughout this stage of fertilization, RNA is spread through the blastula. 



The next step in embryology is known as Gastrulation. This is a series of cellular changes to positions where they form the three main cellsuch layers. The ectoderm forms the tissues associated with the outer layer of our body (skin, hair, sweat glands). The next layer is the mesoderm. This forms the muscles, cartilage, bone, blood along with other connective tissue that are responsible for supporting body movement. This layer also forms the reproductive systems organs as well as the kidneys. The last layer is called the endoderm; this is the inner layer. It is responsible for forming tissues and organs that are associated with the digestive system, the respiratory systems, and other endocrine systems too.

Organogenesis is the series of organized, integrated processes that transform an unstructured mass of cells into a complete organ in the developing embryo. This creates the characteristics of the organs. The internal organs begin this development in humans within the third to eighth weeks in utero (state of the embryo or fetus). The germ layers differ by three seperate processes. This consists of folds, condensation and splits.

CONNECTION WITH SEA URCHIN

Most sea urchins have their eggs free floating in the sea. Some keep them on their spines for protection. In order to prevent the sperm and egg from being washed away, these urchins have developed mechanisms that bring the gametes together. Once a sperm cell encounters an egg of the same species, components of the jelly coat bind and connect to specific egg receptors in the plasma membrane. This then triggers the release of calcium that facilitates fertilization. 

In  sea urchins, early cell divisions are rapid. The proteins that are synthesized during the cleavage process utilize mRNA that is found within the cytoplasm. The first three cell divisions bisect the embryo equally while the fourth cleavage divides the cells in the top half equally. The ones in the bottom half are divided unequally. At this point, the cells continue to divide until they form the blastula.There are ten cycles of cell division for sea urchin embryos in order to make a single epithelial layer. The embryo then begins the grastrulation process (a multipart process which rearranges and invaginizes cells to produce three germ layers).  

This fertilized egg then develops into a free-swimming blastula embryo in twelve hours. The blastula transforms into a echinopluteus larva. This larva has has elongated arms, nutrients, and a cilia  which is used to capture particles of food. It takes up to several months for a larva to be completely developed. The larva proceeds to sinking to the bottom of the sea once the development is complete and begins its process of turning into an adult. Shockingly enough this may only take an hour.