Introduction
Introduction
Why is this study important?
This study is important because the results could reveal how to decrease healing time for wounds and to reduce the risk of scar and infection. By decreasing the time in which it takes wound to heal, people would have shorter recovery times from deep lacerations, minor cuts, and abrasions.
Purpose: The purpose of this experiment is to observe the effect of a 0.1% and a 1% nucleotide/choline stock of the regenerative capabilities of the planarian Dugesia tigrina.
Hypothesis: The hypothesis for this experiment is: If the nucleotide/choline substances used in stimulating the regeneration rate is increased than the regeneration rate will be higher and more successful.
Independent and Dependent Variables: The independent variable for this experiment is the amount of choline the planarian will be exposed to while they are regenerating. This experiment will be testing a 1% Nucleotide/Choline stock solution, a 0.1% Nucleotide/Choline stock solution and a 0% Nucleotide/Choline stock solution (this will be the control). The dependant variable for this experiment is the regenerative capabilities of the planarian and their survival numbers.
Information:
Since the beginning of time men have been intrigued by the notion of regeneration, from Greek mythology to scientist today. The planarian or Dugesia tigrina have been used in many regeneration studies because of their remarkable regenerating capabilities. The freshwater planarians are able to completely regenerate an entirely new individual when cut approximately two thirds of the animal at or below the level of the pharynx. The planarian regeneration is observable in stages. It is from these stages that the regeneration rate was observed and was documented in this study when they were exposed to different percentages of a nucleotide/choline solution substance.
Planarian or Dugesia tigrina are in the phylum Platyhelminthes, class Turbella, order Tricladida, and family Dugesiidae. They are usually about three to fifteen millimeters long. Their mouth is on the ventral side more than half way toward the tail. The pharynx, which may be protruded from the mouth, ends in an intestine. (Encyclopedia Britannica, 1999-2000) The pharynx is long, highly muscular and protrudible through the mouth. The pharynx is how the planarian gathers its food (Pennak, R.W., 1989).
Planarians are able to regenerate so successfully that a very small planarian fragment corresponding to only 1/279 of the organism is still able to form a complete individual. (Alvarado, A., & Newmark, P.A., 1999) One reason planarians regenerate so successfully is because they contain self-renewing cells called, 'neoblasts', which provide the necessary cells for regeneration. Planarian neoblasts, which are scattered throughout the body except in the pharynx, have to proliferate first so that the blastema can be formed to direct localized cellular proliferation allowing regeneration to begin. (Kiyokazu, A. & Wantanabe, K., 1999) Planarians are able to regenerate because of the presence of small, undifferentiated stem cells. The undifferentiated stem cells are the same type of cells from which an embryo develops. They have the ability to be any type of cell in the body regardless of what body part is regenerating on the body. (Bueno, D., Baguna, J., & Romero, R. 1996) While planarians have an abundance of these undifferentiated stem cells the more complex the organism becomes the more differentiated it cells become. Human embryos for example, are simple organisms that contain undifferentiated stem cells and possess the power to regenerate missing parts during their embryogenesis. As humans develop however, they lose this ability as their cells become more differentiated and designed for a specific function. (Alvarado, A., 2000)
A table of the
regeneration cycle of planarian is shown in Fig 1. (Kobayashi, C., Watanabe, K.,
& Agata, K., 1999) The first signal of regeneration of pharynx muscles was
detected at one to one and a half days of regeneration in the posterior region
of the stump. Specifically at one
and a half days of regeneration a slit was formed and is open in the posterior
portion
of the cell mass. (1 d) This cluster of small cells with a slit is identified as
the first sign of the regeneration of a new pharynx.
This is observed by a
histological
observation. Histology is used to
determine how tissues are organized at all structural levels, from cells and
intercellular substances to organs. At
two to three and a half days of regeneration the pharynx rudiment enlarges and
grows into the pharynx cavity. (2d) At three and a half days it became clear
that the position of the pharynx rudiment is the boundary region between the
stump and the blastema. Also at
this time the proximal region of the pharynx lumen is formed. It is initially observed as a slit in the anterior portion of
the pharynx rudiment. By five days
of regeneration the pharynx lumen is opened and enlarged to connect the
intestinal duct to the pharynx cavity. At
five to six days of regeneration the pharynx cavity becomes open.
(Kobayashi, C., Watanabe, K., & Agata, K.)
Choline is a dietary component that is important for the structural
integrity of cell membranes; it is critical for membrane structure and function.
For a developing baby, choline plays a critical role in its health and
helps to ensure a normal development process.
To ensure the developing fetus and infant receive adequate amounts of
choline, large amounts of choline are delivered to the fetus across the placenta
and human milk is an especially good source of choline. (The National Academy of
Sciences, 1999)
