Download - Cell Differentiation
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Cell DifferentiationHow cells specialize to become tissues and
organs
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Current Research in Cell Differentiation
Anthony Atala – researcher on growing new organs.
Able to grow a bladder
Has a dot matrix printer that prints out a heart.
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For simple, hollow organs such as the bladder and trachea, researchers seed scaffolds with living cells and then transplant the entire organ into patients
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July 13, 2012, Hannah Warren, 2, poses with her parents Lee Young-mi and Darryl Warren at Seoul
National University Hospital in Seoul, South Korea.
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The stem cells used came from Hannah's bone marrow through her hip bone. They were then
seeded in a lab onto a plastic scaffold, where it took a week for them to multiply and make a new
windpipe.
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Dr. Doris TaylorUniversity of Minnesota researcher.
You can use detergents to remove all of the cells from connective tissue.
She is holding a heart that has had all of the cells removed.
She has been able to place cells on these hearts and have the cells grow and form a new heart.
She has even been able to make one that beats!
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Liver BudsHuman skin stem cells, reprogrammed into an
embryonic state and mixed with 2 other cell types formed miniature livers that kept mice alive for a
few months.
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Researchers have also worked to create pure cultures of functional cells in the laboratory, hoping that cells could be infused into patients, where they
would establish themselves.
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3 current Strategies:1. Seed scaffolds with living cells and then
transplant entire organ2. Create pure cultures of cells and infuse into
patients.3. Grow and combine cell types together and then
transplant.spray on skin
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Cells
Cells specialize and organize themselves into tissues.
These are the four types of tissues found in humans
What type of tissue makes up the blood?
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Tissues
Tissues organize themselves into organs
So, an organ is different types of tissues working together to do a job.
In the case of the heart, there is muscular, connective, nervous and epithelial tissue in the heart working together to pump blood to the body.
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How a cell decides what it will become
Some of the signals that determine what a cell becomes comes from the cell itself.
Depending on where the cell is certain genes will be turned on and others turned off.
This will help determine the kind of cell it becomes.
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External Factors in Cell differentiation
Chemicals coming from other cells can influence what a cell becomes.
These chemicals usually come from cells that are close by
The chemicals emitted turn on and off certain genes.
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Environmental Signals
Cells also get signals from the environment.
Temperature can be a factor that affects cells.
Heat Shock can cause cells to produce proteins (HSP) to protect them from heat.
Lack of oxygen, pH, UV radiation are other factors that can affect what genes are turned on by a cell.
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Stem Cells
This is a photo of a human stem cell growing on a culture medium
This cell has the potential to become any cell in the human body.
All of the specialized cells have the same DNA as the Stem Cell.
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Fat cells
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Nerve cells
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Specialized cells of the retina
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Macrophage
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Fertilization and the Zygote
If a cell is taken from the Morula stage it can become a person.
The cell is totipotent
If the cell is taken from the blastocyst stage it can become any organ, but it cannot become a person.
Those cells are pluripotent
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Unipotent
Once a human cell starts down a path to become a specialized cell it cannot go back.
For us the cell cannot become anything else, but that particular specialized cell.
At this stage the cell is unipotent.
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RegenerationThere are some creatures who have cells that can go backward.
That is they can go from unipotent to pluripotent
For the salamander some of the cells in its leg can dedifferentiate.
Those cells can become stem cells and then specialize into tissues to form a new leg.
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This Sea Star is regenerating it lost limbs
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The salamander can regenerate the limb, heart, tail, eye tissues, kidney, brain and
spinal cord through out life
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The Zebra fish can regenerate heart tissue
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Deer regenerate their antlers every year. For a white tailed deer this can be 60 lbs.
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The Snow shoe hare can regenerate parts of its ears.
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The Brown Bat can regenerate parts of its wings
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Crayfish can regrow lost claws.
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Sea squirts can regrow a whole new animal
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Gecko’s can regenerate their tails.
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One third of the human liver can regenerate into a whole organ
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This patient has received a liver transplant. It will take up to 6 months for the liver to
regenerate completely
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Internal CuesThe cells position in the blastula helps to determine what it will become as the blastula turns into the gastrula.
Cells on the outside of the gastrula become what’s called ectoderm.
Cells on the inside become what is called endoderm.
The middle germ layer is called the mesoderm.
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General fates of the three germ layers
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Gene Regulation
All cells start out with the same # of chromosomes and the same # of genes.
For a stem cell to become a smooth muscle cell it must turn on the smooth muscle genes and turn off the others.
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Internal cuesWhere the stem cells is helps to determine which genes are turned on and off.
One of the internal cues is transcription factors.
Transcription factors are proteins, made in the cell, that turn genes on.
So where the cell is can cause particular proteins to be made that help to turn genes on.
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Male and FemaleUp to 5 weeks in development the male and female fetuses look the same.
At that point the testes start producing a transcription factor.
This protein, called the SRY factor is produced in the testes.
It flows from cell to cell and turns on The SRY gene in the Y chromosomes of the males.
This gene causes a fetus to develop as a male.
So, until about 6 weeks in development we are all females!
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Heat Shock Factor- External cues
When a cell is too hot it produces heat shock factor (HSF).
This protein goes to the nucleus.
It turns on certain genes to produce compounds that will make the cell membrane resistant to heat.
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Other external factorsSimilar shock factors have been discovered for lack of oxygen (hypoxia).
So cells have a number of fates.
They are affected by their location, the cells next to them and external factors like heat and oxygen.
These whitefish cells are in the morula stage.
What is their potency?