plenty of planaria laboratory investigation
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The Science and Ethics of Stem Cell Research. Plenty of Planaria Laboratory Investigation. What are Planaria?. Freshwater flatworms (phylum: Platyhelminthes) Live in freshwater under leaves and stones Avoid light (“negative phototaxis”) Free living – not parasites - PowerPoint PPT PresentationTRANSCRIPT
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Plenty of Planaria
Laboratory Investigation
The Science and Ethics of Stem Cell Research
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What are Planaria?
Freshwater flatworms (phylum: Platyhelminthes) Live in freshwater under leaves and stones Avoid light (“negative phototaxis”) Free living – not parasites Carnivores – eat decaying meat, insects and larvae
(egg yolks or liver in the lab) 1-20 mm in size Long lived Use sexual or asexual reproduction
This picture has been released it into the public domain.
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Overview of Brown Planaria Dugesia tigrina
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Planaria are complex organisms
GastrovascularSystem
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Nervous System
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Reproductive System
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Excretory/OsmoregulatorySystem
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Why study Planaria to learn about stem cells? Planaria have an amazing ability to regenerate parts of
themselves Planaria regeneration is a great model for demonstrating
stem cell function and complexity of tissue regeneration They can grow easily in the lab
1/279th
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Neoblast = Planaria Stem Cell
20-30% of all the cells in a planaria are Neoblasts.
Neoblasts divide by mitosis and can make more of themselves. They are the only dividing cells in planaria.
When a planaria is wounded, neoblasts migrate to the site and begin dividing
Neoblasts can become ANY cell the planaria needs—nerve cells, flame cells, reproductive cells…
Ann. Rev. Cell. Dev. Biol. 20:725-757, 2004
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Three types of planariawith their neoblasts labeled
with BrdU
BrdU (bromodeoxyuridine) is substituted for thymine during DNA
replication. Only dividing cells—in this case the neoblasts—will show
detectible amounts of BrdU.
(Dev. Biol 220: 142-153, 2000)
A. Phagocata sp.B. Girardia dorotocephalaC. Schmidtea mediterranea
Dugesia sp.
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Neoblasts and Stem Cells are Totipotent
“Totipotent” Stem Cell can become:
Extra Embryonic Blood Nerve Skin
They can become any cell type in the body
In Humans: Totipotent cells are limited to early embryonic division
In Planaria: Neoblasts are always present
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turning on the right genes at the right time in the cells that come from the
dividing stem cells (neoblast).
Regeneration requires…
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Care and Feeding of Planaria The water is very important! Fresh water from a
pond, stream or lake is best; spring water is adequate
Keep cultures in a cool, dark place
Feed planaria at least once a week
Change the water twice a week, especially after feeding
After cutting them, the cultures should not be fed
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Plenty of Planaria
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Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley
Planaria Regeneration, Days 1 - 14
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Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley
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Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley