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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 Presentation
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Plenty of Planaria
Laboratory Investigation
The Science and Ethics of Stem Cell Research
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.
Overview of Brown Planaria
Dugesia tigrina
Planaria are complex organisms
GastrovascularSystem
Nervous System
Reproductive System
Excretory/OsmoregulatorySystem
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
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
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.
Neoblasts and Stem Cells are Totipotent
“Totipotent” Stem Cell
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
turning on the right genes at the right time in the cells that come from the
dividing stem cells (neoblast).
Regeneration requires…
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
Student Laboratory Investigation
Each team will receive 3 planaria:
Experimental Planaria #1Every team will cut this into half, separating
the anterior from the posterior halves.
Experimental Planaria #2This will be cut in a manner determined by your team.
Control PlanariaThis will not be cut.
Used with permission from UC Museum of Paleontology
Plenty of Planaria
Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley
Planaria Regeneration, Days 1 - 14
Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley
Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley
Plenty of Planaria
Laboratory Investigation
The Science and Ethics of Stem Cell Research