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Plenty of Planaria Laboratory Investigation

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

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Plenty of Planaria Laboratory Investigation

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  1. The Science and Ethics of Stem Cell Research Plenty of Planaria Laboratory Investigation

  2. 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.

  3. Overview of Brown PlanariaDugesia tigrina

  4. Planaria are complex organisms Gastrovascular System

  5. Nervous System

  6. Reproductive System

  7. Excretory/Osmoregulatory System

  8. 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 Why study Planaria to learn about stem cells? 1/279th

  9. 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

  10. Three types of planaria with 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. A. Phagocata sp. B. Girardia dorotocephala C. Schmidtea mediterranea Dugesia sp. • (Dev. Biol 220: 142-153, 2000)

  11. “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 Neoblasts and Stem Cells are Totipotent

  12. Regeneration requires… turning on the right genes at the right time in the cells that come from the dividing stem cells (neoblast).

  13. 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

  14. Student Laboratory Investigation Each team will receive 3 planaria: • Experimental Planaria #1 Every team will cut this into half, separating the anterior from the posterior halves. • Experimental Planaria #2 This will be cut in a manner determined by your team. • Control Planaria This will not be cut. Used with permission from UC Museum of Paleontology

  15. Plenty of Planaria

  16. Planaria Regeneration, Days 1 - 14 Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley

  17. Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley

  18. Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley

  19. The Science and Ethics of Stem Cell Research Plenty of Planaria Laboratory Investigation

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