We would like to thank Alejandro S&#225;nchez Alvarado, who supported the initial optimization and development of this technique. Work in Carolyn Adler's laboratory is supported by Cornell University start-up funds.

1. Preparation
<ol>
	<li>Preparation of planaria water17
	<ol>
		<li>Maintain planarians in a 1X Montju&#239;c salt solution. To prepare planarian water, make individual stock solutions of 1 M CaCl2, 1 M MgSO4, 1 M MgCl2, 1 M KCl and 5 M NaCl in ultrapure water. Filter-sterilize with a 0.2 &#181;m bottle-top filterfor long-term storage. 
		Note: Use only ultrapure deionized water (with a resistivity of 18.2 M&#8486; at 25 &#...

<ol>
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitroreductase-mediated+cell/tissue+ablation+in+zebrafish:+a+spatially+and+temporally+controlled+ablation+method+with+applications+in+developmental+and+regeneration+studies.">Nitroreductase-mediated cell/tissue ablation in zebrafish: a spatially and temporally controlled ablation method with applications in developmental and regeneration studies.</a> Nat. Protoc. 3, 948-954 (2008).</li><li>White, D. T., Mumm, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+nitroreductase+system+of+inducible+targeted+ablation+facilitates+cell-specific+regenerative+studies+in+zebrafish.">The nitroreductase system of inducible targeted ablation facilitates cell-specific regenerative studies in zebrafish.</a> Methods. 62, 232-240 (2013).</li><li>Smith-Bolton, R. K., Worley, M. I., Kanda, H., Hariharan, I. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regenerative+growth+in+Drosophila+imaginal+discs+is+regulated+by+Wingless+and+Myc.">Regenerative growth in Drosophila imaginal discs is regulated by Wingless and Myc.</a> Dev. Cell. 16, 797-809 (2009).</li><li>Smith-Bolton, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+Imaginal+Discs+as+a+Model+of+Epithelial+Wound+Repair+and+Regeneration.">Drosophila Imaginal Discs as a Model of Epithelial Wound Repair and Regeneration.</a> Adv. Wound Care. 5, 251-261 (2016).</li><li>Newmark, P. A., S&#225;nchez Alvarado, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Not+your+father's+planarian:+a+classic+model+enters+the+era+of+functional+genomics.">Not your father's planarian: a classic model enters the era of functional genomics.</a> Nat. Rev. Genet. 3, 210-219 (2002).</li><li>Reddien, P. W., S&#225;nchez Alvarado, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fundamentals+of+planarian+regeneration.">Fundamentals of planarian regeneration.</a> Annu. Rev. Cell Dev. Biol. 20, 725-757 (2004).</li><li>Wagner, D. E., Wang, I. E., Reddien, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clonogenic+neoblasts+are+pluripotent+adult+stem+cells+that+underlie+planarian+regeneration.">Clonogenic neoblasts are pluripotent adult stem cells that underlie planarian regeneration.</a> Science. 332, 811-816 (2011).</li><li>Scimone, M. L., Kravarik, K. M., Lapan, S. W., Reddien, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neoblast+specialization+in+regeneration+of+the+planarian+Schmidtea+mediterranea.">Neoblast specialization in regeneration of the planarian Schmidtea mediterranea.</a> Stem Cell Reports. 3, 339-352 (2014).</li><li>van Wolfswinkel, J. C., Wagner, D. E., Reddien, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell+analysis+reveals+functionally+distinct+classes+within+the+planarian+stem+cell+compartment.">Single-cell analysis reveals functionally distinct classes within the planarian stem cell compartment.</a> Cell Stem Cell. 15, 326-339 (2014).</li><li>Adler, C. E., Seidel, C. W., McKinney, S. A., S&#225;nchez Alvarado, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+amputation+of+the+pharynx+identifies+a+FoxA-dependent+regeneration+program+in+planaria.">Selective amputation of the pharynx identifies a FoxA-dependent regeneration program in planaria.</a> Elife. 3, e02238 (2014).</li><li>Adler, C. E., S&#225;nchez Alvarado, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PHRED-1+is+a+divergent+neurexin-1+homolog+that+organizes+muscle+fibers+and+patterns+organs+during+regeneration.">PHRED-1 is a divergent neurexin-1 homolog that organizes muscle fibers and patterns organs during regeneration.</a> Dev. Biol. 427, 165-175 (2017).</li><li>Wong, M. C., Martynovsky, M., Schwarzbauer, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+cell+migration+using+Caenorhabditis+elegans+as+a+model+system.">Analysis of cell migration using Caenorhabditis elegans as a model system.</a> Methods Mol. Biol. 769, 233-247 (2011).</li><li>Margie, O., Palmer, C., Chin-Sang, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=C+elegans+chemotaxis+assay.">C elegans chemotaxis assay.</a> J. Vis. Exp. , e50069 (2013).</li><li>Fang-Yen, C., Gabel, C. V., Samuel, A. D. T., Bargmann, C. I., Avery, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laser+microsurgery+in+Caenorhabditis+elegans.">Laser microsurgery in Caenorhabditis elegans.</a> Methods Cell Biol. 107, 177 (2012).</li><li>Tasaki, J., Uchiyama-Tasaki, C., Rouhana, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+Stem+Cell+Motility+In+Vivo+Based+on+Immunodetection+of+Planarian+Neoblasts+and+Tracing+of+BrdU-Labeled+Cells+After+Partial+Irradiation.">Analysis of Stem Cell Motility In Vivo Based on Immunodetection of Planarian Neoblasts and Tracing of BrdU-Labeled Cells After Partial Irradiation.</a> Methods Mol. Biol. 1365, 323-338 (2016).</li><li>Roberts-Galbraith, R. H., Brubacher, J. L., Newmark, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+functional+genomics+screen+in+planarians+reveals+regulators+of+whole-brain+regeneration.">A functional genomics screen in planarians reveals regulators of whole-brain regeneration.</a> Elife. 5, (2016).</li><li>Arnold, C. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathogenic+shifts+in+endogenous+microbiota+impede+tissue+regeneration+via+distinct+activation+of+TAK1/MKK/p38.">Pathogenic shifts in endogenous microbiota impede tissue regeneration via distinct activation of TAK1/MKK/p38.</a> Elife. 5, (2016).</li><li>Pearson, B. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formaldehyde-based+whole-mount+in+situ+hybridization+method+for+planarians.">Formaldehyde-based whole-mount in situ hybridization method for planarians.</a> Dev. Dyn. 238, 443-450 (2009).</li><li>LoCascio, S. A., Lapan, S. W., Reddien, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eye+Absence+Does+Not+Regulate+Planarian+Stem+Cells+during+Eye+Regeneration.">Eye Absence Does Not Regulate Planarian Stem Cells during Eye Regeneration.</a> Dev. Cell. 40, 381-391 (2017).</li><li>Nishimura, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regeneration+of+dopaminergic+neurons+after+6-hydroxydopamine-induced+lesion+in+planarian+brain.">Regeneration of dopaminergic neurons after 6-hydroxydopamine-induced lesion in planarian brain.</a> J. Neurochem. 119, 1217-1231 (2011).</li><li>Wilson, D. F., Chance, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Azide+inhibition+of+mitochondrial+electron+transport.+I.+The+aerobic+steady+state+of+succinate+oxidation.">Azide inhibition of mitochondrial electron transport. I. The aerobic steady state of succinate oxidation.</a> Biochim. Biophys. Acta. 131, 421-430 (1967).</li><li>Duncan, H. M., Mackler, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electron+Transport+Systems+of+Yeast:+III.+Preparation+and+properties+of+cytochrome+oxidase.">Electron Transport Systems of Yeast: III. Preparation and properties of cytochrome oxidase.</a> J. Biol. Chem. 241, 1694-1697 (1966).</li><li>Buchan, J. R., Yoon, J. H., Parker, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stress-specific+composition,+assembly+and+kinetics+of+stress+granules+in+Saccharomyces+cerevisiae.">Stress-specific composition, assembly and kinetics of stress granules in Saccharomyces cerevisiae.</a> J. Cell Sci. 124, 228-239 (2011).</li><li>Cebri&#224;, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organization+of+the+nervous+system+in+the+model+planarian+Schmidtea+mediterranea:+An+immunocytochemical+study.">Organization of the nervous system in the model planarian Schmidtea mediterranea: An immunocytochemical study.</a> Neurosci. Res. 61, 375-384 (2008).</li><li>Shimoyama, S., Inoue, T., Kashima, M., Agata, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+Neuropeptide-Coding+Genes+Involved+in+Planarian+Pharynx+Extension.">Multiple Neuropeptide-Coding Genes Involved in Planarian Pharynx Extension.</a> Zoolog. Sci. 33, 311-319 (2016).</li><li>Ito, H., Saito, Y., Watanabe, K., Orii, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epimorphic+regeneration+of+the+distal+part+of+the+planarian+pharynx.">Epimorphic regeneration of the distal part of the planarian pharynx.</a> Dev. Genes Evol. 211, 2-9 (2001).</li><li>Bueno, D., Espinosa, L., Bagu&#241;&#224;, J., Romero, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Planarian+pharynx+regeneration+in++tail+fragments+monitored+with+cell-specific+monoclonal+antibodies.">Planarian pharynx regeneration in tail fragments monitored with cell-specific monoclonal antibodies.</a> Dev. 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The authors have nothing to disclose.

This protocol describes a method of selective ablation of the pharynx using sodium azide. Other targeted ablation studies in planarians have used modified surgery to remove photoreceptors21 or pharmacological treatment to ablate dopaminergic neurons22. One significant advantage of chemical amputation over existing methods is that it does not require surgery. The rigid structure of the pharynx compared to the rest of the planarian body facilitates its complete removal from t...

Regeneration is a phenomenon that occurs throughout the animal kingdom, with regenerative capacities ranging from full body regeneration in certain invertebrates to more restricted abilities in vertebrates1. Replacement of functional tissues is a complex process and often entails the simultaneous restoration of multiple cell types. For example, to regenerate the salamander limb, osteoblasts, chondrocytes, neurons, muscles, and epithelial cells need to be replaced2. These newly generated cell types also need to be organized properly to facilitate new limb function. Understanding these complex processes requires techniques that focus on regeneration of specific cell types and their integration into organs.
One of the strategies employed to simplify the study of regenerative responses is the targeted ablation of either certain cell types or larger collections of tissues. For example, in zebrafish, expression of nitroreductase in specific cell types leads to their destruction after application of metronidazole3,4. In Drosophila larvae, expressing pro-apoptotic genes under tissue-specific promoters can selectively ablate specific regions of the imaginal disc5,6. Both of these strategies cause rapid but controlled damage, and have been used to dissect the molecular and cellular mechanisms responsible for regeneration.
In this manuscript, we describe a method to selectively ablate an entire organ called the pharynx in the planarian Schmidtea mediterranea. Planarians are a classical model of regeneration, known for their prolific regenerative ability, where even minute fragments can regrow whole animals 7,8. They have a large, heterogeneous population of stem cells consisting of both pluripotent cells and lineage-restricted progenitors9,10,11. These cells proliferate and differentiate to replace all missing tissues, including the pharynx, nervous, digestive and excretory systems, and muscle and epithelial cells9,10,12. While we know that these stem cells initiate regeneration, we do not fully comprehend the molecular mechanisms that drive them to replace all these different cell types. Defined wounding methods that elicit precise stem cell responses can help delineate this complex process.
The pharynx is a large, cylindrical tube required for feeding, and contains neurons, muscle, epithelial and secretory cells13,29. Normally hidden in a pouch on the ventral side of the animal, it extends through the animal&#39;s single body opening upon sensing the presence of food. To selectively amputate the pharynx, we soak planarians in a chemical called sodium azide, a commonly used anesthetic in C. elegans14,15,16. Its use in planarians was first reported by Adler et al., in 201412. Within minutes of exposure to sodium azide, planarians extrude their pharynges, and with gentle agitation, the pharynx detaches from the animal. We refer to this complete and selective loss of the pharynx as &#34;chemical amputation&#34;. One week after amputation, a fully functional pharynx is restored12. Because the pharynx is required for feeding, functional regeneration can be measured by monitoring feeding behavior. Below, we describe the protocol for chemical amputation, and for assessing the regeneration of the pharynx and restoration of feeding behavior.

<table border="0" cellpadding="0" cellspacing="0" width="1042">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:447px;">Calcium Chloride Dihydrate (CaCl2)</td>
			<td style="width:204px;">Fisher Chemical</td>
			<td style="width:155px;">C79-3</td>
			<td style="width:236px;">Montju&#239;c salt solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Magnesium Sulfate Anhydrous (MgSO4)</td>
			<td>Fisher Chemical</td>
			<td>M65-3</td>
			<td>Montju&#239;c salt solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Magnesium Chloride Hexahydrate (MgCl2)</td>
			<td>Acros/VWR</td>
			<td>41341-5000</td>
			<td>Montju&#239;c salt solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Potassium Chloride (KCl)</td>
			<td>Acros Organics/VWR</td>
			<td>196770010</td>
			<td>Montju&#239;c salt solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Chloride (NaCl)</td>
			<td>Acros Organics/VWR</td>
			<td>207790050</td>
			<td>Montju&#239;c salt solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Bicarbonate (NaHCO3)</td>
			<td>Acros Organics/VWR</td>
			<td>123360010</td>
			<td>Montju&#239;c salt solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nalgene autoclavable polypropylene copolymer lowboy with spigot</td>
			<td>ThermoFisher Scientific/VWR</td>
			<td>2324-0015</td>
			<td>Storing planaria water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Instant Ocean Sea Salt</td>
			<td>Spectrum Brands</td>
			<td>Amazon</td>
			<td>Planaria water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Gentamicin Sulfate</td>
			<td>Gemini Bio-products</td>
			<td>400-100P</td>
			<td>Planaria water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Razor blades</td>
			<td>Electron Microscopy Sciences</td>
			<td>71970</td>
			<td>Mincing liver&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Disposable pastry bags-16&#8221;, 12 pack</td>
			<td>Wilton</td>
			<td>Amazon</td>
			<td>Liver aliquots</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">5 mL syringes</td>
			<td>BD/VWR</td>
			<td>309647</td>
			<td>Liver aliquots</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Petri dishes-35mm/60mm</td>
			<td>Greiner Bio-One/VWR</td>
			<td>82050-536/82050-544</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plastic containers (various sizes)</td>
			<td>Ziploc</td>
			<td>Amazon</td>
			<td>Housing planarians in static culture</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Azide</td>
			<td>Sigma</td>
			<td>S2002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Transfer pipette</td>
			<td>Globe Scientific</td>
			<td>138030</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Forceps - Dumont Tweezer, Style 5</td>
			<td>Electron Microscopy Sciences&#160;</td>
			<td>72700-D (0203-5-PO)</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triton X-100</td>
			<td>Sigma</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DAPI&#160;</td>
			<td>ThermoFisher</td>
			<td>62247</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Streptavidin, Alexa Fluor 488 conjugate</td>
			<td>ThermoFisher</td>
			<td>S11223</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glycerol</td>
			<td>Fisher BioReagents</td>
			<td>BP229-1</td>
			<td></td>
		</tr>
	</tbody>
</table>

chemical amputation and regeneration of the pharynx in the planarian schmidtea mediterranea

Planarians are flatworms that are extremely efficient at regeneration. They owe this ability to a large number of stem cells that can rapidly respond to any type of injury. Common injury models in these animals remove large amounts of tissue, which damages multiple organs. To overcome this broad tissue damage, we describe here a method to selectively remove a single organ, the pharynx, in the planarian Schmidtea mediterranea. We achieve this by soaking animals in a solution containing the cytochrome oxidase inhibitor sodium azide. Brief exposure to sodium azide causes extrusion of the pharynx from the animal, which we call &#34;chemical amputation.&#34;&#160;Chemical amputation removes the entire pharynx, and generates a small wound where the pharynx attaches to the intestine. After extensive rinsing, all amputated animals regenerate a fully functional pharynx in approximately one week. Stem cells in the rest of the body drive regeneration of the new pharynx. Here, we provide a detailed protocol for chemical amputation, and describe both histological and behavioral methods to assess successful amputation and regeneration.

Exposure to sodium azide disrupts the normal motility of planarians, causing animals to stretch and writhe. These movements force the pharynx to emerge from the ventral side of the animal, and after approximately 6 min in sodium azide solution, the white tip of the pharynx can be seen (Figure 1B-left panel). A few minutes later, animals actively contract and fully extend the pharynx by forcefully pushing it out of the body. (<strong c...

Watch this Scientific Journal Video about Chemical Amputation and Regeneration of the Pharynx in the Planarian Schmidtea mediterranea at JoVE.com

Chemical Amputation and Regeneration of the Pharynx in the Planarian Schmidtea mediterranea

The planarian Schmidtea mediterranea is an excellent model for studying stem cells and tissue regeneration. This publication describes a method to selectively remove one organ, the pharynx, by exposing animals to the chemical sodium azide. This protocol also outlines methods for monitoring pharynx regeneration.

Chemical Amputation and Regeneration of the Pharynx in the Planarian Schmidtea mediterranea

Planarians are flatworms that are extremely efficient at regeneration. They owe this ability to a large number of stem cells that can rapidly respond to ...

The overall goal of this amputation procedure is to selectively and completely remove the pharynx from planarians without damaging other organs. This method can help answer key questions in the regeneration field. Such as how stem cells recognize missing organs and initiate their regeneration.The main advantage of this technique is that it is very precise and that other organs are not damaged during the process. I first had the idea for this method when I was anesthetizing planarians with sodium azide. I noticed that exposure to sodium azide caused the pharynx to pop out.Visual demonstration of this method is critical as the amputation requires the proper selection of animals as well as a careful observation of animal movement and morphology. Demonstrating the procedure will be Divya Shiroor, graduate student from my laboratory. Before beginning the procedure, use a plastic transfer pipette to select worms that were fed five to seven days previously into a clean petri dish.Place a flat ruler under the petri dish to confirm that each planarian is at least 6 millimeters in length as they crawl across the dish. Then transfer up to 20 selected worms into 35 millimeter petri dish and use a transfer pipette to remove all planarian water from the dish. Place the dish under a stereo microscope and adjust magnification such that multiple animals can be viewed.Add five milliliters of freshly prepared 100 millimolar sodium azide solution to the dish. Monitor the animals without moving the dish for three to four minutes to observe the extrusion of the pharynx. When at least half of the animals in the dish have fully extended a pharynx use a plastic transfer pipette to aspirate and forcibly dispense the worms around the dish a few times.If any pharynges were fully extended, this vigorous pipetting will cause them to detach. Alternatively, use a pair of fine forceps to grasp the pharynx while lifting the planarian upwards toward the meniscus. As the animal is raised, the surface tension will cause the pharynx to detach.While you're moving the pharynx be careful not to cause accidental injury to the animals. Planarians are very soft bodied and easily damaged, especially when in sodium azide. Use a transfer pipette to move about 15 amputated animals into a new dish containing fresh planarian water and rinse the worms with fresh planarian water three times.Make sure to completely wash out the sodium azide. Even traces of the chemical could cause animals to lyze. Then incubate the worms at 20 degree Celsius for seven days.The day after the amputation, place the worms back under the microscope to determine whether a dark spot is visible on the dorsal side of the worm. To feed the worms, transfer an appropriate volume of liver paste into a microcentrifuge tube and centrifuge the tube briefly to remove any air bubbles. After estimating the volume of the paste pellet, add planarian water to one fifth of its volume.Based on the total volume in the tube, add two percent red food coloring. Mix the food sample thoroughly until the dye is evenly distributed throughout the paste and briefly centrifuge the tube again. Transfer the amputated animals into a new petri dish and place in the dark for approximately one hour.At the end of the incubation, trim approximately one half centimeter from the end of a P200 pipette tip and use the modified tip to transfer 25 microliters of red liver paste into the dish. Allow the animals to feed for 30 minutes. Then place the worms on a white background to score the number of animals that appear red.After approximately 6 minutes in sodium azide solution, the white tip of the pharynx can be seen. A few minutes later the animals actively contract and forcefully eject the pharynx out of their bodies. After approximately 11 minutes of azide exposure, the animals relax at which point the characteristic bell shape of the pharynx becomes clearly visible.It is now ready for amputation. Removing this large unpigmented mass of tissue results in the appearance of a dark spot on the dorsal side of the amputated animals. To monitor pharynx regeneration more precisely, the animals can be stained with fluorescently conjugated streptavidin overnight.By combining food coloring with the liver paste, the animals that eat can be distinguished from the animals that do not eat. The number of red animals can then be quantified to assess the percentage of animals with a functional pharynx. Once mastered, this technique can be completed in 20 or 30 minutes.When attempting this procedure remember to carefully observe planarian movement to pinpoint when amputation should begin. Selective amputations can help address questions such as how stem cells initiate the appropriate lineage decisions to accomplish regeneration. This video should provide a good understanding of how to perform selective removal of the pharynx using sodium azide.Working with sodium azide can be extremely hazardous. Remember to always handle it with gloves, discard waste properly and clean your workspace after the experiment.

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10.6K visualizações.  Cornell University. The overall goal of this amputation procedure is to selectively and completely remove the pharynx from planarians without damaging other organs. This method can help answer key questions in the regeneration field. Such as how stem cells recognize missing organs and initiate their regeneration.The main advantage of this technique is that it is very precise and that other organs are not damaged during the process. I first had the idea for this method when I was anesthetizing planarians w...