Name: generation and long-term maintenance of nerve-free hydra
Uploaded: 2017-07-07T14:00:00
Description: Watch this Scientific Journal Video about Generation and Long-term Maintenance of Nerve-free Hydra at JoVE.com

The authors thank Dr. Dick Campbell (UC Irvine) for discussions about the original protocol for generating and maintaining nerve-free animals, Ms. Rui Wang for help with adapting the syringe and needle technique, and Ms. Danielle Hagstrom and Dr. Rob Steele (UC Irvine) for comments on the manuscript. This work was supported by the RCSA and NSF grant CMMI-1463572.

1. Double Colchicine Treatment
<ol>
	<li>Make a 0.4% colchicine (weight/volume) solution in Hydra medium3,4,17. 
	Caution: Colchicine is acutely toxic, fatal if swallowed, may cause genetic defects, and may cause eye damage. Handle the powder in a fume hood and wear full Personal Protective Equipment (PPE).</li>
	<li>Incubate Hydra vulgaris (AEP strain was used here) that have been starv...

<ol>
	<li>Bode, H. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+interstitial+cell+lineage+of+Hydra:+a+stem+cell+system+that+arose+early+in+evolution.">The interstitial cell lineage of Hydra: a stem cell system that arose early in evolution.</a> J. Cell. Sci. 109, 1155-1164 (1996).</li><li>Hager, G., David, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pattern+of+differentiated+nerve+cells+in+hydra+is+determined+by+precursor+migration.">Pattern of differentiated nerve cells in hydra is determined by precursor migration.</a> Development. 124, 569-576 (1997).</li><li>Campbell, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elimination+of+Hydra+interstitial+and+nerve+cells+by+means+of+colchicine.">Elimination of Hydra interstitial and nerve cells by means of colchicine.</a> J. Cell. Sci. 21, 1-13 (1976).</li><li>Marcum, B. A., Campbell, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+Hydra+lacking+nerve+and+interstitial+cells.">Development of Hydra lacking nerve and interstitial cells.</a> J. Cell. Sci. 29, 17-33 (1978).</li><li>Burns, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3H-colchicine+binding:+Failure+to+detect+any+binding+to+soluble+proteins+from+various+lower+organisms.">3H-colchicine binding: Failure to detect any binding to soluble proteins from various lower organisms.</a> Exp. Cell. Res. 81, 285-292 (1973).</li><li>Lee, H. -. T., Campbell, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+Behavior+of+an+Intergeneric+Chimera+of+Hydra+(Pelmatohydra+oligactis+Interstitial+Cells+Hydra+attenuata+Epithelial+Cells).">Development and Behavior of an Intergeneric Chimera of Hydra (Pelmatohydra oligactis Interstitial Cells Hydra attenuata Epithelial Cells).</a> Biol. Bull. 157 (2), 288-296 (1979).</li><li>Novak, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparing+Hydra+viridis+with+Nerve+Cells+and+No+Interstitial+Cells,+or+with+Neither+of+These+Cell+Types.">Preparing Hydra viridis with Nerve Cells and No Interstitial Cells, or with Neither of These Cell Types.</a> Hydra: Research Methods. , 295-297 (1983).</li><li>Wanek, N., Marcum, B. A., Lee, H. -. T., Chow, M., Campbell, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+hydrostatic+pressure+on+morphogenesis+in+nerve-free+Hydra.">Effect of hydrostatic pressure on morphogenesis in nerve-free Hydra.</a> J. Exp. Zool. 211, 275-280 (1980).</li><li>Minobe, S., Koizumi, O., Sugiyama, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nerve+cell+differentiation+in+nerve-free+tissue+of+epithelial+Hydra+from+precursor+cells+introduced+by+grafting.">Nerve cell differentiation in nerve-free tissue of epithelial Hydra from precursor cells introduced by grafting.</a> Dev. Biol. 172 (1), 170-181 (1995).</li><li>Miljkovic-Licina, M., Chera, S., Ghila, L., Galliot, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Head+regeneration+in+wild-type+hydra+requires+de+novo+neurogenesis.">Head regeneration in wild-type hydra requires de novo neurogenesis.</a> Development. 134 (6), 1191-1201 (2007).</li><li>Wenger, Y., Buzgariu, W., Galliot, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+neurogenesis+in+Hydra+leads+to+compensatory+regulation+of+neurogenic+and+neurotransmission+genes+in+epithelial+cells.">Loss of neurogenesis in Hydra leads to compensatory regulation of neurogenic and neurotransmission genes in epithelial cells.</a> Phil. Trans. R. Soc. B. 371 (20150040), (2015).</li><li>Campbell, R. D., Josephson, R. K., Schwab, W. E., Rushforth, N. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excitability+of+nerve-free+Hydra.">Excitability of nerve-free Hydra.</a> Nature. 262, 388-390 (1976).</li><li>Takaku, Y., Hwang, J. S., 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=Innexin+gap+junctions+in+nerve+cells+coordinate+spontaneous+contractile+behavior+in+Hydra+polyps.">Innexin gap junctions in nerve cells coordinate spontaneous contractile behavior in Hydra polyps.</a> Sci. Rep. 4 (3573), (2014).</li><li>Marcum, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culturing+Epithelial+Hydra.">Culturing Epithelial Hydra.</a> Hydra: Research Methods. , 287-290 (1983).</li><li>David, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+quantitative+method+for+maceration+of+Hydra+tissue.">A quantitative method for maceration of Hydra tissue.</a> Wilhelm Roux Arch. Entwickl. Mech. Org. 171, 259-268 (1973).</li><li>Gr&#246;ger, H., Schmid, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Larval+development+in+Cnidaria:+A+connection+to+Bilateria.">Larval development in Cnidaria: A connection to Bilateria.</a> Genesis. 29 (3), 110-114 (2001).</li><li>Lenhoff, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Water,+Culture+Solutions,+and+Buffers.">Water, Culture Solutions, and Buffers.</a> Hydra: Research Methods. , 29-34 (1983).</li><li>Shenk, M. A., Bode, H. R., Steele, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+Cnox-2,+a+HOM/HOX+homeobox+gene+in+hydra,+is+correlated+with+axial+pattern+formation.">Expression of Cnox-2, a HOM/HOX homeobox gene in hydra, is correlated with axial pattern formation.</a> Development. 117, 657-667 (1993).</li><li>B&#246;ttger, A., 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=Horizontal+Gene+Transfer+Contributed+to+the+Evolution+of+Extracellular+Surface+Structures:+The+Freshwater+Polyp+Hydra+Is+Covered+by+a+Complex+Fibrous+Cuticle+Containing+Glycosaminoglycans+and+Proteins+of+the+PPOD+and+SWT+(Sweet+Tooth)+Families.">Horizontal Gene Transfer Contributed to the Evolution of Extracellular Surface Structures: The Freshwater Polyp Hydra Is Covered by a Complex Fibrous Cuticle Containing Glycosaminoglycans and Proteins of the PPOD and SWT (Sweet Tooth) Families.</a> PLoS One. 7 (12), (2012).</li><li>King, R. S., 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=In+situ+hybridization+protocol+for+enhanced+detection+of+gene+expression+in+the+planarian+Schmidtea+mediterranea.">In situ hybridization protocol for enhanced detection of gene expression in the planarian Schmidtea mediterranea.</a> BMC Dev. Biol. 13 (8), (2013).</li></ol>

Hydra interstitial cells can be eliminated through a double colchicine treatment3,4. In the days following the first treatment, it is critical to prevent contact between individual Hydra to avoid fusion of Hydra pieces into deformed Hydra. Also, animals that can eat unassisted following the first treatment must be removed as the second colchicine treatment may not be sufficient to eliminate the remaining interstitial cells from...

The nervous system of Hydra consists of a nerve net, with neurons associated with both epithelial tissue layers1. The nerve net is denser in the hypostome and peduncle and less dense in the body column2. The nerve cells originate from interstitial stem cells, which are multipotent stem cells that give rise to secretory cells, nematocytes, germ cells, and neurons1. It is possible to eliminate the interstitial cells of Hydra vulgaris through treatment with colchicine3,4, a plant-derived toxin that kills dividing cells. Although colchicine has been found to inhibit microtubule polymerization in other organisms, a previous study has shown that microtubules are present in Hydra throughout the entire treatment, suggesting that colchicine does not act this way in Hydra3. Another study suggests that colchicine does not bind efficiently to tubulin in some organisms, including Tetrahymena pyriformis, Zea mays, Chlamydomonas, and Schizosaccharomyces pombe, which may explain this difference5. The colchicine treatment induces phagocytosis of the interstitial cells by the endodermal epithelial cells3 and thus allows for the creation of animals that are lacking nerve cells, gland cells, and nematocytes. It is unclear why the interstitial cells are particularly susceptible to colchicine treatment. Given that both post-mitotic interstitial cells and the interstitial stem cell lineage are damaged and phagocytosed, Campbell concluded that colchicine was not directly affecting mitotic activity3. Notably, the colchicine treatment works well in Hydra vulgaris, but has been shown to not work as well in other species, such as Hydra oligactis6. A modified treatment with colchicine and hydroxyurea can be used to produce nerve-free Hydra viridis7. Nerve-free Hydra (also sometimes referred to as &#34;epithelial Hydra&#34;8) are therefore a useful tool for studying the roles of these specialized cell types from the interstitial cell lineage in tissue homeostasis and regeneration.
Hydra may be the only known example of an animal capable of living without a nervous system. Nerve-free Hydra serve as a particularly useful model for dissecting the role of the nerve net in regulating Hydra regeneration, homeostasis, and behavior. For example, the introduction of interstitial cells into nerve-free Hydra via grafting allowed for the characterization of nerve cell differentiation as highly region-specific9. Furthermore, because nerve-free Hydra can regenerate, they enable the investigation of alternative, nervous system-independent regeneration pathways. One such example is apical neurogenesis and head formation, which has been shown to depend on cnox-2 function in the nervous system in wildtype Hydra, but appears to be dispensable in nerve-free Hydra, suggesting that there may be an alternative head regeneration process10.
Nerve-free Hydra have also been used to study epithelial cell expression and regulation of neurogenic and neurotransmission genes after the loss of neurogenesis11. Nerve-free Hydra do not exhibit spontaneous contraction bursts12, indicating that these bursts are regulated by the nervous system. Nerve-free Hydra do, however, contract in response to pinching the body column with forceps, suggesting that contraction in response to mechanical stimuli is mediated by coupling through gap junctions in epithelial cells, while spontaneous contractile behavior is mediated by coupling through gap junctions in nerve cells13.
Nerve-free Hydra do not open their mouths when presented with food or reduced glutathione3, suggesting that sensory neurons are necessary to detect the presence of food and signal the mouth to open. In addition, the nerve net seems to play a role in sensing osmotic pressure, because nerve-free animals are unable to autonomously regulate their internal hydrostatic pressure through mouth opening, causing their characteristic balloon-like appearance3,4 (Figure 1B). Regulation of hydrostatic pressure in nerve-free Hydra by frequent manual deflation led to a loss of some abnormal morphology in the hypostome and body column. However, chronic deflation led to interference with growth, elongation, budding, and tissue organization8.
Although nerve-free Hydra are unable to feed and egest on their own, it is possible to maintain them indefinitely in the laboratory by manually force-feeding and burping each animal. Previous publications have described methods of force-feeding and burping nerve-free Hydra, however these protocols involved the use of micropipette tips that must be hand pulled carefully to the appropriate size as well as use of a mouthpiece connected to the pipette by tubing14. Here, a simpler, safer, and more time-efficient method of feeding and burping is described.
In addition, previous studies involved checking for the absence of nerve cells through dissociation of fixed animals into individual cells and examination of cell morphology3,4,15. Here, immunohistochemistry with a monoclonal antibody against the tyrosinated carboxyl-terminus of alpha-tubulin was used as a complimentary method to maceration to check for the depletion of neurons in the hypostome13,16. Previous studies have shown that neurons in the peduncle can also be visualized using this antibody13, however these neurons as well as those in the body column are more difficult to make out. While immunohistochemistry is sufficient to confirm the absence of nerve cells in the hypostome and does not require expertise on cell type morphology, it cannot be used to check for the absence of the interstitial stem cells and the other derivatives of these cells. Dissociation and cell morphology studies are more rigorous and can give a quantitative account of the numbers of each cell type remaining following each stage of the treatment.

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	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:303px;">Colchicine</td>
			<td style="width:75px;">Acros Organics</td>
			<td style="width:119px;">227120010</td>
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			<td height="60" style="height:60px;">Brine Shrimp Eggs</td>
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			<td style="width:167px;">Can be purchased locally</td>
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			<td height="60" style="height:60px;">Brine Shrimp Hatchery Dish</td>
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			<td height="20" style="height:20px;">60 mm x 15 mm Petri Dish</td>
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			<td height="40" style="height:40px;">30 G x 3/4&#34; Hypodermic Needle</td>
			<td style="width:75px;">Covidien</td>
			<td style="width:119px;">1188830340</td>
			<td style="width:167px;">A 27G needle may also be used</td>
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			<td height="20" style="height:20px;">2 x Fine-tip Tweezers</td>
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			<td style="width:75px;">Fisher</td>
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			<td height="20" style="height:20px;">Scalpel</td>
			<td style="width:75px;">Fisher</td>
			<td style="width:119px;">08-920A</td>
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			<td height="20" style="height:20px;">Fetal Bovine Serum (FBS)</td>
			<td style="width:75px;">Gibco</td>
			<td style="width:119px;">10437028</td>
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			<td height="20" style="height:20px;">DAPI (4&#39;,6-Diamidino-2-Phenylindole, Dihydrochloride)</td>
			<td style="width:75px;">Invitrogen</td>
			<td style="width:119px;">D1306</td>
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			<td style="width:119px;">T9028</td>
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			<td style="width:75px;">Sigma</td>
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			<td style="width:119px;">216763</td>
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			<td height="20" style="height:20px;">Paraformaldehyde (PFA)</td>
			<td style="width:75px;">Sigma</td>
			<td style="width:119px;">P6148</td>
			<td style="width:167px;"></td>
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		<tr height="20">
			<td height="20" style="height:20px;">Triton X - 100</td>
			<td style="width:75px;">Sigma</td>
			<td style="width:119px;">T9284</td>
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			<td height="20" style="height:20px;">Tween 20</td>
			<td style="width:75px;">Sigma</td>
			<td style="width:119px;">P1379</td>
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			<td height="20" style="height:20px;width:303px;">Urethane</td>
			<td style="width:75px;">Sigma</td>
			<td style="width:119px;">U2500</td>
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			<td style="width:75px;">VWR</td>
			<td style="width:119px;">53283-916</td>
			<td style="width:167px;">Length of the pipet does not matter</td>
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			<td style="width:75px;">VWR</td>
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			<td style="width:119px;">IBGABBV00397</td>
			<td style="width:167px;">Can be purchased at local home improvement store</td>
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</table>

generation and long-term maintenance of nerve-free hydra

The interstitial cell lineage of Hydra includes multipotent stem cells, and their derivatives: gland cells, nematocytes, germ cells, and nerve cells. The interstitial cells can be eliminated through two consecutive treatments with colchicine, a plant-derived toxin that kills dividing cells, thus erasing the potential for renewal of the differentiated cells that are derived from the interstitial stem cells. This allows for the generation of Hydra that lack nerve cells. A nerve-free polyp cannot open its mouth to feed, egest, or regulate osmotic pressure. Such animals, however, can survive and be cultured indefinitely in the laboratory if regularly force-fed and burped. The lack of nerve cells allows for studies of the role of the nervous system in regulating animal behavior and regeneration. Previously published protocols for nerve-free Hydra maintenance involve outdated techniques such as mouth-pipetting with hand-pulled micropipette tips to feed and clean the Hydra. Here, an improved protocol for maintenance of nerve-free Hydra is introduced. Fine-tipped forceps are used to force open the mouth and insert freshly killed Artemia. Following force-feeding, the body cavity of the animal is flushed with fresh medium using a syringe and hypodermic needle to remove undigested material, referred to here as "burping". This new method of force-feeding and burping nerve-free Hydra through the use of forceps and syringes eliminates the need for mouth-pipetting using hand-pulled micropipette tips. It thus makes the process safer and significantly more time efficient. To ensure that the nerve cells in the hypostome have been eliminated, immunohistochemistry using anti-tyrosine-tubulin is conducted.

Immediately following the initial 8 h colchicine treatment, all Hydra survive. Some of these Hydra will have only tentacle stubs remaining (Figure 3A), while others will have completely lost their tentacles (Figure 3B). Over the following 1 or 2 days, the tentacles will continue to shrink until all Hydra have lost their tentacles. About 1 week following the treatment, t...

Watch this Scientific Journal Video about Generation and Long-term Maintenance of Nerve-free Hydra at JoVE.com

Generation and Long-term Maintenance of Nerve-free Hydra

Through a double treatment with colchicine, a plant-derived toxin that kills dividing cells, nerve-free Hydra vulgaris can be generated. These Hydra cannot feed or egest on their own. This paper describes an improved method for long-term maintenance of nerve free Hydra vulgaris in the laboratory.

Generation and Long-term Maintenance of Nerve-free Hydra

The interstitial cell lineage of Hydra includes multipotent stem cells, and their derivatives: gland cells, nematocytes, germ cells, and nerve cells. The ...

The overall goal of this procedure is to generate and efficiently maintain nerve-free hydra by manual force feeding and burping. This method can help answer key questions in the hydra field about the role of the nerve and various behaviors and biological processes. The main advantage of this technique is that it is simpler, safer and more time efficient than previously published protocols for feeding and burping.Using forceps to manipulate the hydra on the microscope can be difficult and frustrating at first, but it quickly gets easier with practice. Begin by adding Artemia cysts to a tall, narrow glass container that tapers at the bottom. Fill the container with Artemia water, taking care not to exceed one gram of cysts per one liter of water for a higher hatch yield.Cover the top of the container with parafilm and insert a 10 milliliter serological pipette through the parafilm, into the container. Taking care that the pipette tip reaches the bottom of the container. Attach a piece of tubing to an aquarium air pump, then fit the tubing around the pipette to provide air ration to the container.When the Artemia have hatched use an Artemia net to strain the shrimp from the culture and wash the animals for about 20 seconds in deionized water. At the end of the wash, transfer the Artemia into a dish with hydra medium. Under a stereo microscope, use a pair of fine forceps to euthanize the shrimp with light squeezing.Placing the freshly sacrificed Artemia close to the hydra to facilitate a fast feeding. Now grasp the first hydra by the foot with one pair of forceps and pinch the body of the hydra with a second pair of forceps to make the hydra contract. Tap the center of the hypostome to make the hydra open its mouth.If the mouth does not open, puncture the center of the hypostome with the forceps and slightly release the pressure on the tips to stretch out the mouth opening made by the puncture. Quickly insert as many Artemia as possible into the hydra's gastric cavity, until the cavity is full and no more Artemia can be inserted without damaging the hydra, accidentally pulling out any Artemia from inside the cavity or preventing the mouth from closing. If the mouth begins to close, stretch the mouth open with the forceps as just demonstrated, taking care that no Artemia already inside the animal, come out.If the hydra is too small for a whole Artemia, cut the shrimp with the scalpel and fit the hydra smaller pieces. If the Artemia does not stay inside the hydra, it maybe necessary to press the forceps against the Artemia, to hold the Artemia inside until the mouth closes. When all of the hydra have been fed, use a glass pasteur pipette to transfer the hydra into a dish with fresh hydra medium, supplemented with rifampicin, taking care to avoid accidental burping.Between eight and 20 hours after the feeding, use P320 or similar grid sandpaper, to smooth down the point of a 30 gauge hypothermic needle until the tip is flat. Attach the needle to a disposable one milliliter plastic syringe and fill the syringe with fresh rifampicin supplemented hydra medium. Place the hydra culture dish under the microscope and use fine forceps to hold the foot of the hydra.Tap at the center of the hypostome with the syringe needle. If the mouth doesn't open, insert forceps into the hypostome to open the mouth as just demonstrated. Next, use the syringe to very gently flush the medium into the gastric cavity, taking care not to blow away the hydra until all of the debris has been expelled.Then, use a glass pasteur pipette to transfer the burped hydra into a dish with fresh rifampicin supplemented hydra medium. Immediately following an initial eight hour culture treatment, all hydra survived. Some animals will have only tentacle stubs remaining, while others will have completely lost their tentacles.About one week following treatment, the hydra will demonstrate signs of small, stub-like tentacle regrowth before their eventual full regeneration, over the next seven days. After a second treatment, about 10%of the original number of animals that have undergone both treatments recover and grow to a size suitable for experimentation. Dual-treated hydra exhibit tentacles that appear thinner than those of untreated animals, have tissue that is more transparent and appear bloated due to the inability to open their mouths to relieve osmotic pressure.The nerve nets in the heads of untreated hydra display distinct fibers that radiate outward from the mouth, as well as obvious cell bodies. While the same fibers are absent in nerve-free hydra after double treatment with culturezine. Further co staining with DAPI reveals a reduced number of nuclei in nerve-free hydra compared to untreated controls, due to the loss of interstitial cell lineage cells induced by dual culture zine treatment.Once mastered, a single hydra feeding can be completed in under one minute if it is performed properly. After watching this video, you should have a good understanding of how to force feed and burp nerve-free hydra.

generation-and-long-term-maintenance-of-nerve-free-hydra

Research

JoVE Journal

Neuroscience

C. elegans Positive Butanone Learning, Short-term, and Long-term Associative Memory Assays

The memory of experiences and learned information is critical for organisms to make choices that aid their survival. C. elegans navigates its environment through neuron-specific detection of food and chemical odors1, 2, and can associate nutritive states with chemical odors3, temperature4, and the pathogenicity of a food source5.
Here, we describe assays of C. elegans associative learning and short- and long-term associative memory. We modified an aversive olfactory learning paradigm6 to instead produce a positive response; the assay involves starving ~400 worms, then feeding the worms in the presence of the AWC neuron-sensed volatile chemoattractant butanone at a concentration that elicits a low chemotactic index (similar to Toroyama et al.7). A standard population chemotaxis assay1 tests the worms' attraction to the odorant immediately or minutes to hours after conditioning.
After conditioning, wild-type animals' chemotaxis to butanone increases ~0.6 Chemotaxis Index units, its "Learning Index". Associative learning is dependent on the presence of both food and butanone during training. Pairing food and butanone for a single conditioning period ("massed training") produces short-term associative memory that lasts ~2 hours. Multiple conditioning periods with rest periods between ("spaced training") yields long-term associative memory (&lt;40 hours), and is dependent on the cAMP Response Element Binding protein (CREB),6 a transcription factor required for long-term memory across species.8
Our protocol also includes image analysis methods for quick and accurate determination of chemotaxis indices. High-contrast images of animals on chemotaxis assay plates are captured and analyzed by worm counting software in MatLab. The software corrects for uneven background using a morphological tophat transformation.9 Otsu's method is then used to determine a threshold to separate worms from the background.10 Very small particles are removed automatically and larger non-worm regions (plate edges or agar punches) are removed by manual selection. The software then estimates the size of single worm by ignoring regions that are above a specified maximum size and taking the median size of the remaining regions. The number of worms is then estimated by dividing the total area identified as occupied by worms by the estimated size of a single worm.
We have found that learning and short- and long-term memory can be distinguished, and that these processes share similar key molecules with higher organisms.6,8 Our assays can quickly test novel candidate genes or molecules that affect learning and short- or long-term memory in C. elegans that are relevant across species.

C. elegans Positive Butanone Learning, Short-term, and Long-term Associative Memory Assays

Here we describe methods to test C. elegans associative learning and short- and long-term associative memory. These population assays employ the worms abilities to chemotax toward volatile odorants, and form positive associations upon pairing food with the chemoattractant butanone. Increasing the number of conditioning periods induces long-term memory.

The memory of experiences and learned information is critical for organisms to make choices that aid their survival. C. elegans navigates its environment ...

A Polished and Reinforced Thinned-skull Window for Long-term Imaging of the Mouse Brain

In vivo imaging of cortical function requires optical access to the brain without disruption of the intracranial environment. We present a method to form a polished and reinforced thinned skull (PoRTS) window in the mouse skull that spans several millimeters in diameter and is stable for months. The skull is thinned to 10 to 15 &mu;m in thickness with a hand held drill to achieve optical clarity, and is then overlaid with cyanoacrylate glue and a cover glass to: 1) provide rigidity, 2) inhibit bone regrowth and 3) reduce light scattering from irregularities on the bone surface. Since the skull is not breached, any inflammation that could affect the process being studied is greatly reduced. Imaging depths of up to 250 &mu;m below the cortical surface can be achieved using two-photon laser scanning microscopy. This window is well suited to study cerebral blood flow and cellular function in both anesthetized and awake preparations. It further offers the opportunity to manipulate cell activity using optogenetics or to disrupt blood flow in targeted vessels by irradiation of circulating photosensitizers.

We present a method to form an imaging window in the mouse skull that spans millimeters and is stable for months without inflammation of the brain. This method is well suited for longitudinal studies of blood flow, cellular dynamics, and cell/vascular structure using two-photon microscopy.

In vivo imaging of cortical function requires optical access to the brain without disruption of the intracranial environment. We present a method to form ...

A Molecular Readout of Long-term Olfactory Adaptation in C. elegans

During sustained stimulation most sensory neurons will adapt their response by decreasing their sensitivity to the signal. The adaptation response helps shape attention and also protects cells from over-stimulation. Adaptation within the olfactory circuit of C. elegans was first described by Colbert and Bargmann1,2. Here, the authors defined parameters of the olfactory adaptation paradigm, which they used to design a genetic screen to isolate mutants defective in their ability to adapt to volatile odors sensed by the Amphid Wing cells type C (AWC) sensory neurons. When wildtype C. elegans animals are exposed to an attractive AWC-sensed odor3 for 30 min they will adapt their responsiveness to the odor and will then ignore the adapting odor in a chemotaxis behavioral assay for ~1 hr. When wildtype C. elegans animals are exposed to an attractive AWC-sensed odor for ~1 hr they will then ignore the adapting odor in a chemotaxis behavioral assay for ~3 hr. These two phases of olfactory adaptation in C. elegans were described as short-term olfactory adaptation (induced after 30 min odor exposure), and long-term olfactory adaptation (induced after 60 min odor exposure). Later work from L'Etoile et al.,4 uncovered a Protein Kinase G (PKG) called EGL-4 that is required for both the short-term and long-term olfactory adaptation in AWC neurons. The EGL-4 protein contains a nuclear localization sequence that is necessary for long-term olfactory adaptation responses but dispensable for short-term olfactory adaptation responses in the AWC4. By tagging EGL-4 with a green fluorescent protein, it was possible to visualize the localization of EGL-4 in the AWC during prolonged odor exposure. Using this fully functional GFP-tagged EGL-4 (GFP::EGL-4) molecule we have been able to develop a molecular readout of long-term olfactory adaptation in the AWC5. Using this molecular readout of olfactory adaptation we have been able to perform both forward and reverse genetic screens to identify mutant animals that exhibit defective subcellular localization patterns of GFP::EGL-4 in the AWC6,7. Here we describe: 1) the construction of GFP::EGL-4 expressing animals; 2) the protocol for cultivation of animals for long-term odor-induced nuclear translocation assays; and 3) the scoring of the long-term odor-induced nuclear translocation event and recovery (re-sensitization) from the nuclear GFP::EGL-4 state.

A Molecular Readout of Long-term Olfactory Adaptation in C. elegans

Here we describe a molecular readout of long-term olfactory adaptation in Caenorhabditis elegans. The Protein Kinase G, EGL-4, is necessary for stable adaptation responses in the primary sensory neuron pair called AWC. During prolonged odor exposure EGL-4 translocates from the cytosol to nucleus of the AWC.

During sustained stimulation most sensory neurons will adapt their response by decreasing their sensitivity to the signal. The adaptation response helps ...

Improved Preparation and Preservation of Hippocampal Mouse Slices for a Very Stable and Reproducible Recording of Long-term Potentiation

Long-term potentiation (LTP) is a type of synaptic plasticity characterized by an increase in synaptic strength and believed to be involved in memory encoding. LTP elicited in the CA1 region of acute hippocampal slices has been extensively studied. However the molecular mechanisms underlying the maintenance phase of this phenomenon are still poorly understood. This could be partly due to the various experimental conditions used by different laboratories. Indeed, the maintenance phase of LTP is strongly dependent on external parameters like oxygenation, temperature and humidity. It is also dependent on internal parameters like orientation of the slicing plane and slice viability after dissection.
The optimization of all these parameters enables the induction of a very reproducible and very stable long-term potentiation. This methodology offers the possibility to further explore the molecular mechanisms involved in the stable increase in synaptic strength in hippocampal slices. It also highlights the importance of experimental conditions in in vitro investigation of neurophysiological phenomena.

This paper presents a complete methodology to prepare and preserve in vitro acute hippocampal slices from adult mice. This protocol allows the recording of very stable long-lasting long-term potentiation (LTP) for more than 8 hours with a success rate of 95%.

Long-term potentiation (LTP) is a type of synaptic plasticity characterized by an increase in synaptic strength and believed to be involved in memory ...

Long-term Behavioral Tracking of Freely Swimming Weakly Electric Fish

Long-term behavioral tracking can capture and quantify natural animal behaviors, including those occurring infrequently. Behaviors such as exploration and social interactions can be best studied by observing unrestrained, freely behaving animals. Weakly electric fish (WEF) display readily observable exploratory and social behaviors by emitting electric organ discharge (EOD). Here, we describe three effective techniques to synchronously measure the EOD, body position, and posture of a free-swimming WEF for an extended period of time. First, we describe the construction of an experimental tank inside of an isolation chamber designed to block external sources of sensory stimuli such as light, sound, and vibration. The aquarium was partitioned to accommodate four test specimens, and automated gates remotely control the animals&#39; access to the central arena. Second, we describe a precise and reliable real-time EOD timing measurement method from freely swimming WEF. Signal distortions caused by the animal&#39;s body movements are corrected by spatial averaging and temporal processing stages. Third, we describe an underwater near-infrared imaging setup to observe unperturbed nocturnal animal behaviors. Infrared light pulses were used to synchronize the timing between the video and the physiological signal over a long recording duration. Our automated tracking software measures the animal&#39;s body position and posture reliably in an aquatic scene. In combination, these techniques enable long term observation of spontaneous behavior of freely swimming weakly electric fish in a reliable and precise manner. We believe our method can be similarly applied to the study of other aquatic animals by relating their physiological signals with exploratory or social behaviors.

We describe a set of techniques for studying spontaneous behavior of freely swimming weakly electric fish over an extended period of time, by synchronously measuring the animal&#39;s electric organ discharge timing, body position and posture both accurately and reliably in a specially designed aquarium tank inside a sensory isolation chamber.

Long-term behavioral tracking can capture and quantify natural animal behaviors, including those occurring infrequently. Behaviors such as exploration and ...

Simultaneous Long-term Recordings at Two Neuronal Processing Stages in Behaving Honeybees

In both mammals and insects neuronal information is processed in different higher and lower order brain centers. These centers are coupled via convergent and divergent anatomical connections including feed forward and feedback wiring. Furthermore, information of the same origin is partially sent via parallel pathways to different and sometimes into the same brain areas. To understand the evolutionary benefits as well as the computational advantages of these wiring strategies and especially their temporal dependencies on each other, it is necessary to have simultaneous access to single neurons of different tracts or neuropiles in the same preparation at high temporal resolution. Here we concentrate on honeybees by demonstrating a unique extracellular long term access to record multi unit activity at two subsequent neuropiles1, the antennal lobe (AL), the first olfactory processing stage and the mushroom body (MB), a higher order integration center involved in learning and memory formation, or two parallel neuronal tracts2 connecting the AL with the MB.&#160;The latter was chosen as an example and will be described in full. In the supporting video the construction and permanent insertion of flexible multi&#160;channel wire electrodes is demonstrated. Pairwise differential amplification of the micro&#160;wire electrode channels drastically reduces the noise and verifies that the source of the signal is closely related to the position of the electrode tip. The mechanical flexibility of the used wire electrodes allows stable invasive long&#160;term recordings over many hours up to days, which is a clear advantage compared to conventional extra&#160;and intracellular in vivo recording techniques.

Simultaneous extracellular long term recordings from two different brain neuropiles or two different anatomical tracts were established in honeybees. These recordings allow the investigation of temporal aspects of neuronal processing across different brain areas at the single neuron as well as at the ensemble level in a behaving animal.

In both mammals and insects neuronal information is processed in different higher and lower order brain centers. These centers are coupled via convergent ...

Long-term Time Lapse Imaging of Mouse Cochlear Explants

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building the highly ordered, complex structure of the mammalian cochlea proceeds for around ten days. In order to study changes in gene expression over this period and their response to pharmaceutical or genetic manipulation, long-term imaging is necessary. Previously, live imaging has typically been limited by the viability of explanted tissue in a humidified chamber atop a standard microscope. Difficulty in maintaining optimal conditions for culture growth with regard to humidity and temperature has placed limits on the length of imaging experiments. A microscope integrated into a modified tissue culture incubator provides an excellent environment for long term-live imaging. In this method we demonstrate how to establish embryonic mouse cochlear explants and how to use an incubator microscope to conduct time lapse imaging using both bright field and fluorescent microscopy to examine the behavior of a typical embryonic day (E) 13 cochlear explant and Sox2, a marker of the prosensory cells of the cochlea, over 5 days.

Live imaging of the embryonic mammalian cochlea is challenging because the developmental processes at hand operate on a temporal gradient over ten days. Here we present a method for culturing and then imaging embryonic cochlear explant tissue taken from a fluorescent reporter mouse over five days.

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building ...

Isolation, Culture and Long-Term Maintenance of Primary Mesencephalic Dopaminergic Neurons From Embryonic Rodent Brains

Degeneration of mesencephalic dopaminergic (mesDA) neurons is the pathological hallmark of Parkinson&#8217;s diseae. Study of the biological processes involved in physiological functions and vulnerability and death of these neurons is imparative to understanding the underlying causes and unraveling the cure for this common neurodegenerative disorder. Primary cultures of mesDA neurons provide a tool for investigation of the molecular, biochemical and electrophysiological properties, in order to understand the development, long-term survival and degeneration of these neurons during the course of disease. Here we present a detailed method for the isolation, culturing and maintenance of midbrain dopaminergic neurons from E12.5 mouse (or E14.5 rat) embryos. Optimized cell culture conditions in this protocol result in presence of axonal and dendritic projections, synaptic connections and other neuronal morphological properties, which make the cultures suitable for study of the physiological, cell biological and molecular characteristics of this neuronal population.

The causes of degeneration of midbrain dopaminergic neurons during Parkinson&#8217;s disease are not fully understood. Cellular culture systems provide an essential tool for study of the neurophysiological properties of these neurons. Here we present an optimized protocol, which can be utilized for in vitro modeling of neurodegeneration.

Degeneration of mesencephalic dopaminergic (mesDA) neurons is the pathological hallmark of Parkinson&#8217;s diseae. Study of the biological processes ...

Agarose Microchambers for Long-term Calcium Imaging of Caenorhabditis elegans

Behavior is controlled by the nervous system. Calcium imaging is a straightforward method in the transparent nematode Caenorhabditis elegans to measure the activity of neurons during various behaviors. To correlate neural activity with behavior, the animal should not be immobilized but should be able to move. Many behavioral changes occur during long time scales and require recording over many hours of behavior. This also makes it necessary to culture the worms in the presence of food. How can worms be cultured and their neural activity imaged over long time scales? Agarose Microchamber Imaging (AMI) was previously developed to culture and observe small larvae and has now been adapted to study all life stages from early L1 until the adult stage of C. elegans. AMI can be performed on various life stages of C. elegans. Long-term calcium imaging is achieved without immobilizing the animals by using short externally triggered exposures combined with an electron multiplying charge-coupled device (EMCCD) camera recording. Zooming out or scanning can scale up this method to image up to 40 worms in parallel. Thus, a method is described to image behavior and neural activity over long time scales in all life stages of C. elegans.

Agarose Microchambers for Long-term Calcium Imaging of Caenorhabditis elegans

Imaging behavior and neural activity over long time scales without immobilization of the animal is a prerequisite to understand behavior. Agarose microfluidic chambers imaging (AMI) can be used to image neural activity and behavior for all life stages of Caenorhabditis elegans.

Behavior is controlled by the nervous system. Calcium imaging is a straightforward method in the transparent nematode Caenorhabditis elegans to measure ...

A Simplified Method for Ultra-Low Density, Long-Term Primary Hippocampal Neuron Culture

Culturing primary hippocampal neurons in vitro facilitates mechanistic interrogation of many aspects of neuronal development. Dissociated embryonic hippocampal neurons can often grow successfully on glass coverslips at high density under serum-free conditions, but low density cultures typically require a supply of trophic factors by co-culturing them with a glia feeder layer, preparation of which can be time-consuming and laborious. In addition, the presence of glia may confound interpretation of results and preclude studies on neuron-specific mechanisms. Here, a simplified method is presented for ultra-low density (~2,000 neurons/cm2), long-term (&#62;3 months) primary hippocampal neuron culture that is under serum free conditions and without glia cell support. Low density neurons are grown on poly-D-lysine coated coverslips, and flipped on high density neurons grown in a 24-well plate. Instead of using paraffin dots to create a space between the two neuronal layers, the experimenters can simply etch the plastic bottom of the well, on which the high density neurons reside, to create a microspace conducive to low density neuron growth. The co-culture can be easily maintained for &#62;3 months without significant loss of low density neurons, thus facilitating the morphological and physiological study of these neurons. To illustrate this successful culture condition, data are provided to show profuse synapse formation in low density cells after prolonged culture. This co-culture system also facilitates the survival of sparse individual neurons grown in islands of poly-D-lysine substrates and thus the formation of autaptic connections.

Low density cultures of primary hippocampal neurons usually require glia feeder layer to supply neurotrophic factors and sustain longevity. We describe here a simplified method to culture ultra-low density neurons on glass coverslips in the presence of a high density neuronal feeder layer, which facilitates investigation of specific neuronal-autonomous mechanisms.

Culturing primary hippocampal neurons in vitro facilitates mechanistic interrogation of many aspects of neuronal development. Dissociated embryonic ...