1. Preparing the tick membrane chamber
<ol>
	<li>Prepare a flat, non-porous surface such as a plane of glass or ceramic-coated metal base of an arm stand by wiping it down with 70% ethanol and then cover it with a single layer of plastic wrap, making sure that the plastic wrap is flat and without bubbles or wrinkles (see Figure 1A).</li>
	<li>Tape down 100% rayon lens cleaning paper to the prepared surface. Ensure it is flat and slightly taut with tape across all four sides of the paper. Two pieces of 4 in x 6 in lens paper can be made into membranes using the volumes described in step 1.3. 
	NOTE: This is sufficient to make up to 12 feeding chambers (see Figure 1B). If the membrane is for larval ticks, use unryu paper instead of lens cleaning paper.</li>
	<li>Prepare the 00-10 hardness silicone mixture by measuring out 5 mL of each part of the silicone kit into a disposable container, lightly mixing the two liquids before adding 1.5 mL of hexane. Continue mixing until the mixture is homogeneous and thoroughly mixed. 
	NOTE: If making membranes for adult ticks, use 00-50 hardness silicone.</li>
	<li>Use a small squeegee to distribute the silicone mix over the lens paper. Allow to stand for 1 min to ensure that the silicone has soaked into the lens paper. Steadily scrape excess silicone to the side with the squeegee using a small amount of downward pressure. Perform a second pass with the squeegee, exerting no downward pressure, to remove any lines of silicone and produce a smooth layer. 
	NOTE: This step of the procedure may require some practice to produce membranes of optimal thickness for each life stage (adults: 150-200 &#181;m; nymphs: 90-120 &#181;m; larvae: 80-100 &#181;m). A thicker membrane (within the feeding tolerances of the life stage) will usually produce better results by reducing condensation in the chamber and improving the self-healing characteristic of the membrane.</li>
	<li>For larvae only, dip the top of the feeding chamber into Fluon fluoropolymer resin (PTFE-30) several times, allowing it to dry between applications to produce a consistent layer. 
	NOTE: The application of Fluon will form a non-stick layer of fluoropolymer resin similar to a non-stick cooking pan. This will reduce the number of larvae that climb to the top of the chamber21.</li>
	<li>Leave the membrane to cure for at least 24 h in a dust-free environment, such as a closed chemical or biosafety cabinet, before moving on to the next step. See Figure 1C for how the rayon lens paper looks after the silicone has been allowed to dry.</li>
	<li>Prepare the 30-hardness silicone mixture to attach the chambers to the membrane by mixing equal parts of silicone mix A and B.</li>
	<li>Dip the polycarbonate chambers about a quarter of an inch (6 mm) into the silicone mixture, and then place on the membrane sheet, taking care not to overlap any of the tape (Figure 1D).</li>
	<li>Allow the attaching silicone to cure for at least 24 h before moving to the next steps.</li>
	<li>Using a scalpel, carefully cut the membrane around each of the attached chambers, trimming down the edges so that it can fit smoothly into a well of the 6-well plate without much scraping on the sides (Figure 1E). Allow sufficient material outside the chamber to maximize adhesion of the membrane. 
	NOTE: If too much exterior material remains, repeated removal of the chamber from the 6-well plate can cause the membrane to partially detach from the chamber. Repairing detached membranes is described in section 5.</li>
	<li>Cut a small piece of the leftover membrane from each of the corners and the center of the membrane sheet. Remove the plastic wrap from each piece. Measure the pieces with a micrometer to determine the average membrane thickness. 
	NOTE: If the membrane thickness does not fall within the tolerance range for life stage (see step 1.4), the membranes should be discarded and remade. Unryu paper thickness is highly variable due to its thick strands of fiber and thin regions. While this characteristic allows larvae to find regions of optimal thickness, it makes it difficult to determine actual membrane thickness.</li>
	<li>Place the feeding chambers along with one O-ring per chamber into a glass beaker to be autoclaved at 121 &#176;C for at least 20 min to sterilize. Allow the chambers to cool before using them.</li>
</ol>
2. Setting up the tick feed
<ol>
	<li>Prepare a lamp or room so that the lights are on for 16 h and then off for 8 h. If using a lamp, make sure that the water bath in the next step is in the dark for those 8 h.</li>
	<li>Set up a water bath at 34 &#176;C and with supports so that a 6-well plate can sit and float slightly in it. Use small glass beakers sunken in the water bath as supports. Use a transparent cover for the water bath to maintain a light-dark cycle for the ticks; if need be, use a T-stand and plastic wrap to make a cover. To reduce the risk of contamination, add 0.02% benzalkonium chloride to the water bath and set another water bath to 36 &#176;C for warming chilled blood.</li>
	<li>Take out the preprepared, autoclaved membrane chambers, placing the O-ring around the chamber (Figure 1F), and then fill each chamber with enough 70% ethanol to cover the membrane. Let sit in a 6-well plate well for 5 min and then look for any leaks between the chamber and membrane and in the membrane itself. 
	NOTE: If the membrane is leaking, ethanol will accumulate in the base of the well. Leaky membranes should be discarded.</li>
	<li>Empty out the ethanol from the chambers and then let it air dry inside a biosafety cabinet or laminar flow hood. 
	NOTE: This may take several minutes depending on ambient humidity.</li>
	<li>While waiting, heat-inactivate the complement in the blood by heating at 56 &#176;C for 40 min. Supplement mechanically defibrinated bovine blood with 2 g/L glucose.</li>
	<li>After the membrane is dry, apply ~20 &#181;L of phagostimulant to the inside of the chamber and then spread it around the surface by tilting the chamber. See section 6 for instructions regarding preparing a phagostimulant from tick frass.</li>
	<li>Wait until the phagostimulant is dry before adding the ticks to the chamber with either a brush or forceps. Work as quickly as possible when transferring the ticks to the chamber to prevent escape. Put the ticks in a tube on ice for 1-2 min before transferring them to slow down their ability to escape. After the ticks have been transferred, seal the top with parafilm; do not overstretch the parafilm, as the heat from the water bath can cause it to rip. 
	NOTE: Forceps work best with nymphal and adult life stages and brushes work best with larval life stages.</li>
	<li>Add 5 mL of the heat-inactivated blood per well/chamber into a conical tube and place in the water bath set at 36 &#176;C. Bring chilled blood up to at least room temperature before exposing the ticks to it. Set aside four chambers per 6-well plate for easy handling of chambers. More chambers per plate should be avoided, however, depending on the size of the water bath, more plates can be used.</li>
	<li>Add 5 &#181;L of 3 mM ATP and 50 &#181;L of 100x stock of penicillin/streptomycin/fungizone per 5 mL of blood to the tube.</li>
	<li>Transfer 4.5 mL of the blood into a well of a 6-well plate, and then gently place the chamber into the well, adjusting the O-ring height on the chamber so that the membrane sits in the blood but the blood level around the side does not overtop the well. Place the well into the blood at an angle to avoid air bubble formation between the blood and the membrane. 
	NOTE: A completed plate is shown in Figure 2.</li>
	<li>Place the lid of the 6-well plate on top of the feeding chambers; then, put the 6-well plate with chambers into the prepared 34 &#176;C water bath and close the lid. 
	&#8203;NOTE: The lid on top will help stop condensed water from contacting the parafilm and diluting the blood in the wells.</li>
</ol>
3. Maintaining the feeding ticks by changing the blood every 12 h
<ol>
	<li>Aliquot 5 mL of the heat-inactivated blood per well into a tube and warm it up in a 36 &#176;C water bath. Thaw the ATP and penicillin/streptomycin/fungizone in the water bath at the same time.</li>
	<li>Add 5 &#181;L of 3 mM ATP and 50 &#181;L of 100x stock of penicillin/streptomycin/fungizone per well to the blood tube. Transfer 4.5 mL of blood into a well of a fresh 6-well plate.</li>
	<li>Take out the 6-well plate with the tick chamber from the water bath. Remove the chamber from the well and rinse the outside of the chamber and membrane with 10 mL of sterile 1x PBS to remove the blood.</li>
	<li>Using autoclaved filter paper, gently dab dry the membrane and chamber to remove the excess PBS. Replace the parafilm on the top of the chamber. If there is a lot of condensation inside the chamber, dab dry the wet spots with autoclaved filter paper before sealing with fresh parafilm.</li>
	<li>Place the tick chamber into the new 6-well plate with fresh blood, adjusting the O-ring height if needed. Repeat steps 3.3-3.5 for each chamber on the plate. Place the lid of the 6-well plate over the tops of the chambers. Move the new 6-well plate back into the 34 &#176;C water bath.</li>
	<li>Repeat steps 3.1-3.5 every 12 h until the conclusion of the tick feed. Wait for the ticks to detach from the membrane by themselves when engorged or gently remove them from the membrane with soft-touch tweezers while still attached to obtain partially engorged ticks.</li>
</ol>
4. Antifungal treatment
NOTE: Perform only when fungal growth is seen on the membrane. Fungus is likely to form on the blood side of the membrane if the feeding is of sufficient duration. The first indication of fungal contamination is small (1-3 mm) flakes of coagulated blood visible on the membrane. When fungal contamination is noted, antifungal treatments can prolong the duration of the experiment and improve engorgement success.
<ol>
	<li>Dissolve 10,000 U nystatin per mL in distilled water, 5 mL per feeding chamber. Filter-sterilize with a 0.1 &#181;m syringe filter.</li>
	<li>Add 5 mL of nystatin solution per well of a new 6-well plate, one well for each feeding chamber.</li>
	<li>Place PBS-rinsed chambers into the solution. Let sit for 10 min.</li>
	<li>Rinse the treated membranes with PBS before putting back into fresh blood.</li>
	<li>Repeat the antifungal treatment every 2-3 days (depending on the extent of fungal contamination) until the completion of the experiment.</li>
</ol>
5. Re-adhering detached membranes with cyanoacrylate glue
NOTE: Perform only when membrane detachment is noticed.
<ol>
	<li>Membranes may partially detach from the feeding chambers, especially during removal from the 6-well plate. If this happens, rinse the membrane of blood with PBS.</li>
	<li>Gently dry the affected area. It does not need to be perfectly dry, but the presence of moisture causes the glue to set faster. 
	NOTE: Re-adhering the membrane limits the working time, however, depending on detachment size, a faster setting time may be desirable.</li>
	<li>Squeeze a small amount of cyanoacrylate glue into the gap where the membrane has pulled away from the chamber. Hold in place for ~2 min to allow the glue to set.</li>
	<li>Place the chamber back into the blood in the 6-well plate.</li>
</ol>
6. Making phagostimulant
NOTE: Perform at the end of a feed or before a membrane feed has started.
<ol>
	<li>Collect tick feces from either a prior membrane feed or another source of feeding ticks. Store the feces at -20 &#176;C prior to making the phagostimulant. Crush the pellets of tick feces and mix 0.1 g per 1 mL of water. Add 1 mM tripeptide reduced glutathione, dissolve, and mix thoroughly by vortexing.</li>
	<li>Filter-sterilize with a 0.1 &#181;m syringe filter.</li>
	<li>Freeze at -20 &#176;C until needed.</li>
</ol>

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M., 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=Host+tropism+determination+by+convergent+evolution+of+immunological+evasion+in+the+Lyme+disease+system.">Host tropism determination by convergent evolution of immunological evasion in the Lyme disease system.</a> PLoS Pathogens. 17 (7), (2021).</li><li>Bernard, Q., 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=Plasticity+in+early+immune+evasion+strategies+of+a+bacterial+pathogen.">Plasticity in early immune evasion strategies of a bacterial pathogen.</a> Proceedings of the National Academy of Sciences. 115 (16), 3788-3797 (2018).</li><li>Pierce, A. E., Pierce, M. 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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=A+silicone+membrane+for+in+vitro+feeding+of+Ixodes+scapularis+(Ixodida:+Ixodidae).">A silicone membrane for in vitro feeding of Ixodes scapularis (Ixodida: Ixodidae).</a> Journal of Medical Entomology. 51 (4), 878-879 (2014).</li><li>Oliver, J. D., 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=Infection+of+immature+Ixodes+scapularis+(Acari:+Ixodidae)+by+membrane+feeding.">Infection of immature Ixodes scapularis (Acari: Ixodidae) by membrane feeding.</a> Journal of Medical Entomology. 53 (2), 409-415 (2016).</li><li>Oliver, J. 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Artificial membrane feeding of ticks provides a useful tool for a variety of experimental procedures, but is not likely to replace animal feeding for all applications. Maintaining large colonies of ticks at all life stages without animal feeding is generally untenable. Instead, the artificial feeding system is valuable for other purposes such as infecting ticks with pathogens not supported by model hosts, evaluating the impacts of controlled dosages of compounds or microorganisms on the ticks in a simplified feeding envi...

Tick-borne diseases strongly impact the health of humans and animals across the world, being responsible for more than two-thirds of all vector-associated illness in the USA from 2004 to 20161. Additionally, case numbers have been growing in recent years, with more people and livestock being affected by ticks and their associated diseases2,3. While there are likely numerous causes for the upward trend in case numbers, the changing climate is an important factor3,4. The predicted ongoing increase in the number of tick-borne disease cases underlines the need to develop new tools to investigate the relationships between ticks and the pathogens they transmit.
It is known that ticks undergo changes in physiology and gene expression during feeding and that these changes play a role in pathogen transmission5,6. It may be difficult to perform studies that examine the effects of full and partial feeding on pathogen transmission and acquisition using animal models, particularly in situations where rodent models are not susceptible to infection by a particular pathogen. For example, Anaplasma phagocytophilum Variant-1 strain is naturally transmitted between Ixodes scapularis and deer but is unable to infect mice, complicating tick infection in the lab7. Artificial feeding systems can also be applied to help study pathogens such as Borrelia burgdorferi via the use of transgenic mutants that have gene deletions that inhibit transmission or infection8. Using an artificial feeding system helps researchers isolate the genes&#39; role by allowing infection or transmission to only occur on the tick&#39;s side, thereby isolating any host response that may confound such studies.
Similarly, some life stages of ticks involved in disease and animal transmission may not be induced to feed on common laboratory model species. Ixodes scapularis females, for example, must be fed on larger animals, typically rabbits9. While often accessible for laboratory experimentation, the administrative and husbandry requirements of using rabbits exceeds those of small rodents and may be prohibitive for some laboratories. Other tick species, particularly those of veterinary concern, must be fed on cattle or other large animals that are not practical to use in most laboratories. In vitro feeding and infection methods, such as artificial membrane feeding, provide alternatives to using large or exotic host animals.
Additionally, the use of an artificial feeding system allows certain analyses that may not be possible with traditional animal feeding methods. One such example is that, by separating the blood source from the feeding mechanism, examination of the role that different hosts&#39; blood may have in B. burgdorferi transmission becomes possible10. This examination of host blood and the role blood itself plays in the absence of the host immune response is an important factor in being able to understand pathogen transmission cycles and one that artificial feeding systems are able to help answer11. It also becomes possible to quantify the exact transmission numbers of a pathogen during a feed rather than just examining transmission success and establishment in a host8,12.
Some of the first artificial feeding membranes made for hard ticks were made out of animal skins or animal-derived membranes in the 1950s and 1960s13,14. Due to the biological nature of these membranes, there were problems with both the production of new membranes and shelf life. In the 1990s, fully artificial membranes were developed that utilized a backing of netting, paper, or fabric with silicone impregnation15,16. Silicone was ideal as its physical properties mimic skin&#39;s stretchiness and slight tackiness, along with its bio-inherent nature. Building on this, Krober and Guerin, whose work this technique was based on, described a silicone-impregnated rayon membrane feeding technique for the artificial feeding of I. ricinus17.
Refinement of the methods for I. scapularis, a closely related species, has led to notable differences in the hardness of silicone used in membrane impregnation, the recipe for membrane production, dimensions of the chamber, and the attachment stimulant. While the refinements reported in this study have resulted in similar membrane characteristics as those reported by Andrade et al., who also developed a silicone-based membrane based on Krober and Guerin for use in I. scapularis, there is a difference in the silicone impregnation steps, which allows the flexibility to utilize this protocol for immature life stages of I. scapularis15,18. This study also describes additions and technical alterations based on repeated use of this method, best practices that result in a successful feed, and troubleshooting of problems that may arise. This method has been used to feed all active life stages, infect ticks with pathogenic bacteria, and expose ticks to multiple dosages of antibiotics19,20. While the artificial membrane feeding method shown is for I. scapularis, this method is readily adaptable to other species of ticks with minor modifications in membrane thickness.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>00-10 Hardness Silicone</td>
			<td>Smooth-On</td>
			<td>Ecoflex 00-10</td>
			<td>Trial size from Smooth-On Store</td>
		</tr>
		<tr>
			<td>00-50 Hardness Silicone</td>
			<td>Smooth-On</td>
			<td>Ecoflex 00-50</td>
			<td>Trial size from Smooth-On Store</td>
		</tr>
		<tr>
			<td>30 Hardness Silicone</td>
			<td>Smooth-On</td>
			<td>Mold Star 30</td>
			<td>Trial size from Smooth-On Store</td>
		</tr>
		<tr>
			<td>6-well cell culture plates</td>
			<td>Corning Incorporated</td>
			<td>3516</td>
			<td></td>
		</tr>
		<tr>
			<td>Adenosine triphosphate (ATP)</td>
			<td>Millipore Sigma</td>
			<td>A1852-1VL</td>
			<td>Used to make an aqueous solution of 3 mM ATP that has been filter sterlized via 0.2 micometer filter</td>
		</tr>
		<tr>
			<td>Bovine blood</td>
			<td>HemoStat</td>
			<td>DBB500</td>
			<td>Mechanically defibrinated; 500 mL is usually sufficient for one experiment</td>
		</tr>
		<tr>
			<td>Clingwrap</td>
			<td>Fisherbrand</td>
			<td>22-305654&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter Paper</td>
			<td>Fisherbrand</td>
			<td>09-790-2C</td>
			<td>Autoclave and let cool before using. Can use Fine quality instead of medium too</td>
		</tr>
		<tr>
			<td>Fluon (aqueous polytetrafluoroethylene)</td>
			<td>Bioquip</td>
			<td>2871</td>
			<td>Available from other sources such as https://canada-ant-colony.com/products/fluon-ptfe-10ml</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Millipore Sigma</td>
			<td>G8270-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Hexane</td>
			<td>Millipore Sigma</td>
			<td>139386-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Lens paper</td>
			<td>Fisherbrand</td>
			<td>11-995</td>
			<td>100% rayon</td>
		</tr>
		<tr>
			<td>Nystatin &#160;</td>
			<td>Gold Biotechnology</td>
			<td>N-750-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>Fisherbrand</td>
			<td>S37440&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/streptomycin/fungizone</td>
			<td>Gibco</td>
			<td>15240-096</td>
			<td>Or equivalent generic with concentration as follows (10,000 units/mL of penicillin, 10,000 &#181;g/mL of streptomycin, and 25 &#181;g/mL of Amphotericin B)</td>
		</tr>
		<tr>
			<td>Phagostimulant</td>
			<td>Made in House</td>
			<td></td>
			<td>Collected from prior tick feeds</td>
		</tr>
		<tr>
			<td>Polycarbonate Pipe</td>
			<td>McMaster-Carr</td>
			<td>8585K204&#160;</td>
			<td>Cut to 45 mm length, 1.25 inch outer diameter, 1 inch inner diameter. Cutting requires a chop saw grinding wheel.</td>
		</tr>
		<tr>
			<td>Rubber O-rings</td>
			<td>McMaster-Carr</td>
			<td>9452K38&#160;</td>
			<td>5 mm thick, 1.25 inch inner diameter</td>
		</tr>
		<tr>
			<td>Soft touch forceps</td>
			<td>VWR</td>
			<td>470315-238&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Super glue</td>
			<td></td>
			<td></td>
			<td>cyanoacrylate glue</td>
		</tr>
		<tr>
			<td>Unryu paper&#160;</td>
			<td>Art supply stores</td>
			<td></td>
			<td>mulberry fiber 10 g/m2. Purchased at Wet Paint art supply store, St. Paul, MN, USA</td>
		</tr>
	</tbody>
</table>

tick artificial membrane feeding for ixodes scapularis

Ticks and their associated diseases are an important topic of study due to their public health and veterinary burden. However, the feeding requirements of ticks during both study and rearing can limit experimental questions or the ability of labs to research ticks and their associated pathogens. An artificial membrane feeding system can reduce these problems and open up new avenues of research that may not have been possible with traditional animal feeding systems. This study describes an artificial membrane feeding system that has been refined for feeding and engorgement success for all Ixodes scapularis life stages. Moreover, the artificial membrane feeding system described in this study can be modified for use with other tick species through simple refinement of the desired membrane thickness. The benefits of an artificial membrane feeding system are counterbalanced by the labor intensiveness of the system, the additional environmental factors that may impact feeding success, and the need to refine the technique for each new species and life stage of ticks.

A successful feeding depends on whether a partial or full engorgement is desired. Successfully fed I. scapularis turn a shade of gunmetal grey for adults and detach on their own from the membrane. However, if they are at least pea-sized, they may be detached from the membrane when finishing up the feeding. For immature stages of I. scapularis, the size for fully engorged ticks varies, and because, unlike adults, they do not exhibit a color change, detachment is the best way to determine if a tick is ful...

Watch this Scientific Journal Video about Tick Artificial Membrane Feeding for Ixodes scapularis at JoVE.com

Tick Artificial Membrane Feeding for Ixodes scapularis

Presented here is a method to blood feed ticks in vitro via an artificial membrane system to allow for partial or full engorgement of a variety of tick life stages.

Tick Artificial Membrane Feeding for Ixodes scapularis

Ticks and their associated diseases are an important topic of study due to their public health and veterinary burden. However, the feeding requirements of ...

tick-artificial-membrane-feeding-for-ixodes-scapularis

Research

JoVE Journal

Biology

3.0K Views.  University of Minnesota. Presented here is a method to blood feed ticks in vitro via an artificial membrane system to allow for partial or full engorgement of a variety of tick life stages.

Video: Tick Artificial Membrane Feeding for Ixodes scapularis

Testing Nicotine Tolerance in Aphids Using an Artificial Diet Experiment

Plants may upregulate the production of many different seconday metabolites in response to insect feeding. One of these metabolites, nicotine, is well know to have insecticidal properties. One response of tobacco plants to herbivory, or being gnawed upon by insects, is to increase the production of this neurotoxic alkaloid. Here, we will demonstrate how to set up an experiment to address this question of whether a tobacco-adapted strain of the green peach aphid, Myzus persicae, can tolerate higher levels of nicotine than the a strain of this insect that does not infest tobacco in the field.

In this video and assay is demonstrated that tests the tolerance of nicotine to two types of aphids one that infests tobacco plants in the field and one that does not.

Plants may upregulate the production of many different seconday metabolites in response to insect feeding. One of these metabolites, nicotine, is well ...

Preparation of Artificial Bilayers for Electrophysiology Experiments

Planar lipid bilayers, also called artificial lipid bilayers, allow you to study ion-conducting channels in a well-defined environment. These bilayers can be used for many different studies, such as the characterization of membrane-active peptides, the reconstitution of ion channels or investigations on how changes in lipid bilayer properties alter the function of bilayer-spanning channels.  Here, we show how to form a planar bilayer and how to isolate small patches from the bilayer, and in a second video  will also demonstrate a procedure for using gramicidin channels to determine changes in lipid bilayer elastic properties.   We also demonstrate the individual steps needed to prepare the bilayer chamber, the electrodes and how to test that the bilayer is suitable for single-channel measurements.

Planar lipid bilayers, also called artificial lipid bilayers, allow you to study ion-conducting channels in a well-defined environment. Here, we demonstrate the individual steps needed to prepare the bilayer chamber, the electrodes and how to test that the bilayer is suitable for single-channel measurements.

Planar lipid bilayers, also called artificial lipid bilayers, allow you to study ion-conducting channels in a well-defined environment. These bilayers can ...

Crystallizing Membrane Proteins for Structure Determination using Lipidic Mesophases

A detailed protocol for crystallizing membrane proteins by using lipidic mesophases is described. This method has variously been referred to as the lipidic cubic phase or in meso method. The method has been shown to be quite versatile in that it has been used to solve X-ray crystallographic structures of prokaryotic and eukaryotic proteins, proteins that are monomeric, homo- and hetero-multimeric, chromophore-containing and chromophore-free, and alpha-helical and beta-barrel proteins. Recent successes using in meso crystallization are the human engineered beta2-adrenergic and adenosine A2a G protein-coupled receptors. Protocols are presented for reconstituting the membrane protein into the monoolein-based mesophase, and for setting up crystallizations in the manual mode. Additional steps in the overall process, such as crystal harvesting, are to be addressed in future video articles. The time required to prepare the protein-loaded mesophase and to set up a crystallization plate manually is about one hour.

Herein is described the procedure implemented in the Caffrey Membrane Structural and Functional Biology Group to set up manually crystallization trials of membrane proteins in lipidic mesophases.

A detailed protocol for crystallizing membrane proteins by using lipidic mesophases is described. This method has variously been referred to as the ...

Use of a Robot for High-throughput Crystallization of Membrane Proteins in Lipidic Mesophases

Structure-function studies of membrane proteins greatly benefit from having available high-resolution 3-D structures of the type provided through macromolecular X-ray crystallography (MX). An essential ingredient of MX is a steady supply of ideally diffraction-quality crystals. The in meso or lipidic cubic phase (LCP) method for crystallizing membrane proteins is one of several methods available for crystallizing membrane proteins. It makes use of a bicontinuous mesophase in which to grow crystals. As a method, it has had some spectacular successes of late and has attracted much attention with many research groups now interested in using it. One of the challenges associated with the method is that the hosting mesophase is extremely viscous and sticky, reminiscent of a thick toothpaste. Thus, dispensing it manually in a reproducible manner in small volumes into crystallization wells requires skill, patience and a steady hand. A protocol for doing just that was developed in the Membrane Structural &amp; Functional Biology (MS&amp;FB) Group1-3. JoVE video articles describing the method are available1,4. 
The manual approach for setting up in meso trials has distinct advantages with specialty applications, such as crystal optimization and derivatization. It does however suffer from being a low throughput method. Here, we demonstrate a protocol for performing in meso crystallization trials robotically. A robot offers the advantages of speed, accuracy, precision, miniaturization and being able to work continuously for extended periods under what could be regarded as hostile conditions such as in the dark, in a reducing atmosphere or at low or high temperatures. An in meso robot, when used properly, can greatly improve the productivity of membrane protein structure and function research by facilitating crystallization which is one of the slow steps in the overall structure determination pipeline. 
In this video article, we demonstrate the use of three commercially available robots that can dispense the viscous and sticky mesophase integral to in meso crystallogenesis. The first robot was developed in the MS&amp;FB Group5,6. The other two have recently become available and are included here for completeness.	
An overview of the protocol covered in this article is presented in Figure 1. All manipulations were performed at room temperature (~20 &deg;C) under ambient conditions.

Herein is described a robotic approach to high-throughput crystallization of membrane proteins in lipidic mesophases for use in structure determination using macromolecular X-ray crystallography. Three robots capable of handling the viscous and sticky protein-laden mesophase integral to the method are introduced.

Structure-function studies of membrane proteins greatly benefit from having available high-resolution 3-D structures of the type provided through ...

Harvesting and Cryo-cooling Crystals of Membrane Proteins Grown in Lipidic Mesophases for Structure Determination by Macromolecular Crystallography

An important route to understanding how proteins function at a mechanistic level is to have the structure of the target protein available, ideally at atomic resolution. Presently, there is only one way to capture such information as applied to integral membrane proteins (Figure 1), and the complexes they form, and that method is macromolecular X-ray crystallography (MX). To do MX diffraction quality crystals are needed which, in the case of membrane proteins, do not form readily. A method for crystallizing membrane proteins that involves the use of lipidic mesophases, specifically the cubic and sponge phases1-5, has gained considerable attention of late due to the successes it has had in the G protein-coupled receptor field6-21 (<a href="http://www.mpdb.tcd.ie" target="_blank">www.mpdb.tcd.ie</a>). However, the method, henceforth referred to as the in meso or lipidic cubic phase method, comes with its own technical challenges. These arise, in part, due to the generally viscous and sticky nature of the lipidic mesophase in which the crystals, which are often micro-crystals, grow. Manipulating crystals becomes difficult as a result and particularly so during harvesting22,23. Problems arise too at the step that precedes harvesting which requires that the glass sandwich plates in which the crystals grow (Figure 2)24,25 are opened to expose the mesophase bolus, and the crystals therein, for harvesting, cryo-cooling and eventual X-ray diffraction data collection.
The cubic and sponge mesophase variants (Figure 3) from which crystals must be harvested have profoundly different rheologies4,26. The cubic phase is viscous and sticky akin to a thick toothpaste. By contrast, the sponge phase is more fluid with a distinct tendency to flow. Accordingly, different approaches for opening crystallization wells containing crystals growing in the cubic and the sponge phase are called for as indeed different methods are required for harvesting crystals from the two mesophase types. Protocols for doing just that have been refined and implemented in the Membrane Structural and Functional Biology (MS&amp;FB) Group, and are described in detail in this JoVE article (Figure 4). Examples are given of situations where crystals are successfully harvested and cryo-cooled. We also provide examples of cases where problems arise that lead to the irretrievable loss of crystals and describe how these problems can be avoided. In this article the Viewer is provided with step-by-step instructions for opening glass sandwich crystallization wells, for harvesting and for cryo-cooling crystals of membrane proteins growing in cubic and in sponge phases.

Herein is described procedures implemented in the Caffrey Membrane Structural and Functional Biology Group to harvest and cryo-cool membrane protein crystals grown in lipidic cubic and sponge phases for use in structure determination using macromolecular X-ray crystallography.

An important route to understanding how proteins function at a mechanistic level is to have the structure of the target protein available, ideally at ...

Measuring Glutathione-induced Feeding Response in Hydra

Hydra is among the most primitive organisms possessing a nervous system and chemosensation for detecting reduced glutathione (GSH) for capturing the prey. The movement of prey organisms causes mechanosensory discharge of the stinging cells called nematocysts from hydra, which are inserted into the prey. The feeding response in hydra, which includes curling of the tentacles to bring the prey towards the mouth, opening of the mouth and consequent engulfing of the prey, is triggered by GSH present in the fluid released from the injured prey. To be able to identify the molecular mechanism of the feeding response in hydra which is unknown to date, it is necessary to establish an assay to measure the feeding response. Here, we describe a simple method for the quantitation of the feeding response in which the distance between the apical end of the tentacle and mouth of hydra is measured and the ratio of such distance before and after the addition of GSH is determined. The ratio, called the relative tentacle spread, was found to give a measure of the feeding response. This assay was validated using a starvation model in which starved hydra show an enhanced feeding response in comparison with daily fed hydra.

Here we describe a simple assay for the quantification of the feeding response in hydra induced by the reduced form of glutathione. This assay relies on measuring the distance between the apical end of the tentacle and mouth of hydra.

Hydra is among the most primitive organisms possessing a nervous system and chemosensation for detecting reduced glutathione (GSH) for capturing the prey. ...

Microperfusion Technique to Investigate Regulation of Microvessel Permeability in Rat Mesentery

Experiments to measure the permeability properties of individually perfused microvessels provide a bridge between investigation of molecular and cellular mechanisms regulating vascular permeability in cultured endothelial cell monolayers and the functional exchange properties of whole microvascular beds. A method to cannulate and perfuse venular microvessels of rat mesentery and measure the hydraulic conductivity of the microvessel wall is described. The main equipment needed includes an intravital microscope with a large modified stage that supports micromanipulators to position three different microtools: (1) a beveled glass micropipette to cannulate and perfuse the microvessel; (2) a glass micro-occluder to transiently block perfusion and enable measurement of transvascular water flow movement at a measured hydrostatic pressure, and (3) a blunt glass rod to stabilize the mesenteric tissue at the site of cannulation. The modified Landis micro-occlusion technique uses red cells suspended in the artificial perfusate as markers of transvascular fluid movement, and also enables repeated measurements of these flows as experimental conditions are changed and hydrostatic and colloid osmotic pressure difference across the microvessels are carefully controlled. Measurements of hydraulic conductivity first using a control perfusate, then after re-cannulation of the same microvessel with the test perfusates enable paired comparisons of the microvessel response under these well-controlled conditions. Attempts to extend the method to microvessels in the mesentery of mice with genetic modifications expected to modify vascular permeability were severely limited because of the absence of long straight and unbranched microvessels in the mouse mesentery, but the recent availability of the rats with similar genetic modifications using the CRISPR/Cas9 technology is expected to open new areas of investigation where the methods described herein can be applied.

The modified Landis technique enables paired measurement of the hydraulic conductivity of individual microvessels in the mesentery of normal and genetically modified rats under control and test conditions using microperfusion techniques. It provides a convenient method to evaluate mechanisms that regulate microvessel permeability and transvascular exchange under physiological conditions.

Experiments to measure the permeability properties of individually perfused microvessels provide a bridge between investigation of molecular and cellular ...

High-fat Feeding Paradigm for Larval Zebrafish: Feeding, Live Imaging, and Quantification of Food Intake

Zebrafish are emerging as a model of dietary lipid processing and metabolic disease. This protocol describes how to feed larval zebrafish a lipid-rich meal, which consists of an emulsion of chicken egg yolk liposomes created by sonicating egg yolk in embryo media. Detailed instructions are provided to screen larvae for egg yolk consumption so that larvae that fail to feed will not confound experimental results. The chicken egg yolk liposomes can be spiked with fluorescent lipid analogs, including fatty acids and cholesterol, enabling both systemic and subcellular visualization of dietary lipid processing. Several methods are described to mount larvae that are conducive to short- and long-term live imaging with both upright and inverted objectives at high and low magnification. Additionally presented is an assay to quantify larval food intake by extracting the lipids of larvae fed fluorescent lipid analogs, spotting the lipids on a thin layer chromatography plate, and quantifying the fluorescence. Finally, critical aspects of the procedures, important controls, options for modifying the protocols to address specific experimental questions, and potential limitations are discussed. These techniques can be applied not only to focused, hypothesis driven inquiries, but also to a variety of screens and live imaging techniques to study dietary lipid metabolism and the control of food intake.

Zebrafish are emerging as a valuable model of dietary lipid processing and metabolic disease. Described are protocols of lipid-rich larval feeds, live imaging of dietary fluorescent lipid analogs, and quantification of food intake. These techniques can be applied to a variety of screening, imaging, and hypothesis driven inquiry techniques.

Zebrafish are emerging as a model of dietary lipid processing and metabolic disease. This protocol describes how to feed larval zebrafish a lipid-rich ...

Laboratory Protocol for Genetic Gut Content Analyses of Aquatic Macroinvertebrates Using Group-specific rDNA Primers

Analyzing food webs is essential for a better understanding of ecosystems. For example, food web interactions can undergo severe changes caused by the invasion of non-indigenous species. However, an exact identification of field predator-prey interactions is difficult in many cases. These analyses are often based on a visual evaluation of gut content or the analysis of stable isotope ratios (&#948;15N and &#948;13C). Such methods require comprehensive knowledge about, respectively, morphologic diversity or isotopic signature from individual prey organisms, leading to obstacles in the exact identification of prey organisms. Visual gut content analyses especially underestimate soft bodied prey organisms, because maceration, ingestion and digestion of prey organisms make identification of specific species difficult. Hence, polymerase chain reaction (PCR) based strategies, for example the use of group-specific primer sets, provide a powerful tool for the investigation of food web interactions. Here, we describe detailed protocols to investigate the gut contents of macroinvertebrate consumers from the field using group-specific primer sets for nuclear ribosomal deoxyribonucleic acid (rDNA). DNA can be extracted either from whole specimens (in the case of small taxa) or out of gut contents of specimens collected in the field. Presence and functional efficiency of the DNA templates need to be confirmed directly from the tested individual using universal primer sets targeting the respective subunit of DNA. We also demonstrate that consumed prey can be determined further down to species level via PCR with unmodified group-specific primers combined with subsequent single strand conformation polymorphism (SSCP) analyses using polyacrylamide gels. Furthermore, we show that the use of different fluorescent dyes as labels enables parallel screening for DNA fragments of different prey groups from multiple gut content samples via automated fragment analysis.

Most common gut content analyses of macroinvertebrates are visual. Requiring intense knowledge about morphological diversity of prey organisms, they miss soft bodied prey and, due to strong comminution of prey, are nearly impossible for some organisms, including amphipods. We provide detailed, novel genetic approaches for macroinvertebrate prey identification in the diet of amphipods.

Analyzing food webs is essential for a better understanding of ecosystems. For example, food web interactions can undergo severe changes caused by the ...

A Versatile Model of Hard Tick Infestation on Laboratory Rabbits

The use of live animals in tick research is crucial for a variety of experimental purposes including the maintenance of hard tick colonies in the laboratory. In ticks, all developmental stages (except egg) are hematophagous, and acquiring a blood-meal when attached to their vertebrate hosts is essential for the successful completion of their life cycle. Here we demonstrate a simple method that uses easily openable capsules for feeding of hard ticks on rabbits. The advantages of the proposed method include its simplicity, short duration and most importantly versatile adjustment to the needs of specific experimental requirements. The method makes possible the use of multiple chambers (of various sizes) on the same animal, which permits feeding of multiple stages or different experimental groups while reducing the overall animal requirement. The non-irritating and easily accessible materials used minimizes discomfort to the animals, which can be easily recovered from an experiment and offered for adoption or reused if the ethical protocol allows it.

We have developed a simple and versatile system to feed hard ticks on laboratory rabbits. Our non-laborious protocol uses easily accessible materials and can be adjusted depending on the requirements of the various experimental settings. The method allows comfortable monitoring and/or sampling of ticks during the entire feeding period.