This work was supported by the Chair in Poultry Research (M. Boulianne) from the Faculty of Veterinary Medicine of the Universit&#233; de Montr&#233;al. Drs. Boulianne and Parent developed the model. Drs. Boulianne and Parent performed the surgeries. Dr. Burns assisted in developing the anesthesia protocol. Dr. Parent edited the video and wrote the manuscript. Drs Burns, Desrochers and Boulianne edited the manuscript.

All procedures with live animal use were authorized by the Ethical Committee of the Faculty of Veterinary Medicine, Universit&#233; de Montr&#233;al (C&#201;UA, &#39;Comit&#233; d&#39;&#233;thique de l&#39;utilisation des Animaux&#39;).
1. Considerations Before Surgery
<ol>
	<li>Select 10 weeks old specific pathogen free (SPF) leghorn chickens for the surgery. 
	NOTE: Their weight must be between 1.0 and 1.2 kg.</li>
	<li>Withdraw the feed 12 h prior to the procedures to empty the intestinal tract.</li>
	<li>Prior to surgery, place the chickens under general anesthesia following a protocol verified by an anesthesiologist. Premedicate each chicken 15 min prior to the surgery with an intramuscular (IM) injection of midazolam 1 mg/kg and butorphanol 4 mg/kg. Repeat, every 4 h, the injection of butorphanol 4 mg/kg IM or when the breathing pattern changes and frequency increases during anesthesia. For the general anesthesia, during all procedures, administer isoflurane at a concentration between 1.5 and 2.5% with an intratracheal tube. 
	NOTE: The use of premedication for sedation and analgesia is recommended as they&#160;will significantly improve the depth of anesthesia, reduce the quantity of anesthetics necessary during all procedures, as well as enable researchers to control pain levels.</li>
	<li>Monitor the anesthesia by recording body temperature, heart rate and electrocardiogram (ECG), respiratory rate and rhythm, oxygen saturation, expired carbon dioxide (CO2) and neurologic reflexes. 
	NOTE: A person must be assigned to monitor these parameters throughout all the procedures.</li>
	<li>Follow sterility principles throughout the surgical procedures. Ensure that the surgeon and the assistant surgeon dress with sterile gowns, gloves, a mask and protective goggles according to institutional preoperative protocols. Ensure that the surgeon scrubs the hands with a chlorhexidine gluconate impregnated sterile brush up to the elbow with emphasis on fingernails and each finger surface.</li>
	<li>Sterilize the surgical instruments with a sterilizer.</li>
</ol>
2. Surgical Site Preparation
<ol>
	<li>Firstly, manually remove the feathers from the abdomen with a gentle traction.</li>
	<li>Scrub the surgical site with a chlorhexidine gluconate detergent impregnated sterile brush. Gently scrub the skin from the center to the outside for a total contact time of 5 min without coming back to the center.</li>
	<li>Perform 3 alternative passages on the surgical site with a chlorhexidine gluconate solution and isopropyl alcohol using sterile gauzes. 
	NOTE: The passage must start from the middle of the surgical site to the borders to avoid contamination from the non-disinfected areas to the surgical site.</li>
	<li>Place the sterile surgical drape on the chicken.</li>
</ol>
3. Extraction of the Small Intestines from the Abdominal Cavity
<ol>
	<li>Incise the surgical drape with scissors to expose only the skin of the surgical site.</li>
	<li>Incise the skin by performing an &#39;&#39;L&#39;&#39; shape low-midline incision with a scalpel blade #3.
	<ol>
		<li>Start the first incision 1 cm caudal to the sternum and end it at 1 cm cranial to the cloaca.</li>
		<li>Perform the second incision perpendicular to the first incision. Start from the caudal end of the first incision and continue 5 cm to the left side of the abdomen by following the pelvis line. 
		NOTE: This opening will create a flap that will allow an easier extraction of the intestines.</li>
	</ol>
	</li>
	<li>With surgery scissors, cut the peritoneum and abdominal muscles with the same &#39;&#39;L&#39;&#39; shape pattern to open the abdominal cavity. 
	NOTE: This will expose the air sacs. Intestines are located underneath these structures. Air sacs must be humidified with gauzes saturated with sterile saline 0.85 % to avoid desiccation and possible rupture throughout the procedure.</li>
	<li>Insert a Snook spay hook in the abdominal cavity by following the left abdominal wall and work the way around the abdominal air sacs.</li>
	<li>Gently exteriorize the intestines and spread these out on the surgical field. 
	NOTE: Keep intestines humidified by frequently spraying sterile saline 0.9% throughout the procedure. Also, gauzes humidified with sterile saline can be placed on the intestines to avoid desiccation.</li>
	<li>Grab the intestines using a dry sterile gauze and gently pull out the small intestines by manual traction to expose the jejunum. 
	NOTE: Mesenteric vessels are fragile and excessive tension may rupture them which may lead to intestinal ischemic lesions and greatly compromise the outcome of the procedure.</li>
</ol>
4. Fabrication of Intestinal Loops
<ol>
	<li>Creation of loop no. 1.
	<ol>
		<li>Place a simple ligature with a polyglactin multifilament synthetic absorbable material in the proximal jejunum by avoiding the ligature of major mesenteric vessels.</li>
		<li>Place a distal ligature 2 cm away from the proximal ligature. 
		NOTE: Simple ligatures made with multifilament suture material are placed along the intestinal tract to create hermetic segments. A schema (Figure 1) describes the location of all ligatures. The loops consist of a proximal and distal ligature separated by 2 cm.</li>
	</ol>
	</li>
	<li>Creation of interloop no. 1.
	<ol>
		<li>Place a simple ligature 0.5 cm aborally to the distal ligature of loop no.1. 
		NOTE: Between successive loops, there are interloops of 1 cm, i.e. segments making a physical separation between the loops. To likely decrease the possible risk of cross-contamination from one loop to another, a simple ligature is placed in the middle of the interloop (0.5 cm from the distal and proximal ligature of 2 adjacent loops). This reduces the risk of a possible leaked contaminant from a loop to reach the ligature of an adjacent loop. These segments are not mandatory but will decrease the risk of cross-contamination.</li>
	</ol>
	</li>
	<li>Creation of subsequent loops and interloops.
	<ol>
		<li>Repeat steps 4.1 and 4.2 to obtain the number of desired loops. 
		NOTE: In this experiment, 9 loops and 8 interloops were created. Total length amounted to 26 cm. The number of loops can be adjusted depending on the study.</li>
	</ol>
	</li>
</ol>
5. Injection of Clostridium perfringens Strains Into the Loops
<ol>
	<li>Inject with a sterile syringe and needle 26 G the pathogen in loop no.1. Gently insert the needle on the antimesenteric side of the intestine at a 45&#176; angle. 
	NOTE: In this experiment, 0.2 mL of brain heart infusion (BHI) containing 1 x 106 CFU (colony forming units) of C. perfringens in the mid-log growth phase was injected in each loop. 5 different strains were injected in 5 different loops and the 4 remaining loops were injected with a negative control containing no bacteria (sterile BHI), alternating pathogens and sterile BHI loops.</li>
	<li>Repeat step 5.1 to inject all loops.</li>
	<li>Gently replace the intestinal tract in the dorsal area of the abdominal cavity, underneath the air sacs.</li>
</ol>
6. Closure of the Abdominal Cavity
<ol>
	<li>The suture of the peritoneum and abdominal muscles.
	<ol>
		<li>Suture the peritoneum and abdominal muscles along the pelvis (made in step 3.3) with a simple continuous suture pattern using a polyglactin multifilament synthetic absorbable material.</li>
		<li>Suture the peritoneum and abdominal muscles from the sternum to the cloaca (made in step 3.3. with a simple continuous suture pattern using a polyglactin multifilament synthetic absorbable material.</li>
	</ol>
	</li>
	<li>The suture of the skin.
	<ol>
		<li>Using a polyglactin multifilament synthetic material and a simple continuous suture pattern, close the incision of the skin along the pelvis made in step 3.2.</li>
		<li>Using the same multifilament ligature material and a simple continuous suture pattern, close the incision of the skin from the sternum to the cloaca made in step 3.2.</li>
	</ol>
	</li>
</ol>
7. Conclusion
<ol>
	<li>After the surgical procedures, keep the chicken under general anesthesia with proper use of analgesics to minimize animal pain during the infection time. Continue anesthetic monitoring to ensure an adequate anesthesia level.</li>
	<li>After the desired infection time, humanely euthanize the chicken by cervical dislocation under general anesthesia. 
	NOTE: For these procedures, the required time to induce microscopic lesions with C. perfringens pathogenic strains was 7 h.</li>
	<li>With a scalpel blade #3, cut a 0.5 cm to 1 cm long loop section and place it in 10% formalin for fixation overnight and further histopathological analysis.</li>
	<li>With the same scalpel blade, cut the remaining loop section and place it in a sterile microcentrifuge tube for the isolation of the C. perfringens strains in each loop further bacteriologic analysis for their genetic characterization.</li>
	<li>Repeat steps 7.2 and 7.3 for all loops by changing the scalpel blade between every loop.</li>
</ol>

<ol>
	<li>Vitale, A., Chiarotti, F., Alleva, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+animal+models+in+disease+research.">The use of animal models in disease research.</a> Rare diseases and orphan drugs. 2 (1), 1-4 (2015).</li><li>Uzal, F. 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=Animal+models+to+study+the+pathogenesis+of+human+and+animal+Clostridium+perfringens+infections.">Animal models to study the pathogenesis of human and animal Clostridium perfringens infections.</a> Veterinary Microbiology. , (2015).</li><li>Bernier, G., Phaneuf, J. B., Filion, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Necrotic+enteritis+in+broiler+chickens.+III.+Study+of+the+factors+favoring+the+multiplication+of+Clostridium+perfringens+and+the+experimental+transmission+of+the+disease.">Necrotic enteritis in broiler chickens. III. Study of the factors favoring the multiplication of Clostridium perfringens and the experimental transmission of the disease.</a> Canadian Journal of Comparative Medicine. 41 (1), 112-116 (1977).</li><li>Al-Sheikhly, F., Truscott, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pathology+of+necrotic+enteritis+of+chickens+following+infusion+of+broth+cultures+of+Clostridium+perfringens+into+the+duodenum.">The pathology of necrotic enteritis of chickens following infusion of broth cultures of Clostridium perfringens into the duodenum.</a> Avian Diseases. 21 (2), 230-240 (1977).</li><li>Wicker, D. L., Iscrigg, W. N., Trammell, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+control+and+prevention+of+necrotic+enteritis+in+broilers+with+zinc+bacitracin.">The control and prevention of necrotic enteritis in broilers with zinc bacitracin.</a> Poultry Science. 56 (4), 1229-1231 (1977).</li><li>Keyburn, A. L., 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=NetB,+a+new+toxin+that+is+associated+with+avian+necrotic+enteritis+caused+by+Clostridium+perfringens.">NetB, a new toxin that is associated with avian necrotic enteritis caused by Clostridium perfringens.</a> PLoS Pathog. 4 (2), e26 (2008).</li><li>Timbermont, L., 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=Origin+of+Clostridium+perfringens+isolates+determines+the+ability+to+induce+necrotic+enteritis+in+broilers.">Origin of Clostridium perfringens isolates determines the ability to induce necrotic enteritis in broilers.</a> Comp Immunol Microbiol Infect Dis. 32 (6), 503-512 (2009).</li><li>Paradis, M. 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=Efficacy+of+avilamycin+for+the+prevention+of+necrotic+enteritis+caused+by+a+pathogenic+strain+of+Clostridium+perfringens+in+broiler+chickens.">Efficacy of avilamycin for the prevention of necrotic enteritis caused by a pathogenic strain of Clostridium perfringens in broiler chickens.</a> Avian Pathol. 45 (3), 365-369 (2016).</li><li>Valgaeren, B., 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=Lesion+development+in+a+new+intestinal+loop+model+indicates+the+involvement+of+a+shared+Clostridium+perfringens+virulence+factor+in+haemorrhagic+enteritis+in+calves.">Lesion development in a new intestinal loop model indicates the involvement of a shared Clostridium perfringens virulence factor in haemorrhagic enteritis in calves.</a> Journal of Comparative Pathology. 149 (1), 103-112 (2013).</li><li>Goossens, E., 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=The+C-terminal+domain+of+Clostridium+perfringens+alpha+toxin+as+a+vaccine+candidate+against+bovine+necrohemorrhagic+enteritis.">The C-terminal domain of Clostridium perfringens alpha toxin as a vaccine candidate against bovine necrohemorrhagic enteritis.</a> Vet Res. 47 (1), 52 (2016).</li><li>Goossens, E., 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=Toxin-neutralizing+antibodies+protect+against+Clostridium+perfringens-induced+necrosis+in+an+intestinal+loop+model+for+bovine+necrohemorrhagic+enteritis.">Toxin-neutralizing antibodies protect against Clostridium perfringens-induced necrosis in an intestinal loop model for bovine necrohemorrhagic enteritis.</a> BMC Vet Res. 12 (1), 101 (2016).</li><li>Parent, E., Archambault, M., Charlebois, A., Bernier-Lachance, J., Boulianne, 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+chicken+intestinal+ligated+loop+model+to+study+the+virulence+of+Clostridium+perfringens+isolates+recovered+from+antibiotic-free+chicken+flocks.">A chicken intestinal ligated loop model to study the virulence of Clostridium perfringens isolates recovered from antibiotic-free chicken flocks.</a> Avian Pathol. 46 (2), 138-149 (2017).</li><li>Janvilisri, T., 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=Temporal+differential+proteomes+of+Clostridium+difficile+in+the+pig+ileal-ligated+loop+model.">Temporal differential proteomes of Clostridium difficile in the pig ileal-ligated loop model.</a> PLoS One. 7 (9), e45608 (2012).</li><li>Aabo, 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=Development+of+an+in+vivo+model+for+study+of+intestinal+invasion+by+Salmonella+enterica+in+chickens.">Development of an in vivo model for study of intestinal invasion by Salmonella enterica in chickens.</a> Infection and Immunity. 68 (12), 7122-7125 (2000).</li><li>Meurens, F., 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=Early+immune+response+following+Salmonella+enterica+subspecies+enterica+serovar+Typhimurium+infection+in+porcine+jejunal+gut+loops.">Early immune response following Salmonella enterica subspecies enterica serovar Typhimurium infection in porcine jejunal gut loops.</a> Vet Res. 40 (1), 5 (2009).</li><li>Gerdts, V., 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=Multiple+intestinal+'loops'+provide+an+in+vivo+model+to+analyse+multiple+mucosal+immune+responses.">Multiple intestinal 'loops' provide an in vivo model to analyse multiple mucosal immune responses.</a> J Immunol Methods. 256 (1-2), 19-33 (2001).</li><li>Wade, B., 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=The+adherent+abilities+of+Clostridium+perfringens+strains+are+critical+for+the+pathogenesis+of+avian+necrotic+enteritis.">The adherent abilities of Clostridium perfringens strains are critical for the pathogenesis of avian necrotic enteritis.</a> Vet Microbiol. 197, 53-61 (2016).</li><li>Cooper, K. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Virulence+for+chickens+of+Clostridium+perfringens+isolated+from+poultry+and+other+sources.">Virulence for chickens of Clostridium perfringens isolated from poultry and other sources.</a> Anaerobe. 16 (3), 289-292 (2010).</li><li>Cooper, K. K., Songer, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Virulence+of+Clostridium+perfringens+in+an+experimental+model+of+poultry+necrotic+enteritis.">Virulence of Clostridium perfringens in an experimental model of poultry necrotic enteritis.</a> Veterinary Microbiology. 142 (3-4), 323-328 (2010).</li><li>Chalmers, G., Bruce, H. L., Toole, D. L., Barnum, D. A., Boerlin, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Necrotic+enteritis+potential+in+a+model+system+using+Clostridium+perfringens+isolated+from+field+outbreaks.">Necrotic enteritis potential in a model system using Clostridium perfringens isolated from field outbreaks.</a> Avian Diseases. 51 (4), 834-839 (2007).</li></ol>

The authors have nothing to disclose.

Intestinal loops models have been described in numerous species to study host-pathogen interaction and pathogenesis of diseases caused by various intestinal pathogens, such as Clostridium perfringens, Clostridium difficile and Salmonella enterica7,9,13,14,15. It has also been used to analyze the mucosal immune response<sup class="xre...

The use of animal models to study infectious diseases affecting humans and animals is a central tool in assessing virulence factors regulating the pathogenesis of a specific condition as well as to elaborate strategies to prevent or cure diseases1. Despite numerous advantages of using animal models to study various diseases, ethical concerns regarding this practice are arising. Researchers need to minimize animal use while obtaining significant and valid results. The concept of the 3 Rs principles (Replace, Reduce and Refine) was elaborated to ensure that welfare issues were addressed in such trials. In chicken necrotic enteritis studies, in vivo chicken models are used to investigate the etiology, prevention, and treatments of this condition2,3,4,5. Pathogenic strains of C. perfringens carrying specific virulence factors, such as the NetB toxin6, are administered to cause necrotic enteritis in chickens7. The replacement principle is, therefore, difficult to achieve in such case as these virulence factors may not be as critical in other animal species. Most models for necrotic enteritis in chickens use a combination of risk factors, such as coccidiosis and altered diet to induce necrotic enteritis followed by gavage of broth culture containing large numbers of C. perfringens2. These models will induce the disease in a large number of chickens, and mortality can be important in such trials8, thus raising concerns about the reduction and refinement principles in animal research.
Intestinal ligated loops models are a desirable alternative for the study of diseases induced by intestinal pathogens with respect to the principle reduction, and refinement. In these models, intestinal segments called &#39;loops&#39; are created by placing ligatures along the intestinal tract to form independent and hermetic compartments where pathogens can be injected alone9 or with other molecules, such as vaccine candidates10,11. The pathogens of interest are placed in close contact with the intestinal cells and after a few hours of infection time, intestinal samples can be recovered for further analysis. This allows the use of multiple treatment and control groups in the same animal. Statistical analysis can be performed with repeated measures models, which increases the power of discrimination between groups and reduces the number of necessary chickens compared to oral gavage trials. Also, surgical procedures and subsequent infection times are performed under continuous general anesthesia and analgesia, hence minimizing the animal pain. Closed loop ligations are an ideal template for reducing host numbers and creating a more humane system in animal research.
Intestinal ligated loops models are well described in various species, such as calves, rabbits and mice2,9, but poorly described in chickens7. For an optimal use of this surgical model, proper technique and execution are essential for the creation of ligated intestinal loops to avoid damages to the intestinal integrity. The goal of this manuscript is to describe a step by step method in the creation of multiple intestinal loops in a chicken model. This technique is limited by the surgeon&#39;s skill and experience, as accurate procedures are essential for the success of the project.

<table>
	<tbody>
		<tr>
			<td>EZ-Scrub 747</td>
			<td>Becton Dickinson and Company</td>
			<td></td>
			<td>4% chlorhexidine gluconate detergent impregnated sterile brush. No catalog number available. Web address: https://www.bd.com/en-us/offerings/capabilities/infection-prevention/surgical-hand-scrubs/ez-scrub-preoperative-surgical-scrub-brushes&#160;</td>
		</tr>
		<tr>
			<td>Isopropyl alcohol 70% USP 4 L</td>
			<td>Commercial isopropyl alcohol</td>
			<td>P016IP70</td>
			<td>Web address: http://www.comalc.com/products/</td>
		</tr>
		<tr>
			<td>Chlorexidine</td>
			<td>Sigma-Aldrich</td>
			<td>282227-1G</td>
			<td>Chlorhexidine gluconate solution, must be diluted to 4%. Web address: http://www.sigmaaldrich.com/catalog/product/aldrich/282227?lang=fr&#38;region=CA&#38;gclid=EAIaIQobChMI8vHr4_OY1wIV3rrACh2ZWQKuEAAYAiAAEgLKx_D_BwE</td>
		</tr>
		<tr>
			<td>Surgical Drape Small (27 inch x 24 inch) with 3 x 6 inch Fenestration</td>
			<td>Veterinary Specialty Products</td>
			<td>32724</td>
			<td>Web address: http://www.vetspecialtyproducts.com/index.cfm?fuseaction=ecommercecatalog.detail&#38;productgroup_id=15</td>
		</tr>
		<tr>
			<td>Scalpel blades #3</td>
			<td>Swann-Morton</td>
			<td>301</td>
			<td>Web address: https://www.swann-morton.com/product/16.php</td>
		</tr>
		<tr>
			<td>Sterile saline NaCl 0.9%</td>
			<td>Sigma-Aldrich</td>
			<td>S8776-100ML</td>
			<td>Web address: http://www.sigmaaldrich.com/catalog/product/sigma/s8776?lang=fr&#38;region=CA</td>
		</tr>
		<tr>
			<td>Vicryl 3-0</td>
			<td>Ethicon</td>
			<td>D9003</td>
			<td>Polyglactin multifilament absorbable suture material. Web address: http://www.ethicon.com/healthcare-professionals/products/wound-closure/absorbable-sutures/coated-vicryl-polyglactin-910-suture</td>
		</tr>
		<tr>
			<td>Syringe 1 ml with 26G needle</td>
			<td>Becton Dickinson and Company</td>
			<td>329652</td>
			<td>Web address: https://www.bd.com/en-us/offerings/capabilities/diabetes-care/insulin-syringes/bd-1-ml-conventional-insulin-syringes</td>
		</tr>
		<tr>
			<td>Brain Heart Infusion</td>
			<td>Sigma-Aldrich</td>
			<td>1104930500</td>
			<td>Web address: http://www.sigmaaldrich.com/catalog/product/mm/110493?lang=fr&#38;region=CA&#38;cm_sp=Insite-_-prodRecCold_xorders-_-prodRecCold2-1</td>
		</tr>
		<tr>
			<td>Eppendorf tube</td>
			<td>Sigma-Aldrich</td>
			<td>T9661-500EA</td>
			<td>Microcentrifuge tube. Web address: http://www.sigmaaldrich.com/catalog/product/sigma/t9661?lang=fr&#38;region=CA&#38;gclid=EAIaIQobChMI-YizzfiY1wIVRkCGCh30SQjuEAAYAiAAEgLK5fD_BwE</td>
		</tr>
		<tr>
			<td>Formalin solution, buffered neutral, 10%</td>
			<td>Sigma-Aldrich</td>
			<td>HT501128-4L</td>
			<td>Ratio tissue : formalin of 1: 10 for adequate fixation. Web address: http://www.sigmaaldrich.com/catalog/product/sigma/ht501128?lang=fr&#38;region=CA</td>
		</tr>
		<tr>
			<td>Clostridium perfringens strains</td>
			<td>Universit&#233; de Montr&#233;al, Chaire en recherche avicole</td>
			<td>N/A</td>
			<td>Specific to each laboratory, available upon request to correspondant author</td>
		</tr>
	</tbody>
</table>

a ligated intestinal loop model in anesthetized specific pathogen free chickens to study clostridium perfringens virulence

Necrotic enteritis was studied in chickens using various in vivo infection models. Most of these use a combination of predisposing factors, such as coccidiosis and diet, with gavage or administration via the feed using Clostridium perfringens. In these models, the comparison of multiple C. perfringens strains for virulence studies requires a large number of hosts to obtain significant results. Mortality during the course of the study can be high depending on the experimental model, hence raising ethical concerns regarding animal welfare in research. The development of new infection models requiring fewer animals to study pathogenesis, yet providing statistically significant and valid results, is important in reducing animal use in research. Intestinal ligated loop models have been used to study clostridial infections in various species such as mice, rabbits and calves. Following surgical procedures to create ligated loop segments, C. perfringens strains are injected directly into the loops to establish a close contact between the bacteria and the intestinal mucosa. Samples of the small intestine and luminal contents are taken at the termination of the procedures after a few hours. Multiple bacterial strains can be inoculated in each animal, hence reducing the number of required subjects in the experiments. Also, procedures are performed under general anesthesia to reduce animal pain. In chickens, this model would be more appropriate than oral administration to compare C. perfringens strain pathogenicity because fewer animals are needed, no predisposing factors are required to induce the disease, and pain is controlled by analgesics. The intestinal ligated loop model is poorly described in chickens and standardization is essential for its optimal use. This manuscript provides all the necessary steps to create numerous intestinal ligated loops in chickens and brings information on the critical points to obtain valid results.

A schematic of the 9 intestinal loops and 8 interloops is shown in Figure 1. In this model, a total of 9 loops and 8 interloops are created with simple ligatures. A loop consists of proximal and distal ligatures spaced by 2 cm measured from the proximal ligature. Two adjacent loops are separated by an interloop of 1 cm. To decrease the possible risk of cross-contamination between loops by leakage from a ligature, an interloop ligature is placed mid-way from t...

Watch this Scientific Journal Video about A Ligated Intestinal Loop Model in Anesthetized Specific Pathogen Free Chickens to Study Clostridium Perfringens Virulence at JoVE.com

A Ligated Intestinal Loop Model in Anesthetized Specific Pathogen Free Chickens to Study Clostridium Perfringens Virulence

Here we present a protocol to surgically create &#39;intestinal ligated loops&#39; in chicken small intestines. This procedure allows for the comparison of multiple Clostridium perfringens strains&#39; virulence in situ in a single host. This method markedly decreases the number of chickens usually necessary for similar in vivo experiments.

A Ligated Intestinal Loop Model in Anesthetized Specific Pathogen Free Chickens to Study Clostridium Perfringens Virulence

Necrotic enteritis was studied in chickens using various in vivo infection models. Most of these use a combination of predisposing factors, such as ...

a-ligated-intestinal-loop-model-anesthetized-specific-pathogen-free

Research

JoVE Journal

Medicine

9.4K Views.  Université de Montréal. Here we present a protocol to surgically create 'intestinal ligated loops' in chicken small intestines. This procedure allows for the comparison of multiple Clostridium perfringens strains' virulence in situ in a single host. This method markedly decreases the number of chickens usually necessary for similar in vivo experiments.

Video: A Ligated Intestinal Loop Model in Anesthetized Specific Pathogen Free Chickens to Study Clostridium Perfringens Virulence

Biomarkers in an Animal Model for Revealing Neural, Hematologic, and Behavioral Correlates of PTSD

Identification of biomarkers representing the evolution of the pathophysiology of Post Traumatic Stress Disorder (PTSD) is vitally important, not only for objective diagnosis but also for the evaluation of therapeutic efficacy and resilience to trauma. Ongoing research is directed at identifying molecular biomarkers for PTSD, including traumatic stress induced proteins, transcriptomes, genomic variances and genetic modulators, using biologic samples from subjects' blood, saliva, urine, and postmortem brain tissues. However, the correlation of these biomarker molecules in peripheral or postmortem samples to altered brain functions associated with psychiatric symptoms in PTSD remains unresolved. Here, we present an animal model of PTSD in which both peripheral blood and central brain biomarkers, as well as behavioral phenotype, can be collected and measured, thus providing the needed correlation of the central biomarkers of PTSD, which are mechanistic and pathognomonic but cannot be collected from people, with the peripheral biomarkers and behavioral phenotypes, which can.
Our animal model of PTSD employs restraint and tail shocks repeated for three continuous days - the inescapable tail-shock model (ITS) in rats. This ITS model mimics the pathophysiology of PTSD 17, 7, 4, 10. We and others have verified that the ITS model induces behavioral and neurobiological alterations similar to those found in PTSD subjects 17, 7, 10, 9. Specifically, these stressed rats exhibit (1) a delayed and exaggerated startle response appearing several days after stressor cessation, which given the compressed time scale of the rat's life compared to a humans, corresponds to the one to three months delay of symptoms in PTSD patients (DSM-IV-TR PTSD Criterian D/E 13), (2) enhanced plasma corticosterone (CORT) for several days, indicating compromise of the hypothalamopituitary axis (HPA), and (3) retarded body weight gain after stressor cessation, indicating dysfunction of metabolic regulation.
The experimental paradigms employed for this model are: (1) a learned helplessness paradigm in the rat assayed by measurement of acoustic startle response (ASR) and a charting of body mass; (2) microdissection of the rat brain into regions and nuclei; (3) enzyme-linked immunosorbent assay (ELISA) for blood levels of CORT; (4) a gene expression microarray plus related bioinformatics tools 18. This microarray, dubbed rMNChip, focuses on mitochondrial and mitochondria-related nuclear genes in the rat so as to specifically address the neuronal bioenergetics hypothesized to be involved in PTSD.

We describe a rat model of post traumatic stress disorder (PTSD) that reveals the persistent alterations in neuroendocrine function and the delayed long-term, exaggerated fear response, characteristic of PTSD patients. The animal model and methods described here are useful for correlating biomarkers in brain nuclei, which are mechanistic but cannot be measured in patients, with biomarkers in peripheral white blood cells, which can.

Identification of biomarkers representing the evolution of the pathophysiology of Post Traumatic Stress Disorder (PTSD) is vitally important, not only for ...

Functional Assessment of Intestinal Motility and Gut Wall Inflammation in Rodents: Analyses in a Standardized Model of Intestinal Manipulation

Inflammation of the gastrointestinal tract is a common reason for a variety of human diseases. Animal research models are critical in investigating the complex cellular and molecular of intestinal pathology. Although the tunica mucosa is often the organ of interest in many inflammatory diseases, recent works demonstrated that the muscularis externa (ME) is also a highly immunocompetent organ that harbours a dense network of resident immunocytes.1,2 These works were performed within the standardized model of intestinal manipulation (IM) that leads to inflammation of the bowel wall, mainly limited to the ME. Clinically this inflammation leads to prolonged intestinal dysmotility, known as postoperative ileus (POI) which is a frequent and unavoidable complication after abdominal surgery.3 The inflammation is characterized by liberation of proinflammatory mediators such as IL-64 or IL-1&beta; or inhibitory neurotransmitters like nitric oxide (NO).5 Subsequently, tremendous numbers of immunocytes extravasate into the ME, dominated by polymorphonuclear neutrophils (PMN) and monocytes and finally maintain POI.2 Lasting for days, this intestinal paralysis leads to an increased risk of aspiration, bacterial translocation and infectious complications up to sepsis and multi organ failure and causes a high economic burden.6
In this manuscript we demonstrate the standardized model of IM and in vivo assessment of gastrointestinal transit (GIT) and colonic transit. Furthermore we demonstrate a method for separation of the ME from the tunica mucosa followed by immunological analysis, which is crucial to distinguish between the inflammatory responses in these both highly immunoactive bowel wall compartments. All analyses are easily transferable to any other research models, affecting gastrointestinal function.

Postoperative ileus (POI) is a complication of abdominal surgery leading to increased morbidity and a prolonged hospital stay. Because prophylactic or therapeutic strategies are lacking intensified research is necessary. Therefore we established a standardized and feasible mouse model to investigate the pathophysiology of POI and to study potential therapeutic options.

Inflammation of the gastrointestinal tract is a common reason for a variety of human diseases. Animal research models are critical in investigating the ...

A Human Ex Vivo Atherosclerotic Plaque Model to Study Lesion Biology

Atherosclerosis is a chronic inflammatory disease of the vasculature. There are various methods to study the inflammatory compound in atherosclerotic lesions. Mouse models are an important tool to investigate inflammatory processes in atherogenesis, but these models suffer from the phenotypic and functional differences between the murine and human immune system. In vitro cell experiments are used to specifically evaluate cell type-dependent changes caused by a substance of interest, but culture-dependent variations and the inability to analyze the influence of specific molecules in the context of the inflammatory compound in atherosclerotic lesions limit the impact of the results. In addition, measuring levels of a molecule of interest in human blood helps to further investigate its clinical relevance, but this represents systemic and not local inflammation. Therefore, we here describe a plaque culture model to study human atherosclerotic lesion biology ex vivo. In short, fresh plaques are obtained from patients undergoing endarterectomy or coronary artery bypass grafting and stored in RPMI medium on ice until usage. The specimens are cut into small pieces followed by random distribution into a 48-well plate, containing RPMI medium in addition to a substance of interest such as cytokines or chemokines alone or in combination for defined periods of time. After incubation, the plaque pieces can be shock frozen for mRNA isolation, embedded in Paraffin or OCT for immunohistochemistry staining or smashed and lysed for western blotting. Furthermore, cells may be isolated from the plaque for flow cytometry analysis. In addition, supernatants can be collected for protein measurement by ELISA. In conclusion, the presented ex vivo model opens the possibility to further study inflammatory lesional biology, which may result in identification of novel disease mechanisms and therapeutic targets.

A Human Ex Vivo Atherosclerotic Plaque Model to Study Lesion Biology

Atherosclerosis is a chronic inflammatory process. This manuscript illustrates an easy to use ex vivo model to investigate fresh carotid or coronary artery plaques. The ex vivo model allows for the investigation of potential substances on the inflammatory milieu in human atherosclerotic lesions and results can be analyzed by various methods.

Atherosclerosis is a chronic inflammatory disease of the vasculature. There are various methods to study the inflammatory compound in atherosclerotic ...

Facial Nerve Axotomy in Mice: A Model to Study Motoneuron Response to Injury

The goal of this surgical protocol is to expose the facial nerve, which innervates the facial musculature, at its exit from the stylomastoid foramen and either cut or crush it to induce peripheral nerve injury. Advantages of this surgery are its simplicity, high reproducibility, and the lack of effect on vital functions or mobility from the subsequent facial paralysis, thus resulting in a relatively mild surgical outcome compared to other nerve injury models. A major advantage of using a cranial nerve injury model is that the motoneurons reside in a relatively homogenous population in the facial motor nucleus in the pons, simplifying the study of the motoneuron cell bodies. Because of the symmetrical nature of facial nerve innervation and the lack of crosstalk between the facial motor nuclei, the operation can be performed unilaterally with the unaxotomized side serving as a paired internal control. A variety of analyses can be performed postoperatively to assess the physiologic response, details of which are beyond the scope of this article. For example, recovery of muscle function can serve as a behavioral marker for reinnervation, or the motoneurons can be quantified to measure cell survival. Additionally, the motoneurons can be accurately captured using laser microdissection for molecular analysis. Because the facial nerve axotomy is minimally invasive and well tolerated, it can be utilized on a wide variety of genetically modified mice. Also, this surgery model can be used to analyze the effectiveness of peripheral nerve injury treatments. Facial nerve injury provides a means for investigating not only motoneurons, but also the responses of the central and peripheral glial microenvironment, immune system, and target musculature. The facial nerve injury model is a widely accepted peripheral nerve injury model that serves as a powerful tool for studying nerve injury and regeneration.

We present a surgical protocol detailing how to perform a cut or crush axotomy on the facial nerve in the mouse. The facial nerve axotomy can be employed to study the physiological response to nerve injury and test therapeutic techniques.

The goal of this surgical protocol is to expose the facial nerve, which innervates the facial musculature, at its exit from the stylomastoid foramen and ...

Murine Model of Intestinal Ischemia-reperfusion Injury

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, hypotension, necrotizing enterocolitis, bowel transplantation, trauma and chronic inflammation. Intestinal ischemia-reperfusion (IR) injury is a consequence of acute mesenteric ischemia, caused by inadequate blood flow through the mesenteric vessels, resulting in intestinal damage. Reperfusion following ischemia can further exacerbate damage of the intestine. The mechanisms of IR injury are complex and poorly understood. Therefore, experimental small animal models are critical for understanding the pathophysiology of IR injury and the development of novel therapies.
Here we describe a mouse model of acute intestinal IR injury that provides reproducible injury of the small intestine without mortality. This is achieved by inducing ischemia in the region of the distal ileum by temporally occluding the peripheral and terminal collateral branches of the superior mesenteric artery for 60 min using microvascular clips. Reperfusion for 1 hr, or 2 hr after injury results in reproducible injury of the intestine examined by histological analysis. Proper position of the microvascular clips is critical for the procedure. Therefore the video clip provides a detailed visual step-by-step description of this technique. This model of intestinal IR injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

Here we describe the detailed procedure of intestinal ischemia-reperfusion in mice which results in reproducible injury without mortality to encourage the standardization of this technique across the field. This model of intestinal ischemia-reperfusion injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, ...

Vein Interposition Model: A Suitable Model to Study Bypass Graft Patency

Bypass grafting is an established treatment method for coronary artery disease. Graft patency continues to be the Achilles heel of saphenous vein grafts. Research models for bypass graft failure are essential for a better understanding of pathobiological and pathophysiological processes during graft patency loss. Large animal models, such as pigs or sheep, resemble human anatomical structures but require special facilities and equipment. This video describes a rat vein interposition model to investigate vein graft patency loss. Rats are inexpensive and easy to handle. Compared to mouse models, the convenient size of rats permits better operability and enables a sufficient amount of material to be obtained for further diverse analysis. In brief, the inferior epigastric vein of a donor rat is harvested and used to replace a segment of the femoral artery. Anastomosis is conducted via single stitches and sealed with fibrin glue. Graft patency can be monitored non-invasively using duplex sonography. Myointimal hyperplasia, which is the main cause for graft patency loss, develops progressively over time and can be calculated from histological cross sections.

This video demonstrates a model to study the development of myointimal hyperplasia after venous interposition surgery in rats.

Bypass grafting is an established treatment method for coronary artery disease. Graft patency continues to be the Achilles heel of saphenous vein grafts. ...

A Model of Free Tissue Transfer: The Rat Epigastric Free Flap

Free tissue transfer has been increasingly used in clinical practice since the 1970s, allowing reconstruction of complex and otherwise untreatable defects resulting from tumor extirpation, trauma, infections, malformations or burns. Free flaps are particularly useful for reconstructing highly complex anatomical regions, like those of the head and neck, the hand, the foot and the perineum. Moreover, basic and translational research in the area of free tissue transfer is of great clinical potential. Notwithstanding, surgical trainees and researchers are frequently deterred from using microsurgical models of tissue transfer, due to lack of information regarding the technical aspects involved in the operative procedures. The aim of this paper is to present the steps required to transfer a fasciocutaneous epigastric free flap to the neck in the rat.
This flap is based on the superficial epigastric artery and vein, which originates from and drain into the femoral artery and vein, respectively. On average the caliber of the superficial epigastric vein is 0.6 to 0.8 mm, contrasting with the 0.3 to 0.5 mm of the superficial epigastric artery. Histologically, the flap is a composite block of tissues, containing skin (epidermis and dermis), a layer of fat tissue (panniculus adiposus), a layer of striated muscle (panniculus carnosus), and a layer of loose areolar tissue.
Succinctly, the epigastric flap is raised on its pedicle vessels that are then anastomosed to the external jugular vein and to the carotid artery on the ventral surface of the rat's neck. According to our experience, this model guarantees the complete survival of approximately 70 to 80% of epigastric flaps transferred to the neck region. The flap can be evaluated whenever needed by visual inspection. Hence, the authors believe this is a good experimental model for microsurgical research and training.

This paper describes the steps required to raise a fasciocutaneous epigastric free flap and transfer it to the neck in the rat.

Free tissue transfer has been increasingly used in clinical practice since the 1970s, allowing reconstruction of complex and otherwise untreatable defects ...

Intestinal Stem Cell Isolation and Culture in a Porcine Model of Segmental Small Intestinal Ischemia

Intestinal ischemia remains a major cause of morbidity and mortality in human and veterinary patients. Many disease processes result in intestinal ischemia, when the blood supply and therefore oxygen is decreased to the intestine. This leads to intestinal barrier loss and damage to the underlying tissue. Intestinal stem cells reside at the base of the crypts of Lieberk&#252;hn and are responsible for intestinal renewal during homeostasis and following injury. Ex vivo cell culture techniques have allowed for the successful study of epithelial stem cell interactions by establishing culture conditions that support the growth of three-dimensional epithelial organ-like systems (termed "enteroids" and "colonoids" from the small and large intestine, respectively). These enteroids are composed of crypt and villus-like domains and mature to contain all of the cell types found within the epithelium. Historically, murine models have been utilized to study intestinal injury. However, a porcine model offers several advantages including similarity of size as well as gastrointestinal anatomy and physiology to that of humans. By utilizing a porcine model, we establish a protocol in which segmental loops of intestinal ischemia can be created within a single animal, enabling the study of differing time points of ischemic injury and repair in vivo. Additionally, we describe a method to isolate and culture the intestinal stem cells from the ischemic loops of intestine, allowing for the continued study of epithelial repair, modulated by stem cells, ex vivo.

This protocol will enable readers to successfully establish a porcine model of segmental intestinal ischemia and subsequently isolate and culture intestinal stem cells for the study of epithelial repair following injury.

Intestinal ischemia remains a major cause of morbidity and mortality in human and veterinary patients. Many disease processes result in intestinal ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

The Generation of Closed Femoral Fractures in Mice: A Model to Study Bone Healing

Bone fractures impose a tremendous socio-economic burden on patients, in addition to significantly affecting their quality of life. Therapeutic strategies that promote efficient bone healing are non-existent and in high demand. Effective and reproducible animal models of fractures healing are needed to understand the complex biological processes associated with bone regeneration. Many animal models of fracture healing have been generated over the years; however, murine fracture models have recently emerged as powerful tools to study bone healing. A variety of open and closed models have been developed, but the closed femoral fracture model stands out as a simple method for generating rapid and reproducible results in a physiologically relevant manner. The goal of this surgical protocol is to generate unilateral closed femoral fractures in mice and facilitate a post-fracture stabilization of the femur by inserting an intramedullary steel rod. Although devices such as a nail or a screw offer greater axial and rotational stability, the use of an intramedullary rod provides a sufficient stabilization for consistent healing outcomes without producing new defects in the bone tissue or damaging nearby soft tissue. Radiographic imaging is used to monitor the progression of callus formation, bony union, and subsequent remodeling of the bony callus. Bone healing outcomes are typically associated with the strength of the healed bone and measured with torsional testing. Still, understanding the early cellular and molecular events associated with fracture repair is critical in the study of bone tissue regeneration. The closed femoral fracture model in mice with intramedullary fixation serves as an attractive platform to study bone fracture healing and evaluate therapeutic strategies to accelerate healing.

The murine closed femoral fracture model is a powerful platform to study fracture healing and novel therapeutic strategies to accelerate bone regeneration. The goal of this surgical protocol is to generate unilateral closed femoral fractures in mice using an intramedullary steel rod to stabilize the femur.

Bone fractures impose a tremendous socio-economic burden on patients, in addition to significantly affecting their quality of life. Therapeutic strategies ...