This work was supported in part by a grant from the American Otological Society to CAM and by a grant from the University Hospitals Case Medical Center to KNA and CAM. We would like to thank Jeff Churney at Focus Medical Group, Inc. (Hinckley, OH) for providing us with a microscope camera. Video production services provided courtesy of Fusion Creative Marketing, Inc. (Valdosta, GA) We thank Jonathan Frankel and Alex Levitt at CWRU for their comments during the preparation of the video.

Part 1: Anesthesia and preparation for surgery
<ol>
 <li>An adult, female Duncan-Hartley guinea pig from Charles River International Laboratories, Inc. (Wilmington, MA) is anesthetized with ketamine 60 mg/kg and xylazine 12 mg/kg intramuscularly.</li>
 <li>Petroleum lubricant is applied to the eyes to protect the animal from corneal injury due to drying.</li>
 <li>The animal is shaved from the top of the head to the shoulders and between the ears.</li>
 <li>The shaved area is prepped in a sterile fashion first with 7.5% povidone-iodine followed by 70% ethyl alcohol.</li>
 <li>The animal is placed onto an operating table with warming blanket and onto a platform that elevates the head and flexes the neck. The head of the animal is directed away from the surgeon. Adequate flexion of the neck is required in order to adequately expose the occipital ridge.</li>
 <li>The animal is draped in a sterile fashion.</li>
</ol>
Part 2: Incision and exposure of the bony occiput
<ol>
 <li>Bupivacaine plus epinephrine (Marcaine) 0.25% is applied along the prospective incision site (midline dorsal skin incision along the occiput). This causes local vasoconstriction, limiting bleeding, and provides lasting post-operative analgesia after the animal wakes.</li>
 <li>Midline dorsal skin incision is made on the scalp along the occiput. <img src="/files/ftp_upload/1728/1728fig1.jpg" alt="Figure 1" /> Figure 1: Skin incision is made along the dorsal midline, as shown above.</li>
 <li>To gain adequate exposure, the skin is retracted laterally by placing a small curved hemostat on each side of the incision.</li>
 <li>A horizontal incision is made along the neck muscle to expose the bony occiput. At this stage the animal may twitch despite adequate anesthesia due to transection of the greater occipital nerve. Spinal cord transection is a danger with horizontal incision into the suboccipital region. This complication can be avoided by ensuring that underlying bone is always felt underneath the scalpel blade.</li>
 <li>With the suboccipital musculature incised to the bone, a third hemostat is used to retract the superior muscle edge. This hemostat is held in place by the surgical assistant.</li>
 <li>A Lempert periosteal elevator is used to expose the temporo-occipital suture.</li>
 </ol>
 Part 3: Drilling the temporo-occipital suture
 <ol>
 <li>Upon exposure of the temporo-occipital suture (Figure 2), an otologic drill with 1.5 mm diamond burr is used to drill inferio-laterally to the suture. </li>
 <li>Below the outer table of the skull, the spongy texture of the diplo&euml; (The intervening cancellous bone between tables of the skull) will become visible. Once the diplo&euml; has been drilled away, the inner table of the skull appears, along with a faint blue hue that is the sigmoid sinus.</li>
 <li>The margins of the sigmoid sinus are defined without penetrating the vessel. </li>
 <li>Once the bone overlying the sigmoid sinus has been sufficiently thinned, higher magnification is utilized and a straight pick is used to carefully remove the bone overlying the sigmoid sinus.</li>
 </ol>
 <img src="/files/ftp_upload/1728/1728fig2.jpg" alt="Figure 2" /> Figure 2 The area to be drilled partially overlies the temporo-occipital suture.
 Part 4: Obstruction of the Duct
 <ol>
 <li>The skeletonized sigmoid sinus is retracted medially to reveal the operculum. </li>
 <li>A 0.5 mm diamond burr is used to drill medial to the operculum and into the endolymphatic sac and duct. </li>
 <li>The endolymphatic duct is then packed with bone wax using a straight pick. </li>
 <li>The skull defect is then reinforced with Gelfoam (Pfizer, New York, NY). </li>
 <li>4-0 POLYSORB (United States Surgical, Norwalk, CT) suture is used to bring the muscle together. There is then a seamless transition to a subcutaneous suture technique for closing the skin incision. With this closure there is no need to remove sutures afterward and there is no risk that the animal will claw at the site and pull out a suture.</li>
 </ol>
 Part 5: Post-Operative Care
 The guinea pig is put in an incubator to maintain body temperature and checked at 30 minute intervals until awake and able to maintain a sternal position. The animal is inspected for respiration rate and body color. This center uses enrofloxacin (0.2 mL at 22.7 mg/mL, subcutaneously) and buprenorphine (0.05 mL at 0.3mg/mL, subcutaneously) for post-operative infection prophylaxis and pain control, respectively. Analgesic is given once on the day of surgery and twice on post-operative day one and two. Although antibiotics are not necessary for aseptic surgery, a five-day, twice a day course of prophylactic antibiotics may be givenonce on post-operative day three.
 Complications and Management
 <ol>
 <li>Respiratory depression The surgeon should always be aware of the animal s respirations. If breathing slows or stops, discontinue surgery and visually inspect for thoracic movement. If the animal is experiencing respiratory difficulty or labored breathing, check that the mouth and airway are not occluded. </li>
 <li>Sigmoid sinus penetration Use Gelfoam and compression along with the suction tip until bleeding is stopped.</li>
 <li>Dural penetration Cover the defect with Gelfoam.</li>
 <li>Vestibular damage Do not drill more than 1 mm lateral to the sigmoid sinus. Doing so risks injuring the posterior semicircular canal, which would invalidate all data for the guinea pig. </li>
 </ol>

<ol>
	<li>Andrews, J. C., Bohmer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+surgical+approach+to+the+endolymphatic+sac+and+the+cochlear+aqueduct+in+the+guinea+pig.">The surgical approach to the endolymphatic sac and the cochlear aqueduct in the guinea pig.</a> Am J Otolaryngol. 10, 61-66 (1989).</li><li>Kimura, R., Schuknecht, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membranous+hydrops+in+the+inner+ear+of+the+guinea+pig+after+obliteration+of+the+endolymphatic+sac.">Membranous hydrops in the inner ear of the guinea pig after obliteration of the endolymphatic sac.</a> Pract Otolaryngol. , (1965).</li></ol>

Experiments on animals were performed in accordance with the guidelines and regulations set forth by the Institutional Animal Care and Use Committee at Case Western Reserve University.

In the weeks following surgical obstruction of the endolymphatic duct, the animal subject experiences fluctuating sensorineural hearing loss as measured by auditory evoked brainstem response. A sample of auditory brainstem response (ABR) recording is shown in Figure 3. The left ear serves as an unoperated control.
 <a href="http://www.jove.com/files/ftp_upload/1728/1728fig4.jpg"><img border="0" src="/files/ftp_upload/1728/1728fig3tmb.jpg" alt="FIgure 3" /></a> Figure 3: ABR threshold levels at...

surgical induction of endolymphatic hydrops by obliteration of the endolymphatic duct

Surgical induction of endolymphatic hydrops (ELH) in the guinea pig by obliteration and obstruction of the endolymphatic duct is a well-accepted animal model of the condition and an important correlate for human Meniere's disease. In 1965, Robert Kimura and Harold Schuknecht first described an intradural approach for obstruction of the endolymphatic duct (Kimura 1965). Although effective, this technique, which requires penetration of the brain's protective covering, incurred an undesirable level of morbidity and mortality in the animal subjects. Consequently, Andrews and Bohmer developed an extradural approach, which predictably produces fewer of the complications associated with central nervous system (CNS) penetration.(Andrews and Bohmer 1989) 
The extradural approach described here first requires a midline incision in the region of the occiput to expose the underlying muscular layer. We operate only on the right side. After appropriate retraction of the overlying tissue, a horizontal incision is made into the musculature of the right occiput to expose the right temporo-occipital suture line. The bone immediately inferio-lateral the suture line (Fig 1) is then drilled with an otologic drill until the sigmoid sinus becomes visible. Medial retraction of the sigmoid sinus reveals the operculum of the endolymphatic duct, which houses the endolymphatic sac. Drilling medial to the operculum into the area of the endolymphatic sac reveals the endolymphatic duct, which is then packed with bone wax to produce obstruction and ultimately ELH. 
In the following weeks, the animal will demonstrate the progressive, fluctuating hearing loss and histologic evidence of ELH.

Watch this Scientific Journal Video about Surgical Induction of Endolymphatic Hydrops by Obliteration of the Endolymphatic Duct at JoVE.com

Surgical Induction of Endolymphatic Hydrops by Obliteration of the Endolymphatic Duct

This video shows how to surgically obstruct the guinea pig's endolymphatic duct to produce endolymphatic hydrops.

Surgical induction of endolymphatic hydrops (ELH) in the guinea pig by obliteration and obstruction of the endolymphatic duct is a well-accepted animal ...

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11.3K Views.  Case Western Reserve University. This video shows how to surgically obstruct the guinea pig's endolymphatic duct to produce endolymphatic hydrops.

Video: Surgical Induction of Endolymphatic Hydrops by Obliteration of the Endolymphatic Duct

Imaging Effector Memory T cells in the Ear After Induction of Adoptive DTH

Delayed type hypersensitivity (DTH) is an immune reaction in which the main players are CCR7- effector / memory T lymphocytes. Here, we demonstrate a method for inducing and recording the progress of a DTH reaction in the rat ear. This is followed by a demonstration of the preparation of rat ear tissue for two-photon imaging of the CCR7- effector / memory T cell response.
An adoptive DTH is induced by the intraperitoneal injection of GFP-labeled Ova-specific CCR7- effector / memory T cell line (Beeton, C J. Visualized Experiments, Issue 8). Cells are then allowed to equilibrate in the rat for 48 hours before challenge by injecting one ear with saline (control ear) and the other with a 1:1 mix of Ova and Ova conjugated to Texas-Red (Ova-TR) to allow visualization of resident antigen-presenting cells.
We describe a method of tissue preparation useful for imaging the motility of cells within the deep dermal layer during an immune response, in conjunction with visualization of collagen fibers by second harmonic generation. Ear tissue is cut into 5 x 5 mm squares (slightly larger is better) and mounted onto plastic cover slips using Vetbond&trade;, which are then secured using silicone grease in an imaging chamber and superfused by oxygen-bubbled tissue culture medium at 37&deg;C.

Here we demonstrate a method for inducing and recording the progress of a delayed type-hypersensitivity (DTH) reaction in the rat ear. This is followed by a demonstration of the preparation of rat ear tissue for two-photon imaging of the effector / memory T cell response.

Delayed type hypersensitivity (DTH) is an immune reaction in which the main players are CCR7- effector / memory T lymphocytes. Here, we demonstrate a ...

Assay for Neural Induction in the Chick Embryo

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying the formation and initial patterning of the nervous system. This video demonstrates how to graft organizer tissue into a host, a method by which Hensen s node (the organizer in the chick embryo) is grafted to a host competent ectoderm. The organizer graft instructs overlying na ve tissue to adopt a neural fate via neural inducing signals. This mechanism is referred to as neural induction, and constitutes the initial step in the formation of brain and spinal cord in amniotes. This method is essentially used for the characterization of putative neural inducing molecules in chick. This video demonstrates the different steps in the assay for neural induction; First, the donnor embryo is explanted and pinned on a dish. Then, the host embryo is prepared for New culture. The graft is excised and transplanted to the host area pellucida margin. The host is cultured for 18-22 hrs. The assembly is fixed and processed for further applications (e.g. in situ hybridization). This method was originally devised by Waddington 1,2 and Gallera 3,4.

Neural induction is the first step in the formation of the brain. It is a mechanism by which Hensen's node (organizer), instructs adjacent tissue to adopt a neural fate, i.e. to give rise to the nervous system. This video demonstrates an assay for neural induction in chick embryo.

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ...

Microsurgical Clip Obliteration of Middle Cerebral Aneurysm Using Intraoperative Flow Assessment

Cerebral aneurysms are abnormal widening or ballooning of a localized segment of an intracranial blood vessel.  Surgical clipping is an important treatment for aneurysms which attempts to exclude blood from flowing into the aneurysmal segment of the vessel while preserving blood flow in a normal fashion.  Improper clip placement may result in residual aneurysm with the potential for subsequent aneurysm rupture or partial or full occlusion of distal arteries resulting in cerebral infarction.  Here we describe the use of an ultrasonic flow probe to provide quantitative evaluation of arterial flow before and after microsurgical clip placement at the base of a middle cerebral artery aneurysm.  This information helps ensure adequate aneurysm reconstruction with preservation of normal distal blood flow.

Description of the surgical obliteration of a cerebral aneurysm utilizing an ultrasonic flow probe to assess arterial flow prior to and after aneurysm clip placement.

Cerebral aneurysms are abnormal widening or ballooning of a localized segment of an intracranial blood vessel.  Surgical clipping is an important ...

Isolation of Basal Cells and Submucosal Gland Duct Cells from Mouse Trachea

The large airways are directly in contact with the environment and therefore susceptible to injury from toxins and infectious agents that we breath in 1. The large airways therefore require an efficient repair mechanism to protect our bodies. This repair process occurs from stem cells in the airways and isolating these stem cells from the airways is important for understanding the mechanisms of repair and regeneration. It is also important for understanding abnormal repair that can lead to airway diseases 2. The goal of this method is to isolate a novel stem cell population from the mouse tracheal submucosal gland ducts and to place these cells in in vitro and in vivo model systems to identify the mechanisms of repair and regeneration of the submucosal glands 3. This production shows methods that can be used to isolate and assay the duct and basal stem cells from the large airways 3.This will allow us to study diseases of the airway, such as cystic fibrosis, asthma and chronic obstructive pulmonary disease. Currently, there are no methods for isolation of submucosal gland duct cells and there are no in vivo models to study the regeneration of submucosal glands.

Here we demonstrate our protocol for isolation of basal and submucosal gland duct cells from mouse tracheas. We also demonstrate the method of injecting stem cells into the dorsal mouse fat pad to create an in vivo model of submucosal gland regeneration.

The large airways are directly in contact with the environment and therefore susceptible to injury from toxins and infectious agents that we breath in 1. ...

Culturing Primary Rat Inner Medullary Collecting Duct Cells

Arginine-vasopressin (AVP) facilitates water reabsorption by renal collecting duct principal cells and thereby fine-tunes body water homeostasis. AVP binds to vasopressin V2 receptors (V2R) on the surface of the cells and thereby induces synthesis of cAMP. This stimulates cellular signaling processes leading to changes in the phosphorylation of the water channel aquaporin-2 (AQP2). Protein kinase A phoshorylates AQP2 and thereby triggers the translocation of AQP2 from intracellular vesicles into the plasma membrane facilitating water reabsorption from primary urine. Aberrations of AVP release from the pituitary or AVP-activated signaling in principal cells can cause central or nephrogenic diabetes insipidus, respectively; an elevated blood plasma AVP level is associated with cardiovascular diseases such as chronic heart failure and the syndrome of inappropriate antidiuretic hormone secretion.
Here, we present a protocol for cultivation of primary rat inner medullary collecting duct (IMCD) cells, which express V2R and AQP2 endogenously. The cells are suitable for elucidating molecular mechanisms underlying the control of AQP2 and thus to discover novel drug targets for the treatment of diseases associated with dysregulation of AVP-mediated water reabsorption. IMCD cells are obtained from rat renal inner medullae and are used for experiments six to eight days after seeding. IMCD cells can be cultured in regular cell culture dishes, flasks and micro-titer plates of different formats, the procedure only requires a few hours, and is appropriate for standard cell culture laboratories.

Arginine-vasopressin (AVP) controls fine-tuning of body water homeostasis through facilitating water reabsorption by renal principal cells. Here, we present a protocol for the cultivation of primary rat inner medullary collecting duct cells suitable for the elucidation of molecular mechanisms underlying AVP-mediated water reabsorption.

Arginine-vasopressin (AVP) facilitates water reabsorption by renal collecting duct principal cells and thereby fine-tunes body water homeostasis. AVP ...

Induction and Analysis of Epithelial to Mesenchymal Transition

Epithelial to mesenchymal transition (EMT) is essential for proper morphogenesis during development. Misregulation of this process has been implicated as a key event in fibrosis and the progression of carcinomas to a metastatic state. Understanding the processes that underlie EMT is imperative for the early diagnosis and clinical control of these disease states. Reliable induction of EMT in vitro is a useful tool for drug discovery as well as to identify common gene expression signatures for diagnostic purposes. Here we demonstrate a straightforward method for the induction of EMT in a variety of cell types. Methods for the analysis of cells pre- and post-EMT induction by immunocytochemistry are also included. Additionally, we demonstrate the effectiveness of this method through antibody-based array analysis and migration/invasion assays.

A straightforward method is described for the induction of epithelial to mesenchymal transition (EMT) in a variety of cell types. Methods for the analysis of cells in EMT states by immunocytochemistry are included.

Epithelial  to mesenchymal transition (EMT) is essential for proper morphogenesis during  development. Misregulation of this  process has been implicated ...

Isolation of Human Hepatocytes by a Two-step Collagenase Perfusion Procedure

The liver, an organ with an exceptional regeneration capacity, carries out a wide range of functions, such as detoxification, metabolism and homeostasis. As such, hepatocytes are an important model for a large variety of research questions. In particular, the use of human hepatocytes is especially important in the fields of pharmacokinetics, toxicology, liver regeneration and translational research. Thus, this method presents a modified version of a two-step collagenase perfusion procedure to isolate hepatocytes as described by Seglen 1.
Previously, hepatocytes have been isolated by mechanical methods. However, enzymatic methods have been shown to be superior as hepatocytes retain their structural integrity and function after isolation. This method presented here adapts the method designed previously for rat livers to human liver pieces and results in a large yield of hepatocytes with a viability of 77&plusmn;10%. The main difference in this procedure is the process of cannulization of the blood vessels. Further, the method described here can also be applied to livers from other species with comparable liver or blood vessel sizes.

A modified two-step collagenase perfusion procedure for isolation of human hepatocytes is described. This method can also be applied to other mammalian livers. The isolated hepatocytes are available in high yield and viability, making them a suitable model for scientific research in areas such as liver regeneration, pharmacokinetics and toxicology.

The liver, an organ with an exceptional regeneration capacity, carries out a wide range of functions, such as detoxification, metabolism and homeostasis. ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. During a potentially aversive situation, corticotrophin releasing hormone (CRH) is released from the hypothalamus in the brain. This stimulates the release of adrenocorticotrophic hormone (ACTH) from the pituitary gland, which in turn stimulates release of glucocorticoids from the adrenal gland. In horses the glucocorticoid corticosterone is responsible for several adaptations needed to support equine flight behaviour and subsequent removal from the aversive situation. Corticosterone metabolites can be detected in the feces of horses and assessment offers a non-invasive option to evaluate long term patterns of adrenal activity. Fecal assessment offers advantages over other techniques that monitor adrenal activity including blood plasma and saliva analysis. The non-invasive nature of the method avoids sampling stress which can confound results. It also allows the opportunity for repeated sampling over time and is ideal for studies in free ranging horses. This protocol describes the enzyme linked immunoassay (EIA) used to assess feces for corticosterone, in addition to the associated biochemical validation.

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. The method offers a non-invasive option to assess long term patterns in both domestic and free ranging horses. This protocol describes the enzyme linked immunoassay involved and the associated biochemical validation.

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. During a potentially aversive situation, ...

Partial Bile Duct Ligation in the Mouse: A Controlled Model of Localized Obstructive Cholestasis

In rodents, complete bile duct ligation (cBDL) of the common bile duct is an established surgical technique for studying obstructive cholestasis and bile duct proliferation. However, long-term experiments can lead to increased morbidity and mortality. In select mouse strains with underlying liver disease, meaningful comparisons can be made even with ligation of a single lobe of the liver, which can reduce animal losses and expenses. Here, we describe partial bile duct ligation (pBDL) in the mouse, in which only the left hepatic bile duct is ligated, causing biliary obstruction in the left lobe but not the remaining lobes. With careful microsurgical technique, pBDL experiments can be cost-effective, since the unligated lobe serves as an internal control to the ligated lobes, when subjected to the same conditions in the same animal. Unlike cBDL, a separate sham-operated control group is not necessary. pBDL is highly useful to directly compare localized versus systemic effects of cholestasis and other retained bile components. pBDL can also be repurposed as a novel method to investigate mechanisms related to medications and cell migration.

Here, we present partial bile duct ligation as a surgical model of liver injury and regeneration in rodents.

In rodents, complete bile duct ligation (cBDL) of the common bile duct is an established surgical technique for studying obstructive cholestasis and bile ...