התאמת שיטות סנונית Videofluoroscopic אדם מחקר כדי לזהות ולאפיין בליעה במודלי Murine מחלות
Summary
This study successfully adapted human videofluoroscopic swallowing study (VFSS) methods for use with murine disease models for the purpose of facilitating translational dysphagia research.
Abstract
מחקר זה הותאם videofluoroscopic אדם בליעת מחקר שיטות (VFSS) לשימוש עם דגמי מחלה עכבריים לצורך קידום מחקר הבליעה translational. תוצאות מוצלחות תלויות בשלושת מרכיבים קריטיים: חדרי בדיקה המאפשרים האכלה עצמית בעמידה בלתי מרוסן בחלל מצומצם, מתכונים שלהסוות את הטעם / ריח מרתיע של סוכנים בניגוד אוראליים, זמינים מסחרי, ופרוטוקול בדיקת צעד-אחר-צעד ש מאפשר כימות של פיזיולוגיה סנונית. חיסולו של אחד או יותר ממרכיבים אלה יהיה השפעה לרעה על תוצאות המחקר. יתר על כן, יכולת רמת האנרגיה של מערכת השיקוף תקבע איזה לבלוע פרמטרים יכולים להיחקר. רוב מרכזי המחקר fluoroscopes אנרגיה גבוהה מיועד לשימוש עם אנשים ובעלי חיים גדולים יותר, וכתוצאה מכך איכות תמונה ירודה במיוחד כאשר בודקים עכברים ומכרסמים קטנים אחרים. למרות מגבלה זו, זיהינו שבעה VFSפרמטרים S שהם לכימות באופן עקבי בעכברים בעת שימוש פלואורוסקופ אנרגיה גבוה בשילוב עם פרוטוקול VFSS העכברי החדש. לאחרונה הושגו מערכת שיקוף אנרגיה נמוכה עם יכולות רזולוציה הדמיה וגדלה גבוהות במיוחד, שנועדה לשימוש עם עכברים ומכרסמים קטנים אחרים. עבודה ראשונית באמצעות מערכת חדשה זו, בשילוב עם פרוטוקול VFSS העכברי החדש, זיהתה 13 פרמטרים סנונית שהם כימות באופן עקבי בעכברים, שהוא כמעט כפול המספר שהושג באמצעות (כלומר, אנרגיה גבוהה) קונבנציונלית fluoroscopes. זיהוי של פרמטרים סנונית נוספים צפוי כפי שאנו לייעל את היכולות של מערכת חדשה זו. תוצאות עד כה להדגים את התועלת של שימוש במערכת שיקוף אנרגיה נמוכה כדי לזהות ולכמת שינויים עדינים בפיזיולוגיה סנונית שאחרת עשויה להתעלם בעת השימוש בfluoroscopes אנרגיה הגבוהה כדי לחקור מודלים עכבריים מחלה.
Introduction
בליעה (בליעת ירידת ערך) היא סימפטום נפוץ של מצבים רפואיים רבים המשפיעים על אנשים בכל הגילים. דוגמאות כוללות שבץ, מחלת פרקינסון, מחלת אלצהיימר, שיתוק מוחין, ניוון שרירים, טרשת לרוחב amyotrophic (ALS), מחלה באטן, סרטן ראש והצוואר, לידה מוקדמת, והזדקנות מתקדמת. בליעה מתאם גבוהה עם תמותה, בדרך כלל כתוצאה של תת תזונה חמורה או דלקת ריאות שמתפתחת כאשר מזון / נוזל / רוק חיידקים-לאדן הוא להישאף לריאות 1-4. מצבו הרפואי מתיש ומסכנות חיים זה משפיע על יותר מ -15 מיליון בני אדם בכל שנה בארצות הברית לבדה 3. למרות השכיחות הגבוהה ותוצאות שליליות נלוות, אפשרויות טיפול הנוכחיות לבליעה מוגבלות לפליאטיבי (ולא מרפא) מתקרב, כגון שינוי תזונה (למשל, הימנעות consistencies מזון / נוזל הספציפי), שינויים ביציבה (למשל, tucking הסנטר כאשר בליעה), גישות מוטוריות (למשל, תרגילים לחיזוק שרירי בחלל הפה, הלוע, גרון ו), גישות חושיות (למשל, טעם יישום, טמפרטורה, ו / או גירוי מכאני), וצינור האכלה (לדוגמא, תזונה ולחות מנוהלת באמצעות צינור nasogastric (NG) או צינור percutaneous גסטרונומית אנדוסקופית (PEG)). טיפולים אלה משמשים רק טיפול סימפטומטי ולא כמיקוד הגורמים הבסיסיים של הבעיה. ואכן, מכשול עיקרי לגילוי רומן, טיפולים יעילים לבליעה הוא מהמנגנונים פתולוגיים האחראים, אשר צפוי שונים לכל מחלה הידע המדעי המוגבל.
אבחון הפרעת בליעה הוא בעיקר נעשה באמצעות הליך רדיוגרפי נקרא מחקר videofluoroscopic בליעה (VFSS), הידוע גם במחקר סנונית בריום שונה. במהלך שנות 30 פלוס העבר, בדיקת אבחון זה כבר נחשבה זהב סטנדרטי עבור evaluating פונקצית סנונית 5-7. בדיקה זו כרוכה בצורך בסבלנות לשבת או לעמוד בדרכה של קרן רנטגן של מכונה שיקוף בזמן בליעת מזון וסדירויות נוזל מעורבבת עם חומר ניגוד אוראלי מרצון, בדרך כלל 8,9 בריום סולפט או iohexol 10. כמטופל בולע, ניתן לראות מזון ונוזלים המכילים חומר ניגוד בזמן אמת באמצעות צג מחשב בעת נסיעה מן הפה אל הקיבה. מבני רקמות רכים הם גם נראים לעין וניתן להעריך ביחס למבנה ותפקוד. חולים מתבקשים לבצע כמה סנוניות של כל מזון ועקביות נוזלית, אשר כולם וידאו המוקלט לצפייה שלאחר מכן וניתוח מסגרת לפי מסגרת לכמת את הנוכחות ואת מידת הבליעה. רכיבים פיסיולוגיים רבים של בליעה הם בדרך כלל מנותחים, כגון נקודה אנטומיים ההדק של סנונית בלוע, זמן מעבר בולוס דרך הלוע והוושט, במידה ומשך larynהעלאה גאל, מיקום וכמות משקעי פוסט-סנונית, ומופע של וסיבה פיזיולוגית לשאיפה 7,11.
היבטים של פרוטוקול VFSS אדם הותאמו לאחרונה ללימוד חולדות באופן חופשי-מתנהגים; עם זאת, תוצאות היו מוגבלות בגלל החולדות לא נשארו בתחום videofluoroscopic מבט במהלך בדיקת 12. VFSS שעד עתה לא ניסה עם עכברים. הסתגלות מוצלחת של פרוטוקול VFSS האנושי לשימוש עם עכברים וחולדות הייתה לספק שיטת מחקר חדשנית לחקור מאות עכברי קיימים כיום (עכבר וחולדה) מודלים של מחלות שידועות כגורמים לבליעה בבני אדם. שיטה זו חדשה (המכונה מעתה כVFSS עכברי) הייתה לכן לזרז זיהוי ואימות של מודלים עכבריים של בליעה המתאימים לחוקר את המנגנונים הנוירו-פיסיולוגיים הבסיסיים בתוך רקמת שרירים, עצבים, והמוח שפתולוגי ותורם לבליעה iבני אדם n. יתר על כן, VFSS העכברי יאפשר זיהוי של מדדים אובייקטיביים (סמנים ביולוגיים) של פונקצית סנונית / תפקוד לקוי שניתן להשוות באופן ישיר עם בני אדם. אז סמנים ביולוגיים videofluoroscopic בין מינים אלה יכולים לשמש כמדדי תוצאת רומן לכמת את יעילות טיפול בניסויים פרה-קליניים בעכברים וחולדות, שהיה טובים יותר לתרגם לניסויים קליניים עם אנשים.
לשם כך, פרוטוקול VFSS העכברי הוקם באמצעות ~ משני מינים 100 עכברים. כל העכברים היו או C57 או זני C57 / SJL היברידי. עכברי C57 לא עברו שינוי גנטי, ואילו C57 / SJL היה מתח הרקע למושבה של SOD1-G93A המהונדס (או SOD1) עכברים, מודל החיה הנפוצה ביותר של ALS. המושבה SOD1 הייתה 50-50 תמהיל משוער של מהונדס (כלומר, מושפע-ALS) עכברים והמלטת nontransgenic (כלומר, לא נפגע).
פרוטוקול VFSS העכברי מורכב משלושה מרכיבים:
- <li> תאי תצפית מעוצבים מותאמים אישית המאפשרים האכלה ובליעה מרצון בעת שעמדה חסר מעצורים בחלל מצומצם בתוך מכונה שיקוף,
- מתכונים שלהסוות את הטעם / הריח מרתיע של סוכנים בניגוד אוראליים ולייצר radiodensity מספיק כדי לאפשר הדמיה מספקת של בליעה,
- פרוטוקול בדיקת צעד-אחר-צעד הממקסם עמידת בעלי חיים, ממזער את זמן בדיקה כולל וחשיפה לקרינה, ומאפשר כימות של מספר פרמטרים סנונית לכל שלב בבליעה (כלומר, אוראלי, בלוע, וושט).
ההשפעה המשולבת מייצרת מתח נמוך, סביבה נוחה, האכלה עצמי בדיקה המאפשרת הערכה של האכלה טיפוסית והתנהגויות בליעה של עכברים.
Protocol
Representative Results
Discussion
Hundreds of murine (mouse and rat) models are commercially available to study human diseases. However, only three murine disease models have been specifically investigated relative to dysphagia: a mouse model of ALS13,14 and rat models of Parkinson’s disease12,15-17 and stroke18. Each of these preliminary studies utilized different methodologies to assess dysphagia, rendering it impossible to derive meaningful comparisons between species and diseases. This major limitation may be overcome in future studies by utilizing the newly developed murine VFSS protocol that permits objective quantification of numerous swallow parameters in self-feeding animals.
Successful VFSS outcomes are dependent upon three critical components: 1) test chambers that permit self-feeding while standing unrestrained in a confined space, 2) recipes that mask the aversive taste/odor of commercially-available oral contrast agents, and 3) a step-by-step test protocol that permits quantification of swallow physiology. The combined effect produces a comfortable, low stress, self-feeding examination environment that evokes typical feeding and swallowing behaviors. Elimination of one or more of these components will have a detrimental impact on the study results. Examples of negative outcomes include inability to maintain animals in the fluoroscopy field of view, undesirable behaviors that distract from drinking, aversion to the oral contrast agent, and inability to quantify swallow parameters due to insufficient drinking episodes.
A major challenge in obtaining optimal VFSS outcomes was designing a suitable test chamber. Numerous revisions of our prototype design culminated in an observation chamber that sufficiently maintains mice in the field of view and prevents behaviors that distract from drinking. The chambers were made using milling machines to obtain uniform dimensions of the tubes and end-caps, thereby ensuring interchangeability of components for several observation chambers of the same diameter. The inner dimensions (diameter and length) were matched to be slightly larger than an adult mouse’s body size, which resulted in a narrow test chamber that sufficiently permits walking in a straight line and turning around. The narrow design, in combination with strategic positioning of the spout and peg-bowl at only the end, maintains the head and body of mice aligned along the length of the chamber while drinking. Once engaged in drinking, mice remain remarkably self-stabilized at the spout or bowl for several seconds at a time, resulting in minimal movement artifact to interfere with testing. Thus, it is possible to obtain undistorted, close-up observation/video recording and videofluoroscopic imaging of mice while drinking in the lateral and dorsal-ventral planes.
Mice (and other small rodents) are naturally inclined to seek shelter in small spaces. As a result, they freely enter the test chamber (with one end already closed by an end-cap) when it is placed in the home cage, thereby eliminating stress/anxiety caused by handling (i.e., manually picking up the animal to place it in the chamber). Once the mouse enters the chamber, the other end is closed by attaching a 2nd end-cap. This design prevents escape while creating a low anxiety test chamber for mice to freely explore.
The square shape of the chamber provides built-in motion stability that permits it to be used in a free-standing fashion, thus eliminating the need for testing within a standard rodent cage. The entire apparatus is lightweight, portable, stackable for storage purposes, sturdy, easy to clean, and can be autoclaved. While the chambers were initially designed for use with fluoroscopy, they also are compatible with spot-film radiography, neuroimaging (e.g., MRI, PET, CT), and visual observation/video recording of various behaviors.
A second major challenge to overcome was masking the aversive taste/odor of oral contrast agents (i.e., barium sulfate and iohexol). Given that taste sensitivity varies widely among mouse strains19-21 and perhaps with age22,23, it was necessary to identify a single test solution that was palatable to all mice, regardless of strain and age. This outcome is essential to permit direct comparisons of swallow function/dysfunction across strains and ages, while eliminating confounding results due to differences in rheological (e.g., viscosity, density, etc.) and chemical properties of the test solutions. To this end, we developed a simple, rapid palatability screening approach to identify the preferred flavor enhancer to mask the aversive taste/odor of oral contrast agents during murine VFSS. Methods were modeled after the brief exposure test, which requires a lickometer (i.e., lick sensor) to record lick rates during the first 2 min after a water regulation period (i.e., withholding water overnight) to induce thirst24,25. A lickometer was not available for this study; therefore, preference was assessed by behavioral observations, as well as standard video recording methods for lick rate that have been previously validated in our lab13,14. Using this palatability screening approach, chocolate was identified as the preferred flavor enhancer by C57 and C57/SJL strains. Specifically, 100% of the mice in each cage readily drank chocolate-flavored solutions within 30 sec of exposure, with multiple mice simultaneously drinking at the spout. However, the addition of barium resulted in only brief drinking bouts by most mice, regardless of barium or chocolate concentration.
An alternative to barium is iohexol, an iodine-based contrast agent that has only recently been recognized as a suitable alternative to barium sulfate for human VFSS10; thus, it has not yet been standardized for this purpose. Several different concentrations of chocolate-flavored iohexol were offered to mice. Recipes containing up to a 50% solution of stock iohexol (350 mg iodine per ml) were readily drank by most mice after an overnight water regulation period. Higher concentrations resulted in avoidance behaviors. A 50% iohexol (350 mg iodine per ml) solution produced sufficient radiodensity while being swallowed by mice, whereas lower concentrations were markedly less visible and hindered quantification of swallow physiology. Therefore, the optimal test solution for VFSS with mice was identified as a 50% iohexol solution with chocolate flavor added. Repeat palatability testing did not result in avoidance behaviors or adverse events.
A third challenge to overcome was preventing mice from turning/tilting their head while drinking, which obscures visualization of the swallowing mechanism during VFSS. Drinking from a peg-bowl positioned just above the floor at one end of the chamber resolved this problem. There are several additional advantages of using a peg-bowl instead of a sipper tube bottle. For example, a calibrated volume of liquid can be pipetted into the peg-bowl through a ventilation hole in the end-cap of the observation tube. This approach permits quantification of the minute volume of test solution consumed during the brief VFSS test duration. Moreover, the increased surface area of the test solution in the peg-bowl, compared to a small sipper tube opening, may provide increased olfactory stimulation to further motivate drinking. Peg-bowls may be better suited for studying young or smaller strain mice, as the bowl height is a standardized distance from the floor. In contrast, sipper tube lengths must be adjusted to accommodate different sized mice, which adds another potentially confounding variable to consider. Also, mouse models of neurological diseases may have difficulty reaching a sipper tube bottle due to motor impairment of the limbs, whereas they can easily reach a peg bowl. Mice with tongue and/or jaw dysfunction may be unable to sufficiently press the ball in the spout to access the liquid; using peg-bowls can eliminate this confound. For these reasons, the use of peg-bowls over sipper tube bottles is the preferred method of murine VFSS testing. However, the observation chambers were designed to accommodate spout drinking as needed. An important caveat to consider is that lick rates are known to differ between spout and bowl drinking13,26. Therefore, the choice of either spout or peg-bowl for VFSS must be consistent within and between experiments.
A fourth challenge was to identify quantifiable swallow parameters for mice that are comparable to the VFSS parameters commonly used in human research studies and clinical practice. Our preliminary findings showed the type of fluoroscopy system determines which swallow parameters can be investigated in mice. Most research centers and medical settings have high energy (75-95 kV, 1-5 mA) fluoroscopes designed for use with people and larger animals, which result in exceptionally poor image quality when testing mice and other small animals. As an example, a recent study using a high energy fluoroscope with rats was able to identify only 4 quantifiable swallow parameters12, and we were able to identify only 7 swallow parameters for mice in this present study. To overcome this major limitation, we recently obtained a low energy fluoroscopy system called The LabScope (Glenbrook Technologies). The system is a miniature fluoroscope that generates a continuous cone-beam of X-rays with photon energies between 15 and 40 kV and a peak tube current of 0.2 mA (8 W maximum power). The lower energy levels of this system are better attenuated by the thin bone and soft tissue of mice and thus provide higher contrast resolution than conventional (i.e., high energy) fluoroscopes. The X-ray beam of The LabScope is directed at a 5 cm diameter image intensifier, which is markedly smaller than the 15-57 cm diameter image intensifier of conventional fluoroscopes. The minimum source-to-intensifier distance (SID) of The LabScope is ~6 cm (in contrast to ~30 cm for conventional fluoroscopes), which provides increased magnification capabilities. In addition, The LabScope uses patented technology that digitally magnifies the image up to 40 times in real time, without altering the SID. The result is in essence an X-ray microscope that can zoom in and out in real time to view small regions of interest, such as the swallowing mechanism of a mouse.
A major advantage of this low-energy fluoroscopy system is improved radiation safety. In addition to animals receiving lower radiation doses with The LabScope, researchers using the system are exposed to significantly less radiation scatter. The radiation exposure directly in front of the unit at the control panel is 10.3 mR/hr. At a distance 1 m in front of the unit, exposure drops to 580 µR/hr. Most other locations in the room have very low exposure below 10 µR/hr. Despite this improvement, we have taken extra measures to improve radiation safety. For example, leaded acrylic shielding has been added around The LabScope to block scattered X-ray photons, which enables researchers to conduct murine VFSS testing without wearing personal shielding (e.g., lead aprons, thyroid shields, and glasses). In addition, the clear acrylic permits visualization of the mouse from a distance. Further radiation safety is provided by a motorized scissor lift table, which is controlled remotely by the investigator. From a distance up to 3 m from the fluoroscope, researchers can use the remote-controlled device to adjust the vertical and horizontal position of the observation chamber within the X-ray beam. As a result, the anatomical regions of interest can be maintained within the fluoroscopy field of view while the mouse freely moves within the observation chamber. Although the scissor lift was designed for use with The LabScope, it also is compatible for use with conventional fluoroscopes to improve radiation safety for researchers. A final step to improve radiation safety during murine VFSS entails the use of a syringe delivery system for liquids. This system includes a 3-4 foot (or longer, if needed) length of PE tubing, which permits fast and efficient delivery of liquids into the peg-bowl from a distance. This syringe delivery system for liquids, in combination with the observation chambers, also can be used with conventional fluoroscopes.
Preliminary work using The LabScope, in combination with the new murine VFSS protocol, demonstrates a major advantage of over conventional systems: the number of swallow parameters that can be reliably quantified is nearly doubled. However, soft tissue structures of the swallowing mechanism (e.g., tongue, velum, posterior pharyngeal wall, and epiglottis) of mice are not readily visible when using low or high energy fluoroscopy systems. Therefore, we focused on quantifying bolus flow measures rather than the biomechanics of swallowing. We were predominantly interested in parameters that could be quantified based on units of time, area, distance, volume, etc., rather than using Likert-type scale measures. Numerous bolus flow parameters meeting this requirement have been described in the human VFSS literature, such as oral transit time27-29, pharyngeal transit time27-33, and esophageal transit time34-36, to name but a few. Bolus transport through the oral cavity was not readily visible in mice, likely due to the small bolus size during spontaneous drinking. However, we were able to reliably quantify pharyngeal and esophageal transit times, as well as several other measures pertaining to bolus flow and clearance. Identification of additional translational swallow parameters is expected as we optimize the capabilities of The LabScope.
Results of this study showed that mice take several rhythmic licks per swallow during spontaneous drinking, with each small liquid bolus sequentially filling the vallecular space before triggering the pharyngeal swallow. This behavior, which is typical for mammals that use licking as the primary means of ingesting liquid37-40, resembles the rhythmic suck-swallow pattern of human infant swallowing and all infant mammals in general. Infant swallowing physiology is characterized by several rhythmic sucks followed by a reflexive pharyngeal swallow, commonly described as the suck-swallow cycle37,41-43. Thus, the rhythmic tongue and jaw movements involved in the ingestive licking behaviors of mice may be more comparable to ingestive sucking behaviors of human infants rather than cup drinking by children and adults. We have therefore been quantifying the lick rate and lick-swallow ratio of mice for future comparisons with the suck rate and suck-swallow ratio of human infants. Perhaps murine VFSS research will provide insight into developmental swallowing disorders.
As with any new research method, areas for improvement have been identified. For example, the murine VFSS protocol was developed using only C57 and C57/SJL mouse strains; it has not yet been tested with rats. The observation chambers will need to be scaled up in size (diameter and length) to accommodate the larger body size of rats. Also, it is unknown if chocolate-flavored iohexol is suitable as a universal murine VFSS test solution. Therefore, larger scale testing with multiple strains of mice and rats is warranted for this purpose. Also, the use of barium as a contrast agent for murine VFSS should not be ruled out. Mice clearly preferred the iohexol recipes over barium; however more rigorous and systematic attempts at masking the aversive taste/odor of barium may provide palatable alternatives to iohexol. Future studies comparing the effects of iohexol and barium sulfate (as well as other potential oral contrast agents) on taste preference and swallow physiology in mice and rats would undoubtedly provide important information that is directly relevant and translational to human VFSS.
VFSS with humans includes several consistencies of foods and liquid, and dysphagia is most apparent when swallowing thin liquids and dry, solid foods44,45. The murine VFSS protocol is therefore being expanded to include additional consistencies that may facilitate detection and quantification of dysphagia in disease models. It also will be necessary to conduct viscosity testing of the liquid recipes for murine VFSS in order to adjust the viscosities to match those used during human VFSS. Addressing these limitations will facilitate identification of translational VFSS biomarkers of dysphagia that can be directly compared between mice, rats, and humans.
The utility of murine VFSS may be significantly improved by implanting radiopaque markers into soft tissue structures of the swallowing mechanism that are otherwise not visible, thereby permitting investigations of the biomechanics of swallowing. This approach has been successfully used for many years to study the biomechanics of swallowing in infant pigs, using an assortment of metal clips and wires37,42. We expect the use of similar, but smaller, markers in mice would permit quantification of several additional swallow parameters for comparison with larger mammals, including humans. We are currently developing methodology for implanting radiopaque markers into the tongue, soft palate, pharynx, larynx, and proximal esophagus of mice to test this hypothesis.
The video recording frame rate of The LabScope and conventional fluoroscopes is limited to 30 frames per sec (fps). However, our preliminary results showed that the entire pharyngeal stage of swallowing for healthy mice occurs in less than 66 msec (i.e., 2 frames), which is approximately 10 times faster than humans. Thus, the pharyngeal phase of swallowing in mice occurs so quickly that the details are not appreciable with a 30 fps camera. A higher frame rate (likely >100 fps) will be necessary to sufficiently visualize and quantify the extremely rapid and complex movements of the pharyngeal stage of swallowing in mice and other rodents. In conjunction with a higher frame rate, incorporating biplanar technology for 3D fluoroscopic imaging would certainly expand the utility murine VFSS. Therefore, future design considerations should include a higher frame rate camera and biplanar imaging capabilities.
Lastly, low-dose radiation has been shown to cause sterility in female C57 mice, resulting in altered levels of ovarian-stimulated hormones that may confound life-span studies46. Outcomes pertaining specifically to the effects of repeated low-dose radiation exposure associated with VFSS testing have not yet been investigated in mice, other animals, or humans. However, ovarian dysfunction (not related to radiation exposure) in human females has been linked to gastrointestinal motility disorders, and specifically to dysphagia in some cases47, which provides yet another caveat to consider when designing future VFSS studies that include females (animals and humans). Exclusion of females should be avoided, as significant gender differences in swallow function have been reported for people48,49 and would be important to detect and characterize in animal disease models as well. Therefore, outcomes from longitudinal VFSS studies in mice and rats of both sexes have tremendous translational potential for humans relative to dysphagia, as well as to the risks of low-dose radiation exposure associated with repeat VFSS testing.
Disclosures
The authors have nothing to disclose.
Acknowledgements
We graciously thank additional members of the Lever Lab who contributed to data collection (Andries Ferreira, Danarae Aleman, Alexis Mok, Kaitlin Flynn, Elizabeth Bearce, and Matan Kadosh) and manuscript review (Andries Ferreira, Rebecca Schneider, and Kate Robbins). We also acknowledge Roderic Schlotzhauer and Edwin Honse from the MU Physics Machine Shop for their design input and fabrication of the rodent observation tubes used in this study. We are especially appreciative of Malea Jan Kunkel (Radiology Supervisor in the Veterinary Medicine and Surgery Department at the University of Missouri – College of Veterinary Medicine) and Jan Ivey (Manager of the Research Animal Cath Lab at the University of Missouri – School of Medicine) for demonstrating constant patience and motivation while operating the high energy fluoroscopes as we developed the murine VFSS protocol. Funding sources for this study included NIH/NIDCD (TE Lever), NIH/NINDS (GK Pavlath), Otolaryngology – Head and Neck Surgery start-up funds (TE Lever), MU PRIME Fund (TE Lever), Mizzou Advantage (TE Lever), and the MU Center on Aging (TE Lever).
Materials
| Name of Material/ Equipment | Company | Catalog Number | Comments/Description |
| Polycarbonate tubing for observation chambers | McMaster-Carr | 3161T41 | Body of observation tubes, 2"X2" diameter, 0.080" thick wall |
| Polycarbonate sheet for observation chambers | McMaster-Carr | 9115K71 | End-caps for observation tubes, 2"x12"x3/4" |
| Polycarbonate sheet for observation chambers | McMaster-Carr | 8574K281 | Peg-bowls for observation tubes |
| Silicone O-rings for end-caps of observation chambers | McMaster-Carr | 9396K108 | S1138 AS568-029, pack of 25 http://www.mcmaster.com/#o-rings/=t0wt5r |
| Silicone stoppers for observation chambers | McMaster-Carr | 2903K22 | Package of 10 stoppers to plug the oval opening in the top of the observation chamber when using a peg-bowl http://www.mcmaster.com/#catalog/120/3803/=t0y5at |
| Centrifuge tubes for sipper tube bottles | Evergreen Scientific | 222-3530-G80 | 30 ml freestanding centrifuge tubes, with caps, sterile https://www.evergreensci.com/labware-catalog/tubes-and-vials/30-and-50-ml-centrifuge-tubes/ |
| Silcone stoppers for sipper tube bottles | Saint-Gobain Performance Plastics | DX263031-10 | Number 31D, size: 26 mm bottom, 32 mm top, 30 mm high; 10 pack; http://www.labpure.com/en/Products.asp?ID=179&PageBrand=STOPPERS |
| Stopper borers for sipper tube bottles | Thomas Scientific | 3276G40 | Cork Borer Set that ranges from 3/16-15/16 inch http://www.thomassci.com/Supplies/Corks/_/CORK-BORER-SET-316-1516-IN?q=Humboldt |
| Drinking tubes for sipper tube bottles | Ancare | TD-100 | 2 1/2” long drinking tubes with 5/16” opening, straight ball-spout http://www.ancare.com/products/watering-equipment/open-drinking-tubes/straight-tubes-ball-point |
| Iohexol for making oral contrast agent solution | GE Healthcare | 350 mg iodine per ml http://www3.gehealthcare.com/en/products/categories/contrast_media/omnipaque |
|
| Chocolate syrup for flavoring oral contrast agent | Herseys | ||
| 10 ml syringe for syringe delivery system | Becton, Dickinson and Company | 309604 | Luer lock tip syringe without needle, 100 per box http://www.bd.com/hypodermic/products/syringeswithoutneedles.asp |
| Catheter tubing for syringe delivery system | Becton, Dickinson and Company | 427451 | Polyethylene Tubing (Non-Sterile) (PE 240) 100' http://www.bd.com/ds/productCenter/427451.asp |
| Needle for syringe delivery system | Becton, Dickinson and Company | 427560 | 15-gauge needle, fits into PE 240 catheter tubing http://www.bd.com/ds/productCenter/427560.asp |
| Delrin acetal resin rod for syringe delivery system | McMaster-Carr | 8576K15 | 1/2 inch diameter, black http://www.mcmaster.com/#catalog/120/3609/=t0wvaf |
| Acrylic sheeting for scissor lift | Ponoko | Laser cut http://www.ponoko.com |
|
| 3D printed ABS frame | Engineering Rapid Prototyping Facility, University of Missouri | ||
| Brass rods for scissor lift | Amazon | TTRB-03-12-03 | made into axles http://www.amazon.com/Brass-Seamless-Round-Tubing-Length/dp/B000FN898M |
| Drawer slide for scissor lift | Richelieu | 10292G116 | Attaches to base of scissor lift http://www.lowes.com/pd_380986-93052-T35072G16_0__?productId=50041754 |
| 28BYJ-48 stepper motor for scissor lift | 2 each | ||
| ULN2003 Darlington transistor array for scissor lift | Toshiba | ULN2003APG | Used as stepper drivers (2 each) |
| ATTINY85 microcontroller for scissor lift | Atmel | ATTINY85-20PU | 2 each http://www.taydaelectronics.com/attiny85-attiny85-20pu-8-bit-20mhz-microcontroller-ic.html |
| Nylon spur gear | McMaster-Carr | 57655K34 | 2 each http://www.mcmaster.com/#57655k34/=t0yaqz |
| Nylon spur gear rack | McMaster-Carr | 57655K62 | 2 each http://www.mcmaster.com/#57655k62/=t0ybh9 |
| 4-40 nylon machine screws | McMaster-Carr | 95133A315 | Lift assembly http://www.mcmaster.com/#95133a315/=t0yd8q |
| 4-40 nylon hex nuts | McMaster-Carr | 94812A200 | Lift assembly http://www.mcmaster.com/#94812a200/=t0ye29 |
| Buna-N O-Ring AS568A Dash No. 104 | McMaster-Carr | 9452K318 | Lift assembly http://www.mcmaster.com/#9452k318/=t0yem7 |
References
- Shigemitsu, H., Afshar, K. Aspiration pneumonias: under-diagnosed and under-treated. Curr Opin Pulm Med. 13 (2), 192-198 (2007).
- Gresham, S. L. Clinical assessment and management of swallowing difficulties after stroke. Med J Aust. 153 (7), 397-399 (1990).
- Marik, P. E., Kaplan, D. Aspiration pneumonia and dysphagia in the elderly. Chest. 124 (1), 328-336 (2003).
- Marik, P. E. Pulmonary aspiration syndromes. Curr Opin Pulm Med. 17 (3), 148-154 (2011).
- Logemann, J. A., Larsen, K. Oropharyngeal dysphagia: pathophysiology and diagnosis for the anniversary issue of. Diseases of the Esophagus. Dis Esophagus. 25 (4), 299-304 (2012).
- Logemann, J. A. Swallowing disorders. Best practice & research Clinical gastroenterology. 21 (4), 563-573 (2007).
- Martin-Harris, B., Jones, B. The Videofluorographic Swallowing Study. Physical Medicine and Rehabilitation. Clinics of North America. 19 (4), 769-785 (2008).
- Dietsch, A. M., Solomon, N. P., Steele, C. M., Pelletier, C. A. The effect of barium on perceptions of taste intensity and palatability. Dysphagia. 29 (1), 96-108 (2014).
- Stokely, S. L., Molfenter, S. M., Steele, C. M. Effects of barium concentration on oropharyngeal swallow timing measures. Dysphagia. 29 (1), 78-82 (2014).
- Harris, J. A., et al. The Use of Low-Osmolar Water-Soluble Contrast in Videofluoroscopic Swallowing Exams. Dysphagia. , (2013).
- Hillel, A., Miller, R. Bulbar Amyotrophic Lateral Sclerosis: Patterns of Progression and Clinical Management. Head & Neck. 11, 51-59 (1989).
- Russell, J. A., Ciucci, M. R., Hammer, M. J., Connor, N. P. Videofluorographic assessment of deglutitive behaviors in a rat model of aging and Parkinson disease. Dysphagia. 28 (1), 95-104 (2013).
- Lever, T. E., et al. An animal model of oral dysphagia in amyotrophic lateral sclerosis. Dysphagia. 24 (2), 180-195 (2009).
- Lever, T. E., et al. A mouse model of pharyngeal dysphagia in amyotrophic lateral sclerosis. Dysphagia. 25 (2), 112-126 (2010).
- Ciucci, M. R., et al. Tongue force and timing deficits in a rat model of Parkinson disease. Behavioural Brain Research. 222 (2), 315-320 (2011).
- Ciucci, M. R., Schaser, A. J., Russell, J. A. Exercise-induced rescue of tongue function without striatal dopamine sparing in a rat neurotoxin model of Parkinson disease. Behavioural Brain Research. 252, 239-245 (2013).
- Plowman, E. K., Kleim, J. A. Behavioral and neurophysiological correlates of striatal dopamine depletion: A rodent model of Parkinson’s disease. Journal of Communication Disorders. 44 (5), 549-556 (2011).
- Sugiyama, N., et al. A novel animal model of dysphagia following stroke. Dysphagia. 29 (1), 61-67 (2014).
- Bachmanov, A. A., Reed, D. R., Li, X., Beauchamp, G. K. Genetics of sweet taste preferences. Pure Appl Chem. 74 (7), 1135-1140 (2002).
- Ishiwatari, Y., Bachmanov, A. A. NaCl taste thresholds in 13 inbred mouse strains. Chem Senses. 37 (6), 497-508 (2012).
- Pinhas, A., et al. Strain differences in sucrose- and fructose-conditioned flavor preferences in mice. Physiol Behav. 105 (2), 451-459 (2012).
- Midkiff, E. E., Bernstein, I. L. The influence of age and experience on salt preference of the rat. Dev Psychobiol. 16 (5), 385-394 (1983).
- Niimi, K., Takahashi, E. Differences in saccharin preference and genetic alterations of the Tas1r3 gene among senescence-accelerated mouse strains and their parental AKR/J strain. Physiol Behav. , (2014).
- Weijnen, J. A. Licking behavior in the rat: measurement and situational control of licking frequency. Neurosci Biobehav Rev. 22 (6), 751-760 (1998).
- Weijnen, J. A. Lick sensors as tools in behavioral and neuroscience research. Physiol Behav. 46 (6), 923-928 (1989).
- Kobayashi, M., et al. Electrophysiological analysis of rhythmic jaw movements in the freely moving mouse. Physiol Behav. 75 (3), 377-385 (2002).
- Dantas, R., et al. Effect of swallowed bolus variables on oral and pharyngeal phases of swallowing. 258, G675-681 (1990).
- Johnsson, F., Shaw, D., Gabb, M., Dent, J., Cook, I. Influence of gravity and body position on normal oropharyngeal swallowing. American Journal of Physiology. 35 (5), G653-G658 (1995).
- Han, T. T., Paik, N. -. J., Park, J. W. Quantifying swallowing function after stroke: A functional dysphagia scale based on videofluoroscopic studies. Archives of Physical Medicine and Rehabilitation. 82 (5), 677-682 (2001).
- Molfenter, S. M., Steele, C. M. Kinematic and temporal factors associated with penetration-aspiration in swallowing liquids. Dysphagia. 29 (2), 269-276 (2014).
- Kendall, K. A., McKenzie, S., Leonard, R. J., Goncalves, M. I., Walker, A. Timing of events in normal swallowing: A videofluoroscopic study. Dysphagia. 15, 74-83 (2000).
- Choi, K. H., Ryu, J. S., Kim, M. Y., Kang, J. Y., Yoo, S. D. Kinematic analysis of dysphagia: Significant parameters of aspiration related to bolus viscosity. Dysphagia. 26, 392-398 (2011).
- Molfenter, S. M., Steele, C. M. Variation in temporal measures of swallowing: Sex and volume effects. Dysphagia. 28, 226-233 (2013).
- Alves, L. M. T., Secaf, M., Dantas, R. Effect of a bitter bolus on oral, pharyngeal, and esophageal transit of healthy subjects. Arquivos de gastroenterologia. 50 (1), 31-34 (2013).
- Dalmazo, J., Aprile, L. R. O., Dantas, R. O. Esophageal contractions, bolus transit and perception of transit after swallows of liquid and solid boluses in normal subjects. Arquivos de gastroenterologia. 49 (4), 250-254 (2012).
- Kahrilas, P. J., Dodds, W. J., Hogan, W. J. Effect of peristaltic dysfunction on esophageal volume clearance. Gastroenterology. 94 (1), 73-80 (1988).
- German, R. Z., Crompton, A. W., Levitch, L. C., Thexton, A. J. The mechanism of suckling in two species of infant mammal: Miniature pigs and long-tailed macaques. Journal of Experimental Zoology. 261 (3), 322-330 (1992).
- Herring, S. W., Scapino, R. P. Physiology of feeding in miniature pigs. Journal of Morphology. 141 (4), 427-460 (1973).
- Gordon, K. R., Herring, S. W. Activity patterns within the genioglossus during suckling in domestic dogs and pigs: Interspecific and intraspecific. Brain, Behavior, and Evolution. 30 (5-6), (1987).
- Hiiemae, K. M., Palmer, J. B. Food transport and bolus formation during complete feeding sequences on foods of different initial consistency. Dysphagia. 14 (1), 31-42 (1999).
- Thexton, A. J., Crompton, A. W., German, R. Z. EMG activity in the hyoid muscles during pig suckling. Journal of Applied Physiology. 112, 1512-1519 (2012).
- Thexton, A. J., Crompton, A. W., German, R. Z. Transition from suckling to drinking at weaning: A kinematic and electromyographic study in miniature pigs. Journal of Experimental Zoology. 280 (5), 327-343 (1998).
- Goldfield, E. C., Richardson, M. J., Lee, K. G., Margetts, S. Coordination of sucking, swallowing, and breathing and oxygen saturation during early infant breast-feeding and bottle-feeding. Pediatric Research. 60 (4), 450-455 (2006).
- Ottaviano, F. G., Linhares Filho, T. A., Andrade, H. M., Alves, P. C., Rocha, M. S. Fiberoptic endoscopy evaluation of swallowing in patients with amyotrophic lateral sclerosis. Braz J Otorhinolaryngol. 79 (3), 349-353 (2013).
- Inamoto, Y., et al. The effect of bolus viscosity on laryngeal closure in swallowing: kinematic analysis using 320-row area detector CT. Dysphagia. 28 (1), 33-42 (2013).
- Spalding, J. F., Thomas, R. G., Tietjen, G. L., Rein, S. e. r. e. n. e. . Los Alamos National Laboratory. , (1982).
- Palomba, S., Di Cello, A., Riccio, E., Manguso, F., La Sala, G. B. Ovarian function and gastrointestinal motor activity. Minerva Endocrinol. 36 (4), 295-310 (2011).
- Alves, L. M., Cassiani Rde, ., Santos, A., M, C., Dantas, R. O. Gender effect on the clinical measurement of swallowing. Arq Gastroenterol. 44 (3), 227-229 (2007).
- Logemann, J. A., Pauloski, B. R., Rademaker, A. W., Kahrilas, P. J. Oropharyngeal swallow in younger and older women: videofluoroscopic analysis. J Speech Lang Hear Res. 45 (3), 434-445 (2002).
