Research funding was received through the National Institute of Neurological Disorders and Stroke &#160;(NS049177 and NS087834). The authors wish&#160;to acknowledge the intellectual contributions of the late Dr. Paul Bass and his colleagues to the original design of the strain gages; and Carol Tollefsrud for the fabrication and marketing of the strain gages until the cessation of production in 2010 as well as for her insightful correspondence.

All procedures followed National Institutes of Health guidelines and were approved by the Institutional Animal Care and Use Committee at the Penn State Hershey College of Medicine. Rats were housed using common vivarium practices. Note: This protocol uses male Wistar rats &#8805;8 weeks of age and initially weighing 175 - 200 g.
1. Procedures for Fabrication of Strain Gage
<ol>
	<li>Most tooling and components remain available from the original or successor companies and are summarized in Table 1.</li>
	<li>Preparation and Bonding of two single element strain gages
	<ol>
		<li>Handle the strain gage elements (EA-06-031-350) carefully with clean Dumont #5 forceps. To limit unwanted movement of elements, use a small, clean, self-adhesive piece of paper with the adhesive side facing up to secure elements to the work surface without the risk of contamination or excessive adhesion.</li>
		<li>Bond two single strain gage elements back-to-back, to form a dual element. Clean the back of each element film with Isopropyl alcohol and allow drying by evaporation (drying with gauze often introduces fiber contaminants that are difficult to remove). Under stereomicroscope guidance (1 - 3x), and using a clean artist brush (10-0 camel hair), apply a thin film of epoxy-phenolic adhesive to the back of one element and immediately place the opposing back of the second element in contact and align the foil grids&#160;(Figure 1A).</li>
		<li>Place the bonded elements in a 50 - 60 &#176;C oven O/N to fully cure the epoxy. 
		NOTE: Do not clamp the bonded elements since excess epoxy may seep onto the elements and pressure may cause misalignment of the grids. The two-part epoxy has a usable refrigerated-life of only 6 weeks after mixing. Bond and cure a sufficient supply of elements at one time and store them in a clean, dust free, environment for later use.</li>
	</ol>
	</li>
	<li>Sizing and wiring dual element strain gages
	<ol>
		<li>Trim bonded dual elements to a final size of 3 x 3 mm with a #11 scalpel or single edge razor blade. Delay trimming the topmost portion of the dual elements at this time in order to have an area for safely handling the element&#160;(Figure 1A).</li>
		<li>Each element requires a four-conductor wire fabricated from three-conductor, bondable, Teflon insulated wire (P/N 336-FTE). Disassemble one 30 cm braided strand of three-conductor wire into three constituent wires.</li>
		<li>To make a four wire cable, pair one of the resulting single wires with the like-colored wire contained within a second 30 cm length of three conductor wire. In the following steps, these matching colored wires will be joined at the terminal end to form a common wire for the final strain gage (Figure 1B).</li>
		<li>Remove approximately 1mm of Teflon insulation from both ends of each wire with thermal wire strippers. Using activated rosin soldering flux and low temperature solder (melting point 183 &#186;C) tin the wire ends with a soldering pencil.</li>
		<li>For the next stage, a microsoldering tip is needed to form a more discrete solder joint to prevent heat damage to the film layer of the element (Figure 1C). To fabricate a smaller microsoldering tip, wrap a small piece of copper wire (~0.25 mm diameter) once around the standard soldering tip, ensuring that the copper wire extends beyond the length of the standard soldering tip.</li>
		<li>Flux just the solder pads on one side of the bonded dual element with a clean 10-0 brush and solder one single lead and one of the paired common leads to the solder pad (Figure 1D). Residual flux can be removed afterward with a clean brush dipped in resin solvent.</li>
		<li>Repeat the process on the opposite side, ensuring that the remaining common wire lead is soldered to the pad opposite the original common lead.</li>
	</ol>
	</li>
	<li>Testing and epoxying dual element strain gages
	<ol>
		<li>Solder gold socket connectors (E363/0) to the free ends of the wire leads. At this point, connect the strain gage to a recording amplifier (described below) to test the integrity of the dual element assembly.</li>
		<li>Measure the resistance with a good quality volt-ohm meter. Elements register a resistance of approximately 350 &#937;. Resolder inadequate connections at this point with fresh solder.</li>
		<li>If the solder connections and the dual element assembly are deemed satisfactory, trim off any remaining element film.</li>
		<li>Insulate the solder joints on the element solder pads with a thin layer of two-part silicone-rubber epoxy resin (P/N E211). For best results, partly cure the resin for 20 - 30 min prior to application (Figure 1E).</li>
	</ol>
	</li>
	<li>Encapsulating dual element strain gages in silicone
	<ol>
		<li>Cut three pieces of 0.5 mm thick silicone sheet (P/N 20-20) to 15 mm 2 and clean the silicone with distilled water. Cut one piece of silicone sheet into a U-shape in order to accommodate the final dual element assembly without deforming the encapsulating silicone (Figure 1F).</li>
		<li>Coat the inner surfaces of the notch-free silicone sheets with clear silicone adhesive.</li>
		<li>Sandwich the dual element assembly within the notch and the aligned outer sheets, then gently press out any excess silicone, as well as air bubbles, from the center outward. Carefully clamp the encapsulated assembly between two blocks of metal bar stock for 24 hr to ensure uniform thickness and that no deformations occur.</li>
		<li>Allow the excess silicone to remain along the boundaries of the assembly and cure. This excess will be removed when the sheet silicone is trimmed to the desired final dimensions (commonly 6 mm x 8 mm; Figure 1G).</li>
	</ol>
	</li>
	<li>Completion of wire connector and calibration
	<ol>
		<li>Reinforce the solder joint of the gold socket connectors on the individual terminal wire leads with 3 mm (1/8 inch) shrink tubing and align within a plastic electrode pedestal (MS363, Figure 1H). Secure the electrode pedestal and wires with 0.125 and 0.25 inch diameter shrink tubing to prevent disconnection during the experiment (Figure 1I).</li>
		<li>Strain gage signals are processed through a high gain bridge amplifier (P/N AMP-01-SG). Connect the strain gage to the amplifier using a cable with a mated plug (363 - SL/6) to match the electrode pedestal. The threaded cap provides additional security to maintain uninterrupted signals during the experiment.</li>
		<li>Adjust the Bridge, Balance and Gain settings on the amplifier to a dedicated strain gage per manufacturer instructions. Affix the end of the strain gage where the wires exit horizontally to a rigid clamp and calibrate by placing a 1 g static load on the opposite end as originally described by Pascaud and colleagues 2, 16, 17.</li>
	</ol>
	</li>
</ol>
2. Surgical Procedures for Acute Implantation of Strain Gage
<ol>
	<li>Animal Care and Preparation:
	<ol>
		<li>Food deprive experimental animals the night before surgical implantation (water may be provided ad libitum).</li>
		<li>Deeply anesthetize the animal. Thiobutabarbital (100 &#8211; 150 mg/kg; i.p. for rats) is preferred for terminal (i.e., non-survival) strain gage implantation and experimentation due to sustained anesthetic effect and minimal alteration of gastric reflexes in the rat 10. Test for absence of paw pinch reflex to determine depth of anesthesia.</li>
		<li>Prepare the rat for aseptic surgery as dictated by the experimental design and approved IACUC guidelines including sterilizing surgical tools, shaving incision sites, applying vet eye ointment and disinfecting all surgical areas.&#160;NOTE:&#160;If the strain gage is being adapted for chronic use, sterilize the the strain gage only with ethylene oxide (gas) sterilization. The use of heat or chemical sterilization techniques may damage the strain gage.</li>
	</ol>
	</li>
	<li>Tracheal intubation for terminal experiments:
	<ol>
		<li>For long duration, terminal, experiments intubate the rat with a tracheal tube to maintain an open airway. Make a 1 - 2 cm midline incision on the ventral side of the neck from the inferior border of the mandible to the sternal notch.</li>
		<li>Separate the underlying strap muscles using blunt dissection at the midline to expose the trachea. Isolate the trachea from the underlying esophagus and place a loop of 3-0 ethilon suture between the trachea and esophagus to form a ligature.</li>
		<li>Open the trachea anteriorly by making a small incison&#160;in the membrane between two of the cartilaginous rings of the trachea just distal to the thyroid gland. Insert a small piece of polyethylene tubing (P/N PE-270), 5mm in length (and beveled at one end) into the trachea and secure it into place with the ligature.</li>
		<li>Put the strap muscles back in place and suture the overlying skin with 3-0 ethilon.</li>
	</ol>
	</li>
	<li>Strain gage instrumentation to gastrointestinal surface:
	<ol>
		<li>Thread the four corners of the strain gage with 4 - 5 cm lengths of 4-0, or smaller, sterile silk suture using a #14 taper point 3/8 circle needle prior to surgery. Silk suture provides a high level of flexibility and is less likely to damage the silicone encapsulating the strain gage element. 
		NOTE: silk thread is acceptable for non-survival surgeries and for internal applications, where the wicking of bacteria across an epithelial barrier is not a risk. In applications requiring survival surgery, a prolene suture is necessary in order to reduce the risk of infection inherent in the braided cloth fibers of the silk suture.</li>
		<li>Perform a laparotomy by incising the abdominal skin along the midline. Section the rectus abdominus musculature along the connecting linea alba (avascular) to prevent bleeding. Then make a very superficial midline incision in the parietal peritoneum to avoid lacerating underlying abdominal viscera.</li>
		<li>Exteriorize the stomach with the aid of saline soaked cotton tipped applicators. Keep the stomach in position by carefully placing it on a saline soaked gauze pad at the caudal end of the abdominal incision.</li>
		<li>Align the grid of the encapsulated strain gage in parallel with the circular smooth muscle fibers. Using the previously threaded sutures (step 2.3.1), attach the corners of the gage to the ventral serosal surface of the gastric corpus using a #14 taper point 3/8 circle needle. In order to minimize tissue damage and potential bleeding, do not use cutting-edged needles and do not perforate any superficial blood vessels on the surface of the stomach.</li>
		<li>Begin the suture pattern of the gage along the greater curvature of the stomach near the fundus/corpus boundary and proceed next along the fundus/corpus boundary toward the lesser curvature. The serosa underlying the strain gage should neither be slack nor overly stretched in order to obtain the best results.</li>
		<li>Carefully return the stomach to its anatomical position using saline-soaked cotton tipped applicators.</li>
		<li>In an acute model, exteriorize the strain gage leads at the caudal end of the midline incision before closure of the abdominal incision. Secure the free wires to the animal (e.g., hind foot) in order to provide strain relief during manipulation of the animal or terminal wire connector. Close the rectus abdominus muscles and the abdominal skin separately with 3-0 nylon suture. In a chronic model, secure the leads subcutaneously along the dorsal side of the rat and exteriorize them above the skull 18.</li>
		<li>After surgical instrumentation, place animals in a stereotaxic frame to support the head and elevate the upper torso. The latter step helps to reduce respiration artifact during recording. Monitor rectal temperature and maintain at 37&#177;1 &#176;C using a feedback-controlled heating pad.</li>
		<li>At the conclusion of terminal experiments utilizing thiobutabarbital anesthesia, the animal must be euthanized in a manner consistent with American Veterinary Medical Association (AVMA) Guidelines on Euthanasia.</li>
	</ol>
	</li>
	<li>Gastric Motility recordings:
	<ol>
		<li>Amplify the strain gage signal with any commercially available DC bridge amplifier.</li>
		<li>Record the DC output signals on a computer using the chart recorder function of any commercially available data acquisition system. 
		NOTE: A hardcopy of the amplifier output can be generated through a polygraph chart recorder.</li>
	</ol>
	</li>
</ol>
3. Representative Measurement of Gastric Contractions Following Brainstem Stimulation
<ol>
	<li>Exposure of brainstem and fourth ventricle
	<ol>
		<li>After surgical instrumentation, and placement of the Thiobutabarbital-anesthetized animal in a stereotaxic frame, make a 1.5 - 2 cm midline skin incision from the occipital bone toward the base of the neck.</li>
		<li>Separate the connective tissue joining the bilateral muscle bellies of the underlying neck muscles along the midline (muscles from superficial to deep are levator auris&#160;longus cranial portion, levator auris&#160;longus caudal portion, and platysma cranial portion).</li>
		<li>Detach the levator auris&#160;longus from the occipital bone once the midline is clearly defined and exposed.</li>
		<li>Carefully expose the caudal region of the skull by using blunt dissection to detach platysma muscle from the underlying dura mater.</li>
		<li>Use a new 25 G&#160;needle to carefully detach the dura mater along the foramen magnum extending bilaterally to the occipital condyles.</li>
		<li>Use #5 Dumont forceps to remove the pia and arachnoid meninges overlying the fourth ventricle and expose the brainstem.</li>
	</ol>
	</li>
	<li>Administering fourth ventricle thyrotropin releasing hormone or intravenous sodium nitroprusside
	<ol>
		<li>Weigh and dissolve thyrotropin releasing hormone (TRH) in sterile saline to reach a final concentration of 50 &#181;M TRH.</li>
		<li>Weigh and dissolve sodium nitroprusside (SNP) in sterile saline to reach a final concentration of 150 &#181;M SNP.</li>
		<li>Using a 10 &#181;l syringe, administer 2 &#181;l of TRH (final dose equals 100 pmol) to the dorsal surface of the brainstem fourth ventricle to facilitate recording of gastric contractions.</li>
		<li>Using a sterile syringe and 27 G&#160;needle, administer 150 &#181;mol/kg of SNP through the tail vein to facilitate recording of gastric relaxation.</li>
	</ol>
	</li>
</ol>

<ol>
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W., Million, M., Wang, L., Tache, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulation+of+gastric+motility+by+brain-gut+peptides+using+a+novel+non-invasive+miniaturized+pressure+transducer+method+in+anesthetized+rodents.">Modulation of gastric motility by brain-gut peptides using a novel non-invasive miniaturized pressure transducer method in anesthetized rodents.</a> Peptides. 32 (4), 737-746 (2011).</li><li>Am&#233;rico, M. 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=Validation+of+ACB+in+vitro+and+in+vivo+as+a+biomagnetic+method+for+measuring+stomach+contraction.">Validation of ACB in vitro and in vivo as a biomagnetic method for measuring stomach contraction.</a> Neurogastroenterol. 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The authors declare that they have no competing financial interests. The suppliers listed in this manuscript are provided for reference only.

The procedures presented here allow individual laboratories to fabricate sensitive miniature strain gages for biological applications including, but not limited to, gastrointestinal motility in small laboratory animals. Since the commercial manufacture of these strain gages has ceased, laboratories investigating gastrointestinal function are limited to other techniques which may not permit the full range of experimental applications that are available. This report provides an updated and more detailed description of prev...

Experimental studies that record in vivo gastrointestinal (GI) motility across a number of experimental conditions remain a powerful tool for understanding the underlying normal and pathophysiological processes necessary for nutrient homeostasis. Traditionally, numerous experimental methodologies, some with similarities to those found in clinical practice 1, have been employed to directly quantify changes in GI contraction rate 2-5, intraluminal pressure 6, 7, or the GI transit of non-absorbable markers 8, 9 or stable isotopes 10-12. Each of these techniques has unique advantages and disadvantages, which have been addressed previously in the literature. For example, the utility of balloon manometry to quantify pressure changes has been questioned due to the inherent compliance of the balloon material while gastrointestinal recovery of nonabsorbable markers requires euthanizing the experimental animal for a single data point. Recently, the application and validation of a miniaturized arterial pressure catheter has been reported that offers a non-surgical method for monitoring gastric contractility in rats and mice 3. While an orogastrically placed pressure transducer effectively eliminates confounding variables on gastrointestinal function by avoiding invasive surgical procedures, such an approach is only suitable for anesthetized preparations. Furthermore, the lack of visual guidance does not permit consistent placement of the transducer within specific regions of the stomach. As such, this application is restricted to the stomach or colon since visualization, coupled with the relatively stiff transducer wire, within the duodenum or ileum is not an option.
Similarly, the biomagnetic alternate current biosusceptometry (ACB) technique has been validated for GI contraction analysis 4. While the ACB technique provides a noninvasive approach for measuring gastrointestinal contractions, ACB suffers from a similar limitation in that the use of ingested magnetic detection media does not permit precise recording of specific regions of the GI tract. This limitation can be overcome through the surgical implantation of magnetic markers. Nonetheless, the ACB technique necessitates that the animal be anesthetized for data collection.
Ultrasonomicrometry has been employed in some GI studies 13, 14 in order to take advantage of the small size, spatial, and temporal advantages of piezoelectric crystal transmitter/receivers. Waves of gastric smooth muscle contraction are not a high-frequency event and occur at a rate of approximately 3 - 5 cycles/min. Therefore, the temporal advantages of sonomicrometry may be unnecessary to justify the cost. Furthermore, while linear motion is accurately measured with sonomicrometry, limitations have been presented regarding accurate gastrointestinal data interpretation that may result from implanting an insufficient number of crystals 14.
Based upon the original designs of Bass and colleagues 2, 15 this visualized protocol more fully documents the step-by-step fabrication and experimental application of miniature, dual element strain gages that possess high sensitivity and flexibility for recording smooth muscle contractions along the entire GI tract. The dimensions of the strain gage elements are suitable for any rodent application since sensitivity and size of the finished strain gage are most dependent upon the silicone sheets encapsulating the elements. These strain gages are readily adapted for acute and chronic application in anesthetized and freely behaving laboratory animal models thereby providing a single technique for quantifying smooth muscle contractions.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Strain gage element</td>
			<td>Micro-Measurements (Vishay Product Group)</td>
			<td>EA-06-031-350</td>
			<td>&#160;Linear pattern, foil, stress analysis strain gage (2 required) 
			<a href="http://www.vishaypg.com/micro-measurements/">www.vishaypg.com/micro-measurements/</a> 
			or 
			<a href="http://www.vishaypg.com/docs/11070/031ce.pdf">http://www.vishaypg.com/docs/11070/031ce.pdf</a></td>
		</tr>
		<tr>
			<td>epoxy-phenolic adhesive</td>
			<td>M-bond 610</td>
			<td>General purpose adhesive for bonding strain gage elements</td>
			<td><a href="http://www.vishaypg.com/docs/11024/wirecable.pdf">http://www.vishaypg.com/docs/11024/wirecable.pdf</a></td>
		</tr>
		<tr>
			<td>3 conductor insulated wire</td>
			<td>336-FTE</td>
			<td>Fine gage, flexible general purpose wire</td>
			<td><a href="http://www.vishaypg.com/docs/11024/wirecable.pdf">http://www.vishaypg.com/docs/11024/wirecable.pdf</a></td>
		</tr>
		<tr>
			<td>Flux and rosin solvent kit</td>
			<td>FAR-2 M-Flux AR kit</td>
			<td>Liquid solder flux</td>
			<td><a href="http://www.vishaypg.com/docs/11023/soldacce.pdf">http://www.vishaypg.com/docs/11023/soldacce.pdf</a></td>
		</tr>
		<tr>
			<td>Solder</td>
			<td>361A-20R-25</td>
			<td>Optimized and recommended for strain gage applications</td>
			<td><a href="http://www.vishaypg.com/docs/11023/soldacce.pdf">http://www.vishaypg.com/docs/11023/soldacce.pdf</a></td>
		</tr>
		<tr>
			<td>Gold socket connector</td>
			<td>PlasticsOne</td>
			<td>E363/0</td>
			<td>Socket contact for electrode pedestal 
			<a href="http://www.plastics1.com/PCR/Catalog/Item.php?item=407">http://www.plastics1.com/PCR/Catalog/Item.php?item=407</a></td>
		</tr>
		<tr>
			<td>Electrode pedestal</td>
			<td>MS363</td>
			<td>Secure platform for wire contacts</td>
			<td><a href="http://www.plastics1.com/PCR/Catalog/Item.php?item=499">http://www.plastics1.com/PCR/Catalog/Item.php?item=499</a></td>
		</tr>
		<tr>
			<td>6-wire cable</td>
			<td>363 PLUG W/VINYL SL/6</td>
			<td>Pre-fabricated vinyl-coated cable (in customized lengths) with plug adaptor to match electrode pedestal and tinned solder lugs on terminal end</td>
			<td></td>
		</tr>
		<tr>
			<td>Silicone rubber casting compound</td>
			<td>EIS electrical products</td>
			<td>Elan Tron E211</td>
			<td>Potting medium for gage/wire solder joints 
			<a href="http://www.eis-inc.com/">http://www.eis-inc.com</a></td>
		</tr>
		<tr>
			<td>HOTweezers</td>
			<td>Meisei Corporation</td>
			<td>Model 4B</td>
			<td>Wire insulation strippers 
			<a href="http://www.impexron.us/">http://www.impexron.us</a></td>
		</tr>
		<tr>
			<td>Soldering station</td>
			<td>Weller (Apex Tool Group)</td>
			<td>WES 51</td>
			<td>High quality soldering equipment 
			<a href="http://www.apexhandtools.com/weller/index.cfm">http://www.apexhandtools.com/weller/index.cfm</a></td>
		</tr>
		<tr>
			<td>Available through http://www.eis-inc.com or http://www.amazon.com</td>
		</tr>
		<tr>
			<td>Silicone sheet</td>
			<td>Trelleborg Sealing Solutions Northborough-Life Sciences</td>
			<td>Pharmelast 20-20</td>
			<td>Encapsulating strain gauge elements 
			10 B Forbes Road Northborough, MA 01532 (800) 634-2000</td>
		</tr>
		<tr>
			<td>Amplifier</td>
			<td>Experimetria Ltd</td>
			<td>AMP-01-SG</td>
			<td> 
			<a href="http://experimetria.com/Biological_amplifiers.php">http://experimetria.com/Biological_amplifiers.php</a></td>
		</tr>
	</tbody>
</table>

fabrication and implantation of miniature dual-element strain gages for measuring in vivo gastrointestinal contractions in rodents.

Gastrointestinal dysfunction remains a major cause of morbidity and mortality. Indeed, gastrointestinal (GI) motility in health and disease remains an area of productive research with over 1,400 published animal studies in just the last 5 years. Numerous techniques have been developed for quantifying smooth muscle activity of the stomach, small intestine, and colon. In vitro and ex vivo techniques offer powerful tools for mechanistic studies of GI function, but outside the context of the integrated systems inherent to an intact organism. Typically, measuring in vivo smooth muscle contractions of the stomach has involved an anesthetized preparation coupled with the introduction of a surgically placed pressure sensor, a static pressure load such as a mildly inflated balloon or by distending the stomach with fluid under barostatically-controlled feedback. Yet many of these approaches present unique disadvantages regarding both the interpretation of results as well as applicability for in vivo use in conscious experimental animal models. The use of dual element strain gages that have been affixed to the serosal surface of the GI tract has offered numerous experimental advantages, which may continue to outweigh the disadvantages. Since these gages are not commercially available, this video presentation provides a detailed, step-by-step guide to the fabrication of the current design of these gages. The strain gage described in this protocol is a design for recording gastric motility in rats. This design has been modified for recording smooth muscle activity along the entire GI tract and requires only subtle variation in the overall fabrication. Representative data from the entire GI tract are included as well as discussion of analysis methods, data interpretation and presentation.

Representative data from a Thiobutabarbital-anesthetized rat are shown in Figure 2. The top trace represents the gastric corpus contractions from the rat during the brainstem administration of thyrotropin releasing hormone (TRH, 100 pmol), a known motility-enhancing peptide 3, 19. It shows baseline contractions prior to the increase in phasic gastric smooth muscle activity. Note: Analysis of these peaks in gastric contractions follow the original formula devised by Ormsby and Bass 20</sup...

Watch this Scientific Journal Video about Fabrication and Implantation of Miniature Dual-element Strain Gages for Measuring In Vivo Gastrointestinal Contractions in Rodents. at JoVE.com

Fabrication and Implantation of Miniature Dual-element Strain Gages for Measuring In Vivo Gastrointestinal Contractions in Rodents.

The in vivo measurement of smooth muscle contractions along the gastrointestinal tract of laboratory animals remains a powerful, though underutilized, technique. Flexible, dual element strain gages are not commercially available and require fabrication. This protocol describes the construction of reliable, inexpensive strain gages for acute or chronic implantation in rodents.

Fabrication and Implantation of Miniature Dual-element Strain Gages for Measuring In Vivo Gastrointestinal Contractions in Rodents.

Gastrointestinal dysfunction remains a major cause of morbidity and mortality. Indeed, gastrointestinal (GI) motility in health and disease remains an ...

fabrication-implantation-miniature-dual-element-strain-gages-for

Research

JoVE Journal

Bioengineering

10.3K Views.  Penn State University College of Medicine. The in vivo measurement of smooth muscle contractions along the gastrointestinal tract of laboratory animals remains a powerful, though underutilized, technique. Flexible, dual element strain gages are not commercially available and require fabrication. This protocol describes the construction of reliable, inexpensive strain gages for acute or chronic implantation in rodents.

Video: Fabrication and Implantation of Miniature Dual-element Strain Gages for Measuring In Vivo Gastrointestinal Contractions in Rodents.

Fabrication of Electrochemical-DNA Biosensors for the Reagentless Detection of Nucleic Acids, Proteins and Small Molecules

As medicine is currently practiced, doctors send specimens to a central laboratory for testing and thus must wait hours or days to 
receive the results. Many patients would be better served by rapid, bedside tests. To this end our laboratory and others have developed a versatile, reagentless 
biosensor platform that supports the quantitative, reagentless, electrochemical detection of nucleic acids (DNA, RNA), proteins (including antibodies) and small 
molecules analytes directly in unprocessed clinical and environmental samples. In this video, we demonstrate the preparation and use of several biosensors in this 
"E-DNA" class. In particular, we fabricate and demonstrate sensors for the detection of a target DNA sequence in a polymerase chain reaction mixture, an HIV-specific antibody and the drug cocaine. The preparation procedure requires only three hours of hands-on effort followed by an overnight incubation, and their use requires only minutes.

"E-DNA" sensors, reagentless, electrochemical biosensors that perform well even when challenged directly in blood and other complex matrices, have been adapted to the detection of a wide range of nucleic acid, protein and small molecule analytes. Here we present a general procedure for the fabrication and use of such sensors.

As medicine is currently practiced, doctors send specimens to a central laboratory for testing and thus must wait hours or days to 
receive the results. ...

Quantification of Global Diastolic Function by Kinematic Modeling-based Analysis of Transmitral Flow via the Parametrized Diastolic Filling Formalism

Quantitative cardiac function assessment remains a challenge for physiologists and clinicians.&#160;Although historically invasive methods have comprised the only means available, the development of noninvasive imaging modalities (echocardiography, MRI, CT) having high temporal and spatial resolution provide a new window for quantitative diastolic function assessment. Echocardiography is the agreed upon standard for diastolic function assessment, but indexes in current clinical use merely utilize selected features of chamber dimension (M-mode) or blood/tissue motion (Doppler) waveforms without incorporating the physiologic causal determinants of the motion itself.&#160;The recognition that all left ventricles (LV) initiate filling by serving as mechanical suction pumps allows global diastolic function to be assessed based on laws of motion that apply to all chambers. What differentiates one heart from another are the parameters of the equation of motion that governs filling. Accordingly, development of the Parametrized Diastolic Filling (PDF) formalism&#160;has shown that the entire range of clinically observed early transmitral flow (Doppler E-wave) patterns are extremely well fit by the laws of damped oscillatory motion.&#160;This permits analysis of individual E-waves in accordance with a causal mechanism (recoil-initiated suction) that yields three (numerically) unique lumped parameters whose physiologic analogues are chamber stiffness (k), viscoelasticity/relaxation (c), and load (xo).&#160;The recording of transmitral flow (Doppler E-waves) is standard practice in clinical cardiology and, therefore, the echocardiographic recording method is only briefly reviewed. Our focus is on determination of the PDF parameters from routinely recorded E-wave data.&#160;As the highlighted results indicate, once the PDF parameters have been obtained from a suitable number of load varying E-waves, the investigator is free to use the parameters or construct indexes from the parameters (such as stored energy 1/2kxo2, maximum A-V pressure gradient kxo, load independent index of diastolic function, etc.) and select the aspect of physiology or pathophysiology to be quantified.

Accurate, causality-based quantification of global diastolic function has been achieved by kinematic modeling-based analysis of transmitral flow via the Parametrized Diastolic Filling (PDF) formalism. PDF generates unique stiffness, relaxation,&#160;and load parameters and elucidates &#39;new&#39; physiology while providing sensitive and specific indexes of dysfunction.

Quantitative cardiac function assessment remains a challenge for physiologists and clinicians.&#160;Although historically invasive methods have comprised ...

Surgical Technique for the Implantation of Tissue Engineered Vascular Grafts and Subsequent In Vivo Monitoring

The development of Tissue Engineered Vessels (TEVs) is advanced by the ability to routinely and effectively implant TEVs (4-5 mm in diameter) into a large animal model. A step by-step protocol for inter-positional placement of the TEV and real-time digital assessment of the TEV and native carotid arteries is described here. In vivo monitoring is made possible by the implantation of flow probes, catheters and ultrasonic crystals (capable of recording dynamic diameter changes of implanted TEVs and native carotid arteries) at the time of surgery. Once implanted, researchers can calculate arterial blood flow patterns, invasive blood pressure and artery diameter yielding parameters such as pulse wave velocity, augmentation index, pulse pressures and compliance. Data acquisition is accomplished using a single computer program for analysis throughout the duration of the experiment. Such invaluable data provides insight into TEV matrix remodeling, its resemblance to native/sham controls and overall TEV performance in vivo.

Surgical Technique for the Implantation of Tissue Engineered Vascular Grafts and Subsequent In Vivo Monitoring

A step-by-step protocol for the inter-positional placement of Tissue Engineered Vessels (TEVs) into the carotid artery of a sheep using end-to-end anastomosis and real-time digital assessment in vivo until animal sacrifice.

The development of Tissue Engineered Vessels (TEVs) is advanced by the ability to routinely and effectively implant TEVs (4-5 mm in diameter) into a large ...

Gradient Strain Chip for Stimulating Cellular Behaviors in Cell-laden Hydrogel

Artificial guidance for cellular alignment is a hot topic in the field of tissue engineering. Most of the previous research has investigated single strain-induced cellular alignment on a cell-laden hydrogel by using complex experimental processes and mass controlling systems, which are usually associated with contamination issues. Thus, in this article, we propose a simple approach to building a gradient static strain using a fluidic chip with a plastic PDMS cover and a UV transparent glass substrate for the stimulation of cellular behavior in a 3D hydrogel. Overloading photo-patternable cell prepolymer in the fluidic chamber can generate a convex curved PDMS membrane on the cover. After UV crosslinking, through a concentric circular micropattern under the curved PDMS membrane, and buffer washing, a microenvironment for investigating cell behaviors under a variety of gradient strains is self-established in a single fluidic chip, without external instruments. NIH3T3 cells were demonstrated after observing the change in the cellular alignment trend under geometry guidance, in cooperation with strain stimulation, which varied from 15 - 65% on hydrogels. After a 3-day incubation, the hydrogel geometry dominated the cell alignment under low compressive strain, where cells aligned along the hydrogel elongation direction under high compressive strain. Between these, the cells showed random alignment due to the dissipation of the radical guidance of hydrogel elongation and the geometry guidance of the patterned hydrogel.

This article introduces a simple approach to providing non-continuous gradient static strains on a concentric cell-laden hydrogel to regulate cell alignment for tissue engineering.

Artificial guidance for cellular alignment is a hot topic in the field of tissue engineering. Most of the previous research has investigated single ...

An In Vitro Organ Culture Model of the Murine Intervertebral Disc

Intervertebral disc (IVD) degeneration is a significant contributor to low back pain. The IVD is a fibrocartilaginous joint that serves to transmit and dampen loads in the spine. The IVD consists of a proteoglycan-rich nucleus pulposus (NP) and a collagen-rich annulus fibrosis (AF) sandwiched by cartilaginous end-plates. Together with the adjacent vertebrae, the vertebrae-IVD structure forms a functional spine unit (FSU). These microstructures contain unique cell types as well as unique extracellular matrices. Whole organ culture of the FSU preserves the native extracellular matrix, cell differentiation phenotypes, and cellular-matrix interactions. Thus, organ culture techniques are particularly useful for investigating the complex biological mechanisms of the IVD. Here, we describe a high-throughput approach for culturing whole lumbar mouse FSUs that provides an ideal platform for studying disease mechanisms and therapies for the IVD. Furthermore, we describe several applications that utilize this organ culture method to conduct further studies including contrast-enhanced microCT imaging and three-dimensional high-resolution finite element modeling of the IVD.

An In Vitro Organ Culture Model of the Murine Intervertebral Disc

Whole organ culture of the intervertebral disc (IVD) preserves the native extracellular matrix, cell phenotypes, and cellular-matrix interactions. Here we describe an IVD culture system using mouse lumbar and caudal IVDs in their functional spinal units and several applications utilizing this system.

Intervertebral disc (IVD) degeneration is a significant contributor to low back pain. The IVD is a fibrocartilaginous joint that serves to transmit and ...

Rigid Embedding of Fixed and Stained, Whole, Millimeter-Scale Specimens for Section-free 3D Histology by Micro-Computed Tomography

For over a hundred years, the histological study of tissues has been the gold standard for medical diagnosis because histology allows all cell types in every tissue to be identified and characterized. Our laboratory is actively working to make technological advances in X-ray micro-computed tomography (micro-CT) that will bring the diagnostic power of histology to the study of full tissue volumes at cellular resolution (i.e., an X-ray Histo-tomography modality). Toward this end, we have made targeted improvements to the sample preparation pipeline. One key optimization, and the focus of the present work, is a straightforward method for rigid embedding of fixed and stained millimeter-scale samples. Many of the published methods for sample immobilization and correlative micro-CT imaging rely on placing the samples in paraffin wax, agarose, or liquids such as alcohol. Our approach extends this work with custom procedures and the design of a 3-dimensional printable apparatus to embed the samples in an acrylic resin directly into polyimide tubing, which is relatively transparent to X-rays. Herein, sample preparation procedures are described for the samples from 0.5 to 10 mm in diameter, which would be suitable for whole zebrafish larvae and juveniles, or other animals and tissue samples of similar dimensions. As proof of concept, we have embedded the specimens from Danio, Drosophila, Daphnia, and a mouse embryo; representative images from 3-dimensional scans for three of these samples are shown. Importantly, our methodology leads to multiple benefits including rigid immobilization, long-term preservation of laboriously-created resources, and the ability to re-interrogate samples.

We developed protocols and designed a custom apparatus to enable embedding of millimeter-scale specimens. We present sample preparation procedures with an emphasis on embedding in acrylic resin and polyimide tubing to achieve rigid immobilization and long-term storage of specimens for the interrogation of tissue architecture and cell morphology by micro-CT.

For over a hundred years, the histological study of tissues has been the gold standard for medical diagnosis because histology allows all cell types in ...

Fabrication of Ti3C2 MXene Microelectrode Arrays for In Vivo Neural Recording

Implantable microelectrode technologies have been widely used to elucidate neural dynamics at the microscale to gain a deeper understanding of the neural underpinnings of brain disease and injury. As electrodes are miniaturized to the scale of individual cells, a corresponding rise in the interface impedance limits the quality of recorded signals. Additionally, conventional electrode materials are stiff, resulting in a significant mechanical mismatch between the electrode and the surrounding brain tissue, which elicits an inflammatory response that eventually leads to a degradation of the device performance. To address these challenges, we have developed a process to fabricate flexible microelectrodes based on Ti3C2 MXene, a recently discovered nanomaterial that possesses remarkably high volumetric capacitance, electrical conductivity, surface functionality, and processability in aqueous dispersions. Flexible arrays of Ti3C2 MXene microelectrodes have remarkably low impedance due to the high conductivity and high specific surface area of the Ti3C2 MXene films, and they have proven to be exquisitely sensitive for recording neuronal activity. In this protocol, we describe a novel method for micropatterning Ti3C2 MXene into microelectrode arrays on flexible polymeric substrates and outline their use for in vivo micro-electrocorticography recording. This method can easily be extended to create MXene electrode arrays of arbitrary size or geometry for a range of other applications in bioelectronics and it can also be adapted for use with other conductive inks besides Ti3C2 MXene. This protocol enables simple and scalable fabrication of microelectrodes from solution-based conductive inks, and specifically allows harnessing the unique properties of hydrophilic Ti3C2 MXene to overcome many of the barriers that have long hindered the widespread adoption of carbon-based nanomaterials for high-fidelity neural microelectrodes.

Fabrication of Ti3C2 MXene Microelectrode Arrays for In Vivo Neural Recording

We describe here a method for fabricating Ti3C2 MXene microelectrode arrays and utilizing them for in vivo neural recording.

Implantable microelectrode technologies have been widely used to elucidate neural dynamics at the microscale to gain a deeper understanding of the neural ...

High Throughput Yeast Strain Phenotyping with Droplet-Based RNA Sequencing

The powerful tools available to edit yeast genomes have made this microbe a valuable platform for engineering. While it is now possible to construct libraries of millions of genetically distinct strains, screening for a desired phenotype remains a significant obstacle. With existing screening techniques, there is a tradeoff between information output and throughput, with high-throughput screening typically being performed on one product of interest. Therefore, we present an approach to accelerate strain screening by adapting single cell RNA sequencing to isogenic picoliter colonies of genetically engineered yeast strains. To address the unique challenges of performing RNA sequencing on yeast cells, we culture isogenic yeast colonies within hydrogels and spheroplast prior to performing RNA sequencing. The RNA sequencing data can be used to infer yeast phenotypes and sort out engineered pathways. The scalability of our method addresses a critical obstruction in microbial engineering.

A bottleneck in the &#8216;design-build-test&#8217; cycle of microbial engineering is the speed at which we can perform functional screens of strains. We describe a high-throughput method for strain screening applied to hundreds to thousands of yeast cells per experiment that utilizes droplet-based RNA sequencing.

The powerful tools available to edit yeast genomes have made this microbe a valuable platform for engineering. While it is now possible to construct ...

Measuring 3D In-vivo Shoulder Kinematics using Biplanar Videoradiography

The shoulder is one of the human body's most complex joint systems, with motion occurring through the coordinated actions of four individual joints, multiple ligaments, and approximately 20 muscles. Unfortunately, shoulder pathologies (e.g., rotator cuff tears, joint dislocations, arthritis) are common, resulting in substantial pain, disability, and decreased quality of life. The specific etiology for many of these pathologic conditions is not fully understood, but it is generally accepted that shoulder pathology is often associated with altered joint motion. Unfortunately, measuring shoulder motion with the necessary level of accuracy to investigate motion-based hypotheses is not trivial. However, radiographic-based motion measurement techniques have provided the advancement necessary to investigate motion-based hypotheses and provide a mechanistic understanding of shoulder function. Thus, the purpose of this article is to describe the approaches for measuring shoulder motion using a custom biplanar videoradiography system. The specific objectives of this article are to describe the protocols to acquire biplanar videoradiographic images of the shoulder complex, acquire CT scans, develop 3D bone models, locate anatomical landmarks, track the position and orientation of the humerus, scapula, and torso from the biplanar radiographic images, and calculate the kinematic outcome measures. In addition, the article will describe special considerations unique to the shoulder when measuring joint kinematics using this approach.

Biplane videoradiography can quantify shoulder kinematics with a high degree of accuracy. The protocol described herein was specifically designed to track the scapula, humerus, and the ribs during planar humeral elevation, and outlines the procedures for data collection, processing, and analysis. Unique considerations for data collection are also described.

The shoulder is one of the human body's most complex joint systems, with motion occurring through the coordinated actions of four individual joints, ...

A Micropatterning Assay for Measuring Cell Chirality

Chirality is an intrinsic cellular property, which depicts the asymmetry in terms of polarization along the left-right axis of the cell. As this unique property attracts increasing attention due to its important roles in both development and disease, a standardized quantification method for characterizing cell chirality would advance research and potential applications. In this protocol, we describe a multicellular chirality characterization assay that utilizes micropatterned arrays of cells. Cellular micropatterns are fabricated on titanium/gold-coated glass slides via microcontact printing. After seeding on the geometrically defined (e.g., ring-shaped), protein-coated islands, cells directionally migrate and form a biased alignment toward either the clockwise or the counterclockwise direction, which can be automatically analyzed and quantified by a custom-written MATLAB program. Here we describe in detail the fabrication of micropatterned substrates, cell seeding, image collection, and data analysis and show representative results obtained using the NIH/3T3 cells. This protocol has previously been validated in multiple published studies and is an efficient and reliable tool for studying cell chirality in vitro.

We present a protocol for determining multicellular chirality in vitro, using the micropatterning technique. This assay allows for automatic quantification of the left-right biases of various types of cells and can be used for screening purposes.

Chirality is an intrinsic cellular property, which depicts the asymmetry in terms of polarization along the left-right axis of the cell. As this unique ...