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  1. TEER Measurement in Individual Endothelial Cell Cultures Cups
    October 11, 2013
    WPI's EndOhm chambers were designed for making TEER measurement of endothelial cell cultures in individual cups. The EndOhm chambers feature: Compatible with EVOM² Improved accuracy of 1-2Ω Accommodates 6mm, 12mm, 24mm cups and Costar Snapwell cup Sterilized with EtO, alcohol or a bactericide Using WPI's EVOM² resistance meter, EndOhm chambers provide reproducible resistance measurements of endothelial tissue in culture cups. Transfer cups from their culture wells to the EndOhm chamber for measurement rather than using hand-held electrodes. The chamber and the cap each contain a pair of concentric electrodes: a voltage-sensing silver/silver chloride pellet in the center plus an annular current electrode. The height of the top electrode can be adjusted to fit cell culture cups of different manufacture. Endohm's symmetrically apposing circular disc electrodes, situated above and beneath the membrane, allow a more uniform current density to flow across the membrane than with STX2 electrodes. The background resistance of a blank insert is reduced from150Ω (when using WPI's hand-held STX2 electrodes) to less than 5Ω.With EndOhm's fixed electrode geometry, variation of readings on a given sample is reduced from 10-30Ω with STX2 electrodes (depending on the experience of the user) to 1-2Ω. Compared with other resistance measurement methods, EndOhm with EVOM² offers a much more convenient and economic solution to "leaky tissue" measurement. Because of the uniform density of the AC square wave current from EVOM², errors owing to electrode polarization or membrane capacitanceare largely eliminated. EndOhm, together with EVOM², offers the most accurate and economical endothelial ohm meter now available. To date, cups from Costar, Millipore, ICN Biomedicals and Falcon have beenchambers may be sterilized with EtO, alcohol or a bactericide (like Cidex). They are not autoclavable.
  2. REMS Auto Sampler - HTS Robot
    October 11, 2013
    The REMS AutoSampler automates measurements of electrical resistance of transepithelial, transendothelial or Caco-2 cell membranes being grown to confluence on microporous filters of high throughput screening (HTS) 24- and 96-well microplates. It is a computer-controlled, tissue resistance measurement system that offers reproducibility, accuracy, flexibility and ease-of-operation for this kind of measurement. Automated measurement of tissue resistance in cell culture microplates provides the important advantages of speed, precision, decreased opportunity for contamination and the instant availability of measured resistance data on a computer. These measurements are useful in applications such as drug bioavailability studies and studies on the mechanisms of drug transport. The main components of the REMS AutoSampler include: Robotic sampler that moves the electrode over each well of the microplate Electrode which is located on the robotic arm Base plate for the 24-and 96-well tray Windows-based data acquisition card REMS interface unit REMS software to operate the system on a Windows-based computer The REMS AutoSampler automates TEER measurements previously made with WPI's EVOM2 Epithelial Voltohmmeter. Automated tissue resistance measurements up to 20kΩ can be performed on 24- or 96-well HTS microplates. Microplates presently supported include the Corning Costar HTS Transwell-24, Falcon HTS Multiwell insert systems, and Millipore Multiscreen™ CaCo 96-well plate. The REMS AutoSampler is designed to facilitate integration with other robotic systems. Special locating bars are installed on the REMS base platform that allow other system robots to place an HTS tray into a precise location on the REMS base. The REMS AutoSampler automatically measures and records tissue resistance from a user-specified matrix of culture wells on the microplate. According to the specified sequence, the robotic arm moves over the identified wells taking TEER measurements. By means of a x-y-z locating system, the electrode-containing arm is positioned precisely and reproducibly over each well. The ability of the REMS AutoSampler to reproducibly and precisely locate the electrode results in highly reproducible TEER measurements. TEER measurements are stored in the computer as the electrode moves from one well to the next. The Windows-based software provides user-friendly features to acquire, display and store the tissue resistance measurements. The REMS electrode is compact and robust in design. Each of two rod-shaped probes, 1.5mm in diameter, consists of a pair of electrodes: one electrode for injecting current and the other for measuring the voltage. The use of two pairs of electrodes eliminates the error caused by the electrode-liquid interface. To take a measurement, the robot inserts one probe into the center of the filter well and the other into the opening slot of the 24- or 96-well plate. The use of AC current to measure resistance provides several advantages over DC current, including: Absence of offset voltages on measurements There is a zero net current being passed through the membrane, and therefore it is not adversely affected by a current charge No electrochemical deposition of electrode metal. The REMS AutoSampler also features a rinse and calibration check station. If occasional rinsing of the REMS electrode is required, it maybe sent to a ri
  3. TEER Research: WPI's Manual and Robotic Systems
    October 11, 2013
    Transepithelial Electrical Resistance TEER measurements is the most convenient, reliable and non-destructive method for evaluating and monitoring the growth of epithelial tissue cultures in vitro. The confluence of the cellular monolayer is quickly determined by a sharp increase in TEER. TEER measurement technology, which was first introduced by WPI in the mid-1980's, has since been perfected and expanded to include a range of TEER related manual and automatic instrumentation, including: EVOM² - Manual TEER measurement of epithelial cells in 24- and 96-well plates REMS AutoSampler - Automated system for High Throughput Screening (HTS) EVOM2 Volt-Ohm Meter
  4. STX100 Electrodes TEER Measurement
    October 11, 2013
    With the development of a High Throughput Screening (HTS) protocol for faster drug discovery, a new line of cell culture filter plates have been introduced by several major cell culture insert manufacturers. These HTS plates normally have either 24 or 96 individual cell culture inserts "bonded" together as one plate so that it can be handled by a robot apparatus. In response to these developments, WPI has developed an automatic REMS system and a manual electrode, STX100, for TEER measurements using HTS plates. Designed for use with 24-well HTS plates (Corning Costar and BD Falcon) and with 96-well plates (Millipore and BD Falcon) Improved accuracy down to
  5. How to Use an EndOhm Chamber with an EVOM2
    September 03, 2013
    The EVOM2 measures trans epithelial electrical resistance (TEER) in tissue culture research. The EndOhm series of chambers for the EVOM2 are designed to accurately measure trans endothelial electrical resistance. Learn how to setup your EndOhm Chamber with an EVOM2 Epithelial Volt Ohm Meter. See how to equilibrate the sensors when taking a voltage measurement. And, learn how to take resistance and voltage measurements.  
  6. Endohm Maintenance for Long Life
    August 20, 2013
    The EndOhm series of chambers, when used with WPI’s EVOM2 resistance meter or the Millicell ERS, are designed to provide reproducible and accurate resistance measurements of endothelial tissue in culture cups. Resistance values obtained with the EndOhm are consistent with those obtained using a well-designed Ussing Chamber. If an EndOhm is properly cared for, it will enjoy a much longer life. In this article, we will examine how often and what method should be used for cleaning an EndOhm electrode.  How Do I Clean the EndOhm? With use, the electrode surface can become coated with protein or other foreign materials. This build-up, or contamination, can degrade the performance of the system. After every use, rinse the EndOhm electrodes with distilled water and store them dry. Routine Cleaning Clean the EndOhm with distilled water and standard biological detergents (such as Alconox) unless a change in the baseline performance becomes evident. The baseline performance of the EndOhm should be established when the probe is new. This will serve as the reference by which the performance of the EndOhm can be judged as it ages.  Deep Cleaning Periodically clean your EndOhm chambers with Tergazyme, a proteolytic detergent manufactured by Alconox. When performance begins to degrade, then a more aggressive cleaning technique may be considered. Consistent rinsing with distilled water immediately after use, cleaning with Alconox and storing the EndOhm dry when it’s not in use should go a long way to keeping it working well. As far as more aggressive cleaning is concerned, the thing to watch out for is an increase in baseline TEER. Baseline TEER will increase if an accumulation of biological material, such as proteins, adhere to the surface of the voltage an
  7. EVOM2 Remix
    April 30, 2013
    EVOM was the first instrument designed to perform routine Trans Epithelial Electrical Resistance (TEER) measurement in tissue culture research. EVOM2 is the next generation, redesigned for greater useability. The EVOM2 sports the following features: Rechargeable Battery - EVOM2 , which plugs into a standard wall outlet, comes with a NiMH 6V 200mAH rechargeable battery backup. The battery charges whenever the unit is plugged in. If the battery runs low, the EVOM2 automatically shuts down. Simply install the supplied power cord and plug it into the wall outlet. The battery will fully charge in 24 hours. Normal laboratory testing can continue while the EVOM2 recharges. Tilt Bail - The new tilt bail allows the EVOM2 to be free standing, making it much easier to read than the original EVOM. 4.5 Digit Display - The new 4.5 digit readout provides a range of 1-9,999, eliminating the need for a Range toggle switch. External Testing Circuit - The meter testing function was improved. Now, by simply inserting a "dummy" 1000-ohm test electrode (included) into the input jack, the jack, as well as the measuring circuit, can be tested simultaneously. Analog Output - The BNC output is standard with every EVOM2 , providing a port for recording a remote display of the EVOM2 output. Always Ready - Because the meter always displays the current reading, there's no need for a push button to view the current reading. Now, the scientist no longer needs an extra hand to take a measurement. Redesigned with the researcher in mind, the EVOM2 includes the best features and reliability of
  8. EVOM or Volt Meter: Defining the Difference
    April 24, 2013
    A Volt Meter A volt-ohm meter may apply a constant voltage of unknown current across the membrane and damage the cells electrically and also leave a chemicalimbalance in the electrodes. WPI experimented with two volt-ohm meters: An expensive Fluke meter applies a DC voltage of 50 to 80mV, which (in a 1000Ω membrane) will pass 80µA. With a 200Ω membrane, this is 400µA. A discount meter puts out 500mV DC, which will pass 500µA through the membrane. With a 200Ω membrane, this is 2.5mA. Volt Meter Charges or Electrocutes Cells When you use a volt ohm meter to test a cell layer, the Ag/AgCl electrodes accumulate an unbalanced chemical charge. If the cells are not electrocuted in the process, they also accumulate a charge. The unbalanced electrodes can now act as a source of voltage and current that has to be overcome to make an accurate measurement. If a volt ohm meter was employed in a TEER (Trans Epithelial Electric Resistance) measurement and left measuring the cells for more than a few seconds, then the TEER measurement value would probably driftdownwards as the cells and electrodes are changed by the voltage and current applied. In a perfect world, a measuring device minimizes its impact on what it is attempting to measure. These meters are best left to measuring fixed resistors and circuits.   EVOM - Perfect for TEER Reversing Polarity The EVOM² passes a constant current of 10µA through membrane and reverses the polarity 12.5 times per second so that it does not leave a charge behind on either the electrodes or the membrane. The voltage that is present at 10µA on 1000Ω is 10mV. (On a side note, even this is too much for some tissues, like retinal.) Typically, this value on a 200Ωmembrane is 50µV. At either setting, that is much less energy to dissipate in the membrane or to charge the electrodes. The EVOM² passes the 12.5Hz constant current 10µA signal through the two current electrodes (I1 and I2) on the STX through the membrane. The companion electrodes (V1 and V2) measure the voltage that was required to reach the 10µA current and sends this to the processor. The processor converts this to ohms via Ohm's Law (E=I/R) and displays the signal on the digital meter. Since the current is fixedat 10µA, the processor can easily convert the measurement. Built in Averaging The EVOM (a legacy product replaced by the EVOM2) an
  9. EVOM2-How to Equilibrate Your STX2
    April 24, 2013
    The World Precision Instruments (WPI) EVOM2 is used for making trans epithelial electrical resistance (or TEER) measurements. Two silver/silver chloride pellets are used for the electrodes. The chloride ion tends to migrate, which is a reversible reaction. But, because of this chloride ion swapping, the electrodes need to be polarized before each use. Before using the meter for making voltage measurements, equilibrate the electrodes. This video shows you how.   More Info
  10. How To Test Your EVOM2 Meter
    April 24, 2013
    The World Precision Instruments (WPI) EVOM2is used for making trans epithelial electrical resistance (or TEER) measurements. We recommend that you test your EVOM2 before you use it for the first time and then periodically after that. If there is a concern that the meter or the electrode is not functioning properly, test the meter first. This video shows how to test the meter. More Info
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