Epithelial Physiology

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...more

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.

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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...more

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 usability.

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...more

The World Precision Instruments (WPI) EVOM² is 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.

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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.

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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 chemical imbalance 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)...more