| Epithelial Transport |
 |
The movement of salt and water across epithelial membranes was first examined by H.H. Ussing in the nineteen forties. He discovered that Na+ is actively transported across amphibian skin, independent of the concentration gradient. The transport mechanisms discovered decades ago still continue to be of interest to physiologists studying epithelia in many systems and species. Ussing chambers continue to be used today in conjunction with an epithelial voltage clamp to study epithelial transport. The techniques of epithelial voltage clamping can be applied to cultured cells, as well as excised tissues. A full range of products for this application is available from iWorx.
iWorx Features for Epithelial Voltage Clamping
Hardware
The iWorx 408 recorder works together with the Warner Instruments EC 825 or Physiologic Instruments VCC MC6 voltage clamps to record voltage and current outputs from as many as eight epithelial chambers. System noise is very low (<1mV) so, even at low gains, A/D noise will never be a problem. This is particularly important because the voltage changes in this application are very small. The iWorx 408 has two stimulator outputs and eight software-controlled digital outputs. The digital outputs use BNC connectors on the front panel of the iWorx 408, so no special cables are required to connect them to peripheral devices. Its stimulator can be used to control the clamp level, and its digital output can be used to control the clamp state or a perfusion apparatus, such as the valve controller for the VC-6 Perfusion System. The iWorx 408 connects over the USB port so there are no cards to install.
LabScribe2 Software
Stimulator
The LabScribe2 software controls two independent stimulator outputs. Each output can be programmed separately, or combined to produce complex protocols. The stimulator supports a Step output especially designed for voltage clamping. The stimulator can also be set to deliver a holding potential as the rest state for the output.
Digital Outputs
The eight digital output lines can be programmed easily using the LabScribe2 protocol generator. Outputs can be used to open or close perfusion valves included with Warner Instruments VC-6 Perfusion System. A programmed digital output state can also be used to switch a clamp channel from a voltage clamp to a current clamp. Digital output changes are marked in the record with text messages that can later be used to automate analysis or simply to navigate the record.
Display
The display allows you to toggle between a preferred Y-axis scaling set by the user and the best view as determined by the AutoScale feature. Alternately you can zoom-in or zoom-out by factors of two with a single mouse click. In a similar fashion, X-axis scaling can be expanded or compressed by factors of two with a single click.
Real Time Annotations
While recording, you can mark your data with text messages. These marks are searchable and appear in the field of data to which they apply. Marks are time locked to the record and can be used to Go To any marked region of the data. Marks are attached to the record by hitting the Return key or they can be delivered when a digital output line changes state. In this way, automated changes in perfusing solutions, clamp state, or drug deliveries can be marked for later review by the user.
Find and Auto Find
LabScribe2 includes a Find function that can be set to capture values from recorded data that meet specified criteria. For example, this feature may be used to extract I/V data from specified regions of the record for use in an I/V plot.
System Components
iWorx 118 Eight-Channel Data Acquisition System
Accepts current and voltage information from the voltage clamp and controls clamp levels and states.
EC-800 Single Channel, EC-825 Dual Channel, or the VCC MC6 Six-Channel Epithelial Voltage Clamp
These instruments provide one, two or six channels of voltage clamping.
U2500 Dual Channel Ussing Chamber
The U2500 is a dual channel self-contained Ussing chamber. It uses no glass circulation reservoirs. Solution warming is provided by pumping heated water through the chamber halves. Its modular design allows for easy access to the tissue and quick change of culture inserts between experiments.
Optional:
VC-6 Perfusion Valve Control Systems
These systems are configured to control up to six valves. Each valve is individually controlled by a manual switch or an external digital (TTL) signal from the iWorx 118.
SH-27B or SF-28 Inline Solution Heaters
TC-324B Single Channel or TC-344B Dual Channel Heater Controllers
These in-line solution heaters are used to warm solutions as they flow into a chamber, and they can be controlled by single or dual channel heater controllers.
|
|
|
|
The IX-228S Recorder has 10 input channels and both a low voltage and a high voltage stimulator output. This recorder exhibits the high resolution and low noise required for small animal cardiovascular research, Oocyte clamp and high end metabolic research applications.