Wire myography is the preferred technique for the investigation of the structure and function of small vessels and other tubular tissues with diameters of 60 to 400 µm. Suitable tissue samples that may be investigated with wire myography include small veins and arteries, bronchi and ureter.
ADInstruments myographs feature two stainless steel jaws. Two mounting wires are threaded through the vessel lumen (not puncturing the walls) and each wire is secured to each of the jaws. One of the mounting jaws is attached to a micropositioner for the adjustment of vessel circumference and application of tension. The other jaw is attached to a built-in sensitive isometric transducer.
A schematic view of the mounting jaws.
Parameters that can be measured using wire myography include:
- Internal circumference (IC) of the vessel: Calculated using the diameters of the two mounting wires and the distance between them
- Tissue Segment Length: Length of the tissue sample (proximal to distal)
- Wall length of the tissue: Equal to twice the tissue segment length as there is tissue above and below the wires that contributes to the developed tension
- Wall tension: The measured force divided by the wall length
- Effective pressure: The pressure required to extend the vessel to a given IC
- Isometric (force) responses to chemical antagonist/agonists, pharamceutical drugs
LabChartLabChart software (for Windows and Macintosh) combines the familiar simplicity of a traditional strip chart recorder with the powerful analysis features of a digital acquisition system. LabChart software and a PowerLab data acquisition unit provide data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options.
Recording channels can be easily calibrated into appropriate units such as grams or Newtons. LabChart also allows the user to zoom on different sections of the trace while recording and the Data Pad facility can be used to extract important experimental parameters.
Acquisition and analysis capabilities can be further increased with
LabChart Extensions and
LabChart Modules. LabChart Modules are available as part of
LabChart Pro and LabChart Extensions are free for download from the website for existing LabChart users.
DMT Normalization Module (Windows & Macintosh)The
MLS065/6 DMT Normalization Module provides an easy method for the calculation of optimal pretension conditions for microvascular (or any small tubular tissue) research. It allows the user to define the pre-experimental conditions and standardize each piece of tissue.
This module:
- Automatically calculates tissue length
- Provides online and offline determination of effective pressure
- Calculates the pre-tension (micrometer setting) for normalization
The rationale and theory behind normalizing elastic tissues such as microvessels has been extensively investigated by Professor Michael Mulvany (for details see Mulvany MJ, Halpern, W Circulation Research 1977, 41: 19-26). Mulvany determined that the optimal pre-tension conditions (ie internal circumference) for microvascular studies is best defined as the size when the vessel is fully relaxed and under a transmural pressure of 100 mmHg. Therefore the aim of the normalization procedure is to determine the internal circumference at which the vessel would be relaxed and under a transmural pressure of 100 mmHg. This index is denoted as IC100 and is calculated for each vessel mounted on the wire myograph.
The DMT Normalization Module is used to determine the internal circumference, denoted as IC100, which the vessel would have if relaxed and under a transmural pressure of 100 mmHg. This is obtained by stepwise increases in internal circumference whilst measuring the isometric force. An equation is then used to determine when the vessel reaches an effective pressure of 100 mmHg. Following this, the vessel is set to 90% of IC100 (IC1) as this is the internal circumference at which the active force production of the vessel is maximal.
The calculation parameters (including eyepiece calibration, desired target pressure and online averaging times) may be set by the user depending on the particular type of tissue being used and the desired calculations.
GLP and 21 CFR Part 11For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the
GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the
Good Laboratory Practice application page or contact your nearest ADInstruments representative.
Each of these research systems includes a PowerLab and the DMT Normalization Module (Win or Mac). All of the DMT units feature built-in temperature control, ports for filling and injection of drugs, ports for rapid draining (a vacuum pump is required for drainage and is not supplied with the systems) and ports for gas supply. These systems include: - ML870B21 Single Wire Myograph System - Single Wire Myograph (max chamber volume = 10ml) suitable for isometric experimentation.
- ML870B22 Dual Wire Myograph System - Dual Wire Myograph and is ideal for investigating two isolated tissues simultaneously in isometric conditions (the 10 ml chamber can be divided to give 2 x 5 ml).
- ML870B23 Auto Dual Wire Myograph System - Auto Dual Wire Myograph which is similar to the dual chamber wire myograph; however, this system has motorized micropositioners (the 10 ml chamber can be divided to give 2 x 5 ml).
- ML870B24 Multi-Chamber Myograph System - Multi-Chamber Myograph with four chambers (max chamber volume = 8ml in volume) that allow the user to conduct up to 4 separate experiments. It is ideal for work requiring high throughput such as drug screening. This system also includes Tissue Pins as well as the jaws allowing larger tissues such as aorta to be easily mounted.
- ML870B25 Confocal Wire Myograph System - Single channel Confocal Wire Myograph that is specifically designed for use with confocal microscopic techniques. Enables highly resolved images of fluorescent dyes in living tissues to be obtained with a laser-scanning confocal microscope (LSCM). The chamber has a maximum volume of 10ml.
Individual myograph units include:
Additional required equipment (Not supplied by ADInstruments) include:
- Binocular dissecting microscope with at least 40x magnification (Zeiss)
- Optical Fiber Light Source (Schott)