WPI’s popular multi-channel isolated tissue bath system (MYOBATH) was developed in collaboration with top cardiovascular research scientists over a period of several years. The result is a state-of-the-art easy-to-use, cost-effective system for the in vitro study of smooth muscle (vascular and non-vascular), cardiac muscle and other tissue preparations. The MYOBATH provides the only complete solution to tissue bath studies and is available in 2, 3 and 4 channel configurations. Each configuration is sold as a complete ready-to-use assembly consisting of; highly quality PVC heavy base, stainless steel vertical posts, WPI’s unique integrated tissue aeration and stimulation manifold, holding brackets, micrometers, tissue holders and hooks, tissue baths, force transducers, accessories (i.e. tubing, clamps, cables and tissue/stimulation adapters) and we even include WPI’s famous four-channel Transbridge transducer amplifier!

The modular design allows up to four individually mounted organ baths to be studied simultaneously. Multiple systems (i.e. more than 4) can be linked together if more bath setups are required. The convenient compact bench-top design of MYOBATH enables the system to be readily located virtually anywhere.

MYOBATH can also be supplied with an optional water heater/circulator, gravity-fed buffer pre-warming system, transducers, bridge amplifiers, stimulators, PC/Mac-based data-acquisition system and chart recorders.

Myobath Key Features

Stimulation/Aeration Manifold

A unique 4-channel stimulation manifold and 6-channel aeration manifold, designed to regulate flow of O2/CO2 mixtures, is mounted on top of the vertical stainless steel posts (see diagram below). Four regulators (needle valves) are used to regulate flow of O2/CO2 to each individual tissue bath. The remaining two regulators are used to supply O2/CO2 to dissecting dishes and/or an optional buffer reservoir (P/N – 47027). The buffer reservoir holds warm, oxygenated buffer solution to replace that in the organ bath. The tissue baths and buffer reservoir are jacketed and require a heating and recirculating pump to maintain the desired temperature.

Micrometer Heads

One important key feature of the MYOBATH are the micrometer heads used for delicate tissue tension adjustment and measurement. Each MYOBATH channel comes equipped with a high-quality micrometer head which, together with the force transducer, is mounted on to the micrometer head assembly (See figure at right). The tissue preparation is then mounted between the tissue holder (attached to the micrometer) and tissue hook (attached to force transducer). The micrometer provides a convenient way of adjusting and measuring changes in tissue tension and is essential for studying vascular segments where accurate diameter-tension curves need to be constructed for optimizing the passive force placed on the segment (McPherson, '92).

Tissue Holders

There are currently four types of tissue holders available from WPI: atria holder with stimulation feature (AS), vascular holder (V), vascular holder with stimulation feature (VS), and blank holder with stimulation (B). They have been successfully used in the study of cardiac muscle, vascular and non-vascular smooth muscle. In addition, there are five types of Micro Tissue Holders available for micro preparations.

Each tissue holder includes a kit containing a complete assembly of stainless steel wire tissue hooks and ‘S’-hooks. Special ‘stimulation’ tissue holders have a built-in stimulation circuit and external electrodes, which are located in close proximity to the tissue under study. Electrical contact between the tissue holder and stimulator manifold is achieved using screened cables and connectors provided. Stimulus pulses generated using any one of WPI’s range of stimulus isolators and be conveniently connected (via a BNC cable) to the MYOBATH stimulator manifold. Blank tissue holders are also available to enable the user to easily construct custom-made holders for specialized applications.

The AS holder is designed to be used mounting muscle and atria preparations. The tissue is mounted onto the two S-shaped hooks (made from 301/2 gauge needles), The S-hooks measure 2 mm in diameter on both ends with a sharp tip on one end where tissue is pieced. The two point stimulation platinum (Pt) electrodes on the holder are 2.54 mm (0.1 in.) apart.

The V holder is designed to be used for mounting vascular tissue preparations. The bottom hook consists of a V-shaped wire. The top hook is an L-shaped wire. The tissue is mounted as shown. The hooks are made from 0.48 mm (0.019 in.) stainless steel wire. The U-shaped hook measures 6.35 mm (0.25 in.) in base. For V holders which can accommodate U-shaped hooks of different lengths, call WPI for special order.

The VS holder uses the same tissue-mounting mechanism as the V holder, but has two 5 mm flexible platinum stimulation electrodes which can be positioned around the tissue. The stimulation connector and electrodes are designed to be replaceable. The VS holder can only be used in the 25 ml or 50 ml baths.

The B holder is designed to be used with custom-made hooks. The bottom tissue hook is secured with a nylon screw. Stainless steel wire (0.56 mm or 0.022 in.) provided in the Myobath start-up kit, can be used to make the top hook which connects to the strain gauge. Platinum electrodes for point stimulation are identical to those on the AS holder.

 
MICRO TISSUE HOLDER MV100 (P/N 47110)

Five unique specially designed micro-tissue holders are available for microtissue strips, microvessel and other similar studies where the force measurements are less than 10 g. Microtissue holders are designed to be used with the microtissue baths (2 ml and 5 ml volume). Microtissue Holders MH1 and MHS1 are designed for tissue strips as small as 0.5 mm in width and 5 mm in length. The tissue strip is held between two miniature vessel clips with a clamping pressure of 60 grams. These holders are most suitable for measuring isometric force of less than 5-10 grams. MHS1 differs from MH1 only in that it has n in-built stimulation circuit and electrodes.

Microvessel holders MV100, MVS100 and MVS200 (only usable with 5 ml or above baths and Fort 10 transducer) are designed for studying tissue tension and/or contraction and also for measuring the lumen diameter of vessel preparations. The MV100 and MVS100 can be used for microvessel preparations as small as 500-600 microns (ID). MVS200 is designed to be used for larger vessels (> 2 mm ID). MVS100 and MVS200 feature specially designed spiral stimulation electrodes fabricated from 250-micron diameter platinum wire. The two-and-a-half turns of each spiral electrode span appropriately 4-5 mm. The positions of the spiral electrodes can be adjusted with respect to the tissue placement, a feature that is very useful in controlling stimulus intensity.

These microtissue holders (P/N’s MH1, MHS1, MV100, MVS100 and MVS200) are not supplied with the MYOBATH system and must be purchased separately.

Miniature tissue baths (2 ml and 5 ml volume) are designed to reduce the amount of drugs required in pharmacological studies of tissue preparations. Since many drugs are extremely expensive the use of the miniature tissue bath provides an important cost-saving alternative to larger baths requiring increased volume. The 2 ml miniature tissue bath measures approximately 12 mm (ID) X 25 mm (depth), and the 5 ml bath measures approximately 16 mm (ID) X 30 mm (depth). A nylon clamp (PN 14443) is needed for mounting the microtissue baths.

MICRO TISSUE HOLDER MVS 100 (P/N 47120)and MICRO TISSUE HOLDER MVS 200 (P/N 47130)

Gravity fed buffer pre-warming system

A popular alternative to transferring heated tissue buffer from the jacketed glass reservoir to the tissue bath (using a syringe), is to use a gravity fed buffer warming system. The buffer can then be more effectively pre-warmed using the heat-exchanging coils and fed directly and gravitationally to the jacketed tissue baths. The gravity feeding provides excellent temperature and flow control of tissue preparations and also keeps both the buffer and heated water within a closed loop, therefore reducing the likelihood of cross-contamination and/or mess creating when transferring buffers manually. The gravity feeding (GF) system is designed to be conveniently mounted on the base plate of MYOBATH. A plastic buffer reservoir is held above the MYOBATH using a stainless steel rod installed on the back of the base plate. The buffer is pre-warmed in the jacketed glass coils mounted through clamps on the stainless steel rods, before being fed into the tissue baths. Pinch valves and clamps are used to control the flow rate of the buffer. The compact design ensures that buffer transfer is both efficient and convenient. The GF system is available in 2, 3 and 4-channel configurations. The 2 channel version includes one plastic reservoir (1 litre) and holder, two warming coils (100 ml each), two ringstand clamps, four stainless steel rods, fluid distribution manifold, pinch valves, tubing and clamps. A heated water circulator is required for use with the gravity-fed buffer system.

ADDITIONAL COMPONENTS

Transducers/amplifiers: The Myobath is designed to be used together with WPI's force transducers, including the FORT100 (full scale, 100 g, recommended for most work). These transducers can be directly connected to either the 4-channel Transbridge™ amplifier or the more advanced 8-channel Bridge8 amplifiers.

Stimulators: A number of WPI's stimulators (A300, A310) and stimulus isolators (A360, A365, A385) are ideally suited for use with the organ bath system.