Abstract: A movement-responsive system for conducting tests on freely-moving animals is disclosed. The invention includes a container for housing the animal, a mechanism for rotating the cage in response to rotational movement of the animal, and one or more test leads connected to the animal for performance of biomedical tests such as infusion, in vivo ultrafiltration, laser-doppler monitoring of blood flow, electrical stimulation, and in vivo microdialysis. The container is caused to rotate in the opposite (counter-rotation) direction of the sensed direction of rotation of the animal so that the one or more test leads do not become entangled, twisted, disconnected, or clamped. The rotating mechanism includes a simple, reliable sensor assembly including a pair of strategically placed, close-ended limit detectors which are activated by a triggering element, which is also a part of the sensor assembly.

Abstract: An improved linear microdialysis probe assembly has a short semipermeable membrane portion containing a flexible, internal support or reinforcement fiber bonded to long lengths of inlet and outlet robing. Also disclosed is a method of using it to sample the interstitial fluid of a variety of soft tissues in a living animal including dermis, muscle, adipose and subcutaneous tissue, liver and tumors by pulling the fiber, and attached probe, through the tissue of interest with a needle until the membrane is positioned where desired.

Abstract: An improved mercury electrode for electrochemical analysis is formed by a small diameter thread of liquid mercury contained within an inert tube which, at one point along its length, has an short, fixed length of thin walled tubular semipermeable membrane surrounding and forming the electrodes' active surface in order to prevent or reduce fouling of the surface while allowing the mercury thread to be advanced through the membrane to expose a fresh active surface whenever desired.

Abstract: An electrochemical detector cell includes a first block having a planar first working surface, and a first working electrode embedded in the first block member. The first working electrode includes analyte contacting surface disposed co-planarly with the first working surface. A second block member has the second working surface placeable in an opposed, adjacent relation to the first working surface, and has an inlet port disposed an opposed, adjacent relation to the analyte contacting surface of the first working electrode. The second block also includes a coupling means for permitting an analyte delivery tube to be coupled to the second block member to position an end of the analyte delivery tube adjacent to the inlet port. A generally circular circumferential channel for collecting analyte is disposed radially outwardly of the first working electrode. An outlet is disposed at the channel for conducting analyte away from the channel.