Closed loop television tracking of beating heart cells in vitro

The motion of beating heart cells in vitro has been used as a sensitive indicator of the presence of drugs. The combination of closed loop television video tracking and latex microspheres placed on the cells as markers results in an improved measurement of cell motion. Latex microspheres, 5.2 micrometers, are allowed to settle onto beating myocardial heart cells in vitro, where they move in concert with the cell motion. These microspheres, when viewed by televised transmission microscopy with normal optics, present high contrast circular targets that are excellent for closed loop television video tracking techniques. With video tracking, an analog voltage is generated proportional to the horizontal center of intensity of the target being tracked. This signal represents the location of a video demodulator gate that is maintained centered over the video target by feedback control.