Mapping the mechanical pulse of single cardiomyocytes with the atomic force microscope

The atomic force microscope (AFM) was used to analyse the contractile behav iour of embryonic chicken cardiomyocytes. The mechanical pulsing of cardiom yocytes was analysed by observing active single cells as well as cells in a confluent layer. When embedded in a confluent layer, owing to synchronisat ion, pulsing of the cells was often found to be very stable in terms of fre quency and amplitude of the beat, including negative as well as positive am plitudes. Nevertheless, owing to movements of contraction centres within th e layer, a flipping of the sign of the amplitude did sometimes also occur o n a time scale of minutes. In contrast, single cells often changed between active periods of pulsing and periods of complete quietness. Also character istic parameters like beat period and pulse amplitude were observed to be u nstable. Finally, we combined the abilities of the AFM to image adherent si ngle cells and to record locally beat amplitudes, to characterise the pulsi ng behaviour of single cells laterally resolved.