Optical control of excitation waves in cardiac tissue.

In nature, macroscopic excitation waves are found in a diverse range of settings including chemical reactions, metal rust, yeast, amoeba and the heart and brain. In the case of living biological tissue, the spatiotemporal patterns formed by these excitation waves are different in healthy and diseased states. Current electrical and pharmacological methods for wave modulation lack the spatiotemporal precision needed to control these patterns.

Fast measurement of sarcomere length and cell orientation in Langendorff-perfused hearts using remote focusing microscopy.

Rationale: Sarcomere length (SL) is a key indicator of cardiac mechanical function, but current imaging technologies are limited in their ability to unambiguously measure and characterize SL at the cell level in intact, living tissue.

Objective: We developed a method for measuring SL and regional cell orientation using remote focusing microscopy, an emerging imaging modality that can capture light from arbitrary oblique planes within a sample.

Methods And Results: We present a protocol that unambiguously and quickly determines cell orientation from user-selected areas in a field of view by imaging 2 oblique planes that share a common major axis with the cell.

Porphyrins for probing electrical potential across lipid bilayer membranes by second harmonic generation.

Neurons communicate by using electrical signals, mediated by transient changes in the voltage across the plasma membrane. Optical techniques for visualizing these transmembrane potentials could revolutionize the field of neurobiology by allowing the spatial profile of electrical activity to be imaged in real time with high resolution, along individual neurons or groups of neurons within their native networks.,  Second harmonic generation (SHG) is one of the most promising methods for imaging membrane potential, although so far this technique has only been demonstrated with a narrow range of dyes.

Probing the orientational distribution of dyes in membranes through multiphoton microscopy.

Numerous dyes are available or under development for probing the structural and functional properties of biological membranes. Exogenous chromophores adopt a range of orientations when bound to membranes, which have a drastic effect on their biophysical behavior. Here, we present a method that employs optical anisotropy data from three polarization-imaging techniques to establish the distribution of orientations adopted by molecules in monolayers and bilayers.