In this article we develop a simple algorithm for localization of electrical sources in neurons. The algorithm is based on multiple measurements of neuron's action potentials acquired from multiple sensors, such as tetrodes. We show that in many cases this problem can be solved analytically. We also give an alternative formulation of the problem that is applicable when the analytical approach has no solution. We further show that the problem of source localization and the estimation of the source strength are coupled and can be solved simultaneously. Our method was tested on a single-neuron model with complex dendritic geometry and realistically modeled membrane dynamics. Simulation results suggest that our technique is capable of accurately estimating the location and strength of nearby current sources.

We demonstrate that stimulated parametric emission (SPE) microscopy enables label-free, 3-D visualization of internal hemoglobin distribution of live mouse and chicken erythrocytes with high sensitivity. Change in hemoglobin distribution in chicken erythrocytes before and after ethanol fixation is clearly visualized.

The ability to perform high-resolution unstained live imaging is very important to in vivo study of cell structures and functions. Stimulated parametric emission (SPE) microscopy is a nonlinear-optical microscopy based on ultra-fast electronic nonlinear-optical responses. For the first time, we have successfully applied this technique to archive three-dimensional (3D) images of unstained sub-cellular structures, such as, microtubules, nuclei, nucleoli, etc. in live cells. Observation of a complete cell division confirms the ability of SPE microscopy for long time-scale imaging.

Behavior of the mosquitofish (Gambusia affinis) toward the Japanese medaka (Oryzias latipes) was tested under exposure to environmental 17α-ethinylestradiol (EE2), a synthetic derivative of natural estrogen, estradiol. The mosquitofish were exposed to EE2 at different concentrations-0, 0.5, 5.0, and 50.0 ng/L-for 2 days, before their behavioral changes toward the medaka were observed. Results indicate that female mosquitofish became more aggressive at the high level of EE2 (50 ng/L), in terms of how persistently they attempted to approach the medaka. The males showed increased aggressive behavior toward the medaka, by significantly increasing the number and persistence of approach attempts at the low (0.5 and 5 ng/L) levels of EE2. At the highest EE2 concentration (50 ng/L), however, the number of attempts decreased, while the persistence increased in the males showing the same pattern as in the females. All behavioral changes were reversed once EE2 was removed from the environment.

We demonstrate that two distinct images can be simultaneously acquired using the dual-band configuration of stimulated parametric emission (SPE) microscopy, which is based on the four-wave mixing process enhanced by two-photon electronic resonance. The dual-band SPE microscopy utilizes two SPE signals simultaneously generated at different wavelengths. In the experiment, we image stained and unstained biological tissues, and obtain two different images for each sample. Additionally, we propose an axial differential imaging technique to improve the contrast of SPE images, and verify its applicability to biological imaging. #