In this study two-photon imaging and single cell electrophysiological measurements were carried out in PV+ hippocampal interneurons to compare the dendritic calcium dynamics of somatically evoked backpropagating action potentials (BAPs) and in vitro sharp wave oscillation (SPW) activated BAPs at different distances from the soma. In the case of 300 μm thick, non-oscillating slices, the BAP-evoked Ca(2+) (BAP-Ca(2+)) influx propagated along the dendritic tree in a non-uniform manner and its amplitude gradually reduced when measured at more distal regions. In contrast to the evoked BAP-Ca(2+)s, the spontaneous SPW-induced Ca(2+) influx had only a small distance-dependent decrement. Our results suggest that similarly to nicotinic acetylcholine receptor activation, synaptic activity during hippocampal SPWs increases AP backpropagation into distant dendritic segments. Bath application of Nimodipine, a specific Ca(2+) channel blocker and tetrodotoxine decreased the amplitude of the somatically evoked Ca(2+) influx, which suggests that L-type Ca(2+) channels play an important role both during somatically evoked and SPW-induced BAPs.

Project Aquafluosense is designed to develop prototypes for a fluorescence-based instrumentation setup for in situ measurements of several characteristic parameters of water quality. In the scope of the project an enzyme-linked fluorescent immunoassay (ELFIA) method has been developed for the detection of several environmental xenobiotics, including mycotoxin zearalenone (ZON). ZON, produced by several plant pathogenic Fusarium species, has recently been identified as an emerging pollutant in surface water, presenting a hazard to aquatic ecosystems. Due to its physico-chemical properties, detection of ZON at low concentrations in surface water is a challenging task. The 96-well microplate-based fluorescence instrument is capable of detecting ZON in the concentration range of 0.09–400 ng/mL. The sensitivity and accuracy of the analytical method has been demonstrated by a comparative assessment with detection by high-performance liquid chromatography and by total internal reflection ellipsometry. The limit of detection of the method, 0.09 ng/mL, falls in the low range compared to the other reported immunoassays, but the main advantage of this ELFIA method is its efficacy in combined in situ applications for determination of various important water quality parameters detectable by induced fluorimerty—e.g., total organic carbon content, algal density or the level of other organic micropollutants detectable by immunofluorimetry. In addition, the immunofluorescence module can readily be expanded to other target analytes if proper antibodies are available for detection.

A novel, Yb-fiber laser based, handheld 2PEF/SHG microscope imaging system is introduced. It is suitable for imaging of murine skin at an average power level as low as 5 mW at 200 kHz sampling rate. Amplified and compressed laser pulses having a spectral bandwidth of 8 to 12 nm at around 1030 nm excite the biological samples at a ~1.89 MHz repetition rate, which explains how the high quality two-photon excitation fluorescence (2PEF) and second harmonic generation (SHG) images are obtained at the average power level of a laser pointer. The scanning, imaging and detection head, which comprises a conventional microscope objective for beam focusing, has a physical length of ~180 mm owing to the custom designed imaging telescope system between the laser scanner mirrors and the entrance aperture of the microscope objective. Operation of the all-fiber, all-normal dispersion Yb-fiber ring laser oscillator is electronically controlled by a two-channel polarization controller for Q-switching free mode-locked operation. The whole nonlinear microscope imaging system has the main advantages of the low price of the fs laser applied, fiber optics flexibility, a relatively small, light-weight scanning and detection head, and a very low risk of thermal or photochemical damage of the skin samples.

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