Rao V. Yelamarty

Three-dimensional intracellular calcium gradients in single human burst-forming units-erythroid-derived erythroblasts induced by erythropoietin.

We have previously shown that the intracellular free Ca2+ increase induced by erythropoietin is likely related to differentiation rather than proliferation in human BFU-E-derived erythroblasts (1989. Blood. 73:1188-1194). Since cell differentiation involves transcription of specific regions of the genome, and since nuclear endonucleases responsible for single strand DNA breaks observed in cells undergoing differentiation are Ca2+ dependent, we investigated whether the erythropoietin-induced calcium signal is transmitted from cytosol to nucleus in this study. To elucidate subcellular Ca2+ gradients, the technique of optical sectioning microscopy was used. After determining the empirical three-dimensional point spread function of the video imaging system, contaminating light signals from optical planes above and below the focal plane of interest were removed by deconvolution using the nearest neighboring approach. Processed images did not reveal any discernible subcellular Ca2+ gradients in unstimulated erythroblasts. By contrast, with erythropoietin stimulation, there was a two- to threefold higher Ca2+ concentration in the nucleus compared to the surrounding cytoplasm. We suggest that the rise in nuclear Ca2+ may activate Ca2(+)-dependent endonucleases and initiate differentiation. The approach described here offers the opportunity to follow subcellular Ca2+ changes in response to a wide range of stimuli, allowing new insights into the role of regional Ca2+ changes in regulation of cell function.

Adaptive joint transform correlator for real-time colour pattern recognition

Abstract Colour liquid crystal televisions (LCTVs) can be used to perform real-time multi-channel joint transform correlation capable of discriminating between different colours and different shapes. In the future this optical system may be combined with a digital knowledge-based inference processor. Preliminary optical experimental results are presented, which demonstrate how such a system would work.

Measurement of intracellular calcium gradients in single living cells using optical sectioning microscopy

Intracellular free calcium has been recognized as a regulator of many cellular processes and plays a key role in mediating actions of many drugs. To elucidate subcellular spatial calcium changes throughout the cell in three dimensions (3-D), optical sectioning microscopy was applied using digital imaging coupled fluorescence microscopy. The cell was loaded with a fluorescent indicator, fura-2, and a stack of sectional fluorescent images were acquired, digitized and finally stored on-line for post image analysis. Each sectional image was then deconvolved, to remove contaminating light signals from adjacent planes, using the Nearest Neighboring Deconvolution Algorithm (NNDA) and the overall imaging systems empirical Point Spread Function (PSF) that is measured with a 0.25 micrometers fluorescent bead. Using this technique, we measured that the addition of growth factors caused a 2 - 3 fold increase (1) in nuclear calcium compared to cytosolic calcium in blood cells and (2) in both nuclear and cytosolic calcium in liver cells. Such spatial information, which is important in understanding subcellular processes, would not be possible to measure with other methods.

Adaptive Real-Time Pattern Recognition Using Liquid Crystal Televisions

Recently many applications of the liquid crystal television (LCTV) to real-time signal processing have been reported. A basic description of the application of the LCTV to real-time pattern recognition was first reported by Liu et al. [1]. Gregory [2] later also showed a successful space invariant correlation using a LCTV as a spatial light modulator. Both methods were based on the use of a VanderLugt type complex matched spatial filter. The joint transform architecture is an alternative approach to optical pattern recognition [3]. In this paper, a new implementation of the real-time monochromatic and polychromatic joint transform correlator architecture using inexpensive LCTVs will be discussed.