Ruprecht-Karls-Universitšt Heidelberg

Overview Electrophysiology Nonlinear Microscopy Calcium Imaging Modelling Image Processing Single Molecules

Calcium Imaging

The dynamics of the intracellular calcium concentration regulates a broad spectrum of cellular processes like cell motility and intracellular transduction neuronal and hormonal signals. A misregulation of calcium dynamics is involved in the genesis and pathophysiology of numerous deseases, e.g. calcium induced apoptosis.

In particular the dynamics of intracellular calcium ion channels (inositoltrisphosphate, IP3R and ryanodine receptor, RyR) can only be analysed with optical methods. These are based on calcium sensitive dyes (Fluo-4, Fura-2), which only fluoresce with calcium ions bound.

Elementary Calcium Release Events

Ca2+sparksThe smallest events of intracellular calcium signaling are openings of single or small groups of calcium channels. These elementary calcium release events (ECRE or "sparks") have a spatial extension of less than 1-2 µm, which means they are only detectable with confocal laser scanning microscopes. The temporal extension is in the range of 10-200ms so that time resolved measurements are only possible by scanning a singe line or very small frames.

Figure 1 Confocal linescan image of ECREs through RyR type 2 in cardiac muscle cells

This technique is applied to study the effects of physiological modulations and diverse anesthetics on the ryanodine receptor. The detection of ECREs was automated using specifically adapted image processing techniques.

Calcium Oscillations

Oscillations of the intracellular calcium concentration are known as a way of signal trans-duction between cells. Changes in amplitude and frequency of these oscillations can induce cell proliferation or the growth of synapses in neuronal networks.

Figure 2 Analysis of intracellular calcium dynamics in coupled HepG2 cell clusters

We study purine-receptor mediated calcium oscillations in cultured HepG2 carcinoma cells and the effects of anesthetics on the dynamics of calcium oscillations in cultured neurons.