Calcium signals in the cell bodies of avian neurones
In this thesis I have looked at the spatial dynamics of calcium signals in nerve cell bodies. Through this simple second messenger, cells can activate a variety of pathways controlling their growth, secretion and even death. Which pathway is activated depends on the temporal and spatial dynamics of the intracellular calcium signal. I performed measurements on chick dorsal root ganglion neurones using a combination of whole-cell patch clamping and confocal microscopy. Following a 50 msec depolarisation of the neurone, a resulting calcium influx across the plasma membrane is seen to rapidly diffuse to the centre of the cell within 24 2 msec, contrary to previous studies on the diffusion limit of intracellular calcium. The results from these experiments were modelled as a three-dimensional spatial model, solved via finite volume methods within The Virtual Cell modelling environment. This has allowed me to simulate the intracellular calcium dynamics in an unperturbed cell without the inclusion of the calcium indicator dye to see if the inclusion of this additional calcium buffer was responsible for the observed fast diffusion. From this model I have shown that the experimental technique of including a calcium indicator dye in cells does not adversely affect the spatial and temporal properties of the calcium signal it is intended to observe. Furthermore, predictions made from the model have prompted me to look at role of mitochondria in intracellular calcium regulation, clearly demonstrating that significant levels of calcium are accumulated in these organelles following 50 msec depolarisations.