We have constructed a spatio-temporal model of Ca 2+ dynamics in parotid acinar cells, based on new data about the distribution of inositol trisphophate receptors (IPR). The model is solved numerically on a mesh reconstructed from images of a cluster of parotid acinar cells. In contrast to our earlier model (Sneyd et al., 2017b) , which cannot generate realistic Ca 2+ oscillations with the new data on IPR distribution, our new model reproduces the Ca 2+ dynamics observed in parotid acinar cells. This model is then coupled with a fluid secretion model described in detail in a companion paper: A Mathematical Model of Fluid Transport in an Accurate Reconstruction of a

Salivary fluid secretion involves an intricate choreography of membrane transporters to result in the trans-epithelial movement of NaCl and water into the acinus lumen. Current models are largely based on experimental observations in enzymatically isolated cells where the Ca2+ signal invariably propagates globally and thus appears ideally suited to activate spatially separated Cl and K channels, present on the apical and basolateral plasma membrane, respectively. We monitored Ca2+ signals and salivary secretion in live mice expressing GCamp6F, following stimulation of the nerves innervating the submandibular gland. Consistent with in vitro studies, Ca2+ signals were initiated in the apical endoplasmic reticulum. In marked contrast to in vitro data, highly localized trains of Ca2+ transients that failed to fully propagate from the apical region were observed. Following stimuli optimum for secretion, large apical-basal gradients were elicited. A new mathematical model, incorporating these data was constructed to probe how salivary secretion can be optimally stimulated by apical Ca2+ signals.

Salivary gland acinar cells use the calcium (Ca 2+ ) ion as a signalling messenger to regulate a diverse range of intracellular processes, including the secretion of primary saliva. Although the underlying mechanisms responsible for saliva secretion are reasonably well understood, the precise role played by spatially heterogeneous intracellular Ca 2+ signalling in these cells remains uncertain. In this study, we use a mathematical model, based on new and unpublished experimental data from parotid acinar cells (measured in excised lobules of mouse parotid gland), to investigate how the structure of the cell and the spatio-temporal properties of Ca 2+ signalling influence the production of primary saliva. We combine a new Ca 2+ signalling model [described in detail in a companion paper:

No abstract

[1] We constructed a three-dimensional conceptual model of a geothermal system on the Caribbean island of Montserrat. The model was generated using magnetotelluric resistivity data, earthquake hypocenter data, and a three-dimensional P wave velocity model, all plotted using a shared geographical reference. The results of the study suggest a high-temperature fracture-controlled geothermal system at the intersection of two faults in the SW of the island. We also present a "prospectivity index" map that represents a proxy of the spatial variation in harvestable heat flux at 1500 m depth. The index is the product of relative permeability around modeled faults and a proxy for the subsurface temperature calculated using P wave velocity anomalies. Citation: Ryan, G. A., J. R. Peacock, E. Shalev, and J. Rugis (2013), Montserrat geothermal system: A 3D conceptual model, Geophys.