Dr Shawn Adrian Means
BSc MSc Univ. New Mexico, PhD UoA
The influence of space is obvious: if we are too close to a fire we get burned, yet if too far away we don’t enjoy its warmth. Shawn studies impact of spatial distributions in a variety of biological systems over different scales from the intracellular to the population-wide where the importance of space may be more subtle yet profound. Intracellular calcium signalling mechanisms are of particular interest due to their far-ranging importance for neuronal, cardiac, gastro-intestinal or salivary cells to name a few. The spatial distributions of calcium transporters and spatial configurations of intracellular structures are essential to healthy and effective cellular function. These range from short-term ‘facilitated’ learning via increased calcium levels after repeated neuronal stimulations, to heart cell calcium waves contributing to arrhythmias, or calibrations of pacemaking contractions by calcium transfer between organelles in intestines.
Structures in the liver are of current interest. Micro-scaled assemblies of blood vessels surrounded by hepatocytes form the basic metabolic ‘factories’ processing nutrients so essential to human health. Across these structures, also known as ‘sinusoids’, spatial gradients of oxygen, nutrients and even immune cells display higher concentrations near the blood inlets. Traveling down the sinusoid’s roughly 200-500 micron length, hepatocytes further perform varying metabolic roles expressing different levels of key proteins and transporters. These intrinsic spatial arrangements and distributions are hypothesised to influence myriad liver pathologies such as hepatitis-B or fatty liver diseases.
Of further interest are the influences of spatial configuration for neuronal networks — particularly those of neurons releasing recently discovered ‘endocannabinoids,’ or the body’s endogenous versions of cannabinoids. These chemicals diffuse across synaptic gaps and influence the action of dopamine-releasing neurons implicated in ailments such as Parkinson's disease. These dopamine neurons negatively feedback on the endocannabinoid releasing neurons in a (typically biological) complicated and unclear fashion. Applying mathematical and computational methods to this system is currently underway to illuminate how this complicated feedback mechanism is calibrated due to spatial configuration.
Research | Current
- Developing multi-scaled mathematical model of liver structure from the micro- (sinusoidal) to the whole body for investigating impact of spatial distributions on liver disease such as hepatitis-B or fatty liver.
- Developing mathematical model of endocannabinoid release for neuronal systems. Particularly influence of various geometries and spatial distributions on downstream activity due to these chemicals.
- Testing application of spectral methods for representing the action of ion channels in two-state systems by looking at their behaviour in frequency space instead of time.
- Investigating application of software entertainment (e.g., video games) as environment for teaching undergraduate university level mathematical concepts. Game environments -- when effectively engaging -- can be leveraged for education with many topics (e.g., copier repair) so why not with mathematics...
Teaching | Current
EngSci 314 Ordinary Differential Equations (2017, 2016)
Areas of expertise
- Mathematical Modeling with Spatial Dimensions
- Calcium dynamics in biological cells;
- Finite element methods for reaction-diffusion;
- MRI / CT scan image processing & segmentation;
- FEM meshing and refinement.
Selected publications and creative works (Research Outputs)
- Sneyd, J., Means, S., Zhu, D., Rugis, J., Won, J. H., & Yule, D. I. (2017). Modeling calcium waves in an anatomically accurate three-dimensional parotid acinar cell. Journal of Theoretical Biology, 419, 383-393. 10.1016/j.jtbi.2016.04.030
Other University of Auckland co-authors: James Sneyd
- Means, S. A., & Smith? RJ (2016). The impact of human and vector distributions on the spatial prevalence of malaria in sub-Saharan Africa. Journal of Theoretical Biology, 409 (21), 70-85. 10.1016/j.jtbi.2016.08.031
- Means, S. A., & Cheng, L. K. (2014). Mitochondrial calcium handling within the interstitial cells of Cajal. American Journal of Physiology - Gastrointestinal and Liver, 307 (1), G107-G121. 10.1152/ajpgi.00380.2013
- Means, S. A., & Sneyd, J. (2010). Spatio-temporal calcium dynamics in pacemaking units of the interstitial cells of Cajal. Journal of Theoretical Biology, 267 (2).10.1016/j.jtbi.2010.08.008