Mathematical Biology and Physiology Seminar

Full Schedule - Past and Upcoming Talks

Date: January 24, 2014, 12:00 - 13:00

Speaker: Tim Reluga, Math, Penn State University

Title: Exact model reductions for asynchronous boolean networks

Abstract: Boolean networks are a class of finite-state machines used to model cellular biological processes. Boolean networks have a simpler state-space than classical differential equation models and can be easier to parameterize based on qualitative laboratory observations. However, the state spaces still scale exponentially with network size, and model-reduction techniques are very useful in transforming tangled networks into easier-to-understand versions. In this talk, I'll discuss a couple intuitive reduction rules and the challenges of proving basic properties of these rules. Ideas will draw from directed graph theory, topology, modern algebra, and dynamic systems.

Date: February 14, 2014, 12:00 - 13:00

Speaker: Elsa Hansen, postdoc at CIDD

Title: Optimal Within-Host Treatment and the Role of Resource Mediated Competitive Release

Abstract: Experimental results show that treatment can actually accelerate the growth of resistant pathogens via the mechanism of competitive release. It is unknown how treatment should be administered in order to mediate this effect while maintaining health gains. I will discuss an ongoing project where I am applying Pontryagin's Maximum Principle to a within-host model of disease spread to determine how competitive release can modulate the shape of the optimal treatment strategy. I will begin with a brief review of Pontryagin's Maximum Principle and then discuss my progress to date.

Date: February 21, 2014, 12:00 - 13:00

Speaker: Ching-Shan Chou, Assistant Professor, Department of Mathematics, Ohio State University

Title: Cell Polarization in Budding Yeast

Abstract: Cell polarization, in which intracellular substances localize to a particular spot in response to external stimuli or internal cues, is central to cell physiology, and it underlies processes such as cell motility, cell division and cell differentiation. In this talk, I will present our recent works, using budding yeast as a model system, on how cells initiate symmetry breaking preceding the new bud emergence or mating projection. Along with experimental data, our mathematical modeling and simulations reveal potential mechanisms which underlie a biased cell polarity and pheromone concentration dependent cell morphology.

Date: February 28, 2014, 12:00 - 13:00

Speaker: Fred Adler, Math and Biology, University of Utah, SMB president.

Title: Street fighters - Territorial scaling in ant battles

Abstract: The pavement ant Tetramorium caespitum wages huge battles on sidewalks, apparently to establish territorial foraging boundaries for the season. We used empirical data to create a model of where these boundaries will develop as a function of the recruitment strategies of the ants. Larger colonies gain disproportionately large territories, leading to a scaling relationship of colony size with territory size with a slope that can be estimated analytically and which depends in counterintuitive ways on ecological conditions and the strength of recruitment.

Date: March 28, 2014, 12:00 - 13:00

Speaker: Megan Greischar, Entomology and CIDD graduate student.

Title: Games parasites play: optimal transmission investment within the host

Abstract: Malaria parasites must allocate to asexual growth within the host as well as the production of specialized transmission stages to be passed on to new hosts. The optimal balance between growth and transmission is altered by the presence of a coinfecting strain, which represents both a competitor and a potential source of mates. I will discuss current work to identify optimal investment strategies using a mechanistic model of coinfection. Allowing transmission investment to vary through time, we examine the interplay between conflicting selection pressures through the dynamic process of malaria coinfection.

Date: April 4, 2014, 12:00 - 13:00

Speaker: Hye-Won Kang, University of Maryland, Baltimore County

Title: Stochastic modeling of biochemical networks

Abstract: This talk will introduce stochastic modeling and simulation of biochemical processes. Stochasticity may play an important role in case the copy number of some component involved in the biochemical processes is small. A stochastic model for biochemical processes using continuous-time Markov jump processes is considered. In this talk, I will show several examples in biology and their stochastic models. The first part of the talk is about stochastic models in the spatially-homogeneous biological systems. In this part, multiscale approximations of chemical reaction networks will be suggested which help to reduce the network complexity using various scales in species numbers and reaction rates. The second part of the talk is about stochastic models in the spatially-distributed biological systems. Two examples in biology and the models will be introduced: the glycolytic pathway in the distributed system and pattern formation in developmental biology. These examples will show how stochasticity will change the biological systems in different ways.

Date: April 11, 2014, 12:00 - 13:00

Speaker: Brad Peercy, University of Maryland, Baltimore County

Title: Divots in Extracellular Geometry Direct Intracellular Signaling

Abstract: The cellular decision to migrate depends on cascades of intracellular signals initiated by extracellular stimuli. In the biological model system of Drosophila melanogaster, border cells in the epithelium of the developing egg chamber are triggered to migrate or not depending on a secreted morphogen Unpaired. We will describe and discuss our modeling work in three steps of this process: 1) Secretion-diffusion-uptake of Unpaired into-through-from a heterogeneous extracellular domain, 2) Intracellular signaling involving chemical competition and bistability to induce motility, and 3) Force generation between activated cells and their environment to create clustered cell migration.

We can address questions such as what is the effect of microRNAs on the intracellular signaling? Can we explain clustered cell migration with basic force balance dynamics? Are divots creating additional extracellular space sufficient to explain the variety of asymmetric activation patterns seen in prior to migration? This last question will be the main focus of the talk.

This work was conducted as part of the NSF UBM grant to UMBC with undergraduates Xuan Ge, David Stonko, Ann Marie Weideman, and Bilal Moiz, graduate student Lathiena Manning, and faculty co-mentor Dr. Michelle Starz-Gaiano

Date: April 18, 2014, 12:00 - 13:00

Speaker: Hongyu Miao, University of Rochester

Title: Semi-mechanistic Modeling and its Application in Understanding Immune Cell Migration

Abstract: Semi-mechanistic modeling (SMM) is a flexible and powerful technique that allows one to quantitatively describe a dynamic system with unclear or undistinguishable interactions. However, the traditional SMM technique uses constant coefficients to represent unknown interactions and thus may fail to capture the essence of a dynamic process. In the past few years, we have developed the generalized semi-mechanistic modeling (GSMM) technique and paid particular attention to the identifiability analysis and parameter estimation problems associated with GSMM. We applied GSMM to our experiment data on three major immune cell types (CD4, CD8, and antibody-secreting cells) involved in adaptive responses against influenza virus infection in mice. The results suggest several interesting and novel characteristics of immune cell migration heterogeneity and the linkage between cell phenotype and proliferation.

Date: April 25, 2014, 12:00 - 13:00

Speaker: Alexander Petroff, Rockefeller University

Title: Hydrodynamics and collective behavior of the tethered bacterium Thiovulum majus

Abstract: The ecology and dynamics of many microbial systems are shaped by how bacteria respond to evolving nutrient gradients and microenvironments. Here we show how the response of the sulfur-oxidizing bacterium Thiovulum majus to changing oxygen gradients cause cells to organize into large-scale fronts. We show that these dynamics occur in two steps. First, chemotactic cells moving up the oxygen gradient form a front that propagates with constant velocity. We then show, through observation and mathematical analysis, that this front becomes unstable to changes in cell density. Random perturbations in cell density create oxygen gradients, which lead to the formation of millimeter-scale fluid flows. We argue that this flow results from a nonlinear instability excited by stochastic fluctuations in the density of cells. These results provide a mathematically tractable example of how collective phenomena in ecological systems can arise from the individual response of cells to a shared resource.

Date: May 2, 2014, 12:00 - 13:00

Speaker: Joy Zhou, Mathematical Biosciences Institute, Ohio State

Title: Range shifts under climate change: what will accelerated warming do?

Abstract: Rapid climate warming has caused species across the globe to shift their geographic ranges poleward in latitude or upward in elevation. We naturally ask: will species be able to keep up with climate warming? To answer this question, I considered a mathematical model for a single-species population with distinct growth and dispersal stages. I incorporated climate warming by letting the niche curve, a curve describing environmental suitability for population growth on a spatial gradient, shift in one direction. The model can prescribe climate-warming scenarios and environmental heterogeneity in a versatile way. I compared different warming scenarios, and in this talk I will show that acceleration of climate warming imposes extra burden on the species.