• Anna Lin
• Eric Monson
• Brad Marts
• Zheng Gao

Eric E. Monson, Ph.D.

Neuron-Glia Interactions & Signaling

Neurons are essential dynamics elements within the brain, but glial cells (the other brain cells), account for 90% of the cells in our heads. Historically they were thought to only play a supporting role in development, chemical cleanup and structural support for neurons (glia means glue). This relatively passive role was the common understanding because glia are not electrically excitable like neurons. In the past decade, though, with the advent of sensitive, fluorescent ion-sensing molecules, many researchers have observed glial cell excitations in the form of calcium reaction-diffusion waves, which can travel across a cell and even between multiple cells. The most interesting and potentially important part of this activity is that these waves can be triggered by local synaptic (neuron) activity, and when the waves terminate, the glial cells release chemicals which can affect nearby neurons. This sets up a situation in which glial cells are not just passive helper cells, but instead, an active element in a two-way communication with neurons. Neurobiologists are slowly gaining a greater understanding of the details of neuron/glial cell interactions, such as the many chemicals involved, but the function of this cross-talk is still poorly understood.

Most of the research so far in this field has been done on a single, or few, cell basis. But, in the brain, the important dynamics are surely properties of networks, which may have emergent properties not evident by studying the individual elements of the system. So, it is in studying the spatio-temporal dynamics of these type of active networks that we as physicists can bring important tools and understandings. Quantitative analytical techniques, along with nonlinear dynamics concepts and tools may lead to new insights into the function of glial cells in active brain networks.

Specifically, we are performing experiments on rat hippocampal cell cultures (supplied by the Ehlers lab, Duke Neurobiology). Microscopy of cells loaded with fluorescent, calcium-sensitive dyes, give us movies of both neuron and glial cell activity. This spontaneous or stimulated activity is then quantified using various image processing and dimensionality reduction techniques to give us insight into the system's behavior patterns. One particulary intriguing aspect of these dynamics are the separation of timescales involved. Information is transmitted in neurons with velocities near 1 m/s, while in glial cells, calcium waves propagate around 10 µm/s. What patterns of activity can be supported by the neural system while it's communicating with the glial cells which couldn't exist without them? Answers to questions like this will hopefully bring us closer to an understanding of the role of glial cells in brain processes such as cognition and memory.

My background includes an S.B. from MIT in Physics, with some Electrical Engineering. I then moved on to the Univeristy of Michigan, where I got my Ph.D. in Applied Physics. During my time there I did some work in Biophysics, while the bulk of my research was conducted in the lab of Raoul Kopelman in Chemistry. My projects involved many forms of scanned-probe, electron and conventional optical microscopy, work with novel fluorescent chemical sensors, and experiments and simulations of non-classical reaction kinetics. As a postdoc at Michigan I oversaw many aspects of our NCI UIP contract for noninvasive cancer detection and therapy.

Curriculum Vitae

Publications

Journal Articles

Catllá, A.J., Schaeffer, D.G., Witelski, T.P., Monson, E.E. & Lin, A.L., "On Spiking Models for Synaptic Activity and Impulsive Differential Equations", SIAM Review (submitted).

Horton, A.C., Rácz, B., Monson, E.E., Lin, A.L., Weinberg, R.J. & Ehlers, M.D. (8 Dec 2005) Polarized Secretory Trafficking Directs Cargo for Dendrite Growth and Morphogenesis. Neuron 48, 757-771.

Monson, E. & Kopelman, R. (2004) Non-Classical Kinetics of an Elementary A + B -> C Reaction-Diffusion System Showing Effects of a Speckled Initial Reactant Distribution and Eventual Self-Segregation: Experiments. Phys. Rev. E, 69 (2), 021103.

Xu, H., Yan, F., Monson, E.E. & Kopelman, R. (2003) Room-temperature preparation and characterization of poly (ethylene glycol)-coated silica nanoparticles for biomedical applications. J. Biomed. Mater. Res. Part A, 66A, 870-879.

Moreno, M.J., Monson, E., Reddy, R.G., Rehemtulla, A., Ross, B.D., Philbert, M., Schneider, R.J. & Kopelman, R. (2003) Production of singlet oxygen by Ru(dpp(SO3)(2))(3) incorporated in polyacrylamide PEBBLES. Sens. Actuator B-Chem., 90, 82-89.

Sumner, J.P., Aylott, J.W., Monson, E. & Kopelman, R. (2002) A fluorescent PEBBLE nanosensor for intracellular free zinc. Analyst, 127, 11-16.

Kerner, N.K., Black, B., Monson, E. & Meeuwenberg, L. (2002) Training Instructors to Facilitate Collaborative Inquiry. J. Student Centered Learning, 1, 29-36.

Monson, E. & Kopelman, R. (2000) Observation of laser speckle effects and nonclassical kinetics in an elementary chemical reaction. Phys. Rev. Lett., 85, 666-669.

Clark, H.A., Barker, S.L.R., Brasuel, M., Miller, M.T., Monson, E., Parus, S., Shi, Z.Y., Song, A., Thorsrud, B., Kopelman, R., Ade, A., Meixner, W., Athey, B., Hoyer, M., Hill, D., Lightle, R. & Philbert, M.A. (1998) Subcellular optochemical nanobiosensors: probes encapsulated by biologically localised embedding (PEBBLEs). Sens. Actuator B-Chem., 51, 12-16.

Merritt, G., Monson, E., Betzig, E. & Kopelman, R. (1998) A compact near-field scanning optical microscope. Ultramicroscopy, 71, 183-189.

Merritt, G., Monson, E., Betzig, E. & Kopelman, R. (1998) A compact fluorescence and polarization near-field scanning optical microscope.
Rev. Sci. Instrum., 69, 2685-2690.

Lin, A.L., Monson, E. & Kopelman, R. (1997) Nonclassical dimension-dependent kinetics of a photobleaching reaction in a focused laser beam ''phototrap''.
Phys. Rev. E, 56, 1561-1566.

Shortreed, M., Monson, E. & Kopelman, R. (1996) Lifetime enhancement of ultrasmall fluorescent liquid polymeric film based optodes by diffusion-induced self-recovery after photobleaching. Anal. Chem., 68, 4015-4019.

Monson, E., Merritt, G., Smith, S., Langmore, J.P. & Kopelman, R. (1995) Implementation of an NSOM System for Fluorescence Microscopy. Ultramicroscopy, 57, 257-262.

Book Chapters

Monson, E., Brasuel, M., Philbert, M.A. & Kopelman, R. (2003) PEBBLE Nanosensors for in vitro Bioanalysis. In Vo-Dinh, T. (ed.) Biomedical Photonics Handbook. CRC Press, Boca Raton, FL, pp. 59.1-59.14.

Brasuel, M., Kopelman, R., Philbert, M.A., Aylott, J.W., Clark, H.A., Kasman, I., King, M., Monson, E., Sumner, J.P., Xu, H., Hoover, M., Miller, T.J. & Tjalkens, R. (2002) PEBBLE Nanosensors for Real Time Intracellular Chemical Imaging. In Ligler, F., Rowe-Tait, C. (eds.) Optical Biosensors: Present and Future. Elsevier, Amsterdam, pp. 407-536.

Conference Proceedings

Xu, H., Yan, F., Monson, E., Tang, W., Kopelman, R., Schneider, R.J. & Philbert, M.A. (2002) Preparation and Characterization of Poly(ethylene-glycol)-Coated Stober Silica Nanoparticles for Biomedical Applications SPIE (Int. Soc. Opt. Eng.), pp. 383-393.

Horvath, T., Monson, E., Sumner, J.P., Xu, H. & Kopelman, R. (2002) Use of Steady-State Fluorescence Anisotropy with PEBBLE Nanosensors for Chemical Analysis SPIE (Int. Soc. Opt. Eng.), pp. 486-492.

Monson, E. & Kopelman, R. (2001) Observation of Laser Speckle Effects in an Elementary Chemical Reaction. In Drake, J.M., Klafter, J., Levitz, P.E., Urback, M. (eds.) Materials Research Society Symposium, Boston, MA, pp. T7.27.21-T27.27.26.

Monson, E., Lin, A.L. & Kopelman, R. (1996) The anomalous diffusion-limited reaction kinetics of a phototrapping reaction Materials Research Society Symposium, Boston, MA.

Kopelman, S.R., Bakker, E., Monson, E., Merritt, G., Rosenzweig, Z., Shortreed, M., Parus, S., Smith, S., Fox, T., Song, A., Tan, W., Chen, Y. & Shi, Z.Y. (1995) Ultra-Small Fiberoptic Chemical and Biochemical Sensors.
Abstr. Pap. Am. Chem. Soc., 210, 13-MTLS.

Patents

Anker, J., Monson, E., Kopelman, R. & Philbert, M. (2003) Modulated Chemical Sensors. Patent Application No. 10/419,033, Regents of the University of Michigan, USA.

Kopelman, R., Clark, H.A., Monson, E., Parus, S., Philbert, M. & Thorsrud, B. (2002) Optical fiberless sensors. US Patent No. 6,379,955, Regents of the University of Michigan, USA.

Kopelman, R., Clark, H.A., Monson, E., Parus, S., Philbert, M. & Thorsrud, B. (2000) Optical fiberless sensors for analyzing cellular analytes.
US Patent No. 6,143,558, Regents of the University of Michigan, USA.

Ph.D. Thesis

Monson, E.E. (1999) Nano-scale spatial and temporal fluorescence fluctuations in near-field microscopy, photobleaching recovery, and non-classical elementary reaction kinetics Applied Physics. University of Michigan, Ann Arbor, MI, USA.