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Rick T. Mathias, Professor
email: Richard.Mathias@Stonybrook.edu
recent publications from the Lab...
He is recording the frequency domain impedance of an intact lens. Microelectrodes are used to inject random current into one cell and the record voltage in other cells at various locations. A Fast Fourier Analyzer determines the impedance in real time. This technology is used in connection with modern genetics that produces mice lacking specific lens membrane proteins, "knock outs". The impedance technology determines the effect of a "knock out" on the electrical properties of the lens.
He is using the whole cell patch clamp technique to determine membrane transport properties of cells isolated from guinea pig hearts. A glass pipette is sealed to the cell, then the underlying membrane ruptured to allow diffusion from pipette to cell. This allows control of the chemical composition and the voltage within the cell. The membranes of these cells contain a variety of transport proteins. There are ion channels, that allow electrodiffusion of specific ions, ion pumps, that use the energy stored in ATP to pump specific ions against their electrochemical gradient and exchange transporters that use the energy in the electrochemical gradient for one ion to exchange transport a second ion. The patch clamp is used to determine the role of each protein in the electrical activity of the heart.
She is using the whole cell patch clamp technique to study the transport properties of isolated lens epithelial cells. The lens is composed of two types of cells: fiber cells make up the mass and epithelial cells cap the front hemisphere. We mechanically separate these two classes of cells and isolate the epithelial cells for patch clamp analysis. We have been unable to isolate individual fiber cells so we instead identify and clone specific fiber cell membrane proteins and study their function in the oocyte expression system. For the epithelial cells. however, we can directly measure the transport properties of membrane ion channels, pumps and exchange transporters. These proteins help establish standing ionic currents and fluid movement that circulate through the normal lens. We are interested in how these fluxes are generated and their role in homeostasis.
He is measuring the rate of volume change of membrane vesicles when the external osmolarity is abruptly changed. Images of the vesicle are saved using digital video microscopy and later analyzed to determine the water permeability of the membrane. Vesicles are made from cell membrane extracted from normal and "knock out" mouse lenses. This allows us to determine which proteins are involved in membrane water transport.
She is carrying out biochemistry measurements of lens connexins and aquaporins. Site directed mutagenesis, along with RT-PCR, heterologous expression and immunohistochemistry are used to evaluate lens connexins and the membrane proteins involved in membrane water transport.
He is using the dual two electric voltage clamp (Dual TEV) setup to study coupling between Xenopus laevis oocytes expressing connexins. This technique allows to study the pH regulation of the lens gap junction proteins connexin 46 and Connexin 50. This technology is used in connection with impedance studies in the intact lens to asses the coupling of the lens fibers in mice lacking specific lens membrane proteins, "knock outs" and "knock ins".
Graduate Student
Graduate Student
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Professor
Mathias with project assistant Abha Kochhar. Research in biophysics seeks physical insights into how cells and tissues
perform their marvelous repertory of functions, with the ultimate goal to better the
health of mankind. In our lab, research is directed toward understanding two health
problems: the formation of cataracts in the elderly and cardiac arrhythmias that can lead
to sudden death. Though these sound completely unrelated to one another or to biophysical
properties, our work suggests both are related to membrane transport proteins, membrane
voltage and ionic current flow from cell to cell. My early work was on the voltage
distribution and 3-dimensional current spread in a multi-cellular tissue. Because of my
undergraduate and graduate education in the physical sciences and mathematics, I found
this a fascinating problem that started me on a career of biomedical research. Maxwell's
classical equations relating charge and voltage provide part of the picture but ions move
about by diffusion and convection as well as conduction, so the equations of
thermodynamics, describing the coupling of these driving forces to ion fluxes, also apply.
What I found most striking, however, was the degree of control evolution has over the
pattern of flow. The geometry of the cells, the interconnection between cells and the
specific membrane transport proteins in local groups of cells provide enormous
flexibility. In the last 10 years, we have focused on the roles of specific membrane
proteins that generate and direct fluxes of ions, water or neutral solutes.
