John Peter Wikswo, Jr. (born October 6, 1949) is a biological physicist at
Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
. He was born in
Lynchburg, Virginia,
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
.
Wikswo is noted for his work on
biomagnetism and
cardiac electrophysiology
Cardiac electrophysiology is a branch of cardiology and basic science focusing on the electrical activities of the heart. The term is usually used in clinical context, to describe studies of such phenomena by invasive (intracardiac) catheter recor ...
.
Graduate school
In the 1970s, Wikswo was a graduate student at
Stanford University, where he worked under physicist
William M. Fairbank, studying
magnetocardiography
Magnetocardiography (MCG) is a technique to measure the magnetic fields produced by electrical currents in the heart using extremely sensitive devices such as the superconducting quantum interference device (SQUID). If the magnetic field is mea ...
.
Biomagnetism
In 1977 he became an assistant professor in the Department of Physics and Astronomy at
Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
, where he set up a laboratory to study living state physics. In 1980, he made the first measurement of the magnetic field of an isolated nerve, by threading the a frog sciatic nerve through a wire-wound, ferrite-core toroid and detecting the induced current using a
SQUID magnetometer.
At the same time, Wikswo and Ken Swinney calculated the magnetic field of a nerve axon.
This work was followed a few years later by the first detailed comparison of the measured and calculated magnetic field produced by a single nerve axon.
In a related line of study, Wikswo collaborated with Vanderbilt Professor John Barach to analyze the information content of biomagnetic versus bioelectric signals.
Cardiac electrophysiology
One of Wikswo's most important contributions to science is his work in cardiac electrophysiology. In 1987 he began collaborating with doctors at the Vanderbilt Medical School, including Dan Roden, to study electrical propagation in the dog heart.
These studies led to the discovery of the virtual cathode effect in cardiac tissue: during electrical stimulation, the action potential wave front originated farther from the electrode in the direction perpendicular to the myocardial fibers than in the direction parallel to them.
In parallel with these experimental studies, Wikswo analyzed the virtual cathode effect theoretically using the
bidomain The bidomain model is a mathematical model to define the electrical activity of the heart. It consists in a continuum (volume-average) approach in which the cardiac mictrostructure is defined in terms of muscle fibers grouped in sheets, creating a ...
model, a mathematical model of the electrical properties of cardiac tissue that takes into account the anisotropic properties of both the intracellular and extracellular spaces. He first used the bidomain model to interpret biomagnetic measurements from strands of cardiac tissue.
Wikswo realized that the property of unequal anisotropy ratios in cardiac tissue (the ratio of electrical conductivity in the directions parallel and perpendicular to the myocardial fibers is different in the intracellular and extracellular spaces) has important implications for the magnetic field associated with a propagating action potential wave front in the heart. With Nestor Sepulveda, Wikswo use the
finite element method
The finite element method (FEM) is a popular method for numerically solving differential equations arising in engineering and mathematical modeling. Typical problem areas of interest include the traditional fields of structural analysis, heat ...
to calculate the distinctive fourfold symmetric magnetic field pattern produced by an outwardly propagating wave front.
Unequal anisotropy ratios has even an even greater impact during electrical stimulation of the heart. Again using the finite element model, Wikswo, Roth and Sepulveda predicted the
transmembrane potential distribution around a unipolar electrode passing current into a passive, two-dimensional sheet of cardiac tissue.
They found that the region of
depolarization
In biology, depolarization or hypopolarization is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolarization is ess ...
under a
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in wh ...
extends farther in the direction perpendicular to the fibers than parallel to the fibers, a shape that Wikswo named the dog-bone. This prediction immediately explained the virtual cathode effect found experimentally in the dog heart; they were observing the dog-bone shaped virtual cathode. Later simulations using an active, time-dependent bidomain model confirmed this conclusion.
The calculation of the transmembrane potential by a unipolar electrode resulted in another prediction: regions of hyperpolarization adjacent to the cathode in the direction parallel to the myocardial fibers. Reversal of the stimulus polarization provided a mechanism for anodal stimulation of cardiac tissue. In order to test this prediction experimentally, Wikswo mastered the technique of optical mapping using
voltage sensitive dyes
Voltage-sensitive dyes, also known as potentiometric dyes, are dyes which change their spectral properties in response to voltage changes. They are able to provide linear measurements of firing activity of single neurons, large neuronal population ...
, allowing the measurement of transmembrane potential using optical methods. With Marc Lin, Wikswo made high resolution measurements of excitation following stimulation through a unipolar electrode in a rabbit heart, and confirmed four mechanisms of electrical stimulation—cathode make, cathode break, anode make, and anode break—that had been predicted by bidomain calculations.
(Cathode and anode refer to the polarity of the stimulus, and make and break indicate if the excitation occurred following the start or end of the stimulus pulse.) Later experiments using this technique led to the prediction of a new type of
cardiac arrhythmia
Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...
, which Wikswo named
quatrefoil reentry.
SQUID magnetometers
In the 1990s, Wikswo began developing high spatial resolution SQUID magnetometers for mapping the magnetic field, to use in both biomagnetic studies and in non-destructive testing.
As is characteristic of Wikswo's work, he simultaneously developed theoretical methods to image a two-dimensional current density distribution from magnetic field measurements.
VIIBRE
In the first two decades of the 21st century, Wikswo's research has emphasized the development and application of micro- and nano-scale devices for instrumenting and controlling single cells.
In 2001 he founded the Vanderbilt Institute for Integrative Biosystems Research and Education (VIIBRE) to foster and enhance interdisciplinary research in the biophysical sciences and bioengineering at Vanderbilt. Wikswo refocused his research on
systems biology, building microfabricated devices for measuring cellular properties and developing mathematical models of cellular signaling. He has designed
organ-on-a-chip
An organ-on-a-chip (OOC) is a multi-channel 3-D microfluidic cell culture, integrated circuit (chip) that simulates the activities, mechanics and physiological response of an entire organ or an organ system, a type of artificial organ. It cons ...
devices containing small populations of cells to fill the gaps between cell cultures and animals models, for use in
pharmacology and
toxicology
Toxicology is a scientific discipline, overlapping with biology, chemistry, pharmacology, and medicine, that involves the study of the adverse effects of chemical substances on living organisms and the practice of diagnosing and treating e ...
. This work led to a second R&D 100 Award for the MultiWell MicroFormulator, which delivers and removes cell culture media to each of the 96 wells of a
microwell plate
A microplate, also known as a microtiter plate (''Microtiter'' is a registered trademark in the United States, therefore it should not be used generically without attribution), microwell plate or multiwell, is a flat plate with multiple "wells" ...
for toxicology research.
Other positions
He also serves on the scientific advisory boards of Hypres Inc. and CardioMag Imaging Inc.
"Executive Profile: John P. Wikswo Ph.D."
Bloomberg Businessweek, accessed 2014-01-21.
Brief curriculum vitae
* 1970 B.A., Physics, University of Virginia
The University of Virginia (UVA) is a public research university in Charlottesville, Virginia. Founded in 1819 by Thomas Jefferson, the university is ranked among the top academic institutions in the United States, with highly selective ad ...
* 1973 M.S., Physics, Stanford University
* 1975 Ph.D., Physics, Stanford University
* 1975-1977 Research Fellow in Cardiology, Stanford University School of Medicine
* 1977-1982 Assistant Professor of Physics, Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
* 1982-1988 Associate Professor of Physics, Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
* 1988–present Professor of Physics, Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
* 2001–present Gordon A. Cain University Professor, Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
* 2001–present Professor of Biomedical Engineering, Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
* 2001–present Professor of Molecular Physiology and Biophysics, Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
* 2001–present Director, Vanderbilt Institute for Integrative Biosystems Research and Education
* 2005–present A.B. Learned Professor in Living State Physics, Vanderbilt University
Vanderbilt University (informally Vandy or VU) is a private research university in Nashville, Tennessee. Founded in 1873, it was named in honor of shipping and rail magnate Cornelius Vanderbilt, who provided the school its initial $1-million ...
Awards
References
Further reading
*
*
*
*
*
*
External links
VIIBRE website
List of Wikswo's publications
TEDx talk about Systems Biology
{{DEFAULTSORT:Wikswo, John Peter
1949 births
Living people
Stanford University alumni
21st-century American physicists
Vanderbilt University faculty
University of Virginia alumni
Fellows of the American Physical Society