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MAY 1, 2007
APS Contact
Christine Guilfoy
Office: (301) 634-7253
cguilfoy@the-aps.org
Newsroom Opens at 12:00 p.m.
Saturday April 28
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APS Press Room: (202) 249-4174
The Eyes Have It: The Eye
Muscles, Those Go-Getters Of The Anatomical World,
May Provide Clues To Muscular Dystrophy, Myasthenia Gravis
Washington — The eye, often called the window to
the soul, may become a window to the mysteries of muscular dystrophy, a
debilitating muscle disease that often leads to death in early adulthood.
Physiologists are intrigued that muscular dystrophy
spares a few muscles of the body -- notably the vocal cords, some muscles of
the pelvic region and the eye muscles. What is it that allows these muscles
to escape the effects of this deadly disease while other skeletal muscles
are so profoundly affected? At the same time, the eye muscles fall prey to
diseases that do not affect other skeletal muscles. Why?
These are some of the intriguing questions that four
eye muscle experts will explore at the symposium, “Ultra fast and ultra
active: the strange life of the extraocular muscles.” The symposium will
take place at the 120th annual meeting of
The American Physiological Society
(APS), which coincides with Experimental Biology 2007. The
session will be held at 10:30 a.m., Tuesday, May 1 in Room 147A of the
Washington Convention Center.
“We think that by learning what makes these muscles
unique, we will understand why they are spared by some neuromuscular
diseases and targeted by others,” said Francisco H. Andrade, Ph.D., who will
lead the symposium. “These insights will lead, in turn, to better treatment
options for these diseases.”
The speakers, who are among only a handful of experts
on the topic in the U.S., are Linda K. McLoon, Ph.D., a professor at the
University of Minnesota, Minneapolis; Francisco H. Andrade, Ph.D. an
associate professor at the University of Kentucky College of Medicine,
Lexington; Henry J. Kaminski, M.D. the chairman of the neurology and
psychiatry department at the St. Louis University School of Medicine, St.
Louis, Missouri; and Stephen J. Goldberg, Ph.D., a professor (now retired)
at Virginia Commonwealth University, Richmond. Andrade will also lead the
symposium.
On the go
The extraocular muscles are the six small muscles that
move each eye from side to side, up and down and on the slant. When these
muscles don’t work together, it can affect vision. One condition that can
arise when these muscles don’t work together is strabismus, a condition that
affects about 5% of children and arises when the eye muscles don’t work
together properly. This leads to “lazy eye,” in which one eye takes over all
the vision duties. If strabismus is not treated, it results in functional
blindness.
A defining characteristic of these tiny muscles is that
they are nearly always moving, even during sleep. In fact, even when
“staring” at a fixed object, the eyes keep moving over the image. Although
these muscles are very small, they use a lot of energy because they are
always on the go.
And that is a key to Dr. Andrade’s presentation,
“Always active, always hungry: the metabolic design of the extraocular
muscles.” The cells that make up the extraocular muscles contain more
mitochondria, the energy manufacturing structures in all cells, than other
skeletal muscles, such as those of the limbs. This rich population of
mitochondria allows the muscles to keep moving the eye. On the other hand,
this leaves the eye muscles vulnerable to diseases that target the
mitochondria, such as Kearns-Sayre syndrome, a condition that gradually
limits eye movements and eventually immobilizes them completely.
Dr. McLoon will discuss “Dynamic cell biology of
the extraocular muscles.” She looks at satellite cells, a type of cell
involved in muscle growth and injury repair. The extraocular muscles are
richer in satellite cells than the skeletal muscles of the limbs. There is
evidence that eye muscles regenerate much faster than skeletal muscle of the
limbs. This may be a key to why the eyes have a greater ability to withstand
the onslaught of muscular dystrophy. Another very important aim of Dr.
McLoon’s research is to find new drugs to treat strabismus.
Dr. Kaminski will talk about the “Differential
involvement of extraocular muscle by neuromuscular disease.” His work
focuses on myasthenia gravis, an autoimmune disease which disrupts
communication between muscles and nerves. The illness particularly affects
the eye muscles, causing drooping eyelids and double vision. Dr. Kaminski
focuses on the eye’s immune environment. He looks at what role this plays in
the eye muscles’ vulnerability to myasthenia gravis. If this process can be
better understood, it could eventually lead to new treatments. His research
also has implications for Graves disease, an auto-immune thyroid disorder in
which the extraocular muscles get enlarged causing the eyes to bulge out.
Dr. Goldberg will speak on “Eye muscle motor
units: a petite illumination.” His laboratory investigates the motor neurons
of the brainstem which are involved in tongue and eye movements. (When a
doctor asks a patient to follow his or her finger, the patient’s brainstem
functioning is being tested.) This research has applications to strabismus.
When rats have strabismus, they can later recover vision in both eyes, but
humans permanently lose the ability to have normal vision. This finding has
been a tantalizing one for physiologists, who want to find out how rats
manage to recoup their vision. The hope is to find out how this can be
applied to humans.
***
To
schedule an interview with one of the presenters, please e-mail
Christine Guilfoy or call her at (301) 634-7253, prior to
April 28. During the conference, please call the APS press room at (202)
249-4174.
Please
click here for the APS program at Experimental Biology 2007.
Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease. The American Physiological Society has been an
integral part of this scientific discovery process since it was established
in 1887.
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