EMBARGOED FOR RELEASE UNTIL
APRIL 29, 2007
APS Contact
Christine Guilfoy
Office: (301) 634-7253
cguilfoy@the-aps.org
Newsroom Opens at 12:00 p.m.
Saturday April 28
APS Newsroom
East Registration Area
Washington Convention Center
APS Press Room: (202) 249-4174
Breathing Easy: When It Comes To Oxygen, A Bug’s Life Is Full Of It
Washington — Because of new imaging technology,
researchers are getting a better understanding of a physiological paradox:
how insects, which have a respiratory system built to provide quick access
to a lot of oxygen, can survive for days without it.
The insect respiratory system is so efficient that
resting insects stop taking in air as they release carbon dioxide, according
to research by Stefan K. Hetz of Humboldt University in Berlin, Germany.
This allows them to keep oxygen and carbon dioxide levels in balance. Too
great a concentration of oxygen is toxic, causing oxidative damage to the
insect’s tissues, just as it does in humans.
Hetz is one of four speakers at the upcoming symposium
“Respiratory control in insects: integration from the gene to the organism.”
The symposium, sponsored by The American Physiological Society (APS)
takes place 10:30 a.m., Sunday, April 29 during the APS annual
meeting at Experimental Biology 2007 in Room 147A, the
Washington Convention Center in Washington, D.C. Scott Kirkton of Union
College, Schenectady, New York, will lead the symposium of four speakers.
Why bugs don’t pant
Bees consume large amounts of oxygen, and so it might
be tempting to think they are panting – tiny inaudible pants. They are not,
because they do not breathe through noses or mouths. Instead, insects draw
in oxygen through holes in their bodies known as spiracles and pump the
oxygen through a system of increasingly tiny tubes (tracheae) that deliver
oxygen directly to tissues and muscles. Insects typically have a pair of
spiracles for each thoracic and abdominal segment.
The same tubes that transport oxygen into the insect
body usher out carbon dioxide. Insects use different methods to release
carbon dioxide, including opening the thoracic spiracles (the ones closest
to the head) to take in oxygen while exhaling carbon dioxide through the
abdominal spiracles. Insects also use different mechanisms to pump the
oxygen to the tissues.
This system is much more efficient than the system that
vertebrates evolved. Insects deliver much greater volumes of oxygen, in
proportion to their size, than do mammals. They also deliver oxygen
directly to the tissues, while vertebrates dissolve oxygen in blood,
transport it to tissues, and then reconvert the oxygen to usable form.
Live action footage
Because insects take in oxygen through spiracles which
they open and close as needed, and because they can take in a large store of
oxygen, they can live a long time without breathing by closing their
spiracles and curbing their activity.
“Insects are able to survive hypoxic environments,”
explained Kirkton, the symposium chairman. “They can shut down and survive
for hours or days. They have a low metabolic rate and can close their
spiracles. If you compare Lance Armstrong, the bee and the hummingbird, the
bee is the champion of oxygen delivery,” he said. But at the same time,
insects can survive low levels of oxygen for a comparatively long time.
Researchers have been interested in the insect tracheal
respiratory system since 1911 when August Krogh researched moths and
grasshoppers. Krogh’s interest in oxygen delivery led him later to study
blood perfusion in mammalian capillaries, for which he was awarded the Nobel
Prize in 1920. But the advent of synchrotron x-rays, an advanced form of
x-ray scan, has recently allowed scientists to learn much more about how
insects breathe. The new imaging technology allows scientists to observe the
respiration of live bugs.
This advance in technology also comes at a time when
physiologists are learning more about the genes that control breathing. When
physiologists gather at the symposium, they will assess these new
developments and consider a roadmap for future research, said Kirkton.
The symposium, which is also sponsored by the
London-based Journal of Physiology, will feature the following
speakers:
Gabriel Haddad, of the University of California,
San Diego, will speak on the “Genetic basis for hypoxia tolerance in
Drosophila melanogaster.” Haddad is interested in the ability of drosophila
(fruit fly), to survive periods of hypoxia, that is, periods of insufficient
oxygen supply. He is examining the role the fruit fly’s genes play in the
ability of its nerve cells to remain healthy even under hypoxic conditions.
The research aims to lead to better ways to protect humans who suffer
periods of hypoxia due to medical emergency or accidents.
Mark Krasnow, of the Stanford University School
of Medicine, Palo Alto, California, will speak on “Developmental responses
to hypoxia in the insect tracheal system.” Krasnow has studied the
development of the tracheal system in the embryo fruit fly, noting how cells
form into trachea, and how trachea branch to smaller trachea and eventually
connect to form the tracheal network. His laboratory, which has identified
more than 50 genes controlling various aspects of airway development, has
also studied how oxygen-starved cells behave in developing airways.
Krasnow’s laboratory is also investigating the development of the mammalian
lung using mice. The work is aimed at learning more about human lung
diseases and developing ways to reactivate lung development to restore
diseased tissue.
Stefan Hetz, Humboldt University, Berlin,
Germany, will talk on “Spiracular control of tracheal gases in insects.”
Hetz and his colleagues, noting that some insects close their spiracles
during rest, have concluded that the insects’ respiratory system is designed
to deliver large amounts of oxygen while they are active. The drawback is
that, when they are at rest, this level of oxygen is toxic, he has
theorized. Insects close their spiracles during rest to avoid an overdose of
oxygen, which can result in the production of free radicals which cause
tissue damage, he has said. His work could have applications to insect
control in agriculture.
Jake Socha, Argonne National Laboratory,
Chicago, and the University of Chicago will discuss “Control of internal
convection in beetles using active tracheal compression.” Socha, a
biophysicist, is best known to the public for his work on “flying” snakes.
He has used synchrotron x-rays to view working tracheal tubes and air sacs
in living insects that give further clues to how the system works. Insects
employ autoventilation (using wings or legs to pump air through the body),
abdominal pumping (using the muscles in the abdomen to pump air), and
tracheal compression (getting oxygen to the head and thorax).
***
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.
|
