ReSource, Volume 13, 2001 Page: 22
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"These fish are actually trained to exer-
cise by swimming against currents of vari-
ous speeds during their development," says
Brian Bagatto, Ph.D., who just completed
his degree in biology at UNT.
"Looking at the cardiovascular systems
of active and non-active fish, we noted
hearts became more efficient at pumping
blood in active fish," says Bagatto. "This is
because exercise causes lowered oxygen
levels in the growing fish."
UNT researchers will attempt to discover
why lowered oxygen levels in developing
fish produce healthier hearts, while lowered
oxygen rates in developing human babies
seem to have detrimental effects. Bagatto
notes that a human fetus has a lowered
oxygen level when the mother smokes.
The incubation room of
the lab houses eggs of
animals with hearts simi-
lar to human hearts.
Researchers study the
of zebra fish, trained to
exercise by swimming
against currents of
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Although the researchers will conduct
more aquatic studies about low oxygen lev-
els in embryonic hearts, they have already
formed important conclusions about heart
For example, they determined there is
a "critical window" in development when
swimming exercise is most effective in
changing a growing heart. Therefore, they
conclude exercise before or after this "criti-
cal window" has little effect.
Knowing at what point in development
these critical windows occur can provide
insight into how environmental factors may
influence human fetal development.
Like the hearts of the zebra fish, hearts
in the eggs of emus, chickens, quail and
snakes are very similar to human hearts in
their early stages of development. All these
types of eggs are nurtured at one time or
another in the incubation room.
Burggren selects the emu eggs for their
large size and ease of examination. Snake
eggs are chosen because they can absorb
moisture in dry regions. They may provide
valuable information about how life develops
with low water reserves.
More information about hearts is collected
in the experimental room of Burggren's lab.
Like a television studio, it is wired for lights,
camera and action. In this room, Burggren
and his colleagues can view individual red
blood cells in an animal as small as a larval
fish or as large as an emu embryo.
Equipped with the latest in computer
imaging, this lab room includes a bank of
microscopes that serve different purposes. An
inverted microscope allows a specimen to be
viewed from underneath. Another microscope
is attached to a light-sensitive camera and a
computer. The device enables UNT scientists
to view an embryonic fish's entire cardiovas-
cular system at one time. Photographs trace
the paths of its tiny red blood cells.
Burggren can videotape the beating heart
of an intact, undisturbed fish embryo through
a transparent egg to calculate the amount of
blood squeezed out of the heart with each
beat. He illuminates a translucent egg, which
exposes blood circulating through veins. He
can then determine the amount of oxygen in
the blood by looking at the intensity of color
- a bright red indicates more oxygen than a
With a different bank of instruments,
researchers can view the developing hearts
in larger animal eggs. Burggren can measure
blood flow in an emu egg, which weighs
nearly one and one-half pounds.
"Actually, in many ways emu embryos are
just like chick embryos and just like zebra
fish embryos early in development," says
Burggren. "We use them, in part, because
they are large."
Large embryos are better suited for some
experiments because their entire, intact car-
diovascular systems are easier to observe.
Other experiments focus on smaller
embryos because they fit more easily under
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University of North Texas. ReSource, Volume 13, 2001, periodical, 2001; Denton, Texas. (digital.library.unt.edu/ark:/67531/metadc29774/m1/22/: accessed April 27, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting University Relations, Communications & Marketing department for UNT.