 Ocean
Watch
Friday, December 27, 2002
Zebrafish can regrow
parts of their hearts
I recently read about a study showing that zebrafish
can regenerate missing parts of their hearts. Researchers anesthetized 10
of these 1- to 2-inch-long fish, removed 20 percent of their hearts and
then returned the little patients to their tanks.
Eight fish survived this radical surgery and in 10 days
began swimming normally. Two months later, scientists examined the hearts
of these test fish and found they had totally regrown the removed parts
with almost no scarring.
Although many questions remain, this discovery is
exciting to those in the field of regenerative medicine.
But I had my own question about this study: What the
heck is a zebrafish?
A zebrafish, I discovered, is a black-and-silver
striped fish sold in pet shops for freshwater aquariums. Zebrafish, also
called Brachydanio rerio, are natives of India but are easy to breed. U.S.
supply houses raise them by the bucketful for home aquariums and research
labs.
Aquarium owners like zebrafish because they are pretty,
hardy and inexpensive. These fish are good starters for someone setting up
a first aquarium.
But besides making good pets, these little fish are
extremely useful as research animals and teaching aids.
Because zebrafish eggs are transparent, teachers use
this species to study biology. Students can learn how structures and
functions change during embryo development simply by watching.
Researchers like working with zebrafish for several
reasons. One is that these fish carry about 85 percent of the genes
present in humans. Studies using these fish may, therefore, help create
treatments for human ailments.
Zebrafish genes are also famous among scientists for
being easy to mutate or delete, thus making those gene functions easier to
analyze. You can imagine the types of mutations induced by some of the
names given the resulting fish: speed bump, zombie, ogre, lost-a-fin,
piggy tail, snow white, sleepy, Cyclops and Van Gogh.
One zebrafish was named Dracula because it died when
exposed to light. Scientists learned that an enzyme deficiency made the
fish's red blood cells so sensitive to light, they popped. Studies on the
Dracula zebrafish may help humans who have similar enzyme deficiencies,
called porphyrias.
One researcher is breeding zebrafish with fluorescent
organs. These see-through fish can have bright green nerves, blood,
pancreas or any other organ someone wants to study.
Other scientists have bred zebrafish that can detect
water pollutants by glowing a certain color.
To create such radiant fish, biologists extracted
fluorescent genes from jellyfish and injected them into zebrafish eggs. In
the presence of certain substances, such as heavy metals, toxins or other
pollutants for which the color has been specifically aimed, the fish glow
red or green.
Although only those two colors have been produced so
far, researchers can add up to five colors to a zebrafish, a different
color for each given pollutant.
After learning all this, I went to a pet store to check
out these versatile fish, also called danio in the shops. Now, I not only
know about zebrafish hearts, genes, eggs and guts, I have four
entertaining me in a small tank on my desk.
I hope everyone finds some fun in their work over the
holidays. |
