TITLE: RESEARCHERS LINK MARINE TOXINS TO IMPAIRED LEARNING ABILITY IN RATS; STUDY BOLSTERS REPORTS OF SIMILAR HUMAN EFFECT
BYLINE: Scripps Howard News Service
EST. PAGES: 2
DATE: 12/21/97
DOCID: SLMO73550278
SOURCE: St. Louis Post-Dispatch; SLMO
EDITION: THREE STAR; SECTION: NEWS; PAGE: A10
(Copyright 1997)
Lab tests with rats have confirmed for the first time that
toxins produced by the marine bacteria Pfiesteria piscida can
impair learning ability, researchers say in a new report published
Saturday.
The study bolsters reports of similar effects on humans.
A series of studies at Duke University Medical Center in Durham,
N.C., found that rats exposed to the one-celled organisms were
significantly slower in learning and remembering a new task than
identical animals that were not exposed.
Human exposure to Pfiesteria has been blamed for various health
problems, ranging from memory and mental impairment to breathing
difficulty to rashes and open skin sores among watermen and researchers
working with water and fish from several North Carolina rivers
and more recently several tributaries of the Chesapeake Bay in
Maryland and Virginia.
Although the nature of the organism and how its byproducts
attack the brain remain unclear, health authorities in Maryland
this fall identified Pfiesteria as the cause of memory and learning
problems in at least 11 fishermen and boaters in the wake of large
fish kills last summer.
But the research presented in the journal Environmental Health
Perspectives is the first to be published in a scientific publication
that compared behavior in two groups of animals selectively exposed
to the toxins.
"The rats exposed to Pfiesteria toxin were significantly
retarded in their learning" after being injected with aquarium
water containing the toxin, said Edward Levin, the lead investigator
for the study and director of the Integrated Toxicology Program
at Duke. "The effect persisted throughout the 10 weeks the
animals were retested after the injection."
The current study on the toxic effects of the microbe started
after JoAnn Burkholder, an aquatic botanist at North Carolina
State University who first discovered the organism in 1988, and
two colleagues became severely ill in a lab after breathing fumes
from an aquarium tank containing Pfiesteria.
The organism, a type of plankton that is at the base of the
marine food chain, appears to turn tables on fish, using its toxins
to attack and eat fish flesh, creating lesions that eventually
kill the fish. No one knows for sure why Pfiesteria surges to
cause massive fish kills, although experts believe organic runoff
from chicken and perhaps hog farms may be to blame.
There have been no reported fatalities among humans from Pfiesteria,
and the effects of the toxins appear to fade eventually as long
as victims stay away from contaminated water.
In the rat experiments, 26 animals injected with Pfiesteria
and 26 controls were tested for their ability to learn and remember
how to navigate a wagon-wheel-shaped maze of planks, with a food
reward at the end of each spoke that was not replaced. The uninfected
animals quickly learned not to go down the same path twice, but
those injected with Pfiesteria water took much longer to learn.
In a second phase, another group of rats was trained with the
same maze and injected with the toxins. These rats remembered
the drill as well as the control rats, but when the pattern was
changed so that only three spokes held food rewards, the exposed
rats took much longer to catch on to the change.
Other testing showed those exposed to the toxin also had less ability to get used to new surroundings. But when the exposed rats were sacrificed under anesthesia and their brains examined, the researchers were unable to see any brain structure that seemed to have been altered or impaired.
DESCRIPTORS: STUDY; HEALTH; EXPERIMENT; WELLNESS; HEALTH