Small Fish for a Large Task
David Hinton Takes His Medaka West to Monitor California's
Drinking Water p.2
In addition to possible impacts from industrial
emissions, Orange County’s future drinking water picks up
natural organic matter while coursing through agricultural
land. Those dissolved organics can themselves be chemically
transformed into toxic compounds like chloroform and carbon
tetrachloride when the water undergoes chlorination. “The
thing that we’re worried about in human health is that low
amounts of these water purification byproducts could be and
are toxic in appropriate amounts,” he says.
He describes how Orange County allows water
destined for recycling to percolate into the groundwater aquifer
for weeks to months of natural filtering before being pumped
back to the surface and re-purified for drinking. Under a
grant worth $65,000 annually for two years from the private
Water Environmental Research Foundation, some of that recycled
drinking water will be screened by Hinton’s medaka.
Researchers will house the animals in portable
laboratories receiving Santa Anna River water from a well
adjacent to the riverbed. All support systems such as diet
and aeration will be provided and control waters will be adjusted
to match mineral content (hardness) of the test water. “Medaka
are going to be living in the same water that people would
be drinking, and they’re going to live there for a long time,”
Hinton says.
Hinton came to Duke in 2000, filling the first
professorship endowed by the family of Nicholas School benefactor
Pete Nicholas. A Hattiesburg. Miss., native, he has been using
fish to study environmental effects since completing his doctoral
research at the University of Mississippi School of Medicine
in Jackson in 1969. His previous faculty posts before Duke
took him to the University of Louisville School of Medicine,
the University of Maryland School of Medicine in Baltimore,
the West Virginia University Medical Center in Morgantown
and then UC-Davis.
By the time he left UC-Davis, where he directed
the ecotoxicology graduate program for the entire University
of California system, he had already developed special expertise
using medaka as model animals for research.
“Medaka are a national symbol in Japan,” Hinton
says. A native species that also lives wild in parts of Southeast
Asia, the fish have been studied for more than 100 years by
Japanese scientists doing research in genetics and developmental
biology. “The medaka genome project in Japan is almost completed,”
he adds. Some special medaka strains and stocks are on pubic
display in a special exhibit building at the Higashiyami Botanical
Gardens and Zoo in Nagoya. They are even the subjects of children’s
songs.
Since 1975 the usefulness of medaka as live models
that can screen for carcinogenic chemicals has been “repeatedly
demonstrated,” according to a scientific paper describing
their planned use in Orange County. Since 1990, National Toxicology
Program panels have concurred on their usefulness in a variety
of cancer screens, the paper adds. Likewise, the transparency
of all medaka’s egg casings make them valuable for monitoring
chemicals that can harm developing embryos. Lately, medaka
also have proved to be “a sensitive model” for detecting chemicals
that can alter reproductive or immune systems by disrupting
hormones, the paper notes.
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