http://www.findarticles.com/p/articles/mi_m1200/is_10_168/ai_n15650947
Science News
September 3, 2005
Class acts from new pesticides: chemicals
have little effect on mammals
By B. Harder
Insects, be warned. Research on three continents has turned up
two new classes of selective pesticides that immobilize and eventually
kill many insect species by interfering with a cell receptor unique
to the insects. The novel chemicals could potentially prevent
infestations of crops while posing minimal danger to noninsects.
"Both classes of chemicals act at the ryanodine receptor"
making them the first synthetic molecules to demonstrate this
insect-imperiling behavior, says physiologist Daniel Cordova of
DuPont Crop Protection in Newark, Del. By
regulating how calcium moves within animal cells, that receptor
plays an essential role in processes such as muscle contraction...
Now, three research groups--Cordova's DuPont team and two teams
based in Germany and Japan--have produced chemicals that mimic
ryanodine in insect cells. The three teams described their research
on Aug. 28 at a meeting in Washington, D.C., of the American Chemical
Society.
During the 1990s, while attempting to create new weed killers,
scientists at Nihon Nohyaku Co. in Osaka, Japan, developed the
first compounds known as benzenedicarboxamides or phthalic acid
diamides. The chemicals weren't effective as herbicides, but in
some insects they caused distinctive symptoms, including muscle
contractions.
Kenji Tsubata and his Nihon Nohyaku colleagues recently developed
a particularly potent benzenediearboxamide called flubendiamide.
At various concentrations, the compound is lethal to more than
half-a-dozen species of destructive insects, including some that
are resistant to other insecticides.
Even at concentrations at least 100-fold those sufficient to
poison these pests, flubendiamide doesn't appear to harm rats,
honeybees, spiders, or any of several beneficial predatory-insect
species, the Japanese researchers reported. They noted, however,
that the compound can kill silkworms.
Regulatory approval of flubendiamide is
pending in Japan but not yet imminent in the United States or
Europe, says Peter Lummen of Bayer CropScience in Monheim, Germany.
For their part, Lummen and his Bayer colleagues are studying
whether flubendiamide interacts with any of three mammalian ryanodine
receptors. In tests so far, the chemical appears to be inactive
against at least two of the receptors.
In separate research, DuPont chemists invented compounds called
anthranilic diamides that bind 500 to 2,000 times more readily
to the insect receptor than to the mammalian receptors. These
chemicals cause rapid, progressive, and often lethal muscle paralysis
in a range of insects, Cordova reported.
The complementary nature of the recent findings, Lummen says,
hints strongly "that we are on the right track" toward
a safe new class of pesticides.
COPYRIGHT 2005 Science Service, Inc.
COPYRIGHT 2005 Gale Group
