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Science Update
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Screening Plants for Calcium
Crystals
Calcium is the fifth most abundant element in the Earth's crust. While its
essential roles in human health are quite well known, what it does in plants
that it accumulates in is not.
Understanding the mechanisms by which a variety of plants form calcium oxalate
crystals might one day lead to making the nutrient more biologically available
in foods. It might also lead to a reduction in the risk associated with
oxalate, which may contribute to kidney stone formation.
Scientists have begun the first genetic screening system for examining calcium
crystal formation in plants. They have been able to observe differences in
crystal form, distribution, and amount, as well as in the crystallization
process itself.
They will use the screening system to search for genes that determine specific
crystal characteristics. Some plants contain no crystals but still seem to grow
normally, refuting the idea that the crystals are involved in supporting the
plant tissue structure.
Paul Nakata, USDA-ARS
Children's Nutrition Research Center at
Baylor College of Medicine, Houston, Texas; phone (713) 798-6782.
Hormone May Herald Health Problems in Livestock
Adrenomedullin (AM) is a naturally occurring amino acid peptide hormone
produced in many animal tissues, including heart, lung, and kidney. It is
involved in many physiological and pathological processes, and its increase may
be associated with some forms of infection in cattle, goats, pigs, and sheep.
For example, tests have shown that blood concentrations of AM increase
significantly when animals are exposed to cell wall components—called
endotoxins—of disease-causing bacteria. Other tests have demonstrated that
calves harboring internal parasites have more AM in their pancreatic tissue and
blood than healthy calves. Both low-level parasite infections of long duration
and short bouts of high-level infections can also provoke elevated AM levels.
And researchers think it may be possible to use AM levels to detect the
presence of other stresses, too, like metabolic diseases.
Development of a rapid test for abnormal AM levels could perhaps enable
producers to screen their animals for suspected diseases, parasites, or other
stresses. Identifying and treating ailing animals would speed their recovery
and make them safe for marketing—a plus for both producer and consumer.
Theodore H. Elsasser,
USDA-ARS Growth Biology
Laboratory, Beltsville, Maryland; phone (301) 504-8222.
Cotton Improvements in the Bank
The National Cotton Germplasm Genebank at College Station, Texas, maintains
7,456 accessions of U.S. cotton. Soon, up to 6,000 new accessions will arrive
through exchanges with other countries, further swelling an already vast
collection. Researchers hope to mine this mother lode of genetic variation to
achieve cottons with higher yields, stronger fibers, improved seed quality, and
other traits. But to do that, they will need to know which genes govern useful
traits and which molecular markers can be used to flag their location.
As this information is discovered, it will be catalogued in genetic libraries
that will be available to plant breeders eager to speed cotton yield and
quality improvements. It's an international effort that also includes
collaborators at Texas A&M.
Nearly 7.5 million bales of U.S. cotton, worth over $2 billion, were exported
in 1999-2000, and upwards of 12 million bales were processed into textiles by
U.S. mills.
John Yu, USDA-ARS
Crop Germplasm Research
Unit, College Station, Texas; phone (979) 260-9237.
When's Your Burger Really Done?
It turns out that color alone is not a true test of a grilled burger's
doneness. While a brown center sometimes indicates that ground beef is fully
cooked, how the meat was handled before cooking can undermine the accuracy of a
visual test.
Researchers confirmed this by grilling fresh ground beef, as well as beef
frozen in bulk or as patties. Beef that was frozen in bulk, thawed, formed into
patties, and then cooked showed brown color at unsafe temperatures. This
premature browning wasn't evident in frozen patties that were thawed and then
cooked.
As expected, burgers lost the pink color at their centers as they cooked. But
beef patties removed from the grill with pink centers continued to brown for
several minutes. So burgers cooked to 135°F and allowed to sit for about 4
minutes looked the same as those cooked to 160°F, the temperature at which
E. coli bacteria are killed.
Thus, use of a meat thermometer is the only sure way to ensure that grilled
meat is fully cooked.
Bradford W. Berry, USDA-ARS
Food Technology and
Safety Research Unit, Beltsville, Maryland; phone (301) 504-8994. |
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"Science Update" was published in the
July 2001
issue of Agricultural Research magazine.
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