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The endocrine system , specifically relating to sex hormones , and genetic material
can be targets of environmental contaminants . Environmental contaminants in the Rio
Grande region may originate from industrial or agricultural processes and growing
populations lacking proper water and sewage infrastructure . Cliff (Petrochelidon
pyrrhonota ) and cave (P . fulva ) swallows breeding near the Rio Grande were selected to
monitor aromatase activity alterations and DNA damage . Swallows were sampled at six
sites along the Rio Grande from Brownsville to Laredo , and a reference site (Somerville )
350 miles north of the Rio Grande . DNA damage , based on nuclear DNA content , was
determined by flow cytometry . A significantly larger mean half peak coefficient of
variation (HPCV ) of DNA content in contaminated sites compared to a reference site
reflects possible chromosomal damage . No detectable HPCV differences were observed
in cave swallows among locations , notwithstanding the presence of mutagenic
contaminants . Selenium may provide a protective role against genetic damage .
However , cliff swallows from Laredo had significantly higher HPCV values than those
from Somerville . DNA damage could be attributed to metals and polycyclic aromatic hydrocarbons released near Laredo . Brains and gonads , two estrogen -dependent organs ,
were tested for aromatase activity with a tritiated water method . Brain aromatase
activity was higher , though not always statistically , for male cave and male and female
cliff swallows . Dichlorodiphenyldichloroethylene (DDE ) may play a role in the
increased activity . Female cave swallows in Llano Grande appeared to have a greatly
depressed brain aromatase activity , possibly attributed to past human use of toxaphene .
Testicular and ovarian aromatase activity in cliff and cave swallows from Rio Grande
was higher than in those from Somerville , though not always significantly . DDE ,
atrazine , sewage treatment plant contaminants (phthalates , alkylphenols ,
ethynylestradiol ) , metals , or other pollutants could play a role in the increased gonadal
activity . Increased aromatase activity , in association with contaminants , may be easier
to detect in testes of male birds which normally exhibit low levels of estrogen . Siterelated
contaminants may be playing a role in DNA damage and aromatase alterations .
This is the first known study which uses aromatase activity as an endocrine disruptor
indicator in wild birds . |
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