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ENDOCRINEONTROLHormonesn the BalanceAtrazinehas beenwidelyured as an herblcide or morethan fortyyears.Eaclr ear,people n the UnitedstatesapplyaboutT6 million poundr ofit, mortly tofields ofcorr and other monocoicropr.Theyalsoapplyjt to tawnsat homet, andgolf.ourses.Wheredoes t gofron there?nto soiland water Atrazinemolecules real down n tesstlrar ayear,but ihey stillturn up in gioundwater,po.dr,$e s,al d ra r atraz'-e onlrrr l" l olsoilsand water ofthe AmericanMidwest.

l , l l r . bdd' .r ive.s, l \o' ( d I o iaoooqst-) ,o-eHayeshinks so (Figure161).Atrazjne, e suspecis,naybeone ofthe syntheticorqaniccompoufdr with unexpectedsideeffe.ts.Tle compoundsmimic,blocl, or boosr heactionofnaturallrornrones nvolved n reproductjonanddevelopnrent. heyare erdocrinedistuptos.Nayesooled at atrazin effectson Afrjcancraweoftags (Xenopusaevis) ndleopatd rcgs Ranapipjent)in hjs aboratory. fterhe exposedmaletadpoles o theherbjcide, omebecamehermaphrodites, iih maleandfemalereproduciive rgans Atrazine on.entrationsaslow as 0.1pari pei billior could cause uch chanqes.Did atrazine ave similar eflects r the wild? To indoui, Hayes ollected aUve eopardfrogs rom pondsard ditchesacrosshe Midwest. n everyone ofthe

atrazine-contarninatedords sarrpted,male rogs hadabnormalsexorgans.n the pond wjth the mosi atrari92 percentof ilre male5 ad femi.ized sexorgans.Researchersundedby herbicide ndustriesdisputefirdjngr, but other studiesconfnmedatrazinecan cauor amplifyfrog deformlties. he EnvironmentalProtecAgencyfound he data ntriguing.Among otlre.thir9s,this agencyegulateshe applicat ionfchemicalsnagrjculture.lt has called or furth er study ofatrazine spotentiallyhannful elfectson amphibians. t has beenercouraging arrners o do more o minimize he rurofofatrazine lader waterfiom fieldsMFa wti-e ottp ho rone-dis .p ng , -en icats rirfiltratirg aquatichabitats.For nstance, strogensrobntf controlpilh arexcretedfrom he body n urtne acannotbe emoved y standard wastewater reatmertrWi-n pqt.oqend nltd ^ate-e. er!.r .earso i,e 5it cancausemaie ish to developfemale raits Socane+rogen-nrimicking ollutant5 rom industries.n romepenicide cortaminated ales n Florida, ]aalligators rave ow testosierone evelsard an abnormatmallpenis.n NewYork,salamandersevelopedbizaskin colorationpatternsafter beirg exposed o herbjcirjch runoffftom a rew golf coursen tfe neiqhborfood

Figurc36.1 Benefils ndcostsof herbcideappticalions.eft Atraznecan keepcorntieds earyweed reeino need or conslanttil q hatcauses oi roslonTyroneilayes r/gh,suspeclshs chemicalmaye scramblingmph ian ormonatsnas

7/28/2019 Hormones in the Balance

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IM PACT' , IS5UESy,Coneepts

THEENDOCRINEY5TEMHormonesndother ignalng noeclr les recomponeoj pathways hatcontro melabolismgrowth.developmand eprod!c l ion hesame ormone ources ake pendocr ineyslern i near ly lvenebrales.Seclon36S 6NALNG MECHANI5M5A hormone gnas larqel cells wlrch are anycells hal hrceptorsor it. Receplor ctvalion eads o ransductool th signaland he ce lular esponse. Seclion 6.2A MASTER TEGRATGCENTERn vertebrates,he hypolhalamus nd p luitaryglandarconnecled lrucluralyand unct onallyTogether heycoordinate ctivites of manyotherglands hroughouth

OIHERHORMONE0URCESNegatve eedbackLoopso the irypotha musand pit!conlrolrhesecrelion f rngnyg ands.Loca changes n nternalenvonrnentonlro l lhe ecret ioni other lan

Areamplribians,lshes,and alligatorttoo removedfrom your interests? heendocrine isruptorsmaybemeddl ing i ih humans,oo.Between9l8 and1990,spenncountsofmale5 n Wenern countrisdedined byabout40 per.ent. Wouldyou be surprised o learn ratnlen f agri.ulturalregionsmay havetfe lowett countslAs University f Missouri erearchers iscovered,emensamplesfrom nen n Columbia,Missourl, ontaine.lonly about halfa, manynotile spermas he samplesfron men ln New YorkCity and LosAngeles.

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