Bymatinglongsuccessivegenerationsofthoseanimalsthatfailedtodevelophypertensionfromsaltintake,aresistantstrain(the"R"strain)hasbeenevolvedinwhichconsumptionoflargequantitiesofsaltfailstoinfluencethebloodpressuresignificantly.Incontrast,bymatingonlyanimalsthatquicklydevelophypertensionfromsalt,sensitivestrain(the"S"strain)hasalsobeendeveloped.
Theavailabilityofthesetwostrainspermitsinvestigationspossible.Theyprovideaplausiblelaboratorymodelonwhichtoinvestigatesomeclinicalaspectsofthehumanhypertension.Moreimportant,theremightbethepossibilityofdevelopingmethodsbywhichgeneticsusceptibility(敏感性)ofhumanbeingstohighbloodpressurecanbedefinedwithoutwaitingforitsappearance.Radioactivesodium22wasanimportant"tool"inworkingoutthecharacteristicsofthesodiumchloridemetabolism.
21.Thestudyoftheeffectsofsaltonhighbloodpressurewascarriedout_______.
A.asmembersofthesamefamilytendtousesimilaramountsofsalt
B.toexplorethelong-termuseofasodiumbasedsubstance
C.becauseitwasproventhatsaltcausedhighbloodpressure
D.becauseoftheavailabilityofchemicallypuresaltanditsderivatives
22.Themaindifferencebetween"S"and"R"ratsistheir_______.
A.needforsodium22B.rateofmating
C.reactiontosaltD.typeofblood
23.Wecaninferfromthearticlethatsodium22canbeusedto_______.
A.controlhighbloodpressure
B.curehighbloodpressurecausedbysalt
C.tellthe"S"ratsfromthe"R"rats
D.determinewhatasodiumchloridemetabolismislike
24.Themostbeneficialresultsoftheresearchmightbe_______.
A.developmentofdietsfreeofsalt
B.anearlycureforhighbloodpressure
C.controlofgeneticagentsthatcausehighbloodpressure
D.theearlyidentificationofpotentialhighbloodpressurevictims
25.Whichofthestatementsbestrelatesthemainideaofthisarticle?
A.Whensaltisaddedratsandhumanbeingsreactsimilarly.
B.Thenearfuturewillseeacureforhighbloodpressure.
C.Themedicalfieldisdesperatelyinneedofresearch.
D.Atendencytowardhighbloodpressuremaybeahereditaryfactor.
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