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SAMPLE19

[医学类]

Thecomplicationsfrequentlyaccompanyingdiabetes,suchasimpairmentofvisionandofkidneyfunction,arenowthoughttoresultfromthelackofcontinuouscontrolofbloodglucoseconcentrations.Thehealthypancreas,inresponsetoincreasesinbloodglucoseconcentration,releasessmallquantitiesofinsulinthroughoutthedayandtherebymaintainstheconcentrationwithinphysiologicallimits(nomoglycemia).Butthediabeticgenerallyreceivesonlyonelargedosedaily.Thediabetic’sbloodglucoseconcentrationcanthusfluctuategreatlyduringtheintervalbetweendoses,andithasbeensuggestedthatthecomplicationresultfromtheperiodsofhighconcentrationsofbloodglucose(hyperglycemia).Manyinvestigatorsthusbelievethatrestorationofnormoglycemiamighthalttheprogressionofsuchcomplicationsandperhapsevenreversethem.

Therearethreeprimarytechniquesthathavebeeninvestigatedforrestorationofnormoglycemia.Theyare:transplantationofwhole,healthypancreases;transplantationofisletsofLangerthan,thatportionofthepancreasthatactuallysecretesinsulin,andimplantationofartificialpancreases.Therehas,infactbeenagreatdealofsuccessinthedevelopmentofthesetechniquesandeachseems,onthewhole,promising.Nonetheless,itwillundoubtedlybemanyyearsbeforeanyoneofthemisacceptedasatreatmentfordiabetes.

Tomanypeople,theobviousapproachwouldseemtobesimplytotransplantpancreasesfromcadaversinthesamemannerthatkidneysandotherorgansareroutinelytransplanted.Thatwastherationalein1966whenthefirstrecordedpancreaswasperformed.Between1960and1975,therewereforty-sixpancreastransplantsinforty-fiveotherpatientsintheUnitedStatesandfiveothercountries.Butonlyoneofthesepatientsisstillalivewithafunctioninggraftandsurgeonshavefoundthattheprocedureisnotsimpleastheyoncethought.

Thesurvivingpatienthasrequirednoinsulinsincetheoperation.Anotherpatientsurvived638dayswithoutrequiringinsulin.Andonepatientsurvivedatransplantationformorethanayear,butdiedwhenhechosenottotakeimmunosuppressivedrugs.Theseresults,thoughmeager,suggestthattheprocedurehasthepotentialforsuccess.

Therestofthepatients,however,eitherrejectedthetransplantordiedwithinashortperiod.Theredoesnotappeartobeanytechnicalproblemwiththeprocedure.Rather,mostofthepatientswerealreadysoseverelydebilitatedbythecomplicationsofdiabetesthattheycouldnotwithstandthesurgeryandtheimmunosuppressiveregimenrequiredtopreventrejection.Morethanhalfofthepatients,furthermore,alsorequiredakidneytransplant.Mostinvestigatorsnowagreethatthesimultaneoustransplantationofbothorgansistoogreatashocktothepatientandgreatlyincreasesthetotalrisk.

1.Whichofthefollowingbeststatesoneofthemainconclusionsofthetext?

[A]Althoughthetechniquesforpancreastransplantsappeartobetheoreticallycorrect,thereareproblemsthatmustbesolvedbeforetheoperationcanbeusedasatreatmentfordiabetes.

[B]Althoughthetechniquesforpancreastransplantsarestillbeingdeveloped,theexperimentalresultsshowthattheoperationwillbeasuccessfultreatmentfordiabetesinthenearfuture.

[C]Althoughpancreastransplantsarereliable,manydiabeticsarereluctanttoundergotheoperationbecauseofthesideeffectsofimmunosuppressivedrugs.

[D]Althoughpancreastransplantsalonearenotgenerallysuccessful,theoperationcanbeusedinconjunctionwithotherprocedurestotreatdiabetes.

2.Accordingtothetext,widelyspaceddosesofinsulincancause

[A]reversalofnormalkidneyfunction.

[B]delayintheonsetofdiabetes.

[C]radicalchangesintheconcentrationofbloodglucose.

[D]restorationofnormoglycemia.

3.Accordingtothetext,aperiodichighconcentrationofbloodglucoseindiabeticsisapossiblecauseof

[A]deteriorationofthepancreas.

[B]damagetotheeyesandkidneys.

[C]rejectionoftransplantedorgans.

[D]inadequatesecretionofinsulin.

4.Itcanbeinferredfromthetextthatoneoftheimportantcontributingcausesofthefailureofmostpancreastransplantshasbeenthe

[A]reluctanceofpatientstocooperatewithphysicians.

[B]imperfecttechniquesusedintheoperation.

[C]scarcityofimmunosuppressivedrugs.

[D]weakenedconditionofthepatients.

5.Thetextsuggeststhattheauthorconsidersthedataconcerningthesuccessofpancreastransplantstobe

[A]invalid.

[B]indirect.

[C]inaccurate.

[D]insufficient.