Development of structure and function in the mammalian yolk sac: II. Vitamin B12 uptake by rabbit yolk sacs☆
[摘要] WhenrabbityolksacswereincubatedinvitrowithCo57B12,therewasagreateraccumulationofthevitaminthanthatobservedwithfetalileumofasimilarage.Intrinsicfactor,withaspeciesspecificitysimilartothatobservedinfetalandadultintestine,stimulatedB12uptakeseveralfold.TheuptakeofB12,bothinthepresenceandabsenceofIF,wasdepressedwhenDNPoriodoacetatewasaddedtotheincubationmedium.Theadditionof10mMglucoseovercametheDNPinhibitionbutdidnotreversetheiodoacetateeffect.FollowingtheparenteraladministrationofCo57B12topregnantrabbits,thelabelappearedinthefetalorgansandextrafetalmembranes.Theaccumulationintherabbityolksacswasparticularlystrikingafter24–48hours.UnilateralintrauterineinjectionofB12ledtomoreofthelabelappearinginthefetalorgansoftheinjectedhornthaninthenoninjectedcontrolhorn.LigationofthevitellinevesselsdidnotappeartoeffectthetransferofparenterallyadministeredCo57B12tothefetalorgans.ThecontributionofthechorioallantoicplacentaandtheyolksacplacentaoftherabbitinthetransferofB12frommothertofetusisdiscussed.Thedevelopmentalmorphologyofthevisceralyolksacoftherabbitwascomparedwiththatoftherat.Theabsorptivecellsofthevisceralendodermpossesssurfacespecializationsrelatedtotheuptakeofmacromolecules.
[发布日期] [发布机构]
[效力级别] [学科分类] 生物科学（综合）
[关键词] [时效性]
