Nonsegmental organization of positional information in regenerating Ambystoma limbs☆☆☆
[摘要] Positionalinformationincockroachappendageshaspreviouslybeenshowntobeorganizedinhomologous,segmentallyrepeatingsequences(H.Bohn,1970,WilhelmRoux'Arch.Entwicklungsmech.Organismen165,303–341;1970,Develop.Biol.23,355–379).WehaveconductedexperimentstodeterminewhethersimilarsequencesexistinAmbystomalimbs.Thesameordifferentsegmentlevelsoftheselimbswerecombinedbygraftingtogethermaturelimbregionsandbygraftingregenerationblastemastomaturelimbregions.Therepeatingsegmentalsequencehypothesispredictsthatnointercalaryregenerationshouldoccurwhenthesamesegmentlevelsareapposed,andthatonlythepositionalvaluesnecessarytorestoreasinglesegmentsequenceshouldbeintercalatedwhendifferentsegmentlevelsareapposed.Whenregenerationblastemasaregraftedtomaturelimbregions,allofthemissinglimbregionsarerestoredbyintercalaryregeneration,regardlessofthesegmentlevelsthatarecombined.Whenmaturelimbregionsaregraftedtogether,onlythehoststumpsegmentisintercalated,andthisintercalationalsotakesplacewithoutregardtowhichsegmentlevelsarecombined.Theseresultsarenotcompatiblewiththesegmentalsequencehypothesis,andsuggestinsteadthatpositionalinformationisorganizedinasinglelimbsequence.Histologicaldataindicatethatthereasonmorecompleteintercalationdoesnottakeplaceaftergraftingmaturelimbregionsisthatdedifferentiatedcellsareunabletodisplaypositionalinformationanddividelongenoughtorestoremorethanthehostsegment.
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[效力级别] [学科分类] 生物科学（综合）
[关键词] [时效性]
