The nature and origin of the glycosaminoglycans of the embryonic chick vitreous body☆

[摘要] Glycosaminoglycansoftheembryonicchickenvitreouswerecharacterizedandthenwereusedasmarkerstoestablishwhichtissuessynthesizethevitreoushumorduringdevelopment.Theglycosaminoglycansarepredominantlychondroitinsulfatesbyseveralcriteria.Theyareresistanttostreptomyceshyaluronidase,anenzymewhichdegradesonlyhyaluronate,andaredigestedbytesticularhyaluronidaseandchondroitinaseAC,enzymeswhichdegradehyaluronatepluschondroitin4-and6-sulfates.Onelectrophoresisoncelluloseacetatein0.15Mphosphatebuffer,pH6.7,thevitreousglycosaminoglycansmigrateslightlyslowerthanauthenticchondroitinsulfate,but,in0.1NHCl,theymigrateveryclosetochondroitinsulfatestandards.Finally,thedisaccharidesproducedbydigestionoftheseradioactivelylabeledglycosaminoglycanswithchondroitinasesACandABCwereidentifiedasΔdi-4SandΔdi-6S,asexpectedforchondroitin4-and6-sulfate.Byusingincorporationofradioactiveprecursorsintochondroitinsulfatesinvitro,wethandeterminedwhichtissuessynthesizethevitreoushumorinthedevelopingeye.Lateindevelopment,onDay12–13,theisolatedvitreousisveryactiveinchondroitinsulfatesynthesis,whiletheneuralretina,thelens,andthepectenarelessactiveandproduceahighproportionofenzyme-resistantGAG.Theeyetissuesisolatedfromembryoslabeledinovoretainsimilaramountsandtypesofglycosaminoglycans,indicatingthatcellswithinthevitreoussynthesizethevitreoushumorglycosaminoglycansatthistime.Earlierindevelopment,fromDays6to8,theisolatedvitreousincorporatesverylowlevelsofradioactivityintoGAG,buttheneuralretinaincorporateshighlevelsofradioactivityintochondroitinsulfate.Whentheembryosarelabeledinovoandthesametissuesareisolatedfollowingincorporation,thevitreousretainsmoreradioactivechondroitinsulfatethandoestheneuralretina.Thus,thevitreoushumourglycosaminoglycanisinitiallysynthesizedbytheneuralretinaandissecretedintothevitreousspace.

[学科分类] 生物科学（综合）