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00925njm 22002777a 4500 dc Gato Casado, Ángel Luis author Moro Balbás, José Antonio author Pastor Vázquez, Juan Francisco author Represa de la Guerra, Juan author Barbosa Ayucar, Enrique author 1993 Abstraer. Prcvious studies of thc car l y dcvclopment of the ncural tube ha ve shown thc ex istence of an intraneural nuid, which causes a positivc pressure inside this pri­ m ordium, and seems to play a key role in the early dcvcl­ opmcn l of the central nervous syslc m. I n the present sludy wc invest igated the composition and synthesis of lhis int ra neural fluid. By usi n g a scqucntial method, wh ich includes fixation with gl utaraldch yde plus cclylpyridinium chl oride, opening thc ncural cavity after critica! point drying and scan ning clcctron microscopy analysis, we found a water-soluble extracellular matrix that filled up thc brain vesicles of chick embryos al the ea rliest stages of thc ncural tu be. An ultrastructura l study of the neural cpit hcliu m during these stages revea led the cxistcnce of a secretion proccss in the neural cells toward thc apical side, the future neural cavity. An immunocyto­ chemical study to asscs thc nature of the secreted materi­ al has shown that the intraneu ral matrix conta ins chon­ droitin sulphate proteoglycan, which appeared homoge­ n ously distributed throughout lhc neura l cavity. Our findings demonstra te that thc int raneural liquid is a nuid of com plcx composilion and includes chondroiti n su l­ phate protcoglycan as a n osmotically active molccule. Th is suggests a morphogenetic role for the proteoglycan during ea rl y brain enlargcmcnt. Thc neural ectoderm is a polarized epi thelium from carly developmental stages and secretes the in t rancural malrix. Anat. Embryol. 0340-2061 http://uvadoc.uva.es/handle/10324/4443 101 188 106 Anat. Embryol. 188 Fluido intraneural - Composición Chondroitin sulphate proteoglycan and embryonic brain inlargement in the chick