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The expansive force generated by the positive pressure of the neural tube fluid confined inside the brain vesicles has been shown to be a key factor during the earliest stages of brain morphogenesis and development of chick embryos. In a previous study, we demonstrated the existence of an intracavity extracellular matrix rich in condroitin sulfate in this species, which could be involved in the regulation of the expansive process. In this report, scanning electron microscopy and immunohistochemistry show that, after neurulation, a similar extracellular matrix rich in chondroitin sulfate is present inside the brain vesicles of rat embryos during early enlargement of the brain anlage. In vitro treatment of rat embryos with β-D-xyloside (a chemical compound which disrupts chondroitin sulfate synthesis) shows that changes in intralumen chondroitin sulfate concentration are accompanied by significant changes in brain anlage growth. These results support the hypothesis that intracerebral chondroitin sulfate plays a relevant role in the regulation of the expansive process of the brain anlage of rat embryos, and could represent a general mechanism in the early brain development of avian and mammalian embryos. [ABSTRACT FROM AUTHOR]

Epithelial or mesenchymal isolates cultivated on the chicken chorioallantoic membrane singly do not possess the potential for tooth morphogenesis. However, when randomly recombined in vitro, their histogenic interaction relates to tooth formation. After 16 days of continuous culture, surviving recombinants formed an advanced tooth germ. Such structures did not, however, demonstrate uniformity in odontogenesis or in developmental cusp patterns. [ABSTRACT FROM AUTHOR]