Growth of the Early Chick Thyroid and Its Relationship to Thyroid Morphogenesis
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Citation:The Ohio Journal of Science. v101, n3-4 (June-September, 2001), 42-47
We used both qualitative and quantitative techniques to test the hypothesis that lateral expansion of the developing chick thyroid is restricted structurally. To do this, we isolated pharynxes from embryos of stage 13 to stage 15, the period during which evagination is occurring, and measured the amount of pharyngeal floor area occupied by thyroid, using the raised ridge at its periphery to define its limits. These measurements were then compared with volumetric ones of the same thyroids. Additionally, living isolated pharynxes were treated with dihydrocytochalasin B, a compound known to disrupt actin filaments. The results showed that growth of the thyroid (as indicated by its volume) is not accompanied by expansion of the primordium into the surrounding pharyngeal space (as indicated by its area). In addition, treatment with dihydrocytochalasin B caused flattening and spreading of the raised ridge of cells that bounds the thyroid pit suggesting that microfilaments are involved in maintenance of this structure. A discussion of the results in relation to previously reported findings implicates microfilaments in both the formation and maintenance of the peripheral cell ridge.
Author Institution: Department of Biology, John Carroll University
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