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Figure 7 | BMC Developmental Biology

Figure 7

From: The twisted pharynx phenotype in C. elegans

Figure 7

Basal lamina and pseudocoelom development. (A) Embryo during morphogenesis, laserhole immersion fixation. Transverse thin section through the head indicates the region between the pharynx (Ph) and bodywall where basal lamina deposition is taking place (arrowheads point to plasma membrane of body-wall ectodermal cells in each panel). During morphogenesis the border between mesoderm and ectoderm is at first highly irregular; in this example the border has become more regular but there is no apparent "pseudocoelomic" space and one cannot readily distinguish separate basal laminae for mesoderm or ectoderm. (B) Embryo just before hatch, chemical immersion fix. Lengthwise thin section of the head shows a slight separation between body-wall cells and the pharyngeal muscles. Radial muscle filaments have developed and the pharynx is now contractile. Virtually no acccessory pseudocoelom is yet observed here, but at higher power the basal laminae of the mesoderm and ectoderm seem to form separate layers by immersion fixation (not shown). (C) Adult head, fixed by HPF and freeze substitution staining. Transverse thin section shows a widened, highly irregular space, the accessory pseudocoelom, has developed between the ectoderm and mesoderm. (D) Higher power view of same region as in C shows the pseudocoelomic space is filled with flocculent matrix materials. The basal lamina of the ectodermal cells cannot be easily distinguished from this flocculent matrix, whereas the very thick basal lamina of the pharynx is now visible as a prominent electron dense line. Pharynx regions are as follows (metacorpus in A; isthmus in B; isthmus in C and D). Scale bars are 1 micron. Scale bar in A is for first three panels.

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