(1) This indicates a level of plasma membrane invagination comparable with mammalian skeletal muscle.(2) There is a refracting secretion in the space of this invagination presumably protecting the photoreceptor cells.(3) The initial conditions for the appearance of feathers also probably resides in processes common to all ammonites and include placode formation, invagination , and mesenchymal-epithelial interactions.(4) Specifically, the ventral invagination and migration of mesodermal precursors in the embryo are severely impaired, as are head involution, dorsal closure, and the migration of gonadal precursors.(5) In the chick embryo, for example, the ectoderm initially expresses L-CAM; during neural plate invagination , however, L-CAM expression is replaced by that of N-cadherin.(6) Catheters with multiple side holes on several planes are less likely to cause invagination of airway mucosa into the catheter than those with single side or end holes.(7) The internodes have invaginations that are termed cupules.(8) As is typical, many of the latter showed reactive changes, such as large, variably sized nuclei; intranuclear invaginations ; and multinucleation.(9) Intranuclear cytoplasmic invaginations , similar to that seen in non-neoplastic hepatocytes (or in metastatic melanoma) are also frequent.(10) These invaginations represent placental outgrowths and they extend towards the centre, enclosing the central hole into a triangular slit.
