3 years ago

Ultrastructure of endocrine pancreatic granules during pancreatic differentiation in the grass snake, Natrix natrix L. (Lepidosauria, Serpentes)

Ultrastructure of endocrine pancreatic granules during pancreatic differentiation in the grass snake, Natrix natrix L. (Lepidosauria, Serpentes)
Magdalena Kowalska, Weronika Rupik
We used transmission electron microscopy to study the pancreatic main endocrine cell types in the embryos of the grass snake Natrix natrix L. with focus on the morphology of their secretory granules. The embryonic endocrine part of the pancreas in the grass snake contains four main types of cells (A, B, D, and PP), which is similar to other vertebrates. The B granules contained a moderately electron-dense crystalline-like core that was polygonal in shape and an electron-dense outer zone. The A granules had a spherical electron-dense eccentrically located core and a moderately electron-dense outer zone. The D granules were filled with a moderately electron-dense non-homogeneous content. The PP granules had a spherical electron-dense core with an electron translucent outer zone. Within the main types of granules (A, B, D, PP), different morphological subtypes were recognized that indicated their maturity, which may be related to the different content of these granules during the process of maturation. The sequence of pancreatic endocrine cell differentiation in grass snake embryos differs from that in many vertebrates. In the grass snake embryos, the B and D cells differentiated earlier than A and PP cells. The different sequence of endocrine cell differentiation in snakes and other vertebrates has been related to phylogenetic position and nutrition during early developmental stages. Based on their biology, reptiles are unique among the vertebrate taxa. Studies on the differentiation of the grass snake pancreatic cells revealed similarities and differences compared to the same process that has been described in other vertebrates. Based on our studies, we revealed that the endocrine pancreas of the grass snake contains four main types of endocrine cells (A, B, D, PP), which is similar to other vertebrates because it is probably an evolutionarily conserved feature of this gland. Within the main types of granules (A, B, D, PP), different morphological subtypes that indicated their maturity, which may be related to the different content of these granules during the process of maturation, could be distinguished.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/jmor.20775

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