Ultrastructural features of the differentiating thyroid primordium in the sand lizard (Lacerta agilis L.) from the differentiation of the cellular cords to the formation of the follicular lumen

2018

Self Cite

We analyzed the development of the pancreatic ducts in grass snake Natrix natrix L. embryos with special focus on the three-dimensional (3D)-structure of the duct network, ultrastructural differentiation of ducts with attention to cell types and lumen formation. Our results indicated that the system of ducts in the embryonic pancreas of the grass snake can be divided into extralobular, intralobular, and intercalated ducts, similarly as in other vertebrate species. However, the pattern of branching was different from that in other vertebrates, which was related to the specific topography of the snake's internal organs. The process of duct remodeling in Natrix embryos began when the duct walls started to change from multilayered to single-layered and ended together with tube formation. It began in the dorsal pancreatic bud and proceeded toward the caudal direction. The lumen of pancreatic ducts differentiated by cavitation because a population of centrally located cells was cleared through cell death resembling anoikis. During embryonic development in the pancreatic duct walls of the grass snake four types of cells were present, that is, principal, endocrine, goblet, and basal cells, which is different from other vertebrate species. The principal cells were electron-dense, contained indented nuclei with abundant heterochromatin, microvilli and cilia, and were connected by interdigitations of lateral membranes and junctional complexes. The endocrine cells were electron-translucent and some of them included endocrine granules. The goblet cells were filled with large granules with nonhomogeneous, moderately electron-dense material. The basal cells were small, electron-dense, and did not reach the duct lumen.

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Development of the duct system during exocrine pancreas differentiation in the grass snake Natrix natrix (Lepidosauria, Serpentes)

2018

Self Cite

“…Material was dehydrated and embedded in an Epoxy Embedding Medium Kit (Sigma, St. Louis, MO). This procedure of fixation appears to be the best for different embryonic reptilian tissues (Rupik, Kowalska, Swadźba, & Maślak, ; Rupik, Swadźba, Dubińska‐Magiera, Jędrzejowska, & Daczewska, ; Swadźba & Rupik, ). Using a Leica Ultracut UCT microtome (Leica Microsystems, Wetzlar, Germany) semithin and ultrathin sections were cut.…”

Section: Methodsmentioning

confidence: 99%

“…Material was dehydrated and embedded in an Epoxy Embedding Medium Kit (Sigma, St. Louis, MO). This procedure of fixation appears to be the best for different embryonic reptilian tissues (Rupik, Kowalska, Swadźba, & Ma slak, 2016;Rupik, Swadźba, Dubi nska-Magiera, Jędrzejowska, & Daczewska, 2012;.…”

Section: Light and Transmission Electron Microscopymentioning

confidence: 99%

Development of pancreatic acini in embryos of the grass snake Natrix natrix (Lepidosauria, Serpentes)

2019

Self Cite

This study report about the differentiation of pancreatic acinar tissue in grass snake, Natrix natrix, embryos using light microscopy, transmission electron microscopy, and immuno‐gold labeling. Differentiation of acinar cells in the embryonic pancreas of the grass snake is similar to that of other amniotes. Pancreatic acini occurred for the first time at Stage VIII, which is the midpoint of embryonic development. Two pattern of acinar cell differentiation were observed. The first involved formation of zymogen granules followed by cell migration from ducts. In the second, one zymogen granule was formed at the end of acinar cell differentiation. During embryonic development in the pancreatic acini of N. natrix, five types of zymogen granules were established, which correlated with the degree of their maturation and condensation. Within differentiating acini of the studied species, three types of cells were present: acinar, centroacinar, and endocrine cells. The origin of acinar cells as well as centroacinar cells in the pancreas of the studied species was the pancreatic ducts, which is similar as in other vertebrates. In the differentiating pancreatic acini of N. natrix, intermediate cells were not present. It may be related to the lack of transdifferentiation activity of acinar cells in the studied species. Amylase activity of exocrine pancreas was detected only at the end of embryonic development, which may be related to animal feeding after hatching from external sources that are rich in carbohydrates and presence of digestive enzymes in the egg yolk. Mitotic division of acinar cells was the main mechanism of expansion of acinar tissue during pancreas differentiation in the grass snake embryos.

“…Ultrathin sections were collected on 200‐mesh copper grids, stained with uranyl acetate for 20 min and lead citrate for 15 min and studied using a Hitachi H500 transmission electron microscope (Hitachi Ltd, Tokyo, Japan) operating at 75 kV. This fixation procedure appears to be the best one for different embryonic reptilian tissues (Rupik, ; Swadźba & Rupik, ; Rupik, Kowalska, Swadźba, & Maślak, ). The diameter of the pancreatic granules was calculated using free ImageJ software.…”

Section: Methodsmentioning

confidence: 99%

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

2017

Self Cite

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.