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

Abstract

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.

Architecture of the Pancreatic Islets and Endocrine Cell Arrangement in the Embryonic Pancreas of the Grass Snake (Natrix natrix L.). Immunocytochemical Studies and 3D Reconstructions

“…Eggs of the grass snake were incubated at 30 °C and humidity of 100% in small incubators [ 55 , 56 , 57 , 58 ]. They were half-buried in a 1:1 mixture of sand and peat and kept in plastic storage boxes for food with transparent walls.…”

“…The semithin sections have been obtained and stained according to the protocol which was described in [ 57 , 70 ].…”

Structural and ultrastructural studies on the developing vomeronasal sensory epithelium in the grass snake Natrix natrix (Squamata: Colubroidea)

“…The heads of embryos were fixed in a 1:1 mixture of 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1 mol L −1 phosphate buffer (pH 7.4) at 4°C for at least 24 h (Hermyt et al, 2020; Khannoon et al, 2016; Kowalska & Rupik, 2020; Lewandowski et al, 2017; Rupik et al, 2012; Swadźba & Rupik, 2010). After rinsing in phosphate buffer, the VNOs were isolated or only the posterior parts of the heads (without VNOs) were removed.…”