An immunocytochemical study of the cytogenesis of pancreatic endocrine cells in the lizard, Anolis carolinensis

Does the pancreas of gekkotans differentiate similarly? Developmental structural and 3D studies of the mourning gecko (Lepidodactylus lugubris) and the leopard gecko (Eublepharis macularius)

This study investigated the pancreas differentiation of two species of gekkotan families-the mourning gecko Lepidodactylus lugubris (Gekkonidae) and the leopard gecko Eublepharis macularius (Eublepharidae)-based on two-dimensional (2D) histological samples and three-dimensional (3D) reconstructions of the position of the pancreatic buds and the surrounding organs. The results showed that at the moment of egg laying, the pancreas of L. lugubris is composed of three distinct primordia: one dorsal and two ventral. The dorsal primordium differentiates earlier than either ventral primordium. The right ventral primordium is more prominent and distinctive, starting to form earlier than the left one. Moreover, at this time, the pancreas of the leopard gecko is composed of the dorsal and right ventral primordium and the duct of the left ventral primordium. It means that the leopard gecko's left primordium is a transitional structure. These results indicate that the early development of the gekkotan pancreas is species specific. The pancreatic buds of the leopard and mourning gecko initially enter the duodenum by separate outlets, similar to the pancreas of other vertebrates. The pancreatic buds (3 of the mourning gecko and 2 of the leopard gecko) fuse quickly and form an embryonic pancreas. After that, the structure of this organ changes. After fusion, the pancreas of both gekkotans comprises four parts: the head of the pancreas (central region) and three lobes: upper, splenic, and lower. This organ develops gradually and is very well distinguished at hatching time. In both gekkotan species, cystic, hepatic, and pancreatic ducts enter the duodenum within the papilla. During gekkotan pancreas differentiation, the connection between the common bile duct and the dorsal pancreatic duct is associated with intestinal rotation, similar to other vertebrates.

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

During the early developmental stages of grass snakes, within the differentiating pancreas, cords of endocrine cells are formed. They differentiate into agglomerates of large islets flanked throughout subsequent developmental stages by small groups of endocrine cells forming islets. The islets are located within the cephalic part of the dorsal pancreas. At the end of the embryonic period, the pancreatic islet agglomerates branch off, and as a result of their remodeling, surround the splenic "bulb". The stage of pancreatic endocrine ring formation is the first step in formation of intrasplenic islets characteristics for the adult specimens of the grass snake. The arrangement of endocrine cells within islets changes during pancreas differentiation. Initially, the core of islets formed from B and D cells is surrounded by a cluster of A cells. Subsequently, A, B, and D endocrine cells are mixed throughout the islets. Before grass snake hatching, A and B endocrine cells are intermingled within the islets, but D cells are arranged centrally. Moreover, the pancreatic polypeptide (PP) cells are not found within the embryonic pancreas of the grass snake. Variation in the proportions of different cell types, depending on the part of the pancreas, may affect the islet function-a higher proportion of glucagon cells is beneficial for insulin secretion.

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

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.

Identification of the pancreatic endocrine cells of Pseudemys scripta elegans by immunogold labeling

The endocrine pancreatic cells of Pseudemys scripta elegans were investigated immunocytochemically by light and electron microscopy. Insulin-, somatostatin (SST)-1, SST-28 (1-12)-, salmon (s)SST-25-, glucagon-, pancreatic polypeptide (PP)-, peptide tyrosine tyrosine (PYY)-, and neuropeptide tyrosine (NPY)-like immunoreactivities were observed. Insulin cells were immunogold labeled with bonito insulin antiserum and secretory granules were characterized by a wide halo and a dense core of varying shape. Consecutive PAP-immunostained sections showed that SST-28 (1-12), SST-14, and sSST-25 immunoreactivities occurred in the same cells. However, preabsorption tests demonstrated that anti-sSST-25 serum detected the invariant SST-14 molecule. The SST-28 (1-12)/SST-14-immunogold-labeled cells mainly had round or ovoid medium electron-dense granules. Glucagon-IR cells were characterized by round secretory granules with an electron-dense core, with or without a narrow clear halo. There were PP, PYY, and NPY (NPY-like) immunoreactivities in a population of glucagon-IR cells in the pancreatic duodenal region (glucagon/NPY cells). Most of the secretory granules of these glucagon/NPY-like cells had an electron-dense content and were round, although there were also pyriform or ovoid secretory granules which were smaller than those of glucagon-IR cells. Preabsorption tests proved that the NPY-like peptides detected in the endocrine pancreas of P. scripta elegans were more similar to NPY or PYY than to PP.

Development of the endocrine pancreas during larval phases of Rana temporaria. An immunocytochemical and ultrastructural study

The pancreatic endocrine component was studied at different stages of development in the tadpoles of Rana temporaria. The material was embedded in Epon, and serial semithin and thin sections were made in order to correlate ultrastructural features and tinctorial traits of the endocrine cells. Serial semithin sections were also stained with the peroxidase-antiperoxidase immunocytochemical method and with silver impregnations for argyrophilia and argentaffinity. In early larvae (legless tadpoles). A and B cells are present. Both can be found within ducts and exocrine tissue or, more frequently, in cellular clusters among the ducts and acini. These primitive islets are solid structures, surrounded but not penetrated by capillaries. Mitoses were observed in A and B cells. In the following phase (tadpoles with hindlegs), D and pancreatic polypeptide-immunoreactive cells are also present, as well as numerous endocrine cells scattered among exocrine tissue. There is also a change in the vascular-insular pattern: capillaries not only surround but also penetrate the endocrine group. The structure of the endocrine pancreas in older tadpoles is similar. Tinctorial traits and ultrastructural features of endocrine cells are described, and the origin of primitive islets is discussed.

Immunostaining of a cell type in the islets of Langerhans of the monkey Macaca irus by antibodies against S-100 protein

S-100 protein-immunoreactive cells were demonstrated by immunocytochemical procedures in the pancreatic islets of Langerhans in the monkey Macaca irus. By use of antibodies against human S-100 protein or bovine S-100 protein, these cells were observed in all islets in the head and tail portions of the pancreas. Immunostained cells were usually located in the center of the islets or sometimes found in a more widely distributed form, but they were never arranged in a regular concentric fashion. The number of immunoreactive cells varied from one islet to another but it was relatively limited making up only 0.75%-6.3% of all insular cells. With the use of the double-immunoenzymatic procedure for demonstration of the four main endocrine cell types (insulin-, glucagon-, somatostatin- and pancreatic polypeptide producing elements), it was possible to establish that S-100 protein-immunoreactive cells represent a distinct cell type. Antibodies against S-100 protein-stained neuroinsular complexes. The present findings speak in favor of a new cell type to be added to the large variety of S-100 protein-immunoreactive cells outside the central nervous system.

An immunocytochemical and ultrastructural study of the endocrine pancreas of Pseudemys scripta elegans (Chelonia)

Immunocytochemical and ultrastructural methods have shown four cell types in the endocrine pancreas of the turtle Pseudemys scripta elegans: insulin-, glucagon-, somatostatin-, and pancreatic polypeptide-immunoreactive cells. Each endocrine cell type was distributed differently in the duodenal or splenic regions of the turtle pancreas. Round or fusiform insulin- and glucagon-containing cells could be seen as single scattered cells which were more numerous in the duodenal regions, and the cell groups becoming progressively smaller from splenic to duodenal region. Round or fusiform somatostatin cells with thick processes and spindly pancreatic polypeptide cells with long protrusions were less numerous the nearer they were to the splenic regions; they were isolated in the duodenal zone. Insulin cells were surrounded by somatostatin cells and an outer layer of glucagon cells around the cell groups could be seen. Insulin cells were characterized by their round secretory granules which contained a polygonal, irregular or rod-shaped dense core. They also contained numerous clustered mitochondria, large multivesicular bodies, and cilium. Glucagon cells, joined by desmosomes to adjacent ones, had numerous filamentous mitochondria with longitudinal cristae and round electron-dense secretory granules with closely applied membrane. Somatostatin cells contained two kinds of secretory granules, some of which showed an electron-dense core, while others had moderately electron-dense floccular material. PP cells were characterized by round secretory granules, smaller than those of other cell types, and a large euchromatinic nucleus. Lysosomes, microtubules, bundles of microfilaments, a well-developed Golgi apparatus, and scarce rough endoplasmic reticulum were present in the cytoplasm of all these endocrine cell types.

Alterations of endocrine pancreas B cells in a sahelian reptile (Varanus exanthematicus) during starvation

During the long starvation period (November to June) of the lizard (Varanus exanthematicus), pancreatic B cells undergo profound modification. The degeneration of beta granules observed in electron microscopy appears correlated with the diminution of the immunoreactive insulin-like content of the pancreas. The analogy between the phenomena observed here and those reported in animals treated with alloxan is discussed.

Continuous-perifusion tissue culture of fetal and adult pancreas of the lizard Anolis carolinensis

The differentiation of the fetal saurian pancreas in continuous-perifusion tissue culture (CPTC) was examined. Splenic pancreases from 24-day postoviposition fetuses of the green anole, Anolis carolinensis, were grown for 8 to 31 days by CPTC following successful preliminary studies with adult pancreas. Adult anolian endocrine pancreas was maintained by up to 7 days by CPTC. The pancreatic explants were examined morphologically by light and electron microscopy. The functional integrity of the endocrine cells was evaluated by measuring hormone levels of the explants and in the basal medium and by determining the kinetics of hormone release. The pancreatic endocrine cells from fetal and adult anoles were functionally and morphologically intact after CPTC. The exocrine pancreas was not maintained during cultures. This study demonstrates for the first time the growth of the reptilian endocrine pancreas in culture.