Characterization of the endocrine cells in the pancreatic-bile duct system of the rat.

Six types of endocrine cells showing immunolabelling against gut or pancreatic islet hormones were identified in the pancreatic-bile duct system of the normal adult rat at the light and electron microscopic levels. They were located within the epithelial lining of the duct system from the intercalated portion to its duodenal opening. However, the distribution and frequency of each endocrine cell varied along the length of the duct system. While insulin, glucagon, somatostatin, and pancreatic polypeptide cells were widely distributed along the entire duct system, small numbers of cholecystokinin and serotonin cells were confined to the terminal portion. A considerable number of somatostatin cells were concentrated in gland-like pouches of the terminal portion of the common pancreatic-bile duct. When the accessory pancreatic duct was present, insulin, glucagon, and somatostatin cells were also found in its epithelial lining. Electron microscopically, the specific content of the secretory granules of all endocrine cells was confirmed by immunolabelling or cytochemical staining. Further the characteristics of the secretory granules of each endocrine cell type corresponded to those present in the same kind of endocrine cells in gut or pancreatic islet. The duct endocrine cells displayed a particular ultrastructural appearance. The "open type cells" were highly polarized, with their apical cytoplasmic process reaching the duct lumen, whereas "closed type cells" showed long basal cytoplasmic processes with no connection with the duct lumen. In general, insulin, and somatostatin cells were of the "open type", while no morphological connection with the duct lumen was found for glucagon and pancreatic polypeptide cells. The presence of various duct endocrine cells with their particular ultrastructural appearance implies that they may take part in modulating the function of the duct system.     

An ultrastructural study on the endocrine pancreas of Caiman latirostris, with special reference to pancreatic motilin cells.

Pancreatic endocrine cells of Caiman latirostris were investigated by electron microscopy using conventional and immunocytochemical methods. Ultrastructurally, four types of endocrine cells were classified according to the morphology of their secretory granules. Three types of endocrine cells were identified as either glucagon, insulin or somatostatin cells by the presence of such characteristic granules well established in mammals. The remaining endocrine cell type could not be classified by its ultrastructural features alone. Immunocytochemical observations confirmed the ultrastructural classification of glucagon, insulin and somatostatin cells. In addition, endocrine cells immunoreactive for either pancreatic polypeptide (PP) or motilin were identified. Morphometric analysis of PP- and motilin-immunoreactive granules demonstrated that they were the most polymorphous and smallest granules among the pancreatic endocrine cell granules. Although both PP and motilin granules closely resemble each other, motilin granules were smaller in size and more spherical in shape than PP granules.     

Duct-acinar-islet cell tumor of the pancreas

A case of a rare pancreatic tumor, duct-acinar-islet cell tumor is presented. The tumor was incidentally found in the pancreatic body on computed tomography of a 21 year old male suffering from mumps. It was well demarcated from surrounding pancreas, and spherical in shape, measured 2.5 cm in diameter. Histologic and immunohistochemical examinations showed the tumor to consist of three distinct cell populations: duct, acinar and islet cells. Small cell nests consisting of these cellular components, either solely of one cell type or mixed of the three cell types, were separated by broad desmoplastic stroma. Islet (endocrine) cells, which were most predominant, were arranged in a tra-becular pattern or small cell nests. Most of them were positive for glucagon, and a few cells expressed insulin, somatostatin, serotonin or pancreatic polypeptide. These cells were distributed randomly within the cell nests. Ducts, some of which contained goblet cells, were found among the endocrine cell nests. Duct-islet complexes were also observed. The acinar cells were the least conspicuous component. They expressed pancreatic α-amylase. An electron microscopic examination revealed duct cells with intercellular attachments and interdigitations, endocrine cells containing secretory granules, and acinar cells with zymogen granules. No definite evidence suggesting malignancy could be obtained.     

Immunocytochemical studies on the islet and the gut of the arctic lamprey, Lampetra japonica

The endocrine cells and nerves in the islet and the gut of the arctic lamprey Lampetra japonica were examined immunocytochemically by using antisera against brain-gut peptides and amine. The cellular composition of the islets as reported by previous researchers in European species of the lamprey was confirmed in the present study. The islet consisted exclusively of insulin immunoreactive cells in the larvae (ammocoetes), whereas in the adult somatostatin immunoreactive cells were added to the insulin immunoreactive cells; the gut epithelium in the adult was now devoid of somatostatin cells. In the gut of the lamprey, the endocrine cells--which were flask-shaped with a cytoplasmic process extended to the lumen--were classified into three types in the larvae, but were represented by a single type in the adult. In the larval lamprey, the first type was immunoreactive for somatostatin, the second one for gastrin/cholecystokinin (CCK) and the third cell type was immunoreactive for glucagon, pancreatic polypeptide and FMRFamide, simultaneously. In the gut of the adult lamprey, the single type of endocrine cell reacted simultaneously to C-terminal specific anti-glucagon serum, N-terminal specific anti-glucagon serum, anti-bovine PP serum, anti-neuropeptide Y serum and anti-FMRFamide serum. These cells occurred most frequently in the upper intestine, their distribution decreasing from the middle to the lower intestine. Two types of peptide containing nerves were identified in the islet and the gut of the larval and adult lamprey. The first type of neurons (perikarya and fibers) was immunoreactive for serotonin and calcitonin gene-related peptide (CGRP), and was located in the mucous and muscular layer of the intestine and in the islet. The second type of neurons contained both serotonin- and gastrin releasing peptide (GRP)-like immunoreactivities and was scattered exclusively in the muscular layer of the gut. In larval and adult lampreys, a few serotonin/CGRP immunoreactive nerve cell bodies and beaded fibers were found in the connective tissue around the islet cell cords. These nerve fibers were sometimes closely apposed to the blood capillaries and to the islet cells. These findings indicate that a neuroendocrine correlation comparable with that in mammals may have been established in the islet of this most primitive vertebrate.     

Duct-Acinar-Islet Cell Tumor of the Pancreas

Two cases of pancreatic tumor consisting of duct, acinar, and islet components are reported. Both tumors measured about 1.0 cm in diameter and were without definite fibrous encapsulation. Histo-logic, immunocytochemical, and electron microscopic studies revealed three distinct cell populations: duct, acinar, and islet cells. Both endocrine and exocrine components were seen within the same cell nest. Islet components predominated in both cases. Nearly all the cells in the islet component were positive for insulin. Few cells positive for glucagon, somatostatin, or pancreatic polypeptide were present within the tumor cell nests. Duct cells were the least conspicuous cellular element of the tumor; they were positive for mucin and immuno-reactive for cytokeratin and carcinoembryonic antigens (CEA). The acinar component was the minor element of the tumor in both cases. Electron micro-scopic study also confirmed three different cell populations in the tumor: duct cells arranged in a ductal structure with intercellular attachments and microvilli, islet cells containing beta granules, and acinar cells with zymogen granules. The tumors presented herein indicate that both their endocrine and exocrine components might have been derived from a common precursor. The implication and significance of the differentiation of different cells within the same tumor is discussed in relation to the concept of an amine precursor uptake and de-carboxylation (APUD) system.     

Ontogeny, postnatal development and ageing of endocrine pancreas in Bubalus bubalis

The ontogenesis, postnatal development and ageing of the endocrine pancreas in mammals have not been extensively studied. In order to improve understanding of this organ, we studied the buffalo pancreas during fetal and postnatal development. Glucagon, insulin and somatostatin immunoreactive cells (i.c.) were first seen in 2-mo-old embryos. Pancreatic polypeptide (PP) i.c. were observed during the 3rd month of gestation. The early embryo pancreas was almost totally composed of endocrine tissue. The endocrine portion only slightly increased in mass with animal growth, whereas the exocrine portion noticeably increased in mass during the late fetal and postnatal periods. In adults, therefore, the exocrine portion was more evident than the endocrine portion. Three types of islet were observed in fetal and young buffalos: small, large and PP-islets. The small islets were composed of insulin, glucagon, somatostatin and PP i.c. The large islets were primarily composed of insulin i.c. and a few glucagon, somatostatin and PP i.c. The PP islets were mostly composed of PP i.c. with a few somatostatin, insulin and glucagon i.c. The number of large islets greatly diminished by adulthood. Glucagon, insulin, somatostatin and PP i.c. were also seen scattered in the exocrine parenchyma and along the duct epithelium. In the duct epithelium, these cells were either single or grouped, and they sometimes formed a protrusion projecting towards the connective tissue. These morphological features were primarily observed in fetuses and young buffalos.     

Localization of four polypeptide hormones in the saurian pancreas

Glucagon, insulin, somatostatin, and pancreatic polypeptide have been localized in the anolian pancreas using peroxidase-antiperoxidase immunocytochemistry. The most abundant endocrine cell type contains glucagon. Insulin-containing cells are the next most numerous. Somatostatin-immunoreactive cells tend to be localized at the periphery of the islet cords. Pancreatic polypeptide-containing cells are a minor endocrine component scattered throughout the exocrine pancreas and occasionally within the islet areas. No staining was observed after application of antigastrin serum.     

Multiple nonfunctional pancreatic islet cell tumor in multiple endocrine neoplasia type I. A case report

A case of multiple nonfunctional pancreatic islet cell tumor in multiple endocrine neoplasia type I (MEN I) is reported. The patient was a 41-year-old woman who had a past history of thyroid cancer (papillary carcinoma) and hyperparathyroidism due to parathyroid adenoma. Later, a nonfunctional pituitary tumor and five nonfunctional pancreatic tumors were found simultaneously and the patient was finally diagnosed as having MEN I. Following surgical enucleation, the pancreatic tumors were histopathologically diagnosed as benign islet cell tumors. One of them (tumor 3) exhibited a solid nodular pattern while the others showed gyriform patterns. They were divided histochemically and immunohistochemically into three types: two (tumors 1 and 2) produced a single hormone (glucagon), one (tumor 3) produced five (insulin, glucagon, somatostatin, gastrin and pancreatic polypeptide) and the remaining two (tumors 4 and 5) produced two (glucagon and pancreatic polypeptide). Electron microscopically, three types of endosecretory granules were found in the tumor cells of tumor 3 but only one type was found in tumor 4. However, in the tumor 4 extract, glucagon, pancreatic polypeptide, C-peptide, somatostatin, vasoactive intestinal peptide and growth hormone releasing factor were detected by radioimmunoassay. These findings suggest that these pancreatic tumors were both multicellular and multihormonal.     

Gastric Carcinoids of Argyrophil ECL Cells

Histochemical and ultrastructural studies were carried out in four gastric carcinoids, two of which were associated with atrophic gastritis and pernicious anemia. All tumors showed intense argyrophilia and vesicular granules resembling those of endocrine enterochromaffinlike (ECL) cells in normal human gastric mucosa. Tumor cells were found to be unreactive to all the 18 available antiserums to gut hormones, including gastrin, somatostatin, glucagon, and pancreatic polypeptide. The tumors were interpreted as ECL cell argyrophil carcinoids with various degrees of differentiation and atypia.     

Gastric Carcinoids of Argyrophil ECL Cells

Histochemical and ultrastructural studies were carried out in four gastric carcinoids, two of which were associated with atrophic gastritis and pernicious anemia. All tumors showed intense argyrophilia and vesicular granules resembling those of endocrine enterochromaffinlike (ECL) cells in normal human gastric mucosa. Tumor cells were found to be unreactive to all the 18 available antiserums to gut hormones, including gastrin, somatostatin, glucagon, and pancreatic polypeptide. The tumors were interpreted as ECL cell argyrophil carcinoids with various degrees of differentiation and atypia.     

Immunocytochemical identification of cells containing insulin, glucagon, somatostatin, and pancreatic polypeptide in the islets of Langerhans of the guinea pig pancreas with light and electron microscopy

Cell types containing insulin, glucagon, somatostatin, and pancreatic polypeptide were identified in guinea pig islets with light and electron microscopic immunoperoxidase staining. Cells containing immunostainable insulin (B cells) are located throughout the islets, including the islet periphery, and contain irregularly shaped granules (350-550 nm). Granule contents are of variable opacity and are often fragmented but not crystalloid. Cells containing immunoreactive glucagon (A cells) are found in the interior of islets and contain numerous spheroid electron-opaque granules (250-350 nm). Cells containing immunoreactive somatostatin (D cells) have elongate, axonlike processes that end adjacent to islet capillaries. D cells, which are very numerous and distributed uniformly throughout the islet parenchyma, contain small spheroid granules (150-25 nm) of pale electron opacity. Cells with immunoreactive pancreatic polypeptide (F cells) are rare in islets but numerous among the exocrine parenchyma. F cells contain pale spheroid granules (100-200 nm). Morphological criteria are reliable indicators for A cells and B cells, but D cells and F cells require immunostaining for positive identification.     

Immunocytochemical identification of cells containing insulin,glucagon, somatostatin,and pancreatic polypetide in the islets of langerhans of the guinea pig pancreas with light and electron microscopy

Cell types contianing insulin, glucagon, somatostatin, and pancreatic polypetide were identified in guinea pig islets with light and electron microscopic immunoperoxidase staining. Cells containing immunostainable insulin (B cells) are located throughout the islets, including the islet periphery, and contain irregularly shaped granules (350–550 nm). Granule contents are of variable opacity and are often fragmented but not crystalloid. Cells containing immunoreactive glucagon (A cells) are found in the interior of islets and contain numerous shperoid electron-opaque granules (250–350 nm). Cells containing immunoreactive somatostatin(D cells) have elongate, axonlike processes that end adjacent to islet capillaries. D cells, which are very numeous and distributed uniformly throughout the islet parenchyma, contain small spheroid granules (150–250 nm) of pale electron opacity. Cells with immunoreactive pancreatic polypeptide (F cells) are rare in islets but numerous among the exocrine parenchyma. F cells contain pale spheroid granules (100–200 nm). Morphological criteria are reliable indicators for A cells and B cells, but D cells and F cells require immunostaining for positive identification.     

An immunohistochemical study on the pancreatic endocrine cells of the three-toed sloth, Bradypus variegatus.

The cellular composition and relative frequency of the occurrence of pancreatic endocrine cells were studied immunohistochemically in a primitive eutherian and arboreal folivore, the three-toed sloth, since previous histochemical and ultrastructural studies on the endocrine pancreas of the sloth have detected only a single islet cell type, the A cell. In the sloth pancreas, four types of endocrine cells immunoreactive for glucagon, insulin, somatostatin and serotonin (5-hydroxytryptamine) were found as reported in the pancreas of human and common experimental mammals, but pancreatic polypeptide-immunoreactive cells were not detected by either avian- or bovine-pancreatic polypeptide antiserum. The endocrine cells were distributed mainly in the islets and partly also in the exocrine tissue including the pancreatic ducts. Larger or smaller clusters consisting of glucagon- and insulin-immunoreactive cells were also found frequently in the interlobular connective tissue. In the islets, glucagon- and insulin-immunoreactive cells were the most prominent cell type, while somatostatin- and serotonin-immunoreactive cells were sparse. The most striking feature in the sloth pancreas is the high frequency of glucagon-immunoreactive cells, because these cells are by far less in number than insulin-immunoreactive cells in the islets of human and common experimental mammals. This appears to be an intriguing characteristic of the sloth pancreas in a possible relation to the animal's unique metabolic system and the phylogenetical position.     

Morphology and endocrine production of cells in the islets of Langerhans of the Chacma baboon

Biopsies of the pancreas head, tail, and uncinate regions of 6 Chacma baboons (Papio ursinus) were processed for ultrastructural and immunocytochemical (ICC) studies using avidin-biotin peroxidase label for light microscopy (LM) and immunogold for electron microscopy (EM). Survey 0.5 micron sections of Spurrs resin embedded tissue revealed areas of suitable islets. Thin 100-nm sections were then cut and stained from the osmicated blocks for ultrastructural studies. For ICC investigations, 1 micron sections were immunolabeled for LM before areas were selected for thin sectioning for ultrastructural immunolabeling. The baboon endocrine pancreas ultrastructure was found to be similar to that of other mammals with minor differences in islet and secretory granule size and shape and in electron opacity of the secretory granule cores. Insulin glucagon, somatostatin and pancreatic polypeptide (PP) producing cells were described. A small number of cells were seen to contain both glucagon and PP and some D cells were observed to contain a few granules with both the appearance and immunoreactivity of A cell secretory granules. Statistical analysis of 100 secretory granule diameters of each of the 4 cell types in 6 baboons revealed significant differences (p less than 0.001) in size between all but those of the A and D cells. The insulin precursor subunit, C-peptide, and the glucagon precursor, glicentin, were each found together with the final hormone product in their respective secretory granules. The precursors were often located toward the periphery of the secretory granule, suggesting that the conversion of precursor to active hormone may be membrane associated. A nonrandom topographical association was observed between A and D cells, suggesting a strong functional implication.     

Amylin in pancreatic islets and pancreatic endocrine neoplasms

Amylin is a chief constituent of the amyloid present in insulinomas, and is colocalized in beta islet cells. By immunocytochemical staining, all four islet cells including insulin, glucagon, somatostatin (SRIF) and pancreatic polypeptide (PP) cells were positively stained for amylin. The strongly insulin-positive cells corresponded with the strongly amylin-positive cells, and glucagon cells appeared to be strongly positive for amylin, whereas SRIF and PP cells were weakly positive for amylin. Among 37 cases of pancreatic endocrine neoplasms, insulinomas were more stronger stained for amylin than other islet cell tumors; however, amylin staining was the same or weaker than insulin staining. Glucagonomas and PP-omas were weakly positive for amylin, whereas six of 11 gastrinomas were weakly positive for amylin. It is concluded that three orthoendocrine tumors including insulinomas, glucagonomas and PP-omas were all positive for amylin, whereas ectopic hormone secreting gastrinomas were positive for amylin in six of 11 cases (55%). This colocalization of amylin with insulin, glucagon and PP may support a structure-function relationship of amylin and pancreatic hormones. The lesser immunoreactive amylin in pancreatic endocrine neoplasms than in normal islet cells may contribute to autonomous hypersecretion of hormones by pancreatic endocrine neoplasms.     

Malignant islet cell tumor of the pancreas with multiple hormone production and expression of CEA and CA19-9. Report of an autopsy case.

An autopsy case of malignant islet cell tumor of the pancreas is presented. The patient, a 64-year-old woman showed severe hypoglycemia as the initial symptom, and hyperinsulinemia was demonstrated by laboratory examinations. Metastatic tumors in the liver were found by abdominal computed tomography. Autopsy revealed a tumor measuring 6.5 x 3 x 2 cm occupying the pancreas from the body to the tail. From the results of histological and immunohistochemical studies, this was diagnosed as a malignant islet cell tumor producing multiple hormones such as insulin, glucagon, somatostatin and pancreatic polypeptide, as well as expressing the tumor-related antigens CEA and CA19-9. These findings suggested that the tumor cells showed differentiation to both endocrine cells and pancreatic duct cells.     

Colocalization of pancreatic polypeptide and insulin in secretory granules of a pancreatic endocrine neoplasm

A 45-year-old woman presented with clinical symptoms of hypoglycemia of 4 months duration. Laboratory testing confirmed hyperinsulinemia; mild hypercalcemia and hypergastrine-mia were also documented. At the time of operation, 3 pancreatic endocrine neoplasms were found, and a diagnosis of multiple endocrine neoplasia type I was made. Immunohistochem-istry and immunoelectron microscopy showed all the tumors to be plurihormonal, each containing three or more of the following: insulin, glucagon, somatostatin, pancreatic polypep-tide, gastrin, and serotonin. Electron microscopy of 2 tumors revealed numerous atypical granules. In 1 tumor, pancreatic polypeptide and insulin were colocalized in secretory granules by dual-staining immunoelectron microscopy. To our knowledge, this combination of hormones has not been described previously in pancreatic endocrine neoplasms and suggests that such neoplasms, like mature pancreatic endocrine cells, may originate from pluripotential common precursor cells.     

Pancreatic endocrine carcinoma with multiple hormone production in a raccoon (Procyon lotor)

A pancreatic endocrine carcinoma with lung metastases was found in a 15-year-old male raccoon. This tumour was characterized by great variation in cell size and production of multiple polypeptide hormones. Endocrine markers expressed by the neoplastic cells were, in descending order of frequency, chromogranin A, pancreatic polypeptide (PP), glucagon, somatostatin and insulin. Co-expression of PP and glucagon, somatostatin or insulin was demonstrated immunohistochemically with consecutive sections, and cells with both glucagon and insulin were also observed. The pattern of co-expression was similar to that in the earliest stages of murine pancreatic development. Amyloid deposits in the islets of Langerhans, which reacted with antibody to islet amyloid polypeptide, were thought to be associated with age.     

Development of pancreatic islets in pancreatic polypeptide-overexpressing mice

Recently we produced pancreatic polypeptide transgenic (PPTG) mice and found that PP was overexpressed in pancreatic islets. The present study examines development of four islet hormones in PPTG mice at embryonic days (ED) 15, 17, and 19, and in adult animals. Adult PPTG mice showed massive aggregation of PP-positive cells and glucagon-positive cells seen at the central area of the islets. Confocal laser microscopic study showed that three islet hormones (insulin, glucagon and PP) were completely overlapped in islets of PPTG mice. Overlapping of somatostatin/glucagon and somatostatin/PP were also increased at the peripheral area of the islets in adult PPTG mice compared to wild-type mice. In prenatal development of pancreatic islets of PPTG mice, somatostatin/glucagon overlapping cells appeared at ED 15, two days earlier than in wild-type mice. Differentiation of these somatostatin/glucagon double-positive cells into single-positive cells was disturbed in the PPTG mice during perinatal to postnatal periods. Differentiation of glucagon/insulin-double positive cells into single-positive cells was disturbed remarkably in postnatal development of the islets of PPTG mice. The present results suggest that early and overexpression of PP may engender the early appearance of somatostatin producing cells; however, that may disturb differentiation of multihormonal immature endocrine cells into single hormonal mature endocrine cells.     

Malignant Islet Cell Tumor of the Pancreas with Multiple Hormone Production and Expression of CEA and CA19-9

An autopsy case of malignant islet cell tumor of the pancreas is presented. The patient, a 64 year old woman showed severe hypoglycemia as the initial symptom, and hyperinsulinemia was demonstrated by laboratory examinations. Metastatic tumors in the liver were found by abdominal computed tomography. Autopsy revealed a tumor measuring 6.5x3x2cm occupying the pancreas from the body to the tail. From the results of histological and immunohistochemical studies, this was diagnosed as a malignant islet cell tumor producing multiple hormones such as insulin, glucagon, somatostatin and pancreatic polypeptide, as well as expressing the tumor-related antigens CEA and CA19-9. These findings suggested that the tumor cells showed differentiation to both endocrine cells and pancreatic duct cells. Acta Pathol Jpn 41: 150-157, 1991.