The Ultrastructure of the Endocrine Pancreas of the Grass Lizard,Mabuya quinquetaeniata*

Four endocrine cell types were identified ultrastructurally in the pancreas of the grass lizard, Mabuya quinquetaeniata. These cells were similar in shape, location and frequency to the previously described B-, A-, D- and PP-cells. The secretory granules of the B-cells were round or oval in profile, with an internal core of variable shape. The mean diameter of the B-cell granules was 780 nm (range 350–1000 nm). The A-cell granules were round, oval or irregular in shape and highly electron dense, with a narrow electron lucent space between the core and the limiting membrane. The mean diameter of these granules was 450 nm (range 200–750 nm). The D-cell granules were round, oval or irregular and of moderate electron density, with an average diameter of 340 nm (range 200–500 nm). The limiting membrane was closely apposed to the core or separated from it by a narrow lucent space. PP-cell granules were round with high electron density and with a narrow space between the core and the limiting membrane, and their average diameter was 150 nm (range 50–350 nm); these secretory granules accumulated at the cytoplasmic process. Tracing of the cytoplasmic processes of PP-cells in serially cut ultrathin sections revealed that most of these processes ended in the vicinity of blood capillaries, indicating that the PP-cells were endocrine rather than paracrine.     

Immunocytochemical identification of polypeptide YY (PYY) cells in the human gastrointestinal tract

Various parts of the human gastrointestinal tract were investigated immunocytochemically for the occurrence of polypeptide YY (PYY) and pancreatic polypeptide (PP). PYY-immunoreactive cells were observed in the lower part of the ileum, in the colon and in the rectum, and PP-immunoreactive cells were found in the colon and rectum. Both cell types were of the open type, i.e. they extended from the basal lamina to the gut lumen. PYY-immunoreactive cells were seen to emit cytoplasmic processes to the neighbouring goblet cells. This latter observation suggests that PYY cells may exert a paracrine action on the mucus-secreting goblet cells. Staining of consecutive thin plastic sections and staining of the same section simultaneously for two peptides showed that PYY-immunoreactivity did not occur in PP- or enteroglucagon-immunoreactive cells. On the ultrastructural level PYY-immunoreactivity was localized in basal granulated endocrine cells. These cells contained round or slightly oval electron dense granules with a mean diameter of 150 nm (range 100-300 nm).     

Ultrastructure of endocrine cells in the stomach of two teleost fish Perca fluviatilis L. and Ameiurus nebulosus L.

Summary In the gastric mucosa of two teleost species, the perch (Perca fluviatilis) and the catfish (Ameiurus nebulosus) three endocrine cell types were found, located predominantly between the mucoid cells of the gastric mucosa. A fourth cell type is present in the gastric glands of catfish. Each cell type was defined by its characteristic secretory granules. Type-I cells were predominant in both fish. These cells contained round or oval granules with a pleomorphic core. The average diameter of granules was 400 nm for the perch and 270 nm for the catfish. Type-II cells of both species displayed small, highly osmiophilic granules about 100 nm in diameter. The secretory granules of type-III cells (260 nm in the perch and 190 nm in the catfish) were round or slightly oval in shape and were filled with a finely particulate electron-dense material. Type-IV cells of the catfish were found in the gastric glands only. Their cytoplasm was filled with homogeneous, moderately electron-dense granules averaging 340 nm in diameter. The physiological significance of these different morphological types of gastric endocrine cells requires further investigation.     

Co-localization of peptides in the Brockmann bodies of the cod (Gadus morhua) and the rainbow trout (Oncorhynchus mykiss)

Endocrine cells exhibiting immunoreactivity to FMRFamide-like, LPLRFamide-like, neuropeptide Y(NPY)-like and peptide YY(PYY)-like peptides were found in the periphery of the Brockmann bodies of the cod, Gadus morhua, and rainbow trout, Oncorhynchus mykiss. No immunoreactivity or very weak labelling was found with antisera to pancreatic polypeptide (PP). Vasoactive intestinal polypeptide (VIP)-like immunoreactivity was found in nerve fibres, whereas labelling with VIP antiserum in endocrine cells disappeared after preincubation with nonimmune serum. There were always more immunoreactive cells in the rainbow trout than in the cod. No immunoreactivity could be seen with antisera to gastrin/cholecystokinin (CCK) or enkephalin. Double-labelling studies were performed to study the colocalization of the peptides in peripheral endocrine cells. Cells immunoreactive to NPY were also labelled with antisera to FMRFamide, LPLRFamide and PYY. The co-localization pattern of NPY varied; in some Brockmann bodies, a population of the immunoreactive cells showed co-localization and others contained NPY-like immunoreactivity only, whereas in other Brockmann bodies, all NPY-labelled cells also contained FMRFamide-like, LPLRFamide-like and PYY-like immunoreactivity. Cells immunoreactive to PYY similarly contained FMRFamide-like, LPLRFamide-like and NPY-like immunoreactivity, comparable to the patterns observed with NPY. Glucagon-like immunoreactivity was found at the periphery of the Brockmann bodies. A subpopulation of the glucagon-containing cells contained NPY-like immunoreactivity. PYY-like immunoreactivity was also found co-localized with glucagon-like immunoreactivity, as were FMRFamide-like and LPLRFamide-like immunoreactivity. Therefore, either NPY-like and PYY-like immunoreactivity together with FMRFamide-like and LPLRFamide-like immunoreactivity occur in the same endocrine cells of the Brockmann body of the cod and rainbow trout, or a hybrid NPY/PYY-like peptide recognized by both NPY and PYY antisera is present in the Brockmann body.     

Gamma-aminobutyric acid immunoreactivity in the enterochromaffin cells of the rat stomach.

The present immunocytochemical study revealed gamma-aminobutyric acid (GABA) immunoreactivity in the oxyntic and pyloric mucosa of the rat stomach at light- and electron-microscopic levels. GABA-immunoreactive endocrine cells were numerously seen in the lower half portion of the pyloric mucosa but rarely in the oxyntic mucosa. These cells were round or oval in shape and sometimes had a short cytoplasmic process. Serotonin-immunoreactive enterochromaffin (EC) cells were also observed in the oxyntic and pyloric mucosa of the stomach. The distribution and shapes of the immunoreactive cells were similar to those of the GABA-immunoreactive cells. With a double immunolabeling technique using anti-GABA and antiserotonin serum, GABA-immunoreactive endocrine cells showed serotonin immunoreactivity and were identified as EC cells. At the electron-microscopic level the GABA-immunoreactive cells contained round or oval, spindle-like, pear-shaped granules in EC cells. The immunoreaction product in the EC cells was generally confined to the granular cores. These findings suggest that GABA may be synthesized in the EC cells and be released from the granules of the cells after adequate stimuli.     

Immunohistochemical and ultrastructural study of anterior pituitary cells in the female Afghan pika,Ochotona rufescens rufescens

An immunohistochemical study of the anterior pituitary gland of the female Afghan pika was carried out to distinguish the ultrastructural features of GH, PRL, ACTH, TSH and LH cells. The histochemically identified GH cells resembled ultrastructurally oval or round GH cells of the rat laden with large, dense secretory granules. PRL cells were divided into three subtypes based on differences in the diameter of their spherical secretory granules. They lacked polymorphic or irregularly shaped secretory granules. ACTH cells resembled ultrastructurally, in some respects, Siperstein's "corticotrophs" of the rat with peripheral arrangement of secretory granules. However, they were not always stellate, but elongate or angular in shape. The dense secretory granules were concentrated in the peripheral area of cytoplasm. TSH cells were non-stellate, but usually oval in shape, containing the smallest spherical secretory granules (100-200 nm in diameter). Almost all LH cells reacted also with FSH antiserum. They were irregular in shape, sometimes in contact with or surrounded the GH cells. They contained an abundance of medium-sized secretory granules (140-260 nm in diameter) which were larger than those in the LH cells of the female rat throughout the estrous cycle. Large secretory granules in the LH cells of the female pika seemed to be related to the endocrine state of persistent estrus.     

Classifications of somatotropes, lactotropes and corticotropes in the mouse adenohypophysis with immunohistochemistry

Somatotropes, lactotropes and corticotropes of adult male mice were identified with immunohistochemistry in the adenohypophysis fixed by OsO4 alone. Somatotropes were classified into type I somatotropes that contain large (350 nm in diameter) round secretory granules and type II somatotropes that contain small (100-200 nm in diameter) round secretory granules. Most somatotropes were type I somatotropes. Lactotropes were also classified into type I lactotropes that contain irregularly shaped secretory granules and type II lactotropes containing small (100-200 nm in diameter) round secretory granules. Corticotropes are irregular stellate or slender cells with little cytoplasm. They contain round solid secretory granules in various densities along the cell periphery. Most of these are low-density granules (200-300 nm in diameter) and a few are high-density granules (200-250 nm in diameter). These data were compared with the classical data of mouse adenohypophysial cells that were fixed in OsO4 alone and identified only by conventional electron microscopy.     

Behavior of Primary Mesenchyme Cells In situ Associated with Ultrastructural Alteration of the Blastocoelic Material in the Sea Urchin, Anthocidaris crassispina

In the blastula of the sea urchin, Anthocidaris crassispina , a small number of primary mesenchyme cells (PMCs) ingressed from the blastocoel wall taking a bottle shape. The majority of the PMCs followed the first group of PMCs. These ingressed without taking the bottle shape, and became round within the blastocoel wall. After ingression, the PMCs migrated as single cells retaining their round cell contour. The average velocity of their migration was 13.3 μm/hr.
The blastocoel contained Alcian blue (pH 1.0)-positive material which changed its light microscopic configuration from being amorphous in the hatched and mesenchyme blastulae to being fibrous in the early gastrulae. Ultrastructurally, the blastocoelic material in the hatched blastulae was composed of 27 nm diameter granules. In the mesenchyme blastulae and the early gastrulae relatively long 15 nm diameter fibers were seen in addition to the 27 nm diameter granules. The 27 nm diameter granules bound the ruthenium red while the 15 nm diameter fibers did not. The 27 nm diameter granules formed aggregates in the hatched blastulae, and were bound to the 15 nm diameter fibers in the mesenchyme blastulae and early gastrulae to form a fibrous network which was observed by a light microscope.     

Eight types of endocrine cells in the abomasum of sheep

In the ovine abomasum, 8 types of endocrine cells were classified at ultrastructural level. The gastric-type EC cells contained oval and pleomorphic granules with high electron density. The intestinal-type EC cells were filled with oval, irregular and highly dense granules. ECL cells contained irregular granules with high density and wide clear spaces. D cells were filled with round granules showing low to moderate density and finely granular matrix D1 cells contained round or oval granules with variable, low to moderate density and finely granular content. G cells showed round and oval granules with moderate density, densely packed or flocculent content. F cells were filled with oval or elliptic granules showing low density with a finely granular and flocculent matrix. X cells contained round granules with high density and homogeneous material. Gastric-type EC cells, intestinal-type EC cells, D cells, and D1 cells were represented in the cardiac, fundic and pyloric gland areas of the ovine abomasum. ECL cells and F cells were confined to the fundic glands, G cells and X cells to the pyloric glands.     

Identification of lactotropes (PRL cells), somatotropes (GH cells), corticotropes (ACTH cells) and thyrotropes (TSH cells) in the pituitary gland of the musk shrew, Suncus murinus L. (Insectivora), by immunohistochemistry

By means of immunohistochemistry, lactotropes, somatotropes, corticotropes and thyrotropes in the pituitary of the male musk shrew, Suncus murinus L., were identified at the electron-microscopic level. Lactotropes were classified into three types: type I containing large (200-450 nm in diameter) round secretory granules, type II with medium-sized (150-250 nm in diameter) ones and type III with small (50-150 nm in diameter) ones. Somatotropes were also classified into type I somatotropes that contain large (450 nm in diameter) spherical secretory granules and type II somatotropes containing comparatively small (300 nm in diameter) round granules. Both type I and II somatotropes were small and sometimes contained rod-shaped granules. Corticotropes were round or oval cells with round secretory granules in various densities and sizes (150-500 nm in diameter) scattered all over the cytoplasm. Thyrotropes were angular or polyhedral cells containing electron-transparent round secretory granules (200-300 nm in diameter) and large irregularly shaped granules with a maximum diameter of about 1,500 nm. Each type of the cells may be distinguished by its respective ultrastructural characteristics alone without the aid of immunohistochemistry.     

Ultrastructural identification of human secretin cells by the immunogold technique. Their costorage of chromogranin A and serotonin

We have localized secretin in a morphologically distinctive endocrine cell scattered in the epithelium covering the villi and uppermost crypts of the human duodenum and jejunum. The human secretin cell was characterized by relatively large (mean diameter 299 nm +/- 69 SD), fairly irregular granules, the majority of which showed homogeneous distribution of secretin and chromogranin A immunolabelling in a structurally homogeneous core. Other granules had a targetoid pattern due to an inner, argyrophobe, secretin-immunoreactive body surrounded by an argyrophil, chromogranin A immunoreactive mantle. These targetoid granules represent a distinctive ultrastructural marker of the secretin cell. Secretin cell granules have been shown to react with chromogranin A antibodies and Grimelius' silver, while lacking chromogranin B immunoreactivity. About 1/3 of secretin cells also showed serotonin immunostaining.     

An ultrastructural study on gastric endocrine cells in the stomach gland patch of the koala Phascolarctos cinereus

The endocrine cells in the stomach gland patch of the koala (Phascolarctos cinereus) were studied ultrastructurally. They were classified into 3 types based on the ultrastructural profiles of their endocrine granules and tentatively categorized as type I, II, and III endocrine cells. Type I cells contained round granules that were for the most part larger than those observed in the other 2 cell types. The granules ranged from moderate to relatively high in electron density. Type II cells were angular in shape and characterized by the presence of granules that were polymorphous in profile. Contents of the endocrine granules in type II cells also showed a range of high to moderate electron density. Type III cells were oval or pyramidal in shape. They contained highly polymorphous granules that were round, oval, dumbbell-like or comma in shape and characterized by the presence of a clear space or halo separating the high to low electron-dense core from the limiting membrane of granules. Type III cells were observed most often whereas type I and II cells were a less frequent observation.     

Immunoelectron cytochemical localization of motilin and substance P in rabbit bile duct enterochromaffin (EC) cells.

Using an immunoreactive technique the two peptides, motilin and Substance P, have been localized at the ultrastructural level in enterochromaffin (EC) cells. Motilin occurs in cells containing a mixed population of biconcave and round secretory granules whereas Substance P is found in cells with exclusively round granules. These observations confirm the existence of at least two functionally and morphologically different types of EC cell in rabbit bile duct, both of which contain 5-hydroxytryptamine. Classification of the endocrine cells of the gut on a purely morphological basis is clearly impossible, however.     

Light and electron microscopic study on the endocrine cells of the pancreas in a marine teleost,Fugu rubripes rubripes

Summary The pancreatic endocrine tissue of Fugu rubripes rubripes consists of numerous round principal islets (Brockmann bodies) of various sizes scattered around the gall-bladder. The endocrine cells are divided into A-, B-, D-, and F_f-cells. Each cell type was identified by comparing thick and thin sections in both light and electron microscopy. Aldehyde-fuchsin positive B-cells contain numerous round secretory granules (average diameter 300 nm) each of which has a round compact core of moderate density; a narrow space exists between this core and the limiting membrane. Grimelius' silver positive A cells contain round secretory granules (average diameter 360 nm) with a hexagonal or tetragonal crystalline core (average diameter 170 nm) of high density; the silver grains preferentially appear in the space between the limiting membrane and the core. The crystalline core of each -granule often contains an appendix-like structure of variable shape. D cells blackened by the silver impregnation method of Hellman and Hellerström (1960) have round secretory granules (average diameter 320 nm) filled with a flocculent material of low density. The fourth cell type (F_f-cell) has a clear cytoplasm after differential staining for light microscopy. By electron microscopy, this cell has elongated fusiform secretory granules (520 nm average length × 230 nm average width) filled with numerous filaments arranged in parallel with the longitudinal axis. Figures suggesting granule formation in the sacs of the Golgi apparatus were obtained in all of islet cell types. Equivalents of emiocytotic release of secretory granules were encountered in the A and F_f cells.     

Correlative immunocytochemical and electron microscopic studies: identification of (entero)glucagon- somatostatin- and pancreatic polypeptide-like-containing cells in the human colon

Correlative immunocytochemical and electron microscopic studies, using the semi thin-thin technic, were performed to identify the (entero) glucagon, somatostatin and pancreatic polypeptide-like immunoreactive cells of the human colonic mucosa. Mean granule diameter for each cell type was estimated according to two methods and histograms showing the granule size distribution were constructed. A total of 139 immunostained cells identified at the ultrastructural level were analyzed. Mean granule diameter for (entero)glucagon-containing cells was 318 +/- 11 nm but a reduction of granule size with age was noteworthy: granules were larger in the fetus (mean diameter 350 +/- 15) than in adults (mean diameter 310 +/- 10 nm). Somatostatin-containing cells, very rare in adults, were present in the fetal distal colon. Their general mean granule diameter was 354 +/- 18 nm but many cells had a mean granule diameter of more than 400 nm. A pancreatic polypeptide-like immunoreactivity was found only in (entero)glucagon-containing cells, pointing out the possible occurrence of both peptides (or of similar sequences) in the same cells. Previous ultrastructural studies dealing with a tentative classification of the human colonic endocrine cells were compared with the present data.     

Ultrastructural and immunohistochemical study of endocrine cells in the midgut of the cockroach Blaberus craniifer (Insecta,Dictyoptera)

Summary The midgut of Blaberus craniifer is principally made up of columnar epithelial cells which are derived from small regenerative cells found grouped in nidi. Between them, small sparsely granulated cells with clear cytoplasm can be observed lying on the basal lamina. Mainly based on the size, shape and texture of their secretory granules, at least ten types of such endocrine cells have been identified. Five cell types contain a uniform population of dense granules: (1) medium-sized, round to oval granules; (2) small elongated granules; (3) large irregular granules; (4) oval granules with a highly osmiophilic core; (5) oval, haloed granules. Five others are characterized by a heterogeneous population of granules: (6) small, round to oval, variably electron-dense granules; (7) oval medium-sized granules of variable electron density; (8) large irregular granules of variable electron density; (9) small dense granules and large vesicles with filamentous material; (10) small dense granules and very large pale vesicles.In addition, near the regenerative cells, large cells characterized by very large, irregular, dense granules (up to 4 m), lack contact with the lumen, and reach the basal lamina only by slender cytoplasmic processes.Several antisera raised against mammalian peptides and amine were used to reveal axonal fibers and endocrine cells. Serotonin-like immunoreactivity is localized in a profuse innervation of the muscle layers that surround the epithelium, whereas cholecystokinin and methionine-enkephalin antisera stain a more moderate number of axonal fibers. Cholecystokinin-, methionine-enkephalin-, substance P-, vasoactive intestinal peptide-, somatoliberin-, and gonadoliberin-like immunoreactivities were detected in endocrine cells of the epithelium. While most of the cells appear pyramidal, oval, fusiform or bowl-shaped, and seem to lack contact with the lumen, cells reaching it have been detected reacting with antisera to cholecystokinin, substance P, vasoactive intestinal peptide, somatoliberin and gonadoliberin.     

Two types of mammosomatotropes in mouse adenohypophysis

Summary Two types of mammosomatotropes (MS), the small-granule and vesicle-granule MS, were detected in mouse adenohypophysis by electron microscopy and immunohistochemistry. Both cell-types were immunoreactive to prolactin (PRL) and growth hormone (GH) antisera. The small-granule MS contained small, round, solid secretory granules about 100 nm in diameter, and were smaller than the classical GH and PRL cell-types. The vesicle-granule MS contained secretory granules like cored vesicles, and were larger than classical GH and PRL cells. Small-granule MS were immunoreactive to both PRL and GH antisera in the same region of the cell cytoplasm; the vesicle-granule MS, however, were immunoreactive to only PRL antiserum in most cytoplasmic areas, and a positive response to both PRL and GH antisera was confined to only certain small areas.     

Localization of xenin-immunoreactive cells in the duodenal mucosa of humans and various mammals.

Xenin is a 25-amino-acid peptide extractable from mammalian tissue. This peptide is biologically active. It stimulates exocrine pancreatic secretion and intestinal motility and inhibits gastric secretion of acid and food intake. Xenin circulates in the human plasma after meals. In this study, the cellular origin of xenin in the gastro-entero-pancreatic system of humans, Rhesus monkeys, and dogs was investigated by immunohistochemistry and immunoelectron microscopy. Sequence-specific antibodies against xenin detected specific endocrine cells in the duodenal and jejunal mucosa of all three species. These xenin-immunoreactive cells were distinct from enterochromaffin, somatostatin, motilin, cholecystokinin, neurotensin, and secretin cells, and comprised 8.8% of the chromogranin A-positive cells in the dog duodenum and 4.6% of the chromogranin A-positive cells in human duodenum. In all three species, co-localization of xenin was found with a subpopulation of gastric inhibitory polypeptide (GIP)-immunoreactive cells. Immunoelectron microscopy in the canine duodenal mucosa demonstrated accumulation of gold particles in round, homogeneous, and osmiophilic secretory granules with a closely adhering membrane of 187 +/- 19 nm diameter (mean +/- SEM). This cell type was found to be identical to the previously described canine GIP cell. Immunocytochemical expression of the peptide xenin in a subpopulation of chromogranin A-positive cells as well as the localization of xenin immunoreactivity in ultrastructurally characterized secretory granules permitted the identification of a novel endocrine cell type as the cellular source of circulating xenin.     

Immunocytological studies of C cells with anti-calcitonin or antisomatostatin immunoserums in rats treated with vitamin D, thyroxine or benzyl-thiouracil]

In rats treated with vitamin D3, thyroxin or BTU alone or with associations of vitamin D3 + BTU or vitamin D + thyroxin, immunocytochemical studies with an anti-human calcitonin serum show a stimulating effect of vitamin D and of thyroxin and an inhibiting effect of BTU on the C cells of the thyro?d. These results are in agreement with the existence of functional relations between follicular and C cells. A few calcitonin-containing cells are immunoreactive to an anti-somatostatin serum. All the C cells contain both calcitonin and somatostatin when they are grouped in a single big interfollicular cluster.