Peptide and amine producing endocrine-like cells in the chicken thymus

Summary The thymus of the chicken contains at least two types of endocrine-like cells predominating in the juxtacortical medulla. One type stores 5-hydroxytryptamine and is stained by the argentaffin, chromaffin and Schmorl methods. Treatment with reserpine markedly reduces its 5-hydroxytryptamine content. The other cell type is devoid of 5-hydroxytryptamine; if supplied withl-dopa it can produce and store dopamine. Both cell types stain with the argyrophil method of Grimelius and with HCl-basic dye methods believed to reflect the presence of peptides with masked carboxyl groups. In the electron microscope both cell types were found to contain numerous cytoplasmic 2000–3000 ? granules similar to those seen in polypeptide hormone-producing cells elsewhere. The cytoplasmic granules in one of the two endocrine-like cell types are argentaffin and chromaffin, indicating that they are the storage site for 5-hydroxytryptamine. It is suggested that the main secretory products of the two endocrine-like cell types are peptides, possibly regulating lymphatic tissue function.     

Neuroepithelial bodies in the lung of the tree frog,Hyla arborea L.

Summary The endocrine-like cells (ELC), which together with nerve endings form the neuroepithelial bodies, are located on primary and secondary septa in the non-ciliated epithelium of the lung of Hyla arborea. ELC protrude markedly toward the lumen of the lung and are surrounded by pneumocytes, which separate ELC from the lumen by thin cytoplasmic processes. ELC possess a light cytoplasm containing two types of granules: (i) numerous small granules, 50–110 nm in diameter, and (ii) single large granules, 290–860 nm in diameter. Numerous nerve fibers, often forming synaptic junctions, can be observed in contact with ELC.This study was supported by a grant No. 476/II from the Polish Academy of Sciences     

Endocrine cells of the human gastric mucosa

Summary By light and electron microscopy investigation of the human gastric mucosa five types of ultrastructurally different endocrine cells have been detected: 5-hydroxytryptamine storing enterochromaffin (EC) cells, gastrin storing G cells, and functionally undefined ECL, D and D₁ cells. By direct application of Masson's argentaffin reaction as well as of Sevier-Munger's and Grimelius' argyrophil method to electron microscopy specimens, selective deposition of silver grains upon the endocrine granules of such cells was obtained. In particular, only EC cell granules reacted to the argentaffin method, granules of both EC and ECL cells heavily reacted to Sevier-Munger's technique, granules of EC, ECL, G and D₁ cells reacted to Grimelius' technique, while D cell granules failed to react either to argentaffin or argyrophil methods. By the application of the same silver methods to paraffin sections as well as by other selective staining methods for endocrine granules (5-hydroxytryptamine techniques, lead-haematoxylin, HCl-basic dye method), at least four of the above cell types were also identified under light microscope. This opens the way for extensive studies of such cells in conventional histologie specimens.This investigation was supported in part by grant N.70.01022.04 from the Italian Consiglio Nazionale delle Ricerche.     

Exocrine pancreas under experimental conditions

Summary At least four types of endocrine-like cells have been detected histochemically in the mucosa of the human colon and rectum, i.e. argentaffin cells storing 5-hydroxytryptamine (5 HT) and non-argentaffin cells reacting with glucagon, somatostatin and bovine pancreatic peptide (BPP) antibodies. Ultrastructurally, four main types and three rare types of endocrine-like cells have been identified. Among the former cells were: (1) argentaffin EC₁ cells, known to store 5 HT and substance P, (2) poorly argyrophil L cells, corresponding to the glucagon-immunoreactive cells storing enteroglucagon or glucagon-like immunoreactivity (GL1), (3) inconstantly argyrophil F-like cells, possibly corresponding to BPP-immunoreactive cells, and (4) fairly argyrophil H cells of unknown function. Rare D cells, corresponding to somatostatin cells, N cells, corresponding to neurotensin cells, and P cells, of unknown function, have been also found.Supported in part by the Italian National Research Council (Grant N. 76.01558.04)     

Quantification of endocrine cells and ultrastructural study of insulin granules in the large intestine of opossum Didelphis aurita (Wied-Neuwied, 1826)

This study aimed to investigate the distribution of argyrophil, argentaffin, and insulin-immunoreactive endocrine cells in the large intestine of opossums (Didelphis aurita) and to describe the ultrastructure of the secretory granules of insulin-immunoreactive endocrine cells. Fragments of the large intestine of 10 male specimens of D. aurita were collected, processed, and subjected to staining, immunohistochemistry, and transmission electron microscopy. The argyrophil, the argentaffin, and the insulin-immunoreactive endocrine cells were sparsely distributed in the intestinal glands of the mucous layer, among other cell types of the epithelium in all regions studied. Proportionally, the argyrophil, the argentaffin, and the insulin-immunoreactive endocrine cells represented 62.75%, 36.26%, and 0.99% of the total determined endocrine cells of the large intestine, respectively. Quantitatively, there was no difference between the argyrophil and the argentaffin endocrine cells, whereas insulin-immunoreactive endocrine cells were less numerous. The insulin-immunoreactive endocrine cells were elongated or pyramidal, with rounded nuclei of irregularly contoured, and large amounts of secretory granules distributed throughout the cytoplasm. The granules have different sizes and electron densities and are classified as immature and mature, with the mature granules in predominant form in the overall granular population. In general, the granule is shown with an external electron-lucent halo and electron-dense core. The ultrastructure pattern in the granules of the insulin-immunoreactive endocrine cells was similar to that of the B cells of pancreatic islets in rats.     

Endocrine Cells in the Oesophagus of the Ascidian Styela clava,a cytochemical and immunofluorescence study

Summary Immunocytochemical studies have demonstrated the occurrence of an insulin-immunoreactive cell type in the oesophageal epithelium of the Ascidian Styela clava. Staining with aldehyde fuchsin has demonstrated a number of similar small, triangular, cells located on the basement membrane, which may have an endocrine function. Argyrophilic cells have also been found, suggesting the presence of a second endocrine cell type. The absence of argentaffin cells has led us to believe that the cells so far observed do not produce biogenic amines such as 5-HT (5-Hydroxytryptamine). The nature of these cells is discussed with reference to endocrine-like cells found in the digestive tracts of other protochordates.Animals were collected by courtesy of the Admiralty Marine Trials Station, Portsmouth. This research was carried out during the tenure of an S.R.C. grant no. B/RG 82919 to one of us (M.C.T.). —The localisation of polypeptide hormones in the pharynx and gut of protochordates     

Ultrastructural similarity of endocrine-like cells of the human lung and some related cells of the gut

Summary The ultrastructure of endocrine-like cells of the human lung was compared to the ultrastructure of endocrine-like cells of the stomach and pancreas in both adult and foetal material.Three types of endocrine-like cells were found in the human foetal lung. Type 1 or P₁ cells contained very small granules (about 110 nm) of two varieties, cored and vesicular; type 2 or P₂ cells with cored granules measuring about 130 nm; and type 3 cells with cored granules of about 180–190 nm. In the adult lung only one type P_a cells with cored granules could be found.Cells resembling foetal P₁ cells were not found in foetal or adult gastric mucosa, or in the pancreas. In the gastric mucosa cells resembling pulmonary P_a or P₂ cells were moderately represented and often difficult to distinguish from each other. Thus, they were grouped together as gastric P cells. Cells with granules resembling those of pulmonary type 3 cells were found most numerous in the adult oxyntic mucosa. Cells resembling gastric P cells (and pulmonary P₂ cells) were rather numerous in foetal pancreas, but very rare in adult pancreas. Few cells containing granules somewhat resembling those of pulmonary type 3 cells were present in both foetal and adult pancreas.The results were discussed in respect to 1) the similarities between some gastric or pancreatic carcinoids and lung carcinoids, 2) the gastro-pancreatic P cells as a separate cell population, 3) the possible secretion by the lung endocrine-like cells of active substances, either amines or peptides, 4) the similarity between the secretory granules of P_a and P₁ cells and neurosecretory granules of the hypothalamus and between P₂ cells and some endocrine cells of the pituitary.Supported in part by the Italian National Research Council (Grants N. 75.00630.04 and N. 76.01558.04)     

An ultrastructural study of the prostate gland of megascolicid earthworm Lampito mauritii (Kinberg)

The ultrastructure of prostate gland of Lampito mauritii revealed two types of secretory cells. Type 1 cells with a broad basal region and a long apical region contain electron dense oval secretory granules with an increased density at the core region. Numerous electron lucent granules with fine filamentous and electron dense amorphous materials also occur at the basal region of these cells. Type 2 cells contain electron lucent mucous-like secretory granules. This cell type contains exceptionally large Golgi complexes having 20-23 stacked cisternae. Both cell types open into a common lumen and numerous microtubules are visible at the apical end. Junctional complexes, such as desmosomes and septate junctions, are observed in this glandular tissue.     

Distribution and coexistence of chromogranin A-, serotonin-and pancreastatin-like immunoreactivity in endocrine-like cells of the human anal canal

Summary The comparative distribution and coexistence of chromogranin A (CGA)-, serotonin (5-hydroxytryptamine; 5-HT)- and pancreastatin (PST)-like immunoreactivity in endocrine-like cells of the human anal canal was investigated by light-microscopic immunocytochemistry. The largest population of colorectal endocrine-like cells consisted of CGA-immunoreactive (ir) cells, followed by the 5-HT-ir and PST-ir cell population. In the anal transitional zone (ATZ), CGA-and 5-HT-immunoreactivity was equally distributed; ir-PST was confined to a smaller endocrine-like cell population. In the squamous zone and the perianal skin, Merkel cells in the basal layer of the epidermis and hair follicles exhibited ir-CGA and ir-PST but no ir-5-HT. Double immunofluorescence on identical sections revealed distinct coexistence patterns. In the colorectal zone, about 2/3 of the CGA-ir endocrine-like cells also stained for 5-HT, whereas in the ATZ epithelium, CGA- and 5-HT-immunoreactivity completely overlapped. No 5-HT-immunoreactivity could be detected in CGA-ir Merkel cells of the squamous zone of the anal canal and the perianal skin. PST-immunoreactivity was present in about 1/3 of the CGA-ir colorectal and anal transitional endocrine-like cells and in about 1/4 of the Merkel-cell population staining for CGA. These chemically heterogeneous phenotypes of the anal endocrine-like and Merkel cells may reflect a specific regulatory role of these cells in the various epithelial linings of the human anal canal and the perianal skin.     

The amylase-secreting cells of the stomach of the scallop, Pecten maximus: ultrastructural, immunohistochemical and immunocytochemical characterizations

(1) alpha-amylase was extracted and purified from the stomach/digestive gland complex of the scallop Pecten maximus and an anti-serum was induced against the purified amylase by rabbit immunization. (2) The anti scallop amylase was used to localize the amylase-secreting cells in the stomach of Pecten maximus by immunofluorescence and immunogold labelling. The amylase-secreting cells are glandular cells particularly numerous in the main sorting area of the stomach. Their secretory granules were found strongly positive for anti-amylase. Three types of glandular cells were observed, actually corresponding to the three stages of the glandular-cell activity, synthesis, secretion and excretion. (3) The synthesizing cell shows the characteristic features of a protein-synthesizing cell: a conspicuous nucleolus and abundant granular endoplasmic reticulum. In the secretory cell, the secretory granules are formed by the Golgi apparatus and accumulate in the apical part of the cell. The secretory cell is filled with two types of secretory granules which are released in the stomach lumen by apocrine excretion. (4) The present study brings the first demonstration of the synthesis and extracellular release of amylase by glandular cells of the stomach epithelium of a bivalve.     

Argyrophile and argentaffin reactions in individual granules of enterochromaffin cells of reserpine treated guinea pigs

Summary The individual granules of enterochromaffin cells of normal and reserpine treated guinea pigs have been studied by staining slides of the duodenum first by an argentaffin method and subsequently by an argyrophile method. Some argentaffin cells can be shown to contain not only argentaffin granules, but also granules that are purely argyrophile. The relative number of such argentaffin cells is greatly increased following administration of reserpine, as depletion of their 5-hydroxytryptamine content converts argentaffin granules into purely argyrophile ones. On the basis of this finding it is confirmed that the argyrophile granule is merely an argentaffin granule depleted of its 5-HT content, and that the argyrophile (nonargentaffin) and the argentaffin cells represent different phases of a secretory cycle.This investigation was supported by a grant from the Indian Council of Medical Research. I am grateful to Ms. Ciba of India Ltd. for making available reserpine (Serpasil) and solvent for reserpine. It is a pleasure to thank Mr. Anand Parkash for technical assistance and Mr. M. L. Sharma for the photographs.     

Electron microscopic classification of amine-producing endocrine cells by selective staining of ultra-thin sections

Summary The argyrophil, argentaffin and chromaffin reactions were performed directly on ultra-thin sections for examination in the electron microscope. Glutaraldehyde fixation was appropriate for the argentaffin and chromaffin reactions; additional fixation with osmium tetroxide, however, caused impairment of these reactions. Fixation with formaldehyde, but not with glutaraldehyde, was adequate for the argyrophil reaction; post-fixation with osmium tetroxide did not affect this staining. At the light microscopic level the staining reactions were correlated with fluorescence histochemistry according to the method of Falck and Hillarp. The techniques described were used to study certain amine-producing endocrine cell systems: adrenal medullary cells and thyroid parafollicular cells of the mouse, gastric endocrine cells from the oxyntic gland area of the mouse, rat and rabbit. All these cells stained argyrophil. The adrenal medullary cells and one cell type in the oxyntic gland area of the rabbit were strongly argentaffin and chromaffin. The remainder of the cells were non-argentaffin and non-chromaffin but could be induced to give an argentaffin (and chromaffin) reaction after injection of the animals with l-3,4-dihydroxyphenylalanine or l-5-hydroxytryptophan, a treatment which is known to result in the accumulation of the highly reducing dopamine and 5-hydroxytryptamine, respectively, in these endocrine cells. Without exception the precipitates formed in all the staining reactions accumulated selectively over the secretory granules of the cells.The techniques described permit differential staining of consecutive ultra-thin sections for electron microscopic characterization of one and the same cell. They will provide information necessary for correlative studies of the stainable cells at the light and electron microscopic levels.     

Fine structure of the dorsal epithelium of the tongue of the freshwater turtle,Geoclemys reevesii (Chelonia,Emydinae)

Scanning electron microscopy shows that lingual papillae occur all over the dorsal surface of the tongue of the freshwater turtle, Geoclemys reevesii. The surface of each papilla is composed of compactly distributed hemispherical bulges, each composed of a single cell. Microvilli are widely distributed over the surface of cells. Histological examination reveals that the connective tissue penetrates deep into the center of papillae and that the epithelium is stratified columnar. Under the transmission electron microscope, the cells of the basal and the deep intermediate layers of the epithelium appear rounded. A large nucleus lies in the central area of each cell. The cytoplasm contains mitochondria, endoplasmic reticulum and free ribosomes. The cell membrane form numerous processes. The shallow intermediate layer contains two types of cell. The cytoplasm of the first has numerous fine granules, in addition to mitochondria, ribosomes, and endoplasmic reticulum. The other type of cell contains highly electron-dense granules. The surface layer shows two cell types. One type consists of typical mucous cells. The other type of cell contains fine, electron-lucent granules. The latter cells lie on the free-surface side, covering the mucous cells, and have microvilli on their free surfaces.     

Morphology of the bovine epididymis

The epididymis of the bull was divided into six regions, and morphological differences between regions were studied. The epithelium of all regions contained four cell types: principal and basal epithelial cells, and intraepithelial lymphocytes and macrophages. The epithelium of regions II-V also contained a few apical cells. Principal cells of all regions possessed an endocytotic apparatus including stereocilia underlain by canaliculi, coated vesicles, and subapical vacuoles (up to 1 micron in diameter); however, large vacuoles with a flocculent content and multivesicular bodies (up to 5 microns in diameter) were most numerous in regions II, III, and IV. The unique features of principal cells of region I were the presence of well-developed Golgi bodies, few lipid droplets, and whorls of smooth endoplasmic reticulum in the supranuclear cytoplasm. Numerous mitochondria, distended cisternae of rough endoplasmic reticulum, and dense granules characterized the infranuclear cytoplasm of the principal cells of regions II-VI; however, these features were more developed in region V. Apical cells were characterized by the apical location of the nucleus, many mitochondria in the apical cytoplasm, and few microvilli at the luminal border. Basal cells with few cytoplasmic lipid droplets were present throughout the length of the epididymis but appeared more numerous in region V. Intraepithelial lymphocytes were present at all levels of the epithelium but were never seen in the lumen. Intraepithelial macrophages containing heterogeneous granules, eccentric nuclei, and pseudopods were invariably seen near the basal area of the epithelium in all regions. These observations are discussed in an effort to define the role of each cell type in the epididymal epithelium.     

The occurrence of argyrophilic and argentaffin cells in the gut of Ciona intestinalis L.

Summary Argyrophilic and argentaffin cells occur in the stomach and intestinal epithelium of the sea-squirt, Ciona intestinalis L.. These cells are characterized by their basal swelling which contains the nucleus surrounded by small secretory granules and by a filamentous cell-apex which reaches the gut lumen. The cells are scattered unevenly within the epithelium. Their number decreases rapidly towards the lower part of the intestine. The localization, size of granules and their shape are features which differentiate these cells from other secretory cells in the gut epithelium such as mucous cells. These cells are thought to possess an endocrine function.The excellent technical assistance of Mrs. R. Sprang is gratefully acknowledged     

Serotonin-immunoreactive cells of peculiar shape in the urethral epithelium of the human penis

Summary The present study deals with endocrine-like cells in the urethra of human penis. A large number of basal-granulated cells immunoreactive for serotonin were dispersed in the urethral epithelium. No cellular elements were stained positively with antisera against bioactive peptides. The serotonin-immunoreactive cells consisted of a small oval perikaryon and slender processes, and resembled neurons in shape. An apical process reached the urethral lumen. The basal processes frequently branched out in a dendritic fashion, some running laterally for a considerable distance. The number of cells immunoreactive for serotonin was remarkably reduced in subjects over 60 years of age.     

Monoamine-containing granulated cells in the frog lung

Summary The epithelium of the primary bronchus of the frog lung has been studied by fluorescence and electron microscopy. Clusters of five to ten, ovoid, brilliantly yellow fluorescent cells were observed in the basal portion of the epithelium. These cells contained numerous electron-dense granules of variable shape and size. The granules gave a positive argentaffin reaction at the ultrastructural level, suggesting a possible existence of monoamines in the granules. In addition, synaptic contact between the intraepithelial nerves and the cells, which was characterized by the aggregation of the granules toward the presynaptic membrane thickening of the cell, was also noted. These data are discussed in relation to similar studies in birds and mammals, and a possible function of these cells suggested.     

A novel endocrine cell type in the guinea-pig gastric mucosa: cellular source of pro-enkephalin-derived peptides. A histochemical, immunohistochemical, and electron microscopical characterization

A novel endocrine cell type has been identified in the guinea-pig gastric mucosa which preferentially occurs in the oxyntic area. Cells of this type exhibit immunoreactivities for bovine adrenal medulla dodecapeptide (BAM-12P) and in many cases for Met-enkephalin and are thus presumed to contain a pro-enkephalin-like precursor protein. Systematic immunohistochemical investigations show that these cells do not contain immunoreactivities for various enteric hormones, neuropeptides and biogenic amines (serotonin, histamine). However, they do contain immunoreactivity for chromogranin A, an acidic glycoprotein which is common to the majority of entero-endocrine cells. Using silver impregnation techniques BAM-12P immunoreactive cells prove to be argyrophil, but fail to react argentaffin. On the electron microscopical level, these cells contain a well-developed endoplasmic reticulum and Golgi apparatus and numerous polymorphous secretion granules which measure about 290 nm in diameter. The secretion granules are ovoid or pear-shaped but largely plump compared to those of enterochromaffin cells. Light and electron microscopical findings indicate that BAM-12P immunoreactive cells constitute an endocrine cell population of the gastric epithelium in addition to the "established" endocrine cells hitherto known in this location.     

THE ENDOCRINE CELLS IN THE EPITHELIUM OF THE GASTROINTESTINAL MUCOSA OF THE RAT : An Electron Microscope Study

The authors of this study examine the question of whether the so-called enterochromaffin or argentaffin cells of the gastrointestinal tract should be considered as a single cell type. The systematic application of purely morphologic methods has led to the conclusion that the epithelium of the gastrointestinal mucosa comprises endocrine cells of several types. This conclusion is primarily based on the uneven and characteristic distribution of the various cell types along the intestinal tract, an observation precluding the interpretation that the different types correspond to diverse functional stages of the same cell. A specific endocrine function may be attributed to each of the given cell types recognized so far on account of their appearance and their localization in characteristic areas of the gastrointestinal tract. It is acknowledged, however, that a purely morphological study leaves room for doubt. The first cell type is probably responsible for the formation of 5-hydroxytryptamine. Cells of type II are morphologically comparable to the pancreatic A cells and may, therefore, be called intestinal A cells. Cell type III comprises intestinal D cells since their appearance corresponds to that of pancreatic D cells. Cell type IV might well be responsible for catecholamine production, whereas gastrin is in all probability produced in endocrine cell type V. As yet, the thorough morphological study of the gastrointestinal epithelium does not provide information as to additional distinct cellular sites of production of the several other hormones isolated from different parts of the gut.