Characterization of the ultrastructure of gingival mast cells in alloxan-induced diabetic rats

The morphological changes of gingival mast cells of alloxan-induced diabetic rats were studied by electron microscopy. The following observations were made. The cell nucleus and cytoplasm degenerated. The electron density of the granules in the cell cytoplasm clearly decreased. Some granules had dense irregular threads and the granules were surrounded by a thin vacuole. A ghost vacuole formed in some mast cells and disorganized materials accumulated in the cytoplasm. The mast cell nuclei were generally irregular and degenerating mast cells had pyknotic nuclei. General destruction of the cell membrane and granule shedding in some samples was noted and mitochondria with atypical cristae in the cytoplasm of the mast cells were seen. We conclude that the characteristics of the ultrastructure of gingival mast cells in diabetics are distinctive and should be used as criteria for pathogenesis of gingival inflammation.     

Cuprolinic Blue visualization of cytosolic and membrane-associated glycosaminoglycans in the rat junctional epithelium and gingival epithelia

Summary The gingiva of rat molars was studied at the light microscope level using glutaraldehyde as fixative, Cuprolinic Blue for visualizing polyanionic glycosaminoglycans and the autometallographic technique for enhancing the copper signal of the cationic dye. The polyanions were located inside the epithelial cells in the junctional epithelium, whereas a network located along either the plasma membrane or the intercellular spaces, or both, of the gingival oral epithelium and sulcular oral epithelium was evident with autometallography. In these cases, positive staining was limited to the basal and spinous layers, the granular and keratinized layers being unstained. With the transmission electron microscope, electron-dense aggregates were seen in the gingival lamina propria, in the basement membrane and along the plasma membrane of the keratinocytes of the basal and spinous layers of the gingival and sulcular oral epithelia. In the junctional epithelium, Cuprolinic Blue-positive granules, 25 nm in diameter, were seen in the cytoplasm. Together with some vesicles containing electron-dense material, they may account for the staining process noted after autometallography. When the ultra-thin sections were digested with bovine testicular hyaluronidase, the staining was abolished. This indicates that glycosaminoglycans were primarily responsible for the staining pattern visualized with these methods. In the junctional epithelium, the cytosolic location of the 25 nm granules reflects either transcellular transfer between the plasma membrane and the nucleus or accumulation of glycosaminoglycans in this group of keratinocytes. The glycoconjugates located inside vesicles or vacuoles are related to endocytosis and lysosomal degradation. Interstitial glycosaminoglycans seen in the two types of oral epithelium may play a role in the diffusion of water and nutriments.     

Single modified cilia displayed by cells of human internal stratified epithelia (oral cavity,vagina)

Summary Serial sections of human vaginal and keratinized oral-gingival epithelia were investigated for ciliary structures. Most melanocytes of the gingival epithelium lacked cilia, whereas almost all basal keratinocytes of the deeper portion of the epithelial ridges possessed one cilium each. In the suprabasal layers of the ridges only a few keratinocytes exhibited a single cilium. In the basal layer, at the top of the connective tissue papillae, approximately every second keratinocyte displayed a single cilium. In the suprabasal layers above the ridges no ciliated keratinocytes were observed. The basal cells of the vaginal epithelium were endowed with cilia, while cilia were absent from the suprabasal cells. In the human forearm epidermis most melanocytes and keratinocytes are supplied with a single cilium; it has been suggested that they may play a role in light reception. However, the widespread occurrence of 9 + 0 cilia in epithelial cells of internal epithelia and their coincidence with the sites of renewal of keratinocytes suggests that a relationship may exist between solitary cilia and mitotic activity.     

Migration of Merkel cells in the labial mucous epithelium of adult rabbits following mental nerve resection

Summary Merkel cells in the lower labial mucosa of adult rabbits were studied electron microscopically, 9, 21, 28, and 50 days after resection of the mental nerves. By day 9, nerve fibers were completely retracted from the epithelial layer of the mucosa. On and after day 21, Merkel cells were located not only in the basal layer but also in the prickle or more superficial cell layers. The ultrastructure of the migrating Merkel cells was unchanged, both as to the amount and location of the specific cored granules in the cytoplasm, until the cells reached the granular cell layer. The position of the migrating Merkel cells differed from cell to cell, and migration continued for at least 50 days. A remarkably large number of immature Merkel cells was observed in the basal and suprabasal cell layers of the denervated epithelium even by day 50. Therefore, the possibility of the reproduction of Merkel cells exists. The migrating Merkel cells, as well as the keratinocytes in the same cell layer, had degenerated drastically in the parakeratinized cell layer. This seems to indicate that the Merkel cells belong to the line of keratinocytes.     

Ultrastructure of midgut endocrine cells in the adult mosquito, Aedes aegypti

The ultrastructure of endocrine cells in the midgut of the adult mosquito, Aedes aegypti, resembled that of endocrine cells in the vertebrate gastro-intestinal tract. Midgut endocrine cells, positioned basally in the epithelium as single cells, were cone-shaped and smaller than the columnar digestive cells. The most distinctive characteristic of endocrine cells was numerous round secretory granules along the lateral and basal plasma membranes where contents of the granules were released by exocytosis. Secretory granules in each individual cell were exclusively of one type, either solid or 'haloed', and for all cells observed, the range in granule diameter was 60-120 nm. The cytoplasm varied in density from clear to dark. Lamellar bodies were prominent in the apical and lateral cellular regions and did not exhibit acid phosphatase activity. The basal plasma membrane was smooth adjacent to the basal lamina, whereas in digestive cells the membrane formed a labyrinth. Some endocrine cells reached the midgut lumen and were capped by microvilli; a system of vesicles and tubules extended from beneath the microvilli to the cell body. An estimated 500 endocrine cells were distributed in both the thoracic and abdominal regions of the adult midgut. In one midgut, we classified a sample of endocrine cells according to cytoplasmic density and granule type and size; endocrine cells with certain types of granules had specific distributions within the midgut.     

A morphologic study of the ductus of the epididymis of Sus domesticus

The head, body, and tail regions of the epididymal duct (or caput, corpus, and cauda epididymis) in two healthy and sexually mature Sus domesticus males were examined by light microscopy and by scanning or transmission electron microscopy. The epididymal duct is lined with a pseudostratified epithelium with stereocilia and covered by a muscular-connective tissue sheath that is thickest in the tail region. Diameter of the epididymal duct and height of epididymal epithelium are maximal in the head region. Length of the sterocilia and spermatic density are higher in the head and body regions. Somatic cells are abundant in the tail region. The epididymal epithelium is made up of five cell types: basal cells, principal cells, clear cells, narrow cells, and basophilic cells. Abundant secretory units are observed in the supranuclear cytoplasm of columnar principal cells. Each mature secretory unit is constituted by electron-dense secretion granules covered by more than eight layers of cisternae of reticulum between which the mitochondria are intercalated. In the apical cytoplasm the isolated secretion granules become larger and less electron dense. The apical surface is covered by numerous sterocilia. Basal cells are pyramidal and less high than principal cells. The clear cells, arranged between the principal cells, are characterized by the presence of abundant vesicular elements and electron-lucid secretion granules, and by an apocrine secretory process. The narrow cells are characterized by their highly vacuolized cytoplasm. Intermediate cell typologies can be found among basal, principal, clear, and narrow cells, which could be four developmental stages of the same cell type. The basophilic cells are spheroidal and are found at different levels between the epithelial cells and in the connective tissue underlying the epithelium. © 1993 Wiley-Liss, Inc.     

Demonstration of Langerhans cells in the human bronchial epithelium

Ultrastructural and immunohistochemical analysis of six specimens revealed for the first time a small number of Langerhans cells in non-neoplastic bronchial epithelium. These cells were usually found either interspersed perpendicularly between columnar epithelial cells or just above the basal lamina with extending cytoplasmic processes. Usually few Birbeck granules, especially located in the Golgi region, were present throughout the cytoplasm. Immunohistochemical studies were performed on semi-thin sections with a polyclonal anti-S-100 protein. The population of S-100 positive cells represented about 1% of all the epithelial cells. Not all ultrastructurally identified Langerhans cells were shown to be positive for S-100 antigen. Our results suggest that Langerhans cells could be a constant cellular constituent for the normal bronchial epithelium. The exact function of Langerhans cells in the respiratory epithelium remains to be investigated, but they may have an immunologic function, such as antigen presentation to T lymphocytes.     

Dorsal lingual epithelium of Platemys pallidipectoris (Pleurodira,Chelidae)

Scanning electron microscopy reveals that the flat tongue of Platemys pallidipectoris has shallow grooves and no lingual papillae. The surface of the tongue is covered with dome-shaped bulges, each corresponding to a single cell. Short microvilli are distributed over the cell surface. Light microscopy shows a stratified cuboidal epithelium with an underlying strong connective tissue. Transmission electron microscopy indicates four layers. The basal cells of the epithelium are electron-translucent and have a large central nucleus and a cytoplasm with keratin tonofilaments. Plasma cells with abundant rough endoplasmic reticulum and mitochondria occur in the basal layer. Production of secretory granules begins in the more electron-dense intermediate layers and increases as the cells move toward the surface. The membranes of the cells of the deep intermediate layer form processes that project into relatively wide intercellular spaces. In the superficial intermediate layer, the cytoplasm of the cells contains numerous fine granules; these increase in number but not in size in more distal layers. The cells of the surface layer are electron-translucent with a round nucleus. Contents of their fine granules are secreted into the oral cavity. © 1995 Wiley-Liss, Inc.     

Age-related changes in the ultrastructural organization of the human gingival epithelium

By means of transmissive and scanning electron microscopy 103 gingival bioptates in practically healthy persons at the age of 18-80 years have been studied. At ageing essential changes take place in all structural elements of the epithelium. The basal membrane is intermittent and loose. In cytoplasm of the cells of the basal layer epithelium the amount of microfilaments increases essentially, and as a result it becomes electron opaque. Tonofibrillar fasciculi of the spinous layer cells are fragmented, their contours are indistinct. In cytoplasm of the granular layer cells amount of keratohyalin granules increases, their size becomes large and their typical form is lost. In cytoplasm of the basal, spinous and granular layer cells the amount of organells decreases. Mitochondria acquire the appearance of electron translucent cavities with discomplexic, and sometimes, destroyed cristae. Rather great changes occur in intercellular interrelations. In all the layers some intercellular spaces are widen, in the spaces formed isolated desmosomes and other debries of cellular structures are formed. Sharp changes of microrelief of the granular layer epitheliocytes are observed. The ultrastructural rearrangements of epitheliocytes, revealed in the human gingiva, demonstrate certain disturbances in keratinization processes, in mechanical firmness, as well as in barrier function of the epithelial layer.     

Occurrence of unusual heterogeneous lipid-containing granule-storing cells in the main excretory duct epithelium of the male mouse submandibular gland

Summary The fine structure of the main excretory duct epithelium of the male mouse submandibular glands was investigated by scanning and transmission electron microscopy. Three principal cell-types were observed: type I and II, and basal cells. This epithelium was characterized by the presence of intercellular canaliculi. Type-I cells were the most numerous. They had an abundance of mitochondria, well-developed Golgi apparatus, a few electron-lucent lipid-containing granules and poorly developed basal infoldings. These cells were also characterized by many glycogen granules throughout the cytoplasm and abundant smooth endoplasmic reticulum in the apical cytoplasm. Type-II cells were the second most numerous. Their most characteristic feature was the presence of abundant heterogeneous lipid-containing granules having acid phosphatase activity at the periphery. They were concentrated in the infra- and supranuclear cytoplasm. The granules may be derived from mitochondrial transformation and seem to be a special kind of secondary autolysosome. Type-II cells also contained abundant mitochondria throughout the cytoplasm, much smooth endoplasmic reticulum in the apical cytoplasm, a well developed Golgi apparatus adjacent to the heterogeneous lipid-containing granules and no basal infoldings. Basal cells were situated adjacent to the basal lamina. They had a large nucleus and the cytoplasm was filled with glycogen granules.     

Changes in cytokeratin expression in epidermal keratinocytes during wound healing

In order to investigate the re-epithelialization process during wound healing, the hair on the back of guinea pigs was shaved and then excisional wounds were made through the entire thickness of the skin. Histological changes were observed and changes in the expression of different cytokeratin polypeptides were examined using an immunohistochemical technique. Immunohisto chemical study revealed that the proliferating and migrating keratinocytes expressed the same cytokeratins as the basal cells of normal epidermis. In addition, the entire epidermis of fairly remote areas from the edges of the wound where no thickening was observed showed a temporarily abnormal staining pattern. The suprabasal cells in the regenerating epidermis temporarily expressed cytokeratins not only specific for suprabasal cells but also specific for basal cells. The cytokeratins expressed in normal basal keratinocytes were also present in the thickened granular layers. These data indicate that the expression of cytokeratins in the epidermal keratinocytes (even in fairly remote areas from the wound edges) changes during wound healing, that the origin of the migrating keratinocytes from the remaining epidermis seems to be the basal cells in the epidermis, and that the appearance of keratohyalin granules is not related to changes in cytokeratin expression.     

Laryngeal papillomas: local cellular immune response, keratinization and viral antigen

Various parameters of the local cellular response have been studied in 16 laryngeal papillomas from ten patients with recurrent papillomas as well as normal control laryngeal and tracheal tissue by indirect immunofluorescence on frozen sections using monoclonal antibodies specific for T-cell subsets, Langerhans cells (LC) and HLA-DR antigens. Keratinization was investigated with a monoclonal antibody KL1 recognizing an acidic 56.5 Kd keratin, which is a marker of suprabasal cells in stratified squamous epithelium and is absent from the basal layer. The presence of viral antigen was detected with a rabbit antiserum raised against SDS-dissociated purified virus. A mild inflammatory response was observed in most biopsies. Cytotoxic/suppressor T-cells were the predominant cells found in the lesions. Compared with normal epithelium, the number of LC was dramatically reduced in the papillomatous epithelium. High densities of HLA-DR-positive cells were found mainly in the corium. The keratinization process was disturbed in most specimens in that both basal and suprabasal compartments reacted positively with the KL1 monoclonal antibody. Viral antigen was present in the nucleus of very occasional epithelial cells in some samples.     

Fine structure of the excretory system of the deep posterior (Ebner's) salivary glands of the human tongue

Human deep posterior lingual glands (von Ebner's glands) are located beneath the circumvallate papillae. They are formed by tubuloalveolar adenomeres, intercalated ducts and excretory ducts coming together in the main excretory duct. The tubuloalveolar cells, pyramid-shaped, show large and dense secretory granules (clear cored) throughout the cytoplasm, rare basal folds and packed cisternae of rough endoplasmic reticulum (RER) at the basal pole. The columnar cells of the intercalated ducts are arranged in a monolayer. They are characterized by dense, clear-core secretory granules (mostly in the apical cytoplasm), a basal nucleus, well-developed RER and Golgi apparatus, and thin filaments distributed in supra- and perinuclear cytoplasm. Striated ducts are absent. Excretory ducts, coming together in the main duct, are lined by a bistratified epithelium. The inner layer consists of columnar cells showing bundles of tonofilaments with scarce secretory activity. The outer layer is composed of basal cells lying on the basal lamina. The main excretory duct, which opens at the bottom of the vallum, shows a stratified epithelium. The outer side is composed of 2-3 layers of malpighian cells lying on the basal lamina. The inner side consists of a single layer of cuboidal-columnar cells with dense apical granules and well-developed organelles synthesizing and condensing secretions. These cells interpolate with goblet cells, rare mitochondria-rich cells, ciliated cells and numerous small globous cells showing a clear matrix and lacking secretory granules. The cilia show a 9 + 2 microtubular structure with basal bodies provided with striated rootlets. Myoepithelial cells surround with their processes the basal portions of the secretory cells and the intercalated ducts. The conclusions concern some comparative aspects and some hypothesis on the functional role of goblet cells, ciliated cells and epithelial cells lining the different ducts, also in relation to the final secretory product.     

Fine structure of the filiform papilla of beagle dogs

Light and electron microscopic examination of the dorsal lingual epithelium of beagle dogs (Canis domesticus) revealed three different regions: that anterior to the filiform papillae, that posterior to the papillae, and an interpapillary region. Whereas the basal and suprabasal cells are similar throughout, differences characterize the intermediate and surface layers. Keratohyalin granules are common in the intermediate layers in the anterior and interpapillary regions, tonofibrils are prominent in the posterior region, and no keratohyalin granules occur. The surface layer of the interpapillary region is not keratinized, that of the anterior region shows soft keratinization, and that of the posterior region shows hard keratinization. The perimeter of keratohyalin granules is composed of ribosomes 10-20 nm in diameter.     

Fine structure of the dorsal lingual epithelium of the Japanese monkey Macaca fuscata fuscata.

Filiform papillae, which were densely distributed all over the dorsal surface of the lingual body, were crown-shaped, with a central, circular area that sloped in the anterior direction and several branches that surrounded it in a semicircle from the back of the central area. Dome-shaped, fungiform papillae were scattered among these filiform papillae. At the posterior end of the lingual body, there were four circumvallate papillae. Prominent microridges and elevated intercellular borders were widely distributed in the central area of the filiform papillae and the interpapillar region. On the surface of the branches of the filiform papillae, microridges were rarely seen. On the surface of the fungiform papillae, indistinct microridges were observed. Histologically, the dorsal lingual epithelium revealed three different regions: the epithelium on the anterior side of the filiform papillae, the epithelium on the posterior side of the filiform papillae and the interpapillar epithelium. Whereas the basal and suprabasal cells are similar throughout, differences characterize the intermediate and surface layers. Keratohyalin granules appear predominantly in the intermediate layer in the epithelium on the anterior side of filiform papillae. In the epithelium on the posterior side of the filiform papillae, no keratohyalin granules occur and, instead, tonofibrils are prominent. The cells become significantly flattened. In the interpapillar epithelium, no keratohyalin granules are visible, and the tonofilaments occupy almost the entire cytoplasm of most cells in the intermediate and surface layers. The cells are larger in volume in these layers.     

Human gallbladder mucosa ultrastructure: evidence of intraepithelial nerve structures

The zinc iodide-osmium tetroxide (ZIO) fixative-staining method was used along with topographical ultrastructure to investigate cholecystectomized human gallbladders under light and electron microscopic techniques. This method delineated neuronal structures which may be involved in controlling the functions of the gallbladder epithelium. Three epithelial cell types were described in the surface epithelium: 1) Columnar clear cells; 2) dark, tuft osmiophilic cells; and 3) basal clear cells with electron-dense granules and showing intense ZIOphilic staining properties. While mucous granules were delineated in the first two cell types, the columnar epithelial clear cells are of uncertain function(s) and content but are probably absorptive cells. The small basal clear cells displaying intense ZIOphilia are associated with intraepithelial nerve endings. These nerve structures may have a sensory and/or motor function(s); they were detected throughout the gallbladder epithelial lining and mucosa.     

Structure of the epithelium of the parasitic turbellaria Notenera ivanovi (Turbellaria: Fecampiida)

The ultrastructure of the epithelium in Notentera ivanovi (Turbellaria, Fecampiida) has been studied. Notentera ivanovi lacks the digestive system but has a pad of the epidermal cells on the dorsal side of the body, which seems to be similar to the digestive epidermis on LM. Both the ventral and dorsal epithelium are cellular, ciliated and not insunk (fig. 1, a). The ultrastructure of the ventral and dorsal epithelium is similar in essential features. The cells bear abundant microvilli, cilia and are very rich in mitochondria, but the cytoplasm does not contain lysosomes and shows no other indications of phago- or pinocytosis. The basal membrane of epithelial cells forms deep invaginations (fig. 1, [symbol: see text]), partly with dilations (fig. 1, a; 2, a) containing the lamellated material (3, [symbol: see text]). In the basal part of the cells the numerous Golgi apparatus and rare cysternae of the smooth endoplasmic reticulum were observed (fig. 2, a, [symbol: see text]). The epithelium consists of several types of cells, which differ in the structure of secretory granules. The most abundant type of cells contains the granules with the rough-fibrillated content (fig. 1, a; 2, [symbol: see text]; 3, a). The cells of this type cover most part of the body. In some cells the content of such granules becomes condensed and electron-dense granules appear (fig. 3, a, [symbol: see text]). Another type of cells contains the giant granules with the rough-fibrillated content (fig. 3, [symbol: see text]). Third type of the secret is the granules with the finely fibrillated content which is ejected by exocytosis. The cells of the second and third types form a separate areas of the epithelium of the dorsal side of the body but occasionally were observed in the ventral epithelium too. The epithelium of N. ivanovi differs from that in Kronborgia by the abundance and diversity of secretory contents. The role of the epithelium in the digestion remains conjectural. It seems to be mainly the suckering tissue transporting the low molecular nutrients.     

Bipolarity of duodenal enterochromaffin cells in the rat

Summary Enterochromaffin cells of the rat duodenum have been studied immunocytochemically by use of a specific antiserum to serotonin. At the light-microscopic level serotonin immunoreactivity was observed in enterochromaffin cells located in the epithelium of the duodenal mucosa. Most of the serotonin-immunoreactive material was localized to the basal portion of the enterochromaffin cells, but small amounts of immunoreactive material were regularly observed in the apical portion. At the electron-microscopic level serotonin immunoreactivity in enterochromaffin cells was found to be concentrated over the dense cores of the cytoplasmic granules. The majority of these granules was located in the basal cytoplasm of the enterochromaffin cells, but serotonin-immunoreactive granules were also observed in the apical cytoplasm immediately beneath the microvilli. These observations indicate that duodenal enterochromaffin cells are bipolar and that they secrete serotonin both basally, to the circulation, and apically, to the gut lumen. Rat duodenal enterochromaffin cells thus appear to have an exocrine as well as an endocrine function.     

Spreading of embryologically distinct urothelial cells is inhibited by SPARC

The AON epitope of secreted protein acidic and rich in cysteine (SPARC) is a conserved motif expressed by human SPARC in a variety of human cell types. Through the use of a monoclonal antibody that recognizes this epitope, transitional epithelium was found to restrict expression of SPARC to the suprabasal and intermediate layer. Such intracellular expression was defined by immunoreactive signals that localized to the apical plasma membranes of suprabasal and intermediate cells. Polarization of SPARC to apical plasma membranes of suprabasal cells was retained in vitro by a subpopulation of cells that exhibited characteristics of suprabasal cells--cell-cycle quiescence, large cell volumes, and multiple nuclei. In contrast, the basal layer of transitional epithelium in vivo and cycling cells in vitro did not exhibit this apical staining pattern, but instead sequestered the SPARC polypeptide within urothelial cytoplasm and/or nuclei, as revealed by immunohistochemical analysis. Elution of soluble proteins and DNA from urothelial cells revealed the presence of SPARC within the nuclear matrix--and that SPARC colocalized with the nuclear matrix Ki-67 antigen. rSPARC activity was demonstrated and quantified with a rounding assay whereby the spreading of freshly plated cells was inhibited by recombinant SPARC in a concentration- and time-dependent manner. Inhibition of spreading was observed in urothelial cells derived from endoderm (bladder) and mesoderm (ureter) germ layers. Statistically significant differences were seen between urothelial cells from these two layers. Mesodermal cells recovered more slowly from the inhibitory effects of rSPARC, such that at hour 6 endodermal cells underwent significantly more spreading, as shown by a rounding index (RI). These experiments provide new insights about the matricellular trafficking of SPARC and suggest that intra- and extra-cellular localization patterns influence the development, homeostasis, and differentiation of transitional epithelium.