The postbranchial digestive tract of the ascidian, Polyandrocarpa misakiensis (Tunicata: Ascidiacea). 2. Stomach

The organization of the stomach in the compound styelid ascidian, Polyandrocarpa misakiensis, is described, and the morphology and cell types of the stomach is discussed from the phylogenetic viewpoint. The stomach is a sac-like organ whose wall is formed into longitudinal folds. The stomach consists of external and internal epithelium. The internal epithelium is simple columnar, except for the bottom of the folds. There are five cell types: absorptive cells, zymogenic cells, endocrine cells, ciliated mucous cells, and undifferentiated cells. The absorptive cells have numerous microvilli. The apical region of these cells is occupied by coated vesicles. The zymogenic cells have a conical outline and a few microvilli on their apical surfaces. There are secretory granules in the apical region of zymogenic cells. The endocrine cells have low cell height and electron-dense granules around the nucleus. Endocrine cells have one or two cilia and a few microvilli on the apical surfaces. The basolateral part of these cells often bulges into the adjoining cells. Immunoelectron microscopy revealed that some endocrine cells have serotonin-like immunoreactivity. The ciliated mucous cells are restricted to a single ventral groove. They have numerous microvilli and a few cilia on their apical surfaces. Moderately electron-dense granules are accumulated in the apical part of the ciliated mucous cells. Undifferentiated cells, filled with free ribosomes, form a pseudostratified epithelium in the base of each fold. The nucleus of undifferentiated cells has a prominent nucleolus. The pseudostratified epithelium of the pyloric caecum consists of electron-dense and electron-light cells.     

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.     

Ultrastructure of the dental epithelium and odontoblasts during enameloid matrix deposition in cichlid teeth

Teleost enameloid matrix has been proposed to be an ectodermal, mesodermal, or joint ectodermal-mesodermal product. To determine its origin we examined the ultrastructure of the inner dental epithelium (IDE), odontoblasts, enameloid, and dentin matrices of cichlid tooth buds at the stage of enameloid formation. © Alan R. Liss, Inc. Columnar IDE cells had apical and basal terminal webs and contained organelles associated with protein synthesis, including elongated secretory granules containing fibrillar material having cross-striations with 60-nm periodicity. The morphology of IDE secretory granules was typical of procollagen granules observed in a large variety of ectodermal and mesodermal cells synthesizing collagen. In contrast, the paucity of secretory granules within three odontoblast types indicates that these cells probably do not synthesize enameloid matrix. These observations are consistent with the idea that the bulk of the enameloid matrix is itself an ectodermal collagen synthesized and secreted by IDE cells.     

Morphometric and ultrastructural features of the mare oviduct epithelium during oestrus

Morphometric, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations have displayed regional differences in the mare oviductal epithelium. The entire mucosa of the oviduct was lined with a pseudostratified epithelium, which consisted of two distinct cell types, ciliated and non-ciliated. Ciliated cells were predominant in the three different segments of the oviduct and their percentage increased from fimbriae to ampulla and significantly decreased in the isthmus. SEM revealed in the infundibulum finger-like mucosal folds, some of them interconnected, in the ampulla numerous and elaborated branched folds of the mucosa, whereas the isthmus displayed a narrow lumen, short and non-branched mucosal folds. In the ampulla and isthmus the majority of non-ciliated cells showed apical blebs provided or not of short microvilli. TEM displayed different ultrastructural features of ciliated and non-ciliated cells along the oviduct. Isthmus ciliated cells presented a more electron-dense cytoplasm than in infundibulum and ampulla cells and its cilia were enclosed in an amorphous matrix. The non-ciliated cells of infundibulum did not contain secretory granules but some apical endocytic vesicles and microvilli coated by a well developed glycocalyx. Non-ciliated cells of ampulla and isthmus contained secretory granules. Apical protrusions of ampulla displayed two types of secretory granules as well as occasional electron-lucent vesicles. Isthmus non-ciliated cells showed either electron-lucent or electron-dense cytoplasm and not all contained apical protrusions. The electron-dense non-ciliated cells displayed microvilli coated with a well developed glycocalyx. Three types of granules were observed in the isthmus non-ciliated cells. The regional differences observed along the epithelium lining the mare oviduct suggest that the epithelium of the each segment is involved in the production of a distinctive microenvironment with a unique biochemical milieu related to its functional role.     

Localization of gamma-tubulin to the basal foot associated with the basal body extending a cilium

The human oviduct epithelium primarily consists of ciliated cells and secretory cells. Solitary cilia usually extend from the apical surface of the secretory cells. We investigated the localization of -tubulin in the ciliary basal apparatus of both cell types by fluorescence immunohistochemistry and immunoelectron microscopy. In addition to basal bodies, -tubulin was identified in the lateral basal foot, especially the basal foot cap. This observation is consistent with previous observations that microtubules radiate from the basal foot and the basal foot serves as the microtubule organizing centre.     

Structural and ultrastructural features of boar seminal vesicles

The morphological features of boar seminal vesicles were examined by light and transmission microscopy. Boar seminal vesicles consist of glandular tissue arranged in multiple lobules containing a system of ramified secretory tubules. The secretory tubules are composed of a mucosa formed by an epithelium and an underlying lamina propria and, are surrounded by a muscular layer. The epithelium is made up of columnar cells and occasional basal cells. Mast cells are frequently found among epithelial cells. Three types of columnar cells, considered different stages of the secretory cell cycle, are present: principal cells, clear cells and dense cells. Principal cells are functionally differentiated cells characterised by abundant mitochondria, great development of the rough endoplasmic reticulum and presence of secretory granules in their cytoplasm. The apical surface of many principal cells shows apical blebs filled with PAS-positive material. No acid mucosubstances are detected. Microvilli cover the apical surface except in the apical blebs. Dense cells, arranged between principal cells, are also functional differentiated cells but with signs of cellular degeneration. Clear cells are an initial differentiated stage of columnar cells and are characterised by the presence of a poorly developed rough endoplasmic reticulum and by the absence of secretory granules. Proliferating cells are present among columnar cells. Basal cells contain scarce cytoplasm, few organelles and no secretory granules. The lack of mitotic activity in these cells suggests that they do not act as precursors of columnar cells.     

Stomach of Aplysia depilans (Mollusca,Opisthobranchia): a histochemical,ultrastructural, and cytochemical study

We report the results of a morphological, histochemical, and cytochemical characterization of the Aplysia depilans stomach, an organ little studied in opisthobranchs. Very thin ciliated cells with microvilli on their apical surfaces are predominant in the epithelium lining the lumen of the stomach. Many lysosomes with a strong arylsulphatase activity were present in the apical regions of these cells that could also contain some lipid droplets and glycogen. Small peroxisomes were observed, usually around lipid droplets or mitochondria. Bottle-shaped secretory cells are very common in this epithelium and produce a secretion rich in proteins and acidic mucopolysaccharides. Most of the cytoplasm of these mucus-producing cells was filled with a very high number of granules and the nucleus is dislocated to the basal region. Cisternae of rough endoplasmic reticulum were abundant around the nucleus and several Golgi stacks were also present in this area. In spite of the variation in the electron density of the granules, only one type of secretory cell seems to be present in the stomach epithelium, since granules with very different electron densities were frequently found in the same cell. A few neurons were also found in the stomach epithelium of this species. Fibrocytes, muscle cells, nerves, and amebocytes were observed in the connective tissue of the stomach wall.     

Morphological,ultrastructural and histochemical investigation of epipodial sensory structures of Haliotis tuberculata (Gastropoda: Haliotidae)

In this study, we describe the microstructure and ultrastructure of the epipodial papillae and epipodial tentacles of Haliotis tuberculata using light and electron microscopy. The epipodial papillae vary morphologically; they are subdivided into several subpapillae whose surface is covered by small micropapillae. The epipodial tentacles are large extendable conically elongated structures whose surface is differentiated in two regions: the dorsal region with long corrugated folds, and a ventral region composed of three parts, a basal part with the same structure as the dorsal, a middle part with shorter corrugated folds and an apical part with large micropapillae. Although the thin sections and ultrastructure examination show that the epithelium of both organs is morphologically similar and composed of supporting cells, sensory cells and different types of secretory cells, there is a certain specialization in their secretory product. Although the epithelium of both structures was positive for acidic glycoconjugates, the tentacle epithelium was also positive for neutral sugars. Further specific differences were revealed by lectin histochemistry. Because papillae and tentacles can be extended or retracted depending on environmental conditions, they probably have tactile and olfactory functions.     

Zur Cytologie der Rectaldrüsen von Knorpelfischen

The stratified epithelium of the central collecting duct of the elasmobranch(Scylliorhinus canicula, Galeorhinus galeus andRaja batis) rectal gland consists of 3 to 6 layers of cells: one superficial, and several basal cell layers. In the superficial layer normally three different types of cells can be distinguished (a) goblet cells, (b) cells with apical secretory granules and (c) flask-shaped cells. The superficial layer ofScylliorhinus canicula reveals a further cell type, so-called mitochondria-rich cells. The epithelial areas built by these cells are always single-layered. The goblet-cells are very similar to goblet cells found in the intestine of vertebrates. Their dominant structures are a well developed ergastoplasm, a large Golgi-apparatus and mucous granules compactly filling the apical cell region. The cells with apical secretory granules are columnar or dumbbell shaped. They contain a rough-surfaced endoplasmic reticulum and a well developed Golgi-apparatus. The secretory granules are loosely distributed within the Golgi-field and are arranged in one or more rows just below the cell apex. The flask shaped cells are characterized by a cytoplasm rich in small vesicles. They posses few dictyosomes and several small mitochondria. There is some evidence for endocytotic activity. The mitochondria-rich cells are characterized by lateral cell interdigitations, by a basal labyrinth and by numerous mitochondria. They are similar to the excretory cells of rectal gland parenchyma. The cells of the basal epithelium layers are differenciated only to a small extent. They are joined in a loose formation with white blood cells often found in the intercellular spaces. The function of the elasmobranch rectal gland is not restricted to the excretion of concentrated salt solutions. There is also a significant secretion of mucous substances. The tubule glands are primarily excretory, the epithelium cells of the central collecting duct mainly secretory in function.     

Ultrastructure of the sexual segments of the kidney in male and female lizards,Cnemidophorus l. lemniscatus (L.)

Summary Kidneys of adult male and female lizards were studied by electron microscopy, in order to understand the ultrastructure of the collecting duct and a differentiated part thereof, the sexual segment, which is an important accessory sexual organ. First portion of sexual segment in males: The cells are filled with large secretory granules of a wide range of opacities. The granular endoplasmic reticulum is abundant; basal formations of superimposed flat cisternae are frequent. Distended vesicles and microvesicles prevail in the supranuclear, well developed Golgi apparatus. Evidences indicate that secretion of these cells is holocrine. Second portion of sexual segment in males: All of the secretory granules are apical in location and relatively electron-opaque; they show a denser core. This core is formed by a substance which, after lying in contact with ribosomes, enters the secretory vesicles of the highly developed Golgi apparatus. A lighter substance is then condensed around it. The secretion of the granules is merocrine. The granular endoplasmic reticulum is very abundant in these cells, but basal ergastoplasmic formations are lacking. Sexual segment in females: The cells show features similar to those of the male first portion, but they are smaller. Undifferentiated collecting duct: Most of the cells are mucigenic. They have small ovoid, apical secretory granules. The density of the granules varies from cell to cell; when they are electron-lucent, they exhibit laminar or dotted opaque figures. Moderately developed Golgi apparatus and granular endoplasmic reticulum, as well as elongated mitochondria, occur in mucigenic cells. Intercalated among the latter are non-secretory cells. They have very abundant mitochondria, numerous microvilli, many pinocytic and smooth-membrane vesicles, whereas the organelles participating in synthetic processes are poorly developed; their function is most likely related to active solute transport.     

The pelvic kidney of male Ambystoma maculatum (Amphibia,urodela, ambystomatidae) with special reference to the sexual collecting ducts

This study details the gross and microscopic anatomy of the pelvic kidney in male Ambystoma maculatum. The nephron of male Ambystoma maculatum is divided into six distinct regions leading sequentially away from a renal corpuscle: (1) neck segment, which communicates with the coelomic cavity via a ventrally positioned pleuroperitoneal funnel, (2) proximal tubule, (3) intermediate segment, (4) distal tubule, (5) collecting tubule, and (6) collecting duct. The proximal tubule is divided into a vacuolated proximal region and a distal lysosomic region. The basal plasma membrane is modified into intertwining microvillus lamellae. The epithelium of the distal tubule varies little along its length and is demarcated by columns of mitochondria with their long axes oriented perpendicular to the basal lamina. The distal tubule possesses highly interdigitating microvillus lamellae from the lateral membranes and pronounced foot processes of the basal membrane that are not intertwined, but perpendicular to the basal lamina. The collecting tubule is lined by an epithelium with dark and light cells. Light cells are similar to those observed in the distal tuble except with less mitochondria and microvillus lamellae of the lateral and basal plasma membrane. Dark cells possess dark euchromatic nuclei and are filled with numerous small mitochondria. The epithelium of the neck segment, pleuroperitoneal funnel, and intermediate segment is composed entirely of ciliated cells with cilia protruding from only the central portion of the apical plasma membrane. The collecting duct is lined by a highly secretory epithelium that produces numerous membrane bound granules that stain positively for neutral carbohydrates and proteins. Apically positioned ciliated cells are intercalated between secretory cells. The collecting ducts anastomose caudally and unite with the Wolffian duct via a common collecting duct. The Wolffian duct is secretory, but not to the extent of the collecting duct, synthesizes neutral carbohydrates and proteins, and is also lined by apical ciliated cells intercalated between secretory cells. Although functional aspects associated with the morphological variation along the length of the proximal portions of the nephron have been investigated, the role of a highly secretory collecting duct has not. Historical data that implicated secretory activity concordant with mating activity, and similarity of structure and chemistry to sexual segments of the kidneys in other vertebrates, lead us to believe that the collecting duct functions as a secondary sexual organ in Ambystoma maculatum. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Ultrastructural changes in the oviductal epithelium of Merino ewes during the estrous cycle

Isthmic and ampullary oviductal epithelia sampled from Merino ewes at days -1, 1, 3, and 10 of the estrous cycle (estrus = day 0) were studied by scanning and transmission electron microscopy after fixation by vascular perfusion. Secretory cells, ciliated cells, and lymphocytelike basal cells were observed in both isthmic and ampullary epithelium at all stages of the estrous cycle studied and their ultrastructural features were analyzed. Synthesis of lamellated secretory granules occurred in the ampullary secretory cells during the follicular and early luteal phases, and their contents were released by exocytosis into the oviductal lumen during the luteal phase. Granule release was associated with nucleated apical protrusion of these cells into the oviductal lumen. No such secretory activity was displayed by isthmic secretory cells even though a few cells contained nonlamellated granules. Apocrine release of apical vesicles and accompanying cytoplasmic material from apical protrusions of ciliated cells occurred in the isthmus around estrus but not in the ampulla. This unexpected feature has not previously been reported in any other mammal. Dendritic basal cells were distinguished in the lower part of the epithelium by their heterochromatic nuclei, electron-lucent cytoplasm, and lack of attachment zones. No migration of basal cells was observed, and their ultrastructural features were similar in the ampulla and isthmus and at all stages of the estrous cycle examined. The function of these lymphocytelike cells in the epithelium is uncertain, but the presence of phagocytic bodies and lysosomes in 20% of them may indicate a phagocytic role.     

Use of transgenic mice to study the routing of secretory proteins in intestinal epithelial cells: analysis of human growth hormone compartmentalization as a function of cell type and differentiation [published erratum appears in J Cell Biol 1990 Jan;110(1):following 227]

The intestinal epithelium is a heterogeneous cell monolayer that undergoes continuous renewal and differentiation along the crypt-villus axis. We have used transgenic mice to examine the compartmentalization of a regulated endocrine secretory protein, human growth hormone (hGH), in the four exocrine cells of the mouse intestinal epithelium (Paneth cells, intermediate cells, typical goblet cells, and granular goblet cells), as well as in its enteroendocrine and absorptive (enterocyte) cell populations. Nucleotides -596 to +21 of the rat liver fatty acid binding protein gene, when linked to the hGH gene (beginning at nucleotide +3) direct efficient synthesis of hGH in the gastrointestinal epithelium of transgenic animals (Sweetser, D. A., D. W. McKeel, E. F. Birkenmeier, P. C. Hoppe, and J. I. Gordon. 1988. Genes & Dev. 2:1318-1332). This provides a powerful in vivo model for analyzing protein sorting in diverse, differentiating, and polarized epithelial cells. Using EM immunocytochemical techniques, we demonstrated that this foreign polypeptide hormone entered the regulated basal granules of enteroendocrine cells as well as the apical secretory granules of exocrine Paneth cells, intermediate cells, and granular goblet cells. This suggests that common signals are recognized by the "sorting mechanisms" in regulated endocrine and exocrine cells. hGH was targeted to the electron-dense cores of secretory granules in granular goblet and intermediate cells, along with endogenous cell products. Thus, this polypeptide hormone contains domains that promote its segregation within certain exocrine granules. No expression of hGH was noted in typical goblet cells, suggesting that differences exist in the regulatory environments of granular and typical goblet cells. In enterocytes, hGH accumulated in dense-core granules located near apical and lateral cell surfaces, raising the possibility that these cells, which are known to conduct constitutive vesicular transport toward both apical and basolateral surfaces, also contain a previously unrecognized regulated pathway. Together our studies indicate that transgenic mice represent a valuable system for analyzing trafficking pathways and sorting mechanisms of secretory proteins in vivo.     

Ultrastructural immunocytochemistry and lectin histochemistry of the subcommissural organ in the snake Natrix maura with particular emphasis on its vascular and leptomeningeal projections

The ependymal cells of the subcommissural organ (SCO) of the snake Natrix maura display long basal processes which terminate either on blood vessels or on the leptomeninges. The cell body and the basal processes contain a secretory material detectable immunocytochemically at the light-microscopic level using an antibody raised against bovine Reissner's fiber. The present investigation deals with the ultrastructural location in these cells of the (i) immunoreactive material; (ii) concanavalin A (Con A)- and wheat-germ agglutinin (WGA)-binding sites. In the subnuclear region the immunoreactive material was located within dilated cisternae of the rough endoplasmic reticulum and had affinity for Con A but not for WGA. In the supranuclear region the secretory material was exclusively located within numerous granules. Since all these granules showed affinity for WGA, they can be regarded as "post-Golgi" elements. Thus, at variance with the situation in the mammalian SCO, in the ophidian SCO most of the secretion is stored in secretory granules rather than in dilated cisternae of the rough endoplasmic reticulum. In the perivascular and leptomeningeal endings the immunoreactive material was located within granules which, because of their affinity for WGA, should also be regarded as true secretory granules derived from the Golgi apparatus. It is concluded that these granules are transported along the basal processes and accumulated in the perivascular and leptomeningeal endfeet. This observation favours the view of a local release of the content of these granules, since there is no evidence for a reverse transport of these granules all the way back from the distal termination to the apical pole, to be finally released into the ventricle.     

The mouse vomeronasal glands: a light and electron microscopical study

The glands of adult mouse vomeronasal organ (VNO) were studiedwith light- and electro-microscopical techniques. The vomeronasalglands (VN-Gs) consist of several individual glandular complexesdistributed along the long axis of the VNO. The secretory productsreleased from VN-G cells enter into the lumen of the VNO inthe region of transition between the neuroepithelium and thereceptor-free epithelium. The acini show the typical morphologicalfeatures of serous glands. The secretory cells of these aciniare characterized by a round to oval nucleus and a well-developed,rough endoplasmic reticulum, both preferentially located inthe basal part of the cell. The supranuclear region is occupiedby the Golgi apparatus and secretory granules varying in sizeand electron density. They accumulate towards the apical partof the cell. Secretory cells are connected by tight junctions,desmosomes and membrane interdigitations, moreover, they arealso coupled by gap junctions. Axonal terminals containing clearvesicles and dense-cored vesicles are frequently seen betweenthe secretory cells. Secretory cells are directly related tothe thin basal lamina of the acinus; myoepithelial cells arenot present. In the lamina propria, numerous smooth muscle cells,blood vessels and nerve bundles containing both myelinated andunmyelinated axons can be observed. An automatic regulationof the activity of the VN-Gs is discussed in relation to thevomeronasal pump.     

Das Epithel der Tuba uterina des Neugeborenen Elektronenmikroskopische Befunde

Summary An electron microscopical study of the epithelium of the uterine tube was carried out in the newborn. Among the epithelial cells at least two morphologically well defined types can be distinguished: ciliated and non-ciliated cells.The ultrastructure of the cilia and related structures corresponds to what has been described by other authors in ciliated cells of various organs and of different species. Near the basal bodies of the cilia there is a concentration of vesicular mitochondria, which is thought to be evidence of a high metabolic activity in this region of the cell. Large opaque granules in the supranuclear zone of the ciliated cells are, it is suggested, paraplasmatic inclusions, perhaps supporting material for the ciliokinetic processes. There was no evidence of a secretory function of the ciliated cells.Among the non-ciliated cells, which in general show a straight lined luminal border with few microvilli, there are some cells containing dense granules, which are distributed throughout the cytoplasm and concentrated in the luminar side of the cell. The apical parts of these cells are protruding and sometimes digitated or branched; they contain accumulated granular materials and are separated from the rest of the cell after the formation of an intracellular plasmalemma. A similar detachment was found in an other cell type, but here the protruded apical parts of the cells are edematous and do not contain any visible secretory materials. It is uncertain if the detached cytoplasmic substances form a part of a specific secretory product; there are no secretory granules within the cytoplasm. On the contrary, the detachment of cytoplasmic parts may only accompany the excessive proliferation of cells which takes place during this period of growth.     

Ultrastructural, histochemical and cytochemical characterization of intestinal epithelial cells in Aplysia depilans (Gastropoda, Opisthobranchia)

To improve the current knowledge about the digestive system in opisthobranchs, light and electron microscopy methods were used to characterize the epithelial cells in the mid‐intestine of Aplysia depilans. This epithelium is mainly formed by columnar cells intermingled with two types of secretory cells, named mucous cells and granular cells. Columnar cells bear microvilli on their apical surface and most of them are ciliated. Mitochondria, multivesicular bodies, lysosomes and lipid droplets are the main components of the cytoplasm in the region above the nucleus of these cells. Peroxisomes are mainly found in middle and basal regions, usually close to mitochondria. Mucous cells are filled with large secretory vesicles containing thin electron‐dense filaments surrounded by electron‐lucent material in which acidic mucopolysaccharides were detected. The basal region includes the nucleus, several Golgi stacks and many dilated rough endoplasmic reticulum cisternae containing tubular structures. The granular cells are characterized by very high amounts of flat rough endoplasmic reticulum cisternae and electron‐dense spherical secretory granules containing glycoproteins. Enteroendocrine cells containing small electron‐dense granules are occasionally present in the basal region of the epithelium. Intraepithelial nerve fibres are abundant and seem to establish contacts with secretory and enteroendocrine cells.     

The fine structure of the female reproductive tract of adult Loa loa

Weber P. 1987. The fine structure of the female reproductive tract of adult Loa loa. International Journal for Parasitology17: 927–934. The wall of the female reproductive tract of Loa loa was studied by electron microscopy. The wall is composed of a monolayered epithelium covered by a basal lamina. The epithelium of the ovary has a moderately developed basal labyrinth, abundant organelles, and a few secretory granules. In the oviduct, the basal lamina intrudes septa-like into the epithelium. Abundant myofilaments are attached to it. Microvilli cover the luminal cell border. The seminal receptacle contains few muscle cells in its basal lamina. It shows a highly developed spongy zone at its luminal surface. The uterine epithelium contains glycogen deposits and lipid droplets. In its anterior parts it shows a highly developed basal labyrinth and an abundance of secretory granules. The vagina has several layers of muscle cells in the basal lamina. Its epithelium contains few organelles, a small number of secretory granules, and is devoid of storage deposits.     

Regeneration of hamster tracheal epithelium after mechanical injury. IV. Histochemical, immunocytochemical and ultrastructural studies

All stages of regeneration in hamster tracheal epithelium were studied following a denuding mechanical injury. At 1 h all the cells had sloughed from the wound site leaving a bare and sometimes disrupted basal lamina. Viable cells at the wound margins rapidly changed shape, flattened and migrated to cover the denuded lesion by 12 h. In addition, epithelial cells that remained viable demonstrated sublethal changes that included the rapid discharge of mucous granules from secretory cells, internalization of cilia by ciliated cells and evidence of heterophagy in both cell types. By 24 h a wave of epithelial cell divisions occurred, primarily by secretory cells. This produced a multilayered epidermoid metaplasia that was best developed at 48 h. The metaplastic epithelium was largely composed of cells with both secretory (mucous granules) and epidermoid (tonofilament bundles and numerous desmosomes) characteristics. The peroxidase-antiperoxidase (PAP) method demonstrated a few keratin-positive cells in the wound as early as 12 h post-wounding and keratin was demonstrated in more cells by 24 h. All cells in the metaplastic wound epithelium were keratin-positive by 48 h. Following 48 h some of the most superficial keratinized cells sloughed from the epithelium and the keratin content of the remaining cells began to decline. At 72 h pre-ciliated and pre-secretory cells were seen in the wound. Pre-ciliated cells were characterized by an abundant electron-lucent cytoplasm, large pale nucleus, filiform apical microvilli and evidence of ciliogenesis, similar to that seen during fetal development. Pre-ciliated cells often contained apical mucous granules, apparently carried over from the parent secretory cells. With the appearance of these columnar cells the normal mucociliary morphology was restored in small wounds by 120 h, but some persistent epidermoid metaplasia remained in the large wounds through 168 h post-wounding. These data provide further evidence for the important role of secretory cells in the histogenesis of epidermoid metaplasia and the regeneration of normal morphology following injury. The implications of these findings in understanding the histogenesis of other lesions in the tracheo-bronchial epithelium are discussed.     

Ultrastructural immunocytochemistry and lectin histochemistry of the subcommissural organ in the snake Natrix maura with particular emphasis on its vascular and leptomeningeal projections

Summary The ependymal cells of the subcommissural organ (SCO) of the snake Natrix maura display long basal processes which terminate either on blood vessels or on the leptomeninges. The cell body and the basal processes contain a secretory material detectable immunocytochemically at the light-microscopic level using an antibody raised against bovine Reissner's fiber. The present investigation deals with the ultrastructural location in these cells of the (i) immunoreactive material; (ii) concanavalin A (Con A)-and wheat-germ agglutinin (WGA)-binding sites. In the subnuclear region the immunoreactive material was located within dilated cisternae of the rough endoplasmic reticulum and had affinity for Con A but not for WGA. In the supranuclear region the secretory material was exclusively located within numerous granules. Since all these granules showed affinity for WGA, they can be regarded as post-Golgi elements. Thus, at variance with the situation in the mammalian SCO, in the ophidian SCO most of the secretion is stored in secretory granules rather than in dilated cisternae of the rough endoplasmic reticulum. In the perivascular and leptomeningeal endings the immunoreactive material was located within granules which, because of their affinity for WGA, should also be regarded as true secretory granules derived from the Golgi apparatus. It is concluded that these granules are transported along the basal processes and accumulated in the perivascular and leptomeningeal endfeet. This observation favours the view of a local release of the content of these granules, since there is no evidence for a reverse transport of these granules all the way back from the distal termination to the apical pole, to be finally released into the ventricle.