Three-dimensional visualization of the Golgi apparatus: observation of Brunner's gland cells by a confocal laser scanning microscope

The three-dimensional structure of the Golgi apparatus in cells of the Brunner's gland in the mouse was observed by using a confocal laser scanning microscope. Two lectins, FITC-labeled soybean agglutinin and Texas red-labeled Griffonia simplicifolia agglutinin II, were used to visualize the whole Golgi apparatus. Staining with the former lectin, which has been known to label the cis-stacks, showed a lacy dome-like structure situated in the supranuclear region. Staining with the latter lectin, known to label the intermediate-to-trans-stacks and the secretory granules, showed a dome-like structure consisting of network and cobblestone-like patterns in the same region and also granular stainings near the surface of the cobblestone-like patterns and the apical region of a cell. Double-staining demonstrated that the soybean agglutinin-labeled network always surrounded the G. simplicifolia agglutinin II-stained structure. Based on these observations, we propose a new three-dimensional model of the Golgi apparatus: it forms a dome-like structure over a nucleus, a network of cis-stacks forms its outer boundary, and this outer boundary is lined and paved with successive intermediate and trans-stacks. It is thought that secretory granules are released toward the internal space of the Golgi apparatus and transported to the apical cytoplasm through the holes of the network.     

Mechanism of rapid mucus secretion in goblet cells stimulated by acetylcholine

The parasympathetic control of goblet cell secretion and the membrane events accompanying accelerated mucus release were studied in large intestinal mucosal biopsies maintained in an organ culture system. The secretory response of individual goblet cells to 10(-6) M acetylcholine chloride with 3 x 10(-3) M eserine sulfate (a cholinesterase inhibitor) was assessed by light microscopy and autoradiography, by scanning and transmission electron microscopy, and by freeze-fracture. Goblet cells on the mucosal surface are unaffected by acetylcholine. In crypt goblet cells acetylcholine-eserine induces rapid fusion of apical mucous granule membranes with the luminal plasma membrane (detectable by 2 min), followed by sequential, tandem fission of the pentalaminar, fused areas of adjacent mucous granule membranes. These events first involve the most central apical mucous granules, are then propagated to include peripheral granules, and finally spread toward the most basal granules. By 60 min, most crypt cells are nearly depleted. The apical membrane, although greatly amplified by these events, remains intact, and intracellular mucous granules do not coalesce with each other. During rapid secretion membrane-limited tags of cytoplasm are observed attached to the cavitated apical cell surface. These long, thin extensions of redundant apical membrane are rapidly lost, apparently by being shed into the crypt lumen.     

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.     

The ultrastructure of mammary explants from virgin ovariectomized goats during hormone-induced lactogenesis

The effect of insulin (I), cortisol (F) and prolactin (P) on the ultrastructural morphology of epithelial cells of cultured mammary explants from virgin ovariectomized (OV-X) goats were studied. The epithelial cells showed little structural organization and were devoid of fat droplets and secretory protein granules at zero time of culture. The cytoplasm contained few profiles of smooth and rough endoplasmic reticulum and the Golgi apparatus was rudimentary. After being cultured in Waymouth's medium without added hormones the epithelial cells were indistinguishable from epithelial cells of uncultured explants. The addition of I induced changes mainly in the appearance of nucleoli. The nucleoli were enlarged and fibrillogranular areas with light spaces were observed. The most obvious cytological changes of epithelial cells of explants cultured in the presence of I and F are translocation of the nucleus into the basal cytoplasm, increase of rough endoplasmic reticulum, an increase in the size of the Golgi apparatus, presence of one or two lipid droplets and in some cells vacuoles with protein granules were present. Mitochondria were more abundant. The epithelial cells of explants cultured in the presence of I, F and P were characterized by the polarization of organelles within the cytoplasm and by the formation and release of protein granules and small and large fat droplets. The cell nucleus was in the basal cytoplasm, the Golgi apparatus was supranuclear. The rough endoplasmic reticulum was extensively developed and formed large sacs. Golgi vacuoles contained protein granules.(ABSTRACT TRUNCATED AT 250 WORDS)     

THE FINE STRUCTURE OF VON EBNER''S GLAND OF THE RAT

The fine structure of von Ebner's gland was studied in untreated rats and rats stimulated to secrete by fasting-refeeding or injection of pilocarpine. Cytological features were similar to those reported for pancreas and parotid gland. Abundant granular endoplasmic reticulum filled the basal portion of the cell, a well-developed Golgi complex was located in the vicinity of the nucleus, and the apical portion of the cell was filled with dense secretory granules. Dense heterogeneous bodies resembling lysosomes were closely associated with the Golgi complex. Coated vesicles were seen in the Golgi region and also in continuity with the cell membrane. Granule discharge occurred by fusion of the granule membrane with the cell membrane at the secretory surface. Successive fusion of adjacent granules to the previously fused granule formed a connected string of granules in the apical cytoplasm. Myoepithelial cells were present within the basement membrane, and nerve processes were seen adjacent to acinar and myoepithelial cells. Duct cells resembled the intercalated duct cells of the major salivary glands.     

Electron microscopical studies on the thyroid of a cyclostome,Lampetra japonica,during its upstream migration

Summary Electron microscopical studies were made of the thyroid gland of an adult lamprey, Lampetra japonica, in the upstream migration period.The thyroid consists of many usual follicles containing the colloid in their lumina, and a large parafollicle without colloid. The paper concerns only the usual follicle.The follicle cells found in the usual follicle wall are classified into three types; 1. a non-ciliated taller cell, 2. a ciliated taller one, and 3. a non-ciliated cuboidal one. From their cytoplasmic fine structure, it is considered that all these cells are essentially identical and differences among them are due to their functional state.All these type cells are characterized by irregularly developed interdigitations and aggregates of tonofilaments throughout the cytoplasm, especially in the perinuclear region. Although the rough-surfaced endoplasmic reticulum and the Golgi apparatus are fairly well developed in the first and second type cells, the cisternae are not so large-vacuolated but flattened, and the cytoplasm is more compact as compared with that of the higher vertebrate. In the third type cell, the cytomembranes are poorly developed.Large dense inclusion-bodies consisting of heterogeneously dense materials, of lamellar structures, and of less dense vacuoles, which are found often in taller follicle cells, are also characteristic for the lamprey thyroid. The body which might be intimately related to the Golgi apparatus is considered to be a kind of lysosomes and it perhaps corresponds to the yellow pigment observed by light microscopy.In the apical part of the cytoplasm in taller cells, there are three kinds of granules or vesicles; numerous small vesicles considered to be derived from the Golgi apparatus, a few small dense granules which seem to originate from the Golgi region, and a few large less-dense granules.In the third type cell, the cytomembranes are not so well developed as those of the first and second type cells. The large heterogeneously dense bodies and the cytoplasmic granules are very few in number.Around the follicle of the lamprey thyroid, there are a dense basement membrane and a relatively compact connective tissue with few blood capillaries. Characteristic fat cells are found in the connective tissue.     

Electron-microscopic studies on the physiological cell loss in the gastric mucosa of the golden hamster

Summary Fine-structural aspects of physiological cell loss in the gastric mucosa of the golden hamster were observed. As the surface mucous cell ascends along the gastric pit, the cell becomes taller and funnel-like in shape. The interfoveolar cell located at the superficial portion of the gastric pit has many lysosomes and a few lipid droplets in the cytoplasm. The nucleus moves toward the upper region of the cytoplasm, while the Golgi apparatus moves downward toward the infranuclear region. After the rupture of the apical plasma membrane takes place, the lateral and basal plasma membranes of this cell remain in spite of loss of the cell contents. Between the basal plasma membrane of the interfoveolar cell and the capillary endothelium is a thick connective tissue layer characterized by densely packed collagen fibrils. The remaining basal and lateral plasma membranes of the ruptured cell and the thick underlying collagenous layer might play a role in protecting the tissue from potential damage induced by the physiological cell loss.This study was supported in part by a grant from the Research Fund of the Ministry of Education, Science and Culture, Japan.     

Localization of selenium deposits in meristematic cells of Allium sativum L. roots treated with selenium salts

Ultrastructural analysis of garlic roots treated for 24 h with sodium selenate or sodium selenite at the concentrations 80, 160, 320 microM revealed the presence of selenium deposits in meristematic cells. They appeared as small and large granules or aggregates of electron-dense material. Many small granules were localised in plastids but some in mitochondria, endoplasmic reticulum as well as in Golgi apparatus, nucleus and cytoplasm. Sometimes the large granules were seen in cytoplasm but aggregates of electron-dense material only in vacuoles. It seems possible that these deposits represent a non-dissolved form of selenium, i.e. elemental selenium or its complexes with other ions.     

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.     

Morphological evidence for the presence of two cell types in the ependyma of the subcommissural organ of the snake,Natrix maura

Summary Two different types of ependymal cells were found in the subcommissural organ (SCO) of Natrix maura. Most secretory cells showed morphological features resembling the general structure and ultrastructure of cells in the SCO of other vertebrates. This report describes a second population of cells lining a portion of the dorsal groove of the SCO. These cells were not selectively stained by chromalum-hematoxylin and, under the electron microscope, they were characterized by scarce surface differentiations, sparse apical cytoplasm and short basal processes. Flat, parallel cisternae of the rough endoplasmic reticulum produced vesicles that appeared to be transported to the well-developed Golgi apparatus. Dense secretory granules about 200 nm in diameter were found in the Golgi region. Similar granules were seen in the vicinity of the apical plasma membrane; some of them opened toward the ventricle. All these characteristics clearly differentiate this cell group from the other secretory cells lining the SCO laterally and ventrally.     

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.     

[Ciliogenesis in the mucous cells of the quail oviduct. I. Ultrastructural study in the laying quail]

The luminal epithelium of the oviduct (magnum) of laying quails is composed of ciliated cells and mucous cells. Ciliogenesis was observed in some of the mucous cells. Both centrioles of the diplosome migrate to the top of the cell, and one of them induces the formation of a rudimentary cilium. In some of the other cells, that are filled with mucous granules, the formation of basal bodies by an acentriolar pathway was observed. In these cells, numerous, dense fibrous masses are associated with the forming face of the Golgi apparatus. In the Golgi zone, generative complexes composed of a deuterosome and some forming procentrioles were found. Cilia develop from completed basal bodies. During ciliogenesis, the Golgi apparatus is disorganized, and generally the production of mucous granules is arrested. The nucleus is also modified: it becomes larger and the chromatin is dispersed. It is assumed that mucous cells are able to be transformed into ciliated cells in the oviduct of laying quails.     

Effects of colchicine on the gallbladder of the mouse

Summary The effects of colchicine on the mouse gallbladder followed a course depending on the dosage given (0.4–4 mg/100 g body weight). Following 0.5 mg/100 g, by 16 h there was a marked cholestasis with dilatation of the gallbladder and steatosis. There were progressive alterations in the Golgi apparatus and accumulation of vesicles. The apical mucous droplets decreased in number and became pleomorphic and dispersed throughout the cytoplasm. Lipid droplets appeared in numbers on the epithelial cytoplasm. By 48 h the tissues had reverted to normal appearances. When cholecystokinin, pilocarpine or ceruletide were given to animals which had received colchicine 18 h previously, the excess bile from the dilated gallbladder was discharged into the duodenum, remaining apical mucous droplets secreted and electron dense material accumulated in the lateral intercellular space. This formed a quasi-regular array between the epithelial bases and the basement membrane. Biochemically there was a significant decrease in alkaline phosphatase activity and a significant increase in acid phosphatase activity.     

四种淡水养殖鱼类血细胞的细微结构

四种淡水鱼的血细胞形态基本相似。红血球形态与其他低等脊椎动物基本相似。淋巴球绝大部分是小淋巴球:单核球数量较少;四种鱼的嗜中性白血球形态结构差不多,胞核多为蚕豆形,很少见分叶核,分叶一般也只有二叶,这与哺乳类显然不同;嗜酸性白血球的形态结构与其他脊椎动物基本相似;在少数血涂片中看到了嗜碱性白血球。       

An electron microscopical study of absorbing cells in the posterior caput epididymidis of rabbits

Summary The columnar cells in regions 3 and 4 of the ductus epididymidis in rabbits display ultrastructural features characteristic of absorbing cells. The stereocilia show basal anastomoses and often a fibrillar core continuous with a fibrillar web in the apical cytoplasm. Numerous invaginations of the slightly downy apical cell membrane and many thick-walled apical vesicles and vacuoles contain an opaque substance similar to that seen in the lumen. The vacuoles often contain small vesicles or bodies, probably formed from the vacuolar wall by budding. Numerous bodies or vacuoles with moderately dense contents are seen in the Golgi area and in the supranuclear and intranuclear cytoplasm in region 3. In region 4 they are denser and mainly seen above the nucleus. A high acid phosphatase activity was demonstrated in most dense and some light bodies. India ink introduced by way of the rete testis was taken up from the lumen into apical invaginations, vesicles and vacuoles and slowly transferred to denser bodies below the Golgi apparatus.These observations are interpreted as evidence for a resorption of substances from the lumen by a pinocytotic process, and for their storage and perhaps digestion in the dense bodies, which appear to have a lysosomal character. The Golgi apparatus is large with many vesicles of two types and empty cisternae but few typical Golgi vacuoles. The partly granular endoplasmic reticulum is very well developed and has opaque contents. Microtubules run from the terminal bar region into the Golgi area. Thick-walled vesicles occur throughout the cytoplasm, sometimes in continuity with the cell membrane. The basal parts of the cell borders often interdigitate.Supported by a grant from the Swedish State Medical Research Council.     

Function of the cytoskeleton in cells with microridges from the oral epithelium of the carp Cyprinus carpio

Superficial cells of the oral mucosal epithelium in the carp and the cytoskeleton of the epithelial cells are examined by scanning and transmission electron microscopy. Microridges are formed on the surface of the epithelium. Epithelial cells contain two types of vesicles: mucous secretory vesicles and coated vesicles. Most of the mucous vesicles are situated in the center of the cell near the Golgi apparatus. In freeze-fracture replicas, intramembranous particles are abundant in the membranes of the secretory vesicles but rare in the apical plasma membrane. Coated vesicles are situated in the apical and subapical cytoplasm. A great number of thick filaments, considered to be keratin filaments, run randomly throughout the cell to form a meshwork. Thick filaments, which are sparse in the central cytoplasm, are connected to the membranes of the secretory vesicles and other membranous organelles. A layer of closely packed thin filaments, considered to be actin filaments, is found just beneath the apical plasma membrane. Microtubules also occur in the apical cytoplasm and run almost parallel to the cell surface. Both kinds of vesicles are connected to the thin and thick filaments. Their functional significance in the regulation of membrane at the free surface is discussed.     

Ultrastructure of human labial salivary glands. I. Acinar secretory cells

The structure of human labial salivary gland acini was studied by light and electron microscopy. Contrary to previous reports, these glands were pure mucous in nature; no serous elements were present. The acinar cells were found in all stages of maturation. Immature cells were characterized by an extensive and highly organized rough-surfaced endoplasmic reticulum. The Golgi complex was extremely prominent, consisting of stacks of flattened cisternae and swarms of small vesicles. Mucous droplets were almost completely absent. As secretory activity progressed, the endoplasmic reticulum involuted, while the Golgi cisternae became distended and formed many vacuoles. In mature mucous cells, the apical cytoplasm was filled with membrane-bounded mucous droplets, and the nucleus was displaced basally. The droplets frequently showed great variation in density from cell to cell, and even within the same cell they sometimes were quite heterogeneous. They were liberated from the acinar cells by an apocrine process, so that droplets with intact limiting membranes were often observed in the acinar lumen. These droplets soon lysed, their contents fusing into streams of mucus. Occasionally during apocrine secretion a mucous cell failed to reconstitute its apical surface, and its entire contents spilled into the acinar lumen. Unusual cytoplasmic inclusions were present in many of the acinar cells. These inclusions, which were surrounded by a single membrane, consisted of lipid droplets closely associated with bundles of fine filaments.     

Formation of horny cells: the fate of cell organelles and differentiation products in ruminal epithelium

Epithelial cells changing from the granular stage of differentiation to the horny stage are more numerous, and reveal sequential events of transformation in finer detail in the rumen epithelium than in other keratinizing epithelia thus far studied in the electron microscope. Studies of such cells indicate that transformation is initiated by the release of hydrolytic enzymes, as evidenced by the appearance of lysosomes. As lysosomes increase in number, the nucleus, ribosomes, mitochondria, Golgi apparatus, and mucous granules are gradually degraded. Furthermore, marked changes occur in permeability of the plasma membrane as voluminous amounts of the lysed cell components pass through and accumulate in the intercellular space in the form of an amorphous mass. Filaments, keratohyalin granules, and the content of the ER (ER-protein) are not lysed, revealing the action of released enzymes to be specific. During transformation, filaments become displaced toward the cell periphery and keratohyalin granules disperse and mix with the ER-protein in the cell center. Subsequently, the keratohyalin-ER-protein complex infiltrates the filament network whereby a fibrous-amorphous cell content is formed. Loss of fluids through the plasma membrane leads to reduction of cell volume and consolidation of the remaining cell content. The deep interdigitations formed between the cells ultimately interlock the outer part of the epithelium into a cohesive and protective stratum corneum.     

The Golgi apparatus in epidermal mucoid and ellipsoid-vacuolate cells ofAeolidia papillosa andCoryphella rufibranchialis (Nudibranchia)

Summary The epidermal cell layer of the apical end of the ceras was investigated in two species of aeolid nudibranchs. Based on cellular inclusions, mostly two cell types were found: mucoid and ellipsoid-vacuolate cells. Mucoid cells ofCoryphella rufibranchialis have large heterogeneous and fibrillar secretory granules whereas inAeolidia papillosa, the granules are homogeneous, but vary in electron density from one cell to another. Ellipsoid-vacuolate cells contained large quantities of small vacuoles with an included ellipsoidal structure. Both species contained very numerous ellipsoid-vacuolate cells. Secretory granules and ellipsoid-vacuoles appear to arise from the Golgi apparatus and these contents stain with PAS, suggesting a polysaccharide composition. Mucoid cells contained both secretory granules and ellipsoid-vacuoles which may arise from the same Golgi apparatus.