Fine structure of the mandibular gland in Japanese field vole (Microtus montebelli)

The mandibular glands of the Japanese field vole were examined by light microscopy, and transmission and scanning electron microscopies. The acinar cells contained light and coarse secretory granules, and reacted with PAS and stained slightly with AB; they were considered to be seromucous in nature. The acinar epithelium was composed of light and dark cells containing many secretory granules. The intercalated duct cells consisted of light cells possessing a few dense granules. A few cytoplasmic crystalloides of moderate density were observed in occasional light cells. The striated ducts were comprized of two distinct portions, a secretory portion and a typical striated portion without secretory granules. The epithelium secretory portion consisted of light and dark cells containing acidophilic granules and exhibited a sexual dimorphism in these granules: The male epithelia contained the granules of low to high densities, while the female epithelia had only dense granules being smaller than those in the males. The epithelium of typical striated portion was composed of light and dark cells containing fine vacuoles and vesicles.     

Fine structure of the mandibular gland in pika (Ochotona rufescens rufescens)

The mandibular gland of the pika was examined by light microscopy, and transmission and scanning electron microscopies. The acinar cells were noted to be composed of serous cells and seromucous cells. The serous cells containing granules of moderate and high densities were slightly basophile and strongly positive to PAS, but were not stained with AB. The seromucous cells possessing less dense granules were light and moderately positive to PAS and AB. A sexual dimorphism was observed between these cells: Serous cells were considerably more frequent in males and seromucous cells were more numerous in females. Intercalated duct cells consisted of cuboidal light cells containing a few vesicles in the apical region. Striated ducts were comprised of two portions--a secretory portion and a typical striated portion without secretory granules. The secretory portion was composed of light and dark cells having secretory granules varying in size and density. The epithelium of typical striated portion consisted of light and dark cells containing fine vacuoles and vesicles.     

Fine structure of the mandibular gland in volcano rabbit

The mandibular glands of 6 male and 6 female volcano rabbits were examined by means of light and transmission electron microscopy. The acinar cells of the glands were seromucous in nature, and contained faintly basophilic granules. The cells were classified into the light cells containing granules of low or moderate densities and the clear cells having polygonal granules of low density. The preacinar cells were occasionally observed at the site between acinus and intercalated duct. These cells had many weakly basophilic granules which contained fine granular materials of moderate density. The intercalated ducts were composed of light cells containing cored granules. The striated duct cells consisted of light cells and dark cells. Both of them contained a few vacuoles and vesicles, but no secretory granules. No sex-and age-related differences were observed in the mandibular gland of the volcano rabbit. The mandibular gland of the volcano rabbit was similar to the rabbit mandibular gland rather than the pika mandibular gland morphologically.     

Fine structure of the mandibular gland in crest-tailed marsupial-rat (Dasyuroides byrnei)

The mandibular glands of Dasyuroides byrnei were examined by light microscopy, and transmission and scanning electron microscopy. The secretory units consisted of numerous seromucous acini and a few seromucous demilunes. The seromucous acini were almost always capped by demilunes. The acinar seromucous cells contained faintly basophilic, light, coarse, bipatite secretory granules with matrix of low and moderate densities. The demilunar cells were dark compared with acinar seromucous cells and contained acidophilic secretory granules with a fibrillogranular matrix of moderate density. Preacinar cells with a seromucous nature were occasionally present at the junction between the acinus and intercalated duct. These cells had numerous basophilic granules, which were similar to those of acinar seromucous cells. The intercalated ducts consisted of simple cuboidal light cells that had a few small electron-dense granules. The striated ducts were composed of tall columnar light cells containing numerous vesicles, but no secretory granules. The mandibular acini of D. byrnei were composed of two cell types having a seromucous nature, unlike those of the opossum and many other mammals.     

Ultrastructure and complex carbohydrate ultracytochemistry of the cat parotid gland

The structure and glycoconjugate content of the cat parotid gland were analyzed at electron microscopic level by applying morphological techniques and three ultrastructural histochemical methods - HID-TCH-SP, LID-TCH-SP and PA-TCH-SP. This gland appeared as a typical salivary gland composed of acinar secretory cells, intercalated ducts, striated ducts and excretory ducts. The most common configuration of secretory granules consisted of a dense core surrounded by a variable electron-lucent halo. All ductal segments were characterized by the presence of different cell populations and small apical granules greatly different from those localized in the acinar cells. By using HID-TCH-SP we were able to demonstrate that in a few acinar cells there are sulphated sites, whereas PA-TCH-SP staining revealed the presence of vic-glycol radicals in all acinar cells preferentially located on the halo of secretory granules.     

Fine structure of the parotid gland in the pika and the volcano rabbit

The parotid glands of the pika and the volcano rabbit were examined by light and transmission electron microscopy. The acinar cells of the pika consisted of light cells containing basophilic granules of low density, while in the volcano rabbit the acinar cells consisted of light and dark cells containing acidophilic granules of moderate density. Intercalated duct cells were composed of light cells containing a few granules of moderate density. These segments of the two animals were similar in morphology. The striated duct cells in both species were composed of light and dark cells. Most of those in the pika contained a few moderately dense granules. In both animals, no myoepithelial cells were detected around the acini, intercalated ducts or striated ducts, while nerve terminals were observed among the adjacent acinar cells.     

Fine structure of the parotid gland in the crest-tailed marsupial-rat (Dasyuroides byrnei).

The parotid gland of Dasyuroides byrnei was examined by light microscopy, and transmission and scanning electron microscopy. The acini were composed predominantly of seromucous cells with a few mucous cells. The seromucous cells were light or dark cells containing acidophilic spherical granules of moderate to high electron density and had well-developed cytoplasmic organelles-ordinary mitochondria and large mitochondria with tubular cristae, RER with vesicular or tubular elements, and Golgi apparatus with lamellae, vesicles and vacuoles. The mucous cells had basophilic amorphous granules of low electron density, like those of ordinary mucous cells. The intercalated ducts were composed of simple cuboidal light cells having a few electron-dense granules. The striated ducts consisted of tall columnar light cells containing numerous vesicles and mitochondria with tubular cristae, the same as found in acinar seromucous cells.     

Mucin histochemistry of submandibular and parotid salivary glands of man: light and electron microscopy

Light-microscopy showed parotid serous acinar cells to contain neutral mucin, serous and mucous acinar cells of submandibular gland and intercalary ductal cells of both glands to contain acid and neutral mucins, and cells of striated ducts and excretory ducts to contain neutral mucin. Mucins were demonstrated ultrastructurally in a portion of the components of secretory granules of acinar cells and intercalary ductal cells, and in secretory granules of striated and excretory ductal cells. The mucins were all stained by techniques that reveal 1,2-glycols. Secretory granules of submandibular mucous and serous acinar cells and intercalary ductal cells were stained variably by the low iron-diamine technique for acid mucin, and those of mucous acinar cells by the high iron-diamine technique for sulphomucins mucin and possibly consisted of protein. The results suggest that one type of cell may be able to produce a range of secretory products and to package them variously into secretory granules.     

An ultrastructural study of the submandibular glands of the squirrel monkey, Saimiri sciureus

In squirrel monkey (Saimiri sciureus) the position of submandibular glands in the neck, on either side of the trachea, more closely resembles that of rodents than that of other primates. The glands exhibit seromucous acini and mucous tubules with seromucous demilunes. Electron microscopy shows basal cytoplasmic folds and well-developed intercellular tissue spaces and canaliculi only in relation to seromucous cells. Greatly dilated cisternae of the granular endoplasmic reticulum and prominent Golgi membranes are characteristic of the mucous cells. The secretory granules of seromucous and mucous cells are morphologically distinct and indicate chemically different products for the two cell types. Histochemically, the seromucous cell shows the presence of acid mucosubstance as indicated by the PAS and Alcian blue techniques. Preliminary studies showed no appreciable quantity of amylase in submandibular glands. The intercalated duct cell is juxtaposed with the acinar cell or mucous tubule cell. Short luminal microvilli, prominent Golgi complexes and scant apical granules are notable features of intercalated duct cells. Four cell types compose the striated ducts, viz., granular light cells, agranular dark cells, vesiculated dark cells, and basal cells. Peripheral nerves are found in five different locations: in the connective tissue (interstitial), between adjacent myoepithelial and mucous-secreting cells, in the intercellular space between adjacent secretory cells, and between basal plications of striated ducts and between adjacent myoepithelial and intercalated duct cells.     

Fine structure of the parotid and mandibular glands of the cotton rat (Sigmodon hispidus).

The parotid and mandibular glands of the cotton rat were examined by light and transmission electron microscopy. Parotid gland: Acinar cells were serous in nature, and contained electron-dense granules. Intercalated duct cells contained electron-dense granules. Striated duct cells had small granules of moderate and high electron densities. Mandibular gland: Acinar cells were seromucous in nature, and contained granules of low and moderate electron densities. Intercalated duct cells contained granules of moderate and high electron densities. Striated ducts were comprised of two portions - a secretory portion and a striated portion without granules. The secretory portion had many electron-dense granules. A sexual dimorphism was obserbed in these granules, which were smaller and fewer in females than in males.     

Fine structure of the seminal vesicle epithelium of the mouse and golden hamster

The seminal vesicle epithelium of the mouse and golden hamster was examined by light microscopy and by transmission and scanning electron microscopy. By transmission electron microscopy, in the seminal vesicle epithelium of both animals secretory epithelial cells which consisted of mostly light and a few dark cells were observed. The epithelial cells possessed secretory granules which contained a densely stained core. The secretory granules in the mouse epithelium reacted weakly with periodic acid-Schiff (PAS) stain and were slightly stained with alcian blue (AB), and those in the golden hamster exhibited strongly positive reactions with PAS and AB. The nuclei in the mouse tissue were spherical or ovoid, and those in the golden hamster tissue had a few lobes. By scanning electron microscopy, the apical surfaces of most of the epithelial cells were commonly flat or domed, and those of some epithelial cells protruded into the lumen as apocrine-like processes, or possessed small and large orifices. Besides the epithelial cells, there were cells characterized by pseudopodium-like cytoplasmic projections, a few membranous structures, an irregular nucleus, and cytoplasm containing a few dense bodies, in the basal portions of the epithelial cells, or between the basal lamina and the epithelial cells. These cells of the two species were similar in their features.     

Ultrastructure of the principal and accessory submandibular glands of the common vampire bat

The principal and accessory submandibular glands of the common vampire bat, Desmodus rotundus, were examined by electron microscopy. The secretory endpieces of the principal gland consist of serous tubules capped at their blind ends by mucous acini. The substructure of the mucous droplets and of the serous granules varies according to the mode of specimen preparation. With ferrocyanide-reduced osmium postfixation, the mucous droplets are moderately dense and homogeneous; the serous granules often have a polygonal outline and their matrix shows clefts in which bundles of wavy filaments may be present. With conventional osmium postfixation, the mucous droplets have a finely fibrillogranular matrix; the serous granules are homogeneously dense. Mucous cells additionally contain many small, dense granules that may be small peroxisomes, as well as aggregates of 10-nm cytofilaments. Intercalated duct cells are relatively unspecialized. Striated ducts are characterized by highly folded basal membranes and vertically oriented mitochondria. Luminal surfaces of all of the secretory and duct cells have numerous microvilli, culminating in a brush borderlike affair in the striated ducts. The accessory gland has secretory endpieces consisting of mucous acini with small mucous demilunes. The acinar mucous droplets contain a large dense region; the lucent portion has punctate densities. Demilune mucous droplets lack a dense region and consist of a light matrix in which fine fibrillogranular material is suspended. A ring of junctional cells, identifiable by their complex secretory granules, separates the mucous acini from the intercalated ducts. The intercalated ducts lack specialized structure. Striated ducts resemble their counterparts in the principal gland. As in the principal gland, all luminal surfaces are covered by an array of microvilli. At least some of the features of the principal and accessory submandibular glands of the vampire bat may be structural adaptations to the exigencies posed by the exclusively sanguivorous diet of these animals and its attendant extremely high intake of sodium chloride.     

Parotid salivary gland ultrastructure in an omnivorous neotropical bat: evolutionary diversity at the cellular level

The parotid salivary gland in an omnivorous neotropical bat, Carollia perspicillata (L.), was studied by transmission electron microscopy and compared to the parotid gland in other species of bats and in mammals in general. The parotid acinar secretory granules were found to be unique among mammals: they consist of a finely punctate matrix containing a variety of electron dense inclusions ranging from punctate densities to complex cage-like geodesic structures. The parotid acinar product in Carollia perspicillata is intermediate in morphology between that formed by homologous secretory cells in insectivorous/carnivorous bats and that in frugivorous bats. Both the intercalated and striated ducts probably release additional secretory products into the saliva.     

Ultrastructure of human labial salivary glands. 3. Myoepithelium and ducts

Myoepithelial cells were present between the basal lamina and the acinar secretory cells of human labial salivary glands. In form and disposition, they resembled myoepithelial cells in the major salivary glands. Many of these cells possessed single cilia on their upper surfaces. Such cilia occasionally extended into invaginations of the overlying secretory cell. The intercalated ducts were variable in occurrence. Their epithelium ranged from columnar to squamous, and showed few signs of secretory activity. Few intralobular ducts possessed basal striations. While mitochondria were abundant in non-striated cells, they were randomly disposed in both basal and apical cytoplasm, and the basal plasmalemma showed only occasional infoldings. The paucity of true striated ducts in labial salivary glands may be responsible for the high concentration of sodium and chloride in unstimulated labial gland salivary secretions.     

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.     

Ultrastructural aspects of cat submandibular glands

Submandibular glands of five adult female cats were examined by conventional electron microscopic techniques. All gland acini are mucous secreting and each acinus is capped with mucous secreting demilunar cells. Secretory product of demilunar cells is more electron lucent than that of acinar cells. The demilunes show intercellular tissue spaces and intercellular canaliculi whereas similar specializations are absent between acinar cells. Mitochondria and arrays of granular endoplasmic reticulum are more numerous in demilunar cells than in acinar cells. In acinar and demilunar cells secretory droplets first appear as enlarged Golgi saccules which subsequently become closely related to cisternae of the granular endoplasmic reticulum. Filamentous structures, interpreted as mucin molecules, are present in secretory droplets of acinar cells. Intercalated ducts are short, consisting of several junctional cells between acini and striated ducts. Striated ducts are long and tortuous and contain light cells, dark cells and basal cells. Light cells contain numerous membrane bound granules in their distal ends whereas dark cells show electron lucent vesicles in the same position. Basal cells contain a paucity of organelles and membrane plications but exhibit hemidesmosomes along their basal plasma membranes. Myoepithelial cells are abundant in relation to acinar and demilunar cells. Nerve terminals are present in some instances between acinar cells or between acinar and myoepithelial cells.     

II. Ultrastructure of duct cell granules in mammalian submaxillary glands

Summary Discrete, PAS-positive granules of relatively uniform electron-density and size characterise the intercalated duct cells of mammalian submaxillary glands. Smaller, electron-dense organelles are seen in the cells at the junction of the intercalary-striated duct region in the guinea-pig. The large granules of variable electron-density which are observed in the proximal, modified intercalary cells in the rabbit closely resemble the granules in the acinar cells of the guinea-pig. Several populations of granules differing in size are found in the striated granular tubules of the rat and hamster; the organelles in the rat show two grades of electron-density whereas those in the hamster are uniformly dense. Numerous small granules with compactly arranged intragranular material occupy the apical part of the striated ducts of the cat, dog and rabbit. The chemical composition of each population of duct cell granules is unknown. The question whether granules containing kallikrein, trypsin-like enzymes and amylase are stored in the duct cells is discussed.We wish to thank The Wellcome Trust for a travel grant to attend the International Symposium on Vasopeptides (Florence, July 1971) where this work was briefly reported.     

Ultrastructure of sperm storage and male genital ducts in a male holocephalan, the elephant fish, Callorhynchus milii.

In chondrichthyes, the process of spermatogenesis produces a spermatocyst composed of Sertoli cells and their cohort of associated spermatozoa linearly arrayed and embedded in the apical end of the Sertoli cell. The extratesticular ducts consist of paired epididymis, ductus deferens, isthmus, and seminal vesicles. In transit through the ducts, spermatozoa undergo modification by secretions of the extratesticular ducts and associated glands, i.e., Leydig gland. In mature animals, the anterior portion of the mesonephros is specialized as the Leydig gland that connects to both the epididymis and ductus deferens and elaborates seminal fluid and matrix that contribute to the spermatophore or spermatozeugmata, depending on the species. Leydig gland epithelium is simple columnar with secretory and ciliated cells. Secretory cells have periodic acid-Schiff positive (PAS+) apical secretory granules. In the holocephalan elephant fish, Callorhynchus milii, sperm and Sertoli cell fragments enter the first major extratesticular duct, the epididymis. In the epididymis, spermatozoa are initially present as individual sperm but soon begin to laterally associate so that they are aligned head-to-head. The epididymis is a highly convoluted tubule with a small bore lumen and an epithelium consisting of scant ciliated and relatively more secretory cells. Secretory activity of both the Leydig gland and epididymis contribute to the nascent spermatophores, which begin as gel-like aggregations of secretory product in which sperm are embedded. Fully formed spermatophores occur in the ductus. The simple columnar epithelium has both ciliated and secretory cells. The spermatophore is regionalized into a PAS+ and Alcian-blue-positive (AB+) cortex and a distinctively PAS+, and less AB+ medulla. Laterally aligned sperm occupy the medulla and are surrounded by a clear zone separate from the spermatophore matrix. Grossly, the seminal vesicles are characterized by spiral partitions of the epithelium that project into the lumen, much like a spiral staircase. Each partition is staggered with respect to adjacent partitions while the aperture is eccentric. The generally nonsecretory epithelium of the seminal vesicle is simple columnar with both microvillar and ciliated cells.     

Effects of nerve stimulation and denervation on secretory material in submandibular striated duct cells of cats,and the possible role of these cells in the secretion of salivary kallikrein

Striated ducts in cats after 24 hours starvation normally contained glycogen, especially in the basal regions. They also contained neutral mucin and tryptophan in apical parts of "light" cells and small irregular "secretory" granules were found in a similar distribution by electron microscopy.--Parasympathetic nerve stimulation caused a loss of glycogen but no apparent change in the apical secretory material, despite a copious secretion.--Sympathetic stimulation caused a loss of glycogen and an extensive depletion of apical secretory material, although the salivary flow was small.--Parasympathetic denervation caused progressive atrophy of striated ducts and oedematous degeneration of some cells occurred. Persisting "light" cells tended to contain few basal infoldings, few mitochondria and little apical secretory material.--Sympathetic denervation caused a loss of apical secretory material between 2-4 days, which may have been due to "degeneration activation". Thereafter little change was evident but some ductal atrophy had occurred by 32 days.--These changes in ductal secretory material correspond more closely than acinar changes to the alterations in glandular and salivary kallikrein resulting from similar experiments by other workers. It therefore seems likely that submandibular salivary kallikrein in the cat is present in the secretory material of striated ducts.     

Expression of transforming growth factor beta 1 in the submandibular gland of the rat

We employed immunocytochemical and in situ hybridization techniques to study the expression of transforming growth factor beta 1 (TGF-beta 1) in rat submandibular gland. Immunoreactivity for TGF-beta 1 was observed in the cells of granular convoluted tubules (GCTs), striated ducts, and excretory ducts, whereas it was absent in the intercalated ducts and secretory acini in both male and female rats. Immunoelectron microscopy revealed the ultrastructural localization of TGF-beta 1 in the secretory granules of GCT cells. On the other hand, signals for rat TGF-beta 1 mRNA were abundant in the GCT and striated duct cells but were lacking in the excretory duct cells. These results provided evidence for the production of TGF-beta 1 in the GCTs and striated ducts of rat submandibular gland.