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.     

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 of the Djungarian hamster (Phodopus sungarus)

The mandibular gland of the Djungarian hamster was examined by light microscopy, and transmission and scanning electron microscopies. Its acinar cells reacted with periodic acid-Schiff (PAS) and were weakly stained with alcian blue (AB). There were intercellular canaliculi between the acinar cells. These cells therefore appeared to be seromucous. The acinar epithelium was composed of light cells containing various spherical secretory granules. The granular cells of the mandibular gland possessed many acidophilic granules exhibiting a positive reaction to PAS stain. They were frequently observed at the junction of the acini and intercalated ducts in all mandibular glands examined. All of these cells were light and contained secretory granules of varying size and density. The intercalated ducts consisted exclusively of light cells possessing a few round granules of high density in the apical region. The striated ducts were comprised of two portions--a secretory portion and a typical striated portion without secretory granules. The secretory portion consisted of light, dark and specifically light epithelial cells containing acidophilic granules, which exhibited a strongly positive PAS reaction. The epithelium of typically striated portions was composed of light and dark cells containing fine vacuoles in the apical region. The mandibular gland of the Djungarian hamster revealed no histological differences between sexes.     

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 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 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.     

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.     

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.     

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.     

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.     

Ultrastructure of the submandibular gland in the rabbit

The secretory endpieces of the rabbit submandibular gland are unusual in that they consist of seromucous acini (not demilunes) that empty into serous tubules that in turn drain into intercalated ducts. Seromucous granules consist of a moderately dense spherule in a fibrillogranular matrix. Serous granules contain a feltwork of filaments, which are liberated as a tangled skein during exocytosis. Peculiar granulated cells that have secretory granules of complex morphology are present at each end of the serous tubules. Intercalated ducts are, cytologically speaking, relatively simple, but the duct cells may contain a few oblong secretory granules. Striated ducts are typical in structure, although postfixation with ferrocyanide-reduced osmium reveals significant amounts of glycogen in the basal processes. Modified mitochondria are present in striated duct cells, but their frequency varies from rabbit to rabbit. Such mitochondria contain either an array of parallel, rigid cristae linked by intermembranous bridges, or a bundle of helical filaments within an expanded crista. Interspersed with the striated duct cells, especially near the duct origin, are some highly vacuolated cells with sparse mitochondria. Excretory ducts consisting of stratified columnar (sometimes pseudostratified) epithelium often show bleb formation of the luminal surface of the tall cells.     

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.     

Ultrastructure of the human submandibular salivary glands]

By means of electron microscopy cells in the human submandibular glands were studied. It was demonstrated that in acini two types of glandular cells were present: mucosal and seromucosal. In the latter, secretory granules are descrete with electron opaque cores in most of them. Mucocytes are filled with an electron transparent secrete; secretory granules often confluent and their membranes rupture. The acini are surrounded with myoepithelial cells. Intercalated ducts consist of cells with moderately electron opaque granules. In some granules there are dense bodies excentrically situated. In these cells there occur lipid inclusions. Striated ducts are composed of basal (electron transparent) and high cylindric (light and dark) cells. The cylindrical cells have a large amount of mitochondria, deep folds in their basal plasmolemma protruding into cytoplasma. Most of the cells in these parts contain small apically accumulated secretory granules with a dense matrix and separate larger ones scattered in the cell. It is possible to suggest that some secretory granules of ductal or, perhaps, acinar origin contain hormonal products.     

Ultrastructure of the ferret sublingual gland

The sublingual glands of 2 male and 2 female adult ferrets were examined using electron microscopy. The secretory end piece consisted of mucous tubules, serous and mixed acini. The mucous cells showed two different types of granules. The serous cells contained electron-dense secretory granules. The duct system entirely comprised excretory ducts.     

Morphologic diversity of the minor salivary glands of the rat: fertile ground for studies in gene function and proteomics

In this article the locations and histologic and ultrastructural features of all of the minor salivary glands of the rat are presented; similarities and differences among them are highlighted. These glands are almost as diverse morphologically as the major salivary glands of the rat. The acini of von Ebner's glands are serous; those of the anterior and posterior buccal glands and minor sublingual glands are mucous; and those of the glossopalatal, palatal, and Weber's glands are mucous with serous demilunes. The anterior buccal, minor sublingual and von Ebner's glands have striated and stratified columnar ducts, while only the minor sublingual and von Ebner's glands have intercalated ducts. The glossopalatal, palatal, posterior buccal and Weber's glands have none of these ducts; the tubulo-acini drain abruptly into short terminal ducts composed of stratified squamous epithelium. All of the mucous acini react with an antibody to a mucin (Muc19) of the rat major sublingual gland, but in some of the glands the reaction varies in intensity among the acinar cells. Ultrastructurally, the mucous secretory granules of the anterior buccal, glossopalatal, palatal and Weber's glands are biphasic, while those of the minor sublingual and posterior buccal glands are monophasic. Although there is a considerable body of literature concerning the development, innervation, physiology and proteomics of von Ebner's glands, investigation of the other minor salivary glands of the rat ranges from modest to nearly nonexistent.     

Exogenous thyroid hormone affects myoepithelium and proliferation in the developing rat parotid gland

Abstract

In the mature rat parotid gland, myoepithelial cells (MEC) invest intercalated ducts, but not acini. During postnatal development, however, these cells differentiate around both intercalated ducts and acini, then translocate to only intercalated ducts during weaning. Previously, we found that thyroxine (T₄) accelerates translocation of cells with small secretory granules from acini into intercalated ducts and the number of apoptotic cells increased tremendously with high doses. We present here additional analysis of the effects of T₄ on developing rat parotid gland, namely, the distribution of MEC and the proliferation of parenchymal cells. Beginning at age four days, pups were given daily subcutaneous injections of low, medium, and high doses of T₄ or vehicle or no injection. At ages 4, 7, 10, and 15 days, glands were excised and processed for light microscopy. Sections were double-immunostained with antibodies against proliferating cell nuclear antigen (PCNA) and actin, and counterstained with hematoxylin. Proliferative activity was assessed via PCNA histochemistry and MEC were identified using actin histochemistry. MEC in the T₄ groups invested mostly acini at 15 days in vehicle/normal glands and mostly intercalated ducts after 10 days in the T₄ groups. The proliferative activity of acinar cells and MEC in vehicle/normal glands declined progressively with age and T₄ increased the rate of this decline in the MEC in a dose-dependent manner. We conclude that T₄ accelerates the translocation of MEC from acini to intercalated ducts and that an important mechanism is the more rapid decline in the proliferative activity of MEC than in acinar cells in the T₄ groups. Some of the decline in the proliferative activity of all cells in the high and medium dose T₄ groups after seven days may have been due to dose-related thyroxine toxicity.     

Morphologic diversity of the minor salivary glands of the rat: fertile ground for studies in gene function and proteomics

In this article the locations and histologic and ultrastructural features of all of the minor salivary glands of the rat are presented; similarities and differences among them are highlighted. These glands are almost as diverse morphologically as the major salivary glands of the rat. The acini of von Ebner's glands are serous; those of the anterior and posterior buccal glands and minor sublingual glands are mucous; and those of the glossopalatal, palatal, and Weber's glands are mucous with serous demilunes. The anterior buccal, minor sublingual and von Ebner's glands have striated and stratified columnar ducts, while only the minor sublingual and von Ebner's glands have intercalated ducts. The glossopalatal, palatal, posterior buccal and Weber's glands have none of these ducts; the tubulo-acini drain abruptly into short terminal ducts composed of stratified squamous epithelium. All of the mucous acini react with an antibody to a mucin (Muc19) of the rat major sublingual gland, but in some of the glands the reaction varies in intensity among the acinar cells. Ultrastructurally, the mucous secretory granules of the anterior buccal, glossopalatal, palatal and Weber's glands are biphasic, while those of the minor sublingual and posterior buccal glands are monophasic. Although there is a considerable body of literature concerning the development, innervation, physiology and proteomics of von Ebner's glands, investigation of the other minor salivary glands of the rat ranges from modest to nearly nonexistent.     

The effect of aging on the rat submandibular gland: an ultrastructural, cytochemical and biochemical study

The effect of aging on the rat submandibular gland was studied by using ultrastructural, ultrastructural cytochemical and biochemical techniques. There was an age-related clumping of the nucleolar-associated and peripheral chromatin in many of the acinar cells and a decrease in the number of cisternae of rough endoplasmic reticulum. Many aged acinar cells were binucleated. There was also an age-related increase in pigment granules throughout the gland. These membrane bound granules consisted of a lipid droplet and an associated dense cap which had a granular matrix and pigment droplets. The lead capture method for acid phosphatase activity demonstrated that activity was associated with the granular matrix of the dense cap. These results were correlated with the age-related increase in acid phosphatase activity as determined by colorimetric procedures. There was an age-related increase in the number of cells characterized by small secretory granules. These cells were found as part of the intercalated ducts or at the junction of the duct with the acini. Oncocytes were also found as part of the parenchyma of the aged submandibular gland. These cells were characterized by the pleomorphic mitochondria that fill their cytoplasm. Occasionally, cells that possessed extraordinary numbers of mitochondria and small secretory granules were also observed. The determinations of total DNA and RNA revealed and age-related decrease in RNA while there was no significant change in the concentration of DNA.     

A neonatal secretory protein associated with secretion granule membranes in developing rat salivary glands

In the perinatal submandibular gland, the secretion granules of Type I cells contain protein C (89 KD) and those of Type III cells have Bl-immunoreactive proteins (Bl-IP, 23.5-27.5 KD). In this report we used immunocytochemistry at the light and electron microscopic levels to describe the developmental distribution and localization of protein D (175 KD), which is secreted by both Type I and Type III cells. At its first appearance in Type I cells at 18 days and in Type III cells at 19 days post conception, protein D immunoreactivity (D-IR) is associated with secretion granule membranes; this is more pronounced in Type I than in Type III cells. In early postnatal life the label remains membrane associated, but as Type III cells differentiate into seromucous acinar cells, the lower level of label present in these cells is found in the granule content. Label is found associated with the membrane in secretion granules of Type I cells as long as these cells are identifiable in acini, and subsequent to this similarly labeled cells are seen in intercalated ducts. In the sublingual gland (SLG), D-IR is membrane associated in secretion granules of serous demilune cells, and is present in the secretion granule content in mucous acinar cells. D-IR is also found in the lingual serous (von Ebner's) glands, lacrimal gland, and tracheal glands, primarily in the ducts, where it is localized in the content of secretion granules.