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The distribution of amylase in rat parotid glands and von Ebner's glands was examined using ion etching-immunoscanning electron microscopy, which enables both light and electron microscopic observations of identical semi-thin resin sections immunolabeled with anti-α-amylase and immunogold in association with silver enhancement. At the light microscopic level, most acinar secretory granules (SG) and striated duct secretions of parotid glands were strongly stained dark brown. In von Ebner's glands, acinar SG and duct secretions were weakly to strongly stained light to dark brown. At the electron microscopic level, labeling was observed as bright gold-silver particles. The labeling intensity of acinar SG of parotid glands was higher than that of von Ebner's glands. In parotid glands, weak labeling of SG in transitional cells between acini and intercalated ducts, very weak labeling of SG in intercalated ducts, and strong labeling of striated duct secretions were observed. In von Ebner's glands, the secretions and some SG of interlobular ducts were strongly labeled compared to those of intralobular ducts and SG of acini. Less amylase was synthesized in von Ebner's acini compared to parotid acini, whereas von Ebner's ducts may secrete significantly more amylase to modify saliva than parotid ducts.

Tuft cells are present in the mucosal epithelium of a number of hollow organs including the main excretory duct (MED). Despite their distinctive features such as the long, thick, blunt microvilli with prominent rootlets and the large number of vesicles in the apical cytoplasm, the hypolemmal terminal-tuft cell relationship and the true form of the various vesicles and tubules are still controversial. The present study investigated the above mentioned features of tuft cells in the MED of rat submandibular gland by computer three-dimensional (3-D) reconstruction with focus on their function. Computer 3-D reconstruction revealed that nerve endings are present at both sides of the basal portion of the lateral cytoplasmic branch of tufts cells and that the apical tubulovesicular system of these cells consists of two separate components: the complex and coherent vesicles and the small network of tubules. We suggest that such a system may be involved in the rapid changes of surface area observed in tuft cells. Furthermore, our findings demonstrate that the images seen in thin sections and formerly regarded as evidence for the presence of variations in the shape of the tubules and of the vesicles are in reality the product of the different angles at which the tubulovesicular system was sectioned. Finally, a few vesicles and tubules that were not part either of the complex or of the network, also were found.

Although kallikrein has been localised in the striated duct cells of salivary glands, the manner in which it enters the saliva remains unclear. Here, immunocytochemistry was used at both the light- and electron-microscopic levels to localise kallikrein antigenicity. At the light-microscopic level, kallikrein was found at the apices of some, but not all duct cells. At the electron-microscopic level, it was found in small granules situated between the apical vacuoles and the luminal membrane. The kallikrein-containing granules underwent exocytosis at the cell apex.

The fine structure of tuft cells in the main excretory duct of rat submandibular gland was investigated using the high pressure freezing and freeze substitution (HPF-FS) method and compared with that seen with both conventional chemical fixation (CF) method and en bloc treatment with ruthenium red. Some MEDs also were subjected to histochemistry for lectins. The apical vesicles and tubules of tuft cells observed by TEM after the HPF-FS method were different in shape from those treated by CF. With the first method, these vesicles and tubules, which may represent sections of a tubular system, appeared more slender and filled with a material of moderate density. A prominent glycocalyx covering the microvillar plasma membrane was observed in tuft cells processed both with the HPF-FS method and with ruthenium red. The surface of microvilli and the tubulo-vesicular structures of these cells exhibited the same soybean agglutinin (SBA) reactivity, suggesting a relationship between them.

Naked-backed bats of the genus Pteronotus (family Mormoopidae) occur in the Neotropics from Mexico through northern South America. These are relatively small-sized insectivorous species that frequently roost in caves. Eight specimens of naked-backed bats (Pteronotus parnellii) were livetrapped in Suriname and one in Cuba (P. quadridens). Their parotid glands were fixed in an aldehyde mixture designed for field work and postfixed in the laboratory with osmium tetroxide. Tissues were further prepared for electron microscopy by conventional means. The parotid glands of the two species of Pteronotusclosely resemble each other except for the substructure of their serous secretory granules. Serous granules in P. parnellii are bizonal, with a moderately dense inner matrix and an outer, denser corona or crescent. The matrix is occupied by laminae, flakes, and filaments in random array. In contrast, serous granules in P. quadridens consist of a uniform matrix that contains dense, usually stacked toroids or tubules either in random array or packed in bundles. A parotid gland from one specimen of P. parnellii contained an endpiece that consisted of cells that contained giant (up to 9 µm in diameter) serous granules. Serous cells in both species contain aggregates of small, uniformly dense, rod-like, membrane-delimited organelles as well as occasional bundles of cytofilaments. The endpieces are separated from intercalated ducts by a ring of granulated cells that contain secretory granules that often have a bull’s-eye configuration. Intercalated and striated ducts are typical in appearance, except that many of the cells in the latter contain small, dense secretory granules in their apical cytoplasm. The parotid glands in the two species of naked-baked bats differ slightly in terms of acinar secretory granule ultrastructure, but otherwise are fairly conservative. It is thought that the glands in these particular bats might represent the ‘‘basal’’ condition of the salivary glands of insectivorous bats and thus can serve as a reference point for making comparisons to the highly diversified (in terms of diet) phyllostomid bats. Anat Rec 255:105‐115, 1999. r 1999 Wiley-Liss, Inc.

Background Basal folds are slender plications at the basal surface of acinar cells in the salivary glands of many mammalian species. These largely organelle-free folds increase the surface area of the basal plasmalemma manyfold and are unquestionably involved in the translocation of organic and inorganic molecules and water into the acinar cells. Methods Specimens of salivary glands were obtained from over 230 species of live-trapped bats from major areas of the globe. Tissues for electron microscopy were fixed and processed by conventional means. Results A number of the bat species examined had dense material in the intercellular spaces between basal and lateral folds of serous cells in the parotid gland. This intercellular material was particularly prominent in three species of New World bats, viz., Pteronotus parnellii, P. quadridens, and Phyllostomus latifolius, and in one species of Old World bats, Chalinolobus argentatus. This dense material, which has a farinaceous texture, appears not to pass through tight junctions, so it is excluded from the lumina of intercellular canaliculi and acini. The dense material originates in the acinar cells—it is carried to the membranes of the folds via coated vesicles, which empty their dense content by exocytosis into the intercellular space. Similar dense material is present in the intercellular spaces of the basal labyrinth of striated ducts in the two species of Pteronotus. The manner in which this material accumulates in the striated duct is unclear. Conclusions Although the function of the intracellular dense material is undetermined, it appears to be placed strategically to influence molecular traffic into acinar cells or to modulate the paracellular pathway. From a comparative evolutionary perspective, we hypothesize that, in bats, the combination of basal folds and extracellular densities is associated with insectivory. Similar morphologies appear to be lacking in frugivorous or nectarivorous species. Anat. Rec. 251:72–79, 1998. © 1998 Wiley-Liss, Inc.

Background: Many bat species have an extra set of major salivary glands. In some species, the accessory glands are quite similar to the principal one, but in others they may be radically different. Accessory glands usually are associated with the submandibular gland, but the free-tailed bat, Tadarida thersites, also has an accessory parotid gland. In the present study, we compared the accessory parotid gland with its principal counterpart. Methods: Salivary glands were removed from two specimens of free-tailed bats, one of each sex, that had been live-trapped in western Kenya and immersion-fixed in a specially formulated mixture designed for field fixation. Once back in the laboratory, the tissue was further prepared for electron microscopy by conventional means. Results: The secretory endpieces consist of serous tubules composed of typical serous cells that contain numerous dense granules. In contrast, the intralobular duct system shows a radical departure from normal. These ducts are enormous in caliber, their lumina measuring greater than 100 µm in diameter. They appear to arise by amalgamation of the homologues of intercalated and striated ducts into macroducts. The walls of the macroducts consist of intermingled patches of simple cuboidal and simple columnar epithelia that occasionally include a tuft cell and are underlaid by an almost continuous layer of myoepithelium. A few cells have some modified basal striations, but most cells display a cytological organization that differs radically from either of their two putative ancestral cell types. Both tall and short epithelial macroduct cells have a paranuclear collection of ovate mitochondria and aggregates of what presumably are peroxisomes. Macroduct cells in both the female and male are pervaded by a system of tubular smooth endoplasmic reticulum (SER). In the female, the SER gives rise to membranous whorls that consist of numerous plies. As the macroducts approach their termini, a single row of small dense secretory granules appears just beneath their luminal surface. At the lobular periphery, the ducts taper down to become excretory ducts of normal dimensions. Conclusions: An accessory parotid gland occurs in T. thersites, but apparently is absent in the related species, T. brasiliensis. The ultrastructural data are consistent with a possible steroidogenic function, although other features of the gland might relate to the elaboration of a secretory product associated with feeding on chitinous beetles. The macroducts conceivably function as reservoirs of preformed saliva. Anat. Rec. 251:122‐135, 1998.

Background: The mammalian tongue encompasses several sizeable agglomerations of minor salivary glands. The ultrastructure of the various glands in the body of that organ has already been determined. In contrast, almost nothing is known of the structure of Weber's glands, a collection of salivary glands in the root of the tongue. Methods: The entire tongue was extirpated from anesthetized adult male rats that had been perfused with fixative and specimens of tissue that included Weber's glands were dissected from the lingual root. These were prepared for electron microscopic examination by conventional means. Results: Weber's glands in the rat are mixed glands, consisting of long mucous tubules that often are capped by serous demilunes. There appear to be no ducts per se, the mucous tubules increasing in caliber and approaching the crypts of the dorsal lingual surface while still retaining their mucous secretory character. As these ducts near the surface, their lining changes to stratified squamous epithelium. The mucous cells are cytologically similar to those in the sublingual glands of the same animal. Mucous droplets undergo vertical fusion to form centrally situated intra- cellular channels through which mucus is exocytosed, much in the same manner as goblet cells. The serous cells, which have all of the hallmarks of protein-secreting cells, probably empty their secretory granules via cellu- lar extensions that directly reach the tubule lumen since there are no intercellular canaliculi between adjacent mucous cells. Conclusions: The mucus elaborated by Weber's glands undoubtedly aids in swallowing dry food. We postulate that the serous cells in these glands, as in the more anterior von Ebner's glands, might play a role in the mechanism of taste, especially where posteriorly situated, nonlingual taste buds are concerned. Anat. Rec. 249:435-440, 1997. r 1997 Wiley-Liss, Inc.

Background Hart's little fruit bat, Enchisthenes hartii, is uncommon and, although it has been the subject of recent molecular genetic studies, is little known biologically. Because chiropteran salivary glands vary interspecifically in ways that reflect evolutionary history and ecology, we examined the parotid gland in E. hartii to ascertain the extent to which it resembles homologous glands in species to which this bat presumably is related. Methods The parotid glands were prepared for electron microscopic examination by conventional means. Results The parotid gland of E. hartii is structurally unique among all previously studied species of bats (>230 species examined) and other mammals. In contrast to the same gland in other mammals, the parotid gland in E. hartii lacks secretory endpieces. In their place, there is a type of striated duct. Thus, in this species single secretory elements consist of (proceeding in the direction of salivary flow): striated duct—intercalated duct—and a conventionally located striated duct. The proximal ducts possess microvillus-lined intercellular canaliculi, whereas the walls of the distal ducts include occasional dark cells. Some small serous-like granules may be present in the intercalated duct cells. Conclusions The function(s) and biological role of the unique parotid gland in E. hartii are unknown. Nevertheless, the presence of two sets of striated ducts provides two separate glandular components seemingly capable of electrolyte transport. This might be of adaptive significance in enabling this species to make use of tropical nutrient resources that otherwise would be unavailable. The uniqueness of its parotid glands lends support to the current hypothesis that E. hartiishould be classified as a monotypic genus rather than as a species of Artibeus, whose members it resembles morphometrically. Anat. Rec. 249:349-358, 1997. © 1997 Wiley-Liss, Inc.

Background: In previous studies, we determined that the submandibular glands of five species of Neotropical fruit bats in the genus Artibeus had seromucous granules in their demilune cells with substructures that varied interspecifically in accordance with systematic relationships. Moreover, the striated ducts in these frugivores exhibited structural modifications that apparently are related to the consumption of a diet rich in potassium, but deficient in sodium. We now turn our attention to the parotid gland in a large number of species in this genus to determine if it follows the same structural pattern as does the submandibular gland. Methods Members of seven different species of Artibeus were live-trapped in various Neotropical locations. The parotid glands were extirpated from euthanized bats, fixed in the field, and prepared for electron microscopic examination by conventional means. Results The parotid glands in all seven species were virtually identical in morphology. The acinar cells (determined to be seromucous on the basis of ultrastructural criteria) contain large numbers of what appear to be vacuoles, but which are a type of secretory granule. These granules have an electron-lucent matrix and may contain one or several circular membranous profiles arranged either concentrically or in a random array. These granules appear to form by progressive dilatation of the termini of Golgi saccules, with the nascent granules finally severing their connection with the Golgi apparatus. Many of the internal membranous profiles are formed simply by invaginations of the limiting membrane of the granule; others may result from indentation of the limiting membrane by protrusions from adjacent granules; the source of multiple internal membranes in certain granules is unclear. The exocytosis of these granules results in the acinar and intercalated duct lumina being filled with an abundance of membranous material. Such extruded membranes are present in some striated ducts, but not in others, suggesting that they are degraded during passage through the duct system. The striated ducts are of conventional appearance, lacking the frondose processes that are prominent in the submandibular glands of Artibeus. Conclusions The parotid gland in Artibeus shows none of the interspecific ultrastructural variability that characterizes the submandibular gland in bats of this genus. The seromucous acinar cells secrete granules that release phospholipids as well as glycoconjugates into the saliva. Based on the lack of frondose processes with their sodium-transporting portasomes, the striated ducts of the parotid gland are less concerned with electrolyte homeostasis than are those in the submandibular gland. Anat. Rec. 248:176–188, 1997. © 1997 Wiley-Liss, Inc.

Background As part of a continuing investigation of the comparative ultrastructure of chiropteran salivary glands, we examined the submandibular glands of eight species of neotropical fruit bats in the genus Artibeus. We previously described secretory granules of unusual substructure in the seromucous demilunar cells of this organ in some species in this genus. In the present study, we turned our attention to the serous acinar cells in the same glands. Methods Specimens of seven species of Artibeus were collected in neotropical localities. Salivary glands were extirpated in the field and thin slices were fixed by immersion in triple aldehyde-DMSO or in modified half-strength Karnovsky's fixative. Tissues were further processed for electron microscopy by conventional means. Results In contrast to seromucous cells, which exhibit species-specific diversification in bats of this genus, the secretory apparatus and secretory granules in the serous acinar cells are highly conserved across all seven species. The single exception involves the mitochondria in one species. In this instance, some of the serous cell mitochondria in Artibeus obscurus are modified into megamitochondria. Such organelles usually have short, peripheral cristae; a laminar inclusion is present in the matrix compartment of every outsized organelle. Inclusions of this nature never are present in normal-size mitochondria in the serous cells. None of the megamitochondria were observed in the process of degeneration. Conclusions The giant mitochondria in A. obscurus have a matrical structure that is radically different from that of the only other megamitochondria reported to occur in bat salivary glands. The factors that lead to variation in megamitochondrial substructure in different species, as well as the functional capacities of such giant organelles, are unknown. Anat. Rec. 248:13–17, 1997. © 1997 Wiley-Liss, Inc.

The submandibular and sublingual glands of foetal and newborn rats aged 21 days in utero to 7 days after birth were examined morphologically and biochemically. Lipid droplets tended to be localized in secretory cells, especially in their basal cytoplasm. The degree of droplet accumulation varied with the age of the rat. No droplets were observed before and immediately after birth. The number of accumulated droplets peaked 24–48 h after birth, then gradually decreased and reached normal levels by 5 days. In the salivary glands of fasted newborn rats, no lipid droplets were observed throughout the experiment. The amount of triacylglycerol reached its maximum level 1 day after birth; it then decreased gradually until 5 days and after that did not change. The amount of cholesterol did not change during postnatal development. Lipase activity attained its maximum level in the salivary glands immediately after birth and then decreased rapidly. It was higher in the glands of fasted than fed 1-day-old rats. Antiserum) against lipoprotein lipase inhibited the salivary gland lipase activity in a dose-dependent manner, with 5 μl of antiserum producing 60–70% inhibition. Nondashimmune serum had little effect. It was concluded that (1) accumulated lipid in the secretory cell cytoplasm of the salivary glands originates from ingested milk; (2) the principal component of accumulated lipid droplets is triacylglycerol; (3) 60–70% of the total lipase activity represents lipoprotein lipase; (4) an increase of lipoprotein lipase activity is recognizable before the accumulation of triacylglycerol.

TNF-alpha alters leukocyte adhesion molecule expression of cultured endothelial cells like human umbilical vein endothelial cells (HUVEC). This study was designed to investigate the changes in vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and platelet endothelial cell adhesion molecule-1 (PECAM-1) expression with TNF-alpha stimulation in cultured human neonatal dermal lymphatic endothelial cells (HNDLEC). The real-time quantitative PCR analysis on HNDLEC showed that TNF-alpha treatment leads to increases of VCAM-1 and ICAM-1 mRNAs to the 10.8- and 48.2-fold levels of untreated cells and leads to a reduction of PECAM-1 mRNA to the 0.42-fold level of untreated cells. Western blot and immunohistochemical analysis showed that TNF-alpha leads to VCAM-1 and ICAM-1 expressions that were inhibited by antiserum to human TNF receptor or by AP-1 inhibitor nobiletin. In flow cytometry analysis, the number of VCAM-1- and ICAM-1-positive cells increased, and PECAM-1-positive cells decreased with TNF-alpha treatment. Regarding protein amounts produced in cells and amounts expressed on the cell surface, VCAM-1 and ICAM-1 increased in HNDLEC and HUVEC, and PECAM-1 decreased in HNDLEC in a TNF-alpha concentration-dependent manner. VCAM-1, ICAM-1, and PECAM-1 protein amounts in TNF-alpha-stimulated cells were lower in HNDLEC than in HUVEC. This suggests that the lymphatic endothelium has the TNF-alpha-induced signaling pathway, resulting in increased VCAM-1 and ICAM-1 expression to a weaker extent than blood endothelium and PECAM-1 reduction to a stronger extent than blood endothelium.

In addition to their role in electrolyte homeostasis, striated ducts (SDs) in the major salivary glands of many mammalian species engage in secretion of organic products. This phenomenon usually is manifested as the presence of small serous-like secretory granules in the apical cytoplasm of SD cells. The composition of these granules is largely unknown, except in the case of the cat and rat submandibular gland, where the granules have unequivocally been shown to contain kallikrein. In some species, the apical cytoplasm of SD cells contains variable numbers of vesicles, both spherical and elongated, that vary in appearance from 'empty' to moderately dense. In the rat parotid gland, lucent vesicles transport glycoproteins to the luminal surface where they are incorporated into the apical plasmalemma and the glycocalyx. There is a strong possibility that in various species some of these vesicles are involved in transcytosis of antibodies to the saliva from their source (plasma cells) in the surrounding connective tissue. In addition, vesicles may engage in transfer of growth factors from the saliva to the interstitium. In a few species, conventional SDs have been replaced by ducts that are wholly given over to secretion, i.e., they entirely lack basal striations; although such ducts occupy the histological position of conventional SDs, it is not clear whether they represent a new type of duct or merely are modifications of SDs. Broad-based comparisons of ultrastructural and other data about SDs offer some insight into evolutionary history of salivary glands and their role in the adaptive radiation of mammals. Evolutionary patterns emerged when we made interspecific comparisons across mammalian orders. Among the bats, there is a clear relationship between SD secretion and general categories of diet.

The tent-building bat, Uroderma bilobatum, is a small, frugivorous phyllostomid bat with a broad neotropical distribution. Generally found in humid forest, this bat lives in small groups that create daytime "roosts" from large leaves of a variety of tropical plants. Fruit eating engenders a variety of ecological and physiological challenges for bats, some of which could require adaptive features in their salivary glands. The parotid salivary glands of Uroderma bilobatum were prepared for transmission electron microscopy by using methods that have become standard for field work. The parotid gland is extremely unusual in structure. Although the secretory endpieces still produce serous granules with a complex substructure, they are modified into quasi striated ducts. Their basal folds, which are extensive, occasionally harbor some vertically oriented mitochondria, imparting a resemblance to striated ducts. Other evidence for the endpiece origin of these parenchymal components is a well-developed system of intercellular canaliculi, structures that never occur in bona fide striated ducts. The long but sparse intercalated ducts consist of two types of cells, each of which elaborates a modest number of secretory granules of differing substructure. Striated ducts are of conventional morphology, except that a few dark cells shaped like wine glasses are present in their walls. The striated duct cells produce no secretory granules, but their apical cytoplasm may contain some small, empty vesicles. Capillaries lie in longitudinal grooves in the base of the duct cells, an arrangement that might enhance electrolyte exchange. Excretory ducts consist of simple cuboidal epithelium composed of cytologically unspecialized cells that sometimes includes a dark cell. It was concluded that salivary glands could have a major role in adapting species to acquire nutrients from marginal sources, such as tropical fruits, which have a low protein and sodium content. The unusual parotid acinar cells in Uroderma bilobatum are discussed in the context of salivary pH and buffering capacity. Comparisons are made with four other bat species, including an insectivorous species with a salivary pH8.0 and a very high buffering capacity, an intermediate species, and a fruit bat with acidic-stimulated saliva and very low buffering capability. Such interspecific comparisons provide a foundation for hypothesizing that ultrastructural features of the acinar cell basolateral membranes and intercellular canaliculi correlate with differences involving Na/H+ exchangers and release of HCO3- and, thus, are associated with the species differences that are important to diet and nutrient acquisition.

Background:The phyllostomid fringe-lipped bat,Trachops cirrhosus, is sui generis (in a family of ca. 138 species) in that it subsists in part on tropical frogs. These amphibians frequently possess highly toxic integument. We examined the salivary glands of this bat to determine if these glands could be the source of protective factors that permit consump- tion of seemingly unsavory prey. The parotid and principal salivary glands of this bat are similar to homologous glands in other phyllostomids, but the accessory submandibular gland is unique. Methods: The accessory submandibular glands of live-trapped T. cirrho- sus were fixed and processed for transmission electron microscopy by conventional means. Results: The accessory submandibular gland consists of follicles and ducts. The principal cells of the follicular walls have an abundance of rough endoplasmic reticulum (RER), free ribosomes, and extensive Golgi apparatuses. Typically, these cells have relatively few serous secretory granules. The cells contain collections of peculiar lipid droplets, and some of their mitochondria have dense crystalloids within expanded cristae. A layer of irregular, moderately dense bodies lies immediately subjacent to the luminal plasmalemma; it is not clear if these structures are endocy- totic or exocytotic. Clusters of mucous cells, some of which have a single, hugely distended RER cisterna, are ensconced in the follicular walls; mucus from these cells reaches the lumen via intercellular canaliculi. Ducts progress from simple cuboidal to simple columnar epithelium. They lack basal striations, and their constituent cells contain relatively few mitochondria. Follicles and ducts have numerous myoepithelial cells at their periphery, and both are heavily innervated by hypolemmal nerve terminals. Conclusions: The unusual accessory submandibular gland in T. cirrho- sus documents the extreme modifications in gland histology and in cell ultrastructure that have occurred in mammalian families. The cells composing the follicle walls and ducts bear little similarity to typical acinar or duct cells. Duplication of the submandibular gland in some bat lineages might be the key innovation underlying such plasticity. The heavy innervation of both follicles and ducts also implies that these structures are sensitive to and capable of responding to various inputs, perhaps including dietary factors. Anat. Rec. 248:164-175, 1997. r 1997 Wiley-Liss, Inc.

Cytoplasmic crystalloids are abundant in the excretory ducts of the accessory submandibular gland of the long-winged bat, Miniopterus magnator. The crystalloids, which always lack a membranous enclosure, may have an intricate silhouette. They consist of parallel linear densities with a 12.5 nm periodicity. These densities actually may be thin-walled tubules. In some crystalloids, intersecting subcrystalloids produce a complex pattern of decussate densities. In a few rare instances, continuities were detected between a crystalloid and a smooth-surfaced cisternal element. In other mammalian species, similar crystalloids connected to smooth endoplasmic reticulum play a role in steroid metabolism. We postulate that the ductular crystalloids in M. magnator might be involved in production of a factor that influences mating behavior.

The accessory submandibular glands in four species of bats were examined by electron microscopy. These four species represent two independently evolved lineages. The fringe-lipped bat, Trachops cirrhosis, is a Neotropical phyllostomid species, whereas the false vampire bats of southeast Asia, Megaderma lyra and M. spasma, and the heart-nosed bat, Cardioderma cor, of East Africa are megadermatid species. These glands show extreme deviation from typical salivary gland histology: their secretory endpieces are in the form of follicles and their ducts lack the cytological details that permit identification of diverse duct segments. Despite their unusual histology, the secretory endpieces in M. lyra, M. spasma, and C. cor consist of secretory cells that conform to typical secretory cell morphology. In contrast, secretion by follicular cells in T. cirrhosis involves unusual cytoplasmic bodies, and their mitochondria frequently have intracristal crystalloids. Ducts in all four species consist of simple cuboidal to columnar epithelium without basal striations. Follicles and ducts in all four bats are surrounded by numerous myoepithelial cells and are heavily innervated by hypolemmal nerve terminals. Despite their widely separated geographical ranges, all four bat species consume frogs and other vertebrates. Frogs and toads often possess toxic cutaneous glands that provide a chemical defense against predation. It is postulated that the unusual accessory glands in the four frog-eating species secrete toxin-neutralizing salivary factors. The follicular form of the endpieces permits storage of preformed saliva and their coterie of myoepithelial cells and hypolemmal nerve terminals facilitates the sudden and rapid expulsion of saliva into the oral cavity during the consumption of noxious amphibians.

A new, third type of secretory cell was found in the acini of the submandibular gland in rat. In paraffin sections stained with hematoxylin-eosin or reacted with periodic acid-Schiff, acini containing the third type of secretory cells were found as a mass of darkly stained secretory endpieces at the periphery of the lobule. In semi-thin sections stained with toluidine blue, these cells showed numerous dense secretory granules in their cytoplasm. Some acini consisted entirely of these cells, whereas other acini consisted of an admixture of such cells and typical seromucous cells. Acini containing the third type of secretory cell tended to form clusters. Electron microscopically, the cells had well-developed rough endoplasmic reticulum and Golgi apparatus. The secretory granules showed a wide range of variation in substructure, even within the same cell. Well-developed intercellular interdigitation and intercellular canaliculi also were observed between adjacent third type of secretory cells. Although little is known about the biological significance of these cells and the properties of their secretory granules, the present study shows that the rat submandibular gland possesses three types of secretory cells in their secretory endpieces.

Exocrine glands including the submandibular gland, sublingual gland, exocrine pancreas and exorbital lacrimal gland of newborn rats aged 0 to 14 days were examined morphologically, and the following results on the accumulation of lipid droplets were obtained. Lipid droplets tended to localize in secretory cells, especially in their basal cytoplasm. The degree of lipid droplet accumulation varied with the type of exocrine gland. There were large accumulations in the sublingual gland, submandibular gland, and exocrine pancreas, but accumulations were small in the exorbital lacrimal gland. No difference in lipid droplet accumulation was recognized between the 2 types of secretory cells in the sublingual gland. The accumulation of lipid droplets peaked 24-48 hours after birth in the sublingual gland, submandibular gland and exocrine pancreas, but this peak was not clearly observed in the exorbital lacrimal gland. In the group of newborn rats separated from their mothers and therefore not suckled, no lipid droplets were observed in any gland, suggesting a close relationship between lipid droplet accumulation and suckling.

This effect of parasympathectomy was assessed by fluorescent microscopy using nitrobenzoxadiazole-phallacidin, which is known for its specific binding to actin filaments. Resection of the chorda tympani within 48 h after birth inhibited the normal formation of actin in the myoepithelial cells and the maturation of myoepithelial cells. The effect of denervation decreased progressively if the operation was delayed. Denervation 30 days after birth had no effect on development and differentiation of myoepithelial cells. Moreover, the procedure produced no histochemical changes in the myoepithelial cells in mature rats, even two months later. These findings suggest that the parasympathetic innervation is closely involved in the maturation of myoepithelial cells. Further, its involvement is limited to the first 48 h after birth, during which it exerts its neurotrophic effect on the myoepithelial cells present in all the acinar buds.

Myoepithelial cells in the intercalated ducts of rat parotid and exorbital lacrimal glands were examined by scanning electron microscopy. The basal surface of the intercalated ducts revealed myoepithelial cells running parallel with its long axis. These myoepithelial cells were linked with one another, forming a well-developed network, and numerous wrinkles running transversely were observed on the surface of the myoepithelial cells. Also, some myoepithelial cells in the terminal portion linked with those in the intercalated duct. Based on these findings, it is suggested that myoepithelial cells in the intercalated duct may function as a protective wall against constriction of the narrow lumen of the intercalated duct when it is subjected to pressure by the surrounding tissues.

Mammalian salivary glands, which producea huge variety of glycoproteins and mucosubstances, as well as engaging in intense transportof electrolytes, have an obvious appeal for morphologists, physiologists, and biochemists. Despite the versatility of these organs, studies onsalivary glands have been restricted largely toa few commonly available laboratory animals.Comparative studies, though still relativelysparse, have shown that salivary gland histologyis generally similar throughout the class Mammalia, but that both the acinar and duct cellsexhibit considerable ultrastructural variationbetween species [1–3]. To illustrate this morphological variability, the present chapter surveysultrastructural aspects of the parotid, submandibular, and accessory submandibular salivaryglands in bats, order Chiroptera.

A form of crystalloid smooth endoplasmic reticulum (SER) is described in the cytoplasm of seromucous acinar cells in the submandibular salivary gland of male round-eared bats, Tonatia sylvicola. The structure consists of an array of membranous tubules organized in an hexagonal pattern within a latticework of 12-nm filaments running in three planes. At the periphery of the organelle, the tubules are in direct continuity with SER or with transitional elements. Although the function of the organelle is unknown, data are presented that suggest that it is steroidogenic. Given the biology of T. sylvicola, it seems likely that the salivary secretions play some role as a species isolating mechanism or in sexual behavior, or both. Such a salivary gland system has not previously been reported for any mammals.

The ultrastructure of the submandibular glands was studied in 2 species of macaques (Macaca mulatta and Macaca irus). The glands, which were identical in both species, were predominantly serous, but contained scattered mucous acini. The serous cells contained 1 of 2 morphologically distinct secretory granules of complex substructure, whereas mucous droplets were relatively simple in structure. Other parts of the macaque glands were similar to their counterparts in other primates. The close resemblance of the serous granules to each other in the 2 species studied and to 3 other macaque species previously described by others suggests that these monkeys are taxonomically closely related.

The surface morphology of normal mammary glands and mammary carcinomas was examined under the scanning electron microscope after digestion of connective tissue and the basal lamina with collagenase, hyaluronidase and hydrochloric acid (HC1). Two types of cells were clearly identified in the acini of normal glands; granular epithelial cells and stellate myoepithelial cells. Spindle-shaped myoepithelial cells lying longitudinally along the mammary ducts were also recognized. 7, 12-dimethylbenz(a)anthracene-induced mammary carcinomas consisted or irregular masses of cells which had polypoid or columnar processes with rounded heads; the masses appeared to be composed of a single type of rhomboid cell. The tumors lacked the stellate or spindle-shaped myoepithelial cells found in normal acini and ducts.

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.

A case of ameloblastic fibroma which is very rare in comparison with ameloblastoma in occurrence was reported.The patient was a 5 year-old female who visited our hospital because it was noticed during dental inspection that she had an abnormal radiolucent lesion in the right molar region of the mandible. There was slight and diffuse swelling in the right mandibular region extraorally, and a bony expansion in the right molar region intraorally. X-ray examination showed a multilocular radiolucent shadow in the region from C apex to 6 tooth germ. The clinical diagnosis was ameloblastoma. Enucleation was done under general anesthesia. The tumor was a white solid mass with a thick fibrous capsule, and was about 3.0cm in diameter.Light microscopy showed that the tumor was composed of cellular and fibrous tissue in which there were islands and strands of odontogenic epithelium. The fine fibers were moderately stained with Azan stain and the basement membrane between the odontogenic epithelium and connective tissue was stained with both Azan and Reticulin stains. PAS-Alcian blue stain was negative. Histopathological diagnosis was ameloblastic fibroma. Under the electron microscope, tall columnar cells were observed on the periphery of the epithelial islands and strands, and were connected with each other by well developed desmosomes and gap junctions. These findings were discussed in relation to the stage of amelogenesis.There was no sign of recurrence at about a year after the operation.

Changes in myoepithelial cells (MECs) during perinatal development were examined by using the fluorescent probe for actin, nitrobenzoxadiazole (NBD)-phallacidin. By the twentieth day of gestation, there was no distinct fluorescent pattern suggestive of MECs. In newborn and 1-day-old rats, cells with diffuse fluorescence occurred around the acini, representing incipient MECs. Between 3 and 4 days after birth, actin staining was concentrated in strands which were arranged parallel to the long axis of the cell processes. MECs had developed further by the tenth day after birth with an increased number and thickness of their processes. Fully developed MECs were found between the thirtieth and fortieth day. These were stellate and encompassed individual acini.

Gap junctions were observed in rat sublingual gland to link serous cells to serous cells, mucous cells to mucous cells, and myoepithelial cells to myoepithelial cells. In addition to connecting homologous cells, gap junctions were present between conterminous serous and mucous cells. Since the rat sublingual gland is innervated solely by parasympathetic nerves, the presence of gap junctions between disparate secretory cell types raises the possibility that serous and mucous cells in this organ secrete simultaneously in response to parasympathetic stimulation.

By removing connective tissue components with enzymatic digestion followed by HCl-hydrolysis, myoepithelial cells (MECs) of the terminal portion in a variety of exocrine glands of the rat were examined with the scanning electron microscope. The profile of MECs varied considerably from gland to gland; MECs in the lactating mammary gland have a few long cytoplasmic processes in close contact with those of adjacent cells forming a continuous network around the terminal portion. Those of the exorbital lacrimal gland are stellate with many thin radiating processes with tapered ends that terminate freely. MECs in the sublingual gland are characterized by a number of broad and extensive cellular processes. MECs in the submandibular gland are similar in appearance to those of the exorbital lacrimal gland, but with more extensive cellular processes that form a more or less continuous network with those of the adjacent cells. No MECs were observed on the terminal portion of the parotid gland where the cells appear to be lodged on the intercalated duct. The relative surface area covered by MECs per terminal portion was also found to vary significantly, being 24% in the lactating mammary, 17% in the exorbital lacrimal, 48% in the sublingual, and 25% in the submandibular glands. The findings are discussed in relation to the physical properties of secretions in different glands.

In an attempt to elucidate the functions of three types of filiform papillae in the rat's tongue, corrosive resin casts of the microvessels in the filiform papillae were observed under the scanning electron microscope. The filiform papillae were also examined by light and transmission electron microscopy. The three dimensional architecture of the microvessel loops in the small conical filiform papillae was relatively simple with limited divergence and anastomosis in the papillae, whereas that in the large conical filiform papillae formed a complex network which resulted from repeated divergence and anastomosis. The microvessels in the thready filiform papillae branched several times in the primary papillae and then formed a hairpin-like loop in each of the secondary papillae. Under the light and transmission electron microscope, the small and large conical filiform papillae revealed remarkably similar tissue architectures, with the exception of their sizes. However, these two types of filiform papillae were arranged in quite opposite directions. In the large conical filiform papillae, the epithelium on the anterior side of the papillae lacked a granular layer, whereas the epithelium on the posterior side contained a well-developed granular layer. Based on these findings, we presume that the functions of the three type of filiform papillae are as follows. That of the small conical filiform papillae is to take food efficiently into the oral cavity. That of the large conical filiform papillae is to grind further the food which has been crushed with the teeth in coordination with the palate. The thready filiform papillae might function as a heat-releasing organ and be involved in the control of body temperature.