Fine structural and enzyme histochemical observations on the dorsal tail tubercle of Mertensiella caucasica (Urodela,Amphibia)

Summary Dorsal tubercle and skin of Mertensiella caucasica have been investigated with the electron microscope and enzyme histochemical methods. The epidermis of the tubercle consists of 8–9 cell layers, that of normal dorsal skin of 5–6. The tubercle is filled with large mucous glands which are surrounded by an almost complete layer of smooth muscle cells (myoepithelial cells). Their glandular cells undergo cyclical changes and are characterized by specific secretory granules, which differ from those of the relatively small mucous glands of the normal dorsal skin.In the connective tissue of the tubercle a relatively rich supply of nerve fibres has been found, which in part contain synaptic and dense core vesicles or accumulations of mitochondria. In the normal dorsal skin nerve fibres occur less frequently.The following enzymes have been demonstrated in the mucous glands of the tubercle: SDH, acid phosphatase, unspecific esterases, E 600 resistant esterase.The tubercle seems to stimulate the female cloaca chemically and mechanically.     

Fine structure of the excretory system of the deep posterior (Ebner's) salivary glands of the human tongue

Human deep posterior lingual glands (von Ebner's glands) are located beneath the circumvallate papillae. They are formed by tubuloalveolar adenomeres, intercalated ducts and excretory ducts coming together in the main excretory duct. The tubuloalveolar cells, pyramid-shaped, show large and dense secretory granules (clear cored) throughout the cytoplasm, rare basal folds and packed cisternae of rough endoplasmic reticulum (RER) at the basal pole. The columnar cells of the intercalated ducts are arranged in a monolayer. They are characterized by dense, clear-core secretory granules (mostly in the apical cytoplasm), a basal nucleus, well-developed RER and Golgi apparatus, and thin filaments distributed in supra- and perinuclear cytoplasm. Striated ducts are absent. Excretory ducts, coming together in the main duct, are lined by a bistratified epithelium. The inner layer consists of columnar cells showing bundles of tonofilaments with scarce secretory activity. The outer layer is composed of basal cells lying on the basal lamina. The main excretory duct, which opens at the bottom of the vallum, shows a stratified epithelium. The outer side is composed of 2-3 layers of malpighian cells lying on the basal lamina. The inner side consists of a single layer of cuboidal-columnar cells with dense apical granules and well-developed organelles synthesizing and condensing secretions. These cells interpolate with goblet cells, rare mitochondria-rich cells, ciliated cells and numerous small globous cells showing a clear matrix and lacking secretory granules. The cilia show a 9 + 2 microtubular structure with basal bodies provided with striated rootlets. Myoepithelial cells surround with their processes the basal portions of the secretory cells and the intercalated ducts. The conclusions concern some comparative aspects and some hypothesis on the functional role of goblet cells, ciliated cells and epithelial cells lining the different ducts, also in relation to the final secretory product.     

Ultrastructure of the male reproductive accessory glands in the medfly Ceratitis capitata (Diptera: Tephritidae) and preliminary characterization of their secretions

The morphology and the ultrastructure of the male accessory glands and ejaculatory duct of Ceratitis capitata were investigated. There are two types of glands in the reproductive apparatus. The first is a pair of long, mesoderm-derived tubules with binucleate, microvillate secretory cells, which contain smooth endoplasmic reticulum and, in the sexually mature males, enlarged polymorphic mitochondria. The narrow lumen of the gland is filled with dense or sometimes granulated secretion, containing lipids. The second type consists of short ectoderm-derived glands, finger-like or claviform shaped. Despite the different shape of these glands, after a cycle of maturation, their epithelial cells share a large subcuticular cavity filled with electron-transparent secretion. The ejaculatory duct, lined by cuticle, has epithelial cells with a limited involvement in secretory activity. Electrophoretic analysis of accessory gland secretion reveals different protein profiles for long tubular and short glands with bands of 16 and 10 kDa in both types of glands. We demonstrate that a large amount of accessory gland secretion is depleted from the glands after 30 min of copulation.     

Fine structure of the spermatheca and of the accessory glands in Orchesella villosa (Collembola, Hexapoda)

The spermatheca and the accessory glands of the collembolan Orchesella villosa are described for the first time. Both organs exhibit ultrastructural differences, according to the time of the intermolt in which the specimens were observed. A thick cuticular layer lines the epithelial cells of the accessory glands. In the reproductive phase, they are involved in secretory activity; a moderately dense secretion found in the apical cell region opens into the gland lumen. Cells with an extracellular cistern are intermingled with the secretory cells. These cells could be involved in fluid secretion, with the secretory product opening into the cistern which is filled with an electron-transparent material. After the reproductive phase, the gland lumen becomes filled with a dense secretion. The accessory gland secretion may play a protective role towards the eggs. The spermatheca is located between the accessory glands; its epithelium is lined by a thin cuticle forming spine-like projections into the lumen and consists of cells provided with an extracellular cistern. Secretory cells, similar to those seen in the accessory glands, are missing. Cells with a cistern could be involved in the production of a fluid secretion determining sperm unrolling and sperm motility.     

Repugnatorial glands with associated striated muscle and sensory cells inMelibe leonina (Mollusca,Nudibranchia)

Summary The nudibranch molluscMelibe leonina is repellant to some seastars and fish, but not to crab predators. Distinctive subepidermal glands, which are particularly abundant within the cerata and dorsal wall of the oral hood, can be easily seen within the translucent body wall of this slug. The glands can be individually discharged by touching the overlying epidermis and the collected secretion is repugnant to seasters. Ultrastructural analysis reveals that each repugnatorial gland is composed of two types of secretory cell encased by cross-striated muscle. Storage of secretory product within a single, large, intracellular vacuole and cytological features of the muscle investment are consistent with a rapid, all-or-none secretion event, as observed in live tissue. The secretory cells empty into a short duct that opens by a pore. The pore is surrounded by ciliated sensory cells that probably act as mechanoreceptors triggering gland discharge. I argue that one of the two secretory cells releases defensive chemical, whereas the second may produce a protein-rich mucin.     

Specialized mucous glands and their possible adaptive role in the males of some species of Rana (Amphibia,Anura)

A structural and ultrastructural study was carried out on the cutaneous glands in some species of Rana (R. dalmatina, R. iberica, R. italica, R. "esculenta," and R. perezi), giving particular attention to the mucous secretory units. Two different types of mucous glands occur in R. dalmatina, R. iberica, and R. italica. Besides the ordinary mucous units, which are randomly distributed over the body surface in both males and females, a further population of mucous glands was observed on the male dorsal skin. The latter is recognizable by the peculiar morphology of the epithelial cells and some characteristics of the secretory product. Specialized mucous glands are absent in both sexes of R. "esculenta" and R. perezi. The possible adaptive role of the specialized mucous glands is discussed in light of the absence of vocal sacs in males of R. dalmatina, R. iberica, and R. italica. Chemosignals released by sexually dimorphic mucous units may replace vocal communication during the breeding season and so play an important role in female attraction and/or territorial announcement. The morphology and possible function of the specialized mucous glands in the three species of Rana are compared with the breeding glands of other frogs and with the hedonic glands of some urodeles (Salamandridae and Plethodontidae), which are known to produce pheromonal substances during courtship.     

Adrenergic and cholinergic nerves of bovine,guinea pig and hamster salivary glands

Summary The distribution of formaldehyde-induced fluorescence and acetylcholine-esterase (AChE) activity was histochemically investigated in certain salivary glands of the cow (submandibular gland), guinea pig and hamster (submandibular and sublingual glands). Adrenergic nerves occur around the secretory acini of the bovine, guinea pig and hamster submandibular glands, as well as around those of the hamster sublingual gland. The mucous secretory acini of the guinea pig sublingual gland, however, seem to be devoid of adrenergic nerve supply. Except in the sublingual gland of the hamster, no adrenergic nerves occur in relation to duct cells.The pattern of AChE activity is similar to that of adrenergic nerves. Thus, AChE-positive nerves form a network around secretory acini of all the five glands examined. Furthermore, AChE activity was also observed in nerve fibres in close proximity to striated duct cells.Both adrenergic and AChE-containing fibres were observed around blood vessels of different sizes. Ganglionic cells are occasionally to be seen; they all display AChE-activity. No adrenergic ganglionic cells were observed in any of the glands examined.All glands were also studied in the electron microscope. Interest was focussed on the fine structure of the autonomic nerves with special reference to their contents and type of storage vesicles.The content of noradrenaline was chemically determined in each type of salivary gland studied.This work was supported by grants from the University of Umeå and from the Swedish Society for Medical Research and was also carried out within a research organization supported by the Swedish Medical Research Council (projects B73-04X-712-08C and B73-04X-56-09C). The authors are indebted to Miss Kristina Karlsson and Miss Marianne Borg for valuable technical assistance.     

Presence of glycoconjugates in prolactin granules of male rats

Summary Prolactin granules in the anterior pituitary glands of male rats contain densely stained materials at the periphery of the matrix. These occur in both small spherical and large polymorphic types of granules. The presence of densely stained materials around secretory granules may be a useful criterion for identification of prolactin cells since the dense structure was observed in 95% of these cells after conventional staining by uranyl acetate and lead citrate. The localization of glycoconjugates in the prolactin granules was examined by applying concanavalin A (Con A) on the ultrathin sections. HRP-Con A or ferritinconjugated Con A bound specifically to the densely stained materials in the peripheral region of the prolactin granule matrix, indicating that this densely stained matrix contains glycoconjugates; the significance thereof is discussed with reference to the concentration and packaging of secretory product.     

Morphogenetic processes in cultured cells from integumentary glands of deer sambar (Cervus unicolor Kerr)

The present paper describes an attempt to maintain the metatarsal and caudal glands of deer sambar (Cervus unicolor Kerr) in diffusion chambers. Another purpose was to provide information on the secretory granule of these glands. Our results show that cultured gland cells have the capacity to reassociate into islet-like organoids in diffusion chambers. Competence in some epithelial cell types may probably be regulated as a function of growth. Scanning electron microscopy of secretory cells showed that the cells in the culture often had numerous short filopodia and blebs. The secretory granules of the caudal gland were spherical and uniform in size. Some of the secretory granules had pseudopodia-like protrusions. By means of SEM, the present study provides evidence of rapid structural changes in the surfaces of epithelial cells in the course of cultivation. It has been suggested that the structural organization in the cell colonies serves to "guide" the function of secretory cells.     

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 GLANDULAR TRICHOMES OF LEAVES OF NICOTIANA TABACUM L., cv XANTHI

Electron microscopy confirms previous light microscope observations that tobacco leaf trichomes are glandular and that there are two different types. Both the tall trichome (multicellular stalk, unicellular or multicellular head) and the short trichome (unicellular stalk; multicellular head) exhibit characteristics common to gland cells—a dense cytoplasm, numerous mitochondria, and little vacuolation. The tall trichome contains structurally well developed chloroplasts and an elaborate network of endoplasmic reticulum. The short trichome contains undifferentiated plastids and endoplasmic reticulum which parallels the nucleus and plasmalemma. Few dictyosomes are seen either in the short trichome or in the tall trichome. The short trichome appears to undergo structural changes concurrently with the appearance of secretory product within the cells. The most noticeable change is the formation of the extraplasmic space between the cell wall and the plasmalemma. Electron dense secretory product is observed between the plasmalemma and the cell wall and within the intercellular spaces.     

Structural Aspects of the Salt Glands of the Plumbaginaceae

Faraday, C. D. and Thomson, W. W. 1986. Structural aspects ofthe salt glands of the Plumbaginaceae.—J. exp. Bot. 37:461–470. The epidermal salt-secreting glands of 11 species from six differentgenera within the Plumbaginaceae were examined Gland ultrastructurewas considered with respect to species, secretory activity,and secretory product. All mature glands had a similar ultrastructure.Cytoplasmically dense secretory cells contained a full complementof organelles and structures which included numerous mitochondriaand few plastids. Reconstruction of serial paradermal sectionsthrough entire glands revealed that each gland cell generallycontained one or two vacuoles with a convoluted tonoplast inboth secreting and non-secreting states. The absence of numerousvacuoles and vesicles during secretory activity suggested thation secretion was by a transmembrane pathway rather than bya vesicle-mediated pathway. Key words: Salt glands, ultrastructure, Plumbaginaceae     

Ultrastructure of epidermal glands in neotenic reproductives of the termite Prorhinotermes simplex (Isoptera: Rhinotermitidae)

The ultrastructure of epidermal glands in neotenic reproductives of Prorhinotermes simplex is described and their development is compared among young and old neotenics of both sexes. Secretory cells forming the epidermal gland are attached to the cuticle all over the body. The glands are formed by class 1 and class 3 secretory cells and corresponding canal cells with secretory function. Class 1 cells are sandglass-like and class 3 secretory units are located among them. Class 1 cells contain predominantly tubular endoplasmic reticulum, the major part represents the smooth and the minor the rough form. Numerous electron dense granules occur in the cytoplasm, they are always disintegrated prior to be released. Class 3 secretory cells contain a large amount of vacuoles, which are always lucent in males while newly produced vacuoles are dense in females. Dense vacuoles are frequently transformed into lucent ones before being released. Canal cells are locally equipped with microvilli. The conducting canal is surrounded by an electron dense secretion of regular inner structure. The cytoplasm of the canal cell contains numerous mitochondria, rough endoplasmic reticulum and a large proportion of microtubules. The young neotenic reproductives differ from the old ones by a lower amount of secretory products. Epidermal glands probably produce substances inhibiting the occurrence of superfluous reproductives.     

The fine structure of the coxal glands in Myobia murismusculi (Schrank) (Acari: Myobiidae)

The coxal glands of M. murismusculi consist of the proximal tubular portion (tubulus), the distal glandular sac and the terminal excretory duct. The tubulus comprises looped proximal and distal tubes that run in close association with each other. The cells of the proximal tube form numerous short protrusions that project into the neighbouring organs through the pores in their basal lamina. The sac is a distal part of the gland and so it cannot be considered as a homologue of the proximal filter sacculus of other arthropods. A large number of pinocytotic vesicles and lysosome-like bodies in the epithelial lining of the sac imply that the main functions of this organ may be the absorption of substances from the lumen of the gland and their subsequent intracellular transformation. In addition the sac of females was shown to produce dense secretory granules. The ultrastructural features of the glands are discussed and compared to other representatives of Acari.     

Ultrastructure and innervation of water buffalo (Bubalus bubalis) seminal vesicle.

The lining epithelium of secretory end pieces and central glandular duct in the seminal vesicle of the water buffalo (Bubalus bubalis) consists of columnar principal and small polymorphous basal cells. A system of intercellular and even intracellular canaliculi enlarges the secretory surface. The most prominent organelle of the columnar principal cells is the granular endoplasmic reticulum, forming large aggregates of parallel lamellae. Using antibodies against the neural cell adhesion molecule L1 and the neural marker protein gene product 9.5 (PGP 9.5), the innervation pattern of the seminal vesicle becomes evident. The muscular layer surrounding the propria contains a dense network of unmyelinated fibers. Thicker bundles traverse the muscular layer to reach the propria. Around glandular secretory tubules and below the epithelial lining of the glandular duct a tightly woven subepithelial plexus is observed which sends short penetrating branches into the basal zone of the epithelium. These intraepithelial nerves are devoid of Schwann cells and basal lamina (naked axons) and are situated within the intercellular spaces between principal and basal cells. Acetylcholinesterase histochemistry with short (1-2 h) incubation times, dopamine-beta-hydroxylase immunohistochemistry and ultrastructural study of transmitter-containing vesicles was performed. The results suggest that muscular contraction in the seminal vesicle is predominantly under the influence of the sympathetic nervous system, whereas secretory epithelial function is regulated by both sympathetic and parasympathetic fibers.     

Structure of the male reproductive accessory glands of Pterostichus nigrita (Coleoptera: Carabidae), their role in spermatophore formation

Accessory gland secretions of male insects have many important functions including the formation of spermatophores. We used light and electron microscopy to investigate the structure of the accessory glands and posterior vasa deferentia of the carabid beetle Pterostichus nigrita to try to determine where spermatophore material is produced. Each accessory gland and posterior vas deferens had an outer layer of longitudinal muscle, beneath which was a layer of connective tissue and a thin band of circular muscle, all of which surrounded a layer of epithelial cells lining the lumen of the ducts. Based on the ultrastructure of the epithelial cells, and their secretory products, we identified two epithelial cell types in each region (distal and proximal) of the accessory glands and four types in the posterior vas deferens. Most secretory products, which stained positively for proteins and some mucins, were released into the lumen of the ducts by apocrine secretion. The accessory glands produced one type of secretory product whereas in posterior vasa deferentia, four types of secretory products were found layered in the lumen. Our results suggest that most of the structural material used to construct a spermatophore is produced by the cells of the posterior vasa deferentia.     

Preliminary observations on the ultrastructure of the human laryngeal glands: the secreting cells

The secretory portions of human laryngeal glands consist of seromucous and mucous cells. Seromucous cells contain granules either homogeneously dense or endowed with a bipartite structure, consisting of a clear peripheral halo and a central dense portion. In any case, however, they exhibit a morphological appearance different from that observed in seromucous granules of salivary glands. Mucous cells vary considerably according to the functional state.     

Ultrastructure of the Accessory Glands in Female Genitalia of Pholcus phalangioides(Fuesslin, 1775) (Pholcidae; Araneae)

Pholcus phalangioidesdoes not possess receptacular seminis. The uterus externus (genital cavity) itself functions as a sperm storage structure. Two accessory glands are situated in the dorsal part of the uterus externus; they discharge their secretory product into the genital cavity. The secretion is considered to serve primarily as a matrix for sperm storage, i.e. to keep the spermatozoa in a fixed position. The accessory glands consist of numerous glandular units, each being composed of four cells: two secretory cells are always joined and surrounded twice by an inner and an outer envelope cell. Both envelope cells take part in forming a cuticular ductule that leads from the secretory cells to the pore plates of the uterus externus. The inner envelope cell produces the proximal part of the canal close to the microvilli of the secretory cells, whereas the outer envelope cell produces the distal part of the canal leading to the pore plate. Close to the pore the latter exhibits prominent microvilli that might indicate additional secretory activity.     

Distribution of prolactin receptor in frog (Rana ridibunda) dorsal skin during hibernation

The role of prolactin in the regulation of frog skin functions is still unclear particularly during environmental changes. In this study, prolactin receptor (PRLR) was detected in active and hibernating frog dorsal skin using immunohistochemical method. PRLR immunoreactivity in active frogs was observed in the epidermis, in the secretory epithelium of granular glands and the secretory channel cells of the glands. Myoepithelial cells of granular glands that started accumulating secretory material or those with a full lumen were PRLR immunoreactive, while some myoepithelial cells of empty granular glands were negative for PRLR. In hibernating frogs, this immunoreactivity was observed in the same regions; however, immunoreactivity was more intense than that in active frogs. PCNA was employed for detection of proliferative activity of PRL in the dorsal skin, and immunoreactivity was detected in the nuclei of a few epidermis cells and in the duct of glands of active frogs. The number of immunoreactive nuclei in these regions increased in hibernating and in prolactin injected groups. We conclude that prolactin provides morphological and functional integrity of skin stimulating the proliferation and regulating the function of granular glands and plays an important role in the adaptation of amphibians to the long winter period.     

Histomorphology of preorbital gland in territorial and non-territorial male blackbuck Antelope cervicapra, a critically endangered species

The preorbital gland is a specialized dermal gland of antelopes which plays an important role in territorial marking behavior and pheromonal communication. To our knowledge, there is little information available on the role of preorbital gland marks in Indian antelopes (blackbucks). Males are seen averting the gland during behavioural display and territorial marking but the functional aspect of this gland has not been examined. Hence, the aim of this study was to describe the histomorphology of the preorbital gland in territorial and non-territorial male blackbucks to determine its morphology and secretory function. The results showed that the preorbital gland is composed of modified sebaceous and apocrine glands. The apocrine gland is lined by simple cuboidal epithelial cells; the serous parts of the secretory products are often seen in the apical portions of the cells. The myoepithelial cells contain actin filaments lying on the basal membranes of the apocrine gland. There are some considerable histological changes in the presence of the sebaceous and apocrine glands in territorial males in comparison to non-territorial males. The following histological changes associated with occurrence of the sebaceous and apocrine glands have been observed in territorial and non-territorial male blackbucks: (1) increase of size of sebaceous and apocrine glands and (2) increase in density of sebaceous and apocrine glands in territorial males compared to non-territorial males. It is suggested that the higher development (i.e., size) and density of sebaceous and apocrine glands in territorial males could depend on hormone production (i.e., testosterone). Based on the histological observation and the role of sebaceous and apocrine glands in the preorbital gland supported by literature, it is possible to conclude that both territorial and non-territorial blackbuck males may produce pheromonal substances through preorbital gland (secretion) for olfactory communication.