Ultrastructural study of the bacillary, granular and mucoid proboscidial gland cells of Riseriellus occultus (Nemertini, Heteronemertini)

Junoy, J., Montalvo, S., Roldán, C. and García‐Corrales, P. 2000. Ultrastructural study of the bacillary, granular and mucoid proboscidial gland cells of Riseriellus occultus (Nemertini, Heteronemertini). — Acta Zoologica (Stockholm) 81 : 235–242. The ultrastructure of six types (G₅‐G₁₀) of proboscidial gland cells whose cell necks emerge independently on the epithelium surface is analysed and compared with data from other nemerteans. These types differ in cytological features, as well as in the morphology of their respective secretory granules. Secretory granules of the types G₅ and G₆ have a bacillary shape, and differ from each other based on their contents and dimensions. Secretory granules of the types G₇ and G₈ are spherical to ovoid; type G₈ gland cells are monociliated, and their secretory granules contain a paracrystalline material. Types G₉ and G₁₀ gland cells are typically goblet‐shaped; secretory granules in the type G₉ have a spherical shape, contain a homogeneous electron dense material and maintain their individuality, whereas those of the G₁₀ type are elongate and have fibrillar contents, showing a tendency to fuse before they are extruded. The mucus sheet of the proboscis is responsible for lubrication of its epithelial surface. Secretion products of type G₁₀ gland cells form the background substance of this mucus, and those of the G₅ type confer stickiness to it. Type G₉ gland cells could provide the toxic component to the mucus, and type G₇ and G₈ gland cells could be concerned with the production of enzymatic secretions.     

Prostaglandin production from homogenates of separated glandular epithelium and stroma from human endometrium

The biosynthesis of prostaglandins by isolated epithelial glandular and stromal cells was studied after collagenase digestion of endometrium collected from women at various stages of the menstrual cycle. Homogenates of the separate cell types were incubated for 60 minutes with 2.08 μg 1¹⁴C arachidonic acid and the products separated by thin layer chromatography. Both glandular and stromal homogenates synthesised PGF_2α. More PGF_2α was synthesised by glandular epithelium separated from both proliferative and secretory endometrium than by stroma. The ratio of PGF_2α/PGE₂ was greater in glands and stroma isolated from secretory than proliferative endometrium. Small but significant amounts of 6-keto-PGF₁α were produced by all cell types. These results suggest that the increased synthesis of PGF₂α from secretory endometrium is due, at least in part, to increased activity of cyclo-oxygenase enzyme in the glandular epithelium.     

The formation of glandular secretion in larval Austramphilina elongata (Amphilinidea)

The ultrastructure of three types of gland cells of embryos and free-swimming larvae of Austramphilina elongata is described. Type I gland cells contain large, more or less round electron-dense granules which are formed by numerous Golgi complexes. Type II gland cells contain thread-like, membrane-bound secretory granules with longitudinally arranged microtubules inside the granules; secretory droplets are produced by Golgi complexes and the microtubules apparently condense in the cytoplasm or in the droplets. Type III gland cells contain irregular-ovoid membrane-bound granules with coiled up microtubules which have an electron-dense core; the granules are formed by secretionderived from Golgi complexes and the microtubules aggregate around and migrate into the secretion; microtubules are at first hollow and the early secretory granules have a central electron-dense region.     

Flask cells and flask-shaped glandular cells of amphibian skin specifically produce fucose-rich glycoproteins

A battery of horseradish peroxidase-conjugated lectins has been employed as a cytochemical tool for the labelling of specific cell types in amphibian epidermis. Among the lectins used, onlyUlex europaeus I (UEA I) showed specific reaction with the cytoplasm of flask cells. In addition, UEA I stained flask-shaped secretory cells in dermal glands and a reaction on glandular ductal cells was also observed. At the electron microscopic level, lect-in binding was found in granules distributed among mitochondria in the cytoplasm of flask cells and in larger mucous granules of flask-shaped glandular cells, which were released into the lumen. UEA I also stained the extracellular space above flask cells. The labelling was due mainlty to a glycoprotein of mol. wt. approx. 27 kDa. Structural and cytochemical similarities between flask cells and flask-shaped cells of dermal glands could be a consequence of a common secretory role of both cell types.     

Parapodial glandular organs in Spiophanes (Polychaeta: Spionidae)—studies on their functional anatomy and ultrastructure

Parapodial glandular organs (PGOs) of Spiophanes (Polychaeta: Spionidae) were studied using light and electron microscopy. These organs are found in parapodia of the mid body region, starting on chaetiger 5 and terminating with the appearance of neuropodial hooks (chaetiger 14 or 15 in adult individuals). Large PGOs in anterior chaetigers display different species‐specific types of openings whereas small PGOs in posterior parapodia of the mid body region always open in a simple vertical slit. Each PGO is composed of three main complexes: (1) the glandular sac with several distinct epithelia of secretory cells and secretory cell complexes and the reservoir filled with fibrous material, (2) the gland‐associated chaetal complex (including the region of chaetoblasts and follicle cells, follicular canals, two chaetal collector canals, the combined conducting canal, the chaetal spreader including the opening of the glandular organ with associated type‐1 secretory cells, and the gland‐associated chaetae), and (3) a bilayered musculature surrounding the gland. A considerable number of different cell types are involved in the secretory activity, in the guidance of the gland‐associated chaetae, and in the final expulsion of the fibrous secretion at the opening slit. Among these different cell types the type‐5 secretory cells of the proximal glandular complex with their cup‐shaped microvilli emanating thick microfibrils into the lumen of the glandular sac are most conspicuous. Secretory cells with cup‐shaped microvilli being involved in the production of β‐chitin microfibrils have so far only been reported from some representatives of the deep‐sea inhabiting Siboglinidae (Polychaeta). We suggest that the gland‐associated chaetae emerging from inside the PGOs of Spiophanes are typical annelid chaetae formed by chaetoblasts and follicle cells. Functional morphology implies the crucial role of PGOs in tube construction. Furthermore, the PGOs are discussed in consideration of phylogenetic aspects. J. Morphol., 2012. © 2011 Wiley Periodicals, Inc.     

Abnormal ion content, hydration and granule expansion of the secretory granules from cystic fibrosis airway glandular cells

The absence or decreased expression of cystic fibrosis transmembrane conductance regulator (CFTR) induces increased Na(+) absorption and hyperabsorption of the airway surface liquid (ASL) resulting in a dehydrated and hyperviscous ASL. Although the implication of abnormal airway submucosal gland function has been suggested, the ion and water content in the Cystic Fibrosis (CF) glandular secretory granules, before exocytosis, is unknown. We analyzed, in non-CF and CF human airway glandular cell lines (MM-39 and KM4, respectively), the ion content in the secretory granules by electron probe X-ray microanalysis and the water content by quantitative dark field imaging on freeze-dried cryosections. We demonstrated that the ion content (Na(+), Mg(2+), P, S and Cl(-)) is significantly higher and the water content significantly lower in secretory granules from the CF cell line compared to the non-CF cell line. Using videomicroscopy, we observed that the secretory granule expansion was deficient in CF glandular cells. Transfection of CF cells with CFTR cDNA or inhibition of non-CF cells with CFTR(inh)-172, respectively restored or decreased the water content and granule expansion, in parallel with changes in ion content. We hypothesize that the decreased water and increased ion content in glandular secretory granules may contribute to the dehydration and increased viscosity of the ASL in CF.     

Cytodifferentiation in the accessory glands of Tenebrio molitor. XI. Transitional cell types during establishment of pattern

The bean-shaped accessory glands of male Tenebrio consist of a single-layered epithelium which is surrounded by a muscular coat. The epithelial layer, which produces precursors of the wall of the spermatophore, contains eight secretory cell types. Each secretory cell type is in one or more homogenous patches, and discharges granules which form one layer of the eight-layered secretory plug. Maturation begins in cell types 4, 7, and 6 on the last pupal day. A newly identified cell (type 8) in the posterolateral epithelium matures last. Cells of individual types mature in synchrony, and their secretory granules “ripen” in a sequence that is characteristic for each type. As the secretory cells of each patch mature, unusual short-lived cells appear at interfaces between patches. In some cases the secretory granules in these boundary cells have ultrastructural features which are mixtures of the definitive characteristics of granules in adjacent cell types. The transitional cell types disappear at 3–4 days after eclosion. Intermediate cell types are absent in the mature gland and boundaries between the patches are distinct. The transitional cells may form granules of intermediate structural characteristics as a dual response to cellular interaction with adjacent and previously differentiated secretory cells.     

A new glandular sensory organ inCatanema sp. (Nematoda,Stilbonematinae)

Summary A new multicellular glandular sensory organ is described forCatanema sp. (Nematoda, Stilbonematinae). The organs terminate in setae and are distributed in six longitudinal rows along the body. Two types of glandular cells (type A and type B), one monociliary sensory cell and one undifferentiated epidermal cell are combined in the basiepidermal organ. A comparison of epidermal glands as well as sensory organs in Nematoda is made. A causal relationship between the development of such complex, large and numerous glandular sensory organs and the occurrence of species-specific, symbiotic epibacteria inCatanema sp. seems probable, although there is no simple correlation between the distribution of these organs and epibacteria. A mucous cover over the bacterial layer, released by the glandular sensory organs, may create a microenvironment for the interaction between epibionts and host.Abbreviations (used in figures) a amphid - A1–A4 type 1–4 granules of type A gland cell - an annuli - b bacteria - B1–B3 type 1–3 granules of type B gland cell - bl basal lamina - bp basal part of seta - bz basal zone of cuticle - c cuticle - ca canal - cg caudal gland - ci cilium - cz cortical zone of cuticle - d dictyosomes - e epidermis - e co extracellular coat - em extracellular matrix - ep epicuticle - f filaments - gcA type 1 gland cell - gcB type 2 gland cell - i lp inner labial papillae - m mitochondrion - me membranes of type 2 gland cell - mo mouth opening - mz median zone of cuticle - n nucleus - nu nucleolus - p process - pv primary vesicle of type A gland cell - r ribosomes - s seta - sc sensory cell - sp secretory product - tj tight junction - tp terminal part of seta - uc undifferentiated epidermal cell - va vacuoles or vesicles of epidermal cells - ve vesicles of sensory cell     

Ultrastructural changes of the teleostean hatching gland cell during natural and electrically induced precocious secretion.

Ultrastructural changes of the hatching gland during electrically induced precocious secretion were compared with those during natural secretion in the medaka, Oryzias latipes. The gland cells are covered by a layer of epithelial cells, which adjoin one another just on the apical center of each gland cell. When the natural as well as the precocious secretion occurred, each gland cell was swollen upward and rounded, and separation of the epithelial joints occurred, giving rise to an exposure of the apical portion of the gland cells. There were marked differences between these two kinds of secretion process in the behavior of the secretory granules prior to secretion and in the mode of discharge of the secretory substances. The changes which occurred during both types of secretion and which, therefore, seemed to be essential to the secretory processes of this gland cell were the swelling up of the gland cells in the initiation of secretion and the reduction of the electron density of the zymogen granules. These secretion-associated ultrastructural changes are discussed in view of the difference in the maturation of the gland cells.     

Co-localization of the adipokinetic hormones I and II in the same glandular cells and in the same secretory granules of corpus cardiacum of Locusta migratoria and Schistocerca gregaria

Summary The immunocytochemical reactivity of the glandular cells of the corpus cardiacum (CCG-cells) of Locusta migratoria and Schistocerca gregaria was investigated at the electron-microscopic level, using the protein A-gold method, with three antisera against fragments of the adipokinetic hormones AKH I and AKH II. This combination of antisera permitted discrimination between anti-AKH I and anti-AKH II immunoreactivity. Fixation in a mixture of 2% glutaraldehyde and 2% formaldehyde, in combination with low-temperature embedding in Lowicryl K₄M, produced the highest and most consistent selective immunogold labelling of the secretory and ergastoplasmic granules. All secretory granules in all CCG-cells investigated possessed a distinct anti-AKH I-immunopositive reaction, whereas most secretory granules showed a weaker anti-AKH II immunoreaction. Ergastoplasmic granules reacted similar to the secretory granules. The average immunolabelling of the secretory granules was higher in the processes than in the cell bodies of the CCG-cells. The results in Schistocerca gregaria were essentially similar to those in Locusta migratoria. It is concluded that (i) the individual CCG-cells synthesize AKH I as well as AKH II; (ii) these hormones coexist in the same ergastoplasmic and secretory granules; and (iii) these granules contain a higher content of AKH I than AKH II.     

The amylase-secreting cells of the stomach of the scallop, Pecten maximus: ultrastructural, immunohistochemical and immunocytochemical characterizations

(1) alpha-amylase was extracted and purified from the stomach/digestive gland complex of the scallop Pecten maximus and an anti-serum was induced against the purified amylase by rabbit immunization. (2) The anti scallop amylase was used to localize the amylase-secreting cells in the stomach of Pecten maximus by immunofluorescence and immunogold labelling. The amylase-secreting cells are glandular cells particularly numerous in the main sorting area of the stomach. Their secretory granules were found strongly positive for anti-amylase. Three types of glandular cells were observed, actually corresponding to the three stages of the glandular-cell activity, synthesis, secretion and excretion. (3) The synthesizing cell shows the characteristic features of a protein-synthesizing cell: a conspicuous nucleolus and abundant granular endoplasmic reticulum. In the secretory cell, the secretory granules are formed by the Golgi apparatus and accumulate in the apical part of the cell. The secretory cell is filled with two types of secretory granules which are released in the stomach lumen by apocrine excretion. (4) The present study brings the first demonstration of the synthesis and extracellular release of amylase by glandular cells of the stomach epithelium of a bivalve.     

Functional morphology of the mammiliform penial glands ofLittorina saxatilis (Gastropoda)

Summary The functional morphology of the mammiliform penial glands ofLittorina saxatilis has been investigated with both light and electron microscopy. These penial glands line the ventral edge of the penis and orient with the female mantle during copulation. Secretions are released from the penial glands to this interface where they probably function in adhesion. The penial gland secretions comprise heterogeneous granules as well as apocrine and mucous secretions. The heterogeneous granules are produced in separate multicellular glands arranged in a series of lobes that lie outside a thick smooth muscle layer enclosing the lumen. Each glandular lobe is surrounded by a thin layer of smooth muscle. Secretions are transported in individual cellular processes that pass through the thick smooth muscle layer and empty into the lumen. Surrounding the lumen is an epithelium containing apocrine secretory cells as well as occasional goblet-type, mucous cells. The combined action of the muscles forces secretions out of the lumen through the penial papilla, onto the external surface of the mammiliform penial gland. Longitudinal muscles extend into the penial papilla enabling its protrusion or retraction. Retraction of the penial papilla following secretion release is thought to create negative pressure beneath the penial gland producing suction adhesion. The visco-elastic properties of the penial gland secretion are qualitatively different from foot mucus and may represent specialization to an adhesive function.     

Electron microscopic structure of the cephalic gland of the bee Andrena variabilis Smith (Hymenoptera: Apoidea)

The structure of the glandular tissue located beneath the eye sulcus in Andrena variabilis Smith was studied by means of light and electron microscopy. The glandular tissue was found to be constituted of single-layered, high cylindrical epithelial cells. Electron microscopy revealed strong foldings of the cell membrane on the basal pole of the gland cells. Next to the basal lamina, nerve fibres were found with great frequency. The central, perinuclear zone of the gland cells was rich in cell organelles. The lamellae of the rough-surfaced endoplasmic reticulum (rer) were mostly observed near the nuclear membrane. The vesicles and tubules of the smooth-surface endoplasmic reticulum (ser) were found to be congregated in contiguous compact regions. A well-developed and complicated canalicular system was enclosed between the rer and ser compartments, presumably serving as a passage for the secretory products. Membrane-bound electron-dense granules (secretory granules) were also a characteristic finding in the ser. In a small proportion of the gland cells, strong vacuolization indicated the degradation processes. From the light and electron microscopic characteristics of the gland cells, the existence of pheromone-producing secretory activity of exocrine type in the cephalic gland is presumed.     

An ultrastructural study of the prostate gland of megascolicid earthworm Lampito mauritii (Kinberg)

The ultrastructure of prostate gland of Lampito mauritii revealed two types of secretory cells. Type 1 cells with a broad basal region and a long apical region contain electron dense oval secretory granules with an increased density at the core region. Numerous electron lucent granules with fine filamentous and electron dense amorphous materials also occur at the basal region of these cells. Type 2 cells contain electron lucent mucous-like secretory granules. This cell type contains exceptionally large Golgi complexes having 20-23 stacked cisternae. Both cell types open into a common lumen and numerous microtubules are visible at the apical end. Junctional complexes, such as desmosomes and septate junctions, are observed in this glandular tissue.     

Morphology and ultrastructure of the venom glands of the northern pacific rattlesnake Crotalus viridis oreganus

The venom gland of Crotalus viridis oreganus is composed of two discrete secretory regions: a small anterior portion, the accessory gland, and a much larger main gland. These two glands are joined by a short primary duct consisting of simple columnar secretory cells and basal horizontal cells. The main gland has at least four morphologically distinct cell types: secretory cells, the dominant cell of the gland, mitochondria-rich cells, horizontal cells, and “dark” cells. Scanning electron microscopy shows that the mitochondria-rich cells are recessed into pits of varying depth; these cells do not secrete. Horizontal cells may serve as secretory stem cells, and “dark” cells may be myoepithelial cells. The accessory gland contains at least six distinct cell types: mucosecretory cells with large mucous granules, mitochondria-rich cells with apical vesicles, mitochondria-rich cells with electron-dense secretory granules, mitochondria-rich cells with numerous cilia, horizontal cells, and “dark” cells. Mitochondria-rich cells with apical vesicles or cilia cover much of the apical surface of mucosecretory cells and these three cell types are found in the anterior distal tubules of the accessory gland. The posterior regions of the accessory gland lack mucosecretory cells and do not appear to secrete. Ciliated cells have not been noted previously in snake venom glands. Release of secretory products (venom) into the lumen of the main gland is by exocytosis of granules and by release of intact membrane-bound vesicles. Following venom extraction, main gland secretory and mitochondria-rich cells increase in height, and protein synthesis (as suggested by rough endoplasmic reticulum proliferation) increases dramatically. No new cell types or alterations in morphology were noted among glands taken from either adult or juvenile snakes, even though the venom of each is quite distinct. In general, the glands of C. v. oreganus share structural similarities with those of crotalids and viperids previously described.     

The morphology of the mucous gland and its responses to prolactin in the skin of the red-spotted newt

The mucous gland of the red-spotted newt, Notophthalamus viridescens viridescens, Rafinesque was examined by histochemical and ultrastructural techniques and its cytological responses to various hormonal conditions were studied. Its secretory epithelial cells produce and release in merocrine fashion a neutral, unsulphated mucosubstance. The secretory epithelium is bounded peripherally by a thin, but apparent non-functional, myo-epithelium. The duct of this mucous gland consists of a single keratinized tubular cell that extends from the neck region of the gland to the surface of the epidermis. Mucous secretion is absent or greatly reduced on the skins of newts maintained under laboratory conditions for a few weeks but reappears after injection of ovine prolactin. Mucous glands in laboratory conditioned animals show a 4-fold increase in volume brought about by the engorgement of their epithelial cells with secretory granules. Ovine prolactin reduces the volume of the glands to unconditioned levels with a corresponding reduction in granular content, suggesting that prolactin functions in the release of the granules. This view is reinforced by the findings that autotransplantation of the pituitary gland prevents the conditioning effect and that glandular volume increases in auto-transplanted animals given ergocornine. Granular accumulation begins also in hypophysectomized newts but ceases after a week, indicating the need for some hypophyseal factor in the synthesis as well as the release of the granules. Ovine prolactin restores mucous glands of hypophysectomized newts to the unconditioned state. Contrary to earlier findings, ovine prolactin induces a reduction in the volume of the mucous gland in thyroidectomized newts.     

Effects of B-retinyl acetate on human breast epithelium in explant culture

Explants of human breast (obtained aseptically from ten women ages 18-37) were examined and the vitamin A compound B-retinyl acetate was tested (at 3 X 10(-5) and 3 X 10(-6) M) for its effects on the fine structure and growth of the epithelium. In the absence of B-retinyl acetate, cells growing out from the explant (outgrowth cells) underwent squamous metaplasia, began to accumulate many intermediate filaments (tonofilaments), and revealed large desmosomes after 2 weeks in culture. In the presence of either concentration of B-retinyl acetate, the epithelial cells were largely prevented from undergoing squamous metaplasia. The glandular epithelium inside the explant maintained a typical secretory appearance for 2 weeks in control cultures (without the retinoid) and then began to show increased numbers of lysosomes and a loss of secretory granules. These glandular epithelial cells did not undergo squamous metaplasia, but they contained increased numbers of intermediate filaments. In contrast, glandular epithelium cultured in either concentrations of B-retinyl acetate appeared secretory for as long 6 weeks in culture, and intermediate filaments were not obvious. Autoradiographs demonstrated that both concentrations of B-retinyl acetate inhibited cell division in the outgrowth epithelium and in the (internal) glandular epithelium. The ability of B-retinyl acetate to reverse squamous metaplasia in the outgrowth cells was also tested. Outgrowth cells reversed to a more normal ductlike appearance after 6 weeks culture in standard medium followed by only 1 week in 20 micrograms/ml B-retinyl acetate. After 7 weeks in standard medium and 1 week in 10 micrograms/ml B-retinyl acetate, the cells showed a partial reversal of the squamous metaplasia.     

Development of peltate glandular trichomes of peppermint

Cryofixation and conventional chemical fixation methods were employed to examine the ultrastructure of developing peltate glandular trichomes of peppermint (Mentha x piperita). Our results are discussed in relation to monoterpene production and the mechanism of essential oil secretion. Peltate glands arise as epidermal protuberances (initials) that divide asymmetrically to produce a vacuolate basal cell, a stalk cell, and a cytoplasmically dense apical cell. Further divisions of the apical cell produce a peltate trichome with one basal cell, one stalk cell, and eight glandular (secretory) disc cells. Presecretory gland cells resemble meristematic cells because they contain proplastids, small vacuoles, and large nuclei. The secretory phase coincides with the separation and filling of the sub-cuticular oil storage space, the maturation of glandular disc cell leucoplasts in which monoterpene biosynthesis is known to be initiated, and the formation of extensive smooth endoplasmic reticulum at which hydroxylation steps of the monoterpene biosynthetic pathway occur. The smooth endoplasmic reticulum of the secretory cells appears to form associations with both the leucoplasts and the plasma membrane bordering the sub-cuticular oil storage cavity, often contains densely staining material, and may be involved with the transport of the monoterpene-rich secretion product. Associated changes in the ultrastructure of the secretory stage stalk cell are also described, as is the ultrastructure of the fragile post-secretory gland for which cryofixation methods are particularly well suited for the preservation of organizational integrity.     

Fine structure of the external nasal gland of two lizards (Podarcis sicula campestris and Chalcides chalcides)

In this study, we describe the ultrastructural features of the external nasal gland in two lizards: ruin lizard (Podarcis sicula campestris) and seps (Chalcides chalcides). Two secretory cell types, which differ interspecifically, have been found in the secretory endpieces of the glandular tubules in both species examined. An unusual morphological observation was the presence of paracrystalline structures in the secretory granules of the seromucous cells of the external nasal gland of the seps. These structures may be related to the packaging mechanism of glycoproteins or to their macromolecular structure. They may also reflect segregation of heterogeneous subcomponents within the same secretory granule. The striated cells are located in the distal segment of the glandular tubules, and have the typical ultrastructural features of the cells which in some species of reptiles, but not in these two lizards, are known to be capable of elaborating a hyperosmotic saline solution.     

The spermathecal complex in Ips typographus (L.): Differentiation of the spermathecal gland related to age and reproductive state

The spermathecal complex of the bark beetle, Ips typographus, comprises the following elements: spermathecal duct, spermatheca and spermathecal gland. The spermathecal duct connects the vagina and the spermatheca and consists of a cuticular tube surrounded by an epithelial layer and circular muscles. The spermatheca is bottle-shaped and has a cuticle-lined lumen. Muscles are attached to both ends of the spermatheca. The spermathecal gland which is connected to the spermatheca possesses three cell types: glandular, hypodermal, and ductule. The glandular cells have different structural characteristics depending on the age and reproductive state of the females. After the emergence of the brood, two different kinds of secretory material are present in the glandular cells. There is evidence that one type of secretion is emitted during the first few days after brood emergence, while the other type accumulates to be secreted during later stages.