Harderian gland ultrastructure of the black sea bottlenose dolphin (Tursiops truncatus ponticus)

Examination of the Harderian gland structure of the Black Sea bottlenose dolphin, Tursiops truncatus ponticus, at macroscopic, microscopic, and electron microscopic levels shows significant sexual dimorphism. The epithelial cells of male and female glands are different cell types, capable of producing chemically different products. Secretory cells in both sexes contain secretion granules that produce a secretion consisting mainly of proteins and carbohydrates, but thought to be sex-specific in composition. The female glands also contain lipid secretion granules. It is suggested that in the bottlenose dolphin the Harderian gland functions to produce sexually distinct pheromones and may have other physiological activities, e.g., participating in local immunological or endocrine-related reactions. © 1994 Wiley-Liss, Inc.     

An insight into the skin glands,dermal scales and secretions of the caecilian amphibian Ichthyophis beddomei

The caecilian amphibians are richly endowed with cutaneous glands, which produce secretory materials that facilitate survival in the hostile subterranean environment. Although India has a fairly abundant distribution of caecilians, there are only very few studies on their skin and secretion. In this background, the skin of Ichthyophis beddomei from the Western Ghats of Kerala, India, was subjected to light and electron microscopic analyses. There are two types of dermal glands, mucous and granular. The mucous gland has a lumen, which is packed with a mucous. The mucous-producing cells are located around the lumen. In the granular gland, a lumen is absent; the bloated secretory cells, filling the gland, are densely packed with granules of different sizes which are elegantly revealed in TEM. There is a lining of myo-epithelial cells in the peripheral regions of the glands. Small flat disk-like dermal scales, dense with squamulae, are embedded in pockets in the dermis, distributed among the cutaneous glands. 1–4 scales of various sizes are present in each scale pocket. Scanning electron microscopic observation of the skin surface revealed numerous glandular openings. The skin gland secretions, exuded through the pores, contain fatty acids, alcohols, steroid, hydrocarbons, terpene, aldehyde and a few unknown compounds.     

Secretory Mechanism of Fibroin,a Silk Protein,in the Posterior Silk Gland Cells of Bombyx mori

There are two microtubule-microfilament systems in the posterior silk gland cells of Bombyx mori. One is a radial microtubule system; the other is a circular microtubule-microfilament system. These two systems are presumably concerned with the intra-cellular transport of secretory granules of fibroin and the secretion of fibroin into the lumen, respectively. Conventional and scanning electron microscopic observations of the two microtubule-microfilament systems in the posterior silk gland cells are reported. Scanning electron micrographs showed that a number of parallel linear cytoplasmic processes ran circularly on the luminal surface of the posterior silk gland cells. These processes were assumed to correspond to the circular microtubule-microfilament systems. The effects of cytochalasin (B or D), a secretion stimulating agent of fibroin, on the intracellular recording of membrane potential from the posterior silk gland cells are also reported. Exposure to cytochalasin resulted in depolarization of the membrane potential of the gland cells. Possible functional roles of the two microtubule-microfilament systems in the secretory mechanism of fibroin are discussed with reference to the effects of antimitotic reagents and cytochalasin on these two systems.     

An autoradiographic,biochemical, and morphological study of the harderian gland of the mouse

Biochemical and morphological properties of the Harderian gland of the mouse were examined by combining autoradiographic, biochemical, and electron microscopic techniques. Autoradiographs show that the radioactive carbon from [U-¹⁴C]glucose injected into the abdominal cavity is completely incorporated into the acid-insoluble substances within 30 minutes. The results of chemical analysis show that the main components of this gland are glyceryl ether diesters and phospholipids. Scanning electron microscopy shows numerous lipid droplets in the secretory cells and alveolar lumina. Myoepithelial cells lie between the secretory cell base and the basement membrane and have a basket-like distribution of processes as confirmed by hydrochloric acid and collagenase digestions. Myofilaments are demonstrated in the cytoplasm. Two types of secretory cells (A and B) comprise the alveolar epithelium and can be differentiated under the electron microscope. The cytoplasm of both contains numerous vacuoles. The vacuoles are almost empty in A cells, which are a more numerous constituent of the alveolar epithelium than B cells. However, the vacuoles of the B cells contain densely osmiophilic material. In both, cell types show a merocrine mode of secretion. Unmyelinated nerve cell endings occur in the interstices of the connective tissue, and contain clear or cored vesicles.     

A fine structure study of venom gland cells in globiferous pedicellariae from Stronglocentrotus purpuratus (Stimpson)

Cells in secretory glands of globiferous pedicellariae from Strongylocentrotus purpuratus (Stimpson) were studied with the electron microscope and subjected to preliminary light microscopic, histochemical analysis. Specimens for electron microscopic observation were fixed with chilled 2% glutaraldehyde in sea water postfixed in cold 1.33% osmic acid, and embedded in Araldite 502 epoxy resin Samples for histochemical analysis were fixed in the same manner, and then embedded in n-butylmethacrylate. Secretory cells line and fill partially bifurcated, muscular gland sacs located peripherally on each of three jaw elements comprising the pedicellarial head. Cells from venom glands are typically mucoid in appearance, possessing small volumes of basally displaced, vesiculated cytoplasm and an extensive system of vacuoles dominating the apical nine-tenths of each cell. These vacuoles enclose ground substances of various densities and staining affinities. Despite their extensive vacuolation, gland cells contain numerous cytomembrane complexes indicating metabolic activity just prior to fixation. Deciduous endoplasmic reticulum, Golgi complexes, large vacuoles, and various species of vesicles associated with these membrane systems are found in spatial proximity which indicates an apparent biosynthetic association. Preliminary histochemical tests on sections embedded in acrylic plastic indicate vacuolar products may consist of protein and nonsulfated acid mucosubstances. Gland cells are probably holocrine in function, releasing their vacuolar complement upon constriction of the muscular gland sac. There is no evidence indicating delivery of non-membrane bounded, granular secretion to an acellular lumen within the gland sac.     

The morphology of the cement gland apparatus of Larval Pterophyllum scalare Cuv. & Val. (Cichlidae,Teleostei)

Summary The cement gland apparatus of newly hatched Pterophyllum scalare Cuv. & Val. was examined by histology, scanning and transmission electron microscopy. The whole organ is composed of three pairs of endoepithelial, ductless glands, which cause prominent elevations on the larval head and are found in a specific arrangement. Each single gland is represented by an aggregation of elongated, tubular secretory cells surrounding a pyriform acinus. It overlies a basal lamina and is covered by the outer layer of the bilaminar embryonic epidermis.Two different types of secretory cells can be distinguished. One type is restricted to the bottom of the cavity. It is characterized by multiform cytoplasmic protrusions, which project into the gland's cavity. The secretory granules contain a network of light filamentous material. The second type constitutes the side wall of the acinus. It does not develop any protrusions. The contents of the secretory granules is of very high and homogeneous electron density. The mechanism of extrusion is discussed for both cell types. All secretory cells show a strong PAS-reaction. In SEM a circular microridge pattern with attached mucus globules can be recognized on the larval epithelial surface.Dedicated to Prof. Dr. H. Leonhardt on the occasion of his 60th birthday     

Ultrastructure of the cardiac and pyloric glands of the gastric mucosa of the South African hedgehog,Atelerix frontalis

The cardiac and pyloric glands in the gastric mucosa of the South African hedgehog, Atelerix frontalis, are described. The cardiac area of the stomach contains proper cardiac glands and lacks undifferentiated fundic glands. The cardiac glands are simple tubular, coiled, and lined with columnar cells ultrastructurally similar to those of the gastric surface epithelium. Secretory granules with varying electron densities fill the apical cytoplasm of these cells. In contrast to other mammals, these glands lack mucous neck cells. The neck of the pyloric glands contains only a single cell type, whereas the basal regions of these glands contain “light” and “dark” cells. The secretory granules in the “dark” cells and the pyloric neck cells have a moderate electron density and often contain an electron dense core. An electron-lucent cytoplasm with numerous polysomes is characteristic of the “light” cells. Some “light” cells contain electron-dense granules in the apical cytoplasm. The presence of only neutral mucins in the cardiac gland cells denotes the absence of mucous neck cells. The acidic mucins within the pyloric neck cells seem to indicate that these cells are mucous neck cells, whereas the neutral mucins within the basally located pyloric gland cells show at least a partial functional difference from the pyloric neck cells. © 1993 Wiley-Liss, Inc.     

Evidence for the holocrine nature of lipoid secretion by avian epidermal cells: A histochemical and fine structural study of rictus and the uropygial gland

Cells of the avian epidermis (rictus of the chicken), when examined under the light microscope following suitable fat staining, show similarities to epithelial cells of the uropygial gland of chicken and pigeon, an organ which is recognized both morphologically and functionally as a holocrine gland. Evidence thus far from electron microscopic studies strongly suggests that the skin of the bird is also a holocrine gland, although details of cytogenesis and secretion differ somewhat in the two organs.     

Electron microscopic map of surface-spread polytene chromosomes in Drosophila hydei

Surface-spread polytene (SSP) chromosomes of salivary glands from late third-instar larvae were used for the construction of an electron microscopic (EM) photo map of the entire genome of D. hydei. In comparison with the light microscopic chromosome map of Berendes (1963), based on squash preparations, the EM micrographs depict some 40%–50% more bands. — Two different types of chromosome constrictions are described. One type is assumed to be caused by differential distribution of chromosomal proteins; the other one appears to represent underreplicated sections in the salivary gland chromosomes.Dedicated to Prof. Dr. H.J. Becker on the occasion of his 60th birthday     

A correlated light and electron microscopic study of the structure and secretory activity of the accessory salivary glands of the marine gastropods,Conus flavidus and C. vexillum (neogastropoda,conacea)

The structure and secretory activity of the accessory salivary gland in two species of Conus were examined using routine and histochemical techniques of light, scanning and transmission electron microscopy. The composite layers of the accessory salivary gland of Conus are a luminal epithelium, fibromuscular layer, submuscular layer, and a capsule. In C. flavidus and C. vexillum, the luminal epithelium is formed by epitheliocytes and cytoplasmic processes extending from the secretory cells, whose perikarya form the submuscular layer. The processes carry secretory cell products (chiefly Golgi-derived glycoprotein) across the fibromuscular layer and terminate between epitheliocytes (at the bases of the secretory canaliculi) or beyond the surface of the epithelial cells. Conus vexillum is distinguished from C. flavidus by its high content of lipofuscin. Epitheliocytes are the only microvillated cells in the accessory salivary gland of Conus. In C. flavidus, epitheliocytes extrude secretory granules, various types of cytoplasmic blebs and clear vesicles by apocrine “pinching off”. Clear vesicles are shed from the tips of microvilli. The luminal epithelial cells of C. vexillum similarly egest clear vesicles, but normally undergo additional holocrine secretion to release lipofuscin. The secretions of epitheliocytes appear to be major products of the accessory salivary gland: consideration of secretory activities by both epitheliocytes and secretory cells will therefore be necessary when directly investigating accessory salivary gland function in Conus.     

Fine Structure of the Labial Gland in Macrotermes bellicosus (Isoptera,Termitidae)

The labial gland in M. bellicosus corresponds with the acinar type, and occupies the greater part of meso- and metathorax. The acini comprise three secretory cell types, in addition to the central ductule cells and the epithelial cells that make up the efferent ducts. Cell types are mainly distinguished by the size and appearance of their secretory vesicles and the extent of the microvillar contact area with the ductule cells. They probably produce a proteinaceous secretion that may contain digestive enzymes. The labial gland acini in soldiers, on the other hand, contain only one type of secretory cell, which is not comparable with any of the cell types in the worker caste. This difference is in agreement with the multifunctional role of the labial gland according to the termites' polyethism.     

ULTRASTRUCTURE OF SPERMATIUM LIBERATION IN THE MARINE RED ALGA PTILOTA DENSA1

The differentiation of male gametes of the marine red alga Ptilota densa was studied by electron microscopy. Mature primary spermatangia are enveloped by a single cell wall and possess a clearly polar subcellular organization. The nucleus is situated apical to large, striated, fibrous vacuoles which are apparently formed by the repeated fusion of dictyosome vesicles. The transformation and liberation of spermatia from spermatangia involve both the secretion of the fibrous vacuoles at the base of the cell and the subsequent rupturing of the spermatangial cell wall. Liberated spermatia are coated with a thin mucilage layer and contain numerous small vesicles and several mitochondria and dictyosomes. The nucleus is cup-shaped and generally lacks a limiting envelope. These findings are discussed in relation to other light and electron microscopic studies of differentiating spermatangia in red algae.     

Calorie restriction: A new therapeutic intervention for age-related dry eye disease in rats

A decrease in lacrimal gland secretory function is closely related to aging and leads to an increased prevalence of dry eye syndrome. Since calorie restriction (CR) is considered to prevent functional decline of various organs due to aging, we hypothesized that CR could prevent age-related lacrimal dysfunction. Six-month-old male Fischer 344 rats were randomly divided into ad libitum (AL) and CR (−35%) groups. After 6 months of CR, tear function was examined under conscious state. After euthanasia, lacrimal glands were subjected to histological examination, tear protein secretion stimulation test with Carbachol, and assessment of oxidative stress with 8-hydroxy-2 deoxyguanosine (8-OHdG) and 4-hydroxynonenal (HNE) antibodies. CR significantly improved tear volume and tended to increase tear protein secretion volume after stimulation with Carbachol compared to AL. The acinar unit density was significantly higher in the CR rats compared to AL rats. Lacrimal glands in the CR rats showed a lesser degree of interstitial fibrosis. CR reduced the concentration of 8-OHdG and the extent of staining with HNE in the lacrimal gland, compared to AL. Furthermore, our electron microscopic observations showed that mitochondrial structure of the lacrimal gland obtained from the middle-aged CR rats was preserved in comparison to the AL rats. Collectively, these results demonstrate for the first time that CR may attenuate oxidative stress related damage in the lacrimal gland with preservation of lacrimal gland functions. Although molecular mechanism(s) by which CR maintains lacrimal gland function remains to be resolved, CR might provide a novel therapeutic strategy for treating dry eye syndrome.     

Ultrastructure and cytochemistry of the gastric mucosa of a reptile,Tiliqua scincoides

Summary The gastric mucosa of a reptile, the lizard Tiliqua scincoides, has been examined by light and electron microscopy. The gastric pits lead into glands that are extensively coiled in the proximal stomach but become progressively shorter and straighter in the distal stomach. The following epithelial cell types have been identified: (i) Surface mucous cells (SMC) line the entire lumenal surface as well as the pits. They contain mucus granules that stain with periodic acid-Schiff and, like the granules of mammalian SMC, commonly contain an electron dense core that appears not to be mucus (periodic acid-chromic acid-silver methenamine nonreactive). (ii) Glandular mucous cells are present in glands throughout the mucosa. They are probably homologous with the mucous neck and antral gland cells of mammals; like SMC their mucus granules contain nonglycoprotein cores. (iii) Oxynticopeptic cells (OPC) are the predominant cell type in the proximal glands but become infrequent distally. Their fine structure resembles that of OPC in other nonmammalian vertebrates, with features like those of both parietal cells and zymogen cells of mammals, (iv) Endocrine cells of three different types have been identified. Two of these show close similarities to the EC and ECL cells of mammals.The authors thank Mrs. D. Flavell for technical assistance. This study was supported by a grant from the Clive and Vera Ramaciotti Foundations     

Comparative immunocytochemical localization of prolactin and somatotropin in the pituitaries of Lepidosiren paradoxa,Rana temporaria and Ambystoma mexicanum

Summary The cellular binding sites of anti-oPRL IgG and anti-bSTH IgG were demonstrated in the pituitary glands of Lepidosiren paradoxa, Rana temporaria and Ambystoma mexicanum by means of the unlabeled antibody enzyme method by light and electron microscopy (the latter only in Lepidosiren). With the light microscope PRL or PRL-like substances and STH or STH-like substances were revealed in two different cell types in the distal lobe corresponding to the acidophils. However, as a result of the insufficient differentiation of the acidophils in Lepidosiren after staining with Brookes' procedure it was not possible to distinguish the two types of acidophils in this animal. Treatment with low dilutions of both anti-oPRL and anti-bSTH IgG revealed simultaneous immunocytochemical staining in both types of acidophils in Lepidosiren and in Rana. These results, indicating that there is antigenic cross-reaction between anti-oPRL and anti-bSTH IgG and both PRL and STH in these animals, are discussed.The electron microscopic investigations of Lepidosiren revealed that the specific anti-oPRL IgG reactive cells contain granules ranging in size from 200 to 300 nm, while the specific anti-bSTH IgG reactive cells contain smaller immunoreactive granules ranging from 80 to 160nm.     

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

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

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.     

The anatomy of the parotoid gland in Bufonidae with some histochemical findings. II. Bufo alvarius.

The gross and microscopic anatomy of the venom producing parotoid glands of Bufo alvarius has been studied by light and electron microscopy. Histochemical reactions for the presence of venom constituents and of components in biochemical pathways in the synthesis and release of venom were performed. The gland is composed of numerous lobules. Each lobule is an individual unit with a lumen surrounded by a double cell layer. Microvilli of the outer layer interdigitate with microvilli of the inner layer. Cells of the outer layer resemble smooth muscle cells, are rich in adenosine triphosphatase and glucose-6-phosphatase, and contain numerous pinocytotic vesicles, glycogen granules and various organelles. These organelles include "crystalloids" of what seem to be highly organized agranular reticulum. These outer layer cells probably function in some aspects of venom synthesis, active cellular transport and contraction in the discharge of the secretory product. The inner cell layer demonstrates a positive chromaffin reaction, contains steroid material, various organelles, some pinocytotic vesicles and glycogen granules, and appears devoid of a plasmalemma on its inner surface. This layer is probably involved in venom formation and release via an apocrine type of secretion. Bufo alvarius parotid gland shows significant morphological and histochemical differences from that of B. marinus and more nearly resembles a typical steroid producing organ.     

Morphological characterization of female accessory sex glands of Eupolybothrus fasciatus (Newport) (Chilopoda Lithobiomorpha)

The female reproductive system of Eupolybothrus fasciatus (Newport) (Chilopoda Lithobiomorpha) includes three types of well-developed accessory glands, viz. large glands, small glands, and the periatrial gland. External morphology and the ultrastructural organization of these glands have been investigated by light and electron microscopy. The small and large glands are paired and have coiled ducts that open, respectively, into and externally to the genital atrium. By contrast, the periatrial gland is unpaired and is located on the ventral wall of the atrium into which it opens via several small canals. Ultrastructural features show that all three glands consist of two different types of cells: secretory cells and ductule cells. The secretary cells contain prominent secretory granules and are similar to a class of insect epidermal gland cells (class 3) organized as acini surrounding an extracellular lumen into which microvilli project. The granules, which have different morphological features in each gland, could be responsible for important differential functions such as producing a sexual attractant, providing a coating material that protects eggs laid on the ground, and contributing to a fluid that digests spermatophores. © 1996 Wiley-Liss, Inc.     

The pheromonal gland of Lymantria dispar: Morphology and evidence for its innervation

The morphological features of the glandular epithelium that secretes pheromone in the polyphagous pest gypsy moth Lymantria dispar are described by light and electron microscopy. The monolayered gland cells are covered by the folded cuticle of the intersegmental membrane between the 8th and 9th abdominal segments showing neither sites of discontinuity nor distinct openings on its external surface. The cells bear a large, often irregularly shaped nucleus, and contain granules of variable amount and electron‐density. These granules are mostly located in the basal compartment of the cytoplasm, in a labyrinthine zone laying on a basement membrane. The apical membrane of the gland cells bear microvilli and cell–cell contact is established by different junctional structures. Nerve fibers enwrapped in glia are found beneath the basement membrane, in close contact with the secretory cells. This latter finding represents the first evidence of the innervation of the pheromonal gland in L. dispar. J. Morphol. 2009. © 2008 Wiley‐Liss, Inc.