The anterior glands of adult Necator americanus (Nematoda: Strongyloidea)—I Ultrastructural studies

The ultrastructure of the amphidial, oesophageal and excretory glands of N. americanus is described. There are two amphidial glands, and each is attached to a lateral hypodermal cord. Anteriorly the glands become associated with the amphidial sense organs. The amphidial glands synthesize complex secretion granules which appear to release their contents into the sense organ. Secretions thus pass over the amphidial cilia and exit via the amphidial pore. It is suggested that the secretory activity of these glands is under direct nervous control. There are three oesophageal glands, and each synthesizes dense secretion granules. The secretions of the oesophageal glands are released into the lumen of the oesophagus and into the buccal capsule. The two excretory glands are ventral in position and connected to the tubular excretory system. These glands synthesize secretion granules of varying density. Secretions from the excretory glands may exit via the excretory pore, or pass back into the tubular excretory system, or both.     

Paracloacal glands of Alligator mississippiensis: A histological and histochemical study

The histology of the paracloacal 'musk' glands of adult American alligators ( Alligator mississippiensis ) is described. The gland is a single secretory sac with a single duct and a central lumen partially occluded by a central, cylindrical conglomerate of cells and secretion product. The capsule of the gland consists of an outer layer of smooth muscle and an inner layer of connective tissue containing collagen and elastin fibres. Septa carrying blood vessels radiate from the connective tissue layer of the capsule to the border of the central conglomerate. Parenchymal cells containing lipid droplets enlarge from the periphery to the centre of the gland. Secretions formed by degeneration of cells in the central cylinder are concentrated near the secretory duct. Histochemical tests indicate lipids but not mucopolysaccharides in the glandular exudate.     

The ultrastructure and histology of the perinotal epidermis and defensive glands of two species of Onchidella (Gastropoda: Pulmonata)

Histology and electron microscopy were used to describe and compare the structure of the perinotal epidermis and defensive glands of two species of shell-less marine Systellommatophora, Onchidella capensis and Onchidella hildae (Onchidiidae). The notum of both species is composed of a layer of epithelial and goblet cells covered by a multi-layered cuticle. Large perinotal multi-cellular glands, that produce thick white sticky mucus when irritated, are located within the sub-epidermal tissue. The glands are composed of several types of large secretory cell filled with products that stain for acidic, sulphated and neutral mucins, and some irregularly shaped support cells that surround a central lumen. The products of the secretory cells are produced by organelles that are basal in position. The entire gland is surrounded by a well-developed capsule of smooth muscle and collagen, and in addition smooth muscle surrounds the cells within the glands. Based on the size of the gland cells, their staining properties, and the appearance of their stored secretions at the transmission electron microscope level, five different types of secretory cells were identified in O. capensis and four in O. hildae. The products of these cells, which are released by holocrine secretion, presumably mix in the lumen of the duct as they are forced out by contraction of the smooth muscle. The structural similarity of these glands to those of siphonariids, suggest that they have a common ancestry.     

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.     

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.     

Morphology of the exocrine glands of the frog skin

Frog skin contains three distinct types of exocrine glands: granular (poison), mucous, and seromucous. The granular gland forms a syncytial secretory compartment within the acinus, which is surrounded by smooth muscle cells. The mucous and seromucous glands are easily identifiable as distinct glands. The serous and mucous secretory cells are arranged in a semilunar configuration opposite the ductal end and are filled with granules. Within the acinus, located at the ductal pole of the gland, are distinct groups of cells with few or no granules in the cytoplasm. In both the mucous and seromucous gland there is a cell type with abundant mitochondria; the one in the mucous gland is located in the region adjacent to the secretory cells. The duct of these glands is two-layered, with the individual cells appearing morphologically similar to the layers of the skin epithelium as the duct traverses the skin. The duct appears to be patent throughout its length. The morphological heterogeneity and distinct distribution of the cell types within the gland acinus may be indicative of a functional heterogeneity that allows the production of distinctly different types of secretion from the same gland type, depending on the type of stimulus.     

Integumentary structure and its relationship to wiping behaviour in the common Indian tree frog, Polypedates maculatus

Skin of the Indian tree frog, Polypedates maculatus (Rhacophoridae), was studied in the context of self-wiping behaviour which functions to expel and distribute cutaneous secretions recently shown to retard evaporative water loss. The secretions contain both mucus and lipids and are derived from a common gland considered to be homologous with characteristic anuran mucous glands. The glands are bipotent and secrete both mucus and lipoid products which are evidently mixed within the glandular lumen. Another type of gland resembling characteristic anuran serous (or granular) glands is found in dorsal but not ventral skin, whereas the lipid-secreting mucous glands are found in skin associated with all body surfaces. There is no distinct, lipid-secreting gland present in the skin of this species other than the mucous glands. These histochemical data complement the earlier finding that resistance to evaporative water loss in this species is relatively small compared with phyllomedusine 'waterproof frogs which also exhibit wiping behaviour associated with secretion of lipids. Thus, wiping behaviour may have evolved in association with mucous secretions before dominant lipoid secretions resulted from strong selection for water conservation.     

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.     

Ultrastructure and function of the seminal vesicle of Bittacidae (Insecta: Mecoptera)

The fine structure of the seminal vesicle and reproductive accessory glands was investigated in Bittacidae of Mecoptera using light and transmission electron microscopy. The male reproductive system of Bittacidae mainly consists of a pair of testes, a pair of vasa deferentia, and an ejaculatory sac. The vas deferens is greatly expanded for its middle and medio-posterior parts to form a well-developed seminal vesicle. The seminal vesicle is composed of layers of developed muscles and a mono-layered epithelium surrounding the small central lumen. The epithelium is rich in rough endoplasmic reticulum and mitochondria, and secretes vesicles and granules into the central lumen by merocrine mechanisms. A pair of elongate mesodermal accessory glands opens into the lateral side of the seminal vesicles. The accessory glands are similar to the seminal vesicle in structure, also consisting of layers of muscle fibres and a mono-layered elongated epithelium, the cells of which contain numerous cisterns of rough endoplasmic reticulum and mitochondria, and a few Golgi complexes. The epithelial cells of accessory glands extrude secretions via apocrine and merocrine processes. The seminal vesicles mainly serve the function of secretion rather than temporarily storing spermatozoa. The sperm instead are temporarily stored in the epididymis, the greatly coiled distal portion of the vas deferens.     

Cultivation of epithelia from the secretory coil of the ovine apocrine gland: Evidence of secretory cell function and ductal morphogenesis In vitro

Summary The secretory coil of the ovine apocrine gland is composed predominantly of two cell types, secretory cells lining the lumen and myoepithelial cells adjacent to the basement membrane. The glands synthesize a number of hormones and growth factors, but analysis of the functions of these molecules may be hampered by the mixing of apocrine and sebaceous secretions in the pilary canal. The purpose of this study was to isolate the glands and devise simple culture procedures to facilitate investigations of secretory cell function. The most successful approach involved microdissection of the secretory coils individually from skin biopsies and culture in Dulbecco’s modified Eagle’s medium. After 1–2 wk in medium, cell outgrowths were seen from explants. These consisted predominantly of populations of epithelial cells, many containing granules. Smaller granules were usually concentrated around the cell nuclei and accumulated lipophilic dyes. Large granules were unreactive. Western analysis showed that cells in culture synthesized nerve growth factor-like peptides, a feature consistent with one of the functions of the gland in vivo. When isolated secretory coils were explanted to culture dishes coated with matrigel, highly compact, multilayered masses of cells grew out. Subsequently, tubular structures formed. The observations suggest that some differentiated functions of gland cells were retained in vitro and that the procedures described provide a system for the study of apocrine secretions in isolation from those of other skin glands.     

Structure of male accessory glands of Bolivarius siculus (fischer) (Orthoptera,Tettigoniidae) and protein analysis of their secretions

In Tettigoniidae (Orthoptera), male reproductive accessory glands are involved in the construction of a two‐part spermatophore; one part, the spermatophylax, is devoid of sperm and considered a nuptial gift. The morphology, ultrastructure, and secretion protein content of the male reproductive accessory glands from Bolivarius siculus were investigated. Two main groups of gland tubules open into the ejaculatory duct: the “first‐order” glands, a number of large anterior tubules, and the “second‐order” glands, smaller and more numerous tubules positioned posteriorly. Along with a further subdivision of the gland tubules, we here describe for the first time an additional gland group, the intermediate tubules, which open between first and second‐order glands. The mesoderm‐derived epithelium of all glands is a single layer of microvillated cells, which can be either flattened or cylindric in the proximal or distal region of the same gland. Epithelial cells, very rich in RER and Golgi systems, produce secretions of both electron‐dense granules and globules or electron‐transparent material, discharged into the gland lumen by apocrine or merocrine mechanisms, respectively. With one exception, a unique electrophoresis protein profile was displayed by each of the gland types, paralleling their unique morphologies. To assess the contribution of different types of accessory glands to the construction of the spermatophore, the protein patterns of the gland secretions were compared with those of the extracts from the two parts of the spermatophore. All samples showed bands distributed in a wide range of molecular weight, including proteins of very low molecular mass. However, one major high molecular weight protein band (>180 kDa) is seen exclusively in extracts from the first‐order glands, and corresponds to an important protein component of the spermatophylax. J. Morphol., 2009. © 2009 Wiley‐Liss, Inc.     

Ultrastructure of male reproductive accessory glands and ejaculatory duct in the Queensland fruit fly,Bactrocera tryoni (Diptera: Tephritidae)

Ultrastructure of male reproductive accessory glands and ejaculatory duct in the Queensland fruit fly (Q-fly), Bactrocera tryoni, were investigated and compared with those of other tephritid flies. Male accessory glands were found to comprise one pair of mesodermic glands and three pairs of ectodermic glands. The mesodermic accessory glands consist of muscle-lined, binucleate epithelial cells, which are highly microvillated and extrude electron-dense secretions by means of macroapocrine transport into a central lumen. The ectodermic accessory glands consist of muscle-lined epithelial cells which have wide subcuticular cavities, lined with microvilli. The electron-transparent secretions from these glands are first extruded into the cavities and then forced out through small pores of the cuticle into the gland lumen. Secretions from the two types of accessory glands then flow into the ejaculatory duct, which is highly muscular, with epithelial cells rich in rough endoplasmic reticulum and lined with a thick, deeply invaginated cuticle. While there are some notable differences, reproductive accessory glands of male Q-flies generally resemble those of the olive fruitfly, Bactrocera oleae, and to a lesser extent the Mediterranean fruit fly, Ceratitis capitata.     

丹顶鹤胆囊的显微观察

应用光镜及透射电镜观察一例成体雄性丹顶鹤胆囊。结果表明,丹顶鹤胆囊粘粘膜、肌层和外膜三部分组成。粘膜上皮高柱状、游离端有密集排列的微绒毛,胞质面端有许多粘液颗粒,说明上皮细胞具有吸收功能并可分泌粘液。     

The fine structure of epidermal glands of regenerating and mature globiferous pedicellariae of a sea urchin (Lytechinus pictus)

After a globiferous pedicellaria is lost from a sea urchin, a new appendage of the same kind is usually regenerated in the weeks that follow. During the latter part of regeneration, head glands and stalk glands, both of epidermal origin, develop from undifferentiated cells. Head gland cells begin morphological differentiation in the epidermis and then delaminate into the underlying dermis. In the formation of the stalk gland, by contrast, undifferentiated cells delaminate from the epidermis and then begin morphological differentiation in the dermis. During late regeneration, cells in the head and stalk glands are characterized by extensive rough endoplasmic reticulum distended with intracisternal material; moreover, the Golgi complex is closely associated with some of the large cytoplasmic vacuoles. The accumulating secretions of the two glands differ both in fine structure and in site of storage. Head gland secretions are stored intracellularly in the cytoplasmic vacuoles, while stalk gland secretions leave the gland cells in an apocrine fashion and are stored in an extracellular lumen. After regeneration, the mature cells of the head glands and stalk glands contain relatively little distended endoplasmic reticulum, although a Golgi complex is still present. Presumably, mature gland cells, in comparison to regenerating gland cells, produce relatively little secretion; instead, the glandular products elaborated during regeneration are probably stored in the mature glands with little augmentation or turnover.     

Ultrastructure of human labial salivary glands. I. Acinar secretory cells

The structure of human labial salivary gland acini was studied by light and electron microscopy. Contrary to previous reports, these glands were pure mucous in nature; no serous elements were present. The acinar cells were found in all stages of maturation. Immature cells were characterized by an extensive and highly organized rough-surfaced endoplasmic reticulum. The Golgi complex was extremely prominent, consisting of stacks of flattened cisternae and swarms of small vesicles. Mucous droplets were almost completely absent. As secretory activity progressed, the endoplasmic reticulum involuted, while the Golgi cisternae became distended and formed many vacuoles. In mature mucous cells, the apical cytoplasm was filled with membrane-bounded mucous droplets, and the nucleus was displaced basally. The droplets frequently showed great variation in density from cell to cell, and even within the same cell they sometimes were quite heterogeneous. They were liberated from the acinar cells by an apocrine process, so that droplets with intact limiting membranes were often observed in the acinar lumen. These droplets soon lysed, their contents fusing into streams of mucus. Occasionally during apocrine secretion a mucous cell failed to reconstitute its apical surface, and its entire contents spilled into the acinar lumen. Unusual cytoplasmic inclusions were present in many of the acinar cells. These inclusions, which were surrounded by a single membrane, consisted of lipid droplets closely associated with bundles of fine filaments.     

金丝猴食管和胃连接部的组织学研究

本文研究了金丝猴食管和胃连接处的组织结构。金丝猴的食管粘膜为典型的复民鳞状上皮,食管末端含有粘膜腺,粘膜表面有轻微的角质化。管壁外纵肌层有少量的横纹肌。与胃粘膜的连接均位于胃的贲门部以内,两种上皮的连接是突然的,不存在过渡。 贲门腺为少量的分枝管状腺,短而直,由粘膜细胞构成,对PAS染色呈阳性反应。     

Ultrastructural and histochemical observations on secretory phenomena in the resting human mammary gland

Ultrastructure and histochemistry of clinically normal appearing tissue and secretions of non-lactating human mammary glands have been investigated in order to document and analyse secretory phenomena in the resting gland. The material studied originated from women of different ages (18-74 years) who underwent plastic surgery or surgery for various disorders of the breast. The epithelia of small ducts and of alveolar enlargements as well as acini contained moderate amounts of mitochondria and of cisterns of the rough endoplasmic reticulum; the transcisterns of the Golgi apparatus which were surrounded by smooth and coated vesicles, exhibited modest dilatations, the number of lysosomes increased with age; regularly glycogen particles and bundles of intracellular filaments (phi 5 nm) were to be observed. Typical casein vesicles and stages of apocrine secretion of milk fat globules were not seen. The following features indicated secretory activity: differently sized vesicles and granules with flocculent, dense, or light contents were regularly to be seen in the apical cytoplasm often immediately below the apical plasma membrane of the epithelia of the small ducts and even more frequently in the alveolar enlargements. Secretory products of fine granular or filamentous structure, probably containing proteins, were frequently found within the lumen. Different types of lipid and liposome-like particles were detected both in intracellular localization as well as in ductal lumina. As demonstrated by lectin histochemistry the secretory products also contained a considerable amount of carbohydrate components. The composition of the secretory products of the resting gland is of clinical interest since the chronical deposition of secretions, which among others possibly contain enzymes producing oxygen radicals, may lead to pathological changes of mammary gland tissue.     

Study on the morphology of the gall-bladder of the goat

200 gall-bladders of goat were studied for histology and histochemistry. The lining epithelium is tall columnar with striated border. The glands are mucous and serous, and the secretion of both surface and glands is a polyssaccharide-protein complex. The regional differences at neck, body and fundus of the gall-bladder are described. Few enterochromaffin cells with granules, which are PAS-positive and contain 5-hydroxytryptamine, are encountered at the wedge between the granular epithelial cells and the cells lining the crypts. The relationship between these cells and lymphocytic infiltration is discussed. The thick circular muscle layer at the neck region is considered a sphincter of the gall-bladder.     

Scanning electron microscopy of human submandibular gland

The fracture surface of human submandibular gland analyzed by scanning electron microscopy is studied here. Acini showed spherical granules of 0.7 +/- 0.28 micron diameter, their most distinctive feature. Some empty, septate cavities found contiguous to serous acini were considered to be mucous acini. Striated ducts had a circular lumen, with microvilli forming prominences. Blebs, some intact and others ruptured, were interpreted as apocrine secretion. The 'separating zone' of the striated cells was distinguishable from the rest of the cell because the structure of the cell was granular whereas the 'separating zone' was fibrillar.     

Ultrastructure of the tubular accessory gland in Haemaphysalis longicornis (Acari: Ixodidae)

The paired tubular accessory glands in Haemaphysalis longicornis open at the junction of the cervical and the vestibular parts of vagina via short and narrow ducts. The pseudostratified columnar glandular epithelium covered by the muscle layer consists of both secretory and supporting cells. As feeding proceeds, the secretory cells increase in volume. In ovipositing females, well-developed rough endoplasmic reticulum, the Golgi complex, and membranebound granules that are undergoing exocytosis suggest that the secretory cells are involved in protein synthesis. However, in virgin females that fed 10 days, only small dense granules and no secretion activity were observed. The secretions from the tubular accessory gland may be released into the genital tract during the egg passage through the vagina. However, the supporting cells located between the secretory cells become slender during feeding, cohere to each other at the luminal side, and have a very narrow attachment at the basement membrane. Supporting cells probably help maintain secretory cell shape especially during granular discharge into the lumen. © 1994 Wiley-Liss, Inc.