Histological study of the cloacal region and associated structures in the hedgehog tenrec Echinops telfairi

The present investigation is based on several careful dissections and on extensive series of histological sections. It has led us to the conclusion that adult male and female Echinops telfairi are in the possession of a cloaca which represents a primitive feature among mammals. This cloaca is a small, bowl-shaped pouch at the ventro-posterior end of the body. Intestinal, genital and urinary tract open into this cloaca. The opening of the intestinal tract into the cloaca is regulated by a sphincter muscle. In the female the genital and the urinary tract open into the urogenital sinus, a subcompartment of the cloaca. The cloaca of the lesser hedgehog tenrec is lined by a multilayered, non-keratinized squamous epithelium without skin glands. In a small transitory zone between the cloaca and the outer skin the epithelium changes into the keratinized, multilayered squamous epithelium of the epidermis with eccrine and holocrine glands as well as hairs. In addition, there is a distinct circular cloacal sphincter muscle, built up by cross-striated skeletal muscle tissue.

In the terminal parts of intestinal, urinary and genital tracts of male animals the following glandular structures were observed: prostate gland, Cowper's glands and strongly pigmented seminal vesicles; in female animals: the urethral and the Bartholin glands. Both males and females, in addition, possess (a) a cloacal gland, the excretory ducts of which open into the cloaca and (b) a pericloacal gland which is located in the adipose tissue on both sides of the cloaca; it presumably also opens into the cloaca.     

Secretory and basal cells of the epithelium of the tubular glands in the male Mullerian gland of the caecilian Uraeotyphlus narayani (Amphibia: Gymnophiona)

Caecilians are exceptional among the vertebrates in that males retain the Mullerian duct as a functional glandular structure. The Mullerian gland on each side is formed from a large number of tubular glands connecting to a central duct, which either connects to the urogenital duct or opens directly into the cloaca. The Mullerian gland is believed to secrete a substance to be added to the sperm during ejaculation. Thus, the Mullerian gland could function as a male accessory reproductive gland. Recently, we described the male Mullerian gland of Uraeotyphlus narayani using light and transmission electron microscopy (TEM) and histochemistry. The present TEM study reports that the secretory cells of both the tubular and basal portions of the tubular glands of the male Mullerian gland of this caecilian produce secretion granules in the same manner as do other glandular epithelial cells. The secretion granules are released in the form of structured granules into the lumen of the tubular glands, and such granules are traceable to the lumen of the central duct of the Mullerian gland. This is comparable to the situation prevailing in the epididymal epithelium of several reptiles. In the secretory cells of the basal portion of the tubular glands, mitochondria are intimately associated with fabrication of the secretion granules. The structural and functional organization of the epithelium of the basal portion of the tubular glands is complicated by the presence of basal cells. This study suggests the origin of the basal cells from peritubular tissue leukocytes. The study also indicates a role for the basal cells in acquiring secretion granules from the neighboring secretory cells and processing them into lipofuscin material in the context of regression of the Mullerian gland during the period of reproductive quiescence. In these respects the basal cells match those in the epithelial lining of the epididymis of amniotes.     

Organization of unusual idiosomal glands in a water mite, <Emphasis Type="Italic">Teutonia cometes</Emphasis> (Teutoniidae)

The unusual idiosomal glands of a water mite Teutonia cometes (Koch 1837) were examined by means of transmission and scanning electron microscopy as well as on semi-thin sections. One pair of these glands is situated ventrally in the body cavity of the idiosoma. They run posteriorly from the terminal opening (distal end) on epimeres IV and gradually dilate to their proximal blind end. The terminal opening of each gland is armed with the two fine hair-like mechanoreceptive sensilla (‘pre-anal external’ setae). The proximal part of the glands is formed of columnar secretory epithelium with a voluminous central lumen containing a large single ‘globule’ of electron-dense secretory material. The secretory gland cells contain large nuclei and intensively developed rough endoplasmic reticulum. Secretory granules of Golgi origin are scattered throughout the cell volume in small groups and are discharged from the cells into the lumen between the scarce apical microvilli. The distal part of the glands is formed of another cell type that is not secretory. These cells are composed of narrow strips of the cytoplasm leaving the large intracellular vacuoles. A short excretory cuticular duct formed by special excretory duct cells connects the glands with the external medium. At the base of the terminal opening a cuticular funnel strengthens the gland termination. At the apex of this funnel a valve prevents back-flow of the extruded secretion. These glands, as other dermal glands of water mites, are thought to play a protective role and react to external stimuli with the help of the hair-like sensilla.     

The fine structure of the tarsal glands of the honeybee Apis mellifera L. (Hymenoptera)

Summary Tarsal glands are located in the 6th tarsomere of adult honeybee queens, workers and drones. Their structural features are not cast or sex specific. The glandular epithelium is lined by a thin endocuticular layer. A cuticular pocket is formed from a postimaginal delamination of the cuticle secreted by the glandular epithelium. The apical plasma membrane of the glandular cells shows numerous cristae and microvilli lining large crypts that communicate with the subcuticular space. Pinocytotic vesicles, multivesicular bodies and residual dense bodies are present in the apical part of the glandular cells. The RER is well developed in perinuclear and basal parts of the glandular cells, but the Golgi apparatus is a discrete organelle without secretory granules. No exocytotic secretory structures were observed. To reach the glandular pocket, the non-proteinaceous secretory product must pass across the subcuticular space, the cuticular intima, the space between the intima and the cuticular wall, and the cuticular wall of the glandular pocket.     

扩张莫尼茨绦虫(圆叶目:裸头科)节间腺的超微结构及组织化学

用光学显微镜和透射电子显微镜观察了扩张莫尼茨绦虫节间腺形成过程的精细结构及一些组化变化。结果表明：节间腺是扩张莫尼茨绦虫皮层的特化部分,由节片后缘的皮层及其邻近细胞体向绦虫实质组织中陷入开始其形成过程,随着虫体发育的进行,新的陷入不断形成,原陷入的部分不断脱离皮层形成簇状腺体结构。节间腺的数目随着体节的发育不断增加,幼节中仅有少数几个(6～9个),而远端的孕节中多于100个。电镜下可见腺细胞体由细胞质管与腺皮层相联,簇状腺体结构为一合胞体形态,腺细胞体围绕并开口于椭球体或不规则形状的皮层腔中。离腺皮层远的腺细胞体电子密度高并含有与腺皮层相应的典型分泌颗粒,而靠近腺皮层的腺细胞体电子密度低,所含分泌颗粒较少。扩张莫尼茨绦虫节间腺的组化性质尚不完全清楚。糖与蛋白质等组化结果不稳定,随染液pH值及染色时间的变化等多种因素而改变。基于我们的研究及其他研究者的观察表明,节间腺可能参与外源基质形成虫卵的转运,同时他们可能在虫体节片脱落及虫卵溢出时起作用。     

The fine structure of the planarianPolycelis tenuis ijima

Summary The fine structure of the pharynx is presented and demonstrates that the pharyngeal epithelial system is a continuous one. The epithelial lining of the pharyngeal cavity with its characteristic fibrous secretory bodies merges with the outer pharyngeal epithelium at the point of anchorage of the pharynx. A few of these cells are insunk, the nuclei occurring beneath the underlying muscular layers. The nature of the outer epithelium changes towards the free end of the pharynx; the cells become ciliated and in contents come to resemble the inner epithelium which it joins at the tip.The gut cells merge at a transitional zone with the inner pharyngeal epithelium and at this point both bear microvilli and contain rod-shaped apical bodies. Some of these cells are also insunk. Towards the mouth the epithelium shows a greater degree of insinking and exhibits microapocrine secretion. Both inner and outer epithelia bear sense receptors which are concentrated at the lip.At the point of pharyngeal insertion, the sub-epithelial tissue resembles planarian parenchyma, but is rich in gland cells. These glands open on to the outer epithelium especially towards the free end of the pharynx.This research was supported by the Scientific Research Council. Grant No. B/RG/086.     

Histology and ultrastructure of male mullerian gland of Uraeotyphlus narayani (Amphibia: Gymnophiona)

This study reports the anatomy, histology, and ultrastructure of the male Mullerian gland of the caecilian Uraeotyphlus narayani, based on dissections, light microscopic histological and histochemical preparations, and transmission electron microscopic observations. The posterior end of the Mullerian duct and the urinogenital duct of this caecilian join to form a common duct before opening into the cloaca. The boundary of the entire gland has a pleuroperitoneum, followed by smooth muscle fibers and connective tissue. The Mullerian gland is composed of numerous individual tubular glands separated from each other by connective tissue. Each gland has a duct, which joins the central Mullerian duct. The ducts of the tubular glands are also surrounded by abundant connective tissue. The tubular glands differ between the column and the base in regard to the outer boundary and the epithelial organization. The basement membrane of the column is so thick that amoeboid cells may not penetrate it, whereas that around the base of the gland is thin and appears to allow migration of amoeboid cells into and out of the basal aspect of the gland. The epithelium of the column has nonciliated secretory cells with basal nuclei and ciliated nonsecretory cells with apical nuclei. In the epithelium of the base there are secretory cells, ciliated cells, and amoeboid cells. The epithelium of ducts of the tubular glands is formed of ciliated dark cells and microvillated light cells. The epithelium of the central duct is formed of ciliated dark cells also possessing microvilli, ciliated light cells also possessing microvilli, and microvillated light cells that lack cilia. It is regressed during March to June when the testis lobes are in a state of quiescence. The Mullerian gland is active in secretion during July to February when the testis is active in spermatogenesis.     

Fonction catabolique de l'épithélium mammaire

Summary The histochemical (iron, lipopigments, acid phosphatase, leucine aminopeptidase) and cytologic (lysosomes) changes occuring during pregnancy, lactation and involution of mouse, rat, rabbit, guinea-pig mammary glands are studied by light microscopy and electron microscopy.In all the animals examined, the mammary epithelium has an intracellular digestive system which is adapted to subserve two functions. The first one is the segregation of cytoplasmic components which often precedes cellular involution. The second one is the regulation of secretory processes in the non lactating glands. This digestion of endogenous materials results in the formation of various lytic bodies: dense bodies sometimes containing ferritin, vacuolated dense bodies with membranous residues, autophagic vacuoles. The lysosomes can give large complex dense bodies like lipofuscin pigments with or without ferritin.Leucine aminopeptidase which always disappears in the mouse mammary epithelium during lactation is not present in rat, rabbit, guinea-pig mammary epithelium. In these species only the vascular tissue contains the enzyme. This observation indicates that leucine aminopeptidase does not take care of the overproduction of secretory products in the non-lactating glands.Acid phosphatase is concentrated in secretory granules and in lytic bodies: multivesicular bodies, dense bodies with ferritin, vacuolated dense bodies, lipopigments. This enzyme constitutes probably a mechanism for controlling and triggering the destruction of the secretory material with no active elimination.The iron of the mammary epithelium appears in virgin mice older than 30 weeks and in mice, rats, rabbits, guinea-pigs during glandular cells involution. This is a catabolic iron located in lysosomes. Its amount depends upon the iron content of the milk and upon the competitive secretory and catabolic activities of the glandular cells. An explanation of iron disappearance during a second pregnancy and lactation is discussed.     

The cloaca of Myxine glutinosa (Cyclostomata): a scanning electron microscopical and histochemical investigation

The cloaca of Myxine glutinosa was examined by histochemical and scanning electron microscopical methods. No copulation organ could be found in Myxine and no detectable differences in the anatomy of the cloaca between male and female Myxine glutinosa. The anal gland which is the only gland in the cloacal region is situated between rectum and ductus coelomaticus. Like the lateral mucous glands in the epidermis it consists of large mucous gland cells, thread cells and undifferentiated cells. The cloacal epithelium neither develops a spatial separation by folds nor a ciliation is present in the caudal and dorsal part of the cloacal chamber. Therefore female and male myxinoides do not show any structures which would allow transportation of sperm into the abdominal cavity or out of it.     

Olfactory metamorphosis in the Coastal Giant Salamander (Dicamptodon tenebrosus)

This study examined the gross morphology and ultrastructure of the olfactory organ of larvae, neotenic adults, and terrestrial adults of the Coastal Giant Salamander (Dicamptodon tenebrosus). The olfactory organ of all aquatic animals (larvae and neotenes) is similar in structure, forming a tube extending from the external naris to the choana. A nonsensory vestibule leads into the main olfactory cavity. The epithelium of the main olfactory cavity is thrown into a series of transverse valleys and ridges, with at least six dorsal and nine ventral valleys lined with olfactory epithelium, and separated by ridges of respiratory epithelium. The ridges enlarge with growth, forming large flaps extending into the lumen in neotenes. The vomeronasal organ is a diverticulum off the ventrolateral side of the main olfactory cavity. In terrestrial animals, by contrast, the vestibule has been lost. The main olfactory cavity has become much broader and dorsoventrally compressed. The prominent transverse ridges are lost, although small diagonal ridges of respiratory epithelium are found in the lateral region of the ventral olfactory epithelium. The posterior and posteromedial wall of the main olfactory cavity is composed of respiratory epithelium, in contrast to the olfactory epithelium found here in aquatic forms. The vomeronasal organ remains similar to that in large larvae, but is now connected to the mouth by a groove that extends back through the choana onto the palate. Bowman's glands are present in the main olfactory cavity at all stages, but are most abundant and best developed in terrestrial adults. They are lacking in the lateral olfactory epithelium of the main olfactory cavity. At the ultrastructural level, in aquatic animals receptor cells of the main olfactory cavity can have cilia, short microvilli, a mix of the two, or long microvilli. Supporting cells are of two types: secretory supporting cells with small, electron-dense secretory granules, and ciliated supporting cells. Receptor cells of the vomeronasal organ are exclusively microvillar, but supporting cells are secretory or ciliated, as in the main olfactory cavity. After metamorphosis two distinct types of sensory epithelium occur in the main olfactory cavity. The predominant epithelium, covering most of the roof and the medial part of the floor, is characterized by supporting cells with large, electron-lucent vesicles. The epithelium on the lateral floor of the main olfactory cavity, by contrast, resembles that of aquatic animals. Both types have both microvillar and ciliated receptor cells. No important changes are noted in cell types of the vomeronasal organ after metamorphosis. A literature survey suggests that some features of the metamorphic changes described here are characteristic of all salamanders, while others appear unique to D. tenebrosus.     

The structure of the middle ear epithelium of the rat and the effect of Eustachian tube obstruction

Summary The middle ear cavity of the rat is lined with ciliated and squamous epithelium. The arrangement of the ciliated cells, interspersed with secretory cells, in distinct tracts and their continuity with the ciliated epithelium of the Eustachian tube, suggests the existence of a mucociliary transport system for cleaning the middle ear cleft. The secretory cells produce either neutral or sulphated glycoproteins, dependent on their location. In addition to these secretions, the epithelium of the lower part of the Eustachian tube is bathed with secretory products of seromucous glands.Also in the areas with squamous epithelium, numerous small secretory cells, the character of which is only identifiable with the electronmicroscope, are present. It is concluded that the middle ear lining can be considered as a locally modified respiratory epithelium.Blockade of the mucociliary transport system, supposedly a crucial aetiological factor in secretory otitis media, by obstruction of the Eustachian tube, induces pathogenic behaviour of microorganisms normally present in the middle ear. This results in either a transient or a longstanding infective middle ear disease, associated with a large variety of changes of the mucosa, especially with respect to the secretory activity.The data obtained indicate that the increased secretory activity encountered in secretory otitis media cannot be attributed to the isolated effect of tubal occlusion, but rather to an infective process.     

Fine structure of the pygidial glands of Bledius mandibularis (coleoptera : staphylinidae)

The pygidial glands of B. mandibularis produce a mixture of terpenes, fatty acid derivatives, and a benzoquinone. The morphology of these glands is described with particular attention to the ultrastructure of the secretory cells and their efferent ductules. Each functional secretory unit consists of two secretory cells (cortical and medullary) both of which are associated with a common extracellular cuticular ductule. The fenestrated tip of the ductule lies in a cavity bounded by the invaginated plasma membrane of the cortical cell; within the cavity surrounded by the medullary cell, the ductule is divided into a bulb region (where a spherical mass of fine cylinders surrounds the ductule itself) and an unfenestrated switchback region. Inflated cisternae of rough endoplasmic reticulum, filled with flocculent material of low electron density, are abundant in the cortical cytoplasm, and presumably represent primary secretory product en route to the cavity of this cell. The plasma membrane bounding this cavity is much infolded, and the inner surface of this membrane is studded with fine particles. In contrast, few cisternae are inflated in the medullary cell and the corresponding infolded plasma membrane is smooth. The manner in which both cells may cooperate to produce the heterogeneous secretory product is discussed.     

On the Fine Structure of the Alimentary Tract of Cephalodiscus gracilis (Pterobranchia,Hemichordata)

The U-shaped alimentary tract of Cephalodiscus is of exclusively epithelial structure; on the basis of fine structural criteria the entire tract can be divided into two large subdivisions: an anterior one with mouth, mouth cavity, pharynx and oesophagus, and a posterior one with stomach and intestine. The anterior subdivision is built up of a relatively uniform, innervated, pseudostratified, ciliated epithelium with mucus cells which are concentrated in the initial parts of the mouth cavity. Cilia and mucus presumably constitute a mechanism transporting food particles into the stomach. In the area of the gill slits specific vacuolated cells occur which may lend rigidity to the walls of the slits. The gastric epithelium consists of prismatic cells characterized by, among others, large inclusion bodies, which may represent digestive vacuoles, small dense rod-shaped granules and an elaborate system of microridges, at the base of which abundant endocytotic vesicles occur. The dorsal gastric pouch contains cells rich in rough ER and secretory granules, probably containing digestive enzymes. Thus morphological evidence points both to intra- and extracellular digestion. The intestinal epithelium resembles that of the stomach, however, it is lower, its organelles are fewer and it bears, beside cilia, mainly microridges, which towards its distal end become sparse. Both in the gastric and intestinal epithelium small granulated cells have been found, which presumably represent endocrine cells.     

Morphological and biochemical analyses of the salivary glands of the malaria vector, Anopheles darlingi.

Adult Anopheles darlingi salivary glands are paired organs located on either side of the esophagus. The male glands consist of a single small lobe. The female gland is composed of two lateral lobes, with distinct proximal and distal portions, and a medial lobe. The lobes are acinar structures, organized as a unicellular epithelium that surrounds a salivary canal. The general cellular architecture is similar among the lobes, with secretory material appearing as large masses that push the cellular structures to the periphery of the organ. Cells of the proximal-lateral lobes show asynchronous cycles of secretory activity and contain secretory masses with finely filamentous aspect. In the distal-lateral lobes, cells display synchronous cycles of activity, and have a dense secretory product with mottled pattern. Cells of the medial lobe have secretory masses uniformly stained and highly electrondense. Biochemical analysis of the adult female salivary glands revealed apyrase, alpha-glucosidase and lysozyme activities. Alpha-glucosidase and lysozyme activities are detected mostly in the proximal lobes while apyrase is mainly accumulated in the distal lobes. This differential distribution of the analyzed enzymes reflects a specialization of different regions for sugar and blood feeding. Thus, the morphological differences observed in the lobes correlate with functional ones.     

Spermiophagy by the spermathecal epithelium of the salamander Eurycea cirrigera.

The spermathecae of Eurycea cirrigera are exocrine glands in the cloaca that secrete a substance that bathes sperm stored in the lumen after mating and prior to oviposition. Many sperm remain in the spermathecae after oviposition, and the spermathecal epithelium becomes spermiophagic. Pseudopodia enclose sperm into endocytic vacuoles. The vacuoles become associated with primary lysosomes in the cytoplasm. Following formation of secondary lysosomes and resulting condensation of the sperm fragments, residual bodies are exocytized into the surrounding connective tissue stroma. By the start of the next breeding cycle, most sperm remaining from the previous mating have been degraded, but some sperm remain in the lumen, and the viability of these sperm is unknown.     

ULTRASTRUCTURAL DEVELOPMENT OF CAPITATE GLANDULAR HAIRS OF CANNABIS SATIVA L. (CANNABACEAE)

The capitate-sessile and capitate-stalked glands of the glandular secretory system in Cannabis, which are interpreted as lipophilic type glandular hairs, were studied from floral bracts of pistillate plants. These glands develop a flattened multicellular disc of secretory cells, which with the extruded secretory product forms the gland head and the auxiliary cells which support the gland head. The secretory product accumulates beneath a sheath derived from separation of the outer wall surface of the cellular disc. The ultrastructure of secretory cells in pre-secretory stages is characterized by a dense ground plasm, transitory lipid bodies and fibrillar material, and well developed endoplasmic reticulum. Dictyosomes and dictyosome-derived secretory vesicles are present, but never abundant. Secretory stages of gland development are characterized by abundant mitochondria and leucoplasts and by a large vacuolar system. Production of the secretory product is associated with plastids which increase in number and structural complexity. The plastids develop a paracrystalline body which nearly fills the mature plastid. Material interpreted as a secretion appears at the surface of plastids, migrates, and accumulates along the cell surface adjoining the secretory cavity. Extrusion of the material into the secretory cavity occurs directly through the plasma membrane-cell wall barrier.     

Scanning and transmission electron microscopic observations of the cloacal epithelia of the domestic fowl

Summary The epithela of the three divisions (coprodaeum, urodaeum, proctodaeum) of the cloaca of the hen, and of the excretory ducts (colon, ureter, vagina) which join the divisions, are described using light microscopy, and scanning and transmission electron microscopy. Each region of the cloaca has its typical epithelium. Special attention is focussed in this study on the boundaries between the different epithelia. The coprodaeal epithelium does not differ considerably from that of the colon; a transitional zone is not visible. Distinct border zones, however, are observed between the other regions (ureter — urodaeum; vagina — urodaeum and proctodaeum; urodaeum-proctodaeum; proctodaeum — cutis). Although the vaginal opening is generally thought to lie in the urodaeum, our investigations show that at the vaginal opening into the cloaca the ciliated epithelium changes, on one border to a secretory epithelium characteristic of the urodaeum and on the other border to that characteristic of the proctodaeum. These observations are discussed in relation to functional aspects.     

Sperm storage and degradation in the spermathecae of the salamander Eurycea Cirrigera

Spermathecae are exocrine glands in the roof of the female cloaca that store sperm. Cytological and histochemical data indicate that the one type of secretion into the lumen is a glycoprotein. After a period of stasis in the summer, production of the secretion is initiated in the fall, coincident with an increase in ovarian follicular size. By the time of maximal follicular development and most intense mating activity in March and April, the spermathecal epithelium is filled with secretory granules. The secretory material is released into the lumen, enveloping the sperm. Many sperm remain in the spermathecae after oviposition, and most of these sperm are degraded in the spermathecal epithelium or pass through interruptions in the spermathecal walls caused by desquamation. Sperm in contact with the stromal environment are phagocytized by leukocytes. Some sperm, however, may survive in the lumen until at least the following fall. These sperm retain normal cytology, but whether or not they remain fertile and intact until a subsequent ovipository cycle is unknown.     

Sperm storage in Spermathecae of the great lamper eel,Amphiuma tridactylum (Caudata: Amphiumidae)

The spermathecae of ten female Amphiuma tridactylum were examined by light and electron microscopy during the presumed mating and ovipository seasons (March–August) in Louisiana. Spermathecae were simple tubuloalveolar glands in the dorsal wall of the cloaca. Six of the ten specimens were vitellogenic, and all of these specimens contained sperm in their spermathecae and had secretory activity in the spermathecal epithelium. Two nonvitellogenic females also had sperm in their spermathecae and active epithelial cells, whereas the other nonvitellogenic females lacked stored sperm and secretory activity in the spermathecae. In specimens storing sperm from March–May, the sperm were normal in cytology, and secretory vacuoles were contained within the epithelium. In the August sample, however, evidence of sperm degradation was present, and secretory material had been released into the lumen by an apocrine process. We therefore hypothesize that the spermathecal secretions function in sperm degeneration. © 1996 Wiley-Liss, Inc.