Rostellar apparatus of Fernandezia spinosissima (von Linstow, 1894) (Cestoda, Cyclophyllidea, Davaineidae): microanatomy and fine structure

The rostellar apparatus of Fernandezia spinosissima is examined by light and transmission electron microscopy. It is described as composed of rostellum, pseudoproboscis, and two groups of glandular syncytia, one in the rostellum and the other inwards to the rostellum and the pseudoproboscis. The rostellum is a discoid cushion with muscular walls. There are numerous thin vertical muscular fibres and glandular syncytia inside it. Its tegument has slender microtriches. Peripherally, the rostellum is encircled by thin muscle fibres that protrude anteriorly between rostellar hooks and group posteriorly to form retractors. The rostellar hook guards are associated with a complicated network of muscles and nerves. The pseudoproboscis is a thick-walled ring around the apical part of the scolex adjacent to the rostellum. Its tegument has microtriches with modified spines that are interpreted as accessory spines. The walls of the pseudoproboscis possess a loose structure of parallel muscular fibres and glandular processes. The glandular syncytia, interpreted as modified tegumental perikarya, have basophilic cytoplasm and stain positively for protein and carbohydrate. They form cellular processes, which protrude to reach to the tegument. These results provide structural details characterising one of the rostellar types recognized in the order Cyclophyllidea, i.e. the davaineid rostellar apparatus.     

Echinococcus granulosus: secretory activity of the rostellum of the adult cestode in situ in the dog.

Secretary activities associated with the rostellum of adult Echinococcus granulosus were studied using histological, histochemical, and ultrastructural techniques, following rapid fixation of the cestodes in situ in the small intestine of the anaesthetised dog. Studies concentrated on the host-parasite interface from 30 to 35 days postinfection. At this time, contraction of the muscular rostellar pad appeared to be associated with extension of the apical rostellum into a crypt of Lieberkühn. Crypt invasion by the apical rostellum coincided with morphological changes and secretory activity in a group of modified tegumental cells, previously referred to as the rostellar gland. Secretory material, a cystine-rich protein, was observed in the nuclei and cytoplasm of the rostellar gland cells. Release of this material into the interface was seen only following crypt invasion by the apical rostellum. Although the mechanism of release is not clear, it may be analagous to holocrine secretory mechanisms, since apparent degeneration of the rostellar gland region was associated with secretion. Possible functional activities of the secretion associated with hook formation, nutrition, regulation, adhesion, and protection are discussed.     

The ultrastructural localization of acetylcholinesterase activity in the scolex of the cysticercus of Hydatigera taeniaeformis

Acetylcholinesterase activity in the scolex of the cysticercus of Hydatigera taeniaeformis was studied by means of electron microscopy. Acetylthiocholine iodide was used as the substrate and 10(-4) M of eserine used to inhibit acetylcholinesterase activity. The sites of activity were visualized within the microtriches of the distal cytoplasm, muscle bundles, cytoplasm, vesiculated bodies, flame cells and hooks of the rostellar region. Enzyme activity was also localized within the nuclear membrane, neuroplasm, and membranes of nerve cells.     

Peculiarities of rostellum morphology and armature in the genera Kowalewskiella and Himantaurus (Cyclophyllidea: Dilepididae)

Scoleces of two dilepidid genera, Kowalewskiella Baczynska, 1914 and Himantaurus Spasskaja et Spassky, 1971, were investigated. The rostellar hooks of both are of davaineoid type, which is quite uncommon for the family. The morphology of their rostellar apparatus, especially the form of proboscis, differs much. But when the rostellum is retracted, the crown of hooks is folded in the same manner: hooks tips assume anterior direction. The muscular system of rostellar apparatus and the transformation of scolex in the act of rostellum's retraction of Kowalewskiella finds close analogy in Aploparaksis (family Hymenolepididae s.l.), and of Himantaurus--in Paradilepis (family Dilepididae). But such morphological and functional resemblance between scoleces of Kowalewskiella and Aploparaksis from one side and of Himantaurus and Paradilepis from another is undoubtedly a result of convergence. The morphological types of rostellar hooks in these pairs of genera are very different.     

The genus Biuterina Fuhrmann, 1902 (Cestoda,Paruterinidae) in the Old World: redescriptions of four species from Afrotropical Passeriformes

Four species of Biuterina Fuhrmann, 1902 (Cestoda, Cyclophyllidea, Paruterinidae), originally described from Afrotropical passeriform birds, are redescribed and figured on the basis of their type-specimens. These are B. pentamyzos (Mettrick, 1960) from Prionops plumata (Laniidae) in Zimbabwe, B. quelea (Mettrick, 1963) from Quelea quelea (Ploceidae) in Zimbabwe, B. ugandae Baylis, 1919 from Chalcomitra senegalensis (Nectariniidae) in Uganda and B. zambiensis (Mettrick, 1960) from Campephaga flava (Campephagidae) in Zimbabwe. The rostellum of B. quelea is a spherical structure filled with strongly-developed glandular tissue and possessing a weak musculature. The remaining three species have a sucker-like rostellar apparatus with moderately developed glandular tissue in the rostellum and around it. It is considered that the glandular elements are an inherent part of the rostellar apparatus of the paruterinids. An armament consisting of fine, punctiform, spine-like structures arranged in transverse rows on the inner surface of suckers is observed in B. pentamyzos. This is the first record of sucker armature in the Paruterinidae.     

Fine structure of the salivary glands of Triatoma infestans (Hemiptera: Reduviidae)

The fine structure of the salivary glands of adult Triatoma infestans (Hemiptera: Reduviidae) bugs has been analyzed. Stereomicroscopy and scanning electron microscopy showed that each insect presents a pair of salivary glands, each pair containing three distinct units (main, supplementary, and accessory) with different sizes and colors. Transmission electron microscopy demonstrated that all gland units consist of a monolayer of epithelial cells surrounding a large central lumen. The gland units are enveloped by a thick basal lamina containing bundles of muscle cells. Microvilli are present at the apical plasma membrane domain of the gland cells, thus enlarging the available membrane area for saliva secretion towards the large gland lumen, although occasionally budding vesicles could be observed among the microvilli. Cytochemical analysis showed that the salivary gland cells of T. infestans present abundant endoplasmic reticulum profiles and several lipid droplets.     

Programmed cell death in the larval salivary glands of <Emphasis Type="Italic">Apis mellifera</Emphasis> (Hymenoptera,Apidae)

The morphological and histochemical features of degeneration in honeybee (Apis mellifera) salivary glands were investigated in 5th instar larvae and in the pre-pupal period. The distribution and activity patterns of acid phosphatase enzyme were also analysed. As a routine, the larval salivary glands were fixed and processed for light microscopy and transmission electron microscopy. Tissue sections were subsequently stained with haematoxylin-eosin, bromophenol blue, silver, or a variant of the critical electrolyte concentration (CEC) method. Ultrathin sections were contrasted with uranyl acetate and lead citrate. Glands were processed for the histochemical and cytochemical localization of acid phosphatase, as well as biochemical assay to detect its activity pattern. Acid phosphatase activity was histochemically detected in all the salivary glands analysed. The cytochemical results showed acid phosphatase in vesicles, Golgi apparatus and lysosomes during the secretory phase and, additionally, in autophagic structures and luminal secretion during the degenerative phase. These findings were in agreement with the biochemical assay. At the end of the 5th instar, the glandular cells had a vacuolated cytoplasm and pyknotic nuclei, and epithelial cells were shed into the glandular lumen. The transition phase from the 5th instar to the pre-pupal period was characterized by intense vacuolation of the basal cytoplasm and release of parts of the cytoplasm into the lumen by apical blebbing; these blebs contained cytoplasmic RNA, rough endoplasmic reticule and, occasionally, nuclear material. In the pre-pupal phase, the glandular epithelium showed progressive degeneration so that at the end of this phase only nuclei and remnants of the cytoplasm were observed. The nuclei were pyknotic, with peripheral chromatin and blebs. The gland remained in the haemolymph and was recycled during metamorphosis. The programmed cell death in this gland represented a morphological form intermediate between apoptosis and autophagy.     

Fine structure of the spiracular glands in larval Drosophila melanogaster (Meig.) (Diptera : Drosophilidae)

The spiracular glands in the third-instar larvae of Drosophila melanogaster (Diptera : Drosophilidae) were examined with light and electron microscopy. Three club-shaped, unicellular glands are associated with each spiracle. Each gland has a large nucleus with a well-developed nucleolus and polytene chromosomes. Cytoplasmic features include a prominent plasma membrane reticular system (PMRS), which contains electron-dense material and gives rise to endocytotic vesicles. Numerous lipid droplets, mitochondria, free ribosomes, glycogen, lysosomes, and vesicles are scattered throughout the cytoplasm. The smooth endoplasmic reticulum is abundant, but rough endoplasmic reticulum and Golgi complexes are sparse. Small lipid droplets appear to fuse with one another to form larger droplets. In late third-instar glands, normal mitochondria decrease in number; they appear to degenerate and become converted into dense bodies with finely granular interiors. Several microvillous channels containing lipid are present within the cytoplasm. In the lumina of most of these channels are found the distal tips of cuticular ductules. The cuticular ductules merge with one another dorsally to form the main duct that carries the lipoid secretion to the spiracle cleft. The ultrastructure of the spiracular glands is consistent with their roles in the synthesis of lipoid secretion, which is used to provide hydrophobicity of the surface and to trap small particulate matter.     

Autophagy facilitates secretion and protects against degeneration of the Harderian gland

The epithelial derived Harderian gland consists of 2 types of secretory cells. The more numerous type A cells are responsible for the secretion of lipid droplets, while type B cells produce dark granules of multilamellar bodies. The process of autophagy is constitutively active in the Harderian gland, as confirmed by our analysis of LC3 processing in GFP-LC3 transgenic mice. This process is compromised by epithelial deletion of Atg7. Morphologically, the Atg7 mutant glands are hypotrophic and degenerated, with highly vacuolated cells and pyknotic nuclei. The mutant glands accumulate lipid droplets coated with PLIN2 (perilipin 2) and contain deposits of cholesterol, ubiquitinated proteins, SQSTM1/p62 (sequestosome 1) positive aggregates and other metabolic products such as porphyrin. Immunofluorescence stainings show that distinct cells strongly aggregate both proteins and lipids. Electron microscopy of the Harderian glands reveals that its organized structure is compromised, and the presence of large intracellular lipid droplets and heterologous aggregates. We attribute the occurrence of large vacuoles to a malfunction in the formation of multilamellar bodies found in the less abundant type B Harderian gland cells. This defect causes the formation of large tertiary lysosomes of heterologous content and is accompanied by the generation of tight lamellar stacks of endoplasmic reticulum in a pseudo-crystalline form. To test the hypothesis that lipid and protein accumulation is the cause for the degeneration in autophagy-deficient Harderian glands, epithelial cells were treated with a combination of the proteasome inhibitor and free fatty acids, to induce aggregation of misfolded proteins and lipid accumulation, respectively. The results show that lipid accumulation indeed enhanced the toxicity of misfolded proteins and that this was even more pronounced in autophagy-deficient cells. Thus, we conclude autophagy controls protein and lipid catabolism and anabolism to facilitate bulk production of secretory vesicles of the Harderian gland.     

Autophagy facilitates secretion and protects against degeneration of the Harderian gland

The epithelial derived Harderian gland consists of 2 types of secretory cells. The more numerous type A cells are responsible for the secretion of lipid droplets, while type B cells produce dark granules of multilamellar bodies. The process of autophagy is constitutively active in the Harderian gland, as confirmed by our analysis of LC3 processing in GFP-LC3 transgenic mice. This process is compromised by epithelial deletion of Atg7. Morphologically, the Atg7 mutant glands are hypotrophic and degenerated, with highly vacuolated cells and pyknotic nuclei. The mutant glands accumulate lipid droplets coated with PLIN2 (perilipin 2) and contain deposits of cholesterol, ubiquitinated proteins, SQSTM1/p62 (sequestosome 1) positive aggregates and other metabolic products such as porphyrin. Immunofluorescence stainings show that distinct cells strongly aggregate both proteins and lipids. Electron microscopy of the Harderian glands reveals that its organized structure is compromised, and the presence of large intracellular lipid droplets and heterologous aggregates. We attribute the occurrence of large vacuoles to a malfunction in the formation of multilamellar bodies found in the less abundant type B Harderian gland cells. This defect causes the formation of large tertiary lysosomes of heterologous content and is accompanied by the generation of tight lamellar stacks of endoplasmic reticulum in a pseudo-crystalline form. To test the hypothesis that lipid and protein accumulation is the cause for the degeneration in autophagy-deficient Harderian glands, epithelial cells were treated with a combination of the proteasome inhibitor and free fatty acids, to induce aggregation of misfolded proteins and lipid accumulation, respectively. The results show that lipid accumulation indeed enhanced the toxicity of misfolded proteins and that this was even more pronounced in autophagy-deficient cells. Thus, we conclude autophagy controls protein and lipid catabolism and anabolism to facilitate bulk production of secretory vesicles of the Harderian gland.     

The structure and composition of aleurone grains in the barley aleurone layer

Summary Cytochemical methods have been used in conjunction with light and electron microscopy to determine the nature of the inclusions in aleurone grains of barley aleurone layers. Two kinds of inclusions were found: (1) Globoids within globoid cavities which were not enclosed by a membrane: the globoids stained red with toluidin blue due to the presence of phytin, and with lipid stains; (2) Protein-carbohydrate bodies which stained green with toluidin blue. The characteristics of globoids and protein-carbohydrate bodies as seen in the electron microscope are described in detail using both glutaraldehyde- and permanganatefixed tissues. The protein-carbohydrate body was identified by silver-hexaminestaining; this was not caused by carbohydrate but by some component which stained green in toluidin blue and which also occurred in cell walls in a thin band adjacent to the cytoplasm. The characteristics of both bodies are discussed in relation to apparent confusion in their identities in previous electron-microscope studies.     

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 epithelia of the protrusible tongue of Eurycea longicauda guttolineata (Hoolbrook 1838) (Urodela: Plethodontidae)

In this study the lingual and sublingual glands, the lingual stem and the epithelial surface of the protrusible secondary tongue were investigated by light, scanning and transmission electron microscopy. The quality of the secretions of the epithelia was characterized histochemically. The lingual epithelium is formed by superficial (pavement) and goblet cells and at the margin of the tongue pad are also regions covered by ciliated cells. On the dorsal part of the tongue there are goblet cells of type A with mainly acidic secretions and of type B containing neutral secretions. Most of the goblet cells on the ventral side of the tongue (hypoglottis) show a strong alcian blue/PAS positive reaction (type I) and some produce neutral secretions (type II). The glandular cells of the lingual gland react positively to alcian blue and PAS in the apical region of the gland. In contrast there is only alcian blue-positive staining in the basal part of the gland. The size and complexity of the inclusion bodies of the secretory granules increase in a basal direction. In addition, there are ciliated cells in the glandular epithelium. Although the epithelium of the lingual stem is thin, it is double-layered. The cell types observed in this region are identical to those of the ventral part of the protrusible tongue. At the margin of the sublingual gland are trough-like structures. In the center, tubular parts are observed. The cells of this gland are stain strongly with alcian blue (pH 1.0) mainly in the basal part of the gland. The results of this are compared to the tongue pad and the lingual gland of Salamandra salamandra and Ambystoma mexicanum.     

Ultrastructural cytochemistry of the sex pheromone glands of Lutzomyia cruzi male sand flies (Diptera: Psychodidae: Phlebotominae)

The sex pheromone glands of Lutzomyia cruzi male sand flies (Diptera: Psychodidae) were analyzed by cytochemical techniques. In adult males, the epithelium at the fourth abdominal tergite is modified into a glandular epithelium, with large columnar gland cells located side by side. The gland cell cytoplasm contains a large number of mitochondria and peroxisomes, the latter with positive (electron-dense) reaction for catalase, a typical peroxisomal enzyme marker. The gland cell cytoplasm also contains a central vacuolated area, with a large number of electron-lucent vacuoles, not limited by a unit membrane. In well-preserved preparations such vacuoles present a homogenous and slightly electron-dense content, typical of lipid droplets. Indeed, incubation of the tergites with imidazole-buffered osmium tetroxide (to detect lipids) resulted in positive reaction in these vacuoles, as well as in between the microvilli of the gland cells. Use of the osmium–potassium iodide (Os–KI) technique allowed to demonstrate the presence of several endoplasmic reticulum (ER) profiles, as expected in secretory cells. Our data suggest that ER, lipid droplets and peroxisomes are involved in the sand fly pheromone biosynthesis.     

Ultrastructural studies on the secretory cavities ofCitrus deliciosa ten. II. Development of the essential oil-accumulating central space of the gland and process of active secretion

Summary Oil glands ofCitrus deliciosa are multicellular secretory structures, globular to oval in shape, in the centre of which an essential oil-accumulating space is formed. Opening of this space begins from a single cell. It undergoes lysis which later extends to the neighbouring gland cells.Secretory material in form of droplets is produced in plastids, from where it is transported to the parietal cytoplasm of the secretory cells via numerous ER-elements. After fusion of the ER-membranes with the plasmalemma, the exudate reaches the apoplast, through which it is driven to the central cavity of the gland.Peripheral cells of the secretory complex are modified into a protective sheath with thick walls and large vacuoles, while their plastids are differentiated from leucoplasts into typical amyloplasts.     

CYTOLOGICAL ALTERATIONS RELATED TO STIMULATION OF THE ZONA GLOMERULOSA OF THE ADRENAL GLAND

The structure of the zona glomerulosa of the rat adrenal gland stimulated by sodium restriction has been studied by light and electron microscopy. The major changes observed during the course of the experiment in stimulated glands involve cytoplasmic droplets, mitochondria, and the endoplasmic reticulum. There is a progressive decrease in the number of cytoplasmic droplets of low electron opacity. Numerous, greatly elongated mitochondria containing parallel arrays of tubules are noted. These tubules extend from within the mitochondria through gaps in the mitochondrial-limiting membranes into the cytoplasm. In addition, amorphous intramitochondrial deposits, possibly aldosterone precursors, are seen. Increased amounts of smooth-surfaced endoplasmic reticulum, often showing complex arrangements, are another feature of the stimulated zona glomerulosa. Other alterations include the presence of large numbers of dense bodies as well as cytoplasmic droplets of high electron opacity. These observations are discussed in relation to the biosynthesis of aldosterone.     

Sex pheromone gland of the female European corn borer moth,Ostrinia nubilalis (Lepidoptera,Pyralidae): ultrastructural and biochemical evidences

The sex pheromone gland of the female European corn borer moth, Ostrinia nubilalis was studied using light and electron microscopy. The pheromone gland is formed by hypertrophied epidermal cells at the mid-dorsal region of the intersegmental membrane between abdominal segments 8 and 9/10. Active glandular cells contain extensive apical membrane foldings, a single nucleus, many free ribosomes, numerous mitochondria, microtubules and lipid droplets. Smooth endoplasmic reticulum is scanty. In young moths, the glandular cells are smaller in size, the microvilli at the apical membrane are poorly developed and the cytoplasm contains fewer mitochondria, microtubules, and no lipid droplets. The surrounding unmodified epidermal cells are small cuboidal or squamous cells. These cells have ill-defined apical membrane foldings and do not contain lipid droplets in the cytoplasm and the overlying cuticle. Fatty acids analyses revealed the presence of the sex pheromone components, (E)-11-tetradecenyl acetate, and their immediate precursors, methyl (E)-11- and methyl (Z)-11-tetradecenoate, only in the dorsal portion of the cylindrical intersegmental membrane. Results of the present study show that the sex pheromone gland of O. nubilalis is restricted to the dorsal aspect of the intersegmental membrane between segments 8-9/10 and is not a ring-gland.     

Anatomical and ultrastructural study of the secretory cavity development ofCitrus sinensis and Citrus limon: evaluation of schizolysigenous ontogeny

The ontogeny and ultrastructure of secretory oil glands in the fruits of Citrus sinensis and Citrus limon were studied with light and electron microscopy (TEM). Oil glands were initiated by cell division in globular/oval clusters of young meristematic cells under or including also the epidermis. Successively, the central oil cells increased greatly in size by growth and coalescence of one or more vacuoles. Starting from these cells the oil cavity formation and enlargment occurred by schizogenous and lysigenous precesses which overlap one another. The separation of the cell walls, in both Citrus species, was accompanied by strong structural disorganization of the cytoplasm, loss of nuclei, plasmolysis, and followed by autolysis processes. Prior these changes a great quantity of oil droplets filled the cells. In Citrus sinensis this material was formed in the plastids; on the contrary, in Citrus limon oil droplets appeared only in the cytoplasm, and no connection with the plastids was observed. The processes of schizogeny and lysigeny occurred in a centrifugal direction. The peripheral oil chamber cells were so pushed outward and flattened with the progressive expansion of the gland cavity. Also these cells became vacuolated, showed schizogenous processes together with cytoplasm and nuclei breakdown. These cell modifications were preceded by an abundant essential oil synthesis. Electron dense material appeared in the cavity near the boundary cells. Among the cell layers surrounding the cavity, the outer peripheral cells showed very thick walls. These cells, probably, had a protective function, while the inner cells continued, at least in part, to produce and secrete oil compounds. In the two Citrus species the pattern of oil gland development was practically the same, except the different plastid behaviour.     

The development and fine structure of ultimobranchial glands in larval anurans

A comparative optical microscopic and ultrastructural study on the ultimobranchial (UB) glands of three common species of Israeli anurans: Bufo viridis, Hyla arborea, and Rana ridibunda during metamorphosis is presented. The UB glands typically consist of a single follicle with a central lumen, though occasionally secondary follicles are present in Hyla and Rana. A single UB cell type is found which appears either in a very electron-dense "dark" form or as a less dense "light" form, though the ratio of dark: light cells from gland to gland at any one stage of metamorphic development is quite variable. By the end of metamorphosis in Bufo and Hyla all the UB cells are usually of the light variety, whereas in Rana the dark cells persist. The organelles of these secretory cells including secretory granules, granular endoplasmic reticulum, free ribosomes, tonofilaments, microtubules, Golgi bodies, and lipid droplets, their distribution, abundance, and possible functions in relation to metamorphosis are described. Apocrine secretion into the central lumen of the gland is also described and discussed.     

Ultrastructural differentiation of glandular stomach (proventriculus) in chick embryo

Cytochemical characterization of mucosubstances of chick glanular stomach (proventriculus) changes from 15 days of development to postnatal and adult stages was studied. To corroborate these data cytochemical, ultrastructural and ultracytochemical study of chick embryo proventriculus from 7 to 20 days of development was performed. At the 7th day several layers of undifferentiated cells formed an epithelium which covered the walls of the glandular stomach. Mocosubstances were not found. Between the 9th and 5th day a single layer of cylindrical cells was encountered forming invaginations which originated deep glands. Three types of cells were separated from the above mentioned layer, dark, clear and undifferentiated. The dark cells had organelles which are involved in protein synthesis and the clear ones were rich in mitochondria. Argentaffine cells appeared at 15th day instead mucosubstances formed a thin coat on the epithelium at 9th day which increased at the end of development in the apical cytoplasm and gland cells. These observations demonstrate that proventriculus of chick embryo has ultrastructurally differentiated cells involved with enzymatic and hydrochloric acid secretion after the 9th day. These progressive events are correlated with the digestion process of yolk during embryogenesis. At the end of development the proventriculus has completely organized the glandular layer.