Some evidence for the ampullary organs in the European cave salamander Proteus anguinus (Urodela,Amphibia)

Summary The multicellular epithelial organs in Proteus anguinus, which Bugnion (1873) assumed to be developing neuromasts, have been analyzed by lightand electron-microscopy. Their fundamental structure consists of single ampullae with sensory and accessory cells with apical parts that extend into the pit of the ampulla, and of a short jelly-filled canal connecting the ampulla pit with the surface of the skin. The organs are located intra-epithelially and are supported by a tiny dermal papilla. The cell elements of sensory epithelium are apically linked together by tight junctions. The free apical surface of the sensory cell bears several hundred densely packed stereocilia-like microvilli whereas the basal surface displays afferent neurosensory junctions with a pronounced round synaptic body. The compact uniform organization of the apical microvillous part shows a hexagonal pattern. A basal body was found in some sensory cells whereas a kinocilium was observed only in a single cell. The accessory cells have their free surface differentiated in a sparsely distributed and frequently-forked microvilli. The canal wall is built of two or three layers of tightly coalescent flat cells bordering on the lumen with branching microvilli. The ultrastructure of the content of the ampulla pit is presented.In the discussion stress is laid on the peculiarities of the natural history of Proteus anguinus that support the view that the morphologically-identified ampullary organs are electroreceptive. The structural characteristics of ampullary receptor cells are dealt with from the viewpoint of functional morphology and in the light of evolutionary hypotheses of ampullary organs.     

The ultrastructure of Sorubim lima (Teleostei, Siluriformes, Pimelodidae) spermatogenesis: premeiotic and meiotic periods

The ultrastructure of Sorubim lima spermatogenesis during the premeiotic and meiotic periods was studied. Our observations showed that the germ cells in the cysts are connected by cytoplasmic bridges and the mitotic and meiotic divisions are slightly asynchronous. The first and the last spermatogonial generations differ in the cellular and nuclear volume, nucleolus, chromatin condensation, distribution, size, density, and shape of the mitochondria, presence of 'lamellae anulata', amount and dimension of the 'nuages', and movement of the centrioles. In addition to the nuclear prophase structures, the spermatocyte I shows changes in all other cellular organelles and elongated vesicles appear in the cytoplasm. The accentuated cytoplasmic density and thickened walled vesicles are morphological characteristics that differentiate spermatocytes II from the other germ cells in the cysts of Sorubim lima testis.     

Ultrastructure of presumptive light sensitive ciliary organs in larvae of Poecilochaetidae,Trochochaetidae, Spionidae,Magelonidae (Annelida) and its phylogenetic significance

Larvae of Poecilochaetus serpens, Trochochaeta multisetosum and Polydora ciliata possess almost identical unpigmented, ciliary, presumptive light sensitive organs within the prostomium. The data corroborate hypotheses on the close relationship of Poecilochaetidae, Trochochaetidae and Spionidae and are even congruent with inclusion of Poecilochaetidae and Trochochaetidae within Spionidae. The organs in P. serpens, T. multisetosum and P. ciliata are composed of one monociliary receptor cell, one supportive cell and several associated flask shaped bipolar sensory cells. The receptor cell cilium enters the supportive cell cavity through a thin pore, dilates and then branches into a high number of disordered projections. The associated sensory cells bear one or occasionally two cilia, which run horizontally beneath or within the cuticle. The supportive cell cavity is not sealed by any cell contact from the subcuticular extracellular space. The organs in Magelona mirabilis are composed of a single supportive cell, but several receptor cells. No further sensory cells are associated. Each receptor cell sends one cilium into an own invagination of the supportive cell, and the ciliary branches are highly ordered. The examined organs in P. serpens, T. multisetosum and P. ciliata exhibit a unique organization amongst polychaetes. The organs of M. mirabilis are most probably homologous. A homology to ciliary organs of Protodrilida is conceivable. In the lineage leading to Protodrilida, primary larval organs may have been integrated into the adult body organization by heterochrony.     

Fine structure of the secretory and sensory organs on the cephalon and the first pereionite of Trichoniscus alexandrae Caruso (Crustacea, Isopoda)

Trichoniscus alexandrae Caruso is a blind troglobiont isopod; males possess secretory and sensory organs on the cephalon and 1st pereionite consisting of cuticular pits hosting a tuft of setae and gland openings. Such organs are absent in females. Three types of cuticular structures have been observed: (a) lamellar setae, which likely play a role in protecting the gland openings and favouring the evaporation of secretions; (b) contact chemoreceptors, each provided with six bipolar sensory cells, a scolopale cell and enveloping cells; (c) a secretory cell complex, consisting of a long cylindrical slender duct-forming cell, with the function of transporting to the cuticular surface a secretion produced by two deeper secretory cells. The duct-forming cell is characterized by the presence of numerous microtubules in its cytoplasm, and is provided with a flattened duct. It is suggested that the secretion produced by the secretory cells could serve for sex-recognition.     

Sense organs in polychaetes (Annelida)

Polychaetes possess a wide range of sensory structures. These form sense organs of several kinds, including the appendages of the head region (palps, antennae, tentacular cirri), the appendages of the trunk region and pygidium (parapodial and pygidial cirri), the nuchal organs, the dorsal organs, the lateral organs, the eyes, the photoreceptor-like sense organs, the statocysts, various kinds of pharyngeal papillae as well as structurally peculiar sensory organs of still unknown function and the apical organs of trochophore larvae. Moreover, isolated or clustered sensory cells not obviously associated with other cell types are distributed all over the body. Whereas nuchal organs are typical for polychaetes and are lacking only in a few species, all other kinds of sensory organs are restricted to certain groups of taxa or species. Some have only been described in single species till now. Sensory cells are generally bipolar sensory cells and their cell bodies are either located peripherally within the epidermis or within the central nervous system. These sensory cells are usually ciliated and different types can be disinguished. Structure, function and phylogenetic importance of the sensory structures observed in polychaetes so far are reviewed. For evaluation of the relationships of the higher taxa in Annelida palps, nuchal organs and pigmented ocelli appear to be of special importance.     

The functional and structural border between the CSF-and blood-milieu in the circumventricular organs (organum vasculosum laminae terminalis,subfornical organ,area postrema) of the rat

Summary The present study continues a previous investigation on the median eminence (EM) (Krisch et al., 1978). In rats with high levels of neurohormones (LHRH, vasopressin) a limited immunohistochemical labeling of perivascular tanycyte processes can be observed surrounding capillaries in the marginal region of the organum vasculosum laminae terminalis (OVLT) and in the inner part of the subfornical organ (SFO). This labeling extends from the perivascular space a short distance along the tanycyte processes. By conventional electron microscopy and by freeze-etching, tight junctions are demonstrated at a distance from the capillary lumen which corresponds to the borderline of the immunohistochemical labeling of perivascular tanycyte processes in light microscopic preparations. The tight junctions are arranged in several parallel and helical rows and correspond to those found in the median eminence. Consequently, the immunohistochemical labeling in the OVLT and in the SFO marks the intercellular cleft. In the circumventricular organs the immunostaining labels the extension of the perivascular space characterized by the hemal milieu. The perivascular space is separated off by tight junctions from the CSF-milieu of the adjacent neuropil. Furthermore, the present study demonstrates tight junctions in the marginal region of the area postrema (AP) between the perivascular processes of the tanycytes.Supported by the Deutsche Forschungsgemeinschaft (Grant Nr. Kr. 569/2) and Stiftung VolkswagenwerkThe skillful technical assistance of Miss K. Bielenberg, Mrs. A. Hinz and Mrs. Helga Prien is thankfully acknowledged     

Age and growth of the duckbill catfish (Sorubim cf. lima) in the Pantanal.

The Duckbill Catfish, Sorubim lima, is a predator of large South American rivers. The age and growth of S. lima were studied based on the pectoral fin-spines of samples collected from the Cuiabá River, Pantanal. The samples were taken from commercial and experimental hook-and-line fishing. An analysis of the marginal increment suggests that the growth rings are formed once a year during the dry season, from July to September (ANOVA type I: F = 4.183; g.l. = 3 and 104; p = 0.008). The estimate of the parameters that describe von Bertalanffy's growth curve by nonlinear regression of the observed lengths in the age were: L infinity = 56.0 cm (fork length); k = 0.245 year-1; to = -2.605 years. The animals were estimated to have a life span of 9.6 years. The findings indicate that the fork length is a good predictor of the age of individuals of this fish species.     

Fine structure of the sensilla of Peripatopsis moseleyi (Onychophora)

Summary Three types of sensilla occurring on the lips and on the antennae of Peripatopsis moseleyi have been investigated by scanning and transmission electron microscopy. On the lips sensory spines can be found which contain numerous cilia originating from bipolar receptor cells. They reach the tip of the spine where the cuticle is modified. The perikarya of the sensory cells, a large supporting cell with a complicated surface and a second type of receptor, form a bud-like structure and are surrounded by a layer of collagen fibrils. The second receptor cell bears apical stereocilia as well as a kinocilium which are directed towards the centre of the animal — thus the cell appears to be turned upside down. The sensilla of the antennae are 1) sensory bristles containing two or three kinds of receptor cells, one of which bears an apical cilium and one kind of supportive cell and 2) sensory bulbs located within furrows consisting of receptor cells with branched cilia and two kinds of supportive cells which are covered by a modified thin cuticle. According to the electron microscopical findings the sensory spines on the lips are presumably chemoreceptors. The sensory bristles on the antennae can be regarded as mechanoreceptors and the sensory bulbs as chemoreceptors.Supported by the Deutsche Forschungsgemeinschaft (Sto 75/3)     

Ultrastructure of the taste disc in the red-bellied toad Bombina orientalis (Discoglossidae,Salientia)

The taste disc of the red-bellied toad Bombina orientalis (Discoglossidae) has been investigated by light and electron microscopy and compared with that of Rana pipiens (Ranidae). Unlike the frog, B. orientalis possesses a disc-shaped tongue that cannot be ejected for capture of prey. The taste discs are located on the top of fungiform papillae. They are smaller than those in Ranidae, and are not surrounded by a ring of ciliated cells. Ultrastructurally, five types of cells can be identified (mucus cells, wing cells, sensory cells, and both Merkel cell-like basal cells and undifferentiated basal cells). Mucus cells are the main secretory cells of the taste disc and occupy most of the surface area. Their basal processes do not synapse on nerve fibers. Wing cells have sheet-like apical processes and envelop the mucus cells. They contain lysosomes and multivesicular bodies. Two types of sensory cells reach the surface of the taste disc; apically, they are distinguished by either a brush-like arrangement of microvilli or a rod-like protrusion. They are invaginated into lateral folds of mucus cells and wing cells. In contrast to the situation in R. pipiens, sensory cells of B. orientalis do not contain dark secretory granules in the perinuclear region. Synaptic connections occur between sensory cells (presynaptic sites) and nerve fibers. Merkel cell-like basal cells do not synapse onto sensory cells, but synapse-like connections exist between Merkel cell-like basal cells (presynaptic site) and nerve fibers.     

Collar cells in planula and adult tentacle ectoderm of the solitary coral Balanophyllia regia (anthozoa eupsammiidae)

Summary The planula larva of the solitary coral Balanophyllia regia has an ectoderm of flagellate, diplosomal collar cells. The collar of these cells is composed of a ring of microvilli linked with mucus strands. Four types of flagellate gland cells, three types of nematocyst and spirocysts are present in the planula ectoderm. The function of these ectoderm cells is discussed. The mesogloeal muscular and packing tissues of the planula are briefly described. The tentacle of the adult coral, examined for comparison, has an ectoderm of flattened flagellate cells with a shallow collar. Collar cells similar to those of the planula are occasionally found on the tentacle and their function is not known. Independent sensory cells built on a modified collar cell plan with collar of thickened microvilli are common in the tentacle. These are quite separate from the three kinds of tentacular nematocyte. Distended glandular areas occur in the tentacle ectoderm. The flagellate tentacle gastrodermis, muscle and mesogloeal region are briefly described. The evolutionary significance of collar cell ectoderm in a planula is discussed and the occurrence of collar cells throughout the animal kingdom, reviewed.I am most grateful to Paul Tranter of the Plymouth Laboratory for providing material and to Gareth Morgan for assistance with electron microscopy.     

The epithelium of the middle ear in the guinea pig

Summary An electron microscopic study of aldehyde and osmium fixed normal guinea pig middle ear epithelium was made. Numerous branching microvilli occur between the cilia of the ciliated cells. The granules of the secretory cells are always surrounded by a membrane, and they vary in their content of electron dense substance. Half desmosomes are frequent in basal cells. The squamous epithelial cells of the bulla contain few microvilli and pinocytoric invaginations. In the basal part of the squamous epithelium dilations of the intercellular clefts often occur. The luminal part of the intercellular clefts are closed by multiple tight junctions.     

Distribution and morphology of the ampullary organs of the estuarine long-tailed catfish, <Emphasis Type="Italic">Euristhmus lepturus</Emphasis> (Plotosidae,Siluriformes)

Ampullary organs of Euristhmus lepturus occur in high densities along the head and in four parallel pathways along the trunk of the body. Large ampullary pores (125–130 μm) are easily distinguishable from other sensory epithelial pores due to the differences in size and the presence of a collar-like structure. Simple, singular ampullary organs of the head region consist of an ampullary pore connected to a long canal with a diameter of 115–175 μm before terminating as a simple ampulla with an external diameter of 390–480 μm. The ampullary canal is composed of 1–2 layers of flattened squamous epithelial cells, the basement membrane and an interlocking collagen sheath. The innermost cells lining the canal wall are adjoined via tight junctions and numerous desmosomes, as are those of the receptor and supportive cells. Canal wall tissue gives rise to a sensory epithelium containing between 242 and 285 total receptor cells, with an average diameter of 11.7 ± 5.3 μm, intermixed with medially nucleated supportive cells. Each receptor cell (21.38 ± 4.41 μm, height) has an apically positioned nucleus and a luminal surface covered with numerous microvilli. Neural terminals abut the basal region of receptor cells opposite multiple presynaptic bodies and dense mitochondria. Supportive cells extend from the ampullary lumen to the basement membrane, which is adjacent to the complex system of collagen fibres.     

A blood-aqueous barrier to small molecules in the ciliary processes of the vervet monkey (Cercopithecus aethiops)

Summary Sectors of anterior segments of vervet eyes were exposed to solutions of different osmolarities (Cercopithecus aethiops). After hypertonic incubation followed by isotonic fixation, as well as after fixation directly in hypertonic fixative, the ciliary epithelium showed constant changes. These changes consisted of a shrinkage pattern with dilations of intercellular clefts in the superficial region of the epithelium, whereas no dilations occurred in the basal layer. The basal junctional complex of the superficial cell layer was always intact. The detailed structure of this complex is described. The conclusion is drawn that it functions as a barrier to the molecules of the solutes in question, and that it may also have this function in vivo with regard to molecules of similar size.     

Seasonal changes in the fine structure of the accessory sex gland in the mole (Talpa europaea)

The mole has a single pair of accessory sex organs with features of both the prostate and the seminal vesicle, for which the term prostate gland is not appropriate. Seasonal changes occuring in this gland were related to four periods: a) the quiescence period, b) the maturation period, c) the active period and d) the involution period. During the quiescence period the cuboidal epithelial cells display a quasi-embryonic fine structure and are sparse in cytoplasmic organelles, but rich in glycogen and lipopigment. With the onset of sexual activity glycogen and lipopigment disappear and the rough endoplasmic reticulum as well as the Golgi apparatus begin to proliferate. The fully active gland is lined by a low epithelium with parallel stacks of rough endoplasmic reticulum, a large Golgi apparatus and several lysosomes and secretory granules. In the involution period the gland collapses and the epithelial cells are eliminated by hetero- and autophagic processes. During this period a great number of presumably endocrine cells were observed. The results were compared with findings in experimental studies and those on postnatal development of accessory sex glands in laboratory animals.     

Blasenzellen im Bindegewebe des Schlundrings von Cepaea nemoralis L. (Gastropoda,Stylommatophora)

Zusammenfassung Die Blasenzellen stellen ein typisches Zellelement im Bindegewebe der Gastropoden dar. Licht- und elektronenmikroskopische Untersuchungen an Cepaea nemoralis haben gezeigt, daß der größte Teil einer Blasenzelle mit einer veränderlichen Glykogenmenge angefüllt ist. Diese zentrale Glykogenansammlung verdrängt das Zytoplasma mit seinen Organellen auf den peripheren Bereich der Zelle einschließlich der Zellausläufer und einen schmalen Saum um den Zellkern. Das wichtigste Identifizierungs-merkmal der Blasenzelle ist eine sehr spezialisierte — hier als Spaltenapparat bezeichnete — Oberflächendifferenzierung. Die Auswertung von Serienschnitten hat gezeigt, daß diese Oberflächenstruktur durch eine zum Teil verzweigte Invagination des extrazellulären Raumes gebildet wird, die wiederum von der Blasenzelle durch eine mäanderförmig unterbrochene Platte abgedeckt ist. Zwischen dem Spaltenapparat der Blasenzellen und dem Reusenapparat der Podozyten der Niere scheint eine Ähnlichkeit zu bestehen.

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Globular cells of the ganglionic connective tissue sheath of Cepaea nemoralis L. (Gastropoda, Stylommatophora)I. The ultrastructure of the cells

Summary The globular cells are typical elements of the connective tissue of Gastropods. Light- and electronmicroscopic investigations of Cepaea nemoralis have shown, that these cells are filled with variable contents of glycogen, accumulated in the centre of the cell. This crowds the cytoplasm and the cell organelles into the peripheral area, including the cell processes and a narrow band surrounding the nucleus. The typical element of the globular cell is a special differentiation of the cell surface, the so-called Spaltenapparat. The three-dimensional organisation of the Spaltenapparat has been analysed by serial ultrathin sections. The reconstruction shows, that the Spaltenapparat consists of numerous branched invaginations of the extracellular space covered by very small, winding cell processes; there are tiny clefts between them. There appears to be some similarity between the Spaltenapparat of the globular cells and the pedicels of the podocytes of the renal glomerulus.

Frau Prof. Dr. A. Nolte danke ich für anregende Diskussion, Frau R. Dingerdissen und Herrn Dr. Kappert für technische Hilfe.     

Apical protuberances of supporting cells in the regio olfactoria of the mole,Talpa europaea,Linnaeus, 1758 (Insectivora,Talpidae)

Summary The regio olfactoria of the mole, Talpa europaea, was studied by scanning and transmission electron microscopy. Peculiar structural differentiations, i.e. ovoid-shaped, balloon-like protuberances were found on the surface of the supporting cells. The apical portion of these protuberances contained finely dispersed granular material, whereas in their central part vesicular extensions of the smooth endoplasmic reticulum were observed.     

An immunocytochemical and electron-microscopical study of endocrine cells in the gut and pancreas of a stomachless teleost fish,Barbus conchonius (Cyprinidae)

Summary Four immunoreactive endocrine cell types can be distinguished in the pancreatic islets of B. conchonius: insulin-producing B cells, somatostatin-producing A₁ (= D) cells, glucagon-producing A₂ cells and pancreatic poly-peptide-producing PP cells. The principal islet of this species contains only a few PP cells, while many PP cells are present in the smaller islets. Except for the B cell all pancreatic endocrine cell types are also present in the pancreatic duct.At least six enteroendocrine cell types are present in the gut of B. conchonius: 1. a cell type (I) with small secretory granules, present throughout the intestine, and possibly involved in the regulation of gut motility; 2. a C-terminal gastrin immunoreactive cell, probably producing a caerulein-like peptide; these cells are located at the upper parts of the folds, especially in the proximal part of the intestinal bulb; 3. a met-enkephalin-immunoreactive cell, present throughout the first segment; 4. a glucagon-immunoreactive cell, which is rare in the first segment; 5. a PP-immunoreactive cell, mainly present in the first half of the first segment; 6. an immunoreactive cell, which cannot at present be specified, located in the intestinal bulb. The latter four cell types are mostly located in the basal parts of the folds, although some PP-immunoreactive cells can also be found in the upper parts.Most if not all enteroendocrine cells are of the open type. The possible functions of all enteroendocrine cell types are discussed.Abbreviations BPP bovine pancreatic polypeptide - CCK cholecystokinin - GEP gastro-entero-pancreatic - GIP gastric inhibitory peptide or glucose-dependent insulin releasing peptide - PPP pig pancreatic polypeptide - VIP vasoactive intestinal polypeptide     

Electron microscopic investigation of synaptic organization of the trochlear nucleus in cat

Summary Two distinct types of neuron in the cat trochlear nucleus (one large, one small) are described, the - and -motoneurons, respectively. Four types of terminals are observed which establish axo-dendritic synapses. Two of them (Types I and II) perform axo-somatic synapses as well. Terminals en passant (Types I and II) are predominant. The Type I terminal is long and slender with a characteristic distribution of the axoplasmic organelles and the unique feature of a relative narrowing of the synaptic cleft as compared to the width of the neighboring extracellular space. Its vesicle population is pleomorphic and a conspicuous glial barrier surrounds the synaptic zones. The Type II terminal differs slightly from Type I, revealing a wider synaptic cleft and lacking a characteristic distribution of the axoplasmic organelles. The type III terminal is rarely observed performing axo-somatic synapses, but is a common finding in the neuropil. Post-junctional dense bodies are often present in its axodendritic synapses. The Type IV nerve terminal performs axo-dendritic synapses and is characterized by a rich content of large granulated vesicles. Axo-axonal synapses are observed only very rarely.The synaptic organization of the feline trochlear nucleus is compared with the synaptic morphology of the oculomotor nuclei of inframammalian species (Waxman and Pappas, 1971). In addition to certain similarities (e.g., richness of synapses en passant), significant differences are encountered: the present study provides no morphological evidence for electrotonic transmission in the trochlear nucleus of cat.Preliminary report made at the Annual German Jahresversammlung der Anatomischen Gesellschaft, Lausanne, Switzerland, 1973.The authors wish to thank Professor R. Hassler for his valuable discussion. — Dr. W. B. Choi is on leave from the Department of Anatomy, Catholic Medical School, Seoul, Korea.     

The distribution of noradrenergic nerves and small,intensely fluorescent (SIF) cells in the cat urinary bladder

Summary Fluorescence and electron microscopy have been used to study the distribution of noradrenergic nerves in the smooth muscle of the cat urinary bladder. Using the former technique, relatively few fluorescent noradrenergic nerves were observed in the body and fundus, while a rich plexus occurred adjacent to muscle cells of the bladder neck. The trigone could not be distinguished neuromorphologically from detrusor muscle in this region. Electron microscopy showed that the majority of noradrenergic terminals in the body and fundus were associated with presumptive cholinergic axons, while in the bladder neck noradrenergic terminals formed typical neuroeffector relationships with individual smooth muscle cells.Numerous ganglia occurred both in the adventitia and among the smooth muscle bundles, particularly in the bladder neck. The majority of the nerve cell bodies were non-fluorescent, although many contained bright orange autofluorescent granules, believed to be lysosomes. A small minority of ganglion cells were associated with fluorescent noradrenergic nerve terminals, thereby providing structural evidence for limited intraganglionic inhibition. In addition, occasional groups of small intensely fluorescent (SIF) cells were observed in some intramural ganglia and these were subsequently identified in the electron microscope. The possibility that these cells may provide a second inhibitory influence on bladder activity was considered.