Apical Cilia Research Articles

Isolation and culture of epithelial cells from rat ductuli efferentes and initial segment epididymidis

To improve the study of epithelial function in rat ductuli efferentes (efferent ductules) and initial segment epididymis, we developed a primary cell culture system with modifications of the Klinefelter method (1992). The cultured efferent ductal epithelium was grown to confluence and the cells maintained many of the organelles characteristic of these cells in vivo, including dense-staining granules, indented nuclei and apical cilia. Ciliary beat was observed for up to 10 days in culture. Cultured initial segment epithelial cells were elongated and characterized by apical branched microvilli. Electron microscopy revealed intact cell junctions, an endocytotic apparatus and lysosomal granules. Ultrastructurally, the initial segment epithelium contained a well developed Golgi apparatus. For both epithelia, cell characteristics were also confirmed by indirect immunofluorescent staining for cytokeratins 8, 18. Endocytotic activity was detected by the uptake of cationic ferritin at the apical surface and within vesicles. Estrogen receptor and clusterin mRNAs were expressed in the cultured epithelia and no difference was found in their expressions when cultured with or without 10 −9 17-β estradiol. Indirect immunofluorescent staining for clusterin further indicated that this protein was present in the cultures. In conclusion, these in vitro methods will be useful for the investigation of epithelial function in the head of the epididymis.

Ultrastructure of neurons and synapses in the tentacle gastrodermis of the sea anemone Calliactis parasitica.

Little is known about gastrodermal neurons and synapses in the tentacles of sea anemones. Using transmission electron microscopy of serial thin sections of Calliactis parasitica, we have identified both a sensory cell and a ganglion cell with granular vesicles originating from the Golgi complex and have identified four types of synapses in the tentacular gastrodermal nerve plexus. The sensory cell has a recessed apical cilium with a basal body and a perpendicularly oriented centriole, below which are several strands of striated rootlets surrounded by mitochondria. The ganglion cell lacks a cilium and resembles a bipolar neuron, with oppositely directed processes lying parallel to the basally located circular smooth muscle. Both one-way and two-way interneuronal synapses are present with 60- to 90-nm granular vesicles of various densities aligned at the paired electron-dense membranes and fine cross filaments in the intervening 13-nm cleft. Two types of neuroeffector synapses have been located. Dense granular vesicles are present at neuromuscular synapses, whereas less dense vesicles are present at neuroglandular synapses. Most of the synaptic vesicles range from 60 to 120 nm in diameter. Two types of nerve cells and a variety of synaptic loci provide morphological substrates for the spontaneous SS2 conduction pulses in the tentacular gastrodermis of C. parasitica. J Morphol 231:217-223, 1997. © 1997 Wiley-Liss, Inc.

Centripetal transport of herpes simplex virus in human retinal pigment epithelial cells in vitro

Herpes simplex virus displays tropism for neurons and other polarized epithelial cells. We have grown human retinal pigment epithelial cells in culture to study potential mechanisms whereby herpes simplex virus (type I) is transported from the plasma membrane of the cell to the nucleus. The cells were highly polarized as determined by a variety of criteria. They were tightly coupled by junctional complexes, as determined by electron microscopy, immunofluorescent staining of tight junctions and measurements of transepithelial electrical resistances > 200 omega cm2. Immunofluorescence and confocal microscopy were used to visualize microtubule orientation. The microtubules were arranged (i) in a single apical cilium, (ii) in a meshwork beneath the apical membrane and (iii) in longitudinally arranged bundles near the lateral membranes and nucleus. The latter microtubules were primarily oriented with their plus ends directed toward the basal surface of the cells. We infected retinal pigment epithelial cells at the apical surface with virus and assayed the uptake and transport of virus to the nucleus by quantitative immunoblot and immunocytochemical staining for the viral immediate early gene product, infected cell protein 4. The antigen first appeared in retinal pigment epithelial cells 2 h after infection. Treatment of the cells with 33 microM nocodazole, a microtubule-destabilizing drug, delayed the appearance of the viral antigen by 1 h. The effect of nocodazole treatment on microtubule integrity was confirmed by immunofluorescent staining and immunoblots of tubulin. Both cytoplasmic dynein and the ubiquitous form of kinesin were identified in the cells using immunoblots. These novel data indicate that human retinal pigment epithelial cells, like neurons, are susceptible to infection by herpes simplex virus and that the centripetal transport of virus to the nucleus in both cell types is facilitated by microtubules. The orientation of microtubules in retinal pigment epithelial cells suggests that the transport of herpes simplex virus from the apical surface is mediated by a microtubule-activated motor enzyme, possibly kinesin.

Classification of Nerve Cells Dissociated From Tentacles of the Sea Anemone Calliactis parasitica.

Nerve cells from tentacles of the sea anemone Calliactis parasitica were dissociated in 1000 units/ml of collagenase for scanning electron microscopic studies and in 0.125% elastase followed by 12 units/ml of ficin for cell counts using light microscopy. The studies revealed 33 distinguishable neuronal shapes, which were categorized as either sensory cells having an apical cilium or ganglion cells with or without a perikaryal cilium and further subdivided into unipolar, bipolar and multipolar neurons based on the number of processes that extended from the perikaryon. Unipolar sensory cells were characterized by an apical cilium adjacent to the perikaryon and a long, simple or terminally branched axon. Unipolar ganglion cells lacked an apical cilium. Bipolar sensory cells had a neck between the cilium and perikaryon and an oppositely directed axon. Bipolar ganglion cells had isopolar processes or asymmetrical processes, which were simple or complexly branched. One type of bipolar ganglion cell with isopolar processes had a perikaryal cilium. Multipolar sensory cells had a distinct neck between the perikaryon and the cilium and two or more simple or complexly branched processes extending from the triangularly shaped cell body. Multipolar ganglion cells had variously shaped perikarya from which extended three or more short or long processes that were simple or complexly branched. One type of tripolar ganglion cell had a perikaryal cilium. The different types of nerve cells were quantified, and statistical comparisons were made.

Scanning and Transmission Electron Microscopic Analysis of the Introvert of Priapulopsis australis and Priapulopsis bicaudatus (Priapulida)

The introvert of Priapulopsis australis and P. bicaudatus was investigated by scanning and transmission electron microscopy. The scalids, clustered normally in groups of 5 and arranged in 25 longitudinal rows, differ slightly between the two species. All scalids are sensilla containing three kinds of bipolar sensory cells with apical cilia. The cilia of one cell type reach the surface through cuticular tubules. The cilia of the other two receptor cell types are surrounded by 7 stereovilli and lie entirely beneath the cuticle. What previously was considered to be the first ring of pharyngeal teeth in P. australis may be seen by scanning electron microscopy to be a series of 10 conical sensilla. This condition may be derived by reduction from 5 pairs of teeth as found in P. bicaudatus. In turn, each pair of first-ring pharyngeal teeth in P. bicaudatus may have arisen by reduction of the median cusp of each of the 5 teeth in an ancestor, leaving two halves. Additional key words: ultrastructure, sensory receptors The phylum Priapulida is a small group of benthic marine worms comprising only 8 macrobenthic and 9 meiobenthic extant species (Higgins et al. 1993). However, it is of great scientific interest because these species are the last remnants of a fauna that was prominent in Cambrian Seas. The first species described from the Middle Cambrian was Ottoia prolifica Walcott 1911, which dominated the soft-bodied fauna of the Burgess Shale (British Columbia, Canada). Since 1911, several additional genera have been found in the Burgess Shale, in other parts of North America, and in China. The most common representative among the fossils of the Chengjiang fauna, which is found in Yunnan in southwestern China and dates back to the Lower Cambrian, is another priapulid, Maotianshania cylindrica Sun & Hou 1987. During the time-span between the Lower Cambrian (Chengjiang) and the Middle Cambrian (Burgess Shale), evolution seems to have produced little change (see Hou & Sun 1988; Chen et al. 1989, 1991). One biologically and taxonomically important character of the Priapulida is the introvert, the anterior pora Present address: Robert P. Higgins, 2 Pond Lane, Asheville, North Carolina 28804, USA. tion of the body which, when rhythmically everted from and withdrawn into the trunk, performs a locomotory function (Elder & Hunter 1980). The introvert is equipped with 20 or 25 longitudinal rows of scalids; priapulid genera differ in the number, morphology, and arrangement of scalids and in other cuticular structures. Scanning and transmission electron microscopic findings are available for the meiobenthic genera Tubiluchus (see Storch & Alberti 1985; Higgins & Storch 1989) and Meiopriapulus (see Storch et al. 1989), and the macrobenthic genera Halicryptus (see Storch et al. 1990; Storch & Higgins 1991) and Priapulus (see Higgins et al. 1993; Storch et al. 1994). These investigations have shown that in larval and adult Tubiluchus and Halicryptus, and in larval Priapulus, all scalids are sensilla. At the same time, however, these structures gain purchase on the substrate through which the animal is burrowing and thereby have both mechanical and sensory roles. By contrast, the majority of scalids on the introvert of Meiopriapulus fijiensis Morse 1981 (the so-called locomotory scalids) are merely cuticular specializations. In this species, only the two anterior rings of scalids and the posteriormost scalids, uniquely located on the trunk, perform a sensory function. In This content downloaded from 207.46.13.115 on Sat, 08 Oct 2016 04:36:29 UTC All use subject to http://about.jstor.org/terms Introvert of Priapulopsis

Pancreatic duct cell cultures.

The duct cell is a minor cell type of the pancreas, which comprises 10% of the cells and 4% of the volume of the pancreas (39). The predominant acinar cells are much denser than the other cell types because of their large content of zymogen granules (145), thus the duct cells contain less than 4% of the pancreatic protein. The duct cells comprise a tubular epithelium through which the secretions of the acinar cells (digestive enzymes in a small volume of chloride-rich fluid) reach the duodenum. The duct system adds a large volume of a bicarbonate-rich fluid that aids the movement of the digestive enzymes through the duct system and neutralizes stomach acid in the duodenum, although there is considerable species variation in the details of duct cell function (21, 22) . The smallest of the pancreatic ducts, the intralobular ducts (ductules), are in direct epithelial continuity with the acinar cells and tend to project into the acinus as centroacinar cells. Ductular cells comprise about 80% of the cells of the duct system (75). Ductules drain into interlobular ducts and these drain into one or more main ducts. As duct size (luminal diameter and number of cells in circumference) increases, the height of the epithelium and the thickness of surrounding connective tissue increases (39). Duct cells generally exhibit an unspecialized cytoplasm containing a few mucin secre­ tory granules in interlobular and main ducts, apical microvilli, a single apical cilium, and extensive interdigitations of lateral plasma membrane. Small numbers of goblet, brush, and endocrine cells are scattered among the principal cells of interlobular and main ducts (39, 96, 119).

Scanning electron microscopy of the muscle system of Hydra magnipapillata

The fine structure of the ectodermal and endodermal muscle layers of Hydra magnipapillata has been analyzed by scanning electron microscopy after hydrolytic removal of the mesoglea with NaOH and subsequent exposure of the basal and lateral aspects of the layers by mechanical dissection. The ectodermal muscle layer consists of fibrous processes of epithelial cells extending longitudinally to the body axis, whereas the endodermal muscle layer comprises cells with hexagonal bases and several strands of myonemes oriented circularly. In each layer, the muscular elements tightly interdigitate, extending a continuous muscle sheet along the mesoglea. The ectodermal and endodermal muscle sheets communicate with each other via foliate microprojections penetrating the mesoglea. On the lateral aspect of the ectodermal epithelium, spiny nerve fibers run along the upper surface of the muscle processes. The spines are often attached to muscle processes, suggesting that the former monitor muscle contraction. Nerve fibers occasionally come into contact with the mesoglea through narrow gaps between the muscle processes. In the hypostomal ectoderm, a small spindle-shaped cell, probably sensory in nature, extends an apical cilium and a long basal process.

Extracellular giant rickettsiae associated with bacteria in the gill of Crassostrea gigas (Mollusca, Bivalvia)

Extracellular giant rickettsiae closely associated with bacteria with a Gram-negative type wall are reported among the basal insertions of the cilia of the gill epithelium of the oyster Crassostrea gigas (Mollusca, Bivalvia) from the north of Spain. These rickettsiae are extremely pleomorphic cells with a maximum 9 μm length. The internal elements are ribosome-like particles and DNA strands are distributed in some light areas. Some rickettsial cells show one to two vacuole-like dense inclusions formed by curved concentric bands ∼4 nm thick separated by an ∼5-nm light space (myelin-like bodies). Numerous bacteria are closely associated with the rickettsiae in the surrounding zone. The cytopathic effects of this association seemed to give rise to the epithelial lysis and concomitant disappearance of the apical microvilli and cilia and the consequent destruction and disintegration of the gill epithelial cells, where these rickettsiae live in close proximity. This is believed to be the first description of extracellular giant pathogenic rickettsiae of these oyster species.

Multifunctional features of a gastrodermal sensory cell inHydra: three-dimensional study

Computer-assisted, three-dimensional reconstructions of two gastrodermal sensory cells from transmission electron micrographs of serial sections of Hydra revealed a unipolar morphology with the nucleus near an apical cilium and a simple unbranched axon with a widened terminal. The sensory cells were similar in size and shape to a unipolar sensory cell isolated from macerated gastrodermis and examined with scanning electron microscopy. In thin sections, the cells were characterized by the presence of numerous dense-cored vesicles in the axon and its terminal. A few dense-cored vesicles were aligned at electron-dense synaptic foci in the axon terminal of the sensory cell, which formed an axo-axonal synapse with a nearby centrally located ganglion cell and a neuromuscular synapse with the basal myoneme of a digestive cell. The ganglion cell possessed a perikaryal cilium and a slender axon that extended adjacent to the sensory cell terminal, where it formed an en passant axo-axonal synapse in reciprocal arrangement with that of the sensory cell. In addition, the ganglion cell axon formed a neuromuscular synapse in sequence with the sensory cell axo-axonal synapse. The presence of a large number of neurosecretory-like granules, apical cilium and reciprocal interneuronal and neuromuscular synaptic loci suggests that this gastrodermal sensory cell, characterized ultrastructurally for the first time, represents a third type of multifunctional neuron in Hydra. Thus, Hydra may contain primitive stem-like neurons, which are sensory-motor and also function in both neurosecretion and neurotransmission.

Ultrastructural localization of Na +/K +-ATPase in rodent olfactory epithelium

The olfactory epithelium is comprised of bipolar sensory neurons, sustentacular cells, and basal cells. The sensory neurons have apical knobs and cilia, which project into the olfactory mucus toward the nasal lumen, and represent presumptive sites of odorant binding. Ionic currents, measured across this epithelium in both the resting and odorant-stimulated states, are known to be sustained, at least in part, by active transport of sodium. Information identifying the cellular sites of ion transport in olfactory sensory epithelium will therefore aid in elucidating the ionic mechanisms associated with olfactory transduction. The membrane-bound enzyme Na +/K +-ATPase mediates active ion transport in many other cells and tissues. We have consequently employed the cytochemical technique reported by Ernst ( J. Histochem. Cytochem., 20 (1972) 23–38, 1322) to identify possible sites of elevated Na +/K +-ATPase activity in olfactory epithelium. This procedure detects inorganic phosphate (P i) released from an artificial substrate (nitrophenyl phosphate) by enzyme catalytic activity. In the presence of strontium ion, P i is precipitated near regions of high enzymatic activity, then converted to a product visible in the electron microscope. Parallel control preparations were incubated in media (1) supplemented with the specific Na +/K +-ATPase inhibitor ouabain (to abolish formation of specific reaction product); (2) with substrate deleted (to demonstrate possible non-specific binding of Sr 2+ and/or Pb 2+); or (3) with the necessary cofactor K + deleted. In tissues incubated for demonstration of Na +/K +-ATPase activity, reaction product was associated with apical knobs, cilia and dendrites of olfactory receptor neurons at the apical surface. In the more proximal region of the epithelium, reaction product was associated with cell bodies and axons of the sensory neurons, and with the lateral membranes of sustentacular cells. Reaction product was deposited intracellularly, compatible with the known mechanism of the Na +/K +-ATPase enzymatic reaction. In control specimens incubated with ouabain, with substrate deleted, or with K + deleted, only a small quantity of non-specific precipitate was observed. These results are discussed with reference to the various sodium currents implicated in olfactory transduction and transepithelial transport.

Morphology and ultrastructure of the venom glands of the northern pacific rattlesnake Crotalus viridis oreganus.

The venom gland of Crotalus viridis oreganus is composed of two discrete secretory regions: a small anterior portion, the accessory gland, and a much larger main gland. These two glands are joined by a short primary duct consisting of simple columnar secretory cells and basal horizontal cells. The main gland has at least four morphologically distinct cell types: secretory cells, the dominant cell of the gland, mitochondria-rich cells, horizontal cells, and "dark" cells. Scanning electron microscopy shows that the mitochondria-rich cells are recessed into pits of varying depth; these cells do not secrete. Horizontal cells may serve as secretory stem cells, and "dark" cells may be myoepithelial cells. The accessory gland contains at least six distinct cell types: mucosecretory cells with large mucous granules, mitochondria-rich cells with apical vesicles, mitochondria-rich cells with electron-dense secretory granules, mitochondria-rich cells with numerous cilia, horizontal cells, and "dark" cells. Mitochondria-rich cells with apical vesicles or cilia cover much of the apical surface of mucosecretory cells and these three cell types are found in the anterior distal tubules of the accessory gland. The posterior regions of the accessory gland lack mucosecretory cells and do not appear to secrete. Ciliated cells have not been noted previously in snake venom glands. Release of secretory products (venom) into the lumen of the main gland is by exocytosis of granules and by release of intact membrane-bound vesicles. Following venom extraction, main gland secretory and mitochondria-rich cells increase in height, and protein synthesis (as suggested by rough endoplasmic reticulum proliferation) increases dramatically. No new cell types or alterations in morphology were noted among glands taken from either adult or juvenile snakes, even though the venom of each is quite distinct. In general, the glands of C. v. oreganus share structural similarities with those of crotalids and viperids previously described.

Autosomal Recessive Polycystic Kidney Disease: Characterization of Human Peritoneal and Cystic Kidney Cells In vitro

Renal cystic epithelia and peritoneal mesothelia from two humans with autosomal recessive polycystic kidney disease (ARPKD) were grown in culture. Cystic epithelial and mesothelial cells formed continuous monolayers in vitro. By electron microscopy, cystic renal cells exhibited a single apical cilium and numerous short, stubby microvilli, both in situ and in vitro. Mesothelial cells exhibited intra- and extracellular membrane-limited, lipid-filled vesicles and surface microvilli. Cystic kidney cells in vitro stained positive for lectins from Cancanavalia ensiformis (concanavalin A), Triticum vulgaris, Erythrina cristagalli, Ulex europeaus, and Arachis hypogaea. Immunocytochemical and lectin staining revealed the renal and peritoneal cells to be of collecting tubule and mesothelial origin, respectively. Both cell types showed large depositions of glycogen granules in the cytoplasm during propagation in certain culture media; in kidney cells, dibutyryl cyclic adenosine monophosphate (cAMP) abolished glycogen depositions. Glycogen deposition also was observed in liver tissue obtained by needle biopsy from one patient. No bacteria were cultured from nor endotoxin detected in the renal cyst fluid. Relative to serum, the cyst fluids contained low sodium, potassium, and chloride levels. Thus, cultured ARPKD cells demonstrate a number of characteristics that are different from cells derived from the autosomal dominant form of renal cystic disease (ADPKD).

Molecular physiology of olfaction.

Olfactory reception is mediated by olfactory receptor cells located in the olfactory epithelium. These cells are bipolar neurons that extend a dendrite toward the nasal lumen and an axon toward the olfactory bulb in the brain. The dendrite possesses a group of apical cilia embedded in mucus. Odorant recognition and signal transduction are initiated at the membranes of these chemosensory cilia and culminate in excitation of the olfactory receptor cell. Differential activation by odorants of distinct groups of olfactory receptor cells generates patterns of neuronal activity that encode odor quality and concentration. The identities of primary odorant recognition sites at the ciliary membrane remain to be established. However, a significant body of information has become available with respect to olfactory transduction mechanisms. It is now becoming clear that olfactory transduction involves the interplay of several second messenger systems to control the responses of these exquisitely sensitive chemosensory neurons.

Ultrastructure of the mucus-negative vacuolated cells in the metaplastic pyloric gland of the human stomach

Mucus-negative vacuolated cells, often with apical cilia, were found in the metaplastic pyloric gland of the human stomach. These vacuoles were not stained by various mucus stains, but contained neutral fat. Electron microscopic observation revealed that the ciliated cells had prominent autophagosomes in the supranuclear region and sometimes had large vacuoles. These vacuoles were limited by a unit membrane and had electron-lucent contents consisting of small amounts of lipid droplets and lamellar bodies. The non-mucus vacuolated cells might correspond to the mature ciliated cells in which cystic degeneration of the autophagosomes occurred after digestion by lysosomal enzymes.

Ultrastructural observations of the larva ofTubiluchus corallicola (Priapulida)

Larvae ofTubiluchus corallicola van der Land 1968 were investigated by scanning and transmission electron microscopy. The scalids are sensory organs, each has a bipolar receptor cell with a single apical cilium similar to the scalid in the adult. Muscle cells of the larva are more differentiated than previously reported for other Priapulida; the larval arrangement of circular and longitudinal musculature differs from that of the adult, and a diaphragm is reported for the first time in Priapulida. The diaphragm may function in hydrostatic control of eversion and inversion of the introvert and mouth cone. The functional morphology of these two structures is discussed and contrasted with the Kinorhyncha.

Comparative ultrastructural studies of the epidermis, sperm and nerve fibres of Cleistogamia longicirrus and Seritia stichopi (RhabdocoeIa, UmagiIIidae)

The epidermis of Cleistogamia longicirrus consists of columnar, interdigitated cells with apical mitochondria, short microvilli and cilia which have a single horizontal rootlet anchored in the adjacent cytoplasm by transverse bars and a thin side branch. Cells are held together by desmosomes and intermediary junctions. Epidermal cilia have a terminal, electron dense rod between the central microtubules and doublet 1 and a terminal plate; doublets 1 and 6–9 lose one of their microtubules and gradually all doublets lose one microtubule and peripheral doublets disappear. Spermatozoa have a single closed peripheral row of microtubules, numerous electron dense granules and mitochondria and axonemes are of the 9 +“1” type and free for most of their length. Nerve fibres have microtubules and some nerve fibres are surrounded by lamellae and have invaginations of the fibre wall. The epidermis of Seritia stichopi resembles that of Cleistogamia, but cilia have a single horizontal rootlet anchored by transverse bars in the cytoplasm, without a side branch. Spermatozoa also are similar to those of Cleistogamia. Certain ultrastructural similarities between some Umagillidae and Neodermata are apparently due to convergent evolution and do not allow the conclusion that Umagillidae and Neodermata are particularly closely related.

Development of Nerve Cells in Hydrozoan Planulae: II. Examination of Sensory Cell Differentiation Using Electron Microscopy and Immunocytochemistry

The development of sensory cells in hydrozoan planulae of Halocordyle disticha was examined using transmission electron microscopy and light immunocytochemistry. Sensory cells arise in the anterior end of the planula in the ectoderm at 24 hours postfertilization. These cells extend from the free surface of the planula to a ganglionic plexus located just above the mesoglea. The cytomorphosis of sensory cells is characterized by the appearance of a single apical cilium, microtubules, mitochondria, one to several Golgi complexes, electron-dense droplets, dense-cored vesicles, and neurites. The basal end of the sensory cell forms one to several processes (neurites) which contribute to the ganglionic plexus. Apical specialization of the sensory cell precedes basal differentiation. Sensory cells increase in number as planulae develop and many become organized into clusters of 3-6 cells distributed along the entire length of the planula. Within some of these clusters, two morphological types of sensory cells are discernible: light sensory cells and dark sensory cells. Light sensory cells outnumber the dark sensory cells and are the first sensory cells to appear at 24 hours postfertilization. Use of immunocytochemical techniques on wholemounts and paraffin-embedded sections of planulae demonstrates the presence of FMRFamide-like immunoactivity associated with some of the sensory cells. Such FMRFamide-like expression is first detected at 24 hours postfertilization in the anterior ectoderm of the planula. By 96 hours postfertilization, the spatial distribution of FMRFamide-like positive sensory cells is such that many are found in clusters along the entire anterior-posterior axis of the planula. There is, however, an abundance of FMRFamide-like positive cells in the anterior region of the planula just prior to metamorphosis. The apices and cell bodies of the sensory cells exhibit intense immunostaining, whereas the basal processes stain faintly. This study identifies neuropeptide-like substances in nerve cells of cnidarian larvae and demonstrates a developmental correlation between the time of appearance of the synthetic machinery of sensory cells with the pattern of expression of the FMRFamide-like peptide.

Ultrastructure of the tentacles of the apodous holothurian Leptosynapta spp (Holothurioidea: Echinodermata) with special reference to the epidermis and surface coats

The tentacles of the apodous holothurian Genus Leptosynapta have been studied by use of transmission and scanning electron microscopy. The gross anatomy, water vascular system, fibre systems and ectoneural nerve ring are described. A fuzzy coat of attenuated filaments covers the surface of the tentacle, broken only by secretory ducts. A cuticle underlies the fuzzy coat. Bacteria are common in the subcuticular space. Fixation without osmium gives poor preservation of the surface coats. The epidermis consists of a single layer of columnar cells consisting of Type-1, Type-2, support, goblet and uniciliated cells. Type-1 cells secrete electron-dense material and appear to be homologous to adhesive cells of the tentacles of other holothurians. The support cells contain large, granular vesicles not found in other holothurians. Goblet cells contain flocculent mucus and have an apical cilium. Goblet cells are not found in other holothurian tentacles and may function to lubricate and wrap adhering particles to aid their ingestion. The uniciliated cells are rare, poorly developed and the cilium does not extend past the cuticle. The ultrastructure of the tentacles is discussed in relation to those of other holothurians.

Two new digenetic trematodes from Australian freshwater fishes with notes on previously described species

Austrohalipegus anguillicola gen. et sp. nov. is described from the stomach of Anguilla reinhardtii Steindachner. Austrohalipegus is distinguished from other derogenid genera by the absence of filaments on its eggs, by the presence of blindly ending caeca, by having the ventral sucker in the middle of the body, by having the sinus-sac enclose only the hermaphroditic duct, and by the uterus which does not extend posterior to the vitellarium. Austrohalipegus anguillicola is distinctive in having a large temporary sinus-organ formed by a completely eversible hermaphroditic duct. Isoparorchis hypselobagri (Billet) is recorded as juveniles of 1–3 mm in length from the coelom and as larger juveniles and adults from the swim bladder of Tandanus tandanus Mitchell. The miracidium is typically hemiuroid and has a crown of apical spines and cilia in lateral bunches. Experimental infections in which the prosobranch snails Posticobia brazieri and Melanoides tuberculatus were fed embryonated eggs produced infections of mother sporocysts. It is postulated that the life-cycle includes an obligate period of development in the coelom of the definitive host for the Australian form of the species. Stegodexamene watsoni sp. nov. is described from the intestine of Maccullochella peeli (Mitchell). It is distinguished from the two other species of this genus by its considerably larger cirrus pouch and its more extensive vitellaria. Burnellus trichofurcatus (Johnston and Angel) is recorded from new hosts, Arius graeffei Kner and Steindachner and Neosilurus ater (Perugia). Aspects of its biology are discussed. Pretestis australianus Angel and Manter is recorded from a new host, Scortum hilli Castelnau, extending the known range of this species.

Development of apical-surface structures of mouse otic placode.

In 8.0 gestation-day embryos, a central cilium and microvilli were present on the apical surface of the cells of the presumptive otic placode and other ectoderm regions as well. The cilium at this stage lacked a central pair of fibres and was regarded as a primitive cilium with 9+0 composition. The microvilli gained in length and density of distribution as soon as the otic placode began to invaginate in 8.5-d. embryos. With further development in 9.5-11.0-d. embryos, they took on a regular distribution pattern. Narrowing and concomitant bulging out appeared in the cells along the neck of the otic invagination in 8.5-d. embryos. Marked regional differences also occurred in the apical-surface structures of the cells, particularly in the relatively more advanced form of the embryos. Kinocilia of the adult vestibular sensory cells were found to lack a continuous central pair of fibres, resembling the apical cilia of the otic placode. This finding seems to suggest that a vestibular kinocilium represents a direct descendant from the primordial cilium, which generally emerges from the primordial ectodermal cells and is entirely lost from the keratinizing ectoderm in the later development.