The thermo-/hygrosensitive sensilla of the silkmoth,Bombyx mori: morphological changes after dry- and moist-adaptation

Summary The thermo-/hygrosensitive sensilla styloconica of the silk moth Bombyx mori were studied using cryofixation and freez-substitution. These sensilla are characterized by a short poreless cuticular peg, which is double-walled in its distal part. The central lumen is innervated by the unbranched outer dendritic segments of the two presumed hygroreceptor cells. The presumed thermoreceptor cell displays lamellae below the peg base. Within the peg lumen, the dendrites are surrounded by the peridendritic dense coat and the lowdensity matrix. Below the peg base, these structures continue as the dendrite sheath, which is separated from the outer sensillum-lymph space by a layer of the trichogen cell. The central lumen, therefore, is only connected with the inner sensillum-lymph space, but the appearance of the low-density matrix, within the peg, differs from that of the sensillum lymph below the peg. In moist-adapted (24 h) sensilla, the two hygroreceptor dendrites invade the peg for three quarters and one half of its length, respectively, and fill the cross-sectional area of the lumen by 50–80%. In dry-adapted (24 h) sensilla, the dendrites terminate more proximally and fill the cross-section by 35%. The volume of the low-density matrix increases under dry conditions and decreases under humid conditions. At intermediate ambient humidity, the morphology of these sensilla is halfway between the dry-adapted and the moist-adapted state. The effect of dry-adaptation is reversible, so that sensilla that were first dry-adapted and then moist-adapted (24 h each) before cryofixation cannot be distinguished from moist-adapted sensilla. The reduction of the exposed length of the dendrites is interpreted as a shift of the working range of the receptors and/or protection against desiccation. The current theories of sensory transduction in hygroreceptors, in particular the hygrometer and evaporimeter hypotheses, are discussed with respect to the present findings.     

Differentiation of the thermo-/hygrosensitive (no-pore) sensilla on the antenna of Antheraea pernyi (Lepidoptera,Saturniidae): a study of cryofixed material

Summary The morphogenesis of the thermo- and hygro-sensitive sensilla styloconica of Antheraea pernyi was studied, exclusively by cryomethods, during the second half of pupal development. The three major processes taking place during this period are (1) the differentiation of the dendritic outer segments of the sensory cells, especially of the lamellated type-2 receptor, (2) the formation of the receptor-lymph cavities, (3) the formation of tubular structures of unknown function in the inner receptor-lymph cavity, and (4) the elongation of the dendrite sheath. The formation of lamellae in the type-2 dendritic outer segment is achieved by the enfolding of its originally cylindrical cytoplasmic membrane. Autocellular junctions, previously described in the sensilla of adult animals, are found to join the forming lamellae. Close similarities between the junctions and smooth septate junctions are demonstrated. Both the extensive inner and outer receptor-lymph cavities are formed by invagination and folding of the apical cytoplasmic membranes of the three enveloping cells. Formation starts at the most apical projection of the cells and proceeds in a proximal direction. Up to 4-m-long tubular structures appear, exclusively in developmental stages, in the inner receptor-lymph cavity. They are composed of plasma membranes whose inner surface is studded with regularly spaced electron-dense particles. Contacts with the cytoplasmic membrane of the innermost enveloping cell demonstrate that the structures are composed of lipid membranes. During elongation of the dendrite sheath, which in these sensilla is apically attached to the hair wall, an 2-m-long growth-zone is observed at its proximal end. By addition of sheath-forming material to the growth-zone, the latter continuously moves proximally until the sheath is completed.     

Labellar taste organs of Drosophila melanogaster

There are 36 to 42 taste bristles on each half of the labellum of Drosophila melanogaster; most of them are two-pronged with a pouch between them. Some end bluntly with a pore at the tip. Each taste-bristle has two lumina: one is circular, the other crescent-like in cross section. In most bristles four dendrites of chemoreceptor neurons run along the circular lumen. In five to seven taste-bristles only two chemoreceptor neurons are found. A mechanoreceptor neuron sends a dendrite to the base of each taste-bristle. The dendrites are surrounded by four concentrically-arranged sheath cells. The inner cell secretes the cuticular sheath; cells II and III are presumably two trichogens, one secreting the bristle material around the circular lumen, the other around the crescent-like lumen. Cell IV, especially rich in bundles of microtubules, secretes the cuticle of the socket, and corresponds to the tormogen. The neurons have the typical structure found in insect sensilla. In many sensilla one neuron is less electron-dense than the others and may be the water-sensor. On the medial side of the labellum between the pseudotracheae are rows of taste pegs covered by folds. In each peg one chemoreceptor and one mechanoreceptor are found. The number of axons in each labial nerve agrees with the total number of dendrites in all taste organs of each lobe.     

Are the funnel-canal organs the ‘campaniform sensilla’ of the shore crab,Carcinus maenas (Decapoda,Crustacea)?

Summary The funnel-canal organs on the dactyls of the shore crab, Carcinus maenas, are innervated by 3–24 sensory cells with unbranched dendrites, which attain a length of 500–1400 m. The outer dendritic segments are enclosed in a dendritic sheath and pass through the cuticle within a canal. Two dendrite types can be distinguished according to ultrastructural criteria: Type I has a long ciliary segment, A-tubules with an osmiophilic core and arms, and a thick ciliary rootlet. Type II possesses only a short ciliary segment and a thin ciliary rootlet. Each funnel-canal organ contains two type-I dendrites. Their ciliary bases appear a few m distal to those of the type-II dendrites (1 to 22 in number). Two inner and two to eight outer enveloping cells belong to a sensillum. The innermost enveloping cell contains a large scolopale. In the second enveloping cell single scolopale rods are present. Thus, the funnel-canal organs are characterized by structural features typical for mechano-sensitive scolopidia, on the one hand, and for chemoreceptors, on the other. Therefore, the funnel-canal organs are very likely bimodal sensilla (contact chemoreceptors). A comparison with other arthropod sensilla shows that cuticular mechanoreceptors of aquatic crustaceans generally exhibit a scolopidial organization.     

Fine structure of the stretch receptor in the bursa copulatrix of the butterfly,Pieris rapae crucivora

Summary A pair of multipolar stretch-receptive neurons were found in the bursa copulatrix of the female cabbage white butterfly, Pieris rapae crucivora. The cell body of each neuron, about 10 m in diameter, lies on the edge of the muscular region in the antero-lateral wall of the corpus bursae. No special accessory structure, such as a receptor muscle, is associated with the neuron. The several dendrites extend radially into the muscle layer. The dendrites are ensheathed except for their terminal tips, and, on their course, they anchor repeatedly on the epithelial cells or the muscle fibers in such a manner that their basement membranes fuse together. While the ensheathed dendrite is usually 0.1–0.2 m in diameter, it often forms 1–2 m varicosities especially at anchor sites, so that it looks like a varicose, or beaded, chain. The varicosities contain a number of mitochondria, but only microtubules are found in the fine interconnecting parts of the dendrite. The naked dendritic tips terminate in the basement membrane of the epithelial cell. The varicosities, as well as naked tips, seem to be important for stimulus transduction in the sensory cell of this type.     

Innervation of cockroach cercal receptors as revealed by horseradish peroxidase (Insecta,Blattodea)

Summary The innervation of cerci of a desert burrowing cockroach, Arenivaga sp., was determined by horseradish peroxidase backfilling of the cercal nerve and histochemistry. The procedure yielded a high percentage of successful fills and in many cases every neuron filled completely, including dendrites and axons of less than one m. The innervation of the cerci was found to be highly ordered. Upon entering the cercus, the cercal nerve splits into bilateral branches, one on each side of the midline. The nerves branch again at each segment to form fascicles of sensory neurons which innervate the trichobothria, sensilla chaetica and tricholiths, each with a single bipolar neuron. While the cell bodies of neurons are of similar dimensions, the dendrites to the tricholiths are much longer and terminate on the midline side of the sensilla socket where the tricholith shaft attaches.     

Cilia in normal and regenerating islet tissue

Summary Ciliated cells occasionally occur in pancreatic ductule cells and islet -cells of normal Chinese hamsters. In the regenerating pancreatic parenchyma of alloxan-treated Chinese hamsters an increased amount of cilia is observed in the ductule cells and islet -cells. No obvious cilia were found in the other pancreatic cell types of normal and alloxan-treated animals. One and the same ductule cell possesses one, two, or rather often many cilia protruding into the ductule lumen. In the islet -cells there are one or two cilia that often extend into intercellular spaces. The fibre arrangement varies in different parts of the cilia. The basic fibre pattern seems to be 9 + 2, the 9 peripheral fibres consisting of 2 subfibres, and the 2 central being single. The basal bodies (centrioles) consist of 9 groups of 2 or 3 aligned tubular elements. Filaments are associated with the centrioles. The functional significance of the cilia is discussed.This work was supported by grants from the Swedish Medical Research Council (Projects No. K67-12X-718-02 and K68-12X-718-03) and the Medical Faculty, University of Umeå.     

Electron microscopy of the paraventricular organ in the sparrow (Passer domesticus)

Summary Characteristics of the ependymal cells of the Paraventricular Organ (PVO) in the sparrow are strongly dilated ergastoplasmic cisternae filled with a moderately dense substance, the absence of cilia and a long basal process ending around capillaries. Elongated cells having a pale cytoplasm (light cells) are interposed between the ependymal cells. These cells protrude into the ventricle lumen with a bulbous cytoplasmic swelling; centrioles and several dense-core vesicles occur frequently in them.Two types of nerve cells have been identified in the PVO. The more superficial cells — called type-I neurons have a dendrite-like process which, after passing the ependymal layer reach the ventricle surface and end there freely with a bulbous swelling (club). The whole neuron contains dense-core vesicles of an average diameter of 840 Å; the extensive Golgi region is located in the dendrite.The larger type-II neurons situated in the deeper layers show a folded nuclear membrane, large mitochondria and rarely dense-core vesicles; the Golgi apparatus is enclosed in the perikaryon.The nerve cells are embedded in a feltwork of glial and neural processes the latters showing often synaptic (axodendritic) junctions. The majority of the synapses are supposed to occur between the axon-like processes of the typeI neuron and dendrites of the type-II neuron. Axo-somatic synapses can be found not infrequently on the perikarya of the latters.The nature of the free ventricular endings of the neurons and the possible function of the PVO are discussed in the text.     

The cercal receptor system of the praying mantid,Archimantis brunneriana Sauss.

Summary The cerci of the praying mantid, Archimantis brunneriana Sauss., are paired segmented sensory organs located at the tip of the abdomen. Basally the cercal segments are slightly flattened dorso-ventrally and are fused to such a degree that it is difficult to distinguish them. Distally the segments become progressively more flattened laterally and their boundaries become more obvious.Two types of sensilla are present on the cerci, trichoid sensilla and filiform sensilla. Trichoid hairs are longest on the medial side of the cerci and toward the cercal base. On the proximal cercal segments they are grouped toward the middle of each segment while they are more uniformly distributed on the distal segments. Filiform sensilla are found at the distal end of each segment except the last and are most abundant on the middle segments of the cercus. Both the number of cercal segments and the number of sensilla are variable. Trichoid hairs are highly variable in appearance from short and stout to long and thin. They arise from a raised base, have a fluted shaft, and some have a pore at the tip. They are innervated by from one to five dendrites, one of which is always considerably larger than the others. Some of the dendrites continue out into the shaft of the hair.Filiform hairs have fluted shafts and are mounted in a flexible membrane within a cuticular ring in a depression. They are innervated by a single large sensory neuron, the dendrite of which passes across a flattened area on the inner wall of the lumen of the hair. The dendritic sheath forms the lining of the ecdysial canal and is therefore firmly attached to the hair. The dendrite is attached to the sheath by desmosomes distally and is penetrated by projections of the sheath more proximally. A fibrous cap surrounds the dendrite and may hold it in place relative to the hair.The cercal receptor system of Archimantis is compared to those of cockroaches and crickets.     

Freeze-fracture characteristics of insect gustatory and olfactory sensilla

Summary Freeze-fracture data on antennal olfactory and labellar gustatory sensilla of the blowfly Calliphora vicina were compared with those of vertebrate olfactory organs.Insect antennal and vertebrate olfactory axons have similar diameters and show vesicular expansions; insect labellar axons are on average twice as thick and show no vesicular expansions. Vertebrate olfactory and insect labellar and antennal axons display similar intramembranous particle densities. Antennal axons show particle arrangements, resembling tight-junctions. The few extremely thick axons found in labella and antennae show particle arrangements resembling gap-junctions.In regions, proximal to the pores in the insect sensillar hairs, P-faces of olfactory and gustatory cilia show about 200 particles/m². The most proximal and distal portions of the sensory cilia, necklaces and regions in the vicinity of the hair pores respectively, were only encountered in antennal sensilla. P-faces of the ciliary membranes underneath these pores display 1,000–1,200 particles/ m² in unbranched and branched cilia. These values agree with values found in vertebrate olfactory cilia. It is suggested that these high particle densities are related to entities involved in chemoreceptive activities.Accessory cell micropliae have P-face densities of 2,000–3,000 particles/ m², values similar to those found in vertebrate supportive cell microvilli. The membranes of the accessory cells display septate-junctions in areas where these cells overlap themselves, each other and in places where they adhere to the exoskeleton or the basement membrane.     

Ultrastructure and ontogeny of the hair sensilla on the funicle of Calliphora erythrocephala (Insecta,Diptera)

Summary Four envelope cells are responsible for the formation of the basiconical sensilla of Calliphora. They are the thecogen, trichogen, and tormogen cells, and envelope cell 4. In early stages of development the still subepithelial sensory cilia are completely enclosed by the innermost thecogen cell. The first formation movements are initiated by a growth thrust of the hair-forming cell into the exuvial space. The sensory cilia only begin to grow into the hair anlage when the hair-forming cell has almost reached its final length. As soon as growth is completed the trichogen cell, tormogen cell, and envelope cell 4 start to excrete cuticular material. The trichogen cell forms the perforated part of the hair shaft and the stimulus-conducting system consisting of the pore tubules. The tormogen cell is responsible for the excretion of the basal non-perforated hair shaft and sheath cell 4 forms the proximal part of the socket region. The thecogen cell only begin to produce dendritic sheath material when the sensory hair is almost complete.Approximately 7–8 days after pupation the tormogen cell degenerates, having, by this time, produced about two-thirds of the sensilla cuticle. The surrounding envelope cells incorporate cell fragments of the tormogen cell. The trichogen cell continues the secretion where the tormogen cell left off. When the secretion of cuticle is finished the sheath cells begin to withdraw towards the proximal direction and to form microvilli on the apical membrane. The resulting outer receptor lymph space is bordered by envelope cell 4 and the trichogen and thecogen cells. The tormogen cell is absent in the sensilla of the imago.Abbreviations DS dendritic sheath - E4 envelope cell 4 - Ex exuvial space - G glial cell - iD inner dendritic segment - iRL inner receptor lymph space - oRL outer receptor lymph space - oD outer dendritic segment - P pore - PT pore tubules - S sensory cell - T thecogen cell - TO tormogen cell - TR trichogen cell Part 1 of a dissertation accepted by the Faculty of Bio- and Geosciences, University of Karlsruhe     

Ultrastructure of the peg and hair sensilla on the antenna of larval Aedes aegypti (L.)

The antenna of fourth instar larvae of Aedes aegypti has one peg organ of a basiconic type innervated by four neurons. The dendrites are ensheathed to near their terminations at the peg tip by an electron-dense dendritic sheath and by a cuticular sheath. They have easy communication by diffusion with the external environment only at the tip through a peripheral ensheathing membrane and six slit-channels. One of the dendrites resembles a tubular body proximally and may be mechanoreceptive. The peg generally appears to be a contact chemoreceptor. There are three antennal hairs of a typical sensillum trichodeum type innervated at the base by one neuron each. An intricate terminal mechanism at the insertion of the dendrite in the hair is described. These are believed to be tactile hairs. There are also three antennal hairs each innervated by two neurons. The dendrite from one terminates at the base similar to that of a tactile hair, and is believed to function in a similar mechanoreceptive manner. The dendrite from the second neuron extends naked along the length of the hair lumen. It is believed to be primarily chemoreceptive, in a slow-acting general sensory function. In all the sensilla there appear to be secretions produced in the junction body regions of the dendrites, and there is evidence for accumulation of secretory materials in the dendritic tips in some of the sensilla.     

Electron microscope studies of the digestive tract ofBrachionus plicatilis (Rotifera)

Summary The rotiferBrachionus plicatilis was immobilized in an extended state by treatment with acrylamide. Longitudinal sections through whole animals were studied by transmission electron microscopy, and in addition animals were cut in different planes and studied by scanning electron microscopy. By these techniques several structures were characterized which seem to be relevant to the processes of enzymatic digestion and resorption in this species. The inner surfaces of both the stomach and the intestine are provided with rootless cilia, which show different densities, alignments, structures and properties in different compartments. The syncytial wall of the anterior part of the stomach is flat; its plasma membrane toward the stomach lumen is smooth and bears relatively few cilia. The posterior part of the stomach consists of voluminous cells. Their plasma membranes lining the stomach cavity show pits and infoldings that are continuous with a system of vacuoles within the cells containing membrane material probably derived from food organisms. The density of cilia in the posterior part of the stomach is about three times that in the anterior part. The stomach glands contain ribosomes, glycogen granules and secretory bodies, which are accumulated toward the region where these glands drain into the stomach cavity. The orifice of the stomach glands occurs in a permanent intercellular gap between the syncytial anterior stomach and three cells of the posterior part of the stomach. The cells of the intestinum are relatively flat and are characterized by mitochondria, narrow intercellular spaces between shingle-like overlapping wall cells and cilia differing in structure and properties from those of the stomach. The observations confirm the existence of functional differences between stomach and intestine. Digestion of nutrients, supported by secretions of the stomach glands, seems to be performed mainly within the stomach, and resorption of particulate food seems to occur almost exclusively in this part of the alimentary tract. The structural features of the intestine, on the other hand, indicate that small molecules may be transported through its wall and that here, perhaps, processes may take place which demand active transport.Abbreviations ast anterior part of the stomach - bm basal membrane toward pseudocoel - cb cell border between stomach cells - cwh rooted cilia of the wheel organ - dm desmosome structure between intestinum cells - e esophagus - gc glycocalyx (fuzzy coat) - gl gastric gland - isp intercellular space - it intestinum - itl intestinum lumen - m mitochondrion - mbl membranelles in the esophagus - mx mastax - pc pseudocoel - pst posterior part of the stomach - sb secretory bodies - SEM scanning electron microscopy - st stomach - stl stomach lumen - TEM transmission electron microscopy - v (food-) vacuole in cells of the posterior stomach wall - x small vesicle or grana-like structures on the lumen side of the opening of the gastric gland Dedicated to Dr. h.c. Walter Koste on the occasion of his 80th birthday     

Ultrastructure and functional morphology of male genital organs and spermatophore formation inProtodrilus (Polychaeta,Annelida)

Summary The structure and functional morphology of lateral organs and sperm ducts, as well as the mechanisms of spermatophore formation and transfer, are investigated by means of light and electron microscopy in the genusProtodrilus. The sperm ducts are simple, ciliated, intercellular gonoducts with a funnel section surrounded by a thin muscle layer and a tube section opening externally in the anterior region of the lateral organs. No glands are present in the sperm ducts. The lateral organs are formed by long epidermal invaginations enclosing an elongate lumen into which numerous cilia project and a large number of glands open. Five to ten different gland types with strikingly distinctive secretory granules are found in the different species. In addition, special supporting cells, the so-called sponge cells, sensory cells and an underlying nervous tissue are developed in the lateral organs. It is stated that apart from some similarities to the ventral atrium ofNerilla antennata no corresponding organs are known within the Annelida. It is argued that inProtodrilus the spermatophores are formed by the lateral organs as there are a high number of glands opening into the lumen of the organ. The possible origin and genesis of the male gonoducts as well as the mode of spermatophore transfer inProtodrilus is discussed.Abbreviations used in the figures bl basal lamina - cc coelomic cell - ci ciliated cell - cir ciliary root - cr ciliary ring - cu cuticle - cv bs contractile ventral blood sinus - d dissepiment/septum - dbs dorsal blood sinus - es euspermatozoa - f funnel - fi filament - g gut - glo gland openings - lgl lateral organ gland - lm longitudinal muscle - lo lateral organ - lu lumen - mi mitochondrion - mt microtubules - mu muscle - mv microvilli - mvc microvillar crown - n nucleus - ne nervous tissue - o opening - ps paraspermatozoa - rer rough endoplasmatic reticulum - s spermatozoa - sc sponge cell - sg salivary gland - spd sperm duct - spdo sperm duct opening - t tube - tm transverse muscle - vc ventral ciliary band     

Arhabdomeric cells of the median eye retina of scorpions

Summary Based on reconstructions from serial thin sections, arhabdomeric cells within the retina of the median eyes of the scorpion,Androctonus australis, are identified. Each retinula unit (formed by mainly five retinula cells with a fused rhabdom) is associated with one arhabdomeric cell. Extending distally from its soma which is located close to the postretina, the arhabdomeric cell bears an up to 80 m long dendrite that ends at the base of the fused rhabdom. The most noteworthy morphological feature of the dendrite is the presence, at the distal dendrite tip, of numerous finger-like or bulbous evaginations that extend into every one of the five visual cells forming a retinula unit. These and other characteristics strongly suggest that the arhabdomeric cell represents an intrinsically photoinsensitive second neuron involved in visual information processing.This study was supportet by a grant from the Deutsche Forschungs-gemeinschaft (F1 77/8).     

Electron microscope observations on chemo- and mechano-receptor cells of fishes

Summary This paper reports on the fine structure of chemo and mechano-receptor cells found in three species of fishes (Corydoras paleatus, Cnesterodon decemmaculatus, Fitzroyia lineata).Taste cells were studied in the food-finding barbels of adult species belonging to the Genus Corydoras. They are characterized by the presence of a great amount of vesicular material concentrated at the level of the apical and medial region. Most of these cells terminate at the barbel surface by means of a cylindrical or tapered extremity devoid of sensory hairs. It was possible to observe, in some cases, the existence of short and ill defined microvilli. The basal pole of each sensory cell contacts with several sensory nerve fibers. These fibers contain mitochondria and a few vesicles.The fine structure of the olfactory neurons was studied in full-developed embryos of Cnesterodon and Fitzroyia. The olfactory sensory hairs consist of long cilia which project into the lumen of the olfactory pit. Cilia arise from the olfactory knob which is merely an apical swelling of the dendrite. The dendrite of the olfactory neuron shows profiles of small tubules, aligned parallel to its length. Near the basement membrane of the epithelium groups of axons are seen encased in the surface of the sustentacular cells.The mechano-receptor cells studied were: 1.) The sensory cells existing in the neuromasts of the lateral line system of Cnesterodon and Fitzroyia, and 2.) the receptor cells of the ampullar crests of the same species.Neuromast receptor-cells have well developed sensory hairs which consist of cilia and microvilli. It is highly probable that each receptor cell, like those of the vestibular epithelium, bears only one cilium asymmetrically located in relation to the units of the sensory process. One of the most striking characteristics of this type of cell is the existence of a high amount of vesicular material accumulated in the cytoplasm of the basal region; it is at this level that the nerve fibers take contact with the receptor cell membrane.Three main types of neuroepithelial junction are described in the neuromasts (nerve fiber deeply recessed in the cytoplasm, calyx type and knob-like ending). In these junctions the vesicular material is almost exclusively concentrated in the cytoplasm of the receptor cell, while only few vesicles are seen within the neuroplasm of the sensory fibers.The receptor cells occuring in the ampullar crests of Cnesterodon and Fitzroyia show many structural characteristics similar to those present in neuromasts' receptor cells. Like these, they bear sensory hairs consisting of several microvilli and only one cilium which is always asymmetrically located within the group of hairs. The basal region of the cell is filled with a large amount of small vesicles. Nerve endings also show vesicles but they are less in number than inside the cytoplasm of the receptor cell.Comments are made on the apparent significance of the sensory hairs. These structures are considered (in chemo-receptor cells) as devices serving to enlarge the active surface of the cell and increasing by this way the effectiveness of the whole receptive system. In mechano-receptor cells cilia and microvilli may act as levers of different mechanical characteristics which convey stimuli to the receptor-cell cytoplasm.In this paper three main types of neuroepithelial junctions connecting receptor cells with the central nervous system are described.     

Ecto-ATPase/phosphatase activity in the olfactory sensilla of the spiny lobster,Panulirus argus: localization and characterization

Summary Electrophysiological studies have shown that the olfactory organ (antennule) of the spiny lobster, Panulirus argus, has chemoreceptors that are selectively excited by adenine nucleotides in seawater. Biochemical studies have revealed that these same nucleotides can be rapidly dephosphorylated by ectoenzymes associated with the olfactory sensilla (aesthetascs). In this study the distribution of ecto-ATPase/phosphatase activity within aesthetascs was determined cytochemically and the nature of the adenine-nucleotide dephosphorylating activity was dissected biochemically. Cytochemically, the distribution of ATP-dephosphorylating activity was similar to that shown previously for AMP and -glycerol phosphate; i.e., cerium phosphate reaction product was specifically localized to the transitional zone where the sensory dendrites develop cilia and branch to form the outer dendritic segments. Unlike the dephosphorylation of AMP and -glycerol phosphate, Mg²⁺ or Ca²⁺ was required for ecto-ATPase/phosphatase activity. Biochemical measures of both AMP-and ATP-dephosphorylating activity within aesthetascs corroborated the cytochemical evidence that these activities are localized to the transitional zone. A major portion of the AMP dephosphorylation (about 67%) derives from nonspecific alkaline phosphatase activity that is insensitive to levamisole and L-bromotetramisole. In contrast, nonspecific phosphatase activity accounted for a much smaller part of the ATP dephosphorylation (about 15%). Ectoenzymatic activity in the transitional zone may be an important means of removing excitatory/inhibitory nucleotides from this region.Abbreviations ADP Adenosine 5-diphosphate - AMP adenosine 5-monophosphate - AMPCP , -methylene ADP - ASW artificial seawater - ATP adenosine 5-triphosphate - -GP -glycerol phosphate - EM electron microscopy     

Die campaniformen Sensillen im Pedicellus der Florfliege (Chrysopa,Planipennia)

Zusammenfassung Der Pedicellus der Florfliege (Chrysopa) enthält an seinem Distalende fünf campaniforme Sensillen. Sie bestehen aus vier Zellen: einer Sinneszelle, einer trichogenen Zelle (= accessory supporting cell Stuart u. Satir, 1968) und zwei Hüllzellen. Im rezeptorischen Fortsatz der Sinneszelle wurzelt ein umgewandeltes Cilium, dessen Distalende von einer cuticularen Scheide umhüllt wird.

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On the campaniform sensilla of the pedicel of Chrysopa

Summary At the apex of the pedicel in Chrysopa there are five campaniform sensilla, which are arranged in a cycle. They are composed of four cells: two enveloping cells, a trichogen cell (= accessory supporting cell, Stuart and Satir, 1968) and one sense cell. The distal nerve process contains a transformed cilium. The tip of the cilium with the so called tubular body is enveloped by a cuticular sheath.

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Die Untersuchung wurde mit Unterstützung durch die Deutsche Forschungsgemeinschaft durchgeführt.     

Covisualization in living onion cells of putative integrin, putative spectrin, actin, putative intermediate filaments, and other proteins at the cell membrane and in an endomembrane sheath

Summary Covisualizations with wide-field computational opticalsectioning microscopy of living epidermal cells of the onion bulb scale have evidenced two major new cellular features. First, a sheath of cytoskeletal elements clads the endomembrane system. Similar elements clad the inner faces of punctate plasmalemmal sites interpreted as plasmalemmal control centers. One component of the endomembrane sheath and plasmalemmal control center cladding is antigenicity-recognized by two injected antibodies against animal spectrin. Immunoblots of separated epidermal protein also showed bands recognized by these antibodies. Injected phalloidin identified F-actin with the same cellular distribution pattern, as did antibodies against intermediate-filament protein and other cytoskeletal elements known from animal cells. Injection of general protein stains demonstrated the abundance of endomembrane sheath protein. Second, the endomembrane system, like the plasmalemmal puncta, contains antigen recognized by an anti-₁ integrin injected into the cytoplasm. Previously, immunoblots of separated epidermal protein were shown to have a major band recognized both by this antibody prepared against a peptide representing the cytosolic region of ₁ integrin and an antibody against the matrix region of ₁ integrin. The latter antibody also identified puncta at the external face of protoplasts. It is proposed that integrin and associated transmembrane proteins secure the endomembrane sheath and transmit signals between it and the lumen or matrix of the endoplasmic reticulum and organellar matrices. This function is comparable to that proposed for such transmembrane linkers in the plasmalemmal control centers, which also appear to bind cytoskeleton and a host of related molecules and transmit signals between them and the wall matrix. It is at the plasmalemmal control centers that the endoplasmic reticulum, a major component of the endomembrane system, attaches to the plasma membrane.Abbreviations DiOC₆ 3,3-dihexyloxacarbocyanine iodide - GF Gaussian filtering - ML maximum likelihood (algorithm or method) - PBS phosphate-buffered saline     

The endogenous development of four new species of Isospora Schneider, 1881 (Apicomplexa: Eimeriidae) from Australian geckos

Four new species of Isospora are described from Australian geckoes. Isospora gehyrae n. sp. from Gehyra cf. variegata in South Australia have 18.5-22.5×17.5–20.0 m oöcysts with 10.0-12.5×7.5-9.0 m sporocysts; endogenous stages develop in the host cell cytoplasm. Of the two species found in Heteronotia binoei from northern Queensland, Isospora cytoheteronotis n. sp., with oöcysts of 20.0-26.0×17.5-25.0 m and sporocysts of 10.0-13.5×7.5-11.5 m, undergoes endogenous development in its host cell cytoplasm, whereas I. nucleoheteronotis n. sp., with oöcysts of 17.5-22.5×17.5-21.5 m and sporocysts of 9.0-12.5×6.5-10.0 m, develops in the host cell nucleus. I. oedurae n. sp. from Oedura rhombifer in northern Queensland has oöcysts of 22.5-25.0×22.5-24.0 m and sporocysts of 12.5-14.0×7.5-11.5 m, and undergoes endogenous development in its host cell nuclei.