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Densities o fintramembranous particles belonging to various structures of the gustatory and olfactory sensilla of the fly Calliphora vicina compared with those of the olfactory receptor structures of various vertebrate species
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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...
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... of the antennal axons are rather similar to those of vertebrate olfactory axons (Table 1). Particle densities of labellar and antennal axonal P-and E-intramembranous fracture faces are in line with those on the corresponding fracture faces of the olfactory axons of vertebrates (Table 2); the diameters of particles of the axons of the blowfly's labellar sensilla are somewhat smaller than those of the antennal sensilla and of vertebrate olfactory bipolar cells (Table 3). P-faces of the thick axons of antennae and labella occasionally display particle arrangements resembling gap-junctions ( Fig. 2B and 3B, C). ...
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... particle densities tend to be somewhat lower than those of the axons, at least for the P-faces (Table 2). These densities are also lower than those of the Fig. 4. A Survey of an oblique fracture of the dendritic portion of an antannal sensillum with branched cilia. ...
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... particle densities are here higher than in more proximal regions, cs ciliary sheath originating from the glia cell (opposing small arrows); csl ciliary sheath lumen; E E-face; mb multivesicular body; mi mitochondria; mpg glial micropliae; nu nucleus of the sensory cell soma; P P-face Freeze-fracturing of insect chemosensory sensilla. I. Receptor cells dendrites of the olfactory neurons of vertebrates (Table 2). Particle diameters are within the range of those of vertebrate olfactory dendrites (Table 3). ...
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... of necklace particles are similar to those of necklaces of vertebrate olfactory cilia (Table 3). P-face particle densities of the olfactory cilia just above necklace regions appear to be low (Table 2; Fig. 4B). This is also the case when cilia branch in those regions (Fig. 4C). ...
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... to the necklace, P-faces of the olfactory cilia show, after a region which is poor in intramembranous particles (see previous section), regions with particle densities similar to those of the P-faces of vertebrate olfactory cilia (Figs. 4D, 6C, 11 B, 12B, 13B and 14A; Table 2). Comparison of Figs. ...
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... of the never branching labellar gustatory cilia also show such an increase in particle density (Figs. 7D and 9D; Table 2) in the interpseudotracheal sensilla. However, towards more distal regions of trichoid gustatory cilia no particles were observed at all (Fig. 10), but the very tip underneath the single exoskeletal pore was never exposed. ...
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... particle densities of the antennal dendrites are lower than those of the axons and the distal elements of the olfactory cilia. They are also lower than those of the P-faces of dendrites of olfactory neurons of vertebrates (Table 2). Since the dendritic apices may be flat (Fig. 4A) or conical (Fig. 5A), the variation in shape as reported by Steinbrecht (1980a) needs not to be due to fixation procedures, but could also be genuine. ...
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... most conspicuous membrane-bound structure at the base of cilia is the necklace (Fig. 4A, B). This structure, first described by Andres (1969) in olfactory cilia, has been found since then in numerous other types of cilia, both sensory and non-sensory in nature (see Table 2 in Menco 1980d). From that table it has been deduced that chemo-and photosensory cilia usually display more strands in their necklaces than mechano-and non-sensory cilia. ...
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... the necklace region, olfactory cilia (Table 2 and Fig. 4A, B; Steinbrecht 1980a) show few intramembranous particles in their P-faces. The same has been found for insect gustatory cilia (Altner 1977;Altner and Prillinger 1980). ...
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... distal elements of olfactory cilia show higher P-face particle densities than more proximal elements of those cilia (Table 2 and Figs. 4B, C, D, 6C, 11B, 12B, 13B and 14A) has also been observed by Steinbrecht (1980a, b) in Bombyx mori. ...
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... feature may explain the difference in particle distribution over the sensory cilia in both groups of animals. Moreover particle densities underneath these pores are similar to those of vertebrates (Table 2; Menco 1980bMenco , 1982 and the same is true for the particle diameter (Table 3 and Menco 1980b). P-face particle densities of gustatory cilia are lower than those of olfactory cilia (Table2). ...
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... wave-like structure of Fig. 10 indicated by C is an element of such a gustatory cilium fractured below the tip. At this level the P-face particle density is still virtually zero (see also Table 2). ...
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... analogue finding in insects is that insect olfactory cilia show a much higher P-face particle density in the region underneath the pores of the exoskeletal antennal hairs than in ciliary regions below that level. P-face particle densities of cilia underneath pores are in line with P-face particle densities of vertebrate olfactory cilia (Table 2). From these observations it can be concluded that olfactory cilia of insects and vertebrates have a membrane-bound factor which is most likely involved in olfactory receptor and/or transduction functions. ...
Citations
... The outer segments of the dendrites of the receptor neurons, clad in their dendritic sheaths, are situated in the receptor lymph cavity and are bathed in its contents. The membranes of the trichogen and tormogen cells are highly folded, bear a large number of particles on their cytoplasmic surfaces, and are associated with large numbers of mitochondria (Felt and Vande Berg, 1976; Menco and van der Wolk, 1982); thus, their morphological features suggest a high level of metabolic activity. Electrical and chemical measurements demonstrate that these cells pump potassium into the receptor lymph cavity and by so doing create a transepithelial voltage of up to 100 mV, with the receptor lymph cavity positive with respect to the haemolymph (reviewed in Thurm and Kü ppers, 1980). ...
... In addition to the trichogen, tormogen, and thecogen cells, sensilla usually include a glial cell which enfolds the basal portion of the somata group and the initial portions of their axons (Felt and Vande Berg, 1976; Menco and van der Wolk, 1982; Tominaga et al., 1969). ...
Taste sensilla of flies are composed of only a few cells, all of which have different functions. Depending on the species and on the sensillum type, there are from 2-5 neurons, each of which has its own stimulus specificity, and each of which makes a different contribution to the fly's behavior. In addition, taste sensilla include several nonneuronal cells that are important both for the development of the sensillum and for its functioning. The component cells of a sensillum derive from a single epidermal precursor according to a stereotyped sequence of mitoses. This review focuses on the different phenotypes of the component cells of taste sensilla, particularly the stimulus sensitivity and central neuronal anatomy of the receptor neurons, and on the development of this multicellular organ from a single precursor cell.
Specificity and sensitivity of gustatory neurones in response to twenty-two amino acids were studied in larvae of Pieris brassicae L. and Pieris rapae L. (Lepidoptera: Pieridae) using electrophysiological methods. Twelve amino acids stimulated a specific amino acid receptor cell in the lateral styloconic sensillum on the maxillary galea of both species, and a further two evoked single unit responses in the same sensillum of P.brassicae only. Histidine, phenylalanine and tryptophane were the weakest stimulants for P.brassicae, but were among the four best stimulants for P.rapae. In both species, eight amino acids were ineffective. Significant differences in stimulatory effectiveness were found between amino acids. Nutritionally essential amino acids were more effective in both species, as in five other lepidopterous species. Similarities with postulated sites for amino acid recognition in the dipteran Boettcherisca peregrina were found.
Concentration-response (C/R) relations were studied for five amino acids. Significant differences were found in saturated response levels. Parameters characterizing C/R relations were estimated using a logistic model. Comparing C/R parameters with phytochemical data on concentrations of free amino acids in a common host plant, Brassica oleracea L., shows that amino acids are effective stimuli at their natural concentrations. The amino acid chemoreceptor seems able to transmit information about concentration differences of amino acids in the plant tissue.
The illustrations in Robert Hooke’s epoch-making publication Micrographia became the standard reference work for depicting microscopic phenomena. Of the book’s 38 engravings (the “Schemata”), 14 illustrate insects or their body parts, and of its 60 “Observations” (descriptions and speculative discussions) nearly a third concern insects. Here, I provide taxonomically accurate identifications of Micrographia’s insects, and assess, from a present-day entomologist’s perspective, the accuracy of the book’s insect drawings. I also present additional evidence against the widely expressed opinion that Christopher Wren was probably the author of some of those illustrations. Other entomological aspects of Micrographia addressed in this paper are the insightfulness of Hooke’s Observations, the book’s influence on seventeenth century insect studies, and its legacy to modern entomology. Some of Hooke’s writings in the Observations foreshadow those of Swammerdam on insect metamorphosis (Hooke may have understood it in its basic modern sense) and of van Leeuwenhoek on insect population growth. Also in his discussions of insects, Hooke made what is arguably a meaningful contribution to the debate over spontaneous generation. Hooke’s speculations regarding the function of insect body parts such as dipteran compound eyes, halteres and maxillary palps, and coleopteran elytra, were particularly insightful. I conclude that Hooke helped to lay the foundations of entomology.
The fine structure of silkmoth sense hair surfaces has been investigated by freeze etching with Pt/C rotary shadowing. To do this, the hydrophobic layer in the cuticle was removed using 20–25% methanol or ethanol. Freeze-etch patterns of sense hair surfaces, as well as the pore structure and pore distribution, are shown. The hair surface has a nonhelical ‘band’ structure, in which every ‘band’ lies at an oblique angle with respect to the axis of the hair. Each ‘band’ is separated from its neighbour by a 30-nm step. The average density of pores is 11·3 + 2·4 pores μm−2. Freeze-etch patterns of the single and multiple pore tubules are shown. Evidence for direct contact between the pore tubule and dendrite membrane of an olfactory receptor neuron is presented.
The freeze-fracture technique has been used to obtain detailed information about cuticular constituents and outgrowths of the external skeleton of labella and antennae in the bluebottle fly Calliphora vicina and the antennae of the small moth (Yponomeuta spp.). The lamellated exoskeleton has a fibrous endocuticle and an exocuticle lacking fibers. Ductuli connecting the inside of the animal with the outside run perpendicularly through the endocutile and at angles of up to 45° in the exocuticle. Skeletal outgrowths lack fibers and display fracture features similar to those of the exocuticle. Among those having neuronal endings, gustatory, olfactory, and tactile hairs can be recognized. Noninnervated outgrowths can be subdivided into scales and pseudotrichia. Criteria such as shape, length/width-ratio of hairs, texture, presence and place of pores, shape of pores, and form of the socket or base are presented for further classification. Cuticular features of single-walled olfactory hairs of Calliphora are compared with those of several other species. Based on the shape of the pores, five types of hairs can be distinguished using literature data. It is concluded that the freeze-fracture technique is a valuable tool with which to describe the microarchitecture of the insect exoskeleton and supplements scanning electron microscopy, which is useful for describing the overall skeletal features.
The general morphology and methodological peculiarities of insect sensilla are briefly reviewed. The stimulus conducting pore-tubule systems of pheromone-sensitive sensilla of the silkmoths Bombyx mori and Antheraea polyphemus are described. Lipophilic tracers readily enter the hair lumen, while hydrophilic tracers do so only after prolonged extraction with lipid solvents and/or pronase. X-ray microanalysis demonstrates a high potassium content of the sensillum lymph; calcium was only found in the haemolymph above detection limit. Auxiliary cells rapidly take up radioactive leucine administered via the haemolymph. Antibodies against pheromone-binding protein of Antheraea polyphemus label the sensillum lymph of sensilla trichodea, but not of sensilla basiconica in A. polyphemus as well as in B. mori. The cytoplasm of auxiliary cells of the sensilla trichodea is also labelled. The results are discussed in context with present hypotheses on the role of sensillum lymph in stimulus transport and inactivation. © 1992 Wiley-Liss, Inc.
Freeze-fracturing and deep-etching are a well-suited set of methods to study membrane and cytoplasmic features. Various approaches are available. Possible variables include tissue preparation, fracturing only or fracturing followed by etching, modes and materials of replication, and various ways of combining freeze-fracturing and/or deep-etching with (immuno)cytochemistry. Freeze-substitution, in particular combined with embedding in methacrylate resins such as the Lowicryls, is becoming rather widely accepted for purposes of ultrastructural (immuno)cytochemistry. Most investigators active in this field agree that this combination yields superior results compared to (immuno)cytochemistry combined with more conventional means of thin section transmission electron microscopy. Yet relatively little information is available on the variations that can occur with different approaches of freeze-substitution immunocytochemistry. This review deals with some of the variations in freeze-fracturing, freeze-etching, and freeze-substitution as applied to olfactory epithelial structures and with the effectiveness of observations obtained by application of the above sets of methods in relating the special morphology of olfactory epithelial cellular structures with those obtained by other approaches. Indeed, the data obtained continue to provide an integral image in which that morphology can be related to the special biochemistry, cell and molecular biology, and electrophysiology of olfactory epithelial structures. © 1995 Wiley-Liss, Inc.
We studied the birth times of neurons of labellar taste sensilla in blowflies using incorporation of the thymidine analogue 5-bromodeoxyuridine (BrdU) as an indicator of birth time. We found that one of the two main sensillum types, the taste papillae, arise according to a clear spatial gradient of birth times, whereas the other sensillum type, taste hairs, arise without any apparent spatial ordering. Within each sensillum type, there was a strong tendency for either all or none of the neurons to have incorporated BrdU. Among those rare sensilla in which only some of the neurons incorporated BrdU, there were clear patterns of the distribution of labeled and unlabeled neurons per sensillum. These results suggest that subsets of the neurons of a sensillum are siblings, and thus argue against the possibility that the several neurons of a sensillum arise from a single stem cell precursor through repeated asymmetrical divisions. © 1995 John Wiley & Sons, Inc.
Many cilium types have at their proximal base a particulated membrane structure, the so-called ciliary necklace. Necklaces of primary and secondary cilia of olfactory receptor cells and ciliated respiratory cells, and of primary cilia of olfactory supporting cells were studied as a function of embryonic age. Strand numbers in necklaces of primary cilia of these cell types do not differ, but they differ significantly from those of necklaces of secondary cilia. Primary cilia have 2 to 4, but most commonly 3, necklace strands. This is true for necklaces of primary cilia of 8 different nasal cell types: olfactory epithelial basal and glandular cells, vomeronasal receptor and supporting cells, and microvillous respiratory epithelial cells, in addition to the 3 cell types mentioned above. Comparison with other systems suggests that primary cilia resemble flagella of eukaryotic flagellates and spermatozoa of some invertebrates with respect to their number of necklace strands. Average numbers of necklace strands in secondary olfactory cilia increase from 3–4 at the 16th and 17th gestational days to 6–7 in adults. Those in secondary respiratory cilia increase from 2–3 at the 18th and 19th gestational days to 5–6 in adults. Longer cilia have more strands than shorter ones. Necklaces often have free strand endings, also in primary cilia, suggesting that they spiral. Comparing the present data with those in the literature suggests that necklace features occurring during reciliation differ from those of de novo ciliogenesis. Primary and secondary cilia share the following qualities: 1) Membrane regions above necklace strands can differ quite drastically from those below the strands. 2) Necklace particles are firmly associated with cytoskeletal elements underneath the ciliary membrane. Hence, necklaces in primary cilia and in developing and mature secondary cilia may, together with the cytoskeleton underneath the membrane, provide a barrier for lateral diffusion and a region of membrane attachment. The latter may help to determine the shape of cilia.
