| 1. |
- Ekström, Peter, et al.
(author)
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Immunohistochemical evidence for multiple photosystems in box jellyfish.
- 2008
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In: Cell and Tissue Research. - : Springer Science and Business Media LLC. - 1432-0878 .- 0302-766X. ; 333:1, s. 115-124
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Journal article (peer-reviewed)abstract
- Cubomedusae (box jellyfish) possess a remarkable visual system with 24 eyes distributed in four sensory structures termed rhopalia. Each rhopalium is equipped with six eyes: two pairs of pigment cup eyes and two unpaired lens eyes. Each eye type probably captures specific features of the visual environment. To investigate whether multiple types of photoreceptor cells are present in the rhopalium, and whether the different eye types possess different types of photoreceptors, we have used immunohistochemistry with a range of vertebrate opsin antibodies to label the photoreceptors, and electroretinograms (ERG) to determine their spectral sensitivity. All photoreceptor cells of the two lens eyes of the box jellyfish Tripedalia cystophora and Carybdea marsupialis displayed immunoreactivity for an antibody directed against the zebrafish ultraviolet (UV) opsin, but not against any of eight other rhodopsin or cone opsin antibodies tested. In neither of the two species were the pigment cup eyes immunoreactive for any of the opsin antibodies. ERG analysis of the Carybdea lower lens eyes demonstrated a single spectral sensitivity maximum at 485 nm suggesting the presence of a single opsin type. Our data demonstrate that the lens eyes of box jellyfish utilize a single opsin and are thus color-blind, and that there is probably a different photopigment in the pigment cup eyes. The results support our hypothesis that the lens eyes and the pigment cup eyes of box jellyfish are involved in different and specific visual tasks.
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| 2. |
- Ekström, Peter, et al.
(author)
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Pineal neurons projecting to the brain of the rainbow trout, Salmo gairdneri Richardson (Teleostei) - In-vitro retrograde filling with horseradish peroxidase
- 1985
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In: Cell and Tissue Research. - 0302-766X. ; 240:3, s. 693-700
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Journal article (peer-reviewed)abstract
- The morphology of intrapineal neurons that give rise to the pineal tract and project to the brain in the rainbow trout was visualized by the use of neuronal backfilling with horseradish peroxidase (HRP). The tracing was performed on excised pineal organs under in-vitro conditions at 4° C, with filling times ranging from 6 to 24 h. Large multipolar, bipolar and unipolar neurons were visualized in the rostral tip of the pineal organ ("pineal ganglion"). These neurons possessed extended dendritic trees participating in the formation of a circumscribed neuropil-like area. Throughout the pineal organ small bipolar elements were the most ubiquitous type of neuron, however, with markedly smaller numbers in the proximal portion of the pineal end-vesicle. In the pineal stalk, some bipolar neurons were observed to contact the pineal lumen, which is continuous with the third ventricle, via dendritic processes of various types. It could not be established whether any of these CSF-contacting processes were identical with photoreceptor outer segments. The basal processes of the bipolar neurons sometimes possessed distally projecting collaterals. In conclusion, it has been shown that (i) different types of neurons displaying varied patterns of regional distribution contribute to the pineal tract, and (ii) certain CSF-contacting neurons in the pineal organ send axonal processes directly toward the brain.
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| 3. |
- Ekström, Peter, et al.
(author)
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Putative cholinergic elements in the photosensory pineal organ and retina of a teleost, Phoxinus phoxinus L. (Cyprinidae) - Distribution of choline acetyltransferase immunoreactivity, acetylcholinesterase-positive elements and pinealofugally projecting neurons
- 1986
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In: Cell and Tissue Research. - 0302-766X. ; 246:2, s. 321-329
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Journal article (peer-reviewed)abstract
- Putative cholinergic neurons in the photosensory pineal organ of a cyprinid teleost, the European minnow, were studied by use of choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry. Pinealofugally projecting neurons were visualized using retrograde HRP-filling through their cut axons. For comparison, the distribution of choline acetyltransferase immunoreactivity (ChAT-IR) and AChE-positive elements in the retina was investigated. While the distributional patterns of ChAT-IR and strongly AChE-positive perikarya in the retina are similar and may represent the same neuronal population, ChAT-IR and AChE-positive elements in the pineal organ appear to belong to separate populations. In the retina, small- to medium-sized perikarya in the inner nuclear layer, and small perikarya in the ganglion cell layer are ChAT-IR and AChE positive. The entire inner plexiform layer is AChE positive, while only sublaminae 1, 2 and 4 are ChAT-IR. No indication of cholinergic activity was observed in the optic axon layer. In the pineal organ, ChAT-IR is restricted to small perikarya situated rostrally and dorsally in the pineal end-vesicle. AChE-positive neurons are present throughout the pineal end-vesicle and the pineal stalk. The pineal tract (the pinealofugally projecting axons of intrapineal neurons) is strongly AChE positive, but displays no ChAT-IR. The distribution of pinealofugally projecting neurons, labeled with retrogradely transported HRP, is markedly dissimilar to that of the ChAT-IR elements. It is proposed that the photosensory pineal organ transmits photic information to the brain via a non-cholinergic pathway. The possibility that the ChAT-IR neurons represent small local interneurons is discussed in the light of comparative physiological and anatomical findings.
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| 4. |
- Ekström, Peter
(author)
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Retinofugal projections in the eel, Anguilla anguilla L. (Teleostei), visualized by the cobalt-filling technique
- 1982
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In: Cell and Tissue Research. - 0302-766X. ; 225:3, s. 507-524
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Journal article (peer-reviewed)abstract
- The retinofugal projections in the eel were studied by use of the cobalt-filling technique. The optic tract projects contralaterally to the hypothalamic optic nucleus, the anterior periventricular nucleus, the lateral geniculate nucleus, the dorsomedial optic nucleus, four pretectal recipient areas, the optic tectum, and the tegmentum. Small ipsilateral projections were demonstrated in the hypothalamic optic nucleus, the dorsomedial optic nucleus, and the optic tectum.
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| 5. |
- Ekström, Peter, et al.
(author)
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Substance P-like-immunoreactive neurons in the photosensory pineal organ of the rainbow trout, Salmo gairdneri Richardson (Teleostei)
- 1986
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In: Cell and Tissue Research. - 0302-766X. ; 246:2, s. 359-364
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Journal article (peer-reviewed)abstract
- Restricted numbers of substance P-like-immuno-reactive (SPL-IR) neurons were demonstrated in the photosensory pineal organ of the rainbow trout. The small parapineal organ of this teleost species receives a distinct SPL-IR innervation via the habenular nuclei, but displays no intrinsic SPL-IR neurons. Intrapineal SPL-IR neurons were located in the rostral portion of the pineal end-vesicle. Neuronal somata were found in a lateral position with smooth axonal processes extending mediad. Immunoreactive somata and axonal processes were observed intraparenchymally as well as in the pineal lumen. The pattern of immunoreactivity was not changed in excised pineal organs that had been incubated in tissue culture medium in the dark for 18 h. The possibility that the intrapineal SPL-IR neurons are not part of the neural circuitry involved in the transduction of photic information, but may have other functions, is discussed.
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| 6. |
- Garm, Anders, et al.
(author)
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Rhopalia are integrated parts of the central nervous system in box jellyfish
- 2006
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In: Cell and Tissue Research. - : Springer Science and Business Media LLC. - 1432-0878 .- 0302-766X. ; 325:2, s. 333-343
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Journal article (peer-reviewed)abstract
- In cubomedusae, the central nervous system (CNS) is found both in the bell (the ring nerve) and in the four eye-bearing sensory structures (the rhopalia). The ring nerve and the rhopalia are connected via the rhopalial stalks and examination of the structure of the rhopalial stalks therefore becomes important when trying to comprehend visual processing. In the present study, the rhopalial stalk of the cubomedusae Tripedalia cystophora has been examined by light microscopy, transmission electron microscopy, and electrophysiology. A major part of the ring nerve is shown to continue into the stalk and to contact the rhopalial neuropil directly. Ultrastructural analysis of synapse distribution in the rhopalial stalk has failed to show any clustering, which indicates that integration of the visual input is probably spread throughout the CNS. Together, the results indicate that cubomedusae have one coherent CNS including the rhopalia. Additionally, a novel gastrodermal nerve has been found in the stalk; this nerve is not involved in visual processing but is likely to be mechanosensory and part of a proprioceptory system.
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| 7. |
- Garm, Anders, et al.
(author)
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The ring nerve of the box jellyfish Tripedalia cystophora
- 2007
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In: Cell and Tissue Research. - : Springer Science and Business Media LLC. - 1432-0878 .- 0302-766X. ; 329:1, s. 147-157
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Journal article (peer-reviewed)abstract
- Box jellyfish have the most elaborate sensory system and behavioural repertoire of all cnidarians. Sensory input largely comes from 24 eyes situated on four club-shaped sensory structures, the rhopalia, and behaviour includes obstacle avoidance, light shaft attractance and mating. To process the sensory input and convert it into the appropriate behaviour, the box jellyfish have a central nervous system (CNS) but this is still poorly understood. The CNS has two major components: the rhopalial nervous system and the ring nerve. The rhopalial nervous system is situated within the rhopalia in close connection with the eyes, whereas the ring nerve encircles the bell. We describe the morphology of the ring nerve of the box jellyfish Tripedalia cystophora as ascertained by normal histological techniques, immunohistochemistry and transmission electron microscopy. By light microscopy, we have estimated the number of cells in the ring nerve by counting their nuclei. In cross sections at the ultrastructural level, the ring nerve appears to have three types of neurites: (1) small "normal"-looking neurites, (2) medium-sized neurites almost completely filled by electron-lucent vacuoles and (3) giant neurites. In general, only one giant neurite is seen on each section; this type displays the most synapses. Epithelial cells divide the ring nerve into compartments, each having a tendency to contain neurites of similar morphology. The number and arrangement of the compartments vary along the length of the ring nerve.
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| 8. |
- Honkanen, Tapio, et al.
(author)
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Comparative study of the olfactory epithelium of the three-spined stickleback (Gasterosteus aculeatus) and the nine-spined stickleback (Pungitius pungitius)
- 1992
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In: Cell & Tissue Research. - 0302-766X. ; 269:2, s. 267-273
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Journal article (peer-reviewed)abstract
- The olfactory epithelium of the three-spined stickleback (Gasterosteus aculeatus) and the nine-spined stickleback (Pungitius pungitius) has been studied with a conventional histochemical and a novel immunological staining technique. In both species, the sensory epithelium is arranged in folds separated by non-sensory epithelial tissue. In the nine-spined stickleback, intrinsic folds consisting of non-sensory cells are found in the apical part of the sensory epithelium where they divide the surface of the sensory epithelium into small islets. These non-sensory cells are non-ciliated, flattened and piled on top of each other; they contain numerous electron-translucent vesicles. The intrinsic folds are absent from the sensory epithelium of the three-spined stickleback. In both species, axons of receptor cells form a layer of fibers in the sensory epithelium immediately above the basal cells. In the three-spined stickleback, thick branches of the olfactory nerve are frequently found in this layer. These branches are only occasionally observed in the sensory epithelium of the nine-spined stickleback. Thus, the three-spined stickleback and the nine-spined stickleback show considerable differences in the organization of the sensory regions of the olfactory epithelium.
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| 9. |
- van Veen, Theo, et al.
(author)
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Serotonin and opsin immunoreactivities in the developing pineal organ of the three-spined stickleback, Gasterosteus aculeatus L.
- 1984
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In: Cell and Tissue Research. - 0302-766X. ; 237:3, s. 559-564
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Journal article (peer-reviewed)abstract
- 5-hydroxytryptamine (5-HT, serotonin)- and opsin-immunoreactive sites were studied in the developing pineal complex of the stickleback, Gasterosteus aculeatus L., by use of light-microscopic indirect immunoperoxidase techniques. 5-HT immunoreactivity first occurs in the pineal organ at the age of 80 h after fertilization and appears to be localized in cells of the photoreceptor type. The outer segments of a few pineal photosensory cells exhibit opsin immunoreactivity at the age of 84 h after fertilization. The number of cells seems to increase until the pineal organ is completely developed. The increase in the number of 5-HT immunoreactive perikarya runs parallel in time to that of the opsinimmunoreactive outer segments. The cells of the parapineal organ show neither opsin nor 5-HT immunoreactivity. The retina of the embryonic stickleback does not display opsin immunoreactivity until after hatching, which takes place about 144 h after fertilization. These results suggest, in the three-spined stickleback, an earlier light-perception capacity for the developing pineal organ than for the retina.
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| 10. |
- Vecino, Elena, et al.
(author)
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Enkephalin-immunoreactive cells in the mesencephalic tegmentum project to the optic tectum of the teleosts Salmo gairdneri and Salmo salar
- 1991
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In: Cell and Tissue Research. - 0302-766X. ; 264:1, s. 133-137
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Journal article (peer-reviewed)abstract
- Immunocytochemistry using antibodies against Met-enkephalin and Leu-enkephalin has demonstrated a group of large enkephalin-immunoreactive neurons in the nucleus of the rostral mesencephalic tegmentum (mRMT) of two teleost fish, Salmo gairdneri and Salmo salar. Injections of cobalt-lysine in the medial optic tectum retrogradely labeled the above group of tegmental neurons. Tegmental neurons were labeled only ipsilaterally to the injection site. This indicates that enkephalinergic neurons in the nRMT project to the optic tectum, and that at least some of the enkephalinergic axons observed in the optic tectum belong to a tegmento-tectal pathway. Comparable enkephalinergic pathways have been described in reptiles and birds, where pretectal-mesencephalic nuclei contribute to the enkephalin-containing fibers that project to the optic tectum.
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