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1.
We have previously reported immunocytochemical, biochemical, behavioral, and electrophysiological evidence for glutamatergic transmission through (±)--amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA)/kainate receptors in hydra. We now report specific localization of the N-Methyl-D-aspartic acid receptor subunit 1 (NMDAR1) in epithelial, nerve, nematocytes, and interstitial cells of hydra. Macerates of tentacle/hypostome pieces of Hydra vulgaris were prepared on agar-coated slides, fixed with buffered formaldehyde/glutaraldehyde, and fluorescently labeled with monoclonal antibodies against mammalian NMDAR1. Negative controls omitted primary antibody. Digital images were recorded and analyzed. Specific localized and intense labeling was found in ectodermal battery cells, other epithelial cells, nematocytes, interstitial cells, and sensory and ganglionic nerve cells, and in battery cells was associated with enclosed nematocytes and neurons. The labeling of myonemes was more diffuse and less intense. In nerve and sensory cells, punctate labeling was prominent on cell bodies. These results are consistent with our earlier evidence for glutamatergic neurotransmission and kainate/NMDA regulation of stenotele discharge. They support other behavioral and biochemical evidence for a D-serine-sensitive, strychnine-insensitive, glycine receptor in hydra and suggest that the glutamatergic AMPA/kainate-NMDA system is an early evolved, phylogenetically old, behavioral control mechanism.  相似文献
2.
Using a radioimmunoassay for the carboxyl-terminal sequence Arg-Val-NH2, two novel peptides were purified from extracts of the sea anemone Anthopleura elegantissima. These peptides were L-3-phenyllactyl-Tyr-Arg-Ile-NH2 (name: Antho-RIamide I) and its des-phenyllactyl fragment Tyr-Arg-Ile-NH2 (Antho-RIamide II). Immunocytochemical staining showed that these peptides were localized in neurons of sea anemones. Application of low concentrations (10−8 M) of Antho-RIamide I inhibited spontaneous contractions in several muscle groups of sea anemones, whereas Antho-RIamide II was inactive. Antho-RIamide I is the second neuropeptide from sea anemones that bears the unusual, amino-terminal L-3-phenyllactyl blocking group. We suggest that this group renders the peptide resistant against degradation by nonspecific aminopeptidases. In addition, the L-3-phenyllactyl residue might also play a role in receptor binding.  相似文献
3.
Coelenterate neurones produce peptides containing an Arg-Phe-NH2(RF-amide)-like carboxyterminus. RF-amide-like peptides are located in neuronal dense-cored vesicles, indicating that they are released by exocytosis and that they might function as neurotransmitters or neurohormones. Using a radioimmunoassay for the sequence RF-amide, 3 peptides were isolated from the sea anemone Anthopleura elegantissima: < Glu-Gly-Arg-Phe-NH2(Antho-RF-amide), 2(Antho-RWamide I) and 2(Antho-RW-amide II). The general structure of these peptides can be described as 2, where X is an aromatic amino acid. From the hydromedusa Polyorchis penicillatus, the peptide 2(Pol-RF-amide I) was isolated, which also belongs to the 2 family. Using specific antisera, it was shown that all 4 peptides were located in neurones, many of which were associated with smooth muscle fibres. Application of low doses of Antho-RF-amide or of Antho-RW-amide I and II induced contractions of endodermal muscles of sea anemones. This suggests that these peptides are transmitters or modulators at neuromuscular junctions.  相似文献
4.
Summary Planulae are simply structured larvae lacking an overt longitudinal organization. In the course of a rapid metamorphosis, however, they transform into polyps, which display striking structural patterns. Metamorphosis takes place only in response to external stimuli. Surgical removal and transplantation of larval parts reveal that external stimuli, including artificial inducers such as cesium ions, tumor promoters and diacylglycerol, act on the anterior quarter of the larva where sensory cells containing Arg-Phe-amide-like peptides are located. The external stimuli initiate the release of an internal signal, which is transmitted to the posterior end causing the successive transformation of larval into adult tissue. The transformation front moves from the anterior to the posterior quarter in 60 min. The internal signal can be released or bypassed by a transitory lowering of the Mg2+ content of the seawater. By using this procedure, or by administering an extract containing the putative internal signal substance, each isolated part of the larva can be induced to metamorphose separately. Provided there is no time for regeneration after cutting before metamorphosis is initiated, the most anterior fragment forms only stolons, the most posterior fragment forms only a head. The overt pattern of the polyp is, therefore, generated under the influence of a covert anterior-posterior prepattern of the larva.  相似文献
5.
Summary Hydrozoa replace used-up nematocytes (cnidocytes) by proliferation and differentiation from interstitial stem cells (i cells). Repeated pulsed exposure ofHydra to elevated levels of unprotonated ammonia leads to successive loss of the various types of nematocytes: first of the stenoteles, then of the isorhizas and finally of the desmonemes. The loss is due to deficits in supply; the number of nematoblasts and differentiating intermediates is reduced. In the hydroidHydractinia the main process leading to numerical reduction was observed in vivo: mature nematocytes as well as precursors emigrate from their place of origin into the gastrovascular channels where they are removed by phagocytosis. This is a regular means by which these animals down-regulate an induced surplus of nematocytes. With lower effectiveness, pulses of methylamine, trimethylamine and glutamine also induce elimination of the nematocyte lineages. In the long term the population of nerve cells, which are permanently but slowly renewed from interstitial neuroblasts, decreases, too. After 2 months of daily repeated treatment the density of the Arg-Phe-amide-positive nerve cells was reduced to 50% of its normal level. Thus, ammonia induces down-regulation of all interstitial cell lineages. The temporal sequence of the ammonia-induced loss reflects the diverse rates with which the various i cell descendants normally are renewed.  相似文献
6.
Summary An antiserum to the sequence Arg-Phe-amide (RFamide) was used to stain the nervous systems of various physonectid siphonophores. In the stem of Nanomia bijuga, this antiserum stained an ectodermal nerve net, which was interrupted, at regular intervals, by transverse collars of neurons. Injection of Lucifer yellow into the giant axon of the stem showed that this axon was dye-coupled to an ectodermal nerve net that resembled the RFamide-positive network. Ectodermal nets of neurons were also found in the pneumatophore, gastrozooids, tentacles and tentilla. At the junctions of the pneumatophore, the gastrozooids, the dactylozooids and the gonozooids with the stem, and at the junctions of tentacles and tentilla, collars or rings of neurons occurred. The stem was connected to the phyllozooids and nectophores by muscular lamellae, which were bordered by chains of neurons. At the margin of the nectophores, an immunoreactive nerve ring was found. Connected to this ring and located in theseitliche Zapfen (sidely-located patche), were two agglomerations of nerve cells. On the upper side of the bell margin, positioned at 90° relative to the seitliche Zapfen, a delta-shaped neuronal structure was found. This structure was connected to the nerve ring and was associated with a muscle, which ran a short distance along the exumbrellar surface.The nervous systems of Agalma elegans, Forskalia edwardsi, Forskalia leuckarti and Halistemma rubrum resembled that of Nanomia bijuga in all major respects.  相似文献
7.
Summary Within 24 h after the initial phagocytotic uptake of freshly isolated (from host tissue) symbiotic algae (Symbiodinium microadriaticum) by the endodermal cells of the polyp (scyphistoma) stage of the jellyfish Cassiopeia xamachana, the algal population was observed to decline despite evidence of algal cell division. Analyses of the frequency of phago-lysosome fusion as an indicator of possible attempts of the host to digest the algae indicated that, although phago-lysosome fusion did occur, the low frequency of occurrence is inconsistent with the interpretation that the animals digested the algae. Animal cell lysosomes were located predominantly at the apices of the endodermal cells, and the symbiotic algae were transported toward the bases of the endodermal cells.Within 3 days after initial infection, most endodermal cells with algae ceased to be phagocytotically active (with respect to the uptake of carmine particles). Many of these endodermal cells soon migrated into the mesoglea to become what are traditionally referred to as amoebocytes. Within amoebocytes the algae proliferated. The onset of strobilation by the scyphistomae was directly correlated with the increase in the algal population within these amoebocytes.  相似文献
8.
Summary The characteristics of uptake of 3H-noradrenaline (3H-NA) and 3H-adrenaline (3H-A) in the tissues of the sea pansy, Renilla köllikeri, were studied by in vivo incubations. Lineweaver-Burk plots indicated two components of catecholamine accumulation, one representing a high-affinity uptake with an apparent K m of 4.91×10-7 M (3H-NA) or 4.39×10-7 M (3H-A), and the other a low affinity process with an apparent Km of 5.52×10-5 M (3H-NA) or 1.49×10-5 M (3H-A). The high-affinity uptake of both tracers was strongly inhibited at low temperature and in a calcium-free medium, thus suggesting the involvement of a carrier-mediated transport mechanism, but was largely insensitive to sodium omission and ouabain. Accumulations of 3H-NA, but not 3H-A, were highly desipramine-sensitive.Light-microscopic radioautographic studies demonstrated the presence of cells reactive to both 3H-NA and 3H-A in the ectoderm, mesoglea and endoderm. Extraneuronal accumulations of 3H-NA and 3H-A were prominent in some ectodermal cells, in amoebocytes and spicule cells. Reactive neuronal processes were tentatively identified throughout the mesoglea and over all muscle layers on the basis of several morphological criteria. 3H-A, but not 3H-NA label, was more intense over the presumed photocytic zone and circular muscle than elsewhere. These and other observations support a neurotransmitter role for adrenaline (and probably noradrenaline) in control of luminescence and modulation of slow rachidial contractions.Supported by a grant from the Natural Sciences and Engineering Research Council of Canada  相似文献
9.
Summary The larval stage of Polypodium hydriforme is planuliform and parasitic inside the growing oocytes of acipenserid fishes. The larva has inverted germ layers and a special envelope, the trophamnion, surrounding it within the host oocyte. The trophamnion is a giant unicellular provisory structure derived from the second polar body and performing both protective and digestive functions, clearly a result of adaptation to parasitism. The trophamnion displays microvilli on its inner surface, and irregular protrusions anchoring it to the yolk on its outer surface. Its cytoplasm contains long nuclear fragments, ribosomes, mitochondria, microtubules, microfilaments, prominent Golgi bodies, primary lysosomes, and secondary lysosomes with partially digested inclusions.The cells of the larva proper are poorly differentiated. No muscular, glandular, neural, interstitial, or nematocyst-forming cells have been found. The entodermal (outer layer) cells bear flagella and contain rough endoplasmic reticulum; the ectodermal (inner layer) cells lack cilia and contain an apical layer of acid mucopolysaccharid granules. The cells of both layers contain mitochondria, microtubules, and Golgi bodies; their nuclei display large nucleoli with nucleolonema-like structure, decondensed chromatin, and some perichromatin granules. At their apical rims, the ectodermal cells form septate junctions; laterally, the cells of both layers form simple contacts and occasional interdigitations. The lateral surfaces of entodermal cells are strengthened by microtubules.  相似文献
10.
Summary Polyps ofHydra attenuata Pall. were subdivided into four axial fragments (I–IV) of about identical length. Ecto- and endoderm of each of these fragments were separated from each other and dissociated according to the technique of David (1973). Each preparation was qualitatively and quantitatively examined as to its content of nerve cells.The presence of 11 different types of nerve cells (Tardent and Weber, 1976) could be confirmed. While multipolars (M1, M2), symmetrical bipolars (B1, B2) and unipolars (U1, U2) were found in both layers, asymmetrical bipolars (B3–7) are limited to the endoderm (Fig. 1), which, as a whole, contains fewer nervous elements than the ectoderm (Fig. 2). The ecto- and endoderm of the tentacles could not be separated from each other and the dissociation was only partly successful. It was, however, possible to ascertain that among the nerve cells present in the tentacles the most numerous are the symmetrical bipolars (B1, B2).Dr. Epp was awarded a grant of the Swiss National Science Foundation (Nr. 880.480.76). This work was also supported by grant Nr. 3.548.75 of the same Foundation. The authors are indebted to Mr. Chr. Weber for his technical help and advice  相似文献
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