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1.
The attachment of the body of the snail Lymnaea stagnalis to the shell was studied by histochemistry and light and electron microscopy. Muscles of the body wall insert into the connective tissue by way of long thin projections of sarcolemma. The muscle cells end under the basement membrane of a specialised area of the epidermis, the adhesive epithelium. The cells of this epithelium are filled with microfilaments and possess characteristic knob-like microvilli. The epithelium is attached to the shell by way of an adhesive substance containing proteins and mucopolysaccharides.This research was made possible by a grant from the Netherlands Organization for Pure Research (Z.W.O.)  相似文献   

2.
Summary This study describes the neural basis of respiratory behavior in a pulmonate mollusc, Lymnaea stagnalis. We describe and identify muscles of the respiratory orifice (pneumostome) and mantle cavity as well as relevant motor neurons innervating these muscles. All of these identified motor neurons are active during spontaneously occurring respiratory behavior and a sporadically occurring synaptic input, termed Input 3, controls the activities of these motor neurons. This spontaneous input can also be recorded from isolated brain preparations, suggesting that the respiratory motor program is generated centrally. However, evidence is also presented that in semi-intact preparations the role of peripheral feedback is important for the initiation and termination of respiratory behavior in Lymnaea.  相似文献   

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4.
The anatomy of three neurosecretory cell types in the central nervous system (c.n.s.) of the gastropod mollusc Lymnaea stagnalis (L.)- the Dark Green Cells, Yellow Cells and Yellow-green Cells-has been studied by using bright and dark field illumination of material stained for neurosecretion by the Alcian Blue-Alcian Yellow technique. The neuronal geometry of single and groups of neurosecretory cells of the various types has been reconstructed from serial sections, and the likely destination of most of their processes has been determined. Dark Green Cells are monopolar, occur exclusively within the central nervous system (c.n.s.), have few or no branches terminating in neuropile, and send axons to the surface of the pleuro-parietal and pleuro-cerebral connectives. The majority of Dark Green Cell axons however (80-85%), project down nerves which innervate ventral and anterior parts of the head-foot, the neck and the mantle. Dark Green Cell axons can be found in small nerves throughout these areas, and may terminate in a find plexus of axons on the surfaces of the nerves. Since previous experimental work has shown that the Dark Green Cells are involved in osmotic or ionic regulation, these results suggest that the target organ of the Dark Green Cells may be the skin. Yellow Cells occur both within and outside the c.n.s. They are usually monopolar, but can be bipolar. They have several axons which normally arise separately from a single pole of the cell body, or close to it. One or more processes leave the cell proximal to the point where separate axons arise, and may run unbranched for some distance through neuropile before terminating in fine brances and blobs of various sizes. These branches may release hormone inside the c.n.s. Yellow-green Cells are mono-, bi- or multi-polar, and like the Yellow Cells are found both within and outside the c.n.s. Some Yellow-green Cells, though not all, have projections which terminate in neuropile in fine branches and blobs. Yellow-green Cell bodies which occur in nerves can project back along the nerve into the c.n.s. The axons of Yellow Cells and Yellow-green Cells project to release sites in various ways. Some project into the connective tissue shealth of the c.n.s., which serves as a neurohaemal organ, either directly through the surface of a ganglion, or from the pleuro-cerebral or pleuro-parietal connectives. Other axons leave the c.n.s. via nerves leaving the left and right parietal and visceral ganglia; projections into the intestinal, anal, and internal right parietal nerves being most numerous. Axons which may be from either, or both Yellow Cells and Yellow-green Cells, can be found along the entire unbranched lengths of these nerves, and in subsequent branches which innervate organs lying in the anterior turn of the shell. All of these orgnas are closely associated with the lung cavity...  相似文献   

5.
The aminergic innervation of the foot of Lymnaea stagnalis was investigated using electron microscopy, immunocytochemistry, and HPLC. The foot was found to contain large amounts of serotonin and dopamine, though at lower concentrations than are found in nervous tissue. Serotonin containing tissue was concentrated in the ventral surface of the foot, under ciliated areas of the epidermis where it occurred in varicosities, with fine tracts joining these varicosities. Varicosities also occurred in deeper tissues, probably adjacent to mucus cells. Positive fluorescence for serotonin in axons was found in nerves innervating the foot, but few neuronal cell bodies containing serotonin were detected, indicating that most of the innervation was coming from the central ganglia. Axon varicosities were found using TEM on ciliated cells, mucus cells, and muscle cells as well as interaxonal junctions (possibly non-synaptic) within nerves. The neuronal varicosities contacting the ciliated cells and mucus cells contained mostly dense-cored vesicles of between 60 and 100 nm in diameter. Smaller, lucent vesicles also occurred in these terminals. The origin and significance of this innervation is discussed. It is suggested that both serotonin and dopamine may play a large role in controlling ciliary gliding by the foot.  相似文献   

6.
Nicotinamide-adenine-dinucleotide-phosphate-diaphorase (NADPH-d) histochemistry has been applied in the present study to determine the distribution of putative nitric oxide (nitric oxide synthase)-producing cells during embryonic and early postembryonic development in the pond snail, Lymnaea stagnalis L., with special reference to the nervous system. The first NADPH-d-positive structures appear as early as 18% of development (E18, trochophore stage) and correspond to the pair of protonephridia. These structures later show disintegration, although after metamorphosis (E26=75%) staining of their individually spreading cells can be observed until hatching. Peripheral sensory neurons in the foot, mantle edge and lips, and their afferents projecting to the central nervous system reveal NADPH-d activity in the postmetamorphosis period (E25–E27=E60%–E80%) of embryogenesis. After hatching (P1–P3), a number of stained sensory cells appear in the pharynx and esophagus. Some NADPH-d positive neuronal perikarya occur in the pedal and pleural ganglia, and a few weakly stained cells in the cerebral and buccal ganglia of juvenile snails. At the same time, a continuous bundle of reactive fibers is formed in the neuropil both through and through around the circumesophageal ganglion ring. The localization of NADPH-d activity in the developing nervous system of Lymnaea suggests that nitric oxide participates mainly in sensory processes. However, its role in specific intraganglionic integrative events cannot be excluded following embryonic metamorphosis.  相似文献   

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The osphradium of molluscs is assumed to be a sensory organ. The present investigation in Lymnaea stagnalis has established two ultrastructurally different types of dendrites in the sensory epithelium. Cells immunoreactive to leucine-enkephalin and FMRFamide send processes to the sensory epithelium. These neurons of the osphradial ganglion are thus considered to be part of the sensory system, as are methionine-enkephalin-immunoreactive cells in the mantle wall in the vicinity of the osphradium. The complexity of the osphradial ganglion is further demonstrated by serotonin-immunoreactive neurons innervating the muscular coat around the osphradial canal and methionine-enkephalin-immunoreactive cells sending projections to the central nervous system.  相似文献   

9.
Summary Three neuronal systems of the pond snail Lymnaea stagnalis were immunocytochemically investigated at the ultrastructural level with the unlabeled peroxidase-antiperoxidase technique. Preliminary electrophysiological and cell-filling investigations have shown that a cluster of neurons which reacts positively with an antiserum against the molluscan cardio-active peptide FMRFamide, sends axons to the penis retractor muscle. In this muscle anti-FMRF-amide (aFM) positive axons form neuro-muscular synapses with (smooth) muscle fibers. The morphological observations suggest the aFM immunoreactive system to be involved in peptidergic neurotransmission. In the right parietal ganglion a large neuron (LYAC) is penetrated by aFM positive axons which form synapse-like structures (SLS) with the LYAC. The assumption that the SLS represent the morphological basis for peptidergic transmission is sustained by the observation that iontophoretical application of synthetic FMRFamide depolarizes the LYAC. The axons of a group of pedal anti-vasopressin (aVP) positive cells run in close vicinity to the cerebral ovulation (neuro-)-hormone producing cell system (CDC system) Synapses or SLS between the two systems were not observed. The fact that (bath) application of arg-vasopressin induces bursting in the CDC, may indicate that the vasopressin-like substance of the aVP cells is released non-synaptically.  相似文献   

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5-HT (serotonin) is a ubiquitous neurotransmitter that produces ciliary beating in gastropods when applied topically, but ciliary beating caused by gastropod serotonergic neurons has been described in only three neuron pairs. We extend these results to the North American Lymnaea stagnalis appressa, which is a different species from the European Lymnaea stagnalis. We describe a non-serotonergic neuron pair, PeV1, which accelerates pedal sole mucociliary transport and a serotonergic neuron pair, PeD7, which slows mucociliary transport. We compare and discuss development and identified neurons in L. s. appressa and in L. stagnalis, which have homologs to L. s. appressa PeD7 and PeV1 neurons. In addition to PeD7 and PeV1 neurons, we test neurons immunoreactive to Tritonia pedal peptide antibodies with negative results for mucociliary transport. In characterizing PeD7 and PeV1 neurons, we find that PeV1 does not excite PeD7. In semi-intact preparations, a strong increase in PeD7 neuron activity occurs during tactile stimulation, but V1 neurons are inhibited during tactile stimulation. Following tactile stimulation, PeV1 neurons show strong activity. This suggests a distinct difference in function of the two neuron pairs, which both have their axons overlying pedal sole ciliary cells. Application of 5-HT to the pedal sole initiates mucociliary transport in 1.4–1.9 s with a time course similar to that seen when stimulating a PeV1 neuron. This result appears to be through a 5-HT1A-like receptor on the pedal sole. We describe a possible external source of 5-HT on the pedal sole from 5-HT immunoreactive granules that are released with mucus.  相似文献   

12.
Axonal tracing and immunocytochemical techniques were used to study the innervation of the head retractor muscle (HRM) in the pond snail Lymnaea stagnalis L. Fibers of both the superior and inferior cervical nerves which innervate the HRM form endings that comply with the structure of chemical synapses. The somata of neurons with axons in these nerves are located in all except the buccal ganglia of the central nervous system, and this seems to be a special feature of the HRM motor system. By staining the filamentous actin with Oregon-green conjugated phalloidin, we demonstrated that the HRM has a multiterminal innervation and one muscle fiber can contain several synaptic endings which appear to be both morphologically and physiologically different. The morphological diversity of synaptic vesicles suggests a multiplicity of neurotransmitters acting on these nerve-muscle junctions. Immunocytochemical evidence was found for a strong serotonergic and FMRFamidergic innervation of muscle fibers through axons of the inferior cervical nerve. The thin fibers of the inferior cervical nerve possess immunoreactivity to glutamate, gamma-aminobutyric acid (GABA) and choline-acetyltransferase, and form sparser innervation patterns in the muscle. Our results indicate that several neurotransmitters are present in the nerves innervating the Lymnaea HRM and may therefore participate in the control of this muscle. The possible behavioral significance of such different neurotransmitter sets involved in the regulation of contractions is discussed.  相似文献   

13.
14.
Kudikina NP 《Ontogenez》2011,42(3):213-219
Effect of preparations ofa peptide nature (pituitrin and oxytocin) and of a steroid nature (progesterone and hydrocortisone) on embryonic development of freshwater gastropod Lymnaea stagnalis (Mollusca, Gastropoda, Pulmonata) is described. The hormonal preparations used, which differed in chemical nature and physiological activity, may render diverse effects on embryogenesis of the studied mollusk. Of neurohormones, pituitrin rendered the most noticeable and principally stimulating effect. Oxytocin was incorporated in regulatory processes much later and its effect on the rate of realization of particular stages depended more on the quality of occurring changes. In final stages of development, this hormone principally inhibited growth and development of embryos. The female sex hormone progesterone rendered an expressed stimulatory effect, especially notable in later developmental stages of embryos. The hormone hydrocortisone stimulated initial stages of embryogenesis. Its effect was almost not expressed in the final stages. The discovered differences seem to be related both to the functional specificity of the investigated compounds and to specific traits of mechanisms of realization of their effects. A hypothesis is formulated: in gastropods, similarly to vertebrates, the hormones are systemic embryonic and postnatal inducers of differentiation processes.  相似文献   

15.
The guanosine-5-triphosphate (GTP) binding of D1-dopamine (DA) receptor agonist [H3]-SKF 38393 is described. The binding of [H3]-SKF 38393 occurs in two different DA receptors in the presence of guanylyl nucleotides, and in one receptor population in the absence of guanylyl nucleotides. It was shown with GDP--P33 binding analysis that G proteins in the mollusc nervous tissue membranes accelerate exchange of guanosine-5-diphosphate (GDP) for GTP considerably. While binding of [H3]-SKF 38393 was not found with phosphorylation of the membranes by the catalytic subunit of cAMP-dependent protein kinase A, basal and DA-induced GDP GTP exchange was noticeably inhibited with phosphylation in the nervous tissue membranes.A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 4, pp. 451–461, July–August, 1992.  相似文献   

16.
Sinistral and dextral snails have repeatedly evolved by left-right reversal of bilateral asymmetry as well as coiling direction. However, in most snail species, populations are fixed for either enantiomorph and laboratory breeding is difficult even if chiral variants are found. Thus, only few experimental models of chiral variation within species have been available to study the evolution of the primary asymmetry. We have established laboratory lines of enantiomorphs of the pond snail Lymnaea stagnalis starting from a wild population. Crossing experiments demonstrated that the primary asymmetry of L. stagnalis is determined by the maternal genotype at a single nuclear locus where the dextral allele is dominant to the sinistral allele. Field surveys revealed that the sinistral allele has persisted for at least 10 years, that is, about 10 generations. The frequency of the sinistral allele showed large fluctuations, reaching as frequent as 0.156 in estimate under the assumption of Hardy-Weinberg equilibrium. The frequency shifts suggest that selection against chiral reversal was not strong enough to counterbalance genetic drift in an ephemeral small pond. Because of the advantages as a model animal, enantiomorphs of L. stagnalis can be a unique system to study aspects of chirality in diverse biological disciplines.  相似文献   

17.
1. We have found that, in preparations of isolated CNS of the pond snail Lymnaea stagnalis, both serotonin (5HT) and dopamine (DA), as well as their respective precursors, 5HTP and DOPA, are effective in producing fictive intense (muscular) locomotion. 2. Phase-coupled to each of the above pedal rhythms are numerous identifiable pedal neurons including the respiratory interneuron RPeD1, thus suggesting interaction between networks responsible for locomotion and air breathing. 3. The novel DA/DOPA-dependent motor rhythm resembles the 5HT/5HTP-dependent one in terms of activity of identifiable pedal neurons, being however considerably slower than the latter. 4. The results of transection experiments suggest that each of the rhythms is generated by a paired CPG lying entirely within the pedal ganglia.  相似文献   

18.
Multiple site optical recording was used to analyze the neural activity changes caused by conditioned taste aversion (CTA) training in the pond snail Lymnaea stagnalis. In response to electrical stimulation of the median lip nerve, which transmits chemosensory signals of appetitive taste to the central nervous system, we optically detected large numbers of spikes in several parts of the buccal ganglion. The effects of CTA training on the spike responses were examined in two areas of the ganglion where the most active neural responses occurred. In one area (termed Area I) that included the N1 medial (N1M) cells, a class of central pattern generator interneurons involved in feeding behavior, the number of spikes in a period 1500-2000 ms after median lip nerve stimulation was significantly reduced in conditioned animals compared to control animals. In another area (termed Area II) positioned between buccal motoneurons, the B3 and B4CL (cluster) cells, the evoked spike responses were unaffected by CTA training. These results, taken together with our previous results indicating an enhancement of an inhibitory input to the N1M cells during CTA, suggest that an appetitive taste signal transmitted to the N1M cells through the median lip nerves is suppressed during CTA, resulting in a decrease of the feeding response.  相似文献   

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I Kiss 《Malacologia》1979,18(1-2):489-497
The properties of 2 giant electrically coupled neurones (A10 and P1) identified in the visceral and right parietal ganglia of Lymnaea stagnalis were examined. The active and passive electrical parameters of the neurones, as well as the junction between them were measured. The main peripheral and interneuronal connections of the neurones were demonstrated using both electrophysiological and morphological methods. It is shown that the coupled cells are not neurones of the same function, but they are asymmetrical ones. This finding is supported by the following results: (1) the axonal pathways of neurones A10 and P1 are different; (2) there are significant differences in their afferent and efferent connections; (3) though the electrical junction between them is bidirectional, the junctional electrical characteristics prefer P1-A10 transmission. According to the electron microscopic results both neurones are possible neurosecretory cells. The differences demonstrated between the 2 giant neurones may have significance concerning their role in a special neuronal network.  相似文献   

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