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At least 253 records · Page 14Linked to original sources
PubMed1979

ACTH-like immunoreactivity in two electronically coupled giant neurons in the pond snail Lymnaea stagnalis.

Two giant neurons (diameter 130 micron) were identified immunocytochemically by means of the unlabeled antibody enzyme technique with anti-ACTH 1-39 and 1-24 in the pond snail Lymnaea stagnalis. The cells are located in the visceral and the right parietal ganglion, respectively. They contain moderately electron dense elementary granules (diameter 150-160 nm). By means of the intracellular horseradish peroxidase injection technique it was shown that the cells send fibres into the neuropiles of various ganglia and into nerves. Synapses occur on the fine fibre branches in the neuropile. Synapse-like structures were found on the cell bodies and on the major fibres. The giant neurons are electrotonically coupled. With toluidine blue staining for small peptides it was demonstrated that in the central nervous system of the pond snail numerous peptidergic neurons occur in addition to those identified with the classical staining methods for neurosecretion.

Adrenocorticotropic Hormone↗
PubMed1979

An ultrastructural study of the neurosecretory canopy cell of the pond snail Lymnaea stagnalis (L.), with the use of the horseradish peroxidase tracer technique.

The paired, electrotonically coupled neurosecretory Canopy Cells (CC) of the pond snail Lymnaea stagnalis were microiontophoretically injected with horseradish peroxidase (HRP). Whole mount preparations and ultrathin sections of injected CC were studied to describe in detail the morphology of the CC, their axon tracts and neurohaemal areas. The CC release their secretory product at three different sites, viz. from the soma and from axon terminals in the intercerebral commissure and in the median lip nerve. Neural control over the CC occurs by few synapses found exclusively on the CC axon, not on the cell body. One type of "en passant" synapse was identified. Two morphologically distinct types of synapselike structures (SLS) are numerous. The site of electrotonic coupling between the two CC is most probably located in the cerebral commissure. Serial sectioning showed that the axons contact each other over more than 130 micrometers. The contact is very intimate and the axon membranes interdigitate in a complex manner. Gap junctions, which are often described as the sites of electrotonic coupling, were not found.

Animals↗
PubMed1980

Photoperiod-dependent neural control of the activity of the neurosecretory canopy cell in the lateral lobes of the cerebral ganglia of the freshwater pulmonate Lymnaea stagnalis (L.).

In the lateral lobes of the cerebral ganglia of the pulmonate freshwater snail Lymnaea stagnalis (L.) one large neurosecretory canopy cell (CC) and two droplet cells (DC) are present. With the ganglion-transplantation technique and with quantitative electron microscopy it is shown that photoperiodic stimuli control the neurosecretory activity of the CC via a stimulatory extrinsic neural pathway. The eyes do not play an important role in this regulatory process. The neurosecretory activity of the DC is not affected by differences in photoperiod. The significance of the photoperiodic control of CC activity is discussed in relation to the pathway for the endocrine control of reproduction which is known to be photoperiod-dependent.

Animals↗
PubMed1979

Fixed phagocytes in the freshwater snail Lymnaea stagnalis.

Morphological and histochemical examination of the blood and connective tissue of the freshwater snail Lymnaea stagnalis injected with various types of foreign particulate materials has shown the existence of free as well as fixed phagocytic cells. The morphology of the fixed phagocytes is described, and the phagocytic system of the snail is compared with that of other molluscan species.

Animals↗
PubMed1980

Ultrastructural localization of carbonic anhydrase in tissues involved in shell formation and ionic regulation in the pond snail Lymnaea stagnalis.

The ultrastructural localization of carbonic anhydrase (CA) was investigated with the cobalt-bicarbonate method in three epithelia of the pond snail Lymnaea stagnalis. In the epidermis a selective population of "positive cells" was observed. In these cells, CA is confined to the apical and to small parts of the lateral plasma membrane. In cells of the outer mantle epithelium, CA is localized in the lateral and basal parts of the plasma membrane. In cells of the ureter, CA was found apically as well as basally. The localization of CA is discussed in relation to the different functions of the epidermis (electrolyte uptake), mantle (HCO3- secretion, calcification) and ureter (electrolyte uptake, acid-base regulation).

Animals↗
PubMed1991

Immuno-electron microscopy of sorting and release of neuropeptides in Lymnaea stagnalis.

The cerebral caudodorsal cells of the pulmonate snail Lymnaea stagnalis control egg laying and egg laying behavior by releasing various peptides derived from two precursors. The biosynthesis, storage, intracellular breakdown and release of three caudodorsal cell peptides were studied by means of immuno-electron microscopy using antisera raised to fragments of these peptides: (1) Caudodorsal Cell Hormone-I (CDCH-I; derived from precursor I), (2) Caudodorsal Cell Hormone-II (CDCH-II; from precursor II), and (3) alpha-Caudodorsal Cell Peptide (alpha CDCP; from both precursors). After affinity purification of the antisera, the specificity of the sera was confirmed with dotting immunobinding assays. From the ultrastructural immunocytochemical data it has been concluded that the precursor molecules are cleaved at the level of the Golgi apparatus after which the C-terminal parts (containing alpha CDCP) and N-terminal parts (containing DCDH-I or CDCH-II) are sorted and preferentially packaged into large electron-dense granules (MD 150 nm), respectively. Very probably, the content of the large electron-dense granules is degraded within the cell body. The immunoreactivity of the secretory granules increases during discharge from the Golgi apparatus, indicating further processing. At least a portion of the secretory granules contains all three peptides, as shown by double and triple immunopositive stainings whereas other granules appear to contain only one or two of these peptides. The caudodorsal cells release multiple peptides via exocytosis from neurohemal axon terminals into the hemolymph and from blindly ending axon collaterals into the intercellular space of the cerebral commissure (nonsynaptic release).

Amino Acid Sequence↗
PubMed1993

Neurons in a variety of molluscs react to antibodies raised against the VD1/RPD2 alpha-neuropeptide of the pond snail Lymnaea stagnalis.

The VD1 and RPD2 neurons of Lymnaea stagnalis innervate other central neurons, certain skin areas, the pneumostome area, and the auricle of the heart. Recently, a set of four (delta, epsilon, alpha, beta) neuropeptides produced by these giant neurons and by certain other central neurons has been characterized. Although alternative splicing of the preprohormone of these neurons yields at least 10 different alpha neuropeptides, an affinity-purified antiserum directed against a domain common to all alpha neuropeptides has previously been shown to be highly selective in staining VD1, RPD2 and other neurons that produce the preprohormone. Since the gene encoding the neuropeptides is structurally similar to that expressed in R15 of the marine opisthobranch Aplysia californica, we have used the affinity purified antiserum as a marker for VD1/RPD2-related systems in other molluscs. Immunopositive neurons and fibers are observed in the central nervous systems of all species studied (Achatina fulica, Anodonta sp., Aplysia brasiliana, A. californica, Bulinus truncatus, Cepea sp., Eobania vermiculata, Helix aspersa, H. pomatia, Limax maximus, Mytilus edulis, Nassarius reticulatus, Viviparus viviparus). Several medium-sized and small neurons and 1-4 giant neurons are found in the pulmonates and opisthobranchs. The giant neurons in pulmonates have locations in the subesophageal ganglion, axonal branching patterns, and terminal arborizations in the auricle of the heart; all these characteristics are similar to those of VD1 and RPD2. Double-labelling (Lucifer yellow injection, immunocytochemistry) confirms that the two giant neurons in Helix pomatia are Br and Br'. The immunoreactive cells in A. fulica appear to include the VIN and PON neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Functional morphology of the neuroendocrine sodium influx-stimulating peptide system of the pond snail, Lymnaea stagnalis, studied by in situ hybridization and immunocytochemistry.

The functional morphology of the neuroendocrine system producing sodium influx-stimulating (SIS) peptide in the pond snail, Lymnaea stagnalis, was studied by in situ hybridization and immunocytochemistry. The SIS-peptide, which is 76 amino acids long, stimulates sodium uptake from the ambient medium. Two synthetic DNA probes were used for in situ hybridization. The nucleotide sequences were chosen from the cDNA structure; they encode amino acids 8-17 and 64-73, respectively. SIS-peptide sequences 10-20 and 67-76 were synthesized and antibodies were raised to them and affinity-purified. In addition to these antibodies, a monoclonal antibody raised to a bioactive, high-pressure liquid chromatography (HPLC)-purified brain extract was used for immunocytochemistry. Paraffin sections of central nervous systems and of whole snails were studied. The SIS-peptide system could be identified as the previously described yellow cell (YC) system by comparing alternate sections treated with the DNA probes, stained with the antibodies, or stained with alcian blue-alcian yellow. SIS-peptide neurons (approximately 45) occur in the ganglia of the visceral ring and in the proximal parts of visceral nerves. Axons run in the nerves of these and in several nerves of other ganglia. Numerous axon branches penetrate the perineurium forming a vast central neurohemal area. The SIS-peptide system innervates the pericardium, the nephridial gland, the reno-pericardial canal, the ureter, the spermoviduct and gonadal acini, the anterior aorta, the ventral buccal artery, and the penis protractor muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The VD1/RPD2 neuronal system in the central nervous system of the pond snail Lymnaea stagnalis studied by in situ hybridization and immunocytochemistry.

VD1 and RPD2 are two giant neuropeptidergic neurons in the central nervous system (CNS) of the pond snail Lymnaea stagnalis. We wished to determine whether other central neurons in the CNS of L. stagnalis express the VD1/RPD2 gene. To this end, in situ hybridization with the cDNA probe of the VD1/RPD2 gene and immunocytochemistry with antisera specific to VD1 and RPD2 (the alpha 1-antiserum, Mab4H5 and ALMA 6) and to R15 (the alpha 1 and 16-mer antisera) were performed on alternate tissue sections. A VD1/RPD2 neuronal system comprising three classes of neurons (A1-A3) was found. All neurons of the system express the gene. Division into classes is based on immunocytochemical characteristics. Class A1 neurons (VD1 and RPD2) immunoreact with the alpha 1-antiserum, Mab4H5 and ALMA 6. Class A2 neurons (1-5 small and 1-5 medium sized neurons in the visceral and right parietal ganglion, and two clusters of small neurons and 5 medium-sized neurons in the cerebral ganglia) immunoreact with the alpha 1-antiserum and Mab4H5, but not with ALMA 6. Class A3 neurons (3-4 medium-sized neurons and a cluster of 4-5 small neurons located in the pedal ganglion) immunoreact with the alpha 1-antiserum only. All neurons of the system are immunonegative to the R15 antisera. The observations suggest that the neurons of the VD1/RPD2 system produce different sets of neuropeptides. A group of approximately 15 neurons (class B), scattered in the ganglia, immunostained with one or more of the antisera, but did not react with the cDNA probe in in situ hybridization.

Adrenocorticotropic Hormone↗
PubMed1994

Functional morphology of the light yellow cell and yellow cell (sodium influx-stimulating peptide) neuroendocrine systems of the pond snail Lymnaea stagnalis.

Neuroendocrine light yellow cells of the pond snail Lymnaea stagnalis express a neuropeptide gene encoding three different peptides. The morphology of the cell system has been studied by in situ hybridization, using two synthetic oligonucleotides encoding parts of light yellow cell peptides I and III, and by immunocytochemistry with antisera to synthetic light yellow cell peptide II and to two fragments of light yellow cell peptide I. One large cluster of light yellow cells was observed in the ventro-lateral protrusion of the right parietal ganglion, smaller clusters lying in the posterior dorsal part of this ganglion and in the visceral ganglion. The cells had an extended central neurohaemal area. Immunopositive axons projected into all nerves of the ganglia of the visceral complex, into the superior cervical and the nuchal nerves, and into the connective tissue surrounding the central nervous system. Axon tracts ramified between the muscle cells of the walls of the anterior aorta and of smaller blood vessels. Peripheral innervation by the light yellow cell system was only found in muscular tissue of the ureter papilla. The antisera to the two peptide fragments of light yellow cell peptide I not only stained the light yellow cells, but also the identified yellow cells, which have previously been shown to produce the sodium influx-stimulating neuropeptide. The latter cells were negative to the in situ hybridization probes and antisera specific to the light yellow cell system. It is therefore unlikely that the yellow cells express the light yellow cell neuropeptide gene. Nevertheless, the cells contain a neuropeptide sharing antigenic determinants with light yellow cell peptide I.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Expression and translation of the egg-laying neuropeptide hormone genes during post-embryonic development of the pond snail Lymnaea stagnalis.

The neuroendocrine caudodorsal cells of Lymnaea stagnalis express two homologous genes, each encoding a polypeptide precursor. The precursors give rise to "cocktails" of neuropeptides that regulate egg-laying. The expression and translation of both egg-laying hormone genes during post-embryonic development were investigated by in situ hybridization and by electron-microscopic immunocytochemistry. Gene-II-specific transcripts and translation products were not found in caudodorsal cells in animals with shell heights smaller than 10 mm, in contrast to gene-I products that were present even at 3-mm shell height. The onset of expression of gene II coincides with the onset of release of products from the caudodorsal cells into the blood. Large electron-dense granules were found in caudodorsal cells of snails of all developmental stages investigated. These granules form part of the Golgi sorting and packaging pathway. Their presence suggests that differential sorting and packaging is possible during post-embryonic development, like in adults. The relationship of the differential expression of the two genes to the development of the caudodorsal cell system and its targets is discussed.

Amino Acid Sequence↗
PubMed1994

Axonal localization of neuropeptide-encoding mRNA in identified neurons of the snail Lymnaea stagnalis.

mRNA transcripts encoding neuropeptides were detected, by means of in situ hybridization, in the axonal compartments of different types of identified neurons in the central nervous system of the pond snail Lymnaea stagnalis. All cell types studied contained axonal mRNA although the relative intensities of the hybridization signals (i.e., the intensity of the signal over the cell body versus that over the axonal compartment of a particular cell) varied greatly between the different cell types studied. Strong signals over the axonal compartment were obtained with an oligonucleotide probe specific for the molluscan insulin-related peptide gene III mRNA, whereas low signals were obtained, e.g., with a probe for the mRNA encoding the neuropeptide APG-Wamide. Furthermore, some neurons are known to express more than one neuropeptide gene, e.g., the molluscan insulin-related peptide-producing light green cells and the egg-laying hormone-producing caudo-dorsal cells; these cell types express 4 and 2 related neuropeptide genes, respectively. The results may indicate that the different neuropeptide transcripts within a neuron are transported selectively to the axonal compartment.

Animals↗
PubMed1993

Intracellular ATP modulates desensitization of acetylcholine receptors controlling chloride current in Lymnaea neurons.

Chloride current activated by nicotinic acetylcholine receptors (AChR) was examined in dialysed voltage-clamp neurons of Lymnaea stagnalis. Fast superfusion of acetylcholine (ACh) evoked an inward current rapidly rising to a peak followed by a decline due to desensitization. When adenosine triphosphate with Mg2+ (MgATP, 2-10 mM) was added intracellularly the peak of the ACh-induced current was increased and its decay was slowed down. ATP without Mg2+ did not affect desensitization. Mg2+ alone accelerated desensitization. Intracellular treatment with an inhibitor of ATP synthesis, sodium arsenate, increased the desensitization rate and decreased the peak current. MgATP after arsenate wash-out restored the initial characteristics of the response; a mixture of glycolytic substrates had a similar effect. A non-hydrolysable analogue of ATP, adenosine [gamma-thio]triphosphate mimicked ATP action after arsenate removal but was weaker; another non-hydrolysable analogue, adenylyl imidodiphosphate, did not affect desensitization at all. Intracellular treatment of the neurons with alkaline phosphatase accelerated current decay. The data suggest that a change in intracellular ATP concentration modulates AChR desensitization via an enzymatic process that might be phosphorylation of AChR or some associated protein(s). Involvement of Ca2+ homeostasis cannot be excluded. The results are compared with the data obtained on vertebrate tissues under conditions promoting phosphorylation.

Adenosine Triphosphate↗
PubMed1976

The effects of low temperature on Lymnaea truncatula.

A group of 20 young and another of 20 adult Lymnaea truncatula were abundantly supplied with food and kept continuously under cold conditions (5 degrees C) in the laboratory for 3 months and the effects of low temperature on their behavior, growth and reproduction were studied. The results indicate that at low temperature the activity of L. truncatula was markedly reduced but complete hibernation did not occur. The snails seem to be unaffected by the low temperature itself since none (both young and adult) died during the 3 months that they were kept at 5 degrees C. Reduced feeding, even in the presence of abundant food, during the cold conditions caused an almost total inhibiton of growth. Of even more significance was the suppression of reproduction which was connected with the metabolic rate of adult snails kept at low temperature. Young snails seem to profit by exposure to low temperature. On the return to normal laboratory temperature (16-22 degrees C) the young snails became very active, fed voraciously, grew rapidly, tended to live longer and produced more offspring than the controls. Low temperature, however, appears to have an adverse after-effect on the growth and reproduction of mature snails. Relatively, fewer eggs were deposited in this case. The results indicate that under natural field conditions in England, where temperature fluctuations during the usually mild winter months are common, the greater burden of increasing the population in overwintered snails must rest on the younger members of the community.

Age Factors↗
PubMed1992

Differential expression of four genes encoding molluscan insulin-related peptides in the central nervous system of the pond snail Lymnaea stagnalis.

In the pond snail Lymnaea stagnalis, the growth regulating system consists of (1) about 200 neuroendocrine light green cells, located in four clusters in the cerebral ganglia, and (2) the paired canopy cells, located in the lateral lobes. These cells express genes encoding the molluscan insulin-related peptides (MIPs). Six MIP genes have previously been identified. Four of these (I, II, III and V) are expressed in the light green cells and the canopy cells. The MIP-VI gene is a pseudogene. In the present in situ hybridization study, using oligonucleotide probes specific to the transcripts of MIP-I, -II, -III, -IV and -V, no signal was obtained with the MIP-IV probe, indicating that gene IV is also a pseudogene. With the other four probes, two types of light green cells were distinguished. Type-A cells express all four MIP genes, whereas type-B cells do not (or only faintly) express the MIP-I gene. Gene III is relatively strongly expressed in type-B cells. Genes II and V are moderately expressed in both cell types. Type-A cells are mainly located in the periphery of the clusters, whereas type-B cells are present in the center. The canopy cell resembles type-A light green cells. The expression levels of the MIP-II and MIP-V genes are low in the canopy cell. The expression pattern of the MIP genes correlates with the staining pattern of the anti-MIP-C antibody, which has been raised to a synthetic C-fragment shared by MIP-I, -II and -V. Type-A cells stain more intensely with the antibody than type-B cells.

Animals↗
PubMed1976

Studies on the infectivity of Fasciola hepatica miracidia to Lymnaea truncatula. Attachment and penetration of miracidia into non-infected and infected snails.

Fasciola hepatica miracidia labelled in vivo with radioselenium have been used in studies on the capacity of the miracidia to attach to and penetrate the tegument of infected compared with non-infected host snails (Lymnaea truncatula). The results show that the penetration of the larvae into the snail tissue is not influenced by an already existing infection, regardless of its developmental stage.

Animals↗
PubMed1984

Characterisation of multiple immunoreactive neurons in the central nervous system of the pond snail Lymnaea stagnalis with different fixatives and antisera adsorbed with the homologous and the heterologous antigens.

In the central nervous system of the pond snail Lymnaea stagnalis a large number of elements (cells and fibers) can be identified with antisera (a-FM) to the molluscan cardioactive tetrapeptide FMRFamide (Phe-Met-Arg-Phe-NH2). Of these elements some are also reactive to antivasotocin (a-VT) and/or anti-gastrin (a-Gas). These observations suggest that the a-FM positive elements belong to more than one type. Previous results had already indicated that the immunoreactivity of many a-FM positive cells is influenced by the type of fixation. Taking into account the effects of three fixatives on the reactivity of the cells, and their staining characteristics with the two other antisera used, 8 a-FM positive types could be distinguished. Homologous and heterologous adsorptions were carried out to test the specificity of a-FM, a-VT and a-Gas. After homologous adsorptions no staining was obtained. After heterologous adsorptions only part of the multiple staining cells were identified. This indicates that in a-FM, a-VT and a-Gas in addition to (more) selective IgG molecules, less specific IgG molecules occur that can bind to other peptides than those used to raise the antisera (cross-reaction). The (more) selective IgG molecules in a-FM bind to 6 of the a-FM positive types, suggesting that in L. stagnalis a family of FMRFamide-like substances occurs. This conclusion is sustained by results obtained with a-FM adsorbed with fragments of FMRFamide.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

[Fasciola hepatica L.: the productivity of a sporocyst as a function of the size of Lymnaea truncatula Müller].

Experimental studies were undertaken on the rediae of Fasciola hepatica and on their content in two populations of Lymnaea truncatula snails, individually exposed to a single miracidium and fixed for histologic observations just after their death between days 74 and 81 postexposure at 20 degrees C. The numbers of free rediae and of larval stages per snail increased with the shell height. A constant number of free rediae was observed in snails measuring 11 mm and more in size. There was no limit of increase in number for the different types of larval stages, but these increases were lower for the youngest larval types. The number of larval stages per redia also increased with snail size; it was always higher in the first redial generation than in the following generations. Cercariae were produced by 40%-43% of the rediae contained in a snail: 65%-80% of these mature rediae belonged to the first generation and to the first cohort of the second generation.

Animals↗