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PubMed1987

Identification of a UDP-Gal:beta-galactoside beta 1----3-galactosyltransferase in the albumen gland of the snail Lymnaea stagnalis.

Detergent extracts of the albumen gland of the snail Lymnaea stagnalis contain an enzyme activity that transfers Gal from UDP-Gal to acceptor substrates with terminal non-reducing beta-galactose residues. The products formed with lactose (Gal beta 1----4Glc) as the acceptor were characterized by HPLC, and subjected to 400-MHz 1H-NMR and methylation analysis. The main product was shown to have the structure Gal beta 1----3Gal beta 1----4Glc. Therefore, the galactosyltransferase can be identified as a UDP-Gal:beta-galactoside beta 1----3-galactosyltransferase. In view of its linkage and acceptor specificity, the enzyme may be essential to the biosynthesis of galactogen, the main polysaccharide produced by albumen glands of L. stagnalis.

Animals↗
PubMed1983

Partial purification and characterization of the ovulation hormone of the freshwater pulmonate snail Lymnaea stagnalis.

The neurosecretory caudodorsal cells in the cerebral ganglia of the basommatophoran snail Lymnaea stagnalis produce an ovulation hormone (CDCH), which is released from the periphery of the intercerebral commissure. In the present study CDCH has been partially purified, starting with a hydrochloride acid extract of commissures, by gel permeation chromatography on Bio-Gel P-6 followed by cation exchange on SP-Sephadex C-25. This two-step procedure resulted in a ca. 22-fold purification of CDCH. The low purification factor is caused by poor resolution of both purification steps and low recovery on the Bio-Gel P-6 column. With stability tests, proteolytic enzymes, SDS/urea polyacrylamide electrophoresis and isoelectric focussing, purified CDCH was characterized as a stable peptide with a molecular weight of ca. 4700 d and a pI of ca. 9.3. The properties of CDCH are similar to those of the ovulation hormones of opisthobranch snails. Studies on species specificity indicate, however, that it is unlikely that CDCH will cause ovulation when injected in opisthobranchs, or vice versa.

Animals↗
PubMed1983

Effects of two gonadotropic hormones on polysaccharide synthesis in the albumen gland of Lymnaea stagnalis, studied with the organ culture technique.

A medium for culturing organs of the basommatophoran freshwater snail Lymnaea stagnalis is described. One of the accessory sex glands, the albumen gland, which produces proteins and galactogen as nutritive substances for the embryos, was cultured along with parts of the central nervous system (CNS), including the female gonadotropic hormone-producing dorsal bodies (DB). Culture time was 4 days. The cerebral ganglia and the DB appeared to have a strong stimulating influence on polysaccharide synthesis in the albumen gland. The remaining part of the CNS has a weak stimulating effect. The use of extracts (culture time 6-26 hr) of parts of the cerebral ganglia and of the DB showed that not only the dorsal body hormone (DBH), but also the ovulation hormone (CDCH)--a neurohormone produced by the caudodorsal cells located in the cerebral ganglia--stimulates the synthetic activity of the albumen gland. The action of these hormones is direct; i.e., it is not exerted via the gonad. Dose- and time-response relations for the DBH and the CDCH are very similar. No additional rise in stimulation occurred when the two hormones were administered together. Experiments with albumen glands of adult snails demonstrated that the presence of large quantities of secretory material in the gland inhibits the response to DBH and CDCH.

Animals↗
PubMed1983

Effect of the photoperiod on the time schedule of egg mass production in Lymnaea stagnalis, as induced by ovulation hormone injections.

In the pulmonate snail Lymnaea stagnalis the neurosecretory caudo-dorsal cells (CDC) produce an ovulation hormone (CDCH) which is released at the periphery of the cerebral commissure (COM). Time schedules of the successive stages of the egg mass production following CDCH injection (COM extract) were determined at 20 degrees. Ovulation is performed rapidly, within 10 to 20 min. The latencies of the other stages are: egg formation, 20-30 min; egg mass formation, 60-90 min; and oviposition, about 120 min. The duration of oviposition is dependent on the size of the egg mass and varies from 5 to 20 min. At a 16-hr photoperiod all stages start 10 min earlier than at a 12-hr photoperiod. It is suggested that the effect of the photoperiod is achieved by a change of release activities of dorsal bodies and/or of CDC. The possibility that a nervous mechanism is involved in the control of the packaging of the egg cells is discussed.

Animals↗
PubMed1983

A rapid in vivo bioassay of the ovulation hormone of Lymnaea stagnalis.

The neurosecretory caudo-dorsal cells (CDC) of the basommatopora Lymnaea stagnalis produce an ovulation hormone (CDCH), which is released at the periphery of the intercerebral commissure (COM). A rapid in vivo bioassay for CDCH has been established and is based on the dose-dependent relationship between the quantity of injected CDCH (COM-extract) and the number of snails responding with the first stages of the egg-mass production process, as determined 30 min after injection. Three types of scores can be distinguished: (1) no response (very low CDCH doses), (2) ovulation only (O), and (3) ovulation and packaging (O + P). With increasing CDCH doses the number of snails responding with O, O + P, and oviposition increases. It is shown that the O response first increases followed by a decrease, while simultaneously, the P response increases. This is caused by the fact that the packaging latency is dose dependent, i.e., at low doses it is greater than 30 min, whereas at higher doses it is less than 30 min. This agrees with the finding that at low doses the oviposition latencies are longer (ca. 20 min) than at higher doses. The size of the egg mass is not dose dependent. Several factors that influence the responses upon which the bioassay is based have been analyzed, i.e., refractory period, photoperiod, and day-to-day variability of the assay snails. Experiments relating to the development of a bioassay are reported. The half-life of injected CDCH appeared to be 30-40 min.

Animals↗
PubMed1984

Ovulation hormone, nutritive state, and female reproductive activity in Lymnaea stagnalis.

A study of the relation between nutritive state and female reproductive activity as affected by the ovulation hormone (CDCH) has been made in the freshwater pulmonate snail Lymnaea stagnalis. CDCH is produced by the neuroendocrine caudodorsal cells (CDC) in the cerebral ganglia. Spontaneous oviposition ceased within 6 days of the beginning of a starvation period. This is most probably partially due to a reduction in the CDC activities because (1) quantitative electron microscopy showed a nearly 80% decrease in the number of release phenomena in the CDC-axon terminals in the neurohemal area in the intercerebral commissure, and (2) a bioassay showed a considerable reduction in the amount of CDCH in this area. During starvation the ovotestis and the female accessory sex organs became progressively less sensitive and, after 25 days, were completely insensitive to injected CDCH. This was indicated by a decrease in the responses to CDCH injection and, correspondingly, by a gradual increase in the CDCH thresholds for ovulation and egg formation. It is argued that the insensitivity may be caused by a reduction in the activities of the endocrine dorsal bodies. During refeeding, CDCH injections again become effective in inducing egg mass production, followed by resumption of spontaneous oviposition. This suggests a rapid restoration of DB and CDC activities following refeeding.

Animals↗
PubMed1984

Isolation of neurosecretory granules from the neurohaemal areas of peptidergic systems of Lymnaea stagnalis, with special reference to the ovulation hormone-producing caudodorsal cells.

Neurosecretory granules (NSG) were isolated by density-gradient centrifugation from homogenates of the intercerebral commissure (COM) and the median lip nerves (LN) of the freshwater snail Lymnaea stagnalis. COM and LN are rich in axon terminals of the ovulation hormone-producing caudodorsal cells (CDC) and of the growth hormone-producing light green cells (LGC), respectively. Electron microscopy of COM isolates showed that a single fraction contained large numbers of NSG, which were identical to NSG of CDC axon terminals of the intact COM. High ovulation hormone activity was associated with this fraction. LN NSG were also isolated in large numbers in a single fraction. The isolated LN NSG were identical to NSG of intact LGC axon terminals. They appeared to have a higher specific gravity than CDC NSG.

Animals↗
PubMed1985

Environmental and hormonal control of the seasonal egg laying period in field specimens of Lymnaea stagnalis.

A study has been made in field specimens of Lymnaea stagnalis of the relationship between environmental factors (temperature, photoperiod, and food) and spontaneous ovipository activity as well as oviposition evoked by injection of the ovulation hormone (CDCH) during a 1-year cycle. It appeared that spontaneous egg laying started in mid-May and ended in mid-September. It is concluded that it is the quantity of assimilated food that triggers the onset of the egg laying season. Its termination is very likely determined by a synergistic action of environmental factors. It is suggested that these factors control the activities of the CDCH-producing neuro-endocrine caudo-dorsal cells. In winter the snails are completely insensitive to injected CDCH, although many large oocytes are present in the gonad. During 2 months before and after the egg laying season, however, many injected snails respond to CDCH. It is argued that these phenomena are caused by changes in the activities of the endocrine dorsal bodies, which control vitellogenesis and the activities of the female accessory sex organs. The changes in the activities of the dorsal bodies are probably controlled by the synergistic actions of the previously mentioned environmental factors. Oviposition latency (interval between CDCH injection and start of oviposition) is much shorter during the egg laying season than in the nonreproductive period. This must be ascribed to the direct effects of temperature.

Animals↗
PubMed1985

Neuroendocrine control of glycogen mobilization in the freshwater snail Lymnaea stagnalis.

In the freshwater snail Lymnaea stagnalis the anterior mantle region, which mainly consists of large numbers of special glycogen-storing cells, is an important depot for the energy reserves of this snail. In organ culture experiments the central nervous system (CNS), in contrast to other tissues, both inhibits glycogen synthesis (measured as incorporation of [14C]glucose into glycogen) and stimulates glycogen breakdown in anterior mantle tissue (measured as a decreased retention of prelabeled glycogen). These effects are dose dependent, with saturation at the highest doses tested. High-potassium Ringer solution stimulates the secretion of a CNS factor which induces glucose release by anterior mantle tissue. This glucose-release-stimulating effect of the CNS is also dose dependent, but saturation of the response was not achieved. It is concluded that inhibition of glycogen synthesis and stimulation of glycogen breakdown and glucose release are probably effects of a single neurohormone which controls glycogen mobilization from the storage cells in the mantle. Like similar factors in other animal phyla, this putative neurohormone is referred to as a hyperglycemic factor.

Animals↗
PubMed1985

The hyperglycemic factor of the CNS of the freshwater snail Lymnaea stagnalis: interaction with glucose stimulation of glycogen synthesis and evidence for its release during anaerobiosis.

In the freshwater pulmonate snail Lymnaea stagnalis glycogen synthesis in the glycogen storage cells (GC) is stimulated by increasing external glucose concentrations. On the other hand, a hyperglycemic factor from the CNS inhibits glycogen synthesis and stimulates glycogen breakdown in these cells. This CNS factor may be involved in the physiological control of glycogen mobilization. In the present study the interaction between the inhibiting effect of the CNS factor and the stimulating effect of increasing glucose concentrations on glycogen synthesis in isolated GC was investigated. The results, analyzed by determination of the Michaelis-Menten parameters for saturation kinetics, suggest that the CNS factor increases the glucose concentration required for half-maximal stimulation of glycogen synthesis, but does not influence the maximum rate of synthesis (competitive type of inhibition). The role of the hyperglycemic factor during conditions of glycogen breakdown was investigated by extirpation of the cerebral ganglia (-CG), which contain the main release sites of the factor. Extirpation did not affect the hemolymph glucose concentration or the glycogen levels in the GC during starvation. However, -CG animals showed reduced levels of the hyperglycemia normally associated with exposure to anaerobic conditions.

Anaerobiosis↗
PubMed1986

Neurohormonal control of Na+ and Cl- metabolism in the pulmonate freshwater snail Lymnaea stagnalis.

In Lymnaea stagnalis, extirpation of the cerebral ganglia resulted in a significant decrease of the Na+ and Cl- concentrations in the haemolymph. In intact snails, injection of an extract of the cerebral ganglia stimulated the Na+ influx from the external medium in a dose-dependent way. No effect on the Cl- influx was found. Extract injections did not affect the Na+ efflux. The Na+ influx stimulating activity, in relatively high concentrations, was also present in extracts of the median lip nerve (an important neurohaemal area, originating from the cerebral ganglia). The influx-stimulating activity was heat-stable and destroyed by Pronase treatment. It is suggested that in L. stagnalis, Na+ uptake from the medium is controlled by a neurohormone produced by the cerebral ganglia.

Animals↗
PubMed1986

Enzyme cytochemical evidence for the activation of adenylate cyclase in the follicle cells of vitellogenic oocytes by the dorsal body hormone in the snail Lymnaea stagnalis.

It is unknown what cell type(s) in the gonad of the hermaphroditic snail Lymnaea stagnalis is the target(s) of the two gonadotropic hormones, dorsal body hormone (DBH) and caudo-dorsal cell neuro-hormone (CDCH). It was considered that the hormones might act by activating the adenylate cyclase (AC)-cAMP system in the targets. AC activation was determined histochemically. The CDCH (ovulation hormone) titer can be manipulated in vivo by inducing egg laying experimentally ("clean water stimulus"). The effect of the oocyte growth-stimulating DBH and also that of CDCH was studied in in vitro experiments. Only the follicle cells appeared to possess and AC-cAMP system (experiments with forskolin). This system can be activated by DBH, but not by CDCH. Activation can only be brought about in certain stages of the egg-laying process. In vivo this activation was apparent from 30-45 min until 2-3 hr after ovulation, i.e., until 0-1 hr after egg mass deposition. In vitro activation was possible 0-30 min after ovulation. Activation was only obvious in certain stages of oogenesis (not in follicle cells of younger oocyte stages). The results indicate that it is the follicle cells that are the targets for DBH. The possible role of the follicle cells is discussed. The question of what are the targets of CDCH remains unsolved. Apparently this hormone does not act via AC-cAMP, but via another second messenger.

Adenylyl Cyclases↗
PubMed1987

A neuropeptide (Calfluxin) is involved in the influx of calcium into mitochondria of the albumen gland of the freshwater snail Lymnaea stagnalis.

In the course of a study on the role of Ca2+ in the regulation of the secretion process in a female accessory sex gland, the albumen gland of the freshwater snail Lymnaea stagnalis, it appeared that the percentage of mitochondria containing Ca2+ deposits varied significantly in the successive stages of the egg-laying process. Ca2+ was demonstrated at the ultrastructural level with the pyroantimonate precipitation technique. A significant increase of the percentage can be correlated with the onset of synthetic activity. Two gonadotropic (neuro) hormones are known to stimulate synthetic activity, viz. the cerebral caudo-dorsal cell hormone (CDCH) and the dorsal body hormone (DBH). In vitro experiments involving addition of extracts of various parts of the cerebral ganglion-dorsal body (DB) complex to albumen glands showed that neither CDCH nor DBH causes the influx of Ca2+ into the mitochondria of the gland cells, but that another factor is responsible. The factor is present in the cerebral commissure. It is pronase sensitive and heat stable. The factor is released from isolated cerebral ganglia-DB complexes upon stimulation with 8-chlorophenylthio-cAMP. Probably the factor is a CDC peptide. It is called Calfluxin.

Animals↗
PubMed1988

The role of IP3, PKC, and pHi in the stimulus-response coupling of calfluxin-stimulated albumen glands of the freshwater snail Lymnaea stagnalis.

Signal-response coupling was studied in an exocrine female accessory sex gland (albumen gland) of the freshwater snail Lymnaea stagnalis. Glands were incubated in vitro with Calfluxin (CaFl), a neuropeptide which stimulates the influx of Ca2+ into the mitochondria of the secretory cells. This influx, which is considered to reflect an increase of Ca2+ in the cytosol, was measured as the percentage mitochondria containing Ca deposits. Ca deposits. Ca deposits were visualized at the ultrastructural level with the pyroantimonate precipitation technique. The origin of the Ca2+ and the mechanism by which the Ca2+ concentration in the cytosol is elevated were investigated. The results indicate that CaFl stimulates the influx of extracellular Ca2+ and mobilizes intracellular Ca2+. The increase of the percentage of mitochondria containing Ca deposits is sensitive to Ca2+ channel blockers (D600, Co2+, La3+), indicating that Ca2+ channels are involved. Li+ ions suppress the CaFl response, which suggests that the hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2), and thus the production of myo-inositol-1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol (DG) is involved in the Ca2+ mobilization. The protein kinase-C (PKC) stimulator 4-beta-phorbol 12-beta-myrastate 13-alpha-acetate (PMA) mimicked the response to CaFl. The PKC inhibitors trifluoperazine (TFP) and chlorpromazine (CP) markedly decreased the CaFl-stimulated influx of Ca2+ into the mitochondria. The PMA-stimulated influx of Ca2+ into the mitochondria is not dependent on extracellular Ca2+ and is not sensitive to Ca2+ channel blockers. In PMA-stimulated glands, the Na+/H+ exchange blocker amiloride completely abolished the Ca2+ influx into mitochondria. In CaFl-stimulated glands the influx was partly blocked. Increasing the internal pH of the glandular cells with the Na+/H+ ionophore monensin or with NH4Cl mimicked the CaFl response. It is proposed that upon stimulation with CaFl, mobilization of intracellular Ca2+ is mediated via the PKC-stimulated activation of the Na+/H+ exchange, thus leading to an increase of the internal pH. The role of IP3 in the mobilization of intracellular Ca2+ is uncertain.

Animals↗
PubMed1989

Immunocytochemical demonstration of a novel system of neuroendocrine peptidergic neurons in the pond snail Lymnaea stagnalis, with antisera to the teleostean hormone hypocalcin and mammalian parathyroid hormone.

Immunocytochemical staining with antisera raised against trout hypocalcin, the hypocalcemic hormone of the Stannius corpuscles and against bovine parathyroid hormone (bPTH1-84), revealed a new system of neuroendocrine neurons in the pond snail Lymnaea stagnalis. The neurons are located in small groups or single cells in the visceral, parietal, and pedal ganglia of the central nervous system. The axons of these cells are running to the periphery of the pleuroparietal, visceroparietal, and pleuropedal connections, the dorsopedal commissure, and to several nerves originating in the visceral, parietal, and pedal ganglia. The axons are ending with characteristic axonal distensions in the periphery of these connectives, commissure, and nerves. These regions probably act as neurohaemal areas. The affinity of this neuroendocrine system for both the anti-hypocalcin and anti-PTH sera is another indication for a special relationship between hypocalcin and PTH, which possess some immunological resemblance and similar biological activities, although no similarity in primary structure.

Animals↗
PubMed1989

Secretory activity and postembryonic development of the tentacle sensory system controlling growth hormone-producing neurons in Lymnaea stagnalis.

The cerebral neuroendocrine peptidergic light green cells (LGC) of the freshwater snail Lymnaea stagnalis regulate body growth. The LGC are controlled by a tentacle sensory system that consists of two types (S1 and S2) of primary sensory neuron located at the base of each tentacle. Sensory (S2) axons make synaptic contacts (type A synapse-like structures) with the somata and axons of the LGC, where they release the contents of secretory granules, by exocytosis (demonstrated with the ultrastructural tannic acid-Ringer incubation method). Ultracytochemistry indicates that the granule contents are glycoproteinaceous. Furthermore, the S2 axons release secretory material in a nonsynaptic fashion into the interneuronal space of the central nervous system (CNS), at the level of the neuropiles of the cerebral ganglia and of the cerebral commissure. This release occurs by exocytosis from nonsynaptic release sites. It is proposed that the tentacle sensory system not only (synaptically) controls LGC activity but also influences other, remote neuronal targets in the CNS in a nonsynaptic ("at long distance," "paracrine," "hormone-like") fashion. Already in newly hatched snails (with a shell height of 1 mm) S2 axons show a fair rate of exocytotic activity, in both synaptic and nonsynaptic respects. During postembryonic development the secretory capacity of the S2 sensory neurons increases markedly, by increases in (1) the number of axons, (2) the size of the secretory granules, and (3) exocytosis activity. This increased capacity may meet a growing demand of the developing CNS, including the LGC, for neurochemical input from the tentacle sensory system.

Animals↗
PubMed1990

Immunocytochemical localization in the central nervous system of four different insect species of molecules immunoreactive against peptides present in the caudodorsal cells of Lymnaea stagnalis.

The use of polyclonal antisera directed against three peptides (ovulation hormone (CDCH), alpha, and beta caudodorsal cell peptide (alpha- and beta-CDCP) produced by the caudodorsal cells of the snail Lymnaea stagnalis resulted in positive immunoreaction in Sarcophaga bullata (Diptera), Leptinotarsa decemlineata (Coleoptera), Locusta migratoria, and Periplaneta americana (Orthoptera). In three species, colocalization was detected using the antisera against CDCH and alpha-CDCP.

Animals↗
PubMed1992

Light and electron microscopic immunocytochemical demonstration of synthesis, storage, and release sites of the neuropeptide calfluxin in Lymnaea stagnalis.

The cerebral caudodorsal cells (CDC) of the pulmonate snail Lymnaea stagnalis control egg-laying and associated behaviors. They produce various peptides derived from two precursor molecules, proCDCH-I and II, one of which is calfuxin (CaFl). CaFL is involved in the control of the activity of a female accessory sex gland, the albumen gland. At the light microscope level, using an antibody raised against synthetic CaFl, immunoreactivity was demonstrated in all CDC somata as well as in the neurohemal CDC terminals in the periphery of the cerebral commissure and in the CDC axon collaterals in the inner region of the commissure. A group of small neurons in each cerebral ganglion was also immunopositive. At the ultrastructural level, secretory granules (SG) and large electron-dense granules (LG), formed by the Golgi apparatus and thought to be involved in intracellular degradation of secretory material, were clearly immunolabeled. The density of immunolabeling of LG was 3.3 times greater than that of SG, indicating that CaFl is preferentially packed into LG. In the LG, the density of immunolabeling with anti-alpha CDCP (alpha CDCP is also a peptide derived from proCDCH-I and II) was 10 times greater than in SG, suggesting that CaFl and alpha CDCP are processed and sorted in (quantitatively) different ways. In the neurohemal terminals SG release their CaFl-immunopositive contents into the hemolymph by the process of exocytosis, whereas collaterals release such contents into the intracellular space of the intercerebral commissure. It is proposed that neurohemally released CaFl acts upon the albumen gland, whereas CaFl released from the collaterals may influence the activity of central neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗