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J van Minnen

Publications and source records attributed to J van Minnen.

At least 37 records · Page 2Linked to original sources
PubMed1996

Co-evolution of ligand-receptor pairs in the vasopressin/oxytocin superfamily of bioactive peptides.

In order to understand the molecular mechanisms that underlie the co-evolution of related yet functionally distinct peptide-receptor pairs, we study receptors for the vasopressin-related peptide Lys-conopressin in the mollusc Lymnaea stagnalis. In addition to a previously cloned Lys-conopressin receptor (LSCPR1), we have now identified a novel Lys-conopressin receptor subtype, named LSCPR2. The two receptors have a differential distribution in the reproductive organs and the brain, which suggests that they are involved in the control of distinct aspects of reproduction and mediate transmitter-like and/or modulatory effects of Lys-conopressin on different types of central neurons. In contrast to LSCPR1, LSCPR2 is maximally activated by both Lys-conopressin and Ile-conopressin, an oxytocin-like synthetic analog of Lys-conopressin. Together with a study of the phylogenetic relationships of Lys-conopressin receptors and their vertebrate counterparts, these data suggest that LSCPR2 represents an ancestral receptor to the vasopressin/oxytocin receptor family in the vertebrates. Based on our findings, we provide a theory of the molecular co-evolution of the functionally distinct ligand-receptor pairs of the vasopressin/oxytocin superfamily of bioactive peptides.

Amino Acid Sequence↗
PubMed1996

Structure, localization and action of a novel inhibitory neuropeptide involved in the feeding of Lymnaea.

A neuropeptide that strongly inhibits the spontaneous contractions of the oesophagus in Lymnaea has been characterized as GAPRFVamide. Direct mass spectrometry of nervous tissues and immunocytochemical studies show that the peptide is synthesized by neurones in the buccal ganglia and transported to the oesophagus via the dorso-buccal nerve. In accordance with the function of the peptide, immunoreactive fibres are detected within the muscle layer of the oesophagus. Finally, mass spectrometry reveals the presence of a number of unidentified peptides in the nerves that innervate the oesophagus, which suggests that oesophageal activities may be modified by multiple peptides.

Animals↗
PubMed1995

Visualization of agonist-induced internalization of histamine H2 receptors.

Histamine H2 receptors were tagged at the N-terminus with the eight amino acid Flag epitope to allow the immunological identification of the receptor peptide with the monoclonal anti-Flag M2 antibody. The introduction of the epitope did not modify the binding of several H2 ligands to the H2 receptor, nor the ability of histamine to stimulate the H2 receptor mediated cAMP production in HEK-293 cells. Western blots revealed a major protein band of 57 +/- 1 kDa, whereas a second band of 31 +/- 1 kDa was probably the result of a proteolytic breakdown of the 57 kDa band. Immunofluorescence measurements of stably transfected HEK-293 cells revealed the presence of anti-Flag-immunoreactivity in the plasma membrane. This immunoreactivity completely disappeared after a one hour treatment with histamine. The receptor internalization was reversible and blocked by the endocytosis inhibitor phenylarsine oxide. Forskolin did not induce H2 receptor internalization, indicating that histamine causes H2 receptor internalization via a cAMP-independent pathway.

Amino Acid Sequence↗
PubMed1995

Cloning of a molluscan G protein alpha subunit of the Gq class which is expressed differentially in identified neurons.

Through molecular cloning we have identified a molluscan G protein alpha subunit which belongs to the G alpha q family and is expressed in the central nervous system (CNS) of the pond snail, Lymnaea stagnalis. The deduced protein product shares a very high degree of amino sequence identity with vertebrate and invertebrate G alpha q/G alpha 11 subunits (80-82% and 76-77%, respectively). Large parts of the protein have been completely conserved, among which are residues 25-58, including the nucleotide-binding A domain. Especially the C-terminal half (amino acids 195-353), implicated in receptor and effector interactions, is highly conserved (94% sequence identity with murine sequences). This region includes the nucleotide-binding C, G, and I domains, which are identical to cognate motifs of vertebrate G alpha q/11. Like the latter proteins, the Lymnaea G alpha q C-terminus lacks a cysteine that could serve as a substrate for pertussis toxin. In situ hybridization reveals G alpha q-encoding mRNA(s) to be present throughout the CNS. Interestingly, however, close inspection of two identified cell types in the cerebral ganglia, the light-green cells, involved in the regulation of growth and metabolism and the anterior lobe cells which are involved in the control of male aspects of reproduction, indicates that they express the mRNA(s) at significantly different levels. Even within the heterologous cluster of light-green cells there appears to be differential expression of the pertinent mRNA. Such observations have hitherto not been reported for specific cell types occurring in vivo.

Amino Acid Sequence↗
PubMed1995

A novel G protein-coupled receptor mediating both vasopressin- and oxytocin-like functions of Lys-conopressin in Lymnaea stagnalis.

We have cloned a receptor, named LSCPR, for vasopressin-related Lys-conopressin in Lymnaea stagnalis. Lys-conopressin evokes Ca(2+)-dependent Cl- currents in Xenopus oocytes injected with LSCPR cRNA. Expression of LSCPR mRNA was detected in central neurons and peripheral muscles associated with reproduction. Upon application of Lys-conopressin, both neurons and muscle cells depolarize owing to an enhancement of voltage-dependent Ca2+ currents and start firing action potentials. Some neurons coexpress LSCPR and Lys-conopressin, suggesting an autotransmitter-like function for this peptide. Lys-conopressin also induces a depolarizing response in LSCPR-expressing neuroendocrine cells that control carbohydrate metabolism. Thus, in addition to oxytocin-like reproductive functions, LSCPR mediates vasopressin-like metabolic functions of Lys-conopressin as well.

Amino Acid Sequence↗
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

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↗
PubMed1994

Structural identification, neuronal synthesis, and role in male copulation of myomodulin-A of Lymnaea: a study involving direct peptide profiling of nervous tissue by mass spectrometry.

We used a strategy combining immunodetection, peptide chemistry, and a novel method, direct peptide fingerprinting of neurons and small pieces of nerve by using matrix-assisted laser desorption ionization mass spectrometry, to structurally identify and localize the neuropeptide myomodulin-A in the mollusc, Lymnaea stagnalis. Lymnaea myomodulin appeared to be identical to Aplysia myomodulin-A and is produced by many central neurons, including neurons located in the ventral lobe of the right cerebral ganglion that innervate the penis complex via the penis nerve. Myomodulin-A could also be characterized from the penis complex, and physiological concentrations of the peptide enhanced the relaxation rate of electrically induced contractions of the penis retractor muscle in vitro in a dose-dependent fashion.

Animals↗
PubMed1993

Ultrastructural evidence for the axonal localization of caudodorsal cell hormone mRNA in the central nervous system of the mollusc Lymnaea stagnalis.

The technique of in situ hybridization has been used to evaluate the expression of an ovulation hormone mRNA (caudodorsal cell hormone; CDCH) in the central nervous system (CNS) of the mollusc Lymnaea stagnalis. Hybridization with radioactive as well as with nonradioactive labeled oligonucleotide and plasmid probes revealed a specific labeling on cell bodies of caudodorsal cells (CDCs), which are known to produce CDCH, on the light microscopical level. In addition, specific labeling was observed outside the cell bodies, as far as the cerebral commissure, where CDCH is released in the haemolymph. To investigate whether these signals represent an axonal localization of the CDCH mRNA, we performed in situ hybridization at the electron microscopical (EM) level. The results showed an intraaxonal localization of CDCH mRNA with digoxigenin labeled oligonucleotide and plasmid probes. Gold labeling was observed in secretion granules, and double labeling experiments showed that these granules also contain CDCH. This specific intragranular localization suggest that CDCH mRNA is transported through the axon and released by exocytosis in the haemolymph.

Animals↗
PubMed1993

A molecularly defined cardiorespiratory interneuron expressing SDPFLRFamide/GDPFLRFamide in the snail Lymnaea: monosynaptic connections and pharmacology.

1. Neuron-specific expression of alternately spliced exons of the gene encoding the Phe-Met-Arg-Phe-NH2 (FMRFamide) family of neuropeptides and the role of encoded peptides in synaptic transmission were examined in an identified cardiorespiratory interneuron, the visceral white interneuron (VWI), in the snail Lymnaea. 2. In situ hybridization using exon-specific probes showed VWI cytoplasmic expression of the exon encoding the Lymnaea heptapeptides Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRF amide) Ser-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (SDPFLRF amide) but not the exon encoding the tetrapeptides FMRFamide and Phe-Leu-Arg-Phe-NH2 (FLRFamide). 3. The absence of the tetrapeptides (FMRFamide and FLRFamide) in the VWI was indirectly confirmed by the lack of immunoreactivity to a specific antibody raised against the sequence Leu-Tyr. This sequence is present in the Lymnaea tetrapeptide precursor, but not the heptapeptide precursor. 4. The VWI has monosynaptic connections with many identifiable neurons in the CNS. These were excitatory on three clusters of identified neurons [B group (Bgp), E group (Egp), and F group (Fgp)], inhibitory on another cluster [A group (Agp)] or biphasic (excitation followed by inhibition) on a single giant neuron [right pedal dorsal 1 (RPeD1)]. 5. The role of GDPFLRFamide/SDPFLRFamide as putative neurotransmitters was examined by comparing neuronally evoked postsynaptic responses with the effects of focal peptide application. 6. The heptapeptides closely mimicked the inhibitory responses (threshold pressure pipette concentration 10(-9) M) on the Agp cells and RPeD1, including an increase in membrane conductance. FMRFamide was 1 order of magnitude less potent. GDPFLRFamide/SDPFLRFamide, applied either alone or in "cocktails" (combinations of GDPFLRFamide, SDPFLRFamide, FMRFamide, and FLRFamide), did not reproduce the excitatory effect of the VWI on the Bgp, Egp, and Fgp cells. These peptides, applied either together or separately, inhibited the cells. 7. FMRFamide or FLRFamide, but not GDPFLRFamide or SDPFLRFamide, could reproduce the initial depolarizing component of the biphasic response on RPeD1. This only occurred at concentrations of > or = 10(-4) M (10(-3) M was necessary to get spikes on RPeD1) and may not be physiologically significant. 8. We conclude that at least one so far unidentified co-transmitter must be present in the VWI to account for its full range of synaptic responses.

Animals↗
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

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↗
PubMed1992

Identification of putative egg-laying hormone containing neuronal systems in gastropod molluscs.

Of gastropod molluscs, only in the Aplysiidae and the Lymnaeidae have the genes encoding the respective egg-laying hormones been cloned and the neurons controlling egg laying and egg-laying behavior been identified. Immunocytochemistry, using antibodies raised against alpha-CDCP (one of the neuropeptides encoded on the egg-laying hormone gene of Lymnaea stagnalis), identified neurons in various species of gastropods. In the basommatophoran snail, Biomphalaria glabrata, large and small neurons were observed in areas of the central nervous system similar to where immunoreactive cells exist in L. stagnalis, i.e., in the cerebral and pleural ganglia. In the stylommatophoran snail (Helix aspersa) and the slug (Limax maximus), large immunopositive neurons occur in the visceral and right parietal ganglia. In L. maximus, small immunoreactive neurons were found in the cerebral ganglia while in H. aspersa similar cells were observed intermingled with the large cells in the visceral and right parietal ganglia. Similar to the situation in L. stagnalis, in the female part of the reproductive tract of B. glabrata, L. maximus, and A. californica, but not in H. aspersa, neurons and/or fiber tracts are present. The results indicate that egg-laying hormone precursor molecules of gastropod molluscs are phylogenetically closely related. The alpha-CDCP antiserum may allow the identification of hitherto unknown egg-laying regulating systems of gastropod molluscs.

Amino Acid Sequence↗
PubMed1992

Chemical characterization of a novel peptide from the neuroendocrine light yellow cells of Lymnaea stagnalis.

The neuroendocrine light yellow cells of Lymnaea stagnalis form two clusters of cells in the visceral and right parietal ganglion, respectively. These cells are endogenously bursting neurons whose activities are modified during egg-laying and feeding. Using gel permeation chromatography and reverse phase HPLC we have purified two highly related novel peptides from the light yellow cells. These peptides differ only in length, due to truncation of the amino-terminal aspartic acid residue, which causes a major shift in the charge of the molecule. We conclude that the longer peptide is the immediate precursor of the shorter form. Using whole mount immunocytochemistry, it was confirmed that the light yellow cells produce these peptides.

Amino Acid Sequence↗
PubMed1991

Localization of dopamine and its relation to the growth hormone producing cells in the central nervous system of the snail Lymnaea stagnalis.

The distribution of dopamine in the central nervous system of the pond snail Lymnaea stagnalis was investigated by using immunocytochemistry and HPLC measurements. With both methods it was demonstrated that dopamine is predominantly present in the cerebral and pedal ganglia. The dopamine-immunoreactivity was mainly observed in nerve-fibers in the neuropile of the ganglia. Relatively few dopamine-immunopositive cell bodies (diameters 10-30 microns) were found. A large cell in the right pedal ganglion (the so-called RPeD1) stained positively with the dopamine antibody. It has previously been demonstrated that the growth hormone producing cells (GHCs) possess dopamine receptors on their cell bodies. However, dopamine-immunopositive fibers were observed only in the vicinity of the GHC nerve-endings and not close to the GHC cell bodies.

Animals↗
PubMed1991

3'-end fluorochromized and haptenized oligonucleotides as in situ hybridization probes for multiple, simultaneous RNA detection.

We have used fluorescein-, digoxigenin- and biotin-(di)deoxyXTPs and terminal deoxynucleotidyl transferase for small scale labeling of synthetic oligonucleotide probes and here we show the applicability of such probes for the in situ detection of multiple RNA sequences. The enzymatic 3'-end-labeling methods proved to be good alternatives for the chemical fluorochrome and hapten labeling of 5'-end alkylamino-derivatized oligonucleotides. By combining 3'-end fluorescein-, biotin-, and digoxigenin-labeled oligonucleotides, double and triple hybridizations are feasible. For example, we demonstrated simultaneously mRNAs coding for caudodorsal cell hormone, a molluscan insulin-related peptide, and 28 S ribosomal RNA in cryostat sections of the cerebral ganglia of the pond snail Lymnaea stagnalis.

Animals↗
PubMed1990

Evidence for an enkephalinergic system in the nervous system of the pond snail, Lymnaea stagnalis.

Evidence for the presence of an enkephalinergic system in the ganglia of the pond snail, Lymnaea stagnalis, has been obtained with 3 experimental approaches. Scatchard analysis with [3H]etorphine reveals a monophasic high-affinity opiate binding site (Kd 2.3 nM) which is naloxone-sensitive. Immunocytochemical localization of Met- and Leu-enkephalin-like substances as well as alpha-MSH- and ACTH-like materials was demonstrated within specific populations of neurons. Substances with Met- and Leu-enkephalin and Met-enkephalin sulfoxide RIA reactivities were detected also in HPLC fractions corresponding to the retention times of authentic enkephalin standards. Together, the results provide strong evidence for the presence of enkephalinergic mechanisms in the nervous system of Lymnaea stagnalis. Additionally, the report provides indirect evidence for the existence of a macromolecular opioid precursor. This enkephalinergic system shows striking similarities to opioid mechanisms found in vertebrates and bespeaks a common evolutionary origin.

Animals↗