Organization of the musculature of schistosome cercariae

Phalloidin-fluorescein isothiocyanate staining of filamentous actin was used to identify muscle systems within the cercariae of Schistosoma mansoni. Examination of labeled cercariae by confocal scanning laser microscopy revealed distinct organizational levels of myofiber arrangements within the body wall, anterior cone, acetabulum, and esophagus. The body wall throughout showed a typical latticelike arrangement of outer circular and inner longitudinal myofibers, with an additional innermost layer of diagonal fibers in the anterior portion of the body. Circular and longitudinal fibers were also evident in the anterior organ and esophagus and, to some extent, the ventral acetabulum. Most striking was the striation of the cercarial tail musculature.

Characterisation of WE-14 in porcine ocular tissue

WE-14 is derived from the cell-specific posttranslational processing of chromogranin A (CgA) in subpopulations of neuroendocrine cells and neurons. Region- and site-specific chromogranin A, pancreastatin and WE-14 antisera were employed to study the generation of WE-14 in porcine ocular tissues. No chromogranin A or pancreastatin immunostaining was detected in ocular tissue. Immunohistochemistry detected WE-14 immunostaining in a network of nerve fibre bundles and nerve fibres throughout the limbus, cornea, iris and ciliary body with sparse nerve fibres detected throughout the choroid and sclera. Retinal analysis detected intense WE-14 immunostaining in large ovoid cells in the ganglion cell layer with weak immunostaining in a population of small cells in the inner nuclear layer; weak immunostaining was detected within the fibre layers in the inner plexiform layer. Quantitatively, the highest WE-14 tissue concentration was recorded in aqueous retinal and corneal extracts with lower concentrations in the sclera, choroid and anterior uveal tissues. Chromatographic profiling resolved a minor chromogranin A-like immunoreactant and a predominant immunoreactant co-eluting with synthetic human WE-14. This is the first study to demonstrate that WE-14 is generated in neuronal fibres primarily innervating the anterior chamber and in select cell populations in the retina.

Cytochemical studies of the neuromuscular systems of the diporpa and juvenile stages of Eudiplozoon nipponicum (Monogenea: diplozoidae)

Using indirect immuno- and enzyme-cytochemical techniques, interfaced with confocal scanning laser microscopy and standard optical microscopy, neuronal pathways have been demonstrated in whole-mount preparations of the unpaired diporpae and freshly paired juvenile stages of Eudiplozoon nipponicum (Monogenea: Diplozoidae). All 3 main classes of neuronal mediators, cholinergic, aminergic and peptidergic, were identified throughout both central and peripheral elements of a well-differentiated orthogonal nervous system. Neural mapping revealed considerable overlap and similarity in staining of the nervous systems of the diporpa and adult worm. The main differences in the diporpa relate to the innervation of the temporary ventral sucker and dorsal papilla, structures which are unique to the larva and which enable fusion between worms but then disappear. Branches from the longitudinal nerve cords innervate these structures and appear to be involved in the process of somatic fusion, probably giving rise to the inter-specimen connections that later link the 2 central nervous systems in paired adult parasites. In the hindbody, there is extensive haptoral innervation associated with the developing clamps and small central hooks. Reactive neuronal components were found associated with the early stages of clamp development prior to connections being made with the extrinsic adductor muscle bundles. The muscle systems of the diporpa and juvenile stages comprise a lattice-like arrangement of circular, longitudinal and diagonal fibres that make up the body wall, together with buccal suckers, haptoral clamps and associated adductor muscles, and the transient ventral sucker. All have obvious importance to diporpae when they migrate over the gill and undertake body contact, torsion and fusion during the process of pairing. Behaviour during the pairing of diporpae is described.

Microscopical evaluation of neural connectivity between paired stages of Eudiplozoon nipponicum (Monogenea: Diplozoidae)

Diplozoidae monogeneans am fish-gill ectoparasites comprising 2 individuals fused in so-called permanent copula. This unique situation occurs when 2 larvae (diporpee) make contact on the host gin, such that their union triggers maturation into an individual adult worm. The present study examined paired stages of Eudiplozoon nipponioun microscopicaily to ascertain whether somatic fusion involves neural connectivity between these 2 heterogenic larvae. Neuronal pathways were demonstrated in whole-mount preparations of the worm, using indirect immunocytochemical techniques interfaced with confocal scanning laser microscopy for peptidergic and serotoninergic innervations and enzyme cytochemical methodology and light microscopy for cholinergic component. Elements of the central nervous systems of paired worms are connected by commissures in the region of fusion so that the 2 systems are in structural continuity. Interindividual connections were mast apparent between corresponding ventral nerve cords. All 3 classes of neuronal mediators were identified throughout both central and peripheral connections of the 2 nervous systems. The anatomical complexity and apparent plasticity of the diplozoon nervous system suggest that it has a pivotal role not only in motility, feeding, and reproductive behavious but also in the events of larval pairing and somatic fusion.

Structure-activity relationships of an inhibitory nematode FMRFamide-related peptide, SDPNFLRFamide (PF1), on Ascaris suum muscle

FMRFamide-related peptides are widespread among the Nematoda. Among them is a family of extended PNFLRFamide peptides encoded on the flp-1 peptide precursor gene in Caenorhabditis elegans. The most studied peptide from this series is SDPNFLRFamide (PF1). Each residue in this peptide was sequentially substituted with either alanine or the corresponding d-isomer of the native amino acid in order to define structure-function relationships in this peptide using an Ascaris suum muscle tension assay. In general, substitutions in the N-terminal tetrapeptide had only minor consequences for efficacy, while substitutions in the C-terminal tetrapeptide caused more dramatic changes. Such substitutions typically markedly diminished efficacy, but d-isomer substitution at either position 5 (Phe) or 6 (Leu) converted the inhibitory activity of the prototype into excitation. In addition, it has been evident that KPNFLRFamide and SDPNFLRFamide, though encoded on flp-1 and sharing a PNFLRFamide hexapeptide, act through different receptors. KPNFLRFamide directly gates a chloride channel in A. suum muscle cells, while SDPNFLRFamide acts through nitric oxide synthase to open K+ channels in the same tissue. The use of K+ channel blockers and nitric oxide synthase inhibitors in electrophysiological experiments employing A. suum muscle membranes allowed the unambiguous conclusion that the N-terminal lysine is absolutely required for activation of the chloride channel and excludes interaction with the SDPNFLRFamide receptor.

Gene organization and expression of a neuropeptide Y homolog from the land planarian Arthurdendyus triangulatus

Neuropeptide Y is one of the most widespread regulatory peptides within the vertebrate nervous system and shares the C-terminal motif [FY]-x(3)-[LIVM]-x(2)-Y-x(3)-[LIVMFY]-x-R-x-R-[YF] with pancreatic polypeptide, peptide YY, and fish pancreatic peptide Y. All four peptides are believed to have arisen from a single ancestral gene through successive gene duplication events in vertebrates. The origin of this peptide family may date back further still; similarly sized peptide transmitters with an identical C-terminal motif have been identified in molluscs and flatworms and designated neuropeptide F (NPF). Cloning of the npf gene from the parasitic flatworm Moniezia expansa identified some unusual features within the peptide precursor organization but, at the same time, provided support for an evolutionary relationship of npf and npy genes through the presence of a single intron at a conserved position. To extend the analysis of the evolutionary relationships between invertebrate NPF and vertebrate NPY family peptides, the NPF precursor from the turbellarian Arthurdendyus triangulatus was characterized. Sequence analysis revealed the npf transcript to be 362 base pairs in length encoding a single open reading frame of 81 amino acids. The precursor comprises a signal peptide followed by the mature peptide of 36 amino acids in length, terminating in the typical invertebrate GRPRF motif, followed by a carboxyterminal glycyl extension. The NPF precursor of A. triangulatus shows significant similarities to the vertebrate NPY peptides. Indeed, the N-terminus of A. triangulatus prepro-NPF corresponds more closely to that of the vertebrate peptide homologs than to that of other invertebrate NPFs isolated to date. Immunocytochemical localization studies have demonstrated NPF immunoreactivity throughout the nervous system of A. triangulatus, particularly in association with muscular structures. The data support an early evolutionary origin for this peptide transmitter family within the nervous system of basal bilaterians.

Localisation of Globodera pallida FMRFamide-related peptide encoding genes using in situ hybridisation

The present study employed an in situ hybridisation technique to detect the expression of a number of FMRFamide-like peptide encoding (flp) genes, previously identified from Globodera pallida, in whole-mount preparations of the J(2) stage of this worm. gpflp-1, encoding the FMRFamide-related peptide (FaRP) KSAYMRFamide, was expressed in neurones associated with the circumpharyngeal nerve ring and specifically in a number of cell bodies in the lumbar ganglia of the perianal nerve ring. The lumbar ganglia and pre-anal ganglia along with the BDU neurones and a number of cells in the retrovesicular ganglion were observed to express gpflp-2, encoding KNKFEFIRFamide. gpflp-3 (encoding KHEYLRFamide) expression was localised to the anterior ganglion and a number of paired cells posterior to the circumpharyngeal nerve ring whilst expression of gpflp-4, encoding a number of -P(G/Q)VLRFamides, was localised to the retrovesicular ganglion. No expression of gpflp-5 was observed. Identification of the reactive cells has implicated distinct roles for the FaRPs encoded on these genes in regulation of both dorsal and ventral body wall muscles, the musculature of the vulva and in the function of a number of sensory structures in both the head and tail of G. pallida. Comparison with the expression patterns of analogous genes in Caenorhabditis elegans suggests that, whilst some of the encoded peptides are conserved between nematode species, their functions therein are distinct. Furthermore, the expression of some of these genes in a number of interneurones supports the idea that FaRPs fulfil neuromodulatory as well as neurotransmitter roles.

Neuropeptide signaling systems - potential drug targets for parasite and pest control

Current problems of drug resistance in parasites and pests demand the identification of new targets and their exploitation through novel drug design and development programs. Neuropeptide signaling systems in helminths (nematodes and platyhelminths = worms) and arthropods are well developed and complex, play a crucial role in many aspects of their biology, and appear to have significant potential as targets for novel drugs. The best-known neuropeptide family in invertebrates is the FMRFamide-related peptides (FaRPs). Amongst many roles, FaRPs potently influence motor function. The genome sequencing projects of Drosophila melanogaster and Caenorhabditis elegans have revealed unexpected complexity within the FaRPergic systems of arthropods and nematodes, although available evidence for platyhelminths indicates structural and functional simplicity. Regardless of these differences, FaRPs potently modulate motor function in arthropods, nematodes and platyhelminths and there appears to be at least some commonality in the FaRPergic signaling systems therein. Moreover, there is now increasing evidence of cross-phyla activity for individual FaRPs, providing clear signals of opportunities for target selection and the identification and development of broad-spectrum drugs.

Fasting modifies Aroclor 1254 impact on plasma cortisol, glucose and lactate responses to a handling disturbance in Arctic charr

Integrated effects of polychlorinated biphenyl (PCB) and nutritional status on responses to handling disturbance were investigated in the Arctic charr (Salvelinus alpinus). The fish were orally contaminated with Aroclor 1254 and held either with or without food for 5 months before they were subjected to a 10-min handling disturbance. Food-deprived fish were given 0, 1, 10 or 100 mg PCB kg(-1) and the fed fish 0 or 100 mg PCB kg(-1). Plasma cortisol, glucose and lactate levels were measured at 0 (pre-handling), 1, 3, 6 and 23 h after the handling disturbance. Food-deprived control fish had elevated plasma cortisol levels compared with fed fish before handling. These basal cortisol levels were suppressed by PCB in food-deprived fish, and elevated by PCB in fed fish. The immediate cortisol and glucose responses to handling disturbance were suppressed by PCB in a dose-dependent way in food-deprived fish. Although these responses were also lowered by PCB in the fed fish, the effect was much less pronounced than in food-deprived fish. There were only minor effects on plasma lactate responses. Our findings suggest that the stress responses of the Arctic charr are compromised by PCB and that the long-term fasting, typical of high-latitude fish, makes these species particularly sensitive to organochlorines such as PCB.

Mesocestoides corti (syn. M. vogae): modulation of larval motility by neuropeptides, serotonin and acetylcholine

The effect of platyhelminth FaRPs and selected classical neurotransmitters on the motility of intact Mesocestoides corti (syn. M. vogae) tetrathyridial larvae was studied in vitro using a micromotility meter. The effects of the test substances were temperature dependent and these were examined at 4, 23, 30 and 36 degrees C. At 36 degrees C all test substances had concentration-dependent excitatory effects, with thresholds for activity of: 100 nM (GNFFRFamide), 10 microm (YIRFamide), 30 microM (GYIRFamide), 100 nM (serotonin) and 100 microM (acetylcholine). At this temperature significant elevation of motility indices (MI) was recorded within 5 min of the addition of peptide or serotonin. The effect of acetylcholine was slower in onset and appeared 15-20 min post-addition. At 30 degrees C larval motility diminished more rapidly than that recorded at 36 degrees C, following the addition of 1 mM of each test substance. At 23 degrees C only serotonin (1 mM) significantly increased the MI, all other test substances having no apparent effect. Larval movement was completely arrested at 4 degrees C. The results demonstrate for the first time excitatory effects of platyhelminth neuropeptides and acetylcholine on muscle systems in cestode larvae. The fact that the only known cestode FaRP, GNFFRF amide, was more potent than any of the turbellarian FaRPs tested, suggests structural conservation of FaRPs and FaRP receptors within the cestodes.

Antibody-producing cells correlated to body weight in juvenile chinook salmon (Oncorhynchus tshawytscha) acclimated to optimal and elevated temperatures

The immune response of juvenile chinook salmon (Oncorhynchus tshawytscha) ranging in weight from approximately 10 to 55 g was compared when the fish were acclimated to either 13 or 21 degrees C. A haemolytic plaque assay was conducted to determine differences in the number of antibody-producing cells (APC) among fish of a similar age but different body weights. Regression analyses revealed significant increases in the number of APC with increasing body weight when fish were acclimated to either water temperature. These results emphasise the importance of standardising fish weight in immunological studies of salmonids before exploring the possible effects of acclimation temperatures.

Coho salmon Oncorhynchus kisutch strain differences in disease resistance and non-specific immunity, following immersion challenges with Vibrio anguillarum

Two strains of freshwater-reared coho salmon Oncorhynchus kisutch were compared for differences in the activity of selected non-specific immune factors before and after lethal and non-lethal immersion challenges with the marine bacterial pathogen Vibrio anguillarum (Vang). Two disease challenge experiments were performed. The first experimental challenge resulted in no mortality; however, significant strain and challenge treatment effects were detected at Day 16 post-challenge. Strain differences in plasma lysozyme activity were found in pre-challenge samples. The second challenge experiment compared the same strains of coho salmon following immersion challenges in different doses of Vang. The fish were sampled at Days 0, 2, 7, and 18 post-challenge and mortality, plasma lysozyme, and anterior kidney phagocyte respiratory burst activity were compared. There were significant strain differences in mortality in the high dose group. The more disease-resistant strain was found to have higher levels of plasma lysozyme and anterior kidney phagocyte respiratory burst activity. These strain differences were detected at various times in the lethal (high dose) and non-lethal challenge groups. There was a clear relationship between the enhanced survival of the more disease-resistant strain and a more sustained, elevated non-specific immune response following the experimental disease challenges. The results of this study suggest that the basis for strain differences in innate disease resistance is related to the ability of the fish to respond quickly to the initial infection and to maintain the response until the infection is quelled.

Isolation and preliminary biological assessment of AADGAPLIRFamide and SVPGVLRFamide from Caenorhabditis elegans

To date, 9 FMRFamide-related peptides (FaRPs) have been structurally characterised from Caenorhabditis elegans. Radioimmunometrical screening of an ethanolic extract of C. elegans revealed the presence of two additional FaRPs that were purified by reverse-phase HPLC and subjected to Edman degradation analysis and gas-phase sequencing. Unequivocal primary structures for the two FaRPs were determined as Ala-Ala-Asp-Gly-Ala-Pro-Leu-Ile-Arg-Phe-NH(2) and Ser-Val-Pro-Gly-Val-Leu-Arg-Phe-NH(2). Using MALDI-TOF mass spectrometry, the molecular masses of the peptides were found to be 1032 Da (MH) and 875 Da (MH)(+), respectively. Two copies of AADGAPLIRFamide are predicted to be encoded on the precursor gene termed flp-13, while one copy of SVPGVLRFamide is located on flp-18. Synthetic replicates of the peptides were tested on Ascaris suum somatic muscle to assess bioactivity. ADDGAPLIRFamide had inhibitory effects on A. suum muscle strips, which occurred over a range of concentrations from a threshold for activity of 10 nM to 10 microM. SVPGVLRFamide was excitatory on A. suum somatic musculature from a threshold concentration for activity of 1 nM to 10 microM. The inhibitory and excitatory effects of AADGAPLIRFamide and SVPGVLRFamide, respectively, were the same for dorsal and ventral muscle strips as well as innervated and denervated preparations, suggesting that these physiological effects are not nerve cord dependent. Addition of ADDGAPLIRFamide (10 microM) to muscle strips preincubated in high-K(+) and -Ca(2+)-free medium resulted in a normal inhibitory response. Peptide addition to muscle strips preincubated in Cl(-)-free medium showed no inhibitory response, suggesting that the inhibitory response of the peptide may be chloride mediated. A normal excitatory response was noted following the addition of 10 microM SVPGVLRFamide to muscle strips preincubated in high-K(+), Ca(2+)- and Cl(-)-free media.

FMRFamide-related peptides in potato cyst nematodes

This study presents data demonstrating the presence of FMRFamide-related peptides (FaRPs) in potato cyst nematodes (PCN). Five transcripts of FaRP encoding genes, designated gpflp-1 to gpflp-5, were characterised using RACE. In terms of ORFs, gpflp-1 was 444 base pairs (bp) long and coded for four copies of the FaRP, PF3 (KSAYMRFamide) whilst gpflp-2 was 309 bp long and encoded one copy of the peptide, KNKFEFIRFamide. gpflp-3 (420 bp) Encoded two copies of KHEYLRFamide (AF2) and the genes gpflp-4 and gpflp-5 encoded a total of 11 FaRPs, most of which are novel to PCN. FMRFamide-related peptide (FaRP)-like immunoreactivity was observed in both PCN species, Globodera pallida and Globodera rostochiensis, using an antiserum raised against the invertebrate peptide, FMRFamide. Immunopositive neurones were found throughout the central nervous system in the ventral and dorsal nerve cords and the circumpharyngeal and perianal nerve rings. Reactive neurones were also present peripherally, innervating the highly muscular pharynx with a nerve net and ring-like structures. Positive immunostaining was also observed in neurones running toward the stylet protractor muscles and/or the anterior sensory apparatus. This study implicates a role for FaRPs in feeding, host penetration and sensory function of PCN. This is the first study to characterise FaRP encoding genes from a plant-parasitic nematode using a targeted PCR based RACE approach and further underlines the importance and diversity of this neuropeptide group in the phylum Nematoda.

Immunomicroscopical observations on the nervous system of adult Eudiplozoon nipponicum (Monogenea: Diplozoidae)

Neuronal pathways have been examined in adult Eudiplozoon nipponicum (Monogenea: Diplozoidae), using cytochemistry interfaced with confocal scanning laser microscopy, in an attempt to ascertain the status of the nervous system. Peptidergic and serotoninergic innervation was demonstrated by indirect immunocytochemistry and cholinergic components by enzyme cytochemical methodology; post-embedding electron microscopical immunogold labelling revealed neuropeptide immunoreactivity at the subcellular level. All three classes of neuronal mediators were identified throughout both central and peripheral elements of a well-differentiated orthogonal nervous system. There was considerable overlap in the staining patterns for cholinergic and peptidergic components, while dual immunostaining revealed serotonin immunoreactivity to be largely confined to a separate set of neurons. The subcellular distribution of immunoreactivity to the flatworm neuropeptide, GYIRFamide, confirmed neuropeptide localisation in dense-cored vesicles in the majority of the axons and terminal varicosities of both central and peripheral nervous systems. Results reveal an extensive and chemically diverse nervous system and suggest that pairing of individuals involves fusion of central nerve elements; it is likely also that there is continuity between the peripheral nervous systems of the two partner worms.

Physiological effects of FMRFamide-related peptides and classical transmitters on dispersed muscle fibres of the turbellarian, Procerodes littoralis

The physiological effects of selected classical transmitters and FMRFamide-related peptides (FaRPs) on dispersed muscle fibres from the marine turbellarian, Procerodes littoralis have been examined. Confocal scanning laser microscopy coupled with fluorescein isothiocyanate (FITC) or tetramethylrhodamine (TRITC)-labelled phalloidin revealed a highly developed body wall muscle system with circular, longitudinal and diagonal layers of muscle fibres. Dispersed muscle fibres contracted when depolarized by exposure to extracellular media with elevated K+ (15-100 mM) in a concentration-dependent manner, with a maximal response of 87% achieved at > or = 75 mM. 5-Hydroxytryptamine (5-HT) induced concentration-dependent muscle contraction between 0.01 and 1000 microM, with 10 microM producing a near maximal contraction response of 75%. Acetylcholine (ACh) had less pronounced excitatory effects (0.01-1000 microM), inducing contraction of only 32% of the fibres at 100 microM. The flatworm FMRFamide-related peptides (FaRPs), GYIRFamide, YIRFamide and GNFFRFamide each had concentration-dependent myocontractile effects, indicating the occurrence of at least 1 FaRP receptor on P. littoralis muscle fibres. At 10 microM peptide, GNFFRFamide induced contractions in < 40% of the muscle fibres examined, whereas YIRFamide and GYIRFamide induced contraction in 70 and 75% of muscle fibres, respectively. The order of potency of the peptides was: GYIRFamide > YIRFamide > GNFFRFamide. Pre-incubation of the muscle fibres in 5 microM 5-HT significantly reduced the responses to GYIRFamide, YIRFamide and 5-HT, while the responses to high K+ remained unaltered. Muscle fibres pre-incubated in GYIRFamide (0.1 microM) were also less responsive to 5-HT but not to ACh and high-K+. The GYIRFamide analogue, GYIRDFamide, did not induce muscle contraction (0.01-100 microM) per se, but when co-applied with the myoactive peptides GYIRFamide, YIRFamide or GNFFRFamide, it significantly blocked their ability to elicit contractions. This suggests that the peptides tested may act via a common muscle-based neuropeptide receptor. GYIRDFamide did not alter the contractile effects of high K+, 5-HT or ACh. Collectively, these results indicate that FaRPs, 5-HT and ACh all have the potential to cause muscle contraction in flatworms and that 5-HT and FaRPs alter muscle sensitivity to each other, but do not influence the ability of flatworm muscle fibres to contract.

Organisation of the nervous system in the Acoela: an immunocytochemical study

In order to broaden the information about the organisation of the nervous system in taxon Acoela, an immunocytochemical study of an undetermined Acoela from Cape Kartesh, Faerlea glomerata, Avagina incola and Paraphanostoma crassum has been performed. Antibodies to 5-HT and the native flatworm neuropeptide GYIRFamide were used. As in earlier studies, the pattern of 5-HT immunoreactivity revealed an anterior structure composed mainly of commissures, a so-called commissural brain. Three types of brain shapes were observed. No regular orthogon was visualised. GYIRFamide immunoreactive cell clusters were observed peripherally to the 5-HT immunoreactive commissural brain. Staining with anti-GYIRFamide revealed more nerve processes than did staining with anti-FMRFamide. As no synapomorphies were found in the organisation of the nervous system of the Acoela and that of the Platyhelminthes, the results support the view that the Acoela is not a member of the Platyhelminthes.

Comparative study of the spatial relationship between nicotinamide adenine dinucleotide phosphate-diaphorase activity, serotonin immunoreactivity, and GYIRFamide immunoreactivity and the musculature of the adult liver fluke, Fasciola hepatica (Digenea, fasciolidae)

This is the first detailed description of the nitrergic nervous system in a fluke. In this study, the authors analysed the distribution of the nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reactivity in neuronal and nonneuronal tissues of the adult fluke Fasciola hepatica and compared this with the distribution of the musculature using tetramethylrhodamine isothiocyanate-phalloidin. To assess the correlation between the number of muscle cells in different parts of the fluke and the NADPH-d-stained cells, the nuclei were stained with Hoechst 333 42, which is specific for chromatin. The spatial relation between the NADPH-d-positive nerves and the 5-hydroxytryptamine (serotonin; 5-HT)-immunoreactive (-IR) and GYIRFamide-IR nervous elements was also examined. The methods complement each other. NADPH-d-positive staining occurs in both in neuronal tissue and nonneuronal tissue. Large, NADPH-d-stained neurones were localised in the nervous system. The oral and ventral suckers are innervated with many large NADPH-d-stained neurones. In addition, the NADPH-d staining reaction follows closely the muscle fibres in both the suckers, in the body, and in the ducts of the reproductive organs. The presence of NADPH-d activity along muscle fibres in F. hepatica and in other flatworms supports a possible myoinhibitory role for nitric oxide. Neuronal nitric oxide synthase in flatworms may form a novel drug target, which would facilitate the development of a novel anthelminthic.

Novel transcripts of the estrogen receptor alpha gene in channel catfish

Complementary DNA libraries from liver and ovary of an immature female channel catfish were screened with a homologous ERalpha cDNA probe. The hepatic library yielded two new channel catfish ER cDNAs that encode N-terminal ERalpha variants of different sizes. Relative to the catfish ERalpha (medium size; 581 residues) previously reported, these new cDNAs encode Long-ERalpha (36 residues longer) and Short-ERalpha (389 residues shorter). The 5'-end of Long-ERalpha cDNA is identical to that of Medium-ERalpha but has an additional 503-bp segment with an upstream, in-frame translation-start codon. Recombinant Long-ERalpha binds estrogen with high affinity (K(d) = 3. 4 nM), similar to that previously reported for Medium-ERalpha but lower than reported for catfish ERbeta. Short-ERalpha cDNA encodes a protein that lacks most of the receptor protein and does not bind estrogen. Northern hybridization confirmed the existence of multiple hepatic ERalpha RNAs that include the size range of the ERalpha cDNAs obtained from the libraries as well as additional sizes. Using primers for RT-PCR that target locations internal to the protein-coding sequence, we also established the presence of several ERalpha cDNA variants with in-frame insertions in the ligand-binding and DNA-binding domains and in-frame or out-of-frame deletions in the ligand-binding domain. These internal variants showed patterns of expression that differed between the ovary and liver. Further, the ovarian library yielded a full-length, ERalpha antisense cDNA containing a poly(A) signal and tail. A limited survey of histological preparations from juvenile catfish by in situ hybridization using directionally synthesized cRNA probes also suggested the expression of ERalpha antisense RNA in a tissue-specific manner. In conclusion, channel catfish seemingly have three broad classes of ERalpha mRNA variants: those encoding N-terminal truncated variants, those encoding internal variants (including C-terminal truncated variants), and antisense mRNA. The sense variants may encode functional ERalpha or related proteins that modulate ERalpha or ERbeta activity. The existence of ER antisense mRNA is reported in this study for the first time. Its role may be to participate in the regulation of ER gene expression.

The nervous system of Amphilina foliacea (Platyhelminthes, Amphilinidea). an immunocytochemical, ultrastructural and spectrofluorometrical study

The nervous system of young and adult Amphilina foliacea was studied with immunocytochemical, electron microscopical and spectrofluorometrical methods. The general neuroanatomy is described in detail. New data on the structure and development of the brain were obtained. The 5-HT and GYIRFamide-immunoreactivities occur in separate sets of neurones. The innervation of the reproductive organs is described. The fine structure of 2 types of neurones in the CNS, a sensory neurone, a 'glial' cell type, the neuropile and the synapses are described. The level of 5-HT varies between 0.074 and 0.461 microg/g wet weight. This is the first detailed study of the nervous system of A. foliacea. Earlier data on the structure of the nervous system in A. foliacea published in Russian are introduced into the discussion. The study provides data that can be used when considering the phylogenetic position of Amphilinidea.

Classical neurotransmitters in the ovijector of Ascaris suum: localization and modulation of muscle activity

Ascaris suum possesses a well-developed nervous system which is regulated by a number of classical neurotransmitters including acetylcholine (ACh), gamma-aminobutyric acid (GABA), glutamate and serotonin. The vagina vera, the distal part of the ovijector, displays intrinsic, rhythmic activity which has been shown to be modulated by FMRFamide-related peptides (FaRPs) in vitro. Confocal scanning laser microscopy coupled with immunocytochemistry, and histochemical studies, revealed that the nerve plexus of the ovijector contains GABAergic and glutamatergic innervation. Although no distinctive cholinergic or serotoninergic innervation was apparent, cholinesterase activity was localized to discrete areas of the musculature of the vagina vera. The effects of classical transmitters on the activity of the vagina vera in vitro were examined. ACh was excitatory, stimulating a brief but powerful contraction of the vagina vera with a threshold for activity of 1 microM. Both GABA and glutamate were inhibitory, causing a cessation of contractile activity at high concentrations (> 10 microM). Although less potent than glutamate, GABA had more profound effects and induced longer-lasting paralysis of the tissue. The threshold concentrations for activity were 5 microM for glutamate and 10 microM for GABA. Serotonin had no consistent effect on the vagina vera. This study demonstrates that classical transmitters modulate the activity of the ovijector of A. suum.

A confocal microscopical study of the musculature of adult Schistosoma mansoni

Using the filamentous actin marker, FITC-conjugated phalloidin, the major muscle systems of adult male and female schistosomes have been examined. The body wall musculature comprises an outer sheath of circular fibres, within which there is a compact layer of short, spindle-shaped longitudinal fibres and a lattice-like arrangement of inner diagonal fibres. Within the oral sucker and acetabulum 3 fibre types, circular, radial and longitudinal can be distinguished. The wall of the oesophagus is lined by a grid-like array of circular and longitudinal fibres, whereas the walls of the intestinal caeca contain only comparably broad circular fibres. Within the female reproductive system, only circular fibres are present in the oviduct, vitelline duct and uterus. In contrast, the wall of the ootype displays closely arranged circular and longitudinal muscle fibres. Antisera to previously identified myoactive compounds (serotonin [5-hydroxytryptamine, 5-HT], neuropeptide F [Moniezia expansa] and GYIRFamide [Bdelloura candida, Dugesia tigrina]) were used as neuronal markers in a preliminary study of the spatial inter-relationships of specific nerve fibres and various muscle systems. Serotoninergic fibres innervate both suckers and also constitute a subtegumental nerve net. In males they provide innervation to the dorso-ventral muscle fibres of the gynaecophoric canal, and in females they innervate the circular and longitudinal muscle fibres of the ootype. Neuropeptide F and the FMRFamide-related peptide, GYIRFamide are both localized within nerve plexuses associated with the dorso-ventral fibres of the gynaecophoric canal, and are evident in the innervation of the ventral and oral sucker.

Phylogenetic sequence analysis, recombinant expression, and tissue distribution of a channel catfish estrogen receptor beta

An estrogen receptor beta (ERbeta) cDNA fragment was amplified by RT-PCR of total RNA extracted from liver and ovary of immature channel catfish. This cDNA fragment was used to screen an ovarian cDNA library made from an immature female fish. A clone was obtained that contained an open reading frame encoding a 575-amino-acid protein with a deduced molecular weight of 63.9 kDa. Maximum parsimony and Neighbor Joining analyses were used to generate a phylogenetic classification of channel catfish ERbeta on the basis of 25 full-length teleost and tetrapod ER sequences. The consensus tree obtained indicated the existence of two major vertebrate ER subtypes, alpha and beta. Within each subtype, and in accordance with established phylogenetic relationships, teleost and tetrapod ER were monophyletic confirming the results of a previous analysis (Z. Xia et al., 1999, Gen. Comp. Endocrinol. 113, 360-368). Extracts of COS-7 cells transfected with channel catfish ERbeta cDNA bound estrogen with high affinity (K(d) = 0.21 nM) and specificity. The affinity of channel catfish ERbeta for estrogen was higher than previously reported for channel catfish ERalpha. As determined by qualitative RT-PCR, the tissue distributions of ERalpha and ERbeta were similar but not identical. Both ER subtypes were present in ovary and testis. ERalpha was found in all other tissues examined from juvenile and mature fish of both sexes. ERbeta was also found in most tissues except, in most cases, whole blood and head kidney. Interestingly, the pattern of expression of ER subtypes in head kidney always corresponded to the pattern in whole blood. In conclusion, we isolated a channel catfish ERbeta with ligand-binding affinity and tissue expression patterns different from ERalpha. Also, we confirmed the validity of our previously proposed general classification scheme for vertebrate ER into alpha and beta subtypes and within each subtype, into teleost and tetrapod clades.

Functional ryanodine receptor channels in flatworm muscle fibres

Caffeine, which stimulates intracellular Ca2+ release channels known as ryanodine receptor (RyR) channels, induces contraction of individual muscle fibres dissociated from the trematode Schistosoma mansoni, and the turbellarians Dugesia tigrina and Procerodes littoralis. Caffeine is much more potent on S. mansoni fibres (EC50 0.7 mM) than those from D. tigrina or P. littoralis (3.2 mM and 4.6 mM, respectively). These caffeine-induced contractions are blocked by ryanodine, confirming the presence of functional RyR channels in these flatworm muscles. However, the contractions are not blocked by typical RyR channel blockers ruthenium red or neomycin, indicating that there may be important pharmacological differences between the RyR channels in this early-diverging phylum and those of later animals. These studies demonstrate that RyR channels are present in the muscle of these flatworms, and that the sarcoplasmic reticulum stores sufficient Ca2+ to support contraction.

Pharmacology of FMRFamide-related peptides in helminths

Nervous systems of helminths are highly peptidergic. Species in the phylum Nematoda (roundworms) possess at least 50 FMRFamide-related peptides (FaRPs), with more yet to be identified. To date, few non-FaRP neuropeptides have been identified in these organisms, though evidence suggests that other families are present. FaRPergic systems have important functions in nematode neuromuscular control. In contrast, species in the phylum Platyhelminthes (flatworms) apparently utilize fewer FaRPs than do nematodes; those species examined possess one or two FaRPs. Other neuropeptides, such as neuropeptide F (NPF), play key roles in flatworm physiology. Although progress has been made in the characterization of FaRP pharmacology in helminths, much remains to be learned. Most studies on nematodes have been done with Ascaris suum because of its large size. However, thanks to the Caenorhabditis elegans genome project, we know most about the FaRP complement of this free-living animal. That essentially all C. elegans FaRPs are active on at least one A. suum neuromuscular system argues for conservation of ligand-receptor recognition features among the Nematoda. Structure-activity studies on nematode FaRPs have revealed that structure-activity relationship (SAR) "rules" differ considerably among the FaRPs. Second messenger studies, along with experiments on ionic dependence and anatomical requirements for activity, reveal that FaRPs act through many different mechanisms. Platyhelminth FaRPs are myoexcitatory, and no evidence exists of multiple FaRP receptors in flatworms. Interestingly, there are examples of cross-phylum activity, with some nematode FaRPs being active on flatworm muscle. The extent to which other invertebrate FaRPs show cross-phylum activity remains to be determined. How FaRPergic nerves contribute to the control of behavior in helminths, and are integrated with non-neuropeptidergic systems, also remains to be elucidated.