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1.
Sci Rep ; 11(1): 13868, 2021 07 06.
Article in English | MEDLINE | ID: mdl-34230544

ABSTRACT

Humans frequently cooperate for collective benefit, even in one-shot social dilemmas. This provides a challenge for theories of cooperation. Two views focus on intuitions but offer conflicting explanations. The Social Heuristics Hypothesis argues that people with selfish preferences rely on cooperative intuitions and predicts that deliberation reduces cooperation. The Self-Control Account emphasizes control over selfish intuitions and is consistent with strong reciprocity-a preference for conditional cooperation in one-shot dilemmas. Here, we reconcile these explanations with each other as well as with strong reciprocity. We study one-shot cooperation across two main dilemma contexts, provision and maintenance, and show that cooperation is higher in provision than maintenance. Using time-limit manipulations, we experimentally study the cognitive processes underlying this robust result. Supporting the Self-Control Account, people are intuitively selfish in maintenance, with deliberation increasing cooperation. In contrast, consistent with the Social Heuristics Hypothesis, deliberation tends to increase the likelihood of free-riding in provision. Contextual differences between maintenance and provision are observed across additional measures: reaction time patterns of cooperation; social dilemma understanding; perceptions of social appropriateness; beliefs about others' cooperation; and cooperation preferences. Despite these dilemma-specific asymmetries, we show that preferences, coupled with beliefs, successfully predict the high levels of cooperation in both maintenance and provision dilemmas. While the effects of intuitions are context-dependent and small, the widespread preference for strong reciprocity is the primary driver of one-shot cooperation. We advance the Contextualised Strong Reciprocity account as a unifying framework and consider its implications for research and policy.


Subject(s)
Cooperative Behavior , Heuristics , Social Behavior , Adult , Cognition , Female , Humans , Intuition , Male
2.
Nat Hum Behav ; 5(4): 512-521, 2021 04.
Article in English | MEDLINE | ID: mdl-33398149

ABSTRACT

Religions promote cooperation, but they can also be divisive. Is religious cooperation intuitively parochial against atheists? Evidence supporting the social heuristics hypothesis (SHH) suggests that cooperation is intuitive, independent of religious group identity. We tested this prediction in a one-shot prisoner's dilemma game, where 1,280 practising Christian believers were paired with either a coreligionist or an atheist and where time limits were used to increase reliance on either intuitive or deliberated decisions. We explored another dual-process account of cooperation, the self-control account (SCA), which suggests that visceral reactions tend to be selfish and that cooperation requires deliberation. We found evidence for religious parochialism but no support for SHH's prediction of intuitive cooperation. Consistent with SCA but requiring confirmation in future studies, exploratory analyses showed that religious parochialism involves decision conflict and concern for strong reciprocity and that deliberation promotes cooperation independent of religious group identity. PROTOCOL REGISTRATION: The Stage 1 protocol for this Registered Report was accepted in principle on 28 January 2020. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.12086781.v1 .


Subject(s)
Heuristics , Interpersonal Relations , Intuition , Prisoner Dilemma , Religion and Psychology , Cooperative Behavior , Decision Making , Game Theory , Humans , Motivation
3.
Arthropod Struct Dev ; 44(3): 253-79, 2015 May.
Article in English | MEDLINE | ID: mdl-25770075

ABSTRACT

Detailed studies of larval development of Octolasmis angulata and Octolasmis cor are pivotal in understanding the larval morphological evolution as well as enhancing the functional ecology. Six planktotrophic naupliar stages and one non-feeding cyprid stage are documented in details for the first time for the two species of Octolasmis. Morphologically, the larvae of O. angulata and O. cor are similar in body size, setation patterns on the naupliar appendages, labrum, dorsal setae-pores, frontal horns, cyprid carapace, fronto-lateral gland pores, and lattice organs. Numbers of peculiarities were observed on the gnathobases of the antennae and mandible throughout the naupliar life-cycle. The setation pattern on the naupliar appendages are classified based on the segmentation on the naupliar appendages. The nauplius VI of both species undergoes a conspicuous change before metamorphosis into cyprid stage. The cyprid structures begin to form and modify beneath the naupliar body towards the end of stage VI. This study emphasises the importance of the pedunculate barnacle larval developmental studies not only to comprehend the larval morphological evolution but also to fill in the gaps in understanding the modification of the naupliar structures to adapt into the cyprid life-style.


Subject(s)
Thoracica/growth & development , Animals , Brachyura/physiology , Gills/physiology , Larva/growth & development , Larva/ultrastructure , Metamorphosis, Biological , Microscopy, Electron, Scanning , Species Specificity , Thoracica/ultrastructure
4.
Front Psychol ; 6: 1884, 2015.
Article in English | MEDLINE | ID: mdl-26779052

ABSTRACT

Two prescriptive approaches have evolved to aid human decision making: just in time interventions that provide support as a decision is being made; and just in case interventions that educate people about future events that they may encounter so that they are better prepared to make an informed decision when these events occur. We review research on these two approaches developed in the context of supporting everyday decisions such as choosing an apartment, a financial product or a medical procedure. We argue that the lack of an underlying prescriptive theory has limited the development and evaluation of these interventions. We draw on recent descriptive research on the cognitive competencies that underpin human decision making to suggest new ways of interpreting how and why existing decision aids may be effective and suggest a different way of evaluating their effectiveness. We also briefly outline how our approach has the potential to develop new interventions to support everyday decision making and highlight the benefits of drawing on descriptive research when developing and evaluating interventions.

5.
Gen Comp Endocrinol ; 2010 Feb 18.
Article in English | MEDLINE | ID: mdl-20171222

ABSTRACT

This article has been withdrawn at the request of the editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

6.
J Helminthol ; 84(3): 253-65, 2010 Sep.
Article in English | MEDLINE | ID: mdl-19843350

ABSTRACT

FMRFamide-like peptides (FLPs) are a diverse group of neuropeptides that are expressed abundantly in nematodes. They exert potent physiological effects on locomotory, feeding and reproductive musculature and also act as neuromodulators. However, little is known about the specific expression patterns and functions of individual peptides. The current study employed rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) to characterize flp genes from infective juveniles of the root knot nematodes, Meloidogyne incognita and Meloidogyne minor. The peptides identified from these transcripts are sequelogs of FLPs from the free-living nematode, Caenorhabditis elegans; the genes have therefore been designated as Mi-flp-1, Mi-flp-7, Mi-flp-12, Mm-flp-12 and Mi-flp-14. Mi-flp-1 encodes five FLPs with the common C-terminal moiety, NFLRFamide. Mi-flp-7 encodes two copies of APLDRSALVRFamide and APLDRAAMVRFamide and one copy of APFDRSSMVRFamide. Mi-flp-12 and Mm-flp-12 encode the novel peptide KNNKFEFIRFamide (a longer version of RNKFEFIRFamide found in C. elegans). Mi-flp-14 encodes a single copy of KHEYLRFamide (commonly known as AF2 and regarded as the most abundant nematode FLP), and a single copy of the novel peptide KHEFVRFamide. These FLPs share a high degree of conservation between Meloidogyne species and nematodes from other clades, including those of humans and animals, perhaps suggesting a common neurophysiological role which may be exploited by novel drugs. FLP immunoreactivity was observed for the first time in Meloidogyne, in the circumpharyngeal nerve ring, pharyngeal nerves and ventral nerve cord. Additionally, in situ hybridization revealed Mi-flp-12 expression in an RIR-like neuron and Mi-flp-14 expression in SMB-like neurons, respectively. These localizations imply physiological roles for FLP-12 and FLP-14 peptides, including locomotion and sensory perception.


Subject(s)
FMRFamide/metabolism , Helminth Proteins/metabolism , Plant Diseases/parasitology , Tylenchoidea/metabolism , Amino Acid Sequence , Animals , Base Sequence , FMRFamide/chemistry , FMRFamide/genetics , Helminth Proteins/chemistry , Helminth Proteins/genetics , Solanum lycopersicum/parasitology , Molecular Sequence Data , Plant Roots/parasitology , Sequence Alignment , Tylenchoidea/chemistry , Tylenchoidea/genetics
7.
Parasitology ; 136(11): 1257-67, 2009 Sep.
Article in English | MEDLINE | ID: mdl-19646304

ABSTRACT

We have observed that when cercariae penetrate the skin of mice, there is influx into their tissues of Lucifer Yellow and certain labelled molecules of up to 20 kDa molecular weight. This observation was made using a variety of fluorescent membrane-impermeant compounds injected into the skin before the application of cercariae. This unexpected phenomenon was investigated further by transforming cercariae in vitro in the presence of the membrane-impermeant compounds and examining the distribution by microscopy. In schistosomula derived from this procedure, the nephridiopore and surface membrane were labelled while the pre- and post-acetabular glands were not labelled. The region associated with the oesophagus within the pharyngeal muscle clearly contained the fluorescent molecules, as did the region adjacent to the excretory tubules and the germinal mass. We used cercariae stained with carmine to aid identification of regions labelled with Lucifer Yellow. Although the mechanism of this influx is unclear, the observation is significant. From it, we can suggest an hypothesis that, during skin penetration, exposure of internal tissues of the parasite to external macromolecules represents a novel host-parasite interface.


Subject(s)
Fluorescent Dyes/metabolism , Host-Parasite Interactions , Isoquinolines/metabolism , Macromolecular Substances/metabolism , Schistosoma mansoni/physiology , Skin/parasitology , Animals , Carmine/metabolism , Larva , Mice , Microscopy, Confocal , Microscopy, Fluorescence , Schistosoma mansoni/growth & development , Schistosoma mansoni/metabolism , Schistosomiasis mansoni/metabolism , Schistosomiasis mansoni/parasitology
8.
Health Technol Assess ; 11(5): iii, 1-160, 2007 Feb.
Article in English | MEDLINE | ID: mdl-17280623

ABSTRACT

OBJECTIVES: To establish the role and value of written information available to patients about individual medicines from the perspective of patients, carers and professionals. To determine how effective this information is in improving patients' knowledge and understanding of treatment and health outcomes. DATA SOURCES: Electronic databases searched to late 2004, experts in information design, and stakeholder workshops (including patients and patient organisations). REVIEW METHODS: Data from selected studies were tabulated and the results were qualitatively synthesised along with findings from the information design and stakeholder workshop strands. RESULTS: Most people do not value the written information they receive. They had concerns about the use of complex language and poor visual presentation and in most cases the research showed that the information did not increase knowledge. The research showed that patients valued written information that was tailored to their individual circumstances and illness, and that contained a balance of harm and benefit information. Most patients wanted to know about any adverse effects that could arise. Patients require information to help decision-making about whether to take a medicine or not and (once taking a medicine) with ongoing decisions about the management of the medicine and interpreting symptoms. Patients did not want written information to be a substitute for spoken information from their prescriber. While not everyone wanted written information, those who did wanted sufficient detail to meet their need. Some health professionals thought that written information for patients should be brief and simple, with concerns about providing side-effect information. They saw increasing compliance as a prime function, in contrast to patients who saw an informed decision not to take a medicine as an acceptable outcome. CONCLUSIONS: The combination of a quantitative and qualitative review, an exploration of best practice in information design, plus the input of patients at stakeholder workshops, allowed this review to look at all perspectives. There is a gap between currently provided leaflets and information which patients would value and find more useful. The challenge is to develop methods of provision flexible enough to allow uptake of varying amounts and types of information, depending on needs at different times in an illness. This review has identified a number of areas where future research could be improved in terms of the robustness of its design and conduct, and the use of patient-focused outcomes. The scope for this research includes determining the content, delivery and layout of statutory leaflets that best meet patients' needs, and providing individualised information, which includes both benefit and harm information. In particular, studies of the effectiveness and role and value of Internet-based medicines information are needed.


Subject(s)
Pamphlets , Patient Education as Topic/methods , Pharmaceutical Preparations , Drug Labeling , Empirical Research , Humans , Internet , Qualitative Research
9.
Parasitology ; 133(Pt 1): 67-74, 2006 Jul.
Article in English | MEDLINE | ID: mdl-16566851

ABSTRACT

We tested the hypothesis that voltage-operated Ca2+ channels mediate an extracellular Ca2+ influx in muscle fibres from the human parasite Schistosoma mansoni and, along with Ca2+ mobilization from the sarcoplasmic reticulum, contribute to muscle contraction. Indeed, whole-cell voltage clamp revealed voltage-gated inward currents carried by divalent ions with a peak current elicited by steps to +20 mV (from a holding potential of -70 mV). Depolarization of the fibres by elevated extracellular K+ elicited contractions that were completely dependent on extracellular Ca2+ and inhibited by nicardipine (half inhibition at 4.1 microM). However these contractions were not very sensitive to other classical blockers of voltage-gated Ca2+ channels, indicating that the schistosome muscle channels have an atypical pharmacology when compared to their mammalian counterparts. Futhermore, the contraction induced by 5 mM caffeine was inhibited after depletion of the sarcoplasmic reticulum either with thapsigargin (10 microM) or ryanodine (10 microM). These data suggest that voltage-operated Ca2+ channels do contribute to S. mansoni contraction as does the mobilization of stored Ca2+, despite the small volume of sarcoplasmic reticulum in schistosome smooth muscles.


Subject(s)
Calcium Channels/physiology , Calcium/metabolism , Schistosoma mansoni/physiology , Animals , Caffeine/pharmacology , Calcium Channel Blockers , Calcium Channels/metabolism , Electrophysiology , Membrane Potentials , Muscle Contraction/drug effects , Muscles/drug effects , Muscles/physiology , Patch-Clamp Techniques , Ryanodine/pharmacology , Schistosoma mansoni/metabolism , Thapsigargin/pharmacology
11.
Parasitology ; 131 Suppl: S143-67, 2005.
Article in English | MEDLINE | ID: mdl-16569287

ABSTRACT

Flatworm, nematode and arthropod parasites have proven their ability to develop resistance to currently available chemotherapeutics. The heavy reliance on chemotherapy and the ability of target species to develop resistance has prompted the search for novel drug targets. In view of its importance to parasite/pest survival, the neuromusculature of parasitic helminths and pest arthropod species remains an attractive target for the discovery of novel endectocide targets. Exploitation of the neuropeptidergic system in helminths and arthropods has been hampered by a limited understanding of the functional roles of individual peptides and the structure of endogenous targets, such as receptors. Basic research into these systems has the potential to facilitate target characterization and its offshoots (screen development and drug identification). Of particular interest to parasitologists is the fact that selected neuropeptide families are common to metazoan pest species (nematodes, platyhelminths and arthropods) and fulfil specific roles in the modulation of muscle function in each of the three phyla. This article reviews the inter-phyla activity of two peptide families, the FMRFamide-like peptides and allatostatins, on motor function in helminths and arthropods and discusses the potential of neuropeptide signalling as a target system that could uncover novel endectocidal agents.


Subject(s)
Arthropods/physiology , FMRFamide/physiology , Helminths/physiology , Neuropeptides/physiology , Receptors, Neuropeptide/physiology , Signal Transduction/physiology , Animals , Anthelmintics/pharmacology , Arthropods/drug effects , FMRFamide/drug effects , FMRFamide/isolation & purification , Helminths/drug effects , Insecticides/pharmacology , Neuropeptides/classification , Neuropeptides/drug effects , Pest Control/methods , Receptors, Invertebrate Peptide/drug effects , Receptors, Invertebrate Peptide/metabolism , Receptors, Neuropeptide/drug effects , Signal Transduction/drug effects
12.
J Chromatogr A ; 1057(1-2): 49-57, 2004 Nov 19.
Article in English | MEDLINE | ID: mdl-15584222

ABSTRACT

Previous work has shown that the selectivity of reversed-phase columns for HPLC can be described by means of five column parameters: H (hydrophobicity), S* (steric resistance), A (hydrogen-bond acidity), B (hydrogen-bond basicity) and C (cation-exchange capacity). Values of H, S*, etc. can be determined by carrying out retention measurements for 18 test solutes under standardized conditions. The reproducibility of the latter procedure has been evaluated by comparison testing in four different laboratories and found acceptable. An alternative 10-solute test procedure which is more reproducible and convenient (but somewhat less accurate), requires only 2-3 h per column.


Subject(s)
Silicon Dioxide/chemistry , Cation Exchange Resins , Chromatography, High Pressure Liquid/instrumentation , Chromatography, High Pressure Liquid/methods , Hydrogen Bonding , Sensitivity and Specificity
13.
J Chromatogr A ; 1057(1-2): 59-74, 2004 Nov 19.
Article in English | MEDLINE | ID: mdl-15584223

ABSTRACT

The column selectivity parameters (H, S*, A, B and C) described in the preceding paper [L.R. Snyder, A. Maule, A. Heebsch, R. Cuellar, S. Paulson, J. Carrano, L. Wrisley C.C. Chan, N. Pearson, J.W. Dolan, J.J. Gilroy, J. Chromatogr. A 1057 (2004) 49-57] can be used to compare columns in terms of selectivity. A detailed procedure for such column comparisons is presented here, and evaluated by its use in finding suitable replacement columns for 12 different routine separations performed in five different pharmaceutical analysis laboratories.


Subject(s)
Chromatography, Liquid/instrumentation , Hydrogen Bonding , Pharmaceutical Preparations/analysis , Sensitivity and Specificity
14.
Protoplasma ; 223(2-4): 93-102, 2004 Jun.
Article in English | MEDLINE | ID: mdl-15221514

ABSTRACT

A current challenge in plant biology is to identify the structural and functional components of plasmodesmata (PDs). The use of plant tissue as a source material for plasmodesmal characterisation has had limited success, so we have explored the frequency and features of PDs occurring in suspension cell cultures of Arabidopsis thaliana. This material has the advantages of homogeneity, quantity, and ease of disruption. Using light and electron microscopy and immunostaining for callose and calreticulin, we showed that suspension cells laid down abundant PDs in division walls, and that vestiges of these structures were retained as half PDs even when the cell-to-cell contacts were disrupted during culture growth. Although callose was a reliable marker for PD distribution, which was deposited in an organised collar around the neck of PDs, it was not abundant in unstressed cells. Calreticulin and the chemical stain 3,3'-dihexyloxacarbocyanine iodide also provided useful markers when monitoring PDs in cell wall preparations by light microscopy. Purified cell walls were shown to be virtually free of contamination from cytoplasmic components, except for the presence of small amounts of cortical endoplasmic reticulum attached to PDs. Hence, clean cell walls from A. thaliana suspension cells provide a valuable resource for a proteomic approach to the analysis of plasmodesmal components.


Subject(s)
Arabidopsis/cytology , Arabidopsis/ultrastructure , Plasmodesmata/metabolism , Arabidopsis/metabolism , Calreticulin/metabolism , Cell Wall/metabolism , Cell Wall/ultrastructure , Glucans/metabolism
15.
Theor Appl Genet ; 109(3): 488-94, 2004 Aug.
Article in English | MEDLINE | ID: mdl-15067509

ABSTRACT

Two virus resistance loci on linkage groups II and VI have provided the only sources of natural resistance against Pea seed-borne mosaic virus (PSbMV, Potyviridae) in the important crop plant Pisum sativum L. A combination of parallel approaches was used to collate linked markers, particularly for sbm-1 resistance on linkage group VI. We have identified sequences derived from the genes for the eukaryotic translation initiation factors eIF4E and eIF(iso)4E as being very tightly linked to the resistance gene clusters on linkage groups VI and II, respectively. In particular, no recombinants between sbm-1 and eIF4E were found amongst 500 individuals of an F2 cross between the BC4 resistant line (JI1405) and its recurrent susceptible parent 'Scout'. In a different mapping population, the gene eIF(iso)4E was also shown to be linked to sbm-2 on linkage group II. A parallel cDNA-AFLP comparison of pairs of resistant and susceptible lines also identified an expressed tag marker just 0.7 cM from sbm-1. eIF4E and eIF(iso)4E have been associated with resistance to related viruses in other hosts. This correlation strengthens the use of our markers as valuable tools to assist in breeding multiple virus resistances into peas, and identifies potential targets for resistance gene identification in pea.


Subject(s)
Genetic Linkage/genetics , Mosaic Viruses/pathogenicity , Phenotype , Pisum sativum/genetics , Plant Diseases/genetics , Agriculture/methods , Blotting, Southern , Chromosome Mapping , Crosses, Genetic , DNA Primers , DNA, Complementary/genetics , Eukaryotic Initiation Factors/genetics , Genetic Markers/genetics , Pisum sativum/virology , Plant Diseases/virology , Polymorphism, Restriction Fragment Length
16.
J Virol ; 78(5): 2301-9, 2004 Mar.
Article in English | MEDLINE | ID: mdl-14963126

ABSTRACT

We have identified a cellular factor that interacts with the virus genome-linked proteins (VPgs) of a diverse range of potyviruses. The factor, called Potyvirus VPg-interacting protein (PVIP), is a plant-specific protein with homologues in all the species examined, i.e., pea, Arabidopsis thaliana, and Nicotiana benthamiana. The sequence of PVIP does not identify a specific function, although the existence of a "PHD finger" domain may implicate the protein in transcriptional control through chromatin remodeling. Deletion analysis using the yeast two-hybrid system showed that the determinants of the interaction lay close to the N terminus of VPg; indeed, the N-terminal 16 amino acids were shown to be both necessary and sufficient for the interaction with at least one PVIP protein. From a sequence comparison of different potyvirus VPg proteins, a specific amino acid at position 12 was directly implicated in the interaction. This part of VPg is distinct from regions associated with other functional roles of VPg. Through mutation of Turnip mosaic virus (TuMV) at VPg position 12, we showed that the interaction with PVIP affected systemic symptoms in infected plants. This resulted from reduced cell-to-cell and systemic movement more than reduced virus replication, as visualized by comparing green fluorescent protein-tagged wild-type and mutant viruses. Furthermore, by using RNA interference of PVIP in Arabidopsis, we showed that reduced expression of PVIP genes reduced susceptibility to TuMV infection. We conclude that PVIP functions as an ancillary factor to support potyvirus movement in plants.


Subject(s)
Cysteine , Movement , Plant Proteins/metabolism , Plants/metabolism , Plants/virology , Potyvirus/physiology , Viral Core Proteins/metabolism , Amino Acid Motifs , Amino Acid Sequence , Arabidopsis/genetics , Arabidopsis/metabolism , Arabidopsis/virology , Arabidopsis Proteins/chemistry , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Binding Sites , Genome, Viral , Molecular Sequence Data , Mutation , Pisum sativum/genetics , Plant Cells , Plant Diseases/genetics , Plant Diseases/virology , Plant Proteins/chemistry , Plant Proteins/genetics , Plants/genetics , Potyvirus/genetics , Protein Binding , Nicotiana/genetics , Viral Core Proteins/chemistry , Viral Core Proteins/genetics , Virus Replication
17.
Protoplasma ; 222(1-2): 31-43, 2003 Sep.
Article in English | MEDLINE | ID: mdl-14513309

ABSTRACT

Seed transmission of pea seed-borne mosaic virus (PSbMV) depends upon symplastic transport of the virus from infected maternal cells to the embryo. Such transport pathways have not been identified in higher plants. To identify these pathways, we have studied the ultrastructure of the tissues and cells around the micropyle of young developing seeds and compared transmitted and nontransmitted virus isolates. A characteristic of PSbMV infection was the presence of cylindrical inclusions positioned over plasmodesmal openings. The presence of cylindrical inclusions on the testa-endosperm boundary wall, together with immunogold labelling for virus-specific products on the wall and in the endosperm, indicated that symplastic connections existed at this interface. Close examination of the endosperm-suspensor boundary at the base of the suspensor revealed discontinuities in the suspensor sheath wall as porelike structures, which the virus might pass through en route to the embryo. A nontransmitted PSbMV isolate was able to invade the maternal tissues of the developing seed but was excluded from the embryo, although it was detected at a low level in the endosperm. Since the endosperm did not support virus replication, it appeared that passive accumulation determined the amount, timing, and location of the virus relative to the base of the suspensor. Rarely, therefore, could the nontransmitted virus isolate reach the correct location in the endosperm at the correct time for embryo infection via the suspensor to occur.


Subject(s)
Mosaic Viruses/pathogenicity , Pisum sativum/virology , Seeds/virology , Embryo, Mammalian , Embryo, Nonmammalian , Immunohistochemistry , Models, Biological , Pisum sativum/ultrastructure , Plant Diseases/virology , RNA, Plant/analysis , RNA, Viral/analysis , Seeds/ultrastructure
18.
J Parasitol ; 89(3): 623-5, 2003 Jun.
Article in English | MEDLINE | ID: mdl-12880271

ABSTRACT

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.


Subject(s)
Schistosoma mansoni/ultrastructure , Animals , Biomphalaria , Microscopy, Confocal , Microscopy, Electron, Scanning , Muscle Fibers, Skeletal/ultrastructure , Muscles/ultrastructure
19.
Int J Parasitol ; 33(8): 859-76, 2003 Jul 30.
Article in English | MEDLINE | ID: mdl-12865086

ABSTRACT

Caenorhabditis elegans possesses 22 FMRFamide-like peptide (flp) genes predicted to encode 60 different FMRFamide-related peptides with a range of C-terminal signatures. Peptides from five flp genes (1, 6, 8, 9 and 14) are known to modulate the ovijector of Ascaris suum in vitro. This study examines the physiological effects of peptides from the remaining 17 flp genes such that the variety of FMRFamide-related peptide-induced ovijector response types can be delineated. Five categories of response were identified according to the pattern of changes in contractile behaviour and baseline tension. Peptides encoded on 16 flp genes (1, 2, 3, 4, 6, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17 and 20) had qualitatively similar inhibitory (response type 1) actions, with the lowest activity thresholds (1 nM) recorded for peptides with FIRFamide or FLRFamide C-terminal signatures. Peptides encoded on four flp genes (2, 18, 19 and 21), and on the A. suum afp-1 gene, had excitatory actions on the ovijector (response type 2), with PGVLRFamides having the lowest activity threshold (1 nM). An flp-2 peptide (LRGEPIRFamide) induced a transient contraction of the ovijector (activity threshold, 10nM) that was designated response type 3. Response type 4 comprised a transient contraction followed by an extended period of inactivity and was observed with peptides encoded on flp-5 (AGAKFIRFamide, APKPKFIRFamide), flp-8 (KNEFIRFamide) and flp-22 (SPSAKWMRFamide). SPSAKWMRFamide was the most potent peptide tested with an activity threshold of 0.1 nM. A single peptide (AMRNALVRFamide; activity threshold 0.1 microM), encoded on flp-11, induced response type 5, a shortening of the ovijector coupled with an increase in contraction frequency. Although most flp genes encode structurally related peptides that trigger one of the five ovijector response types, flp-2 and flp-11 co-encode FMRFamide-related peptides that induce distinct responses. Within the ovijector of A. suum FaRPs play a complex role involving at least five receptor subtypes or signalling pathways.


Subject(s)
Ascaris suum/drug effects , Caenorhabditis elegans/chemistry , FMRFamide/pharmacology , Genitalia, Female/drug effects , Animals , Ascaris suum/physiology , Caenorhabditis elegans/genetics , Dose-Response Relationship, Drug , FMRFamide/chemistry , FMRFamide/genetics , Female , Genes, Helminth , Genitalia, Female/physiology , Muscle Contraction/drug effects , Muscle Contraction/physiology , Swine/parasitology
20.
Parasitology ; 126(Pt 4): 349-57, 2003 Apr.
Article in English | MEDLINE | ID: mdl-12741514

ABSTRACT

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.


Subject(s)
Central Nervous System/chemistry , Central Nervous System/cytology , Muscle, Skeletal/chemistry , Muscle, Skeletal/innervation , Platyhelminths/chemistry , Platyhelminths/cytology , Acetylcholine/analysis , Animals , Central Nervous System/anatomy & histology , Central Nervous System/growth & development , Cholinergic Fibers/chemistry , Histocytochemistry , Muscle, Skeletal/anatomy & histology , Muscle, Skeletal/cytology , Neuropeptides/analysis , Platyhelminths/anatomy & histology , Platyhelminths/growth & development , Serotonin/analysis
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