The properties of 4 fluorescent lipid compounds in the surface membrane of adult male Schistosoma mansoni worms were examined by fluorescent microscopy and fluorescent recovery after photobleaching (FRAP). The data suggest that the probes N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl) sphingosine (BODIPY FL ceramide) and PKH2 pass through the outer membrane and enter structures in or below the membrane. In contrast 5-(N-octadecanoyl)aminofluorescein (AF18) and N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl) sphingosylphosphocholine (BODIPY FL sphingomyelin) insert into the outer monolayer. The DL values of these latter 2 compounds, 8·83 ± 2·35 × 10−9 cm2 s−1 and 2·76 ± 0·53 × 10−9cm2 s−1, respectively, suggest that they enter different domains. Furthermore, it was observed that both BODIPY FL ceramide and BODIPY FL sphingomyelin entered particular structures in or under the surface membrane. The possible nature of these particles is discussed.

Toxoplasma gondii, the coccidian parasite, is known to induce changes in the behaviour of its intermediate hosts. The high prevalence of this parasite in the human population (20–80%) offers the opportunity of studying the influence of the parasite on human behaviour by screening of a normal population. A total of 224 men and 170 women were tested for toxoplasmosis and their personality profiles were measured by Cattell's questionnaire. Highly significant differences between Toxoplasma-infected and uninfected subjects were observed (P < 0·01). For men the factors G (low superego strength), L (protension), O (guilt proneness), and Q2 (group dependency) were positively influenced in infected subjects. For women the prevailing factors were A (affectothymia, P < 0·01), L (alaxia), O (untroubled adequacy) and Q2 (self-sufficiency). To reveal whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiring Toxoplasma infection, we examined the personality profiles of 164 male patients diagnosed with acute toxoplasmosis during the past 13 years. The existence of a positive correlation between the duration of latent toxoplasmosis and the intensity of superego strength decrease (P < 0·02) suggested that the decrease of superego strength (the willingness to accept group moral standards) was induced by T. gondii infection.

The migration and development of Sanguinicola inermis in carp fingerlings were investigated by quantitative analysis of serial sections of fish and examination of flukes from hosts up to 90 days p.i. Cercariae penetrated through the epidermis and migrated through connective tissue and muscle to establish in the blood system and commence egg production within 28 days p.i. Most flukes established in the ventral blood system and released eggs which accumulated in gill epithelial tissue. A minority of flukes inhabited dorsal blood vessels and shed eggs which lodged in connective tissue and visceral sites. Maximum life-span of the parasite is between 56 and 70 days p.i. and egg production peaked at day 42 p.i.

Analysis of the electrical properties of neurons in the motornervous system of Ascaris suum suggests that it is largely an analogue system. The motorneurons do not conduct action potentials and they release transmitter tonically at their normal resting potential; transmitter release is increased or decreased as a continuous function of membrane potential. Despite extensive physiological descriptions of the electrical properties of the neurons and their synapses, as well as morphological descriptions of the synaptic circuitry of the system, the predicted activities of the neurons in the circuit differ from those observed by direct recording in semi-intact behaving animals. We conclude that the description of the circuit is incomplete. There are several possibilities for the missing elements, including chemical, proprioceptive, and additional neuronal components. Recently, attention has been focussed most heavily on the intercellular chemical signalling systems; in addition to those mediated by classical neurotransmitters, a surprisingly complex array of neuropeptides has been identified. One family of these peptides, the AF peptides, has been analyzed in detail. It comprises at least 20 peptides, and they fall into sequence-related subfamilies. One of these subfamilies, containing 6 peptides, is encoded by a single transcript, suggesting that the AF peptides are under multiple genetic control. All AF peptides tested have potent activity on the motornervous system and or on muscle. There are multiple physiological activities, and cellular localization studies show multiple patterns of cellular expression. Studies on Panagrellus and Caenorhabditis emphasize the diversity of this family and its genetic control.

The cuticle of filarial nematodes is a specialized extracellular matrix that covers the parasite and protects it from adverse conditions of the environment. As a surface structure it is in direct contact with the host defence mechanisms and therefore plays an important role in the molecular host-parasite relationship. Using polyclonal antisera raised against the insoluble components of the cuticle of the adult filarial parasite Brugia pahangi, we have isolated cDNA clones encoding collagen molecules of the cuticle. The protein domain structure of cDNA clone Bpcol-1 was compared with the known structures of cuticular collagens of the nematodes Brugia malayi, Caenorhabditis elegans, Ascaris suum and Haemonchus contortus, confirming interspecies similarities. Using affinity-purified anti-Bpcol-1 antibodies we identified Bpcol-1 antigenic determinants in different nematode extracts, and determined the localization of such epitopes within the cuticle of B. pahangi.

The effects of each of the known platyhelminth neuropeptides were determined on muscle-strip preparations from the liver fluke, Fasciola hepatica. The activity of synthetic replicates of the C-terminal nonapeptide of neuropeptide F (NPF9, Moniezia expansa), and the FMRFamide-related peptides (FaRPs), GNFFRFamide, RYIRFamide, GYIRFamide and YIRFamide, were examined. Muscle-strip activity was recorded from 1 mm segments of muscle prepared from 28 to 32-day-old worms, using a photo-optic transducer system. None of the peptides (≤ 10 μM) altered baseline tension significantly; however, each of the peptides increased the amplitude and frequency of muscle contraction. The threshold for activity of each of the peptides examined was, respectively, 1 nM (RYIRFamide), 0·3 μM (GYIRFamide and YIRFamide), and 10 μM (GNFFRFamide and NPF9). All of the effects were reversible and repeatable, following wash-out. Muscle-strip integrity was tested following experimentation, using arecoline (10 μM) and high-K+ bathing medium (90 mM K+).

The free radical nitric oxide (NO), which is synthesized by nitric oxide synthase (NOS), has recently been discovered to function as a neuronal messenger. The presence of NOS was detected in the nervous system of adult Hymenolepis diminuta with NADPH-diaphorase (NADPH-d) histochemistry. The NADPH-d histochemical reaction is regarded as a selective marker for NOS in neuronal tissue. NADPH-d staining was observed in nerve fibres in the main and minor nerve cords and the transverse ring commissures, and in cell bodies in the brain commissure, along the main nerve cords, in the suckers and the rostellar sac. NADPH-d staining was also observed in the wall of the internal seminal vesicle and the genital atrium. The pattern of NADPH-d staining was compared with that of the 5-HT immunoreactive nervous elements. The NADPH-d staining reaction and the 5-HT immunoreactivity occur in separate sets of neurons. This is the first time the NADPH-d reaction has been demonstrated in the nervous system of a flatworm, indicating that NOS is present and that NO can be produced at this level of evolution.

Cholinergic compounds inhibit FMRFamide-induced contractions in dispersed muscle fibres isolated from adult Schistosoma mansoni. Acetylcholine (ACh) was the most effective cholinergic agonist tested with an EC50 < 100 nM. Less effective were propionylcholine and arecoline with EC50 < 1 μM and butyrylcholine and carbachol with EC50 < 10μM. Choline, muscarine, pilocarpine, nicotine, DMPP (1,1-dimethylphenylpiperazine ) and levamisole were all ineffective. Amongst tested antagonists, d-tubocurarine (100μM), mecamylamine (1 mM), atropine (1 mM), scopolamine (1 mM) and quinuclidinyl benzilate (10 μM) were all ineffective. Bicuculline, picrotoxin and strychnine were also ineffective. However α-bungarotoxin, at 100 nM, was able to block the inhibitory ACh effect. From these data it appears that the cholinergic receptor on the schistosome muscle fibres may be of the nicotinic type, but that its pharmacology is different from that of nicotinic receptors of vertebrates as well as of nematodes or a variety of other invertebrates.

Understanding the temporal and spatial distribution of entomopathogenic nematodes is essential for determining the role of these insect parasites in soil communities and ultimately for their use in suppression of pest insect populations. We measured the vertical and horizontal distribution of endemic populations of entomopathogenic nematodes (Steinernema carpocapsae and Heterorhabditis bacteriophord) in turfgrass. Vertical distribution was determined by taking soil cores every 3 h from 05.00 to 23.00 h, over 4 days, and dividing the cores into 8, 1 cm deep sections. Steinernema carpocapsae was recovered primarily near the soil surface: 50% of positive sections were recovered in the thatch or first 1 cm of soil. S. carpocapsae recovery was lower during the middle of the day and none were recovered in the upper section. H. bacteriophora was recovered uniformly throughout the top 8 cm of soil and its vertical distribution did not change over the course of the day. Horizontal distribution was measured as the number of nematodes recovered from cores taken from 12 randomly selected 0·3 × 0·8 m sections from within four 15·3 × 15·3 m plots. Samples were collected biweekly over a 9-month period. H. bacteriophora had a patchier distribution than S. carpocapsae and both nematode species had more patchy distributions then their potential hosts. Our results support the hypothesis that these two species of nematode utilize different foraging strategies; S. carpocapsae primarily a surface adapted ambusher and H. bacteriophora as a cruise forager.

On the basis of known DNA sequences of Dirofilaria repens and D. immitis we designed specific primers for the amplification by Polymerase Chain Reaction (PCR) of the DNA from the two species. The PCR-based identification was found to be unambiguous and allowed specific diagnosis of microfilariae in blood samples, of developing larvae in the mosquito vector and of immature adults in bioptic material, overcoming the serious constraints of the morphological separation of these filarial parasites at the pre-adult stages. The technique was found to be very sensitive and applicable to samples stored either dry or in various preservation media, with the exception of formalin. The reliable identification of D. repens and D. immitis from bioptic material is expected to greatly enhance the chances of detecting human infections and to further clarify the role of the two parasites as pathogens of man. The possibility of routine identification of developing larvae in the vector will substantially improve the perspectives for epidemiological investigations, particularly in Southern European regions, such as Italy, where the two nematode species are largely sympatric.

Western blot analysis using an anti-globin rabbit serum Rb94 revealed a major band of 17 kDa in extracts of Ostertagia ostertagi adults and 4th-stage larvae. The adult stage globin-like antigen (OoAdGlb) was purified from total worm extracts by liquid chromatography. The protein has an estimated molecular mass of 36 kDa under non-reducing conditions, suggesting a dimeric structure containing 2 non-covalently linked 17 kDa monomers. Tryptic peptides were sequenced and showed strong similarities with the globins of free-living and parasitic nematodes. Immunolocalization revealed the presence of this globin-like antigen in the body wall musculature and/or the cuticle of O. ostertagi adults. An enzyme-linked immunosorbent assay based on the purified OoAdGlb showed no differences in response between calves infected by O. ostertagi and/or Cooperia oncophora and the negative controls.

The participation of neutrophil granulocytes in the cellular reaction to skin microfilariae of Onchocerca volvulus was studied by immunohistochemistry. Skin biopsies were obtained from adult Liberian and Ugandan patients with generalized onchocerciasis after exposure to topically applied diethylcarbamazine (DEC) and from untreated patients. After DEC many damaged microfilariae were observed either in dermal infiltrates or in epidermal microabscesses consisting both of neutrophils and eosinophils. Infiltrates and microabscesses contained some intact granulocytes and many neutrophils releasing myeloperoxidase, elastase, lactoferrin, defensin, lysozyme, α1-antitrypsin and α1-antichymotrypsin. Eosinophils discharged peroxidase and cationic proteins. Released granule proteins and remnants of disrupted granulocytes were found on the surface and in close proximity of damaged microfilariae in dermal infiltrates and epidermal microabscesses. In larger microabscesses neutrophils were predominant. These observations show that neutrophils and not only eosinophils recruit, accumulate, localize around and release their helminthotoxic granule proteins such as myeloperoxidase onto or closely around skin microfilariae of O. volvulus after topical DEC administration. The association between these processes and the damage of the microfilariae indicated that neutrophils together with eosinophils attack and damage microfilariae of O. volvulus after DEC treatment in the skin.

Vasoactive intestinal polypeptide (VIP)-Hke protein was detected by dot blot analysis in the excretions/secretions (E/S) of Nematodirus battus and Ascaridia galli and was confirmed in the E/S of Nippostrongylus brasiliensis. ELISA analysis showed that N. brasiliensis E/S contained the highest proportion of VIP-like protein (28·04 pmoles/mg of total E/S protein) and A. galli E/S contained the lowest (10·89 pmoles/mg of total E/S protein). Peptide histidine isoleucine (PHI)- like protein was detected by dot blot analysis in the E/S products of N. brasiliensis, N. battus and A. galli. ELISA analysis suggested that A. galli E/S contained the highest proportion of PHI (20·77 nmoles/mg of total E/S protein) and N. battus E/S contained the lowest (0·67 nmoles/mg of total E/S protein). The possible significance of VIP-like and PHI-like substances in the E/S of gastrointestinal nematodes is discussed.

Three satellite DNAs previously isolated from the entomopathogenic nematodes Steinernema carpocapsae, Heterorhabditis bacteriophora and Heterorhabditis indicus give hybridization signals only with the S. carpocapsae, H. bacteriophora and H. indicus populations tested, indicating that these satellite sequences are species-specific. Because of their reiteration and their variabilities, we have shown that these sequences are able to discriminate at the interspecific level between the Steinernema and Heterorhabditis species, but also at the intraspecific level between S. carpocapsae strains. Furthermore, in simple squashed nematode experiments, we are able to unambiguously identify S. carpocapsae, H. bacteriophora and H. indicus populations. This last procedure is effective even on a single infective juvenile, with the main advantage that it avoids time-consuming DNA extractions.

The occurrence of classical neurotransmitter molecules and numerous peptidic messenger molecules in nematode nervous systems indicate that although structurally simple, nematode nervous systems are chemically complex. Thus far, studies on one nematode neuropeptide family, namely the FMRFamide-related peptides (FaRPs), have revealed an unexpected variety of neuropeptide structures in both free-living and parasitic species. To date 23 nematode FaRPs have been structurally characterized including 12 from Ascaris suum, 8 from Caenorhabditis elegans, 5 from Panagrellus redivivus and 1 from Haemonchus contortus. Ten FaRP-encoding genes have been identified in Caenorhabditis elegans. However, the full complement of nematode neuronal messengers has yet to be described and unidentified nematode FaRPs await detection. Preliminary characterization of the actions of nematode neuropeptides on the somatic musculature and neurones of A. suum has revealed that these peptidic messengers have potent and complex effects. Identified complexities include the biphasic effects of KNEFIRFamide/KHEYLRFamide (AF1/2; relaxation of tone followed by oscillatory contractile activity) and KPNFIRFamide (PF4; rapid relaxation of tone followed by an increase in tone), the diverse actions of KSAYMRFamide (AF8 or PF3; relaxes dorsal muscles and contracts ventral muscles) and the apparent coupling of the relaxatory effects of SDPNFLRFamide/SADPNFLRFamide (PF1/PF2) to nitric oxide release. Indeed, all of the nematode FaRPs which have been tested on somatic muscle strips of A. suum have actions which are clearly physiologically distinguishable. Although we are a very long way from understanding how the actions of these peptides are co-ordinated, not only with those of each other but also with those of the classical transmitter molecules, to control nematode behaviour, their abundance coupled with their diversity of structure and function indicates a hitherto unidentified sophistication to nematode neuromuscular intergration.

The paper describes the development and analysis of a mathematical framework for the study of the within-host population dynamics of the interaction between macroparasites and the human immune system. Simple models of this interaction based on the proliferation of T cell clones specific to parasite antigen, and the impact of clonal expansion on parasite survival, capture the basic features of age-related changes in worm loads within human communities. The model is generalized to multiple epitopes on a single antigen, and reveals competitive exclusion amongst T cells, with a single clone becoming immunodominant in the absence of cross-reactive responses and genetic variation. The introduction of genetic heterogeneity and concomitant variability in the immunogenicity of specific epitopes induces additional complexity into the dynamical interaction. Most importantly, multiple epitope models with antigenic variation suggest that the immunodominant response may not necessarily be targeted at the epitope at which some strains show the greatest immunogenicity. High immunogenicity at a particular epitope can be masked by genetic variability even though many of the variants are more immunogenic at this epitope by comparison with the epitope to which the immunodominant immunological response is directed.

The suggestion that there may be a limit to the number of niches available to helminth species in the intestine of Anguilla anguilla was investigated by examining the frequency distributions of the number of helminth species per eel and the relationships between maximum and mean infracommunity richness and component community richness in 1 locality over 17 years and in 64 localities throughout Ireland and England. The maximum number of species per eel did not exceed 4 in the 1 locality, or 3 in the 64 localities. In both the single and the several localities, the relationship between maximum and mean infracommunity richness and component community richness was curvilinear and best described by a power or polynomial function. This was interpreted to mean that infracommunity richness became increasingly independent of component community richness, and that infracommunities were saturated at values well below the higher level of helminth richness immediately available for colonization i.e. component community richness. It is argued that these findings cannot be explained by supply-side ecology, pool exhaustion or transmission rates, but only by infracommunity processes acting to impose a fixed limit to the number of species in an infracommunity. Most infracommunities are species poor, and the limiting factors will only operate as species richness rises to determine a maximum. Acceptance of a limit to the number of niches available also resolves the apparent inconsistency between the occurrence and importance of interspecific competition and the nature of isolationist communities.

Neuronal abnormalities have been described in the intestine of helminth-infected rats. However, the physiological ramifications of these changes have not been determined. Here, we examined epithelial ion secretion, indicated by increases in short-circuit current (Isc), evoked by electrical transmural stimulation (TS) of enteric nerves in Ussing-chambered jejunal tissues from Nippostrongylus brasiliensis-infected rats. Rats were examined at 10 and 35 days post-infection (p.i.); non-infected rats served as controls. TS resulted in significantly reduced ion secretion in jejunum from 10 day p.i. rats compared to controls or jejunum from 35 day p.i. rats. The TS response in tissue from infected rats had, unlike controls, no cholinergic component. Tissues from both non-infected and infected rats were equally responsive to the muscarinic agonist bethanechol, suggesting that the cholinergic defect was neuronal and not an inability of the epithelium to respond to cholinergic stimulation. However, increases in Isc evoked by exogenous substance P (SP) in tissue from rats 10 day p.i. were reduced in magnitude to approximately 25% of control values. Concomitant with these physiological changes, tissue from infected rats contained increased amounts of substance P immunoreactivity and intestinal sections displayed increased numbers of substance P-immunoreactive nerve fibre profiles at both 10 and 35 days p.i. Thus, following N. brasiliensis infection there is a shift in the enteric nervous system away from cholinergic to non-cholinergic regulation, associated with increased amounts of the pro-inflammatory neuropeptide, substance P. We speculate that changes in neuronal structure and function are intimately involved in the co-ordinated multicellular response to intestinal parasitic infection and subsequent gut recovery.

Young lambs (6–8 weeks of age) were infected with 50000 infective stage larvae of the trichostrongyle nematode Nematodirus battus. Initial mean adult worm burdens of 23884±1678 (S.E.M.) at day 14 post-infection (p.i.) were reduced significantly (P < 0·01) to a mean burden of 5383±1397 by day 21 p.i. Blood samples were taken and serum analysed using ELISA and Western blotting techniques for IgG antibodies specific for N. battus. Pre-infection serum from young naive animals showed IgG recognition of adult and larval N. battus whole worm homogenate. Recognition of adult antigens became reduced during the first 14 days after infection, followed by a subsequent increase beginning between days 14 and 18 p.i. and peaking at day 28 p.i. IgM recognition of N. battus antigens showed a single response peak, starting between days 14 and 18 p.i., without the pre-infection elevated titre as observed with IgG. These results show that young lambs can mount a significant serum response to a primary infection with N. battus during rejection of adult worms and that lambs receive from their dams IgG antibodies that are capable of recognizing adult and larval N. battus during the first few weeks of life.

Cryostat sections of juvenile and adult female stages of the soybean cyst-nematode, Heterodera glycines, were incubated with 4 different naphthylamide-linked peptide substrates to localize and characterize proteinase activity within the animal. Detected activity was restricted to the intestine and 2 distinct classes of proteinase were identified on the basis of substrate specificity and sensitivity to plant proteinase inhibitors. A cathepsin L-like cysteine proteinase activity capable of hydrolysing the synthetic substrates Z-Ala-Arg-Arg-MNA and Z-Phe-Arg-MNA but not Z-Arg-Arg-MNA or L-Arg-NA was inhibited by an engineered variant of a cysteine proteinase inhibitor from rice (Oc-IδD86). The cleavage of Z-Phe-Arg-MNA was sensitive to inhibition by a combination of Oc-IδD86 and cowpea trypsin inhibitor (CpTI). Degenerate oligonucleotide primers were used to amplify fragments of cysteine proteinase genes from 2 cyst-nematodes, H. glycines and Globodera pallida. Comparison of the H. glycines fragment with known genes established highest homology to cathepsin L-like genes. In contrast, the amplified G. pallida fragment displayed greatest homology to cathepsin B-like genes from Caenorhabditis elegans.