Suppression of the growth and metastasis of mouse melanoma by Taenia crassiceps and Mesocestoides corti tapeworms.

Cancer is still one of the leading causes of death, with an estimated 19.3 million new cases every year. Our paper presents the tumor-suppressing effect of Taenia crassiceps and Mesocestoides corti on B16F10 melanoma, the intraperitoneal application of which followed the experimental infection with these tapeworms, resulting in varying degrees of effectiveness in two strains of mice. In the case of M. corti-infected ICR mice, a strong tumor growth suppression occurred, which was accompanied by a significant reduction in the formation of distant metastases in the liver and lung. Tapeworm-infected C57BL/6J mice also showed a suppression of tumor growth and, in addition, the overall survival of infected C57BL/6J mice was significantly improved. Experiments with potential cross-reaction of melanoma and tapeworm antigens with respective specific antibodies, restimulation of spleen T cells, or the direct effect of tapeworm excretory-secretory products on melanoma cells in vitro could not explain the phenomenon. However, infections with T. crassiceps and M. corti increased the number of leukocytes possibly involved in anti-tumor immunity in the peritoneal cavity of both ICR and C57BL/6J mice. This study unveils the complex interplay between tapeworm infections, immune responses, and melanoma progression, emphasizing the need for further exploration of the mechanisms driving observed tumor-suppressive effects.

Rodents as intermediate hosts of cestode parasites of mammalian carnivores and birds of prey in Poland, with the first data on the life-cycle of Mesocestoides melesi.

BACKGROUND: Rodents constitute an important part of the diet of many carnivore species. This predator-prey food chain is exploited by helminth parasites, such as cestodes, whose larval stages develop in rodents and then mature to the adult stage in predators. The main aim of our study was to use molecular techniques for identification of cestode species recovered from both intermediate and definitive hosts, with a particular focus on the genus Mesocestoides. METHODS: Larval cestodes were obtained during our long-term studies on rodent helminth communities in the Mazury Lake District in the north-east Poland in 2000-2018. Cestode larvae/cysts were collected from body cavities or internal organs (e.g. liver) during autopsies. Adult tapeworms were derived from nine red foxes, three Eurasian badgers and one Eurasian lynx. PCR amplification, sequencing and phylogenetic analyses were conducted employing three genetic markers: 18S rDNA, mitochondrial (mt) 12S rDNA and the mt cytochrome c oxydase subunit 1 (cox1) gene fragment. RESULTS: Altogether 19 Mesocestoides samples were analyzed, including 13 adult tapeworms from definitive hosts and six larval samples from 4 bank voles and 2 yellow-necked mice. Phylogenetic analyses revealed three well-supported trees of similar topology. In each case the Mesocestoides samples formed two separate clades. All isolates from foxes, the lynx isolate and two isolates from rodents grouped with Mesocestoides litteratus. Four isolates from rodents and all three isolates from Eurasian badgers were resolved in a separate clade, most similar to North American M. vogae (syn. M. corti). Examination of fixed, stained adult specimens from Eurasian badgers revealed consistency with the morphology of Mesocestoides melesi. Therefore, this clade is likely to represent M. melesi, a species first described in 1985 from the Eurasian badger Meles meles. Molecular analysis allowed also the identification of Taenia crassiceps, Hydatigera kamiyai and Cladotaenia globifera among larvae derived from rodents. CONCLUSIONS: Molecular and phylogenetic analyses support the recognition of M. melesi as a valid species. Our data represent the first record of the larvae of this species in rodents. This is the first report on the occurrence of H. kamiyai in rodents from Poland.

Differential Effects of the Flavonolignans Silybin, Silychristin and 2,3-Dehydrosilybin on Mesocestoides vogae Larvae (Cestoda) under Hypoxic and Aerobic In Vitro Conditions.

Mesocestoides vogae larvae represent a suitable model for evaluating the larvicidal potential of various compounds. In this study we investigated the in vitro effects of three natural flavonolignans-silybin (SB), 2,3-dehydrosilybin (DHSB) and silychristin (SCH)-on M. vogae larvae at concentrations of 5 and 50 µM under aerobic and hypoxic conditions for 72 h. With both kinds of treatment, the viability and motility of larvae remained unchanged, metabolic activity, neutral red uptake and concentrations of neutral lipids were reduced, in contrast with a significantly elevated glucose content. Incubation conditions modified the effects of individual FLs depending on their concentration. Under both sets of conditions, SB and SCH suppressed metabolic activity, the concentration of glucose, lipids and partially motility more at 50 µM, but neutral red uptake was elevated. DHSB exerted larvicidal activity and affected motility and neutral lipid concentrations differently depending on the cultivation conditions, whereas it decreased glucose concentration. DHSB at the 50 µM concentration caused irreversible morphological alterations along with damage to the microvillus surface of larvae, which was accompanied by unregulated neutral red uptake. In conclusion, SB and SCH suppressed mitochondrial functions and energy stores, inducing a physiological misbalance, whereas DHSB exhibited a direct larvicidal effect due to damage to the tegument and complete disruption of larval physiology and metabolism.

Unique pharmacological properties of serotoninergic G-protein coupled receptors from cestodes.

BACKGROUND: Cestodes are a diverse group of parasites, some of them being agents of neglected diseases. In cestodes, little is known about the functional properties of G protein coupled receptors (GPCRs) which have proved to be highly druggable targets in other organisms. Notably, serotoninergic G-protein coupled receptors (5-HT GPCRs) play major roles in key functions like movement, development and reproduction in parasites. METHODOLOGY/PRINCIPAL FINDINGS: Three 5-HT GPCRs from Echinococcus granulosus and Mesocestoides corti were cloned, sequenced, bioinformatically analyzed and functionally characterized. Multiple sequence alignment with other GPCRs showed the presence of seven transmembrane segments and conserved motifs but interesting differences were also observed. Phylogenetic analysis grouped these new sequences within the 5-HT7 clade of GPCRs. Molecular modeling showed a striking resemblance in the spatial localization of key residues with their mammalian counterparts. Expression analysis using available RNAseq data showed that both E. granulosus sequences are expressed in larval and adult stages. Localization studies performed in E. granulosus larvae with a fluorescent probe produced a punctiform pattern concentrated in suckers. E. granulosus and M. corti larvae showed an increase in motility in response to serotonin. Heterologous expression revealed elevated levels of cAMP production in response to 5-HT and two of the GPCRs showed extremely high sensitivity to 5-HT (picomolar range). While each of these GPCRs was activated by 5-HT, they exhibit distinct pharmacological properties (5-HT sensitivity, differential responsiveness to ligands). CONCLUSIONS/SIGNIFICANCE: These data provide the first functional report of GPCRs in parasitic cestodes. The serotoninergic GPCRs characterized here may represent novel druggable targets for antiparasitic intervention.

Case report: First confirmed case of canine peritoneal larval cestodiasis caused by Mesocestoides vogae (syn. M. corti) in Japan.

Canine peritoneal larval cestodiasis (CPLC) is an unusual parasitic disease in dogs that is caused by asexual proliferation of larval Mesocestoides. A 12 year-old spayed Shetland sheepdog with abdominal distension was referred to the Animal Medical Center at Nihon University, Japan. The presence of ascites was confirmed by abdominal ultrasonography and X-ray imaging. In addition, a number of parasites were observed in the ascitic fluid collected by abdominal paracentesis. Each of the whitish colored parasites was less than 1mm in size. The parasites were morphologically identified as Mesocestoides sp. tetrathyridia. The parasites had four suckers and calcareous corpuscles, but no hooks or rostellum. Mitochondrial (mt) 12S rDNA and mt cytochrome c oxidase subunit 1 DNA amplified from the tetrathyridia were used for molecular identification to species level. DNA sequence analysis showed that the tetrathyridia shared more than 99% identity with M. vogae (syn. M. corti) for each gene. The patient was treated with a standard dose (5mg/kg) of praziquantel, which was administered subcutaneously twice at an interval of 14 days. This resulted in successful deworming. This is the first case that CPLC was diagnosed in a dog that had never been taken outside of Japan, indicating that M. vogae is distributed in this country.

Mesocestoides sp. (Eucestoda, Mesocestoididae) parasitizing four species of wild felines in Southern Brazil.

Leopardus colocolo, Leopardus geoffroyi, Leopardus tigrinus and Puma yagouaroundi are wild feline species endangered mainly due to habitat destruction and vehicle run overs. Seventeen felines hit on the roads were collected in Southern Brazil and examined for parasites. Cestodes were identified as Mesocestoides sp. The parasites were found in the small intestine of the hosts with a prevalence of 66.7% (L. colocolo and L. tigrinus), 60% (P. yagouaroundi) and 50% (L. geoffroyi). Rodents and lizards were found in the stomach contents and they possibly were intermediate hosts of Mesocestoides sp. This is the first report of Mesocestoides sp. in wild felines in Brazil.

Mesocestoides sp. (Eucestoda, Mesocestoididae) parasitizing four species of wild felines in Southern Brazil / Mesocestoides sp. (Eucestoda, Mesocestoididae) parasitando quatro espécies de felinos silvestres no Sul do Brasil

Leopardus colocolo, Leopardus geoffroyi, Leopardus tigrinus and Puma yagouaroundi are wild feline species endangered mainly due to habitat destruction and vehicle run overs. Seventeen felines hit on the roads were collected in Southern Brazil and examined for parasites. Cestodes were identified as Mesocestoides sp. The parasites were found in the small intestine of the hosts with a prevalence of 66.7 percent (L. colocolo and L. tigrinus), 60 percent (P. yagouaroundi) and 50 percent (L. geoffroyi). Rodents and lizards were found in the stomach contents and they possibly were intermediate hosts of Mesocestoides sp. This is the first report of Mesocestoides sp. in wild felines in Brazil.

As espécies Leopardus colocolo, Leopardus geoffroyi, Leopardus tigrinus e Puma yagouaroundi, são felídeos silvestres ameaçados de extinção, principalmente pela destruição do hábitat e morte em rodovias. Dezessete felídeos foram coletados atropelados no sul do Brasil e, analisados na pesquisa de parasitos. Cestóides encontrados foram identificados como Mesocestoides sp. Os parasitos foram encontrados no intestino delgado dos hospedeiros com prevalência de 66,7 por cento (L. colocolo e L. tigrinus), 60 por cento (P. yagouaroundi) e 50 por cento (L. geoffroyi). Roedores e lagartos foram encontrados no conteúdo estomacal, podendo ser os hospedeiros intermediários para Mesocestoides sp. Este é o primeiro registro de Mesocestoides sp. em felídeos silvestres no Brasil.

Mesocestoides corti intracranial infection as a murine model for neurocysticercosis.

Neurocysticercosis (NCC) is the most common parasitic disease of the central nervous system (CNS) caused by the larval form of the tapeworm Taenia solium. NCC has a long asymptomatic period with little or no inflammation, and the sequential progression to symptomatic NCC depends upon the intense inflammation associated with degeneration of larvae. The mechanisms involved in these progressive events are difficult to study in human patients. Thus it was necessary to develop an experimental model that replicated NCC. In this review, we describe studies of a murine model of NCC in terms of the release/secretion of parasite antigens, immune responses elicited within the CNS environment and subsequent pathogenesis. In particular, the kinetics of leukocyte subsets infiltrating into the brain are discussed in the context of disruption of the CNS barriers at distinct anatomical sites and the mechanisms contributing to these processes. In addition, production of various inflammatory mediators and the mechanisms involved in their induction by the Toll-like receptor signaling pathway are described. Overall, the knowledge gained from the mouse model of NCC has provided new insights for understanding the kinetics of events contributing to different stages of NCC and should aid in the formulation of more effective therapeutic approaches.

Dynamics of hepatic stellate cells, collagen types I and III synthesis and gene expression of selected cytokines during hepatic fibrogenesis following Mesocestoides vogae (Cestoda) infection in mice.

In the present study, the relationship between progression of Mesocestoides vogae infection in the liver of mice, the accumulation rate of collagen types I and III, gene expression of fibrogenic factors and cytokines was examined within 6weeks p.i. Due to asexual multiplication, the total number of larvae in the liver increased considerably and 63.4% were found in collagen capsules on day 42 p.i. Intense staining for both collagens was recorded in the activated hepatic stellate cells (HSCs) throughout the period of this study in the inflammatory lesions. With progressing infection, cellular expression of both collagens was confined to the flat cells, myofibroblasts, which were scattered among collagen fibres in parenchymal lesions and capsules. Collagen-positive areas mirrored immunostaining of alpha-smooth muscle actin (alpha-SMA) in HSCs and myofibroblasts. Gene expression of both collagens increased rapidly within 14days p.i. and their expression pattern resembled that for pro-fibrotic cytokine transforming growth factor (TGF)-beta1 and alpha-SMA protein. IL-10 cytokine expression was up-regulated following day 14 p.i. and that of IL-13 was up-regulated early p.i., then transcription elevated gradually mirroring the activity of other pro-fibrotic markers. In contrast, transcription activity of TNF-alpha and IFN-gamma was elevated shortly after infection, followed by the partial down-regulation of gene expression, indicating the lack of larval killing, enhanced granulomatous inflammation and the perpetuation of hepatic fibrosis. Histomorphometric analysis of the parenchymal fibrous lesions, surface areas of larvae surrounded with the inflammatory infiltrates and surface areas of developing or mature larva-containing granulomas, correlated with the proportion of free and encapsulated larvae, immunostaining and gene expression patterns of collagens and pro-fibrotic markers. At a later stage of infection (day 28 p.i. onwards) collagen I-positive areas occupied a greater surface area and formed mature larval capsules and scars in the liver. In contrast, collagen III was less abundant and was localised mainly in the fibrous lesions in damaged parenchyma, suggesting their specific up-regulation as the part of host-protecting and tissue-healing responses.

In vivo response of Mesocestoides vogae to human insulin.

SUMMARY: Successful host invasion by parasitic helminths involves detection and appropriate response to a range of host-derived signals. Insulin signal response pathways are ancient and highly-conserved throughout the metazoans. However, very little is known about helminth insulin signalling and the potential role it may play in host-parasite interactions. The response of Mesocestoides vogae (Cestoda: Cyclophyllidea) larvae to human insulin was investigated, focusing on tyrosine-phosphorylation status, glucose content, survival and asexual reproduction rate. Parasite larvae were challenged with different levels of insulin for variable periods. The parameters tested were influenced by human insulin, and suggested a host-parasite molecular dialogue.

Suppressive activity of epinastine hydrochloride on eosinophil activation in vitro.

The influence of a histamine H1 receptor antagonist, epinastine hydrochloride (EP), on eosinophil functions was examined in vitro and in vivo. The first set of experiments was undertaken to examine whether EP could suppress eosinophilia and IgE hyperproduction induced by Mesocestoides cortii infection in BALB/c mice. The number of peripheral blood eosinophils and levels of IgE were examined 21 days after infection. Oral administration of EP at a daily dose of 0.3 mg/kg, which is the recommended human therapeutic dose, for 21 days was not able to suppress either peripheral blood eosinophilia or IgE hyperproduction, which was observed in mice infected with M. cortii. The second part of the experiment was designed to examine the influence of EP on eosinophil activation induced by stem cell factor (SCF) stimulation in vitro. Eosinophils were obtained from M. cortii-infected mice and stimulated with SCF in the presence of different concentrations of EP for 24 h. The addition of EP into cell cultures suppressed eosinophil activation induced by SCF stimulation as assessed by measuring the contents of acronym for Regulated upon Activation, Normal T cell Expressed and presumably Secreted (RANTES), macrophage inflammatory protein-1beta (MIP-1beta) and leukotriene C4 (LTC4) levels in culture supernatants. The minimum concentration of EP which caused significant suppression of factor productions was 25 ng/ml, which is similar to the concentration in plasma after oral administration of the therapeutic dose in humans. These results may suggest that EP exerts inhibitory effects on eosinophil activation and results in favorable modification of the clinical status of allergic patients.

Mesocestoides lineatus (Goeze, 1782) (Mesocestoididae): new data on sperm ultrastructure.

Spermiogenesis and the ultrastructural characters of the spermatozoon of Mesocestoides lineatus are described by means of transmission electron microscopy, including cytochemical analysis for glycogen. Materials were obtained from a golden hamster (Mesocricetus auratus) after experimental infection with tetrathyridia metacestodes obtained from naturally infected lizards (Anolis carolinensis) from Louisiana. Spermiogenesis in M. lineatus is characterized by the orthogonal growth of a free flagellum, a flagellar rotation, and a proximodistal fusion. The zone of differentiation contains 2 centrioles associated with striated rootlets and a reduced intercentriolar body. The mature spermatozoon of M. lineatus lacks a mitochondrion, and it is characterized by the presence of (1) a single, spiraled, crested body 150 nm thick; (2) a single axoneme of the 9+'1' pattern of trepaxonematan Platyhelminthes; (3) a parallel and reduced row of submembranous cortical microtubules; (4) a spiraled cordon of glycogen granules; and (5) a spiraled nucleus encircling the axoneme.

Ants as first intermediate hosts of Mesocestoides on San Miguel Island, USA.

This study tested the hypotheses that ants (Formicidae) function as a first intermediate host of Mesocestoides (Cestoda: Mesocestoididae) and that deer mice (Peromyscus maniculatus) develop metacestode infections after ingesting cysticercoid or procercoid-infected ants. Field studies were conducted at an island fox (Urocyon littoralis littoralis) breeding facility located on San Miguel Island, California Channel Islands National Park, USA, where > 40% of captive foxes were infected with adult Mesocestoides. Eight percent (8%) of deer mice at the fox pen site were infected with Mesocestoides metacestodes while none were infected at a distant site where foxes were absent (campground), thereby indicating the potential localized presence of a first intermediate host. To test whether ants from San Miguel Island contained Mesocestoides DNA, a polymerase chain reaction (PCR)-based diagnostic assay was developed using nested primers that could detect a single hexacanth larva within pooled samples of ten ants. Ants (Lasius niger and Tapinoma sessile) collected near the fox breeding facility were tested using the nested-PCR assay. Seven of 223 pooled samples of L. niger (3.1%) and 2 of 84 pooled samples of T. sessile (2.4%) tested positive for Mesocestoides DNA, while none of the ants were positive at the campground site. Positive samples were sequenced and found to match DNA sequences from Mesocestoides obtained from island fox and deer mice. Finally, to determine whether ants function as a first intermediate host for Mesocestoides, colony-raised deer mice (n = 47) were fed L. niger (n = 3860) or T. sessile (n = 339) collected from the San Miguel Island fox breeding facility. No mouse became infected with Mesocestoides metacestodes after ingesting ants. While both L. niger and T. sessile from SMI were positive for Mesocestoides DNA, they were not infective to deer mice in the laboratory.

Life-history studies on two molecular strains of mesocestoides (Cestoda: Mesocestoididae): identification of sylvatic hosts and infectivity of immature life stages.

Life-cycle studies were conducted on 2 molecular strains of Mesocestoides tapeworms that represent different evolutionary lineages (clades A and B). Wild carnivores, reptiles, and rodents were examined for tapeworm infections at 2 enzootic sites: (1) San Miguel Island (SMI), a small island off the coast of southern California and (2) Hopland Research and Extension Center (HREC), a field station in northern California. Results indicate that deer mice (Peromyscus maniculatus) and coyotes (Canis latrans) may play an important role in the life cycles of Mesocestoides (clades A and B) in California. Over half the coyotes at HREC and at least a third of the population of island fox (Urocyon littoralis) at SMI were found to harbor clade A adult Mesocestoides spp. One of every 4 Mesocestoides-infected coyotes had tapeworms representing both clades A and B. Experimental inoculations revealed that proglottids (clades A and B) were not directly infectious to rodents, reptiles, or dogs. On the other hand, mice, lizards, and hamsters fed tetrathyridia of Mesocestoides spp. (clades A or B) developed peritoneal tetrathyridial infections. A dog that was fed tetrathyridia (clade B) developed an adult tapeworm infection. Acephalic metacestodes given orally to western fence lizards, laboratory mice, or domestic dogs did not result in metacestode or adult tapeworm infections. Whereas most clade A acephalic metacestodes from dogs were asexually proliferative, clade A tetrathyridia isolated from wild deer mice did not show evidence of asexual replication. Our study supports the hypothesis that a second, as of yet unidentified, intermediate host is necessary to complete the life cycles of Mesocestoides spp., and that acephalic metacestodes represent an aberrant form, incapable of further development.

Pharmacological characterisation of neuropeptide F (NPF)-induced effects on the motility of Mesocestoides corti (syn. Mesocestoides vogae) larvae.

Neuropeptide F is the most abundant neuropeptide in parasitic flatworms and is analogous to vertebrate neuropeptide Y. This paper examines the effects of neuropeptide F on tetrathyridia of the cestode Mesocestoides vogae and provides preliminary data on the signalling mechanisms employed. Neuropeptide F (>/=10 microM) had profound excitatory effects on larval motility in vitro. The effects were insensitive to high concentrations (1 mM) of the anaesthetic procaine hydrochloride suggesting extraneuronal sites of action. Neuropeptide F activity was not significantly blocked by a FMRFamide-related peptide analog (GNFFRdFamide) that was found to inhibit GNFFRFamide-induced excitation indicating the occurrence of distinct neuropeptide F and FMRFamide-related peptide receptors. Larval treatment with guanosine 5'-O-(2-thiodiphosphate) trilithium salt prior to the addition of neuropeptide F completely abolished the excitatory effects indicating the involvement of G-proteins and a G-protein coupled receptor in neuropeptide F activity. Addition of guanosine 5'-O-(2-thiodiphosphate) following neuropeptide F had limited inhibitory effects consistent with the activation of a signalling cascade by the neuropeptide. With respect to Ca(2+) involvement in neuropeptide F-induced excitation of M. vogae larvae, the L-type Ca(2+)-channel blockers verapamil and nifedipine both abolished neuropeptide F activity as did high Mg(+) concentrations and drugs which blocked sarcoplasmic reticulum Ca(2+)-activated Ca(2+)-channels (ryanodine) and sarcoplasmic reticulum Ca(2+) pumps (cyclopiazonic acid). Therefore, both extracellular and intracellular Ca(2+) is important for neuropeptide F excitation in M. vogae. With respect to second messengers, the protein kinase C inhibitor chelerythrine chloride and the adenylate cyclase inhibitor MDL-2330A both abolished neuropeptide F-induced excitation. The involvement of a signalling pathway that involves protein kinase C was further supported by the fact that phorbol-12-myristate-13-acetate, known to directly activate protein kinase C, had direct excitatory effects on larval motility. Although neuropeptide F is structurally analogous to neuropeptide Y, its mode-of-action in flatworms appears quite distinct from the common signalling mechanism seen in vertebrates.

In vitro segmentation induction of Mesocestoides corti (Cestoda) tetrathyridia.

Mesocestoides corti is a suitable model for studying cestode development because of its ability to reproduce asexually and segment in vitro. The cultured parasite is also capable of sexual differentiation and, probably, reproduction. To establish conditions that increase the efficiency of in vitro M. corti larvae (tetrathyridia) segmentation, we tested the effects of an inducing agent and some physical parameters in cultures. We found that a 5% CO2-95% N2 gas phase, an incubation temperature of 39 C (instead of 37 C), and a 24-hr pretreatment with trypsin (10(5) BAEE/ml, BAEE = Na-benzoil-L-arginine ethyl ester unit of trypsin activity) in Roswell Park Memorial Institute (RPMI) 1640 medium supplemented with 20% fetal bovine serum (FBS) are able to increase individually or synergistically the segmentation rate of tetrathyridia. A segmentation rate of up to 100% was achieved on day 4 of culture, when all these conditions were used simultaneously, in comparison with an average rate of 40% obtained not before day 11 in cultures without any inducing treatment. Fetal bovine serum is essential for segmentation, and a concentration of 20% was established as the standard for induction.

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.

In vitro taurocholate-induced segmentation and clustering of Mesocestoides vogae (syn. corti) tetrathyridia (Cestoda)--inhibition byh cestocidal drugs.

Mesocestoides vogae (syn. M. corti) tetrathyridia were cultured in the presence of sodium taurocholate, for the purpose of exploring the suitability of this organism for the in vitro assay of cestocidal drugs. Parasite clustering and segmentation were observed as taurocholate-dependent effects in biphasic and monophasic media, respectively. Interestingly, representative members of two major classes of known cestocidal agents (namely, albendazole and praziquantel) blocked these effects. Furthermore, it was possible to determine a specific concentration of the drugs that inhibited clustering and segmentation (minimum inhibitory concentration). In contrast, no inhibition was obtained in the presence of anthelmintics without cestocidal activity. These observations open the way for further studies focused at understanding how the activity of the drugs is involved in the suppression of the taurocholate-induced effects.

Molecular systematics of Mesocestoides sPP (cestoda: mesocestoididae) from domestic dogs (Canis familiaris) and coyotes (Canis latrans).

The genus Mesocestoides Vaillant, 1863 includes tapeworms of uncertain phylogenetic affinities and with poorly defined life histories. We previously documented 11 cases of peritoneal cestodiasis in dogs (Canis familiaris L.) in western North America caused by metacestodes of Mesocestoides spp. In the current study, DNA sequences were obtained from metacestodes collected from these dogs (n = 10), as well as proglottids from dogs (n = 3) and coyotes (Canis latrans Say, 1823 [n = 2]), and tetrathyridia representing laboratory isolates of M. corti (n = 3), and these data were analyzed phylogenetically. Two nuclear genetic markers, 18S ribosomal DNA and the second internal-transcribed spacer (ITS 2), were sequenced. Phylogenetic analysis of the 18S rDNA data recovered a monophyletic group composed of all samples of Mesocestoides spp., distinct from closely related outgroup taxa (Amurotaenia Akhmerov, 1941 and Tetrabothrius Rudolphi, 1819). Initial analysis of the ITS 2 data resolved 3 clades within Mesocestoides. Two proglottids from dogs formed a basal clade, a second clade was represented by tetrathyridial isolates, and a third clade included all other samples. Interpretation of these data from an apomorphy-based perspective identified 6 evolutionary lineages. We also assessed whether metacestodes from dogs (n = 4) are capable of asexual proliferation in laboratory mice. One tetrathyridial and 2 acephalic isolates from dogs proliferated asexually. Further investigation is warranted to determine which of the lineages represent distinct species and to determine the life history strategies of Mesocestoides spp.

An experimental, NADPH-diaphorase histochemical and immunocytochemical study of Mesocestoides vogae tetrathyridia.

In order to test the role of nitric oxide in flatworms, Mesocestoides vogae tetrathyridia were incubated together with L-arginine, which is the substrate for nitric oxide synthesis, or with NG-nitro-L-arginine, which is an irreversible inhibitor of nitric oxide synthase. Normally, tetrathyridia attach to each other with the aid of their suckers, forming clusters. The rate of cluster formation was followed during the incubations. L-Arginine stimulated, and NG-nitro-L-arginine clearly inhibited, the cluster formation. This is the first time that an effect of nitric oxide has been observed in a flatworm. In addition, the pattern of the NADPH-diaphorase histochemical reaction in the nervous system and the pattern of F-actin filaments in the musculature stained with TRITC-labelled phalloidin were studied. NADPH-d staining occurred in the brain and the main nerve cords but also followed the muscle fibres stained with phalloidin. The pattern of the NADPH-d reaction was compared with that of 5-HT immunoreactivity. The implications of the results are discussed in relation to the background of data on neuronal signal substances in M. vogae.