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PubMed1994

Light and scanning electron microscopic observations of the eggs, daughter rediae, cercariae, and encysted metacercariae of Echinostoma trivolvis and E. caproni.

Light microscopy (LM) and scanning electron microscopy (SEM) were used to determine interspecific differences between various larval stages of 2 allopatric species of 37-collar-spined echinostomes, Echinostoma caproni and E. trivolvis. The abopercular and embryo diameters of the eggs of E. trivolvis were significantly different from those of E. caproni. The abopercular knobs of E. caproni and E. trivolvis have shallow and deep infoldings in the eggshells, respectively. Interspecific differences were noted in the tegument, tegumentary papillae, and spherical bodies around the mouth and in the papilliform process of the two rediae. The cercaria of E. caproni has one ventral tail fin-fold, whereas that of E. trivolvis has two; both species have two dorsal tail fin-folds. The outer metacercarial cyst diameter of E. caproni was significantly greater than that of E. trivolvis. E. caproni has a smoother outer cyst wall than does E. trivolvis.

Animals↗
PubMed1994

Histochemistry of proteinases in the cercariae of Diplostomum pseudospathaceum (Trematoda, Diplostomatidae).

Two distinct endopeptidases were detected histochemically in the cercariae of Diplostomum pseudospathaceum: a serine proteinase occupying the ceca and a cysteine proteinase occupying the penetration glands. The former was relatively resistant to formaldehyde, required either Ca2+ or Mg2+ for its stability, and was sensitive to organic fluorophosphate inhibitors but insensitive to thiol-blocking agents. The latter enzyme required both reducing and divalent cation-complexing agents for its full activity and was sensitive to formaldehyde, thiol-blocking agents, and diazonium salts. Both enzymes hydrolyzed a number of N-blocked L-aminoacyl-, and N-blocked L-peptidyl-naphthylamides bearing L-arginine at the P1 subsite. The pH optima for hydrolysis of the substrates were 8.0 for the serine proteinase and 7.6 for the cysteine proteinase.

Animals↗
PubMed1991

Nervous system of Schistosoma mansoni cercaria: organization and fine structure.

As observed by transmission electron microscopy of serially sectioned Schistosoma mansoni cercaria, the nervous system is distributed throughout the three anatomic segments of the larva-i.e., the anterior organ (oral sucker), the body (midsegment), and the tail. The central ganglion, a neuropile surrounded by cell bodies, is located in the anterior area of the body segment. It tapers anteriorly into two lobes from which a pair of anterior central nerve trunks extend longitudinally. The posterior region of the central ganglion tapers into a pair of nerve trunks (posterior central nerve trunks). Twelve peripheral nerve trunks are evenly distributed around the ganglion. Six trunks course anteriad (anterior peripheral nerve trunks) and six course posteriad (posterior peripheral nerve trunks). A pair of dorsal and ventral nerve trunks, positioned opposite each other, extend the length of the tail. All nerve trunks are unsheathed. The nervous system contains three types of vesicles. Type I vesicles average 47.66 +/- 2.57 nm in diameter, vary in electron density, and have electron-lucent peripheries. Type II vesicles have a mean diameter of 18.41 +/- 2.57 nm, are electron-lucent and are concentrated mostly in the presynaptic area of the synaptic and neuromuscular junctions. The mean diameter of Type III vesicles is 57.47 +/- 16.08 nm. They are electron-dense and are concentrated mostly in the tegumental ciliated papillae and their accompanying dendrites. Two types of synaptic junctions are present.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Transmission electron microscopy of sensory receptors of Echinostoma revolutum (Froelich 1802) cercaria (Digenea: Echinostomatidae).

Nonciliate, uniciliate, and multiciliate receptors were shown by transmission electron microscopy to occur in the body tegument of Echinostoma revolutum (Froelich 1802) cercariae. Detailed studies revealed three types of nonciliate, four types of uniciliate, and one type of multiciliate sensory endings. Most receptors were singly distributed. Only a few of them formed paired receptor complexes in three regions of the cercarial body. These receptor complexes were found to possess nonciliate, uniciliate, and multiciliate sensory endings.

Animals↗
PubMed1987

Protective effect of irradiated metacercariae of Fasciola gigantica and irradiated cercariae of Schistosoma bovis against fascioliasis in goats.

Sensitisation of goats for eight weeks with metacercariae of Fasciola gigantica gamma-irradiated at 3 kr resulted in significant resistance to an homologous challenge with normal metacercariae. However, serum sorbitol dehydrogenase assay suggested that, whereas little damage was produced by immunising infections, considerable hepatic damage was caused by flukes remaining from challenge infections. On the other hand sensitisation with cercariae of Schistosoma bovis gamma-irradiated at 3 kr did not stimulate any resistance against heterologous challenge with F. gigantica.

Animals↗
PubMed2005

Synthesis of new 4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine derivatives with an incorporated thiazolidinone moiety and testing their possible serine protease and cercarial elastase inhibitory effects with a possible prospective to block penetration of Schistosoma mansoni cercariae into the mice skin.

5-Substituted 4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine were synthesized by interaction of 4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-sulfonylhydrazide with some aldehydes to give the corresponding Schiff-bases, which after cyclization gave corresponding thiazolidinones. For some of the thiazolidinones, Mannich bases reaction was carried out. All the derivatives were tested for their possible inhibitory effect on Schistosoma mansoni cercarial elastase (CE). Only, N-(4-methylbenzyledine)-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-sulfonylhydrazide was found to have potent inhibitory effect on the CE activity with IC50 = 264 microM. Upon its use as a paint for mice tails before infection with S. mansoni cercariae, the compound formulated in jojoba oil caused a significant reduction (93%; P-value = 0.0002) in the worm burden. IgG & IgM in mice sera were measured by using several S. mansoni antigens by ELISA. Sera from treated infected mice (TIM) 2, 4, and 6 weeks (W) post infection (PI) showed 1.2 folds lower, 1.2 folds higher, 1.7 folds lower IgM reactivity against soluble cercarial antigenic preparation (CAP), respectively, when compared with sera collected from infected untreated mice (IUM). Sera from TIM 2, 4, and 6WPI showed 1.3, 1.6, and 1.7 folds higher IgG reactivity, respectively against CAP than the IgG reactivity from IUM. Sera from TIM 2, 4 and 6WPI showed 1.5, 1.2 folds lower and 1.4 folds higher IgM reactivity, respectively against soluble worm antigenic preparation (SWAP) when compared with sera collected from IUM. Sera from TIM 2, 4, and 6WPI showed 1.4, 1 folds lower and 1 fold higher IgG reactivity, respectivley to SWAP when compared with sera from IUM. Sera from TIM 2, 4, and 6WPI had generaly lower IgM and IgG reactivities against soluble egg antigen (SEA) when compared with sera from IUM.

Animals↗
PubMed2002

Nitric oxide and its target cells in cercaria of Diplostomum chromatophorum: a histochemical and immunocytochemical study.

In order to advance our knowledge of the nitrergic nervous system in flatworms, the patterns of the NADPH-diaphorase (NADPH-d) reaction and cGMP immunoreactivity, after stimulation with a nitric oxide donor in the presence of an inhibitor of phosphodiesterase, were investigated in cercaria of Diplostomum chromatophorum. This is the first time the presence of NADPH-d activity has been detected in a larval fluke, and the first time the presence of cGMP immunoreactivity has been detected in a flatworm. The NADPH-d reaction occurs in the ventral sucker, the hind body and the tail. cGMP immunoreactivity was detected in the muscle cells of the body and in two pairs of sensory cells at the anterior end of the body and in the middle of the furca. The sensory cells also showed 5-HT immunoreactivity. The spatial relationship between the cGMP and the 5-HT immunoreactivities was studied. By staining with TRITC-labelled phalloidin, the pattern of the muscle fibres was revealed.

Actins↗
PubMed2005

In vitro stimulation of penetration gland emptying by Trichobilharzia szidati and T. regenti (Schistosomatidae) cercariae. Quantitative collection and partial characterization of the products.

Induction of penetration gland emptying by cercariae of the bird schistosomes Trichobilharzia szidati and T. regenti employing linoleic acid, linolenic acid, praziquantel and calcium ionophore A23187 showed that both postacetabular and circumacetabular cells released their content at chosen stimulant concentrations. The gland secretions consisted of soluble and insoluble parts. The former one adhering to the ground seemed to have different saccharide composition from the glands of Schistosoma mansoni. It bound labelled saccharides, thus exhibiting lectin-like activity. Protein profiles of the latter one were identical after stimulation by all four stimulants in T. szidati. The soluble secretions contained several proteolytic enzymes; 31 kDa and 33 kDa cysteine proteases were identified in E/S products of T. szidati and T. regenti, respectively. The circumacetabular glands contained a significant amount of calcium. Immunohistochemistry revealed that the origin of E/S products after in vitro stimulation is in both penetration glands and tegumental structures. No crossreactivity was observed between the bird schistosomes and a serum raised against S. mansoni elastase.

Animals↗
PubMed2006

A cysteine proteinase in the penetration glands of the cercariae of Tylodelphys excavata (Trematoda, Diplostomidae).

A cysteine proteinase was detected in the penetration glands of the cercariae of Tylodelphys excavata and examined by means of biochemical and histochemical methods. The enzyme hydrolyzed azocoll, azocasein, azoalbumin, and N-benzoyl-l-arginine-4-nitroanilide at optimal pH 6.8, 6.4, 6.8, and 6.4, respectively, but was incapable of degrading elastin-orcein at the pH range of 6.0-10.0. Under histochemical conditions, the proteinase cleaved N-benzyloxycarbonyl-l-alanine-2-naphthyl ester and N-benzyloxycarbonyl-l-arginine-2-naphthylamide. A number of N-blocked synthetic substrates with l-methionine, l-leucine, glycine, dl- and l-phenylalanine at the P(1) position were not hydrolyzed. The metal cation complexane ethylenediamine tetraacetic acid (EDTA) and the reducing compound dithioerythritol stimulated the proteinase activity, whereas 0.1 mM zinc sulfate and the specific thiol-blocking reagent p-hydroxymercuribenzoate inhibited it. The proteinase activity was also sensitive to phenylmethylsulfonyl fluoride, leupeptin, tosyl-lysyl-chloromethylketone, and tosyl-phenylalanyl-chloromethylketone. An electrophoretic separation of extract proteins under non-denaturing conditions, at an operative pH of 3.5, in the presence of 5 mM EDTA and 5 mM 2-mercaptoethanol, revealed one main band of a relatively high gelatinolytic activity and two to three faint bands of low and very low activity, one of which was produced by a non-glandular intracellular cysteine proteinase related to cathepsin B. The other faint bands presumably were produced by partly autolysed molecules of the enzyme from the penetration glands.

Animals↗
PubMed1996

A serine proteinase in the penetration glands of the cercariae of Plagiorchis elegans (Trematoda, Plagiorchiidae).

Cercariae of Plagiorchis elegans secrete a serine proteinase from their penetration glands. The enzyme hydrolyzes both azocoll and gelatin at the optimal pH of 8.4 but is incapable of hydrolyzing elastin at the pH range of 7.2-10.0 Ca2+ and Mg2+ activate it, whereas metal chelators (1 mM EGTA, 1 mM EDTA) and serine proteinase inhibitors (1 mM PMSF and 0.1 mM DFP) act as strong inhibitors. The proteinase activity is insensitive to thiol-blocking compounds and to 5 mM 1,10-phenanthroline, a relatively specific chelator of zinc. It appears, therefore, that the active proteinase represents a metalenzyme complex rather than a metalloenzyme. Being capable of hydrolyzing N-blocked L-alanine-1-naphthylester, N-blocked L-methionine-1-naphthylester, and naphthyl AS-D chloroacetate at pH 6.8, the proteinase is insensitive to 1 mM p-nitrophenyl phosphate, an inhibitor of some mammalian esterproteinases. The enzyme does not split N-blocked DL-phenylalanine-2-naphthylester, nonspecific esterase substrates (1-naphthyl acetate, 1-naphthyl butyrate, 5-bromoindoxyl acetate), or several N-blocked L-aminoacyl- and N-blocked L-peptidyl-naphthylamides bearing L-arginine, L-alanine, L-phenylalanine, L-leucine, or L-proline at the P1 subsite. At operative pH values of 4.8 and 3.8 generated during electrophoresis in a stacking and a resolving gel, respectively, the cercarial proteinase migrates toward the cathode. The separated enzyme produces three bands of proteolysis in a gelatin-containing polyacrylamide gel at the optimal pH of 8.4. The presence of the proteinase in the penetration glands, in the secretory canals, and in the secretion from the glands suggests that the enzyme facilitates penetration, thus enabling the larvae to force their way through tissues of their hosts.

Animals↗
PubMed1985

Schistosoma mansoni: visualization with fluorescent lectins of secretions and surface carbohydrates of living cercariae.

Attachment of Schistosoma mansoni cercariae was studied during their explorative movements along a glass surface using labeled lectins as markers. Fluorochrome-labeled lectins selectively labeled surface material produced at the cercarial attachment sites and part of the cercarial surface. The deposited secretions reacted with most of the lectins used but differences in the staining intensity were noted. Secreted material was visualized at the attachment sites within a few seconds after cercarial attachment. The deposited material appeared as "footprints" located at a constant distance from each other. The footprints were formed by a regular cercarial "looping" movement along the glass surface and led to a site of massive deposition of secretions partly covering the body.

Lectins↗
PubMed1990

Schistosoma mansoni: the effect of regional lymphadenectomy on the level of protection induced in mice by radiation-attenuated cercariae.

The lymph nodes which drain the sites of percutaneous vaccination with optimally irradiated cercariae of Schistosoma mansoni were surgically excised in studies to determine their role in the induction of protective immunity. Lymphadenectomy of the axillary and inguinal nodes which drain the abdominal exposure site, or of the cervical node which drains the aural site of exposure, five days prior to vaccination reduced the levels of resistance by two-thirds. Excision of these nodes on Days 5, 10, 15, or 20 postvaccination also significantly reduced the levels of immunity induced, though ablation was less effective at later times. Removal of lymph nodes not draining the site of vaccination had no effect on the induction of resistance. We interpret the results as indicating that successful vaccination of mice against S. mansoni requires the presentation of antigen to lymphocytes in local lymph nodes draining the vaccination site, rather than distant lymphoid organs such as the spleen.

Animals↗
PubMed1994

Identification of Schistosoma mansoni antigens recognized by spleen cells of C57B1/6 mice immunized with ultraviolet-irradiated cercariae.

Spleen cells of C57B1/6 mice immunized twice with Schistosoma mansoni cercariae attenuated by ultraviolet irradiation proliferated and produced interleukin-(II)-2 and/or II-4 in response to both soluble schistosomular and adult worm antigens of 72-68, 60-62, 50, 45, 29.5 and 28 kDa. All of these bands, except the 45 kDa, were also recognized by serum antibodies in Western blotting.

Animals↗
PubMedDate not supplied

Characterization of fucosyllactose determinant-bearing glycoproteins probed by a Biomphalaria alexandrina lectin in Schistosoma mansoni cercariae.

Utilizing a Biomphalaria alexandrina-derived lectin (BaSII) of proven specificity to a Schistosoma mansoni-associated fucosyllactose [(Fuc alpha 1-2) Gal beta 1-4 Glc] determinant, two determinant-bearing glycoproteins of 40 and 37 kDa were found to be synthesized by the cercarial stage of the parasite. The two glycoproteins were isolated by BaSII affinity column chromatography from extracts of cercariae metabolically radiolabelled with 35S-methionine. Treatments with endoglycosidases, alkaline borohydride, as well as concanavalin A column chromatography and analysis by two-dimensional gels indicated that the two glycoproteins are synthesized as a single 33 kDa polypeptide backbone that is differentially glycosylated with one and/or two determinant-bearing N-linked complex-type glycan units of either the biantennary, or, to a lesser extent, the tri- or tetra-antennary types. The two glycoproteins lack other conventional high mannose-type or O-linked glycans, and the distinct structures of the complex-type oligosaccharides accounted solely for the expression of three isomorphs for each determinant-bearing glycoprotein. Based on the structural relatedness of the fucosyllactose determinant to the antigenic mammalian blood group H trisaccharide, our observations may have implications in mechanisms of host-parasite interactions as well as immunoprophylaxis.

Animals↗
PubMed1982

Adenylate cyclase in adults and cercariae of Schistosoma mansoni.

Adenylate cyclase of adult Schistosoma mansoni is activated by serotonin (5-hydroxytryptamine). Serotonin activation is markedly enhanced by GTP. the poorly hydrolyzed analogs of GTP, guanylyl imidophosphate (Gpp(NH)p) and guanosine 5' -(3-0-thio)triphosphate activate the schistosome cyclase in the absence of serotonin. The activating effect of these nucleotides is increased in the presence of serotonin. Female adult schistosomes have only 40% as much NaF-stimulated activity as do the male parasites. In addition, the serotonin stimulation of adenylate cyclase in the females is only 20% as much as the males. Maximal activation of adenylate cyclase with NaF reveals that the adult parasites have tenfold higher activity than the cercariae. cercarial adenylate cyclase shows very poor response to serotonin in the presence of GTP. Serotonin caused more significant activation of cercarial adenylate cyclase in the presence of guanylyl imidophosphate.

Adenylyl Cyclases↗
PubMed1991

Identification of free and conjugated ecdysteroids in cercariae of the schistosome Trichobilharzia ocellata.

Extracts of cercariae of the avian schistosome Trichobilharzia ocellata were analysed for the presence of ecdysteroids by radioimmunoassay, high-performance liquid chromatography monitoring fractions by radioimmunoassay, and gas chromatography/mass spectrometry (selected ion monitoring). Both free ecdysteroids and polar conjugated ecdysteroids were detected in the cercarial extracts. The free ecdysteroid fraction, as well as the hydrolysed polar conjugated ecdysteroid fraction, contained both ecdysone and 20-hydroxyecdysone in approximately equal amounts. The amount of ecdysteroids detected is comparable to those found in other platyhelminths. A possible role for the ecdysteroids in the development of the parasite and/or the interactions between the parasite and its intermediate host, the freshwater snail Lymnaea stagnalis, is discussed.

Animals↗
PubMed1987

Photoreceptor evoked potentials and phototactic behaviour in Cercaria caribbea LXXI cable.

1. Transient potential changes evoked in response to light stimuli, and presumably arising from rhabdomeric eye-spots in the cercarial body, were recorded for the first time, to our knowledge, in helminth parasites. 2. Pigmented Cercaria caribbea LXXI gave a very slowly adapting response to maintained light stimulus, while a non-pigmented variety appeared to emit a stronger, rapidly adapting response to light onset. 3. Swimming towards a directional light source is disrupted by several neuropharmacological agents, which presumably disturb synaptic transmission in the nerve/muscle system. 4. The light evoked potentials were unaffected by these same agents and therefore, appeared to be directly recorded receptor potentials.

Animals↗
PubMed1992

Autoradiographic quantification of the efficacy of niridazole in mice infected with 75Se-labelled cercariae of Schistosoma mansoni.

The effects of the anti-schistosomal drug, niridazole, on the migration of Schistosoma mansoni larvae, biosynthetically radioisotope-labelled with 75[Se]-selenomethionine, was evaluated by autoradiography of compressed tissues of mice treated daily from Days 6 to 10 post-infection with 200 mg kg-1 niridazole. The results were compared with the migration of schistosomula in untreated controls. The distribution of schistosomula was altered in niridazole-treated mice, where there was a delayed migration from the lungs relative to the controls and significantly fewer schistosomula in total appeared to reach the liver. The total percentage of schistosomula detected as autoradiographic foci was significantly lower in treated mice than in the untreated controls. Niridazole-treated mice were free of any foci 10 days after the last treatment and no adult worms were recovered on perfusion of the hepatic portal system relative to control mice from which 5.8% of the infective cercariae were recovered as adult worms at Day 42 post-infection.

Animals↗