Development of Schistosoma mansoni worms in mice analyzed by bright field and confocal microscopy

The blood flukes of mammals (Digenea: Schistosomatidae) are among trematodes unique whose adult worms have separated sexes which are dissimilar in appearance. The developmental features, growth and organogenesis of Schistosoma mansoni were studied in Swiss Webster mice by a digital system for image analysis and confocal microscopy. Data so far obtained showed two phases with significative morphological changes at 3-4 weeks post-infection, and a gradual similar development onwards in the reproductive system and tegument. Our male-dependent phase demonstrated that mating occurs before sexual maturing. At week three, the majority of male worms (59%) had formed the gynaecophoric canal although testicular lobes and tegumental tubercles were absent. By this time, 33% females had an incipient ovary (without cellular differentiation). At week four, 77.2% males presented testicular lobes with few germinative cells while 26% had developing tegumental tubercles. The immature ovary was observed in 69% females. Suckers followed different pattern of growth between male and females. The size of oral and ventral suckers from six-week-old male worms grew abruptly (3.0 fold) more than that of three-week-old. In female worms, maximum growth was attained at week four, reducing in size thereafter. From sixth week onwards, all specimens showed the fully developed reproductive system. Probably, these features are morphological traits which schistosome has experienced from hermaphrodite to dioecy.     

Dolichol phosphate is a rate-limiting factor in mannosyl transferase activity of adult male worms of Schistosoma mansoni

The formation of mannolipid through catalysis by mannosyl transferase of adult females of Schistosoma mansoni was found to be 2-3 fold higher than male worms. In contrast, mannosyl transferase in immature females generated approximately the same amount of mannolipid as male worms, immature or not. Exogenous dolichol phosphate added to homogenates of male worms produced a stoichiometric increase in mannolipid formation. Saturating amounts of dolichol phosphate generated similar mannosyl transferase activities in male and female homogenates, showing that in S. mansoni, dolichol phosphate is the lipid intermediate in the glycosylation reaction and that this mannolipid is a rate-limiting substrate. Thin layer chromatography revealed that the mannolipid was identical in male and female worms. Adult males incubated with ¹⁴C-acetate synthesised several apolar compounds, one of which displayed a R_f identical to that of the mannolipid. When exposed to ¹⁴C-acetate treated males in vitro, untreated females were able to incorporate a compound, which partitioned in the same way as the mannolipid. The increased mannosyl transferase-dependent mannolipid formation in adult females may reflect a higher energy demand by these parasites, which is probably associated with oogenesis.     

Tegumental changes in adult Schistosoma mansoni harbored in mice treated with artemether

A detailed temporal examination was made of alterations induced by artemether in the tegument of adult Schistosoma mansoni worms using scanning electron microscopy (SEM). Mice infected with S. mansoni cercariae 42 days previously were treated intragastrically with artemether at a single dose of 400 mg/kg. Groups of 3 mice were killed at 24 hr, 72 hr, and 7 days after treatment; the worms were collected by perfusion and examined by SEM. Twenty-four hours after artemether treatment, focal damage to the tubercles on the tegumental surface of male worms was seen. In both male and female worms, there was focal swelling and fusion of tegumental ridges, and sometimes peeling. After 72 hr, the damage to the tegument had increased, especially in female worms, with extensive swelling, fusion, and peeling of the tegumental ridges. In the most severely damaged worms, host leukocytes were seen to be adhered to the damaged tegument. Damage to the oral sucker was also occasionally seen in both male and female worms. Seven days after treatment, the appearance of the tegument had returned to normal in some male and female worms, whereas others still showed apparent damage. The results demonstrate that artemether damages the tegument of adult S. mansoni, and the intensity of damage is more severe in female worms than in males.     

Gonadal hormones in experimental Ascaridia galli infection in chickens

Repeated injections of α-estradiol benzoate in immature females, and of testosterone propionate in immature males at the times and doses used, seemed to enable chickens to eliminate Ascaridia galli worms at a greater rate than the untreated controls. No sex difference in number of worms harbored was observed between normal males and females within the limits of age studied. The increase in resistance in hosts that received homologous sex hormones was similar in males and in females.Measurements of worms recovered indicated that gonadal hormones or their products may possibly have an effect upon the growth of the parasites. Injections of α-estradiol benzoate seemed to cause a temporary retardation in the mean rate of growth of the worms, whereas injections of testosterone propionate seemed to cause a temporary acceleration.     

Infrapopulations of Sclerocollum saudii Al-Jahdali, 2010 (Acanthocephala: Cavisomidae) in the rabbitfish Siganus rivulatus (Teleostei, Siganidae) from the Saudi coast of the Red Sea

In infrapopulations of helminth parasites, density-dependent effects, through some form of intra- and interspecific competition, play an important role in shaping and regulating the infrapopulations. The mechanisms responsible for these processes have often been observed in laboratory studies and rarely studied under natural conditions. Here, 24 natural infrapopulations (77-447 individuals) of the acanthocephalan Sclerocollum saudii Al-Jahdali, 2010 from the fish Siganus rivulatus consisted of cystacanths, newly excysted juveniles, immature and mature worms, distributed in a well-defined fundamental niche (anterior 60% of the intestine). Each of these stages exhibited a significantly different longitudinal distribution within this niche. In small infrapopulations, cystacanths and newly excysted juveniles were found in the sixth 10% of the intestine, immature worms in the fifth 10% and mature worms in the anterior 40% of the intestine. However, their proportions followed a clear ascending order in each infrapopulation, and the female-male ratios of both immature and mature worms were distinctly female-biased. In large infrapopulations, mature worms existed partially in the site of immature ones, where a differential mortality among immature females was constantly observed. However, the proportions of immature worms increased significantly and those of mature worms decreased significantly, the mean lengths of immature and mature females decreased dramatically and the female-male ratios were distinctly male-biased. The mean sizes of immature and mature males seemed stable through all infrapopulations. The distribution of mature males and females suggests intense male-male competition for access to females, and reveals that larger females are copulated prior to the smaller ones. The results are statistically significant and suggest that infrapopulation self-regulation is through density-dependent mechanisms, in which immature females may play a key role.     

Changes in behaviour associated with pair formation in the polychaete Harmothoë imbricata (L.)

Spacing between individuals in populations of Harmothoë imbricata has been investigated both on the shore and in the laboratory. Males tend to occur closer together than females, and the mean male‐male individual distance measured was less than the mean distance between females; male—female distances for immature worms were intermediate. When worms mature they pair: the male mounts the female and lies across her dorsal surface. There is evidence that after spawning the members of a pair separate. Contact responses between worms have been investigated in the laboratory. Most encounters between immature worms lead to separation, as a result of one or both worms moving rapidly away from the other or fighting; females show more marked avoidance behaviour than males. The majority of male‐male and female‐female encounters between mature worms also lead to separation but in male‐female encounters the male usually mounts the female. A male which has mounted a female becomes highly aggressive and will attack intruding males but not females.     

Surface ultrastructure of the tegument of Clonorchis sinensis newly excysted juveniles and adult worms.

The tegumental structures of newly excysted juveniles and adult worms of Clonorchis sinensis were studied using scanning and transmission electron microscopy. After excystation the juvenile's tegumental surface is characterized by knoblike protuberances and is armed almost entirely with numerous rows of small spines encircling the body. These spines are double- or triple-pointed on the anterior portion of the body and become single-pointed posteriorly. Four types of presumed sensory structures were observed as follow: A) ciliated knoblike papillae and B) nonciliated platelike papillae, both of which are arranged in rougly a bilaterally symmetrical pattern dorsally, ventrally, and laterally; C) rounded swellings of nonciliated papillae on the lips of the ventral and oral suckers, which are characterized in the transmission electron microscope by a rounded dense body in the apical bulb; and D) a sensory receptor with a bulbous projection having the appearance of a modified cilium, which was not found with SEM likely owing to its being enclosed by an extension of the tegument. In full-grown adult worms, the tegumental surface is knobbed or lobulated in various forms without surface spines. The tegumental structures in the adults appear to be clearly differentiated from those in the juveniles. Upraised, buttonlike papillae, each topped by a short cilium, which are similar to the Type A papillae in the juveniles, are distributed thickly around the oral and ventral suckers, and are rather randomly scattered over the remainder of the body. Some nonciliated swollen papillae were found on the lip of the ventral sucker.     

不同性别和年龄的大仓鼠对黄鼬气味的反应

将雌性成体和雌雄亚成体大仓鼠 (Cricetulustriton)长期 (4周 )暴露给过量的黄鼬 (Mustelasibirica)肛腺分泌物 ,观察其行为和生理状态的变化 ,并通过与我们以前有关黄鼬气味对成年雄鼠影响的研究结果进行比较 ,表明黄鼬气味对不同性别和不同年龄大仓鼠的胁迫效应和生殖抑制存在差异。发现黄鼬气味对雌性大仓鼠的影响较雄性小 ,对亚成体的影响较成体小 ,这与雌性和未成年动物对各种胁迫因素的反应更敏感的普遍现象相反。在成年鼠中 ,雌雄鼠的攻击行为都受到黄鼬气味的抑制 ;但天敌气味使雌性的胁腺膨大 ,对胁腺标记和肾上腺大小无影响 ;成年雄鼠的肾上腺膨大 ,胁腺萎缩 ,标记减少。在亚成体中 ,除了雄性胁腺受到抑制(与成年雄鼠相同 )外 ,雌雄鼠的肾上腺和雌性的胁腺未受影响。亚成体实验鼠的体重都比对照组低 ,但成年鼠的体重未受影响。另外 ,与以往对其它鼠类的研究结果一致 ,天敌气味并不影响成年鼠的生殖器官 ,却抑制了未成年雄鼠的附睾和未成年雌鼠的子宫。这些差异可能和生理基础的性二态以及可能面临的被捕食风险大小有关     

Growth of Enterobius vermicularis in a chimpanzee after anthelmintic treatment

The growth of Enterobius vermicularis in a chimpanzee was investigated by observing worms discharged in feces after administration of pyrantel pamoate. Just after the final molting, immature adult male pinworms developed to a fully mature stage in 2 wk, after passing through a stage corresponding to the so-called Enterobius gregorii, which was surmised to be a younger adult form of E. vermicularis. The frequency distribution of body length forms 2 peaks in both male and female pinworms, with a depression in the transitional forms from the immature to the fully mature stage.This depression seems to be the result of more rapid growth or lower susceptibility to the drug in this transitional stage. Pyrantel pamoate effectively eradicated mature males, but gravid females were continuously observed in the feces after treatment. The complete eradication of pinworm infection by pyrantel pamoate could be achieved by repeated treatment at intervals shorter than 2 wk. This treatment would eradicate male worms first, resulting in females producing only unfertilized eggs, from which only males might hatch.     

Tegumental ultrastructure of the juvenile and adult Himasthla alincia (Digenea: Echinostomatidae)

The tegumental ultrastructure of juvenile and adult Himasthla alincia (Digenea: Echinostomatidae) was observed by scanning electron microscopy. One-, 5- (juveniles) and 20-day-old worms (adults) were harvested from chicks experimentally fed metacercariae from a bivalve, Mactra veneriformis. The juvenile worms were elongated and curved ventrally. The head crown bore 31 collar spines, arranged in a single row. The lip of the oral sucker had 12 paired, and 3 single type I sensory papillae, and the ventral sucker had about 25 type II sensory papillae. The anterolateral surface between the two suckers was densely packed with tegumental spines with 4-7 pointed tips. The adult worms were more elongated and filamentous, and had severe transverse folds over the whole body surface. On the head crown and two suckers, type I and II sensory papillae were more densely distributed than in the juvenile worms. Retractile brush-like spines, with 8-10 digits, were seen on the anterolateral surface, whereas claw-shaped spines, with 2-5 digits, were sparsely distributed posteriorly to the ventral sucker. The cirrus characteristically protruded out, and was armed with small spines distally. The surface ultrastructure of H. alincia was shown to be unique among echinostomes, especially in the digitation of its tegumental spines, the distribution of sensory papillae and by severe folds of the tegument.     

Schistosoma mansoni: dose-related tegumental surface changes after in vivo treatment with praziquantel

The in vivo effects of a range of concentrations of praziquantel (10, 25, 50, 100, 200 and 500 mg/kg body weight of mouse) on the tegumental surface of adult Schistosoma mansoni were studied using scanning electron microscopy. Worms were recovered from mice at 1 and 4 h post-treatment. In general, irrespective of the dose level, male worms exhibited more pronounced and extensive surface alterations which included surface bleeding, swellings, wrinkling and constrictions and surface lesions, particularly on the spined tubercles. In male worms, in particular, the number of worms exhibiting damage and the amount of tegumental surface damage depended, mainly, on the concentration of praziquantel, although, at any given dose level, the extent of the damage increased with time post-treatment.     

Schistosoma mansoni: surface membrane stability in vitro and in vivo

The human complement component C3b is known to bind in vitro to the surfaces of all developmental stages of schistosomes as a consequence of complement activation by the alternative pathway. C3b bound to Schistosoma mansoni parasites has now been used in combination with fluorescent labeled antibodies against C3b to label the surfaces of living schistosomes. Binding of complement components and labeled antibodies to adult schistosomes rendered their surface membrane homogeneously fluorescent. At the ultrastructural level, the label was seen as a dense deposit lying on the tegumental membrane. Surface damage was not observed in labeled adults by electron microscopy. Fluorescent schistosomes were cultured in vitro for periods of up to 2 weeks, during which time the parasites remained fully viable and their surface membrane was still fluorescent. The electron dense deposit persisted, and tegumental damage at the electron microscope level was minimal or absent. Consequently, adult schistosomes would seem able to survive in vitro in the absence of rapid and general turnover of their surface membrane. Loss of fluorescence was observed consistently only at the anterior end of the parasite, including the suckers, a finding which indicates that membrane turnover may occur at different rates on different parts of the body. Fluorescent 3-week-old juveniles and 6-day-old lung stage parasites were cultured under the same conditions with similar results: they remained viable and fluorescent for at least 2 weeks. Results with skin schistosomula were different in the sense that many worms died during culture, and those which survived lost large parts of their fluorescent surface. A few of the surviving and fluorescent schistosomula developed the elongate shape typical of lung stage parasites. Fluorescent viable skin schistosomula were injected intravenously into mice and subsequently recovered from the lungs after varying periods. Fluorescence was lost in a patchy way within a few minutes from some individuals and within several hours from most of the worms. These data permit the following conclusions: C3b is a suitable tracer for membrane renewal in all developmental stages of schistosomes. Very slow membrane renewal in vitro and very rapid renewal in vivo are both compatible with parasite survival.     

Schistosoma mansoni: identification of immunoglobulins associated with the tegument of adult parasites from mice.

Immunocytochemical and immunodiffusion studies were conducted in an attempt to identify the immunoglobulins associated with the tegumental surfaces of Schistosoma mansoni. Peroxidase-labeled monospecific rabbit anti-mouse immunoglobulin class or subclass sera revealed the presence of mouse IgG₁, IgG₂, IgG₃, IgA, and IgM on the surface of adult parasites recovered from mice. These observations were confirmed by double gel diffusion of the various rabbit antisera against an eluate obtained from mouse worms.     

Schistosoma mansoni: fine structural localization of tegumental adenosine triphosphatases

The distribution of Ca2+-dependent adenosine triphosphatase (EC 3.6.1.3.) and nonspecific (Na-K-Mg) adenosine triphosphatase activity in the tegument and subtegumental tissues of Schistosoma mansoni from both mixed and single sex infections was investigated cytochemically. Differences in the distribution of tegumental Ca-adenosine triphosphatase activity in 60- to 70-day-old female worms were found which could be related to the degree of sexual development in the two types of females, with little or no tegumental activity being found in 70-day-old females from single sex infections. In contrast, 28-day-old females from single sex infections showed low levels of tegumental Ca-adenosine triphosphatase activity, suggesting that the lack of tegumental activity in 70-day-old single sex females may be due to a loss or suppression of activity as a consequence of the failure of females in single sex infections to pair and develop to full sexual maturity. No differences in the distribution of nonspecific (Na-K-Mg) adenosine triphosphatase activity between females from mixed and single sex infections were found. The sexual status or age of male worms appeared to have little or no effect on the distribution of tegumental adenosine triphosphatases.     

Infrapopulations of Procamallanus elatensis Fusco & Overstreet, 1979 (Nematoda: Camallanidae) in the rabbitfish Siganus rivulatus (Teleostei, Siganidae) from the Saudi coast of the Red Sea

Factors regulating gastrointestinal nematode infrapopulations are to a great extent density-dependent. Here, 23 natural infrapopulations (41-281 individuals) of the viviparous nematode Procamallanus elatensis (Camallanidae) from the fish Siganus rivulatus were found distributed in a well-defined fundamental niche (posterior 55% of the intestine). Immature worms were mostly found in the anterior third of this niche, while mature worms were found in aggregations posterior to them and followed by gravid females in the posterior 20% of the intestine. This distribution strongly suggests that worms migrate towards the posterior intestine while they mature, copulate and reproduce. In small infrapopulations, the sex ratios were distinctly female-biased and the number of gravid females was low. In large infrapopulations, the sex ratios were distinctly male-biased and the number of gravid females was high. However, the mean lengths of both immature males and females and mature females decreased dramatically as the infrapopulation size increased, while those of mature males increased significantly. These results strongly suggest intraspecific competition and density-dependent regulation of mean worm length, and the increase in the mean length of mature males strongly suggests intense sexual selection and competition between mature males. Production of larvae by female worms decreased significantly as the infrapopulation size increased, suggesting a density-dependent reduction in female worm fertility. The results are statistically significant and strongly suggest that infrapopulation self-regulation is through density-dependent mechanisms, in which development of immature worms, infrapopulation size, sex ratio, sexual selection and carrying capacity of the fundamental niche play essential roles in shaping and regulating the infrapopulations.     

Surface ultrastructure of the developmental stages of Heterophyopsis continua (Trematoda: Heterophyidae).

Ultrastructural observations were made on the tegument of juvenile and adult stages of Heterophyopsis continua using scanning electron microscopy. On the surface posterior to the ventral sucker, the tegumental processes were bandlike in the metacercariae, cobblestonelike in the flukes 2 days postinfection (PI), and velvety at 3 days PI. The anterior surface between the oral and ventral suckers of the metacercariae was packed densely with tegumental spines having a 10- to 14-pointed tip. In flukes 6 days PI, the number of points increased to 15-17. The tegumental spines immediately behind the ventral sucker on the metacercariae surface possessed 5-7 points; posteriorly the points were reduced in size and in number. Ciliate sensory papillae (type I), as single or clumped forms of 2 or 3, were abundant around the oral and ventral suckers of metacercaria and adult worms. The clumped papillae appeared bilaterally symmetrical on the dorsal and ventral surfaces. The ciliate papillae may function in tango-, rheo-, and/or chemoreception. On the lip of the ventral sucker, 6-7 aciliate domed papillae (type II) were arranged in an equidistant manner. At 2 days PI each type II papilla became a clumped form having 2 or 3 papillae. Type II papillae may function as tango- and/or pressure-receptors. The structure and distribution of papillae suggest that the ventral sucker likely functions as a holdfast organ and the oral sucker as a probing organ involved in feeding.     

Schistosoma mansoni: Surface Membrane Isolation with Lectin-Coated Beads

Lectins from Lens culinaris and Arachis hypogaea immobilized on polyacrylamide beads were used for selective isolation of glycosylated surface membrane domains of adult Schistosoma mansoni worms, and the method was compared with the membrane isolation procedure developed with polycationic (Affi-Gel) beads. The lentil lectin proved to be suitable for interaction with surface membrane components: an increment in the specific activities of tegumental phosphohydrolases was observed in the bound fraction with respect to that observed in a total worm homogenate. A characteristic polypeptide pattern on gel electrophoresis was also seen, more restricted than that obtained with the bound Affi-Gel fraction. Immobilized peanut lectin was not successful as a method for isolating membrane material from the tegument of adult worms. Solubilization and dissociation of the lentil lectin-bound enzyme markers was achieved after addition of detergent and competing sugars. Glycosylation of the solubilized enzymes was further confirmed by affinity chromatography with fresh lentil lectin-coated beads. These results, together with histochemical evidences, suggest that the active sites of some of these enzymes are locted within or close to the cytoplasmic leaflet of the surface tegumental membranes, and allow us to propose a model for the double surface membrane complex where some proteins may be crossing the two bilayers.     

Haptenation of adult Schistosoma mansoni and assessment of humorally mediated damage in vitro

Adult Schistosoma mansoni were haptenated with DNP under mild conditions using DNP-liposomes, as devised by Levi-Schaffer et al. (1983, Am. J. Trop. Med. Hyg. 32: 343) for haptenating schistosomula. The effects of complement, alone or with anti-DNP antibodies, on tegumental morphology of DNP-haptenated adult worms were assessed by both scanning and transmission electron microscopy, as a simple model system for possible in vitro effects of complement and anti-schistosomal antibodies on normal adult worms. Complement-mediated cytotoxicity, as measured by tegumental changes in both normal and haptenated worms, was observed and indicates a possible role for complement in humorally mediated damage of adult schistosomes. The damage to haptenated adults in the presence of both complement and anti-DNP was greater than that to nonhaptenated worms similarly treated. However, anti-DNP plus complement caused less damage to normal worms than did complement alone, perhaps the result of blocking by antibodies bound to the tegument via Fc receptors. Evidence herein presented implicates both classical and alternative complement activation by the adult worm's tegument. Tegumental tubercle smoothing was one manifestation of damage, as assessed by SEM. Smoothing appears to progress from spine blunting to disappearance, arguing for resorption rather than shedding as the mechanism for spine loss. Because the spines are mostly actin bundles, we suggest that complement-mediated intrategumental calcium ion flux could lead to spine resorption resulting from actin filament depolymerization and/or calcium-induced severing of actin filaments and dissociation of actin filament cross-linking proteins. This process could have adaptive value to the adult worm, in that the spines may be a repository of readily mobilizable actin molecules for tegumental maintenance and repair.     

Surface ultrastructure of Heterophyes nocens (Trematoda: Heterophyidae).

The surface ultrastructure of Heterophyes nocens (Trematoda: Heterophyidae) was studied by scanning electron microscopy(SEM). The adult worms were recovered from experimentally infected cats and from a naturally infected patient. They were leaf-like, ventrally concave, and ovoid or pyriform in shape. Ciliated knob-like sensory papillae (type I) were observed in single or grouped forms on and around the oral sucker, whereas non-ciliated round swellings (type II papillae) were seen on the lip of the ventral sucker. The tegumental spines around the oral sucker were 5-9 pointed, whereas those between the two suckers were 12-17 pointed. Ventrolaterally, three groups of 5-6 type I papillae were located between the oral and ventral suckers, with single ones alternating between them. The genital sucker was protruded or depressed, depending on the contraction state of the flukes, and the gonotyl spine number ranged 50-60. The number of tip points of tegumental spines was decreased posteriorly; finally they became 1-3 pointed. On the dorsal surface, 4 groups of 4-5 type I papillae were symmetrically located on both lateral sides, and the shape and distribution of tegumental spines were similar to those of the ventral surface. Although the tegumental ultrastructure of H. nocens was generally similar to those of other heterophyids, the genital sucker morphology including the number of gonotyl spines and/or the distribution pattern of tegumental spines and sensory papillae were suggested to be the characteristic features of H. nocens.     

Immunocytochemical localization of the major glutathione S-transferases in adult Schistosoma mansoni

Indirect immunofluorescence was used to investigate the tissue distribution of the major isoenzymes of Schistosoma mansoni glutathione S-transferase (GSH S-transferase). When polyclonal rabbit antisera against GSH S-transferase isoenzymes SmGST-1, -02, and -3 were applied to cryostat or plastic-embedded sections of fixed adult worms, a punctate pattern of enzyme distribution was observed that was restricted to the parenchyma. Labeling was much more pronounced in males than females, consistent with the biochemically determined distribution of these enzymes between the sexes. Intense immunolabeling was noted within the subectocytoplasmic core tissue of the tubercles of the male that appeared to be connected to deep parenchymal cells by immunoreactive cell processes. Immunofluorescence could be blocked completely by prior incubation of antisera with affinity-purified enzyme. Although schistosome GSH S-transferases have been reported to be protective antigens, no immunoreactivity was detected within or on the tegument, including the dorsal spines of the male. The lack of tegumental immunoreactivity was confirmed by immunoblotting of tegumental membrane preparations following SDS-PAGE. Muscle fibers, vitelline cells, and cecal epithelium also failed to react. The fact that the GSH S-transferases were not uniformly distributed among all parenchymal cells suggests the existence of subpopulations of parenchymal cells that are preferentially involved in the conjugation of electrophiles with glutathione.