Sexual Biology of Schistosomes

Moné, Hélène; Boissier, Jérôme

doi:10.1016/s0065-308x(04)57002-1

Cited by 36 publications

(33 citation statements)

References 274 publications

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“…Our results show thus, for the first time, that multiple infections by only male schistosomes induced a protective effect to reinfection by males and that multiple infections by only female schistosomes did not induce a protective effect to reinfection by females. Some of the results obtained in the literature also showed that protection by male parasite is higher than by female parasite: In the synthesis of Dean (1983), Table V, on the 18 results showing a reduction of more than 20%, 12 were obtained from male primo-infections and only 6 from female ones; in the synthesis of Moné and Boissier (2004), Table II, on the 17 results showing a reduction of more than 20%, 12 were obtained from male primo-infections and only 5 from female ones. The difference between male and female protectivities could originate from the higher inflammatory reaction induced by males compared to females in unisexual infections (Boissier et al 2003).…”

Section: Discussionmentioning

confidence: 91%

“…The protective effect of unisexual male or female trickle infections on mice has never been tested. Certainly, the fact that a mass unisexual infection is unable to induce a convincing protective effect (see Moné and Boissier 2004 for review) did not stimulate such experiments. However, it has been shown that trickle infections stimulated greater resistance than single infection (Farah et al 1997) and, more recently, that unisexual male schistosome infection induced a stronger inflammatory response compared to female (Boissier et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Influence of pattern of exposure, parasite genetic diversity and sex on the degree of protection against reinfection with Schistosoma mansoni

et al. 2007

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This paper analyzed, experimentally, the influences of pattern of exposure, parasite genetic diversity, and parasite sex on the degree of protection against reinfection with Schistosoma mansoni in the mouse. The results show that, (1) in infections with one male parasite genotype, successive infections induced a significant decrease in the infectivity of the parasite and significant increases in the spleen and liver weights compared to mass infections, (2) successive infections with one male genotype induced a significant decrease in the infectivity of the parasite compared to successive infections with five male genotypes, and (3) genotype infectivities were determined by the order at which they were used in the successive infections. These results are discussed in terms of protective effect and concomitant immunity and provide an ecological explanation of the natural sex-biased dispersal toward the male schistosomes.

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Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Influence of pattern of exposure, parasite genetic diversity and sex on the degree of protection against reinfection with Schistosoma mansoni

et al. 2007

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“…The weak positive signals were scattered throughout parenchyma, rather than constrained within certain organ(s), as the case in S. mansoni (Ribeiro-paes and Rodrigues 1995). TYR activity has been known to be linked uniquely to egg production in trematodes (Johnson et al 1987), and therefore, the activity in male worms may be explained by the partial hermaphroditism in schistosomes (Atkinson and Atkinson 1980;Moné and Boissier 2004).…”

Section: Discussionmentioning

confidence: 99%

Expression and characterization of two tyrosinases from the trematode Schistosoma japonicum

et al. 2008

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Tyrosinase (TYR) was thought to play a critical role during trematode egg production. In this study, we analyzed two genes (SjTYR1 and SjTYR2), derived from Schistosoma japonicum genome databases, which encode proteins with significant homologies to mammalian TYR. They exhibited the typical TYR topology, including two copper-binding domains and a highly conserved cysteine-rich domain. Semi-quantitative reverse transcription polymerase chain reaction showed that two SjTYR genes were mainly expressed in the female adult worm. A complementary DNA coding the putative common copper center domain of each SjTYR was cloned and inserted into a pET-28a-c(+) prokaryotic expression vector. After purification, the recombinant proteins expressed in Escherichia coli were used to produce their specific antibodies. The native active SjTYRs enzyme appeared to function as a homodimer, the subunits of which were linked to each other via covalent disulfide bonds. Both female and male worms possessed monophenol oxidase and diphenol oxidase activities of TYR. The relative enzymatic activities were 0.165 min(-1) mg(-1) and 0.0805 min(-1) mg(-1), which were inhibited by a copper-chelating agent (allyl thiourea) and correlated with disruption of female egg production. Our results revealed that SjTYRs might play a significant role during eggshell formation.

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“…The sex ratio of acanthocephalan and nematode parasites is frequently biased towards females in both natural and experimental infections (Poulin, 1997), while that of schistosomes is typically male-biased (Mone and Boissier, 2004). The primary sex ratio of animals is expected to be balanced (Fisher, 1930) but later events such as differential survival and infection rates may result in biased sex ratios of parasites within hosts.…”

Section: Introductionmentioning

confidence: 99%

Sex ratios and sex-biased infection behaviour in the entomopathogenic nematode genus Steinernema

Alsaiyah

Ebssa

Zenner

et al. 2009

International Journal for Parasitology

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a b s t r a c tIn experimentally infected insects, the sex ratio of first generation nematodes of five species of Steinernema was female-biased (male proportion 0.35-0.47). There was a similar female bias when the worms developed in vitro (0.37-0.44), indicating that the bias in these species is not due to a lower rate of infection by male infective juveniles (IJs). Experimental conditions influenced the proportion of males establishing in insects, indicating that male and female IJs differ in their behaviour. However, there was no evidence that males are the colonising sex in any species, contrary to what has previously been proposed. Time of emergence from the host in which the nematodes had developed influenced sex ratios in experimental infections. In three species (Steinernema longicaudum, Steinernema glaseri and Steinernema kraussei), early emerged nematodes had a higher proportion of males than those that emerged later, with the reverse trend for Steinernema carpocapsae and Steinernema feltiae. In a more detailed in vitro study of S. longicaudum, the proportion of males was similar whether or not the nematodes passed through the developmentally arrested IJ stage, indicating that the female bias is not due to failure of males to exit this stage. The sex ratio in vitro was independent of survival rate from juvenile to adult, and was female-biased even when all juveniles developed, indicating that the bias is not explained by failure of males to develop to adults. The female-biased sex ratio characteristic of Steinernema populations appears to be present from at least the early juvenile stage. We hypothesise that the observed female bias is the population optimal sex ratio, a response to cycles of local mate competition experienced by nematodes reproducing within insect hosts interspersed with periods of outbreeding with less closely related worms following dispersal. Ó

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Sexual Biology of Schistosomes

Cited by 36 publications

References 274 publications

Influence of pattern of exposure, parasite genetic diversity and sex on the degree of protection against reinfection with Schistosoma mansoni

Influence of pattern of exposure, parasite genetic diversity and sex on the degree of protection against reinfection with Schistosoma mansoni

Expression and characterization of two tyrosinases from the trematode Schistosoma japonicum

Sex ratios and sex-biased infection behaviour in the entomopathogenic nematode genus Steinernema

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