Host susceptibility is altered by light intensity after exposure to parasites.

Translating research advances to natural systems using experimental laboratory studies is often difficult because of the variability between the natural environment and experimental conditions. Because environmental conditions have a large effect on an organism's physiology, responses to stressors like nutrient limitation, temperature, oxygen deprivation, predation, and parasite/pathogen infection are likely to be context dependent. Therefore, it is essential to examine the impact the study environment has on the experimental outcome. Here, we explored the effect of light exposure on susceptibility to parasite infection. The Biomphalaria glabrata / Schistosoma mansoni study system is a well-established model for studying schistosomiasis. It has been general practice to maintain the vector, B. glabrata, in dark conditions after exposure to miracidia of the human pathogen S. mansoni. We evaluated susceptibility of B. glabrata to S. mansoni under 3 different light conditions during the prepatent period, light (125 lx) on a 12-12 cycle, dim light (3 lx) on a 12-12 cycle, and no light (24 hr at 0 lx). We hypothesized that stress due to photoperiod disruption (24 hr of darkness) would result in compromised immune function and lead to higher susceptibility to infection. Prevalence of infected snails differed significantly between the light conditions, and higher susceptibility was observed in the full light and complete dark conditions compared with the low light conditions. The dim conditions are representative of current methods for evaluating susceptibility in this system. Our results indicate that light exposure during the prepatent period can affect infection outcomes, and environmental conditions must therefore be considered when assessing fitness and immune response due to interactions between host genotype and environment.

Efeitos de Piperaceae em Biomphalaria glabrata (Say, 1818)(Mollusca: Planorbidae) / Effects of Piperaceae on Biomphalaria glabrata (Say, 1818) (Mollusca: Plaorbidae)

A esquistossomose é uma doença grave e de evolução crônica, com importante papel sócio-econômico, cuja profilaxia inclui medidas que envolvem saneamento básico, educação sanitária, tratamento de indivíduos infectados e o controle dos caramujos hospedeiros intermediários do Schistosoma mansoni. Uma das medidas mais eficientes para o controle dos caramujos é a aplicação de moluscicidas, sendo os extratos vegetais os mais indicados. As vantagens do uso de extratos vegetais são devidas, principalmente, ao seu baixo custo e baixa ação tóxica para o ambiente. O objetivo deste trabalho foi avaliar a ação de extratos brutos de Piper cubataonum, Piper caldense, Piper cernuum, Peperomia trineura, Peperomia rubricaulis, Peperomia blanda e da substância ativa, ácido caldensínico de Piperaceae em embriões e adultos de Biomphalaria glabrata. Os extratos brutos e a substância ativa foram obtidos de folhas das plantas. Inicialmente todos os extratos e a substância ativa foram testados nas concentrações de 100 ppm e 20 ppm, respectivamente. Procurou-se determinar para cada extrato as concentrações responsáveis pela mortalidade de no mínimo 50% dos espécimes expostos. Os dados de mortalidade de adultos foram submetidos à análise de probito com intuito de estimar a concentração letal para 50% e 90% (CL50 e CL90) da população. Os extratos que apresentaram efeito tóxico em adultos foram P. trineura a 100, 80 e 60 ppm e P. caldense a 100, 80 e 50 ppm. O ácido caldensínico, quando testado em adultos, apresentou efeito tóxico a 20 e 10 ppm. Nas desovas os extratos que demonstraram efeito toxico foram P. trineura a 100, 80, 60 e 50 ppm, P. rubricaulis a 100 e 80 ppm e P. caldense a 100 ppm, apenas para os estádios de blástula, gástrula, e trocófora. Este último extrato apresentou efeito tóxico a 80 ppm somente para blástula e gástrula. P. caldense mostrou-se mais eficiente que P. trineura para causar a mortalidade em B. glabrata a 50 ppm. Os extratos de P. caldense...

Effects of UVB on interactions between Schistosoma mansoni and Biomphalaria glabrata.

Ultraviolet B (UVB, 280-315nm) radiation is detrimental to both of larvae of the digenetic trematode Schistosoma mansoni and its snail intermediate host, Biomphalaria glabrata. We explored effects of UVB on three aspects of the interaction between host and parasite: survival of infected snails, innate susceptibility and resistance of snails to infection, and acquired resistance induced by irradiated miracidia. Snails infected for 1 week showed significantly lower survival than uninfected snails following irradiation with a range of UVB intensities. In contrast to known immunomodulatory effects in vertebrates, an effect of UVB on susceptibility or resistance of snails to infection could not be conclusively demonstrated. Finally, exposure of susceptible snails to UVB-irradiated miracidia failed to induce resistance to a subsequent challenge with nonirradiated miracidia, a result similar to that reported previously with ionizing radiation.

Establishment of the comet assay in the freshwater snail Biomphalaria glabrata (Say, 1818).

The single cell gel electrophoresis or the comet assay was established in the freshwater snail Biomphalaria glabrata. For detecting DNA damage in circulating hemocytes, adult snails were irradiated with single doses of 2.5, 5, 10 and 20 Gy of (60)Co gamma radiation. Genotoxic effect of ionizing radiation was detected at all doses as a dose-related increase in DNA migration. Comet assay in B. glabrata demonstrated to be a simple, fast and reliable tool in the evaluation of genotoxic effects of environmental mutagens.

Lethal and sub-lethal effects of UVB on juvenile Biomphalaria glabrata (Mollusca: Pulmonata).

Although Schistosoma mansoni occurs mainly in the tropics, where intense levels of solar radiation are present, the impact of ultraviolet (UV) light on schistosome transmission is not known. The purpose of this study was to investigate potential effects of UVB (290-320nm) on juvenile Biomphalaria glabrata, the snail intermediate host of S. mansoni. Albino and wild-type snails were exposed to doses of UVB from UV-fluorescent lamps, and the following were measured: survival, photoreactivation (light-mediated DNA repair), effects on feeding behavior, and morphological tissue abnormalities. Irradiation with UVB is lethal to B. glabrata in a dose-dependent manner. Exposure to white light subsequent to UVB irradiation enhances survival, probably by photoreactivation. The shell offers some, but not complete, protection. Experiments in which UVB transmittance through the shell was blocked with black nail polish suggest that injury to both exposed (headfoot) and shell-enclosed (mantle and visceral mass) tissues contributes to mortality in lethally irradiated snails. Wild-type (pigmented) snails are less susceptible to lethal effects of UVB than albino snails, and they may be more capable of photoreactivation. UVB exposure inhibits snail feeding behavior, and causes tentacle forks and growths on the headfoot. Thus, UVB may influence the life cycle of S. mansoni by both lethal and sub-lethal damage to the snail intermediate host. However, the ability of snails to photoreactivate may mitigate these effects.

Behavior of Schistosoma mansoni-induced histopathological lesions in Biomphalaria glabrata submitted to ionizing radiation.

Present report demonstrates that repeated radiation of Schistosoma mansoni-infected Biomphalaria glabrata, totaling 15,000 rads, caused a sudden, albeit transient, suppression of cercarial shedding. Initially, sporocysts practically disappeared from the snail tissues. The more resistant developing cercariae presented nuclear clumping and vacuolation, before undergoing lysis. No host tissue reaction was evident at any time. Thirty-four days after the last irradiation, the snails resumed cercarial elimination. By that time numerous sporocysts and developing cercariae were detected, disseminated throughout snail tissues in a pattern similar to that of a highly malignant neoplasm, with no signs of host cellular reactions, which on the other hand were present in non-irradiated infected controls. The region of the ovo-testis was apparently destroyed after radiation, but returned to its normal appearance around 40 days after the last radiation. Ionizing radiation affected both host and parasite in S. mansoni-infected Biomphalaria glabrata, but the resulting impressive changes were soon reversed.

Effect of gamma radiation on the activity of hemocytes and on the course of Schistosoma mansoni infection in resistant Biomphalaria tenagophila snails.

High doses of gamma radiation (10 Krad) in Biomphalaria tenagophila snails (Taim strain), which have been found to be resistant to Schistosoma mansoni, were not sufficient to impair their resistance to the parasite. The number of hemocytes, as well as their phagocytic activity, were not affected by irradiation, thus showing resemblance with mammal macrophages, which are resistant to gamma irradiation also.

Growth changes induced by gamma radiation on Biomphalaria straminea (Dunker, 1848).

Doses of 60Co gamma radiation with 2.5; 5; 7.5; 10; 15; 20; 25; 30; 35; 40; 45; 50; 55; 60; 80; 160; 320 and 640 Gy were applied to 1, 080 snails Biomphalaria straminea, an intermediate host of Schistosoma mansoni, divided in groups containing 30 mollusks. In addition, 60 non irradiated snails were kept as control. Fifty percent of the population was kept in colonies (allowing cross fertilization) while the other half was maintained in sexual isolation (allowing self fertilization) and during one month their growth was observed through the daily measurement of the shell diameter. Results showed that after 20 Gy doses the growth in shell diameter of irradiated snails was greater than that of the control group after 30 days. At this dose the snail size was the greatest, among all isolated groups. The 80 Gy doses also induced the final shell diameter of isolated snails to be greater then that observed in the control groups. As this effect was most evident among the isolated snails, a possible hormonal role may have been involved in the observed phenomena, which is under investigation with the objective of identifying any future applications that this could have to schistosomiasis control.

Growth changes induced by gamma radiation on Biomphalaria straminea (Dunker, 1848)

Doses of 60Co gamma radiation with 2.5; 5; 7.5; 10; 15; 20; 25; 30; 35; 40; 45; 50; 55; 60; 80; 160; 320 and 640 Gy were applied to 1,080 snails Biomphalaria straminea, an intermediate host of Schistosoma mansoni, divided in groups containing 30 mollusks. In addition, 60 non irradiated snails were kept as control. Fifty percent of the population was kept in colonies (allowing cross fertilization) while the other half was maintained in sexual isolation (allowing self fertilization) and during one month their growth was observed through the daily measurement of the shell diameter. Results showed that after 20 Gy doses the growth in shell diameter of irradiated snails was greater than that of the control group after 30 days. At this dose the snail size was the greatest, among all isolated groups. The 80 Gy doses also induced the final shell diameter of isolated snails to be greater then that observed in the control groups. As this effect was most evident among the isolated snails, a possible hormonal role may have been involved in the observed phenomena, which is under investigation with the objective of identifying any future applications that this could have to schistosomiasis control

Gamma (60)Co DL(50/30) of Biomphalaria glabrata (SAY, 1818).

The variation of resistance to (60)Co gamma-rays of Biomphalaria glabrata was studied. A population of 480 mollusks was observed during 30 days - distributed in 8 groups of snails isolated and 8 groups of snails in colonies - after exposure (30 snails per group per dose) to increasing doses of gamma radiation. Doses of 10, 20, 40, 60, 80, 160, 320 and 640 Gy from a Gamma-cell (60)Co irradiator, were applied to the test groups and two groups control (non-irradiated) of snails - isolated and colony - were kept apart. After have been exposed, the snails were drew back to the aquaria where they were maintained before. The survival was estimated on a daily score of the alive animals in each group-dose, starting after the irradiation exposure day. As a result, the survival self-fertilization forms (DL(50/30) = 218.2 Gy) was found greater than in cross-fecundation forms. These data point to a low radio-resistance on the cross-fertilization forms - the sexual reproductive form - which is most found in nature. The lower radio-resistance of the cross-fertilization forms suggests the presence of some sex-linked hormonal factor related to this phenomenon.

Phenotypic analysis of cellular immune response in Swiss albino mice immunized with antigen extract from exposed B. alexandrina subjected to UV-, gamma irradiation and praziquantel treatment.

Mice were immunized (2x) subcutaneously at zero and 21st day with different antigen preparations. Splenocytes and mesenteric lymph nodes (MLN) cells were obtained from both immunized and control groups at 14th 21st and 42nd day post the 2nd immunization. The direct immunofluorescent assay was applied using anti mouse CD3+, D4+, CD8+, and IgG monoclonal antibodies to detect panel T-cells, T-cell subsets and B-cells respectively. The observations revealed that the splenic CD3+ T-cells did not show any considerable interrelation either between experimental groups or different time intervals post-immunization (P.I.). Meanwhile, UV-irradiated and PZQ-treated groups showed slight increase at the 2nd and 4th week P.I. as compared with the control group. The UV- and gamma-irradiated groups showed a significant elevation in CD4+ T-cells when compared with control group throughout the time of experiment, whereas, PZQ-treated group showed a significant increase at the 2nd and 4th week P.I. only. The frequency of CD8+ T-cells was elevated in all the experimental groups as compared with control group at 2nd, 4th and 6th week P.I. The MLN CD3+, CD4+ and CD8+ T-cells did not reveal any considerable changes between the experimental groups and control throughout the time of the experiment. A gradual decrease was observed in all the experimental groups by proceeding the time of the experiment. Splenic and MLN B-cells did not show considerable changes between the experimental groups and control group during the course of the experiment. It is concluded that these antigens could possibly stimulate cellular immune response upon their use as a protective antigens.

Fecundity changes induced by low-doses of gamma radiation on Biomphalaria straminea (Dunker, 1848)

A population of 420 snails Biomphalaria straminea, an intermediate host of Schistosoma mansoni, received gamma-rays obtained from a 60 Co source in low-doses (0/2,5/5/7,5/10/15/20 and 25 Gy); half population was kept in colonies (allowing cross fertilization) and other half was mantained in sexual isolation (alowing self fertilization). Results showed that 15 Gy stimulates the fertility of both groups but the colonies were more sensitive and at this dose its fertility overpasses the control group dose. The possible hormonal role played in the observed phenomena is under investigation.

Fecundity changes induced by low-doses of gamma radiation on Biomphalaria straminea (Dunker, 1848).

A population of 420 snails Biomphalaria straminea, an intermediate host of Schistosoma mansoni, received gamma-rays obtained from a 60Co source in low-doses (0/2,5/5/7,5/10/15/20 and 25 Gy); half population was kept in colonies (allowing cross fertilization) and the other half was maintained in sexual isolation (allowing self fertilization). Results showed that 15 Gy stimulates the fertility of both groups but the colonies were more sensitive and at this dose its fertility overpasses the control group dose. The possible hormonal role played in the observed phenomena is under investigation.

Effect of UV-irradiation, gamma irradiation and praziquantel on infected Biomphalaria alexandrina snails.

Schistosomiasis control represent the main target of many research programme allover the world. Effect of physical (UV- and gamma-irradiation) treatment as well as chemical (PZQ) treatment on infected laboratory bred Biomphalria alexandrina snails have been studied. Gamma irradiation and PZQ-treatment induced high rate of mortality than UV-irradiated and non-treated control snails. The cercarial production was severely reduced as a result of UV-, gamma-irradiation and PZQ-treatment. Pre-patent period was significantly increased in gamma-irradiated and PZQ-treated groups than UV-irradiated and control groups. Gamma irradiation and PZQ-treatment showed severe effects on hermaphrodite gland and cercariae. Trials of experimental infection in swiss albino mice revealed that low rate of infection (9.7% and 1.3%) was induced by cercarial shedding from UV-irradiated and PZQ-treated snails respectively. Whereas, cercarial production of gamma-irradiated snails failed to induce infection in swiss mice.

Effect of 60Co gamma radiation on Biomphalaria glabrata (Mollusca, Gastropoda) embryos: mortality, malformation and hatching.

A study was carried out on the radiosensitivity of Biomphalaria glabrata embryos submitted to doses of 5, 10, 15, 20 and 25 Gy of 60Co during the cleavage, blastula, gastrula, young trochophore and trochophore stages. Mortality, malformation and hatching were the parameters used to evaluate the damage induced by ionizing radiation. Estimated LD50 values (15 days) showed that the cleavage stage (4.3 Gy) was approximately four times more radiosensitive than the trochophore stage (17.0 Gy). Susceptibility to malformation induction was higher in the blastula, gastrula and young trochophore stages. Several types of morphogenetic malformations were observed, such as head malformations, exogastrulas, shell malformations, and embryos with everted stomodeum, with nonspecific malformations being the most frequent. The types of malformation induced by radiation probably are not radiation-specific and do not depend on the dose applied. The dose of 15 Gy was sufficient to greatly reduce the number of hatching snails regardless of the embryonic stage irradiated. We conclude that the effect of 60Co gamma radiation on B. glabrata embryos presented a specific pattern.

Effect of X-ray on the snails of schistosomiasis in Egypt.

Biomphalaria alexandrina and Bulinus truncatus snails were exposed to sublethal doses 0.2, 3, 5, 10 and 20 rad of X-ray. The survival and reproductive rates of these snails were highly affected by these doses. The maximum survival periods of laboratory populations of Biomphalaria snails were less than those of field ones which means a high sensitivity of laboratory snails to X-ray. The reproductive capacity of irradiated Biomphalaria and Bulinus snails was highly suppressed and this will interrupt Schistosomiasis transmission. A deleterious effect of gametogenesis of irradiated Biomphalaria was histologically proved. After 3 weeks of snail irradiation with high dose (40 rad) the hermaphrodite gland became completely evacuated.

Effect of 60CO gamma radiation on Biomphalaria glabrata (Mollusca, Gastropoda) embryos: mortality, malformation and hatching

A study was carried out on the radiosensitivity of Biomphalaria glabrata embryos submitted to doses of 5, 10, 15, 20 and 25 Gy of 60Co during the cleavage, blastula, gastrula, young trochophore and trochophore stages. Mortality, malformation and hatching were the parameters used to evaluate the damage induced by ionizing radiation. Estimated LD(50) values (15 days) showed that the cleavage stage (4.3 Gy) was approximately four times more radiosensitive than the trochophore stage (l7.0 Gy). Susceptibility to malformation induction was higher in the blastula, gastrula and young trochophore stages. Several types of morphogenetic malformations were observed, such as head malformations, exogastrulas, shell malformations, and embryos with everted stomodeum, with nonspecific malformations being the most frequent. The types of malformation induced by radiation probably are not radiation-specific and do not depend on the dose applied. The dose of 15 Gy was sufficient to greatly reduce the number of hatching snails regardless of the embryonic stage irradiated. We conclude that the effect of (60)Co gamma radiation on B.glabrata embryos presented a specific pattern.

[Malacologic diagnostic methods]. / Metodos de diagnóstico malacológico.

Specific identification of the snail vectors: (a) shell features; (b) animal features (genital organs); (c) biochemical techniques (electrophoresis). The snail infection rates: (a) exposure to light and cercarial identification; (b) snail crushing and identification or the larval forms in the tissues.

Variation of transaminases and lactate dehydrogenase in irradiated Biomphalaria alexandrina snails.

Effect of ultraviolet and gamma radiations on the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LD) in Biomphalaria alexandrina snails, the specific intermediate host of schistosomiasis, was investigated. Changes in the electrophoretic pattern of LD in the species under study were also taken as a measured parameter and the effect of gamma-irradiation on the glutathione content in the haemolymph of the snails have been included.

Studies on fresh water snails, specific intermediate hosts for schistosomiasis 1--isolation of total lipids from native and irradiated snails.

Total lipids were isolated from native and irradiated Biomphalaria alexandrina snails, specific intermediate hosts for Schistosoma mansoni.