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PubMed1998

Remodeling of phospholipid fatty acids in mitochondrial membranes of estivating snails.

The effects of estivation on the phospholipid-specific fatty acid composition of mitochondrial membranes in the hepatopancreas of the terrestrial snail Cepaea nemoralis were investigated. The fatty acid composition of all phospholipids was significantly altered in snails estivating for 6 wk, indicating that substantial remodeling occurs. The most profound changes occurred in cardiolipin (CL). CL of estivating snails was 13-fold more saturated, contained 9-fold more monoenes, and had 45% fewer polyenes than in active snails. These differences were due, in part, to a reduction in linoleic acid (1 8:2n-6) content of CL from estivators. As in mammals, CL of active snails appears to preferentially incorporate 18:2n-6, which accounts for 60% of the acyl chains in this phospholipid. This proportion was reduced by 50% in estivators. Changes in the fatty acyl content of other phospholipids of estivating snails included increased monoenes in phosphatidylethanolamine (PE) and phosphatidylinositol, reduced ratios of n-3/n-6 polyenes in PE and phosphatidylcholine (PC), and an increased n-3/n-6 ratio in phosphatidylserine (PS). Arachidonic acid (20:4n-6) levels were reduced in PS but increased in CL and PC. Taken together, these alterations to fatty acid composition are consistent with decreased biological activity of membrane-related processes which occur in conjunction with the reduction of mitochondrial aerobic metabolism observed during estivation.

Animals↗

PubMed1996

Food selection behaviour of potential biological agents to control intermediate host snails of schistosomiasis: Sargochromis codringtoni and Tilapia rendalli.

The food selection behaviour of two fish species indigenous to Zimbabwe (Tilapia rendalli and Sargochromis codringtoni) was studied under laboratory conditions with a view to considering them as biological agents for snail control. Six glass aquaria were set up and divided into two sets each with two aquaria. One S. codringtoni was introduced into each aquarium of the first set while one T. rendalli was introduced into each aquarium of the other set. In one of the aquaria of each set the fish were supplied with snails and trout food. Snails and weeds were provided, but trout food was excluded in the second aquarium of each set while the third aquarium for each set was provided with trout food, snails and weeds. A fourth aquarium with weeds and snails but no fish was set up as a control. Data collected over 9 weeks showed that T. rendalli was primarily herbivorous while S. codringtoni was shown to be malacophagous. Presence of trout food made no difference in the snail-eating habit of S. codringtoni or the weed-eating behaviour of T. rendalli. However, trout food seemed to be a good protein supplement to T. rendalli as the fish with access to trout food gained more weight and length.

Animals↗

PubMed1995

A repetitive DNA probe for the sensitive detection of Fasciola hepatica infected snails.

Epizootiologic studies on F. hepatica frequently use microscopic techniques for the detection of infected snails, however, the poor efficiency, sensitivity, and specificity associated with these techniques limit their usefulness. A DNA-based test for the identification of snails infected with larval stages of F. hepatica would solve these problems and enable a level of detection accuracy previously unavailable. We have cloned and sequenced a 124 bp fragment of repetitive DNA from F. hepatica which hybridizes specifically with DNA of F. hepatica but not with DNA of its snail intermediate hosts Fossaria cubensis and Pseudosuccinea columella, or with DNA of Fascioloides magna and Paramphistomum liorchis, ruminant trematodes which share the same intermediate host and same enzootic range as F. hepatica. Using this 124 bp fragment as a probe, infection in snails was detected immediately following miracidial penetration, thus a sensitivity equivalent to the minimum biologic unit of the parasite was achieved. This 124 bp repeated sequence belongs to a large family of 124 bp repeats that share a high level of sequence identity and constitute approximately 15% of the F. hepatica genome. We also report here the development of a quick and inexpensive DNA extraction protocol for use in field-collected snails. Thus, we have developed both a highly sensitive and specific DNA probe and a means to use the probe in a large epizootiologic study of F. hepatica where thousands of field-collected snails need to be assayed for infection.

Animals↗

PubMed1996

Experimental infection of Helisoma trivolvis (Colorado strain) snails with cercariae of Echinostoma trivolvis.

A Colorado (CO) strain of Helisoma trivolvis resistant to miracidial infection, but susceptible to Echinostoma trivolvis cercarial penetration, was used to study encystment of cercariae released from naturally infected H.trivolvis (Pennsylvania strain). All 12 snails, 8-10 mm in shell diameter, each exposed to 25 cercariae and necropsied 1-4 days post-exposure were infected with between 9 and 19 cysts per snail (average 14). In all infectivity experiments, regardless of the size (age) of the Colorado strain snails used, encysted metacercariae were recovered from the kidney-pericardial region of experimentally infected snails within 24 h post-exposure. Snails exposed individually with 500 cercariae averaged 230 cysts per snail at 24 h p.i. Cercariae encysted at 6-8 h p.i., but not at 2 and 4 h p.i. Light microscopical observations of the cysts suggested that greater than 99% were viable. Metacercariae subjected to in vitro excystation in an alkaline trypsin-bile salts medium showed excystation rates of 60-85%. In conclusion, H. trivolvis (CO strain) is an excellent experimental second intermediate host for cercarial encystment of E. trivolvis.

Animals↗

PubMed1988

The production of toxic oxygen metabolites by hemocytes of different snail species.

The phagocytic hemocytes of four snail species were investigated for their ability to generate reactive oxygen metabolites upon stimulation by foreign material. Hemocytes of the pond snail Lymnaea stagnalis and of the garden snail Helix aspersa showed a luminol-dependent chemiluminescence (CL) when they phagocytosed zymosan particles. This CL was inhibited by superoxide dismutase (SOD) and sodium azide, indicating the involvement of oxygen intermediates. Hemocytes of the planorbid snails Planorbarius corneus and Biomphalaria glabrata did not give a detectable CL response. This is probably due to the presence of hemoglobin in the hemolymph; after isolation of the cells and subsequent stimulation, however, still no CL could be measured. Hemocytes of all four snail species showed a SOD-sensitive nitroblue tetrazolium (NBT) reduction, indicating the generation of superoxide anions. Regarding the NBT reaction, no differences were observed between strains of B. glabrata that were susceptible or resistant to PR-1 Schistosoma mansoni; neither did exposure to the parasite have an effect on the ability of the hemocytes to reduce NBT. Also, hemocytes from Trichobilharzia ocellata-infected L. stagnalis did not react differently from hemocytes of uninfected snails. It is now clear that phagocytically stimulated hemocytes of several molluscan species can generate reactive forms of oxygen; the relevance of this fact for the phylogeny of killing systems operative in leukocytes is discussed.

Animals↗

PubMed2006

Snail is required for transforming growth factor-beta-induced epithelial-mesenchymal transition by activating PI3 kinase/Akt signal pathway.

Lens epithelial cells undergo epithelial-mesenchymal transition (EMT) after injury as in cataract extraction, leading to fibrosis of the lens capsule. We have previously shown that EMT of primary lens epithelial cells in vitro depends on TGF-beta expression and more specifically, on signaling via Smad3. In this report, we suggest phosphatidylinositol 3-OH kinase (PI3K)/Akt signaling is also necessary for TGF-beta-induced EMT in lens epithelial cells by showing that LY294002, an inhibitor of the p110 catalytic subunit of PI3K, blocked the expression of alpha-smooth muscle actin (alpha-SMA) and morphological changes. We also identify Snail as an effector of TGF-beta-induced EMT. Snail has been shown to be a mediator of EMT during metastasis of cancer. We show that Snail is an immediate-early response gene for TGF-beta and the proximal Snail promoter is activated by TGF-beta through the action of Smad2, 3, and 4. We show that antisense inhibition of Snail expression blocks TGF-beta-induced EMT and furthermore Akt activation. All of these findings suggest that Snail participates in TGF-beta-induced EMT by acting upstream of Akt activation.

Animals↗

PubMed2005

Seasonal modulation of free radical metabolism in estivating land snails Helix aspersa.

We investigated the regulation of free radical metabolism in Helix aspersa snails during a cycle of 20-day estivation and 24-h arousal in summer in comparison with estivation/arousal in winter-snails. In winter-snails (J. Exp. Biol. 206, 675-685, 2003), we had already observed an increase in the selenium-dependent glutathione-peroxidase (Se-GPX) activity in foot muscle and hepatopancreas and in the contents of hepatopancreas GSH-equivalents (GSH-eq=GSH+2 GSSG) during estivation compared with 24-h aroused snails. Summer-estivation prompted a 3.6-fold increase in Se-GPX activity in hepatopancreas, though not in foot muscle. Total-superoxide dismutase and catalase activities in hepatopancreas decreased (by 30-40%) during summer-estivation; however, no changes occurred in the activities of glutathione reductase, glutathione S-transferase and glucose-6-phosphate dehydrogenase in the two organs. GSH-eq levels were increased (by 54%) in foot muscle during estivation, but were unchanged in hepatopancreas. In contrast with winter-snails, oxidative stress markers (lipid peroxidation, carbonyl protein, and the GSSG/GSH-eq ratio) were unaltered during estivation/arousal in summer. These results demonstrate that seasonality modulates not only the absolute activities/levels of antioxidants (enzymes and GSH-eq) in H. aspersa, but also the regulatory process that controls the snail's antioxidant capacity during estivation/arousal. These results suggest that H. aspersa has an "internal clock" controlling the regulation of free radical metabolism in the different seasons.

Animals↗

PubMed2005

The transcriptional repressor Snail promotes mammary tumor recurrence.

Breast cancer recurrence is a fundamental clinical manifestation of tumor progression and represents the principal cause of death from this disease. Using a conditional transgenic mouse model for the recurrence of HER2/neu-induced mammary tumors, we demonstrate that the transcriptional repressor Snail is spontaneously upregulated in recurrent tumors in vivo and that recurrence is accompanied by epithelial-to-mesenchymal transition (EMT). Consistent with a causal role for Snail in these processes, we show that Snail is sufficient to induce EMT in primary tumor cells, that Snail is sufficient to promote mammary tumor recurrence in vivo, and that high levels of Snail predict decreased relapse-free survival in women with breast cancer. In aggregate, our observations strongly implicate Snail in the process of breast cancer recurrence.

Animals↗

PubMed2006

Oscillations of the snail genes in the presomitic mesoderm coordinate segmental patterning and morphogenesis in vertebrate somitogenesis.

The segmented body plan of vertebrate embryos arises through segmentation of the paraxial mesoderm to form somites. The tight temporal and spatial control underlying this process of somitogenesis is regulated by the segmentation clock and the FGF signaling wavefront. Here, we report the cyclic mRNA expression of Snail 1 and Snail 2 in the mouse and chick presomitic mesoderm (PSM), respectively. Whereas Snail genes' oscillations are independent of NOTCH signaling, we show that they require WNT and FGF signaling. Overexpressing Snail 2 in the chick embryo prevents cyclic Lfng and Meso 1 expression in the PSM and disrupts somite formation. Moreover, cells mis-expressing Snail 2 fail to express Paraxis, remain mesenchymal, and are thereby inhibited from undergoing the epithelialization event that culminates in the formation of the epithelial somite. Thus, Snail genes define a class of cyclic genes that coordinate segmentation and PSM morphogenesis.

Animals↗

PubMed2005

Snail and Slug are major determinants of ovarian cancer invasiveness at the transcription level.

OBJECTIVES: The transcriptional factors Snail and Slug have been reported to be important in cell migration during development and also during tumor metastasis. Their expression and role in ovarian cancer, hitherto unexplored, was examined to understand the molecular events in ovarian cancer metastases since the latter is responsible for the high degree of mortality associated with the disease. METHODS: Ectopic expression of mSnail and mSlug in the epithelial ovarian cancer cell line SKOV3 was carried out and stable clones were selected. These were used to examine specific repression of the adherens, tight and desmosomal junction components by the two transcription factors. Furthermore, functional implications with respect to enhanced migration of cells, tumorigenecity and metastasis were also studied. RESULTS: The ectopic expression of Snail or Slug resulted in epithelial-mesenchymal transition (EMT), enhanced motility, invasiveness and tumorigenecity in the cell line SKOV3. In addressing the mechanism by which Snail and Slug lead to loss of intercellular adhesion, specific repression of adherens junction components (E-cadherin and betacatenin), tight junction components (Occludin and ZO-1) and desmosomal junction components (Dsg2) were observed. Snail suppresses expression of adherens and tight junction components, while Slug suppresses expression of all the three junction components; concertedly, bringing down the intercellular adhesion between cells. Further activation of these transcriptional factors in hypoxic conditions revealed a rapid upregulation of Slug expression as an immediate reaction that probably triggers off a signaling cascade leading to Snail expression. CONCLUSIONS: These results indicate distinct roles of the transcriptional factors Snail and Slug during ovarian cancer metastasis and cell survival through mediation of EMT.

Animals↗

PubMed2000

Measuring exposure to Schistosoma japonicum in China. III. Activity diaries, snail and human infection, transmission ecology and options for control.

We used activity diaries and snail detection to relate water contact and Schistosoma japonicum infection among a cohort of 178 residents on two islands in the Dongting Lake, China. Water exposure to each of 12 mapped water zones around the islands was calculated (m(2) min/day) for each subject. Infected Oncomelania hupensis hupensis snails in this area are focal and were found in only five of the 12 zones, with the highest rate being 5.7%. Thirty-one subjects (17%) were re-infected with a mean intensity of 63.2 epg. Mean water contact was 7.9 m(2) min/day; 98% of water exposure was due to economic activity and only 2% due to swimming or bathing, washing and other necessities of daily life. Males had more exposure and infection than females (P<0.05). Infected subjects had more exposure (10.2 m(2) min/day) than those not infected (7.44 m(2) min/day) (P<0.05). Compared with uninfected subjects, those infected had 2.9 times more exposure in infected-snail zones (P<0.01). Also, human infection intensity (epg) correlated well with exposure to infected snail zones (r=0.552, P<0.01). People <20 years old had the highest re-infection (21.4%) and intensity (3.77 epg). Median exposure for 20-49-year-olds (9.00 m(2) min/day) was nearly double that of those aged <20 or >50 years old (5.5 m(2) min/day). We conclude that map-referenced water contact and snail evaluation boosts accuracy of activity-diary measurements in large transmission foci for the Asian schistosome. Protecting against faecal contamination of snail inhabited sites, and against occupational exposure for island residents, should be a priority of future research. Potential strategies for migrating buffaloes and families living on visiting fishing boats are explored.

Adult↗

PubMedDate not supplied

Investigation on interaction of Achatinin, a 9-O-acetyl sialic acid-binding lectin, with lipopolysaccharide in the innate immunity of Achatina fulica snails.

Achatinin, a 9-O-acetyl sialic acid (9-O-AcSA) binding lectin, has been demonstrated to be synthesized in amoebocytes of Achatina fulica snails. This lectin was affinity-purified from Achatina amoebocytes lysate (AAL); it appeared as a single band on native polyacrylamide gel electrophoresis (PAGE) and showed 16 identical subunits of M.W. 15 kDa on sodium dodecyl sulphate (SDS)-PAGE. It was found to be homologous with an earlier reported lectin, Achatinin-H, derived from hemolymph of A. fulica snails (Sen, G., Mandal, C., 1995. The specificity of the binding site of Achatinin-H, a sialic-acid binding lectin from Achantia fulica. Carbohydr. Res., 268, 115-125). Homology between both lectins was confirmed by their similar electrophoretic mobilities, carbohydrate specificity and cross reactivity on immunodiffusion. Achatinin showed in vitro calcium dependent binding to two 9-O-acetylated sialoglyoconjugates (9-O-AcSG) on lipopolysaccharide (LPS) (Escherichia coli 055: B5) of M.W. 40 kDa and 27.5 kDa, which was abolished following de-O-acetylation. Based on the previously defined narrow sugar specificity of Achatinin towards 9-O-AcSAalpha2-->6GalNAc [Sen, G., Mandal, C., 1995. The specificity of the binding site of Achatinin-H, a sialic-acid binding lectin from Achatina fulica. Carbohydr. Res., 268, 115-125], we conclude that LPS contains this lectinogenic epitope at the terminal sugar moiety. The Achatinin-mediated hemagglutination inhibition of rabbit erythrocytes by LPS further confirmed it. The lectin exhibited bacteriostatic effect on Gram-negative bacteria E. coli, DH5alpha and C600. AAL was earlier reported to undergo coagulation in presence of pg level of LPS (Biswas, C., Mandal, C., 1999. The role of amoebocytes in the endotoxin-mediated coagulation in the innate immunity of Achatina fulica snail, Scand. J. Immunol. 49, 131-138). We now demonstrate that Achatinin participates in LPS-mediated coagulation of AAL as indicated by enhanced release of Achatinin from the LPS stimulated amoebocytes and most importantly, by exhibiting a 77% decline in the coagulation of AAL when depleted of Achatinin. Level of Achatinin sharply declined (17-fold) following injection of LPS (20 microg per snail) to the snails, which was reversible by simultaneous injection of LPS and leupeptin implying the presence of LPS-mediated serine protease activity in Achatinin. This was substantiated when purified Achatinin in vitro showed serine protease activity in the presence of LPS followed by its complete blockage in the presence of leupeptin and phenyl methyl sulphonyl fluoride. Therefore, Achatinin, an abundantly available lectin at multiple sites of A. fulica, by virtue of its interaction with LPS, essentially plays a crucial role in the innate immune protection of A. fulica snails.

Animals↗

PubMed2003

Biological characteristics and control of intermediate snail host of Schistosoma japonicum.

Except for imported cases, we have had no new Schistosoma japonicum infection in Japan since 1977. But there are still two habitats of the intermediate snail host: Oncomelania nosophora in the previous endemic areas of Kofu Basin and Obitsu. O. nosophora from Kofu Basin and Obitsu are susceptible to Chinese and Philippine strains of S. japonicum. The number of immigrants from current endemic areas in China or the Philippines is increasing. In order to prevent re-emerging of S. japonicum infections in Japan, we should continue monitoring on those existing snail hosts and investigate an adequate quarantine system. In Japan, elimination of schistosomiasis has been mainly accomplished by control of the snail host. As measures of snail control, cement-lining of ditches and chemical mollusciciding were most effective in Japan. But the cost of this joint program is too expensive compared with health budget in almost developing countries. In endemic areas of Japan, land reformation from paddy field to fruit farm was also effective. The intermediate snail host in the Philippines, Oncomelania quadrasi is much more aquatic than O. nosophora. For control of O. quadrasi, small drainage of the water and land reclamation from swampy field to rice-field were effective. Based on biological characteristics of Oncomelania spp., we can modify the past successful snail control program in Japan to be adapted ecologically and economically to each endemic area of developing countries.

Animals↗

PubMed2006

Hydrological modelling of snail dispersal patterns in Msambweni, Kenya and potential resurgence of Schistosoma haematobium transmission.

Urinary schistosomiasis is an important source of human morbidity in Msambweni, Kenya, where the intermediate host snail, Bulinus nasutus is found in ponds and water pools. In the past, aquatic habitats in the area have been studied separately; however, recent collections of B. nasutus snails and shells indicated that many of these ponds are in fact connected during and following sufficient rains. Satellite imagery and a geographical information system (GIS) were used to survey the main water courses and potential drainage routes, to locate potential source populations of snails and to determine probable snail dispersal routes. The 2 water bodies implicated as being the most important Schistosoma haematobium transmission foci in the area were found to differ in their degree of connectivity to other B. nasutus source habitats. One pond becomes connected even after normal rains, while the other pond requires prolonged rains or flooding to become connected with source habitats. Consequently, the transmission foci differ in their susceptibility to snail population control measures. Spatially explicit dispersal models that consider the spatial and temporal patterns of connectivity between aquatic habitats will contribute to improved snail surveillance and more focused control for urinary schistosomiasis at a local level.

Animals↗

PubMed2000

Spatial variation in susceptibility to infection in a snail-trematode interaction.

Parasites should be better at infecting hosts from sympatric populations than allopatric populations most of the time (parasite local adaptation). In a previous study of a population of snail parasites (Microphallus sp.) from Lake Alexandrina, New Zealand, we found that Microphallus was more infective to snails (Potamopyrgus antipodarum) in shallow water but not in deep water. Here, we repeated the original study and also monitored the development of the parasite. We found that parasites from shallow water were more infective to hosts from shallow water and developed more rapidly in these hosts. In contrast, parasites from deep water were not more infective to hosts from deep water and did not develop more rapidly in them. These results suggest clinal variation in the susceptibility of these snails, with shallow-water snails more susceptible than deep-water snails. We offer 2 possible explanations for these results. First, gene flow in the Microphallus population is primarily from shallow to deep water, leading to an asymmetric pattern of local adaptation. Alternatively, snails from shallow water may be more susceptible for reasons independent of gene flow, perhaps due to differences in host condition between habitats.

Adaptation, Physiological↗

PubMedDate not supplied

The effects of antibodies against proteins of the s100 group on neuron plasticity in sensitized and non-sensitized snails.

The effects of antibodies to a total fraction of s100 proteins and protein s100b on the activity of defensive behavior command neurons LP11 and RP11 were studied in common snails, using non-sensitized animals and animals which had acquired nociceptive sensitization. In non-sensitized snails, application of antibodies against s100 or s100b (0.1 mg/ml) induced membrane depolarization, increased membrane permeability, and suppressed slow excitatory postsynaptic potentials in the responses of neurons to sensory stimulation. Acquisition of sensitization in snails in the presence of antibodies to s100 or s100b (0.1 mg/ml) led to significantly less marked facilitation of synaptic transmission and smaller increases in neuron membrane excitability than in cells of control sensitized animals. The difference in synaptic facilitation in the neurons of control sensitized snails and neurons in sensitized snails given antibody was comparable with the magnitude of synaptic depression due to antibody in non-sensitized animals. At a dose of 0.01 mg/ml, antibody had no effect on these measures of neuron activity. It is suggested that s100 proteins, particularly s100b, are involved in the mechanisms regulating excitability, the membrane potential, and synaptic transmission in command neurons in untrained snails, as well as in the mechanism of plasticity of the electrogenic membranes of nerve cells during the acquisition of nociceptive sensitization.

Action Potentials↗

PubMed2004

Snail and SIP1 increase cancer invasion by upregulating MMP family in hepatocellular carcinoma cells.

Loss of E-cadherin (E-cad) triggers invasion, metastasis, and dedifferentiation in various epithelial carcinomas. Recently, it has been reported that two transcription factors, Snail and SIP1 (Smad interacting protein 1), directly repress transcription of the E-cad gene by binding E-box on E-cad promoter. Our aim is to solve the molecular mechanism of Snail and SIP1 in hepatocellular carcinoma (HCC). We first showed an inverse correlation between E-cad and Snail/SIP 1 expression among five HCC lines with different phenotypes. The result indicated that undifferentiated, but not differentiated type expressed Snail/SIP1. Then, we established transfectants stably expressing Snail and SIP1 in two differentiated cells with E-cad expression. Suppressed expression of E-cad, morphologic change into fibroblastoid feature, and remarkable acceleration of invasion activity were observed in the transfectants. In reverse transcription-polymerase chain reaction series of genes relating to motility and invasion, we demonstrated striking evidence that matrix metalloproteinase (MMP-1), MMP-2, MMP-7, and MT1-MMP expressions were strongly upregulated by Snail. On the other hand, MMP-1, MMP-2, and MT1-MMP expressions were enhanced by SIP1 transfection, however, the intensity was weaker than that in Snail transfection. In conclusion, Snail or SIP1 expression may be induced during HCC progression, where Snail/SIP1 directly represses E-cad gene transcription and activates cancer invasion via the upregulation of the MMP gene family.

Cadherins↗

PubMed2002

Correlation of Snail expression with histological grade and lymph node status in breast carcinomas.

Snail is a zinc finger transcription factor that triggers the epithelial-mesenchymal transition (EMT) by directly repressing E-cadherin expression. Snail is required for mesoderm and neural crest formation during embryonic development and has recently been implicated in the EMT associated with tumour progression. In a series of human breast carcinomas, we have analysed the expression of Snail and that of molecules of the E-cadherin/catenin complexes. We have also correlated these data with the pathological features of the tumours. We show that Snail expression inversely correlates with the grade of differentiation of the tumours and that it is expressed in all the infiltrating ductal carcinomas (IDC) presenting lymph node metastases that were analysed. In addition, Snail is expressed in some dedifferentiated tumours with a negative nodal status. Considering that Snail is involved in the induction of the invasive and migratory phenotype in epithelial cells, these results indicate that it is also involved in the progression of breast ductal tumours, where it could additionally serve as a marker of the metastatic potential.

Breast Neoplasms↗