SEARCH · PubMed Health

Results for “Snails”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources

PubMed2003

Phosphorylation regulates the subcellular location and activity of the snail transcriptional repressor.

The Snail gene product is a transcriptional repressor of E-cadherin expression and an inducer of the epithelial-to-mesenchymal transition in several epithelial tumor cell lines. This report presents data indicating that Snail function is controlled by its intracellular location. The cytosolic distribution of Snail depended on export from the nucleus by a CRM1-dependent mechanism, and a nuclear export sequence (NES) was located in the regulatory domain of this protein. Export of Snail was controlled by phosphorylation of a Ser-rich sequence adjacent to this NES. Modification of this sequence released the restriction created by the zinc finger domain and allowed nuclear export of the protein. The phosphorylation and subcellular distribution of Snail are controlled by cell attachment to the extracellular matrix. Suspended cells presented higher levels of phosphorylated Snail and an augmented extranuclear localization with respect to cells attached to the plate. These findings show the existence in tumor cells of an effective and fine-tuning nontranscriptional mechanism of regulation of Snail activity dependent on the extracellular environment.

Active Transport, Cell Nucleus↗

PubMedDate not supplied

The snail hosts of schistosomiasis: some evolutionary and ecological perspectives in relation to control.

Despite opportunities for radiation provided by spatio-temporal isolation, the basic morphological plan of pulmonate snails has remained conservative. In consequence of the resulting dearth of morphological characters and their plasticity, there is a case for using biochemical characters such as exogenous chemicals released by the snails (e.g. amino acids) and their chemoreception niche as taxonomic aids to classify snails of medical importance. As these same chemicals are used by snails to distinguish conspecifics they could also be used as "environmental antibodies" in controlled release formulations (CRF's) designed to remove target snails in a specific, cost-effective and ecologically acceptable manner. The snails, surface-living bacteria, algae and macrophytic plants are considered as co-evolved, interactive modular systems with strong mutualistic elements. Recently, anthropogenic perturbations such as deforestation, and damming of flowing waters, have benefited these modules whereas others such as river canalization, acid deposition, accumulation of pesticide residues and eutrophication have harmed them. Research is needed to elucidate the factors which limit the growth of snails in primitive habitats, uninfluenced by man, as well as in those subject to harmful anthropogenic factors. The understanding thus gained could be applied to develop cost-effective primary health care strategies to reduce or prevent transmission of schistosomiasis and other water related diseases.

Animals↗

PubMedDate not supplied

A protocol for geographically randomized snail surveys in schistosomiasis fieldwork using the global positioning system.

A protocol was created for performing geographically randomized snail surveys for schistosomiasis research using the global positioning system (GPS). This protocol differs from traditional surveys in its ability to accurately map and measure the spatial distribution of snail habitat. The protocol was used to map irrigation ditches, the primary habitat for Oncomelania hupensis, in two residence areas in Sichuan Province, China. From the 7,450 meters of mapped ditches, snail surveys were performed at 203 random sites along the ditch network. Of these, 116 (57.1%) sites had snails. The total number of living snails captured was 2,014, resulting in an average snail density of 0.27 snails per linear meter of potential habitat.

Animals↗

PubMed1999

[Analysis for spatial distribution of Oncomelania snail in mainland China by geographic information system(GIS) database].

OBJECTIVE: To analyze spatial distribution of Oncomelania snail populations in mainland China by geographic information system (GIS) database. METHODS: Genetic variation experiment data and experimental data of susceptibility of 34 snail populations were collected from nine provinces in China, to set up a database. A world digital map was linked with the database in a software ArcView Release 3.0 a to be used to divide zones with ArcView spatial analyze function and GIS overlaying function. AVHRR NDVI satellite images were collected to form a new one for prevalent season, which were overlaid with distribution maps of heterozygous indices of snail populations, polymorphic locus percentage and infection rates of snail population with schistosome for classifying the images. RESULTS: Spatial analysis showed that distribution maps of genetic heterozygous indices of snail, percentage of polymophic loci and infection rate of snail can be divided into two large zones, i.e., east zone and west zone, both with varied pictures. Analysis for overlaying three-stratum distribution map with AVHRR NDVI satellite image showed four distinctly different spatial zones, including west Sichuan zone, west Yunnan zone, middle zone of river, lake and marshland, and southeast coastal zone. CONCLUSION: It is the first time using GIS to analyze data of Oncomelania population genetics and confirmed the population structure of Oncomelania snails presented discrete sub-population model, which supports the theory of sub-species of Oncomelania spp. Exited in mainland China.

Animals↗

PubMed2003

Increased invasion and matrix metalloproteinase-2 expression by Snail-induced mesenchymal transition in squamous cell carcinomas.

Loss of E-cadherin expression is a major characteristic of highly invasive and metastatic cancers. Epithelial-mesenchymal transition (EMT) has been advocated to be a causative mechanism for the suppression of E-cadherin and tumor progression. Snail is a zinc finger transcription factor that triggers the EMT and is one of the recently identified E-cadherin repressors. The reverse correlation of Snail and E-cadherin expressions has been reported in many types of human cancers including squamous cell carcinoma (SCC). In this study, we showed that three E-cadherin negative SCC cell lines had a fibroblastic morphology, strong expressions of vimentin, a mesenchymal marker gene, and Snail. Compared to other E-cadherin positive SCC cells, these cells showed higher invasive ability and expression of MMP-2, a matrix degrading enzyme which has been demonstrated to be highly expressed in invasive cancer cells. Over-expression of Snail in A431 cells resulted in the loss of E-cadherin expression, the change of their morphology to fibroblastic, and the up-regulation of vimentin gene expression, indicating that an EMT was induced by Snail. Furthermore, these cells became more invasive and showed higher levels of MMP-2 activity and its gene expression. Luciferase analysis demonstrated that the MMP-2 promoter activity was induced by Snail transfection and the promoter region from -262 to -411 relative to the transcriptional start site was necessary for this induction. These results indicate that Snail is a new inducer of MMP-2 expression and suggest that the EMT contributes to the increased invasion not only through the inhibition of cell-cell adhesion but also the up-regulation of MMP-2 expression in SCC cells.

Blotting, Western↗

PubMedDate not supplied

[Selective involvement of opioids in mechanisms of synapse-specific plasticity in Helix lucorum snail during sensitization acquisition].

Effects of met-enkephalin (opioid peptide) and naloxone (opioid antagonist) on nociceptive sensitization were studied in L-RP11 Helix neurons. In control snails sensitizing stimulation produced reversible membrane depolarization and depression of neural responses evoked by sensory stimuli during the short-term stage of sensitization and facilitation of these responses at the long-term stage. Met-enkephalin (10 but not 0.1 microM) suppressed the neural responses evoked by nociceptive stimuli. Sensitizing stimulation during metenkephalin application prevented the facilitation of neural responses evoked by tactile stimulation of snail head, whereas facilitation of neural responses evoked by chemical stimulation of head or tactile stimulation of foot were similar to that in control sensitized snails. Sensitizing stimulation during met-enkephalin and/or naloxone application prevented the facilitation of neural responses evoked by chemical stimulation of snail head, whereas responses evoked by tactile stimulation of snail head or foot were facilitated (as in neurons of control sensitized snails). Opioids are suggested to be involved in regulation of nociceptive mechanisms and selective induction of long-term plasticity in L-RP11 neural inputs activated by tactile of chemical stimulation of snail head.

Action Potentials↗

PubMed2004

[Transcription factors C/EBP inhibition specifically affects synaptic plasticity in the snail's neuron].

In our previous investigations it was found that nociceptive sensitization is followed by a long-term facilitation of synaptic transmission in command neuron of defence behavior. The facilitation is translation- and transcription-dependent. Features of plasticity neurochemical mechanisms of different sensory inputs in the neural cells were determined. NMDA glutamate receptors, serotonin receptors, cAMP as well as serotonin-modulated protein SMP-69 are involved in mechanisms of induction of neural response facilitation in LPl 1 neuron evoked by chemical sensory stimulation of snail head. Protein kinase C is involved in synaptic facilitation-induction mechanisms from other sensory neural input--tactile receptors of snail "head". In this work, participation of C/EBP (CCAAT-enhancing-binding protein) immediate early gene transcription factor was established in mechanisms of synapse-specific plasticity during sensitization in LPl 1 neuron in snail Helix lucorum. Specific binding with C/EBP oligonucleotides were used as C/EBP inhibitors. It was found that sensitization during intracellular oligonucleotide injection selectively suppressed synaptic facilitation in LPl 1 neuron responses evoked by chemical sensory stimulation of snail "head". At the same time, development of synaptic facilitation of the neuron responses evoked by tactile stimulation of snail head or foot was the same as in control sensitized snails. It seems that C/EBP transcription factor is selectively involved in mechanisms of synapse-specific plasticity of sensory input in LPl 1 neuron from snail head chemoreceptors.

Animals↗

PubMed2004

[Prediction of the spatial distribution of Oncomelania snails in marshland of Jiangning County using the Ordinary Kriging].

OBJECTIVE: To explore the methods to predict the distribution of Oncomelania hupensis in the marshland of Jiangning County. METHODS: Semi-variogram was used to analyze the spatial autocorrelation of snails' distribution in the marshland of Jiangning using the Arcview8.1. A prediction map for the snails' distribution was established using the Ordinary Kriging and evaluated using the cross-validation. RESULTS: Analysis showed that the distribution of alive snails in the marshland of Jiangning in the year 2000 was auto-correlated in spatial. The semi-variogram model which was spherical demonstrated that the variation of alive snails in spatial were related with distance apart when the distance was less than 0.0301. The prediction map of the snail distribution in the marshland of Jiangning was established based on the semi-variogram using the Ordinary Kriging. The cross-validation showed that the prediction map could estimate the distribution of snails in the marshland of Jiangning correctly. And the determinant coefficient for the prediction model was 0.973. CONCLUSION: It is feasible to predict the snail distribution in the marshland of Jiangning County by using Ordinary Kringing and data from the surveillance spot.

Animals↗

PubMed2005

[Purification of the effective component from Solanum xanthocarpum and its effect against Oncomelania snails].

OBJECTIVE: To extract and purify the active component from Solanum for Oncomelania snail control, evaluate its effect against the snails and determine its chemical structure. METHODS: Pedicel and seed were moved and the remaining part of the Solanum xanthocarpum fruit was torrefied and ground into powder. The powder was soaked into 95% ethanol and extracted. The residue was treated by ethyl acetate. 7 components were separated by methods of thin layer chromatography (TLC) and column chromatography (CCL). 4 main components were observed for the effect of snail-killing by immersion method. An alkaloid with Rf = 0. 58, named as component A, was confirmed as one of the effective components for Oncomelania snail control. The component A was further purified and received Al and A2 by proper elusion, and their effect was re-tested. The molecular weight and chemical structure of A2 were determined by MS, NMR and IR respectively. RESULTS: The death rate of Oncomelania snails was 94.2% when the concentration of component A was 2.50 mg/L1(28 C ). The flow liquid system (ethyl acetate: chloroform: methanol 11:11:35) applied was the best reagent for separating component A. The death rate of Oncomelania snails in solution of A2 (0.2 mg/L) was 100% (28 degrees C). The molecular weight of A2 was 867 with an mp 298-305 C. CONCLUSION: The effective agent (A2),one of the active components from the fruit of Solanum xanthocar pum, is alpha-solamargine which shows an excellent effect in killing Oncomelania snails.

Animals↗

PubMed2006

[Inverse correlation between Snail and E-cadherin expression in carcinoma cell lines and invasive ability in vitro].

OBJECTIVE: Malignant transformation of epithelial cell frequently coincides with loss of E-cadherin. Here we study the expression of Snail and E-cadherin and correlate their expression with cell differentiation and in vitro invasion. METHODS: The expression and localization of Snail and E-cadherin were studied by Northern blot and laser confocal microscopy in two normal cell lines (MDCK, NIH 3T3) and six carcinoma cell lines (A431, MCF-7, MDA-MB-453, HepG2, MDA-MB-435s, MDA-MB-231). Boyden chamber assay was done to detect the invasive ability of cells in vitro. RESULTS: Snail mRNA and protein were detected in fibroblasts NIH 3T3 and poorly differentiated carcinoma cell lines HepG2, MDA-MB-435s and MDA-MB-231. On the contrary, E-cadherin mRNA and protein were detected in normal epithelial cell line MDCK and well differentiated carcinoma cell lines A431 and MDA-MB-453. In MCF-7 cells, Snail and E-cadherin expressions were revealed both at mRNA and protein levels. The cells with higher expression of Snail had stronger ability of invasion than those with lower expression of Snail. CONCLUSION: There is an inverse correlation between Snail and E-cadherin expressions and their expressions are correlated with cell differentiation and tumor invasiveness.

3T3 Cells↗

PubMed2004

Epidemiology of Schistosoma mansoni infection and its relationship to snail distribution in a village at the Nile bank south to Cairo.

The relationship between epidemiology of S. mansoni infection and snail distribution at a village, related to Guiza Governorate and lies south to Cairo, was investigated. A systematic random sample of houses was selected. All inhabitants of the houses were invited to share in the study. The Number examined was 704. Urine and stools were examined using Nucleopore filtration and standard Kato-Katz techniques, respectively. Snail collection was done from 35 sites along the water bodies related to the village. Snails collected were examined by cercariae shedding under light. Snail differentiation was done. The results showed that the prevalence of Schistosoma mansoni human infection was 25.1 % and GMEC was 2.4 +/- 5.5. Schistosoma haematobium infection was zero percent. Biomphlaria alexandrina snail infection rate was 3.7% with density equal 0.5 +/- 1.3. Bulinus truncatus snail infection rate was zero percent. The pattern of S. mansoni human infection was closely related to snail distribution and infection. Presence of a hybrid species of B. alexandrina and B. glabrata may explain the epidemiological pattern found in the studied village.

Adolescent↗

PubMed2006

[Synergic effects of synthesis arecoline in combination with snail-killing drugs niclosamide].

OBJECTIVE: To prove that synthetic Are combination with snail-killing drug Nic can increase the effects of snail-killing remarkably. METHODS: In indoor immersing experimentation, the experiments were divided into 4 groups, 30 snails in each group, to observe the rate of opening operculum, the rate of climbing adhesion and the rate of death at 3, 6 and 24 hours respectively. In field experimentation, we intermixed 0.1 mg/L Are with 0.2 mg/L Nic as sample as contrasted with 2 mg/L Nic and non-drug group. Immersing method (we chose three slots each size were 10 m x 2 m x 1 m.) and insufflation method (we chose three patch of bottomlands each area were 10 m x 5 m.) were used to kill snails separately and the death rate of fish, at the same time was observed. RESULTS: In the room, as we added 0.1 mg/L Are to the solution of 0.1 mg/L and 0.2 mg/L Nic separately, the opening operculum rate for 6 hours was increased from 20% and 12% to 100% and 95%, the climbing adhesion rate for 6 hours decreased from 17% and 53% to 3% and 5%, the death rate for 24 hours increased from 25% and 40% to 90% and 100%. In the field, the snails death rate in sample group and in contrastive group applied with immersing method and insufflation method for 72 hours were 95.9%, 93.3% and 100%, 95.8%; only one small fish (2 cm long) died in sample group, and all fishes died in Nic group, and all fish were alive in non-drug group. CONCLUSION: It proved that synthetic Are combination with snail-killing drug Nic might decrease Nic dosage and toxicity and increase the effects of snail-killing.

Animals↗

PubMed1991

The component community structure of larval trematodes in the pulmonate snail Helisoma anceps.

Factors that affected the component community structure of larval trematodes in the pulmonate snail Helisoma anceps in Charlie's Pond, North Carolina, were studied over a 15-mo period using a multiple mark-recapture protocol. Patent infections of 8 species were observed in 1,485 of 4,899 snails examined. Reproductive activity, population size, and survival rate of the snail population were estimated to evaluate the extent of resource availability for the parasites. Antagonistic interactions between trematode species that occurred at the infracommunity level had a neglible effect on the composition and structure of the component community. The patterns observed at this level were related to temporal heterogeneity in the abundance of infective stages (mostly miracidia), differential responses of trematode species to the diverse and constantly changing distribution of snail size and abundance, differential mortality of snails infected with certain trematode species, constant recruitment of 1 trematode species over time, and the existence of predictable disturbances such as the complete mortality of the host population and recruitment of a replacement population during a 6-8 wk period. The last factor operated as a reset mechanism for this snail-trematode system once each year. A model of patch dynamics, with snails as patch resources, best explains the organization and dynamics of this system.

Animals↗

PubMed1990

[Life span and cercaria shedding of schistosome-infected snails in mountain region of Yunnan].

The life span and cercaria shedding of infected Oncomelania snails in a mountain region of Shitoudi village, Weishan County, Yunnan Province were observed in simulated local ecological environments. 135 infected snails were isolated for observation 3 months after exposure to miracidia in August, 1987. The snail survival rate from the day of initial cercaria shedding to next June, July, August and September was 27.4, 16.3, 13.3 and 11.9% respectively, and the average number of cercariae shed was 139.9, 29.6, 39.2 and 75 per month respectively. The average life span of infected snails was 171.6 days. The average number of cercariae shed per snail in its whole life was 673.0. It was estimated that the average patent period of infected snails was over half a year. As this is the first report in our country in respect to the life span and cercariae shedding of infected snails in a mountain region, the result might be useful for quantitative analysis of epidemiological factors of schistosomiasis in this kind of endemic areas as well as for formulation of control strategy.

Animals↗

PubMed1985

Biology of Robertsiella kaporensis snails and Malaysian Schistosoma.

Studies on the bionomics and host-parasite relationship of Robertsiella kaporensis and Malaysian Schistosoma were investigated. The study was divided into 4 parts: cultivation of snails, R. kaporensis, and maintenance of Malaysian Schistosoma life cycle, daily cercarial shedding cycle in R. kaporensis, miracidial load and cercarial shedding pattern and the infectivity of Malaysian Schistosoma cercariae. R. kaporensis were cultured in the laboratory with the use of plastic container provided with fine sand. The snails were fed with diatoms and Saraca leaves. The development period for the snail eggs was about 20-30 days, the young grew to maturity in 14-15 weeks, and the average growth rate of snails was 0.23 mm per week. The daily cercarial shedding cycle of snails had shown that the peak emergence of cercariae of Malaysian Schistosoma occurred at night, between 6-10 pm. The miracidial load which yielded the best results in terms of percentage infection rates of snails and cercarial output was the miracidial concentration of 8 miracidia per snail. The study on infectivity of Malaysian Schistosoma cercariae has shown that there was a decrease in infectivity of the cercariae to mammalian hosts as the cercariae increased in age. The percentage infection rate of mice and numbers of worms recovered were highest in mice infected with cercariae of 0-1/2 hr. old. Infection of cercariae fell rapidly after the cercariae were 16 hr. old.

Animals↗

PubMed1985

Medically important snails of Kinmen (Quemoy) Islands.

A survey and collection of the snails of medical importance were conducted in June, 1980 on Kinmen Islands. More than 2,700 snails were collected from 23 different localities. They were preserved, carefully classified, and compared in habitat distribution with snails of Taiwan. A total of fourteen species of snails was found. This study has led to the establishment of snail fauna of Kinmen. The relationships of these snails with some snail-borne diseases are discussed.

Animals↗

PubMed1967

Mathematical simulation of an aquatic snail population.

Techniques for controlling the intermediate snail hosts of schistosomiasis have had to be evaluated by field trials, since the complexity of snail population dynamics has so far made it impossible to predict the effects of these techniques and thereby avoid costly field testing.However, in laboratory studies with Biomphalaria glabrata it was found that the fecundity of these snails was directly proportional to F/NV, where F is the total amount of food in the habitat, N the number of snails, and V the volume of the habitat. The use of this fecundity variable together with data published on snail longevity and fecundity made it possible to construct a mathematical model of a snail population which may eventually be useful for evaluating snail control methods.For preliminary verification of the model, its predictions were compared with a published history of a population of Bulinus globosus in a small pond. The general agreement of the predicted and observed population data indicated that the basic structure of the model was sound.

Animals↗

PubMed1970

Attempts to eradicate snails from impounded water by the use of N-tritylmorpholine.

This paper records attempts to overcome the problems of using a powerful but non-ovicidal molluscicide (N-tritylmorpholine) in eradicating snails from a dam by treating the water twice in 14 days. The first treatment was aimed at the existing snail population and the second at snails hatched from eggs that survived the first application. At each treatment an over-all concentration of 0.25 ppm was applied by spraying a 16% emulsifiable concentrate of N-tritylmorpholine from shore and boat to the water surface. The snails, Biomphalaria pfeifferi and Lymnaea natalensis, were first seen again 8 weeks from the start of the application in the region of 2 inlet furrows. When pretreatment levels of snails were again reached, a second double treatment was applied, again at an over-all concentration of 0.25 ppm but using a 50% paste formulation applied over 3 days for 3 hours per day to the inlet furrows. The snail kill was again 100% as measured by the sampling technique used but again young snails appeared 9 weeks later. The author concludes that single treatments at 5-week intervals probably represent the best means of control with N-tritylmorpholine.

Animals↗