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 451 records · Page 25Linked to original sources

PubMed2006

Snail in the frame of malignant tumor recurrence.

Snail plays an important role in the epithelial-to-mesenchymal transition during development and in tumor progression. Induction of Snail expression coincides with drastic morphological changes in cultured epithelial cells. Recently, a new role for Snail in tumor recurrence has been inferred from a reversible HER-2/neu-induced breast cancer mouse model. Comparative transcriptome analysis of human primary breast cancers suggests that elevated Snail expression is correlated with decreased relapse-free survival. Further characterization of Snail as master regulator in this process might enhance our understanding of the molecular and cellular changes during and after breast tumor recurrence.

Animals↗

PubMed2003

Regulation of tight junctions during the epithelium-mesenchyme transition: direct repression of the gene expression of claudins/occludin by Snail.

Snail is a transcription repressor that plays a central role in the epithelium-mesenchyme transition (EMT), by which epithelial cells lose their polarity. Claudins and occludin are integral membrane proteins localized at tight junctions, which are responsible for establishing and maintaining epithelial cell polarity. We examined the relationship between Snail and the promoter activity of claudins and occludin. When Snail was overexpressed in cultured mouse epithelial cells, EMT was induced with concomitant repression of the expression of claudins and occludin not only at the protein but also at the mRNA level. We then isolated the promoters of genes encoding claudins and occludin, in which multiple E-boxes were identified. Transfection experiments with various promoter constructs as well as electrophoretic mobility assays revealed that Snail binds directly to the E-boxes of the promoters of claudin/occludin genes, resulting in complete repression of their promoter activity. Because the gene encoding E-cadherin was also reported to be repressed by Snail, we concluded that EMT was associated with the simultaneous repression of the genes encoding E-cadherin and claudins/occludin (i.e. the expression of adherens and tight junction adhesion molecules, respectively).

Animals↗

PubMed2001

Invading freshwater snails and biological control in Martinique Island, French West Indies.

Eight alien freshwater snail species were introduced into Martinique Island during the last 50 years. The introduced snails include four planorbids (Biomphalaria straminea, Helisoma duryi, Amerianna carinata and Gyraulus sp.), three thiarids (Melanoides tuberculata, M. amabilis and Tarebia granifera) and one ampullarid (Marisa cornuarietis). Four of these species rapidly colonized the whole Martinican hydrographic system whereas the other four remained restricted to some particular sites. The invasion processes were documented during the last 20 years and showed (i) a rapid invasion of the island by several morphs of M. tuberculata at the beginning of the 80's; (ii) the introduction of T. granifera in 1991 and M. amabilis in 1997; and (iii) the rapid spread of these last two species throughout the island. In the years following its introduction, M. tuberculata was used in biological control experiments against the snail hosts of schistosomiasis, B. glabrata and B. straminea. Experiments were conducted with success in several groups of water-cress beds which constituted the latest transmission sites for schistosomiasis at the beginning of the 80's. A malacological survey carried out in 2000 all over the island showed the absence of B. glabrata but the presence of some residual populations of B. straminea. Long-term studies carried out in Martinique have shown that the thiarids are able to maintain relatively stable populations over a long period of time, thus preventing recolonization by the snail hosts. Within this context the invasion of the hydrographic system of Martinique by thiarid snails has resulted in an efficient and sustainable control of the intermediate hosts of schistosomiasis.

Animals↗

PubMed2002

Infrapopulation sizes of co-occurring trematodes in the snail Ilyanassa obsoleta.

This study addresses the infrapopulation sizes of 2 larval trematode species Himasthla quissetensis and Zoogonus rubellus as they co-occur within their estuarine snail host Ilyanassa obsoleta. Rediae of H. quissetensis and sporocysts of Z rubellus were counted in snails singly infected with each parasite and in snails infected with both. Comparisons of the counts indicate that infrapopulations of H. quissetensis were unaffected by co-occurrence with Z rubellus. However, Z. rubellus infrapopulations were reduced when co-occurring with H. quissetensis. It is proposed that this situation does not result from an interspecific interaction between parasite species. Although this double infection is relatively frequent in certain snail populations, it is contended that these trematode species do not co-occur often enough to evolve responses to one another. However, the host environment must be encountered in each life cycle, and both trematode species must be adapted to use it. On this basis, whatever happens when these 2 species occupy the same host is based on adaptations of the parasites to the host. It is proposed that these parasites are adapted to self-limit their infrapopulations in the snail host. They can, thus, preserve and use the host for many years and thereby enhance total cercarial transmission (fitness). Infrapopulation sizes would be determined by host resource levels, which, among other factors, would be influenced by the presence of multiple parasite species. In single infections, by far the most common situation, host resource levels would be set by the nutritional status or age (size) of the host (or both). The reduced infrapopulation sizes of Z rubellus on co-occurrence suggest that this trematode is more sensitive to host resource levels than is H. quissetensis.

Animals↗

PubMed2002

Undifferentiated cells in the snail myocardium are capable of DNA synthesis and myodifferentiation.

Cellular mechanisms of heart-muscle growth in the snail Achatina fulica have been studied using cytophotometry and electron microscopic autoradiography. Cytophotometric DNA measurements showed that the snail cardiomyocytes are mononucleated cells with diploid nuclei. Ultrastructural analysis of the snail myocardium revealed that, in addition to mature myocytes, it contains small roundish undifferentiated cells (UCs) and poorly differentiated muscle cells. EM autoradiography detected silver grains over the nuclei of UCs 2 h after injection of tritiated thymidine ([(3)H]Tdr), while the nuclei of both mature and poorly differentiated myocytes remained unlabeled. In EM autographs of the myocardial tissue fixed 14 days after [(3)H]Tdr administration, labeled myonuclei were evident, which may suggest some myodifferentiation of prelabeled UCs. Many labeled UCs persist for 14 days after a single [(3)H]Tdr injection, suggesting that not all UCs undergo myodifferentiation after passing through the cell cycle, and that those that do not can enter the next cycle. UCs in the snail myocardium presumably provide not only reserve but also stem cells for myocytes. Thus, the heart muscle of the adult snail consists of mononucleated diploid myocytes with blocked proliferative activity and a renewable population of precursor myogenic cells. The results obtained suggest that the growth of this muscle involves a myoblastic mechanism of myogenesis; this mechanism differs from that of vertebrate cardiac muscle growth, which is non-myoblastic-that is, based on proliferation or polyploidization of cardiomyocytes. Evolutionary aspects of cellular mechanisms of the heart-muscle growth are discussed.

Animals↗

PubMed2001

Effects of trematode infection on metabolism and activity in a freshwater snail, Semisulcospira libertina.

Changes in the metabolism and activity of the freshwater snail Semisulcospira libertina infected with larval trematodes were studied experimentally. In snails up to 11 mm in shell width, crawling distance, feeding frequency, and the proportion of individuals located on vertical walls did not differ among snails infected with mature or immature cercariae, or uninfected snails (p > 0.05). In snails larger than 11 mm, individuals infected with mature cercariae tended to feed more frequently during the light period (p = 0.0081), but the distance they crawled and the proportion of individuals located on vertical walls did not differ, regardless of infection (p > 0.05). Infection with mature cercariae significantly increased the oxygen consumption rate (p = 0.016), which was measured only in the large size.

Animals↗

PubMed1991

Control of schistosome-transmitting snails in Kenya by the North American crayfish Procambarus clarkii.

Snail-transmitted trematode parasites such as schistosomes and liver flukes assume considerable medical and veterinary significance in tropical Africa. We have observed a strong negative association between the presence of medically important pulmonate snails and the crayfish Procambarus clarkii in freshwater habitats in Kenya. This crayfish, introduced into Kenya around 1970, readily consumes these snails in the laboratory. Field enclosure experiments indicate that crayfish exert a significant negative impact on the abundance of Biomphalaria pfeifferi, the intermediate host of the human blood fluke Schistosoma mansoni. It is likely that P. clarkii will continue to spread naturally in Kenya and that schistosome-transmitting snails will be excluded or reduced in numbers where crayfish are present. Procambarus clarkii may represent an alternative, biological means of snail control in East Africa.

Animals↗

PubMed2002

A baseline study of importance of bovines for human Schistosoma japonicum infections around Poyang Lake, China: villages studied and snail sampling strategy.

An epidemiologic survey among four administrative villages around Poyang Lake, in Jiangxi Province, China (two experimental and two controls) is being conducted to determine if bovine infections are responsible for the persistence of human schistosomiasis transmission on Yangtze River marshlands. A previously published paper presented the experimental design and baseline data for humans and bovines. This paper presents basic data for the four villages using remote sensing, and baseline data for snails that includes geographic information systems and remote sensing technology to classify the areas of bovine grazing ranges and habitats suitable for snails. A new method for sampling Oncomelania snails in China is used to determine the distribution, density, and infection rates of snails throughout the grazing ranges from season to season over a four-year period. Hypothetically, treating bovines should reduce infection rates in snails to below the critical number necessary to maintain infections in man and bovines.

Animals↗

PubMed2003

Tetrodotoxin-associated snail poisoning in Zhoushan: a 25-year retrospective analysis.

Outbreaks of paralytic snail poisoning have recently occurred in Asia, especially in China. The epidemiological characteristics of this disease from an outbreak in Zhoushan City, China, were recorded. Forty-two outbreaks of paralytic snail poisoning, involving 309 cases of illness, occurred from 1977 to 2001. Sixteen people (5.2%) died, 48 people (15.5%) required intubations, and 140 people (45.3%) required emergency hospital treatment as a result of these outbreaks. Outbreaks involved multiple marine snail species and occurred primarily during the summer (from June to August) on 11 islands with high population densities. Peak numbers of outbreaks and amounts of snail toxicity occurred from 1978 to 1979, from 1985 to 1987, and from 1992 to 1994. Toxicity varied depending on specimen, region, and season. The toxin involved was identified as tetrodotoxin. The data obtained in this study suggest that snails should not be eaten unless they are certified to be nontoxic.

Animals↗

PubMed1999

Schistosoma japonicum in the black rat, Rattus rattus mindanensis, from Leyte, Philippines in relation to Oncomelania snail colonies with reference to other endoparasites.

This study examined the prevalence of Schistosoma japonicum infections in field rats, Rattus rattus mindanensis, according to different trapping locations. Between October 1995 and January 1996, traps were set in the municipality of Palo, Leyte, Philippines to determine the correlation of rats infected with schistosomiasis to the proximity of the intermediate snail host, Oncomelania hupensis quadrasi, colonies. Of the 22 rats that were caught within a snail colony, 21 (95.5%) were positive for schistosomiasis. Of the 23 rats that were caught 100 meters from a snail colony, 13 (56.5%) were positive for schistosomiasis. Of the 17 rats that were caught approximately 1 km from a snail colony, zero (0%) were positive for schistosomiasis. Infection rates were highest within the habitat of the intermediate host and lowest in rats captured far from snail colonies. Captured rats were also examined for the presence of other endoparasites. Infections of the following were found: Angiostrongylus cantonensis, Gonylonema neoplasticum, Hymenolepis diminuta, Nippostrongylus muris, Strongyloides ratti, Syphacia obvelata, Taenia crassicollis and Trichuris muris, but there was no correlation between trapping location and prevalence. None of the rats were infected with Moniliformis moniliformis, Trichinella spiralis, Trypanosoma lewisi or Vampirolepis nana.

Animals↗

PubMed2002

[Electrophysiological study of 5,6-dihydroxytryptamine effect on defensive reflex conditioning in the snail].

The role of serotonin in expression of membrane properties of identified neurons was studied during defensive reflex conditioning using the neurotoxic analogue of serotonin 5,6-dihydroxytryptamine (5,6-DHT). The defensive reflex conditioning in snails was destroyed on the second day after second injection of 5,6-DHT. Through the 1st weeks after second injection of 5,6-DHT the snails were learned but worse than snails after injection of saline solution. This result shows the recovery of snail's learning ability within 2 weeks after the second injection of 5,6-DHT. It was found that injection of 5,6-DHT prevented the decrease of membrane and threshold potentials of command neurons during defensive reflex conditioning as compared with the snails injected with 5,6-DHT without learning.

5,6-Dihydroxytryptamine↗

PubMedDate not supplied

Effects of a freezing event during hibernation on further survival, reproduction and growth in the partially freezing tolerant land snail Helix aspersa muller (Gastropoda: helicidae).

Tolerance of ectothermic animals to freezing is often estimated by assessing survival a few days after the treatment. However, in the long term, ice formation in the body tissues can affect survival, as well as reproductive capability and growth. The land snail Helix aspersa survives only short durations with ice in its tissues, to a lethal limit of 40 to 60 % of its body water frozen. Adult and immature snails were treated during their winter dormancy period to a freezing event above this limit; their survival was observed both in the short and long term, as well as their ability to reproduce (adults) and grow (immature snails). Treated snails were compared with a control group, which was not frozen. No difference appeared in the survival, reproduction and growth of control and frozen snails. This study confirms partial freezing tolerance in this population of Helix aspersa.

Animals↗

PubMed2001

The effect of ecological parameters on the distribution of snail vectors of schistosomiasis.

The infestation of the water courses showed 32.5% for Biomphalaria alexandrina and 8.75% for Bulinus truncatus. Ecological parameters, showed non significant variations in the water courses harbouring snail vectors and those free from snails except for conductivity in the habitats harbouring B. truncatus. This variation was more highly significant (p<0.001). Of the examined sites, 11.25% were harbouring B. alexandrina and Lymnaea natalenesis living together and 5% of the sites were harbouring B. truncatus and Physa acuta snails. Snail vectors were distributed with different degrees with aquatic plants reflecting the degree of species preference plants for snails' life.

Animals↗

PubMedDate not supplied

[An experimental unit for the recording of the escape reaction of a ground snail to tactile stimulation].

An original working experimental unit for noninvasive objective recording of the magnitude of escape reaction of a ground snail evoked by tactile stimulation is described. A. snail creeps upwards over the cylinder rotating around its horizontal axis. A watching device ensures a constant snail position relative to a light source and a photoelement. A device for tactile stimulation which provides graduated energy of an impact is constructed on the basis of the magnetic circuit of a loudspeaker. In response to a tactile stimulus a snail pulls in its feelers, head, and foot, and the area of snail's shadow decreases. These changes are indicated by the photoelement.

Animals↗

PubMed2003

[Selective effect of the antibody to protein SMP-69 on activity of the defence behavior command neurons in grape snail].

Effects of antibody against serotonin-modulated protein SMP-69 on defence behavior command neurons L-RP11 were studied in semi-intact preparation of snail Helix lucorum. An increase in membrane excitability as well as selective facilitation of neural responses evoked with chemical sensory stimulation of the snail head (0.25-0.5% quinine solution) were determined 1-1.5 hours after antibody application to the neurons. The antibody did not change neural responses evoked with tactile stimulation of the snail head. These effects were similar to those found in L-RP11 neurons after serotonin or cAMP applications as well as after nociceptive sensitization of the snail. It was suggested that protein homologically related the SMP-69 in mammalians was involved in mechanisms of excitability as well as long-term specific plasticity regulation of L-RP11 neurons synaptic inputs from the head chemoreceptors in snail Helix lucorum.

Action Potentials↗

PubMed2003

Cercarial infection in Paludomus petrosus, freshwater snail in Pa La-U Waterfall.

Paludomus petrosus, the freshwater snails found in Pa La-U Waterfall, were examined for cercarial infection of trematodes. The snails were collected every other month from April, 2001 to February, 2002. Collections were taken from two sampling stations. The counts per unit of time' method was used for collection of the snails. The density of snails was highest in June 2001, and the highest of parasite infection rate was in February 2002. Four types of cercariae were found in the snails: Xiphidiocercariae, Amphistome, Furcocercous cercariae type I, and Furcocercous cercariae type II. Xiphidiocercariae were found in April 2001 to February 2002. Amphistome, Furcocercous cercariae type I and Furcocercous cercariae type II were found in February 2002.

Animals↗

PubMed2003

[The influence of some trace elements on bioaccumulation in tissues and bioenergetic metabolism of the edible snail Helix aspersa maxima as determined by HPLC of purine derivatives].

UNLABELLED: The aim of this work was to determine the bioaccumulation of fluoride and some metals (Cu, Zn, Pb) in tissues of snails under strictly controlled conditions expecting with this approach to verify the hypothesis that snails are suitable for the monitoring of environmental hazards. Additionally, the toxicity of fluorides administered orally on the energy balance of the snail's foot was investigated basing on concentrations of nucleosides, nucleotides and their products measured with high-performance liquid chromatography (HPLC). Two parallel snail cultures were started. The effect of dose on tissue levels of fluoride and metals was studied in the first part of the experiment. The second part served to study the effects of fluoride on energy metabolism of foot muscle (Tab. 1). Quantitation of fluoride and metal levels was done in soft tissues (foot, hepatopancreas) and shells of snails. Qualitative and quantitative analysis of purine compounds was performed in slices of foot. Fluoride concentrations in pulverized shells were measured using an ion-selective electrode. Gas chromatography served to determine fluoride concentrations in soft tissues (hepatopancreas and foot). Concentrations of metals were determined spectrophotometrically. Fluoride and metal content was calculated basing on weight of the pulverized sample. Purines were measured in foot muscle slices with high-performance liquid chromatography (HPLC). Concentrations were adjusted for protein content of sample. Concentrations of the following nucleosides, nucleotides and their products were determined: ATP, ADP, AMP, Ado (adenosine), GTP, GDP, GMP, Guo (guanosine), Hyp (hypoxanthine), IMP, Ino (inosine), Xan (xanthine), Urd (uridine), UA (uric acid), NAD+, and NADP (Fig. 1.). Statistical analysis was done with non-parametric test of Kruskal-Wallis, Mann-Whitney U-test and Spearman Rank Correlation Coefficient. CONCLUSIONS: 1. Accumulation in the shell was significantly increased at the lowest concentration of fluoride, but levels remained below those in the foot or hepatopancreas. It can be inferred that due to low sensitivity, accumulation of fluoride in soft tissues is not a suitable indicator for biomonitoring purposes. Shells seem to be more suited for this aim. 2. Due to low sensitivity, accumulation of metals in soft tissues is not a suitable indicator for biomonitoring purposes. 3. Fluoride had a statistically significant effect on the energy metabolism in muscle, especially on the content of AMP and GMP (Fig. 3, 4). The content of adenylate derivatives was increased (Fig. 3, 4) and phosphorylation of ADP to ATP was inhibited (Fig. 2, 5). 4. An increase in TAN and AEC with 1330 mg F-/kg seems to result from inhibition by fluoride of energy-consuming processes (Fig. 5). 5. In cases of high levels of fluoride it seems reasonable to measure the content of AMP, GMP, Guo or the value of AEC which appear to serve as universal indicators of depressed metabolic function (Fig. 3, 4, 5, 6).

Adenosine Diphosphate↗

PubMed2006

Molluscicidal effect of three monoterpenes oils on schistosomiasis and fascioliasis vector snails in Egypt.

Thymol, Linalool and Eugenol showed considerable molluscicidal effect against Biomphalaria alexandrina, Bulinus truncatus and Lymnneae natalensis. The thymol was the potent one at least LC50 and LC90) followed by euganol then linalool. L. natalensis were more sensitive to these compounds followed by B. truncatus and then B. alexandrina. The LC50 & LC90) of thymol were 22 and 34 ppm against B. alexaldrina, 20 and 30 ppm for B. truncatuts and 18 and 29 ppm for L. nalalensis. These values were higher with Eugenol, 28 and 48 ppm for B. alexuadrina, 24 and 44 ppm for B. truncatus and 22 and 40 ppm for L. natalensis. Linalool showed highest values of LCs5 and LC90 against B. alexandrina, 34 and 56 ppm, against B. truncatus 30 and 52 ppm and for L. natalensis 28 and 48 ppm, respectively. Maintaining of B. alexandrina at LC10 of Thymol for one week induced an inhibitory effect in the level of some enzymes (AchE, SDH). It led to increase in the activity of other enzymes (ACP, ALP & G-6-PD). Acetylcholine-sterase activity (AchE) of treated B. alexandrina was significantly reduced by 45.9% when compared to control. The results showed a significant decrease in succinate dehydrogenase activity (SDH) by 46.4% together with a concomitant increase in glucose-6-phosphate dehydrogenase activity level (G-6-PD) by 47.5% in comparison with control. The activities of acid phosphatase and alkaline phosphatase enzymes were found to be higher in the treated snails than in control ones. The percentage increases were 47.2% & 73.2% respectively. The results also showed an elevation in the hemolymph glucose content of treated snails by 51.9% while the tissue glycogen content was reduced by 48.1%. The infection of B. alexandrina with S. mansoni miracidia was greatly reduced by thymol LC10 (sublethal dose). The infection rate reduction was 43.1%. The treated snails' prepatent period was prolonged (34.2 +/- 3.3 days) compared to control (28.4 +/- 1.2 days). A highly significant reduction of total cercarial production per snail occurred in experimental snails as compared to control.

Acyclic Monoterpenes↗