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PubMed2004

[A sampling survey on the distribution of Oncomelania snails in Zhejiang Province].

OBJECTIVE: To find out current distribution of Oncomelania snails and Schistosoma infection in snails in Zhejiang Province, so as to improve the project of schistosomiasis control. METHODS: Investigation spots were selected by stratified cluster sampling method, 100 villages of 34 counties were selected from 7106 villages of 55 counties as survey spots. Synchronously systematic and environmental samplings were used for the survey. Snails were dissected to determine the infection status and spots with sham snails were set to assess the quality of the survey. RESULTS: The result showed that snails were found in 223 strips, 1572 frames and 73,300 m2 area in 32 villages of 21 counties. Snails were found in an area covering 72,640 m2 in 29 villages of 18 counties in hilly region, which accounted for 99.1% of total snail habitats. The significantly larger area with snails was revealed in hilly region than that in water network region (t = 3.04, P < 0.01). 1st, 2nd strata occupied 71,680 m2 snail area, which accounted for 97.8% of total snail area, much higher than that in the 3rd stratum (t = 3.71 , P < 0.01). Snail habitats in the irrigation ditches and canals accounted for 62.6% of total snail area, significantly higher than that of farmland (t = 3.02, P < 0.01). No snails were found infected among 7892 living snails by dissection. The theory value of snail area in Zhejiang Province was 1,361,940 m2. CONCLUSION: It is estimated that the snail-ridden area is about 1,500,000-2,000,000 m2 in the Province, mostly found in the villages of hilly region with a record of snail habitats during the recent 4 years and the primary environment of the snail areas were ditches and canals. No infected snails were found from the survey.

Animals↗

PubMed2006

[Expression of Snail and E-cadherin in pancreatic carcinoma and clinical significance thereof].

OBJECTIVE: To investigate the expression of Snail, a newly discovered inhibitory transcription factor, and E-cadherin in pancreatic carcinoma (PC) and clinical significance thereof. METHODS: Immunohistochemistry was used to examine the expression of Snail and E-cadherin in 56 specimens of PC obtained during operation. PC cells of the line of Panc-1 and transfected with pCMV-Tag2B-Snail, a eucaryotic expression vector coding Snail, so as to obtain a stable clone named Panc-1-Snail. RT-PCR was used to detect the mRNA expression of Snail gene in the Panc-1-Snail cells. Immunofluorescence technique and Western blotting were used to detect the expression of E-cadherin in the Pan-1-Snail cells. Transwell cell culture chamber method was used to examine the invasion ability of the Panc-1-and Panc-1-Snail cells. RESULTS: Twenty of the 56 PC specimens (36%) were positive in Snail, mainly located in the nuclei. Seventeen of the 20 Snail-positive PC specimens were with and 3 without lymph node metastasis (P = 0.006); and 7 of the 8 PC specimens with lymph node metastasis were Snail-positive and only 1 was Snail-negative (P = 0.001). Twenty-six PC specimens showed low expression of E-cadherin with remarkable heterogeneity. Of the 20 Snail-positive PC specimens 13 showed low expression of E-cadherin and only 7 showed normal expression of E-cadherin; and 13 of the 36 Snail-negative PC specimens showed low expression of E-cadherin (P = 0.038). RT-PCR showed strong Snail mRNA expression in the Pan-1 cells. Both Western blotting and immunofluorescence technique showed the depression of E-cadherin expression. The Transwell chamber test showed that the number of penetrating Pan-1-Snail cells after 24-hour incubation was (174 +/- 8)/200X field of view, significantly greater than that of the Pan-1 cells [(96 +/- 4)/200X field of view, P < 0.01]. CONCLUSION: Re-expressed in PC and accelerating the invasion of PC through depressing E-cadherin expression, Snail may present a new marker for predicting the aggressiveness of PC.

Blotting, Western↗

PubMed2003

Host-specific performance and host use in the kleptoparasitic marine snail Trichotropis cancellata.

Generalist parasites may disproportionately use certain hosts because of different benefits associated with each host species. I measured the growth rate of the marine snail Trichotropis cancellata, a facultative kleptoparasite that can suspension feed and steal food, on different hosts to determine the relative nutritional benefits of each host. The variation in tentacle (feeding structure) area among the hosts studied had the potential to provide parasitic snails with different amounts of nutrition for growth. In field experiments, suspension-feeding snails isolated from potential hosts grew at a similar rate to snails on brachiopods and significantly more slowly than snails on the following polychaete worms: Serpula columbiana (Serpulidae), Pseudopotamilla ocellata (Sabellidae), Schizobranchia insignis (Sabellidae), and Eudistylia vancouveri (Sabellidae). However, choice among worm hosts affected snail growth rates only in the fall, when phytoplankton levels are low. At this time, snails parasitizing the sabellids Schizobranchia and Eudistylia grew more quickly than snails on Serpula. In the spring and summer, with high levels of phytoplankton, Trichotropis grew at similar rates on all worm species tested. Trichotropis spent approximately the same time stealing food from each worm host species, >50% of the time the worms had their tentacles extended (the difference among hosts was not significant). This finding demonstrates that the similarity of snail growth rates on different worm species is not due to the snails compensating for poor hosts (worms that provide food at a slower rate) by spending more time stealing food. Snails in choice experiments preferred live Serpula to empty Serpula tubes, indicating that at least some of the cue(s) snails use to identify hosts are derived from living host tissues. In choice racks containing live Serpula and live Schizobranchia, snails did not choose one host worm significantly more often than the other. Because Trichotropis grows faster on sabellids than serpulids in the fall, I predicted that snails in nature would infect sabellids more often than other species. However, snails were usually distributed randomly among host species. In the few cases where the snails showed a significant preference among host species, proportionally more snails were found on serpulids than on sabellids or sabellarids. This study is the first to quantify under natural conditions the growth benefits of a kleptoparasite across the range of possible hosts, and implies that factors other than growth rate influence host choice specificity in the marine kleptoparasite T. cancellata.

Animals↗

PubMed2002

[Study of a new technique on the prevention of Oncomelania hupensis snail dispersal in the irrigation schemes in middle reaches of Yangtze River].

OBJECTIVE: To explore a new technique to prevent the dispersal of Oncomelania hupensis snail through leading flood for irrigation by floodgate in irrigation schemes. METHODS: Hydromechanical and biological were applied and to combine laboratory experiment with the field observation to form a new multidisciplinary regarding snail biological hydraulics and technical line. Findings including characteristics of hydraulics and biomechanics and move regulation etc. Physics parameter of snails were used to design and construct as well as to exam the effect of facilities and rebuilt floodgate which could prevent the snail dispersal. RESULTS: Through five years efforts, the major achievements were found as: 1) the method in testing the special gravity of snail and snail eggs was determined. 2) the special gravity of snail was (1.8 +/- 0.01) g/cm(3) and special gravity snail eggs was (2.29 +/- 0.01) g/cm(3); the classification method and classified criterion of snail size were made based on geometrical characteristics of snail shell. Six special values indicating dropping and start speed of snail in running water were obtained; Five practical formula of snail dropping and start in water were established; threshold value and movement characteristics in water were observed and tested and move mechanism of snail dispersal in water was also clarified. Based on the findings from fundamental research, the facilities of "precipitation pool for snail" and "leading water from middle level of water body" that could prevent snail dispersal were designed and rebuilt in the endemic area. Through examination to these facilities, the rate of precipitating and blocking of snails reached 100%. CONCLUSION: The achievement of the study provided reliable theoretical basis for the rebuilt of floodgate and to development of models that could prevent the dispersal of snail effectively.

Agriculture↗

PubMed1990

Predation and control of laboratory populations of the snail Biomphalaria glabrata by the freshwater prawn Macrobrachium rosenbergii.

Laboratory experiments were conducted on predation by the giant freshwater prawn, Macrobrachium rosenbergii, on Biomphalaria glabrata, a snail intermediate host of human schistosomiasis. Prawns greater than 22 mm carapace length could consume snails of any size. Smaller prawns exhibited a size-specific upper limit on the size of snail they could kill. Below the maximum size of prey consumed, little selectivity for prey size was demonstrated. All prawns heavier than 2.5 g killed the largest size of snail offered (16 mm diameter). Consumption, in terms of the numbers of snails killed, and the snails' wet weight and percentage of prawn body weight eaten per day, increased with prawn size. Large prawns consumed snails at a high rate (39% of body weight per day). Population experiments demonstrated that a prawn of 25 mm carapace length could eliminate 95% of a population of 80 snails in a 20-1 aquarium within 20 days and all snails by day 40. A prawn of 15 mm carapace length could not eliminate all snails. Large snails (24% of the initial population) had some protection from predation because of their size. Although the snails bred continuously, no snails were able to recruit to these populations in the presence of small prawns. In contrast, snail populations in control aquaria without prawns expanded to a mean of 919 snails by the end of the experiment (day 70). Since M. rosenbergii are voracious predators on B. glabrata, exhibit considerable habitat overlap with the snail prey, and are likely to treat snails as highly preferred food, further experimentation on these prawns in the context of biological control of schistosomiasis is warranted. The ready availability of prawns through established prawn hatcheries and the synergistic use of these prawns in aquaculture may ensure the reliability of stocking procedures and meet the standards of availability and cost-effectiveness required of a biological control agent. Polyculture of Macrobrachium with fin fish (Tilapia) indicates that these prawns may be a particularly useful control agent in aquacultural environments.

Animals↗

PubMed1985

Schistosoma mansoni (Gezira) infection in Biomphalaria pfeifferi snails from Gezira and Jebel Marra.

The comparative susceptibility of Biomphalaria snails from Gezira and Jebel Marra to S. mansoni (Gezira) was investigated. Groups of laboratory-bred snails from the two localities were exposed to 0, 1, 2, 3 and 4 miracidia. The growth rate of the snails was followed over the experimental period by measuring the snails' shell size. Sub-groups of infected snails were examined for daughter sporocyst counts by crushing of the snails. Other groups of exposed snails were maintained until cercariae were shed. The exposed snails grew faster than the controls and growth was not dependent on the number of infecting miracidia. Jebel Marra snails grew faster than the Gezira snails and development of the daughter sporocysts within the snails was temperature dependent. Daughter sporocysts were first found on day 19 after exposure when the laboratory temperature ranged between 18 and 25 degrees C and on day 10 at a range of between 28 and 30 degrees C. Daughter sporocysts and cercarial counts overlapped in numbers per snail exposed to 1, 2, 3 and 4 miracidia for both Gezira and Jebel Marra snails. Nine out of 78 Jebel Marra snails were negative for daughter sporocysts, while all of the Gezira snails were positive. This might indicate greater susceptibility of the Jebel Marra snails to the parasite. Our experiments showed that snails from Jebel Marra are capable of supporting an S. mansoni infection from the Gezira until cercariae are shed. The epidemiological significance of the migrant labourers to the Gezira area in the transmission and spread of intestinal schistosomiasis in Jebel Marra is discussed.

Animals↗

PubMed2004

Aquatic snails from mining sites have evolved to detect and avoid heavy metals.

Toxicants in polluted environments are often patchily distributed. Hence, rather than being passive absorbers of pollution, some organisms have evolved the ability to detect and avoid toxicants. We studied the avoidance behavior of Physella columbiana, an aquatic pulmonate snail, in a pond that has been polluted with heavy metals for more than 120 years. Populations of this snail are rare at reference sites and are only robust at heavy-metal-polluted sites. We hypothesized that the snails are able to persist because they have evolved the ability to minimize their exposure to metals by actively avoiding metals in their environment. Using a Y-maze flow tank, we tested the avoidance behavior of snails to heavy-metal-polluted sediments and single-metal solutions of cadmium, zinc, or lead. We also tested the avoidance behaviors of the snails' laboratory-reared offspring raised in nonpolluted conditions. In addition, we tested the avoidance behavior of a small population of snails from a reference pond. Although all the snails we tested were able to detect low concentrations of heavy metals, we found that snails from the polluted site were the most sensitive, that their offspring were somewhat less sensitive, and that snails from the reference site were the least sensitive. This suggests that the ability of polluted-site snails to avoid heavy metals is both genetic and environmental. The concentrations of metals avoided by the snails from the polluted site were below the levels found at hot spots within their natal pond. The snails may be able to persist at this site because they decrease their exposure by moving to less-polluted sections of the pond. One application of our findings is the use of aquatic snails and our Y-maze design as an inexpensive pollution detector. Environmental pollutants such as lead, zinc, and arsenic are a problem throughout the world. People in underdeveloped countries often lack sophisticated pollution detection devices. We have developed a behavioral assay of aquatic pollution that is easy to use, is extremely sensitive (detection below 10 ppb), and can be constructed for fewer than 100 US dollars. Pulmonate snails are widely distributed in tropical, subtropical, and temperate parts of the globe, and they are often common in polluted waters. For countries such as India and Bangladesh, which must test thousands of shallow wells for possible contamination with heavy metals, our assay would be a good initial test. Once snails detected metals, then those samples could be confirmed by spectrometers. We encourage scientists in underdeveloped nations to consider our assay as an option.

Animals↗

PubMed2002

Influence of age and body size on alarm responses in a freshwater snail Pomacea canaliculata.

A hypothesis that size selection of prey by predators elicits size-specific responses from prey was examined. Freshwater snails, Pomacea canaliculata, ages 1, 3, 7, 15, 30, or 60 days, were given an extract of 3-day-old snails, and 3-day-old snails were given extracts of snails of the otherages oreggs. Snails 15 days or younger crawled out of the water in response to the 3-day-old snail extract, but older ones did not. The 3-day-old snails responded to the extracts of snails of all examined ages, but not to the extract of eggs. Snails of four size classes, 3-days-old, small (shell lengths 8-12 mm), medium (13-20 mm), and large (>28 mm) were given extracts of snails of each of these four classes. The 3-day-old snails crawled out of the water in response to the extract of 3-day-old snails, but showed a lower or no response to other extracts. Larger snails buried themselves in the soil in response to the extract of snails of similar sizes. These responses are discussed in the context of the evolution of the snail's avoidance behavior in response to the size-dependent prey choice by the predator.

Adaptation, Physiological↗

PubMed2005

Cancer development induced by graded expression of Snail in mice.

The zinc-finger transcription factor Snail is believed to trigger epithelial-mesenchymal transitions (EMTs) during cancer progression. This idea is supported by analysis of Snail knockout mice, which uncovered crucial role of Snail in gastrulation, and of individuals with cancer, in whom Snail expression is frequently upregulated. However, these results have not shown a direct link between Snail and the pathogenesis of cancer. Here we show that mice carrying hypomorphic tetracycline-repressible Snail transgenes, that increase Snail expression to 20% above normal levels, exhibit no morphological alterations and develop both epithelial and mesenchymal tumours (leukaemias). Suppression of the Snail transgene did not rescue the malignant phenotype, indicating that alterations induced by Snail are irreversible. CombitTA-Snail murine embryonic fibroblasts show similar migratory ability to that of control mouse embryonic fibroblasts (MEFs). However, CombitTA-Snail-MEFs induce tumour formation in nude mice. CombitTA-Snail expression results in increased radioprotection in vivo, although it does not affect p53 regulation in response to DNA damage. In concert with these results, Snail expression is repressed following DNA damage. This regulation of Snail by DNA damage is p53-independent. Our results connect DNA damage with the requirement of a critical level of an EMT regulator and provide genetic evidence that Snail plays essential roles in cancer development in mammals and thereby influences cell fate in the genotoxic stress response.

Animals↗

PubMed1989

[Cercarial shedding of Echinostoma cinetorchis and experimental infection of the cercariae to several kinds of snails].

The development of Echinostoma cinetorchis in several snail species reared in laboratory aquaria was observed. The eggs from adult flukes collected from the intestine of rats were cultivated to miracidia, and exposed to Hippeutis sp. snails. Observations were made for cercarial shedding from the exposed snails. The cercariae shed from the snails were again exposed to several species of fresh water snails in order to observe metacercarial formation in the snails and their infectivity to final hosts. The results obtained in this study were as follows: 1. Twenty miracidia were exposed to each snail of Hippeutis sp. About 58.3% of the above snails (7 out of 12) were dead before shedding the cercariae, and the remainder shed the cercariae for a period of 7 to 9 days before death. 2. Cercarial shedding from the infected snails started from the 25th day after the exposure to miracidia, and the total number of cercariae shed per snail was 684 in average (range; 482-904). 3. The size of rediae developed in the infected Hippeutis sp. snails was 1,242 x 214 microns in average, and the number of rediae per snail was 350 in average (range; 120-510). 4. About 40 to 50 cercariae shed from the Hippeutis sp. snails were each exposed to several species of snails reared in the laboratory. The metacercarial formation was confirmed by dissecting the infected snails, 12 to 16 days after the infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Phagocytic activity of hemocytes of M-line Biomphalaria glabrata snails: effect of exposure to the trematode Echinostoma paraensei.

The phagocytic activity of hemocytes from 6-8-mm M-line Biomphalaria glabrata snails was studied in an in vitro assay using glutaraldehyde-fixed sheep erythrocytes (SRBC) as target cells. For individual snails, the percentage of hemocytes ingesting SRBC during a 1-hr interval, termed the phagocytic activity index (PAI), was determined. Hemocytes from snails infected for 1 day with Echinostoma paraensei had a slightly elevated PAI, but at both 8 and 30 days postexposure (DPE), hemocytes from infected snails had a significantly lower PAI than controls. Hemocytes taken from snails at 8 DPE also had a low PAI using rabbit erythrocytes and yeast as target cells. The low PAI at 8 DPE is attributed to the presence of large numbers of poorly spreading hemocytes with low phagocytic activity. Hemocytes from snails with 30-day infections were well spread but nonetheless had a low PAI. The presence of plasma from 8-day infected snails did not alter the PAI of hemocytes from control snails, nor was the PAI of hemocytes from infected snails changed by plasma from control snails. SRBC preincubated for 60 min in plasma from various groups of M-line snails did not elicit an increase in PAI when presented to hemocytes from control snails; in some cases, as with plasma from 6-8-mm control snails, such preincubation significantly reduced the PAI below levels obtained using SRBC preincubated in culture medium. As compared to hemocytes from snails with normally developing, 8-day-old intraventricular sporocysts (IS), hemocytes from snails exposed to infection but subsequently lacking IS had a significantly higher PAI.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1999

Genomic organization, expression, and chromosome location of the human SNAIL gene (SNAI1) and a related processed pseudogene (SNAI1P).

Some of the zinc finger proteins of the snail family are essential in the formation of mesoderm during gastrulation and the development of neural crest and its derivatives. We have isolated the human SNAIL gene (HGMW-approved symbol SNAI1) and describe its genomic organization, having sequenced a region spanning more than 5882 bp. The human SNAIL gene contains three exons. The SNAIL transcript is 2. 0 kb and is found in placenta and adult heart, lung, brain, liver, and skeletal muscle. It codes for a protein of 264 amino acids and 29.1 kDa. This protein contains three classic zinc fingers and one atypical zinc finger. The human SNAIL protein is 87.5, 58.7, 50.9, 50.7, 55.4, and 31.5% identical to mouse Snail, chicken snail-like, zebrafish snail1, zebrafish snail2, Xenopus snail, and Drosophila snail proteins, respectively. The zinc finger region is 95.5% identical between human and mouse Snail. Because Drosophila snail and twist are important regulators during mesoderm development and because human TWIST mutations have been implicated in craniosynostosis, a cohort of 59 patients with craniosynostosis syndromes were screened for SNAIL mutations. None were found. By somatic cell and radiation hybrid mapping panels, SNAIL was localized to human chromosome 20q13.2, between markers D20S886 and D20S109. A SNAIL-related, putative processed pseudogene (HGMW-approved symbol SNAI1P) was also isolated and maps to human chromosome 2q33-q37.

Adult↗

PubMed2005

[Inhibitory effects of antisense Snail on invasion and migration of ovarian carcinoma cells].

OBJECTIVE: To investigate the inhibitory effects of Snail--a zinc finger transcription factor, anti-sense plasmid on the invasion of ovary carcinoma cell lines in vitro. METHODS: Four human ovarian carcinoma cell lines ES-2, OVCAR3, HO8910, HO8910PM were analyzed for the expression of Snail and E-cadherin mRNA by RT-PCR. Then anti-Snail plasmid transfection was introduced into HO8910 cells using lipofectin 2000 reagent to investigate the inverse correlation between E-cadherin and Snail expression, and the inhibitory effects of anti-sense Snail were also detected by Transwell motility assay and Matrigel invasion assay. RESULTS: The results demonstrated the presence of Snail mRNA in ES-2, HO8910, HO8910PM detected by RT-PCR. By contrast, E-cadherin mRNA was only detected in OVCAR3 by RT-PCR. The inverse relationships were further observed by transient transfection of anti-sense Snail into HO8910 cells, which showed the down-regulated expression of Snail and the re-expression of E-cadherin. The Snail mRNA levels were 0.897 +/- 0.005, 0.865 +/- 0.010, 0.338 +/- 0.014 after 0, 24, 48 h of transfection and that of E-cadherin were 0, 0.130 +/- 0.001, 0.217 +/- 0.005 respectively, the difference was significant between different time points (P < 0.05). Besides the reverse correlation of E-cadherin and Snail, we also found that the mRNA level of fibronectin, a mensenchymal marker, was apparently down-regulated after stable transfection of antisense Snail compared to the control cells [0.191 +/- 0.010 vs 0.582 +/- 0.010 (P < 0.01)]. The motility activity and the invasion activity of anti-sense Snail transfectant cells were significantly decreased compared with those of control cells [48 +/- 2 vs 396 +/- 29 (P < 0.01); 35 +/- 10 vs 219 +/- 72 (P < 0.05) respectively]. CONCLUSIONS: The data indicate a reverse correlation of E-cadherin and Snail expression exists in ovary carcinoma cells. Snail is possibly a potential target for cancer gene therapy blocking invasion and metastasis in human ovary carcinoma.

Cadherins↗

PubMed2006

[Effects of land surface temperature on supervising the existing area of snails].

OBJECTIVE: To discuss the land surface temperature's effect on supervising the areas with snails, comparing the land surface temperature (LST) of the areas with snails with the LST of those without snails. METHODS: Choosing the lake areas of farmland in Jiangxi Province and the beach in the bank of Ganjiang, dividing into four areas according to snails. Picking up the normalized difference vegetation index (NDVI) and LST from the remote sensing data to find the difference between the areas with snails and the areas without snails, so as to illuminate the effects of the LST on distinguishing the areas with snails. RESULTS: The NDVI of Dongfeng Wei (an area from farmland to lake) was 0 - 0.20, the NDVI of the areas with snails was 0.20 - 0.40. The NDVI of four areas is different (chi(2) = 104.69, P < 0.01). The LST of Dongfeng wei was 24 - 30 degrees C, Wuzhoutou without snails is 23 - 28 degrees C, Wuzhoutou with snails is 22 - 26 degrees C, Changjiangzhou was 20 - 24 degrees C. The LST of four areas is different (chi(2) = 115.23, P < 0.01). The analysis farther indicates the NDVI of areas without snails was lower than that of areas with snails, but the LST was higher. CONCLUSION: The NDVI and (or) the LST should be significantly different between the areas with snails and the areas without, it might be concluded that the LST should be a indication to some extent on judging whether some areas may be fit for snails.

Animals↗

PubMed2003

Effects of diet and Echinostoma revolutum infection on energy allocation patterns in juvenile Lymnaea elodes snails.

Resource allocation strategies may be influenced by both biotic and abiotic factors. The purpose of this study was to investigate the effects of both parasitism and diet quality on the growth, reproduction, and survival of the pond snail, Lymnaea elodes. In addition, we assessed parasite growth and reproduction. High-protein (high diet) or low-protein diets (low diet) were fed to juvenile L. elodes snails that were either exposed or sham-exposed to the castrating trematode, Echinostoma revolutum. Host growth was assessed weekly; reproduction and survival were recorded every 2-3 days. We estimated parasite development as the time to parasite release from the host (patency), and parasite reproduction as the number of larvae shed from infected snails at two time points. Diet and infection status had significant effects on snail growth. Infected snails produced few eggs and tended to grow to larger sizes than uninfected snails regardless of diet. In contrast, exposed-uninfected individuals displayed diet-dependent patterns of growth and reproduction. On the high-protein diet, uninfected and exposed-uninfected snails exhibited similar patterns of growth and reproduction, whereas in the low-diet treatment, exposed-uninfected snails exhibited reduced growth and delayed reproduction relative to uninfected individuals. Survival differed among treatments in the latter stages of the study with infected snails exhibiting reduced survival relative to snails from other treatments. Moreover, infected low-diet snails exhibited lower survival than infected high-diet snails. Parasite development and reproduction did not appear to be directly influenced by the quality of host diet. Results from this study suggest that energy allocation patterns are context-dependent in juvenile snails, influenced by parasite exposure and diet quality. Furthermore, parasite reproduction appears to depend more on host size than on the quality of host diet.

Animals↗

PubMed2000

Infection rate of Ehrlichia risticii, the agent of Potomac horse fever, in freshwater stream snails (Juga yrekaensis) from northern California.

Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac horse fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (<15mm). The highest trematode infection rate for large and small snails was recorded in September and the lowest infection rate for large snails was recorded in June (Weed) and October (Montague). The E. risticii PCR infection rate among small snails from both sites was similar and varied monthly between 0 and 3.3%. The PCR infection rate for large snails from Weed was high in May (20.0%) and decreased progressively until November (10.0%). The PCR infection rate for large snails from Montague was 5.0% in May, 26.3% in August and 16. 7% in October. PCR-positive snails were always related to the microscopic detection of trematode stages (virgulate cercariae). This study provides evidence that J. yrekaensis are infected with trematode cercariae that harbor E. risticii. The number of snails harboring trematode stages and the number of PCR positive snails varied with the size of the snails, the month of collection, and the geographic origin.

Animals↗

PubMed2004

Down-regulation of SNAIL suppresses MIN mouse tumorigenesis: modulation of apoptosis, proliferation, and fractal dimension.

OBJECTIVES: Emerging evidence implicates the SNAIL family of transcriptional repressors in cancer development; however, the role of SNAIL in colorectal cancer has not been established. To investigate the importance of SNAIL in colorectal carcinogenesis, we examined the phenotypic and cellular consequences of SNAIL down-regulation in the MIN mouse. METHODS: Twenty-eight male MIN mice were randomized to treatment with an antisense phosphorodiamidate morpholino oligomer (AS-PMO) to SNAIL, saline, or a scrambled sequence control for 6 weeks. Tumors were scored and the molecular/cellular effects of anti-SNAIL treatment were evaluated through immunohistochemical analysis of the uninvolved intestinal mucosa for SNAIL and E-cadherin levels along with rates of apoptosis and proliferation. Furthermore, microarchitectural alterations were determined through measurement of fractal dimension. RESULTS: In the uninvolved mucosa, SNAIL AS-PMO treatment moderately decreased SNAIL protein when compared with saline-treated animals (immunohistochemistry scores 3.0 +/- 0.8 versus 2.1 +/- 0.6, respectively; P=0.01) with a concomitant increase in E-cadherin expression (1.8 +/- 0.6 versus 2.4 +/- 0.5; P < 0.05). Anti-SNAIL PMO, but not scramble control, resulted in a significant decrease in both total tumor number and incidence of tumors >2 mm (22% and 54%, respectively; P < 0.05). Furthermore, this was accompanied by an increased apoptosis rate (2-fold), decreased proliferation (3-fold), and normalization of the fractal dimension in the uninvolved intestinal mucosa. CONCLUSIONS: We show, for the first time, that SNAIL overexpression is important in intestinal tumorigenesis. While this PMO regimen afforded modest SNAIL suppression and hence tumor reduction, this provides compelling evidence for the role of SNAIL overexpression in colonic neoplasia.

Animals↗

PubMed2005

[Effect of transcriptional factor snail on epithelial-mesenchymal transition and tumor metastasis].

BACKGROUND & OBJECTIVE: Transcription factor Snail mediates epithelial-mesenchymal transition (EMT), and is associated with tumor metastasis. This study was designed to observe the enhancive effect of Snail and the reverse effect of antisense-Snail on EMT of tumor cells, and explore the role of Snail in tumor metastasis. METHODS: Snail cDNA was transfected into canine renal epithelial cell line MDCK; antisense-Snail was transfected into human breast cancer cell line MDA-MB231. The expression of epithelial markers E-cadherin, beta-catenin and Cytokeratin 18, mesenchymal marker Fibronectin, metastasis-related marker matrix metalloproteinase-2 (MMP-2), and RhoA were detected by Western blot. The metastatic potential of tumor cells was examined by in vitro cell wound model and Boyden chamber invasion assay. RESULTS: The invasion potential of MDCK cells was enhanced after transfection of Snail. The expression of E-cadherin, beta-catenin, and Cytokeratin 18 was significantly lower in Snail-transfected MDCK cells than in control cells (P < 0.05); the expression of Fibronectin, MMP-2, and RhoA was significantly higher in Snail-transfected cells than in control cells (P < 0.05). Inhibiting the expression of Snail with antisense-Snail in MDA-MB231 cells led to opposite results. CONCLUSION: Snail promotes EMT in normal epithelial cells, and inhibiting the expression of Snail may reverse EMT and suppress tumor metastasis.

Animals↗