To see the other types of publications on this topic, follow the link: Snail.
Dissertations / Theses on the topic 'Snail'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Snail.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Clark, S. A. (Stephanie Ann), University of Western Sydney, of Science Technology and Environment College, and of Science Food and Horticulture School. "Systematics, spatial analysis and conservation genetics of Meridolum corneovirens (Pfeiffer, 1851) and related forms (Gastropoda: Camaenidae) from the Sydney region of Australia." THESIS_CSTE_SFH_Clark_S.xml, 2005. http://handle.uws.edu.au:8081/1959.7/640.
Full textAbstract:
The purpose of the present study is to examine the genetic and morphological variation found in narrow-range endemic terrestrial invertebrate species at different geographic scales, and the ramifications of this for their systematics, management and conservation. The listed endangered land snail Meridolum corneovirens and several related forms are restricted to the Sydney region, and were used to address the above issues. Morphological, anatomical, allozyme and DNA data were obtained for a total of 77 populations from across the known range of Meridolum. A particular emphasis was placed on the forms found across the Sydney region. The analysis of the different datasets, both individually and in combination indicate at least 35 taxa mostly parapatric and seven genera were represented. This includes several previously unrecognised taxa. The analysis supports the conclusion that Meridolum corneovirens belongs to a new genus. This includes several species found from eastern Sydney south along the coast to Nowra. A total of six new species and five new genera are described. The conservation and management of narrow-range endemics such as Meridolum corneovirens provide a number of challenges to conservation managers. The alternative of listing a gene pool rather than listing species separately is proposed and explore<br>Doctor of Philosophy (PhD)
2
Brierley, Matthew Joseph. "Neural network underlying snail feeding." Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239132.
Full text
3
Ungless, M. A. "Conditioning in the snail, Helix aspersa." Thesis, University of York, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242162.
Full text
4
Clark, Stephanie A. "Systematics, spatial analysis and conservation genetics of Meridolum corneovirens (Pfeiffer, 1851) and related forms (Gastropoda: Camaenidae) from the Sydney region of Australia." Thesis, View thesis, 2005. http://handle.uws.edu.au:8081/1959.7/640.
Full textAbstract:
The purpose of the present study is to examine the genetic and morphological variation found in narrow-range endemic terrestrial invertebrate species at different geographic scales, and the ramifications of this for their systematics, management and conservation. The listed endangered land snail Meridolum corneovirens and several related forms are restricted to the Sydney region, and were used to address the above issues. Morphological, anatomical, allozyme and DNA data were obtained for a total of 77 populations from across the known range of Meridolum. A particular emphasis was placed on the forms found across the Sydney region. The analysis of the different datasets, both individually and in combination indicate at least 35 taxa mostly parapatric and seven genera were represented. This includes several previously unrecognised taxa. The analysis supports the conclusion that Meridolum corneovirens belongs to a new genus. This includes several species found from eastern Sydney south along the coast to Nowra. A total of six new species and five new genera are described. The conservation and management of narrow-range endemics such as Meridolum corneovirens provide a number of challenges to conservation managers. The alternative of listing a gene pool rather than listing species separately is proposed and explore
5
Hutcheson, Robert. "Nervous control of sperm release in the snail, Cantareus aspersus." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98730.
Full textAbstract:
The primary objective of my research was to test the hypothesis that the sperm release mechanism in the garden snail, Cantareus aspersus , is under nervous control. It was discovered that separate branches of the intestinal nerve innervate the seminal vesicle and the distal ovotestis duct, and sperm release from the seminal vesicle was achieved by electrical stimulation of this nerve. Stimulation of the penis nerve, right cerebropedal connective nerve, right mesocerebrum, visceral ganglion, and the everted reproductive organs elicited similar responses. Neurobiotin fills of the penis nerve (towards the penis) revealed putative sensory receptors at the base of the penis and within the genital atrium. Spermatophores from mated snails whose reproductive organs were treated with the local anaesthetic Lidocaine weighed significantly less than spermatophores from mated control snails, suggesting that mechanical stimulation during copulation triggers sperm release from the seminal vesicle.
6
Staddon, Julian W. "Peptidergic co-transmission in the pond snail." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360503.
Full text
7
Kennedy, Helen J. "Intracellular Ca'2'+ regulation in snail neurones." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358370.
Full text
8
Bock, Vanessa Leonie. "The Role of Brm, Brg-1, Snail 1 and Snail 2 in the Progression of Non-Melanoma Skin Cancer." Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/4091.
Full textAbstract:
Non-melanoma skin cancer (NMSC) is the most common human cancer worldwide. Squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) make up almost all NMSC. SCC usually arises from actinic keratosis (AK) as a result of exposure to sunlight. SCC and AK provide a useful clinical model to investigate changes involved in the progression of NMSC. This project examines the expression of Brm, Brg-1, Snail 1 and Snail 2 in the progression of NMSC. Brm and Brg-1 are subunits of the SWI/SNF chromatin-remodelling complex which is involved in regulating the access of cell machinery to DNA by altering the structure of chromatin. It has been suggested that loss of this function is involved in carcinogenesis as the cell is unable to access to DNA normally in order to repair mutations or activate apoptosis. The loss of Brm or Brg-1 has been described in several human cancers. Snail 1 and Snail 2 are zinc-finger transcription factors that are known for their role in epithelial to mesenchymal transition (EMT), a process vital to embryological development. Increased expression of these factors leads to a loss of cell-cell adhesion and a migratory phenotype and has been described in some human cancers. In this project, double-label immunohistochemistry was used to determine the relative expression of these proteins in human SCC, BCC, AK and normal skin. The expression of Snail was unable to be determined due to poor specificity of the antibodies used. The expression of both Brm and Brg-1 proteins was found to be dramatically and consistently decreased in SCC and BCC when compared to normal skin and AK. This loss of Brm and Brg-1 occured as the tumour progressed from benign AK to malignant SCC. This finding suggests that the loss of either Brm or Brg-1 constitutes a key step in carcinogenesis. The results of this study identify Brm and Brg-1 as putative tumour suppressors involved in the progression of non-melanoma skin cancer from benign to malignant.
9
Bock, Vanessa Leonie. "The Role of Brm, Brg-1, Snail 1 and Snail 2 in the Progression of Non-Melanoma Skin Cancer." University of Sydney, 2008. http://hdl.handle.net/2123/4091.
Full textAbstract:
Master of Medicine<br>Non-melanoma skin cancer (NMSC) is the most common human cancer worldwide. Squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) make up almost all NMSC. SCC usually arises from actinic keratosis (AK) as a result of exposure to sunlight. SCC and AK provide a useful clinical model to investigate changes involved in the progression of NMSC. This project examines the expression of Brm, Brg-1, Snail 1 and Snail 2 in the progression of NMSC. Brm and Brg-1 are subunits of the SWI/SNF chromatin-remodelling complex which is involved in regulating the access of cell machinery to DNA by altering the structure of chromatin. It has been suggested that loss of this function is involved in carcinogenesis as the cell is unable to access to DNA normally in order to repair mutations or activate apoptosis. The loss of Brm or Brg-1 has been described in several human cancers. Snail 1 and Snail 2 are zinc-finger transcription factors that are known for their role in epithelial to mesenchymal transition (EMT), a process vital to embryological development. Increased expression of these factors leads to a loss of cell-cell adhesion and a migratory phenotype and has been described in some human cancers. In this project, double-label immunohistochemistry was used to determine the relative expression of these proteins in human SCC, BCC, AK and normal skin. The expression of Snail was unable to be determined due to poor specificity of the antibodies used. The expression of both Brm and Brg-1 proteins was found to be dramatically and consistently decreased in SCC and BCC when compared to normal skin and AK. This loss of Brm and Brg-1 occured as the tumour progressed from benign AK to malignant SCC. This finding suggests that the loss of either Brm or Brg-1 constitutes a key step in carcinogenesis. The results of this study identify Brm and Brg-1 as putative tumour suppressors involved in the progression of non-melanoma skin cancer from benign to malignant.
10
Koene, Joris M. "Behavioural and neurobiological aspects of dart shooting in the garden snail Helix aspersa." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0031/NQ64591.pdf.
Full text
11
Rogers, David W. "Dart shooting and postcopulatory sexual selection in the garden snail Helix aspersa." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33833.
Full textAbstract:
During the final stage of courtship, the garden snail Helix aspersa attempts to stab its mating partner with a mucus-coated calcareous "love dart." I present evidence supporting two predictions of the most promising hypothesis for the adaptive significance of this behavior: that the dart serves to increase the reproductive success of the shooter by increasing the numerical representation of its sperm in the recipient's storage organ (the sperm loading hypothesis). First, I demonstrate that once-mated snails store more of the sperm transferred by successful shooters than by unsuccessful shooters. Second, I demonstrate that this biased storage results in higher paternity scores for successful shooters relative to unsuccessful shooters in the clutches of multiply mated recipients. Moreover, I present evidence that body size and mating order influence the outcome of sperm competition in snails. Finally, I propose a novel mechanism to explain the observed pattern of sperm utilization in H. aspersa based on the motility of stored allosperm.
12
Adamo, Shelley A. (Shelley Anne). "An examination of the concept of arousal within the context of the sexual behaviour of the snail, Helix aspersa /." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74344.
Full textAbstract:
Sexual 'arousal' in Helix aspersa can be divided into 2 components, sexual proclivity (the tendency of a snail to respond to conspecific contact with courtship) and sexual arousal (the intensity with which the snail courts). Sexual proclivity and sexual arousal have different effects on feeding and locomotion and are differentially affected by sexual isolation, daily conspecific contact, and by a courtship pheromone found in the digitiform gland mucus. Therefore sexual arousal and sexual proclivity are probably mediated by 2 separate physiological mechanisms. Behavioural state, or the animal's general level of activity, correlates positively with mating behaviour. However, although a central system controlling behavioural state probably exists, it has no direct effect on either sexual proclivity or sexual arousal. Confusion over the term 'arousal', which impedes neuroethological research in this area, would be decreased by the adoption of the terms used in this thesis.
13
Blanchard, Katrina C. "The mechanism of the dart's influence on paternity in the snail, Cantareus aspersus /." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97909.
Full textAbstract:
The courtship behavior of the brown garden snail, Cantareus aspersus , includes a bizarre component where one snail attempts to pierce its mating partner with a sharp, calcareous dart that is covered with mucus. In vitro, the mucus causes conformational changes to the reproductive tract causing sperm to be stored rather than digested. In addition, successful dart shooters have an increased relative paternity compared to unsuccessful shooters. I have tested whether this increased paternity is caused by the mucus delivered on the dart or by the mechanical action of the dart. Mating trials were conducted using dartless and glandless snails, where a future mother was mated to two different potential fathers, receiving an injection of mucus with one mating, and an injection of saline with the second mating. The fathers accompanied by the mucus injection sired significantly more offspring than the fathers accompanied by the saline injection. I conclude that the mucus carried on the dart is responsible for increased paternity levels in Cantareus aspersus.
14
Richards, David Charles. "Competition between the threatened Bliss Rapids Snail, Taylorconcha serpenticola (Hershler et al.) and the invasive, aquatic snail, Potamopyrgus antipodarum (Gray)." Diss., Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/richards/RichardsD1204.pdf.
Full textAbstract:
Due primarily to habitat loss and invasive species, extinction rates for North American mollusk taxa are among the highest for any taxonomic group in the world. Competition between invasive and native species often leads to decreases in native populations. For example, a primary reason for listing the Bliss Rapids snail, Taylorconcha serpenticola as threatened in the Snake River drainage was the perceived impacts of the highly invasive New Zealand mudsnail, Potamopyrgus antipodarum. Despite federal protection of T. serpenticola and the known presence of P. antipodarum in the Snake River drainage for almost 20 years, almost nothing is known about their ecology and competitive interactions. For this dissertation I conducted both field and laboratory studies to determine niche overlaps, spatial patterns, and some life history characteristics of both species. I compared optimal growth temperatures and estimated temperature tolerances for each species, under laboratory conditions; 2) examined stage (size) class fecundity rates and growth rates; and 3) examined photophobic tendencies of both species. I then explored environmental conditions and spatial patterns of both species in Banbury Springs, a tributary of the Snake River, near Hagerman, Idaho, that may have affected their distribution and abundance using regression tree analysis and geostatistical methods. I then conducted several competition experiments between both species under controlled conditions at Banbury Springs, developed competition coefficients, and related their growth rates and competitive outcomes to periphyton abundance and diversity. Finally, I monitored and then modeled seasonal and yearly population density trends of both species in a section of Banbury Springs, where both coexist, using time series analysis. Results of this study show that that both species have niche overlaps (i.e. temperature overlaps, photophobic tendencies, and somewhat similar habitat requirements) and can compete for limited food resources, but may have just enough niche separation or their occupied habitat is heterogeneous enough for them to coexist, at present. It is possible however that not enough time has elapsed for the effects of competition with P. antipodarum to push T. serpenticola to extinction.
15
Reichert, Brian Engebos. "Effects of aging and the environment on Snail Kite demography a reassessment of Snail Kite (Rostrhamus sociabilis plumbeus) vital rates /." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041282.
Full text
16
Paul, Mariel Cathérine [Verfasser], Angelika [Akademischer Betreuer] Schnieke, and Dieter [Akademischer Betreuer] Saur. "Functions of snail homolog 1 (Snail) in pancreatic cancer / Mariel Cathérine Paul. Gutachter: Dieter Saur ; Angelika Schnieke. Betreuer: Dieter Saur." München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1057957852/34.
Full text
17
Virgós, Soler Ariadna. "Efecte represor de Snail en la proliferació cel·lular." Doctoral thesis, Universitat Pompeu Fabra, 2008. http://hdl.handle.net/10803/7212.
Full textAbstract:
La Transició Epiteli-Mesènquima és el mecanisme pel qual les cèl·lules epitelials generades en regions particulars, poden dissociar-se de l'epiteli i migrar cap a nous destins, gràcies a uns canvis morfològics que transformen les cèl·lules epitelials en cèl·lules mesenquimals. Aquest procés fonamental durant el desenvolupament, també és rellevant en la progressió de tumors epitelials malignes i en tots dos casos les cèl·lules perden cohesió i adhesió i guanyen mobilitat. Aquests processos morfogènics impliquen una reorganització important del citoesquelet que serà incompatible amb un estat proliferatiu actiu, fins que les cèl·lules necessitin colonitzar un nou territori.<br/>Snail és un factor clau en la regulació dels processos EMT, tant en el desenvolupament com en la progressió tumoral gràcies a la seva capacitat de reprimir directament la transcripció de gens epitelials i promoure l'expressió de gens mesenquimals.<br/> Uns clons estables de dues línies cel·lulars epitelials, generats en el nostre grup proliferaven més lentament a l'expressar Snail de manera que ens vam proposar descriure el mecanisme utilitzat per Snail per fer disminuir la taxa de proliferació cel.lular al ser expressat ectòpicament en cèl.lules en cultiu que havien patit una EMT.<br/>Els resultats d'aquesta tesi indiquen que Snail bloqueja el cicle cel·lular al ser expressat en cèl·lules epitelials fent que disminueixin els nivells de proteïna CDC25A, fosfatasa que pot activar els complexes CDK-ciclina implicats en la progressió per diverses etapes del cicle. Els nostre estudi suggereix que Snail reté el mRNA de CDC25A al nucli, impedint que sigui exportat i traduit.
18
Lagesson, Annelie. "Predator-induced morphological defences in a freshwater snail." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-44386.
Full textAbstract:
The ability of a certain genotype to express different phenotypes depending on variations in the environment is called phenotypic plasticity. Predator induced defences are among the most studied and wide spread examples of phenotypic plasticity. For example, in freshwaters, predators are constantly shaping communities with their presence and a plethora of defensive adaptations in prey have evolved.In this study, I have analyzed if the freshwater snail Radix balthica show any induced morphological defence when exposed to the molluscivoruos fishes, crusian carp (Carassius carassius) and tench (Tinca tinca). Two treatments were used; without predator and with a non-lethal predator (fish cues), to examine if the snails exposed to predators changed their shells in size, thickness and shape. The study contained snails from both northern Sweden (Umeå) and from southern Sweden (Lund).The experiment conducted on the northern snails of R. balthica did not confirm my hypothesis that snails threatened by a predator (fish cues) express inducible defences. However, there were tendencies pointing in that direction. In contrast, the R. balthica snails from southern Sweden, exposed to fish cues from tench, showed a strong response. Shells were thicker and showed a more rounded shape, i.e. a wider shell and lower apex in the presence of fish compared to in the absence of fish. The rounder shells are more resistant to crushing by molluscivorous fish, due to the fact that the crushing force is more evenly spread over the shell. Thickness and size of the shell also influences the crushing resistance. Shell crushing fish obviously have a strong effect on gastropod communities and are therefore likely to drive the evolution of induced morphological defence in their prey.
19
Gerlach, Justin. "The ecology of the carnivorous snail Euglandina rosea." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308609.
Full text
20
Davies, Charlotte Mary. "Snail-schistosome interactions and the evolution of virulence." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343421.
Full text
21
Blair, Linsey. "Snail-schistosome interactions : implications for coevolution and control." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409725.
Full text
22
Raheem, Dinarzarde Chirantenne. "Land-snail diversity in Sri Lankan rainforest fragments." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613834.
Full text
23
Ashraf, Shovon I. "Snail Protein Family in Drosophila Neurogenesis: a Dissertation." eScholarship@UMMS, 2001. https://escholarship.umassmed.edu/gsbs_diss/53.
Full textAbstract:
The Snail protein functions as a transcriptional regulator to establish early mesodermal cell fate in Drosophila. Later, in germ band-extended embryos, Snail is considered a pan-neural protein based on its extensive expression in neuroblasts. The evidence presented in thesis links snail expression and function in CNS. Cloning and functional characterization of a novel snail homologue, in Drosophila, are also described here. Cloning of this gene, worniu (Chinese for snail), revealed that the neural function of snail is masked by this and another closely related gene escargot. Both Escargot and Worniu contain zinc finger domains that are highly homologous to that of Snail. These three members of Snail protein family are redundantly required for CNS development. Although not affecting formation of neuroblasts, the loss of expression of these three members correlates with disruption of Nb asymmetry and division. Downstream targets of Snail protein family, in these processes, are inscuteable and string. In mutant embryos, which have the three genes deleted, the RNA expression of inscuteable and string is significantly lowered. Consistent with the gene expression defects, the mutant embryos have loss of asymmetric localization of prospero RNA in neuroblasts and nuclear localization of Prospero protein in ganglion mother cells. Transgenic expression of inscuteable and string together, in the snail family deletion mutant, efficiently restores the Prospero expression in GMC, demonstrating that the two genes are key targets of Snail in Nbs. Like in the mesoderm, in CNS Snail function depends on interaction with dCtBP co-repressor. These results suggest that Sna [Snail] family of proteins control both asymmetry and cell division of neuroblasts by activating, perhaps indirectly, the expression of inscuteable and string.
24
Li, Guoyi 1962. "Distribution of APGWamide-like and FMRFamide-like immunoreactive neurons innervating the penis and the dart sac in the mesocerebrum of the snail Helix Aspersa." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68200.
Full textAbstract:
The distribution of APGWamide-like and FMRFamide-like immunoreactive neurons involved in the mating behaviour of the terrestrial snail Helix aspersa have been investigated in the mesocerebrum by retrograde and anterograde labelling and immunostaining techniques. Retrograde labelling shows that 25-40 mesocerebral neurons have an axon in the penis nerve and a similar number of neurons have an axon in the nervus cutaneus pedalis primus dexter (NCPD). It was found that the mesocerebral neurons also project to the nervus cutaneus pedalis secundus dexter (NCSD), the medial lip nerves, the posterior lip nerve, the peritentacular nerve, and the pedal ganglion. Some mesocerebral neurons have multiple projections. Quantitative analysis using confocal laser scanning microscopy indicates that approximately half of the mesocerebral neurons projecting to the penis nerve contain APGWamide-like peptide and half of the mesocerebral neurons projecting to the NCPD contain FMRFamide-like peptide. Some mesocerebral neurons have both peptides. These results are generally in agreement with the hypothesis that the neurons projecting to the penis nerve contain APGWamide, while those projecting to the NCPD contain FMRFamide.
25
Laberge, Shelley. "Morphology and development of mesocerebrum neurons in Helix aspersa maxima." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60497.
Full textAbstract:
The neurons in the mesocerebrum of the right cerebral ganglion control the sexual behaviour of Helix aspersa maxima. The purpose of the present study was to examine the relationship between reproductive development and the development of these neurons. The growth of right mesocerebrum neurons was quantified by filling cells with hexamminecobalt chloride at different ages. The neurite growth phase preceded that of the penis by about four weeks. Total neurite length was linearly correlated with soma diameter as measured in wholemounts. Diameter measurements from sectioned material showed that postembryonic growth in three CNS populations was expressed as increases in soma diameters but not in neuron numbers. The growth rate of right mesocerebrum cells between 5-20 weeks of age was significantly greater than that of the other two populations. Right mesocerebrum development was unaffected by male reproductive tissue ablation. this study shows that growth and development of the right mesocerebrum neurons of H. aspersa maxima occurs relatively late, but is complete prior to the initiation of reproductive behaviour.
26
Gardner, Neville P. "Small-scale distribution of two modern land snail faunas : islands and boundaries of relevance to the interpretation of subfossil assemblages." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315293.
Full text
27
Batlle, Gómez Raquel. "Snail controls TGFB responsiveness and diferentiation of MS cells." Doctoral thesis, Universitat Pompeu Fabra, 2011. http://hdl.handle.net/10803/77655.
Full textAbstract:
The Snail1 transcriptional repressor is a key factor responsible in triggering epithelial to mesenchymal transition. Although Snail1 is widely expressed in early development, it is limited in adult animals to a subset of mesenchymal cells where it has a largely unknown function. In this project we have demonstrated that Snail1 is required to maintain mesenchymal stem cells (MSCs). This effect is associated to the responsiveness to TGF-[beta]1 which showed a strong Snail1 dependence. Snail1-depletion in conditional knock-out adult animals caused a significant decrease in the number of bone marrow-derived MSCs. In culture, Snail1-deficient MSCs prematurely differentiated to osteoblasts or adipocytes and, in contrast to controls, were resistant to the TGF-[beta]1-induced differentiation block. TGF-[beta]1 was unable to up-regulate most of its targets in Snail1 KO MSCs, an effect that was related, but not limited, to defective PTEN repression and Akt activation. Correspondingly, an analysis of human sarcomas also showed enhanced expression of Snail1 in undifferentiated tumors, which was strongly associated with high expression of TGF-[beta] and poor outcome. These results not only demonstrate a new role for Snail1 in TGF-[beta] response and MSC maintenance but also suggest the involvement of MSCs in sarcoma generation.<br>El repressor transcripcional Snail1 ha estat descrit principalment com el responsable de la inducció de la transició epiteli mesènquima. Encara que Snail1 s’expressa durant les etapes més primerenques del desenvolupament embrionari, la seva expressió en adults es veu limitada en un conjunt de cèl•lules mesenquimals sense saber-se la seva funció. En aquest projecte hem demostrat que Snail1 es requereix per mantenir el fenotip més indiferenciat de les cèl•lules mare del mesènquima. Aquesta funció la fa en part, per la capacitat de resposta de la citoquina TGF-[beta] la qual mostra una força dependència amb Snail1. Quan s’elimina Snail1 en ratolins adults provoca una clara disminució en el nombre de cèl•lules mare de la medul•la òssia. Aquestes cèl•lules en cultiu presenten una clara diferenciació prematura a osteoblasts i adipòcits. Pel contrari, tractaments amb TGF-[beta]1 aturen la diferenciació. El TGF-[beta]1 es incapaç de incrementar moltes dianes en cèl•lules mare del mesènquima aïllades del ratolí deficient per snail1, aquest efecte en part es degut a la repressió de PTEN i l’activació de AKT. L’anàlisi de sarcomes humans ens ha mostrat una alta expressió de Snail1, el qual també es troba associada amb una alta expressió de TGF-[beta] i baixa supervivència. Aquests resultats no només demostren una nova funció per Snail1 en resposta a TGF-[beta] i el manteniment de les MSC, sinó que també suggereix que Snail1 podria participar en la generació del sarcoma.
28
Sigurdson, Wade Johannes. "Mechanosensitive ion channels in the freshwater snail, Lymnaea stagnalis." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5737.
Full textAbstract:
Mechano-sensitive ion channels in cells isolated from the heart and circumoesophageal ganglia of a freshwater snail (Lymnaea stagnalis) were characterized as K$\sp+$ selective and sensitive to changes in cell membrane tension. Using the technique of single-channel recording, stretch-activated K$\sp+$ (SAK) channels (30 pS in physiological saline) were shown to have complex permeation properties indicative of multi-ion channels. SAK channels were blocked by milli-molar quantities of quinidine or tetraethyl-ammonium and exhibited selectivity (Tl$\sp+ >$ K$\sp+ >$ Rb$\sp+ >$ Na$\sp+ >$ Li$\sp+$) properties seen in many other K$\sp+$ channels. SAK channels described in Lymnaea ventricular cells or neuron somas and growth cones were activated (increased open probability, P$\sb{\rm o}$) by increases in membrane tension produced by suction on the cell membrane. Stretch-activation was a reversible and repeatable phenomenon, associated with a reduction in a long closed time separating bursts of openings, rather than by an increase in the open time. The SAK channel's stretch-sensitivity was variable between patches, a finding attributable to the inability to accurately determine membrane tension. In spite of this, kinetic analysis of heart SAK channels established the presence of at least two open and three closed states. Similar analysis of neuron SAK channels indicated at least two open and four closed states. In channels from both cell types, only the long closed time constant ($\tau\sb{\rm C4}$, extracted from closed time frequency distributions) showed sufficient mechano-sensitivity to produce the observed increase in P$\sb{\rm o}$ with increasing membrane tension (in one patch, when P$\sb{\rm o}$ increased by a factor of 77 times the zero pressure P$\sb{\rm o}$, $\tau\sb{\rm C4}$ decreased by a factor of 22). In spite of the absence of specific SAK channel antagonists, attempts were made to establish a physiological role for SAK channels. Neurons and heart cells were shown to be resistant to severe hyposmotic insults. Hyposmotic shock resulted in hyperpolarization of the neuron soma resting potential and activation of SAK channels. These results suggested that SAK channels may contribute to osmotic-swelling limitation. SAK channels were found in developing neuron growth cones as well as the cell body. Channel characteristics were similar in both structures and circumstantial evidence points to expression of new SAK channels during neurite development. A new type of mechano-sensitive K$\sp+$ channel was found to coexist with SAK channels in neuron cell bodies and growth cones. These channels were in-activated (SIK) by increases in membrane tension and possessed a greater stretch-sensitivity than SAK channels. Decreased P$\sb{\rm o}$ was found to result from the lengthening of the long closed time in a fashion analogous but opposite to that seen in SAK channels, thus implying a common transduction mechanism. The differing stretch-sensitivities combined with similar permeation properties (6.6 pS in physiological saline; selectivity sequence, Tl$\sp+ >$ K$\sp+ >$ Rb$\sp+ >$ Na$\sp+$) suggested that membrane tension could control cell resting potential and thus modulate voltage-activated Ca$\sp{2+}$ channels and therefore the influx of Ca$\sp{2+}$, a known regulatory ion. SIK and SAK channels could therefore provide a mechanism for linking Ca$\sp{2+}$ influx to tension during axonal outgrowth.
29
Wandelt, Jessica Eve. "Dorsal-Ventral Patterning in the Mud Snail, Ilyanassa obsoleta." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1361%5F1%5Fm.pdf&type=application/pdf.
Full text
30
Geoffroy, Emile. "Mechanisms controlling ovulation in the garden snail Helix aspersa." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82240.
Full textAbstract:
The gonad of the snail Helix aspersa is innervated by a branch of the intestinal nerve. Here it is demonstrated that nerve stimulation causes peristaltic contractions and the acceleration of cilia beating in the proximal part of the hermaphroditic duct. Acetylcholine and serotonin induced peristaltic contractions when applied without nerve stimulation. As well, serotonin induced the acceleration of cilia beating. The neuropeptide FMRFamide caused dilation of the hermaphroditic duct. Pharmacological blocking of acetylcholine and serotonin receptors with concurrent nerve stimulation induced a dilation similar to that caused by FMRFamide application. It is suggested that all three transmitters are released from intestinal nerve terminals to facilitate oocyte transport during ovulation. Nerve stimulation induced an increase in gamete transport rates. Because several candidate chemical messengers failed to induce ovulation when injected into the circulatory system, Helix aspersa appears to initiate ovulation differently from related species. Whereas Aplysia and Lymnaea use hormones, Helix apparently signals ovulation via the intestinal nerve.
31
Grindon, Adele. "Mitochondrial phylogeography of three European helicid land snail species." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523072.
Full text
32
Skomrock, Nicholas David. "The Biogeography of the Caribbean Land Snail Family Annulariidae." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417706937.
Full text
33
Pearson, Edmond Loring. "Induced phenotypic plasticity in the intertidal snail Nucella ostrina /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
Full text
34
Baker, Patrick. "Predation on an introduced marine snail by native crabs." Thesis, Thesis (M.S.)--University of Oregon, 1988, 1988. http://hdl.handle.net/1794/9843.
Full textAbstract:
Typescript.
Includes vita and abstract.
Bibliography: Includes bibliographical references (leaves 55-58).<br>Ceratostoma ioornatum is an introduced marine snail in Puget Sound,
Washington. Two of five native species tested as possible predators ate
Ceratostoma. These two species, the crabs Cancer gracilis and
Lopbppaoopeys bellys, did not eat native snails similar to Ceratpstpma,
but ate native and introduced bivalves more than Ceratpstpma. The
reasons for the differences in predation seemed to be explained by shell
strength of the prey species. The presence of Ceratpstpma adds a new
type of prey to the menu of the two crab species
at the sites studied.
35
Farquharson, Jane. "Studies on the lip colour polymorphism in Cepaea." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334803.
Full text
36
Syed, Naweed Imam. "The neural control of locomotion in Lymnaea." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237078.
Full text
37
Kyriakides, Michael Andreas. "Neural mechanisms underlying modulation and coordination of motor output in Lymnaea stagnalis." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329327.
Full text
38
Buckett, K. J. "Neuronal and peptidergic control of the heart in the snail Lymnaea stagnalis." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377064.
Full text
39
O'Sullivan, T. N. "The chemical behaviour and eco-toxicity of Cu-CRG molluscicides : as used in attempts to control the snail hosts of schistosomiasis." Thesis, University of Sussex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356083.
Full text
40
Porta, de la Riva Montserrat. "Transcriptional activation induced by snail 1 during epithelial-mesenchymal transition." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7205.
Full textAbstract:
La transició epiteli-mesènquima (TEM) és un procés en què cèl lules epitelials, immòbils i amb polaritat apico-basal transiten cap un fenotip mesenquimal o fibroblàstic. L'expressió del factor de transcripció snail1 és suficient per induir TEM en cèl lules en cultiu i és necessari per la majoria de les TEM fisiològiques descrites. Snail1 és un membre de la família de proteïnes amb dits de Zinc que reprimeix gens epitelials (com l'E-cadherina) a través de la unió directa a seqüències especifiques dels promotors anomenades caixes E i posterior reclutament de corepressors. La TEM també es caracteritza per l'activació de gens mesenquimals, però el mecanisme pel qual snail1 indueix l'expressió d'aquests és poc conegut. <br/><br/>En aquest treball demostrem que snail1 actua a nivell transcripcional per incrementar els nivells dels marcadors mesenquimals FN1 (fibronectina) i LEF1 (de l'anglès, lymphoid enhancer-binding factor 1) a través d'un mecanisme nou per aquesta proteïna de dits de Zn que no requereix ni caixes E ni unió directa a l'ADN. A més a més, mostrem que, per a dur a terme l'activació, snail1 coopera amb dos factors de transcripció ja descrits en relació a la TEM: beta-catenina i NF-kappa-B. Els nostres resultats també proven que l'expressió forçada de la E-cadherina evita aquesta cooperació i conseqüent activació gènica. A banda d'aquest mecanisme, també hem descrit que el factor de transcripció TFCP2c, que no havia estat prèviament relacionat amb TEM, és necessari per l'activació del gen FN1 induïda per snail1.<br>Epithelial-mesenchymal transition (EMT) is a cellular process by which no motile epithelial, apico-basal-polarized cells transit towards a motile mesenchymal front-backpolarized phenotype. Expression of the transcription factor snail1 is sufficient to induce EMT in cultured cells and it is required for most of the physiological EMTs described. Snail1 is a member of the Zn finger protein family that represses epithelial genes (such as E-cadherin) by directly binding to specific promoter sequences called E-boxes and subsequent recruitment of corepressors. EMT is also accompanied by activation of mesenchymal genes, however, little is known of how snail1 induces their expression.<br/><br/>In this work we provide evidence that snail1 acts at the transcriptional level to increase the levels of the mesenchymal FN1 (fibronectin) and LEF1 (lymphoid enhancer-binding factor 1) genes through a novel mechanism for this Zn finger protein that does not require neither E-boxes nor direct binding to DNA. Furthermore, we describe a cooperative action in such mechanism between snail1 and two transcription factors previously related to EMT: beta-catenin and NF-kappaB. Our results also show that restoration of E-cadherin levels prevents such cooperation and subsequent activation. In addition, we also demonstrate that TFCP2c, which had not been previously linked to EMT, is also required for snail1-induced transcriptional activation of the FN1 gene.
41
Weller, Mathias. "Expression of Prospero, Snail and Krüppel homologues during spider neurogenesis." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965401316.
Full text
42
Gleyzon, Francois-Xavier. "Shakespeare's spiral : tracing the snail in King Lear and Renaissance." Thesis, Lancaster University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.617807.
Full textAbstract:
This thesis has as its aim the exploration of a figure forgotten in the dramatic text of Shakespeare and Renaissance painting: the garden snail. Taking as its point of departure the emergence of the gastropod object/subject in the text of King Lear as well as its iconic interface in Bellini's painting Allegory of Falsehood (circa 1490), this study sets out to follow the particular path traced by the snail through the oeuvre. From the central scene in which the metaphor of the snail and or" its shell is specifically made manifest when Lear discovers, in a raging storm, the spectacle of Edgar disguised as Poor Tom coming out of his shelter (III.3.6-9) to the monster, this fiend displaying, on the cliffs of Dover, "horns whelked and waved like the enridged sea" (IV.6. 71), this thesis is the trace of a narrative - of a journey of the gaze - during the course of which the cryptic question of the gastropod - "Why a Snail [ ... ]?" (I.5.26) - will not cease to be developed and transformed. Incorporating a wide-ranging post-structuralist critique, the study aims to bring to light the particular functions of this "revealing detail" in both its textual and visual dimension so as to put forward a new and innovatory understanding of the tragedy of King Lear.
43
Soanes, Grant Paul. "Visual and chemical learning in the pond snail, Lymnaea stagnalis." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285369.
Full text
44
Richmond, Larry. "Lead assimilation and its variability in the snail (Helix aspersa)." Thesis, London South Bank University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281639.
Full text
45
Burton, LizaJoy. "Snail-Cathepsin L Signaling in Human Breast and Prostate Cancers." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2017. http://digitalcommons.auctr.edu/cauetds/60.
Full textAbstract:
Prostate and breast cancer are the leading causes of cancer-related death in men and women, respectively, and metastasis is the primary factor underlying the high mortality rates.1 Snail transcription factor is an important molecule that drives prostate and breast cancer metastasis through the process of epithelial mesenchymal transition (EMT). Proteolytic enzymes that promote invasion and metastasis such as the lysosomal cysteine protease cathepsin L (Cat L) have been shown to degrade E-cadherin, promoting the epithelial mesenchymal transition (EMT).2 It has also been shown that silencing Cat L can inhibit transforming growth factor-beta (TGF-β)-mediated EMT by suppressing Snail transcription factor.3 Several recent studies have highlighted an additional unexpected localization and site of action for Cat L within the nucleus in breast, colon and prostate cancer.4 Natural products have been shown to be efficacious in prevention and possible treatment of cancer.5 Specifically, we have been studying Muscadine Grape Skin Extract (MSKE) as a possible candidate to inhibit Snail signaling. MSKE has previously been shown to promote prostate cancer apoptosis.6 We hypothesized that Snail promotes nuclear localization of Cat L, which promotes EMT associated with increased migration and invasion, and that antagonizing Snail-Cat L signaling would lead to mesenchymal epithelial transition (MET). We showed for the first time that MSKE promotes apoptosis through induction of endoplasmic reticulum stress response and autophagy. Additionally, MSKE could inhibit Snail-mediated EMT via scavenging reactive oxygen species. Moreover, Snail could promote nuclear localization of Cat L, which then promoted cleavage of CDP/Cux, increased Snail transcription and decreased E-cadherin transcription by direct promoter binding of cleaved CDP/Cux, leading to EMT associated with increased migration and invasion. Interestingly, Z-FY-CHO, a small molecule specific inhibitor of Cat L, as well as MSKE could antagonize this signaling by promoting nuclear to cytoplasmic re-localization of Cat L. Therefore, we have dissected novel mechanisms of action of Snail and how it can be antagonized by MSKE natural product.
46
Gras, Baptiste. "Étude des propriétés oncogéniques des membres de la famille SNAIL." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10291.
Full textAbstract:
En parallèle à son rôle dans l’initiation de la cascade métastatique, la transition épithéliomésenchymateuse est capable de faciliter la transformation néoplasique par le biais de mécanismes encore indéfinis. Nous avons démontré que, comme SNAIL1 et SNAIL2, l’expression de SNAIL3 est réactivée de façon aberrante dans les cancers humains, en particulier dans les carcinomes mammaires, établissant un lien entre l’ensemble des membres de la famille SNAIL et la tumorigénèse. Expérimentalement, les trois protéines SNAIL induisent une EMT avec des efficacités différentes. Ce différentiel reflète leur capacité à protéger les cellules de l’anoikis et à favoriser la prolifération dans des conditions de faible adhérence en absence d’altération oncogénique. La réversion partielle du processus d’EMT en réponse à l’expression ectopique des protéines ST14/Matriptase ou de l’E-cadhérine inhibe le potentiel oncogénique des protéines SNAIL. Nous avons donc démontré que la perte de protéines responsables du maintien de l’intégrité de l’épithélium contribue à l’activité pro-tumorale des inducteurs d’EMT<br>Beyond its role in initiating the metastatic cascade, cell commitment to the epithelial-to-mesenchymal transition program has been shown to facilitate neoplastic transformation, the underlying mechanisms yet remaining elusive. We herein demonstrate that likewise SNAI1 and SNAI2, the expression of SNAI3 is aberrantly reactivated in human cancers, mainly in breast carcinomas, linking all members of the SNAIL family to tumorigenesis. Experimentally, the three SNAIL proteins trigger EMT with unequal efficiencies. This differential mirrors their ability to protect cells from anoikis and to sustain proliferation in low-adherent conditions in absence of an oncogenic insult. Partial reversion of the EMT-process, achieved through forced expression of the ST14/Matriptase or E-cadherin proteins, alleviates the SNAIL oncogenic potential. We thus demonstrate that loss of epithelial integrity gatekeepers contributes to the tumor promoting activity of embryonic EMT-inducers
47
Osnas, Erik E. "Evolutionary ecology of host defense in a snail-trematode interaction." [Bloomington, Ind.] : Indiana University, 2004. http://wwwlib.umi.com/dissertations/fullcit/3162256.
Full textAbstract:
Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2004.<br>Title from PDF t.p. (viewed Dec. 1, 2008). Source: Dissertation Abstracts International, Volume: 66-01, Section: B, page: 0059. Chairperson: Curtis M. Lively.
48
Cadogan, Anna-Karina. "Characterization of 5-hydroxytryptamine receptors in the snail, Helix aspersa." Thesis, University of St Andrews, 1992. http://hdl.handle.net/10023/14627.
Full textAbstract:
The aim of this investigation was to characterize those 5-HT receptors present in three different tissues of the common garden snail. Helix aspersa, into one or more of the categories already described for vertebrate 5-HT receptors. Specific 5-HT receptor agonists and antagonists which had been developed and used to help characterize, and subsequently classify, the various types of 5-HT receptor in vertebrates, were utilized in this study. The three preparations from Helix included: i) identified neurones in the visceral ganglion ii) the heart and iii) the pharyngeal retractor muscle (PRM). The action of 5-HT on identified neurones in the visceral ganglion was studied using the electrophysiological techniques of both voltage- and current- damp. Under voltage-clamp conditions the response of the identified neurones to iontophoretic application of 5-HT was seen to be an inward current of approximately 3-10 nA. Under current-clamp conditions the response to 5-HT was an excitatory depolarization leading to the firing of action potentials of approximately 3-15 mV. Both responses showed rapid desensitization to repetitive applications of 5-HT and were blocked by tubocurarine. No specific 5-HT receptor antagonist to this 5-HT response in Helix neurones was found. The action of 5-HT was mimicked by 5-CT and a- Me-5-HT both of which showed similar-sized responses to 5-HT, whereas sumatriptan gave smaller responses than those of 5-HT. 5-HT had a positive inotropic effect on the heart. The excitatory action of 5-HT on the heart was studied using an organ bath methodology with application of the 5-HT receptor agonists and antagonists at suitable concentrations. No specific 5-HT receptor antagonist was found for the cardioexcitatory effect of 5-HT. The full rank order of potency for the 5-HT receptor agonists tested was 5-HT > methylergometrine = ergotamine = 5-CT > -Me-5-HT = sumatriptan > methysergide = 2-Me-5-HT = tryptamine 8-OH-DPAT. 5-HT caused relaxation in the PRM and was found to inhibit, in a dose- dependent manner, acetylcholine (ACh)-induced contraction in the muscle. This inhibition of ACh-induced contraction by 5-HT in the PRM was studied using an organ bath methodology with application of 5-HT receptor agonists and antagonists at suitable concentrations. No specific 5-HT receptor antagonist for the inhibition of ACh-induced contraction was found. The rank order of 5-HT receptor agonist potency was 5-HT > 5-CT > sumatriptan = ergotannine = methysergide >> -Me-5-HT = 2-Me-5-HT. The effect of 5-HT on cyclic adenosine 3',5'-monophosphate (cAMP) levels within Helix heart and pharyngeal retractor muscle (PRM) tissue were monitored in this investigation. 5-HT caused a dose-dependent increase in cAMP both in Helix heart and PRM tissue. The 5-HT receptors within Helix are not readily characterized into any of the categories of 5-HT receptor that have been already classified in vertebrates: Helix 5-HT receptors appear to be unique in the fact that they are unclassifiable in terms of the vertebrate 5-HT receptor classification. The evidence presented in this investigation is discussed in terms of the molecular biology of receptors: this includes the hypothesis that the 5-HT receptors particularly in Helix heart and PRM tissue could be related to a family of G-protein-coupled receptors whereas the neuronal 5-HT receptors in Helix are more likely to be integral to an ion channel.
49
Hutchinson, John Michael Christopher. "Design in the shell shape of a terrestrial snail, Trichia hispida." Thesis, University of York, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235782.
Full text
50
Domínguez, Solà David. "Mecanismes de regulació en l'activitat biològica del factor de transcripció Snail." Doctoral thesis, Universitat Pompeu Fabra, 2003. http://hdl.handle.net/10803/7065.
Full textAbstract:
Els factors de transcripció de la família Snail són fonamentals en la "transició epiteli-mesènquima", procés morfogènic essencial en el desenvolupament embrionari i en els fenòmens metastàsics tumorals.<br/>En els mamífers l'activitat d'Snail és modulada per dos mecanismes. (i) En el promotor humà es troben regions definides de resposta a factors repressors, predominants en les cèl·lules epitelials, i elements diferenciats de resposta a inductors de la "transició epiteli-mesènquima". (ii) L'activitat d'Snail és condicionada també per la seva localització subcel·lular, modulada per mecanismes no transcripcionals: la fosforilació d'Snail determina si és o no exclós del nucli. Al citosol no pot actuar com a repressor transcripcional però pot interaccionar amb la xarxa microtubular, que estabilitza i en condiciona el dinamisme. Això coincideix amb l'activació de la GTPasa RhoA i la reorientació dels filaments de vimentina, fets associats a l'adquisició de capacitat migratòria. L'efecte com a repressor transcripcional i la modulació del dinamisme microtubular són possiblement esdeveniments coordinats necessaris per al rol biològic d'Snail en mamífers.<br>Snail family of transcription factors is fundamental to the "epithelial-mesenchymal transition", morphogenic process essential to embryonic development and metastatic phenomena in tumors.<br/>Snail's activity is modulated in two ways in mammals. (i) The human promoter harbors definite regions that respond to repressor factors, which prevail in epithelial cells; and differentiated elements that respond to known inducers of the "epithelial-mesenchymal transition". (ii) Snail's activity is also conditioned by its subcellular localization, mechanism not dependent on its transcriptional control: Snail phosphorylation determines whether Snail is excluded or not from the nucleus. When in the cytosol, Snail is unable to act as a transcriptional repressor, but however binds to the microtubular meshwork, which becomes stabilized and whose dynamism is conditioned as a result. This fact coincides with the activation of the RhoA GTPase and reorientation of vimentin filaments, both phenomena being related to the acquisition of cell motility. The transcriptional repressor and the microtubule dynamics effects are probably two coordinated events necessary to Snail's biological role in mammals.