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The biology of reproduction in two British pulrnonate slugs. The biology of reproduction has been studied in two British slugs, Deroceras reticulatum (Muller) and Anon hortensis (Frussac). The morphogenesis, histology and ultrastructure of the carrefour and anterior genital ducts have been described and discussed in relation to their function. The carrefour morphology of other slugs has been examined. The limacid carrefour is comparable to the basic stylommatophoran arrangement but in the Anionidae it is much simplified. It is concluded that the Arionidae could be an early offshoot from the main line of stylontmatophoran evolution. Evidence for the environmental control of reproduction in pulmonates has been reviewed. Experimental studies indicate that reproductive development and the onset of maturity are controlled by photoperiod. Short days retard and long days accelerate growth and reproductive development. Subsequent reproductive activity is unaffected by photoperiod. Temperature, humidity and food availability have an immediate effect on egg-laying. In general, conditions favourable to the survival of the embryos enhance egg-production. None of these factors induce courtship and copulation but, generally, adverse conditions are inhibitory. Under apparently constant conditions the animals displayed periods of reproductive activity suggesting an endogenous rhythm. This may contribute to the synchronization of breeding cycles in the field. The behavioural and functional changes during courtship, copulation and egg-laying have been described. During courtship the sperm's movement along the reproductive tract follows a consistent chronological pattern. At copulation the sperm packages are inserted directly into the entrance of the bursa copulatrix, but only sperm released before the package has completely entered the bursa travels up the reproductive tract. This sperm is not stored in the carrefour but passes through into the seminal vesicle where it mixes with the animal's own sperm. At egg-laying the oocytes accumulate in the carrefour although fertilization does not necessarily occur there. The incidence of self-fertilization in the pulmonates is discussed.

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<p> Several types of apparatus have been previously developed to give a constant and measurable interfacial area for solvent extraction. In this work, a new and relatively simple device for this purpose has been tested. The organic phase is allowed to rise or fall freely through the aqueous phase in a tube as a cylindrical "slug". In the mass transfer operation, the "slug" of sparingly-soluble organic liquid is held stationary by the downflow of water. The shrinkage rate of the slug can be measured easily and it gives the experimental mass transfer rate. In order to apply the Higbie penetration theory to the experimental conditions, the interfacial velocity and radius ratio of the slug must be known; these factors can be calculated from the hydrodynamics of the system, using the measured value of slug superficial velocity. Finally, a comparison between experimental and theoretical mass transfer results can be made. 1-butanol shows a good agreement (to within 1%) while 1-pentanol and methyl iso-butyl ketone show less satisfactory agreement due to lack of precise data on their molecular diffusivities in water.</p> / Thesis / Master of Engineering (MEngr)

Orientador: Eugenio Spano Rosa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-11T13:16:35Z (GMT). No. of bitstreams: 1 Duarte_Milvio_M.pdf: 5637497 bytes, checksum: 73a45b46e4f664ad34e8514d8a182db5 (MD5) Previous issue date: 2007 / Resumo: Uma mistura de gás e líquido escoando em um tubo para uma larga faixa de vazões tem as fases gás e líquido distribuídas na tubulação de forma intermitente. Esse padrão é caracterizado por uma sucessão de longas bolhas seguidas de pistões de líquido que não ocorrem com tamanhos e periodicidade definidos devido às interações cinemáticas e dinâmicas que ocorrem entre as bolhas e os pistões de líquido. O comprimento, a velocidade e a freqüência das estruturas gás e líquido formadas são influenciados por diversos parâmetros do escoamento podendo-se citar: as vazões de gás e líquido, o diâmetro da linha, a densidade e a viscosidade dos fluidos entre outros. O presente trabalho tem por objetivo analisar o efeito da variação da viscosidade na caracterização das estruturas gás-líquido. O aparato experimental consiste de um misturador gás-líquido posicionado na entrada da seção de testes. Ela consiste de tubo de acrílico transparente de 23,4 m de comprimento, com 26 mm de diâmetro interno, totalizando 900 diâmetros livres. Dois pares de fluidos são testados: ar e água e ar com uma mistura de glicerina. Tomando-se como referência a viscosidade da água, 1 cP, a mistura de glicerina mais água apresenta uma viscosidade de 27 cP. As medidas instantâneas do escoamento tais como comprimentos, velocidades e freqüências são obtidos por meio de quatro estações de medidas. Elas são compostas por um par de sondas paralelas e estão localizadas a 127, 267, 494 e 777 diâmetros do misturador. Os testes são conduzidos para os mesmos pares de vazões de líquido e gás de forma que os efeitos da alteração da viscosidade do líquido possam ser evidenciados. Os resultados são apresentados em termos de valores médios, dos histogramas das populações e também por meio de correlações a medida que elas evoluem do misturador até a saída da seção de testes revelando de que maneira a mudança da viscosidade influi nestes parâmetros / Abstract: A gas-liquid mixture flowing through a pipe for a large flow range has its gas and liquid phases distributed intermittently along the pipe. This flow pattern is characterized by a succession of elongated bubbles and liquid slugs that do not occur with size and frequency defined due to the interactions between bubbles and liquid slugs. The length, speed and frequency of the gas-liquid structures are influenced by several flow parameters such as: gas and liquid flow rates, pipe diameter, fluids densities and viscosities, among others. The main goal of this work is to analyze the viscosity effect on characterization the gas-liquid structure. The experimental apparatus consists of a gas-liquid mixer located at the inlet of the test section. The test section is transparent acrylic pipe with 26 mm ID 23.4 m long. Two couples of fluids are tested: air-water and airglycerin solution. The water viscosity is of 1 cP, while the water-glycerin solution is of 27 cP viscosity. The lengths, speeds and frequencies of the gas-liquid structures are obtained by four measurement stations positioned along the test section. They are made of a couple of parallel wire probes are located at 127, 267, 494 and 777 diameters from the mixer. The tests are performed employing the same liquid and gas flow rates for both A@W and A@G allowing a straightforward analysis of the viscosity variation effects. The results are presented in terms of mean values, population histograms and also through mathematical correlations about the evolution along the test section, disclosing how the viscosity variation affects those parameters / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

Slug est un membre de la famille des protéines Snail impliquées au cours du développement dans le contrôle de la forme et la différenciation cellulaire. Nous avons localisé Slug au cours du développement des glandes mammaires de souris dans les cellules qui participent aux mécanismes de croissance. Seule une sous-population de cellules épithéliales mammaires située dans le compartiment basal de la glande exprime Slug. Cette expression est maintenue pendant les différentes étapes du développement de la glande mammaire, de la puberté jusqu'au début de la gestation. Nous avons observé une perte d'expression dans lobules se différenciant en alvéoles sécrétoires, ensuite une re-expression au stade d' involution. La population exprimant Slug est positive pour la cytokératine 5, décrit comme un marqueur des cellules basales et myoépithéliales, également considéré comme un marqueur de cellules souches ou progénitrices, et elle est incluse dans la population CD24 positive et surexprimant le CD49, connue pour contenir les cellules souches de l'épithélium mammaire. Nous avons constaté que canaux epithéliaux des glandes mammaires de souris Slug knock-out envahissent moins le coussinet adipeux mammaire. En outre, Ils montrent un phénotype de branchements latéraux, ce qui suggère une différenciation précoce. Ce phénotype ressemble le phénotype des glandes mammaires de souris Knock-out pour la P-cadhérine. Nous avons également constaté une diminution de l'expression de la P-cadhérine in vivo dans les glandes mammaires des souris SlugLaZ, et in vitro, dans les cellules épithéliales mammaires transfectées avec un siARN ciblant Slug. Ces cellules montrent un retard de migration cellulaire. Ces observations valident à notre hypothèse que le facteur de transcription Slug contrôle la différenciation des cellules épithéliales au cours de la croissance physiologique de la glande mammaire murine. / Slug is a member of the Snail protein family involved during development in the control of cell shape and differentiation. We located Slug during mammary gland development in mouse in cells participating to the growth mechanisms. Only a distinct sub-population of mammary epithelial cells located in the basal compartment was found to express Slug. This expression is maintained during the various stages of mammary gland development, from puberty until the beginning of gestation. We observed a loss of expression in lobules differentiating into secreting alveoli, followed by re-expression at involution stage. The Slug expressing population was positive for Cytokeratin 5, described as a basal and myoepithelial cell marker, also considered as a stem/progenitor marker, and was included into the (CD24+ CD49++) population, known to contain the mammary epithelial progenitor cells. We found that mammary gland from Slug-deprived mice were slower to invade the mammary fat pad. In addition, they displayed increased lateral branching, suggesting precocious differentiation. This phenotype resembles the phenotype of mammary glands of P-cadherin Knock-out mice. We also found that P-cadherin is down regulated in vivo in SlugLaZ mice mammary gland, and in vitro, in mammary epithelial cells transfected with an siRNA targeting Slug. These cells show a delay in migration. These observations lead to our hypothesis that Slug controls an early epithelial cell differentiation stage during mammary gland physiological growth.

Epithelial-mesenchymal transition (EMT) is an evolutionarily conserved process during which cells lose epithelial characteristics and gain a migratory phenotype. Although downregulation of epithelial cadherins by Snail and other transcriptional repressors is generally considered a prerequisite for EMT, recent studies have challenged this view. Here we investigate the relationship between E-cadherin and P-cadherin expression and localization, Snail function and EMT during gastrulation in chicken embryos. Expression analyses show that while E-cadherin transcripts are detected in the epiblast but not in the primitive streak or mesoderm, P-cadherin mRNA and protein are present in the epiblast, primitive and mesoderm. Antibodies that specifically recognize E-cadherin are not presently available. During EMT, P-cadherin relocalizes from the lateral surfaces of epithelial epiblast cells to a circumferential distribution in emerging mesodermal cells. Cells electroporated with an E-cadherin expression construct undergo EMT and migrate into the mesoderm. An examination of Snail function showed that reduction of Slug (SNAI2) protein levels using a morpholino fails to inhibit EMT, and expression of human or chicken Snail in epiblast cells fails to induce EMT. In contrast, cells expressing the Rho inhibitor peptide C3 rapidly exit the epiblast without activating Slug or the mesoderm marker N-cadherin. Together, these experiments show that epiblast cells undergo EMT while retaining P-cadherin, and raise questions about the mechanisms of EMT regulation during avian gastrulation.