Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 136-153). Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 136-153). Also available online.

Orientador: Kleber Gomes Franchini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-11T13:44:01Z (GMT). No. of bitstreams: 1 Oliveira_MichelVazde_M.pdf: 1365391 bytes, checksum: a8c1dd22f85ed3c7df93982f678f95f7 (MD5) Previous issue date: 2008 / Resumo: Os mioblastos que formam o músculo esquelético são derivados de regiões do miótomo dos somitos. No processo de miogênese ocorre transição de estado proliferativo para um estado de diferenciação que se caracteriza por interrupção do ciclo celular, expressão de genes músculo-específico, reconhecimento célula-célula e formação de miotubos multinucleados. Para o estudo de diferenciação miogênica in vitro a linhagem celular C2C12 é um modelo bem estabelecido. Quando os mitógenos são retirados do meio de cultura (privação de soro fetal bovino), fatores de transcrição específicos são ativados, levando à diferenciação em miotubos. Na progressão do estado proliferativo para o de diferenciação participam diversas proteínas sinalizadoras. Em estudos anteriores demonstramos que a modulação da atividade da FAK tem papel crítico no processo de miogênese de células C2C12. Níveis relativamente elevados de atividade da FAK determinam a manutenção do estado proliferativo (indiferenciado) através de ativação de ciclinas. Também demonstramos que redução transitória da atividade da FAK é essencial para que as mioblastos C2C12 iniciem o processo de diferenciação terminal em miotubos. No presente estudo foi avaliada a hipótese de que a ação da tirosino-fosfatase SHP-2 determina a redução transitória da quinase de adesão focal (FAK) na transição do estado proliferativo para o estado de diferenciação no modelo de miogênese em células C2C12. A privação do soro fetal bovino induziu uma redução transiente (cerca de 80 % por ~2 horas) da fosforilação da FAK no resíduo de Tyr-397, detectada através de anticorpo fosfoespecífico anti-FAK-pY397. Não foi observada mudança na expressão da proteína FAK durante o período experimental. Experimentos de co-imunoprecipitação foram realizados para avaliar se a redução do nível de fosforilação da FAK é acompanhada de sua associação com SHP-2. Observou-se aumento de cerca de 2 vezes na associação entre FAK e SHP-2 no período coincidente com os nível baixos de fosforilação da FAK. Para avaliar o efeito da SHP-2 na redução transitória da pFAK padronizou-se o silenciamento de SHP-2 em células C2C12 nos estados de proliferação e diferenciação. Após a transfecção com siRNASHP2 nas células C2C12 foi feita a extração total de proteínas em diferentes tempos para avaliar o nível de expressão da SHP-2 no estado de proliferação. Foi observada menor expressão desta proteína após 12 horas ao período de transfecção. Depois da transfecção em meio de cultivo com o silenciamento de SHP-2 padronizados em 12 horas as células foram induzidas a se diferenciarem através da privação de soro fetal bovino. A depleção de SHP-2 aboliu a redução transiente da fosforilação da FAK. Observou-se que a depleção de SHP-2 também impediu a diferenciação terminal dos mioblastos privados de soro fetal bovino em miotubos. Esses dados sugerem que a SHP-2 modula o nível de fosforilação da FAK exercendo papel inibitório na ativação da FAK na transição das células C2C12 no estado de proliferação para diferenciação, influenciando a entrada destas células na diferenciação / Abstract: The myoblasts that form the skeletal muscle are derived from regions of the myotome of somites. In the process of myogenesis occurs transition of proliferative status to a state of differentiation which is characterised by disruption of the cell cycle, expression of muscle-specific genes, cell-cell recognition and training of myotubes multinucleate. For the study of the in vitro differentiation myogenic cell line C2C12 is a model well established. Where mitogens are moved from the culture medium (deprivation of fetal bovine serum), specific transcription factors are activated, leading to the differentiation in myotubes. The progression to the proliferative status of differentiation are involves several signaling proteins. In previous studies we showed that the modulation of the activity of FAK plays a critical role in the process of myogenesis of C2C12 cells. Relatively high levels of activity of FAK determine the maintenance of the state proliferative (indistinct) through activation of cyclin. It also demonstrated that transient reduction of the activity of FAK is essential for the myoblasts C2C12 begin the process of terminal differentiation in myotubes. In the present study was evaluated the hypothesis that the action of tirosino-phosphatase SHP-2 determines the reduction of transient focal membership of kinase (FAK) in the transition of proliferative state to the state of differentiation in the model of miogênese in C2C12 cells. The deprivation of fetal bovine serum produces a transient reduction (about 80% by ~ 2 hours) of the phosphorylation of FAK in the residue of Tyr-397, detected by antibody phsphoespecific anti-FAK-pY397. No change was observed in the expression of FAK protein during the trial period. Coimmunoprecitation experiments were performed to evaluate whether the reduction in the level of phosphorylation of FAK is accompanied by its association with SHP-2. There was an increase of about 2 times in the association between FAK and SHP-2 in the period coinciding with the low level of phosphorylation of FAK. To evaluate the effect of SHP-2 on the reduction of transient pFAK standardized up the silencing of SHP-2 in C2C12 cells in the states of proliferation and differentiation. It was observed lower expression of this protein after 12 hours the period of transfection. After Transfection in the midst of cultivation with the silencing of SHP-2 standard in 12 hours the cells were induced to differentiate by deprivation of fetal bovine serum. The depletion of SHP-2 abolished the reduction of transient phosphorylation of FAK. It was observed that the depletion of SHP-2 also prevented the terminal differentiation of myoblasts deprived of fetal bovine serum in myotubes. These data suggest that SHP-2 modulates the level of phosphorylation of FAK acting inhibitory role in the activation of FAK in the transition of C2C12 cells in the state of proliferation to differentiation, influencing the entry of these cells in the differentiation / Mestrado / Ciencias Basicas / Mestre em Clinica Medica

Durant leur cycle de vie, les organismes sont exposés à des variations environnementales capables d'induire des changements physiologiques, morphologiques et comportementaux, résultant d’une plasticité phénotypique. La plasticité phénotypique est la capacité d'un génotype à générer un nouveau phénotype suite à un stress. Ici, nous avons étudié la plasticité phénotypique d’un Cnidaire symbiotique et non-calcifiant, l’anémone de mer Anemonia viridis, à de multiples niveaux de complexité structurale, in vivo et in vitro. In vivo, nous avons identifié les mécanismes sous-jacents de la plasticité phénotypique potentiellement induits par les futurs changements climatiques (acidification et réchauffement des océans). Nos résultats montrent des modifications dans l'utilisation du carbone inorganique par A. viridis exposée à une forte pCO2 lors d’un stress chronique in natura ou lors d’un stress court en conditions contrôlées. Nous avons ainsi observé une diminution des activités anhydrase carbonique, une enzyme clé des mécanismes de concentration du carbone chez les Cnidaires. Nous avons aussi démontré que l'augmentation concomittante de la température modifie la réponse observée lors d'une élévation seule de la pCO2. In vitro, nous avons établi une culture de cellules primaires viables issue de tentacules d’A. viridis en régénération. Nous avons déterminé l'origine gastrodermale des cellules cultivées et validé l'utilisation de ce nouvel outil pour l'étude de la réponse au stress au niveau cellulaire. Ce nouvel outil ouvre une multitude de perspectives pour l'étude des réponses cellulaires aux stress exogènes (changement climatique) et endogènes (contraintes dues à la symbiose) / During the course of their life cycle organisms are exposed to natural environment variations capable of inducing physiological, morphological and behaviour changes, thus a phenotypic plasticity. Phenotypic plasticity is the ability of a genotype to generate a new phenotype following exogeneous or endogeneous stress. Here, we investigated the phenotypic plasticity of the non-calcifying symbiotic cnidarian Anemonia viridis at multiple levels of structural complexity, in vivo and in vitro. In vivo, we determined the mechanisms behind the phenotypic plasticity under expected future climate change (i.e. ocean acidification and ocean warming). Our results show physiological changes in the inorganic carbon use of the sea anemone A. viridis exposed to high pCO2 during a long-term stress in natura or a short-term stress in controlled conditions. We then observed an equivalent decrease in carbonic anhydrase activity, a key enzyme of cnidarian carbon concentrating mechanisms. Also, we demonstrated that an increase in seawater temperature modified the response observed during a high pCO2 scenario. In vitro, we established a viable primary cell culture from regenerating tentacles of A. viridis. We determined the gastrodermal tissue origin of the cultivated cells and validated the use of this new tool to the in vitro study of stress response at the cellular level. The set-up of this powerful in vitro tool will open a multitude of perspectives for the study of cellular responses to exogeneous stress (as global change perturbations) and to endogeneous stress (as the symbiosis constraints experienced by symbiotic cnidarians)

O splicing do pré- RNAm é o processo pelo qual os introns são removidos e os exons são unidos para produzir um RNAm maduro. Esse processo é catalisado por um complexo denominado spliceossomo. RNF113A é uma proteína detectada em complexos pré- e pós-catalíticos. Neste trabalho analisamos a participação de RNF113A no spliceossomo de mamíferos e suas interações com outros componentes do spliceosomo. Nossos resultados mostraram que a super- expressão de RNF113A em células HEK293T aumentam o nível dos snRNAs U1, U2, U5 e U6 e de PRPF19. A imunoprecipitação de RNF113A revelou maior concentração de PRPF19, hBRR2 e SF3b2. Além disso, observamos maior quantidade dos snRNAs U5 e U6 associados à RNF113A. As frações de imunoprecipitação foram analisadas por espectrometria de massas e mostraram interação de RNF113A com proteínas que participam na transcrição, ubiquitinação, maturação do pré-RNAm e splicing. Estes resultados indicam que a associação de RNF113A ao spliceossomo ocorre a partir de suas interações com os snRNAs U5 e U6 e com proteínas relacionadas, como a hBRR2. / Splicing of pre-mRNA is the process by which introns are removed and exons are joined together to produce a mature mRNA competent for translation. It is catalyzed by the complex called spliceosome. RNF113A is a protein detected in pre- and post-catalytic complexes. In this work we analyzed RNF113A participation on spliceosome and its interactions with other spliceosome components. Our results showed that overexpression of RNF113A in HEK293T led to increased levels of U1, U2, U5, U6 snRNAs and PRPF19. RNF113A also associates to PRPF19, hBRR2 and SF3b2, as observed by immunoprecipitation followed by RT-qPCR and western blot. Consistently, U5 and U6 snRNAs were observed in association with RNF113A. Immunoprecipitation fractions were also analyzed by mass spectrometry and results showed interaction of RNF113A with proteins that participate in processes such as transcription, ubiquitination, pre-mRNA maturation and splicing. These results suggest RNF113A associates to spliceosome by interacting with U5 and U6 snRNAs and with related proteins, for example hBRR2.

O mecanismo de ação de fotossensibilizadores (FS) fenotiazínicos (azul de metileno - AM, tionina - TIO e azure B - AB) foi estudado em mitocôndrias e células Hela, e a dosimetria de AM em células HL60. Foi observado que a ligação de AM em mitocôndrias é dependente da concentração de mitocôndrias, concentração de AM e do potencial de membrana mitocondrial (Δ Ψ). A geração de oxigênio singlete a partir de AM é influenciada pelo Δ Ψ, sendo aproximadamente o dobro em mitocôndrias desacopladas. Essa variação se deve a influência do Δ Ψ sobre a relação dímero/monômero (D/M) do AM. A ligação de AM também é reduzida pela metade em mitocôndrias desacopladas. Esses efeitos não foram observados para os outros fotossensibilizadores, embora tenham a mesma carga e estrutura semelhante. Isso indica um efeito diferencial do Δ Ψ sobre o AM. Foi observada a toxicidade desses FSs em células Hela. Sem irradiação, apenas AB se mostrou tóxico. Em amostras irradiadas, AB e AM se mostraram tóxicos. Todos os FSs mostraram capacidade de produzir núcleos sub-diplóides, típicos de apoptose, com a maior eficiência sendo do AB. Em relação a toxicidade no escuro e claro, AB mostrou toxicidade em ambas as condições, TIO mostrou pouca toxicidade em ambas as condições e AM mostrou pouca toxicidade no escuro e alta toxicidade quando irradiado. A dosimetria que favorece apoptose em células HL60 também foi testada, sendo que µM de AM, os melhores resultados para formação de núcleos sub-diplóides foram com 10 2 com irradiação (contínua ou fracionada) de 0,55 J/cm2 . Essas dosagens foram as mais baixas utilizadas, indicando que um aumento na concentração de FS ou de luz tende a levar as células à morte necrótica. Conclui-se que os FSs fenotiazínicos tem afinidade por mitocôndrias e por células, podendo levar a indução de apoptose em doses não tóxicas no escuro. / The mechanism of action of phenotiazinic fotossensitizers (FS) (methylene blue - AM, tionin - TIO and azure B - AB) was studied into mitochondria and Hela cells, and AM dosimetry into HL60 cells was determined. AM binding to mitochondria is dependent of mitochondrial concentration, AM concentration and mitochondrial membrane potentials (Δ Ψ). Singlet oxygen generation from AM is influenced by Δ Ψ, almost doubling in uncoupled mitochondria. This effect is due to the influence of Δ Ψ on AM dimer/monomer (D/M) ratio. Also, AM binding drops to half into uncoupled mitochondria. For all the others FSs studied, these effects were not observed, even though they present the same Δ Ψ action over AM. charge and similar structure. This indicates a specific FSs toxicity was observed in Hela cells. In the dark, only AB showed toxicity. In irradiated samples, AM and AB showed toxicity. All the tested FSs showed capacity to induce sub-diploid nuclei formation, a hallmark of apoptosis, with AB showing the highest efficiency. AB showed high toxicity in both (irradiated and non-irradiated) conditions, TIO showed low toxicity in both conditions and AM showed low toxicity in the dark and high toxicity with laser irradiation. The dose that promotes apoptotic cell death in HL60 cells was also tested. Results 2 were observed at 10 µM AM, with laser irradiation (fraction or continuous) of 0,55 J/cm . These doses were the lowest doses tested, indicating that high doses of FS or laser induce necrotic cell death. We conclude that phenotiazinic FSs have affinity for mitochondria and cells, and induce apoptosis at doses that are not toxic without irradiation

O mecanismo de ação de fotossensibilizadores (FS) fenotiazínicos (azul de metileno - AM, tionina - TIO e azure B - AB) foi estudado em mitocôndrias e células Hela, e a dosimetria de AM em células HL60. Foi observado que a ligação de AM em mitocôndrias é dependente da concentração de mitocôndrias, concentração de AM e do potencial de membrana mitocondrial (Δ Ψ). A geração de oxigênio singlete a partir de AM é influenciada pelo Δ Ψ, sendo aproximadamente o dobro em mitocôndrias desacopladas. Essa variação se deve a influência do Δ Ψ sobre a relação dímero/monômero (D/M) do AM. A ligação de AM também é reduzida pela metade em mitocôndrias desacopladas. Esses efeitos não foram observados para os outros fotossensibilizadores, embora tenham a mesma carga e estrutura semelhante. Isso indica um efeito diferencial do Δ Ψ sobre o AM. Foi observada a toxicidade desses FSs em células Hela. Sem irradiação, apenas AB se mostrou tóxico. Em amostras irradiadas, AB e AM se mostraram tóxicos. Todos os FSs mostraram capacidade de produzir núcleos sub-diplóides, típicos de apoptose, com a maior eficiência sendo do AB. Em relação a toxicidade no escuro e claro, AB mostrou toxicidade em ambas as condições, TIO mostrou pouca toxicidade em ambas as condições e AM mostrou pouca toxicidade no escuro e alta toxicidade quando irradiado. A dosimetria que favorece apoptose em células HL60 também foi testada, sendo que µM de AM, os melhores resultados para formação de núcleos sub-diplóides foram com 10 2 com irradiação (contínua ou fracionada) de 0,55 J/cm2 . Essas dosagens foram as mais baixas utilizadas, indicando que um aumento na concentração de FS ou de luz tende a levar as células à morte necrótica. Conclui-se que os FSs fenotiazínicos tem afinidade por mitocôndrias e por células, podendo levar a indução de apoptose em doses não tóxicas no escuro. / The mechanism of action of phenotiazinic fotossensitizers (FS) (methylene blue - AM, tionin - TIO and azure B - AB) was studied into mitochondria and Hela cells, and AM dosimetry into HL60 cells was determined. AM binding to mitochondria is dependent of mitochondrial concentration, AM concentration and mitochondrial membrane potentials (Δ Ψ). Singlet oxygen generation from AM is influenced by Δ Ψ, almost doubling in uncoupled mitochondria. This effect is due to the influence of Δ Ψ on AM dimer/monomer (D/M) ratio. Also, AM binding drops to half into uncoupled mitochondria. For all the others FSs studied, these effects were not observed, even though they present the same Δ Ψ action over AM. charge and similar structure. This indicates a specific FSs toxicity was observed in Hela cells. In the dark, only AB showed toxicity. In irradiated samples, AM and AB showed toxicity. All the tested FSs showed capacity to induce sub-diploid nuclei formation, a hallmark of apoptosis, with AB showing the highest efficiency. AB showed high toxicity in both (irradiated and non-irradiated) conditions, TIO showed low toxicity in both conditions and AM showed low toxicity in the dark and high toxicity with laser irradiation. The dose that promotes apoptotic cell death in HL60 cells was also tested. Results 2 were observed at 10 µM AM, with laser irradiation (fraction or continuous) of 0,55 J/cm . These doses were the lowest doses tested, indicating that high doses of FS or laser induce necrotic cell death. We conclude that phenotiazinic FSs have affinity for mitochondria and cells, and induce apoptosis at doses that are not toxic without irradiation

En aquest estudi, la toxicitat de diversos metalls pesants i l'arsènic va ser analitzada utilitzant diferents models biològics.En la primera part d'aquest treball, el bioassaig de toxicitat Microtox, el qual està basat en la variació de l'emissió lumínica del bacteri luminiscent Vibrio fischeri, va ser utilitzat per establir les corbes dosi-resposta de diferents elements tòxics com el Zn(II), Pb(II), Cu(II), Hg(II), Ag(I), Co(II), Cd(II), Cr(VI), As(V) i As(III) en solucions aquoses. Els experiments es varen portar a terme a pH 6.0 i 7.0 per tal de mostrar que el pH pot influir en la toxicitat final mesurada d'alguns metalls degut als canvis relacionats amb la seva especiació química. Es varen trobar diferents tipus de corbes dosi-resposta depenent del metall analitzat i el pH del medi. En el cas de l'arsènic, l'efecte del pH en la toxicitat de l'arsenat i l'arsenit es va investigar utilitzant l'assaig Microtox en un rang de pHs comprès entre pH 5.0 i 9.0. Els valors d'EC50 determinats per l'As(V) disminueixen, reflectint un augment de la toxicitat, a mesura que el pH de la solució augmenta mentre que, en el cas de l'As(III), els valors d'EC50 quasi bé no varien entre pH 6.0 i 8.0 i només disminueixen a pH 9.0. HAsO42- i H2AsO3- es varen definir com les espècies més tòxiques. Així mateix, una anàlisi estadística va revelar un efecte antagònic entre les espècies químiques d'arsenat que es troben conjuntament a pH 6.0 i 7.0.D'altra banda, els resultats de dos mètodes estadístics per predir la toxicitat i les possibles interaccions entre el Co(II), Cd(II), Cu(II), Zn(II) i Pb(II) en mescles binàries equitòxiques es varen comparar amb la toxicitat observada sobre el bacteri Vibrio fischeri. L'efecte combinat d'aquests metalls va resultar ser antagònic per les mescles de Co(II)-Cd(II), Cd(II)-Zn(II), Cd(II)-Pb(II) i Cu(II)-Pb(II), sinèrgic per Co(II)-Cu(II) i Zn(II)-Pb(II) i additiu en els altres casos, revelant un patró complex de possibles interaccions. L'efecte sinèrgic de la combinació Co(II)-Cu(II) i la forta disminució de la toxicitat del Pb(II) quan es troba en presència de Cd(II) hauria de merèixer més atenció quan s'estableixen les normatives de seguretat ambiental.La sensibilitat de l'assaig Microtox també va ser determinada. Els valors d'EC20, els quals representen la toxicitat llindar mesurable, varen ser determinats per cada element individualment i es va veure que augmenten de la següent manera: Pb(II) < Ag(I) < Hg(II) &#61627; Cu(II) < Zn(II) < As(V) < Cd(II) &#61627; Co(II) < As(III) < Cr(VI). Aquests valors es varen comparar amb les concentracions permeses en aigues residuals industrials establertes per la normativa oficial de Catalunya (Espanya). L'assaig Microtox va resultar ser suficientment sensible per detectar els elements assajats respecte a les normes oficials referents al control de la contaminació, excepte en el cas del cadmi, mercuri, arsenat, arsenit i cromat. En la segona part d'aquest treball, com a resultats complementaris dels resultats previs obtinguts utilitzant l'assaig de toxicitat aguda Microtox, els efectes crònics del Cd(II), Cr(VI) i As(V) es varen analitzar sobre la taxa de creixement i la viabilitat en el mateix model biològic. Sorprenentment, aquests productes químics nocius varen resultar ser poc tòxics per aquest bacteri quan es mesura el seu efecte després de temps d'exposició llargs. Tot i això, en el cas del Cr(VI), l'assaig d'inhibició de la viabilitat va resultar ser més sensible que l'assaig de toxicitat aguda Microtox. Així mateix, també va ser possible observar un clar fenomen d'hormesis, especialment en el cas del Cd(II), quan s'utilitza l'assaig d'inhibició de la viabilitat. A més a més, diversos experiments es varen portar a terme per intentar explicar la manca de toxicitat de Cr(VI) mostrada pel bacteri Vibrio fischeri. La resistència mostrada per aquest bacteri podria ser atribuïda a la capacitat d'aquest bacteri de convertir el Cr(VI) a la forma menys tòxica de Cr(III). Es va trobar que aquesta capacitat de reducció depèn de la composició del medi de cultiu, de la concentració inicial de Cr(VI), del temps d'incubació i de la presència d'una font de carboni. En la tercera part d'aquest treball, la línia cel·lular humana HT29 i cultius primaris de cèl·lules sanguínies de Sparus sarba es varen utilitzar in vitro per detectar la toxicitat llindar de metalls mesurant la sobreexpressió de proteines d'estrès. Extractes de fangs precedents de diverses plantes de tractament d'aigues residuals i diferents metalls, individualment o en combinació, es varen analitzar sobre cultius cel·lulars humans per avaluar el seu efecte sobre la taxa de creixement i la capacitat d'induir la síntesi de les proteïnes Hsp72 relacionades amb l'estrès cel·lular. No es varen trobar efectes adversos significatius quan els components s'analitzen individualment. Nogensmenys, quan es troben conjuntament, es produeix un afecte advers sobre tan la taxa de creixement com en l'expressió de proteins d'estrès. D'altra banda, cèl·lules sanguínies procedents de Sparus sarba es varen exposar in vitro a diferents concentracions de cadmi, plom i crom. La proteïna d'estrès HSP70 es va sobreexpressar significativament després de l'exposició a concentracions tan febles com 0.1 &#61549;M. Sota les nostres condicions de treball, no es va evidenciar una sobreexpressió de metal·lotioneïnes. Nogensmenys, les cèl·lules sanguínies de peix varen resultar ser un model biològic interessant per a ser utilitzat en anàlisis de toxicitat. Ambdós models biològics varen resultar ser molt adequats per a detectar acuradament la toxicitat produïda per metalls. En general, l'avaluació de la toxicitat basada en l'anàlisi de la sobreexpressió de proteïnes d'estrès és més sensible que l'avaluació de la toxicitat realitzada a nivell d'organisme.A partir dels resultats obtinguts, podem concloure que una bateria de bioassaigs és realment necessària per avaluar acuradament la toxicitat de metalls ja que existeixen grans variacions entre els valors de toxicitat obtinguts emprant diferents organismes i molts factors ambientals poden influir i modificar els resultats obtinguts. / In this study, the toxicity of some metals and arsenic was investigated using three different biological models. In the first part of this work, the Microtox® bioassay, which is based on variation in light emission by Vibrio fischeri luminescent bacteria, was used to establish dose-response curves for several toxic elements, namely, Zn(II), Pb(II), Cu(II), Hg(II), Ag(I), Co(II), Cd(II), Cr(VI), As(V), and As(III), in aqueous solutions. Experiments were carried out at either pH 6.0 or pH 7.0 to indicate that pH may influence the measured toxicity of some elements due to pH-related changes in their chemical speciation. Different types of dose-response curves were found depending on the analyzed metal and pH. In the case of arsenic, effect of pH on either arsenate or arsenite toxicity, was investigated using the Microtox® bioassay within a 5.0 - 9.0 pH range. EC50 values for As(V) were found to decrease, reflecting an increase in toxicity, as pH became basic, whereas in the case of As(III), EC50 values were almost unchanged within a 6.0 - 8.0 pH range and lowered at pH 9.0 only. HAsO42- and H2AsO3- were found to be the most toxic species. A statistical approach revealed an antagonistic effect between the arsenate chemical species found in combination at pH 6.0 or 7.0.On the other hand, results from two mathematical approaches to predict the toxicity of all the possible binary equitoxic mixtures of Co(II), Cd(II), Cu(II), Zn(II), and Pb(II) were compared to the observed toxicity of these mixtures to Vibrio fischeri bacteria. Combined effect of the metals was found to be antagonistic for Co(II)-Cd(II), Cd(II)-Zn(II), Cd(II)-Pb(II), and Cu(II)-Pb(II), synergistic for Co(II)-Cu(II) and Zn(II)-Pb(II) and merely additive in other cases, revealing a complex pattern of possible interactions. The synergistic effect of the Co(II)-Cu(II) combination and the strong decrease of Pb(II) toxicity when in the presence of Cd(II) should deserve much attention when establishing environmental safety regulations. Microtox bioassay sensitivity was also analyzed. EC20 values, which represent a measurable threshold of toxicity, were determined for each element individually and were found to rank as Pb(II) < Ag(I) < Hg(II) &#61627; Cu(II) < Zn(II) < As(V) < Cd(II) &#61627; Co(II) < As(III) < Cr(VI). These values were compared to the concentration levels allowed in industrial wastewater according to the official regulations in Catalonia (Spain). It appears that the Microtox® test is sensitive enough to detect the tested elements with respect to official regulations dealing with pollution control, with the exception of cadmium, mercury, arsenate, arsenite and chromate.In the second part of this work, as a complement to previous results obtained using the standard Microtox® acute toxicity test, the long-term effects of Cd(II), Cr(VI), and As(V) were studied on growth rate and viability of the same biological model. Surprisingly, these poisonous chemicals were found not to be very toxic to these bacteria when measuring their effect on viability or growth after long periods of exposure. Nevertheless, in the case of Cr(VI), the inhibition viability assay resulted to be more sensitive than the Microtox acute toxicity test was. Interestingly, it was possible to observe a clear hormesis phenomenon, especially for Cd(II), under the conditions of the viability assay. In addition, several experiments were performed as an attempt to explain the lack of Cr(VI) toxicity shown by Vibrio fischeri bacteria. The resistance shown by Vibrio fischeri bacteria could be attributed to the capacity of the bacteria to convert Cr(VI) ions into less toxic Cr(III) ions. This capacity of reduction was found to depend on culture medium composition, initial concentration of chromium, incubation time, and the presence of a carbon source. In the third part of this work, the HT29 human cell line and primary cultures of Sparus sarba blood cells were used in vitro to detect metal toxicity thresholds by measuring the overexpression of stress proteins. Sludge extracts from several wastewater treatment plants and metals, individually or in combination, were tested on human cultured cells for evaluating their ability to affect the growth rate and trigger a synthesis of the stress-related HSP72i proteins. No significant adverse effects were found when given individually. When given in combination, they were however found to affect both cell growth and stress proteins expression. On the other hand, blood cells freshly collected from Sparus sarba were exposed in vitro to different concentrations of cadmium, lead or chromium(VI). HSP70 stress protein was significantly overexpressed after exposure to a metal concentration as low as 0.1 µM. Under our experimental conditions, no overexpression of metallothioneins was evidenced. Nevertheless, fish blood cells appear as an interesting biological model for experimental toxicology.Both biological models were found convenient to detect toxicity produced by metals. In general, evaluation of toxicity based on stress proteins overexpression was found to be more sensitive than evaluation of toxicity performed at the organism level.Based on the results, it can be concluded that a battery of bioassays is necessary to accurately evaluate toxicity of metals since important variations between different organisms can be found and a lot of environmental factors may influence as well as modify the obtained results.