Malignant gliomas are the most common primary brain tumors in adults. Patients with these highly malignant tumors have an extremely poor prognosis. The situation with a highly proliferative tumor in a non-proliferating tissue should favor cytostatic treatment but so far the role of conventional chemotherapy has been adjunctive. The concentrations of three sex steroids, estradiol, progesterone and testosterone, were analyzed by radioimmunoassay after celite chromatography in brain tumor samples. Some malignant gliomas had high tissue concentrations of estradiol. Low progesterone levels may suggest steroid consumption. Estramustine (EM), a conjugate of estradiol-17ß and nornitrogen mustard had a dose-dependent antiproliferative effect on several human malignant glioma cell lines. At equimolar concentrations the inhibitory effects of the EM complex were clearly more pronounced than those of estradiol and nornitrogen mustard given alone or in combination. A specific binding protein (EMBP) is important for the cytotoxic action of EM. Using a mouse monoclonal antibody and an indirect antibodyperoxidase technique, EMBP was demonstrated in human glioma cells. Significant amounts of EMBP were also detected in human brain tumor tissue by radioimmunoassay. The mean concentrations (ng/mg protein) in 16 astrocytomas (2.6) and 7 meningiomas (5.1) were higher (p&lt;0.001) than in 18 samples of normal brain (0.5). The presence of the specific binding protein may suggest a selective binding and effect of EM in human brain tumor tissue. Human glioma cells displayed significant uptake, retention and metabolism of estramustine phosphate (EMP). After incubation with ^H-EMP a progressive uptake of radioactivity was recorded during 24 hours. Metabolism of parent EMP into estramustine and estromustine, which is a well known part of the metabolic pathway in man, was also demonstrated. A dose- dependent increase in DNA strand breaks was recorded at EMP- concentrations ranging 10-40 yg/ml. The uptake of ®^Rb, used as a tracer for potassium to study ion transport and membrane permeability, was reduced after incubation with EMP. Scanning electron microscopy gave further evidence for membrane damage. According to flow cytometric analyses exponentially growing glioma cells were accumulated in the G2/M stage and the fraction of Gi/Gq was reduced. EM seems to attack malignant cells in a multifocal fashion on several vital functions including the microtubule, the nucleus, and the cell membrane. The intact EM complex may be important for effects related to microtubule function which add to the cytotoxic potential of its constituents. These experimental findings justify further investigations on the role of sex hormones in brain tumor growth and development and of hormone-linked cytostatics in clinical treatment. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1990, härtill 6 uppsatser.</p> / digitalisering@umu

Thesis (M.S.)--University of Missouri-Columbia, 2007. / "August 2007" The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Includes bibliographical references.

Thesis (Ph. D.) -- University of Texas Southwestern Medical Center at Dallas, 2004. / Vita. Bibliography: 150-177.

Thesis (Ph.D. in Cell Biology, Stem Cells, & Development) -- University of Colorado Denver, 2008. / Typescript. Includes bibliographical references (leaves 138-155). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;

Thesis (Ph.D.)--University of Toledo, 2006. / "In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biomedical Sciences." Major advisor: Zi-Jian Xie. Includes abstract. Document formatted into pages: iii, 156 p. Title from title page of PDF document. Bibliography: pages 64-67, 97-100, 116-117, 125-155.

INTRODUÇÃO: As malformações do desenvolvimento cortical (MDC) resultam de distúrbios no dinâmico processo de corticogênese cerebral e são importante causa de epilepsia grave, atraso do desenvolvimento, déficits motores e cognitivos. O papel do metabolismo na epilepsia humana tem sido extensamente debatido, e há inúmeras evidências que apontam para disfunções bioenergéticas como fatores-chave na ictogênese. Distúrbios metabólicos foram identificados nas malformações corticais com outras modalidades de neuroimagem, tais como a espectroscopia de prótons por ressonância magnética. Para o nosso conhecimento, entretanto, o metabolismo de fósforo em pacientes com epilepsia secundária a MDC não foi extensamente investigado até o momento. OBJETIVOS: O objetivo deste estudo foi avaliar o metabolismo de fosfolipídios in vivo em uma série de pacientes com epilepsia e MDC. MÉTODO: Trinta e sete pacientes com MDC e 31 voluntários foram estudados usando espectroscopia de fósforo por ressonância magnética (31P-ERM) tridimensional em aparelho de 3,0 Tesla. Os voxels nas lesões foram comparados ao córtex frontoparietal dos controles (volumes efetivos de 12,5 cm3). O parênquima aparentemente normal foi avaliado em voxels homólogos de pacientes e controles, abrangendo cinco regiões cerebrais: regiões nucleocapsulares direita e esquerda, córtex frontoparietal parassagital, e centros semiovais direito e esquerdo. Foram utilizados métodos de quantificação para ajustar os dados no domínio do tempo para as seguintes ressonâncias: fosfoetanolamina (PE), fosfocolina (PC), glicerofosfoetanolamina (GPE), glicerofosfocolina (GPC), fosfato inorgânico (Pi), fosfocreatina (PCr), e a-, b- e g-adenosina trifosfato (ATP). Também foram calculados o ATP total (ATPt=a-+b-+g-ATP), fosfodiésteres (PDE=GPC+GPE), fosfomonoésteres (PME=PE+PC), e as razões PME/PDE, PCr/ATPt, e PCr/Pi. O magnésio (Mg2+) e os níveis de pH foram calculados com base nos desvios químicos da PCr, Pi, e -ATP. RESULTADOS: Comparativamente aos controles, e assumindo um valor de p < 0,05 estatisticamente significativo, as lesões apresentaram redução dos valores de pH e aumento de Mg2+. Também foram encontrados redução significativa de GPC e PDE, e aumento da relação PME/PDE nas MDC. O parênquima aparentemente normal também demonstrou redução dos valores de pH no córtex frontoparietal e no centro semioval bilateral. As diferenças nos valores de pH, tanto nas lesões como no parênquima aparentemente normal, permaneceram estatisticamente significativas nos subgrupos individuais de MDC (displasia cortical ou hemimegalencefalia; heterotopia; polimicrogiria e/ou esquizencefalia). Não houve correlação entre o tempo da última convulsão e as alterações do pH. CONCLUSÕES: O Mg2+ e o pH são parâmetros muito importantes na regulação bioenergética e estão envolvidos em múltiplas vias da atividade elétrica cerebral. Nossos dados corroboram a ideia de que distúrbios metabólicos ocorrem nas lesões focais de MDC, com propagação para áreas remotas aparentemente normais. As anormalidades de GPC, PDE, e da razão PME/PDE sugerem que há deficiências na renovação das membranas celulares nas lesões dos pacientes com epilepsia e MDC. / INTRODUCTION: Malformations of cortical development (MCD) result from disruptions in the dynamic process of cerebral corticogenesis and are important causes of severe epilepsy, neurodevelopmental delay, motor deficits and cognitive impairment. Metabolism in human epilepsy has been intensely debated, and there are several evidences pointing to brain bioenergetic disturbances as key factors in ictogenesis. Metabolic impairments in cortical malformations have been identified with other neuroimaging tools, such as proton magnetic resonance spectroscopy. To our knowledge, however, phosphorus metabolism in epilepsy caused by MCD has not been thoroughly investigated hitherto. OBJECTIVES: The aim of this study was to evaluate phospholipids metabolism in vivo in a series of patients with epilepsy and MCD. METHODS: Thirty-seven patients with MCD and 31 control subjects were studied using three-dimensional phosphorus magnetic resonance spectroscopy (31P-MRS) at a 3.0 T scanner. The voxels in the lesions were compared to the frontoparietal cortex of the control subjects (the effective volumes were 12.5 cm3). Normal appearing parenchyma was evaluated in homologous voxels of patients and controls encompassing five cerebral regions: right and left nucleocapsular regions, midline frontoparietal cortex and right and left semioval centers. Quantification methods were applied to fit the time-domain data to the following resonances: phosphoethanolamine (PE), phosphocholine (PC), glycerophosphoethanolamine (GPE), glycerophosphocholine (GPC), inorganic phosphate (Pi), phosphocreatine (PCr), and a-, b-, and g-adenosine triphosphate (ATP). We also estimated the total ATP (ATPt=a-+b-+g-ATP), phosphodiesters (PDE=GPC+ GPE), phosphomonoesters (PME=PE+PC), and the PME/PDE, PCr/ATPt, and PCr/Pi ratios. The magnesium (Mg2+) levels and pH were calculated based on PCr, Pi, and -ATP chemical shifts. RESULTS: Compared to controls and assuming that a p-value < 0.05 indicates significance, the MCD lesions exhibited lower pH values and higher Mg2+ levels. The lesions also presented significant reduction of GPC and PDE, and an increased PME/PDE ratio. The otherwise normal appearing parenchyma also demonstrated lower pH values in the frontoparietal cortex and bilateral centrum semiovale. The differences in pH values, both in the lesions and in the normal appearing parenchyma, remained statistically significant in individual subgroups of MCD (hemimegalencephaly or cortical dysplasia; heterotopia; polymicrogyria and/or schizencephaly). There was no correlation between the time of the last seizure and the pH abnormalities. CONCLUSIONS: Mg2+ and pH are very important in the regulation of bioenergetics and are involved in many electrical activity pathways in the brain. Our data support the idea that metabolic impairments occur in the lesions of MCD, with propagation to remote normal appearing parenchyma. The GPC, PDE, and PME/PDE abnormalities suggest that there are membrane turnover disturbances in MCD lesions.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The culture of coconut (Cocos nucifera L.) has a significant importance in generating employment and income throughout all the year. The in vitro germplasm banks offer several benefits, such as high rates of multiplication, production of arrays free of pathogens, reduction of genetic erosion, reduced demand for space, cost savings with the workforce and facilitating international exchange of germplasm. Therefore, the long-term conservation address these needs, but can also be used to keep recalcitrant and intermediate species. This paper aims at the long-term retention of mature zygotic embryos of dwarf green coconut-tree Jiqui of Brazil (Cocos nucifera L.) in liquid nitrogen at -196 celcius degrees; adapt the application of tetrazolium tests, electrical conductivity and potassium leaching to study the feasibility of cryopreserved embryos and to analyze the viability of embryos after cryopreservation. Zygotic embryos of fruits from a planting of dwarf green coconut-tree Jiqui of Brazil (AveJBr) with 10 at 11 months of maturation were used. Endosperm cylinders with zygotic embryos were placed in sterile containers and sent to the Plant Tissue Culture Laboratory of Embrapa Coastal Tablelands, Aracaju, Sergipe. We evaluated the effects of different periods of dehydration, treatment of cryoprotectants and drying methods on moisture from embryos using the methodology of Assy-Bah & Engelmann (1992) and CPATC methodology. Electrical conductivity tests, potassium leaching and tetrazolium were performed to evaluate the feasibility of zygotic embryos after cryopreservation. After selecting the adapted method from dehydration, AveJBr coconut zygotic embryos were cryopreserved and after 48 hours underwent to a recovery stage in culture medium Y3 liquid. The CPATC methodology with the initial dehydration of embryos in cryoprotectant and subsequent drying in silica gel for four hours promotes lower humidities in mature zygotic embryos of coconut AveJBr. The pre-treatment of mature zygotic embryos of coconut AveJBr with cryoprotectant with 1.75 mol L-1 sucrose + 15% glycerol for 12 and 16 hours promotes lower humidity of the embryos, but also higher viability in electrical conductivity , potassium leaching and tetrazolium. Samples with 10 embryos are sufficient for analysis of electrical conductivity in zygotic embryos of coconut AveJBr not cryopreserved. The incubation period of four to eight hours of embryos is promising for the electrical conductivity analysis in mature zygotic embryos of coconut AveJBr not cryopreserved. The concentration of 0.25% of tetrazolium is indicated for the viability analysis of mature zygotic embryos of coconut AveJBr not cryopreserved. The period of 90 days is not sufficient to the germination evaluation of cryopreserved embryos. / A cultura do coco (Cocos nucifera L.) tem uma importância significativa, por gerar emprego e renda durante todo o ano. Os bancos de germoplasma in vitro oferecem vários benefícios, tais como altas taxas de multiplicação, produção de matrizes livres de patógenos, redução da erosão genética, redução da demanda por espaço, redução de custos com a mão de obra, e simplificação do intercâmbio internacional de germoplasma. Portanto, a conservação a longo prazo supri essas necessidades, como também pode ser utilizado para conservar espécies recalcitrantes e intermediárias. Este trabalho tem como objetivos, a conservação em longo prazo de embriões zigóticos maduros de coqueiro (Cocos nucifera L.) anão verde de Jiqui do Brasil, em nitrogênio líquido a -196 ºC; adaptar a aplicação de testes de tetrazólio, condutividade elétrica e lixiviação de potássio para estudos da viabilidade de embriões criopreservados; e analisar a viabilidade dos embriões após a criopreservação. Foram utilizados embriões zigóticos de frutos com 11 meses de maturação provenientes de um plantio de Coqueiro Anão Verde de Jiqui do Brasil (AveJBr). Cilindros de endosperma com embriões zigóticos foram acondicionados em recipientes estéreis e encaminhados para o Laboratório de Cultura de Tecidos de Plantas da Embrapa Tabuleiros Costeiros, Aracaju, Sergipe. Foram avaliados os efeitos de diferentes tempos de desidratação, tratamentos de crioprotetores e tipos de secagem na umidade dos embriões utilizando a metodologia de Assy-Bah e Engelmann (1992) e metodologia CPATC. Testes de condutividade elétrica, lixiviação de potássio e tetrazólio foram realizados para avaliar a viabilidade dos embriões zigóticos após a criopreservação. Após a seleção do método CPATC, embriões zigóticos de coqueiro AveJBr foram criopreservados e após 48 horas foram submetidos a etapa de recuperação em meio de cultura Y3 líquido. A metodologia CPATC com a desidratação inicial dos embriões em crioprotetores e posterior secagem em sílica gel por quatro horas promove as menores umidades nos embriões zigóticos maduros de coco AveJBr. O prétratamento de embriões zigóticos maduros de coco AveJBr com crioprotetor com 1,75 mol.L-1 de sacarose + 15% de glicerol por 12 e 16 horas promove a menor umidade dos embriões, como também maior viabilidade em testes de condutividade elétrica, lixiviação de potássio e tetrazólio. Amostras com 10 embriões é suficiente para análise de condutividade elétrica em embriões zigóticos de coco AveJBr criopreservados ou não. O período de incubação de embriões de quatro a oito horas é promissor para análise condutividade elétrica em embriões zigóticos maduros de coco AveJBr não criopreservados. A concentração de 0,25% de tetrazólio é indicada para análise de viabilidade de embriões zigóticos maduros de coco AveJBr criopreservados ou não. O período de 90 dias não é suficiente para avaliação da germinação de embriões criopreservados.

O quelóide é um processo cicatricial, com freqüência aumentada em regiões com maior tensão na pele ou onde a pele é mais espessa, caracterizado por exceder-se além dos limites da lesão que o originou e pela tendência à recidiva após sua ressecção. Ambos os sexos são acometidos, com maior incidência entre a primeira e a terceira década de vida e em indivíduos de etnia negra. A relação familial é sugerida como herança autossômica dominante. O quelóide apresenta características moleculares distintas da pele normal envolvendo uma variedade de sinalizações ainda pouco compreendidas e um aumento da expressão de componentes da matriz extracelular, como o colágeno, os glicosaminoglicanos e os proteoglicanos. Este estudo analisou a expressão gênica dos proteoglicanos de superfície celular sindecam-2 e sindecam-4 e dos de matriz extracelular decorim e versicam no tecido derivado de quelóide de indivíduos não tratados em comparação com a pele clinicamente normal. Participaram desse estudo 10 indivíduos portadores de quelóides (grupo Q) e 10 indivíduos não portadores dessa cicatriz (grupo N). A expressão gênica dos proteoglicanos foi amplificada pela reação em cadeia da polimerase por transcrição reversa e analisada através de eletroforese em gel de agarose. Foi realizada a localização dos proteoglicanos nos tecidos através de reação imunohistoquímica com anticorpos para os sindecans-2 e 4. Os grupos foram comparados pelo teste t de Student. Os proteoglicanos de superfície celular mostraram-se aumentados no grupo Q (93% para o sindecam-2 e 152,5% para o sindecam-4) em comparação com o grupo N (P<0,01). Não foram observadas diferenças significativas para os proteoglicanos de matriz extracelular entre os dois grupos. A análise imunohistoquímica mostrou uma distribuição marcante dos sindecans-2 e 4 no componente epitelial, conectivo, vascular e nervoso de toda a casuística. Concluímos que o quelóide apresenta aumento significativo da expressão gênica de sindecam- 2 e sindecam-4, mas não apresenta aumento significativo da expressão gênica de decorim e versicam, em relação à pele normal. / Keloid is a cicatricial process, with frequency increased in regions with bigger tension in the skin or where the skin is thicker, characterized for exceeding beyond the limits of the injury that originated it and for the tendency to relapse after its ressection. Its occurs in both genders, with bigger incidence between the first and the third decade of life and in individuals of black ethnia. The familial relation is consistent with an autosomal dominant inheritance. The keloid presents distinct molecular characteristics of the normal skin involving a variety of still little understood signallings and an increase of the expression of components of the extracellular matrix, as the collagen, the glicosaminoglycans and the proteoglycans. This study analyzed the gene expression of the proteoglycans of cell surface syndecan-2 and syndecan-4 and the ones of extracellular matrix decorin and versican in the keloid tissue from not treated individuals in comparison with the normal skin. Tissue samples was obtained from 10 individuals with keloid (Q group) and 10 individuals with normal skin (N group). The gene expression of the proteoglycans was amplified by reverse transcription polymerase chain reaction and analyzed through agarose gel electrophoresis. The localization of the proteoglycans in the tissues was performed through immunohistochemical reaction using panels of antibodies for syndecans-2 and 4. The groups was compared by the Student?s t test. The proteoglycans of cell surface revealed increased in Q group (93% for sydecan-2 and 152,5% for syndecan-4) in comparison with N group (P<0,01). Significant differences for the proteoglycans of extracellular matrix between the two groups was not observed. The immunohistochemical analysis showed a major distribution of syndecans-2 and 4 in epithelial, connective, vascular and neural components in both groups. We conclude that keloid reveal significant increase of the gene expression of syndecan-2 and syndecan-4, but does not present significant increase of the gene expression of decorin and versican, in relation to the normal skin.

Guanine nucleotide exchange factors (GEFs) regulate and organize diverse cellular processes through their role in converting GTPases from the inactive GDP bound state to the active GTP bound state. An increasing number of GEFs undergo autoregulatory mechanisms through complex intramolecular interactions. Relief of autoinhibition involves specific phosphorylation or binding to lipid and/or effector proteins at sites distal from the catalytic domain, and is often coupled to membrane recruitment. In Cytohesin Arf GEFs, the catalytic Sec7 domain is autoinhibited by a linker region and C-terminal helix flanking a Pleckstrin Homology (PH) domain. Upon binding of the PH domain to low abundance phosphoinositides, the GTPase Arf6-GTP can both relieve autoinhibition and recruit Cytohesins to the plasma membrane. This thesis focuses on determining the molecular mechanism underlying both these functions. The structural mechanisms by which Arf6-GTP binding relieves autoinhibition were studied using biochemical and crystallographic studies. The crystal structure of the Grp1 PH domain in complex with Arf6 revealed that Arf6-GTP binding relieves autoinhibition through competitive sequestration of the inhibitory elements into grooves formed at the periphery of the interface. Importantly, the interaction orients all known membrane targeting components to a common surface. Detailed biochemical studies showed a common mode of binding among Cytohesin family members in which phosphoinositide head group binding primes the interaction with Arf6, and membrane recruitment of both stimulatory and substrate Arf enhances the effect. To assess changes in the Sec7 domain conformation upon activation, Size Exclusion Chromatography in line with Small Angle X-Ray Scattering (SEC-SAXS) was performed. The unique nature of this data led to the development of a novel data analysis and processing strategy. A graphically based, python-extensible software package was created for data normalization, buffer correction, Guinier Analysis, and constant background subtraction. As an unbiased substitute for traditional buffer subtraction, a method to reconstruct the protein scattering through singular value decomposition (SVD) and linear combination of the basis vectors was developed. These methods produced exceptional data quality and allowed versatility for application to other data collection techniques or systems, especially those lacking confident buffer matching or low signal. SEC-SAXS confirmed the overall structure of autoinhibited Grp1 in solution and showed only slight overall changes upon activation by deletion of the autoinhibitory Cterminal helix. Fusion of Arf6 with Grp1 produced a consistently elongated shape in the active state that was incompatible with the autoinhibited or theoretical active positions of the Sec7 domain. Monte Carlo and rigid body modeling using known structural domains revealed a requirement for Sec7-PH linker flexibility in addition to Sec7 domain mobility. These data support an integrated structural model whereby phosphoinositides and Arf-GTP support nucleotide exchange at membranes through allosteric activation, membrane recruitment, and large-scale rearrangement of the Sec7 domain. Overall, these findings offer insight into Cytohesin function that can be applied to assess relief of autoinhibition in the context of other GEFs and GTPases.

Depuis plusieurs années, de nouvelles méthodologies basées sur l’utilisation du champ électrique pour agir ou caractériser les cellules ou les tissus cellulaires génèrent de nombreuses avancées et apportent des nouvelles promesses dans les laboratoires de recherche et dans l'industrie : diagnostic de cancer, ElectroChimioThérapie (insertion d’un médicament en perméabilisant les membranes des cellules), thérapie génique (insertion d’un gène thérapeutique), immunothérapie (vaccins anti-tumoraux obtenus par électrofusion de cellules dendritiques et cellules cancéreuses pour réactiver le système immunitaire).L’application d’ impulsions électriques à des cellules ou dans des tissus cellulaires induit un changement sur leurs propriétés, en particulier sur leurs membranes qui deviennent transitoirement perméables, laissant temporairement le passage aux ions et macro-molécules. Les phénomènes induits lors d’une perméabilisation par application de champ électrique ont été partiellement caractérisés en microscopie epi-fluorescence. Pour effectuer un suivi en temps réel de la dynamique du processus de l’électroperméabilisation, une voie prometteuse consiste à caractériser électriquement l’échantillon. Dans cet objectif, mon travail de thèse consiste à mettre en oeuvre le suivi en temps réel de l’évolution des caractéristiques électriques sur une large bande de fréquences d’un tissu cellulaire ou d’une cellule isolée, avant, pendant et après la sollicitation par un champ électrique pulsé.Dans le cadre de ma thèse un modèle du système biologique et de son environnement a été élaboré, afin de mieux décrire des phénomènes observés expérimentalement: effet des sollicitations électriques sur la viabilité cellulaire, sur la perméabilité de la membrane externe, effets induits sur les composés intracellulaires, dynamique de fusion membranaire. Le degré de perméabilisation de l’objet biologique (cellule ou tissu) dépend de manière fortement non-linéaire de nombreux paramètres, ce qui rend complexe l’élaboration de ce modèle et son interprétation. La détection de ce niveau de perméabilisation est effectuée en temps réel (mesure du niveau de perméabilisation avant, pendant et après l’application de l’impulsion électrique). In fine cette approche devrait permettre d’optimiser le taux de perméabilisation cellulaire en fonction de l’application considérée. Ce système de contrôle individuel du niveau de perméabilisation cellulaire pourrait à terme être parallélisé massivement sur une puce dédiée à l’électroporation d’un grand nombre de cellules. Afin d’avoir une vision multi-échelle des effets, l’étude a été menée sur plusieurs modèles expérimentaux: qui vont du tissu (échelle millimétrique) à la cellule unique, en passant par les échelles intermédiaires (caractérisation de spéroides cellulaires).Dans ces deux derniers cas (sphéroide, cellule unique) l’objet biologique est isolé dans une biopuce microfluidique équipée d’électrodes de mesure et d’application du champ (échelle micrométrique).Les micro-dispositifs que j’ai réalisé pour caractériser en temps réel la perméabilisation de cellules, intègrent une géométrie spécifique d’électrodes, ainsi que d'un réseau de canaux microfluidiques pour contrôler le débit de cellules Le degré de miniaturisation de ces puces permet de travailler au niveau de la cellule unique, et appliquer des champs électriques de forte amplitude, de forte fréquence, localisés spatialement. / The increasing interest for new methodologies based on the use of the electric field to characterize the cells or tissue cells and generate brought promising development in research laboratories and industry: cancer diagnosis, electrochemotherapy (insertion of a drug after cell membranes permeabilization), gene therapy (insertion of a therapeutic gene), immunotherapy (anti-tumor vaccines obtained by electrofusion of dendritic cells and cancer cells to activate the immune system).The application of electrical pulses to cells or cell tissues induces a change in their properties, in particular on their membranes which become transiently permeable, and temporarily allow the passage of ions and macromolecules. Effect linked to the permeabilization phenomenon have been partially characterized by epi-fluorescence microscopy. Nevertheless, in order to perform the real-time monitoring of the electroporation process and know its dynamics, the electrical sample characterization is employed. Thus the aim of this work is to implement a real-time monitoring of dielectrical characteristics changes, on a wide frequency range, of a cellular tissue or a single cell, before, during and after the pulsed electric field application.As part of my thesis a model of the biological system has been developed to better describe the phenomena observed experimentally: effect of electrical stress on cell viability, on the permeability of the outer membrane, induced effects on the intracellular compounds, dynamics of membrane fusion.The degree of permeabilization of the biological sample (cells or tissues) is non linearly dependent of several parameters, which makes complicated the development of the model and its interpretation.The detection of a specific level of permeabilization is done in real time (measure of the level of permeabilization before, during and after the electric pulses application). This cell permeabilization level control could eventually be parallelized on a chip dedicated to the electroporation of a large number of cells. The latter can be used to optimize the electric pulses parameters in order to reach the desired permeabilization level. In order to have a multi-scale overview of the phenomenon, the study was performed on different size-level: from the tissue level (millimeter scale) to the single cell model through the intermediate scales (cell spéroides characterization).In the latter two cases (spheroid, single cell) the biological sample is isolated in a microfluidic biochip where the electric field solicitation are applied (micrometer scale).The microdevice designed and fabricated during this work, allows the real time characterization of the cell permeabilization. Furthermore the miniaturization of the system is crucial to work at the level of the single cell, and make possible the application of electrical fields of high amplitude, high frequency and spatially localized.