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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Bisphenol A, and three related alkylphenols exert rapid estrogenic actions on zebrafish (Danio rerio) oocytes to maintain meiotic arrest

Fitzgerald, Amanda Crane 02 February 2015 (has links)
Bisphenol A (BPA) is an alkylphenol compound used in plastic manufacturing, which enters the aquatic environment through wastewater treatment plants and landfill leachates. Exposure of fish to BPA results in developmental defects, decreased hatching, and increased occurrence of the egg yolk precursor protein vitellogenin in male fish. BPA is an estrogenic like compound (xenoestrogen) that can bind and activate the nuclear estrogen receptors, ERα and ERβ, causing changes in gene transcription (genomic mechanism). However, the ability of BPA to activate rapid estrogen signaling and to disrupt nongenomic physiological responses to estrogens is not known. One important nongenomic estrogen action in fish is to maintain meiotic arrest of oocytes and to prevent precocious oocyte maturation through activation of the transmembrane G-protein coupled estrogen receptor (Gper). Binding of estrogens to Gper on zebrafish oocytes results in rapid activation of epidermal growth factor receptor (Egfr) signaling and subsequent Mapk3/1 activation. We show here that BPA and three structurally-related chemicals, tetrachlorobisphenol A, tetrabromobisphenol A and nonylphenol, can mimic estrogen by activating this mechanism of meiotic arrest through Gper in zebrafish (Danio rerio). BPA bound to zebrafish Gper and inhibited spontaneous oocyte maturation (OM) of denuded oocytes. Treatment of oocytes with Actinomycin D did not block the effects of BPA, suggesting that this inhibition of OM is through a nongenomic mechanism. Incubation of oocytes with a selective GPER antibody and the specific GPER antagonist G-15 blocked the effects of BPA on OM, further suggesting that BPA inhibition of OM is through its interaction with the receptor. Various inhibitors of the EGFR pathway were utilized to determine if the inhibition of OM by BPA is mediated through this mechanism. BPA activation of the Egfr pathway resulted in Mapk3/1 (also known as Erk 1/2) phosphorylation. The results show that BPA disrupts oocyte maturation through a novel mechanism involving activation of a Gper/Egfr/Mapk3/1 pathway with potential adverse impacts on reproductive success. / text
22

Immobilisierung von BPA-Bindeproteinen an der Oberfläche von Hefezellen

Mergler, Magnus. Unknown Date (has links) (PDF)
Techn. Hochsch., Diss., 2003--Aachen.
23

A Study of Crystallization in Bisphenol-A Polycarbonate

Farmer, Robin Sandra 11 December 2001 (has links)
The crystallization behavior of bisphenol-A polycarbonate (BAPC) was studied, focusing on the initial stage of crystallization and the secondary stage of crystallization. Bisphenol-A polycarbonate was the polymer chosen for this study because of its slow crystallization rate. With slow crystallization kinetics, the polymer morphology does not change when quenched below its glass transition temperature, enabling the study of different stages of crystallization through the frozen morphology. The study of the initial stages of crystallization pertained to crystallization times prior to the growth of detectable crystallinity. This study employed BAPC because of the long induction period, a direct result of the slow crystallization kinetics. During the induction period of polycarbonate crystallized at 190°C there was no evidence of polymer chain ordering that was seen in literature for other polymers. The length of the induction period determined by differential scanning calorimetry and wide-angle X-ray diffraction varied by over 6 hours because differential scanning calorimetry can detect a smaller amount of crystallinity than wide-angle X-ray diffraction. Signs of pre-ordering in the literature could be a result of experimental sensitivity. The study of the secondary crystallization dealt with the isothermal lamellar thickening of BAPC crystals during annealing, after crystallization for an extended period of time. Small-angle X-ray scattering and differential scanning calorimetry experiments were performed on bisphenol-A polycarbonate samples crystallized near 190°C for 8 days and annealed at either 223°C or 228°C for various times. The Gibbs-Thomson relationship, which can be defined using the experiments mentioned, yielded two thermodynamic constants, the equilibrium melting temperature and the surface free energy. Including data from literature in the determination of the constants, the equilibrium melting temperature and surface free energy of BAPC is 303°C and 36.6mJ/m2, respectively. Comparing the lamellar thickness measurements by small-angle X-ray diffraction with direct measurements by microscopy was difficult because the morphology of the polymer was not easily seen in the bulk using atomic force microscopy or scanning electron microscopy. Etching the sample was the most promising technique for future investigations of revealing the bulk morphology for direct lamellar thickness measurements. Crystallizing thin films of polycarbonate on calcite substrates allowed the measurement of lamellar thickness using scanning electron microscopy because the lamellae grow epitaxially to the substrate. The measurement of the long spacing in thin film samples was comparable to that of bulk samples. / Master of Science
24

Mechanisms of Chemoresistance in Breast Cancer and Liposarcoma

LaPensee, Elizabeth W. January 2008 (has links)
No description available.
25

Effets du bisphénol A (BPA) sur l’expression de l’axe CXCL12/CXCR4 dans l’endométriose et le cancer endométrioïde de l’ovaire / Effects of Bisphenol A (BPA) on CXCL12/CXCR4 axis expression in endometriosis and endometrioid ovarian cancer

Bourkou, Mohamed Elhaddi January 2014 (has links)
Le cancer endométrioïde de l’ovaire (CEO) ainsi que l’implant endométriosique sont deux tumeurs caractérisées par la présence de cellules épithéliales et stromales ressemblant aux cellules endométriales. Des études antérieures ont mis en évidence des anomalies immunologiques communes à la cellule épithéliale endométriale (CEE), à la cellule endométriosique (CENDO) et à la cellule du CEO (CCEO) suggérant une origine commune endométriale de l’endométriose (ENDO) et du CEO. Selon la théorie de l'implantation, la migration des cellules endométriales vers d'autres sites ectopiques constitue un événement important dans l'étiopathogénie de l’endométriose (ENDO). Récemment, il a été démontré que CXCL12/CXCR4, un axe œstrogèno-dépendant, joue un rôle important dans l’homéostasie cellulaire et contrôle la migration des cellules dans les conditions normales et pathologiques. Ainsi, l'implication des œstrogènes dans la régulation de ce système nous amène à nous questionner sur l’effet du bisphénol A (BPA), un xéno-œstrogène utilisé dans une large gamme de produits, sur l’expression de CXCL12/CXCR4 et sur la migration de la CEE et son développement ectopique en tumeur. Dans ce projet, nous avons utilisé des CEE primaires provenant d’endomètres et d’implants endométriosiques, ainsi que deux lignées néoplasiques (endométriale et endométrioïde ovarienne). Nous avons étudié le rôle du BPA dans l'expression du couple CXCL12/CXCR4 par des méthodes classiques d’ELISA, RT-PCR en temps réel, Western blot et immunocytochimie. La prolifération a été évaluée par méthode colorimétrique et la migration par la technique des deux chambres de Boyden. Le dosage du BPA a été fait par chromatographie en phase gazeuse. Les principaux résultats montrent que l’expression basale du CXCR4 au niveau des différents types de cellules est augmentée par le traitement au BPA en comparaison aux contrôles. Ces résultats démontrent, une fois de plus, une possible origine commune de l’ENDO et CEO. D’autre part, nous avons démontré que le traitement au BPA entraine une augmentation de la migration et de la prolifération des CEE selon un axe CXCL12/CXCR4 dépendant. Ceci pourrait être un mécanisme impliqué dans la genèse de l’endométriose et suggère que le BPA pourrait être le facteur responsable par l’activation de l’axe CXCL12/CXCR4. Ce travail a aussi permis d’identifier une anomalie inhérente au tissu endométrial de patientes endométriosiques et qui consiste en une augmentation de l’expression du récepteur CXCR4, ce qui pourrait constituer un biomarqueur de diagnostic de l’ENDO. En dernier lieu, compte tenu de l'absence de lien entre les concentrations de BPA et celles du CXCL12, la réponse chimiotactique qui serait responsable de la migration de la CEE vers la cavité pelvienne pourrait être dépendante d'autres facteurs du microenvironnement péritonéal, ce qui appuie la nature multifactorielle de l’étiopathogénie de endométriose.
26

Obesogenic molecules breaching Caco-2 cells : intracellular regulation of tight junctions

Hagelby Edström, Tim January 2016 (has links)
Impaired function of the human intestinal epithelial barrier (IEB) might allow for permeability of harmful substances, such as obesogens, which induce obesity and further implications. Tight junction (TJ) proteins are the key component for normal functions of the barrier. In this master thesis, the correlation between increased TJ permeability of the IEB and absorption of obesogens was studied. The effect of obesogens on TJ expression was also investigated. Permeability tests performed on Caco-2 cell monolayers exposed to obesogens showed altered permeability, indicating that obesogens might have an effect on TJ protein expression. Furthermore, impaired monolayers showed increased permeability, which implies that impaired functions of IEB lead to increased absorption of obesogens.
27

Prepubertal bisphenol A exposure in the rat mammary gland mechanism of action for carcinogenesis /

Raghuraman, Nandini. January 2007 (has links) (PDF)
Thesis (M.S.)--University of Alabama at Birmingham, 2007. / Title from PDF title page (viewed Jan. 28, 2010). Includes bibliographical references (p. 30-31).
28

Effect of environmental factors on spermatogenesis. : Ex-vivo assessment of low level of cadmium or bisphenol A on testicular meiotic cells. : Dosage of metals in semen and in DNA of spermatozoa.

Ali Muhammed Wali, Sazan 25 November 2014 (has links)
Nous avons fait l'analyse des flux cytométrie nous a permis d'évaluer les changements dans le nombre de cellules de Sertoli et germinales par le cadmium. Seulement cellules germinales ont diminué dans le temps et de manière dose-dépendante. CS fragmenté, asynapsis et "mitée" CS ont été observés. Cd induit modifications ex-vivo en cours de la méiose. BPA changé chronologie de la méiose et active le point de contrôle de pachytène. Asynapsis et la fragmentation ont été induites. Noyaux leptotène anormaux, et zygotène asynapsed, observées. CS pulvérisé indiqué les anomalies de recombinaison et / ou d'appariement génétique.BPA modifie principales fonctions biologiques et les voies canoniques. Le nombre de gènes affectés par BPA a augmenté au cours du temps d'exposition. Changement Fold augmenté. Quatre fonctions altérées étaient le cancer, la mort cellulaire, le développement cellulaire et la cellule de cellulaire signalisation. Nous insistons sur le fait que les gènes liés à l'ADN interagi ORD réparation perturbés.la mesure des métaux dans le plasma séminal et de l'ADN du sperme des hommes normaux et anormaux. Nous avons utilisé ICP / MS pour mesurer la concentration de métal dans l'ADN de le sperme et plasma séminal. Tous les métaux analysés ont été détectés dans le plasma séminal. De l'ADN de sperme, As, Hg, Sb et Se, ont été non détecté par cette méthode. Aucune correlation des concentrations de métaux entre le plasma séminal et d'ADN de sperme ont été observées. Les concentrations de métaux, dans le sperme normaux et anormaux, visualiser une augmentation significative de Sb dans le plasma séminal et de Al dans l'ADN des spermatozoïdes dans le sperme de groupe anormal. / We did Flow cytometric analysis enabled us to evaluate changes in the number of Sertoli cells and germ cells by cadmium. Only germ cells were decreased in a time and dose dependent manner. Fragmented SC, asynapsis and "motheaten" SC were observed. Cd induced ex-vivo modifications in meiotic process. BPA changed meiotic chronology and activates the pachytene checkpoint. Asynapsis and fragmentation were induced. Abnormal leptotene nuclei, and asynapsed zygotene, observed. Pulverized SC indicated the abnormalities of genetic recombination and/or pairing. Transcriptomic analysis showed that BPA alters main biological functions and canonical pathways. The number of genes affected by BPA increased over the exposure time. Fold change increased. Four impaired functions were cancer, cell death, cellular development and cell to cell signaling. We emphasize that interacted genes linked to DNA DSB repair disturbed.The other part of this thesis is including the measurement of metals in seminal plasma and in sperm DNA of normal and abnormal men. We used ICP/MS to measure the metal concentration in the seminal plasma and sperm DNA. All metals analyzed were detected in seminal plasma. In sperm DNA, As, Hg, Sb and Se, were undetected with this method. No correlation between the seminal plasma and sperm DNA metal concentrations were observed. The metal concentrations, in normal and abnormal semen, visualized a significant increase of Sb in the seminal plasma and of Al in the sperm DNA in the abnormal semen group.
29

Vliv bisfenolu S na vybrané markery meiotického zrání prasečích oocytů / Bisphenol S influence on selected markers of meiotic maturation of porcine oocytes

Černíková, Terezie January 2020 (has links)
Bisphenol A is a widely used chemical in the manufacture of plastics. The presence of BPA in the environment adversely affects human health due to contamination of air, drinking water and food. Growing concerns about the effects of BPA have led to its regulation in production and development of alternative chemicals to BPA, such as bisphenol S (BPS). However, the effects of BPS were not properly tested before its introduction to production and the effects on human reproduction are still unknown. For this reason, it is desirable to test the effect of BPS on mammalian oocyte development. This study hypothesizes that BPS exposure causes inhibition of meiotic maturation of porcine oocytes in vitro. This study aims to investigate the potency of BPS at low concentrations corresponding to normal human exposures to selected porcine oocyte proteins. The results of this study demonstrate the negative effect of BPS on the progression of meiotic maturation and reaching the mature oocyte stage. In addition, the results show an increase in the formation of defective meiotic spindles and a disruption of mitochondrial integrity after exposure to BPS concentrations. However, the effect of BPS on double-strand breaks was not demonstrated in this study, in contrast to the case of BPA. Taken together, the results show...
30

Environmental Endocrine Disrupting Chemicals and Cardiac Arrhythmogenesis

Gao, Xiaoqian 02 June 2015 (has links)
No description available.

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