• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 24
  • 4
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 36
  • 11
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • 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.
31

Charakterisierung von 16alpha-[18F]Fluorestradiol-3,17beta-disulfamat als potentieller Tracer für die Positronen-Emissions-Tomographie

Rodig, Heike 04 May 2002 (has links) (PDF)
In den westlichen Industrieländern ist Brustkrebs die häufigste krebsbedingte Todesursache bei Frauen. Bei der Diagnose von Brustkrebs ist für bestimmte Fragestellungen die Positronen-Emissions-Tomographie (PET) eine wichtige Ergänzung zur Mammographie und Sonographie. Die derzeit eingesetzten PET-Tracer 2-[18F]Fluor-2-desoxy-D-Glucose (FDG) und 16a-[18F]Fluor-17b-estra--diol (FES) können Mammakarzinome bzw. deren Metastasen nicht mit 100%iger Sicherheit nachweisen. Aus diesem Grund wurde eine [18F]-markierte Verbin-dung entwickelt, die möglicherweise die diagnostische Sicherheit bei Brustkrebs erhöhen kann: [18F]16a-Fluorestradiol-3,17b-disulfamat ([18F]FESDS). [18F]FESDS sollt dabei an Estronsulfatase binden, die in Mammakarzinomen signifikant höher exprimiert wird. Es wurde geprüft, ob [18F]FESDS für die Positronen-Emissions-Tomographie eignet ist. Die Ergebnisse zeigten, dass die Estronsulfatase nicht das alleinige Target von [18F]FESDS darstellt. Auch die Carboanhydrase hat eine sehr hohe Affinität zu dem potentiellen Tracer. Durch selektive Hemmung der Carboanhydrase mit Azetazolamid konnte jedoch in vitro die Estronsulfatase dargestellt werden. In vivo ist es nicht gelungen, mit [18F]FESDS die Estronsulfatase bei vorliegender Carboanhydrase-Hemmung besser darzustellen. Die Daten deuten darauf hin, dass eine Darstellung der Estronsulfatase mit der PET weder mit dem Radiotracer [18F]FESDS allein noch bei Koinjektion von [18F]FESDS mit Azetazolamid (zur CA-Hemmung) möglich ist.
32

Efeito vasorelaxante da estrona sobre aorta torácica de ratos: contribuição ao estudo do mecanismo de ação / Vasorelaxant effect of estrone on rat thoracic aorta: contribution to the mechanism of action study

Oliveira, Thiago Sardinha de 19 September 2014 (has links)
Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2015-11-11T18:59:23Z No. of bitstreams: 2 Dissertação - Thiago Sardinha de Oliveira - 2014.pdf: 1412743 bytes, checksum: d9f93cb6e80442a38393a204842830c9 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-11-12T09:26:51Z (GMT) No. of bitstreams: 2 Dissertação - Thiago Sardinha de Oliveira - 2014.pdf: 1412743 bytes, checksum: d9f93cb6e80442a38393a204842830c9 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-11-12T09:26:51Z (GMT). No. of bitstreams: 2 Dissertação - Thiago Sardinha de Oliveira - 2014.pdf: 1412743 bytes, checksum: d9f93cb6e80442a38393a204842830c9 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-09-19 / Endogenous estrogens have been associated with greater vascular protection in premenopausal women, and the increased risk of cardiovascular diseases in postmenopausal women can be associated to the decrease in plasma estrogen levels. Furthermore recently studies showed that the use of estrogens, like estrone, exhibits remarkable vascular effect when used on isolated arteries, however any investigation was made to elucidate the mechanism of action of this compound. So, the present study was designed to investigate the ability of estrone to induce vascular relaxation and modulate NO-dependent signaling pathway and analyzed the role of estrogens receptor on estrone-mediated vascular relaxation, compared with the effects promoted by 17β-estradiol. 12 week-old male Wistar rats were used to the vascular reactivity, which was performed in an organ bath study for an isometric tension recording. To the experimental protocols, concentration-response curves (0.1 - 100μM) to estrone or 17β - estradiol were performed. The mechanism contributing to estrone-induced effects were determined comparing with the vascular effects induced by 17β - estradiol that have its effect vascular well characterized. It was observed that the vascular relaxation promoted by estrone is dependent on the endothelium and the estrogen receptor. The vasorelaxant effect promoted by estrone was significantly altered in the presence of the inhibitor of PI3K signaling pathway (wortmannin) and the Ca2+-CaM complex inhibitor (calmidazolium), showing the involvement of PI3K/Ca2+-CaM signaling pathways. This study demonstrate that estrone promoted vasorelaxant effect on rat thoracic aortic on endotheliumdependent manner and its effect depends on the estrogen receptors that activate the PI3K pathway and the Ca2+-calmodulin complex which subsequently activates the NO/cGMP pathway. These results contribute to the better understanding of the role of estrone in the conjugated equine estrogen (CEE) which could be associated to the benefits effects of estrogens in the CEE therapy. / Os estrogênios endógenos têm sido associados com uma maior proteção do sistema vascular em mulheres na pré-menopausa, uma vez que os riscos de doenças cardiovasculares em mulheres na pós-menopausa são maiores, alterações estas que se devem à diminuição nos níveis plasmáticos de estrogênios. Além disso, estudos recentes mostraram que o uso de estrogênios, como a estrona, apresenta notável efeito vasorelaxante quando avaliado seu efeito em artérias isoladas, no entanto, nenhuma investigação foi realizada para elucidar o mecanismo de acção deste composto. Assim, o presente estudo procurou investigar o efeito da estrona em aorta de ratos, verificando seu efeito em induzir o relaxamento vascular e modular a via de sinalização dependente do óxido nítrico (NO), e ainda o papel dos receptores de estrogênios, comparando com os efeitos promovidos pelo 17β- estradiol. Os animais utilizados neste estudo foram ratos Wistar com 12 semanas de idade, os quais foram utilizados para realização da reatividade vascular em banho de órgãos isolados. Para os protocolos experimentais, curvas de concentraçãoresposta (0,1-100μM) foram feitas para a estrona ou para o 17β-estradiol e as tensões isométricas gravadas. Os mecanismos envolvidos no efeito induzido pela estrona foram determinados através da incubação de inibidores farmacológicos e comparado ao efeito do 17β-estradiol, que tem seu efeito vascular bem caracterizado. Observou-se que a estrona promove efeito vasorelaxante em aorta torácica de ratos, e que o relaxamento vascular promovido por ela é dependente do endotélio e do receptor de estrogênios. Após ativação do receptor de estrogênios, este ativa as vias de sinalização PI3K e Ca2+-CaM que posteriormente ativam a via NO/GMPc. Estes resultados contribuem para o melhor entendimento do papel da estrona em preparações de estrogênios conjugados equinos (CEE), que pode estar associado aos efeitos de benefícios dos estrogênios na terapia CEE.
33

Charakterisierung von 16alpha-[18F]Fluorestradiol-3,17beta-disulfamat als potentieller Tracer für die Positronen-Emissions-Tomographie

Rodig, Heike 08 May 2002 (has links)
In den westlichen Industrieländern ist Brustkrebs die häufigste krebsbedingte Todesursache bei Frauen. Bei der Diagnose von Brustkrebs ist für bestimmte Fragestellungen die Positronen-Emissions-Tomographie (PET) eine wichtige Ergänzung zur Mammographie und Sonographie. Die derzeit eingesetzten PET-Tracer 2-[18F]Fluor-2-desoxy-D-Glucose (FDG) und 16a-[18F]Fluor-17b-estra--diol (FES) können Mammakarzinome bzw. deren Metastasen nicht mit 100%iger Sicherheit nachweisen. Aus diesem Grund wurde eine [18F]-markierte Verbin-dung entwickelt, die möglicherweise die diagnostische Sicherheit bei Brustkrebs erhöhen kann: [18F]16a-Fluorestradiol-3,17b-disulfamat ([18F]FESDS). [18F]FESDS sollt dabei an Estronsulfatase binden, die in Mammakarzinomen signifikant höher exprimiert wird. Es wurde geprüft, ob [18F]FESDS für die Positronen-Emissions-Tomographie eignet ist. Die Ergebnisse zeigten, dass die Estronsulfatase nicht das alleinige Target von [18F]FESDS darstellt. Auch die Carboanhydrase hat eine sehr hohe Affinität zu dem potentiellen Tracer. Durch selektive Hemmung der Carboanhydrase mit Azetazolamid konnte jedoch in vitro die Estronsulfatase dargestellt werden. In vivo ist es nicht gelungen, mit [18F]FESDS die Estronsulfatase bei vorliegender Carboanhydrase-Hemmung besser darzustellen. Die Daten deuten darauf hin, dass eine Darstellung der Estronsulfatase mit der PET weder mit dem Radiotracer [18F]FESDS allein noch bei Koinjektion von [18F]FESDS mit Azetazolamid (zur CA-Hemmung) möglich ist.
34

Sorption, degradation and transport of estrogens and estrogen sulphates in agricultural soils

Scherr, Frank January 2009 (has links)
The fate and behaviour of estrogens in the environment are of concern due to the compounds’ endocrine disruption potential. Estrogens, namely 17β-estradiol (E2), estrone (E1), and estrogen sulphates, i.e. 17β-estradiol-3-sulphate (E2-3S) and estrone-3-sulphate (E1-3S) excreted by livestock constitute a potential source for estrogen contamination in the environment. A method was developed to separate and quantify the hormones by high-performance-liquid-chromatography (HPLC) and ultraviolet detection (UV). A combination of dichloromethane (DCM) and dicyclohexylamine hydrochloride (DCH·HCl) gave recoveries from 97.3 to 107% for E1-3S extraction from aqueous solutions. The recoveries from soil samples ranged from 80.9 to 95.2% (E2-3S), and from 86.3 to 91.7% (E1-3S), respectively. Results of batch sorption studies showed that Freundlich isotherms were nonlinear (N ≠ 1) with Kf values ranging from 34.2 to 57.2, and from 3.42 to 4.18 mg¹-N LN kg⁻¹ for E1, and E1-3S, respectively, indicating the sorption affinity of E1-3S was about an order of magnitude lower than that of E1. The hydrophilic sulphate group of E1-3S possibly shielded the compound from hydrophobic interactions with the soil organic matter and allophanic clay minerals that were proposed as sorbents for E1. Contraction of clay minerals, “salting out” and competitive sorption of artificial urine constituents were likely to have been responsible for observed changes in Freundlich parameters when artificial urine was used as mediator matrix. Plotting the effective distribution coefficient as a function of hypothetical exposure concentrations facilitated the comparison of the sorption behaviour of both compounds as influenced by the mediator solution. The results emphasized that using the CaCl₂ matrix might result in false inferences for the sorption behaviour of these compounds in a dairying environment. The four hormones rapidly degraded in the agricultural soils under aerobic conditions, and the majority of the compounds degraded > 50% within the first 24 hrs. Soil arylsulphatase activities were directly correlated with degradation rate constants of the estrogen sulphates. Estrone was identified as a metabolite of E2 and E1-3S, and these three compounds were observed as metabolites of E2-3S. Single-first order (SFO) and double first-order in parallel (DFOP) kinetics were used to model the degradation and metabolite formation data. The results showed that the DFOP model was in most cases better able to predict the parent compound degradation than the SFO model, and also enabled to estimate accurate degradation endpoints. ER-CALUX® analysis revealed the formation of estrogenicity during E2-3S degradation, which could partly be explained by the formation of the metabolites E2 and E1. Transport studies with E1-3S and E1 showed that the transport and retention of both compounds were significantly influenced by the mediator matrix. While no breakthrough curves (BTCs) were recorded during hormone application in CaCl₂ (10 mM) both hormones were detected in the leachate when applied in artificial urine. Rate-limited sorption processes were proposed for the delayed arrival of the hormone BTCs compared with a conservative bromide tracer. Intense colouration of the leachate during the artificial urine experiments suggested the hormones were likely to be moved by colloid-facilitated transport. Furthermore, the detection of residue hormone and metabolite concentrations implied that degradation of E1-3S and E1 was hampered by urine constituents such as glycine and urea.
35

Optimalizace stanovení endokrinních disruptorů v čistírenských kalech a aplikace metody v reálných vzorcích. / Optimization of endocrine disruptors determination in wastewater treatment plant sludge and application of the method in environmental samples.

Medková, Jaroslava January 2012 (has links)
Hormonaly active compounds in wastewaters represent nowdays a serious problem. Proceses currently used in watewater treatment plants (WWTP) are unefficient in removing these compounds from contaminated wastewaters. The compounds are supposed to sorb onto solid sludge elements and sediments. In this work seven endocrine disruptors were detected in the sludge samples from WWTPs. A new sensitive method for detection of seven selected endocrine disruptors (4-nonylphenol, bisphenol A, estriol, 17β-estradiol, estrone, 17α- ethynylestradiol, irgasan) was developed. The method is based on accelerated solvent extraction (ASE), gel permeation chromatography (GPC) and solid phased extraction. For final extract analysis, gas chromatography coupled with mass spectrometry (GC/MS) was used. The efficiency of this method was tested using artificially contaminated sludge and the method was used to analyse real samples from several WWTPs in Czech Republic. The effect of sludge age on detection of individual analytes was assessed as well. The concentrations of endocrine disruptors measured in the samples reached up to 1 µg/g. The results are comparable or higher then those reported in other works and they show the necessity of further research on endocrine disruptors in the environment.
36

A Study of the fate and transport of estrogenic hormones in dairy effluent applied to pasture soils

Steiner, Laure D. January 2009 (has links)
The disposal of waste from agricultural activities has been recognised as a source of environmental contamination by endocrine disrupting chemicals (EDCs). The New Zealand dairy industry produces a large volume of dairy farm effluent, which contains EDCs in the form of estrogens. Most of this dairy farm effluent is applied onto the land for disposal. Groundwater and soil contamination by estrogens following waste application on the land have been reported overseas, but our understanding of the processes and factors governing the fate of estrogens in the soil is poor. Therefore the main goal of the present study was to better understand the fate and transport of estrogens, in particular 17β-estradiol (E2) and estrone (E1) in soil. In order to quantify E1 and E2 in drainage water and soil samples, chemical analysis by gas-chromatography mass-spectrometry (GC-MS) was carried out. This included sample extraction, sample clean-up through silica gel and gel permeation chromatography, and sample extract derivatisation prior to analysis. In order to develop a reliable method to extract estrogens from soil, research was conducted to optimise E1 and E2 extraction conditions by adjusting the number of sonication and shaking events, as well as the volume and type of solvent. Among five solvents and solvent mixtures tested, the best recovery on spiked and aged soil was obtained using an isopropanol/water (1:1) mix. A microcosm experiment was carried out to determine the dissipation rates of E2 and E1, at 8°C and at field capacity, in the Templeton soil sampled at two different depths (5-10 cm and 30-35 cm). The dissipation rates decreased with time and half-life values of 0.6-0.8 d for E1 and 0.3-0.4 d for E2 were found for the two depths studied. A field transport experiment was also carried out in winter, over three months, by applying dairy farm effluent spiked with estrogens onto undisturbed Templeton soil lysimeters (50 cm in diameter and 70 cm deep). The hormones were applied in dairy farm effluent at 120 mg m⁻² for E2 and 137 mg m⁻² for E1. The results of the transport experiment showed that in the presence of preferential/macropore flow pathways 0.3-0.7% of E2 and 8-13% of E1 was recovered in the leachate at the bottom of the lysimeters after 3 months, and 1-7% of the recovered E2 and 3-54% of the recovered E1 was leached within 2 days of application. These results suggest that leaching of estrogens via preferential/macropore flow pathways is the greatest concern for groundwater contamination. In the absence of preferential/macropore flow pathways, a significant amount (> 99.94%) of both hormones dissipated in the top 70 cm of soil, due to sorption and rapid biodegradation. Surprisingly, in all cases, estrogen breakthrough occurred before that of an inert tracer (bromide). This could not be explained by the advection-dispersion transport of estrogens, nor by their presence as antecedent concentrations in the soil. It was therefore suggested that colloidal enhanced transport of estrogens was responsible for the earlier breakthrough of estrogens and caused the leaching of a fraction of the applied estrogens to a soil depth of 70 cm. A two-phase model, adapted from a state-space mixing cell model, was built to describe the observed estrogen transport processes under transient flow. The model takes into account 3 transport processes namely, advection-dispersion, preferential/macropore flow and colloidal enhanced transport. This model was able to successfully describe the estrogen transport observed from the lysimeters.

Page generated in 0.0419 seconds