Thesis (M.S.)--Brigham Young University. Dept. of Physiology and Developmental Biology, 2006. / Includes bibliographical references (p. 50-58).

No description available.

Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 237-245).

Fresh isolated erythrocyte ghost membranes and erythrocyte suspensions were incubated with an organic hydroperoxide, tert-butyl hydroperoxide, to establish the in vitro oxidative stress models. Circulating erythrocytes from normal individuals were fractionated into subpopulations of different ages by ultracentrifugation and used as an in vivo model. In these models, membrane iPF2alpha-III content accumulation was proportional to oxidative stress and correlated with decreased membrane fluidity. In circulating erythrocytes, membrane iPF2alpha-III increased with age and inversely correlated with membrane fluidity only in the core region. / Oxidative stress is involved in the pathophysiology of a wide variety of human diseases. Isoprostanes, a family of prostaglandin derivatives, are mainly derived from free radical peroxidation of specific polyunsaturated fatty acids (PUFA). Measurement of F2-isoprostanes (F2-iPs) or one specific biologically active isomer (iPF2alpha-III) is considered to be a reliable lipid peroxidation marker in human diseases. However, the association observed between increased plasma/urine F2-iPs and diseases does not necessarily reflect tissue oxidative damages. Circulating erythrocytes, a tissue with limited biosynthetic capacity and poor repair mechanism, would offer a number of advantages for assessment of in vivo oxidative damages. In this thesis, human erythrocyte membrane iPF2alpha-III content was investigated as a new marker for in vivo oxidative stress assessment. Membrane fluidity was used as an indirect marker of cellular function. / To use membrane iPF2alpha-III in a human disease with known oxidative stress burden, 49 Chinese patients on long-term haemodialysis and 31 healthy Chinese subjects were recruited. Both plasma and membrane iPF 2alpha-III showed that haemodialysis patients had increased oxidative stress. Only membrane iPF2alpha-III, but not the conventional used plasma iPF2alpha-III, correlated with membrane fluidity. Furthermore, the significant inverse correlation between membrane iPF 2alpha-III and the core region of membrane fluidity was observed for this group of patients too. Since membrane iPF2alpha-III was shown to provide a link between oxidative stress and erythrocyte function, it would be considered as a new marker of in vivo erythrocyte oxidative stress assessment. (Abstract shortened by UMI.) / Yu Xiongwen. / "July 2005." / Advisers: Wai Kei Christopher Lam; Chung Shun Ho. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3724. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 198-223). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Abstract not available

Orientador: Eneida de Paula / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-07T20:44:09Z (GMT). No. of bitstreams: 1 Prete_PauloSergioCastilho_D.pdf: 3376950 bytes, checksum: fd06e65f64531668e35cf4a9cb817913 (MD5) Previous issue date: 2006 / Resumo: Surfatantes ou detergentes são compostos anfifílicos que, na presença de água, têm a característica de formar agregados micelares. Surfatantes induzem a desestruturação de outros agregados como bicamadas sendo, por isso, usados para ruptura celular ou solubilização de lipídios e proteínas de membrana. A capacidade lítica dos surfatantes resulta de sua estrutura química, que determina o modo de interação dos mesmos com as membranas. Em concentrações mais altas (acima da concentração micelar crítica), os surfatantes desestabilizam as bicamadas lipídicas, levando à formação de micelas-mistas. Ensaios hemolíticos são bons modelos para estudo do efeito lítico de surfatantes em biomembranas. Aplicando em eritrócitos humanos o tratamento quantitativo proposto por Lichtenberg (1985) para estudo da solubilização de bicamadas lipídicas mensurou-se, neste trabalho, as concentrações para início (Csat) e 100% de hemólise (Csol), induzidas por 25 surfatantes clássicos, pertencentes a cinco diferentes famílias. A variação dos valores de Csat, Csol determinada com diferentes hematócritos permitiu o cálculo da constante de ligação surfatante/membrana e da razão surfatante/lipídio de membrana (Re) para início e 100% de hemólise. O parâmetro Re foi usado para classificar os detergentes como fortes, médios ou fracos agentes solubilizantes, com boa correlação com dados da literatura o que nos permitiu propor seu uso para descrever o efeito lítico de surfatantes, como uma alternativa simples e aplicável as membranas biológicas. As transições durante o processo hemolítico foram acompanhadas pela técnica de Ressonância Paramagnética Eletrônica, com uso marcador de spin 5 doxil-estearato (incorporado a 1 mol% nas membranas de eritrócito) e lise induzida pelo surfatante não iônico Triton X100. Concomitante ao aparecimento de hemoglobina e fosfato livres no sobrenadante - indicadores da ruptura da membrana, medidas do parâmetro de ordem daquele marcador de spin permitiram estudar as transições que acontecem durante (membrana:membrana mista) e após (membrana mista:micela mista) a hemólise / Abstract: Surfactants or detergents are amphiphilic compounds that form micellar aggregates in the presence of excess water. Surfactants are able to induce disruption of lamellar aggregates, justifying their use for cell lysis or in the extraction of membrane constituents such as lipids and proteins. The lytic capacity of a given surfactant is determined by its chemical structure, that rules its interaction with the membranes. At high concentration (above the critic micelle concentration), surfactants destabilize lipid bilayer leading to mixed micelle formation. Hemolytic assays are a good model to study the lytic effect of surfactants on biomembranes. In this study we have applied to human erythrocytes the quantitative treatment proposed by Lichtenberg (1985) to describe the solubilization of model lipid membranes. The concentration for onset (Csat) and complete (Csol) hemolysis induced by 25 classic surfactants from five different families were measured. Changes in Csat and Csol values at different hematocrits allowed the determination of the surfactant/membrane lipid molar ratio (Re) for beginning and 100% lysis. The Re arameter was used to classify the surfactants as strong, medium or weak membrane solubilizers. The classification was in good correlation with data in the literature, allowing us to recommend the use of Re parameter to describe the lyric effect of surfactants on biomembranes. The transitions in the hemolytic process were accompanied by Electron Paramagnetic Resonance, using the 5-doxyl-stearate spin-probe (1 mol%, incorporated in the erythrocyte membrane) and the non-ionic surfactant Triton X100. Simultaneously to the appearance of hemoglobin and phosphate released in the supernatant, measurements of the order parameter of the spin probe were used to characterize the transitions that take place during (membrane :mixed membrane) and after (mixed: membrane: mixed micelle) hemolysis / Doutorado / Bioquimica / Doutor em Biologia Funcional e Molecular