The role of the retinal pigment epithelial cells on the viability and renewal of photoreceptors has been well demonstrated in the Royal College of Surgeons (RCS) strain of rat. These rats are characterized by an inherited time-dependent degeneration of their photoreceptors. This degeneration is apparently due to the inability of the retinal pigment epithelial cells to adequately ingest fragments of photoreceptor membrane that are shed during the course of photoreceptor membrane renewal. The buildup of photoreceptor material in the interphotoreceptor space ultimately leads to the degeneration of photoreceptors in these animals. With regard to the pigment epithelial cells, neither the mechanism mediating the ingestion process in normal rats nor the nature of the defect of this process in RCS rats is understood.It is the goal of this proposed research to assay for the presence of phospholipase C in retinal pigment epithelial (RPE) cells and to determine possible modulators of the enzyme in an attempt to associate this with the process of phagocytosis. / Department of Biology

Little is known of the physiological and biochemical mechanisms underlying competitive interactions between alien invasive grasses and native taxa, and how these are affected by resource supply. Consequently, this study compared photosystem II (PS II) function, photosynthetic gas and water exchange, enzyme and pigment concentrations, flowering and biomass accumulation in an indigenous geophyte, Tritonia crocata (L.) Ker. Gawl., grown in monoculture and admixed with the alien grass, Lolium multiflorum Lam., at different levels of water and nutrient supply. Diminished stomatal conductances were the primary cause of reduced net C02 assimilation rates, and consequent biomass accumulation in T. crocata admixed with L. multiflorum at all levels of water and nutrient supply with one exception. These corresponded with decreased soil water contents induced presumably by more efficient competition for water by L. multiflorum, whose biomass was inversely correlated with soil water content. Biochemical impairments to photosynthesis were also apparent in T. crocata admixed with L. multiflorum at low levels of water and nutrient supply. These included a decline in the density of working photosystems (reaction center per chlorophyll RC/ABS), which corresponded with a decreased leaf chlorophyll a content and a decreased efficiency of conversion of excitation energy to electron transport (¥0 / l-^o), pointing to a reduction in electron transport capacity beyond QA~, a decline in apparent carboxylation efficiency and Rubisco content. At low nutrient levels but high water supply, non-stomatal induced biochemical impairments to photosynthesis (decreased RC/ABS, chlorophyll a and Rubisco content) were apparent in T. crocata admixed with L. multiflorum. These attributed to a reallocation of fixed carbohydrate reserves to floral production which increased significantly in T. crocata under these conditions only and associated with a corresponding reduction in the mass of its underground storage organ (bulb). The results of this study did not support the hypothesis that under conditions of low water and low nutrient supply invasive annual grasses would have a lesser impact on the growth and physiology of native geophytes than under resource enriched conditions that favor growth of these grasses. Unresolved is whether resource limitation and allelopathic mechanisms functioned simultaneously in the inhibition of the native geophyte by the alien grass. / Thesis (M. Environmental Science (Ecological Remediation and Sustainable Utilisation))--North-West University, Potchefstroom Campus, 2008.

Understanding why organisms possess particular combinations of visual pigments (VPs) is central to visual ecology. Species that adjust spectral sensitivity by changing retinal VPs provide a powerful tool to investigate this question. Changing chromophores (A1 or A2) and altering opsin expression are mechanisms used to adjust photoreceptor maximum absorbance (λmax). My research explored the function of such dynamic systems in two teleosts, coho salmon and zebrafish. I investigated temporal VP changes in relation to life history and environmental change. In coho, I found a correlation between chromophore shifts and seasonal variations in environmental variables for freshwater and marine life history stages (seasonal hypothesis). These findings provide an alternative explanation to the migration/metamorphosis hypothesis. The latter, suggests that shifts from A-2 to AI at metamorphosis, preceding seaward migration, are preemptive to changes in photic environment. Using exogenous thyroid hormone (TH), which plays a role in coho metamorphosis, I demonstrated that under various rearing conditions and times of year, TH consistently shifted VPs towards A2 dominance. This increased A2 is opposite to that occurring at metamorphosis, further supporting the seasonal hypothesis. While TH induced changes in rod λmax were consistent with a change in A1/A2 ratio, λmax variations in middle wavelength- and long wavelength-sensitive (MWS and LWS) cones were greater than predicted by a shift in A1/A2 ratio alone. I proposed a change in opsin expression to explain MWS and LWS cone λmax variations. In support of this hypothesis, a novel RH2 opsin subtype (expressed in MWS cones) was isolated and sequenced. This second RH2 possessed an E to Q substitution at the position analogous to 122 in bovine RH1 which imposes a hypsochromic shift in X. Further investigation found that changes in coho MWS cone λmax were correlated with ontogeny and the frequency of MWS cones with below 500 nm was reduced in marine compared to freshwater stages. The combination of changes in A1/A2 ratio and opsin expression provides coho with a dynamic spectral tuning mechanism. In zebrafish, I demonstrated the presence of an A1/A2 VP pair, which shifted to A2 dominance with exogenous TH treatment, but not with temperature.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 123-137). Also available via the Internet.

Thesis (Ph.D.(Chemistry))--University of Pretoria, 2009. / Includes abstract in English. Includes bibliographical references. Also available online.

Made available in DSpace on 2014-10-09T12:35:54Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:26Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

The aim of this study was to use pigments to determine freshwater phytoplankton composition . The samples were collected from freshwater lakes in the Czech Republic and Germany. The pigment analyses were conducted using the High Performance Liquid Chromatography (HPLC). The HPLC data were processed by computer program CHEMTAX to calculate the composition of phytoplankton. The obtained pigment data were compared with standard light microscopy which was used to obtain more detailed taxonomic resolution.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-26T10:35:54Z No. of bitstreams: 1 JOÃO ANTONIO BELMINO DOS SANTOS - TESE (PPGEP) 2007.pdf: 4821532 bytes, checksum: 0bbdefd2afdc6796f0a3527001b850e5 (MD5) / Made available in DSpace on 2018-09-26T10:35:54Z (GMT). No. of bitstreams: 1 JOÃO ANTONIO BELMINO DOS SANTOS - TESE (PPGEP) 2007.pdf: 4821532 bytes, checksum: 0bbdefd2afdc6796f0a3527001b850e5 (MD5) Previous issue date: 2007-03-30 / O urucuzeiro (Bixa orellana L) é um arbusto que predomina nas regiões da América Tropical em particular no Brasil, que detém a maior produção mundial. Os pigmentos das sementes do urucum são mais consumidos como pigmento natural e são constituídos basicamente de bixina, com cerca de 80 %, e a norbixina, em menor concentração. O corante obtido através da semente de urucum apresenta-se, para uso industrial, nas formas líquida, pasta ou em pó; entretanto, para a sua industrialização, é imprescindível o conhecimento tecnológico que permita a obtenção de corantes a baixo custo e com qualidade aceitável, tornando o produto capaz de competir no mercado internacional. A otimização de um processo de extração é de fundamental importância e visa não só aumentar o rendimento, mas também, minimizar a contaminação com subprodutos de decomposição. O desenvolvimento de tecnologia que conduza não apenas extração do pigmento bruto, mas principalmente que leve à obtenção de bixina de elevada pureza, conjugada à sua estabilização, é de fundamental importância para agregar valor ao produto. Portanto o objetivo deste trabalho foi realizar uma análise comparativa entre técnicas de processamentos para extração de pigmentos nas sementes de urucum, sendo conduzidos dois tipos de extração de bixina das sementes de urucum: extração lipossolúvel e extração hidrossolúvel. Na extração lipossolúvel, o solvente utilizado foi óleo vegetal comercial e na extração hidrossolúvel, o solvente utilizado foi hidróxido de sódio. Nos sistemas de extração estudados conclui-se que é possível produzir corante de semente de urucum tanto pelo método lipossolúvel como também pelo método hidrossolúvel e que a estabilidade dos pigmentos é afetada em função da concentração de hidróxido de sódio e também em função das temperaturas de armazenamento. / The annatto tree (Bixa orellana L), is a tree with predominance in Tropical America regions particularly in Brazil, which has the biggest world production. The annatto seeds pigments are most used as natural pigment basically and are basically composed of bixin, with level around 80%, and norbixin, in a lower concentration. The pigment obtained through the annatto seeds is applied on the industry as a liquid, paste or powder; however, for its industrialization, technological knowledge which allows the gain of pigments with low cost and with an acceptable quality is indispensable and this technology turns the product capable to compete in the international market. The extraction process optimization is of fundamental importance and seeks not only increase the productivity but also minimize the contamination with the by-products of decomposition. The technological development that leads not only the extraction of gross pigment, but mainly induces the bixin high purity gain, conjugated with its stabilization, is of fundamental importance to add value to the product. Therefore, the objective of this work was to accomplish a comparative analysis between technical of processes in the extraction of pigments from the annatto seeds. It was driven two ways of extraction of annatto pigments seeds: oil soluble extraction and water soluble. In the oil soluble extraction, the solvent used was the commercial vegetal oil and on the water soluble extraction, the solvent used was sodium hydroxide. In the studied extraction systems it is ended that is possible to produce annatto seed pigment with the oil soluble method as well as the water soluble method and that the stability of pigments is affect in function the concentration of hydroxide sodium and also in function of the temperature of storage.

El premio Ig Nobel de Química 2012 fue otorgado al ingeniero sueco Johan Petterson por explicar que el cobre era el responsable de teñir el cabello de verde a los habitantes de una pequeña población sueca. En la naturaleza existen numerosos compuestos verdes de cobre, que se usan como pigmentos, y está presente también en las hemocianinas, enzimas sanguíneas de algunos artrópodos y moluscos. / The 2012 Ig Nobel Prize in Chemistry was awarded to Johan Petterson, a Swedish engineer who discovered that copper was responsible for turning hair green in a little Swedish town. Many green copper compounds used as pigments are present in nature and there are also the hemocyanins, copper-containing proteins found in the blood of some arthropods and mollusks.

Made available in DSpace on 2014-10-09T12:35:54Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:26Z (GMT). No. of bitstreams: 0 / Observações feitas pelo próprio autor sugerem potencial ação do Líquido da Castanha de Caju (LCC) na pigmentação da pele, ação esta semelhante a da hidroquinona. O LCC é um líquido contido na casca da castanha de caju, possui característica de resina líquida, bastante viscosa e de odor forte, sua coloração varia de marrom claro, escuro a preto, dependendo do método de extração utilizado, podendo ser denominado de Natural ou Técnico. Este estudo propôs cultivar melanócitos e queratinócitos em cocultura e posteriormente tratálos com LCC. A L-DOPA, agente estimulador da melanogênese, via da produção de melanina, responsável pela pigmentação da pele, foi utilizada na cocultura para avaliar a ação do LCC. A hidroquinona, conhecido inibidor desta via, foi utilizada na cocultura como controle positivo para o LCC, visto que este poderia apresentar ação semelhante a da hidroquinona. Para a utilização do LCC na cocultura, testes de solubilidade do mesmo para posterior dispersão no meio de cultura, foram necessários, bem como a identificação de seu potencial cito e fototóxico in vitro. Para a realização do teste de fototoxicidade foi construída uma câmara específica, atendendo as normas exigidas pelos guias ©ECVAM DB-ALM: INVITTOX protocol e OECD TG-432, sendo esta qualificada por método validado. Os testes realizados com o LCC (natural e técnico) indicaram potencial ação destes na pigmentação da pele, estimulando a proliferação de melanócitos em cocultura. Este perfil apresentado, pelos extratos de LCC, é contrário ao da hidroquinona, e ao esperado inicialmente, sendo necessário aprofundar estes estudos. No entanto, estes resultados são promissores, sugerindo a descoberta de um novo tratamento para hipocromias. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP