Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

No description available.

Made available in DSpace on 2014-06-11T19:30:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-10-31Bitstream added on 2014-06-13T20:40:50Z : No. of bitstreams: 1 ouchi_ry_dr_sjrp.pdf: 1860080 bytes, checksum: 6ea294f1febce43f75eaaecd7bef2497 (MD5) / A cada ano, milhares de novos compostos químicos entram no mercado, e um volume enorme de resíduos é gerado pela atividade humana, existindo uma grande preocupação com relação aos seus efeitos a curto e longo prazo sobre a saúde e o ambiente. Um grande número dessas substâncias químicas é potencialmente perigoso e pode acarretar efeitos biológicos deletérios, sendo que mudanças a nível molecular são usualmente as primeiras respostas detectáveis da perturbação ambiental. Para avaliar os efeitos em sistemas biológicos, são utilizados bioindicadores, organismos sensíveis a agentes tóxicos. O presente trabalho teve por objetivo analisar os efeitos do Brometo de Etídio (BE), substância potencialmente mutagênica, na mosca da fruta (Drosophila melanogaster), realizando-se sempre comparações com o controle positivo, etilmetanosulfonato (EMS). Escolhemos o brometo de etídio por se tratar de uma substância usada frequentemente em métodos de biologia molecular, sendo tida como mutagênica, apesar de não constar como carcinogênico nas listagens da Agência Internacional para Pesquisa de Câncer (IARC). A pesquisa foi feita ao longo de 25 gerações, e em seis gerações (1ª, 5ª, 10ª, 15ª, 20ª, 25ª gerações) foram analisados: (1) os efeitos sobre padrões morfológicos, (2) a produtividade diária ao longo de 15 dias. Além disso, foram analisadas também: (3) alterações bioquímicas em enzimas do sistema oxidativo, acarretadas pela exposição a diferentes concentrações de brometo de etídio e EMS, (4) alterações gênicas: em nível de transposição do elemento transponível Bari-1 e na expressão dos genes que codificam as proteínas catalase, hsp 70 (heat shock protein), superóxido dismutase... / Each year thousands of new chemicals enter the market, and an enormous volume of waste is generated by human activity. Accordingly, there is a great concern regarding their short and long term health and environmental effects. A large number of these chemicals is potentially dangerous and can cause harmful biological effects, and changes at the molecular level are usually the first detectable responses of environmental disturbance. To evaluate the effects on biological systems, are used bioindicators, organisms sensitive to toxic agents. This study aimed to analyze the effects of Ethidium Bromide (EB), a potentially mutagenic substance, in the fruit fly (Drosophila melanogaster), comparing with a positive control, ethylmethanesulfonate (EMS). We chose ethidium bromide because it is a chemical frequently used in molecular biology techniques, and considered as a mutagenic although it is not included in the lists of the International Agency for Research on Cancer (IARC). The survey was conducted over 25 generations, and in six generations (1st, 5th, 10th, 15th, 20th, 25th generations) were analyzed: (1) the effects on morphological patterns, (2) the daily productivity over 15 days. In addition, we also analyzed: (3) biochemical changes in enzymes of the oxidative system brought about by exposure to different concentrations of ethidium bromide and EMS, (4) genetic alterations: level of transposition of the transposable element Bari-1 and expression genes that encode proteins catalase, hsp 70 (heat shock protein), superoxide dismutase 1 and esterase-6 and (5) longevity. Concerning daily productivity, five replicates were done, involving negative and positive controls (not exposed to any mutagen and with EMS, respectively), and three groups exposed to 1, 5 and 30 µM of EB. The results show that there were... (Complete abstract click electronic access below)

No description available.

Ecotoxicologists adopted median lethal concentration (LC50) methods from mammalian toxicology. This conventional LC50 approach has shortcomings. Fixing the exposure duration and selecting the 50% mortality level result in loss of ecologically relevant information generated at all other times. It also ignores latent mortality that can manifest after exposure ends. as a result, it cannot adequately predict pulsed exposure effects in which concentration, duration, and frequency of pulses change through time. The underlying theory of the dose-response models used to calculate LC50 values, stochastic versus individual effective dose (IED) theory, has not been tested rigorously either. In this study, the effects of exposure duration and concentration on mortality during and after exposures, and the effects of recovery time between two pulses on mortality during a second pulse were quantified. The influences of toxicant modes of action were discussed. The underlying theory for survival distribution models was further explored. Survival analysis was used to incorporate these factors into predictive models and to circumvent some of the aforementioned shortcomings. The experiments were conducted with two contrasting toxicants, copper sulfate (CuSO4) and sodium pentachlorophenol (NaPCP). The amphipod, Hyalella azteca, was used as the model organism. Latent mortality is significantly affected by exposure concentration and an integral part of the lethal effects of toxicants that cause cumulative damage. For toxicants that cause minimal cumulative damage during the exposure, the latent mortality is not significant and can be ignored. Exposure duration did not show any significant effect on latent mortality for either toxicant. It is recommended that for other experimental conditions the effect still needs to be considered. Recovery time had significant effect on mortality during the second pulse for both toxicants. to recover to a similar background level mortality, the time an exposed organism needed to return to a stage similar to its original resistance was much longer for CuSO4 than for NaPCP. The hypothesis that IED is the dominant explanation for the dose-response models was rejected for both toxicants. By effectively incorporating exposure duration and other factors, survival analysis better predicted pulsed exposure consequences than did the conventional LC50 methods.

When animals are exposed to mixtures of environmental pollutants, it is generally assumed that the toxic effects of the individual components are additive. However, examples of synergistic and antagonistic effects have been described. to study the mechanisms of interaction between a metal and a polycyclic aromatic hydrocarbon, mummichog (Fundulus heteroclitus) were injected with combinations of cadmium (Cd) and benzo (a) pyrene (BP). Measured effect parameters were: mortality, BP-metabolite production in isolated hepatocytes and microsomes, hepatic induction of CYP1A (the BP metabolizing enzyme) and metallothionein (the Cd binding protein), and biliary excretion of BP-metabolites. The mortality data demonstrated that both synergistic and antagonistic effects can occur. A Cd dose of 0.32 mg/kg significantly reduced the expected mortality caused by BP. In contrast, a BP dose of 10 mg/kg significantly increased the toxicity of Cd above the expected mortality. to study the mechanisms of these interactive effects, liver cells (hepatocytes) were isolated from fish that were previously injected with combinations of Cd and BP. These cells were exposed to radiolabeled BP to study the rate of BP metabolism, and the formation of BP-metabolites. Cadmium exposure had an overall inhibiting effect on the metabolism of BP. No effects of Cd were observed on the formation of individual metabolites. to distinguish between direct interference of Cd with CYP1A at the active site versus indirect interference by inhibiting CYP1A induction, microsomal preparations were evaluated for enzyme activity and enzyme concentration. While there was no direct effect of Cd on enzyme catalytic activity, there was an effect on CYP1A production. The demonstrated inhibition of BP metabolism by Cd would suggest a reduced excretion of BP-metabolites. However, analysis of bile and water samples after fish were injected with radiolabeled BP demonstrated an enhanced biliary excretion of conjugated BP-metabolites under influence of Cd. Cadmium exposure caused a significant induction of hepatic metallothionein in the fish. When BP was dosed together with Cd, the induction of MT was inhibited. The hypothesis that reactive BP metabolites would compete with Cd for binding sites on MT could not be confirmed. There was no measurable binding of BP to MT.

A sediment toxicity test using the freshwater oligochaetes Lumbriculus variegatus and Tubifex tubifex was performed. We evaluated acute and chronic toxicity affects of copper and cadmium on reproduction in both species and the bioaccumulation of both metals by L. variegatus using artificial sediment. L. variegatus bioconcentrated copper 22‐fold and cadmium 16‐fold after a 14‐day exposure to spiked artificial sediments with 0.02% organic content. The EC50 for T. tubifex varied depending upon endpoint from 2.7 to 2.8 mg/L for cadmium and from 8.4 to 8.9 mg/L for copper. The EC50 for L. variegatus was 2.2 mg/L for cadmium and 3.9 mg/L for copper. Based on these results, L. variegatus appears to be more sensitive to metal toxicity in artificial sediments than T. tubifex.

Doutoramento em Ciências Farmacêuticas / PhD in Pharmaceutical Sciences

Doutoramento em Toxicologia / PhD Degree - Toxicology