Métodos in vitro utilizando epitélio intestinal animal são importantes ferramentas para avaliar a permeabilidade de fármacos, propriedade que é um importante parâmetro de biodiosponibilidade. Considerando que o maior objetivo na indústria farmacêutica é desenvolver novos fármacos com boa biodisponibilidade oral, o projeto teve como objetivo padronizar o modelo de permeação com membrana de intestino de rã (Rana catesbeiana) em células de Franz, comparando seus resultados com ensaios de células Caco-2. Os fármacos modelo utilizados foram os antivirais zidovudina e aciclovir. A quantidade de fármaco permeado foi determinada por método de eletroforese capilar para o método com intestino de rã touro e por HPLC-UV para os ensaios com células Caco-2. O parâmetro de permeação foi o coeficiente de permeabilidade aparente (Papp) dos fármacos para ambos modelos experimentais. Para estabelecimento do protocolo experimental dos estudos de permeabilidade intestinal de rã, foi proposto um projeto fracionado 24-1 com 4 ensaios adicionais usando o software Minitab, e as variáveis foram: secção intestinal, pH da solução de Ringer e temperatura. A análise do planejamento experimental feita pela estimativa dos parâmetros da regressão obtidos através dos resultados do modelo fatorial possibilitou a determinação dos coeficientes da equação matemática que definiu a influência das variáveis sobre o coeficiente de permeabilidade aparente dos fármacos. Os efeitos das variáveis pH e temperatura interpretados conjuntamente apresentaram interferência leve, porém as variáveis fármaco e secção intestinal interpretados juntos tiveram interferência importante, mostrando maior permeação dos fármacos através da secção inicial do intestino da rã. Os resultados de Papp foram: para o metoprolol, pelo método das células Caco-2 foi de 28 x 10-6 cm/s, valor que está de acordo com demais dados de células Caco-2 na literatura e o valor obtido com células de Franz que mais se adequada a estes resultados e demais disponíveis provenientes de outras técnicas na literatura, foi de 28,1 x 10-6 cm/s, em uma das condições do planejamento estatístico utilizando segmento final da membrana epitelial da rã. No caso do aciclovir, o resultado de Papp de 0,48 x 10-6 cm/s também obtido em uma das condições envolvendo segmento intestinal final da rã foi exatamente igual a o valor 0,48 x 10 - 6 cm/s, encontrado com células Caco-2 no presente estudo e estão de acordo com outros valores disponíveis na literatura por Trapani e colaboradores, 2004 e também com células Caco-2. Para zidovudina o valor de Papp obtido em uma das condições utilizando segmento intestinal inicial da rã, de 13 x 10-6 cm/s, foi a que mais se assemelhou ao obtido pela técnica de células Caco-2, 13,6 x 10-6 cm/s, e também está de acordo com demais dados da literatura. / There are lots of different in vitro technics in the literature using animal intestinal epithelium to estimate permeability of drugs, property that is an important parameter of bioavailabity. Considering that the main objective of Pharmaceutical Companies is the development of new drugs with good oral bioavailabity, the aim of this work was to standardize the permeability of antivirals using in vitro/ex vivo method of intestinal epithelium of Rana catesbeiana in Franz cells and compare these results to those obtained from studies using Caco-2 cells. Zidovudine and Acyclovir were selected as model drugs. The amount of drug permeated will be determined by the method of capillary electrophoresis for assays using Rana Catesbeiana and HPLC-UV for studies with Caco-2 cells. The permeation parameter determined was the apparent permeability coefficient (Papp) of drugs for both experimental models. To establish the experimental protocol to studies of intestinal permeability of frog, it was proposed a fractional 24-1 design with 4 additional tests using Minitab software and the variables were: intestinal section, pH of Ringer solution and temperature. The analysis of the experimental design made by the estimate of the regression parameters obtained from the factorial model results allowed the determination of the coefficients of the mathematical equation that defines the influence of the variables on the apparent permeability coefficient of acyclovir and zidovudine. The effects of pH and temperature interpreted jointly presented a slight interference, but the variables drug and intes tinal section interpreted together had major interference, showing greater permeation of drugs through the initial section of the intestine of the frog . The results of Papp were: for metoprolol, with the method of Caco-2 cells was 28 x 10-6 cm/s, a value which is consistent with other data of Caco-2 cells provided in the literature and the condition obtained with Franz cells that are most suitable for these and other results obtained from other techniques available in the literature, was 28.1 x 10-6 cm/s, provided with the final intestinal segment using frog epithelial membrane. In the case of acyclovir, the result of Papp of 0.48 x 10-6 cm/s obtained in one condition with final frog intestinal segment was exactly equal to the value of 0.48 x 10-6 cm/s, found with Caco-2 cells in the present study and are in agreement with other values available in the literature for Trapani and colegues, 2004 and also with Caco-2 cells. The Papp value for zidovudine obtained with the initial gut segment of frog, 13 x 10-6 cm /s was which more resembled that obtained by the technique of Caco-2 cells, 13.6 x 10-6 cm/s and is also consistent with other literature data.

Submitted by (edna.saturno@ufrpe.br) on 2017-02-21T17:09:23Z No. of bitstreams: 1 Sandro Ricardo da Costa.pdf: 720379 bytes, checksum: 054515c8a5c3b3fc9ff3150fc0b86e14 (MD5) / Made available in DSpace on 2017-02-21T17:09:23Z (GMT). No. of bitstreams: 1 Sandro Ricardo da Costa.pdf: 720379 bytes, checksum: 054515c8a5c3b3fc9ff3150fc0b86e14 (MD5) Previous issue date: 2012-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The technique of use of gonadotrophin releasing hormone (GnRH) in the reproduction of amphibians can be used to control spawning throughout the year, avoiding production delays resulting from the seasonality of the reproductive cycle. The objective was to study the induced breeding of bullfrog Lithobates catesbeianus using different types and dosages of GnRH to the optimization of the hormone and the consequent reduction in operating costs in commercial production. Breeders (average weight 650 g) were previously prepared, and conditioned to an average temperature of 26°C, submitted to a photoperiod of 15 hours of light. We tested three different hormone treatments; treatment 1 (T1) with 5 μg Etilamid hydrated acetate, treatment (T2) 2.5 μg Etilamid hydrated acetate and treatment 3 (T3) with 0.8 μg of Buserelin acetate, divided in three experimental groups. For each treatment, three applications were made at intervals of 12 hours hormones application in females and a single one for males. After the hormone treatment was done the extrusion of eggs in females and spermiation in males fertilized eggs hydrated with water at neutral pH. All males responded to the hormones applied resulting in a "pool of sperm" used to fertilize the females. Females of treatments T1 and T2 ovulated in its entirety and there was a failure only in T3. From the first and second trials, it could be detected that the dosages of 2.5 μg Etilamid hydrated acetate and 0.8 μg Buserelin acetate are more technically and economic viable for induced breeding of bullfrog. The average weight of spawning was 92.8 and 93.7 g respectively. The fertilization rate was estimated from the percentage of eclosion, with rates of fertilization rates average with 84.2 % (T2) and 60.3 % (T3). Based on the results, we conclude that the reduction in usual dosages for Etilamid hydrated acetate and the use of Buserelin acetate were efficient on ovulation and spermiation in bullfrogs, but it is necessary to adjust the dosage of Buserelin acetate as well to get a better improvement through environmental control and breeder maturation conditions in further experiments. / A técnica de uso de hormônios liberadores da gonadotrofina (GnRH) na reprodução de anfíbios pode ser usada para controlar as desovas ao longo do ano, evitando atrasos na produção decorrente da sazonalidade do ciclo reprodutivo. Objetivou-se estudar a reprodução induzida da rã touro Lithobates catesbeianus, utilizando diferentes tipos e dosagens do GnRH visando à otimização do hormônio e conseqüente redução nos custos operacionais na produção comercial. Os reprodutores (peso médio de 650 g) foram previamente preparados, sendo climatizados à temperatura média de 26° C, e submetidos a fotoperíodo de 15h luz. Foram testados três diferentes tratamentos hormonais, sendo o tratamento um (T1) com 5 μg/rã de acetato de Etilamida hidratado, o tratamento dois (T2) 2,5 μg/rã de acetato de Etilamida hidratado e o tratamento três (T3) com 0,8 μg/rã de acetato de Busserelina, divididos em três fases experimentais. Em cada tratamento foram feitas três aplicações de hormônios com intervalo de 12 h nas fêmeas, e apenas uma aplicação nos machos. Após o tratamento hormonal foi feita a extrusão dos óvulos nas fêmeas e espermiação nos machos, fecundando e hidratando os ovos com água de pH neutro. Todos os machos responderam aos hormônios aplicados resultando em um ―pool espermático‖, usado na fertilização das fêmeas. As fêmeas dos Tratamentos T1 e T2 ovularam em sua totalidade havendo uma abstenção apenas no T3. Nas primeira e segunda fase experimental, foi detectado que as dosagens de 2,5 μg/rã de acetato de Etilamida hidratado e 0,8 μg/rã de acetato de Busserelina foram mais tecnicamente e economicamente viáveis para indução à reprodução da rã touro. A média no peso das desovas foi de 92,8 e 93,7 g, respectivamente. A taxa de fecundação foi estimada na porcentagem de eclosão das larvas, com índices de fecundação com medias no T2 com 84,2 % e 60,3 % no T3. Com base nos resultados, é possível concluir que houve eficiência com a redução das dosagens usuais para o acetato de Etilamida hidratado e também houve eficiência com o uso do acetato de Busserelina na ovulação e espermiação de rãs, porém se faz necessário ajuste de dosagens para acetato de Busserelina bem como uma melhor adequação entre as condições de controle ambiental e maturação dos reprodutores, afim de melhorar os índices de fecundação em novos experimentos.

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-08-23T12:00:12Z No. of bitstreams: 1 2016 - Siria da Fonseca Jorge.pdf: 4082208 bytes, checksum: 0cf00af2f5c5490e467e6dfd2ecf8938 (MD5) / Made available in DSpace on 2017-08-23T12:00:12Z (GMT). No. of bitstreams: 1 2016 - Siria da Fonseca Jorge.pdf: 4082208 bytes, checksum: 0cf00af2f5c5490e467e6dfd2ecf8938 (MD5) Previous issue date: 2016-12-07 / Hernioplasties are included in the most performed surgeries in Human Medicine. Despite the high frequency, its complications and recurrences still make them the great challenge of modern surgery. Currently several types of screens are available for hernioplasties, it is emphasized that its application in the correction of hernia defects has been exhaustively tested in order to achieve an ideal prosthesis in every sense, with biocompatibility, little or no formation of peritoneal adhesions, texture And flexibility, providing the necessary strength for protection of the viscera and yet allowing perfect movement of the abdomen. The present study had as main objective to evaluate the efficacy and local reaction of the implant using low density polyethylene (LDPE) bullous lamina, bubble wrap and frog-bull skin for correction of hernia defects in the abdominal wall of Rattus norvegicus, Wistar variety. A total of 40 male rats were divided into two groups, one received the blister plastic implant and the other frog skin implant. A follow-up of 3.0 cm in the longitudinal axis by 1.0 cm was taken on the transverse axis including all planes of the abdominal musculature, from the midline towards the left side of the abdominal wall, creating a fault that was covered by one of the prostheses proposed according to the group in question. The animals were evaluated through monitoring of clinical, thermographic, macroscopic, histological and histopathological parameters at 7, 15, 30 and 90 postoperative days. Clinically, none of the two prostheses tested presented alterations such as abscesses, entero-cutaneous fistulas, eventrations or eviscerations. Macroscopically, all the animals had adhesions considered to be mild, mainly in the region of the suture of the prostheses. Infrared thermography proved effective as an evaluation method of inflammation and involution of the prostheses together with the morphological analysis. After analyzing all the results it was concluded that the bullfrog skin caused an initial inflammatory process that was reduced until the cure at 90 postoperative days, being considered a promising biomaterial for hernioplasties and the lamellar PEPD bullous produced a An initial inflammatory process that regressed up to 30 postoperative days, but tripled at 90 postoperative days, being considered a good material for temporary implants up to a maximum of 30 days and new studies with longer implantation periods of this biomaterial So that it is used safely in corrections of hernia defects definitively / As hernioplastias incluem-se nas cirurgias mais realizadas na Medicina Humana. Apesar da alta frequ?ncia, suas complica??es e recorr?ncias ainda as tornam o grande desafio da cirurgia moderna. Atualmente v?rios tipos de telas est?o dispon?veis para hernioplastias, ressalta-se que sua aplica??o na corre??o de defeitos herni?rios tem sido exaustivamente testada com o prop?sito de conseguir uma pr?tese ideal em todos os sentidos, com biocompatibilidade, pouca ou nenhuma forma??o de ader?ncias peritoneais, textura e flexibilidade compat?veis, proporcionando a resist?ncia necess?ria para a prote??o das v?sceras e ainda assim, permitindo a perfeita movimenta??o do abdome. O presente estudo teve como principal objetivo avaliar a efic?cia e rea??o local do implante utilizando polietileno de baixa densidade (PEBD) laminar bolhoso, pl?stico bolha e pele de r?-touro para corre??o de defeitos herni?rios em parede abdominal de Rattus norvegicus, variedade Wistar. Foram utilizados 40 ratos, machos divididos em dois grupos, um recebeu o implante de pl?stico bolha e o outro implante de pele de r?. Foi retirado um seguimento de 3,0 no eixo longitudinal por 1,0 cm no eixo transversal incluindo todos os planos da musculatura abdominal, a partir da linha m?dia em dire??o ao lado esquerdo da parede abdominal, criando-se uma falha que foi recoberta por uma das pr?teses propostas de acordo com o grupo em quest?o. Os animais foram avaliados atrav?s de acompanhamento de par?metros cl?nicos, termogr?ficos, macrosc?picos, histol?gicos e histopatol?gicos aos 7, 15, 30 e 90 dias de p?s-operat?rio. Clinicamente nenhuma das duas pr?teses testadas apresentou altera??es como abscessos, f?stulas entero-cut?neas, eventra??es ou eviscera??es. Macroscopicamente todos os animais apresentaram ader?ncias consideradas leves, principalmente, na regi?o da sutura das pr?teses. A termografia infravermelha se mostrou eficaz como m?todo avaliativo de inflama??o e da involu??o das pr?teses em conjunto com a an?lise morfol?gica. Ap?s a an?lise de todos os resultados concluiu-se que a pele de r?-touro provocou um processo inflamat?rio inicial que foi reduzindo at? a cura aos 90 dias de p?s-operat?rio, sendo considerada um biomaterial promissor para hernioplastias e o PEBD laminar bolhoso produziu um processo inflamat?rio inicial que regrediu at? os 30 dias de p?s-operat?rio, entretanto triplicou aos 90 dias de p?s-operat?rio sendo considerado um bom material para implantes tempor?rios de at? no m?ximo 30 dias e sendo necess?rio novos estudos com per?odos de implanta??o mais longos deste biomaterial para que seja utilizado com seguran?a nas corre??es de defeitos herni?rios de modo definitivo.

No description available.

Synaptic transmission alters the strength of the postsynaptic potential, through a process called short-term synaptic plasticity (STP). In this study, endplate potentials (EPPs) from the frog neuromuscular junction were used to resolve and quantify the presynaptic components involved in enhancement and depression of transmitter release during repetitive stimulation under normal quantal release conditions (2 mM Ca2+, 1mM Mg2+). During trains of stimulation given between 10 - 200 Hz, the amplitude of the EPPs first increased then decreased; a maximum increase of 77% was produced after 2-4 stimuli. EPP amplitudes began to increase at ~ 20 Hz, were maximal at ~ 55 Hz, and thereafter, decreased as the rate of stimulation increased. The integrated total release after 25 stimuli was little changed across frequencies between 10 - 100 Hz. EPPs ran down in two phases: a fast phase, attributed to the depletion of a readily releasable pool (RRP) of synaptic vesicles, followed by a slow phase, attributed to the depletion of vesicles from a depot pool (DP). Depletion of the readily releasable pool of synaptic vesicles (RRP) was determined by quantifying release under the fast and slow time rundowns and subtracting the number of vesicles associated with mobilization to the RRP from the total number of vesicles released during stimulation trains of 50 impulses. Impulses were delivered at 12 different rates ranging from 50 to 200 /s. Estimates of the number of vesicles released from the RRP increased with frequency of stimulation until maximal depletion levels of 5500 - 6000 vesicles were reached at stimulation rates between 90-130/s, assuming a control quantal content of 200 vesicles released per impulse. Depletion was less at lower frequencies when the number of stimuli delivered was identical. When the RRP maximally depleted, release was inversely related to stimulation rate, as would be expected if mobilization from the depot pool was the sole determinate of release during the slow phase. An equation constructed from four known components of enhancement and two components of depression - the depletion of vesicles from a readily releasable pool (RRP) and from the depot pool (DP) that refills the RRP, was used to fit and then simulate EPPs obtained during trains using different patterns of stimulation and varying amounts of extracellular Ca2+; the decay time constant parameters of enhancement, numerically derived from the observed data, were fixed at tau ~ 46, 220, 1600, and 20000 ms. The number of components of enhancement necessary to approximate the data decreased, from four in low (0.14 - 0.2mM) extracellular Ca2+, to one (tau ~ 46 ms) in 2.0 mM extracellular Ca2+, but four components of enhancement were necessary to fit the data when the amplitude of the EPP was not depressed below the control amplitude. This model was able to predict within ~ 3 % EPP amplitudes over a 10-fold range of frequency and Ca2+ concentration.

Amphibians develop in aquatic environments where they are very susceptible to the effects of pesticides and other environmental contaminants. Glyphosate-based herbicides are widely used and have been shown to affect survival and development of tadpoles under laboratory conditions. The goal my thesis is to determine if agriculturally relevant exposure to Roundup WeatherMax®, a herbicide formulation containing the potassium salt of glyphosate and an undisclosed surfactant, influences the survival and development of wood frogs tadpoles (Lithobates sylvaticus) under both laboratory and field conditions. In the field, experimental wetlands were divided in half using an impermeable curtain so that each wetland contained a treatment and control side. Tadpoles were exposed to two pulses of this herbicide at environmentally realistic concentration (ERC, 0.21 mg acid equivalent (a.e.)/L) and predicted environmental concentrations (PEC, 2.89 mg a.e./L), after which survival, growth, development, and expression of genes involved in metamorphosis were measured. Results indicate that exposure to the PEC is extremely toxic to tadpoles under laboratory conditions but not under field conditions. Results from both experimental conditions show sublethal effects on growth and development, and demonstrate that ERC of glyphosate-based herbicides have the potential to alter hormonal responses during metamorphosis. My secondary objectives were to compare the effects of Roundup WeatherMax® to the well-studied Vision® formulation (containing the isopropylamine (IPA) salt of glyphosate and POEA), and to determine which ingredient(s) are responsible for the sublethal effects on development. Survival, growth and gene expression results indicate that Roundup WeatherMax® has greater toxicity than Vision® formulation. Contrary to my prediction, results suggest that, under realistic exposure scenarios, POEA is not the sole ingredient responsible for the observed developmental effects. However, my results demonstrate that chronic exposure to the POEA surfactant at the PEC (1.43 mg/L) is extremely toxic to wood frog tadpoles in laboratory. As part of the Long-term Experimental Wetlands Area (LEWA) project, this research contributes to overall knowledge of the impacts of glyphosate-based herbicides on aquatic communities.

Many prey species lack innate recognition of their potential predators. Hence, learning is required for them to recognize and respond to predation threats. When wild-caught, these same species may show amazing sophistication in their responses to predator cues. They are able to adjust the intensity of their antipredator responses to a particular predator according to the degree of threat posed by that predator. This ability is therefore acquired through learning. While many studies have shown that prey can learn to respond to predator cues through different learning modes, little is known about what the prey are actually learning. The results presented in this thesis show that learned predator recognition goes beyond the simple labelling of predators as dangerous. Using fathead minnows (Pimephales promelas), woodfrog (Rana sylvatica) tadpoles and boreal chorus frog (Pseudacris maculata) tadpoles, I demonstrated that a one time learning event, either through pairing with alarm cues or through social learning, was enough for prey to learn the level of threat associated with the novel predator cues. I showed that the level of danger associated with the predator cues was determined by the concentration of alarm cues when learning through pairing of alarm cues, or by the intensity of antipredator response displayed by the tutors and by the tutor-to-observer ratio when learning occurred through cultural transmission. Moreover, when subsequently exposed to predator cues, prey adjusted their antipredator responses according to the change in concentration of predator cues between the learning event and the subsequent exposure. Prey displayed stronger antipredator responses when exposed to higher concentrations of predator cues and vice versa. When minnows were provided with conflicting information about the danger level associated with a predator, they displayed a safety strategy and used the most recent information available to respond to predation threats. On a longer time scale, the data also suggest that woodfrog tadpoles are able to learn to respond to predation threats according to the risk posed by the predator at different times of day. Finally, I showed that prey learn to recognize particular characteristics of predators and can generalize their antipredator responses to novel species sharing those characteristics. However, generalization of predator recognition is dependent on the level of risk associated with the predator. Threat-sensitive learning is an extremely complex process shaped by the millions of years of selection imposed by predators on prey.

Many prey species lack innate recognition of their potential predators. Hence, learning is required for them to recognize and respond to predation threats. When wild-caught, these same species may show amazing sophistication in their responses to predator cues. They are able to adjust the intensity of their antipredator responses to a particular predator according to the degree of threat posed by that predator. This ability is therefore acquired through learning. While many studies have shown that prey can learn to respond to predator cues through different learning modes, little is known about what the prey are actually learning. The results presented in this thesis show that learned predator recognition goes beyond the simple labelling of predators as dangerous. Using fathead minnows (Pimephales promelas), woodfrog (Rana sylvatica) tadpoles and boreal chorus frog (Pseudacris maculata) tadpoles, I demonstrated that a one time learning event, either through pairing with alarm cues or through social learning, was enough for prey to learn the level of threat associated with the novel predator cues. I showed that the level of danger associated with the predator cues was determined by the concentration of alarm cues when learning through pairing of alarm cues, or by the intensity of antipredator response displayed by the tutors and by the tutor-to-observer ratio when learning occurred through cultural transmission. Moreover, when subsequently exposed to predator cues, prey adjusted their antipredator responses according to the change in concentration of predator cues between the learning event and the subsequent exposure. Prey displayed stronger antipredator responses when exposed to higher concentrations of predator cues and vice versa. When minnows were provided with conflicting information about the danger level associated with a predator, they displayed a safety strategy and used the most recent information available to respond to predation threats. On a longer time scale, the data also suggest that woodfrog tadpoles are able to learn to respond to predation threats according to the risk posed by the predator at different times of day. Finally, I showed that prey learn to recognize particular characteristics of predators and can generalize their antipredator responses to novel species sharing those characteristics. However, generalization of predator recognition is dependent on the level of risk associated with the predator. Threat-sensitive learning is an extremely complex process shaped by the millions of years of selection imposed by predators on prey.

Many essential processes and interactions on atomic and molecular scales occur at ultrafast timescales. The ability to measure and manipulate ultrashort pulses hold the key to probing and understanding these key processes that physicists, engineers, chemists and biologists study today. Measuring ultrashort pulses means that we measure both the intensity (which is a function of time) and the phase of the pulse in time. Or alternately we might measure spectrum and spectral phase (in the corresponding Fourier domain). In the early 1990's, the invention of FROG opened up the field of ultrashort measurement with it's ability to measure the complete pulse. Since then, there have been a whole host of pulse measurement techniques that have been invented to measure all sorts of ultrashort pulses. However, no variation of FROG nor any other fs pulse measurement technique, for that matter, has yet been able to completely measure arbitrary ultraweak femtosecond light pulses such as those found in nature. In this thesis, we will explore a couple of highly sensitive methods in a quest to measure ultraweak ultrashort pulses. We explore the use of Spectral Interferometry, a known sensitive technique as one possibility. We find that it has certain drawbacks that make it not necessarily suitable to tackle this problem. But in the course of our quest, we find that this technique is highly suitable for measuring 10s of picosecond-long shaped pulses. We discuss a couple of developments which make SI highly practical to use for such shaped pulse-measurements. We also develop a new technique which is a variation of FROG, based on the non-linearity of Difference Frequency Generation and Optical Parametric Amplification, which can amplify pulses as weak as a few hundred attojoules to be able to spectrally resolve them and measure the full intensity and phase of these pulses. This technique offers great potential to measure generalized ultraweak ultrashort pulses.

Flamboyant colors are widespread throughout the animal kingdom. While many of these traits arise through sexual selection, bright coloration can also evolve through natural selection. Many aposematic species, for example, use conspicuous warning coloration to communicate their noxiousness to predators. Recent research suggests these signals can also function in the context of mate choice. Studies of warning color evolution can therefore provide new insights into how the interplay of natural and sexual selection impact the trajectory of conspicuous signal evolution. For my dissertation, I investigated the potential for male-male competition to impact the warning color evolution of a species of poison frog. I focused my work on an exceptionally bright and toxic population of the strawberry poison frog (Oophaga pumilio) where males are brighter than females, a classic signature of sexual selection. In Chapter 1, I used theoretical models of predator and frog visual systems to determine which can see the variation in bright warning coloration within this population. I found that birds, the presumed major predator, likely cannot see this variation, indicating that sexual selection can work under the radar of predators in this species. In Chapter 2, I tested the aggressive responses of males using a two-way choice paradigm that manipulated the perceived brightness of stimulus males. I found that males directed more of their behaviors to bright stimulus frogs, and brighter focal frogs more readily approached stimuli and directed more of their attention to the brighter rival. In Chapter 3, I tested the outcomes of dyadic interactions between males of varying brightness and observed male reactions to simulated intruders in their territories. I found that brighter males initiated aggressive interactions with rivals more readily, and brightness asymmetries between males settled interactions in a way that is consistent with classic hypotheses about male sexual signals. In Chapter 4 I sought to describe physiological correlates of male warning color brightness. While male brightness did not co-vary with classic measures of body condition (circulating testosterone and skin carotenoids), it did correlate with toxins sequestered from the diet and thus appears to be a reliable signal of toxicity in this population. / text