The skin is the largest organ of the body and provides many functions. Among tetrapod vertebrates, amphibian skin is semi-permeable and responsible for a greater proportion of water absorption and gas exchange. Myriad factors affect the physiological performance of amphibian skin. Morphological traits linked with amphibian skin physiology or ecology have remained difficult to discern because of a lack of quantitative comparative research and the discovery of sources of intraspecific variation that are mostly ignored in study designs. This thesis aims to address the effects of these sources of variation using a trait that is known to vary between sexes, among seasons, and among body regions and thought to be linked with physiology or ecology, skin thickness. The first source of variation addressed is sexual dimorphism. Specimens of the white-lipped treefrog, Litoria infrafrenata, that display sexual dimorphism in body size and skin thickness were used to test if body size was the main determinate of sexually dimorphic skin thickness. Size corrected values did not significantly differ between males and females, although the sample size was small. Seasonal variation in skin thickness has also been documented in some species, so the American bullfrog (Lithobates catesbeianus), the Northern leopard frog (L. pipiens), and the spring peeper (Pseudacris crucifer) from multiple months of the year were sampled to determine if skin thickness increased in the autumn or winter months. Seasonal skin thickening was only detected in L. catesbeianus, and skin from autumn and winter was significantly thicker than from earlier in the year. This pattern was also detectable in museum specimens collected 80 years ago, although the signal was damped, possibly due to preservation. Using a dataset of 10 species and published data, a general pattern was uncovered whereby the dorsal skin is the thickest region and the ventral thigh region is the thinnest. However, this pattern is not always true for every individual of every species (L. pipiens and P. crucifer) and in some species the dorsal skin is thinnest (Bokermannohyla alvarengai and Litoria infrafrenata). The same dataset found that skin thickness is significantly related to body size, as was found in the chapter on Litoria infrafrenata. Summer specimens of Lithobates catesbeianus were outliers below the interspecific regression line and winter specimens fell within the range of variation of other species, hinting that seasonal skin thickening could be renamed seasonal skin thinning in this species. Finally, a link between ecology and skin thickness was tested using the 10 species from previous analyses and data from the literature. At a phylogenetially broad scale, body size explained a greater amount of the variation in environmental parameters than skin thickness. At smaller taxonomic scales, skin thickness appears more closely linked with ecology. It is concluded that amphibians generally follow an allometric trend for skin thickness and when faced with suboptimal conditions over long periods of time, evolve integumentary structures like iridiophores to compensate for any physiological disadvantage of an ‘ideal’ skin thickness. In the interim, however, skin thickness may change, thus sacrificing e.g. mechanical support.

This project examined the role of the cytoskeleton in regulatory mechanisms of the amiloride-sensitive Na⁺ channels in isolated frog skin epithelium. The epithelium from ventral frog skin is a model tissue which has proved significant in our understanding of the basic principles involved in water and Na⁺ homeostasis. In particular, this project examines ways in which local (non-hormonal) and hormonal regulatory mechanisms adjust the Na⁺ permeability of apical membranes of frog skin epithelium. Both mechanisms contain factors that are known to increase the apical membrane Na⁺ permeability mainly by increases in the number of open channels. The origin of these new open channels is unknown but, it is postulated that they could arise either by activation of quiescent channels already present in the apical membrane, or by recruitment of channels from cytoplasmic stores. Regarding the latter hypothesis, we also examined the idea that the cytoskeleton might somehow be involved in the insertion of Na⁺ channels within vesicles, into the apical membrane. This is based on the fact that the cytoskeleton is involved in a similar mechanism whereby, in the toad urinary bladder, anti-diuretic hormone (ADH) causes the insertion of aggregates with water channels. Much current interest focuses on the role of the cytoskeleton in the regulation of epithelial Na⁺ channels. To test this hypothesis, we used noise analysis to examine the effects of disrupting the cytoskeleton, on two different mechanisms which bring about changes in open channel densities. The mechanisms are: (1) lowering mucosal Na⁺ concentration (non-hormonal), and (2) addition of arginine-vasopressin (A VP) (hormonal). Non-hormonal, autoregulatory changes in apical membrane Na⁺ conductance were examined by investigating the effects of reducing the mucosal Na⁺ concentration. Our results showed that lowering the mucosal Na⁺ concentration induced large increases in the open channel density in order to stabilise the transport rate. In addition, we observed an average 55-60% increase in the open channel probability, which implies that in epithelium from Rana fuscigula, changes of channel open probability are also an important mechanism in the autoregulation of channel densities in response to a reduction in mucosal Na⁺. The hormonal control of Na⁺ channels by A VP has been intensively studied by noise analysis and the patch clamp. Our results confirmed previous reports that A VP increases the Na⁺ transport rate by increasing the number of open Na⁺ channels, primarily through large changes in the total number of channels, without a significant change in open probability. Regarding the role of the cytoskeleton in regulation of Na⁺ channels and/or its possible role in control of inserting putative vesicles with Na⁺ channels, we studied the effects of disrupting the cytoskeleton on the two regulatory mechanisms. Disrupting microtubules with colchicine had no, or very little effect on either of the regulatory mechanisms. On the other hand, the integrity of the microfilaments was very important for the autoregulatory changes in the number of open channels. After cytochalasin B treatment, lowering the mucosal Na⁺ concentration did not result in the usual compensatory changes in channel densities. There was no prior evidence that cytochalasin B had any actual effect on the F-actin network in the frog skin epithelium. Accordingly, modified cytochemical techniques were designed to demonstrate and localise F-actin in the epithelial granular cells. The direct immunofluorescent method proved useful, but did not allow sufficient resolution to examine the changes to different populations of actin in the cells. We then modified an immunogold method to suit our conditions, and the results demonstrated the localisation of different pools of F-actin and showed the effects of the cytochalasin B and vasopressin.

O aumento da prevalência da obesidade mórbida constitui um problema de saúde pública global. A obesidade mórbida pode ser definida por um índice de massa corpórea ( IMC ) superior a 35 Kg/ m²; vem acompanhada por diversas comorbidades e determina custos sócio-econômicos elevados. O único método efetivo a longo prazo no tratamento da obesidade mórbida, na atualidade, é a cirurgia bariátrica. Os procedimentos cirúrgicos para tratar a obesidade foram estimulados sobretudo pelo advento de técnicas videolaparoscópicas com menor morbidade pós-operatória e recuperação precoce. O sucesso operatório da cirurgia bariátrica representa perda de até 50% do excesso de peso dos pacientes em prazos variáveis de aproximadamente 24 meses. Após tal período, o processo de emagrecimento será refletido como excesso e flacidez cutânea generalizados e inicia-se a busca pela melhora da imagem corporal. A realização das cirurgias plásticas de contorno corporal exige ampla compreensão das peculiaridades clínicas desse paciente, e dos riscos de complicações, além de expectativas viáveis quanto aos resultados estéticos. Após as cirurgias de contorno corporal, passado o período pós-operatório recente, constata-se a manutenção de flacidez cutânea residual em graus variados. A obesidade interfere na qualidade dos componentes da pele humana. Entretanto, não há estudos específicos em relação à pele do paciente após perda ponderal maciça. Nesse estudo observacional histomorfométrico realizado entre 2006 e 2008, o autor avalia em biópsias de pele humana da região abdominal epigástrica e hipogástrica, o teor de colágeno e elastina em pacientes após perda ponderal maciça comparativamente a pacientes sem antecedentes de obesidade. Analisando a pele abdominal de mulheres não obesas ( controles epigástricos=15 e controles hipogástricos=25 ) e mulheres após tratamento dessa morbidade ( casos=40), verificou-se neste estudo com significância estatística aceita como p<0,05 que: a) na região epigástrica, o teor de colágeno foi superior no grupo controle em comparação ao grupo de casos; b) na região epigástrica, o teor de fibras elásticas foi superior nos casos; c) na região hipogástrica, não houve diferença estatisticamente significante no teor de colágeno entre os grupos estudados; d) na região hipogástrica, o teor de fibras elásticas foi superior no grupo controle / Morbid obesity is an increasing health problem and it is defined as a body mass index greater than 35 kg/m² with severe obesity related comorbidity or a body mass index greater than 40 kg/m² without comorbidity. The combined direct and indirect cost of obesity has been elevated. Bariatric surgery remains the only durable option for weight loss in the morbidly obese.Advanced laparoscopy procedures, as less invasive therapy, have contributed to fast recovery and acceptable perioperative morbidity. Results of bariatric surgery can reach about 50% of excess weight loss with a 2 year follow-up. As patients lose weight, they get laxity skin and their interest in body contouring surgery begins.Plastic surgery in massive weight loss patient demands attention to reduce risks and viable expectations concern to aesthetic results. However, after body contouring surgery, patients can keep up some laxity or folds of excess skin. Obesity changes the components of skin, but there arent definitive studies about skin in massive weight loss patients. In this histomorphometric comparative study, biopsies of human female abdominal skin were analysed in quantity of collagen and elastic fibers in controls (non obese patients, epigastric topography n=15 and hypogastric topography n=25 ) in comparison to massive weight loss patients (n=40). After statistical analyses with p<0,05 was demonstrated that: a)in epigastric topography, the quantity of collagen was higher in control group; b) in epigastric topography, the quantity of elastic fibers was higher in case group; c) in hypogastric topography, there werent diferences in the quantity of collagen between cases and controls; d) in hypogastric topography, the quantity of elastic fibers was higher in control group

O aumento da prevalência da obesidade mórbida constitui um problema de saúde pública global. A obesidade mórbida pode ser definida por um índice de massa corpórea ( IMC ) superior a 35 Kg/ m²; vem acompanhada por diversas comorbidades e determina custos sócio-econômicos elevados. O único método efetivo a longo prazo no tratamento da obesidade mórbida, na atualidade, é a cirurgia bariátrica. Os procedimentos cirúrgicos para tratar a obesidade foram estimulados sobretudo pelo advento de técnicas videolaparoscópicas com menor morbidade pós-operatória e recuperação precoce. O sucesso operatório da cirurgia bariátrica representa perda de até 50% do excesso de peso dos pacientes em prazos variáveis de aproximadamente 24 meses. Após tal período, o processo de emagrecimento será refletido como excesso e flacidez cutânea generalizados e inicia-se a busca pela melhora da imagem corporal. A realização das cirurgias plásticas de contorno corporal exige ampla compreensão das peculiaridades clínicas desse paciente, e dos riscos de complicações, além de expectativas viáveis quanto aos resultados estéticos. Após as cirurgias de contorno corporal, passado o período pós-operatório recente, constata-se a manutenção de flacidez cutânea residual em graus variados. A obesidade interfere na qualidade dos componentes da pele humana. Entretanto, não há estudos específicos em relação à pele do paciente após perda ponderal maciça. Nesse estudo observacional histomorfométrico realizado entre 2006 e 2008, o autor avalia em biópsias de pele humana da região abdominal epigástrica e hipogástrica, o teor de colágeno e elastina em pacientes após perda ponderal maciça comparativamente a pacientes sem antecedentes de obesidade. Analisando a pele abdominal de mulheres não obesas ( controles epigástricos=15 e controles hipogástricos=25 ) e mulheres após tratamento dessa morbidade ( casos=40), verificou-se neste estudo com significância estatística aceita como p<0,05 que: a) na região epigástrica, o teor de colágeno foi superior no grupo controle em comparação ao grupo de casos; b) na região epigástrica, o teor de fibras elásticas foi superior nos casos; c) na região hipogástrica, não houve diferença estatisticamente significante no teor de colágeno entre os grupos estudados; d) na região hipogástrica, o teor de fibras elásticas foi superior no grupo controle / Morbid obesity is an increasing health problem and it is defined as a body mass index greater than 35 kg/m² with severe obesity related comorbidity or a body mass index greater than 40 kg/m² without comorbidity. The combined direct and indirect cost of obesity has been elevated. Bariatric surgery remains the only durable option for weight loss in the morbidly obese.Advanced laparoscopy procedures, as less invasive therapy, have contributed to fast recovery and acceptable perioperative morbidity. Results of bariatric surgery can reach about 50% of excess weight loss with a 2 year follow-up. As patients lose weight, they get laxity skin and their interest in body contouring surgery begins.Plastic surgery in massive weight loss patient demands attention to reduce risks and viable expectations concern to aesthetic results. However, after body contouring surgery, patients can keep up some laxity or folds of excess skin. Obesity changes the components of skin, but there arent definitive studies about skin in massive weight loss patients. In this histomorphometric comparative study, biopsies of human female abdominal skin were analysed in quantity of collagen and elastic fibers in controls (non obese patients, epigastric topography n=15 and hypogastric topography n=25 ) in comparison to massive weight loss patients (n=40). After statistical analyses with p<0,05 was demonstrated that: a)in epigastric topography, the quantity of collagen was higher in control group; b) in epigastric topography, the quantity of elastic fibers was higher in case group; c) in hypogastric topography, there werent diferences in the quantity of collagen between cases and controls; d) in hypogastric topography, the quantity of elastic fibers was higher in control group