Tribute to R.G. Boutilier: Skin colour and body temperature changes in basking Bokermannohyla alvarengai (Bokermann 1956)

In amphibians solar basking far from water sources is relatively uncommon since the highly permeable amphibian skin does not represent a significant barrier to the accompanying risk of losing water by evaporation. A South American frog, Bokermannohyla alvarengai (Bokermann 1956), however, spends a significant amount of the day exposed to full sun and relatively high temperatures. The means by which this frog copes with potentially high rates of evaporative water loss and high body temperatures are unknown. Thus, in this study, skin colour changes, body surface temperature, and evaporative water loss rates were examined under a mixture of field and laboratory conditions to ascertain whether changes in skin reflectivity play an important role in this animal's thermal and hydric balance. Field data demonstrated a tight correlation between the lightness of skin colour and frog temperature, with lighter frogs being captured possessing higher body temperatures. Laboratory experiments supported this relationship, revealing that frogs kept in the dark or at lower temperatures (20 degrees C) had darker skin colours, whereas frogs kept in the light or higher temperatures (30 degrees C) had skin colours of a lighter hue. Light exhibited a stronger influence on skin colour than temperature alone, suggesting that colour change is triggered by the increase in incident solar energy and in anticipation of changes in body temperature. This conclusion is corroborated by the observation that cold, darkly coloured frogs placed in the sun rapidly became lighter in colour during the initial warming up period (over the first 5 min), after which they warmed up more slowly and underwent a further, albeit slower, lightening of skin colour. Surprisingly, despite its natural disposition to bask in the sun, this species does not possess a 'waterproof' skin, since its rates of evaporative water loss were not dissimilar from many hylid species that live in arboreal or semi-aquatic environments. The natural history of B. alvarengai is largely unknown and, therefore, it is likely that the herein reported colour change and basking behaviour represent a complex interaction between thermoregulation and water balance with other ecologically relevant functions, such as crypsis.

Amphibian secretions for drug discovery studies: A search for new antiparasitic and antifungal compounds

The antiparasitic and antifungal activities of nine amphibian skin secretions were studied in different in vitro models. Seven secretions presented a considerable antiprotozoan activity and one showed promising results against Candida sp. These results can be the basis for the development of new drugs, especially for neglected parasitic diseases. © 2007 Bentham Science Publishers Ltd.

The inguinal macroglands of the frog Physalaemus nattereri (Leptodactylidae): structure, toxic secretion and relationship with deimatic behaviour

Amphibian skin is characterized by the presence of mucous glands, related to cutaneous breathing, reproduction and water balance, and granular glands, related to the production of toxins used in defence. In some species the granular glands can form accumulations in certain regions of the body. This is the case for inguinal macroglands of the leptodactylid frog Physalaemus nattereri, where these structures form a pair of black discs associated with deimatic behaviour. The morphology of the inguinal macroglands and their secretion were studied in this species and correlated to deimatic behaviour. The inguinal macroglands are formed from elongated granular glands that, in contrast with the granular glands of the rest of the skin, have small spherical granules with a proteinic content. In the dermis of the whole body, except for the inguinal macroglands and the inguinal region, a well-developed calcified dermal layer is observed. During deimatic behaviour these macroglands discourage a potential predator from attacking, but if visual cues are insufficient and the predator persists in the attack, atoxic secretion is eliminated in its mouth. This elimination is favoured by the absence of a calcified dermal layer in the macroglands, which makes the dermal region softer than the rest of the dorsal skin.

Hylin a1, the first cytolytic peptide isolated from the arboreal South American frog Hypsiboas albopunctatus ('spotted treefrog')

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The essential role of annexin A1 mimetic peptide in the skin allograft survival

Immunosuppressive drugs have a critical role in inhibiting tissue damage and allograft rejection.Studies have demonstrated the anti-infl ammatory effects of the annexin A1 (AnxA1) in the regulationof transmigration and apoptosis of leucocytes. In the present study, an experimental skin allograftmodel was used to evaluate a potential protective effect of AnxA1 in transplantation survival. Micewere used for the skin allograft model and pharmacological treatments were carried out using eitherthe AnxA1 mimetic peptide Ac2-26, with or without cyclosporine A (CsA), starting 3 days beforesurgery until rejection. Graft survival, skin histopathology, leucocyte transmigration and expressionof AnxA1 and AnxA5 post-transplantation were analysed. Pharmacological treatment with Ac2-26increased skin allograft survival related with inhibition of neutrophil transmigration and inductionof apoptos is, thereby reducing the tissue damage compared with control animals. Moreover, AnxA1and AnxA5 expression increased after Ac2-26 treatment in neutrophils. Interestingly, thecombination of Ac2-26 and cyclosporine A showed similar survival of transplants when compared withthe cyclosporine A group, which could be attributed to a synergistic effect of both drugs. Investigationsin vitro revealed that cyclosporine A inhibited extracellular-signal-regulated kinase (ERK) phosphory-lation induced by Ac2-26 in neutrophils. Overall, the results suggest that AnxA1 has an essential role inaugmenting the survival of skin allograft, mainly owing to inhibition of neutrophil transmigration andenhancement of apoptosis. This effect may lead to the development of new therapeutic approachesrelevant to transplant rejection.

Influence of N-Terminus Modifications on the Biological Activity, Membrane Interaction, and Secondary Structure of the Antimicrobial Peptide Hylin-a1

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mechanism of Action and Relationship Between Structure and Biological Activity of Ctx-Ha: A New Ceratotoxin-like Peptide from Hypsiboas albopunctatus

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Investigation of the cytocidal potential of Rhinella jimi skin methanol extracts

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The Predominance of Alternatively Activated Macrophages Following Challenge with Cell Wall Peptide-Polysaccharide After Prior Infection with Sporothrix schenckii

Sporotrichosis is a subcutaneous mycosis that is caused by the dimorphic fungus Sporothrix schenckii. This disease generally occurs within the skin and subcutaneous tissues, causing lesions that can spread through adjacent lymphatic vessels and sometimes leading to systemic diseases in immunocompromised patients. Macrophages are crucial for proper immune responses against a variety of pathogens. Furthermore, macrophages can play different roles in response to different microorganisms and forms of activation, and they can be divided into classic or alternatively activated populations, as also known as M1 and M2 macrophages. M1 cells can lead to tissue injury and contribute to pathogenesis, whereas M2 cells promote angiogenesis, tissue remodeling, and repair. The aim of this study was to investigate the roles of M1 and M2 macrophages in a sporotrichosis model. Toward this end, we performed phenotyping of peritoneal exudate cells and evaluated the concomitant production of several immunomediators, including IL-12, IL-10, TGF-β, nitric oxide, and arginase-I activity, which were stimulated ex vivo with cell wall peptide-polysaccharide. Our results showed the predominance of the M2 macrophage population, indicated by peaks of arginase-I activity as well as IL-10 and TGF-β production during the 6th and 8th weeks after infection. These results were consistent with cellular phenotyping that revealed increases in CD206-positive cells over this period. This is the first report of the participation of M2 macrophages in sporotrichosis infections. © 2013 Springer Science+Business Media Dordrecht.