RESUMO

Humans accumulate porphyrins in the body mostly during the course of porphyrias, diseases caused by defects in the enzymes of the heme biosynthesis pathway and that produce acute attacks, skin lesions and liver cancer. In contrast, some wild mammals and birds are adapted to accumulate porphyrins without injurious consequences. Here we propose viewing such physiological adaptations as potential solutions to human porphyrias, and suggest certain wild animals as models. Given the enzymatic activity and/or the patterns of porphyrin excretion and accumulation, the fox squirrel, the great bustard and the Eurasian eagle owl may constitute overlooked models for different porphyrias. The Harderian gland of rodents, where large amounts of porphyrins are synthesized, presents an underexplored potential for understanding the carcinogenic/toxic effect of porphyrin accumulation. Investigating how these animals avoid porphyrin pathogenicity may complement the use of laboratory models for porphyrias and provide new insights into the treatment of these disorders.

Assuntos

RESUMO

Parrots and allies (Order Psittaciformes) have evolved an exclusive capacity to synthesize polyene pigments called psittacofulvins at feather follicles, which allows them to produce a striking diversity of pigmentation phenotypes. Melanins are polymers constituting the most abundant pigments in animals, and the sulphurated form (pheomelanin) produces colors that are similar to those produced by psittacofulvins. However, the differential contribution of these pigments to psittaciform phenotypic diversity has not been investigated. Given the color redundancy, and physiological limitations associated with pheomelanin synthesis, we hypothesized that the latter would be avoided by psittaciform birds. Here, we tested this using Raman spectroscopy to identify pigments in feathers exhibiting colors suspected of being produced by pheomelanin (i.e. dull red, yellow, greyish-brown and greenish-brown) in 26 species from the three main lineages of Psittaciformes. We detected the non-sulphurated melanin form (eumelanin) in black, grey and brown plumage patches, and psittacofulvins in red, yellow and green patches, but there was no evidence of pheomelanin. As natural melanins are assumed to be composed of eumelanin and pheomelanin in varying ratios, our results represent the first report of impairment of mixed melanin-based pigmentation in animals. Given that psittaciforms also avoid the uptake of circulating carotenoid pigments, these birds seem to have evolved a capacity to avoid functional redundancy between pigments, likely by regulating follicular gene expression. Our study provides the first vibrational characterization of different psittacofulvin-based colors and thus helps to determine the relative polyene chain length in these pigments, which is related to their antireductant protection activity.

Assuntos

RESUMO

Parrots and allies (Order Psittaciformes) have evolved an exclusive capacity to synthesize polyene pigments called psittacofulvins at feather follicles, which allows them to produce a striking diversity of pigmentation phenotypes. Melanins are polymers constituting the most abundant pigments in animals, and the sulphurated form (pheomelanin) produces colors that are similar to those produced by psittacofulvins. However, the differential contribution of these pigments to psittaciform phenotypic diversity has not been investigated. Given the color redundancy, and physiological limitations associated to pheomelanin synthesis, we hypothesized that the latter would be avoided by psittaciform birds. Here we test this by using Raman spectroscopy to identify pigments in feathers exhibiting colors suspicious of being produced by pheomelanin (i.e., dull red, yellow and grey- and green-brownish) in 26 species from the three main lineages of Psittaciformes. We detected the non-sulphurated melanin form (eumelanin) in black, grey and brown plumage patches, and psittacofulvins in red, yellow and green patches, but no evidence of pheomelanin. As natural melanins are assumed to be composed of eumelanin and pheomelanin in varying ratios, our results represent the first report of impairment of mixed melanin-based pigmentation in animals. Given that psittaciforms also avoid the uptake of circulating carotenoid pigments, these birds seem to have evolved a capacity to avoid functional redundancy between pigments, likely by regulating follicular gene expression. Ours study provides the first vibrational characterization of different psittacofulvin-based colors and thus helps to determine the relative polyene chain length in these pigments, which is related to their antireductant protection activity.

RESUMO

Higher vertebrates synthesize two forms of melanin: eumelanin and pheomelanin. While the adaptive functions of eumelanin are diverse, those of pheomelanin, which is phototoxic and whose production consumes a key intracellular antioxidant (glutathione), are not clear apart from being involved in color patterns that confer concealment. The factors that have favored the evolution of pheomelanin thus remain a mystery, causing this pigment even to have been considered an "accident of nature." A recent hypothesis posits that pheomelanin has evolved because it represents an alternative mechanism to remove excess dietary cysteine, which can be toxic because of its oxidation. We tested for links between pheomelanin-based color and survival in both an intraspecific study of barn swallows Hirundo rustica and an interspecific study of 58 species of birds from North and Central America. As predicted on the basis that birds degrade excess dietary amino acids by transferring their amino group to uric acid synthesis, we found that under equal levels of uric acid in plasma, individuals or species with a higher intensity or greater proportion of plumage colored by pheomelanin (brown and chestnut coloration) had higher relative annual survival rates while controlling for the potentially confounding effects of age, sex, body size, and phylogenetic descent. Likewise, barn swallows with more intense pheomelanin-based coloration had higher prospects to survive the winter after controlling statistically for age, sex, body size, and level of uric acid. This supports the idea that pheomelanic traits evolve because of the removal of excess cysteine in nonstressful conditions, thus avoiding its toxic effects.

Assuntos

RESUMO

La peritonitis es la principal complicación en pacientes que reciben diálisis peritoneal continua ambulatoria. Los microorganismos grampositivos son los que con más frecuencia se aíslan y de estos Staphylococcus aureus es el agente causal predominante. Entre los factores de riesgo para el desarrollo de la infección relacionada con la diálisis peritoneal destacan las alteraciones en la inmunidad celular y humoral, las metabólicas y las enfermedades crónicas concomitantes. El tratamiento debe ser individualizado puesto que hay múltiples esquemas cuya utilización depende del tipo de infección, del organismo causal y de la respuesta inmunológica del paciente. En la mayoría de los casos el padecimiento es benigno y sólo se cura si se identifica tempranamente, y el tratamiento se encamina al lavado exhaustivo de la cavidad

Assuntos