RESUMO
In aquatic systems, bottom sediments have often been considered as the main methylmercury (MeHg) production site. In tropical floodplain areas, however, floating meadows and flooded forests extend over large areas and can be important Hg methylating sites. We present here a cross-system comparison of the Hg net methylation capacity in surface sediments, flooded soils and roots of floating aquatic macrophytes, assayed by in situ incubation with 203Hg and extraction of formed Me203 Hg by acid leaching and toluene. The presence of mono-MeHg was confirmed by thin layer chromatography and other techniques. Study areas included floodplain lakes in the Amazon basin (Tapajós, Negro and Amazon rivers), the Pantanal floodplain (Paraguay river basin), freshwater coastal lagoons in Rio de Janeiro and oxbow lakes in the Mogi-Guaçú river, São Paulo state. Different Hg levels were added in assays performed in 1994-1998, but great care was taken to standardise all other test parameters, to allow data comparisons. Net MeHg production was one order of magnitude higher (mean 13.8%, range 0.28-35) in the living or decomposing roots of floating or rooted macrophyte mats (Eichhornia azurea, E. crassipes, Paspalum sp., Eleocharis sellowiana, Salvinia sp., S. rotundifolia and Scirpus cubensis) than in the surface layer of underlying lake sediments (mean 0.6%, range 0.022-2.5). Methylation in flooded soils presented a wide range and was in some cases similar to the one found in macrophyte roots but usually much lower. In a Tapajós floodplain lake, natural concentrations of MeHg in soil and sediment cores taken along a lake-forest transect agreed well with data on net methylation potentials in the same samples. E. azurea, E. crassipes and Salvinia presented the highest methylation potentials, up to 113 times higher than in sediments. Methylation in E. azurea from six lakes of the Paraguay and Cuiabá rivers, high Pantanal, was determined in the 1998 dry and wet seasons and ranged from 1.8 to 35%. Methylation was lower in washed roots than in untreated roots of E. azurea and methylation in solids isolated from the roots, was higher than in sediments but lower than in untreated roots. This indicates that the methylation in roots zones occurs mainly in the root-associated solids. Floating meadows are sites of intense production of biomass and of highly bioavailable MeHg and appear to be an essential link of the MeHg cycle in tropical aquatic systems.
Assuntos
Mercúrio/metabolismo , Compostos de Metilmercúrio/análise , Raízes de Plantas/química , Poluentes Químicos da Água/análise , Brasil , Desastres , Sedimentos Geológicos/química , Mercúrio/análise , Metilação , Distribuição TecidualRESUMO
We report the case of a 47-year-old woman with a large keloid scar on the sternum who was submitted to a simultaneous scar removal with bilateral breast-reduction mammaplasty. Breast reduction was performed to reduce local skin tension and to provide a skin flap for the full reconstruction of the scar-removal site. The association of these surgical procedures stands as a viable alternative for the reconstruction of the sternum region, producing less keloid scarring.
Assuntos
Mama/patologia , Queloide/cirurgia , Mamoplastia/métodos , Esterno , Retalhos Cirúrgicos , Mama/cirurgia , Feminino , Humanos , Queloide/etiologia , Pessoa de Meia-IdadeRESUMO
Cutaneous injuries of the inferior third of the leg and dorsum of the foot represent a great challenge for plastic surgeons. The poor vascularization and subsequent poor healing encountered in these regions demand detailed knowledge of the local anatomy to select the best surgical alternative for each patient. In patients in whom local or free muscular flaps are not suitable, the fasciocutaneous flaps seem to be a good alternative. The distal pedicled fasciocutaneous flap of the calf was used to cover skin defects of the leg and foot in 22 patients. In 4 patients the authors designed an island flap to prevent a large defect in the donor area and to decrease the time of hospitalization and recovery of the patient. In a severe defect, the flap was used as a cross-leg flap. The results were satisfactory because the flap provided stable coverage for different defects with few complications. The island flap is a good option for achieving a better aesthetic result and can be used in select patients.
Assuntos
Traumatismos do Pé/cirurgia , Traumatismos da Perna/cirurgia , Retalhos Cirúrgicos , Humanos , Retalhos Cirúrgicos/irrigação sanguíneaRESUMO
The lateral calcaneal artery flap is an axial flap which comprises also the saphenous vein and the sural nerve. Its use has been reported for coverage of skin loss of the malleolus and calcaneal area. The donor area should be closed by a split thickness skin graft. In the present report, eight patients who had skin loss on the foot were submitted to reconstruction with the lateral calcaneal flap. In seven there were island flaps and in one a bridge of skin similar to that described by Grabb and Argenta. The etiology was trauma in five patients and decubitus ulcer in three. The results were good. The flap was adequate for the cover on the posterior foot area even after submitted to the strain of normal walking. The advantages were simpler technique and consistency of the anatomical landmarks.
Assuntos
Calcanhar/cirurgia , Transplante de Pele/métodos , Retalhos Cirúrgicos/métodos , Adulto , Idoso , Criança , Calcanhar/irrigação sanguínea , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Ten patients had their vulvar and perineal areas reconstructed using musculocutaneous flaps of the gracilis muscle. Seven patients had extensive resections done for skin carcinomas, two due to traumas and one due to a sequel of Fournier's Syndrome. Reconstruction in tumor cases were performed primarily and the other secondarily. The skin island measured 12 x 8 centimeters and the muscle was taken entirely. The results were satisfactory in all cases. The muscle survived completely, but there was partial skin island loss in 8 instances. In 3 of those cases, there was need for a revision of the flap and skin grafting. The authors concluded that there is always a risk to take the skin island together with the gracilis muscle and the use of the isolated muscle with skin grafting should be considered im most cases.