RESUMO
Skin exposure to ionizing radiation affects the normal wound healing process and greatly impacts the prognosis of affected individuals. We investigated the effect of ionizing radiation on wound healing in a rat model of combined radiation and wound skin injury. Using a soft X-ray beam, a single dose of ionizing radiation (10-40 Gy) was delivered to the skin without significant exposure to internal organs. At 1 h postirradiation, two skin wounds were made on the back of each rat. Control and experimental animals were euthanized at 3, 7, 14, 21 and 30 days postirradiation. The wound areas were measured, and tissue samples were evaluated for laminin 332 and matrix metalloproteinase (MMP) 2 expression. Our results clearly demonstrate that radiation exposure significantly delayed wound healing in a dose-related manner. Evaluation of irradiated and wounded skin showed decreased deposition of laminin 332 protein in the epidermal basement membrane together with an elevated expression of all three laminin 332 genes within 3 days postirradiation. The elevated laminin 332 gene expression was paralleled by an elevated gene and protein expression of MMP2, suggesting that the reduced amount of laminin 332 in irradiated skin is due to an imbalance between laminin 332 secretion and its accelerated processing by elevated tissue metalloproteinases. Western blot analysis of cultured rat keratinocytes showed decreased laminin 332 deposition by irradiated cells, and incubation of irradiated keratinocytes with MMP inhibitor significantly increased the amount of deposited laminin 332. Furthermore, irradiated keratinocytes exhibited a longer time to close an artificial wound, and this delay was partially corrected by seeding keratinocytes on laminin 332-coated plates. These data strongly suggest that laminin 332 deposition is inhibited by ionizing radiation and, in combination with slower keratinocyte migration, can contribute to the delayed wound healing of irradiated skin.
Assuntos
Moléculas de Adesão Celular/metabolismo , Lesões Experimentais por Radiação/metabolismo , Pele/lesões , Pele/efeitos da radiação , Animais , Membrana Basal/efeitos da radiação , Membrana Basal/ultraestrutura , Moléculas de Adesão Celular/genética , Movimento Celular/efeitos da radiação , Epiderme/patologia , Queratinócitos/citologia , Queratinócitos/metabolismo , Queratinócitos/efeitos da radiação , Masculino , Metaloproteinase 2 da Matriz/biossíntese , Metaloproteinase 2 da Matriz/genética , Transporte Proteico/efeitos da radiação , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Lesões Experimentais por Radiação/genética , Lesões Experimentais por Radiação/patologia , Lesões Experimentais por Radiação/fisiopatologia , Ratos , Pele/metabolismo , Pele/fisiopatologia , Regulação para Cima/efeitos da radiação , Cicatrização/efeitos da radiação , CalininaRESUMO
We determine the electric field in mm-sized clouds of cold Rb+ ions, produced by photoionization of laser-cooled 87Rb atoms in a magneto-optical trap, using the Stark effect of embedded Rydberg atoms. The dependence of the electric field on the time delay between the ion plasma production and the probe of the electric field reflects the Coulomb expansion of the plasma. Our experiments and models show expansion times <1micros.
RESUMO
We demonstrate a real-time feedback scheme to manipulate wave-packet oscillations of atoms in an optical lattice. The average position of the atoms in the lattice wells is measured continuously and nondestructively. A feedback loop processes the position signal and translates the lattice potential. Depending on the feedback loop characteristics, we find amplification, damping, or an entire alteration of the wave-packet oscillations. Our results are well supported by simulations.
