RESUMO
PURPOSE: To study the role of transforming growth factor beta1 (TGF-beta1) on cellular radiation sensitivity by analysing mouse lung fibroblasts of different TGF-beta1 genotypes. MATERIALS AND METHODS: Heterozygous TGF-beta1 knock-out mice were mated to produce offspring of different TGF-beta1 genotypes as confirmed by PCR-genotyping. Primary lung fibroblast populations were established from new-born animals of specific genotypes (TGF-beta1(+/+), TGF-beta1(+/-), TGF-beta1(-/-)). Production of TGF-beta1 was tested by ELISA. TGF-beta1 receptor-II mRNA expression was analysed by RT-PCR. Colony formation of untreated, TGF-beta1-treated and/or irradiated primary lung fibroblasts was determined under different medium conditions. RESULTS: Plating efficiencies under different medium conditions were independent of TGF-beta1 genotype. Production of TGF-beta1 correlated with the genotype: heterozygous TGF-beta1 knock-out fibroblasts (TGF-beta1(+/-)) produced 60-65% of wild-type (TGF-beta1(+/+) cells). As expected, homozygous TGF-beta1 knock-out fibroblasts (TGF-beta1(-/-)) did not produce TGF-beta1. Radiation exposure significantly enhanced TGF-beta1 production in TGF-beta1(+/+) cells by a factor of 2. No such stimulation was observed in TGF-beta1(+/-) cells. TGF-beta1(+/-) and especially TGF-beta1(-/-) cells were significantly more radioresistant than TGF-beta1(+/+) cells. TGF-beta1 treatment significantly reduced clonogenic survival for both TGF-beta1(+/+) and TGF-beta1(-/-) cells. TGF-beta1 treatment of TGF-beta1(-/-) cells resulted in an enhancement of radiation sensitivity. CONCLUSION: The data are the first direct evidence that TGF-beta1 is a major autocrine regulator of intrinsic radiation sensitivity of mouse lung fibroblasts.
Assuntos
Fator de Crescimento Transformador beta/deficiência , Fator de Crescimento Transformador beta/genética , Receptores de Ativinas Tipo I/genética , Animais , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Células Cultivadas , Ensaio de Unidades Formadoras de Colônias , Relação Dose-Resposta à Radiação , Fibroblastos/citologia , Fibroblastos/metabolismo , Fibroblastos/efeitos da radiação , Genótipo , Homozigoto , Camundongos , Camundongos Knockout , Proteínas Serina-Treonina Quinases , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Tolerância a Radiação/efeitos dos fármacos , Tolerância a Radiação/genética , Tolerância a Radiação/fisiologia , Receptor do Fator de Crescimento Transformador beta Tipo I , Receptores de Fatores de Crescimento Transformadores beta/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Crescimento Transformador beta/farmacologia , Fator de Crescimento Transformador beta/fisiologia , Fator de Crescimento Transformador beta1RESUMO
The local plane-interface approximation (LPIA) is a method for propagating electromagnetic fields through the inhomogeneous regions (e.g., elements) of an optical system. The LPIA is the superclass of all approximations that replace the usually curved optical interfaces with local tangential planes. Therefore the LPIA is restricted to smooth optical surfaces. A maximum radius of curvature of the optical interface of the order of a few wavelengths is a rough estimate for the validity of the LPIA. Two important approximation levels of the LPIA are the thin-element approximation (TEA) and a geometric-optical version of the LPIA (LPIA(ray)). The latter combines the wave-optical propagation of an electromagnetic field in the homogeneous region of an optical system with a ray-tracing step in the inhomogeneous region. We discuss the regions of validity of the LPIA in general and the approximation levels LPIA(ray) and TEA in detail.
RESUMO
Effects of isoflurane on the DNase I activity in an isolated enzyme preparation and in the DNase I-globular (G) actin complex were investigated. DNase I, DNase I-G actin complex, and G actin were exposed to various (0.2-4.0 vol%) isoflurane concentrations for 180 min. Thereafter, DNase I activity was determined. DNase I activity was inhibited in relation to time and concentration of isoflurane exposure. At concentrations ranging from 0.2 to 1.0 vol% of isoflurane inactive DNase I was activated in the DNase I-G actin complex. The DNase I inhibitor G actin showed a reduced capability to inhibit DNase I following isoflurane exposure. Albumin can inhibit the DNase I inactivation possibly by competition in the reactions between DNase I/albumin and isoflurane. After exposure to isoflurane the absorption maximum of DNase I was identical with the absorption maximum of heat-denatured DNase I. The results suggest a mechanism by which isoflurane may affect DNA in an indirect way at concentrations to which the patient is exposed during clinical anesthesia.
