RESUMEN
The thermal decomposition properties of hexafluoropropane clean gaseous fire-extinguishing agent were studied in tubular reactor from 500 to 750 degrees C and the decomposed gas was characterized by gas chromatography(GC), Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS). Hydrogen fluoride was detected after the decomposed gas was analyzed by pH testing, while pentafluoropropylene was found by GC-MS. The results showed that hydrogen fluoride eliminated from hexafluoropropane was the main reaction, while pentafluoropropylene was the primary product during hexafluoropropane decomposition under high temperature. GC and FTIR results indicated that the reaction temperatures had significant effects on the thermal decomposition of hexafluoropropane. Haxafluropropane was steady at 500 degrees C, whereas started to decompose weakly at 600 degrees C. The degree of the thermal decomposition of hexafluoropropane was enhanced with the temperature increase. And hexafluoropropane underwent intense decompositon at 750 degrees C. FTIR can be used as a new method to study extinguishing mechanism of fluorine-containing fire extinguishing agent online.
RESUMEN
An active artificial cornea which can perform the function of inducing new cornea generation in vivo but does not need culture cells in vitro and which has similar optical and mechanical properties to those of the human cornea was constructed. An animal keratoplasty experiment using the artificial cornea as the implant showed that the animals' corneas could keep smooth surface and clear stroma postoperatively, and that the repopulation of the host's keratocytes, the degradation of the implant and new corneal tissue generation were completed at 5-6 months after surgery. Such an artificial cornea has several advantages over other corneal equivalents constructed in the typical way of tissue engineering: in having similar mechanical and optical properties to those of the human cornea and with no exogenetic cells, it can be used universally in different implantation surgeries without immunoreaction; it is easy to prepare and process into different shapes and sizes on a large scale, and suitable for long-distance transportation and long-term storage. All these characteristics make it a new approach to cornea tissue engineering having potential in many clinical applications.
Asunto(s)
Materiales Biocompatibles/química , Quitosano/química , Colágeno/química , Córnea/citología , Córnea/crecimiento & desarrollo , Glicosaminoglicanos/química , Regeneración Tisular Dirigida/métodos , Animales , Córnea/cirugía , Ensayo de Materiales , ConejosRESUMEN
OBJECTIVE: To review research progress of corneal tissue engineering. METHODS: The recent articles on corneal tissue engineering focus on source and selection of corneal cells, the effects of growth factors on culture of corneal cells in vitro. The preparation and selection of three-dimensional biomaterial scaffolds and their strong and weak points were discussed. RESULTS: The corneal tissue engineering cells come from normal human corneal cells. The embryo corneal cell was excellent. Several kinds of growth factors play important roles in culture, growth and proliferation of corneal cell, and incorporated into matrix. Growth factors including basic fibroblast growth factor, keratinocyte growth factor, transforming growth factor beta 1 and epidermal growth factor was favor to corneal cell. Collagen, chitosan and glycosaninoglycans were chosen as biomaterial scaffolds. CONCLUSION: Human tissue engineering cornea can be reconstructed and transplanted. It has good tissue compatibility and can be used as human corneal equivalents.
Asunto(s)
Colágeno , Córnea/citología , Epitelio Corneal/citología , Ingeniería de Tejidos , Materiales Biocompatibles , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Quitosano , Factor de Crecimiento Epidérmico/farmacología , Células Epiteliales/citología , Epitelio Corneal/efectos de los fármacos , Factores de Crecimiento de Fibroblastos/farmacología , Glicosaminoglicanos , Sustancias de Crecimiento/farmacología , Humanos , Ingeniería de Tejidos/métodos , Factor de Crecimiento Transformador beta1/farmacologíaRESUMEN
Gene expression in Rat-1 fibroblast cells transformed by Tax from human T-cell leukemia virus type 1 was studied using the reverse transcriptase polymerase chain reaction differential display technique. The analysis revealed eight genes that were upregulated and one gene that was suppressed in Tax-transformed cells. Interestingly, at least four of the upregulated genes were interferon-stimulated genes. Promoter analysis of the 2',5'-oligoadenylate synthetase gene, which was activated in both Tax-transformed Rat-1 cells and primary adult T-cell leukemia cells, demonstrated that Tax indirectly activates its interferon-responsive enhancer element in a nuclear factor-kappaB pathway-dependent manner, indicating a close association of interferon signaling with the transformation by Tax.