Time-dependent expression of PEDF and VEGF in blood serum and retina of rats with oxygen-induced retinopathy

The effects of the balance changes of pigment epithelium growth factor (PEDF) and vascular endothelial growth factor (VEGF) in whole-body and retinal tissue on rats with oxygen-induced retinopathy were investigated. Forty-eight neonatal SD rats at the age of 7 days were randomly divided into 4 groups. The neonatal rats in experimental groups were exposed to 75% to 80% oxygen for 5 days and then to normal air, and those in control groups were kept feeding in normal air. At the age of 17 and 22 days, all the neonatal rats received retina angiography with FITC-dextran and the pathological changes of retinal vessels and perfusion were observed. HE staining of the tissue section and the number counting of endothelial cells extending beyond the inner limiting membrane were performed to evaluate the endothelial proliferation. Immunohistochemistry was applied to detect the expression of PEDF and VEGF in retinal tissue, and ELISA to detect their expression in serum. A hypoxic-ischemic proliferation of retina and more endothelial cells extending beyond the inner limiting membrane were found in the neonatal rats in both experimental groups of 17-day old and 22-day old as compared with those in control group with the difference being statistically significant (P<0.01). VEGF staining of the rats in the 17-day old experimental group was significantly stronger, with an increasing positive rate, than that of the rats in the 17-day old control group (P<0.01). PEDF staining of the rats of 22 days old was weaker than that of the rats of 17 days old in the experimental groups (P<0.01). There was no significant difference in serum VEGF concentration among all groups (P>0.05). The serum PEDF concentration in the rats of 17 days old in experimental group was decreased significantly as compared with that in the rats of 17 days old in control group (P<0.01), and in experimental groups, the serum PEDF concentration of the rats of 22 days old was increased as compared with that of the rats of 17 days old (P<0.01). In conclusion, the obviously decreased serum PEDF concentration and the abnormal enhanced expression of VEGF density in local retinal tissue broke down the balance of PEDF/VEGF in whole-body or local tissues, which might play an important role in retinal vascular proliferation.

[Gas pipeline leak detection based on tunable diode laser absorption spectroscopy]

The principle of tunable diode laser absorption spectroscopy and harmonic detection technique was introduced. An experimental device was developed by point sampling through small multi-reflection gas cell. A specific line near 1 653. 7 nm was targeted for methane measurement using a distributed feedback diode laser as tunable light source. The linearity between the intensity of second harmonic signal and the concentration of methane was determined. The background content of methane in air was measured. The results show that gas sensors using tunable diode lasers provide a high sensitivity and high selectivity method for city gas pipeline leak detection.

The influence of low atmospheric pressure on carbon monoxide of n-heptane pool fires

Qualitative theoretical analysis about air pressure influence upon the gas concentration of a fire plume was given, different scale n-heptane pool fires were conducted in a small and a standard compartment room in Lhasa and Hefei, respectively. The experimental results show that, in Lhasa, the average mass burning rates in the small room and the standard room both decrease, burning time increases at about 53% in small room and 45% in standard room more than in Hefei. Whereas for maximum changes of CO concentration, in the small room, in Lhasa, CO concentrations reach about twice bigger peak values at larger increase rates than in Hefei. While in the standard room, in Lhasa and Hefei, there are no significant changes for CO concentration, which agrees well with the theoretical analysis results.