The vertical distributions of VOCs in the atmosphere of Beijing in autumn.

Volatile organic compounds (VOCs) in the air of Beijing City were measured at the heights of 8, 32, 140 and 280 m on the Beijing 325 m meteorological tower in autumn 2005. Concentrations of fifty-five compounds were determined by quantitative analytical methods. Our study utilized GC/MS analysis of 0.5 l air sample that were cryo-concentrated prior to analysis. The vertical distributions of VOCs were also investigated using 1-butene, isopentane, dichloromethane and toluene as representative compounds of several different categories. It is shown that 1-butene followed by 2-butene, isopentane followed by n-pentane, dichloromethane followed by chloroform and toluene followed by benzene are the most abundant compounds in the categories of alkene, alkane, halocarbon and aromatic hydrocarbon, respectively. The concentrations of TVOCs range from 51.2+/-39.7 ppb to 83.6+/-44.4 ppb on clear days, but from 62.9+/-19.0 ppb to 105.0+/-59.2 ppb on haze days. While alkenes and halocarbons contribute little to TVOCs, alkanes provide the largest percentage, ranging from about 46% to 63% at four different heights, which are followed by aromatic hydrocarbons ranging from about 15% to 27%. The vertical distributions of VOCs are complex. On clear days most distribution profiles show a decreasing trend with increasing height. On haze days, however, they exhibit first a decrease with increasing altitude from 8 m to 140 m and then a significant increase at 280 m. These results are understood by analyzing how the vertical distributions of VOCs are affected jointly by several factors such as meteorological parameters and transport property. In addition, principal components analysis (PCA) and cluster analysis show that VOCs have different origins at different heights.

The expression of basic fibroblast growth factor 1 during human embryonic yolk sac hematopoiesis / 中华血液学杂志

<p><b>OBJECTIVE</b>To explore the effect of basic fibroblast growth factor 1 (bFGF1) during embryonic development on hematopoiesis, to study the expression of FGF1, vascular endothelial growth factor receptor (KDR), CD133, CD34 and transcription factors Ihh, SCL, GATA-1, GATA-2 and PU. 1 in the yolk sac, and to learn about the role and relationships of FGF1, hematopoietic cells and transcription factors during embryonic hematopoiesis.</p><p><b>METHODS</b>10 microm sections and total RNA were prepared from 107 human embryos aged 3-12 weeks. Immunohischemical SP staining and RT-PCR were performed.</p><p><b>RESULTS</b>The yolk sac blood islands of human 3 approximately 12 weeks embryos consisted of peripheral vascular endothelial cells and central hematopoietic cells. The expression of FGF1 was firstly found in visceral mesoderm around periphery of yolk sac blood island at day 16, while was little inside it. KDR was not or lowly expressed and CD34 and CD133 were not expressed then. The expression increased, gray value decreased and staining enhanced at day 21. Strong staining of CD34+, CD133+ and KDR+ cells were found in blood island and mesoderm at day 30, their gray values changed from 156 +/- 16, 173 +/- 18 and 160 +/- 14 to 53 +/- 7, 52 +/- 6 and 69 +/- 8 respectively. FGF1 expression was strong positive, the gray value declined dramatically from 161 +/- 13 to 40 +/- 5. Some positive cells formed vessel-like structure along the periphery of blood island. Moderate expression of CD34+, CD133+, KDR+ cells increased at day 45, the cells aggregated into mass in blood island and FGF1+ cells did the same in blood island, while little in mesoderm. Its gray valve was increased. After 7 weeks, CD133+, KDR+, CD34+ cells significantly decreased their gray values increased, the staining became week. FGF1 was weakly expressed in yolk sac and its gray value increased to 179 +/- 22. RT-PCR showed Ihh, SCL, GATA-1 and GATA-2 were expressed at different time in yolk sac. PU. 1 were not expressed at day 16, and then expressed.</p><p><b>CONCLUSIONS</b>The hematopoietic properties of yolk sac may be dependent on signaling through FGF receptors and FGF1 plays an important role in hematopoietic stem cell homeostasis. The FGF pathway regulates primitive hematopoiesis by modulating transcription factors such as Gata1 expression level and activity.</p>

The expression of KDR and VEGF in yolk sac and liver of human embryo / 中华血液学杂志

<p><b>OBJECTIVE</b>To study the expression and distribution of KDR, VEGF and CD34 in yolk sac and liver of human embryo at different development stage.</p><p><b>METHODS</b>Yolk sacs and livers of 15 human embryos were analyzed by the immunohistochemical SP kits for the expression of KDR, VEGF and CD34.</p><p><b>RESULTS</b>KDR, VEGF and CD34 were all expressed in yolk sacs and livers of the embryos. In the intermediate liver group, the grey value of KDR and VEGF were 103.8 +/- 6.1 and 96.4 +/- 6.3, respectively, stronger than that in the late liver group which were 90.4 +/- 6.0 and 87.4 +/- 6.3, respectively (P < 0.05). A positive correlation between the levels of KDR and VEGF was observed (P < 0.05).</p><p><b>CONCLUSION</b>The expression of KDR and CD34 in yolk sac and liver of embryo suggests the presence of hemangioblast in these organs. Interaction of KDR and VEGF might relate to survival, proliferation, migration and differentiation of hemangioblasts.</p>