Evaluation of Soil Labile Phosphorus Using a Double-Labeling (^(32)P and ^(33)P) Technique

Isotopic exchangeability of phosphorus in four Chinese soils with and without P application was studied by 32P and 33P double-labeling technique in relation to routine chemical extractions. The results showed that Bray- Ⅰ and Bray-Ⅱ reagents could extract most of the fast exchangeable P. Not all of the Olsen-P belonged to fast exchangeable P, but it was about the same quantity of fast exchangeable P in a calcareous soil and a neutral soil without P application. Sequential fractionation of the soil phosphorus showed that most of the added radioisotopes in high P fixation red soils were tightly held by iron and aluminium oxides, which could be totally extracted only by 0.1M NaOH solution. In the neutral and calcareous soils most of the radioisotopes added were loosely held on the surface of soil particles and could be extracted by anion exchange resin. Phosphate application increased the resin-P fraction significantly for all the soils studied.

神经母细胞瘤细胞急性缺氧后不协调类33磷蛋白1和缺氧诱导因子-1α蛋白的表达变化

目的 探讨具有神经元特性的神经母细胞瘤细胞在急性缺氧后不协调类33磷蛋白1（Ulip1）与缺氧诱导因子-1α（HIF-1α）表达水平的变化.方法 选择具有神经元特性的神经母细胞瘤细胞株KCNR和BE2,将细胞分别置于正常氧浓度（体积分数为20%O2）和缺氧条件下（1%O2）处理4 h,提取蛋白.采用蛋白质免疫印迹法（Western blotting）定量测定Ulip1和HIF-1α表达.结果 在KCNR和BE2细胞急性缺氧4 h后,HIF-1α表达水平均显著升高,Ulip1的两个异构体Ulip1a和Ulip1b表达水平均降低;其中HIF-1α表达水平在KCNR细胞内升高了1.6倍,在BE2细胞内升高了2.9倍;Ulip1a在KCNR细胞内降低了55%,在BE2细胞内降低了20%;Ulip1b在KCNR细胞内降低了44%,在BE2细胞内降低了13%.结论 Ulip1可能通过影响HIF-1α参与了缺氧诱导的神经细胞损伤及之后的修复过程.