陇东黄土高原农田土壤微生物量碳和颗粒有机碳剖面分布特征

采用野外调查采样与室内分析相结合的方法,对陇东黄土高原农田黑垆土微生物量碳（MBC）和颗粒有机碳（POC）的剖面分布特征进行了研究。结果表明：不同剖面土壤微生物量碳和颗粒有机碳含量随土层变化差异显著或极显著,主要集中在0—20cm和20—40cm土层,呈明显的表聚现象;0—60cm土层MBC含量随着土层深度增加而减小;随着海拔高度增加,0—20cm土层MBC含量整体呈增加趋势,变化范围为180.92~282.53mg/kg;POC含量在0—20cm和20—40cm土层的变化范围分别为1.02~1.68g/kg和0.25~0.96g/kg,40cm以下土层颗粒有机碳含量较低;剖面中不同土层深度微生物量碳、颗粒有机碳占总有机碳（SOC）的比例在0—20cm和20—40cm土层均显著或极显著高于其它土层,MBC/SOC变化范围分别为2.29%~3.70%和1.00%~2.11%,POC/SOC的变化范围分别为13.46%~19.13%和5.08%~16.16%,剖面MBC/SOC与MBC、POC/SOC与POC随土层的变化规律均一致,MBC/SOC和POC/SOC可以作为反映土壤剖面质量变化的指标。

THE EFFECT OF GHRELIN ON GASTRIC EMPTYING AND INTESTINAL TRANSIT IN RATS

Objective To study the effects of Ghrelin on gastric emptying and small intestinal transit in rats. Methods A rat model of postoperative gastrointestinal disfunction was created. The effects of intravenous injection of Ghrelin or calcitonin gene related peptide （GCRP）, after intragastric administration of 99mTc-methylcellulose, on gastric emptying and intestinal trans- mission were observed. Results After intragastric administration of 99m Tc-methylcellulose followed by intravenous Ghrelin （20 μg/kg）, 15 -- 60 rain later the residual 99m Tc-methylcellulose was significantly reduced （F = 248.13, q = 5.15 -- 21.60, P 0.01 ）, showing a dose-dependent manner （q = 3.15 -- 9.64, P 〈 0.05）. 99m Tc-methylcellulose was administrated into the small intes- tine, and followed by intravenous injection of Ghrelin, 15 min later, the residual 99mTc_methylcellulose in ileum 1 was notably de- clined （F = 16.41 ,q = 10.56 ,P〈0.01）, whereas the residual of that in the ileum 2 was markedly increased （q = 11.44 ,P（0.01）. The residual 99mTc-methylcellulose in the stomach after surgery of intestinal obstruction was much more than that in the sham- operation group （t = 2.78, P 〈0.05）. After 15 rain of intravenous administration of ghrlein （4-50 μg/kg）, the residual 99m Tc-methylcellulose in the stomach was markedly decreased, appearing as dose-effect dependencies （t = 3.04--6.22, P〈0.05）. Intrave- nous injection of CGRP （50 μg/kg） could markedly reduce residual 99mTc methylcellulose in the stomach of rats after surgery for intestinal obstruction O=2.31 ,P〈0.05）, but its effect was weaker than that of 20 μg/kg of Ghrelin （t=5.07,P〈0.01）. Conclusion Ghrelin can motivate gastric emptying in rats and improve their symptoms of post-operative ileus.