The Cerrado region of Brazil,one of the fastest-growing agricultural areas in the world,is undergoing very rapid mechanization;this development is good for the country's economy but may also snowball into substant...The Cerrado region of Brazil,one of the fastest-growing agricultural areas in the world,is undergoing very rapid mechanization;this development is good for the country's economy but may also snowball into substantial loss of agricultural land and other environmental degradation if the soil susceptibility and vulnerability to compaction is not well understood.In this study we explored different techniques for estimating soil intrinsic abilities to withstand applied pressure using the prevalent Oxisols of the Cerrado region under native vegetation.Undisturbed samples were collected from three sites within the region and subjected to 1) compressibility test;2) manual penetration resistance test;3) automated penetration resistance test;and 4) packing density analysis.The four methods produced analogous results.Our results showed the significant influence of soil structure on the inherent strength and compaction susceptibility of the soils.We also established the association of soil structure with the mineralogy of the soil.It is noteworthy that the packing density which was developed from very simple and easily obtained parameters could give a picture of the tendency of the soil to compact.Thus,this approach would be useful in developing compaction susceptibility maps for the region.It could be concluded that most of the Oxisols in the Cerrado region would support mechanized agricultural production very successfully.However,there is need for careful management of the mechanization process to avert degradation.The management techniques should include conservationist practices such as no till in order to maintain as much as possible the favorable structure and drainage of these very old soils.展开更多
目的探讨弱氧化性低密度脂蛋白(minimally modified low density lipoprotein,mmLDL)上调在体小鼠肠系膜动脉ETA受体的作用(endothelin type A receptors,ETA)并考察自噬是否参与这一过程。方法小鼠尾静脉注射mmLDL,腹腔注射ClassⅢPI3...目的探讨弱氧化性低密度脂蛋白(minimally modified low density lipoprotein,mmLDL)上调在体小鼠肠系膜动脉ETA受体的作用(endothelin type A receptors,ETA)并考察自噬是否参与这一过程。方法小鼠尾静脉注射mmLDL,腹腔注射ClassⅢPI3K自噬通路抑制剂6-氨基-3-甲基嘌呤(3-methyladenine,3-MA),探究自噬在mmLDL给药处理小鼠中的作用,微血管张力描记仪观察内皮素-1(endothelin-1,ET-1)引起的小鼠肠系膜动脉收缩量效曲线的变化,RT-PCR定量ETA受体mRNA,Western blot检测ETA受体和ClassⅢPI3K、Beclin-1、LC3-Ⅱ/Ⅰ、p62及p-NF-κB、NF-κB的蛋白水平表达。结果mmLDL引起ET-1收缩量效曲线明显增强,表现为Emax值由生理盐水(NS)组的(184.87±7.46)%上升为(319.91±20.31)%(P<0.001),pEC50值由NS组的(8.05±0.05)上升为(9.11±0.09)(P<0.01)。mmLDL在上调ClassⅢPI3K、beclin-1、LC3-Ⅱ/Ⅰ和下调p62蛋白水平的同时,也引起ETA受体mRNA水平、蛋白表达明显增加,增加了p-NF-κB的蛋白水平;腹腔注射3-MA抑制了mmLDL的这些作用。结论mmLDL能通过ClassⅢPI3K/Beclin-1通路激活自噬及下游NF-κB通路上调ETA受体。展开更多
基金Project supported by the Brazilian National Council for Scientific and Technological Development and the Academy of Sciences for the Developing World (TWAS)
文摘The Cerrado region of Brazil,one of the fastest-growing agricultural areas in the world,is undergoing very rapid mechanization;this development is good for the country's economy but may also snowball into substantial loss of agricultural land and other environmental degradation if the soil susceptibility and vulnerability to compaction is not well understood.In this study we explored different techniques for estimating soil intrinsic abilities to withstand applied pressure using the prevalent Oxisols of the Cerrado region under native vegetation.Undisturbed samples were collected from three sites within the region and subjected to 1) compressibility test;2) manual penetration resistance test;3) automated penetration resistance test;and 4) packing density analysis.The four methods produced analogous results.Our results showed the significant influence of soil structure on the inherent strength and compaction susceptibility of the soils.We also established the association of soil structure with the mineralogy of the soil.It is noteworthy that the packing density which was developed from very simple and easily obtained parameters could give a picture of the tendency of the soil to compact.Thus,this approach would be useful in developing compaction susceptibility maps for the region.It could be concluded that most of the Oxisols in the Cerrado region would support mechanized agricultural production very successfully.However,there is need for careful management of the mechanization process to avert degradation.The management techniques should include conservationist practices such as no till in order to maintain as much as possible the favorable structure and drainage of these very old soils.
文摘目的探讨弱氧化性低密度脂蛋白(minimally modified low density lipoprotein,mmLDL)上调在体小鼠肠系膜动脉ETA受体的作用(endothelin type A receptors,ETA)并考察自噬是否参与这一过程。方法小鼠尾静脉注射mmLDL,腹腔注射ClassⅢPI3K自噬通路抑制剂6-氨基-3-甲基嘌呤(3-methyladenine,3-MA),探究自噬在mmLDL给药处理小鼠中的作用,微血管张力描记仪观察内皮素-1(endothelin-1,ET-1)引起的小鼠肠系膜动脉收缩量效曲线的变化,RT-PCR定量ETA受体mRNA,Western blot检测ETA受体和ClassⅢPI3K、Beclin-1、LC3-Ⅱ/Ⅰ、p62及p-NF-κB、NF-κB的蛋白水平表达。结果mmLDL引起ET-1收缩量效曲线明显增强,表现为Emax值由生理盐水(NS)组的(184.87±7.46)%上升为(319.91±20.31)%(P<0.001),pEC50值由NS组的(8.05±0.05)上升为(9.11±0.09)(P<0.01)。mmLDL在上调ClassⅢPI3K、beclin-1、LC3-Ⅱ/Ⅰ和下调p62蛋白水平的同时,也引起ETA受体mRNA水平、蛋白表达明显增加,增加了p-NF-κB的蛋白水平;腹腔注射3-MA抑制了mmLDL的这些作用。结论mmLDL能通过ClassⅢPI3K/Beclin-1通路激活自噬及下游NF-κB通路上调ETA受体。
