A column study of the biological mobilization and speciation of cadmium in soil

An acid sandy loam soil was used in a column study to determine the effect of microorganisms on Cd mobilization in soil and its speciation in column leachates. Non-sterile and sterile (gamma-irradiated) soil columns were initially treated with 90 mg of Cd (NO₃)₂, and approximately 20 mg of added Cd was retained in the soil. Soil columns were subsequently eluted with a sterile nutrient medium for a period of up to 38 days. Non-sterile and sterile soil columns leached with sterile deionized water served as unsupplemented controls. During a leaching period of 38 days, about 36% of the sorbed Cd in soil was mobilized in the presence of microorganisms and nutrients, while less than 16% of the Cd was released from the sterile and unsupplemented soil controls. To characterize the chemical form of the microbially mobilized Cd, the leachates were analyzed by gel filtration chromatography. In this study, 86% to 93% of the mobilized Cd was associated with the low molecular weight inorganic and organic fraction, while the remainder was eluted in the high molecular weight range. The low molecular weight Cd fractions were further examined by solid phase extraction (C₁₈ Sep-Pak), and cation-exchange chromatography. From the various analyses, it was concluded that a significant amount of Cd existed as a hydrophilic organic complex, and the remainder as cationic Cd. Soil microorganisms were mostly responsible for the transformation of Cd in soil and its subsequent mobilization.     

7-甲氧基-4′-羟基-3′-二乙胺甲基异黄酮(MHDF)对大鼠血流动力学和主动脉的作用

本实验观察了MHDF对整体大鼠血流动力学和离体大鼠胸主动脉的作用。结果表明iv MHDF(3～12.8 mg/kg)能降低大鼠左心室±dp/dt_max,V_max,V_pm和LVSP,延长T-dp/dt_max,减慢心率。MHDF还能舒张大鼠胸主动脉,ED₅₀为6.5×10^-6mol/L;非竞争拮抗NA和CaCl₂致主脉收缩,pD₂′为3.11±0.21和3.73±0.07;抑制高K⁺致主动脉收缩,IC₅₀为1.76×10^-5mol/L。提示MHDF对血管的作用与α受体阻断剂不同,而可能与钙拮抗有关。     

Effect of the physiological state of microbial cells on cadmium sorption

Live and dead cells of several strains of bacteria as well as different microbial populations isolated from natural environments were tested for their ability to sorb cadmium (Cd) from a liquid medium (0.05M phosphate buffer, pH 7.2) containing 10 g Cd/ml. The bacterial cultures were grown in a nutrient solution without Cd, harvested, and then suspended in the buffer solution for the uptake assays. The amount of Cd sorbed by dead cells was usually higher than by live cells. Killing of bacteria by chemicals (ethanol, formaldehyde, or propylene oxide) or physical (-radiation) means had a varying effect on Cd uptake by dead cells. Various bacterial strains showed different degrees of resistance to Cd and different uptake levels of this heavy metal with no established correlation. Neither storage of the cells at 4°C for 48 hr after harvesting nor varying incubation times of the bacteria before the Cd uptake experiments had any influence on the amount of Cd sorbed.Paper No. 6609 of the Journal Series of the Agricultural Experiment Station, Pennsylvania State University, University Park, PA 16802     

Beckman EL-ISE电解质分析仪准确性及故障的分析判断

0 引言为了克服离子选择电极（ISE）法的微量电位信号极易受环境温度变化及电子噪声的干扰问题,该仪器采用了参考电极,把参考电极与其测定电极装在同一测量室内,保持其相同的物理环境,使干扰源对所有电极的影响相同. 以内参液作为参考电极的测量对象,测得一个参考电极电位值,再测样品的电极电位值,二者相抵就消除了所叠加的干扰信号.     

心脏直视手术围术期自体血回输335例的监护

0　引言　自体输血是采集患者体内血或回收自体失血,再输回同一患者,献血者与受血者为同一个体,既可以节约临床用血,减少患者费用,更重要是可以避免或减少同种输血传播感染性疾病.我科对335例体外循环心内直视手术患者实行自体血回输,收到较好的社会效益和经济效益.1　临床资料　1998-09/1999-02,我科心脏直视手术共445例,围术期采用自体输血335例,其中先心病226例,瓣膜手术59例,复杂心内畸形37例,冠心病、大血管13例,占同期体外循环心内直视手术75%.患者主要适应证:心脏及大血管外科手术,术前一般情况尚好,无肝、肾、呼吸功能障碍;术前检查…