Revisiting the use of hydroxyethyl starch solutions in equine fluid therapy

The last decade has led to major shifts in opinions on the use of hydroxyethyl starch (HES) solutions in fluid therapy, specifically in human patients with sepsis. The majority of evidence documenting adverse effects of HES solutions on coagulation and renal health come from studies in people. However, these findings have led to investigation into the safety of HES solutions in veterinary species. While there are now studies investigating the effects of HES solutions on coagulation and renal health in dogs, cats and horses, information regarding long-term follow-up, clinical significance of these changes and use of these solutions in critically ill animals is still lacking. The information presented here serves to review the physiology of oncotic pressure and the rationale behind colloid use, specifically HES solutions. Additionally, the foundation of arguments against the use of HES and the available literature regarding HES use in animals will be summarised.     

黄土高原植被恢复过程中土壤表面电化学性质演变特征

土壤胶体表面所带电荷是土壤具有一系列物理、化学性质的根本原因。表面电荷数量、比表面积、表面电荷密度、表面电场强度以及表面电位是土壤胶体颗粒重要性质,影响土壤中物理、化学、生物化学过程。运用带电颗粒表面性质联合分析法,测定黄土高原子午岭地区不同植被类型下土壤表面电荷性质,研究自然植被恢复过程对土壤表面电荷性质的影响。结果表明:随着植被的演替,子午岭林区土壤表面电荷数量、比表面积、表面电荷密度均随植被的恢复增加,变化范围分别为10.88～19.85 cmol·kg~(–1)、40.67～61.71 m~2·g~(–1)和0.22～0.31 c·m~(–2),平均值分别为16.18 cmol·kg~(–1)、54.88 m2·g~(–1)和0.28 c·m~(–2),土壤表面电场强度达108 V·m~(–1)数量级;土壤黏粒、有机碳含量是影响表面电荷性质的主要因素,解释率分别为62.5%和27.9%;土壤基本性质对表面电荷性质的影响由强到弱依次为:黏粒、有机碳、砂粒、全氮、C/N、粉粒、碳酸钙、pH。研究结果对于进一步认识黄土高原土壤颗粒表面性质,加深理解土壤中发生的一系列物理化学过程具有重要意义。     

镉在针铁矿、针铁矿-腐植酸复合胶体中吸附解吸行为比较研究

采用批平衡试验法,比较研究了重金属镉在针铁矿和针铁矿-腐植酸复合胶体中的吸附热力学和动力学行为。结果表明,在试验浓度范围内,两种吸附剂对Cd2＋的等温吸附特征均可用Langmuir、Freundlich和Linear方程加以描述。其中以Langmuir方程的拟合效果最佳,线性相关系数为：0.991、0.999,由此推导出的最大吸附量分别为41.667和45.455mg·g^-1,表明腐植酸与针铁矿复合胶体较单一针铁矿的吸附力有所提高,且所吸附的镉均难以解吸,平均解吸率分别为5.871%和1.068%。胶体对Cd^2＋的吸附是一个快速反应过程,4h达到吸附平衡。Elovich方程是拟合吸附动力学过程的最优方程（相关系数分别为0.987和0.997）。通过计算镉在针铁矿和针铁矿-腐植酸复合胶体中的吸附自由能变化量（ΔG的绝对值均〈40kJ·mol^-1）,推测镉在两种胶体中的吸附为物理吸附过程,其吸附机理可能有氢键、偶极作用力和范德华力等作用,而不存在化学键合作用。     

Soil colloids-bound plasmid DNA: Effect on transformation of E. coli and resistance to DNase I degradation

The adsorption and binding of plasmid p34S DNA on four different colloidal fractions from a Brown soil and clay minerals in the presence of various Ca²⁺ concentrations, the ability of bound DNA to transform competent cells of CaCl₂-treated Escherichia coli, and the resistance of bound DNA to degradation by DNase I were studied. DNA adsorption on soil colloids and clay minerals was promoted in the presence of Ca²⁺. Kaolinite exhibited the highest adsorption affinity for DNA among the examined soil colloids and clay minerals. In comparison with organo-mineral complexes (organic clays) and fine clays (<0.2 μm), DNA was tightly adsorbed by H₂O₂-treated clays (inorganic clays) and coarse clays (0.2-2 μm). The transformation efficiency of bound DNA increased with increasing concentrations of Ca²⁺ at which soil colloid or clay mineral-DNA complexes were formed. DNA bound by kaolinite showed the lowest transformation efficiency, and especially no transformants were observed with kaolinite-DNA complex prepared at 5-100 mM Ca²⁺. Compared to organic clays and fine clays, DNA bound on inorganic clays and coarse clays showed a lower capacity to transform E. coli at different Ca²⁺ concentrations. The presence of soil colloids and minerals provided protection to DNA against degradation by DNase I. Montmorillonite, organic clays and fine clays showed stronger protective effects for DNA than inorganic clays and coarse clays. The protection mechanisms as well as the differences in transforming efficiency of plasmid DNA molecules bound on various soil colloidal particles are discussed. The information obtained in this study is of fundamental significance for the understanding of the horizontal dissemination of recombinant DNA and the fate of extracellular DNA in soil environments.     

Assessment of changes in blood volume in response to resuscitative fluid administration in dogs

Objective: To determine the continuous changes in blood volume in response to fluid administration using an in‐line hematocrit monitor. Design: Prospective study. Setting: Research laboratory. Animals: Four healthy dogs. Interventions: Each dog received intravenous boluses of 80 mL/kg of 0.9% saline (S), 4 mL/kg of 7.5% saline (HS), 20 mL/kg of dextran 70 (D), 20 mL/kg of hetastarch (HES), or no fluids (control, C) on separate occasions. Fluids were administered at 150 mL/min in the S, D, and HES groups, and at 1 mL/kg/min in the HS group. Measurements and main results: Blood volume changes were measured every 20 seconds for 240 minutes using an in‐line hematocrit monitor. There was a rapid rise in blood volume during all infusions. Immediately after the administration of crystalloid fluids, the rapid rise in blood volume ceased. Subsequently, there was a steep decline in blood volume for 10 minutes, and a slower decline thereafter. In contrast, the rise in blood volume continued for at least 10 minutes after the infusion of the colloids was complete, and a plateau was observed for the remainder of the experiment. The blood volume effect, as measured by area under the curve, was significantly greater in the saline group than the other groups during the infusion time and for the 0–240 minutes time period. The areas under the curve for the two colloid solutions were not significantly different from each other during any time periods. The percent increase in blood volume immediately following the infusions was 76.4±10.0 in the S group, 17.1±3.2 in the HS group, 23.0±10.5 in the D group, and 27.2±6.4 in the HES group. At 30 minutes from the start of the infusion, the mean percent increases in blood volumes were 35.2±9.3 in the S group, 12.3±0.9 in the HS group, 35.9±7.3 in the D group, and 36.8±6.5 in the HES group. At 240 h post‐infusion, the mean percent increases in blood volume were 18.0±9.7 in the S group, 2.9±6.1 in the HS group, 25.6±16.1 in the D group, and 26.6±8.6 in the HES group. The C group had a mean percent change in blood volume of ?3.7±3.4 at the end of the experiment. Conclusions: This study indicates that the rapid administration of saline at clinically relevant doses leads to the largest immediate increase in blood volume, although this change is transient because of rapid redistribution of the fluid. Despite a brief increase in blood volume that was almost 3 times the volume administered, hypertonic saline led to the smallest increase in blood volume post‐infusion. The synthetic colloid solutions increased the blood volume by an amount greater than that infused and the effect was sustained for a longer period of time than seen following crystalloid administration, but the maximum increase in blood volume was significantly less than saline. The measurement of continuous changes in blood volume, using an in‐line hematocrit monitor, was a useful means of assessing the dynamic effects of fluid administration in dogs in a research setting.     

Effects of different concentrations of super-absorbent polymers on soil structure and hydro-physical properties following continuous wetting and drying cycles

Super-absorbent polymers (SAPs) are widely used chemical water-saving materials, which play an active role in the accumulation of soil water and the improvement of soil structure. Little is known about their performance with repeated usage or about factors influencing their efficiency under alternate wetting and drying cycles. In this study, various concentrations of SAP (0, 0.1, 0.2 and 0.3%) in soil following three continuous wetting and drying cycles (T1, T2 and T3), were studied to determine effects on soil structure stability and hydro-physical properties. The results indicated that the SAP improved soil water supply capacity under conditions of mild drought (T2) and sufficient irrigation (T3) at concentrations of 0.2 and 0.3%, but a reduction was observed under severe drought conditions (T1), which was negatively correlated with the SAP concentration. The physical adsorption of the SAP by soil and the chemical connection between the SAP and soil mineral colloids as Si-O-Si bonds, -OH bonds and different crystalline silica were the important factors that directly lead to the reduction of water retention capacities of the SAP with alternating wet and dry conditions. Compared with the control, the soil liquid phase ratios of the SAP treatments were increased by 8.8–202.7% in the T1 and T2 cycles, which would have led to a decrease in the soil air phase ratios. After repeated wetting and drying cycles, the SAP treatments increased the amount of >0.25 mm soil aggregates and the contents of water-stable macro-aggregate (R_0.25), and decreased the amount of <0.053 mm soil aggregates, especially with higher concentrations of the SAP. Increases in mean weight diameter (MWD) and geometric mean diameter (GMD), and declines in fractal dimension (D) and unstable aggregates index (E_LT) were all observed with the SAP treatments, which indicated an improvement in soil stability and structure. It was concluded that the distribution and stability of soil aggregates and soil water supply capacity was closely related to SAP concentration, soil moisture condition and the interaction between the SAP and soil particles.     

微生物在不同pH下对水稻土胶体中砷释放的影响

为探讨水稻土胶体与类金属砷（As）的生物地球环境行为,本研究对比分析了微生物在初始pH=3和初始pH=7的不同酸碱条件下对土壤胶体负载As释放的作用差异,并揭示其内在机制。结果表明：在pH=3条件下微生物作用相对较弱,对胶体悬液pH与Eh影响较小,与无菌对照组相比,溶液中Fe²⁺与As含量均有所提高,且释放的As主要为氧化态As（Ⅴ）;在pH=7条件下微生物活性较强,至28 d时可使胶体悬液pH升至8.12,Eh降至-55 mV,形成强还原环境,铁还原溶解量明显增多,Fe²⁺含量是无菌对照组的2.79倍,并且胶体中吸附态As随着Fe的还原溶解而释放,主要为还原态As（Ⅲ）。相关性分析表明,土壤胶体中As的释放与铁氧化物的还原转化有关,溶液中As释放量与Fe²⁺含量呈显著正相关关系,尤其在中性条件下As（Ⅲ）含量与Fe²⁺极显著正相关（r=0.798**,P<0.01）。研究表明,在中性环境条件下较强的微生物活性可提高土壤胶体中铁氧化物的异化还原,同时增强As的释放与转化。     

胶体磨辅助酶法提取金针菇根蛋白的工艺研究

为充分利用金针菇资源,提升其采后价值,以金针菇根为试材,通过单因素试验和正交试验,优化胶体磨辅助酶法提取金针菇根蛋白质的工艺条件。得到最佳提取工艺参数为:胶体磨磨齿间隙20μm,纤维素酶添加量40 mg/g,液料比10∶1(m L/g),酶解时间100 min,金针菇根蛋白提取率为1.326%。胶体磨辅助酶法提取金针菇根蛋白操作简单,提取条件温和,便于工业化生产,具有实际推广价值。