The concentration of ionized magnesium in serum during the periparturient period of non-paretic dairy cows

Ion-selective electrodes have recently been designed for determining the ionized concentration of magnesium (Mg²⁺) in serum. This development may allow new insights into some metabolic diseases of cattle. For this report, the concentrations of Mg²⁺, total magnesium (Mg_tot), ionized calcium (Ca²⁺), total calcium (Ca_tot), and inorganic phosphate (P_i) were determined in sera from seventeen 3-to 16-year-old Brown Swiss and crossed Simmental/Red Holstein cows during the periparturient period. In each animal, a transient increase of Mg²⁺ and Mg_tot serum concentrations was observed in association with the transient decrease in serum concentrations of Ca²⁺, Ca_tot and P_i after parturition. On average, throughout the study, the serum Mg²⁺ concentrations were 68.5% of those of Mg_tot, whereas the serum Ca²⁺ concentrations were 52% of those of Ca_tot. The possible mechanisms involved in the transient increase of Mg²⁺ and Mg_tot serum concentrations are discussed.Abbreviations Ca²⁺ ionized calcium - Ca_tot total calcium - Mg²⁺ ionized magnesium - Mg_tot total magnesium - P_i inorganic phosphate - PTH parathyroid hormone - PTHrP parathyroid homrone related protein     

LF4合金在磷酸盐-氢氧化钠溶液中的微弧氧化

在磷酸盐混合体系中对LF4合金进行微弧氧化，制得了厚达90μm、显微硬度超过1200HV的陶瓷氧化膜。采用电子能谱（EDS）、X射线衍射（XRD）和扫描电镜(SEM）等表面分析方法综合分析了膜层的成分、形貌及结构，并初步讨论了LF4合金微弧氧化膜的形成过程。     

固氮肺炎克氏杆菌的产酸和解磷能力

本文报道了549、258属于肺炎克氏杆菌的这一类联合固氮细菌具有产酸解磷的能力.549在培养过程中能产生多种有机酸成分,使无机磷的有效性提高.它还能利用卵磷脂这种有机磷作为自己的磷源,在其培养过程中产酸量有一定限度,达到一定酸度时,培养环境中的酸基本上就不再增加,维持在一个相对稳定的水平.549、258产酸解磷的结果能够改善植物的磷素营养,从非豆科植物根际联合固氮的研究角度考虑,可以认为产酸的联合固氮细菌具有固氮和解磷的双重性.     

Effect of tri-o-cresyl phosphate and methamidophos on Ca uptake by brain synaptosomes in hens

The effect of tri-o-cresyl phosphate (TOCP) and methamidophos (MET) on potassium-stimulated ⁴⁵Ca uptake by brain synaptosomes in hens was studied. An in vivo test showed that TOCP increased potassium-stimulated calcium uptake 2 h after its administration, but that verapamil suppressed the enhancement of this calcium uptake. An in vitro test showed that lower concentrations of TOCP stimulated calcium uptake by synaptosomes, but that higher concentrations inhibited the uptake. In contrast, all tested concentrations of MET obviously inhibited calcium uptake; however, since calcium uptake was decreased by the administration of verapamil plus either TOCP or MET, the mechanism by which TOCP affects the voltage-operated calcium channel may be different from that of MET. The disruption of calcium homeostasis may be involved in organophosphate-induced delayed neurotoxicity (OPIDN). Calcium channel blocker may ameliorate OPIDN by maintaining calcium homeostasis in nerve cells.     

The Effect of pH and Potassium Phosphate Buffer on the Toxicity of Cadmium for Bacteria

An increase in the pH of Plate Count Agar led to increased toxicity of cadmium (Cd) for Micrococcus luteus ATCC 9341, Staphylococcus aureus ATCC 12600, Clostridium perfringens ATCC 8798, Escherichia coli ATCC 11775 and Pseudomonas aeruginosa ATCC 10145. The effect of the pH on toxicity was not clearly observed with Streptococcus bovis ATCC 9809 and was absent with Bacillus subtilis ATCC 8473.When potassium phosphate buffer was added to the growth medium, the Cd toxicity for M. luteus and B. subtilis was enhanced. The toxicity of Cd for S. bovis decreased when potassium phosphate buffer was added to the medium. When the pH increased at differing phosphate concentrations, the sensitivity of M. luteus to Cd decreased.In the authors’ opinion, the effect of pH on Cd toxicity for bacteria is due to a continuously increasing negative charge towards an alkaline value by most bacteria which increases the affinity of cations towards the cell wall.     

Molecular characterization of potentially zoonotic isolates of Giardia duodenalis in horses

Giardia isolates from eight horses from New York State (NY), USA and two horses from Western Australia (WA) were genetically characterized at the SSU-rDNA and triose-phosphate isomerase (TPI) genes. Phylogenetic analysis of the TPI gene provided strong support for the placement of both isolates of Giardia from horses in WA and a single isolate from a horse in NY within the assemblage AI genotype of G. duodenalis. Another two isolates from horses in NY placed within the assemblage AII genotype of G. duodenalis. Phylogenetic analysis of the TPI gene also provided strong bootstrap support for the placement of four G. duodenalis isolates from horses in NY into a potentially host-specific sub-assemblage of assemblage BIV. The results of this study are consistent with previous studies showing that assemblages AI and AII of G. duodenalis provide the greatest potential zoonotic risk to humans. Horses may therefore constitute a potential source for human infection of Giardia either directly or via watersheds.     

白云石粉对皖南酸性红黄壤磷组分及磷有效性的影响

在施用P肥的基础上配合使用白云石粉,用酸性土壤无机P分级方法测定皖南红黄壤各形态P的含量。结果表明:使用P肥能明显提高土壤全P、无机P和土壤速效P含量;土壤速效P与无机P各组分的相关性以Al-P最好,Fe-P、O-P次之,Ca-P最差。施用白云石粉,当季土壤Ca-P含量及其在无机P中所占的比例明显提高,Al-P的形成受到抑制,但随着时间的推移,却更有利于有效性较高的Al-P含量的增加。     

离子强度和磷酸盐对铁铝矿物及土壤吸附As（V）的影响

选用针铁矿、赤铁矿、水铁矿、水铝矿4种铁铝矿物以及性质差异较大的黑土、紫色土和红壤3种土壤,研究离子强度和磷酸盐对其吸附As(V)的影响。结果表明,在0.01、0.1、1mol.L-13种离子强度下,矿物和土壤对As(V)的吸附量无明显差异或随离子强度增大而增大,其对砷的吸附以专性吸附为主。磷酸盐对矿物和土壤吸附砷的影响与其添加顺序及摩尔浓度比有关。水铝矿和水铁矿在这3种添加顺序下的砷吸附量无明显差异,仅在P/As摩尔比较大时表现出下降趋势;而在针铁矿和赤铁矿两种矿物上,先添加砷时的砷吸附量高于先添加磷时或两者同时添加时,且砷吸附量随P/As摩尔比的增加而逐渐下降。在黑土、紫色土和红壤上,先添加砷比先添加磷或两者同时添加时的砷吸附量均要高,尤其是在紫色土上。随P/As摩尔比升高,土壤对砷的吸附量表现出下降趋势。     

海泡石及钙镁磷肥对烟草主要农艺性状及吸收镉的影响

采用田间小区试验,研究海泡石和钙镁磷肥在400、800 g/m2处理水平下对烟田土壤有效态Cd含量、土壤pH值、烟草Cd含量及主要农艺性状的影响。结果表明,在本试验条件下,海泡石和钙镁磷肥均能有效降低烟田土壤中有效态Cd含量,减少土壤Cd向烟草各组织的迁移转运,2种材料的效果差异不显著;施用海泡石和钙镁磷肥均能小幅度提高土壤pH值,但不能过量施用;400 g/m2钙镁磷肥处理能提高烟叶鲜重,800 g/m2钙镁磷肥和海泡石处理对烟叶鲜重、株高、有效叶数均无显著影响。