内酯类新抗生素泰拉霉素的研究进展

泰拉霉素是动物专用半合成大环内酯类抗生素,对于防治猪和牛的呼吸系统疾病疗效确切。从泰拉霉素的理化性质、作用机制、抗菌活性、药动学和药效学、急慢性毒性及药物残留等方面进行综述,旨在为该药在兽医临床应用提供参考资料。     

市售小麦和玉米中矮壮素残留现状调查

[目的]了解市售小麦和玉米中矮壮素的残留现状。[方法]建立了高效液相色谱-串联质谱分析小麦和玉米中的矮壮素的方法,并对产自4个不同省份的玉米和小麦样品进行了抽样检测。[结果]小麦和玉米样品经甲醇超声提取、高效液相色谱-串联质谱测定,小麦中矮壮素添加浓度分别为0.5～10.0 mg/kg时,平均回收率达96%～103%,变异系数为2.6%～4.3%,玉米中矮壮素添加浓度为0.5～10.0 mg/kg时,平均回收率达92%～98%,变异系数为2.0%～3.7%,最低检出浓度(LOQ)为0.01 mg/kg,方法的准确度、精密度、灵敏度均符合农药残留的分析要求;所测4个省份玉米和小麦样品中矮壮素的残留量水平均低于方法的最低检出浓度(0.01mg/kg)。[结论]为市场小麦和玉米中矮壮素残留监管提供了参考。     

Interactive effects from combining fertilizer and organic residue inputs on nitrogen transformations

Concerns about sustainability of agroecosystems management options in developed and developing countries warrant improved understanding of N cycling. The Integrated Soil Fertility Management paradigm recognizes the possible interactive benefits of combining organic residues with mineral fertilizer inputs on agroecosystem functioning. However, these beneficial effects may be controlled by residue quality. This study examines the controls of inputs on N cycling across a gradient of (1) input, (2) residue quality, and (3) texture. We hypothesized that combining organic residue and mineral fertilizers would enhance potential N availability relative to either input alone. Residue and fertilizer inputs labeled with ¹⁵N (40–60 atom% ¹⁵N) were incubated with 200 g soil for 545 d in a microcosm experiment. Input treatments consisted of a no-input control, organic residues (3.65 g C kg⁻¹ soil, equivalent to 4 Mg C ha⁻¹), mineral N fertilizer (100 mg N kg⁻¹ soil, equivalent to 120 kg N ha⁻¹), and a combination of both with either the residue or fertilizer ¹⁵N-labeled. Zea mays stover inputs were added to four differently textured soils (sand, sandy loam, clay loam, and clay). Additionally, inputs of three residue quality classes (class I: Tithonia diversifolia, class II: Calliandra calothyrsus, class III: Z. mays stover) were applied to the clay soil. Available N and N₂O emissions were measured as indicators for potential plant N uptake and N losses. Combining residue and fertilizer inputs resulted in a significant (P < 0.05) negative interactive effect on total extractable mineral N in all soils. This interactive effect decreased the mineral N pool, due to an immobilization of fertilizer-derived N and was observed up to 181 d, but generally became non-significant after 545 d. The initial reduction in mineral N might lead to less N₂O losses. However, a texture effect on N₂O fluxes was observed, with a significant interactive effect of combining residue and fertilizer inputs decreasing N₂O losses in the coarse textured soils, but increasing N₂O losses in the fine textured soils. The interactive effect on mineral N of combining fertilizer with residue changed from negative to positive with increasing residue quality. Our results indicate that combining fertilizer with medium quality residue has the potential to change N transformations through a negative interactive effect on mineral N. We conclude that capitalizing on interactions between fertilizer and organic residues allows for the development of sustainable nutrient management practices.     

Characterization of soil surface properties following disturbance of a clay soil in southern Manitoba

This research demonstrated the use of a laser profiling system (LPS) and digital imagery as useful tools in measuring soil micro-topography and crop residue cover following a soil disturbance event. The soil micro-topography was characterized in terms of surface roughness using two geostatistical approaches; semivariance analysis and the mean absolute-elevation-difference method. Univariate statistical analysis was also used. All three procedures used to describe surface roughness were successful in detecting changes in surface roughness due to soil disturbance and the addition of corn residue. There was a definite advantage in using the geostatistical approaches to characterize surface roughness as the indices they provide give insight into the characteristics of the surface roughness. Crop residue cover was measured using digital images and image analysis software to contrast the soil and the crop residues.The series of field experiments examined the roles of both soil disturbance and corn residue and their interactions on surface roughness, crop residue cover, exposed surface area, and near-surface porosity. Soil disturbance and the addition of corn residue were both found to be significant factors affecting the surface roughness, crop residue cover, exposed surface area, and near-surface porosity. Due to the interaction and added effects of crop residue, it was also demonstrated that the calculated surface area may not be a measure of exposed soil area, but rather it is a combination of soil and residue surface areas. Similarly, the roughness of a surface does not only reflect the soil clods produced during tillage but that of the residue itself. Furthermore, it was demonstrated that the information gathered by the LPS and digital imagery can be used to evaluate surface characteristics arising from different tillage practices.     

Faster residue decomposition of brittle stem rice mutant due to finer breakage during threshing

In intensive tropical rice (Oryza sativa L.) cropping systems with short fallows, it would be advantageous that rice straw decompose fast enough to facilitate land preparation and planting of the subsequent crop. The straw of a brittle stem rice mutant of IR68 was tested for more rapid decomposition compared with non-brittle IR68 straw. The hypothesis was that the brittle mutant straw would break into smaller pieces during threshing, and that both the smaller piece size and the differences in biochemical straw composition would enable more rapid decomposition. Brittle straw broke into smaller pieces than non-brittle straw during a replicated trial of three threshing methods: hand threshing, pedal threshing, and axial-flow machine threshing. In a litter bag study to determine the effect of straw piece size on decomposition rate of each straw type over 10 weeks, smaller straw pieces decomposed faster than larger pieces as indicated by changes in amount of straw and its C/N ratio over time (P < 0.05), but there was no significant difference between straw types at the same size. It was concluded that the finer breakage of brittle straw during field operations is likely to be more important than the biochemical differences in overall residue decomposition rate.     

油料作物和粮食作物种子中有机氯农药残留分析

为了调查作物种子中有机氯残留的现状和种子脂质含量与种子中有机氯残留的关系,本文通过GC-ECD对某农产品基地的油料作物花生、大豆、芝麻和粮食作物水稻、小麦、玉米种子中有机氯农药残留进行了分析.结果表明,对照WHO/FAO标准,6种作物种子中的滴滴涕(DDT)和六六六(HCH)残留均不超标;总DDT的残留范围是3.8～10.3 ng/g,残留顺序是花生>芝麻>大豆>玉米>小麦>水稻;总HCH的残留范围是4.3～10.7 ng/g,残留顺序是花生>玉米>芝麻>大豆>小麦>水稻.3种油料作物种子中的总DDT残留浓度显著高于3种粮食作物种子中的残留浓度,种子中的总DDT残留浓度与种子脂质含量的对数显著正相关.     

土霉素在鸡蛋中的残留消除研究

研究临床使用常规剂量及养殖环节加大盐酸土霉素可溶性粉剂量后其在鸡蛋中的残留消除规律。对产蛋期蛋鸡分别给予500 mg/L和667 mg/L 50%盐酸土霉素可溶性粉,集中饮水给药,每日1次,连续5 d。分别采集停药后1～12 d的鸡蛋样品,采用UPLC-MS/MS测定鸡蛋中土霉素的残留量。按上述方法给药后,低、高剂量组分别在停药第1天和停药第2天达到土霉素残留量最高。低、高剂量组的最高残留量分别为142. 72、82. 84μg/kg,均低于国家规定的最高残留限量(200μg/kg),不会造成土霉素残留超标。本试验通过研究土霉素可溶性粉在鸡蛋中的残留情况,确定弃蛋期前后土霉素残留量,以期为蛋鸡产蛋期安全用药,保障食品安全提供科学依据。     

南昌市市售蔬菜有机磷农药残留调查及其原因分析

对南昌市市售蔬菜有机磷农药残留超标情况进行了系统调查,发现 21. 1%的样品中有机磷农药残留超标。分析了导致蔬菜有机磷农药残留超标的原因。     

乙氧酰胺苯甲酯在鸡组织中残留的检测及消除规律的研究

本研究建立了抗球虫药乙氧酰胺苯甲酯在鸡组织中残留的紫外ＨＰＬＣ检测方法。经过对鸡各种组织肌肉、肝、肾、脂肪添加高、中、低三个浓度,每个浓度５个样品,共测定２批,证明笔者建立的提取条件的回收纺在８０％以上,变异系数在１０％以内。最低标准物检测限为１ｎｇ,最低组织检测为２．５ｎｇ／ｇ。     

兔组织中阿维菌素残留的高效液相色谱法测定研究

阿维菌素是一种新型大环内酯类广谱抗寄生虫药物。本试验采用乙腈提取,然后通过氧化铝柱净化组织样本,经Ｎ－甲基咪唑与三氟醋酸酐衍生化后,用高效液相色谱－荧光检测器在激发波长为３６５ｎｍ,发射波长为４７０ｎｍ处,对衍生化产物进行测定。