DNA甲基化酶抑制剂对体细胞染色体的影响

在动物的体细胞克隆过程中,供体细胞的细胞核要由高度甲基化状态转变为胚胎细胞的非甲基化状态,从而实现全能性的重新获得。试验利用DNA甲基化酶（5-aza-dc）抑制剂处理供体细胞,尝试建立一种既不影响染色体结构和数目,又能降低供体细胞细胞核的甲基化状态的最适浓度和方法,从而提供一种提高体细胞克隆动物效率的方法。在试验中,用不同浓度的甲基化酶抑制剂（5-aza-dc）处理奶牛成纤维细胞72 h,通过常规染色体核型分析方法制备染色体分裂相,检测其染色体数目、结构等的改变,结果显示,低浓度的甲基化酶抑制剂（0.005和0.01 μmol/L）处理,染色体没有发生明显的畸变（P＞0.05）,染色体能够保持正常的形态,高浓度（0.03与0.05 μmol/L）处理导致染色体畸变率显著增加（P＜0.05）,而0.1 μmol/L的5-aza-dc处理后染色体畸形率增加更为明显（P＜0.01）。总之,此试验的结果说明在对供体细胞做甲基化处理时用0.005和0.01 μmol/L的5-aza-dc处理不会影响细胞染色体结构和数目,但是高浓度处理则会导致染色体畸变率显著增加,不能用于体细胞克隆动物生产。     

Effects of the nitrification inhibitor dicyandiamide on soil mineral N, pasture yield, nutrient uptake and pasture quality in a grazed pasture system

Recent lysimeter studies have demonstrated that the nitrification inhibitor, dicyandiamide (DCD), can reduce nitrate (NO) leaching losses from cow urine patches in grazed pasture systems. The objective of this study was to quantify the effects of fine particle suspension (FPS) DCD on soil mineral N components, pasture yield, nutrient uptake and pasture quality under grazed pasture conditions. A field study was conducted on the Lincoln University dairy farm, Canterbury, New Zealand, from 2002 to 2006. FPS DCD was applied to grazed pasture plots at 10 kg ha^?1 in early May in addition to applied cow urine patches at a nitrogen (N) loading rate of 1000 kg N ha^?1, with DCD reapplied in early August. Soil mineral N levels in the urine patches were monitored. Pasture yield, N and cation concentrations and uptake were measured in treatment urine patches and inter‐urine areas of the pasture. Comparisons were made with control plots which did not receive DCD. NO levels under the DCD‐treated urine patches (0–7.5 cm) were in the order of 10 kg N ha^?1 compared with 40–80 kg N ha^?1 under untreated patches, and soil ammonium (NH) levels were consistently higher under the DCD‐treated patches. The DCD significantly and consistently increased pasture yield in both the urine patches, and inter‐urine areas of the pasture in all 4 years of the trial. Mean annual dry matter (DM) yields over 4 years were inter‐urine areas, 10.3; inter‐urine + DCD, 12.4; urine, 12.4 and urine +DCD 16.0 t DM ha^?1, representing an average DM yield increase of 20 and 29% in inter‐urine and urine patch areas, respectively. On a whole paddock basis, the increase in annual DM yield resulting from DCD application was estimated to be 21%. N, calcium (Ca), magnesium (Mg) and potassium (K) concentrations in pasture were unaffected by treatment with DCD; however, total annual uptake of these nutrients by pasture was significantly higher in all years where DCD had been applied. Pasture DM, protein, carbohydrate, metabolizable energy and fibre levels and sward clover content were not affected by treatment with DCD. The results demonstrate the agronomic value of the DCD treatment in addition to the environmental benefits in a grazed pasture system.     

Formation of phosphoryl triamide by decomposition of thiophosphoryl triamide in soil

Summary Thiophosphoryl triamide inhibits soil urease activity when added to soil and is under consideration as a fertilizer amendment for retarding hydrolysis of urea fertilizer by soil urease. Work reported showed that this compound is a poor inhibitor of jackbean urease and that its ability to retard soil urease activity is due to its decomposition in soil with formation of phosphoryl triamide, which is a potent inhibitor of urease activity. This conclusion was supported by studies showing a close relationship between the peak area of the ³¹P-nuclear magnetic resonance (NMR) signal from phosphoryl triamide in thiophosphoryl triamide solutions that had been incubated with soil for various times and the ability of these solutions to inhibit jackbean urease activity.     

Effects of long-term 2,4-D application on microbial populations and biochemical processes in cultivated soil

Summary The effects of 15 years of field applications of 2,4-dichlorophenoxy acetate (2,4-D) on soil microbial population and biochemical processes were studied in a field cropped with maize followed by potatoes. Amine or ester formulations at the rate of 0.95 kg 2,4-D per hectare applied in May and October every year. Fungal, bacterial, and actinomycete populations, and microbial biomass C and N were reduced by the 2,4-D treatment, the reduction being more marked where the ester was used. N mineralization, nitrification, and potentially mineralizable N were reduced by the 2,4-D ester only, while urease activity was depressed by both formulations. Dehydrogenase activity and soil microbial respiration tended to be temporarily increased by the amine, but were reduced substantially by the ester, indicating that the ester probably interfered with nutrient cycling.     

Effects of concentration,incubation temperature,and repeated applications on degradation kinetics of dicyandiamide (DCD) in model experiments with a silt loam soil

Summary The kinetics of dicyandiamide (DCD) decomposition were studied (at 80% water-holding capacity) in pretreated and non-pretreated soils, using model experiments. DCD was added in different concentrations (6.7, 16.7, and 33.3 g DCD-N g^–1 dry soil) and incubated at various temperatures (10°, 20°, and 30°C). Additionally, DCD decomposition was examined in sterile soil (with or without Fe₂O₃) after inoculation with a DCD-enrichment culture. In the sterile variant, (30°C)the applied dicyandiamide concentration remained constant, even after 36 days. In the sterilized and reinoculated variant, DCD disappeared within 7 days. Addition of Fe₂O₃ powder to the sterilized soil had no effect on DCD degradation. In the pretreated soils, DCD mineralization started immediately at all temperatures and concentrations without a lag phase. A temperature increase of 10°C doubled the mineralization rate. The mineralization rates were independent of the initial concentrations. In the non-pretreated soils (except at 30°C with 16.7 and 33.3 g DCD-N g^–1 dry soil) DCD decreased only after a short (30°C) or a long (10°C) lag phase. These results suggest that an inducible metabolic degradation occurred, following zeroorder kinetics.     

木质纤维素乙醇发酵研究中的关键点及解决方案

该文综述了近年来木质纤维素材料发酵生产乙醇的研究进展，提出了在木质纤维素原料发酵生产乙醇过程中的两大关键点，一是减少和消除原料预处理过程中抑制物及其有害影响；二是含木糖、葡萄糖、甘露糖、半乳糖等多种物质的混合物同时作为底物的乙醇发酵。在对已有研究结果比较和分析基础上，提出相应的解决方案。首先要采取综合的预处理过程，达到提高木质纤维素水解率的同时减少发酵抑制物；然后是提高发酵菌种对混合糖底物的利用能力和发酵生成乙醇的能力以及对抑制物的耐受性，以提高木质纤维素发酵生产乙醇的转化率。     

Effects of pirenzepine on expression of MMP-2 and TIMP-2 in stroma of sclera in chick myopic eyes

AIM:To observe the effect of intravitreal injection of pirenzepine on form-deprivation myopia in chicks. METHODS:Forty-one day old chicks were randomly divided into 4 groups:normal control group, form deprivation group, vehicle control group and pirenzepine injection group. The right eyes of all chicks were used as experimental eyes. The deprived eyes in vehicle control group and pirenzepine injection group received daily intravitreal injection of vehicle control solution(0.01 mol/L PBS) and pirenzepine(1%in PBS), respectively. Optical examinations such as refraction, axial length and equatorial diameter were made at the end of the 5th day. The mRNA and protein levels of matrix metalloproteinase 2(MMP-2) and tissue inhibitor of metalloproteinase-2(TIMP-2), and the activity of MMP-2 were detected by RT-PCR, Western blotting and zymography analysis,respectively. RESULTS:Refraction, axial length and equatorial diameter of the eyes in pirenzepine injection group were significantly lower than those in form deprivation group and vehicle control group(P<0.05), but those were higher(P<0.05) and the eyes were relatively myopic as compared with normal control group. The mRNA expression, protein le vels and activity of MMP-2 in pirenzepine group were significantly higher than those in normal control group(P<0.01), and were significantly lower than those in form deprivation group and vehicle control group(P<0.01, P<0.01). The mRNA and protein levels of TIMP-2 in pirenzepine group were significantly lower than those in normal control group(P<0.01), and was significantly higher than those in form deprivation group and vehicle control group(P<0.01, P<0.01). CONCLUSION:Intravitreal injection of pirenzepine may partly prevent form-deprivation myopia by modulating the expression of MMP-2 and TIMP-2 in the fibrous layer of sclera.     

柳蛎盾蚧危害与丁香防御蛋白活力的关系

在柳蛎盾蚧的未危害期(5月末)、危害盛期(6月末)、危害弱期(7月末)、危害末期(8月末),测定高抗类[什锦丁香等7种(品种)]、中抗类[西南丁香等3种(品种)]、易感类[紫丁香等2种]、高感类(红丁香)13种(品种)丁香叶中的POD,SOD,CAT,PPO,PAL,TI和CI 7种防御蛋白的活性.结果表明:危害时期,丁香种(品种)对丁香防御蛋白活力有极显著影响(P＜0.01).POD活性,在危害盛期,在高抗、中抗类丁香中均显著升高(P＜0.05),而在易感、高感类中应激滞后,即分别在危害弱期和危害末期升高.CAT在易感类和高感类丁香防御上起主导作用,其活性在危害盛期显著升高,而中抗和高抗类未见明显变化.SOD活性,在危害盛期高抗类丁香中无显著变化,而其余3类则显著降低.PPO活性在未危害期的高低与抗性相关,在虫害盛期诱导表达的强弱也与抗性相关;PAL活性未能反映抗性品种间的差异.TI和CI活性,在未危害期的高低与其抗虫性无明显相关性,在危害盛期的升高幅度与抗虫性呈正相关.综上所述,PPO在未危害期的活力可作为筛选丁香抗虫种(品种)的指标,危害盛期POD,PPO,TI和CI活性升高的幅度与丁香抗虫性呈正相关.     

Influence of moisture regime on inhibition of nitrification by DCD

A laboratory study at the Indian Agricultural Research Institute, New Delhi showed that DCD was an efficient nitrification inhibitor under field capacity moisture (???30 kPa) but not so under submerged soil conditions. Nitrification inhibition by DCD was 79.6% after 1 week of incubation and decreased to 59.3% after 3 weeks of incubation under field capacity moisture, while it was only 19.3% after 1 week of incubation and 10.6% and 18.4% after 2 and 3 weeks of incubation under submergence, respectively. DCD can play an important role in reducing N losses from agricultural fields.     

Advances in prevention of nonsteroidal anti-inflammatory drug-induced gastropathy by proton pump inhibitor

Nonsteroidal anti-inflammatory drugs (NSAIDs) are powerful in anti-inflammatory, analgesic and antirheumatic effects, and widely used in treating the corresponding diseases. Over the years, many new dosage forms and structures of NSAIDs appear since aspirin was developed 112 years ago. However, the universal use of NSAIDs produces unavoidable mucosal lesions in gastrointestinal tract. As yet, proton pump inhibitor (PPI) has been used in the treatment of gastropathy induced by NSAIDs. This article will focus on the advances in prevention of NSAIDs-induced gastropathy by proton pump inhibitor.