应用间接血凝试验检测牛肺疫抗体

自制1.5％绵羊红细胞诊断液并用于检测牛肺疫抗体,结果如下:(一)三批标准阳性血清(批号为8601、8301、8001)凝集价均在160倍以上,标准阴性血清(批号为8601)凝集度仅为10倍。15份被检血清IHA的阳性检出率(8/15)高于补体结合反应(CF,6/15)且凝集价均在40倍以上。(二)用牛肝片吸虫病、布氏杆菌病和附红细胞体病阳性血清作类症鉴别诊断,凝集度仅为10倍。(三)把牛肺疫CF8502抗原作倍比稀释,加2个凝集单位牛肺疫阳性血清8601和8301进行间接血凝抑制试验,分别被32倍和16倍稀释的抗原所抑制,本项试验结果表明IHA用于检测牛肺疫,具有检出率高、特异性强、设备要求简单、容易操作等特点,适于在现地推广应用。     

Gut microbiota—a positive contributor in the process of intermittent fasting-mediated obesity control

Historically, intermittent fasting (IF) has been considered as an effective strategy for controlling the weight of athletes before competition. Along with excellent insight into its application in various spaces by numerous studies, increasing IF-mediated positive effects have been reported, including anti-aging, neuroprotection, especially obesity control. Recently, the gut microbiota has been considered as an essential manipulator for host energy metabolism and its structure has been reported to be sensitive to dietary structure and habits, indicating that there is a potential and strong association between IF and gut microbiota. In this paper, we focus on the crosstalk between these symbionts and energy metabolism during IF which hold the promise to optimize host energy metabolism at various physical positions, including adipose tissue, liver and intestines, and further improve milieu internal homeostasis. Moreover, this paper also discusses the positive function of a potential recommendatory strain (Akkermansia muciniphila) based on the observational data for IF-mediated alternated pattern of gut microbiota and a hopefully regulatory pathway (circadian rhythm) for gut microbiota in IF-involved improvement on host energy metabolism. Finally, this review addresses the limitation and perspective originating from these studies, such as the association with tissue-specific bio-clock and single strain research, which may continuously reveal novel viewpoints and mechanisms to understand the energy metabolism and develop new strategies for treating obesity, diabetes, and metabolic disorders.     

石灰性土壤吸磷差异及其与土壤性质的关系

采用等温吸附法研究了24个农田石灰性土壤和4个石灰性生土的磷吸附能力及其与土壤基本理化性质的关系,进而采用通径分析和多元逐步回归分析确定了影响供试石灰性土壤吸附固磷能力的主要土壤性质。研究结果表明:28个供试石灰性土壤的磷等温吸附曲线都很好地拟合了Langmuir等温吸附方程,最大吸磷量(Xm)以4个石灰性生土最大;其次为7个大田褐土性土,9个大田石灰性褐土;8个蔬菜大棚石灰性褐土最小。土壤pH值、CaCO3、活性钙、活性镁、活性铝和小于0.002 mm的土粒均与最大吸磷量呈显著或极显著正相关,而土壤有机质、全氮、速效磷、速效钾和0.2～2.0 mm的土粒均与最大吸磷量呈极显著负相关。经通径分析和反向逐步回归分析可知,影响供试石灰性土壤吸附固磷能力的主要因素为有机质,其次为速效磷和活性钙,土壤有机质、速效磷、活性钙和小于0.002 mm土粒共同决定了供试石灰性土壤95%的最大吸磷量。供试土壤中,8个蔬菜大棚石灰性褐土有机质、全氮、速效磷、速效钾含量相对较高,而吸附固磷能力相对较弱。连年大量有机和无机肥料的投入不仅导致磷在土壤中大量积累,而且由于土壤肥力的逐步提高,其吸附固磷能力下降,土壤中累积的磷素迁移性增强,造成水环境污染的风险增加。     

Fixed Ammonium Content and Maximum Capacity of Ammonium Fixation in Major Types of Tillage Soils in Hunan Province, China

In order to understand the status of fixed ammonium, fixed ammonium content, maximum capacity of ammonium fixation, and their influencing factors in major types of tillage soils of Hunan Province, China, were studied with sampling on fields, and laboratory incubation and determination. The main results are summarized as follows: (1) Content of fixed ammonium in the tested soils varies greatly with soil use pattern and the nature of parent material. For the paddy soils, it ranges from 135.4 ± 57.4 to 412.8 ± 32.4 mg kg⁻¹, with 304.7 ± 96.7 mg kg⁻¹ in average; while it ranges from 59.4 to 435.7 mg kg⁻¹, with 230.1 ± 89.2 mg kg⁻¹ in average for the upland soils. The soils developed from limnic material and slate had higher fixed ammonium content than the soils developed from granite. The percentage of fixed ammonium to total N in the upland soils is always higher than that in the paddy soils. It ranges from 6.1 ± 3.6% to 16.6 ± 4.6%, with 14.0% ± 5.1% in average for the paddy soils and it amounted to 5.8 ± 2.0% to 40.1 ± 17.8%, with 23.5 ± 14.2% in average for upland soils. (2) The maximum capacity of ammonium fixation has the same trend with the fixed ammonium content in the tested soils. For all the tested soils, the percentage of recently fixed ammonium to maximum capacity of ammonium fixation is always bellow 20% and it may be due to the fact that the soils have high fertility and high saturation of ammonium-fixing site. (3) The clay content and clay composition in the tested soils are the two important factors influencing their fixed ammonium content and maximum capacity of ammonium fixation. The results showed that hydrous mica is the main 2:1 type clay mineral in <0.02 mm clay of the paddy soils, and its content in 0.02–0.002 mm clay is much higher than that in <0.002 mm clay of the soils. The statistical analysis showed that both the fixed ammonium content and the maximum capacity of ammonium fixation of the paddy soils were positively correlated with the total 2:1 type clay mineral content and hydrous mica content in <0.02 mm clay and 0.02–0.002 mm clay at the significant level of P_0.01 or P_0.05, respectively, but not correlated with the total 2:1 type clay mineral content and hydrous mica content in <0.002 mm clay significantly. It demonstrated that the ammonium-fixing matrix of the tested soils mainly exists in the 0.02-0.002 mm clay. The above-mentioned results showed that fixed ammonium is a major form of N in the tillage soils in Hunan Province, China. It would play an important role in N nutrition of crops, especially for upland crops, and deserve to be further researched.     

磷、钾盐肥对保水剂吸水、保肥性能的影响

通过对保水剂在不同磷、钾肥料溶液中吸水倍率和对肥料养分吸持量的测定,研究了不同磷、钾盐肥对保水剂吸水、保肥性能的影响。结果表明,所用磷、钾肥磷酸一铵、过磷酸钙、氯化钾、硫酸钾均能显著降低保水剂的吸水倍率,并随肥料浓度的增加,保水剂吸水倍率显著降低,它们之间的关系可用幂函数来表征。4种肥料对保水剂吸水倍率的影响按氯化钾<硫酸钾<磷酸一铵<过磷酸钙顺序递增,它们对聚丙烯酸钠盐型保水剂的影响大于聚丙烯酰胺-丙烯酸盐型保水剂。保水剂在吸水溶胀的同时,也吸持溶解在水中的肥料离子,吸持量的大小因保水剂和肥料种类而不同。肥料浓度达到一定值后,随着保水剂吸水倍率的降低,吸持量也随之降低。     

Effect of intermittent heat treatment on crystallinity in wood cellulose

The effect of intermittent heat treatment on cellulose crystallites in wood was studied to evaluate quantitatively the changes of crystallinity induced by intermittent and continuous heating. The changes in crystallinity were found to be strongly affected by the intermittent heat treatment. The increased crystallinity, the width of the crystals, and the piezoelectric properties were the same for the first intermittent heating as for continuous heating. Further intermittent heating for the same time duration and temperature had no effect on the above properties, probably due to the stopping of the thermal reaction during the interval. Our results suggested that intermittent heat treatment has certain critical cooling temperatures that stop the thermal reaction and are closely related to the duration of the interval. Samples once exposed to a certain duration of heat treatment and then cooled need more time, about twice that of the first duration of intermittent heating compared with continuous heating, to reach maximum crystallinity in wood cellulose.     

Interactive effects of biochar and micronutrients on faba bean growth,symbiotic performance,and soil properties

Leguminous crops are significantly involved in the global symbiotic biological N₂ Fixation (BNF), an eco‐friendly process in the agriculture system. Biochar is considered as a vital amendment in improving growth and quality of crops and soils. Few investigations have been conducted to determine the combination effect of biochar with microelements on growth of legumes and soil properties. This study was designed to study the effect of soybean straw‐derived biochar (SSDB) with or without microelements on soil microbial and chemical properties, growth, yield, and seed chemical composition of faba bean (Vicia faba L.). Results revealed that dehydrogenase (DHA) and phosphatase (P‐ase) activities were markedly improved with the increase of SSDB rates under addition of microelements and their highest values were recorded after 90 d. Significant increases were noticed in nodulation activities, nodulation numbers (30.1–72.8), concentrations of N (1.62–1.93%), P (0.15–0.21%), and K (0.53–0.67%), and seed chemical constituents due to the addition of SSDB in the presence of microelements. Moreover, the combination of biochar with microelements caused significant changes in microbial counts. Overall, this investigation shows the potential and role of SSDB in enhancing the growth quality of faba bean seeds as well as an improvement of soil characteristics.     

Laboratory Assessment of Nostoc 9v (Cyanobacteria) Effects on N2 Fixation and Chemical Fertility of Degraded African Soils

The potential of Nostoc 9v for improving the nitrogen (N)₂–fixing capacity and nutrient status of semi‐arid soils from Tanzania, Zimbabwe, and South Africa was studied in a laboratory experiment. Nostoc 9v was inoculated on nonsterilized and sterilized soils. Inoculum rates were 2.5 mg dry biomass g^?1 soil and 5 mg dry biomass g^?1 soil. The soils were incubated for 3 months at 27 °C under 22 W m² illumination with a photoperiod of 16 h light and 8 h dark. The moisture was maintained at 60% of field capacity. In all soils, Nostoc 9v proliferated and colonized the soil surfaces very quickly and was tolerant to acidity and low nutrient availability. Cyanobacteria promoted soil N₂ fixation and had a pronounced effect on total soil organic carbon (SOC), which increased by 30–100%. Total N also increased, but the enrichment was, in most soils, comparatively lower than for carbon (C). Nitrate and ammonium concentrations, in contrast, decreased in all the soils studied. Increases in the concentration of available macronutrients were produced in most soils and treatments, ranging from 3 to 20 mg phosphorus (P) kg^?1 soil, from 5 to 58 mg potassium (K) kg^?1 soil, from 4 to 285 mg calcium (Ca) kg^?1, and from 12 to 90 mg magnesium (Mg) kg^?1 soil. Positive effects on the levels of available manganese (Mn) and zinc (Zn) were also observed.     

Time-course of nitrogen fixation in two bambara groundnut (Vigna subterranea L. Verdc.) cultivars

TheA-value method, involving the application of a higher¹⁵N rate to a reference non-N₂-fixing plant, was used to assess the magnitude of N₂ fixation in two bambara groundnut cultivars at four growth stages [vegetative, 0–47 days after planting (DAP); early pod-filling, 47–99 DAP; mid-pod-filling, 99–120 DAP; physiological maturity, 120–148 DAP). The cultivars were Ex-Ada, a bunchy type, and CS-88-11, a slightly spreading type. They were grown on a loamy sand. Uninoculated Ex-Ada and CS-88-11 were used as reference plants to measure the N₂ fixed in the inoculated bambara groundnuts. In this greenhouse study, soil was the major source of N in bambara groundnuts during vegetative growth, and during this period it accounted for over 80% of the N accumulaed in the plants. However, N₂ fixation became the major source of plant N during reproductive growth. There were significant differences between the two cultivars in the ability to fix N₂, and at physiological maturity, almost 75% of the N in CS-88-11 was derived from the atmosphere compared to 55% in Ex-Ada. Also, the total N fixed in CS-88-11 at physiological maturity was almost double that in Ex-Ada. Our data indicate that the higher N₂ fixation in CS-88-11 was due to two factors, a higher intensity of N₂ fixation and a longer active period of N₂ fixation. The results also suggest that bambara groundnut genotypes could be selected for higher N₂ fixation in farining systems.     

Differences in common bean rhizobial populations associated with soil tillage management in southern Brazil

Progressive adoption of no-tillage (NT) agriculture in the tropics is finally reversing physical, chemical, and biological erosion of soil and in Brazil, an estimated 19 Mha are now devoted to NT. Common bean (Phaseolus vulgaris L.) is a main component of Brazilian agriculture, and enhancement of yields has been achieved under NT as a result of mitigation of environmental stresses, resulting in higher N₂ fixation. However, the effects of NT on rhizobial diversity are poorly understood. This study evaluated rhizobial diversity in soils planted to common bean under NT or conventional tillage (CT) systems that were compared with natural grassland used for grazing, in the State of Santa Catarina, southern Brazil. Genetic diversity was assessed by the amplification of the DNA by PCR with specific primers (BOX-PCR) and by RFLP-PCR analyses of the 16S rDNA region. A high level of diversity was observed among strains from all three systems, such that the similarity in the clustering analysis of BOX-PCR products ranged from 36% under natural grassland to only 23% for CT strains. High polymorphism was confirmed in the RFLP-PCR analysis; forty-seven different profiles were obtained, none sharing high similarity with the profiles of reference species of common bean rhizobia. These results indicate that other tropical rhizobial species remain to be described. Genetic diversity was higher among the NT than the CT rhizobial strains, especially when the RFLP-PCR profiles were considered. Genetic diversity in the natural grassland was lower than in the cropped systems, possibly due to absence of the host plant and stubble burning in winter. Average yields in the area under NT (e.g. common bean, approximately 1500 kg ha⁻¹) have been about 30% higher than under CT, therefore high rhizobial diversity may be a parameter indicative of superior soil quality.