Development of a magnetic particle-based enzyme immunoassay for the determination of penoxsulam in water

A competitive enzyme-linked immunoassay (ELISA) for the quantitation of Penoxsulam [2-(2,2-difluoroethoxy)-6-(trifluoromethyl-N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-yl))benzenesulfonamide] in ground and surface waters was developed. This immunoassay utilizes magnetic particles as the solid phase to which polyclonal rabbit anti-Penoxsulam antibodies are attached. The ELISA has an estimated detection limit of 0.17 ppb (microg/mL) of Penoxsulam in water. Specificity studies indicate that the antibody can distinguish Penoxsulam from its major metabolites and structurally similar pesticides. Interference studies indicate that the ELISA has a wide tolerance of sample pH and salinity and for compounds commonly found in surface and ground waters. The ELISA was shown to compare favorably to LC-MS/MS on ground and surface water samples (r(2) = 0.957). The various studies performed demonstrate the usefulness of the ELISA technique as a rapid and high-throughput analytical method for the cost-effective monitoring of water samples.     

LED-Induced Chlorophyll Fluorescence Spectral Analysis for the Early Detection and Monitoring of Cadmium Toxicity in Maize Plants

Chlorophyll fluorescence spectral analysis permits detection, monitoring, and evaluation of abiotic stresses upon healthy plants using illumination of a light source in the UV?CVIS spectral range. This technique indirectly assesses the amount of physiological stress caused by photosynthetic damage, specifically damage to photosystem II, in plants. The objective of this study was to detect the toxicity of cadmium in maize plants via spectral analysis of chlorophyll fluorescence. The analysis is noninvasive and nondestructive and is used to follow the temporal evolution of changes in the chlorophyll content and physiological state of Zea mays L. seedlings under cadmium stress. Conventional techniques were also used to evaluate the dry matter production and Cd accumulation in plant leaves. Plants exhibited a notable reduction in dry matter production and chlorophyll levels with the administration of increasing doses of Cd in the nutrient solution. The fluorescence analysis was sensitive to changes caused by Cd in maize plants, detecting damage caused by different treatments before visual symptoms were observed. This technique has a practical application and produces rapid results that can be used in the evaluation of Cd-induced stress in plants and the detection of areas contaminated by this element.     

Faster fermentation of cooked carrot cell clusters compared to cell wall fragments in vitro by porcine feces

Plant cell walls are the major structural component of fruits and vegetables, which break down to cell wall particles during ingestion (oral mastication) or food processing. The major health-promoting effect of cell walls occurs when they reach the colon and are fermented by the gut microbiota. In this study, the fermentation kinetics of carrot cell wall particle dispersions with different particle size and microstructure were investigated in vitro using porcine feces. The cumulative gas production and short-chain fatty acids (SCFAs) produced were measured at time intervals up to 48 h. The results show that larger cell clusters with an average particle size (d(0.5)) of 298 and 137 μm were more rapidly fermented and produced more SCFAs and gas than smaller single cells (75 μm) or cell fragments (50 μm), particularly between 8 and 20 h. Confocal microscopy suggests that the junctions between cells provides an environment that promotes bacterial growth, outweighing the greater specific surface area of smaller particles as a driver for more rapid fermentation. The study demonstrates that it may be possible, by controlling the size of cell wall particles, to design plant-based foods for fiber delivery and promotion of colon fermentation to maximize the potential for human health.     

中国粮食生产的温室气体减排策略以及碳中和实现路径

作为世界上最大的农业生产国和温室气体排放国,我国承诺力争到2030年前实现碳达峰,2060年前实现碳中和。国家“双碳”目标给农业生产带来很大的减排挑战,因为农业源温室气体排放约占我国碳排放总量的14%。粮食生产是农业源非CO₂温室气体的主要排放源,归因于过量灌溉和施肥引起的稻田甲烷(CH₄)和土壤氧化亚氮(N₂O)排放。在碳达峰后,粮食生产温室气体的排放占比和减排重要性将越来越大。我国粮食生产究竟能否实现碳中和,以及如何实现碳中和仍不明确。本文综述了我国粮食生产碳排放的源汇效应和时空特征,总结了稻田CH₄和土壤N₂O减排以及农田土壤固碳的有效措施,解析了固碳减排之间的“此消彼长”效应和应对策略,明确了粮食生产实现碳中和的潜在路径,并对未来固碳减排的研究方向进行了展望。     

Rapid, low-cost cleanup procedure for determination of semivolatile organic compounds in human and bovine adipose tissues

A gas chromatographic/mass spectrometric (GC/MS) method is described for determination of organic environmental pollutants in human and bovine adipose tissues. Compounds such as organochlorine pesticides, polychlorinated biphenyls, polynuclear aromatic hydrocarbons, polychlorinated aromatics, and brominated aromatics are extracted with organic solvents and separated from coextracted lipids on a Florisil column. The eluate is concentrated and compounds are identified and quantitated by GC/MS analysis. The method was evaluated in a single laboratory for ability to recover compounds of environmental and regulatory importance. Except for a few more polar compounds, such as phthalates and phosphates, recoveries averaged about 85%. The elution system maximized recovery and allowed minimal coelution of lipid materials. Detection limits for most compounds studied were in the range of 5-50 ng/g (ppb).     

Worldwide genotyping of castor bean germplasm (<Emphasis Type="Italic">Ricinus communis</Emphasis> L.) using AFLPs and SSRs

Worldwide genetic diversity in 200 individuals comprising 41 castor bean accessions was assessed using amplified fragment polymorphisms (AFLPs) and simple sequence repeats (SSRs). We found that, despite surveying five continents and 35 countries, genetic diversity in castor bean germplasm is relatively low (overall H _e = 0.126 for AFLPs and 0.188 for SSRs) compared to estimates of genetic diversity in other plant species. Our data also show no geographic structuring of genotypes across continents or countries within continents. An assessment of the congruence between AFLP and SSRs indicates a low correlation (R ² = 0.19) between the two data sets, but each marker class nonetheless shows similar patterns of low-genetic diversity and a lack of geographic structure. Our data do suggest that SSRs yield a higher percentage of polymorphic loci, higher heterozyosity and a greater range of genetic distances, and are therefore more informative than are AFLPs on a locus-by-locus basis. Based on comparisons with numerous other plant species, we suggest that the lower genetic variation in this worldwide collection may be due to one or more factors including: sampling strategies that have not captured the full extent of genetic variation in the species; artifactual variation due to long-term germplasm storage and seed regeneration; or intense selection followed by domestic cultivation of a limited number of castor bean genotypes, which are widely propagated for their horticultural and agro-economic value.     

A laboratory investigation of the release of a conservative tracer and herbicide from topsoil aggregates under varying rainfall intensities

Abstract. This paper describes the results of laboratory-based research which investigated the losses of the herbicide, isoproturon, and a non-adsorbing solute, bromide, from topsoil aggregates under high (7 mm h⁻¹ and low 2.7 mm h⁻¹) intensity simulated rainfall. The structures of the micro- and macro-aggregates from a clay soil of the Denchworth Series (from Wytham, Oxfordshire, UK) were observed using a scanning electron microscope, and the slaking of the topsoil aggregates was also investigated in order to provide a context for interpreting the experimental results. The topsoil at Wytham was found to have a bimodal structure with small microaggregates of 0.71 to 1 mm diameter clustered together to form larger macroaggregates of up to several centimetres diameter. Selected aggregates were air dried and then repacked in Buchner funnels to several centimetres depth in order to remove variability in the experimental results due to the effects of surface microrelief. Under saturated surface conditions high intensity simulated rainfall was less efficient at removing both non-adsorbing and adsorbing solutes from the repacked topsoil aggregates than low intensity rainfall. The observed decrease in the concentration of isoproturon and bromide in the leachate with time could be explained by a transport non-equilibrium effect.     

Suckling as a regulator of postpartum rebreeding in cattle: a review

An extended and variable period of anovulation and anestrus occurs in suckled beef cows following parturition. This imposes both biological and economic constraints on the efficiency of beef production. A large body of knowledge has linked these phenomena to an attenuation of neuroendocrine signals that subserve gonadal function. During late gestation, high concentrations of placental estrogen inhibit the synthesis of LH, and pituitary stores of LH are depleted at parturition. Maximum pituitary stores of LH, releasable pools of LH and the ability of hypothalamic centers to respond to positive feedback effects of estradiol occur within 3 to 4 wk after calving in suckled cows. However, the requisite pattern of pulsatile LH secretion, which accompanies similar changes in nonsuckled cows within 2 to 3 wk after calving, occurs in only 30 to 50% of suckled animals. The period of acyclicity that continues in the remainder is exacerbated by poor body condition and may persist in some females for periods exceeding 100 d. Utilizing data from the cow, as well as other species, a model for suckling-induced inhibition of pulsatile LH release is proposed. The biological and economic impact of current and future techniques for controlling suckling-induced anestrus also is considered, including a conceptual analysis of nonbiological limitations.     

Pharmacokinetic studies of ivermectin: effects of formulation

Studies are reported which describe the effects of formulation, animal species, and route of administration on the pharmacokinetics of ivermectin. Biological half-life t1/2 increases in the order: swine (0.5 day) less than dogs (1.8 day) less than cattle approximately equal to sheep (2.8 day). Formulation modifications, based upon the solubility properties of the drug, have been directed towards the development of a nonaqueous injectable formulation for cattle and an aqueous vehicle for horses. Bioavailability following subcutaneous injection in cattle can be regulated by control of injection solvent composition: a vehicle composed of a mixed aqueous-organic solvent exhibits pharmacokinetic properties (i.e., Cp, t1/2, AUC, and F) intermediate between those furnished by an aqueous formulation and via a purely nonaqueous solvent. The longer apparent biological half-life from this latter vehicle (t1/2 = 8.3 days) confirms that a slow absorption process dominates the pharmacokinetics in the nonaqueous injectable product to produce an effective controlled-release formulation. These bioavailability results illustrate the increase in the concentration of an organic solvent and a concomitant decrease in surfactant concentration in a micellar aqueous system for prolonged drug delivery via injection.