Effect of whole and fractionated dietary alfalfa meal on zearalenone toxicosis and metabolism in rats and swine

Experiments were conducted to determine the mechanism by which dietary alfalfa can protect against zearalenone toxicosis. Female weanling rats were fed semipurified diets containing whole alfalfa meal, fractionated alfalfa meal (fiber, solvent extract, and water extract), and purified components of alfalfa (coumestrol, saponin, lignin, coumestrol + lignin, and saponin + lignin) with and without 250 mg zearalenone/kg of diet. All ingredients were provided for 2 weeks at levels corresponding to those found in diets containing 15 and 25% alfalfa. Yorkshire gilts were fed 15 and 25% alfalfa meal with and without 10 mg zearalenone/kg of diet for 4 weeks. The feeding of zearalenone to rats reduced growth and food consumption but this was overcome by 25% alfalfa. Zearalenone also increased the activity of hepatic 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD), the enzyme believed to metabolize zearalenone to alpha- and beta-zearalenols. Dietary alfalfa did not overcome this effect. Alfalfa fiber was the only fraction to partially overcome the growth-depressing effects of zearalenone while the other fractions had no beneficial effects and 3 alpha-HSD was not affected by diet. None of the purified components affected growth parameters or 3 alpha-HSD. The enzyme was also not affected by zearalenone or alfalfa in swine diets. Coumestrol, alpha-zearalenone, and beta-zearalenone were shown to be competitive inhibitors of 3 alpha-HSD in rat liver. It was concluded that the fiber fraction of alfalfa protects against zearalenone toxicity, and that this effect is not dependent on coumestrol or saponin and is not likely mediated through 3 alpha-HSD.     

Discrimination of pasture-fed lambs from lambs fed dehydrated alfalfa indoors using different compounds measured in the fat, meat and plasma

The last decade has seen important developments in the use of carotenoid pigments to authenticate pasture-feeding in ruminants. However, dehydrated alfalfa is sometimes incorporated in grain-based concentrates fed to stall-raised lambs, which may affect the reliability of the pasture-feeding authentication methods based on carotenoids in plasma and fat, due to significant residual carotenoid levels post-dehydration. The aim of this study was to examine whether other compounds can give additional information to authenticate diet and discriminate pasture-fed lambs from lambs fed high levels of alfalfa indoors. Two feeding treatments were compared: pasture-feeding (P) v. stall-feeding with dehydrated alfalfa (A). Each treatment group consisted of seven male Romanov × Berrichon lambs. Pasture-fed (P) lambs grazed a permanent graminaceae-rich pasture maintained at a leafy, green stage, offered ad libitum; they received no supplementation at pasture. A-group lambs were individually penned and fed dehydrated alfalfa and straw; their feed level was adjusted to achieve a similar growth pattern as for P-group lambs. Plasma carotenoid concentration was measured at slaughter by spectrophotometry. The reflectance spectrum of perirenal and subcutaneous caudal fat was measured at 24-h post mortem and used to calculate an index (absolute value of the mean integral (AVMI)) quantifying light absorption by carotenoid pigments present in the fat. The nitrogen (N) stable isotopes ratio (δ15N) in both feed and longissimus dorsi muscle was measured by isotopes ratio mass spectrometry (IRMS). Volatile compounds were analyzed in perirenal fat for five randomly chosen lambs per treatment, using dynamic headspace-gas chromatography-mass spectrometry. Plasma carotenoid concentration and AVMI of the fat did not differ significantly between P- and A-group lambs, but there were significant between-treatment differences in meat δ15N values and in the terpene profiles of perirenal fat. A discriminant analysis performed using three compounds in different animal tissues (δ-cadinene in perirenal fat, δ15N value of the meat and plasma carotenoid concentration) clearly separated pasture-fed lambs from lambs fed high levels of alfalfa indoors.     

The ability of dehydrated hamster and human sperm nuclei to develop into pronuclei.

To determine whether the nuclei of mature mammalian spermatozoa are resistant to dehydrated conditions, nuclei of hamster and human spermatozoa were freeze-dried or treated with various dehydrating agents before injection into hamster oocytes. Freeze-dried nuclei remained capable of developing into pronuclei even after 12 mo of storage at 4 degrees C. The level of DNA synthetic activity in the sperm (male) pronucleus was comparable to that in the egg (female) pronucleus. Sperm nuclei that had been stored in 100% ethanol, 100% methanol, or chloroform-methanol (2:1) mixture for 20 days were also capable of developing into pronuclei. Even the nuclei that had been dehydrated ("fixed") with Carnoy's fluid could develop into morphologically normal pronuclei. However, the level of DNA synthesis in the pronuclei derived from these chemically dehydrated nuclei was generally lower than that in the female pronuclei. Although the genetic integrity of the dehydrated sperm nuclei is yet to be determined, nuclei of mature hamster and human spermatozoa appear to be fairly resistant to dehydrated conditions.     

Influence of nutrient and energy deprivation on cellular response to single and fractionated heat treatments

The effect of hypoglycemia and hypoxia on cell survival following single and fractionated 44 degrees C heat treatments was investigated. These studies show that short-term glucose deprivation or oxygen deprivation does not increase sensitivity to single or fractionated heat treatments compared to normal nutrient conditions. However, simultaneous hypoglycemia and hypoxia leads to an increased sensitivity to single heat treatments, and to an even greater increase in sensitivity to fractionated heat treatments. Sensitivity to heat treatment under nutrient-deprived conditions correlates with intracellular ATP levels at the time of treatment. These data indicate that it is not nutrient concentration per se, but rather the effect of nutrient level on intracellular ATP concentration that affects thermal sensitivity.     

Experimental testing of dynamic energy budget models

1. Dynamic energy budget (DEB) models describing the allocation of assimilate to the competing processes of growth, reproduction and maintenance in individual organisms have been applied to a variety of species with some success. There are two contrasting model formulations based on dynamic allocation rules that have been widely used (net production and net assimilation formulations). However, the predictions of these two classes of DEB models are not easily distinguished on the basis of simple growth and fecundity data.
2. It is shown that different assumptions incorporated in the rules determining allocation to growth and reproduction in two classes of commonly applied DEB models predict qualitatively distinct patterns for an easily measured variable, cumulative reproduction by the time an individual reaches an arbitrary size.
3. A comparison with experimental data from Daphnia pulex reveals that, in their simplest form, neither model predicts the observed qualitative pattern of reproduction, despite the fact that both formulations capture basic growth features.
4. An examination of more elaborate versions of the two models, in which the allocation rules are modified to account for brief periods of starvation experienced in the laboratory cultures, reveals that a version of the net production model can predict the qualitative pattern seen for cumulative eggs as a function of mass in D. pulex . The analysis leads to new predictions which can be easily tested with further laboratory experiments.     

基于产量效应的间作紫花苜蓿/禾本科牧草光能利用特征

为探究紫花苜蓿/禾本科牧草间作下光能利用特性、光能利用诸因素的产量效应及其调控机理,通过2017—2019年3年田间试验,以紫花苜蓿、饲用小黑麦(C3植物)、饲用玉米(C4植物)3种单作模式为对照,研究了紫花苜蓿/小黑麦和紫花苜蓿/玉米两种间作模式下的产量效应、光能利用各因子对产量形成的影响、光能利用特征差异及机理。结果表明: 两种间作模式的土地当量比均大于1,表明两种间作模式的土地利用率都高于单作,均有高于单作的产量效益,且增产潜力较大的是紫花苜蓿/小黑麦间作模式。光能利用各因子对产量的贡献依次是: 叶面积指数(1.531)＞净光合速率(0.882)＞胞间CO₂浓度(0.282)＞蒸腾速率(-0.229)＞冠层开度(-0.291)＞光合有效辐射截获率(-0.681)＞气孔导度(-0.751)。其中,叶面积指数不仅是表征光合能力的重要指标之一,更是以收获营养体为目标的牧草作物产量的重要构成因子,光合特性诸因素中净光合速率是影响产量的主要因子。与单作相比,间作下紫花苜蓿、小黑麦、玉米的净光合速率均存在差异,且表现为相同的规律。间作下净光合速率提高的主要途径为: 小黑麦和玉米通过增强CO₂的羧化固定能力,提高对强光的利用能力,从而提高净光合速率,促进产量增加;而紫花苜蓿则是通过提高功能叶的叶绿素b含量,改变叶绿素构成,增强对光能的收集和传递,从而提高净光合速率,促进其在弱光下光合能力的提高和正常生长。     

Conversion of the energy of a high-current REB into electromagnetic wave energy

Results are presented from a theoretical investigation and quantitative analysis of the physical processes that govern the efficiency of a coaxial device aimed at converting the energy of a relativistic electron beam into the energy of a TEM wave (a wave in a circular cylindrical coaxial waveguide). The key diffractional problem is solved exactly using a simplified theoretical model, which makes it possible to understand the mechanisms for the formation of a TEM wave and determine how the beam parameters and the design parameters of the converter affect the relative fractions of the kinetic energy of a relativistic electron beam and the energy of its own magnetic and electric fields that are transferred into the energy of the TEM wave field. The results obtained are analyzed quantitatively, and prospects for further theoretical and experimental research in this area are outlined.     

Production and utilization of alfalfa

Alfalfa, the most important forage crop grown in the United States, is harvested in this country from 15 million acres, and in the 1946–1947 season yielded 34 million tons of hay used principally for feeding stock. About 700,000 tons of alfalfa meal are used in mixed feeds, primarily for poultry, and also serve as a source for extraction of carotene, chlorophyll and xanthophyll.     

Optimization models for the force and energy in competitive running

 In [2] the author has developed an optimization model for the force and energy in competitive running. In this paper the energy processes in the muscle were described by a three-compartment hydraulic model. Here this is reviewed briefly and applied to the current world records in order to determine the key parameters, maximal force, energy reserves and oxygen uptake. These values agree well with those given in the literature and those obtained by other means. The velocity profiles for 100 m sprints are described equally well. The model is then applied to older world records to deduce a relation between the force and energy by linear regression. Finally the fully parameterized model is used to compute the effects of adverse wind and altitude. Inasmuch as there are data available, there is a good agreement. Received 19 July 1995; received in revised form 27 February 1996     

A generalization of the clonal survival models: Equations for the families of curves obtained with fractionated irradiation

Summary The survival curves obtained when cellular recovery follows various first radiation dose deliveriesDI seem, when semi-logarithmically plotted, to be translated from the part of the curve corresponding to an unfractionated irradiation beyond a doseDR. A possible assumption consistent with such experimental observations is proposed which allows the generalization of any survival modelS = f(D). The derived equationS = f(DR + D - DI)f(DI)/f(DR) is convenient for the whole family of experimental survival curves involving cellular damage repairs when the first radiation doses vary. All the parameters of the family equation can be simultaneously fitted so that their reliability is increased. The generalized equations are given for the four following models: two-hits targets, Chadwick and Leenhouts, Green and Burki, Wideröe. As an example, the Chadwick and Leenhouts generalized model parameters are fitted to a family of experimental survival curves concerningChlorella cells exposed to fractionated and continuous gamma irradiation. The fittings are presented with their confidence limits and are briefly discussed.     

紫花苜蓿的花蜜量和访花蜜蜂数量对种子产量的影响

对10个紫花苜蓿品种的花萼直径、花蜜量、访花蜜蜂数量和种子产量进行了研究,结果表明,紫花苜蓿的单位面积花蜜量与访花蜜蜂数量呈极显著正相关(r=0.93**),访花蜜蜂数量与种子产量呈显著正相关(r=0.87*);紫花苜蓿的花蜜量与花萼直径呈极显著正相关(r=0.99**);紫花苜蓿品种赛特(Sitel)和德宝(Derby)在兰州地区能获得高产、优质的种子。     

Integrating thermodynamic and enzymatic constraints into genome-scale metabolic models

Stoichiometric genome-scale metabolic network models (GEMs) have been widely used to predict metabolic phenotypes. In addition to stoichiometric ratios, other constraints such as enzyme availability and thermodynamic feasibility can also limit the phenotype solution space. Extended GEM models considering either enzymatic or thermodynamic constraints have been shown to improve prediction accuracy. In this paper, we propose a novel method that integrates both enzymatic and thermodynamic constraints in a single Pyomo modeling framework (ETGEMs). We applied this method to construct the EcoETM (E. coli metabolic model with enzymatic and thermodynamic constraints). Using this model, we calculated the optimal pathways for cellular growth and the production of 22 metabolites. When comparing the results with those of iML1515 and models with one of the two constraints, we observed that many thermodynamically unfavorable and/or high enzyme cost pathways were excluded from EcoETM. For example, the synthesis pathway of carbamoyl-phosphate (Cbp) from iML1515 is both thermodynamically unfavorable and enzymatically costly. After introducing the new constraints, the production pathways and yields of several Cbp-derived products (e.g. L-arginine, orotate) calculated using EcoETM were more realistic. The results of this study demonstrate the great application potential of metabolic models with multiple constraints for pathway analysis and phenotype prediction.