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161.
The effects of several experimental parameters on the performance characteristics of a competitive-type immunochromatographic assay of milk progesterone were studied. Increasing the size of the colloidal gold particles used as a label increased both maximal signal obtained and sensitivity of the assay measured as slope of the progesterone standard curve. The concentration of the antibody used to prepare the detection zone was found to be a critical factor, in that low concentrations of antibody resulted in a poor sensitivity. The compatibilities of various buffer systems with the assay were studied. The assay worked well with buffers having a broad pH range of 4·5–8·5. 相似文献
162.
日本紫花牵牛(Pharbilisnilcv.Violet)子叶完全展开后,短日照诱导前、诱导后和两个短日照间的长日照处理对植株的花芽分化都有一定的抑制作用。双向凝胶电泳分析表明,长日照处理的牵牛子叶内存在着短日照处理子叶内没有的两种蛋白质(pI4.1,MW16.5kD;pI4.2,MW16.5kD)。这些蛋白质可能与长日照抑制牵牛植株的花芽分化有一定关系。 相似文献
163.
本文用Liapunov泛函方法研究捕食者有无限时滞效应的捕食-被捕食系统的平衡状态的稳定性.文章提供了判定系统的平衡状态全局渐近稳定的简单条件,不要求积分核指数衰减. 相似文献
164.
蛇胆祛痰作用的实验研究 总被引:2,自引:0,他引:2
用2组小鼠,每组10只。实验组用蛇胆酒灌胃,对照组用生理盐水灌胃,均以气管内酚红排泄法观察。结果示,酚红排泄量实验组比对照组明显为高。说明蛇胆确有增加小鼠气管分泌,稀释痰液的作用 相似文献
165.
Abstract. We studied floristic and diversity patterns and their environmental controls in two landscapes of contrasting topography in the Patagonian steppe. The analyses were focused on the effects of water availability gradients and landscape configuration on plant species distribution and coexistence. Floristic variation was investigated using Correspondence Analysis. The relationship between floristic and environmental variation was analyzed using Canonical Correspondence Analysis and correlation tests. We explored diversity patterns by relating spatial distance to floristic dissimilarities. The floristic gradient was determined by shrub and grass species and was related to precipitation in the flat area, and to precipitation, elevation and potential radiation in the mountain area. Site species richness increased with water availability in both areas. Mean site species richness and species turnover in space was higher in the mountain than in the flat area. Landscape species richness and floristic gradients were more concentrated in the mountain than in the flat area. In contrast to shrubs and grasses, forb species distributions were uncoordinated and probably independent of any environmental gradient. Our results suggest (1) that landscape configuration affects species composition and diversity through its direct effect on abiotic environmental heterogeneity, and (2) that the environmental controls of the community composition vary depending on the plant functional type considered. 相似文献
166.
Magdalena J. Rossowska Parvaneh Ghanel Tetsuo Nakamoto 《Biological trace element research》1995,50(3):229-236
The purpose of this study was to determine the relationship between concentrations of Zn and Cu and the activities of superoxide
dismutase and glutathione peroxidase in the heart and liver of young rat pups whose dams were fed a diet supplemented with
caffeine and/or Zn. Four groups of dams with their newborn pups were fed one of the following diets for 22 d: 20% protein
basal diet; the basal diet supplemented with caffeine (2 mg/100 body wt); the basal diet supplemented with Zn (300 mg/kg diet);
or the basal diet supplemented with caffeine plus Zn. The Cu levels in the livers of the pups were decreased by maternal intake
of the caffeine and Zn diet. The maternal intake of the caffeine diet increased Mn-superoxide dismutase (MnSOD) activity and
Cu, Zn-superoxide dismutase (CUZnSOD) in the heart of the pups. On the other hand, the activity of Cu,ZnSOD was significantly
reduced in the liver of pups whose dams consumed a caffeine, Zn, or caffeine plus Zn diet. Cu, ZnSOD activity in the liver
of the pups seems to be correlated with Cu levels in the tissue. Selenium-dependent glutathione peroxidase (GSH-Px) activities
in the heart and liver showed no difference among the groups. The effect of dietary caffeine and/or Zn on the activity of
antioxidant enzymes in the heart and liver were different in young rats. The activities of these enzymes in the heart were
lower than in the liver of 22-d-old rats. Our experiments indicate that the heart has limited defenses against the toxic effects
of peroxides when compared to the liver. 相似文献
167.
In a model system using intact spruce trees (Picea abies [L.] Karst.) we followed the path of magnesium, calcium and potassium during uptake into the root and during long-range transport into the shoot, by multiple stable isotope labelling. The roots of two- and three-year-old spruce trees originating from soil culture were removed from the soil and, in part or in toto, exposed to labelling solutions containing the stable isotopes 25Mg or 26Mg, 41K and 42Ca or 44Ca. Optical-emission-spectroscopy (ICP-OES) of plant fractions and labelling solutions was combined with the quantitative analysis of stable isotope ratios in sections of shock frozen, cryosubstituted material using the laser-microprobe-mass-analyser (LAMMA). This combination allowed us to distinguish, both in bulk samples and on the cellular level between (i) the fraction of elements originally present in the plant before the start of the labelling, (ii) the material taken up from the labelling solution into the plant and (iii) any material released by the plant into the labelling solution.In single-root labelling experiments, roots of three-year-old spruce trees, grown in nursery soil, were exposed to various pH conditions. The exchange of Mg and Ca with the labelling solution was nearly 100% in the cell walls of the mycorrhized finest roots. This exchange was only slightly affected by a step down to pH 3.5. The absolute Mg and Ca content in the cell walls was moderately reduced by incubation at pH 3.5 and strongly reduced in the presence of Al at this pH. After a pH 3.5 and 2 mM Al treatment we found Al in the xylem cell walls and the cortex cell lumina at elevated concentrations. To analyse the combined effect of high Al and high proton concentrations on the long-range transport, we used a split-root system. The root mass of an intact two-year-old spruce tree, grown in mineral soil, was divided into even parts and both halves incubated in solutions with two sets of different stable isotopes of Mg and Ca (side A: no Al, 25Mg and 42Ca; side B: +Al, 26Mg and 44Ca) and 41K on both sides. We observed a large uptake of Mg, Ca and K into the plant and a pronounced release. The net uptake of all three elements was lower from the Al-doted solution. In cross-sections of the apical shoot we found after seven-day labelling period about 60–70% of the Mg and Ca and 30% of the K content in the xylem cell walls originating from both labelling solutions. The clear majority of the Mg and Ca label originated from the Al-doted side. 相似文献
168.
Quantification of net nitrogen mineralization (NNM) in soils is indispensable in order to optimize N fertilization of crops.
Two long-term laboratory incubation methods were applied to determine rates of net nitrogen mineralization (rNNM) of soils from two sites of arable land (sandy loam soil, silty loam soil) at four temperature levels (2°C, 8°C, 14°C, 21°C).
Since variability within replicates was small, the modified 12-week incubation method of Stanford and Smith (1972) using disturbed
soils allowed to establish reliable Arrhenius functions with reasonable expenditure. The fit of the functions derived from
the 5-month incubation of 23 undisturbed soil columns (4420 cm3) was worse. This was caused by greater variability and less differentiation between temperature levels. Results of both experiments
could be described best by zero-order kinetics. Mean mineralization rates of disturbed samples were approximately twice as
high than those of undisturbed samples. The suitability of both methods for the prediction of NNM at site conditions is discussed.
Actual respiration (AR) at incubation temperatures and substrate induced respiration (SIR) were measured at the end of the
incubation of undisturbed soil columns. The results presented reveal that soil microbial communities develop in a different
manner during long-term incubation at different temperatures. This behavior offends the underlying assumption that soil microbes
remain in steady-state during incubation and that rising rates are physiological reactions to temperature enhancement. Therefore
soil microbial biomass (SMB) dynamics during the experiment has to be accounted for when rates of NNM and Arrhenius functions
are established. R Merck Section editor 相似文献
169.
170.
The rate of Hg2+-assisted chloride release from several mer-[CrCl(diamine)(triamine)]2+ complexes has been measured as a function of pressure, Hg2+ concentration and temperature. The calculated activation volumes are independent of [Hg2+] and temperature and kinetic parametes 104 kHg (25 °c) (M−1 s−1), ΔH‡ (kJ mol−1), ΔS‡ (J K−1 mol−1), ΔV‡ (cc mol−1) are: (en)(dpt): 6.44. 75.5, −52, −5.0; (ibn)(dpt): 5.81, 89.5, −6, −0.03; (Me2tn)(dpt): 22.2, 84.9, −11, −0.5; (tn)(dpt): 29.1, 87, −1, +0.3; (en)(2,3-tri): 1.94, 87.0, −24, −5.7; (en)(Medpt): 0.417, 94.6, −11, −0.8; (tn)(Medpt): 9.14, 98.3, +26, +1.8. 相似文献