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61.
应用鼠-鼠杂交瘤细胞技术建立了三系稳定分泌抗重组人α2a型干扰素(rHu-IFN-α2a)单克隆抗体细胞系1A5、1B5和27A7。细胞连续传代和在液氮中冻存后复苏,分泌抗体能力不变,并且维持在较高水平,细胞培养上清效价1∶256~1∶4096,腹水1∶26×105~1∶27×108。Ig亚类测定,1A5和1B5McAb为IgG1,27A7为IgG2a。三系McAb均识别rHu-IFN-α2a和-α2b,与rHu-IFN-α1和正常大肠菌体裂解液无反应。竞争ELISA试验,三系McAb分别针对rHu-IFN-α2a上三个不同表位。同McAb建立双抗体夹心ELISA对rHu-IFN-α2a和-α2b均可检测到150pg/ml,约10IU/ml的敏感度。用提纯的单抗制备亲和层析柱,单抗偶联率95%以上。三系单抗亲和层析柱均可将粗制rHu-IFN-α2a提纯到97%以上纯度。平均回收率为:1A5单抗柱902%,1B5单抗柱953%,27A7单抗柱947%。比活性平均值依次为194×108IU/mg,197×108IU/mg和164×108IU/mg,残余鼠IgG量均符合规程要求。纯化rHu-IFN? 相似文献
62.
目的:探讨磁共振水成像技术对脊柱疾病诊断的应用价值。方法:采用快速高级自旋回波(FASE)、重T2WI及脂肪抑制序列对300例病人检查行磁共振椎管水成像(MRmyelography,MRM)。结果:MRM显示正常25例,MRM异常275例,清楚显示原发病变与邻近脊髓腔、脊髓、神经根的相关关系。结论:MRM具有无创伤、无辐射、速度快,不需对比剂,患者易接受的特点。MRM与常规MRI图像结合可获得全面、客观的病变信息,MRM图像可取代X线脊髓造影和CT脊髓造影。 相似文献
63.
Artemisia annua hairy roots were grown in liquid-phase bubble column and gas-phase nutrient mist reactors. In most cases the bubble column reactor accumulated more biomass than the mist reactor; the highest final biomass concentrations observed were 15.3 g DW/L in the bubble column reactor and 14.4 g DW/L in the mist reactor. Further analysis showed that the average specific growth rate in the mist reactors was essentially constant and independent of the biomass concentration at the beginning of the mist mode. In contrast, at low packing densities the average growth rate in the bubble column reactors was higher than in the mist reactors, decreasing to comparable rates at high packing densities. Finally, an aerosol deposition model was used to compare the volume of medium captured by the root bed in the mist reactor to the volume of medium required to maintain a specified growth rate. The results suggest that under the current operating conditions, lower growth rates in the mist reactor may be due to insufficient nutrient availability. 相似文献
64.
Quan Zhang Mallory Barnes Michael Benson Elizabeth Burakowski A. Christopher Oishi Andrew Ouimette Rebecca Sanders‐DeMott Paul C. Stoy Matt Wenzel Lihua Xiong Koong Yi Kimberly A. Novick 《Global Change Biology》2020,26(6):3384-3401
Land‐use/cover change (LUCC) is an important driver of environmental change, occurring at the same time as, and often interacting with, global climate change. Reforestation and deforestation have been critical aspects of LUCC over the past two centuries and are widely studied for their potential to perturb the global carbon cycle. More recently, there has been keen interest in understanding the extent to which reforestation affects terrestrial energy cycling and thus surface temperature directly by altering surface physical properties (e.g., albedo and emissivity) and land–atmosphere energy exchange. The impacts of reforestation on land surface temperature and their mechanisms are relatively well understood in tropical and boreal climates, but the effects of reforestation on warming and/or cooling in temperate zones are less certain. This study is designed to elucidate the biophysical mechanisms that link land cover and surface temperature in temperate ecosystems. To achieve this goal, we used data from six paired eddy‐covariance towers over co‐located forests and grasslands in the temperate eastern United States, where radiation components, latent and sensible heat fluxes, and meteorological conditions were measured. The results show that, at the annual time scale, the surface of the forests is 1–2°C cooler than grasslands, indicating a substantial cooling effect of reforestation. The enhanced latent and sensible heat fluxes of forests have an average cooling effect of ?2.5°C, which offsets the net warming effect (+1.5°C) of albedo warming (+2.3°C) and emissivity cooling effect (?0.8°C) associated with surface properties. Additional daytime cooling over forests is driven by local feedbacks to incoming radiation. We further show that the forest cooling effect is most pronounced when land surface temperature is higher, often exceeding ?5°C. Our results contribute important observational evidence that reforestation in the temperate zone offers opportunities for local climate mitigation and adaptation. 相似文献
65.
Humoral antibody response and Ig characterization of the specific agglutinins in rabbits during experimental American trypanosomiasis 总被引:1,自引:0,他引:1
A comparative follow up study of the specific agglutinins detected by direct agglutination (DA) test and the immune response detected by specific lysis (SL), indirect immunofluorescence (IFA), indirect hemagglutination (IHA) and complement fixation (CF) tests in rabbits inoculated with trypomastigotes of T. cruzi is reported here.The specific antibody response was detected first by DA test. Reductive cleavage of sera with 2-mercaptoethanol produced a drop in the agglutinin titer of the sera during the first 30 days of infection.The next test to become positive was SL and later on the IFA, IHA and CF tests became positive simultaneously.When fractions obtained by column chromatography in Sephadex G-200 were tested serologically it was demonstrated that specific antibodies were detected mainly in fraction I (IgM) of the pooled rabbit sera obtained 15 days after inoculation (acute stage), and in fraction II (IgG) of the pooled sera obtained from rabbits 90 days after inoculation (chronic stage).Antigens prepared with trypsinized and formolized epimastigotes of three T. cruzi strains, belonging to each one of the different immunological groups described, worked similarly in the detection of specific agglutinin antibodies.Trypanosoma cruzi agglutinins were highly specific in their reaction with their homologous T. cruzi antigens as was proved by the low agglutinin titer obtained in sera from infected rabbits when, instead of T. cruzi epimastigotes, promastigotes of L. donovani were used as antigen, and by the incapacity of this parasite to absorb the T. cruzi agglutinins. 相似文献
66.
A comparative kinetic analysis of nitrate and ammonium influx in two early-successional tree species of temperate and boreal forest ecosystems 总被引:6,自引:1,他引:6
Xiangjia Min M. Yaeesh Siddiqi Robert D. Guy Anthony D. M. Glass & Herbert J. Kronzucker 《Plant, cell & environment》2000,23(3):321-328
Root NO3 ? and NH4 + influx systems of two early‐successional species of temperate (trembling aspen: Populus tremuloides Michx.) and boreal (lodgepole pine: Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest ecosystems were characterized. NO3 ? and NH4 + influxes were biphasic, consisting of saturable high‐affinity (HATS) and constitutive non‐saturable low‐affinity transport systems (LATS) that were evident at low and relatively high N concentrations, respectively. NO3 ? influx via HATS was inducible (IHATS); nitrate pre‐treatment resulted in 8–10‐fold increases in the Vmax for influx in both species. By contrast, HATS for NH4 + were entirely constitutive. In both species, Vmax values for NH4 + influx were higher than those for NO3 ? uptake; the differences were larger in pine (6‐fold) than aspen (1·8‐fold). In aspen, the Km for NH4 + influx by HATS was approximately 3‐fold higher than for IHATS NO3 ? influx, while in pine the Km for IHATS NO3 ? influx was approximately 3‐fold higher than for NH4 + influx. The aspen IHATS for NO3 ? influx appeared to be more efficient than that of pine (Vmax values for aspen being approximately 10‐fold higher and Km values being approximately 13‐fold lower than for pine). By contrast, only small differences in values for the NH4 + HATS were evident between the two species. The kinetic parameters observed here probably result from adaptations to the N availabilities in their respective natural habitats; these may contribute to the distribution and niche separation of these species. 相似文献
67.
为了改进保健茶中总黄酮含量的测定方法,用80%乙醇提取保健茶样品,用石油醚溶解后过聚酰胺层析柱,甲醇洗脱后在360nm波长下测定洗脱液中的总黄酮含量。实验结果显示,总黄酮含量(以芦丁计)在0~20μg·mL-1范围内线性良好,方法相对标准偏差RSD在2.11%~3.24%之间,回收率在82.6%~113.0%之间。相比国标方法,本方法降低了人为因素对结果的影响、替换了苯的使用、缩短了实验耗时,快速、简便、准确度和精密度良好,可用于测定保健茶中的总黄酮。 相似文献
68.
The segmental series of somites in the vertebrate embryo gives rise to the axial skeleton. In amniote models, single vertebrae are derived from the sclerotome of two adjacent somites. This process, known as resegmentation, is well‐studied using the quail–chick chimeric system, but the presumed generality of resegmentation across vertebrates remains poorly evaluated. Resegmentation has been questioned in anamniotes, given that the sclerotome is much smaller and lacks obvious differentiation between cranial and caudal portions. Here, we provide the first experimental evidence that resegmentation does occur in a species of amphibian. Fate mapping of individual somites in the Mexican axolotl (Ambystoma mexicanum) revealed that individual vertebrae receive cells from two adjacent somites as in the chicken. These findings suggest that large size and segmentation of the sclerotome into distinct cranial and caudal portions are not requirements for resegmentation. Our results, in addition to those for zebrafish, indicate that resegmentation is a general process in building the vertebral column in vertebrates, although it may be achieved in different ways in different groups. J. Morphol. 275:141–152, 2014. © 2013 Wiley Periodicals, Inc. 相似文献
69.
Hilde C. Trannum Hans C. Nilsson Sigurd Øxnevad 《Journal of experimental marine biology and ecology》2010,383(2):111-121
In this study, we aim at investigating the role of physical disturbance in effects of water-based drill cuttings on benthic ecosystems. Today, most of the cuttings discharged from oil and gas installations contain water-based drilling muds, rather than oil-based or synthetic muds. Drill cuttings with water-based muds are assumed to cause only marginal effects on the benthos, mainly resulting from sedimentation. However, this statement has not been experimentally tested, which is the purpose of the present work. Natural sediment particles and water-based drill cuttings were added to benthic communities in layer thicknesses of 3-24 mm in a mesocosm set-up. During the following 6 months, changes in benthic community structure and fluxes of oxygen and nutrients across the sediment water interface were studied. There was a significant reduction in number of taxa, abundance, biomass and diversity of macrofauna with increasing thickness of drill cuttings, which was not observed for the natural sediment particles. The drill cuttings also influenced oxygen consumption and oxygen penetration depth in the sediment, and it was concluded that an organic compound in the drill cuttings initiated a typical eutrophication response. Fluxes of phosphate and silicate were, however, similarly affected by the two types of particles, and maximum fluxes occurred in sediments treated with thin layers (3-6 mm) of particles. As the response of water-based drill cuttings in the present study was a result of factors other than physical disturbance, we recommend a reconsideration of the assumption that water-based drill cuttings only cause sedimentation (burial) effects. 相似文献
70.
KEVIN L DAVIES MALGORZATA STPICZYŃSKA 《Botanical journal of the Linnean Society. Linnean Society of London》2010,164(4):409-421
Phylogenetic analysis indicates that Lycastinae should be incorporated into a more broadly defined Maxillariinae. This is supported by several anatomical features, including the presence of sunken, glandular trichomes in both Lycastinae and Maxillariinae s.s. Until recently, these were known only from vegetative organs, but have since been reported from flowers of Maxillaria dichroma. One character currently used to distinguish between Lycaste and Sudamerlycaste is the distribution of floral trichomes. In this article, we test the reliability of this character, describe the floral micromorphology of Lycaste and Sudamerlycaste and investigate whether their flowers bear sunken hairs. Their floral micromorphology is compared with that of other genera currently assigned to Maxillariinae s.l. Flowers of Lycaste and Sudamerlycaste bear conical or obpyriform papillae and unbranched and unequally branched multicellular trichomes. Contrary to previous reports that trichomes are confined to the column in Sudamerlycaste, they also occur in the tepal axils. Labellar trichomes, although often present in Lycaste, are lacking in Sudamerlycaste. In Lycaste sections Lycaste and Aromaticae, floral trichomes tend to be unbranched, whereas section Intermediae has both unbranched and branched hairs. Branched hairs are more common in Sudamerlycaste. Some hairs are tracheoidal, pitted and lignified. These mainly occur in section Lycaste and, to a degree, in section Intermediae, but are absent from section Aromaticae and most species of Sudamerlycaste. Branched column hairs, present in Sudamerlycaste, are absent from all sections of Lycaste, and tracheoidal column hairs occur only in Sudamerlycaste. Sunken floral hairs are absent from both genera. Trichome structure and distribution may prove useful in distinguishing between these taxa and in elucidating the intergeneric relationships of Maxillariinae s.l.© 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 409–421. 相似文献