甘薯低纤维品种的选育

培育纤维含量低的甘薯品种乃是消费者的一个基本要求。由于甘薯是块根,因而任何品种必然含有一些维管成分的纤维。甘薯品种间维管成分的含量不同,我们对烧煮后纤维含量低的材料进行了选择。甘薯纤维在块根外层或皮层区与木栓和维管形成层结合在一起,在块根中心则与不规则形成层结合在一起。我们还     

用叶绿素荧光试验快速测定硬粒小麦栽培品种的抗旱性

在光合作用的有机物被光线照明时,少部分所吸收的光是以叶绿素荧光的形式反复放射的.叶绿素荧光强度与光合电子传递活性有关,因而通常用叶绿素荧光作为一种光合作用灵敏度的探测方法(Papageorgiou,1975;Lavorel和Etienne,1977).当细胞处于胁迫时,活体叶绿素荧光可以提供监测叶绿体氧化还原膜系统活性的一种手段.目前,越来越多地应用活体叶绿素荧光来研究胁迫对于危害     

Association with the Syndrome "Basses Richesses" of Sugar Beet of a Phytoplasma and a Bacterium-Like Organism Transmitted by a Pentastiridius sp

ABSTRACT The syndrome "basses richesses" of sugar beet (SBR) was first observed in 1991 in Burgundy, France. A cixiid planthopper, Pentastiridius beieri, has been proved to be involved in the transmission to sugar beet of a stolbur phytoplasma, which could be detected in some affected plants. In 2000, periwinkle and sugar beet exposed to field-collected cixiids developed symptoms similar to SBR on sugar beet. Use of 4'-6-diamidino-2-phenylindole (DAPI) staining and transmission electron microscopy confirmed the presence of phytoplasma in some of the plants, which were also positive for this pathogen in a polymerase chain reaction (PCR) analysis. A phloem-restricted gram-negative bacteria was seen in all other plants with symptoms but PCR-negative for phytoplasma. Three primer pairs reported as diagnostic for phloem-limited bacteria were tested but only primers specific for 'Candidatus Phlomobacter fragariae' gave a positive signal, which related to the presence of DAPI-stained bacteria-like objects in diseased plants. Although phytoplasma and bacterium-like organisms were associated with the same macroscopic symptoms on sugar beet, histochemical analysis of phloem cells showed that phytoplasma were associated with cell necrosis and cell wall lignification, while bacteria were associated with these same abnormalities as well as deposit of phenolic compounds in the lumen of phloem cells.     

近百年来养禽业中的化学药品(续)

能量饲料——谷物、脂肪和脂肪酸倾注入江河的饲料加工废料可为养禽业利用。许多废料(玉米糠麸、小麦麸)的蛋白质质量较高,可用作蛋白质添加剂或作为脂肪和能量来源。杂交玉米的发展对养禽业兴旺发达的作用不能低估。家禽日粮含有30～80％玉米。随着玉米产量提高,价格下降,养禽业得以以低廉的成本生产更多的食用产品。日粮中玉米含量增多时,则可因能量水平提高而改进饲料效率。     

Carbon flux and growth in mature deciduous forest trees exposed to elevated CO2

Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees.     

Participation of specific PKC isozymes in the inhibitory effect of ET-1 on progesterone accumulation in cells isolated from early- and mid-phase corpora lutea

Expression of PKC alpha, beta I, beta II, epsilon and micro has been demonstrated in the whole bovine CL with PKC epsilon being differentially expressed as a function of development. In experiment 1 we have investigated the amount of mRNA encoding PKC epsilon at different stages of luteal development (days 1, 4, 10 and 17). In experiment 2, the cellular source of luteal PKC isozymes was determined. Enriched steroidogenic (SC) and endothelial (EC) cells from day-10 CL were used to examine this question by Western blot analysis and immuno-histochemistry. In experiment 3, Western blot analysis was used to examine the ability of ET-1 to activate luteal PKC isozymes in day-10 CL. In experiment 4, the role of luteal PKC isozymes in the ET-1 mediated inhibition of P(4) accumulation in steroidogenic cell cultures from day-4 and day-10 CL was examined. Abundance of PKC epsilon mRNA gradually increased from day-1 to -10 with no further increase on day-17. In experiment 2, PKC epsilon was exclusively detected in SC (LLC and SLC). In contrast, PKC alpha, beta I and beta II were detected in both SC and EC, with EC expressing higher amounts of PKC isozymes. In day-10 CL, ET-1 induced cellular redistribution of PKC alpha, beta I, epsilon but not beta II. Inhibitors specific for conventional PKC isozymes as well as PKC epsilon were able to negate the inhibitory effects of ET-1 on P4 accumulation in the day 10 CL. In the day-4 CL, the inhibitory effect of ET-1 might be mediated via conventional PKC. Thus, an exclusive presence of PKC epsilon in luteal steroidogenic cells, its higher expression along with the ability of ET-1 to stimulate its activation in day-10 CL strongly suggests that this PKC isoform may play an important regulatory role in decreasing P(4) during luteal regression. Inhibition of P(4) by ET-1 in the early CL may be mediated via conventional PKC isozymes.     

Ethoxylated rapeseed oil derivatives as novel adjuvants for herbicides

Ethoxylates of rapeseed oil and of methylated rapeseed oil were synthesized and tested as adjuvants for 2,4-D and phenmedipham. Provided they had less than 6 units of ethylene oxide (EO), 1.0 to 10 g litre(-1) ethoxylates in water induced droplet spreading on barley leaves. In an acetone-based medium all derivatives strongly promoted the foliar uptake of 2,4-D, with no clear influence of the ethoxylation degree. In the same medium there was a negative influence of ethoxylate chain length on the foliar uptake of phenmedipham. In a water-based medium, phenmedipham applied with rapeseed oil emulsified with ethoxylated (20 EO) rapeseed oil displayed uptake rates close to a commercial preparation. The same was true for phenmedipham applied with ethoxylated (2 EO) methylated rapeseed oil. In bioassays, phenmedipham prepared with methylated rapeseed oil emulsified with ethoxylated (20 EO) rapeseed oil was as efficacious on barley as a commercial formulation. The same was true for phenmedipham prepared with ethoxylated (2 EO) methylated rapeseed oil. However, neither rapeseed oil nor methylated rapeseed oil emulsified with ethoxylated (2 EO) methylated rapeseed oil conferred good efficacy to phenmedipham. Hence, ethoxylated rapeseed oil derivatives are promising adjuvants or formulants for herbicides.     

Using 3D animations to teach intracellular signal transduction mechanisms: taking the arrows out of cells

Traditional methods of teaching intracellular biological processes and pathways use figures or flowcharts with the names of molecules linked with arrows. Many veterinary students, presented with such material, simply memorize the names or chemical structures of the molecules and are then likely to forget the material once the examination is completed. To address this problem, the authors designed, created, and field-tested new teaching media that incorporate realistic three-dimensional (3D) animations depicting the dynamic changes that occur in intracellular molecules during cellular activation. Testing found that veterinary students taught using traditional teaching media (e.g., lectures, handouts, textbooks) are proficient in memorizing the names and order of intracellular molecules but unable to appreciate the interactions between these elements or their spatial relationships within cells. In contrast, more than 90% of veterinary students taught using 3D animations not only recall the facts about the intracellular elements but also develop accurate mental images of the interactions among these molecules and their spatial relationships. These findings strongly suggest that the comprehension of complex biological processes by veterinary students can be enhanced by the use of dynamic 3D depictions of these processes in the classroom.     

牛皮纸厂污水对黄鳝代谢的影响

<正> 许多研究工作者,已观察到鱼接触各类应激因子(包括驯养,物理干扰、饥饿和缺氧)时对碳水化合物体内代谢的改变。因应激反应使血萘酚胺和皮质激素类分泌增加,引起鱼体能量的储备产生明显改变。用黄鳝作为实验动物,其平均体重60克。试验开始前鱼在适宜的条件下,置于水簇箱一周。     

Band gap fluorescence from individual single-walled carbon nanotubes

Fluorescence has been observed directly across the band gap of semiconducting carbon nanotubes. We obtained individual nanotubes, each encased in a cylindrical micelle, by ultrasonically agitating an aqueous dispersion of raw single-walled carbon nanotubes in sodium dodecyl sulfate and then centrifuging to remove tube bundles, ropes, and residual catalyst. Aggregation of nanotubes into bundles otherwise quenches the fluorescence through interactions with metallic tubes and substantially broadens the absorption spectra. At pH less than 5, the absorption and emission spectra of individual nanotubes show evidence of band gap-selective protonation of the side walls of the tube. This protonation is readily reversed by treatment with base or ultraviolet light.