Production of panose from maltose by intact cells of Aureobasidium pullulans

Panose, a major component of isomalto-oligosaccharides, was selectively produced from maltose using transglucosylation reaction catalyzed by intact cells of Aureobasidium pullulans. When 50 %(w/v) maltose was used as a substrate, the maximum concentration of panose accumulated in the final reaction mixture was about 50 %(w/w) after 120 hr reaction at 55 °C.     

Rapid screening of an SH2-containing gene using PCR amplification method

Summary To isolate a novel gene that contains an SH2 domain, we devised a rapid and nonradioactive cDNA library screening method using polymerase chain reaction (PCR). For PCR amplification, we designed degenerate oligonucleotide primers from the multialigned DNA sequences of SH2 domains. This method offers an inexpensive and efficient approach for the isolation of clones of interest from cDNA libraries.     

祁连山地区植被特征及其分布规律

分析和讨论了祁连山地区主要植被类型及其分布特征。祁连山地区随着青藏高原的强烈隆升表现为整体抬升,植被具有明显的生态地理边缘效应特征和高原地带性规律。该区植被虽然受到四周的较大影响,但各类高寒植被占有绝对优势,表现出与青藏高原植被整体明显的相似性和广泛的一致性。另一方面,本区植被也有其特殊性及与高原面存在一些差异。因此,建议把祁连山地区做为青藏高原植被区的次一级独立单元     

Genetic transformation and plant regeneration of watermelon using Agrobacterium tumefaciens

Adventitious shoots formed on the proximal cut edges of different cotyledonary explants of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai; cvs. Sweet Gem and Gold Medal] cultured on Murashige and Skoog's (MS) medium with 1 mgl^-1 6-benzyladenine (BA). Light (16-h photoperiod, about 7 Wm^-2 cool-white fluorescent lamps) was essential for shoot formation. To obtain transformed plants, cotyledonary explants of Sweet Gem were cocultured with Agrobacterium tumefaciens LBA4404, a disarmed strain harboring a binary vector pBI121 carrying the CaMV 35S promoter--glucuronidase (GUS) gene fusion used as a reporter gene and NOS promoter-neomycin phosphotransferase gene as a positive selection marker, for 48 h on MS medium with 1 mgl^-1 BA and 200 M -hydroxyacetosyringone. After 48 h of culture, explants were transferred to medium with 1 mgl^-1 BA 250 mgl^-1 carbenicillin, and 100 mgl^-1 kanamycin and cultured in the light. Adventitious shoots formed on the explants after 4 weeks of culture. When subjected to GUS histochemical assay, young leaves obtained from the shoots showed a positive response at a frequency of up to 16%. Preculturing cotyledonary explants on MS medium with 1 mgl^-1 BA for 5 d enhanced the competence of the cells to be transformed by Agrobacterium. Southern blot analysis confirmed that the GUS gene was incorporated into the genomic DNA of the GUS-positive regenerants. The transformed plants were grown to maturity.     

沙打旺组织培养中脱分化细胞的超微结构及细胞核的动态变化

对沙打旺的下胚轴、子叶、幼叶组织培养中脱分化细胞进行了超微结构观察,并着重讨论了细胞核的动态变化。脱分化细胞的细胞质中线粒体墙加,嵴明显;多聚核糖体增多;高尔基体增加;质体中积累淀粉。核仁与核内异染色质之间有一个动态过程。此过程暂称“核仁物质喷射“现象。在致有以下：１．核体出现,半嵌在增大的核仁上,核内异染色质沿核膜凝聚;２．异染色质移向核仁,并与核仁接触,核体消失,部分异质进入核仁;３．核仁物质     

Production of high fructo-oligosaccharide syrup with two enzyme system of fructosyltransferase and glucose oxidase

Summary A novel two enzyme system of fructosyltransferase and glucose oxidase to enhance the content of the net fructo—oligosaccharide (FOS) fractions in the industrial production of FOS syrup from sucrose was devised. The net FOS content in the commercial FOS syrup has been limited only to 55–60 % due to the accumulation of glucose which acts as a feedback inhibitor of the fructosyltransferase. By supplementing glucose oxidase to the conventional FOS reaction system, we could convert the glucose to gluconic acid readily separable from neutral sugars by simple ion exchange operation in the next step. The simultaneous removal of glucose was proved effective in proceeding the reaction by fructosyltransferase further by relieving the product inhibition caused by glucose. By this way, we could raise the net FOS content as high as 90 %.     

热带－亚热带森林中猕猴的食性

采用跟踪观察法对热带－亚热带森林中的猕猴种群的食性及其与植被类型的关系进行了调查,结果表明,猕猴主要选择季雨林或次生季雨林为其觅食场所,栖息地植物的地理分布和种类直接影响其食性,猕猴对植物各部位的采食频度随植物生长期而变化．     

Population differentiation inSpartina patens: Water potential components and bulk modulus of elasticity

Pressure-volume technique was utilized to evaluate salinity response among three populations ofSpartina patens (Ait.) Muhl. from Louisiana Gulf coast marshes. Plants were subjected to salinities of 85 and 425 mol m^?3 for 77 d in a greenhouse. Ψ_w and Ψ_π decreased in all populations in response to increases in salinity. There were 32% decrease in Ψ_sat, 42% decrease in Ψ_tlp in response to salinity changes from 85 to 425 mol m^?3 in the Ferblanc population. Similarly, there were 35% and 41% decrease in Ψ_sat in the Clovelly and Lake Tambour populations, respectively. All populations showed the ability to adapt to the increased salinity as was evidenced by osmotic adjustment. However, the Lake Tambour population appeared to have superior ability to adapt to high salinity through having a significantly lower osmotic potential at saturation (Ψ_sat), osmotic potential at turgor loss point (Ψ_tlp), and maximum turgor potential (Ψ_P(max)) compared to other populations. Ferblanc and Clovelly populations revealed the ability to adapt to saline environments to a lesser extent as compared to the Lake Tambour population. Results indicate that there is a potential for selection of superior strains ofSpartina patens for use in marsh restoration projects aiming at prevention of wetland loss in certain coastal areas.     

Cultivation of mammalian cells as aggregates in bioreactors: effect of calcium concentration of spatial distribution of viability

Recombinant human kidney epithelial 293 cells were cultivated as aggregates in suspension. The concentration calcium ion, in the range of 100 muM to 1mM, affected the rate of aggregate formation. During the course of cultivation the size distribution of aggregates shifted and the fraction of larger aggregates increased. This effect was more profound in cultures with a high calcium concentration. Scanning and transmission microscopic examination of the aggregates revealed that cell packing was greater in the high calcium cultures and that ultrastructural integrity was retained in aggregates from both low and high calcium cultures. Confocal microscopy was applied to examine the viability of cells in the interior of the aggregates. High viability was observed in the aggregates obtained from exponentially growing cultures. Aggregates from the high calcium culture in the stationary phase exhibited lower viability in the interior. With its ease of retention in a perfusion bioreactor, aggregate cultures offer an alternative choice for large-scale operation. (c) 1993 John Wiley & Sons, Inc.     

Conformation and activity ofPhaseolus coccineus var. rubronanus lectin

The conformation of native and denaturedPhaseolus coccineus var. rubronanus lectin was studied by circular dichroism (CD) and correlated to the hemagglutinating activity. The far-UV CD spectrum at 25°C showed a broad, negative band around 223 nm and a positive one at 196 nm. CD data analysis of the lectin indicated a -sheet-rich protein. At high temperatures, the spectrum was blue-shifted with increasing magnitude; these changes correlated well with the loss of the activity. The conformation of lectin betweenpH 2 and 10 remained essentially unchanged. AtpH 13 the CD spectrum resembled that of unordered form with a negative band near 200 nm and the activity was completely lost. The denatured lectin in 6 M guanidine hydrochloride would be renatured upon diluting the denaturant to 0.75 M; the changes in CD spectrum again correlated well with the loss of the activity. The effect of sodium dodecyl sulfate on the lectin was drastic; it sharply increased thea-helix at the expense of the -sheet and reduced the activity; the changes reached a plateau above 20 mM surfactant.