Elevated CO2 and drought alter tissue water relations of birch (Betula populifolia Marsh.) seedlings

The effect of increasing atmospheric CO₂ concentrations on tissue water relations was examined in Betula populifolia, a common pioneer tree species of the northeastern U.S. deciduous forests. Components of tissue water relations were estimated from pressure volume curves of tree seedlings grown in either ambient (350 l l^–1) or elevated CO₂ (700 l l^–1), and both mesic and xeric water regimes. Both CO₂ and water treatment had significant effects on osmotic potential at full hydration, apoplasmic fractions, and tissue elastic moduli. Under xeric conditions and ambient CO₂ concentrations, plants showed a decrease in osmotic potentials of 0.15 MPa and an increase in tissue elastic moduli at full hydration of 1.5 MPa. The decrease in elasticity may enable plants to improve the soil-plant water potential gradient given a small change in water content, while lower osmotic potentials shift the zero turgor loss point to lower water potentials. Under elevated CO₂, plants in xeric conditions had osmotic potentials 0.2 MPa lower than mesic plants and decreased elastic moduli at full hydration. The increase in tissue elasticity at elevated CO₂ enabled the xeric plants to maintain positive turgor pressures at lower water potentials and tissue water contents. Surprisingly, the elevated CO₂ plants under mesic conditions had the most inelastic tissues. We propose that this inelasticity may enable plants to generate a favorable water potential gradient from the soil to the plant despite the low stomatal conductances observed under elevated CO₂ conditions.     

CO2-induced growth enhancements of co-occurring tree species decline at different rates

To elucidate how enriched CO₂ atmospheres, soil fertility, and light availability interact to influence the long-term growth of tree seedlings, six co-occurring members of temperate forest communities including ash (Fraxinus americana L.), gray birch (Betula populifolia), red maple (Acer rubrum), yellow birch (Betula alleghaniensis), striped maple (Acer pensylvanicum), and red oak (Quercus rubra L.) were raised in a glasshouse for three years in a complete factorial design. After three years of growth, plants growing in elevated CO₂ atmospheres were generally larger than those in ambient CO₂ atmospheres, however, magnitudes of CO₂-induced growth enhancements were contingent on the availability of nitrogen and light, as well as species identity. For all species, magnitudes of CO₂-induced growth enhancements after one year of growth were greater than after three years of growth, though species' growth enhancements over the three years declined at different rates. These results suggest that CO₂-induced enhancements in forest productivity may not be sustained for long periods of time. Additionally, species' differential growth responses to elevated CO₂ may indirectly influence forest productivity via long-term species compositional changes in forests.     

重组人IL6／2融合蛋白对6.5Gy照射小鼠造血功能恢复的影响

观察了ｈＦＰＩＬ６／２对６．５Ｇｙγ线照射ＮＩＨ小鼠第１０天造血功能恢复的影响。结果表明：照射小鼠连续４ｄ给予ｈＦＰＩＬ６／２２５０μｇ·ｋｇ－１·ｄ－１,其脾重、ＣＦＵ－８、骨髓有核细胞数及ＣＭ－ＣＦＵ分别比对照组增加５９．０％、２７８．５％、５７．９％和１３８．２％,统计学处理均有显著差异;对此四项指标的改善也明显优于２５μｇ组。另外,２５０μｇ剂量组小鼠外周血象３０ｄ的动态观察结果表明,ｈＦＰＩＬ６／２不但能明显提高红细胞和血红蛋白的最低值,而且能使血小板的恢复提前。提示ｈＦＰＩＬ６／２在促进血小板生成和促进红系造血方面可能具有良好的应用前景。     

黄桃罐头产品质量Fuzzy综合鉴评

本文根据FuzzZ数学理论,运用多级模型的综合评判法,对国内20种黄桃罐头产品质量进行了优劣鉴评。并将其划分为一、二、三、四4个等级。从而为罐头产品质量鉴评,准确地汰劣遴优提供新方法。     

传染性软疣病毒（MCV）的电镜观察

传染性软疣病毒（ＭＣＶ）的电镜观察李德忠,肖同浩,武晓华（广州军区武汉总医院电镜室,武汉４３００７０）吴宁（广州军区武汉总医院皮肤科,武汉４３００７０）关键词传染性软疣病毒,病毒形态,电镜观察曾有研究描述ＭＣＶ的发育周期中有８种形态,也有按发育过程将...     

肝细胞的异质性：葡萄糖和酮体在大鼠肝脏的代谢

用大鼠肝脏门静脉或肝静脉周围的肝细胞来研究葡萄糖和酮体生成的区域分布。肝细胞通过毛地黄皂苷－胶原酶灌流技术分离。门静脉周围肝细胞的γ谷氨酰转肽酶的活性比肝静脉周围肝细胞高２．４倍;而谷氨酰胺合成酶的活性则相反,肝静脉周围肝细胞高出５６倍。门静脉周围肝细胞的内源性葡萄糖合成比肝静脉周围肝细胞高１．５７倍。给予刺激葡萄糖异生的底物,门静脉周围肝细胞的葡萄糖合成则增加１．７－２．１倍。肝静脉周围肝细胞的内源性酮体生成比门静脉周围肝细胞高１．３倍。给予能明显刺激酮体生成的辛酸盐,肝静脉周围肝细胞的酮体生成仅略为增加。我们的结果证实,在基础和刺激的条件下,葡萄糖的异生在门静脉周围肝细胞中优先,而酮体生成仅在肝静脉周围肝细胞占微弱的优势。     

不同盐浓度对红萍生长及若干生理指标的影响

低盐浓度（０．２％ＮａＣｌ）对红萍生长有促进作用,处理组形态比对照厚而大朵,根系较长,且健壮,含水量与对照相似,但高浓度使萍体含水量明显减少。萍体ＮａＣｌ积累量随着培养液中盐浓度的增加而增加。生产指标测定表明,在低盐浓度下生长的红萍,叶绿素含量、固氮酶活性和全氮含量明显增加,可溶性糖含量则最低。低盐浓度促进红萍生长的原因可以归结为光合作用和固氮能力提高的结果。     

The last seven transmembrane and carboxy-terminal cytoplasmic domains of Epstein-Barr virus latent membrane protein 2 (LMP2) are dispensable for lymphocyte infection and growth transformation in vitro.

Specifically mutated Epstein-Barr virus (EBV) recombinants which truncate latent membrane protein 2A (LMP2A) and LMP2B after 260 of 497 amino acids and after 141 of 378 amino acids, respectively, were constructed. Despite truncation before the last seven transmembrane domains and the carboxy terminus, the mutant recombinants were not altered in initiation of primary B-lymphocyte infection or growth transformation, in expression of nuclear protein 1 or 2 or LMP1, or in induction of lytic EBV replication. Cells transformed by mutant virus recombinants were not different from wild-type virus transformants in initial or long-term outgrowth, sensitivity to limiting cell dilution, serum requirement, or clonogenic growth in soft agar. Together with similar analyses of a mutation stopping translation of the LMP2A amino-terminal cytoplasmic domain, these results indicate that LMP2 is not required for primary B-lymphocyte infection in vitro.     

Overexpression of cloned genes using recombinant Escherichia coli regulated by a T7 promoter: II. Two-stage continuous cultures and model simulations

A two-stage culture strategy was studied for continuous high-level production of a foreign protein in the chemically inducible T7 expression system. The first stage is dedicated to the maintenance of plasmid-bearing cells and the second stage to the target protein synthesis by induction of cells coming from the first stage. On entering the second stage, recombinant cells undergo a gradual induction of the target gene expression. These plasmid-bearing cells experience dynamic changes in intracellular compositions and specific growth rates with their individual residence times. Therefore, the overall cultural characteristics in the production stage are really averages of the contributions from the various cells with different residence times. The behavior of the two-stage culture is described by a model, which accounts for dynamic variations of cell growth and protein synthesis rates with cell residence times. Model simulations were compared with experimental results at a variety of operating conditions such as inducer concentration and dilution rate. This model is useful for understanding the behavior of two-stage continuous cultures. (c) 1993 John Wiley & Sons, Inc.     

迎接廿一世纪——记中国无锡第十一届国际植物园协会大会

第十一届国际植物园协会（IABG）大会于1993年9月7日在中国无锡开幕,经苏州、杭州,于9月12日在上海闭幕。9月6日部分与会代表参加了在南京举行的“中国南京国际植物园俱乐部”奠基仪式及江苏省重点实验室南京中山植物园“植物迁地保存实验室”扩建部分开放使用等一系列庆祝活动。参加大会的有来自23个国家和地区的199名代表。大会收到论文74篇,其中板报42篇,大会报告13篇。本次会议的主要议题为“植物园与国家发展”。经过大会报告和交流,明确了世界植物园在继续发挥其保护物种和保护环境的功能之外,必须进一步密切植物园与国家发展的关系。全面发展植物园的十项功能,不仅可以增加植物园对社会的贡献,也有利于提高植物园自身的活力和生存能力。大会选出了以主席岩（木规）邦男,副主席李蔼娃、贺善安、安德列也夫,秘书长艾斯特万为领导核心的新一届理事会。世界植物园两大组织国际植物园协会（IABG）和国际植物园保护组织（BGCI）在无锡签署的合作备忘录标志着国际植物园运动进入了一个新的历史时期。理事会的第一次会议于9月11日在由杭州开往上海的火车上举行。讨论了整顿组织、会员登记、出版IABG通讯及与BGCI合作开展活动等问题。会议确认1994年将在印尼召开IABG-AD第二次会议。第十二届IABG大会将于1