S-PI对香菇酸性蛋白酶的抑制机理及其促进出菇的生化解释

S-PI对纯化的香菇酸性蛋白酶具有强烈的抑制作用,10μmol／L的S-PI可使酶活降低77％,这种抑制属于可逆竞争抛物线型抑制。经25μmol／L酸性蛋白酶水解6小时后,香菇胞外酸性磷酸酶的活性从24．6单位降低到20．8单位,同时C1酶和Cx酶的活性分别比对照降低了76％和58％,这表明香菇酸性蛋白酶不仅直接左右着香菇发育的氮代谢,同时也间接地影响着碳代谢及能量转换。     

籼,粳稻及其杂种粗线期的核型分析

研究了典型籼,粳稻及其杂种粗线期的核型,结果表明：（１）籼稻品种南特号具有两对随体染色体,分别为第十和第十二染色体,粳稻品种巴利拉具１对随体染色体,为第十染色体,杂种南特号／巴利拉的随体染色体与南特号相同;（２）在粗线期,两品种均可见单核仁和双核仁的细胞存在,说明细胞贩核仁数目与随体数目并不对应;（３）两品种的对应染色体之间,在染色体相对长度,臂比及染色粒分布上均无明显差异。     

茶叶中总硒含量及其影响因素的研究

茶叶中硒素总量测定结果表明：土壤含硒量的高低是直接影响茶叶中硒的总量。茶树根、茎、叶、果中均有硒元素,叶片是茶硒积累的主要器官,尤其是老叶,其含量是嫩叶的几倍．茶树品种间含量的差异显著,最大差异达10倍以上．毛茶加工的成品茶含硒量受加工技术措施影响较大,其不同等级的含硒量与级别没有线性关系．     

工业固体废弃物的急性生物毒性研究

工业固体废弃物的急性生物毒性研究谢思琴,顾宗濂,周德智（中国科学院南京土壤研究所,南京２１０００８）Ａｃｕｔｅｂｉｏｔｏｘｉｃｉｔｙｏｆｉｎｄｕｓｔｒｉａｌｓｏｌｉｄｗａｓｔｅｓ￥．ＸｉｅＳｉｑｉｎ;ＧｕＺｏｎｇｌｉａｎａｎｄＺｈｏｕＤｅｚｈｉ（Ｉｎ...     

罗望子的综合利用开发

本文从食品、医药及轻工业等方面介绍了罗望子(Tamarindus indica L.)的国内外应用情况,特别是罗望子多糖在国外的开发利用状况,为我国进一步开发罗望子这一重要经济植物资源提供线索和参考。     

发酵活性豆渣饲料的研究

活性豆渣饲料是新鲜豆渣经微生物发酵而得到的。本文介绍了发酵菌株的筛选过程,并对发酵的最适条件进行了研究。分析结果表明,这种饲料含有蛋白酶等多种酶类,蛋白质、氨基酸的含量均比未发酵的豆渣有所增加,而且克服了豆渣含水量大、易腐败的缺点,有利于畜禽更充分地消化吸收。经动物喂养实验证明．活性豆渣饲料可代替５０％以上的鱼粉,是一种非常理想的蛋白饲料。     

Foreign gene expression (beta-galactosidase) during the cell cycle phases in recombinant CHO cells

Recombinant mammalian cultures for heterologous gene expression typically involve cells traversing the cell cycle. Studies were conducted to characterize rates of accumulation of intracellular foreign protein in single cells during the cell cycle of Chinese hamster ovary (CHO) cells transfected with an expression vector containing the gene for dihydrofolate reductase (dhfr) and the lacZ gene for bacterial beta-galactosidase (a nonsecreated protein). The lacZ gene was under the control of the constitutive cytomegalovirus promoter. These normally attachment-grown cells were adapted to suspension culture in 10(-7) M methotrexate, and a dual-laser flow cytometer was used to simultaneously determine the DNA and foreign protein (beta-galactosidase) content of single living cells. Expression of beta-galactosidase as a function of cell cycle phase was evaluated for cells in the exponential growth phase, early plateau phase, and inhibited traverse of the cell cycle during exponential growth. The results showed that the beta-galactosidase production rate is higher in the S phase than that in the G1 or G2/M phases. Also, when cell cycle progression was stopped at the S phase by addition of aphidicolin, beta-galactosidase content in single cells was higher than that in exponential phase or plateau phase cells and increased with increasing culture time. Although the cells did not continue to divide after aphidicolin addition, the production of beta-galactosidase per unit volume of culture was very similar to that in normal exponential growth. (c) 1993 John Wiley & Sons, Inc.     

High prevalence of a point mutation in the porphobilinogen deaminase gene in Dutch patients with acute intermittent porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant disease characterized by a deficiency of porphobilinogen deaminase (PBGD). Up to now 14 different mutations have been described. In an effort to investigate the molecular epidemiology of AIP we have undertaken a systematic study of different exons of the PBGD gene from a large number of unrelated patients. Here, exon 8 from 82 unrelated Dutch and French AIP patients was examined using single strand confirmation polymorphism analysis (SSCP) after polymerase chain reaction (PCR) amplification. A single base mutation, C to T, at position 346 of the sequence coding for PBGD was observed in 15 Dutch families but in only 1 French family. A simple PCR assay is described to facilitate the diagnosis of this common mutation at the DNA level.     

Elevated ozone decreases the multifunctionality of belowground ecosystems

Elevated tropospheric ozone (O₃) affects the allocation of biomass aboveground and belowground and influences terrestrial ecosystem functions. However, how belowground functions respond to elevated O₃ concentrations ([O₃]) remains unclear at the global scale. Here, we conducted a detailed synthesis of belowground functioning responses to elevated [O₃] by performing a meta-analysis of 2395 paired observations from 222 publications. We found that elevated [O₃] significantly reduced the primary productivity of roots by 19.8%, 16.3%, and 26.9% for crops, trees and grasses, respectively. Elevated [O₃] strongly decreased the root/shoot ratio by 11.3% for crops and by 4.9% for trees, which indicated that roots were highly sensitive to O₃. Elevated [O₃] impacted carbon and nitrogen cycling in croplands, as evidenced by decreased dissolved organic carbon, microbial biomass carbon, total soil nitrogen, ammonium nitrogen, microbial biomass nitrogen, and nitrification rates in association with increased nitrate nitrogen and denitrification rates. Elevated [O₃] significantly decreased fungal phospholipid fatty acids in croplands, which suggested that O₃ altered the microbial community and composition. The responses of belowground functions to elevated [O₃] were modified by experimental methods, root environments, and additional global change factors. Therefore, these factors should be considered to avoid the underestimation or overestimation of the impacts of elevated [O₃] on belowground functioning. The significant negative relationships between O₃-treated intensity and the multifunctionality index for croplands, forests, and grasslands implied that elevated [O₃] decreases belowground ecosystem multifunctionality.