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。     

自由基与软骨基质胶原蛋白类型改变

本文利用ＳＤＳ－聚丙烯酰胺凝胶电泳方法,定量研究了体外培养的软骨细胞和软骨组织基质中Ⅱ型胶原蛋白的含量。结果表明氧自由基（·Ｏ－２和·ＯＨ）和具有自由基性质的物质（黄腐酸,镰刀菌毒素）可使软骨细胞合成,分泌异常的非Ⅱ型的胶原蛋白,同时,硒化合物可明显地抑制此种效应。     

Identification and characterization of glucocorticoid receptors in liver of nude mice

Glucocorticoids regulate the expression of many liver-specific genes via glucocorticoid receptors. The presence of glucocorticoid receptors in liver has been reported in many mammalian species but not in nude mice. In the present study, we demonstrate the presence of specific glucocorticoid receptors in nude mouse liver. The binding of ligands to these receptors could be completely inhibited by RU486, and partially blocked by hydrocortisone and progesterone, whereas estrogen and testosterone had no effect. Hydrocortisone down-regulated the level of glucocorticoid receptors in livers of nude mice and correspondingly enhanced the activities of tyrosine aminotransferase and -glutamyltransferase. Our results indicate that glucocorticoid receptors in nude mouse liver are specific, fully functional, and present at levels 28.5-fold higher than in the liver of normal inbred mice. We suggest that the nude mouse is a valuable model for studies of hepatic glucocorticoid action and may provide a clue to a putative hepatic-thymic interaction.     

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.     

Sequences within the last intron function in RNA 3''-end formation in cultured cells.

In cultured cells, little if any mRNA accumulates from an intronless version of the human gene for triosephosphate isomerase (TPI), a gene that normally contains six introns. By deleting introns either individually or in combinations, it was demonstrated by Northern (RNA) blot hybridization that while the deletion of a greater number of introns generally results in a lower level of product mRNA, not all introns contribute equally to mRNA formation. For example, intron 1 appeared to be dispensable, at least when the remaining introns are present, but deletion of the last intron, intron 6, reduced the level of product mRNA to 51% of normal. To determine how intron 6 contributes to mRNA formation, partial deletions of intron 6 were constructed and analyzed. Deletion of the lariat and acceptor splice sites or the donor, lariat, and acceptor splice sites, each of which precluded removal of the intron 6 sequences that remained, reduced the level of product mRNA to < 1 or 27% of normal, respectively. As measured by RNase mapping and cDNA sequencing, the decrease in mRNA abundance that was attributable to the complete and partial intron 6 deletions was accompanied by an increase in the abundance of pre-mRNA that lacked a mature 3' end, i.e., that was neither cleaved nor polyadenylated. We infer from these and other data that sequences within the final intron facilitate proper 3'-end formation, possibly through an association with the components of a productive spliceosome.     

Monovalent cation effects on intermolecular purine-purine-pyrimidine triple-helix formation.

The binding of a 19-mer guanosine-rich oligodeoxyribonucleotide, TG3TG4TG4TG3T (ODN 1), to a complementary polypurine DNA target was investigated by DNase I footprinting and restriction endonuclease protection assays. Monovalent cations inhibited intermolecular purine-purine-pyrimidine triple-helical DNA formation, with K+ and Rb+ being most effective, followed by NH4+ and Na+. Li+ and Cs+ had little to no effect. Similar results were observed with the G/A-rich oligonucleotide AG3AG4AG4AG3AGCT. Kinetic studies indicated that monovalent cations interfered with oligonucleotide-duplex DNA association but did not significantly promote triplex dissociation. The observed order of monovalent cation inhibition of triplex formation is reminiscent of their effect on tetraplex formation with G/T-rich oligonucleotides. However, using electrophoretic mobility shift assays we found that the oligonucleotide ODN 1 did not appear to form a four-stranded species under conditions promoting tetraplex formation. Taken together, our data suggest that processes other than the self-association of oligonucleotides into tetraplexes might be involved in the inhibitory effect of monovalent cations on purine-pyrimidine-purine triplex formation.     

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.