花粉粒外壁成层现象、外壁外层的结构和被子植物的进化

显花植物的花粉粒外壁被认为由外壁外层所覆盖着的外壁内层组成。这是在形态学和个体发育上所规定的解释。外层内层沉积在可能由质膜起源的切向膜上。外壁外层沉积在没有居间膜(可是,这膜有时存在,但不是切向膜)的原外壁中,在成熟状态中,外壁内层可能或不可能保存具片层的,可能或不可能被一薄的清晰区与外壁外层分隔开,可能或不可能在染色性能和溶解度上与外壁外层有所区别。在这一方面,例如番荔枝科(Annonaceae)和肉豆蔻教(Myristicaceae)花粉粒具片层的内部层次被认为是外壁内层的,跟裸子植物和其他被子植物的外壁内层同源。一如蕨类植物孢子外壁[译者注:原文为花粉外壁(exine),应为孢子外壁(exospore)]的内部基本上具片层的区同源,只有在个体发育上能够证明没有切向膜支持着内部的外壁区时才可以认为花粉是缺乏外壁内层。     

肝癌组织中GD3合成酶的纯化

ＧＤ３合成酶是膜嵌合蛋白,定位于高尔基体,经过制作微粒体,Ｔｒｉｔｏｎ增溶、ＡＨ－Ｓｅｐｈａｒｏｓｅ及ＧＭ３－Ｇｌａｓｓｂｅａｄｓｅ及ＧＭ３－Ｇｌａｓｓｂｅａｄｓ亲和层析等步骤,二乙基亚硝胺诱发大鼠肝癌组织中的ＳＴ２被纯化了３１５９７倍,得率为０．３５％。ＳＤＳ－聚丙烯酰胺凝胶电泳后银染色呈１条蛋白着色带,分子量为５５ｋｄ。     

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.     

QUALITATIVE ANALYSIS OF BIOECOLOGY DIFFERENTIAL SYSTEM

In this paper, the author studies the quartic bioecology differential system:Here n and q are positive constants, l、m and p are constants. The author also proves some theorems of existence and uniqueness of limit cycles of this differential system.     

Microcarrier culture of bowes melanoma cells in serum-free medium with Human plasma fraction IV-4+ V

Bowes melanoma cells were cultivated successfully in a serum-free medium which was constructed by the concept of maximum retention of proteins from fractionated human plasma having growth stimulatory activities. The cells could be cultivated in the serum-free medium without any adaptation period. The major serum-free component of the medium was the fraction IV-4 + V of the Cohn fractionation process of human plasma. Approximately six times increase of tissue-type plasminogen activator (t-PA) activity as compared with that in serum-free medium even though the cell growth was much slower. In addition, the growth stimulatory activities of thrombin and fibronectin were investigated during the cultivation of Bowes melanoma cells in this serum-free medium. These proteins contributed significantly to the enhanced growth of cells by reducing doubling time to 25 and 35 h as compared with 55 h in the serum-free medium without them. Especially, fibronectin supported cells to propagate near to the maximum cell density achieved in the medium with 10% FBS.     

Machine Learning Modeling of Protein-intrinsic Features Predicts Tractability of Targeted Protein Degradation

Targeted protein degradation(TPD) has rapidly emerged as a therapeutic modality to eliminate previously undruggable proteins by repurposing the cell’s endogenous protein degradation machinery. However, the susceptibility of proteins for targeting by TPD approaches, termed‘‘degradability”, is largely unknown. Here, we developed a machine learning model, model-free analysis of protein degradability(MAPD), to predict degradability from features intrinsic to protein targets. MAPD shows accurate perf...     

Mismatch repair processing of carcinogen-DNA adducts triggers apoptosis

The DNA mismatch repair pathway is well known for its role in correcting biosynthetic errors of DNA replication. We report here a novel role for mismatch repair in signaling programmed cell death in response to DNA damage induced by chemical carcinogens. Cells proficient in mismatch repair were highly sensitive to the cytotoxic effects of chemical carcinogens, while cells defective in either human MutS or MutL homologs were relatively insensitive. Since wild-type cells but not mutant cells underwent apoptosis upon treatment with chemical carcinogens, the apoptotic response is dependent on a functional mismatch repair system. By analyzing p53 expression in several pairs of cell lines, we found that the mismatch repair-dependent apoptotic response was mediated through both p53-dependent and p53-independent pathways. In vitro biochemical studies demonstrated that the human mismatch recognition proteins hMutSalpha and hMutSbeta efficiently recognized DNA damage induced by chemical carcinogens, suggesting a direct participation of mismatch repair proteins in mediating the apoptotic response. Taken together, these studies further elucidate the mechanism by which mismatch repair deficiency predisposes to cancer, i.e., the deficiency not only causes a failure to repair mismatches generated during DNA metabolism but also fails to direct damaged and mutation-prone cells to commit suicide.     

A 3.1-kb genomic fragment of Bacillus subtilis encodes the protein inhibiting growth of Xanthomonas oryzae pv. oryzae

AIMS: To clone genes of Bacillus subtilis encoding peptides that inhibit the growth of Xanthomonas orzae pv. oryzae (Xoo). METHODS AND RESULTS: A 3.1-kb DNA fragment from B. subtilis SO113 encoding peptides that inhibit the growth of Xoo (anti-Xoo, showing an inhibition zone) was isolated from a plasmid library of B. subtilis 6 GM15. Sequence analysis revealed that it contained three complete open reading frames (ORFs): ybcO, ybcS and a novel ORF designated ybcPQ. Deleting the last 96 bp of ybcS from the plasmid eliminated the anti-Xoo activity, suggesting that ybcS is required for producing the anti-Xoo activity. However, no anti-Xoo activity could be detected for the plasmid with ybcS alone. Further analysis showed that ybcO, at least, was also required to obtain the anti-Xoo activity. CONCLUSIONS: A fragment of B. subtilis has been cloned that expresses an anti-Xoo activity that requires ybcS and ybcO. SIGNIFICANCE AND IMPACT OF THE STUDY: These genes could be useful for the genetic engineering of resistance to rice bacterial diseases and for the design of new anti-Xoo biocontrol agents.     

Analysis of synonymous codon usage in H5N1 virus and other influenza A viruses

In this study, we calculated the codon usage bias in H5N1 virus and performed a comparative analysis of synonymous codon usage patterns in H5N1 virus, five other evolutionary related influenza A viruses and a influenza B virus. Codon usage bias in H5N1 genome is a little slight, which is mainly determined by the base compositions on the third codon position. By comparing synonymous codon usage patterns in different viruses, we observed that the codon usage pattern of H5N1 virus is similar with other influenza A viruses, but not influenza B virus, and the synonymous codon usage in influenza A virus genes is phylogenetically conservative, but not strain-specific. Synonymous codon usage in genes encoded by different influenza A viruses is genus conservative. Compositional constraints could explain most of the variation of synonymous codon usage among these virus genes, while gene function is also correlated to synonymous codon usages to a certain extent. However, translational selection and gene length have no effect on the variations of synonymous codon usage in these virus genes.