三氧化二砷对食管癌细胞增殖和热休克蛋白70表达的影响

目的：研究三氧化二砷（As2O3）对食管癌细胞增殖和热休克蛋白70（HSP70）表达的影响。方法：通过相差显微镜、流式细胞术、免疫细胞化学染色和免疫印迹分析等方法观察As2O3对人食管癌细胞株EC1的作用效果和作用机制。结果：与对照组相比,经2μmol/L和5μmol/Las2O3作用的细胞出现明显的生长抑制,G2/M期细胞比例增加;2μmol/Las2O3作用48h后经Ecl细胞HSP70（heat shock protein70）及HSC70(heat shock cognate protein70)表达均增加。结论：As2O3诱导食管癌细胞G2/M期阻滞抑制细胞增殖和生长;HSP70的升高是细胞对As2O3作用后出现的应激反应,并与细胞周期阻滞相关。     

Genetic,Molecular, and Genomic Approaches to Improve the Value of Plant Foods and Feeds

Referee: Dr. T.J. Higgins, Chief Research Scientist, CSIRO, Divistion of Plant Industry, Clunies Ross Street, Box 1600, Canberra, 2601, Australia Recent advances in gene isolation, plant transformation, and genetic engineering are being used extensively to alter metabolic pathways in plants by tailormade modifications to single or multiple genes. Many of these modifications are directed toward increasing the nutritional value of plant-derived foods and feeds. These approaches are based on rapidly growing basic knowledge, understanding, and predictions of metabolic fluxes and networks. Some of the predictions appear to be accurate, while others are not, reflecting the fact that plant metabolism is more complex than we presently understand. Tailor-made modifications of plant metabolism has so far been directed into improving the levels of primary metabolites that are essential for growth and development of humans and their livestock. Yet, the list of improved metabolites is expected to grow tremendously after new discoveries in nutritional, medical, and health sciences. Despite our extensive knowledge of metabolic networks, many of the genes encoding enzymes, particularly those involved in secondary metabolism, are still unknown. These genes are being discovered at an accelerated rate by recent advances in genetic and genomics approaches. In the present review, we discuss examples in which the nutritional and health values of plant-derived foods and feeds were improved by metabolic engineering. These include modifications of the levels of several essential amino acids, lipids, fatty acids, minerals, nutraceuticals, antinutritional compounds, and aromas.     

The genetic background of antibiotic resistance among clinical uropathogenic Escherichia coli strains

Molecular Biology Reports - The spreading mechanisms of antibiotic resistance are related to many bacterial and environment factors. The overuse of antibiotics is leading to an unceasing emergence...     

Typhoidal Salmonella: Distinctive virulence factors and pathogenesis

Although nontyphoidal Salmonella (NTS; including Salmonella Typhimurium) mainly cause gastroenteritis, typhoidal serovars (Salmonella Typhi and Salmonella Paratyphi A) cause typhoid fever, the treatment of which is threatened by increasing drug resistance. Our understanding of S. Typhi infection in human remains poorly understood, likely due to the host restriction of typhoidal strains and the subsequent popularity of the S. Typhimurium mouse typhoid model. However, translating findings with S. Typhimurium across to S. Typhi has some limitations. Notably, S. Typhi has specific virulence factors, including typhoid toxin and Vi antigen, involved in symptom development and immune evasion, respectively. In addition to unique virulence factors, both typhoidal and NTS rely on two pathogenicity‐island encoded type III secretion systems (T3SS), the SPI‐1 and SPI‐2 T3SS, for invasion and intracellular replication. Marked differences have been observed in terms of T3SS regulation in response to bile, oxygen, and fever‐like temperatures. Moreover, approximately half of effectors found in S. Typhimurium are either absent or pseudogenes in S. Typhi, with most of the remaining exhibiting sequence variation. Typhoidal‐specific T3SS effectors have also been described. This review discusses what is known about the pathogenesis of typhoidal Salmonella with emphasis on unique behaviours and key differences when compared with S. Typhimurium.     

Gene proximity analysis across whole genomes via PQ trees.

Permutations on strings representing gene clusters on genomes have been studied earlier by Uno and Yagiura (2000), Heber and Stoye (2001), Bergeron et al. (2002), Eres et al. (2003), and Schmidt and Stoye (2004) and the idea of a maximal permutation pattern was introduced by Eres et al. (2003). In this paper, we present a new tool for representation and detection of gene clusters in multiple genomes, using PQ trees (Booth and Leuker, 1976): this describes the inner structure and the relations between clusters succinctly, aids in filtering meaningful from apparently meaningless clusters, and also gives a natural and meaningful way of visualizing complex clusters. We identify a minimal consensus PQ tree and prove that it is equivalent to a maximal pi pattern (Eres et al., 2003) and each subgraph of the PQ tree corresponds to a nonmaximal permutation pattern. We present a general scheme to handle multiplicity in permutations and also give a linear time algorithm to construct the minimal consensus PQ tree. Further, we demonstrate the results on whole genome datasets. In our analysis of the whole genomes of human and rat, we found about 1.5 million common gene clusters but only about 500 minimal consensus PQ trees, with E. Coli K-12 and B. Subtilis genomes, we found only about 450 minimal consensus PQ trees out of about 15,000 gene clusters, and when comparing eight different Chloroplast genomes, we found only 77 minimal consensus PQ trees out of about 6,700 gene clusters. Further, we show specific instances of functionally related genes in two of the cases.     

Phosphorus availability and alkaline phosphatase activities in two Israeli fishponds

1. Alkaline phosphatase activities and the release of orthophosphate from endogenous substrates by these enzymes were measured in waters from two commercial fishponds in the watershed area of Lake Kinneret (Northern Israel). These data were compared with results from the lake at seasons of adequate or limited phosphorus supply. In the fishponds, high Relative Phosphatase Activity ratios (>2) and relatively large amounts of orthophosphate extracted from plankton by autoclaving (average 27% of readily available phosphorus) indicated adequate, or even excess, levels of phosphorus availability despite elevated pond productivity (2 to 3 tons carp/ha/yr). Therefore, we suggest that decreasing routine phosphorus fertilization of these ponds would not affect overall productivity but would eventually lower the amounts of phosphorus reaching Lake Kinneret.
2. In general, the R. P. A. ratio may be a useful index to evaluate phosphorus availability for a wide range of natural waters. Values for this ratio of <1 and >2 appear indicative of limited or adequate phosphorus availability respectively.
3. Three sources of orthophosphate, (Pi), readily available to phytoplankton, are indicated: (1) enzymatically released Pi, (2) Pi in intracellular pools and (3) Pi initially present in the water. Although the first source is always important, relatively greater amounts of Pi are contributed by the other fractions in situations of plentiful phosphorus availability.
4. Activity of free dissolved phosphatases was found in filtered samples of fishpond water. However, neither these enzymes or added phosphatases released significant amounts of Pi from the dissolved organic phosphorus compounds in the filtered water.

     

A sensitive radioisotope assay for pectin methyl esterase activity

The preparation of polygalacturonic acid [¹⁴C]-labeled methyl ester (pectic acid ester) is described. This labeled polysaccharide is employed as the substrate in a simple, sensitive, and rapid assay procedure for measuring pectin methyl esterase activity.     

Axis development: the mouse becomes a dachshund.

Targeted deletion of the gene for GDF11, a novel member of the TGFbeta family, has been found to cause an increase in the number of thoracic and lumbar vertebrae in the mouse. This is the first hint that a secreted factor may influence the specification of segment identity.