嗜热脂肪芽孢杆菌β—半乳糖苷酶的性质

利用硫酸铵分级沉淀、离子交换层析(DEAE-22)、SephadexG-75凝胶过滤从嗜热脂肪芽孢杆菌胞内提纯得B半乳糖甘酶。研究表明,该酶最适表观反应曙度和最适PH分别为60OCT6.4D50OC该酶具有良好的热稳定性.碱金属和碱土金属盐对酶有激活作用,重金属Zn     

First efficacy results of capecitabine with anthracycline- and taxane-based adjuvant therapy in high-risk early breast cancer: a meta-analysis

Background

Capecitabine is effective and indicated for the salvage treatment of metastatic breast cancer. Therefore, it is essential to evaluate the efficacy of capecitabine in the adjuvant setting. There have been two large randomized studies to determine whether patients with high-risk early breast cancer benefit from the addition of capecitabine to standard chemotherapy, but they have yielded inconsistent results. We first undertook a meta-analysis to evaluate the efficacy of the addition of capecitabine over standard treatment.

Methods

PubMed, EBSCO, Web of Science, conference proceedings and key trials were searched from 1998 to 2011. The hazard ratio (HR) was used to evaluate the efficacy of a taxane-anthracycline regimen and a taxane-anthracycline-capecitabine regimen in early breast cancer. All of the data from each study use either fixed-effects or random-effects by Stata.

Findings

We found significant improvement in the additional capecitabine arm versus control in disease-free survival (DFS) (HR = 0.83, 95% CI: 0.71–0.98, P = 0.027), overall survival (OS) (HR = 0.71, 95% CI: 0.57–0.88, P = 0.002), distant recurrence (HR = 0.79, 95% CI: 0.66–0.94, P = 0.008) and the death from breast cancer only (HR = 0.65, 95% CI: 0.51–0.83, P = 0.001). Meanwhile, the subgroup analysis revealed that capecitabine improved the DFS in triple negative (HR = 0.71, 95% CI: 0.53–0.96, P = 0.028), hormone receptor negative (HR = 0.73, CI: 0.56–0.94, P = 0.017) and HER2 negative (HR = 0.81, CI: 0.67–0.98, P = 0.034) patients.

Conclusion

Due to the synergistic effect of taxane and capecitabine, taxane-anthracycline-capecitabine regimen may effectively improve the efficacy in the adjuvant setting and may be a novel generation of adjuvant chemotherapy regimen. The results of the current meta-analysis support this hypothesis and indicate that taxane-based regimen with capecitabine may be an effective, convenient, and well tolerated regimen in patients with early breast cancer.     

Indirect and suboptimal control of gene expression is widespread in bacteria

Gene regulation in bacteria is usually described as an adaptive response to an environmental change so that genes are expressed when they are required. We instead propose that most genes are under indirect control: their expression responds to signal(s) that are not directly related to the genes’ function. Indirect control should perform poorly in artificial conditions, and we show that gene regulation is often maladaptive in the laboratory. In Shewanella oneidensis MR‐1, 24% of genes are detrimental to fitness in some conditions, and detrimental genes tend to be highly expressed instead of being repressed when not needed. In diverse bacteria, there is little correlation between when genes are important for optimal growth or fitness and when those genes are upregulated. Two common types of indirect control are constitutive expression and regulation by growth rate; these occur for genes with diverse functions and often seem to be suboptimal. Because genes that have closely related functions can have dissimilar expression patterns, regulation may be suboptimal in the wild as well as in the laboratory.     

Nicotinamide increases the sensitivity of chronic myeloid leukemia cells to doxorubicin via the inhibition of SIRT1

The NAD-dependent deacetylase Sirtuin 1 (SIRT1) plays a vital role in leukemogenesis. Nicotinamide (NAM) is the principal NAD⁺ precursor and a noncompetitive inhibitor of SIRT1. In our study, we showed that NAM enhanced the sensitivity of chronic myeloid leukemia (CML) to doxorubicin (DOX) via SIRT1. We found that SIRT1 high expression in CML patients was associated with disease progression and drug resistance. Exogenous NAM efficiently repressed the deacetylation activity of SIRT1 and induced the apoptosis of DOX-resistant K562 cells (K562R) in a dose-dependent manner. Notably, the combination of NAM and DOX significantly inhibited tumor cell proliferation and induced cell apoptosis. The knockdown of SIRT1 in K562R cells enhanced NAM+DOX-induced apoptosis. SIRT1 rescue in K562R reduced the NAM+DOX-induced apoptosis. Mechanistically, the combinatory treatment significantly increased the cleavage of caspase-3 and PARP in K562R in vitro and in vivo. These results suggest the potential role of NAM in increasing the sensitivity of CML to DOX via the inhibition of SIRT1.     

5-Azacytidine facilitates osteogenic gene expression and differentiation of mesenchymal stem cells by alteration in DNA methylation

Mesenchymal stem cells (MSCs) are considered to be one of the most promising therapeutic cell sources as they encompass a plasticity of multiple cell lineages. The challenge in using these cells lies in developing well-defined protocols for directing cellular differentiation to generate a desired lineage. In this study, we investigated the effect of 5-azacytidine, a DNA demethylating agent, on osteogenic differentiation of MSCs. The cells were exposed to 5-azacytidine in culture medium for 24 h prior to osteogenic induction. Osteogenic differentiation was determined by several the appearance of a number of osteogenesis characteristics, including gene expression, ALP activity, and calcium mineralization. Pretreatment of MSCs with 5-azacytidine significantly facilitated osteogenic differentiation and was accompanied by hypomethylation of genomic DNA and increased osteogenic gene expression. Taking dlx5 as a representative, methylation alterations of the “CpG island shore” in the promoter caused by 5-azacytidine appeared to contribute to osteogenic differentiation.     

A unique Mycobacterium ESX-1 protein co-secretes with CFP-10/ESAT-6 and is necessary for inhibiting phagosome maturation

The ESX-1 secretion system plays a critical role in the virulence of Mycobacterium tuberculosis and M. marinum. To date, three proteins are known to be secreted by ESX-1 and necessary for virulence, two of which are CFP-10 and ESAT-6. The ESX-1 secretion and the virulence mechanisms are not well understood. In this study, we have examined the M. marinum secretomes and identified four proteins specific to ESX-1. Two of those are CFP-10 and ESAT-6, and the other two are novel: MM1553 (homologous to Rv3483c) and Mh3881c (homologous to Rv3881c). We have shown that Mh3881c, CFP-10 and ESAT-6 are co-dependent for secretion. Mh3881c is being cleaved at close to the C-terminus during secretion, and the C-terminal portion is critical to the co-dependent secretion, the ESAT-6 cellular levels, and interaction with ESAT-6. The co-dependent secretion is required for M. marinum intracellular growth in macrophages, where the Mh3881c C-terminal portion plays a critical role. The role of the co-dependent secretion in intracellular growth correlates with its role in inhibiting phagosome maturation. Both the secretion and the virulence defects of the Mh3881c mutant are complemented by Mh3881c or its M. tuberculosis homologue Rv3881c, suggesting that in M. tuberculosis, Rv3881c has similar functions.     

Variations in the C3, C3a receptor, and C5 genes affect susceptibility to bronchial asthma

Bronchial asthma (BA) is a common chronic inflammatory disease characterized by hyperresponsive airways, excess mucus production, eosinophil activation, and the production of IgE. The complement system plays an immunoregulatory role at the interface of innate and acquired immunities. Recent studies have provided evidence that C3, C3a receptor, and C5 are linked to airway hyperresponsiveness. To determine whether genetic variations in the genes of the complement system affect susceptibility to BA, we screened single nucleotide polymorphisms (SNPs) in C3, C5, the C3a receptor gene (C3AR1), and the C5a receptor gene (C5R1) and performed association studies in the Japanese population. The results of this SNP case-control study suggested an association between 4896C/T in the C3 gene and atopic childhood BA (P=0.0078) as well as adult BA (P=0.010). When patient data were stratified according to elevated total IgE levels, 4896C/T was more closely associated with adult BA (P=0.0016). A patient-only association study suggested that severity of childhood BA was associated with 1526G/A of the C3AR1 gene (P=0.0057). We identified a high-risk haplotype of the C3 gene for childhood (P=0.0021) and adult BA (P=0.0058) and a low-risk haplotype for adult BA (P=0.00011). We also identified a haplotype of the C5 gene that was protective against childhood BA (P=1.4×10^–6) and adult BA (P=0.00063). These results suggest that the C3 and C5 pathways of the complement system play important roles in the pathogenesis of BA and that polymorphisms of these genes affect susceptibility to BA.     

锯缘青蟹精子发生的超微结构

采用透射电镜观察锯缘青蟹精子发生过程中超微结构的变化,结果表明：精原细胞椭圆形,染色质分布于核膜周围,胞质中具嵴少的线粒体,内质网小泡等。初级精母细胞染色质呈非浓缩状,胞质中具众 内质网小泡,特殊的膜系及晶格状结构。次级精母细胞核质间出现由内质小泡聚集成的腔。     

Berberine, a genotoxic alkaloid, induces ATM-Chk1 mediated G2 arrest in prostate cancer cells

Berberine has been shown to possess anti-tumor activity against a wide spectrum of cancer cells. It inhibits cancer cell proliferation by inducing cell cycle arrest, at G1 and/or G2/M, and apoptosis. While it has been documented that berberine induces G1 arrest by activating the p53-p21 cascade, it remains unclear what mechanism underlies the berberine-induced G2/M arrest, which is p53-independent. In this study, we tested the anti-proliferative effect of berberine on murine prostate cancer cell line RM-1 and characterized the underlying mechanisms. Berberine dose-dependently induced DNA double-strand breaks and apoptosis. At low concentrations, berberine was observed to induce G1 arrest, concomitant with the activation of p53-p21 cascade. Upon exposure to berberine at a higher concentration (50μM) for 24h, cells exhibited G2/M arrest. Pharmacological inhibition of ATM by KU55933, or Chk1 by UCN-01, could efficiently abrogate the G2/M arrest in berberine-treated cells. Downregulation of Chk1 by RNA interference also abolished the G2/M arrest caused by berberine, confirming the role of Chk1 in the pathway leading to G2/M arrest. Abrogation of G2/M arrest by ATM inhibition forced more cells to undergo apoptosis in response to berberine treatment. Chk1 inhibition by UCN-01, on the other hand, rendered cells more sensitive to berberine only when p53 was inhibited. Our results suggest that combined administration of berberine and caffeine, or other ATM inhibitor, may accelerate the killing of cancer cells.