低温木聚糖酶的研究进展

低温木聚糖酶在低温下仍具有较高酶活力及催化效率,在应用中能减少工艺流程,节省加热或冷却费用,降低耗能,有着中高温木聚糖酶无法比拟的优势。针对低温木聚糖酶的研究现状,包括来源、分子结构与适冷机制、基因工程及应用等方面进行综述。     

利用异源生物生产青蒿素及其前体的研究进展

青蒿素是从中药青蒿中分离出来的一种倍半萜内酯类化合物,也是目前最有效的抗疟疾药物,对人类健康意义重大。该文通过对青蒿素生物合成途径及其相关酶的介绍,综述了利用异源生物通过组合生物合成途径生产青蒿素及其前体的最新研究进展。     

Glyceraldehyde-3-phosphate, a glycolytic intermediate, prevents cells from apoptosis by lowering S-nitrosylation of glyceraldehyde-3-phosphate dehydrogenase

Glyceraldehyde-3-phosphate (G-3-P), the substrate of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), is a key intermediate in several metabolic pathways. Recently, we reported that G-3-P directly inhibits caspase-3 activity in a reversible noncompetitive mode, suggesting the intracellular G-3-P level as a cell fate decision factor. It has been known that apoptotic stimuli induce the generation of NO, and NO S-nitrosylates GAPDH at the catalytic cysteine residue, which confers GAPDH the ability to bind to Siah-1, an E3 ubiquitin ligase. The GAPDH-Siah-1 complex is translocated into the nucleus and subsequently triggers the apoptotic process. Here, we clearly showed that intracellular G-3-P protects GAPDH from S-nitrosylation at above a certain level, and consequently maintains the cell survival. In case G-3-P drops below a certain level as a result of exposure to specific stimuli, G-3-P cannot inhibit S-nitrosylation of GAPDH anymore, and consequently GAPDH translocates with Siah-1 into the nucleus. Based on these results, we suggest that G-3-P functions as a molecule switch between cell survival and apoptosis by regulating S-nitrosylation of GAPDH.     

Orchitis: a complication of severe acute respiratory syndrome (SARS)

Severe acute respiratory syndrome (SARS) coronavirus has been known to damage multiple organs; however, little is known about its impact on the reproductive system. In the present study, we analyzed the pathological changes of testes from six patients who died of SARS. Results suggested that SARS caused orchitis. All SARS testes displayed widespread germ cell destruction, few or no spermatozoon in the seminiferous tubule, thickened basement membrane, and leukocyte infiltration. The numbers of CD3+ T lymphocytes and CD68+ macrophages increased significantly in the interstitial tissue compared with the control group (P < 0.05). SARS viral genomic sequences were not detected in the testes by in situ hybridization. Immunohistochemistry demonstrated abundant IgG precipitation in the seminiferous epithelium of SARS testes, indicating possible immune response as the cause for the damage. Our findings indicated that orchitis is a complication of SARS. It further suggests that the reproductive functions should be followed and evaluated in recovered male SARS patients.     

Joint models for multivariate longitudinal and multivariate survival data

Joint modeling of longitudinal and survival data is becoming increasingly essential in most cancer and AIDS clinical trials. We propose a likelihood approach to extend both longitudinal and survival components to be multidimensional. A multivariate mixed effects model is presented to explicitly capture two different sources of dependence among longitudinal measures over time as well as dependence between different variables. For the survival component of the joint model, we introduce a shared frailty, which is assumed to have a positive stable distribution, to induce correlation between failure times. The proposed marginal univariate survival model, which accommodates both zero and nonzero cure fractions for the time to event, is then applied to each marginal survival function. The proposed multivariate survival model has a proportional hazards structure for the population hazard, conditionally as well as marginally, when the baseline covariates are specified through a specific mechanism. In addition, the model is capable of dealing with survival functions with different cure rate structures. The methodology is specifically applied to the International Breast Cancer Study Group (IBCSG) trial to investigate the relationship between quality of life, disease-free survival, and overall survival.     

Comparative genomic analysis links karyotypic evolution with genomic evolution in the Indian Muntjac (Muntiacus muntjak vaginalis)

The karyotype of Indian muntjacs (Muntiacus muntjak vaginalis) has been greatly shaped by chromosomal fusion, which leads to its lowest diploid number among the extant known mammals. We present, here, comparative results based on draft sequences of 37 bacterial artificial clones (BAC) clones selected by chromosome painting for this special muntjac species. Sequence comparison on these BAC clones uncovered sequence syntenic relationships between the muntjac genome and those of other mammals. We found that the muntjac genome has peculiar features with respect to intron size and evolutionary rates of genes. Inspection of more than 80 pairs of orthologous introns from 15 genes reveals a significant reduction in intron size in the Indian muntjac compared to that of human, mouse, and dog. Evolutionary analysis using 19 genes indicates that the muntjac genes have evolved rapidly compared to other mammals. In addition, we identified and characterized sequence composition of the first BAC clone containing a chromosomal fusion site. Our results shed new light on the genome architecture of the Indian muntjac and suggest that chromosomal rearrangements have been accompanied by other salient genomic changes. Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.Qi Zhou, Ling Huang, Jianguo Zhang: these authors contributed equally to the paper.Sequence data from this article have been deposited in the GenBank Libraries under Accession No. DQ280153-DQ280188, DQ377335, DQ458964.     

Wnt-4 signaling is involved in the control of smooth muscle cell fate via Bmp-4 in the medullary stroma of the developing kidney

Wnt-4, a member of the Wnt family of secreted signaling molecules, is essential for nephrogenesis, but its expression in the presumptive medulla suggests additional developmental roles in kidney organogenesis. We demonstrate here that Wnt-4 signaling plays also a role in the determination of the fate of smooth muscle cells in the medullary stroma of the developing kidney, as a differentiation marker, smooth muscle alpha-actin (alpha-SMA), is markedly reduced in the absence of its signaling. Wnt-4 probably performs this function by activating the Bmp-4 gene encoding a known differentiation factor for smooth muscle cells, since Bmp-4 gene expression was lost in the absence of Wnt-4 while Wnt-4 signaling led to a rescue of Bmp-4 expression and induction of alpha-SMA-positive cells in vitro. Recombinant Bmp-4 similarly rescued the differentiation of alpha-SMA-expressing cells in cultured Wnt-4-deficient embryonic kidney. The lack of smooth muscle cell differentiation leads to an associated deficiency in the pericytes around the developing vessels of the Wnt-4-deficient kidney and apparently leads to a secondary defect in the maturation of the kidney vessels. Thus, besides being critical for regulating mesenchymal to epithelial transformation in the cortical region in nephrogenesis, Wnt-4 signaling regulates the fate of smooth muscle cells in the developing medullary region.     

Application of the ferrous oxidation-xylenol orange assay for the screening of 5-lipoxygenase inhibitors

5-Lipoxygenase (5-LO) is the key enzyme involved in leukotriene synthesis and its improper regulation is implicated in several inflammatory diseases. A rapid and sensitive assay for 5-LO activity suitable for high-throughput format is not yet available. In this study, we examined whether the ferrous oxidation-xylenol orange (FOX) assay could be applicable for the high-throughput screening of 5-LO inhibitors. Using insect cell lysates overexpressing rat 5-LO, the effects of cofactors of 5-LO such as ATP, Ca2+, and L-alpha-phosphatidylcholine (PC) on the color development of FOX reagents were investigated. ATP quenched substantially color development by hydroperoxide, an intermediate of 5-LO reaction, and an optimum concentration of ATP with little interference was determined as 20 microM. Ethylenediaminetetraacetate (0.4 mM) also affected the complex formation with FOX reagents. On the other hand, neither Ca2+ nor PC influenced complex formation with FOX reagents. Under optimized assay conditions, zileuton, a 5-LO-specific inhibitor, exhibited inhibitory potency (IC50 values of 0.1-0.2 microM) similar to that determined by the conventional spectrophotometric assay. Taken together, this study shows that the FOX assay with some modifications can be employed for high-throughput assay format for the measurement of 5-LO activity at the stage of primary screening.     

Analysis of neuron-like differentiation of human bone marrow mesenchymal stem cells

The objective of the study was to evaluate differentiation of human bone marrow mesenchymal stem cells into true or pseudo neurons after treating with chemical induction medium in vitro. The morphological changes were assessed using interference contrast microscopy. Immunocytochemistry and Western blotting were performed using neuronal markers. Further evaluation was conducted with proteomic profiling, DNA microarray analysis and the whole-cell patch clamp test. After three hours of treatment with chemical induction medium, nearly three-fourths of the hMSCs changed to cells with a neuronal phenotype. The results of immunocytochemistry and Western blotting showed a high expression of neuronal markers in these cells at 3 h which decreased at 24 h. The proteomics analysis showed no change of proteins related to neuronal differentiation. DNA microarray showed downregulation of neuron related genes. The patch clamp test was unable to demonstrate any similarity to true neurons. Our findings suggest that neuron-like cells derived from chemical induction of hMSCs are not the genuine neurons as they resemble true neurons phenotypically but are different in genotypic and electrophysiological characteristics.