天然云杉相容性生物量估算模型

基于150株天然云杉实测材积和生物量数据,利用非线性度量误差方法,建立相容性立木材积与生物量方程,并采用总量直接控制方案和分级联合控制方案研建了地上总生物量与4个分项(干材、干皮、树枝、树叶)的相容性方程系统,其中又采取了独立估计和联合估计两种处理方法进行地上生物量的估计.结果表明: 所建一元、二元相容性立木材积和地上生物量模型的材积和生物量决定系数均在0.85以上,最高达0.99,在胸径基础上增加树高变量能显著提高材积的预估效果,但对生物量的预估效果改进不大.就总量与分量相容性模型而言,分级联合控制方案所建的一元模型好于总量直接控制所建的一元模型,两种方案所建的二元模型效果相当.对一元、二元相容性生物量模型的拟合效果进行对比,结果显示,解释变量的增加明显提高了树枝和树叶生物量的拟合效果,对其他几个分量的拟合效果改善不大.对独立估计和联合估计的对比分析显示,两种估计方法几乎没有差异.     

Involvement of glyceraldehyde-3-phosphate dehydrogenase in the X-Ray resistance of HeLa cells

We investigated changes in the sub-cellular distribution of glycelaldehyde-3-phosphate dehydrogenase (GAPDH) after X-ray irradiation in HeLa cells. Twenty-four h after irradiation at 5 Gy, nuclear GAPDH levels increased 2.6-fold, whereas total GAPDH levels increased only 1.2-fold. Knockdown of GAPDH using specific small interfering RNA (siRNA) led to sensitization to X-ray-induced cell death. These results suggest that GAPDH plays a role in the radioresponse.     

Enhanced resistance of restraint-stressed mice to sepsis

Sepsis remains a major health concern across the world. The effects of stress on host resistance to sepsis are still not very clear. To explore the effects of chronic stress on sepsis(') we examined the impact of restraint stress on the resistance of mice to sepsis. Interestingly, it was found that restraint stress enhanced the antisepsis resistance of mice and the concentrations of the proinflammatory cytokines IL-1, IL-6, IL-12, and TNF-alpha in the blood of stressed mice were dramatically reduced post Escherichia coli infection or LPS treatment as compared with that of controls (p < 0.05). In addition, the mRNA expressions of glucocorticoid-induced leucine zipper (GILZ) were up-regulated in the spleen and peritoneal macrophages of mice receiving restraint stress or dexamethasone treatment. These results demonstrate that restraint stress enhances the resistance of mice to sepsis, supporting corticotherapy for sepsis and proposing restraint-stressed mouse as an animal model to elucidate mechanisms of stress-associated, antisepsis resistance.     

肠炎沙门氏菌鸡源株ompR 基因缺失株的构建及生物学特性与亲本株的比较

【目的】为了探讨ompR基因在肠炎沙门氏菌生物被膜形成及毒力中的作用。【方法】以肠炎沙门氏菌作为母本,运用自杀性载体pGMB151构建了ompR基因缺失株,结晶紫染色法和扫描电镜观察测定缺失株的生物被膜形成能力,细胞的吸附和侵入及小鼠攻毒试验测定缺失株的毒力。【结果】RT-PCR和蛋白表达证明了ompR基因缺失株构建成功;该缺失株不表达纤维素和菌毛,不形成生物被膜;上皮细胞吸附和侵入试验表明缺失株与野生株具有相同的吸附和侵入率;BALB/c鼠腹腔感染性试验表明,缺失株的半数致死量为106.67CFU,而野生株的半数致死量小于2 CFU。【结论】ompR基因既是肠炎沙门氏菌生物膜形成的调控基因,又是重要的毒力基因。     

Quantitative detection of BCR–ABL fusion gene and its application in monitoring chronic myeloid leukemia treatment

The BCR–ABL fusion gene in chromosome translocation, t (9; 22), and its product, p210BCR/ABL oncogenic tyrosine kinase, is the underlying molecular mechanism that leads to the development of CML. Quantitative detection of BCR–ABL fusion gene has become a reliable approach to diagnose and monitor CML. The aim of this study was to evaluate a Roche t (9; 22) kit in CML diagnosis, monitoring treatment responses, and identification of relapse. Using BCR–ABL fusion gene-expressing K562 cells, a series of standard samples were prepared and used to establish a curve for the calculation of BCR–ABL fusion gene expression in patient samples. Our results indicate that PCR detection system with aforementioned kit has good reproducibility. In addition, the relative concentration of BCR–ABL measured by PCR was in agreement with the patient’s response to the Imatinib treatment and bone marrow morphology remission. Furthermore, we found that the relative concentration of BCR–ABL fusion gene increased 1–3 months before CML relapse was clinically and cytogenetically diagnosed, suggesting that the PCR-based BCR–ABL fusion gene detection with t (9; 22) kit is able to diagnose the recurrence of CML at least 1 month earlier than the classic cytogenetic analysis. In conclusion, detection of BCR–ABL fusion gene expression in CML using Roche t (9; 22) kit has great clinical value in the primary diagnosis, monitoring treatment responses, and identification of relapse in CML patients.     

Whole-genome sequences of four Mycobacterium bovis BCG vaccine strains

Mycobacterium bovis Bacille Calmette-Guérin (BCG) is the only vaccine available against tuberculosis (TB). A number of BCG strains are in use, and they exhibit biochemical and genetic differences. We report the genome sequences of four BCG strains representing different lineages, which will help to design more effective TB vaccines.     

Assimilation of Endogenous Nicotinamide Riboside Is Essential for Calorie Restriction-mediated Life Span Extension in Saccharomyces cerevisiae

NAD⁺ (nicotinamide adenine dinucleotide) is an essential cofactor involved in various biological processes including calorie restriction-mediated life span extension. Administration of nicotinamide riboside (NmR) has been shown to ameliorate deficiencies related to aberrant NAD⁺ metabolism in both yeast and mammalian cells. However, the biological role of endogenous NmR remains unclear. Here we demonstrate that salvaging endogenous NmR is an integral part of NAD⁺ metabolism. A balanced NmR salvage cycle is essential for calorie restriction-induced life span extension and stress resistance in yeast. Our results also suggest that partitioning of the pyridine nucleotide flux between the classical salvage cycle and the NmR salvage branch might be modulated by the NAD⁺-dependent Sir2 deacetylase. Furthermore, two novel deamidation steps leading to nicotinic acid mononucleotide and nicotinic acid riboside production are also uncovered that further underscore the complexity and flexibility of NAD⁺ metabolism. In addition, utilization of extracellular nicotinamide mononucleotide requires prior conversion to NmR mediated by a periplasmic phosphatase Pho5. Conversion to NmR may thus represent a strategy for the transport and assimilation of large nonpermeable NAD⁺ precursors. Together, our studies provide a molecular basis for how NAD⁺ homeostasis factors confer metabolic flexibility.The pyridine nucleotide NAD⁺ and its reduced form NADH are primary redox carriers involved in metabolism. In addition to serving as a coenzyme in redox reactions, NAD⁺ also acts as a cosubstrate in protein modification reactions including deacetylation and ADP-ribosylation (1, 2). NAD⁺ also plays an important role in calorie restriction (CR)²-mediated life span extension via regulating NAD⁺-dependent longevity factors (3, 4). CR is the most effective regimen known to extend life span in various species (5, 6). CR also ameliorates many age-related diseases such as cancer and diabetes (5). The Sir2 family proteins are NAD⁺-dependent protein deacetylases, which have been shown to play important roles in several CR models in yeast (3, 7) and higher eukaryotes (8, 9). By coupling the cleavage of NAD⁺ and deacetylation of target proteins, the Sir2 family proteins serve as a molecular link relaying the cellular energy state to the machinery of life span regulation. Mammalian Sir2 family proteins (SIRT1–7) have also been implicated in stress response, cell survival, and insulin and fat metabolism (8–10), supporting a role for SIRT proteins in age-related metabolic diseases and perhaps human aging.In eukaryotes, NAD⁺ is generated by de novo synthesis and by salvaging various intermediary precursors (see Fig. 1A). In yeast, the de novo pathway is mediated by Bna1–5 and Qpt1 (Bna6), which produces nicotinic acid mononucleotide (NaMN) from tryptophan (11). Because the de novo pathway requires molecular oxygen as a substrate, cells grown under anaerobic growth conditions would rely on exogenous NAD⁺ precursors for the nicotinamide (Nam) moiety (11). Yeast cells also salvage Nam from NAD⁺ consuming reactions or nicotinic acid (NA) from environment via Tna1, Pnc1, and Npt1, leading to NaMN production. NaMN is then converted to NAD⁺ via Nma1/2 and Qns1 (see Fig. 1A). Nma1/2 are adenylyltransferases with dual specificity toward NMN and NaMN (12, 13), and Qns1 is a glutamine-dependent NAD⁺ synthetase. Recent studies also showed that supplementing nicotinamide riboside (NmR) and nicotinic acid riboside (NaR) to growth medium rescued the lethality of NAD⁺ auxotrophic mutants (14–16). Assimilations of exogenous NmR and NaR are mainly mediated by a conserved NmR kinase (Nrk1) and three nucleosidases (Urh1, Pnp1, and Meu1). Nrk1 phosphorylates NmR and NaR to produce nicotinamide mononucleotide (NMN) and NaMN, respectively (14, 16). Urh1, Pnp1, and Meu1 catabolize NmR and NaR to generate Nam and NA (15, 16).Open in a separate windowFIGURE 1.Nicotinamide riboside (NmR) is an endogenous metabolite in yeast. A, the current model of the NAD⁺ biosynthesis pathways. Extracellular NmR enters the salvage cycle through Nrk1, Urh1, Pnp1, and Meu1. B, NAD⁺ prototrophic cells release metabolites into growth medium to cross-feed NAD⁺ auxotrophic cells (the npt1Δqpt1Δ and qns1Δ mutants). Micro-colonies of the NAD⁺ auxotrophic mutants become visible after 2-day incubation at 30 °C, which show “gradient” growth patterns descending from the side adjacent to WT. C, Nrk1 is required for NAD⁺ auxotrophic cells to utilize NmR. Anaerobic growth conditions (−O₂) are utilized to block de novo NAD⁺ biosynthesis in the npt1Δ and npt1Δnrk1Δ mutants. D, Nrk1 is required to utilize cross-feeding metabolites. E, cross-feeding activity is modulated by factors in NmR metabolism. Cells defective in NmR utilization (left panel) or transport (middle panel) show increased cross-feeding in spot assays. Overexpressing Nrk1 decreases cross-feeding activity (right panel). The results show growth of the npt1Δqpt1Δ recipient (plated on YPD at a density of ∼9000 cells/cm²) supported by feeder cells (∼2 × 10⁴ cells spotted directly onto the recipient lawn). oe, overexpression.NmR supplementation has recently been shown to be a promising strategy for prevention and treatment of certain diseases (17). For example, NmR protected neurons from axonal degeneration via functioning as a NAD⁺ precursor (18, 19). Given that several NmR assimilating enzymes and NmR transporters have been characterized and many are conserved from fungi to mammals (14, 15, 20–22), NmR has been speculated to be an endogenous NAD⁺ precursor (17, 23). Here, we provided direct evidence for endogenous NmR as an integral part of NAD⁺ metabolism in yeast. We also determined the biological significance of salvaging endogenous NmR and studied its role in CR-induced life span extension. Moreover, we demonstrated that the NmR salvage machinery was also required for utilizing exogenous NMN, which has recently been shown to increase NAD⁺ levels in mammalian cells (24). Finally, we discussed the role of Sir2 in modulating the flux of pyridine nucleotides between alternate routes.     

Properties of a small basic Peptide from pumpkin seeds

A small basic peptide with an unusual amino acid composition has been isolated from the seeds of pumpkin, Cucurbita maxima. Amino acid analysis and sequence data show the protein to be about 36 residues in length, with an approximate composition Lys₁, Arg₁₄, Asp₃, (Glu + Gln)₁₅, Gly₁, Pro₁, Trp₁. On the basis of composition, the molecular weight is approximately 5000 daltons and the nitrogen content by weight is 20.4%. Twelve amino acids are entirely lacking. The peptide is slightly toxic to mouse B-16 melanoma cells, but its in vivo function is unknown. It does not appear to be derived from cucurbitin, the pumpkin storage globulin; however, it could be a storage peptide involved in nitrogen mobilization during the early stages of germination.