Modelling the outbreak of infectious disease following mutation from a non-transmissible strain.

In-host mutation of a cross-species infectious disease to a form that is transmissible between humans has resulted with devastating global pandemics in the past. We use simple mathematical models to describe this process with the aim to better understand the emergence of an epidemic resulting from such a mutation and the extent of measures that are needed to control it. The feared outbreak of a human-human transmissible form of avian influenza leading to a global epidemic is the paradigm for this study. We extend the SIR approach to derive a deterministic and a stochastic formulation to describe the evolution of two classes of susceptible and infected states and a removed state, leading to a system of ordinary differential equations and a stochastic equivalent based on a Markov process. For the deterministic model, the contrasting timescale of the mutation process and disease infectiousness is exploited in two limits using asymptotic analysis in order to determine, in terms of the model parameters, necessary conditions for an epidemic to take place and timescales for the onset of the epidemic, the size and duration of the epidemic and the maximum level of the infected individuals at one time. Furthermore, the basic reproduction number R0 is determined from asymptotic analysis of a distinguished limit. Comparisons between the deterministic and stochastic model demonstrate that stochasticity has little effect on most aspects of an epidemic, but does have significant impact on its onset particularly for smaller populations and lower mutation rates for representatively large populations. The deterministic model is extended to investigate a range of quarantine and vaccination programmes, whereby in the two asymptotic limits analysed, quantitative estimates on the outcomes and effectiveness of these control measures are established.

[Effect of A20 gene induced silencing on the biological behaviors of human nasopharyngeal carcinoma cell].

Objective: To observe the effect of knockdown A20 gene expression on the proliferation, invasion and metastasis of human nasopharyngeal carcinoma cell in vivo and in vivo. Methods: Human nasopharyngeal carcinoma cell 5-8F-H3 was transfected with A20-specific shRNA Tet-on inducible plasmid vectors, and A20 silenced cells were screened by Puromycin. Quantitative RT-PCR and Western blot analysis were used to detect the mRNA level and protein of A20. The cell proliferation was detected by cell counting kit-8 (CCK8) and plate colony formation assays. The cell cycle and apoptosis were measured by flow cytometry. And the ability of cell invasion was measured using Boyden chamber assay in vivo. Subcutaneous tumor formation and liver metastasis in vivo were examined with whole-body fluorescence imaging system to observe the influence of silencing A20 gene expression in nude mice. Results: The stable A20 inducible silencing cells line 5-8F-H3/A20-shRNA was established successfully. Down-regulation of A20 mRNA and protein expression were observed in 5-8F-H3/A20-shRNA cells treated with DOX(both P<0.01). The results of CCK-8 assay (F=18.542, P=0.003), clone formation experiment (F=40.080, P<0.001) and flow cytometry analysis (F=7.398, P=0.024) in vivo showed that the cell proliferation of 5-8F-H3 was remarkably inhibited by down-regulation of A20 gene expression. The results of Boyden chamber assay showed that A20 gene silencing could inhibit the cell invasion ability (F=26.157, P<0.001). Silencing of A20 inhibited tumorigenesis and metastasis via subcutaneous tumor formation and liver metastasis experiments in nude mice. Conclusion: A20 gene is closely related to the malignant biological behaviors of nasopharyngeal carcinoma, and it may serve as a potential molecular target for the treatment of nasopharyngeal carcinoma.

Nupr1/Chop signal axis is involved in mitochondrion-related endothelial cell apoptosis induced by methamphetamine.

Methamphetamine (METH) abuse has been a serious global public health problem for decades. Previous studies have shown that METH causes detrimental effects on the nervous and cardiovascular systems. METH-induced cardiovascular toxicity has been, in part, attributed to its destructive effect on vascular endothelial cells. However, the underlying mechanism of METH-caused endothelium disruption has not been investigated systematically. In this study, we identified a novel pathway involved in endothelial cell apoptosis induced by METH. We demonstrated that exposure to METH caused mitochondrial apoptosis in human umbilical vein endothelial cells and rat cardiac microvascular endothelial cells in vitro as well as in rat cardiac endothelial cells in vivo. We found that METH mediated endothelial cell apoptosis through Nupr1-Chop/P53-PUMA/Beclin1 signaling pathway. Specifically, METH exposure increased the expression of Nupr1, Chop, P53 and PUMA. Elevated p53 expression raised up PUMA expression, which initiated mitochondrial apoptosis by downregulating antiapoptotic Bcl-2, followed by upregulation of proapoptotic Bax, resulting in translocation of cytochrome c (cyto c), an apoptogenic factor, from the mitochondria to cytoplasm and activation of caspase-dependent pathways. Interestingly, increased Beclin1, upregulated by Chop, formed a ternary complex with Bcl-2, thereby decreasing the dissociative Bcl-2. As a result, the ratio of dissociative Bcl-2 to Bax was also significantly decreased, which led to translocation of cyto c and initiated more drastic apoptosis. These findings were supported by data showing METH-induced apoptosis was significantly inhibited by silencing Nupr1, Chop or P53, or by PUMA or Beclin1 knockdown. Based on the present data, a novel mechanistic model of METH-induced endothelial cell toxicity is proposed. Collectively, these results highlight that the Nupr1-Chop/P53-PUMA/Beclin1 pathway is essential for mitochondrion-related METH-induced endothelial cell apoptosis and may be a potential therapeutic target for METH-caused cardiovascular toxicity. Future studies using knockout animal models are warranted to substantiate the present findings.

Changes of axial and radial diffusivities in cerebral white matter led by normal aging.

PURPOSE: Purpose of the study is to reveal the changes of directional diffusion in cerebral white matter (WM) by normal aging. MATERIALS AND METHODS: Thirty-nine volunteers were recruited to examine the changes in the directional diffusion of cerebral white matter (WM) due to normal aging. RESULTS: No significant difference between the older and younger group (P>.05) was detected in the axial diffusivity (λ(ll)) of any of the regions of interest (ROI), while radial diffusivity (λ(perpendicular)) was significantly higher in the older group (P<.05) except for occipital lobe WM. CONCLUSION: λ(ll) and λ(perpendicular) may be used as in vivo markers that differentially and specifically reflect the WM changes of normal aging.

[The function of T7 promoter as cis-acting elements for polymerase II in eukaryotic cell].

Using the chlorampheniol acetyltransterase gene as reporter, the function of phage T7 promoter in mammalian cells was studied by inhibition of transcription with alpha-amanitin. The experiment proved that the reporter under T7 promoter was transcribed by RNA polymerase II. Competitive electropho retic mobility shift assay (CEMSA) with TATA box, CAAT box, GC box and octamer showed that the TATA box was competitive molecular for synthetic T7 promoter. It is possible that T7 promoter is bound with TF II D transcription factor. The TATA box and octamer were inserted into Pvu II site upstream from the T7 promoter of pT7CAT. Two recombinant plasmids, pT7TATACAT and pT7OCTCAT, were constructed and transfected into CHO cells. CAT-activity test showed that T7 promoter strength was increased by octamer factor, not by TATA box. These results suggested that T7 promoter functions as cis-acting elements of RNA polymerase II transcriptional system in eucaryotic cells.

[Quantitative analysis of synephrine in zhishi injection by RP-HPLC].

A reversed phase HPLC method was developed for the determination of synephrine in Zhishi Injection using methanol-water (1:1) containing sodium 1-pentane sulfonate (3.5%, G/V) and acetic acid (0.1%, V/V) as the mobile phase with UV detoction at 275nm. Linear response was obtained in the range of 8-64 micrograms/ml (r = 0.9998), the absolute recovery was 96.2-103.4%, and RSD 2.7%-6.0% (n = 7).