Theoretical study on temperature dependence of cellular uptake of QDs nanoparticles

Cellular uptake kinetics of nanoparticles is one of the key issues determining the design and application of the particles. Models describing nanoparticles intrusion into the cell mostly take the endocytosis process into consideration, and the influences of electrical charges, sizes, concentrations of the particles have been investigated. In this paper, the temperature effect on the cellular uptake of Quantum Dots (QDs) is studied experimentally. QDs are incubated with the SPCA-1 human lung tumor cells, and the nanoparticles on the cell membrane and inside the cell are quantified according to the fluorescence intensities recorded. It is found that the amounts of nanoparticles attached onto the cell membrane and inside the cell both increase with temperature. Based on the experimental results, a model is proposed to describe the cellular uptake dynamic process of nanoparticles. The process consists of two steps: nanoparticles adsorption onto the cell membrane and the internalization. The dynamic parameters are obtained through curve fitting. The simulated results show that the internalization process can be categorized into different phases. The temperature dependent internalization rate constant is very small when below 14?°C. It increases distinctly when temperature rises from 14?°C to 22?°C, but there is no evident increase as temperature further increases above 22?°C. Results show that by incorporating a temperature-independent internalization factor, the model predictions well fit the experimental results.     

The TSC1 and TSC2 tumor suppressors are required for proper ER stress response and protect cells from ER stress-induced apoptosis

Tuberous sclerosis complex (TSC)1 and TSC2 are tumor suppressors that inhibit cell growth and mutation of either gene causes benign tumors in multiple tissues. The TSC1 and TSC2 gene products form a functional complex that has GTPase-activating protein (GAP) activity toward Ras homolog enriched in brain (Rheb) to inhibit mammalian target of rapamycin complex 1 (mTORC1), which is constitutively activated in TSC mutant tumors. We found that cells with mutation in either TSC1 or TSC2 are hypersensitive to endoplasmic reticulum (ER) stress and undergo apoptosis. Although the TSC mutant cells show elevated eIF2α phosphorylation, an early ER stress response marker, at both basal and induced conditions, induction of other ER stress response markers, including ATF4, ATF6 and C/EBP homologous protein (CHOP), is severely compromised. The defects in ER stress response are restored by raptor knockdown but not by rapamycin treatment in the TSC mutant cells, indicating that a rapamycin-insensitive mTORC function is responsible for the defects in ER stress response. Consistently, activation of Rheb sensitizes cells to ER stress. Our data show an important role of TSC1/TSC2 and Rheb in unfolded protein response and cell survival. We speculate that an important physiological function of the TSC1/2 tumor suppressors is to protect cells from harmful conditions. These observations indicate a potential therapeutic application of using ER stress agents to selectively kill TSC1 or TSC2 mutant cells for TSC treatment.     

Cis-elements and trans-factors that regulate expression of the maize Cat1 antioxidant gene in response to ABA and osmotic stress: H2O2 is the likely intermediary signaling molecule for the response

The mechanisms by which the maize antioxidant Cat1 gene responds to abscisic acid (ABA) and osmotic stress have been investigated. Results show that during late embryogenesis, Cat1 expression in vivo is independent of endogenous ABA levels. However, exogenously applied ABA significantly enhances Cat1 expression. Transient assays using particle bombardment show that the proximal ABRE2 element on the Cat1 promoter is responsible for the induction of Cat1 expression by ABA. We further show that ABA induces the expression of Cat1 via the interaction between ABRE2 and one of its binding proteins, CBF1 (Cat1 binding factor 1). Using ABA-deficient mutant embryos, we show that osmotic stress induces Cat1 expression through two alternate signal transduction pathways: an ABA signaling pathway leading to the interaction between the ABRE2 motif and CBF1, and a pathway via the interaction of ABRE2 and CBF2 (Cat1 binding factor 2) that is independent of ABA. The data presented clearly suggest that hydrogen peroxide (H2O2) plays an important intermediary role in the ABA signal transduction pathway leading to the induction of the Cat1 gene.     

Bacterial growth stimulation with exogenous siderophore and synthetic N-acyl homoserine lactone autoinducers under iron-limited and low-nutrient conditions

The growth of marine bacteria under iron-limited conditions was investigated. Neither siderophore production nor bacterial growth was detected for Pelagiobacter sp. strain V0110 when Fe(III) was present in the culture medium at a concentration of <1.0 microM. However, the growth of V0110 was strongly stimulated by the presence of trace amounts of exogenous siderophore from an alpha proteobacterium, V0902, and 1 nM N-acyl-octanoylhomoserine lactone (C(8)-HSL), which is known as a quorum-sensing chemical signal. Even though the iron-binding functionality of a hydroxamate siderophore was undetected in the supernatant of V0902, a hydroxamate siderophore was detected in the supernatant of V0110 under the above conditions. These results indicated that hydroxamate siderophore biosynthesis by V0110 began in response to the exogenous siderophore from V0902 when in the presence of C(8)-HSL; however, C(8)-HSL production by V0110 and V0902 was not detected. Direct interaction between V0902 and V0110 through siderophore from V0902 was observed in the dialyzing culture. Similar stimulated growth by exogenous siderophore and HSL was also observed in other non-siderophore-producing bacteria isolated from marine sponges and seawater. The requirement of an exogenous siderophore and an HSL for heterologous siderophore production indicated the possibility that cell-cell communication between different species was occurring.     

A novel MET-interacting protein shares high sequence similarity with RanBPM, but fails to stimulate MET-induced Ras/Erk signaling

MET is a receptor protein tyrosine kinase for hepatocyte growth factor, a multifunctional cytokine controlling cell growth, morphogenesis, and motility. In our previous study, RanBPM/RanBP9, whose name originated from its ability to interact with Ran, was identified as a MET-interacting protein. RanBPM/RanBP9 activates the Ras/Erk signaling pathway by serving as an adaptor protein of MET to recruit Sos. In this study, we identify a protein sharing a high amino acid sequence identity with RanBPM/RanBP9, especially in its SPRY domain, the region responsible for MET binding. This protein lacks the N-terminal poly-proline and poly-glutamine (Poly-PQ) stretch present in RanBPM/RanBP9 and has less homology with RanBPM/RanBP9 in its mid-region. We subsequently named this protein RanBP10 after demonstrating its interaction with Ran. We show that, like RanBPM/RanBP9, RanBP10 interacts with the tyrosine kinase domain of MET via its SPRY domain and these two proteins can compete with each other to bind to MET. Interestingly, unlike RanBPM/RanBP9, overexpression of RanBP10 cannot induce Erk1/2 phosphorylation and serum response element-luciferase (SRE-LUC) reporter gene expression. More importantly, co-transfection of RanBPM/RanBP9 and RanBP10 significantly represses SRE-LUC reporter gene expression induced by overexpression of RanBPM/RanBP9. Additional binding assays demonstrate that RanBP10 fails to interact with Sos, which explains its inability to activate the Ras/Erk pathway. Furthermore, we show that the N-terminus of RanBPM/RanBP9 with the Poly-PQ stretch is required for recruiting Sos and a truncated RanBPM/RanBP9 lacking this region fails to recruit Sos, indicating that the functional difference between RanBP10 and RanBPM/RanBP9 lies in their sequence difference in their N-termini.     

Partial Protective Effect of Intranasal Immunization with Recombinant Toxoplasma gondii Rhoptry Protein 17 against Toxoplasmosis in Mice

Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite that infects a variety of mammals, including humans. An effective vaccine for this parasite is therefore needed. In this study, RH strain T. gondii rhoptry protein 17 was expressed in bacteria as a fusion with glutathione S-transferase (GST) and the recombinant proteins (rTgROP17) were purified via GST-affinity chromatography. BALB/c mice were nasally immunised with rTgROP17, and induction of immune responses and protection against chronic and lethal T. gondii infections were investigated. The results revealed that mice immunised with rTgROP17 produced high levels of specific anti-rTgROP17 IgGs and a mixed IgG1/IgG2a response of IgG2a predominance. The systemic immune response was associated with increased production of Th1 (IFN-γand IL-2) and Th2 (IL-4) cytokines, and enhanced lymphoproliferation (stimulation index, SI) in the mice immunised with rTgROP17. Strong mucosal immune responses with increased secretion of TgROP17-specific secretory IgA (SIgA) in nasal, vaginal and intestinal washes were also observed in these mice. The vaccinated mice displayed apparent protection against chronic RH strain infection as evidenced by their lower liver and brain parasite burdens (59.17% and 49.08%, respectively) than those of the controls. The vaccinated mice also exhibited significant protection against lethal infection of the virulent RH strain (survival increased by 50%) compared to the controls. Our data demonstrate that rTgROP17 can trigger strong systemic and mucosal immune responses against T. gondii and that ROP17 is a promising candidate vaccine for toxoplasmosis.     

Survival Impact of Delaying Postoperative Radiotherapy in Patients with Esophageal Cancer

The purpose of the current study was to retrospectively assess the effect of postoperative radiotherapy (RT) delay on survival for patients with esophageal cancer. From 2008 to 2011, patients with esophageal cancer who had undergone postoperative RT in five different hospitals in China were reviewed. Clinical data, including time interval between surgery to RT, were prospectively collected. Kaplan-Meier method was conducted to estimate the effect of each variable on progression-free survival (PFS) and overall survival (OS), with differences assessed by log-rank test. Univariate Cox proportional-hazards models were performed for both PFS and OS for all assumed predictor variables. Statistically significant predictor variables (P < .05) on univariate analysis were then included in multivariate Cox proportional-hazards models, which were performed to compare the effects of RT delay on PFS and OS. A total of 316 patients were finally enrolled in this prospectively multicentric study. Time to RT after surgery varied from 12 days to over 60 days (median, 26 days). Multivariate analysis showed that delay to RT longer than the median does not appear to be a survival cost. There was also no statistically difference in PFS (P = .513) or OS (P = .236) between patients stratified by quartiles (≤21 days vs ≧35 days). However, patients with particularly long delays (≧42 days) demonstrated a detrimental impact on OS (P = .021) but not PFS (P = .580). Delaying postoperative RT of esophageal cancer does not impact PFS, but results in a significant reduction on OS if delaying longer than 6 weeks.     

硝尔库勒湖可培养放线菌多样性及其功能酶和抗细菌活性

【目的】认识和了解硝尔库勒湖可培养放线菌的多样性、功能酶和抗细菌活性特点,为今后的开发和利用奠定基础。【方法】应用可培养技术和基于16S r RNA基因序列的系统发育分析硝尔库勒盐湖沉积物中放线菌的多样性。常规方法检测样品成分因子,并筛选了嗜盐放线菌的蛋白酶、淀粉酶和酯酶活性;抑菌圈法检测放线菌新种的抗细菌活性。【结果】分离获得了51个OTUs,分属于24个不同的属,其中15个OTUs代表了放线菌新种;链霉菌属是优势菌属,占全部分离菌株数量的16.25%。硝尔库勒湖放线菌类群数量一定程度上受样品成分因子的协同影响。代表新种的菌株展示了良好的功能酶活性和抗细菌活性,其中代表链霉菌新种的菌株XHU5011不仅具有多种酶活性,而且具有强大的抗金黄葡萄球菌、耻垢分枝杆菌和荧光假单胞菌的能力,具有很好的开发潜能。【结论】硝尔库勒盐湖中存在丰富的可培养放线菌多样性,潜藏着大量的放线菌新资源,并且具有很好的功能酶和天然产物挖掘潜力。