POTASSIUM ALLEVIATES THE INHIBITORY ACTION OF AMMONIUM UPON THE PHOTOSYNTHETIC RECOVERY OF NOSTOC FLAGELLIFORME (CYANOPHYCEAE) DURING REHYDRATION1

Effects of ammonium on the photosynthetic recovery of Nostoc flagelliforme Berk. et M. A. Curtis were assayed when being rehydrated in low‐K⁺ or high‐K⁺ medium. Its photosynthetic recovery was K⁺ limited after 3 years of dry storage. The potassium absorption of N. flagelliforme reached the maximum after 3 h rehydration in low‐K⁺ medium but at 5 min in high‐K⁺ medium. The K⁺ content of N. flagelliforme rehydrated in high‐K⁺ medium was much higher than that in low‐K⁺ medium. The maximal PSII quantum yield (F_v/F_m) value of N. flagelliforme decreased significantly when samples were rehydrated in low‐K⁺ medium treated with 5 mM NH₄Cl. However, the treatment of 20 mM NH₄Cl had little effect on its F_v/F_m value in high‐K⁺ medium. The relative F_v/F_m 24 h EC₅₀ (concentration at which 50% inhibition occurred) value of NH₄⁺ in high‐K⁺ medium (64.35 mM) was much higher than that in low‐K⁺ medium (22.17 mM). This finding indicated that high K⁺ could alleviate the inhibitory action of NH₄⁺ upon the photosynthetic recovery of N. flagelliforme during rehydration. In the presence of 10 mM tetraethylammonium chloride (TEACl), the relative F_v/F_m 24 h EC₅₀ value of NH₄⁺ was increased to 46.34 and 70.78 mM, respectively, in low‐K⁺ and high‐K⁺ media. This observation suggested that NH₄⁺ entered into N. flagelliforme cells via the K⁺ channel. Furthermore, NH₄⁺ could decrease K⁺ absorption in high‐K⁺ medium.     

Identification of bacterial target proteins for the salicylidene acylhydrazide class of virulence-blocking compounds

A class of anti-virulence compounds, the salicylidene acylhydrazides, has been widely reported to block the function of the type three secretion system of several Gram-negative pathogens by a previously unknown mechanism. In this work we provide the first identification of bacterial proteins that are targeted by this group of compounds. We provide evidence that their mode of action is likely to result from a synergistic effect arising from a perturbation of the function of several conserved proteins. We also examine the contribution of selected target proteins to the pathogenicity of Yersinia pseudotuberculosis and to expression of virulence genes in Escherichia coli O157.     

Removal and recovery of phosphorous from swine wastewater by demonstration crystallization reactor and struvite accumulation device

A demonstration crystallization reactor and struvite accumulation device for the removal and recovery of phosphorous was constructed and their performance was evaluated using actual swine wastewater for 3.5 years. The wastewater pH was increased by aeration, and the concentrations of total P and soluble PO(4)-P were reduced by a struvite crystallization reaction induced under a high pH condition. A 30% MgCl(2) addition was effective in enhancing the struvite crystallization reaction. The concentrations of suspended solids, total Zn and total Cu, were also decreased by the settling function of the reactor. On removing the efficiencies of these components, no noticeable seasonal fluctuation in performance was observed during the 3.5-year operation. In terms of maximum yield, 171g struvite was obtained from 1m(3) swine wastewater by the demonstration accumulation device for struvite recovery. The recovered struvite needed only air-drying before use since it was approximately 95% pure even without washing.     

NF-kappaB in breast cancer cells promotes osteolytic bone metastasis by inducing osteoclastogenesis via GM-CSF

Advanced breast cancers frequently metastasize to bone, resulting in osteolytic lesions, yet the underlying mechanisms are poorly understood. Here we report that nuclear factor-kappaB (NF-kappaB) plays a crucial role in the osteolytic bone metastasis of breast cancer by stimulating osteoclastogenesis. Using an in vivo bone metastasis model, we found that constitutive NF-kappaB activity in breast cancer cells is crucial for the bone resorption characteristic of osteolytic bone metastasis. We identified the gene encoding granulocyte macrophage-colony stimulating factor (GM-CSF) as a key target of NF-kappaB and found that it mediates osteolytic bone metastasis of breast cancer by stimulating osteoclast development. Moreover, we observed that the expression of GM-CSF correlated with NF-kappaB activation in bone-metastatic tumor tissues from individuals with breast cancer. These results uncover a new and specific role of NF-kappaB in osteolytic bone metastasis through GM-CSF induction, suggesting that NF-kappaB is a potential target for the treatment of breast cancer and the prevention of skeletal metastasis.     

Phytoestrogen α-zearalanol antagonizes homocysteine-induced imbalance of nitric oxide/endothelin-1 and apoptosis in human umbilical vein endothelial cells

Although the issue of estrogen replacement therapy on cardiovascular health is debatable, it has presumable benefits for endothelial function in postmenopausal women. However, the fear of breast cancer has intimidated women contemplating estrogen treatment and limited its long-term application. An effective alternative remedy not associated with breast carcinoma is in serious demand. This study was designed to examine the effect of phytoestrogen alpha-zearalanol (alpha-ZAL) and 17beta-estradiol (E2) on nitric oxide (NO) and endothelin (ET)-1 levels, apoptosis, and apoptotic enzymes in human umbilical vein endothelial cells (HUVEC). HUVEC cells were challenged for 24 h with homocysteine (10-3 M), an independent risk factor for a variety of vascular diseases, in the presence of alpha-ZAL or E2 (10-9 to 10-6 M). Release of NO and ET-1 were measured with enzyme immunoassay. Apoptosis was evaluated by fluorescence-activated cell sorter analysis. Expression of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), Bax, and Bcl-2 were determined using Western blot. NOS activity was evaluated with 3H-arginine to 3H-citrulline conversion. Our results indicated that Hcy significantly reduced NO production, NOS activity, enhanced ET-1/NO ratio and apoptosis, upregulated iNOS, Bax, and downregulated eNOS, Bcl-2 expression. These effects were significantly attenuated by alpha-ZAL and E2. ZAL displayed a similar potency compared with E2 in antagonizing Hcy-induced effects. In summary, these results suggested that alpha-ZAL may effectively preserve Hcy-induced decrease in NO, increase in ET-1/NO ratio and apoptosis, which contributes to protective effects of phytoestrogens on endothelial function.     

New amperometric and potentiometric immunosensors based on gold nanoparticles/tris(2,2'-bipyridyl)cobalt(III) multilayer films for hepatitis B surface antigen determinations

Two generic, fast, sensitive and novel electrochemical immunosensors have been developed. Initially, a layer of plasma-polymerized Nafion film (PPF) was deposited on the platinum electrode surface, then positively charged tris(2,2'-bipyridyl)cobalt(III) (Co(bpy)(3)(3+)) and negatively charged gold nanoparticles were assembled on the PPF-modified Pt electrode by layer-by-layer technique. Finally, hepatitis B surface antibody (HBsAb) was electrostatically adsorbed on the gold nanoparticles surface. Electrochemical behavior of the {Au/Co(bpy)(3)(3+)}(n) multilayer film-modified electrodes was studied. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS) were adopted to monitor the regular growth of the multilayer films. The performance and factors influencing the performance of the resulting immunosensors were studied in detail. The multilayer film-modified immunosensor was used for hepatitis B surface antigen (HBsAg) determination via the amperometric and potentiometric immunosensor systems, and both systems provided the same linear ranges from 0.05 to 4.5 microg/mL with different detection limits for the amperometric system 0.005 microg/mL and for the potentiometric system 0.015 microg/mL. The immunosensors were used to analyse HBsAg in human serum samples. Analytical results of clinical samples show that the developed immunoassay is comparable with the enzyme-linked immunosorbent assays (ELISAs) method, implying a promising alternative approach for detecting HBsAg in the clinical diagnosis. In addition, the multilayer films also showed better stability for 1 month at least.     

Reagentless amperometric immunosensor for human chorionic gonadotrophin based on direct electrochemistry of horseradish peroxidase

A novel amperometric immunosensor for determination of human serum chorionic gonadotrophin (HCG) was constructed by immobilization of HCG with titania sol-gel on a glassy carbon electrode and the direct electrochemistry of horseradish peroxidase (HRP) labeled to HCG antibody (HRP-anti-HCG). The morphologies of the HCG membrane were characterized to be chemically clean, porous and homogeneous. HRP-anti-HCG was functionally conjugated with the immobilized HCG after incubation in phosphate buffer (PBS) containing HRP-anti-HCG. A direct electron transfer of HRP with a rate constant of 1.35+/-0.40 s(-1) was observed at the HRP-anti-HCG-HCG/titania sol-gel membrane modified electrode in 0.1 M PBS pH 7.0. With a competitive mechanism the differential pulse voltammetric peak current of the immobilized HRP decreased linearly with an increasing HCG concentration from 2.5 to 12.5 mIU/ml in the incubation solution. The HCG immunosensor showed a detection limit of 1.4 mIU/ml, a good accuracy and acceptable precision and reproducibility with an intra-assay CV of 4.7% at 5.0 mIU/ml and an inter-assay precision of 8.1% obtained at 10 mIU/ml. The biosensor displayed a good stability in a storage period of 30 days.     

The association of calmodulin with central spindle regulates the initiation of cytokinesis in HeLa cells

Calmodulin is a major cytoplasmic calcium receptor that performs multiple functions in the cell including cytokinesis. Central spindle appears between separating chromatin masses after metaphase-anaphase transition. The interaction of microtubules from central spindle with cell cortex regulates the cleavage furrow formation. In this paper, we use green fluorescence protein (GFP)-tagged calmodulin as a living cell probe to examine the detailed dynamic redistribution and co-localization of calmodulin with central spindle during cytokinesis and the function of this distribution pattern in a tripolar HeLa cell model. We found that calmodulin is associated with spindle microtubules during mitosis and begins to aggregate with central spindle after anaphase initiation. The absence of either central spindle or central spindle-distributed calmodulin is correlated with the defect in the formation of cleavage furrow, where contractile ring-distributed CaM is also extinct. Further analysis found that both the assembly of central spindle and the formation of cleavage furrow are affected by the W7 treatment. The microtubule density of central spindle was decreased after the treatment. Only less than 10% of the synchronized cells enter cytokinesis when treated with 25 microM W7, and the completion time of furrow regression is also delayed from 10 min to at least 40 min. It is suggested that calmodulin plays a significant role in cytokinesis including furrow formation and regression, The understanding of the interaction between calmodulin and microtubules may give us insight into the mechanism through which calmodulin regulates cytokinesis.