Pt-MWCNT modified carbon electrode strip for rapid and quantitative detection of H2O2 in food.

A single-use screen-printed carbon electrode strip was designed and fabricated. Nanohybrids, prepared by deposition of platinum (Pt) nanoparticles on multi-wall carbon nanotube (MWCNT), was modified on the surface of screen-printed carbon electrode for the development of a fast, sensitive and cost-effective hydrogen peroxide (H2O2) detection amperometric sensor strip. With Pt-MWCNT nanohybrids surface modification, current generated in response to H2O2 by the screen-printed carbon electrode strip was enhanced 100 fold with an applied potential of 300 mV. Quality of as-prepared electrode strip was assured by the low coefficient of variation (CV) (<5%) of currents measured at 5 s. Three linear detection ranges with sensitivity of 75.2, 120.7, and 142.8 µA mM-1 cm-2 were observed for H2O2 concentration in the range of 1-15 mM, 0.1-1 mM, and 10-100 µM, respectively. The lowest H2O2 concentration could be measured by the as-prepared strip was 10 µM. H2O2 levels in green tea infusion and pressed Tofu could be rapidly detected with results comparable to that measured by ferrous oxidation xylenol orange (FOX) assay and peroxidase colorimetric method.

Bisphenol A disrupts steroidogenesis and induces a sex hormone imbalance through c-Jun phosphorylation in Leydig cells.

Bisphenol A (BPA) is a well-known endocrine disrupting chemical (EDC) that is used to manufacture plastic consumer products. It is well known that exposure to BPA can induce defects in gonad development and negatively influences reproductive function in both males and females. In this study, we assessed the effects of BPA on hormone production in Leydig cells, which secrete hormones in the testes and support male fertility. We examined two steroidogenic enzymes, CYP11A1 and CYP19 that involved in sex hormone synthesis in mouse MA-10 Leydig cells. We found that BPA activated CYP gene in both mRNA and protein levels then resulted in alteration of the normal sex hormone ratio. Furthermore, we found that BPA induced c-Jun phosphorylation and contributed to CYP gene expression. Similar results were observed in an animal study. In conclusion, BPA disrupts the hormone environment in testis via steroidogenic gene activation through the JNK/c-Jun signaling pathway.

Intra-particle coupling and plasmon tuning of multilayer Au/dielectric/Au nanocrescents adhered to a dielectric cylinder.

A 3D numerical study on surface plasmon resonance is presented for a multilayer Au/dielectric/Au nanocrescent structure adhered to a dielectric cylinder. Investigations are carried out on the structure's coupling modes, local field enhancement (LFE) and plasmon tuning capability. The cavity coupling via the cylinder is found to be dominant in tuning the plasmon wavelength. This provides the possibility of tailoring the device's plasmon band by adjusting the cylinder's size and material. By using a cylinder with higher permittivity, the plasmon peak significantly shifts to the near- or mid-infrared regime without increasing the size of the crescents, thus increase of radiation loss can be fully avoided. Extra crescent layers can also be added to the structure to induce intra-particle couplings among Au crescents and enlarge the areas of the hot-spots, without shifting the plasmon band. The LFE of the multiple-layer structure is shown to be dramatically increased through the intra-particle coupling among the Au crescents, compared with a single layer Au nanocrescent structure. Further increase of LFE can be achieved by substituting semiconductors for the dielectrics in the structure due to the charge transport at metal-semiconductor interfaces.

The genome of Salmonella enterica serovar gallinarum: distinct insertions/deletions and rare rearrangements.

Salmonella enterica serovar Gallinarum is a fowl-adapted pathogen, causing typhoid fever in chickens. It has the same antigenic formula (1,9,12:--:--) as S. enterica serovar Pullorum, which is also adapted to fowl but causes pullorum disease (diarrhea). The close relatedness but distinct pathogeneses make this pair of fowl pathogens good models for studies of bacterial genomic evolution and the way these organisms acquired pathogenicity. To locate and characterize the genomic differences between serovar Gallinarum and other salmonellae, we constructed a physical map of serovar Gallinarum strain SARB21 by using I-CeuI, XbaI, and AvrII with pulsed-field gel electrophoresis techniques. In the 4,740-kb genome, we located two insertions and six deletions relative to the genome of S. enterica serovar Typhimurium LT2, which we used as a reference Salmonella genome. Four of the genomic regions with reduced lengths corresponded to the four prophages in the genome of serovar Typhimurium LT2, and the others contained several smaller deletions relative to serovar Typhimurium LT2, including regions containing srfJ, std, and stj and gene clusters encoding a type I restriction system in serovar Typhimurium LT2. The map also revealed some rare rearrangements, including two inversions and several translocations. Further characterization of these insertions, deletions, and rearrangements will provide new insights into the molecular basis for the specific host-pathogen interactions and mechanisms of genomic evolution to create a new pathogen.

Coxsackievirus B3-induced apoptosis and caspase-3.

Cell death can be classified into two categories: apoptosis and necrosis. Apoptotic pathway can be either caspase-dependent or caspase-independent. Caspase-independent cytopathic effect (CPE) has been described. In order to evaluate the pattern of HeLa cell death induced by Coxsackievirus B3 (CVB3) and whether apoptosis involves caspase activation, we co-cultivated HeLa cells with CVB3 and detected the cytopathic changes, the alteration of mRNA and protein expression of caspase-3 gene plus caspase-3 activity, as well as analyzing DNA fragmentation before and after caspase-3 activity inhibition. According to the results, we propose that CVB3 may induce apoptosis and necrosis in HeLa cells, the latter appearing much earlier. Caspase-3 is activated at the levels of both transcription and translation, and procaspase-3 is proteolytically cleaved, thus leading to the continuous increasing of both caspase-3 precursor protein and its subunit. However, besides CPE, apoptosis induced by CVB3 is not a direct consequence of the activation of caspase-3, or caspase-3 is not the only effector molecule in apoptotic cell death, for caspase-3 inhibitor can not decrease DNA fragmentation. Some other biochemical mechanisms may participate in the process, whose role weakens the effect of inhibiting caspase-3 activity.