Enhanced constitutive invasion activity in human nontumorigenic keratinocytes exposed to a low level of barium for a long time

We have recently demonstrated that exposure to barium for a short time (≤4 days) and at a low level (5 µM = 687 µg/L) promotes invasion of human nontumorigenic HaCaT cells, which have characteristics similar to those of normal keratinocytes, suggesting that exposure to barium for a short time enhances malignant characteristics. Here we examined the effect of exposure to low level of barium for a long time, a condition mimicking the exposure to barium through well water, on malignant characteristics of HaCaT keratinocytes. Constitutive invasion activity, focal adhesion kinase (FAK) protein expression and activity, and matrix metalloproteinase 14 (MMP14) protein expression in primary cultured normal human epidermal keratinocytes, HaCaT keratinocytes, and HSC5 and A431 human squamous cell carcinoma cells were augmented following an increase in malignancy grade of the cells. Constitutive invasion activity, FAK phosphorylation, and MMP14 expression levels of HaCaT keratinocytes after treatment with 5 µM barium for 4 months were significantly higher than those of control untreated HaCaT keratinocytes. Taken together, our results suggest that exposure to a low level of barium for a long time enhances constitutive malignant characteristics of HaCaT keratinocytes via regulatory molecules (FAK and MMP14) for invasion. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 161–167, 2015.     

Adverse consequences of immediate thrombolysis-related complications: a multi-centre registry-based cohort study of acute stroke

Journal of Thrombosis and Thrombolysis - Complications following thrombolysis for stroke are well documented, and mostly concentrated on haemorrhage. However, the consequences of patients who...     

Correction to: Prenatal attachment: Using measurement invariance to test the validity of comparisons across eight culturally diverse countries

Archives of Women's Mental Health - A Correction to this paper has been published: https://doi.org/10.1007/s00737-021-01122-7     

Elongation mechanism and substrate specificity of 2'',5''-oligoadenylate synthetase.

2',5'-Oligoadenylate synthetase has been purified from a rabbit reticulocyte lysate to a high degree of purity. The enzyme contained no detectable interfering activities that could degrade the nucleoside triphosphate substrate or the oligomeric products. Two basic properties of this enzyme have been examined: the elongation mechanism for the synthesis of oligoadenylates and the substrate specificity for nucleotides. Kinetic studies on the formation of different oligomeric intermediates show that the dimer pppA2'p5'A is the first product to accumulate in predominant proportion during the first period of reaction; the trimer and other longer oligomers appear after a lag phase. The amount of the trimer increases at the expense of the dimer. Preformed dimers and trimers added to the incubation mixture were readily incorporated into higher oligomers, suggesting the free access of these dimers and trimers to the active center after the onset of polymerization of ATP. The results indicate clearly that the enzyme catalyzes the de novo synthesis of the oligonucleotide from ATP and that the mechanism of elongation of the 2',5'-oligonucleotides catalyzed by the enzyme is not processive. Polymerization of a mixture of ATP and another nucleoside triphosphate shows that the enzyme is not only an ATP polymerase. The 2',5'-oligoadenylate synthetase is in fact a 2',5'-nucleotidyltransferase that catalyzes the formation of co-oligonucleotides. However, the purified reticulocyte enzyme catalyzed only the addition of one unit of GMP, UMP, CMP, 2'-dAMP, 3'-dAMP, dCMP, dGMP, or TMP to the 2'-OH end of a preformed oligoadenylate. A procedure for the separation of 2',5'-oligonucleotides with or without the 5'triphosphate end also is described.     

Controlled synthesis of ultrathin MoS2 nanoflowers for highly enhanced NO2 sensing at room temperature

Fabrication of a high-performance room-temperature (RT) gas sensor is important for the future integration of sensors into smart, portable and Internet-of-Things (IoT)-based devices. Herein, we developed a NO₂ gas sensor based on ultrathin MoS₂ nanoflowers with high sensitivity at RT. The MoS₂ flower-like nanostructures were synthesised via a simple hydrothermal method with different growth times of 24, 36, 48, and 60 h. The synthesised MoS₂ nanoflowers were subsequently characterised by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy. The petal-like nanosheets in pure MoS₂ agglomerated to form a flower-like structure with Raman vibrational modes at 378 and 403 cm⁻¹ and crystallisation in the hexagonal phase. The specific surface areas of the MoS₂ grown at different times were measured by using the Brunauer–Emmett–Teller method. The largest specific surface area of 56.57 m² g⁻¹ was obtained for the MoS₂ nanoflowers grown for 48 h. This sample also possessed the smallest activation energy of 0.08 eV. The gas-sensing characteristics of sensors based on the synthesised MoS₂ nanostructures were investigated using oxidising and reducing gases, such as NO₂, SO₂, H₂, CH₄, CO and NH₃, at different concentrations and at working temperatures ranging from RT to 150 °C. The sensor based on the MoS₂ nanoflowers grown for 48 h showed a high gas response of 67.4% and high selectivity to 10 ppm NO₂ at RT. This finding can be ascribed to the synergistic effects of largest specific surface area, smallest crystallite size and lowest activation energy of the MoS₂-48 h sample among the samples. The sensors also exhibited a relative humidity-independent sensing characteristic at RT and a low detection limit of 84 ppb, thereby allowing their practical application to portable IoT-based devices.

Controlled synthesis of ultrathin MoS₂ nanoflowers is crucial to develop a high-performance room-temperature NO₂ gas sensor for the future integration of sensors into smart, portable and Internet-of-Things (IoT)-based devices.     

Electrodeposited nickel–graphene nanocomposite coating: effect of graphene nanoplatelet size on its microstructure and hardness

In this study, the effect of graphene nanoplatelet (GNP) size on the microstructure and hardness of the electrodeposited nickel–graphene nanocomposite coatings were investigated. GNPs with different sizes were prepared by using a high energy ball milling technique. The experimental result revealed the high energy ball milling technique could reduce the size, increase the surface area, and improve the dispersion ability of GNPs. The microstructure, hardness, and components of the nanocomposite coatings were greatly affected by GNP sizes. The highest microhardness was measured to be 273 HV for the nanocomposite coatings containing 5 h-milled GNPs, which is increased up to ∼47% compared to pristine Ni coating. The enhancement in the hardness is attributed to the uniform dispersion of the small GNP sizes inside the Ni matrix and the Ni grain size reduction when using milled GNPs.

The effect of graphene nanoplatelet size on the microstructure and hardness of electrodeposited nickel–graphene nanocomposite coatings was investigated.