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Model Chemical (model + chemical)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Metamorphic inhibition of Xenopus laevis by sodium perchlorate: Effects on development and thyroid histology

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2005
Joseph E. Tietge
Abstract The perchlorate anion inhibits thyroid hormone (TH) synthesis via inhibition of the sodium-iodide symporter. It is, therefore, a good model chemical to aid in the development of a bioassay to screen chemicals for affects on thyroid function. Xenopus laevis larvae were exposed to sodium perchlorate during metamorphosis, a period of TH-dependent development, in two experiments. In the first experiment, stage 51 and 54 larvae were exposed for 14 d to 16, 63, 250, 1,000, and 4,000 ,g perchlorate/L. In the second experiment, stage 51 larvae were exposed throughout metamorphosis to 8, 16, 32, 63, and 125 ,g perchlorate/L. Metamorphic development and thyroid histology were the primary endpoints examined. Metamorphosis was retarded significantly in the first study at concentrations of 250 ,g/L and higher, but histological effects were observed at 16 ,g/L. In the second study, metamorphosis was delayed by 125 ,g/L and thyroid size was increased significantly at 63 ,g/L. These studies demonstrate that inhibition of metamorphosis readily can be detected using an abbreviated protocol. However, thyroid gland effects occur at concentrations below those required to elicit developmental delay, demonstrating the sensitivity of this endpoint and suggesting that thyroidal compensation is sufficient to promote normal development until perchlorate reaches critical concentrations. [source]

dUTP Pyrophosphatase, its appearance in extracellular compartment may serve as a potential biomarker for N -methyl- N' -nitro- N -nitrosoguanidine exposure in mammalian cells

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 10 2006
Meiping Wu
Abstract The monofunctional alkylating agent N -methyl- N' -nitro- N -nitrosoguanidine (MNNG) is a model chemical widely used for studying the molecular events induced by the widespread environmental N -nitroso alkylating carcinogen. Many studies have focused on understanding MNNG-induced mutagenesis and carcinogenesis. However, the search for specific indicators of MNNG exposure is still underway. In this study, we analyzed the proteins in culture medium of human amnion epithelial cells (FL,cells) exposed to MNNG by 2-DE followed by MALDI-TOF,MS, in the hope of finding a specific protein marker suitable for MNNG risk assessment. Image visualization and statistical analysis indicated that 12,spots appeared and 4,spots up-regulated after MNNG exposure. Most of them were identified by MS. These proteins include nuclear isoform of dUTP pyrophosphatase (DUT-N), phosphoglycerate mutase,1, heparan sulfate proteoglycan perlecan, etc., which are involved in multiple cellular functions. Interestingly, 2-DE and MS analyses of cell lysate exposed to MNNG revealed that DUT-N was down-regulated. The appearance of DUT-N in culture medium and its down-regulation in cell lysate was confirmed by Western blot. These data suggest that these proteins, especially DUT-N, could be used as candidate biomarkers for monitoring MNNG exposure. [source]

Preparation and Characterization of Bi3+ -TiO2 and its Photocatalytic Activity

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007
H. Zuo
Abstract Bi3+ -TiO2 photocatalysts were prepared by doping bismuth ion into the TiO2 structure in a sol-gel process. The catalyst samples were then characterized by UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Rodamine-B (RhB) was used in this study as a model chemical with the aim of organic pollutants control. The photocatalytic degradation of RhB demonstrated that an optimal loading of bismuth 0.7,at.,% achieved the highest photodegradation rate, with the rate constant increasing by a factor of 3.89 over neat TiO2 (P25) under UV illumination (, , 320,nm). The degradation of p -nitrobenzonic acid (pNBA) was also examined to prevent/preclude/exclude/ the photosensitization pathway. GC-MS results show that pNBA can be effectively degraded and minerized to small molecules, such as quinone, acetic acid and formic acid. [source]

Mineralization of organic contaminants in sludge-soil mixtures

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2001
Bo Gejlsbjerg
Abstract The mineralization of 14C-labeled linear alkylbenzene sulfonate (LAS), nonylphenol (NP), nonylphenol-di-ethoxylate (NP2EO), di-(2-ethylhexyl)phthalate (DEHP), pyrene, and 1,4-dichlorobenzene (DCB) was investigated in different sludge-soil mixtures and soils. Under aerobic conditions, the mineralization of LAS, NP, and NP2EO was between 50 and 81% of the added amounts after two months, while DEHP and pyrene were mineralized more slowly. The mineralization of the model chemicals was indirectly affected by the amount of sludge in the test mixtures. A higher content of sludge in the mixtures reduced the overall concentration of oxygen, which resulted in a decrease of the mineralization of several of the model chemicals. In sludge-soil mixtures with predominantly anaerobic conditions, the mineralization was slower for all of the chemicals with the exception of DEHP and DCB. The mineralization of DCB was enhanced in mixtures with a high sludge content. No pronounced difference in the mineralization of the model chemicals (except DEHP) was observed when the sludge was mixed with three different agricultural soils. [source]