Structural characterization,thermal properties,and density functional theory studies of PMMA‐maghemite hybrid material

Maghemite (γ‐Fe₂O₃)‐poly(methyl methacrylate) (PMMA) nanocomposites were prepared by grafting 3‐(trimethoxy‐silyl) propyl methacrylate on the surface of maghemite nanoparticles, this process being followed by methyl methacrylate radical polymerization. Three different hybrids with 0.1, 0.5, and 2.5 wt% of maghemite nanoparticles were studied. The results indicate that these nanocomposites consist of a homogeneous PMMA matrix in which maghemite nanoparticles with a bimodal size distribution are embedded. The existence of covalent bonding between silane monomers and atoms on the maghemite surface was evidenced. AFM images showed a clear increase in surface roughness for increasing maghemite content. The thermal stability of PMMA‐maghemite nanocomposites is higher than that of pure PMMA and increases for increasing maghemite content. The results of our theoretical studies indicate that the electron density in the maghemite nanoparticle is not homogenous, the low electron density volumes being supposed to be radical trappers during PMMA decomposition, thus acting as a thermal stabilizer. POLYM. COMPOS., 51–60, 2016. © 2014 Society of Plastics Engineers     

Identification and quantification of prostaglandin E3 in renal medullary tissue of three strains of rats fed fish oil

Three strains of rats were fed a fish oil diet to verify their ability to incorporate and convert dietary eicosapentaenoic acid (20∶5ω3) into trienoic prostaglandins. Our results show that such conversion indeed occurs in kidney medullae homogenates. Specifically, the presence of prostaglandin E₃ (PGE₃) was established by gas chromatographic-mass spectrometric (GC-MS) analysis. That compound was conclusively identified by comparison of fragment ions and their relative intensities with those obtained from authentic PGE₃. Further evidence was provided by studying the recovery of exogenously added PGE₃. The crude ethyl acetate extracts of the medullary homogenates were methylated and cleaned up by liquid-gel chromatography with Lipidex-5000 prior to conversion to PGB₃ for GC-MS analysis. The PGE₃ was quantified by selected ion monitoring (SIM) with [3,3,4,4-²H₄PGE₂ as internal standard. The levels of PGE₃ were similar, about 3 ng/mg of wet tissue, in the 3 strains of rats. Identical in vivo conversion of the 20∶5ω3 fatty acid to PGE₃ could not be positively established by analysis of pooled urine specimens.     

Dynamics and control of solar thermochemical reactors

A general dynamic model for solar-driven thermochemical processes is formulated based on unsteady mass and energy conservation equations coupled to the reaction kinetics. It is applied to two pertinent high-temperature thermochemical reactors for fuel production that make use of concentrated solar energy as the source of process heat, namely: an indirectly irradiated batch-operated packed bed reactor for the carbothermic reduction of zinc oxide, and a directly irradiated continuously operated particle flow reactor for the steam-gasification of petcoke. Model parameter identification and validation is accomplished by comparing numerically simulated and experimentally measured temperatures and outlet product concentrations. A linear feedback controller was implemented using the LQG/LTR design method. Simulations of the controlled reactor system with real solar irradiation data indicates improved quality and steadiness of product composition throughout transient solar input phases and superior solar-to-chemical energy conversion efficiency.     

Mycotoxins produced by Fusarium genus in maize: determination by screening and confirmatory methods based on liquid chromatography tandem mass spectrometry

A confirmatory method for fusariotoxin analysis in maize meal, based on liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS), was developed, and compared with a previously published screening method, based on the same technique. By eluting selectively from a Carbograph-4 clean-up cartridge trichothecenes, fumonisins and macrocyclic lactones, and optimizing LC–MS/MS conditions for every chemical class, a sensitive and reliable determination was performed. Method quantification limits for confirmatory and screening methods were in the range 0.001–0.019 mg/kg and 0.003–0.125 mg/kg, respectively.     

Effects of Physiological and Pathological Urea Concentrations on Human Microvascular Endothelial Cells

Urea is the uremic toxin accumulating with the highest concentration in the plasma of chronic kidney disease (CKD) patients, not being completely cleared by dialysis. Urea accumulation is reported to exert direct and indirect side effects on the gastrointestinal tract, kidneys, adipocytes, and cardiovascular system (CVS), although its pathogenicity is still questioned since studies evaluating its side effects lack homogeneity. Here, we investigated the effects of physiological and pathological urea concentrations on a human endothelial cell line from the microcirculation (Human Microvascular Endothelial Cells-1, HMEC-1). Urea (5 g/L) caused a reduction in the proliferation rate after 72 h of exposure and appeared to be a potential endothelial-to-mesenchymal transition (EndMT) stimulus. Moreover, urea induced actin filament rearrangement, a significant increase in matrix metalloproteinases 2 (MMP-2) expression in the medium, and a significant up- or down-regulation of other EndMT biomarkers (keratin, fibrillin-2, and collagen IV), as highlighted by differential proteomic analysis. Among proteins whose expression was found to be significantly dysregulated following exposure of HMEC-1 to urea, dimethylarginine dimethylaminohydrolase (DDAH) and vasorin turned out to be down-regulated. Both proteins have been directly linked to cardiovascular diseases (CVD) by in vitro and in vivo studies. Future experiments will be needed to deepen their role and investigate the signaling pathways in which they are involved to clarify the possible link between CKD and CVD.     

Is Melanoma Progression Affected by Thyroid Diseases?

Clinical and epidemiological evidence indicate a relationship between thyroid diseases and melanoma. In particular, the hypothyroidism condition appears to promote melanoma spread, which suggests a protective role of thyroid hormones against disease progression. In addition, experimental data suggest that, in addition to thyroid hormones, other hormonal players of the hypothalamic–pituitary–thyroid (HPT) axis, namely the thyrotropin releasing hormone and the thyrotropin, are likely to affect melanoma cells behavior. This information warrants further clinical and experimental studies in order to build a precise pattern of action of the HPT hormones on melanoma cells. An improved knowledge of the involved molecular mechanism(s) could lead to a better and possibly personalized clinical management of these patients.     

Determination of selected mycotoxins in mould cheeses with liquid chromatography coupled to tandem with mass spectrometry

A simple and feasible method is described for analysing nine mycotoxins in cheese matrix. The method involves liquid extraction followed by high performance liquid chromatographic separation and mass spectrometric detection of the analytes, and allows the determination of aflatoxins B1, B2, G1, G2 and M1, ochratoxin A, mycophenolic acid, penicillic acid and roquefortine C simultaneously. Average recoveries of the mycotoxins from spiked samples at concentration levels of 5-200 µg kg^-1 ranged from 96-143%. Within-day relative standard deviations at these concentration levels varied from 2.3-12.1%. The limit of quantification for aflatoxin M1 was 0.6 µg kg^-1 and for the other compounds 5 µg kg^-1. The method developed was applied for analysing these mycotoxins in blue and white mould cheeses purchased from Finnish supermarkets. Roquefortine C was detected in all of the blue mould cheese samples in concentrations of 0.8-12 mg kg^-1. One blue cheese contained also 0.3 mg kg^-1 mycophenolic acid. The other investigated mycotoxins were absent in the samples.