Multivariate Optimization for the Development of a Fast and Simple Ultrasound-Assisted Extraction Procedure for Multielemental Determination in Tea Leaves by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES)

The current study describes a fast and efficient procedure of ultrasound-assisted extraction for determination of Ca, Mg, K, Na, Cu, Zn, Mn, and Al in tea leaves by inductively coupled plasma optical emission spectrometry (ICP OES). The variables of procedure were optimized using the Box–Behnken design and the conditions selected were nitric acid concentration (1.0 mol L^?1), sonication time (7 min), and sonication temperature (75 °C). The extraction efficiency was calculated using the analyte concentration obtained by a total digestion procedure as reference. Accuracy was confirmed by analysis of certified reference material of apple leaves (NIST 1515) and spinach leaves (NIST 1570a) using the procedure proposed. A statistical evaluation using Student’s t test showed that there is no significant difference between the value obtained with the proposed procedure and the certified value, at 95% confidence level. The proposed procedure was successfully applied and is a good alternative to conventional acid digestion procedure and can be applied to routine analysis for determination of Ca, Mg, K, Na, Zn, Mn, Cu, and Al in tea leaves used for the preparation of infusions.     

Method validation for the determination of total mercury in fish muscle by cold vapour atomic absorption spectrometry

A method was validated for the determination of total Hg in fish muscle using continuous flow cold vapour atomic absorption (CVAAS) after microwave digestion in closed vessels. The method was validated according to European Union Regulations 333/2007 and 657/2002, considering the maximum level for the metal in fish, established by European Union regulation 1881/2006. The procedure for determining linear range, selectivity, recovery, precision, trueness, decision limit (CCα), detection capability (CCβ), measurement uncertainty and robustness of the method is reported. The results of the validation process demonstrate the method fulfils the provisions of the Commission Regulation. The selectivity study indicated that there was no matrix effect on the calibration curve between the concentration range of 1.0 and 30.0 μg Hg l(-1). The mean recovery calculated at six levels of fortification was in the range of 94-104%. The limit of detection (LOD) and limit of quantification (LOQ) values were 4.90 and 15.7 μg kg(-1), while the CCα and CCβ values were 0.517 and 0.533 mg kg(-1), respectively, for the maximum contaminant level of 0.500 mg kg(-1). The relative expanded measurement uncertainty of the method was 0.055 mg kg(-1). The method was not affected by slight variations of some critical factors (ruggedness minor changes) as sample mass and volume of the HNO(3) and H(2)O(2) used in the digestion step. The method allowed accurate confirmation analyses of the CRM DORM 3. In fact, the Z-scores attained in a proficiency test round were well below the reference value of 2.0, proving the excellent performance of the laboratory.     

Lyocell混纺——给纺织工业带来的附加效益

Ｌｙｏｃｅｌｌ具有迄今为止在其他纤维素纤维中从未有过的纤维强力特性,Ｌｙｏｃｅｌｌ的产品性能可以有与高质量的、长绒棉相媲美,甚至在某种情况下优于长绒棉。可以认为,在未来纺织工业中,针得到广泛的应用。介绍了Ｌｙｏｃｅｌｌ纤维与胶纤维、莫代尔纤维或棉混纺品的性能。     

Treatment of saline wastewater contaminated with hydrocarbons by the photo-Fenton process

The application of the photo-Fenton process to the treatment of saline wastewater contaminated with hydrocarbons is investigated. Aqueous saline solutions containing raw gasoline were used as a model oil-field-produced water. The dependence on concentrations of the following reagents has been appropriately evaluated: hydrogen peroxide (100-200 mM), iron ions (0.5-1 mM), and sodium chloride (200-2000 ppm). The reactions were monitored by measurement of the absorption spectra and total organic carbon (TOC). Experimental results demonstrate that the photo-Fenton process is feasible for the treatment of wastewaters containing hydrocarbons, even in the presence of high concentrations of salt. The effect of the salt in this process is described through a series of reactions. A simple feedforward neural network model was found to correlate well the observed data for the degradation process.     

Methylmercury Causes Neurodegeneration and Downregulation of Myelin Basic Protein in the Spinal Cord of Offspring Rats after Maternal Exposure

Methylmercury (MeHg) is one of the most dangerous toxic pollutants spread throughout the earth. Chronic MeHg intoxication by contaminated food ingestion is the most common threat to human health, including impairment to the developing fetus. The present study aims at investigating the effects of maternal exposure to MeHg during gestation and lactation on the spinal cord of offspring. Pregnant rats received oral doses of MeHg (40 μg/kg/day) over a period of 42 days (21 gestation and 21 lactation). Control animals received the vehicle only. Total mercury concentration was measured in blood samples from offspring collected at the 41st postnatal day. Counting of motor neurons and immunoreactivity for myelin basic protein (MBP) were assessed in the spinal cords in both control and MeHg-intoxicated animals. Our results showed that MeHg promoted an increase in blood Hg levels. In addition, it caused a reduction in the number of spinal cord motor neurons as well as decreased MBP immunoreactivity in the cervical, thoracic and lumbar segments. Our present findings suggest that MeHg intoxication during rat pregnancy and lactation is associated with a pattern of motor neuron degeneration and downregulation of myelin basic protein in different segments of a developing spinal cord. Further studies are needed to establish the effect of MeHg intoxication in both young and adult rats.     

Ethanol-mediated neutrophil extravasation in feline pancreas

Ethanol is a common cause of both acute and chronic pancreatitis. Studies in other organs suggest that polymorphonuclear neutrophils activated by ethanol may cause tissue injury in a variety of conditions. The aim of this study was to investigate the effects of ethanol on neutrophil extravasation in the feline pancreas. Pancreata were isolated and perfused at different flow rates with varying concentrations of ethanol in either a physiological or neutrophil depleted perfusate. Neutrophil extravasation was assessed by measuring pancreatic tissue myeloperoxidase (MPO) activity. Ethanol at 2.5% (54.25 mmol/liter) was the lowest concentration that still caused significant neutrophil extravasation (3.1+/-0.8 vs 1.9+/-0.2 units, P<0.05) and was accompanied by an increase in vascular resistance of 15%. Reduction of pancreatic perfusion by 15% did not significantly increase neutrophil extravasation. (1.1+/-0.3 vs 1.6+/-0.2 units, NS) Perfusion of the pancreas with neutrophil-depleted blood containing either ethanol or saline, followed by perfusion with an ethanol-free perfusate, showed an increase in neutrophil extravasation in the ethanol group compared to the control group (3.2+/-0.9 vs 1.9+/-0.2 units, P<0.05). In conclusion, ethanol causes neutrophil extravasation in the feline pancreas independent of blood flow changes and occurs despite the absence of direct neutrophil exposure to ethanol.     

The control of protein release from poly(DL-lactide co-glycolide) microparticles by variation of the external aqueous phase surfactant in the water-in oil-in water method

A unique feature of p21 that distinguishes it from the other cyclin-dependent kinase (CDK) inhibitors is its ability to associate with the proliferating cell nuclear antigen (PCNA), an auxiliary factor for DNA polymerases delta and epsilon. While it is now well established that inhibition of cyclin/CDK complexes by p21 can result in G1 cell cycle arrest, the consequences of p21/PCNA interaction on cell cycle progression have not yet been determined. Here, we show, using a tetracycline-regulated system, that expression of wild-type p21 in p53-deficient DLD1 human colon cancer cells inhibits DNA synthesis and causes G1 and G2 cell cycle arrest. Similar effects are observed in cells expressing p21CDK-, a mutant impaired in the interaction with CDKs, but not in cells expressing p21PCNA-, a mutant deficient for the interaction with PCNA. Analysis of cells treated with a p21-derived PCNA-binding peptide provides additional evidence that the growth inhibitory effects of p21 and p21CDK result from their ability to bind to PCNA. Our results suggest that p21 might inhibit cell cycle progression by two independent mechanisms, inhibition of cyclin/CDK complexes, and inhibition of PCNA function resulting in both G1 and G2 arrest.