Fabrication of iron oxide@MOF-808 as a sorbent for magnetic solid phase extraction of benzoylurea insecticides in tea beverages and juice samples.

A novel magnetic metal organic framework composite (Fe3O4@MOF-808) was synthesized by a facile solvothermal method and applied as an adsorbent for the magnetic solid phase extraction (MSPE) of benzoylurea insecticides (BUs) from tea beverages and juice samples. The prepared materials were characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), vibrating sample magnetometry measurements and N2 adsorption-desorption experiments. The adsorption (adsorbent amount, extraction time and pH) and elution (elution solvent, elution volume and time) parameters were investigated in detail. Under the optimized experimental conditions, Fe3O4@MOF-808 exhibited simpler and better reusability than commercial C18, with an equivalent adsorption effect. Notably, π-π interactions, hydrophobic interactions and hydrogen bonding interactions contributed to the good adsorption of BUs by Fe3O4@MOF-808. Finally, a simple and sensitive method was established using Fe3O4@MOF-808-based MSPE coupled with high-performance liquid chromatography (HPLC). It provided low limits of detection (0.04-0.15 ng/mL), wide linear ranges (0.15-50 ng/mL) and satisfactory recoveries (84.6-98.3%). The proposed method was successfully applied for the fast and sensitive determination of BUs in tea beverages and juice samples.

High-permeability alternatives to current dialyzers performing both high-flux hemodialysis and postdilution online hemodiafiltration.

Most high-flux dialyzers can be used in both hemodialysis (HD) and online hemodiafiltration (OL-HDF). However, some of these dialyzers have higher permeability and should not be prescribed for OL-HDF to avoid high albumin losses. The aim of this study was to compare the safety and efficacy of a currently used dialyzer in HD and OL-HDF with those of several other high permeability dialyzers which should only be used in HD. A prospective, single-center study was carried out in 21 patients. Each patient underwent 5 dialysis sessions with routine dialysis parameters: 2 sessions with Helixone (HD and postdilution OL-HDF) and 1 session each with steam sterilized polyphenylene, polymethylmethacrylate (PMMA), and medium cut-off (MCO) dialyzers in HD treatment. The removal ratios (RR) of urea, creatinine, ß2 -microglobulin, myoglobin, prolactin, α1 -microglobulin, α1 -acid glycoprotein, and albumin were compared intraindividually. A proportional part of the dialysate was collected to quantify the loss of various solutes, including albumin. Urea and creatinine RRs with the Helixone-HDF and MCO dialyzers were higher than with the other 3 dialyzers in HD. The ß2 -microglobulin, myoglobin and prolactin RRs with Helixone-HDF treatment were significantly higher than those obtained with all 4 dialyzers in HD treatment. The ß2 -microglobulin value obtained with the MCO dialyzer was also higher than that obtained with the other 3 dialyzers in HD treatment. The myoglobin RR with MCO was higher than those obtained with Helixone and PMMA in HD treatment. The prolactin RR with Helixone-HD was significantly lower than those obtained in the other 4 study sessions. The α1 -microglobulin and α1 - acid glycoprotein RRs with Helixone-HDF were significantly higher than those obtained with Helixone and PMMA in HD treatment. The albumin loss varied from 0.54 g with Helixone-HD to 3.3 g with polyphenylene. The global removal score values ((UreaRR + ß2 -microglobulinRR + myoglobinRR + prolactinRR + α1 -microglobulinRR + α1 -acid glycoproteinRR - albuminRR )/6) were 43.7% with Helixone-HD, 47.7% with PMMA, 54% with polyphenylene, 54.8% with MCO and 59.6% with Helixone-HDF, with significant differences. In conclusion, this study confirms the superiority of OL-HDF over HD with the high-flux dialyzers that allow both treatments. Although new dialyzers with high permeability can only be used in HD, they are in an intermediate position and some are very close to OL-HDF.

Urine metabolome analysis by gas chromatography-mass spectrometry (GC-MS): Standardization and optimization of protocols for urea removal and short-term sample storage.

BACKGROUND: Before derivatization, urine analyzed by gas chromatography-mass spectrometry (GC-MS) requires the complete removal of urea to avoid interferences. We aimed at establishing the most effective sample pretreatment for urea removing; moreover, we explored the impact of two short-term sample storage conditions on urine metabolome. METHODS: 92 aliquots were obtained from a single sample collected from a healthy adult; they were divided into 6 groups. Group 1 consisted of untreated aliquots while groups 2-6 differed from each other for the addition of various defined urease solution volumes combined with either 30 min or 1-hour sonication time. Urine sample storage was tested by comparing 20 fresh aliquots analyzed after collection with 20 aliquots frozen at -80 °C for 72 h. RESULTS: the most effective protocol consisted of the combination between 200 µL urease solution with 1-h sonication time; urease solution volumes >200 µL increase the risk to underestimate metabolite peaks because of sample dilution. Short-term storage of samples at -80 °C pointed out significant changes in the urine metabolic profile compared with that of fresh samples. CONCLUSIONS: our study confirms the importance of urea removal for a reliable recognition and quantitation of metabolites; urine short-term storage at -80 °C should be carefully reconsidered.

Mollecarbamates, Molleureas, and Molledihydroisoquinolone, o-Carboxyphenethylamide Metabolites of the Ascidian Didemnum molle Collected in Madagascar.

The extract of a sample of the tunicate Didemnum molle (MAY13-117) collected in Mayotte afforded eight new metabolites, mollecarbamates A-D (1-4) and molleureas B-E (5-8), along with the two known natural products, N,N'-diphenylethyl urea (10) and molleurea A (11). Another sample of D. molle (MAD11-BA065) collected in Baie des Assassins, Madagascar, afforded molledihydroisoquinolone (9). Mollecarbamates 1-4 are a family of compounds that possess repeating o-carboxyphenethylamide units and a carbamate moiety, while the molleureas 5-8 contain tetra- and penta-repeating carboxyphenethylamide units and a urea bridge in different positions. Molledihydroisoquinolone (9) is a cyclic form of o-carboxyphenethylamide. We propose that these unique natural products are most probably produced by an unprecedented biosynthetic pathway that contains a yet unknown chorismate mutase variant. The structures of the compounds were elucidated by interpretation of the data from 1D and 2D NMR, HRESIMS, and MS/MS analyses of the positive ESIMS experiments. Compounds 1-8 were tested against pathogenic bacteria and in a cytoprotective HIV cell based assay but did not show any significant effects in these assays.

High-repetition rate laser ablation coupled to dielectric barrier discharge postionization for ambient mass spectrometry.

Most ambient sample introduction and ionization techniques for native mass spectrometry are highly selective for polar agents. To achieve a more general sensitivity for a wider range of target analytes, a novel laser ablation dielectric barrier discharge (LA DBD) ionization scheme was developed. The approach employs a two-step mechanism with subsequent sample desorption and post-ionization. Effective ablation was achieved by the second harmonic output (λ=532nm) of a diode pumped Nd:YVO4 laser operating at a high-repetition rate of several kHz and pulse energies below 100µJ. The ejected analyte-containing aerosol was consecutively vaporized and ionized in the afterglow of a DBD plasma jet. Depending on their proton affinity the superexcited helium species in this afterglow produced analyte ions as protonated and ammoniated species, as well as radical cations. The optimization procedure could corroborate underlying conceptual consideration on the ablation, desorption and ionization mechanisms. A successful detection of a variety of target molecules could be shown from the pharmaceutical ibuprofen, urea, the amino acids l-arginine, l-lysine, the polymer polyethylene glycol, the organometallic compound ferrocene and the technical mixture wild mint oil. For a reliable evaluation of the introduced detection procedure spectra from the naturally abundant alkaloid capsaicin in dried capsicum fruits were recorded.

A dimeric urea of the bisabolene sesquiterpene from the Okinawan marine sponge Axinyssa sp. inhibits protein tyrosine phosphatase 1B activity in Huh-7 human hepatoma cells.

Protein tyrosine phosphatase 1B (PTP1B) plays an important role as a negative regulator of the insulin and leptin signaling pathways. Therefore, this enzyme is regarded as an attractive therapeutic target for the treatment of type 2 diabetes and obesity. Our screening program for PTP1B inhibitors led to the isolation of four sesquiterpenes and sterol: N,N'-bis[(6R,7S)-7-amino-7,8-dihydro-α-bisabolen-7-yl]urea (1), (6R,7S)-7-amino-7,8-dihydro-α-bisabolene (2), (1R,6S,7S,10S)-10-isothiocyanato-4-amorphene (3), axinisothiocyanate J (4), and axinysterol (5) from the marine sponge Axinyssa sp. collected at Iriomote Island. Of these, compound 1 was the most potent inhibitor of PTP1B activity (IC50=1.9µM) without cytotoxicity at 50µM in two human cancer cell lines, hepatoma Huh-7 and bladder carcinoma EJ-1 cells. Compound 1 also moderately enhanced the insulin-stimulated phosphorylation levels of Akt in Huh-7 cells. Therefore, compound 1 has potential as a new type of anti-diabetic drug candidate possessing PTP1B inhibitory activity.

[ELEMENTS OF THE LOW MOLECULAR WEIGHT CHAIN OF ANTIOXIDANT DEFENSE IN TISSUES OF THE BLACK SEA MOLLUSC ANADARA KAGOSHIMENSIS BRUGÙIERE].

The content of reduced glutathione (GSH) and the activity of the coupled with it antioxidant enzymes - glutathione peroxidase and glutathione reductase as well the level of glucose, carbamide and amino acids were investigated in the hepatopancreas, gills and foot of the Black, Sea mollusk Anadara kagoshimensis. The highest content of GSH and the highest activity of glutathione peroxidase were found in mollusk foot, evidencing the active antioxidant role of glutathione played both within composition of this enzyme and independently. The maximal content of glucose, amino acids and carbamide was in the hepatopancreas and gills and the minimal - in the anadara's foot. The possible involvement and role of these low molecular weight antioxidants in the defense of mollusk tissues against action of free radical oxidation and in providing adaptation reactions of anadara in hypoxic habitats are considered. Key words: antioxidant complex, glutathione, glucose, carbamide, amino acids, anadara Anadara kagoshimensis, Black Sea.

Flow injection analysis biosensor for urea analysis in urine using enzyme thermistor.

There is a need for analytical methods capable of monitoring urea levels in urine for patients under clinical monitoring to appraise renal function. Herein, we present a practical method to quantify levels of urea in human urine samples using flow injection analysis-enzyme thermistor (FIA-ET) biosensor. The biosensor comprises a covalently immobilized enzyme urease (Jack bean) on aminated silica support, which selectively hydrolyzes the urea present in the sample. Under optimized conditions, the developed biosensor showed a linear response in the range of 10-1,000 mM, R (2) = 0.99, and response time of 90 s in 100 mM phosphate buffer (PB) (flow rate of 0.5 mL/min, sample volume of 0.1 mL, and pH 7.2). The urea-spiked human urine samples showed minimal matrix interference in the range of 10-1,000 mM. Recoveries were obtained (92.26-99.80 %) in the spiked urine samples. The reliability and reproducibility of the developed biosensor were found satisfactory with percent relative standard deviation (% RSD) = 0.741. The developed biosensor showed excellent operational stability up to 30 weeks with 20 % loss in original response when used continuously at room temperature. These results indicate that the developed biosensor could be very effective to detect low and high levels of urea in urine samples.

Cultivos discontinuos alimentados con urea de la cianobacteria Phormidium sp. en función de la salinidad y edad del cultivo / Urea fed-batch cultures of the cyanobacterium Phormidium sp. as a function of the salinity and age of cultures

Se comparó la eficiencia de sistemas de cultivos discontinuos alimentados versus cultivos discontinuos convencionales, en cuanto a concentración de nitrógeno, adicionando 0,2 mM de urea cada tres días al final de la fase exponencial, durante 21 días. Se realizaron cultivos con un volumen de 1500 mL a 15 y 35 UPS de salinidad, enriquecidos con medio ALGAL 8mM NaNO3, a 238 µmol q m-2 s-1, aireación constante, fotoperiodo 12:12 horas y temperatura de 29 ±3°C. Phormidium sp. posee la capacidad de hidrolizar la urea; mostrando una asimilación de 65±7,07% de la misma, con la mayor producción (p<0,05) de clorofila a, ficocianina y proteínas de 20,26±1,24; 203,47±12,83 y 707,87±28,47 µg mL-1en los cultivos alimentados. La producción de pigmentos vario en el tiempo, independientemente a la salinidad y sistema de cultivo, mientras que la producción de proteínas y carbohidratos totales fue directamente proporcional a la edad del cultivo, con valores máximos de 612,74 ± 5,41 µg mL-1 y 8,96±0,08 mg mL-1 respectivamente a los 31 días. La síntesis de lípidos y EPS fueron influenciadas (p<0,05) por la salinidad, presentando los máximos de lípidos a 15 UPS con 12,22±2,91µg mL-1, y los EPS se incrementaron a 35 UPS con 2,00 ± 0,26 y 2,03 ± 0,15 mg mL-1. Estos resultados determinan que los cultivos de Phormidium sp. alimentados con urea y a salinidades de 15 y 35 UPS, representan una alternativa económica para la producción de clorofila a, ficocianina y proteínas, incrementándose un 31,04; 40,72 y 31,94 % respectivamente en comparación con cultivos no alimentados.

Fed-batch system efficiency versus batch cultures was compared in relation to nitrogen concentration, adding 0,2mM urea at the end of the exponential phase, during 21 days. Cultures were carried out in 1500 mL to 1.5 and 3.5 UPS of salinity, enriched with Algal medium 8mM NaNO3, 238 mol q m-2 s-1, constant aeration, photoperiod 12:12 h. and 29 ±3°C. Phormidium sp. is able to hydrolyze urea; showing a total assimilation of 65±7.07%, with the highest (p< 0.05) chlorophyll a, phycocyanin and protein production of 20.26 ± 1.24, 203.47 ± 12.83 and 707.87 ± 28.47 µg mL-1 in the fed-batch cultures. On the other hand, pigment production varies in time, regardless salinity and culture system. Proteins and total carbohydrate production were directly proportional to the age of cultures, with maximum values of 612.74 ± 5.41 µg mL-1 and 8.96 ± 0.08 mg mL-1, respectively. Lipid and EPS were influenced (p< 0.05) by salinity, showing maximum of lipids at 15 UPS with 12.22±2.91 µg mL-1, and EPS at 15 and 35 UPS with 2.00 ± 0.26 and 2.03 ± 0.15 mg mL-1. These results determine that Phormidium sp. cultures fed with urea, to salinities of 15-35 UPS, represent an economic alternative for chlorophyll a, phycocyanin and protein production, with an increase of 31.04, 40.72 and 31.94% respectively in comparison with non-fed cultures.

A facile and efficient strategy to enhance hydrophilicity of zwitterionic sulfoalkylbetaine type monoliths.

In order to prepare zwitterionic HILIC monolithic columns with high polarity, the highly hydrophilic monomer N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA) and crosslinker N,N'-methylenebisacrylamide (MBA) were employed for developing a novel sulfoalkylbetaine type stationary phase. The polymerization parameters were systematically optimized in order to obtain a satisfactory performance for column permeability, mechanical stability, hydrophilicity, efficiency and selectivity. Compared to the previously reported poly(N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine-co-ethylene dimethacrylate) (poly(SPE-co-EDMA)) monolith and the poly(SPDA-co-EDMA) monolith that we developed, a significantly enhanced hydrophilicity was obtained on the poly(SPDA-co-MBA) monolithic column, illustrated by the lowered critical composition of the mobile phase corresponding to the transition from the HILIC to the RP mode. Excellent permeability, reproducibility and stability were achieved on this optimized poly(SPDA-co-MBA) monolith. A column efficiency of 70,000plates/m was obtained for the analysis of bases at a linear velocity of 1.95mm/s. As expected, by studying the influence of mobile phase pH and salt concentration on their retention, a weak electrostatic repulsion interaction for negatively charged analytes was also observed at low organic solvent content on the poly(SPDA-co-MBA) monolithic column. The final optimized poly(SPDA-co-MBA) monolith exhibited good selectivity for a series of polar compounds, such as phenols, bases, benzoic acid derivatives, small peptides, urea and allantoin.

Use of electroporation and reverse iontophoresis for extraction of transdermal multibiomarkers.

BACKGROUND: Monitoring of biomarkers, like urea, prostate-specific antigen (PSA), and osteopontin, is very important because they are related to kidney disease, prostate cancer, and ovarian cancer, respectively. It is well known that reverse iontophoresis can enhance transdermal extraction of small molecules, and even large molecules if reverse iontophoresis is used together with electroporation. Electroporation is the use of a high-voltage electrical pulse to create nanochannels within the stratum corneum, temporarily and reversibly. Reverse iontophoresis is the use of a small current to facilitate both charged and uncharged molecule transportation across the skin. The objectives of this in vitro study were to determine whether PSA and osteopontin are extractable transdermally and noninvasively and whether urea, PSA, and osteopontin can be extracted simultaneously by electroporation and reverse iontophoresis. METHODS: All in vitro experiments were conducted using a diffusion cell assembled with the stratum corneum of porcine skin. Three different symmetrical biphasic direct currents (SBdc), five various electroporations, and a combination of the two techniques were applied to the diffusion cell via Ag/AgCl electrodes. The three different SBdc had the same current density of 0.3 mA/cm(2), but different phase durations of 0 (ie, no current, control group), 30, and 180 seconds. The five different electroporations had the same pulse width of 1 msec and number of pulses per second of 10, but different electric field strengths of 0 (ie, no voltage, control group), 74, 148, 296, and 592 V/cm. Before and after each extraction experiment, skin impedance was measured at 20 Hz. RESULTS: It was found that urea could be extracted transdermally using reverse iontophoresis alone, and further enhancement of extraction could be achieved by combined use of electroporation and reverse iontophoresis. Conversely, PSA and osteopontin were found to be extracted transdermally only by use of reverse iontophoresis and electroporation with a high electrical field strength (> 296 V/cm). After application of reverse iontophoresis, electroporation, or a combination of the two techniques, a reduction in skin impedance was observed. CONCLUSION: Simultaneous transdermal extraction of urea, PSA, and osteopontin is possible only for the condition of applying reverse iontophoresis in conjunction with high electroporation.

Optimization production of acid urease by Enterobacter sp. in an approach to reduce urea in Chinese rice wine.

Urea in alcoholic beverages is a precursor of ethyl carbamate, which is carcinogenic. Acid urease (EC 3.5.1.5) is regarded as a good approach to scavenge the urea. The acid urease of Enterobacter sp. R-SYB082, with lower optimum pH than the widely used commercial acid urease, exhibited a urea removal rate of 66.5% in Chinese rice wine, which was higher than that of the commercial acid urease (58.9%). The production of the acid urease was optimized from 1,100 to 2,504 U L(-1) by an approach which includes the optimization of initial glucose concentration, the elevation of anaerobic level of the reactor by charging CO(2) and in vitro natural activation of the target enzyme by simple cold storage (4°C). These would open up the possibility for developing industrial application of this acid urease for producing high-quality Chinese rice wine.

Phosphorylation of GRK1 and GRK7 by cAMP-dependent protein kinase attenuates their enzymatic activities.

Phosphorylation of G protein-coupled receptors is a critical step in the rapid termination of G protein signaling. In rod cells of the vertebrate retina, phosphorylation of rhodopsin is mediated by GRK1. In cone cells, either GRK1, GRK7, or both, depending on the species, are speculated to initiate signal termination by phosphorylating the cone opsins. To compare the biochemical properties of GRK1 and GRK7, we measured the K(m) and V(max) of these kinases for ATP and rhodopsin, a model substrate. The results demonstrated that these kinases share similar kinetic properties. We also determined that cAMP-dependent protein kinase (PKA) phosphorylates GRK1 at Ser(21) and GRK7 at Ser(23) and Ser(36) in vitro. These sites are also phosphorylated when FLAG-tagged GRK1 and GRK7 are expressed in HEK-293 cells treated with forskolin to stimulate the endogenous production of cAMP and activation of PKA. Rod outer segments isolated from bovine retina phosphorylated the FLAG-tagged GRKs in the presence of dibutyryl-cAMP, suggesting that GRK1 and GRK7 are physiologically relevant substrates. Although both GRKs also contain putative phosphorylation sites for PKC and Ca(2+)/calmodulin-dependent protein kinase II, neither kinase phosphorylated GRK1 or GRK7. Phosphorylation of GRK1 and GRK7 by PKA reduces the ability of GRK1 and GRK7 to phosphorylate rhodopsin in vitro. Since exposure to light causes a decrease in cAMP levels in rod cells, we propose that phosphorylation of GRK1 and GRK7 by PKA occurs in the dark, when cAMP levels in photoreceptor cells are elevated, and represents a novel mechanism for regulating the activities of these kinases.

Breath sample collection through the nostril reduces false-positive results of 13C-urea breath test for the diagnosis of helicobacter pylori infection.

BACKGROUND: One of the disadvantages of '3C-urea breath test is possible interference by urease activity not related to Helicobacterpylori. AIMS: We design the simple and non-invasive modification to avoid the contamination of 13CO(2) produced in the mouth. PATIENTS AND METHODS: One hundred and twenty-nine patients who underwent diagnostic upper endoscopy were enrolled. Within 1 week of the endoscopic procedure, each patient received the modified 13C-urea breath test. Breath samples were collected at baseline and at 1, 3, 5, 10, 15, 20 and 30 min after ingestion of 100 mg 13C-urea solution through the mouth and the nostril at each time point. RESULTS: The breath delta13CO2 value through the nostril at 1 min was already higher in H. pylori-positive patients than in H. pylori-negative patients. Using 2.5% as the cut-off value, the sensitivity and specificity of the modified 13C-urea breath test at 20 min were both 100%, whereas the sensitivity and specificity of the standard 13C-urea breath test were 97.7 and 94%, respectively, using 3% as the cut-off value. CONCLUSIONS: The modified 13C-urea breath test in which breath samples are collected through the nostril provides an easy way of avoiding false-positive results for the detection of H. pylori infection.

Formaldehyde and urea removal in a denitrifying granular sludge blanket reactor.

Simultaneous formaldehyde biodegradation, urea hydrolysis and denitrification in anoxic batch assays and in a continuous laboratory anoxic reactor were investigated. In batch assays, the initial formaldehyde biodegradation rate was around 0.7 g CH(2)Og VSS(-1)d(-1) and independent of the urea concentration (90- 370 mg N-NH(2)CONH(2)l(-1)). Urea was completely hydrolyzed to ammonium in the presence of 430 mg l(-1) formaldehyde and complete denitrification took place in all cases (125 mg N-NO(-)(3)l(-1)). Formaldehyde removal efficiencies above 99.5% were obtained in a lab-scale denitrifying upflow sludge blanket reactor at organic loading rates between 0.37 and 2.96 kg CODm(-3)d(-1) (625-5000 mg CH(2)Ol(-1)). The urea loading rate was increased from 0.06 to 0.44 kg Nm(-3)d(-1) (100-800 mg N-NH(2)CONH(2)l(-1)) and hydrolysis to ammonium was around 77.5% at all loading rates. The denitrification process was always almost complete (100-800 mg N-NO(3)(-)l(-1)), due to the high COD/N ratio of 6.7 in the influent. A minimum value of 3.5 was found to be required for full denitrification. The composition of the biogas indicated that denitrification and methanogenesis occurred simultaneously in the same unit. A good granulation of the sludge was observed.

Dialyzer performance in the HEMO Study: in vivo K0A and true blood flow determined from a model of cross-dialyzer urea extraction.

Inlet and outlet blood urea concentrations (Cin and Cout) can be used to directly measure dialyzer performance if simultaneous blood flow measurements (Qb) are available. Dialyzer clearance, for example, is the product of the urea extraction ratio [ER = (Cin - Cout)/Cin] and Qb. Urea concentrations are measured routinely in all hemodialysis clinics, but Qb is usually reported as the product of the pump rotational speed and pump segment stroke volume, which can be inaccurate at high flow rates. Dialyzer urea extraction is also a function of Qb, dialysate flow (Qd), and the membrane permeability-area coefficient (K0A) for urea. To determine true in vivo values for Qb and K0A in the absence of direct flow measurements, we developed a model based on an existing mathematical equation for hemodialyzer ER under conditions of countercurrent flow. Qb, K0A, and other variables were adjusted to fit the modeled ER to ER measured in 1,285 patients treated with Qb that ranged from 200 to 450 ml/min during the HEMO Study. Fitting was performed by least squares nonlinear regression using parametric and nonparametric methods for estimating true flow. As Qb rose above 250 ml/min, both methods for estimating actual Qb showed increasing deviations from the flow reported by the blood pump meter. Modeled values for K0A differed significantly among dialyzer models, ranging from 71% to 96% of the in vitro values. The previously described 14% increase in K0A, as Qd increased in vitro from 500 to 800 ml/min, was much less in vivo, averaging only 5.5 +/- 1.5% higher. Dialyzer reprocessing was associated with a 6.3 +/- 1.0% reduction in K0A and an approximate 2% fall in urea clearance per 10 reuses (p < 0.001). Multiple regression analysis showed a small but significant dialysis center effect on ER but no independent effects of other variables, including the ultrafiltration rate, diabetic status, race, ethnicity, sex, method of reuse, treatment time, access recirculation, and use of central venous accesses. The new algorithm allowed a more accurate determination of true Qb and in vivo K0A in the absence of direct flow measurements in a large population treated with a wide range of blood flow rates. Application of this technique for more than 1000 patients in the HEMO Study confirmed that in vitro measurements using simple crystalloid solutions cannot readily substitute for in vivo measurements of dialyzer function, and permitted a more accurate calculation of each patient's prescribed dialysis dose and urea volume.

Coupled BAS and anoxic USB system to remove urea and formaldehyde from wastewater.

Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor. The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification. In a first step, individual experiments were carried out to investigate the effects of both compounds on the nitrifying and denitrifying biomass. The BAS reactor was fed with a synthetic medium containing 500 mg N-NH4(+)l(-1) and 100mg N-urea l(-1), that were added continuously to this medium. Neither urea hydrolysis nor inhibition of nitrification was observed. Nitrification efficiency decreased when formaldehyde was fed during shocks at concentrations of 40, 80 and 120 mg C-formaldehyde l(-1). The anoxic USB reactor was fed with a synthetic medium containing nitrate, formaldehyde and urea. Concentrations of formaldehyde in the reactor of 100-120 mg C-formaldehyde l(-1) caused a decrease in the denitrification and urea hydrolysis rates. In a second step, the coupled system was operated at recycling ratios (R) of 3 and 9. Fed C/N ratios of 0.58, 1.0 and 1.5 g C-formaldehyde g(-1) N-NH4(+) were used for every recycling ratio. The maximum nitrogen removal percentages were achieved at a C/N ratio of 1.0 g C-formaldehyde g(-1) N-NH4(+) for both recycling ratios. A fed C/N ratio of 1.5 g C-formaldehyde g(-1) N-NH4(+) caused a decrease in the efficiency of the system with respect to nitrogen removal, due to the presence of formaldehyde in the BAS reactor, which decreased the nitrification. Formaldehyde was completely removed in the BAS reactor and a heterotrophic layer formed around the nitrifying biofilm.

Use of protein folding reagents.

The reagents and methods for purification of the denaturants guanidine hydrochloride (guanidine-HCl) and urea are described. Sulfhydryl reagents (reducing agents) and "oxido-shuffling" (or oxidative regeneration) systems are also discussed.

Electrically driven microseparation methods for pesticides and metabolites: III. Capillary electrochromatography with novel silica-based stationary phases having a surface-bound surfactant moiety.

A silica-based stationary phase with surface bound silylpropyl trialkylammonium functions was introduced and evaluated in the capillary electrochromatography of alkylbenzenes and pesticides. This stationary phase is referred to as octadecyldimethyl(3-trimethoxysilylpropyl) ammonium-silica (ODAS) and has quaternary amine functions that generate an anodic electroosmotic flow (EOF) and octadecyl functions that are responsible for solute retention by a reversed-phase chromatography mechanism. The ODAS stationary phase was characterized over a wide range of elution conditions in term of EOF and retention behavior of alkylbenzene homologous series. The ODAS stationary phase proved useful in the separation of pesticides as well as in the on-column preconcentration of dilute pesticide samples, thus permitting the detection of solution at 7 x 10(-7) M using a UV detector.