Biomedical subjects
Publications and source records attributed to S Dai.
Highly dispersed uranium oxide nanocrystals supported on ordered mesoporous silica matrixes with large surface areas and porosities have been synthesized via a co-assembly methodology; the preliminary catalysis tests showed that these materials have a high catalytic activity for the thermal oxidation of volatile organic compounds (VOCs).
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A unique nanoporous sol-gel glass possessing a highly ordered porous structure (with a pore size of 153 A in diameter) was examined for use as a support material for enzyme immobilization. A model enzyme, alpha-chymotrypsin, was efficiently bound onto the glass via a bifunctional ligand, trimethoxysilylpropanal, with an active enzyme loading of 0.54 wt%. The glass-bound chymotrypsin exhibited greatly enhanced stability both in aqueous solution and organic solvents. The half-life of the glass-bound alpha-chymotrypsin was >1000-fold higher than that of the native enzyme, as measured either in aqueous buffer or anhydrous methanol. The enhanced stability in methanol, which excludes the possibility of enzyme autolysis, particularly reflected that the covalent binding provides effective protection against enzyme inactivation caused by structural denaturation. In addition, the activity of the immobilized alpha-chymotrypsin was also much higher than that of the native enzyme in various organic solvents. From these results, it appears that the glass-enzyme complex developed in the present work can be used as a high-performance biocatalyst for various chemical processing applications, particularly in organic media. Published by John Wiley & Sons
The promoter from rice tungro bacilliform badnavirus (RTBV) is expressed only in phloem tissues in transgenic rice plants. RF2a, a b-Zip protein from rice, is known to bind to the Box II cis element near the TATA box of the promoter. Here, we report that the full-length RTBV promoter and a truncated fragment E of the promoter, comprising nucleotides -164 to +45, result in phloem-specific expression of beta-glucuronidase (GUS) reporter genes in transgenic tobacco plants. When a fusion gene comprising the cauliflower mosaic virus 35S promoter and RF2a cDNA was coexpressed with the GUS reporter genes, GUS activity was increased by 2-20-fold. The increase in GUS activity was positively correlated with the amount of RF2a, and the expression pattern of the RTBV promoter was altered from phloem-specific to constitutive. Constitutive expression of RF2a did not induce morphological changes in the transgenic plants. In contrast, constitutive overexpression of the b-ZIP domain of RF2a had a strong effect on the development of transgenic plants. These studies suggest that expression of the b-Zip domain can interfere with the function of homologues of RF2a that regulate development of tobacco plants.
OBJECTIVE: To evaluate the effect of octreotide on the intragastric pH of patients with duodenal ulcer bleeding during the period of 24 hours and to observe if it can advance the effect of hemostasis by endoscopic injection of epinephrine. METHODS: Twenty-four patients with duodenal ulcer bleeding were randomly divided into three groups, eight in each. Patients in group 1 received an intravenous injection of 0.1 mg of octreotide followed by continuous intravenous drip of octreotide at a constant speed of 25 microg/h for 24 hours. The patients in group 2 received an intravenous injection of 0.1 mg of octreotide followed by continuous intravenous drip of octreotide at a constant speed of 42 microg/h for 24 hours. The patients in group 3 received an intravenous injection of 40 mg of omeprazole followed by continuous intravenous drip of omeprazole at a constant speed of 8 mg/h for 24 hours. Intragastric pH was continuously recorded with a pH meter. The patients with active ulcer bleeding was treated with injection of epinephrine via endoscope and then received intravenous drip of octreotide (with the same dosage as in group 1, n = 42) or omeprazole (with the same dosage as in group 3, n = 54) for 72 hours and were given omeprazole (20 mg Bid). RESULTS: The mean and median intragastric pH values among the patients in group 2 treated by a larger dosage of octreotide (6.7 +/- 0.5 and 6.9 +/- 0.4) were similar to those in the group 3 treated by omeprazole (6.8 +/- 0.4 and 7.0 +/- 0.4). There was no statistically significant difference between these two groups in percentage of intragastric pH above 4, 6, and 7 The mean and median of intragastric pH among the patients in group 1 treated by a smaller dosage of octreotide were statistically significantly smaller (5.2 +/- 0.5 and 5.4 +/- 0.4) than those in the omeprazole group. There was no statistically significant difference between octreotide treatment and omeprazole treatment in terms of volume of blood transfusion (0.7 +/- 0.5 vs. 0.6 +/- 0.4 L), rebleeding rate (11.6% vs. 12.9%), emergency operation rate (7.1% vs. 3.7%), and mortality (2.3% vs. 3.7%). CONCLUSION: Octreotide effectively inhibits the secretion of gastric acid. However, the dosage in common use clinically fails to increase the intragastric pH to the best situation needed for effective hemostasis. Only a large dosage (1.10 mg/d) works.
A double imprinting methodology was developed to synthesize novel materials with hierarchical structures. On the microporous level (1-3 A), metal ions served as template. On the mesoporous level (diameters of 25-40 A), micellar structures produced by self-assembly of surfactant molecules were used as templates. Removal of both metal ions and surfactant micelles resulted in the formation of imprints with different sizes within the silica matrix, each with a specific function. This research opens vast opportunities for the applications of ordered mesoporous materials in the area of molecular recognition such as separations, chemical sensors, and catalysts.
IgA is the predominant immunoglobulin class synthesized in humans and can be subdivided into two subclasses, IgA1 and IgA2, each encoded by a separate gene and differentially expressed depending on age and anatomical localization of the producing cells. Duplication of the alpha1 gene is frequently observed in selected populations. As this duplication may serve to enhance IgA-mediated immunity, we determined its effect on switching and production of IgA in human B cells. We developed a nested PCR strategy, involving sequencing the switch (S) alpha2 region, the only human S region not sequenced to date, to assess the proportion of cells switching to IgA1 and IgA2 in vivo. Our results show that there is no difference in the serum and salivary levels of IgA1 and IgA or rate of switching to IgA1 and IgA between normal donors and individuals carrying alpha1 gene duplications, suggesting involvement of a regulatory step in the production of IgA.
The behavior of complex pollution system in soil composed of aldicarb, a carbamate pesticide, and sodium dodecylbenzenesulfonate (SDBS), an anionic surfactant, was studied by the experiment of shaking sorption balance. The range of concentration of aldicarb and SDBS was 0.4-5.0 and 1-1000 mg/kg of dried soil, respectively. Linear sorption isotherm was well fitted for these two chemicals. SDBS can decrease the sorption of aldicarb in soil remarkably. While the concentration of SDBS increased from 0 to 1000 mg/kg, the linear sorption coefficient can be decreased by 50%. But aldicarb showed no effect on the sorption of SDBS in experiment. In addition the mechanism of the effect of SDBS on sorption of aldicarb was discussed.
OBJECTIVE: To investigate whether within-individual variation is a factor in the generally reported poor tracking of central body fat distribution (CBFD) during development and whether two measurements of CBFD during each measurement occasion would improve the estimate of tracking over time. METHODS: A longitudinal study compared the results of two measurements of body fat (BF) and CBFD during each measurement occasion to the results of one measurement of BF and CBFD during each occasion every 4 months over 1-3 y. A total of 345 boys and 333 girls in three age cohorts of 8, 11 and 14 y at baseline were examined. BF variables were: body mass index (BMI); fat mass and percentage body fat from bioelectrical impedance; two skinfold sums; and abdominal circumference. CBFD variables were: waist/hip and waist/thigh ratios; conicity; and log upper-lower skinfold ratio. RESULTS: Three-year tracking of BF varied from 0.79 to 0.90 for one- and from 0.81 to 0.93 for two-occasion measurements showing no apparent sex- or cohort-effects. Three-year tracking of CBFD was lower than that of BF (0.68-0.75), but improved significantly with two-occasion measurements (0.75-0.82). CONCLUSIONS: Within-individual variation is a significant factor in reported low tracking of CBFD in childhood. Estimates of tracking currently in the literature may underestimate the predictive value of CBFD, possibly because this research has used one-occasion measurement. The increased use of two-occasion measurement should significantly improve the tracking of CBFD during development and provide a more realistic understanding of its predictive value.
The GX2 growing mycelium shows excellent adsorptive capacity on the four kinds of anthraquinone dyes, however, due to the difference of molecular structure of dyes, the adsorption rates are different. Although the dyes show inhibiting effect on the growth of GX2, when the concentration of reactive brilliant blue KN-R is 250 and 400 mg/L, the adsorption rate of dye by the GX2 growing mycelium reaches 100% and 91.4%, respectively. With the increase of salinity (NaCl), the dry weight of GX2 mycelium increases; the diameter of granular mycelium decreases and its adsorption surface area increases accordingly, the salinity shows evident enhancement on the adsorption of reactive brilliant blue KN-R by GX2 growing mycelium in the range of 0%-2% salinity. The adsorption process is influenced by the concentration of carbon source as well, reactive brilliant blue KN-R with the concentration of 120 mg/L can be completely adsorbed only when the concentration of glucose is more than 2.5 g/L. The GX2 growing mycelium has better adsorptive capacity than resting living mycelium and dead mycelium.
The bindings of 3 kinds of aidehyde pollutants, formaldehyde, acetaldehyde, acrolein, with both prokaryotic and eukaryotic DNA, and their genotoxic effect and mechanism were conducted by the shifts of maximum UV absorption peak to determine binding effects and by HPLC to determine binding sites in vitro model system. The shifts of maximum UV absorption peak of prokaryotic DNA contaminated by 3 kinds of aldehyde pollutants are not significant; but after the DNA extracted from prokaryotic bacteria reacting with formaldehyde in tube, the shifts of maximum UV absorption peak of DNA are significant; the shifts of maximum UV absorption peak of eukaryotic DNA contaminated by 3 kinds of aldehyde pollutants are significant also. The reacition of acetaldehyde with dG reduced by NaBH4 was separated and detected by HPLC, the product was determined qualitatively as N2-ethaldeoxyguanosine adduct. The 3 kinds of aldehyde pollutants could bind with cellular DNA to express genotoxic effects; and the N2 site of deoxyguanosine is the possible covalent binding site.
A simple and rapid procedure for detection of low levels DNA damage caused by Aldicarb was developed and compared with some other methods. In the original position the gel was set in high-pH buffer to run electrophoresis after the diluent of bacteria or fragmentized organ was added into hole of agarose gel directly and cells were treated with detergent and high alkaline condition. The impact of Aldicarb to biological individual or ecosystem was assessed according to the quantity of DNA and the extent of DNA migration.
Sulfa drug wastewater was treated with anaerobic/aerobic process. The removal ratios of TOC reached about 50% in anaerobic phase and about 70% in aerobic phase respectively, while volume loading rate of TOC was about 1.2 kg/(m3.d) in anaerobic phase and about 0.6 kg/(m3.d) in aerobic phase. Removal of TOC in anaerobic phase was attributed to the reduction of sulfate.
Hybrid organic/inorganic sol-gel materials containing an encapsulated crown ether ligand were found to selectively remove 91.4 +/- 1.3% of Sr2+ from a solution containing excess of competing ions such as Ca2+. The crown ether ligand, 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-bis(malonate) ligand (Na4oddm), with known high affinity for Sr2+ was encapsulated in hydrophilic SiO2 through a simple sol-gel process. Washing the Sr(2+)-loaded gel with acid or ethylenediaminetetraacetic acid disodium salt recovered the Sr2+ from the sol-gel sorbent and regenerated the doped gel for subsequent Sr2+ intake. The approach reported here is a new alternative to the use of crown ethers in metal ion separation through, for example, solvent extraction or the use of sorbents containing chemically grafted crown ether ligands.
Microtiter plate wells modified with thin (approximately 20 microm) polymeric films capable of optically sensing macromolecular protamine and other polycationic species are described. The plates are prepared by coating the bottom of each well of a conventional 96-well polypropylene plate with an adherent polymer film (a mixture of poly(vinyl chloride) and polyurethane) containing a lipophilic 2',7'-dichlorofluorescein derivative. Surprisingly, optical response toward polycations is shown to result from the extraction of the fluorescein derivative from the polymer film into a lyophobic colloidal phase at the sample/film interface. This new phase is likely composed of a micellular-type ion pair complex between the analyte polycation from aqueous sample phase and the deprotonated form of the fluorescein derivative. Accumulation of the deprotonated fluorescein species in this interfacial region induces an absorbance change measured at 540 nm. Optimized plates can be used to sense protamine concentrations in the range of 0-100 microg/mL in 10 min with little or no response to physiological levels of common cationic species (Na+, K+, Ca2+, etc.). The modified plates are shown to be useful as simple optical detectors for measuring heparin levels in plasma via titrations with protamine and for monitoring protease activities (trypsin and plasmin) that cleave polycationic peptides/proteins such as protamine into smaller peptide fragments that are not detected by the sensing films. Assays for "clot busting" plasminogen activators (streptokinase, urokinase, and tissue plasminogen activator) are also demonstrated using this relatively simple microtiter plate-based polycation detection system.
The gamma subunit was initially identified as an auxiliary subunit of the skeletal muscle calcium channel complex. Evidence for the existence of further gamma subunits arose following the characterization of a genetic defect that induces epileptic seizures in stargazer mice. We present here the first account of a family of at least five putative gamma subunits that are predominantly expressed in brain. The gamma-2 and gamma-4 subunits shift the steady-state inactivation curve to more hyperpolarized potentials upon coexpression with the P/Q type alpha(1A) subunit. The coexpression of the gamma-5 subunit accelerates the time course of current activation and inactivation of the alpha(1G) T-type calcium channel.