Biomedical subjects

Yang Cai

Publications and source records attributed to Yang Cai.

17 recordsLinked to original sources

PubMed2006

An evaluation on the efficacy and safety of amlexanox oral adhesive tablets in the treatment of recurrent minor aphthous ulceration in a Chinese cohort: a randomized, double-blind, vehicle-controlled, unparallel multicenter clinical trial.

OBJECTIVE: The objectives of this study were to clinically determine the topical efficacy and safety of amlexanox oral adhesive tablets in the treatment of recurrent minor aphthous ulcerations (MiRAU) in a Chinese cohort. STUDY DESIGN: A randomized, double-blind, vehicle-controlled, unparallel multicenter clinical trial was carried out. The tablets were applied by subjects themselves 4 times a day for 5 days. Four parameters (pain scale, size change, degree of erythema and exudation, and efficacy index) were recorded both before (baseline) and during the trial (on the morning of days 4 and 6). RESULTS: There were 104 and 108 subjects who fulfilled the trial in the amlexanox group and the vehicle-control group, respectively. Group differences for all parameters but degree of erythema and exudation of day 4 were statistically significant both for the day 4 visit and the day 6 visit (P < .05). No systemic side effects were reported. CONCLUSIONS: Amlexanox oral adhesive tablets are effective and safe in reducing aphthous ulcer pain and lesion size, as well as erythema and exudation in this Chinese cohort.

Adhesives↗

PubMed2005

Functional differentiation of bundle sheath and mesophyll maize chloroplasts determined by comparative proteomics.

Chloroplasts of maize (Zea mays) leaves differentiate into specific bundle sheath (BS) and mesophyll (M) types to accommodate C4 photosynthesis. Consequences for other plastid functions are not well understood but are addressed here through a quantitative comparative proteome analysis of purified M and BS chloroplast stroma. Three independent techniques were used, including cleavable stable isotope coded affinity tags. Enzymes involved in lipid biosynthesis, nitrogen import, and tetrapyrrole and isoprenoid biosynthesis are preferentially located in the M chloroplasts. By contrast, enzymes involved in starch synthesis and sulfur import preferentially accumulate in BS chloroplasts. The different soluble antioxidative systems, in particular peroxiredoxins, accumulate at higher levels in M chloroplasts. We also observed differential accumulation of proteins involved in expression of plastid-encoded proteins (e.g., EF-Tu, EF-G, and mRNA binding proteins) and thylakoid formation (VIPP1), whereas others were equally distributed. Enzymes related to the C4 shuttle, the carboxylation and regeneration phase of the Calvin cycle, and several regulators (e.g., CP12) distributed as expected. However, enzymes involved in triose phosphate reduction and triose phosphate isomerase are primarily located in the M chloroplasts, indicating that the M-localized triose phosphate shuttle should be viewed as part of the BS-localized Calvin cycle, rather than a parallel pathway.

Antioxidants↗

PubMed2005

The oligomeric stromal proteome of Arabidopsis thaliana chloroplasts.

This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. 241 proteins (88% with predicted cTP), mostly assembled in oligomeric complexes, were identified by mass spectrometry with emphasis on distinguishing between paralogues. This is critical because different paralogues in a gene family often have different subcellular localizations and/or different expression patterns and functions. The native protein masses were determined for all identified proteins. Comparison with the few well characterized stromal complexes from A. thaliana confirmed the accuracy of the native mass determination, and by extension, the usefulness of the native mass data for future in-depth protein interaction studies. Resolved protein interactions are discussed and compared with an extensive collection of native mass data of orthologues in other plants and bacteria. Relative protein expression levels were estimated from spot intensities and also provided estimates of relative concentrations of individual proteins. No such quantification has been reported so far. Surprisingly proteins dedicated to chloroplast protein synthesis, biogenesis, and fate represented nearly 10% of the total stroma protein mass. Oxidative pentose phosphate pathway, glycolysis, and Calvin cycle represented together about 75%, nitrogen assimilation represented 5-7%, and all other pathways such as biosynthesis of e.g. fatty acids, amino acids, nucleotides, tetrapyrroles, and vitamins B(1) and B(2) each represented less than 1% of total protein mass. Several proteins with diverse functions outside primary carbon metabolism, such as the isomerase ROC4, lipoxygenase 2 involved in jasmonic acid biosynthesis, and a carbonic anhydrase (CA1), were surprisingly abundant in the range of 0.75-1.5% of the total stromal mass. Native images with associated information are available via the Plastid Proteome Database.

Arabidopsis↗

PubMed2005

New oxorhenium(V) compound for catalyzed oxygen atom transfer from picoline N-oxide to triarylphosphines.

The synthesis and characterization of a new oxorhenium(V) compound is reported; it is [MeReO(edt)(bpym)], 8, where edt = 1,2-ethanedithiolate and bpym = 2,2'-bipyrimidine. Compound 8 was characterized by NMR spectroscopy and single-crystal X-ray analysis. It exists as a six-coordinate Re(V) compound comparable to the previously known [MeReO(edt)(bpy)] and [MeReO(mtp)(bpy)]. Compound 8 catalyzes the oxygen-atom-transfer reaction PicO + PZ3 --> Pic + Z3PO, whereas the other two do not. The kinetics of this reaction with catalyst 8 follows the rate law -d[PicO]/dt = k[8][PicO]/(1 + c[PZ3]). With different phosphines, the rate law has the same k value, 4.17 L mol(-1) s(-1), but different c values. For tritolylphosphine, c = 67.5 L mol(-1) in benzene at 25 degrees C. A mechanism has been proposed to account for these findings. The data establish that an open coordination site on rhenium is necessary for oxygen-atom-transfer reactions.

Journal Article↗

PubMed2005

Catalysis by methyltrioxorhenium(VII): reduction of hydronium ions by europium(II) and reduction of perchlorate ions by europium(II) and chromium(II).

The title reactions occur stepwise, the first and fastest being MeReO3 + Eu2+ --> Re(VI) + Eu3+ (k298 = 2.7 x 10(4) L mol(-1) s(-1)), followed by rapid reduction of Re(VI) by Eu2+ to MeReO2. The latter species is reduced by a third Eu2+ to Re(IV), a metastable species characterized by an intense charge transfer band, epsilon410 = 910 L mol(-1) cm(-1) at pH 1; the rate constant for its formation is 61.3 L mol(-1) s(-1), independent of [H+]. Yet another reduction step occurs, during which hydrogen is evolved at a rate v = k[Re(IV)][Eu2+][H+](-1), with k = 2.56 s(-1) at mu = 0.33 mol L(-1). The 410 nm Re(IV) species bears no ionic charge on the basis of the kinetic salt effect. We attribute hydrogen evolution to a reaction between H-ReVO and H3O+, where the hydrido complex arises from the unimolecular rearrangement of Re(III)-OH in a reaction that cannot be detected directly. Chromium(II) ions do not evolve H2, despite E(Cr) degrees approximately E(EU) degrees. We attribute this lack of reactivity to the Re(IV) intermediate being captured as [Re(IV)-O-Cr(III)]2+, with both metals having substitutionally inert d3 electronic configurations. Hydrogen evolution occurs in chloride or triflate media; with perchlorate present, MeReO2 reduces perchlorate to chloride, as reported previously [Abu-Omar, M. M.; Espenson, J. H. Inorg. Chem. 1995, 34, 6239-6240].

Journal Article↗

PubMed2005

Kinetics of self-decomposition and hydrogen atom transfer reactions of substituted phthalimide N-oxyl radicals in acetic acid.

Kinetic data have been obtained for three distinct types of reactions of phthalimide N-oxyl radicals (PINO(.)) and N-hydroxyphthalimide (NHPI) derivatives. The first is the self-decomposition of PINO(.) which was found to follow second-order kinetics. In the self-decomposition of 4-methyl-N-hydroxyphthalimide (4-Me-NHPI), H-atom abstraction competes with self-decomposition in the presence of excess 4-Me-NHPI. The second set of reactions studied is hydrogen atom transfer from NHPI to PINO(.), e.g., PINO(.) + 4-Me-NHPI <=> NHPI + 4-Me-PINO(.). The substantial KIE, k(H)/k(D) = 11 for both forward and reverse reactions, supports the assignment of H-atom transfer rather than stepwise electron-proton transfer. These data were correlated with the Marcus cross relation for hydrogen-atom transfer, and good agreement between the experimental and the calculated rate constants was obtained. The third reaction studied is hydrogen abstraction by PINO(.) from p-xylene and toluene. The reaction becomes regularly slower as the ring substituent on PINO(.) is more electron donating. Analysis by the Hammett equation gave rho = 1.1 and 1.8 for the reactions of PINO(.) with p-xylene and toluene, respectively.

Journal Article↗

PubMed2005

[Amplification of EMS1 gene in oral carcinogenesis].

OBJECTIVE: To investigate the amplification of EMS1 gene in the carcinogenesis of oral mucosa. METHODS: A total of 78 subjects, including 30 patients with oral leukoplakia (OLK), 33 with oral squamous cell carcinoma (OSCC), and 15 healthy controls, were studied. By using microdissection method, we obtained normal mucosa, hyperplastic epithelia, mild-dysplastic epithelia, moderate-dysplastic epithelia, severe-dysplastic epithelia and primary OSCC tissue. Then we analyzed EMS1 amplification by using differential PCR. RESULTS: EMS1 amplification began from moderate-dysplastic epithelia and occurred in 20.0% OLK cases and 57.6% OSCC cases. In the progress of OSCC, no gene amplification was observed in normal tissues, non-dysplastic OLK and mild-dysplastic OLK, while in the cases with metastasis, amplification frequency increased significantly (P = 0.015). CONCLUSIONS: EMS1 amplification parallels with the progress of oral carcinogenesis, indicating their potential roles in oral carcinogenesis.

Carcinoma, Squamous Cell↗

PubMed2004

[Combination of hemofiltration and peritoneal dialysis in the treatment of severe acute pancreatitis].

OBJECTIVE: To study the therapeutic effects and its mechanism of combination of hemofiltration (HF) and peritoneal dialysis (PD) in the treatment of severe acute pancreatitis (SAP). METHODS: Forty patients with SAP were divided at random into the HF + PD group (therapeutic group, 25 patients) and the non-HF + PD group (contrast group, 15 patients). Both groups were treated by the conventional mode of therapy. The release time of abdominal pain and distention, CT scores, APACHE II scores, the time of hospital stay, cost of treatment in hospital, operative rate and rate of complications and recovered rate of the two groups were compared. Simultaneously, the concentration of serum and fluid filtrated pro-inflammatory cytokines TNF, IL-6 and IL-8 were also determined pro and post the therapy. RESULTS: The time needed for the disappearance of abdominal pain and the amelioration of abdominal distension, CT scores, APACHE II scores, the average hospital stay and hospital cost of the therapeutic group were significantly decreased compared with those of the contrast group. The cytokines detected at the end of 1d, 2d after HF + PD were decreased significantly compared with those observed in pro HF + PD and the contrast group. CONCLUSIONS: The above results show that the cytokines overproduced during the development of SAP can be removed effectively from the circulation and the fluid filtrated by means of HF + PD. The continual deterioration of the local focus and systemtic presentation could be prevented effectively too, and the earlier the treatment of HF + PD, the better the prognosis.

Acute Disease↗

PubMed2004

Minimalism context-aware displays.

Despite the rapid development of cyber technologies, today we still have very limited attention and communication bandwidth to process the increasing information flow. The goal of the study is to develop a context-aware filter to match the information load with particular needs and capacities. The functions include bandwidth-resolution trade-off and user context modeling. From the empirical lab studies, it is found that the resolution of images can be reduced in order of magnitude if the viewer knows that he/she is looking for particular features. The adaptive display queue is optimized with real-time operational conditions and user's inquiry history. Instead of measuring operator's behavior directly, ubiquitous computing models are developed to anticipate user's behavior from the operational environment data. A case study of the video stream monitoring for transit security is discussed in the paper. In addition, the author addresses the future direction of coherent human-machine vision systems.

Awareness↗

PubMed2004

[Centrosome hyperamplificationin oral precancerous lesions and squamous cell carcinomas].

OBJECTIVE: It is currently considered that the defect of mitotic spindle caused by centrosome abnormalities may be one of the reasons for the development of aneuploidy in tumors. This study attempted to elucidate the possible role of centrosome defects in the development and progression of OSCC by investigating the frequency of centrosome amplification in oral precancerous lesions and OSCC. METHODS: Formalin-fixed, paraffin-embedded tissues of 12 cases of normal oral epithelium, 22 case of dysplasia with different degree epithelium dysplasia and 32 cases of OSCC with different differentiation were investigated for centrosome status by using indirect immunofluorescence double staining with antibodies to centrosome protein gamma-tubulin and cytokeratin. The differences and the change trend of centrosome status in these groups were statistically analyzed by SPSS10.0. RESULTS: Normal oral epithelium showed normal centrosomes in epithelium cells, while 16 of 22 cases (72.73%) of dysplasia (DYS) and 27 of 32 cases (84.38%) of OSCC showed the evidence of centrosome amplification and morphological abnormalities characterized by huge size, clump or supernumerary centrosomes in a fraction of epithelium or tumor cells. The percentage of cells with abnormal centrosomes increased gradually from mild-dysplasia epithelium to poorly differentiated OSCC, which positively correlated with the histologicalcytologic grade of oral precancerous lesions and OSCC (P < 0.01). CONCLUSION: Centrosome amplification was an early event and that might play a role in the establishment and perhaps the progression of OSCC. There might be some direct relationship between centrosome defects and the cellular morphological phenotype characteristics of dysplasia and OSCC. Centrosome amplification could be served as an alternative diagnostic indicator of dysplasia and the intervention of centrosome cycle might serve as a particular way for the prevention and treatment of OSCC in the future.

Carcinoma, Squamous Cell↗

PubMed2003

Clp protease complexes from photosynthetic and non-photosynthetic plastids and mitochondria of plants, their predicted three-dimensional structures, and functional implications.

Tetradecameric Clp protease core complexes in non-photosynthetic plastids of roots, flower petals, and in chloroplasts of leaves of Arabidopsis thaliana were purified based on native mass and isoelectric point and identified by mass spectrometry. The stoichiometry between the subunits was determined. The protease complex consisted of one to three copies of five different serine-type protease Clp proteins (ClpP1,3-6) and four non-proteolytic ClpR proteins (ClpR1-4). Three-dimensional homology modeling showed that the ClpP/R proteins fit well together in a tetradecameric complex and also indicated unique contributions for each protein. Lateral exit gates for proteolysis products are proposed. In addition, ClpS1,2, unique to land plants, tightly interacted with this core complex, with one copy of each per complex. The three-dimensional modeling show that they do fit well on the axial sites of the ClpPR cores. In contrast to plastids, plant mitochondria contained a single approximately 320-kDa homo-tetradecameric ClpP2 complex, without association of ClpR or ClpS proteins. It is surprising that the Clp core composition appears identical in all three plastid types, despite the remarkable differences in plastid proteome composition. This suggests that regulation of plastid proteolysis by the Clp machinery is not through differential regulation of ClpP/R/S gene expression, but rather through substrate recognition mechanisms and regulated interaction of chaperone-like molecules (ClpS1,2 and others) to the ClpP/R core.

Adenosine Triphosphatases↗

PubMed2003

Anionic adducts of oligosaccharides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The formation and decomposition (postsource decay, PSD) of anionic adducts in negative ion matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry have been studied. Chloride, a small inorganic anion, has been found to form stable anionic adducts with a variety of neutral oligosaccharides that can survive the MALDI process to give readily identifiable signals (with characteristic isotope patterns) allowing subpicomole detection in the best cases. The matrixes that can aid the formation of chloride adducts of oligosaccharides have gas-phase acidities lower than or close to that of HCl (1373 kJ/mol). In PSD experiments, precursor chloride adducts of oligosaccharides yield fragment ions that retain the charge on the sugar molecule rather than solely forming Cl-, and these fragments can provide structurally informative product ions. In negative ion MALDI, highly acidic oligosaccharides do not form adducts with chloride anions, but mildly acidic saccharides (e.g., containing a carboxylic acid group) form both deprotonated molecules and chloride adducts, and each may provide structural information concerning the oligosaccharide upon decomposition.

Acids↗

PubMed2003

Incremented alkyl derivatives enhance collision induced glycosidic bond cleavage in mass spectrometry of disaccharides.

Electrospray ionization and collision induced dissociation on a triple quadrupole mass spectrometer were used to determine the effect of spatial crowding of incremented alkyl groups of two anomeric pairs of peralkylated (methyl to pentyl) disaccharides (maltose/cellobiose and isomaltose/gentiobiose). Protonated molecules were generated which underwent extensive fragmentation under low energy conditions. For both the 1 --> 4 and 1 --> 6 alpha and beta isomers, at comparable collision energies the methyl derivative exhibited the least fragmentation followed by ethyl, propyl, butyl, and pentyl. Collision energy is converted to rotational-vibrational modes in competition with bond cleavage, as represented by the slope of product/parent ion (D/P) ratio versus offset energy. Variable rotational freedom at the glycosidic linkage with incremented alkyl groups is hypothesized to be responsible for this effect. Discrimination of anomeric configuration was also assessed for these stereoiosmeric disaccharides. A systematic study showed that an increasing discrimination was attained for the 1 --> 4 isomeric pair as the size of the derivative increased from methyl to pentyl. No anomeric discrimination was attained for the 1 --> 6 isomeric pair. Parent and product ion scans confirmed the consistency of fragmentation pathways among derivatives. Chem-X and MM3 molecular modeling programs were used to obtain minimum energy structures and freedom of motion volumes for the permethylated disaccharides. The modeling results correlated with the fragmentation ratios obtained in the mass spectrometer giving strong indication that the collision induced spectra are dependent on the freedom of rotational motion around the glycosidic bond.

Algorithms↗

PubMed2003

Dication induced stabilization of gas-phase ternary beta-cyclodextrin inclusion complexes observed by electrospray mass spectrometry.

Electrospray mass spectrometry (ES-MS) is an important tool for characterization of non-covalent binding in the gas phase. In this study, iron (II) has been introduced as a dication to enhance the detection of cyclodextrin (CD) plus aromatic compound complexes in ES-MS. Evidence that a novel ternary complex comprised of one beta-CD, one iron (II) and one toluene exists as an inclusion complex has been compiled via ES-MS and ES-MS/MS experiments as well as by a computational approach. This evidence strongly suggests that iron (II) serves to modify the conformation of the beta-CD ring, and that toluene inclusion is stabilized by dication interaction with the toluene pi-system and by crimping of the beta-CD ring leading to stronger van der Waals interactions with toluene. Mg(II), another dication of similar radius, showed similar behavior, while added group one cations (H(+) and Na(+)) were ineffective at producing observable ions representative of the complex. The ternary beta-CD complex with iron (II) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) has also been examined. ES-MS and ES-MS/MS experiments suggest that it is the polar portion of 2,4,5-T (i.e., the carboxylic acid moiety) that is favored for inclusion in the beta-CD cavity, rather than the non-polar aromatic part.

Cations, Divalent↗

PubMed2003

Interventional therapy of malignant obstructive jaundice.

OBJECTIVE: To assess the short-term results of interventional therapy for malignant obstructive jaundice. METHODS: In 82 patients with malignant obstructive jaundice, hepatocellular carcinoma was detected in 10 patients, carcinoma of gallbladder in 14, hilar biliary carcinoma in 22, pancreatic carcinoma in 20, and hilar metastatic carcinoma in 16. Percutaneous transhepatic biliary internal and/or external drainage (PTBIED) was performed in 61 patients and percutaneous transhepatic insertion of biliary stent (PTIBS) in 21. RESULTS: The level of total serum bilirubin (TSB) was reduced in 71 patients and less markedly in others. The level of TSB of the 61 patients was reduced from 450.12+/-113.51 micromol/L before operation to 240.25+/-107.81 micromol/L and 90.91+/-101.72 micromol/L 1 and 2 weeks after operation respectively. The TSB level of the 21 patients was reduced from 410.53+/-98.13 micromol/L to 270.23+/-115.64 micromol/L and 105.43+/-97.85 micromol/L 1 and 2 weeks after operation, respectively. No significant difference was found in the effect between PTBIED and PTIBS. Short-term complications developed in 33 patients. Seven patients died 30 days after operation. CONCLUSION: Interventional therapy may be simple, safe and effective in the treatment of malignant obstructive jaundice.

Adult↗

PubMed2002

Stabilization of anionic adducts in negative ion electrospray mass spectrometry.

Attachment of small anions to neutral molecules is an important ionization mechanism in negative ion electrospray mass spectrometry. In this report, the tendency for different anions to remain attached to selected analyte compound classes has been systematically investigated. A rationale for the formation and stability of preferred anionic adducts is proposed in light of thermodynamic considerations. A series of collision-induced dissociation experiments reveals that the gas-phase basicities of the deprotonated analyte molecule ([M - H]-) and the anion moiety play important roles in determining the stability of anionic adducts. Adducts of the form [M - H]-...H+...[anion]- manifest increased stability when the two anions have similar gas-phase basicities. Within certain limitations, the difference in deltaG degrees values for proton combination with [M - H]- and with [anion]- can be used as a first-order predictor of adduct stability. In addition, stability increases with the rising gas-phase basicities of the two moieties. The specific interaction between a small inorganic anion (bisulfate) and a neutral analyte molecule (alpha-D-glucose) in the form of multiple hydrogen bonding has also been affirmed by computer modeling to contribute to the stability of some anionic adducts. Last, the gas-phase basicity of deprotonated alpha-D-glucose (i.e., the gas-phase acidity of alpha-D-glucose) is determined by a "bracketing method" to be in the range of 1373-1407 kJ/mol.

Journal Article↗

PubMed2002

Evaluation of the role of multiple hydrogen bonding in offering stability to negative ion adducts in electrospray mass spectrometry.

An experimental approach, electrospray mass spectrometry (ES-MS), and a theoretical approach employing computer modeling, have been used to characterize the interaction between small inorganic anions and neutral analyte molecules that form anionic adduct species in negative mode ES mass spectrometry. Certain anionic adducts of small saccharides (e.g., alpha-D-glucose, sucrose) have shown exceptional stability in ES mass spectra even when internal energies are raised at high "cone" voltages. Computer modeling studies reveal that multiple hydrogen bonding strengthens the interaction between these neutral molecules and the attaching anion. The equilibrium structures and stabilization energies of these anionic adducts have been evaluated by semi-empirical, ab initio, and density functional theory (DFT) methods. Chloride anion is found to be capable of forming "bridging" hydrogen bonds between monosaccharide rings of polysaccharides resulting in the stabilization of chloride adducts, thus reducing the tendency for the glycosidic bond to decompose. Moreover, the tendency for various hydroxyl hydrogens on saccharide molecules to dissociate in the form of HA (A-, anion) during decomposition of anionic adducts, thereby forming [M - H]-, has also been evaluated by computer modeling.

Journal Article↗