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S Luo

Publications and source records attributed to S Luo.

At least 19 recordsLinked to original sources
PubMed2006

Thermodynamics of hydrogen solution and hydride formation in Pd-Mn alloys. 1. Disordered alloys and a correlation effect.

The thermodynamics of H(2) solution and hydride formation/decomposition have been determined by reaction calorimetry (303 K) for disordered face centered cubic (fcc) Pd-Mn alloys. This alloy system belongs to the expanded lattice category which predicts that and DeltaH(plat) for H(2) absorption should be more exothermic than those for Pd; the experimental results are that the former is more exothermic, at least at the higher Mn contents, but the latter is not. There is a regular decrease in the H capacity (at p(H)2 = 0.2 MPa) with atom fraction Mn. A linear dependence of log p(H)2 upon H content is found in the single hydride phase for all of these alloys suggesting that DeltaH(H) and DeltaS(H) are also linear functions of r in this region. This is confirmed using the Pd(0.875)Mn(0.125) alloy which has no two-phase region (303 K). It is shown for the Pd(0.875)Mn(0.125) alloy and for Pd that the changes of partial enthalpies and entropies with H content are correlated so as to minimize changes of mu(H).

Journal Article↗
PubMed2006

Thermodynamics of hydrogen solution and hydride formation in Pd-Mn alloys. 2. Ordered alloys.

There are marked differences in H(2) solubilities between ordered and disordered Pd-Mn alloys with the largest difference found between the L1(2) and the disordered form of the Pd(3)Mn alloy. The thermodynamics of H(2) solution have been determined for the L1(2) form, the long-period superstructure (lps), and the disordered forms of the Pd(0.80)Mn(0.20) and Pd(0.75)Mn(0.25)(Pd(3)Mn) alloys. Relative partial molar enthalpies and entropies were determined mainly by reaction calorimetry over the range of H contents accessible from p(H)()2 approximately 10 Pa to approximately 0.3 MPa (303 K). The enthalpies for absorption of H(2) are more exothermic over most of the range of H contents for the L1(2) forms of the Pd(3)Mn and Pd(0.80)Mn(0.20) alloys than for their other forms. The reaction enthalpies are constant across a relatively wide range of H contents for the L1(2) form of the Pd(0.80)Mn(0.20) and Pd(3)Mn alloys indicating that there are two-phase coexistence regions (303 K). The H-H attractive interaction, which leads to hydride formation, is much greater for the L1(2) than for the other forms of the Pd(3)Mn alloy and for Pd itself. It has been found that the H-H interaction always decreases in magnitude and, accompanying this, the THS (terminal hydrogen solubility) always increases by alloying Pd.(1) The L1(2) ordered Pd(3)Mn alloy is an exception to this, and therefore, the generalization about THS must be restricted to disordered face centered cubic (fcc) Pd alloys.

Journal Article↗
PubMed2005

Site-directed mutagenesis of gentisate 1,2-dioxygenases from Klebsiella pneumoniae M5a1 and Ralstonia sp. strain U2.

Gentisate 1,2-dioxygenase (GDO, EC 1.13.11.4) is the first enzyme in gentisate pathway that catalyses the ring fission of gentisate to form maleylpyruvate. Phylogenetic tree of amino acid sequences from 11 GDOs demonstrates that the GDOs from different genus share identities between 12.1% and 64.8%. According to the alignment result, four highly conserved histidine residues in GDO from Klebsiella pneumoniae M5a1 and Ralstonia sp. strain U2 were chosen to be substituted with aspartate residues. Enzyme analysis indicated that substitution of any of these four histidine residues had resulted in the complete loss of its catalytic activity.

Amino Acid Sequence↗
PubMed2004

Distribution and shifting trends of bacterial keratitis in north China (1989-98).

AIMS: To study the distribution and shifting trends of bacterial keratitis. METHODS: The data of 2220 corneal isolates from 1 January 1989 to 31 December 1998 were reviewed retrospectively. RESULTS: Positive culture was recovered in 490 isolates. Gram positive cocci and Gram negative bacilli represented 51% and 39.4%, respectively. Pseudomonas aeruginosa was the most common pathogen (32.2%). A gradual increase in the percentage of Gram positive cocci coupled with a decrease of Gram negative bacilli. CONCLUSION: Pseudomonas aeruginosa and coaculase negative Staphylococcus were the most common pathogens in bacterial keratitis in north China.

China↗
PubMed2003

Asbestos related diseases from environmental exposure to crocidolite in Da-yao, China. I. Review of exposure and epidemiological data.

BACKGROUND: Scattered patches of crocidolite, one form of asbestos, were found in the surface soil in the rural county of Da-yao in southwestern China. In 1983, researchers from the West China University of Medical Sciences (WCUMS) discovered that residents of two villages in Da-yao had hyperendemic pleural plaques and excessive numbers of pleural mesotheliomas. AIMS: To review and summarise epidemiological studies, along with other relevant data, and to discuss the potential contribution to environmental risk assessment. METHODS: This report is based on a review of several clinical/epidemiological studies conducted by WCUMS researchers since 1984, which included one cross sectional medical examination survey, one clinical/pathological analysis of 46 cases of mesothelioma, and three retrospective cohort mortality studies. Additional information acquired from reviewing original data first hand during a personal visit along with an interview of medical specialists from Da-yao County Hospital was also incorporated. RESULTS: The prevalence of pleural plaque was 20% among peasants in Da-yao over 40 years of age in the cross sectional survey. The average number of mesothelioma cases was 6.6 per year in the 1984-95 period and 22 per year in the 1996-99 period, in a population of 68 000. For those mesothelioma cases that were histology confirmed, there were 3.8 cases/year in the first period and 9 cases/year in the second. Of the 2175 peasants in this survey, 16 had asbestosis. Lung cancer deaths were significantly increased in all three cohort studies. The annual mortality rate for mesothelioma was 85 per million, 178 per million, and 365 per million for the three cohort studies, respectively. The higher exposed peasants had a fivefold increased mesothelioma mortality compared to their lower exposed counterparts. There were no cases of mesothelioma in the comparison groups where no crocidolite was known to exist in the environment. In the third cohort study, almost one of five cancer deaths (22%) was from mesothelioma. The ratio of lung cancer to mesothelioma deaths was low for all three studies (1.3, 3.0, and 1.2, respectively). CONCLUSIONS: The observation of numerous mesothelioma cases at Da-yao was a unique finding, due mainly to their lifetime exposure to crocidolite asbestos. The finding of cases dying at a younger age and the relatively high ratio of mesothelioma cases to lung cancer could also be another unique result of lifetime environmental exposure to crocidolite asbestos. Although the commercial use of crocidolite has been officially banned since 1984, the incidence of mesothelioma has continued to show a steady increase, particularly among peasants. Since the latency of mesothelioma is approximately 30-40 years, the ban had little effect in the 1990s. The increased awareness and changes in diagnosis over time may also contribute to the increase. Furthermore, exposure to asbestos stoves and walls continued. The government implemented reduction of these exposures. However, from a public health standpoint, the most important issue is the complete avoidance of further exposure to asbestos.

Asbestos, Crocidolite↗
PubMed2001

Oxidized low-density lipoprotein downregulates endothelial basic fibroblast growth factor through a pertussis toxin-sensitive G-protein pathway: mediator role of platelet-activating factor-like phospholipids.

BACKGROUND: Oxidized LDL (oxLDL) inhibits angiogenesis in part by downregulating endothelial basic fibroblast growth factor (bFGF). To determine the mechanism of the downregulation, we investigated the signal transduction pathway involving potential phospholipid mediators. METHODS AND RESULTS: Cultured bovine aortic endothelial cells were incubated with PBS (lipoprotein-free control), LDL, or copper oxLDL under serum-free conditions. At 24 hours, oxLDL (50 microg/mL) decreased bFGF mRNA (Northern blot), bFGF protein (Western blot and ELISA), and concomitant DNA synthesis, all by 40% to 50% compared with PBS. LDL had no effect. Pretreating the cells with 100 ng/mL pertussis toxin (PTX) for 18 hours before oxLDL exposure almost completely blocked the inhibitory effects of oxLDL. In contrast, inhibiting other major cellular signal transduction pathways with PD-98059 (mitogen-activated protein kinase kinase inhibitor), HA-1004 (inhibitor of cGMP- and cAMP-dependent protein kinase), or Ro-31-8220 (protein kinase C inhibitor) or chelating intracellular Ca(2+) with BAPTA-AM failed to attenuate any of the oxLDL effects assayed. Addition to the cultures of WEB 2086, a specific antagonist of the PTX-sensitive G protein-coupled platelet-activating factor (PAF) receptor, blocked the action of oxLDL. Whereas PAF dispersed in the culture medium failed to produce oxLDL-like effects, degradation of PAF and PAF-like phospholipids accumulated in oxLDL with a recombinant human PAF acetylhydrolase eliminated the inhibitory effects of oxLDL on bFGF expression and DNA synthesis. CONCLUSIONS: OxLDL suppresses endothelial bFGF expression and DNA synthesis through a PTX-sensitive heterotrimeric G-protein pathway involving mediator phospholipids similar, but not identical, to PAF.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2001

(31)P NMR of apicomplexans and the effects of risedronate on Cryptosporidium parvum growth.

High-resolution 303.6 MHz (31)P NMR spectra have been obtained of perchloric acid extracts of Plasmodium berghei trophozoites, Toxoplasma gondii tachyzoites, and Cryptosporidium parvum oocysts. Essentially complete resonance assignments have been made based on chemical shifts and by coaddition of authentic reference compounds. Signals corresponding to inorganic pyrophosphate were detected in all three species. In T. gondii and C. parvum, additional resonances were observed corresponding to linear triphosphate as well as longer chain polyphosphates. Spectra of P. berghei and T. gondii also indicated the presence of phosphomonoesters and nucleotide phosphates. We also report that the pyrophosphate analog drug, risedronate (used in bone resorption therapy), inhibits the growth of C. parvum in a mouse xenograft model. When taken together, our results indicate that all the major disease-causing apicomplexan parasites contain extensive stores of condensed phosphates and that as with Plasmodium falciparum and T. gondii, the pyrophosphate analog drug risedronate is an inhibitor of C. parvum cell growth.

Animals↗
PubMed2001

Smads in human trophoblast cells: expression, regulation and role in TGF-beta-induced transcriptional activity.

Smad proteins have recently been shown to be downstream signaling molecules that transduce TGF-beta signals from cell surface to the nucleus. To determine the mechanisms of TGF-beta action in human trophoblast cells, we investigated the expression and regulation of Smad2,3,4, and 7 mRNAs in a normal trophoblast cell line, NPC, and a cell line derived from choriocarcinoma, JEG-3. Messenger RNAs for Smad2,3,4 and 7 were detected in both NPC and JEG-3 cells. TGF-beta1 induced modest increases in Smad2 and Smad4 mRNA levels without affecting Smad3 mRNA expression in both cell lines. Significant increases in Smad7 mRNA levels in both NPC and JEG-3 cells following TGF-beta1 treatment were observed. TGF-beta1 also induced promoter activity of the Smad7 gene, indicating a direct effect at the level of gene transcription. The transcriptional activity of TGF-beta was examined in JEG-3 cells using two TGF-beta responsive reporter constructs, p3TP-Lux and pAR3-Lux. We found that Smad3 and to a lesser extent, Smad2 and Smad4, enhanced, while Smad7 inhibited, TGF-beta1-induced transcriptional activities. The basal and TGF-beta1-induced transcription can be blocked by overexpression of a dominant negative TGF-beta type II receptor. Taken together, these findings demonstrate that in human trophoblast cell lines, the Smad pathway involved in TGF-beta signal transduction is functional and that TGF-beta plays an autocrine role in regulating gene expression.

DNA-Binding Proteins↗
PubMed2001

[The diagnosis and treatment of hypothalamic hamartoma in children].

OBJECTIVE: To investigate the diagnosis and treatment of hypothalamic hamartoma in children. METHODS: Eighteen cases of hypothalamic hamartoma in children, including 9 boys and 9 girls, were examined with CT and MRI. Eleven cases underwent operation. Post-operation follow-up was conducted for 0.5 approximately 6 years. RESULTS: The main clinical features of hypothalamic hamartoma were precocious puberty and gelastic seizures, some combine with other kinds of seizures, mental retardation or congenital abnormalities. The effective rate of surgery was 91%; patients with simple precocious puberty were cured. CONCLUSION: Microsurgery is the first choice of treatment for hypothalamic hamartoma.

Adolescent↗
PubMed2001

A plasma membrane-type Ca(2+)-ATPase co-localizes with a vacuolar H(+)-pyrophosphatase to acidocalcisomes of Toxoplasma gondii.

Ca(2+)-ATPases are likely to play critical roles in the biochemistry of Toxoplasma gondii, since these protozoa are obligate intracellular parasites and the Ca(2+) concentration in their intracellular location is three orders of magnitude lower than in the extracellular medium. Here, we report the cloning and sequencing of a gene encoding a plasma membrane-type Ca(2+)-ATPase (PMCA) of T.gondii (TgA1). The predicted protein (TgA1) exhibits 32-36% identity to vacuolar Ca(2+)-ATPases of Trypanosoma cruzi, Saccharomyces cerevisiae, Entamoeba histolytica and Dictyostelium discoideum. Sequencing of both cDNA and genomic DNA from T.gondii indicated that TgA1 contains two introns near the C-terminus. A hydropathy profile of the protein suggests 10 transmembrane domains. TgA1 suppresses the Ca(2+) hypersensitivity of a mutant of S.cerevisiae that has a defect in vacuolar Ca(2+) accumulation. Indirect immunofluorescence and immunoelectron microscopy analysis indicate that TgA1 localizes to the plasma membrane and co-localizes with the vacuolar H(+)-pyrophosphatase to intracellular vacuoles identified morphologically and by X-ray microanalysis as the acidocalcisomes. This vacuolar-type Ca(2+)-ATPase could play an important role in Ca(2+) homeostasis in T.gondii.

Adenosine Triphosphate↗
PubMed2001

High-throughput semi-automated 96-well liquid/liquid extraction and liquid chromatography/mass spectrometric analysis of everolimus (RAD 001) and cyclosporin a (CsA) in whole blood.

A semi-automated high-throughput liquid/liquid extraction (LLE) assay was developed for RAD001 and cyclosporin A (CsA) in human blood. After addition of internal standard and ammonium hydroxide, samples were extracted twice with methyl tert-butyl ether (MTBE). The organic extract was evaporated to dryness and reconstituted in mobile phase. Where possible, sample transfer and LLE steps were automated using a Tomtec Quadra 96 workstation. Samples were analyzed using ESI-LC/MS/MS employing the transitions of ([M + NH(4)](+) --> [M + H](+)) for CsA and ([M + NH(4)](+) --> [M + H-(CH(3)OH + H(2)O)](+)) for RAD001, under isocratic chromatographic conditions (75:25, (v/v), acetonitrile/20 mM ammonium acetate) with a run time of 3.6 min. A lower limit of quantitation (LLOQ) of 0.368 ng/mL and 5.23 ng/mL was achieved for RAD001 and CsA, respectively, using a sample volume of 0.3 mL for the analysis. The method was validated over a 3-day period and the resulting calibration curves had a correlation coefficient >0.99 over the concentration range 0.368 to 409 ng/mL and 5.24 to 1748 ng/mL for RAD001 and CsA, respectively. The inter-day coefficient of variation (CV) was less than 15% at the LLOQ for both compounds. The method was applied to the analysis of clinical samples. Under normal working conditions four 96-well plates could be extracted and LC/MS analysis completed in less than 28 h. A marked improvement in sample throughput efficiency was realized with this LLE method when compared to existing solid phase extraction (SPE) methods which deal with both RAD001 and CsA.

Chromatography, Liquid↗
PubMed2001

Effect of xiaokuiling prescription on the expression of HSP72, HSP B in gastric mucosa of patients with Helicobacter pylori-associated duodenal ulcer.

In order to investigate the mechanism of Xiaokuiling prescription (XKL) in the treatment of Helicobacter pylori (HP)-associated duodenal ulcer (DU) and the pathophysiologic role of heat shock proteins (HSPs) in the healing of ulcer, the expression of HSP72 and HSP B in gastric mucosa was detected by using SABC immunohistochemistry method and processed by micro-image analysis system. The method of Western blotting was used to measure the contents of HSP72 and HSP B in the tissue emulsion of gastric mucosa. The results were as follows: (1) HSP72 expression of the gastric mucosa in the treated group was obviously increased as compared with that in the control group (P < 0.05); (2) HSP B expression of the gastric mucosa in the treated group was significantly decreased as compared with that in the control group (P < 0.01). It was suggested that the increased expression of HSP72 and the elimination of HP might be related to the mechanism of action of XKL. HSPs might play an pathological and physiological role in the process of healing of gastric ulcer.

Adult↗
PubMed2001

Effect of jianpiyiqi prescription on the expression of heat shock proteins in acetic acid-induced chronic gastric ulcer rats.

To investigate the effect of Jianpiyiqi prescription on the expression of heat shock proteins (HSPs) and the changes of HSPs in gastric-ulcerated rats, the rat model of chronic gastric ulcer was induced by acetic acid. The SABC immunohistochemical method was used to observe HSP70 of mucosa around the gastric ulcer. Imaging analysis was performed. Western dot blot was used to detect HSPs contents in the plasma and gastric mucosal homogenate in each group. The results showed that HSP70 contents of the mucosa around the gastric ulcer in the model group and ranitidine-treated group were increased as compared with control group (P < 0.01). Jianpiyiqi could increase the expression of HSP70 of the mucosa around the gastric ulcer further as compared with that in the model group and ranitidine-treated group (P < 0.01). The HSP70 contents in the serum and mucosa in the model group and ranitidine-treated group were increased as compared with control group (P < 0.01, P < 0.05 respectively). HSP70 of serum and mucosa in the Jianpiyiqi-treated group was higher than in the model group and ranitidine-treated group (P < 0.05, P < 0.01 respectively). It was concluded that HSP might play a role in the process of pathophysiology of gastric ulcer. Jianpiyiqi could enhance gastric ulcer-healing through the protective mechanism of HSPs.

Acetic Acid↗
PubMed2001

Tyrosine improves behavioral and neurochemical deficits caused by cold exposure.

The effects of acute cold stress were assessed behaviorally and neurochemically. The norepinephrine (NE) precursor, tyrosine (TYR), the catecholamine-releasing compound, amphetamine (AMPH), and the adrenoceptor agonist, phenylpropanolamine (PPA), were administered systemically either alone or in conjunction with TYR 30 min prior to cold exposure. All three sympathomimetic treatments dose-dependently improved performance in a forced swim test following hypothermia (T(c)=30 degrees C). AMPH/TYR or PPA/TYR combinations further improved performance vs. either agent given alone. Microdialysis showed elevated hippocampal NE concentrations in response to hypothermia. TYR further elevated NE concentration in cold/restrained rats vs. saline (SAL)-treated controls. These results suggest that sympathomimetic agents, including the nutrient TYR, which enhance noradrenergic function, improve performance in animals acutely stressed by hypothermia.

Adrenergic alpha-Agonists↗
PubMed2001

Construction of a generic reaction knowledge base by reaction data mining.

As synthesis by combinatorial chemistry and high throughput screening have become well-established strategies in the drug discovery process, chemists face increased challenges in managing large amounts of data and using these data to design more diverse and focused libraries. As synthesis is an intuitive and empirical process, however, the classical approaches to computer-assisted synthesis planning do not fully satisfy the needs of the synthetic chemist. We describe a novel computational technique for extracting reaction data and building a generic reaction knowledge base (GRKB) to provide chemists with useful and well-organized knowledge. The method consists of three key steps: (1) the automatic recognition of reaction centers, (2) the definition of a hierarchy of reaction patterns, and (3) the organization of the generic reaction knowledge. Significant reaction knowledge has been discovered via mining a subset of the InfoChem Reaction database. A frame system has been constructed to store and retrieve the GRKB. Applications of this GRKB to synthesis planning are illustrated.

Artificial Intelligence↗
PubMed2001

Association between natural killer cell activity and infection in immunologically normal elderly people.

Congenital patients who lack natural killer (NK) cell activity experience repeated polymicrobial infections. NK cell activity varies significantly among normal people, but it is unknown whether this variation influences their ability to fight infections. This study examined this concern. NK cell activity and other variables, i.e. age, sex, performance status (PS), serum albumin value, lymphocyte and neutrophil counts, various lymphocyte subsets, etc. were determined for 108 immunologically normal elderly subjects who were in nursing homes due to an impaired PS. We analysed for correlations between these variables and the follow-up results of the subjects. Forty-eight subjects developed infection(s) during the first year of follow-up. A low NK cell activity was associated with the development of infection (P = 0.0105, multivariate logistic regression analysis). The relative risk for the development of infection increased in accordance with the decrease in the NK cell activity. Eleven subjects died of infection during the study period. A low NK cell activity was associated with short survival due to infection (P = 0.0056, multivariate Cox's proportional-hazards regression analysis). Our data indicate that low NK cell activity is associated with development of infections and death due to infection in immunologically normal elderly subjects with an impaired PS.

Aged↗
PubMed2001

Heparin modulates integrin function in human platelets.

PURPOSE: Heparin binds to human platelets and can cause activation and aggregation, although the mechanisms are unknown. To determine how heparin alters platelet function, we identified platelet-binding sites for heparin and measured heparin's influence on the function of platelet integrin alpha(IIb)beta(3) (glycoprotein IIb/IIIa). METHODS: Photoaffinity cross-linking and affinity chromatography experiments were performed to identify platelet membrane proteins that bind heparin. Heparin's effect on fibrinogen binding to platelets was measured with a radioligand-binding assay. The translocation to the cytoskeleton of Rap2, a guanosine triphosphate-binding protein, was measured from platelets aggregating in response to heparin and other agonists. RESULTS: Cross-linking and affinity chromatographic experiments positively identified the integrin alpha(IIb)beta(3) as a heparin-binding site. Heparin aggregation was calcium dependent. Low concentrations of unfractionated porcine mucosal heparin (2-5 U/mL) significantly increased fibrinogen I 125 binding to activated platelets, whereas higher doses did not. Heparin-mediated platelet aggregation was completely blocked by GRGDS peptide (5 mmol/L), a competitive inhibitor of fibrinogen binding, and was blocked by EDTA (2 mmol/L), which dissociates the functional integrin complex. Aggregation was associated with Rap2 translocation to the cytoskeleton, a sign of outside-in signaling. CONCLUSIONS: Heparin binds to the alpha(IIb)beta(3) integrin in vitro and ex vivo, and heparin increases fibrinogen binding to the integrin. Heparin-mediated aggregation requires an intact integrin and ligand and leads to Rap2 translocation to the cytoskeleton-an outside-in signal of ligand engagement. Heparin may directly modulate platelet integrin function, most likely through direct binding and modulation of integrin function.

Binding Sites↗