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S Y Xu

Publications and source records attributed to S Y Xu.

At least 19 recordsLinked to original sources
PubMed2006

Organic carbon and nitrogen stable isotopes in the intertidal sediments from the Yangtze Estuary, China.

The natural isotopic compositions and C/N elemental ratios of sedimentary organic matter were determined in the intertidal flat of the Yangtze Estuary. The results showed that the ratios of carbon and nitrogen stable isotopes were respectively -29.8 per thousand to -26.0 per thousand and 1.6 per thousand-5.5 per thousand in the flood season (July), while they were -27.3 per thousand to -25.6 per thousand and 1.7 per thousand-7.8 per thousand in the dry season (February), respectively. The delta(13)C signatures were remarkably higher in July than in February, and gradually increased from the freshwater areas to the brackish areas. In contrast, there were relatively complex seasonal and spatial changes in stable nitrogen isotopes. It was also reflected that delta(15)N and C/N compositions had been obviously modified by organic matter diagenesis and biological processing, and could not be used to trace the sources of organic matter at the study area. In addition, it was considered that the mixing inputs of terrigenous and marine materials generally dominated sedimentary organic matter in the intertidal flat. The contribution of terrigenous inputs to sedimentary organic matter was roughly estimated according to the mixing balance model of stable carbon isotopes.

Carbon Isotopes↗
PubMed2006

Thermal nociception in adult Drosophila: behavioral characterization and the role of the painless gene.

Nociception, warning of injury that should be avoided, serves an important protective function in animals. In this study, we show that adult Drosophila avoids noxious heat by a jump response. To quantitatively analyze this nociceptive behavior, we developed two assays. In the CO2 laser beam assay, flies exhibit this behavior when a laser beam heats their abdomens. The consistency of the jump latency in this assay meets an important criterion for a good nociceptive assay. In the hot plate assay, flies jump quickly to escape from a hot copper plate (>45 degrees C). Our results demonstrate that, as in mammals, the latency of the jump response is inversely related to stimulus intensity, and innoxious thermosensation does not elicit this nociceptive behavior. To explore the genetic mechanisms of nociception, we examined several mutants in both assays. Abnormal nociceptive behavior of a mutant, painless, indicates that painless, a gene essential for nociception in Drosophila larvae, is also required for thermal nociception in adult flies. painless is expressed in certain neurons of the peripheral nervous system and thoracic ganglia, as well as in the definite brain structures, the mushroom bodies. However, chemical or genetic insults to the mushroom bodies do not influence the nociceptive behavior, suggesting that different painless-expressing neurons play diverse roles in thermal nociception. Additionally, no-bridge(KS49), a mutant that has a structural defect in the protocerebral bridge, shows defective response to noxious heat. Thus, our results validate adult Drosophila as a useful model to study the genetic mechanisms of thermal nociception.

Animals↗
PubMed2005

Enhanced dissipation of phenanthrene and pyrene in spiked soils by combined plants cultivation.

Polycyclic aromatic hydrocarbons (PAHs), a class of POPs, are widely distributed in the environment. Phytoremediation has long been recognized as a cost-effective method for removal of PAHs pollutants from soil. This study was conducted to investigate the capability of three plant species separately and their combination to promote the degradation of phenanthrene and pyrene in soil. The performance of three plant species, maize, ryegrass and white clover for phenanthrene and pyrene removal was also compared. The result showed that the presence of vegetation significantly enhances the dissipation of phenanthrene and pyrene in the soil environment. This effect was especially marked with maize. At the end of 60 days treatment, phenanthrene and pyrene concentrations in treated soils declined from an initial 52.52 mg kg-1 and 58.19 mg kg-1 to 4.15 mg kg-1 and 6.77 mg kg-1, respectively, indicating that phenanthrene and pyrene was successfully removed by maize. Around 92.10% of phenanthrene and 88.36% of pyrene were removed from soils planted with maize. Within approximately two months experimental period, the dissipation extent showed that the 4-ring pyrene was more recalcitrant than 3-ring phenanthrene. Although the extents did not differ significantly among three tested species, the rates of degradation were different. The maize treatment had the highest rate of contaminant removal after two months, followed by white clover and annual ryegrass. As compare to single plant cultivation, combined plants cultivation significantly enhanced the destruction rate and extent of phenanthrene and pyrene in soils. Around 98.22% of phenanthrene and 95.81% of pyrene were removed from soils planted with maize and ryegrass. This research indicates the potential for phenanthrene and pyrene mineralization in combined plants cultivation, which may be especially useful for phytoremediation of soils contaminated with PAHs.

Animals↗
PubMed2004

Enhancement of the superconducting transition temperature of MgB2 by a strain-induced bond-stretching mode softening.

We report a systematic increase of the superconducting transition temperature T(c) with a biaxial tensile strain in MgB2 films to well beyond the bulk value. The tensile strain increases with the MgB2 film thickness, caused primarily by the coalescence of initially nucleated discrete islands (the Volmer-Weber growth mode.) The T(c) increase was observed in epitaxial films on SiC and sapphire substrates, although the T(c) values were different for the two substrates due to different lattice parameters and thermal expansion coefficients. We identified, by first-principles calculations, the underlying mechanism for the T(c) increase to be the softening of the bond-stretching E(2g) phonon mode, and we confirmed this conclusion by Raman scattering measurements. The result suggests that the E(2g) phonon softening is a possible avenue to achieve even higher T(c) in MgB2-related material systems.

Journal Article↗
PubMed2003

Oral administration of type II collagen suppresses pro-inflammatory mediator production by synoviocytes in rats with adjuvant arthritis.

The objective of this study was to investigate the effect of the oral administration of type II collagen (CII) on pro-inflammatory mediator production by synoviocytes in rats with adjuvant arthritis (AA). Sprague-Dawley rats were fed with bovine CII either before immunization with Complete Freund's adjuvant (CFA) or after initiation of arthritis. Hind paw secondary swelling was measured and synoviocytes were harvested. Sera from portal vein of oral tolerized rats were collected and in vitro synoviocytes culture or synoviocytes-Peyer's Patches (PP) cells coculture system were developed. Interleukin (IL)-1 activity was measured by a mouse thymocyte activation assayed by MTT dye reduction and tumour necrosis factor (TNF) activity was measured by an L929 cytotoxicity bioassay. Nitric oxide (NO) and malondialdehyde (MDA) levels were measured by biochemical methods. We found that feeding with CII (5, 50 and 500 micro g/kg) for 7 days before immunization significantly suppressed hind paw secondary swelling measured at day 16, 20, 24 and 28 (all P < 0.01) and pro-inflammatory mediator (IL-1, TNF, NO and MDA) production by synoviocytes (all P < 0.01) in rats with AA. Feeding with CII (5, 50 and 500 micro g/kg) for 7 days after initiation of arthritis had a similar effect. CII (1, 10, 100 micro g/ml) had no effect on IL-1 and TNF production by synoviocytes in vitro, but CII 10 micro g/ml suppressed IL-1 and TNF production by synoviocytes-PP cells coculture system (P < 0.01), which was antagonized by anti-TGF-beta antibody (10 micro g/ml) (P < 0.01). Portal serum (1 : 10) from oral tolerized rats suppressed IL-1 and TNF production by synoviocytes (P < 0.01), which was also antagonized by anti-TGF-beta antibody (10 micro g/ml) (P < 0.01). We conclude that oral administration of CII had prophylactic and therapeutic effects on AA and over-production of IL-1, TNF, NO and MDA by synoviocytes was suppressed. Bystander active suppression may be the main mechanism of oral CII in the suppression of synoviocyte function.

Administration, Oral↗
PubMed2002

Functional analysis of iceA1, a CATG-recognizing restriction endonuclease gene in Helicobacter pylori.

iceA1 in Helicobacter pylori is a homolog of nlaIIIR, which encodes the CATG-specific restriction endonuclease NlaIII in Neisseria lactamica. Analysis of iceA1 sequences from 49 H.pylori strains shows that a full-length NlaIII-like ORF is present in 10 strains, including CH4, but in other strains, including strain 60190, the ORFs are truncated due to a variety of mutations. Our goal was to determine whether iceA1 can encode a NlaIII-like endonuclease. Overexpression in Escherichia coli of iceA1 from CH4, but not from 60190, yielded NlaIII-like activity, indicating that the full-length iceA1 is a functional endonuclease gene. Repair of the iceA1 frameshift mutation in strain 60190 and its expression in E.coli yielded functional NlaIII-like activity. We conclude that iceA1 in CH4 is a functional restriction endonuclease gene, while iceA1 in 60190 is not, due to a frameshift mutation, but that its repair restores its restriction endonuclease activity.

Amino Acid Sequence↗
PubMed2002

Reversible structural transition in epitaxial manganite film.

A reversible structural transition of an epitaxial La(2/3)Sr(1/3)MnO3 film deposited on a LaAlO3 substrate has been investigated by means of in situ high-resolution transmission electron microscopy and electron diffraction, combined with image and diffraction calculations. We observe that the crystallographic symmetry of the film can be lowered via electron beam irradiation, leading to a rhombohedral-monoclinic transition. This transition can be attributed to the cooperating effect of the mismatch stress and the irradiation-induced thermal stress.

Journal Article↗
PubMed2002

The protective effects of melatonin from oxidative damage induced by amyloid beta-peptide 25-35 in middle-aged rats.

This work investigated the ability of melatonin to prevent oxidative damage in brain tissue induced by injection of beta-amyloid peptide 25-35 (Abeta25-35) in middle-aged rats. The Morris water maze was used to evaluate the cognitive function of the rats. Thiobarbituric acid-reactive substances and antioxidative enzymes (superoxide dismutase and glutathione peroxidase) activities were measured. It was found that injection of (Abeta25-35) (20 microg) into the rat hippocampus caused an increase in the latency (the time to find the platform), the total swimming distance to the platform, and the starting angles in (Abeta25-35)-treated rats. Furthermore, a significant rise in lipid peroxidation and decrease in antioxidative enzyme activities in brain tissue were found. Melatonin (0.1, 1, and 10 mg/kg, i.g. x 10 days) improved the spatial resolution of amnesic rats in the Morris water maze test. Meanwhile, melatonin antagonized the lipid peroxidation in both the mitochondria (P < 0.01) at the doses of 0.1, 1.0, and 10 mg/kg and in the cytoplasm at the doses of 0.1 and 1.0 mg/kg. Also in the amnesic rats, melatonin (0.1, 1.0, and 10 mg/kg. i.g. x 10 days) stimulated the antioxidative enzyme activities. The results show that melatonin effectively reduced lipid peroxidation and enhanced the antioxidative enzyme activities in Abeta(25-35)-treated rats, which may contribute to the improvement of rats' learning and memory impaired by Abeta(25-35).

Age Factors↗
PubMed2001

Improvement of melatonin to the learning and memory impairment induced by amyloid beta-peptide 25 - 35 in elder rats.

AIM: To investigate improvement of melatonin on learning and memory impairment induced by amyloid beta-peptide 25 - 35 (Abeta25-35) in elder rats. METHODS: Step-down type passive avoidance test, shuttle-box test, and Morris water maze were used together to determine effects of Abeta25-35 and melatonin on learning and memory. Pathological changes were observed by HE, Congo red, and Ag staining. RESULTS: The elder rats were injected bilaterally Abeta25-35 20 microg into the hippocampus to induce learning and memory dysfunction. Melatonin administration (0.1, 1, and 10 mg/kg, ig x 8 d) to the Abeta25-35-treated rats prolonged the latency, shortened the total stimulating time, and decreased the number of errors in the step-down test. Shuttle-box test showed that melatonin improved amnesic rats' performance at the same doses. Melatonin (0.1, 1, and 10 mg/kg ), giving for 10 d, could enhance the spatial resolution of amnesic rats in Morris water maze test. Also in Abeta25-35-treated group, a decrease in the number of neurons in cortex and hippocampus, a massive glial reaction, and neurophilic phenomenon were detected by HE staining; the positive vascular amyloidosis by Congo red and fibrils by Ag staining were observed. Melatonin (0.1 and 1 mg/kg)could inhibit above pathological changes in Abeta25-35 group. CONCLUSION: Melatonin improved the impaired learning and memory induced by Abeta25-35 in elder rats.

Amyloid beta-Peptides↗
PubMed2001

[Separation, purification and identification of angiotensin converting enzyme inhibitory silk fibroin peptide].

Silk fibroin peptides could be obtained from soluble silk fibroin by enzymatic hydrolysis. Its hydrolyzates produced with Alcalase showed significant inhibitory activity against the angiotensin I-converting enzyme (ACE). One inhibitory peptide from the hydrolyzate at a degree of hydrolysis of 20% (sample A20) was purified and identified. Sample A20 was first isolated by size exclusion chromatography(SEC), eluted with 0.01 mol/L hydrochloric acid solution on a Sephadex G-15 column (1.6 cm i.d. x 100 cm). The peak of No. 5 on the SEC chromatography was further purified by reversed-phase HPLC (mu Bondapak C18 P/N 84176 column, 7.8 mm i.d. x 300 mm), eluted with a linear gradient elution with acetonitrile from 0% to 15% at temperature (30 +/- 2) degrees C. Then the pure peptide with ACE inhibitory activity was obtained, the amino acid sequence of which was identified as Gly-Tyr by mass spectrometry.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

[Reclamation of the plant regeneration efficiency of Brassica campestris subsp. chinensis var.Parachinensis].

This investigation has developed an efficient and fast method for plant regeneration from petiole of cotyledon explants of Brassica campestris L. subsp. chinensis Makino var. parachinensis Tsen et Lee. A medium was designed for B. campestris subsp. chinensis var. parachinensis to obtain the high frequency of shoot regeneration, which contained BAP 2 mg/L, NAA 0.75-1.0 mgL and 7.5 mg/L AgNO3 solution to the half of NH4+ concentration's MS basic medium. 60 mL/L coconut milk were added to all of media. In this method, frequency of shoot regeneration of "youqing caixin" reached as high as 91.2% and the number of shoots per explant reached as high as 4.7 plants. The result showed that there was a positive correlation between frequency of shoot regeneration and number of shoots per explant. The little shoots could be observed five days after inoculation and were formed directly. The inducing rate of roots of the shoots reached as high as 100% and the rate of viability of transferred mature plant reached higher than 95%. The regeneration period from petiole with cotyledon to a seedling was shorten to about 49 days. Factors influencing in vitro explant regeneration were studied.

Brassica↗
PubMed2001

[Effects of leflunomide on immunological liver injury].

AIM: To study the effect of leflunomide (Lef) on immunological liver injury in mice. METHODS: Immunological liver injury was induced by tail vein injection of BCG + LPS (BCG 2.5 mg, 1 d, LPS 10 micrograms, 10 d). The ALT, AST, NO level in plasma and MDA, GSHpx in liver homogenate were assayed by spectroscopy. The serum content of TNF-alpha was determined by ELISA. IL-1, IL-2 and ConA-induced splenocyte proliferation response were determined by methods of 3H-infiltrated cell proliferation. RESULTS: Immunological liver injury induced by BCG + LPS was successfully duplicated. Lef (4, 12, 36 mg.kg-1) was found to significantly decrease the serum transaminase (ALT, AST) activity and MDA content in liver homogenate, and improved reduced GSHpx level of liver homogenate. Furthermore, Lef (4, 12, 36 mg.kg-1) significantly reduced TNF-alpha and NO level in serum, and IL-1 production by PM psi. Moreover, the decreased IL-2 production and ConA-induced splenocyte proliferation response were further inhibited. CONCLUSION: Lef showed significant protective action on immunological liver injury in mice.

Adjuvants, Immunologic↗
PubMed2000

Human neutrophil lipocalin (HNL) and myeloperoxidase (MPO). Studies of lung lavage fluid and lung tissue.

Myeloperoxidase (MPO) and human neutrophil lipocalin (HNL) are proteins which are stored in neutrophil granulocytes, in the primary and secondary granules, respectively. These granules or their contents of MPO and HNL are secreted upon activation of the cells, and measurement of these soluble markers in biological fluids, such as bronchoalveolar lavage (BAL), has been proposed to mirror the degree of neutrophil activity in the tissue. We conducted a BAL study in 10 healthy volunteers, with the aim to evaluate the intra-individual variability of the concentration of HNL and MPO recovered in sequential aspirations, during a time period when the concentrations of HNL and MPO in BAL fluids were considered to have equilibrated with those in the underlying tissues. The concentrations of HNL were less variable than those of MPO (coefficients of variability 0.33 +/- 0.07 vs. 0.92 +/- 0.28; P = 0.01), suggesting HNL to be a more useful marker of neutrophil activity within the airspace. The specificity of HNL as a selective index of neutrophil cells was confirmed by means of immunohistochemical staining of uninvolved lung tissue specimens obtained from patients referred to pulmonectomy due to carcinoma. While HNL was located only to intracellular spaces of neutrophils, MPO was in addition located to other cells as well. We speculate that the dynamic changes of pressure across the membranes and flow of solutes during a lavage process might mobilize particulate matter and adherent cells, some of which may be loaded with MPO, and that this may introduce larger variability in the recovery of MPO than of HNL. We conclude that using HNL as a soluble indicator of neutrophil presence is more feasible than using MPO.

Acute-Phase Proteins↗
PubMed2000

Cloning, expression, and purification of a thermostable nonhomodimeric restriction enzyme, BslI.

BslI is a thermostable type II restriction endonuclease with interrupted recognition sequence CCNNNNN/NNGG (/, cleavage position). The BslI restriction-modification system from Bacillus species was cloned and expressed in Escherichia coli. The system is encoded by three genes: the 2,739-bp BslI methylase gene (bslIM), the bslIRalpha gene, and the bslIRbeta gene. The alpha and beta subunits of BslI can be expressed independently in E. coli in the absence of BslI methylase (M.BslI) protection. BslI endonuclease activity can be reconstituted in vitro by mixing the two subunits together. Gel filtration chromatography and native polyacrylamide gel electrophoresis indicated that BslI forms heterodimers (alphabeta), heterotetramers (alpha(2)beta(2)), and possibly oligomers in solution. Two beta subunits can be cross-linked by a chemical cross-linking agent, indicating formation of heterotetramer BslI complex (alpha(2)beta(2)). In DNA mobility shift assays, neither subunit alone can bind DNA. DNA mobility shift activity was detected after mixing the two subunits together. Because of the symmetric recognition sequence of the BslI endonuclease, we propose that its active form is alpha(2)beta(2). M.BslI contains nine conserved motifs of N-4 cytosine DNA methylases within the beta group of aminomethyltransferase. Synthetic duplex deoxyoligonucleotides containing cytosine hemimethylated or fully methylated at N-4 in BslI sites in the first or second cytosine are resistant to BslI digestion. C-5 methylation of the second cytosine on both strands within the recognition sequence also renders the site refractory to BslI digestion. Two putative zinc fingers are found in the alpha subunit of BslI endonuclease.

Amino Acid Sequence↗
PubMed1998

Cloning and expression of the ApaLI, NspI, NspHI, SacI, ScaI, and SapI restriction-modification systems in Escherichia coli.

The genes encoding the ApaLI (5'-GTGCAC-3'), NspI (5'-RCATGY-3'), NspHI (5'-RCATGY-3'), SacI (5'-GAGCTC-3'), SapI (5'-GCTCTTCN1-3', 5'-N4GAAGAGC-3') and ScaI (5'-AGTACT-3') restriction-modification systems have been cloned in E. coli. Amino acid sequence comparison of M.ApaLI, M.NspI, M.NspHI, and M.SacI with known methylases indicated that they contain the ten conserved motifs characteristic of C5 cytosine methylases. NspI and NspHI restriction-modification systems are highly homologous in amino acid sequence. The C-termini of the NspI and NlaIII (5'-CATG-3') restriction endonucleases share significant similarity. 5mC modification of the internal C in a SacI site renders it resistant to SacI digestion. External 5mC modification of a SacI site has no effect on SacI digestion. N4mC modification of the second base in the sequence 5'-GCTCTTC-3' blocks SapI digestion. N4mC modification of the other cytosines in the SapI site does not affect SapI digestion. N4mC modification of ScaI site blocks ScaI digetion. A DNA invertase homolog was found adjacent to the ApaLI restriction-modification system. A DNA transposase subunit homolog was found upstream of the SapI restriction endonuclease gene.

Amino Acid Sequence↗
PubMed1998

Refined genetic mapping of autosomal dominant retinitis pigmentosa locus RP18 reduces the critical region to 2 cM between D1S442 and D1S2858 on chromosome 1q.

Linkage analysis was performed on a large Danish family to refine the position of RP18, the locus for autosomal dominant retinitis pigmentosa, mapped previously between D1S534 and D1S305 in chromosome 1p13-q21. We genotyped the family members for five microsatellite-type DNA polymorphisms and mapped RP18 between D1S422 and D1S2858 to a region of less than 2 cM. No obvious candidate gene has yet been assigned to the chromosomal interval defined here.

Adult↗