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Biomedical subjects

S X Liu

Publications and source records attributed to S X Liu.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Screening and cloning of genes encoding Schistosoma japonicum antigens related to the serum antibodies in Mirotus fortis].

OBJECTIVE: To understand and identify the molecules related to the natural resistance to Schistosoma japonicum infection in Mirotus fortis. METHODS: Sera from Mirotus fortis without schistosome infection were collected. The S. japonicum adult worm cDNA library was immunologically screened with the sera. The positive recombinants were identified, cloned, sequenced and analysed with software and internet. RESULTS: Seven genes encoding antigens relevant to sera antibodies in Mirotus fortis were cloned and sequenced. These antigens included glyceraldehyde 3-phosphate dehydrogenase (GAPDH), serine protease inhibitors (SERPIN), 70 kDa heat shock protein (HSP70), 22.6 kDa membrane-associated antigen, paramyosin (Sj97), cytochrome C and cathepsin B. CONCLUSION: Many protein molecules might have been involved in natural resistance to S. japonicum infection in Mirotus fortis. The above 7 kinds of molecules may be identified as new candidates of vaccine against S. japonicum infection.

Animals↗
PubMed2001

[Cloning and expression of the gene encoding Schistosoma japonicum tropomyosin].

OBJECTIVE: To clone and express the cDNA encoding Schistosoma japonicum tropomyosin. METHODS: The cDNA was amplified by reverse transcription-polymerase chain reaction (RT-PCR). The PCR products were ligated with pGEM-T vectors and then for transformations. After characterization of white clones by agarose gel electrophoresis, endonucleases digestion and PCR, some recombinant plasmids with inserts were used for sequencing. Then the gene was subcloned into prokaryotic expression vector pQE30 and expression was induced by IPTG. RESULTS: The PCR products was 823 bp judged by agarose gel electrophoresis and sequencing. A cDNA encoding S. japonicum tropomyosin, except for 14 amino acids at the amino terminus and 2 at the carboxyl terminus, has been constructed and cloned successfully. The colony, designated pGSjcTM12, was sequenced and shown to be 91.1% identical at the nuclei acid level and 98.1% identical in deduced amino acid sequence to that of S. mansoni tropomyosin. The gene was subcloned into pQE30 and an expressed protein of about 32 kDa was obtained. CONCLUSION: The cloning and expression of the gene encoding S. japonicum tropomyosin had been successfully made.

Amino Acid Sequence↗
PubMed2001

[A study on the recombinant 26 kDa glutathione-S-transferase as a vaccine candidate: dynamics of antibodies in immunized buffaloes and protection against Schistosoma japonicum infections].

OBJECTIVE: To observe the dynamics of antibodies and protection against Schistosoma japonicum infections in buffaloes after immunized with recombinant 26 kDa glutathione-S-transferase (reSjc26GST). METHODS: Buffaloes in 2 villages endemic for schistosomiasis japonica were selected as test and control groups, respectively. In test group initially 96 buffaloes were vaccinated with reSjc26GST, and 90 buffaloes in the control group did not experience vaccination. The indicators included levels of antibodies to reSjc26GST in buffaloes before and after infection with S. japonicum and changes in infection rate. RESULTS: Specific antibodies, which showed a trend of trapezoid increase, were induced in buffaloes after immunized with reSjc26GST. Twenty months after immunization, the infection rate of the test group was decreased by 62.2% when compared with that before vaccination, and by 67.7% when compared with that of the control in the corresponding period. CONCLUSION: Specific antibodies and a certain extent of protection were induced in buffaloes after immunized with reSjc26GST, which played an significant role in ameliorating morbidity.

Animals↗
PubMed2001

[Detection of anti-Spirometra erinaceieuropaei antibody using ELISA].

OBJECTIVE: To study specific diagnosis of Spirometra erinaceieuropaei. METHODS: An enzyme-linked immunosorbent assay (ELISA) was studied using highly pure gene engineering antigen expressed by the recombination of the cloned cysteine proteinase gene of Spirametra erinaceieuropaei with expression vector pMAL-c2. Six sera from patient infected with Spirometra erinaceieuropaei were detected using this method. RESULTS AND CONCLUSION: The results showed that the gene engineering antigen reacted strongly with the sera from Spirometra erinaceieuropaei-infected patients, but did not with the sera from Cysticercus cellulosae-infected patients.

Animals↗
PubMed2001

[Experimental research of NNB composite in repairing mandibular defects in rabbits].

OBJECTIVE: To study the effects of artificial bone composite of basic fibroblast growth factor(bFGF) with natural non organic bone(NNB)in repairing mandibular defects in rabbits,in order to provide an ideal bone replacement material for clinic. METHODS: 15mm x 6mm bilateral mandibular periosteum bone defects were made surgically in 30 New Zealand adult rabbits and each defect as an experimental unit. The defects were randomly repaired with composite bone, NNB,fresh autogenous bone at 3,6,12 weeks after surgery according to the total random design, blank control group was stayed. Specimens obtained were evaluated with general observation, X-ray as well as computerized histological microscopic analysis. RESULTS: New bone formed and calcified earlier in composite bone and the bone area was greater in the same period than that in NNB. The new bone area in composite bone was still smaller than that of autogenous bone at 6 weeks, while at 12 weeks they had no significant differences. The blank defects were not repaired even in the end. CONCLUSION: Composite bone had sound biocompatibility. It was much better than NNB and can be compared with autogenous bone 12 weeks after operation. So it can be an ideal alternative for bone replacement.

English Abstract↗
PubMed2000

Sequence and analysis of chromosome 1 of the plant Arabidopsis thaliana.

The genome of the flowering plant Arabidopsis thaliana has five chromosomes. Here we report the sequence of the largest, chromosome 1, in two contigs of around 14.2 and 14.6 megabases. The contigs extend from the telomeres to the centromeric borders, regions rich in transposons, retrotransposons and repetitive elements such as the 180-base-pair repeat. The chromosome represents 25% of the genome and contains about 6,850 open reading frames, 236 transfer RNAs (tRNAs) and 12 small nuclear RNAs. There are two clusters of tRNA genes at different places on the chromosome. One consists of 27 tRNA(Pro) genes and the other contains 27 tandem repeats of tRNA(Tyr)-tRNA(Tyr)-tRNA(Ser) genes. Chromosome 1 contains about 300 gene families with clustered duplications. There are also many repeat elements, representing 8% of the sequence.

Arabidopsis↗
PubMed2000

Reconstitution of apo-superoxide dismutase by nitric oxide-induced copper transfer from metallothioneins.

Little is known about copper transfer from Cu-metallothionein (Cu-MT) to various target proteins, such as apo-SOD, and the potential role of redox mechanisms in this transfer. We studied Cu transfer from Cu-MT to apo/Zn-SOD in a cell-free model system and found that Cu(5)-MT and Cu(10)-MT were able to reconstitute SOD activity only in the presence of a nitric oxide donor, (Z)-[N-(3-ammoniopropyl)-N-(n-propyl)amino]diazen-1-ium++ +-1,2-diolate (NOC-15). The percentage of reconstitution by Cu(5)-MT and Cu(10)-MT was 34 and 83%, respectively, compared with that reconstituted by free Cu alone. A Cu chelation assay using bathocuproine disulfonate (BCS) showed that NOC-15 induced release of free Cu from Cu(10)-MT but not from Cu(5)-MT. The transfer of Cu from Cu-MT to apo/Zn-SOD was not accompanied by enhanced Cu-dependent generation of ascorbate radicals or hydroxyl radicals as measured by EPR spectroscopy. We found a 70% decrease in the number of 2,2'-dithiodipyridine titratable SH groups on MT after incubation with NOC-15. Overall, our results suggest that Cu-MT could potentially function in a nitric oxide-dependent pathway for the delivery of Cu to apo-SOD in copper-challenged cells.

Animals↗
PubMed2000

Antioxidant and antiapoptotic function of metallothioneins in HL-60 cells challenged with copper nitrilotriacetate.

Antioxidant activity is believed to be an important intracellular function of metallothioneins (MT), yet the specific mechanisms of their antioxidant action are not known. Under conditions when cells are challenged with elevated concentrations of free copper as a result of metabolic disturbances or environmental and occupational exposures, MTs may be ideally suited for antioxidant function as effective copper chelators. In the study presented here, we tested this hypothesis using a recently established model of copper nitrilotriacetate-induced oxidative stress in HL-60 cells. Since copper-induced oxidative stress triggers apoptosis, we further investigated antiapoptotic function of MTs in HL-60 cells. Using a Sephadex G-75 chromatographic partial purification of MTs from cell homogenates with subsequent immuno-dot-blot assay, we showed that zinc pretreatment yielded a pronounced induction of MTs in HL-60 cells. We report that zinc-induced MTs were able to (i) completely bind intracellular copper, (ii) completely quench redox-cycling activity of copper, (iii) significantly inhibit copper-dependent oxidative stress in membrane phospholipids, and (iv) prevent copper-dependent apoptosis and its characteristic biochemical features (cytochrome c release from mitochondria into cytosol, caspase-3 activation, and externalization of phosphatidylserine in plasma membranes). In separate experiments, we used lung fibroblasts derived from MT1, MT2 knockout mice (MT(-)(/)(-)) and MT wild-type (MT(+/+)) mice. ZnCl(2) pretreatment resulted in a more than 10-fold induction of MTs in MT(+/+) cells, whereas the MT content in MT(-)(/)(-) cells remained low, at levels approximately 100-fold lower than in their MT wild-type counterparts. MT(-)(/)(-) cells were very sensitive to Cu-NTA and, most importantly, showed no response to ZnCl(2) pretreatment. In contrast, MT(+/+) cells were relatively more resistant to Cu-NTA, and this resistance was remarkably enhanced by ZnCl(2) pretreatment. Combined, our results demonstrate that metallothioneins function as effective antioxidants and an antiapoptotic mechanism in copper-challenged HL-60 cells.

Animals↗
PubMed2000

Reduction of the oxidative injury to the rabbits with established atherosclerosis by protein bound polysaccharide from Coriolus vesicolor.

Recent evidence has emerged that macrophage glutathione (GSH) content and selenium dependent glutathione peroxidase (SeGSHPx) activity are inversely related to cell-mediated oxidation of LDL, and intervention means to enhance the macrophage GSH-SeGSHPx status may contribute to attenuation of the atherosclerotic process. Our previous works showed that protein bound polysaccharide (PSK) injected intraperitoneally could enhance SeGSHPx activity and mRNA content of mouse macrophages. The aim of the present study is to demonstrate whether PSK can reduce the oxidative injury to the established atherosclerotic rabbits. Using the established atherosclerotic rabbit model, we studied the effect of PSK on oxidatively modified LDL (Ox-LDL), lipoperoxide (LPO) cholesterol contents and SeGSHPx activities of plasma and tissues (aorta, heart and liver) in the established atherosclerotic rabbits. As compared with the control group, Ox-LDL, LPO and cholesterol contents were much lower; SeGSHPx activities and SeGSHPx/LPO ratios were much higher in plasma and tissues (aorta, heart and liver); and the lesion area of aortae was reduced in the PSK group. Through the increment of SeGSHPx activity in macrophages and aortae, PSK enhances their antioxidation potentiality and improves the antioxidant/prooxidant imbalance in them, and thus decreases Ox-LDL, LPO and cholesterol contents of plasma and tissues, and regresses lesion area of aortae in the established atherosclerotic rabbits.

Animals↗
PubMed2000

Prenyltransferase inhibitors block superoxide production by pulmonary vascular smooth muscle.

We recently showed that the farnesyltransferase inhibitor FTI-277 blocks interleukin 1beta (IL-1beta)-induced nitric oxide production in pulmonary vascular smooth muscle cells (SMC), whereas the geranylgeranyltransferase inhibitor GGTI-298 enhances this effect. Here we show that IL-1beta and platelet-derived growth factor (PDGF) stimulate superoxide production by pulmonary vascular SMC and that this effect is blocked by both FTI-277 and GGTI-298, suggesting that farnesylated and geranylgeranylated proteins are required for superoxide production. We also show that FTI-277 and GGTI-298 block superoxide production stimulated by constitutively active mutant H-Ras. Furthermore, superoxide production by IL-1beta, PDGF factor, and constitutively activated Ras is blocked by diphenyleneiodonium, implicating NAD(P)H oxidase as the generating enzyme. Given the role of oxidant radicals in vascular reactivity and injury, the action of both FTI-277 and GGTI-298 in suppressing superoxide generation by an inflammatory cytokine as well as by a potent smooth muscle mitogen may be therapeutically useful.

Animals↗
PubMed2000

[The protective immunity in mice immunized with FhGST or AsGST against Schistosoma japonicum cercariae].

OBJECTIVE: To study the protective immunity against Schistosoma japonicum (Sj) cercariae challenge in mice immunized with FhGST or AsGST. METHODS: There groups of Kunming mice were immunized three times with rSjGST, FhGST and AsGST, respectively. Then 30 cercariae of Schistosoma japonicum were given per mouse by abdominal skin inoculation. Six weeks later, all mice were killed to collect adult worms, liver, spleen and large intestine for worm count and egg count. RESULTS: The worm burden was reduced by 27.8%-36.4% in the three immune groups compared with the two control groups (P < 0.05). rSj26GST, FhGST and AsGST significantly decreased the number of eggs deposited in the tissues. CONCLUSION: FhGST and AsGST could induce protection against S. japonicum cercariae infection.

Animals↗
PubMed1999

Natural antibodies in Microtus fortis react with antigens derived from four stages in the life-cycle of Schistosoma japonicum.

The levels of antibodies which react with the cercarial antigens (CA), schistosomulum stage antigens (SSA), adult-worm antigens (AWA) and soluble egg antigens (SEA) of Schistosoma japonicum were investigated in Microtus fortis and albino mice, using an indirect ELISA. The M. fortis studied fell into three groups: animals caught in the wild; laboratory-bred animals left unchallenged; and laboratory-bred animals that had been challenged with S. japonicum (30 cercariae/animal) 15 days previously. There were also three groups of albino mice: those without infection; those studied 15 days after challenge infection; and those investigated 42 days after infection. The antibodies detected at the highest levels in the laboratory-bred, uninfected voles and in the wild-caught animals were those reacting with SSA, followed, in descending order, by those reacting with AWA, CA and SEA. The levels of natural antibodies to SSA and AWA in these voles were significantly higher than the corresponding levels observed in the uninfected mice and even in the mice infected 15 days previously. The levels of antibodies reacting with CA, SSA, SEA and AWA in the experimentally infected M. fortis were 1.9-, 2.2-, 1.5- and 2.1-fold higher, respectively, than those in the laboratory-bred but uninfected voles. The observations indicate that even uninfected M. fortis produce antibodies which react with S. japonicum, and this presumably results in the natural resistance to infection which has been reported in these rodents.

Animals↗
PubMed1999

Systemic anti-inflammation by synthetic interleukin-1 blockers.

AIM: To study the systemic anti-inflammatory actions of interleukin-1 (IL-1) blockers, OB-101 and OB-186. METHODS: Prevention of palm swelling induced by carrageenin injection was used as an animal model of systemic anti-inflammation efficacy. RESULTS: Both OB-101 and OB-186 (10-30 mg.kg-1) were approximately 10-30-fold more potent than aspirin (300 mg.kg-1) to inhibit carrageenin-induced systemic inflammation. The LD50 of OB-101 and OB-186 were at least 20 g.kg-1 i.g., indicating that they were extremely safe agents with a therapeutic index (LD50/ED50) of at least 2000. CONCLUSION: These IL-1 blockers are extremely safe systemically and are useable for the treatment of systemic inflammation such as rheumatoid arthritis.

Acridines↗
PubMed1998

Mutagenicity of arsenic in mammalian cells: role of reactive oxygen species.

Arsenite, the trivalent form of arsenic present in the environment, is a known human carcinogen that lacked mutagenic activity in bacterial and standard mammalian cell mutation assays. We show herein that when evaluated in an assay (AL cell assay), in which both intragenic and multilocus mutations are detectable, that arsenite is in fact a strong dose-dependent mutagen and that it induces mostly large deletion mutations. Cotreatment of cells with the oxygen radical scavenger dimethyl sulfoxide significantly reduces the mutagenicity of arsenite. Thus, the carcinogenicity of arsenite can be explained at least in part by it being a mutagen that depends on reactive oxygen species for its activity.

Animals↗
PubMed1998

Oxidized cholesterol in oxidized low density lipoprotein may be responsible for the inhibition of LPS-induced nitric oxide production in macrophages.

Previous work has shown that oxidized low density lipoprotein (Ox-LDL) inhibited lipopolysacchride (LPS)-induced nitric oxide (NO) production in macrophages. In this paper, the role of different components of Ox-LDL in the inhibitory effect was studied by measuring nitrite in media. Ox-LDL inhibited LPS-induced NO production in macrophage cell line J774.A1. When compared with Ox-LDL, native and acetylated LDL had a lesser effect on NO production. Pre-clearance of lipid hydroperoxides (LOOH) in Ox-LDL and removal of soluble thiobarbituric acid reactive substances (TBARS) in Ox-LDL solution by dialysis had no influence on the inhibitory effect of Ox-LDL. The protein moiety of Ox-LDL had no effect on NO production, but the lipid moiety inhibited NO production to about the same extent as intact Ox-LDL. Linoleic acid and phosphatidylcholine, the main components of LDL lipid, whether oxidized separately or together, had no effect on NO production. However, if linoleic acid and cholesterol oxidized together, there was very strong inhibition of NO production. Cholesterol oxidized alone also had some inhibitory effect. These results suggest that oxidized cholesterol in Ox-LDL might be responsible for the inhibition of NO production in macrophages.

Animals↗
PubMed1997

Mutagenic effects of a single and an exact number of alpha particles in mammalian cells.

One of the main uncertainties in risk estimation for environmental radon exposure using lung cancer data from underground miners is the extrapolation from high- to low-dose exposure where multiple traversal is extremely rare. The biological effects of a single alpha particle are currently unknown. Using the recently available microbeam source at the Radiological Research Accelerator Facility at Columbia University, we examined the frequencies and molecular spectrum of S1- mutants induced in human-hamster hybrid (A(L)) cells by either a single or an exact number of alpha particles. Exponentially growing cells were stained briefly with a nontoxic concentration of Hoechst dye for image analysis, and the location of individual cells was computer-monitored. The nucleus of each cell was irradiated with either 1,2,4, or 8 alpha particles at a linear energy transfer of 90 keV/microm consistent with the energy spectrum of domestic radon exposure. Although single-particle traversal was only slightly cytotoxic to A(L) cells (survival fraction approximately 0.82), it was highly mutagenic, and the induced mutant fraction averaged 110 mutants per 10(5) survivors. In addition, both toxicity and mutant induction were dose-dependent. Multiplex PCR analysis of mutant DNA showed that the proportion of mutants with multilocus deletions increased with the number of particle traversals. These data provide direct evidence that a single a particle traversing a nucleus will have a high probability of resulting in a mutation and highlight the need for radiation protection at low doses.

Alpha Particles↗