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Biomedical subjects

Xin Liu

Publications and source records attributed to Xin Liu.

At least 145 records · Page 8Linked to original sources
PubMed2004

Using capillary electrophoresis with laser-induced fluorescence to study the interaction of green fluorescent protein-labeled calmodulin with Ca2+- and calmodulin-binding protein.

A separation using capillary electrophoresis with laser-induced fluorescence (CE-LIF) was applied to the study of green fluorescent protein tagged calmoldulin (GFP-CaM) that was expressed from Escherichia coli and purified with Ni(2+)-nitrilotriacetate (Ni-NTA) resin column. It was found that GFP-CaM not only has good fluorescence properties under various conditions similar to GFP, but also retains its calcium-binding ability as the native CaM. GFP-CaM was separated and detected by CE-LIF within 10 min with a limit-of-detection (LOD) of 2 x 10(-10) M for an injection volume of 3 nl, higher than that of common chemical fluorescent-tagged protein method. The results indicated that, as a fluorescence probe, GFP could overcome the drawback of inefficient derivatization of chemical fluorescence probes. The interaction between the GFP-CaM and Ca(2+) was studied in detail using affinity capillary electrophoresis with laser-induced fluorescence and the dissociation constant (K(d)) between GFP-CaM and Ca(2+) was determined to be 1.2 x 10(-5), which is in good agreement with the literature values of untagged CaM (10(-6) to 10(-5)M) obtained by conventional method. As a preliminary application, the interaction between GFP-CaM and OsCBK was also investigated. The method makes it possible to screen the trace amounts of target proteins in crude extracts interacting with CaM under physiological conditions.

Base Sequence↗
PubMed2004

Characterization of a region involved in binding of measles virus H protein and its receptor SLAM (CD150).

Signaling lymphocyte activation molecule (SLAM; also known as CD150) is a newly identified cellular receptor for measles virus (MV). MV Hemagglutinin protein (H) mediates MV entry into host cells by specifically binding to SLAM. Amino acid 27-135 of SLAM was previously shown to be the functional domain to interact with H and used to screen a 10-mer phage display peptide library in this study. After four rounds of screening and sequence analysis, the deduced amino acid sequence of screened peptides SGFDPLITHA and SDWDPLFTHK showed to be highly homologous with amino acid 429-438 of MV H (SGFGPLITHG). Peptides SGFDPLITHA and SDWDPLFTHK specifically inhibited binding of H to SLAM and further inhibition of MV infection suggests that these peptides can be developed to MV blocking reagents and amino acid 429-438 in H protein is functionally involved in receptor binding and may constitute part of the receptor-binding determinants on H protein.

Animals↗
PubMed2004

Haplotypes in the APOA1-C3-A4-A5 gene cluster affect plasma lipids in both humans and baboons.

Genetic studies in non-human primates serve as a potential strategy for identifying genomic intervals where polymorphisms impact upon human disease-related phenotypes. It remains unclear, however, whether independently arising polymorphisms in orthologous regions of non-human primates leads to similar variation in a quantitative trait found in both species. To explore this paradigm, we studied a baboon apolipoprotein gene cluster (APOA1/C3/A4/A5) for which the human gene orthologs have well-established roles in influencing plasma HDL-cholesterol and triglyceride concentrations. Our extensive polymorphism analysis of this 68 kb gene cluster in 96 pedigreed baboons identified several haplotype blocks each with limited diversity, consistent with haplotype findings in humans. To determine whether baboons, like humans, also have particular haplotypes associated with lipid phenotypes, we genotyped 634 well-characterized baboons using 16 haplotype tagging SNPs. Genetic analysis of single SNPs, as well as haplotypes, revealed an association of APOA5 and APOC3 variants with HDL-cholesterol and triglyceride concentrations, respectively. Thus, independent variation in orthologous genomic intervals does associate with similar quantitative lipid traits in both species, supporting the possibility of uncovering human quantitative trait loci genes in a highly controlled non-human primate model.

Animals↗
PubMed2004

Two new flavonol glycosides from Gymnema sylvestre and Euphorbia ebracteolata.

Two new flavonol glycosides, namely kaempferol 3-O-beta-D-glucopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-galactopyranoside (1) and quercetin 3-O-6"-(3-hydroxyl-3-methylglutaryl)-beta-D-glucopyranoside (2), have been isolated from the aerial parts of Gymnema sylvestre and Euphorbia ebracteolata, respectively. Their structures were determined on the basis of chemical and spectroscopic methods.

Euphorbia↗
PubMed2004

Collagen fiber immobilized Myrica rubra tannin and its adsorption to UO2(2+).

Tannins, which are rich in ortho-hydroxyl groups, have a high affinity for UO2(2+). In this paper, Myrica rubra tannin was immobilized on collagen fiber by an aldehydic cross-linking reaction to prepare a novel adsorbent for uranium (UO2(2+)) recovery from wastewater. The adsorption equilibrium, the adsorption kinetics, and the effects of temperature and pH on the adsorption equilibrium were investigated in detail. It was found that the Myrica rubra tannin immobilized on collagen fiber exhibits an excellent adsorption capacity for UO2(2+). The adsorption capacity at 293 K and pH 5.0 was as high as 1.19 mmol UO2(2+)/g (283.3 mgU/g) when the initial concentration of UO2(2+) in solution was 7.5 mmol/L. The adsorption isotherms could be described by the Freundlich equation, and the increase of temperature promoted the adsorption to UO2(2+) . The adsorption kinetics data were fitted very well by the pseudosecond-order rate model, and the equilibrium adsorption capacity calculated by the pseudo-second-order rate model was almost the same as that determined by the actual measurement with the error < or = 4%. The pH has a significant effect on the adsorption process. According to our experiments, the suitable pH scope should be 5-8.

Adsorption↗
PubMed2004

Bombyx mori prothoracicostatic peptide inhibits ecdysteroidogenesis in vivo.

Bombyx prothoracicostatic peptide (Bom-PTSP) is a brain neuropeptide that has recently been reported to have in vitro inhibitory activity to prothoracicotropic hormone (PTTH)-stimulated ecdysteroid biosynthesis in the prothoracic gland of the silkworm, Bombyx mori. In the present report, Bom-PTSP has been shown to significantly decrease hemolymph ecdysteroid titer in the fifth instar larvae when Bom-PTSP was injected into the fifth instar day 8 silkworm larvae, resulting in significant delay in spinning behavior. This is the first evidence that Bom-PTSP inhibits in vivo ecdysteroidogenesis in the silkworm.

Animals↗
PubMed2004

Biopharmaceutics of beta-cyclodextrin derivative-based formulations of acitretin in Sprague-Dawley rats.

Acitretin, an active metabolite of etretinate, is as effective as etretinate in the treatment of psoriasis. Recently, we developed some water-soluble formulations of acitretin with 2-hydroxypropyl-beta-cyclodextrin (HPBCD)/randomly substituted methyl-beta-cyclodextrin (RMBCD). In this study, the biopharmaceutic properties of these formulations were tested in Sprague-Dawley rats. After single intravenous dosing (2.5, 5, or 10 mg/kg) with the HPBCD-based formulation, the area under the plasma concentration-time curve of acitretin increased proportionally with the dose and its clearance remained unchanged within the tested dose range. We also found that the RMBCD-based formulation of acitretin improved its bioavailability and decreased the variations in various pharmacokinetic parameters. The improved biopharmaceutic properties of RMBCD-based acitretin might be attributed to its enhanced aqueous solubility. The elimination of acitretin through bile excretion was also studied. Our results indicated that the major fraction of acitretin (approximately 40%) was excreted in the bile as beta-glucuronide conjugate and only trace amounts were excreted as unconjugated acitretin (approximately 0.5%). This finding further confirmed the importance of conjugated metabolism and biliary excretion in the elimination of this drug.

Acitretin↗
PubMed2004

Improvement of growth and camptothecin yield by altering nitrogen source supply in cell suspension cultures of Camptotheca acuminata.

Nitrate at 70 mM gave the highest biomass of Camptotheca acuminata in suspension culture in MS medium, but a NH4+/NO3- molar ratio of 5:1 (giving a total of 40 mM N) gave the maximum camptothecin yield. A two-stage flask culture system was established to improve culture efficiency; cell dry weight, camptothecin content and yield was increased by 30%, 280% and 340%, respectively when compared with those of control, reaching up to 36 g l(-1), 0.36 mg g(-1), and 12.8 mg l(-1), respectively.

Camptotheca↗
PubMed2004

Genetic dissection methods: designs used for tests of gene-environment interaction.

Given recent advances in the field of molecular genetics, many have recognized the need to exploit either study designs or analytical methods to test hypotheses with gene-by-environment (G x E) interactions. The partial-collection designs, including case-only, partial case-control, and case-parent trio designs, have been suggested as attractive alternatives to the complete case-control design both for increased statistical efficiency and reduced data needs. However, common problems in genetic epidemiology studies, such as, presence of G x E correlation in the population, population mixture, and genotyping error may reduce the validity of these designs. On the basis of previous simulation studies and empirical data and given the potential limitations and uncertainty of assumptions of partial-collection designs, the case-control design is the optimal choice versus partial-collection designs.

Case-Control Studies↗
PubMed2004

Analysis of differential gene expression in the cochlea and kidney of mouse by cDNA microarrays.

Microarray hybridization analysis of gene expression in the cochlea and kidney suggest a relationship between these tissues at the genomic level, indicating the common gene expression, likely serving a common function in both the organs primarily maintaining ion transport, and implied previously from morphological, pharmaco-kinetic and teratogenic studies. The cDNAs of more than 100 genes listed on the hereditary hearing loss homepage were amplified as targets by RT-PCR and were hybridized with probes prepared from total RNA of the cochlea and the kidney. Thirteen of the genes analyzed showed altered fluorescence ratios of more than two logs. Of these, the expressions of 11 genes were over expressed and two were under expressed in the cochlea than in the kidney. Our data is the first report to corroborate the genomic similarities between these two important organs and may help to explain the somewhat similar response of these organs to certain therapeutic drugs.

Animals↗
PubMed2004

Associations between specific serum IgE response and 6 variants within the genes IL4, IL13, and IL4RA in German children: the German Multicenter Atopy Study.

BACKGROUND: Among many published studies of specific IgE response or atopy, only a few showed positive marginal effects for 6 potentially functional single nucleotide polymorphisms (SNPs; C-590T in the IL4 gene, C-1055T and Arg130Gln in the IL13 gene, and Ile50Val, Ser478Pro, and Gln551Arg in the IL4RA gene). SNPs were commonly considered individually, and therefore the true effect could be masked by other genes or environmental factors. OBJECTIVE: We tested the relationship between these 6 SNPs and sensitization to food, mite, cat, and outdoor allergens in unrelated German children drawn from the Multicenter Atopy Study. Gene-gene and gene-environment interactions were also evaluated. METHODS: Multiple logistic regression models were used for the analyses of 4 sensitization outcomes. RESULTS: The variant C-1055T was significantly associated with increased risk of sensitization to food and outdoor allergens, with odds ratios of 3.49 (95% CI, 1.52-8.02) and 2.27 (95% CI, 1.04-4.94), respectively. The effects of the TT genotype on food sensitization appear to depend on variants in the IL4RA gene, in which marginally significant interaction terms were observed. Significant evidence supported an interaction between exposure to maternal smoking and variant Gln551Arg on risk of cat sensitization. In addition, we found that the effect of variant C-590T on sensitization to mite depended on Der p 1 allergen levels in carpet dust samples. CONCLUSIONS: These findings not only suggested that variants in the IL4, IL13, and IL4RA genes play an important role in controlling specific IgE response but also strengthened our understanding of gene-gene and gene-environment interaction on the development of specific sensitization in this study population.

Allergens↗
PubMed2004

Five new Ocotillone-type saponins from Gynostemma pentaphyllum.

Five new ocotillone-type saponins, gynosides A-E (1-5), along with 10 known dammarane-type saponins, were isolated from the aerial parts of Gynostemma pentaphyllum. The structures of these new compounds were determined by NMR analysis and acid hydrolysis. The structure and stereochemistry of gynoside A (1) were confirmed by X-ray crystallography.

Crystallography, X-Ray↗
PubMed2004

Mammalian apoptosis-inducing protein, HAP, induces bacterial cell death.

In attempting to produce the HAP, endoplasmic reticulum (ER) targeted apoptosis-inducing protein, as a GST-fusion protein we found that the expression of HAP, but not GST alone, induced bacterial cell death. The HAP protein inhibited the bacterial growth within 30 min after inducting HAP expression. The transmission electron microscopic examination revealed that the morphology of the bacterial cells expressing hap was changed dramatically: unusually elongated phenotype compared with those of controls and finally leading to cell death. The lethality of HAP was relieved by the addition of vitamin E as a reducing agent and under anaerobic growth conditions. These results suggest that a trace amount of HAP induces bacterial cell death and the death is related with reactive oxygen species (ROS).

Apoptosis↗
PubMed2004

Four new stilbenoids from the lianas of Gnetum montanum f. megalocarpum.

From the lianas of Gnetum montanum Markgr. f. megalocarpum Markgr., four new stilbenoids, gnetumontanins A - D ( 1 - 4) were obtained together with 16 known compounds. Gnetumontanin A ( 1) is the first oligostilbene dimerized from two oxyresveratrol units, gnetumontanin B ( 2) is a new stilbene trimer oligomerized from two oxyresveratrol and one resveratrol units, gnetumontanin C ( 3) is a new stilbenoid with a novel skeleton having a delta-lactone moiety and gnetumontanin D ( 4) is a glucoside of 3. Their structures were determined by means of spectroscopic evidence, especially 2D NMR techniques. Gnetumontanin B showed potent inhibition of TNF-alpha with an inhibitory ratio of 58.1 % (P < 0.05) at a concentration of 10 ( - 5) mol L (-1) and the IC (50) was 1.49 x 10 ( - 6) mol L (-1).

Animals↗
PubMed2004

Prediction of protein secondary structure based on residue pairs.

The GOR program for predicting protein secondary structure is extended to include triple correlation. A score system for a residue pair to be at certain conformation state is derived from the conditional weight matrix describing amino acid frequencies at each position of a window flanking the pair under the condition for the pair to be at the fixed state. A program using this score system to predict protein secondary structure is established. After training the model with a learning set created from PDB_SELECT, the program is tested with two test sets. As a method using single sequence for predicting secondary structures, the approach achieves a high accuracy near 70%.

Algorithms↗
PubMed2004

[Effects of Naoluo Xintong Recipe on expression of HSP70 and bFGF in focal ischemia-reperfusion rats].

OBJECTIVE: To investigate the possible beneficial effects of administration of Naoluo Xintong Recipe (NLXT) on the expression of HSP70 and bFGF in rats subjected to ischemia-reperfusion with qi deficiency and blood stasis syndrome. METHODS: We blindly randomized 40 male Wistar rats into 5 groups which were categorized as follows: (1); sham-operated group; (2) rats subjected to transient middle cerebral artery (MCA) occlusion with qi deficiency and blood stasis syndrome (control group); (3) NLXT-treated group; (4) NLXT-pretreated group; (5) Nao'an Capsule-treated group. Focal brain ischemia was induced by the intraluminal suture MCA occlusion method after qi deficiency and blood stasis syndrome had been made. The rats' brains were harvested at the 24h of reperfusion after 2h of MCA occlusion. The expression of HSP70 and bFGF was measured by by immunohistochemical staining. RESULTS: Strong HSP70 immunoreactivity in neurons was observed in NLXT-treated and NLXT-pretreated groups as compared to control group, and increased bFGF immunoreactivity in neurons was observed in the ischemic hemisphere in NLXT-pretreated group in comparison with the ischemic hemisphere in the control group (P<0.01). NLXT has stronger effects on HSP70 and bFGF than Nao'an Capsule. CONCLUSION: The neuroprotective effects of Naoluo Xintong Recipe may be related to its up-regulation of HSP70 and bFGF in the rat brain after focal cerebral ischemia.

Animals↗
PubMed2004

[Interaction between chlopyrifos and microorganisms in soils].

The experimental results showed that in sterilized soils, the degradation rate of 50 mg x kg(-1), 500 mg x kg(-1) and 5,000 g x kg(-1) chlopyrifos was very slow (only 20% after 60 d), and in soils which previously treated with chlopyrifos, the degradation rate of 50 mg x kg(-1), 500 mg x kg(-1) and 5,000 mg x kg(-1) chlopyrifos was 100%, 90% and 80%, respectively. However, in un-sterilized and untreated soils, the degradation rate was at the medium of the rates mentioned-above, indicating that soil microorganisms played an important role in chlopyrifos degradation, and using chlopyrifos could induce the chlopyrifos degrading ability of soil microorganisms. Compared to the soils untreated with chlopyrifos, the soils treated with 50 mg x kg(-1) and 500 mg x kg(-1) chlopyrifos had somewhat increased bacteria and fungi during a short period of treatment, which recovered to normal level after 60 days. But, when treated with 5,000 mg x kg(-1) chlopyrifos, the bacteria and fungi were inhibited, and couldn't recover after 60 days. Under the same treatment condition, the number of bacteria and fungi was not different between soils previously treated and untreated with chlopyrifos, which indicated that enhanced degradation of chlopyrifos was not decided by the numbers of bacteria and fungi, but by their ability of enhanced degradation.

Bacteria↗