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Biomedical subjects

Xin Liu

Publications and source records attributed to Xin Liu.

At least 73 records · Page 4Linked to original sources
PubMed2006

Identification of AtENT3 as the main transporter for uridine uptake in Arabidopsis roots.

Previous studies have shown that Arabidopsis equilibrative nucleoside transporters (AtENTs) possess transport activities when produced in yeast cells and are differentially expressed in Arabidopsis organs. Herein, we report further analysis on the nucleoside transport activities and transcriptional patterns of AtENT members. The recombinant proteins of AtENTs 3, 6, and 7, but not those of AtENTs 1, 2, 4, and 8, were found to transport thymidine with high affinity. Contrary to previous suggestion that AtENT1 may not transport uridine, this work showed that recombinant AtENT1 was a pH-dependent and high-affinity transporter of uridine. When grown on MS plates, the AtENT3 knockout plants were more tolerant to the cytotoxic uridine analog 5-fluorouridine than wild-type plants and the knockout plants of AtENT1 or AtENT6. Consistent with this observation, the AtENT3 knockout line exhibited a significantly decreased ability to take up [(3)H]uridine via the roots when compared with wild-type plants and the plants with mutated AtENT1 or AtENT6. This indicates that AtENT3, but not AtENTs 1 and 6, is the main transporter for uridine uptake in Arabidopsis roots. The transcription of AtENTs 1, 3, 4, 6, 7, and 8 was regulated in a complex manner during leaf development and senescence. In contrast, the six AtENT members were coordinately induced during seed germination. This work provides new information on the transport properties of recombinant AtENT proteins and new clues for future studies of the in vivo transport activities and physiological functions of the different ENT proteins in Arabidopsis plants.

Aging↗
PubMed2006

Evaluation of affymetrix severe acute respiratory syndrome resequencing GeneChips in characterization of the genomes of two strains of coronavirus infecting humans.

Severe acute respiratory syndrome (SARS) was discovered during a recent global outbreak of atypical pneumonia. A number of immunologic and molecular studies of the clinical samples led to the conclusion that a novel coronavirus (SARS-CoV) was associated with the outbreak. Later, a SARS resequencing GeneChip was developed by Affymetrix to characterize the complete genome of SARS-CoV on a single GeneChip. The present study was carried out to evaluate the performance of SARS resequencing GeneChips. Two human SARS-CoV strains (CDC#200301157 and Urbani) were resequenced by the SARS GeneChips. Five overlapping PCR amplicons were generated for each strain and hybridized with these GeneChips. The successfully hybridized GeneChips generated nucleotide sequences of nearly complete genomes for the two SARS-CoV strains with an average call rate of 94.6%. Multiple alignments of nucleotide sequences obtained from SARS GeneChips and conventional sequencing revealed full concordance. Furthermore, the GeneChip-based analysis revealed no additional polymorphic sites. The results of this study suggest that GeneChip-based genome characterization is fast and reproducible. Thus, SARS resequencing GeneChips may be employed as an alternate tool to obtain genome sequences of SARS-CoV strains pathogenic for humans in order to further understand the transmission dynamics of these viruses.

Genome, Viral↗
PubMed2006

An amino acid substitution matrix for protein conformation identification.

Amino acid substitution matrices play an essential role in protein sequence alignment, a fundamental task in bioinformatics. Most widely used matrices, such as PAM matrices derived from homologous sequences and BLOSUM matrices derived from aligned segments of PROSITE, did not integrate conformation information in their construction. There are a few structure-based matrices, which are derived from limited data of structure alignment. Using databases PDB_SELECT and DSSP, we create a database of sequence-conformation blocks which explicitly represent sequence-structure relationship. Members in a block are identical in conformation and are highly similar in sequence. From this block database, we derive a conformation-specific amino acid substitution matrix CBSM60. The matrix shows an improved performance in conformational segment search and homolog detection.

Amino Acid Sequence↗
PubMed2006

Polymorphisms in polycyclic aromatic hydrocarbon metabolism and conjugation genes, interactions with smoking and prostate cancer risk.

The relationship between cigarette smoking and prostate cancer remains unclear. Any potential association may depend on the individuals' ability to metabolize and detoxify cigarette carcinogens--such as polycyclic aromatic hydrocarbons. To investigate this, we studied the association between prostate cancer and smoking, as well as the main and modifying effects of functional polymorphisms in genes that metabolize polycyclic aromatic hydrocarbons (CYP1A1 Ile(462)Val, microsomal epoxide hydrolase His(139)Arg) and detoxify reactive derivatives (GSTM1 null deletion, GSTT1 null deletion, GSTP1 Ile(105)Val and Ala(114)Val) using a family-based case-control design (439 prostate cancer cases and 479 brother controls). Within the entire study population, there were no main effects for smoking or any of the polymorphisms. However, the nondeleted GSTM1 allele was inversely associated with prostate cancer [odds ratio (OR), 0.50; 95% confidence interval (95% CI), 0.26-0.94] among men with less aggressive disease (Gleason score < 7 and clinical tumor stage < T2c) and positively associated (OR, 1.68; 95% CI, 1.01-2.79) with prostate cancer in men with more aggressive disease (Gleason score > or = 7 or clinical tumor stage > or = T2c). We also found a statistically significant negative multiplicative interaction between the GSTM1 nondeleted allele and heavy smoking (> 20 pack-years) in the total study population (P = 0.01) and in Caucasians (P = 0.01). Among Caucasians, heavy smoking increased prostate cancer risk nearly 2-fold in those with the GSTM1 null genotype (OR, 1.73; 95% CI, 0.99-3.05) but this increased risk was not observed in heavy smokers who carried the GSTM1 nondeleted allele (OR, 0.95; 95% CI, 0.53-1.71). Our results highlight the importance of considering genetic modifiers of carcinogens when evaluating smoking in prostate cancer.

Case-Control Studies↗
PubMed2006

Vitamin D receptor genotypes/haplotypes and prostate cancer risk.

The vitamin D receptor (VDR) gene has been associated with prostate cancer, although previous results are somewhat equivocal. To further study this, we did a family-based case-control study (N = 918) of the association between prostate cancer and six common VDR variants: Cdx2, FokI, BsmI, ApaI, TaqI, and the poly-A microsatellite. Looking at each variant alone, only FokI and ApaI were associated with disease. The FokI FF genotype was inversely associated with prostate cancer among men with less advanced disease (i.e., Gleason score <7 and tumor stage <T2c), where the odds ratio OR was 0.56 [95% confidence interval (95% CI), 0.31-1.01; P = 0.05]. ApaI, carrying one or two copies of the A allele, exhibited a weak inverse association with disease (OR, 0.64; 95% CI, 0.39-1.03; P = 0.06); this association was strengthened in Caucasian men with more advanced disease (OR, 0.44; 95% CI, 0.21-0.93; P = 0.03). We observed inverse associations between disease and the four-locus FBAt haplotype (OR, 0.48; 95% CI, 0.30-0.76; P = 0.002) and the fbaT haplotype (OR, 0.60; 95% CI, 0.38-0.95; P = 0.03; i.e., in comparison with the FbaT haplotype). These were stronger among men with more advanced disease: for FBAt, the OR was 0.31 (95% CI, 0.16-0.61; P = 0.0008); for fbaT, the OR was 0.32 (95% CI, 0.16-0.64; P = 0.001). These observations support a role for VDR variants in prostate cancer risk but suggest that any potential causal variant(s) may reside on the haplotypes reported here. This would help explain the somewhat equivocal results for VDR genotype-level associations with prostate cancer.

Case-Control Studies↗
PubMed2006

Down syndrome candidate region 1 isoform 1 mediates angiogenesis through the calcineurin-NFAT pathway.

Down syndrome candidate region 1 (DSCR1) is one of more than 50 genes located in a region of chromosome 21 that has been implicated in Down syndrome. DSCR1 can be expressed as four isoforms, one of which, isoform 4 (DSCR1-4), has recently been found to be strongly induced by vascular endothelial growth factor A (VEGF-A(165)) and to provide a negative feedback loop that inhibits VEGF-A(165)-induced endothelial cell proliferation in vitro and angiogenesis in vivo. We report here that another DSCR1 isoform, DSCR1-1L, is also up-regulated by VEGF-A(165) in cultured endothelial cells and is strongly expressed in several types of pathologic angiogenesis in vivo. In contrast to DSCR1-4, the overexpression of DSCR1-1L induced the proliferation and activation of the transcription factor NFAT in cultured endothelial cells and promoted angiogenesis in Matrigel assays in vivo, even in the absence of VEGF-A. Similarly, small interfering RNAs specific for DSCR1-1L and DSCR1-4 had opposing inhibitory and stimulatory effects, respectively, on these same functions. DSCR1-4 is thought to inhibit angiogenesis by inactivating calcineurin, thereby preventing activation and nuclear translocation of NFAT, a key transcription factor. In contrast, DSCR1-1L, regulated by a different promoter than DSCR1-4, activates NFAT and its proangiogenic activity is inhibited by cyclosporin, an inhibitor of calcineurin. In sum, DSCR1-1L, unlike DSCR1-4, potently activates angiogenesis and could be an attractive target for antiangiogenesis therapy.

Active Transport, Cell Nucleus↗
PubMed2006

CXCR2 blockade reduces radical formation in hyperoxia-exposed newborn rat lung.

Inflammation contributes greatly to the pathogenesis of bronchopulmonary dysplasia. In previous studies, we showed that blocking neutrophil influx by treatment with SB265610, a selective CXCR2 antagonist, could partly reduce superoxide accumulation and preserve alveolar development in 60% O(2)-exposed newborn rats. The purpose of this study was to further investigate the role of neutrophils in the formation of reactive oxygen and nitrogen species mediating hyperoxia-impaired lung development. We found that hydroxyl radical formation and lipid peroxidation in rat lungs were significantly increased during 60% O(2) exposure. These increases were attenuated by the administration of SB265610. In addition, SB265610 largely inhibited protein nitration induced by hyperoxia. SB265610 partly prevented the hyperoxia-enhanced bronchoalveolar lavage (BAL) protein content in 60% O(2)-exposed animals. Our results demonstrate that neutrophils have a pivotal role in hydroxyl radical formation, lipid peroxidation and protein nitration. Taken together with our previous studies, the present findings show that blocking neutrophil influx protects alveolar development and improves lung function in part by preventing reactive oxygen/nitrogen species accumulation.

Animals↗
PubMed2006

Co-involvement of the mitochondria and endoplasmic reticulum in cell death induced by the novel ER-targeted protein HAP.

HAP (a homologue of the ASY/Nogo-B protein), a novel human apoptosis-inducing protein, was found to be identical to RTN3. In an earlier study, we demonstrated that HAP localized exclusively to the endoplasmic reticulum (ER) and that its overexpression could induce cell apoptosis via a depletion of endoplasmic reticulum (ER) Ca(2+) stores. In this study, we show that overexpression of HAP causes the activation of caspase-12 and caspase-3. We still detected the collapse of mitochondrial membrane potential (Deltaomegam) and the release of cytochrome c in HAP-overexpressing HeLa cells. All the results indicate that both the mitochondria and the ER are involved in apoptosis caused by HAP overexpression, and suggest that HAP overexpression may initiate an ER overload response (EOR) and bring about the downstream apoptotic events.

Animals↗
PubMed2006

[Biological evaluation of artificial skin substitute].

Multiple kinds of Artificial Skin Substitute are now available. However, except for the Homo Skin Graft there is no Artificial Skin Substitute that can be used as permanent Artificial Skin Substitute. During the past 20 years, more and more scholars around the world have expressed increased interests in the research and development of Artificial Skin Graft that can be utilized as satisfying permanent Artificial Skin Substitute. We conducted our research on the biological evaluation of medical devices of Collagen-Chitosan(C-C) Artificial Skin Substitute according to the National Standard (GB/T16886. 1-1997). The following experiments were conducted: (1)Cytotoxicity, (2)Systemic toxicity(acute toxicity), (3)Haemocompatibility, (4)Sensitization, (5)Intracutaneous reactivity, (6)Pyrogen test, (7)Genotoxicity. The experiment results demonstrate that all biological functional indexes of the Artificial Skin Graft meet the National Standards. Therefore, we conclude that C-C Artificial Skin Graft is characteristic of good biological compatibility. It is non-irritant and has no systemic and cellular toxicity, no genotoxicity, no pyrogen, and no allergen.

Animals↗
PubMed2006

[Genotypic analysis of familial dilated vestibular aqueduct syndrome].

OBJECTIVE: To analyze clinical manifestation of patients from two families with dilated vestibular aqueduct syndrome (DVAS). Their genotypic patterns were discriminated with the genetic testing methods for PDS gene. METHOD: The twin sisters from pedigree and the brother and sister from pedigree 2 all suffered from sensorineural hearing loss. All patients from these two families were confirmed to have enlarged vestibular aqueduct by temporal bone CT scan. Exon 7+8 and their flanking area sequences were analyzed by direct sequencing. All other exons and their flanking sequences were screened by DHPLC. The amplicons of exons which showed abnormal DHPLC wave pattern were further sequenced. RESULT: The parents of two families are non-consanguineous, hearing normal couples with no other family members with hearing loss. Both families have two offspring with DVAS. The clinical features of all patients were progressive hearing loss, good communication ability but with thickness pronunciation. Both twin sisters from pedigree are homozygous for the splice site mutation (IVS 7-2 A-G) affecting the 3 splice site consensus sequence of intron 7. The brother and sister of pedigree 2 are compound heterozygotes for 1199 ins T mutation and a missense mutation (1229 C-T). CONCLUSION: Familial DVLS is typical hereditary disease. The patients with DVLS have similar clinical manifestation and the same genotypic changes in PDS.

Adult↗
PubMed2006

[Analysis of effect of microsatellite markers on Escherichia coli F4 (K88) receptor in different swine breeds].

Four microsatellite markers linked with Escherichia-coli F4 receptor gene were selected from chromosome 13 of pig (authorization) to analyze difference in hereditary between the genotype and F4 receptor adhesive appearance. Results showed that the microsatellite markers were highly polymorphic and the heterozygosities ranged from 0.6117 to 0.7500. The value of PIC was over 0.5749 and the heredity diversity of Chinese pig breeds more higher than oversea's. On F4ab adhesive appearance of S0222, the difference among genotypes was significant in SZL breed. The AC genotype of SW458 had no adhesive appearance in SZL and LW breeds. Marker SW458 can thus be potentially used as a genetic marker for E. coli F4 resistive gene.

Animals↗
PubMed2006

[A pilot study on the quality management system of in-vitro diagnostic reagents].

This article makes a pilot study on the key points of the quality management system of in-vitro diagnostic reagents by analyzing the technical characteristics and production methods of these products as well as the status in quo, and problems the in-vitro diagnostic reagent industry in China is facing nowadays. It can serve as a reference to the supervision departments and the manufacturers in this field which are establishing and running the quality management system.

China↗
PubMed2006

[Transrectal ultrasound-guided ethanol sclerotherapy for Müllerian duct cyst accompanied with ejaculatory duct obstruction].

OBJECTIVE: To evaluate the efficacy and safety of transrectal ultrasound-guided ethanol sclerotherapy in the treatment of Müllerian duct cyst accompanied with ejaculatory duct obstruction. METHODS: Under the transrectal ultrasound guidance, 3 cases of prostate Müllerian duct cyst were treated by 20 G needle puncture and ethanol injection, and closely followed up by ultrasonic monitored on follow-up examinations. RESULTS: All the cysts involuted completely 6 months after the treatment. Symptoms caused by ejaculatory duct obstruction were relieved in all the patients. No severe complications occurred. CONCLUSION: Transrectal ultrasound-guided ethanol sclerotherapy is an effective and safe method for the treatment of Müllerian duct cyst accompanied with ejaculatory duct obstruction.

Adult↗
PubMed2006

[Patients suffered from enlarged vestibular aqueduct syndrome in Chifeng deaf and dumb school detected by Pendred's syndrome gene hot spot mutation screening].

OBJECTIVE: To investigate the incidence of hot spot mutation of PDS gene by genetic screening testing method in Chifeng City, Inner Mongolia. The feasibility and effectiveness of genetic screening method in finding enlarged vestibular aqueduct syndrome were confirmed by temporal bone CT scan. METHODS: DNA were extracted from peripheral blood of 141 students of Chifeng Deaf and Dumb school. PDS IVS7-2 A-G mutation, the most common PDS mutation in Chinese population, was analyzed by direct sequencing for PDS exon 7, exon 8 with intron 7. The individuals found with homozygous or heterozygous PDS IVS7-2 A-G mutation were given further temporal CT scan, ultrasound scan of thyroid and thyroid hormone assays. The results of PDS genetic screening and temporal bone CT scan were compared with each other. RESULTS: The sequencing results revealed twenty cases carrying PDS IVS7-2 A-G mutation, of whom nine cases were homozygous mutation and eleven cases were heterozygous mutation. Eighteen cases underwent temporal bone CT scan except two cases that left the school due to other health problem. Sixteen cases were confirmed to be enlarged vestibular aqueduct syndrome (EVAS) by CT scan and the shape and function of thyroid were clinically normal by ultrasound scan of thyroid and thyroid hormone assays, respectively. CONCLUSIONS: The patients suffered from EVAS can be diagnosed by the screening for the PDS hot spot mutation which has unique advantage in epidemiologic study in large scale deaf population. The preliminary data of this study suggested relatively high incidence of EVAS in Chifeng area.

Adolescent↗
PubMed2006

[Involvement of nitric oxide in regulation of salt stress-induced ABA accumulation in maize seedling].

Possible regulation of salt stress-induced ABA accumulation by nitric oxide (NO) in maize seedling was investigated. Both NO and ABA contents of maize leaves and root tips were increased in response to salt stress (Fig.1,2). Similar to the effects of salt stress, ABA contents of maize leaves and root tips were increased after the treatment of maize leaves with sodium nitroprusside (SNP, a nitric oxide donor) alone (Fig.3). Compared to the salt stress-induced ABA accumulation, this SNP-induced ABA increase was much faster, suggesting that NO may be an intermediate signal from salt stress to ABA accumulation. When NO production inhibitors L-NAME and NaN(3) treatments were applied, salt stress-induced ABA accumulation was lowered (Fig.4). Treatment with NO scavenger cPTIO also inhibited the salt stress-induced ABA increase (Fig.5). From these results it is deduced that NO is involved in regulation of ABA accumulation under salt stress.

Abscisic Acid↗
PubMed2006

[Specific induction of anti-leukemia effects by umbilical cord cell-derived CD8+ T cytotoxic lymphocytes].

OBJECTIVE: To explore the specific anti-leukemia immune response of CD8+ cytotoxic T lymphocyte (CTL) derived from cord blood (CB) ex vivo and evaluate the feasibilities and values of the CTL for specific immunotherapy. METHODS: Dendritic cells (DC) were induced from mononuclear cells (MNC) by combination cytokines in 10 CB samples. Loading U937 cell lysate antigen on the mature DC, they could stimulate the lymphocytes of the same origin to generate CTL. MidiMACS was used to isolate CD8+ CTL. Analysis of DC was performed by inverted microscopy, scanning electron microscopy and flow cytometry. Methyl thiazolyl tetrazolium (MTT) assay was used to evaluate the cytotoxicity of the CTL. RESULTS: Cocultured with GM-CSF, IL-4, TNF-alpha and PGE2, CB-MNC could be induced into functional DC with typical morphology. The mean cytotoxicity of CD8+ CTL to U937 cells was significant stronger than that of CD8- CTL and TL at the same E: T ratios. The mean cytotoxicity rate of CD8+ CTL to U937 cells was higher than that to K562 cells [(66.36 +/- 12.43)% vs (41.97 +/- 14.24)%] at E: T ratio of 40: 1 (P < 0.05). The cytotoxicity of CD8- CTL to K562 cells showed no difference from that to U937 cells (P > 0.05). CONCLUSION: Mature CB-DC loading U937 cell antigens could induce CB-T lymphocytes to generate leukemia-specific CD8+ CTL. The cytotoxicity of the CD8+ CTL is specific against U937 cells and is more potent than that of CD8- CTL.

CD8-Positive T-Lymphocytes↗
PubMed2006

[Outcome of fatal pulmonary embolism post coronary intervention].

OBJECTIVE: To study the occurrence, management and prognosis of fatal pulmonary embolism in patients underwent coronary intervention in our department. METHOD: Seven patients had fatal pulmonary embolism after coronary intervention in six years, we analysis each patient by the occurrence, prognosis, management of the disease. RESULTS: During the last 6 years, 7 [five males, mean age (55.9 +/- 11.7) years, 5 after coronary angiography and 2 after percutaneous coronary intervention] patients developed fatal pulmonary embolism after PCI. All 7 patients presented respiratory and cardiac arrest within 24 hours post coronary intervention. Three patients died, one patient experienced brain death and another three patients survived and are alive without complication till now. CONCLUSION: The fatal pulmonary embolism is a scarce complication after coronary intervention with high acute mortality and satisfactory outcome for survivors.

Adult↗