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Biomedical subjects

X Xiao

Publications and source records attributed to X Xiao.

At least 145 records · Page 8Linked to original sources
PubMed1998

[The surgical treatment of tetralogy of fallot in 136 adults].

OBJECTIVE: To summarize the experience of surgical treatment of tetralogy of Fallot (TOF) in adults. METHOD: From April 1975 to December 1997, 136 adult patients underwent total corrective repair of tetralogy of Fallot. The patient age ranged from 14 to 52 years old. The ventricular septal defects were closed with Dacron patch in 112 patients, with pericardial patch in 24 patients. A right ventricular outflow patch was required to eliminate right ventricular outflow tract obstruction in 126 patients. RESULT: Five patients died during hospitalization, with a hospital mortality of 3.68%. Four early postoperative deaths were due to severe low cardiac output syndrome. CONCLUSION: In view of current improved and standardized techniques, we conclude that the total corrective repair of TOF may have an excellent result in adult patients.

Adolescent↗
PubMed1998

[Analysis of clinicopathologic changes of infection in dead patients after renal transplantation].

OBJECTIVE: To prevent renal transplantation patients from infection. METHOD: Autopsies of 24 patients who had died after renal transplantation were studied. RESULT: The incidence of infection was 66.7% and the lethal infective complications amounted for 50%. The most infectious agents were bacteria, fungi, tuberculosis, virus and actinomyces. CONCLUSION: Pathological features and clinical manifestations of lesions were caused by aforementioned agents. Some management can prevent renal transplantation recipients from infection.

Adolescent↗
PubMed1998

[The study of precedent subgingival flora colonization on four kinds of crown and bridge restorative materials].

The purpose of this in vitro study was to investigate the effects of microbial colonization on different crown or fixed bridge-used restorative materials and discuss the standards for evaluating those materials microscopically. Four kinds of restorative materials such as SDA-II type medium alloy, ceramic-fused-to-metal material, heat cure composite resin for crown restoration, Plat castable ceramics and four species of precedent subgingival flora (A. viscosus, F. nucleterm, C. ochracea, S. sanguis) were used. The material specimen had been continuously anaerobic cultured with the experimental bacterial fluid for 3, 7 and 14 days respectively, then the OD values of the specimenwashing fluid which could stand for the biomass of colonized bacteria on the surfaces of materials were measured. The results indicated that the quantity of precedent subgingival flora colonization on the surfaces of different restorative materials varied among different species of bacteria, which might concern with the surface structure, composition, property of anticorrosion and antisoluability of those materials.

Actinomyces viscosus↗
PubMed1998

[Research on inhibition of sodium fluoride on five subgingival bacteria in vitro].

This in vitro study was aimed at observing inhibition action of fluoride on 5 common periodontal bacteria in subgingival microflora. The liquid media two-fold dilution method was used to determine the minimal inhibition concentration (MIC) of sodium fluoride (NaF) to 9 strains of bacteria representing the main periodontopathic species(P. gingivalis, A. actinomycetemcomitans, P. intermedius) and the periodontal beneficial species (S. sanguis) and 1 strain of S. sorbrinus. The results showed that all the bacteria were inhibited at different concentration of NaF. The MIC values ranged from 128 micrograms/ml for P. gingivalis and A. actinomycetemcomitans, 256 micrograms/ml for S. sorbrinus, 1024 micrograms/ml for P. intermedius to 2048-4096 micrograms/ml for S. sanguis. The results suggest that NaF can also be used as a periodontal anti-bacterium agent and those preparations containing about 1000 micrograms/ml fluoride can be used effectively against the periodontopathic bacteria without disturbing the local ecological balance.

Aggregatibacter actinomycetemcomitans↗
PubMed1998

[Analysis of rhodopsin and peripherin/RDS genes in Chinese patients with retinitis pigmentosa].

PURPOSE: To disclose the mutation of rhodopsin and peripherin/RDS genes among Chinese patients with retinitis pigmentosa as there was no identified mutation through sequencing reported in Chinese. METHODS: Genomic DNA was prepared from the peripheral lymphocytes. Gene fragments of the rhodopsin and peripherin/RDS genes were amplified by the polymerase chain reaction. The PCR products were analyzed by Heteroduplex-SSCP technique. PCR samples with aberrant migrational bands were identified through direct sequencing or cloning sequencing. RESULTS: Three different mutations in the rhodopsin gene were found in 3 of the 83 patients with retinitis pigmentosa(Va1104Phe, Lys311Glu, Pro347Leu). Two of the three mutations have not been reported before. One of the two (heterozygous, Va1104Phe) was found in an isolated patient and the other (homozygous, Lys311Glu) in a family with autosomal recessive retinitis pigmentosa. Mutation of peripherin/RDS gene was not found in the 83 patients. CONCLUSION: Mutation in the rhodopsin gene is the common cause in Chinese patients with retinitis pigmentosa, either autosomal dominant, recessive or sporadic.

Base Sequence↗
PubMed1998

Color vision defects with variation in the exon 5 of red and green pigment genes.

PURPOSE: To investigate correlation of variation in the exon 5 of red and green pigment genes with color vision defects. METHODS: Exon 5 of the red and green pigment genes in 11 protans, 19 deutans and 38 normal controls were analyzed by heteroduplux-SSCP analysis. RESULTS: In all 11 protans and 8 of the 19 deutans, defects of the red or green pigment gene could be identified. The C polymorphism (A/C at codon 283) in green pigment gene was present in 8 of 44 trichromats and 5 of 24 dichromats. Specific electrophoretic bands were found in 2 normal controls and a deutan. CONCLUSIONS: Variation in the exon 5 of the red and green pigment genes is the most common cause for color vision defects. Heteroduplex-SSCP analysis is a suitable way in screening specific variation in visual pigment genes.

Chromosomes, Human, X↗
PubMed1997

Adeno-associated virus (AAV) vector antisense gene transfer in vivo decreases GABA(A) alpha1 containing receptors and increases inferior collicular seizure sensitivity.

In the inferior colliculus, adeno-associated virus (AAV) vectors are capable of gene transfer and stable, long-term expression, but it remained to be shown if this in vivo gene transfer could alter focal seizure sensitivity in the inferior colliculus. Because GABA receptors directly modulate inferior collicular seizures, AAV vectors were constructed with a cytomegalovirus (CMV) promoter and a truncated, human GABA(A) alpha1 cDNA in both the sense and antisense orientations. Seven days after collicular microinjection of the sense vectors (1 microl; 3 x 10(9) particles/microl), neurons exhibited GABA(A) alpha-like immunoreactivity in amounts far exceeding endogenous concentrations. Unilateral or bilateral sense vector infusion had no effect on inferior collicular seizure parameters or on [3H]zolpidem binding. In contrast, bilateral infusion of the antisense AAV-GABA(A) alpha1 vector (1 microl; 3 x 10(8) particles/microl) caused a 137% increase in the seizure duration. Moreover, unilateral antisense vector infusion produced a localized, 48% decrease in [3H]zolpidem binding. Thus, in the inferior colliculus, antisense AAV-CMV vectors can reduce a specific receptor subunit protein and change receptor function that directly influences in vivo seizure sensitivity.

Animals↗
PubMed1997

Gene transfer by adeno-associated virus vectors into the central nervous system.

Adeno-associated virus (AAV) vectors are derived from a nonpathogenic and defective human parvovirus. Although currently unable to display the integration specificity featured by its wild-type parent, the recombinant AAV (rAAV) system has continued to attract enormous interest primarily due to its unique features such as safety, high titers, broad host range, transduction of quiescent cells, and vector integration. Recently, rAAV-mediated in vivo gene transfers have demonstrated efficient long-term transduction (from 3 months to more than 1.5 years) and lack of cytotoxicity and cellular immune responses in the target tissues, especially in the CNS. Alternative approaches using rAAV plasmid DNA in nonviral gene delivery systems also generated promising results. Propelled by various efforts to improve the system, rAAV vectors will provide numerous opportunities to explore the potential therapeutic applications in humans.

Animals↗
PubMed1997

Cancer gene therapy using a novel adeno-associated virus vector expressing human wild-type p53.

Previous studies have indicated that transfer of wild-type (wt) p53 cDNA into cancer cells can suppress the tumor phenotype in vitro and in vivo. In this study we examined the effects of wt p53 transduction in the human cancer cell line H-358 (that bears a homozygous deletion of p53) using a novel recombinant adeno-associated viral vector engineered to express wt p53 (rAAVp53). Western blot analysis demonstrated the expression of wt p53 in H-358 cells following infection with rAAVp53. Furthermore, rAAVp53 inhibited the growth of the neoplastic cells and also mediated cytotoxicity. Cell cycle analysis of rAAVp53-infected cells showed a significant increase in the percentage of cells arrested at the G1-S checkpoint. H-358 cells infected with rAAVp53 underwent apoptosis as demonstrated by the morphological appearance of DAPI-stained nuclei. Direct injection of rAAVp53 into H-358 tumors implanted subcutaneously in immunodeficient nu/nu mice inhibited tumor growth completely in three of the five animals tested. Mock-infected and rAAV control treated tumors showed no growth inhibition. In situ staining in nu/nu mice detected the presence of wild-type p53 protein in residual tumor cells following rAAVp53 administration. The impressive in vivo efficacy of the rAAVp53 suggests a bystander effect. We conclude that rAAV may be effective as a gene transfer vector in the delivery of p53 to cancer cells.

Animals↗
PubMed1997

Cellular recombination pathways and viral terminal repeat hairpin structures are sufficient for adeno-associated virus integration in vivo and in vitro.

The human parvovirus adeno-associated virus (AAV) is unique in its ability to target viral integration to a specific site on chromosome 19 (ch-19). Recombinant AAV (rAAV) vectors retain the ability to integrate but have apparently lost this ability to target. In this report, we characterize the terminal-repeat-mediated integration for wild-type (wt), rAAV, and in vitro systems to gain a better understanding of these differences. Cell lines latent for either wt or rAAV were characterized by a variety of techniques, including PCR, Southern hybridization, and fluorescence in situ hybridization analysis. More than 40 AAV-rAAV integration junctions were cloned, sequenced, and then subjected to comparison and analysis. In both immortalized and normal diploid human cells, wt AAV targeted integration to ch-19. Integrated provirus structures consisted of head-to-tail tandem arrays with the majority of the junction sequences involving the AAV inverted terminal repeats (ITRs). No complete viral ITRs were directly observed. In some examples, the AAV p5 promoter sequence was found to be fused at the virus-cell junction. Data from dot blot analysis of PCR products were consistent with the occurrence of inversions of genomic and/or viral DNA sequences at the wt integration site. Unlike wt provirus junctions, rAAV provirus junctions mapped to a subset of non-ch-19 sequences. Southern analysis supported the integration of proviruses from two independent cell lines at the same locus on ch-2. In addition, provirus terminal repeat sequences existed in both the flip and flop orientations, with microhomology evident at the junctions. In all cases with the exception of the ITRs, the vector integrated intact. rAAV junction sequence data were consistent with the occurrence of genomic rearrangement by deletion and/or rearrangement-translocation at the integration locus. Finally, junctions formed in an in vitro system between several AAV substrates and the ch-19 target site were isolated and characterized. Linear AAV substrates typically utilized the end of the virus DNA substrate as the point of integration, whereas products derived from AAV terminal repeat hairpin structures in the presence or absence of Rep protein resembled AAV-ch-19 junctions generated in vivo. These results describing wt AAV, rAAV, and in vitro integration junctions suggest that the viral integration event itself is mediated by terminal repeat hairpin structures via nonviral cellular recombination pathways, with specificity for ch-19 in vivo requiring additional viral components. These studies should have an important impact on the use of rAAV vectors in human gene therapy.

Base Sequence↗
PubMed1997

A novel 165-base-pair terminal repeat sequence is the sole cis requirement for the adeno-associated virus life cycle.

Adeno-associated virus (AAV) replication is dependent on two copies of a 145-bp inverted terminal repeat (ITR) that flank the AAV genome. This is the primary cis-acting element required for productive infection and the generation of recombinant AAV (rAAV) vectors. We have engineered a plasmid (pDD-2) containing only 165 bp of AAV sequence: two copies of the D element, a unique sequence adjacent to the AAV nicking site, flanking a single ITR. When assayed in vivo, this modified hairpin was sufficient for the replication of the plasmid vector when Rep and adenovirus (Ad) helper functions were supplied in trans. pDD-2 replication intermediates were characteristic of the AAV replication scheme in which linear monomer, dimer, and other higher-molecular-weight replicative intermediates are generated. Compared to infectious AAV clones for replication, the modified hairpin vector replicated more efficiently independent of size. Further analysis demonstrated conversion of the input circular plasmid to a linear substrate with AAV terminal repeat elements at either end as an initial step for replication. This conversion was independent of both Rep and Ad helper genes, suggesting the role of host factors in the production of these molecules. The generation of these substrates suggested resolution of the modified terminal repeat through a Holliday-like structure rather than replication as a mechanism for rescue. Production of replicative intermediates via this plasmid substrate were competent not only for AAV DNA replication but also for encapsidation, infection, integration, and subsequent rescue from the chromosome when superinfected with Ad and wild-type AAV. These studies demonstrate that this novel 165-bp ITR substrate is sufficient in cis for the AAV life cycle and should provide a valuable reagent for further dissecting the cis sequences involved in AAV replication, packaging, and integration. In addition, this novel plasmid vector can be used as a substrate for both rAAV vector production and synthetic plasmid vector delivery.

DNA, Viral↗
PubMed1997

Role for highly regulated rep gene expression in adeno-associated virus vector production.

Recent success achieving long-term in vivo gene transfer without a significant immune response by using adeno-associated virus (AAV) vectors (X. Xiao, J. Li, and R. J. Samulski, J. Virol. 70:8098-8108, 1996) has encouraged further development of this vector for human gene therapy. Currently, studies focus on the generation of high-titer vectors by using the two-plasmid helper-vector system in adenovirus (Ad)-infected cells. To examine the effects of the AAV replication (rep) genes on recombinant AAV (rAAV) vector production, we have constructed a series of AAV helper plasmids that contain strong heterologous promoters in place of the endogenous p5 promoter. Although high-level rep gene expression was achieved, rAAV DNA failed to replicate in the absence of Ad infection. Moreover, unregulated overexpression of Rep78/68 led to substantially lower rAAV yields in the presence of Ad (10(4-5) versus 10(7-8)). In contrast, under similar conditions, reduced Rep78/68 expression resulted in much higher rAAV yields (10(9)). Molecular characterization showed that overexpression of the rep gene decreased rAAV DNA replication and severely inhibited capsid (cap) gene expression. Interestingly, a reduced rep level enhanced cap gene expression and supported normal rAAV DNA replication. These studies suggest a critical role for regulated rep gene expression in rAAV production and have facilitated the development of a new AAV helper plasmid that increases vector production eightfold over currently used constructs.

Adenoviridae↗
PubMed1997

Efficient gene transfer into primary and immortalized human fetal glial cells using adeno-associated virus vectors: establishment of a glial cell line with a functional CD4 receptor.

Adeno associated virus (AAV) is a non-pathogenic dependent parvovirus with a broad host range, capable of high levels of transduction and stable integration into the host cell genome. We have investigated the potential for using AAV as a vector for gene transfer into glial cells of the human fetal nervous system. Recombinant AAV vectors expression either the reporter gene beta-galactosidase or a human CD4 receptor were able to transduce both primary glial cells of the human fetal nervous system and an SV40 immortalized human fetal glial cell line (SVG). No difference in transduction efficiency was observed between the primary cells and the cell line which in both cases was as high as 95%. Stable transfectants of the glial cell line expressing the CD4 receptor were selected. An SVG/CD4 expressing line was then established. The presence of the CD4 receptor was confirmed by immunohistochemistry, Westerm immuno-blotting and flow cytometric analysis. The CD4 receptor was shown to be functional by infection of the SVG/CD4 cell line with the human immunodeficiency virus (HIV). Upon infection, the SVG/CD4 cells produced 20-fold higher levels of the HIV intracellular core antigen P24 than the CD4 negative parental cells and in addition formed syncytia. The use of AAV vectors should prove useful in biological investigations of human glial cells and offers promise as a means of ex vivo and in vivo gene delivery.

Anti-Bacterial Agents↗
PubMed1997

[Diagnosis and management of piriform sinus fistulae in children].

In 12 patients with piriform sinus fistula, aged from 1.5 to 10 years all but one patient presented themslves with inflammatory swelling in the region of the left lobe of the thyroid gland. During acute infection, the involvement of the left thyroid lobe was verified by ultrasonography and scintigraphy. Barium swallow examination was the diagnostic finding that all the 11 patients had a left-sided fistula. One patient presented with a painless cyst in the left thyroid lobe. Six patients operated on 4 underwent fistulectomy. In patient the fistula was not found. In the patient who had a cyst in the thyroid lobe, fistulectomy and cystectomy were done. All these patients did well postoperatively without recurrence. Six other patients were followed up without operation with in 1-6 years. Five patients remained asymptomatic. One patient had 3 recurrences during a 2 years follow-up period. Piriform sinus fistula is the most common underlying abnormality in the patients with acute suppurative thyroiditis. A better understanding about this rare branchial anomaly is of clinical importance.

Branchial Region↗
PubMed1997

[Experimental studies on somatic gene therapy for diabetes. I. Structuring of recombinant from human insulin gene and ammalian expression vector PRC/CMV].

To develop a model somatic gene therapy system for diabetes, we constructed a human insulin expression vector in non B cells. As the first step, an insulin cDNA fragment of 260 bp, generated by a complet digestion of PBCA with EcoR I and BamH I, was inserted into the EcoR I/BamH I site of plasmid PBS.SK by ligation of cohevise-ended DNA to construct transition plasmid PBS.INS. Then the plasmid PBS.INS was completly digested by Hind III and Xbal I. The small DNA fragment containing insulin cDNA gene was subcloned to the expression plasmid PRC/CMV to form recombinant PRC/CMV.INS.

DNA, Complementary↗
PubMed1997

Exon-by-exon screening for RB germline mutations using Heteroduplex-SSCP analysis.

OBJECTIVE: To disclose the nature of RB1 germline mutations in Chinese and to develop a practical and effective way for mutational screening. METHODS: Leukocyte DNA was prepared from 8 Chinese patients with hereditary retinoblastoma. PCR combined with nonisotopic heteroduplex-SSCP analysis was used to screen leukocyte DNA for RB1 germline mutations, exon-by-exon, without the use of restriction endonuclease digestion. The mutations were finally identified by sequencing. In order to testify the effectiveness of this method, the same method was used to detect other 17 samples which have been previously analyzed by other methods. RESULTS: Heterozygous germline mutations were detected in the leukocyte DNA of 6 out of 8 Chinese patients: G del/codon 46, T del/codon 131, CAGAA del/codon 257-258, GCAgta-->GCAgca/donor of exon 16, C-->T/codon 661, and C-->T/codon 787. Heteroduplex-SSCP analysis may detect RB1 germline mutations in 68% (17/25) unselected patients, which is more effective than SSCP(56%) or heteroduplex analysis(64%) alone. The corrected RB1 mutation detection rate may be 80% if the samples were previously analyzed by Southern blotting, which is much higher than those reported on literature. CONCLUSION: Mutations involving a few base pairs in RB1 gene are common in Chinese. Heteroduplex-SSCP analysis is more useful and effective than SSCP or heteroduplex analysis alone for the rapid screening for unknown mutations.

Female↗