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Biomedical subjects

Y Xiang

Publications and source records attributed to Y Xiang.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Changes in patterns and resistances of bacteria from 731 patients with bacteremia in 11 years].

OBJECTIVE: To study the changes in patterns and resistances of bacteria from patients with bacteremia in 11 years. METHODS: Diffusion tests were used to measure the antibiotic sensitivity of bacteria isolated from the patients with bacteremia. RESULTS: The proportion of staphylococcus epidermidis in bacteremia increased significantly. The proportion of methicillin-resistant Staphylococcus aureus (MRSA) in bacteremia caused by staphyiococcus increased markedly. Resistance of MRSA and methlcillin-sensitive staphylococcus aureus (MSSA) to penicillin, and gentamycin increased significantly. Compared 1986-1990, with 1991-1996, the resistance of S. epidermidis to penicillin, erythromycin and methicillin increased markedly, so did resistance of pseudomonas aeruginosa to carbenicillin, and piperacillin, resistance of E. coli to gentamycin and cefoperazone, resistance of klebsiella to ampicillin and carbenicillin. The resistance of enterobacteriaceae which induced beta-lactamase to the first to the third generation of cephalosporins was relatively high. CONCLUSION: The resistance of bacteria to the commonly used antibiotics was produced in various degrees.

Adolescent↗
PubMed1996

Correction of the mutation responsible for sickle cell anemia by an RNA-DNA oligonucleotide.

A chimeric oligonucleotide composed of DNA and modified RNA residues was used to direct correction of the mutation in the hemoglobin betaS allele. After introduction of the chimeric molecule into lymphoblastoid cells homozygous for the betaS mutation, there was a detectable level of gene conversion of the mutant allele to the normal sequence. The efficient and specific conversion directed by chimeric molecules may hold promise as a therapeutic method for the treatment of genetic diseases.

Alleles↗
PubMed1996

Mutation of vaccinia virus gene G2R causes suppression of gene A18R ts mutants: implications for control of transcription.

This report provides genetic evidence that two vaccinia virus genes, A18R and G2R, both of which affect the fidelity of viral transcription in vivo, interact with each other or act on a common biochemical pathway. Previous experiments with the antipoxviral drug isatin-beta-thiosemicarbazone suggest that lethal mutation of gene G2R would compensate for mutations in gene A18R. We therefore tested the hypothesis that gene G2R is an extragenic suppressor of A18R mutations. First, we constructed a recombinant which contains both a G2R deletion mutation and an A18R temperature-sensitive mutation and found that this recombinant was viable. Second, we isolated both cold-sensitive and temperature-insensitive phenotypic revertants of A18R temperature-sensitive mutants and found in both cases that the revertants contained G2R mutations. In the case of the cold-sensitive revertants, we were able to prove that the cold-sensitive phenotype mapped to the G2R gene. Combined with the biochemical data on A18R and G2R, these results imply that the A18R and G2R genes interact with each other either directly or indirectly in a fashion which affects the fidelity of intermediate and late viral transcription.

Adenosine Triphosphatases↗
PubMed1996

The binding mode of an E-64 analog to the active site of cathepsin B.

Two binding modes of the isobutyl-NH-Eps-Leu-Pro inhibitor to cathepsin B have been proposed. Molecular docking using an empirical force field was carried out to distinguish between the two modes. The search began with manual docking, followed by random perturbations of the docking conformation and cycles of Monte Carlo minimization. Finally, molecular dynamics was carried out for the most favorable docking conformations. The present calculations predict that the isobutyl-NH-Eps-Leu-Pro inhibitor preferentially binds to the S' rather than the S subsites of cathepsin B. The S' binding mode prediction is supported by the X-ray crystal structure of cathepsin B bound to a closely related ethyl-O-Eps-Ile-Pro inhibitor, which was found to bind in the S'subsite with the C-terminal epoxy ring carbon making a covalent bond to the sulfur atom of Cys29. This agreement, in turn, validates our docking strategy. Furthermore, the calculations provide evidence that the dominant contribution to the total stabilization energy of the enzyme-inhibitor complex stems from the strong electrostatic interaction between the negatively charged C-terminal carboxylate group of the ligand and the positively charged imidazolium rings of His110 and His111. The latter are stabilized and held in an optimal orientation for interactions with the C-terminal end of the ligand through a salt bridge between the side chains of His110 and Asp22. By comparison with the crystal structure, some insight into the specificity of the epoxyldipeptide family towards cathepsin B inhibition has been extracted. Both the characteristics of the enzyme (e.g. subsite size and hydrophobicity) as well as the nature of the inhibitor influence the selectivity of an inhibitor towards an enzyme.

Binding Sites↗
PubMed1996

Fine mapping and characterization of the Rous sarcoma virus Pr76gag late assembly domain.

The p2 region of the Rous sarcoma virus (RSV) Gag polyprotein contains an assembly domain, which is required late in replication for efficient budding of virus-like particles from cells (J. W. Wills, C. E. Cameron, C. B. Wilson, Y. Xiang, R. P. Bennett, and J. Leis, J. Virol. 68:6605-6618, 1994). This domain, referred to as the L domain, was previously mapped to the 11 amino acids of p2b. Through the analysis of a series of deletion and substitution mutations, the L domain has now been fine mapped to a highly conserved amino acid sequence, PPPPYV of p2b. Sequences flanking PPPPYV motif can be deleted without any effect on budding. Defects caused by L-domain deletions can be rescued by placing a wild-type copy of the sequence at several other positions in RSV Gag. A proline-rich P(S/T)APP motif is found in many retroviral Gag polyproteins; the motif found in the p6 region of human immunodeficiency virus type 1 has been implicated in late functions of the virus. Substitution of the RSV L domain with this motif in a 10-amino-acid sequence derived from visna leukemia virus results in wild-type release of virus particles from cells. In contrast, the slightly different sequences from Gibbon ape leukemia virus, Moloney leukemia virus, PSAPP alone, or a proline-rich SH3 binding sequence do not efficiently rescue RSV L-domain mutations.

Amino Acid Sequence↗
PubMed1996

Cordocentesis: a useful method for prenatal diagnosis.

OBJECTIVE: To evaluate the efficacy and safety of cordocentesis for prenatal diagnosis of various fetal diseases. PATIENTS AND METHODS: Fetal blood sampling was performed in 30 pregnancies from gestational week 19 to 36 for various prenatal diagnoses. We used Aloka SSD-650 real-time ultrasound scanner with 3.5 mHz curvilinear transducer during the procedure. A regular 22-gauge spinal needle was used for fetal blood sampling. RESULTS: Twenty-five cordocentesis were successful at the first attempt. A second attempt of cordocentesis succeeded in three cases. In the remaining two cases, intrahepatic vein sampling and cardiocentesis were employed respectively. The duration of procedure was shorter than 15 minutes in 25 cases. 1-6 ml of fetal blood was obtained from each case. Fetal blood was diluted with amniotic fluid in four samples. Maternal blood contamination never happened. No lethal complication occurred in our series. CONCLUSION: It is believed that cordocentesis is a safe and useful method for prenatal diagnosis, and intrahepatic vein sampling is an alternative choice when cordocentesis has failed.

Cordocentesis↗
PubMed1996

[Study on infertility caused by infections of Chlamydia trachomatis and ureaplasma urealyticum].

OBJECTIVE: To explore the effects of chlamydia trachomatis (CT) and ureaplasma urealyticum (UU) infections on male and female infertility. METHODS: Samples from cervical canal or male urethra of 1198 infertile patients (599 couples) were studied and from 167 normal fertile men and women served as control. The fluorescent monoclonal antibody technique and the culture method were used for CT and UU assays respectively. RESULTS: The positive rates of CT and UU infections in infertile group were 25.5% (306/1 198) and 35.9% (167/1 198) respectively, while 6.6% (11/167) and 15.6% (26/167) in the control group respectively. There were significant differences between the 2 groups (P < 0.01). After treatment of positive patients, the pregnancy rates were higher in those patients became negative than that in patients remained positive (P < 0.01). CONCLUSION: The CT and UU infections were one of the factors causing infertility.

Adult↗
PubMed1996

[Cordocentesis for prenatal diagnosis of fetal diseases].

For the purpose of prenatal diagnosis, 30 fetal blood samplings were performed in 30 pregnant women from 19 to 36 gestational weeks. The samples were taken with a 22-gauge needle guided by ultrasound. Twenty-five cordocenteses were succeeded at the first attempt. A second attempt was needed in other 5 cases. The duration of procedure was less than 15 minutes in 83.3% cases. 1-6 ml fetal blood was obtained for each case. No lethal complication occured in our series. It is believed that cordocentesis could be a useful tool for prenatal diagnosis, and the intrahepatic-vein sampling is a preferable alternative choice if cordocentesis fails.

Cordocentesis↗
PubMed1996

[Statistical models and their application in descriptive epidemiology of cancer].

There are some limitations or disadvantages of statistical methods traditionally used in descriptive epidemiology of cancer. It can not handle the true relationships of several variables under srudy, and the effectiveness of a variable may often be confounded by other variables. This paper describes two kinds of multivariable regression models frequently used in descriptive epidemiology of cancer, such as the age-period-cohort (APC) model for the analysis of cancer incidence or mortality rate and the relative survival (RSR) model for the analysis of cancer survival rate. Detailed statistical methods, model fitting, parameter estimation, etc., are presented and two examples are used for illustration using data sets of oesophageal and stomach cancers diagnosed in urban Shanghai. The advantages of multivariable regression models are able to adjust effectiveness of confounder factors, and give estimations and evaluations of adjusted relative risks for the population.

Adult↗
PubMed1996

Antenatal diagnosis and management of Dandy-Walker syndrome.

The Dandy-Walker syndrome (DWS) can be accurately diagnosed in utero by sonographic demonstration of characteristic morphologic changes of the fetus, which includes hydrocephalus, incomplete cerebellar vermis and a posterior fossa cyst. We present a case of Dandy-Walker syndrome diagnosed antenatally. The associated anomalies are reviewed, and the value of antenatal diagnosis is discussed.

Adult↗
PubMed1996

[Protective effects of chrominum on myocardial damage in rats].

To prove the protective effects of trivalent chromium (Cr3+) on myocardial damage, its ultrastructure and electro-physiological changes were observed in different groups of rats with intraperitoneal injection of normal saline, Cr3+ and selenium, and injection of adriamycin (ADR) by their tail vein. Results of ultrastructural observations showed nuclear margin of myocardial cells was obscure, cytoplasm became coarse and sparse, mitochondria vacuolar, myocardiofibril loose, broken and lytic in the group treated with ADR, myocardiopathic changes reduced and myocardial filaments arranged in good order in that with Cr3+ and selenium. QRS complex, Q-T interval, APD50 and APD90 in electrocardiograph (ECG) prolonged in the group with ADR and selenium, and no changes were observed in that with Cr3+. It suggests Cr3+ and selenium have apparently protective effects on rat's myocardium, and Cr3+ also can reverse the changes in ECG caused by ADR, which is of importance in prevention and treatment of cardiovascular diseases.

Animals↗
PubMed1995

Seeking women's voices: setting the context for women's health interventions in two rural counties in Yunnan, China.

If interventions to improve health are truly to benefit women, they must be developed from the start with a critical understanding of women's own perceptions of their health problems and needs, and how these concerns are linked to other facets of women's lives. To obtain such understanding, it is crucial for health planners to seek out women in the communities where they live, to encourage them to speak in their own voices about their health and lives, and to be genuinely committed to listening to what the women have to say. This paper presents results of focus group discussions with village women in two rural counties in Yunnan, China. The data are derived from 28 focus group discussions conducted by the Women's Reproductive Health and Development Program in Yunnan as part of a comprehensive assessment of reproductive health needs in poorer, more remote areas of the two counties. The discussions were held to ascertain what village women themselves feel to be their most pressing health problems, and how these relate to work, family, social status and their use of health services. Results show how women's health and their use of health services are rightly intertwined with their labor roles, harsh environmental conditions and oppressive poverty. Widespread breakdowns in the village-level primary health care network lead village women to express a profound lack of confidence in local health services. The findings have several implications for planning and implementation. Demands on women's scarce time need to be explicitly considered when designing health education activities and health service delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Identifying the mechanism of protein loop closure: a molecular dynamics simulation of the Bacillus stearothermophilus LDH loop in solution.

The 'loop' involving residues 98-110 in Bacillus stearothermophilus lactate dehydrogenase (BSLDH) is of great interest as substrate-induced 'loop' closure is thought to be rate-limiting and essential in catalyzing the reaction and in determining substrate specificity. Consequently, we have explored the mechanism underlying 'loop' opening in BSLDH through a molecular dynamics simulation at high temperature (1000 K) in the presence of explicit solvent, starting from the X-ray structure of BSLDH complexed with the co-enzyme NAD+ and oxamate at 2.5 A. During the simulation, a significant conformational change occurred, as evidenced by sharp dihedral angle transitions, hydrogen bond breaking and formation and large root mean square deviations from the starting structure; these changes define the criteria for 'loop' opening. The mechanical elements responsible for 'loop' opening, i.e. 'loop' hinges and flap, are defined through a combination of order parameters, dihedral angle changes and their correlations and the dynamical cross-correlation map of atomic displacements for the 'loop' residues. The results indicate that the 'loop' consists of two flexible hinge regions on either side of a relatively rigid three-residue segment that undergoes a significant spatial displacement during 'loop' opening. 'Loop' opening is made possible through an array of correlated dihedral angle changes and intra-'loop' rearrangements of hydrogen-bond interactions. The present findings are compared to previous work related to 'loop' opening and site-directed mutagenesis experiments.

Amino Acid Sequence↗
PubMed1995

Use of 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil as a novel antiviral agent for hepatitis B virus and Epstein-Barr virus.

A novel anti-hepatitis B virus (anti-HBV) agent, 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU), was synthesized and found to be a potent anti-HBV and anti-Epstein-Barr virus agent. Its in vitro potency was evaluated in 2.2.15 and H1 cells for anti-HBV and anti-Epstein-Barr virus activities, respectively. In vitro cytotoxicity in MT2, CEM, 2.2.15, and H1 cells was also assessed, and the results indicated high antiviral selectivities of L-FMAU in these cells.

Antiviral Agents↗
PubMed1995

[Rapid detection of numerical aberrations of chromosomes in the first trimester of pregnancy by using fluorescence in situ hybridization (FISH)].

Fluorescence in situ hybridization (FISH) has been applied for rapid prenatal diagnosis of common numerical aberrations of chromosomes. We used FISH with chromosome 13, 18 and 21 specific probes on 528 uncultured mesenchymal chorionic villi cell samples to detect the chromosomal abnormalities, and we also performed the conventional chromosome analysis of cultured cells from parallel samples. The results showed, in samples disomic with respect to the probed chromosomes, and average of 1 percent (range 0-18 percent) had three hybridization signals. By contrast, in the samples trisomic or triploidic for the probed chromosomes, an average of 70 percent (52-84 percent) (chromosome 13), 73 percent (68-84 percent) (chromosome 18), and 76 percent (54-90 percent) (chromosome 21, including one case of mosaic trisomy 21) of the nuclei displayed three signals. The whole test took about 24 hours. We concluded that FISH can provide a rapid and accurate method for the first trimester prenatal idetification of selected numerical aberrations of chromosomes.

Chorionic Villi Sampling↗
PubMed1995

Mosaicism confined to placenta in pregnancies with adverse outcome.

Chorionic villi and fetal tissues from 50 pathological human conceptions at gestational weeks 9-40 were cultured and cytogenetically analyzed to explore the existence of chromosomal mosaicism confined to the extraembryonic tissues and to clarify the relationship between confined placental mosaicism and adverse outcome of pregnancy. Chorionic villi and fetal tissues from 12 second trimester gestations terminated for social reasons served as a control group. In two pathological gestations, true mosaicism was found exclusively in chorionic cells and could not be confirmed in cells derived from the fetal tissues. One of these was severely growth retarded. Concordant results were obtained in all other cases.

Abortion, Induced↗