Biomedical subjects

Shu Chen

Publications and source records attributed to Shu Chen.

At least 37 records · Page 2Linked to original sources

PubMed2006

[The development and clinical application of papillomavirus genotyping by DNA chip].

OBJECTIVE: To develop a new platform for genotyping human papillomavirus (HPV) and to investigate its effect in clinical application. METHODS: A pair of common primers of 18 HPV subtypes for PCR, was designed in HPV conservative L1 region. Genotyping probes for detecting 15 high-risk HPV subtypes 16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66 and 68, together with 3 low-risk HPV 6, 11 and 42 were selected respectively from Genbank and fixed on membrane to make DNA chip. PCR amplification and DNA chip technology were optimized. 100 clinical samples were used to investigate the effect of HPV genotyping DNA chip. Veracity of the genotyping results was verified by sequencing. RESULTS: From the 100 clinical samples, 30 were found to be HPV positive, including high-risk HPV subtypes 16, 18, 33, 45, 51, 58, and 66, and low-risk HPV 6, 11 and 42. The sensitivity tested by standard samples was up to 10 copies of HPV DNA. CONCLUSION: The HPV genotyping system developed here with DNA chip showed high sensitivity and specificity, suitable to be applied in clinical practice for HPV diagnosis and investigation on the prevalence of HPV sub-types.

DNA Probes, HPV↗

PubMed2006

[Effect of angiotensin II on differentiation of umbilical cord blood CD34+ cells into megakaryocytes].

This study was aimed to investigate the effect of angiotensin II on differentiation of cord blood CD34+ cells into megakaryocytes in vitro. The CD34+ cells from eight fresh umbilical cord blood samples sorted by a high-gradient magnetic cell sorting system (MACS) were cultured in serum-free culture medium containing thrombopoietin (TPO) 50 ng/ml, IL-3 10 ng/ml, stem cell factor (SCF) 50 ng/ml and different concentrations of angiotensin II (0, 50, 100, 1000 microg/ml) for 14 days. Mononuclear cells (MNC) were counted by automatic cell analyzer. Cultured CD41+ cell and platelet counts in cultured system, and cell cycle were analyzed by flow cytometry. CD41 specific monoclonal antibody staining was observed by immunofluorescence microscopy. The results showed that as compared with the control group, the number of MNC not increased significantly (P > 0.05), but the number of CD41+ cells and platelets increased significantly in treatment group (P < 0.05). Cell cycle analysis revealed that the amounts of 4N cells increased and apoptosis cells obviously existed in treatment group (P < 0.05). After fluorescence staining, more CD41+ cells of different sizes were observed by means of fluorescence microscopy in both groups. It is concluded that angiotensin II can induce the cord blood CD34+ cells to differentiate towards megakaryocyte, and enhance the function of megakaryocyte to produce platelet.

Angiotensin II↗

PubMed2006

[Study on interaction of anionic surfactant SDS and bovine serum albumin by fourier transform infrared spectroscopy].

FTIR spectroscopy was applied to investigate the interaction of anionic surfactant Sodium Dodecyl Sulfate (SDS) and Bovine Serum Albumin (BSA). Amide band I of BSA was analyzed to obtain the change in secondary structure of BSA when different concentration of SDS was added and during different interaction period. In short interaction period and at low concentration of SDS, the alpha-helixes increased and the random coil decreased. In long interaction period or at high concentration of SDS, SDS unfolded the protein by decreasing the alpha-helix structure and increasing the random coil.

Animals↗

PubMed2005

Resistance after single-dose nevirapine prophylaxis emerges in a high proportion of Malawian newborns.

The administration of single-dose nevirapine to women in labor and their infants can prevent HIV-1 mother-to-child transmission. We examined nevirapine resistance in infants who were HIV-1 infected despite single-dose nevirapine prophylaxis, including 18 Ugandan infants (HIVNET 012 trial, nine subtype A and nine subtype D) and 23 Malawian infants (NVAZ trial, all subtype C). Nevirapine resistance was more frequent in infants with subtype C than with subtypes A and D (87 versus 50%, P = 0.016).

Anti-HIV Agents↗

PubMed2005

Genetic modifiers affecting severity of epilepsy caused by mutation of sodium channel Scn2a.

Mutations in the voltage-gated sodium channels SCN 1 A and SCN 2 A are responsible for several types of human epilepsy. Variable expressivity among family members is a common feature of these inherited epilepsies, suggesting that genetic modifiers may influence the clinical manifestation of epilepsy. The transgenic mouse model Scn 2 a(Q 54) has an epilepsy phenotype as a result of a mutation in Scn 2 a that slows channel inactivation. The mice display progressive epilepsy that begins with short-duration partial seizures that appear to originate in the hippocampus. The partial seizures become more frequent and of longer duration with age and often induce secondary generalized seizures. Clinical severity of the Scn 2 a(Q 54) phenotype is influenced by genetic background. Congenic C57BL/6J.Q 54 mice exhibit decreased incidence of spontaneous seizures, delayed seizure onset, and longer survival in comparison with [C57BL/6J x SJL/J]F(1).Q 54 mice. This observation indicates that strain SJL/J carries dominant modifier alleles at one or more loci that determine the severity of the epilepsy phenotype. Genome-wide interval mapping in an N(2) backcross revealed two modifier loci on Chromosomes 11 and 19 that influence the clinical severity of of this sodium channel-induced epilepsy. Modifier genes affecting clinical severity in the Scn 2 a(Q 54) mouse model may contribute to the variable expressivity seen in epilepsy patients with sodium channel mutations.

Alleles↗

PubMed2005

Sortase A contributes to pneumococcal nasopharyngeal colonization in the chinchilla model.

Sortase A (SrtA) is required to anchor neuraminidase, beta-galactosidase, and possibly other LPXTG motif proteins to the pneumococcal cell surface. We examined the role of SrtA in Streptococcus pneumoniae nasopharyngeal (NP) colonization in the chinchilla model. The srtA mutant colonized the nasopharynx at a significantly lower level than the D39 parent strain during the second and third week of the carriage, and was eliminated from nasopharynx one week earlier than the D39 pneumococci. Our data indicate that SrtA contributes to pneumococcal NP colonization in this animal model.

Aminoacyltransferases↗

PubMed2005

Heat shock factor 1-deficient mice exhibit decreased recovery of hearing following noise overstimulation.

Heat shock proteins (Hsps) can enhance cell survival in response to stress. Heat shock factor 1 (Hsf1) is the major transcription factor that regulates stress-inducible Hsp expression. We previously demonstrated the presence of Hsf1 in the rodent cochlea and also demonstrated that a heat shock known to precondition the cochlea against noise trauma results in Hsf1 activation in the rodent cochlea. In the present study, we used an Hsf1-deficient (Hsf1-/- mouse model to determine whether eliminating the Hsf1-dependent stress pathway would influence hearing loss and/or recovery from a moderate-intensity noise. Hsf1-/- mice and their normal littermates (Hsf1+/+) were exposed to a 98-dB, broadband (2-20 kHz) noise for 2 hr, and auditory brainstem response thresholds were measured at three frequencies (4, 12, and 20 kHz) 3 hr, 3 days, and 2 weeks after noise. Hsf1-/- mice had greater hearing loss than Hsf1+/+ mice, with significant differences in recovery observed at all frequencies tested by 2 weeks after noise. Increased outer hair cell loss was also observed in Hsf1-/- mice following noise. These studies provide evidence for the importance of Hsf1 in cochlear protection, recovery, and/or repair following noise overstimulation.

Animals↗

PubMed2005

A sensitive non-isotopic assay for acetylcholine receptor autoantibodies.

BACKGROUND: Detection and measurement of serum acetylcholine receptor autoantibodies (AChRAb) are useful in the diagnosis and management of myasthenia gravis (MG). An immunoprecipitation assay (IPA) based on AChR labelled with 125I-alpha bungarotoxin is widely used for measurement of AChRAb, but a non-isotopic assay of sensitivity and specificity comparable to IPA is not available as yet. METHODS: A new AChRAb ELISA, which is based on the ability of AChRAb to compete with 3 different AChR monoclonal antibodies (MAbs 1-3) for binding sites on affinity purified fetal and adult-type AChR preparations, is described. The sensitivity and specificity of the ELISA were assessed by comparing assay results with a conventional IPA. RESULTS: There was good agreement between the IPA and the ELISA for measurement of AChRAb (r = 0.85; n = 83; p <0.001). 76/83 MG sera were positive in the ELISA, whilst 72/83 were positive by IPA. Eight sera were positive in the ELISA (inhibition range 18%-46%) but negative by IPA (0.33-0.47 nmol/L toxin bound) and 4 sera were negative in the ELISA (inhibition range -1% to15%) whilst positive by IPA (0.56-2.9 nmol/L toxin bound). Overall 80/83 (96%) of the MG sera were AChRAb positive in one or both assays. In addition, all 191 control serum samples which were negative for AChRAb by IPA were below or equal to 16% of inhibition in our ELISA. The AChRAb ELISA also showed good inter-assay and intra-assay precision. CONCLUSION: The AChRAb ELISA we have described has sensitivity and specificity at least as high as our current radioactive IPA. It has good precision and good handling characteristics making it suitable for routine use.

Adult↗

PubMed2005

Surface-enhanced Raman scattering studies of 1,10-phenanthroline adsorption and its surface complexes on a gold electrode.

This paper reports on the interface processes of 1,10-phenanthroline (phen) at a roughened Au electrode by surface-enhanced Raman scattering (SERS) for the first time. Both the adsorption and coordination of phen on the roughened gold electrode have been studied. In comparison to the normal Raman spectrum of phen monohydrate, the frequency and relative intensity change significantly in the SERS spectra. As evidenced by cyclic voltammetry, the electrochemical behavior of the Au electrode is strongly modified by the adsorbed phen. It was found that a new pair of redox peaks appeared in the cyclic voltammogram only when both phen and X (X = Cl-, Br-) were present. Information on coordination bonds of Au-N and Au-X as well as on adsorbed bonds of Au-N(ad) and Au-X(ad), was obtained by the SERS spectra. In situ SERS investigations together with electrochemical measurements convincingly prove the formation of surface complexes 1,10-phenAu2X6 or [1,10-phenAuX2]AuX4 during the electro-oxidation process of Au while phen and X coadsorbed on the surface.

Journal Article↗

PubMed2005

Nevirapine (NVP) resistance in women with HIV-1 subtype C, compared with subtypes A and D, after the administration of single-dose NVP.

OBJECTIVE: In the Human Immunodeficiency Virus (HIV) Network for Prevention Trials (HIVNET) 012 trial in Uganda, 6-8 weeks after single-dose nevirapine (SD-NVP), NVP resistance mutations were detected at a higher rate in women with HIV-1 subtype D than in women with subtype A. Here, we evaluate the rate of NVP resistance mutations in women with subtype C. METHODS: NVP resistance mutations were detected using the ViroSeq HIV-1 Genotyping System. RESULTS: The portion of women with any NVP resistance mutation was higher in those with subtype C (45/65 [69.2%] in the NVP and zidovudine trial, Malawi) than in those in the HIVNET 012 trial with either subtype A (28/144 [19.4%]; P<.0001) or subtype D (35/97 [36.1%]; P<.0001). In a multivariate model, subtype (C vs. A: odds ratio [OR], 8.73 [95% confidence interval {CI}, 4.29-17.76]; C vs. D: OR, 3.38 [95% CI, 1.65-6.93]) and viral load at delivery (OR, 2.35 [95% CI, 1.62-3.40]) independently predicted NVP resistance mutations, but maternal age, parity, and time between SD-NVP and the 6-8-week visit did not. CONCLUSIONS: The rate of NVP resistance mutations after SD-NVP was significantly higher in women with HIV-1 subtype C than in women with subtype A or D. Studies are needed to assess the clinical significance of this finding.

Adult↗

PubMed2005

Sensitive non-isotopic assays for autoantibodies to IA-2 and to a combination of both IA-2 and GAD65.

BACKGROUND: A sensitive ELISA for measurement of IA-2 autoantibodies has been developed and assessed. Also, a combination ELISA for detection of both GAD65 autoantibodies and IA-2 autoantibodies is described. METHODS: The IA-2 autoantibody assay is based on the ability of IA-2 autoantibodies to form a bridge between IA-2 intracellular fragment coated onto ELISA plate wells and liquid-phase IA-2 labelled with biotin. The combination ELISA uses plates coated with both IA-2 and GAD65 and a mixture of IA-2-biotin and GAD65-biotin. Assay sensitivity was assessed using the WHO reference (NIBSC 97/550) for islet cell antibodies. IA-2 autoantibody measurements by ELISA were compared with measurements in immunoprecipitation assays (IPAs) based on 125I or 35S labelled IA-2. Combination ELISA results were compared with results obtained for individual autoantibodies. RESULTS: As little as 15 units/mL of NIBSC 97/550 was detectable in the IA-2 autoantibody ELISA compared to 125 units/mL by 125I-IA-2 IPA. 110/216(51%) sera from patients with type 1 DM were positive in the IA-2 autoantibody ELISA while 97/216 (45%) and 91/216 (42%) were positive in the 125I-IA2 and 35S-IA-2 IPAs, respectively. The IA-2 autoantibody ELISA showed 100% specificity for type 1 DM. The combination ELISA was able to detect GAD65 and/or IA-2 autoantibodies in 183/216 (85%) diabetic sera and 183/216 (85%) were also found positive for autoantibodies to IA-2 and/or to GAD65 in the assays for individual antibodies. Autoantibody measurements in the individual autoantibody assays and in the combination ELISA showed good agreement by Pearson correlation (r=0.92, n=216, p<0.001) and by Bland and Altman analysis. CONCLUSIONS: Sensitive and specific ELISAs for measurement of autoantibodies to IA-2 and to a combination of IA-2 and GAD65 have been developed. These assays are suitable for screening large numbers of samples in diabetes prediction and prevention trials.

Antibody Specificity↗

PubMed2005

Variants of the natural resistance-associated macrophage protein 1 gene (NRAMP1) are associated with severe forms of pulmonary tuberculosis.

Although genetic factors may affect susceptibility to tuberculosis, studies that have assessed variants of the natural resistance-associated macrophage protein 1 gene (NRAMP1) and their association with tuberculosis in humans have yielded conflicting results. It is likely that NRAMP1 polymorphisms may be associated with progression to severe forms of pulmonary tuberculosis rather than with susceptibility to Mycobacterium tuberculosis infection. To test this possibility, we examined NRAMP1 variants at the INT4 and D543N loci, as well as their association with severe forms of pulmonary tuberculosis, in 127 patients with active pulmonary tuberculosis and in 91 ethnically matched, healthy control subjects in areas of China where tuberculosis is endemic. We found that NRAMP1 polymorphisms at these 2 loci were significantly associated with 2 severe forms of pulmonary tuberculosis: sputum smear-positive tuberculosis and cavitary tuberculosis. The NRAMP1 variants were not associated with pulmonary M. tuberculosis infection, when analyses of all patients with tuberculosis and all control subjects were performed. The findings of the present study support the hypothesis that genetic variants of NRAMP1 may have an effect on bacilli growth and on outcomes of pulmonary tuberculosis, but not on susceptibility to M. tuberculosis infection.

Adult↗

PubMed2005

Cloning and characterization of a plant defensin VaD1 from azuki bean.

A recombinant mungbean defensin VrD1 was previously shown to exhibit antifungal and bruchid-resistant activity. To study the function and regulation of VrD1, genomic DNAs of plant defensins were isolated from Vigna radiata VC6089A and azuki bean Vigna angularis Kao Hsiung No. 6. The azuki bean defensin genomic DNA VaD1 was sequenced and converted to VaD1 cDNA. VaD1 defensin was purified from Vigna angularis Kao Hsiung No. 6 to apparent homogeneity. The complete amino acid sequence of the purified VaD1 was determined and was found to be exactly the same as the sequence deduced from VaD1 cDNA. VaD1 is a basic protein containing 46 amino acids with four conserved disulfide bonds and shares high sequence homology (78.3%) with VrD1. VaD1 inhibited the growth of Fusarium oxysporum, Fusarium oxysporum f. sp. pisi, Staphylococcus epidermidis, and Salmonella typhimurium. VaD1 also inhibited in vitro protein synthesis and bruchid larval development, but was less active than the recombinant VrD1.

Amino Acid Sequence↗

PubMed2005

Purification and partial characterization of two chitinases from the mycoparasitic fungus Talaromyces flavus.

Chitinases were produced by Talaromyces flavus CGMCC 3.4301 when it was grown in the presence of chitin. Two chitinases from the culture filtrate of T. flavus were purified to homogeneity by fractional ammonium sulphate precipitation, ion-exchange chromatography on DEAE-Sepharose and Phenyl-Sepharose hydrophobic interaction chromatography. By SDS-PAGE, the molecular weight of the two enzymes was estimated to be 41 and 32 kDa, respectively. The 41 kDa chitinase (CHIT41) had a 4.0 pH optimum; the 32 kDa chitinase (CHIT32) optimum activity was at pH 5.0. The optimum temperature for the two chitinase activities was 40 degrees C. The two chitinases had activity against cell wall of Verticillium dahliae, Sclerotinia sclerotiorum and Rhizoctonia solani, and inhibited spore germination and germ tube elongation of Alternaria alternata, Fusarium moniliforme, and Magnaporthe grisea.

Antifungal Agents↗

PubMed2005

Autoimmune oophoritis as a mechanism of follicular dysfunction in women with 46,XX spontaneous premature ovarian failure.

OBJECTIVE: To assess the association between serum adrenal cortex autoantibodies and histologically confirmed autoimmune lymphocytic oophoritis. DESIGN: Controlled, prospective. SETTING: Tertiary research center. PATIENT(S): Two hundred sixty-six women with 46,XX spontaneous premature ovarian failure. INTERVENTION(S): Ovarian biopsy in 10 women. MAIN OUTCOME MEASURE(S): Serum adrenal cortex autoantibodies assessed by indirect immunofluorescence and autoimmune oophoritis assessed by immunohistochemical lymphocyte markers. RESULT(S): We obtained a histologic diagnosis of autoimmune oophoritis in four women who tested positive for adrenal cortex autoantibodies and excluded this diagnosis in ovarian biopsies from six women who tested negative for adrenal cortex autoantibodies (4/4 vs. 0/6). Women with histologically confirmed autoimmune oophoritis had a greater total ovarian volume as assessed by transvaginal sonography (11.4 +/- 5.6 mL vs. 1.5 +/- 0.4 mL) (mean +/- SEM). They were also more likely to have subclinical adrenal insufficiency and clinical signs of androgen deficiency (3/4 vs. 0/6). Overall, 10/266 women tested positive for adrenal cortex autoantibodies (3.8%, 95% confidence interval: 1.8%-6.5%). CONCLUSION(S): In women who present with 46,XX spontaneous premature ovarian failure as their primary concern there is a clear association between serum adrenal cortex autoantibodies and the presence of histologically confirmed autoimmune oophoritis.

Adolescent↗

PubMed2005

Affordable, abbreviated roche monitor assay for quantification of human immunodeficiency virus type 1 RNA in plasma.

The cost for the Roche Monitor assay kit can be reduced 50% by using only the 1:1, 1:25, and 1:625 human immunodeficiency virus (HIV) and the 1:1 quantitation standard dilutions. This abbreviated test applied to 1,774 mostly African samples had results nearly identical to those obtained following the package insert instructions. To make this approach feasible, Roche would have to provide additional lysis buffer and master mix.

Female↗

PubMed2005

Analysis of the interaction between human steroid 21-hydroxylase and various monoclonal antibodies using comparative structural modelling.

OBJECTIVE: To study the interaction between human steroid 21-hydroxylase (21-OH) and monoclonal antibodies (MAbs) to 21-OH directed to 3 different epitopes recognised by 21-OH autoantibodies characteristic of autoimmune Addison's disease. DESIGN: Build comparative structural models of 21-OH, 21-OH MAbs and complexes of 21-OH-21-OH MAbs and study the effects of 21-OH MAbs on 21-OH enzyme activity. Then, analyse the relationship between sites important for binding of 21-OH MAbs and 21-OH autoantibodies and sites important for 21-OH enzyme activity. METHODS: Variable (V) regions of 21-OH MAbs (M21-OH1, M21-OH3, M21-OH5) were sequenced and models of the MAbs built using structures of antibodies in the database as templates. A comparative model of 21-OH was built using the crystal structure of rabbit cytochrome p450 2c5/3LVdH as template. 21-OH enzyme activity was measured in terms of conversion of [3H]progesterone to deoxycorticosterone and the effect of purified MAb IgGs on 21-OH enzyme activity was assessed. RESULTS: M21-OH1, M21-OH3 and control MAb had no effect on 21-OH enzyme activity with 88.8% +/- 24% (n = 6), 86.7% +/- 7.6% (n = 6) and 86.5% +/- 10.6% (n = 6) of activity remaining in the presence of the respective IgGs. This was consistent with the epitopes for M21-OH1 and M21-OH3 being located distant from 21-OH enzyme active sites in our 21-OH model. The epitope for M21-OH5 which inhibited 21-OH enzyme activity (48.5 +/- 8.3% activity remaining; P < 0.001 compared with control MAb IgG) was found close to the redox protein binding site in our 21-OH model. CONCLUSIONS: A comparative model of 21-OH has been produced. Analysis of experimental data in the context of the model suggests that M21-OH5 inhibits 21-OH enzyme activity through interference with redox protein binding.

Animals↗

PubMed2005

Gender differences in perinatal HIV acquisition among African infants.

OBJECTIVE: We investigated gender-specific risks of mother-to-child transmission (MTCT) at birth and at 6 to 8 weeks among infants born to HIV-infected African women. DESIGN: Follow-up study of infants enrolled in 2 randomized, phase III, clinical trials to prevent MTCT, conducted in Blantyre, Malawi, in southeast Africa. METHODS: Infants were enrolled at birth and monitored postnatally, and their HIV status was assessed at birth and at 6 to 8 weeks (assessment beyond 6-8 weeks is ongoing). Statistical analyses were stratified according to gender, and comparisons were made with descriptive, univariate, and multivariate statistical tests. MTCT was estimated at birth and at 6 to 8 weeks among infants who were not infected at birth. RESULTS: Overall, 966 boys and 998 girls were enrolled. The rate of HIV transmission at birth was 9.5% (187 of 1964 infants). However, at birth significantly more girls (12.6%) than boys (6.3%) were infected with HIV. This association remained significant after controlling for maternal viral load and other factors. Among infants who were uninfected at birth, 8.7% (135 of 1554 infants) acquired HIV by 6 to 8 weeks; of these infants, more girls acquired HIV (10.0%), compared with boys (7.4%). CONCLUSIONS: Female infants may be more susceptible to HIV infection before birth and continuing after birth. Alternatively, in utero mortality rates of HIV-infected male infants may be disproportionately higher and thus more HIV-infected female infants are born. In areas of sub-Saharan Africa, where HIV infection rates are high among women of reproductive age, the magnitude of the gender transmission differences observed in this study could have clinical, preventive, and demographic implications.

Birth Weight↗