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author:("Li, yiha")
1.  Adenovirus-delivered PDCD5 counteracts adriamycin resistance of osteosarcoma cells through enhancing apoptosis and inhibiting Pgp 
In the present study, we investigated the roles of PDCD5 (programmed cell death 5) in multidrug re-sistance (MDR) of osteosarcoma cells and the possible lurking mechanisms. An adenovirus expression vector of PDCD5 was constructed and transfected into human adriamycin-resistant osteosarcoma cell line Saos-2/ADM. We found that up-regulation of PDCD5 could significantly enhance the sensitivity of Saos-2/ADM cells towards vincristine, methotrexate, cisplatin and arsenic trioxide (As2O3), and could decrease the capacity of cells to efflux adriamycin. PDCD5 could significantly down regulate the expression of P-glycoprotein (Pgp), but not affect the expression of multidrug resistance associated protein (MRP) or the glutathione S-transferase (GST). PDCD5 was also able to significantly increase the apoptotic activity of modified osteosarcoma cells. Further study of the biological functions of PDCD5 might be helpful in the understanding of the mechanisms of multidrug resistance (MDR) in osteosarcoma and exploring PDCD5 based adjuvant genetic therapy.
PMCID: PMC4307499  PMID: 25664052
Osteosarcoma; MDR; PDCD5; apoptosis
2.  The Feasibility Study of Non-Invasive Fetal Trisomy 18 and 21 Detection with Semiconductor Sequencing Platform 
PLoS ONE  2014;9(10):e110240.
Recent non-invasive prenatal testing (NIPT) technologies are based on next-generation sequencing (NGS). NGS allows rapid and effective clinical diagnoses to be determined with two common sequencing systems: Illumina and Ion Torrent platforms. The majority of NIPT technology is associated with Illumina platform. We investigated whether fetal trisomy 18 and 21 were sensitively and specifically detectable by semiconductor sequencer: Ion Proton.
From March 2012 to October 2013, we enrolled 155 pregnant women with fetuses who were diagnosed as high risk of fetal defects at Xiamen Maternal & Child Health Care Hospital (Xiamen, Fujian, China). Adapter-ligated DNA libraries were analyzed by the Ion Proton™ System (Life Technologies, Grand Island, NY, USA) with an average 0.3× sequencing coverage per nucleotide. Average total raw reads per sample was 6.5 million and mean rate of uniquely mapped reads was 59.0%. The results of this study were derived from BWA mapping. Z-score was used for fetal trisomy 18 and 21 detection.
Interactive dot diagrams showed the minimal z-score values to discriminate negative versus positive cases of fetal trisomy 18 and 21. For fetal trisomy 18, the minimal z-score value of 2.459 showed 100% positive predictive and negative predictive values. The minimal z-score of 2.566 was used to classify negative versus positive cases of fetal trisomy 21.
These results provide the evidence that fetal trisomy 18 and 21 detection can be performed with semiconductor sequencer. Our data also suggest that a prospective study should be performed with a larger cohort of clinically diverse obstetrics patients.
PMCID: PMC4203771  PMID: 25329639
3.  Smoking and Major Depressive Disorder in Chinese Women 
PLoS ONE  2014;9(9):e106287.
To investigate the risk factors that contribute to smoking in female patients with major depressive disorder (MDD) and the clinical features in depressed smokers.
We examined the smoking status and clinical features in 6120 Han Chinese women with MDD (DSM-IV) between 30 and 60 years of age across China. Logistic regression was used to determine the association between clinical features of MDD and smoking status and between risk factors for MDD and smoking status.
Among the recurrent MDD patients there were 216(3.6%) current smokers, 117 (2.0%) former smokers and 333(5.6%) lifetime smokers. Lifetime smokers had a slightly more severe illness, characterized by more episodes, longer duration, more comorbid illness (panic and phobias), with more DSM-IV A criteria and reported more symptoms of fatigue and suicidal ideation or attempts than never smokers. Some known risk factors for MDD were also differentially represented among smokers compared to non-smokers. Smokers reported more stressful life events, were more likely to report childhood sexual abuse, had higher levels of neuroticism and an increased rate of familial MDD. Only neuroticism was significantly related to nicotine dependence.
Although depressed women smokers experience more severe illness, smoking rates remain low in MDD patients. Family history of MDD and environmental factors contribute to lifetime smoking in Chinese women, consistent with the hypothesis that the association of smoking and depression may be caused by common underlying factors.
PMCID: PMC4152240  PMID: 25180682
4.  Meta-analysis based on weighted ordered P-values for genomic data with heterogeneity 
BMC Bioinformatics  2014;15:226.
Meta-analysis has become increasingly popular in recent years, especially in genomic data analysis, due to the fast growth of available data and studies that target the same questions. Many methods have been developed, including classical ones such as Fisher’s combined probability test and Stouffer’s Z-test. However, not all meta-analyses have the same goal in mind. Some aim at combining information to find signals in at least one of the studies, while others hope to find more consistent signals across the studies. While many classical meta-analysis methods are developed with the former goal in mind, the latter goal has much more practicality for genomic data analysis.
In this paper, we propose a class of meta-analysis methods based on summaries of weighted ordered p-values (WOP) that aim at detecting significance in a majority of studies. We consider weighted versions of classical procedures such as Fisher’s method and Stouffer’s method where the weight for each p-value is based on its order among the studies. In particular, we consider weights based on the binomial distribution, where the median of the p-values are weighted highest and the outlying p-values are down-weighted. We investigate the properties of our methods and demonstrate their strengths through simulations studies, comparing to existing procedures. In addition, we illustrate application of the proposed methodology by several meta-analysis of gene expression data.
Our proposed weighted ordered p-value (WOP) methods displayed better performance compared to existing methods for testing the hypothesis that there is signal in the majority of studies. They also appeared to be much more robust in applications compared to the rth ordered p-value (rOP) method (Song and Tseng, Ann. Appl. Stat. 2014, 8(2):777–800). With the flexibility of incorporating different p-value combination methods and different weighting schemes, the weighted ordered p-values (WOP) methods have great potential in detecting consistent signal in meta-analysis with heterogeneity.
PMCID: PMC4089554  PMID: 24972803
Fisher’s combined probability test; Meta-analysis; Ordered p-values; Weighted order statistic
5.  Capillary zone electrophoresis-multiple reaction monitoring from 100 pg of RAW 264.7 cell lysate digest 
The Analyst  2013;138(11):3181-3188.
Capillary zone electrophoresis-multiple/single reaction monitoring (CZE-MRM/SRM), which employed an electrokinetically driven sheath-flow electrospray interface, was used for the rapid and highly sensitive detection of protein analytes in complex tryptic digests. MRM channels were developed against a commercial exponential mixture of bovine proteins. Five proteins spanning four orders of magnitude concentration range were confidently detected from only 2.5 ng of the digest mixture; the mass detection limits (S/N=3) of two detected proteins, alpha-casein and glutamate dehydrogenasewere about 600 zmole and 30 amole, respectively. This technique was then applied to a RAW 264.7 cell lysate digest. Three proteins were confidently and reproducibly detected from 100 pg of this digest. The sample amount corresponds to the approximate protein content from a single cell, which suggests that CZE-MRM may be a useful analytical tool in chemical cytometry. In addition to providing highly sensitive detection of proteins in complex mixtures, this system is highly rapid; migration time of the protein digests was less than 10 min.
PMCID: PMC3670666  PMID: 23591184
Capillary zone electrophoresis; electrokinetic sheath flow electrospray; multiple reaction monitoring; single reaction monitoring; protein digests; RAW 264.7 cell line; picogram tryptic digests analysis
6.  A two-step hierarchical hypothesis set testing framework, with applications to gene expression data on ordered categories 
BMC Bioinformatics  2014;15:108.
In complex large-scale experiments, in addition to simultaneously considering a large number of features, multiple hypotheses are often being tested for each feature. This leads to a problem of multi-dimensional multiple testing. For example, in gene expression studies over ordered categories (such as time-course or dose-response experiments), interest is often in testing differential expression across several categories for each gene. In this paper, we consider a framework for testing multiple sets of hypothesis, which can be applied to a wide range of problems.
We adopt the concept of the overall false discovery rate (OFDR) for controlling false discoveries on the hypothesis set level. Based on an existing procedure for identifying differentially expressed gene sets, we discuss a general two-step hierarchical hypothesis set testing procedure, which controls the overall false discovery rate under independence across hypothesis sets. In addition, we discuss the concept of the mixed-directional false discovery rate (mdFDR), and extend the general procedure to enable directional decisions for two-sided alternatives. We applied the framework to the case of microarray time-course/dose-response experiments, and proposed three procedures for testing differential expression and making multiple directional decisions for each gene. Simulation studies confirm the control of the OFDR and mdFDR by the proposed procedures under independence and positive correlations across genes. Simulation results also show that two of our new procedures achieve higher power than previous methods. Finally, the proposed methodology is applied to a microarray dose-response study, to identify 17 β-estradiol sensitive genes in breast cancer cells that are induced at low concentrations.
The framework we discuss provides a platform for multiple testing procedures covering situations involving two (or potentially more) sources of multiplicity. The framework is easy to use and adaptable to various practical settings that frequently occur in large-scale experiments. Procedures generated from the framework are shown to maintain control of the OFDR and mdFDR, quantities that are especially relevant in the case of multiple hypothesis set testing. The procedures work well in both simulations and real datasets, and are shown to have better power than existing methods.
PMCID: PMC4000433  PMID: 24731138
Multiple testing; Overall false discovery rate; Mixed-directional false discovery rate; Benjamini-Hochberg procedure; Microarray; Time course; Dose response
7.  Associations of Educational Attainment, Occupation, Social Class and Major Depressive Disorder among Han Chinese Women 
PLoS ONE  2014;9(1):e86674.
The prevalence of major depressive disorder (MDD) is higher in those with low levels of educational attainment, the unemployed and those with low social status. However the extent to which these factors cause MDD is unclear. Most of the available data comes from studies in developed countries, and these findings may not extrapolate to developing countries. Examining the relationship between MDD and socio economic status in China is likely to add to the debate because of the radical economic and social changes occurring in China over the last 30 years.
Principal findings
We report results from 3,639 Chinese women with recurrent MDD and 3,800 controls. Highly significant odds ratios (ORs) were observed between MDD and full time employment (OR = 0.36, 95% CI = 0.25–0.46, logP = 78), social status (OR = 0.83, 95% CI = 0.77–0.87, logP = 13.3) and education attainment (OR = 0.90, 95% CI = 0.86–0.90, logP = 6.8). We found a monotonic relationship between increasing age and increasing levels of educational attainment. Those with only primary school education have significantly more episodes of MDD (mean 6.5, P-value = 0.009) and have a clinically more severe disorder, while those with higher educational attainment are likely to manifest more comorbid anxiety disorders.
In China lower socioeconomic position is associated with increased rates of MDD, as it is elsewhere in the world. Significantly more episodes of MDD occur among those with lower educational attainment (rather than longer episodes of disease), consistent with the hypothesis that the lower socioeconomic position increases the likelihood of developing MDD. The phenomenology of MDD varies according to the degree of educational attainment: higher educational attainment not only appears to protect against MDD but alters its presentation, to a more anxious phenotype.
PMCID: PMC3909008  PMID: 24497966
8.  Childhood Sexual Abuse and the Development of Recurrent Major Depression in Chinese Women 
PLoS ONE  2014;9(1):e87569.
Our prior study in Han Chinese women has shown that women with a history of childhood sexual abuse (CSA) are at increased risk for developing major depression (MD). Would this relationship be found in our whole data set?
Three levels of CSA (non-genital, genital, and intercourse) were assessed by self-report in two groups of Han Chinese women: 6017 clinically ascertained with recurrent MD and 5983 matched controls. Diagnostic and other risk factor information was assessed at personal interview. Odds ratios (ORs) were calculated by logistic regression.
We confirmed earlier results by replicating prior analyses in 3,950 new recurrent MD cases. There were no significant differences between the two data sets. Any form of CSA was significantly associated with recurrent MD (OR 4.06, 95% confidence interval (CI) [3.19–5.24]). This association strengthened with increasing CSA severity: non-genital (OR 2.21, 95% CI 1.58–3.15), genital (OR 5.24, 95% CI 3.52–8.15) and intercourse (OR 10.65, 95% CI 5.56–23.71). Among the depressed women, those with CSA had an earlier age of onset, longer depressive episodes. Recurrent MD patients those with CSA had an increased risk for dysthymia (OR 1.60, 95%CI 1.11–2.27) and phobia (OR 1.41, 95%CI 1.09–1.80). Any form of CSA was significantly associated with suicidal ideation or attempt (OR 1.50, 95% CI 1.20–1.89) and feelings of worthlessness or guilt (OR 1.41, 95% CI 1.02–2.02). Intercourse (OR 3.47, 95%CI 1.66–8.22), use of force and threats (OR 1.95, 95%CI 1.05–3.82) and how strongly the victims were affected at the time (OR 1.39, 95%CI 1.20–1.64) were significantly associated with recurrent MD.
In Chinese women CSA is strongly associated with recurrent MD and this association increases with greater severity of CSA. Depressed women with CSA have some specific clinical traits. Some features of CSA were associated with greater likelihood of developing recurrent MD.
PMCID: PMC3906190  PMID: 24489940
Immunobiology  2012;218(1):64-75.
Dendritic cells (DCs) are antigen presenting cells capable of inducing specific immune responses against microbial infections, transplant antigens, or tumors. DCs have been shown to possess a high plasticity showing different phenotypes in response to their microenvironment. For example, tumor-associated DCs can acquire an angiogenic phenotype thus promoting tumor growth. Further, DCs cultured in vitro under different conditions are able to upregulate the expression of endothelial markers and to express angiogenic factors. Indeed, it has been shown that soluble factors such as VEGF of PGE-2, that are present in the microenvironment of several tumors, affect the biology of these cells. We hypothesize that in addition to soluble factors the adhesion to different substrates will also define the phenotype and function of DCs. Herewith we demonstrate that murine myeloid(m) DCs upregulate endothelial markers such as VE-Cadherin, and to a lesser extent TIE-2, and decrease their immune capabilities when cultured on solid surfaces as compared with the same cells cultured on ultra-low binding (ULB) surfaces. On the other hand, the expression of angiogenic molecules at the level of RNA was not different among these cultures. In order to further investigate this phenomenon we used the murine ID8 model of ovarian cancer which can generate solid tumors when cancer cells are injected subcutaneously or a malignant ascites when they are injected intraperitoneally. This model gave us the unique opportunity to investigate DCs in suspension or attached to solid surfaces under the influence of the same tumor cells. We were able to determine that DCs present in solid tumors showed higher levels of expression of endothelial markers and angiogenic molecules but were not able to respond to inflammatory stimuli at the same extent as DCs recovered from ascites. Moreover, mDCs cultured on ULB surfaces in the presence of tumor factors do not expressed endothelial markers. Taking into account all these data we consider that tumor factors might be responsible for inducing angiogenic properties in DCs, but that in some settings the expression of endothelial markers such as VE-Cadherin and TIE-2 might be a function of attachment to solid surfaces and independent of the angiogenic properties of these cells.
PMCID: PMC3413747  PMID: 22551928
Dendritic cells; endothelial markers; angiogenesis; antigen presentation; ovarian cancer
10.  Clinical Features of Patients with Dysthymia in a Large Cohort of Han Chinese Women with Recurrent Major Depression 
PLoS ONE  2013;8(12):e83490.
Dysthymia is a form of chronic mild depression that has a complex relationship with major depressive disorder (MDD). Here we investigate the role of environmental risk factors, including stressful life events and parenting style, in patients with both MDD and dysthymia. We ask whether these risk factors act in the same way in MDD with and without dysthymia.
We examined the clinical features in 5,950 Han Chinese women with MDD between 30–60 years of age across China. We confirmed earlier results by replicating prior analyses in 3,950 new MDD cases. There were no significant differences between the two data sets. We identified sixteen stressful life events that significantly increase the risk of dysthymia, given the presence of MDD. Low parental warmth, from either mother or father, increases the risk of dysthymia. Highly threatening but short-lived threats (such as rape) are more specific for MDD than dysthymia. While for MDD more severe life events show the largest odds ratio versus controls, this was not seen for cases of MDD with or without dysthymia.
There are increased rates of stressful life events in MDD with dysthymia, but the impact of life events on susceptibility to dysthymia with MDD differs from that seen for MDD alone. The pattern does not fit a simple dose-response relationship, suggesting that there are moderating factors involved in the relationship between environmental precipitants and the onset of dysthymia. It is possible that severe life events in childhood events index a general susceptibility to chronic depression, rather than acting specifically as risk factors for dysthymia.
PMCID: PMC3873934  PMID: 24386213
11.  Suicidal Risk Factors of Recurrent Major Depression in Han Chinese Women 
PLoS ONE  2013;8(11):e80030.
The relationship between suicidality and major depression is complex. Socio- demography, clinical features, comorbidity, clinical symptoms, and stressful life events are important factors influencing suicide in major depression, but these are not well defined. Thus, the aim of the present study was to assess the associations between the above-mentioned factors and suicide ideation, suicide plan, and suicide attempt in 6008 Han Chinese women with recurrent major depression (MD). Patients with any suicidality had significantly more MD symptoms, a significantly greater number of stressful life events, a positive family history of MD, a greater number of episodes, a significant experience of melancholia, and earlier age of onset. Comorbidity with dysthymia, generalized anxiety disorder (GAD), social phobia, and animal phobia was seen in suicidal patients. The present findings indicate that specific factors act to increase the likelihood of suicide in MD. Our results may help improve the clinical assessment of suicide risk in depressed patients, especially for women.
PMCID: PMC3842272  PMID: 24312196
12.  Coupling methanol denaturation, immobilized trypsin digestion, and accurate mass and time tagging for liquid chromatography-based shotgun proteomics of low nanogram amounts of RAW 264.7 cell lysate 
Analytical chemistry  2012;84(20):8715-8721.
We report the shotgun proteomic analysis of mammalian cell lysates that contain low nanogram amounts of protein. Proteins were denatured using methanol, digested using immobilized trypsin, and analyzed by UPLC-ESI-MS/MS. The approach generated more peptides and higher sequence coverage for a mixture of three standard proteins than the use of free trypsin solution digestion of heat- or urea-denatured proteins. We prepared triplicate RAW 264.7 cell lysates that contained 6 ng, 30 ng, 120 ng, and 300 ng of protein. An average of 2 ± 1, 23 ± 2, 134 ± 11, and 218 ± 26 proteins were detected for each sample size, respectively. The numbers of both protein and peptide IDs scaled linearly with the amount of sample taken for analysis. Our approach also outperformed traditional methods (free trypsin digestion of heat- or urea-denatured proteins) for 6 ng to 300 ng RAW 264.7 cell protein analysis in terms of number of peptides and proteins identified. The use of accurate mass and time (AMT) tags resulted in the identification of an additional 16 proteins based on 20 peptides from the 6 ng cell lysate prepared with our approach. When AMT analysis was performed for the 6 ng cell lysate prepared with traditional methods, no reasonable peptide signal could be obtained. In all cases, roughly ~30% of the digested sample was taken for analysis, corresponding to the analysis of a 2 ng aliquot of homogenate from the 6 ng cell lysate.
PMCID: PMC3477608  PMID: 22971241
13.  CZE-ESI-MS/MS system for analysis of subnanogram amounts of tryptic digests of a cellular homogenate 
Proteomics  2012;12(0):3013-3019.
We report the performance of capillary zone electrophoresis coupled with an electrokinetically pumped electrospray interface and an Orbitrap-Velos mass spectrometer for high sensitivity protein analysis. We first investigated the system for quantitation of the tryptic digest of bovine serum albumin (BSA). The system produced outstanding linearity with respect to peak height, number of peptide IDs, and spectral counts across the range of 12 nM to 750 nM (60 amol to 3.5 fmol) of BSA injected. One peptide produced a detection limit of 0.3 nM (1.5 amol) injected. We also analyzed 700 pg of a tryptic digest prepared from a RAW264.7 cell lysate; 10 proteins were identified in triplicate analyses after filtering the data with peptide confidence value as high. This sample size corresponds to the protein content of ~10 eukaryotic cells.
PMCID: PMC3670668  PMID: 22888077
Electrokinetically driven sheath flow interface; CZE-ESI-MS/MS; Protein digests
14.  Quantitative Multiple Reaction Monitoring of Peptide Abundance Introduced via a Capillary Zone Electrophoresis-Electrospray Interface 
Analytical chemistry  2012;84(14):6116-6121.
We demonstrate the use of capillary zone electrophoresis with an electrokinetic sheath-flow electrospray interface coupled to a triple quadrupole mass spectrometer for the accurate and precise quantification of leu-enkaphalin in a complex mixture using multiple-reaction monitoring (MRM). Assay time is <6 minutes, with no re-equilibration required between runs. A standard curve of Leu-enkephalin was performed in the presence of a background tryptic digest of bovine albumin. We demonstrate reasonably reproducible peak heights (21% relative standard deviation), retention times (better than 1% relative standard deviation), and robust electrospray quality. Our limit-of detection (3σ) was 60 pM, which corresponds to the injection of 115 zeptomole of peptide. This is a 10–20-fold improvement in mass sensitivity than we have obtained by nano HPLC/MRM and substantially better than reported for LC/MS/MS. Further quantification was performed in the presence of stable-isotope labeled versions of the peptides; under these conditions, linearity was observed across nearly four orders of magnitude. The concentration detection limit was 240 pM for the stable-isotope labeled quantification.
PMCID: PMC3674544  PMID: 22690842
15.  Assumption weighting for incorporating heterogeneity into meta-analysis of genomic data 
Bioinformatics  2012;28(6):807-814.
Motivation: There is now a large literature on statistical methods for the meta-analysis of genomic data from multiple studies. However, a crucial assumption for performing many of these analyses is that the data exhibit small between-study variation or that this heterogeneity can be sufficiently modelled probabilistically.
Results: In this article, we propose ‘assumption weighting’, which exploits a weighted hypothesis testing framework proposed by Genovese et al. to incorporate tests of between-study variation into the meta-analysis context. This methodology is fast and computationally simple to implement. Several weighting schemes are considered and compared using simulation studies. In addition, we illustrate application of the proposed methodology using data from several high-profile stem cell gene expression datasets.
PMCID: PMC3307113  PMID: 22285559
16.  CZE-ESI-MS/MS as an alternative proteomics platform to UPLC-ESI-MS/MS for samples of intermediate complexity 
Analytical Chemistry  2012;84(3):1617-1622.
We demonstrate the use of capillary zone electrophoresis with an electrokinetically pumped sheath-flow electrospray interface for the analysis of a tryptic digest of a sample of intermediate protein complexity, the secreted protein fraction of Mycobacterium marinum. For electrophoretic analysis, 11 fractions were generated from the sample using reversed phase liquid chromatography; each fraction was analyzed by CZE-ESI-MS/MS, and 334 peptides corresponding to 140 proteins were identified in 165 min of mass spectrometer time at 95% confidence (FDR<0.15%). In comparison, 388 peptides corresponding to 134 proteins were identified in 180 min of mass spectrometer time by triplicate UPLC-ESI-MS/MS analysis each using 250 ng of the unfractionated peptide mixture at 95% confidence (FDR<0.15%). 62% of peptides identified in CZE-ESI-MS/MS and 67% in UPLC-ESI-MS/MS were unique. CZE-ESI-MS/MS favored basic and hydrophilic peptides with low molecular mass. Combining the two data sets increased the number of unique peptides by 53%. Our approach identified more than twice as many proteins as the previous record for CE proteome analysis. CE-ESI-MS/MS is a useful tool for the analysis of proteome samples of intermediate complexity.
PMCID: PMC3277681  PMID: 22182061
17.  Capillary electrophoresis with Orbitrap-Velos mass spectrometry detection 
Talanta  2011;88:324-329.
Capillary electrophoresis can provide fast and efficient separations of peptides. However, the high speed separation and limited loading capacity of capillary electrophoresis requires the use of a fast and sensitive detector. While laser-induced fluorescence provides exquisite sensitivity and millisecond response time, it inherently generates a low information content signal. In contrast, mass spectrometry provides an information rich signal that is attractive for peptide analysis. The recently introduced Velos-Orbitrap mass spectrometer is capable of fast and sensitive tandem MS acquisition and simultaneous high accuracy MS acquisition, which is well suited for coupling with fast and efficient separation methods for peptide analysis. We evaluated this instrument as a detector for peptide separation by capillary electrophoresis. In MS mode, we observed low attomole detection limits for a number of peptides in a tryptic digest of standard proteins with high mass resolution (30,000 at m/z 400). The response time of the Orbitrap at this resolution was ~0.70 seconds, which was adequate to reconstruct the peak shape and area of our electrophoretic peaks. The linear ion-trap successfully recorded tandem MS spectra of tryptic peptides at 20 nM concentration.
PMCID: PMC3266533  PMID: 22265506
18.  High efficiency and quantitatively reproducible protein digestion by trypsin-immobilized magnetic microspheres 
Journal of Chromatography. a  2011;1220:68-74.
Aldehyde- and NHS-activated magnetic microspheres were used to immobilize trypsin (CHO-trypsin and NHS-trypsin), and their performance for protein digestion was evaluated by reversed phase liquid chromatography-electrospray ionization-tandem mass spectrometry using an LTQ Orbitrap Velos instrument. NHS-trypsin provided greater sequence coverage and identified more peptides for the digestion of bovine serum albumin. A one-minute digestion at room temperature using the immobilized trypsin also identified more peptides (96 ± 6 vs. 48 ± 1) and produced higher sequence coverage (90 ± 2% vs. 75 ± 2%) than traditional free trypsin digestion for 12 hours at 37 °C. Analysis of 15 nM (0.001 mg/mL) BSA digested by NHS-trypsin in 1 min. at room temperature consistently yielded one detected peptide; 150 nM BSA generated 22 peptides. Peptide intensity and protein spectral count were used to evaluate the run-to-run digestion reproducibility of NHS-trypsin with a three-protein-mixture. Three high intensity peptides for each protein generated intensity ratios from 0.70 to 1.09 and spectral count ratios from 0.78 to 1.18. Finally, RAW 264.7 cell lysates were digested by NHS-trypsin for 10 min. and 30 min. at room temperature; 604 and 697 protein groups, respectively, were identified by RPLC-ESI-MS/MS, with a peptide false discovery rate of less than 1%. Digestion by solution phase trypsin for 12 hours at 37 °C resulted in identification of 878 protein groups.
PMCID: PMC3253205  PMID: 22176736
protein digestion; trypsin-immobilized magnetic microspheres; reproducibility; RPLC-ESI-MS/MS
19.  Noninvasive Fetal Trisomy (NIFTY) test: an advanced noninvasive prenatal diagnosis methodology for fetal autosomal and sex chromosomal aneuploidies 
BMC Medical Genomics  2012;5:57.
Conventional prenatal screening tests, such as maternal serum tests and ultrasound scan, have limited resolution and accuracy.
We developed an advanced noninvasive prenatal diagnosis method based on massively parallel sequencing. The Noninvasive Fetal Trisomy (NIFTY) test, combines an optimized Student’s t-test with a locally weighted polynomial regression and binary hypotheses. We applied the NIFTY test to 903 pregnancies and compared the diagnostic results with those of full karyotyping.
16 of 16 trisomy 21, 12 of 12 trisomy 18, two of two trisomy 13, three of four 45, X, one of one XYY and two of two XXY abnormalities were correctly identified. But one false positive case of trisomy 18 and one false negative case of 45, X were observed. The test performed with 100% sensitivity and 99.9% specificity for autosomal aneuploidies and 85.7% sensitivity and 99.9% specificity for sex chromosomal aneuploidies. Compared with three previously reported z-score approaches with/without GC-bias removal and with internal control, the NIFTY test was more accurate and robust for the detection of both autosomal and sex chromosomal aneuploidies in fetuses.
Our study demonstrates a powerful and reliable methodology for noninvasive prenatal diagnosis.
PMCID: PMC3544640  PMID: 23198897
Noninvasive Fetal Trisomy (NIFTY) test; Massively parallel sequencing; Autosomal aneuploidies; Sex chromosomal aneuploidies
20.  A replaceable microreactor for on-line protein digestion in a two-dimensional capillary electrophoresis system with tandem mass spectrometry detection 
Journal of chromatography. A  2010;1218(15):2007-2011.
We describe a two-dimensional capillary electrophoresis system that incorporates a replaceable enzymatic microreactor for on-line protein digestion. In this system, trypsin is immobilized on magnetic beads. At the start of each experiment, old beads are flushed to waste and replaced with a fresh plug of beads, which is captured by a pair of magnets at the distal tip of the first capillary. For analysis, proteins are separated in the first capillary. A fraction is then parked in the reactor to create peptides. Digested peptides are periodically transferred to the second capillary for separation; a fresh protein fraction is simultaneously moved to the reactor for digestion. An electrospray interface is used to introduce peptides into a mass spectrometer for analysis. This procedure is repeated for several dozen fractions under computer control. The system was demonstrated by the separation and digestion of insulin chain b oxidized and β-casein as model proteins.
PMCID: PMC3038187  PMID: 21030030
Two dimensional capillary electrophoresis; ESI-MS; Magnetic beads
21.  The impact of educational status on the clinical features of major depressive disorder among Chinese women 
Journal of Affective Disorders  2012;136(3):988-992.
Years of education are inversely related to the prevalence of major depressive disorder (MDD), but the relationship between the clinical features of MDD and educational status is poorly understood. We investigated this in 1970 Chinese women with recurrent MDD identified in a clinical setting.
Clinical and demographic features were obtained from 1970 Han Chinese women with DSM-IV major depression between 30 and 60 years of age across China. Analysis of linear, logistic and multiple logistic regression models were used to determine the association between educational level and clinical features of MDD.
Subjects with more years of education are more likely to have MDD, with an odds ratio of 1.14 for those with more than ten years. Low educational status is not associated with an increase in the number of episodes, nor with increased rates of co-morbidity with anxiety disorders. Education impacts differentially on the symptoms of depression: lower educational attainment is associated with more biological symptoms and increased suicidal ideation and plans to commit suicide.
Findings may not generalize to males or to other patient populations. Since the threshold for treatment seeking differs as a function of education there may an ascertainment bias in the sample.
The relationship between symptoms of MDD and educational status in Chinese women is unexpectedly complex. Our findings are inconsistent with the simple hypothesis from European and US reports that low levels of educational attainment increase the risk and severity of MDD.
PMCID: PMC3314924  PMID: 21824664
Major depressive disorder; Education; Socio-economic status; Symptom
22.  Clinical features and risk factors for post-partum depression in a large cohort of Chinese women with recurrent major depressive disorder 
Journal of Affective Disorders  2012;136(3):983-987.
Post partum depression (PPD) is relatively common in China but its clinical characteristics and risk factors have not been studied. We set out to investigate whether known risk factors for PPD could be found in Chinese women.
A case control design was used to determine the impact of known risk factors for PPD in a cohort of 1970 Chinese women with recurrent DSM-IV major depressive disorder (MDD). In a within-case design we examined the risk factors for PPD in patients with recurrent MDD. We compared the clinical features of MDD in cases with PPD to those without MDD. Odds ratios were calculated using logistic and ordinal regression.
Lower occupational and educational statuses increased the risk of PPD, as did a history of pre-menstrual symptoms, stressful life events and elevated levels of the personality trait of neuroticism. Patients with PPD and MDD were more likely to experience a comorbid anxiety disorder, had a younger age of onset of MDD, have higher levels of neuroticism and dysthymia.
Results obtained in this clinical sample may not be applicable to PPD within the community. Data were obtained retrospectively and we do not know whether the correlations we observe have the same causes as those operating in other populations.
Our results are consistent with the hypothesis that the despite cultural differences between Chinese and Western women, the phenomenology and risk factors for PPD are very similar.
PMCID: PMC3315022  PMID: 21824665
Postpartum depression; Major depressive disorder; Neuroticism; Anxiety disorder
23.  Resemblance of Symptoms for Major Depression Assessed at Interview versus from Hospital Record Review 
PLoS ONE  2012;7(1):e28734.
Diagnostic information for psychiatric research often depends on both clinical interviews and medical records. Although discrepancies between these two sources are well known, there have been few studies into the degree and origins of inconsistencies.
Principal findings
We compared data from structured interviews and medical records on 1,970 Han Chinese women with recurrent DSM-IV major depression (MD). Correlations were high for age at onset of MD (0.93) and number of episodes (0.70), intermediate for family history (+0.62) and duration of longest episode (+0.43) and variable but generally more modest for individual depressive symptoms (mean kappa = 0.32). Four factors were identified for twelve symptoms from medical records and the same four factors emerged from analysis of structured interviews. Factor congruencies were high but the correlation of factors between interviews and records were modest (i.e. +0.2 to +0.4).
Structured interviews and medical records are highly concordant for age of onset, and the number and length of episodes, but agree more modestly for individual symptoms and symptom factors. The modesty of these correlations probably arises from multiple factors including i) inconsistency in the definition of the worst episode, ii) inaccuracies in self-report and iii) difficulties in coding medical records where symptoms were recorded solely for clinical purposes.
PMCID: PMC3256142  PMID: 22247760
24.  The relationship between neuroticism, major depressive disorder and comorbid disorders in Chinese women 
Journal of Affective Disorders  2011;135(1-3):100-105.
The personality trait of neuroticism is a risk factor for major depressive disorder (MDD), but this relationship has not been demonstrated in clinical samples from Asia.
We examined a large-scale clinical study of Chinese Han women with recurrent major depression and community-acquired controls.
Elevated levels of neuroticism increased the risk for lifetime MDD (with an odds ratio of 1.37 per SD), contributed to the comorbidity of MDD with anxiety disorders, and predicted the onset and severity of MDD. Our findings largely replicate those obtained in clinical populations in Europe and US but differ in two ways: we did not find a relationship between melancholia and neuroticism; we found lower mean scores for neuroticism (3.6 in our community control sample).
Our findings do not apply to MDD in community-acquired samples and may be limited to Han Chinese women. It is not possible to determine whether the association between neuroticism and MDD reflects a causal relationship.
Neuroticism acts as a risk factor for MDD in Chinese women, as it does in the West and may particularly predispose to comorbidity with anxiety disorders. Cultural factors may have an important effect on its measurement.
PMCID: PMC3220767  PMID: 21824661
Major depressive disorder; Anxiety disorders; Neuroticism
25.  A comparison of the clinical characteristics of Chinese patients with recurrent major depressive disorder with and without dysthymia☆ 
Journal of Affective Disorders  2011;135(1-3):106-110.
The relationship between major depressive disorder (MDD) and dysthymia, a form of chronic depression, is complex. The two conditions are highly comorbid and it is unclear whether they are two separate disease entities. We investigated the extent to which patients with dysthymia superimposed on major depression can be distinguished from those with recurrent MDD.
We examined the clinical features in 1970 Han Chinese women with MDD (DSM-IV) between 30 and 60 years of age across China. Logistic regression was used to determine the association between clinical features of MDD and dysthymia and between dysthymia and disorders comorbid with major depression.
The 354 cases with dysthymia had more severe MDD than those without, with more episodes of MDD and greater co-morbidity for anxiety disorders. Patients with dysthymia had higher neuroticism scores and were more likely to have a family history of MDD. They were also more likely to have suffered serious life events.
Results were obtained in a clinically ascertained sample of Chinese women and may not generalize to community-acquired samples or to other populations. It is not possible to determine whether the associations represent causal relationships.
The additional diagnosis of dysthymia in Chinese women with recurrent MDD defines a meaningful and potentially important subtype. We conclude that in some circumstances it is possible to distinguish double depression from recurrent MDD.
PMCID: PMC3221043  PMID: 21824660
Major depressive disorder; Dysthymia; Symptom; Comorbidity

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