Biomedical subjects

Jian Chu

Publications and source records attributed to Jian Chu.

10 recordsLinked to original sources

PubMed2006

Characterizing variation in sex steroid hormone pathway genes in women of 4 races/ethnicities: the Study of Women's Health Across the Nation (SWAN).

This report characterizes genotypes and haplotypes in 6 genes (27 single nucleotide polymorphisms [SNPs]) from the Sex Steroid Hormone Genetics Protocol developed though the DNA Repository of the Study of Women's Health Across the Nation (SWAN) Genetics Study. The SWAN Genetics Study is a component of a longitudinal study describing health-related attributes of the menopausal transition in African American, Caucasian, Chinese, Hispanic, and Japanese women. At baseline, SWAN recruited menstruating women, aged 42 to 52 years, who were not using exogenous hormones. During the sixth and seventh years of the study, buccal cells in a mouthwash slurry and whole blood were collected for a DNA repository. Immortalized cell lines were created and genotyped in 1,538 specimens from 1,757 women who participated in the SWAN Genetics Study. DNA from those cells was genotyped for genes in the sex steroid hormone pathway. SNPs were evaluated for genotype and allele frequencies (and differences) according to race/ethnicity and haplotyped in anticipation of studying their associations with health-related measures. We demonstrated that allele frequencies differed significantly by race/ethnicity. There was substantial linkage disequilibrium among many of the SNPs and only a few SNPs showed significant Hardy-Weinberg disequilibrium within race/ethnicity. Finally, there are a number of haplotype patterns that vary according to race/ethnicity, including a "yin-yang" pattern for 17HSD among Caucasian, Chinese, and Japanese women, but not among African American women. Repository specimens developed in anticipation of genomic or metabolomics studies can extend the contribution of the parent study by developing hybrid strategies that support both SNP association studies as well as coarse and fine mapping to evaluate possible genomic locations of causal variants.

Adult↗

PubMed2006

Aromatase gene (CYP 19) polymorphisms and endogenous androgen concentrations in a multiracial/multiethnic, multisite study of women at midlife.

A limited number of studies have focused on androgens in women's health, particularly at the genetic level. We evaluated testosterone and estradiol (E2) levels among women in relation to 5 single nucleotide polymorphisms (SNPs) of the aromatase (CYP 19) gene, the cytochrome P450 enzyme that converts androgens to estrogens. We related 5 aromatase SNPs (CYP 19 rs2414096, CYP 19 rs936306, CYP 19 rs2446405, CYP 19 rs1008805, and CYP 19 rs749292) to serum androgen and E2 markers in 1,538 participants of the Study of Women's Health Across the Nation (SWAN), including 412 African American, 807 Caucasian, 151 Chinese, and 168 Japanese women. Aromatase allele and genotype frequencies differed significantly among racial/ethnic groups. Compared with other genotypes of the CYP 19 rs936306 polymorphism, the TT genotype was associated with a significant difference in the testosterone to E2 (T:E2) ratio--lower testosterone and higher E2 levels--especially in African American women. Japanese women with the AA genotype of the CYP 19 rs749292 polymorphism had lower testosterone and E2 levels but higher levels of sex hormone-binding globulin (SHBG) compared with Japanese women with the AG and GG genotypes. Among Caucasian women, there was markedly lower SHBG levels among those with the AA genotype of the CYP 19 rs2414096 polymorphism compared with other genotypes, after adjusting for age and body mass index. Three of 5 aromatase gene SNPs were associated with variation in serum androgen concentrations among women, both within and between racial/ethnic groups. Aromatase genetic markers may be important in understanding the emerging associations reported between endogenous androgens and women's health status.

Adult↗

PubMed2006

CYP1A1 and CYP1B1 polymorphisms and their association with estradiol and estrogen metabolites in women who are premenopausal and perimenopausal.

The purpose of this study was to relate measured concentrations of estradiol (E2) and the urinary estrogen metabolites 2-hydroxyestrone (2-OHE1) and 16alpha-hydroxyestrone (16alpha-OHE1) to single nucleotide polymorphisms (SNPs) from CYP1A1 and CYP1B1, the primary genes involved in estrogen catabolism. We investigated the association of 4 CYP1A1 SNPs (CYP1A1 rs4646903, CYP1A1 rs1531163, CYP1A1 rs2606345, and CYP1A1 rs1048943) and 2 CYP1B1 SNPs (CYP1B1 rs162555 and CYP1B1 rs1056836) to circulating serum E2 concentrations and the urinary estrogen metabolites 2-OHE1 and 16alpha-OHE1. The associations were evaluated in 1,340 participants of 4 racial/ethnic groups from the Study of Women's Health Across the Nation (SWAN) who were premenopausal and perimenopausal. There was substantial variation in the allele frequencies of the SNPs for African American and Caucasian women. There was, however, remarkable comparability between Chinese and Japanese women; their CYP1A1 and CYP1B1 allele frequencies differed by only < or =11%. There was significant variation in E2 concentrations by genotype within racial/ethnic group for CYP1A1 rs2606345. In particular, Japanese women with the CC genotype had lower E2 concentrations than did Japanese women with the AC genotype. Chinese women with the CC genotype had higher 2-OHE1 concentrations than did Chinese women with the AC genotype. Further, African American women with the CC genotype had higher 16alpha-OHE1 concentrations than did those with other genotypes. CYP1A1 rs2606345 may play an important role in estrogen metabolism in women who are premenopausal and perimenopausal.

Aryl Hydrocarbon Hydroxylases↗

PubMed2006

Sex steroid hormone polymorphisms, high-density lipoprotein cholesterol, and apolipoprotein A-1 from the Study of Women's Health Across the Nation (SWAN).

We evaluated potential associations between single nucleotide polymorphism (SNP) variants in estrogen receptor (ERalpha and ERbeta) genes, high-density lipoprotein (HDL) cholesterol, and apolipoprotein A-1 (apoA-1) concentrations in women of 4 races/ethnicities. Participants included 1,520 African American, Caucasian, Chinese, and Japanese women from the Study of Women's Health Across the Nation (SWAN) who were premenopausal or perimenopausal and who were also enrolled in the SWAN Genetics Study, which collected blood for lipid analyses and carried out lymphocyte transformation from which DNA was extracted and genotyped. We evaluated SNPs from ERalpha and ERbeta genes (ESR1 and ESR2, respectively), including ESR1 rs9340799, ESR1 rs2234693, ESR1 rs728524, ESR1 rs3798577, ESR2 rs1255998, ESR2 rs1256065, and ESR2 rs1256030. The mean HDL cholesterol and apoA-1 values for these women were 1.47 mmol/L and 1.51 g/L, respectively. Japanese women with the ESR1 rs3798577 TC genotype had significantly lower apoA-1 (P=0.02) and HDL cholesterol levels (P=0.03) than did those with the TT genotype. African American women with the ESR1 rs728524 GG genotype had higher HDL cholesterol levels than did women with the AA or AG genotypes (P=0.05). ESR2 rs1256030 and ESR2 rs1256065 genotypes were associated with HDL cholesterol concentrations in Chinese women (P=0.05). Although associations were identified between the ESR1 and ESR2 SNP variants and lipids in these women, these associations were not consistently observed across the 4 racial/ethnic groups, nor were the associations consistently inclusive of both HDL cholesterol and apoA-1. These genetic variants provide limited evidence of associations with lipids that may help explain the cardioprotective effect of premenopausal status in women.

Adult↗

PubMed2006

The association of bone mineral density with estrogen receptor gene polymorphisms.

The purpose of this investigation was to evaluate single nucleotide polymorphism (SNP) variants of the estrogen receptor genes ESR1 and ESR2 and bone mineral density (BMD) of the lumbar spine (LS-BMD) or total hip (hip BMD) in women of 4 races/ethnicities who were premenopausal or in early perimenopause. The sample consisted of 1,301 participants from the Study of Women's Health Across the Nation (SWAN) with measures of BMD and genotyping; of these, 295 were African American, 693 were Caucasian, 151 were Chinese, and 162 were Japanese. We evaluated the potential association of LS-BMD or hip BMD with 4 SNPs from the ESR1 gene (ESR1 rs9340799, ESR1 rs2234693, ESR1 rs728524, and ESR1 rs3798577), and 3 SNPs from the ESR2 gene (ESR2 rs1255998, ESR2 rs1256030, and ESR2 rs1256065). Unadjusted mean LS-BMD values ranged from 1.141+/-0.14 g/cm(2) in African American women to 1.031+/-0.11 g/cm2 in Japanese women; unadjusted mean hip BMD values ranged from 1.053+/-0.14 g/cm2 in African American women to 0.862+/-0.10 g/cm2 in Chinese women. African American and Japanese women with the ESR1 rs2234693 (PvuII) CC genotype had higher LS-BMDs than did their peers with the TT genotype (P=0.009 and P=0.04, respectively). Japanese women with the ESR1 rs3798577 CC or TC genotypes had lower LS-BMD than did Japanese women with the TT genotype (P=0.02 and P=0.01, respectively). Caucasian women with the TC genotype for ESR2 rs1256030 had lower LS-BMDs than did those with the CC genotype (P=0.02). Chinese women who were heterozygous for ESR2 rs1256030 or ESR2 rs1256065 had significantly higher LS-BMDs and hip BMDs than did the referent groups for each of these SNPs (CC and AA, respectively). Associations between BMD and ESR1 and ESR2 genotypes varied by race/ethnicity and by bone site. Our results differ from those previously reported for 2 ESR1 genotypes (ESR1 rs2234693 [PvuII] and ESR1 rs9340799 [XbaI]). Moreover, 2 ESR1 and 3 ESR2 SNPs we studied have not previously been examined with respect to BMD. Among these, ESR2 rs1256030 and ESR2 rs1256065 appear to have an effect at both the lumbar spine and hip in Chinese women and may warrant further study.

Adult↗

PubMed2004

A SISO mixed H2/l1 optimal control problem and its solution.

Study of the SISO mixed H(2)/l(1) problem for discrete time systems showed that there exists a unique optimal solution which can be approximated within any prescribed missing error bound in l(2) norm with solvable suboptimal solutions and solvable superoptimal solutions.

Algorithms↗

PubMed2004

Robust H(infinity) output feedback control for a class of uncertain Lur'e systems with time-delays.

In this work, the analysis of robust stability and design of robust H infinity output feedback controllers for a class of Lur'e systems with both time-delays and parameter uncertainties were studied. A robust H infinity output feedback controller based on Linear Matrix Inequalities (LMIs) was developed to guarantee the robust stability and H infinity performance of the resultant closed-loop system. The presented design approach is based on the application of descriptor model transformation and Park's inequality for the bounding of cross terms and is expected to be less conservative compared to reported design methods. Finally, illustrative examples are advanced to demonstrate the superiority of the obtained method.

Algorithms↗

PubMedDate not supplied

Adaptive terminal sliding mode control for high-order nonlinear dynamic systems.

An adaptive terminal sliding mode control (SMC) technique is proposed to deal with the tracking problem for a class of high-order nonlinear dynamic systems. It is shown that a function augmented sliding hyperplane can be used to develop a new terminal sliding mode for high-order nonlinear systems. A terminal SMC controller based on Lyapunov theory is designed to force the state variables of the closed-loop system to reach and remain on the terminal sliding mode, so that the output tracking error then converges to zero in finite time which can be set arbitrarily. An adaptive mechanism is introduced to estimate the unknown parameters of the upper bounds of system uncertainties. The estimates are then used as controller parameters so that the effects of uncertain dynamics can be eliminated. It is also shown that the stability of the closed-loop system can be guaranteed with the proposed control strategy. The simulation of a numerical example is provided to show the effectiveness of the new method.

Journal Article↗

PubMedDate not supplied

Predictive functional control (PFC) and its application in chlorinated polyethylene process.

The main principle and the characteristic of Predictive Functional Control (PFC) strategy are presented in this paper and the corresponding control system aid design software APC-PFC is also introduced. For a chlorinated polyethylene (CPE) process, a design scheme of cascade predictive functional control system is described and the control performance is improved obviously.

Algorithms↗

PubMedDate not supplied

Optimization of block-floating-point realizations for digital controllers with finite-word-length considerations.

The closed-loop stability issue of finite-precision realizations was investigated for digital controllers implemented in block-floating-point format. The controller coefficient perturbation was analyzed resulting from using finite word length (FWL) block-floating-point representation scheme. A block-floating-point FWL closed-loop stability measure was derived which considers both the dynamic range and precision. To facilitate the design of optimal finite-precision controller realizations, a computationally tractable block-floating-point FWL closed-loop stability measure was then introduced and the method of computing the value of this measure for a given controller realization was developed. The optimal controller realization is defined as the solution that maximizes the corresponding measure, and a numerical optimization approach was adopted to solve the resulting optimal realization problem. A numerical example was used to illustrate the design procedure and to compare the optimal controller realization with the initial realization.

Analog-Digital Conversion↗