Biomedical subjects

Qi Tian

Publications and source records attributed to Qi Tian.

16 recordsLinked to original sources

PubMed2026

CHST5 gene mutations contribute to high myopia by disrupting collagen fiber organization.

High myopia (HM) is a leading cause of irreversible vision loss in working-age adults. Its pathogenesis is characterized by alterations in the microstructure and composition of collagen fibers, and genetic factors make a substantial contribution. In this study, we identify carbohydrate sulfotransferase 5 (CHST5) as a candidate gene for HM in humans and mice, with its mutations disrupting collagen fiber organization. The c.444C>A (p.S148R) variant in CHST5, a gene critical for sulfating corneal keratan sulfate (KS), completely co-segregates with HM in a Chinese family. Screening of CHST5 variants in 320 HM patients identifies two additional ones. We further find that Chst5 is expressed primarily in the cornea and sclera of mouse ocular tissues, and that the mutant protein CHST5S148R loses its Golgi localization. Homozygous mutant Chst5S126R mice exhibit HM phenotypes, including myopic refractive error (RE), significantly thinner sclera and cornea, notable microstructural changes in scleral and corneal collagen fibers, and shorter corneal KS chains. Our findings suggest that CHST5 NM_024533.5 c.444C>A (p.S148R) causes loss of proper protein localization, likely impairing its sulfotransferase function. This defect disrupts the organization of corneal and scleral collagen fibers and ultimately contributes to the development and progression of HM.

CHST5↗

PubMed2006

Inhibition of PPAR-alpha activity in mice with cardiac-restricted expression of tumor necrosis factor: potential role of TGF-beta/Smad3.

A shift in energy substrate utilization from fatty acids to glucose has been reported in failing hearts, resulting in improved oxygen efficiency yet perhaps also contributing to a state of energy deficiency. Peroxisome proliferator-activated receptor (PPAR)-alpha, the principal transcriptional regulator of cardiac fatty acid beta-oxidation (FAO) genes, is downregulated in heart failure, and this may contribute to reduced fatty acid utilization. Cardiomyopathic states are also accompanied by elevated levels of circulating cytokines, such as tumor necrosis factor (TNF), as well as increased local production of cytokines and profibrotic factors, such as transforming growth factor (TGF)-beta. However, whether these molecular pathways directly modulate cardiac energy metabolism and PPAR-alpha activity is not known. Therefore, FAO capacity and FAO gene expression were determined in mice with cardiac-restricted overexpression of TNF (MHCsTNF(3)). MHCsTNF(3) hearts had significantly lower FAO capacity and decreased expression of PPAR-alpha and FAO target genes compared with control hearts. Surprisingly, TNF had little effect on PPAR-alpha activity and FAO rates in cultured ventricular myocytes, suggesting that TNF acts indirectly on myocyte FAO in vivo. We found that TGF-beta expression was upregulated in MHCsTNF(3) hearts and that treatment of cultured myocytes with TGF-beta significantly suppressed FAO rates and directly impaired PPAR-alpha activity, a result reproduced by Smad3 overexpression. This work demonstrates that TGF-beta signaling pathways directly suppress PPAR-alpha activity and reduce FAO in cardiac myocytes, perhaps in response to locally elevated TNF. Although speculative, TGF-beta-driven repair mechanisms may also include the additional benefit of limiting FAO in injured myocardium.

Animals↗

PubMed2006

B cells expressing a natural polyreactive autoantibody have a distinct phenotype and are overrepresented in immunoglobulin heavy chain transgenic mice.

Despite stringent regulation of disease-associated autoantibodies, a substantial proportion of circulating Abs in sera of healthy individuals exhibit self-reactivity. These Abs are referred to as naturally occurring or natural autoantibodies (NAAs). To understand the origin and function of NAAs, we have generated a new site-directed transgenic mouse model in which a prerearranged VDJ gene coding for the H chain of a typical polyreactive NAA, ppc1-5, is inserted into the IgH locus. This H chain, when combined with its original L chain, the lambda1 L chain, yields a NAA that characteristically binds a variety of self and non-self Ags including ssDNA, actin, ubiquitin, and nitrophenyl phosphocholine. Despite their autoreactivity, B cells expressing ppc1-5H/lambda1 NAA are not negatively selected, but rather are overrepresented in the transgenic mice. The shift toward lambda1 expression mainly occurs during the transition of immature to mature B cells in the spleen, suggesting a BCR selection process. The ppc1-5H/lambda1 B cells exhibit a phenotype that is different from those of the known mature B cell populations, and they are located predominantly in the lymphoid follicles of the spleen and the lymph nodes. These B cells are functionally active, producing high levels of Abs in vivo and responding well to BCR stimulation in vitro. The findings indicate that the ppc1-5/lambda1 natural autoantibodies originate from a distinct B cell subset that may be positively selected by virtue of its poly/autoreactivity.

Animals↗

PubMed2006

Effect of drug concentration on adsorption of levofloxacin by polyacrylonitrile haemofilters.

We studied an in vitro model of continuous venovenous haemofiltration to determine levofloxacin adsorption by polyacrylonitrile (PAN) filters. Four doses of levofloxacin (5, 25, 50 and 100 mg) were used, resulting in circulating concentrations of levofloxacin at 120 min of 3.56+/-0.14, 15.84+/-2.08, 31.42+/-1.95 and 58.23+/-1.10 mg/L, respectively. Adsorption at 2 h was 0.65+/-0.17, 5.99+/-2.49, 12.30+/-2.34 and 30.13+/-1.32 mg, respectively (P<0.001). From 2h to 4h, increasing the blood pump rate and the ultrafiltration rate had no effect on adsorption. When the concentration was decreased from 3.55+/-0.13 mg/L at 4h to 2.16+/-0.11 mg/L at 5 h by addition of lactated Ringer's solution, adsorption decreased from 0.67+/-0.16 mg to 0.21+/-0.25 mg (P<0.05). These data show that adsorption of levofloxacin by PAN haemofilters is concentration dependent and reversible in vitro and suggest that adsorption by haemofilters is unlikely to affect levofloxacin pharmacokinetics significantly in vivo.

Acrylic Resins↗

PubMed2006

Selection of anti-double-stranded DNA B cells in autoimmune MRL-lpr/lpr mice.

Abs to DNA and nucleoproteins are expressed in systemic autoimmune diseases, whereas B cells producing such Abs are edited, deleted, or inactivated in healthy individuals. Why autoimmune individuals fail to regulate is not well understood. In this study, we investigate the sources of anti-dsDNA B cells in autoimmune transgenic MRL-lpr/lpr mice. These mice are particularly susceptible to lupus because they carry a site-directed transgene, H76R that codes for an anti-DNA H chain. Over 90% of the B cells are eliminated in the bone marrow of these mice, and the few surviving B cells are associated with one of two Vkappa editors, Vkappa38c and Vkappa21D. Thus, it appears that negative selection by deletion and editing are intact in MRL-lpr/lpr mice. However, a population of splenic B cells in the H76R MRL-lpr/lpr mice produces IgG anti-nuclear Abs, and these mice have severe autoimmune organ damage. These IgG Abs are not associated with editors but instead use a unique Vkappa gene, Vkappa23. The H76R/Vkappa23 combination has a relatively high affinity for dsDNA and an anti-nuclear Ab pattern characteristic of lupus. Therefore, this Vkappa gene may confer a selective advantage to anti-DNA Abs in diseased mice.

Amino Acid Sequence↗

PubMed2006

Peroxisome proliferator-activated receptor alpha agonist, clofibrate, has profound influence on myocardial fatty acid composition.

The hypolipidemic fibrates have been identified as agonists of the peroxisome proliferator-activated receptor alpha (PPARalpha), which plays a critical role in the regulation of cardiac fatty acid metabolism. Despite the widespread clinical use of fibrates, their role in myocardial oxidative stress and fatty acid composition is less known. In this study, male Sprague-Dawley rats were treated with either vehicle (olive oil, 1 ml/kg) or clofibrate (300 mg/kgday i.p.) for 1-14 days. Lipid peroxidation in heart homogenate was determined by thiobarbituric acid reactive substance (TBARS) assay. Results show that hearts from clofibrate-treated rats are more susceptible to FeSO(4)-induced TBARS production. The antioxidants including catalase and glutathione-related enzymes were marginally affected. We demonstrated that myocardial fatty acid composition was dramatically altered by clofibrate treatment. In hearts from clofibrate-treated rats, the principal n-6 polyunsaturated fatty acids (PUFAs), linoleic acid (C18:2 n-6) and arachidonic acid (C20:4 n-6), was significantly reduced, while the content of the principal n-3 PUFA, docosahexaenoic acid (C22:6 n-3), was markedly increased. The overall effect was to reduce n-6/n-3 ratio and increase the unsaturation extent of myocardial fatty acids. Functional study showed that hearts from clofibrate-treated rats had an improved recovery of post-ischemic contractile function and reduced ischemia/reperfusion (I/R)-induced infarct size. The data shows that clofibrate has a profound impact on cardiac fatty acid composition, which may contribute to its cardioprotective effect.

Animals↗

PubMed2006

Deranged energy substrate metabolism in the failing heart.

Control of energy metabolism in the heart is closely linked to cardiac performance. Dysregulation of energy-generating pathways occurs in many forms of heart disease, including heart failure. Uncertainty exists as to whether these alterations in the way adenosine triphosphate (ATP) is produced serve to protect the heart from excessive oxygen demands or have untoward long-term consequences. Regulation of fatty acid beta-oxidation (FAO), the principal source of ATP in the healthy heart, occurs at multiple levels, including a strong gene transcriptional component. In the heart, members of the peroxisome proliferator-activated receptor (PPAR) family of transcription factors are the primary regulators of FAO gene expression. PPARs are ligand activated by endogenous lipids and synthetic small molecules, thus providing attractive targets for pharmaceutical intervention. This article discusses controversies surrounding our understanding of cardiac energy metabolism in heart failure and the role that PPAR family members may play, either as contributors to or as potential adjunctive therapy for cardiac disease.

Acyl Coenzyme A↗

PubMed2006

[A study on K469E polymorphism of ICAM1 gene and ICAM1 plasma level in patients with coronary heart disease].

OBJECTIVE: To study the linkage between K469E polymorphism of intercellular adhesion molecule 1(ICAM1) gene with ICAM1 plasma level and coronary heart disease (CHD) in Han population of China. METHODS: One hundred and sixty-four controls without CHD and 160 patients with CHD were enrolled in our study. By nested PCR with allele-specific oligonucleotide primers, all patients and controls were genotyped for the ICAM1 polymorphism. And the ICAM1 plasma level was measured by ELISA. RESULTS: In the patients with CHD, both K allele frequency and the plasma level of ICAM1 were higher than those in control (P<0.05). The individual with K allele had higher plasma level of ICAM1 than that without K allele (344.34+/-128.59 microg/L vs 303.54+/-108.74 microg/L, P=0.008). K allele enhanced the risk of CHD (P<0.01, OR=2.158, 95%CI: 1.250-3.727). There was the K allele cooperation with smoking in influencing the risk of CHD. CONCLUSION: There is the polymorphism of ICAM1 K469E gene in Han population of China, and the K allele may be a genetic factor influencing the risk of CHD.

China↗

PubMed2005

Expression of man, a formin homology domain-containing gene in the mouse limb.

Formin defines a family of structurally related proteins that have two formin homology domains (FH1 and FH2). Various mutations in the formin locus result in limb deformity, suggesting that these genes play indispensable roles in the limb development. Here we report the isolation of a novel cDNA, man, from the mouse limb, which contains two conserved FH1 and FH2 domains. Its expression is described and possible functional significance is discussed.

Journal Article↗

PubMed2005

Gabor wavelet associative memory for face recognition.

This letter describes a high-performance face recognition system by combining two recently proposed neural network models, namely Gabor wavelet network (GWN) and kernel associative memory (KAM), into a unified structure called Gabor wavelet associative memory (GWAM). GWAM has superior representation capability inherited from GWN and consequently demonstrates a much better recognition performance than KAM. Extensive experiments have been conducted to evaluate a GWAM-based recognition scheme using three popular face databases, i.e., FERET database, Olivetti-Oracle Research Lab (ORL) database and AR face database. The experimental results consistently show our scheme's superiority and demonstrate its very high-performance comparing favorably to some recent face recognition methods, achieving 99.3% and 100% accuracy, respectively, on the former two databases, exhibiting very robust performance on the last database against varying illumination conditions.

Algorithms↗

PubMed2005

Regulation of Wnt gene expression.

Members of the Wnt gene family play important roles in the regulation of a number of basic developmental processes. Because Wnt is such a potent morphogen, its expression must be controlled tightly and precisely. While many review papers focused on Wnt signaling downstream of the receptor, this review addresses regulations of Wnt itself on several levels, including the transcriptional level, RNA splicing, the post-transcriptional level, the translational level, and the post-translational level. It is these multiple, precise and tight regulations that guarantee that Wnts function correctly both temporally and spatially.

Animals↗

PubMed2005

[Plasma activated coagulation factor VII and Msp I polymorphism in elderly patients with coronary heart disease].

OBJECTIVE: To investigate the association of activated coagulation factor VII(F7a) and its gene Msp I polymorphism with coronary heart disease in elderly patients. METHODS: This was a case-control study, and the method of candidate gene was adopted. F7 genotypes were identified with polymerase chain reaction amplified genomic deoxyribonulieic acid (DNA) and Msp I restriction fragment length polymorphism analysis, and the level of plasma F7a was detected with recombinant tissue factor method for 108 elderly patients with coronary heart disease and 120 sex- and age-matched healthy control subjects. RESULTS: (1) Plasma F7a levels was significantly higher in elderly patients with coronary heart disease than in healthy control subjects (2.88 +/- 0.62 vs 2.58 +/- 0.60 microg/L, P < 0.05), and was significantly higher in old myocardial infarction than in stable angina pectoris (3.12 +/- 0.62 vs 2.76 +/- 0.60, P < 0.05). F7a was shown to be a risk factor for coronary heart disease in elderly patients by Logistic regression analysis (OR=1.21 P < 0.05). (2) The allelic frequencies were in accordance with Hardy-Weinberg equilibrium. The results suggested that the distribution of genotype and allelic frequencies in the groups displayed no significant difference, and there was no difference between the subgroups of coronary heart disease in elderly patients, either (P > 0.05). (3) F7a level was significantly higher in RR genotype than in Q allele carriers (2.72 +/- 0.60 vs 1.98 +/- 0.59 microg/L, P < 0.05) and was associated with F7 gene polymorphism. CONCLUSION: Plasma F7a level may be an independent risk factor of coronary heart disease in elderly patients, and it may be influenced by the Msp I polymorphism of F7 gene.

Aged↗

PubMed2004

GABAergic system gene expression predicts clinical outcome in patients with neuroblastoma.

PURPOSE: Neuroblastoma (NB) is a common childhood malignancy characterized by heterogeneous clinical behavior. The purpose of this study was to identify potential NB biomarkers that may improve outcome prediction. PATIENTS AND METHODS: The suppression subtractive hybridization (SSH) technique was used to identify the genes differentially expressed between NB and control tissue. RNA isolated from 235 primary NB tumor samples obtained from the Children's Cancer Group was evaluated for expression of the candidate markers using quantitative reverse transcriptase polymerase chain reaction (Taqman assays). The association between the mRNA expression levels in the identified candidate genes and clinical outcome was evaluated. RESULTS: SSH analysis identified differential expression of members of the GABAergic gene family in NB. Lower levels of gamma-aminobutyric acid (GABA) receptor-associated protein (GABARAP) gene expression predict decreased survival among all patients. GABA(A) delta receptor subunit gene expression was predictive of a poor outcome among Evans stage IV-S patients. An index of five coexpressed GABA(A) receptor subunits was identified (GABA(A) profile [GAP score]). Patients with a higher GAP score (> -1) had a survival advantage. Multivariate analysis showed that GABARAP and GABA(A) alpha2 receptor subunit gene expression levels and GAP score remained predictors of clinical outcome after accounting for current prognostic indicators. CONCLUSION: Dysregulation of the GABAergic system may constitute a fundamental event in the development of NB, and assessment of GABAergic system gene expression could provide improved patient stratification and potential new therapies.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Statistical modeling of complex backgrounds for foreground object detection.

This paper addresses the problem of background modeling for foreground object detection in complex environments. A Bayesian framework that incorporates spectral, spatial, and temporal features to characterize the background appearance is proposed. Under this framework, the background is represented by the most significant and frequent features, i.e., the principal features, at each pixel. A Bayes decision rule is derived for background and foreground classification based on the statistics of principal features. Principal feature representation for both the static and dynamic background pixels is investigated. A novel learning method is proposed to adapt to both gradual and sudden "once-off" background changes. The convergence of the learning process is analyzed and a formula to select a proper learning rate is derived. Under the proposed framework, a novel algorithm for detecting foreground objects from complex environments is then established. It consists of change detection, change classification, foreground segmentation, and background maintenance. Experiments were conducted on image sequences containing targets of interest in a variety of environments, e.g., offices, public buildings, subway stations, campuses, parking lots, airports, and sidewalks. Good results of foreground detection were obtained. Quantitative evaluation and comparison with the existing method show that the proposed method provides much improved results.

Algorithms↗

PubMed2004

[Relationship between fibrinogen B beta gene FGB -455G/A polymorphism and atherosclerotic cerebral infarction].

OBJECTIVE: To explore the distribution of fibrinogen (FGB) B beta polymorphism in Chinese Han population and the association of the polymorphisms with the occurrence of atherosclerotic cerebral infarction (ACI). METHODS: The B beta gene FGB -455G/A polymorphism was identified by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) in 132 patients with ACI and 148 healthy controls matching on age and sex. Turbidimetric assays were performed to measure the plasma fibrinogen levels of all cases. RESULTS: The plasma fibrinogen level in ACI group (3.42+/-0.52 g/L), was significantly higher than that in the controls (2.96+/-0.42g/L), P<0.001. The A allele was associated with the elevated plasma fibrinogen levels in both patients and controls. Among the A allele carriers, smokers had significantly higher plasma fibrinogen levels than did the non-smokers (P<0.05). The distribution of B beta gene FGB -455G/A polymorphism was in accordance with the Hardy-Weinberg equilibrium (P>0.05). The A allelic frequency in ACI group (0.258) was significantly higher than that in the control group (0.152) (P<0.05). Logistic regression analysis showed that the cases carrying A allele (GA+AA genotype) had 1.653 times the risk of ACI. CONCLUSION: The study demonstrates that A allele of the B beta gene FGB -455G/A polymorphism may be a susceptible predictor of the occurrence of ACI, particularly in smokers.

Aged↗

PubMed2002

Loss of desmoglein 2 suggests essential functions for early embryonic development and proliferation of embryonal stem cells.

Desmoglein 2 (Dsg2) is a Ca(2+)-dependent adhesion molecule of desmosomes and is synthesized in all desmosome-bearing tissues from their earliest appearance onward. To examine the function of Dsg2, its gene was inactivated by homologous recombination in embryonal stem (ES) cells for the generation of knockout mice. DSG2 -/- mice and a considerable number of DSG2 +/- mice died at or shortly after implantation. On the other hand, DSG2 -/- blastocysts developed an apparently normal trophectoderm layer, the first tissue known to produce desmosomes, and hatched properly. Immunofluorescence analyses of these blastocysts showed, however, that the distribution of the desmosomal plaque protein desmoplakin was disturbed, whereas the adherens junction proteins E-cadherin and beta-catenin appeared to be unaffected. Unexpectedly, we found that Dsg2 seems to be essential for the inner cell mass and the ES cell population derived there from. We present evidence that Dsg2, which is located in desmoplakin-negative wild-type ES cells in non-desmosomal junctions, is needed for normal ES cell proliferation. Our observations thus reveal that important Dsg2 functions are desmosome-independent during early development and are needed for ES cell and early embryo survival.

Animals↗