Search PubMed⌕ Search

Biomedical subjects

X Xu

Publications and source records attributed to X Xu.

At least 91 records · Page 5Linked to original sources
PubMed2002

Reliability of serial urine HCG as a biomarker to detect early pregnancy loss.

BACKGROUND: To examine the reliability of HCG as a biomarker for early pregnancy loss, five experienced researchers independently assessed data from 153 menstrual cycles, determining whether each cycle represented 'no conception,' a 'continuing conception' or a 'conception lost.' METHODS: Urine samples were analysed by immunoradiometric assay using a combination of capture antibodies for the intact heterodimer (B109) and for an epitope common to the beta subunit and the beta core fragment (B204). For each cycle, HCG data were presented as graphs of daily assay results. Summary statistics for HCG assays from 46 women who had undergone bilateral tubal ligation represented baseline values. RESULTS: Pairwise agreement among the assessors for any of the three options ranged from 78-89%. At least three experts agreed for 147 cycles (96%), accounting for 28 conception losses and 19 continuing conceptions. The multi-rater kappa was 0.62 for the conception lost category and 0.68 for continuing conceptions, indicating substantial agreement. CONCLUSION: The main sources of disagreement involved deciding whether there was sufficient information for assessment, interpreting cycle parameters such as cycle length or bleeding event, and interpreting a distinct HCG rise pattern that does not exceed the baseline value obtained from the sterilized women.

Abortion, Spontaneous↗
PubMed2002

Epidemiology survey of rhegmatogenous retinal detachment in Beixinjing District, Shanghai, China.

PURPOSE: To investigate the recent incidence and related risk factors of rhegmatogenous retinal detachment (RRD) in Chinese people. METHODS: This study was an incidence survey based on data for 108,132 persons in Beixinjing District, Shanghai, China. Patients with RRD were inpatients, outpatients, and patients from the local health network. Patients with RRD were compared with control subjects who were matched by sex, age, and block of residence. Previous population data were used to estimate the whole and specific incidence of RRD. Some factors relevant to the incidence of RRD were found by comparing the patients with RRD with the control subjects. RESULTS: Between January 1996 and December 1999, 61 cases of RRD occurred. The annual incidence of RRD was 11.3 cases per 100,000 population in 1996, 14.1 cases per 100,000 population in 1997, 14.1 cases per 100,000 population in 1998, and 17.9 cases per 100,000 population in 1999. The average annual incidence was 14.4 cases per 100,000 population (95% confidence interval, 10.0-18.6). There were 29 males and 32 females with RRD. The incidence of RRD among persons older than 40 years was high, especially among those between 40 and 59 years of age. The proportion of individuals with high myopia (more than -6 diopters) was significantly higher in the patient group than in the control group (P < 0.001). CONCLUSION: The annual incidence of RRD among a local Chinese population increased over 4 years. This disease is strongly associated with high myopia and age.

Adolescent↗
PubMed2002

Cardiogenesis in the Drosophila model: control mechanisms during early induction and diversification of cardiac progenitors.

The dorsal vessel of Drosophila displays developmental, functional, and morphological similarities to the primitive linear heart tube of early vertebrate embryos. Because these similarities extend to the genetic and molecular level, Drosophila has become a fruitful model to study control mechanisms of early heart development. Herein we summarize recently obtained insights into control mechanisms during early induction and diversification of cardiac progenitors in Drosophila. We also show that induction of tinman, a key cardiogenic gene, in the dorsal mesoderm by Dpp (Drosophila BMP) involves protein/protein interactions between Tinman and the Smad proteins Mad and Medea, in addition to their DNA-binding activities to specific tinman enhancer sequences. Furthermore, we present evidence that binding of a high-mobility-group protein, HMG-D, to the Dpp-responsive enhancer of tinman as well as to the Tinman protein may be involved in the formation of a fully active enhancer complex.

Animals↗
PubMed2002

Type-2 diabetes family history delays the onset of type-1 diabetes.

Type-1 diabetes (T1D) is an autoimmune disease leading to insulin deficiency. Its occurrence is influenced by genetic and environmental factors. The human leukocyte antigen (HLA) region on chromosome 6 accounts for 45% of the genetic susceptibility for the disease, mainly the HLA-DQB1*0201 and HLA-DQB1*0302 alleles. Among the environmental factors involved, early exposure to cow's milk seems to be a trigger. In this study, we investigated the occurrence of T1D in 253 Lebanese Caucasian patients, in relation to HLA-DQB1*0201, HLA-DQB1*0302, HLA-DQB1*0602, gender, and early exposure to cow's milk, as well as to family history of T1D and type-2 diabetes (T2D). Our genetic analysis results show that in the patients studied, 77% and 40% were positive for BQ1*0201 and BQ1*0302, respectively. As for BQ1*0602, only 0.8% of patients were positive for this T1D protective allele, compared with 24% among the controls. Furthermore, our results did not show any gender preference of the disease or any effects of early intake of cow's milk on the age at onset of T1D. When family history of T2D or T1D was studied, our results show a novel finding whereby an immediate family history of T2D, but not T1D, delays the age at onset of T1D.

Adult↗
PubMed2002

SNPkit: an efficient approach to systematic evaluation of candidate single nucleotide polymorphisms in public databases.

There is widespread interest in devising genotyping methods for SNPs that are robust, inexpensive, and simple to perform. Although several high-throughput SNP genotyping technologies have been developed, including the oligonucleotide ligation assay, real-time PCR, and mass spectrometry, the issues of simplicity and cost-effectiveness have not been adequately addressed. Here we describe the application of a novel computer software package, SNPkit, which designs SNP genotyping assays based on a classical approach for discriminating alleles, restriction enzyme digestion. SNPkit can be used in genotyping assays for almost any SNPs including those that do not alter "natural" restriction sites. Using this method, 164 SNPs have been evaluated in DNA samples from 48 immortalized cell lines of randomly selected Chinese subjects. Sixty-two (37.8%) of the SNPs appeared to be common (frequencies of the minor alleles are > or = 5%) and were subsequently applied to a larger population-based sample. Overall, by using SNPkit, we have been able to validate and genotype accurately a large fraction of publicly available SNPs without sophisticated instrumentation.

Algorithms↗
PubMed2002

Hyaluronan metabolism in rat tail skin following blockage of the lymphatic circulation.

This study was undertaken to explore the effects of lymphatic blockage on the metabolism of hyaluronan in the skin. In initial experiments, [3H] hyaluronan was injected subcutaneously into the tail skin of rats that either had no surgical intervention (control) or into those that had their lymphatic drainage blocked two hours earlier (acute lymphedema) or after the lymphatics had been blocked for three months (chronic lymphedema). The removal of tritiated hyaluronan from the injection sites was determined by the appearance of [3H] in the plasma. The results showed that the clearance of injected hyaluronan was delayed in rats with lymphatic blockage. The half- life of injected hyaluronan in the controls was approximately 70-75 hr, compared with approximately 105-110 hr in the lymph blocking rats. The levels of radioactivity in the plasma from rats with both acute and chronically blocked lymphatics were lower than that of control rats during the entire follow up period. In addition, biochemical analysis revealed that there was a significant increased amount of hyaluronan in the tail skin three months after lymphatic blocking. These results suggest that lymph absorption is an important factor in the transport of hyaluronan from the interstitium. Blockage of regional draining lymphatics likely impairs the catabolism of hyaluronan, which stagnates in skin tissue.

Animals↗
PubMed2001

Proliferation of primitive myeloid progenitors can be reversibly induced by HOXA10.

Recent studies show that several Hox transcription factors are important for regulation of proliferation and differentiation in hematopoiesis. Among these is H0XA10, which is selectively expressed at high levels in the most primitive subpopulation of human CD34(+) bone marrow cells. When overexpressed, H0XA10 increases the proliferation of early progenitor cells and can lead to the development of myeloid leukemia. To study the effects of H0XA10 on primitive hematopoietic progenitors in more detail, transgenic mice were generated with regulatable H0XA10 expression. The transgenic mouse model, referred to as tetO-HOXA10, contains the H0XA10 gene controlled by a tetracycline-responsive element and a minimal promoter. Thus, the expression of H0XA10 is inducible and reversible depending on the absence or presence of tetracycline or its analog, doxycycline. A retroviral vector containing the tetracycline transactivator gene (tTA) was used to induce expression of the H0XA10 gene in bone marrow cells from the transgenic mice. Reverse transcription-polymerase chain reaction analysis confirmed regulatable H0XA10 expression in several transgenic lines. H0XA10 induction led to the formation of hematopoietic colonies containing blastlike cells and megakaryocytes. Moreover, the induction of H0XA10 resulted in significant proliferative advantage of primitive hematopoietic progenitors (spleen colony-forming units [CFU-S(12)]), which was reversible on withdrawal of induction. Activation of H0XA10 expression in tet0-H0XA10 mice will therefore govern proliferation of primitive myeloid progenitors in a regulated fashion. This novel animal model can be used to identify the target genes of HOXA10 and better clarify the specific role of HOXA10 in normal and malignant hematopoiesis.

Animals↗
PubMed2001

[Risk factors of chronic obstructive pulmonary disease in patients with chronic bronchitis].

OBJECTIVE: To explore the risk factors of chronic obstructive pulmonary disease (COPD) in patients with chronic bronchitis in following-up 8 years. METHODS: The baseline survey of the study was carried out on 1,999 patients with chronic bronchitis screened out from 67,251(15 years or more) rural people in 1992. In 2000, 1,114 patients were reexamined by simple random sampling method. RESULTS: 869 (78.0% of 1,114) with complete data entered analysis of this study. Smoking, and family history of COPD were associated significantly positively with the decrement per capita yearly of FEV1(forced expiratory volume in the first second) and/or FEV1/FVC (forced vital capacity) ratio. Ex-smoking decreased the decrement of lung function in smokers. The accumulative incidence of COPD was associated positively with smoking and family history of COPD and negatively with baseline FEV1 and FEV1/FVC. The relative risk of COPD was not significantly different between non-smokers and ex-smokers. CONCLUSION: For Chinese rural patients with chronic bronchitis, aging, smoking, family history of COPD, lower pulmonary function are independent risk factors of COPD while sex is not one. Ex-smoking can almost decrease the relative risk of COPD to the approximative risk level of non-smoking.

Adult↗
PubMed2001

Direct extraction of specific pharmacophoric flavonoids from gingko leaves using a molecularly imprinted polymer for quercetin.

A new straightforward approach to extract active components from Chinese traditional herb was reported by using a molecularly imprinted polymer (MIP) as the sorbent material. The MIP was prepared using quercetin, a typical active compound of the flavonoid family in gingko leaves as the template. Acrylamide was used as the functional monomer and two polar solvent tetrahydrofuran was used as the porogen. Afterwards, the polymer was evaluated by chromatographic analysis. It exhibited high selectivity for quercetin and good affinity to its structural analogues. Specific binding amount of quercetin on the MIP in the solvent methanol was 12 microg/g polymer by the cartridge test. The MIP cartridge could directly trap a specific class of compounds including quercetin and kaempferol from the hydrolyzate of gingko leaves. The result demonstrated the possibility of direct extraction of certain pharmacophoric constituents from herb by MIP technology. The compounds extracted were confirmed by time-of-flight mass spectrometry.

Chromatography, High Pressure Liquid↗
PubMed2001

Molecular effects of Eya1 domain mutations causing organ defects in BOR syndrome.

Eya1 is a critical gene for mammalian organogenesis. Mutations in human EYA1 cause branchio-oto-renal (BOR) syndrome, an autosomal dominant disorder characterized by varying combinations of branchial, otic and renal anomalies, whereas deletion of mouse Eya1 results in the absence of multiple organ formation. Eya1 and other Eya gene products share a highly conserved 271 amino acid Eya domain that is required for protein-protein interaction. Recently, several point mutations that result in single amino acid substitutions in the conserved Eya domain region of EYA1 have been identified in BOR patients; however, the molecular and developmental basis of organ defects that occurred in BOR syndrome is unclear. To understand how these point mutations cause disease, we have analyzed the functional importance of these Eya domain missense mutations with respect to protein complex formation and cellular localization. We have demonstrated that these point mutations do not alter protein localization. However, four mutations are crucial for protein-protein interactions in both yeast and mammalian cells. Our results provide insights into the molecular mechanisms of organ defects detected in human syndromes.

Amino Acid Sequence↗
PubMed2001

Body mass index and asthma in adults in families of subjects with asthma in Anqing, China.

We conducted a cross-sectional study of 7,109 adults from families of subjects with asthma in the province of Anhui, China. Asthma was defined either as a combination of physician-diagnosed asthma, airway responsiveness to methacholine at < or = 25 mg/ml and two or more respiratory symptoms or asthma attacks ("asthma"); or as a combination of airway responsiveness to methacholine at < or = 8 mg/ml and two or more respiratory symptoms or asthma attacks ("symptomatic airway hyperresponsiveness [AHR]"). After adjusting for intensity of cigarette smoking and other variables, both extremes of the body mass index (BMI) distribution were associated with symptomatic AHR in men and women (p < 0.01). In the multivariate analysis, both under- and overweight were associated with asthma in women, and underweight was associated with asthma in men. Among men, those with BMIs of 16 and 30 kg/m(2) had 2.5 and 2.3 times higher odds of symptomatic AHR, respectively, than those whose BMI was 21 kg/m(2) (95% CI for OR(16 vs. 21 kg/m)(2) = 1.4 to 3.8; 95% CI for OR(30) (vs.) (21) (kg/m)(2) = 1.2 to 5.0). Among women, those with BMIs of 16 and 30 kg/m(2) had 2.0 and 2.3 times higher odds of symptomatic AHR than those whose BMI was 21 kg/m(2) (95% CI for OR(16) (vs.) (21) (kg/m)(2) = 1.3 to 3.1; 95% CI(30) (vs.) (21) (kg/m)(2) = 1.2 to 4.5). Among adults in families of subjects with asthma living in rural China, both underweight and overweight are associated with an increased risk of asthma.

Adult↗
PubMed2001

Defining the peptide nucleic acids (PNA) length requirement for PNA binding-induced transcription and gene expression.

Induction of gene expression has great potential in the treatment of many human diseases. Peptide nucleic acid (PNA) as a novel DNA-binding reagent provides an ideal system to induce gene-specific expression. In our recent studies, we have demonstrated that PNA bound to double-stranded DNA targets and, therefore, generated single-stranded D-loops and induced transcription of target genes both in vitro and in vivo. Most importantly, we have demonstrated that treatment of cultured human cells with PNAs led to expression of an endogenous target gene. Therefore, the study of the molecular mechanism of PNA binding-induced gene expression will have great implications for the gene therapy of many human diseases. In the current study, we have investigated the PNA length requirement for PNA binding-induced transcription initiation. Using a series of PNAs with different lengths, we have determined that PNAs with lengths of 16 approximately 18 nt induce very high levels of transcription in a HeLa nuclear extract in vitro transcription system. Transfection of the PNA-bound GFP reporter gene plasmid into human normal fibroblast (NF) cells led to a similar result. Gel-mobility shift assays revealed very strong binding affinities of these PNAs. DNA footprinting analysis further demonstrated the specificity of PNAs binding to the targets. These results lead to important understanding of the molecular mechanism of transcription initiation and highly valuable information in PNA design, especially for PNA binding-induced, gene-specific expression.

Base Sequence↗
PubMed2001

Multiple genetic changes are associated with mammary tumorigenesis in Brca1 conditional knockout mice.

Germline mutations in the tumor suppressor gene BRCA1 predispose women to breast cancer, however somatic mutations in the gene are rarely detected in sporadic cancers. To understand this phenomenon, we examined mouse models carrying conditional disruption of Brca1 in mammary epithelium in either p53 wild type (wt) or heterozygous backgrounds. Although a p53(+/-) mutation significantly accelerated tumorigenesis, both strains developed mammary tumors in a stochastic fashion, suggesting that multiple factors, in addition to p53 mutations, may be involved in Brca1 related tumorigenesis. A unique feature of Brca1 mammary tumors is their highly diverse histopathology accompanied by severe chromosome abnormalities. The tumors also display extensive genetic/molecular alterations, including overexpression of ErbB2, c-Myc, p27 and Cyclin D1 in the majority of tumors, while they were virtually ERalpha and p16 negative. Translocations involving p53 were also identified which lead to abnormal RNA and protein products. In addition, we generated cell lines from mammary tumors and found that the cells retained many of the genetic changes found in the primary tumors, suggesting that these genes may be players in Brca1-associated tumorigenesis. Despite their distinct morphology, all cultured tumor cells were Tamoxifen resistant but highly sensitive to Doxorubicin or gamma-irradiation, suggesting that these methods would be effective in treatment of this disease.

Animals↗
PubMed2001

The structure and function of a gene encoding a basic peptide from prawn white spot syndrome virus.

Prawn white spot syndrome virus (WSSV) is the major pathogen responsible for the high mortality of cultured prawns. A gene (termed as p6.8) encoding a basic peptide was found by screening the cDNA and DNA libraries of WSSV. The peptide was highly homologous with proteins rich in arginine and lysine. A fusion protein containing the p6.8 and green fluorescent protein (GFP) genes was cloned into pBV220 and expressed in E. coli. Gel mobility shift assay indicated that the peptide encoded by p6.8 had the capability of binding DNA and might be involved in DNA packaging.

Amino Acid Sequence↗
PubMed2001

Diminished expression of S100A2, a putative tumor suppressor, at early stage of human lung carcinogenesis.

To identify and understand early events in lung carcinogenesis, we used a cDNA array to screen for genes that are expressed differentially in normal human bronchial epithelial (NHBE) cells and a tumorigenic cell line (1170-I) derived from immortalized HBE cells after exposure to cigarette smoke condensate in vivo. Among these genes, we have identified the S100A2 gene, which encodes a nuclear calcium-binding protein, as being down-regulated in the 1170-I cells. Because this gene has been implicated as a tumor suppressor in breast cancer, we examined its potential role as a tumor suppressor in lung carcinogenesis. Levels of S100A2 transcript and protein, which were high in NHBE cells, decreased by up to 50% in immortalized HBE cells (BEAS-2B and 1799) and to low to nearly undetectable levels in transformed (1198) and tumorigenic (1170-I) HBE cells. Furthermore, S100A2 mRNA and protein were undetectable in 8 and expressed at a reduced level in 3 of 11 non-small cell lung cancer (NSCLC) cell lines. Positive immunohistochemical staining of S100A2 was detected in the majority (75-83%) of normal and hyperplastic lung tissues, whereas it was detected in <10% of metaplastic lung tissues, squamous cell carcinoma, and adenocarcinoma. Treatment of 1170-I HBE and NSCLC cells with 5-aza-2'-deoxycytidine resulted in partial restoration of S100A2 expression in seven of eight cell lines. Indeed, CpG methylation was detected in the promoter region of the S100A2 gene. Our results suggest that S100A2 expression is suppressed early during lung carcinogenesis, possibly by hypermethylation of its promoter, and that its loss may be a contributing factor in lung cancer development or a biomarker of early changes in this process.

Animals↗
PubMed2001

A genomewide search for quantitative-trait loci underlying asthma.

A genomewide screen for quantitative-trait loci (QTLs) that underlie asthma was performed on 533 Chinese families with asthma, by the unified Haseman-Elston method. Nine asthma-related phenotypes were studied, including forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), airway responsiveness as indicated by methacholine (MTCH)-challenge test, serum total immunoglobulin E (TIgE), serum-specific immunoglobulin E, eosinophil count in peripheral blood, and skin-prick tests with three different allergens (cockroach, Dermatophagoides pteronyssinus, and D. farinae). Our study showed significant linkage between airway responsiveness to MTCH and D2S1780 on chromosome 2 (P<.00002) and provided suggestive evidence (P<.002) for six additional possible QTLs: D10S1435 and D22S685, for FEV1; D16S412, for FVC; D19S433, for airway responsiveness to MTCH; D1S518, for TIgE; and D4S1647, for skin reactivity to cockroach. No significant or suggestive evidence of linkage for the other four traits was found.

Adult↗
PubMed2001

E2F repression by C/EBPalpha is required for adipogenesis and granulopoiesis in vivo.

The C/EBPalpha transcription factor is required for differentiation of adipocytes and neutrophil granulocytes, and controls cellular proliferation in vivo. To address the molecular mechanisms of C/EBPalpha action, we have identified C/EBPalpha mutants defective in repression of E2F-dependent transcription and found them to be impaired in their ability to suppress cellular proliferation, and to induce adipocyte differentiation in vitro. Using targeted mutagenesis of the mouse germline, we show that E2F repression-deficient C/EBPalpha alleles failed to support adipocyte and granulocyte differentiation in vivo. These results indicate that E2F repression by C/EBPalpha is critical for its ability to induce terminal differentiation, and thus provide genetic evidence that direct cell cycle control by a mammalian lineage-instructive transcription factor couples cellular growth arrest and differentiation.

3T3 Cells↗