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Biomedical subjects

Yan Li

Publications and source records attributed to Yan Li.

At least 181 records · Page 10Linked to original sources
PubMed2006

Ambulatory arterial stiffness index: rationale and methodology.

OBJECTIVES: Increased arterial stiffness is associated with the development of cardiovascular disease and may even predict its development at an early stage. Increased pulse pressure is seen as a marker of increased arterial stiffness and can be readily measured by ambulatory blood pressure monitoring. We propose another surrogate measure of arterial stiffness derived from ambulatory blood pressure monitoring that may predict cardiovascular mortality over and above pulse pressure, namely, the dynamic relationship between diastolic and systolic blood pressure over 24 h--the ambulatory arterial stiffness index. METHODS: Using all blood pressure readings over the 24-h period from 11 291 (5965 women; mean age 54.6 years) patients referred for ambulatory blood pressure monitoring to a blood pressure clinic, diastolic blood pressure was plotted against systolic blood pressure, and the regression slope was calculated; ambulatory arterial stiffness index was defined as one minus this regression slope. RESULTS: Both ambulatory arterial stiffness index and pulse pressure were higher in women (0.42 vs. 0.40 and 57.0 vs. 55.3 mmHg, respectively). For the entire group, the correlation between ambulatory arterial stiffness index and pulse pressure was 0.5. CONCLUSIONS: Ambulatory arterial stiffness index is a new measure that is readily available from ambulatory blood pressure monitoring and may provide added prognostic information for cardiovascular outcome.

Adult↗
PubMed2006

Longitudinal analysis of genotype distribution of influenza A virus from 2003 to 2005.

Influenza A viruses cause yearly epidemics, in part, due to their ability to overcome immunity from previous infections through acquisition of mutations. Amino acid sequences encoded by genes 4 (HA), 6 (NA), 7 (M), and 8 (NS) from 77 H3N2 influenza A isolates, collected between November 2003 and March 2005, were analyzed to determine the extent to which the viruses mutated within epidemic periods and between the epidemics. Nucleotide and amino acid sequences were stable throughout the epidemics but experienced substantial changes between epidemics. Major changes occurred in the HA gene in 5 to 7 amino acids and the NA gene in 11 to 13 amino acids and changes of 5 amino acids occurred in the M and NS genes. In the HA gene, changes occurred in sites known to be epitopes that determine the hemagglutination inhibition reactivity, and these were shown to be associated with a change of strain from A/Fujian/411/2002-like to A/California/7/2004-like viruses. Our findings indicate that genotype determination promises to be a rapid approach for detecting new strains of influenza A viruses in a population.

Amino Acid Sequence↗
PubMed2006

Room temperature formation of ammonia by oxidizing hydrogenated cerium nanoparticles in the air.

Ammonia formation was observed when hydrogenated cerium nanoparticles prepared by hydrogen plasma-metal reaction (HPMR) were exposed to the air at room temperature. This novel phenomenon represents a successful example of room temperature cleavage of dinitrogen and may find application in low temperature synthesis of ammonia under thermodynamically favorable conditions. A possible mechanism is also proposed. We suggest that the oxidation of cerium hydride offers chemical force to drive the hydrogen atoms out of the lattice. The monoatomic H released to the surface is highly active and readily reacts with N2 to yield ammonia. Some surface processes, which we know little about at the moment, are likely to be involved so as to lower the energy barrier of nitrogen dissociation. Further investigation is required to elucidate the detailed mechanism.

Air↗
PubMed2006

Serial analysis of gene expression (SAGE) in the rat limbal and central corneal epithelium.

PURPOSE: To identify genes preferentially expressed in the stem-cell-rich limbal epithelium of the rat cornea. METHODS: The limbal and central corneal epithelial cells of 6-week-old rats were isolated by microdissection. Serial analysis of gene expression (SAGE) libraries were constructed and analyzed, and in situ hybridization, reverse transcription-polymerase chain reaction (RT-PCR) and cDNA cloning were conducted by conventional procedures. RESULTS: The rat limbal and central corneal epithelial SAGE libraries consisted of 41,894 and 40,691 tags, respectively. After annotation, this was reduced to 759 transcripts specific for the limbal library and 844 transcripts specific for the central corneal library; 2292 transcripts overlapped. Transcripts encoding proteins with metabolic functions comprised the major functional category in both libraries. In situ hybridization and/or RT-PCR results of 12 of the most abundant, highly enriched transcripts in the limbal epithelium were in general agreement with the SAGE data and showed that these proteins are also expressed in the conjunctival epithelium. Interesting limbal-enriched transcripts encode WDNM1-like protein (similar to WDNM1/Expi, a putative secreted proteinase and inhibitor of metastasis), mesothelin (a cancer marker), marapsin (a trypsin-like serine protease that may control cell growth and migration), K4 and K15 (both cytokeratins), and membrane-spanning four-domain subfamily A member 8B. WDNM1-like protein was cloned and confirmed as a member of the four-disulfide core family. CONCLUSIONS: The SAGE results extend the database of genes expressed in the rodent cornea and suggest an association between several genes preferentially expressed in the limbal epithelium with cellular proliferation and migration.

Animals↗
PubMed2006

Voltage-gated potassium channels: regulation by accessory subunits.

Voltage-gated potassium channels regulate cell membrane potential and excitability in neurons and other cell types. A precise control of neuronal action potential patterns underlies the basic functioning of the central and peripheral nervous system. This control relies on the adaptability of potassium channel activities. The functional diversity of potassium currents, however, far exceeds the considerable molecular diversity of this class of genes. Potassium current diversity contributes to the specificity of neuronal firing patterns and may be achieved by regulated transcription, RNA splicing, and posttranslational modifications. Another mechanism for regulation of potassium channel activity is through association with interacting proteins and accessory subunits. Here the authors highlight recent work that addresses this growing area of exploration and discuss areas of future investigation.

Action Potentials↗
PubMed2006

Activation of Sirt1 decreases adipocyte formation during osteoblast differentiation of mesenchymal stem cells.

UNLABELLED: In vitro, mesenchymal stem cells differentiate to osteoblasts when exposed to bone-inducing medium. However, adipocytes are also formed. We showed that activation of the nuclear protein deacetylase Sirt1 reduces adipocyte formation and promotes osteoblast differentiation. INTRODUCTION: Mesenchymal stem cells (MSCs) can differentiate into osteoblasts, adipocytes, chondrocytes, and myoblasts. It has been suggested that a reciprocal relationship exists between the differentiation of MSCs into osteoblasts and adipocytes. Peroxisome proliferator-activated receptor gamma2 (PPARgamma2) is a key element for the differentiation into adipocytes. Activation of Sirt1 has recently been shown to decrease adipocyte development from preadipocytes through inhibition of PPARgamma2. MATERIALS AND METHODS: We used the mouse mesenchymal cell line C3H10T1/2 and primary rat bone marrow cells cultured in osteoblast differentiation medium with or without reagents affecting Sirt1 activity. Adipocyte levels were analyzed by light microscopy and flow cytometry (FACS) after staining with Oil red O and Nile red, respectively. Osteoblast and adipocyte markers were studied with quantitative real-time PCR. Mineralization in cultures of primary rat bone marrow stromal cells was studied by von Kossa and alizarin red staining. RESULTS: We found that Sirt1 is expressed in the mesenchymal cell line C3H10T1/2. Treatment with the plant polyphenol resveratrol as well as isonicotinamide, both of which activate Sirt1, blocked adipocyte development and increased the expression of osteoblast markers. Nicotinamide, which inhibits Sirt1, increased adipocyte number and increased expression of adipocyte markers. Furthermore, activation of Sirt1 prevented the increase in adipocytes caused by the PPARgamma-agonist troglitazone. Finally, activation of Sirt1 in rat primary bone marrow stromal cells increased expression of osteoblast markers and also mineralization. CONCLUSIONS: In this study, we targeted Sirt1 to control adipocyte development during differentiation of MSCs into osteoblasts. The finding that resveratrol and isonicotinamide markedly inhibited adipocyte and promoted osteoblast differentiation may be relevant in the search for new treatment regimens of osteoporosis but also important for the evolving field of cell-based tissue engineering.

Adipocytes↗
PubMed2006

[The association of MMP-13 polymorphism with susceptibility to esophageal squamous cell carcinoma and gastric cardiac adenocarcinoma].

Matrix metalloproteinase-13 (MMP-13) belongs to a family of enzymes that degrade all components of the extracellular matrix. Polymorphism in the promoter region of the MMP-13 gene may modify its transcriptional activity and protein level. This study was designed to investigate the correlation of MMP-13 A-77G single nucleotide polymorphism (SNP) with susceptibility to esophageal squamous cell carcinoma (ESCC) and gastric cardiac carcinoma (GCA) in a population from a high-incidence region of Hebei province. MMP-13 promoter SNP (A-77G) was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis in 316 ESCC patients, 243 GCA patients and 609 healthy controls. The overall genotype and allelotype distributions of MMP-13 in ESCC and GCA patients were not significantly different from those in healthy controls (P>0.05). When stratified for smoking status, the A/A, A/G, G/G genotype frequencies of MMP-13 in GCA patients and smoker controls group were 27.1%, 44.1%, 28.8% and 17.8%, 60.5%, 21.7% respectively. There was a significant difference between the two groups (chi2=9.01, P=0.01). The A/G genotype frequency in GCA patients was significantly lower than that in the controls, when compared to the A/A genotype, suggesting that individuals with the A/G genotype may have reduced susceptibility to GCA in the smoker group (OR=0.48, 95% CI=0.280.83). However, the G/G genotype showed no significant influence on the risk of developing GCA. Thus, in the region of Hebei Province where there is a high incidence of GCA and ESCC, the MMP-13 A-77G SNP may not be associated with cancer susceptibility. The A/G genotype may confer protection against GCA for smokers.

Adenocarcinoma↗
PubMed2006

Origins of PM10 determined by the micro-proton induced X-ray emission spectra of single aerosol particles.

The micro-proton induced X-ray emission (micro-PIXE) spectrum of a single aerosol particle (SAP) was considered as its fingerprint for tracing its origin. A proton microprobe was used to extract fingerprints of SAPs. Environmental monitoring samples of PM(10) were collected from a heavy industrial area of Shanghai and were analyzed by proton microprobe for finding their pollution sources. In order to find the sources of SAPs collected from environmental monitoring sites, a fingerprint database of SAPs collected from various pollution sources was established. The origins of samples collected through environmental monitoring were identified by comparison of the micro-PIXE spectra of SAPs with those of SAPs in the fingerprint database using a pattern recognition technique. The results of this study show that most of the measured PM(10) is derived from metallurgic industry, soil dust, coal combustion, automobile exhaust, and motorcycle exhaust. The study also shows that the proton microprobe is an ideal tool for the analysis of SAPs. The unidentified particles of PM(10) are classified into seven classes by hierarchical cluster analysis based on the element peak intensity in the spectra.

Aerosols↗
PubMed2006

A highly sensitive and rapid assay for protein determination in human urine and penicillin using a Rayleigh light-scattering technique with benzeneazo-8-acetylamino-1-naphthol-3,6-disulfonic acid sodium salt.

A simple and sensitive method was conducted for the determination of trace amounts of proteins with benzeneazo-8-acetylamino-1-naphthol-3,6-disulfonic acid sodium salt (azophloxine, AP) using a Rayleigh light-scattering (RLS) technique. At pH 2.60 and in the presence of an emulsifier OP microemulsion, the RLS of AP can be greatly enhanced by proteins, owing to the interaction between AP and protein. The enhanced intensity is proportional to the concentration of proteins. Four proteins, including bovine serum albumin (BSA), human serum albumin (HSA), lysozyme (Lys) and gamma globulin (gamma-G) have been tested. For example, the linear range of BSA was 0 - 0.06 microg mL(-1) with detection limits of 2.38 ng mL(-1). The method was applied to the analysis of protein in human urine and penicillin samples with satisfactory results. The relative standard deviation was in all instances less than 4.0%, and the recovery was in the range of 97.5 - 104%.

Azo Compounds↗
PubMed2006

Diabetes and function in different cognitive systems in older individuals without dementia.

OBJECTIVE: To examine the relation of type 2 diabetes to the level of function in five different cognitive systems in older individuals without dementia. RESEARCH DESIGN AND METHODS: Participants were 882 older men and women without dementia participating in the Rush Memory and Aging Project, a longitudinal clinical-pathological study of aging and dementia. They underwent uniform evaluations, which included clinical classification of dementia, and detailed cognitive function testing from which previously established summary measures of episodic memory, semantic memory, working memory, perceptual speed, visuospatial ability, and global cognition were derived. Diabetes was identified by history and direct medication inspection. RESULTS: Diabetes was present in 116 (13%) participants. In separate linear regression models controlling for age, sex, and education, diabetes was associated with lower levels of semantic memory (P < 0.001) and perceptual speed (P = 0.005), but not with episodic memory, working memory, or visuospatial ability or with a measure of global cognition. The associations of diabetes with cognition were reduced when controlling for several vascular variables, and the associations were substantially stronger in current smokers than in individuals who never smoked or formerly smoked. CONCLUSIONS: These results suggest that type 2 diabetes is associated with cognitive impairment, especially in semantic memory and perceptual speed and that these effects may be modified by smoking status.

Aged↗
PubMed2006

Human Bocavirus infection, Canada.

Human Bocavirus was detected in 18 (1.5%) of 1,209 respiratory specimens collected in 2003 and 2004 in Canada. The main symptoms of affected patients were cough (78%), fever (67%), and sore throat (44%). Nine patients were hospitalized; of these, 8 (89%) were <5 years of age.

Adolescent↗
PubMed2006

Triple reassortant H3N2 influenza A viruses, Canada, 2005.

Since January 2005, H3N2 influenza viruses have been isolated from pigs and turkeys throughout Canada and from a swine farmer and pigs on the same farm in Ontario. These are human/classical swine/avian reassortants similar to viruses that emerged in US pigs in 1998 but with a distinct human-lineage neuraminidase gene.

Animals↗
PubMed2006

Chimpanzee adenovirus antibodies in humans, sub-Saharan Africa.

Human sera from the United States, Thailand, and sub-Saharan Africa and chimpanzee sera were tested for neutralizing antibodies to 3 chimpanzee adenoviruses. Antibodies were more common in humans residing in sub-Saharan Africa than in humans living in the United States or Thailand. This finding suggests cross-species transmission of chimpanzee adenoviruses.

Adenoviridae Infections↗
PubMed2006

Short-term heart retention and distribution of intramyocardial delivered mesenchymal cells within necrotic or intact myocardium.

Cell therapy with bone marrow mesenchymal stem cells (BMSCs) is a new strategy for treating ischemic heart failure, but data concerning the distribution and retention of transplanted cells remain poor. We investigated the short-term myocardial retention of BMSCs when these cells are directly injected within necrotic or intact myocardium. 111Indium-oxine-labeled autologous BMSCs were injected within either 1-month-old infarction (n = 6) or normal myocardium (n = 6) from rats. Serial in vivo pinhole scintigraphy was scheduled during 1 week in order to track the implanted cells. The myocardial retention of BMSCs was definitely higher in myocardial infarction than in normal myocardial area (estimated percent retention at 2 h: 63 +/- 3% vs. 25 +/- 4%, p < 0.001) and the estimated cardiac retention values were unchanged in both groups along the 7 days of follow-up. On heart sections at day 7, labeled BMSCs were still around the injection site and appeared confined to the scarred tissue corresponding either to the infarct area or to the myocardium damaged by needle insertion. BMSCs have a higher retention when they are injected in necrotic than in normal myocardial areas and these cells appear to stay around the injection site for at least a 7-day period.

Animals↗
PubMed2006

[HLA-B gene polymorphism detected by high-resolution sequence-based typing in Guangdong Han populations].

OBJECTIVE: To investigate the genetic polymorphism of HLA-B locus in Guangdong Han population and compare the characteristic of the allele frequency distribution with that in other populations. METHODS: A total of 562 cord blood samples from Guangzhou Cord Blood Bank were analyzed by sequence-based typing. Then the sequences encompassing exons 2, 3, and 4 for HLA-B gene were analyzed by direct sequencing of PCR products. The allele frequency distribution of HLA-B in this population was compared with that in other populations. RESULTS: A total of 59 different HLA-B alleles were detected, and among them were 6 HLA-B alleles with frequencies higher than 5%: HLA-B*4601 (14.5%), HLA-B*400101 (14.4%), HLA-B*1502 (11.5%), HLA-B*1301 (8.6%), HLA-B*5801 (8.1%) and HLA-B*380201 (6.4%); the total frequency of these six alleles was 63.5%. At the same time, there were 30 kinds of HLA-B allele with frequencies lower than 0.5%; the total frequency of these alleles was 4.9%. Maximum variation at HLA-B was seen in the HLA-B*15 allele family (nine alleles). Comparison of the HLA-B frequencies in different populations showed a close relationship of Guandong Han population with the Chinese populations from Hong Kong and Singapore, respectively. CONCLUSION: The results have shown the characteristic of HLA-B distribution and provided more accurate genotypic data that may serve as normal reference value for the Han population in Guangdong, China.

Asian People↗
PubMed2006

[Association of polymorphisms of p21cip1 and p27kip1 genes with susceptibilities of esophageal squamous cell carcinoma and gastric cardiac adenocarcinoma].

BACKGROUND & OBJECTIVE: Researches showed that polymorphisms of p21(cip1) and p27(kip1) genes have associations with susceptibilities of breast cancer, lung cancer, prostate cancer, and so on. This study was to investigate the possible association of functional polymorphisms of p21(cip1) and p27(kip1) genes with susceptibilities of esophageal squamous cell carcinoma (ESCC) and gastric cardiac adenocarcinoma (GCA) in a population from a high incidence region in north China. METHODS: The single nucleotide polymorphisms (SNPs) in the 3'-untranslated region of p21(cip1) gene and in codon 109 of p27(kip1) gene were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 299 ESCC patients, 256 GCA patients, and 437 healthy controls from a high incidence region of north China. RESULTS: The frequency of p21(cip1) T allelotype was significantly higher in ESCC patients than in healthy controls (42.8% vs. 36.7%, P=0.02). The frequency of p27(kip1) V allelotype was significantly higher in ESCC and GCA patients than in healthy controls (96.8% and 96.1% vs. 92.9%, P=0.001, P=0.02). The distribution of p21(cip1) genotypes among ESCC patients was significantly different from that among healthy controls (P=0.04); compared with the combination of the C/C and C/T genotypes, the T/T genotype significantly elevated the risk of developing ESCC [adjusted odds ratio (OR)=1.93, 95% confidence interval (CI)=1.12-3.94]. The distribution of p27(kip1) genotypes among ESCC and GCA patients were significantly different from that among healthy controls (P=0.002, P=0.01); compared with the combination of V/G and G/G genotypes, the V/V genotype significantly elevated the risk of developing ESCC and GCA (adjusted OR=2.44, 95% CI=1.21-4.02; adjusted OR=2.01, 95% CI=1.12-3.68). When stratified for smoking and family history of upper gastrointestinal cancers (UGIC), compared with the combination of V/G and G/G genetypes, the V/V genotype significantly elevated the risk of developing both ESCC and GCA in smokers (adjusted OR=2.24, 95% CI=1.14-4.03; adjusted OR=2.61, 95% CI=1.25-3.82) and ESCC in individuals with positive family history of UGIC (adjusted OR =2.04, 95% CI=1.04-3.43). The combination of p21(cip1) T/T and p27(kip1) V/V genotypes significantly elevated the risk of developing ESCC and GCA (adjusted OR=3.78, 95% CI=1.46-5.89; adjusted OR=2.56, 95% CI=1.06-4.78). CONCLUSION: In north China, p21(cip1) polymorphisms might be correlated with the susceptibility of ESCC, p27(kip1) polymorphisms might be correlated with the susceptibilities of ESCC and GCA, and they might have synergetic effect on ESCC and GCA development.

Adenocarcinoma↗
PubMed2006

[Survey of contraceptive knowledge in married couples at reproductive age in 5 Chinese cities].

OBJECTIVE: To survey the married couples at reproductive age for contraceptive knowledge in 5 Chinese cities. METHODS: The data derived from a questionnaire-based research conducted in 2002 on family planning among married couples in 5 Chinese cities were statistically analyzed. RESULTS: The total rate of good contraceptive knowledge was 70.10% in the couples. Among all the contraceptive measures, condom use was the most familiar one. The understanding of contraceptive knowledge in couples working in official departments and educational institutes was better than that among the couples working in common enterprises, affected by such factors as gender, geographic regions, educational background and willingness of child-bearing. CONCLUSION: The married couples in the Chinese cities have generally good understanding of contraceptive knowledge, which can be affected by different factors among different populations.

Adult↗