Biomedical subjects

Li Wang

Publications and source records attributed to Li Wang.

At least 109 records · Page 6Linked to original sources

PubMed2006

A novel approach for improving the productivity of ubiquinone-10 producing strain by low-energy ion beam irradiation.

Agrobacterium tumefaciens ATCC4452 cells were irradiated by nitrogen ion beam, a new mutagen, with energy of 10 keV and fluence ranging from 2.6x10(14) ions/cm2 to 6.5x10(15) ions/cm2. A similar "saddle shape" survival curve due to ion beam irradiation appeared again in this study. Some mutants with high yield of ubiquinone-10 were induced by ion implantation. High mutation rate and wide mutation spectrum were also observed in the experiment. These results suggested that the mutagenic effect of such low-energy ion influx into bacterium cells could result from multiple processes involving direct collision of particles with cytoplasm, nucleolus, and cascade atomic and molecular reactions due to plentiful primary and secondary particles.

Agrobacterium tumefaciens↗

PubMed2006

Gene expression profiles of CD34+ cells in myelodysplastic syndromes: involvement of interferon-stimulated genes and correlation to FAB subtype and karyotype.

To gain insight into the poorly understood pathophysiology of the myelodysplastic syndromes (MDSs), we have determined the gene expression profiles of the CD34+ cells of 55 patients with MDS by using a comprehensive array platform. These profiles showed many similarities to reported interferon-gamma-induced gene expression in normal CD34+ cells; indeed the 2 most up-regulated genes, IFIT1 and IFITM1, are interferon-stimulated genes (ISGs). Alterations in the expression of ISGs may play a role in the hematologic features of MDS, such as peripheral blood cytopenias. Up-regulation of IFIT1 is a potential diagnostic marker for MDS. We determined whether distinct gene expression profiles were associated with specific FAB and cytogenetic groups. CD34+ cells from patients with refractory anemia with ringed sideroblasts (RARS) showed a particular gene expression profile characterized by up-regulation of mitochondrial-related genes and, in particular, of those of heme synthesis (eg, ALAS2). CD34+ cells from patients with the del(5q) had a distinct gene expression profile, characterized by down-regulation of genes assigned to 5q, and up-regulation of the histone HIST1 gene cluster at chromosome 6p21 and of genes related to the actin cytoskeleton. This study provides important and new insights into the pathophysiology of MDS.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Evolutionary scenario for acquisition of CAG repeats in human SCA1 gene.

We investigated the CAG repeat sequence of the spinocerebellar ataxia type 1 (SCA1) gene in various species of primates to reveal how human has acquired the repeat structure with interruptions. Our results demonstrate no repetitive structure in the region corresponding to the human CAG repeats in prosimians and New World monkeys like in rodents, perfect (uninterrupted) CAG repeats in Old World monkeys, and interrupted CAG repeats in hominoids. Comparative analysis on the secondary structures of the primate SCA1 transcripts suggests the human prototype was built in the common ancestor of simians. We show an evolutionary scenario for acquisition of CAG repeats with interruptions in the human SCA1 gene.

Amino Acid Sequence↗

PubMed2006

Further understanding human disease genes by comparing with housekeeping genes and other genes.

BACKGROUND: Several studies have compared various features of heritable disease genes with other so called non-disease genes, but they have yielded some conflicting results. A potential problem in those studies is that the non-disease genes contained a large number of essential genes--genes which are indispensable for humans to survive and reproduce. Since a functional disruption of an essential gene has fatal consequences, it's more reasonable to regard essential genes as extremely severe "disease" genes. Here we perform a comparative study on the features of human essential, disease, and other genes. RESULTS: In the absence of a set of well defined human essential genes, we consider a set of 1,789 ubiquitously expressed human genes (UEHGs), also known as housekeeping genes, as an approximation. We demonstrate that UEHGs are very likely to contain a large proportion of essential genes. We show that the UEHGs, disease genes and other genes are different in their evolutionary conservation rates, DNA coding lengths, gene functions, etc. Our findings systematically confirm that disease genes have an intermediate essentiality which is less than housekeeping genes but greater than other human genes. CONCLUSION: The human genome may contain thousands of essential genes having features which differ significantly from disease and other genes. We propose to classify them as a unique group for comparisons of disease genes with non-disease genes. This new way of classification and comparison enables us to have a clearer understanding of disease genes.

Adolescent↗

PubMed2006

Intratumor genomic heterogeneity correlates with histological grade of advanced oral squamous cell carcinoma.

To assess the difference in genetic aberration patterns among the invasive tumor front (ITF), center/superficiality and the stroma adjacent to oral squamous cell carcinoma (OSCC), we studied loss of heterozygosity (LOH) and microsatellite instability (MI) at chromosome 9p21 and 17p13 on the three regions by combining laser capture microdissection (LCM) and PCR. We studied 20 OSCC patients with TP53 on chromosome 17p13 and RPS6 on chromosome 9p21. Genomic DNA samples from the ITF, center/superficial and stromal cells adjacent to the tumor were prepared from cryosections using laser-assistant microdissection, then LOH and MI were determined. Cells at the ITF, center/superficiality and stroma showed a high frequency of LOH and MI on chromosomes 17p13 (TP53) and 9p21 (RPS6). Comparison of the patterns of allelic loss and MI encountered at the ITF, center/superficial and stromal cells revealed no concordance. The frequency of RPS6 and TP53 aberration at the epithelial compartment (both ITF and center, 64.7%, 11/17; 70.6%, 12/17) was statistically higher than the stroma (23.5%, 4/17; 43.8%, 7/16) (p<0.05). Furthermore, for the epithelial compartment, the aberrations proportions of TP53 rose from 60.0% (9/15) to 64.7% (11/17) between the center/superficial part and ITF. Also the rate of RPS6 increased from 29.4% (5/17) to 58.8% (10/17) between the center/superficial parts and ITF. The overall frequency of the two markers was statistically higher at the ITF (20/32) than the center/superficial part (15/34) (p<0.05). The current study revealed that intratumor genetic heterogeneity exists in the different histological areas of OSCCs and some particular tumor cell genotypes have correlation with histological patterns.

Adult↗

PubMed2006

[A new bioassay model of antibiotic susceptibility by corneofungimetry].

OBJECTIVE: To study the value of a new bioassay model of antibiotic susceptibility by corneofungimetry which is more similar to human internal environment. METHODS: Twenty-one healthy adult volunteers, 12 males and 9 females, aged 32 (22 - 41), were randomly divided into two groups to receive itraconazole 200 mg Bid or 200 mg qd or bid for one week. Stratum corneum strippings were taken from the forearm skin once before administration of itraconazole and 1, 4, 7, 10, 14, 21, 28, and 35 days after administration of itraconazole. Spores of selected fungi (Trichophyton rubrum, T. mentagrophytes, Microsporum canis, Candida albicans, C. glabrata and C. tropicalis) were deposited and cultured on the strippings. PAS stain was used after one-week culture to observe the growth of the fungi by computerized-assisted image analysis to measure the area covered by the yeasts and the dermatophyte. RESULTS: All fungi grew on all the stratum corneum strippings with different numbers of hyphae. The areas covered by hyphae and spores decreased gradually after administration of itraconazole, became the smaller on the seventh day (P = 0.01 or P < 0.01), and began to increased since the 10 th day, and became almost the same sizes as those before the administration of itraconazole on the 35 th day. CONCLUSION: Similar to the human internal environment, corneofungimetry is a useful new model of bioassay for antibiotic susceptibility.

Adult↗

PubMed2006

Upregulation of type I interleukin-1 receptor after traumatic spinal cord injury in adult rats.

Post-traumatic inflammation response has been implicated in secondary injury mechanisms after spinal cord injury (SCI). Interleukin-1 (IL-1) is a key inflammatory mediator that is increasingly expressed after SCI. The action of IL-1 is mediated through its functional receptor, type I interleukin-1 receptor (IL-1RI). However, whether this receptor is expressed after SCI remains to be elucidated. In the present study, the temporospatial expression of IL-1RI was detected in rats that received a moderate contusive SCI (a 10 g rod dropped at a height of 12.5 mm) at the ninth to tenth thoracic vertebral level using a widely used New York University impact device. Our study demonstrated that IL-1RI was slightly increased at 4 h post-injury compared to the normal or sham-operated controls, reached the peak at 8 h at mRNA level (4.44-fold, P<0.01) and 1 d at protein level (2.62-fold, P<0.01). IL-1RI remained at its elevated levels for a relatively long duration (4 h-7 days). Spatially, IL-1RI was observed throughout the entire length of a 10 mm-long cord segment containing the injury epicenter. Colocalization of IL-1RI was found in neurons, oligodendrocytes, astrocytes, and activated microglia. Our results suggest that the elevated expression of IL-1RI after SCI may contribute to posttraumatic inflammation responses of IL-1.

Animals↗

PubMed2006

Identification of integrin alpha1 as an interacting protein of protein tyrosine phosphatase PRL-3.

PRL-3 is a newly identified protein tyrosine phosphatase associated with tumor metastasis. It is over-expressed in various cancers, such as colorectal cancer, gastric cancer, and ovarian cancer, and is correlated with the progression and survival of cancers. Although PRL-3 plays a causative role in promoting cancer cell invasion and metastasis, the molecular mechanism is unknown. To investigate PRL-3's roles in tumorigenesis and signal transduction pathway, we screened the human placenta brain cDNA library with the bait of PRL-3 in yeast two-hybrid system. Then we identified integrin alpha1 as a PRL-3-interacting protein for the first time, and verified this physical association with pull-down and co-immunoprecipitation assays. Furthermore, we found that PRL-3 could down-regulate the tyrosine-phosphorylation level of integrin beta1 and increased the phosphorylation level of Erk1/2. Our present discovery will provide new clues for elucidating the molecular mechanism of PRL-3 in promoting cancer invasion and metastasis.

Amino Acid Sequence↗

PubMed2006

High-throughput screening for the asymmetric transformation reaction of L-histidine to D-histidine by capillary array electrophoresis.

Asymmetric transformation reaction of L-histidine to D-histidine was studied by homemade capillary array electrophoresis for the first time. The enantiomeric excess value of asymmetric histidine products can be directly determined from the electrophoretogram of capillary array electrophoresis. The experiment results showed that the optimized asymmetric transformation reaction condition was in the presence of salicylaldehyde as catalyst and acetic acid as solvent.

Aldehydes↗

PubMed2006

Deviation of optical constants extracted in terahertz transmission spectroscopy.

We present a simulation with a Lorentz oscillator model to evaluate the accuracy of the extracted optical constants in terahertz transmission spectroscopy. The contributions of various error sources including the deflection of the incident angle, the delay-line timing error, and two other kinds of noises are analyzed. It is revealed that the influence of the deflection angle is an approximate parabolic dependence. The delay-line timing uncertainty introduces an exponential frequency dependence in the deviation of the extinction coefficient and a distinct change in the refractive index data in the resonant region. When background and 1/f noises are introduced, the deviation mainly concentrates in the resonant region.

Journal Article↗

PubMed2006

Integrated optical filter arrays fabricated by using the combinatorial etching technique.

A combinatorial etching technique is developed to fabricate integrated narrow bandpass filters on a single substrate. It is highly efficient for fabrication of integrated filter arrays in optical regions. A monolithic filter array has been fabricated by using the technique with a two-step deposition process. The filter contains 32 elements in the near-infrared region. The relative full width at half-maximum (FWHM) sigmalambda/lambda of the filter elements is less than 0.2%. Such a narrow bandpass filter array can be utilized in many optical applications.

Journal Article↗

PubMed2006

Identification of the linear epitope for Fc-binding on the bovine IgG2 Fc receptor (boFcgamma2R) using synthetic peptides.

To identify the linear epitope for Fc-binding on the bovine IgG2 Fc receptor (boFcgamma2R), peptides derived from the membrane-distal extracellular domain (EC1) of boFcgamma2R corresponding to the homologous region of human FcalphaRI were synthesized. Binding of bovine IgG2 to the different peptides was tested by Dot-blot assay, and the peptide showing maximal binding was further modified by truncation and mutation. The minimum effective peptide 82FIGV85 located in the putative F-G loop of the EC1 domain was found to bind bovine IgG2 specifically and inhibit the binding of bovine IgG2 to the receptor. The Phe82, Ile83 and Val85 residues within the linear epitope were shown to be critical for IgG2-binding. Such functional epitope peptide should be very useful for understanding the IgG-Fcgamma interaction and development of FcR-targeting drugs.

Amino Acid Sequence↗

PubMed2006

Effect of functional group (fluorine) of aromatic thiols on electron transfer at the molecule-metal interface.

Electron transfer at the molecule-metal interface of self-assembled monolayers of 1,1';4',1''-terphenyl-4''-thiol (BBB) and its partially fluorinated counterpart (BFF: p-thiophenyl-nonafluorobiphenyl) on Au(111) is investigated by core-hole clock spectroscopy. Ultrafast electron transfer at the BBB/Au(111) interface in the low-femtosecond regime (on the same time scale as the C 1s core-hole lifetime, approximately 6 fs) was observed. In contrast, for BFF/Au(111), the interface electron transfer was forbidden during the core-hole decay. This strongly suggests that fluorination of phenyl rings significantly enhances the localization of the excited electrons in the LUMO.

Journal Article↗

PubMed2006

Study on the synthesis of poly(diglycidyl maleate-co-stearyl methacrylate) and morphology conversion of their self-assembly systems.

A novel polymer of poly(diglycidyl maleate-co-stearyl methacrylate) (P(DGMA-co-SMA)) was synthesized by reaction between poly(maleic anhydride-co-stearyl methacrylate) (P(MA-co-SMA)) and epichlorohydrin. The self-assembly behavior of the resultant copolymer was investigated. It was found that the spheral aggregates could converse to nanorods after being aged for 2.5 days and nanolines composed of the nanorods were obtained after being aged for an additional 5.5 days. The mechanism of their self-assembly behavior and morphology conversion of self-assembly systems is discussed.

Magnetic Resonance Spectroscopy↗

PubMed2006

Ultrafast electron transfer from oligo(p-phenylene-ethynylene)thiol to gold.

The electron transfer dynamics of oligo(p-phenylene-ethynylene) (OPE) SAM on Au(111) was studied by resonant photoemission spectroscopy. The ultrafast electron transfer from OPE molecules to Au substrate was clearly observed. The time scale for this charge transfer is much less than 6 fs, the core-hole lifetime for C 1s. This strongly suggests that there is an intense interfacial electronic coupling between OPE molecules and the Au substrate.

Journal Article↗

PubMed2006

Exercise is associated with reduced risk for incident dementia among persons 65 years of age and older.

BACKGROUND: Alzheimer disease and other dementing disorders are major sources of morbidity and mortality in aging societies. Proven strategies to delay onset or reduce risk for dementing disorders would be greatly beneficial. OBJECTIVE: To determine whether regular exercise is associated with a reduced risk for dementia and Alzheimer disease. DESIGN: Prospective cohort study. SETTING: Group Health Cooperative, Seattle, Washington. PARTICIPANTS: 1740 persons older than age 65 years without cognitive impairment who scored above the 25th percentile on the Cognitive Ability Screening Instrument (CASI) in the Adult Changes in Thought study and who were followed biennially to identify incident dementia. MEASUREMENTS: Baseline measurements, including exercise frequency, cognitive function, physical function, depression, health conditions, lifestyle characteristics, and other potential risk factors for dementia (for example, apolipoprotein E epsilon4); biennial assessment for dementia. RESULTS: During a mean follow-up of 6.2 years (SD, 2.0), 158 participants developed dementia (107 developed Alzheimer disease). The incidence rate of dementia was 13.0 per 1000 person-years for participants who exercised 3 or more times per week compared with 19.7 per 1000 person-years for those who exercised fewer than 3 times per week. The age- and sex-adjusted hazard ratio of dementia was 0.62 (95% CI, 0.44 to 0.86; P = 0.004). The interaction between exercise and performance-based physical function was statistically significant (P = 0.013). The risk reduction associated with exercise was greater in those with lower performance levels. Similar results were observed in analyses restricted to participants with incident Alzheimer disease. LIMITATIONS: Exercise was measured by self-reported frequency. The study population had a relatively high proportion of regular exercisers at baseline. CONCLUSION: These results suggest that regular exercise is associated with a delay in onset of dementia and Alzheimer disease, further supporting its value for elderly persons.

Age of Onset↗

PubMed2006

A novel substitution at the translation initiator codon (ATG-->ATC) of the lipoprotein lipase gene is mainly responsible for lipoprotein lipase deficiency in a patient with severe hypertriglyceridemia and recurrent pancreatitis.

A patient with severe hypertriglyceridemia and recurrent pancreatitis was found to have significantly decreased lipoprotein lipase (LPL) activity and normal apolipoprotein C-II concentration in post-heparin plasma. DNA analysis of the LPL gene revealed two mutations, one of which was a novel homozygous G-->C substitution, resulting in the conversion of a translation initiation codon methionine to isoleucine (LPL-1). The second was the previously reported heterozygous substitution of glutamic acid at residue 242 with lysine (LPL-242). In vitro expression of both mutations separately or in combination demonstrated that LPL-1 had approximately 3% protein mass and 2% activity, whereas LPL-242 had undetectable activity but normal mass. The combined mutation LPL-1-242 exhibited similar changes as for LPL-1, with markedly reduced mass, and for LPL-242, with undetectable activity. These results suggest that the homozygous initiator codon mutation rather than the heterozygous LPL-242 alteration was mainly responsible for the patient phenotypes.

Adolescent↗

PubMed2006

Composite thin film by hydrogen-bonding assembly of polymer brush and poly(vinylpyrrolidone).

Based on hydrogen-bonding layer-by-layer (LBL) assembly in aqueous solution, poly(vinylpyrrolidone) (PVPON) and a spherical polymer brush with a poly(methylsilsesquioxane) (PSQ) core and poly(acrylic acid) (PAA) hair chains were used to fabricate composite multilayer thin films. Hydrogen bonding as the driving force was confirmed by FT-IR spectrometry. A simple method (Filmetric F20) was introduced to determine the thickness and refractive index of the films. The film thickness was found to be a linear function of the number of bilayers. The average increase in thickness per bilayer is 28.3 nm. The film morphology was characterized with scanning electron microscopy and atomic force microscopy. The images obtained from the two instruments show a great resemblance. The films were further calcined to get an inorganic film by removing the organic components, or treated with tetrabutylammonium fluoride (TBAF) to remove the PSQ core and get an organic film. The optical properties and morphological changes induced by these treatments were also studied.

Journal Article↗