Biomedical subjects

Liwei Wang

Publications and source records attributed to Liwei Wang.

43 records · Page 3Linked to original sources

PubMed2003

Genome-wide search for loss of heterozygosity in Chinese patients with sporadic colorectal cancer.

In an attempt to integrally investigate the loss of tumor suppressor genes and search for putative suppressor loci associated with tumor occurrence and progression, we conducted a genome-wide loss of hetero zygosity (LOH) study of 83 tumor samples obtained from Chinese patients with sporadic colorectal cancer. We employed 400 fluorescence-labeled microsatellite marker primers to amplify the corresponding loci of the genomic DNA and then electrophoresed the polymerase chain reaction products and analyzed the fluorescent signals. The LOH frequencies were high (>35%) but were not associated with the tumor stage and progression in 20 loci, including the regions where TP53, E-cadherin, deleted in colorectal carcinoma (DCC), phosphatase and tensin homolog deleted on chromosome 10 (PTEN), mothers against decapentaplegic, Drosophila, homolog of 2 (MADH2) and mothers against decapentaplegic, Drosophila, homolog of 4 (MADH4) reside. Loss of other loci, including two narrow regions on chromosome 2, was found to relate to the tumor stage, suggesting that this genomic instability may contribute to tumor progression.

Adult↗

PubMed2002

Regulatory volume decrease is actively modulated during the cell cycle.

Nasopharyngeal carcinoma cells, CNE-2Z, when swollen by 47% hypotonic solution, exhibited a regulatory volume decrease (RVD). The RVD was inhibited by extracellular applications of the chloride channel blockers tamoxifen (30 microM; 61% inhibition), 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, 100 microM; 60% inhibition), and ATP (10 mM; 91% inhibition). The level and time constant of RVD varied greatly between cells. Most cells conducted an incomplete RVD, but a few had the ability to recover their volume completely. There was no obvious correlation between cell volume and RVD capacity. Flow cytometric analysis showed that highly synchronous cells were obtained by the mitotic shake-off technique and that the cells progressed through the cell cycle synchronously when incubated in culture medium. Combined application of DNA synthesis inhibitors, thymidine and hydroxyurea arrested cells at the G1/S boundary and 87% of the cells reached S phase 4 h after being released. RVD capacity changed significantly during the cell cycle progression in cells synchronized by shake-off technique. RVD capacity being at its highest in G1 phase and lowest in S phase. The RVD capacity in G1 (shake-off cells sampled after 4 h of incubation), S (obtained by chemical arrest), and M cells (selected under microscope) was 73, 33, and 58%, respectively, and the time constants were 435, 769, and 2,000 sec, respectively. We conclude that RVD capacity is actively modulated in the cell cycle and RVD may play an important role in cell cycle progress.

Adenosine Triphosphate↗

PubMed2002

The correlation between physiological and psychological responses to odour stimulation in human subjects.

OBJECTIVES: To correlate physiological and psychological responses to odour stimulation. METHODS: Olfactory event-related potentials (OERP) were recorded from human subjects in response to different odour pulse protocols. Pulse duration and interstimulus interval (ISI) were varied while the subjects recorded pulse detection by a button press. RESULTS: There was a correlation between odour strength and OERP. The amplitude of the OERP (peak positive-peak negative) declined by 48% with repetitive stimulation for all stimulus strengths. The time constant for this decline (adaptation) was concentration dependent and varied from 10 to 4 s for increasing odorant strength (from 35 to 200 ms pulse of saturated amyl acetate vapour diluted 1:3 at 3 l min(-1) at 24 degrees C). The psychometric test score (cognitive odour perception) was also concentration dependent and increased with increasing stimulus strength at all ISIs except the lowest value; 2.5 s. At this ISI adaptation/habituation interfered with the dose-response. The decline of the psychometric test score with increasing stimulus frequency (decreasing ISI) was more rapid (tau approximately 2.5 s) than that of the OERP. The psychometric test score declined to zero at a constant rate and was not dependent upon stimulus strength. CONCLUSIONS: Continuous olfactory stimulation results in a shut-down of cognitive perception with a time constant of around 2.5 s while the response of the physiological system (receptors, transduction and relay system) declines by about 50% with a slower time course (> or = 4 s). This former process defines habituation in the olfactory system while the latter describes adaptation. Since the adaptation process is concentration dependent the rate of adaptation contains information about odour strength, thus both the amplitude of the OERP and the rate of adaptation could encode stimulus strength.

Adaptation, Physiological↗

PubMed2002

Cell cycle-dependent expression of volume-activated chloride currents in nasopharyngeal carcinoma cells.

Patch-clamping and cell image analysis techniques were used to study the expression of the volume-activated Cl(-) current, I(Cl(vol)), and regulatory volume decrease (RVD) capacity in the cell cycle in nasopharyngeal carcinoma cells (CNE-2Z). Hypotonic challenge caused CNE-2Z cells to swell and activated a Cl(-) current with a linear conductance, negligible time-dependent inactivation, and a reversal potential close to the Cl(-) equilibrium potential. The sequence of anion permeability was I(-) > Br(-) > Cl(-) > gluconate. The Cl(-) channel blockers tamoxifen, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), and ATP inhibited I(Cl(vol)). Synchronous cultures of cells were obtained by the mitotic shake-off technique and by a double chemical-block (thymidine and hydroxyurea) technique. The expression of I(Cl(vol)) was cell cycle dependent, being high in G(1) phase, downregulated in S phase, but increasing again in M phase. Hypotonic solution activated RVD, which was cell cycle dependent and inhibited by the Cl(-) channel blockers NPPB, tamoxifen, and ATP. The expression of I(Cl(vol)) was closely correlated with the RVD capacity in the cell cycle, suggesting a functional relationship. Inhibition of I(Cl(vol)) by NPPB (100 microM) arrested cells in G(0)/G(1). The data also suggest that expression of I(Cl(vol)) and RVD capacity are actively modulated during the cell cycle. The volume-activated Cl(-) current associated with RVD may therefore play an important role during the cell cycle progress.

Adenosine Triphosphate↗

PubMed2002

Crystallization and preliminary X-ray diffraction analysis of FKBP12 complexed with a novel neurotrophic ligand.

A novel neurotrophic ligand, (3R)-4-(p-Toluenesulfonyl)-1,4-thiazane-3-carboxylic acid-L-Leucine ethyl ester, has been complexed with FKBP12 and crystallized using the hanging-drop vapor-diffusion method. Crystals belong to P2(1) space group, with unit cell parameters a=41.2, b=29.6, c=41.5 A, beta=114.0 degrees. The crystals diffract to 1.8 A resolution limit.

Crystallography, X-Ray↗

PubMed2002

[The distributive features of three kinds of metabolic genes polymorphisms in population of Han nationality in south area of China].

OBJECTIVE: To find out the distributive features of some metabolic genes polymorphisms in Han population of south area of China. METHODS: Study population was obtained from the controls of a community based case-control study, which included 290 blood relatives (inner control) and 404 non-blood relatives (outer control). RESULTS: Frequencies of CYP1A1, GSTM1 and GSTT1 polymorphisms had no significant difference among confounding factors, such as sex, living areas, stomach cancer family history and history of tobacco smoking etc. Some controls showed significant difference in age group and alcohol drinking which would be adjusted in analysis of the relationship between polymorphisms and cancers. CYP1A1 Ile/Val and Val/Val genotypes were 33.43% and 5.62% respectively, which were similar to other results from Chinese and Japanese, but higher than those from Caucasians in American, Europe and African-Americans. GSTM1 null allele frequency was 53.48% in our population, which showed difference even among Chinese in different areas. GSTT1 null allele frequency was 45.78%, which was significantly higher than that in Caucasians and African-American. CONCLUSION: The frequencies of CYP1A1 Ile/Val, Val/Val and GSTT1 null in Han population in south area of China are significantly higher than those in other races, while the ethnic difference of frequency of GSTM1 null is less.

China↗

PubMed2002

[Study on the Relationship between susceptibility of stomach neoplasm cancer and polymorphism of inducible nitric oxide synthase gene].

OBJECTIVE: To study the relationship between polymorphism of inducible Nitric Oxide Synthase (iNOS) gene and the susceptibility of intestinal type stomach cancer and stomach cardia cancer in Chinese people. METHODS: A community-based case-control study was designed. Ninety-three intestinal type of stomach cancer and 50 stomach cardia cancer patients with endoscopy and pathology diagnosis were identified as cases. Two hundred and forty-six controls served as controls. RESULTS: C-->T polymorphism was found in exon 16 of iNOS gene, which changed the coding amino acid from serine to leucine, and formed a recognition site identified by Tsp 509 I restriction enzyme (we called it C-->T polymorphism). The T allele gene frequency in the control group was 13.21%. No statistically significant difference was found between C-->T polymorphism alone and the increased susceptibility to intestinal stomach cancer or stomach cardia cancer. A significant type 2 multiplicative interaction was found in increasing both the risk of intestinal stomach cancer and stomach cardia cancer when both C-->T polymorphism and tobacco smoking exposure existed. An additive interaction model, which showed statistically significant difference, was found to increase only the risk of stomach cardia cancer when CagA antibody shared negative but C-->T polymorphism occurred. CONCLUSION: C-->T polymorphism of iNOS gene was considered as one of the possible susceptible genes, which specifically increased the risk of tobacco-related but CagA negative types of intestinal stomach cancer and stomach cardia cancer.

Antibodies, Bacterial↗