Biomedical subjects

Wei Liang

Publications and source records attributed to Wei Liang.

39 records · Page 3Linked to original sources

PubMed2003

[Seasonal variations of soil microbial biomass, respiration rate and CH4 emission in black earth rice fields].

The measurements of soil microbial biomass C, respiration rate and CH4 emissions during one rice growth period in black earth rice fields showed that the soil microbial biomass C and respiration rate were depressed significantly by the application of slow-releasing urea at the early stage of rice growth period (P < 0.05), but almost not affected by intermittent irrigation. The CH4 emission was decreased by 32.5% in the intermittent irrigation treatments, but not significantly affected by the application of slow-releasing urea, compared to the control. It was significantly related to soil microbial biomass C in slow-releasing urea treatments.

Biomass↗

PubMed2002

Within the fold: assessing differential expression measures and reproducibility in microarray assays.

BACKGROUND: 'Fold-change' cutoffs have been widely used in microarray assays to identify genes that are differentially expressed between query and reference samples. More accurate measures of differential expression and effective data-normalization strategies are required to identify high-confidence sets of genes with biologically meaningful changes in transcription. Further, the analysis of a large number of expression profiles is facilitated by a common reference sample, the construction of which must be carefully addressed. RESULTS: We carried out a series of 'self-self' hybridizations in which aliquots of the same RNA sample were labeled separately with Cy3 and Cy5 fluorescent dyes and co-hybridized to the same microarray. From this, we can analyze the intensity-dependent behavior of microarray data, define a statistically significant measure of differential expression that exploits the structure of the fluorescent signals, and measure the inherent reproducibility of the technique. We also devised a simple procedure for identifying and eliminating low-quality data for replicates within and between slides. We examine the properties required of a universal reference RNA sample and show how pooling a small number of samples with a diverse representation of expressed genes can outperform more complex mixtures as a reference sample. CONCLUSION: Analysis of cell-line samples can identify systematic structure in measured gene-expression levels. A general procedure for analyzing cDNA microarray data is proposed and validated. We show that pooled reference samples should be based not only on the expression of individual genes in each cell line but also on the expression levels of genes within cell lines.

Brain Neoplasms↗

PubMed2002

Solubilization of drugs by physiological mixtures of bile salts.

PURPOSE: The solubilization of a number of steroids was determined in bile salt simple micelles and a bile salt/phospholipid micellar system to provide a better basis to predict the extent of drug solubilization in vivo. METHODS: Excess solid drug was dispersed in taurodeoxycholate or mixed micelle solutions prepared with fixed mole ratios of taurocholate, taurodeoxycholate, taurochenodeoxycholate, glycodeoxycholate, glycocholate, and glycochenodeoxycholate with egg phosphatidylcholine. Drug concentrations were determined from the absorbance following centrifugation. Using NMR spectroscopy, the diffusivities of the simple and mixed micelles were 2 x 10(-6) and 8 x 10(-7) cm2/s, respectively. RESULTS: From the change in the concentration of drug in solution with a change in the lipid concentration, the solubilization ratio (SR) was calculated. The SR and aqueous solubility were used to calculate the micelle/aqueous partition coefficients (Km/w). Km/w was correlated with octanol/water partition (Po/w) for the TDC and mixed micelle data sets with correlation lines of logKm/w = 0.74logPo/w + 1.55 (r2 = 0.91) and logKm/w = 0.61 logPo/w + 2.44 (r2 = 0.95), respectively. CONCLUSIONS: With such data, a refined, predictive relationship between the in vitro and the in vivo solubilization with additional information concerning the bile salt/lipid concentration in the human intestine appears possible.

Bile Acids and Salts↗