Biomedical subjects

Y Luan

Publications and source records attributed to Y Luan.

10 recordsLinked to original sources

PubMed2004

Model-based methods for identifying periodically expressed genes based on time course microarray gene expression data.

MOTIVATION: The expressions of many genes associated with certain periodic biological and cell cycle processes such as circadian rhythm regulation are known to be rhythmic. Identification of the genes whose time course expressions are synchronized to certain periodic biological process may help to elucidate the molecular basis of many diseases, and these gene products may in turn represent drug targets relevant to those diseases. RESULTS: We propose in this paper a statistical framework based on a shape-invariant model together with a false discovery rate (FDR) procedure for identifying periodically expressed genes based on microarray time-course gene expression data and a set of known periodically expressed guide genes. We applied the proposed methods to the alpha-factor, cdc15 and cdc28 synchronized yeast cell cycle data sets and identified a total of 1010 cell-cycle-regulated genes at a FDR of 0.5% in at least one of the three data sets analyzed, including 89 (86%) of 104 known periodic transcripts. We also identified 344 and 201 circadian rhythmic genes in vivo in mouse heart and liver tissues with FDR of 10 and 2.5%, respectively. Our results also indicate that the shape-invariant model fits the data well and provides estimate of the common shape function and the relative phases for these periodically regulated genes.

Algorithms↗

PubMed2001

Quantitative determination of nitrendipine and its metabolite dehydronitrendipine in human plasma using liquid chromatography-tandem mass spectrometry.

A sensitive and high-throughput LC-MS-MS method was developed for simultaneous determination of nitrendipine (NIT) and its major metabolite, dehydronitrendipine (DNIT) in human plasma using nifedipine as the internal standard. Plasma samples were prepared based on a simple liquid-liquid extraction. The extracted samples were analyzed on a Zorbax SB C(18) column interfaced with a triple quadrupole tandem mass spectrometer. Positive atmospheric pressure chemical ionization was employed as the ionization source. The analytes were detected by use of selected reaction monitoring mode. Standard curves were linear (r > or = 0.995) over the concentration range of 0.4-40 ng/mL for NIT and 0.2-20 ng/mL for DNIT. The intra- and inter-run precision was measured to be below 8.5% for NIT and DNIT. The inter-run accuracy was less than 4% for the analytes. The overall extraction recoveries of NIT and DNIT were determined to be about 75% and 78% on average, respectively. The chromatographic run time was approximately 3 min. More than 120 samples could be assayed daily with this method, including sample preparation, data acquisition and processing. The method developed was successfully used to investigate plasma concentrations of NIT and DNIT in a pharmacokinetic study of volunteers who received NIT orally.

Antihypertensive Agents↗

PubMed2001

[Determination of amlodipine in human plasma by liquid chromatography-tandem mass spectrometry].

AIM: To develop a sensitive and specific LC/MS/MS method for determination of amlodipine in human plasma. METHODS: Amlodipine and internal standard 4'-hydroxypropafenone were extracted from plasma using liquid-liquid extraction, then separated on a Zorbax C8 column. The mobile phase consisted of acetonitrile-water-formic acid (75:35:1), at a flow-rate of 0.4 mL.min-1. A Finnigan TSQ tandem mass spectrometer equipped with electrospray ionization source was used as detector and was operated in the positive ion mode. Selected reaction monitoring (SRM) using the precursor-->product ion combinations of m/z 409-->238 and m/z 358-->116 was used to quantify amlodipine and internal standard, respectively. RESULTS: The linear calibration curves were obtained in the concentration range of 0.4-16.0 ng.mL-1. The limit of quantification was 0.4 ng.mL-1. Each plasma sample was chromatographed within 3.7 min. The method was successfully used in several pharmacokinetic studies for amlodipine. More than 1,500 plasma samples were assayed within two weeks. CONCLUSION: The method is proved to be suitable for clinical investigation of amlodipine pharmacokinetics, which offers advantages of specificity, speed, and greater sensitivity over the previously reported methods.

Amlodipine↗

PubMed2000

Confocal imaging and timing of secretion of matrix proteins by osteoblasts derived from avian long bone.

Primary osteoblasts derived from avian long bone have been evaluated in terms of spatial and temporal expression of known osteoblastic marker proteins during the early phases of cell culture. Confocal imaging of matrix proteins revealed that osteocalcin, bone sialoprotein, osteopontin, and osteonectin were restricted to the cell interior at day 4 of culture; secretion and deposition into the extra-cellular matrix of bone sialoprotein and osteopontin was evident at 8 and 12 days of culture. Osteocalcin and osteonectin were not deposited in the matrix within the timeframe of the study. Total collagen levels produced and alkaline phosphatase activity were substantial by day 4 of culture, and increased from that point 4.0- and 5.5-fold, respectively, by culture day 12. The expression of type I collagen, PTHrP receptor, osteopontin, bone sialoprotein and osteocalcin was followed by Northern blot analysis. Type I collagen and osteopontin mRNA were expressed at constant levels throughout the culture period. Over the 12 days of culture both PTH/PTHrP receptor and bone sialoprotein mRNA expression were found to increase by 2.3- and 2.5-fold, respectively. In contrast, the expression of osteocalcin message decreased by 2.5-fold by day 8 of culture.

Animals↗

PubMed1997

[Human papillomavirus type 16 E6 oncogene and expression of P53, RB and PCNA in human cervical carcinoma].

The aim of this study was to get some insights into the relationship between human papillomavirus type 16 E6 transforming gene and the expressed products of tumor suppressor gene, the P53, RB and proliferation cell nuclear antigen (PCNA) in human cervical carcinoma. 44 formalin-fixed paraffin-embedded cervical carcinoma sections were screened for P53, RB and PCNA by immunohistochemical assay with their monoclonal antibodies, and for the presence of HPV16 E6 ORF by in situ hybridization with HPV16 E6 DNA probe we have successfully labeled. The presence of HPV16 E6 gene was detected in 27 of 44 specimens (61.3%), including 8 of P53 protein positive (29.63%), 14 of RB protein positive (52.85%), and 20 of PCNA positive (74.07%). Of 17 HPV16 E6 negative cases, there were 7 of P53 protein positive (41.17%), 9 of RB protein positive (52.94%), 12 of PCNA positive (70.58%). There were no HPV16 E6 gene in control group. In positive cases PCNA only expressed in base cells. Our date indicated that HPV16 E6 ORF and PCNA had significantly related to cervical carcinoma. We could not find the relationship between HPV16 E6 ORF and P53, RB, PCNA in cervical carcinoma. There were some HPV16 E6-positive cases, obviously with strong P53, RB immunostaining in cytoplasm but not in nuclei, PCNA immunostaining was strong at the edge of the cervical carcinoma cells than in nuclear of them.

Carcinoma↗

PubMed1996

Basic fibroblast growth factor: an autocrine growth factor for epiphyseal growth plate chondrocytes.

Basic fibroblast growth factor (bFGF) is a permissive mitogen for cultured chondrocytes and has been localized in the specific zones of the epiphyseal growth plate. In this study, we demonstrate that bFGF present in cartilage originates from within the cellular constituents of this tissue. Utilizing reverse transcription coupled to the polymerase chain reaction (PCR), bFGF mRNA was found in extracts of cartilage tissue. Immunocytochemical studies revealed that bFGF was present intracellularly in freshly isolated proliferative chondrocytes and in the extracellular matrix (ECM) after 24 h of culture. Western blot analysis of protein extracts from isolated proliferative chondrocytes identified a bFGF immunoreactive species with a molecular weight of approximately 18 kDa. In situ hybridization confirmed the presence of bFGF mRNA in freshly isolated proliferative chondrocytes. The bFGF in the ECM seemed to be sequestered and not available for biological activity, since these cells still required exogenous bFGF for cell proliferation. This sequestered bFGF could be released to stimulate cell proliferation when cultures were treated with plasmin, a proteolytic enzyme. These data support the hypothesis that bFGF is synthesized by chondrocytes and functions as an autocrine/paracrine mitogen via its deposition into the ECM with subsequent release from the ECM of cartilage being a critical step in biological activity. In addition, the study provides further evidence that locally produced bFGF plays an important role in normal growth and development of cartilage tissue.

Animals↗

PubMed1992

[Study on variation of plasma gamma-aminobutyric acid concentration in rat model of hepatic encephalopathy due to fulminant hepatic failure].

The plasma gamma-aminobutyric acid (GABA) concentration was measured by a radio-receptor assay in rat model of hepatic encephalopathy due to fulminant hepatic failure (FHF) induced by intraperitoneal injection of D-galactosamine (GalN). The results showed that, in FHF group, the plasma GABA increased parallelly with the degree of hepatic encephalopathy after GalN i.p. (r = 0.944, P less than 0.05). In about 48 h, mean plasma GABA concentration was elevated nearly 8-fold. These findings suggest that, in liver failure, elevated plasma GABA concentration may play a role in the pathogenesis of hepatic encephalopathy.

Animals↗

PubMed1990

[Reconstitution of rabbit brain GABA binding protein (receptor) on Xenopus oocytes].

Gurdon's Xenopus laevis oocyte translation system has been extensively employed to investigate the molecular biology of gamma-aminobutyric acid (GABA) receptors in the brains of embryonic chick, rat, etc. As GABA and its receptor may play a role in the pathogenesis of hepatic encephalopathy and a rabbit model of fulminant hepatitis has been established, we reconstituted the rabbit model of fulminant hepatitis has been established, we reconstituted the rabbit brain GABA binding protein (receptor) on Xenopus laevis oocytes to offer a base for further study of the pathological effects of GABA receptor at molecular level. In this report, total RNA was extracted from rabbit brain by guanidine hydrochloride method. The total RNA was then subjected to oligo-(dT)-cellulose affinity chromatography to isolate mRNA. All the RNA samples achieved a high purity with an average OD260/OD280 ratio of about 2.10. The clear bands of 18 S and 28S rRNA in electrophoresis implied that the RNA was not degraded and was therefore available for expression. After two days of incubation of the oocytes injected with mRNA, radioreceptor assay indicated that saturable and specifically displaceable GABA binding sites were implanted onto the oocyte membrane. This result led us to the conclusion that rabbit brain GABA binding protein (receptor) can be reconstituted by injecting exogenous mRNA inclusive of those encoding the receptor into Xenopus oocytes. However, the functional activity of the reconstituted receptor as a GABA gated chloride ion channel needs to be further characterized by patch clamping.

Animals↗

PubMed1990

[QSAR studies on the anticonvulsant activity of 5-substitutedphenyl-1-hydro- and 1-propyl-3-pyrazolidinones].

The chemical structure and anticonvulsant activity relationship of some 5-substituted phenyl-3-pyrazolidinone derivatives were studied. Six pairs (1-hydro and 1-propyl substituted) of compounds were designed and synthesized according to the Topliss improved method, and a compound with the highest anticonvulsant activity was found, i.e. 5-(4-fluorophenyl)-1-propyl-3-pyrazolidinone, ED50 14.7 mg/kg (MES Test). QSAR analysis showed that the hydrophobic constant sigma pi greatly influenced their anticonvulsant activity, and the steric parameter (B4) and electronic parameter (I x 10(2] of the substitutions on the phenyl ring can improve the correlation coefficient (r). Smaller steric volume and more powerful electron withdrawing effect of the substitution on the 5-phenyl ring increased the anticonvulsant activity.

Animals↗

PubMed1987

Yeast calmodulin: structural and functional differences compared with vertebrate calmodulin.

Calmodulin of the baker's yeast (Saccharomyces cerevisiae) showed a similar affinity for Ca2+ to that of vertebrate calmodulin. The maximum binding number of Ca2+ to yeast calmodulin was, however, 3 mol/mol, which is lower than that of vertebrate calmodulin (4 mol/mol). The same maximum activity of porcine brain phosphodiesterase was attained when 100 times higher concentration of yeast calmodulin than that of vertebrate calmodulin was added. On the other hand, the maximum activation of chicken gizzard myosin light chain kinase was attained with 1,000 times higher concentration of yeast calmodulin than that of vertebrate calmodulin, and the maximum activity with yeast calmodulin was less than 1/5 of that with vertebrate calmodulin. Several amino acid substitutions observed in the yeast calmodulin, particularly at the alpha-helical rod connecting the two globular domains, may affect the interaction mode of various target enzymes with this calmodulin.

3',5'-Cyclic-AMP Phosphodiesterases↗