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Biomedical subjects

L Ye

Publications and source records attributed to L Ye.

At least 19 recordsLinked to original sources
PubMed2006

Spatial analysis for spring bloom and nutrient limitation in Xiangxi bay of three Gorges Reservoir.

The spatial and temporal dynamics of physical variables, inorganic nutrients and phytoplankton chlorophyll a were investigated in Xiangxi Bay from 23 Feb. to 28 Apr. every six days, including one daily sampling site and one bidaily sampling site. The concentrations of nutrient variables showed ranges of 0.02-3.20 mg/L for dissolved silicate (Si); 0.06-2.40 mg/L for DIN (NH(4)N + NO(2)N + NO(3)N); 0.03-0.56 mg/L for PO(4)P and 0.22-193.37 microg/L for chlorophyll a, respectively. The concentration of chlorophyll a and inorganic nutrients were interpolated using GIS techniques. The results indicated that the spring bloom was occurred twice in space during the whole monitoring period (The first one: 26 Feb.-23 Mar.; the second one: 23 Mar.-28 Apr.). The concentration of DIN was always high in the mouth of Xiangxi Bay, and PO(4)P was high in the upstream of Xiangxi Bay during the whole bloom period. Si seems no obvious difference in space in the beginning of the spring bloom, but showed high heterogeneity in space and time with the development of spring bloom. By comparing the interpolated maps of chlorophyll a and inorganic variables, obvious consumptions of Si and DIN were found when the bloom status was serious. However, no obvious depletion of PO(4)P was found. Spatial regression analysis could explained most variation of Chl-a except at the begin of the first and second bloom. The result indicated that Si was the factor limiting Chl-a in space before achieved the max area of hypertrophic in the first and second bloom period. When Si was obviously exhausted, DIN became the factor limiting the Chl-a in space. Daily and bidaily monitoring of Site A and B, representing for high DIN: PO(4)P ratio and low DIN:PO(4)P ratio, indicated that the concentration of Si was decreased with times at both site A and B, and the dramatically drop of DIN was found in the end monitoring at site B. Multiple stepwise regression analysis indicated that Si was the most important factor affect the development of spring bloom both at site A and B in time series.

China↗
PubMed2006

Six cases of ectopic ACTH syndrome caused by thymic carcinoid.

The ectopic ACTH syndrome (EAS) caused by thymic carcinoid is rare and its diagnosis remains a challenge to the endocrinologist. Here are six cases of EAS with a typical Cushing habitus accompanied by hyperpigmentation and hypokalemia. For all six patients, the high dose (8 mg) dexamethasone suppression test (HDDST) showed lack of suppression, computed tomography (CT) scanning documented anterior mediastinal masses, and the mediastenal tumors removed were confirmed as ACTH secreting thymic carcinoids by positive ACTH and NSE staining. Our data indicate that HDDST chest radiologic imaging and other laboratory examinations will greatly assist in diagnosing the thymic carcinoid-induced EAS at an earlier stage, which will significantly improve the long-term survival of the patient.

ACTH Syndrome, Ectopic↗
PubMed2006

Amelogenins in human developing and mature dental pulp.

Amelogenins are a group of heterogenous proteins first identified in developing tooth enamel and reported to be present in odontoblasts. The objective of this study was to elucidate the expression and function of amelogenins in the human dentin-pulp complex. Developing human tooth buds were immunostained for amelogenin, and mRNA was detected by in situ hybridization. The effects of recombinant amelogenins on pulp and papilla cell proliferation were measured by Brd U immunoassay, and differentiation was monitored by alkaline phosphatase expression. Amelogenin protein was found in the forming dentin matrix, and amelogenin mRNA was localized in the dentin, presumably in the odontoblast processes. Proliferation of papilla cells was enhanced by recombinant human amelogenin rH72 (LRAP+ exon 4), while pulp cells responded to both rH72 and rH58 (LRAP), with no effect by rH174. These studies suggest that odontoblasts actively synthesize and secrete amelogenin protein during human tooth development, and that low-molecular-weight amelogenins can enhance pulp cell proliferation.

Alternative Splicing↗
PubMed2006

Achieving biological nitrogen removal via nitrite by salt inhibition.

The principal aim of this paper is to develop and evaluate an approach to obtain nitrogen removal bypassing nitrate. The method is based on the addition of sodium chloride (NaCI), selective inhibitor of nitrite oxidizers, to influent. Validation of the new method was conducted on laboratory-scale experiments applying the SBR activated sludge process to domestic wastewater with low C/N ratio. With the aerobic-anoxic sequence, three parallel SBRs achieving complete nitrification-denitrification are dosed by a certain concentration of NaCI to influent. The high nitrite accumulation, depending on the salinity in the influent and the application duration of salt, was obtained in SBRs treating saline wastewater. Optimum dosage and application duration of salt, which interact to determine the performance and stabilization of nitrite accumulation, were determined by experiment. In order to evaluate the method, the response of the biological treatment system to salt concentration was also explored. The repeatability of the method was further verified under various operational conditions. Microbial population tests supported the presumption that nitrite oxidizers are inhibited by salt addition and washed out of the system. The presented method is valuable to offer a solution to realize nitrogen removal via nitrite under normal conditions.

Bacteria↗
PubMed2005

Establishment of stable HeLa cell lines expressing enzymatically active hepatitis C virus RNA polymerase.

The hepatitis C virus RNA polymerase (NS5B) is strictly required for viral replication and thus represents an attractive target for antiviral drug development. In this study, stable HeLa cell lines with an integrated NS5B gene were selected by G418 and then confirmed by genome PCR. Subsequently, transcription and expression of the integrated NS5B genes were demonstrated by RT-PCR and Western blot analysis. Further analysis demonstrated enzymatic activity of the expressed NS5B polymerase. The stable HeLa cell lines should be useful for the identification of NS5B inhibitors and for studying the mechanisms of HCV replication.

Gene Expression↗
PubMed2005

Two cis-acting elements in negative RNA strand of Hepatitis C virus involved in synthesis of positive RNA strand in vitro.

Sequences at the 3'-ends of both positive and negative strands of Hepatitis C virus (HCV) RNA harbor cis-acting elements required for RNA replication. However, little is known about the properties of the negative RNA strand as a template for the synthesis of positive RNA strand. In this study, a purified recombinant HCV RNA-dependent RNA polymerase (RdRp) was used to investigate the synthesis of positive RNA strand using the 3'-terminal region of negative RNA strand ((-)3'T RNA) as template. A mutagenesis analysis was performed to evaluate the role of the 3'-proximal stem-loop and the first 3'-cytidylate (3'C) of the negative RNA strand in the synthesis of the positive RNA strand. A negative RNA strand of wild type (wt) HCV as template was able to direct the synthesis of a full-length positive RNA strand. Deletion of the 3'-proximal stem-loop resulted in an approximately 90% decrease in RNA synthesis. Disruption of the 3'-proximal stem-loop structure by nucleotide substitutions led to a 70-80% decrease in RNA synthesis. However, the restoration of the stem-loop by compensatory mutations in the stem region restored also the RNA synthesis. Likewise, the deletion or substitution of the first 3'C by guanylate (G) led to a 90% decrease in the RNA synthesis; while the substitution by adenylate (A) or uridylate (U) resulted in a 60-80% decrease in the RNA synthesis only. These findings demonstrate that the 3'-proximal stem-loop and the first 3'C of the negative RNA strand of HCV are two cis-acting elements involved in the synthesis of the positive RNA strand.

3' Untranslated Regions↗
PubMed2003

Epitope mapping and specificity of the anti-alpha-synuclein monoclonal antibody Syn-1 in mouse brain and cultured cell lines.

While alpha- and beta-synuclein largely overlap in their expression in the vertebrate brain, only alpha-synuclein accumulates in the fibrillar aggregates typical of Parkinson's disease. It is thus critical to have immunological reagents that distinguish between these two protein isoforms. The monoclonal antibody Syn-1 (Transduction Labs) has been frequently used for the specific detection of alpha-synuclein. In this report, the epitope for Syn-1 is localized within residues 91-99 of human alpha-synuclein. Sequence differences exist in this domain that account for the specificity of Syn-1 for alpha- versus beta-synuclein. However, Syn-1 also displays reactivity with additional species (approximately 45 kDa) in brain homogenates from both wild-type and alpha-synuclein null mice, indicating a potential for cross-reactivity with a protein species that is unrelated to alpha-synuclein in brain tissue or extracts.

Animals↗
PubMed2003

The Dentin matrix protein 1 (Dmp1) is specifically expressed in mineralized, but not soft, tissues during development.

Dentin Matrix Protein 1 (Dmp1) was originally identified from dentin. However, its expression and function in vivo are not clear. To clarify these two issues, we have generated mice carrying a truncated Dmp1 gene by using gene targeting to replace exon 6 with a lacZ gene. Northern blot analysis shows the expected 5.8-kb Dmp1-lacZ fusion transcript and loss of the wild-type 2.8-kb Dmp1 transcript, confirmed by a lack of immunostaining for the protein. Using heterozygous animals, we demonstrate that Dmp1 is specific for mineralized tissues. Not previously shown, Dmp1 is also expressed in pulp cells. Dmp1-deficient embryos and newborns display no apparent gross abnormal phenotype, although there are a modest expansion of the hypertrophic chondrocyte zone and a modest increase in the long bone diameter. This suggests that DMP1 is not essential for early mouse skeletal or dental development.

Animals↗
PubMed2002

Establishment of a hepatocellular carcinoma cell line with unique metastatic characteristics through in vivo selection and screening for metastasis-related genes through cDNA microarray.

PURPOSE: To establish a hepatocellular carcinoma (HCC) cell line from lung metastatic lesions of human HCC in nude mice so as to provide a suitable model for the study of lung-metastasis-related molecular mechanisms. METHODS: HCC clone cells MHCC97-H were inoculated into BALB/c nude mice, and the pulmonary metastatic lesions were harvested and re-implanted into nude mice for the second round of in vivo selection. The same procedure was repeated twice. A new cell line from the third round of lung metastases was established. RESULTS: A human HCC cell line with unique metastatic characteristics was established by in vivo selection. This cell line, designated as HCCLM3, was polygonal epithelial cell with hypotriploid karyotype and population doubling time of 34.9 h. The cells were positive for alpha fetoprotein (AFP), albumin, cytokeratin 8 (CK8), and negative for hepatitis B surface antigen (HBsAg) by immunocytochemistry. Fluorescence polymerase chain reaction (PCR) showed HBV DNA integration in the cellular genome. When 5 x 10(6) cells were injected subcutaneously into nude mice, tumorigenicity was 100%, with a latency period of 11+/-1 days. Five weeks after s.c. injection, the pulmonary metastatic rate was 100%, the median number of lung metastases being 121 per mouse. After orthotopic implantation of tumor tissue into nude mouse liver for 35 days, widespread loco-regional and distant metastases occurred, with 100% abdominal wall metastases, 80% intra-abdominal cavity metastases, 100% intrahepatic metastases, 70% diaphragm metastases, and 100% pulmonary metastases. The median number of lung metastatic lesions was 268 per mouse. Gene expression profile of HCCLM3 was compared by cDNA microarray with MHCC97-L, a clonal cell strain from the same parental cell line but with low metastatic potential; 25 differentially expressed genes were identified, 18 of which showed decreased expression and seven increased expression in HCCLM3, including the decreased expression of cell cycle control gene Rb2, mismatch repair gene hMSH2, and signal transduction gene protein kinase C beta2, and increased expression of signal transduction gene MAP kinase, kinase 6. CONCLUSIONS: A new HCC cell line characterized by high pulmonary metastases via s.c. and orthotopic inoculation was established, which provides a new model for the study of liver cancer metastasis. Its gene expression profile could help in the understanding of the mechanism of metastasis and provide potential targets for anti-metastasis intervention.

Animals↗
PubMed2001

[Expression of type I and type II 5alpha-reductase isoenzymes in prostate cancer tissues].

OBJECTIVE: To study the relative tissue distribution and expression pattern of type I and type type II 5alpha-reductase isozymes in prostate cancer tissues. METHODS: Immunohistochemistry and RT-PCR method were used to investigate qualitatively and semi-quantitatively the expression of type I and type II 5alpha-reductases in prostate tissues from 15 normal persons and 15 patients with prostate cancer. RESULTS: Two isozymes were detected in both normal and cancerous prostate tissues with the two methods. Both 5alpha-reductases were mainly localized in the cytoplasm, and higher degree of staining was observed in epithelial cells than in stroma. Significantly higher level of type I 5alpha-reduetase expression was observed in cancerous tissue than in normal tissue. The expression level of type I 5alpha-reduetase was positively correlated with the tumor stage and grade, and serum PSA concentration. The expression of type II 5alpha-reductase was very weak in prostate cancer tissue. CONCLUSION: The type I 5alpha-reductase, not type II, is involved in the pathogenesis of protate cancer. Selective type I 5alpha-reductase inhibitors or dual inhibitors of both type human 5alpha-reductase isoforms can be used in the treatment of prostate cancer.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2001

Expression and activity of the Hxt7 high-affinity hexose transporter of Saccharomyces cerevisiae.

High-affinity hexose transport is required for efficient utilization of low hexose concentrations by the baker's yeast Saccharomyces cerevisiae. These low concentrations occur during the late exponential phase of batch growth on hexoses, during hexose-limited chemostat or fed-batch culture, or during growth on sugars such as sucrose and raffinose that are hydrolysed to hexoses outside the cell. The expression of the Hxt7 high-affinity glucose transporter of S. cerevisiae was examined during batch growth on glucose medium in a wild-type strain and a strain expressing only HXT7 (i.e. with null mutations in HXT1-HXT6). In the wild-type strain, HXT7 transcription was repressed at high glucose and was detected when the glucose in the culture approached depletion. In the HXT7-only strain, transcription of HXT7 was constitutive throughout the glucose growth phase and was increased further at low glucose concentrations. After glucose depletion, the levels of HXT7 mRNA declined rapidly in both strains. In contrast, the Hxt7 protein was relatively stable after glucose depletion. By monitoring the subcellular localization of an Hxt7::GFP fusion protein it was observed that Hxt7 was localized in the plasma membrane, even when expressed at high glucose concentrations in the HXT7-only strain. After glucose depletion Hxt7 was gradually endocytosed and targeted to the vacuole for degradation. The Hxt7::GFP fusion protein was a fully functional hexose transporter with a catalytic centre activity of approximately 200/sec. It is concluded that repression of HXT7 and degradation of Hxt7 at high glucose concentrations is dependent on a high glucose transport capacity.

Culture Media↗
PubMed2001

Development of a flow injection capillary chemiluminescent ELISA using an imprinted polymer instead of the antibody.

A flow injection competitive assay analogous to enzyme immunoassays has been developed using a molecularly imprinted polymer instead of the antibody. A glass capillary was modified by covalently attaching an imprinted polymer to the inner capillary wall. The herbicide 2,4-dichlorophenoxyacetic acid was used as a model analyte. The analyte was labeled with tobacco peroxidase, and chemiluminescence was used for detection in combination with a photomultiplier tube or a CCD camera. In a competitive mode, the analyte-peroxidase conjugate was passed together with the free analyte through the polymer-coated capillary mounted in a flow system. After a washing step, the chemiluminescent substrate was injected and the bound fraction of the conjugate was quantified by measuring the intensity of the emitted light. Calibration curves corresponding to analyte concentrations ranging from 0.5 ng mL(-1) to 50 microg mL(-1) (2.25 nM-225 microM) were obtained. A lowered detection limit by 2 orders of magnitude was obtained when detection was done in discontinuous mode and the chemiluminescence light was conducted inside the photomultiplier tube by an optical fiber bundle, thus yielding a dynamic range of 5 pg mL(-1)-100 ng mL(-1) (22.5 pM-450 nM).

2,4-Dichlorophenoxyacetic Acid↗
PubMed2001

Helix proximity in OxlT, the oalate:formate antiporter of oxalobacter formigenes. Cross-linking between TM2 and TM11.

Experiments were designed to evaluate the proximity of transmembrane helices two (TM2) and eleven (TM11) in the tertiary structure of OxlT, the oxalate:formate exchange transporter of Oxalobacter formigenes. A tandem duplication of the Factor Xa protease cleavage site (IEGRIEGR) was inserted into the central cytoplasmic loop of an OxlT cysteine-less derivative in which an endogenous cleavage site had been eliminated by mutagenesis (R248Q). Using this host, double cysteine derivatives were constructed so as to pair one of seventeen positions in TM2 with one of four positions in TM11. Following treatment of membrane vesicles with Cu(II)(1,10-phenanthroline)(3), molecular iodine, or N,N'-o-phenylenedimaleimide, samples were exposed to Factor Xa, and disulfide bond formation was assessed after SDS-polyacrylamide gel electrophoresis by staining with antibody directed against the OxlT C terminus. In the absence of disulfide bond formation, exposure to Factor Xa revealed the expected C-terminal 22-kDa fragment, a result unaffected by the presence of reductant. By contrast, after disulfide formation, OxlT mobility remained at 35 kDa, and appearance of the 22-kDa fragment required addition of 200 mm dithiothreitol prior to electrophoresis. The four TM11 positions chosen for cysteine substitution lie on a helical face known to interact with substrate. Similarly, TM2 positions supporting disulfide trapping were also confined to a single helical face. We conclude that TM2 and TM11 are in close juxtaposition to one another in the tertiary structure of OxlT.

Bacterial Proteins↗
PubMed2001

Long-term potentiation in hippocampus of rats is enhanced by endogenous acetylcholine in a way that is independent of N-methyl-D-aspartate receptors.

By using extracellular recordings of field potential, the exact pathway by which the endogenous ACh influencing the induction of long-term potentiation (LTP) in CA1 area was analysed in slices of rat hippocampus. The results showed that: (1) the application of (-) huperzine A, an AChE inhibitor extracted from Chinese herb Qian Ceng Ta (Huperzia Serrata), could enhance the induction of LTP, while this drug showed little effect on the second components of multiple population spikes that were recorded in Mg(2+)-free medium and had proven to be N-methyl-D-aspartate (NMDA) receptor-mediated response; and (2) scopolamine, a muscarinic receptor antagonist, could significantly suppressed the induction of LTP, while most of the suppressive effect of scopolamine was blocked when slices were pretreated by bicuculline, a gamma-aminobutyric acid (GABA(A)) receptor antagonist. These results suggest that endogenous ACh potentiates the induction of LTP through the inhibition of GABAergic interneurons that modulate pyramidal neurons, but not through the activation of NMDA receptors located on pyramidal neurons.

Acetylcholine↗
PubMed2001

Chemiluminescence imaging ELISA using an imprinted polymer as the recognition element instead of an antibody.

An imaging assay analogous to competitive enzyme immunoassays has been developed using a molecularly imprinted polymer instead of an antibody. The antigen 2,4-dichlorophenoxyacetic acid (2,4-D) was labeled with tobacco peroxidase, and the chemiluminescence reaction of luminol was used for detection. Microtiter plates (96 or 384 wells) were coated with polymer microspheres imprinted with 2,4-D, which were fixed in place by using poly(vinyl alcohol) as glue. In a competitive mode, the analyte-peroxidase conjugate was incubated with the free analyte in the microtiter plate, after which the bound fraction of the conjugate was quantified. After addition of the chemiluminescent substrates, light emission was measured in a high-throughput imaging format with a CCD camera. Calibration curves corresponding to analyte concentrations ranging from 0.01 to 100 microg/mL were obtained.

2,4-Dichlorophenoxyacetic Acid↗