Biomedical subjects

Y Yu

Publications and source records attributed to Y Yu.

At least 91 records · Page 5Linked to original sources

PubMed2001

Characterization and tissue expression of a novel human gene npdc1.

We report the molecular characterization of a novel human homologue of mouse npdc1 (neural proliferation, differentiation and control, 1) gene, designated human npdc1 (hnpdc1). hnpdc1 was identified by large-scale sequencing of fetal liver cDNA libraries and the full-length cDNA was obtained by PCR amplification. The hnpdc1 gene, which contains nine exons, was mapped to human chromosome 15. It encodes a polypeptide of 325 amino acids, which shows high homology (77% identity) to the mouse NPDC1. Sequence analysis has shown that hNPDC1 protein contains a putative signal peptide of 34 amino acids, a transmembrane segment, and a typical bipartite nuclear localization signal. Northern blot and dot blot hybridization indicates that, just like mnpdc1, hnpdc1 mRNA is strongly expressed in adult brain (especially in hippocampus, frontal lobe and temporal lobe) and about 1.82-fold higher in adult brain than that in fetal brain. Unlike mnpdc1, however, hnpdc1 contains two transcripts instead of only one (1.5 kb), and has high expression levels in prostate, pituitary gland, and mammary glands. These results support that hNPDC1 plays a role in the control of neural cell proliferation and differentiation, and suggest that it may be involved in the development of several secretion glands.

Amino Acid Sequence↗

PubMed2001

Enhancement of human cord blood CD34+ cell-derived NK cell cytotoxicity by dendritic cells.

NK cells and dendritic cells (DCs) are both important in the innate host defense. However, the role of DCs in NK cell-mediated cytotoxicity is unclear. In this study, we designed two culture systems in which human cord blood CD34(+) cells from the same donor were induced to generate NK cells and DCs, respectively. Coculture of the NK cells with DCs resulted in significant enhancement of NK cell cytotoxicity and IFN-gamma production. However, NK cell cytotoxicity and IFN-gamma production were not increased when NK cells and DCs were grown together separated by a transwell membrane. Functional studies demonstrated that 1) concanamycin A, a selective inhibitor of perforin/granzyme B-based cytolysis, blocked DC-stimulated NK cytotoxicity against K562 cells; and 2) neutralizing mAb against Fas ligand (FasL) significantly reduced DC-stimulated NK cytotoxicity against Fas-positive Jurkat cells. In addition, a marked increase of FasL mRNA and FasL protein expression was observed in DC-stimulated NK cells. The addition of neutralizing mAb against IL-18 and IL-12 significantly suppressed DC-stimulated NK cell cytotoxicity. Neutralizing IFN-gamma Ab almost completely inhibited NK cell cytotoxicity against Jurkat cells. These observations suggest that DCs enhance NK cell cytotoxicity by up-regulating both perforin/granzyme B- and FasL/Fas-based pathways. Direct interaction between DCs and NK cells is necessary for DC-mediated enhancement of NK cell cytotoxicity. Furthermore, DC-derived IL-18 and IL-12 were involved in the up-regulation of NK cell cytotoxicity, and endogenous IFN-gamma production plays an important role in Fas-mediated cytotoxicity.

Anti-Bacterial Agents↗

PubMed2001

Resonance-enhanced signal detection and transduction in the Hodgkin-Huxley neuronal systems.

The ability of signal detection and transduction of the Hodgkin-Huxley neuronal systems, associated with rhythmic oscillations in the presence of external modulations, is studied. Both inhibitory and excitatory modulations, regarded as the total effects of the environment in which the neurons are located, are able to modulate the frequencies of the rhythmic oscillations of the neurons. Either subthreshold or suprathreshold rhythmic oscillations can provide the neural system with an effect of frequency selection in processing external signal. Resonance among the noise, the noise-induced oscillation, and the signal enhances intensively the capability of the neurons in processing the weak signal, especially when frequency of the signal is around that of the noise-induced rhythmic oscillation. Thus, the neuronal system can be adjusted to an optimal sensitive state for signal processing through the environmental modulations.

Action Potentials↗

PubMed2001

Proteomic analysis of apoptosis initiation induced by all-trans retinoic acid in human acute promyelocytic leukemia cells.

The irreversible destiny of apoptosis in its early stage might play a critical role in the apoptosis of human acute promyelocytic leukemia (APL) cell line induced by all-trans retinoic acid (ATRA). To characterize protein alterations during the apoptosis-initiation phase and to understand the metabolic status at that time, we investigated the protein profiles in the apoptosis-initiation phase of APL cell line HL-60 by proteomic analysis. ATRA-withdrawal was conducted to demonstrate that there was committed initiation phase of apoptosis triggered by 10(-6) M ATRA at day 3. Only after that time point, ATRA-treated cells irreversibly went to apoptosis. Also at that time point, the positive regulators of apoptosis such as STAT3 increased at protein level, whereas negative regulators (Bcl-2 and p-STAT3) decreased. In addition, caspase-3 also increased after that time. Furthermore, comparative proteomic analysis was utilized to examine the protein expression profiles during the initiation stage of apoptosis. Our results showed 12 upregulated and 7 downregulated proteins experiencing twofold alteration, including key regulators of signal transduction such as G-proteins and nucleic receptors, proteins related with metabolism, oxidation and reduction, proteins associated with the nucleus and cytoskeleton-related proteins. Some of them could be positive modulators to trigger apoptosis, whereas others could contribute to intracellular defense against apoptosis induced by exogenous triggers. The results above suggest that there is a subtle balance between apoptosis and the intracellular defense against apoptosis. Once the balance is disturbed, cells would irreversibly initiate to undergo the execution of apoptosis.

Amino Acids↗

PubMed2001

A framework for sequencing the rice genome.

Rice is an important food crop and a model plant for other cereal genomes. The Clemson University Genomics Institute framework project, begun two years ago in anticipation of the now ongoing international effort to sequence the rice genome, is nearing completion. Two bacterial artificial chromosome (BAC) libraries have been constructed from the Oryza sativa cultivar Nipponbare. Over 100,000 BAC end sequences have been generated from these libraries and, at a current total of 28 Mbp, represent 6.5% of the total rice genome sequence. This sequence information has allowed us to draw first conclusions about unique and redundant rice genomic sequences. In addition, more than 60,000 clones (19 genome equivalents) have been successfully fingerprinted and assembled into contigs using FPC software. Many of these contigs have been anchored to the rice chromosomes using a variety of techniques. Hybridization experiments have shown these contigs to be very robust. Contig assembly and hybridization experiments have revealed some surprising insights into the organization of the rice genome, which will have significant repercussions for the sequencing effort. Integration of BAC end sequence data with anchored contig information has provided unexpected revelations on sequence organization at the chromosomal level.

Chromosome Mapping↗

PubMed2001

The genomic organization of the gene encoding the vanilloid receptor: evidence for multiple splice variants.

Vanilloid receptor subtype-1 (VR1) is a nonselective cation channel that is expressed in sensory neurons and is activated by multiple noxious stimuli. Rat Vr1, stretch-inactivated channel (SIC), and vanilloid receptor 5' splice variant (VR.5'sv) have been hypothesized to be derived from a common VR gene. Characterization of the genomic structure encoding the 5' portion of rat Vr1 confirmed that VR.5'sv is derived from the VR gene; however, SIC seemed to be derived from two related but independent genes. We also deduced the genomic organization of the human gene VR1. Comparative studies of rat and human VR genes showed substantial conservation in genomic organization. The splice site flanking exon-intron 7 in rat and human VR1 diverged from the expected consensus sequence; this may help to explain the skipping of exon 7 within VR.5'sv and other VR splice variants.

5' Untranslated Regions↗

PubMed2001

Cloning, mapping, and characterization of a human homologue of the yeast longevity assurance gene LAG1.

We have identified LASS2, a previously unknown human homologue of the yeast longevity assurance gene LAG1. The LASS2 transcript is highly expressed in liver and kidney, which is very different from the expression of the previously identified human LAG1 homologue LAG1Hs-1. Radiation hybrid mapping studies indicated that LASS2 is located on chromosome 1q11. Yeast two-hybrid screening and glutathione S-transferase pull-down assays showed that the LASS2 protein interacts with several membrane-associated receptors or transporters. Furthermore, LASS2 protein was able to inhibit the colony formation of human hepatoma cells in vitro, which suggests that this gene may be involved in the regulation of cell growth.

Amino Acid Sequence↗

PubMed2001

Regulation of sodium-calcium exchange and mitochondrial energetics by Bcl-2 in the heart of transgenic mice.

Our previous work in cultured cells has shown that the maintenance of mitochondrial Ca(2+) homeostasis is essential for cell survival, and that the anti-apoptotic protein Bcl-2 is able to maintain a threshold level of mitochondrial Ca(2+) by the inhibition of permeability transition. To test whether Bcl-2 also affects the mitochondrial Na(+)-Ca(2+) exchange (NCE), a major efflux pathway for mitochondrial Ca(2+), studies using transgenic mice that overexpress Bcl-2 in the heart have been performed. NCE activity was determined as the Na(+)-dependent Ca(2+) efflux in the isolated mitochondria. Overexpression of Bcl-2 led to a significant reduction of NCE activity as well as increased resistance to permeability transition in the mitochondria of transgenic heart. This was accompanied by increased matrix Ca(2+) level, enhanced formation of NADH and enhanced oxidation of pyruvate, an NAD(+)-linked substrate. Furthermore, there was induction of cellular Ca(2+) transport proteins including the Na(+)-Ca(2+) exchanger of the sarcolemma (NCX). Bcl-2 not only stimulates NCX expression in the sarcolemma but also attenuates the Na(+)-Ca(2+) exchange in the mitochondria. These results are consistent with the protection by Bcl-2 against apoptosis in heart following ischemia/reperfusion.

Animals↗

PubMed2001

Calcium-dependent interleukin-8 gene expression in T84 human colonic epithelial cells.

OBJECTIVE AND DESIGN: IL-8 is a chemokine that activates and recruits neutrophils and plays a major role in intestinal inflammation. Signal transduction pathways mediated by protein kinases are central in regulating IL-8 gene expression, however, little is known about the role of Ca2+ in this event. In this study, we characterize the effect of intracellular Ca2+ on interleukin-8 gene expression in T84 human colonic epithelial cells. MATERIALS AND METHODS: Cells were stimulated with Ca2+ ionophore, A23187 or thapsigargin, a Ca2+-ATPase inhibitor. Semi-quantitative RT-PCR was used to examine IL-8 mRNA and ELISA for protein quantification. Reporter gene techniques were used to determine transcription rate. RESULTS: A23187 and thapsigargin caused a dose- and time-dependent accumulation of IL-8 mRNA and protein production which was dependent on the release of Ca2+ from intracellular stores. FK506, a specific inhibitor of calcineurin, inhibited A23187- and thapsigargin-induced IL-8 mRNA expression in a dose dependent manner. Reporter gene studies and actinomycin D chase experiments showed that A23187 and thapsigargin enhanced IL-8 gene transcription and stabilized IL-8 mRNA transcripts, respectively. CONCLUSION: Intracellular Ca2+ plays an important role in regulating IL-8 transcriptionally and posttranscriptionally through calcium/calmodulin-dependent calcineurin.

Adenocarcinoma↗

PubMed2001

Frequency sensitivity in Hodgkin-Huxley systems.

The frequency sensitivity of weak periodic signal detection has been studied via numerical simulations for both a single neuron and a neuronal network. The dependence of the critical amplitude of the signal upon its frequency and a resonance between the intrinsic oscillations of a neuron and the signal could account for the frequency sensitivity. In the presence of both a subthreshold periodic signal and noise, the signal-to-noise ratio (SNR) of the output of either a single neuron or a neuronal network present the typical characteristics of stochastic resonance. In particular, there exists a frequency-sensitive range of 30-100 Hz, and for signals with frequencies within this range the SNRs have large values. This implies that the system under consideration (a single neuron or a neuronal network) is more sensitive to the detection of periodic signals, and the frequency sensitivity may be of a functional significance to signal processing.

Artifacts↗

PubMed2001

Increased Tie2 expression, enhanced response to angiopoietin-1, and dysregulated angiopoietin-2 expression in hemangioma-derived endothelial cells.

Infantile hemangiomas are endothelial tumors that grow rapidly in the first year of life and regress slowly during early childhood. Although hemangiomas are well-known vascular lesions, little is known about the mechanisms that cause the excessive endothelial cell proliferation in these most common tumors of infancy. To investigate the molecular basis of hemangioma, we isolated endothelial cells from several proliferative-phase lesions and showed that these cells are clonal and exhibit abnormal properties in vitro (E. Boye, Y. Yu, G. Paranya, J. B. Mulliken, B. R. Olsen, J. Bischoff: Clonality and altered behavior of endothelial cells from hemangiomas. J Clin Invest 2001, 107:745-752). Here, we analyzed mRNA expression patterns of genes required for angiogenesis, including members of the vascular endothelial growth factor (VEGF)/VEGF receptor family and the angiopoietin/Tie family, in hemangioma-derived and normal endothelial cells. KDR, Flt-1, Tie1, Tie2, and angiopoietin-2 (Ang2) were strongly expressed in cultured hemangioma-derived endothelial cells and in hemangioma tissue. In contrast, there was little expression of angiopoietin-1 (Ang1) or VEGF. We found Tie2 mRNA and protein up-regulated with a concomitant increase in cellular responsiveness to Ang1 in most hemangioma-derived endothelial cells. Ang2 mRNA was down-regulated in response to serum in hemangioma-derived endothelial cells, but not in normal endothelial cells, suggesting altered regulation. These findings implicate Tie2 and its ligands Ang1 and Ang2 in the pathogenesis of hemangioma.

Angiopoietin-1↗

PubMed2001

Interactions between organic flocculant PAN-DCD and dyes.

Organic flocculant polyacrylonitrile-dicyandiamide (PAN-DCD) was characterized by IR, 1H NMR and 13C NMR spectra. Polar groups, such as triazine, carboxyl, amidine, carbonamide and non-polar groups, such as methylene were identified in the macromolecular chain of PAN-DCD. The flocculant effectively decolorized the examined dyes in their aqueous solutions under acid condition. By comparing the IR spectra of dyes with that of PAN-DCD and that of flocs formed, weak chemical interactions between amino in PAN-DCD side chain and sulfonic acid group in the dye molecules were observed through the formation of -NH3+ SO3(-)-, NH2+ SO3(-)- or/and =NH+ SO3(-)-. By using equilibrium dialysis technique, the hydrophobic interactions between PAN-DCD and the dyes in the binding process were also observed from the experimental results. The binding extent of PAN-DCD to dye KN-R was greater than that of MO. The addition of urea into the binding system of KN-R by PAN-DCD reduced the first binding constant K from 12.2 x 10(5) (without urea) to 3.48 x 10(5) (with urea).

Acrylic Resins↗

PubMed2001

Overexpression of c-erbB2 protein correlates with disease-stage and chromosomal gain at the c-erbB2 locus in non-small cell lung cancer.

Overexpression of the c-erbB2 protein is observed in a variety of malignancies including non-small cell lung cancer (NSCLC). We aimed to determine the rate of c-erbB2-overexpression in our tumour collection and to clarify its correlation with the chromosomal status at the c-erbB2 locus 17q21 in NSCLC. Eighty-nine NSCLC were analysed immunohistochemically using a polyclonal c-erbB2 antibody (DAKO). The staining was scored according to the guidelines of the Clinical Trial Assay recommendations (0-3+). Of these, 44 cases were also analysed by comparative genomic hybridisation (CGH). Overexpression was observed in 37% of the cases (score>1) which was associated with higher disease stages and a positive nodal status in adenocarcinomas. Chromosomal gains at 17q21 were clearly correlated with overexpression of the gene (P=0.009). In addition, there was a highly significant correlation between the c-erbB2 expression comparing the whole section immunostaining analysis and a 127 lung tumour tissue array which included 74 of the 89 cases that were analysed by the classical procedure. We conclude that c-erbB2 is a marker of tumour progression in NSCLC which can be observed on protein level and reflects chromosomal alterations at 17q21.

Adult↗

PubMed2001

Engineering chromosomal rearrangements in mice.

The combination of gene-targeting techniques in mouse embryonic stem cells and the Cre/loxP site-specific recombination system has resulted in the emergence of chromosomal-engineering technology in mice. This advance has opened up new opportunities for modelling human diseases that are associated with chromosomal rearrangements. It has also led to the generation of visibly marked deletions and balancer chromosomes in mice, which provide essential reagents for maximizing the efficiency of large-scale mutagenesis efforts and which will accelerate the functional annotation of mammalian genomes, including the human genome.

Animals↗

PubMed2001

Overexpression of gamma-aminobutyric acid transporter subtype I leads to susceptibility to kainic acid-induced seizure in transgenic mice.

Gamma-aminobutyric acid (GABA) is the principal inhibitory neurotransmitter, and the GABAergic synaptic transmission is normally terminated by the rapid uptake through GABA transporters. With transgenic mice ubiquitously overexpressing GABA transporter subtype I (GAT1), the present study explored the pathophysiological role of GAT1 in epileptogenesis. Though displaying no spontaneous seizure activity, these mice exhibit altered electroencephalographic patterns and increased susceptibility to seizure induced by kainic acid. In addition, the GABA(A) receptor and glutamate transporters are up-regulated in transgenic mice, which perhaps reflects a compensatory or corrective change to the elevated level of GAT1. These preliminary findings support the hypothesis that excitatory and inhibitory neurotransmission, and seizure susceptibility can be altered by neurotransmitter transporters.

ATP-Binding Cassette Transporters↗

PubMed2001

Towards the development of molecularly imprinted artificial receptors for the screening of estrogenic chemicals.

Molecularly imprinted polymers are prepared using various steroid compounds as the templates. The imprinted polymers can selectively re-bind the original print molecules, which leads to versatile potential applications. The feasibility of using these artificial receptors to replace their biological counterparts for preliminary screening of a chemical library is demonstrated. A steroid library composed of 22 closely related compounds is screened with an estrogen specific polymer. The print molecule is identified with accuracy and structural similarities of other members are correlated with normalized retention indices. Molecularly imprinted artificial receptors are envisioned as being useful for screening purposes in drug discovery or for identifying endocrine-disrupting chemicals.

Chromatography↗

PubMed2001

The 3'-untranslated region of human interleukin-8 mRNA suppresses IL-8 gene expression.

Although adenosine/uridine (AU)-rich sequences in the 3'-untranslated region (UTR) of the interleukin-8 (IL-8) gene have been suggested to contribute to its post-transcriptional regulation, the molecular basis whereby this occurs still needs to be understood. To investigate the role of the 3'-UTR on human IL-8 gene regulation, chimeric reporter genes were generated by adding full length or differentially deleted 3'-UTR of the IL-8 gene to chloramphenicol acetyltransferase (CAT). Addition of the entire IL-8 3'-UTR markedly reduced CAT mRNA and protein expression in COS 7 cells. In a reporter gene study, IL-8 3'-UTR destabilized CAT mRNA, which was dependent on active transcription in COS 7 cells. A 357-base sequence (nucleotides (nt) 2387-2743 of genomic DNA) within 3'-UTR, designated e, suppressed CAT gene expression by accelerating CAT mRNA turnover. A 26-base AU-rich sequence (nt 2552-2577) within e, containing four AUUUA pentamers that form two UAUUUAUU and one UUAUUUAU octamers, did not suppress CAT gene expression. However, deletion of the AU-rich sequences attenuated the inhibitory effect of e on CAT gene expression. Elimination of the first 100 bases (nt 2386-2486) attenuated the potency of fragment e, but much weaker than elimination of the first 146 bases (nt 2387-2533). This study gives new insights in unravelling the molecular mechanisms involved in the post-transcriptional regulation of the IL-8 gene.

3' Untranslated Regions↗

PubMed2001

The protein kinase Pho85 is required for asymmetric accumulation of the Ash1 protein in Saccharomyces cerevisiae.

The Ash1 protein is a daughter cell-specific repressor of HO gene transcription in Saccharomyces cerevisiae. Both ASH1 mRNA and protein are localized to the incipient daughter cell at the end of mitosis; Ash1 then inhibits HO transcription in the daughter cell after cytokinesis. Mother cells, in contrast, contain little or no Ash1 and thus are able to transcribe HO. We show that deletion of PHO85, which encodes a cyclin-dependent protein kinase, causes reduced transcription of HO and that this reduction is dependent on ASH1. In pho85 mutants, Ash1 protein is no longer asymmetrically localized and is present, instead, in both mother and daughter cells. Initially, it appears to be localized properly but then persists as daughter cells mature into mother cells. In contrast, ASH1 mRNA is localized appropriately to daughter cells in pho85 mutants. We observe that Ash1 protein is phosphorylated by Pho85 in vitro and that Ash1 stability increases in a pho85 mutant. These data suggest that phosphorylation of Ash1 by Pho85 governs stability of Ash1 protein.

Cell Division↗