Search PubMed⌕ Search

Biomedical subjects

Y Huang

Publications and source records attributed to Y Huang.

At least 91 records · Page 5Linked to original sources
PubMed2003

Cardiomyocyte apoptosis is associated with increased wall stress in chronic failing left ventricle.

AIMS: We examined cardiomyocyte apoptosis in chronic heart failure (HF) and its possible link to elevated wall stress. METHODS AND RESULTS: Moderate HF was produced in sheep by sequential coronary microembolization. Six months later, the animals remained in a stable compensated haemodynamic state of HF. Apoptosis of cardiomyocytes in left ventricles was verified using Western blotting based on increased expression of: the apoptosis-associated death receptor Fas (1.5-fold); its ligand (FasL, 2.0-fold); and an upstream protease caspase-8 (2.7-fold) as well as its active cleavage peptide, p20 (5.6-fold). Previously we have reported the elevated expression of caspase-3 in the same animal model. The occurrence of apoptotic cardiomyocytes (0.3%) was quantified by TUNEL assays. Haemodynamic analysis indicated that ventricular dilatation, without wall thickening, caused a 2-fold increase in LV wall stress which, together with LV end-diastolic pressure, was linearly correlated with expression of Fas/FasL. Immunohistochemical studies localized FasL and caspase-8 to intercalated discs, suggesting that wall stress may play a role in initiating cardiomyocyte apoptosis. CONCLUSION: Apoptosis of cardiomyocytes in chronic HF is associated with increased wall stress, which may be responsible for the activation of a Fas/FasL and caspase-8 interaction in the region of intercalated discs.

Animals↗
PubMed2003

Evidence for disaggregation of oligomeric G(o)alpha induced by guanosine-5;-3-O-(thio)triphosphate activation.

Myristoylated G(o)alpha was expressed in and highly purified from Escherichia coli strain JM109 cotransformed with pQE60 (G(o)alpha) and pBB131 (N-myristoyltransferase, NMT). Non-denaturing gel electrophoresis and gel filtration analysis revealed that the G(o)alpha, in its GDP-bound form, could form oligomers involving dimer, trimer, tetramer, pentamer, or hexamer and guanosine 5;-3-O-(thio)triphosphate (GTPgammaS) activation induced disaggregation of the G(o)alpha oligomers to monomers. The G(o)alpha was crosslinked by a cross-linker, N,N-1,4-phenylenedimaleimide (p-PDM), yielding multiple crosslinked products. In contrast, no obvious cross-linking occurred when G(o)alpha was pretreated with GTPgammaS. Immunoblot analysis also demonstrated oligomerization of the purified G(o)alpha proteins and its disaggregation triggered by GTPgammaS. These results provided direct evidence for the "disaggregation-coupling" theory and the disaggregation action of GTPgammaS may further elucidate the regulatory role of GDP/GTP exchange in G protein-coupled signal transduction pathways.

Blotting, Western↗
PubMed2003

Distribution of Bacteroides forsythus genotypes in a Japanese periodontitis population.

Bacteroides forsythus is an important pathogen in periodontal diseases and has been associated with advanced and refractory periodontitis. The difficulties associated with culturing this species have meant that the distribution and pathogenic mechanisms of B. forsythus remain unclear. In this study, the arbitrarily primed polymerase chain reaction (AP-PCR) method was used to investigate the genotype distribution of B. forsythus in a Japanese periodontitis population, as well as the relationship between AP-PCR genotypes and periodontal status. B. forsythus reference strain, ATCC 43037T and 137 clinical bacterial isolates from 64 subjects were separated into 11 distinct AP-PCR genotypes using a single randomly-sequenced primer, 5'-CCGGCGGCG-3' (A-05). The majority (80.9%) of B. forsythus strains examined belonged to AP-PCR genotypes I, II, III and IV (accounting for 39.7%, 20.6%, 10.3% and 10.3%, respectively). Types I and III primarily consisted of isolates from chronic periodontitis subjects (80.8% and 85.7%, respectively), while Types II and IV consisted mainly of isolates from aggressive periodontitis subjects (85.7% and 100%, respectively). Except for three subjects who harbored two different B. forsythus genotypes in the oral cavity, all subjects only infected with one genotype intraindividually. These results demonstrate that the AP-PCR method is useful for genotypic analysis of B. forsythus. This species showed a genetic diversity among the investigated population. A clonal nature of B. forsythus infection is suggested. Furthermore, different AP-PCR genotypes of B. forsythus appear to be associated with different types of periodontitis.

Acute Disease↗
PubMed2003

Arsenic trioxide-induced mitotic arrest and apoptosis in acute promyelocytic leukemia cells.

Arsenic trioxide (As(2)O(3)), an effective drug for the treatment of acute promyelocytic leukemia (APL), can induce apoptosis and partial differentiation in APL cells in vitro and in vivo. However, As(2)O(3) also induces apoptosis in cancer cells other than APL with complex mechanisms, which seem to be cell type dependent. In this study, we report that APL cells (NB4 cell line) are arrested at early mitotic phase before the collapse of mitochondrial transmembrane potential (Deltavarphi(m)) and apoptosis after treatment with pharmacological concentrations (1.0-2.0 micro M) of As(2)O(3). We have also made the following new discoveries: (1) 0.5 micro M As(2)O(3) that fails to induce apoptosis has no effects on cell cycle distribution. (2) With inhibition of As(2)O(3)-induced Deltavarphi(m) collapse and apoptosis, dithiothreitol also effectively inhibits As(2)O(3)-induced mitotic arrest, suggesting that both As(2)O(3)-induced apoptosis and mitotic arrest involve proteins with thiol groups. (3) 1.5 mM caffeine that relieves cells from G(2)/M arrest also inhibits As(2)O(3)-induced Deltavarphi(m) collapse and apoptosis, (4) 1.0 micro M As(2)O(3) increases the expression of both cyclin B(1) and hCDC20 whereas it inhibits Tyr15 phosphorylation of p34(cdc2). In conclusion, our results strongly support that there is a tight link between As(2)O(3)-induced apoptosis and mitotic arrest, the latter being one of common mechanisms for As(2)O(3)-induced apoptosis in cancer cells.

Antineoplastic Agents↗
PubMed2003

Cobalt chloride and low oxygen tension trigger differentiation of acute myeloid leukemic cells: possible mediation of hypoxia-inducible factor-1alpha.

Cellular and systemic O(2) concentrations are tightly regulated to maintain delicate oxygen homeostasis. Although the roles of hypoxia in solid tumors have been widely studied, few studies were reported regarding the possible effects of hypoxia on leukemic cells. Here, we showed for the first time that low concentrations of cobalt chloride (CoCl(2)), a hypoxia-mimicking agent, and 2-3% O(2) triggered differentiation of various subtypes of human acute myeloid leukemic (AML) cell lines, including NB4, U937 and Kasumi-1 cells, respectively, from M3, M5 and M2b-type AML, but CoCl(2) did not modulate AML subtype-specific fusion proteins promyelocytic leukemia-retinoic acid receptor alpha (PML-RARalpha) and AML1-ETO. Treatment with CoCl(2) also induced primary leukemic cells from some AML patients to undergo differentiation. Similar to what occurs in solid tumor cells, CoCl(2)-mimicked hypoxia also increased the level of hypoxia-inducible factor (HIF)-1alpha protein and its DNA-binding activity in leukemic cells. The CoCl(2) induction of HIF-1alpha protein and its DNA-binding activity were inhibited by 3-morpholinosydnonimine, which also blocked CoCl(2)-induced cell differentiation in leukemic cells. These results provide an insight into a possible link of hypoxia or HIF-1alpha and leukemic cell differentiation, and are possibly of significance to explore clinical potentials of hypoxia or hypoxia-mimicking agents and novel target-based drugs for differentiation therapy of leukemia.

Antigens, CD↗
PubMed2003

An in vitro model for investigating intestinal adhesion of potential dairy propionibacteria probiotic strains using cell line C2BBe1.

AIMS: The purposes of this study were to screen the adhesion properties of dairy propionibacteria strains and evaluate whether C2BBe1 could be used in the screening of potential probiotic strains. METHODS AND RESULTS: Thirteen dairy propionibacteria strains and two control strains, Lactobacillus acidophilus MJLA1 and Bifidobacterium lactis BDBB2, were tested for adhesion to C2BBe1. Electron microscopic observations demonstrated that the control strains, L. acidophilus MJLA1 and B. lactis BDBB2, had similar adhesive ability to C2BBe1 as had been previously shown to Caco-2. Only one of the 13 strains of dairy propionibacteria, strain P. jensenii 702, demonstrated adhesion to C2BBe1. CONCLUSIONS: C2BBe1 can provide an alternative to Caco-2 for assessing in vitro adhesion properties of probiotic strains. Adhesion properties of dairy propionibacteria were strain-dependent. SIGNIFICANCE AND IMPACT OF THE STUDY: C2BBe1 is highly suitable for application in bacterial adhesion studies, and was used successfully to select a new potential probiotic.

Animals↗
PubMed2003

Feasibility of an HA2 domain-based periodontitis vaccine.

In a rat periodontitis model, preinoculation with the Porphyromonas gingivalis HA2 binding domain for hemoglobin provided protection from disease. Protection was associated with induced anti-HA2 immunoglobulin G (IgG) humoral antibodies. The IgG subclass ratios suggested that relatively lower Th2/Th1-driven responses were directly associated with protection when rHA2 was administered in saline.

Animals↗
PubMed2003

A mechanosensitive cation channel in endothelial cells and its role in vasoregulation.

Ca2+ is an important intracellular second messenger in signal transduction of endothelial cells. It has long been recognized that a mechanosensitive Ca2+-permeable channel is present in vascular endothelial cells. The activity of this channel may increase intracellular Ca2+ level in endothelial cells. A recent finding is that the activity of this channel may be regulated by cGMP through a protein kinase G-dependent pathway. Inhibition of the channel by cGMP abolishes the Ca2+ influx elicited by flow. Several inhibitors of the cation channel including Gd3+, Ni2+, and SK&F-96365 also inhibit the Ca2+ influx due to flow stimulation. These data suggest that a mechanosensitive cation channel is the primary pathway mediating the flow-induced Ca2+ entry in vascular endothelial cells. Another important finding is that the opening of this mechanosensitive channel by KT5823 leads to endothelium-dependent vascular dilation. Therefore, it appears that this channel may play a crucial role in the regulation of vascular tone.

Animals↗
PubMed2002

Binding affinities and geometries of various metal ligands in peptide deformylase inhibitors.

Removal of the N-terminal formyl group from newly synthesized proteins by the enzyme peptide deformylase (PDF) is essential for normal growth of bacteria but not higher organisms. Recently, PDF has been explored as a target for novel antibiotics. Screening a collection of natural products for antimicrobial activity identified actinonin and two matlystatin analogs as potent PDF inhibitors. A number of synthetic analogs of these natural products were prepared and their inhibitory potency determined. Previous work has shown that PDF is an iron metalloproteinase also containing a catalytic glutamic acid residue. Ligation of the ferrous cation is an essential feature of potent inhibitors. The structures of actinonin, a matlystatin analog and a synthetic inhibitor complexed with PDF were determined by crystallography. A quantum mechanics/molecular mechanics (QM/MM) method was used to reproduce the geometry of known complexes, to predict the protonation state in the active site and to predict the geometry of additional complexes. The requirement for protonation of the active site glutamate anion is an important factor in understanding the potency of inhibitors with acidic iron-ligating groups such as hydroxamate and carboxylate. Even though potent inhibitors of PDF have been discovered, their bacteriostatic mechanism of action and the rapid development of resistance in vitro may limit their potential as antibacterial drugs.

Amidohydrolases↗
PubMed2002

Formulation factors in preparing BTM-chitosan microspheres by spray drying method.

Chitosan (CTS) microspheres were prepared by a spray drying method using type-A gelatin and ethylene oxide-propylene oxide block copolymer as modifiers. Surface morphological characteristics and surface charges of prepared microspheres were investigated by using scanning electron microscopy (SEM) and microelectrophoresis. The particle shape, size and surface morphology of microspheres were significantly affected by the concentration of gelatin. Betamethasone disodium phosphate (BTM)-loaded microspheres demonstrated good drug stability (less 1% hydrolysis product), high entrapped efficiency (95%) and positive surface charge (37.5 mV). The in vitro drug release from the microspheres was related to gelatin content. Microspheres containing gelatin/CTS 0.4 approximately 0.6(w/w) had a prolong release pattern for 12 h. These formulation factors were correlated to particulate characteristics for optimizing BTM microspheres in pulmonary delivery.

Anti-Inflammatory Agents↗
PubMed2002

Mitochondrial gene rearrangements confirm the parallel evolution of the crab-like form.

The repeated appearance of strikingly similar crab-like forms in independent decapod crustacean lineages represents a remarkable case of parallel evolution. Uncertainty surrounding the phylogenetic relationships among crab-like lineages has hampered evolutionary studies. As is often the case, aligned DNA sequences by themselves were unable to fully resolve these relationships. Four nested mitochondrial gene rearrangements--including one of the few reported movements of an arthropod protein-coding gene--are congruent with the DNA phylogeny and help to resolve a crucial node. A phylogenetic analysis of DNA sequences, and gene rearrangements, supported five independent origins of the crab-like form, and suggests that the evolution of the crab-like form may be irreversible. This result supports the utility of mitochondrial gene rearrangements in phylogenetic reconstruction.

Amino Acid Sequence↗
PubMed2002

Genomic-scale analysis of gene expression profiles in TNF-alpha treated human umbilical vein endothelial cells.

OBJECTIVE AND DESIGN: TNF-alpha is a potent proinflammatory cytokine that plays an important role in immunity and inflammation, and in the control of cell proliferation, differentiation and programmed cell death. However, it is known that TNF-alpha is also the founding member of a still growing family of cytokines with diverse bioregulative functions. Its detailed molecular mechanisms on endothelial activation and injury remain to be elucidated. This study was aimed at determining genomic-scale gene expression profiles in TNF-alpha treated human endothelial cells. MATERIALS AND METHODS: In this study cultured human umbilical vein endothelial cells (HUVECs) were stimulated with TNF-alpha (10 ng/ml) for 2 and 16 h, respectively, and the gene expression pattern was profiled using a cDNA array representing 14,000 gene/cDNA clusters. RESULTS: In total, 72 known human genes were identified the expression levels of which altered over 2-fold in response to TNF-a stimulation. Such alteration was confirmed for IL-8 and MCP-1, with an independent quantitative mRNA assay. It was observed that genes with related biological functions were often temporally co-regulated. CONCLUSIONS: These results indicate the transcriptional pathways mediated by TNF-alpha inside the HUVECs. Expression profiling in HUVECs responding to TNF-alpha stimulation should give an understanding of the molecular mechanisms involved in vascular inflammation.

Cells, Cultured↗
PubMed2002

Tumor-specific transcriptional targeting of suicide gene therapy.

Transcriptional targeting of gene expression has been plagued by the weakness of tissue-specific promoters. Thus, to increase promoter strength while maintaining tissue specificity, we constructed a recombinant adenovirus containing a binary promoter system with a tumor-specific promoter (CEA; carcinoembryonic antigen) driving a transcription transactivator, which then activates a minimal promoter to express a suicide gene (HSV-tk; herpes simplex virus thymidine kinase). This ADV/binary-tk induced equal or greater cell killing in a CEA-specific manner in vitro compared with the CEA-independent killing of a vector with a constitutive viral promoter driving HSV-tk (ADV/RSV-tk). To monitor adenovirus-mediated HSV-tk gene expression in vivo, we employed noninvasive nuclear imaging using a radioiodinated nucleoside analog ([((1)31)I]-FIAU) serving as a substrate for HSV-tk. [((1)31)I]-FIAU-derived radioactivity accumulated after intratumoral injection of ADV/binary-tk only in the area of CEA-positive tumors with significantly less spread to the adjacent liver tissue than after administration of the universally expressed ADV/RSV-tk. Both viruses exhibited similar antitumor efficacy upon injection of liver metastases. Importantly, in vivo dose escalation studies demonstrated significantly reduced toxicity after intravenous administration of ADV/binary-tk versus ADV/RSV-tk. In summary, the increased therapeutic index of this novel, amplified CEA-driven suicide gene therapy vector is a proof of principle for the powerful enhancement of a weak tissue-specific promoter for effective tumor restricted gene expression.

Adenoviridae↗
PubMed2002

The application of a hot deformation SEM stage, backscattered electron imaging and EBSD to the study of thermomechanical processing.

The technique of combining in situ hot-deformation and high resolution electron backscattered diffraction (EBSD) has been applied to study the mechanisms operating during the thermomechanical processing of metals. A simple hot tensile-straining stage is installed in a field emission gun scanning electron microscope equipped with an EBSD system and has been used successfully for a number of preliminary investigations. These investigations include substructure formation, dynamic subgrain and grain growth, superplastic deformation in aluminium alloys, and dynamic recrystallization in copper. Despite the surface topography, which inevitably increases during plastic deformation, channelling contrast backscattered electron micrographs have been successfully obtained after strains of up to approximately 50%. Good quality EBSD maps have been obtained after strains of up to 100%. Most observations and measurements from the in situ experiments are consistent with what is known about the mechanisms occurring in the bulk. The microstructures revealed in the centre of the in situ samples after later repolishing are generally similar to those at the surface.

Journal Article↗
PubMed2002

Expression of the mel gene from Pseudomonas maltophilia in Bacillus thuringiensis.

AIMS: The objective of this work was to express a novel mel gene, responsible for melanin formation, in Bacillus thuringiensis. METHODS AND RESULTS: A novel mel gene from Pseudomonas maltophilia was sub-cloned into B. thuringiensis using a shuttle vector plasmid and electroporation. Results revealed that the mel gene was expressed under the control of the CryIIIA promoter in B. thuringiensis and conferred u.v. protection on the recipient strain. CONCLUSIONS: The novel mel gene from Ps. maltophilia expressed in B. thuringiensis conferred u.v. protection on the recipient strain. SIGNIFICANCE AND IMPACT OF THE STUDY: Products containing B. thuringiensis for pest control are sensitive to u.v. degradation. As melanin has the ability to act as a u.v. absorber, a recombinant B. thuringiensis strain producing melanin provides a new stability for B. thuringiensis preparations.

Bacillus thuringiensis↗
PubMed2002

Stimulation of chloride secretion by baicalein in isolated rat distal colon.

The effect of baicalein on mucosal ion transport in the rat distal colon was investigated in Ussing chambers. Mucosal addition of baicalein (1-100 microM) elicited a concentration-dependent short-circuit current (I(sc)) response. The increase in I(sc) was mainly due to Cl(-) secretion. The presence of mucosal indomethacin (10 microM) significantly reduced both the basal and subsequent baicalein-evoked I(sc) responses. The baicalein-induced I(sc) were inhibited by mucosal application of diphenylamine-2-carboxylic acid (100 microM) and glibenclamide (500 microM) and basolateral application of chromanol 293B (30 microM), a blocker of K(v)LQT1 channels and Ba(2+) ions (5 mM). Treatment of the colonic mucosa with baicalein elicited a threefold increase in cAMP production. Pretreating the colonic mucosa with carbachol (100 microM, serosal) but not thapsigargin (1 microM, both sides) abolished the baicalein-induced I(sc). Addition of baicalein subsequent to forskolin induced a further increase in I(sc). These results indicate that the baicalein evoked Cl(-) secretion across rat colonic mucosa, possibly via a cAMP-dependent pathway. However, the action of baicalein cannot be solely explained by its cAMP-elevating effect. Baicalein may stimulate Cl(-) secretion via a cAMP-independent pathway or have a direct effect on cystic fibrosis transmembrane conductance regulator.

1-Methyl-3-isobutylxanthine↗
PubMed2002

Effect of 17beta-estradiol exposure on vasorelaxation induced by K(+) channel openers and Ca(2+) channel blockers.

17beta-Estradiol has been shown to relax blood vessels partly through inhibition of Ca(2+) channels at supraphysiological concentrations; however, it is unknown whether acute exposure of the isolated artery rings to near physiological concentrations of sex steroid hormones could modulate the ionic channels that are involved in regulation of vascular tone. Brief incubation (20 min) with 17beta-estradiol (1-3 nmol/l) did not alter the relaxant response to three blocking agents of L-type voltage-sensitive Ca(2+) channels, nifedipine, diltiazem and verapamil in either endothelium-intact or endothelium-denuded rat mesenteric artery rings. In contrast, 17beta-estradiol at 3 nmol/l significantly attenuated the relaxation induced by K(+) channel openers, cromakalim and pinacidil in endothelium-denuded rings. Similarly, preincubation with progesterone (3 nmol/l) inhibited pinacidil-induced relaxation with much less effect on cromakalim-induced relaxation. It appears that 17beta-estradiol and progesterone attenuated the cromakalim- and pinacidil-induced relaxation in a different manner. These results suggest that acute exposure to female sex steroid hormones at near physiological levels may reduce the activity of ATP-sensitive K(+) channels in the rat arteries.

Animals↗