Biomedical subjects

Guohong Li

Publications and source records attributed to Guohong Li.

14 recordsLinked to original sources

PubMed2006

Removal of direct dyes by coagulation: the performance of preformed polymeric aluminum species.

Removal of three direct dyes (Direct Black 19, Direct Red 28, and Direct Blue 86) by coagulation with three different Al based coagulants was investigated. The main purpose of this paper is to examine the coagulation features of polymeric aluminum coagulants in treatment of dye-polluted waters and the emphasis was placed on the roles of preformed Al species, particularly Al(13). The performance of Al(13) in coagulation of dyes was observed through jar tests by comparing traditional Al salt, polyaluminum chloride (PACl), and purified Al(13). The results showed that under most cases Al(13) had significantly higher efficiency in removal of direct dyes than traditional Al salt and commercial PACl with the exception of Direct Red 28 removal under high pH range. The coagulation of direct dyes could be greatly affected by pH. Reducing pH was favorable for preformed Al species in a broad pH range. For traditional Al coagulant, efficient dye removal only occurred in a relatively narrow pH range of near 6.0. The outstanding coagulation behavior of Al(13) could be ascribed to its high charge neutralization ability, relative stability and potential self-assembly tendency.

Aluminum Compounds↗

PubMed2006

Histone H2B monoubiquitination functions cooperatively with FACT to regulate elongation by RNA polymerase II.

Over the past years, a large number of histone posttranslational modifications have been described, some of which function to attain a repressed chromatin structure, while others facilitate activation by allowing access of regulators to DNA. Histone H2B monoubiquitination is a mark associated with transcriptional activity. Using a highly reconstituted chromatin-transcription system incorporating the inducible RARbeta2 promoter, we find that the establishment of H2B monoubiquitination by RNF20/40 and UbcH6 is dependent on the transcription elongation regulator complex PAF, the histone chaperone FACT, and transcription. H2B monoubiquitination facilitates FACT function, thereby stimulating transcript elongation and the generation of longer transcripts. These in vitro analyses and corroborating in vivo experiments demonstrate that elongation by RNA polymerase II through the nucleosomal barrier is minimally dependent upon (1) FACT and (2) the recruitment of PAF and the H2B monoubiquitination machinery.

Animals↗

PubMed2006

Onset of motion and dynamic reordering of a vortex lattice.

Time resolved transport measurements on a driven vortex lattice in an undoped 2H-NbSe2 crystal show that the response to a current pulse is governed by healing of defects as the lattice evolves from a stationary to a moving steady state and that the response time reflects the degree of order in the initial vortex state. We find that stationary field cooled vortex lattices become more ordered with decreasing temperature and identify a temperature below which a qualitative change in the response signals the disappearance of topological defects.

Journal Article↗

PubMed2006

Methods to identify and functionally analyze factors that specifically recognize histone lysine methylation.

Histone lysine methylation plays an important role in the regulation of gene expression and impacts many fundamental biological processes, such as cellular identity. Despite great efforts, the mechanisms behind the downstream consequences of histone methyl-recognition remain poorly understood. Here, we describe various methods to investigate specific histone lysine-methyl recognition, including the use of short peptides, histone octamers, and the more physiological nucleosomal arrays. We also discuss techniques that are well suited to assess functional aspects of binding as it relates to transcriptional regulation.

Affinity Labels↗

PubMed2006

Acanthocytes of Stropharia rugosoannulata function as a nematode-attacking device.

Efficient killing of nematodes by Stropharia rugosoannulata Farlow ex Murrill cultures was observed. This fungus showed the ability to immobilize the free-living nematode Panagrellus redivivus Goodey within minutes and to immobilize the pine wilt nematode Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle within hours on agar plates. Moreover, P. redivivus worms were completely degraded by the fungus within 24 to 48 h. The cultures of S. rugosoannulata studied shared the characteristic of abundantly producing cells with finger-like projections called acanthocytes. We showed that the nematode-attacking activity of this fungus is carried out by these spiny acanthocytes and that mechanical force is an important factor in the process. Furthermore, the growth and nematode-attacking activity of the fungus in soil were also determined, and our results suggest that acanthocytes are functional in soil.

Acanthocytes↗

PubMed2005

Phosphatidylinositol-3-kinase signaling mediates vascular smooth muscle cell expression of periostin in vivo and in vitro.

OBJECTIVE: Periostin is dramatically upregulated in rat carotid arteries after balloon injury. The objective of the present study was to understand mechanisms underlying periostin upregulation in balloon-injured rat carotid arteries and in cultured vascular smooth muscle cells (VSMCs). METHODS AND RESULTS: Periostin protein was strongly expressed at 3 days (in the medial SMCs) and 7 days (in the neointima) after injury. It was also abundantly expressed in the neointima in the late phase (at 14 and 28 days) after injury. Periostin upregulation was mediated through PI-3-kinase-dependent signaling pathway. In vivo, wortmannin, a PI-3-kinase inhibitor, inhibited balloon injury-induced Akt phosphorylation and periostin mRNA expression. In vitro, periostin mRNA expression in cultured VSMCs was stimulated by growth factors (transforming growth factor-beta1 (TGF-beta1), fibroblast growth factors (FGFs), PDGF-BB, and angiotensin II). This stimulatory effect was inhibited by the PI-3-kinase inhibitor LY294002. Further, periostin protein was mostly located in the cytoplasma of VSMCs in culture and abundantly secreted into the culture medium (CM) after stimulation with FGF-2, which significantly promoted VSMC migration in vitro. Immunodepletion of periostin from the VSMC-CM or blockade of periostin function with an anti-periostin antibody significantly reduced VSMC migration. CONCLUSIONS: Upregulation of periostin expression in rat carotid arteries following balloon injury and in cultured VSMCs after stimulation by growth factors is mediated through PI-3-kinase-dependent signaling pathway. Periostin protein secreted by VSMCs plays a significant role in regulating VSMC migration in vitro.

Androstadienes↗

PubMed2005

Arterial macrophages and regenerating endothelial cells express P-selectin in atherosclerosis-prone apolipoprotein E-deficient mice.

P-selectin expression has been reported in platelets, endothelial cells, and vascular smooth muscle cells in response to vascular injury. Here, we report P-selectin expression on macrophages in the arterial wall after carotid denudation injury and spontaneous atherosclerosis in atherosclerosis-prone apoE-deficient (apoE(-/-)) mice. Double-immunofluorescence staining revealed robust P-selectin expression in macrophage-rich regions of both denudation-induced carotid neointimal lesions and innominate atherosclerotic plaques. Co-localization of P-selectin with macrophages was verified at the single cell level using double immunostaining plus 4,6-diamidino-2-phenylindole (for nuclei) counterstaining. No platelet staining was seen in association with the macrophage staining, excluding platelet contamination. Furthermore, P-selectin mRNA expression was readily detectable in macrophage-rich plaques of atherosclerotic innominate arteries and blood monocyte-derived macrophages from apoE(-/-) mice. Strong P-selectin expression was also seen in the areas of regenerated endothelium after arterial injury. In addition, co-localization of P-selectin with vascular smooth muscle cells was readily observed in denudation-injured carotid arteries at 7 and 14 days. We conclude that macrophages in carotid injury-induced neointimal lesions and spontaneous atherosclerotic plaques of the innominate artery acquire the ability to express P-selectin, as does regenerating endothelium. These findings provide a potential new paradigm in macrophage-mediated vascular inflammation, atherosclerosis, and neointimal hyperplasia after arterial injury.

Animals↗

PubMed2005

Interaction in vitro of type III intermediate filament proteins with higher order structures of single-stranded DNA, particularly with G-quadruplex DNA.

Cytoplasmic intermediate filament (cIF) proteins interact strongly with single-stranded (ss) DNAs and RNAs, particularly with G-rich sequences. To test the hypothesis that this interaction depends on special nucleotide sequences and, possibly, higher order structures of ssDNA, a random mixture of mouse genomic ssDNA fragments generated by a novel "whole ssDNA genome PCR" technique via RNA intermediates was subjected to three rounds of affinity binding to in vitro reconstituted vimentin IFs at physiological ionic strength with intermediate PCR amplification of the bound ssDNA segments. Nucleotide sequence and computer folding analysis of the vimentin-selected fragments revealed an enrichment in microsatellites, predominantly of the (GT)n type, telomere DNA, and C/T-rich sequences, most of which, however, were incapable of folding into stable stem-loop structures. Because G-rich sequences were underrepresented in the vimentin-bound fraction, it had to be assumed that such sequences require intramolecular folding or lateral assembly into multistrand structures to be able to stably interact with vimentin, but that this requirement was inadequately fulfilled under the conditions of the selection experiment. For that reason, the few vimentin-selected G-rich ssDNA fragments and a number of telomere models were analyzed for their capacity to form inter- and intramolecular Gquadruplexes (G4 DNAs) under optimized conditions and to interact as such with vimentin and its type III relatives, glial fibrillary acidic protein, and desmin. Band shift assays indeed demonstrated differential binding of the cIF proteins to parallel four-stranded G4 DNAs and, with lower affinity, to bimolecular G'2 and unimolecular G'4 DNA configurations, whereby the transition regions from four- to single-strandedness played an additional role in the binding reaction. In this respect, the binding activity of cIF proteins was comparable with that toward other noncanonical DNA structures, like ds/ss DNA forks, triplex DNA, four-way junction DNA and Z-DNA, which also involve configurational transitions in their interaction with the filament proteins. Association of the cIF proteins with the corresponding nonfolded G-rich ssDNAs was negligible. Considering the almost universal involvement of ssDNA regions and G-quadruplexes in nuclear processes, including DNA transcription and recombination as well as telomere maintenance and dynamics, it is plausible to presume that cIF proteins as complementary constituents of the nuclear matrix participate in the cell- and tissue-specific regulation of these processes.

Animals↗

PubMed2003

Interaction in vitro of type III intermediate filament proteins with Z-DNA and B-Z-DNA junctions.

The selection of DNA fragments containing simple d(GT)(n) and composite d(GT)(m). d(GA)(n) microsatellites during affinity binding of mouse genomic DNA to type III cytoplasmic intermediate filaments (cIFs) in vitro, and the detection of such repeats, often as parts of nuclear matrix attachment region (MAR)-like DNA, in SDS-stable DNA-vimentin crosslinkage products isolated from intact fibroblasts, prompted a detailed study of the interaction of type III cIF proteins with left-handed Z-DNA formed from d(GT)(17) and d(CG)(17) repeats under the topological tension of negatively supercoiled plasmids. Although d(GT)(n) tracts possess a distinctly lower Z-DNA-forming potential than d(CG)(n) tracts, the filament proteins produced a stronger electrophoretic mobility shift with a plasmid carrying a d(GT)(17) insert than with plasmids containing different d(CG)(n) inserts, consistent with the facts that the B-Z transition of d(GT)(n) repeats requires a higher negative superhelical density than that of d(CG)(n) repeats and the affinity of cIF proteins for plasmid DNA increases with its superhelical tension. That both types of dinucleotide repeat had indeed undergone B-Z transition was confirmed by S1 nuclease and chemical footprinting analysis of the plasmids, which also demonstrated efficient protection by cIF proteins from nucleolytic and chemical attack of the Z-DNA helices as such, as well as of the flanking B-Z junctions. The analysis also revealed sensibilization of nucleotides in the center of one of the two strands of a perfect d(CG)(17) insert toward S1 nuclease, indicating cIF protein-induced bending of the repeat. In all these assays, vimentin and glial fibrillary acidic protein (GFAP) showed comparable activities, versus desmin, which was almost inactive. In addition, vimentin and GFAP exhibited much higher affinities for the Z-DNA conformation of brominated, linear d(CG)(25) repeats than for the B-DNA configuration of the unmodified oligonucleotides. While double-stranded DNA was incapable of chasing the Z-DNA from its protein complexes, and Holliday junction and single-stranded (ss)DNA were distinguished by reasonable competitiveness, phosphatidylinositol (PI) and, particularly, phosphatidylinositol 4,5-diphosphate (PIP(2)) turned out to be extremely potent competitors. Because PIP(2) is an important member of the nuclear PI signal transduction cascade, it might exert a regulatory influence on the binding of cIF proteins to Z- and other DNA conformations. From this interaction of cIF proteins with Z- and bent DNA and their previously detected affinities for MAR-like, ss, triple helical, and four-way junction DNA, it may be concluded that the filament proteins play a general role in such nuclear matrix-associated processes as DNA replication, recombination, repair, and transcription.

Animals↗

PubMed2003

Type III intermediate filament proteins interact with four-way junction DNA and facilitate its cleavage by the junction-resolving enzyme T7 endonuclease I.

The isolation from proliferating mouse and human embryo fibroblasts of SDS-stable crosslinkage products of vimentin with DNA fragments containing inverted repeats capable of cruciform formation under superhelical stress and the competitive effect of a synthetic Holliday junction on the binding of cytoplasmic intermediate filament (cIF) proteins to supercoiled DNA prompted a detailed investigation of the proteins' capacity to associate with four-way junction DNA and to influence its processing by junction-resolving endonucleases. Electrophoretic mobility shift analysis of reaction products obtained from vimentin and Holliday junctions under varying ionic conditions revealed efficient complex formation of the filament protein not only with the unstacked, square-planar configuration of the junctions but also with their coaxially stacked X-conformation. Glial fibrillary acidic protein (GFAP) was less efficient and desmin virtually inactive in complex formation. Electron microscopy showed binding of vimentin tetramers or octamers almost exclusively to the branchpoint of the Holliday junctions under physiological ionic conditions. Even at several hundredfold molar excess, sequence-related single- and double-stranded DNAs were unable to chase Holliday junctions from their complexes with vimentin. Vimentin also stimulated bacteriophage T7 endonuclease I in introducing single-strand cuts diametrically across the branchpoint and thus in the resolution of the Holliday junctions. This effect is very likely due to vimentin-induced structural distortion of the branchpoint, as suggested by the results of hydroxyl radical footprinting of Holliday junctions in the absence and the presence of vimentin. Moreover, vimentin, and to a lesser extent GFAP and desmin, interacted with the cruciform structures of inverted repeats inserted into a supercoiled vector plasmid, thereby changing their configuration via branch migration and sensibilizing them to processing by T7 endonuclease I. This refers to both plasmid relaxation caused by unilateral scission and, particularly, linearization via bilateral scission at primary and cIF protein-induced secondary cruciform branchpoints that were identified by T7 endonuclease I footprinting. cIF proteins share these activities with a variety of other architectural proteins interacting with and structurally modulating four-way DNA junctions. In view of the known and hypothetical functions of four-way DNA junctions and associated protein factors in DNA metabolism, cIF proteins as complementary nuclear matrix proteins may play important roles in such nuclear matrix-associated processes as DNA replication, recombination, repair, and transcription, with special emphasis on both the preservation and evolution of the genome.

Bacteriophage T7↗

PubMed2002

Fibroblast growth factor receptor-1 signaling induces osteopontin expression and vascular smooth muscle cell-dependent adventitial fibroblast migration in vitro.

BACKGROUND: Increased expression of osteopontin (OPN), fibroblast growth factors (FGFs), and their type-1 receptor (FGFR-1) is associated with neointima formation and atherosclerosis. This study tested the hypothesis that ligand activation of FGFR-1 stimulates OPN expression in rat aortic smooth muscle cells (RASMCs), explored the signaling pathway involved, and assessed the functional consequences of activating this pathway on adventitial fibroblast (AF) migration in vitro. METHODS AND RESULTS: Exogenous FGF-1 stimulated expression of OPN mRNA and protein in RASMCs in vitro in a dose- and time-dependent manner. OPN mRNA induction by FGF-1 was completely inhibited by either actinomycin D or cycloheximide, selective inhibitors of RNA polymerase and protein synthesis, respectively. OPN mRNA induction by FGF-1 was attenuated by PD 166866, a highly selective and potent FGFR-1 tyrosine kinase inhibitor. Addition of either PP2 or PD98059, specific inhibitors of Src and mitogen-activated extracellular signal-regulated kinase (MEK)/mitogen-activated protein (MAP) kinases, respectively, attenuated FGF-1-stimulated OPN mRNA expression. FGF-1 treatment of RASMCs enhanced RASMC-conditioned medium-stimulated AF migration; this effect was inhibited by pretreatment of RASMCs with either PD166866 or PP2. Immunodepletion of OPN from RASMC-conditioned medium inhibited both basal and FGF-1-stimulated AF migration. CONCLUSIONS: This in vitro study provided a first indication that ligand-activated FGFR-1 plays a significant role in upregulation of OPN expression at the transcriptional level via signaling to Src/MEK/MAP kinases in RASMCs and that this pathway is functionally significant in mediating AF migration via stimulation of OPN expression.

Animals↗

PubMed2002

Interaction in vitro of type III intermediate filament proteins with triplex DNA.

As previously shown, type III intermediate filaments (IFs) select from a mixture of linear mouse genomic DNA fragments mobile and repetitive, recombinogenic sequences that have also been identified in SDS-stable crosslinkage products of vimentin and DNA isolated from intact fibroblasts. Because these sequences also included homopurine.homopyrimidine (Pu.Py) tracts known to adopt triple-helical conformation under superhelical tension, and because IF proteins are single-stranded (ss) and supercoiled DNA-binding proteins, it was of interest whether they have a particular affinity for triplex DNA. To substantiate this, IF-selected DNA fragments harboring a (Pu.Py) segment and synthetic d(GA)(n) microsatellites were inserted into a vector plasmid and the constructs analyzed for their capacity to interact with IF proteins. Band shift assays revealed a substantially higher affinity of the IF proteins for the insert-containing plasmids than for the empty vector, with an activity decreasing in the order of vimentin > glial fibrillary acidic protein > desmin. In addition, footprint analyses performed with S1 nuclease, KMnO(4), and OsO(4)/bipyridine showed that the (Pu.Py) inserts had adopted triplex conformation under the superhelical strain of the plasmids, and that the IF proteins protected the triple-helical insert sequences from nucleolytic cleavage and chemical modification. All these activities were largely reduced in extent when analyzed on linearized plasmid DNAs. Because intramolecular triplexes (H-DNA) expose single-stranded loops, and the prokaryotic ssDNA-binding proteins g5p and g32p also protected at least the Pu-strand of the (Pu.Py) inserts from nucleolytic degradation, it seemed likely that the IF proteins take advantage of their ssDNA-binding activity in interacting with H-DNA. However, in contrast to g5p and E. coli SSB, they produced no clear band shifts with single-stranded d(GA)(20) and d(TC)(20), so that the interactions rather appear to occur via the duplex-triplex and triplex-loop junctions of H-DNA. On the other hand, the IF proteins, and also g32p, promoted the formation of intermolecular triplexes from the duplex d[A(GA)(20).(TC)(20)T] and d(GA)(20) and d(TC)(20) single strands, with preference of the Py (Pu.Py) triplex motif, substantiating an affinity of the proteins for the triplex structure as such. This triplex-stabilizing effect of IF proteins also applies to the H-DNA of (Pu.Py) insert-containing plasmids, as demonstrated by the preservation of intramolecular triplex-vimentin complexes upon linearization of their constituent supercoiled DNAs, in contrast to poor complex formation from free, linearized plasmid DNA and vimentin. Considering that (Pu.Py) sequences are found near MAR/replication origins, in upstream enhancer and promoter regions of genes, and in recombination hot spots, these results might point to roles of IF proteins in DNA replication, transcription, recombination, and repair.

Animals↗

PubMed2002

Interaction in vitro of type III intermediate filament proteins with supercoiled plasmid DNA and modulation of eukaryotic DNA topoisomerase I and II activities.

To further characterize the interaction of cytoplasmic intermediate filament (cIF) proteins with supercoiled (sc)DNA, and to support their potential function as complementary nuclear matrix proteins, the type III IF proteins vimentin, glial fibrillary acidic protein, and desmin were analyzed for their capacities to interact with supercoiled plasmids containing a bent mouse gamma-satellite insert or inserts capable of non-B-DNA transitions into triplex, Z, and cruciform DNA, that is, DNA conformations typically bound by nuclear matrices. While agarose gel electrophoresis revealed a rough correlation between the superhelical density of the plasmids and their affinity for cIF proteins as well as cIF protein-mediated protection of the plasmid inserts from S1 nucleolytic cleavage, electron microscopy disclosed binding of the cIF proteins to DNA strand crossovers in the plasmids, in accordance with their potential to interact with both negatively and positively supercoiled DNA. In addition, the three cIF proteins were analyzed for their effects on eukaryotic DNA topoisomerases I and II. Possibly because cIF proteins interact with the same plectonemic and paranemic scDNA conformations also recognized by topoisomerases, but select the major groove of DNA for binding in contrast to topoisomerases that insert into the minor groove, the cIF proteins were able to stimulate the enzymes in their supercoil-relaxing activity on both negatively and positively supercoiled plasmids. The stimulatory effect was considerably stronger on topoisomerase I than on topoisomerase II. Moreover, cIF proteins assisted topoisomerases I and II in overwinding plasmid DNA with the formation of positive supercoils. Results obtained with the N-terminal head domain of vimentin harboring the DNA binding region and terminally truncated vimentin proteins indicated the involvement of both protein-DNA and protein-protein interactions in these activities. Based on these observations, it seems conceivable that cIF proteins participate in the control of the steady-state level of DNA superhelicity in the interphase nucleus in conjunction with such topoisomerase-controlled processes as DNA replication, transcription, recombination, maintenance of genome stability, and chromosome condensation and segregation.

Animals↗

PubMed2002

[Study on the constituents from Neonauclea sessilifolia].

Seven compounds were isolated from Neonauclea sessilifolia. They are paeonol, 3,4-dihydroxybenzoic acid, scopoletin, anthraquinnones chrysophanol, 4H-1-benzopyran-4-one,5,7-dihydroxy-2-methyl, beta-sitosterol and stigmasterol glucoside. These compounds were isolated at first time from this genus and this plant.

Acetophenones↗