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Haitao Li

Publications and source records attributed to Haitao Li.

At least 37 records · Page 2Linked to original sources
PubMed2005

Extensive submacular haemorrhage in polypoidal choroidal vasculopathy managed by sequential gas displacement and photodynamic therapy: a pilot study of one-year follow up.

BACKGROUND: Polypoidal choroidal vasculopathy (PCV) with peculiar vascular lesions presents frequently as recurrent submacular haemorrhage. The best treatment is still not certain. It is the authors' objective to evaluate the 1-year safety and efficacy of photodynamic therapy (PDT) using verteporfin for persistent macular PCV after pneumatic displacement of the massive submacular haemorrhage with intravitreal perfluoropropane (C(3)F(8)). METHODS: A prospective, non-comparative, interventional case series on patients with extensive and thick submacular haemorrhage secondary to PCV, which was displaced pneumatically with intravitreal pure 0.4 ml C(3)F(8). Fluorescein angiography and indocyanine green angiography were repeated 1-2 weeks later to delineate any persistent active leaking polypoidal lesions, which were then treated with PDT. Retreatment might be considered in each follow up at every 3 months. RESULTS: Six eyes of six patients with the mean age of 53.6 years had been recruited and completed 1-year follow up. The mean baseline Snellen equivalent best-corrected visual acuity (BCVA) was 6/92 and the mean final BCVA at 1 year was 6/17. The mean improvement in logMAR BCVA after the sequential treatments was seven lines (range +3 to +19 lines) (Wilcoxon signed-ranks test, P = 0.03). All patients had at least moderate visual gains. No patient suffered serious complications from PDT. CONCLUSIONS: This first report on combined treatment with intravitreal gas injection and sequential PDT on PCV seems to be a well-tolerated option. Further comparative studies with larger sample size and longer follow up are warranted.

Choroid↗
PubMed2004

Involvement of protein radical, protein aggregation, and effects on NO metabolism in the hypochlorite-mediated oxidation of mitochondrial cytochrome c.

Cytochrome c (cyt c)-derived protein radicals, radical adduct aggregates, and protein tyrosine nitration have been implicated in the pro-apoptotic event connecting inflammation to the development of diseases. During inflammation, one of the reactive oxygen species metabolized via neutrophil activation is hypochlorite (HOCl); destruction of the mitochondrial electron transport chain by hypochlorite is considered to be a damaging factor. Previous study has shown that HOCl induces the site-specific oxidation of cyt c at met-80. In this work, we have assessed the hypothesis that exposure of cyt c to physiologically relevant concentrations of HOCl leads to protein-derived radical and consequent protein aggregation, which subsequently affects cyt c's regulation of nitric oxide metabolism. Reaction intermediates, chemical pathways available for protein aggregation, and protein nitration were examined. A weak ESR signal for immobilized nitroxide derived from the protein was detected when a high concentration of cyt c was reacted with hypochlorite in the presence of the nitroso spin trap 2-methyl-2-nitrosopropane. When a low concentration of cyt c was exposed to the physiologically relevant levels of HOCl in the presence of 5,5-dimethyl-pyrroline N-oxide (DMPO), we detected DMPO nitrone adducts derived from both protein and protein aggregate radicals as assessed by Western blot using an antibody raised against the DMPO nitrone adduct. The cyt c-derived protein radicals formed by HOCl were located on lysine and tyrosine residues, with lysine predominating. Cyt c-derived protein aggregates induced by HOCl involved primarily lysine residues and hydrophobic interaction. In addition, HOCl-oxidized cyt c (HOCl-cyt c) exhibited a higher affinity for NO and enhancement of nonenzymatic NO synthesis from nitrite reduction. Furthermore, HOCl-mediated cyt c oxidation also resulted in a significant elevation of cyt c nitration derived from either NO trapping of the cyt c-derived tyrosyl radical or cyt c-catalyzed one-electron oxidation of nitrite.

Animals↗
PubMed2004

Measuring single-molecule nucleic acid dynamics in solution by two-color filtered ratiometric fluorescence correlation spectroscopy.

This work presents a general method for determining single-molecule intramolecular dynamics in biomolecules by using a reporter fluorophore, whose fluorescence is quenched or partially quenched as a result of intramolecular motion, and a remote observer fluorophore. These fluorophores were excited independently with two different lasers, and the ratio of the two fluorophores' fluorescence was calculated. The time-varying ratio was then filtered to reduce contributions from molecules outside the overlapped laser volume and then correlated. The rates of opening and closing of a DNA hairpin were measured by using both fluorescence correlation spectroscopy and this method for comparison. We found at 50 pM, where molecules were studied one by one as they diffused through the probe volume, we obtained accurate opening and closing rates and could also measure dynamic heterogeneity. To demonstrate applicability to a more complex biological molecule we then probed intramolecular motions in the dimer of a human telomerase RNA fragment (hTR(380-444)), in the presence of an excess of monomer. The motion was found to occur on the time scale of 180-750 micros and slowed with increasing magnesium ion concentration. Blocking experiments using complementary oligonucleotides suggested that the motion involves substantial changes in dimer tertiary structure. This method appears to be a general method for selectively studying intramolecular motion in large biomolecules or complexes.

Base Sequence↗
PubMed2004

Molecule by molecule direct and quantitative counting of antibody-protein complexes in solution.

We have used two-color fluorescence coincidence detection to directly count individual protein-antibody complexes of protein G or herpes simplex virus labeled with one or more red- and blue-excited antibodies. This allowed quantitative measurement of the concentration of the protein-antibody complexes over 3 orders of magnitude down to the femtomolar level. Single molecule measurements in diluted serum are also possible. The sample preparation is simple, takes place in solution, and requires no separation. Both the antibody affinity and complex dissociation rate are important in determining the sensitivity of the method. At present, the sensitivity limit of 50 fM is determined by the encounter rate of the labeled analyte with the probe volume. This method can be used to detect and quantitate proteins and to measure the stoichiometry, equilibrium constant, and dissociation rate of protein-protein complexes at low concentrations.

Animals↗
PubMed2004

Polypoidal choroidal vasculopathy in elderly Chinese patients.

PURPOSE: To investigate the frequency and clinical features of polypoidal choroidal vasculopathy (PCV) in a consecutive series of elderly Chinese patients. METHODS: A restrospective analysis of 166 consecutive patients 50 years or older with diagnosis of exudative age-related macular degeneration (AMD) was conducted. Color fundus photographs were taken and fluorescein and indocyanine green (ICG) angiography were performed in all patients. RESULTS: Of the 166 patients, 37 patients (22.3%) initially suspected of having exudative AMD were ultimately diagnosed as having PCV. Twenty-seven men (73.0%) were affected, 32 patients (86.5%) were unilaterally involved. Of 42 eyes with PCV, 27 eyes (64.3%) demonstrated polypoidal dilations with branching vascular network, and the other 15 eyes (35.7%) showed scattered polypoidal dilations without identifiable continuous branching vascular network on ICG angiography. The predominant location for these lesions was at the macular region in 26 eyes (61.9%), the temporal vascular arcade in 9 eyes (21.4%), the peripapillary area in 6 eyes (14.3%), and the midperiphery in 1 eye (2.4%). CONCLUSIONS: PCV is a common disease in elderly Chinese patients. In our study group PCV mainly affected men and was mostly unilateral. Most of the lesions were located in the macular region and temporal vascular arcade.

Age Distribution↗
PubMed2004

Comparative genomics identifies a flagellar and basal body proteome that includes the BBS5 human disease gene.

Cilia and flagella are microtubule-based structures nucleated by modified centrioles termed basal bodies. These biochemically complex organelles have more than 250 and 150 polypeptides, respectively. To identify the proteins involved in ciliary and basal body biogenesis and function, we undertook a comparative genomics approach that subtracted the nonflagellated proteome of Arabidopsis from the shared proteome of the ciliated/flagellated organisms Chlamydomonas and human. We identified 688 genes that are present exclusively in organisms with flagella and basal bodies and validated these data through a series of in silico, in vitro, and in vivo studies. We then applied this resource to the study of human ciliation disorders and have identified BBS5, a novel gene for Bardet-Biedl syndrome. We show that this novel protein localizes to basal bodies in mouse and C. elegans, is under the regulatory control of daf-19, and is necessary for the generation of both cilia and flagella.

Animals↗
PubMed2004

Isotherm analysis of phenol adsorption on polymeric adsorbents from nonaqueous solution.

Macroporous poly(methyl methacrylate-co-divinylbenzene) (PMMA), interpenetrating polymer adsorbent based on poly(styrene-co-divinylbenzene) (PS) and poly(methyl methacrylate-co-divinylbenzene) (PMMA/PS), and macroporous cross-linked poly(N-p-vinylbenzyl acetylamide) (PVBA) were prepared for the adsorption of phenol from cyclohexane. The sorption isotherms of phenol on the three polymeric adsorbents were measured and fitted to Langmuir and Freundlich isotherms. It is shown that the Langmuir isotherm, which is based on a homogeneous surface model, is unsuitable to describe the sorption of phenol on the adsorbents from nonaqueous solution and the Freundlich equation fits the tested three adsorption systems well. The isosteric enthalpy was quantitatively correlated with the fractional loading for the sorption of phenol onto the three polymeric adsorbents. The surface energetic heterogeneity patterns of the adsorbents were described with functions of isosteric enthalpy. The results showed that the tested three polymeric adsorbents exhibited different surface energetic heterogeneity patterns. The initial isosteric enthalpy of phenol sorption on polymeric adsorbent has to do with the surface chemical composition and is free from the pore structure of the polymeric adsorbent matrix. Forming hydrogen bonds between phenol molecules and adsorbent is the main driving force of phenol sorption onto PVBA and PMMA adsorbent from nonaqueous solution. When phenol is adsorbed on PMMA/PS, pi-pi interaction resulting from the stacking of the benzene rings of the adsorbed phenol molecules and the pendant benzene ring of adsorbent is involved.

Journal Article↗
PubMed2004

Characterization of the effects of oxygen on xanthine oxidase-mediated nitric oxide formation.

Under anaerobic conditions, xanthine oxidase (XO)-catalyzed nitrite reduction can be an important source of nitric oxide (NO). However, questions remain regarding whether significant XO-mediated NO generation also occurs under aerobic conditions. Therefore, electron paramagnetic resonance, chemiluminescence NO-analyzer, and NO-electrode studies were performed to characterize the kinetics and magnitude of XO-mediated nitrite reduction as a function of oxygen tension. With substrates xanthine or 2,3-dihydroxybenz-aldehyde that provide electrons to XO at the molybdenum site, the rate of NO production followed Michaelis-Menten kinetics, and oxygen functioned as a competitive inhibitor of nitrite reduction. However, with flavin-adenine dinucleotide site-binding substrate NADH as electron donor, aerobic NO production was maintained at more than 70% of anaerobic levels, and binding of NADH to the flavin-adenine dinucleotide site seemed to prevent oxygen binding. Therefore, under aerobic conditions, NADH would be the main electron donor for XO-catalyzed NO production in tissues. Studies of the pH dependence of NO formation indicated that lower pH values decrease oxygen reduction but greatly increase nitrite reduction, facilitating NO generation. Isotope tracer studies demonstrated that XO-mediated NO formation occurs in normoxic and hypoxic heart tissue. Thus, XO-mediated NO generation occurs under aerobic conditions and is regulated by oxygen tension, pH, nitrite, and reducing substrate concentrations.

Animals↗
PubMed2004

Fundus analysis and visual prognosis of macular hemorrhage in pathological myopia without choroidal neovasculopathy.

PURPOSE: To analysis and evaluate the fundus characteristics and visual prognosis of macular hemorrhage in pathological myopia without choroidal neovasculopathy. METHODS: Thirty-seven patients (38 eyes) of pathological myopia with macular hemorrhage and without choroidal neovascularization (CNV) underwent color photograph and fundus fluorescein angiography (FFA) examinations. Indocyanine green angiography (ICGA) was also performed on 11 patients (11 eyes). Follow-up ranged from 3 to 21 months. RESULTS: The macular hemorrhage in pathological myopia without CNV demonstrated oval, less than 1PD, without edema and exudation. Lacquer cracks appeared at the site of previous subretinal bleeding in 84.2% of the eyes. The visual acuities were improved in 81.6% of eyes during the follow-up period. ICGA revealed linear hypofluorescence in 7 of 11 eyes (63.6%), indicating a ruptured Bruch's membrance at the onset of subretinal bleeding. CONCLUSION: A rupture of choriocapillaris complex and Bruch's membrane causes macular hemorrhage of pathological myopia without CNV, leading to the formation of a new lacquer crack. Its prognosis is favorable.

Adolescent↗
PubMed2003

Studies on the structure and dynamics of the human telomeric G quadruplex by single-molecule fluorescence resonance energy transfer.

We have investigated the structure and unfolding kinetics of the human telomeric intramolecular G quadruplex by using single-molecule fluorescence resonance energy transfer. An exploration of conformational heterogeneity revealed two stable folded conformations, in both sodium- and potassium-containing buffers, with small differences between their enthalpies and entropies. Both folded conformations can be opened by the addition of a 21-base complementary DNA oligonucleotide. The unfolding of both substates occurs at the same rate, which showed dependence on the monovalent metal cation present. Temperature-dependence studies in 100 mM KCl gave an apparent activation enthalpy and entropy of 6.4 +/- 0.4 kcal.mol-1 and -52.3 +/- 1.4 cal.mol-1.K-1, respectively, indicating that the unfolding is entropically driven and can occur easily. In contrast, in 100 mM NaCl the respective values are 14.9 +/- 0.2 kcal.mol-1 and -23.0 +/- 0.8 cal.mol-1.K-1, suggesting a more significant enthalpic barrier. Molecular modeling suggests that the two species are likely to be the parallel and antiparallel quadruplex structures. The unfolding free energy barrier is estimated to be between 3 and 15 kBT based on Kramers' theory. We conclude that under near-physiological conditions these structures coexist and can interconvert on a minute time scale.

Base Composition↗
PubMed2003

Identification of a new RNA.RNA interaction site for human telomerase RNA (hTR): structural implications for hTR accumulation and a dyskeratosis congenita point mutation.

The enzyme telomerase is a ribonucleoprotein that has a critical role in the maintenance of stable telomeres in organisms that possess linear chromosomes. Using a recently developed single molecule fluorescence coincidence method, we have studied the RNA component of telomerase (hTR) and directly observed multimerisation of hTR in solution. RNA mutagenesis and blocking oligonucleotides were employed to identify the single-stranded internal loop J7b/8a as an important and specific hTR.hTR interaction site. This observation was confirmed by studies on a model RNA fragment (hTR(380-444)), comprising part of the H/ACA domain, the internal loop J7b/8a and the CR7 domain, that was found to dimerise. Substitution mutagenesis within the proposed RNA.RNA interaction site of hTR(380-444) resulted in a loss of dimerisation potential and insertion of the dyskeratosis congenita mutation C408G led to a significant reduction in dimer formation. Together, these results suggest that this RNA.RNA interaction site may be functionally relevant.

Binding Sites↗
PubMed2003

Ultrasensitive coincidence fluorescence detection of single DNA molecules.

We have detected individual DNA molecules labeled with two different fluorophores in solution by using two-color excitation and detection of coincidence fluorescence bursts. The confocal volumes of the two excitation lasers were carefully matched so that the volume overlap was 30% of the total confocal volume illuminated. This method greatly reduces the level of background fluorescence and, hence, extends the sensitivity of single molecule detection down to 50 fM. At these concentrations, the dual-labeled DNA is detectable in the presence of a 1000-fold excess of single-fluorophore-labeled DNA. We demonstrate that we can detect 100 fM dual-labeled DNA diluted in 1 microM unlabeled DNA, which was not possible with single color detection. This method can be used to detect rare molecules in complex mixtures.

DNA↗
PubMed2003

Characterization of the magnitude and kinetics of xanthine oxidase-catalyzed nitrate reduction: evaluation of its role in nitrite and nitric oxide generation in anoxic tissues.

In addition to nitric oxide (NO) generation from specific NO synthases, NO is also formed during anoxia from nitrite reduction, and xanthine oxidase (XO) catalyzes this process. While in tissues and blood high nitrate levels are present, questions remain regarding whether nitrate is also a source of NO and if XO-mediated nitrate reduction can be an important source of NO in biological systems. To characterize the kinetics, magnitude, and mechanism of XO-mediated nitrate reduction under anaerobic conditions, EPR, chemiluminescence NO-analyzer, and NO-electrode studies were performed. Typical XO reducing substrates, xanthine, NADH, and 2,3-dihydroxybenz-aldehyde, triggered nitrate reduction to nitrite and NO. The rate of nitrite production followed Michaelis-Menten kinetics, while NO generation rates increased linearly following the accumulation of nitrite, suggesting stepwise-reduction of nitrate to nitrite then to NO. The molybdenum-binding XO inhibitor, oxypurinol, inhibited both nitrite and NO production, indicating that nitrate reduction occurs at the molybdenum site. At higher xanthine concentrations, partial inhibition was seen, suggesting formation of a substrate-bound reduced enzyme complex with xanthine blocking the molybdenum site. The pH dependence of nitrite and NO formation indicate that XO-mediated nitrate reduction occurs via an acid-catalyzed mechanism. With conditions occurring during ischemia, myocardial xanthine oxidoreductase and nitrate levels were determined to generate up to 20 microM nitrite within 10-20 min that can be further reduced to NO with rates comparable to those of maximally activated NOS. Thus, XOR catalyzed nitrate reduction to nitrite and NO occurs and can be an important source of NO production in ischemic tissues.

Animals↗
PubMed2003

Electrophilic tetraalkylammonium nitrate nitration. II. Improved anhydrous aromatic and heteroaromatic mononitration with tetramethylammonium nitrate and triflic anhydride, including selected microwave examples.

A new one-pot nitration employing tetramethylammonium nitrate and trifluoromethanesulfonic anhydride in dichloromethane to provide a ready source of the nitronium triflate nitrating agent is presented. Rapid and selective nitration with a variety of aromatic and heteroaromatic substrates is achieved resulting in the synthesis of several novel organic compounds. A distinct advantage is the removal of undesired byproducts by aqueous workup. This very mild nitration permits large-scale syntheses and gives high isolated product yields that often require no further purification. This tetramethylammonium nitrate-based nitration also has been applied to microwave-assisted conditions, and the results with several compounds are outlined.

Journal Article↗
PubMed2002

The discovery of novel small molecule non-peptide gonadotropin releasing hormone (GnRH) receptor antagonists.

A novel series of non-peptide derivatives 1, 14, and 15 that bind with high affinity to the human GnRH receptors is discussed. The discovery was made from screening our in-house libraries that contained the active structure 2 along with a trace amount of a second active structure 1 that was derived from an acid-induced rearrangement. From this structure type 1, a series of guanidine and non-guanidine containing analogues were prepared and tested as GnRH receptor antagonists. Compounds derived from this series bind to both human and rat GnRH receptors and antagonize GnRH-mediated increases in inositol phosphate production in cells containing recombinant human receptors. These compounds or their analogues may be useful as therapeutic agents for the treatment of hormone-dependent pathologies including prostate, breast and ovarian cancers.

Animals↗
PubMed2002

Definition of an Fc receptor-related gene (FcRX) expressed in human and mouse B cells.

The recent identification of five human Fc receptor (FcR) homologs, hFcRH1-5, has extended the known FcR family and identified an unanticipated richness of the chromosome 1q region in genes encoding potential Ig-binding proteins. In a database search for additional relatives of this family we identified expressed sequence tag representatives of a new FcR-related molecule (hFcRX) and its mouse ortholog (mFcRX). The FcRX cDNAs were cloned from human lymph node and mouse spleen cDNA libraries. hFcRX is located centromeric of FcgammaRII and FcgammaRIII at 1q23, and its mouse ortholog resides in a syntenic region of chromosome 1. The genes encode proteins with 67% interspecies identity that lack both N-linked glycosylation sites and transmembrane regions. Two of the four FcRX domains are Ig-like, and share characteristics similar to FcgammaRI domains 2 and 3, having 28% overall extracellular identity with hFcgammaRI and 27% identity with mFcgammaRI respectively. FcRX transcripts are found primarily in secondary lymphoid tissues, where they are expressed by B lineage cells. FcRX thus may function as a secreted or intracellular protein in normal and neoplastic B cells.

Amino Acid Sequence↗
PubMed2002

[Comparative study of the image observation of earlypostburn brain edema in severely burned dogs].

OBJECTIVE: To explore the diagnostic value of MRI and SPECT in early postburn brain edema in severely burned dogs. METHODS: Twenty-six mongrel dogs were randomized into control (n = 6) and burned groups in which every 5 dogs were allotted to each of following time points: 6, 12, 18 and 24 postburn hours (PBHs). The dogs in burn groups were inflicted with 50% TBSA of III degree skin burn and were infused with 5% glucose solution after 6 PBHs, so that severe early postburn brain edema was produced. MRI and SPECT were employed to observe dynamically the brain of dogs in all groups. The results were collected and compared with one another. RESULTS: The results indicated that with MRI brain morphological change of early brain edema could be shown as early as within 12 PBH and diffuse brain edema became more obvious with elapse of time. The changes might be difficult to be found by MRI when T(1)WISIR decreased below 10%. T(2)WI SIR increased by 8.29% at 24 PBH with blurred demarcation between the brain gray and white matters. There was diffused and progressive nuclide ((99)TCm-ECD) concentration in the brain tissue as shown by SPECT at 6 PBH. The radio-nuclide taking ratio increased significantly after 12 PBH, especially at 24 PBH (P < 0.01) when compared with that before burn. CONCLUSION: Combined application of MRI and SPECT could evidently increase sensitivity and specificity in the diagnosis of early postburn brain edema.

Animals↗