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Biomedical subjects

Hua Li

Publications and source records attributed to Hua Li.

At least 73 records · Page 4Linked to original sources
PubMed2005

Phenylalanine side chain behavior of the intestinal fatty acid-binding protein: the effect of urea on backbone and side chain stability.

The equilibrium unfolding behavior of the intestinal fatty acid-binding protein has been investigated by (19)F-NMR after incorporation of 4-fluorophenylalanine and by pulsed field gradient diffusion (1)H-NMR. At low urea concentrations (0-3 m) but prior to the global unfolding that begins at 4 m urea, the protein exhibits dynamic motion in the backbone and an expanded hydrodynamic radius with no major change in the side chain orientation. As monitored by two-dimensional (19)F-(19)F nuclear Overhauser effect, the distance between two phenylalanine residues (Phe(68) and Phe(93)) located in the two different beta-sheets that enclose the internal cavity did not change up to 4 m urea. Additionally, the chemical shifts of these two residues changed almost identically as a function of denaturant. At all urea concentrations, as well as in the native protein, multiple conformations exist. These conformers interconvert at different rates under different conditions, ranging from slow exchange by showing separate peaks in the native state to intermediate exchange at intermediate urea concentrations. Residual structure persisted around Phe(62) even at very high concentrations of denaturant, suggesting that region as a nucleation site during folding. The results were compared with previous studies examining the backbone behavior (Hodsdon, M. E., and Frieden, C. (2001) Biochemistry 40, 732-742) and suggest that the side chains show more stability than the backbone prior to global unfolding of the protein.

Animals↗
PubMed2005

Simulation of the influences of bathing solution and crosslink density on the swelling equilibrium of ionic thermo-sensitive hydrogels.

The influences of the bathing solution and crosslink density on the swelling equilibrium of ionic thermo-sensitive hydrogels due to temperature stimulus are studied by mathematical modeling. The model used is termed the multi-effect-coupling thermal-stimulus (MECtherm) model with consideration of multiphases and multiphysics. It is used for the steady-state numerical simulation of the hydrogels in swelling equilibrium after it is verified well by comparison with available experimental data concerning the variation of volume swelling ratio with temperature. The phenomenon of volume phase transition is simulated for the thermal-stimulus responsive hydrogel. Simulations predict well the influences of the bathing solution concentration and crosslink density of polymeric network on the swelling equilibrium of the hydrogels.

Chemical Phenomena↗
PubMed2005

Recurring challenges from a necrotrophic fungal plant pathogen: a case study with Leptosphaeria maculans (causal agent of blackleg disease in brassicas) in Western Australia.

BACKGROUND: Blackleg disease of Brassica napus, caused by the necrotrophic fungus Leptosphaeria maculans, causes severe yield losses in Australia, Europe and Canada. In Western Australia, it nearly destroyed the oilseed rape industry in 1972 when host genotypes and conducive environmental conditions favoured severe epidemics. The introduction of cultivars with polygenic resistance and the adoption of sound cultural practices two decades later helped to manage the disease. These were abandoned by many farmers in recent years in favour of the effective but ephemeral resistance conferred by the single dominant gene-based resistance derived from B. rapa ssp. sylvestris. Recently, several cultivars carrying this gene have collapsed widely within a period of 3 years after their commercial release. An environment conducive to the disease and the association of the pathogen with susceptible hosts in Western Australia for over 80 years together have led to the proliferation of L. maculans races, amounting to half of all races delineated to date from Europe, including the United Kingdom, Canada and Australia. SCOPE: This review demonstrates the problems that emerge when traditional cultural practices employed, along with cultivars containing polygenic resistance to a serious necrotrophic pathogen, are discarded in preference to the exclusive deployment of effective but ephemeral single dominant gene-based resistance to the disease across Southern Australia. CONCLUSIONS: Single dominant gene-based resistance currently available, on its own, will not confer durable resistance to blackleg disease in oilseed rape. Return to earlier management practices, including reliance upon polygenic resistance and induced resistance, may be the best currently available options to maintain production in regions across Southern Australia predisposed to severe epidemics.

Ascomycota↗
PubMed2005

Nerve-pathways of acupoint Fengch'ih in rat by anterograde transport of HRP.

AIM: To study the nervous-pathways of Fengch'ih acupuncture by means of anterograde transport of aqueous solution of horseradish peroxidase (HRP). METHODS: Fifty Wistar rats were randomly divided into 1, 2, 3, 4, and 5 d groups, and every group had 10 animals. HRP (30% aqueous solution) was injected into a Fengch'ih. Serial, transverse or capital, 40 microm sections of the cervical spinal ganglia, cervical and thoracic spinal cord segment and brain were cut on a cryotome. Sections were incubated for HRP histochemistry according to the tetramethylbenzidine (TMB). Part of the sections were counterstained with neutral red. RESULTS: After 1 d of survival times, many labeled cell bodies were found in 1-4 cervical spinal ganglia, anterior horn of 1-4 cervical spinal cord, ventromedial division of facial nucleus, accessory facial nucleus ipsilaterally. With increasing survival times, the intensity of labeled cells were slightly decreased. CONCLUSION: Fengch'ih may bring into full play its effect by correlation of posterior ear branch of facial nerve and anterior branch of 2-3 cervical nerve with 1-4 cervical the anterior horn of the spinal cord, ventromedial division of facial nucleus, accessory facial nucleus.

Acupuncture Points↗
PubMed2005

Two microtubule-associated proteins of the Arabidopsis MAP65 family function differently on microtubules.

The organization and dynamics of microtubules are regulated by microtubule-associated proteins, or MAPs. In Arabidopsis (Arabidopsis thaliana), nine genes encode proteins of the evolutionarily conserved MAP65 family. We proposed that different MAP65s might have distinct roles in the interaction with microtubules. In this study, two AtMAP65 proteins, AtMAP65-1 and AtMAP65-6, were chosen to test this hypothesis in vitro. Although both fusion proteins were able to cosediment with microtubules in vitro, different properties on tubulin polymerization and microtubule bundling were observed. AtMAP65-1 was able to promote tubulin polymerization, enhance microtubule nucleation, and decrease the critical concentration for tubulin polymerization. It also induced the formation of large microtubule bundles by forming cross-bridges between microtubules evenly along the whole length of microtubules. In the presence of AtMAP65-1, microtubule bundles were more resistant to cold and dilution treatments. AtMAP65-6, however, demonstrated no activity in promoting tubulin polymerization and stabilizing preformed microtubules. AtMAP65-6 induced microtubules to form a mesh-like network with individual microtubules. Cross-bridge-like interactions were only found at regional sites between microtubules. The microtubule network induced by AtMAP65-6 was more resistant to high concentration of NaCl than the bundles induced by AtMAP65-1. Purified monospecific anti-AtMAP65-6 antibodies revealed that AtMAP65-6 was associated with mitochondria in Arabidopsis cells. It was concluded that these two MAP65 proteins were targeted to distinct sites, thus performing distinct functions in Arabidopsis cells.

Arabidopsis↗
PubMed2005

Improving in vitro development of cloned bovine embryos with hybrid (Holstein-Chinese Yellow) recipient oocytes recovered by ovum pick up.

In the present study, oocytes from F1 hybrid cattle, as well as their parental lines, were recovered by ovum pick up (OPU) and used as recipient cytoplasm for somatic cell nuclear transfer (SCNT). Four F1 hybrid (Holstein dam x Chinese Yellow sire), 10 Holstein and four Chinese Yellow cattle were subjected to OPU once weekly. There were no significant differences among breeds for number of recovered oocytes per session (overall average, 7.8+/-0.5; mean+/-S.E.M.), quality of the recovered oocytes, or oocyte maturation rate (72-73%). Matured oocytes were all used as recipient cytoplasm (without selection) and a single batch of cumulus cells collected from a Holstein cow were used as donor cells. Although reconstructed embryos initiated cleavage sooner when the recipient cytoplasm was from hybrid cattle versus the two parental breeds, the overall cleavage rate was indistinguishable among breeds. At Day 8, the blastocyst rate from the cleaved embryos (51% versus 37% and 27%), the total number of cells per blastocyst (135+/-4.1 versus 116+/-3.6 and 101+/-4.2), and the percentage of Grade-A (excellent quality) blastocysts (54% versus 42% and 29%) in the hybrid group were all higher than that of Holstein and Yellow groups. Furthermore, the proportion of blastocysts obtained at Day 7 (as a percentage of the total number of blastocysts) was greater in the hybrid group than in Holstein and Yellow groups (89% versus 71% and 63%). In conclusion, the use of F1 hybrid oocytes as recipient cytoplasm significantly improved in vitro development of cloned bovine embryos relative to oocytes derived from the parental lines.

Animals↗
PubMed2005

AP-3 directs the intracellular trafficking of HIV-1 Gag and plays a key role in particle assembly.

Gag proteins direct the process of retroviral particle assembly and form the major protein constituents of the viral core. The matrix region of the HIV-1 Gag polyprotein plays a critical role in the transport of Gag to the plasma membrane assembly site. Recent evidence indicates that Gag trafficking to late endosomal compartments, including multivesicular bodies, occurs prior to viral particle budding from the plasma membrane. Here we demonstrate that the matrix region of HIV-1 Gag interacts directly with the delta subunit of the AP-3 complex, and that this interaction plays an important functional role in particle assembly. Disruption of this interaction eliminated Gag trafficking to multivesicular bodies and diminished HIV particle formation. These studies illuminate an early step in retroviral particle assembly and provide evidence that the trafficking of Gag to late endosomes is part of a productive particle assembly pathway.

Adaptor Protein Complex 3↗
PubMed2005

Effects of annealing temperature on magnetic property and structure of amorphous Co49Pt51 alloy nanowire arrays prepared by direct-current electrodeposition.

Co49Pt51 nanowire arrays with an average diameter of 35 nm and lengths up to several micrometers were grown in an ordered porous anodic aluminum oxide (AAO) template using direct-current electrodeposition. The as-deposited samples were annealed at 100, 200, 300, 400, 500, 600, and 700 degrees C, respectively. The temperature dependence of the magnetic property of the Co49Pt51 nanowire arrays associated with the microstructure was analyzed by X-ray diffraction and a vibrating sample magnetometer. Magnetic measurements show that the samples both as-prepared and annealed at low temperatures have excellent perpendicular anisotropy. The perpendicular coercivity (Hc(perpendicular)) of Co49Pt51 alloy nanowire arrays increases dramatically as the annealing temperature (T(A)) rises, reaches a maximum(Hc(perpendicular) = 2770 Oe) at 400 degrees C, and then decreases sharply as T(A) rises further. This phenomenon should be attributed to the special structure of the nanowire arrays/AAO, and the microstructure factors significantly change during the annealing process.

Journal Article↗
PubMed2005

[Antigen analysis of Angiostrongylus cantonensis in different developmental stages].

OBJECTIVE: To analyze the difference among antigens of Angiostrongylus cantonensis in different developmental stages and identify dominant diagnostic antigen for angiostrongyliasis. METHODS: Antigens of A. cantonensis in different developmental stages were analyzed by SDS-PAGE and immunoblot. RESULTS: The protein bands of all developmental stages were similar on SDS-PAGE. The Mr 40000, 50000, 66000 and 80000 antigens reacted not only with the sera of rats infected by A. cantonensis but also with the sera of normal rats. The Mr 104000 antigen could be discerned by sera of rats infected with A. cantonensis for 2 weeks. The Mr 32000 antigen could be recognized by sera of rats 2 weeks after infection, and the reaction became stronger with the infection continued. CONCLUSION: The Mr 40000, 50000, 66000 and 80000 antigens might result in the unspecific reaction in the immunodiagnosis of angiostrongyliasis using the crude antigen of A. cantonensis. The Mr 104000 of larva, Mr 33000 of adult females and Mr 32000 of the worms might be used as candidate antigens in early diagnosis and epidemiological survey of angiostrongyliasis.

Angiostrongylus cantonensis↗
PubMed2005

NMR studies of 4-19F-phenylalanine-labeled intestinal fatty acid binding protein: evidence for conformational heterogeneity in the native state.

(19)F-Nuclear magnetic resonance (NMR) studies have been carried out after incorporation of 4-(19)F-phenylalanine into the intestinal fatty acid binding protein (IFABP), a protein composed of two beta-sheets containing a large hydrophobic cavity into which ligands bind. NMR spectra have been obtained with both the ligand-free and ligand-bound (oleate) forms. There are 29 residues involved in van der Waals or hydrophobic interactions or both to form a U-shaped ligand binding pocket (Sacchettni J. C., Scapin G., Gopaul D., and Gordon J. I. (1992) J. Biol. Chem. 267, 23534-23545). The protein contains eight phenylalanines, and all are included in those residues that line the pocket. Peak assignments were made using site-specific incorporation of 4-(19)F-phenylalanine. Fluorine is a highly sensitive probe to monitor the conformation and dynamics of the side chains in native state. We find that chemical exchange in the binding pocket exists in the native apo- and holo-state. Of the eight phenylalanine residues, Phe2, Phe47, Phe62, Phe68, and Phe93 are arranged on one side of the binding pocket, and all exist in two conformations with Phe2, Phe47, and Phe62 showing exchange cross-peaks with minor conformation in (19)F-(19)F nuclear Overhauser effect (NOESY) spectra. The line widths of Phe68 and Phe93 are broader than those of other phenylalanine residues and can be deconvoluted into two peaks. Phe47, Phe62, Phe68, Phe93, and Trp82 have been proposed to be involved in the early stage of collapse (Ropson, I. J., and Frieden, C. (1992) Proc. Natl. Acad. Sci U.S.A. 89, 7222-7226), but a temperature study suggests that Phe47 behaves differently than other residues and may be more involved in a later stage of folding, for example, side chain stabilization. In the holo-form, Phe17 shows an extra exchange cross-peak in addition to those exchange cross-peaks observed in apo-form. Holo-IFABP exhibits broader line width than the apo-form, suggesting more flexibility of the binding cavity upon ligand binding.

Animals↗
PubMed2005

Resolution of overlapping capillary electrophoresis peaks by using chemometric analysis: quantification of the components in compound reserpine tablets.

The application of multivariate curve resolution with alternating least squares (MCR-ALS) methods to second-order data from capillary electrophoresis with diode array detector (CE-DAD) is reported. Initial qualitative solutions obtained by evolving factor analysis (EFA) and pure-variable detection method can be further optimized by a simultaneous analysis of multiple electrophoresis run data with ALS regression. While unknown samples are analyzed simultaneously against the corresponding standards in different composition ratios, the exact amounts of common components in different CE runs can be determined by the traditional calibration curve method, and quantification can thus be achieved. The above methods are applied to the determination of the components in compound reserpine tablets in overlapping peaks from CE. The quantification results are compared with those of the first derivative of the electropherogram method and artificial neural network (ANN) method.

Electrophoresis, Capillary↗
PubMed2005

Genistein inhibited retinal neovascularization and expression of vascular endothelial growth factor and hypoxia inducible factor 1alpha in a mouse model of oxygen-induced retinopathy.

The effects of genistein on neovascularization, vascular endothelial growth factor (VEGF), and hypoxia inducible factor 1alpha (HIF1alpha) protein expression in a mouse model of oxygen-induced retinopathy were studied. The model of oxygen-induced retinal neovascularization was induced in newborn C57BL/6 mice by exposing 7-day-old mice to 75% oxygen for 5 days and then housing them in room air (relative hypoxia). Retinopathy was assessed by quantitation of vascular cell nuclei anterior to inner limiting membrane. Judged by relative fluorescence using a confocal scanning laser microscope coupled to a computer, VEGF and HIF1alpha protein expression were investigated. Genistein markedly inhibited the numbers of nuclei protruding above the inner limiting membrane under relative hypoxia conditions. The levels of nuclei numbers were suppressed by 50, 100, and 200 mg/kg body weight /day genistein to 87.4%, 72.0%, and 59.4%, respectively, compared to that untreated with genistein. VEGF protein was constitutively expressed in the preretinal area under normoxia conditions. Genistein markedly inhibited relative-hypoxia-elicited VEGF expression elevation in a dose-dependent manner. HIF1alpha expression was also observed in normoxia conditions. There was a 2.4-fold induction in preretinal HIF1alpha expression in oxygen-reared animals when compared to room-air-reared animals. Genistein dose-dependently suppressed HIF1alpha protein expression. These results indicated that the inhibition of VEGF and HIF1alpha protein expression by genistein may partly account for its effect on retinal neovascularization in vivo, and genistein could be an effective agent in the prevention and treatment of ocular neovascularization.

Angiogenesis Inhibitors↗
PubMed2005

A note on joint versus gene-specific mixed model analysis of microarray gene expression data.

Currently, linear mixed model analyses of expression microarray experiments are performed either in a gene-specific or global mode. The joint analysis provides more flexibility in terms of how parameters are fitted and estimated and tends to be more powerful than the gene-specific analysis. Here we show how to implement the gene-specific linear mixed model analysis as an exact algorithm for the joint linear mixed model analysis. The gene-specific algorithm is exact, when the mixed model equations can be partitioned into unrelated components: One for all global fixed and random effects and the others for the gene-specific fixed and random effects for each gene separately. This unrelatedness holds under three conditions: (1) any gene must have the same number of replicates or probes on all arrays, but these numbers can differ among genes; (2) the residual variance of the (transformed) expression data must be homogeneous or constant across genes (other variance components need not be homogeneous) and (3) the number of genes in the experiment is large. When these conditions are violated, the gene-specific algorithm is expected to be nearly exact.

Algorithms↗
PubMed2005

Cetyltrimethylammonium bromide-enhanced chemiluminescence determination of uric acid using a luminol-hexacyanoferrate(III)-hexacyanoferrate(II) system.

A chemiluminescence (CL) method using flow injection (FI) was developed for the determination of uric acid based on the enhancement chemiluminescence intensity of luminol-hexacyanoferrate(III)-hexacyanoferrate(II) in the presence of cetyltrimethylammonium bromide and the uric acid species. The linear range was 7.0 x 10(-10) - 9.0 x 10(-7) M with a detection limit (3sigma) of 2.58 x 10(-10) M, which was about two orders of magnitude lower than those reported. The proposed method was used for the determination of uric acid in real samples.

Cetrimonium↗
PubMed2005

[Value of the antigen with molecular mass of 32 000 in immunodiagnosis of Angiostrongylus cantonensis].

OBJECTIVE: To evaluate the specificity and sensitivity of immunodiagnosis with the antigen with molecular mass of 32 000 of Angiostrongyliasis cantonensis(AC32). METHODS: The major antigenic protein AC32 was purified from the antigens of A.cantonensis adult worm by electroelution from SDS-polyacrylamide gels. AC32-enzyme linked immunosorbent assay (ELISA) and adult worm antigen (AWA)-ELISA were used to detect the specific IgG in the sera of normal rats (n=5) and rats with angiostrongyliasis (n=61), sera of healthy individuals (n=50) and patients (n=50) with angiostrongyliasis, schistosomiasis and other parasitosis. RESULTS: The positivity rate in AC32-ELISA of the sera from rats with angiostrongyliasis was 100%; without false positive results or cross reaction between AC32 and the sera of the normal control and patients infected with parasites other than A.cantonensis. CONCLUSION: AC32 of A.cantonensis is a valuable candidate antigen for immunodiagnosis of angiostrongyliasis with high sensitivity and specificity.

Angiostrongylus cantonensis↗
PubMed2005

[The genetic diversity of the second exon about SLA-DQB in some Chinese native pigs].

Polymorphism of the second exon about SLA-DQB genes in some Chinese native pigs was investigated employing PCR-SSCP analysis and DNA cloning sequencing. Combined with the sequences in GenBank, 73 new alleles were gained, among them function alleles of SLA-DQB were sixty-eight, five alleles of pseudogene (SLA-DXB) were gained. There were disequilibrium distribution of the alleles in all breeds, the same allele was shared by most breeds. C08 allele existed in 11 breeds of six groups and in the wild pigs of Yunnan and Sichuan province, and its frequency reached 55.10%. More than five sequences were found in each individual, suggesting duplication in these loci examined, there were three copies about SLA-DQB genes. The variable sites based on nucleotide and amino acids reached to eighty-one and forty-nine, respectively. The values of allelic diversity (H=0.889) and the nucleotide diversity (Pi=0.047) were revealed very high, from both values of H and Pi were higher in the beta pleated sheet region than those in alpha helix region in Chinese native pigs. In general, values of H and Pi in Huanan pigs and Xinan pigs were higher, vice versa in Tibet pigs. The genetic distance within group were showed the same order as comparison Pi values, hence we concluded the different rate of nucleotide substitution were positive correlated with the degree of nucleotide diversity in Chinese domestic groups. The genetic distances about SLA-DQB gene between groups were detected as follow: the great genetic distance were existed between the Jianghai and Huabei groups, and the smallest genetic distance were existed between the Huazhong and Gaoyuan groups.

Alleles↗