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Q Hua

Publications and source records attributed to Q Hua.

At least 19 recordsLinked to original sources
PubMed2003

Microtubule associated protein tau binds to double-stranded but not single-stranded DNA.

Tau, a major microtubule-associated protein of the neuron, which is known to promote the assembly of and to stabilize microtubules, has also been seen associated with chromatin in neuronal cell lines, but its role in this subcellular compartment is still unknown. In this study, the binding of tau to DNA was investigated using the electrophoretic mobility shift assay. Using polynucleotide as probe, we found that tau bound to double-stranded but not to single-stranded DNA. Formation of tau-polynucleotide complex was disrupted by alkaline pH and a high concentration of NaCl, but was not affected by dithiothreitol. Electron microscopy revealed that the protein associated with the nucleic acid in a necklacelike manner. DNA-cellulose chromatography and radioimmunodot-blot analyses showed that calf thymus histones VI-S, VII-S and VIII-S could replace both recombinant human brain tau352 (tau-23) and tau441 (tau-40) from DNA. Thus, tau appears to bind to DNA reversibly in the presence of histones.

Animals↗
PubMed2002

Integration of the information from gene expression and metabolic fluxes for the analysis of the regulatory mechanisms in Synechocystis.

Synechocystis was grown under autotrophic, mixotrophic and heterotrophic conditions, and the gene expression patterns at the mRNA and protein levels were measured by using semi-quantitative RT-PCR and two-dimensional electrophoresis (2DE), respectively. Moreover, the intracellular metabolic flux distributions in Synechocystis grown under different trophic conditions were also determined using the carbon isotope labeling technique. By combining the information obtained from the transcript levels, protein abundance and metabolic fluxes, the regulatory mechanisms of some enzymes involved in the central metabolism of Synechocystis during growth in the different culture conditions were analyzed. It was found that depending on the energy source available to cyanobacterial cells, the enzymes required for central metabolism were differently regulated according to different mechanisms. The expression of several genes, such as rbcLS and gap2, was light-regulated transcriptionally, while the gene gnd was regulated in response to an apparent flux requirement but by an unknown mechanism. The expression of other genes was independent of the presence of light. The reactions catalyzed by G6PDH, Fbp, PfkA and FbaA were not regulated through enzyme synthesis but by a change in metabolite concentrations. The enzyme PrK was post-translationally regulated by light, probably through the operation of ferredoxin/thioredoxin system. For the enzyme RubisCO, both transcriptional and post-translational regulation was observed. These findings demonstrate that the information obtained from the analysis of mRNA expression, protein expression, and metabolic flux distribution is necessary to understand the regulatory events in complex cellular networks.

Cyanobacteria↗
PubMed2001

The dimerization domain of HNF-1alpha: structure and plasticity of an intertwined four-helix bundle with application to diabetes mellitus.

Maturity-onset diabetes mellitus of the young (MODY) is a human genetic syndrome most commonly due to mutations in hepatocyte nuclear factor-1alpha (HNF-1alpha). Here, we describe the crystal structure of the HNF-1alpha dimerization domain at 1.7 A resolution and assess its structural plasticity. The crystal's low solvent content (23%, v/v) leads to tight packing of peptides in the lattice. Two independent dimers, similar in structure, are formed in the unit cell by a 2-fold crystallographic symmetry axis. The dimers define a novel intertwined four-helix bundle (4HB). Each protomer contains two alpha-helices separated by a sharp non-canonical turn. Dimer-related alpha-helices form anti-parallel coiled-coils, including an N-terminal "mini-zipper" complementary in structure, symmetry and surface characteristics to transcriptional coactivator dimerization cofactor of HNF-1 (DCoH). A confluence of ten leucine side-chains (five per protomer) forms a hydrophobic core. Isotope-assisted NMR studies demonstrate that a similar intertwined dimer exists in solution. Comparison of structures obtained in multiple independent crystal forms indicates that the mini-zipper is a stable structural element, whereas the C-terminal alpha-helix can adopt a broad range of orientations. Segmental alignment of the mini-zipper (mean pairwise root-mean-square difference (rmsd) in C(alpha) coordinates of 0.29 A) is associated with a 2.1 A mean C(alpha) rmsd displacement of the C-terminal coiled-coil. The greatest C-terminal structural variation (4.1 A C(alpha) rmsd displacement) is observed in the DCoH-bound peptide. Diabetes-associated mutations perturb distinct structural features of the HNF-1alpha domain. One mutation (L12H) destabilizes the domain but preserves structural specificity. Adjoining H12 side-chains in a native-like dimer are predicted to alter the functional surface of the mini-zipper involved in DCoH recognition. The other mutation (G20R), by contrast, leads to a dimeric molten globule, as indicated by its 1H-NMR features and fluorescent binding of 1-anilino-8-naphthalene sulfonate. We propose that a glycine-specific turn configuration enables specific interactions between the mini-zipper and the C-terminal coiled-coil.

Amino Acid Sequence↗
PubMed2001

A thermophilic mini-chaperonin contains a conserved polypeptide-binding surface: combined crystallographic and NMR studies of the GroEL apical domain with implications for substrate interactions.

A homologue of the Escherichia coli GroEL apical domain was obtained from thermophilic eubacterium Thermus thermophilus. The domains share 70 % sequence identity (101 out of 145 residues). The thermal stability of the T. thermophilus apical domain (Tm>100 degrees C as evaluated by circular dichroism) is at least 35 degrees C greater than that of the E. coli apical domain (Tm=65 degrees C). The crystal structure of a selenomethione-substituted apical domain from T. thermophilus was determined to a resolution of 1.78 A using multiwavelength-anomalous-diffraction phasing. The structure is similar to that of the E. coli apical domain (root-mean-square deviation 0.45 A based on main-chain atoms). The thermophilic structure contains seven additional salt bridges of which four contain charge-stabilized hydrogen bonds. Only one of the additional salt bridges would face the "Anfinsen cage" in GroEL. High temperatures were exploited to map sites of interactions between the apical domain and molten globules. NMR footprints of apical domain-protein complexes were obtained at elevated temperature using 15N-1H correlation spectra of 15N-labeled apical domain. Footprints employing two polypeptides unrelated in sequence or structure (an insulin monomer and the SRY high-mobility-group box, each partially unfolded at 50 degrees C) are essentially the same and consistent with the peptide-binding surface previously defined in E. coli GroEL and its apical domain-peptide complexes. An additional part of this surface comprising a short N-terminal alpha-helix is observed. The extended footprint rationalizes mutagenesis studies of intact GroEL in which point mutations affecting substrate binding were found outside the "classical" peptide-binding site. Our results demonstrate structural conservation of the apical domain among GroEL homologues and conservation of an extended non-polar surface recognizing diverse polypeptides.

Amino Acid Sequence↗
PubMed2001

[Dynamic variance of intracellular metabolic energies under rhythmical control for dissolved oxygen in PHB mixed cultivation].

The mixed cultivation using cheaper carbon source-wasted food material contained glucose and lactate at the same time was conducted in 5L fermentor, within which glucose was converted to lactate by L. delbrueckii in anaerobic condition and the lactate was converted to PHB by R. eutropha in aerobic condition. Considering dissolved oxygen concentration may affect the level of intracellular ATP and NADPH of the metabolic pathways for R. eutropha in lactate under autotrophy or heterotrophy, rhythmical oscillated control for DO based on chaos control method was consequently presented. This method was employed to satisfy two strains for opposite oxygen preferences, moreover, excite the intracellular metabolic energy simultaneously. The values examined through spectrophotofluorimetry represented that both ATP and NADPH exhibited fluctuations in accordance with the DO rhythm. By means of this control design, the concentration of PHB can be doubled than the usual under stable DO control.

3-Hydroxybutyric Acid↗
PubMed2001

[The experimental study of intratemporal facial nerve regeneration in chitin chamber].

OBJECTIVE: To investigate the feasibility of intratemporal facial nerve regeneration in a chitin chamber. METHODS: A left 6 mm intratemporal facial nerve gap was created in adult white rabbit, and a total of 48 animals were used. The proximal and distal stumps were bridged with chitin chamber (experimental group) and silicone chamber (control group). Regeneration of the nerve was assessed by gross observation, nerve electrophysiological test, histological examination and digital morphological analysis in both groups. RESULTS: 1. Three months after implantation, the proximal transected neural stump was connected with the distal stump in the chitin chamber. Five months after operation, the regenerated nerve exhibited a more nature fascicular organization and the chitin tubes were completely absorbed. 2. Nerve evoked potentials showed better conduction ability in the chitin chamber. There were no significant difference in electrophysiological indices between the two chamber groups. 3. Most of the regenerated nerve fibers were myelinated nerve fibers, and axons and myelins had similar histograms between the experimental and control groups. 4. Five months after operation, the mean percentage of recovery of the regenerated nerve fiber area, axonal area and axonal number were more than 71% in the experimental group. There was no significant difference between the control and experimental groups. CONCLUSION: These results suggested that intratemporal facial nerve could regenerate effectively within the chitin chamber in rabbits and such kind of chamber may be clinically useful.

Animals↗
PubMed2000

Energetics and carbon metabolism during growth of microalgal cells under photoautotrophic, mixotrophic and cyclic light-autotrophic/dark-heterotrophic conditions.

Chlorella pyrenoidosa was cultivated under photoautotrophic, mixotrophic and cyclic light-autotrophic/dark-heterotrophic conditions. The influence of light on the carbon and energy metabolism of microalgae was investigated by the use of metabolic flux analysis. The respiratory activity of microalgae in the light was assessed from the autotrophic flux distribution. Results showed that the glycolytic pathway, tricarboxylic acid cycle and mitochondrial oxidative phosphorylation maintained high activities during illumination, indicating little effect of light on these pathways, while the flux through the pentose phosphate pathway during illumination was very small due to the light-mediated regulation. The theoretical yields of biomass on ATP decreased in the following order: heterotrophic culture>mixotrophic culture>autotrophic culture, and a significant amount of the available ATP was required for maintenance processes in microalgal cells. The energy conversion efficiency between the supplied energy to culture, the absorbed energy by cells and the free energy conserved in ATP were analyzed for the different cultures. Analysis showed that the heterotrophic culture generated more ATP from the supplied energy than the autotrophic and mixotrophic cultures. The maximum thermodynamic efficiency of ATP production from the absorbed energy, which was calculated from the metabolic fluxes at zero growth rate, was the highest in the heterotrophic culture and as low as 16% in the autotrophic culture. By evaluating the energy economy through the energy utilization efficiency, it was found that the biomass yield on the supplied energy was the lowest in the autotrophic cultivation, and the cyclic culture gave the most efficient utilization of energy for biomass production.

Journal Article↗
PubMed2000

Characterization of energy conversion based on metabolic flux analysis in mixotrophic liverwort cells, Marchantia polymorpha.

In order to characterize the contributions of respiratory and photosynthetic actions to energy conversions, the mixotrophic cells of Marchantia polymorpha were cultivated in the medium containing 10kg/m(3) glucose as an organic carbon source. The cultures were conducted with the supply of ordinary air (0.03% CO(2)) at constant incident light intensities of 50 and 180W/m(2). From the results of metabolic analysis, it was found that the cell yield based on ATP synthesis was estimated to be 6.3x10(-3)kg-dry cells/mol-ATP in these cultures. Under the examined conditions, energy conversion efficiency through respiration was larger than that through photosynthesis, and efficiency of overall energy conversion to ATP was maximized when the sum of energies from glucose and light captured by the cells was approximately 7.2x10(5)J/(hkg-dry cells). Taking into account the efficiency of overall energy conversion, a batch culture of M. polymorpha in a bioreactor was carried out by regulating incident light intensity ranging from 9 to 58W/m(2). In the culture with light regulation, the cell yield of 6.2x10(-9)kg-dry cells/J was achieved on the basis of energy provided to the system throughout the culture, and this value was 2.3 and 9.3 times as large as those obtained in the cultures under constant incident light intensities of 50 and 180W/m(2), respectively.

Journal Article↗
PubMed2000

Secondary structure and structure-activity relationships of peptides corresponding to the subunit interface of herpes simplex virus DNA polymerase.

The interaction of the catalytic subunit of herpes simplex virus DNA polymerase with the processivity subunit, UL42, is essential for viral replication and is thus a potential target for antiviral drug discovery. We have previously reported that a peptide analogous to the C-terminal 36 residues of the catalytic subunit, which are necessary and sufficient for its interaction with UL42, forms a monomeric structure with partial alpha-helical character. This peptide and one analogous to the C-terminal 18 residues specifically inhibit UL42-dependent long chain DNA synthesis. Using multidimensional (1)H nuclear magnetic resonance spectroscopy, we have found that the 36-residue peptide contains partially ordered N- and C-terminal alpha-helices separated by a less ordered region. A series of "alanine scan" peptides derived from the C-terminal 18 residues of the catalytic subunit were tested for their ability to inhibit long-chain DNA synthesis and by circular dichroism for secondary structure. The results identify structural aspects and specific side chains that appear to be crucial for interacting with UL42. These findings may aid in the rational design of new drugs for the treatment of herpesvirus infections.

Amino Acid Sequence↗
PubMed2000

[Clinical and experimental study on effect of Chanbei Kechuanping in treating bronchial asthma].

OBJECTIVE: To observe the clinical effect of Chanbei Kechuanping (CBKCP) on bronchial asthma and to explore its mechanism. METHODS: Ninety-six patients of bronchial asthma were randomly divided into two groups, the CBKCP treated group and the control group (treated by Guilong Kechuanning). The changes on symptoms and signs of asthma, pulmonary function, T-lymphocyte subsets, plasma soluble interleukin-2 receptor (sIL-2R), thromboxane B2(TXB2) and 6-keto-prostaglandin F1 alpha(6-keto-PGF1 alpha) were observed before and after treatment. RESULTS: (1) The markedly effective rate and effective rate in the CBKCP treated group were higher than those in the control group. The pulmonary function, including 1 second forced expiratory volume, maximum expiratory flow rate and forced lung expiratory vital capacity were all improved in both groups, but the effect was more obvious in the CBKCP treated group. (2) As compared with the control group, CBKCP showed more obvious effect in lowering sIL-2R, T-lymphocyte subset and raising 6-keto-PGF1 alpha. Experimental study of guinea pig with asthma model showed that CBKCP could markedly prolong the latent time of asthma attack, lower the percentage of mast cells in total cells in the alveoli lavage solution, blood acidophic cell count and degranulation rate of mast cells, and decrease IgE, IL-4 and TXB2 levels as well as increase the 6-keto-PGF1 alpha level. CONCLUSION: CBKCP has favorable therapeutic effect on asthma attack, it might play the role partly by regulating the functional T-lymphocyte subsets, reducing the level of IgE, sIL-2R, IL-4 and TXB2, and increasing the level of 6-keto-PGF1 alpha.

Adolescent↗
PubMed2000

Metabolic control analysis for lysine synthesis using Corynebacterium glutamicum and experimental verification.

Metabolic control analysis was carried out for the lysine biosynthetic pathway in Corynebacterium glutamicum ATCC 21253 using mechanism-based kinetic models developed for enzymatic reactions for this pathway. The rate-limiting steps during lysine production were determined with the aid of flux control coefficients, which indicated that the lysine synthesis flux is governed mainly by both aspartokinase and permease activity in the export system. Analyses indicated that an increase in the activity of aspartokinase would significantly alleviate its effect on the overall flux, and the limiting step is expected to shift to permease and other lysine synthetic enzymes. The influences of many participating precursors and cofactors on lysine synthesis flux were also investigated through the calculation of response coefficients for individual parameters. Although most parameters were not found to exert significant influences on lysine flux, extracellular lysine concentration was found to have a substantial effect on lysine production, and detailed analysis indicated that a decrease in the external lysine concentration will enhance the metabolite synthesis considerably and shift the control from export step to other steps. Although a decrease in external pH (pH0) seems to increase lysine flux, consideration of the export carrier concentration in response to external pH confirmed the optimum pH0 to be 7.0. Two types of recombinant strains overexpressing aspartokinase and dihydrodipicolinate synthase were constructed to verify the results obtained from metabolic sensitivity analysis.

Journal Article↗
PubMed1999

Development of a kinetic model for L-lysine biosynthesis in Corynebacterium glutamicum and its application to metabolic control analysis.

A mathematical model describing intracellular lysine synthesis by Corynebacterium glutamicum in batch fermentation was developed. The model is based on material balance equations of the key metabolites, and includes mechanistically based, experimentally matched rate equations for individual enzymes. From the measurements of the levels of intra- and extracellular metabolites during cultivation, the kinetic parameters in the model were identified through the decomposition of the network of reactions. The model predictions and experimental observations were in reasonable agreement. Using the model developed, metabolic control analysis was carried out to identify the rate-limiting steps, by evaluating the control on the overall lysine synthesis flux exerted by individual enzymatic reactions, which suggested how the control on lysine synthesis changes from aspartokinase to lysine permease as fermentation proceeded and indicated that lysine production could be enhanced by improving aspartokinase activity of this strain through genetic manipulation.

Journal Article↗
PubMed1999

Metabolic flux analysis for efficient pyruvate fermentation using vitamin-auxotrophic yeast of Torulopsis glabrata.

The metabolism of a vitamin-auxotrophic pyruvate-producing microorganism, Torulopsis glabrata IFO 0005, was investigated by metabolic flux analysis. Particular attention was focused on the effect of culture conditions, such as dissolved oxygen (DO) concentration and thiamine concentration, on specific pathway activities. The results of metabolic flux analysis indicate that the thiamine concentration significantly affected pyruvate dehydrogenase and pyruvate decarboxylase activities, and plays an important role in cell growth and pyruvate production. Metabolic flux analysis was also utilized to clarify the metabolism of this strain during pyruvate fermentation under different oxygen supply conditions, and the reason for the enhanced pyruvate production under conditions of 30-40% DO concentration was clarified from the viewpoint of intracellular flux distributions. Based on the analysis of the effect of thiamine concentration on the metabolic fluxes, we conducted a fed-batch experiment where the initial thiamine concentration was reduced to 30 microg/l and thiamine was added at 10 microg/l during fermentation when the cell growth rate decreased to 0.2 h(-1). With separate addition of thiamine, the overall pyruvate yield could be improved by 15% due to the decrease of ethanol production.

Journal Article↗
PubMed1999

[Experimental study on carotid artery resection with vascular replacement by an autogenous vein graft].

OBJECTIVE: In order to observe the survival rate and the histologic changes of the reestablished common carotid artery system. METHOD: A planned resection of the carotid artery was done and the common carotid artery system was reestablished by interposing an autogenous external jugular vein graft in 15 white rabbits. RESULT: 12 survived, the other 3 rabbits died from graft thrombosis, the survival rate was 80%. Histologic examination demonstrated the smooth internal tunic in the anastomotic part of the carotid-jugular and no graft thrombosis. Angiography demonstrated the free circulation of the blood and no aneurysm in the anastomotic vein. CONCLUSION: It is concluded that it is possible that in selected patients, a planned resection of the carotid artery with replacement by interposing an autogenous external jugular vein graft will be done.

Anastomosis, Surgical↗
PubMed1998

[Facial nerve regeneration through autologous non-nerve grafts].

This study investigated the rabbits facial nerve regeneration over a 8 mm transectional gap of the bucal branches through autologous degenerated skeletal muscle and autologous vein respectively. At 20 weeks following the implantation of the mentioned non-neural materials, all the nerve defects of the experimented animals were repaired. In the electrophysiologic indices and morphometeric analysis, the differences between the respective experimental group and the nerve autografts group had no statistical significance. The results indicated that the non-neural tissues could guide facial nerve regenerating effectively, which suggested that they can be clinically practicable.

Animals↗
PubMed1997

Behçet's-like syndrome associated with idiopathic CD4+ T-lymphocytopenia, opportunistic infections, and a large population of TCR alpha beta+ CD4- CD8- T cells.

Herein we report a patient with Behçet's like syndrome, idiopathic CD4+ T-lymphocytopenia, opportunistic infections, and a large polyclonal population of TCR alpha beta + CD4- CD8- T cells. Microfluorimetric analysis of peripheral blood mononuclear cells revealed CD4+ T-cell counts of 10 +/- 5/mm3. The CD3+ T cells were 99% TCR alpha beta +, of which 74 +/- 5% were CD4- CD8-. No clonal populations were detected by southern analysis for T-cell receptor V beta gene rearrangements. No evidence of human immunodeficiency virus infection was present, although nocardia, candida, pneumocystis, cytomegalovirus, and herpes infections were documented. The concomitant presence of opportunistic infections and a large population of TCR alpha beta + CD4- CD8- T cells suggests a pathogenic association and an intense immune response to microbial lipid or lipoglycan antigens presented in the context of CD1 molecules. This case demonstrates the potential for idiopathic CD4+ T-lymphocytopenia to occur in Behçet's-like syndrome with lethal consequences.

Behcet Syndrome↗
PubMed1997

[Effects of aerobic exercise on regulation of activities of hepatic low density lipoprotein receptor in hypercholesterolemic rats].

The present study is to determine the effects of exercise on the regulatory role in activities of hepatic low density lipoprotein receptor (LDL-R) in experimental hypercholesterolemic (HC) rats. Using a specific assay for the binding of 125I-LDL receptor to homogenate, the activity of hepatic LDL-R were measured. It was observed that the activity of LDL-R in HC decreased by 37% as compared with the normal control (NC) rats. HC rats also had a higher levels of serum total cholesterol (TC), LDL-Cholesterol (LDL-C) and apolipoprotein B (Apo B). The rats fed on high-cholesterol diet combined with exercise for 12 weeks (HE) had lower TC, LDL-C and Apo B levels than those of HC rats, and had a higher hepatic LDL-R activity which was 26% higher than that of HC rats. These finding suggested: (1) LDL-R activity may be regulated downward in cholesterol-loaded rats; (2) Exercise may enhance the utilization and degradation of intracellular cholesterol, and may have a feedback effect on the down-regulated synthesis of LDL-R, thus increase the uptake of LDL-C and lower plasma level of lipid.

Animals↗