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Biomedical subjects

Z Hu

Publications and source records attributed to Z Hu.

At least 91 records · Page 5Linked to original sources
PubMed2001

[The millipore rapid screening of hydantoinase production strains].

OBJECTIVE: To find a strain with a higher hydantoinase activity. METHODS: The millipore rapid screening method was established to select the strains. The effects of several solvents on the rate of biotransformation were compared. RESULTS: A hydantoinase production strain has been selected by the millipore rapid screening method. Tween-80 (1%) is found to be a suitable solvent to dissolve the substrate. CONCLUSION: A new method is provided for rapid selection of hydantoinase production strains from large-scale samples. The difficulty in dissolving the substrate has been resolved to some extent.

Amidohydrolases↗
PubMed2001

[Studies of the resistance of the recombinant alphavirus RNAs containing dengue-2 PrM gene to virus infection].

The amplified PrM gene of dengue-2 virus was cloned into the downstream SP6 promoter-pSFV vector and the recombinant plasmid (pSF.rM2) DNA which contained sense- or antisense-PrM gene, was selected. pSF.rM2 DNA and helper DNA linearized by the enzyme SpeI digestion were both transcribed in vitro into recombinant RNAs which contained the capping analog on the 5'-end and contaansfected into BHK cells by electroportation. The the transfected host cells were challenged with dengue-2 virus and the resistant efficiency of recombinant virus RNAs containing sense- or antisense-PrM gene to virus infection were observed, respectively. The recombinant plasmids (pSFV-PrM) containing sense- or antisense-PrM gene were selected with determination of the nucleotide sequence. The recombinant virus particles were obtained with recombinant RNA and helper RNA co-transfected into BHK cells. Host cells transfected with antisense-PrM RNA derived complete resistance to dengue-2 virus replication and the efficiency was higher than that of the recombinant virus RNA containing sense-PrM gene.

Alphavirus↗
PubMed2001

[Synthesis of galacto-oligosaccharides by immobilized Bacillus stearothermophilus].

Bacillus stearothermophilus was embedded in sodium alginate, chitosan, gelatin respectively and utilized for galacto-oligosaccharides (GOS) production. By comparing with each other in the enzyme recovery, optimal reaction conditions, yields of GOS and mechanical strength of the carriers, the gelatin was selected as better carrier for immobilization. pH, temperature, lactose concentration, lactose conversion and mass transfer resistance of carrier significantly influenced the Yield of GOS. The maximum yield of GOS was 31.2% in a stirred reactor with lactose concentration at 60%. It remained about 88% after 96 h (8 batches) reaction. A packed bed was employed for a continuous reaction at space velocity 0.09 h-1, where GOS yield and reactor productivity was 31.5% and 17.4% respectively. It lost about 20% of its original yield of GOS after 140 h reaction. Products were separated by active charcoal columm. The chemical structure of tetrasaccharide identified by 13C-NMR was beta-D-Gal-(1-->3)-D-Gal-(1-->6)-Dal-(1-->4)-D-Glu.

Alginates↗
PubMed2001

Effects of polyamines on organogenesis and somatic embryogenesis of Lycium barbarum calli.

Levels of three endogenous free polyamines (PAs), Put, Spd and Spm, were detected during organogenesis and somatic embryogenesis (SE) of Lycium barabrum (L.) calli. The predominant forms of PAs in organogenesis and SE were found to be Put and Spd, respectively. In both developmental pathways, the changes of Put content were very similar, i.e., it accumulated quickly in the initial stages of calli differentiation and then decreased; with the further morphogenesis, increase in Put level was also observed. The highest level of Spd was obtained at day 1 of calli organogenesis; while, after 1 day of culture for calli SE, Spd level began to increase and reached a maximum at day 10. The treatments with exogenous PAs had positive effects on both organogenesis and SE, especially those of Spd on organogenesis and SE and Put on SE. However, Put showed no effects on adventitious bud formation. CHA, which inhibits the activity of Spd synthetase, prevented both adventitious bud formation and further development of somatic embryo into plantlet. Although MGBG, a specific inhibitor of S-adenosyl methionine decarboxylases, had little effects on organogenesis, it reduced the number of somatic embryo and the plantlets subsequently regenerated. Such inhibitions could be reversed by Spd (50 mumol/L). These results from organogenesis and SE of the same specie indicate that PAs influenced these two in vitro morphogenesis pathways.

Lycium↗
PubMed2001

[Effect of microgravity simulation with clinostat on different strains in Anabaena oryza].

The Biological responses of Anabana oryza (different strains) to microgravity simulation with clinostat were analyzed. The simulation of growth rate was observed under clinoration all the strains, especially in flight strains (AoR16 and AoSR16-17). Anabana oryza HB23 showed higher activity than flight strains in photosynthesis and respiration. The nitrogen which flight strains with high nitrogrnase activity fixed under culturing in ground was used to accumulate phycobiliprotein in cell and excrete ammonium out of cell after meeting the normal metabolism, however, it was mainly used to simulate growth rate under culturing with clinostat. menwhile, it was different from space flight that microgravity simulation with clinostat was not able to induced the phenotype segregation in Anabana oryzae.

Anabaena↗
PubMed2001

[Research of the chorda tympani nerve in cholesteatoma].

OBJECTIVE: To investigate the ultrastructure of the chorda tympani nerve and analyze the taste and facial nerve functions in patients with cholesteatoma. METHODS: 1. The tympanic segments of chorda tympani nerves were collected for ultrastructural investigations in 19 cholesteatoma cases who underwent canal-wall-down tympanoplasty. 2. All these patients received a spatial (regional) taste test preoperatively and postoperatively, respectively. Multiple loci were tested in a given order (front of the tongue, foliate papillae, circumvallate papillae, and soft palate). The solutions used in this study were 1.0 mol/L sodium chloride (salty), 1.0 mol/L sucrose (sweet), 0.032 mol/L citric acid (sour) and 0.001 mol/L quinine hydrochloride (bitter). The analyses of variance was used. 3. House-Brackmann facial nerve grading system was conducted to evaluate the facial nerve function preoperatively and postoperatively. RESULTS: 1. There were obvious ultrastructural damages in all the chorda tympani nerves, such as swelling (100%), disarrangement (100%), vacuoles formation of myelin (89%), edema of Schwann cells (95%), intracytoplasmic vacuoles in Schwann cell (89%) and proliferation of the collagen tissue (89%). 2. Two patients complained of change of taste after operation. The analyses of variance showed that the taste function of the ipsilateral side of tympanoplasty were not statistically altered for each stimulus at each locus (P > 0.05). 3. No facial palsy occurred postoperatively. CONCLUSION: This research suggested that the chorda tympani nerves underwent ultrastructural changes in patients with cholesteatoma. The dissection of chorda tympani nerve would not affect the taste and facial nerve functions.

Adolescent↗
PubMed2001

[Effect of radix angelicae sinensis decoction for supplementing blood on inhibiting the increase of endothelial cell monolayer permeability induced by hypoosmotic solution].

OBJECTIVE: To study effect of radix Angelicae sinensis decoction for supplementing blood (RASDSB) on inhibiting the increase of endothelial cell monolayer permeability induced by hypoosmotic solution. METHODS: The endothelial cells isolated from newborn bovine aorta were cultured on polycarbonate microporous filter membrane to develop compact endothelial monolayer. Fluid filtration coefficient (Kf), filtration volume (Jv) and osmotic reflective coefficient (sigma) to protein of the endothelial monolayer were measured treated by hypoosmotic solution (changing concentration of serum in M199 solution from 20% to 2%) for 120 min or by hypoosmotic solution containing 10(-4) g x ml(-1) RASDSB for 120 min after perfused Hanks balanced salt solution containing 5 g x L(-1) albumin. RESULTS: Kf and Jv of the endothelial monolayer treated by hypoosmotic solution increased and sigma of that decreased. RASDSB could inhibit above-mentioned change. Morphological analysis demonstrated that RASDSB could inhibit widening of intercellular distance and enlargement of cellular area in the endothelial monolayer induced by hypoosmolality. CONCLUSION: Hypoosmotic solution could increase endothelial cell monolayer permeability and RASDSB could inhibit the increase.

Angelica sinensis↗
PubMed2000

Stimulation of the mitogen-activated protein kinase cascade and tyrosine phosphorylation of the epidermal growth factor receptor by hepatopoietin.

Hepatopoietin (HPO) is a novel human hepatotrophic growth factor, which specifically stimulates proliferation of cultured primary hepatocytes in vitro and liver regeneration after liver partial hepatectomy in vivo. Recently, the identification of the mitogenic effect of HPO on hepatoma cell lines and the existence of HPO-specific receptors indicate that HPO acts via its specific cell surface receptor. However, the molecular mechanism of HPO action is not fully elucidated. In this report, we examined the signal transduction events induced by HPO in hepatoma cell line (HepG2). Our results demonstrated that HPO induces phosphorylation of mitogen-activated protein kinase kinase and mitogen-activated protein kinase (MAPK) in a rapid and transient manner. HPO stimulates tyrosine phosphorylation of epidermal growth factor receptor (EGFR). Furthermore, we observed that both MAPK activation and the mitogenic effect of HPO on HepG2 cells were completely blocked by AG1478, a specific inhibitor of EGFR tyrosine kinase activity. However, the effects of HPO were not antagonized by an EGFR-blocking antibody, mAb528, which blocks the interaction between epidermal growth factor and EGFR, indicating that stimulation of tyrosine phosphorylation of EGFR by HPO was not mediated by epidermal growth factor. In contrast, genistein, a general tyrosine kinase inhibitor, significantly attenuated the tyrosine phosphorylation of EGFR in response to HPO. In conclusion, our results suggest that tyrosine phosphorylation of EGFR may play a critical role in MAPK activation and mitogenic stimulation by HPO.

Enzyme Inhibitors↗
PubMed2000

Determination of proteins at nanogram levels based on their enhancement effects of Rayleigh light scattering on dibromomethylchlorophosphonazo.

A new Rayleigh light scattering (RLS) assay of protein was conducted in this paper. At the optimum pH conditions, and in the presence of Tween-20, the weak RLS of dibromomethylchlorophosphonazo (DBM-CPA) can be enhanced greatly by the addition of proteins. Based on this, the reactions of DBM-CPA and proteins were studied. A new quantitative determination method for proteins has been developed. The method is simple, practical and relatively free from interference from coexisting substances, as well as much more sensitive (the dynamic ranges of 0.065-40.05 microg ml(-1) and detection limit of 30 ng ml(-1) for bovine serum albumin (BSA)) than most of the existing assays. The determination results of human body serum samples are identical to those by the CBB method, with relative S.D. of six determination of 0.5-2.2%.

Blood Proteins↗
PubMed2000

Cloning, nucleotide sequence, and heterologous expression of the biosynthetic gene cluster for R1128, a non-steroidal estrogen receptor antagonist. Insights into an unusual priming mechanism.

R1128 substances are anthraquinone natural products that were previously reported as non-steroidal estrogen receptor antagonists with in vitro and in vivo potency approaching that of tamoxifen. From a biosynthetic viewpoint, these polyketides possess structurally interesting features such as an unusual primer unit that are absent in the well studied anthracyclic and tetracyclic natural products. The entire R1128 gene cluster was cloned and expressed in Streptomyces lividans, a genetically well developed heterologous host. In addition to R1128C, a novel optically active natural product, designated HU235, was isolated. Nucleotide sequence analysis of the biosynthetic gene cluster revealed genes encoding two ketosynthases, a chain length factor, an acyl transferase, three acetyl-CoA carboxylase subunits, two cyclases, two oxygenases, an amidase, and remarkably, two acyl carrier proteins. Feeding studies indicate that the unusual 4-methylvaleryl side chain of R1128C is derived from valine. Together with the absence of a dedicated ketoreductase, dehydratase, or enoylreductase within the R1128 gene cluster, this suggests a functional link between fatty acid biosynthesis and R1128 biosynthesis in the engineered host. Specifically, we propose that the R1128 synthase recruits four subunits from the endogenous fatty acid synthase during the biosynthesis of this family of pharmacologically significant natural products.

Anthraquinones↗
PubMed2000

Native purification of biomolecules with temperature-mediated hydrophobic modulation liquid chromatography.

The high-resolution purification of native enzymes is impeded by the limitations in the mobile-phase choices required for conventional hydrophobic separations such as in reverse-phase chromatography. To avoid problems associated with varying the composition of the mobile phase, we developed a stationary phase with a hydrophobicity that can be modulated by slight variations in temperature to bind and elute biomolecules. This chromatographic matrix was tested on nucleotide analogs, amino acids, and protein samples. Visualization of the temperature-dependent hydrophobic interaction with the chromatographic matrix was performed with fluorescence microscopy of CY3-ATP. Amino acids adsorbed to the column according to their known hydrophobicities, confirming the hydrophobic nature of their interaction with the matrix. Biomolecules were separated by modulating the hydrophobicity of the column matrix with slight adjustments to the running temperature between 22 and 37 degrees C without changing the mobile phase. Freedom in the choice of a mobile phase for both the loading and the elution of samples provides great practical advantages by eliminating the need for buffer-exchange steps and allowing more native conditions for purifying delicate enzymes, such as myosin.

Acrylic Resins↗
PubMed2000

Intratumoral injection of adenoviral vectors encoding tumor-targeted immunoconjugates for cancer immunotherapy.

The efficacy and safety of a new immunotherapy protocol for cancer were tested in a severe combined immunodeficient mouse model of human skin and metastatic lung melanoma. The protocol involves intratumoral injections of replication-incompetent adenoviral vectors encoding immunoconjugates composed of the Fc region of an IgG1 immunoglobulin conjugated to a tumor-targeting domain. One targeting domain is factor VII that binds to tissue factor expressed on endothelial cells lining the tumor neovasculature and on tumor cells; the active site of factor VII was mutated to inhibit the initiation of blood coagulation. Another targeting domain is a single-chain Fv antibody that binds to a cognate antigen expressed on human melanoma cells. The adenoviral vectors infect mainly the cells of the injected tumor, which synthesize and secrete the immunoconjugates. The bloodborne immunoconjugates induce a cytolytic immune response against the targeted neovasculature endothelial cells and tumor cells. The mouse model experiments showed that intratumoral delivery of the factor VII immunoconjugate, either alone or together with the single-chain Fv immunoconjugate, resulted in growth inhibition and regression of the injected tumor, and also of distant metastatic tumors, without evidence of damage to normal organs. There was extensive destruction of the tumor neovasculature, presumably mediated by the factor VII immunoconjugate bound to tissue factor on neovasculature endothelial cells. Because tissue factor is generally expressed on neovascular endothelial cells and tumor cells, a factor VII immunoconjugate could be used for immunotherapy against a broad range of human solid tumors.

Adenoviridae↗
PubMed2000

Role of an interdomain Gly-Gly sequence at the regulatory-substrate domain interface in the regulation of Escherichia coli. D-3-phosphoglycerate dehydrogenase.

The regulatory and substrate binding domains of D-3-phosphoglycerate dehydrogenase (PGDH, EC 1.1.1.95) from Escherichia coli are connected by a single polypeptide strand that contains a Gly-Gly sequence approximately midway between the domains. The potential flexibility of this sequence and its strategic location between major domain structures suggests that it may function in the conformational change leading from effector binding to inhibition of the active site. Site-directed mutagenesis of this region (Gly-336-Gly-337) supports this hypothesis. When bulky side chains were substituted for the glycines at these positions, substantial changes in the ability of serine to inhibit the enzyme were seen with little effect on the activity of the enzyme. The effect of these substitutions could be alleviated by placing a new glycine residue at position 335, immediately flanking the original glycine pair. On the other hand, substituting a glycine at position 338 revealed a critical role for the side chain of Arg-338. This residue may function in stabilizing the conformation about the Gly-Gly turn, resulting in a specific orientation of the adjacent domains relative to each other. Rotation about the phi or psi bonds of either Gly-336 or Gly-337 would have a profound effect on this orientation. The data are consistent with this as a role for the Gly-Gly sequence between the regulatory and substrate binding domains of PGDH.

Binding Sites↗
PubMed2000

Kinetics of two-liquid-phase Taxus cuspidata cell culture for production of Taxol.

The effects of different organic solvents (paraffin, organic acid, alcohol and ester) and their volumetric fractions on the cell growth and Taxol production were studied in two-liquid-phase and the two-stage culture. A kinetic model, incorporated the effects of the toxicity of organic solvents was developed for two-liquid-phase culture of Taxus cuspidata in the two-stage Taxol production. The results showed that the proposed kinetic model could fit the experimental data satisfactorily. The results also showed that Taxol production could reach the optimal value when 10-logP was in the range of 2 to 5 and the volumetric fraction of the organic solvents at the corresponding the highest Taxol production should be lower when 10-logP was high.

Journal Article↗
PubMed2000

Oxidation-state speciation of

The analytical utility of chemically modified microelectrodes for oxidation-state speciation of redox couples by cyclic voltammetry has been explored. [Re(I)(DMPE)3]+/[Re(II)(DMPE)3]2+, where DMPE = 1,2-bis(dimethylphosphino)ethane, was studied at carbon-fiber microelectrodes of approximately 5 microm in radius coated with Nafion-entrapped solgel-derived silica (Nafion-silica) composite. The results are compared with cyclic voltammetry of [Fe(CN)6]3-/[Fe(CN)6]4- at bare carbon-fiber microelectrodes. At both microelectrodes, the cathodic and anodic limiting currents are linearly proportional to the concentrations of the reducible and oxidizable species of a redox couple, respectively. The shape of the cyclic voltammogram and the magnitude of the steady-state limiting current are not affected by the potential at which the scan starts. Speciation of both forms of a redox couple could be achieved voltammetrically at the microelectrodes. However, a considerably slower scan rate was required to achieve steady state at the modified electrode because of the smaller diffusion coefficients of [Re(I)(DMPE)3]+ and [Re(II)(DMPE)3]2+ in the Nafion-silica composite. The detection limit at the modified electrode was considerably lower (5 x 10(-9) M for [Re(I)(DMPE)3]+) than at the bare electrode (6 x 10(-5) M for [Fe(CN)6]3- and [Fe(CN)6]4-) because of the substantial preconcentration of [Re(I)(DMPE)3]+ by the Nafion-silica composite.

Journal Article↗