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Biomedical subjects

Juan Zhang

Publications and source records attributed to Juan Zhang.

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

Black and green teas equally inhibit diabetic cataracts in a streptozotocin-induced rat model of diabetes.

Green and black teas were given at 1.25% in the drinking water to streptozotocin-induced diabetic rats for 3 months. Normal and diabetic control groups were also studied. As expected, diabetic animals had significantly increased glucose in lens and plasma. Lens and red blood cell sorbitol were significantly increased as a result of the aldose reductase pathway activation. Plasma and lens lipid thiobarbituric acid-reactive substances and protein glycation were also significantly elevated. Both teas significantly inhibited diabetic cataracts and caused significant reductions in the biochemical pathway implicated in the development of the pathology. After corrections for glucose, it was found that the teas retard the development of diabetic cataracts by a hypoglycemic effect that in turn inhibits the biochemical indicators of pathology. There were significant correlations between glucose, cataract score, and these indicators. Green tea but not black tea caused a significant decline in triglycerides in the diabetic animals. Tea may be a simple, inexpensive means of preventing or retarding human diabetes and the ensuing complications. Tea also should be investigated as an adjunct therapy for diabetes treatment.

Animals↗
PubMed2005

FT-ICR mass spectrometry in the drug discovery process.

The high mass accuracy and resolution of Fourier transform (FT)-ion cyclotron resonance (ICR) mass spectrometry are making it an increasingly useful tool in drug discovery and development. The basics of FT-ICR are described here, including modern ion sources and fragmentation methods. Although FT-ICR is not a high-throughput method in the traditional sense, previously difficult and complex problems are being efficiently approached using steadily improving instruments and magnets. Applications are surveyed in fields such as proteomics, metabonomics, natural product analysis and non-covalent complexes.

Chemistry, Pharmaceutical↗
PubMed2005

AtbHLH29 of Arabidopsis thaliana is a functional ortholog of tomato FER involved in controlling iron acquisition in strategy I plants.

AtbHLH29 of Arabidopsis, encoding a bHLH protein, reveals a high similarity to the tomato FER which is proposed as a transcriptional regulator involved in controlling the iron deficiency responses and the iron uptake in tomato. For identification of its biological functions, AtbHLH29 was introduced into the genome of the tomato FER mutant T3238fer mediated by Agrobacterium tumefaciencs. Transgenic plants were regenerated and the stable integration of AtbHLH29 into their genomes was confirmed by Southern hybridization. Molecular analysis demonstrated that expression of the exogenous AtbHLH29 of Arabidopsis in roots of the FER mutant T3238fer enabled to complement the defect functions of FER. The transgenic plants regained the ability to activate the whole iron deficiency responses and showed normal growth as the wild type under iron-limiting stress. Our transformation data demonstrate that AtbHLH29 is a functional ortholog of the tomato FER and can completely replace FER in controlling the effective iron acquisition in tomato. Except of iron, FER protein was directly or indirectly involved in manganese homeostasis due to that loss functions of FER in T3238fer resulted in strong reduction of Mn content in leaves and the defect function on Mn accumulation in leaves was complemented by expression of AtbHLH29 in the transgenic plants. Identification of the similar biological functions of FER and AtbHLH29, which isolated from two systematically wide-diverged "strategy I" plants, suggests that FER might be a universal gene presented in all strategy I plants in controlling effective iron acquisition system in roots.

Arabidopsis↗
PubMed2005

[Construction of adeno-associated virus vector containing human papilloma virus 16 E7 gene and its expression in eukaryotic cells].

OBJECTIVE: To construct recombinant adeno-associated virus vector containing human papilloma virus (HPV) 16E7 gene and identify its effectiveness of expression in eukaryotic cell. METHODS: Recombinant adeno-associated virus particles containing HPV16E7 gene were generated by co-transfection of plasmids pAAV-MCS-E7, pAAV-RC and pAAV-helper into HEK293 cells. The viral particles were collected and purified. The vector titer was measured by southern blot. After the eukaryotic cells were transfected by virus particles, RT-PCR and western blot analysis were performed to identify rAAV expression. RESULTS: The recombinant adeno-associated virus vector containing HPV16E7 gene was correctly constructed. The vector titer measured by southern blot was approximately 1 x 10(11)/ml. After the eukaryotic cells were transfected by the recombinant adeno-associated virus vector, the expression of HPV16E7 gene was identified by RT-PCR and western blot. CONCLUSIONS: Recombinant adeno-associated virus HPV16E7 vector is successfully constructed and can stably express in eukaryotic cells.

Adenoviridae↗
PubMed2005

[The promoter activity of the DNA sequence corresponding to HCV 5'UTR in HepG2].

OBJECTIVE: To study the promoter activity in HepG2 cells of the DNA sequence corresponding to the HCV 5'UTR. METHODS: Plasmids, 5'UTR-Luc(+) and 5'UTR-Luc(-) carrying the forward and reverse DNA sequences corresponding to the HCV 5'UTR respectively were constructed, and subsequently transfected into HepaG2 cells. The luciferase activity and the mRNA of the luciferase gene were then detected. The 5'UTR sequence was cloned into a GFP vector to make 5'UTR-EGFP, and then the GFP expression was confirmed by fluorescence microscopy. RESULTS: 5'UTR-Luc(+) had an obvious luciferase activity whereas 5'UTR-Luc(-) had nearly no luciferase activity. The former had a high level of luciferase mRNA while the latter could not be detected. An intense green fluorescence expression was observed in the cells transfected with the plasmid of 5'UTR-EGFP. CONCLUSION: The forward DNA sequence corresponding to HCV 5'-UTR had an obvious promoter activity in hepG2 cells. It may play an important role in the replication of HCV.

5' Untranslated Regions↗
PubMed2004

Phospholipase D1 regulates high-affinity IgE receptor-induced mast cell degranulation.

To investigate the role of phospholipase D (PLD) in FcepsilonRI signaling, the wild-type or the catalytically inactive forms of PLD1 or PLD2 were stably overexpressed in RBL-2H3 mast cells. FcepsilonRI stimulation resulted in the activation of both PLD1 and PLD2. However, PLD1 was the source of most of the receptor-induced PLD activity. There was enhanced FcepsilonRI-induced degranulation only in cells that overexpressed the catalytically inactive PLD1. This dominant-negative PLD1 enhanced FcepsilonRI-induced tyrosine phosphorylations of early signaling molecules such as the receptor subunits, Syk and phospholipase C-gamma which resulted in faster release of Ca(2+) from intracellular sources. Therefore, PLD1 negatively regulates signals upstream of the Ca(2+) response. However, FcepsilonRI-induced PLD activation required Syk and was downstream of the Ca(2+)response, suggesting that basal PLD1 activity rather than that activated by cell stimulation controlled these early signaling events. Dominant-negative PLD1 reduced the basal phosphatidic acid formation in unstimulated cells, which was accompanied by an increase in FcepsilonRI within the lipid rafts. These results indicate that constitutive basal PLD1 activity by regulating phosphatidic acid formation controls the early signals initiated by FcepsilonRI aggregation that lead to mast cell degranulation.

Animals↗
PubMed2004

Inactivation of c-Cbl or Cbl-b differentially affects signaling from the high affinity IgE receptor.

The Cbl family of proteins negatively regulate signaling from tyrosine kinase-coupled receptors. Among the three members of this family, only c-Cbl and Cbl-b are expressed in hemopoietic cells. To examine the role of c-Cbl and Cbl-b in Fc epsilon RI signaling, mast cell cultures from wild-type, c-Cbl(-/-), and Cbl-b(-/-) mice were generated. Cell growth rates and cell surface expression of Fc epsilon RI were similar in the different cell populations. Compared with control cells, Cbl-b inactivation resulted in increases in Fc epsilon RI-induced Ca(2+) response and histamine release. Fc epsilon RI-induced tyrosine phosphorylation of total cellular proteins, Syk, and phospholipase C-gamma was also enhanced by Cbl-b deficiency, whereas receptor-initiated phosphorylation of Vav, JNK, and p38 kinases was not changed in these cells. In contrast to Cbl-b, c-Cbl deficiency had no detectable effect on Fc epsilon RI-induced histamine release or on the phosphorylation of total cellular proteins or Syk. The absence of c-Cbl increased the phosphorylation of ERK after receptor stimulation, but resulted in slightly reduced p38 phosphorylation and Ca(2+) response. These results suggest that Cbl-b and c-Cbl have divergent effects on Fc epsilon RI signal transduction and that Cbl-b, but not c-Cbl, functions as a negative regulator of Fc epsilon RI-induced degranulation.

Animals↗
PubMed2004

Serine 171, a conserved residue in the gamma-aminobutyric acid type A (GABAA) receptor gamma2 subunit, mediates subunit interaction and cell surface localization.

Serine 171 in the GABA(A) receptor gamma2 subunit is highly conserved in the ligand-gated ion channel superfamily. In this paper, we report that mutating serine 171 within gamma2 to glycine or cysteine prevents the interaction of gamma2 with alpha2 and beta1 when these subunits are co-expressed in human embryo kidney 293 cells, resulting in intracellular retention of gamma2. Structure analysis based on a three-dimensional homology model of gamma2 (Ernst, M., Brauchart, D., Boresch, S., and Sieghart, W. (2003) Neuroscience 119, 933-943) reveals that serine 171 may play a critical role in the formation and stabilization of an exposed turn structure that is part of the subunit interaction site. Mutation of serine 171 in the gamma2 subunit could therefore result in alteration of the structure of the subunit interaction site, preventing correct subunit assembly.

Amino Acid Sequence↗
PubMed2004

Matrix-dependent cationization in MALDI mass spectrometry.

The matrix dependence in cationization processes, the competition between cationization and protonation and the question of whether gas-phase cation transfer or attachment of free cations dominates in matrix-assisted laser desorption/ionization mass spectrometry were studied. Two different sample preparation methods were employed, the dried-droplet sample preparation and a mixture of solid matrix, analyte and salt. The latter ensures that the formation of cation adducts takes place in the gas phase. By monitoring the suppression of matrix signals for different matrices, it was found that matrices with high gas-phase metal ion binding energies require high analyte concentrations for matrix suppression to occur. By comparing the mass spectra obtained using sinapinic acid or sinapinic methyl ester as a matrix, a correlation between cationization and deprotonation of matrix molecules was found. It is also demonstrated that attachment of free gas-phase cations, rather than cation transfer from the cationized matrix, is the predominant process in cationization.

Anti-Bacterial Agents↗
PubMed2004

Fifth dimension of life and the 4/5 allometric scaling law for human brain.

Brain cells are not spherical. The basal metabolic rate (B) of a spherical cell scales as B approximately r2, where r is the radius of the cell; that of a brain cell scales as B approximately r(d), where r is the characteristic radius of the cell and d is the fractal dimensionality of its contour. The fractal geometry of the cell leads to a 4/5 allometric scaling law for human brain, uniquely endowing humans with a 5th dimension and successfully explains why the scaling exponent varies during rest and exercise. A striking analogy between Kleiber's 3/4 law and Newton's second law is heuristically illustrated. A physical explanation is given for the 4th dimension of life for three-dimensional organisms and the 5th dimension for human brain.

Basal Metabolism↗
PubMed2004

[The relationship of angiotensin I-converting enzyme gene polymorphism with diabetic retinopathy and diabetes myocardial infarction].

OBJECTIVE: To investigate the relationship of angiotensin I-converting enzyme (ACE) gene polymorphism to diabetic retinopathy and diabetes myocardial infarction. METHODS: ACE insertion/deletion(I/D) polymorphism was determined by PCR. RESULTS: No evidence showed that ACE gene was associated with diabetic retinopathy. By comparison of the type 2 diabetes patients with myocardial infarction versus those without-myocardial infarction, it was found that the frequencies of homozygote DD (41.2% versus 33.2%) and of allele D (64.7% versus 55.0%) increased remarkably; the difference was statistically significant (P<0.05). CONCLUSION: Allele D(RR=1.50) and genotype DD(RR=1.33) seemed to be a genetic risk factor for type 2 diabetes myocardial infarction.

Adult↗
PubMed2004

[Resonance light scattering study on interaction of solochrome cyanine R with protein and light scattering determination of trace protein].

The resonance light scattering (RLS) of Solochrome Cyanine R(SCR) is greatly enhanced by proteins. Based on this phenomenon, a novel method for the determination of protein by using SCR as a labeling agent was developed. In the pH 4.0 solution the enhanced intensity of RLS at 400 nm is proportional to the concentration of protein. The linear range for bovine serum albumin (BSA) is 0-5.0 mg x L(-1) and the limit of detection is 44.4 microg x L(-1). The method is simple, rapid, sensitive, stable, and tolerant of many foreign substances. It has been used to determine proteins in human urine samples with satisfactory results.

Animals↗
PubMed2004

[Thermo-alkali-stable catalase from Thermoascus aurantiacus and its potential use in textile bleaching process].

The effect of growth and fermentation conditions on the production of catalase by T. aurantiacus WSH 03-01 was investigated in shaking flasks. Catalase activity reached 1594 u/mL when the culture was grown on a complex carbon source containing 20 g/L dextrin and 1% (V/V) ethanol, which was 23% higher than the sum produced on 20 g/L dextrin and 1% (V/V) ethanol, respectively. It was concluded that dextrin might act as a major carbon source in the complex, while ethanol was rather a stimulator than a carbon source. The stimulation effect of ethanol on catalase production was postulated to be two aspects; catalase-dependent alcohol metabolism is activated by acute alcohol, thus more catalase need to be synthesized for that use, named direct induction. As for indirect induction, which may result from little amount of H2O2 generation in process of NADH regeneration in respiratory chain. Peptone was shown to be a favorable nitrogen source for catalase production and its optimum concentration was found to be 10 g/L. Catalase production by T. aurantiacus WSH 03-01 was further improved by optimizing the initial pH, volume of medium in flasks as well as the concentration of external H2O2. Under the optimum culture conditions, the activity of catalase reached 2762 u/mL, which was nearly 6.8 times higher than that of the initiate conditions. Furthermore, the potential application of this novel catalase in the treatment of textile bleaching effluents was evaluated. Thermo-and alkaline stability of this catalase was compared with the commercial available catalases produced from bovine and Aspergillus niger. The crude enzyme from T. aurantiacus WSH 03-01 showed stronger stabilities at (70 degrees C, 80 degrees C, 90 degrees C) and (pH 9.0, pH 10.0, pH 11.0) than the other two types of catalases, indicating a great application potential in the clean production process of textile industry.

Catalase↗
PubMed2003

Alterations in granule matrix and cell surface of focal adhesion kinase-deficient mast cells.

Focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase that plays an important role in many cellular processes and is tyrosine phosphorylated after FcepsilonRI aggregation in mast cells. In mice, null mutation of the fak gene results in a lethal phenotype in which the embryos fail to develop past day 8.5 of gestation. To study the role of FAK in these mast cells, 8.5-day embryos were isolated and placed in culture with IL-3 and stem cell factor (SCF). Although FAK was not required for the development of mast cells in culture, the FAK(-/-) embryo-derived mast cells had several distinct characteristics. Compared with the controls, the mast cells that lack FAK were less metachromatic and by electron microscopy had granules that appeared largely electron lucid, although their histamine content was unchanged. The FAK-deficient mast cells had a reduction in the content of chondroitin/dermatan sulfate, the major glycosaminoglycan component of the granular matrix. The FAK-deficient cells had fewer microvilli that were fused with each other, giving the cell surface a ruffled appearance. There was also a 3-fold increase in the number of cells highly expressing beta(7) integrin. However, signal transduction from the high affinity IgE receptor for the secretion of histamine was similar in the wild-type, heterozygote, and the FAK-deficient cells. The FcepsilonRI-induced tyrosine phosphorylation of paxillin, Crk-associated tyrosine kinase substrate (CAS), and mitogen-activated protein kinase proteins was independent of FAK. These results indicate that FAK plays a role in regulating the glycosaminoglycan content of the secretory granules and influences the cell surface morphology of mast cells.

Animals↗
PubMed2003

Role of electrons in laser desorption/ionization mass spectrometry.

A nonmetallic sample support for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry enhances the positive ion yield by 2 orders of magnitude and generally affects the charge balance in the desorption plume. We interpret the effects of the target material and of the sample preparation on MALDI mass spectra as a result of photoelectrons emitted upon laser irradiation of a metal target covered by a thin sample layer. These electrons are shown to play an important role in MALDI and laser desorption/ionization because they decrease the yield of positive ions, reduce ions with higher oxidation states, and affect the ion velocity distribution as well as the mass resolution. Understanding the role of these photoelectrons helps to clarify previously obscure aspects of the ion formation mechanism in MALDI.

Animals↗
PubMed2003

Cloning and characterization of a GABAA receptor gamma2 subunit variant.

We have cloned a novel gamma-aminobutyric acid type A (GABAA) receptor gamma2 subunit variant named gamma2XL. gamma2XL contains an alternatively spliced exon, resulting in the addition of 40 amino acids to the N-terminal extracellular domain between Ser171 and Tyr172. We show that gamma2XL failed to localize to the cell surface when it was coexpressed with the alpha2 and beta1 subunits in human embryonic kidney 293 cells. Expression of gamma2XL in 293 cells suppressed GABAA receptor binding in a dose-dependent manner by preventing GABAA receptor cell-surface localization. We also generated a gamma2 mutant with Ser171 and Tyr172 converted to glycine and threonine, respectively. We demonstrate that this mutant has a significantly lower affinity for the alpha2 and beta1 subunits and failed to reach the cell surface when coexpressed with these subunits. Together, our results indicate that Ser171 and Tyr172 in the gamma2 subunit constitute a critical motif. When this motif is disrupted by insertion of the alternative exon, access of the gamma2 subunit to the cell surface is prevented.

Alternative Splicing↗