Biomedical subjects

Z Zhang

Publications and source records attributed to Z Zhang.

At least 199 records · Page 11Linked to original sources

PubMed2001

Calcitonin receptor gene polymorphism in japanese women: correlation with body mass and bone mineral density.

We have identified a polymorphism at position 1377 of the calcitonin receptor (CTR) gene which generates CC, CT, or TT genotype. In this study, the genotypes of the CTR and their relationship with the body height, the body weight, the bone mineral density (BMD), and osteocalcin levels were examined in 152 healthy Japanese women aged 16-43 years. The CTR genotypic frequencies in the Japanese population were 77.0% for CC, 20.4% for CT, and 2.6% for TT. The height, BMD, and osteocalcin levels were not significantly different among these three genotypes. The body weight adjusted for height in these three groups was significantly different in the order of TT, CT, and CC (P = 0.0454 by analysis of covariance). In combined analysis of the VDR genotype (B,b) and the CTR genotype (C,T), the body height was found to be significantly different between CCB and others (P = 0.0236). In addition, analysis of the CTR genotypic frequency using 64 blood samples from Japanese and 47 blood samples from Caucasians indicated that there was a significant difference between the two races (P < 0.0001). We found that C allele was predominant in the Japanese population, however, Caucasians have an almost equal ratio of the C and T. In conclusion, the CTR allele is one of the genetic factors regulating body weight in Japanese women.

Absorptiometry, Photon↗

PubMed2001

[The biological function of platelet-derived growth factor-BB in the osteoblast-osteoclast co-culture system].

OBJECTIVE: To investigate the biological effects of platelet-derived growth factor (PDGF)-BB on the osteoclasts in the osteoblast-osteoclast co-culture system. METHODS: The human osteoblasts and osteoclasts were isolated from the iliac crest of patients and co-cultured in the same system. The PDGF-BB or PDGF-BB + NO synthase inhibitor, N(G)-monomethyl-L-arginine (L-NMMA) was administered to the co-culture system. The tartrate-resistant acid phosphatase (TRAP) activities in the medium were measured by enzyme kinetics. The resorption pits were stained by toludine blue. The area and number of the resorption pits were determined with the Leica Quantimet 500 system. RESULTS: Under the stimuli of PDGF-BB in the co-culture system, TRAP activities changed from 1.40 U/L +/- 0.12 U/L to 1.46 U/L +/- 0.08 U/L (P > 0.05) in the medium, and the area and number of resorption pits was changed from (427 +/- 149) micrometer(2) and (13.3 +/- 0.9) per slice to (436 +/- 147) micrometer(2) and (14.1 +/- 1.2) per slice respectively (P > 0.05). After the L-NMMA was applied to the system, the TRAP activities rose significantly from 1.46 U/L +/- 0.10 U/L to 2.47 U/L +/- 0.38 U/L along with the increase of dose of PDGF-BB, and the number and area of the resorption pits increased significantly from 436 micrometer(2) +/- 147 micrometer(2) and (14.1 +/- 1.2) per slice to 592 micrometer(2) +/- 171 micrometer(2) and (22.5 +/- 1.7) per slice. Both the TRAP activities and resorption pits rose significantly after the L-NMMA was administered. Comparisons of different treatment groups were made using analysis of variance (ANOVA) with multiple comparisons and a Student-Newman-Keuls test. CONCLUSIONS: The nitric oxide (NO) was produced by osteoblasts stimulated by PDGF-BB in the osteoblast-osteoclast co-culture system. Therefore, the direct promotion effects of PDGF-BB on the osteoclasts were inhibited.

Acid Phosphatase↗

PubMed2001

Identification of common binding sites for calmodulin and inositol 1,4,5-trisphosphate receptors on the carboxyl termini of trp channels.

Homologues of Drosophila Trp (transient receptor potential) form plasma membrane channels that mediate Ca(2+) entry following the activation of phospholipase C by cell surface receptors. Among the seven Trp homologous found in mammals, Trp3 has been shown to interact with and respond to IP(3) receptors (IP(3)Rs) for activation. Here we show that Trp4 and other Trp proteins also interact with IP(3)Rs. The IP(3)R-binding domain also interacts with calmodulin (CaM) in a Ca(2+)-dependent manner with affinities ranging from 10 nm for Trp2 to 290 nm for Trp6. In addition, other binding sites for CaM and IP(3)Rs are present in the alpha but not the beta isoform of Trp4. In the presence of Ca(2+), the Trp-IP(3)R interaction is inhibited by CaM. However, a synthetic peptide representing a Trp-binding domain of IP(3)Rs inhibited the binding of CaM to Trp3, -6, and -7 more effectively than that to Trp1, -2, -4, and -5. In inside-out membrane patches, Trp4 is activated strongly by calmidazolium, an antagonist of CaM, and a high (50 microm) but not a low (5 microm) concentration of the Trp-binding peptide of the IP(3)R. Our data support the view that both CaM and IP(3)Rs play important roles in controlling the gating of Trp-based channels. However, the sensitivity and responses to CaM and IP(3)Rs differ for each Trp.

Amino Acid Sequence↗

PubMed2001

The bifunctional Entamoeba histolytica alcohol dehydrogenase 2 (EhADH2) protein is necessary for amebic growth and survival and requires an intact C-terminal domain for both alcohol dahydrogenase and acetaldehyde dehydrogenase activity.

The intestinal protozoan pathogen Entamoeba histolytica lacks mitochondria and derives energy from the fermentation of glucose to ethanol with pyruvate, acetyl enzyme Co-A, and acetaldehyde as intermediates. A key enzyme in this pathway may be the 97-kDa bifunctional E. histolytica alcohol dehydrogenase 2 (EhADH2), which possesses both alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase activity (ALDH). EhADH2 appears to be a fusion protein, with separate N-terminal ALDH and C-terminal ADH domains. Here, we demonstrate that EhADH2 expression is required for E. histolytica growth and survival. We find that a mutant EhADH2 enzyme containing the C-terminal 453 amino acids of EhADH2 has ADH activity but lacks ALDH activity. However, a mutant consisting of the N-terminal half of EhADH2 possessed no ADH or ALDH activity. Alteration of a single histidine to arginine in the putative active site of the ADH domain eliminates both ADH and ALDH activity, and this mutant EhADH2 can serve as a dominant negative, eliminating both ADH and ALDH activity when co-expressed with wild-type EhADH2 in Escherichia coli. These data indicate that EhADH2 enzyme is required for E. histolytica growth and survival and that the C-terminal ADH domain of the enzyme functions as a separate entity. However, ALDH activity requires residues in both the N- and C-terminal halves of the molecule.

Alcohol Dehydrogenase↗

PubMed2001

[Cloning and identifying renal cell carcinoma differentially expressed genes and their significance].

OBJECTIVE: To Clone study the differentially expressed new genes in renal cell carcinoma (RCC). METHODS: Using a technique known as suppression subtractive hybridization to construct the library which contains the differently expressing cDNAs between RCC and normal kidney cells. Then the RCC specifically expressed genes were cloned. RESULTS: Human RCC subtractive library with high subtractive efficiency was set up successfully. The amplified library contained 350 positive clones. Sequence analysis were performed for 5 clones. All the sequences were unknown previously and the cDNA insert GYLZ-RCC18 had three copies. Northern blot analysis showed that GYLZ-RCC18 cDNA expressed highly in RCC, but no signal could be detected in normal kidney. Using SMART RACE technique, the full length of novel gene of GYLZ-RCC18 was obtained. CONCLUSIONS: The highly efficient cDNA subtractive library may have formed solid foundation for screening and cloning new and specific oncogenes or tumor suppressor genes of RCC. The novel differentially expressed genes may provide an important clue for studying the mechanism of occurrence and development of RCC.

Carcinoma, Renal Cell↗

PubMed2001

Expression and sequence analysis of the Blumeria graminis mitogen-activated protein kinase genes, mpk1 and mpk2.

Mitogen-activated protein (MAP) kinases represent a group of serine/threonine kinases which play a pivotal role in signal transduction processes in eukaryotic cells. Using degenerate PCR primer design based on published and aligned MAP kinase sequences we have cloned and characterised two MAP kinase genes from the barley powdery mildew fungus, Blumeria graminis. We have utilised 'step down' PCR to attain the full length mildew genomic clones. The single-copy genes, named mpk1 and mpk2, encode putative proteins of 356 and 410 amino acids and carry three and four introns, respectively. Expression studies, using RT-PCR, reveal a differing pattern of tissue gene expression with mpk1 and mpk2 during germling morphogenesis and this is compared with the constitutive expression of the 'control' beta-tubulin gene.

Amino Acid Sequence↗

PubMed2001

Shape of the quantum diffusion front.

We show that quantum diffusion has well-defined front shape. After an initial transient, the wave packet front (tails) is described by a stretched exponential P(x,t) = A(t)exp(-absolute value of [x/w](gamma)), with 1 < gamma < infinity, where w(t) is the spreading width which scales as w(t) approximately t(beta), with 0 < beta < or = 1. The two exponents satisfy the universal relation gamma = 1/(1-beta). We demonstrate these results through numerical work on one-dimensional quasiperiodic systems and the three-dimensional Anderson model of disorder. We provide an analytical derivation of these relations by using the memory function formalism of quantum dynamics. Furthermore, we present an application to experimental results for the quantum kicked rotor.

Journal Article↗

PubMed2001

Plant tissue-based chemiluminescence flow biosensor for glycolic acid.

A novel plant tissue-based chemiluminescence (CL) biosensor for glycolic acid combined with flow injection analysis is proposed in this paper. The spinach tissue acts as the molecular recognition element. Glycolic acid is oxidized by oxygen under the catalysis of glycolate oxidase in the tissue column to produce hydrogen peroxide, which can react with luminol in the presence of peroxidase of spinach tissue to generate a CL signal. The CL emission intensity was linear with glycolic acid concentration in the range of 4 x 10(-3)-4 x 10(-6) mol/L and the detection limit was 1.3 x 10(-6) mol/L. The biosensor was stable for about 3 weeks. A complete analysis, including sampling and washing, could be performed in 1.5 min with a relative standard deviation of 1.7%.

Biosensing Techniques↗

PubMed2001

Increased inwardly rectifying potassium currents in HEK-293 cells expressing murine transient receptor potential 4.

Drosophila transient receptor potential (Trp) and its mammalian homologues are postulated to form capacitative Ca2+ entry or store-operated channels. Here we show that expression of murine Trp4 in HEK 293 cells also leads to an increase in inwardly rectifying K+ currents. No similar increase was found in cell lines expressing Trp1, Trp3 or Trp6. Consistent with typical characteristics of inward rectifiers, the K+ currents in Trp4-expressing cells were blocked by low millimolar concentrations of Cs+ and Ba2+, but not by 1.2 mM Ca2+, and were only slightly inhibited by 5 mM tetraethylammonium. Single channel recordings of excised inside-out patches revealed the presence of two conducting states of 51 pS and 94 pS in Trp4-expressing cells. The outward current in the excised patches was blocked by 1 mM spermine, but not by 1 mM Mg2+. How Trp4 expression causes the increase in the K+ currents is not known. We propose that Trp4 either participates in the formation of a novel K+ channel or up-regulates the expression or activity of endogenous inwardly rectifying K+ channels.

Animals↗

PubMed2001

Topological testing of the mechanism of homology search promoted by RecA protein.

To initiate homologous recombination, sequence similarity between two DNA molecules must be searched for and homology recognized. How the search for and recognition of homology occurs remains unproven. We have examined the influences of DNA topology and the polarity of RecA-single-stranded (ss)DNA filaments on the formation of synaptic complexes promoted by RecA. Using two complementary methods and various ssDNA and duplex DNA molecules as substrates, we demonstrate that topological constraints on a small circular RecA-ssDNA filament prevent it from interwinding with its duplex DNA target at the homologous region. We were unable to detect homologous pairing between a circular RecA-ssDNA filament and its relaxed or supercoiled circular duplex DNA targets. However, the formation of synaptic complexes between an invading linear RecA-ssDNA filament and covalently closed circular duplex DNAs is promoted by supercoiling of the duplex DNA. The results imply that a triplex structure formed by non-Watson-Crick hydrogen bonding is unlikely to be an intermediate in homology searching promoted by RecA. Rather, a model in which RecA-mediated homology searching requires unwinding of the duplex DNA coupled with local strand exchange is the likely mechanism. Furthermore, we show that polarity of the invading RecA-ssDNA does not affect its ability to pair and interwind with its circular target duplex DNA.

DNA↗

PubMed2001

Decay characteristics of surface mounds with contrasting interlayer mass transport channels.

The decay characteristics of three-dimensional (3D) islands formed on surfaces are investigated theoretically considering two types of interlayer mass transport mechanisms. If an adatom on a given layer can easily descend from any site along the periphery of the layer, an optimal island slope and a constant terrace width will be selected during the decay. In contrast, if the adatom can descend primarily through selective (such as kinked) sites, the decay will be accompanied by a gradual increase in the island slope. These generic conclusions provide the basis for a microscopic understanding of the decay of nanostructures in fcc(111) and fcc(100) metal homoepitaxy and are applicable to other systems as well.

Journal Article↗

PubMed2001

Protein analysis of an individual Caenorhabditis elegans single-cell embryo by capillary electrophoresis.

We present a simple one-dimensional electrophoretic map of the expressed proteins in a Caenorhabditis elegans embryo. The embryo was taken from an adult nematode, injected into a 50-microm I.D. capillary, and lysed. The proteins were fluorescently labeled and then separated by capillary electrophoresis and detected by laser-induced fluorescence. Over 20 components were resolved in the 22-min separation. The dynamic range was outstanding for this separation, noise in the baseline was less than 0.01% the amplitude of the largest component.

Animals↗

PubMed2001

Photophysical process of hexadecyl 4-biphenylamino benzoate.

The photophysical properties of hexadecyl 4-biphenylamino benzoate (HBAB), the molecule of which possesses a polar end composed of donor (triphenylamino group) and acceptor (ester group) and a long non-polar alkyl tail, have been carefully studied in different conditions. The results show that the twisted intramolecular charge transfer (TICT) emission is given in polar solvents at room temperature and intramolecular charge transfer (ICT) emission is given at 77 K. These can be supported by the solvent effect, temperature effect and the quenching process.

Acetates↗

PubMed2001

Photophysical processes of 1,3-dicarbazolypropane.

The photophysical processes of 1,3-dicarbazolypropane (DCZP), which possesses two fluorogen, carbazoly, and one carbonic chain composed of three carbon atoms, were studied. The formation of intermolecular excimer, intramolecular excimer and triple exciplexes have been investigated in the system of DCZP and 1,4-dinitrilebenzene (DNB) with steady state fluorescence spectroscopy. The experimental results show that with the addition of DNB into the lower concentration solution of DCZP in benzene, the fluorescence of intramolecular excimer of DCZP, (D-D)*, is quenched while the ((D-D)A)* type triple exciplex (one molecule of DCZP with one molecule of DNB) is formed and with the addition of DNB into higher concentration solution of DCZP, the formation of (DDA)* type triple exciplex (two molecules of DCZP with one molecule of DNB) is also confirmed.

Carbazoles↗

PubMed2001

Activation of Trp3 by inositol 1,4,5-trisphosphate receptors through displacement of inhibitory calmodulin from a common binding domain.

Mammalian homologues of Drosophila Trp form plasma membrane channels that mediate Ca(2+) influx in response to activation of phospholipase C and internal Ca(2+) store depletion. Previous studies showed that human Trp3 is activated by inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) and identified interacting domains, one on Trp and two on IP(3)R. We now find that Trp3 binds Ca(2+)-calmodulin (Ca(2+)/CaM) at a site that overlaps with the IP(3)R binding domain. Using patch-clamp recordings from inside-out patches, we further show that Trp3 has a high intrinsic activity that is suppressed by Ca(2+)/CaM under resting conditions, and that Trp3 is activated by the following: a Trp-binding peptide from IP(3)R that displaces CaM from Trp3, a myosin light chain kinase Ca(2+)/CaM binding peptide that prevents CaM from binding to Trp3, and calmidazolium, an inactivator of Ca(2+)/CaM. We conclude that inhibition of the inhibitory action of CaM is a key step of Trp3 channel activation by IP(3)Rs.

Amino Acid Sequence↗

PubMed2001

Association of a 27-bp repeat polymorphism in ecNOS gene with ischemic stroke in Chinese patients.

OBJECTIVE: To investigate the association between a 27-bp repeat polymorphism of the ecNOS gene in 364 patients with ischemic stroke and 516 control subjects. BACKGROUND: The incidence of stroke in China is higher than that of coronary artery disease. Furthermore, ischemic stroke is more prevalent than hemorrhagic stroke. A 27-bp repeat polymorphism in intron 4 of the endothelial constitutive nitric oxide synthase (ecNOS) gene has been reported to associate with coronary artery disease in an Australian population, but no association was found between this polymorphism and ischemic stroke in a Japanese population. METHODS: All patients and unrelated control subjects were screened by CT. All participants lived in central China. Multivariate logistic regression analysis was used to determine the independent roles of this ecNOS gene polymorphism and covariates in ischemic stroke. RESULTS: These results indicated an association between the ecNOS a allele and ischemic stroke in the Chinese patients studied (7.8 versus 17.0%; OR = 2.44; 95% CI = 1.60 to 3.71, p < 0.0001). CONCLUSION: The ecNOS a allele in intron 4 may be an independent risk factor for ischemic stroke in the Chinese population studied, especially in those lacking other conventional risk factors.

Aged↗

PubMed2001

Molecular dynamics simulations of urea and thermal-induced denaturation of S-peptide analogue.

Molecular dynamics simulations of the S-peptide analogue AETAAAKFLREHMDS in water at 278 and 358 K, and in 8 M urea at 278 K were performed. The results show agreement with experiments. The helix is stable at low temperature (278 K), while at 358 K, unfolding is observed. The effects of urea on protein stability have been studied. The data support a model in which urea denatures proteins by: (1) diminishing the hydrophobic effect by displacing water molecules from the solvent shell around nonpolar groups; and (2) binding directly to amide units (NH and CO groups) via hydrogen bonds. The results of cluster analysis and essential dynamics analysis suggest that the mechanism of urea and thermal-induced denaturation may not be the same.

Amino Acid Sequence↗

PubMed2001

Estrogen receptor alpha and estrogen receptor-related receptor alpha1 compete for binding and coactivator.

The human estrogen receptor (ERalpha) and the human estrogen receptor-related receptor (ERRalpha1, NR3B1a) are members of the steroid/thyroid hormone receptor superfamily. We previously cloned an isoform of ERRalpha1 cDNA and demonstrated that ERRalpha1 binds to the human lactoferrin gene promoter and enhances estrogen responsiveness during transient transfection experiments. In this study, we show that ERRalpha1 and ERalpha may interfere in each other's transcriptional activity by competition for binding and coactivator. A VP16-ERRalpha1 chimera was constructed and transiently transfected into human endometrial carcinoma HEC-1B cells. This chimera activated reporter constructs containing the human lactoferrin gene estrogen response element (ERE) and the synthetic palindromic 3X-ERE, suggesting that ERRalpha1 binds to these EREs. Therefore, ERRalpha1 can compete with ERalpha for binding to the same EREs. ERRalpha1 is organized into modules which include a N-terminal region that shows repression function, a Zn-finger region that binds DNA and an activation region at the C terminus. The activation function of ERRalpha1 was mapped to the conserved AF2 region in the C-terminus by deletion analysis. The transactivation activity of ERRalpha1 can be enhanced by coactivator (SRC-1a) and suppressed by ERalpha in the presence of estrogen, suggesting that SRC-1a is required by both receptors for their activity. The repression of ERRalpha1 activation function by estrogen bound ERalpha, however, could not be reversed by increasing concentration of SRC-1a in the cells. This finding is consistent with the squelching phenomenon that exists between ERalpha and other steroid receptor family members. The studies demonstrated that ERRalpha1 and ERalpha may potentially regulate the same target gene independently as well as interfere with each other's functional activity by competition for binding and coactivator.

Binding Sites↗