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Biomedical subjects

X Zhu

Publications and source records attributed to X Zhu.

At least 397 records · Page 22Linked to original sources
PubMed1999

[Nucleotide sequence at position -155 to +25 of the 5' flanking region of the angiotensinogen gene of Han people].

OBJECTIVE: To study the polymorphism of 5'-flanking region of angiotensinogen gene and relations to essential hyperfension. METHODS: The nucleotide sequence at position -155 to +25 of the 5'-flanking region in angiotensinogen gene of Han people in Chinese population was identified by applying PCR-single stranded conformational polymorphism(SSCP) and PCR-directed sequencing. RESULTS: (1) The Han people carry an adenylate(A), instead of a cytidylate(C) at position -20 of the 5'-flanking region of AGT gene; (2) A new mutation T-->A at position -46 was detected and A-allele frequencies was similar in both hypertensives and normotensive controls. CONCLUSIONS: The variant T-->A at position -46 of AGT gene was not associated with hypertension, but an adenylate (A) at position -20 of the 5'-flanking region of AGT gene. might be an genetic marker for Hans people.

5' Flanking Region↗
PubMed1999

[Immunohistochemical and pathological study of capsaicin in the treatment of rabbit animal model with allergic rhinitis].

OBJECTIVE: To determine the desensitization effect of capsaicin. METHODS: Toluene-2,4-diisocyanate(TDI) sensitized white rabbits used as animal models of allergic rhinitis were treated with capsaicin. At the end of treatment, the changes in the nasal mucosa were studied by immunohistochemical and pathological methods. RESULTS: Our results showed that the symptoms of allergic rhinitis were remarkably relieved after capsaicin treatment. Immunohistochemical study revealed that substance P immunoreactive fibers in the nasal mucosa showed a marked decrease after capasicin application, but the density and number of SP-IR fibers were significantly increased in the control group. Hematoxylin and eosin staining demonstrated that no edema was found in the nasal mucosa and small vessels were normal after capsaicin application, but edema, vasodilation and inflammatory cell infiltration were discovered in the control group. CONCLUSION: The results suggested that local capsaicin treatment was a selective, and non-traumatic method to induce a long lasting desensitization of the nasal mucosa, to alleviate nasal congestion, rhinorrhea and sneezing, and to reduce the sensory neuron sensitivity of the mucosa.

Administration, Intranasal↗
PubMed1999

[A Raman spectral studies of rare-earth (REE) fluoro-carbonate minerals].

The Raman spectra of REE fluoro-carbonate minerals were studies by a type of RIT-30 laser Raman spectrometer. On the basis of Raman spectral properties, REE fluoro-carbonate minerals can be divided into three groups: Ba-REE fluoro-carbonate mineral, Ca-REE fluoro-carbonate mineral and REE fluoro-carbonate mineral. Obviously, a differential kind of mineral is different in the vibration frequency of the Raman spectra. They are as follows: Cordylite v1-1 088, v2-967, v3-1 538, v4-720, 628; Hauheite v1-1 089,v3-1 525, 1 596, v4-720, 649; Cerbaite v1-1 088, v2-911, v3-1 516, v4-718,625; Parisite v1-1 095,1 075, v2-915, v3-1 461, v4-744, 732; Bastnesite v1-1 098, v2-835, v3-1 476, 1 447, v4-732.

English Abstract↗
PubMed1999

[Sensitizing effect of nonionic microemulsion on phosphorus in crystal violet heteropoly molybdophosphoric acid].

A highly sensitive and convenient spectrophotometric method for phosphorus was developed. The sensitizing effect of nonionic microemulsion Triton X-100/n-C5H11OH/n-C0H20/H2O on the ion-association of heteropoly molybdophosphoric acid with crystal violet was higher than that of micelle Triton X-100/H2O. This result showed, by the measurement of distribution constant KD, that the binding constant K and the number of binding sites n of CV were related to the greater solubilization capacity of CV-PMo in nonionic microemulsion system than that in micelle.

English Abstract↗
PubMed1999

[Sensitizing effect of nonionic microemulsion on the derivative spectrophotometric determination of trace iron with sulfosalicylic acid].

The sensitizing effect of O/W microemulsion of Triton X-100/n-C5H11OH/n-C9H20/H2O as a medium on the derivative spectrophotometry of Fe-Sal was studied. The results show that the sensitivity of determination in O/W microemulsion was higher than that in micelle. The reagent Sal has higher distribution coefficient KD and constant K in microemulsion than in the micelle system and lower binding in O/W microemulsion than in the micelle system. This results also illustrate that O/W microemulsion has more solubilization for Sal than micelle does, so that O/W microemulsion has more sensitizing reaction than micelle does.

English Abstract↗
PubMed1998

Functional interaction between InsP3 receptors and store-operated Htrp3 channels.

Calcium ions are released from intracellular stores in response to agonist-stimulated production of inositol 1,4,5-trisphosphate (InsP3), a second messenger generated at the cell membrane. Depletion of Ca2+ from internal stores triggers a capacitative influx of extracellular Ca2+ across the plasma membrane. The influx of Ca2+ can be recorded as store-operated channels (SOC) in the plasma membrane or as a current known as the Ca2+-release-activated current (I(crac)). A critical question in cell signalling is how SOC and I(crac) sense and respond to Ca2+-store depletion: in one model, a messenger molecule is generated that activates Ca2+ entry in response to store depletion; in an alternative model, InsP3 receptors in the stores are coupled to SOC and I(crac). The mammalian Htrp3 protein forms a well defined store-operated channel and so provides a suitable system for studying the effect of Ca2+-store depletion on SOC and I(crac). We show here that Htrp3 channels stably expressed in HEK293 cells are in a tight functional interaction with the InsP3 receptors. Htrp3 channels present in the same plasma membrane patch can be activated by Ca2+ mobilization in intact cells and by InsP3 in excised patches. This activation of Htrp3 by InsP3 is lost on extensive washing of excised patches but is restored by addition of native or recombinant InsP3-bound InsP3 receptors. Our results provide evidence for the coupling hypothesis, in which InsP3 receptors activated by InsP3 interact with SOC and regulate I(crac).

Animals↗
PubMed1998

[Heat strain for personnel wearing three levels of protective ensembles at moderate and heavy workloads].

The effects of individual protective ensembles and workloads on personnel's physiological heat strain were experienced by personnel in a hot environment (35 degrees C, 55% relative humidity). Six young males performed treadmill tests at both moderate (ML: 1.11 m/s, 5% grade) and heavy (HL: 1.34 m/s, 5% grade) workloads. They wore three levels of protective ensembles: protective mask only (PM), protective clothing only (PC), and full protective ensembles (FP). Tests lasted 60 min and 45 min, respectively, for ML and HL. Physiological measurements included heart rate (HR), rectal (Tre) and skin (Tsk) temperature, sweat rate (SR), and sweat evaporative rate (ER). Differences between the ensembles and the workloads were significant for HR responses. The increase rate in Tre and Tsk, and SR, ER were significantly reduced from PM and PC to FP condition during ML and Hl tests. The sweat evaporation restriction of ensembles and the increase of heat production from exercise are the main factors of enhancing the heat strain.

Adult↗
PubMed1998

PhLPs and PhLOPs in the phosducin family of G beta gamma binding proteins.

In this study, we identify new isoforms of the retinal phosducin and investigate the expression of the phosducin family, showing that an isoform, PhLP1, has sequence homology with Phd and Gbeta gamma binding capability, whereas two isoforms (phosducin-like orphan proteins, PhLOPs) share sequence homology with Phd but fail to bind Gbeta gamma. Original identification of PhLP1 and the PhLOPs was from a human retina cDNA library, using a PCR product for library hybridization screening that contained a predicted functional epitope domain. The screen identified Phd and three related, but distinct, recombinants (PhLP1, PhLOP1, and PhLOP2). By RT-PCR, all isoforms are expressed in either retina or forskolin-stimulated Y79 retinoblastoma cells; however, the new isoforms are below the level of detection on Northern blot analysis. The predicted amino acid translation of each homologue revealed major differences, arising from either splice variants or gene duplication of Phd. To test the functional interaction of all phosducin isoforms with Gbeta gamma in vitro, a glutathione S-transferase (GST) fusion protein was developed for each member. Biochemical interaction with purified retinal transducin Gbeta gamma was verified for GST-Phd and demonstrated for GST-PhLP1; however, neither GST-PhLOP1 nor GST-PhLOP2 bound Gbeta gamma. Comparable results were observed when the GST-phosducin fusion proteins selectively sequestered Gbeta gammas from retinal extracts or when functional Gbeta gamma interactions were assessed using surface plasmon resonance technology. Phosducin and its isoforms are widely distributed in body tissues where they may participate in signal transduction pathways. Phd and PhLP1 possess an 11-amino acid conserved epitope domain (TGPKGVINDWR) that controls the high-affinity binding of Gbeta gamma; these isoforms are implicated in the G-protein signaling pathway. The phosducin-like orphan proteins (PhLOPs) fail to bind Gbeta gamma, suggesting that the PhLOP isoforms may participate in still unidentified signaling pathways.

Amino Acid Sequence↗
PubMed1998

Truncated V2 vasopressin receptors as negative regulators of wild-type V2 receptor function.

Accumulating evidence suggests that G protein-coupled receptors (GPCRs) can form dimeric or oligomeric arrays. Based on this concept, we have tested the hypothesis that truncated GPCRs can act as negative regulators of wild-type receptor function. Using the GS-coupled V2 vasopressin receptor as a model system, we systematically analyzed the ability of N- and C-terminal V2 receptor fragments to interfere with the activity of the wild-type V2 receptor coexpressed in COS-7 cells. Several N-terminal V2 receptor truncation mutants were identified that strongly inhibited the function (as determined in cAMP and radioligand binding assays) and cell surface trafficking of the coexpressed full-length V2 receptor. However, these truncation mutants did not interfere with the function of other GS-coupled receptors such as the D1 dopamine and the beta2-adrenergic receptors. Dominant negative effects were only observed with mutant receptors that contained at least three transmembrane domains. In addition, immunoblotting experiments showed that all V2 receptor truncation mutants displaying dominant negative activity (but not those mutant receptors lacking this activity) were able to form heterodimers with the full-length V2 receptor, suggesting that complex formation between mutant and wild-type V2 receptors underlies the observed inhibition of wild-type receptor function. Given the high degree of structural homology shared by all GPCRs, our findings should also be applicable to other members of this receptor superfamily.

Amino Acid Sequence↗
PubMed1998

Crystal structures of acutolysin A, a three-disulfide hemorrhagic zinc metalloproteinase from the snake venom of Agkistrodon acutus.

Acutolysin A alias AaHI, a 22 kDa hemorrhagic toxin isolated from the snake venom of Agkistrodon acutus, is a member of the adamalysin subfamily of the metzincin family and is a snake venom zinc metalloproteinase possessing only one catalytic domain. Acutolysin A was found to have a high-activity and a low-activity under weakly alkaline and acidic conditions, respectively. With the adamalysin II structure as the initial trial-and-error model, the crystal structures were solved to the final crystallographic R-factors of 0. 168 and 0.171, against the diffraction data of crystals grown under pH 5.0 and pH 7.5 conditions to 1.9 A and 1.95 A resolution, respectively. One zinc ion, binding in the active-site, one structural calcium ion and some water molecules were localized in both of the structures. The catalytic zinc ion is coordinated in a tetrahedral manner with one catalytic water molecule anchoring to an intermediate glutamic acid residue (Glu143) and three imidazole Nepsilon2 atoms of His142, His146 and His152 in the highly conserved sequence H142E143XXH146XXGXXH152. There are two new disulfide bridges (Cys157-Cys181 and Cys159-Cys164) in acutolysin A in addition to the highly conserved disulfide bridge Cys117-Cys197. The calcium ion occurs on the molecular surface. The superposition showed that there was no significant conformational changes between the two structures except for a few slight changes of some flexible residue side-chains on the molecular surface, terminal residues and the active-site cleft. The average contact distance between the catalytic water molecule and oxygen atoms of the Glu143 carboxylate group in the weakly alkaline structure was also found to be closer than that in the weakly acidic structure. By comparing the available structural information of the members of the adamalysin subfamily, it seems that, when lowering the pH value, the polarization capability of the Glu143 carboxylate group to the catalytic water molecule become weaker, which might be the structural reason why the snake venom metalloproteinases are inactive or have a low activity under acidic conditions.

Acids↗
PubMed1998

Trp proteins form store-operated cation channels in human vascular endothelial cells.

Members of the Trp protein family have been suggested as the structural basis of store-operated cation conductances. With this study, we provide evidence for the expression of three isoforms of Trp (hTrp1, 3 and 4) in human umbilical vein endothelial cells (HUVEC). The role of Trp proteins in store regulation of endothelial membrane conductances was tested by expression of an N-terminal fragment of hTrp3 (N-TRP) which exerts a dominant negative effect on Trp channel function presumably due to suppression of channel assembly. Depletion of intracellular Ca2+ stores with IP3 (100 microM) or thapsigargin (100 nM) induced a substantial cation conductance in sham-transfected HUVEC as well as in HUVEC transfected with hTrp3. In contrast, HUVEC transfected with N-TRP failed to exhibit store-operated currents. Our results suggest the involvement of Trp related proteins in the store-operated cation conductance of human vascular endothelial cells.

Calcium Channels↗
PubMed1998

Synthesis and biochemical characterization of an analogue of CheY-phosphate, a signal transduction protein in bacterial chemotaxis.

CheY is a signal transduction protein of the bacterial chemotaxis system that acts as a molecular switch to alter the swimming behavior of the bacterium. When CheY becomes phosphorylated at Asp57, CheY-Pi interacts with flagellar motor proteins, including FliM, to increase the likelihood that the flagellar motor will change its sense of rotation, increasing the frequency of tumbling. The structure of CheY in its dephosphorylated (inactive) state has been intensively investigated. The short lifetime ( approximately 20 s) of the aspartyl phosphate has precluded the complete structural determination of CheY-Pi. We have synthesized an analogue of CheY-Pi by alkylating an aspartate-to-cysteine mutant at position 57 of CheY to add a phosphonomethyl group at Cys57. This analogue, phosphono-CheY, is stable for months. Phosphono-CheY binds to two of the targets of CheY-Pi, FliM and CheZ, in a manner similar to that of CheY-Pi and much better than either unphosphorylated CheY or the unmodified form of D57C CheY. Phosphono-CheY also binds Mg(II) with a dissociation constant of approximately 6 mM at neutral pH and moderate salt level. These observations indicate that phosphono-CheY is a good biochemical analogue of CheY-Pi.

Alkylation↗
PubMed1998

Display of sequence variation in PCR-amplified mitochondrial DNA regions of Echinococcus by single-strand conformation polymorphism.

Echinococcosis, a disease caused by infection with the larval stage of a tapeworm parasite of the genus Echinococcus, is of major socio-economic importance, and studying genetic variability within and between Echinococcus populations has important implications for disease control and epidemiology. Various DNA approaches have been used to study Echinococcus genetics, but most methods do not allow the accurate display or definition of mutational/allelic variation. To overcome this limitation, we established a mutation scanning approach. Single-strand conformation polymorphism (SSCP) of two different enzymatically amplified mitochondrial (mt) DNA regions was evaluated using seven different genotypes of Echinococcus (defined as G1, G4, G6, G8, O, V and M2). The NADH dehydrogenase 1 gene (ND1) or the cytochrome c oxidase subunit 1 (CO1) were amplified by polymerase chain reaction from parasite DNA, denatured and directly subjected to electrophoresis in a non-denaturing gel matrix. Each of the seven genotypes examined could be delineated from one another based on characteristic and reproducible banding patterns. The results demonstrate the usefulness of SSCP for the direct visual display of sequence variation in mtDNA of Echinococcus without the need for DNA sequencing or restriction analyses, and indicate its potential for studying allelic variability in a range of other genes.

Animals↗
PubMed1998

Intracellular expression of Fc gamma RIII (CD16) and its mobilization by chemoattractants in human eosinophils.

We characterized the existence, translocation, and reabsorption during cellular activation of a constitutively expressed intracellular CD16 in the human eosinophil. By two-color flow cytometry, we showed that 6.5+/-0.3% of nonpurified eosinophils expressed surface CD16. After digestion with phosphatidylinositol-specific phospholipase C, surface CD16 on both neutrophils and eosinophils decreased substantially, suggesting that eosinophil CD16 is a glycosyl-phosphatidylinositol-linked isoform. However, CD16 was substantially expressed intracellularly in human eosinophils. Epitope-specific binding to CLB-gran11 mAb from non-NA2/NA2 donors demonstrated that intracellular eosinophil CD16 also differed from the transmembrane isoform of CD16 expressed on NK cells or macrophages. Western blot analysis performed with 3G8 or DJ130c mAb showed a broad band at approximately 65 to 80 kDa, which was the same as neutrophil CD16 from the same NA2/NA2 donors. Upon stimulation by chemoattractants C5a, FMLP, or platelet-activating-factor, eosinophilic intracellular CD16 was rapidly translocated to the eosinophil surface, expressed maximally at 30 s, and then gradually disappeared from the cell surface during the next 10 min. Intracellular flow cytometry of stimulated eosinophils and sandwich ELISA of stimulated eosinophil supernatants demonstrated that the disappearance was due to its rapid release into medium and reabsorption by the cells. Our data identify a CD16B that is consistently expressed intracellularly but only rarely on the surface of nonactivated human eosinophils. This CD16 is transiently expressed during stimulation by chemoattractants.

Blotting, Western↗
PubMed1998

Interaction of phosducin and phosducin isoforms with a 26S proteasomal subunit, SUG1.

PURPOSE: Retinal phosducin (Phd) and phosducin-like protein 1 (PhLP1) selectively bind G-protein beta/gamma subunits (Gbetagamma). Our laboratory has recently identified two phosducin-like orphan proteins (PhLOP1 and PhLOP2) that lack the ability to interact with Gbetagamma. In search of potential functional protein partner(s) for these phosducin orphans, we examined their protein-protein interactions using a yeast two-hybrid screen. METHODS: A bovine retina yeast expression cDNA library was screened with the GAL4 DNA binding domain (BD) fusion of PhLOP1. Quantitative analysis of the selected positives with PhLOP1 and other Phd isoforms was assessed by growth and beta-galactosidase activity. Further molecular, biochemical, and immunological detection methods utilizing glutathione S-transferase (GST)-Phd isoform fusion proteins and the potential partner were also performed. RESULTS: A member of the superfamily of putative ATPases was selected in the yeast two hybrid screen. Further characterization identified a direct interaction of this putative ATPase with PhLOP1, as well as Phd and PhLP1, but not with PhLOP2. A database search verified this ATPase as a bovine orthologue of the yeast SUG1 (ySUG1), a putative transcriptional mediator and a subunit of the 26S proteasome complex. Our experiments reveal that the carboxy-terminus of PhLOP1 is essential for the protein-protein interaction with SUG1, but it alone is not sufficient to mediate SUG1 interaction. CONCLUSIONS: Based on these experimental results, Phd, PhLP1 and PhLOP1 have protein-protein interaction with SUG1. PhLOP1, a truncated amino-terminal splice variant of Phd, is the best candidate for the interaction with SUG1 among the four Phd isoforms studied, which suggests a potential function for PhLOP1.

Adenosine Triphosphatases↗
PubMed1998

Expression of a novel isoform of cyclin I in human testis.

A new isoform of cyclin I, designated cyclin ITI, was cloned from the human testis cDNA-lambda gt10 library by using a approximately 0.5 kb PCR fragment that was obtained by using primers based on the published cyclin I sequence from the human brain. The cyclin ITI cDNA is 1443-bp long and has an ORF of 178 aa with the first ATG Met start codon at nt 1 and has the well-conserved sequence of cyclin box. The 5' flanking sequence of 728-bp has a high similarity (99.6%) with the 5'-intron of the human beta-polymerase gene. The nt sequence of cyclin ITI cDNA has high similarity (99.3%) with the cyclin I gene sequence. The cyclin ITI was found to have three amino acids mutations at nt 25, 172, 223, respectively, including one in the well-conserved sequence of cyclin box. Northern blot analysis indicated that the cyclin ITI is expressed in human testis at increased level compared to other tissues. The in vitro translated protein of the cyclin ITI cDNA was recognized specifically by the antibodies raised against the human sperm proteins, indicating its presence in human sperm. This new isoform may have a physiological role in spermatogenesis and/or human sperm cell function--especially in capacitation and/or acrosome reaction.

Amino Acid Sequence↗