Biomedical subjects
Publications and source records attributed to C Zhang.
The title compound, [Mn2(C11H13NO3)2(C7H5O2)2], is a centrosymmetric dinuclear manganese(III) complex in which the two Mn atoms are bridged by two alkoxo groups and supported by two carboxylate groups, with an Mn.Mn distance of 2.8720 (15) A.
Action of protein kinases and phosphatases contributes to myocardial hypertrophy. PRL-3, a protein tyrosine phosphatase, was identified in a cDNA library from an explanted human heart obtained from a patient with idiopathic cardiomyopathy. PRL-3 is expressed in heart and skeletal muscle, exhibiting approximately 76% identity to the ubiquitous tyrosine phosphatase PRL-1, which was reported to increase cell proliferation. PRL-3 was cloned into E. coli and purified using affinity chromatography. PRL-3 activity was determined using the substrate 6,8-difluoro-4-methylumbelliferyl phosphate, and was inhibited by vanadate and analogs. HEK293 cells expressing PRL-3 demonstrated increased growth rates versus nontransfected cells or cells transfected with the catalytically inactive C104S PRL-3 mutant. The tyrosine phosphatase inhibitor, potassium bisperoxo (bipyridine) oxovanadate V, normalizes the growth rate of PRL-3 expressing cells to that of parental HEK293 cells in a concentration-dependent manner. Using FLIPR analysis, parental HEK293 cells mobilize calcium when stimulated with angiotensin-II (AngII). However, calcium mobilization is inhibited in cells expressing wild-type PRL-3 when stimulated with AngII, while cells expressing the inactive mutant of PRL-3 mobilize calcium to the same extent as parental HEK293 cells. Western blots comparing PRL-3 transfected cells to parental HEK293 cells showed dephosphorylation of p130(cas) in response to AngII. These data suggest a role for PRL-3 in the modulation of intracellular calcium transients induced by AngII.
The myeloperoxidase-derived oxidant hypochlorous acid (HOCl) is thought to contribute to endothelial dysfunction, but the mechanisms underlying this inhibitory effect are unknown. The present study tested the hypothesis that HOCl and L-arginine (L-Arg) react to form novel compounds that adversely affect endothelial function by inhibiting nitric oxide (NO) formation. Using spectrophotometric techniques, we found that HOCl and L-Arg react rapidly (k = 7.1 x 10(5) m(-1) s(-1)) to form two major products that were identified by mass spectrometry as monochlorinated and dichlorinated adducts of L-Arg. Pretreatment of bovine aortic endothelial cells with the chlorinated L-Arg metabolites (Cl-l-Arg) inhibited the -induced formation of the NO metabolites nitrate (NO(3)(-)) and nitrite (NO(2)(-)) in a concentration-dependent manner. Preincubation of rat aortic ring segments with Cl-L-Arg resulted in concentration-dependent inhibition of acetylcholine-induced relaxation. In contrast, blood vessels relaxed normally to the endothelium-independent vasodilator sodium nitroprusside. In vivo administration of Cl-L-Arg to anesthetized rats increased carotid artery vascular resistance. A greater than 10-fold excess of L-Arg was required to reverse the inhibitory effects of Cl-L-Arg in vivo and in vitro. Reaction of HOCl with D-arginine (D-Arg) did not result in the formation of inhibitory products. These results suggest that HOCl reacts with L-Arg to form chlorinated products that act as nitric-oxide synthase inhibitors.
We present the first direct measurements of the pion valence-quark momentum distribution which is related to the square of the pion light-cone wave function. The measurements were carried out using data on diffractive dissociation of 500 GeV/c pi(-) into dijets from a platinum target at Fermilab experiment E791. The results show that the /q&q> light-cone asymptotic wave function describes the data well for Q2 approximately 10 (GeV/c)(2) or more. We also measured the transverse momentum distribution of the diffractive dijets.
We have studied the diffractive dissociation into dijets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where t(min)-->0), we find that when the per-nucleus cross section for this process is parametrized as sigma = sigma0Aalpha, alpha has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calculations of color-transparency.
Explore the source record for details and available documents.
The type-I ribosome-inactivating protein trichosanthin (TCS) has a broad spectrum of biological and pharmacological activities, including abortifacient, anti-tumour and anti-HIV activities. We have found for the first time that TCS stimulated the production of reactive oxygen species (ROS) in JAR cells (a human choriocarcinoma cell line) in a time- and concentration-dependent manner by using the fluorescent probe 2',7'-dichlorofluorescein diacetate with confocal laser scanning microscopy. ESR spectral studies and the inhibition of ROS formation by the superoxide radical anion (O(2)(-.)) scavenger superoxide dismutase, the H(2)O(2) scavenger catalase and the hydroxyl radical (OH(.)) scavenger mannitol suggested the involvement of O(2)(-.), H(2)O(2) and OH(.). TCS-induced ROS formation was shown to be dependent on the presence of both extracellular and intracellular Ca(2+); moreover, ROS production paralleled the intracellular Ca(2+) elevation induced by TCS, suggesting that ROS production might be a consequence of Ca(2+) signalling. TCS-induced activation of caspase-3 was initiated within 2 h; however, TCS-induced production of ROS was initiated within 5 min, suggesting that the production of ROS preceded the activation of caspase-3. Simultaneous observation of the nuclear morphological changes via two-photon laser scanning microscopy and ROS production via confocal laser scanning microscopy revealed that ROS is involved in the apoptosis of JAR cells. The involvement of ROS was also confirmed by the inhibition of TCS-induced cell death by the antioxidant Trolox and the ROS scavengers catalase and mannitol. Diethylenetriaminepenta-acetic acid, an inhibitor of metal-facilitated OH(.) formation, markedly inhibited TCS-induced cell death, suggesting that TCS induced OH(.) formation via the Fenton reaction. The finding that ROS is involved in the TCS-induced apoptosis of JAR cells might provide new insight into the anti-tumour and anti-HIV mechanism of TCS.
Formation of mature excitatory synapses requires the assembly and delivery of NMDA receptors to the neuronal plasma membrane. A key step in the trafficking of NMDA receptors to synapses is the exit of newly assembled receptors from the endoplasmic reticulum (ER). Here we report the identification of an RXR-type ER retention/retrieval motif in the C-terminal tail of the NMDA receptor subunit NR1 that regulates receptor surface expression in heterologous cells and in neurons. In addition, we show that PKC phosphorylation and an alternatively spliced consensus type I PDZ-binding domain suppress ER retention. These results demonstrate a novel quality control function for alternatively spliced C-terminal domains of NR1 and implicate both phosphorylation and potential PDZ-mediated interactions in the trafficking of NMDA receptors through early stages of the secretory pathway.
We report results of a search for flavor-changing neutral current (FCNC), lepton flavor, and lepton-number violating decays of the D0 (and its antiparticle) into three and four bodies. Using data from Fermilab charm hadroproduction experiment E791, we examine modes with two leptons (muons or electrons) and a rho(0), K( *0), or straight phi vector meson or a nonresonant pi(pi), Kpi, or KK pair of pseudoscalar mesons. No evidence for any of these decays is found. Therefore, we present branching-fraction upper limits at 90% confidence level for the 27 decay modes examined (18 new).
During replication, the lengthy genome of dsDNA viruses is translocated with remarkable velocity into the limited space within the preformed procapsid. We previously found that a viral-encoded RNA (pRNA) played a key role in bacterial virus phi29 DNA translocation. Design of mutant pRNA sets containing two and three inactive mutant pRNAs, respectively, led to the conclusion that the stoichiometry of pRNA in DNA packaging is the common multiple of 2 and 3. Together with studies using binomial distribution of mutant and wild-type pRNA, it has been confirmed that six pRNAs of phi29 form a hexagonal complex to drive the DNA translocating machine. These findings have brought about commonality between viral DNA packaging and other universal DNA/RNA-riding processes including DNA replication and RNA transcription. Chemical modification was used to compare the structures of active and inactive as well as free and procapsid-bound pRNA. Our results explain why certain pRNA mutants are inactive in DNA packaging while remaining competent in procapsid binding, since the mutations were located in a domain involved in DNA translocation that is dispensable for procapsid binding. A mutant pRNA that had reduced procapsid binding was revealed to have a structural alteration within the procapsid-binding region that may account for the binding deficiency. Chemical probing of procapsid-bound pRNA revealed a large area of protection, while a 3-base bulge, C(18)C(19)A(20), was accessible to chemicals. A pRNA with a deletion of this 3-base bulge was fully competent to form dimers, bind procapsids, and inhibit phi29 virion assembly in vitro; however, its activity in DNA packaging and virion assembly was completely lost. The results suggest that this bulge is not involved in procapsid binding but may interact with other DNA-packaging components. A computer model showing the location of the CCA bulge was presented.
This case-control study was conducted in Lima, Peru, from June 1997 through January 1998 to assess whether plasma concentrations of carotenoids (alpha-carotene, beta-carotene, lycopene, lutein, zeaxanthin, beta-cryptoxanthin), retinol, and tocopherols (alpha-tocopherol and gamma-tocopherol) are decreased in women with preeclampsia. A total of 125 pregnant women with preeclampsia and 179 normotensive pregnant women were included. Plasma concentrations of antioxidants were determined using high performance liquid chromatography. After adjusting for maternal demographic, behavioral, and reproductive characteristics and total plasma lipid concentrations, the authors found a linear increase in risk of preeclampsia with increasing concentrations of alpha-tocopherol (odds ratio of the highest quartile = 3.13; 95% confidence interval: 1.06, 9.23, with the lowest quartile as the reference group; p value of the test of linear trend = 0.040). The risk of preeclampsia decreased across increasing quartiles of concentrations for retinol (odds ratio of the highest quartile = 0.32; 95% confidence interval: 0.15, 0.69, with the lowest quartile as the reference group; p value of the test of linear trend = 0.001). Some of these results are inconsistent with the prevailing hypothesis that preeclampsia is an antioxidant-deficient state. Preliminary findings confirm an earlier observation of increased plasma concentrations of alpha-tocopherol among women with preeclampsia as compared with normotensive pregnant women.
A porous ceramic material [hydroxyapatitetricalcium phosphate (HA-TCP)] was implanted in the femora of 30 dogs to investigate the possibility of using this material to repair segmental bone defects. A bone segment, 1.5 cm in length, was removed from the diaphysis of one femur in each dog to create the defect. Cylinders of corresponding size were inserted into the defects. The animals were divided into three groups with recovery times of 2 months, 4 months, and 6 months, respectively. The implants were harvested and subjected to biomechanic tests (bending strength) and X-ray diffraction analysis. The bending strengths of the implant construct increased gradually over time postoperatively. The values of strength for the three different time groups had significant variations (p < 0.05). The X-ray diffraction analysis indicated that the peaks of the TCP included in the cylinders decreased in intensity after implantation and tended to be similar to those of natural bone by 6 months after operation. Conversely, the peaks for the HA had fewer changes compared with preimplantation values. Based on the results of this experiment it was concluded that the porous HA-TCP ceramic cylinders have potential for repair of segmental bone defects if assisted by adequate stabilizing fixtures during the early postoperative period.
The authors measured maternal third trimester plasma folate, vitamin B(12), and homocyst(e)ine concentrations among 125 women with preeclampsia and 179 normotensive women in Lima, Peru (1997-1998), to determine whether these analytes were associated with the occurrence of preeclampsia. Logistic regression procedures were used to calculate maximum likelihood estimates of odds ratios and 95% confidence intervals. Relative to women in the upper quartile of the control distribution of maternal plasma folate concentrations, women with values in the lowest quartile experienced a 1.6-fold increased risk of preeclampsia (odds ratio = 1.6; 95% confidence interval: 0.8, 3.2). There was no evidence of an increased risk of preeclampsia associated with low plasma vitamin B(12) concentrations. The unadjusted relative risk of preeclampsia increased across successively higher quartiles of plasma homocyst(e)ine level (odds ratios were 1.0, 1.0, 1.5, and 2.9, respectively, with the lowest quartile used as the referent; p for linear trend = 0.0004). After adjustment for maternal age, parity, gestational age, use of prenatal vitamins, whether the pregnancy had been planned, and educational attainment, the relative risk between extreme quartiles was 4.0 (95% confidence interval: 1.8, 8.9). These findings are consistent with earlier reports suggesting that hyperhomocyst(e)inemia in pregnancy may be a risk factor for preeclampsia.
ADP ribosylation factors (ARFs) are critical in the vesicular trafficking pathway. ARF activity is controlled by GTPase-activating proteins (GAPs). We have identified recently a novel tentative ARF GAP derived from human fetal liver, ARFGAP3 (originally named as ARFGAP1). In the present study, we demonstrated that ARFGAP3 had GAP activity in vitro and remarked that the GAP activity of ARFGAP3 was regulated by phospholipids, i.e. phosphatidylinositol 4,5-diphosphate as agonist and phosphatidylcholine as antagonist. ARFGAP3 is a predominantly cytosolic protein, and concentrated in the perinuclear region. Its transient ectopic overexpression in cultured mammalian cells reduced the constitutive secretion of secreted alkaline phosphatase, indicating that ectopic overexpression of ARFGAP3 inhibits the early secretory pathway of proteins in vivo. These results demonstrated that ARFGAP3 is a novel GAP for ARF1 and might be involved in intracellular traffic of proteins and vesicular transport as predicted.
We report the molecular characterization of a novel human homologue of mouse npdc1 (neural proliferation, differentiation and control, 1) gene, designated human npdc1 (hnpdc1). hnpdc1 was identified by large-scale sequencing of fetal liver cDNA libraries and the full-length cDNA was obtained by PCR amplification. The hnpdc1 gene, which contains nine exons, was mapped to human chromosome 15. It encodes a polypeptide of 325 amino acids, which shows high homology (77% identity) to the mouse NPDC1. Sequence analysis has shown that hNPDC1 protein contains a putative signal peptide of 34 amino acids, a transmembrane segment, and a typical bipartite nuclear localization signal. Northern blot and dot blot hybridization indicates that, just like mnpdc1, hnpdc1 mRNA is strongly expressed in adult brain (especially in hippocampus, frontal lobe and temporal lobe) and about 1.82-fold higher in adult brain than that in fetal brain. Unlike mnpdc1, however, hnpdc1 contains two transcripts instead of only one (1.5 kb), and has high expression levels in prostate, pituitary gland, and mammary glands. These results support that hNPDC1 plays a role in the control of neural cell proliferation and differentiation, and suggest that it may be involved in the development of several secretion glands.
The molecular mechanism of nuclear envelope (NE) assembly is poorly understood, but in a cell-free system made from Xenopus eggs NE assembly is controlled by the small GTPase Ran [1,2]. In this system, Sepharose beads coated with Ran induce the formation of functional NEs in the absence of chromatin [1]. Both generation of Ran-GTP by the guanine nucleotide exchange factor RCC1 and GTP hydrolysis by Ran are required for NE assembly, although the roles of the GDP- and GTP-bound forms of Ran in the recruitment of precursor vesicles and their fusion have been unclear. We now show that beads coated with either Ran-GDP or Ran-GTP assemble functional nuclear envelopes in a cell-free system derived from mitotic human cells, forming pseudo-nuclei that actively transport proteins across the NE. Both RCC1 and the GTPase-activating protein RanGAP1 are recruited to the beads, allowing interconversion between Ran-GDP and Ran-GTP. However, addition of antibodies to RCC1 and RanGAP1 shows that Ran-GDP must be converted to Ran-GTP by RCC1 before precursor vesicles are recruited, whereas GTP hydrolysis by Ran stimulated by RanGAP1 promotes vesicle recruitment and is necessary for vesicle fusion to form an intact envelope. Thus, the GTP-GDP cycle of Ran controls both the recruitment of vesicles and their fusion to form NEs.
From a sample of 848+/-44 D(+)(s)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)(s)-->pi(-)pi(+)pi(+))/gamma(D(+)(s)-->straight phipi(+)) = 0.245+/-0.028(+0.019)(-0.012). Using a Dalitz plot analysis of this three body decay, we find significant contributions from the channels rho(0)(770)pi(+), rho(0)(1450)pi(+), f(0)(980)pi(+), f(2)(1270)pi(+), and f(0)(1370)pi(+). We also present the values obtained for masses and widths of the resonances f(0)(980) and f(0)(1370).
From a sample of 1172 +/- 61 D(+)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)-->pi(-)pi(+)pi(+))/gamma(D(+)-->K-pi(+)pi(+)) = 0.0311 +/- 0.0018(+0.0016)(-0.0026). Using a coherent amplitude analysis to fit the Dalitz plot of these decays, we find strong evidence that a scalar resonance of mass 478(+24)(-23) +/- 17 MeV/c(2) and width 324(+42)(-40) +/- 21 MeV/c(2) accounts for approximately half of all decays.