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H Zhang

Publications and source records attributed to H Zhang.

At least 505 records · Page 28Linked to original sources
PubMed2000

Peroxisome proliferator-activated receptor delta (PPARdelta )-mediated regulation of preadipocyte proliferation and gene expression is dependent on cAMP signaling.

The peroxisome proliferator-activated receptor gamma (PPARgamma) is a key regulator of terminal adipocyte differentiation. PPARdelta is expressed in preadipocytes, but the importance of this PPAR subtype in adipogenesis has been a matter of debate. Here we present a critical evaluation of the role of PPARdelta in adipocyte differentiation. We demonstrate that treatment of NIH-3T3 fibroblasts overexpressing PPARdelta with standard adipogenic inducers led to induction of PPARgamma2 expression and terminal adipocyte differentiation in a manner that was strictly dependent on simultaneous administration of a PPARdelta ligand and methylisobutylxanthine (MIX) or other cAMP elevating agents. We further show that ligands and MIX synergistically stimulated PPARdelta-mediated transactivation. In 3T3-L1 preadipocytes, simultaneous administration of a PPARdelta-selective ligand and MIX significantly enhanced the early expression of PPARgamma and ALBP/aP2, but only modestly promoted terminal differentiation as determined by lipid accumulation. Finally, we provide evidence that synergistic activation of PPARdelta promotes mitotic clonal expansion in 3T3-L1 cells with or without forced expression of PPARdelta. In conclusion, our results suggest that PPARdelta may play a role in the proliferation of adipocyte precursor cells, whereas activation of endogenous PPARdelta in 3T3-L1 cells appears to have only minor impact on the processes leading to terminal adipocyte differentiation.

1-Methyl-3-isobutylxanthine↗
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

Use of high-performance liquid chromatography-tandem mass spectrometry to distinguish Panax ginseng C. A. Meyer (Asian ginseng) and Panax quinquefolius L. (North American ginseng).

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed to distinguish Asian ginseng (Panax ginseng C. A. Meyer) and North American ginseng (Panax quinquefolius L.). The method is based on the baseline chromatographic separation of ginsenoside Rf and 24(R)-pseudoginsenoside F11, two potential chemical markers present in ginseng root methanolic extracts, and their unambiguous on-line identification using tandem mass spectrometry. Consistent with the literature, 24(R)-pseudoginsenoside F11 was detected in abundance in North American ginseng roots in excess of 0.1% (w/w) of the dried root. In contrast to some reports, 24(R)-pseudoginsenoside F11 was also identified in Asian ginseng roots at trace levels using LC-MS-MS but at less than 0.0001% (w/w). Besides showing identical tandem mass spectra to authentic 24(R)-pseudoginsenoside F11, the corresponding compound in Asian ginseng root coeluted with standard under different HPLC conditions, thus confirming this compound as 24(R)-pseudoginsenoside F11. Another ginsenoside often used to distinguish Asian and North American ginseng, ginsenoside Rf, was found in abundance in Asian ginseng roots at more than 0.021% (w/w). In Asian ginseng roots, the ratio of ginsenoside Rf to 24(R)-pseudoginsenoside F11 exceeded 700:1. The limit of detection of ginsenoside Rf or 24(R)-pseudoginsenoside F11 was 120 pg injected on-column, and the limit of quantification was 240 pg on-column. In summary, LC-MS-MS analysis of ginseng products for the presence and ratio of ginsenoside Rf and 24(R)-pseudoginsenoside F11 may be used for the unambiguous identification of Asian and North American ginsengs.

Asia↗
PubMed2000

Regulation of cellular growth by the Drosophila target of rapamycin dTOR.

The TOR protein kinases (TOR1 and TOR2 in yeast; mTOR/FRAP/RAFT1 in mammals) promote cellular proliferation in response to nutrients and growth factors, but their role in development is poorly understood. Here, we show that the Drosophila TOR homolog dTOR is required cell autonomously for normal growth and proliferation during larval development, and for increases in cellular growth caused by activation of the phosphoinositide 3-kinase (PI3K) signaling pathway. As in mammalian cells, the kinase activity of dTOR is required for growth factor-dependent phosphorylation of p70 S6 kinase (p70(S6K)) in vitro, and we demonstrate that overexpression of p70(S6K) in vivo can rescue dTOR mutant animals to viability. Loss of dTOR also results in cellular phenotypes characteristic of amino acid deprivation, including reduced nucleolar size, lipid vesicle aggregation in the larval fat body, and a cell type-specific pattern of cell cycle arrest that can be bypassed by overexpression of the S-phase regulator cyclin E. Our results suggest that dTOR regulates growth during animal development by coupling growth factor signaling to nutrient availability.

Amino Acid Sequence↗
PubMed2000

Illumination for coherent soft X-ray applications: the new X1A beamline at the NSLS.

The X1A soft X-ray undulator beamline at the NSLS has been rebuilt to serve two microscopy stations operating simultaneously. Separate spherical-grating monochromators provide the resolving power required for XANES spectroscopy at the C, N and O absorption edges. The exit slits are fixed and define the coherent source for the experiments. The optical design and the operational performance are described.

Journal Article↗
PubMed2000

Negative regulation of cytosolic phospholipase A(2) by melatonin in the rat pineal gland.

In this paper evidence that supports a new role for melatonin as a negative endogenous regulator of cytosolic phospholipase A(2) (cPLA(2)) is presented. When rat pineal glands were incubated in culture, time-dependent release of arachidonic acid (AA) was observed, which was significantly inhibited by a known 85-kDa cPLA(2) inhibitor, methyl arachidonyl fluorophosphonate. Co-incubation with melatonin inhibited the AA release in a concentration-dependent manner, and this decrease was accompanied by a reduction of cPLA(2) protein and mRNA expression. Melatonin-receptor agonists, 2-iodo-N-butanoyl-5-methoxytryptamine and 5-methoxycarbonylamino-N-acetyltryptamine, also decreased AA release and cPLA(2) protein and mRNA levels, while pre-incubation with the melatonin receptor antagonists luzindole and 2-phenylmelatonin abolished the melatonin effect. In vivo, as melatonin production reflected a typical diurnal variation, endogenous non-esterified AA and cPLA(2) mRNA levels in the rat pineal gland showed an off-phase diurnal pattern in relation to melatonin levels. Intravenous administration of isoproterenol, which has been shown to elevate melatonin production, also decreased the levels of non-esterified AA and cPLA(2) mRNA significantly. Direct administration of melatonin to rats by intravenous injection decreased the levels of non-esterified AA, cPLA(2) protein and mRNA in rat pineal glands. In conclusion, melatonin endogenously down-regulates cPLA(2) expression, presumably through melatonin-receptor-mediated processes.

Amino Acids↗
PubMed2000

[Clinical investigation of effects of bizhongxiao decoction (BZX) on rheumatoid arthritis on active phase].

Ninety-six patients with rheumatoid arthritis(RA) on active phase were divided into BZX-treated group(BZXG) and methotrexate-treated group(MTXG). The results showed that after 1-month treatment, symptoms and signs, such as joint tenderness, arthralgia, arthroncus, of patients in BZXG improved notably(P < 0.01 or P < 0.05), while those of patients in MTXG did not improve, there was significant difference between these two groups(P < 0.01 or P < 0.05). After 3-month treatment, these symptoms and signs improved in both groups(P < 0.01 or P < 0.05), but BZX had a better effect than MTX. ESR, CRP, RF, C3, IgG, IgA and IgM decreased significantly in both groups after treatment(P < 0.01 or P < 0.05), ESR, CRP in BZXG decreased more and faster than those in MTXG. In BZXG the obviously efficient rat was 70%, the total efficacy rate was 94%, while in MTXG was 52% and 87% respectively. It is indicated that BZX can improve symptoms and signs of patients with RA, has better and faster effects on acute phase reaction than MTX; and it has anti-immunologic effects similar to MTX, and has no obvious side effect.

Adolescent↗
PubMed2000

Main-group-element calix[4]arenes: variable coordination and conformational isomerism at phosphorus and silicon.

Treatment of calix[4]arene (1b) with trichloromethylsilane yields two conformers of calix[4]SiMe(OH), the cone 2b-C and the partial cone 2b-PC. These are isolated and structurally characterized, and their thermodynamic activation parameters are determined in solution [Ea = 117(3) kJ/mol, delta H = 5(4) kJ/mol]. Similar parameters are found for the p-tert-butylcalix[4]arene analogues 2a-C and 2a-PC. Deprotonation of 2b with butyllithium yields calix[4]SiMe(OLi) (8b). The structure of 8b is solvent dependent: 8b contains a five-coordinate silicon in THF and a four-coordinate silicon in benzene. Similar behavior is found for the p-tert-butylcalix[4]arene analogues. The five-coordinate phosphorus analogue of the anion in 8, p-tert-butylcalix[4]PMe (11a), is synthesized from the phosphonium triflate salt p-tert-butylcalix[4]PMe(OH)OTf (10a(OTf)) via treatment with butyllithium. The structure of 11a shows the geometry around phosphorus to be very close to a pure trigonal bipyramid. The X-ray structure of 10a(OTf) cannot be obtained, but its iodide analogue 10a(T) is synthesized and structurally characterized. The cation in 10a(I) adopts the partial cone conformation in the solid state, similar to 2b-PC. Treatment of 8b with methyl trifluoromethanesulfonate yields the methyl phenyl ether calix[4]SiMe(OMe) (3b). This species and its p-tert-butyl analogue 3a are structurally characterized. Both adopt the partial cone conformation. The SiMe group in 3b can be removed via treatment with fluoride to yield the monomethylated calix[4]arene 4b in 50-60% overall yield based on 1b.

Journal Article↗
PubMed2000

c-Src regulates the interaction between connexin-43 and ZO-1 in cardiac myocytes.

Connexin-43 is known to interact directly with ZO-1 in cardiac myocytes, but little is known about the role of ZO-1 in connexin-43 function. In cardiac myocytes, constitutively active c-Src inhibited endogenous interaction between connexin-43 and ZO-1 by binding to connexin-43. In HEK293 cells, by contrast, a connexin-43 mutant lacking the Src phosphorylation site (Tyr265) interacted with ZO-1 despite cotransfection of a constitutively active c-Src. Moreover, in vitro binding assays using recombinant proteins synthesized from regions of connexin-43 and ZO-1 showed that the tyrosine-phosphorylated C terminus of connexin-43 interacts with the c-Src SH2 domain in parallel with the loss of its interaction with ZO-1. Cell surface biotinylation revealed that, by phosphorylating Tyr265, constitutively active c-Src reduces total and cell surface connexin-43 down to the levels seen in cells expressing a mutant connexin-43 lacking the ZO-1 binding domain. Finally, electrophysiological analysis showed that both the tyrosine phosphorylation site and the ZO-1-binding domain of connexin-43 were involved in the regulation of gap junctional function. We therefore conclude that c-Src regulates the interaction between connexin-43 and ZO-1 through tyrosine phosphorylation and through the binding of its SH2 domain to connexin-43.

Cell Line↗
PubMed2000

Altered enteroendocrine cell expression in T cell receptor alpha chain knock-out mice.

Mice lacking T cell receptor alpha chain (TCRalpha(-/-)) develop inflammation of the colon. We have examined the effect of this inflammation on the colonic epithelium by studying markers of epithelial cuff, enteroendocrine, and immune cell differentiation. Using immunohistochemical techniques, colons were compared in normal C57/BL6 and murine TCR alpha(-/-) mice aged 2 and 3 weeks and 3-11 months. TCR alpha(-/-) mice aged 3-11 months had histologic evidence of inflammation with increased expression of CD45, CD4+, CD8+, and B220+ cells and a decrease in expression of IgA+ cells. There was a decrease in the number of cholecystokinin, serotonin, and neurotensin enteroendocrine expressing cells in the colon of TCR alpha(-/-) mice. These changes were not present in 2-3-week-old suckling/weaning mice. In contrast, peptide tyrosine tyrosine (PYY), glucagon-like peptide-1, and gastrin expression did not change and small intestinal enteroendocrine cells remained unaltered. The change in colonic enteroendocrine cell expression appears to be a specific response, since only a subset of these cells was altered, and the epithelium was intact by histologic analysis. The absence of functional T cells in TCR alpha(-/-) colon has a marked effect on differentiation of a specific subpopulation of enteroendocrine cells, prior to loss of integrity of the epithelium.

Age Factors↗
PubMed2000

Assessing the contribution of natural sources to regional atmospheric mercury budgets

Naturally mercury-enriched substrate is a long-lived source of mercury to the global atmospheric mercury cycle. Field flux chambers, laboratory gas exchange chambers and micrometeorological methods may be applied to estimate emissions from these sources. However, field chamber experimental design may affect the magnitude of the fluxes measured, and the laboratory chamber only provides a minimum estimate of flux. Many factors, such as mercury concentration and speciation in substrate, light, precipitation, and temperature, influence the emission of mercury from the substrate. Mercury concentration in the substrate is a dominant factor controlling emissions and may be used to predict emissions from regions of mercury enrichment. Mercury fluxes measured from three areas of natural enrichment and three areas with low levels of mercury enrichment are 1-5 orders of magnitude greater than the value applied to global belts of natural enrichment. Preliminary scaling of emissions from one of these areas and for western North America indicates that mercury enriched areas may be significant sources of mercury to the atmosphere, and that their contribution to regional and global atmospheric budgets needs to be reassessed.

Journal Article↗
PubMed2000

Air/water exchange of mercury in the Everglades I: the behavior of dissolved gaseous mercury in the Everglades Nutrient Removal Project

From 1996 to 1998 we determined dissolved gaseous mercury (DGM) in waters of the Everglades Nutrient Removal Project (ENR), a constructed wetlands. The concentrations of DGM measured in these waters (mean 7.3 +/- 9.5 pg l(-1)) are among the lowest reported in the literature, and suggest a system often near or slightly above equilibrium with Hg in ambient air. DGM exhibited both seasonal and diel trends, peaking at midday and during the summer. A simple box budget model of DGM in waters of the Everglades was developed using an interactive spreadsheet based on a mass balance among light-induced reduction of HgII (production of DGM), Hg0 oxidation (removal), and Hg0 evasion in a box (water column) consisting of a surface region with sunlight available and a lower dark region. The modeling results suggest high sensitivity of hourly DGM concentrations to DGM production rates and initial DGM levels. The sensitivity to Hg oxidation is lower than the sensitivity to DGM production. The model performance demonstrates successful simulations of a variety of DGM trends in the Everglades. In particular, it clearly demonstrates how it is possible to measure comparable rates of evasion over several Everglades sites with different DGM concentrations.

Journal Article↗
PubMed2000

Air/water exchange of mercury in the Everglades II: measuring and modeling evasion of mercury from surface waters in the Everglades Nutrient Removal Project

During the period 1996-1998, and covering each of the four climatic seasons, we measured evasion of Hg using flux chambers over waters of the Everglades Nutrient Removal Project (ENR), a constructed wetlands. In situ water evasion fluxes of total gaseous mercury (primarily Hg0) measured at seven Everglades sites typically show low evasion rates (< 3 ng m(-2) h(-1)), which are smaller on average than those measured in northern systems. Evasion exhibits a strong diel cycle, with the highest values during midday, and evasion rates are correlated with dissolved gaseous mercury (DGM), solar radiation, wind speed, and water temperature. A thin film model was adapted and applied to estimate evasion fluxes for these Everglades waters based on our measurements of DGM. The results suggest that the typical thin film model underestimates evasion for the Everglades waters, at least on a short time scale.

Journal Article↗
PubMed2000

Fas (CD95/APO-1) plays a role in the pathophysiology of focal cerebral ischemia.

The purpose of this study was to investigate the role of fas antigen, a member of the TNF receptor family, in cell death after focal cerebral ischemia. Focal ischemia was induced in the Sprague-Dawley rat. Evidence for apoptosis was determined by morphology as well as the presence of DNA fragmentation by the end labeling technique (TUNEL). Immunohistochemistry was performed to detect expression of both fas and fas ligand (fasL). In a separate set of experiments, two groups of mice were studied: lpr (that have a loss of function mutation for fas) and wild type. Infarct volume was measured at 24 hr as well as evidence for apoptosis. Twenty-four hours after ischemia, there was evidence for apoptosis based on morphological criteria as well as the TUNEL technique in the rat. Immunohistochemistry demonstrated increased expression of both fas and fasL in the ischemic region, with maximal staining occurring between 24-48 hr for both. Twenty-four hours after ischemia in the mice, there was evidence of apoptosis in both groups, however, the mutant mice (lpr) had significantly smaller infarcts as compared to the wild type. There was no difference in the cerebrovasculature of the two groups of mice. These data support the hypothesis that apoptosis plays a role in the pathophysiology of focal cerebral ischemia. Furthermore, these data suggest that fas-mediated apoptosis contributes to this process.

Animals↗
PubMed2000

Direct in situ measurements of labile inorganic and organically bound metal species in synthetic solutions and natural waters using diffusive gradients in thin films.

The emerging technique of DGT (diffusive gradients in thin films) is shown to be capable of performing new speciation measurements in situ in natural waters. In DGT, metals are bound to a resin layer after passing through a well-defined diffusion layer. Cd was measured in solutions containing glycine, EDTA, and fulvic (FA) and humic acids (HA) by atomic absorption spectroscopy (AAS), anodic stripping voltammetry (ASV), and DGT. DGT measured similar labile fractions to ASV, with detailed differences being consistent with a thicker diffusion layer allowing more dissociation of labile complexes and a slower diffusion of FA and HA complexes through the gel. When single measurements are made in complex solutions with DGT, precise quantification is impossible due to uncertainties concerning the distribution of species with different diffusion coefficients. A new procedure was proposed based on the advantage of DGT of being able to control the pore size of the diffusive gel layer. Small (inorganic) species diffuse freely through all gels but larger FA and HA (organic) complexes diffuse less freely in more constrained gels. When measurements were made on known solutions of Cu and FA or HA, it was possible to quantify the inorganic and organic species separately. They agreed well with predictions made using the WHAM speciation code. Multiple DGT units were also deployed in situ in a stream with high dissolved organic carbon (14.6 mg/L). The systematic differences between the devices with different gel compositions enabled determination, for the first time, of the in situ concentrations of both labile inorganic and organic species in natural water. A single DGT device with a constrained gel can be used to quantify inorganic species directly, providing absolute accuracy is not required. This ability of DGT to measure well-defined fractions of metals in situ using a simple device gives it considerable potential as a regulatory tool. A direct speciation measurement may be preferable to modeling approaches which require diverse input data that are difficult to determine.

Benzopyrans↗
PubMed2000

Drosophila pro-apoptotic Bcl-2/Bax homologue reveals evolutionary conservation of cell death mechanisms.

Genetic analysis of programmed cell death in Drosophila reveals many similarities with mammals. Heretofore, a missing link in the fly has been the absence of any Bcl-2/Bax family members, proteins that function in mammals as regulators of mitochondrial cytochrome c release. A Drosophila homologue of the human killer protein Bok (DBok) was identified. The predicted structure of DBok is similar to pore-forming Bcl-2/Bax family members. DBok induces apoptosis in insect and human cells, which is suppressible by anti-apoptotic human Bcl-2 family proteins. A caspase inhibitor suppressed DBok-induced apoptosis but did not prevent DBok-induced cell death. Moreover, DBok targets mitochondria and triggers cytochrome c release through a caspase-independent mechanism. These characteristics of DBok reveal evolutionary conservation of cell death mechanisms in flies and humans.

Amino Acid Sequence↗
PubMed2000

A C. elegans mediator protein confers regulatory selectivity on lineage-specific expression of a transcription factor gene.

The Caenorhabditis elegans caudal homolog, pal-1, is required for neurogenesis in the male tail. We show that expression of pal-1 in the postembryonic neuroblast cell V6 can be initiated by two alternate pathways. One pathway, acting in wild type, requires a regulatory element in the fifth pal-1 intron. The other pathway, independent of this element, is normally repressed by the newly identified gene sop-1, which encodes a homolog of the mammalian Mediator complex protein TRAP230. In sop-1 mutants, pal-1 is activated by a pathway that is stimulated by bar-1/beta-catenin, a component of the Wnt signal transduction pathway. The results support a physiological role of the Mediator complex in conveying regulatory signals to the transcriptional apparatus.

Amino Acid Sequence↗