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C Wang

Publications and source records attributed to C Wang.

At least 145 records · Page 8Linked to original sources
PubMed2001

Xenotransplantation of immunodeficient mice with mobilized human blood CD34+ cells provides an in vivo model for human megakaryocytopoiesis and platelet production.

The study of megakaryocytopoiesis has been based largely on in vitro assays. We characterize an in vivo model of megakaryocyte and platelet development in which human peripheral blood stem cells (PBSCs) differentiate along megakaryocytic as well as myeloid/lymphoid lineages in sublethally irradiated nonobese diabetic/severe combined immunodeficient (NOD-SCID) mice. Human hematopoiesis preferentially occurs in the bone marrow of the murine recipients, and engraftment is independent of exogenous cytokines. Human colony-forming units-megakaryocyte (CFU-MK) develop predominantly in the bone marrow, and their presence correlates with the overall degree of human cell engraftment. Using a sensitive and specific flow cytometric assay, human platelets are detected in the peripheral blood from weeks 1 to 8 after transplantation. The number of circulating human platelets peaks at week 3 with a mean of 20 x 10(9)/L. These human platelets are functional as assessed by CD62P expression in response to thrombin stimulation in vitro. Exogenous cytokines have a detrimental effect on CFU-MK production after 2 weeks, and animals treated with these cytokines have no circulating platelets 8 weeks after transplantation. Although cytokine stimulation of human PBSCs ex vivo led to a significant increase in CFU-MK, CD34+/41+, and CD41+ cells, these ex vivo expanded cells provided only delayed and transient platelet production in vivo, and no CFU-MK developed in vivo after transplantation. In conclusion, xenogeneic transplantation of human PBSCs into NOD/SCID mice provides an excellent in vivo model to study human megakaryocytopoiesis and platelet production.

Animals↗
PubMed2001

Direct acetylation of the estrogen receptor alpha hinge region by p300 regulates transactivation and hormone sensitivity.

Regulation of nuclear receptor gene expression involves dynamic and coordinated interactions with histone acetyl transferase (HAT) and deacetylase complexes. The estrogen receptor (ERalpha) contains two transactivation domains regulating ligand-independent and -dependent gene transcription (AF-1 and AF-2 (activation functions 1 and 2)). ERalpha-regulated gene expression involves interactions with cointegrators (e.g. p300/CBP, P/CAF) that have the capacity to modify core histone acetyl groups. Here we show that the ERalpha is acetylated in vivo. p300, but not P/CAF, selectively and directly acetylated the ERalpha at lysine residues within the ERalpha hinge/ligand binding domain. Substitution of these residues with charged or polar residues dramatically enhanced ERalpha hormone sensitivity without affecting induction by MAPK signaling, suggesting that direct ERalpha acetylation normally suppresses ligand sensitivity. These ERalpha lysine residues also regulated transcriptional activation by histone deacetylase inhibitors and p300. The conservation of the ERalpha acetylation motif in a phylogenetic subset of nuclear receptors suggests that direct acetylation of nuclear receptors may contribute to additional signaling pathways involved in metabolism and development.

Acetylation↗
PubMed2001

In vivo substrates and the contribution of the common phospholipase D, PLDalpha, to wound-induced metabolism of lipids in Arabidopsis.

The common plant phospholipase D (PLD), PLDalpha, has been proposed to be involved in wound-induced production of jasmonic acid. To better understand the role(s) of PLDalpha in the wound response, detailed lipid analysis was carried out to determine the in vivo substrates and the contribution of PLDalpha in wound-induced lipid metabolism in Arabidopsis thaliana. Mechanical wounding of Arabidopsis leaves resulted in significantly less hydrolysis of phosphatidylcholine (PC) in PLDalpha-deficient than in wild-type plants. Hydrolysis of phosphatidylethanolamine, phosphatidylglycerol (PG), and phosphatidylinositol within 30 min of wounding was not significantly different in PLDalpha-deficient and wild-type leaves. Phosphatidic acid (PA) levels increased rapidly in wild-type and, to a lesser extent, in PLDalpha-deficient plants. The acyl composition of the PA generated by wounding suggests that the major in vivo substrate of PLD in wild-type leaves was PC, and that PG hydrolysis accounted for 10-15% of the wound-induced PA in wild-type leaves. Comparison of the acyl compositions of the wound-induced PA of wild-type and PLDalpha-deficient leaves indicated that PLDalpha hydrolyzed PG more readily than other PLD isoforms did. Wounding produced substantial increases in free linoleic and linolenic acids in wild-type plants, whereas PLDalpha-deficient plants showed only a slight increase in linoleic acid and no significant increase in linolenic acid. These results demonstrate that PLDalpha and at least one other PLD isoform, as well as other hydrolytic enzymes, are active in mechanically wounded Arabidopsis leaves, and PLDalpha is involved in wound-induced metabolism of polyunsaturated fatty acids.

Arabidopsis↗
PubMed2001

The effect of mutating arginine-469 on the substrate binding and refolding activities of 70-kDa heat shock cognate protein.

On the basis of the X-ray structure of DnaK, we obtained an energy-minimized model for the C-terminal domain of rat 70-kDa heat shock cognate protein (hsc70). The model suggests that Arg-469 may play an important role in maintaining the substrate-bound conformation of hsc70. To verify this hypothesis, we substituted cysteine for Arg-469 and generated the hsc70(R469C) mutant. Compared to the wild-type hsc70, the mutant was more accessible to cleavage by endopeptidase Lys-C, implying that the overall structure of hsc70(R469C) is relatively loose. Moreover, hsc70(R469C) did not form tightly associated complexes with S-carboxymethyl-alpha-lactalbumin, an unfolded protein. The amount of heptapeptide FYQLALT bound to hsc70(R469C) was also decreased as determined by gel filtration. Thus, the affinity of hsc70(R469C) for polypeptide substrates is reduced. In the presence of DnaJ, the capability of hsc70(R469C) to refold the denatured luciferase was decreased by 50%. Therefore, for hsc70, reduction in affinity for substrates may affect its DnaJ-dependent refolding activity.

Animals↗
PubMed2001

Chip-based capillary electrophoresis/mass spectrometry determination of carnitines in human urine.

A chip-based capillary electrophoresis/mass spectrometry (CE/MS) system is described for the CE separation and on-line electrospray detection of carnitine and selected acylcarnitines from mixtures of analytical standards as well as extracts of fortified human urine. Chip-based CE/MS experiments in two different laboratories were carried out using a triple-quadrupole mass spectrometer and a quadrupole time-of-flight (QTOF) mass spectrometer, respectively. The glass chips used with both systems were comparably equipped with a microfabricated capillary electrophoresis (CE) channel but with different electrosprayers. The quadrupole chip-based CE/MS experiments employed a miniature coupled microsprayer, which allowed coupling of the microelectrospray process via a micro liquid junction at the exit of the CE capillary channel. Selected ion monitoring (SIM) CE/MS experiments were employed for all of the quadrupole CE/MS work. The QTOF CE/MS full-scan single MS and MS/MS experiments were carried out in another laboratory using accurate mass measurement TOF mass spectrometry techniques. The electrospray process that was employed with the QTOF system differed in that an inserted nanoelectrospray capillary needle was carefully affixed into a flat-bottomed hole that was aligned with the CE channel exit orifice. SIM CE/MS using the described quadrupole system provided acceptable ion current electropherograms from fmole levels from analytical standard solutions of carnitine and acylcarnitines that were manually injected (loaded) onto the chip. In addition, the corresponding electropherograms for human urine fortified with the target carnitine and acylcarnitines at a 10-20 microg/mL (35-124 microM) level were obtained via SIM CE/MS techniques. The measured CE separation efficiency for the SIM CE/MS electropherograms was determined to be 2860 plates (peak width at half-height method or N = 5.54(T/WO.5(2)), and carnitine and three acylcarnitines were separated in less than 48 s. In contrast, using quadrupole-TOF technologies, the same samples could be diluted by a factor of 2-4 to obtain a comparable detector response for the target compounds. In the full-scan, single mass analyzer mode (m/z 150-500), the CE separation efficiency was measured to be 2600 plates, but mass measurement accuracy was less than 5.0 ppm for the quaternary cations. In the CE/MS/MS mode, full-scan collision-induced dissociation (CID) mass spectra were obtained with a mass accuracy of < or =10 ppm for the higher mass ions and < or =27 ppm for the lower mass product ions. These results demonstrate the feasibility for on-chip CE separation and electrospray mass spectrometric detection for these important compounds in synthetic mixtures, as well as in human urine extracts.

Carnitine↗
PubMed2001

Stimulation of taxol production and excretion in Taxus spp cell cultures by rare earth chemical lanthanum.

The trivalent ion of a rare earth element, lanthanum, was tested for elicitor-like effects on taxol production in suspension cultures of four different Taxus spp cells. In T. yunnanensis cell cultures, the lanthanum ion at concentrations from 1.15 to 23.0 microM stimulated taxol production. The lanthanum ion also promoted taxol excretion by the T. yunnanensis cells considerably. The maximum stimulation of taxol production was achieved by the addition of 5.8 microM La3+ to the culture during mid-log growth phase, increasing the volumetric taxol yield by nearly threefold, from 2.61+/-0.37 to 9.89+/-1.92 mg l(-1) over a 28 day culture period. At higher concentrations, i.e. 23.1 and 46.2 microM, however, the lanthanum ion caused significant growth inhibition. For the other three Taxus cell lines, namely an embryo and a leave cell of T. chinensis and a stem cell of T. chinensis marv, the addition of lanthanum ion to the culture only had a significant effect on taxol production by the T. chinensis marv stem cells, increasing the volumetric yield by about threefold to 4.69+/-0.76 mg l(-1). These results suggest that lanthanum has elicitor-like effects on secondary metabolite synthesis of plant cell cultures.

Cell Culture Techniques↗
PubMed2001

Effect of liver transplantation on islet allografts: up-regulation of Fas ligand and apoptosis of T lymphocytes are associated with islet graft tolerance.

BACKGROUND: Liver allografts in spontaneously tolerant strain combinations can protect other organs of the same donor origin from rejection and reverse ongoing rejection in previously placed grafts. The aims of this study were to examine whether liver allografts have the same protective effect on islet allografts and to investigate the underlying mechanisms. METHODS: PVG islets were transplanted beneath the kidney capsule of streptozotocin-induced diabetic DA rats with or without liver allografting. The cellular infiltrate, and the extent of apoptosis and of Fas ligand (FasL) expression in the islet grafts were evaluated on days 2, 4, and 7 after transplantation by means of immunostaining and the in situ terminal deoxynucleotide transferase-mediated dUTP nick end labeling assay. Donor and recipient mixed lymphocyte reactions (MLR) were determined at 7 days or 100 days after islet transplantation. RESULTS: Islet allografts transplanted alone were rapidly rejected within 5-8 days. Rejection was delayed, but not prevented, when islets were transplanted simultaneously with the liver. Liver transplantation 1 month before islet transplantation resulted in long-term survival (>100 days) of islet grafts in three of seven animals, whereas the other four died of liver rejection with functional islet grafts. Liver transplantation on day 4 after islet grafting reversed ongoing islet rejection and led to indefinite islet graft survival in three of seven cases. There was a progressive increase of cellular infiltration in all of the islet allografts, but the intensity of the infiltrate did not correlate with the outcome of the islet allografts. Islet rejection was characterized by an early dominance of monocytes/macrophages and CD25+ T cells in the infiltrates, a high incidence of apoptotic beta cells in grafts, and a sensitized status in the MLR. Tolerance of islet allografts was associated with increased numbers of dendritic cells in the graft infiltrates, up-regulation of FasL, and prominent apoptosis of alloreactive leukocytes in the islet grafts, as well as donor-specific MLR suppression in long-term survivors. CONCLUSIONS: These results demonstrate that the extent of the protective effect of liver transplantation on islet allografts varies with the time of liver grafting, ranging from delay in islet rejection to complete islet acceptance. Islet graft tolerance induced by liver transplantation is the result of an immune process that involves up-regulation of Fas ligand expression on, and apoptosis of, islet graft infiltrating lymphocytes.

Animals↗
PubMed2001

Role of direct interaction in BRCA1 inhibition of estrogen receptor activity.

The BRCA1 gene was previously found to inhibit the transcriptional activity of the estrogen receptor [ER-alpha] in human breast and prostate cancer cell lines. In this study, we found that breast cancer-associated mutations of BRCA1 abolish or reduce its ability to inhibit ER-alpha activity and that domains within the amino- and carboxyl-termini of the BRCA1 protein are required for the inhibition. BRCA1 inhibition of ER-alpha activity was demonstrated under conditions in which a BRCA1 transgene was transiently or stably over-expressed in cell lines with endogenous wild-type BRCA1 and in a breast cancer cell line that lacks endogenous functional BRCA1 (HCC1937). In addition, BRCA1 blocked the expression of two endogenous estrogen-regulated gene products in human breast cancer cells: pS2 and cathepsin D. The BRCA1 protein was found to associate with ER-alpha in vivo and to bind to ER-alpha in vitro, by an estrogen-independent interaction that mapped to the amino-terminal region of BRCA1 (ca. amino acid 1-300) and the conserved carboxyl-terminal activation function [AF-2] domain of ER-alpha. Furthermore, several truncated BRCA1 proteins containing the amino-terminal ER-alpha binding region blocked the ability of the full-length BRCA1 protein to inhibit ER-alpha activity. Our findings suggest that the amino-terminus of BRCA1 interacts with ER-alpha, while the carboxyl-terminus of BRCA1 may function as a transcriptional repression domain. Oncogene (2001) 20, 77 - 87.

BRCA1 Protein↗
PubMed2001

Integrated system for high-throughput protein identification using a microfabricated device coupled to capillary electrophoresis/nanoelectrospray mass spectrometry.

An integrated microsystem providing rapid analyses of trace-level tryptic digests for proteomics application is presented. This modular microsystem includes an autosampler and a microfabricated device comprising a sample introduction port and an array of separation channels together with a low dead-volume facilitating the interface to nanoelectrospray mass spectrometry. Sequential injection and separation of peptide standards and tryptic digests was achieved with a throughput of up to 30 samples per hour with less than 3% sample carryover. Replicate injections of peptide mixtures indicated that reproducibility of migration time was typically better than 2.3% relative standard deviation (RSD) whereas RSD values of 3.7-11.8% were observed on peak height. Mass spectral detection of submicromolar protein digests (< 7 femtomoles/injection) was achieved using a quadrupole/time of flight instrument in less than 2 min/per sample with peak widths of 1.8-7.0 s. The analytical potential of this integrated device for the identification of gel isolated proteins from Neisseria meningitidis immunotype L3 has been demonstrated using both peptide mass-fingerprint database searching and on-line tandem mass spectrometry.

Amino Acid Sequence↗
PubMed2001

Gelatinous transformation of bone marrow from a starch-free diet.

Gelatinous marrow transformation is characterized by marrow hypoplasia, fat atrophy, and gelatinous material deposition, and usually develops as a hematologic complication of chronic wasting disorders. Most of the cases associated with severe nutritional deficiency were seen in anorexia nervosa due to a depletion of protein or fat. This report describes a case of gelatinous transformation attributed to a specific restriction of carbohydrates in diet. The hematologic deficiency was eventually recovered after the patient resumed a regular starch-containing diet. This brief report illustrates the potential side effect of the compulsive dietary behavior on the hematologic system.

Adult↗
PubMed2001

Effect of photodynamic therapy (PDT) on the expression of pro-apoptotic protein Bak in nasopharyngeal carcinoma (NPC).

BACKGROUND AND OBJECTIVE: To investigate the effect of photodynamic therapy (PDT) on expression of the pro-apoptotic gene Bak in nasopharyngeal carcinoma (NPC). STUDY DESIGN/MATERIALS AND METHODS: Apoptosis and expression of the pro-apoptotic gene Bak on the tumor tissues from both pre- and post-PDT were determined using the in situ end labeling (ISEL), standard immunohistochemistry technique and western blot, respectively, in 24 patients with either persistent or recurrent NPC after radiotherapy. RESULTS: Before PDT, apoptotic index (AI) in tumor tissue was 1.2 +/- 0.6. At 6, 12, 24 and 48 hours after PDT, AI were 6.5 +/- 3.1, 23.6 +/- 8.3, 67.2 +/- 14.2 and 89.3 +/- 8.1, respectively. PDT caused apoptosis in a time-dependent fashion. Immunohistochemical assay indicated that 75% (18/24) of the patients had an upgrade expression of Bak protein in their tumor tissues after PDT. Increases in expression of Bak from PDT were also confirmed by western blot analysis. CONCLUSIONS: PDT probably causes NPC cell apoptosis through an upregulation of the pro-apoptotic protein Bak expression.

Adult↗
PubMed2001

Sequential transplantation induces islet allograft tolerance.

Liver transplantation (LT) in some rat strain combinations can induce tolerance to other organ grafts of liver donor strain. The aim of the study was to examine the effect of LT on islet allografts. Islets were isolated by collagenase digestion and purified by dextran-gradient separation. Islets from two donor animals (>2,000) were transplanted under the left kidney capsule of streptozotocin-induced diabetic rats. The liver was implanted orthotopically. The results showed that concurrent LT and islet transplantation (IT) prolonged survival of islet allografts modestly, but islet allografts survived indefinitely when LT was performed before or after IT. LT delayed or reversed ongoing islet graft rejection. IT could trigger rejection in otherwise tolerated liver grafts. We conclude that sequential IT-LT or LT-IT can induce islet allograft tolerance or liver rejection and that the mechanisms involved may differ from those involved with LT simultaneously with either IT or vascularized organ grafts.

Animals↗
PubMed2001

Antigenic load and peripheral chimeric levels in entire and partial liver allograft recipients.

Orthotopic partial liver transplantation (PLT) models were developed in rats to explore the unique role of the liver in transplant tolerance. In PVG rats, syngeneic PLT established that surgical reduction to one-third of the liver and orthotopic transplantation permitted survival. Allogeneic PLT in the PVG to DA liver-tolerant model, both 50% and 33%, did not affect the tolerogeneic property of the liver, with all PLT recipients surviving indefinitely. Blood samples taken at various time points for detection of donor cells using flow cytometry showed a steady increase in donor cell chimerism in both PLT and whole liver transplantation (WLT) recipients that persisted throughout the 3-month observation period. At each time point, the level of donor cell chimerism in PLT was higher than that in WLT. We conclude that transplantation of one-third of the liver is compatible with survival in rats. Reduction of antigenic load by means of hepatectomy does not affect the tolerogenic effect of the liver in the PVG to DA LT model because of the remarkable regeneration capability of the liver. Peripheral chimeric levels increase progressively after WLT, suggesting that this is an ongoing immunological phenomenon. The earlier and increased chimerism after PLT may be associated with liver regeneration.

Animals↗
PubMed2001

Expression of angiopoietin-2 gene and its receptor Tie2 in hepatocellular carcinoma.

To explore the relationship of angiogenesis-related angiopoietin-2 gene and its receptor Tie2 with angiogenesis and the biology of hepatocellular carcinoma (HCC), angiopoietin-2 gene, Tie2 and CD34 protein expression in 22 resected HCC, 8 cirrhotic and 8 control liver specimens were investigated by in situ hybridization and immunohistochemistry respectively, and the level of angiopoietin-2 and Tie2 expression in HCC were compared in terms of tumor biological parameters. It was found that CD34 was not expressed in control liver, expressed scarcely in cirrhotic liver (17.8 +/- 13.5/HP), but intensively expressed in HCC (86.3 +/- 34.8/HP, P < 0.01). Tie2 receptor was not expressed in controls, expressed at low level in cirrhotic liver (11.3 +/- 8.7/HP), while strongly positive in the microvascular endothelia of HCC (52.4 +/- 16.7/HP, P < 0.01). The level of Tie2 receptor expression in HCC was closely related with tumor diameter, angiogenesis and portal invasion. Angiopoietin-2 gene was not expressed in control liver, expressed mildly in cirrhotic liver (11.2 +/- 9.7/HP), but extensively in tumor zone (36.4 +/- 17.5/HP), the level of angiopoietin-2 expression was closely related with angiogenesis, portal invasion and histological grading of HCC. It is concluded that angiogenesis is increased in HCC; angiopoietin-2/Tie2 expression in human hepatic carcinoma is closely related with angiogenesis, which are probably involved in the HCC angiogenesis regulation, promoting the development and metastasis of human hepatic cancer.

Angiopoietin-2↗
PubMed2001

Enhancement of Taxol production and excretion in Taxus chinensis cell culture by fungal elicitation and medium renewal.

An endophytic fungus, Aspergillus niger, isolated from the inner bark of a Taxus chinensis tree, was used as an elicitor to stimulate the Taxol (paclitaxel) production in a Taxus chinensis cell suspension culture. Different elicitor doses and elicitation times were tested in a batch culture; and the highest volumetric Taxol yield was achieved when 40 mg of the fungal elicitor (carbohydrate equivalent) l(-1) was added to the culture during the late exponential-growth phase. The elicitation resulted in a more than two-fold increase in the Taxol yield and about a six-fold increase in total secretion. The Taxol yield was further improved substantially by applying medium renewal and re-elicitation to the culture. In particular, with repeated medium renewal (in a way similar to medium perfusion) and a second elicitation of the culture, the volumetric Taxol yield was increased to 67.1+/-7.5 mg l(-1), which was about seven times the amount obtained in the non-elicited batch culture. The Taxol productivity of the perfusion-like culture with repeated fungal elicitation was 1.5 mg l(-1) day(-1), which was about 40% higher than that of the elicitor-treated batch culture and three times the productivity of the non-elicited batch culture.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Modification of fatty acids changes the flavor volatiles in tomato leaves.

Expression of the yeast Delta9 desaturase gene in tomato (Lycopersicon esculentum Mill.) resulted in changes in the profiles of fatty acids in tomato leaves. Transgenic leaves displayed a dramatic increase in cis-Delta9 16:1, which only existed in a small quantity in control leaves. Also higher, but not as dramatic, were 18:1 and 16:3 fatty acids. Several fatty acids, viz. 16:0, 18:0, and 18:3 declined in transgenic leaves. Changes in fatty acids were accompanied by changes in certain volatile compounds derived from fatty acids. On a percentage basis, most notable increases (>3-fold) were 1-hydroxy-2-butanone, 1-penten-3-ol, heptanal, 3-hexen-1-ol, 2-octanol,cis-3-hexenal, hexanal and 2-nonenal. Several flavor compounds not known to be biochemically derived from fatty acids, viz. 2-ethyl-furan, 5-ethyl-2-[5H]-furanone, eugenol, and 2-ethylthiophene also showed sharp increases in transgenic leaves.

Fatty Acids↗
PubMed2001

Volatile compounds of endophyte-free and infected tall fescue (Festuca arundinacea Schreb.).

Volatile compounds produced by intact plants and ground leaf tissue from endophyte-infected (E+) and endophyte-free (E-) tall fescue (Festuca arundinacea Schreb.) were collected by a purge-and-trap procedure and analyzed by gas chromatography/mass spectrometry The volatile compound profile from ground leaf tissue was similar between E+ and E- clonal plants; however, the sheaths of E+ clonal plants produced higher levels of 1-octen-3-ol, a characteristic volatile compound derived from lipid peroxidation in fungi, which was absent in E- clonal plants. Intact plants produced fewer volatiles than macerated leaves. At 25 degrees C, (Z)-3-hexen-1-ol acetate was the most abundant compound, accounting for 77 and 89% of the total volatile emission from E+ and E- plants, respectively. Higher temperature (32 degrees C) significantly reduced the production of (Z)-3-hexen-1-ol acetate. Nonanal was the most abundant compound at 32 degrees C accounting for 52 and 45% of the total volatile emission from E+ and E- plants. Treatment of E+ and E- plants with jasmonic acid (JA) dramatically altered the volatile compound profile. The levels of (E)-beta-ocimene increased more than 200-fold and accounted for at least 43% of the total volatile emission. Although the presence of endophyte resulted in some qualitative and quantitative differences in the production of volatile compounds, they are unlikely to account for the differences in insect resistance between E+ and E- plants. Nevertheless, the production of a unique spectrum of volatiles after JA treatment may represent a significant plant-based defense response in tall fescue that is independent of endophyte.

Claviceps↗