Biomedical subjects

J Wu

Publications and source records attributed to J Wu.

At least 217 records · Page 12Linked to original sources

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

DNA synthesis and mitotic clonal expansion is not a required step for 3T3-L1 preadipocyte differentiation into adipocytes.

Upon differentiation induction of 3T3-L1 preadipocytes by a hormone mixture containing 1-isobutyl-3-methylxanthine, dexamethasone, and insulin, the preadipocytes undergo approximately 2 rounds of mitotic clonal expansion, which just precedes the adipogenic gene expression program and has been thought to be an essential early step for differentiation initiation. By inducing 3T3-L1 preadipocytes with each individual hormone, it was determined that the mitotic clonal expansion was induced only by insulin and not by 1-isobutyl-3-methylxanthine or dexamethasone. Cell number counting and fluorescence-activated cell-sorting analysis indicated that a significant fraction of 3T3-L1 preadipocytes differentiated into adipocytes without mitotic clonal expansion when induced with the combination of 1-isobutyl-3-methylxanthine and dexamethasone. Furthermore, when normally induced 3T3-L1 preadipocytes were treated with PD98059 (an inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1) to block the activation of extracellular signal-regulated kinase (Erk) 1 and Erk2, the mitotic clonal expansion was blocked, but adipocyte differentiation was not affected. These observations were confirmed by bromodeoxyuridine labeling. The differentiated adipocytes induced with 1-isobutyl-3-methylxanthine and dexamethasone or standard hormone mixture plus PD98059 were not labeled by bromodeoxyuridine. Thus, it is evident that 3T3-L1 preadipocytes could differentiate into adipocytes without DNA synthesis and mitotic clonal expansion. Our results also suggested that activation of Erk1 and Erk2 is essential to but not sufficient for induction of mitotic clonal expansion.

1-Methyl-3-isobutylxanthine↗

PubMed2001

Complexation of trivalent lanthanide cations by galactitol in the solid state. The crystal structure and an FT-IR study of 2NdCl3.galactitol.14H2O.

The crystal structure of 2NdCl3.galactitol.14H2O has been determined. The crystal system is triclinic, space group: -1, with unit-cell dimensions: a = 9.736(2), b = 10.396, c = 8.027 A; alpha = 108.05(3), beta = 92.68(3), gamma = 88.44(3) degrees, V= 771.6(3) A3, Z = 2. Each Nd atom is coordinated to nine oxygen atoms, three from the alditol and six from water molecules, with Nd-O distances from 2.461 to 2.552 A. The seventh water molecule is hydrogen-bonded by the hydroxyl hydrogen on O-1 (O-1-H-ll...O-10, 2.639 A). The FT-IR spectra of 2NdCl3.galactitol.14H2O and 2PrCl3.galactitol.14H2O are analogous, and show that Pr and Nd have the same coordination mode. The IR results are consistent with the crystal structures.

Carbohydrates↗

PubMed2001

Sugar interaction with metal ions. The crystal structure and Raman spectra study of SmCl3-galactitol complex.

The crystal structure of 2SmCl3.galactitol.14H2O has been determined. The crystal system is triclinic, space group: P-1. The unit cell dimensions: a = 9.683(2) A, b = 10.341(2) A, c = 7.990(2) A; alpha = 108.01(3) degrees, beta = 92.71(3) degrees, gamma = 88.42(3) degrees. Each Sm atom is coordinated to nine oxygen atoms, three from the alditol and six from water molecules, with Sm-O distance from 2.417 to 2.520 A. The seventh water molecule is hydrogen-bonded by the hydroxy hydrogen on O-3 (O(3)-H(13)...O(10), 2.635 A). After forming complexes the peaks have shifted and the relative intensities have changed in the IR and Raman spectra, which are corresponding to the changes in bond distances and bond angles of the structures. The IR and Raman spectra of Pr-, Nd- and Sm-galactitol complexes are similar, which show that the three metal ions have the same coordination mode.

Crystallography, X-Ray↗

PubMed2001

Insulin-like growth factor I alters renal function and stimulates renin secretion in late gestation fetal sheep.

While it is known that treatment with insulin-like growth factor I (IGF-I) stimulates growth of the fetal kidney, nothing is known about the short term or long term effects of IGF-I on fetal renal function. To investigate the acute effects of IGF-I on fetal renal function and on the activity of the fetal renin-angiotensin system, studies were carried out in 12 chronically catheterized fetal sheep aged 120 +/- 1 days, before and during a 4 h I.V. infusion of IGF-I at 80 ug h-1. Seven control fetuses were infused over the same period with vehicle (0.1% bovine serum albumin in 0.15 M saline). IGF-I infusion increased plasma IGF-I concentrations by about 80%. There was a small fall in arterial PO2 (P < 0.01), arterial PCO2 increased (P < 0.05), plasma lactate levels increased (P < 0.01) and arterial pH fell (P < 0.05). Fractional bicarbonate reabsorption increased and bicarbonate excretion decreased (P < 0.05). Infusions of IGF-I had no sustained effect on fetal arterial pressure. Glomerular filtration rate (GFR) did not change significantly during IGF-I infusion, but renal blood flow (RBF) fell (P < 0.05). Therefore filtration fraction relative to control values increased (P < 0.05), suggesting that efferent arteriolar vasoconstriction had occurred. IGF-I infusion led to an antidiuresis (P < 0.01), a rise in urinary osmolality (P < 0.05) and a fall in free water clearance (P < 0.01). Since fetal PO2 fell, it is probable that these effects were mediated by arginine vasopressin. The excretion rates of sodium, chloride and phosphate were all reduced by 4 h of infusion (P < 0.05), because their fractional reabsorption rates were all increased (sodium, P < 0.01; chloride, P < 0.01; and phosphate, P < 0.05). Plasma renin concentration increased by 275 +/- 52% during infusion of IGF-I (P < 0.005). Plasma renin activity also increased (P < 0.005), while circulating angiotensinogen concentrations fell (P < 0.05). In the adult, IGF-I increases both RBF and GFR, enhances tubular reabsorption and stimulates the renin-angiotensin system. In the fetus, however, it decreased RBF and had no effect on GFR, but was associated with enhanced tubular function and intense stimulation of renin secretion. Some of these effects of IGF-I on fetal renal function may be involved in maturation of the kidney in preparation for life after birth.

Acid-Base Equilibrium↗

PubMed2001

Preparation and novel reduction reactions of vinamidinium salts.

Substituted acetic acids and formamides react in the presence of phosphorus oxychloride to yield the vinamidinium hexafluorophosphate salts 5a-d, 6a-d, and 7 in moderate to good unoptimized recrystallized yields (40-67%) as easily handled nonhygroscopic solids. The 1,3-differentially substituted vinamidinium salts 8 was prepared by amine exchange in 81% yield as are the cyclic diazapinium salts 9 and 10 in > 76% yield. The symmetrical 2-chlorovinamidinium 11 was prepared by displacement of 3 in 71% yield. The 2-chlorovinamidinium salts are cleanly reduced to the parent vinamidinium salts 12-16 using HI or PPh3/pTSA in up to 99% assay yield.

Cyclooxygenase 2↗

PubMed2001

Solution structure of the second extracellular loop of human thromboxane A2 receptor.

Thromboxane A(2) receptor (TP receptor), a prostanoid receptor, belongs to the G protein-coupled receptor family, composed of three intracellular loops and three extracellular loops connecting seven transmembrane helices. The highly conserved extracellular domains of the prostanoid receptors were found in the second extracellular loop (eLP(2)), which was proposed to be involved in ligand recognition. The 3D structure of the eLP(2) would help to further explain the ligand binding mechanism. Analysis of the human TP receptor model generated from molecular modeling based on bacteriorhodopsin crystallographic structure indicated that about 12-14 A separates the N- and C-termini of the extra- and intracellular loops. Synthetic loop peptides whose termini are constrained to this separation are presumably more likely to mimic the native loop structure than the corresponding loop region peptide with unrestricted ends. To test this new concept, a peptide corresponding to the eLP(2) (residues 173-193) of the TP receptor has been made with the N- and C-termini connected by a homocysteine disulfide bond. Through 2D nuclear magnetic resonance (NMR) experiments, complete (1)H NMR assignments, and structural construction, the overall 3D structure of the peptide was determined. The structure shows two beta-turns at residues 180 and 185. The distance between the N- and C-termini of the peptide shown in the NMR structure is 14.2 A, which matched the distance (14.5 A) between the two transmembrane helices connecting the eLP(2) in the TP receptor model. This suggests that the approach using the constrained loop peptides greatly increases the likelihood of solving the whole 3D structures of the extra- and the intracellular domains of the TP receptor. This approach may also be useful in structural studies of the extramembrane loops of other G protein-coupled receptors.

Circular Dichroism↗

PubMed2001

Rhamnolipid production by Pseudomonas aeruginosa under denitrification: effects of limiting nutrients and carbon substrates.

Being biosurfactants, rhamnolipids create severe foaming when produced in aerobic Pseudomonas aeruginosa fermentation. The necessary reduction of aeration causes oxygen limitation and restricts cell and product concentrations. In this study, we evaluate the new strategy of rhamnolipid production under denitrification conditions. Because hydrocarbons used in earlier aerobic fermentations were not metabolizable in the absence of oxygen, other potential C substrates were examined, including palmitic acid, stearic acid, oleic acid, linoleic acid, glycerol, vegetable oil, and glucose. All were found able to support cell growth under anaerobic denitrification. The growth on the two solid substrates (palmitic acid and stearic acid) was slower but could be enhanced substantially by initial addition of rhamnolipids (0.06 g/L). The effects of different limiting nutrients (N, P, S, Mg, Ca, and Fe) were also investigated. The commonly used N limitation could not be adopted in the denitrifying fermentation because the nitrate added for anaerobic respiration would also be assimilated for growth. P limitation was most effective, giving four- to fivefold higher specific productivity than the conventional N limitation. S limitation was comparable to N limitation; Mg limitation was much poorer. Ca and Fe were ineffective in limiting cell growth. The new strategy was further evaluated in a P-limited fermentation with palmitic acid as the substrate. The fermentation was first carried out under denitrification and later switched to aerobic condition. The specific productivity under denitrification was found to be about one-third that of the aerobic condition. The denitrification process was, however, free of foaming or respiratory limitation. Much higher cell concentrations may be employed to attain higher volumetric productivity and product concentrations, for more economical product recovery and/or purification.

Aerobiosis↗

PubMed2001

Polypyrrole-coated capillary coupled to HPLC for in-tube solid-phase microextraction and analysis of aromatic compounds in aqueous samples.

In-tube solid-phase microextraction (SPME) based on a polypyrrole (PPY)-coated capillary was investigated for the extraction of aromatic compounds from aqueous solutions. The PPY-coated capillary was coupled on-line to HPLC that was programmed with an autosampler to achieve automated in-tube SPME and HPLC analysis. Three groups of aromatics, including both polar and nonpolar compounds, were examined. The results demonstrated that the PPY coating had a higher extraction efficiency than the currently used commercial capillary coatings, especially for polycyclic aromatic compounds and polar aromatics due to the increasing pi-pi interactions, interactions by polar functional groups, and hydrophobic interactions between the polymer and the analytes. In addition to the functional groups in the PPY coating, which contributed to the higher extraction efficiency and selectivity toward analytes, the coating's porous surface structure,which was revealed by electron microscopy experiments, provided a high surface area that allowed for high extraction efficiency. It was found that the extraction efficiency and selectivity could be tuned by changing the coating thickness. The preliminary study of the extraction mechanism indicated that analytes were extracted onto the PPY coating mainly by an adsorption mechanism. The method was used for the extraction and analysis of both polar and nonpolar aromatics in aqueous samples.

Journal Article↗

PubMed2001

Study of B Decays to Charmonium States: B-->eta(c)K and B --> chi(c0)K.

In a sample of 9.66x10(6)B&Bmacr; pairs collected with the CLEO detector we make the first observation of B decays to an eta(c) and a kaon. We measure branching fractions B(B+-->eta(c)K+) = (0.69(+0.26)(-0.21)+/-0.08+/-0.20)x10(-3) and B(B degrees -->eta(c)K degrees ) = (1.09(+0.55)(-0.42)+/-0.12+/-0.31)x10(-3), where the first error is statistical, the second is systematic, and the third is from the eta(c) branching fraction uncertainty. From these we extract the eta(c) decay constant in the factorization approximation, f(eta(c)) = 335+/-75 MeV. We also search for B decays to a chi(c0) and a kaon. No evidence for a signal is found and we set 90% C.L. upper limits: B(B+-->chi(c0)K+)<4.8x10(-4) and B(B degrees -->chi(c0)K degrees )<5.0x10(-4).

Journal Article↗

PubMed2001

Distinct T cell developmental consequences in humans and mice expressing identical mutations in the DLAARN motif of ZAP-70.

The protein tyrosine kinase, ZAP-70, is pivotally involved in transduction of Ag-binding signals from the TCR required for T cell activation and development. Defects in ZAP-70 result in SCID in humans and mice. We describe an infant with SCID due to a novel ZAP-70 mutation, comparable with that which arose spontaneously in an inbred mouse colony. The patient inherited a homozygous missense mutation within the highly conserved DLAARN motif in the ZAP-70 kinase domain. Although the mutation only modestly affected protein stability, catalytic function was absent. Despite identical changes in the amino acid sequence of ZAP-70, the peripheral T cell phenotypes of our patient and affected mice are distinct. ZAP-70 deficiency in this patient, as in other humans, is characterized by abundant nonfunctional CD4(+) T cells and absent CD8(+) T cells. In contrast, ZAP-70-deficient mice lack both major T cell subsets. Although levels of the ZAP-70-related protein tyrosine kinase, Syk, may be sufficiently increased in human thymocytes to rescue CD4 development, survival of ZAP-70-deficient T cells in the periphery does not appear to be dependent on persistent up-regulation of Syk expression.

Amino Acid Motifs↗

PubMed2001

Follicular dendritic cell accessory activity crosses MHC and species barriers.

Productive follicular dendritic cell (FDC)-B cell interactions appear to involve critical ligand-receptor interactions. Immune complexes (IC) on FDC activate complement and provide FDC with a complement-derived CD21 ligand (CD21L), which bind CD21, while antigen in the IC binds on the B cell-BCR. Further, FDC-FcgammaRIIB binds Fc regions of antibodies in IC and reduces coligation of BCR and FcgammaRIIB minimizing an inhibitor of B cell activation. Given that Fc receptors and complement receptors bind immunoglobulins and complement fragments of other species, we reasoned that FDC accessory activity should cross MHC and species barriers. This prediction was tested using memory lymphocytes from OVA-immune mice and TT-immune humans in combination with FDC from murine lymph nodes and human tonsils. Human and murine FDC converted IC into potent immunogens (specific antibody increased from background to thousands of ng / ml). MHC barriers did not restrict this activity and human FDC worked with murine lymphocytes and murine FDC worked with human lymphocytes. Furthermore, stimulation via MHC-dependent allogeneic or zenogeneic mechanisms did not promote antibody production by FDC. Polyclonal responses stimulated by lipopolysaccharide and pokeweed mitogen were also promoted (10 - 100-fold) and anti-CD21 blocked FDC activity. These results substantiate the hypothesis that FDC are necessary for strong recall responses and that FDC-CD21L is critical.

Animals↗

PubMed2001

Rice genomics: current status of genome sequencing.

Since its establishment in 1991, the Rice Genome Research Program (RGP) has produced some basic tools for rice genome analysis, including a cDNA catalogue, a genetic linkage map and a yeast artificial chromosome (YAC)-based physical map. For the further development of rice genomics, RGP launched in 1998 an international collaborative project on rice genome sequencing. A P1-derived artificial chromosome (PAC)-based, sequence-ready physical map has been constructed using the PCR markers from cDNA sequences (expressed sequence tag [EST] markers). Selected PAC clones with 100-150 kb inserts from chromosomes 1 and 6 have been subjected to shotgun sequencing. The assembled genomic sequences, after predicting the gene-coding region, have been published both through a public database and through our website. As of January 2000, 1.9 Mb from 13 PAC clones were published. Future prospects for understanding rice genomic information at the nucleotide level are discussed.

DNA, Plant↗

PubMed2001

Sleep deprivation as a model experimental antidepressant treatment: findings from functional brain imaging.

This paper reviews the functional brain imaging studies in depressed patients treated with sleep deprivation. Sleep deprivation is an excellent experimental model of antidepressant treatments which offer new opportunities to understand the basic neural mechanisms. Its antidepressant effects are efficacious and rapid; sleep deprivation is easy to administer, inexpensive, and relatively safe; it can be studied in patients, normal controls, and animals; and it may lead to new treatments and new paradigms for antidepressant therapies. Seven published papers, coming from five different research centers, using either positron emission tomography (PET) with 18fluorodeoxyglucose (FDG) or single photon emission computerized tomography (SPECT) with Technetium-99-bexamethyl propyleneamine oxime (HMPAO) have relatively consistent findings. First, before sleep deprivation, responders have significantly elevated metabolism compared with non-responders, and usually the normal controls, in the orbital medial prefrontal cortex, and especially in the ventral portions of the anterior cingulate cortex. Secondly, after sleep deprivation, these hyperactive areas normalize in the responders. The magnitude of the clinical improvement was significantly correlated with decreased local glucose metabolic rate or cerebral blood flow in three studies. The results are consistent with some but not all functional brain imaging studies of antidepressant medications in depressed patients. Finally, a SPECT study using a radioactively labeled D2 receptor antagonist suggests that the antidepressant benefits of sleep deprivation are correlated with endogenous release of dopamine.

Brain↗

PubMed2001

Acrolein induces activation of the epidermal growth factor receptor of human keratinocytes for cell death.

Acrolein, which is a highly reactive formaldehyde generated by lipid peroxidation, can affect skin and cause various disorders. The effect of exposure of human keratinocytes to acrolein on cell surface-oriented signal transduction into cells was examined. Incubation of human keratinocytes with a relatively low concentration (50 microM) of acrolein caused a prompt and selective induction of tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) as a 180-kDa molecule during the period from 5-30 min after the start of incubation. This early event was followed by an increase in the density and number of phosphotyrosine-containing proteins during the period from 60-120 min after the start of incubation. The catalytic activity of EGFR as measured by the levels of autophorphorylation and phosphorylation of an exogenously added substrate, casein, in in vitro kinase assay, greatly increased as early as 1 min after the start of incubation and then decreased gradually 30 min later. MAP family kinases, including ERK, JNK, and p38 kinase, and the potentially downstream transcription factor c-Jun were all promoted for phosphorylation/activation during a period of 5-30 min. Selective prompt phosphorylation/activation of EGFR followed by phosphorylation of MAP family kinases and c-Jun and their blockade by a specific EGFR inhibitor, AG1478, suggested that activation of EGFR is the major, and possibly single, cell surface element for intracellular signal transduction in acrolein-treated cells. Incubation of human keratinocytes with 50 microM of acrolein induced atypical apoptosis with morphologic apoptotic features with low-grade oligonucleoside-sized DNA fragmentation. Partial inhibition of such a cytopathic effect of acrolein on human keratinocytes by preincubation with AG1478 suggests the involvement of an EGFR-mediated signal pathway for atypical apoptosis. These results provide new information on acrolein-induced cell surface-oriented signal transduction to human keratinocytes, and this information may be useful for understanding the pathogenesis of a number of skin diseases in response to environmental acrolein and acrolein-generating ultraviolet irradiation.

Acrolein↗

PubMed2001

Cepharanthine activates caspases and induces apoptosis in Jurkat and K562 human leukemia cell lines.

Cepharanthine (CEP) is a known membrane stabilizer that has been widely used in Japan for the treatment of several disorders such as anticancer therapy-provoked leukopenia. We here report that apoptosis was induced by low concentrations (1-5 microM) of CEP in a human leukemia T cell line, Jurkat, and by slightly higher concentrations (5-10 microM) in a human chronic myelogenous leukemia (CML) cell line K562, which expresses a p210 antiapoptotic Bcr-Abl fusion protein. Induction of apoptosis was confirmed in both Jurkat and K562 cells by DNA fragmentation and typical apoptotic nuclear change, which were preceded by disruption of mitochondrial membrane potential and were induced through a Fas-independent pathway. CEP treatment induced activation of caspase-9 and -3 accompanied by cleavage of PARP, Bid, lamin B1, and DFF45/ICAD in both Jurkat and K562 cells, whereas caspase-8 activation and Akt cleavage were observed only in Jurkat cells. The CEP-induced apoptosis was completely blocked by zVAD-fmk, a broad caspase inhibitor. Interestingly, CEP treatment induced remarkable degradation of the Bcr-Abl protein in K562 cells, and this degradation was prevented partially by zVAD-fmk. When used in combination with a nontoxic concentration of herbimycin A, lower concentrations (2-5 microM) of CEP induced obvious apoptosis in K562 cells with rapid degradation or decrease in the amount of Bcr-Abl and Akt proteins. Our results suggest that CEP, which does not have bone marrow toxicity, may possess therapeutic potential against human leukemias, including CML, which is resistant to anticancer drugs and radiotherapy.

Alkaloids↗

PubMed2001

Quantitative determination of noncovalently bound acridinium in protein conjugates by liquid chromatography/electrospray ion trap mass spectrometry.

A sensitive and robust liquid chromatography/electrospray ion trap mass spectrometry (LC/MS/MS) method has been developed for the quantitative determination of noncovalently bound acridinium free acid in protein-acridinium conjugates. The lower level of quantitation (LOQ) for acridinium free acid was determined to be 0.6 ng. The assay was validated with a linear concentration range of 0.6-60 ng. The method requires minimum sample handling and is specific, reproducible, and provides a new aspect for protein-acridinium conjugate characterization.

Acridines↗

PubMed2001

Selective analysis of phosphopeptides within a protein mixture by chemical modification, reversible biotinylation and mass spectrometry.

A new method combining chemical modification and affinity purification is described for the characterization of serine and threonine phosphopeptides in proteins. The method is based on the conversion of phosphoserine and phosphothreonine residues to S-(2-mercaptoethyl)cysteinyl or beta-methyl-S-(2-mercaptoethyl)cysteinyl residues by beta-elimination/1,2-ethanedithiol addition, followed by reversible biotinylation of the modified proteins. After trypsin digestion, the biotinylated peptides were affinity-isolated and enriched, and subsequently subjected to structural characterization by liquid chromatography/tandem mass spectrometry (LC/MS/MS). Database searching allowed for automated identification of modified residues that were originally phosphorylated. The applicability of the method is demonstrated by the identification of all known phosphorylation sites in a mixture of alpha-casein, beta-casein, and ovalbumin. The technique has potential for adaptations to proteome-wide analysis of protein phosphorylation.

Amino Acid Sequence↗