Biomedical subjects

W Zhu

Publications and source records attributed to W Zhu.

At least 37 records · Page 2Linked to original sources

PubMed2002

Morphine 6 glucuronide stimulates nitric oxide release in mussel neural tissues: evidence for a morphine 6 glucuronide opiate receptor subtype.

We have previously demonstrated that Mytilus edulis pedal ganglia contain opiate alkaloids, i.e., morphine and morphine 6 glucuronide (M6G), as well as mu opiate receptor subtype fragments exhibiting high sequence similarity to those found in mammals. Now we demonstrate that M6G stimulates pedal ganglia constitutive nitric oxide (NO) synthase (cNOS)-derived NO release at identical concentrations and to similar peak levels as morphine. However, the classic opiate antagonist, naloxone, only blocked the ability of morphine to stimulate cNOS-derived NO release and not that of M6G. CTOP, a mu-specific antagonist, blocked the ability of M6G to induce cNOS-derived NO release as well as that of morphine, suggesting that a novel mu opiate receptor was present and selective toward M6G. In examining a receptor displacement analysis, both opiate alkaloids displaced [3H]-dihydromorphine binding to the mu opiate receptor subtype. However, morphine exhibited a twofold higher affinity, again suggesting that a novel mu opiate receptor may be present.

Animals↗

PubMed2002

Dracunculus medinensis and Schistosoma mansoni contain opiate alkaloids.

The results of analysis, by high-performance liquid chromatography coupled with electrochemical detection and by nano-electrospray-ionization, double quadrupole/orthogonal-acceleration, time-of-flight mass spectrometry, indicate that adult Dracunculus medinensis and Schistosoma mansoni both contain the opiate alkaloid morphine and that D. medinesis also contains the active metabolite of morphine, morphine 6-glucuronide. From these and previous observations, it would appear that many helminths are probably using opiate alkaloids as potent immunosuppressive and antinociceptive signal molecules, to down-regulate immunosurveillance responsiveness and pain signalling in their hosts.

Animals↗

PubMed2001

Two-component method to enantiopure quinolizidinones and Indolizidinones. Total synthesis of (-)-lasubine II.

The reaction of iodides 1 and enantiopure beta-amino esters 2 mediated by potassium carbonate in acetonitrile at 65 degrees C provides quinolizidinones or indolizidinones 3, together with piperidines or pyrrolidines 4. Hydrolysis of 4 to the corresponding carboxylic acids followed by treatment of acetic anhydride/triethylamine gives 3 in high yields. Using 3a as a key intermediate, (-)-lasubine II is synthesized in four steps. [reaction: see text]

Indolizines↗

PubMed2001

Role of the alpha(v)beta6 integrin in human oral squamous cell carcinoma growth in vivo and in vitro.

Expression of the alpha(v)beta6 integrin is strikingly upregulated in several types of carcinoma, including human oral squamous cell carcinoma (SCC). Employing a neutralizing monoclonal antibody to alpha(v)beta6, we investigated its role in cell adhesion, proliferation, migration, and in vivo growth of an invasive human SCC line, termed HSC-3. We found that alpha(v)beta6 is strictly required for HSC-3 cell growth in a three-dimensional collagen gel and also prominently contributes to cell migration in two different assay systems. In addition, the anti-alpha(v)beta6 antibody inhibited the invasive growth of HSC-3 cells transorally injected into nude mice. In the presence of the coinjected antibody, the average tumor size at 10 days was reduced by 59%. Histologically, antibody-treated tumors appeared less invasive than control tumors. Furthermore, intravenous application of a neutralizing antibody to the alpha(v) integrin subunit retarded HSC-3 tumor growth. These results point to a possible critical role of the alpha(v)beta6 integrin in controlling growth and invasion of human oral cancer cells.

Animals↗

PubMed2001

Cytoplasmic O-glycosylation prevents cell surface transport of E-cadherin during apoptosis.

Cellular adhesion is regulated by members of the cadherin family of adhesion receptors and their cytoplasmic adaptor proteins, the catenins. Adhesion complexes are regulated by recycling from the plasma membrane and proteolysis during apoptosis. We report that in MCF-7, MDA-MB-468 and MDCK cells, induction of apoptosis by agents that cause endoplasmic reticulum (ER) stress results in O-glycosylation of both beta-catenin and the E-cadherin cytoplasmic domain. O-glycosylation of newly synthesized E-cadherin blocks cell surface transport, resulting in reduced intercellular adhesion. O-glycosylated E-cadherin still binds to beta- and gamma-catenin, but not to p120-catenin. Although O-glycosylation can be inhibited with caspase inhibitors, cleavage of caspases associated with the ER or Golgi complex does not correlate with E-cadherin O-glycosylation. However, agents that induce apoptosis via mitochondria do not lead to E-cadherin O-glycosylation, and decrease adhesion more slowly. In MCF-7 cells, this is due to degradation of E-cadherin concomitant with cleavage of caspase-7 and its substrate poly(ADP-ribose) polymerase. We conclude that cytoplasmic O-glycosylation is a novel, rapid mechanism for regulating cell surface transport exploited to down-regulate adhesion in some but not all apoptosis pathways.

Animals↗

PubMed2001

Lipopolysaccharide-stimulated or granulocyte-macrophage colony-stimulating factor-stimulated monocytes rapidly express biologically active IL-15 on their cell surface independent of new protein synthesis.

Although IL-15 shares many of the biological activities of IL-2, IL-2 expression is primarily under transcriptional regulation, while the mechanisms involved in the regulation of IL-15 are complex and not completely understood. In the current study, we found that CD14(+) monocytes constitutively exhibit both IL-15 mRNA and protein. IL-15 protein was found stored intracellularly and stimulation of CD14(+) monocytes with either LPS or GM-CSF resulted in mobilization of IL-15 stores to the plasma membrane. This rapidly induced surface expression was the result of a translocation of preformed stores, confirming that posttranslational regulatory stages limit IL-15, because it was not accompanied by an increase in IL-15 mRNA and occurred independent of de novo protein synthesis. After fixation, activated monocytes, but not resting monocytes, were found to support T cell proliferation, and this effect was abrogated by the addition of an IL-15-neutralizing Ab. The presence of preformed IL-15 stores and the ability of stimulated monocytes to mobilize these stores to their surface in an active form is a novel mechanism of regulation for IL-15.

Adult↗

PubMed2001

Involvement of the bed nucleus of the stria terminalis in hippocampal cholinergic system-mediated activation of the hypothalamo--pituitary--adrenocortical axis in rats.

This study was designed to determine the effect of the bed nucleus of the stria terminalis (BNST) in hippocampal cholinergic system-mediated activation of the hypothalamo--pituitary--adrenocortical (HPA) axis in the rat. Neurons in the BNST were lesioned by bilateral injection of the cell-selective neurotoxin, ibotenic acid (1.5 microg/microl of solution per side). Two weeks later, neostigmine was microinjected into the rats' hippocampus. Rats in which ibotenic acid had been injected into the BNST showed attenuated expression of c-Fos in the hypothalamic paraventricular nucleus (PVN) and blunted elevation of plasma adrenocorticotropic hormone (ACTH) after microinjection of neostigmine into the hippocampus compared with rats in which saline had been injected into the BNST. The results of this study indicate that the BNST relays signals of hippocampal cholinergic system-mediated activation of the HPA axis in rats.

Acetylcholine↗

PubMed2001

Transcription activating property of autoantigen SG2NA and modulating effect of WD-40 repeats.

Autoantibodies to intracellular proteins have been detected in sera of patients with various forms of cancer. Nuclear autoantigen SG2NA (S, G2 phase nuclear antigen) was isolated using autoantibodies from a patient with bladder and lung cancers and its expression is enhanced in the S and G2 phases of the cell cycle. Molecular cloning revealed that the C-terminal region of SG2NA contains six WD-40 repeats, motifs that are present in a large family of proteins with diverse functions. We show that the N-terminal region of SG2NA (aa 1-391) acted as a strong transcriptional activator in both yeast and mammalian cells. In contrast, the C-terminal WD-40 repeats had an inhibitory effect on transcription activation. We performed molecular swapping experiments by substituting the WD-40 repeats of SG2NA with those of yeast Met30 and Cdc4 and showed that the WD-40 regions from either Met30 or Cdc4 were capable of reproducing transcription repression function. The SG2NA WD-40 repeats were also able to repress basal level transcription and transactivation function of a GAL4-VP16 chimera. These observations suggest that some WD-40 repeats may have, as one of their functions, a negative regulatory role in the biological activities of their own and perhaps other proteins.

Animals↗

PubMed2001

Crystal structure of heme oxygenase from the gram-negative pathogen Neisseria meningitidis and a comparison with mammalian heme oxygenase-1.

We report the crystal structure of heme oxygenase from the pathogenic bacterium Neisseria meningitidis at 1.5 A and compare and contrast it with known structures of heme oxygenase-1 from mammalian sources. Both the bacterial and mammalian enzymes share the same overall fold, with a histidine contributing a ligand to the proximal side of the heme iron and a kinked alpha-helix defining the distal pocket. The distal helix differs noticeably in both sequence and conformation, and the distal pocket of the Neisseria enzyme is substantially smaller than in the mammalian enzyme. Key glycine residues provide the flexibility for the helical kink, allow close contact of the helix backbone with the heme, and may interact directly with heme ligands.

Animals↗

PubMed2001

[Rehabilitation therapy for short bowel syndrome].

OBJECTIVE: To investigate the effect of rehabilitation therapy for short bowel syndrome on patients' nutritional status and intestinal adaptation. METHODS: Twenty seven patients with short bowel syndrome with the average age of 38.5 +/- 19.3 years, the residual small intestine of the length of 15 to 80 cm, ileocecal valve being preserved in 15 cases, and an average time between the onset of short bowel syndrome and rehabilitation therapy of 86 +/- 105 d received 29 courses of rehabilitation therapy including enteral or parenteral nutrition, glutamine, recombinant human growth hormone and rehabilitation diet from January 1997 to July 2000. RESULTS: After the treatment, the patients' nutritional status improved markedly, their intestinal absorptive capacity improved too. Eight patients were followed up for more than 2 y, 4 of them (50%) had weaned from total parenteral nutrition. Thirteen patients were followed up for more than 1 y, 10 of them (76.9%) had weaned from total parenteral nutrition. CONCLUSION: Rehabilitation therapy for short bowel syndrome improves patients' nutritional status effectively and promote intestinal adaptation. Early initiation of rehabilitation therapy promotes intestinal adaptation, and increases patients' liability to wean from total parenteral nutrition.

Adolescent↗

PubMed2001

Calcineurin plays a critical role in the development of pressure overload-induced cardiac hypertrophy.

BACKGROUND: Although activation of the Ca(2+)-dependent phosphatase calcineurin has been reported to induce cardiomyocyte hypertrophy, whether calcineurin is involved in pressure overload-induced cardiac hypertrophy remains controversial. METHODS AND RESULTS: We examined in the present study the role of calcineurin in pressure overload-induced cardiac hypertrophy using transgenic mice that overexpress the dominant negative mutant of calcineurin specifically in the heart. There were no significant differences in body weight, blood pressure, heart rate, heart weight, and the cardiac calcineurin activity between the transgenic mice and their littermate wild-type mice at basal state. The activity of calcineurin was markedly increased by pressure overload produced by constriction of the abdominal aorta in the heart of wild-type mice but less increased in the heart of the transgenic mice. Pressure overload induced increases in heart weight, wall thickness of the left ventricle, and diameter of cardiomyocytes; reprogramming of expressions of immediate early response genes and fetal-type genes; activation of extracellular signal-regulated protein kinases; and fibrosis. All these hypertrophic responses were more prominent in the wild-type mice than in the transgenic mice. CONCLUSIONS: These results suggest that calcineurin plays a critical role in the development of pressure overload-induced cardiac hypertrophy.

Animals↗

PubMed2001

Isoproterenol activates extracellular signal-regulated protein kinases in cardiomyocytes through calcineurin.

BACKGROUND: Extracellular signal-regulated kinases (ERKs) and calcineurin have been reported to play important roles in the development of cardiac hypertrophy. We examined here the relation between calcineurin and ERKs in cardiomyocytes. METHODS AND RESULTS: Isoproterenol activated ERKs in cultured cardiomyocytes of neonatal rats, and the activation was abolished by chelation of extracellular Ca(2+) with EGTA, blockade of L-type Ca(2+) channels with nifedipine, or depletion of intracellular Ca(2+) stores with thapsigargin. Isoproterenol-induced activation of ERKs was also significantly suppressed by calcineurin inhibitors in cultured cardiomyocytes as well as in the hearts of mice. Isoproterenol failed to activate ERKs in either the cultured cardiomyocytes or the hearts of mice that overexpress the dominant negative mutant of calcineurin. Isoproterenol elevated intracellular Ca(2+) levels at both systolic and diastolic phases and dose-dependently activated calcineurin. Inhibition of calcineurin also attenuated isoproterenol-stimulated phosphorylation of Src, Shc, and Raf-1 kinase. The immunocytochemistry revealed that calcineurin was localized in the Z band, and isoproterenol induced translocation of calcineurin and ERKs into the nucleus. CONCLUSIONS: Calcineurin, which is activated by marked elevation of intracellular Ca(2+) levels by the Ca(2+)-induced Ca(2+) release mechanism, regulates isoproterenol-induced activation of ERKs in cardiomyocytes.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Field cooling induced changes in the antiferromagnetic structure of NiO films.

The magnetic anisotropy in antiferromagnetic 500 A thick NiO films, before and after the establishment of an exchange bias field with Co84Fe16 ferromagnetic layers, was measured using magnetic linear dichroism in soft x-ray absorption. Both <111> textured NiO and untextured NiO films show exchange-bias induced in-plane magnetic anisotropy of nearly equal magnitude and with the Ni moment axis being nearly parallel to the exchange bias field direction. These results represent the first observation of the key step in the exchange biasing process, namely, repopulation of the antiferromagnetic domains whose magnetization axis is closest to the exchange bias field direction.

Journal Article↗

PubMed2001

Artifact-free matrix-assisted laser desorption ionization time-of-flight mass spectra of tert.-butyldimethylsilyl ether derivatives of cyclodextrins used for the synthesis of single-isomer, chiral resolving agents for capillary electrophoresis.

Artifact-free, high-resolution matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectra have been obtained for the labile, single-isomer, tert.-butyldimethylsilyl ether derivatives of alpha-, beta- and gamma-cyclodextrins by optimizing the MALDI sample preparation method. 2,5-Dihydroxybenzoic acid, a 3:1 mixture of 2,5-dihydroxybenzoic acid and 1-hydroxyisoquinoline, and 2,4,6-trihydroxyacetophenone were investigated as MALDI matrices with methanol and acetonitrile as matrix solvents. Partial-to-complete loss of the tert.-butyldimethylsilyl groups was observed when the commonly used 2,5-dihydroxybenzoic acid was the MALDI matrix and/or methanol was the solvent, both with and without trifluoroacetic acid as additive. Loss of the labile tert.-butyldimethylsilyl groups was avoided with 2,4,6-trihydroxyacetophenone as MALDI matrix and acetonitrile as matrix solvent. Good ion intensities were achieved for the (M+Na)+ and (M+K)+ quasimolecular ions in the positive-ion mode. Minor byproducts were observed in some of the samples and the information was used to aid the optimization of the synthetic work.

Artifacts↗

PubMed2001

Endoplasmic reticulum localized Bcl-2 prevents apoptosis when redistribution of cytochrome c is a late event.

The disruption of mitochondrial function is a key component of apoptosis in most cell types. Localization of Bcl-2 to the outer mitochondrial and endoplasmic reticulum membranes is consistent with a role in the inhibition of many forms of apoptosis. In Rat-1 cells, a Bcl-2 mutant targeted exclusively to the endoplasmic reticulum (Bcl-cb5) was effective at inhibiting apoptosis induced by serum starvation/myc, or ceramide but not apoptosis induced by etoposide. The former conditions cause a decrease in mitochondrial transmembrane potential (Deltapsi(m)) as an early event that precedes the release of cytochrome c from mitochondria. By contrast, when cells are exposed to etoposide, a situation in which cytochrome c release and membrane localization of the pro-apoptotic protein Bax precede loss of Deltapsi(m), wild type Bcl-2 but not Bcl-cb5 prevents apoptosis. Therefore, Bcl-2 functions in spatially distinct pathways of apoptosis distinguished by the order of cytochrome c release and loss of Deltapsi(m).

Amino Acid Chloromethyl Ketones↗

PubMed2001

Presence of morphine and morphine-6-glucuronide in the marine mollusk Mytilus edulis ganglia determined by GC/MS and Q-TOF-MS. Starvation increases opiate alkaloid levels.

Morphine and morphine-6-glucuronide, a morphine metabolite, have been identified and quantified in Mytilus edulis pedal ganglia at a level of 2.67+/-0.44 and 0.98+/-0.14 ng/ganglia, respectively by high performance liquid chromatography coupled to electrochemical detection. These opiate alkaloids were further identified by both gas-chromatography mass spectrometry and nanoflow electrospray ionization double quadrupole orthogonal acceleration Time of Flight mass spectrometry. In animals that were starved, the morphine level rose to 6.38+/-0.88 ng/ganglion and the morphine 6-glucoronide rose to a level of 23.0+/-3.2 ng/ganglion after 30 days. These studies demonstrate that opiate alkaloids are present as naturally occurring signal molecules whose levels respond to stress, i.e., starvation. Opiate alkaloids were not found in the animal's incubation media or food, demonstrating their synthesis occurred in the respective tissue. These new method of opiate alkaloid detection, conclusively proves that morphine and morphine-6-glucuronide are present in animal tissues.

Animals↗

PubMed2001

Arginine methylation of STAT1 modulates IFNalpha/beta-induced transcription.

Transcriptional induction by interferons requires the tyrosine and serine phosphorylation of STAT transcription factors. The N-terminal region is highly homologous among the STAT proteins and surrounds a completely conserved arginine residue. Here we demonstrate arginine methylation of STAT1 by the protein arginine methyl-transferase PRMT1 as a novel requirement for IFNalpha/beta-induced transcription. Methyl-thioadenosine, a methyl-transferase inhibitor that accumulates in many transformed cells, inhibits STAT1-mediated IFN responses. This inhibition arises from impaired STAT1-DNA binding due to an increased association of the STAT inhibitor PIAS1 with phosphorylated STAT1 dimers in the absence of arginine methylation. Thus, arginine methylation of STAT1 is an additional posttranslational modification regulating transcription factor function, and alteration of arginine methylation might be responsible for the lack of interferon responsiveness observed in many malignancies.

Amino Acid Sequence↗

PubMed2001

The elevation of plasma adrenocorticotrophic hormone and expression of c-Fos in hypothalamic paraventricular nucleus by microinjection of neostigmine into the hippocampus in rats: comparison with acute stress responses.

We have reported that the microinjection of neostigmine into the hippocampus of rats induced responses similar to stress responses in terms of catecholamines and glucose in plasma. In order to test the hypothesis that hippocampal neostigmine injection is a possible animal model of acute stress responses, we investigated c-Fos expression in the hypothalamic paraventricular nucleus (PVN) and plasma levels of adrenocorticotrophic hormone (ACTH) after hippocampal neostigmine injection and compared these levels with those resulting from stressful conditions such as immobilization and insulin-induced hypoglycemia. The patterns of expression of Fos-ir in the PVN after microinjection of neostigmine into the hippocampus were not different from those seen in the two stressful situations. After microinjection of neostigmine, plasma ACTH levels significantly increased. Taken together, the results of this study indicate that microinjection of neostigmine into the hippocampus is a potential experimental model for acute stress responses.

Adrenocorticotropic Hormone↗