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Biomedical subjects

W Wu

Publications and source records attributed to W Wu.

At least 325 records · Page 18Linked to original sources
PubMed1997

[A study on the inhibitory effects of several chemicals on the production of nitrogen oxide in alveolar macrophage induced by asbestos].

Induction of chrysotile produced in Mang ai to the production of nitrogen oxide (NO) and effects of mixed rare earths (MRE), sodium selenite (SS) and aluminium citrate on the production of NO in alveolar macrophage (AM) induced by asbestos fiber were observed by in vitro cell culture technique and determination of nitrite ion content in the culture medium. Results showed that chrysotile fiber could increase nitrite ion content in the culture medium, with an obvious dose-dependent relationship. MRE, selenite, and aluminium citrate all could inhibit the production of NO in AM induced by asbestos, and its inhibitiory effects increased with the concentration of the above-mentioned chemicals. It suggests antagonism of MRE and selenite to pathogenicity of asbestos may be used in practice.

Aluminum Compounds↗
PubMed1997

[Effects of vasoactive intestinal peptide, alpha-chymotrypsin, pancreozymin, lipase, phospholipase A2 and collagenase on the viscoelasticity properties of red blood cell suspension].

Using Low Shear-30 Rheometer, we studied the effects of vasoactive intestinal peptide, alpha-chymotrypsin, pancreozymin, lipase, phospholipase A2 and collagenase on the viscoelasticity properties of RBC suspension. The result showed that these drugs could increase the values of eta 0.512 and A. I. It suggests that these drugs could increase the degree of RBC aggregation. Among the drugs and concentrations, there is no significant difference.

Blood Viscosity↗
PubMed1996

Six-fold rotational symmetry of ClpQ, the E. coli homolog of the 20S proteasome, and its ATP-dependent activator, ClpY.

ClpQ (HslV) is a homolog of the beta-subunits of the 20S proteasome. In E. coli, it is expressed from an operon that also encodes ClpY (HslU), an ATPase homologous to the protease chaperone, ClpX. ClpQ (subunit Mr 19,000) and ClpY (subunit Mr 49,000) were purified separately as oligomeric proteins with molecular weights of approximately 220,000 and approximately 350,000, respectively, estimated by gel filtration. Mixtures of ClpY and ClpQ displayed ATP-dependent proteolytic activity against casein, and a complex of the two proteins was isolated by gel filtration in the presence of ATP. Image processing of negatively stained electron micrographs revealed strong six-fold rotational symmetry for both ClpY and ClpQ, suggesting that the subunits of both proteins are arranged in hexagonal rings. The molecular weight of ClpQ combined with its symmetry is consistent with a double hexameric ring, whereas the data on ClpY suggest only one such ring. The symmetry mismatch previously observed between hexameric ClpA and heptameric ClpP in the related ClpAP protease is apparently not reproduced in the symmetry-matched ClpYQ system.

ATP-Dependent Proteases↗
PubMed1996

Pituitary lineage determination by the Prophet of Pit-1 homeodomain factor defective in Ames dwarfism.

The gene apparently responsible for a heritable form of murine pituitary-dependent dwarfism (Ames dwarf, df) has been positionally cloned, identifying a novel, tissue-specific, paired-like homeodomain transcription factor, termed Prophet of Pit-1 (Prop-1). The df phenotype results from an apparent failure of initial determination of the Pit-1 lineage required for production of growth hormone, prolactin or thyroid-stimulating hormone, resulting in dysmorphogenesis and failure to activate Pit-1 gene expression. These results imply that a cascade of tissue-specific regulators is responsible for the determination and differentiation of specific cell lineages in pituitary organogenesis.

Alleles↗
PubMed1996

mu-Opioid and delta-opioid receptors are expressed in brainstem antinociceptive circuits: studies using immunocytochemistry and retrograde tract-tracing.

Opioid-produced antinociception in mammals seems to be mediated in part by pathways originating in the periaqueductal gray (PAG) and the rostroventral medulla (RVM), and these pathways may include serotonergic neurons. In the present study, we examined the relationship of the cloned mu- and delta-receptors (MOR1 and DOR1, respectively) to PAG neurons projecting to the RVM, and RVM neurons projecting to the dorsal spinal cord. This was carried out by combining immunocytochemical staining for MOR1, DOR1, and serotonin with fluorescent retrograde tract-tracing. Of 133 retrogradely labeled cells in the RVM, 31% were immunoreactive for MOR1. Of the double-labeled cells, 41% also were immunoreactive for 5HT. Fifty-three percent of retrogradely labeled cells were apposed by DOR1-ir varicosities; 29% of the apposed cells were immunoreactive for 5HT. In the mesencephalon, cells retrogradely labeled from the RVM were usually surrounded by MOR1-ir structures; however, retrogradely labeled cells were never observed to be immunoreactive for MOR1. Similarly, retrogradely labeled cells in the caudal midbrain were seldom, if ever, labeled for DOR1; however, they frequently were apposed by DOR1-ir varicosities. Of 156 retrogradely labeled profiles from three rats, 52 (33%) were apposed by DOR1-ir varicosities. We conclude that both mu- and delta-opioid receptors could be involved in the antinociception mediated by the PAG-RVM-spinal cord circuit. In addition, opioids seem likely to have both direct and indirect effects on spinally projecting RVM cells in general, and on serotonergic RVM cells in particular.

Animals↗
PubMed1996

Misincorporation by HIV-1 reverse transcriptase promotes recombination via strand transfer synthesis.

Genome heterogeneity in retroviruses derives from poor fidelity of the reverse transcriptase (RT) and recombination via RT-catalyzed strand transfer synthesis. RTs lack proofreading ability, and they proficiently extend primers with mismatched termini. Recombination reactions carried out in vitro are accompanied by a high frequency of base substitution errors, suggesting a relationship. Here we provide evidence that misincorporation during RNA-directed DNA synthesis promotes strand transfer recombination. Experiments involved measurement of DNA synthesis, RNase H-directed cleavage, and strand transfer synthesis from preformed mismatched primers on RNA templates by human immunodeficiency virus (HIV) RT in vitro. A significant pause in synthesis occurred from a G(primer). rA(template) mismatch compared to the synthesis from a correctly paired (T.A) primer. The misincorporation-induced pause allowed an unusually large area of RT-RNase H-directed cleavage of the template RNA beneath the primer. Strand transfer to an acceptor molecule with sequence identical to the template RNA was about 50% more efficient than if the primer had had a correctly paired terminus. Overall transfer was measured over a large region of homology. Assuming that enhanced transfer occurs primarily at the site of the mismatch, the actual increase in transfer at that site must have been 1-2 orders of magnitude. Inclusion of a different acceptor molecule with complete complementarity to the originally mismatched 3' primer terminus resulted in an additional 2-fold increase in strand transfer efficiency. Overall, these results suggest the mechanism by which misincorporation during minus strand DNA synthesis in retroviral replication would promote high frequency recombination.

DNA Primers↗
PubMed1996

Reduction of ferricyanide by thiamine or thiamine pyrophosphate.

The colorimetric assay for the activity of pyruvate dehydrogenase (EC 1.2.4.1) developed by Itokawa is based on a coupled reduction of ferricyanide and the formation of Prussian blue (Brian Research 94, 475-484). In this assay system, we found that the coenzyme, thiamine pyrophosphate, itself reduced ferricyanide independent of both the enzyme and the substrate. Similar effect was also observed with thiamine, but not with thiochrome. The reduction of ferricyanide by thiamine or thiamine pyrophosphate was blocked by trichloroacetic acid. Measurement of the activity of purified pyruvate dehydrogenase based on monitoring the reduction of ferricyanide as described by Schwartz et al (Biochem. Biophys. Res. Commun. 31, 495-500) has been widely used. Our findings clearly disprove the assumption that reduction of ferricyanide is dependent on pyruvate dehydrogenase and invalidate assays for thiamine-dependent dehydrogenases based on the reduction of ferricyanide.

Animals↗
PubMed1996

Identification of CD8 as a peanut agglutinin (PNA) receptor molecule on immature thymocytes.

Differentiation of most T lymphocytes occurs within the thymus and is characterized by variable expression of CD4/CD8 coreceptor molecules, increased surface density of T cell antigen receptor (TCR) alpha beta proteins, and decreased expression of glycan chains recognized by the galactose-specific lectin peanut agglutinin (PNA). Although appreciated for several decades that PNA agglutination is useful for the physical separation of immature and mature thymocyte sub-populations, the identity of specific PNA-binding glycoproteins expressed on immature thymocytes remains to be determined. In the current report, we studied the expression of PNA-specific glycans on immature and mature T cells and used lectin affinity chromatography and immunoprecipitation techniques to characterize PNA-binding glycoproteins on thymocytes. Our data demonstrate that PNA-specific glycans are localized on a relatively small subset of thymocyte surface proteins, several of which were specifically identified, including CD43, CD45, and suprisingly, CD8 molecules. CD8 alpha and CD8 alpha' proteins bound to PNA in the absence of CD8 beta expression showing that O-glycans on CD8 beta glycoproteins are not necessary for PNA binding and that glycosylation of CD8 alpha and CD8 alpha' proteins proceeds effectively in the absence of CD8 beta. Finally, we demonstrate that PNA binding of CD8 is developmentally regulated by sialic acid addition as CD8 proteins from mature T cells bound to PNA only after sialidase treatment. These studies identify CD8 as a PNA receptor molecule on immature thymocytes and show that PNA binding of CD8 on immature and mature T cells is developmentally regulated by sialic acid modification.

Animals↗
PubMed1996

Discrimination among pheromone component blends by interneurons in male antennal lobes of two populations of the turnip moth, Agrotis segetum.

A difference in female pheromone production and male behavioral response has previously been found in two populations of the turnip moth, Agrotis segetum, originating from Sweden and Zimbabwe, respectively. In this study, we investigated the pheromone response of antennal lobe interneurons of males of the two populations by intracellular recordings, stimulating with single pheromone components and various inter- and intra-populational pheromone blends. Three major physiological types of antennal lobe neurons were established in the two populations according to their responses to different stimuli. One type responded broadly to almost all the stimuli tested. The second type responded selectively to some of the single components and blends. The third type did not respond to any single components but did respond to certain blends. Furthermore, some neurons of the second and third type recognized strain specific differences in ratios between pheromone components. Both projection neurons and local interneurons were found among these three types. Two pheromone responding bilateral projection neurons are reported for the first time in this paper.

Animals↗
PubMed1996

Nucleosomal peptide epitopes for nephritis-inducing T helper cells of murine lupus.

Nucleosome-specific T helper (Th) cells provide major histocompatibility complex class II-restricted, cognate help to nephritogenic antinuclear autoantibody-producing B cells in lupus. However, the lupus Th cells do not respond when components of the nucleosome, such as free DNA or histones, are individually presented by antigen-presenting cells. Thus critical peptide epitopes for the pathogenic Th cells are probably protected during uptake and processing of the native nucleosome particle as a whole. Therefore, herein we tested 145 overlapping peptides spanning all four core histones in the nucleosome. We localized three regions in core histones, one in H2B at amino acid position 10-33 (H2B(10-33)), and two in H4, at position 16-39 (H4(16-39)) and position 71-94 (H4(71-94)), that contained the peptide epitopes recognized by the pathogenic autoantibody-inducing Th cells of lupus. The peptide autoepitopes also triggered the pathogenic Th cells of (SWR x NZB)F1 lupus mice in vivo to induce the development of severe lupus nephritis. The nucleosomal autoepitopes stimulated the production of Th1-type cytokines, consistent with immunoglobulin IgG2a, IgG2b, and IgG3 being the isotypes of nephritogenic autoantibodies induced in the lupus mice. Interestingly, the Th cell epitopes overlapped with regions in histones that contain B cell epitopes targeted by autoantibodies, as well as the sites where histones contact with DNA in the nucleosome. Identification of the disease-relevant autoepitopes in nucleosomes will help in understanding how the pathogenic Th cells of spontaneous systemic lupus erythematosus emerge, and potentially lead to the development of peptide-based tolerogenic therapy for this major autoimmune disease.

Amino Acid Sequence↗
PubMed1996

Differences in mutagenesis during minus strand, plus strand and strand transfer (recombination) synthesis of the HIV-1 gene in vitro.

We have developed an HIV nef-Escherichia coli lacZ fusion system in vitro that allows the detection of low frequency mutations, including frameshifts, deletions and insertions. A portion of the nef gene that encompasses a hypervariable region was fused in-frame with a downstream lacZalpha peptide coding region. The resulting lacZalpha peptide fusion protein remained functional. Any frameshift mutations in the nef insert would put the downstream lacZ alpha peptide gene out of frame, eliminating alpha complementation. With this system we compared the error rates of frameshift mutations that arise during DNA-directed and RNA-directed DNA synthesis. Results showed that DNA-directed and RNA-directed DNA synthesis did not contribute equally to the generation of mutations. DNA-directed DNA synthesis generated frameshift mutations at a frequency approximately 10-fold higher than those arising from RNA-directed DNA synthesis. RNA-directed DNA synthesis in the presence of acceptor templates showed an increase in mutation rate and differences in the mutation spectrum. The enhancement of mutation rate was caused by the appearance of mutations at three new locations that correlated with likely recombination sites. Results indicate that recombination is another source of mutations during viral replication.

Base Sequence↗
PubMed1996

Regulation of ornithine decarboxylase gene expression by the Wilms' tumor suppressor WT1.

The importance of ornithine decarboxylase (ODC) to cell proliferation is underscored by the complex array of cell-specific mechanisms invoked to regulate its synthesis and activity. Misregulation of ODC has severe negative consequences on normal cell function, including the acquisition of tumorigenic growth properties by cells overexpressing ODC. We hypothesize that ODC gene expression is a candidate target for the anti-proliferative function of certain tumor suppressors. Here we show that the Wilms' tumor suppressor WT1 binds to multiple sites within the human ODC promoter, as determined by DNase I protection and methylation interference assays. The expression of WT1 in transfected HCT 116, NIH/3T3 and HepG2 cells represses activity of the ODC promoter controlling expression of a luciferase reporter gene. In contrast WT1 expression enhances ODC promoter activity in SV40-transfected HepG2 cells. Both the extent of modulation of ODC gene expression and the mediating WT1 binding elements are cell specific. Constructs expressing WT1 deletion mutants implicate two regions required for repressor function, as well as an intrinsic activation domain. Understanding the regulation of ODC gene expression by WT1 may provide valuable insights into the roles of both WT1 and ODC in development and tumorigenesis.

3T3 Cells↗
PubMed1996

In serum-free culture thyroid hormones can induce full expression of chondrocyte hypertrophy leading to matrix calcification.

A serum-free culture system has been developed to examine the biologic factors involved in the regulation of cellular maturation, extracellular matrix assembly, and calcification in the physis of the bovine fetal growth plate. Isolated prehypertrophic chondrocytes in high density culture undergo a process of cellular maturation whereby full expression of the hypertrophic phenotype is characterized first by type X collagen synthesis followed by matrix calcification. Using this culture system, we compared the capacity of tri-iodothyronine (T3) with thyroxine (T4) to stimulate expression of the hypertrophic phenotype and matrix calcification in three (B, C, and D) maturationally distinct prehypertrophic chondrocyte subpopulations. The B cell subpopulation was the most mature followed by C and D subpopulations in order of decreasing maturity. Comparisons were made to cultures in fetal calf serum (FCS). In Dulbecco's modified Eagle's medium supplemented with insulin, transferrin, and selenium, both hormones (T3/T4) separately induced, in a dose-dependent manner, chondrocyte maturation to the hypertrophic phenotype characterized by increased type X collagen mRNA and induction of protein synthesis of this molecule, together with increased alkaline phosphatase activity, and eventually calcification of the extracellular matrix. Such cellular maturation to the hypertrophic phenotype was not observed in the absence of T3 or T4 with subpopulations C and D. Only in older fetuses (> 210 days) was this observed and then only in the B subpopulation. Furthermore, T3 was at least 50-fold more potent than T4. The effects of T3 were most pronounced with the most immature cells (subpopulations C and D) where, in the case of the subpopulation C, in contrast to 0.5 nM T3 50 nM T4 was unable to induce expression of the hypertrophic phenotype. Alkaline phosphatase activity was also increased in the C cell subpopulation treated with 1 nM T3 (35.5 U/micrograms of DNA) over that supplemented with 50 nM T4 (7.8 U/micrograms of DNA). Furthermore, matrix calcification, measured by the incorporation of 45Ca2+ into the cell layer, always occurred earlier in cells cultured with T3 compared with T4. Cellular maturation to the hypertrophic phenotype was not accompanied by significant changes in DNA content; this ordinarily increases during culture in the presence of serum. Compared with cells cultured in the presence of serum, either thyroid hormone more potently induced cellular maturation. This study demonstrates that the most immature chondrocytes at the prehypertrophic stage are direct targets for T3 and T4 and, to a much a lesser degree, that either hormone is able to induce full chondrocyte hypertrophy from an early maturational stage leading to matrix calcification. But T3 is much more potent than T4. These studies also offer a new serum-free chemically defined medium containing T3 or T4 for the culture of defined prehypertrophic chondrocytes that supports matrix assembly, hypertrophic expression, followed by matrix calcification.

Animals↗
PubMed1996

Potential roles of gene expression change in adult rat spinal motoneurons following axonal injury: a comparison among c-jun, off-affinity nerve growth factor receptor (LNGFR), and nitric oxide synthase (NOS).

The present study investigates expression of nitric oxide synthase (NOS), immediate early genes (IEGs, c-jun, and c-fos), and low-affinity nerve growth factor receptor (LNGFR) in adult rat spinal motoneurons in response to three conditions of axonal injury: distal axotomy, root avulsion, and root avulsion followed by a peripheral nerve (PN) graft implantation. Expression of c-jun and LNGFR were predominately observed in motoneurons of the distal axotomized segment where most motoneurons survived. In contrast, expression of NOS was exclusively found in motoneurons of the rootavulsed segment where most motoneurons died. c-fos was not expressed in motoneurons following either distal axotomy or root avulsion. In animals with PN graft implantation, a double fluorescent labeling technique was used to evaluate motoneuron regeneration. Expression of NOS was completely inhibited in all motoneurons that regenerated into the PN graft, but was not inhibited in those that did not regenerate. Moreover, regenerated motoneurons expressed LNGFR and c-jun while the nonregenerated motoneurons expressed NOS. Results of the present study have shown that motoneurons undergo changes in expression of cellular molecules in response to the axonal injury. The expression of c-jun and LNGFR may be related to the regenerative process while expression of NOS is more likely involved in the degenerative process. The results also show that PN graft implantation can alter the expression of cellular molecules and reduce motoneuron death due to root avulsion. The survival-promoting effects of PN graft implantation (presumably the effects of neurotrophic factors) may be achieved by modifying certain cellular molecules such as NOS.

Animals↗
PubMed1996

Expression of the 25-kDa heat-shock protein (HSP27) correlates with resistance to the toxicity of cadmium chloride, mercuric chloride, cis-platinum(II)-diammine dichloride, or sodium arsenite in mouse embryonic stem cells transfected with sense or antisense HSP27 cDNA.

Embryonic stem (ES) cells were transfected with the protein-coding region of rat HSP27 cDNA placed in sense or antisense orientation in vector pcDNA3 under the control of the constitutive cytomegalovirus (CMV) promoter. Compared with nontransfected ES cells, five sense HSP27 cDNA-transfected ES cell clones displayed up to fourfold increases in expression of HSP27 mRNA and up to sixfold increases in expression of HSP27 protein, whereas four antisense HSP27 cDNA-transfected ES cell lines exhibited synthesis of antisense HSP27 RNA and a 50-85% decrease in HSP27 protein expression. Compared to the parental ES cell lines or ES cells transfected with the vector lacking any HSP27 sequence, all ES cell lines overexpressing HSP27 were resistant to killing by cadmium chloride (CdCl2), mercuric chloride (HgCl2), cis-platinum(II)-diammine dichloride (cDDP), sodium arsenite (NaAsO2), and heat while ES cell lines expressing reduced HSP27 were more sensitive to metal toxicity and heat. The relative toxicities of the tested metals to ES cells were cDDP > NaAsO2 > HgCl2 > CdCl2. Protection of ES cells against metal or heat toxicity was positively correlated with the level of HSP27. These data confirm in ES cells previous reports of the ability of HSP27 to protect other cell types against heat and demonstrate that HSP27 protects mammalian cells against the toxic effects of diverse metals.

Animals↗
PubMed1996

Effects of hypothyroidism on the vulnerability to ventricular fibrillation in dogs: a comparative study with amiodarone.

It has been shown that thyroid hormone has a significant effect on the heart and that suppression of thyroid function may contribute to the antiarrhythmic effect of amiodarone. The study was aimed at investigating the effects of hypothyroidism, compared with those of amiodarone, on vulnerability to ventricular fibrillation in dogs. In this study, 25 adult dogs were randomly divided into three groups: a hypothyroid group following total thyroidectomy (n = 9), an amiodarone group (n = 8, 400 mg per day, 4 weeks), and a control group (n = 8). Both amiodarone and control groups were subjected to sham surgery. Five to 8 weeks after surgery, ventricular fibrillation threshold and other electrophysiological parameters were determined. Right ventricular effective refractory period, monophasic action potential duration, and ventricular fibrillation threshold were significantly increased in both the thyroidectomized and amiodarone-treated animals. There was no significant change in monophasic action potential duration dispersion. The incidence of ventricular fibrillation during ischemia and reperfusion was significantly reduced in both treated groups compared with the sham-operated euthyroid controls. These observations suggest that hypothyroidism has a significant antifibrillatory effect in dogs. Homogeneous prolongation of repolarization and refractoriness may contribute to the antifibrillatory action of hypothyroidism.

Action Potentials↗