Biomedical subjects

M Ding

Publications and source records attributed to M Ding.

At least 109 records · Page 6Linked to original sources

PubMed1999

The role of hydroxyl radical as a messenger in the activation of nuclear transcription factor NF-kappaB.

Although it is generally believed that reactive oxygen species activate NF-kappaB, a primary oxidative stress-responsive transcription factor, it is unclear which one among these species causes NF-kappaB activation. Our hypothesis is that hydroxyl radical (*OH) functions as a messenger for the activation of NF-kappaB. Jurkat cells, macrophages and JB6 cells were used to test this hypothesis. Cr(VI), silica and ZnO were used as sources of *OH radicals. None of these *OH generating systems involves exogenous H2O2. Cr(VI) expressed enhanced activity in induction of NF-kappaB in Jurkat cells. This activation of NF-kappaB was decreased by a metal chelator, diethylene triaminepentaacetic acid or a H2O2 scavenger, catalase, but was increased by superoxide dismutase. Mn(II), which reacts with Cr(IV) to inhibit this metal ion-mediated *OH generation, decreased the NF-kappaB activation. Sodium formate, an *OH radical scavenger, also inhibited the NF-kappaB activation. Electron spin resonance measurements show that Cr(VI) was reduced by Jurket cells to Cr(IV) and Cr(V). During the reduction process, molecular oxygen was reduced to O2 and then to H2O2, which reacted with Cr(IV) and Cr(V) to generate *OH radical. The *OH generation correlated with the Cr(VI)-induced NF-kappaB activation. Similarly, silica caused NF-kappaB activation in macrophages via the *OH radical-mediated reaction. This radical was generated via metal mediated reaction from H2O2, which was generated by the reduction of molecular oxygen via O2- as an intermediate during the silica-stimulated 'respirable burst'. Silica particles did not cause *OH generation either in Jurket or in JB6 cells and thus did not cause any observable NF-kappaB activation in these cells. ZnO induced NF-kappaB activation in JB6 cells through the generation of *OH resulting from light irradiation of ZnO which was measured by electron spin resonance. The results thus show that *OH radical functions as a messenger for NF-kappaB activation. Antioxidants, which scavenge *OH radical or its precursors, inhibit NF-kappaB activation. Metal chelators, which make metal ions incapable of generating *OH from H2O2, inhibit activation of this transcription factor.

Animals↗

PubMed1999

Antioxidant properties of aspirin: characterization of the ability of aspirin to inhibit silica-induced lipid peroxidation, DNA damage, NF-kappaB activation, and TNF-alpha production.

Electron spin resonance (ESR) was used to investigate the reaction of aspirin toward reactive oxygen species, such as hydroxyl radicals (*OH), superoxide radicals (O2-) and H2O2. The Fenton reaction (Fe(II) + H2O2 ---> FE(III) + *OH + OR) was used as a source of *OH radicals. The results show that aspirin is an efficient *OH radical scavenger with a reaction rate constant of k = 3.6 x 10(10) M(-1) sec(-1), which is faster than several well established antioxidants, such as ascorbate, glutathione and cysteine. However, aspirin is not a good scavenger for O2- or H2O2. Through its antioxidant property, aspirin exhibited a protective effect against silica-induced lipid peroxidation and DNA strand breakage. Aspirin also inhibited the activation of nuclear transcription factor-kappaB induced by silica, lipopolysaccharide or the transition metal, Fe(II), as demonstrated by electrophoretic mobility shift assay. The results show that aspirin functions as an antioxidant via its ability to scavenge *OH radicals. This antioxidant property may explain some of its various physiological and pharmacological actions.

Animals↗

PubMed1999

Induction of TNFalpha in macrophages by vanadate is dependent on activation of transcription factor NF-kappaB and free radical reactions.

Vanadium-induced TNFalpha production is believed to play an important role in respiratory disease associated with air pollution and occupational exposure. While vanadium is able to induce TNFalpha in macrophages or airway epithelial cells, the underlying mechanism is not well defined. In the present study, mechanisms of vanadate-induced TNFalpha production were analyzed in the murine Raw264.7 cells. Vanadate induces a significant amount of TNFalpha at both the protein and mRNA levels, and the induction is vanadate dose-dependent. The mechanism analysis was focused on transcriptional regulation of TNFalpha gene by vanadate. Transient transfection studies show that the TNFalpha gene promoter was activated by vanadate and this activation was associated with an increase in DNA binding activity of the nuclear factor-kappaB (NF-kappaB). Mutation of the NF-kappaB binding site in the gene promoter led to a loss of the promoter responsiveness to vanadate, indicating requirement of NF-kappaB. This is supported by evidence that inhibition of NF-kappaB activation by SN50, a specific NF-kappaB inhibitor, resulted in a decrease in the TNFalpha production. A role of reactive oxygen species (ROS) was explored in vanadate activity. The result shows that vanadate-induced TNFalpha production is elevated by NADPH, which enhances vanadate-mediated generation of ROS, but is inhibited by an antioxidant, N-acetyl-L-cysteine (NAC). Modification of TNFalpha production is associated with an enhancement or a repression of NF-kappaB activity by NADPH or NAC, respectively. Taken together, these results indicate that: (a) activation of the TNFalpha gene promoter contributes to the vanadate-induced TNFalpha production; (b) NF-kappaB is required for the vanadate-induced promoter activity of TNFalpha gene; (c) free radical reactions are involved in the vanadate-induced TNFalpha production and NF-kappaB activation.

Animals↗

PubMed1999

Vanadate induces apoptosis in epidermal JB6 P+ cells via hydrogen peroxide-mediated reactions.

Apoptosis is a physiological mechanism for the control of DNA integrity in mammalian cells. Vanadium induces both DNA damage and apoptosis. It is suggested that vanadium-induced apoptosis serves to eliminate DNA-damaged cells. This study is designed to clarify a role of reactive oxygen species in the mechanism of apoptosis induced by vanadium. We established apoptosis model with murine epidermal JB6 P+ cells in the response to vanadium stimulation. Apoptosis was detected by a cell death ELISA assay and morphological analysis. The result shows that apoptosis induced by vanadate is dose-dependent, reaching its saturation level at a concentration of 100 microM vanadate. Vanadyl (IV) can also induce apoptosis albeit with lesser potency. A role of reactive oxygen species was analyzed by multiple reagents including specific scavengers of different reactive oxygen species. The result shows that vanadate-induced apoptosis is enhanced by NADPH, superoxide dismutase and sodium formate, but was inhibited by catalase and deferoxamine. Cells exposed to vanadium consume more molecular oxygen and at the same time, produce more H2O2 as measured by the change in fluorescence of scopoletin in the presence of horseradish peroxidase. This change in oxygen consumption and H2O2 production is enhanced by NADPH. Taken together, these results show that vanadate induces apoptosis in epidermal cells and H2O2 induced by vanadate plays a major role in this process.

Animals↗

PubMed1999

The impact of genetic removal of GFAP and/or vimentin on glutamine levels and transport of glucose and ascorbate in astrocytes.

The importance of the intermediate filament (IF) proteins glial fibrillary acidic protein (GFAP) and vimentin for astrocyte function was studied by investigating astrocytes prepared from GFAP-/- and/or vimentin-/- mice. The rate of glucose uptake through facilitative hexose transporters was not affected by depletion of GFAP or vimentin. Similarly, the absence of these IF proteins did not affect ascorbate uptake, under control or cyclic AMP-stimulated conditions, or ascorbate efflux through volume-sensitive organic anion channels. However, compared with wild-type astrocytes, glutamine concentrations were increased up to 200% in GFAP-/- astrocytes and up to 150% in GFAP+/- astrocytes and this increase was not dependent on the presence of vimentin. GFAP-/- astrocytes in culture still contain IFs (made of vimentin and nestin), whereas GFAP-/- vim-/- cultured astrocytes lack IFs. Thus, glutamine levels appear to correlate inversely with GFAP, rather than depend on the presence of IFs per se. Furthermore, the effect of GFAP is dose-dependent since the glutamine concentration in GFAP+/- astrocytes falls between those in wild-type and GFAP-/- astrocytes.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1999

Urothelial hinge as a highly specialized membrane: detergent-insolubility, urohingin association, and in vitro formation.

Urothelial surface is covered by numerous plaques (consisting of asymmetric unit membranes or AUM) that are interconnected by ordinary looking hinge membranes. We describe an improved method for purifying bovine urothelial plaques using 2% sarkosyl and 25 mM NaOH to remove contaminating membrane and peripheral proteins selectively. Highly purified plaques interconnected by intact hinge areas were obtained, indicating that the hinges are as detergent-insoluble as the plaques. These plaque/hinge preparations contained uroplakins, an as yet uncharacterized 18-kDa plaque-associated protein, plus an 85-kDa glycoprotein that is known to be hinge-associated in situ. Examination of the isolated, in vitro-resealed bovine AUM vesicles by quick-freeze deep-etch showed that each AUM particle consists of a 16-nm, luminally exposed "head" anchored to the lipid bilayer via a 9-mm transmembranous "tail", and that an AUM plaque can break forming several smaller plaques separated by newly formed particle-free, hinge-like areas. These data lend support to our recently proposed three-dimensional model of mouse urothelial plaques. In addition, our findings suggest that urothelial plaques are dynamic structures that can rearrange giving rise to new plaques with intervening hinges; that the entire urothelial apical surface (both plaque and hinge areas) is highly specialized; and that these two membrane domains may be equally important in fulfilling some of the urothelial functions.

Animals↗

PubMed1999

Vanadate-induced activation of activator protein-1: role of reactive oxygen species.

The present study was undertaken to test the hypothesis that the toxicity and carcinogenicity of vanadium might arise from elevation of reactive oxygen species leading to activation of the transcription factor activator protein-1 (AP-1). The AP-1 transactivation response has been implicated as causal in transformation responses to phorbol esters and growth factors. To investigate the possible activity of vanadium in the activation of AP-1, we treated mouse epidermal JB6 P+ cells stably transfected with an AP-1 luciferase reporter plasmid with various concentrations of vanadate. This resulted in concentration-dependent transactivation of AP-1. Superoxide dismutase (SOD) and catalase inhibited AP-1 activation induced by vanadate, indicating the involvement of superoxide anion radical (O2-*), hydroxyl radical (*OH) and/or H2O2 in the mechanism of vanadate-induced AP-1 activation. However, sodium formate, a specific *OH scavenger, did not alter vanadate-induced AP-1 activation, suggesting a minimal role for the *OH radical. NADPH enhanced AP-1 activation by increasing vanadate-mediated generation of O2-*. N-acetylcysteine, a thiol-containing antioxidant, decreased activation, further showing that vanadate-induced AP-1 activation involved redox reactions. Calphostin C, a specific inhibitor of protein kinase C (PKC), inhibited activation of AP-1, demonstrating that PKC is involved in the cell signal cascades leading to vanadate-induced AP-1 activation. Electron spin resonance (ESR) measurements show that JB6 P+ cells are able to reduce vanadate to generate vanadium(IV) in the presence of NADPH. Molecular oxygen was consumed during the vanadate reduction process to generate O2-* as measured by ESR spin trapping using 5,5-dimethyl-L-pyrroline N-oxide as the spin trapping agent. SOD inhibited the ESR spin adduct signal, further demonstrating the generation of O2-* in the cellular reduction of vanadate. These results provide support for a model in which vanadium, like other classes of tumor promoters, transactivates AP-1-dependent gene expression. In the case of vanadium, AP-1 transactivation is dependent on the generation of O2-* and H2O2, but not *OH.

Acetylcysteine↗

PubMed1999

Molecular analysis of microdissected de novo glioblastomas and paired astrocytic tumors.

Glioblastoma multiforme (GBM) often displays morphological heterogeneity in that low-grade (LG) area with well-differentiated cells are commonly found adjacent to high-grade (HG) area with poorly-differentiated cells. This heterogeneity may cause difficulty in obtaining representative tumor samples. Nevertheless, the genetic composition of these cells has only been occasionally examined. In the present study, we examined 29 de novo glioblastomas in which distinct LG and HG areas of sufficient volumes could be identified. These areas were microdissected from paraffin-embedded tissues and analyzed for genetic alterations: p53 mutations and immunohistochemistry; allelic losses at 17p13.1, 9p21, and 10q23-25; and amplification of the epidermal growth factor receptor (EGFR) gene and immunohistochemistry. We also examined 14 paired astrocytic tumors, in which a primary Grade II astrocytoma progressed over a period of time to a Grade III or Grade IV tumor. Our findings showed that the LG areas of the de novo glioblastomas exhibited numerous genetic aberrations, the proportion of which was increased in the HG areas. Genetic abnormalities seen in the LG areas were conserved in the HG areas suggesting that these morphologically different cellular subsets were derived from a common transformed clone. Also, the LG areas were genetically different from Grade II astrocytomas of the paired tumor group, in spite of their morphological similarity. In particular, the LG areas had more deletions on 10q23-25 (75% vs 20%, p = 0.04), but fewer p53 mutations (24% vs 71%, p = 0.003) and less p53 protein labeling (45% vs 79%, p = 0.04). These differences suggest that LG and HG areas in de novo glioblastoma are genetically closer to each other compared with paired low- and high-grade tumors that have progressed over time. Moreover, only a small proportion (17%) of our de novo glioblastomas exhibited EGFR amplification while a high proportion (62%) showed either p53 mutations or allelic loss of 17p13.1. We speculate that some de novo GBMs with copious LG areas may constitute a separate group with rapid progression from Grade II astrocytomas.

Adult↗

PubMed1999

Quantitative assessment of Parkinson's disease deficits.

OBJECTIVE: To quantitatively analyze the tremor and rigidity due to Parkinson's disease. METHODS: 38 patients with Parkinson's disease (PD) ranging in age from 45 to 72 years and 211 normal subjects aged from 16 to 76 years were investigated. The frequency and range of tremor, the muscle tone of the upper limbs in elbow were detected by a computerized video motion detecting system and a new invented apparatus which can detects skeletal muscle tone. RESULTS: For the PD patients, the frequency of resting tremors was detected in 4 to 6 per second. For extensor and flexor in the PD patients, the value of muscle tone was higher than that of normal subjects and the value of muscle tone in flexor was higher than that of extensor. The rigidity increased gradually with repeat passive movement. The curves of rigidity were shown on computer screen or printed out. The data of rigidity were compared with the M-A Scale. A patient who was suspected to suffer from PD above by the equipments and found the muscle tone was higher than normal. In another PD patient the rigidity was obvious at one side and the muscle tone in "normal side" was also high. These equipments were used to record changes of rigidity and tremor in one more PD patient taking with different drugs in order to see the drug effect. CONCLUSION: Quantitative methods are useful to analyse the motion disorders due to PD.

Aged↗

PubMed1999

[A preliminary report on two distinct tumor-suppressor regions on chromosome 1p36.2-p36.3 in human hepatocellular carcinomas].

OBJECTIVE: Both cytogenetic and molecular genetic analyses have unveiled non-random genomic alterations in the distal short arm of human chromosome 1 associated with a number of human malignancies including heptatocellular carcinoma (HCC). The aim of this investigation is to determine the precise region of deletion that may harbor the putative tumor suppressor genes in HCC. METHODS: For the study of the loss of heterozygosity (LOH), 38 cases of hepatitis B virus (HBV) associated HCC and their corresponding non-tumor liver tissues were detected with 43 microsatellite polymorphic markers particularly focusing on 1p. RESULTS: Twenty-eight of the 38 (74%) tumors showed LOH on at least one locus on 1p36.2-p36.3. Two distinct smallest common deleted regions (SCDRs) with different patterns of deletion were identified. The first SCDR is located on locus D1S2795 at 1p36.3, between loci D1S2145 and D1S2893. The second SCDR is located at 1p36.2, between loci D1S244 and D1S489. Both of the SCDRs have not been previously described in HCC. In addition, a region of possible homozygous deletion (HD) was also detected within the second SCDR between loci D1S1597 and D1S489 by comparative multiplex PCR. This is the first observation of a possible homozygous deletion on the distal short arm of chromosome 1 in HCC as well as in human tumors. CONCLUSIONS: The high-resolution deletion mapping of 1p36.2-p36.3 in HCC in this study confirmed the presence of two distinct regions of deletion. Our data strongly suggest the presence of at least two tumor suppressor regions on 1p36.2-p36.3 and play an important role in the pathogenesis of HBV associated HCC. These results also provide a basis for further studies directed at cloning potential tumor suppressor genes in these regions.

Carcinoma, Hepatocellular↗

PubMed1999

[HLA-DRB1 typing by PCR-sequence specific primers for paternity determination].

HLA-DRB1 typing by PCR-SSP technique was first used for paternity testing. The analysis of 42 paternity cases shows that this identification method is simple, fast and reliable and has high exclusion probability of paternity (66.3%). This method can also be applied to the study of transplantation, HLA associated disease and anthropogenesis.

Forensic Medicine↗

PubMed1999

[Simultaneous analysis of alkali metals and alkaline earth metals in Chinese herbal medicine by ion chromatography].

A simple and rapid method for the analysis of cations by using ion chromatography was developed. The results showed that the content ratio of Na+, NH4+, K+, Mg2+, Ca2+ in rhizoma chuanxiong and semen zizyphi spinosae are different. The detection limits of cations (S/N = 3) were 0.001-0.013 mg/L. The calibration curves of peak areas for all analytes were linear over two or three orders of magnitude with a regression coefficient (r2) of 0.9995-1.0000.

Chromatography↗

PubMed1999

[Investigating the phenomenon of total erythrocyte destruction during an in-vitro hemolysis test by roller pump].

This study sought to address the question, "will the phenomenon of 'total erythrocyte destruction' come about during a long time of in vitro hemolysis test by roller pump". One-day-old boving blood was employed in the test by Polystan pump(group A) and Cobe pump (group B). TMB method was used to measure the level of plasma-free hemoglobin. The samples of plasma-free hemoglobin were taken at the time before pumping and pumping for 4,6,8,10, 12,14 and 16 hours. The index of hemolysis was calculated according to Koller's formula. The results showed that the levels of plasma-free hemoglobin in the two groups both increased linearly during the puming of blood. The index of hemolysis was 0.2960 mg/L group A, and 0.3993 mg/L in group B; no statistically significant difference was noted between the two groups. These data indicated that no phenomenon of "total erythrocyte destruction" was observed in this hemolysis test by roller pump.

Erythrocytes↗

PubMed1999

[Determination of anions in recycle sodium formate from sodium hydrosulfite industry with single column ion chromatography].

The analysis of recycle materials from industrial waste water of sodium hydrosulfite production was made by single-column anion exchange chromatography. The recycle material was sodium formate (HCOONa) in which various anions, such as SO(3)2-, Cl-, thiosulfate, hydroxyethyl sulfonate (HOC2H4SO3-), hydroxyethyl thiosulfate (HOC2H4S2O3-), SO(4)2- and NO3- as impurities were existed simultaneously. Except hydroxyethyl sulfonate anion, all other ions can be separated by using anion exchange column Shim-pack IC-Al (4.6 mm i.d. x 100 mm) with the mixture of 1.8 mmol/L of phthalic acid and 1.35 mmol/L of Tri(hydroxymethyl) aminomethane as eluent. The flow rate of mobile phase is 1.0 mL/min. The injection volume was 20 microL. The column oven temperature was controlled at 40 degrees C. Hydroxyethyl sulfonate anion and SO(3)2- could not be separated at the above conditions, but they did not interfere the determination of HCOO-. The detection limits for HCOO-, SO(3)2-, NO3-, S2O(3)2-, HOC2H4S2O3-, Cl- and SO(4)2- were 1.0, 0.7, 1.4, 5.0, 0.7, 0.2 and 2.0 mg/L, respectively. The recoveries were between 96%-102%, and the relative standard deviations (RSD) were lower than 6.0% (n = 5) for all seven ions. This method is characterized by rapidity, sensitivity and simultaneous determination of several kinds of ions.

English Abstract↗

PubMed1999

[Direct determination of purine bases in tea by reversed-phase high performance liquid chromatography].

A reversed-phase high performance liquid chromatographic(RP-HPLC) method for the direct determination of three purine bases(theobromin, theophyllin and caffeine) in tea was developed. An ODS column with Zorbax SB-C18(4.6 mm i.d. x 250 mm, 5 microns) was employed. The aqueous solution of methanol containing 0.05% of acetic acid and 0.25% of N,N-dimethylformamide(DMF) was used as eluent with a flow rate of 0.8 mL/min. In this method, the aqueous extract of tea can be injected into HPLC directly, but in current HPLC methods for purine bases the coexisted tea polyphenols must be pre-separated. The three purine bases in tea were separated without any interference from the coexisted tea polyphenols. This method is simple (without any special sample pretreatment) and sensitive with detection limits (S/N = 3) of 0.7, 0.9 and 1.8 mg/L for theobromin, theophyllin and caffeine respectively. The linear range of the calibration curve of peak area for the three purine bases were from 6 mg/L to 1,000 mg/L with a correlation coefficient (r) of 0.998-0.999.

Caffeine↗

PubMed1999

[The morphological structure of classical swine fever virus and some characteristics of its multiplication].

Some characteristics of the multiplication of classical swine fever virus(CSFV) Thiverval strain were studied by means of the immunofluorescence technique. Under optimum culture conditions, the concentration of CSFV in the culture liquid multiplicated by MPK cells is ten times higher than by PK-15 cells. The half-life period of CSFV at 37 degrees C is 3 hour. The location of CSFV's replication in host cells is detected by the monoclonal antibodies of the structural protein E2 and the non-structural protein p120 of CSFV. Based on the above results, the ultrastructure of CSFV particles inside host cells was further studied using electron microscope and the changes of the ultrastructure of CSFV-infected cells are shown. The possible reasons for lower viral titre are also discussed in this paper.

Animals↗

PubMed1998

Altered taurine release following hypotonic stress in astrocytes from mice deficient for GFAP and vimentin.

Astrocytes maintain their volume in response to changes in osmotic pressure in their environment by an afflux/influx of ions and organic osmoequivalents. The initial swelling of an astrocyte transferred to a hypoosmotic medium is thus reversed within minutes. The mechanisms which trigger this process as well as the sensors for cell volume are largely unknown, however, the cytoskeleton appears to be involved. We have addressed the role of one component of the cytoskeleton, the intermediate filaments, in the maintenance of astrocytic cell volume. Astrocytes from wild type mice were compared with cells from mice deficient for either glial fibrillary acidic protein (GFAP-/-) or vimentin (vimentin-/-) and with astrocytes from mice deficient for both proteins (GFAP-/-vim-/-). Whereas GFAP-/- and vimentin-/- cultured or reactive astrocytes retain intermediate filaments, the GFAP-/-vim-/- astrocytes are completely devoid of these structures. The rate of efflux of the preloaded osmoequivalent 3H-taurine from primary and passaged cultures of astrocytes was monitored. A reduction of NaCl (25 mM) in the perfusion medium led to a 400-900% increase of 3H-taurine afflux in astrocytes from wild type mice. The stimulated efflux was not significantly affected in astrocytes from GFAP-/- or vimentin-/- mice. However, the efflux from astrocytes from GFAP-/-vim-/- mice was 25-46% lower than the wild type levels. The results strengthen the role of the cytoskeleton in astrocyte volume regulation and suggest an involvement of intermediate filaments in the process.

Animals↗

PubMed1998

Antisense knockdown of inducible nitric oxide synthase inhibits induction of experimental autoimmune encephalomyelitis in SJL/J mice.

We used an antisense oligodeoxynucleotide (ODN) complementary to inducible nitric oxide synthase (iNOS) to inhibit experimental autoimmune encephalomyelitis (EAE) in female SJL/J mice, an animal model for multiple sclerosis. The antisense ODN was administered intraventricularly to mice daily for 10 days beginning at the time of adoptive transfer of myelin basic protein-specific T lymphocytes. The antisense ODN treatment significantly reduced the clinical score of EAE and blocked iNOS mRNA and protein synthesis, as well as iNOS enzyme activity within the central nervous system. The levels of nitric oxide and cyclic guanosine monophosphate were also significantly reduced by the antisense ODN treatment. Neither sense nor random ODN affected clinical EAE or iNOS expression. Moreover, the protein and enzyme activity level of constitutive neuronal nitric oxide synthase was not affected by the antisense ODN. Thus, we have shown that the iNOS antisense ODN specifically blocked iNOS expression and ameliorated the induction of EAE.

Animals↗