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Biomedical subjects

M Ding

Publications and source records attributed to M Ding.

At least 145 records · Page 8Linked to original sources
PubMed1997

The kinetics and regulation of the induction of type II nitric oxide synthase and nitric oxide in human fetal glial cell cultures.

Our understanding of how human glial cells are induced to produce nitric oxide and how the production is regulated may allow us to better design therapeutic strategies for treating inflammatory diseases of the central nervous system in man. Cultures of human fetal astrocytes and microglia produce inducible nitric oxide synthase and nitric oxide in response to Interferon gamma and Interleukin 1 beta. The mRNA for the enzyme was induced by 2 h and returned to baseline by day 2; the protein was expressed by 24 h and was present in cells for the entire 7 days of culture. Nitric oxide was not seen in cell supernatants until day 3 reaching a peak by day 7. Footprints of nitric oxide production such as NADPH diaphorase and nitrotyrosine staining as well as cGMP production were not significantly above background until day 3 to day 4, rising steadily until day 7. These data suggest that while the type II nitric oxide synthase is induced in human glial cells within 24 h of stimulation, it is not a functionally active enzyme until 48-72 h later, implying that there is a posttranslational regulation of the enzyme limiting nitric oxide production in these cells.

Brain↗
PubMed1997

Prevalence of hepatitis G virus in hepatitis C virus (HCV)-infected patients and in HCV-contaminated intravenous immunoglobulin products.

Hepatitis GB virus C/hepatitis G virus (HGV) is an RNA virus, which appears to be transmitted by parenteral exposure to contaminated blood and blood products, and may be associated with clinical hepatitis in humans. The prevalence of HGV was investigated in hepatitis C virus (HCV)-infected patients, and (HCV)-contaminated immune globulin intravenous products (IGIV), manufactured prior to the introduction of viral inactivation processing, and in recipients of these lots. Nested primers, specific for the 5' non-coding region of HGV, were designed and used to test 100 chronic HCV patients, 10 HCV RNA-positive IGIV lots and 36 of the recipients of these products. Hepatitis G virus specificity of the polymerase chain reaction (PCR) products was confirmed by sequencing a number of the amplified products and comparing the results with the published prototype sequence for HGV RNA. HGV RNA was detected in 23 of the 100 (23%) HCV-infected patients. The level of alanine aminotransferase (ALT) was lower in HCV-HGV coinfected patients than those with HCV infection alone. Hence, the severity of HCV infections is not influenced by HGV. Two of the 10 (20%) IGIV lots tested positive for HGV RNA; however, none of the serum samples from recipients of IGIV contained detectable HGV RNA although many were infected with HCV. This suggests that the transmission of HGV RNA from IGIV to the recipients is less efficient than that seen for HCV.

Adult↗
PubMed1997

Fractal timing of verbal transforms.

The paper deals with the timing pattern of perceptual change elicited by multiple repetitions of a syllable (the verbal-transformation effect). We show that the distribution of the dwell time, the time spent perceiving a given phonemic form before switching to another form, obeys a power law with an exponent valued between 1 and 2. This result is robust, occurring for meaningless syllables and for English words of different initial phonemic salience. Experiment 2 demonstrates that subjects are aware of the temporal dynamics of perceptual change. On the basis of these results, it is argued that within this paradigm the notion of a mean dwell time is ill defined and there is apparently no characteristic time scale for perceptual change.

Adolescent↗
PubMed1997

Age variations in the properties of human tibial trabecular bone.

We tested in compression specimens of human proximal tibial trabecular bone from 31 normal donors aged from 16 to 83 years and determined the mechanical properties, density and mineral and collagen content. Young's modulus and ultimate stress were highest between 40 and 50 years, whereas ultimate strain and failure energy showed maxima at younger ages. These age-related variations (except for failure energy) were non-linear. Tissue density and mineral concentration were constant throughout life, whereas apparent density (the amount of bone) varied with ultimate stress. Collagen density (the amount of collagen) varied with failure energy. Collagen concentration was maximal at younger ages but varied little with age. Our results suggest that the decrease in mechanical properties of trabecular bone such as Young's modulus and ultimate stress is mainly a consequence of the loss of trabecular bone substance, rather than a decrease in the quality of the substance itself. Linear regression analysis showed that collagen density was consistently the single best predictor of failure energy, and collagen concentration was the only predictor of ultimate strain.

Adolescent↗
PubMed1997

[Selective extraction of organotin from biological sample by supercritical fluid extraction].

The preliminary separation and concentration of organotin compounds from the matrix of biological samples is necessary, due to the very low content of organotin and the fat included in samples will largely interfere the analysis of organotins. In this work, supercritical fluid extraction (SFE) for the preliminary separation and concentration of organotin has been studied. Pure CO2 was used as mobile phase. The extractives can be used to supercritical fluid chromatographic (SFC) analysis of organotins. The model sample was prepared by adding diphenyltin (DPT) to soya powder. The effects of the pressure and temperature on SFE were investigated. A small amount of fat was also extracted together with organotins. Extract was injected into SFC system, in which a Kapcell Pak ODS column was used for separation of organotin and fat. The effect of pressure on the extraction percentage of DPT and fat was investigated at 40 degrees C. At lower pressure (10-15 MPa), a maximum extraction efficiency (63%) was attained for DPT, while the fat is extracted only 28.3%. The increase in temperature is advantageous for the selective extraction of DPT. However, the extraction efficiency of DPT decreased as the extraction temperature was increased. When a lower pressure (10 MPa) and a higher temperature (50 degrees C) were used, the organotin (DPT) was extracted up to a maximum (59.9%) within 30 min, while fat was extracted only 4.9%.

Chromatography, Supercritical Fluid↗
PubMed1997

[High performance liquid chromatographic analysis of organic acids in foods].

Because of the speed, selectivity, reliability, and simple sample preparation high performance liquid chromatography (HPLC) is the preferred method for simultaneous separation and determination of organic acids in foods. Ion exchange chromatography, ion exclusion chromtography and reversed phase HPLC are the most common chromatographic modes for analysis of organic acids in foods. The development and application of the three chromatographic modes are reviewed with 54 references. Ion exchange chromatography is most satisfactory for analysis of organic acids in foods, because organic acids are not interfered by other organic compounds, and inorganic anions in foods are determined simultaneously with organic acids.

Carboxylic Acids↗
PubMed1997

[High performance liquid chromatographic determination of reducing sugars in fruit juices with laser resonance Raman detection].

A liquid chromatographic method using semi-microcolumn separation combined with laser resonance Raman detection was developed for the determination of monosaccharides in fruit juices. Reducing sugars (galactose, glucose, mannose, arabinose, xylose and ribose) were derivatized with 4-dimethylaminoazobenzene-4'-sulfonyl (DABSYL) hydrazine. The derivatives of the monosaccharides exhibited strong resonance Raman scattering at 1136 cm(-1) when Ar+ laser emission line 488.0 nm was used. A semi-microcolumn Inertsil ODS-2 (250 mm x 1.5 mm i.d.) was used to the separation of the monosaccharide derivatives. The saccharides eluted within 25 min. However the excess DABSYL hydrazine was retained strongly with a retention time of about 60 min. In order to reduce the longer analysis time, the excess DABSYL hydrazine was removed by adding glyoxylic acid and then Na2CO3 aqueous solution when the derivation reaction was finished. As a result, the analysis time was reduced to about a half of its initial run time. The sensitivity of resonance Raman detection greater two orders of magnitude than refractive index (RI) detection. The detection limit of glucose is 10 ng (5.5 pmol). The high selectivity of Raman detection came from the facts that only the interested compounds in a given sample was derived with the Raman labeling reagent and that only the characteristic Raman bands of the derivatives were selectively detected. In this work, in spite of the coexisting large quantities of organic acids in fruit juice, the determined values of glucose agreed well with those obtained by RI detection without any derivatization procedure.

Beverages↗
PubMed1997

[Elution behaviors of cations on the serial columns combining a cation exchange column with an ion exclusion column].

The elution behaviors of cations (Na+, NH4+, K+, Ca2+ and Mg2+) on the serially connected cation exchange column (ICS-C25) and ion exclusion column (TSKgel OApak-A) were investigated. As shown in Figure 1, three peaks were observed for each cation when a mixture of tartaric acid (TA) and 2,6-pyridinedicarboxylic acid (PDC) was used as eluent. In ion exchange chromatography, the background conductivity (G0) of carboxylic acid (HR) eluent which is based on the dissociation of HR, can be expressed as follows: G0 = C0H lambdaH + C0R lambdaR (1) where C0H and C0R are the initial concentration, lambdaH and lambdaR are the equivalent concentration of H+ and R-, respectively. The concentration of eluent anion R- in mobile phase is reduced when the cations (M) are eluted from cation exchange column, because the R- forms some complexes with the cations. At this time, the conductivity (G) of the eluent will be G = CM lambdaM + (C0R - C'R) lambdaR + (C0H - CM) lambdaH (2) where CM is the concentration of cations, and C'R is a reduce of R-. The peaks on chromatogram results from a change in conductance (deltaG), and in the conditions of the paper. DeltaG = G - G0 = CM (lambdaM - lambdaH) - C'TA lambdaTA - C'PDC lambdaPDC (3). On the ion exclusion column, the eluent anion TA and PDC were retained at different capacity factor by an ion exclusion mechanism while the cations have not any retention. That is to say, the first peak of each cation is caused by elution of the cation and the depletion of eluent ion (H+) in the mobile phase. The second and third peaks have appeared corresponding to the depletion of TA and PDC anion in mobile phase, respectively.

English Abstract↗
PubMed1997

[The mutiplication of Sindbis virus and host BHK-21 cell apoptosis].

The process of apoptosis of BHK-21 cells induced by Sindbis virus (SbV) infection is reported here in details. The nuclear DNA cleavage can be first detected at 6 h after SbV infection, followed by the chromatin margination and condensation at 12 h and the DNA ladder can be detected at 24 h after infection. The details of apoptosis body's formation can be revealed by electron microscopy: First, the outer nuclear membrane protrudes where the condensed chromatin accumulates, then the chromatin get into the budding area with the inner nuclear membrane and separate from the nuclear. Progressively, we cloned the gene of SbV nonstructure protein 2 (nsP2) into the eukaryotic expression vector pMAMneo, and it can be expressed transiently. The DNA cleavages, the basic characteristics of apoptosis also can be detected in some cells. Together with the sequence analysis of nsP2 and the other former results, we conclude that the nsP2 may have direct relation with the SbV-induced apoptosis.

Animals↗
PubMed1996

Antisense blockade of inducible nitric oxide synthase in glial cells derived from adult SJL mice.

Increasing evidence suggests a correlation between cytokine-induced nitric oxide synthase (iNOS) and demyelination in Multiple sclerosis (MS). Inhibition of iNOS may therefore be a novel therapeutic approach in MS. To test an antisense oligodeoxynucleotide (ODN) knockdown strategy for inhibiting iNOS, we used lipopolysaccharide (LPS) together with gamma-interferon (IFN-gamma) to induce iNOS in adult mouse mixed glial cell cultures. We administered an iNOS-derived antisense phosphorothiorate oligodeoxynucleotide (S-ODN) to block the induction. The antisense ODN treatment resulted in significant inhibition of LPS and IFN-gamma induced iNOS mRNA and protein expression. It also inhibited nitric oxide (NO) and cyclic GMP (cGMP) production in a dose dependent fashion. Sense and random S-oligo had no effect in any of these studies. These data indicate the efficacy and specificity of the antisense oligodeoxynucleotide approach in inhibiting iNOS in glial cells.

Animals↗
PubMed1996

Characterization of a GTPase-activating protein that stimulates GTP hydrolysis by both ADP-ribosylation factor (ARF) and ARF-like proteins. Comparison to the ARD1 gap domain.

ADP-ribosylation factors (ARFs) are approximately20-kDa guanine nucleotide-binding proteins that participate in vesicular transport in the Golgi and other intracellular compartments and stimulate cholera toxin ADP-ribosyltransferase activity. Both GTP binding and hydrolysis are necessary for its physiological functions, although purified mammalian ARF lacks detectable GTPase activity. An ARF GTPase-activating protein (GAP) was purified >15,000-fold from rat spleen cytosol using (NH4)2SO4 precipitation and chromatography on Ultrogel AcA 34, DEAE-Sephacel, heparin-Sepharose, hydroxylapatite, and Ultrogel AcA 44. In fractions ( approximately100-kDa proteins) from Ultrogel AcA 44, a major protein band of approximately50 kDa on SDS-polyacrylamide gel electrophoresis correlated with GAP activity, consistent with it being a homodimer, thus differing from an ARF GAP purified from rat liver (Makler, V., Cukierman, E., Rotman, M., Admon, A., and Cassel, D. (1995) J. Biol. Chem. 270, 5232-5237). Purified spleen GAP accelerated hydrolysis of GTP bound to recombinant ARF1, ARF3, ARF5, and ARF6; no effect of NH2-terminal myristoylation was observed. ARF GAP also activated GTP hydrolysis by ARL1, which is 56% identical in amino acid sequence to ARF1, but lacks ARF activity. ARD1 is a 64-kDa guanine nucleotide-binding protein that contains an 18-kDa ARF domain at its carboxyl terminus; the ARF domain lacks the amino-terminal alpha-helix found in native ARF and hence is similar to the amino-terminal truncated mutant Delta13ARF1. Both the ARF domain of ARD1 and Delta13ARF1 were poor substrates for ARF GAP. The non-ARF1 domain of ARD1 enhanced the GTPase activity of the ARF domain, but not that of the ARF proteins and Delta13ARF1, i.e. it lacks the relatively broad substrate specificity exhibited by ARF GAP.

ADP-Ribosylation Factor 1↗
PubMed1996

High molecular weight microtubule-associated proteins contain O-linked-N-acetylglucosamine.

We have examined the post-translational modification of high molecular weight microtubule-associated proteins (MAPs) have shown that MAP1, MAP2, and MAP4 are glycosylated. The presence of carbohydrate residues on these proteins was indicated by labeling with biotin hydrazide following periodate oxidation, a specific and well established method for detecting saccharide moieties on proteins. Both MAP2 and MAP4 were also labeled in vitro by UDP-[3H]galactose in the presence of galactosyltransferase. Labeling by galactosyltransferase indicated that MAP2 and MAP4 contained terminal nonreducing GlcNAc residues, and they appeared to be O-linked to the proteins as shown by their sensitivity to beta-elimination. Chromatographic analysis showed that the GlcNAc residues were directly linked to the proteins as monosaccharides. Thus, we have added MAP2 and MAP4 to the list of intracellular O-GlcNAc-modified proteins, which includes other cytoskeletal proteins such as cytokeratins 8, 13, and 18 and neurofilament proteins NF-L and NF-M. We further characterized the O-GlcNAc modification of MAP2, and stoichiometric analysis indicated that nearly 10% of the MAP2 isolated from rat brain is modified by O-GlcNAc. However, this estimate is thought to reflect the minimal level of O-GlcNAc modification present on MAP2. We have also shown that both the O-GlcNAc and biotin hydrazide-reactive carbohydrate moieties are located on the projection domain of MAP2. Three O-GlcNAc-containing peaks were observed following fast protein liquid chromatography of a tryptic digest of MAP2, suggesting that multiple modification sites exist. The specific modification sites and functional significance of the O-GlcNAc glycosylation on the high Mr MAPs remain to be determined.

Acetylglucosamine↗
PubMed1996

Interleukin-1 involvement in the induction of leukemia inhibitory factor mRNA expression following axotomy of sympathetic ganglia.

Axotomy of superior cervical (sympathetic) ganglia (SCG) results in increased neuropeptide gene expression. In vitro, neuropeptide gene expression is similarly increased by exposure to the inflammatory cytokine interleukin-1 (IL-1). The effect of IL-1 in-vitro has been shown to be mediated by leukemia inhibitory factor (LIF). Since IL-1 regulates neuropeptide expression via LIF in vitro, we asked whether axotomy in vivo produces an increase in LIF mRNA, and whether that increase is regulated by IL-1 activity. Within 6 h following axotomy, ganglionic LIF mRNA is substantially elevated. Moreover, axotomy produces a rapid and transient increase in intraganglionic IL-1 beta mRNA, followed rapidly by an increase in ICAM-1 mRNA, thereby suggesting a local source of IL-1 activity. Pretreatment with the anti-inflammatory agent dexamethasone (DEX) reduces the increases of both IL-1 beta and LIF mRNAs following axotomy. mRNA encoding the specific signal-transducing Type I IL-1 receptor is present in unlesioned SCG in vivo, and increases following axotomy. Local application of IL-1 beta in vivo induces LIF mRNA even in uninjured ganglia, though not to the extent seen with axotomy. DEX treatment blocks this IL-1 beta-mediated increase in LIF mRNA. Therefore, DEX blocks the induction of LIF mRNA by inhibiting both the production of IL-1 and its action on LIF gene expression. Axotomy of a homozygous IL-1 receptor type I gene knockout mouse leads to a delayed and/or diminished induction of LIF mRNA in SCG, but does not prevent LIF mRNA expression. We conclude that while IL-1 is likely to be involved in the cascade of gene expression that follows axotomy, it alone is not sufficient to mediate the full induction of LIF mRNA by axotomy.

Animals↗
PubMed1996

Environmental radiation real-time monitoring system permanently installed near Qinshan Nuclear Power Plant.

An environmental radiation real-time monitoring system with high pressure ionization chamber was developed. It has been installed permanently in the vicinity of Qinshan Nuclear Power Plant, the first built in mainland China. The system consists of four basic components: environmental radiation monitors; data communication network; a data processing center; and a remote terminal computer situated in Hangzhou. It has provided five million readings of environmental radiation levels as of January 1993.

Air Pollutants, Radioactive↗