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Biomedical subjects

S Ding

Publications and source records attributed to S Ding.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Purification and properties of glutamate dehydrogenase from Pseudomonas pseudoalcaligenes].

Glutamate dehydrogenase was purified from the crude extract of Pseudomonas pseudoal-caligenes. The enzyme had a molecular weight of 290,000 and was composed of six subunits with identical molecular weight of 47,000. The enzyme was highly specific for NADP(H) and the substrates. The biochemical properties such as kinetic parameters and heat stability were also examined. The purified GDH showed considerable loss of activity upon freezing.

Glutamate Dehydrogenase↗
PubMed1998

[Heat strain for personnel wearing three levels of protective ensembles at moderate and heavy workloads].

The effects of individual protective ensembles and workloads on personnel's physiological heat strain were experienced by personnel in a hot environment (35 degrees C, 55% relative humidity). Six young males performed treadmill tests at both moderate (ML: 1.11 m/s, 5% grade) and heavy (HL: 1.34 m/s, 5% grade) workloads. They wore three levels of protective ensembles: protective mask only (PM), protective clothing only (PC), and full protective ensembles (FP). Tests lasted 60 min and 45 min, respectively, for ML and HL. Physiological measurements included heart rate (HR), rectal (Tre) and skin (Tsk) temperature, sweat rate (SR), and sweat evaporative rate (ER). Differences between the ensembles and the workloads were significant for HR responses. The increase rate in Tre and Tsk, and SR, ER were significantly reduced from PM and PC to FP condition during ML and Hl tests. The sweat evaporation restriction of ensembles and the increase of heat production from exercise are the main factors of enhancing the heat strain.

Adult↗
PubMed1998

High-resolution in vivo measurements of transverse relaxation times in rats at 7 Tesla.

A multi-echo imaging sequence suitable for high-resolution and accurate in vivo transverse relaxation time (T2) mapping has been implemented. The sequence was tested on phantoms and was used to measure T2 values in vivo in the rat brain, muscle, and fat at 7 T. Brain T2 maps are shown and regional variations in brain T2 are reported (41.8 ms in cortex, 47.9 ms in hippocampus). Results are compared to literature values obtained at lower field in vivo as well as high-field T2 measurements on excised rat tissues. The reported T2 values are generally smaller compared to lower-field-strength literature values. A discussion of the possible causes of these field effects on T2 is included (dipolar interaction, fast chemical exchange, and diffusion in susceptibility gradients).

Adipose Tissue↗
PubMed1998

Improved coverage in dynamic contrast-enhanced cardiac MRI using interleaved gradient-echo EPI.

An interleaved gradient-echo echo-planar imaging (IGEPI) sequence was modified for and applied to dynamic contrast-enhanced imaging of the heart. Using IGEPI, images with 3.0 x 3.9 mm nominal in-plane resolution are acquired in 100 ms, enabling eight slices per heartbeat for a heart rate of 60 beats/min. The acquisition speed and use of saturation prepulses allows acquisition of short- and long-axis images during the same contrast bolus. IGEPI maintains the acquisition characteristics required for performing a quantitative first-pass perfusion analysis as well as providing improved coverage compared with conventional fast gradient echo.

Contrast Media↗
PubMed1998

Multiple-quantum MAS NMR spectroscopy of spin-3/2 quadrupolar spin systems using shaped pulses.

An investigation of the effect of shaping the pulses in multiple-quantum magic-angle nuclear magnetic resonance experiments was carried out on polycrystalline samples containing spin-32 quadrupolar nuclear spins. Both theoretical analysis and numerical simulations show that there exist types of shaped pulses that are more advantageous than the usual rectangular pulses in exciting multiple-quantum coherences and converting these into single-quantum coherences or zero-quantum coherences (in z-filtering cases). The sensitivities can be enhanced without loss of resolution or increasing the RF offset dependences. Moreover, properly shaped pulses can moderate the requirements on the RF power and sample spinning speeds. Especially important for application purposes is the finding that lattice site quantification can also be improved by the use of certain shaped pulses.

Magnetic Resonance Spectroscopy↗
PubMed1998

Potassium tetracyanoplatinate (II) trihydrate (K2Pt(CN)4 x 3H2O) studied by high resolution solid state 13C MAS NMR.

Prudent analysis of the solid state 13C MAS NMR spectra of polycrystalline K2Pt(CN)4 x 3H2O (KTCP)- reveals that in crystals of this compound there are two types of carbon nuclei with slightly different 13C chemical shift tensors, contrary to what is found for the solution NMR spectrum and previous static powder NMR studies on this compound and the high resolution solid state NMR studies on other similar compounds. The 13C MAS spectra measured at different rotor spinning speeds are satisfactorily simulated though the use of a newly developed computer program based on a novel density matrix formulation. The present method is eminently successful even though the spectra are rather complicated because of (1) the relatively large anisotropies of the chemical shift tensors; (2) the high-order dipolar interactions between 13C and 14N nuclei because of the strong quadrupolar coupling constants of 14N nuclei; and (3) the indirect J-coupling between the 13C and 195Pt. The principal elements as well as their orientations of the two 13C chemical shift tensors are evaluated from the spectral simulations.

Carbon Isotopes↗
PubMed1998

p53 mutation is a poor prognostic indicator for survival in patients with hepatocellular carcinoma undergoing surgical tumour ablation.

Forty-two patients with hepatocellular carcinoma (HCC) were resected and their tumours were analysed for p53 mutations by GC-clamped denaturing gradient gel electrophoresis (DGGE), single-strand conformation polymorphism (SSCP) and gene sequencing. All the exons have been analysed in this study. Eight of 12 HCCs with cirrhosis due to viral hepatitis and the two patients with sarcomatoid changes displayed p53 mutations. In contrast, no mutation was observed in the fibrolamellar variant (n = 9), non-cirrhotics (n = 13) and alcoholic cirrhosis (n = 6). The mutations observed were in exons 5-8. Two mutations were observed in codons 136 and 213 as well as a T insertion between residues 156 and 157 (exon 5) and these are reported for the first time in HCC. Likewise, the silent mutation polymorphism in codon 213 was noticed in 3 of the 42 patients. Survival analysis of these patients after surgery showed the mean and median survival in patients with wild-type p53 to be 60 and 43 months respectively. In the group with p53 mutations, the mean and median survival was 15 and 12 months. The difference was statistically significant (P= 0.003).

Adolescent↗
PubMed1998

[Mechanism of IL-6 secretion in bone marrow cells from multiple myeloma patients].

OBJECTIVE: To explore the mechanism of interleukin-6(IL-6) secretion in bone marrow cells from patients with multiple myeloma(MM). METHODS: Expression of IL-6 in bone marrow mononuclear cells(BMMNC) from MM patients(n = 16) and controls(n = 19) was detected by using double labelled immunofluorescence. RESULTS: In MM group, the positive rates of IL-6 expression were 15.4% +/- 6.5% in BMMNC, 7.9% +/- 2.9% in myeloma cells, and 4.5% +/- 1.2% in stromal cells, while in controls the positive rates were 4.6% +/- 2.3% in BMMNC, 2.6% +/- 1.1% in stromal cells and 0.7% +/- 0.1% in plasma cells, respectively. The positive rates in MM group were all significantly higher than those in controls(P < 0.001). The cytoplasmic IgG+ and vWF+ cells percentages in BMMNC were also significantly higher in MM group than those in controls. CONCLUSION: Elevated IL-6 in MM patients was secreted by both myeloma cells and stromal cells, and the mechanism of both autocrine and paracrine may be involved in pathogeneses of multiple myeloma.

Adult↗
PubMed1998

[Both myeloma cells and bone marrow stromal cells are involved in the overproduction of interleukin 6 in multiple myeloma].

OBJECTIVE: To investigate the mechanism of interleukin 6 (IL-6) overexpression in multiple myeloma(MM). METHODS: Human myeloma cells(KM3) and bone marrow stromal cells(BMSCs) were fixed by paraformaldehyde. KM3 cells and BMSCs (fixed and non-fixed) were co-cultured in 10%FCS-RPMI1640. IL-6 activity in the supernatant was determined by B9 cell proliferation test. RESULTS: Both non-fixed myeloma cells and BMSCs could automatically secret IL-6, while the fixed cells did not. Co-cultures of fixed one with non-fixed the other of either kind of the cells could significantly increase the IL-6 activity in the supernatants. The promoting effect on IL-6 production was greater in BMSCs from MM patients than that in BMSCs from normal controls. CONCLUSION: There exists dual mechanism of IL-6 overproduction in MM, i.e. both autocrine and paracrine of IL-6 are involved in the pathogenesis of MM.

Bone Marrow Cells↗
PubMed1998

[Establishment and biological characterization of a transplantable BALB/c mouse erythroblastic leukemia model].

OBJECTIVE: Biological characterization of a BALB/c mouse transplantable erythroblastic leukemia model EL9611. METHODS AND RESULTS: The original erythroblastic leukemia (EL) mouse was obtained by 7,12-DMBA induction. The spleen cell suspension from the original EL mouse was injected into the same inbred BALB/c strain mice. After successive transplantation for 20 generations, the incidence of EL was 100% without spontaneous remission. There was a linear relationship between the survival time of the EL mice and the number of leukemic cells inoculated. When 10(6) leukemic cells were inoculated intravenously, the EL mice survived 10.2 +/- 1.3 days. Invasion of leukemic cells involved mainly in the bone marrow, the spleen and the liver. There was no obvious infiltration of leukemic cells in lymph-nodes and thymus. In peripheral blood, there were a large number of leukemic cells and most of them were basophilic or polychromatophilic erythroblasts. At the advanced stage, the mice developed anemia and thrombocytopenia. The reaction of the leukemic cells for hemoglobin staining was positive or weakly positive. While the peroxydase reaction was negative, Thy-1 antigen and Fc-recepter were not presented. No virus-like particles was found in the cells under electron microscope. EL9611 leukemia model was sensitive to some antitumor drugs used in clinical therapy. CONCLUSION: The establishment of EL9611 leukemia model offered a useful tool for studying proliferation and differentiation of erythroid cells, as well as pathogenesis and experimental treatment of non-virus erythroid malignancy.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

[An algorithm for ECG data compression and its real-time realization with single chip computer].

ECG data compression has been greatly improved since 1960 s. Although the error of compression can be controlled accurately, the reported algorithm at present can not be processed in real-time with a microcomputer. In this paper an algorithm for ECG data compression is expounded which can be realized in real-time with a single chip computer. The algorithm has not only adjustable precision but also an average compression rate of 10.34, especially a pretty high compression ratio for frequent arrhythmic patients.

Algorithms↗
PubMed1997

High levels of recombinant CYP3A4 expression in Chinese hamster ovary cells are modulated by coexpressed human P450 reductase and hemin supplementation.

Expression of recombinant cytochrome P450s (P450s) in mammalian cells has been used as a powerful tool to study these enzymes. However, the activity of CYP3A4 expressed in several stable mammalian cell lines was much lower than native enzyme in human liver. The low level of recombinant CYP3A4 may have been due to the low copy number of the cDNA. In addition, the low activity is caused by the low level of P450 reductase in these cells. To achieve high levels of CYP3A4 expression, we employed gene amplification of the CYP3A4 cDNA in Chinese hamster ovary (CHO) cells followed by transfection of the P450 reductase cDNA. Using this strategy, we have obtained a cell line, designated D3A4, with high levels of recombinant CYP3A4. The content of spectrally active P450 was 14 pmol/mg total cellular protein. Hemin treatment increased the P450 content 2-fold. Upon coexpression of P450 reductase in DHR/3A4 cells, enzyme activity of CYP3A4 was stimulated 15-fold, despite a 40% decrease in spectrally active P450. Interestingly, the latter effect was not due to a decrease in CYP3A4 mRNA. Treatment of these cells with hemin, however, counteracted the P450 reductase-mediated decrease of spectrally active P450. These data demonstrate that P450 reductase has a strong influence on the levels of recombinant P450 holoenzyme, possibly by modulating the level of heme in CHO cells. Concomitantly our results show that the gene amplification strategy provides a powerful approach to obtain a high level of functional recombinant P450.

Animals↗
PubMed1997

Molecular cloning of a new unc-33-like cDNA from rat brain and its relation to paraneoplastic neurological syndromes.

Anti-CV2-autoantibodies from patients with paraneoplastic neurological syndromes were used to purify protein(s) related to this disease. A novel cDNA, c-22, was obtained by PCR with primers based on amino-acid sequence of peptides obtained from this protein and rat brain cDNA as template. The deduced amino-acid sequence of c-22 shows homology to the Unc-33 gene from C. elegans in which mutations lead to defects in neuritic outgrowth and axonal guidance and cause uncoordinated movements of the nematode. Several consensus sites for putative protein kinase C phosphorylation were found, suggesting that the c-22 gene product may be a phosphoprotein. Northern hybridizations show that the apparently unique 3.8-kb mRNA of c-22 is present in rat brain tissue and its expression is developmentally regulated: the levels of C-22 mRNA, detectable in brain at embryonic day 17 (E17), increase up to post-natal day 7 (P7) and decline rapidly to an almost undetectable level in adult.

Amino Acid Sequence↗
PubMed1997

Two novel subgenomic RNAs derived from RNA 3 of tomato aspermy cucumovirus.

Two abundant subgenomic RNAs, designated RNA 3B and RNA 5, were found to be associated with the V strain of tomato aspermy cucumovirus (V-TAV). Sequence determination showed that the 3'-terminal 323 nucleotides (nt) of RNA 3B was identical to RNA 5, whereas its 5'-terminal 163 nt was a direct repeat (one nt difference) of the 5'-half of RNA 5, and that both RNAs are completely homologous to the 3'-terminal untranslated region of TAV RNA 3. TAV RNAs 3B and 5 were also detected in the infection of a pseudorecombinant virus consisting of TAV RNA 3 and RNAs 1 and 2 from cucumber mosaic virus. Furthermore, only RNA 5, not RNA 3B, was detected in a TAV mutant in which one of the repeats was deleted from RNA 3. These genetic studies clearly show that both RNA species are derived from TAV RNA 3. However, in contrast to TAV RNAs 4 and 4A, which encode coat protein and 2b protein, respectively, RNAs 3B and 5 represent a novel class of subgenomic RNAs from TAV that do not function as mRNAs. Possible functional roles for such a class of viral subgenomic RNAs are discussed.

Base Sequence↗
PubMed1997

[Application of spectrophotometry to evaluation of the levels and the influence of chemotherapeutic drugs on ATP of malignant cell lines].

To evaluate the value of ATP spectrophotometry for malignant tumor in vitro chemosensitivity test, Hela and L929 cell lines, which were derived from human cervical carcinoma and mouse fibroma respectively, were investigated. The results showed that when the cellular numbers were > or = 2 x 10(5), the linearity between the ATP concentrations and the cellular numbers was observed, with all 2 cell types studied, and that when L929 cells were incubated with cis-platinum (1x, 2x, 5x x plasma peak concentration, PPC), a marked fall in ATP concentrations was observed and a clear dose-response curve was obtained, but no decrease of ATP concentrations was measured after incubation with adriamycin (1x, 2x, 5x x PPC). This study suggests that ATP spectrophotometry is a cheap, feasible method for studying the energy metabolism and the influence of chemotherapeutic drugs on ATP concentrations of malignant tumor.

Adenosine Triphosphate↗
PubMed1997

[A new medicinal plant Pterocapus indicus].

It has been 70 years since Ptercapus indicus Willd. was introduced into China. The red sap from its incision of the bark becomes a kind of red crystal after some hours of exposure to air, which is used as an astringent and against other diseases. Its physicochemical properties, elements and amino acids have been analysed. The structural analysis shows that the crystal is a macromolecular compound of tannic condensation and glucoside.

Drugs, Chinese Herbal↗