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Biomedical subjects

Q Guo

Publications and source records attributed to Q Guo.

At least 199 records · Page 11Linked to original sources
PubMed1990

Drug binding by branched DNA: selective interaction of the dye stains-all with an immobile junction.

The thiacarbocyanine dye Stains-All (4,5:4',5'-dibenzo-3,3'-diethyl-9-methylthiacarbocyanine bromide) is one of a large number of cyanine dyes introduced as photosensitizers in the photographic industry. Stains-All is used in histology as a stain for nucleic acids, proteins, polysaccharides, and lipids. We report here that the dye colors branched DNA molecules differently from linear duplexes and use footprinting experiments with methidiumpropyl-EDTA-Fe(II) [MPE.Fe(II)] and bis(o-phenanthroline)copper(I) [(O-P)2Cu(I)] to show that Stains-All interacts preferentially at the branch point of a four-arm DNA structure. A titration experiment allows us to estimate that the interaction of the dye with the branch has a dissociation constant below 45 nM, tighter than that of ethidium or methidium by over 2 orders of magnitude. Probing the interaction with the purine-specific reagent diethyl pyrocarbonate (DEPC) implies that the dye induces an asymmetric distortion near the branch in the major grooves of double helix in the junction.

Absorption↗
PubMed1990

Drug binding by branched DNA: selective interaction of tetrapyridyl porphyrins with an immobile junction.

The differential binding of a number of water-soluble cationic porphyrins to a branched DNA molecule is reported. Tetrakis(4-N-methylpyridiniumyl)porphine (H2TMpyP-4) interacts near the branch point with an immobile DNA junction formed from four 16-mer strands. Its Cu(II) and Ni(II) derivatives show stronger preferential binding in the neighborhood of the branch point. Axially liganded derivatives, Zn, Co, and Mn, also interact near this branch point, but in a different way. We use the reagents methidiumpropyl-EDTA.Fe(II) [MPE.Fe(II)] and bis(o-phenanthroline)copper(I) [(OP)2Cu(I)] to cleave complexes of DNA duplex controls and the junction with these porphyrins. The resulting cleavage patterns are consistent with previous evidence that the branch point provides a strong site for intercalative binding agents, which is not available in unbranched duplexes of identical sequence. The preferential scission by (OP)2Cu(I) in the presence of Ni and Cu porphyrins near the branch point exceeds that seen for any agents we have studied. This hyperreactivity is not seen in the case of porphyrins with axial ligands, ZnTMpyP-4, CoTMpyP-4, and MnTMpyP-4, although these also interact near the branch point. The Zn derivative tends to protect sites close to the branch point from cutting, while the Co and Mn porphyrins moderately enhance cleavage of sites in this region.

Base Sequence↗
PubMed1990

Drug binding by branched DNA molecules: analysis by chemical footprinting of intercalation into an immobile junction.

Branched DNA structures interact with drugs differently from unbranched control duplexes of similar sequence. A specific interaction between the reagent (methidiumpropyl-EDTA).Fe(II) [MPE.Fe(II)] and a branched DNA molecule formed from 16-mer oligonucleotide strands has been reported [Guo, Q., Seeman, N. C., & Kallenbach, N. R. (1989) Biochemistry 28, 2355-2359]. The structure of the branched molecule is thought to be made up of two double-helical stacking domains with an overall twofold symmetry across the branch site. The MPE-Fe(II) interaction occurs predominantly at or adjacent to the branch site and is eliminated by a second intercalator, propidium iodide. Further studies on the nature and properties of this site are presented here. Comparison of the patterns of scission of linear duplex and branched tetramer by EDTA.Fe(II), MPE.Fe(II), and Cu(I)-(o-phenanthroline)2 [(OP)2Cu(I)] provides a higher resolution picture of the site of enhanced binding. In particular, the sensitive footprinting afforded by (OP)2Cu(I) allows us to localize the major site of preferential interaction with propidium precisely to the branch point itself, with a roughly twofold symmetric pattern of cuts resulting. In detail, the differential pattern with respect to each duplex control is distinct for each arm of the junction. Excess propidium results in apparent reversal of the crossover isomer of the junction, indicating a possible additional avenue for the action of drugs in biological systems--effects on the products of recombination.

Base Sequence↗
PubMed1990

Investigation of blood flow dynamics by NMR angiography.

Gradient-echo sequences with different amount of flow velocity compensation have been studied using cardiac gating in cine mode MR angiography. The initial results on the leg of a healthy volunteer indicate that the circulatory dynamics may be studied qualitatively by means of these flow-sensitive angiograms.

Blood Flow Velocity↗
PubMed1990

Treatment of experimental Coxsackie B-3 viral myocarditis with Astragalus membranaceus in mice.

A murine model system for observing the effect of Astragalus Membranaceus (AM) on experimental myocarditis caused by Coxsackie B-3 virus (CB3V) was developed in 4-week-old male BALB/C mice. Gross, histopathologic and ultrastructural examinations of the infected-AM treated group showed that the severity and involved area of the myocardial lesions became milder and smaller than those in the infected-NS treated mice. The total lesion area, and the total lesion area/total myocardial area examined (%) and virus titer in the former group were also smaller and lower than those in the latter group. The results suggest that AM is effective in the inhibition of Coxsackie B virus propagation and protection of myocardium in mouse myocarditis.

Animals↗
PubMed1989

DNase I cleavage of branched DNA molecules.

We report here a potentially useful signature of branched DNA structures. The base 5' to the branch and the five bases flanking the 3' side of the branch site are protected from cleavage by DNase I in both three- and four-arm branched DNA molecules. Our procedure is to measure the cleavage profile for each 5' -labeled strand in a control duplex and compare this with that of the same strand in a branched structure under conditions yielding less than one cut per strand. The resulting cleavage pattern in an immobile four-arm junction is roughly 2-fold symmetric, consistent with the pattern of Fe(II).EDTA-induced cleavage that has been observed previously. In the three-arm junction, the DNase I cleavage pattern is asymmetric, indicating lack of 3-fold symmetry. A variable pattern of protection occurs to the 5' side of the branch in some strands only for both three- and four-arm junctions, extending 2-4 residues 5' to the branch.

Base Sequence↗
PubMed1989

Site-specific interaction of intercalating drugs with a branched DNA molecule.

The interaction of a stable branched DNA molecule with an intercalative drug is probed by hydroxyl radical scission. Methidiumpropyl-EDTA.Fe(II) [MPE.Fe(II)], consisting of an intercalating ring system tethered to EDTA.Fe(II), produces the hydroxyl radicals by means of a Fenton reaction. The cleavage patterns of each labeled strand in a branched tetramer of four 16-mers are compared with those of the same strands in unbranched duplex controls. Strong differences between the profiles corresponding to scission of branched and duplex DNA molecules are seen in each of the strands at low MPE/DNA ratios. A specific site in the branched structure interacts preferentially with the drug, while other regions of the molecule are protected from cleavage. At 4 degrees C, cutting at strand positions demarcating the site of enhanced affinity is observed to be 60-100% more efficient than at the corresponding sequence positions in the control duplex DNA molecules; the degree of protection is comparable. Cleavage in the vicinity of the preferred site occurs at residues flanking the branch point. The reactive Fe(II) group appears to be centered within two residues of the branch point, and the site of preferential intercalation may be between the two base pairs abutting the branch point in one of the two helical domains. The pattern of preferential cutting at this site is eliminated in the presence of excess propidium diiodide, another intercalative drug.

DNA↗
PubMed1989

[Effect of dexamethasone on Coxsackie B-2 virus-infected rat beating heart cells in culture].

The effects of dexamethasone (Dex) on cultured rat beating heart cells infected with 100 TCID-50 Coxsackie virus B-2 (CB2V) were observed. The beating % began to decrease in the infected group 2 or 3 d post-challenge. Meanwhile, the cytopathic effect (CPE) appeared rapidly from 1+ to 3+. In the infected and Dex-treated group 1 h after inoculation, the beating % and CPE in the whole flask were significantly higher and less, respectively, than that in the group infected (P less than 0.05) at the same intervals. At 5 d after challenge, the beating % in the whole flask was significantly higher than that in the infected group. The cardiac enzyme-aspartate aminotransferase (AST) in the infected group was higher than that in the infected and Dex-treated group (P less than 0.01) through 3-5 d post-challenge. Moreover, the AST levels in these 2 groups were also higher than that in the uninfected group, Dex control group at the same intervals (P less than 0.01). Ultrastructural findings were parallel to the results of CPE through 1-5 d post-challenge in these 4 groups. It is suggested that the protective effect of Dex on cultured beating heart cells infected with CB2V occurred in the early stages after infection. It is surmised that steroids can probably save the lives of patients with severe myocarditis if the conventional therapy for protecting the myocardium and improving immunity were administered together.

Animals↗
PubMed1989

[Treatment of ulcerative colitis by traditional Chinese medicine and dynamic study of immune functions].

The effect of the traditional Chinese medicinal herbs enema and enteric-coated capsules in the treatment of ulcerative colitis (UC) were compared in 260 cases. The immune complexes and the dynamic change of autoantibodies were monitored in 28 out of the 260 cases before and after treatment. The following results were observed. (1) There was no significant difference in the total effective rate between the enema group and the oral capsule group (93.3% and 87.5% respectively), but the recovery rates of purulent hemafecia, mucusfecia and erosion accompanying colitis, etc. in the former group were higher than those in the latter (P less than 0.01). (2) The circulating immune complexes were found 43 times above the normal range in 17 cases with positive rate 60.7%, and tended to decrease as the condition became better after treatment. Antinuclear antibodies were determined by the indirect fluorescent immune method and the indirect enzyme labelling method and the positive rates were 53.6% and 64.7% respectively, both being much higher than those in the controls (P less than 0.01).

Adult↗
PubMed1989

[Cytotoxic effects of changrolin, lidocaine and amiodarone on ultrastructure of cultured rat beating cardiac myocytes].

Ultrastructural and morphological alterations of cultured rat beating cardiac myocytes treated with changrolin (CRL), lidocaine (Lid), and amiodarone (Ami) were studied. After the cultures were treated with CRL 100 micrograms/ml for 24 h, the beating of the myocytes stopped, the configuration and fine structure were destroyed, while the nuclei showed pyknotic deformation and reduced in size. The membrane and structures of mitochondria were disrupted and myofibrils fragmented and disrupted. In addition, a lot of vacuoles with characteristic dense particles were found in the cytoplasm. Similar alterations were seen when Lid 1000 micrograms/ml and Ami 50 micrograms/ml were added to the cultures. Normal beating networks of myocytes were examined under inverted microscopy after the cultured cells were treated with CRL 25 micrograms/ml, Lid 250 micrograms/ml or Ami 6.25 micrograms/ml. The ultrastructure of some regions of the myocytes showed very slight damage. The results indicated that the dosage of CRL and Lid generally used in anti-arrhythmic therapy basically exerted no harm to myocytes. However, caution should be taken when Ami was given intravenously, since its effective serum concentration was close to the dosage which could cause slight damage to the ultrastructure of cultured cells.

Amiodarone↗
PubMed1987

[Expression of the surface antigen in human gastric cancer cells and the relation to cell cycles--correlated analysis with flow cytometry].

Expression of tumor-associated antigen in different gastric cancer cell lines and different phases of cell cycle was studied cytochemically. The antigen was recognized by the monoclonal antibody (McAb) PC1 against gastric cancer cells. By using the McAb PC1 as first antibody, the indirect immunofluorescence stain and the peroxidase-anti-peroxidase (PAP) stain were done on the gastric cancer cell lines (MGC 803, SGC 7901 and BGC 823). It was shown that PC1 antigen was mainly expressed on the membrane of these cells and only a certain percentage of the cells gave the positive reaction with different intensities. It was obvious that the expression of PC1 antigen was heterogeneous in nature. The heterogeneity of the PC1 antigen expression in gastric cancer cells might be due to either various subpopulations in the cell lines or different phases of cell cycle. In order to go further into the question, we studied quantitatively the expression of PC1 antigen in gastric cancer cell lines (MGC 803, STC 7901 and BGC 823) and the relationship between the antigen expression and cell cycle by double fluorescence stain and two-dimensional flow cytometry. It was found that expression levels of PC1 antigen in these cell lines were in the following order: MGC 803 greater than SGC 7901 greater than BGC 823. The PC1 antigen predominantly expressed on G1 phase for MGC 803 and G1, G2-M phase for SGC 7901 respectively. And uniform low level of PC1 antigen expression was found for BGC 823 throughout the cell cycle. Therefore, the PC1 antigen expression is dependent on cell cycle in MGC 803 and SGC 7901 cell lines.

Antigens, Neoplasm↗
PubMedDate not supplied

Segmental transcatheter hepatic artery chemoembolization with iodized oil for hepatocellular carcinoma: antitumor effect and influence on normal tissue.

PURPOSE: Segmental transcatheter arterial embolization (TAE) with use of iodized oil mixed with an anticancer drug, followed by injection of gelatin sponge particles, was undertaken to evaluate its antitumor effect and its influence on normal tissue in patients with hepatocellular carcinoma (HCC). PATIENTS AND METHODS: Histologic findings in 12 patients who underwent hepatectomy after segmental TAE were compared with findings on plain radiographs and computed tomographic (CT) scans. Visualization of the portal veins contiguous to the tumor on radiographs and the pattern of iodized oil accumulation in the tumor and vicinity on CT scans after TAE were assessed. RESULTS: Complete necrosis of the tumor was achieved in 10 cases (83%), while complete necrosis of daughter nodules and capsular invasion was observed histologically in eight of these 10 patients (80%). The degree of tumor necrosis correlated with the pattern of iodized oil accumulation in and near the tumor. Partial necrosis of normal tissue near the tumor correlated with accumulation of iodized oil. CONCLUSION: Segmental TAE may be an excellent therapeutic method for treatment of HCC that is localized in one or a few segmental or subsegmental regions.

Aged↗