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Biomedical subjects

Z Song

Publications and source records attributed to Z Song.

At least 145 records · Page 8Linked to original sources
PubMed1995

Mechanochemical study of NaDNA and NaDNA-netropsin fibers in ethanol-water and trifluoroethanol-water solutions.

Highly oriented calf-thymus NaDNA fibers, prepared by a wet-spinning method, were complexed with netropsin in ethanol-water and trifluoroethanol (TFE)-water solutions. The relative fiber length, L/L0, was measured at room temperature as a function of ethanol or TFE concentration to obtain information on the B-A conformational transition. The B-A transition point and transition cooperativity of the fibers were calculated. The binding of netropsin to NaDNA fibers was found to stabilize B form and to displace the B-A transition to higher ethanol concentration, as indicated by its elongational effect on the fiber bundles. An increased salt concentration was found to reduce netropsin binding. In netropsin-free ethanol solution, the dissociation of bound netropsin from the DNA fibers was observable. Pure B-NaDNA fibers were found to be more stable in TFE solution than in ethanol solution. This was interpreted as being due to a different steric factor and a larger polarity of TFE compared with ethanol, resulting in its smaller capacity to reduce the water activity and dielectric constant of the medium in the immediate vicinity of DNA fibers. Therefore, the effect of netropsin binding on the B-A transition of NaDNA fibers became less obvious in TFE solution. In another series of experiments, L/L0 was measured as a function of temperature to obtain information on the helix-coil transition, or melting, as well as the B-A transition of NaDNA and NaDNA-netropsin fibers. The melting temperature and helix-coil transition width were calculated from the melting curves. A phenomenological approach was used to describe the melting behavior of the fibers in and around the B-A transition region. The effect of netropsin on the melting of DNA fibers was attributed mainly to the stabilization of B-DNA and to a higher melting cooperativity in the B-DNA region.

Animals↗
PubMed1995

Significance of flow cytometry in the diagnosis and treatment of bladder tumors.

The results of application of flow cytometry (FCM) in analysis of 139 bladder irrigations of DNA contents in tumor cells from 52 cases of bladder tumors are reported. A comparison was made between this assay and cytological examinations as well as pathological grading. The results suggested that the accuracy of cytological analysis was apparently lower than the cell DNA measurement by flow cytometry, the higher the tumor pathological grading and the deeper the infiltration, the higher the heteroploid DNA contents in the tumor cells. Treatment of high heteroploid bladder tumor required radical cystectomy while the efficiency of simple electrosection or partial cystectomy appeared inferior. When FCM and the bladder tumor pathological grading had a high degree of correlation, especially in the high grading tumor, recurrence was high even when chemical treatment with bladder instillation of BCG was adopted. However, FCM cannot substitute for cystoscopy.

Adult↗
PubMed1995

[Chemical constituents of Clematis intricata Bunge].

Five compounds were isolated from the aerial part of Clematis intricata for the first time. On the basis of spectral data (UV, IR, MS, 1HNMR and 13CNMR), they were identified as scopoletin, caffeic acid, inositol, 1-tria-contanol and beta-sitosterol.

Caffeic Acids↗
PubMed1994

Differential expression of cell surface sialoglycoconjugates on wild-type and cultured Ehrlich tumor cells as revealed by quantitative lectin-gold ultrastructural cytochemistry.

Three variants of the classical Ehrlich ascites tumor (EAT) cell have been studied by quantitative, sialic acid-specific, lectin-gold ultrastructural cytochemistry. Electron microscopic examination revealed pronounced differences in the surface morphology of the three cell variants. The wild-type Ehrlich cells (EAT-wt), grown in the peritoneal cavity of mice, exhibited a smooth surface profile. A variant form selected for growth as monolayer on basement membrane (EAT-c) showed a complex surface profile with numerous microvilli. The third variant (EAT-c/m), the cultured cells reinoculated into mice and passaged 20-25 times as ascites, presented a smooth surface profile similar to the EAT-wt cells. Quantitative single as well as double lectin-gold labeling revealed significant differences in the nature of cell surface sialoglycoproteins. The most significant finding was the presence of cell surface Neu5Ac alpha 2-6Gal residues as detected with the Sambucus nigra lectin on EAT-c and EAT-c/m cells, whereas EAT-wt cells contained little or none of such carbohydrate sequences. On the contrary, labeling by Maackia amurensis lectin, which recognizes the Neu5Ac alpha 2-3Gal beta 1-4GlcNAc sequence, was intense on all three Ehrlich cell variants; it was 20-60 times greater than alpha-2,6-linked sialic acid-containing glycoconjugates. Specific cell surface lectin binding combined with morphologic study appears to have identified a small subpopulation of cells within the ascites tumor that are capable of attaching to and growing on a basement membrane.

Animals↗
PubMed1994

A novel cysteine-rich sequence-specific DNA-binding protein interacts with the conserved X-box motif of the human major histocompatibility complex class II genes via a repeated Cys-His domain and functions as a transcriptional repressor.

The class II major histocompatibility complex (MHC) molecules function in the presentation of processed peptides to helper T cells. As most mammalian cells can endocytose and process foreign antigen, the critical determinant of an antigen-presenting cell is its ability to express class II MHC molecules. Expression of these molecules is usually restricted to cells of the immune system and dysregulated expression is hypothesized to contribute to the pathogenesis of a severe combined immunodeficiency syndrome and certain autoimmune diseases. Human complementary DNA clones encoding a newly identified, cysteine-rich transcription factor, NF-X1, which binds to the conserved X-box motif of class II MHC genes, were obtained, and the primary amino acid sequence deduced. The major open reading frame encodes a polypeptide of 1,104 amino acids with a symmetrical organization. A central cysteine-rich portion encodes the DNA-binding domain, and is subdivided into seven repeated motifs. This motif is similar to but distinct from the LIM domain and the RING finger family, and is reminiscent of known metal-binding regions. The unique arrangement of cysteines indicates that the consensus sequence CX3CXL-XCGX1-5HXCX3CHXGXC represents a novel cysteine-rich motif. Two lines of evidence indicate that the polypeptide encodes a potent and biologically relevant repressor of HLA-DRA transcription: (a) overexpression of NF-X1 from a retroviral construct strongly decreases transcription from the HLA-DRA promoter; and (b) the NF-X1 transcript is markedly induced late after induction with interferon gamma (IFN-gamma), coinciding with postinduction attenuation of HLA-DRA transcription. The NF-X1 protein may therefore play an important role in regulating the duration of an inflammatory response by limiting the period in which class II MHC molecules are induced by IFN-gamma.

Amino Acid Sequence↗
PubMed1994

A mechanochemical study of MgDNA fibers in ethanol-water solutions.

Highly oriented calf-thymus MgDNA fibers, prepared by a wet spinning method, were studied with a simple mechanochemical set-up. The relative fiber length, L/Lo, was measured with the fibers submerged in ethanol-water solutions. In one type of experiment L/Lo was measured as a function of ethanol concentration at room temperature. No substantial decrease in L/Lo with increasing ethanol concentration was observed, indicating that MgDNA fibers stay in the B form even when the water activity is very low. For low ethanol concentrations the fiber structure is stable and does not dissolve even at very high water activities. In a second type of experiment, the heat-induced helix-coil transition was manifested by a marked contraction of the fibers. The transition temperature decreases linearly with increasing ethanol concentration between 52 and 68% ethanol. At higher ethanol concentrations the helix-coil transition temperature increases due to strong aggregation within the DNA fibers, and above 77% ethanol the fibers do not contract at all, not even at the upper temperature limit of the experiments, approximately 80 degrees C. This behavior is discussed with reference to dried DNA and the P form of DNA. The helix-coil transition temperature of the MgDNA fibers in 70% ethanol does not show any dependence on the MgCl2 concentration. It is shown that the Poisson-Boltzmann cylindrical cell model can account qualitatively for this lack of salt dependence.

Animals↗
PubMed1993

Differences in cell surface carbohydrates, and in laminin and fibronectin synthesis, between adherent and non-adherent Ehrlich ascites tumor cells.

Differences in cell surface carbohydrates and in laminin and fibronectin synthesis between 2 Ehrlich ascites tumor (EAT) cell lines, the adherent and non-adherent EAT cells, have been studied. The adherent EAT (a-EAT) cells grow in monolayer in vitro in the presence of fetal bovine serum. The classical, or non-adherent EAT (na-EAT), cells grow in suspension in ascites form in the peritoneal cavity of mice, and they do not adhere when cultured in vitro. Both EAT cell lines express surface glycoproteins reactive with Maackia amurensis lectin (MAL) and Griffonia simplicifolia isolectin GS I-B4. However, only a-EAT cells react with elderberry (Sambucus nigra) bark lectin (SNA), suggesting that there are some differences in the sialylation of cell surface carbohydrate moieties between these 2 EAT cell lines. Removal of cell surface sialic acid by treating a-EAT cells with Vibrio cholerae neuraminidase did not abolish the ability of these cells to adhere to laminin- or fibronectin-coated plates, indicating that the sialic acid of the cell surface glycoproteins is not essential for their adhesion to these extracellular matrices. Therefore, the difference in sialylation of cell surface glycoproteins is not responsible for the difference in cell adhesion between these 2 lines of EAT cells. Both EAT cell lines express detectable amounts of laminin but not fibronectin on their surfaces; they both secrete fibronectin and entactin into the medium. The na-EAT cells (but not the a-EAT cells) also secrete laminin A chain into the culture medium; however, no B chain was detected in the culture medium of either cell line. The laminin isolated from the cell surface of na-EAT cells reacts with GS I and MAL lectins, but not with SNA, whereas the laminin isolated from a-EAT cells reacts with SNA, as well as GS I and MAL.

Animals↗
PubMed1993

Detection of bovine leukemia virus RNA in serum using the polymerase chain reaction.

A method was developed for detecting bovine leukemia virus (BLV) RNA in serum samples using a pair of primers from the BLV polymerase gene in the polymerase chain reaction (PCR). The PCR was able to detect 3800-7600 molecules of BLV RNA. At this level of sensitivity eleven pools of adult and one fetal bovine serum appeared free from BLV contamination.

Animals↗
PubMed1993

The isolation of a yeast artificial chromosome (YAC) contig extending for 2 megabases in the vicinity of the von Hippel Lindau disease gene.

Von Hippel Lindau disease (VHL) is a rare autosomal dominant disease associated with tumors and cysts in multiple organ systems. The VHL disease gene is tightly linked to the polymorphic DNA marker 233E2 (D3S720) and flanked by 479H4 (D3S719) on its telomeric and RAF1 on its centromeric side. Two additional markers, D3S1038 and D3S601, have also been identified, and these markers, like D3S720, are very tightly linked to VHL. Previously 93 cosmid clones were mapped to the larger region, 3p24.2-pter, surrounding the VHL disease gene. Using a Southern-based screening strategy on pools of YAC clones we have isolated a contig of overlapping YAC clones that extends about 0.7 megabase centromeric, and about 1.3 megabases telomeric of D3S720 and contains all three tightly linked VHL markers. Individual YACs in this contig were hybridized to grids containing cosmids localized between 3p24.2-pter and to several cosmids localized by fluorescent in situ hybridization (FISH) to 3p25. A total of 28 cosmids were positioned on this contig of overlapping YAC clones. We have also identified homologous YAC clones to many additional cosmid clones localized between 3p24.2-p25, although these have not yet been precisely localized relative to the contig of YAC clones. This contig of YAC clones probably contains the VHL disease gene and should facilitate the isolation and characterization of this gene.

Base Sequence↗
PubMed1993

[Formation of mouse chimeras from early embryonic pluripotential stem cell].

Three chimeric mice were produced by injecting the embryonic stem cell-CCE cells into the cavity of 3.5 day host blastocysts from Kunming and C57BL/6J mice. By analyses of glucose phosphate isomerase (GPI-1), the results show a contribution from CCE cells in heart tissue of female Kunming chimera. Breeding experiments demonstrated that all chimeric mice were fertile but none of 3 chimeras produced germ line transmission.

Animals↗
PubMed1993

[The multi-channel VEPs topography in optic neuritis].

The multi-channel VEPs topographies of 20 normal persons and 22 patients suffered from optic neuritis were recorded. In normal subjects, the topography showed symmetric distribution by full-field stimulation and paradoxical lateralization by half-field stimulation. In patients with optic neuritis, it showed asymmetric distribution most on the temperal side, some on the nasal side and occasionally in the middle by full-field stimulation. The result suggests that the optic nerve may be damaged on either temperal or nasal. The effect of the early diagnosis and evaluating treatment using topography is also discussed.

Adult↗
PubMed1992

The formation of A-DNA in NaDNA films is suppressed by netropsin.

Oriented films of NaDNA complexed with netropsin were studied with deuterium nuclear magnetic resonance (2H NMR), X-ray diffraction and ultraviolet (UV) linear dichroism to obtain information about the influence of netropsin on the structural arrangement of the DNA bases and on the B-A transition. The results of these studies clearly demonstrate a strong suppression of the formation of A-DNA at relative humidities (RHs) down to about 50%. The suppression was complete in the NaDNA-netropsin complex studied with 2H NMR which had a netropsin input ratio, r, of 0.22 drug/base pair. The sample used for UV linear dichroism had a similar input ratio while the X-ray diffraction samples had input ratios between 0.033 and 0.39 drug/base pair. Together, the results of these studies are in agreement with previous infrared (IR) linear dichroism studies of the conformation of the sugar-phosphate backbone in NaDNA-netropsin complexes, which showed that the B-A transition is suppressed for r-values down to approximately 0.1 drug/base pair (Fritzsche, H., Rupprecht, A. and Richter, M., Nucleic Acids Res. 12 (1984) 9165-9177).

Animals↗