PubMed Health⌕ Search

Biomedical subjects

F Ding

Publications and source records attributed to F Ding.

At least 19 recordsLinked to original sources
PubMed2001

Determination of the molecular mass distribution of synthetic polymers by size-exclusion electrochromatography.

The performance of size-exclusion electrochromatography (SEEC) for the mass distribution analysis of synthetic polymers was studied and compared to conventional, pressure-driven size-exclusion chromatography (SEC). Electroosmotic flow control, within-day, day-to-day and column-to-column repeatability were determined for SEEC with respect to retention and separation efficiency. It was shown that by using the retention ratio instead of the migration time, the precision of the mass distribution calculations is sufficiently high, and that similar distributions were obtained for a sample analyzed by pressure-driven SEC and by SEEC. Furthermore, hexafluoroisopropanol was demonstrated to be a new and potent solvent for SEEC. It was used for the separation of narrow polymethylmethacrylate standards and several commercially important polymers such as polycarbonate, polycaprolactam and poly(ethylene terephthalate), using UV detection in the deep UV region (195-230 nm).

Chromatography, Gel↗
PubMed2001

Oscillatory electroosmosis-enhanced intra/inter-particle liquid transport and its primary applications in the preparative electrochromatography of proteins.

The concept of generating an oscillatory electroosmotic flux inside the porous particle to enhance the intra-particle mass transport was presented and a new kind of electrochromatography carried out in a five-compartment electrolyzer were developed. The adsorbent was packed in the central compartment, while the neighboring compartments were used as the elution compartments and the electrode compartments, respectively. Chromatographic separations of human serum albumin on Blue Sepharose Fast Flow, bovine serum albumin (BSA) on DEAE-Sepharose Fast Flow, and BSA on hydroxyapatite were carried out, respectively. The adsorption isotherms were shown to be independent of electric field, while the increase in the electric field strength resulted in a linear increase in the magnitude of electroosmotic flux and the improvement of the breakthrough behavior in all cases. The experiment results have demonstrated the effectiveness of the oscillatory electroosmosis in enhancing intra- and inter-particle mass transport and its high potential to large-scale chromatography.

Adsorption↗
PubMed2001

Genomic imprinting disrupted by a maternal effect mutation in the Dnmt1 gene.

Maintenance of genomic methylation patterns in mammalian somatic cells depends on DNA methyltransferase-1 (Dnmt1). Mouse oocytes and preimplantation embryos lack Dnmt1 but express a variant of this protein called Dnmt1o. We eliminated Dnmt1o by deletion of the oocyte-specific promoter and first exon from the Dnmt1 locus. Homozygous animals were normal, but most heterozygous fetuses of homozygous females died during the last third of gestation. Although genomic methylation patterns were established normally in Dnmt1o-deficient oocytes, embryos derived from such oocytes showed a loss of allele-specific expression and methylation at certain imprinted loci. Transient nuclear localization of Dnmt1o in 8-cell embryos suggests that this variant of Dnmt1 provides maintenance methyltransferase activity specifically at imprinted loci during the fourth embryonic S phase.

Animals↗
PubMed1999

Experimental studies on affinity chromatography in an electric field.

A multicompartment electrolyzer, which has been used for preparative electrophoresis [Z. Liu, Z. Huang, J.-Y. Cong, et al., Sep. Sci. Technol. 31 (1996) 427], is applied for carrying out affinity chromatography in an alternating electric field. The effect of electric field strength on the adsorption and desorption characteristics is experimentally examined with human serum albumin and Blue Sepharose Fast Flow as a model system. It is shown that the existence of an electric field leads to a significant change in the adsorption capacity of the blue dye, which may be used for establishing a preferential adsorption to achieve a high resolution. The adsorption speed increases slightly with respect to the increase of electric field strength, while adsorption capacity in the presence of an electric field is independent of the electric field strength. Different elution behavior is observed as function of adsorption condition and a high recovery of the adsorbed protein is obtained when the adsorption is carried out in the presence of an electric field.

Buffers↗
PubMed1999

Identification of a protein component of a mammalian tRNA(Sec) complex implicated in the decoding of UGA as selenocysteine.

This report describes a novel RNA-binding protein, SECp43, that associates specifically with mammalian selenocysteine tRNA (tRNA(Sec)). SECp43, identified from a degenerate PCR screen, is a highly conserved protein with two ribonucleoprotein-binding domains and a polar/acidic carboxy terminus. The protein and corresponding mRNA are generally expressed in rat tissues and mammalian cell lines. To gain insight into the biological role of SECp43, affinity-purified antibody was employed to identify its molecular partners. Surprisingly, the application of native HeLa cell extracts to a SECp43 antibody column results in the purification of a 90-nt RNA species identified by direct sequencing and Northern blot analysis as tRNA(Sec). The purification of tRNA(Sec) by the antibody column is striking, based on the low abundance of this tRNA species. Using recombinant SECp43 as a probe for interacting protein partners, we also identify a 48-kDa interacting protein, which is a possible component of the mammalian selenocysteine insertion (SECIS) pathway. To our knowledge, SECp43 is the first cloned protein demonstrated to associate specifically with eukaryotic tRNA(Sec).

Amino Acid Sequence↗
PubMed1998

Electrophoretic affinity chromatography: method validation.

A new method for preparative-scale separation of biomolecules, electrophoretic affinity chromatography (EAC), is proposed in this paper. Separation by EAC is carried out in a long and ribbon-like multicompartment electrolyser separated by membranes, in which the two central compartments are used for packing the gel matrix and for sample loading respectively. Next to the central compartments are the elution compartments and electrode compartments. The electric field is applied perpendicular to the fluid flow in the compartments. Adsorption and desorption steps may both be carried out in the presence of an electric field, which transports the target components into the gel compartment for adsorption and the impurities into the elution compartments for washing. After the adsorption step an elution solution is introduced and the product is released from the gel matrix and washed out. Separation of human serum albumin (HSA) from human serum gives HSA product of high purity, as demonstrated by isoelectric focusing analysis. The characteristics of electrophoretic binding of HSA on Blue Sepharose Fast Flow are examined. The preliminary results show that this new method has advantages in terms of high rate of mass transfer and ease of scaling up, which are of particular interest when large-scale separation of biomolecules is considered.

Adsorption↗
PubMed1998

[Effect of herbs 814 on tumor necrosis factor a production from alveolar macrophages in vitro].

OBJECTIVE: To study the influence of herbs 814 on the secretion of tumor necrosis factor alpha (TNF-alpha) from hamster alveolar macrophages (AMs) in vitro and elucidate mechanism of herbs 814's prevention of emphysema. METHODS: AMs of hamster were collected by bronchial alveolar lavage (BAL). The lung lavage cells were adjusted to 5 x 10(5)/ml and seeded in each well of a 24-well tissue culture plates. The herbs 814 was added into these wells before or after lipopolysaccharide (LPS) stimulation and then cultured supernatants were collected. TNF-alpha production in the supernatants was tested by ELISA, TNF-alpha cytotoxicity was assayed using L929 cells which were susceptible to TNF-alpha and a monoclonal antibody (MAb) that neutralizes rhTNF-alpha was utilized to identify the cytotoxicity of cultured TNF-alpha. RESULTS: ELISA showed that TNF-alpha production in the supernatants with 814 added was lower than those either in LPS-stimulated or non LPS-stimulated supernatants and there was a significant decrease in the supernatants of higher concentration (1:5) of herbs 814. Cytotoxicity test showed that TNF-alpha cytotoxic activity in the supernatants into which herbs 814 was added was lower than one in the LPS-stimulated supernatants and there was a significant decrease in the supernatants of higher concentration (1:5) of herbs 814. Meanwhile, MAb significantly reduced cytotoxicity of LPS-stimulated culture supernatants. CONCLUSIONS: Herbs 814 could inhibit the secretion of TNF-alpha and prevent the lung damage mediated by TNF-alpha.

Animals↗
PubMed1996

Biochemical properties of a novel U2AF65 protein isoform generated by alternative RNA splicing.

A variety of RNA binding proteins with one or more RNA recognition (RNP-CS) motifs play essential roles in the pre-mRNA splicing process. One such factor, the U2 snRNP auxiliary factor large subunit (U2AF65), contains three RNP-CS motifs each of which is required for high affinity binding to polypyrimidine tracts. Here we report the isolation of a natural cDNA variant of human U2AF65, U2AF65 (S), which is shortened by a 12 nucleotide in frame deletion between RNP-CS2 and -CS3 motifs. A portion of the U2AF65 (S) cDNA was reported previously but was not characterized further. We observe that the U2AF65 (S) variant predominates in a variety of tissues and cell lines, and is generated together with the U2AF65 (L) form (2) by alternative 5' splice site selection from a single gene. The corresponding histidine-tagged recombinant proteins bind with similar affinities to model RNA substrates containing strong or weak polypyrimidine tracts. Both U2AF65 (S) and (L) protein isoforms reconstitute splicing activity with similar kinetic profiles in U2AF-depleted (splicing-deficient) HeLa nuclear extracts. Finally, the thermal stabilities of the protein isoforms are essentially equivalent. Thus, the presence or absence of the peptide segment, VSPP (residues 345-348), in the linker region between RNP-CS2 and -CS3 does not detract from the intrinsic RNA binding and splicing properties of the U2AF65 protein. The biological implications of alternative splicing for the function and evolution of RNA binding proteins are discussed.

Alternative Splicing↗
PubMed1996

Multichannel flow electrophoresis and its applications in purification of proteins, enzymes, and antibodies.

Multichannel flow electrophoresis (MFE) is a novel preparative electrophoresis technique designed for continuous separation of proteins based on their different isoelectric points. A computer controlled MFE apparatus is developed and the effects of operation parameters such as electric field strength, buffering pH, and sample introducing flow rate on MFE separation efficiency are investigated. The application of MFE is first exemplified by continuous separation of BSA and HBB mixture. Then continuous purification of urokinase from urine extracts is conducted, in which 10 x 10(4) IU urokinase product whose specific activity is higher than 40,000 IU/mg is obtained per hour. Finally, MFE is applied in the continuous purification of anti-urokinase mouse IgG from mouse serum and yields 2.1 mg mouse IgG per hour with high purity demonstrated by SDS-PAGE. The preliminary results presented have confirmed the workability of MFE and pointed out its high application potential in biochemical process.

Antibodies↗
PubMed1995

[Expression and loss of heterozygosity of DCC gene in human lung cancer].

The level of DCC mRNA expression was evaluated in tissue specimens from lung cancer patients by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) combined with Southern blot analysis. Obvious reduction of DCC gene expression was observed in 4 of 7 specimens (55%). In two specimens DCC transcript could only be detected after Southern blot hybridization of RT-PCR product. The average level of DCC expression in cancer tissue was about 45% of normal tissue as estimated by laser densitometer. We also studied DNA samples for loss of heterozygosity (LOH) at DCC locus at two polymorphic sites. Among the 15 specimens including 7 samples for RT-PCR, 9 (60%) were informative at either of two polymorphic sites. LOH was observed in 5 (55%). Two at the MspI-RFLP (restriction fragment length polymorphism) site and 3 at the site of VNTR (variable number of tandem repeat). These results suggest that allele loss and decreased expression of DCC gene are frequent events and the possible involvement of DCC gene in the pathogenesis of human lung cancer.

Adenocarcinoma↗
PubMed1994

[Studies of the suppressive effect of cDNA RA538 on three human cancer cell lines].

As previously reported, transfer of RA538 into parental esophageal cancer EC8712 cell line induced its terminal differentiation and apoptosis. To further study the biological effects of this cDNA, an expression plasmid containing an insert of the putative coding fragment (about 0.3kb) of RA538 and neo resistance gene was constructed (designated pRA538-0.3-neo) and transferred into three different human cancer cell lines: EC8712, HL60 and GLC, a cell line derived from an adenocarcinoma of the lung. After selection in G418-containing culture media, the growth rate, 3H-thymidine incorporation rate, cell morphology, colony-formation in soft-agar, and heterotransplantation into nude mice of the surviving cell populations were tested. In situ hybridization verified the uptake and expression of the 0.3kb fragment of RA538 in these G418 resistant cell populations. Significant reduction in growth rate and suppression of malignant phenotype were observed in all these cells in comparison with their parental cancer cell lines.

Adenocarcinoma↗
PubMed1994

[Expression of cDNA RA538 induces terminal differentiation and apoptosis of its parental malignant cell line in vitro].

A full-length cDNA (RA538) was isolated from human esophageal cancer cell line EC8712 after retinoic acid treatment. An expression vector of this cDNA (pRA538) was cotransfected with the neo gene (pDORneo) into parental cancer cell line EC8712. The cell colonies obtained after selection in G418-containing culture medium showed very poor growth, reduced (by 68%-76%) 3H-TdR uptake and morphological changes characteristic of terminal differentiation and programmed cell death (apoptosis). In situ hybridization with RA538 probes revealed expression of mRNA of RA538 in the cytoplasm of the transfected cells. The cells transfected solely with pDORneo after G418 selection showed normal growth pattern and no RA538 expression. However, none of the control cells EC8712 survived the G418 selection. Thus the expression of cDNA RA538 has a similar effect on the esophageal cancer cell EC8712 as the retinoic acid does.

Animals↗
PubMed1993

Hemolytic disease of the newborn caused by maternal anti-Dib: a case report in Taiwan.

Possibly the first case of hemolytic disease caused by anti-Dib in a Chinese infant is reported. The infant developed jaundice soon after birth; based on study, the jaundice has been diagnosed as a result of maternal anti-Dib which was most likely induced by previous pregnancies. The phenotype of the mother's red cells was Di (a+b-). The frequency of the Dia antigen among Chinese in Taiwan is 3.2%. In Orientals, hemolytic disease of the newborn caused by maternal anti-Dib is likely to be more severe than that caused by anti-Dia.

Blood Group Antigens↗
PubMed1993

[Clinical and experimental study on yi-gan-ning granule in treating chronic hepatitis B].

This paper reports that 320 patients with chronic hepatitis B (CHB) were treated with Yi-ganning Granule (YGNG) and the pharmacodynamics of YGNG in the animal study. As control, another 70 patients with CHB receiving oleanolic acid granule (OAG) were compared to 68 patients in YGNG group. YGNG is consisted of Astragalus membranaceus , Artemisia capillaris, Codonopsis pilosula, et al. Each patient has taken YGNG or OAG for 3 months. The result showed YGNG was effective on recovering the liver function and OAG had similar effect. The sero-negative conversion rates of HBsAg, HBeAg, HBcAb and positive conversion rate of HBeAb in the YGNG group were 33.1%, 40.5%, 10.5% and 15.5% respectively, which were much better than that in OAG group (P < 0.05-0.001). The result of 6 months follow up showed that 60 of 62 patients receiving YGNG were in stabilized state. The result in the animal study demonstrated that YGNG had significant protection from the liver damage caused by CCl4. YGNG could decrease serum ALT level and protect the liver function of carbohydrate, fat, protein metabolism and detoxication. YGNG could induce interferon in vivo and play an important role in seroconversion of negative DHBV-DNA and improvement of pathological morphology in viral hepatitis B.

Adolescent↗