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Biomedical subjects

Y H Tan

Publications and source records attributed to Y H Tan.

At least 109 records · Page 6Linked to original sources
PubMed1983

The nucleotide sequence of a new human repetitive DNA consists of eight tandem repeats of 66 base pairs.

Three cloned human DNA fragments obtained from a fibroblast genomic DNA were sequenced and identified as containing members of the well-known 300-bp Alu family of interspersed, middle-repetitive DNA sequences. One of these cloned DNA fragments, p16, also contains members of a new repetitive DNA family, which repeats several thousand times in the human genome. Each member of the new 528-bp family consists of eight tandem repeats of a 66-bp sequence. An AluI recognition site is present at the same location in each repeat, and a 25-bp sequence occurs twice (as a tandem repeat) in each of the eight repeats. There is no sequence homology between the new 528-bp family and the 300-bp Alu family, and the new family lacks the flanking 7- to 20-bp direct repeats as well as the dAMP-rich sequences characteristic of the 300-bp Alu family. Construction of a putative evolutionary tree indicates that six duplication events are needed to give rise to the eight tandemly repeated 66-bp units in the new 528-bp family.

Base Sequence↗
PubMed1983

Monoclonal antibodies directed against human fibroblast interferon: characterization and functional studies.

Spleen cells from BALB/c mice, immunized with SDS-acrylamide gel purified human fibroblast interferon (HuIFN-beta) were fused with mouse myeloma cells. Culture fluids from the resulting hybrid cells were screened for HuIFN-beta specificity by the following tests: a solid-phase RIA using partially purified HuIFN-beta, a protein-transfer RIA using electrophoretically resolved and immobilized HuIFN-beta, and a bioassay which tests residual HuIFN-beta activity in the supernatant following immunoprecipitation. Six HuIFN-beta-specific hybridomas were identified; two were capable of partially neutralizing HuIFN-beta activity. All six antibodies bind to the beta 1-IFN polypeptide synthesized in E. coli cells containing a cloned beta 1-IFN DNA sequence. All six monoclonal antibodies were found to be IgG3/kappa.

Animals↗
PubMed1983

Isolation of HuIFN-beta by immunosorbent and high-pressure liquid chromatography.

A procedure for isolating HuIFN-beta without the use of SDS or other denaturants has been developed. The procedure involves the chromatography of IFN on an antibody affinity column followed by reversed-phase HPLC. The specific activity of the resulting IFN-beta is 4 X 10(8) u/mg protein, and overall recovery is about 76%. The procedure provides a method for isolating pure HuIFN-beta in its native form with an efficiency much higher than any other method reported to date.

Cells, Cultured↗
PubMed1983

Enhancement of actinomycin D- and cis-diamminedichloroplatinum(II)-induced killing of human fibroblasts by human beta-interferon.

When normal or transformed human fibroblasts are incubated with actinomycin D, RNA synthesis is irreversibly inhibited, and the treated cells eventually die. This cell-killing effect of actinomycin D is significantly enhanced by pretreating the cells with human interferon. This effect of interferon is species specific and appears to be under the control of gene(s) located on human chromosome 21. Enhancement of cell killing effect of cis-platinum by interferon pretreatment is also observed.

Cell Survival↗
PubMed1981

Radioimmunoassay for human beta interferon.

Pure human beta interferon (Hu IFN-beta) (formerly human fibroblast interferon) was used to raise antibodies in rabbits. Anti-IFN-beta immunoglobulins from rabbit serum were purified by IFN-beta affinity chromatography and were used in the development of a sandwich-type radioimmunoassay for Hu IFN-beta. This radioimmunoassay consisted of (i) incubating Hu IFN-beta with anti-IFN-beta immunoglobulins immobilized on Sepharose 4B beads and (ii) incubating the resulting solid-phase IFN antibody complex with 125I-labeled anti-Hu IFN-beta immunoglobulins. The amount of 125I-labeled anti-Hu IFN-beta bound to the complex was linearly proportional to the amount of antiviral activity present in the complex from 0 to 500 U of standard IFN-beta per ml; 1 U of antiviral activity was equivalent to about 40 cpm of 125I-labeled anti-IFN immunoglobulins in the radioimmunoassay. The results of the radioimmunoassay were not influenced by the protein content of the IFN sample assayed, and the degree of intraassay variability was low; coefficients of variability were 9.4% at 5 U/ml and 1.1% at 500 U/ml. Thus, compared with the traditional antiviral assay for IFN, this radioimmunoassay was equally sensitive and more precise. In addition, it was highly specific for Hu IFN-beta and took only 5 h to complete.

Biological Assay↗
PubMed1981

Human interferon for clinical trials: removal of pyrogen by a simple two-step procedure.

Commonly used preparations of human interferon are pyrogenic when used in humans for clinical trials. We describe a simple two-step procedure for the purification of human fibroblast interferon, employing Blue Sepharose chromatography and high-speed centrifugation. Such preparations are devoid of pyrogenic activity in a rabbit test system and are much more suitable for use in human clinical trials than previously used preparations.

Animals↗
PubMed1981

Kinetics of human immune interferon production and blastogenesis.

We studied some of the requirements for production of immune interferon (IFN-gamma) by human peripheral leucocytes following stimulation with concanavalin A (Con A). Synthesis of IFN-gamma commenced 2 hr after the cells were exposed to the lectin and continued for about 20 hr thereafter. IFN-gamma production during the latter period was independent of free Con A in the culture medium but it was sustained by continued Con A binding and required active de novo protein synthesis. Egg lecithin, which inhibits the blastogenic response, did not affect IFN-gamma production.

Cells, Cultured↗
PubMed1980

Human fibroblastoid interferon: immunosorbent column chromatography and N-terminal amino acid sequence.

Three mice and one rabbit were inoculated with purified human fibroblastoid interferon. Neutralizing activity to human fibroblastoid interferon was observed in the serum of these animals with the rabbit showing the highest anti-interferon titers (10(6) neutralizing units/mL). Rabbit antiserum was coupled to cyanogen bromide activated Sepharose, and the resulting material was tested for use in the purification of human fibroblastoid interferon. Pure interferon obtained by this procedure was analyzed, and we report the sequence of the first 13 N-terminal amino acid residues of this protein.

Amino Acid Sequence↗
PubMed1980

Phase I pharmacotoxicology study of human fibroblast interferon in human cancers.

Twelve patients with advanced cancer were treated with human fibroblast interferon. Interferon administered im in doses up to 10 x 10(6) U three times weekly for 2 weeks was associated with highly variable, but detectable, plasma levels. Bolus interferon given iv was associated with a reproducible, immediate peak of activity followed by a rapid loss of detectable activity. Continuous infusion of interferon over 2 hours resulted in a slowly increasing dose-related level to a maximum near the end of the infusion followed by a loss of detectable activity for about 1 hour following infusion. Interferon administered both im and iv caused a mild, easily tolerated pyrexia as the only regularly occurring side effect. In 1 patient interferon treatment suppressed a malignant clone of circulating blasts trisomic for chromosomes No. 8 and 21 from 59 to 0%.

Adult↗
PubMed1979

The isolation and amino acid/sugar composition of human fibroblastoid interferon.

Human fibroblastoid interferon produced from an established human cell line was purified by controlled-pore glass and concanavalin A-Sepharose column chromatography followed by preparative two-dimensional gel electrophoresis. The purification procedure provided a 10% recovery of pure interferon with good reproducibility. The purified protein was homogeneous with respect to its molecular weight of 20,000 and net electrical charge at pH 2.5. Interferon of high specific activity of 5 x 10(8) units/mg of protein was directly demonstrated in the polyacrylamide gel before staining with Coomassie brilliant blue. Parallel purification of a sham-induced interferon preparation did not yield an equivalent product indicating the purified interferon is not derived from uninduced cells or from the fetal calf serum of the tissue culture growth medium. Pure interferon was radioiodinated by Bolton-Hunter reagent. Amino acid analysis of the pure preparation shows interferon to be a leucine-rich glycoprotein containing a high percentage of glutamic/glutamine residues and that disulfide bridges(s) are important for its biological activity.

Amino Acids↗
PubMed1978

Purification and in vitro labeling of interferon from a human fibroblastoid cell line.

Interferon was produced from a clonal human fibroblastoid line. This cell line was derived from an established fibroblastoid culture treated with ethylmethane sulfonate and is capable of producing higher amounts human interferon than primary human fibroblast cultures. The interferon produced from this cell line was purified by concanavalin A and phenyl-Sepharose column chromatography followed by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified interferon was then labeled with [125I]-iodine, with [3H]5-dimethylaminonaphthalene-1-sulfonyl-chloride and with sodium [3H]borohydride after periodate oxidation. An appreciable amount of biological activity was retained after both tritium labelings but not after iodination. When subjected to electrophoresis in the presence of sodium dodecyl sulfate all three radioactive interferon preparations comigrated with the purified interferon preparation as a single protein component with a molecular weight of 19,000. Both purified and radioactive preparations were also shown to migrate with the antiviral activity in polyacrylamide gels in the absence of sodium dodecyl sulfate. The specific activity of purified interferon preparations ranged from 2 X 10(8) to 10 X 10(8) units/mg of protein.

Cell Line↗
PubMed1978

Chemical modifications of tyrosyl residue(s) and action of human-fibroblast interferon.

Partially purified and purified human fibroblastoid interferon were iodinated and nitrated under experimental conditions in which the most likely amino acyl residue modified was tyrosine(s). The modification resulted in a loss of human interferon activity suggesting that tyrosyl residue(s) is associated with the antiviral action of human interferon.

Cell Line↗
PubMed1977

Effect of human interferon preparations on lymphoblastogenesis in Down's syndrome.

The best characterised properties of human interferon, its antiviral (AV) and cell multiplication inhibitory (CMI) activities, are controlled, in an unexplained manner, by genes on chromosomes 21 (refs 1-4; 14-16). Human and animal interferons have various immunosuppressive effects, among them the inhibition in vitro of DNA synthesis in activated lymphocytes. Using mitogen- and antigen-stimulated lymphocytes from normal subjects (disomic 21) and others with Down's syndrome (trisomic 21), we have found that DNA synthesis is inhibited to a greater degree in the latter by both fibroblastoid and leukocyte interferons. We suggest that this property is also regulated by genes on chromosome 21.

Cell Proliferation↗
PubMed1977

A mechanism for the induction and regulation of human fibroblastoid interferon genetic expression.

Some commonly used inducers such as viruses and double-stranded RNA are known to inhibit cellular protein synthesis. We have now shown that conventional inhibitors of macromolecular synthesis such as cycloheximide, 2-(4-methyl-2, 6-dinitroanilino)-N-methyl propionamide (MDMP) and I-beta-D-ribofuranosylbenzimidazole (DRB) can induce the production of significant amounts of interferon in human fibroblastoid cell lines. The interferon-inducing activity of these inhibitors depends on the concentration as well as the time of treatment with the inhibitors. These findings lead to the suggestion that the induction of human interferon may be mediated by a reduction in the critical concentration of a rapidly turning over repressor(s) which normally represses the interferon gene(s) in uninduced cells.

Aniline Compounds↗