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Biomedical subjects

K K Chen

Publications and source records attributed to K K Chen.

At least 109 records · Page 6Linked to original sources
PubMed1986

Recombinant human granulocyte colony-stimulating factor: effects on normal and leukemic myeloid cells.

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D+) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in Escherichia coli. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with 125I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D+) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D+) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D+) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be O-glycosylated and to have a molecular weight of 19,600.

Animals↗
PubMed1986

Monkey erythropoietin gene: cloning, expression and comparison with the human erythropoietin gene.

The erythropoietin (Epo) gene from Cynomolgus monkeys has been isolated from a kidney cDNA library using mixed 20-mer oligodeoxynucleotide probes. The gene encodes a 168 amino acid (aa) mature protein with a calculated Mr of 18,490 and a presumptive signal peptide of 24 aa. The Epo gene, when transfected into Chinese hamster ovary (CHO) cells, produces a glycosylated protein with an apparent Mr of 34,000. The expressed product is biologically active in vivo. The monkey gene exhibits 92% and 94% homology to the human gene at the aa and nucleotide sequence levels, respectively. When compared with the human Epo, monkey Epo has an additional 3-aa residue at the N terminus of the mature protein and a deletion of an internal lysine residue.

Amino Acid Sequence↗
PubMed1985

Results of irradiation in the treatment of locoregional breast cancer recurrence.

A retrospective review is presented of 255 patients with chest wall and/or regional nodal recurrent breast cancer treated between January 1956 through December 1981 at the University of Texas M. D. Anderson Hospital; 61 patients had such massive or diffuse disease that only palliative irradiation was given, and 194 patients were treated with curative intent and form the basis of this report. All patients treated with radical irradiation received greater than or equal to 4500 rad, and 65% of the patients received boost therapy through reduced fields. Thirty-two percent of patients were treated only to a single recurrent site, 11% of two sites, and 57% to the chest wall and regional nodes. Failure to control recurrent disease within or on the border of the irradiated field occurred in 27% of patients. Of 62 patients treated to the local recurrence site, 27% had further recurrences in adjacent unirradiated sites. The patients with the greatest success for tumor control (78%) and survival at 5 years (48% disease-free) are those patients with histologically negative nodes at time of mastectomy and a single chest wall recurrence. Possible prognostic factors are discussed: initial clinical stage, age of the patient, axillary histology at the time of mastectomy, disease-free interval between mastectomy and recurrence, number and size of recurrences, and prior chest wall recurrence.

Female↗
PubMed1985

Cloning and expression of the human erythropoietin gene.

The human erythropoietin gene has been isolated from a genomic phage library by using mixed 20-mer and 17-mer oligonucleotide probes. The entire coding region of the gene is contained in a 5.4-kilobase HindIII-BamHI fragment. The gene contains four intervening sequences (1562 base pairs) and five exons (582 base pairs). It encodes a 27-amino acid signal peptide and a 166-amino acid mature protein with a calculated Mr of 18,399. The erythropoietin gene, when introduced into Chinese hamster ovary cells, produces erythropoietin that is biologically active in vitro and in vivo.

Amino Acid Sequence↗
PubMed1984

Secretion of foreign proteins from Saccharomyces cerevisiae directed by alpha-factor gene fusions.

Fusions between the cloned yeast alpha-factor structural gene and chemically synthesized DNA segments encoding human protein analogs have been constructed. The gene fusions encode hybrid proteins that include the first 89 amino acids of the native alpha-factor precursor fused to either a small (beta-endorphin, 31 amino acids) or large (alpha-interferon, 166 amino acids) foreign protein. Proteolytic cleavage sites involved in alpha-factor maturation from the native precursor immediately precede the foreign peptide in the hybrid protein. The alpha-factor promoter was utilized to express the gene fusions in Saccharomyces cerevisiae and resulted in the efficient secretion of the foreign proteins into the culture medium. The processing of the hybrid proteins has been characterized by amino acid sequence analysis of the secreted proteins. The proteolytic cleavages involved in the maturation of alpha-factor peptides from the native precursor also occur accurately in the hybrid protein. In addition, cleavages occurred on the carboxyl side of two lysines within the beta-endorphin peptide. Internal cleavages in the interferon protein were also detected. However, in this case, the cleavages occurred at a very low frequency such that greater than 95% of the secreted interferon remained intact.

Amino Acid Sequence↗
PubMed1982

A mercury-thiol affinity system for rapid generation of overlapping labeled DNA fragments for DNA sequencing.

We describe an in vitro protocol for quickly generating overlapping terminal-labeled restriction fragments for DNA sequence analysis via the Maxam-Gilbert technique. The protocol involves introducing mercurated nucleotides into one end of a region to be sequenced, partial digestion with several restriction enzymes and terminal-labeling, separation of the mercurated restriction enzymes and terminal-labeling, separation of the mercurated restriction fragments from non-mercurated ones on a thiol column and resolution of the different mercurated fragments on one preparative agarose gel. The protocol was used to determine the nucleotide sequence of a 980 base pair cDNA that contains the coding region for a variable surface glycoprotein of Trypanosoma brucei. It could just as quickly and easily be used to obtain many terminal-labeled overlapping restriction fragments covering a region of several kilobases.

Animals↗
PubMed1980

Sequences of two kinetoplast DNA minicircles of Tryptanosoma brucei.

Kinetoplast DNA of Trypanosoma brucei is composed of a network of about 10,000 interlocked minicircle DNA molecules (1.0 kilobase) that are catenated with about 50 maxicircle DNA molecules (23 kilobases). Several different DNA . DNA hybridization techniques using individual minicircle DNA sequences cloned in Escherichia coli have indicated that each minicircle molecule contains about one-fourth of its sequence in common with most other minicircles and the remaining three-fourths in common with about 1 out of every 300 minicircles. We have determined the complete sequence of two cloned minicircle DNA molecules that were released from the total kinetoplast DNA network by different restriction enzymes; one minicircle is 1004 base pairs long, the other is 983 base pairs. Both are about 72% dA + dT. They share about 27% of their sequences; the largest continuous region in common is 122 base pairs of near-perfect homology. Twelve other regions of perfect homology equal to or greater than 10 base pairs are also present. Both sequences contain a large number of translation termination codons in all potential translation reading frames. The largest oligopeptide potentially specified by one minicircle sequence is 52 amino acids; the largest by the other minicircle sequence is 71 amino acids. One minicircle contains a decanucleotide sequence that is repeated in tandem five times. It is proposed that massive recombination among the interlocked minicircles in the kinetoplast DNA network may account for much of the homology observed in the two minicirce sequences.

Base Sequence↗
PubMed1975

Cerebroside sulfatase activity in cultivated human skin fibroblasts and amniotic fluid cells;.

In an effort to improve the precision in prenatal monitoring for metachromatic leukodystrophy, levels of cerebroside sulfatase were determined in fibroblasts and amniotic fluid cells. Cells from MLD patients demonstrated no significant sulfatide hydrolysis, whereas cultures from heterozygous subjects hydrolyzed diminished but definite amounts of sulfatide. Cells from a fetus with low arylsulfatase A activity were able to cleave considerable amounts of sulfatide; enzyme assays performed postnatally suggest that the infant is heterozygous for MLD. This report documents the value of cerebroside sulfatase assays in the in utero monitoring for MLD.

Amniotic Fluid↗