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P J DeVries

Publications and source records attributed to P J DeVries.

5 recordsLinked to original sources
PubMed2000

Expression, purification, and characterization of human recombinant thrombopoietin in Chinese hamster ovary cells.

Thrombopoietin (TPO) is a primary regulator of megakaryocytopoiesis, a process through which megakaryocytes proliferate and mature into platelets. Recombinant human TPO (rhTPO) was expressed in Chinese hamster ovary (CHO) cells and purified from the culture medium. The cDNA encoding full-length TPO, including the native signal peptide sequence, was amplified by PCR from a human fetal liver cDNA library. The product was cloned into a mammalian expression vector under the control of the SV40 early promoter and enhancer. Secreted rhTPO was purified in three conventional chromatography steps. It migrates on SDS-PAGE as a broad band, characteristic of a heavily glycosylated protein, with an average molecular mass of 85 kDa. rhTPO expressed in CHO cells is biologically active in vitro as demonstrated by its ability to stimulate the proliferation of a megakaryocytic cell line and to trigger the JAK/STAT signal transduction pathway. rhTPO also shows activity in vivo as judged by the elevation of platelet count in treated mice.

Animals↗
PubMed1993

Three-color immunofluorescence imaging of Drosophila embryos by laser scanning confocal microscopy.

We present a simple means for triple-labeling biological specimens by immunofluorescence using a laser scanning confocal microscope for imaging with a krypton/argon laser as a light source. Three separate images of fluorescein-, lissamine rhodamine- and cyanine-5-labeled antibodies are collected and subsequently merged to form the triple-labeled image, which is displayed at full-image resolution (24 bit) on a second image processing system. The technique is illustrated using immunofluorescence localization of three segmentation proteins in Drosophila embryos.

Animals↗
PubMed1986

Site specificity of DNA methylation and expression of herpes simplex thymidine kinase gene.

Analysis of the methylation pattern of a single-copy herpes simplex virus thymidine kinase gene integrated into the genome of mouse L cells revealed that hypomethylation of five specific AvaI sites correlates with expression of the TK gene in all of the cell lines tested. Of these specific sites, one lies 5' to the coding region, one 3' to the coding region, and three lie within the coding region of the thymidine kinase gene. Analysis of methylation at a variety of other sites using other methylation-sensitive endonucleases revealed considerable variation in the methylation patterns, apparently unrelated to gene expression and subject to variation with time in culture.

Animals↗
PubMed1984

Ultraviolet-induced reactivation, amplification, and hypomethylation of a herpes simplex virus thymidine kinase gene.

A line of mouse cells containing a methylated inactive herpes simplex virus thymidine kinase (TK) gene was irradiated with ultraviolet (UV) light in an attempt to induce expression of the inactive TK gene. UV irradiation was shown to be capable of inducing expression of the viral TK gene in a dose-dependent manner. Analysis of the methylation pattern of the viral TK gene indicated that the active TK gene in three UV-induced TK+ cell line was methylated to a lesser extent than was the inactive viral TK gene in the parental cells. Analysis of the copy number of the viral TK gene in parental and UV-induced cell lines also revealed that the viral TK gene was amplified 3- to 20-fold in three of four UV-induced TK+ cell lines tested.

Gene Amplification↗