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Biomedical subjects

D L Slate

Publications and source records attributed to D L Slate.

34 records · Page 2Linked to original sources
PubMed1981

S phase-specific synthesis of dihydrofolate reductase in Chinese hamster ovary cells.

We investigated the cell cycle modulation of dihydrofolate reductase (DHFR; tetrahydrofolate dehydrogenase, 7,8-dihydroxyfolate:NADP+ oxidoreductase, EC 1.5.1.3) levels in methotrexate-resistant Chinese hamster ovary cells synchronized by mitotic selection. DNA content and DHFR concentration were analyzed throughout the cell cycle by standard biochemical techniques and by double fluorescence staining utilizing the fluorescence-activated cell sorter. We found an S phase-specific period of DHFR biosynthetic activity. Commencing within hour 2 of S phase and continuing throughout the duration of S phase, there is a 90% increase in DHFR specific activity. This results from an approximately 2.5-fold increase in the level of DHFR, while total soluble protein increases 50% during the same period. This increase is the result of new synthesis of DHFR molecules initiated after the cell is physiologically committed to DNA replication. This increase in DHFR activity through S phage parallels the increasing rate of [3H]thymidine incorporation during the same interval. The maximum peak of DHFR activity is coincident with the maximum rate of DNA synthesis, both activities occurring during the bulk of DNA replication within the last stages of the 6.5-hr S phase.

Animals↗
PubMed1980

Assignment of the murine interferon sensitivity and cytoplasmic superoxide dismutase genes to chromosome 16.

Both hybrids of mouse and human microcells and whole cell hybrids generated by the fusion of primary mouse cells and SV40-transformed human fibroblasts were used to establish the syntenic association of the murine cytoplasmic superoxide dismutase and the interferon sensitivity genes on mouse chromosome 16. This assignment adds two new markers to chromosome 16 and provides another example of an evolutionarily conserved linkage. This finding also provides an animal model both for cellular responsiveness to interferon and for Down's syndrome.

Animals↗
PubMed1979

Fibroblast interferon in man is coded by two loci on separate chromosomes.

We have examined viral and poly(rl):poly(rC) induction of interferon synthesis in several human, mouse and Chinese hamster cell lines, and in hybrids derived from the fusion of such cells. We observed species and cell-type differences in inducer effectiveness and in the kinetics of interferon production. In some cases, parental characteristics are preserved in somatic cell hybrids, and in other cases, the expression of the donor phenotype is modulated by the epigenetic state of the recipient cell. Mapping studies in human/mouse and human/Chinese hamster hybrids indicate that there are at least two structural genes for human fibroblast interferon. Chromosomes 2 and 5 each contain genetic information for the synthesis of fibroblast interferon. Gene dosage experiments indicate that one gene is on the long arm of chromosome 2 and another is on the short arm of chromosome 5. Leukocyte interferon genes could not be mapped to these chromosomes, but this negative result could be influenced by the epigenetic state of the hybrid cells.

Cell Line↗
PubMed1979

Biological detection of specific mRNA molecules by microinjection.

We have used direct microinjection of messenger RNA into individual mouse and human cells to assay for specific translation products. We have been able to detect the synthesis of human fibroblast interferon, thymidine, kinase, hypoxanthine phosphoribosyltransferase, adenine phosphoribosyltransferase, and propionyl-CoA carboxylase in response to injected mRNA. Using the interferon system as a model, we have quantitated interferon synthesis and followed partial purification of interferon mRNA sequences on sucrose density gradients. The methods we have utilized should be applicable to other systems in which sensitive assays exist for gene products and should provide a screening procedure for isolating specific mRNA sequences.

Adenine Phosphoribosyltransferase↗
PubMed1978

Presence of human chromosome 21 alone is sufficient for hybrid cell sensitivity to human interferon.

Human/mouse somatic cell hybrids with chromosome 21 as the only detectable human genetic material were sensitive to both human leukocyte and fibroblast interferons. The presence of additional human chromosomes decreased the amount of interferon needed to attain a given level of virus resistance. Decreased cytopathic effects, decreased virus yields, and the appearance of a specific phosphorylated protein associated with interferon treatment were all observed in hybrids maintaining only human chromosome 21. The phosphorylated protein found in extracts of these human interferon-treated hybrid cells was of mouse origin.

Animals↗
PubMedDate not supplied

Intracellular expression of P-glycoprotein in a human colon tumor cell line.

A number of human tumor cell lines originating in tissues which normally express high levels of P-glycoprotein were examined for the expression of mdr-1 RNA and P-glycoprotein and their sensitivity to doxorubicin and vincristine. There was a wide variation in expression levels and in drug sensitivity among the cell lines. In the human colon tumor cell line, LS 174T, high levels of P-glycoprotein and mdr-1 RNA were observed, but this line was very sensitive to doxorubicin and vincristine. Immunoprecipitation of P-glycoprotein from preparations of membrane and cytoplasmic proteins and immunofluorescence studies using anti-P-glycoprotein antibodies revealed that P-glycoprotein in these cells is not associated with the plasma membrane, but is, instead, found intracellularly. These results emphasize the need for functional analysis of P-glycoprotein in cells that express this mediator of multidrug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

RS-33295-198: a novel, potent modulator of P-glycoprotein-mediated multidrug resistance.

A novel multidrug resistance modulator, RS-33295-198, circumvented drug resistance in human, mouse, and Chinese hamster cell lines overexpressing P-glycoprotein. It enhanced the antiproliferative activity of doxorubicin, vincristine, etoposide, and paclitaxel and increased doxorubicin retention in multidrug-resistant hamster CHRC5 cells. RS-33295-198 modulated doxorubicin resistance in a murine P388/ADR leukemia model when administered ip via continuous minipump delivery, ip by bolus injection, and orally; it also improved the efficacy of vincristine toward P388/VCR leukemia when given ip or po. RS-33295-198 showed weak activity in enhancing doxorubicin efficacy against a multidrug-resistant human sarcoma xenograft.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Modulation of doxorubicin efficacy in P388 leukemia following co-administration of verapamil in mini-osmotic pumps.

Co-administration of doxorubicin and verapamil in Alzet mini-osmotic pumps increased the survival of B6D2F1 mice bearing the multidrug-resistant P388/ADR leukemia. A range of doxorubicin and verapamil combinations was studied to define dose-dependent efficacy and toxicity. High doses of doxorubicin (10 mg/kg/day) and verapamil (150 mg/kg/day) could be administered alone without any effect on survival. However, combining high doses of these two agents resulted in host toxicity. Doxorubicin doses of 1 to 10 mg/kg/day in combination with verapamil at 25-100 mg/kg/day were found to improve survival compared with either agent alone. Combination therapy also improved the survival of mice bearing the drug-sensitive P388/0 leukemia when compared to anthracycline treatment alone. The efficacy of the mini-osmotic pump delivery protocol was compared with other regimens delivering the same total cumulative dose of doxorubicin via repeated i.p. injections.

Animals↗