Robert T. Schimke

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The rate of dihydrofolate reductase synthesis in the AT3000 line of methotrexate-resistant murine Sarcoma 180 cells is approximately 200to 250-fold greater than that of the sensitive, parental line. We have purified cDNA sequences complementary to dihydrofolate reductase mRNA and subsequently used this probe to quantitate dihydrofolate reductase mRNA and(More)
nate; DEAE, diethylainiiioethyl; DPN, TPN, diand triphosphopyridine mincleotides; ATP, adenosine triphosphate; red, reduced; ox, oxidized. * Aided by grants to Daniel I. Arnoii from the USPHS, the Office of Naval Research, and the Charles F. Kettering Foundation. 1 Bachofen, R., B. B. Buchanan, and 1). I. Arnon, these PROCEEDINGS, 51, 690 (1964). 2(More)
This paper reports that there are major differences between mammalian cell lines in the propensity to progress into subsequent cell cycles when mitosis is inhibited with agents that disrupt the assembly of the mitotic spindle apparatus (Colcemid, nocodazole, and taxol). Human HeLa S3 cells, which represent one extreme, remain arrested in mitosis, with(More)
Methotrexate-resistant Leishmania tropica contain two separate regions of DNA amplification, one encoding the bifunctional thymidylate synthetase-dihydrofolate reductase (TS-DHFR) characteristic of protozoans and the other of yet unknown function. The amplified DNAs are initially found as extrachromosomal closed circular forms, which are unstable in the(More)
The response of the mammal to varying dietary protein intake under conditions in which amino acid and energy requirements are adequately satisfied is a form of adaptation involving the utilization of varying proportions of carbohydrate and amino acids as sources of energy, and is therefore analogous to the adaptation seen in bacteria on change in form of(More)
We have investigated whether reporter genes influence cytoplasmic regulation of gene expression in tobacco and Chinese hamster ovary (CHO) cells. Two genes, uidA encoding β-glucuronidase (GUS) from Eseherichia coli and Luc, encoding firefly luciferase (LUC), were used to analyze the ability of a cap, polyadenylated tail, and the 5′- and 3′-untranslated(More)
Leishmania tropica promastigotes that are highly resistant to methotrexate, a dihydrofolate reductase inhibitor, have been developed. Organisms resistant to 1 mM methotrexate have a 40-fold increase in dihydrofolate reductase which is associated with thymidylate synthetase, and they contain amplified regions of DNA that may be directly visualized on stained(More)
Using multiparameter flow cytometric analysis, we find that senescent cells accumulate in a unique cell-cycle compartment characterized in cell-cycle arrest in G1 and a significantly reduced nucleocytoplasmic ratio (genome size/cell mass) relative to cycling cells. With respect to gross cellular phenotype, the quiescent state of senescent cells differs from(More)