Induction and inhibition of Friend erythroleukemia cell differentiation by pyrimidine analogs: analysis of the requirement for intracellular accumulation and incorporation into DNA.

Alkyldeoxyuridines which differ from thymidine by a C5 substitution of straight or branched alkyl chains of two to six carbon atoms have been tested for their ability to be taken up, phosphorylated, and incorporated into DNA. Analysis of the uptake of 5-ethyl-2'-deoxyuridine and 5-propyl-2'-deoxyuridine (n-PrdU)--similar to both thymidine and 5-bromo-2'-deoxyuridine--indicates that transport is dependent upon a functional cellular thymidine kinase. All of the aforementioned pyrimidines with the exception of n-PrdU are phosphorylated to the triphosphate and incorporated into DNA. The homologs 5-iso-propyl-2'-deoxyuridine (iso-PrdU) and 5-hexyl-2'-deoxyuridine are neither transported into the cell, phosphorylated, nor incorporated into DNA. These analogs were tested (i) for their ability to induce in the absence of dimethyl sulfoxide and (ii) to determine whether they enhance or inhibit dimethyl sulfoxide-induced differentiation of Friend erythroleukemia cells. Inhibition of erythroid differentiation appears to require the incorporation of thymidine analogs into DNA, and thus only 5-ethyl-2'-deoxyuridine and 5-bromo-2'-deoxyuridine were effective in inhibiting dimethyl sulfoxide-induced differentiation. The observation that iso-PrdU, and to a lesser extent n-PrdU and 5-propyldeoxyuridine monophosphate, induce differentiation under conditions in which they are not detectable intracellularly is strong evidence that this class of inducer acts at the cell membrane.

[Concentration dependent effect of 5-ethyl-2'-deoxyuridine on experimental and clinical herpetic keratitis (author's transl)]. / Konzentrationsabhängige Wirksamkeit von 5 Athyl-2-desoxyuridin (ADU) bei herpetischen Keratitiden im Tierexperiment und in der Klinik.

Concentration dependent effect of 5-ethyl-2'-deoxyuridine (EDU) on epithelial regeneration and on herpes keratitis in rabbit has been studied. Successfull completion of the experimental studies was followed by clinical treatment of 10 otherwise therapy resistent metaherpetic cases using 2% EDU eye drops and 0,5% subconjunctival injections. With nine patients under this therapy improvement and healing of the corneal processes was achieved.

Effect of hCG on protein synthesis and progesterone production in the bovine luteal cells.

The study was carried out to investigate whether the luteal steroidogenesis in response to tropic stimulus is mediated through de novo synthesis of protein(s). Luteal cell suspension was prepared by collagenase-DNAse treatment of the bovine corpora lutea, weighing 4-6 g. Cells equivalent to 250 micrograms of protein were incubated in a total volume of 550 microliter of medium 199 with or without various test substances. Production of progesterone by the luteal cells was stimulated by hCG in a dose dependent manner. Incorporation of 3H-leucine into the cellular proteins was concomitantly enhanced. Emetine, cycloheximide and puromycin inhibited both basal and hCG stimulated protein synthesis as well as progesterone production in the cells. Thus, luteal steroidogenesis induced by hCG seems to be dependent upon de novo synthesis of a protein(s).

Differential substrate specificity of DNA polymerase beta and of a DNA polymerase induced by herpes simplex virus type 2 towards thymidine triphosphate analogues.

Several triphosphates of 5-substituted deoxyuridine (dU), such as 5-ethyl-, 5-n-propyl-, 5-n-hexyl- and 5-isopropyldeoxyuridine triphosphates and 5-trifluorothymidine triphosphate are substrates for HeLa cell DNA polymerase beta (2'-deoxynucleoside-5'-triphosphate:DNA-deoxynucleotidyltransferase, EC 2.7.7.7) and for a DNA polymerase isolated from HeLa cells infected with herpes simplex virus type 2 (HSV-2) strain 75. At the concentration tested (50 microM), all these analogues were incorporated more readily into DNA by the virus-coded enzyme than by DNA polymerase beta from the host cell. The DNA polymerase coded by HSV-2 showed an affinity for deoxythymidine triphosphate (dTTP) and the analogues studied higher than that of DNA polymerase beta. Analogues are preferential substrates for the viral enzyme, since they readily substitute for dTTP during synthesis in vitro. In contrast, arabinosylthymine-5'-triphosphate was readily incorporated into DNA by the host cell DNA polymerase beta, but inhibited the DNA polymerase specified by HSV-2.

[Studies with azlocillin, mezlocillin, penicillin-g-potassium and sisomicin on tolerance in the cornea and the kinetics of inhibiting concentrations in the cornea and aqueous humor in rabbits]. / Untersuchungen zur Verträglichkeit an der Cornea und zur Kinetik von Hemmstoffkonzentrationen in Hornhaut und Kammerwasser des Kaninchens mit den Antibiotika Azlocillin, Mezlocillin, Penicillin G-Kalium und Sisomicin.

We studied the effect of azlocillin, mezlocillin and sisomicin in concentrations of 1, 2.5 and 5% on the regeneration of stromal corneal wounds in rabbits following subconjunctival injections and treatment with eye drops. Concentrations of the antibiotics were also determined in corneal tissue and in aqueous humor and compared with that of penicillin G-potassium. Together with azlocillin, sisomicin proved to be the most effective and the safest. Mezlocillin only inhibited wound regeneration slightly and thus mezlocillin appears to be inferior to the other two antibiotics investigated in the local treatment of the eye.

Differential incorporation of thymidylate analogues into DNA by DNA polymerase alpha and by DNA polymerases specified by two herpes simplex viruses.

Several triphosphates (TP) of 5-substituted deoxyuridine (dU), like 5-ethyl (Et), 5-n-propyl (n-Pr), 5-iso-propyl (iso-Pr), 5-n-hexyl (n-Hx), and 5-trifluorothymidine (F3-dT) were used as substrates for HeLa DNA polymerase alpha and for two herpes simplex virus (HSV)-coded DNA polymerases isolated from HeLa cells infected with HSV-1, strain C42 (wild-type), or its mutant resistant to phosphonoformate (PFAr). All polymerases were purified up to the DNA-cellulose column step and they showed comparable specific activities. The incorporation into DNA studied with all the alkyl analogues of dUTP is several times higher with the virus enzymes than with DNA polymerase alpha. The DNA polymerase of the mutant virus incorporates dUTP analogues to a lower extent than the wild-type polymerase. The two virus enzymes also differ in the Km and Vmax values for different substrates, indicating that the mutation to PFAr has affected the structure of the virus DNA polymerase. Surprisingly, all three enzymes use F3-dTTP as substrate for DNA synthesis to an equal but limited extent.