ABSTRACT
NCB-20 neurohybridoma cells were exposed to isomers of hexachlorocyclohexane (HCH) for periods of time ranging from 5-45 min, and intracellular free calcium [Ca++]i levels were determined using the INDO1/AM method. Exposure to lindane (gamma HCH) produced a dose-dependent increase in [Ca++]i, significant increases being observed with exposures from 10-400 microM. During exposure, [Ca++]i increased to a peak and then declined over the next 45 min. After 45 min levels were still elevated above control levels. This action of the gamma isomer of HCH was shared by the alpha and beta isomers. The potencies of the isomers were alpha (0.5), beta (0.75) and gamma (1.0). The effects of HCH isomers on [Ca++]i in neurohybridoma cells are similar to those reported for the isomers using rat brain synaptosomes. The ability of lindane to increase [Ca++]i may explain the previously reported ability of lindane to increase spontaneous and evoked (under low quantal release conditions) release of transmitter from frog neuromuscular junction. The relevance of this effect to mammalian CNS hyperexcitability, however, remains unsettled. These effects occur at concentrations of lindane higher than those effective in antagonizing GABA-mediated inhibition, and they lack the specificity shown by the isomers under other circumstances.
Subject(s)
Calcium/metabolism , Hexachlorocyclohexane/pharmacology , Neurons/metabolism , Tumor Cells, Cultured/metabolism , Cell Line , Neurons/cytology , Neurons/drug effects , Stereoisomerism , Tumor Cells, Cultured/drug effectsSubject(s)
DNA , Polyribonucleotides , Terbium , Animals , Cattle , DNA, Single-Stranded , Energy Transfer , Guanosine Monophosphate , Structure-Activity Relationship , Thymus GlandABSTRACT
The induction of variants of L5178Y mouse-lymphoma cells resistant to 1-beta-D-arabinofuranosylcytosine (ara-C) has been investigated. The spontaneous mutation frequency was low, around 3 X 10(-8). Resistant variants were induced in a dose-dependent fashion following treatment with ethyl methanesulphonate (EMS), ethidium bromide and 2-acetylaminofluorene, but not with gamma-irradiation. With EMS as mutagen the frequency of ara-C-resistant variants was much lower than that obtained using other selective agents, whereas it was higher with the mutagens acetylaminofluorene and ethidium bromide. Out of 42 resistant clones examined, 38 showed normal sensitivity to thymidine and were destignated as Class 1, the remaining four (Class 2) were usually resistant to thymidine. Cells in Class 1 did not accumulate detectable amounts of ara-C and had negligible deoxycytidine kinase activity. They were about 3000-fold more resistant to the toxic effects of ara-C than were wild-type cells. Cells in Class 2 had a reduced ability to accumulate are-C and had 50% of the deoxycytidine kinase activity of wild-type cells. They were only 20 times more resistant to ara-c than were wild-type cells. The enzymatic defect in these cells is obscure but the phenotypic properties probably result from subtle alterations in the pool of deoxycytidine nucleotides.
Subject(s)
Cytarabine/pharmacology , Drug Resistance , Leukemia L5178/genetics , Leukemia, Experimental/genetics , Mutation , 2-Acetylaminofluorene/pharmacology , Animals , Cell Line , Ethidium/pharmacology , Ethyl Methanesulfonate/pharmacology , Mice , Mutagens , Thymidine/pharmacologyABSTRACT
Evidence that the fluorophore sempervirene binds to nucleic acids is presented. The complexes were studied by fluorescence intensity, spectra, decay lifetime, and polarization methods. Both fluorescent and nonfluorescent complexes are formed. The sempervirene is rigidly fixed to DNA. If ethidium bromide and sempervirene are bound to DNA, energy can be transferred from sempervirene to ethidium. Sempervirene is taken up by mammalian cells and appears in the cytoplasm. This unusual new probe should be useful in molecular and cellular investigations.
Subject(s)
DNA , Secologanin Tryptamine Alkaloids , Animals , Binding Sites , Bone Marrow Cells , Cattle , Cell Line , Cricetinae , Edetic Acid , Ethidium , Kidney , Mathematics , Microscopy, Fluorescence , Microscopy, Polarization , Nucleic Acid Conformation , Sodium Chloride , Spectrometry, Fluorescence , Time FactorsSubject(s)
Kidney/metabolism , Phenanthridines/metabolism , Saccharomyces cerevisiae/metabolism , Animals , Bone Marrow/metabolism , Bone Marrow Cells , Cattle , Cell Membrane/metabolism , Culture Techniques , Ethidium/metabolism , RNA/metabolism , RNA, Ribosomal/metabolism , Ribosomes/metabolism , Spectrometry, FluorescenceSubject(s)
DNA , Phenanthridines , RNA, Ribosomal , RNA, Transfer , Animals , Cattle , Chemical Phenomena , Chemistry , Fluorometry , Kinetics , Liver , Mathematics , Optical Rotation , Saccharomyces , Serum Albumin, Bovine , Sodium Chloride , Sucrose , Temperature , Thymus Gland , ViscositySubject(s)
Euglena , Saccharomyces , Viscosity , Fluoresceins/metabolism , Fluorescence , Fluorometry , Methods , TemperatureSubject(s)
Adenosine Triphosphate , Saccharomyces/enzymology , Transferases/antagonists & inhibitors , Adenosine Triphosphate/antagonists & inhibitors , Bicarbonates , Binding Sites , Cell-Free System , Centrifugation , Chemical Phenomena , Chemical Precipitation , Chemistry , Culture Media , Drug Synergism , Glutamine , Hot Temperature , Methods , Mutation , Phosphotransferases , Quaternary Ammonium Compounds , Time Factors , Transferases/isolation & purification , Uracil NucleotidesSubject(s)
DNA , Phenanthridines , RNA , Animals , Cattle , Chemical Phenomena , Chemistry , Electrochemistry , Energy Transfer , Fluorescence , Fluorometry , Male , Oscillometry , Radiation Effects , Salmonidae , Spermatozoa , Thymus Gland , Time Factors , Ultraviolet RaysABSTRACT
The control of pyrimidine biosynthesis in a yeast mutant deficient for uracil, adenine, and histidine has been studied in vivo. The uracil mutation causes accumulation of ureidosuccinic acid and dihydroorotic acid in the cells. Accumulation is prevented when the pyrimidine nucleotide level in the cell is raised, apparently owing to feedback inhibition in the pyrimidine system. Investigation of the coupling of purine and pyrimidine systems shows that a high level of purine nucleotides can reverse inhibition in the pyrimidine internal feedback loop. Under certan conditions this reversal may affect only the first step of the pyrimidine system so that ureidosuccinic acid is synthesized and the next element of the pyrimidine pathway, dihydroorotic acid, is not synthesized. Other aspects of coupling between the pyrimidine system and other systems are presented.
