The mutagenic potency of 1,8-dinitropyrene in cultured mouse lymphoma cells

Although non-toxic, 1,8-dinitropyrene (1,8-DNP) was mutagenic for mouse lymphoma L5178Y cells when assayed for induced resistance to 6-thioguanine, methotrexate, ouabain and 1-β-D-arabinofuranosyl cytosine. In bacteria, nitropyrenes are potent inducers of frame-shift mutations, and the induction of ouabain-resistant mutants, believed to be due to base-pair substitutions, suggests that the mechanism of action may be different in mouse cells and bacteria. Long treatment times were required to detect 1,8-DNP-induced mutants in L5178Y cells, suggesting the possibility of an inducible activation system. 4-Nitroquinoline 1-oxide was both toxic and mutagenic to these same 4 mutation assays after short (2 h) treatment times. The dilemma that exists when comparing the mutagenic potential of test chemicals when concentration of mutagen, treatment times and toxicity are markedly different, is discussed.     

Occurrence of resistance to neomycin and kanamycin in Bacillus popilliae and certain serotypes of Bacillus thuringiensis: Mutation potential in sensitive strains

Serotypes of Bacillus thuringiensis and the commercial strain of Bacillus popilliae were examined for their inherent resistance to antibiotics and their mutation potential in respect to neomycin and kanamycin, the presence of which would preclude the use of plasmids marked by genes for resistance to the antibiotics. Clones on initial plates were detected by the recurrence of resistance colonies at superimposable sites on serial replicaplates containing the antibiotic. Susceptible strains were selected for the determination of their antibiotic-resistance mutation potential. Three varieties of B. thuringiensis were found to be doubly resistant, seven varieties were singly resistant (Neo^r), and three other varieties, including B. popilliae, were susceptible to both antibiotics. Estimates of mutation ratios revealed that three serotypes developed no resistant mutants to either antibiotics in populations as high as 3.0 × 10¹⁰; seven other serotypes developed no resistance to kanamycin in populations as high as 4.6 × 10⁹ cells. Three other serotypes exhibited mutation ratios as high as 1.6 × 10^?2. We were unable to determine the mutation ratio for B. popilliae.     

Was globin evolution very rapid in its early stages?: A dubious case against the rate-constancy hypothesis

Summary Goodman et al's (1975) claim of accelerated evolution in the early stages of globin evolution is based on an erroneous assignment of the time of divergence of vertebrate myoglobin and hemoglobin. When this is corrected, there is no basis for their claim. The data are much more consistent with the nearly constant rate expected on the neutral mutation-random drift hypothesis than with the uneven rates expected if most amino acid changes were caused by substitution of favorable mutants through Darwinian selection. In addition, the majority of the codons determined by their maximum parsimony method have turned out to be wrong when compared to the actual nucleotide sequences of rabbit and human hemoglobins determined by direct sequencing.Contribution No. 1314 from the National Institute of Genetics, Mishima, 411 Japan.     

Isolation of recombinant plasmids and phage carrying the lexA gene of Escherichia coli K-12

The lexA gene of Escherichia coli K-12 was cloned from the plasmid pLC44-14 into pBR322. Plasmids carrying lexA+ were selected by their ability to complement a recessive tsl mutation, which is believed to be a mutation in lexA. The smallest lexA+ recombinant plasmid, pJL21, contained an EcoRI-PstI fragment 2.9 kilobases (kb) in length; two larger plasmids also contained this fragment, and genetic material to one or both sides of the EcoRI-PstI fragment. Plasmids homologous to pJL21, but carrying a dominant mutation, lexA3, or one of three recessive amber mutations in lexA, termed spr, were also isolated. To clone the EcoRI-PstI fragment onto a lambda vector, the PstI end was first converted to an EcoRI end by attachment of a 100-base pair PstI-EcoRI fragment isolated from the plasmid ColE1; the resultant EcoRI fragment was then cloned into the lambda vector lambda gt4. A restriction map of pLC44-14 was obtained for nine restriction enzymes. The orientation of this map was determined relative to the E. coli genetic map by complementation of the gene ubiA+ and by comparison with restriction enzyme digests of another plasmid, pLC11-9, which carries dnaB, a gene closely linked to lexA, but does not carry lexA.     

Induction,ultrastructure, isolation,and tissue culture of chlorophyll mutants in carrot

Summary Seeds ofDaucus carota “Danvers” were treated with ethyl methanesulfonate (EMS) for 6-hr periods at concentrations of 0.01, 0.03, 0.1, 0.3, 1.0, and 3.0% to induce plastid mutants. In these treatments, there was a gradual decrease in percent germination from control up to 1.0% EMS and no germinations at 3.0%. The number of chlorophyll mutants increased with dose of mutagen. One mutant plant was isolated from the 0.1% treatment and it had leaf sections of green, white layered on green and pure white; and white and green striped petioles. Histogenic analysis of this mutant showed it to be a GGW chimera, the “all-white” sectors being GWW, arising from displacement of L-II by L-III. Electron micrographs of the white sections showed plastids that had dilated thylakoids typical of PS-I mutants. So called “mixed cells” of normal and mutant plastids were found, suggesting a plastome mutation. Leaf and petiole sections have been successfully cultured through the development of callus, and both green and white plants have been regenerated. Regenerated white plantlets were insensitive to 10 mM methyl viologen (paraquat), whereas green tissues were killed by the herbicide. Support for some of this work was provided by the Miami University Faculty Research Committee and the Comprehensive Employment and Training Act (CETA). This paper will be included as part of the dissertation work of P. D. Miller.     

Effects of metabolic inhibitors on cell lethality and mutation induction in Chinese hamster cells. I. Inhibitors of de novo purine synthesis and a comparison with the effects of caffeine

The effect of pre- and posttreatment incubation of UV-irradiated and ethyl methanesulphonate (EMS) treated cells with non-toxic concentrations of inhibitors of de novo purine synthesis (dnPS) on expression of potentially lethal and premutational damage at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V79 cells has been examined. The concentrations of inhibitors used were shown to profoundly perturb de novo DNA synthesis, by measurements of [¹⁴C]formate uptake, and cell cycle progression by flow cytofluorimetry. Postincubation in 6-methyl mercaptopurine ribonucleoside (MMPR) usually but not invariably potentiated the cytotoxic effects of UV and EMS but azaserine (AZS) and methotrexate (MTX) were without effect. No effects on mutant frequencies were observed on posttreatment with any of these agents. Caffeine produced the least effect on dnPS, but invariably potentiated lethal damage. This potentiation of lethal damage is not mediated by dnPS inhibition as has been suggested for Chinese hamster ovary (CHO) cells.     

L'âge du complexe récifal des côtes de meuse entre verdun et commercy et la stratigraphie de l'oxfordien dans l'est du bassin de Paris

The question of the age of «Hauts de Meuse coral rag is studied again using new faunas of brachiopods and ammonites collected above, below and inside the coral rag. Ammonites fauna of the well known «Calcaires de Creuë is revised. Results obtained agree closely.The «Hauts de Meuse coral rag grew up during Middle Oxfordian time; and extend part of the Plicatilis zone (Antecedens Subzone) and the whole Transversarium Zone up to the basis of the Bifurcatus Zone, for the first time identified in Lorraine. So it span a short depositional time, about 1 MY, with a high deposition rate, the thickness of the coral rag being more than 100 meters, reaching 150 meters in Saint-Mihiel area. Towards SE, on the other side of the Marne Gap, the sudden change into basinal facies go with a reducing of thickness and deposition rate.Upper Oxfordian deposits show a relative uniformity of facies and thickness. At the top of Middle Oxfordian limestones, the age of the discontinuity and the Sequanian renewal of deposition is basal Bifurcatus Zone. Erosional renewal and terrigeneous deposits are a wide spread event by the beginning of Upper Oxfordian.In the paleontological part, species upon which are based new ages and interpretations are only figured, except the species new or with new paleontological data, which are described. Type specimen of Perisphinctes mosensisBayle, from the «Calcaires de Creuë, is described and photographically figured for the first time.     

Eine einfache methode zur erfassung der parameter von spitzwinkeligen gastropodengehäusen

The D.M. Raup & A. Michelson model of assessing shell-coiling constitutes a method which simplifies the measuring of spiral-coiling gastropod shells. With, this method the information is obtained by measuring the photograph of the object.The newly developed method has the advantage of dispensing with an exact shell orientation (horizontally located axis) and magnification.Instead of photographing the object with a camera the shell is placed upon photographic paper and in this manner a contact showing the shell outlines can be achieved by exposing and developing the print. Correct information is then obtained by means of the conversion factors (1–3) as outlined in this paper.     

Random recirculation of small T lymphocytes from thoracic duct lymph in the mouse

The migration of ⁵¹Cr-labeled nylon-wool separated mouse thoracic duct T cells has been followed in order to determine whether there is a circulation of small (nondividing) T cells through the small intestine. Approximately 6% of the injected dose of T-TDL localized in the small intestine (minus Peyer's patches). Experiments revealed that this gut-localizing cell population consisted almost entirely, if not exclusively, of lymphoblasts present in mouse T-TDL. When lymphoblasts and small lymphocytes from mouse T-TDL were separated by velocity sedimentation, and the migration of separated fractions was studied, we found large cells (66% blasts) migrated well to the gut but poorly to the lymph nodes, whereas small cells (2% blasts) showed minimal migration to the gut but localized randomly in lymph nodes and spleen. The in vivo distribution of small cells from T-TDL was similar to that of T-PLN. Furthermore, the recirculatory patterns of both ⁵¹Cr-labeled T-TDL and T-PLN were found to be identical as accessed by their rate of recovery in the thoracic duct lymph of recipient mice. These results support the notion that the vast majority of T-TDL and T-PLN are part of a common pool of recirculating T cells which recirculate randomly through lymph nodes and spleen and not the small intestine.