Changes in RNA polymerase II in a cell cycle-specific temperature-sensitive mutant of hamster cells

tsAF8 cells are a temperature-sensitive mutant of BHK cells that arrest at the nonpermissive temperature in the G₁ phase of the cell cycle. The activity of solubilized RNA polymerase II and its ability to bind [³H]-γ-amanitin decrease in tsAF8 cells at 40.6°, with a half-life of ～ 10 hr. No appreciable changes occur in these two parameters in tsAF8 cells at 34° or in BHK cells at either 34° or 40.6°. Protein synthesis is not appreciably affected for at least 24 hr after tsAF8 cells are shifted to 40.6°. These results indicate that in tsAF8 cells at the nonpermissive temperature, there is a defect in either the synthesis, the assembly, or the stability of RNA polymerase II, and that the loss of RNA polymerase II molecules is not due to widespread cellular damage.     

Determination of therapeutic and toxic concentrations of doxepin and loxapine using gas—liquid chromatography with a nitrogen-sensitive detector, and gas chromatography—mass spectrometry of loxapine

A gas—liquid chromatographic procedure is presented for the determination of therapeutic and toxic serum levels of doxepin and loxapine, using a nitrogen—phosphorus-sensitive detector. Amitriptyline is used as the internal standard. The method is accurate, sensitive and specific with no derivatization required prior to analysis. An advantage of the procedure is the small serum sample size needed for analysis and the selectivity and sensitivity of the detector, with the limit of detection being 3 and 2 μg/l for doxepin and loxapine, respectively. Nine cases of doxepin and loxapine misuse are presented. Serum doxepin concentrations ranged from 113 to 439 μg/l, with a loxapine concentration of 192 μg/l observed in one patient. The presence of the tricyclics was identified and confirmed by gas chromatography—mass spectrometry and the mass spectrum of loxapine is reported.     

On the identity of dnaP and dnaF genes of Bacillus subtilis

Summary The dnaP strains of Bacillus subtilis are altered in the initiation of DNA replication at high temperature (Riva et al., 1975). Fine mapping of the gene shows that it is located very close to the dnaF gene, described by Karamata and Gross (1970) and mapped by Love et al. (1976) in the polC region. The phenotype of both mutants is indistinguishable: the DNA synthesis stops at non permissive temperature after synthesizing an amount of DNA equivalent to the completion of the rounds of replication already initiated; at permissive temperature they are abnormally sensitive to MMS and are reduced in the ability to be transformed. Both mutants are to be considered as belonging to the dnaF locus.The dnaF gene is very close to the polC gene, which specifies the DNA polymerase III of B. subtilis. The DNA polymerase III of the dnaF mutants is not temperature sensitive in vitro, however, the level of this enzyme is lower by a factor of 4 or 5 in the dnaF mutants, at the permissive temperature. Following shift of dnaF cultures to the non permissive temperature, the level of DNA polymerase III activity specifically decreases further by a factor of at least 10 in the mutant, whereas the DNA polymerase I level is unaffected.The possible roles of the dnaF gene in the control of the cellular level of the DNA polymerase III, and the possibility of a regulatory role of DNA polymerase III in the initiation of DNA replication in bacteria are discussed.Abbreviations and symbols HPUra 6-(p-hydroxyphenylazo)-uracil; mic, minimum inhibitory concentration - MMS methyl-methanesufonate - Pol I Pol II and Pol III: DNA polymerase I, II and III respectively - PCMB parachloro-mercuri-benzoate     

The ultrastructure of the symbionts ofRhizocarpon geographicum,Parmelia conspersa andUmbilicaria pustulata growing under dryness conditions

Summary The dryness-induced ultrastructural changes of both myco- and phycobiont of three lichen species (R. geographicum, P. conspersa, andU. pustulata) have been studied over three months and half, period of time. During this time other ecological factors, such as rock substratum, temperature, light and gas interchange were unaltered compared to the natural conditions. A large number of ultrastructural changes were observed in the mycobiont as well as in the phycobiont (Trebouxia) and often, cells showed a highly disorganized morphology. The most important ultrastructural modifications were: 1. pyrenoglobuli of the algae were peripheral, 2. new and unknown structures were observed in the phycobionts of bothR. geographicum andU. pustulata as well as in the mycobiont of the latter species.     

The immune response of allophenic mice to the synthetic polymer GLΦ

The immune response of allophenic mice of type C57BL/6(A × SJL) F₁ to GL administered in complete Freund's adjuvant was tested. Control mice of the three strains C57BL/6, A, and SJL are all nonresponders to this antigen. However, the F₁ generations of C57BL/6 × A, C57BL/6 × SJL, and A × SJL were all responders to the antigen, so that the complementarity of at least two genes is confirmed. The allophenic mice showed no further complementation beyond the F₁ generation, a result which may argue against the possibility that more than two genes control the response to GL in these mouse strains. Characterization of the allophenic mice over several months showed that they exhibit chimeric drift, both in their coat color and in peripheral white blood cell population. There is no apparent correlation of coat color to the lymphocyte composition of the mice at any one time. The mice are true chimeras, since killing of the two populations of white blood cells with two different anti-H-2 sera produced a 100 percent killing. The immune response of individual allophenic mice to GL showed a good correlation to the number of A × SJL lympho-cytes in the animal.Abbreviations used in this paper are GL an amino acid polymer of 57 %l-glutamic acid, 38%l-lysine, and 5%l-phenylalanine - GLT¹⁵ an amino acid polymer ofl-glutamic acid,l-lysine, and 15 %l-tyrosine - (T,G)-A-L an amino acid polymer having a polylysine backbone with side chains of polyd-l-alanine, terminating in short sequences of tyrosine and glutamic acid - GAT₁₀ an amino acid polymer of 60%l-glutamic acid, 30%l-alanine, and 10%l-tyrosine - GLA₅ an amino acid polymer of 57%l-glutamic acid, 38%l-lysine, and 5%l-alanine - DNP 2,4 dinitrophenyl - BGG bovine gamma globulin - FCS fetal calf serum - PWBC peripheral white blood cell - SWBC spleen white blood cell - T cell thymus-derived lymphocyte - B cell bone marrow-derived lymphocyte     

Yeast RNA polymerase I: A eukaryotic zinc metalloenzyme

Microwave excitation spectrometry and metal binding inhibition studies show that zinc is a catlytically essential component of the highly purified RNA polymerase I from yeast, the first eukaryotic RNA polymerase I available in quantities sufficient for such studies. It contains 2.4 g-atom of zinc based on a molecular weight of 6.5 × 10⁵ (8). Copper, iron, manganese and magnesium are absent, i.e., below the limits of detection, 10^?13 to 10^?14 g-atoms. A number of derivatives of 1,10-phenanthroline reversibly inhibit the polymerase catalyzed reaction, apparently by forming a ternary polymerase·Zn·OP complex while the nonchelating isomer, 1,7-phenanthroline, is ineffective.