Proceedings of the National Academy of Sciences

Pauling, Linus; Blethen, John

doi: N/Apmid: 16592173

Observed energy levels of 162Er from the normal state J = 0 to the excited rotational state J = 18 correspond to values of the moment of inertia and rotational frequency that indicate that a pronounced change in structure occurs at about J = 14. It is shown that the observed values agree well with the values calculated on the assumption that there is resonance between a more stable prolate structure with a core of two spherons and a less stable superprolate structure with a core of three spherons in line.

Rudland, P. S.; Seifert, W.; Gospondarowicz, D.

doi: N/Apmid: 4527822

Addition of serum to quiescent mouse fibroblasts induces a series of macromolecular changes (a pleiotypic response) followed by DNA synthesis and cell division. A new pituitary hormone, fibroblast growth factor, and hydrocortisone acting at physiological concentrations can completely replace exogenously added serum for the induction of these events in lines of BALB/c 3T3 cells. The induction of cell growth is specific for cultured fibroblasts; no stimulation is observed for mouse epithelial cells or virally transformed fibroblasts.

Blamire, John; Flechtner, Valerie R.; Sager, Ruth

doi: N/Apmid: 4277629

The experiments described in this paper implicate chloroplast protein synthesis in the regulation of nuclear DNA replication. The inhibition of nuclear DNA replication in the lower eukaryote, Chlamydomonas reinhardi strain 21gr, was examined after growth of cells with a series of antibiotics (streptomycin, neamine, spectinomycin, cleocin, chloramphenicol, and rifampicin) each of which has a known effect upon chloroplast RNA or protein synthesis in this organism. Each antibiotic inhibited nuclear DNA replication at drug concentrations at which there was little or no inhibition of adenine incorporation into chloroplast DNA. That chloroplast DNA was replicating under these conditions rather than merely being repaired, was shown first by the high incorporation rates and second by a 14N-15N density transfer experiment in which chloroplast DNA doubled in the presence of streptomycin, while no incorporation into nuclear DNA was detected. A small DNA peak, Component III, located between nuclear and chloroplast DNA's in CsCl gradients, possibly mitochondrial, was more pronounced in DNA from antibiotic-inhibited cultures than from controls.

Bloom, Arthur D.; Nakamura, Frank T.

doi: N/Apmid: 4368696

We here report the establishment of a seemingly permanent hybrid cell line formed by fusion of the cells of two biochemically mutant human lymphocyte lines. One parental line (UM-1-6TGr) was deficient in hypoxanthine-guanine phosphoribosyl transferase (IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8), and had two marker chromosomes. The second parental line (UM-21-5) was a clonal derivative of a citrullinemic lymphocyte line, and was, like the line of origin, dificient in argininosuccinic acid synthetase L-Citrulline: L-aspartate ligase (AMP-forming), EC 6.3.4.5. This line also had a marker chromosome, which was a B5 with a very prominent secondary constriction. After trypsinization of both parental lines, followed by addition to the fusion mixture of β-propiolactone-inactivated Sendai virus, the cells were placed in a doubly selective medium (hypoxanthine-aminopterin-thymidine-containing medium in which the arginine was replaced with citrulline) to prevent the proliferation of the mutant parents. Under selective conditions, 97-99% of cells were found to be tetraploid, containing the three marker chromosomes; and the specific activities of the hybrid line transferase and synthetase were intermediate between normal and mutant line values. Furthermore, the UM-1-6TGr and UM-21-5 lines were producers of gamma and mu heavy chains of immunoglobulin, and of kappa light chains, as determined by immunodiffusion and immunofluorescence, and the hybrid line continued to synthesize and to secrete detectable levels of these same immunoglobulins. These studies demonstrate the genic and cytogenetic stability of this hybridized lymphocyte cell line, and prove that hybridization per se does not extinguish the activity of either the regulatory of structural genes involved in immunoglobulin synthesis.

Shizuya, Hiroaki; Livingston, Dennis M.; Richardson, Charles C.

doi: N/Apmid: 4604644

We have isolated a specialized transducing phage carrying the polC locus of E. coli K-12. A strain of E. coli lacking the lambda attachment site was infected with bacteriophage λ. Lysogens carrying λ at the tonA locus were isolated by selecting λ-immune, T5-resistant strains. Transducing phages of dapC, dapD and polC, which map within 0.2 min of tonA, were obtained in lysates prepared from two of the lysogens. The isolated phage, λdpolC, is defective but can transduce four different polC temperature-sensitive mutants. After lysogenation with the transducing phage, DNA polymerase III activity is restored to normal levels in extracts of a polC strain lacking polymerase III activity. However, attempts to obtain increased levels of DNA polymerase III in extracts of induced lysogens carrying λdpolC have been unsuccessful.

Shiokawa, K.; Pogo, A. O.

doi: N/Apmid: 4605329

Three different classes of poly(A)-containing RNA have been identified in the yeast system. They have been characterized by their kinetics of labeling, by their localization in the nuclear, membranous, and soluble cytoplasmic fractions, and by their size. The evidence indicates that the membrane-bound poly(A)-containing RNA is a product of the nuclear poly(A)-containing RNA and is the precursor of the polysomal poly(A)-containing RNA. In addition, it has been demonstrated that transport of mRNA is coupled with protein synthesis.

Chou, George I. N.; Katz, Dvorah; Gunsalus, I. C.

doi: N/Apmid: 4527812

The octane (OCT) plasmid in Pseudomonas putida derived from the ω-hydroxylase-carrying strain of Coon and coworkers is transferable to the camphor (CAM) plasmid-bearing strain by conjugation or by transduction. While the majority of the Cam +Oct+ exconjugants segregate Cam+ or Oct+ cells, exconjugants with stable Cam +Oct+ phenotype (CAM-OCT) can be detected at a low frequency. The transductants are all of the CAM-OCT phenotype. In the stable Cam +Oct+ strains, the OCT plasmid resembles the CAM plasmid with respect to curing by mitomycin C, transfer in conjugation, and reaction to ts (temperature-sensitive) mutation specifically affecting CAM plasmid replication. Therefore, it is suggested that certain regions of homology exist between the CAM and OCT plasmids that enable them to recombine to form a single plasmid, and to overcome the incompatibility barrier that prevents their coexisting.

Levitzki, Alexander; Atlas, Daphne; Steer, Michael L.

doi: N/Apmid: 4528016

Turkey erythrocyte ghosts (empty membranes) possess a class of receptors that can bind both L-3Hisoproterenol and DL-3Hpropranolol. The binding of 3Hisoproterenol to these receptors occurs with a dissociation constant of 0.15 μM and can be fully inhibited by 1 μM propranolol. The binding of 3Hpropranolol occurs with a dissociation constant of 2.5 nM and can be fully inhibited by 0.2 mM DL-isoproterenol. Ligand binding is sensitive to sonication, boiling, and 8 M urea. The cells possess 500 to 1000 β-adrenergic receptors per cell. Binding of propranolol to the β-receptor was found to be stereospecific for the L stereoisomer. If one assumed a 1:1 relationship between β-adrenergic receptors and adenylate cyclase, the turnover number of this adenylate cyclase would be close to 100 min-1.

Smith, Helene S.; Hackett, Adeline J.

doi: N/Apmid: 4369359

The effect of 2′,6′-dimethyl-N(4′)-benzyl-N(4′)- desmethylrifampicin on viral transformation induced by two unrelated oncogenic viruses was compared. Transformation of Balb/3T3 cells by the small, DNA-containing papova virus simian virus 40 was completely normal under conditions where transformation by the large, RNA-containing oncornavirus murine sarcoma virus was inhibited more than 150-fold. For these experiments a resistant variant of Balb/3T3 was selected that grows well in high concentrations of the drug, is not dependent on the drug for growth, and is probably not blocked at the level of drug uptake. These data show that dimethyl-benzylrifampicin specifically inhibits oncornavirus-induced transformation rather than nonspecifically inhibiting cellular growth or transformation.

Simpson, Robert T.

doi: N/Apmid: 4604338

Calf-thymus chromatin was fractionated by ion-exchange chromatography on ECTHAM-cellulose and sucrose gradient sedimentation. ECTHAM-cellulose is a cationic adsorbent prepared by coupling tris(hydroxymethyl)aminomethane to cellulose with epichlorohydrin. The capacity of these fractionated chromatins to support RNA synthesis by DNA-dependent RNA polymerase of Escherichia coli was examined, using procedures that permit measurement of binding site frequency. Unfractionated calf thymus chromatin has 5-10% as many binding sites as protein-free DNA. By combination of the two fractionation methods, chromatin samples were obtained containing as few as 2% and as many as 47% of the number of binding sites found on protein-free DNA.