Interpretation of Diffusion Susceptibility Data Obtained with 50-μg Carbenicillin Discs Against Gram-Negative Organisms

A total of 284 clinical isolates of various species of Enterobacteriaceae, Pseudomonas aeruginosa, P. maltophilia, and Acinetobacter anitratum were tested for susceptibility to carbenicillin by the standardized Bauer-Kirby disc diffusion technique and a microtiter broth dilution method. The data obtained led to the following proposed criteria for the interpretation of the results of disc susceptibility tests. Enterobacteriaceae that yield zones of inhibition equal to or greater than 20 mm in diameter around 50-mug discs of carbenicillin are designated as sensitive to the drug; isolates that yield zones measuring from 18 to 19 mm in diameter are reported as of equivocal (intermediate) susceptibility to the drug, whereas those enterobacterial isolates that are characterized by zones of inhibition of 17 mm or less in diameter are interpreted as resistant to carbenicillin. Isolates of P. aeruginosa, P. maltophilia, and A. anitratum yielding zones of 14 mm or more in diameter around 50-mug discs of carbenicillin are reported as sensitive, whereas those isolates that are characterized by zones of 13 mm or less in diameter are reported as resistant to this drug.     

Deoxyribonucleic Acid Synthesis in Ultraviolet-Light-Irradiated Chinese Hamster Cells

Two mammalian cell lines, Chinese hamster ovary (CHO) which can recover colony-forming ability between fractionated doses of ultraviolet light (UV), and Chinese hamster B-14FAF28 which cannot recover, were tested for the ability to bypass UV-induced photoproducts in DNA during postirradiation DNA synthesis. The molecular weight distributions of newly synthesized DNA in UV-irradiated populations of both cell lines showed evidence for photoproduct bypass. Hence, the bypass mechanism does not correlate with recovery after UV.     

Biological Ion Exchanger Resins: II. QUERP Water and Ion Exchange Selectivity

Biological selectivity is shown to vary with medium osmotic strength and temperature. Selectivity reversals occur at 4°C and at an external osmolality of 0.800 indicating that intracellular hydration and endosolvent (intracellular water) structure are important determinants in selectivity. Magnetic resonance measurements of line width by steady-state nuclear magnetic resonance (NMR) indicate a difference in the intracellular water signal of 16 Hz between the K form and Na form of Escherichia coli, providing additional evidence that changes in the ionic composition of cells are accompanied by changes in endosolvent structure. The changes were found to be consistent with the thermodynamic and magnetic resonance properties of aqueous electrolyte solutions. Calculation of the dependence of ion-pairing forces on medium dielectric reinforces the role of endosolvent structure in determining ion exchange selectivity.     

Anisotropic Absorption of Linearly Polarized Light by Cylindrical Molecules

A general theory relating the orientation of the transition moment in a chromophore to incident light, linearly polarized at an arbitrary angle, is discussed for cylindrical molecules. Experimental verification of this theory is presented for molecules of tobacco mosaic virus (TMV), T₂ DNA, and polyadenylic acid (poly-A).     

Immunological and Biophysical Separation of Dengue-2 Antigens

Antigenic compositions of slowly sedimenting dengue-2 hemagglutinin (SHA) and soluble complement-fixing antigen (SCF) were compared with the virion (rapidly sedimenting hemagglutinin, RHA) by radioimmune precipitation (RIP), RIP inhibition, kinetic neutralization, and neutralization blocking tests with the use of hyperimmune mouse ascitic fluids. RHA and SHA were unable to inhibit completely the RIP of each other by anti-RHA, and neutralization by anti-RHA was not blocked by SHA. This indicated that SHA is serologically related, but not identical, to RHA. SHA differed from RHA in that SHA lacked the “core” polypeptide but contained the two envelope polypeptides. In addition, SHA contained a polypeptide with a molecular weight of 16,500 daltons and a suggestion of several other proteins. These data, when considered with other evidence, suggest that SHA is a special form of “incomplete virus.” SCF was unable to inhibit the RIP of SHA or RHA or to block neutralizing antibodies. Further, anti-SCF did not neutralize RHA or precipitate significant levels of SHA or RHA. Polyacrylamide gel electrophoresis separated SCF from structural polypeptides by molecular size. This evidence suggests that SCF is a nonstructural antigen.     

Catalase-like crystals in parathyroid gland cells of Rana temporaria L.

Summary Crystalline inclusions in parathyroid gland cell nuclei of Rana temporaria were studied by electron microscopy using a specimen tilting stage. Images were analysed by optical diffraction. Results were compared with X-ray and electron microscopic data of trigonal bovine liver catalase to which a striking resemblance of the inclusions was found.We are grateful to Professor R. Mosebach (Giessen) for discussions, to the Deutsche Forschungsgemeinschaft for a grant (La 229/4) and instruments and to Messrs. Spindler & Hoyer, Göttingen and Messrs. Rank Precision Instruments, Nürnberg for putting apparatus at our disposal and performing diffraction photographs.     

Enhanced extractability of articular cartilage proteoglycans in osteoarthrosis (Short Communication)

Tissue contents of small, easily extracted, proteoglycans, relatively poor in keratan sulphate, were compared in normal and osteoarthrotic cartilage. Although the amounts of small proteoglycans were similar in each tissue, as were the collagen contents, some proteoglycans in the diseased cartilage were much more readily extracted than those in the normal tissue.     

Comparison of the effects of ultraviolet light and ethylmethanesulphonate upon the frequency of mitotic recombination in yeast

Summary Host-cell reactivation of gamma-irradiated phage T1 in strains of E. coli K-12 has been compared with HCR of UV-irradiated phage in these same strains and with the radiation sensitivities of these strains (Fig. 1–4). The pattern of the HCR of gammairradiated phage in these strains is like that of the HCR of UV-irradiated phage. HCR in strains whose genotype is uvr ⁺rec^- is like that of the wild type; whereas, HCR is minimal in strains which are uvr ^-. It is suggested that some type of gamma-ray-induced base damage in phage DNA is repaired in uvr ⁺ strains.This work was supported by the United States Atomic Energy Commission Contract No. AT(11-1)-1686. — This is report No. COO-1686-6.Supported in part by the United States Public Health Service Training Grant No. 5T1 RH-80-02(67).     

Characterization of protein–polysaccharides of articular cartilage from mature and immature pigs

Protein-polysaccharides of femoral articular cartilage from pigs of ages 9 months and 5 weeks were compared after extraction at pH6.8 with iso-osmotic sodium acetate followed by 0.63m-calcium acetate. The cartilage from the younger animals had a higher moisture content and contained considerably larger amounts of protein-polysaccharide, but less than half as much collagen/g. dry weight, than cartilage from the older pigs. There was notably less keratan sulphate in the fractions from the less mature animals. After gel filtration on 6% agarose, elution profiles of the calcium acetate extracts were similar to those of the sodium acetate extracts of the same tissue. Chemical analyses, however, showed that in both age-groups the extraction procedure had achieved a sequential solubilization of protein-polysaccharides in that the initial extracts contained a higher proportion of keratan sulphate than those that were extracted subsequently. Both extracts from the older animals contained up to 25% of a relatively small protein-polysaccharide that was retarded on 6% agarose and that had a lower protein content and less keratan sulphate than the larger protein-polysaccharides. In contrast, in extracts from the less mature cartilage only about 5% of the protein-polysaccharides were small enough to be retarded by 6% agarose, suggesting that the small components may not be precursors of the larger. The average length of chondroitin sulphate chains, as calculated from the analytical data, was the same in the smaller protein-polysaccharides as in the larger.