Comparison of the protein-synthesizing machinery in the skeletal muscle of normal and dystrophic Bar Harbor mice

1. Although the total weight of leg muscle increased with the age of a normal mouse the DNA and RNA content per leg did not change significantly. 2. The weight of leg muscle from a dystrophic mouse was only about 45% of that from a normal mouse but the DNA and RNA contents were the same and hence similar DNA/RNA ratios were obtained. 3. The total ribosome contents of normal and dystrophic mice were the same on a whole-leg basis, and for both the free ribosomes were about 60% of the total. However, comparison with similar data from liver suggested that some loss of ribosomes occurred during the isolation procedure. 4. The polyribosome patterns obtained by density-gradient centrifugation were the same for normal and dystrophic muscle, and comparable polyribosome fractions of different sizes obtained from such gradients had similar capacities for the incorporation of radioactive amino acids in a standard protein-synthesizing system. 5. By using a standard protein-synthesizing system with normal polyribosomes similar extents of incorporation were found with normal- or dystrophic-muscle pH5 fraction or partially purified transfer RNA preparation. 6. It is concluded that there is no absolute difference between the protein-synthesizing systems of normal and dystrophic mouse muscle and that the observed apparent differences result from concentration differences caused by changes in muscle volume. 7. A possible cause of the failure of dystrophic muscle to resynthesize myofibrils is also suggested.     

Determination of Antibiotic Susceptibility of Rickettsia by the Plaque Assay Technique

Plaque formation by various rickettsiae was completely inhibited by commercial antibiotic discs impregnated with tetracycline, chloramphenicol, nitrofurantoin, and erythromycin; partial inhibition was observed around discs containing nalidixic acid and sulfisoxazole, but no inhibition was seen around discs containing cephalothin, ampicillin, oxacillin, kanamycin, polymyxin B, streptomycin, or penicillin.     

Cell population density and phenotypic expression of tissue culture fibroblasts from heterozygotes of Lesch-Nyhan's disease (inosinate pyrophosphorylase deficiency)

Radioautographic examination of skin fibroblasts grown in tissue culture from normal donors revealed heavy labeling of almost all cells following incubation with tritiated hypoxanthine. Cells from patients with Lesch-Nyhan's disease, lacking inosinate pyrophosphorylase, had only 10 grains or less per cell. When normal and abnormal cells were mixed prior to culture, there was a progressive increase, with culture time, in the percentage of heavily labeled cells so that by 96 hr, when the cells were confluent, over 95% of the cells were heavily labeled. Reduction of cell density by subculture produced a reversion to original values. Cultures from three obligatory heterozygotes revealed the expected mixed population of cells. This appears to be a practical approach to the identification of the heterozygote.Aided by USPHS CA08748 and GM15508, and the Health Research Council of the City of New York.     

Effect of the Route of Inoculation on Antibody Formation in Guinea Pigs Immunized with Parainfluenza Virus Vaccines

The efficiency of the intramuscular route of immunization of guinea pigs was compared with the intraperitoneal route when trivalent parainfluenza virus vaccine was employed as immunogen. When the routes of immunization were compared by effective dose 50, the intramuscular route was more effective. Likewise, a statistical evaluation of conversion rates and of titers revealed significantly higher values for the intramuscular than for the intraperitoneal route to all three components in two of the lots of vaccine tested.     

Interaction of the exr and lon Genes in Escherichia coli

Strains of Escherichia coli carrying the gene lon typically produced excess capsular polysaccharide, and were sensitive to ultraviolet light (UV) irradiation, thymine starvation, and nalidixic acid, forming long filaments after these treatments. Sensitivity was reduced by a number of posttreatments. In the presence of a second UV sensitivity gene, exr, some of these properties were suppressed: long filaments were not formed, the effect of lon on UV and nalidixic acid sensitivity was greatly reduced, and irradiation posttreatments gave an enhancement of survival characteristic of exr rather than lon strains. Production of capsular polysaccharide was not affected by the exr gene.     

Formation of an unusual hybrid in the development of human adenosine 5′-triphosphate–creatine phosphotransferase

1. Starch-gel analysis of extracts from adult human muscle, heart and brain reveals a hybrid creatine kinase with an abnormally high electrophoretic mobility. 2. Hybridization in vitro confirms that the postulated hybrid is formed from a combination of brain- and muscle-type enzyme sub-units. 3. The relative electrophoretic mobility of the hybrid is not affected by changing the starch concentration in the gel or by the buffer system used, or by electrophoresis in thin layers of Sephadex. 4. It is concluded that hybrid formation results in a net increase on the dimeric enzyme of from 4 to 6 negative charges. 5. During development a sharp increase in the rate of production of muscle-type enzyme sub-units occurs in heart at 10–13 weeks' gestation and in muscle at 18–20 weeks' gestation. The latter change is accompanied by a relative decrease in the concentration of brain-type sub-units.     

Influence of Relative Humidity on the Survival of Some Airborne Viruses

A system for studying the effects of relative humidity (RH) and temperature on biological aerosols, utilizing a modified toroid for a static aerosol chamber, is described. Studies were conducted at 23 C and at three RH levels (10, 35, and 90%) with four viruses (Newcastle disease virus, infectious bovine rhinotracheitis virus, vesicular stomatitis virus, and Escherichia coli B T3 bacteriophage). Virus loss on aerosol generation was consistently lower at 90% than at 10 or 35% RH. When stored at 23 C, Newcastle disease virus and vesicular stomatitis virus survived best at 10% RH. Infectious bovine rhinotracheitis virus and E. coli B T3 bacteriophage survived storage at 23 C best at 90% RH.     

An Ion Displacement Membrane Model

The usual assumption in treating the diffusion of ions in an electric field has been that the movement of each ion is independent of the movement of the others. The resulting equation for diffusion by a succession of spontaneous jumps has been well stated by Parlin and Eyring. This paper will consider one simple case in which a different assumption is reasonable. Diffusion of monovalent positive ions is considered as a series of jumps from one fixed negative site to another. The sites are assumed to be full (electrical neutrality). Interaction occurs by the displacement of one ion by another. An ion leaves a site if and only if another ion, not necessarily of the same species, attempts to occupy the same site. Flux ratios and net fluxes are given as functions of the electrical potential, concentration ratios, and number of sites encountered in crossing the membrane. Quantitative comparisons with observations of Hodgkin and Keynes are presented.