Variation in the ribosomal RNA genes among individuals of Vicia faba

Summary Length heterogeneity in the ribosomal repeat of Vicia faba is due to the presence of variable numbers of a 325 bp subrepetitive element within the nontranscribed spacer region. The distribution of size classes among 88 individuals within a population was investigated by blot-hybridization. We find that individual plants can exhibit more than 20 size classes and that hybridization patterns are highly diverse from individual to individual, more so than for any species so far investigated. In contrast, no such differences are observed in patterns for different tissues from a single plant or from parental to F₁ generation. Some changes were observed in the F₂ generation. We conclude that unequal recombination can give rise to the diversity that we observe for the V. faba rDNA repeats.     

Antigen-induced lymphomagenesis: identification of a murine B cell lymphoma with known antigen specificity

CH12, a murine B cell lymphoma derived in B10 H-2aH-4bp/Wts mice after transfer of SRBC hyperimmunized spleen cells into an adult-thymectomized, sublethally irradiated, syngeneic recipient, is demonstrated to bear surface IgM specific for a determinant found on SRBC and ChRBC. The Ig specificity has been demonstrated by rosetting assays and complement-dependent hemolysis. The removal of CH12 surface IgM by capping with anti-mu or with anti-CH12 idiotype, but not with anti-gamma or with irrelevant anti-idiotype, eliminated the formation of rosettes between CH12 and SRBC or ChRBC. The absorption of CH12 Ig produced in vitro, with either SRBC or ChRBC but not with HRBC, removed all hemolysin activity against SRBC, demonstrating that only one CH12 product was responsible for the reactivity with both SRBC and ChRBC. CH12 has a surface phenotype of a relatively mature B cell expressing surface Ig (IgM-mu,kappa) and la antigens, but lacking Thy-1 or detectable Fc or C3 receptors. CH12 also expresses the antigen Lyt-1. Growth of CH12 in vivo or in vitro results in the generation of up to 3% direct PFC and serum hemolysin, which shows that CH12 is not irretrievably "frozen". The generation of PFC and serum hemolysin is associated with increased population density, and the rate of PFC and serum hemolysin accumulation cannot be explained by simple cell division. A continuously secreting hybridoma derived from CH12 was used to purify the CH12 IgM to facilitate studies of protein sequence and idiotype.     

Intermittent cyclophosphamide in pemphigus vulgaris and bullous pemphigoid

Cyclophosphamide, given in widely spaced doses, was used in the treatment of a patient with pemphigus vulgaris and a patient with bullous pemphigoid. To our knowledge, this form of therapy has not previously been reported in these two diseases. The distinct advantages of the larger intermittent dose method of cyclophosphamide therapy over the more conventional daily dose regimen are discussed.     

Die Suppression der außerkaryotisch bedingten Streptomycin-Abhängigkeit bei Chlamydomonas reinhardii

Zusammenfassung Die Streptomycin-Abhängigkeit der Mutante sd₃ wird außerkaryotisch vererbt. Nach Übertragung auf streptomycin-freies Medium entstehen in einer Häufigkeit von 10^-7 bis 10^-6 streptomycin-empfindliche Zellen. Diese Revertanten unterscheiden sich in verschiedenen Merkmalen von dem ebenfalls streptomycin-sensiblen Wildtyp. Die Reversion kommt also nicht durch Rückmutation zustande. Durch Kreuzungsexperimente konnte gezeigt werden, daß die Mutation, die zur Suppression der Streptomycin-Abhängigkeit führt, auf der extranucleären DNS stattgefunden hat.

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Suppression of the extranuclear streptomycin dependence in Chlamydomonas reinhardii

Summary The streptomycin-dependent mutant sd₃ shows uniparental inheritance. From their transfer on streptomycin-free medium streptomycin-sensitive cells result in a frequency of 10^-7 to 10^-6. These revertants differ in several marks from likewise sensitive wild-type cells. Therefore they were formed not by backmutation. Crossings showed, that also this suppression took place on the extranuclear DNA.

     

Sodium Content of Community Water Supplies in California

The amount of sodium ion in water used for ingestion may be critical in effective use of a low sodium dietary regimen. Waters containing not over 20 mg of sodium per liter are provided for in the sodium restricted diets set forth by the American Heart Association. For diets containing more than 500 mg of sodium a day, waters of greater sodium content may be used if proper dietary adjustments are made.While assessment of the long-term average sodium content of a community water supply is difficult, the determined values for sodium lend to classification within range categories. The larger community water supplies in California are presented within several range categories of sodium content.The more commonly used water softeners add sodium to water. The sodium-restricted patient should be cautioned against their use. Similar consideration should probably be given to water supplies of retirement communities where the potential for disorders requiring sodium restriction is greater than in the general population.     

BEHAVIORAL CHARACTERISTICS OF DANGEROUS DRIVERS—Importance of Correction

Studies of accident-prone drivers emphasize the frequency of unstable, aggressive or antisocial personalities expressing themselves through the automobile as a real and a symbolic weapon. Such expressions may be voluntary or unconscious and may also lead a driver to injure himself or seek injury from others.Because of the great public danger from such drivers, it is urgent that judges and enforcers of the law recognize the psychic motivation in habitual violation and withhold driving privileges from violators until a psychic adjustment has been made. Physicians can contribute in gaining acceptance for this attitude of enforcement, and in setting up adequate psychiatric procedures for correction of violators.     

Analysis of the structure of a common cold virus, human rhinovirus 14, refined at a resolution of 3.0 A

Human rhinovirus 14 has a pseudo T = 3 icosahedral structure in which 60 copies of the three larger capsid proteins VP1, VP2 and VP3 are arranged in an icosahedral surface lattice, reminiscent of T = 3 viruses such as tomato bushy stunt virus and southern bean mosaic virus. The overall secondary and tertiary structures of VP1, VP2 and VP3 are very similar. The structure of human rhinovirus 14, which was refined at a resolution of 3.0 A [R = 0.16 for reflections with F greater than 3 sigma(F)], is here analyzed in detail. Quantitative analysis of the surface areas of contact (proportional to hydrophobic free energy of association) supports the previously assigned arrangement within the promoter, in which interactions between VP1 and VP3 predominate. Major contacts among VP1, VP2 and VP3 are between the beta-barrel moieties. VP4 is associated with the capsid interior by a distributed network of contacts with VP1, VP2 and VP3 within a promoter. As the virion assembly proceeds, the solvent-accessible surface area becomes increasingly hydrophilic in character. A mixed parallel and antiparallel seven-stranded sheet is composed of the beta C, beta H, beta E and beta F strands of VP3 in one pentamer and beta A1 and beta A2 of VP2 and the VP1 amino terminus in another pentamer. This association plays an essential role in holding pentamers together in the mature virion as this contact region includes more than half of the total short non-bonded contacts between pentamers. Contacts between protomers within pentamers are more extensive than the contacts between pentamers, accounting in part for the stability of pentamers. The previously identified immunogenic regions are correlated with high solvent accessibility, accessibility to large probes and also high thermal parameters. Surface residues in the canyon, the putative cellular receptor recognition site, have lower thermal parameters than other portions of the human rhinovirus 14 surface. Many of the water molecules in the ordered solvent model are located at subunit interfaces. A number of unusual crevices exist in the protein shell of human rhinovirus 14, including the hydrophobic pocket in VP1 which is the locus of binding for the WIN antiviral agents. These may be required for conformational flexibility during assembly and disassembly. The structures of the beta-barrels of human rhinovirus 14 VP1, VP2 and VP3 are compared with each other and with the southern bean mosaic virus coat protein.     

Depletion flocculation and depletion stabilization of erythrocytes

At dextran (Mw ≈ 500,000) concentrations from 2 to ≈10%, suspensions of normal human erythrocytes flocculate in small convex agglutinates. At dextran concentrations > 10%, the erythrocytes resegregate in a stable monodisperse suspension. At all these dextran concentrations, the erythrocytes are coated with considerable amounts of dextran. It can be argued that at dextran concentrations from 2 to 10%, as well as at dextran concentrations > 10%, there is a thin layer, which is depleted of dextran, between the dextran layer adsorbed onto the erythrocytes and the bulk dextran solution. It can also be shown that there is a repulsive interaction between the two layers of dextran: one adsorbed and one free. When the adsorbed dextran layer is the most concentrated, stability must ensue, and when the dextran in free solution is the most concentrated, flocculation should occur. Below 7% dextran, the concentration of free dextran is higher than the adsorbed concentration; above 10% dextran that situation is reversed. These data correlate well with the depletion flocculation predicted for the lower concentration and the depletion stabilization predicted for the higher dextran concentration.

     

Measures of geographic range size: the effects of sample size

A number of methods have been used for quantifying the sizes of the geographic ranges of species. The consequences of different levels of sampling (the proportion of actual spatial occurrences) are explored for eight of these, using data on the occurrences of butterfly species on a 10 × 10 km grid across Britain. For all methods, the percentage error of estimation (PEE) decreases with the number of 10 × 10 km squares which a species occupies, most rapidly for extent measures, and more rapidly for area measures than for measures of numbers of units occupied. The rate of decline in PEE itself falls as sampling effort increases. At a given sampling level, rank correlations between range sizes measured by different methods are generally high, but there is no consistent change in the magnitude of these correlations as the level of sampling increases. The composition of the set of species with the smallest range sizes changes with the level of sampling.