Characterization of the self association of Avian sarcoma virus integrase by analytical ultracentrifugation.

Retroviral integration protein (IN) has been shown to be both necessary and sufficient for the integration of reverse-transcribed retroviral DNA into the host cell DNA. It has been demonstrated that self-assembly of IN is essential for proper function. Analytical ultracentrifugation was used to determine the stoichiometry and free energy of self-association of a full-length IN in various solvents at 23.3 degrees C. Below 8% glycerol, an association stoichiometry of monomer-dimer-tetramer is observed. At salt concentrations above 500 mM, dimer is the dominant species over a wide range of protein concentrations. However, as physiological salt concentrations are approached, tetramer formation is favored. The addition of glycerol to 500 mM NaCl, 20 mM Tris (pH 8.4), 2 mM beta-mercaptoethanol significantly enhances dimer formation with little effect on tetramer formation. Furthermore, as electrostatic shielding is increased by increasing the ionic strength or decreasing the cation size, dimer formation is strengthened while tetramer formation is weakened. Taken together, the data support a model in which dimer formation includes favorable buried surface interactions which are opposed by charge-charge repulsion, while favorable electrostatic interactions contribute significantly to tetramer formation.     

The effects of amphotericin B on the interaction of Candida albicans with fibroblast cultures

Sublethal amounts of amphotericin B inhibited the interaction of Candida albicans with cultured fibroblasts. Different C. albicans clinical isolates exhibited varying degrees of sensitivity to the drug, but those isolates that were the most infective in control cultures appeared to be the most resistant to amphotericin B mediated infection inhibition. Although amphotericin B inhibited germ tube formation at the sublethal concentration of 0.3 microgram/mL, lower concentrations inhibited infection without preventing germination. The extent of this latter activity varied with the isolate and amphotericin B concentration and appeared to be related to sublethal effects on germinated yeasts. While amphotericin B effectively prevented new fibroblast infection, it did not dissociate those yeasts which had established an infection before its addition.     

Interaction of smooth muscle tropomyosin and smooth muscle myosin. Effect on the properties of myosin

Several techniques were used to investigate the possibility that smooth muscle tropomyosin interacts with smooth muscle myosin. These experiments were carried out in the absence of actin. The Mg2+-ATPase activity of myosin was activated by tropomyosin. This was most marked at low ionic strength but also occurred at higher ionic strength with monomeric myosin. For myosin and HMM, the activation of Mg2+-ATPase by tropomyosin was greater at low levels of phosphorylation. There was no detectable effect of tropomyosin on the Mg2+-ATPase activity of S1. The KCl dependence of myosin viscosity was influenced by tropomyosin, and in the presence of tropomyosin, the 6S to 10S transition occurred at lower KCl concentrations. From the viscosity change, an approximate stoichiometry of 1:1 tropomyosin to myosin was estimated. The phosphorylation dependence of viscosity, which reflects the 10S-6S transition, also was altered in the presence of tropomyosin. An interaction between myosin and tropomyosin was detected by fluorescence measurements using tropomyosin labeled with dansyl chloride. These results indicate that an interaction occurs between myosin and tropomyosin. In general, the interaction is favored at low ionic strength and at low levels of phosphorylation. This interaction is not expected to be competitive with the formation of the actin-tropomyosin complex, but the possibility is raised that a direct interaction between myosin and tropomyosin bound to the thin filament could modify contractile properties in smooth muscle.     

Individualgeschichte und Gesangsauspr?gung beim Star (Sturnus vulgaris) in einer Kolonie

Zusammenfassung Die Lautäußerungen der Stare können in Gesangsstrophen und Pfeiflaute unterteilt werden. Pfeiflaute sind kurz (bis 2 s) und einfach gebaut, während die Strophen wesentlich länger andauern (meist über 20 s) und sich aus zahlreichen komplex gebauten Untereinheiten zusammensetzen. In einer Kolonie bei Frankfurt am Main, in der die Individuen durch Farbringe gekennzeichnet sind, wurde der individuelle Variationsspielraum der Lautäußerungen analysiert. In den Feinstrukturen der Pfeifthemen glichen sich die Koloniemitglieder weitgehend aneinander an. In den Feinstrukturen der Motivtypen der Gesangsstrophen traten dagegen große individuelle Unterschiede auf. , die während Jahren in der gleichen Kolonie brüteten, sangen nur sehr wenige gemeinsame Motivtypen. Die Repertoiregröße variierte zwischen 17–39 Motivtypen. Im Herbstgesang traten 5 bisher noch nicht beobachtete Motivtypen auf. Es gibt somit deutliche Hinweise darauf, daß auch der adulte Star neue Laute erlernen kann.

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Individual history and song structure of Starlings (Sturnus vulgaris) living in a colony

Summary Starling's song can be divided into warbling and whistles. Whistles have a short and simple structure, whereas warbling is sung in long sequences (most often more than 20 s). In the warbling one can distinguish many different subunits (repetition of motifs). The individual variability of songs was studied in a colony near Frankfurt/Main in West Germany, where starlings were colour banded since 1969. The following results were obtained:Birds from the same colony uttered nearly identical or very similar microstructures in the species-specific whistle themes. Different to the whistle themes very distinct individual differences characterized the warbling. Only a few motif types were common among colony members. The individual repertoire size ranged from 17 to 39 motif types. Comparison of the song of one individual between the breeding season and the following autumn shows that motifs, which were not observed during spring occurred in the autumn. This observation is a hint that starlings are capable to learn new motif types even as adults.

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Stipendium der Alexander-von-Humboldt-Stiftung     

The effect of ranitidine on cellular immunity in patients with multiple myeloma

Summary Multiple myeloma is characterized by an increased susceptibility to infections and to other malignancies. In a double-blind, placebo-controlled study the potential impact of immunomodulation by ranitidine was studied in 20 patients with multiple myeloma. Three patients were untreated, while 17 after previous cytotoxic therapy were in a stable phase of their disease. All were without clinical signs of infections and at that time had not been treated with other immunomodulating agents. The patients were randomized to oral ranitidine 300 mg twice a day for 21 days or placebo, and several immunological parameters related to multiple myeloma were studied. The blood monocyte chemotactic response was improved in patients treated with ranitidine, and superoxide anion production increased from 2.02 nmol/min to 3.86 nmol/min (median values), while it was unchanged in patients given placebo (2.19–2.25 nmol/min) (P <0.005 between groups). Among ranitidine-treated patients spontaneous NK cell activity was unchanged, while in vitro interleukin-2- and interferon--stimulated NK cell activity decreased (P <0.03, respectively). As production of oxygen radicals constitutes an important mechanism of monocyte killing activity against microorganisms and probably against malignant cells, it is suggested that ranitidine may be of beneficial impact in the treatment of multiple myeloma.     

Are prealbumin plasma levels linked to amino acid supply from peripheral tissues in liver cirrhosis?

Summary Prealbumin plasma level is considered a good index of liver function in liver cirrhosis. However, plasma protein levels depend not only on liver function, but also on amino acid supply which is consequent to nutritional status.In 12 cirrhotics we measured prealbumin plasma levels and the lower limb venous-artero difference of amino acid plasma levels in blood samples taken from femoral vein and femoral artery in post-absorptive conditions considered as a direct index of protein release from peripheral tissues and an indirect index of protein nutritional status.In arterial and in venous plasma amino acid sum was 1.86±0.40 (mean + sd) and 2.00 ± 0.04 mMol/l respectively.Prealbumin plasma levels were found directly correlated with the venousartero difference of amino acid plasma levels (r = 0.57p < 0.05) and of glutamate + glutamine levels (r = 0.73p < 0.007).In conclusions, these data suggest that prealbumin plasma levels are linked to amino acid supply from peripheral tissues in cirrhotics.     

The codon 408 mutation associated with haplotype 2 is predominant in Polish families with phenylketonuria

Summary The incidence of phenylketonuria (PKU) in the western part of Poland is 1 in 5000 live births. Restriction fragment length polymorphism (RFLP) haplotypes at the phenylalanine hydroxylase locus have been analysed in 46 Polish families with PKU. Among 43 fully-informative families 16 RFLP haplotypes were identified. Haplotype 2 is the most frequently (62%) associated with Polish PKU alleles, and the codon 408 mutation is in complete linkage disequilibrium with this haplotype in Poland. This finding is in agreement with observations in other eastern European countries (German Democratic Republic, Czechoslovakia, and Hungary) and in contrast to the genotype distribution observed in western European countries. The present observation suggests the spread of classical PKU, due to the codon 408 mutation associated with haplotype 2, from east to west in European populations. Perhaps more important for genetic counselling, 62% of all PKU chromosomes in the Polish population can now be detected using only one mutantspecific oligonucleotide probe.