IgM-autoantibodies against isologous erythrocytes also react with isologous IgG(Fc)

The mechanisms by which the adaptive immune system of animals discriminate between foreign and self components are not known. It is generally believed that antibodies are produced only in response to foreign agents. However, against this axiom there is mounting evidence that normal animals produce autoantibodies against a variety of self components. In two murine model systems, a high proportion of IgM-producing cells secrete autoantibodies. In one model, the autoantibodies are specific for isologous mouse IgG(Fc) and in the other, the autoantibodies are specific for antigens revealed on the surface of mouse erythrocytes (RBC) by proteolytic enzymes. The function of these two autoimmune responses is a mystery. Here we show that the two responses are related. The lysis of mouse RBC, modified with bromelain (brom) by IgM autoantibodies was completely inhibited by isologous IgG(Fc), and antibodies against mouse IgG(Fc) formed precipitin bands with solubilized membranes from mouse RBC. We conclude that mouse RBC membranes and IgG(Fc) have at least one antigenic determinant in common and that this determinant is the target for autoimmune responses in normal mice.     

Interspecific variability of DNA content in Amphibia

Resumen Fueron determinados por citofotometría los valores de DNA en 33 especies de Amphibia, en las que estaban incluidas 30 especies de Salientia, 1 de Gymnophiona y 2 de Caudata, y fueron comparadas con sus constituciones cromosomicas. Las variaciones encontradas sugieren que hubo aumento de DNA, independientemente, en las diferentes familias estudiadas y que en general, las especies más primitivas filogeneticamente, poseen menor cantidad de DNA, cuando comparadas a los valores encontrados para las más evoluidas.

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This work was supported by PHS Grant No. GM-14577-03-NIGMS, by the CNPq and by the FPIB. Our thanks to Dr. L. D.Vizotto for collecting and classifying several specimens used in this work, as well as for the phylogenetical approach.     

Reaction of 6-aminopenicillanic acid with frequentin

Zusammenfassung 6-Aminopenizillansäure setzt sich mit Frequentin, einem Schimmelmetaboliten, unter gewissen Temperatur- und pH-Bedingungen um. Der entstandene Komplex stellt wahrscheinlich eine Tautomerenmischung aus Enamin und Enolimin dar, die beide durch Wasserstoffbrücken stabilisiert werden.     

Nouveau principe de stimulation électrique: L'excitation ambipolaire par courant alternatif,sinusoïdal pur,de fréquence moyenne

Summary Impulses of amplitude-modulated middle-frequency current (20 000 c.p.s.) stimulate nerve simultaneously at both poles. No polarity effect is observed, because no rectification occurs in the stimulation circuit if pure sine-wave middle-frequency current is employed. This principle is demonstrated by using bipolar longitudinal stimulation that, above threshold, elicits action currents, with latency difference corresponding to the distance between the stimulating electrodes. With supramaximum strength, maximum action currents are obtained at either pole, as is the case with ordinary cathodal stimuli of supramaximum strength applied to one pole or the other. Middle-frequency stimulation, therefore, has to be regarded asambipolar, i.e. does not depend on polarity. With second harmonic distortion, however, rectification occurs in the stimulation circuit and contamination by direct-current component ensues. Middle-frequency stimulation can be applied across nerve, since the excitatory effect does not apparently depend on longitudinal current flow. This method allows the action current to be recorded at the site of stimulation with minimum stimulus artefact.