Modulation of myelopoiesis by different bacterial cell-wall components: induction of colony-stimulating activity (by pure preparations, low-molecular-weight degradation products, and a synthetic low-molecular analog of bacterial cell-wall components) in vitro.

Chemically pure preparations of three structurally unrelated components of the cell wall of gram-negative bacteria (BCWC), lipid A, outer-membrane lipoprotein, and murein, were tested for lymphocyte mitogenicity and the ability to induce colony-stimulating activity (CSA) in various serum-free tissue-culture systems. All three components were B-cell mitogens and induced CSA in spleen-cell cultures. However, in lymphnode-cell cultures the concentrations of these agents required for either mitogenicity or CSA induction differed markedly. Moreover, in contrast to thymidine incorporation, CSA induction was not influenced by pre-irradiation of the cells. Conversely, after removal of phagocytic cells with the iron-magnet technique, CSA was no longer inducible by BCWC, while lymphocyte proliferation was barely impaired. All three BCWC readily induced CSA release in cultures of adherent peritoneal cells without influencing the release of a cytoplasmic enzyme. BCWC-dependent CSA release from adherent peritoneal cells was not influenced by pretratment of the cultures with anti-immunoglobulin, but completely suppressed by preincubation with anti-macrophage-1.2 alloantiserum and complement. CSA induction in macrophage cultures was also achieved with a low-molecular-weight synthetic muramyldipeptide and degradation products of lipoprotein. The results suggest that the induction of CSA is not directly related to the mitogenic, immunogenic, or antigenic properties of the BCWC, but that BCWC-mediated CSA production is caused by a direct “hormone-like” interaction of the agents with mature macrophages.     

Mycologische Notizen

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The buffering capacity of the internal phase of thylakoids and the magnitude of the pH changes inside under flashing light

The buffering capacity inside thylakoids is determined and the magnitude of flash-induced pH changes inside is calibrated in the pH range from 6.4 to 8.1. The work is based on flash-induced absorption changes of neutral red in a chloroplast suspension in which the outer phase is strongly buffered by bovine serum albumin. It is shown that neutral red is bound inside thylakoids. The binding can be described by a simple isotherm with an apparent K_m = 4 μM and saturation at 1 neutral red per 17 chlorophylls. The apparent pK of neutral red is shifted from 6.6 in solution to 7.25 when bound inside. It is demonstrated that neutral red is a clean indicator of pH changes inside, i.e. when properly used it shows no response to other events. Although bound it reports pH changes which occur in the internal osmolar (aqueous) volume of thylakoids. This is obvious from the influence of chemically very different buffers on the magnitude of the absorption changes of neutral red. These act in a manner proportional to their calculated buffering capacity in aqueous solution. The intrinsic buffering capacity of the internal phase is determined with the aid of these buffers, at pH 7.2 it is between 0.8 and 1 mM (at 60 mosM). The absence of large variations in the buffering capacity in the range from pH 6.4 to 8.1 suggests that proteinaceous groups are involved in addition to the lipids which may dominate the buffering capacity at lower pH. The magnitude of the internal pH change is approx. 0.6 (at pH 7.3) under stimulation of both photosystems with a short xenon flash of light.     

Die Umkehrung der Polarität des ungefurchten Eies von Rana fusca und ihre Folgeerscheinungen

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Flora des Peterwardeiner Grenz — Regiments Nr. 9

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Extremitätentrausplantationen an Anuren

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Effects of polyamines and polyanions on a cyclic nucleotide-independent and a cyclic AMP-dependent

The phosphorylation of phosvitin in vitro by a cyclic nucleotide-independent protein kinase (phosvitin kinase) derived from rooster liver is markedly stimulated by the divalent cation, Mg²⁺. In addition, the activity is further stimulated by low concentrations of the polyamines putrescine, spermidine and spermine leading to higher rates of phosphate incorporation than could be obtained at any concentration of Mg²⁺. Spermine is inhibitory at higher concentrations. The polyamines shift the Mg²⁺ requirement for maximal activity to lower concentrations. The activity of a cyclic AMP-dependent histone kinase from beef heart is not altered by the presence of polyamines. Heparin is a potent inhibitor of phosvitin kinase but has no effect on histone kinase. Polyribonucleotides (polyadenylic acid and transfer RNA) inhibit both types of kinases, but the degree of inhibition of phosvitin kinase is variable and depends upon the type of the polyanion present. Spermidine and spermine, but not Mg²⁺, efficiently counteract the inhibitory action of heparin and tRNA. The results suggest that, also in vivo, naturally occurring polyamines and polyanions such ass tRNA may have a regulatory function on protein kinases.