The inhibition of systrophe in different organisms

Summary The phenomenon of systrophe following different stimuli was comparatively investigated in the cells of different plant organisms. In all cases systrophe could be inhibited by metabolic inhibitors. The influence of colchicine, cytochalasin B, vinblastine and APM (amiprophos-methyl) varied.     

Tyrosine-Phosphorylated Caveolin-1 Blocks Bacterial Uptake by Inducing Vav2-RhoA-Mediated Cytoskeletal Rearrangements

Certain bacterial adhesins appear to promote a pathogen''s extracellular lifestyle rather than its entry into host cells. However, little is known about the stimuli elicited upon such pathogen host-cell interactions. Here, we report that type IV pili (Tfp)-producing Neisseria gonorrhoeae (P⁺GC) induces an immediate recruitment of caveolin-1 (Cav1) in the host cell, which subsequently prevents bacterial internalization by triggering cytoskeletal rearrangements via downstream phosphotyrosine signaling. A broad and unbiased analysis of potential interaction partners for tyrosine-phosphorylated Cav1 revealed a direct interaction with the Rho-family guanine nucleotide exchange factor Vav2. Both Vav2 and its substrate, the small GTPase RhoA, were found to play a direct role in the Cav1-mediated prevention of bacterial uptake. Our findings, which have been extended to enteropathogenic Escherichia coli, highlight how Tfp-producing bacteria avoid host cell uptake. Further, our data establish a mechanistic link between Cav1 phosphorylation and pathogen-induced cytoskeleton reorganization and advance our understanding of caveolin function.     

Inhibition of ROCK activity allows InlF-mediated invasion and increased virulence of Listeria monocytogenes

Listeria monocytogenes is an intracellular bacterial pathogen that causes life-threatening disease. The mechanisms used by L. monocytogenes to invade non-professional phagocytic cells are not fully understood. In addition to the requirement of bacterial determinants, host cell conditions profoundly influence infection. Here, we have shown that inhibition of the RhoA/ROCK pathway by pharmacological inhibitors or RNA interference results in increased L. monocytogenes invasion of murine fibroblasts and hepatocytes. InlF, a member of the internalin multigene family with no known function, was identified as a L. monocytogenes -specific factor mediating increased host cell binding and entry. Conversely, activation of RhoA/ROCK activity resulted in decreased L. monocytogenes adhesion and invasion. Furthermore, virulence of wild-type bacteria during infection of mice was significantly increased upon inhibition of ROCK activity, whereas colonization and virulence of an inlF deletion mutant was not affected, thus supporting a role for InlF as a functional virulence determinant in vivo under specific conditions. In addition, inhibition of ROCK activity in human-derived cells enhanced either bacterial adhesion or adhesion and entry in an InlF-independent manner, further suggesting a host species or cell type-specific role for InlF and that additional bacterial determinants are involved in mediating ROCK-regulated invasion of human cells.     

Inulin Occurrence in Sphenoclea (Sphenocleaceae)

Abstract: Within the angiosperms the Asterales-Campanulales complex forms a relatively clearly circumscribed dade that is characterized by inulin as storage carbohydrate. The genus Sphenoclea (Sphenocleaceae) is traditionally placed in the Asterales-Campanulales complex. In testing fresh plant material of S. zeylanica for the first time, the occurrence of inulin as storage carbohydrate could be proven.     

Phlorotannins of phaeophycea Laminaria ochroleuca

From the mixture of acetylated phenols of Laminaria ochroleuca several fractions consisting of one or more components were isolated and analysed. Several substances, new or known from other seaweeds were identified: tetraphlorethol-A-nonacetate, fucophlorethol-B-octacetate, fucodiphlorethol-C-decacetate, pentafuhaloltridecacetate, and heptafuhaloloctadecacetate. A structure for an isomer of tetraphlorethol-A-nonacetate named tetraphlorethol-B-nonacetate was suggested. Additional phlorotannins were shown to be present, for which only partial structures could be proven.     

Polyhydroxyphenyläther aus Laminaria ochroleuca

After acetylation of the phenolic fraction, the following compounds were isolated from Laminaria ochroleuca: phloroglucinol triacetate, diphlorethol pentaacetate (2,4,6,3′,5′-pentaacetoxydiphenyl ether) and triphlorethol C heptaacetate (1-acetoxy-3,5-bis(2,4,6-triacetoxyphenoxy)benzene).     

The PilC adhesin of the Neisseria type IV pilus-binding specificities and new insights into the nature of the host cell receptor

Type IV pili of Neisseria gonorrhoeae and Neisseria meningitidis mediate the first contact to human mucosal epithelial cells, an interaction which is also critical for the interaction with vascular endothelial cells. The PilC proteins have been characterized as the principal pilus-associated adhesin. Here we show that PilC2 exhibits a defined cell and tissue tropism, as it binds to human epithelial and endothelial cell lines, but not to human T cells or fibroblasts. Piliated gonococci and PilC2 exhibit similar patterns of binding to human epithelial and endothelial cells, supporting the function of PilC as the key pilus adhesin. Although CD46 has previously been suggested to be a pilus receptor, several observations indicate that neisserial type IV pili and the pilus adhesin PilC2 interact with epithelial cells in a CD46 independent manner. Biochemical approaches were used to characterize the nature of host cell factors mediating binding of piliated gonococci and PilC2 protein. Our data indicate that the putative host cell receptor for gonococcal pili and the PilC2 pilus adhesin is a surface protein. Glycostructures were found to not be involved in binding. Moreover, we observed the uptake of purified PilC2 protein together with its receptor via receptor-mediated endocytosis and subsequent receptor re-exposure on the cell surface. Our data support the existence of a specific pilus receptor and provide intriguing information on the nature of the receptor.     

Ca2+-requirement for a blue-light-induced chloroplast translocation inEremosphaera viridis

Summary The light-mediated translocation of chloroplasts inEremosphaera viridis is dependent on blue light near 450 nm, while wavelengths longer than 500 nm are inactive. The plastid translocation results in an aggregation of the organelles close to the nucleus in the center of the cell. After cessation of irradiation, the cells begin to redistribute their plastids in the cytoplasm immediately. Treatments that alter the Ca²⁺ concentration in the cytoplasm ofEremosphaera suggest that the translocation is regulated by calcium. Ultrastructural investigation ofEremosphaera reveals a very characteristic, multilayered and highly-ordered cell wall.     

Brominated phlorethols and nonhalogenated phlorotannins from the brown alga Cystophora congesta

The following phlorotannins were isolated from the brown alga Cystophora congesta and characterized as their acetates: phloroglucinol triacetate, bromodiphlorethol pentaacetate, diphlorethol pentaacetate, bromotriphlorethol-A₁-heptaacetate, bromotriphlorethol-A₂-heptaacetate, tetraphlorethol-C-nonaacetate and fucodiphlorethol-D-decaacetate. The substances bromodiphlorethol pentaacetate, bromotriphlorethol-A₁-heptaacetate and bromotriphlorethol-A₂-heptaacetate are the first brominated members of this series to be described. Triphlorethol-A- heptaacetate was isolated previously from C. congesta.