Algal Turbidity Hampers Ornament Perception,but Not Expression,in a Sex‐Role‐Reversed Pipefish

Sexual ornaments are used both in intra‐ and intersexual contexts, and these signals have evolved to function in the particular habitat the animal is adapted to. Habitat characteristics may, however, change rapidly due to anthropogenic effects, sometimes at rates too fast for many organisms to adaptively respond. In aquatic ecosystems, eutrophication is currently changing chemical as well as visual properties of the environment. Algae blooms increase water turbidity, and the reduction of water transparency thus has the potential to alter visual ornaments and their perception. However, results are not congruent. Rather, algae turbidity may decrease, increase, or leave ornaments unaffected. The effect seems to depend on exposure time, condition, population and species. Here, we found that the perception of sexual signals, but not their expression, was hampered by turbidity in the sex‐role‐reversed pipefish Nerophis ophidion. In a laboratory experiment we found that female sexual ornaments (i.e., blue color markings and a skinfold) and fecundity was unaffected by turbidity. Male adaptive mate choice for larger females with large ornament was, however, hampered under turbid conditions, whereas in clear water males choose larger, more ornamented females. Thus, we show that water turbidity had no effect on signal expression but did hamper ornament perception and consequently randomized mate choice.     

Genetic characterization of the Guinea-Bissau family of Mycobacterium tuberculosis complex strains

In a previous study of Mycobacterium tuberculosis complex isolates from Guinea-Bissau in West Africa, we identified a unique group of strains, designated here as the Guinea-Bissau family of strains, which, although genotypically closely related, phenotypically demonstrated a considerable heterogeneity. We conducted here a detailed genotypic analysis of a subset (n = 35) of these isolates. Based on the data obtained, and by comparison of known corresponding genes in mycobacteria outside the M. tuberculosis complex, we propose that the Guinea-Bissau strains belong to a unique branch of the M. tuberculosis complex tree in between classical M. tuberculosis and classical M. bovis. These observations are discussed in their significance in M. tuberculosis complex classification.     

pH6 antigen of Yersinia pestis interacts with plasma lipoproteins and cell membranes

The bacterial pathogen Yersinia pestis expresses a potential adhesin, the pH6 antigen (pH6-Ag), which appears as fimbria-like structures after exposure of the bacteria to low pH. pH6-Ag was previously shown to agglutinate erythrocytes and to bind to certain galactocerebrosides. We demonstrate that purified pH6-Ag selectively binds to apolipoprotein B (apoB)-containing lipoproteins in human plasma, mainly LDL. Binding was not prevented by antibodies to apoB. pH6-Ag interacted also with liposomes and with a lipid emulsion, indicating that the lipid moiety of the lipoprotein was responsible for the interaction. Both apoB-containing lipoproteins and liposomes prevented binding of pH6-Ag to THP-I monocyte-derived macrophages as well as pH6-Ag-mediated agglutination of erythrocytes. Binding of pH6-Ag to macrophages was not dependent on the presence of LDL receptors. Treatment of the cells with Triton X-100 or with methyl-beta-cyclodextrin indicated that the binding of pH6-Ag was partly dependent on lipid rafts. We suggest that interaction of pH6-Ag with apoB-containing lipoproteins could be of importance for the establishment of Y. pestis infections. Binding of lipoproteins to the bacterial surface could prevent recognition of the pathogen by the host defence systems. This might be important for the ability of the pathogen to replicate in the susceptible host.     

1,1'-bis(anilino)-4-,4'-bis(naphtalene)-8,8'-disulfonate acts as an inhibitor of lipoprotein lipase and competes for binding with apolipoprotein CII

Lipoprotein lipase (LPL) is dependent on apolipoprotein CII (apoCII), a component of plasma lipoproteins, for function in vivo. The hydrophobic fluorescent probe 1,1'-bis(anilino)-4,4'-bis(naphthalene)-8,8'-disulfonate (bis-ANS) was found to be a potent inhibitor of LPL. ApoCII prevented the inhibition by bis-ANS, and was also able to restore the activity of inhibited LPL in a competitive manner, but only with triacylglycerols with acyl chains longer than three carbons. Studies of fluorescence and surface plasmon resonance indicated that LPL has an exposed hydrophobic site for binding of bis-ANS. The high affinity interaction was characterized by an equilibrium constant Kd of 0.10-0.26 microm and by a relatively high on rate constant kass = 2.0 x 10(4) m(-1) s(-1) and a slow off-rate with a dissociation rate constant kdiss = 1.2 x 10(-4) s(-1). The high affinity binding of bis-ANS did not influence interaction of LPL with heparin or with lipid/water interfaces and did not dissociate the active LPL dimer into monomers. Analysis of fragments of LPL after photoincorporation of bis-ANS indicated that the high affinity binding site was located in the middle part of the N-terminal folding domain. We propose that bis-ANS binds to an exposed hydrophobic area that is located close to the active site. This area may be the binding site for individual substrate molecules and also for apoCII.     

Lipoprotein lipase from rainbow trout differs in several respects from the enzyme in mammals

Previously we found lipase activity with characteristics similar to lipoprotein lipase (LPL) in tissues from rainbow trout [Biochim. Biophys. Acta 1255 (1995) 205], whereas no equivalent to the related hepatic lipase could be found. An equivalent to apolipoprotein CII was also identified and characterized [Gene 254 (2000) 189]. We present here the full nucleotide sequence for LPL from rainbow trout (Oncorhynchus mykiss) and have investigated some properties of the enzyme. In contrast to what has been found in mammals, LPL mRNA was expressed in livers of adult trout. This indicates that trout LPL carries out functions that hepatic lipase has evolved to take over in mammals. Trout LPL was unstable at 37 degrees C compared with bovine and human LPL. Two sequence differences that may relate to the instability are that trout LPL lacks the disulfide bridge in the C-terminal domain and lacks Pro(258). This residue is conserved in LPL from all mammals and has been shown to be critical for enzyme stability at 37 degrees C. On chromatography on heparin-Sepharose trout and chicken LPL eluted at higher salt concentration than bovine (or other mammalian) LPL. The C-terminal end of LPL has been implied in heparin binding and the higher heparin affinity of the trout and chicken enzymes may be because they have 17 and 15 extra amino acid residues at the C-terminal end, of which three residues are positively charged.     

Tumour necrosis factor-alpha interacts with biglycan and decorin

The interaction of beta-arrestin-1 with the somatostatin receptor type 2A (sst2A) was monitored using both biochemical and confocal imaging approaches. We show that, using transient transfection of either beta-arrestin-1 or its dominant negative Delta-arrestin-1 in CHO cells stably transfected with the sst2A, beta-arrestin-1 is colocalized with the receptor in endosomal vesicles after somatostatin-induced sequestration. However, this interaction leads to a role of beta-arrestin-1 in the desensitization of the sst2A rather than in the internalization process of the receptor-ligand complex.     

Effects of citrinin on iron-redox cycle

The ability of the mycotoxin citrinin to act as an inhibitor of iron-induced lipoperoxidation of biological membranes prompted us to determine whether it could act as an iron chelating agent, interfering with iron redox reactions or acting as a free radical scavenger. The addition of Fe3+ to citrinin rapidly produced a chromogen, indicating the formation of citrinin-Fe3+ complexes. An EPR study confirms that citrinin acts as a ligand of Fe3+, the complexation depending on the [Fe3+]:[citrinin] ratios. Effects of citrinin on the iron redox cycle were evaluated by oxygen consumption or the o-phenanthroline test. No effect on EDTA-Fe2+-->EDTA-Fe3+ oxidation was observed in the presence of citrinin, but the mycotoxin inhibited, in a dose-dependent manner, the oxidation of Fe2+ to Fe3+ by hydrogen peroxide. Reducing agents such as ascorbic acid and DTT reduced the Fe3+-citrinin complex, but DTT did not cause reduction of Fe3+-EDTA, indicating that the redox potentials of Fe3+-citrinin and Fe3+-EDTA are not the same. The Fe2+ formed from the reduction of Fe3+-citrinin by reducing agents was not rapidly reoxidized to Fe3+ by atmospheric oxygen. Citrinin has no radical scavenger ability as demonstrated by the absence of DPPH reduction. However, a reaction between citrinin and hydrogen peroxide was observed by UV spectrum changes of citrinin after incubation with hydrogen peroxide. It was also observed that citrinin did not induce direct or reductive mobilization of iron from ferritin. These results indicate that the protective effect on iron-induced lipid peroxidation by citrinin occurs due to the formation of a redox inactive Fe3+-citrinin complex, as well as from the reaction of citrinin and hydrogen peroxide.     

Proteomic 2DE database for spot selection,automated annotation,and data analysis

We present a software solution that enables faster and more accurate data analysis of 2DE/MALDI TOF MS data. The software supports data analysis through a number of automated data selection functions and advanced graphical tools. Once protein identities are determined using MALDI TOF MS, automated data retrieval from online databases provides biological information. The software, called 2DDB, reduces analysis time to a fraction without losing any quality compared to more manual data analysis. The database contains over 100,000 data entries, and selected parts can be reached at http://2ddb.org.