Loss of penicillinase plasmids of Staphylococcus aureus after treatment with L-ascorbic acid

When 2 clinical strains of plasmid-mediated penicillin-resistant Staphylococcus aureus were treated with 1 mM sodium ascorbate for 6 h, 12-35% colony-forming units (CFU) irreversibly lost their ability to produce beta-lactamase. Agarose gel electrophoresis showed the disappearance of the plasmid bands from the lysates of colonies in which susceptibility to penicillin was induced by ascorbate treatment. Since ascorbic acid is a compound that is completely non-toxic, the possibility of its therapeutic use in the treatment of multiresistant bacterial diseases is proposed.     

Functional analysis of tryptophans alpha 62 and beta 120 on HLA-DM.

In the endocytic pathway of antigen-presenting cells, HLA-DM catalyzes the exchange between class II-associated invariant chain peptide (CLIP) and antigenic peptides onto major histocompatibility complex class II molecules. At low pH of lysosomal compartments, both HLA-DM and HLA-DR undergo conformational changes, and it was recently postulated that two partially exposed tryptophans on HLA-DM might be involved in the interaction between the two molecules. To define contact regions on HLA-DM, we have conducted site-directed mutagenesis on those two hydrophobic residues. The HLA-DM alphaW62A,betaW120A (DM(W62A/W120A)) double mutant was expressed in HLA-DR(+) HeLa cells expressing invariant chain, and the activity of this DM molecule was assessed. Flow cytometry analysis of cell surface DR-CLIP complexes revealed that DM(W62A/W120A) removes CLIP as efficiently as its wild-type counterpart. DM(W62A/W120A) was found in the endocytic pathway by immunofluorescence, and DM-DR complexes were immunoprecipitated from these cells at pH 5. Finally, mutations alphaW62A and betaW120A on HLA-DM did not affect the association with HLA-DO. The complex egresses the endoplasmic reticulum and accumulates in endocytic vesicles. Moreover, DO and DM(W62A/)W120A were co-immunoprecipitated at pH 7. We conclude that the alpha62 and beta120 tryptophan residues are not required for the activity of DM, nor are they directly implicated in the interaction with DR or DO.     

Peroxiredoxins are involved in two independent signalling pathways in the abiotic stress protection in Vitis vinifera

Peroxiredoxins (Prxs) play major roles in preventing oxidative damage and their function is consistent with the presence of Prx isoforms in most, if not all, cellular compartments and their expression is dependent on environmental conditions. The aim of this study was to identify and characterize genes encoding Prxs in Vitis vinifera. Quantitative real time polymerase chain reaction (qRT PCR) was used to determine their response to irradiance, heat, and water stress. We identified seven vvprx genes, two of which were especially responsive to water stress, followed by heat stress, but no major changes were observed after high irradiance. The vvprxIIF targeted to mitochondria was the most responsive to water stress and it might be involved in drought tolerance through H₂O₂ signalling. The vvprxII-2, a putative PrxII, is targeted to the chloroplasts and was the most responsive to heat stress. It might be related with abscisic acid-dependent thermotolerance. Additional key words: abscisic acid, antioxidants, grapevine, heat stress, photosynthesis, qRT PCR, water stress.     

Sex differences in leadership during group movement in mantled howler monkeys (Alouatta palliata)

Benefits of group life depend in large part on whether animals remain cohesive, which often requires collective decisions about where and when to move. During a group movement, the leader may be considered as the individual occupying the vanguard position of the group progression, when its movement evokes following by other group members. In nondespotic societies, individuals with greater incentives to move frequently are leaders. During 15 months of observations (1,712 contact hours), we investigated two mantled howler monkey (Alouatta palliata) groups at La Flor de Catemaco (Los Tuxtlas, Mexico) to examine whether sex and female reproductive state influenced leadership likelihood in two contexts: movements toward feeding trees; movements associated with loud calls, a group-defense behavior used by males of this genus. Females led and occupied forward positions during group movements toward feeding trees more often than adult males. Adult females led these movements more frequently when they were gestating than when they were lactating or cycling. There were no differences between sexes in the leadership of group movements associated with loud calls. Leadership by gestating females is perhaps the result of their higher nutritional/energetic needs when compared with cycling females, and of their greater mobility when compared with lactating females carrying dependent offspring. Female leadership during movements toward feeding trees may be a mechanism to optimize access to food resources in mantled howler monkeys.     

A unique hairpin-type tail-anchored SNARE starts to solve a long-time puzzle

Macroautophagy mediates recycling of intracellular material by a multistep pathway, ultimately leading to the fusion of closed double-membrane structures, called autophagosomes, with the lysosome. This event ensures the degradation of the autophagosome content by lysosomal proteases followed by the release of macromolecules by permeases and, thus, it accomplishes the purpose of macroautophagy (hereafter referred to as autophagy). Because fusion of unclosed autophagosomes (i.e., phagophores) with the lysosome would fail to degrade the autophagic cargo, this critical step has to be tightly controlled. Yet, until recently, little was known about the regulation of this event and the factors orchestrating it. A punctum in this issue highlights the recent paper by Noboru Mizushima and his collaborators that answered the question of how premature fusion of phagophores with the lysosome is prevented prior to completion of autophagosome closure.     

Stream Noise,Hybridization, and Uncoupled Evolution of Call Traits in Two Lineages of Poison Frogs: Oophaga histrionica and Oophaga lehmanni

According to the acoustic adaptation hypothesis, communication signals are evolutionary shaped in a way that minimizes its degradation and maximizes its contrast against the background noise. To compare the importance for call divergence of acoustic adaptation and hybridization, an evolutionary force allegedly promoting phenotypic variation, we compared the mate recognition signal of two species of poison frogs (Oophaga histrionica and O. lehmanni) at five localities: two (one per species) alongside noisy streams, two away from streams, and one interspecific hybrid. We recorded the calls of 47 males and characterized the microgeographic variation in their spectral and temporal features, measuring ambient noise level, body size, and body temperature as covariates. As predicted, frogs living in noisy habitats uttered high frequency calls and, in one species, were much smaller in size. These results support a previously unconsidered role of noise on streams as a selective force promoting an increase in call frequency and pleiotropic effects in body size. Regarding hybrid frogs, their calls overlapped in the signal space with the calls of one of the parental lineages. Our data support acoustic adaptation following two evolutionary routes but do not support the presumed role of hybridization in promoting phenotypic diversity.     

Bifunctional 3-hydroxy-4-pyridinone derivatives as potential pharmaceuticals: synthesis, complexation with Fe(III), Al(III) and Ga(III) and in vivo evaluation with 67Ga

A series of extra-functionalized 3-hydroxy-4-pyridinone chelators of hard metal ions, containing different side-chains with peptidomimetic groups, was studied to assess the effect of those groups on the physico-chemical properties, the metal-chelating affinity and the in vivo behaviour of the compounds, in view of their potential pharmaceutical applications. Besides the synthesis of the chelators, the study of their properties in aqueous solution alone and in the presence of M ³⁺ (M = Fe, Ga and Al) was performed by potentiometric/spectroscopic techniques. The octanol/water partition coefficient values of these hydroxypyridinone derivatives cover ca. 3 orders of magnitude (1.1 > log P > −2). They all form very stable tris-chelated M(III) complexes, the pFe and pGa values ranging up to five orders of magnitude. The in vivo studies showed the effect of the ligands on the biodistribution of ⁶⁷Ga citrate and also of ⁶⁷Ga-complexes in mice, in view of the potential use of the ligands or complexes as metal decorporating or as imaging agents, respectively. Although almost all these peptidomimetic hydroxypyridinone derivatives present very rapid clearance rate from most organs, the L-ornithine derivative (H₂L⁹) shows to be superior to the others and as good as Deferiprone as metal decontaminant of Ga. Concerning the ⁶⁷Ga complexes, the benzyl-propylamine (H₂L³) shows considerable bone retention, thus suggesting its potential application as imaging agent.Electronic Supplementary Material Supplementary material is available for this article at An erratum to this article can be found at     

Specific Midgut Region Controlling the Symbiont Population in an Insect-Microbe Gut Symbiotic Association

Many insects possess symbiotic bacteria that affect the biology of the host. The level of the symbiont population in the host is a pivotal factor that modulates the biological outcome of the symbiotic association. Hence, the symbiont population should be maintained at a proper level by the host''s control mechanisms. Several mechanisms for controlling intracellular symbionts of insects have been reported, while mechanisms for controlling extracellular gut symbionts of insects are poorly understood. The bean bug Riptortus pedestris harbors a betaproteobacterial extracellular symbiont of the genus Burkholderia in the midgut symbiotic organ designated the M4 region. We found that the M4B region, which is directly connected to the M4 region, also harbors Burkholderia symbiont cells, but the symbionts therein are mostly dead. A series of experiments demonstrated that the M4B region exhibits antimicrobial activity, and the antimicrobial activity is specifically potent against the Burkholderia symbiont but not the cultured Burkholderia and other bacteria. The antimicrobial activity of the M4B region was detected in symbiotic host insects, reaching its highest point at the fifth instar, but not in aposymbiotic host insects, which suggests the possibility of symbiont-mediated induction of the antimicrobial activity. This antimicrobial activity was not associated with upregulation of antimicrobial peptides of the host. Based on these results, we propose that the M4B region is a specialized gut region of R. pedestris that plays a critical role in controlling the population of the Burkholderia gut symbiont. The molecular basis of the antimicrobial activity is of great interest and deserves future study.