Role of thylakoid Ndh complex and peroxidase in the protection against photo-oxidative stress: fluorescence and enzyme activities in wild-type and ndhF-deficient tobacco

An Ndh-deficient mutant of tobacco ( Nicotiana tabacum cv. Petit Havana) was prepared by disrupting the ndhF gene in a transplastomic approach. The mutant (Δ ndhF ) showed 10% of the Ndh complex activity (EC 1.6.5.3) and 8% of the NDH-F polypeptide of that of non-transformed plants. However, in Δ ndhF , NDH-A, another Ndh polypeptide, was still present at 50% of the level in non-transformed plants. Δ ndhF tobacco showed higher sensitivity than non-transformed plants to photo-oxidative stress (as judged by chlorophyll bleaching) caused by increased light intensity and paraquat applications. These photo-oxidative treatments increased the amount and activity of the Ndh complex, thylakoid peroxidase, post-illumination chlorophyll fluorescence and non-photochemical quenching (NPQ) of chlorophyll fluorescence in non-transformed but not in Δ ndhF tobacco. Highly stressed non-transformed plants showed a rapid post-rise decline of chlorophyll fluorescence, probably indicating a re-oxidation of reduced plastoquinone. The results indicate that, in normal plants, the Ndh complex and thylakoid peroxidase (EC 1.11.1.7) provide and remove electrons, respectively, to balance the redox level of the intermediates of cyclic electron transport. In this way, they optimize the generation of the transmembrane H⁺ gradient of thylakoids and, as a consequence, increase the NPQ and the protection against photo-oxidative stress.     

Adapting pharmacokinetic properties of a humanized anti-interleukin-8 antibody for therapeutic applications using site-specific pegylation.

A neutralizing anti-interleukin-(IL-)8 monoclonal antibody was humanized by grafting the complementary determining regions onto the human IgG framework. Subsequent alanine scanning mutagenesis and phage display enabled the production of an affinity matured antibody with a >100-fold improvement in IL-8 binding. Antibody fragments can be efficiently produced in Escherichia coli but have the limitation of rapid clearance rates in vivo. The Fab' fragment of the antibody was therefore modified with polyethylene glycol (PEG) in order to obtain a more desirable pharmacokinetic profile. PEG (5-40 kDa) was site-specifically conjugated to the Fab' via the single free cysteine residue in the hinge region. In vitro binding and bioassays showed little or no loss of activity. The pharmacokinetic profiles of the 20 kDa, 30 kDa, 40 kDa, and 40 kDa branched PEG-Fab' molecules were evaluated in rabbits. Relative to the native Fab', the clearance rates of the PEGylated molecules were decreased by 44-175-fold. In a rabbit ear model of ischemia/reperfusion injury, all PEGylated Fab' molecules were as efficacious in reducing oedema as the original monoclonal antibody. These studies demonstrate that it is possible to customize the pharmacokinetic properties of a Fab' while retaining its antigen binding activity.     

Are ants botanists? Ant associative learning of plant chemicals mediates foraging for carbohydrates

1. Although associative learning is widespread across animals, its ecological importance is difficult to assess because learning is rarely studied in the field, where informative cues are juxtaposed against complex backgrounds of uninformative noise. 2. Ants rely heavily on chemical cues for foraging and engage in many ecologically important interactions with plants. Nevertheless, little is known about the role of associative learning of plant chemicals in ant foraging for carbohydrates. 3. In a field setting, the present study investigated whether the distantly related ant species Formica podzolica (Formicinae subfamily) and Tapinoma sessile (Dolichoderinae subfamily) exhibited associative learning of the chemical cues from two co-occurring plant species that are taxonomically and chemically distinct (Asteraceae: Helianthella quinquenervis and Apiaceae: Ligusticum porteri). 4. For two consecutive summers, ants were trained to forage from artificial sugar-rich baits associated with the leaf chemicals from either H. quinquenervis or L. porteri for 24 h, after which a two-choice test was deployed to assess whether ants would be more likely to select baits associated with the same (versus different) plant chemicals on which they had been trained. 5. The present study demonstrates associative learning of chemicals from both plant species, and these effects were consistent between ant species and years; training increased bait occupancy from 42% on the untrained scent to 66% on the trained scent. These results indicate that associative odour-learning may be widespread across ants and serve as an important mechanism mediating ant selection of resources.     

Ultrastructure of Elasmobranch and Teleost Erythrocytes

The ultrastructure of circulating erythrocytes of Raja clavata and Torpedo marmorata (Elasmobranchs) and Rutilus rutilus and Gobio gobio (Teleosts) was comparatively described in relation to their function. The existence of intranuclear hemoglobin and the degradation of cytoplasmic organelles are related to hemoglobin storage. Lysosome-like vesicles and microtubular marginal bands are also common elements of these cells. Thus, the presence of numerous cytoplasmic organelles in circulating erythrocytes suggests a certain immaturity, in relation to those in mammals.     

Local adaptation versus historical isolation as sources of melanin‐based coloration in the white‐throated thrush Turdus assimilis

Local adaptation seems to be one of the causes of variation in melanin‐based colors in bird plumages, related mainly to the heterogeneity of the environmental conditions along the distribution of a species. Based on comparisons of genetic (mtDNA sequences), ecological (niche models), and quantitative colorimetric data, we explored variation in plumage coloration of the white‐throated thrush Turdus assimilis, a Mesoamerican species whose dorsal color varies from brown (northern and central Mexico) to dark gray (southern Mexico and Central America). Our results suggest the existence of two major patterns of coloration in this bird, which are congruent with the genetic structure, and comparisons of ecological niche models showed that population's niches were more similar than expected by chance, suggesting that color variation in plumage of T. assimilis is not consequence of local adaptation to different environmental conditions. Our results also showed that a greater geographic distance between populations is correlated with greater colorimetric differences, suggesting that color variation in T. assimilis may be consequence of historical isolation.