Trophic ecology of two Pithecopus species (Anura: Phyllomedusidae) living in syntopy in southern Bahia,Brazil

To coexist, two species should use available resources in different ways. These differences may happen in three different dimensions: temporal, spatial and trophic. In frogs, differences in trophic dimensions are mainly due to different sizes and types of ingested prey. We studied the diet of two syntopic Pithecopus species, addressing prey selectivity and sharing of food resources. Fieldwork was undertaken at the Michelin Ecological Reserve, southern Bahia, between the years 2011 and 2012. Stomach contents were retrieved using a flushing procedure and data on prey availability was obtained. Of the 16 invertebrate categories found in the environment, 11 were consumed by P. rohdei and 12 by P. nordestinus, features that characterize a generalist diet. The most abundant category in the diet of P. nordestinus was Diptera while Hemiptera was the most consumed prey category for P. rohdei. Trophic niche overlap was high considering the size of ingested prey and lower for categories. The selectivity index showed that both species used the resources available in the environment in a slightly different way. The differences found concerning trophic ecology of these two species seem to be sufficient to allow coexistence in the studied area.     

Floral nectaries in Sapindaceae <Emphasis Type="Italic">s.s.</Emphasis>: morphological and structural diversity,and their systematic implications

We investigated the morphology and structure of the floral nectary in 11 Neotropical genera belonging to the subfamilies Dodonaeoideae and Paullinioideae (Sapindaceae) from southern South America representing three tribes (Dodonaeaeae, Paullinieae, and Melicocceae), in relation to other floral traits in species with contrasting morphological flower characteristics. Nectary organization was analyzed under light, stereoscopic, and scanning electron microscopes; Diplokeleba floribunda N.E. Br. was also observed using transmission electron microscopy. Our comparative data may contribute to the understanding of floral nectary evolution and systematic value in this family. The nectaries were studied in both staminate and pistillate flowers. All the floral nectaries are typical of Sapindaceae: extrastaminal, receptacular, structured, and persistent. The anatomical analysis revealed a differentiated secretory parenchyma and an inner non-secretory parenchyma; the nectary is supplied by phloem traces and, less frequently, by phloem and xylem traces. Nectar is secreted through nectarostomata of anomocytic type. The anatomical analysis showed the absence of nectary in the three morphs of Dodonaea viscosa flowers. Nectary ultrastructure is described in D. floribunda. In this species, the change in nectary color is related to progressive accumulation of anthocyanins during the functional phase. We found relatively small variation in the nectary structural characteristics compared with large variation in nectary morphology. The latter aspect agreed with the main infrafamilial groupings revealed by recent phylogenetic studies, so it is of current valuable systematic importance for Sapindaceae. In representatives of Paullinieae, the reduction of the floral nectary to 4–2 posterior lobes should be interpreted as a derived character state.     

Dynamic single gold nanoparticle visualization by clinical intracoronary optical coherence tomography

The potential use of Gold Nanoparticles (GNPs) as contrast agents for clinical intracoronary frequency domain Optical Coherence Tomography (OCT) is here explored. The OCT contrast enhancement caused by GNPs of different sizes and morphologies has been systematically investigated and correlated with their optical properties. Among the different GNPs commercially available with plasmon resonances close to the operating wavelength of intracoronary OCT (1.3 µm), Gold Nanoshells (GNSs) have provided the best OCT contrast due to their largest scattering cross section at this wavelength. Clinical intracoronary OCT catheters are here demonstrated to be capable of three dimensional visualization and real‐time tracking of individual GNSs. Results here included open an avenue to novel application of intravascular clinical OCT in combination with GNPs, such as real time evaluation of intravascular obstructions or pressure gradients.

     

Maintenance of oxidative phosphorylation protects cells from Actinobacillus actinomycetemcomitans leukotoxin-induced apoptosis

Subnanomolar concentrations (3 × 10⁻¹⁰ M) of Actinobacillus actinomycetemcomitans leukotoxin (Ltx) trigger apoptosis of JY cells, as shown by a decrease in mitochondrial transmembrane potential (ΔΨ_m), hyperproduction of reactive oxygen species (ROS) and release of cytochrome c from the intermembrane space. When compared with heat-inactivated leukotoxin (ΔI Ltx) controls, ATP levels in Ltx-treated JY cells continued to decrease during a 24 h experiment while cytoplasmic ADP concentrations were increasing. These results suggest that a blockage occurred in ATP/ADP exchange. To maintain ATP/ADP exchange, JY cells were transfected with bcl -2 and bcl -x_L and incubated with Ltx. ATP levels of the transfected cells decreased to 67% (JY/ bcl -2) and 73% (JY/ bcl-x _L) after the experiment. Furthermore, cytochrome c remained localized to the mitochondrial fraction of Ltx-treated JY/ bcl -2 and JY/ bcl-x _L cells, whereas its presence in the cytoplasmic fraction of JY/ gen cells suggests an uncoupling of electron transport. Expression of bcl -2 and bcl-x _L in cells inhibited downstream apoptotic events such as cleavage of poly(ADP-ribose) polymerase, DNA fragmentation and activation of a family of caspases. The results indicate that Ltx induces apoptosis through a mitochondrial pathway that involves decreased levels of the ADP in the mitochondrial matrix, a lack of substrate for ATP synthetase and arrest of oxidative phosphorylation.     

Effect of codon optimization on the enhancement of the β-carotene contents in rice endosperm

A β-carotene is the most well-known dietary source as provitamin A carotenoids. Among β-carotene-producing Golden Rice varieties, PAC (Psy:2A:CrtI) rice has been previously developed using a bicistronic recombinant gene that linked the Capsicum Psy and Pantoea CrtI genes by a viral 2A sequence. To enhance β-carotene content by improving this PAC gene, its codon was optimized for rice plants (Oryza sativa L.) by minimizing the codon bias between the transgene donor and the host rice and was then artificially synthesized as stPAC (stPsy:2A:stCrtI) gene. The GC content (58.7 from 50.9%) and codon adaptation index (0.85 from 0.77) of the stPAC gene were increased relative to the original PAC gene with 76% DNA identity. Among 67 T₁ seeds of stPAC transformants showing positive correlations between transgene copy numbers (up to three) and carotenoid contents, three stPAC lines with a single intact copy were chosen to minimize unintended insertional effects and compared to the representative line of the PAC transgene with respect to their codon optimization effects. Translation levels were stably increased in all three stPAC lines (3.0-, 2.5-, 2.9-fold). Moreover, a greater intensity of the yellow color of stPAC seeds was correlated with enhanced levels of β-carotene (4-fold, 2.37 μg/g) as well as total carotenoid (2.9-fold, 3.50 μg/g) relative to PAC seeds, suggesting a β-branch preference for the stPAC gene. As a result, the codon optimization of the transgene might be an effective tool in genetic engineering for crop improvement as proven at the enhanced levels of translation and carotenoid production.