Three‐dimensional microscale modelling of CO2 transport and light propagation in tomato leaves enlightens photosynthesis

We present a combined three‐dimensional (3‐D) model of light propagation, CO₂ diffusion and photosynthesis in tomato (Solanum lycopersicum L.) leaves. The model incorporates a geometrical representation of the actual leaf microstructure that we obtained with synchrotron radiation X‐ray laminography, and was evaluated using measurements of gas exchange and leaf optical properties. The combination of the 3‐D microstructure of leaf tissue and chloroplast movement induced by changes in light intensity affects the simulated CO₂ transport within the leaf. The model predicts extensive reassimilation of CO₂ produced by respiration and photorespiration. Simulations also suggest that carbonic anhydrase could enhance photosynthesis at low CO₂ levels but had little impact on photosynthesis at high CO₂ levels. The model confirms that scaling of photosynthetic capacity with absorbed light would improve efficiency of CO₂ fixation in the leaf, especially at low light intensity.     

Tetraspanins on the surface of Schistosoma mansoni are protective antigens against schistosomiasis

Schistosomes are blood-dwelling flukes that infect 200 million people worldwide and are responsible for hundreds of thousands of deaths annually. Using a signal sequence trap, we cloned from Schistosoma mansoni two cDNAs, Sm-tsp-1 and Sm-tsp-2, encoding the tetraspanin (TSP) integral membrane proteins TSP-1 and TSP-2. We raised antibodies to recombinant TSP fusion proteins and showed that both proteins are exposed on the surface of S. mansoni. Recombinant TSP-2, but not TSP-1, is strongly recognized by IgG1 and IgG3 (but not IgE) from naturally resistant individuals but is not recognized by IgG from chronically infected or unexposed individuals. Vaccination of mice with the recombinant proteins followed by challenge infection with S. mansoni resulted in reductions of 57% and 64% (TSP-2) and 34% and 52% (TSP-1) for mean adult worm burdens and liver egg burdens, respectively, over two independent trials. Fecal egg counts were reduced by 65-69% in both test groups. TSP-2 in particular provided protection in excess of the 40% benchmark set by the World Health Organization for progression of schistosome vaccine antigens into clinical trials. When coupled with its selective recognition by naturally resistant people, TSP-2 seems to be an effective vaccine antigen against S. mansoni.     

Adaptation to climate through flowering phenology: a case study in Medicago truncatula

Local climatic conditions likely constitute an important selective pressure on genes underlying important fitness‐related traits such as flowering time, and in many species, flowering phenology and climatic gradients strongly covary. To test whether climate shapes the genetic variation on flowering time genes and to identify candidate flowering genes involved in the adaptation to environmental heterogeneity, we used a large Medicago truncatula core collection to examine the association between nucleotide polymorphisms at 224 candidate genes and both climate variables and flowering phenotypes. Unlike genome‐wide studies, candidate gene approaches are expected to enrich for the number of meaningful trait associations because they specifically target genes that are known to affect the trait of interest. We found that flowering time mediates adaptation to climatic conditions mainly by variation at genes located upstream in the flowering pathways, close to the environmental stimuli. Variables related to the annual precipitation regime reflected selective constraints on flowering time genes better than the other variables tested (temperature, altitude, latitude or longitude). By comparing phenotype and climate associations, we identified 12 flowering genes as the most promising candidates responsible for phenological adaptation to climate. Four of these genes were located in the known flowering time QTL region on chromosome 7. However, climate and flowering associations also highlighted largely distinct gene sets, suggesting different genetic architectures for adaptation to climate and flowering onset.     

The major histocompatibility complex-restricted antigen receptor on T cells. IX. Role of accessory molecules in recognition of antigen plus isolated IA

Antibody inhibition studies were done to determine which molecules on the surface of the T cell hybridomas other than their receptors for antigen plus IAd were involved in interaction with antigen-presenting B cells, with artificial IAd membranes on glass beads, or with anti-receptor antibodies coupled to Sepharose beads. We found that T cell LFA-1 was only involved when B cells were used to present antigen plus IAd, whereas T cell L3T4 was involved in the response of T cells to antigen plus IAd either on cells or in artificial membranes, but not if anti-receptor antibodies were used to stimulate the T cells. From these results we concluded that LFA-1 may be involved in the recognition of a ligand on cells that was not present in artificial membranes, but that L3T4 might interact with a nonpolymorphic portion of class II molecules present in both intact antigen-presenting cells and the antigen-presenting artificial membranes.     

Synthesis of theophylline derivatives and study of their activity as antagonists at adenosine receptors

The synthesis of oligo(ethylene glycol)-alkene substituted theophyllines in positions 7 and/or 8 is described. The binding activity at adenosine receptors of selected derivatives was studied. Compound 2 showed high affinity for human A_2B receptor (K_i = 4.16 nM) with a selectivity K_iA2A/K_iA2B of 24.1, and a solubility in water of 1 mM. The alkenyl substituent in some of the theophylline derivatives allows for covalent attachment of them onto hydrogen-terminated silicon substrate surfaces via hydrosilylation. Alternatively, an azido group was incorporated to an oligo(ethylene glycol)theophylline derivative as an anchor for tethering the molecules on ethynyl presenting surfaces via click reaction.     

The diagonal band of Broca is involved in the pressor pathway activated by noradrenaline microinjected into the periaqueductal gray area of rats

AimsThe dorsal periaqueductal gray area (dPAG) is involved in cardiovascular modulation. Previously, we reported that noradrenaline (NA) microinjection into the dPAG caused a pressor response that was mediated by vasopressin release into the circulation. However, the neuronal pathway that mediates this response is as yet unknown. There is evidence that chemical stimulation of the diagonal band of Broca (dbB) also causes a pressor response mediated by systemic vasopressin release. In the present study, we evaluated the participation of the dbB in the pressor response caused by NA microinjection into the dPAG as well as the existence of neural connections between these areas.Main methodsWith the above goal, we verified the effect of the pharmacological ablation of the dbB on the cardiovascular response to NA microinjection into the dPAG of unanesthetized rats. In addition, we microinjected the neuronal tracer biotinylated-dextran-amine (BDA) into the dPAG and looked for efferent projections from the dPAG to the dbB.Key findingsThe pharmacologically reversible ablation of the dbB with local microinjection of CoCl₂ significantly reduced the pressor response caused by NA microinjection (15 nmol/50 nL) into the dPAG. In addition, BDA microinjection into the dPAG labeled axons in the dbB, pointing to the existence of direct connections between these areas.SignificanceThe present results indicate that synapses within the dbB are involved in the pressor pathway activated by NA microinjection into the dPAG and direct neural projection from the dPAG to the dbB may constitute the neuroanatomic substrate for this pressor pathway.     

The actions of fisetin on glucose metabolism in the rat liver

Fisetin is a flavonoid dietary ingredient found in the smoke tree (Cotinus coggyria) and in several fruits and vegetables. The effects of fisetin on glucose metabolism in the isolated perfused rat liver and some glucose‐regulating enzymatic activities were investigated. Fisetin inhibited glucose, lactate, and pyruvate release from endogenous glycogen. Maximal inhibitions of glycogenolysis (49%) and glycolysis (59%) were obtained with the concentration of 200 µM. The glycogenolytic effects of glucagon and dinitrophenol were suppressed by fisetin 300 µM. No significant changes in the cellular contents of AMP, ADP, and ATP were found. Fisetin increased the cellular content of glucose 6‐phosphate and inhibited the glucose 6‐phosphatase activity. Gluconeogenesis from lactate and pyruvate or fructose was inhibited by fisetin 300 µM. Pyruvate carboxylation in isolated intact mitochondria was inhibited (IC₅₀ = 163.10 ± 12.28 µM); no such effect was observed in freeze‐thawing disrupted mitochondria. It was concluded that fisetin inhibits glucose release from the livers in both fed and fasted conditions. The inhibition of pyruvate transport into the mitochondria and the reduction of the cytosolic NADH‐NAD⁺ potential redox could be the causes of the gluconeogenesis inhibition. Fisetin could also prevent hyperglycemia by decreasing glycogen breakdown or blocking the glycogenolytic action of hormones. Copyright © 2010 John Wiley & Sons, Ltd.     

Spatial Heterogeneity and Nestmate Encounters Affect Locomotion and Foraging Success in the Ant Dorymyrmex goetschi

The spatial structure of habitats contains physical barriers that restrict the performance of diverse behavioural tasks. In heterogeneous habitats, information acquisition may allow animals to improve the performance of diverse activities such as foraging and locomotion. Nonetheless, changes in locomotion performance and their effects on the foraging success of animals have been scarcely studied. We examined these relationships in the harvester ant Dorymyrmex goetschi (subfamily Dolichoderinae) under laboratory conditions. In an experimental arena, we offered a food patch located at a fixed distance from the nest entrance. Landscape heterogeneity was created using wooden cubes arranged in different types of spatial distribution. We video recorded the behaviour of different colonies and quantified the number of active foragers, number of head contacts per capita per inbound trip, path length by workers that transported a food load from the resource patch to the nest, time invested in inbound travels, and the number of prey captured per colony. During the initial phase of patch exploitation, the number of foragers and prey captured were significantly lower than during the half and final phases of the experiment. Landscapes with greater spatial heterogeneity increased travel time and diminished locomotion velocity. A multiple regression analysis revealed that greater antennal contacts and locomotion velocities increased prey removal. Therefore, in this study, we documented a formal link between variables that characterize the movement paths of individuals and the foraging success of a colony. Information transfer between individuals generated a collective work with a concomitant improvement of food exploitation.     

Sexually dimorphic tegumental gland openings in Laniatores (Arachnida,Opiliones), with new data on 23 species

Sexually dimorphic glands often release sexual pheromones both in vertebrates and invertebrates. Species of Laniatores (Arachnida, Opiliones) seem to depend on chemical communication but few studies have addressed this topic. In this study, we review the literature for the Phalangida and present new data for 23 species of Laniatores. In 16 taxa, we found previously undescribed sexually dimorphic glandular openings on the femur, patella, metatarsus, and tarsus of legs I and metatarsus of legs III and IV. For the other species, we provide scanning electron micrographs of previously undescribed sexually dimorphic setae and pegs located on swollen regions of the legs. We also list additional species in which males have swollen regions on the legs, including the tibia, metatarsus, and tarsus of legs I, trochanter and tibia of legs II, femur, metatarsus, and tarsus of legs III, and metatarsus and tarsus of legs IV. The function and biological role of the secretions released by these glands are discussed. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Evaluation of Toxoplasma gondii placental transmission in BALB/c mice model

Toxoplasma gondii infection is common worldwide and highly important to pregnant women as it can be transmitted to the fetus via the placenta. This study aimed at evaluating the prevention of placental transmission in two different strains after chronic infection with each one of the strains. A BALB/c mice model was inoculated 30 days before breeding (immunization) and re-infected 12 and 15 days after pregnancy (challenge). Seven experimental groups were assayed: G1: ME49-immunization (type II), M7741-challenge (type III); G2: M7741-immunization, ME49-challenge; G3, ME49-immunization; G4: M7741-immunization; G5: ME49-challenge; G6: M7741-challenge; G7: saline solution inoculation. Serology, mouse bioassay, PCR and RLFP of the uterus, placenta and fetus were performed to determine the congenital transmission of the strains challenged after chronic infection. IgG T. gondii antibodies were detected in G1, G2, G3 and G4, but not in G5, G6 and G7. All animals of G5 and G6 were IgM-positive. Congenital infection was not detected by bioassay and PCR. Nonetheless, placentas from G3 and G4 resulted positive but no corresponding fetal infection was detected. G1 and G2 did not show the genotype of the strain challenged during pregnancy, only those of chronic infection. Thus, the chronically infected BALB/c mice showed no re-infection after inoculation with another strain during pregnancy. Further studies with different parasite loads and different mice lineages are needed.