Influence of Prey Size on the Capture of Social Wasps (Hymenoptera: Vespidae) by the Orb-Web Spider Nephilengys cruentata

The objective of the present study was to evaluate the plasticity of the hunting behavior of the spider Nephilengys cruentata (Araneae: Nephilidae) facing different species of social wasps. Considering that wasps can consume various species of spiders and that their poison can be used as defense against many predators, the effect of the corporal size of the prey was evaluated in the behavior of N. cruentata. Predation experiments were conducted using three species of social wasps of different sizes and the data registered in this research were compiled through annotations and filming of the hunting behavior of each spider, in relation to the offered prey. The results revealed that the size of the wasp and the sequential offer of prey change the hunting behavior of the spider, and prey of large size have high influence on this behavior.

Burrow ventilation and associated porewater irrigation by the polychaete Marenzelleria viridis

Burrow ventilation of benthic infauna generates water currents that irrigate the interstices of the sediments surrounding the burrow walls. Such activities have associated effects on biogeochemical processes affecting ultimately important ecosystem processes. In this study, the ventilation and irrigation behavior of Marenzelleria viridis, an invasive polychaete species in Europe, was analyzed using different approaches. M. viridis showed to perform two types of ventilation: (1) muscular pumping of water out of the burrow and (2) cilia pumping of water into the burrow. Flowmeter measurements presented muscular pumping in time averaged rates of 0.15 ml min(-1). Oxygen needle electrodes positioned above the burrow openings revealed that muscular undulation of the worm body pumps anoxic water out of the burrow. On the other hand, microscope observations of the animal showed that ventilation of oxygen-rich water in the burrow occurs by ciliary action. The volume of water irrigated by M. viridis appears to vary linearly within the first 24 h incubation, with rates ranging from 0.003 to 0.01 ml min(-1). From those rates we could estimate that the time averaged rate of cilia ventilation should be about 0.16 ml min(-1). Since the cilia pumping into the burrow occurs in periods of 24 +/- 12 min and at 50-70% of the measured time, considerable amounts of water from deeper sediments may percolate upwards to the sediment surface. This water is rich in reduced compounds and nutrients and may have important associated ecological implications in the ecosystem (e.g. affecting redox conditions, organic matter degradation, benthic recruitment and primary production). (C) 2010 Elsevier B.V. All rights reserved.

A crucial role for IL-6 in the CNS of rats during fever induced by the injection of live E. coli

Interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, and IL-6 have been established as important mediators of fever induced by lipopolysaccharide (LPS) from Gram-negative bacteria. Whether these pro-inflammatory cytokines are also important in mediating fever induced by live bacteria remains less certain. We therefore investigated the following: (1) the synthesis of TNF-alpha, IL-1 beta, and IL-6 during E. coli-induced fever and (2) the effect of blocking the action of cytokines within the brain on E. coli-induced fever. Body or tail skin temperature (bT or Tsk, respectively) was measured by biotelemetry or telethermometry, every 30 min, during 6 or 24 h. Depending on the number of colony-forming units (CFU) injected i.p., administration of E. coli induced a long-lasting increase in bT of male Wistar rats. The duration of fever did not correlate with the number of CFU found in peritoneal cavity or blood. Because 2.5 x 10(8) CFU induced a sustained fever without inducing a state of sepsis/severe infection, this dose was used in subsequent experiments. The E. coli-induced increase in bT was preceded by a decrease in Tsk, reflecting a thermoregulatory response. TNF-alpha, IL-1 beta, and IL-6 were detected at 3 h in serum of animals injected i.p. with E. coli. In the peritoneal exudates, TNF-alpha, IL-1 beta, and IL-6 were detected at 0.5 and 3 h after E. coli administration. Moreover, both IL-1 beta and IL-6, but not TNF-alpha, were found in the cerebrospinal fluid (CSF) and hypothalamus of animals injected with E. coli. Although pre-treatment (i.c.v., 2 mu l, 15 min before) with anti-IL-6 antibody (anti-IL-6, 5 mu g) reduced E. coli-induced fever, pre-treatment with either IL-1 receptor antagonist (IL-1ra, 200 mu g) or soluble TNF receptor I (sTNFRI, 500 ng) had no effect on the fever response. In conclusion, replicating E. coli promotes an integrated thermoregulatory response in which the central action of IL-6, but not IL-1 and TNF, appears to be important.

Galactose Recognition by the Apicomplexan Parasite Toxoplasma gondii

Toxosplasma gondii is the model parasite of the phylum Apicomplexa, which contains numerous obligate intracellular parasites of medical and veterinary importance, including Eimeria, Sarcocystis, Cryptosporidium, Cyclospora, and Plasmodium species. Members of this phylum actively enter host cells by a multistep process with the help of microneme protein (MIC) complexes that play important roles in motility, host cell attachment, moving junction formation, and invasion. T. gondii (Tg)MIC1-4-6 complex is the most extensively investigated microneme complex, which contributes to host cell recognition and attachment via the action of TgMIC1, a sialic acid-binding adhesin. Here, we report the structure of TgMIC4 and reveal its carbohydrate-binding specificity to a variety of galactose-containing carbohydrate ligands. The lectin is composed of six apple domains in which the fifth domain displays a potent galactose-binding activity, and which is cleaved from the complex during parasite invasion. We propose that galactose recognition by TgMIC4 may compromise host protection from galectin-mediated activation of the host immune system.

Antimicrobial effectiveness of silver nanoparticles co-stabilized by the bioactive copolymer pluronic F68

Abstract Background Silver nanoparticles (AgNps) have attracted much interest in biomedical engineering, since they have excellent antimicrobial properties. Therefore, AgNps have often been considered for incorporation into medical products for skin pathologies to reduce the risk of contamination. This study aims at evaluating the antimicrobial effectiveness of AgNps stabilized by pluronic™ F68 associated with other polymers such as polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Methods AgNps antimicrobial activity was evaluated using the minimum inhibitory concentration (MIC) method. The action spectrum was evaluated for different polymers associated with pluronic™ F68 against the gram negative bacteria P. aeuroginosa and E. coli and the gram positive bacteria S. Aureus. Results AgNps stabilized with PVP or PVA and co-stabilized with pluronic™ F68 are effective against E. coli and P. aeruginosa microorganisms, with MIC values as low as 0.78% of the concentration of the original AgNps dispersion. The antimicrobial action against S. aureus is poor, with MIC values not lower than 25%. Conclusions AgNps stabilized by different polymeric systems have shown improved antimicrobial activity against gram-negative microorganisms in comparison to unstabilized AgNps. Co-stabilization with the bioactive copolymer pluronic™ F68 has further enhanced the antimicrobial effectiveness against both microorganisms. A poor effectiveness has been found against the gram-positive S. aureus microorganism. Future assays are being delineated targeting possible therapeutic applications.

Pacta sunt servanda versus the social role of contracts: the case of Brazilian agriculture contracts

This study explores the instability created by contradictory court decisions related with contract breaches. Forward marketing contracts represent an important source of resources to finance Brazilian agriculture, however a large number of contract breaches were observed during a period of marked increase in soy prices. The study analyzed 161 judicial appeal decisions and a survey was carried with 70 farmers. The results show the difference of judges' interpretation and the existence of second order effects. The effects of court decisions were more requirements of guarantees and the reduction in the number of contracts. Those soybean farmers who did not breach their contracts have also been negatively affected by the strategic reactions of trading and processing companies. The concept of "social function of the contract" introduced in Brazilian civil code led to a higher degree of instability in contracts, raising transaction costs and motivating private economic sanctions.