Critical analysis of phospholipid hydrolyzing activities in ripening tomato fruits. Study by spectrofluorimetry and high-performance liquid chromatography

Using the spectrofluorimetric method described by Wittenaueret al. [Wittenauer, L.A., Shirai, K., Jackson, R.L., and Johnson, J.D. (1984)Biochem. Biophys. Res. Commun. 118, 894–901] for phospholipase A₂ (PLA₂) measurement, we have detected a phospholipase activity in Ailsa Craig and in mutantrin tomatoes at their normal harvest time (mature green stage). This activity in Ailsa Craig tomatoes increased at the beginning of fruit ripening (green-orange stage) and then decreased slowly. The decrease in activity, however, was greater when ripening occurred after tomato picking at normal harvest time than when ripening occurred on tomato plants. This phospholipase activity was always higher inrin tomatoes than in normal ones. Thin-layer chromatography of compounds obtained after incubation of tomato extract demonstrated a decrease in the substrate 1-acyl-2-{6[(7-nitro-2,1,3, benzoxadiazol-4-yl)amino]-caproyl}-sn-glycero-3-phosphocholine (C₆-NBD-PC), and an increase in one product (NBD-aminohexanoic acid), but failed to detect the second product (1-acyl-sn-glycero-3-phosphocholine). We, therefore, developed a new one-step method for separation and quantification of a mixture of phospholipids and other lipids, using straight-phase-high-performance liquid chromatography with light-scattering detection. This method detected another fatty acid-releasing activity in enzyme extract from green-orange tomatoes. This lipolytic enzyme (or family of enzymes) slowly produced free fatty acids when 1-oleoyl-sn-glycero-3-phosphocholine was added as substrate. The production of fatty acids was stoichiometric and more rapid when 1-oleoyl-sn-glycero-3-phosphate and 1-oleoyl-sn-glycerol were used as substrates. On the other hand, the same tomato extract was unable to hydrolyze 1,2-dioleoyl-sn-glycero-3-phosphate and 1,2-dioleoyl-sn-glycerol. Crude tomato extract exhibited lipid acyl hydrolase activity according to the definition of Galliard [Galliard, T. (1979), inAdvances in the Biochemistry and Physiology of Plant Lipids (Appelqvist, L.A., and Liljenberg, C. eds.), pp. 121–132, Elsevier, Amsterdam]. But in order to demonstrate whether tomato extract contains PLA₂ activity and/or lysophospholipase activity, further work on purified tomato extract will be necessary.     

Human amniotic membrane for guided bone regeneration of calvarial defects in mice

Due to its biological properties, human amniotic membrane (hAM) is widely studied in the field of tissue engineering and regenerative medicine. hAM is already very attractive for wound healing and it may be helpful as a support for bone regeneration. However, few studies assessed its potential for guided bone regeneration (GBR). The purpose of the present study was to assess the potential of the hAM as a membrane for GBR. In vitro, cell viability in fresh and cryopreserved hAM was assessed. In vivo, we evaluated the impact of fresh versus cryopreserved hAM, using both the epithelial or the mesenchymal layer facing the defect, on bone regeneration in a critical calvarial bone defect in mice. Then, the efficacy of cryopreserved hAM associated with a bone substitute was compared to a collagen membrane currently used for GBR. In vitro, no statistical difference was observed between the conditions concerning cell viability. Without graft material, cryopreserved hAM induced more bone formation when the mesenchymal layer covered the defect compared to the defect left empty. When associated with a bone substitute, such improved bone repair was not observed. These preliminary results suggest that cryopreserved hAM has a limited potential for GBR.

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Sequestration, Maintenance, and Tissue Distribution of Pyrrolizidine Alkaloid N-Oxides in Larvae of Two Oreina Species

Oreina cacaliae and O. speciosissima are leaf beetles that, as larvae and adults, sequester pyrrolizidine alkaloid N-oxides (PAs) as defensive compounds from their host plants Adenostyles alliariae and Senecio nemorensis. As in most Oreina species, O. speciosissima is also defended by autogenously produced cardenolides (mixed defensive strategy), whereas O. cacaliae does not synthesize cardenolides and is exclusively dependent on host-plant-acquired PAs (host-derived defense). Adults of the two Oreina species were found to have the same PA storage capacity. The larvae, however, differ; larvae of O. speciosissima possess a significantly lower capability to store PAs than O. cacaliae. The ability of Oreina larvae to sequester PAs was studied by using tracer techniques with ¹⁴C-labeled senecionine N-oxide. Larvae of the two species efficiently take up [¹⁴C]senecionine N-oxide from their food plants and store the alkaloid as N-oxide. In O. cacaliae, there is a slow but continuous loss of labeled senecionine N-oxide. This effect may reflect the equilibrium between continuous PA uptake and excretion, resulting in a time-dependent tracer dilution. No noticeable loss of labeled alkaloid is associated with molting. Senecionine N-oxide is detectable in all tissues. The hemolymph is, with ca. 50–60% of total PAs, the major storage compartment, followed by the integument, with ca 30%. The alkaloid concentration in the hemolymph is approximately sixfold higher than in the solid tissues. The selectivity of PA sequestration in larvae is comparable to PA sequestration in the bodies of adult beetles.     

Influence of Social Environment on Genetically Based Subfamily Signature in the Honeybee

In honeybees, the cuticular hydrocarbon profiles are partly genetically based and differ between subfamilies, which suggests that they might be used by the workers as labels for subfamily recognition. This ability could potentially form the basis for nepotistic conflicts between subfamilies that would be detrimental to the inclusive fitness of the colony. Here we have compared the subfamily hydrocarbon profiles of 5-day-old workers maintained in isolation with those kept in their parental colony. We demonstrate that the cuticular hydrocarbon profiles tend to be less distant between most subfamilies within the hive compared with those held in isolation. The main consequence of this partial homogenization of the majority of subfamily signatures may result in a reduction of the number of recognizable subfamilies in the colony. Nevertheless, a few subfamilies retain very distinct cuticular hydrocarbon profiles.     

Effect of Gravity on Film Boiling Heat Transfer and Rewetting Temperature during Quenching

This paper describes the experimental strategy developed to improve the modeling of liquid-vapor flows during the chill down of rocket engines by cryogenic fluid in microgravity. A similarity analysis is performed to determine the relevant dimensionless numbers for the design of an experiment similar to engine flows. A literature review on reduced gravity quenching experiments, and on rewetting temperature and film boiling heat transfer shows the lack of validated models for microgravity. Experimental results obtained with the quenching of a glass tube by FC72 during parabolic flight are presented. Especially the impact of gravity and subcooling on rewetting temperature and film boiling heat transfer is investigated. Results show an increase in rewetting temperature, and a decrease in film boiling heat transfer under reduced gravity in agreement with the literature. The comparison of 0 g flow pattern with corresponding tests on ground points out a behavior at 0 g closest to 1 g upflow than 1 g downflow.     

Recent progress towards the understanding of metal–salen catalysed asymmetric alkene epoxidation

The history of the development of useful catalyst systems for the asymmetric epoxidation of alkenes is described. An overview is presented of the present state of understanding of the mechanism of the most successful catalysts to date, metal–salen complexes. Recent results from the chromium–salen series are presented and their implications for the mechanism are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Extracellular serotonin is enhanced in the striatum, but not in the dorsal hippocampus or prefrontal cortex, in rats subjected to an operant conflict procedure.

In rats trained in an operant fixed-interval-30-s schedule of food reward (FI-30s), acute exposure to contingent footshock resulted in a response suppression that was released by diazepam (DZP; 4 mg/kg ip) but not by buspirone (0.25 or 0.50 mg/kg ip). Compared with baseline, hippocampal and cortical extracellular levels of serotonin (5-HText) did not change, regardless of operant period (punished or nonpunished) and drug. In contrast, in the striatum, an increase of 5-HText levels (535%) occurred during the punished period, counteracted by DZP. This effect was observed only in rats that were low responders during both nonpunished and punished periods, that is, those that exerted an efficacious control over responding. Uncontrollable shocks or exposure to an unfamiliar open field did not modify striatal 5-HText. Together, these results suggest that an acute activation of 5-HT neurons afferent to the striatum allows the rats to efficiently block responses that are negatively reinforced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

La réglementation de la cryptologie en france de 1990 à 2005

The cryptology has been for a long time the fact of the army. The cryptography was considered not as a mean of communication but as a weapon. Nowadays, in France the cryptography can be used with a free access. The supply, the importation and the exportation of means and services of cryptology have been liberalized. The purpose of this article is to study the relations between liberty and security in the frame of the cryptology, for France. The process of liberalization can be explain by the deregulation in the telecommunication field for a small part, and by the emergence of the electronic trade for the biggest part. The security has not been forgotten. The cryptology is not a tool as the others. Some few restrictions of authorizations and declarations have been maintained. The non respect of these restrictions can generate sanctions not always used. The relation liberty/security appeared also in the electronic signature, adopted by the European Union in 1999 and in the European countries, especially in France. The electronic signature, by the way of the certification services need to use the cryptology, to be recognized and protected. The industrials have succeed, with the liberalization of the cryptology and their software, to build a famous system, not already finished: the security of the society information.     

NMR studies of the Brønsted acidity of solids. Application to superacidic solids

¹H broad-line NMR at 4 K has been used to study the acid strength of Brønsted solid and liquid acids and superacids in the presence of water as base. From the simulation of the spectra, the number of hydronium ions per acid site is deduced and is used to rank the compounds.