Characterization of an ATP diphosphohydrolase activity (APYRASE,EC 3.6.1.5) in rat blood platelets

In the present report we describe an apyrase (ATP diphosphohydrolase, EC 3.6.1.5) in rat blood platelets. The enzyme hydrolyses almost identically quite different nucleoside di- and triphosphates. The calcium dependence and pH requirement were the same for the hydrolysis of ATP and ADP and the apparent Km values were similar for both Ca²⁺-ATP and Ca²⁺-ADP as substrates. Ca²⁺-ATP and Ca²⁺-ADP hydrolysis could not be attributed to the combined action of different enzymes because adenylate kinase, inorganic pyrophosphatase and nonspecific phosphatases were not detected under our assay conditions. The Ca²⁺-ATPase and Ca²⁺-ADPase activity was insensitive to ATPase, adenylate kinase and alkaline phosphatase classical inhibitors, thus excluding these enzymes as contaminants. The results demonstrate that rat blood platelets contain an ATP diphosphohydrolase involved in the hydrolysis of ATP and ADP which are vasoactive and platelet active adenine nucleotides.     

Alternative Oxidase Expression in the Mouse Enables Bypassing Cytochrome c Oxidase Blockade and Limits Mitochondrial ROS Overproduction

Cyanide-resistant non-phosphorylating respiration is known in mitochondria from plants, fungi, and microorganisms but is absent in mammals. It results from the activity of an alternative oxidase (AOX) that conveys electrons directly from the respiratory chain (RC) ubiquinol pool to oxygen. AOX thus provides a bypath that releases constraints on the cytochrome pathway and prevents the over-reduction of the ubiquinone pool, a major source of superoxide. RC dysfunctions and deleterious superoxide overproduction are recurrent themes in human pathologies, ranging from neurodegenerative diseases to cancer, and may be instrumental in ageing. Thus, preventing RC blockade and excess superoxide production by means of AOX should be of considerable interest. However, because of its energy-dissipating properties, AOX might produce deleterious effects of its own in mammals. Here we show that AOX can be safely expressed in the mouse (MitAOX), with major physiological parameters being unaffected. It neither disrupted the activity of other RC components nor decreased oxidative phosphorylation in isolated mitochondria. It conferred cyanide-resistance to mitochondrial substrate oxidation and decreased reactive oxygen species (ROS) production upon RC blockade. Accordingly, AOX expression was able to support cyanide-resistant respiration by intact organs and to afford prolonged protection against a lethal concentration of gaseous cyanide in whole animals. Taken together, these results indicate that AOX expression in the mouse is innocuous and permits to overcome a RC blockade, while reducing associated oxidative insult. Therefore, the MitAOX mice represent a valuable tool in order to investigate the ability of AOX to counteract the panoply of mitochondrial-inherited diseases originating from oxidative phosphorylation defects.     

ENHANCEMENT OF ETHANOL PRODUCTION BY SIMULTANEOUS SACCHARIFICATION AND FERMENTATION (SSF) OF RICE STRAW USING ETHOXYLATED SPAN 20

In this work, four nonionic surfactants based on sorbitan monolaurate (Span 20) were synthesized by introducing ethylene oxide gas (n = 20, 40, 60, 80 ethylene oxide units) into Span 20 to give four new surfactants with different hydrophilic–lipophilic balance (HLB), namely, E(20), E(40), E(60), and E(80). The structures of the prepared nonionic surfactants were elucidated using Fourier-transform infrared (FT-IR) and ¹H-nuclear magnetic resonance (NMR) spectroscopy. The surface-tension measurements were recorded. The effects of the prepared nonionic surfactants on the simultaneous saccharification and fermentation (SSF) of microwave/alkali-pretreated rice straw to produce ethanol were investigated. From the obtained data, it was found that the addition of the nonionic surfactants at 2.5 g/L had a positive effect on SSF. The maximum ethanol yield (76 and 55%) was obtained after 72 hr for rice straw using Kluyveromyces marxianus and Saccharomyces cerevisiae, respectively. Also, it was found that the ethanol yield increases with increasing HLB of the prepared nonionic surfactants by increasing ethylene oxide units. The adsorption of nonionic surfactants on lignocelluloses is proposed to be due to hydrophobic and hydrogen bonding interactions between nonionic surfactants and the lignin part in the lignocelulose. It can be concluded that additions of surface-active compounds, such as nonionic surfactants, increase enzymatic conversion of rice straw for bioethanol purposes.     

Breeding ecology of the Little Bittern Ixobrychus minutus in northeast Algeria

Capsule This is the first study of the reproductive ecology of the Little Bittern Ixobrychus minutus in North Africa. During the study period, clutch size exhibited a sharp drop concurrent with a steady human encroachment and 30% habitat loss.

Aim To investigate the status, nest-site selection, breeding parameters, chick development and chick diet of Little Bittern in Algeria, under deteriorating habitat conditions

Methods Data were collected during surveys of all major Algerian wetlands (2002–08) and monitoring of breeding at Boussedra, a freshwater marsh in northeast Algeria, during the years 2005 and 2008.

Results Egg-laying spanned the period of 10 May to 30 June with one recorded case of a double brood in early July (n = 30). The mean clutch size in 2005 was 6.2?±?0.4 sd eggs per nest (n = 6 clutches), which was significantly higher than that of 2008, which amounted to 4.3?±?0.5 sd eggs per nest (n = 6 clutches), and this decline was associated with increased disturbance and loss of habitat. Overall, clutches suffered from a low rate of predation (17.6%) and displayed a high hatching rate (85.7%).

Conclusion Breeding parameters of the Little Bittern in North Africa are similar to elsewhere in Europe.     

Efficiency of different application methods of biocontrol agents and biocides in control of Fusarium root rot on some citrus rootstocks

Abstract

The efficiency of two biocontrol agents (Trichoderma harzianum NB and Bacillus subtilis NB) and two commercial biocides (Plant Guard and Rhizo-N) in controlling Fusarium root rot disease on some citrus rootstocks was evaluated under artificially infested soil in green house.

Fusrium root rot on citrus rootstocks seedlings i.e. sour orange (SO), volkamer lime (VL), rangpur lime (RP) and cleopatra mandarin (CL) was successfully controlled by dipping the root system of such seedlings in water suspensions of each biological treatment i.e. Trichoderma harzianum (spore suspension 5×10⁶ spore/ml), Bacillus subtilis (cell suspension 8×10⁷ cell/ml), Plant Guard (3 g/l) and Rhizo-N (4 g/l), then transplanted into artificially infested soil with Fusarium solani and drenched with enough water suspension of such biological treatments. Plant Guard (3 g/l) and Rhizo-N (4 g/l) were highly effective treatments in decreasing infection and severity of the disease, Fusarium density in rhizosphere soil and colonization of Fusarium solani in the roots of all tested seedlings.

Meanwhile, root dipping or soil drenching with the same treatments individually gave the least effect in reducing root rot incidenceon all tested rootstocks compared with application of the two methods together.

It should be noted that using biocontrol agents and commercial biocides could be successfully used in controlling root rot pathogens on citrus in commercial greenhouses or under field conditions before transplanting in new reclaimed lands in the desert.     

Effects of garlic on Schistosoma mansoni harbored in albino mice: Molecular characterization of the host and parasite

Garlic has been used for its health benefits for thousands of years. Modern research confirmed many of the healing properties of garlic, including its antiparasitic activity. This study was designed to evaluate the antischistosomal action of garlic through detecting the changes in DNA profile of Schistosoma mansoni worms and the infected mouse. Forty mice were subcutaneously infected with ~ 200 Schistosoma mansoni cercariae/mouse. Infected mice were divided into four equal groups: non-treated, prophylactic, therapeutic, and continuously-treated. Non-infected control and garlic-treated groups were assigned for the sake of comparison. Garlic extract (50 mg/kg bw/mouse) was given orally, day after day, at a fixed daytime. Seven weeks post-infection, adult schistosomes were recovered by perfusion and the livers of the mice were excised out and were processed for DNA extraction and Random Amplification of Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR). The results showed that garlic exerted no major changes in the genome of schistosomes. Nevertheless, that schistosomal infection induced genetic alterations in the DNA of mice, and garlic was able to ameliorate such alterations to a great extent.     

Correlation between mass transfer coefficient k<Subscript>L</Subscript>a and relevant operating parameters in cylindrical disposable shaken bioreactors on a bench-to-pilot scale

Background

Among disposable bioreactor systems, cylindrical orbitally shaken bioreactors show important advantages. They provide a well-defined hydrodynamic flow combined with excellent mixing and oxygen transfer for mammalian and plant cell cultivations. Since there is no known universal correlation between the volumetric mass transfer coefficient for oxygen k_La and relevant operating parameters in such bioreactor systems, the aim of this current study is to experimentally determine a universal k_La correlation.

Results

A Respiration Activity Monitoring System (RAMOS) was used to measure k_La values in cylindrical disposable shaken bioreactors and Buckingham’s π-Theorem was applied to define a dimensionless equation for k_La. In this way, a scale- and volume-independent k_La correlation was developed and validated in bioreactors with volumes from 2 L to 200 L. The final correlation was used to calculate cultivation parameters at different scales to allow a sufficient oxygen supply of tobacco BY-2 cell suspension cultures.

Conclusion

The resulting equation can be universally applied to calculate the mass transfer coefficient for any of seven relevant cultivation parameters such as the reactor diameter, the shaking frequency, the filling volume, the viscosity, the oxygen diffusion coefficient, the gravitational acceleration or the shaking diameter within an accuracy range of +/? 30%. To our knowledge, this is the first k_La correlation that has been defined and validated for the cited bioreactor system on a bench-to-pilot scale.

     

Spectrin-like repeats 11-15 of human dystrophin show adaptations to a lipidic environment

Dystrophin is essential to skeletal muscle function and confers resistance to the sarcolemma by interacting with cytoskeleton and membrane. In the present work, we characterized the behavior of dystrophin 11-15 (DYS R11-15), five spectrin-like repeats from the central domain of human dystrophin, with lipids. DYS R11-15 displays an amphiphilic character at the liquid/air interface while maintaining its secondary α-helical structure. The interaction of DYS R11-15 with small unilamellar vesicles (SUVs) depends on the lipid nature, which is not the case with large unilamellar vesicles (LUVs). In addition, switching from anionic SUVs to anionic LUVs suggests the lipid packing as a crucial factor for the interaction of protein and lipid. The monolayer model and the modulation of surface pressure aim to mimic the muscle at work (i.e. dynamic changes of muscle membrane during contraction and relaxation) (high and low surface pressure). Strikingly, the lateral pressure modifies the protein organization. Increasing the lateral pressure leads the proteins to be organized in a regular network. Nevertheless, a different protein conformation after its binding to monolayer is revealed by trypsin proteolysis. Label-free quantification by nano-LC/MS/MS allowed identification of the helices in repeats 12 and 13 involved in the interaction with anionic SUVs. These results, combined with our previous studies, indicate that DYS R11-15 constitutes the only part of dystrophin that interacts with anionic as well as zwitterionic lipids and adapts its interaction and organization depending on lipid packing and lipid nature. We provide strong experimental evidence for a physiological role of the central domain of dystrophin in sarcolemma scaffolding through modulation of lipid-protein interactions.     

Fluoxetine and nortriptyline affect NTPDase and 5'-nucleotidase activities in rat blood serum

Depression is a serious condition associated with considerable morbidity and mortality. Selective serotonin reuptake inhibitors and tricyclic antidepressants, such as fluoxetine and nortriptyline, respectively, were commonly used in treatment for depression. Selective serotonin reuptake inhibitors have been associated with increased risk of bleeding complications, possibly as a result of inhibition of platelet aggregation. ATP, ADP and adenosine are signaling molecules in the vascular system and nucleotidases activities are considered an important thromboregulatory system which functions in the maintenance of blood fluidity. Therefore, here we investigate the effect of in vivo (acute and chronic) and in vitro treatments with the antidepressant drugs on nucleotidases activities in rat blood serum. In acute treatment, nortriptyline decreased ATP hydrolysis (41%), but not altered ADP and AMP hydrolysis. In contrast, fluoxetine did not alter NTPDase and ecto-5'-nucleotidase activities. A significant inhibition of ATP, ADP, and AMP hydrolysis were observed in chronic treatment with fluoxetine (60%, 32%, and 42% for ATP, ADP, and AMP hydrolysis, respectively). Similar effects were shown in chronic treatment with nortriptyline (37%, 41%, and 30% for ATP, ADP, and AMP hydrolysis, respectively). In addition, there were no significant changes in NTPDase and ecto-5'-nucleotidase activities when fluoxetine and nortriptyline (100, 250, and 500 microM) were tested in vitro. Our results have shown that fluoxetine and nortriptyline changed the nucleotide catabolism, suggesting that homeostasis of vascular system can be altered by antidepressant treatments.