Aphid (Hemiptera: Aphidoidea) diversity in Tunisia in relation to seed potato production

Winged morphs of aphids were investigated from 2002 to 2004 in 4 Tunisian regions of potato seeds production in order to know the aphid diversity and the potential vectors of Potato Virus Y. This is a very important contribution to the knowledge of aphid fauna in Maghreb. A total of 50,030 aphids were caught using yellow water traps and one suction trap. 130 taxa were identified including 103 species. Ten species are well represented in all regions prospected and typical species were also observed in every region. Some differences in species diversity appeared between regions which are discussed considering weather condition and vegetation.     

Cyanide Production by Rhizobacteria and Potential for Suppression of Weed Seedling Growth

Rhizobacteria strains were characterized for ability to synthesize hydrogen cyanide and for effects on seedling root growth of various plants. Approximately 32% of bacteria from a collection of over 2000 isolates were cyanogenic, evolving HCN from trace concentrations to >30 nmoles/mg cellular protein. Cyanogenesis was predominantly associated with pseudomonads and was enhanced when glycine was provided in the culture medium. Concentrations of HCN produced by rhizobacteria were similar to exogenous concentrations inhibiting seedling growth in bioassays, suggesting that cyanogenesis by rhizobacteria in the rhizosphere can adversely affect plant growth. Growth inhibition of lettuce and barnyardgrass by volatile metabolites of the cyanogenic rhizobacteria confirmed that HCN was the major inhibitory compound produced. Our results suggest that HCN produced in the rhizospheres of seedlings by selected rhizobacteria is a potential and environmentally compatible mechanism for biological control of weeds. Received: 13 December 2000/Accepted: 6 February 2001     

不同胁迫预处理提高水稻幼苗抗寒性期间蛋白质的变化

水稻(Oryza sativa L.)幼苗经盐、热激和冷三种不同胁迫预处理均提高了幼苗的抗寒性。与未预处理苗相比,在处理后、低温伤害后和常温下恢复2d的三个时期,不同胁迫预处理苗的可溶性和热不稳定蛋白含量变化趋势甚为相似,但热稳定蛋白含量变化则各有异同。SDS-PAGE图谱分析显示,不同胁迫预处理提高水稻幼苗抗寒性时,其可溶性蛋白、热稳定和热不稳定蛋白组成变化亦各有异同。除诱导出共有的新多肽外,还各自诱导出特有的新多肽。结果表明,植物对不同胁迫的交叉适应存在一定的共同机理,但亦可看出植物对同一种环境胁迫似乎不是以同一的机理去适应。     

Caffeine reversal of sleep deprivation effects on alertness,mood and repeated sprint performances in physical education students

The aim of this study was to evaluate the effects of caffeine ingestion and partial sleep deprivation on mood and cognitive and physical performances. In randomised order, 12 healthy male physical education students completed four test sessions at 18:00 h after placebo or 5 mg/kg of caffeine ingestion during a baseline night (RN) (bed time: from 22:00 to 07:00 h), or during a night of partial (four hrs) sleep deprivation (PSD). During each test session, participants performed a reaction time test, a vigilance test, the 10 s Wingate cycling test during (measuring peak power (PP) and anaerobic capacity), and the 5 m multiple shuttle test (measuring peak distance (PD), total distance (TD), and fatigue index (FI)). Compared to RN, simple reaction time, vigilance, PP, PD, TD, and FI were altered by PSD the following day after placebo ingestion with increased reaction time and FI and reduced PP, PD, TD, and vigilance (p < 0.001). Moreover, during PSD condition, PP, PD, and TD were significantly higher after caffeine ingestion in comparison with placebo ingestion (p < 0.05). However, both simple reaction times and vigilance were significantly lower after caffeine ingestion in comparison with placebo during PSD (p < 0.05). Caffeine is an effective strategy to maintain physical and cognitive performances the day after PSD.     

Qualitative behavior of stage-structured populations: application to structural validation

 The transient behavior of a class of nonlinear differential systems representing stage-structured populations is studied. The qualitative dynamics are described in terms of succession of extrema for the state variables, or for the integrated difference between two trajectories. The rules giving the possibilities of extrema are derived, they characterize the classical stage-structured models. These rules can be compared with experiments to validate the structure of the model. An explanation for the disagreement of this transition scheme with some experiments could be an unexpected interaction with another variable. A new model taking the interaction into account thus engenders new transition rules, which are to be compared with experiments. These results are illustrated with experiments on copepods, showing how the qualitative experimental features can help the construction and the validation of the models. Received: 13 May 1996 / Revised version: 20 March 1998     

Purification and characterization of Dolichos lablab lectin

The mannose/glucose-binding Dolichos lablab lectin (designated DLL) has been purified from seeds of Dolichos lablab (hyacinth bean) to electrophoretic homogeneity by affinity chromatography on an ovalbumin- Sepharose 4B column. The purified lectin gave a single symmetric protein peak with an apparent molecular mass of 67 kDa on gel filtration chromatography, and five bands ranging from 10 kDa to 22 kDa upon SDS-PAGE. N-Terminal sequence analysis of these bands revealed subunit heterogeneity due to posttranslational proteolytic truncation at different sites mostly at the carboxyl terminus. The carbohydrate binding properties of the purified lectin were investigated by three different approaches: hemagglutination inhibition assay, quantitative precipitation inhibition assay, and ELISA. On the basis of these studies, it is concluded that the Dolichos lablab lectin has neither an extended carbohydrate combining site, nor a hydrophobic binding site adjacent to it. The carbohydrate combining site of DLL appears to most effectively accommodate a nonreducing terminal alpha-d-mannosyl unit, and to be complementary to the C-3, C-4, and C-6 equatorial hydroxyl groups of alpha-d-mannopyranosyl and alpha-d-glucopyranosyl residues. DLL strongly precipitates murine IgM but not IgG, and the recent finding that this lectin interacts specifically with NIH 3T3 fibroblasts transfected with the Flt3 tyrosine kinase receptor and preserves human cord blood stem cells and progenitors in a quiescent state for prolonged periods in culture, make this lectin a valuable tool in biomedical research.      

Transposition mechanism,molecular characterization and evolution of IS<Emphasis Type="Italic">6110</Emphasis>, the specific evolutionary marker of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> complex

The mycobacterial insertion sequence IS6110 proved crucial in deciphering tuberculosis (TB) transmission dynamics. This sequence was also shown to play an important role in the pathogenicity (transmission ability and/or virulence) of Mycobacterium tuberculosis, the main causative agent of TB in humans. In this study, we explored the usefulness of IS6110 and its potential as a phylogenetic/typing marker. We also analyzed the genetic polymorphism and evolutionary trends (selective pressure) of its transposase-encoding open reading frames (ORFs), A and B, using the maximum likelihood method. Both ORFs evolved chronologically through random single nucleotide polymorphisms. They were subjected to strict purifying selection more tight on orfA, with no evidence of significant recombination events. OrfA proved to have a crucial role in regulating the transpositional process. Several analyses showed that IS6110 acquisition antedated the emergence of the Mycobacterium tuberculosis complex. This original copy of IS6110 element was functionally optimal. In conclusion, this study not only demonstrated the usefulness of IS6110 in terms of phylogenetic and typing purposes and its transpositional mechanism, but also informed the scientific community on its evolutionary history.