Role of Organic Acids in Sunflower Tolerance to Heavy Metals

Exposure of Helianthus annuus L. seedlings to Al³⁺, Cd²⁺ or Zn²⁺ resulted in a marked decrease of fresh and dry masses of the shoots and the roots. The increase of Al³⁺, Cd²⁺ or Zn²⁺ uptake was accompanied by a significant decrease of nitrate, phosphorus and K⁺ uptake. There was a significant increase of malic and citric acid contents in the shoots and roots of heavy metal-treated seedlings whereas the change in fumaric acid was insignificant. Al³⁺ and Zn²⁺ alone stimulated excretion of malic and citric acids to the rhizosphere. Addition of high concentrations of malic or citric acid alleviate to some extent the inhibitory effect of Al³⁺ and Zn²⁺ on plant growth. This revised version was published online in July 2006 with corrections to the Cover Date.     

Root Proliferation,Proton Efflux,and Acid Phosphatase Activity in Common Bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis>) Under Phosphorus Shortage

The impact of phosphorus (P) availability on root proliferation, proton efflux, and acid phosphatase activities in roots and leaves was investigated in two lines of common bean (Phaseolus vulgaris): BAT 477 and CocoT. Phosphorus was supplied as KH₂PO₄ at 0 and 60 μmol per plant (0P and 60P, respectively). Under P shortage, the plant growth was more restricted in CocoT than in BAT 477, shoots being more affected than roots. The root area increased significantly at 0P in both lines. Up to 1 week following P shortage, the proton efflux increased in both lines despite a higher extent in BAT 477 as compared to CocoT. Root acid phosphatase activity was significantly higher under P limitation in the both lines, this trend being more pronounced in BAT 477 than in CocoT. This was also true for the leaf acid phosphatase. Regardless of the bean line, higher values were recorded for the old leaves as compared to the young ones for this parameter. Interestingly, a significant correlation between Pi content in old leaves and their acid phosphatase activity was found in P-lacking (0P) plants of the both bean lines, suggesting that acid phosphatase may contribute to increase the phosphorus use efficiency in bean through the P remobilization from the old leaves. As a whole, our results highlight the significance of the root H⁺ extrusion and the acid phosphatase activity rather than the root proliferation in the relative tolerance of BAT 477 to severe P deficiency.     

Commercial opportunities for pesticides based on plant essential oils in agriculture, industry and consumer products

In spite of intensive research on plant natural products and insect-plant chemical interactions over the past three decades, only two new types of botanical insecticides have been commercialized with any success in the past 15 years, those based on neem seed extracts (azadirachtin), and those based on plant essential oils. Certain plant essential oils, obtained through steam distillation and rich in mono- and sesquiterpenes and related phenols, are widely used in the flavouring and fragrance industries and in aromatherapy. Some aromatic plants have traditionally been used for stored product protection, but the potential for development of pesticides from plant essential oils for use in a wide range of pest management applications has only recently been realized. Many plant essential oils and their major terpenoid constituents are neurotoxic to insects and mites and behaviourally active at sublethal concentrations. Most plant essential oils are complex mixtures. In our laboratory we have demonstrated that individual constituents of oils rarely account for a major share of the respective oil’s toxicity. Further, our results suggest synergy among constituents, including among those that appear non-toxic in isolation. Repellent effects may be particularly useful in applications against public health and domestic pests, but may be useful in specific agricultural applications as well. In all of these applications, there is a premium on human and animal safety that takes priority over absolute efficacy. In agriculture, the main market niche for essential oil-based pesticides is in organic food production, at least in developed countries, where there are fewer competing pest management products. There is also scope for mixing these oils with conventional insecticides and for enhancing their efficacy with natural synergists. Some examples of field efficacy against agricultural pests are discussed.     

Molecular mechanisms for changes in hepatic protein synthesis induced by schistosomiasis infection in mice

Mice infected with Schistosoma mansoni and littermate controls were evaluated serially for 12 weeks. Infected mice gained weight at the same rate as controls, but starting with the sixth week their livers became enlarged with granulomas and fibrous tissue, and they developed hypoalbuminemia. To evaluate the regulation of the albumin and type I collagen gene expression, total RNA was isolated from infected and control mice and translated in an mRNA-dependent rabbit reticulocyte lysate system. Protein synthesis was decreased 1.5-3-fold with RNA from infected vs. control liver. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the cell-free products showed a reduction in albumin but an increase in type I procollagen synthesis in infected mice. Immunoprecipitation of the cell-free product confirmed that albumin synthesis was reduced in greater proportion than other liver proteins in schistosome-infected mice. Hybridization of RNA from infected liver with cloned mouse albumin cDNA (pmalb-2) demonstrated a reduction in albumin mRNA to 37% of control, while hybridization with a chick type I pro alpha 2 collagen cDNA probe (pCg-45) revealed increased procollagen mRNA in infected liver beginning at 6 weeks postinfection. These results suggest that in murine schistosomiasis a reduction in biologically active albumin mRNA results in decreased albumin synthesis and may be responsible in part for hypoalbuminemia. In addition, increased collagen mRNA is associated with increased collagen synthesis during hepatic fibrosis.     

Population models with Allee effect: a new model

In this paper, we develop several population models with Allee effects. We start by defining the Allee effect as a phenomenon in which individual fitness increases with increasing density. Based on this biological assumption, we develop several fitness functions that produce corresponding models with Allee effects. In particular, a rational fitness function yields a new mathematical model, which is the focus of our study. Then we study the dynamics of 2-periodic systems with Allee effects and show the existence of an asymptotically stable 2-periodic carrying capacity.     

New polymorphic mtDNA restriction site in the 12S rRNA gene detected in Tunisian patients with non-syndromic hearing loss

The 12S rRNA gene was shown to be a hot spot for aminoglycoside-induced and non-syndromic hearing loss since several deafness-associated mtDNA mutations were identified in this gene. Among them, we distinguished the A1555G, the C1494T and the T1095C mutations and C-insertion or deletion at position 961. One hundred Tunisian patients with non-syndromic hearing loss and 100 hearing individuals were analysed in this study. A PCR-RFLP analysis with HaeIII restriction enzyme showed the presence of the A1555G mutation in the 12S rRNA gene in only one out of the 100 patients. In addition, PCR-RFLP and radioactive PCR revealed the presence of a new HaeIII polymorphic restriction site in the same gene of 12S rRNA site in 4 patients with non-syndromic hearing loss. UVIDOC-008-XD analyses showed the presence of this new polymorphic restriction site with a variable heteroplasmic rates at position +1517 of the human mitochondrial genome. On the other hand, direct sequencing of the entire mitochondrial 12S rRNA gene in the 100 patients and in 100 hearing individuals revealed the presence of the A750G and A1438G polymorphisms and the absence of the C1494T, T1095C and 961insC mutations in all the tested individuals. Sequencing of the whole mitochondrial genome in the 4 patients showing the new HaeIII polymorphic restriction site revealed only the presence of the A8860G transition in the MT-ATP6 gene and the A4769G polymorphism in the ND2 gene.     

Structure of N-terminal cyanogen bromide fragment of human plasma albumin.

The complete amino acid sequence of 87 residues of cyanogen bromide fragment CB1 (Asp), the N-terminal fragment of human plasma albumine molecule, has been established. The sequence was determined from the characterization of all tryptic peptides and of chymotryptic arginine-containing peptides in the fragment digested. Overlaps were obtained by tryptic and chymotryptic cleavage of the maleylated S-sulfo derivative of fragment CB1(Asp). Residue 34 is the only cysteine residue in the albumin molecule and it was determined in the form of S-carboxymethyl-cysteine. Edman and dansyl-Edman degradation were used for the sequential analysis.     

Population dynamics in a spin-glass model of chemical evolution

Summary We introduce a simple model describing the evolution of a population of information-carrying macromolecules. We discuss the asymptotic dependence of the variability of the population on different parameters, representing the severity or the fluctuations of the environment. We show the existence of a transition separating a neutralist evolutionary regime from a trapped one. We investigate the dependence of the evolutionary behavior of the population on the correlation properties of the fitness landscape.     

Albumin and collagen mRNA expression in normal and analbuminemic rodent liver: analysis by in situ hybridization using biotinylated probes

We used in situ nucleic acid hybridization cytochemistry to examine cell types and subcellular sites expressing albumin (alb) or pro alpha 2 collagen (col) mRNA in livers from normal and analbuminemic rodents. Biotinylated cDNA or RNA probes were applied to aldehyde-fixed, non-frozen sections and the resulting DNA-RNA or RNA-RNA hybrids were subsequently visualized by enzymatic detection of either peroxidase or alkaline phosphatase conjugated to anti-biotin IgG or streptavidin. In normal rat liver, alb mRNA was expressed in all hepatocytes and was localized to discrete subcellular structures distributed as aggregates in the cytoplasm and in specific structures encircling the nucleus; these subcellular structures most likely represent the endoplasmic reticulum and nuclear envelope. In mouse liver, pro alpha 2 col mRNA was identified in a subpopulation of sinusoidal lining cells which have the morphological appearance of lipocytes. In liver from analbuminemic rats, a small number of hepatocytes, distributed throughout the hepatic lobule, expressed alb mRNA at high levels; the subcellular distribution of this alb mRNA was essentially identical to that observed in normal rat hepatocytes. Since non-radioactive in situ hybridization detected mRNA within the boundaries of individual cells and showed its precise subcellular location under conditions in which there was excellent preservation of tissue morphology, this procedure should be useful for a wide variety of histopathologic studies.     

Acute toxicity of kaolin and essential oils from Mentha pulegium and Zingiber officinale against different stages of Callosobruchus maculatus under laboratory conditions

Naturally derived compounds such as essential oils and natural mineral are relatively cheap, non-toxic to food grains and environmentally friendly and would be suitable alternatives for currently used chemical insecticides if they have high insecticidal effectiveness. In the present study, acute toxicity of kaolin and essential oils from Mentha pulegium and Zingiber officinale were assessed on different stages of Callosobruchus maculatus at 28?±?2?°C, 65?±?5% R. H and dark condition. The calculated LC₅₀ values on the egg, larvae and adult stages of C. maculatus were 1.15, 2.33 and 2.18?μl/ml air for Z. officinale and 0.07, 0.11 and 0.09?μl/ml air for M. pulegium, respectively. The result showed that M. pulegium was more effective essential oil against different stages of C. maculatus compared with the Z. officinale, and also the egg and adult stages of C. maculatus were more susceptible against essential oils compared with larval stage. The LC₅₀ values of kaolin were 0.71 and 0.18?mg/cm² on egg and adult of C. maculatus, respectively. The combination of tested essential oils with kaolin increased mortality of C. maculatus adults compared with their application alone. It was found that tested essential oils and kaolin had high potential in controlling different stages of C. maculatus.