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E S Calderon-Aranda B Selisko E J York G B Gurrola J M Stewart L D Possani 《European journal of biochemistry》1999,264(3):746-755
The Na+-channel-affecting toxin Cn2 represents the major and one of the most toxic components of the venom of the Mexican scorpion Centruroides noxius Hoffmann. A monoclonal antibody BCF2 raised against Cn2 has been shown previously to be able to neutralize the toxic effect of Cn2 and of the whole venom of C. noxius. In the present study the epitope was mapped to a surface region comprising the N- and C-terminal segments of Cn2, using continuous and discontinuous synthetic peptides, designed on the basis of the sequence and a three-dimensional model of Cn2. The study of peptides of varying length resulted in the identification of segments 5-14 and 56-65 containing residues essential for recognition by BCF2. The peptide (abbreviated SP7) with the highest affinity to BCF2 (IC50 = 5.1 microM) was a synthetic heterodimer comprising the amino acid sequence from position 3-15 (amidated) of Cn2, bridged by disulfide to peptide from position 54-66, acetylated and amidated. Similar affinity was found with peptide SP1 [heterodimer comprising residues 1-14 (amidated) of Cn2, bridged with synthetic peptide 52-66 (acetylated)]. SP1 and SP7 were used to induce anti-peptide antibodies in mouse and rabbit. Both peptides were highly immunogenic. The sera obtained were able to recognize Cn2 and to neutralize Cn2 in vitro. The most efficient protection (8.3 microgram Cn2 neutralized per mL of serum) was induced by rabbit anti-SP1 serum. 相似文献
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José Domingos Ribeiro Neto Bruno Ximenes Pinho Sebastian Tobias Meyer Rainer Wirth Inara Roberta Leal 《Entomologia Experimentalis et Applicata》2012,144(2):209-215
Leaf‐cutting ants (LCA) are polyphagous and dominant herbivores throughout the Neotropics that carefully select plant individuals or plant parts to feed their symbiotic fungus. Although many species‐specific leaf traits have been identified as criteria for the choice of food plants, the factors driving intraspecific herbivory patterns in LCA are less well studied. Herein, we evaluate whether or not drought‐stressed native plants are a preferred food source using free‐living colonies of two leaf‐cutting ants, Atta sexdens L. (Hymenoptera: Formicidae: Attini), in combination with five plant species, Ocotea glomerata Nees (Lauraceae), Lecythis lurida S. A. Mori (Lecythidaceae), Miconia prasina DC (Melastomataceae), Tovomita brevistaminea Engl. (Clusiaceae), and Tapirira guianensis Aubl. (Anacardiaceae), and Atta cephalotes L., in combination with two plant species, O. glomerata and Licania tomentosa Benth. (Chrysobalanaceae). In dual‐choice bioassays, ants removed about three times more leaf area from drought‐stressed plants compared to control plants. Both leaf‐cutting ant species consistently preferred drought‐stressed plants for all species tested, except T. guianensis. The mean acceptability index – expressing the preference for one of two options on a scale of 0 to 1 – of drought‐stressed plants ranged from 0.65 to 0.86 across plant species, and the preference did not differ significantly among the tested plant species. Our results suggest that selection of drought‐stressed individuals is a general feature of food plant choice by leaf‐cutting ants irrespective of ant or plant species. As human‐modified forest assemblages across the Neotropics are increasingly prone to drought stress, the documented preference of Atta for drought‐stressed plants may have tangible ecological implications. 相似文献
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<Emphasis Type="Italic">Xenopus laevis</Emphasis> (Daudin, 1802), a new exotic amphibian in Portugal
Rui Rebelo Patrícia Amaral Marta Bernardes João Oliveira Paulo Pinheiro Domingos Leitão 《Biological invasions》2010,12(10):3383-3387
The African clawed frog Xenopus laevis has been introduced at several locations, including Mediterranean climate-type regions. In 2006, several individuals of this
species were found inhabiting a stream at Oeiras, about 20 km W of Lisbon, Portugal. Although the place and time of introduction
are not clearly identified, there are reasons to believe that this population may be the result of an almost 30-year-old introduction
proceeding from research laboratories located nearby. Field surveys were conducted in 2007 and 2008 on the distribution and
abundance of this species in the region. The species was found in two streams, about 5 km from each other. While being locally
abundant, the adults of X. laevis are smaller than those from South Africa and California. In spite of an abundant production of eggs and tadpoles at one of
the streams, no tadpoles were found in advanced developmental stages. Until now, most individuals were found in heavily urbanized
areas that should constrain their ability to cross overland to other water bodies. An eradication program may be feasible,
but the presence of adults on two streams indicates that the species may be expanding, in spite of the urban landscape. 相似文献
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