Trichinella spiralis: strong antibody response to a 49 kDa newborn larva antigen in infected rats

In this work, we analyzed the kinetics of anti-Trichinella spiralis newborn larva (NBL) antibodies (Ab) and the antigenic recognition pattern of NBL proteins and its dose effects. Wistar rats were infected with 0, 700, 2000, 4000 and 8000 muscle larvae (ML) and bled at different time intervals up to day 31 post infection (p.i.). Ab production was higher with 2000 ML dose and decreased with 8000, 4000 and 700 ML. Abs were not detected until day 10, peaked on day 14 for the 2000 ML dose and on day 19 for the other doses and thereafter declined slowly from 19 to 31 days p.i. In contrast, Abs to ML increased from day 10, peaked on day 19 and remained high until the end of the study. Abs bound strongly at least to three NBL components of 188, 205 and 49 kDa. NBL antigen of 188 and 205 kDa were recognized 10-26 days p.i. and that of 49 kDa from day 10 to day 31 p.i. A weak recognition towards antigens of 52, 54, 62 and 83 kDa was also observed during the infection. An early recognition of 31, 43, 45, 55, 68 and 85 kDa ML antigens was observed whereas the response to those of 43, 45, 48, 60, 64 and 97 kDa (described previously as TSL-1 antigens) occurred late in the infection. A follow-up of antigen recognition up to day 61 with the optimal immunization dose (2000 ML) evidenced a decline of Ab production to the 49 kDa NBL antigen 42 days p.i., which suggested antigenic differences with the previously reported 43 kDa ML antigen strongly recognized late in the infection. To analyze the stage-specificity of the 49 kDa NBL antigen, polyclonal antibodies (PoAb) were obtained in rats immunized with 49 kDa NBL antigen. PoAb reacted strongly with the 49 kDa NBL component in NBL total soluble extract but no reactivity was observed with soluble antigen of the other T. spiralis stages. Albeit with less intensity, the 49 kDa component was also recognized by PoAb together with other antigens of 53, 97 and 107 kDa, in NBL excretory-secretory products (NBL-ESP). Thus, our results reveal differences in the kinetics of anti-NBL and ML Ab responses. While anti-NBL Abs declined slowly from day 19 until the end of the experiment, Abs to ML antigen remained high in the same period. It is remarkable the optimal Ab response to NBL antigens with 2000 ML infective dose and the reduced number of NBL antigens identified throughout the experimental T. spiralis infection, standing out the immunodominant 49 kDa antigen. Interestingly, this antigen, which was prominently expressed in NBL somatic proteins, was also detected in NBL-ESP.     

Contrasting patterns in trophic niche evolution of polymorphic Arctic charr populations in two subarctic Norwegian lakes

Hydrobiologia - Lipid biomarkers in sediments, which are indicative of biological production, provide important information regarding the environmental conditions in and around lakes, and can be...     

Regulation of 35S-TBPS binding by bicuculline is region specific in rat brain

The allosteric regulation of specific 35S-TBPS binding to the convulsant site on the GABAA receptor/chloride (Cl-) ionophore complex was studied in various brain regions in an attempt to characterize regional heterogeneity of the protein subunits forming the complex. Bicuculline methiodide (BIC), a GABAA antagonist, enhanced binding in cortex (CTX), substantia nigra (SN) and cerebellum (CBL), inhibited binding in inferior colliculus (IC) and did not affect binding in superior colliculus (SC). Similar results were found in CBL and IC using SR-95531, another GABAA antagonist. The levels of endogenous GABA in the different tissue samples could not account for the regional differences in binding. When the functional regulation of these receptors was measured using 36Cl- uptake in microsomes, muscimol-stimulated uptake was completely blocked by BIC in CBL and IC but was not affected by BIC in SC. Additionally, picrotoxin completely blocked muscimol-stimulated uptake in CBL but had no effect in IC or SC. These findings provide a functional basis for regional heterogeneity of GABAA receptor.     

Mutagenesis of human DNA polymerase lambda: essential roles of Tyr505 and Phe506 for both DNA polymerase and terminal transferase activities

DNA polymerase (pol) λ is homologous to pol β and has intrinsic polymerase and terminal transferase activities. However, nothing is known about the amino acid residues involved in these activites. In order to precisely define the nucleotide-binding site of human pol λ, we have mutagenised two amino acids, Tyr505 and the neighbouring Phe506, which were predicted by structural homology modelling to correspond to the Tyr271 and Phe272 residues of pol β, which are involved in nucleotide binding. Our analysis demonstrated that pol λ Phe506Arg/Gly mutants possess very low polymerase and terminal transferase activities as well as greatly reduced abilities for processive DNA synthesis and for carrying on translesion synthesis past an abasic site. The Tyr505Ala mutant, on the other hand, showed an altered nucleotide binding selectivity to perform the terminal transferase activity. Our results suggest the existence of a common nucleotide-binding site for the polymerase and terminal transferase activities of pol λ, as well as distinct roles of the amino acids Tyr505 and Phe506 in these two catalytic functions.     

Differential ability of genotypes of 2,4-diacetylphloroglucinol-producing Pseudomonas fluorescens strains to colonize the roots of pea plants

Indigenous populations of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing fluorescent Pseudomonas spp. that occur naturally in suppressive soils are an enormous resource for improving biological control of plant diseases. Over 300 isolates of 2,4-DAPG-producing fluorescent Pseudomonas spp. were isolated from the rhizosphere of pea plants grown in soils that had undergone pea or wheat monoculture and were suppressive to Fusarium wilt or take-all, respectively. Representatives of seven genotypes, A, D, E, L, O, P, and Q, were isolated from both soils and identified by whole-cell repetitive sequence-based PCR (rep-PCR) with the BOXA1R primer, increasing by three (O, P, and Q) the number of genotypes identified previously among a worldwide collection of 2,4-DAPG producers. Fourteen isolates representing eight different genotypes were tested for their ability to colonize the rhizosphere of pea plants. Population densities of strains belonging to genotypes D and P were significantly greater than the densities of other genotypes and remained above log 6.0 CFU (g of root)(-1) over the entire 15-week experiment. Genetic profiles generated by rep-PCR or restriction fragment length polymorphism analysis of the 2,4-DAPG biosynthetic gene phlD were predictive of the rhizosphere competence of the introduced 2,4-DAPG-producing strains.     

Two new scorpion toxins that target voltage-gated Ca2+ and Na+ channels

This report describes the isolation, primary structure determination, and functional characterization of two similar toxins from the scorpion Parabuthus granulatus named kurtoxin-like I and II (KLI and KLII, respectively). KLII from P. granulatus is identical to kurtoxin from Parabuthus transvaalicus (a 63 amino-acid long toxin) whereas KLI is a new peptide containing 62 amino acid residues closely packed by four disulfide bridges with a molecular mass of 7244. Functional assays showed that both toxins, KLI and kurtoxin from P. granulatus, potently inhibit native voltage-gated T-type Ca(2+) channel activity in mouse male germ cells. In addition, KLI was shown to significantly affect the gating mechanisms of recombinant Na(+) channels and weakly block alpha(1)3.3Ca(V) channels expressed in Xenopus oocytes. KLI and kurtoxin from P. granulatus represent new probes to study the role of ion channels in germ cells, as well as in cardiac and neural tissue.     

Isolation and characterization of a potato cDNA corresponding to a 1-aminocyclopropane-1-carboxylate (ACC) oxidase gene differentially activated by stress

1-Aminocyclopropane-1-carboxylate (ACC) oxidase enzyme catalyses the final step in ethylene biosynthesis, converting 1-aminocyclopropane-1-carboxylic acid to ethylene. A cDNA clone encoding an ACC oxidase, ST-ACO3, was isolated from potato (Solanum tuberosum L.) by differential screening of a Fusarium eumartii infected-tuber cDNA library. The deduced amino acid sequence exhibited similarity to other ACC oxidase proteins from several plants species. Northern blot analysis revealed that the ST-ACO3 mRNA level increased in potato tubers upon inoculation with F. eumartii, as well as after treatment with salicylic acid and indole-3-acetic acid, suggesting a cross-talk between different signalling pathways involved in the defence response of potato tubers against F. eumartii attack.     

Sexual phase of the ferns Odontosoria schlechtendalii and Odontosoria scandens (Dennstaedtiaceae)

The results of morphogenesis studies of the sexual phase of Odontosoria schlechtendalii and O. scandens are presented in this paper. In O. schlechtendalii and O. scandens the spores are triletes, non-chlorophyllous, and germinación is of the Vittaria-type, devoid of perine, the exine is smooth and sometimes coarsely ridged to reticulate. The development pattern is of the Adiantum-type. The adult gametophyte is cordate-spathulate, with probable presence of anteridiogen in O. schlechtendalii, both species are glabrous. Sex organs are of the common type of the leptosporangiate ferns. The first leaves appeared after 56-92 days of culture, with petiole and plate divide narrow, trichomes bifurcate and stomate anomocytic.