Redox regulation of free amino acid levels in Arabidopsis thaliana

Abiotic stresses induce oxidative stress, which modifies the level of several metabolites including amino acids. The redox control of free amino acid profile was monitored in wild‐type and ascorbate or glutathione deficient mutant Arabidopsis thaliana plants before and after hydroponic treatment with various redox agents. Both mutations and treatments modified the size and redox state of the ascorbate (AsA) and/or glutathione (GSH) pools. The total free amino acid content was increased by AsA, GSH and H₂O₂ in all three genotypes and a very large (threefold) increase was observed in the GSH‐deficient pad2‐1 mutant after GSH treatment compared with the untreated wild‐type plants. Addition of GSH reduced the ratio of amino acids belonging to the glutamate family on a large scale and increased the relative amount of non‐proteinogenic amino acids. The latter change was because of the large increase in the content of alpha‐aminoadipate, an inhibitor of glutamatic acid (Glu) transport. Most of the treatments increased the proline (Pro) content, which effect was due to the activation of genes involved in Pro synthesis. Although all studied redox compounds influenced the amount of free amino acids and a mostly positive, very close (r > 0.9) correlation exists between these parameters, a special regulatory role of GSH could be presumed due to its more powerful effect. This may originate from the thiol/disulphide conversion or (de)glutathionylation of enzymes participating in the amino acid metabolism.     

Molecular cloning and characterization of horse DQA cDNA

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number L33909     

Determination of Frost Tolerance in Winter Wheat and Barley at the Seedling Stage

Detailed studies were made on changes in the quantity of 1.4 MDa rRNA precursor in barley and wheat cultivars with different degrees of frost tolerance. When analysing genotypes with different LT₅₀ values a close negative correlation was found between the quantity of 1.4 MDa molecular mass rRNA precursor and the forst tolerance of the given barley or wheat cultivar. The results suggest that a technique based on low temperature phosphorus incubation at the seedling stage could be suitable for the selection of genotypes on the basis of this character in applied research.     

Evaluation of gill nets, fyke nets, and mark-recapture methods to estimate the number of Hirudinea and Crustacea on fish.

Twenty species of fishes (n = 20,759) were collected from Dauphin Lake, Manitoba, Canada, to determine the types and numbers of ectoparasites they harbored. Counts of ectoparasites on fishes collected with different gear were compared to evaluate different methods of collection and to estimate rates of recruitment of ectoparasites by fishes. Ectoparasites were found on 11 species of fishes and the majority of these were parasitic leeches (Myzobdella moorei, Cystobranchus verilli, and Placobdella montifera) and parasitic Crustacea (Argulus appendiculosus and Lernaea cyprinacea). Some fishes also were infested by neascus-type metacercariae (blackspot) or had tumors (lymphocystis). The prevalence of ectoparasites was correlated with the abundance, feeding habits, and spatial distribution of fish species. Argulus appendiculosus and blackspot were more prevalent on benthic fishes, whereas M. moorei and tumors were more prevalent on limnetic fishes. Mark-recapture records showed that fishes occupying shallow (less than or equal to 1.5 m) water had a higher prevalence of infestation and 28 of 29 infected fishes caught by gill nets were captured in shallow water. Placobdella montifera was the only ectoparasite found on fishes from deep (1.5-3.5 m) water and the only species that was acquired by fishes previously released with no ectoparasite (2 of 239 fishes). The littoral zone (less than or equal to 1.5 m) comprises only 14% of the surface area and 3% of the volume of Dauphin Lake, yet 72% of all gill-netted fishes harboring ectoparasites were collected there. Intensities of ectoparasites estimated from gill net and pound net samples were similar, but prevalence of ectoparasites estimated from samples obtained with gill nets was lower.     

Isolation of an acute-phase phosphorylcholine-reactive pentraxin from channel catfish (Ictalurus punctatus).

1. Channel catfish (Ictalurus punctatus) serum contains a protein that precipitates pneumococcal C-polysaccharide (CPS) in a calcium-dependent fashion. 2. The serum titer of this protein follows an acute-phase pattern in catfish injected with turpentine. 3. A non-glycosylated, phosphorylcholine (PC)-reactive protein (PRP) with molecular mass ca 100 kDa, was isolated from channel catfish acute-phase sera by affinity chromatography on PC-Sepharose 4B. 4. Contaminating proteins with molecular masses ca 700 kDa and ca 20 kDa that co-eluted with PRP from PC-Sepharose appear to be aggregated and native low-molecular weight factors (LMFs), respectively. 5. Purified PRP has gamma mobility but in serum samples PRP has gamma-beta mobility. 6. Electron microscopy confirmed that PRP has planar, pentagonal symmetry. 7. The amino terminus of PRP is blocked, but based on comparison of amino-acid compositions channel catfish PRP is clearly similar to human CRP and is most like CRPs from the dogfish (Mustelus canis) and rainbow trout (Oncorhynchus mykiss).     

Nesting activity of cavity-nesting bees and wasps is lower in small-scale apple orchards compared to nearby semi-natural habitats

1. Commercially reared cavity-nesting bees have been studied mainly in large, intensively managed orchards. However, knowledge on wild cavity-nesting bee and wasp communities and their potential limitations in smaller orchards remain insufficient.
2. We compared the colonization rate of trapnests, nesting success, parasitism and response to flower resources of cavity-nesting bees and wasps between apple orchards and nearby semi-natural habitats (SNHs).
3. Trapnests were placed in orchards and neighbouring SNHs. Colonization dynamics were studied and herbaceous flower resources were estimated. Furthermore, nest and brood cell quantity, number of alive offspring and nest parasitism rate were assessed.
4. We found a higher colonization rate in the SNHs than in the orchards. Both bees and wasps made more nests, completed more brood cells and had a higher number of alive offspring in the SNHs. The number of bee nests in the orchards showed a positive correlation with the species richness of the flowering plants. The nest parasitism of wasps was higher in the SNHs.
5. Apple orchards in the studied small-scale system were generally less colonized by cavity-nesting hymenopterans than nearby SNHs that can be important reservoirs of these ecosystem service provider hymenopterans. Our results highlight the importance of diverse flowering herbaceous vegetation in the understory that increased the number of bee nests in orchards and that could have a positive effect on the nesting activity of the bee species active in summer. Therefore, management practices that support flowering plant species in the understory vegetation are highly recommended in such orchards.

     

Chelation affects the conformation, lability and aggregation of channel catfish (Ictalurus punctatus) phosphorylcholine-reactive protein (PRP).

1. Phosphorylcholine-reactive protein (PRP) affinity-purified from channel catfish (Ictalurus punctatus) serum on phosphorylcholine-Sepharose, eluted from Bio-Gel A-5M as a 94.6 +/- 2.4 kDa protein when the gel filtration column buffer (Tris-saline) contained 25mM ethylenediaminetetraacetic acid (EDTA). 2. PRP chelated with EDTA immediately after affinity purification and gel-filtered in Tris-saline-EDTA, eluted as a 75.5 +/- 2.67 kDa protein referred to as fast-PRP (F-PRP). 3. PRP and F-PRP were identical on SDS-PAGE. Both resolved as a broad band of protein (ca 86-100 kDa) on non-reducing gels or as a ca 100 kDa protein after reduction with 2-mercaptoethanol (2-ME). 4. After gel-filtration in Tris-saline-EDTA, nearly complete reduction of 100 kDa PRP was achieved on SDS-PAGE. However, the protein regained its resistance to reduction upon storage at -60 degrees C. 5. SDS-PAGE and native PAGE also revealed that during storage, PRP and F-PRP combined to form 3 different aggregates referred to as aggregated-PRP (aggPRP). These aggregates are readily dissociated in the presence of 2-ME, suggesting a covalent interaction between adjacent pentamers comprising decameric aggPRPs. 6. PRP, F-PRP, and aggPRP have similar amino acid compositions.     

Intestinal pathology and site specificity of the acanthocephalan Neoechinorhynchus carpiodi Dechtiar, 1968, in quillback, Carpiodes cyprinus (Lesueur)

Intestinal pathology and site specificity of Neoechinorhynchus carpiodi Dechtiar, 1968, in quillback, Carpiodes cyprinus (Lesueur), from Dauphin Lake, Manitoba, was investigated. Neoechinorhynchus carpiodi elicits the formation of a nodule at the point of proboscis attachment. Over 98% of the worms were attached in sections 6-8 of the intestine. Fish had clusters of 1-8 nodules, cluster size increased with worm burden, and the volume of nodules increased with worm numbers. Nodule number, size, and pathology was related to intensity of infection and to depth of proboscis penetration. Three types of pathology were noted. Type I nodules had few worms and the proboscides were attached in the lamina propria; Type II nodules harbored more worms and the proboscides penetrated to, but not through, the stratum compactum; and Type III nodules had the greatest numbers of N. carpiodi and proboscides penetrated through the stratum compactum. Hyperplasia, vascularization, and collagen deposition were extensive, especially in Type III nodules. An epithelium-lined channel was present in most nodules. Type III nodules were most anterior (75% of the time), harbored the greatest proportion of immature worms regardless of cluster size, and had more gravid females. The largest nodules (Type III pathology) were well vascularized, long-lasting, and appeared to be the preferred microhabitat for the parasite.