Lesions of the hypothalamic arcuate nucleus produce a temporary hyperalgesia and attenuate stress-evoked analgesia

In an attempt to elucidate the role of β-endorphin in the modulation of ‘basal’ nociceptive threshold and in the mediation of the antinociception (analgesia) evoked by stress, a series of lesions of the arcuate nucleus, the origin of the central system of β-endorphinergic neurones, were performed. These lesions produced an ～80% depression in the level of β-endorphin immunoreactivity in both the hypothalamus and periventricular β-endorphinergic fibre-containing tissue. A 50% decrease in the neurointermediate lobe content of immunoreactivity, but no change in the levels of this in the anterior lobe was also observed. Arcuate lesioned rats were significantly hyperalgesic in comparison to sham animals on day 4 post-operation, but on days 10 and 12, the basal nociceptive threshold of lesioned and sham groups did not differ significantly. On day 12 post-surgery upon exposure to 5 min foot-shock stress, lesioned rats developed a significantly smaller increase in tail-flick latency than did sham animals. These data are evidential of the importance of the arcuate nucleus in the determination of basal nociceptive threshold and in the generation of the analgesia which accompanies stress and are, further, suggestive of a role of central β-endorphin in the mediation of these processes.     

Patch occupancy and abundance of local populations in landscapes differing in degree of habitat fragmentation: a case study of the colonial black‐headed gull,Chroicocephalus ridibundus

Aim This study investigated whether habitat fragmentation at the landscape level influences patch occupancy and abundance of the black‐headed gull, Chroicocephalus ridibundus, and whether the response of the species to environmental factors is consistent across replicated landscape plots. Location Water bodies (habitat patches) in southern Poland. Methods Surveys were conducted in two landscape types (four plots in each): (1) more‐fragmented landscape, in which habitat patches were small (mean size 2.2–6.2 ha) and far apart (mean distance 2.5–3.1 km); and (2) less‐fragmented landscape, in which habitat patches were large (mean size 9.2–16.5 ha) and separated by short distances (mean 0.9–1.4 km). Observations were performed twice in 284 potential habitat patches during the 2007 breeding season. Results Colonies were significantly more frequent and larger in the less‐fragmented landscapes than in the more‐fragmented ones. Probability of patch occupancy and number of breeding birds were positively related with patch size and these relationships were especially strong in the more‐fragmented landscapes. In the less‐fragmented landscapes, the occurrence of black‐headed gulls was negatively related to the distance to the nearest local population, but in the more‐fragmented landscapes such a relationship was not detected. As distance to the nearest habitat patch increased, the probability of the patch occupancy decreased in the more‐fragmented landscapes. Moreover, abundance was negatively influenced by distance to the nearest habitat patch, especially strongly in more‐fragmented landscapes. Proximity of corridors (rivers) positively influenced the occupation of patches regardless of landscape type. The number of islets positively influenced occupancy and abundance of local populations, and this relationship was stronger in the more‐fragmented landscapes. Main conclusions Our results are in agreement with predictions from metapopulation theory and are the first evidence that populations of black‐headed gulls may have a metapopulation structure. However, patch occupancy and abundance were differentially affected by explanatory variables in the more‐fragmented landscapes than in the less‐fragmented ones. This implies that it is impossible to derive, a priori, predictions about presence/abundance patterns based on only a single landscape.     

Proteolytic Activity of Pseudomonas aeruginosa Isolates with TTSS-Mediated Cytotoxicity and Invasiveness to Host Cells

Over 100 of Pseudomonas aeruginosa isolates representing the two TTSS genotypes (exoU ⁻/exoS ⁺ or exoU ⁺/exoS ⁻) were cultured in different media in order to evaluate their proteolytic activities and find a relationship between proteolytic activity and the cytotoxic and/or invasive phenotypes displayed by the strains upon infection of RAW 264.7 murine macrophage-like cells and pulmonary microvascular endothelial cells (PME). The elastolytic activity, protein concentration, and total proteolytic activity (TPA) were measured in culture supernatants. No significant differences were observed in the median elastolytic activities among cytotoxic/noninvasive, noncytotoxic/invasive, and cytotoxic/invasive phenotypes displayed by P. aeruginosa strains. The only significant difference was noted when isolates of the two different TTSS genotypes were grown in a calcium-depleted minimal medium for induction of TTSS (MI). The exoU ⁻/exoS ⁺ isolates showed significant higher levels of the median elastolytic activity when compared to the exoU ⁺/exoS ⁻ isolates. These two groups of isolates secreted the elastase B (LasB) with distinct molecular masses 158 or 116 kD, respectively. The strains of the two TTSS genotypes secreted similar amount of total proteins; however, the higher values of TPA were observed for the isolates of the exoU ⁺ /exoS ⁻ genotype when grown in MI medium. We concluded that there is no direct relationship between secretion of proteases with elastolytic activity and the cytotoxic and/or invasive phenotypes of the isolates observed upon infection of both RAW 264.7 and PME monolayers. Further studies are needed to find out whether others factors beside proteases could influence the mechanism of host cells intoxication mediated by the P. aeruginosa TTSS-delivered toxins.     

ABA may affect the dormancy in triticale caryopses by inhibition of embryo class I RNases,enzymes involved in P<Subscript>i</Subscript> release

The main objective of this study was to analyze the differences in profiles of RNase activities from triticale embryos (Triticosecale, cv. Ugo) between dormant and non-dormant caryopses and to determine the influence of exogenous abscisic acid (ABA) on the activities of these enzymes. The major RNase from the examined tissue was detected following SDS-PAGE, with substrate-based gel assay, described by Yen and Green (Plant Physiol 97:1487–1493, 1991). The activities of enzymes were characterized according to their pH optima, ion dependence, EDTA sensitivity and DNase activity. In embryos with arrested growth (in a natural way by dormancy or artificially by ABA treatment), the activity of two enzymes—24 and 27 kDa—belonging to class I RNases was completely inhibited, whereas that of two other RNases of this family—23 and 25 kDa—was detectable. However, the activity of the class I ribonucleases (enzymes responsible for cellular P_i release) was very low. Moreover, in contrast with non-dormant caryopses, imbibing embryos of dormant or ABA-treated seeds contained 13- and 14-kDa enzymes. These enzymes have not been classified so far, and their specific properties are different from the generally accepted properties of ribonucleolytic enzymes. In addition to the above results, the P_i content in the analyzed samples was determined by the Ames (Methods Enzymol 8:115–118, 1966) method. The results suggest a very low and constant level of inorganic phosphate in dormant samples as well as an evidently decreasing P_i content in embryos under the influence of ABA treatment. The inhibition of the class I RNases activity induced by abscisic acid implies that one of the roles of ABA in seed dormancy may consist in arresting the catabolic release of P_i, which results in retarding the embryo’s growth.     

Revealing Sulfate-Reducing Microorganisms in Oilfield Waters (Flysch Carpathians,South-eastern Poland)

Sulphidogenous microorganism communities were isolated from selected oilfield waters in the Flysch Carpathians of south-eastern Poland. Organisms were incubated using the microcosms method with application of two media: minimal medium and modified Postgate C medium with yeast extract or trisodium citrate or monocyclic hydrocarbons from the BTEX group (benzene, toluene, ethylbenzene, and xylene) as the sole carbon source. Activity of sulphidogenic, autochthonous microorganism communities was noted only on the Postgate medium. Beside active sulphate reduction – max. 70%, ca. 74% biodegradation of organic compounds was also observed in the cultures. The highest content of sulphate-reducing bacteria (SRB) in the COD (ca. 83%) was noted in cultures, in which trisodium citrate and yeast extract were applied as the sole carbon source. Molecular analysis indicated not only the presence of SRB such as Desulfobacterium autothrophicum, Desulfovibrio desulfuricans, but also other microorganisms, e.g., Geobacter metallireducens. All these taxa are obligatory or facultative anaerobes, with metabolism linked mostly with elemental sulphur and/or its oxidized forms, as well as iron. Analysis of the mineral composition of the residues confirmed the presence of elemental sulphur, testifying for the active reduction of sulphates by incompletely oxidizing sulphate reducers assigned to the SRB group. Based on the obtained results, it is concluded that the physical and chemical properties of the oilfield waters are favorable for the growth and development of sulphidogenic microorganism assemblages and mineral-forming processes conducted by them.     

Stepwise sRNA targeting of structured bacterial mRNAs leads to abortive annealing

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Disruption of Homocitrate Synthase Genes in <Emphasis Type="Italic">Candida albicans</Emphasis> Affects Growth But Not Virulence

Two genes, LYS21 and LYS22, encoding isoforms of homocitrate synthase, an enzyme catalysing the first committed step in the lysine biosynthetic pathway, were disrupted in Candida albicans using the SAT1 flipper strategy. The double null lys21Δ/lys22Δ mutant lacked homocitrate synthase activity and exhibited lysine auxotrophy in minimal media that could be fully rescued by the addition of 0.5–0.6 mM l-lysine. On the other hand, its virulence in vivo in the model of disseminated murine candidiasis appeared identical to that of the mother, wild-type strain. These findings strongly question a possibility of exploitation of homocitrate synthase and possibly also other enzymes of the lysine biosynthetic pathway as targets in chemotherapy of disseminated fungal infections.     

Viola roxolanica n. sp.

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