Physiological and behavioral responses of the mud snails Hydrobia glyca and Hydrobia ulvae to extreme water temperatures and salinities: implications for their spatial distribution within a system of temperate lagoons

Physiological responses (oxygen consumption) and behavioral responses (feeding and activity) of the mud snails Hydrobia ulvae and Hydrobia glyca at different salinities (20 per thousand-80 per thousand) and temperatures (20 degrees and 30 degrees C) were studied. After 24 h under experimental conditions, both Hydrobia species already showed maximal activities (>90%) for a wide salinity range (30 per thousand-70 per thousand), with significant differences in activity between species only outside the usual salinity range of the studied lagoon. In contrast, egestion rates of H. glyca were significantly higher at the lowest salinities tested (30 per thousand and 40 per thousand) irrespective of water temperature, whereas egestion rates of H. ulvae were always significantly higher (57% on average) at 20 degrees C than at 30 degrees C and at the usual salinities found in the field (40 per thousand and 50 per thousand). Both species showed an oxyregulatory response to dissolved oxygen concentrations ranging from saturation to 1.5 mg O(2) L(-1), although specific oxygen consumption rates were significantly higher at 30 degrees C than at 20 degrees C (Q(10)=1.47+/-0.08 for H. ulvae and Q(10)=12.1+/-0.06 for H. glyca) and at the lowest salinities (30 per thousand-50 per thousand for H. ulvae and 30 per thousand-40 per thousand for H. glyca). On average, specific rates were higher for the smaller-sized H. glyca (1.64+/-0.03 microg O(2) mg(-1) ash-free dry weight [AFDW]) than for H. ulvae (1.35+/-0.03 microg O(2) mg(-1) AFDW). Despite the overlapping of their tolerances to high temperatures and salinities, the observed interspecies differences could play a certain role in the distribution of H. ulvae and H. glyca in the studied habitat. In particular, the decreasing feeding activity but increasing respiration of H. ulvae at 30 degrees C for salinities that usually occur in the studied lagoon could represent disadvantages to H. glyca during the warm period.     

Synthetic antimicrobial peptides as agricultural pesticides for plant-disease control

There is a need of antimicrobial compounds in agriculture for plant-disease control, with low toxicity and reduced negative environmental impact. Antimicrobial peptides are produced by living organisms and offer strong possibilities in agriculture because new compounds can be developed based on natural structures with improved properties of activity, specificity, biodegradability, and toxicity. Design of new molecules has been achieved using combinatorial-chemistry procedures coupled to high-throughput screening systems and data processing with design-of-experiments (DOE) methodology to obtain QSAR equation models and optimized compounds. Upon selection of best candidates with low cytotoxicity and moderate stability to protease digestion, anti-infective activity has been evaluated in plant-pathogen model systems. Suitable compounds have been submitted to acute toxicity testing in higher organisms and exhibited a low toxicity profile in a mouse model. Large-scale production can be achieved by solution organic or chemoenzymatic procedures in the case of very small peptides, but, in many cases, production can be performed by biotechnological methods using genetically modified microorganisms (fermentation) or transgenic crops (plant biofactories).     

A diagnosis of pneumococcal peritonitis secondary to pyo-salpinx in a young healthy female by culturing peritoneal pus

Pneumococcal intra-abdominal infections of female genital tract origin are rare. A 33-year-old woman with peritonitis due to Streptococcus pneumoniae serotype 3 was reported. The patient did not have any of the known predisposing conditions for intra-abdominal pneumococcal infection. The clinical presentation included signs of multiorgan failure. Peritoneal toilette, bilateral salpingectomy and antibiotic treatment were promptly administered. The patient remained febrile, developed respiratory failure and required a repeated laparotomy and a prolonged antimicrobial treatment. Penicillin susceptible S. pneumoniae was isolated from the pus collected at surgery. Thus, culturing of intra-operative specimens should never be neglected to establish the correct microbiologic diagnosis.     

Viroids

Viroids are small, circular RNA pathogens, which infect several crop plants and can cause diseases of economic importance. They do not code for proteins but they contain a number of RNA structural elements, which interact with factors of the host. The resulting set of sophisticated and specific interactions enables them to use the host machinery for their replication and transport, circumvent its defence reactions and alter its gene expression. Although found in plants, viroids have a distant relative in the animal world: hepatitis delta virus (HDV), a satellite virus of hepatitis B virus, which has a similar rod-like structure and replicates in the nucleus of infected cells. Viroids have also a cellular relative: the retroviroids, found in some plants as independent (non-infectious) RNA replicons with a DNA copy. In this review, we summarize recent progress in understanding viroid biology. We discuss the possible role of recently identified viroid-binding host proteins as well as the recent data on the interaction of viroids with one part of the host's defence machinery, the RNA-mediated gene silencing and how this might be connected to viroid replication and pathogenicity.     

Host-specific effect of P1 exchange between two potyviruses

The potyviruses Plum pox virus (PPV) and Tobacco vein mottling virus (TVMV) have distinct host ranges and induce different symptoms in their common herbaceous hosts. To test the relevance of the P1 protein in host compatibility and pathogenicity, hybrid viruses were constructed in which the P1 coding sequence of PPV was completely or partially replaced by the corresponding sequences from TVMV. Infections induced by these chimeric viruses revealed that the TVMV P1 and a PPV/TVMV hybrid P1 proteins are functionally equivalent in herbaceous plants to the P1 protein of a PPV isolate adapted to these hosts, in spite of having high sequence divergence. Moreover, the presence of TVMV P1 sequences enhanced the competence of a low-infectivity PPV-D-derived chimera in Nicotiana clevelandii . Conversely, all PPV/TVMV hybrids were unable to infect Prunus persicae , a specific host for PPV, suggesting that TVMV P1 is not functionally competent in this plant. Together, these data highlight the importance of the P1 protein in defining the virus host range.     

Inter-specific scaling of phytoplankton production and cell size in the field

This study tests the hypothesis that the interspecific scalingof phytoplankton production and cell size in the field followsthe -power scaling law. Published data of cell size and in situ,cell-specific carbon production rates by single phytoplanktonspecies, collected in surface waters of lakes, rivers, estuariesand oceans, are reviewed. Across more than nine orders of magnitudein cell volume, 98% of the variability in carbon productionrates was explained by cell size. The slope (b) in the log–logrelationship between carbon production rate and cell volumedid not differ significantly from 1, either for diatoms (b =1.01) or for dinoflagellates (b = 0.89). For all phytoplanktonspecies considered together, which included also cyanobacteriaand haptophytes, b took a value of 0.91, which is significantlyhigher than . The observed nearly isometric scaling relationshipsbetween production rate and cell volume suggest that there isno relationship between phytoplankton growth rate and cell size.The present analysis confirms recent evidence showing that phytoplanktonmetabolism in natural conditions does not follow the -powerscaling rule. It is argued that allometric models of planktongrowth and metabolism should incorporate scaling parametersmeasured in situ on natural phytoplankton assemblages, ratherthan those obtained in the laboratory with monospecific cultures.     

Prognostic Value of Serum Selenium Levels in Alcoholics

In alcoholics, exposure of Kupffer cells to intestinal-borne Gram-negative bacteria increases free radical release, which may, in turn, enhance cytokine secretion, creating a positive feedback loop, which contributes to liver inflammation. Impaired antioxidant mechanisms further aggravates this scenario. Some trace elements, such as selenium, are main cofactors of antioxidant enzymes. Some authors have found low Se levels in alcoholics in relation either with undernutrition, liver dysfunction, or intensity of alcoholism, but in general, Se supplementation has no effect on survival. In this study we measured serum Se in 16 controls and 76 alcoholics, 34 of them cirrhotics, 68 of whom were followed up for a median period of 38 months; 17 died during this period. Se levels were lower in patients than in controls and were related to prothrombin activity and nutritional status, more closely to this last parameter (stepwise logistic regression analysis). Patients who died showed lower Se values than those who survived. Se values over the median were associated with better survival, assessed by Kaplan–Meier curves and log-rank test. However, in multivariate analysis (Cox regression model), prothrombin activity displaced serum Se as a prognostic factor. We conclude that serum Se levels are low in alcoholics; these low values depend more heavily on impaired nutrition but also on liver dysfunction; although low Se levels were associated with a higher mortality, prothrombin activity displaced serum Se when survival was assessed using Cox’s regression model.     

Tetrahydroisoquinolines functionalized with carbamates as selective ligands of D2 dopamine receptor

A series of tetrahydroisoquinolines functionalized with carbamates is reported here as highly selective ligands on the dopamine D2 receptor. These compounds were selected by means of a molecular modeling study. The studies were carried out in three stages: first an exploratory study was carried out using combined docking techniques and molecular dynamics simulations. According to these results, the bioassays were performed; these experimental studies corroborated the results obtained by molecular modeling. In the last stage of our study, a QTAIM analysis was performed in order to determine the main molecular interactions that stabilize the different ligand-receptor complexes. Our results show that the adequate use of combined simple techniques is a very useful tool to predict the potential affinity of new ligands at dopamine D1 and D2 receptors. In turn the QTAIM studies show that they are very useful to evaluate in detail the molecular interactions that stabilize the different ligand-receptor complexes; such information is crucial for the design of new ligands.     

Increases in leaf nitrogen concentration and leaf area did not enhance spur survival and return bloom in almonds (<Emphasis Type="Italic">Prunus dulcis</Emphasis> [Mill.] DA Webb)

Mature almond trees bear fruit mainly on short shoots called spurs, with only a small percentage of fruit produced laterally on long 1-year-old shoots. As a result, maintenance of large numbers of healthy spurs per tree is critical for fruit production. However, spurs that bear fruit have lower leaf area, leaf nitrogen content, and CO₂ assimilation rate than non-fruiting spurs. This has been correlated with reduced percentages of spur survival and return bloom the following season. Thus, we hypothesized that spur leaf area, and ultimately spur health could be enhanced through application of foliar sprays and soil nitrogen treatments that would enhance leaf nitrogen content and spur leaf area. To test our hypothesis, we selected almond trees exhibiting significant yield differences as a consequence of differential soil rates of nitrogen fertilization (N rate) for three prior years (140, 224, and 392 kg/ha). In each tree, three spur types [non-fruiting spurs (F0); spurs with one fruit (F1); spurs with two fruit (F2)] were selected on the east side of the canopy and tracked for one complete season (2011–2012). Four foliar treatments (nutrient replacement, nutrient replacement with biostimulant, nitrogen, and non-spray) were directly applied to individual spurs in each N rate in the spring of 2011 and characteristic such as leaf nitrogen, and fruit quality were recorded throughout the season. In winter of 2012, spur survival and return bloom were addressed through individual visual inspection of the tagged spurs. In this experiment, soil and foliar N treatments effectively increased spur leaf area, fruit, and leaf nitrogen concentration. In the high N treatment, the leaf nitrogen values exceeded the critical nitrogen concentration established for almond trees and the critical leaf area for spur survival and blooming thresholds established by past research in this area. However, none of these positive changes in leaf N or leaf area improved spur survival and/or return boom of any spur type. Indeed, survival and hull + shell weight tended to be lower in the population of fruiting spurs with the highest leaf area and leaf nitrogen concentration and the return bloom probabilities were always lower in fruiting spurs than in non-fruiting spurs, independent of the nitrogen rate. These results and the relationship between nitrogen rate and spur survival are discussed.