Trophic interactions within the microbial food web in a tropical floodplain lake (Laguna Bufeos, Bolivia)

Whether the primary role of bacterioplankton is to act as "remineralizers" of nutrients or as direct nutritional source for higher trophic levels will depend on factors controlling their production and abundance. In tropical lakes, low nutrient concentration is probably the main factor limiting bacterial growth, while grazing by microzooplankton is generally assumed to be the main loss factor for bacteria. Bottom-up and top-down regulation of microbial abundance was studied in six nutrient limitation and dilution gradient-size fractionation in situ experiments. Bacteria, heterotrophic nanoflagellates (HNF), ciliates and rotifers showed relatively low densities. Predation losses of HNF and ciliates accounted for a major part of their daily production, suggesting a top-down regulation of protistan populations by rotifers. Phosphorus was found to be strongly limiting for bacterial growth, whereas no response to enrichment with Nitrogen or DOC was detected. HNF were the major grazers on bacteria (g-0.43 d(-1)), the grazing coefficient increased when ciliates were added (g- 0.80 d(-1)) but decreased when rotifers were added (g- 0.23 d(-1)) probably due to nutrient recycling or top-down control of HNF and ciliates by rotifers.     

Control of planar cell polarity by interaction of DWnt4 and four-jointed

The Drosophila eye and the wing display specific planar cell polarity. Although Frizzled (Fz) signaling has been implicated in the establishment of ommatidial and wing hair polarity, evidence for the Wnt gene function has been limited. Here we examined the function of a Drosophila homolog of Wnt4 (DWnt4) in the control of planar polarity. We show that DWnt4 mRNA and protein are preferentially expressed in the ventral region of eye disc. DWnt4 mutant eyes show polarity reversals mostly in the ventral domain, consistent with the ventral expression of DWnt4. Ectopic expression of DWnt4 in the dorsoventral (DV) polar margins is insufficient to induce ommatidial polarity but becomes inductive when coexpressed with Four-jointed (Fj). Similarly, DWnt4 and Fj result in synergistic induction of hair polarity toward the source of expression in the wing. Consistent with genetic interaction, we provide evidence for direct interaction of DWnt4 and Fj transmembrane protein. The extracellular domain of Fj is required for direct binding to DWnt4 and for the induction of hair polarity. In contrast to the synergy between DWnt4 and Fj, DWnt4 antagonizes the polarizing effect of Fz. Our results suggest that DWnt4 is involved in ommatidial polarity signaling in the ventral region of the eye and its function is mediated by interacting with Fj.     

Bilateral autogenous breast reconstruction using perforator free flaps: a single center's experience

The authors present a single center's experience in bilateral breast reconstruction using perforator free flaps. The aim of this study was to show their indications, surgical technique, and results. A series of 53 patients underwent this procedure between February of 1996 and October of 2002. The surgical procedures were performed on patients with bilateral breast cancer (11 patients), patients with unilateral breast cancer and contralateral prophylactic mastectomy (22 patients), patients who had undergone bilateral prophylactic mastectomy (18 patients), a patient with Poland's syndrome, and a patient whose aesthetic breast augmentation had failed. Primary and secondary bilateral breast reconstructions were done in 18 and four patients, respectively. Eighteen patients who had earlier undergone breast reconstruction with implants had a tertiary breast reconstruction. Combined reconstruction (primary with secondary and primary with tertiary reconstruction) was done in 13 patients. Ninety-eight deep inferior epigastric perforator flaps and eight superior gluteal artery perforator flaps were used. The average operative time was 10 hours (range, 8 to 14.5 hours) for the simultaneous bilateral reconstruction. Total flap necrosis occurred in two cases (one deep inferior epigastric perforator flap and one superior gluteal artery perforator flap). Partial flap necrosis was not encountered, and fat necrosis was found in one deep inferior epigastric perforator flap (1 percent). Two pulmonary infections, one deep vein thrombosis, and one cardiac arrhythmia occurred as postoperative complications. The mean hospital stay was 9 days (range, 6 to 20 days). Abdominal bulging was reported in one patient. There were no recurrent disease or cancer manifestations, with an average follow-up of 3.5 years. This series clearly shows that perforator flaps are reliable and useful tools for bilateral breast reconstruction. This technique decreases the donor-site morbidity and offers an excellent aesthetic and long-term outcome and high patient satisfaction.     

The congener; A neglected area in the study of behaviour

This paper seeks a deeper understanding of the congener as a factor in animal and human behaviour. It does so, not by concentrating on analyses of stimulus exchanges - largely specific to the species - by which a congener is recognized, but on the more general questions of why a notion of congener exists at all and why it plays such an extraordinary important role in animal and human behaviour.Three separate approaches, by way of anthropomorphic psychology, a paraphysical energy model and the physical theory of the implicate order, lead to the recognition of a certain inseparability of self and congener; and to an interpretation of the content of the notion of congener and of the behaviour in relation to it, in terms of the fundamental concept of energy and the even more fundamental one of order.Dedicated to Professor Gerard P. Baerends, one of my valued guides in ethology.     

Temperature-dependent membrane fatty acid and cell physiology changes in coccoid forms of Campylobacter jejuni.

The effect of temperature and the availability of nutrients on the transition of spiral Campylobacter jejuni cells to coccoid forms was investigated. Ageing of spiral C. jejuni cells in either nutrient-poor or nutrient-rich environments resulted in the formation of nonculturable coccoid cells at 4, 12, and 25 degrees C after different periods, with the cells incubated at 4 degrees C in nutrient-deficient media remaining culturable the longest. To study the phenomenon, ATP levels, protein profiles, and fatty acid compositions were monitored under conditions where the transition from spiral to coccoid cells occurred. During storage, the levels of intracellular ATP were highest in cells incubated at low temperatures (4 and 12 degrees C) and remained constant after a small initial decrease. During the transformation from spiral to coccoid forms, no alteration in protein profiles could be detected; indeed, inhibition of protein synthesis by chloramphenicol did not influence the transition. Furthermore, DNA damage by gamma irradiation had no effect on the process. Membrane fatty acid composition of cocci formed at low temperatures was found to be almost identical to that of spiral cells, whereas that of cocci formed at 25 degrees C was clearly different. Combining these results, it is concluded that the formation of cocci is not an active process. However, distinctions between cocci formed at different temperatures were observed. Cocci formed at 4 degrees C show characteristics comparable to those of spirals, and these cocci may well play a role in the contamination cycle of C. jejuni.(ABSTRACT TRUNCATED AT 250 WORDS)     

UL52 Primase Interactions in the Herpes Simplex Virus 1 Helicase-Primase Are Affected by Antiviral Compounds and Mutations Causing Drug Resistance

Herpes simplex virus 1 (HSV-1) UL5/8/52 helicase-primase complex is required for DNA unwinding at the replication fork and synthesis of primers during virus replication, and it has become a promising novel target for antiviral therapy. Using molecular cloning, we have identified three separate domains of UL52. Co-immunoprecipitation experiments in extracts from cells transiently expressing HA-tagged UL5, FLAG-UL8, and enhanced GFP-tagged UL52 domains revealed that the N-terminal domain of UL52 primase binds UL5 helicase and the middle domain interacts with the UL8 accessory protein. In addition, an interaction between the single strand DNA-binding protein ICP8 and the UL52 middle domain was observed. The complex between UL5 and UL52 was stabilized by the antiviral compound BAY 54-6322, and mutations providing resistance to the drug obliterate this effect. Our results also suggest a mechanism for accommodating conformational strain resulting from movement of UL5 and UL52 in opposite directions on the lagging strand template, and they identify molecular complexes that can be further examined by structural biology techniques to resolve the mechanism of primer synthesis during herpesvirus replication. Finally, they help to explain the mechanism of action of a novel class of antiviral compounds currently being evaluated in clinical trials.     

Evaluation of coagulation activation after Rhinovirus infection in patients with asthma and healthy control subjects: an observational study

Background

Asthma exacerbations are frequently triggered by rhinovirus infections. Both asthma and respiratory tract infection can activate haemostasis. Therefore we hypothesized that experimental rhinovirus-16 infection and asthmatic airway inflammation act in synergy on the haemostatic balance.

Methods

28 patients (14 patients with mild allergic asthma and 14 healthy non-allergic controls) were infected with low-dose rhinovirus type 16. Venous plasma and bronchoalveolar lavage fluid (BAL fluid) were obtained before and 6 days after infection to evaluate markers of coagulation activation, thrombin-antithrombin complexes, von Willebrand factor, plasmin-antiplasmin complexes, plasminogen activator inhibitor type-1, endogenous thrombin potential and tissue factor-exposing microparticles by fibrin generation test, in plasma and/or BAL fluid. Data were analysed by nonparametric tests (Wilcoxon, Mann Whitney and Spearman correlation).

Results

13 patients with mild asthma (6 females, 19-29 y) and 11 healthy controls (10 females, 19-31 y) had a documented Rhinovirus-16 infection. Rhinovirus-16 challenge resulted in a shortening of the fibrin generation test in BAL fluid of asthma patients (t = -1: 706 s vs. t = 6: 498 s; p = 0.02), but not of controls (t = -1: 693 s vs. t = 6: 636 s; p = 0.65). The fold change in tissue factor-exposing microparticles in BAL fluid inversely correlated with the fold changes in eosinophil cationic protein and myeloperoxidase in BAL fluid after virus infection (r = -0.517 and -0.528 resp., both p = 0.01).Rhinovirus-16 challenge led to increased plasminogen activator inhibitor type-1 levels in plasma in patients with asthma (26.0 ng/mL vs. 11.5 ng/mL in healthy controls, p = 0.04). Rhinovirus-16 load in BAL showed a linear correlation with the fold change in endogenous thrombin potential, plasmin-antiplasmin complexes and plasminogen activator inhibitor type-1.

Conclusions

Experimental rhinovirus infection induces procoagulant changes in the airways of patients with asthma through increased activity of tissue factor-exposing microparticles. These microparticle-associated procoagulant changes are associated with both neutrophilic and eosinophilic inflammation. Systemic activation of haemostasis increases with Rhinoviral load.

Trial registration

This trial was registered at the Dutch trial registry (http://www.trialregister.nl): NTR1677.     

Influence of extraction solvent system on the extractability of lipid components from the biomass of Nannochloropsis gaditana

Microalgae oils are considered to be promising alternative sources of omega-3 LC-PUFA. The aim of this work was therefore to evaluate different solvent (mixtures), currently accepted for use in the food industry, for the extraction of lipids from Nannochloropsis gaditana, an omega-3 LC-PUFA-rich microalga. Importantly, not only the total lipid yield but also the lipid class, eicosapentaenoic acid, carotenoid, and sterol yield were investigated. It was shown that the highest yield for each of the components was obtained with dichloromethane/ethanol (1:1). All extracts except the one obtained with dichloromethane/ethanol (1:1) were enriched in neutral lipids and depleted in polar lipids, when compared to the total lipid extract (chloroform/methanol 1:1). Hexane/isopropanol (3:2) seems to be the second best option: it has the advantage of performing better at criteria such as toxicity, but has the disadvantage that almost half of the interesting oil cannot be recovered.     

Impact of land-use intensity on the conservation of functional and phylogenetic diversity in temperate semi-natural plant communities

The earth is facing a worldwide decline in biodiversity, with land-use change identified as one of the most important drivers. There is evidence that the loss of diversity has a significant impact on ecosystem functioning. Earlier research focused on species richness, but more recent, functional and phylogenetic diversity came into the picture as the stronger determinants of ecosystem processes. The effects of increasing land-use intensity on functional (FD) and phylogenetic diversity (PD), however, are still poorly understood. We studied how FD and PD are affected by land-use intensity in temperate plant communities. Our results show that land-use intensity has a clear impact on species richness, but also affects functional and phylogenetic diversity. Intensive agricultural areas fail to support high and sustainable levels of functional and phylogenetic diversity. These results highlight the need for the protection of biodiversity in nature reserves and the conservation of areas with extensive agricultural practices. Because species richness may influence the measures of functional and phylogenetic diversity, we compared the observed FD and PD values with random values generated with a matrix-swap null model. The observed discrepancy between species loss and the loss of FD and PD calls for an integrated approach to biodiversity conservation, in which the different components of biodiversity are considered together.     

Limnology and trophic status of glacial lakes in the tropical Andes (Cajas National Park,Ecuador)

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