Light and Phosphate Competition Between Cylindrospermopsis raciborskii and Microcystis aeruginosa is Strain Dependent

The hypothesis that outcomes of phosphorus and light competition between Cylindrospermopsis raciborskii and Microcystis aeruginosa are strain dependent was tested experimentally. Critical requirements of phosphorus (P*) and of light (I*) of two strains of each species were determined through monoculture experiments, which indicated a trade-off between species and also between Microcystis strains. Competition experiments between species were performed using the weakest predicted competitors (with the highest values of P* and of I*) and with the strongest predicted competitors (with the lowest values of P* and of I*). Under light limitation, competition between the weakest competitors led C. raciborskii to dominate. Between the strongest competitors, the opposite was observed, M. aeruginosa displaced C. raciborskii, but both strains co-existed in equilibrium. Under phosphate limitation, competition between the weakest competitors led C. raciborskii to exclude M. aeruginosa, and between the strongest competitors, the opposite was observed, M. aeruginosa displaced C. raciborskii, but the system did not reach an equilibrium and both strains were washed out. Hence, outcomes of the competition depended on the pair of competing strains and not only on species or on type of limitation. We concluded that existence of different trade-offs among strains and between species underlie our results showing that C. raciborskii can either dominate or be displaced by M. aeruginosa when exposed to different conditions of light or phosphate limitation.     

The first record of Lutzomyia longipalpis in the Argentine northwest

In 2004, the urban presence of Lutzomyia longipalpis was recorded for the first time in Formosa province. In 2006, the first autochthonous case of human urban visceral leishmaniasis (VL) was recorded in Misiones in the presence of the vector, along with some canine VL cases. After this first case, the vector began to spread primarily in northeast Argentina. Between 2008-2011, three human VL cases were reported in Salta province, but the presence of Lu. longipalpis was not recorded. Captures of Phlebotominae were made in Tartagal, Salta, in 2013, and the presence of Lu. longipalpis was first recorded in northwest Argentina at that time. Systematic sampling is recommended to observe the distribution and dispersion patterns of Lu. longipalpis and consider the risk of VL transmission in the region.     

Molecular dynamics of water in the neighborhood of aquaporins

Present knowledge obtained by molecular dynamics (MD) simulation studies regarding the dynamics of water, both in the vicinity of biological membranes and within the proteinaceous water channels, also known as aquaporins (AQPs), is reviewed. A brief general summary of the water models most extensively employed in MD simulations (SPC, SPC/E, TIP3P, TIP4P), indicating their most relevant pros and cons, is likewise provided. Structural considerations of water are also discussed, based on different order parameters, which can be extracted from MD simulations as well as from experiments. Secondly, the behaviour of water in the neighbourhood of membranes by means of molecular dynamics simulations is addressed. Consequently, the comparison with previous experimental evidence is pointed out. In living cells, water is transported across the plasma membrane through the lipid bilayer and the aforementioned AQPs, which motivates this review to focus mostly on MD simulation studies of water within AQPs. Relevant contributions explaining peculiar properties of these channels are discussed, such as selectivity and gating. Water models used in these studies are also summarised. Finally, based on the information presented here, further MD studies are encouraged.     

Testing methods to estimate abundance of Magellanic Penguins Spheniscus magellanicus

Capsule Using simulations in a geographical information system our results showed that systematic sampling with quadrats was the most accurate, precise and cost-effective method to survey Magellanic Penguin colonies.

Aims To determine which sampling method gives better estimations of penguin abundance.

Methods A virtual colony was generated deriving spatial parameters from a real survey and applying Kriging interpolation. Three sampling methods were then applied on this virtual colony: random sampling with quadrats; systematic sampling with quadrats; systematic sampling with fixed-width transects. The estimated abundance for each trial was compared to the abundance of the virtual colony to have a measure of accuracy and precision.

Results Systematic sampling with quadrats estimated penguin abundance better than random or systematic sampling with transects since it achieved 100% accuracy and great precision after sampling only 2.1% of the virtual colony.

Conclusion The use of a simulated colony allowed the comparison of several sampling methods traditionally used in Magellanic Penguin surveys. The results of this study are important in order to standardize sampling protocols for Magellanic Penguins and to have more comparable estimations to detect trends over time. Also, the methodological approach used here could be used to assess sampling methods for other colonial bird species.     

The Properties of Chondrocyte Membrane Reservoirs and Their Role in Impact-Induced Cell Death

Impact loading of articular cartilage causes extensive chondrocyte death. Cell membranes have a limited elastic range of 3–4% strain but are protected from direct stretch during physiological loading by their membrane reservoir, an intricate pattern of membrane folds. Using a finite-element model, we suggested previously that access to the membrane reservoir is strain-rate-dependent and that during impact loading, the accessible membrane reservoir is drastically decreased, so that strains applied to chondrocytes are directly transferred to cell membranes, which fail when strains exceed 3–4%. However, experimental support for this proposal is lacking. The purpose of this study was to measure the accessible membrane reservoir size for different membrane strain rates using membrane tethering techniques with atomic force microscopy. We conducted atomic force spectroscopy on isolated chondrocytes (n = 87). A micron-sized cantilever was used to extract membrane tethers from cell surfaces at constant pulling rates. Membrane tethers could be identified as force plateaus in the resulting force-displacement curves. Six pulling rates were tested (1, 5, 10, 20, 40, and 80 μm/s). The size of the membrane reservoir, represented by the membrane tether surface areas, decreased exponentially with increasing pulling rates. The current results support our theoretical findings that chondrocytes exposed to impact loading die because of membrane ruptures caused by high tensile membrane strain rates.     

Structure–activity relationships of 6-(aminomethylphenoxy)-benzoxaborole derivatives as anti-inflammatory agent

A series of novel 6-(aminomethylphenoxy)benzoxaborole analogs was synthesized for the investigation of the structure–activity relationship of the inhibition of TNF-alpha, IL-1beta, and IL-6, from lipopolysaccharide stimulated peripheral blood mononuclear cells. Compounds 9d and 9e showed potent activity against all three cytokines with IC₅₀ values between 33 and 83 nM. Chloro substituted analog 9e (AN3485) is considered to be a promising lead for novel anti-inflammatory agent with a favorable pharmacokinetic profile.     

Synthesis and biological evaluation against Leishmania amazonensis of a series of alkyl-substituted benzophenones

Nine O-alkyl and O-prenyl derivatives were synthesized from commercial 2,4-dihydroxybenzophenone, 4,e4,4′-dihydroxybenzophenone and were evaluated for their leishmanicidal activity against promastigote forms of Leishmania amazonensis, as well their toxicity in murine macrophages. All derivatives exhibited better biological activity than their hydroxylated benzophenones precursors, and new compound LFQM-123 (3c) was 250-fold more active than its precursor 4,4′-dihydroxybenzophenone (3). Moreover, some of the results were comparable to the standard drug Amphotericin B, suggesting that the increase in lipophilicity could facilitate protozoa membrane permeation. In this study we confirmed that benzophenone derivatives exhibit leishmanicidal properties, with relatively low toxicity, and thus could be exploited as promise prototypes for the design and development of new drug for the treatment of leishmaniasis.     

Trends of karyotypical evolution in the pearl cichlid,Geophagus brasiliensis,from southern Brazil

Chromosomal rearrangements such as inversions can facilitate speciation even in the presence of gene flow. The present study aims to analyze the karyotypic variation in six populations of Geophagus brasiliensis from southern Brazil. All specimens showed 2n = 48 chromosomes, but three karyotypes were found to have one, two or three pairs of submetacentric chromosomes. Although G. brasiliensis did not exhibit variation in the diploid number, it presented a wide interpopulational variation mainly regarding the karyotype formula and specific chromosomal markers. Differences in the location of the major and minor rDNA loci were observed among the populations. Moreover, different patterns were observed in the distribution of the constitutive heterochromatin, presenting intra- and interpopulational variation. This supports the hypothesis that this taxon represents a complex species or that cryptic species are included in this group, indicating a possibleprocess of sympatric speciation. By potentially restricting gene flow between heterokaryotypes, the segregating chromosome rearrangements we describe for G. brasiliensis may play a role in diversification in this species complex.     

Selection of ceramic fluorapatite‐binding peptides from a phage display combinatorial peptide library: optimum affinity tags for fluorapatite chromatography

Peptide affinity tags have become efficient tools for the purification of recombinant proteins from biological mixtures. The most commonly used ligands in this type of affinity chromatography are immobilized metal ions, proteins, antibodies, and complementary peptides. However, the major bottlenecks of this technique are still related to the ligands, including their low stability, difficulties in immobilization, and leakage into the final products. A model approach is presented here to overcome these bottlenecks by utilizing macroporous ceramic fluorapatite (CFA) as the stationary phase in chromatography and the CFA‐specific short peptides as tags. The CFA chromatographic materials act as both the support matrix and the ligand. Peptides that bind with affinity to CFA were identified from a randomized phage display heptapeptide library. A total of five rounds of phage selection were performed. A common N‐terminal sequence was found in two selected peptides: F4‐2 (KPRSMLH) and F5‐4 (KPRSVSG). The peptide F5‐4, displayed by more than 40% of the phages analyzed in the fifth round of selection, was subjected to further studies. Selectivity of the peptide for the chemical composition and morphology of CFA was assured by the adsorption studies. The dissociation constant, obtained from the F5‐4/CFA adsorption isotherm, was in the micromolar range, and the maximum capacity was 39.4 nmol/mg. The chromatographic behavior of the peptides was characterized on a CFA stationary phase with different buffers. Preferential affinity and specific retention properties suggest the possible application of the phage‐derived peptides as a tag in CFA affinity chromatography for enhancing the selective recovery of proteins. Copyright © 2013 John Wiley & Sons, Ltd.