Structural heterogeneity of linear habitats positively affects Barred Warbler Sylvia nisoria,Common Whitethroat Sylvia communis and Lesser Whitethroat Sylvia curruca in farmland of Western Poland

Capsule Structural heterogeneity was the most important factor influencing the distribution of Barred Warbler Sylvia nisoria, Common Whitethroat S. communis and Lesser Whitethroat S. curruca in linear habitats in farmland of Western Poland.

Aims To investigate the occurrence of three species of Sylvia warblers in relation to the spatial structure of linear habitats in the agricultural landscape of Western Poland where, in contrast to Western Europe, field boundaries are not managed in terms of their size or spatial structure.

Methods In 2008, the distribution of breeding territories of Sylvia warblers in linear habitats was estimated in farmland of Western Poland. Redundancy detrended analysis was used to assess the relationship between bird abundance and seven linear habitat variables in ninety-four 150?m sections.

Results Sylvia warblers differed in habitat requirements, however heterogeneity affected their distribution to the greatest extent. In addition, Barred Warbler preferred high shrub volume and wider sections, whereas Common Whitethroat was attracted by brambles and nettles and Lesser Whitethroat favoured shrubs. All species avoided a high proportion of low vegetation.

Conclusion Structural heterogeneity resulted in highly preferred linear habitats for Sylvia warblers. Thus, maintaining or increasing structural heterogeneity of linear habitats may be a very effective tool for the conservation of farmland bird populations.     

On flower visitors and true pollinators: The case of protandrous Heracleum sphondylium L. (Apiaceae)

Hogweed (Heracleum sphondylium L.), a common European umbellifer, is very variable in terms of flower and inflorescence morphology. Its flowers are visited by numerous insects, yet little is known about the importance of the particular insect taxa. I observed umbels of two colour morphs (subspecies) of Heracleum sphondylium growing in NE Poland, which were visited by more than 108 insect species during two study seasons. Analysis of the insects' importance suggests that the most efficient pollinators are the medium-sized flies Eriozona syrphoides, and Lucilia spp. (Diptera). Bumblebees Bombus terrestris (Hymenoptera), beetles of genus Stenurella spp. and Dasytes spp. (Coleoptera) and flies Eristalis spp., Meliscaeva cinctella, Phaonia angelicae and Thricops nigrifrons also contribute to pollination of the studied plants, but their efficiency shows considerable seasonal variation. Although the dense umbels of the white flowered H. sphondylium subsp. sphondylium are generally more attractive for insect visitors than the loose yellowish inflorescences of H. sphondylium subsp. sibiricum, these taxa do not seem to attract different sets of the pollinators. For both subspecies, flowers in the staminate phase were visited significantly more often than those in the pistillate phase. Some flower visitors visited the staminate phase only, which suggests they may be parasites rather than pollinators.     

Novel regulatory mechanisms for generation of the soluble leptin receptor: implications for leptin action

Background

The adipokine leptin realizes signal transduction via four different membrane-anchored leptin receptor (Ob-R) isoforms in humans. However, the amount of functionally active Ob-R is affected by constitutive shedding of the extracellular domain via a so far unknown mechanism. The product of the cleavage process the so-called soluble leptin receptor (sOb-R) is the main binding protein for leptin in human blood and modulates its bioavailability. sOb-R levels are differentially regulated in metabolic disorders like type 1 diabetes mellitus or obesity and can, therefore, enhance or reduce leptin sensitivity.

Methodology/Principal Findings

To describe mechanisms of Ob-R cleavage and to investigate the functional significance of differential sOb-R levels we established a model of HEK293 cells transiently transfected with different human Ob-R isoforms. Using siRNA knockdown experiments we identified ADAM10 (A Disintegrin And Metalloproteinase 10) as a major protease for constitutive and activated Ob-R cleavage. Additionally, the induction of lipotoxicity and apoptosis led to enhanced shedding shown by increased levels of the soluble leptin receptor (sOb-R) in cell supernatants. Conversely, high leptin concentrations and ER stress reduced sOb-R levels. Decreased amounts of sOb-R due to ER stress were accompanied by impaired leptin signaling and reduced leptin binding.

Conclusions

Lipotoxicity and apoptosis increased Ob-R cleavage via ADAM10-dependent mechanisms. In contrast high leptin levels and ER stress led to reduced sOb-R levels. While increased sOb-R concentrations seem to directly block leptin action, reduced amounts of sOb-R may reflect decreased membrane expression of Ob-R. These findings could explain changes of leptin sensitivity which are associated with variations of serum sOb-R levels in metabolic diseases.     

Ultrastructure of the spermatozoa of the flatworms Phaenocelis peleca and Boninia divae (Platyhelminthes, Polycladida)

The ultrastructure of spermatozoa of the acotylean Phaenocelis peleca and the cotylean Boninia divae is described. All spermatozoa are filiform and biflagellate with a 9+"1" microtubular pattern in the axoneme. Sperm characters in P. peleca follow the morphologies described for other acotyleans, with axonemes exiting the sperm shaft at the distal end and remaining in close contact with the sperm membrane. The nucleus occupies the proximal region of the shaft, and two types of dense bodies and mitochondria are located at the distal end. Unlike other members of the Cotylea, the axonemes of B. divae spermatozoa are incorporated into the sperm shaft, leaving the shaft at some distance from the distal end and then remaining free. This type of morphology is characteristic for acotyleans. Additionally, the spermatozoa of B. divae contain only one type of dense bodies plus a unique structure, which we call a central core. The nucleus in this species is unique as well; it shows periodic constrictions and rings of electron-dense granules, characters that further contribute to the distinct status of Boniniidae.     

Cell surface properties as factors involved in Proteus vulgaris adhesion to stainless steel under starvation conditions

The purpose of these investigations was to evaluate the influence of limited nutrient availability in the culture medium on Proteus vulgaris biofilm formation on surfaces of stainless steel. The relationship between the P. vulgaris adhesion to the abiotic surfaces, the cellular ATP levels, cell surface hydrophobicity and changes in the profiles of extracellular proteins and lipopolysaccharides was examined. In all experimental variants the starvation conditions induced the bacterial cells to adhere to the surfaces of stainless steel. Higher ATP content and lower cell surface hydrophobicity of P. vulgaris cells was observed upon nutrient-limited conditions. Under starvation conditions a reduction in the levels of extracellular low molecular weight proteins was noticed. High molecular weight proteins formed the conditioning layer on stainless steel plates, making the bacteria adhesion process more favorable. The production of low molecular weight carbohydrates promoted more advanced stages of P. vulgaris biofilm formation process on the surfaces of stainless steel upon starvation.     

Oxidative stress in the testis of hyperglycemic rabbits treated with repaglinide

In the present study, the induction of oxidative stress was examined in the testis of alloxan-induced diabetic rabbits. In addition, the protective effect of repaglinide, an oral anti-diabetic, at a dose of 1 mg daily was studied after four and eight weeks of the treatment. For these purposes, the levels of superoxide dismutase (Cu,Zn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), glutathione (GSH), ascorbic acid (AA), lipid peroxidation products (LPO) and protein carbonyl groups (PCG) were quantified. Hyperglycemia resulted in significant increases in the antioxidative enzymes, Cu, Zn-SOD, CAT, GSH-Px, and GSSG-R after four and eight weeks, respectively. There was also an increase in GSH level, and a decrease in the level of AA. These effects were accompanied by an elevation in testicular LPO levels and PCG levels. Repaglinide was found to normalize the activity of GSSG-R and levels of GSH and AA, and blunted the increased lipid peroxidation, however no decrease in PCG levels were observed. In conclusion, some oxidative changes provoked in the testis of rabbits by hyperglycemia, were found to be reduced with repaglinide treatment at therapeutic dose.     

N-terminal brain natriuretic propeptide levels correlate with procalcitonin and C-reactive protein levels in septic patients

The aim of this study was to find the relationship between N-terminal brain natriuretic propeptide (NT-proBNP), procalcitonin (PCT) and C-reactive protein (CRP) plasma concentrations in septic patients. This was a prospective study, performed at Medical University Hospital No. 5 in łódź. Twenty patients with sepsis and severe sepsis were included in the study. N-terminal brain natriuretic propeptide, procalcitonin and C-reactive protein concentrations, and survival were evaluated. In the whole studied group (128 measurements), the mean NT-proBNP, procalcitonin and C-reactive protein concentrations were, respectively: 140.80±84.65 pg/ml, 22.32±97.41 ng/ml, 128.51±79.05 mg/l. The correlations for the NT-proBNP level and procalcitonin and C-reactive protein levels were 0.3273 (p<0.001) and 0.4134 (p<0.001), respectively. NT-proBNP levels correlate with PCT and CRP levels in septic patients. In the survivor subgroup, the mean NT-proBNP plasma concentrations were significantly lower than in the non-survivor subgroup.     

Mutational analysis of the N-glycosylation sites of Duffy antigen/receptor for chemokines

The Duffy antigen/receptor for chemokines (DARC) is a seven-transmembrane glycoprotein carrying the Duffy (Fy) blood group antigen. The polypeptide chain of DARC contains two NSS motifs at positions 16 and 27 and one NDS motif at position 33 that represent canonical sequences for efficient N-glycosylation. To verify whether all of these three sites are occupied by a sugar chain, we generated mutants in which potential N-glycosylation sites (AsnXSer) were removed by replacement of serine by alanine. Seven DARC glycosylation variants, missing one (S18A, S29A, S35A), two (S18A.S29A, S18A.S35A, S29A.S35A), or three (S18A.S29A.S35A) glycosylation sites, were obtained. cDNA encoding DARC mutants was cloned into the eukaryotic expression vector pcDNA3.1/myc-HisA and expressed in human K562 cells. Stable transfectants expressing wild-type or mutated forms of Duffy were then lysed, purified by metal-affinity chromatography, and subjected to Western blots with an anti-Duffy monoclonal antibody. The gel electrophoresis data indicate that all three canonical sites are used for sugar attachment.     

Novel properties of antimicrobial peptides

Endogenous peptide antibiotics are known as evolutionarily old components of innate immunity. Due to interaction with cell membrane these peptides cause permeabilization of the membrane and lysis of invading microbes. However, some studies proved that antimicrobial peptides are universal multifunctional molecules and their functions extend far beyond simple antibiotics. In this review we present an overview of the general mechanism of action of antimicrobial peptides and discuss some of their additional properties, like antitumour activity, mitogenic activity, role in signal transduction pathways and adaptive immune response.     

SDF-1 alone and in co-operation with HGF regulates biology of human cervical carcinoma cells

Stromal Derived Factor-1 (SDF-1)-CXCR4 axis plays a pivotal role in biology and metastasis of several tumors. The aim of this study was to see if SDF-1 alone or in combination with Hepatocyte Growth Factor (HGF) affects biology of human cervical carcinoma (HCC) cells. We found that HCC cell lines investigated in our study highly express CXCR4 on their surface. CXCR4 was also expressed on tumor cells in tissue sections derived from cervical cancer patients. At the same time normal cervical epithelium was negative for CXCR4 expression what suggests a strong correlation between CXCR4 and malignant cell phenotype. Subsequently, we studied a potential role of the SDF-1-CXCR4 axis in HCC and noticed that SDF-1 (i) chemoattracted HCC cells, (ii) enhanced their scattering, (iii) stimulated nuclear localization of beta-catenins and upregulated their target gene cyclin D1 and (iv) at the molecular level induced calcium flux and activated RAS-MAPK, PI3-AKT and JAK-STAT pathways. SDF-1-mediated functions were additionally enhanced in the presence of HGF. Thus, our data show that the SDF-1-CXCR4 axis affects biology of HCC cells. Furthermore, we postulate that this axis might become a potential target to prevent progression of cervical cancer.