Effect of hypoxia on photosynthetic activity and antioxidative response in gametophores of <Emphasis Type="Italic">Mnium undulatum</Emphasis>

The effects of hypoxia caused by complete submerging of Mnium undulatum gametophores in water, on their photosynthetic activity and the activity of two antioxidative enzymes: superoxide dismutase (SOD) and catalase (CAT) were investigated. The net photosynthesis was strongly inhibited throughout the experiment, and the strong drop in the maximum quantum yield of the PSII (F_v/F_m) was also observed. Three classes of SOD: MnSOD, FeSOD, Cu/ZnSOD and three isoforms of Cu/ZnSOD were identified. A significant decrease in activity of MnSOD, FeSOD and one Cu/ZnSOD isoform was observed after 24 and 48 h of hypoxia. FeSOD activity decreased already after 1 h of submerging in water and its activity remained at the low level during whole period of the experiment. CAT activity was also strongly inhibited in response to hypoxia stress. The obtained results suggest relationships between photosynthetic activity and antioxidative system in M. undulatum gametophores under oxygen deficiency stress.     

Comprehensive review of antimicrobial activities of plant flavonoids

Flavonoids are one of the largest classes of small molecular secondary metabolites produced in different parts of the plant. They display a wide range of pharmacological and beneficial health effects for humans, which include, among others, antioxidative activity, free radical scavenging capacity, coronary heart disease prevention and antiatherosclerotic, hepatoprotective, anti-inflammatory, and anticancer activities. Hence, flavonoids are gaining high attention from the pharmaceutical and healthcare industries. Notably, plants synthesize flavonoids in response to microbial infection, and these compounds have been found to be a potent antimicrobial agent against a wide range of pathogenic microorganisms in vitro. Antimicrobial action of flavonoids results from their various biological activities, which may not seem very specific at first. There are, however, promising antibacterial flavonoids that are able not only to selectively target bacterial cells, but also to inhibit virulence factors, as well as other forms of microbial threats, e.g. biofilm formation. Moreover, some plant flavonoids manifest ability to reverse the antibiotic resistance and enhance action of the current antibiotic drugs. Hence, the development and application of flavonoid-based drugs could be a promising approach for antibiotic-resistant infections. This review aims to improve our understanding of the biological and molecular roles of plant flavonoids, focusing mostly on their antimicrobial activities.

     

Lack of evidence on hybrid swarm in the sympatric population of Pinus mugo and P. sylvestris

Natural hybridisation between the taxa from Pinus mugo complex and P. sylvestris was postulated in several sympatric populations of the species in Europe. However, due to the absence of precise methods for identification of hybrid seeds and hybrid trees, the frequency of hybridisation and its influence on the genetic structure of relict P. mugo populations has not been clarified so far. In the present study, the species-specific chloroplast DNA (cpDNA) marker and isozymes were applied to test the hybridisation hypothesis in a postulated hybrid swarm population of the species from “Bór na Czerwonem” reserve at the northern foothills of Tatra Mts., Poland. The cpDNA marker was used to identify hybrids within two groups of polycormic (multi-stemmed) and monocormic (single-stemmed) pines from this population. Allelic frequencies at isozyme loci from both groups were compared to frequencies found in allopatric populations of the species. Additionally, cpDNA haplotypes of seedlings derived from open pollinated seeds were studied to detect the possibility of successful cross-pollination. The mixture of seedlings with P. sylvestris and P. mugo cpDNA haplotypes was derived from one parental tree that indicates hybridisation. However, all the mature polycormic pines had cpDNA haplotypes species specific to P. mugo and the isozyme frequencies were similar to frequencies found in three allopatric populations of P. mugo from Tatra Mts. (mean genetic distance, Dn=.027). The differences were much larger in comparisons with monocormic pines from this area (Dn=.085) and two P. sylvestris samples from distant allopatric populations (Dn=.077). Nearly all monocormic pines had cpDNA species specific to P. sylvestris and isozyme frequencies similar to other populations of this species (mean Dn=.004). Only one P. sylvestris-like monocormic tree had cpDNA of P. mugo and can be considered as a hybrid. The results do not provide evidence supporting the hybrid swarm hypothesis. Rather, the results suggest that mature hybrids have a low frequency within this population and (rare) hybridisation is not reciprocal but unidirectional with P. mugo as pollen donor.     

Assessment of the influence of viscoelasticity of cornea in animal ex vivo model using air‐puff optical coherence tomography and corneal hysteresis

Application of the air‐puff swept source optical coherence tomography (SS‐OCT) instrument to determine the influence of viscoelasticity on the relation between overall the air‐puff force and corneal apex displacement of porcine corneas ex vivo is demonstrated. Simultaneous recording of time‐evolution of the tissue displacement and air pulse stimulus allows obtaining valuable information related in part to the mechanical properties of the cornea. A novel approach based on quantitative analysis of the corneal hysteresis of OCT data is presented. The corneal response to the air pulse is assessed for different well‐controlled intraocular pressure (IOP) levels and for the progression of cross‐linking‐induced stiffness of the cornea. Micrometer resolution, fast acquisition and noncontact character of the air‐puff SS‐OCT measurements have potential to improve the in vivo assessment of mechanical properties of the human corneas.      

Social Calls Provide Tree‐dwelling Bats with Information about the Location of Conspecifics at Roosts

Animals can use signals emitted by other animals as sources of information. Auditory signals are important in communication networks, as they can potentially convey information about the location and state of conspecifics and other species over long distances. Signalling is important in fission–fusion societies, in which animals from the same social group temporarily split into subgroups and frequently change roost sites. We used playbacks of social calls of the noctule Nyctalus noctula produced in roosts, to show how bats might maintain group cohesion and to test the hypothesis that noctules can locate conspecifics when returning from foraging trips by eavesdropping on or communicating with roosting individuals. Noctules responded strongly to broadcasted social calls. Their reactions included inspections and landing on a loudspeaker broadcasting social calls and occasional social vocalisation. Responses by other bat species to the noctule social calls were negligible. The high amplitude, low‐frequency vocalisations emitted by noctules in roosts can propagate over long distances and allow group members to announce their position. Bats can extract information about the location of roosts containing conspecifics by eavesdropping or by communication. Social calls may thus be sufficient to locate conspecifics in roosts and maintain spatial associations of groups in mammals.     

Fournier Gangrene Caused by <Emphasis Type="Italic">Candida albicans</Emphasis> in an Infant After Cardiac Surgery

Fournier gangrene is a rare, rapidly progressive, life-threatening condition. We report a 23-day-old boy with pulmonary atresia and ventricular septal defect treated surgically, who developed Fournier gangrene. Emergency surgery was performed with tissue sampling for microbiological examination. Candida albicans was confirmed; caspofungin followed by fluconazole was administered with excellent results.     

Improved pre-concentration and detection methods for volatile sulphur breath constituents

Suitability of different types of pre-concentration (solid phase microextraction and sorbent trapping) and detection (flame photometric detector (FPD) and mass selective detector (MSD)) for gas chromatographic determination of sulphur-containing compounds (H₂S, MeSH, EtSH, DMS, COS and CS₂) in breath-gas was assessed in this study. Several factors like influence of humidity, influence of oxygen, or stability of target compounds in extraction vessels (SPME vials and sorbent tubes) were investigated. Despite poor stability of VSCs in SPME vials and matrix effects (unfavorable influence of humidity), SPME was found to be a fast and reliable enrichment method, which coupled with mass selective detector provided satisfactory LODs of target compounds at the ppt level (from 0.15 ppb for CS₂ to 2.3 ppb for H₂S). Application of sorbent trapping with two-bed sorbent tubes containing Tenax TA and Carboxen 1000 gave excellent LODs (0.03–0.3 ppb for 200 ml sample and MSD). Stability of investigated VSCs in sorbents was found to be very poor (30–40% losses after 2 h). FPD showed satisfactory sensitivity only when it was coupled with sorbent trapping. Breath samples were collected into Tedlar bags in a CO₂-controlled manner. Humidity was removed during sampling (permeation dryer – Nafion) to avoid unfavorable water dependent effects during analysis.     

Atrial natriuretic factor receptor guanylate cyclase signaling: new ATP-regulated transduction motif

ANF-RGC membrane guanylate cyclase is the receptor for the hypotensive peptide hormones, atrial natriuretic factor (ANF) and type B natriuretic peptide (BNP). It is a single transmembrane spanning protein. Binding the hormone to the extracellular domain activates its intracellular catalytic domain. This results in accelerated production of cyclic GMP, a second messenger in controlling blood pressure, cardiac vasculature, and fluid secretion. ATP is the obligatory transducer of the ANF signal. It works through its ATP regulated module, ARM, which is juxtaposed to the C-terminal side of the transmembrane domain. Upon interaction, ATP induces a cascade of temporal and spatial changes in the ARM, which, finally, result in activation of the catalytic module. Although the exact nature and the details of these changes are not known, some of these have been stereographed in the simulated three-dimensional model of the ARM and validated biochemically. Through comprehensive techniques of steady state, time-resolved tryptophan fluorescence and Forster Resonance Energy Transfer (FRET), site-directed and deletion-mutagenesis, and reconstitution, the present study validates and explains the mechanism of the model-based predicted transduction role of the ARM’s structural motif, ⁶⁶⁹WTAPELL⁶⁷⁵. This motif is critical in the ATP-dependent ANF signaling. Molecular modeling shows that ATP binding exposes the ⁶⁶⁹WTAPELL⁶⁷⁵ motif, the exposure, in turn, facilitates its interaction and activation of the catalytic module. These principles of the model have been experimentally validated. This knowledge brings us a step closer to our understanding of the mechanism by which the ATP-dependent spatial changes within the ARM cause ANF signaling of ANF-RGC.     

‘Click’ chemistry synthesis and capillary electrophoresis study of 1,4‐linked 1,2,3‐triazole AZT‐systemin conjugate

The Cu(I) catalyzed Huisgen 1,3‐dipolar azide‐alkyne cycloaddition (CuAAC) was applied for a nucleoside‐peptide bioconjugation. Systemin (Sys), an 18‐aa plant signaling peptide naturally produced in response to wounding or pathogen attack, was chemically synthesized as its N‐propynoic acid functionalized analog (Prp‐Sys) using the SPPS. Next, CuAAC was applied to conjugate Prp‐Sys with 3′‐azido‐2′,3′‐dideoxythymidine (AZT), a model cargo molecule. 1,4‐Linked 1,2,3‐triazole AZT‐Sys conjugate was designed to characterize the spreading properties and ability to translocate of cargo molecules of systemin. CuAAC allowed the synthesis of the conjugate in a chemoselective and regioselective manner, with high purity and yield. The presence of Cu(I) ions generated in situ drove the CuAAC reaction to completion within a few minutes without any by‐products. Under typical separation conditions of phosphate ‘buffer’ at low pH and uncoated fused bare‐silica capillary, an increasing peak intensity assigned to triazole‐linked AZT‐Sys conjugate was observed using capillary electrophoresis (CE) during CuAAC. CE analysis showed that systemin peptides are stable in tomato leaf extract for up to a few hours. CE‐ESI‐MS revealed that the native Sys and its conjugate with AZT are translocated through the tomato stem and can be directly detected in stem exudates. The results show potential application of systemin as a transporter of low molecular weight cargo molecules in tomato plant and of CE method to characterize a behavior of plant peptides and its analogs. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

A Novel Attempt to Standardize Results of CFD Simulations Basing on Spatial Configuration of Aortic Stent-Grafts

Currently, studies connected with Computational Fluid Dynamic (CFD) techniques focus on assessing hemodynamic of blood flow in vessels in different conditions e.g. after stent-graft’s placement. The paper propose a novel method of standardization of results obtained from calculations of stent-grafts'' “pushing forces” (cumulative WSS—Wall Shear Stress), and describes its usefulness in diagnostic process. AngioCT data from 27 patients were used to reconstruct 3D geometries of stent-grafts which next were used to create respective reference cylinders. We made an assumption that both the side surface and the height of a stent-graft and a reference cylinder were equal. The proposed algorithm in conjunction with a stent-graft “pushing forces” on an implant wall, allowed us to determine which spatial configuration of a stent-graft predispose to the higher risk of its migration. For stent-grafts close to cylindrical shape (shape factor φ close to 1) WSS value was about 267Pa, while for stent-grafts different from cylindrical shape (φ close to 2) WSS value was about 635Pa. It was also noticed that deformation in the stent-graft’s bifurcation part impaired blood flow hemodynamic. Concluding the proposed algorithm of standardization proved its usefulness in estimating the WSS values that may be useful in diagnostic process. Angular bends or tortuosity in bifurcations of an aortic implant should be considered in further studies of estimation of the risk of implantation failure.