An in vitro study of the impact of 4mT static magnetic field to modify the differentiation rate of rat bone marrow stem cells into primordial germ cells

This investigation was performed to evaluate the differentiation capacity and alteration in genes expression patterns during in vitro differentiation of bone marrow stem cells into primordial germ cells using static magnetic field (4 mT) and BMP-4 (25 ng/ml). The rate of differentiation was investigated using the Real Time-PCR method for tracing expression of differentiation markers (Oct-4, Nanog, C-Myc, Fragilis, Mvh and Stella). Then, immunocytochemical reaction was carried out for detection of marker proteins (Oct4 and Mvh). Increasing of the exposure time of the 4 mT SMF (24 and 48 h) and treatment time with 25 ng/ml BMP4 (48 and 96 h) indicated a marked decrease in expression of pluripotency genes (Oct-4, Nanog and C-Myc) and Oct4 protein and increase in primordial germ cell-specific genes (Fragilis, Mvh and Stella) and Mvh protein compared with the control group. Final results showed that in a synergistic manner, the combination of SMF with BMP4 exaggerates the differentiation potential of BMSCs to PGCs by activating the MAPK pathway and altering the Ca²⁺ concentration.     

Molecular simulation of zeolite flexibility

We present a transferable force field able to model the structure of zeolites when different cation types are considered. Based on simple functional forms and interactions, it can be easily implemented in most common molecular simulation codes. The optimised force field is validated on structural properties (lattice parameters and Si–O–Al angles) for a large variety of zeolites, including faujasites of different Si/Al ratio and different extra-framework cation types (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺ and Co²⁺). The transferability of the force field was successfully tested on zeolites of different topologies such as FAU, LTA, MFI, FER and TON. The predictive capabilities of the potential were tested on structural deformations of alkaline earth Na, Co-X faujasites with different ion-exchange ratios.     

Further investigations on the polypeptides and reconstitution of prasinophycean ejectisomes

Ejectisome fragments were isolated from the prasinophyte Pyramimonas grossii and subjected to different treatments, i.e. Percoll density gradient centrifugation, incubation at pH 2.5 or at pH 10.8, or incubation in 6 M guanidine hydrochloride. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that Percoll density gradient centrifugation did not improve the purity of the ejectisome fragment-enriched fractions. The ejectisome fragments withstood pH 2.5 and pH 10.8 treatment, and no loosely bound polypeptides became detached. The disintegration of ejectisome fragments was achieved in 6 M guanidine hydrochloride, and reassembly into filamentous, ejectisome-like structures occurred after dialysis against distilled water. Fractions enriched either in ejectisome fragments or in reconstituted ejectisome-like structures were dominated by three polypeptides with relative molecular weights of approximately 12.5–19 kDa and two additional polypeptides of 23 and 26 kDa. A polyclonal antiserum directed against an ejectisome fragment-enriched fraction weakly cross-reacted with these polypeptides, and no significant immuno-labelling of ejectisome fragments was registered. A positive immuno-label was achieved using immunoglobulin (IgG) fractions which were gained by selectively incubating nitrocellulose stripes of these polypeptides with the antiserum.     

The effects of pulsed magnetic field exposure on the permeability of leukemia cancer cells

Purpose: The newer methods of cancer treatment require new idea of drug delivery in cancer cells. Due to numerous researches electromagnetic field affect on cell function and cell membrane for possible therapeutic and drug delivery. In this article, we determined in vitro uptake of fluorescent dyes into the attached K562 cells due to time-varying magnetic field exposure. Method and material: The K562 cells were exposed to magnetic pulses via Magstim stimulator and double 70?mm coil. The strength and duration of pulses in all experiments were the same and three different frequencies of 0.25, 1 and 10?Hz pulses for 56, 112 and 28 numbers of pulses were applied (nine experimental groups) and uptake of Ly and PI was measured in each group. Result: Our results show that magnetic field can efficiently increase permeability. Among the treatment groups, the system gives the optimal permeabilization when cells are exposed to a train of 28 pulses with 1?Hz frequency.     

A new solution for biomedical experiments

This article discusses mutual interactions phenomena especially in the case of Transverse ElectroMagnetic (TEM) cell applications as an exposure system in technical and biomedical studies. Problem of mutual interactions between tested objects placed in the electromagnetic field (EMF) is described. A new device for exposure system is presented. Its role is elimination of mentioned harmful phenomenon that leads to falsifications of results.     

Ethical consideration in invasion ecology: A marine perspective

Biological introductions of species to regions outside their known natural distribution are considered a major threat to native marine biodiversity and a key consideration for ecological management. For most invasive species in marine systems, however, little is known about potential impacts. If we are to increase our knowledge of the processes and mechanisms behind the spread of nonindigenous species or determine economic or ecological impacts, manipulative ecological field experiments are the best way to unambiguously ascribe causal relationships. For studies of invasions, such research may result in species spread and the establishment of new viable populations. Is it ethical then, to take the risk of potentially modifying or endangering other species, populations or ecosystems? Is it possible to mitigate the risks? Or should invasion ecologists work under restrictions that limit their ability to fully assess the impact of invaders? Consideration of the ethics of experimentation is rarely carried out. As a consequence, we propose a decision model that includes possible risk of escape/establishment versus the value of the research to allow researchers and/or managers to critically evaluate what type of experimental approach is appropriate.     

Predicting plant invasions under climate change: are species distribution models validated by field trials?

Climate change may facilitate alien species invasion into new areas, particularly for species from warm native ranges introduced into areas currently marginal for temperature. Although conclusions from modelling approaches and experimental studies are generally similar, combining the two approaches has rarely occurred. The aim of this study was to validate species distribution models by conducting field trials in sites of differing suitability as predicted by the models, thus increasing confidence in their ability to assess invasion risk. Three recently naturalized alien plants in New Zealand were used as study species (Archontophoenix cunninghamiana, Psidium guajava and Schefflera actinophylla): they originate from warm native ranges, are woody bird‐dispersed species and of concern as potential weeds. Seedlings were grown in six sites across the country, differing both in climate and suitability (as predicted by the species distribution models). Seedling growth and survival were recorded over two summers and one or two winter seasons, and temperature and precipitation were monitored hourly at each site. Additionally, alien seedling performances were compared to those of closely related native species (Rhopalostylis sapida, Lophomyrtus bullata and Schefflera digitata). Furthermore, half of the seedlings were sprayed with pesticide, to investigate whether enemy release may influence performance. The results showed large differences in growth and survival of the alien species among the six sites. In the more suitable sites, performance was frequently higher compared to the native species. Leaf damage from invertebrate herbivory was low for both alien and native seedlings, with little evidence that the alien species should have an advantage over the native species because of enemy release. Correlations between performance in the field and predicted suitability of species distribution models were generally high. The projected increase in minimum temperature and reduced frosts with climate change may provide more suitable habitats and enable the spread of these species.     

Viscoelastic shear properties of the corneal stroma

The cornea is a highly specialized transparent tissue which covers the front of the eye. It is a tough tissue responsible for refracting the light and protecting the sensitive internal contents of the eye. The biomechanical properties of the cornea are primarily derived from its extracellular matrix, the stroma. The majority of previous studies have used strip tensile and pressure inflation testing methods to determine material parameters of the corneal stroma. Since these techniques do not allow measurements of the shear properties, there is little information available on transverse shear modulus of the cornea. The primary objectives of the present study were to determine the viscoelastic behavior of the corneal stroma in shear and to investigate the effects of the compressive strain. A thorough knowledge of the shear properties is required for developing better material models for corneal biomechanics. In the present study, torsional shear experiments were conducted at different levels of compressive strain (0–30%) on porcine corneal buttons. First, the range of linear viscoelasticity was determined from strain sweep experiments. Then, frequency sweep experiments with a shear strain amplitude of 0.2% (which was within the region of linear viscoelasticity) were performed. The corneal stroma exhibited viscoelastic properties in shear. The shear storage modulus, G′, and shear loss modulus, G″, were reported as a function of tissue compression. It was found that although both of these parameters were dependent on frequency, shear strain amplitude, and compressive strain, the average shear storage and loss moduli varied from 2 to 8 kPa, and 0.3 to 1.2 kPa, respectively. Therefore, it can be concluded that the transverse shear modulus is of the same order of magnitude as the out-of-plane Young's modulus and is about three orders of magnitude lower than the in-plane Young's modulus.