Polymer shape dynamics induced by spatially correlated noise

In this paper, we examine the influence of a spatially correlated noise on a 2D polymer-like particle. The molecule is modeled with harmonic potential for bonds and angular interactions and a global Lennard–Jones potential. We present a method for generating a spatially correlated noise if the time and spatial terms in the correlation function factorize. The dynamics of polymer’s shape transformation process is investigated by means of Fourier analysis. An increase in correlation length results in the environmentally induced stiffening of the chain

Effective one-component model of binary mixture : molecular arrest induced by the spatially correlated stochastic dynamics

Spatially correlated noise (SCN), i.e. the thermal noise that affects neighbouring particles in a similar manner, is ubiquitous in soft matter systems. In this work, we apply the over-damped SCN-driven Langevin equations as an effective, one-component model of the dynamics in dense binary mixtures. We derive the thermodynamically consistent fluctuation-dissipation relation for SCN to show that it predicts the molecular arrest resembling the glass transition, i.e. the critical slow-down of dynamics in the disordered phases. We show that the mechanism of singular dissipation is embedded in the dissipation matrix, accompanying SCN. We are also able to identify the characteristic length of collective dissipation, which diverges at critical packing. This novel physical quantity conveniently describes the difference between the ergodic and non-ergodic dynamics. The model is fully analytically solvable, one-dimensional and admits arbitrary interactions between the particles. It qualitatively reproduces several different modes of arrested disorder encountered in binary mixtures, including e.g. the re-entrant arrest. The model can be effectively compared to the mode coupling theory

Reinterpreting polymer unfolding effect induced by a spatially correlated noise

This paper provides additional insight into the effect of spontaneous unfolding of the model polymeric chain driven by spatially correlated noise, described in M. Majka, P.F. Góra, Phys. Rev. E86, 051122 (2012). We examine the statistical data on the linearized chain substructures to find that the global unfolding effect arises mainly from the cumulation of short, 2-segment-long fragments, scattered along the chain. This supports an alternative view of spatially correlated noise as both the source of disturbance and the conformation preserving factor

Inicijalna desorpcija reakcijskog drva bukovine

The research aimed to obtain empirical data for modeling the initial desorption in reaction wood from the cross-section of the green beech (Fagus sylvatica L.) log. Firstly, we analyzed the chemical composition, macro and microscopic structure of tension and opposite wood tissue. Then, the Equilibrium Moisture Content (EMC) was measured by the Dynamic Vapor Sorption method during the initial desorption. The used air parameters were specific for the mild drying schedule of green beech timber (t = 20, 35, and 50 °C, Relative Humidity (RH) ranging from 95 to 0 %). Relationships between the EMC of reaction wood and drying parameters were modeled using the Response Surface Method (RSM). The tests revealed: different hygroscopic properties of tension and opposite wood, the dependence of EMC value on temperature, and differences between EMC values for initial (first) and second desorption. Moreover, it was confirmed that, during initial desorption, the EMCs of reaction wood are significantly higher than reference EMC data. The differences in the EMC value are up to 0.14 kg/kg (for air with RH above 90 %). The presented polynomial model of the initial desorption of reaction beech wood can improve drying schedules for beech sawn timber with a high amount of reaction tissue.Cilj je ovog istraživanja modeliranje inicijalne desorpcije poprečnog presjeka reakcijskog drva bukve (Fagus sylvatica L.) na temelju empirijskih podatka. Najprije je istražen kemijski sastav drva te je analizirana makroskopska i mikroskopska struktura reakcijskoga i opozitnog drva. Zatim je metodom dinamičke sorpcije pare izmjeren ravnotežni sadržaj vode tijekom inicijalne desorpcije. Drvo je podvrgnuto blagom režimu sušenja (t = 20, 35 i 50 °C, te relativnoj vlažnosti zraka u rasponu od 95 do 0 %). Odnosi između ravnotežnog sadržaja vode reakcijskog drva i parametara sušenja modelirani su metodom odzivne površine. Ispitivanjem su dobivena različita higroskopska svojstva reakcijskoga i normalnog drva, ovisnost ravnotežnog sadržaja vode o temperaturi sušenja te razlike između vrijednosti ravnotežnog sadržaja vode pri inicijalnoj (prvoj) i drugoj desorpciji. Također je potvrđeno da je ravnotežni sadržaj vode reakcijskog drva tijekom inicijalne desorpcije znatno veći od referentnih vrijednosti ravnotežnog sadržaja vode normalnog drva. Razlike u vrijednostima ravnotežnog sadržaja vode kreću se do 0,14 kg/kg (pri relativnoj vlažnosti zraka većoj od 90 %). Prikazani polinomski model inicijalne desorpcije reakcijskog drva bukve može poslužiti za poboljšanje režima sušenja bukove piljene građe s velikim udjelom reakcijskog drva

Introduction of exogenous HSV-TK suicide gene increases safety of keratinocyte-derived induced pluripotent stem cells by providing genetic "emergency exit" switch

Since their invention in 2006, induced Pluripotent Stem (iPS) cells remain a great promise for regenerative medicine circumventing the ethical issues linked to Embryonic Stem (ES) cell research. iPS cells can be generated in a patient-specific manner as an unlimited source of various cell types for in vitro drug screening, developmental biology studies and regenerative use. Having the capacity of differentiating into the cells of all three primary germ layers, iPS cells have high potential to form teratoma tumors. This remains their main disadvantage and hazard which, until resolved, prevents utilization of iPS cells in clinic. Here, we present an approach for increasing iPS cells safety by introducing genetic modification—exogenous suicide gene Herpes Simplex Virus Thymidine Kinase (HSV-TK). Its expression results in specific vulnerability of genetically modified cells to prodrug—ganciclovir (GCV). We show that HSV-TK expressing cells can be eradicated both in vitro and in vivo with high specificity and efficiency with low doses of GCV. Described strategy increases iPS cells safety for future clinical applications by generating “emergency exit” switch allowing eradication of transplanted cells in case of their malfunction

Regenerative potential of the product CardioCell derived from the Wharton's jelly mesenchymal stem cells for treating hindlimb oschemia

In recent years, mesenchymal stem cells (MSCs) have emerged as a promising therapeutic modality in regenerative medicine. They hold great promise for treating civilization-wide diseases, including cardiovascular diseases, such as acute myocardial infarction and critical limb ischemia. MSCs isolated from Wharton’s jelly (WJ-MSCs) may be utilized in both cell-based therapy and vascular graft engineering to restore vascular function, thereby providing therapeutic benefits for patients. The efficacy of WJ-MSCs lies in their multipotent differentiation ability toward vascular smooth muscle cells, endothelial cells and other cell types, as well as their capacity to secrete various trophic factors, which are potent in promoting angiogenesis, inhibiting apoptosis and modulating immunoreaction. Ischemic limb disease is caused by insufficient nutrient and oxygen supplies resulting from damaged peripheral arteries. The lack of nutrients and oxygen causes severe tissue damage in the limb, thereby resulting in severe morbidities and mortality. The therapeutic effects of the conventional treatments are still not sufficient. Cell transplantations in small animal model (mice) are vital for deciphering the mechanisms of MSCs’ action in muscle regeneration. The stimulation of angiogenesis is a promising strategy for the treatment of ischemic limbs, restoring blood supply for the ischemic region. In the present study, we focus on the therapeutic properties of the human WJ-MSCs derived product, Cardio. We investigated the role of CardioCell in promoting angiogenesis and relieving hindlimb ischemia. Our results confirm the healing effect of CardioCell and strongly support the use of the WJ-MSCs in regenerative medicine

Use of 3D organoids as a model to study idiopathic form of Parkinsons disease

Organoids are becoming particularly popular in modeling diseases that are difficult to reproduce in animals, due to anatomical differences in the structure of a given organ. Thus, they are a bridge between the in vitro and in vivo models. Human midbrain is one of the structures that is currently being intensively reproduced in organoids for modeling Parkinson’s disease (PD). Thanks to three-dimensional (3D) architecture and the use of induced pluripotent stem cells (iPSCs) differentiation into organoids, it has been possible to recapitulate a complicated network of dopaminergic neurons. In this work, we present the first organoid model for an idiopathic form of PD. iPSCs were generated from peripheral blood mononuclear cells of healthy volunteers and patients with the idiopathic form of PD by transduction with Sendai viral vector. iPSCs were differentiated into a large multicellular organoid-like structure. The mature organoids displayed expression of neuronal early and late markers. Interestingly, we observed statistical differences in the expression levels of LIM homeobox transcription factor alpha (early) and tyrosine hydroxylase (late) markers between organoids from PD patient and healthy volunteer. The obtained results show immense potential for the application of 3D human organoids in studying the neurodegenerative disease and modeling cellular interactions within the human brain

The strategy of fusion genes construction determines efficient expression of introduced transcription factors

The main goal in gene therapy and biomedical research is an efficient transcription factors (TFs) delivery system. SNAIL, a zinc finger transcription factor, is strongly involved in tumor, what makes its signaling pathways an interesting research subject. The necessity of tracking activation of intracellular pathways has prompted fluorescent proteins usage as localization markers. Advanced molecular cloning techniques allow to generate fusion proteins from fluorescent markers and transcription factors. Depending on fusion strategy, the protein expression levels and nuclear transport ability are significantly different. The P2A self-cleavage motif through its cleavage ability allows two single proteins to be simultaneously expressed. The aim of this study was to compare two strategies for introducing a pair of genes using expression vector system. We have examined GFP and SNAI1 gene fusions by comprising common nucleotide polylinker (multiple cloning site) or P2A motif in between them, resulting in one fusion or two independent protein expressions respectively. In each case transgene expression levels and translation efficiency as well as nuclear localization of expressed protein have been analyzed. Our data showed that usage of P2A motif provides more effective nuclear transport of SNAIL transcription factor than conventional genes linker. At the same time the fluorescent marker spreads evenly in subcellular space