Magyar Tanítóképző 40 (1927) 6

Magyar Tanítóképző A Tanítóképző-intézeti Tanárok Országos Egyesületének folyóirata 40. évfolyam, 6. szám Budapest, 1927. júniu

Calculations of Higher Twist Distribution Functions in the MIT Bag Model

We calculate all twist-two, three and four parton distribution functions involving two quark correlations using the wavefunction of the MIT bag model. The distributions are evolved up to experimental scales and combined to give the various nucleon structure functions. Comparisons with recent experimental data on higher twist structure functions at moderate values of $Q^{2}$ give good agreement with the calculated structure functions.Comment: 26 pages LaTeX document, 11 figures include

Dyrk1A Influences Neuronal Morphogenesis Through Regulation of Cytoskeletal Dynamics in Mammalian Cortical Neurons

Down syndrome (DS) is the most frequent genetic cause of mental retardation. Cognitive dysfunction in these patients is correlated with reduced dendritic branching and complexity, along with fewer spines of abnormal shape that characterize the cortical neuronal profile of DS. DS phenotypes are caused by the disruptive effect of specific trisomic genes. Here, we report that overexpression of dual-specificity tyrosine phosphorylation-regulated kinase 1A, DYRK1A, is sufficient to produce the dendritic alterations observed in DS patients. Engineered changes in Dyrk1A gene dosage in vivo strongly alter the postnatal dendritic arborization processes with a similar progression than in humans. In cultured mammalian cortical neurons, we determined a reduction of neurite outgrowth and synaptogenesis. The mechanism underlying neurite dysgenesia involves changes in the dynamic reorganization of the cytoskeleton

The stress-responsive kinase DYRK2 activates heat shock factor 1 promoting resistance to proteotoxic stress

To survive proteotoxic stress, cancer cells activate the proteotoxic-stress response pathway, which is controlled by the transcription factor heat shock factor 1 (HSF1). This pathway supports cancer initiation, cancer progression and chemoresistance and thus is an attractive therapeutic target. As developing inhibitors against transcriptional regulators, such as HSF1 is challenging, the identification and targeting of upstream regulators of HSF1 present a tractable alternative strategy. Here we demonstrate that in triple-negative breast cancer (TNBC) cells, the dual specificity tyrosine-regulated kinase 2 (DYRK2) phosphorylates HSF1, promoting its nuclear stability and transcriptional activity. DYRK2 depletion reduces HSF1 activity and sensitises TNBC cells to proteotoxic stress. Importantly, in tumours from TNBC patients, DYRK2 levels positively correlate with active HSF1 and associates with poor prognosis, suggesting that DYRK2 could be promoting TNBC. These findings identify DYRK2 as a key modulator of the HSF1 transcriptional programme and a potential therapeutic target

A mezőgazdaság műszaki fejlesztésének lehetséges megoldása

Az Európai Unió piacán az innovációt versenyképesen alkalmazó termeléssel vehet részt a magyar mezőgazdaság. A tanulmány a piaci szempontoknak elsőbbséget adó termelésfejlesztés elvi alapjait mutatja be, kitérve a megvalósítás lehetőségeire is. A tanulmányban a rendszer-szemlélet dominál. A mezőgazdasági rendszerek eredményes működéséhez korszerű inputokra, rugalmasan használható technológiai megoldásokra és mindezeket ésszerűen megvalósító szakértelemre valamint eszközökre van szükség. Mivel a feltételek oldaláról a gépesítésben meglévő elmaradás jelenti a szűk keresztmetszetet, ezért a tanulmány kissé részletesebben elemzi az e területen jelentkező feladatokat. ------------ Hungarian agriculture will only be capable of being effective on the market of the European Union if it produces in a competitive and innovative way. The basic principles of a production development where marketing aspects have a priority, along with the possibilities of their implementation, are described in the present paper, in which the systemic approach is dominating. Up-to-date input, flexible technological solutions, and skills and tools for their reasonable implementation are required in order to run agricultural systems in an effective way. Since the lag in mechanisation constitutes the bottle-neck among conditions tasks in this field are analysed in a somewhat more detailed way

Block Polyelectrolyte Additives Modulate the Viscoelasticity and Enable 3D Printing of Gelatin Inks at Physiological Temperatures

We demonstrate the utility of block polyelectrolyte (bPE) additives to enhance viscosity and resolve longstanding challenges with the three-dimensional printability of extrusion-based biopolymer inks. The addition of oppositely charged bPEs into solutions of photocurable gelatin methacryloyl (GelMA) results in complexation-driven self- assembly of the bPEs, leading to GelMA/bPE inks that are printable at physiological temperatures, representing stark improvements over GelMA inks that suffer from low viscosity at 37 °C leading to low printability and poor structural stability. The hierarchical microstructure of the self-assemblies (either jammed micelles or three-dimensional networks) formed by the oppositely charged bPEs, as confirmed by small angle X-ray scattering, is attributed to the enhancements in the shear strength and printability of the GelMA/bPE inks. Varying bPE concentration in the inks is shown to enable tunability of the rheological properties to meet the criteria of pre- and post-extrusion flow characteristics for 3D bioprinting, including prominent yield stress behavior, strong shear thinning, and rapid recovery upon flow cessation. Moreover, the bPE self-assemblies also contribute to the robustness of the photocrosslinked hydrogels – photocrosslinked GelMA/bPE hydrogels are shown to exhibit higher shear strength than photocrosslinked GelMA hydrogels. We envision this study to serve as a practical guide for the bioprinting of bespoke extrusion inks where bPE are used as scaffolds and viscosity enhancers that can be emulated in a range of biopolymers and photocurable precursors

Polyelectrolyte Complex Hydrogel Scaffoldings Enable Extrusion-based 3D Bioprinting of Low-Viscosity Bioinks

We generate self-assembled biocompatible scaffolds with excellent structural integrity based on complex-forming block polyelectrolytes that enable extrusion-based 3D bioprinting of large constructs from low-viscosity bioinks. Despite remarkable progress of biofabrication techniques in tissue engineering, the development of extrudable bioinks that perform optimally at physiological temperatures remains a major challenge. Most biopolymer and photocurable precursor solutions exhibit low viscosities at 37 °C, resulting in undesirable flows and loss of form prior to chemical crosslinking. Temperature-sensitive bioinks, such as gelatin methacryloyl (GelMA), can be deposited near their gelling point, but suffer from suboptimal temperature-induced pre-gelation, poor cell viability emerging from long holding times in the cooled cartridges, inefficient temperature transfer from the print bed, and discontinuous layer-by-layer fabrication. Here, we demonstrate that block polyelectrolyte additives serve as effective viscosity enhancers when added to non-extrudable precursor solutions. Rapid, electrostatic self-assembly of block polyelectrolytes into either jammed micelles or interconnected networks provides hydrogel scaffoldings that form nearly instantly, lend initial structural robustness upon deposition, and enhance shear and tensile strength of the cured bioinks. Moreover, our approach enables continuous extrusion without the need of chemical crosslinking between individual layers, paving the way for fast biomanufacturing of human-scale tissue constructs with improved inter-layer bonding