Participation of IIb-IIIa glycoprotein in spontaneous platelet aggregation

In some patients with stable and unstable angina pectoris and in some donors without clinical manifestations of cardiovascular diseases and other pathologies, spontaneous platelet aggregation was completely suppressed by glycoprotein IIb-IIIa antagonists blocking the interaction of this glycoprotein with fibrinogen. Antibodies inhibiting binding of glycoprotein Ib with von Willebrand factor had no effect on the level and rate of spontaneous platelet aggregation. In the donor group, the level of spontaneous aggregation was almost 1.5-fold higher in persons with a certain genetic polymorphism (Leu-->Pro substitution in position 33 of glycoprotein IIIa). The level of spontaneous aggregation correlated with the amount of glycoprotein IIb-IIIa on the platelet surface (r = 0.41).     

Band Gap of Pb(Fe0.5Nb0.5)O3 Thin Films Prepared by Pulsed Laser Deposition

Ferroelectric materials have gained high interest for photovoltaic applications due to their open-circuit voltage not being limited to the band gap of the material. In the past, different lead-based ferroelectric perovskite thin films such as Pb(Zr,Ti)O₃ (Pb,La)(Zr,Ti)O₃ and PbTiO₃ were investigated with respect to their photovoltaic efficiency. Nevertheless, due to their high band gaps they only absorb photons in the UV spectral range. The well-known ferroelectric PbFe_0.5Nb_0.5O₃ (PFN), which is in a structure similar to the other three, has not been considered as a possible candidate until now. We found that the band gap of PFN is around 2.75 eV and that the conductivity can be increased from 23 S/µm to 35 S/µm during illumination. The relatively low band gap value makes PFN a promising candidate as an absorber material.     

High Energy Storage Density in Nanocomposites of P(VDF-TrFE-CFE) Terpolymer and BaZr0.2Ti0.8O3 Nanoparticles

Polymer materials are actively used in dielectric capacitors, in particular for energy storage applications. An enhancement of the stored energy density can be achieved in composites of electroactive polymers and dielectric inorganic fillers with a high dielectric permittivity. In this article, we report on the energy storage characteristics of composites of relaxor terpolymer P(VDF-TrFE-CFE) and BaZr_0.2Ti_0.8O₃ (BZT) nanoparticles. The choice of materials was dictated by their large dielectric permittivity in the vicinity of room temperature. Free-standing composite films, with BZT contents up to 5 vol.%, were prepared by solution casting. The dielectric properties of the composites were investigated over a wide range of frequencies and temperatures. It was shown that the addition of the BZT nanoparticles does not affect the relaxor behavior of the polymer matrix, but significantly increases the dielectric permittivity. The energy storage parameters were estimated from the analysis of the unipolar polarization hysteresis loops. The addition of the BZT filler resulted in the increasing discharge energy density. The best results were achieved for composites with 1.25–2.5 vol.% of BZT. In the range of electric fields to 150 MV/m, the obtained materials demonstrate a superior energy storage density compared to other P(VDF-TFE-CFE) based composites reported in the literature.     

Subcellular Distribution of Persistent Sodium Conductance in Cortical Pyramidal Neurons

Cortical pyramidal neurons possess a persistent Na⁺ current (I_NaP), which, in contrast to the larger transient current, does not undergo rapid inactivation. Although relatively quite small, I_NaP is active at subthreshold voltages and therefore plays an important role in neuronal input–output processing. The subcellular distribution of channels responsible for I_NaP and the mechanisms that render them persistent are not known. Using high-speed fluorescence Na⁺ imaging and whole-cell recordings in brain slices obtained from mice of either sex, we reconstructed the I_NaP elicited by slow voltage ramps in soma and processes of cortical pyramidal neurons. We found that in all neuronal compartments, the relationship between persistent Na⁺ conductance and membrane voltage has the shape of a Boltzmann function. Although the density of channels underlying I_NaP was about twofold lower in the axon initial segment (AIS) than in the soma, the axonal channels were activated by ∼10 mV less depolarization than were somatic channels. This difference in voltage dependence explains why, at functionally critical subthreshold voltages, most I_NaP originates in the AIS. Finally, we show that endogenous polyamines constrain I_NaP availability in both somatodendritic and axonal compartments of nondialyzed cortical neurons.SIGNIFICANCE STATEMENT The most salient characteristic of neuronal sodium channels is fast inactivation. However, a fraction of the sodium current does not inactivate. In cortical neurons, persistent current (I_NaP) plays a prominent role in many important functions. Its subcellular distribution and generation mechanisms are, however, elusive. Using high-speed fluorescence Na⁺ imaging and electrical recordings, we reconstructed the I_NaP in soma and processes of cortical pyramidal neurons. We found that at near-threshold voltages I_NaP originates predominately from the axon, because of the distinctive voltage dependence of the underlying channels and not because of their high density. Finally, we show that the presence of endogenous polyamines significantly constrains I_NaP availability in all compartments of nondialyzed cortical neurons.     

Transitions in the model of epithelial patterning.

We analyze pattern formation in the model of cell communication in Drosophila egg development. The model describes the regulatory network formed by the epidermal growth factor receptor (EGFR) and its ligands. The network is activated by the oocyte-derived input that is modulated by feedback loops within the follicular epithelium. We analyze these dynamics within the framework of a recently proposed mathematical model of EGFR signaling (Shvartsman et al. [2002] Development 129:2577-2589). The emphasis is on the large-amplitude solutions of the model that can be correlated with the experimentally observed patterns of protein and gene expression. Our analysis of transitions between the major classes of patterns in the model can be used to interpret the experimentally observed phenotypic transitions in eggshell morphology in Drosophila melanogaster. The existence of complex patterns in the model can be used to account for complex eggshell morphologies in related fly species.     

Comparison of biomaterial delivery vehicles for improving acute retention of stem cells in the infarcted heart

Cell delivery to the infarcted heart has emerged as a promising therapy, but is limited by very low acute retention and engraftment of cells. The objective of this study was to compare a panel of biomaterials to evaluate if acute retention can be improved with a biomaterial carrier. Cells were quantified post-implantation in a rat myocardial infarct model in five groups (n = 7–8); saline injection (current clinical standard), two injectable hydrogels (alginate, chitosan/β-glycerophosphate (chitosan/ß-GP)) and two epicardial patches (alginate, collagen). Human mesenchymal stem cells (hMSCs) were delivered to the infarct border zone with each biomaterial. At 24 h, retained cells were quantified by fluorescence. All biomaterials produced superior fluorescence to saline control, with approximately 8- and 14-fold increases with alginate and chitosan/β-GP injectables, and 47 and 59-fold increases achieved with collagen and alginate patches, respectively. Immunohistochemical analysis qualitatively confirmed these findings. All four biomaterials retained 50–60% of cells that were present immediately following transplantation, compared to 10% for the saline control. In conclusion, all four biomaterials were demonstrated to more efficiently deliver and retain cells when compared to a saline control. Biomaterial-based delivery approaches show promise for future development of efficient in vivo delivery techniques.     

Immunization with a complex preparation: a new method of influenza prevention. The basis for using a complex preparation for preventing influenza

A combined preparation for influenza prevention (CPIP) consisting of an interferon inducer stimulating immunogenesis and killed influenza vaccine is proposed. Twenty five inducers-stimulators have been tested: polynucleotides, polysaccharide and lipopolysaccharide extracted from Salmonella typhosa. Intranasal administration of CPIP to laboratory animals markedly stimulates interferon, secretory, and circulating antibody synthesis. Resistance to fatal influenza infection develops within 18 hours after administration of CPIP and its intensity increases in the following 14 days (the observation period.