Rapid Growth Cone Uptake and Dynein‐Mediated Axonal Retrograde Transport of Negatively Charged Nanoparticles in Neurons Is Dependent on Size and Cell Type

Nanoparticles (NPs) are now used in numerous technologies and serve as carriers for several new classes of therapeutics. Studies of the distribution of NPs in vivo demonstrate that they can be transported through biological barriers and are concentrated in specific tissues. Here, transport behavior, and final destination of polystyrene NPs are reported in primary mouse cortical neurons and SH‐SY5Y cells, cultured in two‐compartmental microfluidic devices. In both cell types, negative polystyrene NPs (PS(?)) smaller than 100 nm are taken up by the axons, undergo axonal retrograde transport, and accumulate in the somata. Examination of NP transport reveals different transport mechanisms depending on the cell type, particle charge, and particle internalization by the lysosomes. In cortical neurons, PS(?) inside lysosomes and 40 nm positive polystyrene NPs undergo slow axonal transport, whereas PS(?) outside lysosomes undergo fast axonal transport. Inhibition of dynein in cortical neurons decreases the transport velocity and cause a dose‐dependent reduction in the number of accumulated PS(?), suggesting that the fast axonal transport is dynein mediated. These results show that the axonal retrograde transport of NPs depends on the endosomal pathway taken and establishes a means for screening nanoparticle‐based therapeutics for diseases that involve neurons.     

Functionalization of Isotactic Polypropylene with Citraconic Anhydride

Summary Functionalization of isotactic polypropylene i-PP) with citraconic anhydride (CA) was carried out in 1,2,4-trichlorobenzene solution with dicumyl peroxide as an initiator at 160 °C under nitrogen atmosphere.atmosphere. Chemical and physical structures and thermal behavior of the synthesized graft copolymers with different anhydride units were determined by volumetric titration (acid number), FTIR and ¹H-NMR spectroscopy, X-ray powder diffraction, DSC and TGA thermal analyses. It was shown that the crystallinity and thermal behavior of grafted i-PP’s depend on anhydride unit concentration in grafted i-PP; grafting reaction proceeds selectively which is not accompanied by oligomerization of CA and degradation main chain as in known maleic anhydride/PP system. This fact was explained by inhibition effect of α-methyl group in CA grafted unit on the chain β-scission reactions and no homopolymerization of CA in chosen grafting conditions. Functionalized i-PPs showed high thermal stability in comparison with virgin i-PP.     

The Functional Role of Loops and Flanking Sequences of G-Quadruplex Aptamer to the Hemagglutinin of Influenza a Virus

Nucleic acid aptamers are generally accepted as promising elements for the specific and high-affinity binding of various biomolecules. It has been shown for a number of aptamers that the complexes with several related proteins may possess a similar affinity. An outstanding example is the G-quadruplex DNA aptamer RHA0385, which binds to the hemagglutinins of various influenza A virus strains. These hemagglutinins have homologous tertiary structures but moderate-to-low amino acid sequence identities. Here, the experiment was inverted, targeting the same protein using a set of related, parallel G-quadruplexes. The 5′- and 3′-flanking sequences of RHA0385 were truncated to yield parallel G-quadruplex with three propeller loops that were 7, 1, and 1 nucleotides in length. Next, a set of minimal, parallel G-quadruplexes with three single-nucleotide loops was tested. These G-quadruplexes were characterized both structurally and functionally. All parallel G-quadruplexes had affinities for both recombinant hemagglutinin and influenza virions. In summary, the parallel G-quadruplex represents a minimal core structure with functional activity that binds influenza A hemagglutinin. The flanking sequences and loops represent additional features that can be used to modulate the affinity. Thus, the RHA0385–hemagglutinin complex serves as an excellent example of the hypothesis of a core structure that is decorated with additional recognizing elements capable of improving the binding properties of the aptamer.     

Synthesis,characterization, mesomorphic and electrical properties of tetrakis(alkylthio)-substituted lutetium(III) bisphthalocyanines

The synthesis of new lutetium(III) bisphthalocyanines substituted with alkylthio groups (1–5) is described. These compounds (Pc₂Lu) are soluble in most common organic solvents and have been fully characterized (elemental analysis, FT-IR, UV–Vis spectroscopy, mass spectrometry). The thermal stabilities of the Pc compounds were determined by thermogravimetric analysis (TGA). The mesogenic properties of these new materials forming columnar-hexagonal (Col_h) mesophases were studied by differential scanning calorimetry (DSC), optical microscopy and X-ray diffraction. The compounds 2–5 exhibit a double clearing point. DC electrical properties of these compounds in different phases were determined by measuring I–V characteristics and dark current of their thin films on interdigital electrodes. The measurements were carried out in ambient air, in vacuum and in high purity nitrogen (N₂) flow in the temperature range between 300 and 420 K. Dark current measurements obtained in the crystal, liquid crystal (LC) and isotropic liquid phases were in agreement with the phase transitions of these compounds obtained by DSC and optical microscopy results. The relation between the phase transition and conductivity of the Pc₂Lu derivatives were investigated. Also, the influence of the nature of the substituted group (alkylthia and alkoxy) upon the DC electrical properties of the Pc₂Lu derivatives was investigated. The DC conductivities and the thermal activation energies depending on alkyl chain lengths of these compounds were found to be in the range of 10^?8 to 10^?5 S/cm and 0.12–0.38 eV in solid phase.     

Implanted Si m.o.s.f.e.t.s for high-speed applications

Si m.o.s.f.e.t.s with a channel length of 0.8 ?m have been fabricated using boron implantation to adjust the threshold voltage. With microwave design appropriate to keeping the parasitics small, fmax values between 10 and 12 GHz are realised also with ion implantation. Large-signal switching times of 48 ps, small-signal switching times of 44 ps and delay times of 50 ps have been achieved.     

Analytic solution of the unsteady inverse heat-conduction problem

An algorithm is given for an approximate analytic solution of the unsteady inverse heat-conduetion problem for infinite and semi-infinite objects. The solution found in this manner is used to solve a special inverse problem of free diffusion.     

On the role of silicon during growth of vpe GaAs-layers

The role of silicon as the possible background dopant in epitaxial GaAs layers grown by the Ga-AsCl₃-H₂ process has been investigated. To this end the dependence of the donor concentration on AsCl₃ partial pressure and deposition temperature was measured with and without injection of a known partial pressure of SiCl₄ into the deposition zone. A considerably larger donor concentration was found in the former case. These data were compared with calculated values obtained from a thermodynamic treatment in which both the injected SiCl₄ and the chlorosilanes generated by reaction of the gas phase components with the quartz reactor were taken into account. The experimental findings and their qualitative agreement with the computed behavior lend support to the thesis that silicon is responsible for the background doping. The unexpectedly low values of the background doping suggest that the formation of chlorosilanes is a kinetically limited process.     

Steroid biosynthetic enzyme activities in leachate-exposed female perch (Perca fluviatilis) as biomarkers for endocrine disruption

Studies have shown that adult female perch in a freshwater lake, Molnbyggen, Sweden, have a reproductive disorder caused by unidentified endocrine disrupting compounds (EDCs) leaching from a local refuse dump. The adverse effects include shallow open sores, low ratio of sexually mature individuals, low gonadosomatic index and low circulating levels of androgens. We hypothesised that the low androgen levels could be a result of impaired production and/or stimulated excretion of androgens by EDCs. From October 2000 to November 2001, at time-points important in the perch reproductive cycle, adult female perch were collected in Molnbyggen and in the reference lake, Djursj?n. The activities of three key enzymes in androgen biosynthesis: 17alpha-hydroxylase (17OHlase), 17,20-lyase (lyase) and 17beta-hydroxysteroid dehydrogenase (17betaHSD) were determined in head kidney or ovary. The relationship between enzyme activities and plasma steroid concentrations was examined. Ovarian histopathology and the determination of brain aromatase activity were also included in the study. Similar 17OHlase, 17betaHSD and aromatase activities were found in Molnbyggen females and reference fish throughout the year. Head kidney 17OHlase showed a positive correlation to cortisol levels (r=0.754; p<0.001) but not to androgen levels. Molnbyggen females exhibited lower ovarian lyase activity during vitellogenesis than reference fish. Atretic oocytes were on most occasions more frequent in sexually immature than in sexually mature females. The results suggest that neither 17OHlase, 17betaHSD nor aromatase is the target for EDCs disrupting the androgen homeostasis of exposed female perch. Further investigation is needed to establish the role of decreased ovarian lyase activity in endocrine homeostasis, but the possibility of increased excretion of androgens should also be examined.     

Increased Surface Integrity in Porous Tungsten from Cryogenic Machining with Cermet Cutting Tool

In order to eliminate the process of backfilling porous tungsten with a plastic infiltrant during machining to prevent unwanted smearing of surface pores, cryogenic machining is investigated as a viable alternative. Porous tungsten is mainly used in the manufacture of dispenser cathodes where demands for surface quality and dimensional tolerances are extremely high. For these reasons, the ability of cryogenic machining to provide increased surface integrity and tool life compared to conventional dry machining is explored. Moreover, some preliminary results of machining with various cutting edge radii and effects on surface stress state are presented. Overall, cryogenic machining does provide significant surface quality and tool wear improvements over conventional dry machining practices.     

Estimation of functional dependency parameters at zero median value of noises in measurements

In the paper, we study a problem of estimating functional dependency parameters by empirical data with random noises. A specific feature of the formulation is a replacement of a traditional assumption of zero mathematical expectation of a noise by the condition of equality to zero of a median value of the noise. We represent an algorithm for constructing estimates of parameters minimizing a mathematical expectation of losses including the variant of spline approximation. We interpret such estimates. The results of the experiments are given.