p25/Cdk5-mediated retinoblastoma phosphorylation is an early event in neuronal cell death

In large models of neuronal cell death, there is a tight correlation between Cdk5 deregulation and cell-cycle dysfunction. However, pathways that link Cdk5 to the cell cycle during neuronal death are still unclear. We have investigated the molecular events that precede p25/Cdk5-triggered neuronal death using a neuronal cell line that allows inducible p25 expression. In this system, no sign of apoptosis was seen before 24 hours of p25 induction. Thus, at that time, cell-cycle-regulatory proteins were analysed by immunoblotting and some of them showed a significant deregulation. Interestingly, after time-course experiments, the earliest feature correlated with p25 expression was the phosphorylation of the retinoblastoma protein (Rb). Indeed, this phosphorylation was observed 6 hours after p25 induction and was abolished in the presence of a Cdk5 inhibitor, roscovitine, which does not inhibit the usual Rb cyclin-D kinases Cdk4 and Cdk6. Furthermore, analyses of levels and subcellular localization of Cdk-related cyclins did not reveal any change following Cdk5 activation, arguing for a direct effect of Cdk5 activity on Rb protein. This latter result was clearly demonstrated by in vitro kinase assays showing that the p25-Cdk5 complex in our cell system phosphorylates Rb directly without the need for any intermediary kinase activity. Hence, Rb might be an appropriate candidate that connects Cdk5 to cell-cycle deregulation during neuronal cell death

Decay and interference effects in visuospatial short-term memory

No description supplie

Effects of rural non-farm employment on economic vulnerability and income distribution of small farms in Croatia

Replaced with revised version of paper 10/06/09.rural non-farm employment, rural poverty, Croatia, income distribution, Agribusiness, International Development, Labor and Human Capital, Q12, P25, O15, O18,

Deterioration rate of renewable polyurethanes composites prior to ultra violet irradiation exposure

Polyurethanes (PU's) made from renewable and sustainable materials are one of the most important groups of polymers because of their versatility with wide range of grades, densities and stiffness. In this project, polymers based on renewable materials such as rapeseed (RS) and sunflower oil (SF) were synthesized and cross-linked to form polyurethanes. The effect of prolonged exposure up to 1000 h upon UVB light, in general promotes photodegradation for both RS and SF-based polyurethanes, both neat and also composites loaded with TiO2. The addition of 10% Degussa P25 TiO2 pigment, gives the greater degradation while PUs loaded with 5% Kronos 2220 show the slowest rates of degradation due to the effect of the coating of this pigment. The photostabiliser Tinuvin 770 offers high protection from UVB, thus lead the combination of Tinuvin 770 with Degussa P25 promotes the highest protection from UVB exposure. Moreover, addition of Tinuvin 770 at the stage of preparation of the PUs also greatly reduced the undesirable yellow colouration prevalent during PU synthesis

Time-resolved Microwave Conductivity. Part 2.-Quantum-sized TiO_2 and the Effect of Adsorbates and Light Intensity on Charge-carrier Dynamics

Charge-carrier recombination dynamics after a pulsed laser excitation are investigated by time-resolved microwave conductivity (TRMC) for quantum-sized (Q-) TiO_2 and P25, a bulk-phase TiO_2. Adsorbed scavengers such as HNO_3, HC, HCIO_4, isopropyl alcohol, trans-decalin, tetranitromethane, and methyl viologen dichloride result in different charge-carrier recombination dynamics for Q-TiO_2 and P25. The differences include a current doubling with isopropyl alcohol for which electron injection into Q-TiO_2 is much slower than into P25 and relaxation of the selection rules of an indirect-bandgap semiconductor due to size quantization. However, the faster interfacial charge transfer predicted for Q-TiO_2 due to a 0. 2 eV gain in redox overpotentials is not observed. The effect of light intensity is also investigated. Above a critical injection level, fast recombination channels are opened, which may be a major factor resulting in the dependence of the steady-state photolysis quantum yields on l^(–1/2). The fast recombination channels are opened at lower injection levels for P25 than for Q-TiO_2, and a model incorporating the heterogeneity of surface-hole traps is presented

Improving activity of commercial P25 titanium dioxide photocatalyst

Titanium dioxide (TiO2) is recognized as one of the most active photocatalysts for degradation of organic pollutants. Among the available commercial TiO2, particular attention is focused on the P25 TiO2 having a mixture of anatase-rutile phases and act as the benchmark for the TiO2 photocatalysts. While numerous studies have been reported on the high activity of the P25 TiO2 for degradation of organic pollutants, improving the activity of the P25 TiO2 remained as a great challenge. On the other hand, impregnation method has been used conventionally to introduce metal oxide on the photocatalyst. This method is usually followed by calcination at high temperature to convert the metal precursor to metal oxide. Controversial results have been reported on the activity of P25 TiO2 after calcination process. It was reported that the calcined P25 TiO2 at 773 K showed two times higher activity than the untreated one for decolorization of methyl orange [1]. In contrast, the activity of P25 TiO2 was found to decrease with the increase of the calcination temperatures for decomposition and reduction reactions of NO [2], photodegradation of light hydrocarbons mixture [3] and butanol [4]. In the present study, the effect of calcination temperatures on the activity of P25 TiO2 was examined for photocatalytic removal of 2,4-dichlorophenoxyacetic acid (2,4-D) as the model of organic pollutants. The activity of the P25 TiO2 was slightly improved when the photocatalyst was calcined at 573 K, but decreased when calcined at 773 K. The P25 TiO2 were further modified by different metal oxides, i.e., copper oxide, cobalt oxide, and lanthanum oxide by impregnation method, followed by calcination at 773 K. All the series gave similar results; 1) addition of the metal oxides did not affect much the crystallinity, phase composition, and morphology of the P25 TiO2, 2) only small amount of added metal oxide (ca. 0.1-0.5 mol%) led to the improved photocatalytic activity, while addition of high loading amount decreased the activity of P25 TiO2, 3) the increased photocatalytic activity might be due to the ability of added metal oxide to suppress the charge recombination without blocking the active sites of the P25 TiO2. Among the investigated series and under the same reaction conditions, the La(0.1 mol%)/P25 TiO2 gave the highest photocatalytic activity for the removal of 2,4-D. After 1 hour reaction, the La(0.1 mol%)/P25 TiO2 gave ca. 1.25 times higher photocatalytic activity than the unmodified P25 TiO2 [5]

Biological functions of CDK5 and potential CDK5 targeted clinical treatments.

Cyclin dependent kinases are proline-directed serine/threonine protein kinases that are traditionally activated upon association with a regulatory subunit. For most CDKs, activation by a cyclin occurs through association and phosphorylation of the CDK\u27s T-loop. CDK5 is unusual because it is not typically activated upon binding with a cyclin and does not require T-loop phosphorylation for activation, even though it has high amino acid sequence homology with other CDKs. While it was previously thought that CDK5 only interacted with p35 or p39 and their cleaved counterparts, Recent evidence suggests that CDK5 can interact with certain cylins, amongst other proteins, which modulate CDK5 activity levels. This review discusses recent findings of molecular interactions that regulate CDK5 activity and CDK5 associated pathways that are implicated in various diseases. Also covered herein is the growing body of evidence for CDK5 in contributing to the onset and progression of tumorigenesis

Improved photocatalytic properties of doped titanium-based nanometric oxides

Photocatalysis is considered one of the most promising technologies for applications in the environmental field especially in the abatement of water-soluble organic pollutants. In this field, titanium dioxide nanoparticles have drawn much attention recently; however, the use of this oxide presents some limitation since it allows to obtain high photoresponse and degradation efficiency only under UV light irradiation, that represents the 3 to 4% of the solar radiation, so preventing its environmental large-scale applications under diffuse daylight. In this work the photocatalytic efficiencyoftitanium-based oxides systems containing alkaline earth metals such as barium and strontium, prepared by a simple sol-gel method was investigated, evaluating the degradation of methylene blue as model compound under UV and visible light irradiation. The results were compared with those obtained with Degussa P25 titanium dioxide. The achieved degradation percentage of methylene blue are very promising showing that under visible light irradiation it is possible to obtain a maximum dye removal percentage ~ 50 % higher than that obtained with the Degussa P25

On the Observability of "Invisible" / "Nearly Invisible" Charginos

It is shown that if the charginos decay into very soft leptons or hadrons + $\not{E}$ due to degeneracy/ near- degeneracy with the LSP or the sneutrino, the observability of the recently proposed signal via the single photon (+ soft particles) + $\not{E}$ channel crucially depends on the magnitude of the \SNU mass due to destructive interferences in the matrix element squared. If the \SNU's and, consequently, left-sleptons are relatively light, the size of the signal, previously computed in the limit \MSNU \to \infty only, is drastically reduced. We present the formula for the signal cross section in a model independent way and discuss the observability of the signal at LEP 192 and NLC energies.Comment: 27 pages, Late