Influence of video content type on the usefulness of reinforcement learning algorithms in DASH systems

The article presents the result of research on DASH (Dynamic Adaptive Streaming over HTTP) systems. In the proposed solution, the adaptive algorithm is based on the RL (Reinforcement Learning) paradigm. The Pensieve algorithm was chosen as the basis for the tests. This algorithm is widely discussed in the scientific literature and therefore the study and analysis of its properties is useful in a wide range of solutions using DASH. The main contribution of the presented test results to the development of knowledge on video streaming services consists in the analysis of the impact of the characteristics of video materials on the effectiveness of the adaptation process implemented by the developed RL model. The presented results show that this influence should not be omitted in any in-depth analyses of the characteristics of DASH systems

Downregulation of Polo-like kinase-1 (PLK-1) expression is associated with poor clinical outcome in uveal melanoma patients

Introduction. Uveal melanoma (UM) is the most common primary eye tumour in adults. Distant metastases are seen in 50% of cases regardless of treatment, which contributes to high mortality rates. Polo-like kinase-1 (PLK-1) is a protein regulator of mitotic entry and cytokinesis. Increased PLK-1 expression has been shown in different tumours, which makes its inhibition a potential treatment target. To date, no study has been published to discuss the prognostic role of PLK-1 expression in patients with uveal melanoma. Material and methods. We assessed by immunohistochemistry PLK-1 expression in uveal melanoma cells collected in 158 patients treated by primary enucleation. We determined the correlation between PLK-1 levels evaluated by the immunoreactivity scale (IRS) method and detailed clinical as well as histological parameters. Additionally, we determined the association between PLK-1 expression levels and long-term prognosis. Results. Elevated PLK-1 expression in tumour cells, defined as IRS > 2, was observed in 70% (111/158) of cases, whereas low expression or no expression was seen in the remaining 30% (47/158) of patients. There was a significant correlation between low PLK-1 expression and a higher clinical tumour stage (pT, p = 0.04) as well as a higher AJCC prognostic stage group (p = 0.037). We observed an inverse correlation between PLK-1 expression and tumour cell pigment content (p = 0.0019). There was no correlation between PLK-1 expression and other histological parameters such as mitotic rate or histological subtype. The Kaplan-Meier’s analysis demonstrated that low PLK-1 expression was associated with significantly reduced overall survival (p = 0.0058). A similar trend, albeit not significant, was observed for disease-free survival (p = 0.088). Conclusions. Downregulated PLK-1 expression is a negative prognostic factor in uveal melanoma. It warrants further, multicentre research on prognostic role of PLK-1 expression and possibility of PLK-1 inhibition in uveal melanoma

Biochemical and structural characterization of SplD protease from Staphylococcus aureus.

Staphylococcus aureus is a dangerous human pathogen. A number of the proteins secreted by this bacterium are implicated in its virulence, but many of the components of its secretome are poorly characterized. Strains of S. aureus can produce up to six homologous extracellular serine proteases grouped in a single spl operon. Although the SplA, SplB, and SplC proteases have been thoroughly characterized, the properties of the other three enzymes have not yet been investigated. Here, we describe the biochemical and structural characteristics of the SplD protease. The active enzyme was produced in an Escherichia coli recombinant system and purified to homogeneity. P1 substrate specificity was determined using a combinatorial library of synthetic peptide substrates showing exclusive preference for threonine, serine, leucine, isoleucine, alanine, and valine. To further determine the specificity of SplD, we used high-throughput synthetic peptide and cell surface protein display methods. The results not only confirmed SplD preference for a P1 residue, but also provided insight into the specificity of individual primed- and non-primed substrate-binding subsites. The analyses revealed a surprisingly narrow specificity of the protease, which recognized five consecutive residues (P4-P3-P2-P1-P1') with a consensus motif of R-(Y/W)-(P/L)-(T/L/I/V)↓S. To understand the molecular basis of the strict substrate specificity, we crystallized the enzyme in two different conditions, and refined the structures at resolutions of 1.56 Å and 2.1 Å. Molecular modeling and mutagenesis studies allowed us to define a consensus model of substrate binding, and illustrated the molecular mechanism of protease specificity

Substrate specificity of the SplD protease at the P1 subsite.

<p>Substrate preference of SplD at P1 subsite was determined using a positional scanning synthetic combinatorial library (PS-SCL) of a general structure Ac-P4-P3-P2-P1-AMC as described in Materials and Methods. Vertical bars indicate the activity of the enzyme against each tested sub-library (fluorescence of released AMC) normalized to the most active sub-library. Residues fixed at P1 subsite are indicated with the single-letter amino acid code. X indicates randomized substrate position.</p

The crystal structure of SplD demonstrates canonical conformation of the catalytic triad and the oxyanion hole.

<p>(Upper panel) Catalytic triad residues and the main chain fragment constituting the oxyanion hole of SplD (limon) superposed with corresponding residues of chymotrypsin (black). (Lower panel) Electron density (contoured at 1.1σ) around SplD fragment depicted in the upper panel. Red sphere represents a water molecule. Dashed lines represent hydrogen bonds.</p