A recently introduced neural networks architecture, 'adaptive spline neural networks' with FIR=IIR synapse, is used to define a general class of physical-like sound synthesis model. To reduce ...computational cost, use is made of power-of-two synapses followed by a CR-spline-based flexible activation function the shape of which can be modified through its control points. The learning phase is performed by an efficient combinatorial optimisation algorithm, Tabu Search, for both power-of-two weights and CR-spline control points.
Streptococcus pneumoniae possesses large zinc metalloproteinases on its surface. To analyse the importance in virulence of three of these metalloproteinases, intranasal challenge of MF1 outbred mice ...was carried out using a range of infecting doses of wild type and knock-out pneumococcal mutant strains, in order to compare mice survival.
Observation of survival percentages over time and detection of LD50s of knock out mutants in the proteinase genes in comparison to the type 4 TIGR4 wild type strain revealed two major aspects: i) Iga and ZmpB, present in all strains of S. pneumoniae, strongly contribute to virulence in mice; (ii) ZmpC, only present in about 25% of pneumococcal strains, has a lower influence on virulence in mice.
These data suggest Iga, ZmpB and ZmpC as candidate surface proteins responsible for pneumococcal infection and potentially involved in distinct stages of pneumococcal disease.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The availability of almost one thousand complete mitochondrial genome (mtDNA) sequences of chordates provides an almost unique opportunity to analyse the evolution of this genome in the phylum ...Chordata, and to identify possible divergent evolutionary trends followed by the three chordate subphyla: Vertebrata, Cephalochordata and Tunicata.Here, we review some genome-level features of mtDNA, such as genetic code, gene content, genome architecture and gene strand asymmetry, mostly focusing on differences existing between tunicates and remaining chordates. Indeed, tunicate mtDNAs show a surprisingly high variability in several genome-level features, even though the current tunicate taxon sampling is absolutely insufficient and is focused mainly on the class Ascidiacea. On the contrary, a stabilization of the mtDNA structural and evolutionary features is observed in both cephalochordates and vertebrates, where genome-level features are almost invariant. Thus, different evolutionary dynamics, probably related to divergent functional constraints, have modelled the overall mtDNA structure and organization of the three chordate subphyla.
The macrolide efflux gene mef(A) of the Streptococcus pyogenes clinical strain 2812A was found to be carried by a 52-kb chromosomal genetic element that could be transferred by conjugation to the ...chromosome of other streptococcal species. The characteristics of this genetic element are typical of conjugative transposons and was named Tn1207.3. The size of Tn1207.3 was established by pulsed-field gel electrophoresis (PFGE), and DNA sequencing analysis showed that the 7,244 bp at the left end of Tn1207.3 were identical to those of the pneumococcal Tn1207.1 element. Tn1207.3-like genetic elements were found to be inserted at a single specific chromosomal site in 12 different clinical isolates S. pyogenes exhibiting the M phenotype of resistance to macrolides and carrying the mef(A) gene. Tn1207.3 was transferred from S. pyogenes 2812A to Streptococcus pneumoniae, and sequence analysis carried out on six independent transconjugants showed that insertion of Tn1207.3 in the pneumococcal genome always occurred at a single specific site as in Tn1207.1. Using MF2, a representative S. pneumoniae transconjugant, as a donor, Tn1207.3 was transferred again by conjugation to S. pyogenes and Streptococcus gordonii. The previously described nonconjugative element Tn1207.1 of S. pneumoniae appears to be a defective element, part of a longer conjugative transposon that carries mef(A) and is found in clinical isolates of S. pyogenes.
Microglial cells, the resident phagocytes in the brain, share many phenotypical and functional characteristics with peripheral macrophages, suggesting that they may participate in an innate immune ...response against microorganisms invading the central nervous system (CNS). In this study, we demonstrate that the microglial cells constitutively exhibit antibacterial activity in vitro against Streptococcus pneumoniae. By using a Pneumococcal surface protein C (PspC)-deleted strain and its wild-type counterpart, we found that the extent of such an activity is significantly influenced by the presence of a PspC molecule on the bacterial surface. The PspC- mutant FP20 is indeed more susceptible than the PspC+ strain HB565 to microglial killing. Interestingly, this phenomenon is observed when using a medium supplemented with heat-inactivated foetal bovine serum (FBS). Electron microscopy studies indicate that the microglial cells interact more efficiently with PspC- than with PspC+ pneumococci. Moreover, upon infection with the PspC- mutant, microglial cells produce levels of TNF-alpha, MIP-2, IL-10 and nitric oxide, significantly higher than those observed with PspC+ bacteria. These findings indicate that the lack of PspC significantly enhances the susceptibility of S. pneumoniae to both bactericidal activity and secretory response by the microglial cells, suggesting that this molecule may play an important role in the invasion of CNS by pneumococcus.
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