Centriole maturation in the amoebae ofPhysarum polycephalum

Summary The precise geometry of pro-centriole formation has been studied inPhysarum polycephalum amoebae. The spatial references used were the posterior and the anterior kinetosomes which are unequivocally defined by the presence of the posterior para-kinetosomal structure, the microtubular array 4 and the microtubular arrays 1, 2, and 3. The observations made suggest that pro-centrioles follow a maturation process. A pro-centriole formed during the n^th cell cycle becomes the posterior kinetosome during the (n + 1)^th cell cycle and the anterior one during all the following cell cycles. Pro-centriole formation occurs late in the cell cycle. This observation disagrees with a role of pro-centriole formation in the regulation of S phase in contrast to what has been suggested in other eucaryotic cells.     

A novel task scheduling approach based on dynamic queues and hybrid meta-heuristic algorithms for cloud computing environment

Task scheduling is one of the most challenging aspects to improve the overall performance of cloud computing and optimize cloud utilization and Quality of Service (QoS). This paper focuses on Task Scheduling optimization using a novel approach based on Dynamic dispatch Queues (TSDQ) and hybrid meta-heuristic algorithms. We propose two hybrid meta-heuristic algorithms, the first one using Fuzzy Logic with Particle Swarm Optimization algorithm (TSDQ-FLPSO), the second one using Simulated Annealing with Particle Swarm Optimization algorithm (TSDQ-SAPSO). Several experiments have been carried out based on an open source simulator (CloudSim) using synthetic and real data sets from real systems. The experimental results demonstrate the effectiveness of the proposed approach and the optimal results is provided using TSDQ-FLPSO compared to TSDQ-SAPSO and other existing scheduling algorithms especially in a high dimensional problem. The TSDQ-FLPSO algorithm shows a great advantage in terms of waiting time, queue length, makespan, cost, resource utilization, degree of imbalance, and load balancing.     

Studies of oligonucleotide interactions by hybridisation to arrays: the influence of dangling ends on duplex yield.

Effects of dangling ends on duplex yield have been assessed by hybridisation of oligonucleotides to an array of oligonucleotides synthesised on the surface of a solid support. The array consists of decanucleotides and shorter sequences. One of the decanucleotides in the array was fully complementary to the decanucleotide used as solution target. Others were complementary over seven to nine bases, with overhangs of one to three bases. Duplexes involving different decanucleotides had different overhangs at the 3' and 5' ends. Some duplexes involving shorter oligonucleotides had the same regions of complementarity as these decanucleotides, but with fewer overhanging bases. This analysis allows simultaneous assessment of the effects of differing bases at both 5' and 3' ends of the oligonucleotide in duplexes formed under identical reaction conditions. The results indicate that a 5' overhang is more stabilising than a 3' overhang, which is consistent with previous results obtained with DNA overhangs. However, it is not clear whether this is due to the orientation of the overhang or to the effect of specific bases.     

Promotion of Cancer Cell Invasiveness and Metastasis Emergence Caused by Olfactory Receptor Stimulation

Olfactory receptors (ORs) are expressed in the olfactory epithelium, where they detect odorants, but also in other tissues with additional functions. Some ORs are even overexpressed in tumor cells. In this study, we identified ORs expressed in enterochromaffin tumor cells by RT-PCR, showing that single cells can co-express several ORs. Some of the receptors identified were already reported in other tumors, but they are orphan (without known ligand), as it is the case for most of the hundreds of human ORs. Thus, genes coding for human ORs with known ligands were transfected into these cells, expressing functional heterologous ORs. The in vitro stimulation of these cells by the corresponding OR odorant agonists promoted cell invasion of collagen gels. Using LNCaP prostate cancer cells, the stimulation of the PSGR (Prostate Specific G protein-coupled Receptor), an endogenously overexpressed OR, by β-ionone, its odorant agonist, resulted in the same phenotypic change. We also showed the involvement of a PI3 kinase γ dependent signaling pathway in this promotion of tumor cell invasiveness triggered by OR stimulation. Finally, after subcutaneous inoculation of LNCaP cells into NSG immunodeficient mice, the in vivo stimulation of these cells by the PSGR agonist β-ionone significantly enhanced metastasis emergence and spreading.     

Characterization of heparin oligosaccharides binding specifically to antithrombin III using mass spectrometry

Heparan sulfate (HS) is a sulfated glycosaminoglycan attached to a core protein on the cell surface. Protein binding to cell surface HS is a key regulatory event for many cellular processes such as blood coagulation, cell proliferation, and migration. The concept whereby protein binding to HS is not random but requires a limited number of sulfation patterns is becoming clear. Here we describe a hydrophobic trapping assay for screening a library of heparin hexasaccharides for binders to antithrombin III (ATIII). The hexasaccharide compositions are defined with their building block content in the following format: (DeltaHexA:HexA:GlcN:SO 3:Ac). Of five initial compositions present in the library, (1:2:3:6:1), (1:2:3:7:1), (1:2:3:7:0), (1:2:3:8:0), and (1:2:3:9:0), only two are shown to bind ATIII, namely, (1:2:3:8:0) and (1:2:3:9:0). The use of amide hydrophilic interaction (HILIC) liquid chromatography-mass spectrometry permitted reproducible quantitative analysis of the composition of the initial library as well as that of the binding fraction. The specificity of the hexasaccharides binding ATIII was confirmed by assaying their ability to enhance ATIII-mediated inhibition of Factor Xa in vitro.     

Interaction of apicoplast-encoded elongation factor (EF) EF-Tu with nuclear-encoded EF-Ts mediates translation in the Plasmodiumfalciparum plastid

Protein translation in the plastid (apicoplast) of Plasmodium spp. is of immense interest as a target for potential anti-malarial drugs. However, the molecular data on apicoplast translation needed for optimisation and development of novel inhibitors is lacking. We report characterisation of two key translation elongation factors in Plasmodium falciparum, apicoplast-encoded elongation factor PfEF-Tu and nuclear-encoded PfEF-Ts. Recombinant PfEF-Tu hydrolysed GTP and interacted with its presumed nuclear-encoded partner PfEF-Ts. The EF-Tu inhibitor kirromycin affected PfEF-Tu activity in vitro, indicating that apicoplast EF-Tu is indeed the target of this drug. The predicted PfEF-Ts leader sequence targeted GFP to the apicoplast, confirming that PfEF-Ts functions in this organelle. Recombinant PfEF-Ts mediated nucleotide exchange on PfEF-Tu and homology modeling of the PfEF-Tu:PfEF-Ts complex revealed PfEF-Ts-induced structural alterations that would expedite GDP release from PfEF-Tu. Our results establish functional interaction between two apicoplast translation factors encoded by genes residing in different cellular compartments and highlight the significance of their sequence/structural differences from bacterial elongation factors in relation to inhibitor activity. These data provide an experimental system to study the effects of novel inhibitors targeting PfEF-Tu and PfEF-Tu.PfEF-Ts interaction. Our finding that apicoplast EF-Tu possesses chaperone-related disulphide reductase activity also provides a rationale for retention of the tufA gene on the plastid genome.     

Fragile sites and breakpoints in constitutional rearrangements and in human sperm chromosomes

Summary Recently, it has been suggested that an association exists between breakpoints involved in constitutional rearrangements and fragile sites; however, statistical analyses of this relationship are controversial. We have analyzed 1200 breakpoint from different constitutional rearrangements, 1522 breakpoints with respect to their recurrence and 217 breakpoints from sperm chromosomes as reported by several authors. The coincidence between breakpoints and fragile sites was 35.3%, 43.6% and 41.9% respectively. The statistical significance of these coincidences depends on whether factors such as the relative length of the bands or the recurrence of the rearrangements are taken into account.     

Genetic Aspects of Myoclonus–Dystonia Syndrome (MDS)

Myoclonus–dystonia (M–D) is an autosomal-dominant movement disorder with onset in the first two decades of life. Mutations in the epsilon-sarcoglycan gene (SGCE, DYT11) on chromosome 7q21–q31 represent the major genetic cause of M–D in some populations. The syndrome was related with mutations in two other genes (DRD2 and DYT1). A second locus has been reported in one large M–D family (DYT15, 18p11), but no gene has been identified yet. In this review, we discuss genetic aspects of myoclonus–dystonia.