Education and older adults at the University of the Third Age

This article reports a critical analysis of older adult education in Malta. In educational gerontology, a critical perspective demands the exposure of how relations of power and inequality, in their myriad forms, combinations, and complexities, are manifest in late-life learning initiatives. Fieldwork conducted at the University of the Third Age (UTA) in Malta uncovered the political nature of elder-learning, especially with respect to three intersecting lines of inequality - namely, positive aging, elitism, and gender. A cautionary note is, therefore, warranted at the dominant positive interpretations of UTAs since late-life learning, as any other education activity, is not politically neutral.peer-reviewe

FACT Prevents the Accumulation of Free Histones Evicted from Transcribed Chromatin and a Subsequent Cell Cycle Delay in G1

The FACT complex participates in chromatin assembly and disassembly during transcription elongation. The yeast mutants affected in the SPT16 gene, which encodes one of the FACT subunits, alter the expression of G1 cyclins and exhibit defects in the G1/S transition. Here we show that the dysfunction of chromatin reassembly factors, like FACT or Spt6, down-regulates the expression of the gene encoding the cyclin that modulates the G1 length (CLN3) in START by specifically triggering the repression of its promoter. The G1 delay undergone by spt16 mutants is not mediated by the DNA–damage checkpoint, although the mutation of RAD53, which is otherwise involved in histone degradation, enhances the cell-cycle defects of spt16-197. We reveal how FACT dysfunction triggers an accumulation of free histones evicted from transcribed chromatin. This accumulation is enhanced in a rad53 background and leads to a delay in G1. Consistently, we show that the overexpression of histones in wild-type cells down-regulates CLN3 in START and causes a delay in G1. Our work shows that chromatin reassembly factors are essential players in controlling the free histones potentially released from transcribed chromatin and describes a new cell cycle phenomenon that allows cells to respond to excess histones before starting DNA replication

Crystalline phases involved in the hydration of calcium silicate-based cements: Semi-quantitative Rietveld X-ray diffraction analysis

Chemical comparisons of powder and hydrated forms of calcium silicate cements (CSCs) and calculation of alterations in tricalcium silicate (Ca3SiO5) calcium hydroxide (Ca(OH)2) are essential for understanding their hydration processes. This study aimed to evaluate and compare these changes in ProRoot MTA, Biodentine and CEM cement. Powder and hydrated forms of tooth coloured ProRoot MTA, Biodentine and CEM cement were subjected to X-ray diffraction (XRD) analysis with Rietveld refinement to semi-quantitatively identify and quantify the main phases involved in their hydration process. Data were reported descriptively. Reduction in Ca3SiO5 and formation of Ca(OH)2 were seen after the hydration of ProRoot MTA and Biodentine; however, in the case of CEM cement, no reduction of Ca3SiO5 and no formation of Ca(OH)2 were detected. The highest percentages of amorphous phases were seen in Biodentine samples. Ettringite was detected in the hydrated forms of ProRoot MTA and CEM cement but not in Biodentine

Markov clustering versus affinity propagation for the partitioning of protein interaction graphs

<p>Abstract</p> <p>Background</p> <p>Genome scale data on protein interactions are generally represented as large networks, or graphs, where hundreds or thousands of proteins are linked to one another. Since proteins tend to function in groups, or complexes, an important goal has been to reliably identify protein complexes from these graphs. This task is commonly executed using clustering procedures, which aim at detecting densely connected regions within the interaction graphs. There exists a wealth of clustering algorithms, some of which have been applied to this problem. One of the most successful clustering procedures in this context has been the Markov Cluster algorithm (MCL), which was recently shown to outperform a number of other procedures, some of which were specifically designed for partitioning protein interactions graphs. A novel promising clustering procedure termed Affinity Propagation (AP) was recently shown to be particularly effective, and much faster than other methods for a variety of problems, but has not yet been applied to partition protein interaction graphs.</p> <p>Results</p> <p>In this work we compare the performance of the Affinity Propagation (AP) and Markov Clustering (MCL) procedures. To this end we derive an unweighted network of protein-protein interactions from a set of 408 protein complexes from <it>S. cervisiae </it>hand curated in-house, and evaluate the performance of the two clustering algorithms in recalling the annotated complexes. In doing so the parameter space of each algorithm is sampled in order to select optimal values for these parameters, and the robustness of the algorithms is assessed by quantifying the level of complex recall as interactions are randomly added or removed to the network to simulate noise. To evaluate the performance on a weighted protein interaction graph, we also apply the two algorithms to the consolidated protein interaction network of <it>S. cerevisiae</it>, derived from genome scale purification experiments and to versions of this network in which varying proportions of the links have been randomly shuffled.</p> <p>Conclusion</p> <p>Our analysis shows that the MCL procedure is significantly more tolerant to noise and behaves more robustly than the AP algorithm. The advantage of MCL over AP is dramatic for unweighted protein interaction graphs, as AP displays severe convergence problems on the majority of the unweighted graph versions that we tested, whereas MCL continues to identify meaningful clusters, albeit fewer of them, as the level of noise in the graph increases. MCL thus remains the method of choice for identifying protein complexes from binary interaction networks.</p

Mutant Versions of the S. cerevisiae Transcription Elongation Factor Spt16 Define Regions of Spt16 That Functionally Interact with Histone H3

In eukaryotic cells, the highly conserved FACT (FAcilitates Chromatin Transcription) complex plays important roles in several chromatin-based processes including transcription initiation and elongation. During transcription elongation, the FACT complex interacts directly with nucleosomes to facilitate histone removal upon RNA polymerase II (Pol II) passage and assists in the reconstitution of nucleosomes following Pol II passage. Although the contribution of the FACT complex to the process of transcription elongation has been well established, the mechanisms that govern interactions between FACT and chromatin still remain to be fully elucidated. Using the budding yeast Saccharomyces cerevisiae as a model system, we provide evidence that the middle domain of the FACT subunit Spt16 – the Spt16-M domain – is involved in functional interactions with histone H3. Our results show that the Spt16-M domain plays a role in the prevention of cryptic intragenic transcription during transcription elongation and also suggest that the Spt16-M domain has a function in regulating dissociation of Spt16 from chromatin at the end of the transcription process. We also provide evidence for a role for the extreme carboxy terminus of Spt16 in functional interactions with histone H3. Taken together, our studies point to previously undescribed roles for the Spt16 M-domain and extreme carboxy terminus in regulating interactions between Spt16 and chromatin during the process of transcription elongation