Essential and checkpoint functions of budding yeast ATM and ATR during meiotic prophase are facilitated by differential phosphorylation of a meiotic adaptor protein, Hop1

A hallmark of the conserved ATM/ATR signalling is its ability to mediate a wide range of functions utilizing only a limited number of adaptors and effector kinases. During meiosis, Tel1 and Mec1, the budding yeast ATM and ATR, respectively, rely on a meiotic adaptor protein Hop1, a 53BP1/Rad9 functional analog, and its associated kinase Mek1, a CHK2/Rad53-paralog, to mediate multiple functions: control of the formation and repair of programmed meiotic DNA double strand breaks, enforcement of inter-homolog bias, regulation of meiotic progression, and implementation of checkpoint responses. Here, we present evidence that the multi-functionality of the Tel1/Mec1-to-Hop1/Mek1 signalling depends on stepwise activation of Mek1 that is mediated by Tel1/Mec1 phosphorylation of two specific residues within Hop1: phosphorylation at the threonine 318 (T318) ensures the transient basal level Mek1 activation required for viable spore formation during unperturbed meiosis. Phosphorylation at the serine 298 (S298) promotes stable Hop1-Mek1 interaction on chromosomes following the initial phospho-T318 mediated Mek1 recruitment. In the absence of Dmc1, the phospho-S298 also promotes Mek1 hyper-activation necessary for implementing meiotic checkpoint arrest. Taking these observations together, we propose that the Hop1 phospho-T318 and phospho-S298 constitute key components of the Tel1/Mec1- based meiotic recombination surveillance (MRS) network and facilitate effective coupling of meiotic recombination and progression during both unperturbed and challenged meiosis

Budding yeast ATM/ATR control meiotic double-strand break (DSB) levels by down-regulating Rec114, an essential component of the DSB-machinery

An essential feature of meiosis is Spo11 catalysis of programmed DNA double strand breaks (DSBs). Evidence suggests that the number of DSBs generated per meiosis is genetically determined and that this ability to maintain a pre-determined DSB level, or "DSB homeostasis", might be a property of the meiotic program. Here, we present direct evidence that Rec114, an evolutionarily conserved essential component of the meiotic DSB-machinery, interacts with DSB hotspot DNA, and that Tel1 and Mec1, the budding yeast ATM and ATR, respectively, down-regulate Rec114 upon meiotic DSB formation through phosphorylation. Mimicking constitutive phosphorylation reduces the interaction between Rec114 and DSB hotspot DNA, resulting in a reduction and/or delay in DSB formation. Conversely, a non-phosphorylatable rec114 allele confers a genome-wide increase in both DSB levels and in the interaction between Rec114 and the DSB hotspot DNA. These observations strongly suggest that Tel1 and/or Mec1 phosphorylation of Rec114 following Spo11 catalysis down-regulates DSB formation by limiting the interaction between Rec114 and DSB hotspots. We also present evidence that Ndt80, a meiosis specific transcription factor, contributes to Rec114 degradation, consistent with its requirement for complete cessation of DSB formation. Loss of Rec114 foci from chromatin is associated with homolog synapsis but independent of Ndt80 or Tel1/Mec1 phosphorylation. Taken together, we present evidence for three independent ways of regulating Rec114 activity, which likely contribute to meiotic DSBs-homeostasis in maintaining genetically determined levels of breaks

Cerebral blood volume, genotype and chemosensitivity in oligodendroglial tumours

INTRODUCTION: The biological factors responsible for differential chemoresponsiveness in oligodendroglial tumours with or without the −1p/−19q genotype are unknown, but tumour vascularity may contribute. We aimed to determine whether dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) could distinguish molecular subtypes of oligodendroglial tumour, and examined the relationship between relative cerebral blood volume (rCBV) and outcome following procarbazine, lomustine and vincristine (PCV) chemotherapy. METHODS: Pretherapy rCBV was calculated and inter- and intraobserver variability assessed. Allelic imbalance in 1p36, 19q13, 17p13, 10p12–15, and 10q22–26 and p53 mutation (exons 5–8) were determined. rCBV was compared with genotype and clinicopathological characteristics (n=37) and outcome following PCV chemotherapy (n=33). RESULTS: 1p/19q loss was seen in 6/9 grade II oligodendrogliomas, 6/14 grade II oligoastrocytomas, 4/4 grade III oligodendrogliomas, and 3/10 grade III oligoastrocytomas. rCBV measurements had good inter- and intraobserver variability, but did not distinguish histology subtype or grade. Tumours with 1p/19q loss had higher rCBV values (Student’s t-test P=0.001). Receiver operating characteristic analysis revealed a cut-off of 1.59 for identifying genotype (sensitivity 92%, specificity 76%). Tumours with high and low rCBV showed response to chemotherapy. The −1p/−19q genotype, but not rCBV, was strongly associated with response, progression-free and overall survival following PCV chemotherapy. Tumours with high rCBV and intact 1p/19q were associated with shorter progression-free and overall patient survival than those with intact 1p/19q and low rCBV or high rCBV and 1p/19q loss. CONCLUSION: rCBV identifies oligodendroglial tumours with 1p/19q loss, but does not predict chemosensitivity. The prognostic significance of rCBV may differ in oligodendroglial tumours with or without the −1p/−19q genotype

Radiological progression of cerebral metastases after radiosurgery: assessment of perfusion MRI for differentiating between necrosis and recurrence

To assess the capability of perfusion MRI to differentiate between necrosis and tumor recurrence in patients showing radiological progression of cerebral metastases treated with stereotactic radiosurgery (SRS). From 2004 to 2006 dynamic susceptibility-weighted contrast-enhanced perfusion MRI scans were performed on patients with cerebral metastasis showing radiological progression after SRS during follow-up. Several perfusion MRI characteristics were examined: a subjective visual score of the relative cerebral blood volume (rCBV) map and quantitative rCBV measurements of the contrast-enhanced areas of maximal perfusion. For a total of 34 lesions in 31 patients a perfusion MRI was performed. Diagnoses were based on histology, definite radiological decrease or a combination of radiological and clinical follow-up. The diagnosis of tumor recurrence was obtained in 20 of 34 lesions, and tumor necrosis in 14 of 34. Regression analyses for all measures proved statistically significant (χ2 = 11.6–21.6, P < 0.001–0.0001). Visual inspection of the rCBV map yielded a sensitivity and specificity of 70.0 respectively 92.9%. The optimal cutoff point for maximal tumor rCBV relative to white matter was 2.00 (improving the sensibility to 85.0%) and 1.85 relative to grey matter (GM), improving the specificity to 100%, with a corresponding sensitivity of 70.0%. Perfusion MRI seems to be a useful tool in the differentiation of necrosis and tumor recurrence after SRS. For the patients displaying a rCBV-GM greater than 1.85, the diagnosis of necrosis was excluded. Salvage treatment can be initiated for these patients in an attempt to prolong survival

Dynamics and transport near quantum-critical points

The physics of non-zero temperature dynamics and transport near quantum-critical points is discussed by a detailed study of the O(N)-symmetric, relativistic, quantum field theory of a N-component scalar field in $d$ spatial dimensions. A great deal of insight is gained from a simple, exact solution of the long-time dynamics for the N=1 d=1 case: this model describes the critical point of the Ising chain in a transverse field, and the dynamics in all the distinct, limiting, physical regions of its finite temperature phase diagram is obtained. The N=3, d=1 model describes insulating, gapped, spin chain compounds: the exact, low temperature value of the spin diffusivity is computed, and compared with NMR experiments. The N=3, d=2,3 models describe Heisenberg antiferromagnets with collinear N\'{e}el correlations, and experimental realizations of quantum-critical behavior in these systems are discussed. Finally, the N=2, d=2 model describes the superfluid-insulator transition in lattice boson systems: the frequency and temperature dependence of the the conductivity at the quantum-critical coupling is described and implications for experiments in two-dimensional thin films and inversion layers are noted.Comment: Lectures presented at the NATO Advanced Study Institute on "Dynamical properties of unconventional magnetic systems", Geilo, Norway, April 2-12, 1997, edited by A. Skjeltorp and D. Sherrington, Kluwer Academic, to be published. 46 page

Adenosine A2A receptors modulate BDNF both in normal conditions and in experimental models of Huntington’s disease

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, enhances synaptic transmission and regulates neuronal proliferation and survival. Functional interactions between adenosine A2A receptors (A2ARs) and BDNF have been recently reported. In this article, we report some recent findings from our group showing that A2ARs regulate both BDNF functions and levels in the brain. Whereas BDNF (10 ng/ml) increased the slope of excitatory postsynaptic field potentials (fEPSPs) in hippocampal slices from wild-type (WT) mice, it was completely ineffective in slices taken from A2AR knock-out (KO) mice. Furthermore, enzyme immunoassay studies showed a significant reduction in hippocampal BDNF levels in A2AR KO vs. WT mice. Having found an even marked reduction in the striatum of A2AR KO mice, and as both BDNF and A2ARs have been implicated in the pathogenesis of Huntington’s disease (HD), an inherited striatal neurodegenerative disease, we then evaluated whether the pharmacological blockade of A2ARs could influence striatal levels of BDNF in an experimental model of HD-like striatal degeneration (quinolinic acid-lesioned rats) and in a transgenic mice model of HD (R6/2 mice). In both QA-lesioned rats and early symptomatic R6/2 mice (8 weeks), the systemic administration of the A2AR antagonist SCH58261 significantly reduced striatal BDNF levels. These results indicate that the presence and the tonic activation of A2ARs are necessary to allow BDNF-induced potentiation of synaptic transmission and to sustain a normal BDNF tone. The possible functional consequences of reducing striatal BDNF levels in HD models need further investigation

Covalent Attachment of Proteins to Solid Supports and Surfaces via Sortase-Mediated Ligation

BACKGROUND: There is growing interest in the attachment of proteins to solid supports for the development of supported catalysts, affinity matrices, and micro devices as well as for the development of planar and bead based protein arrays for multiplexed assays of protein concentration, interactions, and activity. A critical requirement for these applications is the generation of a stable linkage between the solid support and the immobilized, but still functional, protein. METHODOLOGY: Solid supports including crosslinked polymer beads, beaded agarose, and planar glass surfaces, were modified to present an oligoglycine motif to solution. A range of proteins were ligated to the various surfaces using the Sortase A enzyme of S. aureus. Reactions were carried out in aqueous buffer conditions at room temperature for times between one and twelve hours. CONCLUSIONS: The Sortase A transpeptidase of S. aureus provides a general, robust, and gentle approach to the selective covalent immobilization of proteins on three very different solid supports. The proteins remain functional and accessible to solution. Sortase mediated ligation is therefore a straightforward methodology for the preparation of solid supported enzymes and bead based assays, as well as the modification of planar surfaces for microanalytical devices and protein arrays

Risk Factors of Peritoneal Recurrence and Outcome of Resected Peritoneal Recurrence After Liver Resection in Hepatocellular Carcinoma: Review of 1222 Cases of Hepatectomy in a Tertiary Institution

10.1245/s10434-012-2260-3Annals of Surgical Oncology1972246-225

Workplace Accidents among Nepali Male Workers in the Middle East and Malaysia: A Qualitative Study

There are many Nepali men working in the Middle East and Malaysia and media reports and anecdotal evidence suggest a high risk of workplace-related accidents and injuries for male Nepali workers. Therefore, this study aims to explore the personal experiences of male Nepali migrants of unintentional injuries at their place of work. In-depth, face-to-face interviews (n = 20) were conducted with male Nepali migrant workers. Study participants were approached at Kathmandu International Airport, hotels and lodges around the airport. Interviews were transcribed and analysed using thematic analysis. Almost half of study participants experienced work-related accident abroad. The participants suggested that the reasons behind this are not only health and safety at work but also poor communication, taking risks by workers themselves, and perceived work pressure. Some participants experienced serious incidents causing life-long disability, extreme and harrowing accounts of injury but received no support from their employer or host countries. Nepali migrant workers would appear to be at a high risk of workplace unintentional injuries owing to a number of interrelated factors poor health and safety at work, pressure of work, risk taking practices, language barriers, and their general work environment. Both the Government of Nepal and host countries need to be better policing existing policies, introduce better legislation where necessary, ensure universal health (insurance) coverage for labour migrants, and improve preventive measures to minimize the number and severity of accidents and injuries among migrant workers