Medulloblastoma: advances and challenges

Medulloblastoma, a cancer of the posterior fossa, is the most common malignant brain tumor in children. Although 80% of patients with average-risk medulloblastoma are cured, their quality of life is often compromised by treatment-related side effects. Recently, molecular and genomic studies have shown medulloblastoma to be a heterogeneous disease made up of distinct disease subtypes. The importance of this finding is that response to therapy appears to be subtype-specific. Nevertheless, most patients are still treated according to risk stratification methods based on the clinically defined presence or absence of disseminated disease, which take no account of these newly defined subtypes. The potential, however, to vastly reduce therapy-mediated toxicity to patients with tumor subtypes that have good outcomes, while improving therapy through targeting for the poor responders, is now palpable. Critical to this effort will be the ongoing refinement of our understanding of medulloblastoma subgroups at the molecular level and the development of mouse models that faithfully recapitulate tumor subtypes

A Possible 1.8 K Refrigeration Cycle for the Large Hadron Collider

The Large Hadron Collider (LHC) under construction at the European Laboratory for Particle Physics, CERN, will make use of superconducting magnets operating below 2.0 K. This requires, for each of the eight future cryogenic installations, an isothermal cooling capacity of up to 2.4 kW obtained by vaporisation of helium II at 1.6 kPa and 1.8 K. The process design for this cooling duty has to satisfy several demands. It has to be adapted to four already existing as well as to four new refrigerators. It must cover a dynamic range of one to three, and it must to allow continuous pump-down from 4.5 K to 1.8 K. A possible solution, as presented in this paper, includes a combination of cold centrifugal and warm volumetric compressors. It is characterised by a low thermal load on the refrigerator, and a large range of adaptability to different operation modes. The expected power factor for 1.8 K cooling is given, and the proposed control strategy is explained

A combined FEG-SEM and TEM study of silicon nanodot assembly

Nanodots forming dense assembly on a substrate are difficult to characterize in terms of size, density, morphology and cristallinity. The present study shows how valuable information can be obtained by a combination of electron microscopy techniques. A silicon nanodots deposit has been studied by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) to estimate essentially the dot size and density, quantities emphasized because of their high interest for application. High resolution SEM indicates a density of 1.6 × 1012 dots/cm2 for a 5 nm to 10 nm dot size. TEM imaging using a phase retrieval treatment of a focus series gives a higher dot density (2 × 1012 dots/cm2) for a 5 nm dot size. High Resolution Transmission Electron Microscopy (HRTEM) indicates that the dots are crystalline which is confirmed by electron diffraction. According to HRTEM and electron diffraction, the dot size is about 3 nm which is significantly smaller than the SEM and TEM results. These differences are not contradictory but attributed to the fact that each technique is probing a different phenomenon. A core-shell structure for the dot is proposed which reconcile all the results. All along the study, Fourier transforms have been widely used under many aspects

Mitochondrial uncoupling as a regulator of life-history trajectories in birds: an experimental study in the zebra finch.

Mitochondria have a fundamental role in the transduction of energy from food into ATP. The coupling between food oxidation and ATP production is never perfect, but may nevertheless be of evolutionary significance. The 'uncoupling to survive' hypothesis suggests that 'mild' mitochondrial uncoupling evolved as a protective mechanism against the excessive production of damaging reactive oxygen species (ROS). Because resource allocation and ROS production are thought to shape animal life histories, alternative life-history trajectories might be driven by individual variation in the degree of mitochondrial uncoupling. We tested this hypothesis in a small bird species, the zebra finch (Taeniopygia guttata), by treating adults with the artificial mitochondrial uncoupler 2,4-dinitrophenol (DNP) over a 32-month period. In agreement with our expectations, the uncoupling treatment increased metabolic rate. However, we found no evidence that treated birds enjoyed lower oxidative stress levels or greater survival rates, in contrast to previous results in other taxa. In vitro experiments revealed lower sensitivity of ROS production to DNP in mitochondria isolated from skeletal muscles of zebra finch than mouse. In addition, we found significant reductions in the number of eggs laid and in the inflammatory immune response in treated birds. Altogether, our data suggest that the 'uncoupling to survive' hypothesis may not be applicable for zebra finches, presumably because of lower effects of mitochondrial uncoupling on mitochondrial ROS production in birds than in mammals. Nevertheless, mitochondrial uncoupling appeared to be a potential life-history regulator of traits such as fecundity and immunity at adulthood, even with food supplied ad libitum

Strong polarization of the residual nucleus in a heavy-ion induced transfer reaction

A strong polarization of 20Ne levels has been observed in the 16O(16O, 12C)20Ne* reaction along an axis perpendicular to the reaction plane. This polarization differs from that reported in the (7Li, t) reaction, when the same nuclear levels were populated. D.W.B.A. calculations which fitted both angular distributions and polarization in the (7Li, t) reaction and which can also describe the (16O, 12C) angular distributions fail to reproduce the associated 20Ne* polarization

Changes in the critical frequency of fusion after surgical healing of the retinal detachment.

peer reviewedThe operation for detachment of the retina is an urgent one. Every postponement lessens the surgical healing prospects and also the post-operative re-gaining of visual function. The earlier the operation is performed, the more chance vision, field of vision and critical frequency of fusion have of reaching their normal values. The operation for detachment performed in less than one month is able to regain a vision of 1, and a complete field of vision (with the exception of the scotoma produced by operative chorioretinitis). But even in these favourable cases the measurements of the critical frequency of fusion often show a definite defect which includes the whole of the area of detachment. The critical frequency of fusion is a very sensitive test, that even shows up minimal defects of function. The falling off of the critical frequency of fusion which is still present after a favourable outcome of the detachment operation does not lead to any subjective disturbances. © 1948 S. Karger AG, Basel