Born Effective Charges and Infrared Response of LiBC

Calculations of the zone center optical mode frequencies (including LO-TO splitting), Born effective charges Z$^*_{\alpha\alpha}$ for each atom, dielectric constants $\epsilon_{0}$ and $\epsilon_{\infty}$, and the dielectric response in the infrared, using density functional linear response theory, are reported. Calculated Raman modes are in excellent agreement with experimental values (170 cm$^{-1}$ and 1170 cm$^{-1}$), while it will require better experimental data to clarify the infrared active mode frequencies. The Born effective charges Z$^*_{\alpha \alpha}$ (i) have surprisingly different values for B and C, and (ii) show considerable anisotropy. Relationships between the effective charges and LO-TO splitting are discussed, and the predicted reflectivity in the range 0 -- 1400 cm$^{-1}$ is presented. These results hold possible implications for Li removal in LiBC, and C substition for B in MgB$_2$.Comment: 6 pages, 3 figure

Plantation vs. natural forest: Matrix quality determines pollinator abundance in crop fields

In terrestrial ecosystems, ecological processes and patterns within focal patches frequently depend on their matrix. Crop fields (focal patches) are often surrounded by a mosaic of other land-use types (matrix), which may act as habitats for organisms and differ in terms of the immigration activities of organisms to the fields. We examined whether matrix quality affects wild pollinator abundance in crop fields, given that the species (Apis cerana) generally nest in the cavities of natural trees. We examined fields of a pollination-dependent crop surrounded by plantations and natural forests, which comprised the matrix. Our analysis revealed a clear positive effect of the natural forest on the pollinator abundance, but the plantation forest had little effects. These indicate that agricultural patches are influenced by their matrix quality and the resulting crop pollinator abundance, suggesting the importance of matrix management initiatives such as forest restoration surrounding agricultural fields to improve crop production

Brevianes Revisited

Breviones are a new family of secondary metabolites that were originally isolated from the New Zealand endemic fungus Penicillium brevicompactum var. Dierckx. These compounds are generally characterized by a new carbon skeleton, known as breviane, which that has three possible structural variations, such as breviane, abeo-breviane, and abeo-norbreviane. Brevianes present a basic diterpenic tricyclic core that is mevalonic in origin and is similar to that of perhydrophenanthrene. The core bears four methyl groups at positions C4, C8, C10, and C13 and has defined stereochemistry at positions C5, C8, C9, C10, and C14. The C1'-C7' side chain has been proposed to have a polyketide biosynthetic origin and is joined to the diterpenic moiety through carbons C2'-C15'. The cyclization and lactonization of this part of the molecule leads to the characteristic breviane spiranic ring fused to the α-pyrone

Paroxysmal exercise-induced dyskinesia and epilepsy is due to mutations in SLC2A1, encoding the glucose transporter GLUT1

Paroxysmal exercise-induced dyskinesia (PED) can occur in isolation or in association with epilepsy, but the genetic causes and pathophysiological mechanisms are still poorly understood. We performed a clinical evaluation and genetic analysis in a five-generation family with co-occurrence of PED and epilepsy (n = 39), suggesting that this combination represents a clinical entity. Based on a whole genome linkage analysis we screened SLC2A1, encoding the glucose transporter of the blood-brain-barrier, GLUT1 and identified heterozygous missense and frameshift mutations segregating in this and three other nuclear families with a similar phenotype. PED was characterized by choreoathetosis, dystonia or both, affecting mainly the legs. Predominant epileptic seizure types were primary generalized. A median CSF/blood glucose ratio of 0.52 (normal >0.60) in the patients and a reduced glucose uptake by mutated transporters compared with the wild-type as determined in Xenopus oocytes confirmed a pathogenic role of these mutations. Functional imaging studies implicated alterations in glucose metabolism in the corticostriate pathways in the pathophysiology of PED and in the frontal lobe cortex in the pathophysiology of epileptic seizures. Three patients were successfully treated with a ketogenic diet. In conclusion, co-occurring PED and epilepsy can be due to autosomal dominant heterozygous SLC2A1 mutations, expanding the phenotypic spectrum associated with GLUT1 deficiency and providing a potential new treatment option for this clinical syndrome

Peptide and Peptide-Like Modulators of 20S Proteasome Enzymatic Activity in Cancer Cells

The involvement of the ubiquitin–proteasome pathway in the degradation of critical intracellular regulatory proteins suggested a few years ago the potential use of proteasome inhibitors as novel therapeutic agents being applicable in many different disease indications, and in particular for cancer therapy. This article reviews recent salient medicinal chemistry achievements in the design, synthesis, and biological characterization of both synthetic and natural peptide-like proteasome inhibitors, updating recent reviews on this class of agents. As shown herein, different compound classes are capable of modulating the subunit-specific proteolytic activities of the 20S proteasome in ways not previously possible, and one of them, bortezomib, has provided proof-of-concept for this therapeutic approach in cancer clinical settings

Consensus Paper: Radiological Biomarkers of Cerebellar Diseases

Hereditary and sporadic cerebellar ataxias represent a vast and still growing group of diseases whose diagnosis and differentiation cannot only rely on clinical evaluation. Brain imaging including magnetic resonance (MR) and nuclear medicine techniques allows for characterization of structural and functional abnormalities underlying symptomatic ataxias. These methods thus constitute a potential source of radiological biomarkers, which could be used to identify these diseases and differentiate subgroups of them, and to assess their severity and their evolution. Such biomarkers mainly comprise qualitative and quantitative data obtained from MR including proton spectroscopy, diffusion imaging, tractography, voxel-based morphometry, functional imaging during task execution or in a resting state, and from SPETC and PET with several radiotracers. In the current article, we aim to illustrate briefly some applications of these neuroimaging tools to evaluation of cerebellar disorders such as inherited cerebellar ataxia, fetal developmental malformations, and immune-mediated cerebellar diseases and of neurodegenerative or early-developing diseases, such as dementia and autism in which cerebellar involvement is an emerging feature. Although these radiological biomarkers appear promising and helpful to better understand ataxia-related anatomical and physiological impairments, to date, very few of them have turned out to be specific for a given ataxia with atrophy of the cerebellar system being the main and the most usual alteration being observed. Consequently, much remains to be done to establish sensitivity, specificity, and reproducibility of available MR and nuclear medicine features as diagnostic, progression and surrogate biomarkers in clinical routine