Glutamate spill-over in substantia nigra pars compacta

N-Methyl-D-aspartate glutamate receptors (NMDARs) contribute to neural development, plasticity and survival, but they are also linked with neurodegeneration. NMDARs at synapses are activated by coincident glutamate release and depolarization. NMDARs distal to synapses can sometimes be recruited by 'spill-over' of glutamate during high-frequency synaptic stimulation or when glutamate uptake is compromised, and this influences the shape of NMDAR-mediated postsynaptic responses. In substantia nigra dopamine neurons, activation of NMDARs beyond the synapse during different frequencies of presynaptic stimulation has not been explored, even though excitatory afferents from the subthalamic nucleus show a range of firing frequencies, and these frequencies change in human and experimental Parkinson's disease. This study reports that high-frequency stimulation (80 Hz/200 ms) evoked NMDAR-excitatory postsynaptic currents (EPSCs) that were larger and longer lasting than those evoked by single stimuli at low frequency (0.1 Hz). MK-801, which irreversibly blocked NMDAR-EPSCs activated during 0.1-Hz stimulation, left a proportion of NMDAR-EPSCs that could be activated by 80-Hz stimulation and that may represent activity of NMDARs distal to synapses. TBOA, which blocks glutamate transporters, significantly increased NMDAR-EPSCs in response to 80-Hz stimulation, particularly when metabotropic glutamate receptors (mGluRs) were also blocked, indicating that recruitment of NMDARs distal to synapses is regulated by glutamate transporters and mGluRs. These regulatory mechanisms may be essential in the substantia nigra for restricting glutamate diffusion from synaptic sites and keeping NMDAR-EPSCs in dopamine neurons relatively small and fast. Failure of glutamate transporters may contribute to the declining health of dopamine neurons during pathological conditions.Funding from The Wellcome Trust (092611/B/10/Z), The Isaac Newton Trust, and a BBSRC-DTP Studentship to PGM.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/ejn.1307

CRANKITE: a fast polypeptide backbone conformation sampler

Background: CRANKITE is a suite of programs for simulating backbone conformations of polypeptides and proteins. The core of the suite is an efficient Metropolis Monte Carlo sampler of backbone conformations in continuous three-dimensional space in atomic details. Methods: In contrast to other programs relying on local Metropolis moves in the space of dihedral angles, our sampler utilizes local crankshaft rotations of rigid peptide bonds in Cartesian space. Results: The sampler allows fast simulation and analysis of secondary structure formation and conformational changes for proteins of average length

New surgical approach for late complications from spinal cord injury

BACKGROUND: The most frequent late complications in spinal cord injury result from arachnoiditis and consequent alterations in dynamics of cerebrospinal fluid flow. A surgical procedure carried out on patients with these alterations, resolved the various pathologies more efficiently in all cases. METHODS: From October 2000 to March 2006, 23 patients were selected for surgery: three showed signs of syringomyelia, three presented with microcystic lesions, three presented with arachnoid cysts in different locations but always confluent to the scar area, and 14 showed evidence of tethered cords. The surgery consisted of laminectomy at four levels, followed by dural opening in order to remove all the arachnoiditis at the level of the scar and to remove the altered arachnoid and its cysts, at least at two levels above and below the lesion. The dentate ligaments were cut at all exposed levels. RESULTS: The patients had no postoperative problems and not only retained all neurological functions but also showed neurological recovery. According to the motor and sensory scale of the American Spinal Injury Association, the recoveries were motor 20.6% (P < 0.001), touch 15.6% ((P < 0.001) and pinprick 14.4% (P < 0.001). These patients showed no signs of relapse at 4–66 month follow-up. CONCLUSION: This alternative surgery resolved the pathologies provoking neurological deterioration by releasing the complete spinal cord at the level of the scar and the levels above and below it. It thus avoids myelotomies and the use of shunts and stents, which have a high long-term failure rate and consequent relapses. Nevertheless, this surgical procedure allows patients the chance to opt for any further treatment that may evolve in the future

Genetic Determinants of Circulating Sphingolipid Concentrations in European Populations

Sphingolipids have essential roles as structural components of cell membranes and in cell signalling, and disruption of their metabolism causes several diseases, with diverse neurological, psychiatric, and metabolic consequences. Increasingly, variants within a few of the genes that encode enzymes involved in sphingolipid metabolism are being associated with complex disease phenotypes. Direct experimental evidence supports a role of specific sphingolipid species in several common complex chronic disease processes including atherosclerotic plaque formation, myocardial infarction (MI), cardiomyopathy, pancreatic beta-cell failure, insulin resistance, and type 2 diabetes mellitus. Therefore, sphingolipids represent novel and important intermediate phenotypes for genetic analysis, yet little is known about the major genetic variants that influence their circulating levels in the general population. We performed a genome-wide association study (GWAS) between 318,237 single-nucleotide polymorphisms (SNPs) and levels of circulating sphingomyelin (SM), dihydrosphingomyelin (Dih-SM), ceramide (Cer), and glucosylceramide (GluCer) single lipid species (33 traits); and 43 matched metabolite ratios measured in 4,400 subjects from five diverse European populations. Associated variants (32) in five genomic regions were identified with genome-wide significant corrected p-values ranging down to 9.08 x 10(-66). The strongest associations were observed in or near 7 genes functionally involved in ceramide biosynthesis and trafficking: SPTLC3, LASS4, SGPP1, ATP10D, and FADS1-3. Variants in 3 loci (ATP10D, FADS3, and SPTLC3) associate with MI in a series of three German MI studies. An additional 70 variants across 23 candidate genes involved in sphingolipid-metabolizing pathways also demonstrate association (p = 10(-4) or less). Circulating concentrations of several key components in sphingolipid metabolism are thus under strong genetic control, and variants in these loci can be tested for a role in the development of common cardiovascular, metabolic, neurological, and psychiatric diseases

Dictyostelium discoideum as a Model to Study Inositol Polyphosphates and Inorganic Polyphosphate

The yeast Saccharomyces cerevisiae has given us much information on the metabolism and function of inositol polyphosphates and inorganic polyphosphate. To expand our knowledge of the metabolic as well as functional connections between inositol polyphosphates and inorganic polyphosphate, we have refined and developed techniques to extract and analyze these molecules in a second eukaryotic experimental model, the amoeba Dictyostelium discoideum. This amoeba, possessing a well-defined developmental program, is ideal to study physiological changes in the levels of inositol polyphosphates and inorganic polyphosphate, since levels of both molecules increase at late stages of development. We detail here the methods used to extract inositol polyphosphates using perchloric acid and inorganic polyphosphate using acidic phenol. We also present the postextraction procedures to visualize and quantify these molecules by polyacrylamide gel electrophoresis and by malachite green assay

Integrating isotopes and documentary evidence : dietary patterns in a late medieval and early modern mining community, Sweden

We would like to thank the Archaeological Research Laboratory, Stockholm University, Sweden and the Tandem Laboratory (Ångström Laboratory), Uppsala University, Sweden, for undertaking the analyses of stable nitrogen and carbon isotopes in both human and animal collagen samples. Also, thanks to Elin Ahlin Sundman for providing the δ13C and δ15N values for animal references from Västerås. This research (Bäckström’s PhD employment at Lund University, Sweden) was supported by the Berit Wallenberg Foundation (BWS 2010.0176) and Jakob and Johan Söderberg’s foundation. The ‘Sala project’ (excavations and analyses) has been funded by Riksens Clenodium, Jernkontoret, Birgit and Gad Rausing’s Foundation, SAU’s Research Foundation, the Royal Physiographic Society of Lund, Berit Wallenbergs Foundation, Åke Wibergs Foundation, Lars Hiertas Memory, Helge Ax:son Johnson’s Foundation and The Royal Swedish Academy of Sciences.Peer reviewedPublisher PD

Evaluating compliance to a low glycaemic index (GI) diet in women with polycystic ovary syndrome (PCOS)

<p>Abstract</p> <p>Background</p> <p>A low Glycaemic Index (GI) diet may decrease some long-term health risks in Polycystic Ovary Syndrome (PCOS) such as endometrial cancer. This study was performed to assess compliance to a low GI diet in women with PCOS. Food diaries prospectively collected over 6 months from women on a low GI diet or healthy eating diet were analysed retrospectively. The women were recruited for a pilot randomised control trial investigating whether a low GI diet decreased the risk of Endometrial Cancer. Nine women with PCOS completed 33 food diaries (17 from women on a low GI diet and 16 from women on a healthy eating diet) recording 3023 food items (low GI group:n = 1457; healthy eating group:n = 1566). Data was analysed using Foster-Powell international values inserted into an SPSS database as no scientifically valid established nutrition software was found. The main outcome measures were mean item GI and Glyacemic Load (GL), mean meal GL, percentage high GI foods and mean weight loss.</p> <p>Findings</p> <p>Women allocated the low GI diet had a statistically significant lower GI of food items (33.67 vs 36.91, p < 0.05), lower percentage of high GI foods (4.3% vs 12.1%, p < 0.05) and lower GL of food items and meals.</p> <p>Conclusion</p> <p>Women with PCOS on a low GI diet consumed food items with a significantly lower mean GI and GL compared to the healthy eating diet group. Longer term compliance needs evaluation in subsequent studies to ascertain that this translates to reduced long term health risks.</p> <p>Trial Registration</p> <p>ISRCTN: <a href="http://www.controlled-trials.com/ISRCTN86420258">ISRCTN86420258</a></p