Neurofibrillary degeneration in progressive supranuclear palsy and corticobasal degeneration: tau pathologies with exclusively "exon 10" isoforms

Pathological tau proteins that constitute the basic matrix of neuronal inclusions observed in numerous neurodegenerative disorders are disease specific. This is mainly the consequence of the aggregation of specific sets of tau isoforms according to the diseases, i.e., six isoforms in Alzheimer's disease (AD) and exclusively the three tau isoforms lacking the corresponding sequence of exon 10 (E10-) in Pick's disease (PiD). By using antibodies specific to the different tau isoforms and one- and two-dimensional gel electrophoresis followed by western blots, we demonstrate herein a third group of neurodegenerative disorders characterized by intraneuronal inclusions exclusively constituted of tau isoforms containing the sequence corresponding to exon 10, progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). Together, tau isoforms with exon 10 clearly differentiate three groups of neurodegenerative diseases: AD, PiD, and PSP/CBD. For each group, the neuropathological and clinical phenotypes are most likely related to specific sets of tau isoforms expressed by the vulnerable neuronal populations. The recently described mutations of the tau gene responsible for familial frontotemporal dementias also support this hypothesis.     

Anthocyanin from strawberry (Fragaria ananassa) with the novel aglycone, 5-carboxypyranopelargonidin

An anthocyanin, 1, with the novel 4-substituted aglycone, 5-carboxypyranopelargonidin, was isolated in small amounts from the acidified, methanolic extract of strawberries, Fragaria ananassa Duch., by preparative HPLC after purification by partition against ethyl acetate, Amberlite XAD-7 and Sephadex LH-20 column chromatography. It was identified mainly by 2D NMR spectroscopy and electrospray LC-MS as the 3-O-beta-glucopyranoside of 5-carboxy-2-(4-hydroxyphenyl)-3,8-dihydroxy-pyrano[4,3,2-de]-1-benzopyrylium, an anthocyanidin which is homologous to 5-carboxypyranomalvidin (vitisidin A) reported in red wines and 5-carboxypyranocyanidin recently isolated from red onions. By comparison of UV-Vis absorption spectra, 1 showed in contrast to 2, pelargonidin 3-O-beta-glucopyranoside, a local absorption peak around 360 nm, a hypsochromic shift (8 nm) of the visible absorption maximum, and lack of a distinct UV absorption peak around 280 nm. The similarities between the absorption spectra of 1 in various acidic and neutral buffer solutions implied restricted formation of the instable colourless equilibrium forms, which are typical for most anthocyanins in weakly acidic solutions. The molar absorptivity (epsilon) of 1 varied little with pH contrary to similar values of for instance the major anthocyanin in strawberry, 2. However, 2 revealed higher epsilon-values than 1 at all pH values except 5.1. At pH 5.1, the epsilon-value of 1 (6250) was nearly four times the corresponding value of 2 (1720), which showed the potential of 5-carboxypyranopelargonidin derivatives as colorants in solutions with pH around 5. The colours of 1 and 2 in buffered solutions with pH 1.1 and pH 6.9 have been described by the CIELAB coordinates h(ab) (hue angle), C* (chroma), and L* (lightness).     

Electromagnetic field exposure and health among RF plastic sealer operators

Operators of RF plastic sealers (RF operators) are an occupational category highly exposed to radiofrequency electromagnetic fields. The aim of the present study was to make an appropriate exposure assessment of RF welding and examine the health status of the operators. In total, 35 RF operators and 37 controls were included. The leakage fields (electric and magnetic field strength) were measured, as well as induced and contact current. Information about welding time and productivity was used to calculate time integrated exposure. A neurophysiological examination and 24 h ECG were also carried out. The participants also had to answer a questionnaire about subjective symptoms. The measurements showed that RF operators were exposed to rather intense electric and magnetic fields. The mean values of the calculated 6 min, spatially averaged E and H field strengths, in line with ICNIRP reference levels, are 107 V/m and 0.24 A/m, respectively. The maximum measured field strengths were 2 kV/m and 1.5 A/m, respectively. The induced current in ankles and wrists varied, depending on the work situation, with a mean value of 101 mA and a maximum measured value of 1 A. In total, 11 out of 46 measured RF plastic sealers exceeded the ICNIRP reference levels. RF operators, especially the ready made clothing workers had a slightly disturbed two-point discrimination ability compared to a control group. A nonsignificant difference between RF operators and controls was found in the prevalence of subjective symptoms, but the time integrated exposure parameters seem to be of importance to the prevalence of some subjective symptoms: fatigue, headaches, and warmth sensations in the hands. Further, RF operators had a significantly lower heart rate (24 h registration) and more episodes of bradycardia compared to controls.     

Bird orientation: compensation for wind drift in migrating raptors is age dependent

Despite the potentially strong effect of wind on bird orientation, our understanding of how wind drift affects migrating birds is still very limited. Using data from satellite-based radio telemetry, we analysed the effect of changing winds on the variation of the track direction of individual birds. We studied adults and juveniles of two raptor species, osprey Pandion haliaetus and honey buzzard Pernis apivorus, on autumn migration between North Europe and Africa, and demonstrate an important difference between the age categories of both species in the extent of wind drift. For juveniles, side- and following-wind components affected the rates of movement perpendicular to and along the mean direction, respectively, to a similar degree, suggesting full wind drift. By contrast, for adults the rate of crosswind displacement was significantly smaller than the effect of wind on forward movement, showing much reduced wind drift (29%). This indicates that adults have acquired a more sophisticated orientation system, permitting detection of and compensation for wind drift, than juveniles. These drift effects are likely to reduce the ability of juveniles to locate species-specific wintering areas in case of rapid climatic wind change.     

Regulation of heptaspanning-membrane-receptor function by dimerization and clustering

G-protein-coupled receptors form homomers and heteromers; agonist-induced conformational changes within interacting receptors of the oligomer modify their pharmacology, signalling and/or trafficking. When these receptors are activated, the oligomers rearrange and cluster and a novel mechanism of receptor-operation regulation by oligomer intercommunication is possible. This intercommunication would be assisted by components of the plasma membrane and by scaffolding proteins. Receptor cross-sensitization, cross-desensitization and novel, integrated receptor responses can then develop between oligomeric receptor complexes of the cluster without direct contact between them. This concept gives a new perspective to the understanding of neurotransmission and neuronal plasticity.     

On the substrate specificity of human CYP27A1: implications for bile acid and cholestanol formation

The mitochondrial sterol 27-hydroxylase (CYP27A1) is required for degradation of the C27-sterol side chain in bile acid biosynthesis. CYP27A1 seems, however, to have roles beyond this, as illustrated by patients with a deficient sterol 27-hydroxylase due to mutations of the CYP27A1 gene [cerebrotendinous xanthomatosis (CTX)]. These subjects have symptoms ranging from accumulation of bile alcohols and cholestanol to accelerated atherosclerosis and progressive neurologic impairment. The present work describes a detailed investigation on the substrate specificity of recombinant human CYP27A1. In accordance with some previous work with rat liver mitochondria, the activity in general increased with the polarity of the substrate. An obvious example was the finding that cholesterol was 27-hydroxylated more efficiently than cholesterol oleate but less efficiently than cholesterol sulfate. The oxysterols 24S-hydroxycholesterol and 25-hydroxycholesterol were 27-hydroxylated less efficiently than cholesterol, possibly due to steric hindrance. Surprisingly, sterols with a 3-oxo-Delta4 structure were found to be hydroxylated at a much higher rate than the corresponding sterols with a 3beta-hydroxy-Delta5 structure. The rates of hydroxylation of the sterols were: 7alpha-hydroxy-4-cholesten-3-one>4-cholesten-3-one>7alpha-hydroxycholesterol>24-hydroxy-4-cholesten-3-one> cholesterol>25-hydroxy-4-cholesten-3-one>24-hydroxycholesterol>or=25-hydroxycholesterol. The possibility is discussed that the findings may have implications for oxysterol-mediated regulation of gene expression. The very high activity of CYP27A1 towards the cholestanol precursor 4-cholesten-3-one may be of importance in connection with the accumulation of cholestanol in patients with CTX.     

Modelling zinc-binding proteins with GADGET: genetic algorithm and distance geometry for exploring topology

A novel combination of optimization methods (Genetic Algorithm with Distance Geometry) has been developed and shown to find near-optimal solutions to a set of imposed structural constraints. With this modelling tool (GADGET), the fold-space of a variety of small zinc-binding proteins was investigated under the constraints required to form a zinc-binding site (or pair of sites). Analysis of the results concentrated on the ring-finger domain as the "classic" zinc-finger domains were too constrained to provide much topological variety, whilst the TFIIH domain (which has large unstructured loops) did not behave well. The intermediate ring-finger domain, however, was found to adopt a variety of different folds, many of which had near-optimal scores under the fitness function employed in GADGET (forming good secondary structures and zinc-coordination). Although the native fold was dominant amongst the solutions, the discovery of good alternate folds shows that even the eight residues constrained to form two zinc-binding sites was not sufficient to uniquely determine the native fold. Despite this, the fold-space of 48 theoretically possible folds was greatly reduced with just six topologies found in significant numbers.     

A novel nuclear export signal and a REF interaction domain both promote mRNA export by the Epstein-Barr virus EB2 protein

A striking characteristic of mRNA export factors is that they shuttle continuously between the cytoplasm and the nucleus. This shuttling is mediated by specific factors interacting with peptide motifs called nuclear export signals (NES) and nuclear localization signals. We have identified a novel CRM-1-independent transferable NES and two nuclear localization signals in the Epstein-Barr virus mRNA export factor EB2 (also called BMLF1, Mta, or SM) localized at the N terminus of the protein between amino acids 61 and 146. We have also found that a previously described double NES (amino acids 213-236) does not mediate the nuclear shuttling of EB2, but is an interaction domain with the cellular export factor REF in vitro. This newly characterized REF interaction domain is essential for EB2-mediated mRNA export. Accordingly, in vivo, EB2 is found in complexes containing REF as well as the cellular factor TAP. However, these interactions are RNase-sensitive, suggesting that the RNA is an essential component of these complexes.     

Reduced immunocompetence and cost of reproduction in common eiders

Immunocompetence may be especially important in long-lived species where infectious organisms may have detrimental effects upon future reproductive value of hosts. The resource demand for immunocompetence may reduce resource availability for reproduction and a trade-off between these traits has therefore been proposed. Capital breeders, such as the common eider (Somateria mollissima), rely upon accumulated body reserves during reproduction. Eiders lose more than 40% of pre-breeding body mass during egglaying and incubation and many females abandon their ducklings to other females after hatching. Results from our observational study show that levels of leukocytes (i.e., lymphocytes, heterophils and heterophil/lymphocyte ratio) are not related to body mass early in the incubation period. However, eider females with low initial body mass showed signs of immunosuppression (i.e., decreased late levels of lymphocytes) and increased response towards stressors (i.e., increased heterophil/lymphocyte ratio) later in the incubation period. Moreover, females with low lymphocyte levels more frequently abandoned their brood, and females abandoning young had an increased return rate to the next breeding season. However, among brood abandoning females return rate was lower for the females with low lymphocyte levels. These results suggest that immunosuppression, as indicated by low lymphocyte levels, is a reproductive cost that may be partly compensated for by abandoning young.     

Distinct effects on heparan sulfate structure by different active site mutations in NDST-1

Heparan sulfate polymerization and modification take place in the Golgi compartment. The modification reactions are initiated by glucosaminyl N-deacetylase/N-sulfotransferase (NDST), a bifunctional enzyme that removes N-acetyl groups from selected N-acetyl-d-glucosamine units followed by N-sulfation of the generated free amino groups. Four isoforms of NDST have been identified. NDST-1 and -2 have a wide and largely overlapping tissue distribution, but it is not known if they can act on the same heparan sulfate chain. We have introduced point mutations into NDST-1 cDNA, which selectively destroy the N-deacetylase or N-sulfotransferase activity of the enzyme [Wei, Z., and Swiedler, S. J. (1999) J. Biol. Chem. 274, 1966-70 and Sueyoshi, T., et al. (1998) FEBS Lett. 433, 211-4]. Stable 293 cell lines expressing the NDST-1 mutants were then generated. Structural analyses of heparan sulfate synthesized by these cells and by cells overexpressing wild-type NDST-1 demonstrate that the N-deacetylation step is not only prerequisite but also rate-limiting, determining the degree of N-sulfation. Transfection of mutant NDST-1 lacking N-deacetylase activity had no effect on heparan sulfate sulfation, while cells expressing wild-type enzyme or NDST-1 lacking N-sulfotransferase activity both resulted in the production of oversulfated heparan sulfate. Since no increase in the amount of N-unsubstituted glucosamine residues was seen after transfection of the mutant lacking N-sulfotransferase activity, the results also suggest that two different enzyme molecules can act on the same glucosamine unit. In addition, we show that oversulfation of heparan sulfate produced by cells tranfected with wild-type NDST-1 or the mutant lacking N-sulfotranferase activity results in decreased sulfation of chondroitin sulfate.