Meta-analysis of the literature on diagnostic accuracy of SPECT in parkinsonian syndromes

Background  

Parkinson's disease (PD) is the second most common neurodegenerative disorder. One of the most widely used techniques to diagnose PD is a Single Photon Emission Computer Tomography (SPECT) scan to visualise the integrity of the dopaminergic pathways in the brain. Despite this there remains some discussion on the value of SPECT in the differential diagnosis of PD. We did a meta-analysis of all the existing literature on the diagnostic accuracy of both pre- and post-synaptic SPECT imaging in the differential diagnosis of PD.     

Non-Human Primates Harbor Diverse Mammalian and Avian Astroviruses Including Those Associated with Human Infections

Astroviruses (AstVs) are positive sense, single-stranded RNA viruses transmitted to a wide range of hosts via the fecal-oral route. The number of AstV-infected animal hosts has rapidly expanded in recent years with many more likely to be discovered because of the advances in viral surveillance and next generation sequencing. Yet no study to date has identified human AstV genotypes in animals, although diverse AstV genotypes similar to animal-origin viruses have been found in children with diarrhea and in one instance of encephalitis. Here we provide important new evidence that non-human primates (NHP) can harbor a wide variety of mammalian and avian AstV genotypes, including those only associated with human infection. Serological analyses confirmed that >25% of the NHP tested had antibodies to human AstVs. Further, we identified a recombinant AstV with parental relationships to known human AstVs. Phylogenetic analysis suggests AstVs in NHP are on average evolutionarily much closer to AstVs from other animals than are AstVs from bats, a frequently proposed reservoir. Our studies not only demonstrate that human astroviruses can be detected in NHP but also suggest that NHP are unique in their ability to support diverse AstV genotypes, further challenging the paradigm that astrovirus infection is species-specific.     

Methane oxidation coupled to oxygenic photosynthesis in anoxic waters

Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atmosphere. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addition of oxygen enhanced the rates of methane oxidation. An equally pronounced stimulation was also observed when the anoxic water samples were incubated in the light. Our combined results from molecular, biogeochemical and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidation of methane fuelled by in situ oxygen production by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidation coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes.     

Chemopreventive and renal protective effects for docosahexaenoic acid (DHA): implications of CRP and lipid peroxides

Background

The fish oil-derived ω-3 fatty acids, like docosahexanoic (DHA), claim a plethora of health benefits. We currently evaluated the antitumor effects of DHA, alone or in combination with cisplatin (CP) in the EAC solid tumor mice model, and monitored concomitant changes in serum levels of C-reactive protein (CRP), lipid peroxidation (measured as malondialdehyde; MDA) and leukocytic count (LC). Further, we verified the capacity of DHA to ameliorate the lethal, CP-induced nephrotoxicity in rats and the molecular mechanisms involved therein.

Results

EAC-bearing mice exhibited markedly elevated LC (2-fold), CRP (11-fold) and MDA levels (2.7-fold). DHA (125, 250 mg/kg) elicited significant, dose-dependent reductions in tumor size (38%, 79%; respectively), as well as in LC, CRP and MDA levels. These effects for CP were appreciably lower than those of DHA (250 mg/kg). Interestingly, DHA (125 mg/kg) markedly enhanced the chemopreventive effects of CP and boosted its ability to reduce serum CRP and MDA levels. Correlation studies revealed a high degree of positive association between tumor growth and each of CRP (r = 0.85) and leukocytosis (r = 0.89), thus attesting to a diagnostic/prognostic role for CRP. On the other hand, a single CP dose (10 mg/kg) induced nephrotoxicity in rats that was evidenced by proteinuria, deterioration of glomerular filtration rate (GFR, -4-fold), a rise in serum creatinine/urea levels (2–5-fold) after 4 days, and globally-induced animal fatalities after 7 days. Kidney-homogenates from CP-treated rats displayed significantly elevated MDA- and TNF-α-, but reduced GSH-, levels. Rats treated with DHA (250 mg/kg, but not 125 mg/kg) survived the lethal effects of CP, and showed a significant recovery of GFR; while their homogenates had markedly-reduced MDA- and TNF-α-, but -increased GSH-levels. Significant association was detected between creatinine level and those of MDA (r = 0.81), TNF-α ) r = 0.92) and GSH (r = -0.82); implying causal relationships.

Conclusion

DHA elicited prominent chemopreventive effects on its own, and appreciably augmented those of CP as well. The extent of tumor progression in various mouse groups was highly reflected by CRP levels (thus implying a diagnostic/prognostic role for CRP). Further, this study is the first to reveal that DHA can obliterate the lethal CP-induced nephrotoxicity and renal tissue injury. At the molecular level, DHA appears to act by reducing leukocytosis, systemic inflammation, and oxidative stress.     

Transmembrane segment 3 of the Glut1 glucose transporter is an outer helix

A model has been proposed for the structure of the Glut1 glucose transporter based on the results of mutagenesis studies and homology modeling in which eight transmembrane segments form an inner helical bundle surrounded by four outer helices. The role of transmembrane segment 3 in this structural model was investigated using cysteine-scanning mutagenesis in conjunction with the membrane-impermeant, sulfhydryl-specific reagent, p-chloromercuribenzenesulfonate (pCMBS). Twenty-one Glut1 mutants were created from a fully functional, cysteine-less, parental Glut1 molecule by successively changing each residue along transmembrane helix 3 to a cysteine. The single cysteine mutants were then expressed in Xenopus oocytes, and their expression levels, transport activities, and sensitivities to pCMBS were determined. Cysteine substitution at methionine 96 abolished transport activity, whereas substitutions at the other positions resulted in either modest reductions or no significant effect on transport activity. In striking contrast to all other helices that have been examined to date, only one of the 21 helix 3 single-cysteine mutants was inhibited by pCMBS, suggesting that only a small portion of this helix is exposed to the external solvent. This result is consistent with predictions based on our current structural model, in which helix 3 is one of four outer helices that surround the inner helical bundle that comprises the aqueous substrate-binding cavity. An updated two-dimensional model for the orientation of the 12 transmembrane helices and the conformation of the exofacial glucose-binding site of Glut1 is presented that is consistent with existing experimental data.     

Phosphoinositide-dependent kinase-2 is a distinct protein kinase enriched in a novel cytoskeletal fraction associated with adipocyte plasma membranes

By recombining subcellular components of 3T3-L1 adipocytes in a test tube, early insulin signaling events dependent on phosphatidylinositol 3-kinase (PI 3-kinase) were successfully reconstituted, up to and including the phosphorylation of glycogen synthase kinase-3 by the serine/threonine kinase, Akt (Murata, H., Hresko, R.C., and Mueckler, M. (2003) J. Biol. Chem. 278, 21607-21614). Utilizing the advantages provided by a cell-free methodology, we characterized phosphoinositide-dependent kinase 2 (PDK2), the putative kinase responsible for phosphorylating Akt on Ser-473. Immunodepleting cytosolic PDK1 from an in vitro reaction containing plasma membrane and cytosol markedly inhibited insulin-stimulated phosphorylation of Akt at the PDK1 site (Thr-308) but had no effect on phosphorylation at the PDK2 site (Ser-473). In contrast, PDK2 activity was found to be highly enriched in a novel cytoskeletal subcellular fraction associated with plasma membranes. Akt isoforms 1-3 and a kinase-dead Akt1 (K179A) mutant were phosphorylated in a phosphatidylinositol 3,4,5-trisphosphate-dependent manner at Ser-473 in an in vitro reaction containing this novel adipocyte subcellular fraction. Our data indicate that this PDK2 activity is the result of a kinase distinct from PDK1 and is not due to autophosphorylation or transphosphorylation of Akt.     

Linkage analysis of a derived glucose phenotype in the Genetic Analysis Workshop 13 simulated data using a variety of Haseman-Elston based regression methods

A variety of Haseman-Elston type regression procedures were used to perform a genome scan across five chromosomes, using replicates 1-5 of the Genetic Analysis Workshop 13 simulated data. The traits of interest were variables corresponding to 'baseline' and 'slope' effects derived from the fasting glucose phenotypes. Performance in terms of detecting the locations of known trait loci was poor for all methods, even when all five replicates were combined to produce a large data set (9230 sib pairs). All methods performed well, however, when applied to new simulated data in which the true genetic effects were allowed to explain a greater proportion of the overall variance.     

Nomenclature of the GLUT/SLC2A family of sugar/polyol transport facilitators

The recent identification of several additional members of the family of sugar transport facilitators (gene symbol SLC2A, protein symbol GLUT) has created a heterogeneous and, in part, confusing nomenclature. Therefore, this letter provides a summary of the family members and suggests a systematic nomenclature for SLC2A and GLUT symbols.     

Cysteine-scanning mutagenesis and substituted cysteine accessibility analysis of transmembrane segment 4 of the Glut1 glucose transporter

A low resolution model has been proposed for the exofacial conformation of the Glut1 glucose transporter in which eight transmembrane segments form an inner helical bundle stabilized by four outer helices. The role of transmembrane segment 4, predicted to be an inner helix in this structural model, was investigated by cysteine-scanning mutagenesis in conjunction with the substituted cysteine accessibility method using the membrane-impermeant, sulfhydryl-specific reagent, p-chloromercuribenzenesulfonate (pCMBS). A functional, cysteine-less, parental Glut1 molecule was used to produce 21 Glut1 point mutants by individually changing each residue along transmembrane helix 4 to a cysteine. The single cysteine mutants were then expressed in Xenopus oocytes, and their expression levels, transport activities, and sensitivities to pCMBS were determined. In striking contrast to all of the other seven predicted inner helices, none of the 21 helix 4 single-cysteine mutants was demonstrably inhibited by pCMBS. However, cysteine substitution within helix 4 resulted in an unusually high number of severely transport-defective mutants. The low absolute transport activities of two of these mutants (G130C and G134C) were due to their extremely low levels of expression, presumably a result of structural instability and consequent degradation in oocytes, suggesting that these two residues play an important role in maintaining the native structure of Glut1. The other two transport-defective mutants (Y143C and E146C) exhibited low specific transport activities, implying that these two residues play an important role in the transport cycle. Based on these data, we conclude that the exoplasmic end of helix 4 lies outside the inner helical bundle in the exofacial configuration of Glut1.