Protocol of a prospective study on the diagnostic value of transcranial duplex scanning of the substantia nigra in patients with parkinsonian symptoms

Background  

Parkinson's disease (PD) is the second most common neurodegenerative disorder. As there is no definitive diagnostic test, its diagnosis is based on clinical criteria. Recently transcranial duplex scanning (TCD) of the substantia nigra in the brainstem has been proposed as an instrument to diagnose PD. We and others have found that TCD scanning of substantia nigra duplex is a relatively accurate diagnostic instrument in patients with parkinsonian symptoms. However, all studies on TCD so far have involved well-defined, later-stage PD patients, which will obviously lead to an overestimate of the diagnostic accuracy of TCD.     

Floristic variation and willow carr development within a southwest England wetland

Abstract. Woodland colonization on wetlands is considered to have a detrimental effect on their ecological value, even though detailed analysis of this process is lacking. This paper provides an evaluation of the ecological changes resulting from succession of poor fen (base‐poor mire) to willow wet woodland on Goss Moor NNR in Cornwall, UK. Different ages of willow carr were associated with eight understorey communities. During willow colonization, in the ground flora, there was a progressive decrease in poor fen species and an associated increase in woodland species, which appeared to be related to an increase in canopy cover and therefore shade. The most diverse community was found to be the most recent willow and was dominated by poor fen species. The oldest willow was the second most diverse and was associated with a reduction in poor fen species and an increase in woodland species. Architectural features were used successfully to assess the general condition and structure of willow. Tree height and DBH were identified as useful parameters to accurately assess willow age in the field. The implications of active intervention to remove willow in order to conserve the full range of communities within the hydrosere are discussed.     

Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco

Berkowski, B & Klug, C. 2011: Lucky rugose corals on crinoid stems: unusual examples of subepidermal epizoans from the Devonian of Morocco. Lethaia, Vol. 45, pp. 24–33. In the fossil record, evidence for true epizoans, i.e. living animals inhabiting other living host‐animals, is rather rare. A host reaction is usually needed to proof the syn vivo‐settling of the epizoan. Herein, we provide a first report of such an epizoan biocoenosis from various strata of the Early Devonian of Hamar Laghdad, the world‐renowned Moroccan mud‐mound locality. In this case, solitary rugose corals settled as larvae on crinoid stems, perhaps at a spot where the epidermis was missing for some reason (injury, disease). Both the crinoid and the coral began to grow around each other. By doing so, the affected crinoid columnals formed a swelling, where ultimately only an opening slightly larger than the coral orifice remained. We discuss both macroecological and small‐scale synecological aspects of this biocoenosis. The coral profited from its elevated home because it reached into more rapid currents providing the polyp with more food than at the densely populated seafloor, which was probably covered by a coral‐meadow around the mounds and hydrothermal vents. □Corals, crinoids, Early Devonian, epizoans, Morocco, Rugosa.     

The Human Scavenger Receptor CD36: GLYCOSYLATION STATUS AND ITS ROLE IN TRAFFICKING AND FUNCTION*

Human CD36 is a class B scavenger receptor expressed in a variety of cell types such as macrophage and adipocytes. This plasma membrane glycoprotein has a wide range of ligands including oxidized low density lipoprotein and long chain fatty acids which involves the receptor in diseases such as atherosclerosis and insulin resistance. CD36 is heavily modified post-translationally by N-linked glycosylation, and 10 putative glycosylation sites situated in the large extracellular loop of the protein have been identified; however, their utilization and role in the folding and function of the protein have not been characterized. Using mass spectrometry on purified and peptide N-glycosidase F-deglycosylated CD36 and also by comparing the electrophoretic mobility of different glycosylation site mutants, we have determined that 9 of the 10 sites can be modified by glycosylation. Flow cytometric analysis of the different glycosylation mutants expressed in mammalian cells established that glycosylation is necessary for trafficking to the plasma membrane. Minimally glycosylated mutants that supported trafficking were identified and indicated the importance of carboxyl-terminal sites Asn-247, Asn-321, and Asn-417. However, unlike SRBI, no individual site was found to be essential for proper trafficking of CD36. Surprisingly, these minimally glycosylated mutants appear to be predominantly core-glycosylated, indicating that mature glycosylation is not necessary for surface expression in mammalian cells. The data also show that neither the nature nor the pattern of glycosylation is relevant to binding of modified low density lipoprotein.Human CD36, originally identified in platelets as glycoprotein IV (1), is a class B scavenger receptor localized to the plasma membrane. It is not expressed ubiquitously but is present in a variety of different cells and tissue types including epithelial cells (2), macrophages (3), endothelial cells of the microvasculature (4), and smooth muscle (5). Its function is complex, and its involvement in different disease scenarios, such as cancer (6), atherosclerosis (3, 7, 8), malaria (9), and insulin resistance (10), most likely reflects the interaction of the receptor with a particular ligand in a specific cell type. For example, CD36 expressed in monocytic macrophages functions as a scavenger receptor for the uptake of oxidized LDL² (3, 11). Under certain physiological conditions, this results in the lipid loading of macrophages at the site of tissue damage in the arterial wall, leading to foam cell formation and plaque development, a key early stage in the pathogenesis of atherosclerosis (8, 12). In fat and muscle cells, CD36 plays an essential role in lipid homeostasis by uptake of long chain fatty acids (13). In this case CD36 deficiency has been linked to disorders in lipid metabolism, giving rise to increased incidences of insulin resistance and cardiomyopathies (11, 14, 15).Although much is known about the function of CD36, less is known about its structure. CD36 has no bacterial homologues but is a member of a protein family that also includes the mammalian proteins LIMPII (16), CLA-1 (17), SRBI (18), and the Drosophila proteins Croquemort (19) and emp (20). The sequence of 471 amino acids has two short hydrophobic regions at the carboxyl and amino termini separated by a large hydrophilic region (21); however, the topology of the protein is unclear with both ditopic (22) and type I (23) topological models proposed. Both are consistent in predicting that the large hydrophilic region is extracellular, which is clearly supported by epitope mapping studies (24). The protein is heavily modified post-translationally. The six extracellular cysteines, which are highly conserved within the orthologous CD36 subfamily, have been shown to be linked by disulfide bonds in bovine Cd36 (25), and the remaining four cysteines, two at each terminus, are palmitoylated (26), lending credence to the ditopic topological model.CD36 is also modified by N-linked glycosylation, which accounts for the observation that the protein migrates with an apparent molecular mass of 78–94 kDa on SDS-PAGE (4, 27) despite a theoretical mass for the polypeptide of 53 kDa. N-Linked glycosylation is a common modification of extracellular and secreted proteins, and defects in the glycosylation pathways lead to a wide range of serious diseases known collectively as congenital disorders of glycosylation (28). Glycosylation can be important for correct folding of proteins (29, 30) either by directly inducing and/or stabilizing the tertiary fold of the polypeptide (31) or via an affinity for lectin chaperones such as calnexin or calreticulin (32). Glycosylation has also been shown to be important for the trafficking of certain glycoproteins through affinity for lectin transport machinery (33). The glycosylation status of bovine Cd36 has already been determined with all eight putative sites shown to be glycosylated (34). Human and bovine CD36 are 83% identical (93% when similar residues are included) and share 7 glycosylation sites (human has 10 putative glycosylation sites). In the related mouse SRBI, which is 33% identical (54% similar) to human CD36, there are 11 putative N-linked glycosylation sites, only 3 of which are shared with the human protein. Site-directed mutagenesis of each of the 11 sites independently in SRBI in an otherwise wild type protein indicates that all are glycosylated, with two (Asn-108 and Asn-173) important for either trafficking or folding. Mutagenesis of either of these two residues resulted in very little cell surface expression of the protein (35); however, neither site is conserved in human CD36.To gain further understanding of the role of glycosylation of CD36, we used mutagenesis and biophysical analysis (mass spectrometry and gel electrophoresis) to identify unequivocally which glycosylation sites are occupied in human CD36. Antibody and ligand binding studies with these mutant proteins also provided insights into the role of glycosylation and site occupancy in the trafficking and function of the protein.     

Spindle-E cycling between nuage and cytoplasm is controlled by Qin and PIWI proteins

Transposable elements (TEs) are silenced in germ cells by a mechanism in which PIWI proteins generate and use PIWI-interacting ribonucleic acid (piRNA) to repress expression of TE genes. piRNA biogenesis occurs by an amplification cycle in microscopic organelles called nuage granules, which are localized to the outer face of the nuclear envelope. One cofactor required for amplification is the helicase Spindle-E (Spn-E). We found that the Spn-E protein physically associates with the Tudor domain protein Qin and the PIWI proteins Aubergine (Aub) and Argonaute3 (Ago3). Spn-E and Qin proteins are mutually dependent for their exit from nuage granules, whereas Spn-E and both Aub and Ago3 are mutually dependent for their entry or retention in nuage. The result is a dynamic cycling of Spn-E and its associated factors in and out of nuage granules. This implies that nuage granules can be considered to be hubs for active, mobile, and transient complexes. We suggest that this is in some way coupled with the execution of the piRNA amplification cycle.     

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.