Explore the vast range of titles available.

The myelin sheath is a tightly packed multilayered membrane structure insulating selected axons in the central and the peripheral nervous systems. Myelin is a biochemically unique membrane, containing a specific set of proteins. In this study, we expressed and purified recombinant human myelin P2 protein and determined its crystal structure to a resolution of 1.85 A. A fatty acid molecule, modeled as palmitate based on the electron density, was bound inside the barrel-shaped protein. Solution studies using synchrotron radiation indicate that the crystal structure is similar to the structure of the protein in solution. Docking experiments using the high-resolution crystal structure identified cholesterol, one of the most abundant lipids in myelin, as a possible ligand for P2, a hypothesis that was proven by fluorescence spectroscopy. In addition, electrostatic potential surface calculations supported a structural role for P2 inside the myelin membrane. The potential membrane-binding properties of P2 and a peptide derived from its N terminus were studied. Our results provide an enhanced view into the structure and function of the P2 protein from human myelin, which is able to bind both monomeric lipids inside its cavity and membrane surfaces.

Accumulation of prion protein (PrPSc) in the central nervous system is the hallmark of transmissible spongiform encephalopathies. However, in some of these diseases such as scrapie or chronic wasting disease, the PrPSc can also accumulate in other tissues, particularly in the lymphoreticular system. In recent years, PrPSc in organs other than nervous and lymphoid have been described, suggesting that distribution of this protein in affected individuals may be much larger than previously thought. In the present study, 11 non-nervous/non-lymphoid organs from 16 naturally scrapie infected sheep in advanced stages of the disease were examined for the presence of PrPSc. Fourteen infected sheep were of the ARQ/ARQ PRNP genotype and 2 of the VRQ/VRQ, where the letters A, R, Q, and V represent the codes for amino-acids alanine, arginine, glutamine and valine, respectively. Adrenal gland, pancreas, heart, skin, urinary bladder and mammary gland were positive for PrPSc by immunohistochemistry and IDEXX HerdChek scrapie/BSE Antigen EIA Test in at least one animal. Lung, liver, kidney and skeletal muscle exhibited PrPSc deposits by immunohistochemistry only. To our knowledge, this is the first report regarding the presence of PrPSc in the heart, pancreas and urinary bladder in naturally acquired scrapie infections. In some other organs examined, in which PrPSc had been previously detected, PrPSc immunolabeling was observed to be associated with new structures within those organs. The results of the present study illustrate a wide dissemination of PrPSc in both ARQ/ARQ and VRQ/VRQ infected sheep, even when the involvement of the lymphoreticular system is scarce or absent, thus highlighting the role of the peripheral nervous system in the spread of PrPSc.

Membrane excitability in different tissues is due, in large part, to the selective expression of distinct genes encoding the voltage-dependent sodium channel. Although the predominant sodium channels in brain, skeletal muscle, and cardiac muscle have been identified, the major sodium channel types responsible for excitability within the peripheral nervous system have remained elusive. We now describe the deduced primary structure of a sodium channel, peripheral nerve type 1 (PN1), which is expressed at high levels throughout the peripheral nervous system and is targeted to nerve terminals of cultured dorsal root ganglion neurons. Studies using cultured PC12 cells indicate that both expression and targeting of PN1 is induced by treatment of the cells with nerve growth factor. The preferential localization suggests that the PN1 sodium channel plays a specific role in nerve excitability.

To establish a standard for genotype/phenotype studies on the myelin of zebrafish (Danio rerio), an organism increasingly popular as a model system for vertebrates, we have initiated a detailed characterization of the structure and biochemical composition of its myelinated central and peripheral nervous system (CNS; PNS) tissues. Myelin periods, determined by X-ray diffraction from whole, unfixed optic and lateral line nerves, were approximately 153 and approximately 162 Angstrom, respectively. In contrast with the lability of PNS myelin in higher vertebrates, zebrafish lateral line nerve myelin exhibited structural stability when exposed to substantial changes in pH and ionic strength. Neither optic nor lateral line nerves showed swelling at the cytoplasmic apposition in CaCl(2)-containing Ringer's solution, in contrast with nerves from other teleost and elasmobranch fishes. Zebrafish optic nerve showed greater stability against changes in NaCl and CaCl(2) than lateral line nerve. The nerves from zebrafish having mutations in the gene for myelin basic protein (mbpAla2Thr and mbpAsp25Val) showed similar myelin periods as the wildtype (WT), but gave approximately 20% less compact myelin. Analysis of proteins by SDS-PAGE and Western blotting identified in both CNS and PNS of WT zebrafish two orthologues of myelin P0 glycoprotein that have been characterized extensively in trout--intermediate protein 1 (24 kDa) and intermediate protein 2 (28 kDa). Treatment with endoglycosidase-F demonstrated a carbohydrate moiety of approximately 7 kDa, which is nearly threefold larger than for higher vertebrates. Thin-layer chromatography for lipids revealed a similar composition as for other teleosts. Taken together, these data will serve as a baseline for detecting changes in the structure and/or amount of myelin resulting from mutations in myelin-related genes or from exogenous, potentially cytotoxic compounds that could affect myelin formation or stability.

Polyclonal antisera against two related command neuropeptides (CNP2 and CNP4) described in neurons of the terrestrial snail Helix were used in a study of the nervous system of the earthworm Lumbricus. The CNP-like peptides belong to the same neuropeptide subfamily and bear a C-terminal signature sequence Tyr-Pro-Arg-X. The distribution patterns of immunoreactive (IR) neurons were studied in the central nervous system (CNS), skin, and stomatogastric nervous system of the earthworm. IR neurons were found in all CNS ganglia, the patterns being similar for both antibodies used. Several clusters of IR cells were observed in the cerebral and subesophageal ganglia. In the ventral cord ganglia, the number of IR cells decreased in the rostro-caudal direction, and the IR cells sent their fibers mostly into the median fiber bundle. Segmental nerves contained no IR fibers. After injury of the worm body, the number of IR neurons in the CNS significantly increased. In the skin, IR sensory neurons were present in sensory buds. The stomatogastric ganglia only contained IR fibers. Numerous scattered IR neurons were found in the inner subepithelial layer of the esophagus and formed the enteric plexus in which the cell bodies displayed a segmentally repeated pattern. Possible involvement of CNP-like-IR neurons in central integratory processes, sensory processes, and the regulation of feeding is discussed.

Myelin, the insulating sheath made by extensive plasma membrane wrapping, is dependent on the presence of highly adhesive molecules that keep the two sides of the membrane in tight contact. The Po glycoprotein (Po) is the major component of the peripheral nervous system (PNS) myelin of mammals. The exact role that Po protein has played in the evolution of myelin is still unclear, but several phylogenetic observations suggest that it is a crucial component in the development of myelin as a multi-lamellar membrane structure. Sharks, which appeared in the fossil record about 400 million years ago, are the first fully myelinated organisms. In this study we investigated the expression pattern of shark myelin Po to suggest a way it might have played a role in the evolution of myelin in the central nervous system. We found that sharks have more than two isoforms (32, 28 and 25 kD), and that some of these might not be fully functional because they lack the domains known for Po homophilic adhesion.

A summary is provided of the available data on the composition of gangliosides and glycosphingolipids in the peripheral nervous system (PNS) including myelins and their antigenic properties. The composition of gangliosides and glycosphingolipids in the PNS is very different from that in the central nervous system (CNS), both quantitatively and qualitatively. One major difference is the abundance of neolacto-series gangliosides in the PNS, with the backbone structure Gal beta 1-4GlcNAc beta1-3Gal beta 1-4Glc1-1'Cer. Their abundance contrasts with the abundance of ganglio-series gangliosides in the CNS. The neolacto-series gangliosides are localized mainly in the myelins of the PNS. In addition to gangliosides, other acidic and neutral glycosphingolipids in the neolactoseries are also characteristic of the myelins of the PNS. The ceramide (fatty acid and sphingosine base) compositions of gangliosides in the PNS are different from those in the CNS gangliosides, having greater percentages of long-chain fatty acids and dehydrosphingosines than found in the CNS gangliosides.

Background: A small number of malignant peripheral nerve sheath tumours (MPNSTs) are low grade, and the nature of these low grade tumours has never been systematically assessed. Aims: To describe the clinicopathological, immunohistochemical, and ultrastructural features of low grade MPNST and to discuss the main differential diagnoses. Methods: Four cases of low grade MPNST were studied, including one coexistent with neurofibromatosis type 1. The tumours were analysed with respect to nuclear atypia, cellularity, nuclear enlargement, hyperchromasia, mitotic rate, and necrosis. Immunohistochemistry was performed by standard techniques, and an ultrastructural study was performed on one tumour. Results: The ages of the patients ranged from 32 to 72 years (mean, 58). Two were male and two were female. Three tumours occurred in the deep tissue, including one in the retroperitoneum, and one was located in the dermal and subcutaneous tissue. The maximum diameters of the tumours ranged from 3.5 to 8.0 cm. Microscopically, all tumours showed moderate hypercellularity, an increased nuclear to cytoplasmic ratio, and hyperchromasia, but exhibited varied growth patterns, including those that were atypical neurofibroma-like, low grade fibromyxoid sarcoma-like, low grade epithelioid, and haemangiopericytoma-like. All tumours showed immunoreactivity for S-100 protein and vimentin. Conclusions: These findings suggest that careful clinical and histological evaluation, along with S-100 protein immunostaining, are essential for the accurate diagnosis of low grade MPNST.

The expression of Bcl-2, Bcl-X, Mcl-1, and Bax was examined by immunohistochemical methods in 93 tumors of nervous system origin, including 49 gliomas (30 astrocytomas and 19 glioblastoma multiforme (GMs)), 16 medulloblastomas (MBs), 19 neuroblastomas (NBs; 9 undifferentiated and 10 differentiated), and 9 miscellaneous neuroectodermal neoplasms. Among the 49 gliomas, immunopositivity (defined as > or = 10%) was observed for Bcl-2 in 45 (92%), Bcl-X in 48 (98%), Mcl-1 in 49 (100%), and Bax in 48 (98%) of 49 specimens. In 11 (37%) of 30 astrocytomas (WHO grades I to III), the tumor specimens were composed predominantly of malignant cells with strong-intensity Bcl-2 immunostaining, whereas none of the 19 GMs (WHO grade IV) exhibited strong-intensity Bcl-2 immunoreactivity (P = 0.001). Similarly, Mcl-1 immunointensity was strong in 15 (50%) of 30 astrocytomas, compared with only 2 (11%) of 19 GMs (P = 0.005). The percentage of Mcl-1-immunopositive tumor cells was also higher in astrocytomas than GMs (P < 0.002). Thus, contrary to a priori expectations, the expression of the anti-apoptotic proteins Bcl-2 and Mcl-1 was significantly higher in astrocytomas than in GMs. Of the 16 MBs, immunopositivity was found for Bcl-2 in 4 (25%), Bcl-X in 9 (56%), Mcl-1 in 8 (50%), and Bax in 16 (100%) of the cases. The intensity of immunostaining was strong for Bcl-2 in only 1 (6%) specimen, for Bcl-X in 3 (19%), and for Mcl-1 in 2 (12.5%), in contrast to Bax immunostaining, which was strong in 12 (75%) tumors. Significantly higher percentages of Bax-immunopositive tumor cells were also found in MBs, compared with Bcl-2, Bcl-X, and Mcl-1 (P < 0.0001). All 19 NBs were immunopositive for Bcl-2, Bcl-X, Mcl-1, and Bax. Higher percentages of Bcl-X- and Mcl-1-immunopositive tumor cells were observed in well differentiated tumors (P = 0.04 and 0.004, respectively). The intensity of Mcl-1 immunostaining was also generally higher in differentiated than undifferentiated NBs (strong immunointensity in 7 of 10 versus 0 of 9; P = 0.002). Conversely, strong-intensity Bax immunostaining was associated with undifferentiated histology (5 of 9 (56%) versus 1 of 10 (10%); P = 0.03). Taken together, these findings begin to delineate trends in the regulation of the relative levels of the Bcl-2 family proteins, Bcl-2, Bcl-X, Mcl-1, and Bax in gliomas, MBs, NBs, and some of their histological subtypes. The suggestion that expression of some of these Bcl-2 family genes may be differentially regulated in association with tumor progression and differentiation provides insights into the diverse biology and clinical behavior of these tumors of nervous system origin.