bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational Correlates of the Epitopes of Human Myelin Basic Protein Peptide 80–89
Authors: Whitaker John N. , Moscarello Mario A. , Herman Paula K. , Epand Richard M. , Surewicz Witold K. 
Published: October 2006

AbstractDifferent epitopes residing within the decapeptide of residues 80–89 of human myelin basic protein (MBP) exist in the MBP‐like material detected in human CSF and urine. In the present study, the structure of human MBP peptide 80–89 was examined by a combination of physical measurements and correlated with its varying immunochemical reaction with three polyclonal antisera. At least two epitopes are present in the decapeptide. Progressive shortening and reduction in net negative charge of MBP peptide 80–89 to form peptides 81–89, 82–89, 83–89, and 84–89 revealed an epitope not present in intact MBP. Circular dichroism and Fourier‐transform infrared of these MBP peptides in water demonstrated random structure that was partially changed to β‐structure in the shorter peptides. In methanol, used as a model for a lipid environment, the random structure was diminished and was replaced by α‐helix and β‐structure, especially in the shorter peptides. The findings indicate that the range of epitopes present in this decapeptide is influenced by conformation, which, unexpectedly, becomes progressively less random as the peptide becomes smaller, especially in a hydrophobic environment. This behavior has implications for the immunochemical detection of small antigens or antibodies to them in tissue extracts or body fluids.
Sulfated Glucuronyl Paragloboside in Rat Brain Microvessels
Authors: Miyatani Nobuyuki , Kohriyama Tatsuo , Maeda Yasuhiro , Yu Robert K. 
Published: October 2006

AbstractIn patients with neuropathy associated with para‐proteinemia, there are monoclonal immunoglobulin M antibodies reacting with myelin‐associated glycoprotein and sulfated glucuronyl glycolipids. There are indications that the monoclonal antibodies may be responsible for these neuropathies. However, the mechanism by which the antibodies gain access to the nervous tissue, which is separated by the blood‐brain barrier or blood‐nerve barrier, is still unknown. In this study, we examined the presence of the sulfated glucuronyl glycolipid antigens on brain endothelial cells. Micro‐vessels were isolated from adult Lewis rat brain cortex. Sulfated glucuronyl paragloboside (SGPG) was detected in the acidic lipid fraction by a TLC immunostaining method. Immunofluorescence studies showed positive staining on the surface of microvessels. In addition, SGPG could be detected in the cultured endothelial cells of human umbilical vein. These findings suggest that the endothelial cells contain an‐tigenic sites for interaction with the autoantibodies. This type of interaction may result in damages to the endothelial cell function and may be responsible for changes in the blood‐brain barrier permeability and the ensuing penetration of large molecules, such as immunoglobulins, into the endo‐neurial space.
Variability in the Structural Requirements for Binding of Human Monoclonal Anti‐Myelin‐Associated Glycoprotein Immunoglobulin M Antibodies and HNK‐1 to Sphingoglycolipid Antigens
Authors: Ilyas Amjad A. , Chou Denise K. H. , Jungalwala Firoze B. , Costello Catherine , Quarles Richard H. 
Published: October 2006

AbstractA high proportion of patients with neuropathy have immunoglobulin M (IgM) paraproteins that react with carbohydrate determinants on the myelin‐associated glycoprotein (MAG) and two sphingoglycolipids, 3‐sulfoglucuronyl paragloboside (SGPG) and 3‐sulfoglucuronyl lactosaminyl paragloboside. In order to characterize the fine specificities of these human antibodies further, the binding of 10 anti‐MAG paraproteins to several chemically modified derivatives of SGPG was compared with the binding to intact SGPG by both TLC‐overlay and enzyme‐linked immunosorbent assay. The following derivatives were tested: the desulfated lipid, glucuronyl paragloboside (GPG); the methyl ester of GPG (MeGPG); the methyl ester of SGPG, 3‐sulfomethylglucuronyl paragloboside (SMeGPG); and 3‐sulfoglucosyl paragloboside (SGlcPG) produced by reduction of the carboxyl group of the glucuronic acid with sodium borohydride. All 10 IgM paraproteins and the related mouse IgM antibody, HNK‐1, reacted most strongly with intact SGPG, but variations in the reactivity with the derivatives revealed striking differences in the structural requirements for binding between the antibodies. Five distinct patterns of reactivity were observed: (a) three of the human antibodies and HNK‐1 exhibited partial reactivity with the sulfated derivatives, SMeGPG and SGlcPG, but not with GPG or MeGPG, indicating an absolute requirement for the sulfate group; (b) two of the human antibodies reacted only with GPG, demonstrating a requirement for the free carboxyl group on the glucuronic acid; (c) three of the antibodies bound to SMeGPG, SGlcPG, and GPG, but not to MeGPG, suggesting that at least one negative charge was needed for binding; (d) one antibody bound to SMeGPG and GPG, but not to SGlcPG or MeGPG, suggesting that both the carbonyl group and at least one negative charge were required; and (e) another antibody bound to MeGPG, SMeGPG, and SGlcPG, but not to GPG, a pattern that is difficult to explain simply based on the chemical structures. Interestingly, only those antibodies that exhibited reactivity with GPG bound to a third, minor, unidentified glycolipid of normal peripheral nerve that chromatographs faster than SGPG. The results clearly demonstrate heterogeneity in the fine specificities of the anti‐MAG antibodies that may affect their pathogenic properties.
Characterization of Opioid Receptors in Cultured Neurons
Authors: Vaysse Pierre J.‐J. , Zukin R. Suzanne , Fields Kay L. , Kessler John A. 
Published: October 2006

AbstractThe appearance of μ‐, δ‐, and k‐opioid receptors was examined in primary cultures of embryonic rat brain. Membranes prepared from striatal, hippocampal, and hypothalamic neurons grown in dissociated cell culture each exhibited high‐affinity opioid binding sites as determined by equilibrium binding of the universal opioid ligand (‐)‐[3H]bremazocine. The highest density of binding sites (per mg of protein) was found in membranes prepared from cultured striatal neurons (Bmax= 210 ± 40 fmol/mg protein); this density is approximately two‐thirds that of adult striatal membranes. By contrast, membranes of cultured cerebellar neurons and cultured astrocytes were devoid of opioid binding sites. The opioid receptor types expressed in cultured striatal neurons were characterized by equilibrium binding of highly selective radioligands. Scatchard analysis of binding of the μ‐specific ligand [3H]D‐Ala2,N‐Me‐Phe4,Gly‐ol5‐enkephalin to embryonic striatal cell membranes revealed an apparent single class of sites with an affinity (KD) of 0.4 ± 0.1 nM and a density (Bmax) of 160 ± 20 fmol/mg of protein. Specific binding of (‐)‐[3H]bremazocine under conditions in which μ‐ and δ‐receptor binding was suppressed (k‐receptor labeling conditions) occurred to an apparent single class of sites (KD= 2 ± 1 nM;Bmax= 40 ± 15 fmol/mg of protein). There was no detectable binding of the selective δ‐ligand [3H]D‐Pen2,d‐Pen5‐enkephalin. Thus, cultured striatal neurons expressed μ‐ and k‐receptor sites at densities comparable to those found in vivo for embryonic rat brain, but not δ‐receptors.
Inositol Metabolism During Neuroblastoma B50 Cell Differentiation: Effects of Differentiating Agents on Inositol Uptake
Authors: Reboulleau Christian P. 
Published: October 2006

AbstractInositol uptake was studied in the rat CNS neuroblastoma B50 cell line. Eadie‐Hofstee analysis of the uptake pattern reveals two defined modes of inositol entry into the cell. The high‐affinity uptake component requires the presence of extracellular sodium and is inhibited by phloridzin. Analysis of the uptake velocities of the high‐affinity uptake component provided the following apparent kinetic parameters: Km= 13.7 μM and Vmax= 14.7 pmol/mg of protein/min (without correcting for residual diffusion) and Km= 12.9 μM and Vmax= 12.3 pmol/mg of protein/min (with correction). At physiological concentrations, the high‐affinity . transport process contributes approximately 70% to total uptake; the remainder is due to a low‐affinity diffusion‐like process. Uptake inhibition studies reveal that the uptake process is sensitive to ouabain, amiloride, and dichlorobenzamil inhibition but relatively insensitive to cytochalasin B or phloretin. When neuroblastoma B50 cells are induced to differentiate morphologically with high extracellular calcium or with dibutyryl cyclic AMP, a significant decrease in inositol uptake is observed. The dibutyrl cyclic AMP‐mediated inhibition of uptake affects only the high‐affinity uptake component and is noncompetitive in nature. The high extracellular calcium‐mediated inhibition is less specific; it involves “disappearance” of the high‐affinity process, some inhibition of the low‐affinity process, and an increase of inositol efflux. The significance of these observations is discussed in the context of neuroblastoma B50 cell differentiation.
Regional Central Nervous System Oligosaccharide Storage in Caprine β‐Mannosidosis
Authors: Boyer Philip J. , Jones Margaret Z. , Rathke Eileen J. S. , Truscott Nancy K. , Lovell Kathryn L. 
Published: October 2006

AbstractGoats affected with β‐mannosidosis, an autosomal recessive disease of glycoprotein metabolism, have deficient activity of the lysosomal enzyme β‐mannosidase along with tissue storage of oligosaccharides, including a trisaccharide [Man(β1–4)GlcNAc(β1–4)GlcNAc] and a disaccharide [Man(β1–4)GlcNAc]. CNS myelin deficiency, with regional variation in severity, is a major pathological characteristic of affected goats. This study was designed to investigate regional CNS differences in oligosaccharide accumulation to assess the extent of correlation between oligosaccharide accumulation and severity of myelin deficits. The concentrations of accumulated disaccharide and trisaccharide and the activity of β‐mannosidase were determined in cerebral hemisphere gray and white matter and in spinal cord from three affected and two control neonatal goats. In affected goats, the content of trisaccharide and disaccharide in spinal cord (moderate myelin deficiency) was similar to or greater than that in cerebral hemispheres (severe myelin deficiency). Thus, greater oligosaccharide accumulation was not associated with more severe myelin deficiency. Regional β‐mannosidase activity levels in control goats were consistent with the affected goat oligosaccharide accumulation pattern. The similarity of trisaccharide and disaccharide content in cerebral hemisphere gray and white matter suggested that lysosomal storage vacuoles, more numerous in gray matter, may not be the only location of stored CNS oligosaccharides.
Role of Endogenous Taurine on the Glutamate Analogue‐Induced Neurotoxicity in the Rat Hippocampus In Vivo
Authors: Menéndez Nieves , Solís Jose María , Herreras Oscar , Herranz Antonio Sánchez , Martín del Río Rafael 
Published: October 2006

AbstractThe glutamate analogues N‐methyl‐d‐aspartate (NMDA), kainic acid (KA), and quisqualic acid (QA), prepared in different hypertonic media, were perfused in vivo in the hippocampal CA1 field of rats using a microdialysis technique. Extracellular taurine levels, estimated after analysis of the taurine content of dialysates, increased during perfusion of all three agonists but varied according to the osmolarity of the medium. The NMDA‐induced increase in extracellular taurine content was only slightly inhibited by perfusion of 150 and 300 mM sucrose. The KA‐evoked increase was partially dependent on extracellular osmolarity, because addition of 50 and 150 mM sucrose caused a dose‐dependent inhibition that was not augmented using higher sucrose concentrations. QA caused a taurine increase that was totally abolished by addition of 50 mM sucrose. These results indicate that the rise in extracellular taurine level elicited by QA and part of the increase elicited by KA are probably due to a release caused by the cellular swelling that these substances evoke, a finding substantiating the previously proposed osmoregulatory role of taurine. However, almost all the increase in extracellular taurine content caused by NMDA and all the osmotically insensitive part of the KA‐evoked rise cannot be explained as release triggered by cell swelling and may reflect a function of taurine other than osmore‐gulation.
Uptake and Storage of Choline by Rat Brain: Influence of Dietary Choline Supplementation
Authors: Klein Jochen , Köppen Andrea , Löffelholz Konrad 
Published: October 2006

AbstractIn order to elucidate the regulation of the levels of free choline in the brain, we investigated the influence of chronic and acute choline administration on choline levels in blood, CSF, and brain of the rat and on net movements of choline into and out of the brain as calculated from the arteriovenous differences of choline across the brain. Dietary choline supplementation led to an increase in plasma choline levels of 50% and to an increase in the net release of choline from the brain as compared to a matched group of animals which were kept on a standard diet and exhibited identical arterial plasma levels. Moreover, the choline concentration in the CSF and brain tissue was doubled. In the same rats, the injection of 60 mg/kg choline chloride did not lead to an additional increase of the brain choline levels, whereas in control animals choline injection caused a significant increase; however, this increase in no case surpassed the levels caused by chronic choline supplementation. The net uptake of choline after acute choline administration was strongly reduced in the high‐choline group (from 418 to 158 nmol/g). Both diet groups metabolized the bulk (>96%) of newly taken up choline rapidly. The results indicate that choline supplementation markedly attenuates the rise of free choline in the brain that is observed after acute choline administration. The rapid metabolic choline clearance was not reduced by dietary choline load. We conclude that the brain is protected from excess choline by rapid metabolism, as well as by adaptive, diet‐induced changes of the net uptake and release of choline.
Enhanced Sensitivity of “Metabotropic” Glutamate Receptors After Induction of Long‐Term Potentiation in Rat Hippocampus
Authors: Aronica E. , Frey U. , Wagner M. , Schroeder H. , Krug M. , Ruthrich H. , Catania M. V. , Nicoletti F. , Reymann K. G. 
Published: October 2006

AbstractStimulation of [3H]inositol monophosphate <[3H]InsP) formation by ibotenate or trans‐1‐aminocyclopentyl‐l, 3‐dicarboxylic acid (t‐ACPD) in rat hippocampal slices was enhanced after tetanic stimulation of die Schaffer collaterals projecting to the CA1 region (in vitro) or the perforant pathway projecting to the dentate gyms (in freely moving animals). This effect was observed 5 h (but not 2 h) after long‐term potentiation (LTP) induction and was abolished if tetanic stimulation was performed in the presence of specific antagonists of N‐methyl‐D‐aspartate receptors. The delayed increase in excitatory amino acid‐induced polyphosphoinositide (PPI) hydrolysis was accompanied by an enhanced responsiveness to norepinephrine, whereas the basal and carbamylcholine‐stimulated [3H]InsP formation were unchanged. These results suggest that an increased activity of „metabotropic” glutamate receptors may contribute to the synaptic mechanisms enabling the late expression and or maintenance of LTP. Accordingly, LTP decayed more rapidly (within 5 h) in rats repeatedly injected with LiCl (60–120 mg/kg, i.p., for 10 days), a treatment that led to a reduced efficacy of ibotenate and norepinephrine in stimulating PPI hydrolysis in hippocampal slices.
Effect of Ethanol on γ‐Aminobutyric Acid and Glycine Receptor‐Coupled Cl− Fluxes in Rat Brain Synaptoneurosomes
Authors: Engblom A. C. , Akerman K. E. O. 
Published: October 2006

AbstractChloride fluxes in Synaptoneurosomes in response to additions of γ‐aminobutyric acid, glycine, and ethanol were measured using a chloride‐sensitive fluorescent probe 6‐methoxy‐N‐(3‐sulfopropyl) quinolinium (SPQ). The C1− gradient was directed outward by bathing cells in a medium low in C1− concentration. The Synaptoneurosomes responded to both γ‐aminobutyric acid and glycine by outflow of C1− ions, as judged from an increase in SPQ fluorescence. These effects were inhibited by picrotoxin and strychnine, respectively. Ethanol also produced an outflow of C1− ions from the Synaptoneurosomes. Both picrotoxin and strychnine inhibited this effect. When the antagonists were used together, the inhibiting effect was additive. These results indicate that ethanol affects both γ‐aminobutyric acid and glycine receptor‐linked chloride fluxes in the rat brain.
Endopeptidase‐24.11, a Cell‐Surface Peptidace of Central Nervous System Neurons, Is Expressed by Schwann Cells in the Pig Peripheral Nervous System
Authors: Kioussi Chrissa , Matsas Rebecca 
Published: October 2006

AbstractEndopeptidase‐24.11 is a 90‐kDa surface glycoprotein with the ability to hydrolyze a variety of biologically active peptides. Interest in this enzyme is based on the consensus that it may play a role in the termination of peptide signals in the central nervous system. In the present study, we have investigated the distribution of endopeptidase‐24.11 in two nerves of the peripheral nervous system of newborn pigs: the sciatic, composed of a mixture of myelinated and nonmyelinated axons, and the cervical sympathetic trunk in which >99% of the axons are nonmyelinated. The endopeptidase was monitored enzymatically, as well as by immunoblotting and immunocytochemistry using mono‐ and polyclonal anti‐endopeptidase antibodies. Endopeptidase‐24.11 was detected in both the sciatic nerve and the cervical sympathetic trunk. Membrane preparations from sciatic nerve hydrolyzed I25I‐insulin B‐chain, and more than 50% of the activity was inhibited by phosphoramidon with an IC50 concentration of 3.2 nM Moreover, a 90‐kDa polypeptide was detected by immunoblotting of sciatic nerve membranes. The type of cells expressing the endopeptidase was determined by immunohistochemistry. In teased nerve preparations, these cells were identified morphologically as myelinand non‐myelin‐forming Schwann cells. Endopeptidase‐24. 11 was also expressed by cultured Schwann cells from sciatic nerve and cervical sympathetic trunk maintained for 3 h in vitro. The presence of endopeptidase‐24.11 on the Schwann cell surface raises the possibility of a potential role for the enzyme in nerve development and/or regeneration.
Effects of Surgical Sympathetic Denervation on myo‐Inositol Trisphosphate Production and Contraction in the Dilator and Sphincter Smooth Muscles of the Rabbit Iris: Evidence for Interaction Between the Cyclic AMP and Calcium Signaling Systems
Authors: Abdel‐Latif Ata A. , Zhang Yawen 
Published: October 2006

AbstractThe effects of norepinephrine (NE), carbachol (CCh), NaF, 3‐isobutyl‐l‐methylxanthine (IBMX), and high K+ concentration (80 mM) depolarization on inositol trisphosphate (IP3) accumulation, cyclic AMP (cAMP) formation, and contraction were investigated in the dilator and sphincter smooth muscles of the sympathetically denervated as well as the normal rabbit eye. (a) In the denervated dilator muscle, NE‐stimulated IP3 production and contraction are enhanced, (b) In the sphincter muscle of rabbits that have undergone sympathetic denervation, CCh‐stimulated IP3 production and contraction are attenuated, (c) The increase in tension by a maximal effective dose of NaF (20 mM) in the dilator was 12.5 and 18 mg of tension/mg wet weight in normal and denervated tissue, respectively, and in the sphincter was 33.8 and 15.2 mg of tension/mg wet weight in normal and denervated tissue, respectively. NaF had no effect on cAMP formation, (d) Addition of NE had no effect on cAMP formation in both the normal and denervated dilator, whereas basal and IBMX‐induced cAMP formation increased in the denervated sphincter over that of the normal tissue by 15 and 60%, respectively, (e) Isoproterenol (5 μM) increased cAMP formation in the normal and denervated sphincter by 47 and 91%, respectively, (f) Whereas CCh inhibits cAMP formation in the normal sphincter, it lost its inhibitory effect in the sphincter with denervation. (g) IBMX (0.1 mM) attenuated the CCh‐stimulated IP3 production and contraction of the sphincter by ∼30% of their respective controls, (h) High K+ concentration depolarization attenuated contraction in both dilator and sphincter muscles with denervation. These observations suggest that an increase in the level of cAMP in the iris sphincter due to sympathetic denervation could lead to inhibition of phospholipase C (or other target sites, such as phosphorylation of the muscarinic receptor, Gp protein itself, myosin light chain kinase, or the IP3 receptor), IP3 production, and contraction. In conclusion, we suggest that the supersensitivity and subsensitivity observed after surgical sympathetic denervation of the iris dilator and sphincter muscles, respectively, are causal by alterations in the efficiency of coupling, probably through the Gp proteins, between their respective receptors and the breakdown of polyphosphoinositides by phospholipase C. In addition, we propose that the sympathetic nervous system can regulate, through alterations in cAMP levels, the muscarinic stimulation of IP3 accumulation and contraction in the iris sphincter. These findings add further support to tie hypothesis that there are reciprocal interactions between the cAMP and IP3‐Ca2+ signaling systems and the contractile response in the iris smooth muscle.