bluuebunny/crossref_metadata_2025_split huggingface dataset:
AXONAL TRANSPORT OF PHOSPHOLIPIDS IN RAT VISUAL SYSTEM1
Authors: Toews Arrel D. , Goodrum Jeffry F. , Morell Pierre 
Published: October 2006

Abstract— Seventeen day old rats were injected intraocularly with a phospholipid precursor, [32P]phosphate, and a glycoprotein precursor, [3H]fucose. Animals were killed between 1 h and 21 days later, and structures of the visual pathway (retina, optic nerve, optic tract, lateral geniculate body, and superior colliculus) were dissected. Radioactivity in phospholipids ([32P] in solvent‐extracted material) and in glycoproteins ([3H] in solvent‐extracted residue) was determined. Incorporation of [3H]fucose into retinal glycoproteins peaked at 6–8 h. Labelled glycoproteins were present in superior colliculus by 2h after injection, indicating a rapid rate of transport; maximal labelling was at 8–10 h after injection. Incorporation of [32P]phosphate into retinal phospholipids peaked at 1 day after injection. Phospholipids were also rapidly transported since label was present in the superior colliculus by 3 h after injection: however, maximal labelling did not occur until 5–6 days. These results indicate that newly synthesized phospholipids enter a preexisting pool, part of which is later committed to transport at a rapid rate.Transported phospholipids were catabolized at the nerve endings with a maximum half‐life of several days; there was minimal recycling of precursor label.Lipids were fractionated by thin‐layer chromatography, and radioactivity in individual phospholipid classes determined. Choline and ethanolamine phosphoglycerides were the major transported phospholipids, together accounting for approx 85% of the total transported lipid radioactivity. At early time points, the ratio of radioactivity in choline phosphoglycerides to that in ethanolamine phosphoglycerides increased in structures progressively removed from the site of synthesis (retina) but by 2 days approached a constant value. In each structure, choline phosphoglyceride‐ethanolamine phosphoglyceride radioactivity ratios decreased with time, rapidly at first, but plateaued by 2 days. These results indicate that choline phosphoglycerides are committed to transport sooner than ethanolamine phosphoglycerides.Some experiments were also conducted using [2‐3H]glycerol as a phospholipid precursor. Results concerning incorporation of this precursor into individual phospholipid classes and their subsequent axonal transport were comparable to those obtained using [32P]phosphate, with the following exceptions: (a) incorporation of [2‐3H]glycerol into retinal phospholipids was relatively rapid (near‐maximal levels at 1 h after injection) although transport to the superior colliculus showed an extended time course very similar to [32P]‐labelled lipids; (b) [2‐3H]glycerol was somewhat less efficient than [32P]phosphate in labelling lipids committed to transport relative to labelling those which remained in the retina; and (c) [2‐3H]glycerol did not label plasmalogens.
EFFECTS OF X‐IRRADIATION INDUCED LOSS OF CEREBELLAR GRANULE CELLS ON THE SYNAPTOSOMAL LEVELS AND THE HIGH AFFINITY UPTAKE OF AMINO ACIDS1
Authors: Rohde B. H. , Rea M. A. , Simon J. R. , McBride W. J. 
Published: October 2006

Abstract— Crude synaptosomal (P2) preparations were obtained from the cerebella of rats in which the granule cell population had been selectively reduced by X‐irradiation treatment and from the cerebella of control animals. In the P2 fraction from control cerebella, the level of glutamate was greater than any other of the 5 amino acids measured and was 2‐fold higher than taurine, which was present at the next highest level. The content of taurine was slightly higher than that found for aspartate and was 3‐fold greater than that observed for GABA. Alanine and glycine were present in the lowest amounts. The levels of glutamate and aspartate were significantly (P < 0.05) lower by 25 and 15%, respectively, in the P2 fraction isolated from the X‐irradiated cerebella in comparison to control values. The content of taurine, GABA, glycine, and alanine were not changed by the X‐irradiation treatment. The uptake of 1.0 μm‐l‐[3H]glutamate and l‐[3H]aspartate was reduced approx 20% by X‐irradiation treatment, whereas the uptake of 1.0 μm‐[3H]GABA and [3H]taurine was unchanged. A more detailed kinetic analysis of l‐[3H]glutamate uptake revealed there was a 20% decrease in the Vmax value with X‐irradiation treatment and no change in the apparent Km value.In a second study, the uptake of l‐[3H]glutamate, l‐[3H]aspartate and [3H]GABA was measured using P2 fractions obtained from the cerebella of rats in which the population of granule, stellate and basket cells had been reduced by X‐irradiation treatment. The uptake of 1.0μm‐l‐[3H]glutamate, l‐[3H]aspartate and [3H]GABA was significantly (P < 0.05) reduced to 57, 68, and 59%, respectively, of control values. A more detailed kinetic analysis of [3H]GABA uptake revealed no significant change in the apparent Km and a 35% decrease in the Vmax value.The data are discussed in terms of glutamate being the excitatory neurotransmitter released from granule cells and GABA being the inhibitory neurotransmitter released from basket cells.
IN VITRO SYNTHESIS OF THE MYELIN BASIC PROTEINS IN THE DEVELOPING MOUSE BRAIN: PROPERTIES OF A HOMOGENATE SYSTEM
Authors: Carey Gregory D. , Campagnoni Anthony T. 
Published: October 2006

Abstract—An in vitro system using mouse brain homogenates has been developed to study the synthesis of the myelin basic proteins. Incorporation of [3H]leucine into protein in this system did not require additional energy sources. The system was slightly stimulated by glucose and strongly inhibited by puromycin. Myelin basic proteins were isolated from incubation mixtures by conventional techniques of solvent extraction and column chromatography, and finally separated into the large and small components by polyacrylamide gel electrophoresis in an acetic acid‐urea system. Gels were stained, sliced, dissolved, and counted, and relative rates of incorporation of label into the two basic proteins were determined at several ages. The ratio of radioactivity incorporated into the small (S) and large (L) basic proteins, over a 30 min incubation period, was found to increase from 0.97 at 10 days to 1.59 at 21 days and decline thereafter.These data generally agree with earlier studies on the in vivo synthesis of the myelin basic proteins in mice. An interesting feature of the time course was that incorporation of [3H]leucine into the purified myelin basic proteins relative to incorporation into total protein in the homogenate increased almost 2‐fold during the course of the 30‐min incubation. This suggested that post‐translational processing of at least one of the two basic proteins was occurring. To examine this possibility further, experiments were conducted in which incorporation was allowed to proceed for 2–5 min, before being inhibited with puromycin; the incubation was then continued for up to 25 min longer. Although total incorporation was inhibited immediately after puromycin addition, label was found to continue to accumulate in the basic proteins to the extent of 30–100% above controls. These data support the notion that the MBPs are synthesized as precursors and then processed to yield authentic myelin basic proteins and that this processing can occur in vitro.
RESOLUTION OF BRAIN TROPONIN COMPLEX
Authors: Mahendran C. , Berl S. 
Published: October 2006

AbstractAffinity chromatography was used to partially purify the troponin complex from crude regulatory proteins obtained from bovine brain cortex. Three components were obtained from this partially purified troponin complex by treatment with 6 M‐urea and 1 mM‐EGTA followed by chromatography on DEAE‐Sephadex‐A50. The effects of the three components on skeletal muscle actin activated MgATPase activity of muscle myosin (ATP phosphohydrolase, EC 3.6.1.3.) suggested that they were analogous to that of the skeletal muscle troponins I, C, and T. The apparent molecular weights of the brain troponin subunits (I, C, and T) were 18, 700, 14, 000 and 36, 400, respectively. The molecular weights of the former two proteins were less than those reported for the analogous skeletal muscle troponins. Thus, brain actomyosin complex may be regulated in a manner similar to that of striated muscle actomyosin.
EFFECT OF TEMPERATURE AND IONOPHORES ON THE PERMEABILITY OF SYNAPTOSOMES
Authors: CARVALHO C. A. M. , CARVALHO A. P. 
Published: October 2006

AbstractSynaptosomes swell rapidly in isosmotic solutions of glycerol or urea, but the swelling in solutions of larger non‐electrolytes, such as erythritol, glucose or sucrose is slower. The permeability of synaptosomes to non‐electrolytes is temperature dependent, and the low activation energies for the permeation of urea (13 kcal/mol) and erythritol (9.5 kcal/mol) indicate that the penetration of non‐electrolytes into the synaptosomes does not imply complete dehydration of the molecules.The relative permeability of synaptosomes to cations, as measured by the rate of swelling in isosmotic solutions of acetate salts is in the order: NH+4 > Na+ > Li+ > K+ > Ca2+. The ionophores, X‐537A and nigericin, or valinomycin + FCCP, which promote exchange of cations for H+, cause swelling of synaptosomes in solutions of potassium salts of acetate or propionate, but not in KCI, whereas H+ release is higher in KCI medium. This suggests that the organic unions cross the membrane after combining with H+ to form the respective weak acids. The relative permeability to anions is in the order: acetate ≃ propionate > Cl− > SO2‐4≃ maleate ≃ succinate.The energies of activation for the permeability of synaptosomes to potassium acetate in the presence of X‐537A or gramicidin D are 13 kcal/mol and 7.5 kcal/mol, respectively, which reflects different mechanisms of action for the two ionophores in the membranes.
Characterization of Corticosterone‐Induced Protein Synthesis in Hippocampal Slices
Authors: Etgen Anne M. , Martin Michelle , Gilbert Russell , Lynch Gary 
Published: October 2006

Abstract: Corticosterone significantly increases the incorporation of [3H]leucine into specific cytosol protein(s) isolated from in vitro hippocampal slices prepared from adult male albino rats. The present study showed that in slices coincubated with glucocorticoid plus a protein synthesis inhibitor (1 mm‐cycloheximide), no such enhancement of amino acid incorporation was observed, suggesting that the hormone acts in the hippocampus to increase de novo protein synthesis. Further experiments demonstrated that the steroid‐induced protein synthesis was first detectable (+ 5.7%) following a 30‐min exposure of slices to corticosterone; slices incubated for 1 or 2 h both showed a 12% increase in synthesis of the affected protein(s) when compared with controls. In an attempt to determine whether the glucocorticoid alteration of protein metabolism was receptor‐mediated, hippocampal slices were also incubated with 10 nm‐progesterone, a steroid known to compete for corticosterone binding to its cytosol receptor. Progesterone alone, which does not translocate cytoplasmic receptors to the nucleus, did not alter hippocampal protein metabolism and effectively blocked the induction by corticosterone of the 54K protein(s). These studies provide evidence that in the rat hippocampus corticosterone interacts with high‐affinity steroid receptors to regulate the synthesis of specific protein(s).
Catecholamine Concentration in the Developing Rat Brain after γ‐Hydroxybutyric Acid
Authors: Lundborg P. , Hedner T. , Engel J. 
Published: October 2006

AbstractThe effect of the GABA receptor agonist γ‐hydroxybutyric acid (GHBA) on brain catecholamine concentration was investigated in 1 to 28 day old rats. The infant rats were given GHBA in various doses (375–1500 mg/kg) and the effects on whole brain or regional brain concentration of dopamine (DA) and noradrenaline (NA) were measured. Brain DA concentration increased in a dose‐dependent way already from two days of postnatal age. In the regional brain study of the 14‐ and 28‐day‐old animals the increase in DA concentration was found to be almost exclusively located in the striatal region. Generally, no changes in NA concentration were found in the whole brain or various brain regions at any of the ages after GHBA. It is concluded that the inhibitory striatal‐nigral neurons, utilizing GABA as a transmitter, are functionally developed during early postnatal age.
Studies on the Mechanism of Action of Avermectin B1a: Stimulation of Release of γ‐Aminobutyric Acid from Brain Synaptosomes
Authors: Pong Sheng‐Shung , Wang Ching C. , Fritz Lawrence C. 
Published: October 2006

Abstract:Avermectin B1a, a novel macrocyclic lactone antiparasitic agent, causes a marked and sustained increase of γ‐aminobutyric acid release from rat brain synaptosomes. A concentration of 8‐10 μM of avermectin B1a produced the maximal effect (310 ± 30% of the control), while the half‐maximal level was achieved at 2‐3 μM. The drug also stimulated γ‐aminobutyric acid release (251 ± 11% of the basal level) from synaptosomes in calcium‐free medium, which was 28 ± 4% lower than that in the 1.8 mm‐Ca2+ medium. The compound did not, however, affect the synaptosomal release of glutamate. At the lobster neuromuscular junction, avermectin B1a reduced the input resistance of muscle fibers in control Ringer's solution as well as in Ringer's solution in which Co2+ was substituted for Ca2+. This observation is in accord with the Ca2+ independent stimulation of γ‐aminobutyric acid release seen with synaptosomes. A good correlation between antiparasitic activity and γ‐aminobutyric acid‐releasing activity has been found among various derivatives of avermectin B1a, which suggests that the ability of the drug to release this neurotransmitter may be the basis of its antiparasitic action.
The Sequential Alterations of Endoneurial Cholesterol and Fatty Acid in Wallerian Degeneration and Regeneration
Authors: Yao Jeffrey K. , Natarajan V. , Dyck Peter James 
Published: October 2006

Abstract:The endoneurial nonpolar lipids were serially examined throughout Wallerian degeneration and regeneration. Following nerve crush in the rat, the endoneurial content of cholesterol falls and cholesteryl ester content rises dramatically. The maximal alteration of this ratio corresponds reasonably well with events of myelin ovoid dissolution to sudanophilic amorphous lipids. Thereafter, as regenerative events overshadow degenerative events the ratio is slowly restored toward normal. The increased cholesteryl esters are probably synthesized within endoneurium from free fatty acids which become available when myelin is degraded. The endoneurial free fatty acid content presumably represents the net effect of phospholipid degradation, cholesterol esterification, cholesteryl ester hydrolysis, and fascicular entry and exit. Free fatty acids become significantly elevated by 12 days, probably reach a peak between 16 and 60 days, and thereafter return to normal with fiber regeneration. The fatty acid composition of cholesteryl esters from crushed nerves is markedly different from those of normal sciatic nerves. The altered fatty acid composition of cholesteryl esters from myelin suggests that both synthesis and hydrolysis exhibit substrate specificity toward chain length and unsaturation, with oleate being the most favored substrate.
A Radioassay for GM1 Ganglioside Concentration in Cerebrospinal Fluid
Authors: Ginns Edward , French Joseph 
Published: October 2006

Abstract:A radioassay for the rapid determination of GM1, ganglioside concentration in small volumes of CSF from individual patients is described. The assay utilizes the high‐affinity interaction between cholera enterotoxin and GM1 ganglioside. The lower detection limit of GM1 ganglioside by this radioassay under the described incubation conditions is 2.5 ng/ml. The radioassay‐determined lumbar CSF GM1 ganglioside concentrations in a small group of patients with diverse neurologic disorders are presented. The radioassay GM1 ganglioside concentration is in good agreement with the GM1 ganglioside concentration determined, in one patient, by the tlc‐densitometry technique.
Biosynthesis of Peripheral Nervous System Myelin Proteins In Vitro
Authors: Smith Marion Edmonds 
Published: October 2006

Abstract:Myelin prepared from spinal roots and sciatic nerves of young rats (24 days of age) after incubation with [3H] amino acids in glucose‐Krebs Ringer bicarbonate contained a considerable amount of radioactivity incorporated into the proteins. When these were separated on SDS‐polyacrylamide gels, peaks of radioactivity were found to correspond to the P0, 23K, P1, and P2 proteins. Although very little Fast‐Green‐stained protein was visible in the high molecular weight region of the gels (>27,000), much radioactivity was located in this area. Incorporation of [3H] amino acids into the myelin proteins continued up to 3 h and was dependent on glucose, but not on O2‐CO2 replacement of air in the flask, whereas cycloheximide inhibited incorporation by 80%. Much less amino acid was incorporated into myelin protein of old rats. High molecular weight proteins appeared to be more metabolically active than other myelin proteins, as estimated by the percent of total counts incorporated/amount of Fast‐Green staining, and their activity decreased less with age. The 23K and P° proteins incorporated [3H] amino acid in approximate proportion to their con‐tent. P0 was less, and P2 somewhat more metabolically active than their con‐tents would predict. [3H]fucose also was incorporated in vitro into P0 and P1 (probably 19K) proteins as well as into the high molecular weight proteins, while glucosamine served less well as a glycoprotein precursor. This preparation may be useful for examining further parameters of PNS myelin synthesis, assembly, and the effects of neurotoxic agents.
Characterization of Alkylgalactolipids from Calf Brain by High Performance Liquid Chromatography
Authors: Yahara Shoji , Kishimoto Yasuo 
Published: October 2006

Abstract:Minor nonpolar galactolipids were isolated from the total lipids of calf brain stem by column chromatography and were separated by preparative thin‐layer chromatography into four groups. The material recovered from the bottom band of the thin‐layer chromatography consisted of monogalactosyl diglyceride and its 1‐0‐alkyl isomer, alkylgalactolipid, present in a molar ratio of 11 :9. After perbenzoylation. they were separated by preparative thin‐layer chromatography and characterized. The fatty acid compositions of these lipids were similar to each other and to those of the ester‐linked fatty acids of cerebroside esters. The major alkyl group of alkylgalactolipid was palmityl, and the other, minor components were oleyl. myristyl, and stearyl ethers. Perbenzoylated derivatives of these lipids were further separated by reverse‐phase high performance liquid chromatography. The chromatograms from these two lipids were similar; however, most of the peaks were still mixtures of homologs containing different fatty acids or an alkyl group.
Identification of Ca2+‐Activated Neutral Protease in the Peripheral Nerve and Its Effects on Neurofilament Degeneration
Authors: Kamakura Keiko , Ishiura Shoichi , Sugita Hideo , Toyokura Yasuo 
Published: October 2006

Abstract:Rat sciatic nerve segments were incubated in five different media. Disappearance of neurofilament (NF) triplet proteins (200K, 160K, and 68K MW) occurred in medium containing Ca2+ and was inhibited by the addition of E‐64‐c or leupeptin. Therefore, the presence in the peripheral nerve of an enzyme whose properties are similar to those of Ca2+‐activated neutral protease (CANP) is suggested. The extraction of crude CANP from rat sciatic nerve was performed. CANP activity was completely recovered (0.129 ± 0.008 U/g) in the precipitate salted out by the addition of 0 to 50% saturated ammonium sulfate to the soluble fraction of the peripheral nerve (crude CANP). Properties of the crude CANP were examined using NF as a substrate and were found to be similar to those of the CANP extracted from skeletal muscle. Identification of the crude CANP with the CANP extracted from rat skeletal muscle was performed using the immunoreplica method. Bands corresponding to 73K were detected in both CANPs.
Striatal GABAergic Neuronal Activity Is Not Reduced in Parkinson's Disease
Authors: Perry Thomas L. , Javoy‐Agid France , Agid Yves , Fibiger Hans C. 
Published: October 2006

Abstract:The content of y‐aminobutyric acid (GABA) and the activities of glutamic acid decarboxylase (GAD) and tyrosine hydroxylase (TH) were measured in whole putamen obtained at autopsy from 13 patients dying with idiopathic Parkinson's disease and 13 appropriate control subjects. Mean GABA content was significantly elevated (by 28%) in the putamen of the Parkinson's disease patients. TH activity was markedly reduced, while there was no significant reduction of GAD activity in the putamen of these patients. GABA content was also measured in both sides of the striatum in rats which had received unilateral injections of 6‐hydroxydopamine (6‐OHDA) in the vicinity of the axons of the nigrostriatal projection. Mean GABA content was found significantly elevated (by 33%) in the ipsilateral striatum. Loss of dopaminergic nigrostriatal neurons, in both human Parkinson's disease and in the rat 6‐OHDA model, is accompanied by increased striatal GABA content. The assumption that GABAergic neurotransmission is reduced in the striatum in Parkinson's disease may not be correct.
Isolation of a Ca2+‐Dependent Actin‐Fragmenting Protein from Brain, Spinal Cord, and Cultured Neurones
Authors: Petrucci T. C. , Thomas C. , Bray D. 
Published: October 2006

Abstract:Extracts of ox spinal cord and chicken brain were fractionated by ion‐exchange chromatography and assayed for their ability to reduce the viscosity of muscle F‐actin solutions. Two distinct peaks of activity were obtained, one of which was further purified by affinity chromatography on a DNAase‐actin Sepharose column. Following molecular exclusion chromatography, the actin component appeared as a complex of 1 molecule of a protein with molecular weight 90,000 and 2 molecules of actin (42,000). This tightly bound complex was resistant to most methods of protein separation, but was resolvable into its component proteins by sodium dodecyl sulphate acrylamide gel electrophoresis. The protein of molecular weight 90,000 could be eluted from such a gel in a fully active form. The activity of the protein from ox spinal cord was closely similar to that of gelsolin, an actin‐fragmenting protein originally isolated from rabbit lung macrophages. Like gelsolin, the protein from ox spinal cord produced fragmentation of muscle F‐actin filaments at Ca2+ concentrations greater than 10‐7M, and had a nucleating effect on the polymerisation of muscle actin; the latter was measured most easily by the enhancement of fluorescence of muscle actin conjugated to N‐(1‐pyrenyl)iodoacetamide. Nucleation was more effective in the presence of Ca2+, but also occurred in its absence, and the same was true of complex formation between the 90,000 protein and muscle G‐actin. On the basis of its actin‐fragmenting activity, we estimate that the 90,000 molecular weight protein constitutes 0.2% of the protein initially extracted from ox spinal cord. A very similar protein, indistinguishable in its action on actin but containing variable amounts of a protein of molecular weight 85,000 as well as 90,000, was isolated from chicken brain. A similar protein was also detected in pure cultures of sympathetic neurones by enrichment on a DNAase‐actin affinity column and by immune blotting and by immuno‐fluorescence. We conclude that a protein similar, if not identical to macrophage gelsolin is present in neurones and that it probably plays a part in the actin‐based movements of these cells.