bluuebunny/crossref_metadata_2025_split huggingface dataset:
ACETYLCHOLINESTERASE OF RAT SYMPATHETIC GANGLION: MOLECULAR FORMS, LOCALIZATION AND EFFECTS OF DENERVATION
Authors: Glsiger V. , Vlgny M. , Gautron J. , Rieger F. 
Published: October 2006

Abstract— In sucrose gradient centrifugation, acetylcholinesterase (AChE, EC 3.1.1.7.) from the rat superior cervical ganglion (SCG) has been found to contain four molecular forms, characterized by their sedimentation coefficients (4 S, 6.5 S, 10 S and 16 S). Homogenization of the ganglia in various media showed that the 4 S enzyme was readily solubilized in water whereas solubilization of the 6.5 S and 10 S forms was quantitative only in media containing Triton X‐100. In order to solubilize the 16 S form, high concentrations of salt (NaCl 1 M) and detergent had to be present. AChE analysed by non‐denaturing polyacrylamide gel electrophoresis separated into five bands. Although both distribution patterns were stable, i.e. each form or band preserved its characteristic sedimentation or electrophoretic migration when reanalysed, there was no 1:1 correlation between the forms isolated by sedimentation and the bands obtained by electrophoresis: one band might contain more than one form of enzyme, and conversely one form gave rise to several bands. It was therefore impossible to derive molecular weights from electrophoretic migration in non‐denaturing gels. However, it could be shown that the results obtained by both methods of analysis were consistent.Acetylcholinesterase from other nervous structures was analysed: in pre‐ and postganglionic nerves, the main forms were 10 S and 6.5 S, with a small proportion of 4 S; the 16 S form was not detected. In other sympathetic ganglia, the distribution of forms was identical to that of the superior cervical ganglion. In rachidian ganglia, no 16 S form could be found.Following the section of the preganglionic nerve, the acetylcholinesterase activity of the superior cervical ganglion decreased by 50% in 3 days, and then rose again to about 80% of its original value after 2 weeks. These effects mainly reflected variations in the major 4 S and 10 S forms. The 16 S form, in contrast to its disappearance from denervated muscles, increased transiently during the first 2 weeks after denervation, reaching about twice its original activity.A concomitant cytochemical study of normal and denervated ganglia showed that after preganglionic denervation, AChE localized in the sympathetic neurones decreased markedly and remained low even during the recovery phase. During this period a cholinesterasic activity appeared in the perineuronal glia. Controls established that the enzyme synthetized in the glia is AChE.
PELIZAEUS‐MERZBACHER DISEASE: BRAIN LIPID AND FATTY ACID COMPOSITION
Authors: Bourre J. M. , Bornhofen J. H. , Araoz C. A. , Daudu O. , Baumann N. A. 
Published: October 2006

Abstract— Biochemical analysis of the leukodystrophy brain from a case of Pelizaeus‐Merzbacher disease, classical type, was performed. A decrease in the amount of solid material present was found. The lyophilized brain weight was reduced to 76% of normal with a slightly greater decrease in the amount of extractable lipid. Total myelin was diminished to 7% of normal. Among specific lipids plasmalogens were present in slightly lowered amounts. Cerebrosides and sulphatides were drastically reduced to 8% of normal, whereas sphingomyelin was less severely affected. Fatty acids from phospholipids were close to normal, only enols being slightly diminished. Analysis of pure cerebrosides and sulphatides revealed that the a‐hydroxylated compounds as well as very long chain fatty acids (over C18, especially C23 to C26) were greatly reduced. For chain lengths over C18, the ratio of leukodystrophy fatty acid to normal fatty acid was close to 10%. The defect in very long chain fatty acids is estimated at 99.2% in total brain.Thus, we have found a marked decrease in the amount of very long chain fatty acids and a less marked decrease in sphingolipids. The reduced amount of these acids appears to be partially offset by an increase in the amount of medium‐chain fatty acids in sphingolipids. We conclude that one aspect of Pelizaeus‐Merzbacher disease may be a defect in the synthesis of myelin very long chain fatty acids (as these acids are far much reduced than any other myelin molecule).
ISOLATION AND CHARACTERIZATION OF BOVINE BRAIN CATHEPSIN D
Authors: Whitaker John N. , Seyer Jerome M. 
Published: October 2006

Abstract—Bovine brain cathepsin D was purified 1774‐fold with a 19% recovery by affinity chromatography on immobilized pepstatin. Approximately 2 mg of enzyme protein were isolated from 150 g (wet weight) of bovine brain. The enzyme eluted from gel filtration as a single peak with a molecular weight of 40,000–42,000. On polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the predominant band migrated with a molecular weight of 48,000: however, less distinct bands were also present in the molecular weight ranges of 31,000 and 13,000. The isolated enzyme had isoelectric points over a range of pH 5–7 with 3 major peaks occurring at pH 5.6, 6.1, and 6.6. The amino acid composition of brain cathepsin D showed substantial differences from that reported for cathepsin D isolated from bovine spleen. Amino‐terminal sequence analysis revealed an Asp‐Val‐lle sequence by Edman degradation. With hemoglobin as the substrate the enzyme had an apparent K, of 60mM.
SYNAPTIC VESICLES ISOLATED FROM RAT HEART:l‐[3H]NOREPINEPHRINE UPTAKE PROPERTIES1
Authors: Bareis Donna Lynn , Slotkin Theodore A. 
Published: October 2006

Abstract—A fraction containing synaptic vesicles was isolated from rat heart by differential centrifugation, and the uptake ofl‐[3H]norepinephrine was studiedin vitro., Uptake was highly dependent upon time and temperature, and was linear for 6 min at 30° or 4 min at 37°C. About 80% of the measured uptake required both ATP and Mg2+and was inhibited by nanomolar concentrations of reserpine; no inhibition was obtained with cocaine. These properties are characteristic of storage vesicle uptake as opposed to synaptic membrane uptake. Uptake of norepinephrine was saturable and displayed a singleKmvalue of 2 μM. The uptake was completely stereospecific, as unlabeleddl‐norepinephrine was less than half as effective as unlabeledl‐norepinephrine in reducing uptake ofl‐[3H]norepinephrine. Norepinephrine uptake could be inhibited by various phenethylamines and indoleamines following the rank order: reserpine > harmaline > 5‐hydroxytryptamine > dopamine > norepinephrine. The vesicle preparation also incorporated [3H]5‐hydroxytryptamine and [3H]dopamine. 5‐Hydroxytryptamine uptake displayed aKmof 0.5 μM and a maximal uptake equivalent to that seen with norepineph‐rine; dopamine uptake followed complex kinetics. Administration of reserpinein vivoor destruction of sympathetic neurons by long‐term guanethidine treatment both eliminated the ability of the preparation to take up norepinephrine. Synaptic vesicles of cardiac sympathetic neurons thus resemble vesicles prepared from other central and peripheral catecholaminergic tissues; this method may be used readily to examine drug effects on rat heart synaptic vesicle function.
CYCLIC AMP IN THE RAT CEREBRAL CORTEX AFTER ACTIVATION OF NORADRENALINE NEURONS OF THE LOCUS COERULEUS
Authors: Korf J. , Sebens Jantiena B. 
Published: October 2006

Abstract—The levels of cyclic AMP in the rat brain were studied in vivo following destruction or stimulation of the noradrenergic pathway originating in the locus coeruleus. After chronic lesion of the locus coeruleus no alterations in cyclic AMP content were found. Electrical stimulation of the locus coeruleus produced an elevation of cyclic AMP in the cerebral cortex of chloral hydrate anaesthetized rats of 30%. Maximal increases were found after 15–60 s stimulation at a frequency of 30–100 Hz. This maximal response was slightly inhibited by phenoxybenzamine, an α‐adrenergic blocking agent, and by the β‐blocker propranolol. When the α and β blockers were administered together a highly significant decrease in cyclic AMP response was observed. Pretreatment of the rats with reserpinc +α methyl‐p‐tyrosine prevented the cyclic AMP response. In addition to the effect in the cerebral cortex, cyclic AMP‐levels were also enhanced in the hippocampus, in the striatum and in the hypothalamus. These results suggest that the locus coeruleus regulates a small fraction of cerebral cyclic AMP levels, by both α‐ and β‐adrenergic receptors.
PROTEINS OF AXONAL TRANSPORT: INTERACTION OF RAPIDLY TRANSPORTED PROTEINS WITH LECTINS
Authors: Karlsson J.‐O. 
Published: October 2006

Abstract—Rapidly transported fucose‐labelled glycoproteins from the optic system of the rabbit were solubilised with the non‐ionic detergent Berol 172.The major labelled components were bound to wheat germ agglutinin or Concanavalin A coupled to Sepharose but not to other lectins or glycoproteins. It was concluded that rapidly transported proteins contain exposed N‐acetyl‐D‐glucosamine
HOMOCARNOSINOSIS: INCREASED CONTENT OF HOMOCARNOSINE AND DEFICIENCY OF HOMOCARNOSINASE IN BRAIN
Authors: Perry Thomas L. , Kish Stephen J. , Sjaastad Ottar , Gjessing Len R. , Nesbakken Ragnar , Schrader Harald , Lösken Aagot C. 
Published: October 2006

AbstractBiochemical studies were carried out on a brain biopsy obtained from a 40 y old woman with homocarnosinosis. This patient and 2 of her siblings have a progressive neurological disorder characterized by spastic paraplegia, dementia and retinal pigmentation. Homocarnosine concentrations in their CSF, as well as in the CSF of their neurologically normal mother, are elevated 20‐40‐fold. Homocarnosine content was 4 times higher in the patient's frontal cortex than in biopsied cortex from a large group of control subjects. The activity of the synthetic enzyme, homocarnosine‐carnosine synthetase. was not increased in the homocarnosinosis patient's brain. Homocarnosinase activity, however, was undetectable in the patient's brain biopsy, while it could readily be measured in comparable biopsies from control subjects. We conclude that homocarnosinase deficiency is probably inhcrited as an autosomal recessive trait, but that it is unlikely of itself to have caused the neurological syndrome affecting our patients.
BACLOFEN: EFFECTS ON AMINO ACID RELEASE AND METABOLISM IN SLICES OF GUINEA PIG CEREBRAL CORTEX
Authors: Potashner S. J. 
Published: October 2006

AbstractSlices of guinea‐pig cerebral cortex were used to investigate the effects of the antispastic drug β‐(p‐chlorophenyl)‐γ‐aminobutyrate (Baclofen, Lioresal) on the release and metabolism of several amino acids. Electrical stimulation of slices evoked (1) a relatively large release, probably from nerve terminals, of 14C‐labelled tissue glumate, aspartate and γ‐aminobutyrate (GABA) synthesized via metabolism of D‐[U‐14C]glucose and (2) a relatively small release, probably not from nerve terminals, of 14C‐labelled tissue alanine and threonine‐serine‐glutamine and of exogenous radiolabeled glutamate, aspartate, GABA and α‐aminoisobutyrate that had been taken up from the medium. Baclofen (4μM) preferentially inhibited the release of 14C‐labelled tissue glutamate and aspartate. It had no effect on the concentrations and specific radio‐activities of most of the labelled tissue amino acids in the slices. However, it increased the turnover of 14C‐labelled tissue glycine approx 4‐fold and elevated the specific radio activity of tissue alanine by 40%. It was concluded that Baclofen affects transmission not by modulating the release of the inhibitory amino acid GABA, but by selectively suppressing the release of the excitatory amino acids glutamate and aspartate from nerve terminals. Provided that this action obtains in the spinal cord, it may at least partly underlie the antispastic action of Baclofen as glutamate and aspartate are presumed to be the transmitters released from terminals of non‐nociceptive primary afferent fibers and excitatory interneurons, respectively. The Baclofen‐induced increase in glycine turnover suggests an additional effect on inhibitory glycinergic interneurons in the spinal cord.
SUBCELLULAR DISTRIBUTION OF [3H]QUINUCLIDINYL BENZYLATE BINDING ACTIVITY IN VERTEBRATE RETINA AND ITS RELATIONSHIP TO OTHER CHOLINERGIC MARKERS
Authors: Moreno‐Yanes Jose A. , Mahler Henry R. 
Published: October 2006

Abstract— The subcellular distribution of binding sites for tritiated quinuclidinyl benzylate ([3H]QNB) was studied in cow retina. Primary fractions showing higher specific activity than homogenate were P2 (synaptosomal‐mitochondrial) and P3 (microsomal). P2 was subfractionated on a Ficoll gradient with the P2B subfraction exhibiting the greatest enrichment in [3H]QNB binding. Similar subfractionation of P2 on a discontinuous sucrose gradient showed that fractions of particles banding in 0.8m and in the 0.8‐1.0 m‐sucrose interface also exhibit the greatest enrichment of [3H]QNB binding. When subjected to Scatchard analysis, this reaction shows a density of sites equal to 0.212‐0.294 pmol per mg of protein. By plotting the apparent dissociation constant (KD) values vs protein concentration a‘true’KD value of 0.73 nM was obtained. Only one set of binding sites was found using three different concentrations of protein. The reaction was specificially antagonized by atropine (DI50= 7 nM) and scopolamine (DI50= 9 nM) whereas carbamylcholine and d‐tubocurarine exhibited DI50's of 0.4 and 0.15 mM, respectively. For P3 the binding of [3H]QNB is characterized by one set of binding sites with ni= 0.250 pmol per mg of protein and an apparent KD of 8.2 nM, and a DI50 for atropine of 15 nM. The [3H]QNB binding sites showed a subcellular distribution similar to that of acetylcholinesterase and choline acetyltransferase.P1 fractions accounted for 40–60% of the total activity of the three cholinergic markers. Purification of the crude P1 yielded an additional fraction in which the cholinergic markers showed an enrichment with respect to homogenate and P1. Synaptosomes isolated from this fraction exhibited the unusual ultrastructure expected from nerve endings in the outer synaptic layer of retina.The possible location of the muscarinic cholinergic transmitter system in the vertebrate retina is discussed.
Rat Brain Protein Synthesis Declines During Postdevelopmental Aging
Authors: Dwyer Barney E. , Fando Juan L. , Wasterlain Claude G. 
Published: October 2006

Abstract: Using improved methods to measure brain protein synthesis in vivo (Dunlop et al., 1975) we have established that brain protein synthesis significantly declines in forebrain, cerebellum and brain stem when mature rats (3 months old) are compared to old rats (22.5 months old). The incorporation of (3H) L‐lysine into forebrain protein is reduced 11% in 10.5 month old rats compared to 3 month old rats. A further reduction of 9% occurred between 16.5 months and 22.5 months. Our data suggest that reduced levels of protein synthesis initiation may be responsible, at least in part, for this age‐related decline.
The Extrusion of Sodium Ions from Presynaptic Nerve Endings of Rat Cerebral Cortex
Authors: Logan J. G. 
Published: October 2006

Abstract(Na+‐K+) ATPase is present in synaptosomal preparations and it is assumed to represent the sodium‐potassium pump. 10 μm‐noradrenaline activates (Na+‐K+) ATPase approximately 100%, but 50 μm‐noradrenaline does not stimulate the rate of 22Na extrusion from synaptosomes. The results suggest that it is unlikely that the noradrenaline stimulation of (Na+‐K+) ATPase is part of a feedback mechanism whereby released noradrenaline can influence the activity of the presynaptic sodium pump.
Effects of In Vitro Hypoxia and Lowered pH on Potassium Fluxes and Energy Metabolism in Rat Brain Synaptosomes
Authors: Pastuszko Anna , Wilson David F. , Erecińska Maria , Silver Ian A. 
Published: October 2006

Abstract:Synaptosomes isolated on isosmotic Ficoll density gradients are an effective model for some aspects of neuronal function. They maintain metabolic energy levels ([ATP]/[ADP] [Pi1) and transplasma membrane electrical potentials very similar to those of neurons in the intact brain. The concentration of K+ in the external medium (K+‐sensitive electrode), O2 uptake, and cytochrome c reduction (550 nm minus 540 nm) were simultaneously monitored in synaptosomal suspensions. Oxidative metabolism is the primary source of intrasynaptosomal ATP and at pH 7.4 anaerobiosis results in K+ leakage at 4.5 ± 0.8 nmol/min/mg protein with glucose as substrate and 10.7 T 1.9 nmol/min/mg protein with lactate plus pyruvate (10:1) as substrate. Reintroduction of oxygen initiates complete (ouabain‐sensitive) reuptake of K. at initial rates of 35.4 ± 3.2 nmol/min/mg protein and 18 ± 1.7 nmol K‐/min/mg protein, respectively. The rates of K+ leakage and reuptake fall when the pH is lowered from 7.4 to 6.0 but recover fully if the pH is raised to the original value. The rates of K1 release and uptake decrease when the Na‐ concentration in the medium is decreased and increase when the Ca2‐ concentration is decreased. The intrasynaptosomal [K+] under aerobic conditions was 77.3 ± 3 MM and the calculated K+ diffusion potential was ‐72 mV. Anaerobic incubation of the synaptosomes for up to 20 min and at pH values from 7.4 to 6.0 did not produce irreversible impairment of any of the measured variables. These results suggest that permanent loss of brain function following prolonged hypoxia and ischemia is not due to irreversible damage to the synapses with respect to these parameters but rather to impairment of some other neuronal functions.
An Aminopeptidase from Bovine Brain Which Catalyzes the Hydrolysis of Enkephalin
Authors: Hersh Louis B. , McKelvy Jeffrey F. 
Published: October 2006

Abstract:An aminopeptidase from bovine brain which catalyzes the hydrolysis of the tyrosyl1‐glycine2 bond of methionine5‐enkephalin has been purified to electrophoretic homogeneity. The enzyme also catalyzes the hydrolysis of di‐peptides, tripeptides, and amino acid β‐naphthylamides. The enzyme can be inactivated by dialysis against EDTA, and reconstituted with divalent metal ions. Inhibition of the enzyme is observed in the presence of p‐chloromercuribenzoate and puromycin, the latter compound not being hydro‐lyzed by the enzyme. The enzyme is composed of a single polypeptide chain of molecular weight approx. 100,000. The properties of this enzyme are similar to those reported for other brain aminopeptidases active on enkephalin, although distinct differences are observed.
Regional Cerebral Glucose Utilization in Rats with Portacaval Anastomosis
Authors: Mans Anke M. , Biebuyck Julien F. , Davis Donald W. , Bryan Robert M. , Hawkins Richard A. 
Published: October 2006

Abstract:Regional cerebral glucose utilization was measured using [2‐14C]glucose in rats with an end‐to‐side portacaval anastomosis. The experiments were conducted in two groups of rats 4 to 8 weeks after portacaval shunting was established. One group was paralyzed and given N2O:O2 (70:30), whereas the other was conscious, unstressed, and unaware of the experiment. In both groups the rate of glucose utilization was decreased in almost all brain structures by an average of 20% after portacaval shunting. The results showed definitively that cerebral energy metabolism was reduced at a time when there were no obvious neurological abnormalities.
Regulation of γ‐Aminobutyric Acid/Barbiturate Receptor‐Gated Chloride Ion Flux in Brain Vesicles by Phospholipase A2: Possible Role of Oxygen Radicals
Authors: Schwartz Rochelle D. , Skolnick Phil , Paul Steven M. 
Published: October 2006

AbstractPreincubation of brain membranes with phospholipase A2 (PLA2) has been shown previously to affect the binding characteristics of various recognition sites associated with the γ‐aminobutyric acid (GABA) receptor complex. In the present study, we have investigated the effects of PLA2 (from Naja naja siamensis venom) on the functional activity of the GABA receptor/chloride ion channel. PLA2 (0.001–0.02 U/mg protein) preincubation decreased pentobarbital‐induced 36Cl‐ efflux and musci‐mol‐induced 36Cl‐ uptake in rat cerebral cortical synaptoneurosomes. The effect of PLA2 was prevented by EGTA and two nonselective PLA2 inhibitors, mepacrine and bromophenacyl bromide. The removal of free fatty acids by addition of bovine serum albumin both prevented and reversed the effect of PLA2. Products of the catalytic activity of PLA2, such as the unsaturated free fatty acids, arachidonic and oleic acids, mimicked the effect of PLA2. However, the saturated fatty acid, palmitic acid, and lysophosphatidyl choline had no effect on pentobarbital‐induced 36Cl‐ efflux. Because unsaturated free fatty acids are highly susceptible to peroxidation by oxygen radicals, the role of oxygen radicals was investigated. Xanthine plus xanthine oxidase, a superoxide radical generating system, mimicked the effect of PLA2, whereas the superoxide radical scavenger, superoxide dismutase, diminished the effects of PLA2 and arachidonic acid on pentobarbital‐induced 36Cl‐ efflux. Similarly, the effect of PLA2 was also inhibited by methanol (1 mM), a scavenger of the hydroxyl radical, and by catalase. These data indicate that exogenously added PLA2 induces alterations in membrane phospholipids, possibly promoting the generation of oxygen radicals and fatty acid peroxides which can ultimately modulate GABA/barbitu‐rate receptor function in brain.
Distribution of Calmodulin‐ and Cyclic AMP‐Stimulated Protein Kinases in Synaptosomes
Authors: Dunkley P. R. , Jarvie P. E. , Rostas J. A. P. 
Published: October 2006

AbstractThe subcellular location of calmodulin‐ and cyclic AMP‐stimulated protein kinases was assessed in synaptosomes which were prepared on Percoll density gradients. The distribution of the protein kinases between the outside and the inside and between the soluble and membrane fractions was determined by incubating intact and lysed synaptosomes, as well as supernatant and pellet fractions obtained from lysed synaptosomes, in the presence of [γ‐32P]ATP. Protein kinase activity was assessed by the labelling of endogenous proteins, or exogenous peptide substrates, under conditions optimized for either calmodulin‐or cyclic AMP‐stimulated protein phosphorylation. When assessed by calmodulin‐stimulated autophosphorylation of the α subunit of calmodulin kinase II, 44% of this enzyme was on the outside of synaptosomes, and 41% was in the 100,000 g supernatant. Using an exogenous peptide substrate, the distribution of total calmodulin‐stimulated kinase activity was 27% on the outside and 34% in the supernatant. The high proportion of calmodulin kinase II on the outside of synaptosomes is consistent with its known localization at postsynaptic densities. The proportion of calmodulin kinase II which was soluble depended on the ionic strength conditions used to prepare the supernatant, but the results suggest that a major proportion of this enzyme which is inside synaptosomes is soluble. When assessed by cyclic AMP‐stimulated phosphorylation of endogenous substrates, no cyclic AMP‐stimulated kinase activity was observed on the outside of synaptosomes, whereas 21% was found with an exogenous peptide substrate. This suggests that if endogenous substrates are present on the outside of synaptosomes, then the enzyme does not have access to them. The cyclic AMP‐stimulated protein kinase present inside synaptosomes was largely bound to membranes and/or the cytoskeleton, with only 10% found in the supernatant when assessed by endogenous protein phosphorylation and 25% with an exogenous substrate. The markedly different distribution of the calmodulin‐ and cyclic AMP‐stimulated protein kinases presumably reflects differences in the functions of these enzymes at synapses.