bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative Changes in Myelin Proteins in a Peripheral Neuropathy Caused by Tullidora (Karwinskia humboldtiana)
Authors: Aoki Kazuko , Muñoz‐Martinez E. J. 
Published: October 2006

Abstract:Peripheral nerve demyelination was induced in cats by oral administration of ether extracts of Tullidora (Karwinskia humboldtiana). Proteins from several hindlimb nerves, spinal roots, and dorsal columns of the spinal cord were subjected to slab gel electrophoresis and quantified by densitometry. In Tullidora‐treated cats with severe motor disturbances, specific myelin proteins were reduced by at least 50% in motor nerves and less than 25% in cutaneous axons. There was a greater decrease of these proteins in the distal than in the cephalad segments of the sciatic nerve; no changes were detected either in the spinal roots or in the white matter of the spinal cord. Electron microscopy revealed intense demyelination in the motor nerves only. Both the density of the 100 Å‐thick neurofilaments and the relative proportion of a polypeptide with a molecular weight of 68,000 were considerably increased in the affected nerves. It is tentatively concluded that the active principles of Tullidora may enter the axons through the motor nerve terminals. The distal segments of the motor nerves would then be preferentially affected and demyelination could result from axonal damage.
Noradrenaline, a Transmitter Candidate in the Retina
Authors: Osborne N. N. 
Published: October 2006

Abstract:The occurrence, metabolism, uptake, and release of noradrenaline were studied in the bovine retina with the following results. (1) Small amounts of noradrenaline occur in the retina and are restricted to the area corresponding to the inner nuclear and plexiform layers. (2) Retinal tissue can metabolise [14C]dopamine to form quantities of [14C]noradrenaline. (3) [14C]Noradrenaline can also be partly metabolised to form [14C]normetanephrine. (4) When bovine retinas were incubated with 5 × 10‐7 M‐[3H]noradrenaline for 20 min and processed for autoradiography, most of the label was associated with apparent nerve processes in the inner plexiform layer. Biochemical analysis showed that more than 95% of the label was noradrenaline. (5) [14C]Noradrenaline uptake saturated with increasing noradrenaline concentrations and followed Michaelis‐Menten kinetics. This uptake could be accounted for by two processes, a high‐affinity system with a Km1 of 5 × 10‐8 M and a Vmax1 of 0.193 pmol/mg/10 min and a low‐affinity system with a Km2 of 6.3 × 10‐5 M and a Vmax2 of 0.109 nmol/mg/10 min. (6) Noradrenaline uptake was strongly dependent on temperature and sodium, less dependent on potassium, and independent of calcium and magnesium ions. (7) Centrally acting drugs, such as desipramine, imipramine, desmethylimipramine, and amitriptyline, inhibited noradrenaline uptake by more than 55% at the concentration of 5 × 10‐5 M. These drugs at the same concentration diminished dopamine uptake by less than 30%. (8) Noradrenaline uptake is stereospecific, the (‐) isomer having a greater affinity for the uptake sites than the (+) isomer. (9) [14C]Noradrenaline in the retina could be released by increasing the external potassium concentration. This release was calcium‐dependent and was blocked by 20 mM‐cobalt chloride. The present studies could be interpreted as supporting the idea that noradrenaline acts as a transmitter in the retina.
The Metabolism of Purine and Pyrimidine Nucleotides in Rat Cortex During Insulin‐Induced Hypoglycemia and Recovery
Authors: Chapman Astrid G. , Westerberg Eva , Siesjö Bo K. 
Published: October 2006

Abstract:Brains of paralysed rats with insulin‐induced hypoglycemia were frozen in situ after spontaneous EEG activity had been absent for 5 or 15 min (“coma”). Recovery (30 min) was achieved in a different group of rats by administering glucose after a 30‐min coma period. Purine and pyrimidine nucleotides, nucleosides and free bases were determined in the cortical extracts by high pressure liquid chromatography (HPLC). The ATP values obtained with the HPLC method were in excellent agreement with those obtained using standard enzymatic/fluorometric techniques, while values for ADP and AMP obtained with the HPLC method were significantly lower. Comatose animals showed a severe (40‐80%) reduction in the concentrations of all nucleoside triphosphates (ATP. GTP, UTP and CTP) and a simultaneous increase in the concentrations of all nucleoside di‐ and monophosphates, including that of IMP. The adenine nucleotide pool size decreased to 50% of control level. The concentrations of the nucleosides adenosine, inosine, and uridine increased 50‐ to 250‐fold, while the concentrations of the purine bases, xanthine and hypoxanthine, rose 2‐ and 30‐fold, respectively. There were no increases in the concentrations of adenine, guanine, or xanthosine. Following glucose administration there was a partial (ATP, UTP and CTP) or almost complete (GTP) recovery of the nucleoside triphosphate levels. During recovery, the levels of nucleosidc di‐ and monophosphates and of adenosine decreased to values close to control; the rise in the inosine level was only partially reversed, and the concentrations of hypoxanthine and xanthine rose further. The adenine nucleotide pool size was only partially restored (to 67% of control value). The adenine nucleotide pool size was not increased by i.p. injection of adenosine or adenine under control condition, or during the posthypoglycemic recovery period.
Regional CNS Levels of Acetylcholine and Choline During Hypoglycemic Stupor and Recovery
Authors: Gorell Jay M. , Navarro Carolyn P. , Schwendner Susan P. W. 
Published: October 2006

Abstract:During insulin stupor in mice, acetylcholine levels in cerebral cortex, cerebellum. brainstem, striatum, and hippocampus were unchanged from control values despite brain glucose concentrations 3‐10% of normal, whereas choline levels rose 2.4‐3.6‐fold in all five CNS regions. Brain acetylcholine and choline levels did not change during recovery following glucose injection. The data suggest that. in hypoglycemic stupor, (1) overall rates of acetylcholine synthesis and degradation remain balanced within each of the CNS regions studied: (2) the biochemical mechanism that elevates brain choline levels is unlikely to be related only to cholinergic synaptic processes: and (3) brain choline levels need not rise for stupor to occur.
Decarboxylation of p‐Tyrosine: A Potential Source of p‐Tyramine in Mammalian Tissues
Authors: Bowsher Ronald R. , Henry David P. 
Published: October 2006

Abstract:The question of the existence of a p‐tyrosine decarboxylase pathway for the formation of p‐tyramine in mammalian tissues remains unresolved. Development of a sensitive and specific assay for p‐tyrosine decarboxylase has permitted demonstration of this activity in rat tissues and human kidney. Tyrosine decarboxylase was purified to electrophoretic homogeneity by pH 5.0 precipitation, ammonium sulfate precipitation, gel filtration, phenyl‐Sepharose chromatography, DEAE‐Sephacel chromatography, and preparative isoelectric focusing. A specific rabbit antiserum to tyrosine decarboxylase was also obtained. Purified tyrosine decarboxylase possessed a narrow pH dependency with an optimum at 8.0. Benzene and certain other organic solvents dramatically stimulated tyrosine decarboxylase activity of purified enzyme. Purified tyrosine decarboxylase activity also decarboxylated L‐DOPA, 5‐hydroxytryptophan, 3,4‐dihydroxyphenylserine, o‐tyrosine, m‐tyrosine, phenylalanine, histidine, and tryptophan, which suggested that the purified enzyme was aromatic L‐amino acid decarboxylase. This conclusion was supported by a constant ratio of 5‐hydroxytryptophan decarboxylase to tyrosine decarboxylase throughout the purification scheme and by parallel immunoprecipitation of decarboxylase activities by the specific antityrosine decarboxylase antisera. Thus, we report that p‐tyrosine is decarboxylated by aromatic L‐amino acid decarboxylase and that this metabolic transformation may be an important source of p‐tyramine in mammalian tissues. In conclusion, neuronal tissues that synthesize catecholamines or serotonin should now be considered capable of synthesizing p‐tyramine and other biogenic amines.
Evoked Release of Proteins from Central Neurons In Vivo
Authors: Greenfield Susan A. , Chéramy André , Glowinski Jacques 
Published: October 2006

Abstract:Push‐pull cannulae were implanted in both substantiae nigrae and caudate nuclei of the halothane‐anesthetized cat. The release of total protein, acetylcho‐linesterase, and nonspecific cholinesterases was examined. Following direct application of potassium to one substantia nigra, changes occurred in the local release of total protein and acetylcholinesterase, but not nonspecific cholinesterases; changes also were observed in both caudate nuclei and the contralatera/ substantia nigra. The local evoked release of acetylcholinesterase and of total protein differed in the extent to which they were calcium‐dependent. Control studies suggest that release of these compounds, both spontaneous and evoked, is related, at least in part, to neuronal activity. The significance of the neuronal release of proteins is discussed.
Changes in the Concentration of Enolase Isozymes and S‐100 Protein in Degenerating and Regenerating Rat Sciatic Nerve
Authors: And Kanefusa Kato , Satoh Toyohiko 
Published: October 2006

Abstract:Levels of enolase isozymes (ãã, ãγ, and γγ forms) and S‐100 protein in rat sciatic nerves were determined during their degeneration and regeneration processes. The sciatic nerves were unilaterally crushed or severed. The rats were killed 1,2,6, and 8‐9 weeks later, and both the proximal and distal portions of the damaged nerves were dissected. Control samples were obtained from the untreated contralateral hindlimbs. Enolase isozymes and S‐100 protein in the nerve segments were determined with the enzyme immunoassay method. The control nerves contained about 40, 90, and 30 pmol/mg protein of ãã, ãγ, and γγ enolases, respectively, and 0.85 μg/mg protein of S‐100 protein. These levels were not affected by repetitive electrical stimulation of the nerve fibers in vivo. The levels of the nervous system‐specific forms of enolase (ãγ and γγ) and S‐100 protein decreased markedly within a week in the distal portion of the crushed nerve (ãγ, 27 pmol/mg; γγ, 5.5 pmol/mg; S‐100 protein, 0.36 μg/mg) with apparently no change in the concentration of aa enolase. These levels in the proximal portion of the crushed nerve remained unaltered. The sensory and motor functions impaired by the sciatic nerve crush showed a recovery more or less after 4‐9 weeks. This recovery was accompanied by a gradual regaining of the specific proteins in the distal portion of injured nerves (ãγ, 64 pmol/mg; γγ, 13 pmol/mg; S‐100 protein, 0.63 μg/mg at the 8‐9th week).
The Metabolism of Dopamine by Both Forms of Monoamine Oxidase in the Rat Brain and Its Inhibition by Cimoxatone
Authors: Fowler Christopher J. , Benedetti Margherita Strolin 
Published: October 2006

Abstract:In the rat brain, dopamine is metabolised by both A and B forms of monoamine oxidase (MAO), although the A form of the enzyme is the major component. The Km of MAO‐A toward dopamine (120 μM) is lower than the Km, of MAO‐B toward this substrate (340 μM). The activity of MAO‐A was lower in old rats than in young rats, and the same degree of decrease was found for 5‐hydroxy‐tryptamine as for dopamine as substrates for this enzyme form. The activity of MAO‐B was higher in the old rats, the degree of increase being the same for dopamine as for β‐phenethylamine as substrates for this enzyme form. The K1 values of the inhibition of MAO‐A by cimoxatone and MD770222 (the principal plasma metabolite of cimoxatone) were independent of the substrate used to assay for activity, but were lower than the K1 values for the inhibition of MAO‐B by these compounds.
Alterations in the Content of Amino Acid Neurotransmitters Before the Onset and During the Course of Methoxypyridoxine‐Induced Seizures in Individual Rabbit Brain Regions
Authors: Nitsch Cordula , Schmude Bernd , Haug Pat 
Published: October 2006

Abstract:In rabbits, generalized seizures were induced by methoxypyridoxine, and changes in amino acid concentrations of 15 brain regions were investigated before seizure onset and during the course of sustained epileptiform activity. As previously reported, γ‐aminobutyric acid (GABA) concentration decreased preictally in most regions. At the same time, taurine level was elevated in the hypothalamus, thalamus, hippocampus, caudatum, and frontal cortex. After 90 min of seizures, it was significantly decreased in the hypothalamus, periaqueductal grey, substantia nigra, frontal cortex, and cerebellum. Glycine content was reduced preictally only in the substantia nigra; after seizure onset its concentration rose in all brain areas. Glutamate content in the frontal cortex decreased before seizure onset; after 1.5 h of seizures, its concentration in cerebellum, caudatum, and hippocampus was reduced. Aspartate level was decreased in most areas after sustained seizures; in putamen, however, it was elevated. In contrast, glutamine content increased preictally in the superior colliculus and in all brain areas by ˜200% after 90 min of seizures. Alanine and valine content also rose markedly in most brain areas after prolonged seizures, and threonine showed the same tendency. The single brain regions were observed to respond to methoxypyridoxine in highly individualistic ways. For example, the glycine content of the substantia nigra, which is believed to utilize this amino acid as a neurotransmitter, decreased preictally. The potential importance of the superior colliculus in seizure induction is considered in view of the early rise in glutamine level. The antagonistic preictal behavior of taurine and GABA is discussed with respect to synthesis, uptake from the blood, and antiepileptic properties.
Microanalysis of Endogenous Acetylcholine Released from the Hemidiaphragm of the Rat
Authors: Häggblad J. , Eriksson H. , Heilbronn E. 
Published: October 2006

Abstract:A chemiluminescence method for the determination of endogenous acetylcholine was adapted to transmitter released from the hemidiaphragm of the rat. Released choline and acetylcholine were isolated and concentrated using KI3 precipitation. Between 1 and 20 pmol of acetylcholine may be measured without sample dilution. The detection limit for acetylcholine luminescence is 1.0 pmol; thus, with an observed precipitation recovery of ˜30%, the lowest detectable released amount is 3.5 pmol. The limitations of the method are discussed.
Protein Synthesis and Rapid Axonal Transport During Regrowth of Dorsal Root Axons
Authors: Perry G. W. , Krayanek Susan R. , Wilson David L. 
Published: October 2006

Abstract:Damage to the sciatic nerve produces significant changes in the relative synthesis rates of some proteins in dorsal root ganglia and in the amounts of some fast axonally transported proteins in both the sciatic nerve and dorsal roots. We have now analyzed protein synthesis and axonal transport after cutting the other branch of dorsal root ganglia neurons, the dorsal roots. Two to three weeks after cutting the dorsal roots, [35S]methionine was used to label proteins in the dorsal root ganglia in vitro. Proteins synthesized in the dorsal root ganglia and transported along the sciatic nerve were analyzed on two‐dimensional gels. All of the proteins previously observed to change after sciatic nerve damage were included in this study. No significant changes inproteins synthesized in dorsal root ganglia or rapidly transported along the sciatic nerve were detected. Axon regrowth from cut dorsal roots was observed by light and electron microscopy. Either the response to dorsal root damage is too small to be detected by our methods or changes in protein synthesis and fast axonal transport are not necessary for axon regrowth. When such changes do occur they may still aid in regrowth or be necessary for later stages in regeneration.
Identification of Intrinsic Sialidase and Sialoglycoprotein Substrates in Rat Brain Synaptic Junctions
Authors: Cruz Tony F. , Gurd James W. 
Published: October 2006

Abstract:Sialidase activity associated with rat brain synaptic junctions (SJ) and synaptic membranes (SM) was determined. Both fractions released sialic acid from exogenous glycopeptides and gangliosides. SJ accounted for 5–10% of the total sialidase activity recovered from SM following extraction with Triton X‐100, and the specific activity of SJ sialidase was 60% of that of the parent SM fraction. Intrinsic SJ sialidase hydrolysed 12–15% of the sialic acid associated with endogenous SJ glycoproteins. Sialic acid residues associated with SJ glycoproteins were labelled with sodium borotritide and SJ proteins fractionated by affinity chromatography on concanavalin A‐agarose. SJ glycoproteins that reacted with concanavalin A (con A+ glycoproteins) accounted for 25% of the total SJ [3H]sialic acid. Intrinsic SJ sialidase hydrolysed 20% of the [3H]sialic acid associated with these glycoproteins. Each molecular weight class of con A+ glycoprotein previously shown to be a specific component of the postsynaptic apparatus contained sialic acid and was acted on by intrinsic SJ sialidase.
An Aminopeptidase from Mouse Brain Cytosol That Cleaves N‐Terminal Acidic Amino Acid Residues
Authors: Kelly J. A. , Neidle E. L. , Neidle A. 
Published: October 2006

Abstract:An aminopeptidase with specificity directed toward peptides with acidic N‐terminal amino acid residues has been isolated from mouse brain cytosol. Purification by ion‐exchange chromatography and gel filtration resulted in an enzyme that hydrolyzed aspartyl‐phenylala‐nine methyl ester at a rate of 13.2 μu,mol/min/mg protein at pH 7.5, an increase in specific activity of 1000‐fold over that of brain homogenate. Its apparent molecular weight, determined by gel filtration, is ˜450,000. Dipeptides with N‐terminal aspartyl residues are cleaved preferentially to glutamic‐containing analogs, and a neutral amino acid (or histidine) is necessary in the adjacent position. For pep‐tides of the form aspartyl‐X, relative activity was 100, 81, 71, 66, 19, or 0, where X was alanine, serine, leucine, phenylalanine, histidine, or proline, respectively. Tripep‐tides were more rapidly hydrolyzed than dipeptides; however, activity tended to decline with increasing chain length. The acidic aminopeptidase can account for almost all of the activity of brain cytosol toward the N‐terminal aspartyl residue of angiotensin II, aspartyl‐phenylalanine methyl ester or aspartyl‐alanine, and the N‐terminal glu‐tamyl residue of adrenocorticotropin(5‐10). The enzyme was unaffected by bestatin or amastatin. It was inhibited by o‐phenanthroline and EDTA. The latter effect could be reversed completely by Zn2+ and partially by Mn2+ or Mg2+; Co2+ and Fe2+ had no effect; Ca2+ was inhibitory. These properties distinguish the brain acidic aminopeptidase from aminopeptidase A isolated from human serum or pig kidney and the aspartyl aminopeptidase of dog kidney.
Blood‐Brain Transfer of Galactose in Experimental Galactosemia, with Special Reference to the Competitive Interaction Between Galactose and Glucose
Authors: Gjedde Albert 
Published: October 2006

AbstractThe interaction between glucose and galactose during transport across the cerebral capillary endothehum was studied in anesthetized rats. Although galactose is present in the diet of suckling mammals and is a potential substrate for brain metabolism in adult mammals, its effect on glucose transport in adult rats is unknown. A kinetic model was formulated to analyze the effect of chronically elevated galactose levels on glucose transport in adult rats. The analysis indicated that galactose and glucose compete for the same transport mechanism in the cerebral capillary endothelium. The Tmax of glucose and galactose were both about 380 μmol 100 g‐1 min‐1 and the Kt of galactose (30 mM) was about three times that of glucose (10 mM). During prolonged galactosemia in adult rats, neither the Tmax, nor the Kt of either competitor changed substantially when compared with rats subjected to acute galactosemia. At 10 mM galactose in plasma in rats with acute galactosemia, the inhibition of glucose transport, simulated a 25% reduction of plasma glucose, and in rats with chronic galactosemia a 20% reduction. This moderate effect is in contrast to the effect of galactose in suckling rats in which 10 mM galactose in plasma reduced the glucose transport to a level corresponding to a 50% reduction of the plasma glucose concentration.
Tubulin‐Associated Calmodulin‐Dependent Kinase: Evidence for an Endogenous Complex of Tubulin with a Calcium‐Calmodulin‐Dependent Kinase
Authors: Goldenring James R. , Casanova James E. , DeLorenzo Robert J. 
Published: October 2006

AbstractA Ca2+‐calmodulin kinase that phosphorylates tubulin and microtubule‐associated proteins as major substrates has been purified and characterized from brain cytoplasm. It is important to determine if cytoskeletal proteins are major natural substrates for this kinase system. This report demonstrates that a significant fraction of brain cytosolic calmodulin‐dependent kinase activity exists in tight association with tubulin in the form of a stable complex. The tubulin‐calmodulin kinase complex displayed an apparent molecular weight on gel filtration of approximately 1.8 × 106 daltons. The specific activity of tubulin kinase in the complex was enriched over 20‐fold in comparison with brain cytosol. Although purified tubulin alone did not adhere to a calmodulin column, the tubulin associated with the calmodulin kinase complex did bind specifically to the calmodulin affinity resin. The kinase activity was shown to be tightly associated in complex with tubulin by (1) copurification, (2) isolation on gel filtration chromatography, (3) isolation on ion‐exchange chromatography, and (4) binding to calmodulin. The kinase complexed with tubulin was identical to the previously purified kinase as judged by several criteria including (1) subunit molecular weights, (2) isoelectric points, (3) autophosphorylation characteristics, (4) calmodulin binding properties, (5) kinetic parameters of tubulin phosphorylation, (6) phosphoamino acid phosphorylation sites on α‐and β‐tubulin, and (7) identical subunit 125I‐tryptic peptide maps. The results indicate that a significant fraction of this previously purified calmodulin kinase is endogenously associated with tubulin in brain cytoplasm and may play a role in mediating some of the effects of calcium on neuronal function.
Regulation of Rat Pineal α1‐Adrenoceptors
Authors: Sugden David , Klein David C. 
Published: October 2006

Abstract:Some aspects of the physiological regulation of the pineal α1‐adrenoceptor have been studied using the selective, high‐affinity ligand [125I] iodo‐2‐[β‐(4‐hydroxyphenyl)ethylaminomethyl]tetralone ([125I]HEAT). Pineal glands taken from rats housed in a diurnal lighting cycle showed no circadian rhythm in the number of specific [125I]HEAT binding sites, although a characteristic rhythm in pineal melatonin was seen. It was established that the pineal α1‐adrenoceptor is under neural control because interruption of neural stimulation of the pineal by bilateral superior cervical ganglionectomy (SCGX) or by exposing rats to constant light for 3 weeks doubled receptor density but did not change affinity for [125I]HEAT. Administration of various α1‐adrenoceptor agonists either acutely (i.p. injection) or chronically (s.c. infusion) did not alter the number of specific [125I]HEAT binding sites. Together these results indicate that the pineal α1‐adrenoceptor, like the pineal β‐adrenoceptor, is regulated by sympathetic nerve activity, probably through the physiological release of the neurotransmitter norepinephrine. However the absence of a circadian rhythm in α1‐adrenoceptor number and lack of down‐regulation by adrenergic agonists imply different mechanisms of regulation.