bluuebunny/crossref_metadata_2025_split huggingface dataset:
TURNOVER OF RIBOSOMAL RNA IN THE RAT BRAIN *
Authors: Dawson D. M. 
Published: October 2006

SUMMARYRibosomal RNA from rat brain has been partially purified by sodium dodecyl‐sulphate treatment of microsomes, and density gradient centrifugation.The apparent half‐life of ribosomal RNA after labelling with a pyrimidine precursor was 6 days. Classes of ribosomal RNA with longer half‐lives could not be excluded.There was evidence for re‐utilization of the labelled precursors.
STUDIES OF WATER SOLUBLE LIPOPROTEINS IN RAT BRAIN*
Authors: Herschkowitz N. , Mckhann† G. M. , Shooter E. M. 
Published: October 2006

Abstract—The occurrencc of water soluble lipoprotein in the 105,000 g supernatant of rat brain homogenate has been demonstrated.The lipoproteins of brain differed from those of the serum with respect to lipid composition, density and reaction to serum lipoprotein antibodies.Acrylamide gel electrophoresis resolved the brain supernatant into four zones which stained with lipid dye. It was possible to demonstrate that these zones also contained protein by double staining of the gel for lipid and protein. Two of the zones differed in their mobility from serum lipoprotein.Preparative acrylamide gel electrophoresis isolated protein fractions in supematant which contained both lipid and protein and permitted preliminary identification of the lipoprotein bands amongst all the protein bands resolved by acrylamide gel electrophoresis.
URIDINE NUCLEOTIDES IN BRAIN*†
Authors: Wong Kim Ping , Sourkes T. L. 
Published: October 2006

Abstract—Two uridine nucleotides, UDPG and UDPGA, have been measured in brain by a procedure whereby they are extracted from tissue with subsequent utilization, either directly with (UDPGA) or after dehydrogenation (UDPG), in a glucuronidation reaction with harmol or harmalol as cosubstrate. The concentrations of UDPG and UDPGA in brains of a few species of animals examined are, respectively, 11.5–23.3 μmoles/100 g and 0.7–2.5 μmoles/100 g tissue. The ratios of UDPGA to UDPG range from 4% to 11%. The role and importance of these uridine nucleotides in brain are discussed.
TRANSPORT OF SULPHATE, THIOSULPHATE AND IODIDE BY CHOROID PLEXUS IN VITRO1
Authors: Robinson R. J. , Cutler R. W. P. , Lorenzo A. V. , Barlow C. F. 
Published: October 2006

Abstract—Isolated choroid plexuses of rabbits and cats were incubated in artificial cerebrospinal fluid medium containing [35S]sulphate, [35S]thiosulphate or [125I]iodide and combinations thereof. After 1 hr incubation the mean ratio of tissue concentration to medium concentration was 2·46 for [35S]sulphate, 2·39 for [35S]thiosulphate, and 270 for [125I]iodide. Uptake of all three anions was greatly reduced at 0° and by addition of dinitrophenol to the medium. Other inhibitors selectively reduced the uptake of particular anions; non‐radioactive sulphate and thiosulphate reduced both [35S]sulphate and [35S]‐thiosulphate uptake with much less effect on [125I]iodide uptake, while non‐radioactive iodide and thiocyanate greatly reduced [125]iodide uptake with little or no effect on [35S]sulphate or [35S]thiosulphate uptake. It was concluded:(a) that sulphate and thiosulphate, like iodide, were accumulated by choroid plexus in vitro by active transport;(b) that sulphate and thiosulphate share and compete for a transport mechanism which is separate from the iodide transport mechanism; and(c) that the transport of sulphate out of cerebrospinal fluid demonstrated in vivo could occur at least in part in the choroid plexus.
CHANGES IN THE OSMIOPHILIA OF MYELIN AND LIPID CONTENT IN THE KITTEN OPTIC NERVE
Authors: Banik N. L. , Blunt M. J. , Davison A. N. 
Published: October 2006

Abstract—Myelin osmiophilia has been shown to develop significantly later than myelin staining by Luxol fast blue and Sudan black, in the developing kitten optic nerve. These histological changes are accompanied by alterations in the lipid composition of the optic nerve. Although myelination commences at about 10 days post partum in the nerve the appearance of cerebrosides is unexpectedly delayed. Changes in fatty acid chain length and lipid composition of optic nerve are consistent with the suggestion that ‘early’ myelin may be unchanged glial plasma membrane.
STUDIES ON SODIUM TRANSPORT IN RAT BRAIN NERVE‐ENDING PARTICLES
Authors: Ling C.‐M. , Abdel‐Latif A. A. 
Published: October 2006

Abstract— (1) Nerve‐ending particles isolated from crude mitochondrial preparations from rat brain by discontinuous Ficoll density gradient ultracentrifugation were shown to possess a Mg2+ and energy‐dependent transport system for Na+.(2) Ouabain or iodoacetate plus cyanide exerted an inhibitory effect on the outfiux but not the influx of Na+.(3) When K+ was added to a medium containing particles loaded with Na+ (22Na), an immediate release of Na+ from these particles was observed; this suggests the existence of a Na+–K+ exchange transport system.(4) The K+ effect was inhibited by 10‐4 M‐ouabain only at low (about 3·3 mm), but not at high (20 mm), K+ concentrations.(5) The uptake and release of Na+ by the nerve‐ending particles were found to be temperature‐dependent.(6) Only nerve‐ending particles with intact synaptosomal membranes were found to transport Na+ actively.
NUCLEOTIDE METABOLISM IN RAT BRAIN
Authors: Santos J. N. , Hempstead K. W. , Kopp L. E. , Miech R. P. 
Published: October 2006

Abstract— The uptake, the conversion to nucleotides, and their incorporation into RNA for labelled glycine, aspartate, the free bases and nucleosides of purines and pyrimidines were investigated with cortical slices of rat cerebrum. At the end of a 1‐hr incubation time the slice‐to‐medium ratio of the radioactivities for labelled aspartate, glycine, adenine and adenosine were 34, 26, 20 and 5, respectively, while the slice‐to‐medium ratios for hypoxanthine, inosine, guanine, guanosine, xanthine, orotate, cytidine, cytosine, uridine, and uracil ranged from 1.3:1 to 2:1. Over 99 per cent of the total radioactivity taken up by the cortical slices was present in the TCA supernatant and 86, 82, 65, 50, 34, 23, 20 and 1.6 per cent of this radioactivity was in the form of nucleotides at the end of a 1‐hr incubation with labelled adenine, adenosine, hypoxanthine, inosine, uridine, orotate, cytidine, and glycine, respectively.The incorporation of various radioactive precursors into RNA of cortical slices suggests that nucleotides originating from either de novo synthesis or preformed purine derivatives enter the same nucleotide pool utilized for RNA synthesis. The supernatant fraction from homogenized cerebrum was investigated for the presence of various anabolic and catabolic enzymes associated with nucleotide metabolism. These results were correlated with the data from the RNA incorporation studies, and a possible role for AMP: pyrophosphate phosphoribosyltransferase (adenine phosphoribosyltransferase, I.U.B. 2.4.2.7) to achieve intercellular transfer of AMP is discussed.
THE METABOLISM OF γ‐AMINOBUTYRIC ACID (GABA) IN THE LOBSTER NERVOUS SYSTEM–GLUTAMIC DECARBOXYLASE*
Authors: Molinoff P. B. , Kravitz E. A. 
Published: October 2006

Abstract— The glutamic acid decarboxylase has been purified from the lobster central nervous system. Potassium ion (0‐075 m) and β‐mercaptoethanol (0‐025 m) were essential for enzyme activity. Enzyme had about 60 per cent of its optimal activity in the absence of added pyridoxal phosphate. Carbonyl reagents (10−4m‐hydroxylamine or amino oxyacetic acid) would abolish this residual activity. The pH optimum of the enzyme was about 8‐0.Standard Michaelis‐Menten kinetics were applied to the decarboxylation of glutamate and a Km of 0.02 m was calculated. GABA inhibited the reaction (Ki= 1.25 × 10−3m), but the inhibition showed anomalous behaviour when graphed by the method of Lineweaver and Burk (1934). The GABA inhibition resembled competitive inhibition, but curves rather than straight lines intersecting at a common point on the velocity axis were obtained. This effect remains unexplained.Preliminary studies failed to reveal any subunit structure of the enzyme. The sedimentation coefficient (.S20.w) was 6‐55 in a sucrose density gradient in an ultracentrifuge. This was unchanged by the addition of any of the agents that influence enzyme activity.The subcellular localization of the decarboxylase was explored in crude homogenates of lobster central nervous system prepared in various ways. The major proportion (about 90 per cent) of the enzyme activity was in the soluble fraction.‘Particulate’enzyme could be prepared, but gentle suspension of this material in buffer liberated most of the activity.A contaminant in the radioactive substrates led to the production of radioactive GABA without the simultaneous evolution of CO2. In this case, GABA production required active enzyme but was not an exclusive property of the glutamic decarboxylase activity.
THE METABOLISM OF TRITIATED DOPAMINE IN REGIONS OF THE RAT BRAIN IN VIVO—II
Authors: Taylor K. M. , Laverty R. 
Published: October 2006

Abstract— The levels of tritiated catecholamines and metabolites were measured in regions of the rat brain at intervals after the intraventricular injection of [3H]dopamine, [3H]nor‐adrenaline and [3H]normetanephrine. The disappearance of catecholamines and appearance of metabolites with time and the regional turnover rates of these amines indicate that the major pathway of the metabolism of noradrenaline and dopamine actively released from physiological storage sites is to the neutral alcoholic metabolites. The acid metabolites, homovanillic acid and 3,4‐dihydroxyphenylacetic acid appear to be only minor products of normal dopamine metabolism in rat brain regions including the striate, but are the main end products of the metabolism of excess exogenous dopamine.The active metabolism of stored noradrenaline to alcohol metabolites is also indicated by the increase in neutral alcohol metabolites accompanying the increased noradrenaline turnover when rats were subjected to electroshock stress. Therefore in the rat brain, neutral alcohol metabolites of dopamine and noradrenaline have great significance in the study of physiological catecholamine turnover in any region.
THE EFFECT OF PHOSPHOLIPASES ON THE UPTAKE OF ATROPINE AND ACETYLCHOLINE BY SLICES OF MOUSE BRAIN CORTEX
Authors: Heilbronn E. 
Published: October 2006

Abstract—The uptake of [3H]atropine, [3H]acetylcholine and [14C]inulin in mouse brain cortex slices was studied in slices treated with phospholipases A or C. In control experiments the slices took up atropine and acetylcholine against a concentration gradient, indicating active uptake. This uptake was decreased by ouabain, by anaerobic conditions and by an increase in the potassium ion concentration.The phospholipases were found to decrease the uptake of atropine and particularly that of acetylcholine in the slices. The uptake of labelled inulin in enzyme‐treated slices, as compared to untreated slices, was not decreased, indicating no change in the inulin space. The effect of the phospholipases was time dependent and, up to a certainlimit, concentration dependent. The effect of ouabain in decreasing the uptake of atropine was not eliminated by the enzyme treatment. The effect of anaerobic conditions in decreasing the uptake was weak after treatment with phospholipases. The effect of higher concentrations of potassium ions was abolished by treatment with phospholipase A.The results emphasize the importance of phospholipids as substances controlling structural order in membranes and suggest their participation in active transport.
ELECTROLYTE DISTRIBUTION IN RABBIT SUPERIOR CERVICAL GANGLION1
Authors: Woodward J. K. , Bianchi C. P. , Erulkar S. D. 
Published: October 2006

Abstract— Superior cervical ganglia of the rabbit were removed and analysed for Na+, K+, Ca2+, Mg2+ and Cl−. The mean electrolyte content in μmole/g wet wt. was as follows: Na+, 64.7 ± 1.3; K+, 65.1 ± 2.7; Ca2+, 3.71 ± 0.28; Mg2+, 3.70 ± 0.50; and Cl−, 50.15 ± 2.26. Water content was 0.76 ± 0.01 ml/g wet wt. Extracellular space was 0.37 ± 0.01 ml/g, and the vascular space 0.0238 ± 0.0002. The mean resting potential of the rabbit superior cervical ganglion was – 68.6 mv. After correction for extracellular electrolyte content, the potential differences, ENa, EK and Ecl, were estimated to be +33.6 mv, –96.9 mv and ‐41.1 mv, respectively, in the ganglia.Permeability coefficients for K+, Na+, and Cl− were estimated to be 1:0.06:0.02. Replacement of sodium in physiological saline solution by lithium results in a displacement of 94 per cent of the sodium content of the ganglion and 69 per cent of the potassium after 30 min of equilibration.
THE DISTRIBUTION OF SYNAPTOSOMAL OXIDATIVE ENZYMES AFTER EXPOSURE TO DEOXYCHOLATE1,2
Authors: Moore W. V. , Lindall A. W. 
Published: October 2006

Abstract— The distributions of NADH2 dehydrogenase, NADH, cytochrome c reductase and cytochrome oxidase have been determined utilizing synaptosomal isolation techniques. Deoxycholate was used to determine compartmentation and/or ‘latency’ of these activities. NADPH, dehydrogenase proved to be a soluble and mitochondrial enzyme and the activity of this enzyme was not appreciably changed by deoxycholate treatment. NADHg cytochrome c reductase proved to be a mitochondrial enzyme with considerable activity in microsomal fractions. Deoxycholate treatment increased activity in the synaptosomal fraction 8.3‐fold. A bimodal activation pattern was observed with synaptosomal and mitochondrial NADH, cyrochrome c reductase upon exposure to increasing concentrations of deoxycholate, with enhancement of activity at 0.25 % (w/v) and 0.50 % (w/v) deoxycholate. The enzyme was stable at concentrations of deoxycholate less than 0.25% (w/v) but was irreversibly inactivated at concentrations higher than 0.25% (w/v). The mechanism of this activation pattern appeared to be a combination of enzyme release and inactivation. Similar results were not observed in liver mitochondria.Cytochrome oxidase, a known mitochondrial marker, exhibited a 17‐fold increase in synaptosomal activity with deoxycholate treatment. The synaptosomal cytochrome oxidase activity after deoxycholate treatment approached the activity in the free mitochondrial fraction. The percentage of mitochondrial protein in synaptosomal fractions was estimated to be about 30 per cent from a comparison of the respective total (deoxycholate‐treated) activities. On the basis of these data we suggest that the synaptosomal fraction possesses a relatively sizable energy‐producing potential which may be of significance in vivo.
TRANSAMINATION OF AMINO ACIDS IN HOMOGENATES OF RAT BRAIN
Authors: Benuck M. , Stern F. , Lajtha A. 
Published: October 2006

Abstract— The aminotransferase activity of homogenates of brains from adult and neonatal rats has been investigated. Aminotransferase activity was demonstrated wtih 15 of 22 amino acids incubated with seven keto acids. The basic amino acids exhibited little or no activity.

The greatest activity was obtained when glutamate or aspartate was incubated with α‐ketoglutarate or oxaloacetate. Significant activity was also observed when the neutral aliphatic and aromatic amino acids were incubated with these two keto acids.
Activity with pyruvate was obtained principally upon incubation with glutamate and alanine. Most of the other amino acids that underwent transamination with α‐ketoglutarate also did so with pyruvate, although at a lower rate.
When phenylpyruvate was added to the medium, glutamate, phenylalanine and tyrosine transaminated most actively.
Incubations with 11 amino acids and glyoxylic acid demonstrated aminotransferase activity, with glutamate and ornithine being the most active substrates.
α‐Ketoisocaproate and α‐ketoisovalerate accepted amino groups primarily from the branched‐chain amino acids. Except for glutamate, activity with other amino acids was low or not detectable.
A comparison of aminotransferase activity in the newborn brain with that in the adult brain showed that the greatest change in activity occurred for glutamate with pyruvate or for alanine with α‐ketoglutarate, these activities increasing about 10‐fold from birth to adulthood; during this time activities with most other amino acids increased two‐ to threefold. Amino transfers from the branched‐chain amino acids showed no increase with maturation, and some reactions, such as that with methionine and a number of keto acids, decreased from birth to adulthood.
Our results correspond in general to previous studies of aminotransferase activity in brain and in liver. However, our study also indicates a possible second aminotransferase acting on the branched‐chain amino acids, the presence of aminotransferase activity for methionine and asparagine, and relatively high aminotransferase activity for glutamine or ornithine when incubated with glyoxylic acid rather than other keto acids. Moreover, phenylpyruvate and glyoxylate are active in amino transfers and may serve as substrates for a number of aminotransferases.
PROTEIN DEGRADATION IN SQUID GIANT AXONS
Authors: Orrego F. 
Published: October 2006

Abstract—Axoplasm extruded from giant axons of the Chilean squid, Dosidicus gigas, contained a low level of neutral proteinase‐like activity, equivalent to 4 × 10−6 mg of chymotrypsin per mg of axoplasmic protein. The enzyme was active at physiological pH and ionic strength. Activity was completely inhibited by 1 mM‐para‐hydroxymercuribenzoate and was enhanced by divalent metal cations, especially Ca2+. Axoplasm also exhibited proteinase activity at pH 4.8. Both neutral and acid proteinase like activities were also present in the axonal sheath containing Schwann cells, but their specific activities relative to those in the axoplasm were different. A physiological role, related to the axoplasmic flow of protein, is discussed for the axoplasmic neutral proteinase‐like activity.
EFFECTS OF POTASSIUM AND GLUTAMATE ON BRAIN CORTEX SLICES: UPTAKE AND RELEASE OF GLUTAMIC AND OTHER AMINO ACIDS
Authors: Arnfred T , Hertz L 
Published: October 2006

Abstract— Effects of an increased concentration of K+ (55 mm) in the medium on fluxes of glutamate and other amino acids in the presence and absence of 10 mm‐glutamate were studied. The following observations were made:(1) The efflux of glutamate is slightly increased by excess K+. The glutamate efflux is smaller than the potassium fluxes.(2) The K+‐induced increase of glutamate efflux is enhanced under anoxia or in glutamate‐containing media.(3) The influx of glutamate is unaffected or slightly increased by excess K+.(4) The efflux of GABA is increased by excess K+, both in the absence and in the presence of glutamate.(5) Efflux of glutamine, leucine and lysine is increased by excess K+, but only provided that glutamate is also present in the medium.(6) Efflux of glutamate and of GABA is increased by addition of 10 mm‐glutamate.
MEDIATION BY β‐ADRENERGIC RECEPTORS OF EFFECT OF NOREPINEPHRINE ON PINEAL SYNTHESIS OF [14C]SEROTONIN AND [14C]MELATONIN
Authors: Wurtman R. J. , Shein H. M. , Larin F. 
Published: October 2006

AbstractRat pineal organs maintained in organ culture converted [14C]tryptophan to [14C]serotonin and [14C]melatonin. The synthesis of both indoles was stimulated by the presence of norepinephrine or dibutyryl adenosine 3′,5′‐monophosphate. This effect of norepinephrine could be blocked by the α‐adrenergic blocking drug, propranolol, but was not modified by the a‐adrenergic blocking agent, phenoxybenzamine. Neither blocking agent modified the pineal response to dibutyryl adenosine 3′,5′‐monophosphate. Unlike dibutyryl adenosine 3′,5′‐monophosphate, the naturally occurring adenosine phosphates did not stimulate synthesis of [14C]melatonin in vitro.
EFFECT OF TETANUS TOXIN ON THE CONTENT OF GLYCINE, GAMMA‐AMINOBUTYRIC ACID, GLUTAMATE, GLUTAMINE AND ASPARTATE IN THE RAT SPINAL CORD12
Authors: Fedinec A. A. , Shank R. P. 
Published: October 2006

AbstractTetanus toxin injected intramuscularly induced no significant changes in the levels of glycine, GABA, glutamate, glutamine or aspartate in extracts of spinal cord from rats killed at timed intervals during the development of local and generalized tetanus. The amino acid contents in the hemisegment (longitudinal one‐half) of the spinal cord (L2‐L6) on the injected side (left gastrocnemius muscle) did not differ significantly from the contents in the hemisegment of the spinal cord on the non‐injected side. Nor were there any consistent changes in the contents of the amino acids in either hemisegment of the spinal cord as the tetanic symptoms became progressively more severe. Hence, the amino acid pool in the spinal cord was relatively stable despite the metabolic changes known to occur in tetanus. Our observations are consistent with the view of Johnston, De Groat and CURTIS (1969) who suggested that if glycine were indeed a spinal inhibitory neurotransmitter released by interneurons affected by tetanus toxin, the toxin should interfere with the release of the amino acid rather than deplete the transmitter stores.
CAPACITIES FOR BINDING AMINO ACIDS BY tRNAs FROM RAT BRAIN AND THEIR CHANGES DURING DEVELOPMENT
Authors: Barra H. S. , Uñates Lilia E. , Sayavedra Marta S. , Caputto R. 
Published: October 2006

Abstarct–The total tRNA and some specific tRNAs from the 100,000g soluble fraction of rat brain were measured during development (postnatal ages 4–55 days). For determination of specific tRNAs we developed a method that measured their capacities to bind specific amino acids. Levels of total tRNA were decreased in the soluble fraction from the brains of 55‐day‐old rats in comparison to those for the 4‐day‐old rats. The aminoacylation capacities of tRNAs for phenylalanine, lysine, proline, valine, leucine, alanine and isoleucine were diminished in the 55‐day‐old rats in comparison to those for 4‐day‐old rats when expressed per unit wet weight of brain. When the 4‐ to 55‐day changes in aminoacylation capacity of each specific tRNA was expressed relative to that of the total tRNA, tRNAPhe and tRNALysLys were diminished; tRNAPro, tRNAVel, tRNAGIY and tRNALeu showed no significant changes; and tRNAA1a and tRNAIle were increased. Incorporation of amino acids into a material insoluble in hot TCA (probably proteins) in a ribosome‐free system occurred in the brain preparations. Out of ten different amino acids studied, arginine and tyrosine exhibited the highest values for this type of transfer.
FAST AXOPLASMIC TRANSPORT OF ACETYLCHOLINESTERASE IN MAMMALIAN NERVE FIBRES
Authors: Ranish N. , Ochs S. 
Published: October 2006

Abstract— Acetylcholinesterase (acetylcholine acetyl‐hydrolase, EC 3.1.1.7) is carried down mammalian nerve fibres by the fast axoplasmic transport system. This conclusion was derived from experiments involving the ligation of cat sciatic nerves at two sites placed 83.5 mm apart. The enzyme accumulated in segments of nerve proximal to the upper ligation in a linear fashion over a period of at least 20 h. At approximately 5 h the accumulation of enzyme ceased in the nerve segment proximal to the distal ligation within the isolated length of nerve, an observation indicating that the portion of AChE free to move within the isolated nerve had been depleted during this period of time. The freely moving fraction of AChE was estimated to be 15% of the total enzyme activity present in the nerve (10% in the proximo‐distal direction and 5% in the retrograde direction). The rate of AChE downflow (as estimated from the intercept of the curve plotting accumulation with the line denoting when depletion started) was 431 mm/day within a 95% confidence interval of 357–543 mm/day. In view of the variability, our results demonstrated that AChE was being carried by the fast axoplasmic transport system, which in earlier studies was estimated to have a characteristic rate close to 410 mm/day.An accumulation of AChE was also found on the distal side of the ligations that represented a movement of AChE in the distal‐proximal direction in the fibres. This retrograde transport was smaller in amount (about one‐half) than the proximo‐distal rate of transport, or close to 220 mm/day. The rate of AChE transport was discussed in relation to the ‘transport filament’ hypothesis of fast axoplasmic transport.