bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECTS OF ADDED SUBSTANCES ON RNA AND PROTEIN SYNTHESIS IN IMMATURE NEURONS
Authors: Hemminki Kari 
Published: December 2006

Abstract— A newly described method for the isolation of morphologically intact neurons from newborn rat brain was used to study the influence of inhibitors and neuroactive substances on RNA and protein synthesis in these cells in vitro. Incorporation of [14C]‐uridine into RNA and [3H]leucine into protein proceeded rapidly and continued up to 3 h. When the incorporation mixture was chased at 20 min with an excess of nonradioactive uridine and leucine, hardly any degradation of labelled RNA was noted during the following 2 h 40 min. In contrast, the specific radioactivity of proteins decreased by 22 per cent indicating turnover of cellular proteins.Incorporation of labelled leucine into protein was markedly inhibited in the presence of NaF and cycloheximide but not affected in the presence of chloramphenicol or pancreatic RNase. A mixture of ATP + GTP depressed the incorporation by 38 per cent. The responses to ATP + GTP and RNase indicated that the incorporation system was typically cellular. Acetylcholine, γ‐aminobutyrate, noradrenaline and phenylalanine in the incubation medium depressed the incorporation of labelled uridine into RNA by 10–30 per cent and 5‐hydroxytryptamine by 75 per cent. Acetylcholine, γ‐aminobutyrate and noradrenaline had no effect on protein synthesis, while 5‐hydroxytryptamine and phenylalanine inhibited the incorporation by 60–80 per cent. Testosterone and prednisolone depressed both RNA and protein synthesis while thyroxine caused slight but non‐significant stimulation.
THE INHIBITION OF RAT BRAIN ATP: CITRATE OXALOACETATE‐LYASE BY L‐GLUTAMATE1
Authors: Szutowicz A. , Stepie M. , Angielski S. 
Published: December 2006

Abstract—

Among 16 amino acids tested only D‐ and L‐glutamate were found to be specific inhibitors of citrate lyase from adult rat brain. Glutamate also inhibited citrate lyase from the liver of starved animals while it was without effect on lyase from those refed with carbohydrate. L‐Glutamate did not inhibit the citrate lyase from brains of newborn rats.
The inhibitory effect of L‐glutamate was increased when the time of preincubation was prolonged, but only in the presence of both ATP and MgCl2. This time‐dependent inhibition could be reversed by addition of high concentrations of ATP.
L‐Glutamate was without effect on Km and Vmax values for MgCl2. Excess of Mg2+ ions was indispensable for glutamate inhibition.
L‐Glutamate was shown to be competitive with respect to the ATP inhibitor of the lyase, with a Ki of 0.3mM.
The mechanism of L‐glutamate inhibition may be due to the reaction of a glutamate‐Mg complex with the phosphorylated intermediary form of the lyase, resulting in the formation of a lyase‐glutamate complex.
The physiological significance of the inhibitory action of glutamate is discussed.
CHANGES IN THE ACETYLCHOLINE CONTENT OF DIFFERENT BRAIN REGIONS OF THE RAT DURING A LEARNING EXPERIMENT1
Authors: Matthies H. , Rauca Ch. , Liebmann H. 
Published: December 2006

Abstract— The ACh content of the rat hippocampus, visual cortex, auditory cortex and corpus striatum was estimated as so‐called free, labile‐bound and stable bound acetylcholine at different times after the learning of a brightness discrimination.In the hippocampal region the free acetylcholine was highly increased immediately after the training, whereas the stable bound ACh and the labile‐bound fraction rose 70 min and 4 h respectively‐after completion of training.Only small alterations of the ACh fractions were observed in the visual and auditory cortices. In the corpus striatum no changes appeared.
EFFECTS OF LESIONS AND DRUGS ON BRAIN TRYPTAMINE
Authors: Marsden C. A. , Curzon G. 
Published: December 2006

Abstract— The effects of various drugs and lesions on rat brain 5‐hydroxytryptamine and tryptamine were determined. Monoamine oxidase inhibition caused a proportionately greater increase in tryptamine than in 5‐hydroxytryptamine, reserpine depleted 5‐hydroxytryptamine but had no effect on tryptamine while p‐chlorophenylalanine lowered 5‐hydroxytryptamine but increased tryptamine. α‐Methyl‐p‐tyrosine reduced striatal dopamine with no effect on either 5‐hydroxytryptamine or tryptamine. Increasing brain tryptophan by amphetamine administration. 24 h food deprivation or giving L‐tryptophan did not increase brain tryptamine. However a high dose of L‐tryptophan (100 or 200mg/kg) together with a monoamine oxidase inhibitor caused a proportionately much greater increase in tryptamine than in 5‐hydroxytryptamine. Raphe lesions reduced 5‐hydroxytryptamine by 64 per cent and tryptamine by only 29 per cent while intraventricular 6‐hydroxydopamine lowered striatal dopamine (56 per cent), had no effect on 5‐hydroxytryptamine but reduced tryptamine by 24 per cent, suggesting that tryptamine can be formed in both 5‐HT and catecholaminergic neurones.The results are discussed in relation to the formation, distribution, storage and possible transmitter function of tryptamine in rat brain.
ESTIMATION OF NORADRENALINE AND ITS MAJOR METABOLITES SYNTHESIZED FROM [3H]TYROSINE IN THE RAT BRAIN
Authors: Nielsen M 
Published: December 2006

Abstract— A new procedure is described for the estimation of [3H]noradrenaline (NA) and its major metabolites free and conjugated 3‐methoxy‐4‐hydroxyphenylglycol (MOPEG) and free and conjugated 3,4‐dihydroxyphenylglycol (DOPEGI in the rat brain. The procedure involves adsorption on to alumina, cation exchange chromatography. enzymatic hydrolysis of conjugates and thin‐layer‐chromatography after intraventricular (IVT) or intravenous injection of [3H]tyrosine. In a time‐course study the formation and accumulation of the metabolites have been measured from 15min to 23h after IVT injection of [3H]tyrosine. [3H]MOPEG and [3H]DOPEG were found in almost equal amounts during the synthesis phase of [3H]NA as well as during the storage and disappearance phase of [3H]NA.The maximum levels of conjugated [3H]MOPEG and conjugated [3H]DOPEG were found 2 h after IVT [3H]tyrosine. At this time interval the levels of free [3H]MOPEG and free [3H]DOPEG amounted to 25% and 11%, respectively of the corresponding conjugates. Increasing doses of IVT injected [3H]tyrosine (10‐90 °Ci) revealed that the accumulation of [3H]NA and metabolites was linear up to about 50 °Ci. Following intravenous instead of IVT injection of [3H]tyrosine. much higher doses (325 °Ci) were needed to obtain measurable amounts of total [3H]MOPEG and [3H]DOPEG‐SO4 in the rat brain.The formation of labelled NA metabolites from [3H]NA in the rat brain in vim measured as total [3H]MOPEG and [3H]DOPEG‐SO4 was influenced by drugs affecting [3H]NA synthesis, release and metabolism. Synthesis inhibition with a‐methyltyrosine (250mg‐kg−1) or FLA‐63 (30mg‐kg−1) and inhibition of monoamine oxidase with pargyline (75mg‐kg−1) or clorgyline (2mg‐kg−1) strongly decreased the accumulation of total [3H]MOPEG and [3H]DOPEG‐SO4. Noradrenaline receptor blockade with phenoxybenzamine (20mg‐kg−1) increased both total [3H]MOPEG and [3H]DOPEG‐SO4 to about 160% of the control values. NA release and uptake inhibition induced by d‐amphetamine (10mg‐k−1) or phenylethylamine (two doses of 80mg‐kg−1) decrease strongly the levels of [3H]NA and [3H]DOPEG‐SO4. whereas total [3H]MOPEG was only very slightly decreased or even increased as compared to controls.
THE SUBCELLULAR DISTRIBUTION OF [14C]GABA AND [3H]DOPAMINE IN THE RETINA
Authors: Attlrwill C. K. , Neal M. J. 
Published: December 2006

Abstract— Rabbit retinae were homogenized in isotonic sucrose and subjected to differential and density gradient centrifugation. Preliminary electron microscopic examination of some of the fractions indicated that in addition to the subcellular particles usually observed in brain homogenates, the photoreceptor cells gave rise to several characteristic fragments. These included fragmented outer limbs, aggregations of mitochondria from the inner segments, and photoreceptor terminals. Unlike the synaptosomes formed from the conventional type of synapses in the retina, these photoreceptor terminals appeared to sediment mainly in the low speed crude nuclear pellet (P1).Retinae were incubated with low concentrations of [14C]GABA and/or [3H]dopamine prior to subcellular fractionation and in these experiments the P2 pellet was further fractionated on sucrose density gradients. Analysis of the radioactivity in the fractions showed that labelled GABA was accumulated by osmotically sensitive particles which had the sedimentation characteristics of synaptosomes. The panicles accumulating [3H]dopamine appeared to belong to a different, slightly lighter, population than those accumulating [14C]GABA. It is tentatively suggested that the particles accumulating labelled GABA were synaptosomes because the fractions containing these particles also possessed most of the GAD activity of the gradient. In contrast, GABA‐T and MAO activity was found in the dense fractions of the gradients usually associated with mitochondria.When retinae were incubated with a high concentration of labelled GABA a‘lighter’population of particles seemed to accumulate the amino acid than when a low external GABA concentration was used. These results suggest that the high and low affinity uptake processes for GABA in the retina may have different cellular sites.
DEVELOPMENTAL AND AGING CHANGES IN PROTEIN CONCENTRATION AND 2′,3′‐CYCLIC NUCLEOSIDEMONOPHOSPHATE PHOSPHODIESTERASE ACTIVITY (EC 3.1.4.16) IN HUMAN CEREBRAL WHITE AND GRAY MATTER AND SPINAL CORD
Authors: Toews A. D. , HORROCKS L. A. 
Published: December 2006

Abstract— The concentration of protein as assayed by the Lowry method and the specific activity of 2′.3’‐cyclic nucleosidemonophosphate phosphodiesterase (CNP), an enzyme characteristic of the myelin sheath, were determined in human CNS tissues obtained at autopsy from subjects ranging in age from 26 weeks gestation to 83 y.CNP activity in cerebral white matter samples was very low until approx 2 months of age when it increased rapidly, reaching near‐adult levels by 2 y of age. CNP activity in adult (15–60 y) cerebral white matter was 8.1 ± 1.0 μmol/min/mg protein (mean ±s.d.). The protein concentration of cerebral white matter increased from 64 mg/g wet tissue at 26 weeks gestation to adult levels (118.5 ± 10.0 mg/g wet tissue) by 16–18 months. CNP activity in cerebral gray matter was initially very low and showed only a small increase during development to adult values of approx 1.4 μmol/min/mg protein. In spinal cord, adult values (3.7 ± 0.56 μmol/min/mg protein) were found shortly after birth. The increase in CNP activity to near‐adult values occurred earlier in cross‐sections of cervical spinal cord than in cerebral white matter. The increase in spinal cord protein concentration showed a similar trend (adult values = 103.1 ± 9.5 mg/g wet tissue).The white matter protein concentration decreased significantly with age over the 15–83 y interval examined but the CNP specific activity in white matter did not. The protein concentration of the 61–83 y group was 8% lower than that of the 15–60 y group. The spinal cord protein concentration decreased significantly and the spinal cord CNP specific acitivity increased significantly with increasing time between death and sample freezing. The sex of the individual had no significant effect on any of the variables examined.The developmental curves obtained for these tissues are consistent with the hypothesis that CNP is an intrinsic myelin component in human CNS myelin. The marked increase in CNP activity in white matter coincides with the period of rapid myelin deposition as determined by other parameters. CNP activity may be useful as an index of myelination in human CNS tissues.
METABOLIC RELATIONSHIPS BETWEEN MYELIN SUBFRACTIONS: ENTRY OF GALACTOLIPIDS AND PHOSPHOLIPIDS 1
Authors: Benjamins Joyce A. , Miller S. L. , Morell P. 
Published: December 2006

Abstract— Partially purified myelin from the brains of 17‐day‐old rats was separated into 4 subfractions on a three‐step sucrose gradient by virtue of heterogeneity in density and particle size. Precursor‐product relationships between different membrane fractions were investigated by determining the specific radioactivity of individual lipids in each subcellular fraction 15 min after intracranial injection of an appropriate precursor. Rats were injected with [2‐3H]glycerol. myelin subfractions prepared, and individual lipids separated by TLC. For choline and ethanolamine phospholipids, specific radioactivity was highest in the densest fraction (D), intermediate in the next densest fraction (C), and lowest in the lighter fractions (B and A). Similar results were observed for cerebroside and sulphatide when [3H]galactose was the precursor. These data are consistent with (but do not prove) a precursor‐product relationship for individual lipids from the densest to the lightest subfraction.Another experimental design involving time staggered injections of [3H] and [14C] precursors was developed which enables a more definitive result with regard to precursor‐product relationships to be obtained. A precursor‐product relationship between a given lipid in a dense myelin membrane fraction, and the same lipid in a lighter subfraction, would be indicated by a change in isotope ratio. If there is no precursor‐product relationship. Ihe isotope ratio should be constant. Such experiments were done with [3H] and [14C]glycerol. The data indicated that phosphatidyl ethanolamine and its plasmalogen analog were added first to the densest subfraction and then in turn to the lighter subfractions. In contrast, phosphatidyl choline and its plasmalogen analog were added “simultaneously” (i.e. with delays of much less than 15min) to each of the subfractions. Similar experiments with [3H] and [14C]galactose showed that cerebroside, sulphatide and galactosyl diglyceride also entered the subfractions simultaneously rather than in sequential order. Thus the assembly of the myelin sheath involves an obligate order of addition of certain lipids. while other lipids are probably added in a random order.
GLUTAMINE UPTAKE AND METABOLISM BY THE ISOLATED TOAD BRAIN: EVIDENCE PERTAINING TO ITS PROPOSED ROLE AS A TRANSMITTER PRECURSOR
Authors: Shank R. P. , Aprison M. H. 
Published: December 2006

Abstract— Hemisections of toad brains, when incubated in a physiological medium containing no glutamine. released considerable amounts of this amino acid into the medium. When glutamine was included in the medium at a concentration of 0.2 mm the net efflux from the tissue was reduced but not totally prevented. Although there was no net uptake of glutamine, the tissue did accumulate [U‐14C]glu‐tamine and some of this labelled glutamine was rapidly metabolized to glutamate, GABA and aspartate. The precursor‐product relationship for the metabolism of glutamine to glutamate differed from the classic single compartment model in that the specific radioactivity of glutamate rose very quickly to approx one‐tenth that of glutamine, but increased slowly thereafter. These data suggest that the [14C]glutamine was taken up into two metabolically distinct compartments and/or that some of the [14C]glutamine was converted to [14C]glutamate during the uptake process.The uptake of [14C]glutamine was diminished when the tissue was incubated in a non‐oxygenated medium or when Na+ was omitted (substituted with sucrose) and K+ was concomitantly elevated. However, on a relative basis, the incorporation of radioactivity into glutamate and GABA was increased by these incubation conditions. The metabolism of glutamine to aspartate was greatly depressed when the tissue was not oxygenated. The glutamate formed from [U‐14C]glutamine taken up by the tissue was converted to GABA at a faster rate than was glutamate derived from [U‐14C]glucose. [U‐14C]gly‐cerol or exogenous [U‐14C]glutamate. This suggests that glutamine was metabolized to GABA selectively; i.e. on a relative basis, glutamine served as a better source of carbon for the synthesis of GABA than did glucose, glycerol or exogenous glutamate.When the brain hemisections were incubated in the normal physiological medium with or without glutamine. there was very little efflux of glutamate, GABA or aspartate from the tissue. However when NaCl was omitted from the medium (substituted with sucrose) and K+ was elevated to 29 miu. a marked efflux of these three amino acids into the medium did occur, and over a period of 160min, the content of each amino acid in the tissue was depleted considerably. When glutamine (0.2 mm) was included in the Na+ deficient‐high K.+ medium, the average amount of glutamate, GABA and aspartate in the tissue plus the medium was greater than when glutamine was not included in the medium. Such data indicate that CNS tissues can utilize glutamine for a net synthesis of glutamate, GABA and aspartate.The results of this study provide further evidence in support of the concept that the functional (transmitter) pools of glutamate and GABA are maintained and regulated in part via biosynthesis from glutamine. One specific mechanism instrumental in regulating the content of glutamate in nerve terminals may be a process of glutamine uptake coupled to deamidation.
RELATED CHANGES IN AMOUNTS OF ACh AND ATP IN RESTING AND ACTIVE TORPEDO NERVE ELECTROPLAQUE SYNAPSES
Authors: Israel M. , Lesbats B. , Manaranche R. , Marsal J. , Mastour‐Frachon P. , Meunier F. M. 
Published: December 2006

Abstract— Closely related changes in the levels of acetylcholine (ACh) and adenosine triphosphate (ATP) in the electric organ of Torpedo exist during rest and synaptic activity. The present work clarifies these relations by showing:

That both substances are involved in an oscillatory process induced by nerve stimulation.
Both substances are present in synaptic vesicles; the size of the bound pool of ACh is Ca2‐dependent and is large when Ca2+ is low. Free ACh and transmission are restored when Ca2+ is present in the incubation medium.
The amount of ATP in the tissue is also Ca2+‐dependent but is low when Ca2+ is omitted. The addition of Ca2+ to the physiological medium restores the amount of ATP in the tissue.
There is a postsynaptic release of ATP triggered by transmitter depolarization. This release was measured after single nerve impulses.
When added to the incubation medium, nucleotides strongly inhibit transmitter release. It is suggested that the postsynaptic release of ATP regulates transmitter release.
MODULATION OF CYCLIC AMP LEVELS IN THE BOVINE SUPERIOR CERVICAL GANGLION BY PROSTAGLANDIN E, AND DOPAMINE
Authors: Tomasi V. , Biondi Carla , Trevisani A. , Martini Marta , Perri V. 
Published: December 2006

Abstract— Dopamine, norepinephrine, carbamylcholine and PGE1 (prostaglandin E1). increased cyclic AMP concentrations in slices of bovine superior cervical ganglia. PGF1α was less effective and neither PGE2 nor PGF2α had any effect. Dopamine and PGE, alone or in combination, did not modify low Km cyclic AMP phosphodiesterase activity. Combinations of dopamine and PGE, showed a marked synergistic effect, increasing ganglionic cyclic AMP to a much greater extent than that observed when the two compounds were tested alone. Norepinephrine (10 μM), which increased cyclic AMP as much as 10 μm‐dopamine, showed no synergistic effect when tested in the presence of PGE1 or other PGs. Phentolamine, fluphenazine and triflupromazine blocked the dopamine effect without suppressing its synergism with PGE1 Adenylate cyclase of synaptosomes isolated from the ganglia under a variety of experimental conditions appeared to be as responsive to PGE1 as the slices, but it was poorly stimulated by dopamine and was not synergistically modulated by dopamine in the presence of PGE1These and other data are interpreted as indicating the presence of both a PGE1‐sensitive and a PGE1‐modulated dopamine‐sensitive adenylate cyclase in the cervical ganglion. These adenylate cyclases are tentatively assigned to pre‐ and post‐synaptic structures respectively.
THE EFFECT OF INTRAOCULAR INJECTION OF CORDYCEPIN ON RETINAL RNA SYNTHESIS AND ON RNA AXONALLY TRANSPORTED DURING REGENERATION OF THE OPTIC NERVES OF GOLDFISH
Authors: Ingoglia Nicholas A. 
Published: December 2006

Abstract— The presence of relatively large amounts of RNA has been demonstrated in regenerating axons of the goldfish optic nerve. Previous experiments have suggested that this R NA may be composed of only small molecular weight 4S RNA. The present experiments were performed in order to see if inhibiting RNA transport by intraocular injections of cordycepin causes a selective depletion of 4S RNA arriving in the contralateral optic tectum, and thus add further evidence that 4S RNA is axonally transported.Optic nerves were crushed in a group of goldfish and 18 days later 10.0 /tg of cordycepin was injected into the right eye followed 3 h later by injections of [3H]uridine into the same eye. Six days later the amount of axonally transported [3H]RNA was decreased by 89% compared with non‐cordycepin treated controls. The effect of cordycepin on retinal RNA synthesis was shown by autoradiography to be primarily on retinal ganglion cell RNA synthesis with lesser effects on other cellular elements of the retina. SDS polyacrylamide gel electrophoresis at both 1 and 6 days after intraocular injections of cordycepin and [3H]uridine, showed that cordycepin blocks the retinal synthesis of ribosomal RNAs but appeared to have little effect on the synthesis of 4S RNA. When transported RNA in the tectum was fractionated by gel electrophoresis 6 days after injection, it was found that the amount of ribosomal RNA was decreased by approx 70% as a result of cordycepin pretreatment. This correlated well with the effect of cordycepin on the transport of available RNA precursors (also decreased by approx 70%) and is consistent with the contention that in these experiments ribosomal RNA is synthesized in the tectum itself and is not axonal. The amount of [3H] 4S RNA arriving in the tectum, however, was decreased by greater than 90% suggesting that its presence in the tectum was not entirely dependent on the availability of 3H precursors for local synthesis in the tectum.These results are consistent with data suggesting that 4S RNA is the predominant, if not the only, RNA species axonally transported during regeneration of goldfish optic nerves.
A FLUOROMETRIC ASSAY FOR CHOLINE ACETYLTRANSFERASE and ITS USE IN THE PURIFICATION OF THE ENZYME FROM HUMAN PLACENTA
Authors: Hersh Louis B. , Coe Barbara , Casey Lynette 
Published: December 2006

Abstract— A fluorometric assay for choline acetyltransferase has been developed. This assay is based on coupling the choline acetyltransferase dependent formation of acetyl‐CoA from acetylcholine and coenzyme A, to the reactions catalyzed by the enzymes citrate synthase and malic dehydrogenase. Although this assay is not as sensitive as previously described radiometric assays, it can be conveniently used during enzyme purification.Employing this assay method, choline acetyltransferase has been purified from human placenta to a specific activity of 92.7 μmol acetylcholine formed/min/mg protein.