bluuebunny/crossref_metadata_2025_split huggingface dataset:
CALCIUM FLUXES IN CULTURED AND BULK ISOLATED NEURONAL AND GLIAL CELLS
Authors: Lazarewicz J. W. , Kanje M. , Sellström A. , Hamberger A. 
Published: October 2006

Abstract— The influx and efflux of 45Ca has been studied in cultured human glioma and mouse neuroblastoma cells and in isolated fractions enriched in synaptosomes, neuronal and astrocytic perikarya from rabbit brain.The uptake of 45Ca was somewhat more efficient in glioma compared to neuroblastoma cells, whereas there was little difference in the rate of 45Ca uptake by isolated glial cells and neuronal perikarya. Isolated synaptosomes showed the highest rate of 45Ca accumulation. An increase of K concentration to 50 mm in the medium, with a corresponding lowering of Na, stimulated both glioma and glial as well as synaptosomal 45Ca uptake more markedly than the uptake by neuroblastoma cells and neuronal perikarya. Lowering the Na concentration and replacing it by choline had no effect on the cultured cells and astrocytes. Na‐free media caused massive stimulation of 45Ca influx in all fractions and cells tested.The efflux of 45Ca was studied after preloading of cells. Three phases could be resolved from the desaturation curves. All cells had nearly similar half‐lives for 45Ca efflux under standard conditions. Pulses of media containing 50 mm‐K stimulated 45Ca efflux from glioma cells and astrocytes more efficiently than from neuroblastoma cells, neuronal perikarya and synaptosomes. The stimulated release was exclusively seen in Ca‐containing media in experiments with the cultured cells and in Ca‐free media in experiments with cell perikarya. The effect of transmitter pulses on the release of 45Ca was examined in a limited series. Acetylcholine and isoproterenol were found to stimulate 45Ca release more actively from glia than from neurons.
THYROID HORMONE INHIBITION OF SYNAPTOSOME AMINO ACID UPTAKE AND PROTEIN SYNTHESIS1
Authors: Verity M. A. , Brown W. J. , Cheung M. K. , Czer G. T. 
Published: October 2006

Abstract— 3,3′,5‐Triiodothyronine (T3) inhibited L‐[14C]leucine uptake into synaptosomes. Inhibition was competitive with a Ki of 3.1 × 10−5m. Hofstee plot revealed an inverted hyperbolic curve suggestive of a two carrier or carrier plus diffusion mediated system for amino acid uptake. Both the carrier mediated and diffusional components were inhibited by thyroid analogues. l‐Thyroxine and analogues inhibited the incorporation of l‐[14C] leucine into cerebral synaptosome protein. At 50 μm, the triiodo‐compounds were more inhibitory than tetraiodo‐>3,5‐triiodo‐l‐thyronine >3,3′,5‐triiodothyropro‐pionic> l‐thyroxine >3,5‐diiodo‐l‐tyrosine. Thyroid analogue inhibition was not seen in liver or brain mitochondrial protein synthesis. 3,3′,5‐Triiodothyronine had no effect on respiratory control or 2,4‐DNP stimulated synaptosome respiration supported by malate plus pyruvate. Ouabain did not inhibit [14C]leucine uptake into adult synaptosomes. There was synergistic inhibition of synaptosome protein synthesis by thyroid analogues in the presence of 0.2 mm‐ouabain. 3,3′,5‐Triiodothyronine had no effect on synaptosome fraction ATPase or Na‐K ATPase. Addition of T3 induced further inhibition of synaptosome protein synthesis in the presence of either chloramphenicol (100μm) or cycloheximide (50μg/ml). [14C]Glycine uptake and incorporation into synaptosome protein was inhibited by 3,3′,5‐triiodothyronine. There was no inhibition of [14C]proline uptake or incorporation.The above evidence and kinetic data strongly favor a selective competitive block in amino acid transport at the synaptosome membrane leading to a decreased rate of protein synthesis.
SUBCELLULAR ANALYSIS OF THE MOLECULAR FORMS OF ACETYLCHOLINESTERASE IN RAT SKELETAL MUSCLE
Authors: McLaughlin Jack , Engel W. King , Reddy N. Bojji 
Published: October 2006

AbstractAcetylcholinesterase (AChE, EC 3.1.1.7) activity of rat gastrocnemius muscle homogenized in 1 M‐NaCl and 0.5% Triton X‐100 was separated by velocity sedimentation in sucrose gradients into three molecular forms with sedimentation coefficients of about 4S, 10S and 16S. The distribution of homogenate AChE activity among the three peaks was 53, 34 and 13% respectively. The different molecular forms were found to be heterogeneously distributed in subcellular fractions prepared from sucrose homogenates of muscle, as follows: Subfractions of the crude sarcolemmal fraction were prepared by discontinuous sucrose gradient centrifugation. AChE was recovered in the greatest yield and with the highest specific activity in a light density subfraction (0.6/0.8 M‐sucrose interface). The AChE activity in this light density subfraction was mainly (81‐88%) the 10S form of the enzyme. The velocity sedimentation profiles of the AChE activity in the more dense subfractions were markedly different in that 16S AChE was a major component.
PURIFICATION AND COMPARISON OF 2′,3′‐CYCLIC NUCLEOTIDE 3′‐PHOSPHOHYDROLASES FROM BOVINE BRAIN AND SPINAL CORD
Authors: Drummond Robert J. , Hamill Elizabeth B. , Guha Arabinda 
Published: October 2006

AbstractThe membrane‐bound enzyme 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase has been purified from acetone powders of bovine white matter and spinal cord. Affinity chromatography on AMP‐Sepharose has been used as the final step in the chromatographic purifications. The yield was about 3 mg of purified enzyme per 100 g of tissue in each instance. The enzymes from the two sources were indistinguishable by chromatography, gel electrophoresis, and amino acid analysis; the enzyme from spinal cord, however, has shown a specific activity of 225 units/mg compared to 342 units/mg for the enzyme from white matter. Both proteins had a molecular weight of 100,000 by gel filtration and 50,000 by sodium dodecyl sulfate‐gel electrophoresis under reducing conditions. The properties of the enzyme, including amino acid composition determined on the purified soluble protein and on the protein purified by sodium dodecyl sulfate‐gel electrophoresis, were those of a basic hydrophobic protein.
EFFECT OF BRAIN CORTEX PHOSPHOLIPIDS ON ADENYLATE‐CYCLASE ACTIVITY OF MOUSE BRAIN
Authors: Leon A. , Benvegnu D. , Toffano G. , Orlando P. , Massari P. 
Published: October 2006

Abstract—Intravenous injection of a sonicated dispersion of bovine brain phospholipids results in a significant change in both NaF‐dependent and dopamine dependent adenylate cyclase activity. High dosage of phospholipids inhibits the dopamine dependent, but not the NaF dependent, adenylate cyclase activity. The stimulation of cyclase activity is accompanied by an increased level of cAMP in mice brains. Treatment with haloperidol abolishes the increase in cAMP. Among individual phospholipids, phosphatidylserine is the most active component for inducing the activation of DA‐dependent adenylate cyclase activity.
SODIUM AND POTASSIUM IONS AND ACCUMULATION OF LABELLED d‐ASPARTATE AND GABA IN CRUDE SYNAPTOSOMAL FRACTION FROM RAT CEREBRAL CORTEX
Authors: Takagaki G. 
Published: October 2006

Abstract—The accumulation of labelled d‐aspartate into crude synaptosomal fraction (P2) prepared from the rat cerebral cortex proceeded by a ‘high affinity’ system (Km= 15.1 μm The maximal velocity of d‐aspartate uptake was higher than that of the ‘high affinity’ component of l‐aspartate uptake and almost equal to that of l‐glutamate under the same incubation conditions. Negligible metabolism of labelled d‐aspartate was observed in the P2 fraction. These findings are in accord with those which have been reported for rat cerebral cortical slices. The following observations were made on d‐aspartate uptake into rat cerebral P2 fraction. (1) The requirement of sodium is almost absolute and obligatory. (2) The affinity of the carrier for the substrate is increased by increasing sodium concentration in the medium, but the maximal velocity is not altered. (3) It is suggested that sodium ion is co‐transported mole for mole with the substrate molecule. (4) Omission of potassium from the medium inhibits the uptake competitively. (5) Ouabain is a competitive inhibitor on the uptake. (6) Whereas thallium, rubidium and ammonium are efficient substitutes for potassium in exhibiting Na–K ATPase activity of the P2 fraction, the uptake is activated only by rubidium in the absence of potassium. These observations were in common with the uptake of l‐aspartate as well as of l‐ and d‐glutamate, but not with GABA uptake. The requirement of sodium for the uptake of d‐glutamate was indicated to be higher than that in the uptake of the other amino acids. Mutual inhibitions of the uptake among l‐ and d‐isomers of glutamate and aspartate suggested that a common carrier is involved in the transport. Mechanisms of the transport of these amino acids in the crude synaptosomal fraction were discussed.
QUANTITATION AND CHARACTERIZATION OF BRAIN TUBULIN (COLCHICINE‐BINDING ACTIVITY) IN DEVELOPING HYPOTHYROID RATS
Authors: Gonzales Linda W. , Geel S. E. 
Published: October 2006

Abstract—The influence of early hypothyroidism on the concentration and biochemical properties of soluble and particulate tubulin from the cerebral cortex and cerebellum was investigated during development in the rat. Cellular soluble tubulin concentration (pmol colchicine bound/μg DNA) was approx 16% lower in both brain areas of hypothyroid animals compared to controls at 25 days of age. No effect of thyroid hormone deficiency was observed when tubulin concentration was expressed in terms of tissue protein or weight. The particulate tubulin concentration was approx 20% lower in the cerebral cortex of 25‐day‐old hypothyroid rats although the distribution of tubulin between soluble and particulate fractions was similar to controls. The incorporation of [14C]leucine into cerebral cortical tubulin in vitro (c.p.m. in tubulin/c.p.m. in total protein) was not significantly altered by the hormonal deficiency. Thus there was no apparent evidence of a selective defect in tubulin synthesis. Tubulin from hypothyroid rats behaved similarly to control samples with respect to the effects of pharmacological agents and temperature, lability of binding, chromatographic profile and electrophoretic mobility on sodium dodecyl sulfate polyacrylamide gels.
AXONAL TRANSPORT OF SELECTED PARTICLE‐SPECIFIC ENZYMES IN RAT SCIATIC NERVE IN VIVO AND ITS RESPONSE TO INJURY
Authors: Schmidt Robert E. , McDougal David B. 
Published: October 2006

Abstract— Orthograde and retrograde axoplasmic transport of selected axonal organelles were examined by monitoring accumulation of enzyme activities residing in various types of particles proximal and distal to a ligature placed on rat sciatic nerve as a function of time after tying.Proximal to the tie, activity of acetylcholinesterase (AChE, EC 3.1.1.7; probably in small endoplasmic reticulum‐like particles) accumulated for 2 days; then, during the next 5 days, the accumulation disappeared. Activities of glutamic dehydrogenase (GDH, EC 1.4.1.3) and monoamine oxidase (MAO, EC 1.4.3.4) (both located in mitochondria) accumulated steadily for 7 days. Accumulation of monoamine oxidase activity was more rapid than that of glutamic dehydrogenase during the first day or two. Acid phosphatase (acid P'tase, EC 3.1.3.2; in lysosomes) activity also accumulated throughout the week of observation. Accumulation of all four enzyme activities proximal to the ligature was blocked by nerve crush or subepineurial vinblastine injection 1 cm or more proximal to the site of the tie.Distal to the ligature, AChE activity accumulated early (14 h), and then gradually disappeared in the course of the week. MAO activity also accumulated, with a maximum at 2 days, and no further change thereafter. GDH activity, on the other hand, showed little accumulation during the first 2 days, but did appear in modest amounts at the end of the week. Distal accumulation of acid P'tase kept pace with proximal accumulation for the first day, and continued more slowly for another day, after which there was no further change.This system has been used to study the effects of axonal crush injury upon anterograde and retrograde axoplasmic transport. A tie applied at various times after injury, proximal to the site of injury, was used to show that orthograde transport of AChE was maintained for 1 day after tying, but at 2 days had fallen 50% or more, and within a week was down to 20–25% of control. At 3 days after injury retrograde transport of AChE activity was not different from the control. Orthograde transport of acid P'tase activity was depressed 35% by injury. Retrograde transport of acid P'tase was inhibited more than 50% both at 3 and at 7 days after injury. Transport of the mitochondrial enzymes was not measurably affected.
BRAIN pH MEASUREMENTS USING A DIFFUSIBLE, LIPID SOLUBLE pH SENSITIVE FLUORESCENT INDICATOR
Authors: Sundt Thoralf M. , Anderson Robert E. , Van Dyke Russell A. 
Published: October 2006

Abstract—Brain tissue pH was measured in cats at normocapnia hypocapnia, hypercapnia, and death from anoxia using a pH sensitive fluorescent indicator (umbelliferone) with both molecular and ionic fluorophors. A ratio analysis of the indicator's calibrated 450 nm fluorescent tissue washout curves from 340 and 370 nm excitation permitted direct determinations using a nomogram. Possible errors in these measurements related to differential quenching, absorption, and changes in the redox state of the indicator were investigated in vitro and in vivo for brain tissue and blood. In animals with preserved autoregulation, brain pH varied linearly with arterial pH (art pH 7.0, brain pH 6.98: art pH 7.4, brain pH 7.24). Brain pH at death fell to 6.68. An analysis of the indicator clearance curves suggests these measurements reflect a component of the intracellular space and the lipid solubility of the indicator suggests this is a membranous component.
A METHOD FOR DETERMINATION OF ACETYLCHOLINE BY SLOW PYROLYSIS COMBINED WITH MASS FRAGMENTOGRAPHY ON A PACKED CAPILLARY COLUMN
Authors: Polak R. L. , Molenaar P. C. 
Published: October 2006

Abstract—A new procedure is described for the estimation of ACh by pyrolysis‐gas chromatography/ mass spectrometry.ACh iodide and the iodides of ACh‐d16 or propionylcholine are slowly demethylated at 250°C by pyrolysis on the tip of a glass probe after insertion into the heated entrance of a glass tube leading to a packed capillary column. The volatile tertiary amines are then carried by helium to the column and trapped in its initial part which is kept at about 60°C. After 2–3 min the chromatography is started when the amines are released by heating this part to the ambient temperature in the oven (165°C).Peaks due to demethylated ACh and propionylcholine are well separated. The limit of detection is about 0.3pmol. After pyrolysis of mixtures of ACh and either ACh‐d16 or propionylcholine the peak amplitudes are linearly related to the doses.
DIHYDROMUSCIMOL, THIOMUSCIMOL AND RELATED HETEROCYCLIC COMPOUNDS AS GABA ANALOGUES
Authors: Krogsgaard‐Larsen P. , Hjeds H. , Curtis D. R. , Lodge D. , Johnston G. A. R. 
Published: October 2006

AbstractA series of heterocyclic GABA analogues related to muscimol (5‐aminomethyl‐3‐isoxazolol) were tested as depressants of the firing of GABA sensitive neurones on the cat spinal cord, and as inhibitors of the sodium‐independent binding of GABA to rat brain membranes. Furthermore, the compounds were examined as inhibitors of GABA uptake into rat brain slices and as inhibitors of the activities of the GABA‐metabolizing enzymes L‐glutamate 1‐carboxylyase and GABA:2‐oxoglutarate aminotransferase.Dihydromuscimol [(RS)‐4,5‐dihydromuscimol] and thiomuscimol (5‐aminomethyl‐3‐isothiazolol) were approximately equipotent to muscimol as bicuculline‐sensitive depressants of neuronal firing and as inhibitors of GABA binding. The structurally related compounds isomuscimol (3‐aminomethyl‐5‐isoxa‐zolol) and azamuscimol (5‐aminomethyl‐3‐pyrazolol) were much weaker than muscimol as GABA agonists. The affinity of the compounds for GABA receptor sites in vitro is in agreement with their relative potency as GABA receptor agonists in vivo. The rat brain synaptic membranes used for the GABA receptor binding studies were prepared by two procedures, which were shown to have a pronounced influence on the observed potency of the inhibitors of GABA binding.The compounds were weak or inactive as inhibitors of the uptake of GABA into rat brain slices and of the activity of GABA: 2‐oxoglutarate aminotransferase in vitro. Azamuscimol and 2‐methylaza‐muscimol were moderately potent inhibitors.of the activity of L‐glutamate 1‐carboxylyase in vitro. This inhibition by azamuscimol was timedependent following pseudo‐first‐order kinetics, consistent with azamuscimol acting as a catalytic inhibitor.The structure of the heterocyclic rings of these zwitterionic compounds is a factor of critical importance for interaction with GABA receptors. The present structure‐activity analysis demonstrates that heterocyclic GABA analogues having a high degree of delocalization of the negative charges have low affinity for the GABA receptors.
EFFECTS OF d‐ AND l‐AMPHETAMINE ON LOCAL CEREBRAL GLUCOSE UTILIZATION IN THE CONSCIOUS RAT1
Authors: Wechsler L. R. , Savaki H. E. , Sokoloff L. 
Published: October 2006

AbstractAmphetamine, a potent sympathomimetic amine, has powerful stimulant actions in the central nervous system. These actions are believed to be related to the influence of amphetamine on release and uptake of catecholamine neurotransmitters. The [14C]deoxyglucose method makes it possible to study changes in cerebral metabolic rate in different areas of gray and white matter. Because of the close relationship between metabolic rate and functional activity, this method may be used to identify specific structures in the brain in which functional activity is altered. The [14C]deoxyglucose method was used to explore for changes in metabolic rate produced by d‐and l‐amphetamine (5 mg/kg) in forty gray and four white matter structures in normal conscious rats. d‐Amphetamine produced increases in local cerebral glucose utilization in a number of components of the extrapyramidal motor system, as well as in some other structures known to contain dopamine‐producing and/or dopaminoceptive cells. The largest increases after d‐amphetamine administration occurred in the subthalamic nucleus and the zona reticulata of the substantia nigra. l‐Amphetamine produced increases in some but not all of these same structures, and these were generally smaller than those observed with d‐amphetamine. Decreases in local cerebral glucose utilization after either d‐ or l‐amphetamine administration were found in the habenula and the suprachiasmatic nuclei of the hypothalamus. The effects in the suprachiasmatic nuclei may reflect their normal diurnal rhythm in metabolic rate. These results indicate that amphetamines may influence behavior through effects on specific regions of the brain. Only some of these regions have previously been studied as possible sites of action of amphetamine.
THE METABOLISM OF GABA AND OTHER AMINO ACIDS IN RAT SUBSTANTIA NIGRA SLICES FOLLOWING LESIONS OF THE STRIATO‐NIGRAL PATHWAY
Authors: Minchin M. C. W. , Fonnum F. 
Published: October 2006

AbstractThe metabolism of GABA and other amino acids from various radioactive precursors has been studied in the rat substantia nigra using a sensitive double isotope dansyl derivative assay. Labelled acetate gave greater labelling of glutamate than of glutamine in substantia nigra slices whereas the reverse was the case for cerebral cortex slices.Unilateral transection of the striato‐nigral pathway caused a parallel decrease in the GABA and GAD content of the substantia nigra. It also reduced the total synthesis of GABA from all labelled precursors used, namely acetate, glutamate and glucose. After incubation with [1‐14C]acetate the specific activity of glutamate and aspartate, but not that of GABA, increased on the lesioned side compared with the normal side. The specific activity of glutamate, but not that of GABA or aspartate, decreased after incubation with [U‐14C]glucose on the lesioned side compared with the normal side. The results could be explained by the previously proposed hypothesis concerning differential labelling of metabolic pools by the two precursors. [U‐14C]Glutamate lead to increased labelling of GABA on the lesioned side relative to the normal side.Incubation of slices from substantia nigra with β‐mercaptopropionic acid caused a decrease of labelling of GABA from glucose and acetate, probably as the result of GAD inhibition. The labelling pattern of the other amino acids, apart from that of glutamate which showed a decrease when synthesised from acetate, did not change appreciably.
INHIBITION PATTERN BY ANALOGS INDICATES THE PRESENCE OF TEN OR MORE TRANSPORT SYSTEMS FOR AMINO ACIDS IN BRAIN CELLS
Authors: Sershen Henry , Lajtha Abel 
Published: October 2006

Abstract— We surveyed the transport systems present in the brain for amino acids. Cellular transport was measured in brain slices, and capillary transport was estimated by measuring in vivo the short‐term (15 s) extraction by brain from the blood. Specific analog inhibition of uptake was used to distinguish the classes. Amino acid levels (close to physiological) were such that primarily the ‘low‐affinity’ transport was measured.In brain tissue we could distinguish 10 overlapping amino acid transport classes. Five of these, described in a number of tissues, were characterized by their substrates: alanine (A system), leucine (L system), alanine‐serine‐cysteine (ASC system), glutamic acid (Glu system), and arginine (Ly+ system), respectively. The others distinguished were each fairly specific for one of the following five amino acids: glycine, proline, γ‐aminobutyric acid (GABA), taurine, and lysine. Of these 10 systems only 4 could be clearly found in capillary transport: L, ASC, Ly +, and Glu.The properties and the distribution of the transport systems are different. Examples are that at least one of the systems is present primarily only in neurons (GABA), and one primarily in glia (taurine). The specificity of some of the systems, e.g. A, is altered during development. In contrast to the properties of most other systems, there is little Na+, energy, or temperature dependence of the L system. This is reflected in the properties of capillary neutral amino acid transport when the L system is the predominant one.
INFLUENCE OF TEMPERATURE ON THE VELOCITY AND ON THE ISOTOPE PROFILE OF SLOWLY TRANSPORTED LABELED PROTEINS
Authors: Cancalon Paul 
Published: October 2006

Abstract— Slow intra‐axonal flow of [3H]leucine labeled proteins has been studied in the garfish olfactory nerve. Because of the homogeneity of the nerve a very well defined peak of slowly transported radioactivity is observed. The velocity of slow flow increases linearly with temperature. Between 14 and 28°C, the rate of the peak apex increases from 0.26 to 1.57 mm/day and the rate of the leading edge of the wavefront from 0.54 to 2.75 mm/day. Extrapolation of the rate‐temperature function indicates that slow flow should stop at 11°C. However, a velocity of 0.1 mm/day was determined for experiments conducted at 10°C. Between 15 and 25°C a Q10 of 3.7 was determined for the peak apex and of 3.3 for the leading edge of the wavefront. The Q10's are significantly larger than the value of 2.2 found for fast transport (Gross & Beidler, 1975) and support the possibility of at least partial differences between the mechanisms of fast and slow transport. A very small peak was found to migrate in front of the main peak. The positioning of this peak seems to be similar to one found by Lasek & Hoffman (1976) in rat ventral motor neurons.A temperature dependent exponential decrease of the slow moving peak height was measured and it can be estimated that only 1% of the slowly transported radioactivity reaches the synapses. Most of the slow radioactivity appears to remain in the axon behind the peak. The plateau height was also found to decrease exponentially with time. The rate of disappearance greatly affects the profile determined by the slowly transported labeled proteins along the nerve.