bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Kainic Acid Injections on Guanylate Cyclase Activity in the Rat Caudatoputamen, Nucleus Accumbens and Septum
Authors: Walaas Ivar 
Published: October 2006

Abstract:The activity of soluble and particulate guanylate cyclase (EC 4.6.1.2) has been compared with the distribution of neurotransmitter candidates in three rat forebrain nuclei, and the effects of local kainic acid injections into these nuclei have been tested. Soluble guanylate cyclase was highly concentrated in both the caudatoputamen and the nucleus accumbens, with lower activity found in the septum. This distribution coincided with markers for acetylcholine and monoamines, but not with markers for γ‐aminobutyrate (GABA) or glutamate neurons. In contrast, particulate guanylate cyclase was equally active in all regions. Local injections of kainic acid, which destroyed cholinergic and GABA neurons in the caudatoputamen and in the nucleus accumbens, caused a rapid (70–90%) decrease in the soluble guanylate cyclase and a slower 50‐60% fall in the particulate guanylate cyclase in these nuclei. In the septum, where kainate destroyed GABA cells but not cholinergic neurons, the guanylate cyclase activity was unchanged after the lesion. Thus, both the soluble and particulate guanylate cyclases appear to be concentrated in local neurons in the caudatoputamen and nucleus accumbens. In the septum, however, most of the guanylate cyclase activity is located outside kainate‐sensitive neurons.
Turnover In Vivo of Lactosyl‐ceramide and Other Glycosphingolipids in the Adult Rat Brain
Authors: Barkai Amiram I. 
Published: October 2006

Abstract:The quantitative contribution of glucose to the biosynthesis of lactosyl‐ceramide and other glycosphingolipids was studied in the adult rat brain in vivo using a semicompartmental model. Half‐lives of glucose carbon in both the total carbon pool and the carbohydrate residue of the lipid were calculated. In all glycolipids the half‐life of carbohydrate units was six to eight times shorter than the half‐life of carbon in the total carbon pool of the same lipid. This carbohydrate half‐life appears to be closely related to the turnover rate of the glycolipid. The shortest carbohydrate half‐life (2.2 days) was obtained for lactosyl‐ceramide followed by gangliosides. galactosyl‐ceramides, and sulphatides. The results indicate that lactosyl‐ceramide may serve as a branch point for the biosynthesis of cerebral gangliosides in vivo rather than occur as a breakdown product of more complex molecules.
Influence of the Ionic Environment on the Conformation of Aspartic Acid and Possible Relevance to Its Neurotransmitter Action
Authors: Esposito Gennaro , Motta Andrea , Temussi Piero A. 
Published: October 2006

Abstract:The conformational changes of aspartic acid, a possible neurotransmitter, induced by increasing ionic strength were investigated by means of NMR spectros‐copy. The effects of Li, Na, K, and Cs chlorides in basic and neutral conditions were characterized. The effects of the presence of both Ca2+ and Na+ or K+ were also examined. The results always showed a relative stabilization of the two conformers with gauche carboxylates at the expense of the anticonformer. The significant quantitative difference found between Na+ and K+ in basic solutions, as well as between calcium‐free and calcium‐containing solutions, may bear some relevance for the role of aspartate as a CNS neurotransmitter.
Characterization and Location of Met5‐Enkephalin‐Arg6‐Phe7 Stored in Various Rat Brain Regions
Authors: Yang H.Y. T. , Panula P. , Tang J. , Costa E. 
Published: October 2006

Abstract:A specific antiserum against met5‐enkepha‐lin‐arg6‐phe7 was raised and used to study the distribution and characterization of met5‐enkephalin‐arg6‐phe7‐like immunoreactive material in rat brains by radioimmunoassay and immunohistochemical procedures. The antiserum appears to be directed to the COOH‐terminus of the peptide, as it fails to cross‐react with met5‐enkeph‐alin, met3‐enkephalin‐arg6, met5‐enkephalin‐arg6‐arg7, met6‐enkephalin‐lys6, and leu‐enkephalin. However, it cross‐reacts with phe‐met‐arg‐phe by about 10% and with phe‐met‐arg‐phe‐NH2 to an insignificant degree. The highest content of met5‐enkephalin‐arg6‐phe7 was found in the striatum, which contains a dense network of immunoreactive varicose fibers and terminals, as well as immunoreac tive cell bodies. The met5‐enkephalin‐arg6‐phe7 in striatum can be released in a Ca2+‐dependent manner by a depolarizing concentration of KC1, raising the possibility of a neu‐roregulatory role for met5‐enkephalin‐arg6‐phe7. Characterization of the immunoreactive material by gel filtration and high pressure liquid chromatography revealed the presence of multiple forms of immunoreactive material in some brain regions.
Characterization of the Ca2+‐ and Mg2+‐Dependent ATPases in Electrophorus Electroplax Microsomes
Authors: Amende L. M. , Chock S. P. , Albers R. W. 
Published: October 2006

Abstract: Electrophorus electroplax microsomes were examined for Ca2+‐ and Mg2+‐dependent ATPase activity. In addition to the previously reported low‐affinity ATPase, a high‐affinity (Ca2+,Mg2+)‐ATPase was found. At low ATP and Mg2+ concentrations (200 μM or less), the high‐affinity (Ca2+,Mg2+)‐ATPase exhibits an activity of 18 nmol Pi, mg‐1min‐1 with 0.58 μM Ca2+. At higher ATP concentrations (3 mM), the low‐affinity Ca2+‐ATPase predominates, with an activity of 28 nmol Pi mg‐1min‐1 with 1 mM Ca2+. In addition, Mg2+ can also activate the low‐affinity ATPase (18 nmol Pi mg‐1min‐1). The high‐affinity ATPase hydrolyzes ATP at a greater rate than it does GTP, ITP, or UTP and is insensitive to ouabain, oligomycin, or dicyclohexylcarbodiimide inhibition. The high‐affinity enzyme is inhibited by vanadate, tri‐fluoperazine, and N‐ethylmaleimide. Added calmodulin does not significantly stimulate enzyme activity; rinsing the microsomes with EGTA does not confer calmodulin sensitivity. Thus the high‐affinity ATPase from electroplax microsomes is similar to the (Ca2+,Mg2+)‐ATPase reported to be associated with Ca2+ transport, based on its affinity for calcium and its response to inhibitors. The low‐affinity enzyme hydrolyzes all tested nucleoside triphosphates, as well as diphosphates, but not AMP. Vanadate and N‐ethylmaleimide do not inhibit the low‐affinity enzymes. The low‐affinity enzyme reflects a nonspecific nucleoside triphosphatase, probably an ectoenzyme.
Synaptosomal and Brain Mitochondrial Lipids in Hibernating and Cold‐Acclimated Golden Hamsters
Authors: Demediuk Paul , Moscatelli Ezio A. 
Published: October 2006

Abstract:Synaptosomes and mitochondria were isolated from the brains of warm‐adapted, hibernating, and cold‐acclimated golden hamsters (Mesocricetus auratus). Lipid extracts of these subcellular fractions were prepared and assayed for plasmenylethanolamin (ethanolamine plasmalogen) and cholesterol levels. The ganglioside composition of synaptosomes was also determined. Samples from the hibernating animals showed characteristic changes in lipid composition. These changes include decreases in plasmenylethanolamine levels and a shift in the ganglioside composition toward a higher percentage of the more polar gangliosides. Those animals which were exposed to cold and did not hibernate (cold‐acclimated) showed no such changes. Fatty acid analyses of synaptosomal and mitochondrial ethanolamine glycerophospholipids demonstrated a similar trend. Samples from hibernators showed decreases in 16:0, 18:0, and 22:6 (n‐3), and increases in 16:1, 18:1, and 20:4 (n‐6) fatty acids. No changes were detectable in samples from cold‐acclimated animals, indicating that hibernating and cold‐acclimated hamsters represent chemically distinct populations.
Molecular Forms of Acetylcholinesterase: Regulation in a Testosterone‐Sensitive Nerve‐Muscle Axis
Authors: Bleisch William V. , Luine Victoria N. , McEwen Bruce S. 
Published: October 2006

Abstract:We measured the distribution of molecular forms of acetylcholinesterase (AChE) in muscles of a song bird, the zebra finch, and found a pattern similar to those reported in other vertebrates. As in other species, the most rapidly sedimenting form of the enzyme decreases to barely detectable levels following denervation. In the muscles of the syrinx, castration causes a large decrease in AChE activity, but has little or no effect on the relative abundance of AChE forms. This suggests that the number of AChE catalytic sites is changing without affecting the distribution of catalytic sites among the molecular forms. This is in marked contrast with the effect of denervation in the syrinx, which causes changes in the distribution of activity, as well as in total activity.
Light Enhances the Turnover of Phosphatidylinositol in Rat Retinas
Authors: Schmidt Susan Y. 
Published: October 2006

Abstract:Light stimulation of isolated rat retinas is shown to enhance the turnover of phosphatidylinositol (PI) as demonstrated by a light‐dependent increase in [3H]inositol incorporation and concurrent hydrolysis of existing PI. Studies with rat retinas incubated with [3H]inositol and then microdissected at the level of the outer plexiform layer into photoreceptor cell and inner retina layers indicated that the light‐enhanced incorporation of [3H]inositol was associated with the photoreceptor cell layer. The rate of PI hydrolysis in retinas prelabeled in vivo with [3H]inositol was higher in light than in dark incubations and was higher in the photoreceptor cell layer than within the inner retina. Within the photoreceptor cell layer, PI turnover involved 2%/min of the total PI contentin dark and 6–8%/min in light. In contrast to what has been reported for stimulus‐enhanced turnover of PI in some tissues, this light‐enhanced turnover of PI in the retina was not associated with detectable reductions in PI content. Parallel studies of sodium (22Na) uptake demonstrated that the photoreceptor cells remained functional during these incubations as they retained the capacity to restrict the entry of 22Na in light but not in dark.
Elevation of Intracellular Cyclic AMP and Stimulation of Adenylate Cyclase Activity by Vasoactive Intestinal Peptide and Glucaeon in the Retinal Pigment Epithelium
Authors: Koh Shav‐Whey M. , Chader Gerald J. 
Published: October 2006

AbstractBoth vasoactive intestinal peptide (VIP) and glucagon rapidly elevated cyclic AMP levels in embryonic chick retinal pigment epithelium (RPE), in culture as well as in freshly dissected tissue. In cultured cells, the half‐maximal activities of VIP and glucagon were 5 × 10‐8M and 3 × 10‐8M, respectively. After 3 min of reaction, VIP elevated intracellular cyclic AMP by 100‐fold; elevation with glucagon was up to 10‐fold. Both neuropeptides stimulated adenylate cyclase activity in RPE membranes. Glucagon showed a half‐maximal activity of 1 × 10‐8M. VIP remained more effective than glucagon in stimulating adenylate cyclase activity, but the doseresponse curve was shifted to a higher concentration range when compared to that of the VIP‐elevated intracellular cyclic AMP.
Reciprocal Regulation of Ornithine Decarboxylase and Choline Kinase Activities by Their Respective Reaction Products in the Developing Rat Cerebellar Cortex
Authors: Gilad Gad M. , Gilad Varda H. 
Published: October 2006

AbstractChanges in the activity of choline kinase were measured in the cerebellum during development. Early transient increase was found in the enzyme activity just prior to and during birth. This period of increase did not coincide with the periods of transient elevation in ornithine decarboxylase and choline acetyltransferase previously observed in the developing cerebellum. The effects of the naturally occurring polyamines (putrescine, spermidine, and spermine) on choline kinase and choline acetyltransferase activities, and of phosphorylcholine (the product of the reaction catalyzed by choline kinase) on ornithine decarboxylase and choline acetyltransferase activities, were also examined. Choline acetyltransferase activity was not influenced by either polyamines or phosphorylcholine. However, choline kinase activity from 7‐day‐old, but not from adult, cerebellum was increased 25% in the presence of 4 mM spermine. In contrast, low spermidine concentrations (<2 mM) inhibited choline kinase activity selectively in 7‐day‐old cerebellum. Ornithine decarboxylase activity from 7‐day‐old cerebellum was inhibited in a concentration‐dependent manner by phosphorylcholine. The present data together with other previous reports suggest that: (a) polyamines may play a role in choline utilization during development via their regulation of choline kinase activity, on the one hand, and of acetylcholinesterase activity on the other; and (b) during development, a reciprocal regulation of choline kinase and ornithine decarboxylase activities by their respective reaction products may exist, whereby choline kinase activity is regulated in a complex manner by polyamines and, in turn, ornithine decarboxylase is inhibited by phosphorylcholine.
Degradation of NAD by Synaptosomes and Its Inhibition by Nicotinamide Mononucleotide: Implications for the Role of NAD as a Synaptic Modulator
Authors: Snell C. R. , Snell P. H. , Richards C. D. 
Published: October 2006

AbstractWe have found NAD to be rapidly degraded by extracellular enzymes present on intact rat brain synaptosomes. The enzyme involved had the specificity of an NADase cleaving the molecule at the nicotinamide‐glycoside linkage and was inhibited by nicotinamide mononucleotide (NMN). This inhibitor did not displace specific binding of NAD to rat brain membranes or affect electrical activity in the guinea pig hippocampus. Therefore, inclusion of NMN in binding assays allowed unambiguous demonstration of two specific NAD binding sites on rat brain synaptosomal membranes (KD1, 82 nM, KD2, 1.98 μM). The depressant action of NAD on the evoked synaptic activity of the guinea pig hippocampus was not blocked after inhibition of NAD degradation with NMN. The physiological implications of these results for the function of NAD as a neurotransmitter or neuro‐modulator in the CNS are discussed.
GABA Induces Functionally Active Low‐Affinity GABA Receptors on Cultured Cerebellar Granule Cells
Authors: Meier Eddi , Drejer Jørgen , Schousboe Arne 
Published: October 2006

AbstractThe effect of γ‐aminobutyric acid (GABA) and its agonists muscimol and 4,5,6,7‐tetrahydroisoxazolo[5‐4‐c]pyridin‐3‐ol (THIP) on the development of GABA receptors on cerebellar granule cells was studied by cultivation of the cells in media containing these substances. It was found that the presence of 50 μM GABA in the culture media led to the induction of low‐affinity GABA receptors (KD 546 ± 117 nM) in addition to the high‐affinity receptors (KD 7 ± 0.5 nM) which were present regardless of the presence of GABA in the culture media. The functional activity of the GABA receptors was tested by investigating the ability of GABA to modulate evoked glutamate release from the cells. It was found that GABA could inhibit evoked glutamate release (ED50 10 ± 3 (μM) only when the cells had been cultured in the presence of 50 νM GABA, 50 μM muscimol, or 150 μM THIP, i.e., under conditions where low‐affinity GABA receptors were present on the cells. This inhibitory effect of GABA could be blocked by 120 μM bicuculline and mimicked by 50 μM muscimol or 150 μM THIP whereas 150 μM (‐)‐baclofen had no effect. It is concluded that GABA acting extracellularly induces formation of low‐affinity receptors on cerebellar granule cells and that these receptors are necessary for mediating an inhibitory effect of GABA on evoked glutamate release. The pharmacological properties of these GABA receptors indicate that they belong to the so‐called GABAA receptors.
Catabolism of myo‐Inositol to Precursors Utilized for De Novo Glycerolipid Biosynthesis
Authors: Fliesler Steven J. , Kelleher Paula A. , Anderson Robert E. 
Published: October 2006

Abstract:Systemic injection of [2‐3H]myo‐inositol into frogs resulted in the incorporation of more than half of the label into glycerolipid classes other than phosphoinositides in retinal rod outer segment membranes. Following methanolysis and differential extraction of isolated lipid classes, radioactivity was recovered primarily in the aqueous phase. After phospholipase C hydrolysis of the total membrane lipids, 97% of the radioactivity was extractable with organic solvents, and 70% of the label in lipids was in 1,2‐diglycerides. These results indicate that the label was incorporated primarily into the glyceryl moiety of the membrane glycerolipids. Intraocular injection of frog eyes or in vitro incubation of frog retinas with [2‐3H]myo‐inositol resulted in the incorporation of radioactivity almost exclusively into phosphoinositides in rod outer segment membranes. Incubation of retinas with [U‐14C]glucuronic acid did not result in the formation of labeled retinal lipids. These results suggest that myo‐inositol can be catabolized systemically to precursors utilized for glycerolipid biosynthesis in the retina.
Release of Purines, Noradrenaline, and GABA from Rat Hippocampal Slices by Field Stimulation
Authors: Jonzon Bror , Fredholm Bertil B. 
Published: October 2006

Abstract:Labelled adenine, noradrenaline (NA), and γ‐aminobutyric acid (GABA) were taken up by the transversely cut hippocampal slice. [3H]NA and [14C]GABA were retained as such, [3H]‐ (or [14C]‐) adenine mainly as adenine nucleotides. There was a spontaneous overflow of all three types of compounds ranging from 0.1 (GABA) to 0.21 (NA) %/min. The rate of [3H]NA overflow increased rapidly during electrical field stimulation. The release rate was well maintained over a 15‐min period. The rate of [14C]GABA release also increased rapidly but it was not maintained over a 15‐min period even if uptake and/or metabolism was inhibited by nipecotic acid (1 mM) and aminooxyacetic acid (AOAA, 0.1 mM). The bulk of the purines was released after the stimulation period. For all compounds the amounts released were frequency‐ and calcium‐dependent. At a frequency of 3 Hz a 10 V stimulation was sufficient to cause a maximal [3H]NA release and 20 V to cause maximal [14C]GABA release, but 14C‐purine release was increased further by increasing the voltage to 40 V. The evoked purine release was inhibited by a nucleoside uptake inhibitor (dipyridamole). On stimulation of [3H]NA‐labelled slices the released radioactivity was composed of >95% unchanged NA. The specific activities of NA in the slice and in the superfusate were practically identical. In [3H]adenine‐labelled slices the released radioactivity was composed of adenosine, inosine, and hypoxanthine, but the activity in the slice of ATP, ADP, and AMP. The specific activity of the released purines was about four times higher than that of the purines retained in the slice but similar to that of the hypoxanthine in the slice. It is suggested that the purine release induced by electrical field stimulation differs in important respects from the release of a traditional neurotransmitter such as NA and that it depends on the intracellular formation of adenosine from a labile fraction of adenine nucleotides that is affected by neurotransmission.
Cerebral Ammonia Metabolism in Hyperammonemic Rats
Authors: Cooper åArthur J. L. , Mora Sol N. , Cruz Nancy F. , Gelbard Alan S. 
Published: October 2006

Abstract:The short‐term metabolic fate of blood‐borne [13N]ammonia was determined in the brains of chronically (8‐ or 14‐week portacaval‐shunted rats) or acutely (urease‐treated) hyperammonemic rats. Using a “freezeblowing” technique it was shown that the overwhelming route for metabolism of blood‐borne [13N]ammonia in normal, chronically hyperammonemic and acutely hyperammonemic rat brain was incorporation into glutamine (amide). However, the rate of turnover of [13N]ammonia to L‐[amide‐13N]glutamine was slower in the hyperammonemic rat brain than in the normal rat brain. The activities of several enzymes involved in cerebral ammonia and glutamate metabolism were also measured in the brains of 14‐week portacaval‐shunted rats. The rat brain appears to have little capacity to adapt to chronic hyperammonemia because there were no differences in activity compared with those of weight‐matched controls for the following brain enzymes involved in glutamate/ammonia metabolism: glutamine synthetase, glutamate dehydrogenase, aspartate aminotransferase, glutamine transaminase, glutaminase, and glutamate decarboxylase. The present findings are discussed in the context of the known deleterious effects on the CNS of high ammonia levels in a variety of diseases.
Axonal Transport of Polyamines in Intact and Regenerating Axons of the Rat Sciatic Nerve
Authors: Lindquist T. D. , Sturman J. A. , Gould R. M. , Ingoglia N. A. 
Published: October 2006

Abstract:The axonal transport of putrescine or its polyamine derivatives spermidine or spermine is a subject of some debate. We investigated this question by injecting [3H]putrescine into the lumbar spinal cord of the rat and measuring the accumulation of radioactivity central to ligatures placed on intact and regenerating sciatic nerves. In normal nerves, approximately twice as much radio activity built up proximal to these ligatures 2 or 3 days after injection than at more distal ligatures used to control for accumulation of radioactivity which might be due to tissue damage alone. In regenerating nerves the amount of radioactivity accumulating at the ligature was approx imately five times that at the distal ligature and two to three times greater than in intact nerves. The identity of the radioactivity in regenerating nerves, determined on an amino acid analyzer, was found to be primarily spermidine and an unknown compound that migrated as a frontal elution peak. Autoradiographic analysis showed that the radioactivity was largely confined to axons, but a significant amount of the silver grains was associated with Schwann cells and myelin sheaths surrounding labeled axons in both intact and regenerating nerves. The data indicate that polyamine derivatives of putrescine are transported axonally in rat sciatic nerves, and some of this transported material accumulates in Schwann cells surrounding the labeled axons. These processes are apparently augmented during regeneration of the injured axons.
[3H]GBR‐12935 Binding to the Dopamine Transporter Is Decreased in the Caudate Nucleus in Parkinson's Disease
Authors: Janowsky Aaron , Vocci Frank , Berger Paul , Angel Itzchak , Zelnik Nethanel , Kleinman Joel E. , Skolnick Phil , Paul Steven M. 
Published: October 2006

AbstractThe specific binding of [3H]GBR‐12935 to membranes prepared from human caudate nucleus is saturable (Bmax 1.36 ± 0.18 pmol/mg protein), sodium dependent, and of high affinity (KD 2.34 ± 0.18 nM). Freezing of tissue from rat brain, or refrigeration followed by freezing, results in a small but significant (20%) decrease in specific [3H]GBR‐12935 binding when compared to the binding observed in fresh (nonfrozen) tissue, and this decrease may account, in part, for the differences in specific binding between rat and human brain membranes. Despite small differences in binding site density between fresh and frozen tissue there is a good correlation (r= 0.98; p < 0.01) between the potencies of a series of drugs in displacing specific [3H]GBR‐12935 binding to human caudate membranes and rat striatum as well as in inhibiting dopamine uptake in rat striatal synaptosomes (r= 0.96; p < 0.01). The specific binding of [3H]GBR‐12935 to membranes prepared from the caudate nuclei of patients with Parkinson's disease is decreased compared to membranes prepared from age‐and sex‐matched controls. These data suggest that [3H]GBR‐12935 binds in a sodium‐dependent fashion to the dopamine transport complex in human brain and that specific binding is decreased by a pathological degeneration of dopaminergic neurons to the caudate nucleus.