bluuebunny/crossref_metadata_2025_split huggingface dataset:
Concentration and In Vivo Synthesis of Cholecystokinin in Subcortical Regions of the Rat Brain
Authors: Goltermann Nils R. , Rehfeld Jens F. , Petersen Hans Røigaard 
Published: October 2006

AbstractThe in vivo biosynthesis of cholecystokinin (CCK) in subcortical regions of the rat brain was studied by intracisternal pulse injections of [35S]methionine. The rats were killed 1.0 or 1.5 h after the injection. Subcortical CCK extracted in boiling water and acetic acid was immunoabsorbed by an antiserum specific for the COOH‐terminal sequence of CCK. Gel chromatography of the absorbed CCK separated four molecular forms with elution constants (Kav) of 0.08, 0.50 (corresponding to the tritriacontapeptide amide, CCK‐33), 1.10 (corresponding to the COOH‐terminal octapeptide, CCK‐8), and 1.40 (a component which may correspond to the COOH‐terminal tetrapeptide amide). Significant incorporation of [35S]methionine occurred in the largest (Kav∼ 0.08) and octapeptide‐like form only. Chasing with methionine indicated a precursor relationship between the largest form and CCK‐8. The results demonstrate a substantial synthesis of CCK also in subcortical regions of the brain.
Endogenous Amino Acid Release from Rat Cerebellum In Vitro
Authors: Foster Alan C. , Roberts Peter J. 
Published: October 2006

AbstractThe release of six endogenous amino acids from superfused rat cerebellar slices was investigated. Only l‐glutamate, and GABA exhibited a calcium‐dependent, potassium‐stimulated release. Glutamine release was significantly inhibited during the stimulation period. Experiments were also performed with slices from cerebella which had received previously, injections of 2 μg kainic acid. This procedure failed to modify the release of any amino acid. At this time point (24 h), cell bodies of inhibitory neurons utilising GABA as their transmitter, have largely been destroyed; thus, the lack of effect on GABA release in particular, may indicate that the mechanisms for transmitter release from terminals are still operative under these conditions.
Brain Poly(A)RNA During Aging: Stability of Yield and Sequence Complexity in Two Rat Strains
Authors: Colman P. D. , Kaplan B. B. , Osterburg H. H. , Finch C. E. 
Published: October 2006

Abstract:To evaluate whether major age‐related changes occur during aging in the brain, we determined the sequence complexity of total poly(A)RNA and polysomal poly(A)RNA of brains from Sprague‐Dawley and Fischer 344 male rats, aged 2‐32 months. RNA complexity, determined by RNA‐driven hybridization reactions with nonrepetitive DNA, was 6‐7 × 108 nucleotides for total poly(A)RNA, whereas polysomal poly(A)RNA had a sequence complexity of 2.3‐2.8 × 108 nucleotides. Sprague‐Dawley rats had polysomal poly(A)RNA with a yield per gram of brain and a complexity that was 20% greater than Fischer 344 rats.No age differences in total or polysomal poly(A)RNA complexity were detected in either strain. Mixtures of polysomal poly(A)RNA from different age groups gave complexity values that were indistinguishable from the complexity of each component, thereby indicating that most (>80%) of the RNA sequences are common to all age groups studied. Analysis of total poly(A)RNA hybridization kinetics indicated that the major kinetic component had similar pseudo‐first‐order rate constants and complexity in all age groups. Consideration of interassay variation suggests that the limits of age changes in poly(A)RNA sequence complexity or content are 10%. Thus, age changes may be smaller than interstrain differences in the rat. We conclude that if genomic function is grossly impaired during aging, as presumed in many contemporary theories, the impairments are not expressed in most brain cells.
Purification and Some Properties of Choline Acetyltransferase from Catfish Brain
Authors: Su Y. Y. Thomas , Wu J.‐Y. , Lam Dominic M. K. 
Published: October 2006

Abstract:Choline acetyltransferase (CAT) from catfish brain has been purified to electrophoretic homogeneity by a combination of ammonium sulfate fractionation, gel filtration, and preparative polyacrylamide gel electrophoresis. The purified enzyme solutions showed only one protein band on both 7.5% polyacrylamide gel and gradient (3.5% to 15%) polyacrylamide gel with the enzyme activity coincident with the protein band. Furthermore, when the gel slice from which the enzyme was extracted was applied to a gradient polyacrylamide gel, a single protein band was also obtained. The purified enzyme preparations represented a 1510‐fold purification over the crude homogenate. The moiecular weight of the enzyme was estimated as 128.000 and 140,000 from gel filtration and gradient (3.5% to 15%) polyacrylamide gel, respectively. On sodium dodecyl sulfate‐gel, the purified enzyme preparations showed two protein bands, with molecular weights of 34,000 and 68,000. Since the native enzyme may be a tetramer, the 68.000 subunit may be a dimer of the smallest subunit. The maximum activity of the enzyme appears at pH 7.2; the values of Km for choline and for acetyl CoA are 400 and 92 μM, respectively, and Vmax was obtained as 2.2 × 10‐3μmol/min/mg protein. CAT antibodies were obtained from rabbit that had received six biweekly injections with a total of 120 μg of the purified protein. Double immunodiffusion test with CAT antibodies and a crude enzyme extract from catfish brains showed only a single, sharp precipitin band, suggesting that the antibodies are specific only to CAT and antigen and that the purified CAT preparation is monodisperse.
Regulation of Adenosine‐Sensitive Adenylate Cyclase from Rat Brain Striatum
Authors: Anand‐Srivastava Madhu B. , Johnson Roger A. 
Published: October 2006

Abstract:An adenosine‐sensitive adenylate cyclase has been characterized from rat brain striatum. In whole homogenates as well as in particulate fractions, N6‐phenylisopropyl adenosine (PIA), 2‐chloroadenosine, and adenosine N′‐oxide were equipotent in stimulating adenylate cyclase. Although GTP inhibited basal as well as PIA‐stimulated activity of whole homogenates, the enzyme showed an absolute dependency on GTP for stimulation by PIA, dopamine, epinephrine, and norepinephrine in a particulate fraction derived from discontinuous sucrose gradient centrifugation. Adenosine exerts two effects on this adenylate cyclase, stimulation at low concentrations and inhibition at high concentrations, suggesting the presence of two adenosine binding sites. The stimulation of adenylate cyclase by PIA was dependent on the concentration of Mg2‐. The degree of stimulation by PIA was greater at a low concentration of Mg2+, which suggests that stimulation by PIA was accompanied by increasing the apparent affinity for Mg2+. Activation of adenylate cyclase by PIA was blocked by theophylline or 3‐isobutyl‐ 1‐methylxanthine (IBMX). The pH optimum for basal or (PIA + GTP)‐stimulated activities was broad, with a peak between 8.5 and 9.5. In the presence of GTP, stimulation by an optimal concentration of PIA was additive, with maximal stimulation by the catecholamines. Phospholipase A2 treatment at a concentration of 1 U/ml for 5 min completely abolished the stimulatory effect of dopamine, whereas PIA‐stimulated activity remained unaltered. These data suggest that rat brain striatum either has a single adenylate cyclase, which is stimulated by catecholamines and adenosine by distinct mechanisms, or has different cyclase populations, stimulated by either adenosine or catecholamines.
Sodium‐Dependent Efflux of [3H]GABA from Synaptosomes Probably Related to Mitochondrial Calcium Mobilization
Authors: Sandoval Maria Elena 
Published: October 2006

Abstract:It has been suggested that mitochondria might modify transmitter release through the control of intracellular Ca2+levels. Treatments known to inhibit Ca2+retention by mitochondria lead to an increased transmitter liberation in the absence of external Ca2+, both at the frog neuromuscular junction and from isolated nerve endings. Sodium ions stimulate Ca2+efflux from mitochondria isolated from excitable tissues. In the present study, the effect of increasing internal Na+ levels on [3H]γ‐aminobutyric acid ([3H]GABa) release from isolated nerve endings is reported. Results show that the efflux of [3H]GABA from prelabeled synaptosomes is stimulated by ouabain, veratrine, gramicidin D, and K+‐free medium, which increase the internal sodium concentration. This effect was not observed when Na+ was omitted from the incubation medium and it was independent of external Ca2+, the experiments having been performed in a Ca2+‐free, EGTA‐containing medium. Since preincubation of synaptosomes with 2,4‐diaminobutyric acid did not prevent the stimulatory effect of increased internal Na+ levels on [3H]GABA efflux, it appears to be unrelated to an enhanced activity of the outward carrier‐mediated GABA transport. These results suggest that the augmented release of [3H]GABA may be due to an increased Ca2+efflux from mitochondria eiicited by the accumulation of Na+ at the nerve endings. Sandoval M. E. Sodium‐dependent efflux of [3H]GABA from synaptosomes probably related to mitochondrial calcium mobilization. J. Neurochem. 35, 915–921 (1980).
Studies on the Wolfgram High Molecular Weight CNS Myelin Proteins: Relationship to 2′,3′‐Cyclic Nucleotide 3′‐Phosphodiesterase
Authors: Sprinkle Terry Joe , Wells Michael R. , Garver Fred A. , Smith Dennis B. 
Published: October 2006

Abstract:Evidence is presented that the major protein components of the high molecular weight CNS myelin proteins designated as the Wolfgram protein doublet (W1 and W2) contain the enzyme 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase (EC 3.1.4.37, CNP). CNP is a basic hydrophobic protein containing about 830 to 840 amino acid residues. When electrophoresed on SDS polyacrylamide gels, CNP appears as a protein doublet, separated by a molecular weight difference of about 2500–3000 in bovine, human, rat, guinea pig, and rabbit. A similar protein doublet has been identified as the Wolfgram proteins W2 and W1 in myelin and in the chloroform‐methanol‐insoluble pellet obtained from myelin. Moreover, the relative Coomassie blue staining intensity of the CNP2 plus CNPI protein doublet among the species examined was remarkably similar to that observed for electrophoresed myelin and chloroform‐methanol‐insoluble pellet derived from myelin. Antisera raised against purified bovine CNP recognized the W1 and W2 proteins isolated from bovine and human brain. The amino acid composition of pure bovine CNP is presented and compared with the compositions of several rat and bovine Wolfgram proteins obtained by other investigators. Our electrophoretic, compositional, and immunological data support the contention that the enzyme CNP is a major component of the Wolfgram protein doublet.
Cleavage of Rabbit Myelin Basic Protein by Pepsin
Authors: Martenson Russell E. , Liithy Vivian , Deibler Gladys E. 
Published: October 2006

Abstract:Rapid cleavage of bovine and guinea pig myelin basic proteins by pepsin at pH 6.0 is limited to the Phe‐Phe bond in the middle of the molecule. In the rabbit protein, however, rapid cleavages occur elsewhere in addition to the Phe87‐Phe88 bond in regions in which there are amino acid substitutions. Rapid cleavage occurs at the Leu151‐Phe152 bond, at which Ile‐151 has been replaced by Leu, the residue that actually contributes the scissile bond. Rapid cleavages occur at the Phe44‐Phe45 and Leu109‐Ser110 bonds, which in the bovine and guinea pig proteins are relatively resistant under the experimental conditions (pH 6.0). The increased susceptibility of these bonds in the rabbit protein appears to be related to the replacement of Gly‐46 by Ser and the change in the sequence immediately NH2‐terminal to Leu‐109, from Leu‐Ser to Thr‐Val. These cleavages of the rabbit protein at the four very susceptible bonds have permitted us to isolate peptides (1‐44), (45‐87), (88‐109), (110‐151), and (152‐168) in high yield. We have also isolated peptides (88‐151), (1‐14), and (15‐44) in low yield; the latter two result from limited cleavage at the relatively resistant Tyr14Leu15 bond. Peptide (88‐109) has been chromatographically resolved into species differing in the degree of methylation of Arg‐105; this resolution is thought to result from differences in hydrogen bonding ability of the guanidinium groups.
Change of Cyclic AMP Level in Synaptosomes from Cerebral Cortex; Increase by Adenosine Derivatives
Authors: Kobayashi Kazuo , Kuroda Yoichiro , Yoshioka Masanori 
Published: October 2006

Abstract:The endogenous level of cyclic AMP in incubated synaptosomes from cerebral cortex of guinea pigs was investigated after the addition of various agents to the incubation medium. It appeared that the synaptosomal suspension already contained exogenous adenosine. Preincubation with theophyl‐line or with adenosine deaminase (ADase) decreased both the exogenous level of adenosine and the intrasynaptosomal level of cyclic AMP. The level of cyclic AMP was reincreased by the addition of adenosine agonists, especially 2‐chloroadenosine. This increase was antagonized by deoxyadenosine and was not inhibited by dipyridamole. These results suggest that the adenosine derivatives in the synaptic cleft regulate the level of cyclic AMP in nerve terminals through adenosine receptor on the presynaptic membrane. ADP, ATP, dopamine, and histamine also stimulate the formation of cyclic AMP in the ADase‐treated synaptosomes.
Brain Slice Protein Degradation and Development
Authors: Dunlop David S. , van Elden Walter , Plucinska Izabela , Lajtha Abel 
Published: October 2006

Abstract:Protein degradation rates were measured in brain slices prepared from rats of various ages. This was done by adding the protein synthesis rate, determined by incorporation of a labeled precursor, and the net protein degradation rate, determined by measuring the changes with time of total free amino acids. These rates are about 30% higher than those previously calculated from data on protein synthesis rates and protein accumulation rates in vico. The protein degradation rates in brain slices diminish with age; i.e., 2‐day cerebellum > 2‐day cerebral hemisphere > 12‐day cerebral hemisphere > young adult cerebral hemisphere. Protein degradation rates in slices from young brain are initially slightly higher than protein synthesis rates, resulting in a small net degradation with time. Unlike slices from adult brain, the protein degradation rates in slices from young brain decline only modestly with time for as much as 100 min of incubation. The characteristics of protein degradation in brain slices from young animals are roughly similar to some of the data calculated for protein degradation in vivi. suggesting that this system may prove useful for studying factors which control or affect brain protein degradation.
[3H]Propyl β‐Carboline‐3‐Carboxylate Binds Specifically to Brain Benzodiazepine Receptors
Authors: Nielsen Mogens , Schou Henning , Braestrup Clam 
Published: October 2006

Abstract:Ethyl β‐carboline‐3‐carboxylate has recently been isolated from human urine and it was proposed that derivatives of this compound might be related to an endogenous ligand for benzodiazepine receptors. In the present study we investigated high‐affinity binding of [3H]propyl β‐carboline‐3‐carboxylate ([3H]PrCC) to rat brain membranes. [3H]PrCC binds specifically and with high affinity (half‐maximal binding at ca. 1 nM) to rat brain membranes. The regional and subcellular distributions of specific [3H]PrCC binding are similar, but not identical, to the distributions of [3H]flunitrazepam or [3H]‐diazepam binding. The total numbers of binding sites labelled by [3H]PrCC and [3H]flunitrazepam in rat cerebellum are closely similar, and both ligands bind to cerebellar membranes in a mutually exclusive way. The pharmacological selectivity of [3H]PrCC and [3H]diazepam binding is almost identical. Binding of [3H]PrCC, like binding of [3H]diazepam, can be increased in vitro by muscimol, GABA and SQ 20.009. Although subtle differences in binding characteristics were observed, these results indicate that [3H]PrCC and benzodiazepines bind to a common recognition site on benzodiazepine receptors.
A Simple Radioenzymatic Method to Measure Picogram Amounts of DOPA in Brain and Biological Fluids
Authors: Argiolas A. , Gessa G. L. 
Published: October 2006

Abstract:A simple radioenzymatic method for the determination of DOPA is described. The method is based on the conversion of DOPA to 3‐O‐[methyl‐3H]DOPA by catechol‐O‐methyltransferase in the presence of S‐adenosyl‐[methyl‐3H]methionine and purification of the labelled product by Sephadex G10 and Dowex 50 W × 4 ion exchange resin. The method has been applied to the assay of endogenous DOPA in different brain areas and to measuring DOPA accumulation after inhibition of aromatic amino acid DOPA decarboxylase.
Distribution of Protein I, a Synapse‐Specific Phosphoprotein, and Adenylate Cyclase in the Rat Spinal Cord
Authors: Ueda Tetsufumi , Stratford Carol A. , Larson James 
Published: October 2006

Abstract:The longitudinal and transverse distributions of the synapse‐specific phosphoprotein Protein I and adenylate cyclase in the rat spinal cord were studied. Protein I was found to be enriched in all cervical and midlumbar (L3‐L5) segments, and sparse in midthoracic and sacral segments. Adenylate cyclase activity was high in all cervical and lumbosacral segments, and low in mid‐thoracic segments. Cross‐sectionally, both Protein I and adenylate cyclase were more enriched in the dorsal half than in the ventral half in the various segments studied. The similar topographical distributions of Protein 1 and adenylate cyclase in the spinal cord support the idea that adenylate cyclase may be intimately associated with Protein I in the nervous system, and could thereby regulate the state of in vivo phosphorylation of Protein I through formation of cyclic AMP.
Studies on Lipase in Rat Brain
Authors: Mizobuchi Masato , Shirai Kohji , Matsuoka Nobuo , Saito Yasushi , Kumagai Akira 
Published: October 2006

Abstract:Lipase activity was measured in homogenates of rat cerebral hemispheres using radioactive glycerol trioleate emulsified with Triton X‐100 as substrate. The labeled oleic acid was separated from the ester with a methanol‐chloroform‐heptane mixture. Under these assay conditions, the activity showed pH optima at about 5.5 and 7.5. The final products of these lipase activities were suggested to be free fatty acid and glycerol.
Regional Distribution of Catalase in the Adult Rat Brain
Authors: Brannan Timothy S. , Maker Howard S. , Raes Ingrid P. 
Published: October 2006

Abstract:Catalase activity was measured in 11 areas of perfused adult rat brain. The hypothalamus and substantia nigra contained the highest activities. The corpus callosum. a white‐matter structure, contained intermediate activity. The caudate‐putamen and frontal cortex contained the lowest activities. Regional catalase bears some relationship to the reported distribution of microperoxisomes, but considerable activity is present in areas with few microperoxisomes. Catalase may function as one of the systems detoxifying H2O2 formed in CNS amine metabolism.
Inhibition by Neurotoxic Phospholipases A2 of Synaptosomal Uptake of γ‐Aminobutyric Acid
Authors: Ng Ronald H. , Howard Bruce D. 
Published: October 2006

Abstract:A comparison has been made of the abilities of several neurotoxic and nontoxic phospholipases A2 from snake venoms to inhibit the intake of γ‐aminobutyric acid into synaptosomes from rat cerebral cortex. The neurotoxic phospholipases A2 inhibited GABA uptake more than the nontoxic enzymes did. However, there was a poor correlation between the measured specific enzyme activity of a phospholipase A2 and its ability to inhibit the uptake of GABA.
Control of Thy‐1 Glycoprotein Expression in Cultures of PC12 Cells
Authors: Doherty Patrick , Walsh Frank S. 
Published: October 2006

AbstractThe effects of nerve growth factor (NGF) and cholera toxin on the expression of the Thy‐1 glycoprotein were examined in cultures of naive and primed PC12 cells using an enzyme‐linked immunoadsorbent assay (ELISA). With primed PC12 cells, NGF induced a rapid increase in Thy‐1 expression over a time course similar to that of neurite regeneration, with half‐maximal and maximal increases apparent at 0.6 and 6 ng/ml NGF. Cholera toxin and dibutyryl cyclic AMP, but not B‐cholera toxin or antibodies to the toxin receptor, were found to inhibit NGF‐induced increases in Thy‐1. Morphological differentiation of naive PC12 cells induced by NGF, but not cholera toxin, was also associated with increased expression of Thy‐1. Despite showing a synergistic effect on morphological differentiation, cholera toxin was again found to inhibit NGF‐induced increases in Thy‐1 expression in cultures of naive PC12 cells. These data suggest that agents that interact directly or indirectly with adenylate cyclase may regulate the responsiveness of PC12 cells to NGF, and as such modulate the expression of the Thy‐1 glycoprotein.
Subcellular Localization and Characterization of Vasopressin Binding Sites in the Ventral Septal Area, Lateral Septum, and Hippocampus of the Rat Brain
Authors: Poulin Paule , Lederis Karl , Pittman Quentin J. 
Published: October 2006

Abstract[Arg8]‐Vasopressin (AVP) has been shown to exert characteristic central physiological actions in the ventral septal area of the rat brain. This study reports the characterization of receptors for AVP in synaptic plasma membranes prepared from the ventral septal area, the lateral septum, and the hippocampus. Binding of [3H]AVP was temperature and time dependent, linearly related to protein concentration, saturable, and specific. Scatchard plot analysis suggested the presence of a population of binding sites in the three brain areas with dissociation constants and maximal binding capacities, respectively, of 1.06 ± 0.39 nM and 24.0 ± 7.01 fmol/mg of protein (mean ± SEM; n = 3) for the ventral septal area, 0.92 ± 0.13 nM and 47.0 ± 4.96 fmol/mg of protein (n = 3) for the lateral septum, and 0.91 ± 0.14 nM and 25 ± 5.02 fmol/mg of protein (n = 3) for the hippocampus. In all three brain regions, the rank order of potencies of several vasopressin analogs, unrelated peptides, and other compounds for competitive displacement of ligand indicated a receptor with properties resembling those of the V1‐like receptor for AVP. These data document the presence of a high‐affinity, V1‐like vasopressin receptor in the rat ventral septal area for which the pharmacological properties are similar to those previously reported in physiological studies.
Identification of α2‐Adrenergic Receptors in Chicken Pineal Gland Using [3H]Rauwolscine
Authors: Bylund David B. , Rudeen P. Kevin , Petterborg Larry J. , Ray‐Prenger Carla 
Published: October 2006

AbstractThe norepinephrine‐induced inhibition of avian pineal N‐acetyltransferase activity appears to be mediated by α2‐‐adrenergic receptors. In this study, α2‐adrenergic receptors in the chicken pineal gland were directly identified by radioligand binding. Membrane preparations of pineal glands from chickens from 1 to 6 weeks of age were examined using [3H]rauwolscine, a selective α2‐adrenergic receptor antagonist, to characterize the binding sites. The results indicate no ontological change in either the affinity (KD) or density of receptor binding sites (Bmax) during the time span examined. The binding was saturable and of high affinity with a mean KD of 0.27 ± 0.01 nM and a mean Bmax of 242 ± 12 fmol/mg protein. Further characterization of these binding sites indicated that the α2‐adrenergic receptor is of the α2A subtype, since prazosin and ARC‐239 bound with low affinities and oxymetazoline bound with high affinity.