bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential Release of Enkephalin and Enkephalin‐Containing Peptides from Perfused Cat Adrenal Glands
Authors: Vindrola Osvaldo , Ase Ariel , Finkielman Samuel , Nahmod Victor E. 
Published: October 2006

AbstractWe have compared the enkephalin‐like material derived from proenkephalin released from perfused cat adrenal glands stimulated with pilocarpine (5 X 10‐4M) and nicotine (5 X 10–6M). In addition, two doses of acetylcholine (10‐5 and 10‐4M) and 50 mM K+ were tested. Free Met‐enkephalin immunoreactivity and total Met‐enkephalin immunoreactivity, as determined by enzymatic digestion of large enkephalin‐containing fragments, were coreleased with catecholamines. Free Met‐enkephalin immunoreactivity represented 13% of total immunoreactivity for nicotinic stimulation, 46% for pilocarpine, 33% for 10‐5M acetylcholine, 22% for 10‐4M acetylcholine, and 16% for 50 mM K+. Analysis of the perfusate by gel filtration showed that 80% of the total Met‐enkephalin immunoreactivity whose release was induced by pilocarpine was eluted in fractions corresponding to fragments of low molecular weight, whereas these fractions accounted only for 10% of the total Met‐enkephalin immunoreactivity whose release was induced by nicotine. HPLC analysis of low‐molecular‐weight peptide fractions revealed that Met‐enkephalin, Met‐enkephalin‐Arg‐Gly‐Leu, and Met‐enkephalin‐Arg‐Phe represented 69% of total Met‐enkephalin immunoreactivity whose release was induced by pilocarpine. These results indicate that selective activation of muscarinic receptors is followed by release of low‐molecular‐weight material, whereas nicotine application also yielded high‐molecular‐weight peptides. Furthermore, increasing the acetylcholine concentration from 10‐5 to 10‐4M and using 50 mM K+ increased proportionally the high‐molecular‐weight peptide secretion. Results are discussed in relation to the existence of a heterogeneous population of granules, either in the same cell or in different cells, containing proenkephalin‐derived peptides. It appears that, under physiological conditions, different enkephalin‐containing peptides might be secreted from the cat adrenal gland. The response might also be modified when nonphysiologic stimuli are applied.
Specific [3H]SCH23390 Binding to Dopamine D1 Receptors in Cerebral Cortex and Neostriatum: Evidence for Heterogeneities in Affinity States and Cortical Distribution
Authors: Reader Tomás A. , Brière Richard , Gottberg Estela , Diop Laurent , Grondin Louise 
Published: October 2006

AbstractThe tritiated antagonist SCH23390 was used to identify dopamine D1 receptors in the cerebral cortex and neostriatum. The kinetic properties of binding were investigated in parallel experiments with membrane preparations from both tissues. The densities of receptors (Bmax) and the dissociation constants (KD) were determined from saturation curves, and the specificity of binding verified in competition experiments using agonists and antagonists. The cortical D1 receptor displays the same pharmacological selectivity (including stereospecificity) and kinetic properties as the neostriatal D1 receptor. From both the dissociation kinetics by dilution and the competition curves, it could be established that there is an heterogeneity of binding, probably due to high‐ and low‐affinity states. Endogenous dopamine, 4‐hydroxy‐3‐methoxyphenylacetic acid, 3,4‐dihydroxyphenylacetic acid, and 3‐methoxytyramine contents, as well as D1 receptor distribution, were measured for the neostriatum and four localized cortical areas: anterior cingulate. primary somatosensory, primary visual, and piriform‐entorhinal. For the regions examined, the distribution of D1 receptors is heterogeneous, but correlates very well (r > 0.98) with the endogenous levels of dopamine and its major metabolites.
Effects of 5,6‐Dihydroxytryptamine on the Release, Synthesis, and Storage of Serotonin: Studies Using Rat Brain Synaptosomes
Authors: Wolf William A. , Bobik Alex 
Published: October 2006

Abstract5,6‐Dihydroxytryptamine is a neurotoxic analogue of serotonin which can have profound cardiovascular effects within minutes of administration in vivo (Korner and Head, 1981). These effects have been attributed to 5,6‐dihydroxytryptamine‐induced serotonin release, although there has been no biochemical assessment of the extent to which this occurs. The present study utilized an in vitro synaptosomal assay to determine the short‐term effects of 5,6‐dihydroxytryptamine on endogenous serotonin release, synthesis, storage, and metabolism. 5,6‐Dihydroxytryptamine produced a rapid depletion of serotonin. At lower concentrations of 5,6‐dihydroxytryptamine (0.1–1 μM), this depletion was associated primarily with an increase in the levels of 5‐hydroxyindoleacetic acid, the deaminated metabolite of serotonin, with small increases in the amount of serotonin release. At higher concentrations (10–100 μM), a greater proportion of the depicted serotonin was released with less metabolism occurring. When metabolism was prevented by inhibiting monoamine oxidase, the amount of serotonin which was released equalled the amount of serotonin depletion. Thus monoamine oxidase activity was important in controlling the amount of serotonin which could be released by 5,6‐dihydroxytryptamine. Further studies demonstrated that an impairment in serotonin synthesis and vesicular storage could account for the rapid depletion produced by 5,6‐dihydroxytryptamine. Taken together, the results indicate that 5,6‐dihydroxytryptamine acts to displace serotonin from vesicular stores into the cytoplasm where it can either be deaminated by monoamine oxidase or be released. Moreover, it is hypothesized that the intraneuronal concentration of 5,6‐dihydroxytryptamine is important in determining the extent of serotonin release, because it can inhibit the deamination of serotonin by monoamine oxidase.
Glutamate Dehydrogenase Activity Is Markedly Higher in a “Golgi‐Bergmann”‐Like Glial Clone than in Other Astroglial Cell Lines
Authors: Cambier Danièle , Pessac Bernard 
Published: October 2006

AbstractGlutamate appears to be the neurotransmitter of granule cells, the major neuronal population of the cerebellar cortex. To determine the role of astroglial cells in the synthesis of glutamate, we have measured the specific activity of glutamate dehydrogenase (GDH) in clonal cell lines that might be the in vitro equivalents of the different cerebellum astroglial cell types. In conditions where GDH operates in the direction of glutamate synthesis, the specific activity of GDH measured in the “Golgi‐Bergmann”‐like clone was 4–6 times higher than in the “velate protoplasmic”‐ or “fibrous‐like” astrocytic clones. These data correlate well with the intense immunoreactivity to GDH in Golgi‐Bergmann astrocytes in vivo that has been recently reported.
γ‐Aminobutyric Acid and Pentobarbital Enhance 2‐[3H]Oxoquazepam Binding to Type I Benzodiazepine Recognition Sites in Rat and Human Brain
Authors: Corda M. G. , Giorgi O. , Longoni B. , Ongini E. , Barnett A. , Montaldo S. , Biggio G. 
Published: October 2006

Abstract2‐Oxoquazepam (2oxoquaz) is a novel benzodiazepine which shows preferential affinity for type I benzodiazepine recognition sites. In the present study, we analyzed the effect of γ‐aminobutyric acid (GABA), pentobarbital, and chloride ions on [3H]2oxoquaz and [3H]flunitrazepam ([3H]FNT) binding to membrane preparations from rat and human brain. GABA stimulated [3H]‐2oxoquaz and [3H]FNT binding in a concentration‐dependent manner. The maximal enhancement produced by GABA on [3H]2oxoquaz binding was higher than that produced on [3H]FNT binding in both rat and human tissues. In the rat brain, the effect of GABA on [3H]2oxoquaz was similar throughout different brain areas, whereas the effect on [3H]FNT binding was lower in the cerebral cortex and hippocampus than in the cerebellum. Moreover, both [3H]2oxoquaz and [3H]FNT binding were stimulated by chloride ions and pentobarbital. The results are consistent with the hypothesis that type I benzodiazepine recognition sites are linked functionally to the GABA recognition site and the chloride ionophore.
Induction of Glutamine Synthetase in Rat Astrocytes by Co‐Cultivation with Embryonic Chick Neurons
Authors: Wu Doris K. , Scully Sheila , Vellis Jean de 
Published: October 2006

AbstractCo‐cultivation of confluent rat astrocyte cultures with embryonic chick neurons resulted in induction of glutamine synthetase activity in the astrocytes. This induction of glutamine synthetase in astrocytes by neurons was independent of induction by hydrocortisone and forskolin, but was dependent on the length of co‐cultivation and the number of neurons present in the co‐culture. Cycloheximide and actinomycin D inhibited the induction of glutamine synthetase in astrocytes by neurons, whereas cytosine arabinoside had no apparent effect. Results suggest that this induction of glutamine synthetase in astrocytes is mediated by cell contact with neurons and may represent a specific neuronal and glial interaction.
Changes of Phospholipid‐Metabolizing and Lysosomal Enzymes in Hypoglossal Nucleus and Ventral Horn Motoneurons During Regeneration of Craniospinal Nerves
Authors: Alberghina M. , Stella A. M. Giuffrida 
Published: October 2006

AbstractIn order to study the biochemical changes associated with the cell body response to axonal crush injury, two systems, hypoglossal nucleus and spinal cord ventral horn, were used. The time intervals chosen were7, 14, and 28 days after unilateral crushing of the right hypoglossal nerve and cervicothoracic nerves of the rabbit. Non‐crushed, contralateral nerves were used as controls. Three groups of enzyme activities were tested: (a) phospholipase A2, acyl CoA:2‐acyl‐sn‐glycero‐3‐phosphocholine acyl‐transferase, and choline phosphotransferase, as indicators of phospholipid degradation and biosynthesis; (b) seven hydrolases, namely, β‐D‐glucuronidase, β‐iV‐acetyl‐d‐hex‐osaminidase, arylsulfatase A, galactosylceramidase, GM1‐ganglioside β‐galactosidase, and acid RNase, as indicators of lysosomal activity; and (c) free and inhibitor‐bound alkaline RNase, as an index of RNA metabolism. Changes could be grouped into three distinct patterns. Compared to contralateral control, choline phosphotransferase showed a slight increase, whereas phospholipase A2 and most lyso somal hydrolases showed a significant increase of activity, especially evident in the ventral spinal cord neurons 14–28 days after crushing. These changes correlate with known increases of membrane and organelle numbers, including lysosomes, in motor and sensory neurons during peripheral regeneration. In contrast, free and acid alkaline RNase activity significantly decreased in the injured sides compared to the controls. This change can probably be correlated with a stabilization of RNAs needed for increased protein synthesis. No changes in total alkaline RNase and acyltrans‐ferase activities in either regeneration model were observed.
Regional Changes in the Cellular Level of Adenine Nucleotides in Ischemic Rat Brain Subjected to Single Embolization
Authors: Yamada Kenji , Uozumi Tohru , Kawasaki Takashi , Yamada Kazuo , Sogabe Takashi , Ohta Keiji 
Published: October 2006

AbstractRegional changes in adenine nucleotides in the rat brain were studied after 1 h of ischemia produced by the embolization method. The animals were divided into three groups according to neurological symptoms: sham‐operation group, group A (hemiparesis only), and group B (he‐miparesis with unconsciousness). Marked ATP depletion was detected in the hippocampus on the embolized side and extended to the other regions on the same side in group B. The results suggest that this damage in regional energy metabolism arises from regional reduction in blood flow and/or tissue vulnerability. ATP levels in the hypothalamus, hippocampus, and striatum on the opposite side of embolization decreased markedly in group B, and may be caused by extension of brain edema or diaschisis.
Calcium Homeostasis in Digitonin‐Permeabilized Bovine Chromaffin Cells
Authors: Kao Lung‐Sen 
Published: October 2006

AbstractThe regulation of cytosolic calcium was studied in digitonin‐permeabilized chromaffin cells. Accumulation of 45Ca2+ by permeabilized cells was measured at various Ca2+ concentrations in the incubation solutions. In the absence of ATP, there was a small (10–15% of total uptake) but significant increase in accumulation of Ca2+ into both the vesicular and nonvesicular pools. In the presence of ATP, the permeabilized cells accumulated Ca2+ into carbonyl cyanide m‐chlorophenyl hydrazone (CCCP)‐sensitive and ‐insensitive pools. The CCCP‐sensitive pool—mainly mitochondria—was active when the calcium concentration was > 1 μM and was not saturated at 25 μM. The Ca2+ sequestered by the CCCP‐insensitive pool could be inhibited by vanadate and released by inositol trisphosphate, a combination suggesting that this pool was the endoplasmic reticulum. The CCCP‐insensitive pool had a high affinity for calcium, with an EC50 of ∼1 μM. When the Ca2+ concentration was adjusted to the level in the cytoplasm of resting cells (0.1 μM), the presumed endoplasmic reticulum pool was responsible for ∼90% of the ATP‐stimulated calcium uptake. At a calcium level similar to the acetylcholine‐stimulated level in intact cells (5–10 μM), most of the Ca2+ (>95%) went into the CCCP‐sensitive pool.
Characterization of N‐[3H]Methylcarbamylcholine Binding Sites and Effect of N‐Methylcarbamylcholine on Acetylcholine Release in Rat Brain
Authors: Araujo D. M. , Lapchak P. A. , Collier B. , Quirion R. 
Published: October 2006

AbstractThe present experiments show that N‐[3H]‐methylcarbamylcholine ([3H]MCC) binds specifically and with high affinity to rat hippocampus, frontal cortex, and striatum. The highest maximal density of binding sites was apparent in frontal cortex and the lowest in hippocampus. [3H]MCC binding was potently inhibited by nicotinic, but not muscarinic, agonists and by the nicotinic antagonist dihydro‐β‐erythroidine in all three brain regions studied. The effect of unlabeled MCC on acetylcholine (ACh) release from slices of rat brain was tested. The drug significantly enhanced spontaneous ACh release from slices of hippocampus and frontal cortex, but not from striatal slices. This effect of MCC to increase ACh release from rat hippocampus and frontal cortex was antagonized by the nicotinic antagonists dihydro‐β‐erythroidine and d‐tubocurarine, but not by α‐bungarotoxin or by the muscarinic antagonist atropine. The MCC‐induced increase in spontaneous ACh release from hippocampal and frontal cortical slices was not affected by tetrodotoxin. The results suggest that MCC might alter cholinergic transmission in rat brain by a direct activation of presynaptic nicotinic receptors on the cholinergic terminals. That this alteration of ACh release is apparent in hippocampus and frontal cortex, but not in striatum, suggests that there may be a regional specificity in the regulation of ACh by nicotinic receptors in rat brain.
Sulfation of Rat Apolipoprotein E
Authors: Gebicke‐Haerter Peter J. , Shooter Eric M. 
Published: October 2006

AbstractThe synthesis of a 37‐kilodalton (kDa) protein which has been shown recently to be identical with apolipoprotein E (apo‐E) was increased after sciatic nerve injury of the rat. When regeneration of the nerve was allowed, its synthesis returned to control levels at about 8 weeks post injury. In this report it is shown that similar time‐course studies of the protein in the rat optic nerve revealed a delayed increase of the protein but a comparably high level of synthesis at 3 weeks post injury. This level was maintained up to at least 18 weeks after crush. Furthermore, two‐dimensional electrophoresis revealed that the characteristic “trailing” of the protein is due to its sialylation, because it was reduced after neuraminidase treatment. This treatment, however, detected a neuraminidase‐resistant heterogeneous form in CNS tissue and a homogeneous form in peripheral nervous tissue. The trailing persisted up to 18 days of culture of optic nerve explants, of CNS glial cells, and of peritoneal macrophages, but disappeared during the first culture days of sciatic nerve explants and was not observed in Schwann cell culture media. Incorporation studies with 35SO4 revealed that apo‐E was the major sulfated protein in culture media conditioned by CNS glial cells, whereas sulfation of the protein was undetectable in Schwann cell cultures. Because macrophages are likely to be the major source of apo‐E in both peripheral and central glial cell cultures as well as in injured optic and sciatic nerves, it is hypothesized that resident cells of sciatic nerves secrete potent sulfatases. As a result, sialic acid residues may be more susceptible to degradation. Furthermore, the affinity of apo‐E toward heparan sulfate proteoglycans of the extracellular matrix may be increased, which results in its preferential accumulation in the peripheral nerve.
Fructose 2,6‐Bisphosphate Changes in Rat Brain During Ischemia
Authors: Yamamoto Masaaki , Hamasaki Naotaka , Maruta Yoshiro , Tomonaga Masamichi 
Published: October 2006

Abstract:Brain ischemia was produced by bilateral ligation of the common carotid arteries of spontaneously hypertensive rats. The concentrations of fructose 2,6‐bisphosphate and other glycolytic intermediates as well as of pyridine and adenine nucleotides were measured in frozen brain samples. In contrast to the decrease reported in hepatocytes under anoxic conditions, the fructose 2,6‐bisphosphate content was increased by 20–30% during the early stages of ischemia. Elevation in fructose 1,6‐bisphosphate level and lactate formation followed the rise in fructose 2,6‐bisphosphate content, a finding suggesting that this compound plays a key role in the compensatory acceleration of glycolysis under ischemic conditions in vivo.
Toxicity of 1‐Methyl‐4‐Phenylpyridinium for Rat Dopaminergic Neurons in Culture: Selectivity and Irreversibility
Authors: Michel P. P. , Dandapani B. K. , Knusel B. , Sanchez‐Ramos J. , Hefti F. 
Published: October 2006

Abstract:Cultures of dissociated embryonic rat mesencephalic cells were exposed to 10 μM 1‐methyl‐4‐phenylpyridinium (MPP+), a concentration shown earlier to result in loss of >85% of tyrosine hydroxylase (TH)‐positive neurons without affecting the total number of cells observed by phase‐contrast microscopy. To characterize better the selectivity of the toxic action of MPP+, other parameters were measured reflecting survival and function of dopaminergic or nondopaminergic neurons. Exposure of cultures to 10 μM MPP+ for 48 h reduced TH activity to 11% of control values without reducing protein levels. [3H]Dopamine uptake was reduced to < 4% of control values, whereas the uptake of γ‐[3H]aminobutyric acid ([3H]GABA) was not affected in these cultures. This same treatment failed to reduce the number of cholinergic cells visualized in septal cultures and did not affect either choline acetyltransferase activity or high‐affinity choline uptake. To assess for possible recovery of dopaminergic neurons, cultures were exposed to 10, 1.0, or 0.1 μM MPP+ for 48 h and then kept for up to 6 days in MPP+‐free medium. After exposure to 10 μM MPP+, the number of TH‐positive neurons, their neurite density, TH activity, and [3H]dopamine uptake remained at constant, reduced levels throughout the period of observation after termination of exposure, whereas GABA uptake remained normal. Treatment with lower concentrations of MPP+, i.e., 1.0 and 0.1 μM, induced less pronounced dopaminergic toxic effects. However, no recovery was seen after posttreatment incubation in toxin‐free medium. These findings provide evidence that MPP+ treatment results in highly selective and irreversible toxicity for cultured dopaminergic neurons.
Precursors for Cholesterol Synthesis (7‐Dehydrocholesterol, 7‐Dehydrodesmosterol, and Desmosterol): Cholesterol/7‐Dehydrocholesterol Ratio as an Index of Development and Aging in PNS but Not in CNS
Authors: Bourre J. M. , Clément M. , Gérard D. , Legrand R. , Chaudière J. 
Published: October 2006

Abstract:In rat sciatic nerve, the 7‐dehydrocholesterol content decreased dramatically during the postnatal period and slowly during adulthood and aging. In contrast, the 7‐dehydrodesmosterol content peaked at 14 days and was nearly undetectable after 60 days. The desmosterol content peaked at 21 days and was nearly undetectable after 1 year. The cholesterol content increased up to 21 days and remained nearly constant thereafter. In brain (in contrast to sciatic nerve), 7‐dehydrodesmosterol and desmosterol contents decreased dramatically during development and slightly during adulthood and aging; the 7‐dehydrocholesterol content peaked at 21 days and remained constant during aging. Only 7‐dehydrocholesterol was dramatically more concentrated in PNS than in CNS. In brain, the cholesterol/7‐dehydrocholesterol ratio increased during development and remained stable after 6 months. In contrast, in sciatic nerve, this ratio continuously increased during development and aging (950‐fold between 5 days and 18 months). Thus, the cholesterol/7‐dehydrocholesterol ratio is a useful biochemical index of development and aging in the PNS.
Expression of Functional D2 Dopamine Receptors Following Differentiation of Y‐79 Human Retinoblastoma Cells
Authors: Monsma Frederick J. , Barton Anne C. , Sibley David R. 
Published: October 2006

Abstract:Y‐79 human retinoblastoma cells grown in serumfree medium in monolayer culture have previously been shown to undergo differentiation in response to dibutyryl cyclic AMP (Bt2cAMP). We report here that Y‐79 cells treated in this manner also express very high levels of functional D2 dopamine receptors. In control Y‐79 cells, cultured in suspension, D2 dopamine receptors, quantified via saturation analysis with the D2 antagonist [3H]methylspiperone, are expressed at a level of ∼3 fmol/106 cells (∼1,800 receptor sites/cell). Differentiation is initiated by attachment of the cells to the culture dish with poly‐D‐lysine and fibronectin and continued culture in serum‐free medium. After 8 days in serumfree culture, differentiation is further induced with continuous Bt2cAMP treatment. Using this differentiation protocol, D2 receptor levels increase up to a maximum of 30 fmol/106 cells (18,000 receptors/cell) on day 20, the limit of culture viability. Cultures of 15–17 days (7–9 days of Bt2cAMP treatment) expressing receptor levels of 15–20 fmol/106 cells are used for pharmacological and functional characterization of D2 dopamine receptors. The pharmacology of competition for [3H]methylspiperone binding to differentiated Y‐79 (dY‐79) cell membranes by a series of dopaminergic antagonists verifies the D2 receptor nature of this site, exhibiting appropriate affinities and the following rank order of potency: YM‐09151‐2 ∼ spiperone > domperidone ∼ (+)‐butaclamol ∼ fluphenazine > chlorpromazine > (–)‐sulpiride > (+)‐sulpiride > promethazine > (+)‐SCH 23390 ≫ (–)‐butaclamol. Inhibition of [3H]methylspiperone binding by dopaminergic agonists in dY‐79 cell membranes indicates the presence of multiple agonist affinity states, which can be converted to a homogeneous low‐affinity state by addition of guanine nucleotides. In addition, incubation with dopamine or other D2‐selective agonists results in an ∼50% reduction in forskolin‐stimulated cyclic AMP production in lysed dY‐79 cells, which can be blocked by D2‐selective antagonists. These data indicate that the D2 receptors expressed in these cells are indeed functional. The ability to induce high levels of expression of functional D2 dopamine receptors in a cultured human cell line should provide an excellent model system with which to examine the molecular events involved in the expression and regulation of this receptor system.