bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Lipid Structure on the Capacity of Myelin Basic Protein to Alter Vesicle Properties: Potent Effects of Aliphatic Aldehydes in Promoting Basic Protein‐Induced Vesicle Aggregation
Authors: Epand Richard M. , Dell Karen , Surewicz Witold K. , Moscarello Mario A. 
Published: October 2006

AbstractThe capacity of myelin basic protein or of poly‐l‐lysine to promote leakage of carboxyfluorescein from vesicles or the aggregation of vesicles was studied. The vesicles were composed of phosphatidylcholine as the sole or major lipid component. Addition of 10% sphingomyelin, 10% phosphatidylglycerol, 10% egg or bovine brain phosphatidylethanolamine, or 30% dodecanal had relatively little effect on the extent of carboxyfluorescein release in the presence of either myelin basic protein or poly‐l‐lysine. In contrast with these results, the extent of vesicle aggregation was very sensitive to lipid composition. Addition of 10% phosphatidylglycerol induced more aggregation than the other phospholipids tested. Admixing 10% of a partially degraded sample of bovine brain phosphatidylethanolamine also led to a large amount of aggregation induced by the myelin basic protein. This latter aggregation appeared more specific for the basic protein, as it occurred to a much smaller extent with poly‐l‐lysine. In general, the effects of the myelin basic protein on either carboxyfluorescein release or vesicle aggregation were similar to, although somewhat greater than, that of poly‐l‐lysine. The aggregation of vesicles containing degradation products of phosphatidylethanolamine can be ascribed largely to the presence of aliphatic aldehydes. The effect of aliphatic aldehydes was specific in that the aliphatic alcohol, hexadecanol, or the short‐chain aldehydes, acetaldehyde or butyraldehyde, did not promote myelin basic protein‐induced vesicle aggregation. In addition, poly‐l‐lysine was less effective than the basic protein in aggregating vesicles containing aliphatic aldehydes. Other proteins such as bovine serum albumin and ribonuclease had no effect. Aliphatic aldehydes are produced as a result of the degradation of plasmalogens, a class of phospholipids abundant in myelin. Plasmalogenase activity is elevated in multiple sclerosis. The interaction between myelin basic protein and membranes containing aldehydes may thus be of particular biological importance.
Serotonin Receptor Changes in Dementia of the Alzheimer Type
Authors: Cross A. J. , Crow T. J. , Ferrier I. N. , Johnson J. A. , Bloom S. R. , Corsellis J. A. N. 
Published: October 2006

AbstractSerotonin receptors were assessed in postmortem brains of control and Alzheimer‐type dementia (ATD) patients using ligand binding techniques. Differential losses of serotonin S1 and S2 receptors were present in neocortex, hippocampus, and amygdala of ATD patients, whereas no significant changes were observed in basal forebrain and basal ganglia. Losses of S1 receptors were significantly age‐related in the ATD group, suggesting they occurred at a later stage of the disease process. Losses of S2 receptors were considerably greater (with a reduction to 35% of control in temporal cortex) and were not age‐related in ATD. Significant correlations were observed within the ATD group between S2 receptor binding and somatostatin immuno‐reactivity in temporal and frontal cortices. Thus the loss of S2 receptors in ATD may be a relatively early change in the disease process, and may precede the changes in ascending serotonergic neurones.
Benzodiazepine Receptor Binding Following Amygdala‐Kindled Convulsions: Differing Results in Washed and Unwashed Brain Membranes
Authors: Niznik H. B. , Burnham W. M. , Kish S. J. 
Published: October 2006

AbstractThe binding of [3H]flunitrazepam and [3H]RO5–4864 was measured in unwashed brain homogenates and in extensively washed brain membranes from amygdala‐kindled and “yoked” control rats sacrificed 2 weeks following the sixth stage 5 convulsion. In unwashed homogenates, [3H]flunitrazepam binding was reduced in both the hypothalamus and ipsilateral right cortex of kindled rats (unchanged in other areas). In washed brain membranes, [3H]flunitrazepam binding was unaltered in these regions; it was bilaterally elevated, however, in both the amygdala and hippocampus (unchanged in other areas). In washed membranes, the in vitro addition of ‐γ‐aminobutyric acid enhanced [3H]flunitrazepam binding to a similar extent in kindled and control membranes. These data indicate that the type of benzodiazepine binding abnormality observed after kindling depends on the type of tissue preparation employed in the assay procedure.
Ornithine Decarboxylase Activity in Brain Regulated by a Specific Macromolecul, the Antizyme
Authors: Laitinen Paivi H. , Huhtinen Riitta‐Liisa , Hietala Oili A. , Pajunen Antti E. I. 
Published: October 2006

Abstract:Mouse brain ornithine decarboxylase activity is about 70‐fold higher at the time of birth compared with that of adult mice. Enzyme activity declines rapidly after birth and reaches the adult level by 3 weeks. Immuno‐reactive enzyme concentration parallels very closely the decrease of enzyme activity during the first postnatal week, remaining constant thereafter. The content of brain antizyme, the macromolecular inhibitor to ornithine decarboxylase, in turn is very low during the first 7 days and starts then to increase and at the age of 3 weeks it is about six times the level of that in newborn mice. This may explain the decrease in enzyme activity during brain maturation, and suggests the regulation of polyamine biosynthesis by an antizyme‐mediated mechanism in adult brain.
Subcellular Fractionation of Rat Sciatic Nerve and Specific Localization of Ganglioside LM1 in Rat Nerve Myelin
Authors: Chou K. H. , Nolan C. E. , Jungalwala F. B. 
Published: October 2006

Abstract:Subcellular fractionation of rat sciatic nerve was developed to determine the specific localization of gangliosides in the nerve membrane fractions. Myelin, microsomal, and a plasma membrane‐like fraction were isolated and purified by sucrose density gradient centrifugation. These subfractions were characterized by electron microscopy, marker enzyme assays, and their protein and lipid profile. In rat sciatic nerve myelin, 90 mol% of the total gangliosides were monosialogangliosides. LM1 (sialosyl‐lactoneotetraosylceramide) (61 mol%) and GM3 (21%) were the major gangliosides of the rat nerve myelin. Two other neolacto series of gangliosides, viz., sialosyl‐lactoneonorhexaosylceramide and sialosyl‐lactoneooctasylceramide, were also localized mostly in the myelin fraction. GM1 was only a minor (< 2%) ganglioside in myelin. The ganglioside patterns of the microsomal and plasma membrane‐like fractions were similar with minor quantitative differences and were entirely different from that of myelin. Monosialogangliosides were –70–75 mol% of the total in these fractions. The major gangliosides of the microsomal and plasma membrane‐like fractions were GM3 (–40%) and GM1 (–20%). LM1 in these fractions was minimal (less than –5%). Significant amounts of GM3 with N‐glycolylneuraminic acid (–10%) and GM1b (4–14%) were also identified in the microsomal and plasma membrane‐like fractions but not in myelin. These and the higher lactoneo series of gangliosides have not been previously reported to be present in the rat nervous system. Almost exclusive localization of LM1 in myelin in rat peripheral nervous system is consistent with our previous observation that deposition of LM1 in the nerve with age was very similar to that of myelin marker lipids cerebrosides and sulfatides.
Relationships Among ATP Synthesis, K+ Gradients, and Neurotransmitter Amino Acid Levels in Isolated Rat Brain Synaptosomes
Authors: Dagani Fiorenzo , Erecinska Maria 
Published: October 2006

Abstract:Correlations were made among ATP synthesis, transmembrane K+ gradients, and leakage of three amino acid neurotransmitters, γ‐aminobutyric acid (GABA), aspartate, and glutamate, in rat brain synaptosomes incubated under normoxic and respiration‐limited conditions. Even under normoxic conditions, a substantial proportion of total ATP synthesis (8%) was provided by glycolysis. Limitation of respiration by ∼30% through addition of amobarbital (Amytal) caused a twofold decrease in the cre‐atine phosphate/creatine ([CrP]/[Cr]) ratio, and consequently the [ATP]/[ADP] ratio, and a threefold increase in lactate production. There was a detectable decrease in intracellular [K+] and small rises in external GABA, aspartate, and glutamate concentrations. More severe limitations in ATP synthesis caused larger declines in the [CrP]/[Cr] ratio and progressive leakage of K+ and neurotransmitter amino acids. A comparison of ΔGATP and ΔGNa,k showed the former to be larger by 6 kcal, which indicates that the plasma membrane Na+/K+ pump operates at far from equilibrium. Under respiration‐limited conditions, even when total ATP synthesis decreased by ∼80% and [ATP] declined to <0.4 mM ΔGATP was still larger than ΔGNa,k. It is suggested that during hypoxia and ischemia, the activity of the plasma membrane Na+/K+ pump in brain becomes limited by [ATP], which falls below the Am value for the low‐affinity regulatory site on the enzyme. This failure of the pump and consequent collapse of the ion gradients may contribute to the leakage of neurotransmitter amino acids that occurs in these pathological states.
Amphetamine‐Induced Dopamine Release in the Rat Striatum: An In Vivo Microdialysis Study
Authors: Butcher Steven P. , Fairbrother Iain S. , Kelly John S. , Arbuthnott Gordon W. 
Published: October 2006

AbstractThe effects of a number of biochemical and pharmacological manipulations on amphetamine (AMPH)‐induced alterations in dopamine (DA) release and metabolism were examined in the rat striatum using the in vivo brain microdialysis method. Basal striatal dialysate concentrations were: DA, 7 nM; dihydroxyphenylacetic acid (DOPAC), 850 nM; homovanillic acid (HVA), 500 nM; 5‐hydroxyindoleacetic acid (5‐HIAA), 300 nM; and 3‐methoxytyramine (3‐MT), 3 nM. Intraperitoneal injection of AMPH (4 mg/kg) induced a substantial increase in DA efflux, which attained its maximum response 20–40 min after drug injection. On the other hand, DOPAC and HVA efflux declined following AMPH. The DA response, but not those of DOPAC and HVA, was dose dependent within the range of AMPH tested (2–16 mg/kg). High doses of AMPH (>8 mg/kg) also decreased 5‐HIAA and increased 3‐MT efflux. Depletion of vesicular stores of DA using reserpine did not affect significantly AMPH‐induced dopamine efflux. In contrast, prior inhibition of catecholamine synthesis, using α‐methyl‐p‐tyrosine, proved to be an effective inhibitor of AMPH‐evoked DA release (<35% of control). Moreover, the DA releasing action of AMPH was facilitated in pargyline‐pretreated animals (220% of control). These data suggest that AMPH releases preferentially a newly synthesised pool of DA. Nomifensine, a DA uptake inhibitor, was an effective inhibitor of AMPH‐induced DA efflux (18% of control). On the other hand, this action of AMPH was facilitated by veratrine and ouabain (200–210% of control). These results suggest that the membrane DA carrier may be involved in the actions of AMPH on DA efflux.
Levels and Distribution of the Calcium‐Modulated Proteins S100 and Calmodulin in Rat C6 Glioma Cells
Authors: Zimmer Danna B. , Van Eldik Linda J. 
Published: October 2006

AbstractTo understand better the mechanisms involved in the transduction of a calcium signal into an intracellular response via multiple calcium‐modulated proteins, we have examined the calcium‐modulated proteins, S100 and calmodulin, and their intracellular targets in rat C6 glioma cells. Subconfluent, confluent, and postconfluent C6 cells contain predominantly, if not exclusively, the S100β polypeptide. The level of S100β in C6 cells increases approximately 20‐fold from subconfluency to postconfluency whereas the level of calmodulin increases only about twofold. The subcellular distribution of S100β and calmodulin in mitotic cells is similar. However, the subcellular distribution of these proteins in interphase cells is different and appears to change with cell density. Gel overlay analysis demonstrated that the S100– and calmodulin‐binding protein profiles are significantly different and that some of the binding proteins appear to change in intensity with cell density. These data demonstrate that S100β is the predominant S100 polypeptide in C6 cells and suggest that changes in S100β and S100β‐binding proteins may be involved in regulating S100‐mediated intracellular processes in C6 cells. Our studies also suggest that the levels of S100 and calmodulin may be differentially regulated in C6 cells.
Requirement of ATP for Exocytotic Release of Catecholamines from Digitonin‐Permeabilized Adrenal Chromaffin Cells
Authors: Morita Kyoji , Ishii Shuta , Uda Hiroshi , Oka Motoo 
Published: October 2006

AbstractCultured chromaffin cells were preincubated with digitonin to deplete endogenous ATP from the cell cytoplasm. Catecholamine release from these digitonin‐pretreated cells was then studied in the presence and absence of exogenous ATP to elucidate a possible involvement of the cytoplasmic ATP in the exocytotic process. The preincuba‐tion of the cells with digitonin in the ATP‐free permeabilizing medium resulted in a marked decline of the releasing response to a calcium challenge. Furthermore, the declined activity of catecholamine release caused by digitonin pre‐treatment was restored by the presence of ATP, but not by other adenine nucleotides, and this recovery was observed in a manner dependent on the concentration of ATP. These findings, therefore, seem to indicate that a decrease in the releasing activity of the digitonin‐pretreated cells may be due to the removal of endogenous ATP from the cytoplasmic space of the cells, thus suggesting that the cytoplasmic ATP may be involved in the exocytotic mechanism of catecholamine secretion.
Kainic Acid Inhibits the Synaptosomal Plasma Membrane Glutamate Carrier and Allows Glutamate Leakage from the Cytoplasm but Does Not Affect Glutamate Exocytosis
Authors: Pocock Jennifer M. , Murphie Helen M. , Nicholls David G. 
Published: October 2006

AbstractKainate inhibits the exchange of d‐aspartate into guinea‐pig cerebrocortical synaptosomes. Kainate inhibits the Ca2+‐independent efflux of endogenous glutamate in the presence of a trapping system for the released amino acid but potentiates a Ca2+‐independent net efflux of endogenous and labelled glutamate and aspartate in the ab‐sence of the trap. Dihydrokainate has a similar effect. No discrepancy is seen between the release of endogenous and exogenously accumulated amino acid. These results are consistent with the presence of a slow leak of glutamate or aspartate from the cytoplasm independent of the kainate‐sensitive Na+‐cotransport pathway. In the presence of the trap, glutamate effluxes by both pathways, whereas in the absence of the trap, the Na+‐cotransport pathway opposes the leak. Neither in the presence or absence of the glutamate trap does kainate induce, inhibit, or otherwise affect the Ca2+‐dependent release of endogenous glutamate. The results enable many of the apparent complexities in the presynaptic actions of kainate to be resolved.
Subcellular Localization of Rat Brain Insulin Binding Sites
Authors: Marks J. L. , Maddison J. , Eastman C. J. 
Published: October 2006

AbstractFractions and subcellular structures were prepared from rat brain homogenate and their purity was assessed using enzyme markers, γ‐aminobutyric acid binding, DNA content, and electron microscopy. Insulin binding was highest on the plasma membrane preparations and approximately 50% less so on brain homogenate crude mi‐tochondrial (P2), myelinated axon, and synaptosome preparations. Very low levels of binding were found on mitochondria and nuclei. Differences in binding between fractions were due to numbers of binding sites, and not variable binding affinity. There was a close relationship between insulin binding and the activity of Na/K ATPase (E.C. 3.6.1.4) in all fractions (r= 0.98). Insulin binding to the P2 was compared with plasma membrane fractions in seven brain regions, and the results demonstrated the same close relationship between insulin binding and plasma membrane content in all regions except hypothalamus. Plasma membrane insulin binding was well represented by the binding on P2 membranes in all regions except hypothalamus and brainstem. It was concluded that insulin binding is distributed evenly over the surface of brain cells and is not increased on nerve endings.
Characteristics of Phorbol Ester‐ and Agonist‐Induced Down‐Regulation of Astrocyte Receptors Coupled to Inositol Phospholipid Metabolism
Authors: Pearce Brian , Morrow Christine , Murphy Sean 
Published: October 2006

AbstractWe have examined some of the characteristics of phorbol ester‐ and agonist‐induced down‐regulation of astrocyte receptors coupled to phosphoinositide metabolism. Our results show that preincubation of [3H]inositol‐labelled astrocyte cultures with phorbol 12‐myristate 13‐acetate (PMA) resulted in a time‐ (t1/2, 1–2 min) and concentration‐dependent (IC50, 1 nM) decrease in the accumulation of [3H]inositol phosphates (IP) evoked by muscarinic receptor stimulation. Much longer (30–40 min) preincubation periods with higher concentrations (IC50, 600 μM) were required to elicit the same effect with the receptor agonist carbachol. Following preincubation, agonist‐stimulated [3H]IP accumulation recovered with time; in both cases pretreatment levels of inositol lipid metabolism were attained within 2 days. Both phorbol ester and agonist pre‐treatments were also effective in reversing the carbachol‐evoked mobilisation of 45Ca2+ in these cells. However, their effects on phosphoinositide metabolism were found not to be additive. Although neither pretreatment affected the incorporation of [3H]inositol into phosphoinositides, both resulted in a loss of membrane muscarinic receptors as assessed by [3H]N‐methylscopolamine binding. In washed membranes prepared from [3H]inositol‐labelled cultures, the guanine nucleotide analogue, guanosine 5′‐O‐thiotri‐phosphate (GTP‐γ‐S), caused a dose‐dependent increase in [3H]IP formation. This response was enhanced when carbachol was also included in the incubation medium, although the agonist alone was without effect. Pretreatment with either PMA or carbachol had no effect on GTP‐γ‐S‐stimulated [3H]IP accumulation but did reduce the ability of carbachol to augment this response. Similar findings were obtained when membranes were exposed directly to PMA. Phorbol ester pretreatment was also effective in reversing the increase in [3H]IP accumulation and 45Ca2+ mobilisation evoked by noradrenaline. However, following preincubation with carbachol there was no loss of nor‐adrenaline‐stimulated phosphoinositide breakdown although its ability to mobilise 45Ca2+ was blocked.
Two Developmentally Regulated Isoenzymes of Calmodulin‐Stimulated Protein Kinase II in Rat Forebrain
Authors: Rostas John A. P. , Seccombe Margaret , Weinberger Ron P. 
Published: October 2006

AbstractSoluble calmodulin‐stimulated protein kinase II has been purified from adult and 10‐day‐old rat forebrain. By autoradiography, the α/β subunit ratios of the 10‐day and adult enzymes were 0.67 ± 0.03 and 2.20 ±0.15, respectively. By silver staining, the α/β subunit ratios were 1.02 ± 0.06 and 2.36 ±0.10, respectively. The apparent holoenzyme molecular masses of the purified 10‐day and adult enzymes were 500,000 daltons and 700,000 daltons. However, varying the purification conditions revealed higher and lower molecular mass forms at both ages and suggested that the form of the kinase that is usually purified is merely that which has the highest affinity for calmodulin‐Sepharose and may not be the form of the kinase that exists in vivo. The subunits of the adult and 10‐day enzymes were indistinguishable by one‐ and two‐dimensional electrophoresis and one‐dimensional proteolytic peptide maps. These results are consistent with the suggestion that at least two developmentally regulated isoenzymes of this kinase exist in rat forebrain.
Analysis of the 5’Region of the Human Tyrosine Hydroxylase Gene: Combinatorial Patterns of Exon Splicing Generate Multiple Regulated Tyrosine Hydroxylase Isoforms
Authors: Bourdellès B. Le , Boularand S. , Boni C. , Horellou P. , Dumas S. , Grima B. , Mallet J. 
Published: October 2006

AbstractA single human gene has been described to encode multiple tyrosine hydroxylase (TH) mRNAs. The study of this variation has been extended by S1 mapping experiments and by analysis of the 5’region of the TH gene. Four different mRNAs were found to originate solely from alternative splicing of two exons. Comparison of the 5’flanking regions of human and rat genes discloses several highly conserved segments, likely to play an important role in the regulation of TH gene expression.
Acute Uteroplacental Ischemic Embryo: Lactic Acid Accumulation and Prostaglandin Production in the Fetal Rat Brain
Authors: Magal Ella , Goldin Ehud , Harel Shaul , Yavin Ephraim 
Published: October 2006

AbstractA new experimental model for studying the effects of acute ischemia on brain development in the near‐term fetal rat has been devised. Ischemic conditions are achieved by complete clamping of blood vessels branching from the uterine vasculature into each individual fetus for designated times followed by removal of the clamps to permit reperfusion. Accumulation of lactic acid in the fetal orain depends on the length of the restriction period, reaching a plateau level of 29 μmol/g tissue at about 30 min. It also depends on the reperfusion time. Thus after a period of 15 min of restriction lactate levels show an increase over the next 30‐min reperfusion to a value of 25.5 μmol/g followed by a rapid decrease to normal values by 3 h of reperfusion. Restriction of 15 min followed by reperfusion of 45 min causes an elevation of prostaglandin E2 (PGE2) level from 12.4 ± 0.86 ng/g to 21.1 ± 0.6 ng/g (p < 0.001). This elevation in PGE2 level is less apparent after 20 min of restriction. No effects are seen on the level of PGF2α. Both PGE2 and PGF2α accumulate in vitro in a time‐dependent manner by brain paniculate fraction. In vitro synthesis of both PGE2 and PGF2α is inhibited by indomethacin (100% and 68%, respectively) and AA861 (94% and 76%, respectively). BW755c and nordihydro‐guaiaretic acid do not affect PGE2 formation but enhance PGF2a production by 112% and 152%, respectively. Paniculate fractions from restricted brain produce less PGF2α than control brains (6.38 ± 1.62 versus 11.43 ± 2.2, p < 0.01). The new experimental model should be adequate for studying the consequences of perinatal ischemia on the developing brain.