bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional Acetylcholine Metabolism in Brain During Acute Hypoglycemia and Recovery
Authors: Ghajar J. B. G. , Gibson G. E. , Duffy T. E. 
Published: October 2006

Abstract:Insulin‐induced hypoglycemia in normothermic rats caused progressive neurological depression and differentially altered regional cerebral acetylcholine metabolism. Reductions of plasma glucose from 7.7 mM (control) to 2.5‐1.7 mM (moderate hypoglycemia associated with decreased motor activity) or 1.5 mM (severe hypoglycemia with lethargy progressing to stupor) decreased glucose concentrations in the cerebral cortex, striatum, and hippocampus to < 10% of control. Moderate hypoglycemia diminished acetylcholine concentrations in cortex and striatum (21% and 45%, respectively) and reduced [1‐2H2, 2‐2H2]choline incorporation into acetylcholine (62% and 41%, respectively). Severe hypoglycemia did not reduce the acetylcholine concentration or synthesis in cortex and striatum further. The concentrations of choline rose in the cortex (+ 53%) and striatum (+ 130%) of animals that became stuporous but a similar rise in [1‐2H2, 2‐2H2]choline left the specific activities of choline in these structures unchanged. Even severe hypoglycemia did not alter the hippocampal cholinergic system. In rats that developed hypoglycemic stupor and were then treated with glucose, the animals recovered apparently normal behavior, and the concentrations of acetylcholine and the incorporation of [1‐2H2, 2‐2H2]‐choline into acetylcholine returned to control values in the striatum but not in the cerebral cortex. Thus, impaired acetylcholine metabolism in selected regions of the brain may contribute to the early symptoms of neurological dysfunction in hypoglycemia.
Chromatin Proteins Share Antigenic Determinants with Neurofilaments
Authors: Wood John N. , Lathangue Nicholas B. , McLachlan Donald R. , Smith Bryan J. , Anderton Brian H. , Dowding Alan J. 
Published: October 2006

Abstract:Antigenic determinants common to distinct proteins may be unambiguously identified by the use of monoclonal antibodies. Some monoclonal antibodies to mammalian neurofilaments have recently been shown to cross‐react with the neurofibrillary tangles found at high density in the brains of senile dements with Alzheimers disease (SDAT). Here, we show that these antibodies also cross‐react with chromatin proteins, including the linker histones H1 and H10. Elevated levels of histone H10 have also been reported in SDAT brains.
Muscarinic Cholinergic Receptors in Human Foetal Brain: Characterization and Ontogeny of [3H]Quinuclidinyl Benzilate Binding Sites in Frontal Cortex
Authors: Ravikumar B. V. , Sastry P. S. 
Published: October 2006

Abstract:Twenty‐two frontal cortices from normal human foetal brains of gestational ages ranging from 16 to 40 weeks and five postnatal brains ranging from 5 to 50 years were analysed for the ontogeny of muscarinic receptors using [3H]quinuclidinyl benzilate (QNB) as the ligand. QNB binding sites were shown to be stable up to 41/2 months of storage at – 70°C. QNB binding was characterized in frontal cortices of 28‐week‐old foetal brains as muscarinic receptors by the following criteria: (1) it was localised mainly in particulate fraction; (2) binding was saturable at a concentration of 1.5 nM; (3) the cholinergic antagonists atropine and scopolamine competed for the binding, with IC50 values of 1 and 0.8 nM, respectively. The agonists oxotremorine, carbachol, and pilocarpine gave IC50 values of 1, 15 and 18 μM, respectively. Nicotinic receptor ligands and noncholinergic drugs could not compete for the binding. Bimolecular association and dissociation rate constants for the reversible binding are 6.23 ± 108M−1± min−1 and 2.0 ± 10−2± min−1, respectively. The equilibrium dissociation constant is 33 pM. The KD obtained by saturation binding data is 103 pM. Ontogeny of muscarinic receptors showed three distinct phases: In phase I, they appear between 16 and 18 weeks [average concentration 109 fmol/mg protein of total particulate fraction (TPF)] and slowly increase up to 20 weeks (average concentration 147 fmol/mg protein TPF). Phase II is a lag period between 20 and 24 weeks at which time receptor concentration does not change perceptibly (average concentration 167 fmol/mg protein TPF). Phase III is a rapid increase of receptors occurring in the third trimester, reaching a maximum at birth (average concentration 450 fmol/mg TPF). After birth the receptor content declines and the values in adult frontal cortices are 50% of that at birth, indicating synapse elimination postnatally. Affinity of the receptor to QNB did not change during foetal development. Sodium chloride and GTP decrease the agonist affinity, as observed by carbachol competition of QNB binding. This effect was observed even at 16–18 weeks. The magnitude of sodium effect remained two‐ to threefold at all ages but the GTP effect increased from about 1.4‐fold at 16–18 weeks to two‐ to threefold at birth. These results suggest that the modulatory elements appear simultaneously with the receptors.
Human Blood—Brain Barrier Insulin Receptor
Authors: Pardridge William M. , Eisenberg Jody , Yang Jing 
Published: October 2006

Abstract:A new model system for characterizing the human brain capillary, which makes up the blood–brain barrier (BBB) in vivo, is described in these studies and is applied initially to the investigation of the human BBB insulin receptor. Autopsy brains were obtained from the pathologist between 22–36 h postmortem and were used to isolate human brain microvessels which appeared intact on both light and phase microscopy. The microvessels were positive for human factor 8 and for a BBB‐specific enzyme marker, γ‐glutamyl transpeptidase. The microvessels avidly bound insulin with a high‐affinity dissociation constant, KD= 1.2 > 0.5 nM. The human brain microvessels internalized insulin based on acid‐wash assay, and 75% of insulin was internalized at 37°C. The microvessels transported insulin to the medium at 37°C with a t1/2=$70 min. Little of the 125I‐insulin was metabolized by the microvessels under these conditions based on the elution profile of the medium extract over a Sephadex G‐50 column. Plasma membranes were obtained from the human brain microvessels and these membranes were enriched in membrane markers such as γ‐glutamyl transpeptidase or alkaline phosphatase. The plasma membranes bound 125I‐insulin with an ED50= 10 ng/ml, which was identical to the 50% binding point in intact microvessels. The human BBB plasma membranes were solubilized in Triton X‐100 and were adsorbed to a wheat germ agglutinin Sepharose affinity column, indicating the BBB insulin receptor is a glycoprotein. Affinity cross‐linking of insulin to the plasma membranes revealed a 127K protein that specifically binds insulin. These studies demonstrate (a) the biochemistry of the human BBB may be investigated using the human brain microvessel model system, and (b) the human BBB insulin receptor has structural characteristics typical of the insulin receptor in peripheral tissues and may be part of a combined endocytosis‐exocytosis system for the transport of the peptide through the BBB in man.
Chronic Low‐Level Lead Exposure Impairs Embryonic to Adult Conversion of the Neural Cell Adhesion Molecule
Authors: Cookman Gillian R. , King William , Regan Ciaran M. 
Published: October 2006

AbstractThe neural cell adhesion molecule (N‐CAM) is a complex of surface glycoproteins that are developmentally regulated and believed to be intimately involved in the orderly structuring of the CNS. Here the effect of chronic low‐level lead exposure on their expression in the postnatally developing cerebellum is described. Rat pups were chronically exposed to lead via their dam's drinking water which contained either 200 or 400 mg PbCl2/L from time of birth. Pup postnatal blood lead levels ranged between 10 and 20 μg/dl until day 16 after which they became elevated to 40 μg/dl on day 20. During this period the developmental sialylation state of N‐CAM, which is believed to regulate cell‐cell interaction, fibre outgrowth, and synapse formation, was monitored by rocket immunoelectrophoresis. In control animals the expected desialylation of N‐CAM was found to occur at times coincident with postnatal synapto‐genesis. In contrast, desialylation in animals chronically exposed to lead was found to be significantly impaired when blood lead levels exceeded 20 μg/dl. This could not be attributed to lead‐induced undernutrition or alterations in immu‐noprecipitate formation. These observations could account for the neurobehavioural deficits that are known to be induced at similar blood lead levels, and the potential contribution of impaired N‐CAM desialylation to synaptic elaboration is discussed.
Noninvasive Demonstration of In Vivo 3‐Fluoro‐3‐Deoxy‐D‐Glucose Metabolism in Rat Brain by 19F Nuclear Magnetic Resonance Spectroscopy: Suitable Probe for Monitoring Cerebral Aldose Reductase Activities
Authors: Kwee Ingrid L. , Nakada Tsutomu , Card Peter J. 
Published: October 2006

AbstractThe metabolism of 3‐fluoro‐3‐deoxy‐D‐glucose (3‐FDG) in rat brain in vivo was investigated noninvasively using 19F nuclear magnetic resonance (NMR) Spectroscopy. Following an intravenous infusion of 3‐FDG, 400 mg/kg, four resonances assigned to the α and β anomers of 3‐FDG, 3‐fluoro‐3‐deoxy‐D‐sorbitol, and 3‐fluoro‐3‐deoxy‐D‐fructose were clearly resolved in brain, a result indicating that 3‐FDG is metabolized primarily into the aldose reductase sorbitol (ARS) pathway. An orally administered aldose reductase inhibitor, sorbinil, caused reduction of the flux of 3‐FDG into the ARS, an observation suggesting that the method can be applied in quantitative studies of ARS path way activities. Studies of 24‐h urine specimens showed that in addition to the two metabolites observed in brain, F‐was excreted into the urine. 3‐FDG appears to be a suitable metabolic probe for assessing glucose metabolism in the ARS pathway by in vivo 19F NMR Spectroscopy.
Turnover of Brain Monoamine Oxidase Measured In Vivo by Positron Emission Tomography Using l‐[11C]Deprenyl
Authors: Arnett Carroll D. , Fowler Joanna S. , MacGregor Robert R. , Schlyer David J. , Wolf Alfred P. , Långström Bengt , Halldin Christer 
Published: October 2006

AbstractThe distribution of carbon‐11‐labeled L‐deprenyl, an irreversible inhibitor of monoamine oxidase type B (MAO‐B), was determined in the baboon brain by positron emission tomography. The irreversible blood‐to‐brain transfer constant (influx constant, Ki) was measured using a complete metabolite‐corrected arterial plasma concentration curve. This influx constant was used as a measure of functional enzyme activity for sequential determinations of MAO‐B recovery following a single high dose of unlabeled l‐deprenyl. The half‐life for turnover of MAO‐B was thus determined to be 30 days. Using appropriate irreversible inhibitors, this procedure should be generally useful for determining enzyme turnover rates in any organ in vivo and can be applied to some human studies as well.
Cold Blockade of Axonal Transport Activates Premitotic Activity of Schwann Cells and Wallerian Degeneration
Authors: Oaklander Anne Louise , Spencer Peter S. 
Published: October 2006

AbstractBetween 3 and 4 days after transection of cat sciatic nerve, Schwann cell‐associated premitotic activity spreads anterogradely along degenerating distal nerve stumps at a rate of approximately 200 mm/day. We investigated whether fast anterograde axonal transport contributes to the initiation of this component of Wallerian degeneration. Axonal transport was blocked in intact and transected cat sciatic nerves by focally chilling a proximal segment to temperatures below 11°C for 24 hr. Incorporation of [3H]thymidine (a marker of premitotic DNA synthesis) was then measured 3 and 4 days posttransection in cold blocked‐ and control‐degenerating nerves. Effects of cold block prior to and concomitant with nerve transection were studied. Results failed to support the hypothesis that Schwann‐cell premitotic activity after axotomy is associated with entry into the axon of mitogenic substances and their anterograde fast transport along the distal stump. Instead, data suggested that progressive anterograde failure of fast anterograde transport distal to transection serves to effect the Schwann‐cell premitotic response to axotomy.
Biochemical Characterization of Different Molecular Forms of the Neural Cell Adhesion Molecule L1
Authors: Sadoul Karin , Sadoul Rémy , Faissner Andreas , Schachner Melitta 
Published: October 2006

AbstractThe neural cell adhesion molecule L1 is a phosphorylated, integral membrane glycoprotein that is recovered from adult mouse brain tissue by immunoaffinity chromatography as a set of polypeptides with apparent molecular masses of 200, 180, 140, and 80 kilodaltons (L1–200, L1–180, L1–140, and L1–80, respectively). It has been shown that L1–140 and the phosphorylated L1–80 is generated from L1–200 by mild proteolytic treatment of intact cells. In the present study we have investigated the structural relationships between the different molecular forms of L1 and their location with regard to the surface membrane. We could show that L1–200 has two preferred cleavage sites, one that generates the amino terminal, extracellularly exposed L1–140 and the carboxy terminal L1–80 that spans the membrane. Cleavage at the other site leads to the generation of the amino terminally located L1–180 and the membrane‐attached, phosphorylated carboxy terminal L1–30. This site is cleaved during treatment of live cultured cells with broad‐spectrum, protease‐free phospholipase C (but not phosphatidylinositol‐specific phospholipase C) or exposure to sodium azide or cyanogen bromide. Other conditions that cause damage to cells do not lead to the generation of L1–180 and L1–30, suggesting a particular cell‐intrinsic cleavage mechanism. L1–180 is truly soluble in aqueous solutions, since it can be recovered from culture supernatants and in the supernatant of a crude membrane fraction after incubation for 2 h at 37°C. Although trypsin treatment alone does not release L1–140 into the supernatant, combination of phospholipase C and mild tryptic treatment leads to the release of L1–140 and L1–50, the latter being most likely the extracellularly exposed domain of L1–80 that is complementary to the membrane‐integrated phosphorylated L1–30. Phase separation experiments with Triton X‐114 show that the released forms of L1–180 and L1–140 distribute into the aqueous phase, whereas they distribute into the detergent phase when in association with L1–200 or L1–80. However, when L1–80 is cleaved to yield the soluble L1–50 and membrane‐anchored L1–30, L1–140 is released into the supernatant together with L1–50. A strong affinity of L1–200, L1–140, and L1–80 to each other is also indicated by the fact that they incorporate together into liposomes and separate only under strong detergent conditions. Also, a strong tendency to aggregate is observed for L1‐containing liposomes, but not for those containing the adhesion molecules neural cell adhesion molecule and myelin‐associated glycoprotein. Although the physiological roles of the soluble L1 forms, their mode of generation, and the strong affinity for each other remain to be investigated, the availability of soluble forms of L1 opens the possibility to use them as probes for the functional properties of L1 in assay systems involving live cells in vitro.
Opiate‐Inhibited Adenylate Cyclase in Rat Brain Membranes Depleted of Gs‐Stimulated Adenylate Cyclase
Authors: Childers Steven R. 
Published: October 2006

AbstractOpiate agonists inhibit adenylate cyclase in brain membranes, but under normal conditions the maximal inhibition is small (10–15%). When rat brain membranes were preincubated at pH 4.5, washed, and then assayed for adenylate cyclase at pH 7.4, stimulation of activity by agents (fluoride, guanylyl‐5′‐imidodiphosphate, cholera toxin) that act through the stimulatory GTP‐binding coupling protein (Gs) protein was lost. At the same time, inhibition of basal adenylate cyclase by opiate agonists was increased to a maximum of 30–40%. Opiate inhibition was maximal at low magnesium concentrations (<5 mM), required guanine nucleotides, and decreased the Vmax, not Km, of the enzyme. Incubation of membranes with per tussis toxin lowered the apparent affinity for agonists in inhibiting activity. The δ opioid agonists were more potent than μ agonists, and the Ke values for naloxone in blocking agonist inhibition were similar for both μ and δ agonists (50–90 nM). These results suggest that inhibition of adenylate cyclase in brain is not mediated by μ opiate receptors, but whether classic high‐affinity δ and k receptors are involved with this enzyme cannot be confirmed by these experiments.
High‐Resolution Proton Magnetic Resonance Spectroscopy of Rabbit Brain: Regional Metabolite Levels and Postmortem Changes
Authors: Petroff Ognen A. C. , Ogino Takashi , Alger Jeffry R. 
Published: October 2006

AbstractThe changes in 16 cerebral metabolites produced by cardiac arrest and subsequent room temperature auto‐lysis were studied using high‐resolution proton nuclear magnetic resonance spectroscopy. Biopsies of rabbit cerebral cortex, cerebral white matter, and cerebellum were quantitatively analyzed for acetate, alanine, γ‐aminobu‐tyric acid, creatine, glutamate, glycine, inositol, lactate, N‐acetylaspartate, phosphocreatine, succinate, taurine, and threonine. Of these, N‐acetylaspartate and the total creatine pool are the best candidates for use as concentration reference standards linking in vitro to in vivo 1H nuclear magnetic resonance measurements. Both changed little immediately after death, and they varied in a distinctive way among cortex, white matter, and cerebellum.
ADP‐Ribosylation of Highly Purified Rat Brain Mitochondria
Authors: Masmoudi A. , Islam F. , Mandel P. 
Published: October 2006

AbstractHighly purified synaptic and nonsynaptic mitochondria were prepared from rat brain, and their ADP‐ribosyl transferase and NAD glycohydrolase activities were investigated. Data show that there is no significant difference in ADP‐ribosyl transferase activity between these two types of subcellular preparations. However, NAD glycohydrolase activity appeared to be much higher in nonsynaptic mitochondria. The specific activity of both enzymes was investigated in the presence of the inhibitor nicotinamide or its analogue 3‐aminobenzamide or other adenine nucleotides, such as ATP or ADP‐ribose. The inhibitory effect of nicotinamide or 3‐aminobenzamide on ADP‐ribosyl transferase appears rather weak compared with their effect on NAD glycohydrolase activity. However, ADP‐ribose and ATP appeared more effective in inhibiting ADP‐ribosyl transferase. Our results provide evidence for the existence of ADP‐ribosyl transferase activity in rat brain mitochondria. When NAD glycohydrolase was inhibited totally by nicotinamide, the transfer of ADP‐ribose from NAD to mitochondrial proteins still occurred. The chain length determinations show that the linkage of ADP‐ribose to mitochondrial proteins is oligomeric.
Effects of D‐2 Antagonists on Frequency‐Dependent Stimulated Dopamine Overflow in Nucleus Accumbens and Caudate‐Putamen
Authors: May Leslie J. , Wightman R. Mark 
Published: October 2006

AbstractStimulated dopamine overflow has been measured with in vivo voltammetry in the caudate‐putamen and nucleus accumbens. Overflow was induced by electrical stimulation of the medial forebrain bundle with 120 1‐ms, 300‐μA, biphasic pulses at frequencies between 10 and 60 Hz. Overflow was measured with a Nafion‐coated, carbon‐fiber electrode used with fast‐scan voltammetry (300 V s‐1). Quantification and identification of dopamine concentrations down to 100 nM in vivo is possible with this technique. The overflow curves were fit to a kinetic model that describes the measured response as a function of uptake (characterized by a Vmax and Km) and release (characterized by the concentration of dopamine released per stimulus pulse). Overflow curves in both regions could be described with similar kinetic parameters except for the Vmax, which in the nucleus accum bens was only 60% of that measured in the caudate‐putamen. Uptake inhibition by nomifensine (20 mg kg‐1) caused an apparent 15‐fold change in the value of Km in the nucleus accumbens, similar to results previously reported in the caudate‐putamen. In contrast, metoclopramide (10 mg kg‐1) and sulpiride (100 mg kg‐1) altered the apparent amount of dopamine released per stimulus pulse without a change in the uptake kinetics.
In Vivo Administration of Ethanol Enhances the Function of the γ‐Aminobutyric Acid‐Dependent Chloride Channel in the Rat Cerebral Cortex
Authors: Sanna E. , Concas A. , Serra M. , Biggio G. 
Published: October 2006

Abstract:The effect of in vivo administration of ethanol on the γ‐aminobutyric acidA (GABAA) receptor‐coupled chloride channel was studied by measuring ex vivo t‐[35S]butylbicyclophosphorothionate ([35S]TBPS) binding in the rat cerebral cortex. Intragastric administration of ethanol (0.5–1 g/kg) elicited in 40 min a significant decrease of [35S]TBPS binding to unwashed cortical membrane preparations, an effect mimicked by diazepam (0.5–1 mg/kg, i.p.). However, Scatchard plot analysis indicated that, unlike the case with diazepam, the decrease was entirely due to a reduction in the apparent affinity of [35S]TBPS receptors with no change in the total number of binding sites. Moreover, ethanol, like diazepam, reduced the increase of [35S]TBPS binding elicited by isoniazid (350 mg/kg, s.c.), an inhibitor of the GABAergic transmission. Finally, ethanol markedly potentiated the inhibitory action of diazepam on [35S]TBPS binding. The results suggest that ethanol, like benzodiazepines, enhances the function of the GABAA‐coupled chloride channel.
In Vivo Measurements of Ethanol Concentration in Rabbit Brain by 1H Magnetic Resonance Spectroscopy
Authors: Petroff Ognen A. C. , Novotny Edward J. , Ogino Takashi , Avison Malcolm , Prichard James W. 
Published: October 2006

Abstract:In vivo 1H magnetic resonance spectroscopy was used to measure the cerebral ethanol concentration in the rabbit after both intraarterial and intragastric administration. There was good agreement between cerebral and blood ethanol concentrations at all times after administration by either route. Cerebral ethanol levels, measured using in vivo 1H spectroscopy, agreed well with those measured in perchloric acid extracts of brain, analyzed by both high‐resolution 1H spectroscopy and gas chromatography. Ethanol may be useful as an indicator to measure cerebral blood flow by 1H spectroscopy and chemical shift‐selective magnetic resonance imaging.