bluuebunny/crossref_metadata_2025 huggingface dataset:
Slow Orthograde Axonal Transport of Radiolabelled Protein in Sciatic Motoneurones of Rats with Short‐Term Experimental Diabetes: Effects of Treatment with an Aldose Reductase Inhibitor or myo‐Inositol
Authors: Mayer J. Heidi , Tomlinson David R. , McLean W. Graham
Published: October 2006

Abstract: This study examined the effect of streptozotocin diabetes of 5 weeks duration on the profile of slow orthogradely transported radiolabelled protein in rat sciatic motoneurones. The diabetic rats showed a retardation of the tail of the slow‐component profile. This selective retardation was unaffected by treatment with an aldose reductase inhibitor, although this treatment reduced the accumulation of sorbitol and prevented the depletion of myo‐inositol in the sciatic nerves of the treated diabetic rats. Other groups, treated with myo‐inositol, had normal or elevated sciatic nerve myo‐inositol levels in the presence of accumulated sorbitol. The axonal transport profiles from both control and diabetic myo‐inositol‐treated groups gave normal tail velocities but an altered shape such that retardation of the tail of the profile may have been present in both. The study concludes that rats with 5 weeks streptozotocin diabetes show retardation of the velocity of the most slowly transported proteins in sciatic motoneurones, and that this defect is not linked to the polyol pathway.
S100a0 (αα) Protein Is Present in Neurons of the Central and Peripheral Nervous System
Authors: Isobe Toshiaki , Takahashi Kiyoshi , Okuyama Tsuneo
Published: October 2006

Abstract: The cellular distribution of S100 subunits in human brain and peripheral nerves was studied by means of an immunohistochemical technique using antibodies specific to the a subunit or the β subunit of S100 protein. The results indicate that the distribution of the a subunit and the β subunit is different among cell types in the nervous tissue, and that neurons in the brain and peripheral nerves contain only the a subunit, or S100a0 protein. The subunit distribution also appears to be different at an intracellular level, where the immunoreaction products for the a subunit show granular arrangement whereas those for the β subunit are found diffusely in the cytoplasm.
Ontogeny of Brain Neurotensin in the Rat: A Radioimmunoassay Study
Authors: Bissette Garth , Richardson Charles , Kizer John S. , Nemeroff Charles B.
Published: October 2006

Abstract: Concentrations of neurotensin‐like immunoreactivity in several discrete brain areas were measured by radioimmunoassay in rats of different ages (2, 5, 10,20, 30, and 60 days). Neurotensin‐like immunoreactivityincreased steadily from 2 to 30 days of age in the hypothalamus and then plateaued, while the preoptic area andamygdala concentrations peaked at 30 days of age. Brain‐stem neurotensin‐like immunoreactivity concentrationsincreased from 2 to 10 days of age and decreased from20 to 60 days of age. Several other regions showed nosignificant age‐associated changes in neurotensin‐like im‐munoreactivity.
In Vivo Regulation of [3H]Acetylcholine Recognition Sites in Brain by Nicotinic Cholinergic Drugs
Authors: Schwartz Rochelle D. , Kellar Kenneth J.
Published: October 2006

Abstract: The in vivo regulation of [3H]acetylcholine ([3H]ACh) recognition sites on nicotinic receptors in rat ‐ brain was examined by administering drugs that increase stimulation of nicotinic cholinergic receptors, either directly or indirectly. After 10 days of treatment with the cholinesterase inhibitor diisopropyl fluorophosphate, [3H]ACh binding in the cortex, thalamus, striatum, and hypothalamus was decreased. Scatchard analyses indicated that the decrease in binding in the cortex was due to a reduction in the apparent density of [3H]ACh recognition sites. In contrast, after repeated administration of nicotine (5–21 days), the number of [3H]ACh recognition sites was increased in the cortex, thalamus, striatum, and hypothalamus. Similar effects were observed in the cortex and thalamus following repeated administration of the nicotinic agonist cytisin. The nicotinic antagonists mecamylamine and dihydro‐β‐erythroidine did not alter [3H]ACh binding following 10–14 days of administration. Further, concurrent treatment with these antagonists and nicotine did not prevent the nicotine‐induced increase in these binding sites. The data indicate that [3H]ACh recognition sites on nicotinic receptors are subject to up‐ and down‐regulation, and that repeated administration of nicotine results in a signal for up‐regulation, probably through protracted desensitization at the recognition site.
3,4‐Dihydroxyphenylethylamine and 5‐Hydroxytryptamine Metabolism in the Rat: Acidic Metabolites in Cisternal Cerebrospinal Fluid Before and After Giving Probenecid
Authors: Curzon G. , Hutson P. H. , Kantamaneni B. D. , Sahakian B. J. , Sarna G. S.
Published: October 2006

Abstract: 3,4‐Dihydroxyphenylethylamine (DA, dopamine) and 5‐hydroxytryptamine (5‐HT) turnover values were determined in freely moving male rats by measuring the rates of accumulation of the acidic metabolites of the above transmitters, i.e., 3,4‐dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5‐hydroxyindoleacetic acid (5‐HIAA) in cisternal cerebrospinal fluid (CSF) samples after probenecid (200 mg/kg i.p.) administration. Determinations on samples before and after acid hydrolysis showed that the latter procedure was necessary for DA turnover determination. Thus whereas total (DOPAC + HVA) increased linearly with time after probenecid, free (DOPAC + HVA) did not. This was because the percentage of DOPAC + HVA in conjugated form increased with time. Determinations on a group of 28 rats during the dark (red light) period showed that cisternal amine metabolite concentrations before probenecid injection did not parallel turnover values. This was probably because individual differences in metabolite egress strongly affect the pre‐probenecid values. The poor correlations between CSF tryptophan and 5‐HT turnover suggested that differences of brain tryptophan concentration were not major determinants of differences of brain 5‐HT metabolism within this group of normal rats. Considering that the rats were of similar weight and that the turnover values were all determined at approximately the same time of day, the three‐ to fourfold ranges of the turnover values are remarkable. The positive correlation between the DA and 5‐HT turnovers of individual rats suggests the existence of common effects on DA and 5‐HT turnover in normal rats.
Reconstituted P2/Myelin‐Lipid Multilayers
Authors: Sedzik J. , Blaurock A. E. , Hoechli M.
Published: October 2006

Abstract: A complex forms when bovine P2 protein is added to single‐bilayer vesicles created by sonicating myelin lipids. The complex was studied by biochemical analysis, freeze‐fracture (FF) and thin‐section electron microscopy (EM), and by X‐ray diffraction. Smaller amounts of P2 cause the vesicles to aggregate and fuse whereas larger amounts (4 wt%) cause multilayers to form. Binding saturates at 15 wt% P2. FF EM shows that large, flat multilayers form within 15 min of addition of P2. Only smooth fracture faces are seen, as expected for a peripheral membrane protein. X‐ray diffraction shows a constant repeating distance in the multilayers: 86.0 ± 0.7 Å between the centers of bilayers in the range 4 wt% P2/(P2 + lipid) 15 wt%. Assuming a 53 Å‐thick bilayer, the space between bilayers is 33 Å wide. This is a wider space than for myelin basic protein (MBP) (20–25 Å wide). The respective widths are consistent with a compact, globular structure for P2 and a flattened shape for MBP. Calculated electron‐density profiles of the lipids with and without P2 reveal the protein largely in the interbilayer spaces, with a small part possibly inserted into the lipid headgroup layers. The different proportions of P2 in the sciatic nerve of various species are tentatively correlated with the different average widths observed by X‐ray diffraction for the cytoplasmic space (major period line) between bilayers in the respective sciatic myelins.
Axoplasmic Transport and Turnaround of Neurotoxic Esterase in Hen Sciatic Nerve
Authors: Carrington Clark D. , Abou‐Donia Mohamed B.
Published: October 2006

Abstract: We have recently found that there is a proximo‐distal delay in the recovery of neurotoxic esterase (NTE) following inhibition along the sciatic nerve of the hen. To determine whether this delay could be due to a requirement for the transport of newly synthesized NTE from the cell body, we investigated the transport of NTE by measuring the rate of accumulation of activity at either one or two ligations. Although rapid turnaround of accumulated protein confounds calculation of the transport rate, it appeared that NTE is transported down the hen sciatic nerve at a rate close to 300 mm/day. Acetylcholinesterase (AChE) was found to be transported at a rate of about 500 mm/day, which is close to the expected rate of fast axoplasmic transport in the chicken. The relatively rapid turnaround of NTE compared with the retrograde transport rate precluded the estimation of a retrograde transport rate. A model is presented that accounts for turnaround as a result of exchange between mobile and stationary transport pools. Exchange of NTE between pools may account for the rapid turnaround of NTE described in this paper and for the proximo‐distal delay in recovery as a dilution of newly synthesized NTE in the anterograde fast transport pool by inhibited protein as it travels down the nerve.
Cellular Origin of Ischemia‐Induced Glutamate Release from Brain Tissue In Vivo and In Vitro
Authors: Drejer Jørgen , Benveniste Helene , Diemer Nils H. , Schousboe Arne
Published: October 2006

Abstract: The uptake and release of d‐[3H]aspartate (used as a tracer for endogenous glutamate and aspartate) were studied in cultured glutamatergic neurons (cere‐bellar granule cells) and astrocytes at normal (5 mM) or high (55 mM) potassium and under conditions of hypo‐glycemia, anoxia or “ischemia” (combined hypoglycemia and anoxia). In glutamatergic neurons it was found that “ischemic” conditions led to a 2.4‐fold increase in the potassium‐induced release of d‐[3H]aspartate as compared to normal conditions. Hypoglycemia or anoxia alone affected the release only marginally. The ischemia‐induced increase in the evoked d‐[3H]aspartate release was shown to be calcium‐dependent. In astrocytes no difference was found in the potassium‐induced release between the four conditions and the K+‐induced release was not calcium‐dependent. The uptake of d‐[3H]‐aspartate was found to be stimulated at high potassium in both glutamatergic neurons (98%) and in astrocytes (70%). This stimulation of d‐aspartate uptake, however, was significantly reduced under conditions of anoxia or “ischemia” in both cell types. In glutamatergic neurons (but not in astrocytes) hypoglycemia also decreased the potassium stimulation of d‐aspartate uptake. In a previous report it was shown, using the microdialysis technique, that during transient cerebral ischemia in vivo the extracellular glutamate content in hippocampus was increased eightfold. In the present paper it is shown that essentially no increase in extracellular glutamate is seen under ischemia when the perfusion is performed using calcium‐free, cobalt‐containing perfusion media. The results from the in vitro and in vivo experiments indicate that the glutamate accumulated extracellularly under ischemia in vivo originates from transmitter pools in glutamatergic neurons. Moreover, the released glutamate cannot be efficiently disposed of due to a lack of activation by potassium of the high‐affinity glutamate uptake system in neurons and astrocytes under ischemic conditions.
Effects of Taurine on Calcium Ion Uptake and Protein Phosphorylation in Rat Retinal Membrane Preparations
Authors: Lombardini J. B.
Published: October 2006

Abstract: The effects of taurine on ATP‐dependent calcium ion uptake and protein phosphorylation of rat retinal membrane preparations were investigated. Taurine (20 mM) stimulates ATP‐dependent calcium ion uptake by twofold in crude retinal homogenates. In contrast, it inhibits the phosphorylation of specific membrane proteins as shown by acrylamide gel electrophoresis and autoradiography. The close structural analogue of taurine, 2‐aminoethylhydrogen sulfate, demonstrates similar effects in both systems, i.e., stimulation of ATP‐dependent calcium ion uptake and inhibition of protein phosphorylation, whereas isethionic acid and guanidinoethanesulfonate have no effect on either system. A P1 subcellular fraction of the retinal membrane preparation that contains photoreceptor cell synaptosomes has a higher specific activity for the uptake of calcium ions. Phosphorylation of specific proteins in the P1 fraction is also inhibited by the addition of 20 mM taurine. Taurine has no effect on retinal ATPase activities or on phosphatase activity, thus suggesting that it directly affects a kinase system.
Effect of Iron Chelators on Dopamine D2 Receptors
Authors: Ben‐Shachar Dorit , Finberg J. P. M. , Youdim Moussa B. H.
Published: October 2006

Abstract: Nutritional iron deficiency induced in rats causes a selective reduction of [3H]spiperone binding in caudate nucleus. This effect can be reversed by iron supplementation in vivo. The possibility that iron may be involved in the dopamine D2 receptor was investigated by examining the effect of various iron and noniron chelators on the binding of [3H]spiperone in rat caudate nucleus. Iron chelators 1, 10‐phenanthroline, 2,4,6‐tripyridyl‐s‐triazine, α,α′‐dipyridyl, and desferrioxamine mesylate inhibited the binding of [3H]spiperone. The inhibition by 1,10‐phenanthroline was noncompetitive and reversible. In the presence of FeCl2 or FeCl3, the inhibitory effect of 1,10‐phenanthroline was potentiated. Iron salts or chelators were without effect on the binding of [3H]dihydroalprenolol to β‐adrenoreceptors in caudate nucleus; thus the action of iron chelators on the dopamine D2 receptor tends to be selective. Incubation of caudate nucleus membrane prepared from iron‐deficient rats with FeCl2 or FeCl3 did not reverse the diminished binding of [3H]spiperone. The present study indicates that if iron is involved in the physiological regulation of dopamine D2 agonist‐antagonist binding sites, it is more complex than hitherto considered.
Cholinergic‐ and Adrenergic‐Stimulated Inositide Hydrolysis in Brain: Interaction, Regional Distribution, and Coupling Mechanisms
Authors: Gonzales Rueben A. , Crews Fulton T.
Published: October 2006

Abstract: Carbachol and norepinephrine were used as agonists to compare and contrast cholinergic and adrenergic stimulation of inositide breakdown in rat brain slices. Carbachol acts through a muscarinic (possibly M1) receptor and norepinephrine acts through an α1 adrenoceptor. Studies in cerebral cortical slices indicated that both agonists stimulated the production of inositol‐1‐ phosphate and glycerophosphoinositol. Although the initial rates for the stimulation of inositol phosphate release were similar for the two ligands, the response to norepinephrine continued for 60 min and was larger compared with carbachol which plateaued at 30 min. The presence of carbachol did not affect the ED50 for norepinephrine. Concentrations of carbachol near the ED50 in combination with norepinephrine resulted in an additive response whereas maximal concentrations of carbachol and norepinephrine resulted in a less than additive response in the cortex. This negative interaction was also seen in the hippocampus and hypothalamus but not in the striatum, brainstem, spinal cord, olfactory bulb, or cerebellum. Norepinephrine had a larger response than carbachol in the hippocampus, striatum, and spinal cord, but the reverse was true in the olfactory bulb. Manganese (1 mM) stimulated the incorporation of [3H]inositol into phosphatidylinositol (PtdIns) four‐ to fivefold but not into polyphosphoinositides. The stimulation by manganese of PtDIns labelling increased the monstimulated release of inositol phosphates but did not affect the stimulated release of inositol phosphates by carbachol or norepineph rine. These data suggest that: (a) there may be a common pool of inositides that can be hydrolyzed by cholinergic and/or adrenergic agonists in certain brain areas; (b) manganese may stimulate the labelling of a pool of PtdIns that does not interact with the receptor‐coupled pool of inositides; and (c) there may be differences in the basic mechanisms coupling receptor occupation and inositide breakdown for cholinergic and adrenergic receptors.
Distribution of Glucose‐ 1,6‐Bisphosphate and IMP‐Activated Glucose Bisphosphatase in Brain and Retina
Authors: Yip Vera , Carter Joyce G. , Dick Evan , Rose Zelda B. , Lowry Oliver H.
Published: October 2006

The activity of glucose‐1,6‐bisphosphatase and the level of its substrate were measured in 16 gray areas and four fiber areas of mouse brain and 10 layers or sublayers of monkey retina. Because of the low activity of the enzyme and the small sample sizes, it was necessary to develop a method with two different amplification steps (overall amplification about 106). The enzyme ranged in activity 100‐fold from a low in monkey retina photoreceptor cells to a high in the pyramidal layer of the hippocampus. However, in gray areas of the brain proper the range was only about fourfold. This, together with its requirement for IMP, suggests that the enzyme has a widespread metabolic function related to states of increased neuronal activity. Glucose‐1,6‐bisphosphate levels varied from 80 to 960 μmol/kg dry weight in different areas of mouse brain and from 44 to 200 μmol/kg dry weight in different layers of monkey retina. In general, the glucose bisphosphate levels correlated positively with the bisphosphatase activities; however, the three areas with the highest enzyme concentrations did not fit this pattern.
m‐Octopamine: Normal Occurrence with p‐Octopamine in Mammalian Sympathetic Nerves
Authors: Ibrahim K. E. , Couch M. W. , Williams C. M. , Fregly M. J. , Midgley J. M.
Published: October 2006

The development of a radiochemical enzyme assay for p‐octopamine in 1969 led to its identification in a large number of invertebrate nerve systems and in mammalian sympathetic nerves. The original method by which p‐octopamine was measured has now been found to be nonspecific; however, modifications of this procedure can determine both m‐ and p‐octopamine. We recently developed a new specific method for the unequivocal identification and quantitative determination in tissue of the six octopamine and synephrine isomers. With this method—negative chemical ionization gas chromatography‐mass spectrometry—the more physiologically active m‐octopamine has been found in association with p‐octopamine in 10 organs of the rat. m‐Octopamine is present in concentrations equal to those of p‐octopamine in heart, spleen, and liver and in concentrations from 30 to 60% of p‐octopamine in adrenals, vas deferens, brain, kidney, large intestine, bladder, and lungs. In vivo inhibition of monoamine oxidase markedly increased the concentrations of both m‐ and p‐octopamine in all organs examined. Both amines were virtually absent from all organs except the adrenals following chemical sympathectomy with 6‐hydroxydopamine, thereby establishing that m‐ and p‐octopamine are localized within sympathetic nerve endings.
Thyrotropin‐Releasing Hormone Receptor Binding Sites: Autoradiographic Distribution in the Rat and Guinea Pig Brain
Authors: Pazos Angel , Cortés Roser , Palacios José M.
Published: October 2006

Abstract: Thyrotropin‐releasing hormone (TRH) binding sites were labeled in vitro in mounted brain tissue sections from rat and guinea pig brains with [3H]methyl TRH and localized autoradiographically using 3H‐sensitive film. Regional densities of TRH binding sites were measured by computer‐assisted microdensitometry. The distribution of sites in both species was highly heterogeneous. In both guinea pig and rat brains, the highest densities of binding sites were seen in the amygdaloid nuclei and the perirhinal cortex. In contrast, in other brain areas, a clear difference between the distribution of sites in rat and guinea pig was found. The temporal cortex, pontine nuclei, and interpeduncular nucleus, which contained high densities of binding in the guinea pig, were scarcely labeled in the rat. The accessory olfactory bulb and the septohippocampal area presented in the rat higher concentrations of binding sites than in the guinea pig. Other brain areas showing intermediate to low densities in both species were accumbens nucleus, bed nucleus of the stria terminalis, dentate gyrus, facial and hypoglossal nuclei, and gelatinosus subnucleus of the trigeminal nerve, among others. The anterior pituitary also presented low to intermediate concentrations of receptors. The distribution of TRH sites here described does not completely correlate with that of endogenous TRH, but is in good agreement with previous biochemical data. The results are discussed in correlation to the physiological effects that appear to be mediated by TRH.
Human Phenol Sulfotransferase: Correlation of Brain and Platelet Activities
Authors: Young William F. , Laws Edward R. , Sharbrough Frank W. , Weinshilboum Richard M.
Published: October 2006

Abstract: Phenol sulfotransferase (PST; EC 2.8.2.1) catalyzes the sulfate conjugation of phenolic and catechol neurotransmitters and drugs. The human blood platelet has been the most thoroughly studied source of PST because of the possibility that the regulation of the enzyme in this easily accessible tissue might reflect the regulation of PST in the CNS. The human brain and platelet contain at least two forms of PST, forms designated as thermostable (TS) and thermolabile (TL) PST. TS PST catalyzes the sulfate conjugation of micromolar concentrations of phenol and p‐nitrophenol and TL PST catalyzes the sulfate conjugation of dopamine and other monoamines. This study was performed to determine whether individual variations in the activities of human platelet TS and TL PST reflect individual variations in cerebral cortical PST activities. PST activities were measured in platelets and in cerebral cortical tissue obtained from 15 patients with epilepsy during clinically indicated neurosurgery. There was a highly significant correlation between the activities of the TS form of PST in cerebral cortex and platelets of these patients (r = 0.940, p < 0.001), but there was not a significant correlation between activities of the TL form of PST in the two tissues (r = 0.396, p > 0.14). In addition to variations in the level of enzyme activity, there are also wide individual variations in the thermal stability of platelet TS PST. When the thermal stabilities of platelet and cerebral cortical TS PST were compared in these same patients, the slopes calculated from semilogarithmic plots of thermal inactivation data were strongly correlated for cerebral cortex and platelet samples (r = 0.9598, p < 0.001). Therefore, individual variations in both basal enzyme activity and the thermal stability of platelet TS PST activities directly reflect individual variations in cerebral cortical TS PST activities and thermal stability in patients with epilepsy who were undergoing neurosurgery.
Lipid Peroxidation‐Induced Inhibition of γ‐Aminobutyric Acid Uptake in Rat Brain Synaptosomes: Protection by Glucocorticoids
Authors: Braughler J. Mark
Published: October 2006

Abstract: Incubation of rat brain synaptosomes with xanthine and xanthine oxidase (X/XO) resulted in an inhibition of γ‐aminobutyric acid (GABA) uptake. The inhibitory effects of X/XO were temperature‐ and time‐dependent, and were characterized by an increased Km for GABA and a decresed Vmax. Inhibition of GABA uptake by X/XO was associated with both the formation of malonyldialdehyde (MDA) and conjugated dienes, indicating that lipid peroxidation was involved. Studies with catalase, superoxide dismutase (SOD), mannitol, and chelated iron suggested that hydroxyl radical (OH·) was probably responsible for the initiation of lipid peroxidation. Both the peroxidation of synaptosomal membranes and the inhibition of GABA uptake by X/XO were enhanced by the addition of ADP and FeCl2. The X/XO‐induced inhibition of GABA uptake by synaptosomes could be prevented by preincubation of synaptosomes with certain glucocorticoids prior to X/XO exposure. Methylprednisolone sodium succinate (MPSS), dexamethasone sodium phosphate (DMSP), and prednisolone sodium succinate (PSS) all prevented the inhibition of GABA uptake by X/XO. MPSS was most effective at concentrations around 100 μM, DMSP was slightly more potent, and PSS was optimal at around 300 μM. On the other hand, hydrocortisone sodium succinate (HCSS) was ineffective at preventing X/XO‐induced inhibition of GABA uptake at concentrations up to 3 mM. The steroids are presumed to work through a mechanism that blocked the formation of lipid peroxides, as MPSS inhibited the formation of conjugated dienes in synaptosomes exposed to X/XO at a concentration that also protected GABA uptake.
Characterization of Membrane‐Bound Aminopeptidases from Rat Brain: Identification of the Enkephalin‐Degrading Aminopeptidase
Authors: Hersh Louis B.
Published: October 2006

Abstract: Rat brain aminopeptidase activity was solubilized from membranes by incubation with thiols. This novel procedure resulted in the release of the same two aminopeptidases (MI and MII) previously shown to be solubilized by the nonionic detergent Triton X‐100. The solubilized aminopeptidases MI and MII were resolved by ion‐exchange chromatography and further purified by hydroxylapatite chromatography. Aminopeptidase MI was shown to hydrolyze only the β‐naphthylamides of arginine and lysine whereas aminopeptidase MII exhibited a broad specificity with respect to amino acid β‐naphthylamides. Only aminopeptidase MII hydrolyzed Leu‐enkephalin at a significant rate, indicating that this enzyme can account for the membrane‐bound enkephalin aminopeptidase activity. The enkephalin‐degrading aminopeptidase is potently inhibited by opioid (α‐neo‐endorphin and dynorphin) as well as nonopioid (substance P, somatostatin, and angiotensin I) peptides in the range of 0.2–2.0 μM The regional distribution of aminopeptidases MI and MII in rat brain are rather different, with aminopeptidase MII distribution more closely paralleling the distribution of opiate receptors.
Postischemic Cerebral Lipid Peroxidation In Vitro: Modification by Dietary Vitamin E
Authors: Yoshida Shinichi , Busto Raul , Watson Brant D. , Santiso Mercedes , Ginsberg Myron D.
Published: October 2006

Abstract: Using an in vitro system, we studied the effect of postischemic reoxygenation on cerebral lipid peroxidation in relation to the dietary intake of vitamin E (VE) in rats. Homogenates prepared from VE‐deficient, ‐normal, and ‐supplemented brains, which were previously rendered ischemic for 30 min by decapitation, were incubated under air or nitrogen gas for 60 min. The extent of peroxidation in brain tissue was estimated by a thiobarbituric acid (TBA) test and by diene conjugation in total lipid extracts. The brain levels of α‐tocopherol and of total and free fatty acids (FAs) were also determined. Aerobic incubation increased TBA reactants in all dietary groups; the effect was largest in the VE‐deficient group, intermediate in the VE‐normal group, and smallest in the VE‐supplemented group. In contrast, nitrogen incubation did not alter the basal levels of TBA reactants except for a small rise associated with VE deficiency. Conjugated dienes changed in parallel with TBA reactants. α‐Tocopherol decreased after aerobic incubation and also, to a lesser degree, after nitrogen incubation in each dietary group. Only in the reoxygenated samples of the VE‐deficient group was there a significant fall in total polyunsaturated FAs. The levels of free FAs continuously increased throughout ischemia and subsequent incubation. However, the level of free polyunsaturated FAs was similar after aerobic and nitrogen incubation in each dietary group, and was not affected by VE. Thus, cerebral reoxygenation after ischemia propagates peroxidative reactions within esterified polyunsaturated FAs. The modification by VE of reoxygenation‐induced lipid peroxidation suggests free radical mediation.
Ribosome Biogenesis and Nucleolar Ultrastructure in Neuronal and Oligodendroglial Rat Brain Cells
Authors: Stoykova A. S. , Dabeva M. D. , Dimova R. N. , Hadjiolov A. A.
Published: October 2006

Abstract: The absolute amounts of precursor to ribosomal RNA (pre‐rRNA) and ribosomal RNA (rRNA) in isolated rat brain neuronal and oligodendroglial nuclei were determined. The amount of the major pre‐rRNA and rRNA species in neuronal nuclei was about twofold higher than in oligodendroglial nuclei. The relative rate of pre‐rRNA synthesis in vivo was 2.3‐ to 2.7‐fold higher in neuronal as compared with oligodendroglial nuclei. This corresponds to a 2.7‐fold higher activity of the “template‐bound” RNA polymerase I in isolated neuronal nuclei, whereas the activity of the “free” enzyme in both neuronal and glial nuclei was almost identical. The higher transcription rates of rRNA genes correlated with the markedly more prominent fibrillar component in neuronal nucleoli. The turnover times of the major pre‐rRNA and rRNA species in neuronal and oligodendroglial nuclei were similar, except for 45S pre‐rRNA, which turned over at an 1.5‐fold slower rate in neuronal nuclei. The relative rates of processing of pre‐rRNA and of nucleocytoplasmic transport of rRNA in neuronal cells were 2.7‐fold higher than in oligodendroglial cells and corresponded to the differences in rRNA gene transcription rates. The established ribosome formation features correlated with an abundant (neurons) or exceedingly scarce (oligodendrocytes) nucleolar granular component. The turnover rate of cytoplasmic ribosomes in rat brain neurons was twofold slower than in oligodendrocytes, largely because of the about fivefold higher amount of ribosomes in the cytoplasm of neurons. We conclude that ribosome formation and turnover in neuronal and oligodendroglial cells are adapted to the protein synthetic levels in these two types of brain cells.
Dopaminergic Regulation of Cone Retinomotor Movement in Isolated Teleost Retinas: I. Induction of Cone Contraction Is Mediated by D2 Receptors
Authors: Dearry Allen , Burnside Beth
Published: October 2006

Abstract: In the retinas of lower vertebrates, retinal photoreceptors and melanin pigment granules of the retinal pigment epithelium (RPE) undergo characteristic movements in response to changes in light intensity and to signals from an endogenous circadian clock. To identify agents responsible for mediating light and/or circadian regulation of these retinomotor movements, we investigated the effects of hormones and neurotransmitters on cone, rod, and RPE movements in the green sunfish, Lepomis cyanellus. We report here that 3,4‐dihydroxyphenylethylamine (dopamine) mimics the effect of light by inducing light‐adaptive retinomotor movements in all three cell types. In isolated dark‐cultured retinas, dopamine induced light‐adaptive cone contraction with a halfmaximal effect at 10−8M. This effect of dopamine was inhibited by antagonists with a potency order characteristic of D2 receptor mediation. The dopamine uptake blocker benztropine also induced light‐adaptive cone contraction in isolated dark‐cultured retinas, suggesting that there is continuous dopamine release in the dark but that concomitant uptake normally prevents activation of cone contraction. That dopamine plays a role in light regulation of cone movement is further suggested by the observation that light‐induced cone contraction was partially inhibited by sulpiride, a selective D2 dopamine antagonist, or by Co2+, a blocker of synaptic transmission. Sulpiride also promoted dark‐adaptive cone elongation in isolated light adapted retinas, suggesting that continuous dopamine action is required in the light to maintain the light‐adapted cone position. Dopamine can act directly on D2 receptors located on rod and cone inner/outer segments: dopamine induced light‐adaptive retinomotor movements in isolated distal fragments of dark‐adapted photoreceptors cultured in the dark. Together our results indicate that dopamine induces light‐adaptive retinomotor movements in cones, rods, and RPE cells by activating D2 receptors. We suggest that, in vivo, dopamine plays a role in both light and circadian regulation of retinomotor movements.
Low Levels of γ‐Aminobutyric Acid in Cerebrospinal Fluid of Dogs with Epilepsy
Authors: Löscher Wolfgang , Schwartz‐Porsche Dorothea
Published: October 2006

Abstract: γ‐Aminobutyric acid (GABA) levels were determined in cisternal cerebrospinal fluid (CSF) of 19 epileptic dogs with generalized tonic‐clonic (grand mal) seizures using a radioreceptor assay. Thirty‐four healthy age‐matched dogs served as controls. The average CSF GABA level in epileptic dogs (40 pmol/ml) was significantly lower than that determined in controls (66 pmol/ml). Treatment with phenobarital or primidone seemed not to affect CSF GABA levels.
Brain α‐Ketoglutarate Dehydrogenase Complex: Kinetic Properties, Regional Distribution, and Effects of Inhibitors
Authors: Lai James C. K. , Cooper Arthur J. L.
Published: October 2006

Abstract The substrate and cofactor requirements and some kinetic properties of the α‐ketoglutarate dehydrogenase complex (KGDHC; EC 1.2.4.2, EC 2.3.1.61, and EC 1.6.4.3) in purified rat brain mitochondria were studied. Brain mitochondrial KGDHC showed absolute requirement for α‐ketoglutarate, CoA and NAD, and only partial requirement for added thiamine pyrophosphate, but no requirement for Mg2+ under the assay conditions employed in this study. The pH optimum was between 7.2 and 7.4, but, at pH values below 7.0 or above 7.8, KGDHC activity decreased markedly. KGDHC activity in various brain regions followed the rank order: cerebral cortex > cerebellum ≧ midbrain > striatum = hippocampus > hypothalamus > pons and medulla > olfactory bulb. Significant inhibition of brain mitochondrial KGDHC was noted at pathological concentrations of ammonia (0.2–2 mM). However, the purified bovine heart KGDHC and KGDHC activity in isolated rat heart mitochondria were much less sensitive to inhibition. At 5 mM both β‐methylene‐D,L‐aspartate and D,L‐vinylglycine (inhibitors of cerebral glucose oxidation) inhibited the purified heart but not the brain mitochondrial enzyme complex. At approximately 10 μM, calcium slightly stimulated (by 10–15%) the brain mitochondrial KGDHC.

At concentrations above 100 μM, calcium (IC50= 1 mM) inhibited both brain mitochondrial and purified heart KGDHC. The present results suggest that some of the kinetic properties of the rat brain mitochondrial KGDHC differ from those of the purified bovine heart and rat heart mitochondrial enzyme complexes. They also suggest that the inhibition of KGDHC by ammonia and the consequent effect on the citric acid cycle fluxes may be of pathophysiological and/or pathogenetic importance in hyperammonemia and in diseases (e.g., hepatic encephalopathy, inborn errors of urea metabolism, Reye's syndrome) where hyperammonemia is a consistent feature. Brain accumulation of calcium occurs in a number of pathological conditions. Therefore, it is possible that such a calcium accumulation may have a deleterious effect on KGDHC activity.
Lack of Change in Basal Ganglia Neuropeptide Content Following Subacute 1‐Methyl‐4‐Phenyl‐1,2,3,6‐Tetrahydropyridine Treatment of the Common Marmoset
Authors: Jenner P. , Taquet H. , Mauborgne A. , Benoliel J. T. , Cesselin F. , Rose S. , Javoy‐Agid F. , Agid Y. , Marsden C. D.
Published: October 2006

Abstract Treatment of common marmosets with 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine(MPTP; 1–4mg/kgfor up to 4 days) caused a profound parkinsonian state. Ten days from the start of MPTP treatment, all animals showed marked motor impairment, consisting of bradykinesia and akinesia, limb rigidity, postural abnormalities, loss of vocalisation and blink reflex, and, on occasions, postural tremor. Measurement of caudate‐putamen monoamine content at this time showed a profound loss in 3,4‐dihydroxyphenyl‐ethylamine, homovanillic acid, and 3,4‐dihydroxyphenylacetic acid concentrations. Measurement of neuropeptide concentrations in the caudate‐putamen, internal and external segments of the globus pallidus, nucleus accumbens, substantia nigra, frontal cortex, and hippocampus showed met‐enkephalin, leu‐enkephalin, and cholecystokinin (CCK‐8) concentrations to be unaffected by MPTP treatment. There was a small decrease in the substance P content of frontal cortex, but otherwise the content of this neuropeptide was unaltered. Parkinsonism in the marmoset, induced by MPTP treatment 10 days earlier, does not alter neuropeptide concentrations in the manner observed in Parkinson's disease.
Utilization of Plasma Fatty Acid in Rat Brain: Distribution of [14C]Palmitate Between Oxidative and Synthetic Pathways
Authors: Miller Joseph C. , Gnaedinger Jean M. , Rapoport Stanley I.
Published: October 2006

Abstract: Radioactivity within individual brain compartments was determined from 5 min to 44 h after intravenous injection of [14C]palmitate into awake Fischer‐344 rats, aged 21 days or 3 months. Total radioactivity peaked broadly between 15 min and 1 h after injection, declined rapidly between 1 and 2h, and then more slowly. In 3‐month‐old rats, the lipid and protein brain fractions were maximally labeled within 15 min after [14C]palmitate injection, then retained approximately constant label for up to 2 days. Radioactivity in the aqueous brain fraction comprised mainly radioactive glutamate and glutamine, and peaked at 45 min, when it comprised 48% of total brain radioactivity, then decreased to 27% of the total at 4h, 15% at 20h, and 10% at 44 h. Percent distribution of radioactivity within the different brain compartments, 4 h after intravenous injection of [14C]palmitate, was similar in 21‐day‐old and 3‐month‐old rats, despite higher net brain uptake in the younger animals. The results indicate that about 50% of plasma [14C]palmitate that enters the brain of adult rats is incorporated rapidly into stable protein and lipid compartments. The remaining [14C]palmitate enters the aqueous fraction after β‐oxidation, and is slowly lost. At 4 h after injection, 73% of brain radioactivity is within the stable brain compartments; this fraction increases to 86% by 20 h.
Regional Variation in the Levels of Transferrin in the CNS of Normal and Myelin‐Deficient Rats
Authors: Connor James R. , Phillips Terry M. , Lakshman M. R. , Barron Kevin D. , Fine Richard E. , Csiza Charles K.
Published: October 2006

Abstract: Transferrin (Tf), the iron mobilization protein, is synthesized mainly in the liver. Recently, both Tf and a mRNA for Tf have been demonstrated in oligodendrocylcs in the rat brain. The present study used a biochemical assay for determining the levels of Tf in various brain regions of normal rats compared with the level of those obtained from rats with a genetic mutation characterized by an almost complete failure to develop myelin. In myelin‐deficient (md) rats, no Tf‐positive oligodendrocytes were seen immunohistochemically in the gray or white matter of the CNS. Quantitatively, levels of Tf throughout the CNS of the md rat were decreased to ∼5% of the normal values despite a normal hepatic synthetic rate. In the normal rat brain, the cerebellum contained the highest concentration of Tf, followed by the pons, the cerebral cortex, and the caudate‐putamen, with the latter two sites being similar. Regional variation in the amount of Tf was in general agreement with published reports on the variation of iron and Tf receptor levels in the CNS. Immunohistochemical examination with antiserum to galactocerebroside (a myelin‐specific lipid) was used for extending biochemical reports that glycoiipid‐synthesizing enzymes are deficient in md rats. No immunostaining in the md rat was observed following immunoreaction for galactocerebroside, whereas white matter oligodendrocytes were intensely marked in the normal rat. Robust astrogliosis was present in both the gray and white matter of the md rats. It is not known at present whether the ábility to accumulate Tf is necessary for oligodendrocytic survival or if Tf accumulation is more directly related to myelinogenesis. The lack of Tf in the md rat suggests a critical role for oligodendrocytes in Tf accumulation and, consequently, iron regulation in the CNS.
Effects of Nucleus Basalis Lesions on the Muscarinic and Nicotinic Modulation of [3H] Acetylcholine Release in the Rat Cerebral Cortex
Authors: Meyer Edwin M. , W. Arendash Gary , Judkins Jennifer H. , Ying Lily , Wade Cathy , Ken William R.
Published: October 2006

Presynaptic muscarinic and nicotinic receptors in the cerebral cortex reportedly inhibit and increase acetyl‐choline (ACh) release, respectively. In this study, we investigated whether these receptors reside on cholinergic nerve terminals projecting to the cerebral cortex from the nucleus basalis magnocellularis (nbm). Adult male rats received unilateral infusions of ibotenic acid (5 μg/1 μl) in the nbm. Two weeks later, cerebral cortical cholinergic markers (choline acetyltransferase activity, high‐affinity choline uptake, and coupled ACh synthesis) were significantly reduced in synaptosomes prepared from the lesioned hemispheres compared to contralateral controls. The depolarization‐induced release of [3H]ACh from these synaptosomes was also reduced in the lesioned hemispheres, reflecting the reduced synthesis of transmitter. However, the nbm lesions had no effect on the inhibition of release induced by 100 μM oxotremorine. Synaptosomal [3H]ACh release was not altered by nicotine or the nicotinic agonists anabaseine and 2‐(3‐pyridyl)‐l, 4, 5, 6‐tetrahydropyrimdine. Nicotine (10–100 μM) did increase [3H]ACh release in control and lesioned hemispheres in cortical minces, but to a similar extent. These results suggest that neither muscarinic nor nicotinic receptors modulating ACh release reside on nbm‐cholinergic terminals.
Large Alterations in Ganglioside and Neutral Glycosphingolipid Patterns in Brains from Cases with Infantile Neuronal Ceroid Lipofuscinosis/Polyunsaturated Fatty Acid Lipidosis
Authors: Svennerholm Lars , Fredman Pam , Jungbjer Birgitta , Månsson Jan‐Eric , Rynmark Britt‐Marie , Boström Kerstin , Hagberg Bengt , Norén Lars , Santavuori Pirkko
Published: October 2006

Lipid composition was studied on cerebral tissue from nine children who had died of a progressive encepha‐lopathy called the infantile form of neuronal ceroid lipofus‐cinosis (INCL) or polyunsaturated fatty acid lipidosis (PFAL). In the terminal stage of the disease, the concentrations of all lipid classes were found to be significantly reduced in the cerebral and cerebellar cortex and white matter. The concentration of gangliosides of the cerebral cortex was 15% and that of cerebrosides (galactosylceramide) in white matter 0.2–5% of the normal values for the children's ages. The reduction of gangliosides mainly affected those of the gangliotetraose series, particularly GDI a. The fatty acids of the linolenic acid series were strongly reduced in ethanolamine and serine phosphoglycerides. A very large increase up to 100‐fold of oligoglycosphingolipids of the globo series and two fucose‐containing lipids of the neo‐lacto series was found in the forebrain of the three advanced cases examined. The brain tissue also contained very high concentrations of mono‐, d ‐, and trisialogangliosides of the lacto and neolacto series, gangliosides with type 1 chain, dominating. The structures of the gangliosides were tentatively identified by gas chromatography‐mass spectrometry and monoclonal antibodies with carefully determined epitope specificity. The gangliosides and neutral glycosphingolipids had very similar fatty acid composition, consisting of about 40% stearic acid and 40% C24‐acids.
Polyamine Changes in Reversible Cerebral Ischemia
Authors: Paschen W. , Schmidt‐Kastner R. , Djuricic B. , Meese C. , Linn F. , Hossmann K.‐A.
Published: October 2006

Abstract: Putrescine, spermidine, and spermine levels were measured in the cortex, caudoputamen, and hippocampus of rats during 30 min of severe forebrain ischemia (induced by occlusion of both carotid and vertebral arteries) and subsequent recirculation. During ischemia, polyamine levels did not change significantly. During postischemic recirculation, however, putrescine levels dramatically increased whereas those of spermine and spermidine did not change, with the exception of the severely damaged caudoputamen, where the concentration declined after 24 h. The increase of putrescine is explained by postischemic activation of ornithine decarboxylase and inhibition of S‐adenosylmethionine decarboxylase. It is suggested that the accumulation of putrescine during postischemic recirculation may be responsible for the delayed neuronal death occurring after ischemia.
Brain Metabolism and Intracellular pH During Ischaemia and Hypoxia: An In Vivo 31P and 1H Nuclear Magnetic Resonance Study in the Lamb
Authors: Hope P. L. , Cady E. B. , Chu A. , Delpy D. T. , Gardiner R. M. , Reynolds E. O. R.
Published: October 2006

Abstract: Brain metabolism and intracellular pH were studied during and after episodes of ischaemia and hypoxia‐ischaemia in lambs anaesthetised with sodium pentobarbitone. 31P and 1H magnetic resonance spectroscopy methods were used to monitor brain pHi and brain concentrations of Pi, phosphocreatine (PCr), β‐nucleoside triphosphate (βNTP), and lactate. Simultaneous measurements were made of cerebral blood flow and cerebral oxygen and glucose consumption. Cerebral ischaemia sufficient to reduce oxygen delivery to 75% of control values was associated with a fall in brain pHi and increase in brain Pi. Progressively severe hypoxia‐ischaemia was associated with a progressive fall in brain pHi, PCr, and βNTP and increase in brain pi In two animals the increase in brain lactate during hypoxia‐ischaemia measured by 1H nuclear magnetic resonance (NMR) could be quantitatively accounted for by the increased net uptake of glucose by the brain in relation to oxygen, but was insufficient to account for the concomitant aci‐dosis according to previous estimates of brain buffering capacity. In four animals brain pHi, PCr, pi, and βNTP had returned to normal 1 h after the hypoxic‐ischaemic episode. In one animal brain pHi had reverted to normal at a time when 1H NMR indicated persistent elevation of brain lactate.
Biotin Transport Through the Blood‐Brain Barrier
Authors: Spector Reynold , Mock Donald
Published: October 2006

Abstract: The unidirectional influx of biotin across cerebral capillaries, the anatomical locus of the blood‐brain barrier, was measured with an in situ rat brain perfusion technique employing [3H]biotin. Biotin was transported across the blood‐brain barrier by a saturable system with a one‐half saturation concentration of ∼ 100 μM. The permeability‐surface area products were 10−4 s−1 with a biotin concentration of 0.02 μM in the perfusate. Probenecid, pantothenic acid, and nonanoic acid but not biocytin or biotin methyles‐ter (all 250μM) inhibited biotin transfer through the blood‐brain barrier. The isolated rabbit choroid plexus was unable to concentrate [3H]biotin from medium containing 1 nM [3H]biotin. These observations provide evidence that: (1) biotin is transported through the blood‐brain barrier by a saturable transport system that depends on a free carboxylic acid group, and (2) the choroid plexus is probably not involved in the transfer of biotin between blood and cerebro‐spinal fluid.