bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cerebral Blood Flow and Metabolism During Hypoglycemia in Newborn Dogs
Authors: Hernández Milton J. , Vannucci Robert C. , Salcedo Alberto , Brennan Robert W. 
Published: October 2006

Abstract: Cerebral blood flow (CBF) and cerebral metabolic rates (CMR) were studied in newborn dogs during insulin‐induced hypoglycemia. Pups were anesthetized, paralyzed, and artificially ventilated with a mixture of 70% nitrous oxide and 30% oxygen to maintain normoxia and normocarbia. Experimental animals were given regular insulin (0.3 units/gm IV); controls received normal saline. CBF was determined using a modification of the Kety‐Schmidt technique employing 133Xe as indicator. Arteriovenous differences for oxygen, glucose, lactate, and β‐hydroxybutyrate (β‐OHB) were also measured, and CMRo2 and CMRsubstrates calculated. Two groups of hypoglycemic dogs were identified; those in which blood glucose levels were greater than 0.5 mm (group 1), and those in which they were less than 0.5 mm (group 2). CBF did not change significantly from control values of 23 ± 10 ml/min/100 g (mean ±s.d.) at both levels of hypoglycemia. Similarly, hypoglycemia did not alter CMRo2, significantly from its initial level of 1.05 ± 0.37 ml O2/min/100 g. Glucose consumption in brain during normoglycemia accounted for 95% of cerebral energy supply with minimal contributions from lactate (4%) and β‐OHB (0.5%). During hypoglycemia, CMRglucose. declined by 29 and 52% in groups 1 and 2, respectively, while CMR,lactate increased to the extent that this metabolite became the dominant fuel for oxidative metabolism in brain. The cerebral utilization of β‐OHB was unaltered by hypoglycemia. The findings indicate that insulin‐induced hypoglycemia in the newborn dog is associated with an increase in cerebral lactate utilization, supplementing glucose as the primary energy fuel and thereby preserving a normal CMRo2. These metabolic responses may contribute to the tolerance of the immature nervous system to the known deleterious effects of hypoglycemia.
Distribution of GABA Receptors in the Rat Cerebellum
Authors: Kingsbury A. E. , Wilkin G. P. , Patel A. J. , Balázs R. 
Published: October 2006

Abstract: The distribution of GABA receptors in the cerebellum is not homogeneous. In comparison with detergent‐treated membranes from the whole tissue the number of [3H]muscimol binding sites per mg protein (Bmax) is about doubled in preparations enriched in large fragments of the cerebellar glomeruli, and it is about one‐third in the dissected deep nuclei. On the other hand, the apparent affinity (Kd) is similar in the different preparations. Comparison of the results with earlier studies suggests a heterogeneity in cerebellar GABA receptors and/or their control.
The Utilization of Choline and Acetyl Coenzyme A for the Synthesis of Acetylcholine
Authors: Jope Richard S. , Jenden Donald J. 
Published: October 2006

AbstractAcetylcholine synthesis in rat brain synaptosomes was investigated with regard to the intracellular sources of its two precursors, acetyl coenzyme A and choline. Investigations with α‐cyano‐4‐hydroxycinnamate, an inhibitor of mitochondrial pyruvate transport, indicated that pyruvate must be utilized by pyruvate dehydrogenase located in the mitochondria, rather than in the cytoplasm, as recently proposed. Evidence for a small, intracellular pool of choline available for acetylcholine synthesis was obtained under three experimental conditions. (1) Bromopyruvate competitively inhibited high‐affinity choline transport, perhaps because of accumulation of intracellular choline which was not acetylated when acetyl coenzyme A production was blocked. (2) Choline that was accumulated under high‐affinity transport conditions while acetyl coenzyme A production was impaired was subsequently acetylated when acetyl coenzyme A production was resumed. (3) Newly synthesized acetylcholine had a lower specific activity than that of choline in the medium. These results indicate that the acetyl coenzyme A that is used for the synthesis of acetylcholine is derived from mitochondrial pyruvate dehydrogenase and that there is a small pool of choline within cholinergic nerve endings available for acetylcholine synthesis, supporting the proposal that the high‐affinity transport and acetylation of choline are kinetically coupled.
Suppressive Effect of Triethyllead on Entry of Proteins into the CNS Myelin Sheath In Vitro
Authors: Konat G. , Clausen J. 
Published: October 2006

AbstractIncorporation of [14C]leucine into the myelin sheath was studied in brain stem slices prepared from 22‐day‐old rats. Individual major myelin proteins were separated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. There was a time lag before incorporation of the label into proteolipid protein (PLP) and intermediate protein (IP) reached maximal rates. Labelling of basic proteins (BP) and Wolfgram proteins (WP) revealed a much shorter lag in entry. Appearance of radioactive proteins in the myelin sheath was significantly hampered by triethyllead (PbEt3) added to the incubation medium at micromolar concentrations. Inhibition values were highest in the case of PLP and were closely followed by the values for IP. BP and WP were less inhibited, although incorporation of these proteins into myelin was still suppressed more than was synthesis of total homogenate protein. Thus, myelin‐forming cells seem to be unduly vulnerable to the toxin relative to the rest of the tissue. Furthermore, the results indicate an interference of PbEt3 with certain posttranslational processes involved in furnishing of integral myelin proteins.
Bovine P2 Protein: Sequence at the NH2‐Terminal of the Protein
Authors: Weise Michael J. , Hsieh Diane L. , Levit Shimon , Brostoff Steven W. 
Published: October 2006

AbstractSequence data from key fragments of the P2 protein established the order of cyanogen bromide (CNBr) peptides in the structure of the protein and the primary structure for approximately one‐half of the molecule. Data were obtained from the three tryptic peptides of blocked NH2‐terminal CNBr peptide (CN3), the large CNBr peptide of P, protein (CN1), and a fragment obtained from P2 by cleavage at tryptophan with 2‐(2‐nitrophenylsulfenyl)‐3‐methyl‐3′‐bromoindolenine. This last fragment was found to contain an overlapping sequence that proved the juxtaposition of CN 1 and CN3 in P2 protein. Thus, based on this fact and the characteristics of the CNBr peptides, the P2 structure is composed of CNBr peptides in the order: CN3‐CN1‐CN2(Va1)‐CN2(Lys). A comparison was made between the partial sequence of P2 protein and the equivalent portion of the structure of bovine myelin basic protein. The structures of these two proteins were found to be distinctly different although certain similarities are found.
l‐Histidine Decarboxylase in the Human Brain: Properties and Localization
Authors: Barbin G. , Palacios J. M. , Garbarg M. , Schwartz J. C. , Gaspar P. , Javoy‐Agid F. , Agid Y. 
Published: October 2006

AbstractThe properties of the histamine‐forming enzyme in human brain samples were studied utilizing a radiochromatographic procedure. The influence of postmortem conditions was checked with rat brains, and the results indicated that the enzyme activity is not altered in situ for a delay not exceeding 4 h at ambient temperature. Moreover, tissue blocks or homogenates can be stored at low temperatures for up to 3 months with a good preservation of the enzyme activity. The data indicate that histamine synthesis in the human brain involves the „specific” histidine decarboxylase (HD, EC 4.1.1.22) and not the aromatic l‐amino acid decarboxylase; (1) the optimum pH is 7.4 at 10‐6m‐l‐histidine; (2) the apparent Km is about 3.10‐5m; (3) it is inhibited by α‐hydrazino histidine and brocresine but not affected by α‐methyl DOPA. Moreover, a major portion of the enzyme is localized in a subcellular fraction containing nerve terminals and it shows an uneven regional distribution which parallels that observed in the brain of other mammalian species. Taken together these data strongly suggest that histamine could play a neurotransmitter role in the human brain.
Brain Cyclic Nucleotide Responses to Anesthesia With Halothane Delivered in Air or Purified Oxygen
Authors: Divakaran P. , Rigor B. M. , Wiggins R. C. 
Published: October 2006

AbstractInhalation of either 0.5% or 1.0% halothane in air caused a slight decrease in the cAMP concentration in rat cerebral cortex and cerebellum. During recovery, concentrations returned to normal in 3 h, or less. In contrast, cGMP decreased sixfold in cerebellum, but increased twofold in cortex. Recovery time for cerebellum was several hours. When oxygen was used as the carrier gas for halothane delivery, cAMP in the cortex doubled, in striking contrast to the case with halothane in air. Oxygen alone had no apparent effect. The cGMP effect of halothane delivered in oxygen appeared the same as for halothane in air. Thus, the cAMP effects of brain halothane are related to the enrichment of oxygen.
Turnover of Molecular Species of Sphingomyelin in Microsomes and Myelin of Rat Brain
Authors: Freysz L. , Mandel P. 
Published: October 2006

Abstract:The metabolism of sphingomyelins containing short‐chain fatty acids (C18:sphingomyelin) and those containing long‐chain fatty acids (C24:sphingomyelin) in microsomes and myelin from rat brain were studied for periods from 1 to 60 days after intracisternal injection of [32P]Na2HPO4. In microsomes the half‐lives of both molecular species of sphingomyelin were 14 days. In myelin the half‐life of C18:sphingomyelins was 69 days, whereas C24: sphingomyelins exhibit a high degree of metabolic stability. The results suggest that in myelin the sphingomyelins containing short‐chain fatty acids may be located in the inner leaflet of the bilayer and those containing long‐chain fatty acids may be located in the outer leaflet.
3H‐Saxitoxin Binding to Nerve Membranes: Inhibition by Phospholipase A2 and by Unsaturated Fatty Acids
Authors: Baumgold Jesse 
Published: October 2006

Abstract:The mechanism by which phospholipase A2 (EC 3.1.1.4) inhibits the binding of 3H‐saxitoxin (STX) to membranes from lobster walking‐leg nerves was examined. It was concluded that this inhibition of the binding was due to the accumulation of unsaturated fatty acids and lysophosphatides, products of the lipase action, in the 3H‐STX binding site. The destruction of the lipids themselves did not appear to cause the loss of the binding. The following evidence was presented in support of these conclusions. (1) Among the phospholipases tested, phospholipase A2 was the most effective in inhibiting the binding. Phospholipase A2 is also the only lipase that produces fatty acids and lysophosphatides. (2) The addition of fatty acid‐free bovine serum albumin protected the 3H‐STX binding sites from the inhibitory action of phospholipase A2; fatty‐acid‐free bovine serum albumin is capable of binding free fatty acids and lysophosphatides, thus preventing these products from interacting with the STX binding sites. (3) The addition of exogenous unsaturated fatty acids or lysophosphatides to membrane material inhibited the binding. These findings show that the STX binding activity is sensitive to unsaturated fatty acids and to lysophosphatides.
Analysis of Messenger RNA Coding for S100 Protein in the Mammalian Brain
Authors: Mahony James B. , Brown Ian R. 
Published: October 2006

Abstract:S100 protein is a brain‐specific protein which is absent at birth and first appears in rabbit brain 2–3 days after birth. To determine how the synthesis of this brain‐specific protein is regulated, mRNA was isolated from brain polysomes and assayed for S100 protein mRNA activity by in vitro translation in a heterologous cell‐free system and immunoprecipitation of released polypeptides with rabbit anti‐S I00 protein antiserum. 5100 protein mRNA was detected primarily in small polysomes containing five to eight ribosomes, and virtually no S 100 protein mRNA was present in polysomes containing more than eight ribosomes. S100 protein mRNA was not detected in brain polysomes at stages prior to the induction of synthesis of S100 protein, i.e., in fetal brain or in 1‐day neonates. The amount of S100 protein mRNA in polysomes of the cerebral cortex and cerebellum was measured to see if it correlated with the level of S100 protein in the two regions of adult brain. The cerebellum, which contained three to four times the level of S100 protein in the cerebral cortex, contained four times more S100 protein mRNA.
Comparison of 2′,3′‐Cyclic Nucleotide 3′‐Phosphodiesterase and the Major Component of Wolfgram Protein W1
Authors: Drummond Robert J. , Dean Grace 
Published: October 2006

Abstract:Wolfgram protein preparations from myelin are heterogeneous mixtures having major components with molecular weights in the 43,000 to 60,000 range. Through the use of an SDS‐slab gel electrophoretic system of high resolving power, the Wolfgram 1 (W1) component described by Nussbaum et al. (1977) has been resolved into two components; bovine Wla and Wlb proteins are found to have mobilities identical to those of the two 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase (2′,3′‐CN 3′‐ase) components, CNa and CNb (Drummond, 1979). Crossed immunoelectrophoresis with bovine 2′,3′‐CN 3′‐ase demonstrates that CNa and CNb are antigenically indistinguishable. Rat and bovine Wolfgram proteins Wla and Wlb, but not the W2 proteins, display cross reactivity with antiserum directed against bovine 2′,3′‐CN 3′‐ase. Chymotryptic and Staphylococcus aureus V8 protease peptide profiles indicate structural similarities between proteins CNa ‐Wla and CNb‐Wlb. It is concluded that an inactivated form of 2′,3′‐CN 3′‐ase is a major component of Wolfgram protein W1. These results are consistent with the studies on the histochemical localization of rat W1 protein by Roussel et al. (1977, 1978).
Cation‐Sensitive Neutral Endopeptidase: Isolation and Specificity of the Bovine Pituitary Enzyme
Authors: Wilk Sherwin , Orlowski Marian 
Published: October 2006

Abstract:A highly purified preparation of a cation‐sensitive neutral endopeptidase was obtained from bovine pituitaries. The enzyme constitutes almost 0.1% of the protein in bovine pituitary homogenates. Polyacrylamide gel electrophoresis of the enzyme showed a single protein band, and in gel filtration experiments on calibrated Sepharose 6B columns the enzyme eluted slightly ahead of thyroglobulin, suggesting an apparent molecular weight of about 700,000. Polyacrylamide gel electrophoresis in SDS‐containing buffers indicated the presence of three major components with molecular weights ranging from about 24,000 to 28,000. The enzyme hydrolyzes bonds between hydro‐phobic and small neutral amino acids in both model synthetic substrates and biologically active peptides such as substance P, LH‐RH, and bradykinin. Peptide bonds in which the carbonyl group is contributed by a glutamyl or arginyl residue are also hydrolyzed, especially if they are preceded in the sequence by hydrophobic amino acids. Leupeptin exclusively inhibited enzymatic activity toward the arginine‐containing substrates. This observation, together with the high molecular weight and broad specificity of the enzyme, raised the possibility that the isolated enzyme represents a proteolytic complex composed of units with distinctly different activities. Preliminary attempts to dissociate the enzyme into catalytic units of lower molecular weight were not successful and led to loss of activity.
Effects of Dietary Amino Acids on Brain Amino Acids and Transmitter Amines in Rats with a Portacaval Shunt
Authors: Kamata Shinkichi , Okada Akira , Watanabe Takehiko , Kawashima Yasunaru , Wada Hiroshi 
Published: October 2006

Abstract:The etiologic relationship between disturbances in metabolism of amino acids and amines and hepatic coma was investigated by examining the effects of diets containing various mixtures of amino acids on brain amine metabolism in rats with a portacaval shunt, using a method for simultaneous analysis of amino acids and amines. Rats with a portacaval shunt were fed on four different amino acid compositions with increased amounts of various amino acids suspected to be etiologically related to hepatic coma, such as methionine, phenylalanine, tyrosine, and tryptophan. The animals were killed 4 weeks after operation. During the experimental period, these animals did not become comatose, but exhibited various behavioral abnormalities. Marked increase in the plasma and brain levels of the augmented amino acids, especially methionine and tyrosine, were observed in rats with a portacaval shunt. Brain noradrenaline, dopamine, and serotonin levels were significantly decreased when the brain tyrosine level was increased. These results indicate that in rats with a portacaval shunt the dietary levels of amino acids greatly influence the brain levels of both amino acids and transmitter amines.
Effect of Triethyl Tin on Myelination in the Developing Rat
Authors: Blaker William D. , Krigman Martin R. , Thomas David J. , Mushak Paul , Morell Pierre 
Published: October 2006

Abstract:Myelinogenesis in developing rats was studied following chronic dosing with triethyl tin (TET), at a level of 1.0 mg TET/kg body wt/day. Experiments included starved controls with body weights depressed by 17 to 40% to equal those of the TET‐treated groups. Rats at ages of 16, 21, and 30 days showed decreases relative to well‐nourished controls in body weight, forebrain weight, myelin yield, cerebroside level, and specific activity of brain 2′,3′‐cyclic nucleotide‐3′‐phosphohydrolase when dosed with TET. At 30 days, myelin and cerebroside yields were reduced by approximately 55%, while CNP activity was reduced by less than 20%. No differences in the forebrain myelin protein composition between control, starved, and TET animals were noted. The rate of myelin protein synthesis relative to brain total protein (assayed by incorporation of intracranially injected [3H]glycine into brain homogenate and myelin proteins) was decreased in the TET rats in proportion to the decreased yield of myelin, but no particular myelin protein was preferentially affected. Matching starved controls exhibited similar body weight decreases, less pronounced forebrain weight decreases, and little or no decrease in myelin concentration. There was a relative increase in the myelin protein synthesis rate in the starved rats, indicating preferential utilization of limited protein precursors for myelin protein synthesis. Spinal cord myelin was also decreased in the TET rats, but less severely than in the forebrain. At all ages optic, but not sciatic, nerves showed decreases in myelin concentration with TET treatment. We conclude that TET inhibits forebrain growth and CNS myelination more severely than can be accounted for by a general metabolic insult.
The Activity of Rat Pineal and Brain Tyrosine Hydroxylase During the Daily Cycle of Light and Darkness as Determined by the Modified 14CO2 Assay Method
Authors: Watanabe Shuzo , Tom Michio , Ichiyama Arata , Kataoka Tohru 
Published: October 2006

Abstract:A previous published assay method for tyrosine hydroxylase by the evolution of 14CO2 was modified to a two‐step procedure to allow reliable measurement of large numbers of samples containing low tyrosine hydroxylase activity. The reliability of the method was examined in detail. Properties of rat brain and pineal tyrosine hydroxylase solubilized with 0.2% Triton X‐100 were as follows. The apparent Km values of the brain enzyme for L‐tyrosine with 1 mM‐(6‐dl)‐5,6,7,8‐tetrahydro‐L‐erythro‐biopterin (BPH4) as cofactor and for BPH4 with 62 μM‐L‐tyrosine as substrate were approximately 25 μM and 85 μM, respectively. The Km for L‐tyrosine with 1 mM‐(6‐dl)‐5,6,7,8‐tetra‐hydro‐6‐methylpterin (6MPH4) as cofactor and for 6MPH, with 210 μM‐L‐tyrosine as substrate were 68 μM and 270 μM, respectively. The marked substrate inhibition by high concentrations of L‐tyrosine was observed only when BPH4 was used as cofactor. High concentrations of BPH4 inhibited the reaction slightly. The kinetic properties of tyrosine hydroxylase in the pineal extract were similar to those of the brain enzyme, except that a Lineweaver‐Burk plot of reciprocal velocity versus the reciprocal concentration of BPH4 with 62 μM‐L‐tyrosine as substrate deviated downward at a BPH4 concentration of about 100 μM. Analyses of the plot indicated that the peculiar kinetic property may represent either the reaction occurring at two independent sites or with two forms (61.‐and 6d‐isomers) of the tetrahydrobiopterin cofactor, with apparent Kmfor BPH4 of 23 μM and 1025 μM, respectively, or the negatively cooperative ligand binding with a Hill coefficient of 0.72. Based on the results obtained as reported above the standard assay conditions of tyrosine hydroxylase in tissue extracts were established. Using the assay method and conditions, the absence of the daily rhythmicity of tyrosine hydroxylase in rat pineal glands and three discrete brain areas was demonstrated. The findings, especially on pineal tyrosine hydroxylase, are discussed in relation to the daily change of noradrenaline turnover.
Differential Uptake of Horseradish Peroxidase Isoenzymes by Cultured Neuroblastoma Cells
Authors: Chan Kwan Y. , Haschke Richard H. 
Published: October 2006

Abstract:The endocytotic uptake and intracellular decay of horseradish peroxidase isoenzymes C and A by cultured mouse neuroblastoma cells were analyzed quantitatively by a direct spectrophotometric assay. At concentrations below 1 mg/ml, the rate of uptake of the isoenzyme C was more than three times as much as the isoenzyme A. This differential uptake suggests that previous claims of horseradish peroxidase being endocytosed only in the nonselective fluid phase are oversimplified. The implication of this selectivity in the biological significance of retrograde axonal transport of proteins by neuronal systems is discussed.
Dopamine Uptake by Rat Striatal Synaptosomes: Time‐and Temperature‐Dependent Decay and Protection by Dithiothreitol and Dopamine
Authors: Schoemaker Hans , Nickolson Victor J. 
Published: October 2006

Abstract:The uptake of [3H]dopamine (DA) into rat striatal synaptosomes in the presence of a monoamine oxidase inhibitor was studied using a filtration technique. After a 10‐min preincubation period, a fast initial uptake of [3H] DA was seen. Uptake reached a maximum after 4 min of incubation. If incubation was continued for more than 7 min, a gradual decrease in synaptosomal [3H]DA levels was found. Uptake was dependent on preincubation time; initial uptake velocity and maximal uptake decreased irreversibly with increasing preincubation periods. Moreover, the capacity of the synaptosomes to retain the [3H]DA during longer incubation times was progressively affected. The decrease in initial uptake activity was due to a decrease in the Vmax of the transport system. Dithiothreitol (2.8 mM) protected synaptosomal uptake activity against deterioration at 37°C. Also, DA itself (10‐7M) stabilized the uptake mechanism if added to the suspension before preincubation was started. Since [3H]DA uptake observed after loading the synaptosomes with labeled DA was similar to the uptake seen if the synaptosomes were not previously loaded with DA, it was concluded that under these conditions synaptosomal DA is completely exchangeable with exogenous substrate. Prolonged storage of the synaptosomes at 0°C also resulted in a time‐dependent decrease in uptake activity (t1/2= 116 min). The addition of unlabeled DA or dithiothreitol to the suspension did not affect instability at 0°C.