bluuebunny/crossref_metadata_2025_split huggingface dataset:
GLUTATHIONE PEROXIDASE LEVELS IN BRAIN
Authors: Marchena O. de , Guarnieri M. , McKhann G. 
Published: October 2006

AbstractGlutathione peroxidase activity in brains of various animals was examined. Enzyme activity was low, approximately 10 nmol of glutathione oxidized min−1 mg protein−1 or less. This result suggests that brain tissues contain insufficient glutathione peroxidase activity to provide protection from peroxidative damage and that an alternative mechanism may be present.
SUBCELLULAR DISTRIBUTION OF ENZYMES OF TRANSMETHYLATION AND TRANSSULPHURATION IN RAT BRAIN1
Authors: Rassin D. K. , Gaull G. E. 
Published: October 2006

Abstract—Certain of the sulphur containing amino acids have been associated with synaptic transmission in the central nervous system. The enzymes involved in the synthesis of these putative neurotransmitter or modulator compounds have a different subcellular distribution in rat brain from those enzymes that catalyse the synthesis of other compounds in this pathway. Methionine adenosyltransferase and 5‐methyltetrahydrofolate‐homocysteine methyltransferase catalyse reactions that maintain the methylation functions of the pathway and are found in soluble fractions. Cystathionine β‐synthase, cystathionase, cysteine dioxygenase and cysteine sulphinic acid decarboxylase catalyse the synthesis of those sulphur‐containing amino acids implicated in neurotransmitter functions and these enzymes have both paniculate and soluble components. Serine hydroxymethyltransferase, which also has a particulate fraction in brain, is responsible for the synthesis of the neurotransmitter glycine, in addition to its role in the methionine‐related metabolism of folate.
BIOCHEMICAL MATURATION OF HUMAN CENTRAL NERVOUS SYSTEM MYELIN1
Authors: Fishman M. A. , Agrawal H. C. , Alexander Angela , Golterman J. , Martenson R. E. , Mitchell R. F. 
Published: October 2006

Abstract—A developmental study of the lipid and protein composition of human CNS myelin was undertaken. The relative concentrations of the major lipid classes, cholesterol, glycolipids and phospholipids exhibited little change except for a modest decrease in the concentration of the phospholipids. In contrast to the total phospholipids, marked variations in the relative concentrations of individual phospholipids were found. Sphingomyelin increased over two‐fold, and phosphatidyl choline decreased to almost half its original concentration.While the concentration of total myelin protein remained constant during maturation, variations in the concentrations of individual proteins were observed. Basic protein constituted 8·5 per cent of the total myelin proteins in the newborn brain and increased to about 30 per cent of the protein in the older ages. The concentrations of proteolipid protein and DM‐20 seemed to increase with age, while the relative amounts of high molecular weight proteins decreased.The presence of myelin basic protein in newborn human brain was confirmed by electrophoretic studies involving several different polyacrylamide gel systems and by immunodiffusion experiments which showed a reaction of identity between a constituent present in the fraction containing the presumptive myelin basic protein and authentic myelin basic protein isolated from adult human brain.
PROTEOLYTIC DIGESTION OF BOVINE BRAIN WHITE MATTER PROTEOLIPID
Authors: Lees Marjorie B. , Chan D. S. 
Published: October 2006

Abstract—Proteolipids were previously considered to be resistant to proteolytic digestion. In the present study, crude bovine white matter proteolipid, proteolipid apoprotein, and chemically modified proteolipids were subjected to the action of the following proteolytic enzymes in the absence and presence of detergents: trypsin, α‐chymotrypsin, elastase, thermolysin and collagenase. The course of digestion was followed by the release of Fluorescamine‐reactive groups. Tryptic digestion of the crude proteolipid and the apoprotein in the absence of detergent amounted to 10 and 40% respectively of the digestion in the presence of detergent. Peptide mapping and protein analyses of both the soluble digests and the insoluble residues confirmed digestion. In the presence of either sodium deoxycholate or Triton X‐100, essentially all of the crude proteolipid and 60% of the proteolipid apoprotein were solubilized by trypsin. Digestion of the apoprotein was observed only in preparations which had not been dried. In the absence of detergent, (1) the oxidized crude proteolipid was more susceptible to tryptic digestion than were either the unoxidized or carboxymethylated preparations, (2) both the apoprotein and the oxidized proteolipid were digested by thermolysin or α‐chymotrypsin, and (3) all preparations were attacked by elastase.
EFFECT OF EXTRINSIC DENERVATION ON ENDOGENOUS NORADRENALINE AND [3H]NORADRENALINE UPTAKE IN THE GUINEA‐PIG COLON
Authors: Gabella G. , Juorio A. V. 
Published: October 2006

Abstract—The concentration of noradrenaline was studied in the proximal colon of the guinea‐pig, where intrinsic adrenergic neurons are present in the myenteric plexus. The noradrenaline content is higher than in the myenteric plexus of other parts of the alimentary tract. After extrinsic denervation of the colon, about 25% of the original content of noradrenaline remains in the myenteric plexus, and this is considered to be the amount due to the intrinsic adrenergic neurons; also a substantial noradrenaline uptake activity is still detectable. On the other hand, in the part of the wall formed by circular muscle‐submucous plexus‐submucosa‐mucosa, which has control values close to those of the ileum, extrinsic denervation causes a nearly complete depletion of noradrenaline. This is considered as evidence that the intrinsic neurons do not project to the circular musculature, or the submucosa or mucosa.
EFFECT OF ELECTRICAL STIMULATION AND CHLORPROMAZINE ON THE UPTAKE AND RELEASE OF TAURINE, γ‐AMINOBUTYRIC ACID AND GLUTAMIC ACID IN MOUSE BRAIN SYNAPTOSOMES
Authors: Lähdesmäki P. , Pasula M. , Oja S. S. 
Published: October 2006

Abstract—The concentrations of taurine and GABA were determined in isolated mouse brain synaptosomes incubated in Krebs‐Ringer phosphate medium (pH 7·4). The concentration of GABA gradually decreased during incubation, but that of taurine remained approximately unchanged. In the presence of chlorpromazine the amount of GABA in the synaptosomes increased, but the efflux and influx of GABA were slightly reduced. The content and efflux of both taurine and GABA increased in electrically stimulated synaptosomes, and the influx of taurine, GABA and glutamate into the synaptosomes similarly increased. All three amino acids are taken up by the synaptosomes through at least two mechanisms: low‐affinity and high‐affinity. In the high‐affinity system the Km values were 33 μm for taurine, 24 μm for GABA and 68 μm for glutamate, and in the low‐affinity one 1·1 mil, 0·9 mm and 1·2mm, respectively. The influx capacity (Vmax) was highest for glutamate, second highest for GABA and lowest for taurine.
STRUCTURE AND BIOLOGICAL ACTIVITY OF A SERIES OF CONFORMATIONALLY RESTRICTED ANALOGUES OF GABA
Authors: Krogsgaard‐Larsen P. , Johnston G. A. R. , Curtis D. R. , Game C. J. A. , McCulloch R. M. 
Published: October 2006

Abstract—Microelectrophoretic methods were used to study the effects on spinal neurones of a series of conformationally restricted analogues of GABA, most of which are structurally related to musci‐mol (3‐hydroxy‐5‐aminomethylisoxazole). 3‐Hydroxy‐5‐(l‐aminoethyl)isoxazole and 3‐hydroxy‐5‐(2‐aminoethyl)isoxazole were GABA‐like depressants comparable in effectiveness with GABA. The inhibitors of GABA uptake 4,5,6,7‐tetrahydroisoxazolo[4,5‐c]pyridin‐3‐ol and nipecotic acid (piperidine‐3‐carboxylic acid) reversibly enhanced the depressant action of GABA. 3‐Hydroxy‐5‐dimethylaminomethly‐isoxazole, 5,6,7,8‐tetrahydro‐4H‐isoxazolo[4,5‐d]azepm‐3‐ol, 4,5,6,7‐tetrahydroisoxazolo[4,5‐c]pyridin‐3‐ol, and nipecotic acid reversibly antagonized the postsynaptic action of glycine.A structure‐activity correlation was made in an indirect attempt to elucidate some comformational requirements for interaction of GABA with its postsynaptic receptor and the binding site of its uptake system. The results seem to indicate that different conformations of GABA are required for these interactions.
REGULATION OF NERVE GROWTH FACTOR SYNTHESIS IN MOUSE SUBMAXILLARY GLANDS BY TESTOSTERONE1
Authors: Ishii D. N. , Shooter E. M. 
Published: October 2006

Abstract—It has long been known that the activity of nerve growth factor (NGF) in extracts obtained from the male mouse submaxillary gland is higher than in extracts from the female gland, and that the activity present in female glands can be increased by testosterone treatment. This communication presents a study of the mechanism of the testosterone effect. Of several different steroids administered to female Swiss–Webster mice only testosterone propionate led to increased gland NGF activity. The increase did not appear to be due to an enhancement of the activity of pre‐existing molecules on sympathetic nerve fiber outgrowth, or due to an altered affinity for the specific antibodies used in the estimation of NGF content, but appeared rather to be due to an accumulation of NFG molecules. The kinetics of change in the male gland NGF content upon castration and secondary testosterone propionate stimulation was analyzed by application of the plateau principle. The rate of loss of NGF from this organ was not measureably different between the castrate and testosterone propionate stimulated state. On the other hand, there was estimated to be a 10‐fold difference in the rate of input between the basal and steroid stimulated state. Tracer amounts of radioiodine labelled NGF administered i.v. was not accumulated by the gland, and there is no evidence for uptake of this protein from the circulation. We, therefore, infer that the increased NGF concentration in male submaxillary glands is due to a 10‐fold increase in the rate constant of synthesis.
α‐METHYLTRYPTOPHAN: EFFECTS ON CEREBRAL MONOOXYGENASES IN VITRO AND IN VIVO
Authors: Gál E. M. , Christiansen P. A. 
Published: October 2006

Abstract—Following administration of x‐methyltryptophan (AMTP) (50 mg/kg) there was a time dependent decrease of serotonin and a concomitant increase of α‐methyl‐5‐hydroxy‐tryptamine (AM‐5‐HT) in most cerebral areas. AMTP is hydroxylated to α‐methyl‐5‐hydroxytryptophan (AM‐5‐HTP) by cerebral tryptophan hydroxylase in vitro and in vivo. Hydroxylation of AMTP in vitro and in vivo was markedly inhibited in p‐chlorophenylalanine (p‐CP) treated rats. After administration of AMTP, the conversion in vivo of tyrosine to norepinephrine was inhibited. This inhibition was not apparent in p‐CP pretreated animals. p‐Chloroamphetamine (p‐CA) (10 mg/kg) lowered serotonin and AM‐5‐HT levels in some areas of the brain, but unlike p‐CP, alone or in combination with AMTP it did not significantly inhibit hydroxylation of tryptophan (Trp). AMTP, as substrate of tryptophan hydroxylase, has a Km of 1.08 × 10‐4 M (using 6‐MPH4, as cofactor) and as competitive inhibitor, a K1 of 2.09 × 10‐4M with L‐Trp as substrate. AMTP becomes an uncompetitive inhibitor when its concentration is equal to or exceeds that of L‐Trp. D‐AMTP is neither a substrate nor an inhibitor of tryptophan hydroxylase. DL‐AM‐5‐HTP (K1, 1.5 × 10‐5 M) and AM‐5‐HT (K1 4.0 × 10‐5 M) are competitive inhibitors.
THE LEVELS OF LABILE INTERMEDIARY METABOLITES IN MOUSE BRAIN FOLLOWING RAPID TISSUE FIXATION WITH MICROWAVE IRRADIATION1
Authors: Medina M. A. , Jones D. J. , Stavinoha W. B. , Ross D. H. 
Published: October 2006

Abstract—The levels of several labile glycolytic and organic phosphate metabolites in mouse brain were determined following rapid inactivation with 2450 MHz microwave irradiation. The levels of ATP in mouse brain following a 0·25 s exposure in a 6 kW microwave oven was found to be 2·416 ± 0·061. Whole brain levels of 8 labile intermediary metabolites in 0·4 s irradiated samples were comparable to those reported using the previously‐described methods of freeze‐blowing or whole‐animal immersion. Analysis of these same metabolites in 4 gross areas of brain did not reveal any anoxic changes betwen superficial and deeper brain areas. The advantages of the mcrowave irradiation inactivation technique for regional brain studies of labile intermediary metabolites is discussed.
THE QUANTITATIVE HISTOCHEMISTRY OF MULTIPLE SCLEROSIS PLAQUES: ACID PROTEINASE AND OTHER ACID HYDROLASES1
Authors: Hirsch Hilde E. , Duquette P. , Parks Mary Ellen 
Published: October 2006

Abstract— Sensitive micromethods were used to study the plaques, adjacent white matter and remote, grossly normal white matter from two cases of multiple sclerosis and to compare them with white matter from normal controls. Lipid‐free dry wt/unit of volume was found to be similar for plaques and for normal white matter, reflecting a high water content of plaque tissue and establishing a base for comparison of enzyme activities. Elevations of acid proteinase in and around plaques were confirmed, but they were far exceeded by the increases in acid phosphatase; other acid hydrolases (β‐galactosidase, β‐glucuronidase and dipeptidyl arylamidase II) showed no significant or consistent changes. However, an acid lipase‐esterase hydrolysing 4‐methylumbelliferyl oleate was about 30% as active in plaques as in normal‐appearing white matter. Glucose‐6‐phosphate dehydrogenase was unchanged except in one plaque, but lactic dehydrogenase was markedly elevated both in plaques and adjacent white matter. The grossly normal white matter of MS patients, although histologically far from normal (showing gliosis, perivascular infiltrations and small plaques), did not differ significantly from controls with regard to the activity of any of the enzymes studied. DNA levels were much reduced in plaques, but comparisons were difficult because of the apparent gliosis in normal white matter.Decreases in dry wt/unit vol, reflecting partial demyelination, could be shown to extend in a gradient to a distance of about 2 mm. from the edge of certain plaques.
PINEAL SEROTONIN N‐ACETYLTRANSFERASE ACTIVITY: PROTECTION OF STIMULATED ACTIVITY BY ACETYL‐CoA AND RELATED COMPOUNDS
Authors: Binkley Sue , Klein D. C. , Weller Joan L. 
Published: October 2006

Abstract—Rat pineal serotonin N—acetyltransferase activity increases 30–70‐fold at night in the dark and then decreases rapidly when animals are exposed to light. Activity of the enzyme is also stimulated by l‐norepinephrine in organ culture. When homogenates of glands stimulated by dark in vivo or NE in vitro are incubated at 37°C, enzyme activity will also rapidly decrease. This decrease can be prevented by one of the cosubstrates of the enzyme, acetyl–CoA. Protection can also be conferred by cysteamine (β‐mercaptoethylamine, HS–CH2–CH2–NH2) which is the terminal portion of the CoA molecule. This protection mechanism could be involved in the physiological control of enzyme activity.
OCCURRENCE AND FORMATION OF γ‐GLUTAMYLPUTRESCINE IN MAMMALIAN BRAIN
Authors: Nakajima T. , Kakimoto Y. , Tsuji M. , Konishi H. 
Published: October 2006

Abstract—An unknown radioactive compound was detected in the basic fraction of the trichloroacetic acid extract of rat brain injected with radioactive putrescine. This compound was purified from bovine brain and identified as γ‐glutamylputrescine by comparison of its behaviour with that of the synthesized glutamylamides. The amide seemed to be metabolized as rapidly as putrescine in rat brain.
HOMOVANILLIC ACID AND 3‐METHOXY‐4‐ HYDROXYPHENYLETHYLENEGLYCOL PRODUCTION BY THE MONKEY SPINAL CORD
Authors: Kesslex J. A. , Gordon E. K. , Reid J. L. , Kopin I. J. 
Published: October 2006

AbstractThe release of homovanillic acid (HVA) and 3‐methoxy‐4‐hydroxyphenylethyleneglycol (MHPG) into CSF by the monkey spinal cord was investigated with spinal subarachnoid perfusion of 20 rhesus monkeys. The preperfusion concentration of HVA in lumbar CSF was 365 ng/ml and in cisternal CSF was 365 ng/ml, while the concentrations of MHPG were 28.3 and 40.4 ng/ml respectively. HVA originating from the spinal cord appeared in the perfusate at a rate of 2.4 and MHPG at 1.4 ng/min. Treatment with probenecid either intraperitoneally or intrathecally did not alter the rate of release into CSF of these metabolites by the spinal cord but did significantly increase the rate of appearance in the cisterna magna of HVA originating from the brain. MHPG and HVA in lumbar CSF are therefore derived in part from spinal cord metabolism.
KINETICS OF COMPETITIVE INHIBITION OF NEUTRAL AMINO ACID TRANSPORT ACROSS THE BLOOD‐BRAIN BARRIER
Authors: Pardridge W. M. 
Published: October 2006

Abstract—The transport of tryptophan across the blood‐brain barrier is used as a specific example of a general approach by which rates of amino acid influx into brain may be predicted from existing concentrations of amino acids in plasma. The kinetics of inhibition of [14C]tryptophan transport by four natural neutral amino acids (phenylalanine, leucine, methionine, and valine) and one synthetic amino acid (α‐methyl tyrosine) is studied with a tissue‐sampling, single injection technique in the barbiturate‐anesthetized rat. The equality of the K1 (determined from cross‐inhibition studies) and the Km (determined from auto‐inhibition data) for neutral amino acid transport indicate that these amino acids compete for a single transport site in accordance with the kinetics of competitive inhibition. Based on equations derived for competitive inhibition, apparent Km values are computed for the essential neutral amino acids from known data on amino acid transport Km and plasma concentrations. The apparent Km values make possible predictions of the in vivo rates of amino acid influx into brain based on given plasma amino acid concentrations. Finally, a method is presented for determining transport constants from saturation data obtained with single injection techniques.
THE METABOLISM OF LABELLED CHOLINE IN NEURONAL AND GLIAL CELLS OF THE RABBIT IN VIVO1
Authors: Francescangeli E. , Goracci G. , Piccinin G. L. , Mozzi R. , Woelk H. , Porcellati G. 
Published: October 2006

Abstract—[Methyl‐3H]choline has been injected intraventricularly into adult rabbits, and the rate of synthesis of phosphatidylcholine, choline plasmalogen and sphingomyelin (and their hydrosoluble precursors) in isolated neuronal and glial cells has been investigated. At all time intervals examined, the injected radioactivity was incorporated only into the base moiety of the choline lipids in both cell types. Maximum labelling of the two choline phosphoglycerides occurred in neurons 150 min after administration, whereas the highest specific radioactivity for glial phosphatidylcholine and choline plasmalogen was reached at 6 and 10 h, respectively. At any time interval examined, the neuronal and glial choline plasmalogen displayed a higher specific radioactivity than the corresponding diacyl‐derivative. The two phosphoglycerides incorporated the base in both cell populations at a faster rate than did whole brain tissue. Sphingomyelin was labelled in both cells at a low rate and acquired measurable radioactivity levels only after 2 h from isotope administration.Highest levels of radioactivity for phosphorylcholine and cytidine‐5′‐diphosphocholine were reached in both neurons and glia 1‐2 h after administration, but these levels per unit protein were higher in glial than in neuronal cells.
KINETICS OF ENTRY OF PROTEINS INTO THE MYELIN MEMBRANE1
Authors: Benjamins Joyce A. , Iwata Roderick , Hazlett James 
Published: October 2006

AbstractBrain slices were prepared from 17‐day old rats, and incubated with [3H]glycine or [3H]‐leucine to label proteins. Myelin was isolated from the slices, and the proteins were separated by discontinuous gel electrophoresis in buffers containing sodium dodecyl sulfate. Radioactive basic and Wolfgram proteins appeared in myelin at similar initial rates, and their entry was nearly linear between 15 and 120 min with no detectable lag. Radioactive proteolipid protein appeared in myelin at one‐fourth the rate of the basic and Wolfgram proteins between 0 and 30 min, then entered at a rate comparable to the other proteins between 45 and 120 min.When cycloheximide (0.2 mM) or puromycin (1.0 mM) was added, appearance of newly labeled basic and Wolfgram proteins in myelin stopped while proteolipid protein continued to appear in myelin at a normal rate for at least 30 min. Chase experiments with unlabeled glycine had similar effects. These results indicate the existence of a previously synthesized precursor pool of proteolipid protein with a 30‐min interval between synthesis of proteolipid protein and its appearance in myelin.Incorporation of [3H]fucose into glycoprotein of the myelin sheath was studied, as was inhibition of incorporation of radioactivity by the use of either cycloheximide, or dilution with unlabeled fucose. The results indicated fucosylation of a sizable pool of presynthesized protein and a delay of 30 min between fucosylation of these polypeptides and their subsequent appearance in myelin as glycoproteins.
MONOAMINE OXIDASE ACTIVITY IN NORMAL and LESCH‐NYHAN FIBROBLASTS
Authors: Edelstein Susan B. , Castiglione Carmela M. , Breakefield Xandra O. 
Published: October 2006

AbstractMonoamine oxidase (MAO) activity was studied in cultured skin fibroblasts from 10 Lesch‐Nyhan patients, a Lesch‐Nyhan variant and 11 controls matched for age. sex and race. Activity (predominantly type A) was measured in cell homogenates using tryptamine as the substrate. For each line activity varied with the conditions of culture. Activity increased 3‐10 fold as cultures went from logarithmic to stationary phase of growth. When cultures were confluent, activity was lowered by frequent feedings or the use of fresh medium and serum. Activity for each line remained fairly stable during successive passages, but rose 3‐8 fold as cultures became senescent. When comparing activity between control and Lesch‐Nyhan lines, cells were cultured under standardized conditions. The mean value of MAO activity in Lesch‐Nyhan lines was approximately one fourth of the mean activity in control lines (P < 0.012), In the control population, the distribution of activity appeared to be bimodal. Activities in the Lesch‐Nyhan lines fell completely within the lower portion of the control distribution. Cells from a Lesch‐Nyhan patient who lacked several of the neurologic symptoms of the disease (including self‐mutilation) had an MAO activity 6 fold greater than the control mean. although his hypoxanthine phosphoribosyltransferase activity was <3% of control levels.It appears that: (1) MAO activity is low in fibroblasts from typical Lesch‐Nyhan patients: (2) the severity of neurologic symptoms may be correlated with levels of MAO activity: and (3) some interaction between purine and catecholamine metabolism can affect nerve function.