bluuebunny/crossref_metadata_2025 huggingface dataset:
SUBCELLULAR DISTRIBUTION OF ENZYMES OF TRANSMETHYLATION AND TRANSSULPHURATION IN RAT BRAIN1
Authors: Rassin D. K. , Gaull G. E.
Published: October 2006

—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

—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

—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

—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

—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

—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

—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 GAMMA‐AMINOBUTYRIC ACID (GABA) SYSTEM IN BRAIN DURING ACUTE AND CHRONIC ETHANOL INTOXICATION
Authors: Sytinsky I. A. , Guzikov B. M. , Gomanko M. V. , Eremin V. P. , Konovalova N. N.
Published: October 2006

Abstract— The effects of acute and chronic ethanol intoxication on the GAGA system of rats have been investigated. Under the terminal conditions provoked. by ethanol (6–8 g/kg, i.p.) the brain GABA content sharply increased. There was a simultaneous decrease of 35–40% in the glutamate decarboxylase (GAD) activity of the cerebellum and cerebral hemispheres. In contrast, the transaminase, GABA‐T was either unchanged, or it increased: by 28% only in cerebellum and by 1.5–2.0–fold in liver and kidney. It is suggested that effects of acute ethanol intoxication at different doses (2–8 g/kg) on the brain GABA system is connected with the phases of the functional condition of the CNS and a disturbance of homeostatic function. Chronic ethanol consumption caused a decrease in brain GABA. an increase of GAD activity in cerebellum and cerebral hemispheres, and no change in GABA‐T activity. The activity of this last enzyme was increased 1.5–2.0‐fold in liver and kidneys of rats consuming a diet containing 10% ethanol daily. A 50‐fold purified preparation of GABA‐T obtained from pig brain was inhibited by butanol‐l and propanol‐1 (0.03–0.6m) with no effect of ethanol. It is suggested that the mechanisms involved in the ethanol effect on nervous cells are linked with the GABA system and the phases of the functional condition of the CNS.
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.
COMPARISON OF THE EFFECTS OF DEPOLARIZING AGENTS AND NEUROTRANSMITTERS ON REGIONAL CNS CYCLIC GMP LEVELS IN VARIOUS'ANIMALS
Authors: Kinscherf Dorothy A. , Chang M. M. , Rubin E. H. , Schneider D. R. , Ferrendelli J. A.
Published: October 2006

Abstract— The effects of 121 mm‐K+, 10 mm‐glutamate, 5 mm‐GABA, 1 mm‐glycine, 0.1 mm‐NE, and 1–10 μmACh on cyclic GMP levels in tissue slices prepared from cerebral cortex and cerebellum of mouse, rabbit, guinea‐pig, cat, and rat were studied. Basal levels of cyclic GMP in the cerebella of mice, guinea‐pigs and cats were 4–15 and 70 pmol/mg prot in rat, whereas in the cerebral cortex of the same animals, levels were only 0.6–2 pmol/mg prot. In contrast, basal levels of the cyclic nucleotide were 1–2 pmol/mg prot in both of these regions in rabbit brain. Only 121 mm‐K+ was capable of increasing cyclic GMP levels in all the tissues studied. Elevations ranged from 30% in rat cerebral cortex to 2800% in mouse cerebellum. Glutamate produced a 30–1000% rise of cyclic GMP levels in all tissues except rabbit cerebellum. NE elevated levels of cyclic nucleotide 2‐ to 3‐fold in slices of cerebellum from all species studied but had no effect in cerebral cortex. GABA and glycine had no effect in any tissue except mouse cerebellum. ACh had no consistent effect on levels of cyclic GMP in any brain region investigated. These results suggest that mechanisms regulating cyclic GMP levels in mammalian CNS vary among brain regions and among animal species.
DISAGGREGATION OF BRAIN POLYSOMES AFTER ADMINISTRATION OF d‐LYSERGIC ACID DIETHYLAMIDE (LSD) IN VIVO
Authors: Holbrook L. , Brown I. R.
Published: October 2006

Abstract— Polysomes from three major brain regions of the young rabbit were disaggregated after in vivo administration of d‐LSD. The effect was transient and demonstrated maximal shift after 30–60 min with a return to normal levels by 4 h. Brain polysome disaggregation was elicited by LSD dosages of either 10 or 100/μg/kg body wt. The polysome shift was not caused by RNase degradation and during maximal disaggregation there was a measurable decrease in protein synthesis.
NEURAMINIDASE‐RELEASABLE SURFACE SIALIC ACID OF CULTURED ASTROBLASTS EXPOSED TO ETHANOL
Authors: Noble E. P. , Syapin P. J. , Vigran R. , Rosenberg A.
Published: October 2006

Abstract— Chronic exposure of intact cultured primary hamster astroblasts, clonal line NN, to 100 mM ethanol resulted in significant increases (10–52%) in the releasability of sialic acid from the cell by exogenously added Clostridium perfringens neuraminidase. Enzymatically releasable sialic acid was from the glycoprotein but not the ganglioside fraction of the cell. Addition of ethanol to the medium did not affect the enzymatic hydrolysis of sialyllactose nor did ethanol, over a concentration range of 0–200 mM, alter the enzymatic release of sialic acid from intact NN cells. The total cellular sialic acid content was independent of length of cell exposure to ethanol but varied with the age of the cells. These data suggest that exposure of cells for prolonged periods to ethanol results in steric modification of surface glycoproteins.
SOLUBLE PROTEINS IN NORMAL and DISEASED HUMAN BRAIN
Authors: Smith Carolyn B. , Bowen D. M.
Published: October 2006

Abstract– Six brain regions (frontal cortex, parts of the basal ganglia, thalamus and substantia nigra) were examined from over 80 human brains obtained at post‐mortem. After elimination of patients with evidence of either ‘cerebral hypoxia’, lingering modes of death or abnormal brain morphology brain extracts were found to contain a characteristic pattern of 6 major soluble‐acidic protein bands (neuronin‐type proteins). As judged by studies using cortical biopsy specimens these proteins are relatively unaffected by post‐mortem changes. Moreover, in adulthood the pattern is not noticeably age‐dependant. Two of the protein bands have been identified as S‐100 (neuronin S‐1 and 2) while a third (neuronin S‐5) is similar in most respects to antigen α (14‐3‐2). S‐100 is increased in brains with evidence of marked gliosis. The other protein bands have not been identified. Two of them (neuronin S‐3 and 4) are rarely depleted while the concentration of neuronin S‐6 is affected particularly in extracortical regions in controls with either lingering modes of death and/or ‘cerebral hypoxia’ and in all regions in most patients with Alzheimer's disease, senile dementia and mixed senile and vascular dementia.
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

—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

—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

The 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.
EARLY RESPONSE OF RAT BRAIN TRYPTOPHAN HYDROXYLASE ACTIVITY TO CYCLOHEXIMIDE, PUROMYCIN AND CORTICOSTERONE
Authors: Azmitia C. , McEwen B. S.
Published: October 2006

Abstract— The activity of tryptophan hydroxylase was measured in whole homogenates of midbrain and forebrain areas of the rat brain. A significant elevation of tryptophan hydroxylase in midbrain and forebrain was found within 1 h after injection of corticosterone hemisuccinate Na salt (10mg/kg) into normal rats. A further elevation of tryptophan hydroxylase at 4 h after injection occurred only in the midbrain region. A rapid alteration of tryptophan hydroxylase was also observed following intracistemal injection of a protein synthesis inhibitor, cydoheximide. A significant depression of 50% of normal levels occurred both in midbrain and forebrain regions within 1 h. However. 4 h after injection only the midbrain tryptophan hydroxylase level was depressed, and this depression was 16% of normal levels. This temporal and spatial pattern following cydoheximide injection was not the result of changes in the ability of cydoheximide to inhibit in vivo protein synthesis since [3H]valine incorporation into protein was shown to be equally depressed at both 1 and 5 h in both the midbrain and forebrain. Puromycin blocked [3H]valine incorporation into proteins in the midbrain and forebrain. but only caused a depression of 16% of tryptophan hydroxylase in the midbrain at 4 h. The aminonucleoside derivative of puromycin has no effect on protein synthesis or on tryptophan hydroxylase. Cydoheximide had no effect on tryptophan hydroxylase in vitro. The data suggest that cydoheximide and corticosterone produce an early (1 h) effect on tryptophan hydroxylase unrelated to de novo protein synthesis in regions known to contain perikaryon (midbrain) and axon terminals (forebrain) of 5‐HT‐containing neurons. The later (4h) effects of these two compounds and puromycin on tryptophan hydroxylase in the perikaryon (midbrain) region of 5‐HT‐containing neurons probably result from alteration in de novo protein synthesis. The half time of tryptophan hydroxylase in midbrain region is calculated to be 12 h.
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.
LEVELS OF CEREBRAL CORTICAL GLYCOLYTIC AND CITRIC ACID CYCLE METABOLITES DURING HYPOGLYCEMIC STUPOR AND ITS REVERSAL
Authors: Gorell Jay M. , Law Maggie M. , Lowry O. H. , Ferrendelli J. A.
Published: October 2006

Abstract— Blood glucose, cerebral cortical glucose, and eight metabolites of the glycolytic pathway and citric acid cycle were measured during insulin hypoglycemic stupor and during the first 100s after glucose administration. In hypoglycemic mice that had lost righting ability, blood and brain glucose were decreased 89% and 96% respectively, but glucose‐6‐phosphate fell only 23%. Other glycolytic and citric acid cycle intermediates were decreased 31–77%. Fructose bisphosphate, 3‐phosphoglycerate and phosphopyruvate fell more than glucose‐6‐phosphate, but less than pyruvate and lactate. Citrate fell less than a‐ketoglutarate and malate. These results suggest that in severe hypoglycemia there is a decrease in brain glucose utilization, mediated by phosphofructokinase, but probably caused by decreased neuronal activity. An intravenous injection of glucose restored brain glucose to 75% of normal within 10s and caused return of righting ability within 60s. Glucose‐6‐phosphate, fructose bisphosphate, 3‐phosphoglycerate, and phosphopyruvate rose to normal or near normal levels within 60s, whereas pyruvate, lactate, citrate, ã‐ketoglutarate, and malate changed little in this period. This suggests that although glucose given to hypoglycemic animals rapidly enters the glycolytic pathway in brain (and behavior is almost normal), total neuronal activity, and hence overall glucose metabolism, remains subnormal for several minutes.
Sandhoff disease: ganglioside GM and asialo‐GM2 accumulation in the cerebrospinal fluid
Authors: BERNHEIMER H. , MOLZER BRUNHILDE , DEISENHAMMER E.
Published: October 2006

In an earlier investigation it was found that ganglioside GM2 the typical neuronal storage product in GMz‐gangliosidosis, was accumulated also in the cerebrospinal fluid (CSF) of a Tay‐Sachs patient. The asialo derivative of ganglioside GM2, GM2, which is a concomitant storage product in the brain of these patients, was not detected in the CSF of the patient investigated (BERNHEIMER, 1968). In the present account, a report is made on the accumulation of ganglioside GM2 and of GM2 in the CSF of a patient affected by Sandhoff disease.
KINETICS OF ENTRY OF PROTEINS INTO THE MYELIN MEMBRANE1
Authors: Benjamins Joyce A. , Iwata Roderick , Hazlett James
Published: October 2006

Brain 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

Monoamine 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.
A STUDY OF PROPOSED DETERMINANTS OF BRAIN TRYPTOPHAN CONCENTRATION IN RATS AFTER PORTOCAVAL ANASTOMOSIS OR SHAM OPERATION
Authors: Bloxam D. L. , Curzon G.
Published: October 2006

Liver dysfunction was produced in rats by surgical portocaval anastomosis (PCA), and the time‐course of changes in brain tryptophan and 5‐HT metabolism studied in relation to plasma changes possibly influencing brain tryptophan concentration.

Brain tryptophan and 5‐hydroxyindolylacetic acid (5‐HIAA) levels were increased greatly and maximally on the day after PCA and remained high. 5‐HT changes were less marked but had a similar time‐course. Plasma total tryptophan was little changed but plasma free tryptophan was raised. The latter change showed a similar time‐course to that of brain tryptophan but was not large enough to account completely for it. Sham operation was followed by significant but transient increases in plasma free tryptophan, brain tryptophan and 5‐HIAA but these were much smaller than after PCA.

Brain tryptophan did not correlate with plasma total tryptophan either in control or PCA rats but it correlated significantly with plasma free tryptophan in both groups. However brain levels were much higher in PCA rats than in controls with similar plasma free tryptophan levels at all times from the first day after operation. The increase of brain tryptophan in anastomosed rats not accounted for by plasma free tryptophan was explained neither by insulin changes nor by an increase of the insulin/glucagon ratio nor by changes in plasma concentrations of those amino acids which compete with tryptophan for entry into brain. The results therefore indicate an unknown influence on brain tryptophan concentration in PCA rats. As tyrosine changes in brain and plasma after PCA were very similar to those of tryptophan this influence may not be specific to tryptophan. Results suggest that under the conditions used brain tryptophan concentrations of both PCA and control rats are more influenced by changes of plasma free tryptophan concentration than by changes of plasma concentrations of competing amino acids.
DETERMINATION OF CATECHOLAMINES IN RAT BRAIN PARTS BY REVERSE‐PHASE ION‐PAIR LIQUID CHROMATOGRAPHY
Authors: Felice Lawrence J. , Felice Joan D. , Kissinger Peter T.
Published: October 2006

Abstract—

An improved method for the measurement of catecholamines in brain parts has been developed, based on reverse‐phase ion‐pair chromatography. The new method offers the advantages of high efficiency microparticulate liquid chromatography packings and the flexibility of ion‐pair chromatography. By this approach norepinephrine and dopamine (DA) have been measured in the hypothalamus and corpus striatum of the rat brain during various stages of development (15, 21, 30 days). Data are reported on the basis of the whole part and per weight of tissue. For the adult animals, the following concentrations (ng/g wet tissue) were observed for the hypothalamus: NE = 2261 ± 274, DA = 440 ± 103, and for the corpus striatum: DA = 11,888 ± 1840. The overall precision of the method was ±5.6% relative s.d. The absolute recovery was 60 ± 5% relative s.d. and was constant over the range of 1 ng to 1 μg of dopamine or norepinephrine per tissue sample. The relative retention behavior of 18 neurologically important catechol derivatives is reported for reverse‐phase chromatography with octyl sulfate as the stationary phase modifier.
PROTEIN TURNOVER IN PHOTORECEPTOR CELLS OF ISOLATED LIMULUS LATERAL EYES
Authors: KRAUHS J. M. , MAHLER H. R. , MOORE W. J.
Published: October 2006

Abstract— A system was devised for the study of protein turnover in isolated lateral eyes of Limulus. In eyes incubated in a medium containing L‐[3H]leucine, radioactivity of the fraction soluble in trichloroacetic acid increased steadily during 8 h. Amino‐acid incorporation into proteins was investigated by scintillation counting of trichloroacetic‐acid precipitates and by radioautography. At least 89% of the incorporation was inhibited by puromycin and 86% by emetine, an inhibitor of cytoplasmic protein synthesis. Label accumulated preferentially in the rhabdomes, which contain the visual pigment. Radioautography indicated that labeled protein, probably synthesized in the cytoplasm, was distributed in the microvilli of the photoreceptor cells in a diffuse pattern. In contrast to in vivo results, the photoreceptor cells in isolated eyes were labeled to a greater extent in light than in the dark. These different kinetics of labeling were both explained by the hypothesis that light increased the rate of degradation of proteins (particularly opsin) in the visual cells.
MEASUREMENT OF PROTEIN TURNOVER IN RAT BRAIN1
Authors: Chee Po Yok , Dahl June L.
Published: October 2006

Abstract— Degredation rates of rat brain proteins were measured by following the decay in specific radioactivity of carboxyl labelled aspartate and glutamate over a 17‐day period. Initial labelling of these amino acids was achieved by a single intraperitoneal injection 0f NaH14CO3. The non‐linear decay curve for total brain proteins could be approximated by assuming that the mixture contained two classes of proteins with half‐lives of 3.3 and 8.7 days, respectively. Half‐lives of 2.5 and 7.7 days were estimated for such protein classes in the microsomal fraction. The half‐lives of soluble proteins, synaptic membranes, cell body and synaptic mitochondria were 3.1, 5.8, 5.6 and 8.4 days, respectively. Identical results were obtained if the change in specific activity of intact protein labeled by NaH14CO3 was followed.

Two‐fold slower decay rates were obtained when brain proteins were labeled with a pulse of [4,5‐3H]leucine or [l‐14C]leucine. Half‐lives calculated for the two classes of proteins in whole brain were 8.4 and 16.5 days, respectively with [4,5‐3H]leucine and 8.9 and 14.2 days, respectively with [1‐14C]leucine. These results indicate the very significant reutilization of this amino acid in brain. Sodium [14C]bicarbonate is a more satisfactory isotopic precursor for accurate assessment of rates of protein turnover in brain.
SELECTIVE PURIFICATION OF A SINGLE POPULATION OF GLUCOCORTICOID RECEPTORS FROM RAT BRAIN
Authors: De Kloet E. Ronald , Burbach Peter
Published: October 2006

Abstract— A 200‐fold purification of glucocorticoid receptors from rat brain was achieved with 21% recovery using affinity chromatography via deoxycorticosterone hemisuccinate covalently coupled to BSA‐Sepharose 4B. Subsequent chromatography of the affinity column eluate via a DE‐52 anionexchanger revealed that this purification concerned selectively one of the two glucocorticoid receptor systems in rat brain.
SERUM DOPAMINE‐β‐HYDROXYLASE IN SCHIZOPHRENIC PATIENTS
Authors: Fujita K. , Ito T. , Maruta K. , Teradaira R. , Beppu H. , Nakacami Y. , Kato Y. , Nagatsu T. , Kato T.
Published: October 2006

Abstract— Dopamine‐β‐hydroxylase (DBH) activity in serum was decreased significantly in schizophrenic patients (16.17 ± 12.60 μmol/min/1 of serum, mean ± S.D., n = 149) when compared with that of normal controls (42.53 ± 30.94 μmol/min/1 of serum, mean ± S.D., n= 153) and neurotic patients. Long duration of disease did not cause any significant changes in serum DBH activity except a tendency for increase in patients of lodger than 18 years duration. We also examined the possibility that the serum DBH deficiency in the schizophrenic group was an artifact of treatment with antipsychotic drugs, especially phenothiazines. No significant difference was observed between the patients treated with the drugs and the patients not receiving the drugs.
REGIONAL DISTRIBUTION OF ENZYMES ASSOCIATED WITH NEUROTRANSMISSION BY MONOAMINES, ACETYLCHOLINE AND GABA IN THE HUMAN BRAIN
Authors: Mackay A. V. P. , Davies P. , Dewar A. J. , Yates C. M.
Published: October 2006

Abstract— The activities of tyrosine hydroxylase (T‐OH). DOPA decarboxylase (DDC). dopamine‐β‐hydroxylase (DβH). monoamine oxidase (MAO), choline acetyltransferase (ChAT), acetylcholinesterase (AChE), l‐glutamic acid decarboxylase (GAD) and the concentrations of DNA and RNA were measured in 13–20 areas of post‐mortem brain tissue from neurologically and psychiatrically normal individuals. Emphasis has been put on regional distribution rather than establishing normal values and detailed comparisons have been made with previously published work on the normal human brain. Despite expressing all results relative to an internal reference point there was substantial inter‐brain variability. There was no apparent relation between age, sex, medication, cause of death or time lag between death and dissection and any of the enzyme activities. Enzyme activities were fairly evenly distributed throughout cerebral cortex whereas clear differences existed along the rostro‐caudal axis of the brain. It is hoped that this paper, with its companion paper on amine and metabolite concentrations, will be useful as a reference work for investigators of the chemical pathology of the human brain.
PURIFICATION AND CHARACTERIZATION OF AN NADP + ‐LINKED ALCOHOL OXIDO‐REDUCTASE WHICH CATALYZES THE INTERCONVERSION OF γ‐HYDROXYBUTYRATE and SUCCINIC SEMIALDEHYDE1
Authors: Kaufman Elaine E. , Nelson Thomas , Goochee Charles , Sokoloff Louis
Published: October 2006

Abstract— An NADP+ ‐linked enzyme, capable of interconverting γ‐hydroxybutyrate and succinic semialdehyde, has been isolated from hamster liver and brain. The enzyme which was isolated from liver has been purified 300‐fold and exhibits a single band by polyacrylamide gel electrophoresis. The molecular weight of the enzyme is ‐ 31,000 as estimated from gel filtration and 38,000 as estimated from sodium dodccyl sulfate gel electrophoresis. The enzyme is inhibited by amobarbital, diphenylhy‐dantoin, 2‐propylvalerate, and diethyldithiocarbamate, but not by pyrazole. The enzymes from brain and liver appear to be very similar with regard to their molecular weights and their kinetic constants for γ‐hydroxybutyrate and succinic semialdehyde.
GLUTAMATE DECARBOXYLASE ACTIVITY IN STRIATAL SLICES: CHARACTERIZATION OF THE INCREASE FOLLOWING DEPOLARIZATION1, 2
Authors: Gold Barry I. , Roth Robert H.
Published: October 2006

Abstract— The activity of glutamate decarboxylase in rat striatal slices was estimated following preincubation in either a non‐depolarizing medium or in a depolarizing medium. GAD activity was significantly increased following preincubation in normal Krebs‐Ringer‐phosphate medium as compared to activity in slices which were not preincubated. GAD activity in slices which were depolarized in high potassium Krebs‐Ringer‐phosphate medium was further increased when compared to activity in slices which were preincubated in normal medium. The depolarization‐induced increase in GAD activity was graded in response to the time of depolarization, and both the increase following preincubation in normal medium and the increase following preincubation in high potassium displayed a relative requirement for calcium. In addition, net GABA formation from endogenous glutamate was increased in slices preincubated in high potassium medium as compared to net GABA formation from endogenous glutamate in slices preincubated in non‐depolarizing medium. In support of the use of [14C]CO2 trapping as an estimate of GAD activity in slices, preincubation of slices in the presence of the GAD inhibitor glutamic acid γ‐hydrazide caused a concentration‐related inhibition of [14C]CO2 evolution.
TRYPTOPHAN TRANSPORT ACROSS THE BLOOD‐BRAIN BARRIER DURING ACUTE HEPATIC FAILURE
Authors: Mans Anke M. , Biebuyck Julien F. , Saunders Stuart J. , Kirsch Ralph E. , Hawkins Richard A.
Published: October 2006

Abstract— Tryptophan transport across the blood‐brain barrier was studied using a single injection dual isotope label technique, in the following three conditions: normal rats, rats with portacaval shunts, and rats with portacaval shunts followed 65 h later by hepatic artery ligation. In both normal rats and those with acute hepatic failure the tryptophan transport system was found to be comprised of two kinetically distinct components. One component was saturable and obeyed Michaelis‐Menten kinetics (normal: Vmax= 19.5 nmol.min−1.g−1. Km= 113 μM; hepatic failure: Vmax, = 33.8 nmol.min−1.g−1, Km= 108 μM), and the second was a high capacity system which transported tryptophan in direct proportion to concentration over the range tested (normal: K= 0.026 ml.min−1.g−1; hepatic failure: K= 0.067 ml.min−1.g−1). Since the saturable low capacity component transports several neutral amino acids, and their collective plasma concentration is high in relation to the individual Kms, tryptophan transport by this component is reduced by competitive inhibition under physiological conditions. Thus it was calculated that in normal rats approx 40% of tryptophan influx occurs via the high capacity system. During acute hepatic failure transport via both components was increased substantially, approximately doubling the rate of tryptophan penetration of the blood‐brain barrier at all concentrations tested. The contribution by the high capacity component became even more significant than in normal rats, accounting for about 75% of all tryptophan passage from plasma to brain. Brain tryptophan content was 29.9 nmol/g in normal rats and rose to 45.2 nmol/g in rats with portacaval shunts and 50.5 nmol/g in those with acute hepatic failure, correlating with the increased rate of tryptophan transport. In a previous study we found that plasma competing amino acids were greatly increased during acute hepatic failure. Calculations predict that these increased concentrations would cause a reduction in tryptophan transport by the low capacity system. However, because of the increase in the rate of transport by the high capacity component, net tryptophan entry across the blood‐brain barrier was actually increased. This increased rate of transport clearly contributes to the increased content of brain tryptophan found during hepatic failure.