bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of nuclear diagnostics for the National Ignition Facility (invited)
Authors: Glebov V. Yu. , Meyerhofer D. D. , Sangster T. C. , Stoeckl C. , Roberts S. , Barrera C. A. , Celeste J. R. , Cerjan C. J. , Dauffy L. S. , Eder D. C. , Griffith R. L. , Haan S. W. , Hammel B. A. , Hatchett S. P. , Izumi N. , Kimbrough J. R. , Koch J. A. , Landen O. L. , Lerche R. A. , MacGowan B. J. , Moran M. J. , Ng E. W. , Phillips T. W. , Song P. M. , Tommasini R. , Young B. K. , Caldwell S. E. , Grim G. P. , Evans S. C. , Mack J. M. , Sedillo T. J. , Wilke M. D. , Wilson D. C. , Young C. S. , Casey D. , Frenje J. A. , Li C. K. , Petrasso R. D. , Séguin F. H. , Bourgade J. L. , Disdier L. , Houry M. , Lantuejoul I. , Landoas O. , Chandler G. A. , Cooper G. W. , Leeper R. J. , Olson R. E. , Ruiz C. L. , Sweeney M. A. , Padalino S. P. , Horsfield C. , Davis B. A.
Published: October 2006

The National Ignition Facility (NIF) will provide up to 1.8MJ of laser energy for imploding inertial confinement fusion (ICF) targets. Ignited NIF targets are expected to produce up to 1019 DT neutrons. This will provide unprecedented opportunities and challenges for the use of nuclear diagnostics in ICF experiments. In 2005, the suite of nuclear-ignition diagnostics for the NIF was defined and they are under development through collaborative efforts at several institutions. This suite includes PROTEX and copper activation for primary yield measurements, a magnetic recoil spectrometer and carbon activation for fuel areal density, neutron time-of-flight detectors for yield and ion temperature, a gamma bang time detector, and neutron imaging systems for primary and downscattered neutrons. An overview of the conceptual design, the developmental status, and recent results of prototype tests on the OMEGA laser will be presented.
Tissue Doppler optical coherence elastography for real time strain rate and strain mapping of soft tissue
Authors: Wang Ruikang K. , Ma Zhenhe , Kirkpatrick Sean J.
Published: October 2006

The authors present a tissue Doppler optical coherence elastography (tDOCE) method to image tissue movements, strain rates, and strains of soft tissue in real time. The method exploits the Doppler effect in optical coherence interferograms induced by tissue motion and measures the phase changes between successive A scans to resolve the instantaneous tissue displacement. The tDOCE system is capable of displaying the strain rates and strain maps of tissue subjected to a dynamic compression in real time. The system is demonstrated by the use of a heterogeneous tissue phantom with known mechanical properties.
Transition of Galactosyltransferase 1 fromTrans-Golgi Cisterna to theTrans-Golgi Network Is Signal Mediated
Authors: Schaub Beat E. , Berger Bea , Berger Eric G. , Rohrer Jack
Published: October 2006

The Golgi apparatus (GA) is the organelle where complex glycan formation takes place. In addition, it is a major sorting site for proteins destined for various subcellular compartments or for secretion. Here we investigate β1,4-galactosyltransferase 1 (galT) and α2,6-sialyltransferase 1 (siaT), two trans-Golgi glycosyltransferases, with respect to their different pathways in monensin-treated cells. Upon addition of monensin galT dissociates from siaT and the GA and accumulates in swollen vesicles derived from the trans-Golgi network (TGN), as shown by colocalization with TGN46, a specific TGN marker. We analyzed various chimeric constructs of galT and siaT by confocal fluorescence microscopy and time-lapse videomicroscopy as well as Optiprep density gradient fractionation. We show that the first 13 amino acids of the cytoplasmic tail of galT are necessary for its localization to swollen vesicles induced by monensin. We also show that the monensin sensitivity resulting from the cytoplasmic tail can be conferred to siaT, which leads to the rapid accumulation of the galT–siaT chimera in swollen vesicles upon monensin treatment. On the basis of these data, we suggest that cycling between the trans-Golgi cisterna and the trans-Golgi network of galT is signal mediated.
A Eukaryotic Capsular Polysaccharide Is Synthesized Intracellularly and Secreted via Exocytosis
Authors: Yoneda Aki , Doering Tamara L.
Published: October 2006

Cryptococcus neoformans, which causes fatal infection in immunocompromised individuals, has an elaborate polysaccharide capsule surrounding its cell wall. The cryptococcal capsule is the major virulence factor of this fungal organism, but its biosynthetic pathways are virtually unknown. Extracellular polysaccharides of eukaryotes may be made at the cell membrane or within the secretory pathway. To test these possibilities for cryptococcal capsule synthesis, we generated a secretion mutant in C. neoformans by mutating a Sec4/Rab8 GTPase homolog. At a restrictive temperature, the mutant displayed reduced growth and protein secretion, and accumulated ∼100-nm vesicles in a polarized manner. These vesicles were not endocytic, as shown by their continued accumulation in the absence of polymerized actin, and could be labeled with anti-capsular antibodies as visualized by immunoelectron microscopy. These results indicate that glucuronoxylomannan, the major cryptococcal capsule polysaccharide, is trafficked within post-Golgi secretory vesicles. This strongly supports the conclusion that cryptococcal capsule is synthesized intracellularly and secreted via exocytosis.
FLUID COMPARTMENTATION AND ELECTROLYTES OF CAT CEREBRAL CORTEX IN VITRO–I SWELLING AND SOLUTE DISTRIBUTION IN MATURE CEREBRAL CORTEX*
Authors: Bourke Robert S. , Tower Donald B.
Published: October 2006

The distribution of indicator solutes (inulin, sucrose, raffinose, thiocyanate, chloride, and isethionate) and the swelling in slices of adult cat cerebral cortex incubated in vitro have been investigated for a variety of incubation media and conditions. Where appropriate, these data have been compared with analogous data obtained on cat cerebral cortex in vivo (Bourkeet al., 1965) and with data previously reported for slices of rat cerebral cortex (Pappius and Elliott, 1956; Pappiuset al., 1962) and guinea pig cerebral cortex (Varon and McIlwain, 1961; Keeseyet al., 1965) incubated in vitro under comparable conditions.

In addition to substantial agreement of present data with previously reported in vitro data, a number of new findings have been added by the present study: (a) a component of slice swelling which is K+‐dependent; (b) the association of slice swelling with presence of a diffusible, external anion (Cl−) and its prevention by replacement with a relatively non‐diffusible anion (isethionate−); (c) variation of the size of slice chloride spaces as a direct function of slice swelling; (d) dependence of the size of slice fluid spaces accessible to inulin and sucrose upon time, during incubation, of solute addition and upon K+ concentration of the incubation medium; (e) indications of the dynamic and presumably metabolically‐dependent nature of indicator solute distribution; and (f) the mobility of a portion of the fluid of swelling associated with changing the K+ concentration but not the tonicity of the medium during incubation.

At least five operationally‐defined fluid compartments may be inferred from the present data : (1) interstitial or extracellular space(s) readily accessible to all solutes and of a size which can be minimally estimated from direct determinations in viuo; (2) additional fluid space(s) accessible to most solutes, including inulin and sucrose, under apparently suboptimal conditions of slice metabolism in vitro; (3) fluid space(s) prone to swell under in vitro conditions and readily accessible in vitro to chloride and thiocyanate but not to inulin or sucrose; (4) fluid space(s) which swell reversibly in the presence of added external K+ (or Rb+) and are inaccessible to all usual indicator solutes; and (5) after exclusion of the foregoing, the remaining fluid presumably comprising most of the intracellular space(s).

The data have been discussed in terms of the morphological complexity of cerebral cortex, in terms of applicability to studies of cortical electrolyte distribution, and in terms of the general problem of delineating cerebral interstitial spaces.
THE EFFECTS OF PRECURSOR LOADING IN THE CEREBRAL METABOLISM OF 5‐HYDROXYINDOLES
Authors: Moir A. T. B. , Eccleston D.
Published: October 2006

—Using either tryptophan or 5‐hydroxytryptophan as the precursor, and examining the metabolites in whole rat brain and in brain regions of dog, the pattern of metabolites resembled that found under physiological conditions only after tryptophan administration. From these and other observations on the cerebral 5‐hydroxyindoles the main conclusions are firstly, that there are regional differences within brain in storage, turnover or metabolic fate of 5‐HT. Secondly, that the normal pathway appears to be well localized biochemically with linking of its succeeding steps, and thirdly, that turnover through the system is normally controlled by intracerebral tryptophan 5‐hydroxylase in both rats and dogs although there are differences between the species in the cerebral metabolism of 5‐HT.
THE EFFECTS OF ANOXIA UPON ENERGY SOURCES AND SELECTED METABOLIC INTERMEDIATES IN THE BRAINS OF FISH, FROG AND TURTLE1
Authors: McDougal D. B. , Holowach J. , Howe M. C. , Jones E. M. , Thomas C. A.
Published: October 2006

Abstract—

The levels of the main cerebral energy reserves, ATP, P‐creatine, glycogen and glucose, and of several glycolytic intermediates and lactate, were measured in the brains of fish (Carassius auratus), turtle (Pseudemys scripta elegans) and frog (Rana pipiens). The levels of glycogen in these brains were 2‐9 times higher than those reported for mammals. In frog, cerebral glycogen levels were 35 per cent higher during the winter than in spring. The P‐creatine: ATP ratios were 3 instead of the more usual (mammalian) value of 1. The levels of other intermediates were similar to those found in mammalian brain.

When anoxia was produced by decapitation, changes in the various substances measured were similar to those in mammalian brain, but were much slower. The initial rate at which high‐energy phosphate was used could be calculated from these changes. Values of 1.1 m‐equiv./kg/min for fish and frog and of 0.46 m‐equiv./kg/min for turtle were found, which are 1/20 and 1/50, respectively, of the rate in mouse brain. The rate of disappearance of high‐energy phosphate reserves followed first‐order kinetics for 4 hr in turtle and for at least an hour in the other species.

Changes in metabolites as the experiment progressed were interpreted to indicate a progressively falling intracellular pH, prolonged inhibition of phosphofructokinase, and a long period of hexokinase inhibition.
THE EFFECTS OF A THIAMINE ANTAGONIST, PYRITHIAMINE, ON LEVELS OF SELECTED METABOLIC INTERMEDIATES and ON ACTIVITIES OF THIAMINE‐DEPENDENT ENZYMES IN BRAIN and LIVER1
Authors: Holowach Jean , Kauffman F. , Ikossi Maria G. , Thomas Charlotte , McDougal D. B.
Published: October 2006

Abstract—

(1) The effects of thiamine deficiency as produced by pyrithiamine injections have been studied in the weanling mouse. Selected metabolites were measured in extracts from brain and liver of quick‐frozen animals. Pyruvate and α‐oxoglutarate dehydrogenases and transketolase were also measured.

(2) In deficient brain, pyruvate and α‐oxoglutarate levels were greatly increased. Xylulose‐5‐P and 6‐P‐gluconate were more than doubled. Lactate, glucose‐6‐P, glucose and P‐creatine were moderately elevated, and ATP was increased a little. Glutamate was depressed.

(3) In deficient liver, α‐oxoglutarate was much increased and ATP was twice normal. Glycogen, glucose, glucose‐6‐P, 6‐P‐gluconate, pyruvate, and glutamate were not different from the controls. Lactate was depressed.

(4) Pyruvate dehydrogenase activity was reduced to 25 per cent or less in brain and liver. Transketolase and α‐oxoglutarate dehydrogenase activities were reduced to 50 per cent in both organs.

(5) Thiamine treatment, within 5 hr, largely reversed the metabolite changes brought on by pyrithiamine in brain. At the same time pyruvate and α‐oxoglutarate dehydrogenase activities were increased 60 per cent or more in both brain and liver. Transketolase activity in liver was only increased 20 per cent at this time, however, and in brain was unchanged.

(6) The results are interpreted to indicate that inhibition of pyruvate and α‐oxoglutarate dehydrogenases in brain is sufficient to depress in vivo function. The same seems true for the inhibition of α‐oxoglutarate dehydrogenase in liver. However, the changes seen in brain 6‐P‐gluconate and xyluIose‐5‐P probably depend on factors other than, or in addition to, the decrease in transketolase activity. It seems worthy of emphasis that in spite of the partial metabolic blocks high‐energy phosphate stores were actually increased.
ASSAY AND REGIONAL DISTRIBUTION OF A SOLUBLE PROTEIN CHARACTERISTIC OF THE NERVOUS SYSTEM*
Authors: Moore B. W. , Perez V. J. , Gehring M.
Published: October 2006

Abstract An assay, based on complement fixation, was described for the S‐100 protein, a protein characteristic of the nervous system. It was found to be distributed in all parts of the nervous system both peripherally and centrally. It was not possible to deduce from the distribution the localization in cell type, but in human brain the concentration in each of twenty‐six areas was consistent from brain to brain.
GLYCOGEN, AMMONIA AND RELATED METABOLITES IN THE BRAIN DURING SEIZURES EVOKED BY METHIONINE SULPHOXIMINE1
Authors: Folbergrová Jaroslava , Passonneau Janet V. , Lowry O. H. , Schulz D. W.
Published: October 2006

Abstract— The levels of ATP, P‐creatine, glucose, glycogen, lactate, glutamate and ammonia were measured in mouse brain after administration of the convulsive agent methionine sulphoximine (MSO). No changes were observed in ATP and P‐creatine levels either before or during the seizures. Lactate levels were unchanged until the onset of seizures (4–5 hr) at which time the levels increased an average of 65 per cent. Glucose and glycogen levels increased progressively. Just before the onset of seizures the levels had increased 95 and 62 per cent, respectively. During the seizures both substances had increased a total of 130 per cent. Comparable changes were found in cerebral cortex, cerebellum and subcortical forebrain. Through the use of quantitative histochemical methods it was found that the greatest increases in glycogen occurred in layers I and III (layers II and IV were not analysed). Progressively smaller changes were found in layers V and VI and no increase at all was found in the subjacent white matter. Glucose, in contrast to glycogen, increased to about the same degree in all cerebral layers and in subjacent white matter.

The increase in glycogen after MSO administration may be related to the fact that MSO also causes an increase in the ratio of brain to serum glucose levels. This would indicate that an increase in intracellular glucose had occurred.

Ammonia levels were increased 300–400 per cent in both cerebrum and cerebellum. A time study in cerebellum showed that the increase begins early and reaches maximal levels long before the onset of seizures. Glutamate levels were reduced by small but statistically significant amounts in both cerebrum and cerebellum. Administration of methionine sulphoximine completely prevented seizures and the increase in lactate, but did not prevent the increases in glycogen and glucose. The rise in ammonia was reduced but not prevented.

During 20 sec of complete ischaemia (decapitation) ATP, P‐creatine and glucose fell somewhat more rapidly than normal in brain of animals undergoing MSO seizures. From the changes it was calculated that the metabolic rate had been increased about 20 per cent by the seizure.

A new sensitive and specific enzymic method for determination of tissue ammonia is presented together with evised enzymic procedures for lactate and glutamate.
A COMPARATIVE STUDY OF BRAIN AND LIVER MITOCHONDRIA FROM NEW‐BORN AND ADULT RATS
Authors: Gregson N. A. , Williams P. L.
Published: October 2006

Abstract—

A method has been developed for the estimation of organelle number in subcellular fractions and applied to the estimation of the mitochondrial content of brain and liver from new‐born and adult rats.

The respiratory enzyme content per mitochondrion of the adult brain was 3·5 times greater than that of the neonate. This increase in enzyme content was not correlated with an increase in the mean size of the organelle.

The succinate dehydrogenase activity per mitochondrion of the livers from neonatal and adult rats showed no obvious change. There was, however, an increase in the mean size of the organelle.

These findings are discussed with reference to the development of the brain and to the development of mitochondria.
LARGE SCALE PREPARATION OF A CRUDE MEMBRANE FRACTION FROM OX BRAIN
Authors: Rodnight R. , Weller M. , Goldfarb P. S. G.
Published: October 2006

Abstract— Two procedures are described for preparing from ox brain grey matter a subcellular fraction enriched in neuronal membranes. In the first, an angle rotor was used to fractionate the crude mitochondrial and nuclear fraction and yielded 1·3–1·4 g of membrane protein from 200 g of tissue. The second procedure employed essentially the same principle except that a zonal rotor was used to fractionate in the final stage. The two methods gave comparable results for yields of protein, Na‐K‐Mg AT Pase and succinate dehydrogenase.
PROPERTIES AND REGIONAL DISTRIBUTION OF HISTIDINE DECARBOXYLASE IN RAT BRAIN
Authors: Schwartz J. C. , Lampart C. , Rose C.
Published: October 2006

—Properties of the histamine‐forming enzyme in rat brain were studied, utilizing a sensitive fluorometric assay. The optimum pH was related to substrate concentration and found to be6·4 at 10−2m‐histidine; the apparent Km was about 4·10−4m; enzyme activity was inhibited by α‐hydrazino ‐histidine and brocresine but was not affected by α‐methyl DOPA or benzene. These different data suggest that the 'specific’histidine decarboxylase (EC 4.1.1.22)—and not the aromatic l‐aminoacid decarboxylase—is involved. Determination of enzyme activity and histamine level in different areas of the rat brain revealed important regional differences, the two values being roughly parallel.
REGIONAL DISTRIBUTION AND RATE OF PRODUCTION OF FREE FATTY ACIDS IN RAT BRAIN
Authors: Bazán N. G. , de Bazán Haydeé E. P. , Kennedy Wendy G. , Joel C. D.
Published: October 2006

Abstract— We have found the levels of free fatty acids (FFA) in rat brain to be much lower than had been previously supposed.

An unusually rapid and linear production of FFA occurred in brains of adult rats during the period from 30 s to 4 min after decapitation. Under the same conditions the production of FFA in the brain of the newborn rat or in the liver or spleen of the adult rat was much slower. The major sources of the FFA produced in the brain of the adult rat under these conditions were lipids other than triglycerides. FFA, like norepinephrine, occurred in much higher concentration in the hypothalamic region and the brain stem than in the remainder of the brain.

We have proposed a hypothesis suggesting that norepinephrine might regulate membrane‐associated processes in the central nervous system by stimulating the enzymic splitting of the polar lipids of neuronal membranes. This action of norepinephrine might be mediated by adenosine 3′,5′‐phosphate in a manner analogous to that by which norepinephrine stimulates the enzymic splitting of triglycerides in adipose tissue.

Liquid nitrogen and Freon‐12 have been compared for their respective efficacies in the rapid freezing of rat brain in situ.
THE ISOLATION OF SYNAPTOSOMES FROM THE BRAIN OF A TELEOST FISH, CENTRIOPRISTES STRIATUS
Authors: Whittaker V. P , Greengard P
Published: October 2006

Abstract— The brain of a typical teleost fish, sea bass (Centrioprisles striatus), yielded subcellular fractions similar to those previously isolated from mammalian brain upon homogenization and differential and density gradient centrifuging. In particular, a well‐defined synaptosomal fraction accounting for most of the bound acetylcholine of the tissue was obtained, although possibly because of the large amount of myelin in fish brain this and other fractions were not as homogeneous as the corresponding ones from guinea pig cerebral cortex. No difficulty was experienced in adapting the methods to the relatively small amounts of tissue (about 200 mg) obtainable from each fish. The isolation of synaptosomes in good yield indicates that teleost central presynaptic terminals have essentially the same physical properties as those of higher forms, permitting detachment and sealing under conditions of moderate liquid shear.
METABOLISM OF THE ASPARTYL MOIETY OF N‐ACETYL‐l‐ASPARTIC ACID IN THE RAT BRAIN
Authors: Nadler J. V. , Cooper J. R.
Published: October 2006

The metabolism of N‐acetyl‐l‐aspartic acid (NAA) was studied in rat brain. [Aspartyl‐U‐14C]NAA was metabolized predominantly by deacylation. Studies of NAA biosynthesis from l‐[U‐14C]aspartic acid have confirmed previous reports that NAA turns over slowly in rat brain. However, intracerebrally‐injected N‐acetyl‐l‐[U‐14C]asparticacid was rapidly metabolized. Exogenous NAA appears to be taken up rapidly into a small, metabolically‐active pool. This pool serves as substrate for a tricarboxylic acid cycle associated with the production of glutamate for the biosynthesis of glutamine. The bulk of the NAA content in brain appears to be relatively inactive metabolically.
INCORPORATION OF PHOSPHATE INTO RAT BRAIN DURING SLEEP AND WAKEFULNESS
Authors: Reich P. , Geyer Sharon J. , Steinbaum Lola , Anchors M. , Karnovsky M. L.
Published: October 2006

Abstract— Labelled inorganic phosphate (32P1) was administered intraventricularly to unrestrained sleeping and waking adult rats. After about 20 min of sleep or a comparable period of wakefulness, as monitored by EEG and EMG, the animals were frozen in liquid nitrogen and the brains were analysed. One group of animals (A) was not previously acclimatized to the apparatus. A second group (B) was acclimatized. The specific radioactivity of a phosphoprotein fraction was elevated during sleep in group A but not in group B. The specific radioactivity of the phosphatides of group B was depressed in sleeping as compared with waking animals. This effect was not observed in group A. No significant difference was detected between the EEG patterns of sleeping animals in groups A and B, as evaluated by standard criteria. These observations suggest that the physiological conditions attributable to environmental, emotional or other determinants can influence shifts in brain metabolism during the sleep‐wakefulness cycle.
COMPARATIVE STUDIES ON SYNAPTOSOMES: UPTAKE OF [N‐Me‐3H]CHOLINE BY SYNAPTOSOMES FROM SQUID OPTIC LOBES
Authors: Dowdall M. J. , Simon E. J.
Published: October 2006

Abstract— The uptake of [N‐Me‐3H]choline into synaptosomes from squid optic lobes was studied using a Millipore filtration technique. When incubated in an artificial sea water medium at 26°C, but not at 0°C, the synaptosomes rapidly accumulated choline, most of which could be recovered as unchanged free choline. The accumulated choline was readily released by treatment of the synaptosomes with Triton X‐100 or exposing them to hypo‐osmotic conditions. The influx of choline increased with increasing concentrations of choline and could be resolved into saturable and non‐saturable components. Kinetic analysis revealed the presence of two saturable components one of high affinity (Km about 2 μm) and one of lower affinity (Km 25 μm). The rate of choline uptake by these synaptosomes was considerably greater than by mammalian brain synaptosomes. Both high and low affinity systems were Na+‐requiring and inhibited by hemicholinium no. 3, levorphanol and dextrorphan. NaCN, 2,4‐dinitrophenol and ouabain also inhibited choline uptake, the high affinity system being particularly sensitive to these agents. It is suggested that the high affinity system is specific for cholinergic terminals.
THE RELATIVE SIGNIFICANCE OF CO2‐FIXING ENZYMES IN THE METABOLISM OF RAT BRAIN
Authors: Patel M. S.
Published: October 2006

To evaluate the relative significance of CO2‐fixing enzymes in the metabolism of rat brain, the subcellular distribution of pyruvate carboxylase, phosphoenolpyruvate carboxykinase, NADP‐isocitrate dehydrogenase and NADP‐malate dehydrogenase, as well as the fixation of H14CO3− by the cytosol and the mitochondria was investigated. Pyruvate carboxylase and phosphoenol‐pyruvate carboxykinase are mainly localized in the mitochondria whereas NADP‐isocitrate dehydrogenase and NADP‐malate dehydrogenase are present in both the cytosol and the mitochondria. In the presence of pyruvate rat brain mitochondria fixed H14CO3− at a rate of about 170 nmol/g of tissue/min whereas these organelles fixed negligible amounts of H14CO3− in the presence of α‐ketoglutarate or phosphoenolpyruvate. Rat brain cortex slices fixed H14CO3− at a rate of about 7 nmol/g of tissue/min and it was increased by two‐fold when pyruvate was added to the incubation medium. The carboxylation of α‐ketoglutarate and pyruvate by the reversal of the cytosolic NADP‐isocitrate dehydrogenase and NADP‐malate dehydrogenase respectively was very low as compared to that by pyruvate carboxylase. The rate of carboxylation reaction of both NADP‐isocitrate dehydrogenase and NADP‐malate dehydrogenase was only about 1/10th of that of decarboxylation reaction of the same enzyme. It is suggested that under physiological conditions these two enzymes do not play a significant role in CO2‐fixation in the brain. In rat brain cytosol, citrate is largely metabolized to α‐ketoglutarate by a sequential action of aconitate hydratase and NADP‐isocitrate dehydrogenase. The operation of the citrate‐cleavage pathway in rat brain cytosol is demonstrated. The data show that among four CO2‐fixing enzymes, pyruvate carboxylase, an anaplerotic enzyme, plays the major role in CO2‐fixation in the brain.
THE UPTAKE OF 36Cl INTO ASTROCYTES IN TISSUE CULTURE BY A POTASSIUM‐DEPENDENT, SATURABLE PROCESS
Authors: Gill T. H. , Young O. M. , Tower D. B.
Published: October 2006

Abstract— Previous suggestions that the K+‐dependent uptake of chloride by mammalian cerebral cortex is localized to cortical astrocytes has been investigated in two lines of neural cells in tissue culture. Hamster astrocytes and mouse neuroblastoma cells were each cultured on small glass cover slips in Eagle's (astrocytes) or Dulbecco's (neuroblastoma) supplemented media. At 48 h, cultures were incubated at 37°C for 1–60 min in the presence of 36Cl plus [3H]inulin (as a measure of extracellular space). In media containing approximately 140 mm chloride, the rate of uptake of 36Cl by the astrocytes was a function of the concentration of K+ (range 5–54 mm) in the medium, and the uptake was characterized by saturation kinetics and an apparent Km of 38·5 mm. The uptake was temperature and apparently energy dependent, significantly inhibited by 5 or 10 mm Br‐, I‐, SCN‐ or ClO4‐, and competitively inhibited by 10 mm acetazolamide (Ki= 27·1 mm). None of these characteristics were observed with neuroblastoma cultures studied under similar conditions. In chloride‐free media, the cellular K/Na ratio of the astrocytes shifted from the usual value of 4·55 to a value of 0·29, the culture medium became more alkaline than normal, and the cells spontaneously sloughed from the cover slips but remained normally viable. Our observations are the first to provide direct support for previous suggestions that there is a mediated, K+‐dependent coupled cation, chloride and fluid uptake by mammalian cerebrocortical glia and that this uptake is an enzymatically catalysed process. The observations have been discussed in terms of a presumed central role for astrocytes in modulating the external ionic milieu of the neurons they surround and in terms of implications for epilepsy, stroke and cortical edema.
COMPARTMENTATION OF AMINO ACID METABOLISM IN THE RAT POSTERIOR PITUITARY
Authors: Minchin M. C. W. , Beart P. M.
Published: October 2006

—Isolated rat posterior pituitary glands were incubated with [14C]glucose or [14C]acetate and the incorporation of radioactivity into several amino acids was followed. The results indicated that radioactivity was incorporated from [14C]glucose into a large pool of glutamate which appeared to be responsible for a large proportion of GABA synthesis in the gland. The specific activity of glutamine was always less than that of glutamate when [14C]glucose was the precursor employed, whereas [14C]acetate labelled a glutamate pool which had approximately the same specific activity as that of glutamine. The results are discussed with reference to the compartmentation of amino acid metabolism in the nervous system.
THE BINDING OF TRIETHYLTIN TO RAT BRAIN MYELIN
Authors: Lock E. A. , Aldridge W. N.
Published: October 2006

—A high affinity binding site for triethyltin was found in rat brain myelin with an affinity of approx 6·6 × 105m−1 at pH 7·5. Competitive binding studies showed that triethyl‐lcad had about the same affinity and trimethyltin 30 times lower affinity than triethyltin. Hexachlorophane and 3,5‐diiodo‐4′‐chlorosalicylanilide did not prevent triethyltin binding to rat brain myelin. Since triethyltin, hexachlorophane and 3,5‐diiodo‐4′‐chlorosalicylanilide all produce similar oedematous lesions in the brain of rats, whereas triethyl‐lead and trimethyltin do not, it is concluded that the high affinity triethyltin binding site either is not involved or is not the only factor in oedema production.
THE EFFECT OF HCO3− ON THE SWELLING AND ION UPTAKE OF MONKEY CEREBRAL CORTEX UNDER CONDITIONS OF RAISED EXTRACELLULAR POTASSIUM
Authors: Bourke R. S. , Kimelberg H. K. , West C. R. , Bremer A. M.
Published: October 2006

Abstract— Increasing the HCO3− concentration of incubation media containing raised K+ concentrations (18‐71 mm) caused increased swelling of monkey cerebral cortex slices. This swelling was mainly associated with increased intracellular levels of Na+ and Cl− ions. It was independent of the type of buffer used and was not a result of the increased Na+ concentration in the media due to added HCO3− or the increased osmolarity. The levels also were unaffected by alteration of the pH in the range of 6·9‐ 7·8 or pCO2 in the range of 3–81 mm Hg.

The anatomical locus of this HCO3− stimulated swelling appeared in electron micrographs to be an expanded glial compartment. The significance of these findings is discussed in terms of the transport processes involved and the role of glial cells in maintaining correct cerebro‐cortical ion balances under normal and pathological conditions.
HIGH AFFINITY CHOLINE UPTAKE: IONIC AND ENERGY REQUIREMENTS
Authors: Simon J. R. , Kuhar M. J.
Published: October 2006

Abstract— High affinity choline uptake into rat hippocampal synaptosomes was examined at 37°C when various ions were deleted from normal Kreb's‐Ringer media. When sodium chloride was replaced by sucrose, lithium chloride, cesium chloride or rubidium chloride, choline uptake was markedly reduced. When the sodium concentrations of the Kreb's media were gradually reduced to zero, the uptake was gradually reduced in parallel. A kinetic analysis performed at low and normal sodium concentrations revealed changes in Km and Vmax values.

When several non‐chloride sodium salts were utilized, the uptake was reduced in all cases suggesting also a chloride‐dependence in addition to the sodium‐dependence. Omission of calcium chloride or magnesium sulfate from the media did not alter uptake.

Sodium‐dependent choline uptake was examined over a range of potassium concentrations (0–35 DIM). It was found that uptake was maximal between potassium concentrations of 0.35–4.8 mm but was reduced at both lower and higher potassium concentrations. The kinetics of uptake were examined under varying potassium concentrations, and at low potassium, only a change in Vmax was observed while at high potassium concentrations, there were changes in both Km and Vmax values.

Preincubation and incubation of synaptosomes with 0.1 m‐ouabain, 0.1 mm‐2,4‐dinitrophenol and 1 mm‐KCN caused a reduction in sodium‐dependent uptake. When dextrose was omitted from the preincubation and incubation media there was also a reduction in sodium‐dependent uptake. By contrast, the sodium‐independent uptake was unaffected by the metabolic inhibitors or omission of dextrose, and had a very low Q10. When various incubation temperatures were utilized in uptake experiments, the Q10 for the interval 37‐27°C was 2.7 and the activation energy was 22.7 kcal/mol.

Slightly different ionic dependences were observed when animals pretreated with pentobarbital of oentylenetetrazol were utilized as the source of synaptosomes.
MOUSE NEUROBLASTOMA CELL ADENYLATE CYCLASE: REGULATION BY 2‐CHLOROADENOSINE, PROSTAGLANDIN E1 AND THE CATIONS Mg2+, Ca2+ AND Mn
Authors: Blume A. J. , Foster Carolyn J.
Published: October 2006

—Some basic kinetic properties of adenylate cyclase in cell free preparations of mouse neuroblastoma were investigated. Production of cAMP from ATP by the enzyme requires the presence of either Mg2+ or Mn2+ in addition to ATP. In the presence of Mg2+, the Km for ATP is 120 ± 15 μM and the interaction of ATP and adenylate cyclase appears to be non‐cooperative (Hill coefficient of 1). Magnesium ion concentrations in excess of the ATP concentration cause stimulation although similar excess concentrations of Mn2+ cause inhibition.

Prostaglandin E1 and 2‐chloroadenosine activate the enzyme. The Km of the cyclase for 2‐chloroadenosine is 6 μm. Activation by 2‐chloroadenosine leads to an increase in Vmax but does not effect the Km for ATP. At a fixed ATP concentration, the extent of activation caused by prostaglandin E1 and 2‐chloroadenosine is inversely related to the Mg2+ concentration.

Calcium ion causes inhibition of adenylate cyclase from 0.1 to 4mM with a Ki of 5 ± 10−4m. Ca2+ interaction with the enzyme in the absence or presence of either 2‐chloroadenosine or prostaglandin E1 appears cooperative (i.e. Hill coefficients of ˜2). Ca2+ inhibition is non‐competitive with respect to either ATP or 2‐chloroadenosine but is progressively diminished by increasing Mn2+ concentrations.

Divalent cation effects and activation by 2‐chloroadenosine and prostaglandin E1 of the neuroblastoma adenylate cyclase are compared with ion effects and hormone activation of the enzyme obtained from non‐neuronal tissue.
UPTAKE AND METABOLISM OF GLUTAMATE IN ASTROCYTES CULTURED FROM DISSOCIATED MOUSE BRAIN HEMISPHERES
Authors: Schousboe A. , Svenneby G. , Hertz L.
Published: October 2006

Abstract— Uptake kinetics of l‐glutamate in cultured, normal glia cells obtained from the brain hemispheres of newborn mice were measured together with the activities of the glutamate metabolizing enzymes, glutamic‐oxaloacetate‐transaminase, glutamate dehydrogenase and glutamine synthetase. During 3 weeks of culturing, the activities of the enzymes rose from low neonatal values toward the levels in the adult brain (206, 12.3 and 25.9 nmol. min−1. mg−1 cell protein for the three enzymes, respectively). The uptake kinetics indicated an unsaturable component together with an uptake following Michaelis‐Menten kinetics with a Km of 220 μm and a Vmax of 7.9 nmol. min−1. mg−1 cell protein. The saturable glutamate uptake was inhibited by d‐glutamate, l‐aspartate and α‐aminoadipate whereas l‐glutamine, GABA and glutarate had no effect. The uptake which was Ca2+‐independent had a Km for sodium of 18mm and it was stimulated by an increase in the external potassium concentration from 5 to 10 and 25 mm. The results suggest that glia cells are important for the uptake of glutamate from synaptic clefts and for the subsequent metabolism of glutamate.
THE APPEARANCE OF REGIONAL VARIATIONS IN METABOLISM AT A CRITICAL LEVEL OF DIFFUSE CEREBRAL OLIGEMIA
Authors: Welsh F. A. , Durity F. , Langfitt T. W.
Published: October 2006

Abstract—

Increased intracranial pressure was used to produce graded cerebral oligemia in the rabbit. When cerebral perfusion pressure (CPP) was 40 Torr or above, oligemia was not severe enough to cause a decrease in ATP. When CPP was 20 Torr or below, a rapid depletion of ATP occurred. When CPP equalled 30 Torr, animals were distributed at the two extremes, with pronounced diminution of ATP correlating with loss of electrical activity and with increased NADH tissue fluorescence. In addition this critical stage of oligemia was marked by the appearance of regional variations in metabolism. Furthermore, ischemic regions could be visualized in sections of frozen brain by virtue of increased NADH fluorescence.
THE EFFECT OF ISCHAEMIA AND RECIRCULATION ON PROTEIN SYNTHESIS IN THE RAT BRAIN
Authors: Cooper Helen K. , Zalewska Teresa , Kawakami S. , Hossmann K.‐A. , Kleihues P.
Published: October 2006

Abstract— Rats were subjected to cerebral compression ischaemia for 15min and were subsequently recirculated with blood for periods up to 3 h. In vivo incorporation of intravenously administered L‐[1–14C]valine into total brain proteins was found to be severely inhibited (about 20% of controls) after 45 min of recirculation. After 3 h, protein synthesis had increased, the specific radioactivity of proteins then being about 40% of controls. The post‐ischaemic inhibition of protein synthesis was accompanied by a breakdown in polyribosomes and a concomitant increase in ribosomal subunits. In vitro incorporation of L‐[1–14C]phenylalanine by a postmitochondrial supernatant system derived from animals subjected to 15 min ischaemia and 15 min recirculation was also severely reduced and showed, in contrast to control animals, no response to the addition of a specific inhibitor of polypeptide chain initiation (Poly(I)). Together with the in vivo accumulation of ribosomal subunits this indicates a block in peptide chain initiation during the early stages of recirculation.

Polyribosomes from animals subjected to 15 min ischaemia without recirculation showed a normal rate of in vitro protein synthesis which was inhibited by Poly(I) to a similar extent as polyribosomes from control animals. These results suggest that the post‐ischaemic inhibition in chain initiation develops during the early stages of recirculation rather than during the ischaemic period itself.
γ‐VINYL GABA (4‐amino‐hex‐5‐enoic acid), A NEW SELECTIVE IRREVERSIBLE INHIBITOR OF GABA‐T: EFFECTS ON BRAIN GABA METABOLISM IN MICE1
Authors: Jung M. J. , Lippert B. , Metcalf B. W. , Böhlen P. , Schechter P. J.
Published: October 2006

Abstract— γ‐Vinyl GABA (4‐amino‐hex‐5‐enoic acid, RMI 71754) is a catalytic inhibitor of GABA‐T in vitro. When given by a peripheral route to mice, it crosses the blood‐brain barrier and induces a long‐lasting, dose‐dependent, irreversible inhibition of brain GABA transaminase (GABA‐T). Glutamate decarboxylase (GAD) is only slightly affected even at the highest doses used. γ ‐Vinyl GABA has little or no effect on brain succinate semialdehyde dehydrogenase, aspartate transaminase and alanine transaminase activities. GABA‐T inhibition is accompanied by a sustained dose‐dependent increase of brain GABA concentration. From the rate of accumulation of GABA it was estimated that GABA turnover in brain was at least 6.5 μmol/g/h. Based on recovery of enzyme activity the half‐life of GABA‐T was found to be 3.4 days, that of GAD was estimated to be about 2.4 days. γ ‐Vinyl GABA should be valuable for manipulations of brain GABA metabolism.
CEREBRAL METABOLIC AND VASCULAR EFFECTS OF BARBITURATE THERAPY FOLLOWING COMPLETE GLOBAL ISCHEMIA
Authors: Steen P. A. , Milde J. H. , Michenfelder J. D.
Published: October 2006

Complete global cerebral ischemia was induced in dogs by temporary ligation of the ascending aorta for 10min. Prior to the ischemic period, half of the animals were given pentobarbital 30‐38 mg/kg, a maneuver previously reported to prevent or attenuate cerebral damage in this same model. Cerebral blood flow (CBF) and cerebral metabolic rate (CMRO2) were followed from prior to the ischemic period to 6 h post‐ischemia. At varying time intervals following ischemia, brain biopsies were obtained and analyzed for cerebral metabolites to determine the cerebral energy state. Only a few differences were observed between pentobarbital‐treated and untreated animals. Post‐ischemic CMRO2, stabilized at a significantly lower level in treated than in untreated animals. However, CBF was proportionately lower and thus O2 delivery relative to O2 needs in the two groups was comparable. Also in both groups, the CBF and CMRO2 stabilized at levels significantly below pre‐ischemia controls. Cerebral energy stores in both groups were depleted after 10min of ischemia but were restored to near normal within 4min post‐ischemia. Total restoration of the adenine nucleotide pool and ATP were delayed as was the return of brain lactate to normal. A 10min period of post‐ischemic hyperemia was observed in all animals and in the initial 4min post‐ischemia CMRO2 was also increased. The latter is probably accounted for by the O2 needs for restoration of cerebral energy and O2 stores. We conclude that cerebral protection as provided by barbiturates following complete global ischemia cannot be accounted for by any measurable effect on CBF, CMRO2, or the cerebral energy stores during the initial 6 h post‐ischemia.
LYSINE METABOLISM IN THE RAT BRAIN: THE PIPECOLIC ACID‐FORMING PATHWAY
Authors: Chang Yung‐Feng
Published: October 2006

Abstract—

Employing both the intraventricular and intraperitoneal injection techniques, 14C‐l‐lysine at non‐overloading concentrations was found to be metabolized to l‐14C‐pipecolic acid at significantly high levels in the rat. Labeled pipecolic acid in the brain and liver was only found at rather low levels 24 h after intraperitoneal administration of 14C‐l‐lysine regardless of non‐labeled lysine metabolite overload. A marked enhancement of pipecolic acid labeling was only found in the brain when 14C‐l‐lysine was intraventricularly administered to animals under various lysine metabolite overloads. While overloading doses of non‐labeled saccharopine or α‐aminoadipate did not significantly alter the labeling patterns of pipecolic acid in the brain, liver or urine when 14C‐l‐lysine was intraperitoneally administered, pipecolate overloading markedly reduced labeled pipecolic acid levels in the brain, liver and urine. These results indicate: pipecolic acid formation is subject to product inhibition, and saccharopine is not in the pathway of pipecolic acid synthesis from l‐lysine. The labeling pattern of lysine metabolites was not significantly affected by the overloading injection of pipecolic acid when 14C‐l‐lysine was intraventricularly administered suggesting a blood‐brain barrier for pipecolate. Besides 14C‐pipecolic acid, labeled α‐aminoadipic acid was also found at significant levels mostly in the brain. Labeled saccharopine was not detected in any tissues or urine samples analyzed. The 14C‐l‐lysine metabolic pattern of the newborn rats did not seem to be any different from the adult rats, i.e. labeled pipecolic acid was also detected in substantial quantities in the brain, liver and urine 5 h after injection. 14C‐d‐Lysine was mainly metabolized to l‐14C‐pipecolic acid through either route of administration. These experimental evidences indicate that the pipecolic acid‐forming pathway is a significant route for lysine metabolism in the rat, and that the rat brain probably utilizes this pathway mainly for lysine metabolism. The present study also discusses the potential neurological significance of the pipecolic acid pathway in relation to the major lysine metabolic pathway (the saccharopine pathway).
EFFECTS OF OSMOLAR CHANGES ON ISOLATED MITOCHONDRIA OF BRAIN AND LIVER
Authors: Holtzman D. , Lewiston N. , Herman M. M. , Desautel M. , Brewer E. , Robin E.
Published: October 2006

Abstract— The effects of altered osmolarity on respiration and fine structure were compared in isolated rat cerebral versus liver mitochondria.

Polarographic study of cerebral mitochondria in hypo‐osmolar media showed inhibition of State 3 (ADP‐dependent) respiration which was not reversed by dinitrophenol. In hyperosmolar media, State 3 respiration was transiently inhibited and State 4 (ADP‐independent) respiration increased with the NAD‐linked substrate pair, glutamate and malate. With succinate as substrate, respiration was not affected by moderate hyperosmolarity. In the most hyperosmolar medium, State 3 respiration was inhibited with both substrates.

In contrast to the results with cerebral mitochondria, State 4 respiration was increased in hypo‐osmolar media and State 3 respiration was persistently inhibited in hyperosmolar media in liver mitochondria with both substrates.

In both cerebral and liver mitochondria, cytochrome c oxidase (EC 1.9.3.1.) activity was mildly inhibited in hypo‐osmolar media and increased in hyperosmolar media.

Electron microscopy showed that liver mitochondria were swollen in hypo‐osmolar media and condensed in hyperosmolar media. Cerebral mitochondria showed mild rarefaction in hypo‐osmolar media and, in hyperosmolar media, more than half the mitochondria showed either no or minimal changes in fine structure.

Our results suggest that there are differences in metabolic control and structure between mitochondria from different cell types, which may be important in the cellular metabolic response to pathologic changes in water or osmolarity.
UNILATERAL BRAIN INJURY IN THE RABBIT; REVERSIBLE AND IRREVERSIBLE DAMAGE OF THE MEMBRANAL ATPases
Authors: Rigoulet M. , Guerin B. , Cohadon F. , Vandendreissche M.
Published: October 2006

Abstract—

Modifications of some membranal enzymatic activities in rabbit brain edema induced by cold injury were studied. The edema was characterized by the tissue H2O content and the K+/Na+ ratio. Comparison of the respiratory rate of isolated mitochondria in the state 3 and 4 and the ADP/O ratio suggested an alteration in the ATP synthesis mechanism. The oligomycin sensitive ATPase activity was severely reduced in mitochondria isolated from edematous cells.

The alteration of the ouabain sensitive Na+‐K+‐ATPase was first qualitative in the sense where the response of the ATPase to the K+/Na+ ratio was modified. A loss of the total activity was then observed. Intravenous injection of CDP choline induced a regression of the edema, a restoration of the sensitivity of the mitochondrial ATPase towards oligomycin and a restoration of the sensitivity of the Na+‐K+‐ATPase to the K+/Na+ ratio. These results suggest that the reversible damages of the cells induced by cold injury were due to a disorder at the protein‐lipid interaction level.
MANGANESE‐INDUCED BEHAVIORAL DYSFUNCTION AND ITS NEUROCHEMICAL MECHANISM IN GROWING MICE
Authors: Chandra Satya V. , Shukla Girja S. , Saxena D. K.
Published: October 2006

Abstract— Suckling mice were exposed to manganese from birth indirectly through their mothers and then directly through drinking water after weaning. The growth and development of these mice and their age‐matched controls were almost identical. Motor activity of offspring measured at 30‐day intervals showed a significant increase at 60 and 90 days in manganese‐treated mice compared to controls. Increased motor activity was associated with significant elevation in the levels of dopamine and norepinephrine in the corpus striatum of treated mice. The levels of striatal tyrosine, homovanillic acid and manganese were also significantly increased in mice after manganese exposure. Thus an animal model of early manganese poisoning has been developed with a possible role of striatal amines in the production of behavioral dysfunction in the treated mice. Implications of these findings are discussed in relation to the manifestations of the psychiatric phase of early manganese poisoning in man.