bluuebunny/crossref_metadata_2025_split huggingface dataset:
SYNTHETIC AMINO ACIDS AND THE NATURE OF l‐DOPA TRANSPORT AT THE BLOOD‐BRAIN BARRIER
Authors: Wade L. A. , Katzman R. 
Published: October 2006

Abstract—The blood‐brain barrier transport of amino acids has been measured using the carotid injection technique in the rat. The synthetic amino acids, 2‐aminobicyclo(2,2,1)heptane‐2‐carboxylic acid (BCH) and α‐(methylamino)isobutyric acid (MeAIB), were model substrates in the Ehrlich cell for the leucine (L) and alanine (A) neutral amino acid transport mechanisms, respectively. The uptake (±)b‐[carboxyl‐14C]BCH at the same rate for the five brain regions tested suggested a similarity between regions for the L transport mechanism. At injectant concentrations of 0·1 mm (similar to naturally occurring aromatic neutral amino acids), BCH was mainly taken up by a saturable mediated transport mechanism (K1, 0·16 mm and Vmax, 0·03/μmol/g per min). At higher concentrations, uptake by a nonsaturable or diffusional mechanism could be demonstrated. When BCH was added as a second amino acid to l‐[3‐14C]DOPA, the saturable component of l‐DOPA transport was significantly inhibited. MeAIB had no measurable effect on the rate of l‐DOPA transport. These results suggested that the mediated transport mechanism for l‐DOPA at the cerebral capillaries is similar to the l‐neutral amino acid transport system.
ARE MYELIN PROTEINS SYNTHESIZED IN RETINAL GANGLION CELLS?1
Authors: Prensky A. L. , Fujimoto Karen , Agrawal H. C. 
Published: October 2006

Abstract—We studied the incorporation of radioactivity into individual proteins of myelin by sodium dodecyl sulfate polyacrylamide gel electrophoresis after the injection of [3H]tryptophan into the right eye of developing rabbits. We found that the specific activity of basic protein (c.p.m./mg of basic protein) and the specific activity of DM‐20 and proteolipid protein (c.p.m./mg total myelin protein applied to the gel) did not approach the ratio predicted by decussation of the fibres of the rabbit optic nerve. The specific activity of Wolfgram protein, however, approached an expected ratio of 15:1. We therefore concluded that myelin basic protein, DM‐20 and proteolipid protein were probably not synthesized in retinal ganglion cells.
INTERRELATIONS BETWEEN POLYAMINES AND NUCLEIC ACIDS: CHANGES OF POLYAMINE AND NUCLEIC ACID CONCENTRATIONS IN THE DEVELOPING RAT BRAIN
Authors: Seiler N. , Lamberty Ursula 
Published: October 2006

Abstract—The rat brain concentrations of protein, RNA, DNA, putrescine, and of the polyamines spermidine and spermine, were studied during development. Putrescine formation is apparently controlled by ornithine decarboxylase. Spermidine and spermine concentrations change in inverse directions to their anabolic enzymes. It has been presumed, therefore, that the low concentrations of the polyamine‐synthesizing enzymes in immature brain are compensated for, by high putrescine and S‐adenosylmethionine concentrations.In agreement with previous findings for fish brain, the changes in RNA and spermidine concentrations were most closely correlated. The functions of DNA: spermine are directly correlated only during the periods of brain maturation, after cell proliferation has nearly ceased.
COMPARATIVE STUDIES ON THE MEMBRANE ACTIONS OF DEPRESSANT DRUGS: THE ROLE OF LIPOPHILICITY IN INHIBITION OF BRAIN SODIUM AND POTASSIUM‐STIMULATED ATPase1
Authors: Roufogalis B. D. 
Published: October 2006

Abstract—Depressant drugs are considered to exert their pharmacological effects as a result of membrane interactions determined by their physico‐chemical properties. In this study, a correlation was found between lipid solubility and potency of various local anaesthetics, antihistamines, tricyclic antidepressants and phenothiazine tranquilizers as inhibitors of the Na, K‐ATPase activity of a microsomal membrane fraction from bovine brain cortex. Depressant drugs such as chlorpromazine, which have the greatest lipid solubilities, were competitive inhibitors of Na activation but noncompetitive toward K activation, whereas drugs such as tetracaine with lower lipid solubilities were competitive inhibitors of K activation but noncompetitive toward Na activation. Drugs with intermediate lipid solubilities were mixed competitive‐noncompetitive inhibitors of both Na and K activation. Both chlorpromazine and tetracaine competitively inhibited cation activation by a heterotropic allosteric mechanism, probably mediated through membrane conformational changes. Whereas quaternization or a decrease in the incubation pH interfered with the ability of chlorpromazine to inhibit Na activation in a competitive fashion, these changes did not affect the ability of tetracaine to compete with K activation. In addition Mn, Ca and phosphatidyl serine were very effective non‐competitive antagonists of chlorpromazine inhibition of Na, K‐ATPase, whereas these agents competitively antagonized tetracaine inhibition to a lesser extent. These data suggest that the more lipid soluble phenothiazines penetrate into and react in hydrophobic areas of the membrane microenvironment, resulting in a membrane perturbation which interferes with Na activation. On the other hand the less lipid soluble local anaesthetics probably act at superficial sites near the membrane surface, resulting in a different membrane perturbation which interferes with the K activation mechanism. It is suggested that lipid solubility may be a significant factor in determining selectivity in the membrane interactions of various pharmacological agents and hence differences in pharmacological activity among different classes of depressant drugs.
RATE OF STEROL FORMATION BY RAT BRAIN GLIA AND NEURONS IN VITRO AND IN VIVO
Authors: Jones J. P. , Nicholas H. J. , Ramsey R. B. 
Published: October 2006

Abstract—The ability of 11‐day‐old rat glial and neuronal cells to biosynthesize sterol was studied as a function of time in vivo and in vitro. The in vitro experiments utilized [2‐14C]mevalonic acid as precursor. Glial‐enriched cell preparations demonstrated a greater ability to incorporate [2‐14C]mevalonic acid into isoprenoid material than did neuronal‐enriched preparations. Approximately 4 h were required for maximal uptake of labelled mevalonate by the glial preparations. Further metabolism of the isoprenoid material, involving squalene turnover and sterol demethylation, was still evident even after 15 h of incubation. In vivo, sterol biosynthesis was studied by intraperitoneal injection of sodium [2‐14C]acetate and [U‐14C]glucose, sacrifice of the animals at 2 or 24 h, subsequent isolation of glial‐ and neuronal‐cell enriched fractions and analysis of labelled isoprenoid material. Glial‐enriched fractions again contained the bulk of the labelled isoprenoid material.
EVIDENCE FOR REVERSIBLE INHIBITION OF BRAIN DOPAMINE‐β‐HYDROXYLASE ACTIVITY IN VIVO BY AMPHETAMINE ANALOGUES1
Authors: Stolk J. M. 
Published: October 2006

Abstract—Rats treated with d‐amphctamine have a decreased ability to convert intracisternally injected radioactive dopamine to noradrenaline. This effect is dose‐related and reversible by increasing the dose of injected dopamine. L‐Amphetamine is equipotent to the d‐isomer, but para‐hydroxyamphetamine reduces noradrenaline formation only slightly. Like the amphetamines, imipramine produces significant inhibition of noradrenaline from labelled dopamine; however, dopamine content after imipramine, but not after the amphetamines, was consistently decreased, suggesting that imipramine's effect on conversion of labelled dopamine to noradrenaline is mediated by interference with membranal transport systems. Conversion of labelled tyrosine to noradrenaline increases after imipramine. In contrast, noradrenaline accumulating from labelled tyrosine is decreased by d‐ or l‐amphetamine. The divergent effects of the amphetamines and imipramine on noradrenaline accumulation from labelled tyrosine suggest that the amphetamines' effect on in vivo dopamine‐β‐hydroxylase activity are not solely attributable to interference with transport and, therefore, suggest a direct effect on the enzyme.
ACTIVITY OF ALDEHYDE DEHYDROGENASE, ALDEHYDE REDUCTASE, AND ACETYLCHOLINE ESTERASE IN STRITATUM OF RATS BEARING ELECTROLYTIC LESIONS OF THE MEDIAL FOREBRAIN BUNDLE
Authors: Duncan R. J. S. , Sourkes T. L. , Dubrovsky B. O. , Quik Maryka 
Published: October 2006

Abstract—A number of enzymes have been measured in the striatum of rats in which the dopamine‐containing nerve terminals had been unilaterally destroyed by means of unipolar electrolytic lesions of the medial fore‐brain bundle. Fourteen and 28 days after such lesions the tyrosine hydroxylase activity of the striatum was reduced to immeasurably low values, but neither aldehyde dehydrogenase, aldehyde reductase, nor acetylcholine esterase was affected when compared with the striatum from the intact side of the same rat or with those from control rats. These results indicate that in the rat the 3 enzymes are not localized with tyrosine hydroxylase, in the dopaminergic nerve terminals of the striatum. This conclusion is supported by a study of the subcellular localization of aldehyde dehydrogenase in rat brain. This enzyme is distributed between the cytosol and the particulate fraction of brain homogenates separated by centrifugal techniques. with no exceptionally high concentration of the enzyme in the synaptosomal fraction. Because neither of the enzymes of post‐deaminative catabolism of dopamine is concentrated in the dopaminergic nerve terminals of the striatum of the rat, it is proposed that in this species the amine is not necessarily taken up by the nerve terminals prior to catabolism.
THE PENETRATION OF THE MEMBRANE OF BRAIN MITOCHONDRIA BY ANIONS
Authors: Minn A. , Gayet J. , Delorme P. 
Published: October 2006

Abstract—The permeability of the membrane of rat brain non‐synaptosomal mitochondria, towards inorganic and substrate anions, was assessed by measuring the rate of swelling that occurred when mitochondria were suspended in an iso‐osmotic solution of a permeant anion, in the presence of a permeant cation such as NH+4 or K+ in the presence or absence of valinomycin. In NH+4‐phosphate swelling was higher than it was in KCI or K+‐phosphate, which showed the prevalence of the mechanism of phosphate transport previously demonstrated in liver mitochondria. The entry of succinate and L‐malate seemed to require the presence in the inner mitochondrial membrane of specific carriers. as previously postulated for liver mitochondria, but the rate of swelling of brain mitochondria was lower than that of liver organelles. In K+‐succinate, in the presence of antimycin, added ATP induced swelling and this was attributable to the simultaneous permeation both of the anion and the cation. Fumarate did not penetrate into brain mitochondria. Practically no swelling was recorded in NH+4 or K+‐citrate, which indicated that this anion penetrated poorly into the isolated brain mitochondria even in the presence of malate. Swelling occurred in NH+4‐L‐glutamate in the presence of rotenone, and the entry of this anion seemed to follow a gradient of concentration although the presence of a specific translocator in the inner mitochondrial membrane might be concerned. The entry of glutamate was independent of that of phosphate and N‐ethylmaleimide appeared to be a specific inhibitor of this entry. Swelling in K+‐L‐glutamate, in the presence of rotenone, was enhanced by the addition of valinomycin or ATP but in the latter case when osmotic equilibrium was reached swelling was not reversed by oligomycin. In conclusion, the lesser extent of swelling of isolated brain mitochondria compared with liver mitochondria could be attributed to the heterogeneity of the populations of these organelles, each population possessing its own characteristics of membrane permeability. Observations of electron micrographs of brain mitochondria incubated in iso‐osmotic substrate anions confirmed the heterogeneous rate of swelling of these particles.
FACTORS INFLUENCING BRAIN AND TISSUE LEVELS OF TRYPTAMINE: SPECIES, DRUGS AND LESIONS
Authors: Sloan J. W. , Martin W. R. , Clements T. H. , Buchwald W. F. , Bridges S. R. 
Published: October 2006

Abstract—With a modification of the spectrophotofluorometric (SPF) method of HESS & UDENFRIEND (1959) (J. Pharmac. exp. Ther.127, 175‐177), brain tryptamine levels in the rat (20.9 ng/g) and guinea‐pig (20.7 ng/g) were found to be less than those in the dog (32.1 ng/g) and cat (52.2 ng/g). Regional distribution studies in the dog and cat showed that tryptamine was present in all major brain regions with highest concentrations in the spinal cord. Blood levels of tryptamine in the guinea‐pig, dog and cat (6‐7 ng/ml) were lower than brain levels. Pargyline significantly increased brain tryptamine in both the dog and cat; whereas, isocarboxazid (after 4 h) increased brain tryptamine levels in the dog but decreased brain levels in the cat. Reserpine (0.5‐1.0 mg/kg per day for 1‐4 days) did not significantly decrease brain, spinal cord or blood tryptamine levels in the dog. Spinal cord transection did not decrease tryptamine levels below the lesion in the chronic spinal dog.
FACTORS INFLUENCING THE EFFLUX OF [3H]GAMMAAMINOBUTYRIC ACID FROM SATELLITE GLIAL CELLS IN RAT SENSORY GANGLIA
Authors: Minchin M. C. W. 
Published: October 2006

Abstract—The spontaneous efflux of [3H]GABA from the satellite glial cells of rat dorsal root ganglia and the efflux evoked by 64 mM‐K+ were studied in the presence of 10‐5M‐amino‐oxyacetic acid and found not to be affected by 10‐4M‐D 600 or by elevated (9.6mM) Ca2+ in the absence of Mg2+. [3H]GABA efflux was increased by replacing sodium ions in the washing medium by choline ions and 64 mM‐K+ failed to increase the efflux further. The drugs veratridine (10‐6 and 10‐4M) and batrachotoxin (10‐8 and 10‐6 M) failed to alter the spontaneous efflux of [3H]GABA from the glial cells.A variety of compounds, including amino acids, a GABA analogue and a GABA antagonist were tested for their ability to affect [3H]GABA efflux. The results indicated that compounds which inhibit GABA uptake into glial cells were also able to stimulate [3H]GABA efflux from these cells.The results are discussed with reference to possible mechanisms involved in the release of GABA from glial cells.
RELEASE OF RADIOACTIVE GLUTAMIC ACID FROM THIN SECTIONS OF GUINEA‐PIG OLFACTORY CORTEX IN VITRO
Authors: Matsui S. , Yamamoto C. 
Published: October 2006

Abstract—Slices from the guinea‐pig olfactory cortex were incubated in the medium containing [14C]glutamate and release of radioactive compounds was subsequently studied in the standard or high potassium media or during repetitive stimulation of the lateral olfactory tract (LOT) while electrical activity of the tissue was monitored. In 50 mm‐potassium concentration, the pre‐ and postsynaptic potentials were completely suppressed and effluxes of total 14C and [14C]glutamate increased. No significant increase in [14C]glutamine was found. When Ca2+ concentration was reduced from 2·4 to 0·12 mm, the postsynaptic potential disappeared and release of [14C]glutamate in 50 mm‐potassium decreased to about a third of that in 2·4 mm‐Ca2+. Repetitive LOT stimulation enhanced release of total 14C in thinner slices but caused no significant increase in [14C]glutamate efflux. These findings were discussed in relation to the possibility that glutamate is a mediator between the LOT fibres and cortical neurons.
ISOLATION AND PARTIAL CHARACTERIZATION OF FRACTIONS ENRICHED IN SYNAPTOSOMES FROM CHICK BRAIN
Authors: Oestreicher A. B. , van Leeuwen C. 
Published: October 2006

Abstract—–From a pool of hemispheres, optic lobes and cerebellum of chick 3 fractions containing synaptosomes have been prepared. They were obtained by subcellular fractionation of a homogenate and centrifugation of a crude mitochondrial suspension on a discontinuous Ficoll density gradient in iso‐osmoticsucrose. The synaptosomal fractions were isolated from bands at the interface of 5–9, 9–12 and 12–16% Ficoll. The characterization of these fractions by marker enzymes, such as lactate dehydrogenase, acetyl‐cholinesterase, monoamine oxidase, acid phosphatase and rotenone‐sensitive and ‐insensitive NADH: cytochrome c reductase is reported. Electron microscopic analyses showed that the first fraction (AB) at the 5–9% Ficoll interface contained myelin and other membrane fragments as well as synaptosomes, the second fraction (C) at the 9–12% Ficoll interface contained mainly synaptosomes, and the third fraction (D) at the 12–16% Ficoll interface contained synaptosomes and free mitochondria. A fourth fraction (E) was obtained as a pellet, and was enriched in free mitochondria. There was fair agreement between the distribution pattern of the marker enzyme activities and the particles of the fractions seen by electron microscopy. The content of glycoprotein‐bound N‐acetylneuraminic acid and total phospholipid of these fractions has been determined. Relative to the mitochondrial fraction (E) the synaptosome fraction contained on basis of particulate protein, respectively, 2–3 times as much protein‐bound N‐acetylneuraminic acid and 10–20 per cent more total phospholipid.
CHEMICAL SPECIFICITY OF DOPAMINE TRANSPORT IN THE NIGRO‐NEOSTRIATAL PROJECTION
Authors: McGeer E. G. , Searl K. , Fibiger H. C. 
Published: October 2006

Abstract—Axoplasmic transport of dopamine in the nigro‐neostriatal system has previously been shown by the specific accumulation of labelled dopamine in the striatum following injections of labelled DOPA or dopamine into the substantia nigra. To test the specificity, 17 different labelled materials (pipecolic acid, inulin, taurine, GABA, glycine, histidine, histamine, serotonin, 5‐HTP, D‐amphetamine, 3‐methoxytyramine, dopamine, tyramine, norepinephrine, octopamine and high and low specificity activity DOPA) were injected into the substantia nigra and the distribution of radioactivity in the brain studied after 6 and 24 h. Only the catecholamines and octopamine gave evidence of specific accumulation in the ipsilateral striatum although some of the other compounds caused diffuse labelling of the striatum along with other brain areas.
THE EFFECT OF INDUCED HYPOTHERMIA UPON OXYGEN CONSUMPTION IN THE RAT BRAIN
Authors: Hägerdal M. , Harp J. , Nilsson L. , Siesjöu B. K. 
Published: October 2006

Abstract—The effect of hypothermia upon cerebral metabolic rate for oxygen (CMRO2) was studied in artificially ventilated rats, anaesthetized with nitrous oxide. Cerebral blood flow was measured with a modification of the Kety and Schmidt technique using 133xenon. CMRO2, was found to decrease linearily with temperature in the temperature range 37°C‐22°C. At normal temperatures CMRO2, fell by about 5 per cent per degree C. At a body temperature of 22°C both cerebral blood flow and CMRO2, were reduced to about 25 per cent of normal.
ON THE SPECIFICITY OF TRYPSIN (EC 3.4.4.4) OF NERVE ENDING PARTICLES TO INHIBIT NOREPINEPHRINE TRANSPORT1,2
Authors: Hitzemann Barbara A. , Hitzemann R. J. , Loh H. H. 
Published: October 2006

Abstract—The Na+ and energy dependent uptake of norepinephrine into cortical rat brain homogenates or purified nerve ending particles (NEP) is reduced by prior trypsin treatment. In contrast, the uptake of dopamine, serotonin, choline and γ‐aminobutyric acid is markedly less sensitive to the effect of trypsin. Kinetic analyses indicate that the trypsin‐induced decrease of norepinephrine uptake is non‐competitive. In the dose range studied, trypsin did not appreciably alter the protein content or morphology of NEP. However, in a dose related fashion, trypsin decreased the glycoprotein content of NEP measured as the loss of protein bound N‐acetylneuraminic acid.
SERUM ‘ANTI‐MYELIN ANTIBODIES’: A SPECTROFLUOROMETRIC ASSAY PROCEDURE1
Authors: Suzuki K. , Bornstein M. B. , Tiffany Carol W. 
Published: October 2006

Abstract—A simple spectrofluorometric procedure has been devised to determine serum antibodies, directed to constituents of the myelin sheath. It is an adaptation of the indirect immunofluorescent technique. A suspension of highly purified bovine myelin is incubated successively with a test rabbit serum and fluoresceinisothiocyanate‐conjugated anti‐rabbit gamma‐globulin. Intensity of fluorescence in the final myelin suspension is determined spectrofluorometrically. Sera from rabbits with experimental allergic encephalomyelitis, induced by whole bovine spinal cord, generally gave fluorescence at least 10 times that of normal rabbit serum. Fluorescence of sera with high demyelinating activity was more intense than that of sera with equivocal demyelinating activity. The assay is specific for immunoglobulins directed to myelin constituents, organ‐specific and species‐independent. Rabbit anti‐galactosylceramide serum with known demyelinating activity gave high fluorescence similar to that in sera of rabbits inoculated with whole spinal cord. Galactosylceramide could absorb a substantial portion of‘anti‐myelin antibodies’of the anti‐galactosylceramide serum but it did not absorb‘anti‐myelin antibodies’of serum of rabbits with whole tissue‐induced experimental allergic encephalomyelitis. This assay system may be useful for further studies of ‘anti‐myelin antibodies’.
POSTNATAL CHANGES IN FREE AMINO ACID, DNA, RNA AND PROTEIN CONCENTRATIONS OF MINIATURE SWINE BRAIN1
Authors: Badger T. M. , Tumbleson M. E. 
Published: October 2006

Abstract—Postnatal developmental characteristics of miniature swine brain were evaluated through the first 9 weeks of age. Differential growth rates of cerebrum, cerebellum and brain stem were defined in terms of DNA, RNA, protein and free amino acid concentrations at ages 5, 21, 35 and 63 days. Within the experimental conditions provided, hyperplasia ceased just prior to ages 21, 35 and 63 days for cerebellum, brain stem and cerebrum, respectively. An additional cerebral growth spurt, observed between weaning at age 35 days and sacrifice at age 63 days, may be indicative of impaired brain development due to inadequate nutrition provided by the dam's milk. Developmental changes in mean concentrations of brain free amino acids varied with anatomical area and differed somewhat from those of other species previously reported. For example, mean cerebral concentrations of aspartic acid, γ‐aminobutyric acid and asparagine + glutamine decreased significantly (P < 0·05) with age and mean glutamic acid concentration was 5 times that of taurine.