bluuebunny/crossref_metadata_2025_split huggingface dataset:
A COMPARISON OF THYMIDYLATE SYNTHETASE ACTIVITIES FROM 5‐FLUORODEOXYURIDINE SENSITIVE AND RESISTANT VARIANTS OF MOUSE NEUROBLASTOMA1
Authors: Baskin F. , Rosenberg R. N. 
Published: October 2006

Abstract— We have previously described a 5‐fluorodeoxyuridine (FUdR) resistant variant of mouse neuroblastoma possessing an 8‐fold elevation in methylenetetrahydrofolate: dUrd‐5′‐P C‐methyltransferase (EC2.1.1.b) [trivial name: thymidylate synthetase] specific activity relative to that of the sensitive parental clone. This increased specific activity is not associated with a change in cytoplasmic inhibitors or activators, a decreased degradation rate of the enzyme, or the synthesis of a new species with an increased Vmax, but appears to represent an increased synthesis of the enzyme species found in the sensitive parental clone. More resistant cell populations demonstrate even higher specific activities of this enzyme.The enzymatic activities from both the FUdR sensitive and resistant cells have identical stabilities to sonication, freezing, heat, urea, and sodium dodecyl sulfate, are equally and strongly inhibited by 5‐fluorodeoxyuridine‐5′‐phosphate, and have the same affinity for the substrate 2′‐deoxyuridine‐5′‐phosphate (Km= 1·4 = 10−6m). Both are stimulated by the addition of mercaptans and partially protected from heat denaturation in the presence of substrate.Unlike Don Chinese hamster cells (Conrad & Ruddle 1972) an actinomycin d pulse of neuroblastoma cells in monolayer culture did not increase the thymidylate synthetase specific activity. Mixed growth of FUdR sensitive and resistant cells produced only additive activities.
PROTEINS OF AXONAL TRANSPORT: INVESTIGATION OF SOLUBILITY CHARACTERISTICS AND BEHAVIOUR IN GEL FILTRATION
Authors: Karlsson J.‐O. 
Published: October 2006

Abstract—Rapid axonal transport of proteins in retinal ganglion cells of the rabbit was studied following intraocular injections of labelled amino acids. Approximately 10% of the transported radioactivity was found in the supernatant following homogenization and high‐speed centrifugation of the nerve terminal region. Relatively simple manipulations with ionic strength, pH and the presence of a chelating agent could solubilize an equivalent amount of radioactivity from the pellet. Lithium diiodosalicylate solubilized most rapidly transported membrane proteins. Gel filtration of readily soluble rapidly transported radioactivity gave a main macromolecular radioactive peak with an approximate mol. wt. of 500,000 dalton as determined on Sephadex G‐200. However, gel filtration on Sepharose CL‐6B gave a mol. wt. of about 160,000 for the same radioactive peak. SDS polyacrylamide gel electrophoresis of rapidly transported soluble proteins and fractions derived from these proteins via gel filtration and ion exchange chromatography revealed in all cases a very complex picture of labelled polypeptides. Thus rapid axonal transport of soluble proteins in this system seems to involve many different macro‐molecules
A METHOD FOR THE ASSAY OF CONJUGATED 3,4‐DIHYDROXYPHENYLGLYCOL, A MAJOR NORADRENALINE METABOLITE IN THE RAT BRAIN
Authors: Nielsen M. , Braestrup C. 
Published: October 2006

Abstract—We present the first published procedure for the measurement of endogenous conjugated 3,4‐dihydroxyphenylglycol (DOPEG) in the rat brain. Conjugated DOPEG is estimated from brain extracts after enzymic hydrolysis, isolation of hydrolysed DOPEG on alumina, methylation of DOPEG to 3‐methoxy‐4‐hydroxyphenylglycol (MOPEG) and gas chromatographic quantification of MOPEG. The level of conjugated DOPEG in the CNS of rats (65.7 ± 0.7 ng/g whole brain tissue corrected for recovery) almost equals the level of conjugated MOPEG. The sensitivity of the method is about 6 ng/g brain tissue. After inhibition of monoamine oxidase with clorgyline (30mg/kg) conjugated DOPEG and MOPEG both disappeared from the brain with a half‐life of about 1 h. Turnover calculations indicate that conjugated DOPEG and MOPEG are the two major noradrenaline end‐metabolites in the rat brain.The method of estimating conjugated DOPEG also allows the measurement of noradrenaline, dopamine and total MOPEG in an extract from one half of a rat brain.
FACTORS REQUIRED FOR Ca‐SENSITIVE ACETYLCHOLINE RELEASE FROM CRUDE SYNAPTIC VESICLES
Authors: Hata F. , Kuo C. H. , Matsuda T. , Yoshida H. 
Published: October 2006

Abstract— Studies were made on intracellular factors required for the release of ACh from crude synaptic vesicles prepared from rat brain. A factor stimulating ACh release in the presence of calcium ions was found in the cell sap.Cell sap obtained by hypotonic shock of a crude mitochondrial fraction stimulated ACh release from the synaptic vesicles in the presence of ATP and magnesium ions. Calcium ions were essential for its effect and the optimum concentration of calcium was about 10−4m. The stimulatory factor in cell sap passed through a cellulose or collodion membrane or ultrafiltration membrane UM 10, but not through that of an ultrafiltration membrane UM 05. The factor was not affected by trypsin or α‐chymotrypsin, but was inactivated by pronase or carboxypeptidase‐A. Thus it seemed to be a peptide‐like substance with a rather low molecular weight. Cyclic‐AMP, cyclic‐GMP, colchicine and vinblastne did not affect ACh release under our experimental conditions.
THE EFFECT OF CORDYCEPIN ON THE APPEARANCE OF [3H]RNA IN THE GOLDFISH OPTIC TECTUM FOLLOWING INTRAOCULAR INJECTION OF [3H]URIDINE
Authors: Ingoglia N. A. , Sellin L. C. , Lindquist T. D. 
Published: October 2006

Abstract— Although biochemical and electron microscopic evidence has shown that RNA molecules may be found within axons, the origin of this RNA is not known. In order to determine if the RNA found in axons is synthesized in the nerve cell body and axonally transported, we have studied the effect of the RNA inhibitor cordycepin (3′‐deoxyadenosine) on the retinal synthesis and axonal migration of radioactive RNA. Ten μg of cordycepin was injected into the right eye of 11 fish and 3 h later [3H]uridine was injected into the same eye. Twelve control fish were injected with [3H]uridine only and all fish were sacrificed 6 days later. Results of RNA extraction of retina and tecta showed that cordycepin decreased retinal RNA synthesis by approx 24%, while inhibiting the amount of [3H]RNA appearing in the contralateral tectum by 74%. Since the transport of RNA precursors was depressed by only 50%, (significantly different from the effect on RNA, P < 0.01) it seems unlikely that the action of cordycepin in decreasing tectal [3H]RNA levels was due solely to a decrease in the availability of labeled precursors for tectal RNA synthesis.For the purpose of blocking tectal RNA synthesis, 200 μg of cordycepin was injected intracranially several days after the intraocular injection of [3H]uridine. This route of cordycepin administration failed to significantly block the appearance of [3H]RNA in the tectum, suggesting that at least some of the [3H]RNA in the tectum was synthesized before arrival in the tectum itself.To be sure that cordycepin itself was not being transported, we injected cordycepin into the right eye of fish and 5 days later, injected fish intracranially with [3H]uridine. Autoradiograms were prepared and grains were counted over the fiber layers of left (experimental) and right (control) tecta. No significant difference was observed in the number of grains of left vs right tecta indicating that cordycepin itself is not axonally transported.These experiments support earlier findings from our laboratory which suggest that RNA may be axonally transported in goldfish optic fibers.
THE NON‐SYNCHRONOUS SYNTHESIS OF MYELIN COMPONENTS DURING EARLY STAGES OF MYELINATION IN THE RAT OPTIC NERVE1
Authors: Detering Nancy K. , Wells M. A. 
Published: October 2006

Abstract—Analysis of lipids and proteins in whole optic nerves during initial stages of myelination indicate a sequential deposition of myelin components. During this period sulfatide levels increase from 4 nmol/pair of nerves at 9 days to 29 nmol/pair of nerves at 21 days. Cerebrosides are not detected until the 12th day and attain a level of 46 nmol/pair of nerves in the 21‐day old rat. Plasma‐logen values increase from 2.1 to 31 nmol/pair of nerves and cholesterol values from 12 to 158 nmol/pair of nerves between 9 and 21 days. High molecular weight proteins are present in samples from 9‐day old rats analyzed by discontinuous sodium dodecyl sulphate‐polyacrylamide gel electrophoresis. Under identical conditions myelin basic proteins are first observed in the 10 day sample, and the proteolipid protein is first detected in the 12 day sample. The 2′, 3′‐cyclic nucleotide 3′‐phosphohydrolase activity increases from 1.13 to 5.50 μmol/min per mg protein between 9 and 21 days.
POSTNATAL ALTERATIONS IN EFFECTS OF POTASSIUM ON UPTAKE AND RELEASE OF GLUTAMATE AND GABA IN RAT BRAIN CORTEX SLICES
Authors: Schousboe A. , Lisy V. , Hertz L. 
Published: October 2006

Abstract—The uptake and release of glutamate and of GABA, as well as the effect of high potassium concentrations (35 or 80 mM) hereupon, were studied by aid of 14C‐labelled amino acids in brain cortex slices from rats of different ages between birth and adulthood. Both the extent of the uptake (i.e. the tissue/medium ratio of 14C at, or close to, equilibrium) and the rate of uptake (i.e. the tissue/ medium ratio of 14C after short (5 min) incubation periods) increased with age. Differences were, however, found between glutamate and GABA, and the extent of the GABA uptake had a distinct maximum during the second postnatal week. At all ages, high concentrations of potassium caused a decrease in the rate of GABA uptake but were without effect on the rate with which glutamate was taken up. The release of the two amino acids occurred with approximately the same half‐time (50 min) in slices from animals of at least 14 days of age. Before that time the release of glutamate was somewhat faster, whereas that of GABA was much slower, especially during the first postnatal week (half‐time 90 min). The ontogenetic alterations in the effect of excess potassium were complex and varied both between the two potassium concentrations used and between the two amino acids. The results are thus compatible with the existence of different transport systems for the two amino acids, They also suggest that glutamate may exert other functions in addition to its role as a putative transmitter.
INHIBITION OF ACETYLCHOLINE SYNTHESIS AND OF CARBOHYDRATE UTILIZATION BY MAPLE‐SYRUP‐URINE DISEASE METABOLITES
Authors: Gibson G. E. , Blass J. P. 
Published: October 2006

AbstractThe branched‐chain 2‐oxo acids which accumulate in maple‐syrup‐urine disease inhibited the production of acetylcholine and of lipids, proteins, nucleic acids and of CO2. in sliced adult rat brains incubated with [U‐14C] glucose. Inhibition of the biosynthetic reactions was proportional to the inhibition of CO2 production, even though the flux of radioactivity into the biosynthetic products was less than 2% of that to CO2.The oxo acids reduced the production of 14CO2, from [U‐14C] glucose and from [2‐14C]pyruvic acid more than from [1‐14C]pyruvic acid in sliced brains. They inhibited the solubilized oxoglutarate dehydrogenase complex more than they did the solubilized pyruvate dehydrogenase complex. Valine and isoleucine, which also accumulate in maple‐syrup‐urine disease, inhibited pyruvate kinase from rat brain allosterically. Quantitative comparison of the effects of the disease metabolites on cell‐free systems with their effects on fluxes in intact cells indicated that the inhibition of oxoglutarate dehydrogenase appeared to be functionally significant. The residual activities of the other enzymes studied were adequate to support the normal flux of carbohydrates.The oxo acids were effective at concentrations within the range reported to occur in patients with maple‐syrup‐urine disease. The effects on biosyntheses including that of acetylcholine would be expected to impair brain development and function and could be important in the development of brain disease in the patients. In contrast to the results with metabolites from maple‐syrup‐urine disease, metabolites which accumulate in phenylketonuria (phenylalanine and 2‐oxo‐3‐phenylpropionic acid) did not inhibit carbohydrate utilization or the biosynthetic reactions studied, under the conditions of these experiments.
DISTRIBUTION AND OPTICAL ACTIVITY OF THE BASIC PROTEIN IN BOVINE PERIPHERAL NERVE MYELIN
Authors: Uyemura K. , Kato‐Yamanaka T. , Kitamura K. 
Published: October 2006

Abstract— Antiserum to BF protein isolated from bovine spinal roots has been used to study the distribution of the protein in other species and tissues.Significant amounts of protein could be demonstrated in bovine, pig and rabbit peripheral nerve myelin. It was, however, scarcely detectable in guinea pig peripheral nerve myelin. There was BF protein in rabbit spinal cord as well as in peripheral nerve, but little or no BF protein in the liver, kidney, muscle or brain. BF protein in bovine spinal cord was localized in the myelin. The ratio of the BF protein to the encephalitogenic protein in the spinal cord myelin was around 0.15:1.0. BF protein was extractable from peripheral nerve myelin by saline as well as by acid solutions.The circular dichroism spectrum of the BF protein in aqueous solution suggested that this protein contained a very large amount of β‐structure. This structure was not considered to be the result of acid denaturation because the protein purified from the saline extract of peripheral nerve also showed a similar spectrum.
CORRELATION OF DNA ACCUMULATION RATE WITH THYMIDYLATE SYNTHETASE AND THYMIDINE KINASE ACTIVITIES IN DEVELOPING RAT CEREBELLUM: EFFECT OF THYROXINE1
Authors: Clark B. R. , Weichsel M. E. 
Published: October 2006

Abstract— Using the method of least squares, a logistic curve was fitted to the data points for DNA content in neonatal rat cerebellum versus postnatal age (day 0 is the day of birth). The resultant equation was differentiated to give an expression for the rate of cerebellar DNA accumulation in units of ng/h per mg wet cerebellum. The DNA accumulation rate in control rats increased from 77.0 at 2 days of age to a maximum of 108 at 7 days of age and declined thereafter to a minimum of 16.3 on day 15. Thyroxine treatment significantly (P < 0.05) increased the rate to 89.8 (117% of control) at 2 days of age, and a significant elevation was maintained to 6 days of age at which time a maximum rate of 115 (114% of control) was attained. The rate was significantly decreased below control at 9 and 12 days of age, and reached a minimum of 9.22 on day 15.The developmental pattern for the activity of cerebellar thymidylate synthetase (EC 2.1.1.6), in units of pmol/h per mg wet cerebellum, closely paralleled the pattern for DNA accumulation rate in both control and thyroxine‐treated animals. In controls, thymidylate synthetase activity increased from 98.6 at 2 days of age to a maximum of 125 at 7 days of age and declined thereafter to a minimum of 30.0 at 15 days of age. In thyroxine‐treated animals, the activity was significantly increased to 118 (122% of control) at 4 days of age and remained significantly elevated through 6 days of age at which time a maximum activity of 154 (115% of control) was attained; thereafter, the activity was significantly decreased below control and reached a minimum of 16.9 (56.3% of control) on day 15. The developmental pattern for the activity of cerebellar thymidine kinase (EC 2.7.1.21) did not parallel the DNA accumulation rate quite so closely, in neither treated nor control animals, as did the pattern for thymidylate synthetase activity.These data suggest that thymidylate synthetase activity in the developing rat cerebellum may be more important for maintenance of replicative DNA synthesis than is thymidine kinase activity. In addition, the thyroxine‐induced acceleration of the increase and subsequent decline in rate of DNA accumulation and in the activities of thymidylate synthetase and thymidine kinase in developing rat cerebella is probably the result of alterations in the number of external granular cells undergoing replicative DNA synthesis.
SIALYLTRANSFERASES IN RAT BRAIN: INTRACELLULAR LOCALIZATION AND SOME MEMBRANE PROPERTIES
Authors: Ng S.‐S. , Dain J. A. 
Published: October 2006

Abstract— Total rat cerebral homogenate, with nuclei removed, yielded sialyltransferase activity peaks that were distinct from the protein distribution profile in a continuous sucrose density gradient. Marker enzyme studies and electron microscopic examinations on the gradient fractions suggested that most of the sialyltransferase activities were not associated with the synaptosomes.The sialyltransferases appeared to be localized in the smooth microsomal membranes and the Golgi complex derivatives. The sialyltransferase activities were stimulated by non‐ionic detergent mixture, Triton CF‐54/Tween 80 (2/1, w/w), the effect being much more pronounced with exogenous substrates. The stimulatory effect was dependent on detergent concentration. With 1 mg detergent mixture per mg enzyme protein, the percent increases in enzyme activities with the different substrates were: endogenous glycolipids, 100; endogenous glycoproteins, 50; exogenous GM1a, 700; exogenous DS‐fetuin, 230. The action of the nonionic detergents appears to be on a hydrophobic segment of the enzyme molecule, bearing the active site, which is buried in the membrane lipid bilayer. This was substantiated by the partial trypsin resistance of the sialyltransferase activities and the abolition of that resistance when trypsiniza‐tion was performed in the presence of nonionic detergents. Furthermore, the sialyltransferase activities were markedly inhibited by organic solvents; and these inhibitory effects were inversely proportional to the solvent dielectric constants.
ONTOGENESIS AND REGIONAL DISTRIBUTION OF HISTAMINE AND HISTAMINE‐N‐METHYLTRANSFERASE IN THE GUINEA PIG BRAIN1
Authors: TUOMISTO LEENA 
Published: October 2006

Abstract—The ontogenetic development and the regional distribution of histamine (HA) and histamine‐N‐methyltransferase (HMT, EC 2.1.1.8) in guinea pig brain and pituitary gland were studied. The samples were taken every fourth day beginning on the 28th foetal day. The HA concentration in the brains of the youngest foetuses was almost undetectable. A significant increase in HA concentrations occurred between days 40 and 44, which coincides with the period of rapid growth of nerve cell processes in this species. After this, a steep increase continued to the end of gestation in the hypothalamus, and to a lesser degree in the medulla‐midbrain and in the forebrain. In all parts of the brain the adult HA levels were reached by the time of birth. The HMT activity increased 15‐fold from the 28th foetal day to the adult and reached ca. 80% of the adult activity by the time of birth. The HMT activity developed earlier in the midbrain than in the forebrain or in the cerebellum, but after the birth the regional distribution of HMT was fairly even. In the pituitary gland the HA concentration and HMT activity increased hundredfold and tenfold, respectively.The developmental patterns of HA and HMT in the guinea pig brain give support to the concept that HA might be a neurotransmitter in the brain.
5‐HYDROXYTRYPTAMINE CATABOLISM IN THE RAT BRAIN DURING ONTOGENESIS
Authors: BOURGOIN S. , ARTAUD F. , ADRIEN J. , HERY F. , GLOWINSKI J. , HAMON M. 
Published: October 2006

Abstract—Although the serotoninergic innervation is immature in the brains of young rats, the 5‐HIAA content is similar to that found in adults. As indicated by the ratio of 5‐HIAA to 5‐HT levels in the brain stem and the forebrain, the catabolism of the indolamine was more rapid during the first 3 postnatal weeks than in adults. This was contirmed by measuring the total formation of [3H]5‐HIAA from [3H]5‐HT newly synthesized from L‐[3H]tryptophan in brain stem slices of young and adult rats.Electrolytic lesions of midbrain raphe nuclei (B7 and B8) performed on the 5th postnatal day resulted in parallel decreases in brain 5‐HT and 5‐HIAA levels; this ruled out the possibility that 5‐HIAA might be formed from 5‐HT synthesized outside serotoninergic neurons, using peripheral 5‐hydroxytryptophan. Inhibition of 5‐HT storage by reserpine pretreatment did not alter the higher capacity of newborn tissues to catabolize exogenous [3H]5‐HT. Therefore, possible differences in 5‐HT binding in serotoninergic neurons between newborn and adult rats were not likely to account for the differences in 5‐HT catabolism. Estimation of the rate of 5‐HIAA efflux from the brain after MAO inhibition did not reveal marked changes with age.The activity of MAO type A, the enzyme involved in 5‐HT catabolism, was higher during early life than later on. This could be shown by using 5‐HT as substrate and clorgyline as a selective inhibitor. An opposite pattern of development was seen for MAO B, measured with benzylamine as substrate and deprenyl as selective inhibitor.These results suggest that the high 5‐HIAA levels found in the brains of young rats can be attributed mainly to the presence of high MAO A activity during early life.
RAPID CONCURRENT AUTOMATED FLUORIMETRIC ASSAY OF NORADRENALINE, DOPAMINE, 3, 4‐DIHYDROXYPHENYLACETIC ACID, HOMOVANILLIC ACID AND 3‐METHOXYTYRAMINE IN MILLIGRAM AMOUNTS OF NERVOUS TISSUE AFTER ISOLATION ON SEPHADEX G10
Authors: WESTERINK B. H. C. , KORF J. 
Published: October 2006

Abstract—A semi‐automated fluorimetric assay technique for the concurrent estimations of noradrenaline, dopamine, 3, 4‐dihydroxyphenylacetic acid, homovanillic acid and 3‐methoxytyramine is described. The method is based on a rapid manually performed isolation of the catecholamines and metabolites on small columns of Sephadex G10, followed by automated fluorimetric dection in continuous flow systems. Samples containing no more that 2‐5 ng (NA, DA, DOPAC or HVA) or 10 ng 3‐MT could be reproducibly measured. The small Sephadex G10 columns has proven to be an excellent alternative to the currently used columns of alumina or ion‐exchange resins.
AROMATIC ACID METABOLITES OF PHENYLALANINE IN THE BRAIN OF THE HYPERPHENYLALANINEMIC RAT: EFFECT OF PYRIDOXAMINE
Authors: Loo Yen Hoong , Scotto Lois , Horning Marjorie G. 
Published: October 2006

Abstract— Phenylalanine levels approaching those found in clinical phenylketonuria were produced in the brain of suckling rats by injections of p‐chlorophenylalanine and L‐phenylalanine. The predominant aromatic acid metabolite found in the brain of these animals was phenylacetic acid with decreasing amounts of phenylpyruvic, phenyllactic, and mandelic acids.The disposition of [3H]pyridoxamine in the brain of normal and hyperphenylalaninemic animals was found to be similar. Pyridoxamine was rapidly phosphorylated in the brain, and excess vitamer was converted mainly to pyridoxal. Pyridoxamine, when injected repeatedly, was effective in significantly reducing the amount of phenylacetate that accumulated in the brain over a period of 6 h. The significance of these findings is discussed.