bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lack of dihydrofolate reductase activity in brain tissue of mammalian species: possible implications1
Authors: Makulu D. R. , Smith E. F. , Bertino J. R. 
Published: October 2006

AbstractIT IS becoming increasingly clear that folates play a vital, yet until recently an unrecognized, role in the development and function of the brain. Thus several groups of patients have been found with severe maldevelopment of the brain and mental retardation associated with inborn errors of folate metabolism resulting from congenital deficiency in one or more enzymes involved in folate metabolism (ARAKAWA et al., 1965; 1966; 1967; MUDD, LEVY and ABELES, 1969; ARAKAWA, 1970). The presence of folate coenzymes in brain tissue has been reported by several investigators (ALLEN and KLIPSTEIN, 1970; MCCLAIN and BRIDGERS, 1969). MCCLAIN and BRIDGERS (1969) showed that much less of the folates in brain are in the form of the N5‐methyl derivatives than is the case for folates in plasma, red blood cells and liver. Appreciable activity of several folate interconverting enzymes have been demonstrated in brain tissue; for example, N5‐methyl tetrahydrofolate homocysteine methyl transferase has been found to exist in higher levels in brain than in liver or kidney (MANGUM, 1972); N5‐methyl FH,N‐dimethyl‐dopamine methyl transferase (LADURON, 1972) and serine transhydroxymethylase (EC 2.1.1; L‐Serine: tetrahydrofolate 5, 10‐hydroxymethyl transferase) (BRIDGERS, 1968) have recently been detected in brain. The last enzyme is known to catalyse a reaction responsible for the generation of a major portion of one‐carbon units. In mouse brain, the activity of this enzyme declines during the first 2 weeks of extra‐uterine life (BRIDGERS, 1968).The aim of the present study was to determine the levels of dihydrofolate reductase(5,6,7,8‐tetrahydrofolate:NADP+ oxidoreductase; EC 1.5.1.3) in mammalian brain tissues in comparison to the levels in other tissues. This enzyme occupies the first and key position in folate metabolism, reducing the metabolically inert vitamin, folic acid, to tetrahydrofolate. This enzyme also functions in thymidylate synthesis to regenerate tetrahydrofolate from dihydrofolate, a product of the reaction (HWHREYS and GREENBERG, 1958). In this reduced state the molecule can accept one‐carbon units from various sources to give rise to metabolically active coenzyme forms of folate. This communication reports the complete absence of dihydrofolate reductase in brain tissue of several mammalian species.
ISOLATION OF N‐ACETYLGLUTAMINE, PYROGLUTAMIC ACID AND THE BUTYL ESTER OF PYROGLUTAMIC ACID FROM HUMAN BRAIN1
Authors: Auditore J. V. , Wade L. 
Published: October 2006

Abstract N‐acetyl‐l‐glutamine, pyroglutamic acid, and the butyl ester of pyroglutamic acid were isolated in pure form from an aqueous extract of human brain. These compounds were isolated by combination of paper and ion exchange chromatography. The isolated substance identified as N‐acetyl‐l‐glutamine did not react with the ninhydrin reagent but yielded glutamic acid and ammonia upon acid hydrolysis. An acetyl hydrazide was identified by paper chromatography from hydrazinolysates of the isolated substance. The glutamic acid liberated by hydrolysis had the l‐configuration. The results of elementary analysis of the isolated compound were in full accord with the analysis calculated for synthetic N‐acetyl‐l‐glutamine. A large amount of pyroglutamic acid and a substance identical with the butyl ester of pyroglutamic acid were isolated in pure form. The results of our studies suggest that pyroglutamic and the butyl ester derivative were artifacts formed during the isolation and purification procedures.
ISOLATION OF PURIFIED BASIC PROTEIN FROM HUMAN BRAIN
Authors: Banik N. L. , Davison A. N. 
Published: October 2006

Abstract—A simplified method for the isolation of an encephalitogenic basic protein from myelin is described. The basic polypeptide is easily extracted from the interfacial protein which separates when chloroform‐methanol extracts of myelin are treated with a synthetic upper phase containing citrate. Evidence is presented for the purity and identity of the protein. The disc polyacrylamide gel electrophoretic pattern of this protein was consistent with a high degree of homogeneity.
PRECURSOR INCORPORATION INTO CORTICAL PROTEIN DURING FIRST EXPOSURE OF RATS TO LIGHT; CELLULAR LOCALIZATION OF EFFECTS
Authors: Rose S. P. R. , Sinha A. K. , Broomhead S. 
Published: October 2006

Abstract—The rate of incorporation of [3H]lysine into acid‐insoluble material in vivo was determined in neurons and neuropil from the visual cortex of dark‐reared rats, littermates exposed to the light for varying lengths of time and normally reared controls. Following onset of light exposure, the elevation of incorporation was confined to the neuronal fraction. On continuous exposure for up to 96 h, the level of incorporation in the neuronal fraction dropped to that of the dark control value. In dark‐reared animals, the rate of incorporation in the neuronal fraction was 68 per cent of that in neuropil, in normals it was 150 per cent. On onset of exposure, the ratio in light exposed animals approached the normal level, but on prolonged continuous exposure both light exposed and normal ratios dropped to the dark control value once more. This drop did not occur if the animals were exposed to a 12 h light/dark cycle. These results are taken as suggesting that part of the protein synthesis of the visual cortex is functionally controlled, and that neuronal and neuropil fractions show a metabolic relationship which can be affected by environmental changes. The failure to show a depression of incorporation in prolonged exposure, by comparison with earlier results under somewhat different behavioural conditions, was taken as further evidence for the ‘state‐dependence’ of a number of brain biochemical parameters.
THE EFFECT OF THE CONVULSANT 3‐MERCAPTOPROPIONIC ACID ON ENZYMES OF THE γ‐AMINO‐BUTYRATE SYSTEM IN THE RAT CEREBRAL CORTEX
Authors: De Lores Arnaiz Georgina Rodríguez , De Canal Martha Alberici , Robiolo Blanca , De Pacheco Marta Mistrorigo 
Published: October 2006

Abstract—The activities of GABA enzymes in rat cerebral cortex were studied after the administration of the convulsant, 3‐mercaptopropionic acid (MP). We found that MP markedly inhibited glutamate decarboxylase (EC 4.1.1.15) and activated GABA‐aminotransferase (EC 2.6.1.c). The level of GABA appeared to be decreased during convulsions but thereafter returned to normal. The study of the subcellular distribution of GABA enzymes after the administration of MP indicated that the glutamate decarboxylase present in the nerve endings was not affected, while GABA aminotransferase in the mitochondria was activated to a similar extent to that observed in the original homogenate. These results together with the recovery of glutamate decarboxylase activity in cortical homogenates by dialysis suggested a reversible type of inhibition, whereas the effect on GABA‐aminotransferase seemed to be more permanent.
STUDIES ON RAPIDLY LABELLED NUCLEAR RNA OF RAT BRAIN
Authors: Oravec M. 
Published: October 2006

Abstract—Methyl albumin kieselguhr chromatography (MAK) has been employed to separate rat brain nuclear RNA, labelled in vivo with [3H]uridine, into three major fractions. The first fraction (QI RNA) is ribosomal in nature for it has a high G + C/U ratio and is methylated by [methyl‐3H] methionine. The other two fractions (Q2 RNA and TD RNA) are DNA‐like for they exhibit a low G + C/U ratio and are labelled minimally by methionine. Pure ribosomal RNA chromatographs almost entirely in the Q1 RNA fraction.Labelling studies indicate that ribosomal RNA and DNA‐like RNA behave differently. Initially, the label in the DNA‐like RNA fractions increases rapidly and in a linear fashion for the first 30 min, but thereafter decreases rapidly and reaches a steady state level by 1 h and remains so up to at least the 2 h period. In contrast, the labelling of ribosomal RNA is much slower than that of DNA‐like RNA during the first 30 min; however, unlike DNA‐RNA, the labelling of ribosomal RNA still continues to increase linearly thereafter. Thus, during longer labelling periods, ribosomal RNA is labelled more rapidly than DNA‐like RNA. It appears that the labelling of ribosomal RNA relative to DNA‐like RNA is more rapid in liver than in brain.
SOME FACTORS AFFECTING THE UPTAKE, BINDING AND RETENTION OF [3H]CORTISOL BY THE CHICK EMBRYO RETINA AS RELATED TO ENZYME INDUCTION
Authors: Chader G. J. 
Published: October 2006

Abstract—The accumulation of [3H]cortisol by the embryonic chick neural retina was studied at a time of rapid biochemical differentiation. In retinal cultures, uptake of steroid was decreased by inhibitors of energy metabolism and of sulphhydryl groups but not by inhibitors of macromolecular synthesis. The retention of steroid was inhibited by dinitrophenol and N‐ethyl maleimide (NEM) over a 3 h incubation period. This inhibition may be due, in part, to the effect of NEM on the binding of steroid to intraretinal receptor as can be demonstrated by gel filtration. Neuraminidase had no effect on [3H]cortisol uptake or retention but markedly inhibited the induction of glutamine synthetase by the steroid. Uptake and retention of steroid at 37° was greater in the retinal nuclear pellet than in the cytosol fraction; the reverse was true at 4°. After treatment with NEM, [3H]cortisol accumulation in the nuclear pellet was drastically decreased, with approximately the same level of uptake as that seen at 4°. A temperature‐dependent, sulphhydryl‐sensitive process of steroid translocation from cytoplasm to nucleus may thus be indicated.
SOME PROPERTIES OF A MAJOR STRUCTURAL GLYCOPROTEIN OF SCIATIC NERVE
Authors: Wood J. G. , Dawson R. M. C. 
Published: October 2006

AbstractThe major protein of rat sciatic nerve is a glycoprotein which consists of a protein moiety attached to galactose, mannose and perhaps other sugars. On controlled tryptic digestion, it splits into a glycopeptide and a smaller fragment similar in molecular size to peripheral nerve basic proteins. Both the basic proteins of peripheral nervous system (PNS) myelin and the glycoprotein are antigenically active when administered to guinea pigs and produce sciatic nerve lesions similar to those described for experimental allergic neuritis. It is suggested from the amino acid analysis and its antigenic properties that the protein moiety of the glycoprotein may contain a sequence which is similar to the basic proteins of PNS myelin.
FREE AMINO ACIDS IN DEVELOPING RAT RETINA
Authors: Macaione S. , Ruggeri P. , Luca F. De , Tucci G. 
Published: October 2006

Abstract—During postnatal growth the free amino acids pattern of rat retina differs at various developmental stages. The adult level for individual amino acids is reached on the 30th day of maturation. During differentiation the taurine, glutamic acid, GABA, glutamine, aspartic acid, glycine arginine, methionine and histidine levels increase while proline. alanine, ornithine and tyrosine decrease.
PROPERTIES OF ACETYLCHOLINESTERASE FROM RAT BRAIN
Authors: Wenthold R. J. , Mahler H. R. , Moore W. J. 
Published: October 2006

Abstract—Acetylcholinesterase (EC 3.1.1.7) from cerebral cortex of mature rats was purified by means of affinity chromatography, to a specific activity of 4.5 mmol acetylthiocholine hydrolysed × min−1× mg−1 protein. The enzyme is a glycoprotein and contains a single subunit with a mol. wt of about 80,000. Electrofocusing either a pure or a crude preparation of the enzyme produces six enzymatically active bands with a range of isoelectric points from 5.04 to 5.54. Gel filtration yields oligomers with molecular weights of about 150,000, 320,000, 500,000 and 650,000, with 60 per cent of the activity in the 150,000 fraction. The gel fractions with molecular weights 150,000 and 320,000 produce the same isoelectric patterns. Different subcellular fractions of the cortex show different characteristic isoenzyme patterns.
EFFECTS OF MAPLE SYRUP URINE DISEASE METABOLITES ON MOUSE l‐FIBROBLASTS IN VITRO: A FINE STRUCTURAL AND BIOCHEMICAL STUDY
Authors: Bissell M. G. , Bensch K. G. , Herman M. M. 
Published: October 2006

Abstract—The branched‐chain amino and ketoacids [i.e. l‐leucine, l‐isoleucine, l‐valine, alpha‐ketoisocaproic acid (AKICA), alpha‐keto‐beta‐methylvaleric acid (AKBMVA) and alpha‐ketoisovaleric acid (AKIVA)] were administered to mouse strain l fibroblasts in tissue culture in an attempt to study the effects of increased levels of the compounds in an in vitro system. All of these compounds are found to be elevated in the blood of patients with Maple Syrup Urine Disease (MSUD).With AKICA, l‐leucine, AKIVA and AKBMVA, there was a decreased growth rate at concentrations of 10 to 30 times the levels found in Maple Syrup Urine Disease. Combined administration of the above six compounds at the maximum blood levels noted in MSUD produced a significantly decreased growth rate. Electron microscopic studies revealed numerous annulate lamellae in cells treated with AKICA and in those treated with a combination of all six MSUD compounds. AKICA‐treated cells contained elevated concentrations per cell of free fatty acids, triglycerides, sterols and some classes of phospholipids. Isotope labelling experiments were performed using [U‐14C] AKICA and [3H]isoleucine, which were added to l‐cell suspension cultures containing various levels of unlabelled AKICA. Labelled AKICA and isoleucine were both taken up by the cells. The net uptake of isoleucine was inhibited by AKICA in concentrations found in MSUD. Folch‐Lees extraction of cells treated with labelled AKICA revealed increased 14C counts only in the lower lipid phase.The growth inhibition and annulate lamellae observed with AKICA treatment may be due to an arrest of the cells in phase G1 of the cell growth cycle, possibly due to decreased isoleucine uptake. It is proposed that a similarly‐mediated arrest in the proliferation of oligodendroglial cells during the critical period of myelination gliosis might account for the myelination abnormalities reported in MSUD.
INCORPORATION OF d‐[3H]GLUCOSAMINE INTO THE SIALOGLYCOPROTEIN GP‐350 OF ADULT RAT BRAIN
Authors: Van Nieuw Amerongen A. , Ferwerda W. , Roukema P. A. 
Published: October 2006

Abstract—The incorporation of d‐[3H]glucosamine into the nervous specific sialoglycoprotein GP‐350 has been studied in adult rat brain. Both the 100,000 g supernatant fluid and the 12,500 g pellet were used for the investigation, since GP‐350 could only be detected in the soluble cell fraction (Van Nieuw Amerongenet al., 1972) and in the synaptosomal membranes, sedimenting in the crude mitochondrial fraction (Van Nieuw Amerongen & Roukema, 1973, 1974). GP‐350 was separated from the other proteins by polyacrylamide gel electrophoresis at pH 7.5 and the incorporation of radioactivity into GP‐350 was measured at different time intervals, ranging from 1 to 96 h after the administration of the radioisotope. The maximal incorporation of radioactivity into the soluble GP‐350 was obtained after about 2 h and into the membrane‐bound GP‐350 after about 3 h. After 2 h there is a very rapid decrease of the radioactivity of GP‐350 from the soluble cell fraction (up to 70 per cent within 2 h). Thereafter the disappearance is more gradual and of the same order as that found for the membrane‐bound fraction of GP‐350. The half‐life of the soluble GP‐350 was estimated to be 19 h and for the membrane‐bound GP‐350 a value of 18 h was calculated. Compared to the total pool of brain (glyco) proteins and specific nervous (glyco) proteins GP‐350 has a very rapid turnover. The rapid initial decrease of the radioactivity from the soluble GP‐350 may be interpreted in terms of a rapid transport of the newly‐synthesized GP‐350 from the cytoplasma of the perikaryon to the membranes of the synaptic region by an axoplasmic flow.
CHANGES IN VESICULAR DOPAMINE‐β‐HYDROXYLASE RESULTING FROM TRANSMITTER RELEASE
Authors: Fillenz Marianne , West D. P. 
Published: October 2006

Abstract—Exposure of rats to 3°C for up to 30 min leads to a decrease of 30 per cent in the dopamine‐β‐hydroxylase activity of the vesicular pellet of the heart; this is greater than can be accounted for by loss of soluble DBH from the two populations of noradrenaline storage vesicles known to be present in the heart. Cold exposure in the presence of α‐methyltyrosine causes a much smaller reduction in dopamine‐β‐hydroxylase activity; this suggests that there is a decrease in transmitter release when synthesis is inhibited. The noradrenaline concentration of the vesicular pellet rises briefly during cold exposure and is then maintained at control levels; the early rise is absent in the presence of α‐methyltyrosine. The use of the noradrenaline : dopamine‐β‐hydroxylase ratio as an index of saturation of vesicular storage capacity suggests that during cold exposure an increased synthesis rate leads to increased filling of vesicles.
REACTIONS OF FREE AND tRNA BOUND GLUTAMATE AND GLUTAMINE
Authors: Murthy M. R. V. , Roux Huguette 
Published: October 2006

Abstract—[14C]‐Glutamate and [14C]‐glutamine were incorporated into calf brain tRNA in the presence of homologous aminoacyl‐tRNA synthetases. When the tRNAs were then deaminoacylated and chromatographed, a number of radioactive products were found in addition to the original amino acids. One of the products of glutamate transformation was identified to be glutamine. Formation of the radioactive products of glutamate in the presence and absence of tRNA indicated that glutamine was produced from glutamate at the level of the free amino acid followed by the incorporation of both substances into tRNA. Examination of the products of deaminoacylation of glutaminyl‐tRNA showed that glutamine underwent structural alterations at the level of the aminoacyl‐tRNAs to give rise to a cyclic derivative of glutarimide. This reaction was specific for glutamine, and constituted approximately 15 per cent of the total radioactivity in the deaminoacylation products of glutaminyl‐tRNA.
ON THE DEVELOPMENT OF SYMPATHETIC NERVE TRUNK VESICLES DURING AXONAL TRANSPORT: DENSITY GRADIENT ANALYSIS OF DOPAMINE β‐HYDROXYLASE IN BOVINE SPLENIC NERVE
Authors: Lagercrantz H. , Kirksey D. F. , Klein R. L. 
Published: October 2006

Abstract—Dopamine β‐hydroxylase was used as a marker enzyme for sympathetic nerve vesicles which were studied by density gradient technique in bovine splenic nerves. The enzyme analyses were complicated by the occurrence of inhibitors which had to be carefully neutralized with copper. The inhibitor was mainly found in the soluble fraction and no evidence for the occurrence of endogenous inhibitors in the nerve vesicles was obtained.A great variation in density of the dopamine β‐hydroxylase containing particles was observed. This was probably mainly due to the variation in vesicle maturation since dopamine β‐hydroxylase was distributed more towards the lighter gradient fractions in the proximal nerve segment preparations compared with intrasplenic nerve segment preparations. Noradrenaline/protein and noradrenaline/dopaminc β‐hydroxylase ratios were found to be increased about 1·7‐fold in the vesicle fraction isolated from the proximal nerve segments to those from the intrasplenic segments. A further increase of the noradrenaline/dopamine β‐hydroxylase ratio was observed in a fraction with the same density isolated from the spleen. On the basis of these findings the noradrenaline/protein ratio was calculated to be about 500‐600 nmol/mg in the nerve terminal vesicles.
FORSSMAN HAPTEN N‐ACETYL‐α‐D‐GALACTOSAMINIDASE IN RAT BRAIN AND KIDNEY1
Authors: Israel M. , Bach G. , Miyatake T. , Naiki M. , Suzuki K. 
Published: October 2006

Abstract—Forssman hapten (N‐acetyl‐α‐galactosaminosyl‐N‐acetyl‐β‐galactosaminosyl‐α‐galactosyl‐β‐galactosyl‐glucosylceramide), prepared from sheep erythrocytes was specifically labelled with tritium at the terminal N‐acetyl‐α‐galactosamine moiety by the galactose oxidase‐sodium [3H]borohydride method. Activities to cleave the terminal N‐acetyl‐α‐galactosamine from Forssman hapten were detected in the high‐speed supernatant of the frozen‐thawed and sonicated crude mitochondrial fraction from adult rat brain and kidney. The optimal pH of the reaction was approximately 4·4. The reaction was linear for at least 1 h for the kidney enzyme and up to 3 h for the brain enzyme. Taurocholate was required for the activity. The optimal concentration was 1·5‐2 mg/ml. Several other detergents and bile salts tested could not replace taurocholate. The apparent Km of the brain and kidney enzymes were 1·0×10−4M and 3·5×10−4m, respectively. During development, Forssman hapten‐cleaving activities of both brain and kidney gradually declined in specific activity as the animal matured. These changes were similar to those of nonspecific p‐nitrophenyl N‐acetyl‐α‐galactosaminidase. Several rat organs examined all showed detectable activities to cleave Forssman hapten.
NEONATAL UNDERNUTRITION AND RNA SYNTHESIS IN DEVELOPING RAT BRAIN1
Authors: De Guglielmone AliciaE. R. , Soto Ana M. , Duvilanski Beatriz H. 
Published: October 2006

Abstract—Underfeeding of newborn rats results in a decreased body and brain weight at 10, 20 and 30 days of age. The DNA and RNA content of the brain in these animals are similar to those of normal controls. The in vivo and in vitro synthesis of RNA in brain is significantly decreased in undernourished rats at 10 days of age when compared with controls. The metabolic transformation of 3H‐orotic acid to nucleotides is also diminished. A short period of food rehabilitation produces ‐an improvement in the above mentioned alterations. However, a reduced incorporation of label into microsomal RNA persists even in the last condition. The results suggest that malnutrition, during the first days of life, alters the metabolism of cerebral RNA.
THE METABOLISM OF [14C]GLUCOSE BY THE BRAINS OF SUCKLING RATS INTOXICATED WITH INORGANIC LEAD
Authors: Patel A. J. , Michaelson I. A. , Cremer J. E. , Balázs R. 
Published: October 2006

Abstract—The development with age of the pattern of distribution of glucose carbon characteristic of the adult brain was studied in 7‐, 13‐, 19‐ and 24‐day‐old rats suckling from mothers maintained on a diet containing 4·5% lead acetate or on a normal diet. In normal rats the rapid and extensive conversion of glucose carbon into amino acids associated with the tricarboxylic acid cycle has been shown to develop in the cerebellum and the cerebral cortex during the same period as previously observed for the whole forebrain. A significant retardation was observed in both brain parts of rats suckling from mothers ingesting lead. In comparison with glutamate, aspartate and γ‐aminobutyrate, the labelling of glutamine was particularly low. The concentration of glutamine was not affected in the forebrain, but it was elevated in the cerebellum. The age‐dependent rise in the amounts of glutamate and aspartate was also retarded, but it would appear that the contribution of this effect to the depressed labelling of amino acids was small. There was no evidence of impaired entry of glucose into the brain from the blood. Although in comparison with undernourished animals, the growth retardation of the lead‐treated rats is similar, several of the effects observed on the developing brain seem to be distinct.