bluuebunny/crossref_metadata_2025 huggingface dataset:
THE LABELLING OF THE GANGLIOSIDIC FRACTION FROM BRAINS OF RATS EXPOSED TO DIFFERENT LEVELS OF STIMULATION AFTER INJECTION OF [6‐3H]‐GLUCOSAMINE
Authors: Maccioni Alicia H. R. , Giménez María Soffía , Cuputto R.
Published: October 2006

Abstract—

[6‐3H] Glucosamine was injected into rats and then they were submitted for 1 h to light (about 1100 lux) and sound, while their controls were kept in darkness. Two series of experiments were done: in one, the animals received the injection intracerebrally; in the other, the injection was intraperitoneal. In both series the ratios of specific radioactivities (c.p.m./μmol of NANA) in mitochondria1 gangliosidic fractions to those in synaptosomal gangliosidic fractions were higher for rats exposed to illumination and sound −+ 74 per cent, P < 0·01 and + 49 per cent, P < 0·001 (in respectively, experiments with intracerebral and intraperitoneal injections) than for animals kept in dark. For animals iqjected intraperitoneally the specific radioactivity of the mitochondria1 gangliosidic fraction from rats exposed to light was higher (+ 11 per cent, P < 0.05) than that obtained from animals kept in dark. For synaptosomes the specific radioactivity of the gangliosidic fraction obtained from animals exposed to light was lower (−15 per cent, P < 0.01) than that obtained from animals kept in dark.

In animals kept under the experimental conditions already described for more than 1 h the differences tended to disappear. No differences were observed between the two groups of rats in the amounts of radioactivity found in the brain.
THE EFFECTS OF PHENYLPYRUVATE AND HYPERPHENYLALANINEMIA ON INCORPORATION OF [6‐3 H]GLUCOSE INTO MACROMOLECULES OF SLICES OF RAT CEREBRAL CORTEX1
Authors: Glazer R. I. , Weber G.
Published: October 2006

Abstract—

The effects of phenylpyruvate and hyperphenylalaninemia on the incorporation of [6‐3H]glucose into lipids, proteins and nucleic acids were examined in differentiating and adult rat brain. Foetal brain was most sensitive to inhibition by phenylpyruvate in vitro, with significant effects occurring at 2·5 mM for labelling of lipids and proteins and at 5 mM for labelling RNA and DNA. Older age groups were less affected, and cortical slices from adult brain were slightly or not at all affected by phenylpyruvate.

The inhibition by phenylpyruvate of incorporation of [6‐3H]glucose into nucleic acids, proteins, and lipids could be further distinguished by the reversibility of the effect on nucleic acid and protein synthesis at high levels of glucose and the irreversibility of the effect on lipid synthesis. Lipid synthesis was most sensitive to inhibition by phenylpyruvate at the stage of fatty acid synthesis, with lesser effect on the formation of glyceride glycerol.

Exposure in utero of the foetal brain to maternal hyperphenylalaninemia resulted in reduction of 26–38 per cent in the subsequent incorporation in vitro of [6‐3H]glucose into lipids, proteins, RNA and DNA of brain slices from foetal animals. Feeding hyperphenylalaninemic pregnant rats a high‐glucose diet significantly protected the foetal brain from the neurotoxicity accompanying the hyperphenylalanemia.
ANTIGEN—ANTIBODY CROSSED ELECTROPHORESIS OF WATER‐SOLUBLE RAT BRAIN ANTIGENS
Authors: Bock Elisabeth , Mellerup E. T. , Rafaelsen O. J.
Published: October 2006

Abstract—

A method of separation by antigen‐antibody crossed electrophoresis was applied to the study of water‐soluble rat brain antigens. Five different rat brain preparations were used as antigens for immunization. The extract from Triton X‐100 treated brains gave the best antibody response. An antiserum containing 27 precipitating antibodies was obtained. The preparation of antigens for immunoelectrophoresis was investigated. Treatment with demineralized water gave the highest number of antigen‐antibody precipitates. Treatment with detergents and sonication gave a higher total protein yield, but the number of precipitates was unaffected.
THE EFFECT OF BICUCULLINE, METRAZOL, PICROTOXIN AND STRYCHNINE ON THE RELEASE OF [3H]GABA FROM RAT BRAIN SLICES
Authors: Johnston G. A. R. , Mitchell J. F.
Published: October 2006

Abstract—

Each of the four convulsants used significantly influenced the release of [3H]‐GABA from brain slices, without affecting [3H]GABA uptake. Bicuculline (10−5M, but not 10‐fold higher or lower concentrations) potentiated the electrically evoked release of [3H]GABA but not the resting release, whereas metrazol (10−4 to 10−6 M) was found to inhibit resting but not electrically evoked release. Strychnine (10−4 and 10−5 M) and picro‐toxin (10−4 M) inhibited electrically evoked release.
STRUCTURAL AND BIOCHEMICAL MATURATION OF THE CEREBRAL PALLIUM IN RABBIT FETUSES: MORPHOGENESIS AND LIPIDS
Authors: Dekaban A. S. , Patton V. M. , Cain D. F.
Published: October 2006

Abstract—

Morphological parameters of maturation of the cerebral pallium in rabbit fetuses ranging between 20 days of gestation (d.g.) and the early neonatal stage are expressed semi‐quantitatively and correlated with progressive changes in the brain lipids, glycolipids and nucleic acids. Dual expression of the chemical values, using as referents both the dry weight of the tissue and the DNA unit, reveal the crucial stage in brain development when rapid cell proliferation is replaced by rapid cell growth; this stage in rabbit fetuses occurred between 28 and 30 d.g. Between 20 d.g. and the early neonatal phase the RNA decreased moderately when expressed per unit of DNA. Even at the time of term birth the cortical nerve cells of the rabbit showed signs of immaturity including a relatively small nuclear volume.

On the dry weight basis, the lipids of the cerebral pallium exhibited little change in composition during fetal development; however, cerebrosides rose substantially between 30 d.g. and the early neonatal phase. When expressed per unit of DNA, all lipids and glycolipids continued to increase progressively in a pattern characteristic of growth throughout the prenatal period studied. This increase was also apparent when the lipid constituents were expressed per total pallium at the progressive gestational stages.

The molar ratios of phospholipids:cholesterol:cerebrosides in the pallium of rabbits of different ages were as follows: in adult rabbits‐2.9: 2.6: 1.0, in the newborn‐2.9: 1.3: 0.2 and in the 30 d.g. fetuses‐3.0: 1.2:0.44. These values reflect the fact that during maturation the content of phospholipids changes little, whereas that of cholesterol and especially erebrosides increases markedly.
THE CIRCULAR DICHROISM OF SYNAPTOSOMAL MEMBRANES: STUDIES OF INTERACTIONS WITH NEUROPHARMACOLOGICAL AGENTS1
Authors: Moore W. V. , Wetlaufer D. B.
Published: October 2006

The circular dichroic spectrum of synaptosomal membranes was highly reproducible and qualitatively similar to that of erythrocyte membranes. The spectrum exhibited a minimum at 224 nm, a shoulder at 212 nm and a maximum at 195 nm. The mean molar ellipticity at the maximum and minimum was approximately +8000 and –8000 respectively. The protein components were the dominant source of the CD signal. Quantitative estimates showed negligible contributions to the spectrum from cholesterol, phosphatidyl serine and TV‐acyl sugars. Phospholine iodide, eserine, decamethonium, tetramethyl ammonium chloride and acetylcholine at concentrations of 10‐3 and 10‐4M did not produce detectable perturbations of the membrane circular dichroism. The circular dichroic spectrum of d‐tubocurarine exhibited a maximum at 198 nm and a minimum at 212 nm. Addition of d‐tubocurarine to membrane suspensions in the cuvette yielded a complex spectrum representing the result of a simple additive combination of the circular dichroic spectra of d‐tubocurarine and the membranes. However, preincubation of the membranes with 3 x 10‐3m d‐tubocurarine at 0‐4°C for 5‐10 min followed by sedimentation, several washes and resuspension resulted in a circular dichroic spectrum which appeared to involve no change in the membrane contribution, but there was a substantial decrease in the molar ellipticity of the d‐tubocurarine remaining with the membranes.
ACETYLCHOLINESTERASE IN DEVELOPING CHICK EMBRYO BRAIN
Authors: Iqbal Z. , Talwar G. P.
Published: October 2006

–Acetylcholinesterase has been assayed at different stages of development to see whether changes in the activity of this enzyme are correlated in any way with the ontogenesis of electrical activity in the brain of growing chick embryo. The specific activity of the enzyme was highest in the synaptosomal fraction of the brain. The activity of the enzyme increased progressively with the age of the embryo. There were three isozymic forms of the enzyme in the 6‐day‐old embryo brain. A new isozyme appeared around the 9th day. The Km values of the enzyme for acetylthiocholine from 6‐ and 20‐day‐old embryo brains were 6.5 ± 10‐5m and 3.3 ± 10‐5m respectively. Enzyme preparations from 6‐day‐old embryos were found to lose 50 per cent of their activity when heated at 50°C for 10 min. Under similar conditions the loss in activity in 18‐day‐old embryo brain enzyme was 22 per cent.
EFFECTS OF DENERVATION ON THE INCORPORATION OF 32P INTO PHOSPHATIDYL INOSITOL AND OTHER PHOSPHOLIPIDS OF RAT DIAPHRAGM
Authors: Steinberg H. R , Durell J
Published: October 2006

Abstract— At 24 h after denervation of the rat hemidiaphragm, incorporation of 32P into phosphatidyl inositol was depressed relative to incorporation of 32P into phosphatidyl choline (measured 75 min after injection of the isotope intraperitoneally). The ratio of the specific radioactivity of phosphatidyl choline to the specific radioactivity of Pi was unaffected by denervation which implies that denervation had depressed incorporation of isotope into phospatidyl inositol. Denervation did not cause a measurable change in the pool size of phosphatidyl inositol relative to that of phosphatidyl choline. The effect of denervation on incorporation of 32P into phosphatidyl inositol was not entirely a direct consequence of the cessation of ACh release at the motor end‐plate since the effect was clearly manifest in strips of muscle not containing motor end‐plates, but the magnitude of the denervation effect was slightly greater in the strips of denervated hemidiaphragm which contained motor end‐plates.
CHANGES IN AMOUNT OF COLCHICINE‐BINDING PROTEIN (TUBULIN) IN RABBIT BRAIN DURING DEVELOPMENT1
Authors: Dedburn Dianna A. , Dahl D. R.
Published: October 2006

Colchicine binding was used as a measure of the levels of microtubule protein (tubulin) in several regions of rabbit brain during postnatal development. All regions studied showed a decrease in tubulin per mg of total protein; however, each region showed an increase in total tubulin from 1 day of age to adulthood. The net change in tubulin during development coincided with a proliferation of dendrites (which are rich in microtubules) and a decrease in microtubules from spindle apparatus, axons and astrocytes. We suggest that the total amount of tubulin changes in response to demands of the maturing brain cell for microtubules with different functional roles.
TRANSPORT AND TURNOVER OF NEUROHYPOPHYSIAL PROTEINS OF THE RAT
Authors: Norströ A. , Sjöstrand J.
Published: October 2006

Axonal transport and turnover rate of proteins in the supraoptico‐neurohypo‐physial tract were studied after injection of 35S cysteine into the region of the supraoptic nucleus. The proximo‐distal migration of labelled proteins from the nerve cell bodies to the axon terminals in the neurohypophysis was followed by measuring the radioactivity of neurohypophysial proteins at various time intervals (4 h to 30 days) after isotope injection. A rapidly transported phase of proteins with a minimal transport rate of approximately 60 mm/day was demonstrated. An accumulation of protein‐bound radioactivity was also observed in the neural lobe at 9 days after isotope injection, representing slowly transported proteins (0‐5 mm/day). In addition, an intermediate phase of axonal transport (1‐5 mm/day) was found.

Fractionation of neurohypophysial proteins by polyacrylamide gel disc electrophoresis revealed that a predominating portion of the radioactivity was recovered in a single protein component (fraction A) at 4 h as well as at 30 days after isotope injection. This protein component was shown to be a constituent both of the rapid and the slow phase of axonal transport. With time an increasing amount of radioactivity was found in another protein component (fraction B), which reached a maximum at 14 days after injection and then remained fairly constant up to 30 days.

When the turnover rates of neurohypophysial proteins were estimated, a half‐life of 1‐2 days and 8 days was calculated for the rapidly and slowly transported proteins, respectively.
STUDY ON THE INHIBITION OF BRAIN GLUTAMATE DECARBOXYLASE BY PYRIDOXAL PHOSPHATE OXIME‐O‐ACETIC ACID
Authors: Tapia R. , Sandoval M. E.
Published: October 2006

The kinetics of the inhibition of mouse brain glutamate decarboxylase by pyri‐doxaI‐5′‐phosphate oxime‐O‐acetic acid (PLPOAA) was studied. The inhibition was noncompetitive with regard to glutamic acid; it could be partially reversed by pyridoxal phosphate, but only when the concentration of the latter in the incubation medium was higher than that of pyridoxal‐5′‐phosphate oxime‐O‐acetic acid. The inhibition produced by aminooxyacetic acid, which is remarkably greater than that produced by PLPOAA, was also partially reversed only when an excess of pyridoxal phosphate was added. Both in the presence and in the absence of a saturating concentration of pyridoxal phosphate, the activity of the enzyme was decreased by PLPOAA at a 10−4m concentration to a value of about 50 per cent of the control value obtained without added coenzyme. This activity could not be further reduced even when PLPOAA concentration was increased to 5 × 10−3m. This same minimal activity of glutamate decarboxylase was obtained after dialysis of the enzymic preparation, or after incubation with glutamic acid in the cold followed by filtration through Sephadex G‐25. The addition of pyridoxal phosphate to the dialysed or glutamic acid‐treated enzyme restored the activity to almost the control values. PLPOAA did not affect the activity of glutamate decarboxylase from E. coli or that of DOPA decarboxylase and GABA transaminase from mouse brain. To account for the results obtained it is postulated that brain glutamate decarboxylase has two types of active site, one with firmly bound, non‐dialysable pyridoxal phosphate and the other with loosely bound, dialysable coenzyme; PLPOAA behaves as a weak inhibitor probably because it can combine mainly with the loosely bound coenzyme site, while aminooxyacetic acid is a potent inhibitor probably because it can block both the ‘loosely bound coenzyme’ and the ‘firmly bound coenzyme’ sites.
ENZYMES OF NUCLEIC ACID METABOLISM IN THE BRAINS OF YOUNG AND ADULT RATS
Authors: Guroff G. , Brodsky Marcia
Published: October 2006

A number of precursors of RNA are incorporated several‐fold more readily into the RNA of brain slices from 10‐day‐old rats than into RNA of slices from adult animals. The brains of the young animals show moderately higher levels of some of the anabolic enzymes of RNA metabolism including RNA polymerase (nucleosidetriphosphate: RNA nucleotidyltransferase; EC 2.7.7.6) and substantially lower levels of the degradative enzymes, the nucleoside phosphorylases. The data suggest that all the enzymes work in a concerted fashion to produce an increased rate of synthesis in young animals rather than that any single controlling enzymic event is responsible.
MECHANISM OF ACTION OF β‐N‐OXALYL‐L‐α, β‐DIAMINOPROPIONIC ACID, THE LATHYRUS SATIVUS NEUROTOXIN
Authors: Cheema P. S. , Padmanaban G. , Sarma P. S.
Published: October 2006

The source of ammonia in the brain tissue of young rats treated with β‐N‐oxalyl‐l‐α, β‐diaminopropionic acid (ODAP) has been studied. ODAP administration to 12‐day‐old rats causes a significant increase in the levels of adenylic acid deaminase in the brain. Glutaminase activity also shows an increase under these conditions. An increase in the levels of acid protease and transglutaminase is also observed in the brain of ODAP‐treated animals. Glutamate dehydrogenase activity is decreased slightly. Glutamine synthetase enzyme is not affected. Aspartate‐α‐ketoglutarate transaminase and aspartate‐pyruvate transaminase activities are enhanced in the brain tissue of ODAP‐treated rats. It is held that protein degradation, especially the cleavage of free and protein‐bound amide bonds, may be responsible for excess ammonia liberation in the brain of ODAP‐treated young rats.
TYROSINE HYDROXYLASE IN BOVINE CAUDATE NUCLEUS
Authors: Nagatsu T. , Sudo Y. , Nagatsu I.
Published: October 2006

Approximately 80 per cent of tyrosine hydroxylase activity in bovine caudate nucleus was particle‐bound. The rest of the activity was found in the soluble fraction. The enzyme activity in crude tissue preparations was inhibited, probably by the presence of endogenous inhibitors. Dilution of crude tissue preparations such as the crude mitochondrial fraction caused an increase in the specific activity. The particle‐bound enzyme was solubilized by incubation with trypsin. The presence of deoxycholate increased the degree of solubilization. The activity of the solubilized enzyme from the washed particles was also inhibited, but the subsequent purification by ammonium sulphate could eliminate the inhibition. The solubilized enzyme was partially purified by ammonium sulphate fractionation and Sephadex G‐150 chromatography. A tetrahydropteridine and ferrous ion were required as cofactors for the partially purified enzyme. Among various divalent cations, only ferrous ion could activate the partially purified enzyme. The enzyme was inhibited by L‐α‐methyl‐p‐tyrosine and catecholamines such as dopamine. The optimum pH was found between 5.5 and 6.0. Km values toward tyrosine, 2‐amino‐4‐hydroxy‐6,7‐dimethyltetrahydropteridine and Fe2+, were approximately 5 × 10−5 M, 1 × 10−4 M and 4 × 10−4 M, respectively.
EXCHANGE OF TAURINE IN BRAIN SLICES OF ADULT and 7‐DAY‐OLD RATS
Authors: Oja S. S.
Published: October 2006

Abstract— The influx or efflux of taurine in brain slices prepared from adult and 7‐day‐old rats was studied in Krebs‐Ringer bicarbonate‐glucose medium with 0,2 and 10 mm‐taurine. The exchange of taurine between the slices and the medium was slow, and no steady‐state concentration was reached within the experimental period of 150 min. In both experimental groups there was a net influx of taurine into the slices from 10 mm‐taurine and a slight net efflux from the slices into 2 mm‐taurine. The rate of influx from 10 mm‐taurine was about the same in the two groups after an initial period of faster influx into the slices of adult rats. There was some rapid initial efflux into 0 and 2 mm‐taurine solutions from the slices from 7‐day‐old rats, but with prolonged incubation these slices were better able to maintain their intracellular taurine than the slices from adult rats. The reasons and significance of the high cerebral concentration of taurine in immature brain in vivo are briefly discussed in the light of the present and earlier studies.
ELONGATION OF MITOCHONDRIAL FATTY ACIDS DURING BRAIN DEVELOPMENT1
Authors: Yatsu F. , Moss Sylvia
Published: October 2006

Abstract— Elongation of mitochondrial fatty acids was studied in whole brain samples from rats before, during and after the period of myelination. The mitochondria were isolated by centrifugation in a discontinuous sucrose gradient and incubated under N2 in a medium containing NADH, NADPH, ATP and acetyl‐[1‐14C]coenzyme A. Fatty acids were extracted, methylated and analysed by gas‐liquid chromatography. A distinct pattern emerged in which brain mitochondria from rats undergoing myelination synthesized longer chain fatty acids preferentially, particularly C22:4. Mitochondria from brains of mature rats synthesized shorter chain fatty acids preferentially, mainly C18:0 and C20:4. We suggest that eicosamonoenoic acid (C22:1) is a precursor in vivo of nervonic acid (C24:1).
ISOLATION AND CHARACTERIZATION OF GLYCOSAMINOGLYCANS FROM BRAIN OF CHILDREN WITH PROTEIN‐CALORIE MALNUTRITION
Authors: Chandrasekaran E. V. , Mukherjee K. L. , Bachhawat B. K.
Published: October 2006

Abstract— The uronic acid containing glycosaminoglycans (GAGs) were isolated from the brains of 1‐year‐old and 4‐year‐old kwashiorkor children and characterised by constituent analyses. A marked reduction is the total GAG concentration of brain was noticed in both cases of kwashiorkor. In the 1‐year‐old kwashiorkor brain, hyaluronic acid is the most predominant GAG (73.5 per cent) whereas heparan sulphate, chondroitin sulphates and low sulphated chondroitin sulphate constituted less than 10 per cent. In the 4‐year‐old kwashiorkor brain, the proportion of hyaluronic acid was 27.5 per cent, low sulphated chondroitin sulphate 31.2 per cent, chondroitin sulphates 28.3 per cent and heparan sulphate 10 per cent. This marked reduction in the concentration as well as qualitative changes in GAG in protein‐calorie malnutrition as compared to the normal is discussed in relation to brain function.
CHOLESTEROL ESTERS IN DEVELOPING RAT BRAIN: ENZYMES OF CHOLESTEROL ESTER METABOLISM1
Authors: Eto Y. , Suzuki K.
Published: October 2006

Abstract— Three enzymes of cholesterol ester metabolism, a cholesterol‐esterifying enzyme which incorporates free fatty acids into cholesterol esters without participation of CoA, and two cholesterol ester hydrolases with differing pH optima, all showed distinct changes in developing rat brains. The specific activity of the esterifying enzyme was approx. 20 percent of the adult level at birth, increased gradually to the adult level by 20 days of age and remained constant thereafter. The pH 4.2 hydrolase at birth also had a specific activity of about 20 per cent of the adult level but it increased rapidly to reach a peak at 13 days, by which time the activity had increased eight‐fold. The activity declined somewhat thereafter to reach the adult level by 23–30 days. In contrast, there already was 60 per cent of the adult specific activity of the pH 6.6 cholesterol ester hydrolase at birth. The activity remained constant until 12 days and then doubled during the next two weeks, reaching a broad peak, then declining slightly to reach the adult activity by 50 days. Therefore, the developmental changes of both of the hydrolases appeared to be related to the process of myelination. The period of active myelination (10–30 days) was characterized by the sharp rise in the activity of pH 6.6 cholesterol ester hydrolase and by the rapid decrease of pH 4.2 cholesterol ester hydrolase.
MODULATORS OF GLUTAMINASE ACTIVITY
Authors: Weil‐Malherbe H.
Published: October 2006

Abstract— The activating effect of GTP on particulate preparations of glutaminase from rat brain or rat kidney was competitively inhibited by cyclic guanosine 3′,5′‐monophosphate (c‐GMP). Similarly, the effect of ATP was inhibited by cyclic adenosine 3′,5′‐monophosphate (c‐AMP). In the absence of an added activator, the glutaminase activity of brain or kidney particles, if measurable, was also inhibited by c‐GMP and c‐AMP. GTP was a stronger activator than ATP, and c‐GMP was a stronger inhibitor than c‐AMP, for the enzyme from either tissue. The K1, of c‐GMP was about 40 mM, that of c‐AMP was about 60 mM, as determined with a brain preparation.

Soluble preparations of glutaminase from pig brain and pig kidney were activated, in decreasing order of efficiency, by riboflavin phosphate, GTP, ATP and orthophosphate. The relative potencies were similar for the soluble enzymes from brain and kidney and also in the particulate and soluble forms of the brain enzyme. The apparent Km, values for the soluble brain enzyme were about the same (9–10 mM) whether riboflavin phosphate, GTP, ATP or 100 mM orthophosphate were used as activators. The Km increased with concentrations of orthophosphate lower than 100 mM, but was not significantly affected by changes in the concentrations of the other activators. Results for the kidney enzyme were similar, but the Km, tended to be somewhat lower. The estimation of the apparent KA with either the brain or kidney enzyme preparation indicated that affinities and activating efficiency were related.

The activating effects of carboxylic acids on the soluble brain enzyme were similar to those on the particulate brain enzyme in terms of some correlation to the number of carboxylic groups per molecule and the potentiation by orthophosphate, but in the soluble kidney enzyme these effects were less marked or absent.
EFFECT OF HYPERPHENYLALANINEMIA ON VITAMIN B6, METABOLISM IN DEVELOPING RAT BRAIN
Authors: Loo Y. H. , Mack Kathryn
Published: October 2006

Abstract— The turnover of the different forms of B6 vitamers in the brains of normal and hyperphenylalaninemic preweanling rats was compared after administration of a load of [14C]pyridoxol. Metabolic transformations occurred in the following sequence: oxidation of pyridoxol to pyridoxal, which was in turn phosphorylated to the 5′‐phosphate ester. No significant amount of pyridoxamine was formed during the 8‐h experimental period. Pyridoxamine 5′‐phosphate was derived from pyridoxal 5′‐phosphate. The specific radioactivity of pyridoxal phosphate in the hyperphenylalaninemic brain was significantly lower and increased at a slower rate than in control brains. This difference could not be accounted for by either a deficient supply or inhibited activity of the enzyme, pyridoxal kinase. The synthesis of pyridoxamine 5′‐phosphate in the experimental animals also lagged behind the controls. Decreased activity of enzymes dependent on pyridoxal phosphate as cofactor would explain the slower turnover of this B6‐coenzyme.
MYELIN SYNTHESIS IN PERIPHERAL NERVE IN VITRO: SULPHATIDE INCORPORATION REQUIRES A TRANSPORT LIPOPROTEIN1,2,3
Authors: Pleasure D. E. , Prockop D. J.
Published: October 2006

Abstract— Sciatic nerves from 18‐day‐old chick embryos incorporated 35SO4 into myelin sulphatide in vitro. Sulphatide in a microsomal subfraction of the nerve was rapidly labelled with 35SO4, and a lipoprotein fraction in the nerve served to transfer the [35S]sulphatide from the microsomal subfraction to myelin. Puromycin and cycloheximide inhibited the incorporation of [35S]sulphatide into myelin after a lag period of about 2 h. These agents did not alter the rate of appearance of [35S]sulphatide in the microsomal subfraction, and did not diminish the capacity of myelin to take up [35S]sulphatide from the lipoprotein fraction; instead, they appeared to interfere with the incorporation of [35S]sulphatide into myelin by decreasing the available pool of the transport lipoprotein. Partial characterization of the [35S]labelled lipoprotein fraction indicated that it had a density of 1.06–1.08. The lipoprotein was highly aggregated, but, after incubation with SDS and mercaptoethanol, it was dissociated into sulphatide‐containing micelles and proteins.
PYRUVATE METABOLISM IN THE LOBSTER NERVE AS AFFECTED BY THE PARTIAL PRESSURE OF CARBON DIOXIDE: OBSERVATIONS ON THE SYNTHESIS OF ACETYLCHOLINE AND ON METABOLIC COMPARTMENTATION
Authors: Cheng S.‐C.
Published: October 2006

Abstract— In the lobster nerve the fixation of CO, at various levels of pCO2 was studied by the incorporation of [l‐14C]pyruvate. Incorporation of 14C was solely dependent on CO2 fixation since the C‐1 was decarboxylated in the formation of acetyl‐CoA. Paired‐nerve studies with [2‐14C]pyruvate afforded a study of pyruvate metabolism in the lobster nerve. [I14C]Pyruvate was incorporated to nearly the same extent at all levels of pCO2 including zero pCO2, a finding that suggested metabolic recycling of CO2. The magnitude of the metabolic recycling of C‐1 of pyruvate or pyruvate dismutation was estimated to be nearly 20 per cent of total CO2 fixation. Re‐evaluation of the relative contributions of the CO2 fixation. and acetyl‐CoA pathways on the basis of more extensive data gave a ratio of 2:3.

The pCO2 affected synthesis of ACh and the level of citrate. With increasing pCO2, the specific radioactivity of ACh decreased much more than the content of ACh. The decrease in the specific radioactivity of ACh but not that of citrate further suggested metabolic compartmentation. The implication of these findings is discussed.

Alanine functioned as a metabolic sink for the incorporated pyruvate. Pyruvate levels were estimated to be approximately 0.1 nmol/mg of protein.
THE EFFECT OF TOPICAL APPLICATION OF DIETHYL‐α‐FLUOROGLUTARATE ON THE METABOLISM AND ELECTRICAL ACTIVITY IN VIVO OF CAT CEREBRAL CORTEX1
Authors: Cohen H. P. , Vasconetto C. , Ayala G.‐F.
Published: October 2006

Abstract— The effect of topical application of diethyl‐α‐fluoroglutarate on the primary response of cat cerebral cortex to thalamic stimulation was investigated, and samples of the involved tissue and of homologous contralateral control tissue were removed at appropriate times for biochemical analyses. Changes in electrocortical response were first noted 30–40 min after topical application of 10 μ1 (52.7 μmol) of the drug to the pericruciate gyrus. A rapid reduction in amplitude of the surface negative component of the primary response was observed initially, followed by amplitude reduction and rapid disappearance of the primary response throughout the cortical field within a few minutes after the change first observed at the surface. The effects were interpreted either as a direct action of the drug on the somadendritic membrane or an inhibition of the excitatory synaptic impingement.

Analyses of the tissues removed at the time of maximum electrocortical response indicated profound metabolic changes, including depletion of energy reserves and several Krebs cycle intermediates. Large increases in tissue levels of glucose, glucose 6‐phosphate, and pyruvate were found. Changes in amino acids comprised depletion of glutamate with increased tissue levels of aspartate, GABA, NH3, threonine, serine and alanine.

Tissues were also removed at 10 min after topical application of the drug but before the advent of electrocortical changes. Decreased levels of glutamate were associated with a rise in tissue aspartate. Tissue levels of the other amino acids were unchanged. Glucose, glucose 6‐phosphate and pyruvate levels were increased, lactate and ATP levels were unchanged, and P‐creatine, α‐KG and malate levels were reduced. We believe that the observed pattern of changes represents responses of the cerebral cortex to either a block in the synthesis of glutamate or in oxidation of pyruvate, with consequent interference with oxidative and energy metabolism and eventual depression of cortical electrical activity.
BIOSYNTHESIS AND BIODEGRADATION OF RAT BRAIN GANGLIOSIDES STUDIED IN VIVO
Authors: Holm M. , Svennerholm L.
Published: October 2006

Abstract— Metabolic relationships between the four major brain gangliosides, GM1, GD1a, GDlb and GT1 were studied in vivo. Labelled acetate and glucosamine were injected intracerebrally into 6–12‐day‐old rats and the radioactivities of the cerebral gangliosides were analysed. Radioactivity from [3H]acetate was determined in sialic acid, sphingosine and stearic acid and from [1‐14C]glucosamine in hexosamine and sialic acid. The gangliosides were labelled in proportion to their pool size. In 6 day‐old rats the labelling was approx. 30 per cent lower in the sialidase‐stable sialyl group than in the labile one. When the brain gangliosides were labelled in 12‐day‐old rats, however, the specific activities of sialidase‐labile and stable sialyl groups were the same at 0.5 months after the injection of precursors and disappeared at the same rate. The results indicate that at the age of 6 days a small pool of monosialogangliosides exists, which is converted to di‐ and trisialogangliosides. The degradation of gangliosides was studied by following the radioactivities in sphingosine and stearic acid from 2 to 6 months after the injection of labelled acetate. The specific activities of sphingosine and stearic acid decreased simultaneously at the same rate in all the four major gangliosides. The specific activity of stearic acid was the same in total brain lipids as in gangliosides. The half‐lives for the degradation of the gangliosides were age‐dependent and estimated to 60 days in adult rats. They were much shorter in younger rats but no reliable figures could be determined.
HUMAN BRAIN‐SPECIFIC ALPHA2‐GLYCOPROTEIN: PURIFICATION BY AFFINITY CHROMATOGRAPHY AND DETECTION OF A NEW COMPONENT; LOCALIZATION IN NERVOUS CELLS1
Authors: Warecka Krystyna , Møller H. J. , Vogel H.‐M. , Tripatzis I.
Published: October 2006

Abstract— Human brain‐specific alpha2‐glycoprotein was purified by means of Sepharose immunoadsorbents. A further brain‐specific protein was found by this method. This component appears to be present in brain in low concentrations only and has been enriched by affinity chromatography. Glial cells of human brain were separated from neurons by a density centrifugation method and four fractions were obtained: neuropil, neuronal perikarya, nuclei and debris. Each fraction was checked by light and phase contrast microscopy to estimate the intactness of the cells and any contamination by other fractions, and also immunologically for determination of brain‐specific alpha2‐glyco‐protein. The results indicate that localization of this brain‐specific protein is in the cyto‐plasm of the glial cells. The results are discussed in terms of a possible role of this protein in the inflammatory response and in some demyelinating diseases.
SYNTHESIS OF GLYCOPROTEINS IN BRAIN: IDENTIFICATION, PURIFICATION AND PROPERTIES OF GLYCOSYL TRANSFERASES FROM PURIFIED SYNAPTOSOMES OF GUINEA PIG CEREBRAL CORTEX
Authors: Bosmann H. B.
Published: October 2006

Abstract— Four glycoprotein:glycosyl transferases (a fetuin:N‐acetylglucosaminyl transferase; a bovine submaxillary mucin: N‐acetylgalactosaminyl transferase; a collagen: glucosyl transferase and an orosomucoid: galactosyl transferase) were purified 34‐, 45‐, 37‐ and 47‐fold, respectively, from synaptosomes prepared from guinea pig cerebral cortex. Purifications were achieved by centrifugation and by column chromatography on Sephadex G‐100 and G‐150 of 0, 1% (w/v) Triton X‐100 extractsof the purified cerebral cortical synaptosomes. The enzymes were separated from endogenous acceptors and were highly specific for specific macromolecular acceptors; small molecules were ineffective as acceptors. The fetuin: N‐acetylglucosaminyl transferase functioned only with fetuin minus N‐acetylneuraminic acid, galactose and N‐acetylglucosamine; the bovine submaxillary mucin: N‐ acetylgalactosaminyl transferase with bovine submaxillary much minus N‐acetylneuraminic acid and N‐acetylgalactosamine; the collagen: glucosyl transferase with collagen minus glucose; and the orosomucoid: galactosyl transferase with either orosomucoid minus N‐acetylneuraminic acid and galactose or fetuin minus N‐acetylneuraminic acid and galactose. Each transferase required a specific (XDP)‐monosaccharide for transfer. The transferases were entirely dependent on either Mn2+ or Mg2+ for activation and Fe2+ and Hg2+ inhibited each of the four enzymes. The optimum pH's for the enzymes were: for fetuin: N‐acetylglucosaminyl transferase, 7, 4–8.0; for bovine submaxillary mucin: N‐acetylgalactosaminyl transferase, 7, 7; for collagen: glucosyl transferase, 7, 7 and for orosomucoid: galactosyl transferase, 6, 6. The enzymes were distributed subsynaptosomally primarily in the synaptosomal plasma membrane and in the mitochondria of the synaptosome. The respective values for Km (μM) and Vmex (pmoles/h/mg of protein) for the transferases were: fetuin: N‐acetylglucosaminyl transferase, 12 and 143; for bovine submaxillary mucin: N‐acetylgalactosaminyl transferase, 25 and 166; for collagen: glucosyl transferase, 4 and 10 and for orosomucoid:galactosyl transferase, 8 and 111.
THE EFFECTS OF ELECTRICAL STIMULATION AND IONIC ALTERATIONS ON THE METABOLISM OF AMINO ACIDS AND PROTEINS IN EXCISED SUPERIOR CERVICAL GANGLIA OF THE RAT1
Authors: McBride W. J. , Klingman J. D.
Published: October 2006

Abstract— The effects of supramaximal electrical stimulation on the metabolism of amino acids and proteins in incubated superior cervical ganglia of the rat were studied by the use of a gas‐liquid chromatographic (GLC) assay procedure. Stimulation at 5 Hz for 2 h caused an apparent increase in tissue levels of free amino acids, with alanine, serine, glycine, valine, threonine, isoleucine and aspartate (+ asparagine) most noticeably affected. The amino acid composition (partial) of the TCA‐insoluble proteins of resting and stimulated ganglia was approximately the same after 60 min of incubation, but there was less TCA‐insoluble protein in the stimulated ganglia. The addition of amino acids (at plasma concentrations) to the standard media had no apparent affect on the amino acid composition of this protein fraction. Stimulation for 0, 5 h initially increased the efflux of alanine, valine, proline and ornithine into the incubation media but prolonged stimulation (for 4–0 h) decreased the efflux of alanine, serine, glycine and isoleucine and increased the efflux of lysine into the incubation media. The leakage of amino acids from the ganglia appeared to be a sodium‐dependent process.

The incorporation of 14C from [U‐14C]glucose into glutamate (+ glutamine) and aspartate (+ asparagine) was greater in stimulated than in resting ganglia. However, the conversion of glutamate carbons from [U‐14C]l‐glutamate into aspartate was not affected by stimulation. Incorporation of 14C from [U‐14C]glucose into glycine and serine was apparently not affected by stimulation during the 60 min of incubation. However, serine was the only amino acid which exhibited a higher specific radioactivity in stimulated ganglia than in resting ganglia incubated for 4 h in standard media. Lithium ions had the apparent specific effect of increasing the labelling with 14C from [U‐14C]glucose into ornithine, and increasing the efflux and overall metabolism of serine in the ganglia. Incorporation of 14C from [U‐14C]glucose into proteins was lower in the stimulated than in the resting ganglia if compensation was made for the higher radioactivity available in the total free amino acid pool of the stimulated ganglia.

The rate of 14C incorporation from [U‐14C]glutamate into the TCA‐insoluble proteins of resting ganglia was greater when no other amino acids at concentrations approximating plasma levels were added to the bathing media; this rate was lower in stimulated than in resting ganglia.
ENERGY METABOLISM IN THE BRAINS OF l‐PHENYLALANINE‐TREATED CHICKS1
Authors: Granett Sandra E. , Wells W. W.
Published: October 2006

Abstract— When day‐old chicks were injected intraperitoneally with 1.62mmoles of l‐phenylalanine, they developed a condition resembling narcosis. Simultaneously, whole brain levels of phenylalanine were 2–4 μmol/g, whereas those in control brain were 0.06 μmol/g. Examination of some glycolytic intermediates in the brain revealed significant decreases in fructose‐1,6‐diphosphate, l‐α‐glycerol phosphate and lactate, in comparison to the levels of these compounds in the saline‐injected control animals. Levels of glucose and glucose‐6‐phosphate either increased or did not change, whereas levels of glycogen did not differ significantly. Phosphocreatine increased reciprocally with the decrease in inorganic phosphate. The levels of adenine nucleotide (energy charge) were not affected. Utilization of cerebral high‐energy phosphates was depressed by 50–70 per cent when determined as a function of metabolic rate in the brain at 15‐ and 30‐s periods of ischaemia according to the ‘closed‐system’ technique. Explanations for these data have been examined, such as toxicity of phenylacetate and inhibition of glycolytic enzymes by phenylpyruvate and l‐phenylalanine and their relevance to this study is discussed.
DIFFERENTIATION OF CHICK EMBRYO CEREBRAL HEMISPHERES: A CRITICAL EYALUATION OF A BULK PREPARATION OF NEUROBLASTS AND SPONGIOBLASTS
Authors: Judes C. , Jacob M. , Kister L.
Published: October 2006

Abstract— A critical evaluation of a previously described method of bulk preparation of neuroblasts and spongioblasts from chick embryo cerebral hemispheres furnished the following results.

A major loss of total RNA occurs during the preparation of the cell fractions.

The loss occurred mainly during the dissociation of the tissue and the following centrifugations.

The missing RNA's were found in the supernatants after cell centrifugation at low speed.

There was a selective loss of transfer RNA amounting to 70–80 per cent relative to ribosomal RNA.

The relative proportions of the 29, 18 and 5s ribosomal RNA's were constant, but there was a decrease in their proportion relative to heavy‐molecular weight, rapidly‐labelled nuclear RNA.

The ribosomal RNA's in the low‐speed supernatant could be resedimented at 35,000 g whereas most transfer RNA could not.

The results are consistent with a loss of fragments of cytoplasm containing ribosomes and with additional extraction of transfer RNA during the preparation.
EFFECTS OF EXCITATION AND ANAESTHESIA ON THE GLUTAMINE CONTENT OF THE RAT BRAIN WITH A REFERENCE TO THE ADMINISTRATION OF GLUTAMINE
Authors: Dobkin J.
Published: October 2006

Abstract— A study of the factors affecting the ghtamine content in brain of rats showed that it was significantly decreased by intraperitoneal injection of physiological saline and by the stimulus of decapitation. It fell markedly at the stage of delirium (excitement) of pentobarbitone sodium anaesthesia and returned to the original value in light and deep surgical anaesthesia; after pentylenetetrazol injection the glutamine content showed a tendency to decrease but this change was only significant in relation to its post‐saline level when the convulsant and 0.9 % NaCl were given to lightly‐anaesthetized animals.

The i.p. administration of glutamine temporarily abolished the decrease in its concentration in the brain caused by injection and decapitation but never raised it above the original level. Many rats previously treated with glutamine showed no signs of excitement during the induction period of pentobarbitone sodium anaesthesia, and those which were excited showed a comparatively smaller decrease of brain glutamine content. whereas in the anaesthetic state there was no change in the content of brain glutamine after glutamine had been administered. Pentylenetetrazol given at the dose level of 200 mg/kg, but not at that of 100 mg/kg, resulted in the uptake of the added glutamine by the brain up to its normal concentration. Hence, the added glutamine did not readily enter normal or anaesthetized brain, but did penetrate the hyperactive brain where its level had fallen.

The brain levels of free glutamic and aspartic acids were not affected, in general, by procedures which increased cerebral activity. Glutamate was decreased by deep anaesthesia, whereas aspartate was not significantly altered in any of the conditions which were tested.

The significance of these results in relation to cerebral ammonia metabolism and possible changes of the permeability of the tissue to glutamine in different functional states is discussed.
INHIBITION OF GABA TRANSAMINASE ACTIVITY BY 4‐AMINOTETROLIC ACID
Authors: Beart P. M. , Uhr M. L. , Johnston G. A. R.
Published: October 2006

Abstract— The influence of the following acetylenic analogues of GABA on GABA‐metabolizing enzymes was studied in vitro: 4‐amino‐, 4‐morpholino‐, 4‐piperazino‐, 4‐piperidino‐ and 4‐pyrrolidinotetrolic acid. 4‐Aminotetrolic acid was a linear competitive inhibitor of GABA transaminase activity in extracts of rat cerebral mitochondria and a linear noncompetitive inhibitor of this enzyme activity in extracts of P. fluorescens when activity was measured with GABA as the variable substrate. From these results it was calculated that the dissociation constants for the binding of 4‐aminotetrolic acid to the pyridoxal form of these enzymes are approx. 1 mM. The other substituted tetrolic acids did not influence either transaminase activity under the conditions studied. None of the substituted tetrolic acids influenced the L‐glutamic acid decarboxylase activity in extracts of rat cerebral cortex and of E. coli.
BIOCHEMICAL EFFECTS OF THE ANTICONVULSANTS TRIMETHADIONE, ETHOSUXIMIDE AND CHLORDIAZEPOXIDE IN RAT BRAIN
Authors: Nahorski S. R.
Published: October 2006

Abstract— The concentrations of several metabolites, including glucose, glycogen, hexose phosphates, adenine nucleotides phosphocreatine, amino acids and some tricarboxylate cycle intermediates, have been estimated in cerebral tissues of rats treated with anticonvulsant doses of trimethadione, ethosuximide and chlordiazepoxide.

Anticonvulsant administration, in each case, produced an increase in brain glucose, but only trimethadione and ethosuximide resulted in elevated brain/blood glucose ratios. It was concluded that the apparent rise in intracellular glucose with the latter drugs may, in part, be the result of a stimulation of glucose transport from blood into the brain. Anticonvulsant administration was also shown to result in a depression of some tricarboxylate cycle intermediates. The pattern of these metabolite changes was in effect similar to those reported independently in mice treated with anaesthetics and it was therefore concluded that these differences probably reflected a depression in metabolic rate.

Metabolic alterations in general do not indicate aetiology but rather effects of the drug activities. However, a role implicating increased intracellular glucose levels with membrane stabilization is discussed.
DNA POLYMERASE ACTIVITY FROM THE BRAIN OF OCTOPUS VULGARIS LAM
Authors: Libonati M. , Liguori G. , Giuditta A.
Published: October 2006

Abstract— The DNA polymerase of the optic lobes of Octopus vulgaris Lam has been solubilized and some of its properties have been investigated. The enzyme catalyses the incorporation of [3H]thymidine triphosphate into a DNase‐sensitive, acid‐insoluble product in the presence of DNA, the four deoxynucleoside triphosphates and Mg2+. The pH optimum is between pH 9.2 and 9.6, the optimal concentration of Mg2+ is between 10 and 30 mM and the optimal temperature is in the range 27°‐30°C. The content of enzyme per mg protein is highest in the vertical and optic lobes and lowest in the suboesophageal lobe.
STUDIES ON THE INCORPORATION OF [14C]AMINO ACIDS INTO PROTEIN BY ISOLATED RAT BRAIN NUCLEI1
Authors: Dravid A. R. , Wong E.
Published: October 2006

—Various parameters of the in vitro incorporation of [14C]amino acids into protein by cell nuclei isolated and purified from rat brain and liver were investigated. Nuclei purified through 2.2 m sucrose solution were capable of amino acid incorporation in vitro; and washing procedure to eliminate hypertonic sucrose before incubation was essential since sucrose in high concentration was inhibitory. Microbial contamination was found to be a serious source of error and the use of sterile conditions for incubation were necessary to obtain reproducible and valid results. Using completely sterile conditions, Na +, K+, RNase, DNase, puromycin, cycloheximide and chloramphenicol were without any effect on the ability of brain and liver nuclei to incorporate labelled amino acids into protein. Results of time‐course and preincubation experiments revealed that some factors essential for amino acid incorporation pass out of the nucleus into the medium. In addition, approximately 15 per cent of the labelled nuclear proteins with higher specific radioactivity was recovered in the incubation medium. Incorporation of [14C]leucine was proportional to the concentration of labelled amino acid and to the number of nuclei, and it is suggested that carefully controlled conditions of incubation are essential to obtain valid comparisons between different types of nuclei in terms of their relative abilities to incorporate amino acids in vitro. No evidence was obtained indicating isotope dilution phenomenon in these experiments. Whether or not in vitro incorporation of amino acid by nuclei represents protein synthesis is discussed.