bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECTS OF GLUTAMATE AND OTHER AMINO ACIDS ON THE RETINA1
Authors: Harreveld A. Van , Fifkova Eva
Published: October 2006

The application of unlabelled glutamate to the isolated chicken retina charged with [14C]glutamate caused an increase in the tissue transparency and a release of the label into the superfusion fluid. The processes causing the change in transparency were‘desensitized’by a prolonged application of unlabelled glutamate, whereas the release of the labelled amino acid was relatively unaffected. Mg2+ tended to depress the change in transparency caused by stimulation with unlabelled glutamate but had little effect on the release of labelled glutamate from the retina. The effect of a Ca2+‐free superfusion fluid on the transparency and release of glutamate varied from retina to retina. Aspartate (in higher concentrations) elicited a change in transparency and release of the label in a manner similar to that of glutamate. Glutamine caused a change in transparency accompanied by a release of labelled glutamine and in some experiments the release of a small amount of labelled glutamate. Homocysteic acid elicited marked changes in transparency but no release of labelled glutamate. Pyroglutamate depressed both the change in transparency and the release of labelled glutamate caused by the unlabelled amino acid. Gamma‐aminobutyric acid and glycine had no effect on the transparency of the tissue or on the release of amino acids. We have discussed the possibility that a release of glutamate from the intracellular compartment into the extracellular space is involved in the mechanism of spreading depression.
AMOUNTS AND TURNOVER RATES OF BRAIN PROTEINS IN MORPHINE‐TOLERANT MICE
Authors: Hahn D. L. , Goldstein A.
Published: October 2006

Abstract— Mice were injected intracerebrally with radioactive leucine 30 min before decapitation. A double‐label technique was used; e.g. [3H]leucine in control, untreated mice and [14C]leucine in morphine‐tolerant (dependent) mice. Proteins were extracted sequentially from mouse brain with aqueous buffer, Triton X‐100, and sodium lauryl sulphate. Each extract was subjected to electrophoresis on discontinuous, porosity‐gradient acrylamide gels. When the protein patterns from untreated, acutely morphinized mice were compared with those from morphine‐tolerant (dependent) mice, we observed no differences in the amounts of protein or of radioactivity in any of the 55 discrete bands.
THE DESMOSTEROL REDUCTASE ACTIVITY OF RAT BRAIN DURING DEVELOPMENT1
Authors: Hinse C. H. , Shah S. N.
Published: October 2006

Abstract— The reduction of desmosterol by cell‐free preparations from developing rat brain was established and the age‐dependent alterations in reductase activity were correlated with levels of desmosterol in brain. An increase in enzymic activity followed closely the sharp increase in levels of desmosterol that was observed at about 5 days of age and that reached a maximum at 8‐11 days of postnatal age. Furthermore, the abrupt decrease in the desmosterol content of brain at 13‐15 days of age was associated with a decrease in enzymic activity. We suggest that the enzyme may be substrate‐induced and that this attribute may be of significance with respect to the ontogenesis of myelin. Cerebral desmosterol reductase exhibited a specific requirement for NADPH and was primarily a particulate enzyme.
IMMUNOCHEMICAL STUDIES ON THE BRAIN SPECIFIC PROTEIN
Authors: Kawakita Hidenori
Published: October 2006

Abstract— In the soluble brain proteins of various species‐man, ox, cat, rabbit, rat, mouse, hen, snake, frog and fish–there is a protein group which migrates more slowly than Moore's S‐100 protein and faster than the albumin fraction on disc electrophoresis. The protein group is absent from any organs other than brain, and has a different pattern and number of fractions in different species. Immunochemically, the protein fraction group of the mammalian brains shows some common and identical distinctive antigenic determinants compared with the brain protein of the other animals‐hen, snake, frog and fish. The protein group was designated the ‘SPR’ proteins, which were separated to ‘PII,’, ‘PIII’, ‘PIV’ and ‘Pv’ fractions. Common antigenic determinants are found in these fractions. The protein group is found in human brain in larger amounts in grey matter than in white matter and in small amounts in the cellular nuclei of human and bovine brain.
EFFECT OF VITAMIN B6 ON PHENYLALANINE METABOLISM IN THE BRAIN OF NORMAL AND p‐CHLOROPHENYLALANINE‐TREATED RATS
Authors: Loo Y. H. , Mack Kathryn
Published: October 2006

Abstract— A phenylketonuria‐like state was produced in the preweanling rat, and the metabolism of phenylalanine in the normal and phenylketonuric brain was compared. The effect of B6 vitamers on the disposition of phenylalanine was also investigated. Phenylalanine was metabolized mainly by transamination and to a lesser extent by decarboxylation in both the normal and phenylketonuric‐like brain. Small amounts of amine were detected in all the brains throughout the experimental period. More than 95 percent of the metabolized amino acid appeared as aromatic acids, which steadily accumulated and remained in the brain for the duration of the experiment. No change in the metabolic pattern was produced by pyridoxol. In striking contrast, pyridoxamine prevented the accumulation of acidic metabolites in the brains of all animals tested. We suggest that pyridoxamine phosphate and/or pyridoxamine is actively associated with the removal of excess keto acids and aldehydes from the brain.
THE RELEASE OF AMINO ACIDS FROM THE HEMISECTED SPINAL CORD DURING STIMULATION
Authors: Roberts P. J. , Mitchell J. F.
Published: October 2006

Abstract— Isolated frog or toad hemicords were incubated for 40 min with either [14C]glycine, [3H]GABA, l‐[14C]glutamate. l‐[14C]aspartate, l‐[14C]serine, l[14C]threonine or l‐[3H]leucine, and the release of these compounds from the cord was measured under resting conditions and during electrical stimulation. Stimulation of spinal roots produced no significant change in the efflux of any of the compounds tested. Direct stimulation of the rostral cord however, produced a large increase in the efflux of [14C]glycine, [3H]GABA, l‐[14C]glutamate and l‐[14C]aspartate. These increased effluxes were calcium dependent, the effects of stimulation being reduced in a calcium‐free, or magnesium‐supplemented (10 mM) medium. Stimulation failed to produce an increase in the efflux of l‐[14C]serine, l‐[14C]threonine, l‐[14H]leucine, [14C]mannitol or [14C]urea. These results are consistent with the suggestions that glycine, GABA, glutamate and aspartate may be synaptic transmitters in the spinal cord.
EFFECTS OF ENVIRONMENTAL COMPLEXITY ON AMINO ACID INCORPORATION INTO RAT CORTEX AND HIPPOCAMPUS IN VIVO
Authors: Levitan I. B. , Mushynski W. E. , Ramirez G.
Published: October 2006

Abstract— Amino acid incorporation in vivo was investigated in the cortex and hippocampus of rats raised in enriched and deprived environments for various periods of time following weaning. At early times after weaning (7 days), the incorporation of l‐[3H]leucine into all sub‐cellular fractions of both cortex and hippocampus was higher in enriched than in deprived rats. At 16 days, incorporation into synaptosomal sub‐cellular fractions was higher in enriched than in deprived hippocampus, and lower in enriched than in deprived cortex; incorporation into perikaryal fractions of both brain regions was the same in the two groups of animals. Incorporation into subcortical nuclear protein fractions was higher in enriched rats at this time. At 35 days, the only difference between enriched and deprived rats was a lower incorporation into cortical synaptosomal sub‐fractions in the former. Experiments involving double labelling and electrophoresis indicate that there is no stimulation or inhibition of the synthesis of any particular protein in hippocampal nuclear and synaptosomal sub‐fractions of enriched rats. Synaptosomal proteins of cortex have a greater half‐life in enriched than in deprived rats; proteins of perikaryal fractions of cortex, and of all fractions of hippocampus, are turning over at the same rate in enriched and deprived animals.
INCORPORATION OF CARBON FROM GLUCOSE INTO CEREBRAL AMINO ACIDS, PROTEINS AND LIPIDS, AND ALTERATIONS DURING RECOVERY FROM HYPO‐GLYCAEMIA1
Authors: Stone W. E. , Tews Jean K. , Whisler K. E. , Brown Donna J.
Published: October 2006

Abstract— [U‐14C]Glucose was given to dogs by intravenous infusion to maintain a fixed level of specific radioactivity of the plasma glucose. The time course of incorporation of 14C into free amino acids, proteins and lipids of the cerebrum was observed for periods up to 2 h. Labelling of amino acids closely related to the tricarboxylic acid cycle increased progressively throughout the infusion, approaching specific radioactivities per μg‐atom of carbon equal to that of the plasma glucose. No significant dilution by unlabelled carbon entering the metabolic pathways was apparent.

In dogs subjected to profound insulin hypoglycaemia, [U‐14C]glucose mixed with unlabelled glucose was given to bring about recovery. The incorporation of 14C into glutamate, glutamine and aspartate during a 40‐min period was greater than during a comparable period in control animals, whereas the incorporation into serine was reduced. When considered in relation to alterations in amino acid levels, the data suggest that during recovery from hypoglycaemia the rates of synthesis of amino acids related to the tricarboxylic acid cycle are increased. During the period of recovery the rates of incorporation of 14C from glucose into proteins exceeded the pre‐insulin rates to a degree surpassing the increased incorporation into free amino acids. The labelling of the ganglioside, cerebroside‐sulphatide and cephalin fractions was also increased, The rates of incorporation into the lecithin‐sphin‐gomyelin and cholesterol fractions during recovery were the same as in the pre‐insulin period. Hypoglycaemia decreased the cerebral content of the phospholipid fractions; the lecithin‐sphingomyelin fraction returned toward normal during recovery, whereas the cephalins did not increase significantly.

The electrographic patterns and the occurrence of convulsive activity are discussed, both in insulin hypoglycaemia and during recovery.
CHANGES OF THYMIDINE KINASE IN THE DEVELOPING RAT BRAIN
Authors: Yamagami S. , Mow K. , Kawakita Y.
Published: October 2006

Abstract— Thymidine kinase (ATP: thymidine‐5′‐phosphotransferase EC 2.7.1.21) of the supernatant fraction from 6‐day‐old rat brain possessed a pH optimum of 8.0 and required the presence of 5mM‐ATP and 2.5 mM‐MgCl2 for maximum activity. The activity was completely inhibited by addition of 1.8 mM‐TTP. The enzyme activity was lost if the same supernatant fraction was refrozen and thawed. Km was 2.8 × 10−6 M for [6‐3H]thymidine.

Following subcellular fractionation of rat brain, the greatest proportion and highest specific activity of thymidine kinase was found in the supernatant fraction. Thymidine kinase activities reached a maximum at 6 days of age and then dropped sharply during maturation. Comparative studies of thymidine kinase activities of cerebrum, cerebellum and the remainder of the brain during growth indicated that the activity in the cerebellum was usually higher than those in the cerebrum and the remainder, and the biggest differences obtained at 6 days after birth corresponded with the peak in cerebellar activity.
THE BIOSYNTHESIS OF CHOLESTEROL AND OTHER STEROLS BY BRAIN TISSUE
Authors: Ramsey R. B. , Jones J. P. , Nicholas H. J.
Published: October 2006

Abstract— The distribution of [14C]labelled material into subcellular fractions of 30‐day‐old rat brain was studied as a function of time, following intracerebral injection of [2‐14C] mevalonic acid. As in the adult and 15‐day‐old brain, the microsomal fraction was indicated as the site of sterol synthesis. Unlike the 15‐day‐old animal, the myelin fraction from the 30‐day‐old rat was the predominately labelled fraction at 2 weeks after injection of the animal. Significant amounts of [14C]cholesterol were not present until about 4 h after injection. In order to ascertain whether different populations of cholesterol were being labelled, depending on the age of the animal injected, we compared the labelling of myelin and non‐myelin components in animals injected at 15 or at 30 days of age, and sacrificed, respectively, from 14 to 29 days or from 1 to 28 days after injection. Our results indicated that there was an apparent shift of labelled sterol from non‐myelin to myelin fractions at about 37–44 days of age.
THE EFFECT OF NEONATAL THYROIDECTOMY ON THE DEVELOPMENT OF THE ADENOSINE 3′,5′‐MONOPHOSPHATE SYSTEM IN THE RAT BRAIN
Authors: Schmidt M. J. , Robison G. A.
Published: October 2006

Abstract— The effect of neonatal thyroidectomy on the cyclic AMP system in the developing rat brain was examined. Administration of 131I at birth led to a 16 per cent reduction in brain weight and a 70 per cent reduction in body weight by 40 days of age. The level of cyclic AMP in the brain increased 5‐fold between birth and 40 days of age and this increase was partially reduced by early thyroidectomy. A similar increase in the activity of adenyl cyclase and phosphodiesterase was observed during development, but thyroidectomy produced no detectable changes in the activity of either enzyme. The activity of the cyclic AMP‐dependent protein kinase was already maximal at birth and also was unaffected by thyroidectomy.

Norepinephrine increased levels of cyclic AMP 4‐ to 5‐fold in brain slices prepared from adult rats, but was without effect on slices prepared from newborn or 3‐day‐old rats. The response to norepinephrine in thyroidectomized rats did not differ from that in control rats at any of the ages examined. Our findings indicate that neonatal hypothyroidism does not deleteriously affect the development of the cyclic AMP system in the rat brain.
LIPID CONTENT IN BRAIN AND SPINAL CORD DURING EXPERIMENTAL ALLERGIC ENCEPHALO‐MYELITIS IN RATS1
Authors: Maggio B. , Cumar F. A. , Maccioni H. J.
Published: October 2006

Abstract— The content of cerebrosides, sulphatides, gangliosides, cholesterol and phospholipids was evaluated in the brain and spinal cord of rats during the acute and recovery stages of experimental allergic encephalomyelitis (EAE). During the acute stage there was a significant decrease of sulphatides and gangliosides in spinal cord; in brain, only sulphatides were diminished. In the recovery stage, cerebrosides and gangliosides were decreased in the brain, whereas the lipid content of the spinal cord was similar to that in control animals. Cholesterol esters were detected in the brain and spinal cord during both periods. The results show that the changes are not the same for brain and spinal cord during the acute and recovery stages and that glycosphingolipids from either white or grey matter seem to be preferentially altered.
ESTIMATION OF LEVELS OF SEROTONIN AND 5‐HYDROXYINDOLES IN WHOLE BLOOD BY AN AUTOANALYTICAL PROCEDURE: OBSERVATIONS ON THE BLOOD‐BRAIN BARRIER1
Authors: Welch K. M. A. , Meyer J. S. , Kwant Susan
Published: October 2006

Abstract— We describe a method for the fluorometric determination of 5‐hydroxyindoles in the physiological range of 0.010–1.30 μg/ml of whole blood by means of an autoanalytical procedure. Serotonin is dialysed free from haemolysed blood constituents and a complex between 5‐HT and o‐phthaldialdehyde is formed in the dialysand to provide a considerable increase over the native fluorescence of 5‐HT in strong acid. The method has been evaluated and considered to be accurate for the continuous monitoring of levels of 5‐HT in whole blood and for the determination of cerebral arteriovenous differences. The range of values for human patients with cerebrovascular disease was 0.09–0.34 μg/ml of whole blood. In experimental studies on the baboon the range was 0.538–1.28 μg/ml. A mean positive cerebral arteriovenous difference for 5‐HT (and possibly other 5‐hydroxyindoles) of 0.037 μg/ml was measured in 10 baboons. This finding suggests the possibility of physiological movement of 5‐HT and 5‐hydroxyindoles into brain across the blood‐brain barrier.
THE ABSENCE OF ‘SURPLUS’ ACETYLCHOLINE FORMATION IN PRISMS PREPARED FROM RAT CEREBRAL CORTEX
Authors: Bourdois P. S. , Szerb J. C.
Published: October 2006

Abstract— Prisms of rat cerebral cortex incubated without cholinesterase inhibitor showed an increase in ACh content during the first hour of incubation. The effects of adding cholinesterase inhibitors during the second hour depended on the potassium concentration. At 6 mM‐K+ there was only a small rise in ACh but when K+ was raised to 25 mM a large increase in ACh content was observed. It is proposed that the increase in ACh is due to the reuptake of released ACh.
CORRELATION BETWEEN ELECTRICAL ACTIVITY AND SPLITTING OF PHOSPHOLIPIDS BY SNAKE VENOM IN THE SINGLE ELECTROPLAX
Authors: Bartels Eva , Rosenberg Philip
Published: October 2006

Abstract— Cottonmouth moccasin snake venom (SV) was applied to the innervated membrane of the isolated single cell of the Sachs electric organ (electroplax) of the electric eel, Electrophorus electricus. Concentrations as low as 0.05 μg/ml irreversibly antagonized depolarization by carbamylcholine, whereas concentrations of 0.1 mg/ml or higher were required to directly and irreversibly depolarize and block electrical excitation. The active component of the venom was stable to boiling at acid pH, destroyed by boiling at alkaline pH and nondialyzable and corresponded to those fractions containing maximum phospholipase A activity demonstrable when isolated by paper electrophoresis and Sephadex filtration. Phospholipase C and lysolecithin in concentrations of 1 mg/ml and 0.2 mg/ml, respectively, depolarized and blocked electrical excitation, whereas lower concentrations did not antagonize depolarization by carbamylcholine. Triton X‐100 (0.01 mg/ml) antagonized carbamylcholine, whereas 10‐fold higher concentrations directly blocked electrical excitation. Hyaluronidase had no effect on resting or action potential but decreased the depolarizing response to carbamylcholine.

At minimal concentrations which blocked the depolarizing response to carbamylcholine, SV caused only slight splitting of phospholipids in single cells of the Sachs organ. A concentration (1 mg/ml) of SV which blocked electrical excitation caused 80–100 per cent splitting of lecithin, phosphatidylethanolamine and phosphatidylserine, the three principal phospholipids of the electric tissue. Similar percentages of splitting of the latter two phospholipids but only about one‐third of the lecithin occurred at SV concentration of 0.1 mg/ml. These results indicate that electrical excitability in the eel electroplax can be maintained in the presence of extensive phospholipid splitting. Depolarization and block of electrical excitation by relatively high concentrations of SV may have resulted from splitting of phospholipids, especially lecithin, or may have reflected action of lysophosphatide detergents produced as a result of the action of phospholipase A upon membranal phospholipids.
HISTOCHEMISTRY OF MYELIN XIV PERIPHERAL NERVE MYELIN PROTEINS: ELECTROPHORETIC AND HISTOCHEMICAL CORRELATIONS
Authors: Csejtey J. , Hallpike J. F. , Adams C. W. M. , Bayliss O. B.
Published: October 2006

Abstract— Myelin from the peripheral nervous system has been shown to contain two basic protein components and an electrophoretically slower‐moving major protein, the ‘J’ band. The ‘J’ band protein cannot be selectively removed by aqueous or organic solvents and does not correspond to proteolipid or acidic protein. Histochemical stains applied to peripheral nervous systems myelin proteins separated by polyacrylamide electrophoresis indicate that ‘J’ band protein is analogous with the neurokeratin of the nerve sheath. Trypanophilia observed histochemically in unfixed myelin is principally due to basic proteins. With prolonged tryptic digestion ‘J’ band protein is degraded. Thus, previous classifications of myelin proteins based on trypsin sensitivity have been modified. All peripheral nervous system myelin proteins should be regarded as trypsin‐sensitive, the basic protein being relatively more and the ‘J’ band protein relatively less susceptible.
THE HIPPOCAMPUS AND SEPTAL AREA AS PRIMARY TARGET SITES FOR CORTICOSTERONE1
Authors: Knizley H.
Published: October 2006

—Two groups of totally adrenalectomized male rats (220‐260 g) were injected intraperitoneally with different amounts of [1,2‐3H] corticosterone. One group received 1 μg of hormone (50 μCi/μg), and the other received 20 μg (2·5 μCiμg). All animals were decapitated at 15 min and various tissues including the pituitary, cerebellum, pons‐medulla, cerebral cortex, hypothalamus, septal area, and hippocampus were assayed for radioactivity and protein content. In the 1‐μg group, the hippocampus contained more cpm/mg of protein (P<0·05) than all the other areas including the hypothalamus. The septal area and pituitary gland values were higher (P<0·05) than all the other areas except the hippocampus. In the 20‐μg group there was a significant reduction (P<0·05) in the values (cpm/mg of protein) for the hippocampus, septal area and cerebral cortex, but no change in the values for the pituitary, hypothalamus, and pons‐medulla. These data suggest that the hippocampus and septal area are primary target sites for corticosterone because they take up more hormone than other nervous tissue loci and demonstrate a limited capacity for hormonal uptake. The pituitary gland tends to concentrate the hormone but does not demonstrate a limited capacity for uptake. The hypothalamus does not concentrate the hormone or demonstrate a limited capacity for uptake, and the data suggest that it is not a primary target site for corticosterone.
THE NATURE OF THE INCREASED RATE OF DNA SYNTHESIS IN SCRAPIE‐AFFECTED MOUSE BRAIN
Authors: Kimberlin R. H.
Published: October 2006

—In vivo studies have been made of the incorporation of radioactive thymidine into acid insoluble components of control and scrapie‐affected mouse brain. Experiments with hot trichloroacetic acid extracts of brain and with purified preparations of DNA have confirmed that there is an increased rate of DNA synthesis in scrapie brain which is entirely associated with nuclei. No increase was found in the rate of DNA synthesis in cytoplasmic fractions of scrapie brain. Hydroxyapatite chromatography of heat denatured and renatured DNA suggests that in scrapie brain there is a similar increase in the rates of synthesis of the poorly, moderately and highly reiterated (i.e. satellite) species of nuclear DNA. Experiments involving brain dissection indicate that the increased rate of DNA synthesis in scrapie does not take place exclusively in the subependymal layer of the lateral ventricles. From these and previously reported studies using radioautographic techniques it is concluded that the increased DNA synthesis in scrapie brain is not associated specifically with cells undergoing mitosis.
THE RELATIONSHIP BETWEEN DNA SYNTHESIS AND THE SYNTHESIS OF NUCLEAR PROTEINS IN RAT BRAIN DURING DEVELOPMENT1
Authors: Burdman J. A.
Published: October 2006

—The incorporation of [3H]thymidine into nuclear DNA of rat brain progressively increased from birth until the 8th postnatal day and it was lowest in the adult brain. When isolated nuclei from brain cells were separated into a neuronal‐ and a glial‐rich fraction (composed of glial and neuroblast nuclei in young animals), the specific radioactivity of the DNA was higher in the glial‐rich fraction at all ages investigated. The incorporation of [3H]leucine into proteins of rat brain was considerably higher in the 8‐than in the 1‐day‐old rat. The greatest difference in the rate of protein synthesis between 8‐ and 1‐day‐old brain occurred in the nuclear proteins, especially those associated with DNA. There was an accumulation of protein and RNA in nuclei from brain cells from birth to the 8th postnatal day. The increased content of proteins occurred primarily in the fraction soluble in buffered saline (nuclear sap).
THE PATTERN OF METHYLATION OF RNA IN PERIPHERAL NERVE OF THE CHICK DURING DEVELOPMENT1
Authors: Mezei Catherine , Hu Y.‐W.
Published: October 2006

The pattern of the methylation of RNA was investigated in organ cultures of the sciatic nerve of the chicken. Nerve tissue from 14‐day embryos, 17‐day embryos and 3‐day‐ old chicks was incubated with [methyl‐3H]methionine or with [2‐14C]uridine and [methyl‐3H]methionine simultaneously for various periods of time. Subsequently, RNA was extracted from the tissues and the purified preparations were fractionated by polyacrylamide gel electrophoresis. The electrophoretic patterns of the rapidly labelled RNA changed during the three developmental stages. The incorporation of both uridine and the methyl groups from methionine was highest in the‘heavy’RNA species of the 14‐day embryonic nerve during the 0.5 and 1.0 h incubation periods. In contrast, in the nerves of 3‐day‐old chicks during a 0.5 h pulse with both precursors, methylation was almost entirely limited to the transfer RNA species. Furthermore, the incorporation of uridine in the nerves from 3‐day‐old animals revealed the presence of a heterogeneous population of rapidlylabelled, unmethylated species of RNA, most of which migrated between the smaller ribosomal RNA and transfer RNA components of the bulk RNA. The pattern of uridine incorporation and the methylation of the rapidly‐labelled RNA of the 17‐day embryonic nerve represented a transitional state between that of the 14‐day embryos and that of the 3‐day‐old chicks. The 17‐day embryonic stage of development corresponded to the phase of the onset of rapid deposition of myelin lipids in the sciatic nerve. Pulse‐chase experiments on the embryonic nerves indicated that a number of methylated precursors of ribosomal RNA and labile, heterogeneous, probably DNA‐like RNA were synthesized.
BRAIN MITOCHONDRIAL HEXOKINASE AND ADENYLATE KINASE: EFFECT OF OSMOTIC CONDITIONS ON ENZYME ACTIVITIES
Authors: Mayer R. J.
Published: October 2006

The activities of mitochondrial hexokinase and adenylate kinase have been measured in various osmotic conditions. Sucrose, potassium chloride and ammonium acetate were used as solutes. The total hexokinase activity of mitochondrial suspensions increased steadily with decreasing osmolarity of the sucrose or salt solutions. The hexokinase activity of mitochondrial suspensions in water was 93 per cent of that measured in the presence of Triton X‐100.The increase in hexokinase activity was irreversible even after very short exposure (90 s) to hypo‐osmotic conditions. Total adenylate kinase activity was not affected by osmotic conditions. Adenylate kinase activity increased hyperbolically in supernatants prepared from mitochondrial suspensions with decreasing osmolarity of the sucrose or salt solutions. Besides monitoring adenylate kinase leakage as a measure of outer mitochondrial membrane disruption, mitochondrial swelling was followed by measurement of the turbidity of mitochondrial suspensions at 520 nm. The data has been interpreted in terms of binding of some hexokinase to the inner mitochondrial membrane.
THE EFFECTS OF ELECTROSHOCK SEIZURES ON POTASSIUM TRANSPORT WITHIN SYNAPTOSOMES FROM RAT BRAIN
Authors: Escueta A. V. , Appel S. H.
Published: October 2006

—Potassium transport was assessed within synaptic terminals isolated from cerebral cortices of rats which experienced one or two maximal electroshock (ES) convulsions daily. No significant change in endogenous K content was present after 2 consecutive days of ES‐seizures. However, K decreased 22 % and 41 % after 4 and 6 days of convulsions respectively. After 6 days, synaptosomes from ES rats were able to accumulate K to the same extent as controls and were inhibited by ouabain to an equivalent extent (50%). When these synaptosomes from ES rats were preloaded with high concentrations of K, K leaked out at an increased rate. When diphenylhydantoin (DPH) was administered intraperitoneally from the second to the sixth day of ES‐convulsions, the decrease in endogenous K induced by chronic convulsions was corrected. In ion‐free media or with 50 mM Na, DPH had no effects on the enhanced efflux of K observed in vitro after ES‐seizures. However, with high Na (50–100 mm) and low K (0.2–1 mm) DPH stimulated K uptake but did not affect the ouabain inhibition. Under conditions optimal for K uptake (50 mm Na and 10 mm K), DPH did not affect K accumulation but it prevented in vitro ouabain inhibition. Our results indicate that repeated ES‐convulsions decreased K content within isolated nerve terminals by enhancing its passive leakage. In vivo DPH prevented the effects of ES‐seizures by stimulating the Na‐K pump and not by directly blocking the K leak.
POLYAMINE TURNOVER IN DIFFERENT REGIONS OF RAT BRAIN1
Authors: Shaskan E. G. , Snyder S. H.
Published: October 2006

The dynamics of the formation and disappearance of polyamines in rat brain have been examined after intraventricular administration of a tracer dose of [3H]putrescine. After 2 days [3H]putrescine was no longer detectable in any brain region examined. [3H] Spermidine and [3H] spermine were formed in all brain areas. In the midbrain, hypothalamus and cerebellum (regions which manifested the greatest initial accumulation of tritium) the specific radioactivity of spermidine declined with a half‐life of 16‐19 days. However, in areas with a low initial accumulation of tritium (the medulla‐pons, internal capsule, cerebral cortex and corpus striatum) the specific radioactivity of spermidine changed very little between 2 and 19 days after the putrescine administration. Levels of [3H]spermine increased continuously in all brain areas for a 14‐day period after the putrescine injection.
Free choline levels in the rat brain
Authors: Eade Isabel , Hebb Catherine , Mann S. P.
Published: October 2006

Choline levels in nervous tissue have been investigated by a number of workers in recent years. The values have varied widely from 39.3 nmol/g (Ewetz, Sparf and Söbo, 1970) to 700 nmol/g (Smith and Saelens, 1967). Many of the values published may have been too high for one of the following reasons: (1) post mortem formation of choline, (2) hydrolysis of phospholipids (PL) by extractants and (3) inadequate assay systems. In the past we too have obtained values which we can now with confidence say were too high due to the post mortem formation of choline. In a method which employed bioassay as an end‐step after extraction of choline by acid‐ethanol the values we obtained were 138 ±27 nmol/g. Despite criticism of this method by Ewetzet al. (1970) and Schuberth, Sparf and Sundwall (1970a) we were reasonably sure that the assay system was both sensitive and specific, and that extraction with acid‐ethanol did not lead to liberation of choline from PL, especially since values for plasma choline by this method were in a number of trial extractions as low as 8 nmol/ml. In view of these results we decided to re‐investigate free choline levels in the brain using a method similar to that of Ewetzet al. (1970) in that the living animal (in this case anaesthetized) was frozen in liquid nitrogen before removing the brain, and comparing the results of three different methods of analysis applied to brain extracts prepared in this way.
PYRIDOXAL PHOSPHATE AND GLUTAMATE DECARBOXYLASE IN SUBCELLULAR PARTICLES OF MOUSE BRAIN AND THEIR RELATIONSHIP TO CONVULSIONS1
Authors: M. Pérez de la Mora  , Feria‐Velasco A. , Tapia R.
Published: October 2006

The subcellular distribution of pyridoxal phosphate (PLP) was studied in mouse brain, as well as the effect of pyridoxal phosphate‐γ‐glutamyl hydrazone (PLPGH—a convulsant drug which decreases both PLP levels and glutamate decarboxylase activity [GAD] in whole brain) upon both the PLP concentration and the GAD activity in subcellular fractions. An electron microscopic evaluation of the subcellular particles of control and PLPGH‐treated animals was also carried out. The main findings were the following: (1) PLP was localized mainly in the supernatant and crude mitochondrial fractions; two‐thirds of the amount present in the latter were located in the subfraction containing pure mitochondria, and the remainder was in the synaptosomal fraction. After osmotic disruption of synaptosomes, PLP was found in both the intrasynaptosomal mitochondria and the synaptoplasm. (2) Treatment of mice with PLPGH decreased levels of PLP in several brain fractions, this effect being much more notable in the soluble fractions than in the particulate fractions. After osmotic disruption of the synaptosomes, a specific decrease of PLP in the synaptoplasm was observed. (3) Treatment with PLPGH produced also an inhibition of GAD activity in most of the fractions studied, when this enzyme was assayed in the absence of PLP. In general, the inhibition was greater in those fractions in which levels of PLP were also affected. In synaptosomes, this correlation between the decreased levels of PLP and decreased activity of GAD occurred only in the synaptoplasm. (4) The activation of GAD by PLP added to incubation mixtures was much greater in those fractions from PLPGH‐treated animals which displayed extensive inhibition of GAD, in comparison to the corresponding fractions from control animals. (5) No ultrastructural changes were detected in the subcellular fractions from treated animals. Our results show that the decreases of both the levels of PLP and the activity of GAD (as previously found in whole brain) actually occur in the synaptosomes, a finding that supports the hypothesis that the role of PLP in the mechanisms controlling excitability can be explained, at least in part, by its regulatory action on GAD activity, which in turn determines the rate of GABA synthesis at the nerve endings.
CHARACTERIZATION AND LOCALIZATION OF ACID HYDROLASE ACTIVITY IN THE SYNAPTOSOMAL FRACTION FROM RAT CEREBRAL CORTEX
Authors: Verity M. A. , Gade G. F. , Brown W. J.
Published: October 2006

Synaptosomes were prepared from the cerebral cortex of adult rats by a rapid technique of centrifugation in a Ficoll‐sucrose discontinuous gradient. The synaptosomal fraction contained 40 per cent of the total gradient activity of acid α‐naphthyl phosphatase (EC 3.1.3.2). Quantitative electron microscopy of this fraction revealed rare, typical, extrasynaptosomal dense body lysosomes. pH‐activity profiles of free and Triton X‐100 (total) activities were prepared for α‐naphthyl phosphatase, β‐glucuronidase (EC 3.2.1.31), β‐galactosidase (EC 3.2.1.23), arylsulfatase (EC 3.1.6.1) and N‐acetylglucosaminidase (EC 3.2.1.30). The ratios of total to free activity varied in the order: arylsulfatase > β‐galactosidase > β‐glucuronidase > N‐acetylglucosaminidase > acid phosphohydrolase. Incubation of synaptosomal fractions at pH 5 and 37°C produced significant activation of β‐galactosidase and N‐acetylglucosaminidase but no activation of cryptic lactate dehydrogenase (EC 1.1.1.27). Hyposmotic suspension and subfractionation of the synaptosomal fraction produced considerable solubilization of lactate dehydrogenase, arylsulfatase and β‐galactosidase but only partial liberation of α‐naphthyl phosphatase, the remainder being associated with synaptosomal membrane fragments. Incomplete equilibrium sedimentation of synaptosomes in a continuous sucrose gradient (0·55‐1·5 M) provided a broad lactate dehydrogenase and Na + K ATPase (EC 3.6.1.4) peak (peak I) at low sucrose densities. β‐Glucuronidase, β‐glucosidase and α‐naphthyl phosphatase were significantly present in peak I. Conversely, N‐acetylglucosaminidase, arylsulphatase and β‐galactosidase were predominantly located in denser particles sedimenting through 1·2 M sucrose (peak II). Electron microscopy confirmed the heterogeneity of this second peak and the presence of numerous extrasynapto‐somal dense body lysosomes.
IMMUNOCHEMICAL STUDIES ON GLUTAMIC ACID DECARBOXYLASE (EC 4.1.1.15) FROM MOUSE BRAIN1
Authors: Matsuda T. , Wu J.‐Y. , Roberts E.
Published: October 2006

Purified homogenous glutamic acid decarboxylase (GAD) from mouse brain and rabbit antiserum prepared to partially purified GAD gave only one sharp precipitin band in the Ouchterlony double diffusion test. GAD activity was inhibited partially by incubating with the antiserum. The maximal extent of inhibition was approximately 50 per cent. In the presence of antiserum all enzyme activity could be precipitated. The precipitates formed by GAD and antiserum had about 50 per cent of the enzyme activity and the Km values for both glutamic acid and pyridoxal phosphate were significantly higher than those of the control system. Pyridoxal phosphate protected GAD from inhibition only slightly, even at very high concentrations. The results suggest that the antibodies may not react with the catalytic site, but rather that the inhibition of enzyme activity is attributable to indirect effects.
Inhibition of the uptake of 5‐hydroxytryptamine, noradrenaline and dopamine into rat brain homogenates by various hydroxylated tryptamines
Authors: Hoax A. S. , Baumgarten H. G. , Schlossberger H. G.
Published: October 2006

Recent work has shown that intracerebral injections of 5,6‐dihydroxytryptamine (5,6‐DHT) lead to a fairly selective and long lasting depletion of 5‐HT in the rat CNS (BAUMGARTEN, BJORKLUND, LACHENMAYER, NOBIN and STENEVI, 1971; DALY, FUXE and JONSSON, 1973). This effect appears to result from a degeneration of the serotonin‐containing neurons (BAUMGARTEN and LACHENMAYER, 1972a). 5,6‐DHT does, however, to a lesser extent affect both NA and dopamine (DA) containing nerve terminals (BAUMGARTEN et al., 1971). In an attempt, therefore, to find compounds having a more specific toxic action we have investigated several other hydroxylated tryptamines. In order to obtain information about the differential affinities of these analogues for neuronal uptake sites we have examined their effects on the uptake of [3H]5‐HT and (±)‐[3H]NA into synaptosomes in homogenates of rat hypothalamus and of [3H]DA uptake into a similar preparation from the rat corpus striatum. It is known that the uptake of these putative transmitters in rat brain homogenates is predominantly into the synaptosome fraction (KANNENGIESSER, HUNT and RAYNAUD, 1973; COYLE and SNYDER, 1969).
SUBCELLULAR SITE OF THE PHOSPHATIDYLINOSITOL EFFECT. DISTRIBUTION ON DENSITY GRADIENTS OF LABELLED LIPIDS FROM RESTING AND ACTIVE SYMPATHETIC GANGLIA OF THE RAT1
Authors: Burt D. R. , Larrabee M. G.
Published: October 2006

Localization of the increased [32P]‐labelling of phosphatidylinositol, caused by arrival of presynaptic impulses in a sympathetic ganglion, was investigated by subcellular fractionation of ganglia that had been labelled before homogenization. Paired superior cervical ganglia were excised from adult rats and incubated with 32P1 and [methyl‐14C]choline for 4 h at 37°C. The preganglionic nerve of one ganglion of each pair was stimulated repetitively (10/s) during the last 3 h of incubation. The ganglia were then softened with collagenase, homogenized, and fractionated by density gradient centrifugation. Succinate dehydrogenase served as marker for the distribution of mitochondria on the gradient, and [14C]ACh for synaptosomes. [32P]‐labelling of lipids was measured relative to that of phosphatidylcholine. The average changes in relative labelling that were caused by neuronal activity ranged as follows over the homogenate and the various fractions: phosphatidylinositol (PI), increased 39–75%; phosphatidylethanolamine, decreased 10–20%; diphosphatidylglycerol, not significantly affected. The increase in PI labelling was much greater in the denser fractions, in which synaptosomes and mitochondria were concentrated, than in the less dense fractions. The distribution of the PI effect on the gradient could be reasonably well explained by assuming that synaptosomes and mitochondria both contributed to the increase in PI labelling in proportion to the amount of their respective markers in a fraction. One‐third or more of the total increase could thus be associated with synaptosomes and one‐third or more with mitochondria, although alternative association with other structures could not be excluded. The implications of the inferred association with synaptosomes and mitochondria are discussed, current knowledge of the PI effect caused by impulses entering sympathetic ganglia is summarized, and suggestions concerning its physiological significance are reviewed. It is concluded that PI may have multiple roles in neuronal activity.
SULPHATE ESTER FORMATION FROM CATECHOLAMINE METABOLITES AND PYROGALLOL IN RAT BRAIN IN VIVO
Authors: Eccleston D. , Ritchie I. M.
Published: October 2006

—A sulphotransferase enzyme capable of utilizing ethanolic or glycolic catecholamine metabolites and other phenols as substrates was studied in rat brain in vivo following the intraventricular injection of sodium [35S]sulphate and the subsequent isolation and identification of the labelled sulphate esters. A quantitative examination was made possible by the injection of increasing amounts of substrates of the enzyme together with sodium [35S]sulphate and the application of Michaelis‐Menten kinetics. 3‐Methoxy‐4‐hydroxyphenylethyleneglycol and 3,4‐dihydroxyphenylethyleneglycol were shown to be readily esterified as was 3‐methoxy‐4‐hydroxyphenylethanol (‘half‐saturating dose’ of 5‐1, 34 and 18 nmol respectively). Three esters of pyrogallol were isolated after its administration. This compound was also shown to inhibit sulphate ester formation from both substituted glycols, probably by competitive inhibition. The amines 5‐hydroxytryptamine and normetanephrine were not found to be substrates for the sulphotransferase system in brain.
REGULATION OF TYROSINE HYDROXYLASE ACTIVITY IN MOUSE NEUROBLASTOMA CLONE N1E‐115
Authors: Richelson E.
Published: October 2006

Abstract— Mouse neuroblastoma (clone N1E‐115) cells in the logarithmic growth phase were incubated for 12 days. From early log phase to late stationary phase, the specific activity of tyrosine hydroxylase (EC 1.14.3a) increased greater than 30‐fold. The increase in tyrosine hydroxylase per cell and per dish was 12‐ and 2700‐fold, respectively. When cell division was stopped by removing serum or by adding 0.1 mm‐5‐fluorodeoxyuridine and 0.1 mm‐uridine, the enzyme activity was also found to increase. These results show that tyrosine hydroxylase is regulated in neuroblastoma clone N1E‐115.
EFFECT OF HYPERPHENYLALANINEMIA ON FATTY ACID COMPOSITION OF LIPIDS OF RAT BRAIN MYELIN
Authors: Johnson R. C. , Shah S. N.
Published: October 2006

Abstract— We have studied the fatty acid compositions of cerebral myelin lipids in phenyl‐alanine‐treated and control rats. The proportion of long chain fatty acids and the ratio of unsaturated to saturated fatty acids of whole brain lipids was low in the penylalanine‐treated animals. Both of these reductions were more pronounced in the myelin from phenylalanine‐treated rats. The ratio of unsaturated to saturated fatty acids in ethanolamine phosphatides was markedly decreased in the hyperphenylalaninemic condition. The reduction in the proportion of long chain fatty acids was predominant in non‐hydroxy fatty acids in cerebrosides and ethanolamine phosphatides. The lipid composition of the myelin expressed as mole percentages of individual phospholipid and sphingolipid components was not significantly different in the two groups of rats, nor did it change with age. Our results indicate a deficiency in the fatty acid elongation and desaturation system in the brains of phenylalanine‐treated rats. We suggest that in hyperphenylalaninemic rats, a reduction in the amounts of unsaturated fatty acid and long chain fatty acid alters, respectively, the biochemical reactivity and the stability of the myelin.
PROTEIN SYNTHESIS IN THE BRAIN OF OCTOPUS VULGARIS, LAM
Authors: Prozzo N. , Giuditta A.
Published: October 2006

Abstract— The process of protein synthesis in the brain of Octopus vulgaris Lam has been examined after systemic administration of [3H]leucine and upon incubation of the tissue in sea water containing the radioactive precursor. After injection of [3H]leucine in the branchial heart, the radioactivity of the TCA‐soluble fractions of the three main brain divisions reached a maximum in about 30 min and decreased thereafter, while incorporation into the protein fractions was complete in approx. 2 h. Per unit wet weight the radioactivity of brain proteins was higher than that of most other organs. In vitro the rate of incorporation of [3H]leucine in the protein fraction of the optic lobe remained low for more than 1 h, but increased several fold thereafter. Preincubation of the tissue in sea water abolished the lag period. Similar effects were observed in the vertical lobe as well as in the optic lobe of young and adult octopuses but not in the white body, a non‐nervous organ. The process of protein synthesis in the optic lobe is markedly inhibited by puromycin, cycloheximide and chloramphenicol. Electrophoretic analysis on polyacrylamide gels indicated that the soluble proteins labelled in vitro and in vivo are similar.
EVIDENCE FOR EXTRANORADRENERGIC DOPAMINE‐β‐HYDROXYLASE ACTIVITY IN RAT SALIVARY GLAND
Authors: Coyle J. T. , Wooten G. F. , Axelrod J.
Published: October 2006

—Three days after superior cervical ganglionectomy of adult Sprague‐Dawley rats, the levels of endogenous norepinephrine, the uptake process for [3H]norepinephrine and the activity of tyrosine hydroxylase decreased 99 per cent in the ipsilateral salivary gland. In contrast, the activity of dopamine‐β‐hydroxylase and DOPA decarboxylase fell to 30 per cent of the activity of the contralateral innervated gland. Examination of the cofactor requirements, the characteristics of activation by cupric ion and the immunologic identity of this residual hydroxylase activity indicated that it was authentic dopamine‐β‐hydroxylase. The residual dopamine‐β‐hydroxylase in the denervated gland had the same subcellular distribution as the enzyme in the innervated salivary gland. Procedures that caused atrophy or hypertrophy of the acinar cells did not affect the total content of dopamine‐β‐hydroxylase in the denervated salivary gland. Chemical sympathectomy with 6‐hydroxy‐dopamine caused a 40 per cent decrement in the serum levels of dopamine‐β‐hydroxylase but a 30 per cent increase in its activity in the denervated salivary gland. Although denervation caused a complete loss of endogenous norepinephrine in the salivary gland, it resulted in only a 15 per cent decrement in the levels of endogenous octopamine and β‐phenylethanolamine, two other products of dopamine‐β‐hydroxylase.
MINIMUM DURATION OF TRANS‐SYNAPTIC STIMULATION REQUIRED FOR THE INDUCTION OF TYROSINE HYDROXYLASE BY RESERPINE IN THE RAT SUPERIOR CERVICAL GANGLION
Authors: Zigmond R. E. , Mackay A. V. P. , Iversen L. L.
Published: October 2006

—The period during which trans‐synaptic stimulation is required by the rat superior cervical ganglion for induction of tyrosine hydroxylase by reserpine has been studied. Ganglia were decentralized on one side at various times before or after an injection of reserpine. The tyrosine hydroxylase activity of the denervated and control ganglia was assayed 72 h after drug treatment. When decentralization was performed 8 h after an injection of reserpine the increase in tyrosine hydroxylase activity was blocked in the denervated ganglia. Decentralization 12 h after reserpine treatment or later had no effect on the enzyme induction. The actual increase in tyrosine hydroxylase activity occurred between 24 and 48 h after injection of reserpine.