bluuebunny/crossref_metadata_2025_split huggingface dataset:
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 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.
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.
THE HIPPOCAMPUS AND SEPTAL AREA AS PRIMARY TARGET SITES FOR CORTICOSTERONE1
Authors: Knizley H. 
Published: October 2006

Abstract—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

Abstract—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

Abstract—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

AbstractThe 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

AbstractThe 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

Abstract—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

AbstractThe 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.
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

AbstractThe 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

AbstractSynaptosomes 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

AbstractPurified 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

AbstractRecent 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).