bluuebunny/crossref_metadata_2025_split huggingface dataset:
REGULATION OF CYCLIC ADENOSINE 3′, 5′‐MONOPHOSPHATE CONCENTRATION IN CHICK CEREBRAL HEMISPHERES DURING DEVELOPMENT
Authors: Patton M. W. , Nahorski S. R. , Rogers K. J. 
Published: October 2006

Abstract— Investigations have been carried out into developmental aspects of cyclic AMP metabolism and responsiveness to neurohormones in chick cerebral hemispheres. The in vivo cyclic AMP concentration, measured after freeze‐blowing, was found to be highest in the embryonic brain, and changes in the cyclic nucleotide content produced by ischaemia increased with age. The magnitude of the in vivo increases in cyclic AMP produced by isoprenaline and by histamine decreased throughout the first postnatal month. The onset of isoprenaline‐ and histamine‐induced cyclic AMP accumulation in brain slices occurred around 17 days embryonic age, reached a maximum at about 3 days post‐hatch and fell to approx 50% of this response at 28 days of age. Adenosine stimulated cyclic AMP formation to a similar extent at all ages studied.The activities of adenylate cyclase and cyclic AMP phosphodiesterase of hemisphere homogenates were found to reach maximum near the time of hatching. Since the overall pattern of responsiveness of the cerebral cyclic AMP system to neurohormones does not correlate with these variations in enzyme activities, it is suggested that changes occurring at the synaptic receptor level may explain the developmental variations observed.
DEVELOPMENTAL EFFECTS ON PROTEIN SYNTHESIS RATES IN REGIONS OF THE CNS IN VIVO AND IN VITRO
Authors: Dunlop D. S. , Van Elden W. , Lajtha A. 
Published: October 2006

Abstract— Protein synthesis rates have been determined quantitatively in several regions of the nervous system of rats of various ages. The developmental changes in these regions are generally similar with a high rate maintained from several days before birth to about 4 days of age (1.9–2.1% h−1). A decline in the rate ensues thereupon which continues till approx 30 days of age, whence the curve flattens though continuing slowly downward with increasing age. In the young three regions, cerebellum, pineal and pituitary, exhibit exceptionally higher rates (40–50%) than the cerebral hemispheres, pons‐medulla, mid brain or cord, which all display curves of similar magnitude and shape. While the rate in the cerebellum eventually declines with age to within 10% of the rate in cerebral hemisphere, rates in the pineal and pituitary though decreasing remain far above (100%) rates in cerebral hemisphere even in adults.The rate in vitro for slices of cerebellum follows a pattern similar to that shown previously for cerebral hemispheres: in the very young rates are 70–80% of the in vivo value but decline much more rapidly with age and in adult represent only 10–15% of the rate in vivo.A markedly different pattern is seen in whole (unsliced) pituitaries wherein in vitro rates parallel in vivo rates with increasing age at approx 70–80% of the in vivo rate. Pineals appear to follow a similar pattern.
THE EFFECTS OF REPEATED‐LYSERGIC ACID DIETHYLAMIDE INJECTIONS ON CATECHOLAMINE LEVELS AND TYROSINE HYDROXYLASE ACTIVITY IN RAT BRAIN REGIONS
Authors: Peters D. A. V. , Tang S. 
Published: October 2006

Abstract—Daily injections of 100 μg/kg of d‐lysergic acid diethylamide (LSD) for 14 days produced a significant decrease in the dopamine level in rat brain corpus striatum which was still apparent 15 days after the last LSD treatment. Further LSD injections did not change the amount of dopamine depletion. In cerebral cortex, 14 days of LSD injections produced a significant decrease in the norepinephrine level and a significant increase in tyrosine hydroxylase activity. The elevated tyrosine hydroxylase activity was still present 15 days after the final LSD injection but only in those animals receiving daily vehicle injections during this period. Pre‐treatment of rats with daily saline injections for 2 weeks before the 2 week period of LSD treatment prevented both the reduced norepinephrine content and elevated tyrosine hydroxylase activity usually found 24 h after the last LSD injection.
EFFECTS OF DIAMINOPROPIONATE, DEOXYADENOSINE, AND THEOPHYLLINE ON STIMULATED FORMATION OF CYCLIC AMP AND GMP BY DEPOLARIZING AGENTS IN SLICES OF GUINEA‐PIG CEREBRAL CORTEX
Authors: SHIMIZU H. , YAMAMURA Y. 
Published: October 2006

Abstract—In incubated slices of guinea‐pig cerebral cortex depolarizing agents such as veratridine and high potassium ions caused 50 to 80‐fold increases of adenosine 3', 5'‐cyclic monophosphate (cyclic AMP) levels and these responses were inhibited about 50% by 2, 3‐diaminopropionate and 2'‐deoxyadenosine: the former is a specific antagonist for glutamate‐elicited accumulation of cyclic AMP and the latter selectively for adenosine‐elicited accumulation. Methylxanthines were powerful ‘inhibitors’toward the responses not only to depolarizing agents but also to glutamate and adenosine. These findings are consistent with the hypothesis that releases of both glutamate and adenosine are involved in the depolarization‐elicited increases of cyclic AMP levels.Guanosine 3', 5'‐cyclic monophosphate (cyclic GMP) levels in the slices were also elevated by veratridine as well as by glutamate, but always to a lesser extent (8 ∼ 12 times the control value) than cyclic AMP levels were. The responses for cyclic GMP both to veratridine and glutamate were ‘augmented’by methylxanthines and were not inhibited by 2, 3‐diaminopropionate. Thus, glutamate appears to cause the increase of cyclic GMP levels through a different mechanism or site of action from that for cyclic AMP.
THE DEVELOPMENT OF D‐AMINO ACID OXIDASE IN RAT CEREBELLUM
Authors: WEIMAR W. R. , NEIMS A. H. 
Published: October 2006

Abstract—D‐Amino acid oxidase (D‐amino acid: O2 oxidoreductase (deaminating), EC 1.4.3.3; D‐AAO) activity is biochemically undetected in rat brain stem, cerebellum and forebrain until 14 days after birth. Adult levels are attained by day 30 in the brain stem, and by day 36 in the cerebellum. At adulthood, forebrain D‐AAO activity per g wet weight of tissue is less than 2% that of the cerebellum. In contrast to the pattern in the CNS, substantial D‐AAO activity is present in both liver and kidney 2 days before birth and adult levels are approached within 2 weeks of birth. Nonetheless, D‐AAO activities in rat liver, kidney, brain stem and cerebellum are likely to be due to a single enzyme which has properties very similar to the purified hog D‐AAO. The late ontogenesis of D‐AAO activity in cerebellum and brain stem relative to that in liver and kidney parallels reported phylogenetic data.Histochemical staining for D‐AAO in rat cerebellar cortex is absent until 15 days after birth when activity is first observed in some cells of the external germinal zone and adjacent molecular layer. These cells appear to migrate to a final destination around the Purkinje cell soma and leave processes at the pial surface. By 21 days of age an adult pattern of staining is manifest throughout the cerebellum but it is of weak intensity. The adult pattern includes some staining in the granular layer which seems to be associated with mossy fibers and certain cerebellar glomeruli, and strong staining at the pial surface, in the molecular layer, and in cells surrounding, but not within, the Purkinje cell soma. The data suggest that the biochemical appearance of D‐AAO in developing cerebellum derives from two sources: one associated with differentiation of one of the last cell types to form from the external germinal zone, and the other with maturation of mossy fibers and their synapses (cerebellar glomeruli).
THE EFFECT IN VITRO OF VOLATILE ANESTHETICS ON THE ACTIVITY OF CHOLINESTERASES1
Authors: BRASWELL L. M. , KITZ R. J. 
Published: October 2006

Abstract—Because the mechanism of anesthesia is unknown, the relationship between anesthetics and enzymes essential to brain function may be an important one. Therefore, the effect of 8 volatile anesthetics on the enzymatic activity of solubilized, purified dog brain and human erythrocyte acetylcholinesterase (AChE) and human serum cholinesterase (ChE) was studied in vitro. Serum ChE was found to be insensitive to saturated solutions of all the anesthetics studied. However, brain and erythrocyte AChE were reversibly inhibited in a dose‐dependent manner by all 8 anesthetics in concentrations exceeding those used in clinical practice. Kinetic analysis revealed a mixed (competitive, non‐competitive) type of inhibition with the exception of the ether‐crythrocyte AChE interaction which was characterized by competitive inhibition. Ether and methoxyflurane were found to depress the AChE activity the most and isoflurane and enflurane the least. The concentrations of anesthetic in the gas phase necessary for 50% inhibition of erythrocyte AChE activity (I50) were calculated for 5 anesthetics and found to correlate with their water‐gas partition coefficients. These data suggest that the effect in vitro of volatile anesthetics on the catalytic activity of cholinesterases is a variable one and may be unrelated to anesthetic potency in vivo. The implications of these data concerning anesthetic‐active site interactions are discussed.
EFFECTS OF EPILEPTIC SEIZURES ON BRAIN RIBOSOMES: MECHANISM AND RELATIONSHIP TO CEREBRAL ENERGY METABOLISM
Authors: WASTERLAIN C. G. 
Published: October 2006

Abstract—Epileptic seizures were induced electrically in rats paralyzed and ventilated with oxygen. Dissociation of brain polysomes and increase in ribosomal dimers were observed after multiple (25 or more) seizures, but were not seen after shorter treatments (up to 10 seizures). Polysomal dissociation and dimer formation occurred in vivo and were accompanied by decreased amino acid incorporation into brain proteins in cell‐free systems in vitro. These events paralleled changes in brain energy reserves rather than changes in behavior.
GANGLIOSIDES IN NERVOUS TISSUE CULTURES AND BINDING OF 125I‐LABELLED TETANUS TOXIN, A NEURONAL MARKER
Authors: Dimpfel W. , Huang R. T. C. , Habermann E. 
Published: October 2006

Abstract— —Continuous cell lines, primary cell cultures derived from embryonic CNS, and homogenates made from adult and embryonic CNS were compared with respect to their lipid pattern and their ability to bind 125I‐labelled tetanus toxin. In parallel experiments de novo synthesis of gangliosides in the cell lines was studied, using [14C]glucosamine as precursor. Of the total lipid only gangliosides were specifically labelled by [14C]glucosamine. The patterns of the de novo synthesized gangliosides corresponded to those present in the respective cells.Pronounced binding of 125I‐labelled toxin was only detectable in tissues containing long‐chain gangliosides (ganglioside C which represents GDIb and GTI).Accordingly, hybrid (neuroblastoma x glioma) cells, due to their lack of long‐chain gangliosides, bound just‐discernible amounts of labelled toxin. When previously exposed to gangliosides, their binding of tetanus toxin tremendously increased.It was concluded that only the long‐chain gangliosides in the neuronal cells are functionally involved in the binding of the tetanus toxin and that these acceptors of tetanus toxin can be transplanted.
EFFECTS OF PRE‐ OR POSTNATAL DEXAMETHASONE, ADRENOCORTICOTROPHIC HORMONE AND ENVIRONMENTAL STRESS ON PHENYLETHANOLAMINE N‐METHYLTRANSFERASE ACTIVITY AND CATECHOLAMINES IN SYMPATHETIC GANGLIA OF NEONATAL RATS
Authors: Gianutsos G. , Moore K. E. 
Published: October 2006

Abstract— Injections of dexamethasone (0.1 mg/kg/day, s.c.) on the first 2–3 days of life increased the phenylethanolamine‐N‐methyltransferase (PNMT) activity and epinephrine content of the superior cervical ganglion (SCG) and stellate ganglion of neonatal rats; the dopamine content was unaltered while norepinephrine was slightly reduced in these ganglia. Dexamethasone did not alter the PNMT activity or epinephrine content of the salivary glands or heart. The PNMT activity and epinephrine content of the SCG remained elevated for 10–14 days. Pretreatment with 6‐hydroxydopamine did not alter the dexamethasone effects.Injections of adrenocorticotrophic hormone (ACTH) (25 munits/rat twice a day) or exposure to a cold stress (4°C, 3 times a day) on the first 2–3 days of life, elevated the plasma concentration of corticosterone, and also increased the PNMT activity and epinephrine content in SCG of neonatal rats. Injecting pregnant rats with dexamethasone or ACTH, or exposing them to cold or restraint stress on the last 3 days of gestation increased the PNMT activity and epinephrine content in the SCG of their pups. These results indicate that the actions of dexamethasone on neonatal sympathetic ganglia may be mimicked by increasing the plasma concentration of endogenous adrenocortical steroids.
STIMULATED INCORPORATION OF AMINO ACIDS INTO PROTEINS OF SYNAPTOSOMAL FRACTIONS INDUCED BY DEPOLARIZING TREATMENTS
Authors: Wedege E. , Luqmani Y. , Bradford H. F. 
Published: October 2006

Abstract— Rat cortical synaptosome preparations incorporated l‐amino acids into protein at a linear rate over 30–60 min. Synaptosomes showed large increases in incorporation after treatment with electrical pulses, veratrine or K+. This was inhibited (controls, 73%; electrically stimulated 58%) by cycloheximide and by chloramphenicol (28 and 44% respectively). Omission of Ca2+ from the medium had no effect, but the absence of Na+ greatly diminished the stimulus‐induced increase in incorporation due to pulses. Electrical pulses, veratrine and K+ (in order of effectiveness), all showed their greatest proportional effects on amino acid incorporation into the Triton‐X‐100 insoluble portions of the synaptosomal membrane: the ‘junctional complex’, soluble in SDS, and the residue. Tetrodotoxin (1 μm), although ineffective when potassium was the stimulus, prevented or reduced the respiratory response, K+ loss and differential amino acid release, as well as the amino acid incorporation into protein observed with pulses and veratrine.C‐6 glioma cells showed no stimulus‐dependent increase in incorporation. Preliminary data, of gel electrophoretic analysis, on the proteins labelled under our conditions is presented.
ADENOSINE UPTAKE BY CHOLINERGIC SYNAPTOSOMES FROM TORPEDO ELECTRIC ORGAN
Authors: Meunier F. M. , Morel N. 
Published: October 2006

AbstractPure cholinergic synaptosomes prepared from the electric organ of Torpedo are able to take adenosine up efficiently and convert it to ATP. The apparent Km of the adenosine uptake is 2.4 μM and the Vm: 518 pmol/30′/mg prot. The uptake system exhibits a high specificity towards adenosine, as shown by the lack of competition with analogues. Tubercidin blocks the uptake competitively and dipyridamole is a very potent non competitive inhibitor (Ki= 4 × 10‐8 M).Considering that during nerve activity ATP is released extracellularly and can modulate transmitter release, the physiological significance of adenosine uptake is discussed as a possible mechanism to terminate the ATP action.
RELATIONSHIP BETWEEN SYNAPTOSOMAL UPTAKE AND RELEASE OF [14C]GABA, [14C]DIAMINOBUTYRIC ACID AND [14C]β‐ALANINE1
Authors: Redburn Dianna A. 
Published: October 2006

Abstract[14C]GABA is taken up by rat brain synaptosomes via a high affinity, Na+‐dependent process. Subsequent addition of depolarizing levels of potassium (56.2 MM) or veratridine (100 μM) stimulates the release of synaptosomal [14C]GABA by a process which is sensitive to the external concentration of divalent cations such as Ca2+, Mg2+, and Mn2+. However, the relatively smaller amount of [14C]GABA taken up by synaptosomes in the absence of Na+ is not released from synaptosomes by Ca2+ ‐dependent, K +‐stimulation.[14C]DABA, a competitive inhibitor of synaptosomal uptake of GABA (Iversen & Johnson, 1971) is also taken up by synaptosomal fractions via a Na + ‐dependent process; and is subsequently released by Ca2+ ‐dependent, K+‐stimulation. On the other hand, [14C]β‐alanine, a purported blocker of glial uptake systems for GABA (Schon & Kelly, 1974) is a poor competitor of GABA uptake into synaptosomes. Comparatively small amounts of [14C] β‐alanine are taken up by synaptosomes and no significant amount is released by Ca2+ ‐dependent, K+‐stimulation.These data suggest that entry of [14C]GABA into a releasable pool requires external Na+ ions and maximal evoked release of [14C]GABA from the synaptosomal pool requires external Ca2+ ions. The GABA analogue, DABA, is apparently successful in entering the same or similar synaptosomal pool. The GABA analogue, β‐alanine, is not.None of the compounds or conditions studied were found to simultaneously affect both uptake and release processes. Compounds which stimulated release (veratridine) or inhibited release (magnesium) were found to have minimal effect on synaptosomal uptake. Likewise compounds (DABA) or conditions (Na+‐free medium) which inhibited uptake, had little effect on release.
REGULATION OF CYCLIC NUCLEOTIDE PHOSPHODIESTERASES OF CEREBRAL CORTEX BY Ca2+ AND CYCLIC GMP
Authors: Filburn Charles R. , Colpo Frank , Sacktor Bertram 
Published: October 2006

Abstract—Cyclic nucleotide phosphodiesterase activity of porcine cerebral cortical extracts was measured with 0.1–100 μM‐cyclic AMP and cyclic GMP and found to be dependent on both Ca2+ and added cyclic nucleotides. With decreasing substrate concentration activity with cyclic GMP became more dependent on Ca2+ whereas hydrolysis of cyclic AMP became less dependent. Cyclic GMP at 3 μM stimulated the hydrolysis of 0.1–10μM‐cyclic AMP in the absence of Ca2+ (< 10‐10M) but inhibited activity with 200 μM‐Ca2+ present. This differential, substrate‐ and Ca2+‐dependent regulation was attributed to the presence of at least two types of phosphodiesterase distinguishable by DEAE‐column chromatography. In the absence of Ca2+, activity with 1 μM‐cyclic GMP eluted in one minor peak followed by two major peaks, D‐I and D‐II. Activity with 1 μM‐cyclic AMP eluted almost entirely in D‐II. Hydrolysis of cyclic AMP in D‐II was activated by cyclic GMP. With added Ca2+ plus a Ca2+‐dependent regulator (CDR), activity with 1 μM‐cyclic GMP was markedly increased and eluted entirely at D‐I. Total activity with 1 μM‐cyclic AMP was only moderately increased and eluted as D‐I with a shoulder at D‐II. Elution profiles with 100 μM‐substrate were relatively independent of substrate, with D‐I predominant with Ca2+·CDR present and D‐II predominant in its absence. Kinetic analysis of rechromatographed D‐I showed a 20‐ to 40‐fold activation by Ca2+·CDR that was largely due to an increase in Vmax, with only 50% decreases in Km Both substrates competitively inhibited hydrolysis of the other with Ki values equal to their respective Km values (1.7 μM for cyclic GMP and 48 μM for cyclic AMP with Ca2+‐CDR present). Studies with theophylline and trifluoperazine indicate differential, substrate‐dependent inhibitions of both enzymes. These findings demonstrate that phosphodiesterase activity in neural tissue is subject to regulation by Ca2+, cyclic GMP, and inhibitors in a complex, substrate‐specific and concentration‐dependent manner.
COLD RESISTANCE OF THE BRAIN DURING HIBERNATION: THE ROLE OF STEARYL CoA DESATURASE IN BRAIN AND LIVER AS THE SOURCE FOR MONOENES
Authors: Goldman Stephen S. 
Published: October 2006

Abstract—Brain and liver stearyl CoA desaturase activity and its associated microsomal electron transport chain was investigated in both the warm‐adapted and hibernating hamster.It was shown that the activity of this enzyme in brain was essentially the same in both the warm‐adapted and hibernating hamster. In liver an 8‐fold increase in desaturase activity was observed for the hibernator without corresponding increases in the activity of the microsomal electron transport chain.It is concluded that the increase of monoenes in brain that contributes to the lipid adaptation probably results from peripheral production of these fatty acids.
INDUCTION AND PROPERTIES OF PYRUVATE KINASE OF THE CEREBRAL HEMISPHERE OF RATS OF VARIOUS AGES1
Authors: Chainy G. B. N. , Kanungo M. S. 
Published: October 2006

Abstract—The induction of pyruvate kinase (ATP: pyruvate 2‐O phosphotransferase, EC 2.7.1.40; PK) by estradiol or testosterone in the cerebral hemisphere of male and female rats of different ages was studied. There is a marked decrease in the activity of the enzyme of normal male and female rats with increasing age. Orchiectomy decreases its activity in young and old rats, but not in adult rats. Ovariectomy decreases its activity significantly in all the ages. Estradiol (50μg/100g body wt.) induces its activity in castrated male and female rats, but its effect is greater in female rats. A higher dose of estradiol (100μg/100g body wt.) has age‐ and sex‐dependent induction. Testosterone (50 and 100μg/100g body wt.) has very little effect on its activity in castrated male and female rats of the three ages. The Km values for PEP and ADP, and the Kt values for ATP and l‐phenylalanine for the partially purified enzyme of the cerebral hemisphere of normal young and old rats are the same. Preincubation of the enzyme with l‐alanine reverses the l‐phenylalanine induced inhibition. The concentration of l‐alanine required for this effect is the same for both ages. The concentration of Mg2+ required to reverse the inhibitory effect of ATP is the same for young and old rats. Estradiol and testosterone added directly to the incubation mixture do not have any effect on the enzyme activity. These data suggest that the nature of the enzyme molecule does not change with age, but that its induction properties change with age.
EVIDENCE FOR THE HETEROGENEITY OF L‐2,4‐DIAMINOBUTYRIC ACID UPTAKE IN RAT CORTEX
Authors: Kennedy A. J. , Neal M. J. 
Published: October 2006

Abstract—The uptake of L‐[3H]DABA by rat cerebral cortex slices was studied. Analysis of the kinetic data obtained provides evidence that DABA entry is mediated by both high and low affinity carriers. When cortical slices were incubated in the presence of equimolar [3H]DABA and [14C]GABA the ratio of entry of the two radionuclides was found to depend upon the loading concentration. The specificity of the uptake of 1 μM and 1 mM‐L‐DABA was examined: GABA and DABA were relatively potent inhibitors of 1 μM‐DABA uptake whereas an equal concentration of histidine did not produce significant inhibition. In contrast, DABA and histidine were markedly more potent as inhibitors of 1 mM‐DABA uptake than was GABA. It is concluded from these experiments that L‐DABA is transported into cortical slices by a carrier which has high affinities for both DABA and GABA and by a second lower affinity carrier which prefers DABA as a substrate to GABA. On the basis of a comparison of the effects of inhibitors on [3H]DABA and [3H]GABA uptake it is estimated that approx 26% of DABA uptake at 1 μM does not occur by the high affinity carrier whereas at 1 mM‐DABA this proportion rises to 62–67%.