bluuebunny/crossref_metadata_2025 huggingface dataset:
ONTOGENETIC DEVELOPMENT OF NEOSTRIATAL DOPAMINE RECEPTORS IN THE RAT 1
Authors: Spano P. F. , Kumakura K. , Govoni S. , Trabucchi M.
Published: December 2006

Abstract— The actions of dopamine and apomorphine on the kinetic properties of striatal adenylate cyclase were investigated during ontogenesis in the rat. The maximum stimulatory effect of dopamine (5 × 10−5 M) was constant from birth to maturity (1 to 60 days of age). In contrast, the stimulatory effect elicited by apomorphine (5 × 10−5 M) was almost the same as that of dopamine in 6‐day‐old rats, but it declined during maturation reaching 50% of the initial value at 60 days of age. The apparent Km value for dopamine did not change during development, while the Km for apomorphine was higher in the adult than in the newborn. Apomorphine appeared to have a greater affinity than dopamine for the striatal adenylate cyclase both in adult and newborn rats.
GANGLIOSIDE COMPOSITION AND BIOSYNTHESIS IN CULTURED CELLS DERIVED FROM CNS
Authors: Duffard R. O. , Fishman P. H. , Bradley R. M. , Lauter C. J. , Brady R. O. , Trams E. G.
Published: December 2006

Abstract— Cultured mouse neuroblastoma cells (clone N18) contained a homologous series of gangliosides, GM3, GM2, GM1 and GD1a; the total lipid bound sialic acid (LBSA) was 3.3 nmol per mg of protein, of which GD1a comprised two‐thirds. In contrast, neonatal hamster astrocytes (clone NN) and human glioblastoma cells (Cox clone) contained mainly GM3, which represented 95% of the 2 nmol of LBSA per mg protein in these cells. When the cells were grown in the presence of [14C]galactose, label was incorporated into all of the gangliosides isolated from the cells. The labeling pattern corresponded to the ganglioside composition of the cell lines; GD1a was more extensively labeled in N18 cells and GM3 was the major labeled ganglioside extracted from glial cells. In addition to in rivo biosynthesis, in vitro synthesis of gangliosides was also determined. The activities of five glycosyltransferases of the ganglioside biosynthetic pathway were measured in homogenates of the three cell lines. The neuroblastoma cells contained all five enzyme activities whereas the two glial cell lines were deficient in UDP‐N‐acetylgalactosamine: GM3N‐acetylgalactosaminyltransferase activity, which catalyzes the synthesis of GM2 from GM3. The results indicated that cells of neuronal origin contain the more complex gangliosides associated with CNS and the requisite biosynthetic enzymes and that cells of glial origin are missing these complex gangliosides and the key glycosyltransferase required for their synthesis.
THE IN VIVO BIOSYNTHESIS OF CHOLESTEROL FROM (3RS,2R) [2‐14C,2‐3H]MEVALONIC ACID IN THE BRAINS OF RATS ON NORMAL AND PROTEIN DEFICIENT DIETS.1 THE STEREOCHEMISTRY OF TRITIUM ATOMS AT C‐7 AND C‐15
Authors: Sliwowski J. K. , Reddy V. R. , Caspi E.
Published: December 2006

Abstract— 3RS.2R) [2‐14C,2‐3H]Mevalonic acid was injected into the midline thalamus section of the brain of 13‐day old rats born and nursed by mothers fed isocaloric diets containing 8% and 25% casein. After 4.5 h. the rats were killed, the brains removed, and the biosynthesized cholesterols were isolated. It was determined that the overall outcome of biosynthetic events at C‐7 and C‐15 in cholesterol biosynthesized in the rat liver homogenates and in the midline thalamus of the brain of rats raised on the 8% and 25% casein diets is the same.
CHOLINE: HIGH AFFINITY UPTAKE IN VIVO BY RAT HIPPOCAMPUS
Authors: Samaras G. M. , Contrera J. F.
Published: December 2006

Abstract— [3H]Choline uptake has been measured in vivo in the rat hippocampus. Pharmacological agents and lesions which profoundly affect sodium‐dependent, high‐affinity [3H]choline uptake in vivo similarly affect [3H]choline uptake measured in vitro. Pentobarbital (65 mg/kg) and oxotremorine (0.75 mg kg) cause a decrease in [3H]choline uptake. Scopolamine (5 mg/kg) and iontophoretically applied extracellular potassium cause an increase in [3H]choline uptake. Septal lesions cause a decrease in [3H]choline uptake. Application of the general method may allow direct examination of presynaptic function and neural integration in the undisrupted living mammalian brain.
PEROXIDATION OF RAT BRAIN MITOCHONDRIAL LIPIDS1
Authors: Sharma O. P.
Published: December 2006

Abstract— Phospholipids, particularly phosphatidylcholine, are the main substrates for lipid peroxidation in rat brain mitochondria. The neutral lipids do not undergo peroxidation. The lipoproteins of mitochondria in their native form protect the phospholipids from auto‐oxidation. The mitochondrial protein fraction stimulates peroxide formation presumably due to its surface active properties.
NEUROCHEMISTRY OF THE MUCOPOLYSACCHARIDOSES: BRAIN LIPIDS AND LYSOSOMAL ENZYMES IN PATIENTS WITH FOUR TYPES OF MUCOPOLYSACCHARIDOSIS AND IN NORMAL CONTROLS
Authors: Constantopoulos George , Dekaban Anatole S.
Published: December 2006

Abstract— Lipids and certain lysosomal enzymes were measured in the cerebral gray and white matter and in the liver of unaffected controls and six patients with mucopolysaccharidosis (MPS). Three of the patients had MPS Type I (Hurler), one Type II (Hunter), one Type IIIA (Sanfilippo A) and one Type V (Scheie). The glycosaminoglycans (GAG) of those tissues have been fully characterized previously (Constantopouloset al., 1976).

Results of the present study: the normally minor brain monosialogangliosides GM2 and GM3 were markedly increased in the gray and to a lesser extent in the white matter of all the patients, except the patient with MPS Type V. On an average GM2 comprised 8.2 and 6.3, and GM3 11.8 and 6.0% of the total ganglioside neuraminic acid of the gray and white matter respectively in all patients with MPS I, II, and IIIA (normal subjects had less than 1).

Ceramide dihexoside was also increased in the gray matter of the patients with MPS I, MPS II and MPS IIIA.

The sphingolipid abnormalities were found only in tissues containing excessive amounts of partially degraded dermatan and heparan sulfates or heparan sulfate alone.

Of the six acid hydrolases assayed, the activity of /f‐glucosaminidase was increased in both brain and liver, while that of α‐galactosidase and β‐galactosidase was diminished, particularly in the liver.

These results suggest that the partially degraded heparan sulfate (and perhaps the dermatan sulfate) which accumulate in the tissues of the patients with MPS may inhibit catabolic enzymes of various sphingolipids. In turn, accumulation of sphingolipids could be responsible at least for some of the brain damage and the mental retardation in MPS I, II and IIIA.
THE CONTROL OF PYRUVATE DEHYDROGENASE IN ISOLATED BRAIN MITOCHONDRIA
Authors: Booth R. F. G. , Clark J. B.
Published: December 2006

Abstract— The activity and control of the pyruvate dehydrogenase complex in isolated rat brain mitochondria has been studied. The activity of this complex in mitochondria as isolated from normal fed rats was 78 ± 10nmol.min−1 mg mitochondrial protein−1 (n = 18) which represented 70% of the total pyruvate dehydrogenase activity. The pyruvate dehydrogenase in isolated brain mitochondria could be inactivated by incubation in the presence of ATP, oligomycin and NaF. The rate of inactivation was dependent upon the added ATP concentration but inactivation below approx 30% of the total pyruvate dehydrogenase activity could not be achieved. The inactivation of pyruvate dehydrogenase in brain mitochondria was inhibited by pre‐incubation with pyruvate. Reactivation of inactivated pyruvate dehydrogenase in rat brain mitochondria was incomplete in the incubation medium unless 10mM‐Mg2++ 1 mM‐Ca2+ were added; NaF, however, prevented any reactivation (Fig. 4). It is concluded that the pyruvate dehydrogenase complex in rat brain mitochondria is controlled in a manner similar to that in other tissues, and that pyruvate protection of pyruvate dehydrogenase activity may be important in maintaining brain energy metabolism.
PROTEIN COMPOSITION OF AXONS and MYELIN FROM RAT and HUMAN PERIPHERAL NERVES
Authors: Micko Steven , Schlaepfer W. W.
Published: December 2006

Abstract— Proteins of rat and human peripheral nerves were studied in whole nerve homogenates and in purified myelin and axonal preparations of peripheral nerve. Both myelin and axonal fractions were obtained from desheathed and minced nerve segments by flotation and sedimentation, respectively, in 0.85 m‐sucrose following hypotonic treatment. The purity of myelin and axonal preparations was confirmed by electron microscopic examination of pelleted material. Nerve proteins were analyzed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis at pH 8.3 and 7.4. Major protein bands of fresh whole nerve homogenates corresponded to polypeptide bands of either the purified myelin or axon preparations. The most prominent electrophoretic band in peripheral nerve was identified as a myelin glycoprotein with molecular weight of 27,000. The major polypeptides of axon preparations had molecular weights of 200,000, 150,000, 69,000, 55,000 and 27,000. The latter two proteins were believed to represent tubulin and residual major myelin protein, respectively. The three largest axonal polypeptides were believed to be derived from neurofilaments, which represented the predominant organelle of the purified axons. Collagen was also seen in whole nerve homogenates and in purified axons but could be distinguished by its metachromatic staining with Coomassie blue.
NUCLEAR‐CYTOSOL INTERACTIONS THAT FACILITATE RELEASE OF RNA FROM MOUSE BRAIN NUCLEI
Authors: Weck P. K. , Johnson T. C.
Published: December 2006

Abstract— Mouse brain nuclei were incubated in vitro under conditions that primarily lead to the synthesis of radioactive polydisperse and messengerlike nuclear RNA. After incubation the effects of Mg2 concentrations, nucleoside triphosphate levels and brain cytosol were examined with regard to their ability to influence the release of RNA from brain nuclei. The presence of 8 mM‐MgCl2 and a total of 0.3 mM‐nuclcoside triphosphates during the labelling procedure allowed only a minimal amount of RNA to be released. However, when the MgCl2 was decreased to 2 mM and the nucleoside triphosphates were increased to 1 mM, a stimulation of RNA release was observed. The addition of unfractionated brain cytosol under these conditions resulted in an inhibition of RNA release.

G‐100 Sephadex filtration removed detectable RNase activity from the cytosol preparations and allowed the identification of fractions that were able to facilitate nuclear RNA release by 3‐fold. The fractions that stimulated release did not have detectable levels of RNase, protease or DNA‐dependenl RNA polymerase. Under conditions that provided maximum nuclear RNA release by both labelled mouse brain and neuroblastoma nuclei, no release of DNA could be measured. The cytosol fractions that facilitated RNA release did not have a high affinity for nuclear RNA or an ability to stimulate nuclear RNA synthesis. However, other components in the cytosol were shown to stimulate RNA metabolism in isolated mouse brain nuclei and to have a relatively high binding affinity to nuclear RNA. Further purification of the RNA release components in the brain cytosol by DEAF. Sephadex chromatography allowed an increase in specific activity of at least 40‐fold. The thermal lability, effective filtration size, and solubility in phenol suggested that the cytosol factors that facilitiated nuclear RNA release were associated with cellular proteins.
EFFECT OF SALTS ON THE PHYSICAL AND KINETIC PROPERTIES OF HUMAN PLACENTAL CHOLINE ACETYLTRANSFERASE
Authors: Hersh Louis B. , Peet Martha
Published: December 2006

Abstract— The effects of salt on the properties of human placental choline acetyltransferase have been examined. Increases in enzyme activity, thermal denaturation and susceptibility to proteolysis can be related to increases in ionic strength, rather than to specific salt effects. Increased ionic strength increases the maximal velocity (Km) of the reaction, with no change in the kinetic parameter Vmax/Km (choline). The pH‐Km profile, measured over the range of 6.5–8.0, indicates the requirement of a dissociated acidic residue whose pKa is below 7.5 at high ionic strength, and a protonated residue whose pKa is above 7.5 at low ionic strength. It is proposed that the conformation of the enzyme is different at high ionic strength and at low ionic strength, and that these different conformational states of the enzyme result in different rate‐determining steps of the reaction.
KINETICS OF ADENOSINE UPTAKE INTO ASTROCYTES
Authors: Hertz L.
Published: December 2006

Abstract— Kinetics for uptake of adenosine, a putative inhibitory transmitter, were measured in normal, i.e. non‐transformed, astrocytes in cultures obtained from the dissociated, cortex‐enriched superficial parts of the brain hemispheres of newborn DBA mice. The uptake kinetics indicated a minor, unsaturable component together with a rather intense (Vmax 0.36nmol/min per mg protein) high affinity (Km 3.4 μm) uptake following Michaelis‐Menten kinetics and inhibited by 100 μm‐papaverine. The Vmax was about two times higher than that reported in the literature for brain slices suggesting that a considerable part of the adenosine uptake in brain slices occurs into glial cells. Such an accumulation of adenosine into normal astrocytes may play a major role in nucleoside and nucleotide metabolism in the brain and help in regulating the extracellular adenosine concentration.
REGIONAL ACCUMULATION OF TRYPTOPHAN AND SEROTONIN METABOLISM FOLLOWING TRYPTOPHAN LOADING IN DIABETIC RATS
Authors: MacKenzie R. G. , Trulson M. E.
Published: December 2006

Abstract— Streptozotocin‐induced diabetes in rats reduces brain tryptophan but is without effect on the central levels of 5‐hydroxytryptamine (5‐HT) or 5‐hydroxyindoleacetic acid (5‐HIAA). The present work investigates the effect of diabetes on the accumulation of brain tryptophan, 5‐HT and 5‐HIAA in various brain regions following a systemic tryptophan load. The results indicate that diabetes severely restricts the uptake of tryptophan by brain but that the tryptophan that is accumulated is normally converted to 5‐HT and 5‐HIAA. Possible mechanisms which might explain the apparent resistance of 5‐HT metabolism to decreased precursor levels in diabetics are discussed.
THE SPONTANEOUS AND ELECTRICALLY EVOKED RELEASE, FROM SLICES OF GUINEA‐PIG CEREBRAL CORTEX, OF ENDOGENOUS AMINO ACIDS LABELLED VIA METABOLISM OF d‐[U‐14C]GLUCOSE
Authors: Potashner S. J.
Published: December 2006

Abstract— In an effort to identify neurotransmitters in slices of guinea‐pig cerebral cortex, a study was made of the release of endogenous amino acids which had become labelled via metabolism of d‐[U‐14C]glucose. While incorporation of 14C into endogenous glutamate, aspartate, GABA, alanine and threonine‐serine‐glutamine (unseparated) was large enough to permit measurement of their release, that into other amino acids was not. In parallel experiments, the release of exogeneous labelled glutamate, aspartate, GABA and α‐aminoisobutyrate was examined. Electrical field stimulation evoked a transient increase in the release of all the adequately labelled endogenous amino acids and all the exogenous amino acids. The stimulated ‘increase’ in the release of each of the endogenous 14C‐labelled transmitter candidates (glutamate, aspartate and GABA) was larger than that of any other amino acid (except that of exogenous GABA). When the experiments were performed without the glucose (5 mm) usually present in the medium bathing the slices, larger amounts of each labelled amino acid were released from the slices than in the presence of glucose. Moreover, the pattern of selective release of the endogenous labelled transmitter candidates was much more pronounced in the absence of glucose. It is likely that in the absence of glucose, release from the tissue was larger because cells in the slice were relatively depolarized and uptake of amino acids into cells was impaired. Because previous evidence suggests that over 90% of glucose consumption occurs in the ‘large metabolic compartment’ which is thought to be composed of neuronal elements, neurons were probably the main site from which the larger release of endogenous 14C‐labelled transmitter candidates was evoked. The exogenous amino acids were probably released from several cellular elements in the slices. It was concluded that the pattern of a selective release of the endogenous labelled transmitter candidates may have been indicative of a transmitter releasing mechanism in nerve terminals.
CAPABILITY OF TUBULIN AND MICROTUBULES TO INCORPORATE AND TO RELEASE TYROSINE AND PHENYLALANINE AND THE EFFECT OF THE INCORPORATION OF THESE AMINO ACIDS ON TUBULIN ASSEMBLY
Authors: Arce C. A. , Hallak Marta E. , Rodriguez J. A. , Barra H. S. , Caputio R.
Published: December 2006

Abstract— Incorporation of [14C]tyrosine into the C‐terminal position of α‐tubulin of rat brain cytosol was 10‐fold higher for non‐assembled than for assembled tubulin. The incorporation into tubulin from disassembled microtubules was higher than into non‐assembled tubulin; therefore, the low incorporation into microtubules was not due to a lower acceptor capacity of their tubulin constituent.

[14C]Tyrosine was released from assembled and non‐assembled [14C]tyrosinated tubulin by the action of an endogenous carboxypeptidase. Release from non‐assembled tubulin was shown by incubating a tubulinyl‐[14C]tyrosine preparation in the presence of CaCl2 at a concentration that abolished microtubule formation. Release from microtubules was inferred from the observation that the percentages of [14C]tyrosine released and the decrease of the specific radioactivity of the recovered microtubules were practically identical and did not change after a 10‐fold dilution of the incubated microtubules.

[3H]Phenylalanine was released from a preparation of tubulinyl‐[3H]phenylalanine also by an enzymatic activity.

The capacity of a tubulin preparation to incorporate tyrosine was increased 43% by pre‐treatment with endogenous carboxypeptidase.

Tubulin tyrosinated in vitro was assembled to the same extent as native tubulin. After a mixture of tubulinyl‐[14C]tyrosine and tubulinyl‐[3H]phenylalanine was partially assembled, the ratio of 14C/3H found in the microtubules was the same as in the non‐assembled tubulin fraction.
TWO FORMS OF NEURONAL ACTIN
Authors: Choo Q. L. , Bray D.
Published: December 2006

Abstract— —Cultures of neurons essentially free of non‐neuronal cells were prepared from chick sympathetic neurons and from sensory neurons that had been enriched on a simple density gradient. The proteins of these cultures were examined by two‐dimensional gel electrophoresis and two species found in each type of nerve cell that ran close to, but not precisely with, muscle actin. They comigrated with the β and γ actins previously seen in developing myoblasts (Whalenet al., 1976). Peptide patterns obtained from the two neuronal proteins by limited papain digestion, as well as from three analogous proteins of cultured fibroblasts and purified chicken muscle actin, were extremely similar. The same two species, in similar amounts, were found in soluble and residual fractions of cultured neurons produced by brief detergent treatment; in fractions enriched for neuronal processes or cell soma from cultured sensory ganglia; and in purified actin recovered from material released upon gentle homogenisation of embryonic chick brains.
RNA METABOLISM IN THE GOLDFISH RETINA DURING OPTIC NERVE REGENERATION1, 2
Authors: Burrell Harry R. , Dokas Linda A. , Agranoff Bernard W.
Published: December 2006

Abstract— In goldfish, regeneration of the optic nerve following axotomy is accompanied by changes in retinal RNA metabolism. Approximately 4 days after unilateral optic nerve crush, there is an increased uptake of 3H‐labeled precursors of RNA into cells of the retina as well as an increase in labeling of total retinal RNA following incubation for 3–4 h in vitro. Subfractionation indicates that the resultant labeled free ribosomai RNA has a much higher specific activity than that from membrane‐bound ribosomes in post‐crush, as compared to normal retinas. Total retinal RNA content also increases, reaching a peak value about 8 days after axotomy, coincident with the time of observed maximum labeling of ribosomal RNA. No change in the total protein or DNA content of the retina is detected during this period as a result of the optic nerve crush.

Saturating amounts of uridine or adenosine in the medium eliminate the general effects of enhanced uptake of the precursors on RNA labeling. Elevated labeling of poly(A)‐containing RNA in retinal cytoplasm is nevertheless detected 10–14 days after optic nerve crush with no change in the labeling of the polyadenylate segment. A decrease in the labeling of poly(A)‐containing nuclear RNA, from a significantly greater amount than that of normal retinas to a significantly lower one, occurs during the period of observed increased labeling of cytoplasmic poly(A)‐containing RNA. The results indicate that in addition to changes in RNA precursor metabolism, optic nerve regeneration is characterized by alterations in the labeling of free and membrane‐bound retinal ribosomes as well as in the post‐transcriptional processing of messenger RNA.
Synthesis and Degradation of Retinal Proteins in Darkness and During Photic Stimulation
Authors: III A. Ames , Parks J. M. , Nesbett F. B.
Published: December 2006

Abstract: Rabbit retinas were maintained in a physiological state in vitro and exposed to 0.5‐h pulses of labeled leucine. Protein synthesis was determined from incorporation of the label, and degradation from its subsequent release. The retinas were treated as test‐control pairs. The control retina remained in darkness while the test retina was subjected to photic stimulation, either during labeling to determine the effect on synthesis or after labeling to determine the effect on degradation. 3H and 14C alternated as test and control labels. The two retinas were combined for solubilization. Their proteins were separated according to size by gel electrophoresis. Each gel was cut into 95 slices and each slice was differentially counted. The isolated retinas synthesized new protein rapidly and reproducibly. The average S.D. of the isotope ratios measured on gel slices from replicate experiments was 2.2% of the mean. Retinas driven by flashing light of constant intensity exhibited a marked increase in ganglion cell firing and accumulated 38% more (p = 0.005) 2‐deoxyglucose than their controls kept in darkness. However, they did not differ from the controls in the incorporation of labeled leucine into total protein or into any of the protein fractions separated on the gel, the largest deviation from unity in the 95 testcontrol ratios being 1.7%. Continuous light and flashing light of increasing intensity also markedly affected function and energy metabolism, but had no significant effects on leucine incorporation. None of the stimuli affected degradation, though the experiments would have been less sensitive to a change in degradation than to a change in synthesis. These results indicate that the synthesis and degradation of proteins are little affected by a marked increase in functional activity.
Comparison of the Development of the Fatty Acid Content and Composition of the Brain of a Precocial Species (Guinea Pig) and a Non‐Precocial Species (Rat)
Authors: Patel T. B. , Clark J. B.
Published: December 2006

Abstract: The fatty acid compositions of the brains of a precocial (guinea pig) and a non‐precocial (rat) species have been studied as a function of development. In the rat brain the total fatty acid content expressed as mg g wet wt.‐1 increased more than fourfold during the period from 5 days after birth to adulthood. However, the percentage composition of this total fatty acid content when expressed per individual fatty acid remained fairly constant, with the exception of nervonic acid (C24:l) which also increased fourfold on a percentage basis. In the guinea pig brain, however, at birth the total fatty acid content, expressed as mg g wet wt.‐1, is the same as that of the adult, the concentration doubling during the period from 25 days before birth until birth. Again, if the fatty acid content is analysed and expressed on a percentage basis, the relative concentrations of the individual fatty acids remain fairly constant over the period from 25 days before birth until adulthood, with the exception of nervonic (C24:l) acid which increases about fivefold from 25 days before birth to birth and only marginally (20%) from birth to adulthood. These results are discussed in relationship to the onset of neurological competence in the two species. It is concluded that the increase in fatty acid content (both total and individually) of the brains of these species as a function of the foetal and neonatal development follows a pattern which is similar to the pattern of development of certain key enzymes of energy metabolism and of neurological competence.
Regulation of Prenatal and Postnatal Protein Synthesis in Mouse Brain
Authors: Gilbert Brian E.
Published: December 2006

Abstract: Regulation of protein synthesis during prenatal and postnatal brain development was examined using postmitochondrial supernatant (PMS) fractions and isolated ribosome‐pH 5 enzyme systems from fetal, neonatal, and adult neural tissue. The rate of polyuridylic acid (poly‐U)‐dependent protein synthetic activity was inversely proportional to the endogenous rate of protein synthesis in either the PMS fractions or ribosomal preparations. A careful analysis of the kinetics of the poly‐U‐dependent polypeptide synthesis revealed that there was a lag in the time at which certain of the PMS preparations could begin to utilize the poly‐U template as sole source of mRNA. The lag period was dependent upon the developmental age of the neural tissue used and the Mg2+ concentration of the protein synthesis reaction. Since previous work reported that the observed developmental decrease in the rate of polypeptide synthesis utilizing a poly‐U template could not be measured in a purified ribosomal‐pH 5 enzyme system, ribosomes were obtained by several isolation techniques to determine if the purification procedure might have affected the ribosomes in some manner by removing a specific protein(s) involved in ribosome‐cytosol interactions. At 6 mM‐Mg2+ the rate of poly‐U‐dependent protein synthesis was inversely proportional to the rate of endogenous synthesis and depended upon the method used to isolate the ribosomes: microsomes ∼Triton X‐100‐treated < DOC‐treated < KCl‐treated. However, there was no age‐dependent effect with any of the ribosomal preparations. The data suggest that there is a developmental modulating effect of ribosomal activity in PMS preparations which is not found in association with the isolated ribosome‐pH 5 enzyme protein synthesizing system.
Characterization of [3H]Guanine Nucleotide Binding Sites in Brain Membranes
Authors: Childers Steven R. , Snyder Solomon H.
Published: December 2006

Abstract: [3H]GTP [guanosine triphosphate] and [3H]GMP‐PNP [guanosine 5′‐(β,8‐imino)triphosphate, a nonmetabolized analog of GTP] have been utilized as ligands to characterize binding sites of guanine nucleotides to rat brain membranes. Binding of both [3H]GTP and [3H]GMP‐PNP is saturable, with respective KD values of 0.76 and 0.42 μM. The number of binding sites for GMP‐PNP (4 nmol/g) is three times greater than for GTP (1.5 nmol/g). This discrepancy is caused by rapid degradation of GTP to guanosine by brain membranes, which can be partially prevented by addition of 100 μM‐ATP. The binding of [3H]guanine nucleotides is selective, with approximately equipotent inhibition by GTP, GDP, and GMP‐PNP (at 0.2‐1.0 μM), but no inhibition by other nucleotides at 100 μM concentrations. The binding sites for guanine nucleotides in brain membranes appear not to be associated with microtubules, since treatments that reduce [3H]colchicine binding by 65% have no effect on [3H]GTP binding. [3H]Guanine nucleotide binding is widely distributed in various organs, with highest levels in liver and brain and lowest levels in skeletal muscle. The characteristics of these binding sites in brain show specificity properties of sites that regulate neurotransmitter receptors and adenylate cy‐clase.
Cyclic AMP in Female Mouse Brain is Altered by the Adrenocorticotropic Hormone(4–9) Analogue Organon 2766
Authors: Schneider David R. , Felt Barbara T. , Murphy Sharon , Goldman Harold
Published: December 2006

Abstract: Cyclic AMP content was determined in 12 brain regions of young adult female mice at 30 min and at 24 h following an intraperitoneal injection of the tri‐substituted adrenocorticotropic hormone(4–9) [ACTH(4–9)] analogue Organon 2766 [ORG 2766]. Animals were killed by focused 3.5 kW microwave radiation applied for 350 ms. Unlike previously reported responses in male mice, at 30 min post‐injection there were no detectable differences in cyclic AMP content between the placebo and ORG 2766‐treated animals. By contrast, 24 h after injection, the content of cyclic AMP was changed significantly in 8 of the 12 brain regions examined: medulla‐pons, septal area, thalamus, hypothalamus, hippocampus, olfactory bulb, and parietal and occipital cortices. In most of the regions examined, differences consisted of 50% or greater reductions of tissue cyclic AMP content. The changes were unrelated to the estrus cycle of these animals
Properties of Detergent‐Dispersed Adenylate Cyclase from Cerebral Cortex. Presence of an Inhibitor Protein
Authors: Sano Mamoru , Drummond George I.
Published: December 2006

Abstract: Adenylate cyclase was solubilized from washed paniculate fraction of rabbit cerebral cortex with the nonionic detergent Lubrol 12A9 and subjected to either gel filtration on Ultrogel AcA 34 or chromatography on DEAE Bio‐Gel A. By both procedures the enzyme was resolved into two components, one insensitive to guanyl 5′‐yl imidodiphosphate [Gpp(NH)p] and NaF but stimulated by Ca2+ and calmodulin, and another that was sensitive to Gpp(NH)p and NaF but relatively insensitive to Ca2+ and calmodulin. The data support the possibility that two independent forms of adenylate cyclase exist in cerebral cortex, one regulated by guanine nucleotide regulatory protein and another by Ca2+‐calmodulin. Fractions containing the guanylnucleotide‐sensitive activity were found to contain a factor that inhibited basal and Ca2+‐stimulated adenylate cyclase in the Ca2+‐sensitive fraction. The inhibitor was inactivated by heating at 60°C and by incubation with trypsin. Inhibition was not time‐dependent, and it was not due to destruction of cAMP by phosphodiesterase or of ATP by ATPase. Inhibitory action was not reversed by calmodulin and therefore it does not appear to be a calmodulin binding protein. Sucrose density gradient sedimentation indicated a sedimentation coefficient of 4S for the inhibitor; by this technique it co‐sedimented with the adenylate cyclase sensitive to Gpp(NH)p and NaF.
The Development of Pre‐ and Postsynaptic Components of the Noradrenergic System in the Rat Cerebellum
Authors: Waddington G. , Banks P.
Published: December 2006

Abstract: Evidence based on the ability to accumulate [3H]noradrenaline by a mechanism sensitive to desmethylimipramine suggests that there is a period of hyperinnervation of the cerebellum by noradrenergic fibres around the beginning of the second postnatal week. Different developmental profiles for specific noradrenaline uptake and noradrenaline content indicate that invasion of the tissue by noradrenergic fibres precedes their full acquisition of transmitter. Developmental increases in the density of β‐receptors and adenyl cyclase responsiveness to isoproterenol lags behind those of the presynaptic components and does not begin until the hyperinnervation is declining around day 12.
Enhancement of Depolarization‐Induced Release of γ‐Aminobutyric Acid from Brain Slices by Antibodies to Ganglioside
Authors: Frieder Brina , Rapport Maurice M.
Published: December 2006

Abstract: The effect of antibodies to GM1 ganglioside on release of neurotransmitters from rat brain slices was studied. Depolarization‐induced (40 mM‐KCl or veratrine) release of γ‐aminobutyric acid was markedly enhanced. Depolarization‐induced release of norepinephrine was only slightly enhanced, whereas that of serotonin was unaffected. No effect on spontaneous release was observed for any of these three neurotransmitters. These results show that antibodies that can bind to synaptic membrane antigens may alter neurotransmitter release and that antibodies directed against GM1 ganglioside exhibit a measure of specificity in producing such an effect.
Gonadal Influences on the Sexual Differentiation of Monoamine Oxidase Type A and B Activities in the Rat Brain
Authors: Vaccari A. , Caviglia A. , Sparatore A. , Biassoni R.
Published: December 2006

Abstract: The sex‐dependent differentiation of monoamine oxidase (MAO) in the hypothalamus of 60‐day‐old, Charles River rats was found to involve only type A (MAO‐A), and not type B (MAO‐B) enzyme. In vivo inhibition of type A by clorgyline, and type B by (−)deprenyl, however, tended to decrease the specific activity of both types of MAO to a smaller extent in the female than in the male hypothalamus. When masculinization was prevented by neonatal administration of estradiol (E) to males, hypothalamic MAO‐A and MAO‐B activities increased in both control and MAO‐inhibited rats. Androgenization of females, however, had little effect on the MAO activity. Whereas the effects of neonatal estrogenization were attributable neither to a direct influence of E nor to a sexual difference in the peripheral clearance of the MAO‐inhibitor used, single, high doses of steroids to adult, but not to newborn rats, did acutely affect the kinetics of MAO‐A. The activity of MAO‐A was also decreased by high concentrations of E or TS in vitro. The imprinting for patterns of hypothalamic MAO‐A and MAO‐B in the two sexes results, probably, from genetic predetermination. Neonatal changes in the homeostasis of gonadal hormones may result in type‐MAO nonspecific effects in adulthood, whereas the short‐term effects of high concentrations of steroids may be selective for the A form.
Heterogeneity of Rat Brain Acetylcholinesterase: A Study by Gel Filtration and Gradient Centrifugation
Authors: Rakonczay Z. , Vincendon G. , Zanetta J‐P.
Published: December 2006

Abstract: According to their solubilization properties, two classes of acetyl‐cholinesterases (AChE) can be detected in the adult rat brain: a “soluble” species (easily solubilized without detergent), and a membrane‐bound species (solubilized only in the presence of detergent). The latter was found to be homogeneous by gel filtration (Stokes radius 8.05 ± 0.35 nm) and sucrose gradient centrifugation (9.75 ± 0.2 S) in the presence of Triton X‐100. The “soluble” AChE gives three stable species in the presence of the same detergent with Stokes radii and sedimentation constants of 10.9 ± 0.5 nm and 16 ± 2 S; 6.75 ± 0.30 nm and 10.7 ± 0.4 S; 5.37 ± 0.35 nm and 4.37 ± 0.1 S. Co‐chromatography and co‐sedimentation or the reduction and alkylation of disulfide bridges show that all the soluble species are different from the membrane‐bound AChE. The possibility that soluble and membrane‐bound AChE are completely different molecules is discussed.
Monovalent Cations and Striatal Tyrosine Hydroxylase
Authors: Kuczenski Ronald
Published: December 2006

Abstract: The kinetic properties of soluble tyrosine hydroxylase from rat striatum and the activation of the enzyme by the polyanion heparin were assessed as a function of the monovalent cations K+, Na+, tetramethylammonium (TMA+), and Tris. Substitution of K+ or Na+ for TMA+ or Tris can alter the kinetic properties of tyrosine hydroxylase in the absence of heparin, the nature of the interaction of the enzyme with heparin and also the kinetic properties of the heparin‐activated enzyme. The data suggest that monovalent cations can support unique conformational states of the enzyme.
Sulfur Amino Acid Metabolism in the Developing Rhesus Monkey Brain: Subcellular Studies of Taurine, Cysteinesulfinic Acid Decarboxylase, γ‐Aminobutyric Acid, and Glutamic Acid Decarboxylase
Authors: Rassin David K. , Sturman John A. , Gaull Gerald E.
Published: December 2006

Abstract: Taurine, cysteinesulfinic acid decarboxylase (CSAD), glutamate, γ‐aminobutyric acid (GABA), and glutamic acid decarboxylase (GAD) were measured in subcellular fractions prepared from occipital lobe of fetal and neonatal rhesus monkeys. In addition, the distribution of [35S]taurine in subcellular fractions was determined after administration to the fetus via the mother, to the neonate via administration to the mother prior to birth, and directly to the neonate at various times after birth. CSAD, glutamate, GABA, and GAD all were found to be low or unmeasurable in early fetal life and to increase during late fetal and early neonatal life to reach values found in the mother. Taurine was present in large amounts in early fetal life and decreased slowly during neonatal life, arriving at amounts found in the mother not until after 150 days of age. Significant amounts of taurine, CSAD, GABA, and GAD were associated with nerve ending components with some indication that the proportion of brain taurine found in these organelles increases during development. All subcellular pools of taurine were rapidly labeled by exogenously administered [35S]taurine. The subcellular distribution of all the components measured was compatible with the neurotransmitter or putative neuro‐transmitter functions of glutamate, GABA, and taurine. The large amount of these three amino acids exceeds that required for such function. The excess of glutamate and GABA may be used as a source of energy. The function of the excess of taurine is still not clear, although circumstantial evidence favors an important role in the development and maturation of the CNS.
Composition and Subcellular Distribution of Glycoproteins and Glycosaminoglycans Undergoing Axonal Transport in Garfish Olfactory Nerves
Authors: Elam John S.
Published: December 2006

Abstract: The study examined the subcellular distribution of [3H]glucos‐amine‐labeled glycoconjugates undergoing axonal transport in 100,000 ×g soluble and two membranous subfractions of the garfish olfactory nerve. Analysis was made of intact glycoconjugates and of glycopeptides and glycosaminoglycans derived from these molecules by limit protease digestion. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis revealed labeling of a variety of high‐molecular‐weight molecules with a lower molecular weight distribution in the soluble fraction than in the membranous fractions. Following protease digestion, nearly two‐thirds of transported radioactivity in glycopeptides was recovered in the plasma membrane‐enriched subfraction, with the remainder equally divided between soluble and higher density membrane fraction. Comparison of the distribution of glycopeptide radioactivity and chemically assayed hexosamine revealed transport labeling of a large variety of different‐sized neutral and acidic glycopeptides in all subfractions. Transport labeling of most glycoprotein carbohydrate chains was in proportion of their hexosamine content.

Transported glycosaminogiycan label was most heavily concentrated in the plasma membrane fraction, whereas hexosamine was most concentrated in the higher density membrane fraction. The labeling pattern suggested both transported and nontransported pools of these molecules. The specific glycosaminoglycans chondroitin sulfate and heparan sulfate were recovered in all subfractions, whereas hyaluronic acid was confined to the soluble fraction.
S‐Adenosylmethionine Decarboxylase Levels in Rat Retina During Postnatal Development
Authors: Ruggeri P. , De Luca G. , Crisafulli A. , Macaione S. , Di Giorgio R. M. , Ientile R.
Published: December 2006

Abstract: S‐Adenosylmethionine decarboxylase from rat retina is similar to that isolated from other rat tissues with regard to kinetic parameters. pH optimum, putrescine requirement, and sensitivity to spermine. The enzymic activity increases during the first 7 days of postnatal life but decreases until the 20th day. After this period AdoMet decarboxylase activity increases, to reach the highest values at the 90th day. This behavior suggests that such enzymic activity is responsible for spermidine and spermine levels in rat retina and that a high content of retinal spermine might have a role in the photoreceptor outer segment renewal.
Myelin‐Associated Glycoprotein Is the Antigen for a Monoclonal IgM in Polyneuropathy
Authors: Braun Peter E. , Frail Donald E. , Latov Norman
Published: December 2006

Abstract: Recent studies show that IgM monoclonal antibody from patients with IgM paraproteinemia and peripheral neuropathy reacts with a protein component of human PNS myelin and an analogous component or components of human CNS myelin. We have now demonstrated that the antigen for this antibody is a specific glycoprotein component of myelin, referred to as myelin‐associated glycoprotein (MAG). Human PNS and CNS myelin proteins were separated by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis on pore‐gradient slabs, and MAG was identified by the immuno‐electroblot procedure with rabbit anti‐MAG (rat). The identical band(s) were stained by an analogous procedure with patient serum as the first antibody. Human PNS MAG had an apparent molecular weight of 107,000. Human CNS MAG appeared as three bands: 113,000, 107,000, and 92,000. Passage of myelin proteins through a concanavalin A‐Sepharose column removed the staining component. Purified patient IgM, added to a lithium diiodosalicylate extract of myelin, immunoprecipitated MAG. This antibody also cross‐reacted with MAG from bovine CNS, but not from rabbit, rat, or mouse.
Basic Proteins of Rodent Peripheral Nerve Myelin: Immunochemical Identification of the 21.5K, 18.5K, 17K, 14K, and P2 Proteins
Authors: Greenfield S. , Weise M. J. , Gantt G. , Hogan E. L. , Brostoff S. W.
Published: December 2006

Abstract: Proteins in peripheral nervous system and central nervous system myelin and homogenates of sciatic nerve and brain from young and adult mice and rats were characterized with affinity‐purified anti‐P2 and anti‐myelin basic protein sera after electrophoretic transfer from sodium dodecyl sulfate‐polyacrylamide gels to nitrocellulose sheets. Using this method we have identified a component of rodent peripheral nervous system myelin as P2 protein. Peripheral nervous system myelin also showed the presence of four basic proteins in addition to P2 protein. These were found to be analogous to the 14, 17, 18.5, and 21.5K species found in the central nervous system myelin. A number of high‐molecular‐weight proteins were also detected with anti‐myelin basic protein serum in peripheral nervous system, as well as central nervous system myelin. In addition, we report the presence of a high‐molecular‐weight P2 cross‐reactive protein in rodent brain stem homogenates, but not in central nervous system myelin.
Intrinsic Protein Phosphorylation in Synaptosomal Plasma Membrane Fragments: A Comparison of Cerebral Cortex Tissue from Several Species, Including Human Biopsy Specimens
Authors: Martinez‐Millan Luis , Rodnight Richard
Published: December 2006

Abstract: Intrinsic protein phosphorylation was studied in synaptosomal membrane fragments made from cerebral cortex tissue taken from the following species: human (biopsy specimens), ox, rat, rabbit, guinea pig and mouse. Membrane fragments from all species exhibited a qualitatively similar range of protein acceptors phosphorylated by cyclic AMP‐dependent protein kinase activity; contrary to a previous report, no evidence for cyclic GMP‐dependent protein kinase activity was found in the human material. With the exception of membrane fragments prepared from ox brain, all the preparations exhibited the same range of Ca2+‐dependent protein kinase activity. Ox brain obtained from a slaughterhouse yielded membranes containing no Ca2+‐dependent protein kinase activity, but this may have been due to unavoidable postmortem losses.
Synaptic Membrane Antigens in Developing Rat Brain Cerebral Cortex and Cerebellum
Authors: Mahadik S. P. , Korenovsky A. , Ciccarone V. , Laev H.
Published: December 2006

Abstract: The contents of five synaptic membrane antigens (56K, 58K, 62K, 63K, and 64K) were determined in rat cerebral cortex and cerebellum at eight developmental time points: E9, E14, P < 1, P5, P14, P28, P60, and P180 (E, embryonic; P, postnatal). In cerebral cortex, the five antigens showed five different developmental patterns with respect both to specific content (i.e., quantity per unit of membrane) and total content (i.e., quantity per cortex). The 56K, 58K, and 62K polypeptides were first detected at E14, increased slightly to P5, then increased rapidly from P5 to P28 by 14‐, 11‐, and 18‐fold, respectively. From P28 to PI80, the patterns of these antigens showed very large differences. The 63K and 64K antigens were first detected at P14 and P28, respectively. The specific content of 63K antigen continued to increase steadily throughout adult life; in contrast, the specific content of the 64K antigen did not change appreciably. In cerebellum only three antigens (56K, 58K, and 62K) were detected. These three antigens showed different developmental patterns. The 56K polypeptide was first detected at E14; its specific content increased very rapidly to a maximum at P < 1; it then decreased, first slowly, and then more rapidly, disappearing at P60. The 58K polypeptide also was detectable at E14 and increased very rapidly to a maximum at P < 1. It then decreased markedly to P5, followed by an increase, returning almost to its maximum level at P14. It then slowly decreased disappearing at P180. The 62K antigen was first detected at P14 and then it slowly decreased with disappearance at P60. The patterns with respect to total contents per cerebellum were similar for the three antigens, with a maximum at P28. We conclude that the highest increase in the contents of these antigens roughly corresponds to the period of maximal synaptogenesis (P9 to P28) in both regions. Differences among developmental patterns probably reflect changing molecular machinery required for development and functional differentiation of synapses in different brain regions. The fine structure of these patterns suggests that the quantitative measurement of synaptic membrane antigens will be useful for delineating complex processes occurring during synaptogenesis.