bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Excitatory Amino Acid‐Stimulated Phosphoinositide Hydrolysis and N‐[3H]Acetylaspartylglutamate Binding in Rat Brain: Selective Inhibition of Phosphoinositide Hydrolysis by 2‐Amino‐3‐Phosphonopropionate
Authors: Schoepp Darryle D. , Johnson Bryan G.
Published: October 2006

Abstract: The activation of phosphoinositide hydrolysis by ibotenate (IBO) in brain slices and the binding of N‐[3H]acetylaspartyl‐L‐glutamate (NAAG) to brain membranes are biochemical parameters previously shown to be selectively inhibited by 2‐amino‐4‐phosphonobutyrate (AP4). We have examined whether the binding of [3H]NAAG and stimulation of phosphoinositide hydrolysis by IBO are indexing the same or different populations of AP4‐sensitive excitatory amino acid sites in brain. L‐AP4 and D,L‐2‐amino‐3‐phosphono‐propionate (D,L‐AP3) were found to be about equipotent inhibitors of IBO‐stimulated phosphoinositide hydrolysis. L‐AP4 and D,L‐AP3 did not inhibit stimulation of phosphoinositide hydrolysis by the cholinoceptor agonist carbachol. The L‐isomers of serine‐O‐phosphate and α‐aminoadipate were selective inhibitors of IBO‐stimulated phosphoinositide hydrolysis, but were less potent than L‐AP4 or D,L‐AP3. When these compounds were examined for their ability to inhibit [3H]NAAG binding to membranes of rat forebrain, the relative order of potency was L‐α‐aminoadipate = D‐α‐aminoadipate < L‐AP4 < L‐serine‐O‐phosphate < D‐AP4 < D,L‐AP3. Concentrations of NAAG up to 10−2M did not stimulate phosphoinositide hydrolysis. Thus, although both assays are sensitive to L‐AP4 inhibition, they appear to represent disparate excitatory amino acid sites in brain. Furthermore, D,L‐AP3 appears to be a more selective inhibitor of excitatory amino acid‐stimulated phosphoinositide hydrolysis than L‐AP4, and might be a more useful pharmacological tool to define the function of these receptor sites in brain.
Changes in Intracellular Free Magnesium During Hypoglycaemia and Hypoxia in Cerebral Tissue as Calculated from 31p‐Nuclear Magnetic Resonance Spectra
Authors: Brooks K. J. , Bachelard H. S.
Published: October 2006

Abstract: 3lP‐nuclear magnetic resonance spectra of super‐fused cerebral tissues were obtained under normal, hypogly‐caemic, and hypoxic conditions. Concentrations of free intracellular magnesium were calculated from differences in chemical shifts between the α‐ and β‐resonances of the nucleoside phosphates. Control levels of 0.33 mM were significantly increased to 0.52 mM in hypoglycaemia and to 0.57 mM in severe hypoxia. Removal of calcium from the superfusing medium increased the free intracellular Mg2+ concentration to 0.63 mM
Metabolism of Catecholamine Esters by Cultured Bovine Brain Microvessel Endothelial Cells
Authors: Scriba Gerhard K. E. , Borchardt Ronald T.
Published: October 2006

Abstract: The metabolism of epinine (N‐methyldopamine) and epinine diesters (acetyl, benzoyl, pivaloyl, and isobutyryl) by brain endothelium was investigated using primary cultures of bovine brain microvessel endothelial cells. 3,4‐Dihy‐droxyphenylacetic acid (DOPAC), the product of monoamine oxidase (MAO)‐mediated degradation of epinine, was the only metabolite detected by HPLC with electrochemical detection following incubation of the cell monolayers with epinine or its esters. This metabolism could be inhibited by the MAO inhibitors pargyline, clorgyline, and deprenyl, with the system being most sensitive to inhibition by clorgyline. Compared with epinine, incubation of cell monolayers with the diester prodrugs led to increased drug (epinine plus epinine diesters) tissue levels. With the exception of the diacetyl ester, lower levels of DOPAC were observed with the diester prodrugs than with the parent compound. Hydrolysis by serine‐de‐pendent esterases appears to be necessary for the subsequent oxidation by MAO. The permeabilities of epinine and the diester prodrugs through endothelial cell monolayers grown on porous supports were related to their lipophilicity and molecular weight.
Characterization of Insulin‐Like Growth Factor‐I Receptors in PC 12 Pheochromocytoma Cells and Bovine Adrenal Medulla
Authors: Dahmer Mary K. , Ji Li , Perlman Robert L.
Published: October 2006

Abstract: Competitive binding studies indicated that PC 12 cells have receptors for insulin‐like growth factor‐I (IGF‐I). There are ∼ 11,100 ± 1,500 IGF‐I receptors/cell; these receptors have an apparent KD for IGF‐I of 7.2 ± 0.6 nM. Covalent cross‐linking of l25I‐IGF‐I to PC 12 cells labeled a 125,000‐130,000‐Mr protein, presumably the α‐subunit of the IGF‐I receptor. Although PC 12 cells also have insulin receptors, the 125I‐IGF‐I appeared to be cross‐linked to IGF‐I receptors, because 100 nM IGF‐I competed for labeling but 100 nM insulin did not. Bovine chromaffin cells also have IGF‐I receptors. The protein tyrosyl kinase activity of IGF‐I receptors from bovine adrenal medulla and PC 12 cells was examined after purification of the receptors by wheat germ agglutinin‐Sepharose chromatography. IGF‐I (10 nM) stimulated autophosphorylation of the β‐subunits of the IGF‐I receptors from both preparations; the β‐subunits from both sources had Mr values of ∼97,000. IGF‐I also stimulated phosphorylation of the synthetic substrate poly(Glu:Tyr)4:1 by both receptor preparations. IGF‐I (IC50 of ∼0.2 nM) was much more potent than insulin at stimulating phosphorylation of poly(Glu:Tyr) by the bovine adrenal medulla preparation. A maximal concentration of IGF‐I (10 nM) increased phosphorylation approximately threefold. IGF‐I was slightly more effective than insulin at stimulating the phosphorylation of poly(Glu:Tyr) by the PC 12 cell receptor preparation, but neither ligand produced a maximal effect at concentrations up to 100 nM. This result probably reflects the presence of comparable numbers of IGF‐I and insulin receptors on PCI 2 cells. Our data indicate that the IGF‐I receptors on PC 12 cells are similar to IGF‐I receptors in the adrenal medulla and other tissues. Presumably these receptors are responsible for the stimulation of PC 12 cell replication by IGF‐I.
Ca2+‐Dependent Regulation of Presynaptic Stimulus‐Secretion Coupling
Authors: Verhage Matthijs , Besselsen Elly , Da Silvas Fernando H. Lopes , Ghijsen Wim E. J. M.
Published: October 2006

Abstract: In the present study, we have investigated the role of Ca2+ in the coupling of membrane depolarization to neurotransmitter secretion. We have measured (a) intracellular free Ca2+ concentration ([Ca2+Ji) changes, (b) rapid 45Ca2+uptake, and (c) Ca2+‐dependent and ‐independent release of endogenous glutamate (Glu) and γ‐aminobutyric acid (GABA) as a function of stimulus intensity by elevating the extracellular [K+] to different levels in purified ijierve terminals (synaptosomes) from rat hippocampus. Duriijg stimulation, Percoll‐purined synaptosomes show an increased 45Ca2+ uptake, an elevated [Ca2+]i, and a Ca2+‐dependejnt as well as a Ca2+‐independent release of both Glu and GABA. With respect to both amino acids, synaptosomes respond on stimulation essentially in the same way, with maximally a fourfold increase in Ca2+‐dependent (exocytotic) release. Ca2+‐depen‐dent transmitter release as well as [Ca2+]; elevations show maximal stimulation at moderate depolarizations (30 mM K+). A correlation exists between Ca2+‐dependent release of both Glu and GABA and elevation of [Ca2+]i. C2+‐dependent release is maximally stimulated with an elevation of [Ca2+]Iof 60% above steady‐state levels, corresponding with an intracellular concentration of ∼400 nM, whereas elevations to 350 nM are ineffective in stimulating Ca2+‐dependent release of both Glu and GABA. In contrast, Ca2+‐independent release of both Glu and GABA shows roughly a linear rise with stimulus intensity up to 50 mM K+. 45Ca2+ uptake on stimulation also shows a continuous increase with stimulus intensity, although the relationship appears to be biphasic, with a plateau between 20 and 40 mM K+. These findings indicate that Ca2+‐dependent, exocytotic transmitter release is not simply enhanced by larger depolarizations of the plasma membrane and that a strong Ca2+‐dependent regulatory mechanism exists in synaptosomes for the trigger of exocytosis, operating at a mean [Ca2+]i of between 350 and 400 nM. Ca2+ transport and buffering mechanisms possibly involved in this regulation and the role of the membrane potential are discussed.
Activation of Guanylate Cyclase by Bradykinin in Rat Sensory Neurones Is Mediated by Calcium Influx: Possible Role of the Increase in Cyclic GMP
Authors: Burgess G. M. , Mullaney I. , McNeill M. , Coote P. R. , Minhas A. , Wood J. N.
Published: October 2006

Abstract: Bradykinin, which activates polymodal nociceptors, increased cyclic GMP (cGMP) in a capsaiciiji‐sensitive population of cultured sensory neurones from rat dorsal root ganglia (DRG) by stimulating guanylate cyclase, but had no effect on cyclic AMP (cAMP). In nonneunbnal cells from DRG, bradykinin increased cAMP, but not cpMP. The bra‐dykinin‐induced increase in cGMP in thej neurones was completely blocked by removal of extracellular Ca2+, or by incubation of the cells with the calcium channel blockers nifedipine and verapamil. Pretreatment of the| neurones with either dibutyryl cGMP or sodium nitroprusside (which elevates cGMP) inhibited bradykinin‐induced formation of inositol phosphates. It is possible that cGMP could be involved in the regulation of polyphosphoinositide turnover in DRG neurones.
Mixed Competitive and Allosteric Antagonism by Gallamine of Muscarinic Receptor‐Mediated Second Messenger Responses in N1E‐115 Neuroblastoma Cells
Authors: Lee Norman H. , El‐Fakahany Esam E.
Published: October 2006

Abstract: The antagonistic effects of gallamine on muscarinic receptor‐linked responses were investigated in N1E‐115 neuroblastoma cells. M1 muscarinic receptor‐mediated phos‐phoinositide hydrolysis induced by carbamylcholine was antagonized by gallamine, with a Ki value of 33 μM. By comparison, gallamine was four‐ to fivefold less potent in blocking noncardiac M2 muscarinic receptor‐mediated inhibition of cyclic AMP formation, with a Ki value of 144 μM. The resulting Arunlakshana‐Schild plots of the antagonism of both responses by gallamine were linear and exhibited slopes not differing from 1, a result indicative of a competitive mechanism. To elucidate further the nature of gallamine's inhibitory actions, experiments were performed where the effects of gallamine in combination with the known competitive muscarinic antagonist, N‐methylscopolamine (NMS), were studied. In the presence of both antagonists, a supraadditive shift in the carbamylcholine dose‐response curve was demonstrated for the two responses, a result suggestive of an allosteric mode of interaction between gallamine and NMS binding sites. Confirmation that gallamine allosterically modifies the muscarinic receptor was provided by radioligand binding studies. Gallamine competition curves with either [N‐methyl‐3H]scopolamime methyl chloride ([3H]NMS) or [N‐methyl‐3H]quinuclidinyl benzilate methyl chloride ([3H]NMeQNB) were unusually shallow. Furthermore, gallamine decelerated the rate of dissociation of receptor‐bound [3H]NMS > [3HJNMeQNB in a dose‐dependent manner. The present study demonstrates that whereas gallamine antagonizes carbamylcholine‐mediated responses in N1E‐115 cells in a competitive manner, an allosteric component of its action is revealed in the presence of muscarinic antagonists such as NMS.
A Protein Kinase Activity Is Associated with and Specifically Phosphorylates the Neural Cell Adhesion Molecule LI
Authors: Sadoul Remy , Kirchhoff Frank , Schachner Melitta
Published: October 2006

Abstract: The neural cell adhesion molecule LI is a phos‐phorylated integral membrane glycoprotein that is recovered from adult mouse brain by immunoaffinity chromatography as a set of polypeptides with apparent molecular masses of 200, 180, 140, 80, and 50 kilodaltons (LI‐200, LI‐180, Ll‐140, LI‐80, and LI‐50, respectively). In the present study, we show that two kinase activities are associated with im‐munopurified L1: One specifically phosphorylates L1‐200 and L1‐80 but not L1‐180, L1‐140, or L1‐50. This pattern of hosphorylation corresponds to the one described for L1 after metabolic phosphate incorporation into cultures of cerebellar cells. In both cases, serine is the main amino acid that is labeled by radioactive phosphate. The kinase activity is not activated by Ca2+, calmodulin, phosphatidylserine, diolein, cyclic AMP, or cyclic GMP, a result suggesting that the enzyme is distinct from Ca2+/calmodulin‐dependent kinases, from protein kinase C, or from cyclic AMP/cyclic GMP‐dependent kinases and may belong to the independent kinase group. The other kinase phosphorylates only casein but not L1, utilizes GTP as well as ATP, and is strongly inhibited by heparin. Because the primary structure of the L1 protein does not contain consensus sequences characteristic for known kinases, we believe that the catalytic activities detectable in immunopurified L1 are due to kinases that are strongly enough associated with L1 to withstand the stringent purification procedures.
Distribution of Activity Converting 4‐Aminobutyraldehyde to γ‐Aminobutyric Acid in Subcellular Fractions of Mouse Brain
Authors: Asakura Tadashi , Ikeda Yoshitaka , Matsuda Makoto
Published: October 2006

Abstract: The subcellular distribution of activity of 4‐amino‐butyraldehyde dehydrogenase (ABAL‐DH) was studied in mouse brain. ABAL‐DH was localized mainly in the crude mitochondrial fraction; most of the activity in this fraction was found in the subfraction containing synaptosomes, and the remainder was in the mitochondrial fraction. After osmotic disruption of synaptosomes, most of the activity was located in the synaptic cytosol, and the remainder was in the synaptic mitochondria. Sucrose density subfractionation of synaptosomes revealed that γ‐aminobutyric acid, glutamic acid decarboxylase, and ABAL‐DH localized in a denser region of gradient fraction than the region containing acetylcholinesterase and choline acetyltransferase.
Subacute and Chronic In Vivo Lithium Treatment Inhibits Agonist‐ and Sodium Fluoride‐Stimulated Inositol Phosphate Production in Rat Cortex
Authors: Godfrey Philip P. , McClue Steven J. , White Alison M. , Wood Andrew J. , Grahame‐Smith David G.
Published: October 2006

Abstract: We have investigated the effects of in vivo lithium treatment on cerebral inositol phospholipid metabolism. Twice‐daily treatment of rats with LiCl (3 mEq/kg) for 3 or 16 days resulted in a 25–40% reduction in agonist‐stimulated inositol phosphate production, compared with NaCl‐treated controls, in cortical slices prelabelled with [3H]inositol. A small effect was also seen with 5‐hydroxytryptamine (5‐HT) 24 h after a single dose of LiCl (10 mEq/kg). Dose–response curves to carbachol and 5‐HT showed that lithium treatment reduced the maximal agonist response without altering the EC50 value. This inhibition was not affected by the concentration of LiCl in the assay buffer. Stimulation of inositol phosphate formation by 10 mM NaF in membranes prepared from cortex of 3‐day lithium‐treated rats was also inhibited, by 35% compared with NaCl‐treated controls. Lithium treatment did not alter the kinetic profile of inositol polyphosphate formation in cortical slices stimulated with carbachol. Muscarinic cholinergic and 5‐HT2 bindings were unaltered by lithium, as was cortical phospholipase C activity and isoproterenol‐stimulated cyclic AMP formation. [3H]Inositol labelling of phosphatidylinositol 4,5‐bisphosphate was significantly enhanced by 3‐day lithium treatment. The results, therefore, indicate that subacute or chronic in vivo lithium treatment reduces agonist‐stimulated inositol phospholipid metabolism in cerebral cortex; this persistent inhibition appears to be at the level of G‐protein–phospholipase C coupling.
Biochemical Aspects of Chick Embryo Retina Development: The Effects of Glucocorticoids
Authors: Tesoriere Giovanni , Vento Renza , Taibi Gennaro , Calvaruso Giuseppe , Schiavo Maria Rita
Published: October 2006

Abstract: In chick embryo retina during development, DNA synthesis and the activities of DNA polymerase, thymidine kinase, thymidylate synthetase, and ornithine decarboxylase (ODC) declined in parallel from day 7 to 12. The administration in ovo of hydrocortisone reduced significantly, particularly at 8–10 days of incubation, both DNA synthesis and the four enzyme activities tested. The effect was dose dependent, reaching the maximum with 50–100 nmol of hydrocortisone, 8–16 h after treatment. The highest inhibition was found for ODC activity (70%), followed by thymidine kinase activity (62%) and DNA synthesis (45%), whereas activities of DNA polymerase and thymidylate synthetase were reduced only by 30%. The inhibitory effect was exerted by all the glucocorticoids tested, with dexamethasone and hydrocortisone being the most efficacious. The results support the view that glucocorticoids reduce the proliferative events in chick embryo retina, particularly at 8–10 days of embryonic life.
Glucocorticoids Modify Differentially Dopamine‐ and Prostaglandin E1‐Mediated Cyclic AMP Formation by the Cultured Human Astrocytoma Clone D384
Authors: Balmforth Anthony J. , Yasunari Kenichi , Vaughan Peter F. T. , Ball Stephen G.
Published: October 2006

Abstract: The effects of steroid hormones on the cyclic AMP responses to stimulation of human astrocytoma cells (D384) by dopamine, prostaglandin E1 (PGE1), and isoprenaline were investigated. Incubation of D384 cells with dexamethasone resulted in a potentiation of the PGE1 and isoprenaline responses and a marked attenuation of the dopamine response. The time courses of the effects of dexamethasone on dopamine and PGE1 responses were similar, requiring long‐term (at least 18 h) incubation of cells with the steroid. Concentration‐response curves of dexamethasone effects on dopamine and PGE1 responses yielded similar Ka apparent values, suggesting a common mechanism. Cycloheximide, a protein synthesis inhibitor, prevented the effects of dexamethasone. Only steroids with glucocorticoid activity reproduced the dexamethasone effects. Direct stimulation of Gs with 5‐guanylylimidodiphosphate and adenylate cyclase with forskolin revealed no significant differences in their activities in dexamethasone‐treated and untreated cells. Furthermore, a comparison of the dopamine and PGE1 concentration‐response curves obtained from dexamethasone‐treated and untreated cells suggested that the affinity of the receptors for their agonists remained unchanged. These results suggest that glucocorticoids may alter protein synthesis and thereby the number of receptors expressed by D384 cells.
Rat Brain Slices Produce and Liberate Kynurenic Acid upon Exposure to l‐Kynurenine
Authors: Turski Waldemar A. , Gramsbergen Jan Bert P. , Traitler Helmut , Schwarcz Robert
Published: October 2006

Abstract: The incorporation of l‐kynurenine (L‐KYN) into kynurenic acid (KYNA) was examined in rat brain slices. KYNA was measured in the slices and in the incubation medium after purification by ion‐exchange and HPLC chromatography. In pilot experiments, the formation of KYNA was confirmed by gas chromatography. KYNA was produced stereoselectively from l‐KYN, and ∼90% of the newly synthesized KYNA was recovered from the incubation medium. Intracellular KYNA was not actively retained by the tissue and was lost from the cells upon repeated washes. Thus, regulation of the levels of extracellular KYNA appears to occur at the level of l‐KYN uptake and/or kynurenine transaminase, the biosynthetic enzyme of KYNA. KYNA production from l‐KYN was linear up to 4 h and reached a plateau at a l‐KYN concentration of 250 γM. The process was effectively inhibited by the transaminase inhibitor aminooxyacetic acid (IC50, ∼25 γM), and showed pronounced regional distribution (hippocampus > cortical areas > thalamus ± cerebellum). The conversion of l‐KYN to KYNA was dependent on oxygenation and on the presence of glucose in the incubation medium. Neither deletion of Ca2+ or Mg2+ nor addition of 20 mM Mg2+ had any effect. However, KYNA production was significantly attenuated in the absence of Cl− or in the presence of 50 mM K+ in the incubation medium. In Na+‐free medium, the production of KYNA from l‐KYN was increased by 30%. Experiments with ibotenate‐lesioned striatal slices demonstrated a small neuronal component of the process, but indicated that the majority of KYNA in the brain is produced in and liberated from glial cells. The processes described here are suggested to underlie the role of KYNA as a neuromodulator and possible endogenous neuroprotective agent and anticonvulsant.
Quantitation and Characterization of Peptides from the C‐Terminal Flanking Region of Rat and Bovine Preprotachykinins
Authors: McGregor Gerard P. , Kage Reinhard , Thim Lars , Conlon J. Michael
Published: October 2006

Abstract: Sequence analysis of cDNAs has shown that the biosynthetic precursors of substance P (α‐,β‐, and γ‐prepro‐tachykinins) contain a common amino acid sequence in the C‐terminal flanking region that has not been conserved between species. Antisera have been raised against the synthetic peptide Tyr‐Glu‐Arg‐Ser‐Ala‐Met‐Gln‐Asn‐Tyr‐Glu, which represents rat β‐preprotachykinin‐(117‐126)‐peptide, and used in radioimmunoassays. Antiserum R50 reacted strongly with C‐flanking peptides in extracts of rat and bovine tissues whereas antiserum GP‐4 reacted only with the rat peptides. The primary structure of the predominant molecular form of prepro tachykinin C‐flanking peptide in an extract of bovine corpus striatum was established as: Ala‐Leu‐Asn‐Ser‐Val5‐Ala‐Tyr‐Glu‐Arg‐Ser10‐Val‐Met‐Gln‐Asp‐Tyr15‐GIu. This sequence represents β‐preprotachykinin‐(111‐126)‐peptide which is equivalent to γ‐preprotachykinin‐(96‐111)‐peptide. A C‐flanking peptide with similar chromatographic properties was identified in extracts of rat brain and gut together with a second immunoreactive component that may represent a fragment or a posttranslationally modified variant. A peptide corresponding to the 37‐amino‐acid residue C‐flanking peptide derived from α‐preprotachykinin was not detected in the extracts as expected from the known low abundance of SaL‐preprotachykinin mRNA in rat brain and gut.
Effects of dl‐2‐Amino‐5‐Phosphonovalerate on Metabolism of Catecholamines in Synaptosomes from Rat Brain
Authors: Yee Daniel K. , Pastuszko Anna , Nelson David , Wilson David F.
Published: October 2006

Abstract: Incubation of synaptosomes from rat brain with dl‐2‐amino‐5‐phosphonovalerate (APV) stimulated an increased release of dopamine, and this effect was strictly dependent on the extrasynaptosomal calcium level. APV increased biosynthesis of dopamine from tyrosine by 30%, whereas monoamine oxidase activity was inhibited by 30%. When synaptosomes were incubated with radioactive dopamine, APV caused a large decrease in incorporation of label into 3,4‐dihydroxyphenylacetic acid but greatly increased incorporation into norepinephrine and its N‐methyl derivatives. Quantification of dopamine and its metabolites in synaptosomes, using electrochemical detection, indicated that the presence of APV resulted in changes in the absolute levels of the aforementioned dopamine metabolites similar to the changes in radiolabel incorporation. Omission of Ca2+ from the extrasynaptosomal medium greatly diminished the APV‐induced changes in catecholamine metabolism. The metabolic changes appear to largely result from an increased intrasynaptosomal Ca2+ level due to the APV‐induced increase in calcium permeability of the plasma membrane.
In Vitro Phosphorylation of Bovine Adrenal Chromaffin Cell Tyrosine Hydroxylase by Endogenous Protein Kinases
Authors: George Robert J. , Haycock John W. , Johnston Jeffrey P. , Craviso Gale L. , Waymire Jack C.
Published: October 2006

Abstract: Under phosphorylating conditions, addition of Ca2+ or cyclic AMP to the 100,000 g supernatant of purified bovine adrenal chromaffin cells increases both the incorporation of 32P into tyrosine hydroxylase and the activity of the enzyme. Combining maximally effective concentrations of each of these stimulating agents produces an additive increase in both the level of 32P incorporation into tyrosine hydroxylase and the degree of activation of the enzyme. The increased phosphorylation by Ca2+ is due to stimulation of endogenous Ca2+‐dependent protein kinase activity and not inhibition of phosphoprotein phosphatases. When the chromaffin cell supernatant is subjected to diethylaminoethyl (DEAE) chromatography to remove calmodulin and phospholipids, tyrosine hydroxylase is no longer phosphorylated or activated by Ca2+; on the other hand, phosphorylation and activation of tyrosine hydroxylase by cyclic AMP are not affected. Subsequent replacement of either Ca2+ plus calmodulin or Ca2+ plus phosphatidylserine to the DEAE‐fractionated cell supernatant restores the phosphorylation, but not activation of the enzyme. Reverse‐phase HPLC peptide mapping of tryptic digests of tyrosine hydroxylase from the 100,000 g supernatant shows that the Ca2+‐dependent phosphorylation occurs on three phosphopeptides, whereas the cyclic AMP‐dependent phosphorylation occurs on one of these peptides. In the DEAE preparation, either cyclic AMP alone or Ca2+ in the presence of phosphatidylserine stimulates the phosphorylation of only a single phosphopeptide peak, the same peptide phosphorylated by cyclic AMP in the crude supernatant. In contrast, Ca2+ in the presence of calmodulin stimulates the phosphorylation of three peptides having reverse‐phase HPLC retention times that are identical to peptides phosphorylated by Ca2+ addition to the crude unfractionated 100,000 g supernatant. Rechromatography of the peaks from each of the in vitro phosphorylations, either in combination with each other or in combination with each of the seven peaks generated from phosphorylation of tyrosine hydroxylase in situ, established that cyclic AMP, Ca2+/phosphatidylserine, and Ca2+/calmodulin all stimulate the phosphorylation of the same reverse‐phase HPLC peptide: in situ peptide 6. Ca2+/calmodulin stimulates the phosphorylation of in situ peptides 3 and 5 as well. Thus, tyrosine hydroxylase can be phosphorylated in vitro by protein kinases endogenous to the chromaffin cell. Phosphorylation occurs on a maximum of three of the seven in situ phosphorylated sites, and all three of these sites can be phosphorylated by a Ca2+/calmodulin‐dependent protein kinase.
Identification of Adenosine Receptor in Rat Pineal Gland: Evidence for A‐2 Selectivity
Authors: Sarda Nicole , Gharib Abdallah , Reynaud Denis , Pacheco Ling Ou Henri
Published: October 2006

We have examined the binding of the adenosine agonist radioligands [3H]cyclohexyIadenosine (3H]CHA), R‐N6‐[3H]phenylisopropyladenosine ([3H]R‐PIA), and 5′‐N‐ethylcarboxamido[3H]adenosine ([3H]NECA) to membranes prepared from rat pineal gland. The results showed that the A‐1‐selective ligands (CHA and R‐PIA) had ±10% specific binding. By contrast, [3H]NECA, a nonselective A‐l/A‐2 li‐gand, gave 72% specific binding of the total binding. This specific binding was insensitive to cyclopentyladenosine (50 M) or R‐PIA (50 μM). To characterize this binding, we sed the N‐ethylmaleimide pretreatment method. Under these conditions, this binding was of high affinity with a KD of 51 ± 10 nM and an apparent Bmax of 1,060 ± 239 fmol/ mg of protein. Specific binding was unaffected by the presence of MgCl2 (10 mM) but was sensitive to guanylyliinidodi‐ phosphate (100 μM) (‐25%), a result suggesting the involvement of an N‐protein mechanism in the coupling of the adenosine receptor labeled by [3H]NECA to other components of the receptor complex. The rank of activity of adenosine analogues in displacing specific [3H]NECA binding was NECA ± 2‐chloroadenosine ±S‐adenosyl‐L‐homocysteine ± CHA. Binding was also displaced by 3‐isobutyl‐l‐meth‐ylxanthine (IC50= 23.6 μM). These findings are consistent with the selective labeling by [3H]NECA of an A‐2‐type adenosine receptor in rat pineal membranes.
Decreased Cyclic AMP Degradation in NG 108‐15 Neuroblastoma × Glioma Hybrid Cells and S49 Lymphoma Cells Chronically Treated with Drugs that Inhibit Adenylate Cyclase
Authors: Thomas John M. , Vagelos Randall , Hoffman Brian B.
Published: October 2006

The increase in hormone‐stimulated cyclic AMP accumulation observed in a variety of intact cells after chronic pretreatment with drugs that inhibit adenylate cyclase activity has been attributed to an increase in adenylate cyclase activity following withdrawal of the inhibitory drug. In NG 108–15 mouse neuroblastoma X rat glioma hybrid cells (NG cells) chronically treated with the muscarinic cholinergic agonist carbachol, we have found a significant decrease in the apparent degradation rate constant for cyclic AMP, in addition to an increase in the prostaglandin E1 (PGE1)‐stimulated cyclic AMP synthesis rate in intact cells. In carbachol‐pretreated NG cells that were stimulated with a maximally effective dose of PGE1, and that accumulated steady‐state cyclic AMP concentrations fourfold or more higher than in control cells, the apparent rate constant for degradation was about 53% lower than the value for control cells. In carbachol‐pretreated cells stimulated with a submaximal dose of PGE1 to yield a steady‐state cyclic AMP concentration comparable to control cells, the apparent rate constant was 31% lower than the value for control cells. In S49 mouse lymphoma cells (S49 cells) chronically treated with an analog of the inhibitory agonist somatostatin, the first‐order rate constant for cyclic AMP degradation in intact cells following isoproterenol stimulation was 29% lower than the value for control cells. Despite these changes in the kinetics of cyclic AMP degradation in intact NG cells and S49 cells, there was either no change or a minimal change (less than 10%) in phosphodiesterase activities assayed in extracts of cells chronically exposed to inhibitory drugs. These data suggest that an alteration in cyclic AMP degradation as well as in cyclic AMP synthesis is an important factor in the withdrawal response following chronic treatment of cells with drugs that inhibit adenylate cyclase.
Retinoic Acid Rapidly Decreases Phosphatidylinositol Turnover During Neuroblastoma Cell Differentiation
Authors: Ponzoni M. , Lanciotti M.
Published: October 2006

Phosphatidylinositol (PI) turnover has recently been implicated in the regulation of cell proliferation and transformation. We have investigated its role in differentiation using LAN‐1 cells, a human neuroblastoma cell line that can be induced to differentiate along the neuronal pathway by retinoic acid (RA). We have found that treatment of LAN‐1 cells with RA is followed by a rapid decrease of inositol phospholipid metabolism, using myo‐[1,2‐3H]inositol or [1(3)‐3H]glycerol. No changes were observed in both [3H]inositol and [3H]glycerol uptake within 24 h of RA treatment. Decreased incorporation of the metabolic precursor into PI 4‐monophosphate and PI 4,5‐bisphosphate occurred within 1 h of RA treatment. No changes were seen in the specific radioactivity of the precursor pools up to 1 h of treatment with RA. Analysis of labeled PI metabolites from prelabeled cells indicated a rapid decrease of inositol 1,4,5‐trisphosphate and 1,2‐diacylglycerol content within 1 min of induction of LAN‐1 cell differentiation. These findings constitute the earliest reported events in neuroblastoma cell differentiation.
Biosynthesis of the Myelin 2′,3′‐Cyclic Nucleotide 3′‐Phosphodiesterases
Authors: Gillespie C. Stewart , Bernier Lise , Brophy Peter J. , Colman David R.
Published: October 2006

We have investigated the site of synthesis of the 2′,3′‐cyclic nucleotide 3′‐phosphodiesterases (CNPs I and II) in rat brain. Rapid kinetics of incorporation of CNPs into oligodendrocyte plasma membrane in the intact brain are consistent with their synthesis on free polysomes. This hypothesis was confirmed by the translation in vitro of RNA isolated from free and bound polysomes, respectively. Unlike myelin basic protein (MBP) mRNAs, CNP mRNAs are not enriched in a myelin‐associated pool of RNA. MBPs, but not CNPs, were found to readily associate in vitro with membrane vesicles derived from rough endoplasmic reticulum. The avidity of MBPs in binding to membranes is probably related to the previously observed spatial segregation of MBP mRNAs into actively myelinating cellular processes of the oligodendrocyte. Such a segregation would ensure that newly synthesized MBPs are immediately incorporated into myelin. In contrast, the CNPs probably associate with the cytoplasmic surface of the oligodendrocyte plasma membrane through interaction with a membrane‐bound receptor.
Glycyl‐l‐Glutamine Stimulates the Accumulation of A12 Acetylcholinesterase but Not of Nicotinic Acetylcholine Receptors in Quail Embryonic Myotubes by a Cyclic AMP‐Independent Mechanism
Authors: Lotwick Helen S. , Haynes L. W. , Ham J.
Published: October 2006

Myotubes prepared from the Japanese quail embryo at 9 days gestation were cultivated in the presence of glycyl‐L‐glutamine (Gly‐Gln, β‐endorphin C‐terminal dipeptide) or glycyl‐glutamic acid (Gly‐Glu), and changes in the activity of acetylcholinesterase (AChE) molecular forms and binding of 125I‐α‐bungarotoxin (αBGT) to cell surface nicotinic acetylcholine receptors were measured. The A12 oligomer was the major form of AChE in the cultures. The activity of all molecular forms of the enzyme was increased in the presence of Gly‐Gln, but Gly‐Glu did not alter AChE activity. In cells infected with the temperature‐sensitive mutant, La31C, of Rous sarcoma virus (ts‐RSV) and transferred to the nonpermissive temperature, the A12 form of AChE was absent, but its activity could be induced following exposure of the cells to Gly‐Gln. When cells treated in this way were incubated in the presence of collagenase, there was a small but significant loss of A12 AChE activity, indicating that Gly‐Gln stimulated the activity of a pool of this oligomer which was mainly but not entirely intracellular. Neither Gly‐Gln nor Gly‐Glu influenced 125I‐αBGT binding after exposure of the cells to the peptides for any duration. Neither Gly‐Gln nor Gly‐Glu influenced the accumulation of cyclic AMP in the cultures. β‐Endorphin is one of a family of peptides that coexist transiently with acetylcholine in lower motoneurones of vertebrates in the perinatal period. This report provides evidence for the selective trophic activity of one of its derivatives toward the postsynaptic cholinergic system in avian muscle cells.
Oral Penicillin
Authors: McDermott Walsh , Bunn Paul A. , Benoit Maria , DuBois Rebeckah , Haynes Willetta
Published: October 2006

It is possible to attain serum concentrations of penicillin after oral administration comparable to those attained after intramuscular injection by the use of approximately five times as much penicillin. As the concentrations attained following the ingestion of penicillin by four different methods were all of the same order of magnitude, it would seem that the present problem in oral administration is analogous to that with intramuscular administration,
i.e.
, to find the ideal vehicle whereby the duration of the serum concentration can be prolonged.
The Nutritive Value of Fusaria
Authors: Vinson Leonard J. , Cerecedo Leopold R. , Mull Robert P. , Nord F. F.
Published: October 2006

It has been shown that
Fusarium lini
B. grown on an artificial stock culture medium when supplemented with thiamin provides adequate amounts of the B-complex vitamins for normal growth, reproduction and lactation in mice, and that it compares very favorably with brewer's yeast in its food value.
Growth-Retarding Effect of Corn in Nicotinic Acid-Low Rations and Its Counteraction by Tryptophane
Authors: Krehl W. A. , Teply L. J. , Sarma P. S. , Elvehjem C. A.
Published: October 2006

Either 50 mg 1(-)tryptophane or 1.0 mg nicotinic acid per 100 gms of ration completely counteracts the growth retardation caused by the inclusion of 40 per cent. corn grits in a low protein ration. A possible explanation of this observation is discussed.
Electron Shadow Micrography of the Tobacco Mosaic Virus Protein
Authors: Williams Robley C. , Wyckoff Ralph W. G.
Published: October 2006

Two improvements are described in the use of shadow electron micrography for the observation of particles of macromolecular dimensions. One involves the substitution of gold for chromium as shadowing metal. The thinner gold film that can be employed gives a truer representation of the shape of particles so small that shape and size are significantly altered by the thickness of the shadowing metal deposited on them. The other consists in metal-shadowing small particles deposited on a very smooth surface such as that of polished glass and the handling of this metal film as a replica of the glass surface and the particles resting on it. This technique permits the photography of particles whose direct observation is disturbed by the fine structure that is brought out by shadowing a collodion substrate. Application of these methods to the electron micrography of the tobacco mosaic virus protein shows that its fibrils are rods about 125A both in height and breadth. Though the rods appear segmented, these segments have not been found to have a length that is constant or a small integral multiple of an underlying unit.
Increasing and Prolonging Blood Penicillin Concentrations Following Intramuscular Administration
Authors: Bronfenbrenner Jack , Favour Cutting B.
Published: October 2006

(1) Restriction of fluid intake to 1,500 cc and the salt intake to 3 gm a day doubles the penicillin blood level following interrupted intramuscular injections of penicillin. (2) The administration of benzoic acid to a patient on an unrestricted diet may double the penicillin blood level during similar treatment. (3) The combination of these two procedures results in a four- to eight-fold increase in penicillin blood level with a prolonged effective blood concentration.
Concerted Antibiotic Effect of Penicillin, Methionine, Threonine and Methionine Sulfoxide Upon Brucella, Eberthella, Salmonella, and Shigella
Authors: Shwartzman Gregory
Published: October 2006

Penicillin susceptibility of highly refractory Gram-negative organisms may be greatly enhanced upon addition of methionine, threonine and methionine sulfoxide. The action of amino acids appears to be synergistic rather than additive. Methionine is essential for the enhancement. Threonine and methionine sulfoxide facilitate the effect of methionine following a reciprocal quantitative relationship.
Creatinuria in Diabetics and an Evaluation of Methods for Determining Total Creatinine
Authors: Caspe Saul , Davidson Benjamin , Truhlar Joseph
Published: October 2006

Creatinuria was found in all 42 diabetic clinic subjects of both sexes taken at random.

Total creatinine determined in the urines of diabetics by the Albanese modification showed a variable deviation (in magnitude and direction) when compared with total creatinine obtained by the Folin method.
Ovum Aging and
p
H Imbalance as a Cause of Chromosomal Anomalies in the Hamster
Authors: Adachi Kimiko , Ingalls Theodore H.
Published: October 2006

Using female hamsters mated in estrus, we have produced triploid embryos as manifestations of pregnancy wastage by combining delays of 3 to 4 hours in fertilization with exposure of the animals to hypoxia. Among the triploid embryos only XXX and XXY karyotypes occurred, indicating derivation from XX-containing ova. These findings have relevance to human reproduction.
Human Lymphocytes: Similarity of B and T Cell Surface Morphology
Authors: Alexander Elaine L. , Wetzel Bruce
Published: October 2006

When viewed by scanning electron microscopy, human lymphocytes fixed in suspension and processed with minimal cell loss appear uniformly covered with short microvilli. Contrary to previous reports, lymphocytes from subpopulations selectively enriched for T cells are villous and indistinguishable from B lymphocytes. Whereas lymphocyte surface architecture can change rapidly and substantially in response to environmental modifications, such as contact with an underlying surface, these alterations are similar for both B and T cells and do not serve to distinguish these subpopulations.
Conjugal Transfer of a Chromosomal Gene Determining Production of Enterotoxin in
Vibrio cholerae
Authors: Vasil Michael L. , Holmes Randall K. , Finkelstein Richard A.
Published: October 2006

Matings between strains of
Vibrio cholerae
differing in toxinogenicity, nutritional requirements, and antibiotic susceptibilities were performed in order to determine the location of the gene
tox
that controls production of cholera enterotoxin. Segregation analysis shows that
tox
is linked to a gene required for histidine biosynthesis. Our data indicate that the
tox
gene is located on the bacterial chromosome and not on a plasmid in the strains of
V. cholerae
studied.
Disc Shedding in Rodlike and Conelike Photoreceptors of Tree Squirrels
Authors: Anderson Don H. , Fisher Steven K.
Published: October 2006

Electron microscopic observations suggest that the rodlike and conelike photoreceptors of diurnal tree squirrels shed outer segment discs. Twenty-four hours after injection of tritiated L-leucine, the rodlike photoreceptors show a band of radioactivity at the base of the outer segment. The conelike photoreceptor outer segments show only a pattern of diffuse labeling. These results strongly suggest that disc shedding can occur in photoreceptor outer segments in which proteins are diffusely renewed.
Dichloroacetamide Antidotes for Thiocarbamate Herbicides: Mode of Action
Authors: Lay Ming-Muh , Hubbell James P. , Casida John E.
Published: October 2006

Thiocarbamate sulfoxides formed on metabolic sulfoxidation of thiocarbamate herbicides in plants and mammals are effective carbamoylating agents for glutathione and other tissue thiols. Dichloroacetamides that protect corn from thiocarbamate herbicide injury induce more rapid detoxification of the thiocarbamate sulfoxides by increasing their rate of carbamoylation of glutathione through elevation of the root glutathione level and glutathione
S
-transferase activity.
Effects of Frontal Eye Field and Superior Colliculus Ablations on Eye Movements
Authors: Schiller Peter H. , True Sean D. , Conway Janet L.
Published: October 2006

Two parallel neural pathways are primarily responsible for the control of saccadic eye movements—one mediated through the frontal eye fields and the other through the superior colliculus. When both pathways are disrupted, control of saccadic eye movements is lost. Disruption of either pathway alone produces only subtle deficits.
Conditioning and Reversal of Short-Latency Multiple-Unit Responses in the Rabbit Medial Geniculate Nucleus
Authors: Gabriel Michael , Saltwick Steven E. , Miller Joseph D.
Published: October 2006

Rabbits were conditioned to avoid shock signaled by a tone. A second tone was randomly interspersed but did not signal shock. Neuronal activity 5 to 40 milliseconds after tone onset was greater to the shock-signaling tone than to the other tone. This difference reversed when the signal value of the tones was reversed.
Insular biogeography: of mice and mites
Authors: Dritschilo William , Cornell Howard , Nafus Donald , O'Connor Barry
Published: October 2006

The number of mite species using cricetid rodents in North America is related to the host distributional areas. The age and latitude of the distributional areas have unimportant effects on the number of mite species using a rodent species. The relation between species and area is analogous to species equilibrium numbers of island faunas.
5-Iododeoxyuridine Potentiation of the Replication in Vitro of Several Unrelated RNA and DNA Viruses
Authors: Green Jon A. , Baron Samuel
Published: October 2006

Enhancement of the replication of unrelated viruses (three RNA viruses and one DNA virus), representative of four major virus groups, occurs in human, rodent, or avian cells treated in vitro with 5-iododeoxyuridine (IdU). The results suggest that the potentiation of viral replication by IdU is a widespread phenomenon.
Spleen Cells Transmit Osteopetrosis in Mice
Authors: Walker Donald G.
Published: October 2006

Osteopetrosis was induced in lethally irradiated, normal mice of grey-lethal and microphthalmic stocks by cell infusions prepared from the spleens of osteopetrotic littermates. Failure of skeletal remodeling became evident within a few weeks after transplantation as calcified cartilage and bone accumulated excessively in the active metaphyses of the long bones. The massive lesions produced were extensively infiltrated with abnormal osteoclasts.
Photochemical Air Pollution: Transport from the New York City Area into Connecticut and Massachusetts
Authors: Cleveland W. S. , Kleiner B. , McRae J. E. , Warner J. L.
Published: October 2006

Photochemical air pollution resulting from primary emissions in the New York City metropolitan area is transported by prevailing winds on a 300-kilometer northeast trajectory through Connecticut and as far as northeastern Massachusetts. As a result, southwestern Connecticut has the highest ozone concentrations in the region and there is a substantial increase in ozone concentrations in Massachusetts. The ozone concentrations of air entering the New York City metropolitan area are often already above the federal standard of 0.08 part per million, but the concentration distribution is well below concentration distributions at downwind sites in Connecticut.
Preneoplastic Lesions in the Human Breast
Authors: Jensen H. M. , Rice J. R. , Wellings S. R.
Published: October 2006

A subgross sampling technique with histological confirmation was used to study the pathology of 119 whole human breasts, either cancer-associated (that is, containing cancer or contralateral to a cancer) or taken from random routine autopsies. Atypical lobules were observed much more frequently in the cancer-associated group than in the group of routine autopsy breasts. Atypical lobules showed varying degrees of anaplasia that formed a continuum between normal epithelium and carcinoma in situ, usually of the common ductal type. As apparent markers for increased cancer risk, atypical lobules in the human breast may be homologous to hyperplastic alveolar nodules that are abundant in high mammary cancer strains of mice. This indirect evidence supports the hypothesis that atypical lesions are common preneoplastic lesions in the human mammary gland.
Egg Transport in the Rabbit Oviduct: The Roles of Cilia and Muscle
Authors: Halbert S. A. , Tam P. Y. , Blandau R. J.
Published: October 2006

Ciliary ovum transport through the oviductal ampulla was investigated, in vivo, by blocking smooth muscle activity. Isoproterenol eliminated rapid muscle-induced egg movements, yet the egg and its surrounding cells reached the site of fertilization within normal time limits. The role of cilia in ovum transport thus seems more important than that of the smooth muscle.
Control of Gamete Formation (Exflagellation) in Malaria Parasites
Authors: Carter Richard , Nijhout Mary M.
Published: October 2006

The only stages of malaria parasites capable of establishing an infection in a mosquito are the gametocytes that circulate in the blood of the vertebrate host. Within minutes of ingestion by a mosquito the gametocytes transform into mature gametes in the process of "exflagellation." This process is controlled in vitro solely by the change in
p
H in the blood as it moves from the environment of the circulation to that of the atmosphere, the
p
H rise being mediated by the fall in carbon dioxide tension as the blood equilibrates with the atmosphere.
Insect Photoperiodism: The "T Experiment" as Evidence for an Hourglass Mechanism
Authors: Bowen M. F. , Skopik S. D.
Published: October 2006

"T experiments" demonstrate that the clock controlling termination of larval diapause in
Ostrinia nubilalis
is an hourglass mechanism that measures 8 hours of darkness. Circadian oscillations are not involved in photoperiodic time measurement in this species.
Spatial Frequency—Contingent Color Aftereffects
Authors: May James G. , Matteson Halsey H.
Published: October 2006

Two-dimensional Fourier analysis of checkerboards reveals that major components are at a 45° angle to the check edges. After adapting to chromatic checkerboards, subjects who viewed achromatic grating stimuli reported that complementary color aftereffects are aligned with spatial frequency components rather than with the edges in the pattern.