bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorylation‐Dependent Immunoreactivity of Neurofilaments Increases During Axonal Maturation and β,β′‐Iminodipropionitrile Intoxication
Authors: Watson D. F. , Griffin J. W. , Fittro K. P. , Hoffman P. N.
Published: October 2006

Abstract: The immunoreactivity of the high‐molecular‐weight neurofilament (NF) subunit toward antibodies that react with phosphorylation‐related epitopes was determined at different anatomic sites in the PNS of rats during normal maturation and after intoxication with β,β′‐iminodipropionitriIe (IDPN). A maturational increase in the relative binding of phosphor‐ylation‐dependent antibodies compared to phosphorylation‐inhibited antibodies occurred from age 3 to 12 weeks. An increase in phosphorylation‐related immunoreactivity with increasing distance from the cell bodies was present in ventral and dorsal roots at all ages. The degree of phosphorylation‐related immunoreactivity was greater for centrally directed axons in the dorsal roots of the L5 ganglion than for peripherally directed axons. IDPN, a toxin that impairs NF transport, caused a marked increase in reactivity toward the phos‐phorylation‐dependent antibody. NFs from IDPN‐treated rats also bound less of an antibody that is normally phosphorylation independent and this inhibition of binding was sensitive to phosphatase digestion. In each instance, greater degrees of phosphorylation‐dependent immunoreactivity correlate with conditions known to exhibit slower net rates of axonal tran; port of NF proteins
Inhibition of Excitatory Amino Acid‐Stimulated Phosphoinositide Hydrolysis in the Neonatal Rat Hippocampus by 2‐Amino‐3‐Phosphonopropionate
Authors: Schoepp Darryle D. , Johnson Bryan G.
Published: October 2006

Abstract: The effects of excitatory amino acid agonists and α‐amino‐ω‐phosphonocarboxylic acid antagonists on phosphoinositide hydrolysis in hippocampal slices of the 7‐day neonatal rat were examined. Significant stimulation of [3H]inositol monophosphate formation was observed with ibotenate, quisqualate, l‐glutamate, l‐aspartate, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid, l‐homocys‐teate, and kainate. N‐Methyl‐D‐aspartate had no effect. Of these agonists, ibotenate and quisqualate were the most potent and efficacious. Stimulations by ibotenate and quisqualate were partially inhibited by l‐2‐amino‐4‐phosphonobutyrate (10−3M), but this antagonist had no effect on l‐glutamate, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazoIepropionic acid, or kainate. At 10−3M, D,L‐2‐amino‐3‐phosphonopropionate completely inhibited ibotenate and quisqualate stimulations, partially inhibited l‐glutamate stimulation, and had no effect on α ‐ amino ‐3‐ hydroxy ‐5‐ methyl ‐4‐ isoxazolepropionic acid‐, kainate‐, or carbachol‐induced [3H]inositol monophosphate formation. Concentration‐effect experiments showed D,L‐2‐amino‐3‐phosphonopropionate to be five times more potent as an antagonist of ibotenate‐stimulated phosphoinositide hydrolysis than L‐2‐amino‐4‐phosphonobuty‐rate. Thus in the neonatal rat hippocampus, like in the adult rat brain, D,L‐2‐amino‐3‐phosphonopropionate is a selective and relatively potent inhibitor of excitatory amino acid‐stimulated phosphoinositide hydrolysis. Because this glutamate receptor is uniquely sensitive to D,L‐2‐amino‐3‐phosphono‐propionate, these studies provide further pharmacological evidence for the existence of a novel excitatory amino acid receptor subtype that is coupled to phosphoinositide hydrolysis in brain.
A Kainate Receptor Linked to Nitric Oxide Synthesis from Arginine
Authors: Garthwaite J. , Southam E. , Anderton M.
Published: October 2006

Abstract: In slices of young rat cerebellum, the glutamate analogue kainate induced a large accumulation of cyclic GMP, which was inhibited by non‐TV‐methyl‐D‐aspartate antagonists. Quisqualate and a‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazoIepropionate evoked only small cyclic GMP responses and inhibited the effect of kainate. When tested in cerebellar cell suspensions, glutamate was also a potent antagonist of the cyclic GMP response to kainate. Superoxide dismutase enhanced the response in the isolated cells, whereas haemoglobin and methylene blue were inhibitory. The response in slices was Ca2+ dependent, augmented by arginine, and inhibited by l‐NG‐mono‐methylarginine in a manner that could be reversed by additional arginine. It is concluded that stimulation of kainate receptors leads to activation of the enzyme that synthesises nitric oxide from arginine and that activation of soluble guanylate cyclase by the released nitric oxide accounts for the cyclic GMP generation.
Quisqualic Acid Modulates Kainate Responses in Cultured Cerebellar Granule Cells
Authors: Gallo Vittorio , Giovannini Claudio , Levi Giulio
Published: October 2006

Abstract: The activation of kainic acid and quisqualic acid receptors in cultured cerebellar granule cells stimulated the release of preaccumulated d‐[3H]aspartate. The effect of kainate could be distinguished from that of quisqualate by its sensitivity to the antagonists kynurenic acid and 2,3‐cis‐piperidine dicarboxylic acid. At a concentration of kainic acid (50 μM) close to its half‐maximal releasing effect, simultaneous addition of quisqualic acid (10–50 μM) resulted in a significant dose‐dependent inhibition of the kainate‐induced component of d‐[3H]aspartate release, which was monitored by the progressive decrease in sensitivity of the evoked release to kynurenic acid. In contrast, when kainic acid was used at a subeffective concentration (10 μM), addition of low doses of quisqualate (2–5 μM) resulted in a synergistic effect on d‐[3H]aspartate release. Under these conditions, the effect of the two agonists was sensitive to kynurenic acid. Kainic acid (50–100 μM) also caused a dose‐dependent, kynurenic acid‐sensitive accumulation of cyclic GMP (cGMP) in granule cell cultures. Quisqualic acid was, by itself, ineffective and prevented, in a dose‐dependent manner, the kainate‐induced cGMP formation (IC50= 5 μM). Finally, the guanylate cyclase activator sodium nitroprusside greatly enhanced cGMP formation but had no effect on d‐[3H]aspartate release. Together, these results demonstrate the existence of complex interactions between quisqualic and kainic acids and indicate that the effects of the two glutamate agonists on d‐[3H]aspartate release and on cGMP accumulation are independent.
Myelin Proteins in Reverse Micelles: Tight Lipid Association Required for Insertion of the Folch‐Pi Proteolipid into a Membrane‐Mimetic System
Authors: Vacher Monique , Waks Marcel , Nicot Claude
Published: October 2006

Abstract: The solubility and reactivity of the Folch‐Pi proteolipid from bovine CNS have been studied in reverse micelles of sodium bis(2‐ethylhexyl)sulfosuccinate, isooctane, and water. Such a membrane‐mimetic system resembles the aqueous spaces of the native myelin sheath in terms of its physicochemical properties. Although the proteolipid is completely insoluble in water, it can be inserted into the water‐containing micellar system. In contrast, the lipid‐depleted protein failed to be incorporated into these organized assemblies. The lipid requirements for insertion of the proteolipid were studied, therefore, after delipidation by several precipitations with isooctane, a nondenaturing solvent. Novel extraction procedures and quantitative analyses by HPLC of the protein‐bound lipids revealed the persistence of a lipidprotein complex (6 ± 1 mol of lipid/mol of protein) displaying optimal micellar solubilization. Competition experiments carried out with brain lipids provide evidence for a preference of the myelin protein for sulfatide, phosphatidylinositol, and phosphatidylserine, in that order. The resulting proteolipid, although differing in relative composition, showed good solubility in the membrane‐mimetic system. In contrast, reconstitution experiments carried out with the lipid‐depleted protein resulted in weak lipid binding and poor micellar incorporation. These results suggest that the tightly bound acidic lipids may stabilize a protein conformation required for insertion into the micellar system.
Characteristics of Sorbitol Uptake in Rat Glial Primary Cultures
Authors: Stahl Bernd , Wiesinger Heinrich , Hamprecht Bernd
Published: October 2006

Uptake of [U‐14C]sorbitol was studied in astroglia‐rich rat primary cultures. Initial rate of sorbitol uptake is proportional to sorbitol concentration between 20 μM and 400 mM. Sorbitol transport is not inhibited by glucose, fructose, and a variety of structurally related polyols, or by cy‐tochalasin B, an inhibitor of glucose transport. Phloretin, phlorizin, filipin, and n‐hexanol, all compound that alter the properties of biological membranes, and the sulfhydryl reagent p‐chloromercuribenzoate inhibit sorbitol uptake to various degrees. Variation in the concentrations of extracellular Na+ and K+ does not affect transfer of sorbitol across the cell membrane. It is concluded that sorbitol is taken up into glial cells by a diffusion process, not involving a carrier and probably not through the lipid bilayer, but through a proteinaceous channel‐like structure.
Dual Effects of K+ Depoiarisation on Inositol Polyphosphate Production in Rat Cerebral Cortex
Authors: Baird John G. , Nahorski Stefan R.
Published: October 2006

Depoiarisation of [3H]inosito]‐prelabejled slices of rat cerebral cortex with elevated extracellular Kr induced a rapid and marked increase in inositol polyphosphate accumulation. Addition of the muscarinic antagonist atropine (10 μM) markedly inhibited the K+‐induced accumulation of inositol tetrakisphosphate (InsP4), with only a slight reduction in stimulated inositol bis‐ and trisphosphate levels. Inhibitory effects on InsP4 were noted at the earliest time period measured (30 s) and suggested the involvement of released endogenous acetylcholine in part of the response. The atropine‐insensitive component of depoiarisation did not! appear to be secondary to release of noradrenaline, histamine, or 5‐hydroxytryptamine, because addition of prazosip, mepyr‐amine, or ketanserin was without effect on the K+ response. Furthermore, secretion of a neuropeptide that could stimulate phosphoinositide hydrolysis was unlikely, because the peptidase inhibitor bacitracin was also without effect. The results suggest that endogenous acetylcholine can stimulate phosphoinositide metabolism by interacting with muscarinic receptors and that this is particularly evident on InsP4 accumulation. Atropine‐insensitive responses may be secondary to Ca2+ entry via voltage‐sensitive channels.
Ganglioside Composition in Human Meningiomas
Authors: Davidsson Pia , Fredman Pam , Collins V. Peter , von Hoist Hans , Mansson Jan‐Eric , Svennerholm Lars
Published: October 2006

The ganglioside composition in meningioma specimens from 20 patients was analyzed to find potential me‐ningioma‐associated structures. The characterization was performed by immunological staining with specific monoclonal antibodies to gangJioside antigens and fast atom bombardment‐mass spectrometry. The major gangliosides were GM3 and GD3, and most of the meningioma specimens could be divided into a “GM3‐rich” or a “GD3‐rich” group. Gangliosides of the gangliotetraose series were represented by GM1, GD1 a, GDlb, and GT1b, which were found in minor amounts in all the specimens. The ratios of GM1/ GD1a and GD1a/GDlb differed from that in normal brain, and therefore existence of this series could not be explained by contamination with brain material. Ganglioside 3′‐isoLM1, found in human malignant glioma, could not be detected in any meningioma specimen.
Synthesis of l‐3,4‐Bihydroxyphenylalanine by Tyrosine Hydroxylase cDNA‐Transfected C6 Cells: Application for Intracerebral Grafting
Authors: Uchida Kohichi , Takamatsu Ken , Kaneda Norio , Toya Shigeo , Tsukada Yasuzo , Kurosawa Yoshikazu , Fujita Keisuke , Nagatsu Toshiharu , Kohsaka Shinichi
Published: October 2006

In the present study, we obtained genetically manipulated nonneuronal cells which synthesize a catecholamine precursor for future use in intracerebral grafting. Human type 1 tyrosine hydroxylase (TH; EC 1.14.16.2) cDNA was inserted into eukaryotic expression vector pKCRH2 and was co‐transfected into C6 cells with plasmid pSV2neo. Expression of the TH minigene was screened by immuno‐histochemical staining with TH antibody and immunoblot‐ting analysis. Several clones of the C6 transfectahts that produce TH molecules were obtained. These cells showed TH activity, and the product, L‐3,4‐dihydroxyphenylalanine (L‐DOPA), was detected intracellulary due to the ajbsence of L‐amino acid decarboxylase (EC 4.1.1.28) activity. It was found that a large amount of L‐DOPA was released from the cells into the culture medium. These transfectants were transplanted into rat brain, and the expression of TH was examined immunohistochemically. On the 10th day following transplantation, a mass of C6 cells which was heavily stained with TH antibody was observed in the brain. These findings may provide us with an opportunity to investigate the effects of intracerebral transplantation of nonneuronal cells that produce catecholamine or its precursor.
Muscarinic and Quisqualate Receptor‐Induced Phosphoinositide Hydrolysis in Primary Cultures of Striatal and Hippocampal Neurons. Evidence for Differential Mechanisms of Activation
Authors: Ambifosini Anna , Meldolesi Jacopo
Published: October 2006

Several neurotransmitters activate polyphosphoinositide (PPI) hydrolysis in CNS neurons as the first step of a transmembrane signalling cascade that may lead to neuronal ircuit modulation. Muscarinic and quisqualate rejceptor‐riggered PPI hydrolysis was investigated in neuronal primary cultures. A clear increase in inositol phosphates (Ins‐Ps) was detected as early as 15 s after the agonist addition;! at this time, the increases of inositol 1,4,5‐trisphosphate (measured by HPLC) were relatively larger with respect to the other Ins‐Ps. Ins‐P accumulation was maintained in part in a. Ca2+‐free medium, excluding that Ca2+ entry is the fundamental step of the receptor‐induced PPI hydrolysis. Acute dell pre‐treatment with phorbol dibutyrate, an activator of protein kinase C, was able to inhibit 50% of the response to carbachol, and almost completely the quisqualate effect, suggesting a negative feedback modulation by the enzyme. Finaljly, per tussis toxin failed to inhibit muscarinic responses, whereas it blocked ±70% of the quisqualate stimulation. The two receptors therefore appear coupled to phosphodiesterase by two different G proteins. The comparison of the results obtained by stimulating the two receptor systems suggests that the generation of the same intracellular signal at two distinct receptor types may occur by different coupling mechanisms, and be differently regulated even in the same neuronal preparations.
Differential Effects of Iodide and Chloride on Allosteric Interactions of the GABAA Receptor
Authors: Abel Marc S. , Blume Arthur J. , Garrett Kennon M.
Published: October 2006

t‐[35S]Butylbicyclophosphorothionate ([35S]TBPS) has been shown to bind to the GABAA receptor complex. The binding is modulated allosterically by drugs that interact at components of the receptor complex. The present studies were designed to evaluate the influence of ionic environment and state of equilibrium on the allosteric modification of [35S]TBPS binding. In both I‐ and Cl‐ under nonequilibrium conditions, diazepam, γ‐aminobutyric acid (GABA), and pentobarbital (PB) stimulate and methyl 6,7‐dimethoxy‐4‐ethyl‐β‐carboline‐3‐carboxylate (DMCM) inhibits [35S]TBPS binding. In addition, there is an inhibitory component to the effect of GABA and PB at higher drug concentrations. These effects are blocked by the appropriate antagonists for each drug. In Cl‐, the stimulation of [35S]TBPS binding by drugs disappears at equilibrium, whereas the inhibition by GABA and PB persists. The inhibitory effect of DMCM in Cl‐ also disappears at equilibrium. When assayed in I‐ at equilibrium. however, DMCM stimulates [35S]TBPS binding. In addition, bicuculline, which is without effect under nonequilibrium conditions in either Cl‐ or I‐, stimulates [35S]TBPS binding in I‐ at equilibrium. The persistent effects of DMCM, bicuculline, and GABA in I‐ are accompanied by alterations in the affinity of [35S]TBPS for its receptor. In addition, the stimulation of [35S]TBPS binding by GABA is associated with a decreased number of [35S]TBPS binding sites. These data demonstrate that receptor complex interactions with anions influence the responsiveness to drug binding.
Effects of Dihydropyridine Calcium Channel Ligands on Rat Brain γ‐Aminobutyric AcidB Receptors
Authors: Al‐Dahan Muna I. , Thalmann Robert H.
Published: October 2006

This study shows that low nanomolar concentrations of the calcium channel antagonist nifedipine displaced [3H]baclofen labeling of γ‐aminobutyric acidB (GABAB) receptors, whereas similar concentrations of two calcium channel agonists stimulated this GA‐BAB receptor labeling. Neither effect was likely to be due to dihydropyridine (DHP) binding to baclofen recognition sites, because the inhibitory ligand nifedipine primarily affected apparent receptor density rather than affinity. Although these results could reflect the coupling of GABAB receptors with calcium channels, they do not rule out other, possibly more direct interactions between GABAB receptors and DHP binding sites. These DHP effects occur at much lower concentrations and display other significant differences from previously reported effects of DHPs on other transmitter receptors.
Use of Microdialysis for Monitoring Tyrosine Hydroxylase Activity in the Brain of Conscious Rats
Authors: Westerink B. H. C. , De Vries J. B. , Duran R.
Published: October 2006

An on‐line microdialysis system was developed which monitored the 3,4‐dihydroxyphenylalanine (DOPA) formation in the striatum during infusion of a submicromolar concentration of an l‐aromatic amino‐acid decarboxylase inhibitor (NSD 1015). The absence of DOPA in dialysates of 6‐hydroxydopamine‐pretreated rats and the disappearance of DOPA after administration of α‐methyl‐p‐tyrosine indicated that the dialyzed DOPA was derived from dopaminergic nerve terminals. Next we investigated whether the steady‐state DOPA concentration in striatal dialysates could be considered as an index of tyrosine hydroxylase activity. The increase in DOPA output after intraperitoneal administration of haloperidol or γ‐butyrolactone and the decrease in DOPA output after intraperitoneal administration of apomorphine are in excellent agreement with results of postmortem studies, in which a decarboxylase inhibitor was used to measure the activity of tyrosine hydroxylase. The effect of haloperidol on DOPA formation was not visible when a U‐shaped cannula (0.80 mm o.d.) was used. Some methodological problems related to microdialysis of the haloperidol‐induced increase in DOPA formation are discussed. We concluded that the proposed model is a powerful and reliable in vivo method to monitor tyrosine hydroxylase activity in the brain. The method is of special interest for investigating the effect of compounds which are not able to pass the blood‐brain barrier. As an application of the method in the latter situation, we report the effect of infusion the neurotoxin 1‐methyl‐4‐phenylpyridinium ion (10 mmol/L infused over 20 min) on the activity of striatal tyrosine hydroxylase.
Lipid Compositions of Different Regions of the Human Brain During Aging
Authors: Söderberg M. , Edlund C. , Kristensson K. , Dallner G.
Published: October 2006

The neutral and phospholipid compositions of various regions of the human brain were analyzed using autopsy material covering the life period between 33 and 92 years of age. The protein content was also measured and, on a weight basis, this content is unchanged in the cerebellum, pons, and medulla oblongata, whereas in the 90‐year‐old group it decreases in the hippocampus, gray matter, and nucleus caudatus. In white matter, the protein content decreases continuously with age. The phospholipid composition is characteristic of the region investigated, but remains unchanged during aging. The total phospholipid content exhibits only a 5–10% decrease in the oldest age group. The content of dolichol and its polyisoprenoid pattern are also characteristic of the region analyzed. Between 33 and 92 years of age, the amount of dolichol in all portions of the brain increases three‐to fourfold, but the isoprenoid pattern remains constant. The level of dolichyl‐P varies between different regions, but only a moderate increase is seen with age. Ubiquinone content is highest in the nucleus caudatus, gray matter, and hippocampus, and in all areas this content is decreased to a great extent in the oldest age groups. All regions of the human brain are rich in cholesterol, but alterations in the amount of this lipid are highly variable during aging, ranging from no change to a 40% decrease.
Synthesis of Apolipoprotein A‐1 in Pig Brain Microvascular Endothelial Cells
Authors: Weiler‐Güttler Hartmut , Sommerfeldt Michaela , Papandrikopoulou Anastasia , Mischek Uwe , Bonitz Dorothea , Frey Andreas , Grupe Matthias , Scheerer Joachim , Gassen Hans G.
Published: October 2006

In an approach toward the identification of hitherto unknown proteins involved in the function of the blood–brain barrier, we constructed a pig brain microvessel‐derived cDNA library that is enriched in blood–brain barrier specific sequences by means of subtractive cloning. Sequence analysis of selected clones revealed that one of the cDNAs encoded porcine apolipoprotein (apo) A‐1. The identity of apo A‐1 mRNA was further confirmed by in vitro translation of RNA from brain microvascular endothelial cells and subsequent immunoprecipitation with an antibody against human apo A‐1. We further investigated the expression of apo A‐1 mRNA in several tissues and in endothelial cells of the pig. It is shown that cultured brain microvascular endothelial cells provide an in vitro model to study the expression and function of apo A‐1 in the microvasculature of the brain.
Glutamate Increases Glycogen Content and Reduces Glucose Utilization in Primary Astrocyte Culture
Authors: Swanson Raymond A. , Yu Albert C. H. , Chan Pak H. , Sharp Frank R.
Published: October 2006

The glycogen content of primary cultured astrocytes was approximately doubled by incubation with 1 mM L‐glutamate or L‐aspartate. Other amino acids and excitatory neurotransmitters were without effect. The increase in glycogen level was not blocked by the glutamate receptor antagonist kynurenic acid but was completely blocked by the glutamate uptake inhibitor threo‐3‐hydroxy‐D,L‐aspartate and by removal of Na+ from the medium. Incubation with radiolabeled glucose and glutamate revealed that the increased glycogen content was derived almost entirely from glucose. Glutamate at 1 mM was also found to cause a 53 ± 12% decrease in glucose utilization and a 112 ± 69% increase in glucose‐6‐phosphate levels. These results suggest that the glycogen content of astrocytes is linked to the rate of glucose utilization and that glucose utilization can, in turn, be affected by the availability of alternative metabolic substrates. These relationships suggest a mechanism by which brain glycogen accumulation occurs during decreased neuronal activity.
12‐O‐Tetradecanoylphorbol 13‐Acetate and Forskolin Modify Muscarinic Receptor‐Linked Ca2+ Mobilization in SH‐SY5Y Neuroblastoma Cells Through Different Mechanisms
Authors: Åkerman Karl E. O. , Heikkilä Jari E.
Published: October 2006

The phorbol ester, 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), which causes differentiation of SH‐SY5Y neuroblastoma cells, reduces carbachol binding and carbachol‐stimulated Ca2+ mobilization in these cells. The decrease in responsiveness to carbachol is due partially to a reduction in the amount of Ca2+ released by the cells and partially to a decrease in the sensitivity of the cells to carbachol. These effects probably can be attributed to a reduction in muscarinic receptor number and a decrease in receptor affinity, respectively. Forskolin, an alkaloid known to cause an increase in cellular cyclic AMP, enhances Ca2+ influx into the cells without affecting the cytosolic free Ca2+ concentration. The alkaloid causes an apparent restoration of the reduced Ca2+ release, caused by TPA, but does not affect the sensitivity of the cells to carbachol. Forskolin increases the decay of carbachol‐induced increase in cytosolic Ca2+. The effects of TPA appear to be linked directly to receptor function, whereas those of forskolin are due to the effect of cyclic AMP on cellular Ca2+ metabolism.
Tetrasialoganglioside GQ1b Reactive Monoclonal Antibodies: Their Characterization and Application for Quantification of GQ1b in Some Cell Lines of Neuronal and Adrenal Origin(S)
Authors: Yamamoto Hideki , Tsuji Shuichi , Nagai Yoshitaka
Published: October 2006

Seven monoclonal antibodies (MAbs) directed tetrasialoganglioside (GQ1b) were established, purified GQ1b being used for immunization and hybridoma screening. All of the MAbs reacted strongly with GQ1b, although they also reacted with other gangliosides, with different specificities and reactivities. Some MAbs (1H10, 2C7, and 3F4) reacted with GD3, GT1a, GQ1b, and GP1c. MAb 1H4 showed broad specificity. It reacted with GD3, GD1b, GD2, GT1a, GT1b, GQ1b, GQ1c, and GP1c. MAbs 7F5, 4E7, and 4F10 recognized GT1a, GQ1b, and GP1c. MAb 4F10 was more specific for GQ1b than the other MAbs. Using MAb 4F10, we determined, by means of an immunoassay, the quantities of endogenous GQ1b in some neuronal and adrenal cell lines, GOTO (human neuroblastoma), Neuro2a (mouse neuroblastoma), and PC12 (rat pheochromocytoma). PC12 and Neuro2a cells contained at least 5.1 X 106 and 3.9 X 105 molecules/cell of GQ1b, respectively. In contrast, no GQ1b was detected in GOTO cells, which are known for their specific neuritogenic response to this particular ganglioside when exogenously added.
Comparison of the Soluble and Membrane‐Bound Forms of the Puromycin‐Sensitive Enkephalin‐Degrading Aminopeptidases from Rat
Authors: Dyer Simon H. , Slaughter Clive A. , Orth Kim , Moomaw Carolyn R. , Hersh Louis B.
Published: October 2006

Enkephalin degradation in brain has been shown to be catalyzed, in part, by a membrane‐bound puromycinsensitive aminopeptidase. A cytosolic puromycin‐sensitive aminopeptidase with similar properties also has been described. The relationship between the soluble and membrane forms of the rat brain enzyme is investigated here. Both of these aminopeptidase forms were purified from rat brain and an antiserum was generated to the soluble enzyme. Each of the aminopeptidases is composed of a single polypeptide of molecular mass 100 kilodaltons as determined by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and sizeexclusion chromatography. The antisoluble aminopeptidase antiserum reacts with both enzyme forms on immunoblots and inhibits both with nearly identical inhibition curves. The isoelectric points (pI = 5.0) of both forms were shown to be identical. N‐terminal sequencing yielded a common sequence (P‐E‐K‐R‐P‐F‐E‐R‐L‐P‐T‐E‐V‐S‐P‐I‐N‐Y) for both enzyme forms, and peptide mapping yielded 26 peptides that also appeared identical between the two enzyme forms. Studies on the nature of the association of the membrane enzyme form with the cell membrane suggest that this enzyme form does not represent the soluble form trapped during the enzyme preparation. It is suggested that the membrane form of the puromycin‐sensitive aminopeptidase is identical to the soluble enzyme and that it associates with the membrane by interactions with other integral membrane proteins.
(R)‐N‐[4,4‐Bis(3‐Methyl‐2‐Thienyl)but‐3‐en‐1‐yl]Nipecotic Acid Binds with High Affinity to the Brain γ‐Aminobutyric Acid Uptake Carrier
Authors: Braestrup Claus , Nielsen Erik B. , Sonnewald Ursula , Knutsen Lars J. S. , Andersen Knud Erik , Jansen Jens Aas , Frederiksen Kristen , Andersen Peter H. , Mortensen Alicja , Suzdak Peter D.
Published: October 2006

(R)‐N‐[4,4‐Bis(3‐methyl‐2‐thienyl)but‐3‐en‐l‐yl]nipecotic acid (NO 328) has previously been shown to be a potent anticonvulsant in both mice and rats. Here, we report that NO 328 is a potent inhibitor of γ‐[3H]aminobutyric acid ([3H]GABA) uptake in a rat forebrain synaptosomal preparation (IC50= 67 nM) and in primary cultures of neurons and astrocytes. Inhibition of [3H]GABA uptake by NO 328 is apparently of a mixed type when NO 328 is preincubated before [3H]GABA uptake; the inhibition is apparently competitive without preincubation. NO 328 itself is not a substrate for the GABA uptake carrier, but NO 328 is a selective inhibitor of [3H]GABA uptake. Binding to benzodiazepine receptors, histamine H1 receptors, and 5‐hydroxytryptaminelA receptors was inhibited by NO 328 at 5—30 μM, whereas several other receptors and uptake sites were unaffected. [3H]NO 328 showed saturable and reversible binding to rat brain membranes in the presence of NaCI. The specific binding of [3H]NO 328 was inhibited by known inhibitors of [3H]GABA uptake; GABA and the cyclic amino acid GABA uptake inhibitors were, however, less potent than expected. This indicates that the binding site is not identical to, but rather overlapping with, the GABA recognition site of the uptake carrier. The affinity constant for binding of [3H]NO 328 is 18 nM, and the Bmax is 669 pmol/g of original rat forebrain tissue. The regional distribution of NaCl‐dependent [3H]NO 328 binding followed that of synaptosomal [3H]GABA uptake. It is concluded that NO 328 is a potent and selective inhibitor of neuronal and glial GABA uptake and that [3H]NO 328 is a useful radioligand for labeling the GABA uptake carrier in brain membranes. In the mouse brain in vivo, [3H]NO 328 likewise showed saturable and reversible binding that could be displaced by analogues of NO 328. Further studies are needed to demonstrate whether the uptake carrier is indeed labeled by [3H]NO 328 in vivo.
Interactions of Phencyclidine Receptor Agonist MK‐801 with Dopaminergic System: Regional Studies in the Rat
Authors: Rao Tadimeti S. , Kim Helen S. , Lehmann John , Martin Louis L. , Wood Paul L.
Published: October 2006

Interactions of the potent phencyclidine receptor agonist MK‐801 with the dopaminergic system were examined in various brain regions in the rat. MK‐801 increased dopamine (DA) metabolism in the pyriform cortex, entorhinal cortex, prefrontal cortex, striatum, olfactory tubercle, amygdala, and septum without affecting DA metabolism in the cingulate cortex and nucleus accumbens. In pyriform cortex and amygdala, MK‐801 was more potent than phencyclidine at increasing DA metabolism. Local injections of MK‐801 into ventral tegmental area and into the amygdala/pyriform cortex interface indicated that MK‐801 may act at the cell body as well as the nerve terminal level to increase DA metabolism and that ongoing dopaminergic neuronal activity is a prerequisite for full drug action.
Acid Homeostasis Following Partial Ischemia in Neonatal Brain Measured In Vivo by 31P and 1H Nuclear Magnetic Resonance Spectroscopy
Authors: Corbett Ronald J. T. , Laptook Abbot R.
Published: October 2006

The purpose of this study was to investigate neonatal brain energy metabolism, acid, and lactate homeostasis in the period immediately following partial ischemia. Changes in brain buffering capacity were quantified by measuring mean intracellular brain pH, calculated from the chemical shift of Pi, in response to identical episodes of hypercarbia before and after ischemia. In addition, the relationship between brain buffer base deficit and intracellular pH was compared during and following ischemia. Thus, in vivo 31P and 1H nuclear magnetic resonance spectra were obtained from the brains of seven newborn piglets exposed to sequential episodes of hypercarbia, partial ischemia, and a second episode of hypercarbia in the postischemic recovery period. For the first episode of hypercarbia, brain buffering was similar to values reported for adult animals of other species (percentage pH regulation = 54 ± 16%). During ischemia, the brain base deficit per unit change in pH was −19 ± 5 mM/pH unit, which is similar to values reported for adult rats. By 20–35 min postischemia, brain acidosis partly resolved in spite of a net increase in lactate concentration. Therefore, the consumption of lactate could not explain acid homeostasis in the first 35 min following ischemia. We conclude that H+/HCO‐3 or other proton equivalent translocation mechanisms must be sufficiently developed in piglet brain to support acid regulation. This is surprising, because a substantial body of evidence implies these processes would be less active in immature brain. The second episode of hypercarbia, from 35 to 65 min postischemia, resulted in a smaller decrease in brain pH compared with the first episode, a result indicating an increase in brain buffering capacity (percentage pH regulation = 79 ± 29%). This was associated with a parallel decrease in brain lactate content, and therefore acid regulation could be attributed to either continued ion translocation or the consumption of lactate. A mild decrease in brain pH and content of energy metabolites was observed, a finding suggesting that the metabolic consequences of severe postischemic hypercarbia are neither particularly dangerous or beneficial.
α1‐Adrenergic Receptor Mediates Arachidonic Acid Release in Spinal Cord Neurons Independent of Inositol Phospholipid Turnover
Authors: Kanterman Robert Y. , Felder Christian C. , Brenneman Douglas E. , Ma Alice L. , Fitzgerald Sandra , Axelrod Julius
Published: October 2006

The α1‐adrenergic receptor has been shown to mediate the release of arachidonic acid in FRTL5 thyroid cells and MDCK kidney cells. In primary cultures of spinal cord cells, norepinephrine stimulated release of arachidonic acid (from neurons only) and turnover of inositol phospholipids (from neurons and glia) via α1‐adrenergic receptors. These two responses were dissociated by treatment with phorbol ester and pertussis toxin, which inhibited production of inositol phosphates with no appreciable effect on release of arachidonic acid. Extracellular calcium was required for release of arachidonic acid, but not for production of inositol phosphates. The calcium channel blockers nifedipine and verapamil inhibited release of arachidonic acid only. However, 8‐(N,N‐diethylamino)octyl‐3,4,5‐trimethoxybenzoate (TMB‐8), a compound that blocks intracellular calcium release, diminished production of inositol phosphates, but had little effect on release of arachidonic acid. These results suggest that α1‐adrenergic receptors couple to release of arachidonic acid in primary cultures of spinal cord cells by a mechanism independent of activation of phospholipase C, possibly via the activation of phospholipase A2.
Induction of c‐fos mRNA Expression in Rat Striatum by Neuroleptic Drugs
Authors: Miller Jeannette C.
Published: October 2006

The effect of selective dopamine D2 receptor‐acting drugs on striatal c‐fos mRNA expression in the rat has been investigated by Northern hybridization and autoradiography to determine a possible role for c‐fos in the initiation of adaptive changes in D2 receptor number by neuroleptic drugs. The neuroleptic drug haloperidol, a D2 receptor antagonist, was found to produce a rapid and transient induction of c‐fos mRNA expression as compared with the expression in animals treated with saline. This induction by haloperidol was found to be dose dependent and D2 receptor mediated, inasmuch as a D2 agonist completely reversed the induction and the inactive isomer of the neuroleptic butaclamol, which does not produce an increase in D2 receptors, had no effect on c‐fos mRNA expression. From these data, it can be concluded that c‐fos expression in striatum is under dopamine D2 receptor‐mediated inhibitory control. It is suggested that c‐fos may play a role in the initiation of the increase in D2 receptor number produced by chronic neuroleptic drug treatment.
Bacitracin: A New Antibiotic Produced by a Member of the
B. subtilis
Group
Authors: Johnson Balbina A. , Anker Herbert , Meleney Frank L.
Published: October 2006

A new antibiotic "bacitracin" has been recovered from a strain of the
B. subtilis
group of organisms. It is neutral, water-soluble, non-toxic and relatively heat stable.
In vitro
it is active chiefly against Grampositive organisms, but the gonococcus and meningococcus are susceptible to its action. It is also active
in vivo
against experimentally produced hemolytic streptococcal infections in mice and gas gangrene infections in guinea pigs. Clinical use in hemolytic streptococcal and staphylococcal infections in man have given encouraging results.
A Systematic Assessment of Early African Hominids
Authors: Johanson D. C. , White T. D.
Published: October 2006

A large sample of Pliocene fossil hominid remains has been recovered from the African sites of Hadar in Ethiopia and Laetolil in Tanzania. These collections, dating approximately between 2.9 and 3.8 million years ago, constitute the earliest substantial record of the family Hominidae. This article assesses the phylogenetic relationships of the newly discovered fossil hominids and provides a taxonomy consistent with that assessment. A new taxon,
Australopithecus afarensis
, has been created to accommodate these Pliocene hominid fossils.
Visual Tracking and the Primate Flocculus
Authors: Miles F. A. , Fuller J. H.
Published: October 2006

Purkinje cells in the primate flocculus discharge specifically in relation to visual tracking, effectively generating a velocity profile of the target during pursuit. It is suggested that these neurons supply oculomotor centers with the velocity command signals needed to support pursuit eye movements.
Exocrine Pancreas: Evidence for Topographic Partition of Secretory Function
Authors: Malaisse-Lagae F. , Ravazzola M. , Robberecht P. , Vandermeers A. , Malaisse W. J. , Orci L.
Published: October 2006

The pattern of amylase, lipase, and chymotrypsinogen content found in pancreatic exocrine tissue surrounding the islets of Langerhans (periinsular halos) differs from that of the rest, or teleinsular part, of the pancreas. Such a topographic partition of secretory function may play a role in the regulation of pancreatic juice composition.
Stroke in Rats Produced by Carotid Injection of Sodium Arachidonate
Authors: Furlow Thomas W. , Bass Norman H.
Published: October 2006

Unilateral cerebrovascular occlusion was produced in heparinized rats within 60 seconds after an injection of sodium arachidonate (in doses exceeding 0.45 milligram per kilogram) into the carotid artery. Electroencephalographic activity over the affected cerebral hemisphere was suppressed, and cerebral blood flow decreased by half. Microscopic examination revealed complete obstruction of the hemispheric microcirculation by platelet aggregates.
Reciprocation of Renin Dependency with Sodium Volume Dependency in Renal Hypertension
Authors: Gavras Haralambos , Brunner Hans R. , Thurston Herbert , Laragh John H.
Published: October 2006

An angiotensin II inhibitor was administered to rats with two-kidney Goldblatt hypertension. The inhibitor produced a marked drop in blood pressure after 5 weeks but no significant change after 15 weeks of hypertension. However, even after 15 weeks of hypertension, following sodium depletion by either diuretics or a low sodium diet, the animals again became renin dependent as readministration of the inhibitor induced a significant fall in blood pressure. The data indicate that two-kidney Goldblatt hypertension is initially renin dependent but subsequently becomes sodium volume dependent in a way similar, although more protracted, to that already described for one-kidney Goldblatt hypertension.
Intracellular Distribution of Free Potassium in
Chironomus
Salivary Glands
Authors: Palmer Lawrence G. , Civan Mortimer M.
Published: October 2006

Potassium activities have been measured in the nucleus and cytoplasm of
Chironomus
salivary gland cells, using potassium-selective electrodes. The data provide the first rigorous evidence that potassium is at electrochemical equilibrium across the nuclear membrane. In addition, no difference in potassium chemical activity was found between nucleus and cytoplasm.
The Antiquity of Oxygenic Photosynthesis: Evidence from Stromatolites in Sulphate-Deficient Archaean Lakes
Authors: Buick Roger
Published: October 2006

The Tumbiana Formation, about 2700 million years old, was largely deposited in ephemeral saline lakes, as judged by the unusual evaporite paragenesis of carbonate and halite with no sulfate. Stromatolites of diverse morphology occur in the lacustrine sediments, some with palimpsest fabrics after erect filaments. These stromatolites were probably accreted by phototropic microbes that, from their habitat in shallow isolated basins with negligible sulfate concentrations, almost certainly metabolized by oxygenic photosynthesis.
Graphitic Carbon in the Allende Meteorite: A Microstructural Study
Authors: Smith Piers P. K. , Buseck Peter R.
Published: October 2006

High-resolution transmission electron microscopy shows that carbon in the Allende carbonaceous chondrite meteorite is predominantly a poorly crystalline graphite. Such material is of interest as an important carrier of the isotopically anomalous noble gases found in carbonaceous chondrites.
The C
7
Cluster: Structure and Infrared Frequencies
Authors: Heath J. R. , Sheeks R. A. , Cooksy A. L. , Saykally R. J.
Published: October 2006

Observation and characterization of the C
7
cluster are reported. Carbon clusters are produced by laser vaporization of a graphite target followed by supersonic expansion of the vaporized material within a gas dynamically focused argon jet. Thirty-six sequential rovibrational lines of the ν
4
antisymmetric stretch fundamental of C
7
are probed by gated detection of diode laser absorption. The observed spectrum is characteristic of a symmetrical linear molecule. Analysis of the spectrum indicates an effective average bond length of 1.2736(4) angstroms and a vibrational frequency of 2138.1951(10) reciprocal centimeters, in excellent agreement with ab initio calculations. This work will facilitate the astrophysical detection of this cluster.
Tail Pinch Induces Eating in Sated Rats Which Appears to Depend on Nigrostriatal Dopamine
Authors: Antelman Seymour M. , Szechtman Henry
Published: October 2006

Mild tail pinch reliably and rapidly induced eating, gnawing, or licking behavior in all animals tested. Eating was by far the predominant response. Pharmacological analysis of the involvement of the brain catecholamines in tail-pinch behavior suggests that it is critically dependent on the nigrostriatal dopamine system.
Muscle Activation: Effects of Small Length Changes on Calcium Release in Single Fibers
Authors: Ridgeway E. B. , Gordon A. M.
Published: October 2006

In single muscle fibers, small (1 percent) changes of length have a marked effect of both the calcium activation and the tension elicited by a constant current stimulus. The decrease in tension with shortening is accounted for almost entirely by a decrease in calcium release, rather than by changes in mechanical factors, such as filament geometry.
Rapid Redistribution of Auxin-Rregulated RNAs During Gravitropism
Authors: McClure Bruce A. , Guilfoyle Tom
Published: October 2006

Gravitropism, the bending of plants in response to gravity, is caused by differential growth rates on two sides of a responding organ. The general belief, although somewhat controversial, is that auxins play a major role in gravitropism by controlling the rate of cell extension. The tissue print technique was used to ascertain the distribution of auxin-regulated RNAs during the gravitropic response of soybean hypocotyls. In vertically oriented seedlings, auxin-regulated RNAs are symmetrically distributed in the elongating region of the hypocotyl. In horizontally orientated seedlings the distribution becomes asymmetrical within 20 minutes and the greatest asymmetry coincides with the onset of rapid bending. The results provide a clear correlation between the dynamic expression of genes under auxin control and a morphogenetic phenomenon traditionally known as an auxin response.
Ventricular Obstruction: Effect on Drinking Induced by Intracranial Injection of Angiotensin
Authors: Buggy James , Fisher Alan E. , Hoffman William E. , Johnson Alan Kim , Phillips M. Ian
Published: October 2006

Lesions of the subfornical organ (SFO) severely attenuated drinking induced by injections of angiotensin II into the lateral ventricles, but a few days (4 to 14) later a recovery of the drinking response is observed. A possible explanation for this is that other dipsogenic sites are involved which are beyond the interventricular foramen and that SFO lesions produce an obstruction by edema or debris at the foramen which blocks access of cerebrospinal fluid-borne angiotensin to those sites. This hypothesis is supported by tracer studies and by direct injection into the third ventricle of SFO-lesioned animals. Other studies reported implicate the anteroventral third ventricle as a likely site for angiotensin receptors.
Behavioral Characterization of
d
- and
l
-Amphetamine: Neurochemical Implications
Authors: Segal David S.
Published: October 2006

Various doses of
d
- and
l
-amphetamine affect the temporal pattern of rat behavior in the following ways: First, the patterns of activity produced by
d
- and
l
-amphetamine are similar but out of phase; that is, the response to
d
-amphetamine has a relatively shorter latency whereas the effects of
l
-amphetamine persist for longer periods of time. Second,
d
-amphetamine is approximately five times as potent as
l
-amphetamine in its effects on both the total amount of locomotor activity and the duration of stereotypy. Both amphetamine-induced locomotion and stereotypy may be mediated by the same neurochemical mechanisms.
Secretion of a Nerve Growth Factor by Primary Chick Fibroblast Cultures
Authors: Young Michael , Oger Joël , Blanchard Muriel H. , Asdourian Hovan , Amos Harold , Arnason Barry G. W.
Published: October 2006

Normal primary chick embryo fibroblast cultures produce a nerve growth-promoting factor which cross-reacts with monospecific antibody to pure male mouse submaxillary gland nerve growth factor (NGF). When taken together with the earlier demonstration that mouse L
2
cells and 3T3 cells also produce an NGF-like protein, these findings suggest that secretion of this factor may be a general property of fibroblast.
Transforming Potential of the Anticancer Drug Adriamycin
Authors: Price Paul J. , Suk William A. , Skeen Pamela C. , Chirigos Michael A. , Huebner Robert J.
Published: October 2006

A Fischer rat embryo cell system in vitro, which had been shown to be highly accurate in identifying chemical carcinogens and to have application in the study of chemicals having anticancer properties, was used to study the anticancer drug adriamycin. At a nontoxic dose adriamycin not only did not protect the cells from transformation by the carcinogen 3-methylcholanthrene, but was found in two separate experiments to act on its own as a transforming agent.
Goldfish Retina: Functional Polarization of Cone Horizontal Cell Dendrites and Synapses
Authors: Stell William K. , Lightfood David O. , Wheeler Thomas G. , Leeper Harold F.
Published: October 2006

In serial electron micrographs we observed that dendrites of goldfish cone horizontal cells are either central or lateral in ribbon synaptic triads, depending on cone and horizontal cell type. The chromatic properties of cone horizontal cell responses may be explained if the cone horizontal cells act as interneurons, receiving from cones through their central processes but acting on cones through their lateral processes.
Cochlear Tuning Properties: Concurrent Basilar Membrane and Single Nerve Fiber Measurements
Authors: Evans E. F. , Wilson J. P.
Published: October 2006

Removal of perilymph from the cochlea has been reported to destroy the sharp tuning of cochlear neurons. That these changes are mechanical in origin is refuted by the concurrent recording of sharp neural tuning with broad basilar membrane responses from the same region of the partially drained cat cochlea. A second cochlear filter is therefore necessary.