摘要:

Abstract:The specific binding of [3H]l‐[2‐(diphenyl‐methoxy)ethyl]‐4‐(3‐phenyl‐2‐propenyl)piperazine([3H]GBR 12783) to the dopamine (DA) neuronal carrier present in membranes prepared from rat striatum was not affected when Cl–was replaced by either Br–or NO3–. In media containing Cl–, Br–, or NO3–,d‐amphetamine and DA competed with the radioligand in a monophasic manner with Hill coefficients of close to 1 (0.94–1.12). Replacement of CT by Br–impaired the ability of some substrates (d‐amphetamine, DA,p‐hydroxyamphetamine, andm‐tyramine) to compete with [3H]GBR 12783. The potency of Br–to decrease the affinity of substrates for the specific binding site was significantly correlated (t = 7.07, p<0.001) with their affinity for this binding site. These results suggest that the various substrates tested could bind to recognition sites in which Cl–is differently involved; as a consequence, substrates could bind to the neuronal carrier by means of partly different links. In experiments dealing with the specific uptake of [3H]DA, F–, NO3–, is‐ethionate–, or acetate–was unable to substitute for Cl–, whereas Br–was quite a total substitute. Replacement of Cl–by equimolar concentrations of either NO3or isethionate–resulted in inhibition curves of DA specific uptake with Hill coefficients of close to 1 (0.77 and 1.04, respectively); this indicates that both NO3–and isethionate” are devoid of inhibitory effects on neuronal uptake and are quite ineffective substitutes for Cl–. Kinetic analyses performed in different experimental conditions provide consistent results revealing that decreasing the CT concentration induced a raise in apparent Km of DA without modification of the Fmax. On the other hand, the apparent Km values of Cl–for the stimulation of the neuronal uptake of DA decreased when the DA concentration increased. These data are consistent with a co‐transport of C

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09327.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:We have examined PC12 cells for the localization of binding sites for vesamicol [l‐2‐(4‐phenylpiperidino) cyclohexanol], a compound that has previously been shown to bind to cholinergic vesicles and to inhibit the uptake of acetylcholine. Initial studies presented in this article demonstrate the existence of a specific, saturable vesamicol binding site in PC12 cells. Subsequent experiments show that these binding sites reside in a membrane population that is distinct from catecholamine‐containing compartments with respect to density and antigenic composition. In particular, vesamicol binding compartments have a lower density than Catecholaminergic vesicles and, unlike these latter vesicles, do not appear to contain the vesicle‐specific proteins syn‐aptophysin and SV2 as part of the same membrane. These results suggest that vesicular transport proteins for acetylcholine and catecholamines are differentially sorted to distinct membrane compartments in

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09328.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:Inhibitory regulation of dopamine neurons is mediated by dopamine autoreceptor and γ‐aminobutyric acidB receptor opening of potassium channels. Increased potassium conductance by either receptor is G protein dependent. To evaluate the role of G proteins in vivo, pertussis toxin (PTX) was microinjected into the A10 dopamine region and changes in dopamine metabolism and synthesis measured. PTX produced an elevation in dopamine metabolism and synthesis in the A10 region and nucleus accumbens for up to 4 days after injection. By day 7 the levels of the dopamine precursor and metabolites had returned to normal. A less consistent increase was also measured in the A9 dopamine region and the prefrontal cortex. Although dopamine synthesis and metabolism had returned to normal by day 7, the in vitro ADP‐ribosylation of G proteins in the A10 region by PTX remained depressed by approximately 50% from day 1 to day 14 after administration, returning to normal by day 30. The data suggest that in vivo ribosylation of G proteins may lead to a short‐term attenuation of the tonic inhibitory control of dopamine neurons, which can be compensated for by PTX‐insensitive me

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09329.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:Rat thyroid tissue and three rat medullary thyroid carcinoma cell lines, 6‐23, WE4/2, and CA77, have been examined for substance P (SP) and SP‐like peptide expression. Analysis by combined HPLC and radioimmunoassay revealed the presence of SP in thyroid and 6‐23 cell extracts. The presence of SP‐encoding mRNAs was also detected in 6‐23 cells by solution hybridization‐nuclease protection analysis. SP‐encoding mRNA expression was increased (fourfold) by maintaining the 6‐23 cells in low serum (2%) for 4 or 10 days. The 6‐23 cells also expressed other SP‐like immunoreactive species, which were chromatographically and immunologically distinct from established tachykinin peptides. WE4/2 cells did not contain SP but did display SP‐like immunoreactivity (SPLI), which migrated like the unidentified SPLI in 6‐23 cells. CA77 cells did not contain SP or SP‐encoding mRNA but did contain SPLI that migrated identically to the unidentified SPLI in the other cell lines. This novel SPLI was detected with an antiserum directed against the SP carboxyl terminus and to a lesser extent with an antiserum directed against the neurokinin A carboxyl terminus, but it showed minimal cross‐reactivity using an anti‐serum directed against the midportion of SP. Treatment with 50 mMKC1 resulted in secretion of this SPLI from CA77 cells. Gel filtration analysis demonstrated that this novel SPLI had an apparent molecular weight of ∼ 1,000. These results are discussed in terms of cell lines that express tachykinin peptides and in terms of the molecular nature of the

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09330.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The role of the entorhinal cortex and the adrenal gland in rat hippocampal lactate formation was assessed during and after a short‐lasting immobilization stress and elec‐troconvulsive shock (ECS). Extracellular lactate was measured on‐line using microdialysis and enzyme reactions (a technique named lactography); in some rats, unilateral lesions of the entorhinal cortex were made or the bilateral adrenal glands were removed. The stress‐evoked increase in hippocampus lactate was not altered either ipsi‐ or contralateral to an entorhinal cortex lesion. The response to ECS was attenuated only in the hippocampus ipsilateral to the entorhinal cortex lesion. Removal of bilateral adrenal glands caused some delay in the increase in hippocampal lactate after ECS and a major reduction in the stress‐evoked lactate response. These results indicate that (1) the entorhinal cortex is activated by ECS, thereby activating hippocampal lactate efflux and presumably metabolism, and (2) the adrenal gland is essential in the response to stress and, to a minor extent, in the ECS‐altered hippocamp

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09331.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:We have generated a transgenic mouse line strikingly overexpressing the human ornithine decarboxylase (ODC) gene in their brain. Brain ODC activity was increased in the transgenic animals by a factor of 70 in comparison with their nontransgenic littermates. The content of brain putrescine, the product of ODC, was>60 μmol/g of tissue in the transgenic mice, whereas in the normal animals it was below the level that could be detected by an HPLC method. The concentrations of the higher polyamines (spermidine and spermine) were not significantly different from control values. 31P nuclear magnetic resonance (31P NMR) Spectroscopy analyses revealed a significantly reduced (40%) free Mg2+concentration as calculated from the chemical shift differences of the nucleoside triphosphate a and ft peaks in the brains of the transgenic animals. The lower free Mg2+concentration in the brains of ODC transgenic mice was not a consequence of altered intracellular pH or changes in cellular high‐energy metabolites.1H NMR showed no differences in brain choline/N‐acetylaspartate and total creatine/N‐acetylaspartate ratios between the two animal groups. These ODC transgenic animals may serve as models in vivo for studies on cerebral postischemic events and on epilepsy, as polyamines are supposed to be involved in these pro

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09332.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:When PC12D cells, a subline of PC12 cells, were cultured with nerve growth factor (NGF), outgrowth of neurites was promoted even when RNA synthesis was blocked. This property of PC12D cells may enable us to resolve the mechanism of the outgrowth of neurites that is induced in a transcription‐independent manner. The outgrowth of neurites from PC12D cells was also stimulated in response to fibroblast growth factor (FGF) and was slightly stimulated in response to epidermal growth factor (EGF). The brief exposure of intact PC12D cells not only to NGF but also to FGF or to EGF stimulated a protein kinase activity in extracts of such cells that catalyzed phosphorylation of microtubule‐associated protein 1 (MAP‐1) and MAP‐2 in vitro. Similar dose‐response relationships for the effects of NGF and of FGF on the activation of the kinase and on the outgrowth of neurites were observed. The effects of combinations of NGF and FGF or EGF were not additive in terms of either the outgrowth of neurites or the increase in the kinase activity. Treatment of cells with phorbol 12‐myristate 13‐acetate (PMA) also stimulated the kinase activity that phosphorylated MAPs in vitro. However, the level of the enzymatic activity that resulted from the combined treatment of cells with PMA and NGF was additive, as is the case with dibutyryl cyclic AMP and NGF. These findings suggest that NGF, FGF, and EGF may stimulate the activity of the same MAP kinase. The close relationship between the activation of the kinase and the outgrowth of neurites from PC12D cells in response to various agents suggests that activation of the kinase may play an important role in the outgrowt

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09333.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The N‐linked Oligosaccharide structures of human myelin‐associated glycoprotein (MAG) and P0have been characterized by serial lectin affinity chromatography (SLAC) of14C‐glycopeptides.14C‐Glycopeptides were prepared from purified MAG derivative and P0by extensive proteolytic digestion andN‐14C‐acetylation. Assuming that all the14C‐glycopeptides were radiolabelled to the same specific radioactivity, the relative occurrence of the Oligosaccharide structures was correlated to the amount of incorporated radioactivity. Sixteen and 15 fractions were generated by SLAC of MAG and P014C‐glycopeptides, respectively. Despite this tremendous structural heterogeneity, the Oligosaccharide “fingerprints’ of MAG and P0obtained by SLAC displayed similarities: (a) of the three types of N‐linked oligosaccharides, the complex type accounted for 80.4% and 94.9% of MAG and P0radioactivity, respectively; (b) biantennary complex oligosaccharides were the major structures present on MAG and P0; (c)60% of MAG and P0oligosaccharides possessed a bisectingN‐acetylglucosamine residue; and (d) large amounts of oligosaccharides with an α(l‐6)fucose residue were found in both MAG and P0and, noticeably, 25% of the tri‐ and/or tetraantennary and 90% of the bisected biantennary oligosaccharides of both glycoproteins contained α(l‐6)fucose residues in the core. This study demonstrates that MAG and P0, both belonging to the immunoglobulin superfamily, display structural similarities in their N

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09334.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The epitope for HNK‐1 and patient's monoclonal autoantibodies in demyelinating polyneuropathy associated with immunoglobulin M gammopathy is borne by different types of N‐linked Oligosaccharide structures in human PO and myelin‐associated glycoprotein (MAG). Fourteen glycopep‐tide fractions bearing different Oligosaccharide structures were obtained from either MAG or P0glycopeptides by serial lectin affinity chromatography on concanavalin A‐Sepharose,Phaseolus vulgariserythrophytohemagglutinin‐agarose,Pisum sativumagglutinin‐agarose, andPhaseolus vulgarisleucophytohemagglutinin‐agarose. As shown by dot‐TLC plate immunostaining, the same MAG and P0glycopeptide fractions were recognized by HNK‐1 and patient's immunoglobulin M, confirming that these antibodies display similar specificities. The antigenic carbohydrate was present in glycopeptide fractions that either interact withPisum sativumagglutinin‐agarose or were bound byAleuria aurantiaagglutinin‐digoxigenin, indicating that these structures contained α(l‐6)fucose residues. This study demonstrates that the L2/ HNK‐1 epitope is borne mainly or even exclusively by N‐linked Oligosaccharide structures

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09335.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The induction of protooncogenec‐fosin the CNS after administration of several convulsants has been studied. The organochlorine insecticide γ‐hexachlorocyclohexane (γ‐HCH, lindane) has been shown to inducec‐fosexpression in different brain areas. Pentylenetetrazole and picrotoxin, a known γ‐aminobutyric acid‐receptor antagonist, have also been considered. The administration of two nonconvulsant isomers of γ‐HCH, α‐HCH, and δ‐HCH, before the mentioned toxicants, affects the protooncogene expression in different ways. The differential pattern of expression displayed byc‐fosafter these treatments suggests the presence of diverse mechanisms of action

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1992.tb09336.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY