摘要:

Since the identification of 2‐phenylethylamine (β‐phenylethylamine; PE) as a biogenic amine, there has been much discussion about what role, if any, it may have in the CNS. Indeed, the low endogenous concentration of PE in the brain and its relatively low potency in behavioral and pharmacological experiments have led some researchers to conclude that perhaps PE possessed no physiological role at all but that it was merely a metabolic by‐product. Our findings have caused us to conclude otherwise, and in this article we review the neurochemical, neuropharmacological, and neurophysiological findings that lead us to propose that PE is a neuromodulator of catecholamine neurotransmission in t

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05764.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The ganglioside composition of 59 meningiomas has been compared with a molecular genetic analysis of chromosome 22 in the same specimens. Major gangliosides were GM3 (II3NeuAc‐LacCer) and/orGD3 [II3(NeuAc)2‐LacCer]. In specimens with no or partial deletions of chromosome 22, the GM3 ganglioside predominated, and the mean value for GM3, 61% of total sialic acid, was around four times higher than that for GD3. A loss of chromosome 22, found in 56% of the specimens, was shown to be associated with an increase in the proportion of ganglioside GD3, with the ratio between mean values of GM3 and GD3 being ∼ 1:1. Logistic regression revealed that the probability of predicting monosomy of chromosome 22 by the GD3 proportion wa

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05765.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:Synaptosomes from rat forebrain can easily be isolated by combining centrifugation with partition in an aqueous two‐phase system composed of dextran T500 and polyethylene glycol 4000 in which synaptosomes have an extreme affinity for the upper phase. The fraction thus obtained has been characterized by electron microscopy and biochemical markers for synaptosomes and some other cell components. The contamination by microsomes, free mitochondria, and myelin was 4.4, 3.2, and 0.1%, respectively. The morphometric analysis of the electron micrographs shows that>60% of the structures are synaptosomes. This preparation of the isolation procedure is remarkably short (<1 h), formance as assayed by their respiratory activities and ATP level in the absence and presence of depolarizing agents. Synaptosomes prepared by phase partition release the neurotransmitter glutamate in a Ca2+‐dependent manner. The duration of the isolation procedure is remarkably short (<1 h), no ultracentrifuge is required, and the method can be applied for small‐ or large‐scale prepa

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05766.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:Intracellular free [Ca2+]jwas measured using fura‐2 in synaptosomes prepared from cerebral cortices of adult male rats (12 weeks). L‐(+)‐Glutamate, d‐(‐)‐glutamate, and quisqualate produced similar dose‐dependent increases in [Ca2+]i, with EC50values of 0.38 μM, 0.74 μM, and 0.1 μM, respectively, and maximum increases of approximately 40%. Ibotenate showed less affinity (EC504.4 μM) but had a greater maximum effect (57%).N‐methyl‐d‐aspartate (NMDA) and α‐ amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) did not increase [Ca2+]i‐The increases in [Ca2+]iinduced by quisqualate and ibotenate were not diminished in the absence of extrasynaptosomal Ca2+. l‐2‐Amino‐4‐phosphonobutyrate (L‐AP4) (1 μM) completely blocked the changes in [Ca2+]iinduced by l‐(+)‐glutamate, d‐(‐)‐glutamate, quisqualate, or ibotenate. The effects of quisqualate and ibotenate on [Ca2+]iwere also blocked by coincubation of synaptosomes with l‐(+)‐serine‐O‐phosphate (L‐SP) (1 mM) (which, like L‐AP4, blocks the effects of quisqualate and ibotenate on inositol phospholipid metabolism). 6‐Cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) had no effect on agonist‐mediated increases in [Ca2+]iwhen coincubated with either quisqualate or ibotenate. These data are consistent with the existence of presynaptic glutamate receptors (of the excitatory amino acid metabotropic type) which activate phospholipase C leading to the e

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05767.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The labeling of retina ganglion cell and optic tectum phospholipids was determined in chickens given an intraocular injection of32P and then either exposed to light or maintained in the dark. Significantly higher labeling was found in the optic tectum phospholipids of light‐exposed compared with dark‐maintained animals after 3–24 h of labeling. In the ganglion cells, the labeling of phospholipids increased in dark with respect to light at 15 and 30 min of labeling; from 60 min to 24 h, the labeling of phospholipids was significantly higher in light with respect to dark, even if the precursor pool showed a higher labeling in dark at all times studied. When labeling was allowed to proceed in the dark for 30 min and then half of the animals were exposed to light for 15 min, the labeling of ganglion cell phospholipids of light‐exposed animals was significantly higher than those of animals kept in the dark. No individual phospholipid accounted for the differences observed in the labeling of the total phospholipid pool. These results are interpreted as an increase in the biosynthesis of phospholipids in the ganglion cell somas in light with respect

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05768.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:Incubation of various authentic peptides with rat CSF in vitro and analysis of their products by HPLC demonstrated the presence in CSF of a peptidyl dipeptidase [peptidyl dipeptide hydrolase; angiotensin I converting enzyme (ACE); kininase II; EC 3.4.15.1] which sequentially degraded bradykinin (BK) by liberating the carboxy‐terminal dipeptides and converted angiotensin I to angiotensin II. This CSF enzyme was gel‐chromatographed by means of HPLC., and the molecular weight was estimated. The susceptibility to various peptidase inhibitors of the rat CSF enzyme, as well as the effect of NaC1 on the degradation of BK and Hip‐His‐Leu catalyzed by it, was also determined. These properties were compared with those of ACE or kininase II from brain or other tissues, as described in the literature. NaC1 was shown to exert specific and concentration‐dependent effects on each step of the sequential degradation of BK, via BK(1–7) to BK(l–5), catalyzed by the enzyme. In addition, the enzyme system for metabolism of BK appears to differ between rat CSF and blood, the former containing exclusively kininase II, whereas the latter contains both kininase I (carboxypeptidase N; EC 3.4.12.7) an

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05769.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The effect of vigabatrin (γ‐vinyl‐γ‐aminobutyric acid), a new anticonvulsant drug, on the transmitter amino acids in rat cisternal CSF was studied. CSF was collected through a permanently implanted polyethylene cannula from freely moving rats at 5, 24, 48, and 96 h after administration of 1,000 mg/kg of vigabatrin. The free γ‐aminobutyric acid (GABA) level was elevated maximally (13.5‐fold;p<0.01) at 24 h after injection, The homocarnosine (GABA‐histidine) level also was increased (123%;p<0.01) at 24 h after injection, and its concentration remained at the same level for the next 3 days. Glycine and taurine concentrations had increased [31% (p<0.05) and 63% (p<0.01), respectively] at 5 h after injection. It is interesting that the levels of glutamate and aspartate increased [330% (p<0.05) and 421% (p<0.01), respectively] at 96 h after injection, the time when the free GABA level had returned to the baseline concentration and the vigabatrin level was 3% of the maximal concentration. The present study indicates that a single dose of vigabatrin in rats elevates levels of both the inhibitory and excitatory amino acids in CSF. However, the temporal profile of observed changes in relation to vigabatrin injection shows that neither the long‐lasting elevation of GABA content nor the increase in glutamate and aspartate levels correlates with the level of vigabatrin in CSF. These findings suggest that the excitatory mechanisms are also augmented following acute administration of vigabatrin, especially when the content of GABA had decreased to the baseline level and the level of vi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05770.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:In primary cultures of cerebellar granule cells, glutamate, aspartate, andN‐methyl‐d‐aspartate (NMDA) induced a dose‐dependent release of [3H]arachidonic acid ([3H]AA) which was selective for these agonists and was inhibited by NMDA receptor antagonists. The agonist‐induced [3H]AA release was reduced by quinacrine at concentrations that inhibited phospholipase A2(PLA2) but affected neither the activity of phospholipase C (PLC) nor the hydrolysis of phosphoinositides induced by glutamate or quisqualate. Thus, the increased formation of AA was due to the receptor‐mediated activation of PLA2rather than to the action of PLC followed by diacylglycerol lipase. The receptor‐mediated [3H]AA release was dependent on the presence of extracellular Ca2+and was mimicked by the Ca2+ionophore ionomycin. Pretreatment of granule cells with either pertussis or cholera toxin failed to inhibit the receptor‐mediated [3H]AA release. Hence, in cerebellar granule cells, the stimulation of NMDA‐sensitive glutamate receptors leads to the activation of PLA2that is mediated by Ca2+ions entering through the cationic channels functioning as effectors of NMDA receptors. A coupling through a toxin‐sensitive GTP‐binding pr

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05771.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:The production of14CO2and [14C]acetylcholine from [U‐14C]glucose was determined in vitro using tissue prisms prepared from the dorsolateral striatum (a region developing extensive neuronal loss following ischemia) and the paramedian neocortex (an ischemia‐resistant region) following 30 min of forebrain ischemia and recirculation up to 24 h. Measurements were determined under basal conditions (5 mMK+) and following K+depolarization (31 mMK+). The production of14CO2by the dorsolateral striatum was significantly reduced following 30 min of ischemia for measurements in either 5 or 31 mMK+but recovered toward preischemic control values during the first hour of recirculation. Further recirculation resulted in14CO2production again being reduced relative to control values but with larger differences (20–27% reductions) detectable under depolarized conditions at recirculation times up to 6 h. Samples from the paramedian neocortex showed no significant changes from control values at all time points examined. [14C]Acetylcholine synthesis, a marker of cholinergic terminals that is sensitive to changes in glucose metabolism in these structures, was again significantly reduced only in the dorsolateral striatum. However, even in this tissue, only small (nonstatistically significant) differences were seen during the first 6 h of recirculation, a finding suggesting that changes in glucose oxidation during this period were not uniform within all tissue components. The results of this study provide evidence that in a region susceptible to ischemic damage there were specific changes during early recirculation in the metabolic response to depolarization. This apparent inability to respond appropriately to an increased need for energy production could contribute to the further deterioration of cell function in vivo and ultimately to the death of some

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05772.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract:Three distinct antipeptide antisera generated against synthetic peptides that represent parts of the primary sequence of the α‐subunit of the (pertussis toxin‐sensitive) guanine nucleotide binding protein Gowere used in two‐dimensional immunoblots of membranes of neuroblastoma × glioma (NG108–15) cells. Each antiserum identified two distinct polypeptides of some 39 kDa. These had apparent isoelectric points of 5.5 and 5.8. Differentiation of NG108–15 cells in response separately to dibutyryl cyclic AMP (cAMP), 8‐bromo cAMP, forskolin, and prostaglandin E1produced elevated levels of Goα, as has previously been noted in onedimensional immunoblots. Two‐dimensional analysis demonstrated that the cAMP‐induced increases in levels of Goα were only of the more acidic isoform. The two isoforms were both substrates for pertussis toxin‐catalysed ADP‐ribosylation and did not appear to represent differentially phosphorylated forms of the same polypeptide. Separation of the two forms of Goα could be achieved in one‐dimensional sodium dodecyl sulphate‐polyacrylamide gel electrophoresis when 4Mdeionized urea was included in the resolving gel. The more slowly migrating band was the acidic form and corresponded exactly in mobility with the major form of Gofrom both rat and mouse brain. There was no equivalent in brain of the more rapidly migrating form of Gofrom the cells. In agreement with the data from two‐dimensional gels, only the more slowly migrating form was expressed in considerably higher amounts following cAMP‐induced differentiation of NG108–15 cells. Of these two forms of “Go,” the acidic species is equivalent to Gofrom brain, but the basic form is not identical with Go, whi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1990.tb05773.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY