ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10847.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The benzodiazepine receptor from rat brain was solubilised and purified 5200‐fold by affinity chromatography. The affinity column contained an immobilized benzodiazepine (delorazepam) and biospecific elution with 6 mm‐chlorazepate was achieved. The purified receptor is apparently homogeneous in SDS‐polyacrylamide gel electrophoresis. The native protein had a molecular weight of 240,000, and the subunit one of 60,000. The dissociation constant (KD) is 8 nmfor [3H]diazepam. A correlation exists between the value of affinity obtained for benzodiazepine derivatives and their known pharmacological effectiv

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10848.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The mechanism of involvement of monoamine oxidase (MAO) in catecholamine‐stimulated prostaglandin (PG) biosynthesis was studied in the particulate fraction of rat brain homogenates. High concentrations of either noradrenaline (NA) or dopamine (DA) stimulated effectively PGF2αformation. The same amount of 2‐phenylethylamine (PEA) acted similarly, provided that it was administered together with a catecholamine analogue or metabolite possessing the 3,4‐dihydroxyphenyl nucleus–3, 4‐dihydroxyphenylalanine (DOPA), 3,4‐dihydroxyphenylacetic acid (DOPAC), 3,4‐dihydroxyphenyl‐glycol (DOPEG), 3,4‐dihydroxyphenylacetaldehyde (DOPAL), or α‐methylnoradrenaline (α‐met‐NA)–or with SnCl2. In the absence of PEA, these compounds were ineffective with regard to stimulation of PGF2αformation. Catalase, pargyline, or indomethacin abolished completely PGF2αformation elicited either by catecholamines or by PEA plus a 3,4‐dihydroxyphenyl compound or SnCl2. With regard to the stimulation of PGF2αformation in the presence of α‐met‐NA, PEA could be replaced by H2O2, generated by the glucose oxidase(GOD)‐glucose system. The effect of H2O2was inhibited by indomethacin or catalase, but pargyline was ineffective. It is assumed that catecholamines play a dual role in the activation of PG biosynthesis in brain tissue. During the enzymatic decomposition of catecholamines MAO produces H2O2, which stimulates endoperoxide synthesis. Simultaneously, catecholamines as hydrogen donors promote the nonenzymatic transformation of endoperoxides into PGF2α. The possible physiological

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10849.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The presence and identity of 5′‐terminal cap structures in rat brain polysomal mRNA were investigated by radiolabeling the mRNA by periodate oxidation and [3H]sodium borohydride reduction or byβ‐elimination of 5′‐terminal nucleoside and incorporation of32P in the presence of polynucleotide kinase. The labeled mRNAs were digested with nucleases and the cap structures were isolated and identified by chromatographic and electrophoretic procedures. The results showed that rat brain mRNAs contained cap 1 and cap 2 structures and no caps of the zero type. The proportion of cap 2 was higher than that of cap 1. Both caps had 7‐methylguanosine (m7G) as the 5′‐terminal nucleoside, which was linked to the next nucleoside by an inverted triphosphate bridge, as in other eukaryotic mRNAs. The most prominent nucleoside in the 5′‐penultimate position was 6‐methyl‐2′‐O‐methyiadenosine [m6A(m)] followed by 2′‐O‐methyladenosine [A(m)], which together contributed to nearly 70% of both cap 1 and cap 2 structures. 2′‐O‐Methylguanosine [G(m)] accounted for approximately 18%, the rest being made up of 2′‐O‐meth

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10850.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The role of cap structures in the translation of brain mRNA was examined by measuring protein biosynthesisin vitroin wheat germ and reticulocyte systems programmed by mRNA that was either untreated or oxidized by periodate or from which 5′‐terminal 7‐methylguanosine (m7G) was removed by oxidation andβ‐elimination. In another series of reactions, amino acid incorporation into polypeptides was measured in the absence and in the presence of varying concentrations of the cap analogue 7‐methylguanosine 5′‐triphosphate (pppm7G). The results indicated that any of the above treatments interfered with brain mRNA translation, the degree of inhibition depending on the translation system used, the concentration of mRNA, and the source of initiation factors. Homologous brain initiation factors were superior to reticulocyte factors in providing a partial relief from inhibition of translation caused by these treatments. It was also found that synthesis of the brain‐specific protein S‐100 was inhibited byβ‐elimination of mRNA, by pppm7G, or by the presence of capped globin mRNA, indicating that the mRNA for this protei

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10851.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:After the intracranial injection of [methyl‐3H]thymidine the specific activity of rat cortical DNA increases rapidly, reaching a maximum at about 5 h. More than half of the radioactive DNA disappears from the tissue in the following few hours. During the same period of time the concentration of radioactive DNA in liver remains essentially constant. Minor variations occur in both organs after 41 h. An apparent rapid turnover of DNA is also present in a fraction of purified neuronal perikarya prepared from the cerebral corte

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10852.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The accumulation ofγ‐aminobutyric acid (GABA) after inhibition of GABA‐T (4‐aminobutyrate: 2‐oxoglutamate aminotransferase, EC 2.6.1.19) by various doses of aminooxyacetic acid (AOAA) and gabaculine was studied in four different regions of the mouse brain. The dose‐response curve for GABA accumulation after treatment with AOAA was linear up to 10 mg/kg i.p., and then leveled off. The increase in GABA accumulation after gabaculine treatment was linear up to 100 mg/kg i.p. No further increase was observed with doses up to 300 mg/kg i.p. The selectivity of both GABA‐T inhibitors was assessed by measuring their effects on the content of free amino acids in mouse brain. Apart from the substantial increase in the GABA concentration, there were significant decreases in the content of glutamic acid, aspartic acid, alanine and glutamine, and an increase in ornithine content after administration of gabaculine. The same changes in amino acid content were observed after treatment with AOAA, but the level of lysine was also increased and the change in alanine level was biphasic. All these changes, however, were very small compared with the large increase in GABA level. A method for estimating the rate of the GABA turnover in vivo by measuring the initial rate of GABA accumulation after administration of AOAA or gabaculine is proposed, and the validity of the two techniques is discussed. The effect of diazepam on GABA levels and on the gabaculine‐induced accumulation of GABA was studied. The results obtained with diazepam show that this method can provide valuable insight into the effects of drugs on GABAergic mech

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10853.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The uptake and metabolism of H‐Pro‐[3H]Leu‐Gly‐NH2([3H]PLG) in rat brain was investigated by reverse‐phase paired‐ion high pressure liquid chromatography. Followingin vitroincubation of [3H]PLG with rat brain subcellular preparations, the microsomal‐cytosol fraction was about twice as active in degrading PLG as the crude mitochondrial‐synaptosomal fraction. For both enzyme preparations the pH optimum was found at pH 7–7.5. The major labeled metabolite was [3H]leucine, whereas3H‐labeled Leu‐Gly‐NH2as the only labeled peptide intermediate was found in trace amounts. After intravenous injection of [3H]PLG the uptake of unmetabolized peptide in the brain appeared to be very low: 0.008% and 0.001% of the administered dose/g tissue at 2 and 5 min after injection respectively, while at longer survival times intact peptide was below the detection limit. Compared with the intravenous route of administration, intracerebroventricular injection of [3H]PLG yielded much higher brain concentrations of unmetabolized PLG. Following both routes of administration, the metabolite profile was in agreement with that obtained afterin vitroincubation. However, thein vivoexperiments also showed considerable incorporation of [3H]leucine liberated from [3H]PLG into proteins. Both thein vitroandin vivoresults indicate that the initial cleavage of PLG in rat brain occurs at the NH2‐terminus and that the dipeptide intermediate H‐Leu‐Gly‐NH2is subsequently hydrolyzed to its const

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10854.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The effect of different psychotropic drugs on the rate of DOPA accumulation after administration of a decarboxylase inhibitor (NSD 1015) was compared in the substantia nigra (SN) and caudate nucleus (CN) by a new radioenzymatic method. Inhibition of monoamine oxidase with pargyline or stimulation of dopamine (DA) receptors with apomorphine,N‐n‐propyl‐norapomorphine ord‐amphetamine reduced DOPA formation in the CN and SN to the same extent. Vice versa, both inhibition of DA receptors with haloperidol or (‐)sulpiride and depletion of DA concentration with reserpine enhanced DOPA formation to a greater extent in the CN than in the SN. Apomorphine antagonized not only the effect of haloperidol and (‐)sulpiride, but also, and even more effectively, that of reserpine. The results indicate that DA synthesis in the SN is controlled by both end‐product inhibition and DA receptor‐medi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10855.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:To investigate the release of adenine compounds from defined neuronal pathways, we employed a hippocampal slice preparation in which a selective‐loading of the releasable pools was achievedin vivowith the aid of axonal transport. By injecting radioactive adenosine stereotaxically into the entorhinal cortex, the major afferent system to the dentate gyrus (the perforant path) was loaded within 20–36 h, at which time the rats were killed and hippocampal slices were prepared. The efflux of radioactive material, as recovered from the perfusate and measured in a scintillation counter, was found to be significantly increased in response to electrophysiologically controlled stimulation of the perforant path but not to stimulation of an alternative fiber tract, the fimbria. These findings provide supportive and more direct evidence for an activation‐coupled release of adenosine derivatives from presynaptic sites in the central nervous s

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb10856.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY