摘要:

Abstract:Tyrosine hydroxylase activity in the rat pineal gland was measured by means of HPLC determination of the amount of l‐3,4‐dihydroxyphenylalanine formed. Enzyme activity showed a clear day‐night rhythm, paralleling that of plasma melatonin levels in the same animals, with values being high during the dark period apparently because of changes inVmax. In animals maintained under constant illumination for 3 days, tyrosine hydroxylase activity and plasma melatonin level rhythms were completely abolished, a result indicating that both are under photoperiodic co

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05566.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:A 150,000‐gsupernatant from axoplasm of the giant axon of the stellate nerve of the squid and from rat sciatic and goldfish optic nerves was found to be able to incorporate covalently [3H]putrescine and [3H]spermidine into an exogenous protein (N,N′‐dimethylcasein). Incorporation of radioactivity was inhibited by CuSO4, a specific inhibitor of transglutaminases, the enzymes mediating these reactions in other tissues. Analysis of pH and temperature range and enzyme kinetics displayed characteristics predicted for transglutaminase‐mediated reactions. Transglutaminase activity increased during regeneration of both vertebrate nerves, but greater activity was found in segments of nerve containing no intact axons than in either intact segments or in segments containing regenerating axons. Polyacrylamide gel electrophoresis of endogenous modified proteins (in the absence ofN,N′‐dimethylcasein) showed labeling of 18‐, 46‐ and 200‐kilodalton proteins by both [3H]putrescine and [3H]spermidine. Analysis of the protein‐bound radioactivity from intact and regenerating rat sciatic nerves demonstrated it to be predominantly in the form of the parent radioactive polyamine. These experiments demonstrate the covalent modification of proteins by polyamines at low levels in squid axoplasm and at relatively higher levels in rat sciatic and goldfish optic nerves. In the latter two cases, the activity of these modification reactions may be due in part to the modification of axonal proteins, but the majority of the activity occurs in nonneuronal

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05567.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:The effect of protein‐modifying reagents on the activity of a purified preparation of a thyroliberin‐hydrolysing pyroglutamate aminopeptidase, solubilised from synaptosomal membranes of guinea‐pig brain by treatment with papain, was investigated. The results indicated that tyrosine, histidine, arginine, and possibly lysine residues were necessary for expression of catalytic activity and that these tyrosine, histidine, and arginine residues were probably located at the active site of the enzyme. Cysteine, serine, glutamate, and aspartate residues were not involved in the expression of catalytic act

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05568.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:The distribution of α‐(γ‐aminobutyryl)‐hypusine was examined in several organs of the rabbit and in the brain of the rat, rabbit, dog, ox, and monkey. The peptide occurred only in the brains, but appeared to be absent from dog brain. Concentrations were higher in the cerebral hemispheres than in other portions of the brain. No significant difference between white and gray matter was o

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05569.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:We measured putrescine levels in minute sites of single rat brains using a sensitive, specific assay involving gas chromatography‐mass spectrometry. The putrescine level was measured in 20 sites of single rat brains: three sites in the cerebral cortex, six sites in the hypothalamus, three sites in the basal ganglia, three sites in the thalamus, three sites in the limbic system, and two sites in the cerebellum. The level of putrescine was very high in the hypothalamus, high in the basal ganglia and limbic system, and low in the thalamus, cerebellum, and two of the three sites in the cerebral cortex. The highest levels were in the anterior hypothalamic area and the lateral hypothalamic area, and the lowest levels were in the vermis and the lobe of the cerebellu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05570.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:The binding of [35S]t‐butylbicyclophosphorothionate ([35S]TBPS), a γ‐aminobutyric acid (GABA)‐activated chloride ionophore ligand; [3H]diazepam, a benzodiazepine agonist; and [3H]muscimol, a GABA receptor probe, were used to assess the effects at 100 μMof deltamethrin, dichlorodiphenyltrichloroethane (DDT), and three experimental insecticides—a DDT‐pyrethroid hybrid, GH414 (cycloprothrin), and two DDT‐analogues, GH266 and GH149 (EDO), on GABA receptor ionophore complexes in a rat brain membrane preparation. GH266 and GH149 were found to inhibit a greater percentage of [35S]TBPS binding than the same concentration of deltamethrin or DDT, although GH414 had little effect. GH266 and GH149 enhanced [3H]diazepam binding by nearly 200%, in contrast to the inhibitory effects of deltamethrin, DDT, and GH414. GH266 and GH149 also caused a dramatic enhancement of [3H]muscimol binding, 367 and 236% of control, respectively, whereas DDT and deltamethrin caused only a moderate enhancement. The effects of the insecticides on binding affinity and density were examined for each of the ligands. The results show a differential interaction of the insecticides on the various ligand

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05571.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:Cytosolic (100,000g) fractions of fetal rabbit brain and placenta tissue convert [1–14C]arachidonic acid into several oxidation products identified with the lipoxygenase [12‐hydroxyeicosatetraenoic acid (12‐HETE) and 15‐HETE]and cyclooxygenase [prostaglandin E2(PGE2)] pathways. Formation of 12‐HETE and 15‐HETE by fetal brain is time‐dependent, reaching a plateau after 40 min and is linear with protein concentration. An apparent affinity constant of 0.06 mMand aVmaxof 0.1 μmol/h/g wet weight are presumably responsible for the excessive accumulation of 12‐HETE and 15‐HETE in comparison to PGE2(Km=0.5 mM). The latter is synthesized by the placenta particulate fraction but almost exclusively by the brain cytosol. Compared to brain, the activity of the placenta tissue is exceedingly higher and in addition to 12‐HETE and 15‐HETE there is a substantial formation of 12–l‐hydroxyheptadecatrienic acid. Formation of 12‐HETE and 15‐HETE at 21 days is as effective as at 31 days gestation and is strongly inhibited by nordihydroguaiaretic acid (93%), BW755c (99%), and AA861 (84%) but not by indomethacin. Placenta and brain tissues of intrauterine growth retarded fetuses after ligation of placental blood vessels fail to convert arachidonic acid into other eicosanoids. Loss of enzymatic activity also observed in normal tissue after prolonged storage cannot be restored by the addition of several SH age

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05572.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:Acetylcholine (ACh) synthesis in homogenates of rat soleus muscles had two components. One component, specifically inhibited by bromoacetylcholine (BrACh), had aKmfor choline of 0.26 mM; the other, resistant to BrACh, had aKmfor choline of 45 mM. The component with a lowKmwas absent from denervated muscle, and was identical in kinetic terms to ACh synthesising activity in homogenates of sciatic nerve. It is therefore considered choline acetyltransferase (ChAT)‐specific. The use of BrACh as a specific inhibitor of ChAT activity allowed the calculation of ACh synthesis at individual motor end‐plates in the soleus muscle of the rat: 2.1 × 10−‐3nmol h−1. Since the number of muscle fibres and the number of motor units are known for this muscle, ACh synthesis per motor unit could be calculated: 0.15 nmol h−1. It is concluded that BrACh can be used as a specific inhibitor of ChAT activity in homogenates of skeletal muscle and that its use will obviate the necessity of dividing biopsied muscle or small rodent muscles into neural and aneu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05573.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:N‐Methylisoquinolinium ion (N‐MIQ) has been found to inhibit the biosynthesis of catecholamines; it inhibited tyrosine hydroxylase activity in striatal tissue slices. In this article, the effects of N‐MIQ and an analogue,N‐methylquinolinium ion, on monoamine oxidase (MAO) activity were examined to see their effects on the catabolism of catecholamines. MAO‐A in human placental mitochondria was strongly inhibited by N‐MIQ in competition with the substrate. The apparentKivalue of N‐MIQ was found to be 20.4 ±1.1 μM, whereas that ofN‐methylquinolinium ion was 54.6 ± 4.5 μM.MAO‐B in human brain synaptosomes and liver mitochondria was found to be inhibited by N‐MIQ, but the inhibition proved to be noncompetitive. The inhibition of MAO‐B by N‐MIQ was completely reversible by dialysis of the incubation mixture. MAO‐A in human brain and liver mitochondria was more sensitive to the inhibitor than MAO‐B. By quantitative analysis of N‐MIQ, using HPLC, it was found not to be catabolized by the incubation with mitochondria, suggesting that the inhibition was due to N‐MIQ itself and not due to any metabolic product. The inhibition of MAO by N‐MIQ is discussed in terms of its possible involv

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05574.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:The effects of corticostriatal deafferentation (de‐cortication) and destruction of intrinsic neurons (intrastriatal kainate injection) on the extracellular concentration, and veratrine‐releasable pools, of endogenous amino acids in the rat striatum were examined using the in vivo brain dialysis technique. Intracellular amino acid content was also determined. Decortication reduced selectively intra‐and extracellular levels of glutamate (Glu) and aspartate (Asp). Extracellular changes were more pronounced than those in tissue content. γ‐Aminobutyric acid (GABA), tau‐nne (Tau), and phosphoethanolamine (PEA) levels were not affected, whereas nonneuroactive amino acids were increased at 1 week but not at 1 month postlesion. The intracellular pool of Glu and Asp was also reduced in kainate‐lesioned striata. However, extracellular levels of these compounds were not affected significantly by this treatment. The tissue content of all other amino acids was decreased, the most prominent change being in the concentration of GABA. Extracellular GABA concentration was also reduced dramatically, whereas the concentrations of nonneuroactive amino acids were increased to varying degrees. These data suggest that transmitter pools of neuroactive amino acids are an important supply for their extracellular pools. Lesion‐induced alterations in nonneuroactive amino acids are discussed with regard to the loss of metabolic pools, glial reactivity, and changes in blood‐brain bamer transport. Veratrine induced a massive release of neuroactive amino acids such as Glu, Asp, GABA, and Tau into the extracellular fluid, and a delayed increase in PEA. Extracellular levels of neuroactive amino acids were raised slightly. Decortication reduced, selectively, the amounts of Glu and Asp released by veratrine. GABA, Tau, and PEA effluxes were also decreased in kainate‐lesioned striata. These findings are consistent with the proposed roles of an acidic amino acid as the corticostriatal transmitter, and of GABA as a transmitter in intrinsic striatal neurons. The existence of releasable pools of Tau and PEA within kainate‐sensitive striatal neurons would also

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb05575.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY