摘要:

Abstract:Extracts of ox spinal cord and chicken brain were fractionated by ion‐exchange chromatography and assayed for their ability to reduce the viscosity of muscle F‐actin solutions. Two distinct peaks of activity were obtained, one of which was further purified by affinity chromatography on a DNAase‐actin Sepharose column. Following molecular exclusion chromatography, the actin component appeared as a complex of 1 molecule of a protein with molecular weight 90,000 and 2 molecules of actin (42,000). This tightly bound complex was resistant to most methods of protein separation, but was resolvable into its component proteins by sodium dodecyl sulphate acrylamide gel electrophoresis. The protein of molecular weight 90,000 could be eluted from such a gel in a fully active form. The activity of the protein from ox spinal cord was closely similar to that of gelsolin, an actin‐fragmenting protein originally isolated from rabbit lung macrophages. Like gelsolin, the protein from ox spinal cord produced fragmentation of muscle F‐actin filaments at Ca2+concentrations greater than 10‐7M, and had a nucleating effect on the polymerisation of muscle actin; the latter was measured most easily by the enhancement of fluorescence of muscle actin conjugated toN‐(1‐pyrenyl)iodoacetamide. Nucleation was more effective in the presence of Ca2+, but also occurred in its absence, and the same was true of complex formation between the 90,000 protein and muscle G‐actin. On the basis of its actin‐fragmenting activity, we estimate that the 90,000 molecular weight protein constitutes 0.2% of the protein initially extracted from ox spinal cord. A very similar protein, indistinguishable in its action on actin but containing variable amounts of a protein of molecular weight 85,000 as well as 90,000, was isolated from chicken brain. A similar protein was also detected in pure cultures of sympathetic neurones by enrichment on a DNAase‐actin affinity column and by immune blotting and by immuno‐fluorescence. We conclude that a protein similar, if not identical to macrophage gelsolin is present in neurones and that it probably plays a part in the actin‐based

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08119.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:A sensitive assay, which cross‐reacts with and is specific for diverse opioid peptides, is described. This is based on the prior acetylation of samples and subsequent radioimmunoassay with an antiserum highly specific for the acetylated NH2terminus of opioid peptides. The result is a procedure that can be used to investigate multiple forms of opioid peptides in extracts of biological material. The sensitivity of the assay is ˜15 fmol of β‐endorphin per incubation tube, i.e., ˜ 100‐fold greater sensitivity than the radioreceptor assay used in our laboratory. The peptide concentration required for 50% displacement of trace ranged from 0.65 nM (β‐endorphin) to 1.6 nM (Met‐enkephalin). The assay apparently shows an absolute requirement for a free (or acetylated) NH2terminus corresponding to either a Leu‐ or Met‐enkephalin sequence. Use of the assay with and without prior acetylation of sample provides a method for estimation of the ratio of acetylated:nonacetylated opioid peptides in crude or fractionated extracts. The procedure is used to investigate the forms of opioid peptide found in rat br

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08120.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:We measured the distribution of molecular forms of acetylcholinesterase (AChE) in muscles of a song bird, the zebra finch, and found a pattern similar to those reported in other vertebrates. As in other species, the most rapidly sedimenting form of the enzyme decreases to barely detectable levels following denervation. In the muscles of the syrinx, castration causes a large decrease in AChE activity, but has little or no effect on the relative abundance of AChE forms. This suggests that the number of AChE catalytic sites is changing without affecting the distribution of catalytic sites among the molecular forms. This is in marked contrast with the effect of denervation in the syrinx, which causes changes in the distribution of activity, as well as in total activity.

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08121.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The molecular parameters of tyrosine hydroxylase (EC 1.14.16.2) from rat adrenal, rat striatum, and human pheochromocytoma were determined by combined gel filtration and sucrose gradient ultracentrifugation. The enzyme from rat adrenal has a calculated molecular weight of 228,000, a Stokes radius of 60.9 Å, a sedimentation coefficient of 9.10S, and a frictional ratio of 1.39. The enzyme from rat striatum has a calculated molecular weight of 210,000, a Stokes radius of 54.3 Å, a sedimentation coefficient of 9.38S, and a frictional ratio of 1.28. Tyrosine hydroxylase from human pheochromocytoma tissue has a calculated molecular weight of 255,000, a Stokes radius of 68.2 Å, a sedimentation coefficient of 9.08S, and a frictional ratio of 1.50. These results indicate that the tyrosine hydroxylases from central and peripheral tissue in the rat are quite similar although the human enzyme appears to be significantly larg

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08122.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:In the rat brain, dopamine is metabolised by both A and B forms of monoamine oxidase (MAO), although the A form of the enzyme is the major component. The Kmof MAO‐A toward dopamine (120 μM) is lower than the Km, of MAO‐B toward this substrate (340 μM). The activity of MAO‐A was lower in old rats than in young rats, and the same degree of decrease was found for 5‐hydroxy‐tryptamine as for dopamine as substrates for this enzyme form. The activity of MAO‐B was higher in the old rats, the degree of increase being the same for dopamine as for β‐phenethylamine as substrates for this enzyme form. The K1values of the inhibition of MAO‐A by cimoxatone and MD770222 (the principal plasma metabolite of cimoxatone) were independent of the substrate used to assay for activity, but were lower than the K1values for the inhibition of MAO‐

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08123.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Protein gene product (PGP) 9.5 is a new brain‐specific protein originally detected by high‐resolution two‐dimensional electrophoresis of the soluble proteins of human brain and other organs. We have purified this protein from human brain and raised a rabbit antihuman PGP 9.5 antiserum. The protein has a monomer molecular weight of ˜27,000 and is present in brain at concentrations at least 50 times greater than in other organs. Im‐munoperoxidase labelling has localised PGP 9.5 to neurones in the human cerebral cortex with no evidence of staining of glial elements. PGP 9.5 is estimated to be present in brain at concentrations of 200‐500 μg/g wet weight and represents a major protein component of neuronal cytoplasm. This new neurone‐specific cytoplasmic marker may prove useful in studies of neuronal development and in the detection of neuronal damage in disease of the n

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08124.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:A study was made of the actions of the excitant neurotoxin, kainic acid, on the uptake and the release ofd‐[2,3‐3H]aspartate (d‐ASP) in slices of guinea pig cerebral neocortex and striatum. The slices took upd‐ASP, reaching concentrations of the amino acid in the tissue which were 14–23 times that in the medium. Subsequently, electrical stimulation of the slices evoked a Ca2+‐dependent release of a portion of thed‐ASP. Kainic acid (10‐5‐10‐3M) produced a dose‐dependent inhibition ofd‐ASP uptake. The electrically evoked release ofd‐ASP was increased 1.6–2.0 fold by 10‐5and 10‐4M kainic acid. The kainate‐enlarged release was Ca2+‐dependent. Dihydrokainic acid, an analogue of kainic acid with little excitatory or toxic action, did not increased‐ASP release but depressedd‐ASP uptake. Attempts were made to block the action of kainic acid with baclofen and pentobarbital, compounds which depress the electrically evoked release ofl‐glutamate (l‐GLU) andl‐aspartate (l‐ASP). Baclofen (4 × 10‐6M), an antispastic drug, and pentobarbital (10‐4M), an anesthetic agent, each inhibited the electrically evoked release ofd‐ASP and prevented the enhancement of the release above control levels usually produced by 10‐4M kainic acid. It is proposed that 10‐5and 10‐4M kainic acid may enhance the synaptic release ofl‐GLU andl‐ASP from neurons which use these amino acids as transmitters. This action is prevented by baclofen and pentobarbital. In view of the possibility that cell death in Huntington's disease could involve excessive depolarization of striatal and other cells by glutamate, baclofen might be effectiv

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08125.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Neonatal treatment of rats with monosodium glutamate (MSG) has been demonstrated to destroy cell bodies of neurons in the arcuate nucleus including the brain beta‐endorphin (B‐END) system. The effects on opiate receptors of the loss of B‐END is unknown. Neonatal rats were treated with MSG as previously described. After reaching maturity (7‐9 months), MSG‐treated rats and litter‐matched untreated control rats were decapitated and brains dissected into brain regions. Opiate receptor assays were run with [3H]morphine (mu receptor ligand) and [3H]D‐alanine2‐D‐leucine5(DADL) enkephalin (delta receptor ligand) for each brain region for both MSG and control rats simultaneously. Scatchard plot analyses showed a selective increase in delta receptors in the thala‐mus only. No corresponding change in mu receptors in the thalamus was found. The cross‐competition IC50data supported this conclusion, showing a loss in the potency of morphine in displacing [3H]DADL enkephalin in the thalamus of MSG‐treated rats. This shift in delta receptors produced an IC50displacement pattern in thalamus, ordinarily a mu‐rich area, similar to that of striatum or cortex, delta‐rich areas, again indicating an increase in delta receptors. Similar changes in delta receptors in other brain regions were not found. These results represent one of the few examples of a selective and localized shift in delta with no change in mu sites. Furthermore, the delta increase may reflect an up‐regulation of the receptors in thalamus after chronic loss o

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08126.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:At the subcellular level, the synthesis of ceramide from free lignoceric acid and sphingosine in brain required reconstituted enzyme system (particulate fraction, heat‐stable and heat‐labile factors) and pyridine nucleotide (NADPH). The mitochondrial electron transfer inhibitors (KCN and antimycin A), energy uncouplers (oligomycin and 2,4‐dinitrophenol), and carboxyatractyloside, which prevents the transport of ATP and ADP through the mitochondrial wall, inhibit the synthesis of ceramide in the presence of NADPH but have very little effect in the presence of ATP. Similar to the synthesis of ceramide, the synthesis of ATP from NADPH and NADH by the particulate fraction also required cytoplasmic factors (heat‐stable and heat‐labile factors). Moreover, ATP, but not its analog (AMP‐CH2‐P‐O‐P), can replace NADPH, thus suggesting that the function of the pyridine nucleotide is to provide ATP for the synthesis of ceramide. The cytoplasmic factors were not required for the synthesis of ceramide in the presence of ATP. The maximum velocity for synthesis of ceramide from free fatty acids of different chain lengths (C16‐C26) was bimodal, with maxima around stearic acid (C18) and behenic acid (C22). The relative rate of synthesis of ceramide parallels the relative distribution of these fatty acids in brain cerebros

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08127.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:In rabbits, generalized seizures were induced by methoxypyridoxine, and changes in amino acid concentrations of 15 brain regions were investigated before seizure onset and during the course of sustained epileptiform activity. As previously reported, γ‐aminobutyric acid (GABA) concentration decreased preictally in most regions. At the same time, taurine level was elevated in the hypothalamus, thalamus, hippocampus, caudatum, and frontal cortex. After 90 min of seizures, it was significantly decreased in the hypothalamus, periaqueductal grey, substantia nigra, frontal cortex, and cerebellum. Glycine content was reduced preictally only in the substantia nigra; after seizure onset its concentration rose in all brain areas. Glutamate content in the frontal cortex decreased before seizure onset; after 1.5 h of seizures, its concentration in cerebellum, caudatum, and hippocampus was reduced. Aspartate level was decreased in most areas after sustained seizures; in putamen, however, it was elevated. In contrast, glutamine content increased preictally in the superior colliculus and in all brain areas by ˜200% after 90 min of seizures. Alanine and valine content also rose markedly in most brain areas after prolonged seizures, and threonine showed the same tendency. The single brain regions were observed to respond to methoxypyridoxine in highly individualistic ways. For example, the glycine content of the substantia nigra, which is believed to utilize this amino acid as a neurotransmitter, decreased preictally. The potential importance of the superior colliculus in seizure induction is considered in view of the early rise in glutamine level. The antagonistic preictal behavior of taurine and GABA is discussed with respect to synthesis, uptake from the blood, and antiepileptic propert

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb08128.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY